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IPC-7530A
2017 - March
Guidelines for Temperature
Profiling for Mass Soldering
Processes (Reflow and Wave)
Supersedes IPC-7530
May 2001
An international standard developed by IPC

Association Connecting Electronics Industries

®
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IPC-7530A
®

Guidelines for
Temperature Profiling
for Mass Soldering
Processes (Reflow
and Wave)

Developed by the Thermal Profiling Guide Task Group (5-22h) of the

Assembly & Joining Committee (5-20) of IPC

Supersedes: Users of this standard are encouraged to participate in the

IPC-7530 - May 2001 development of future revisions.

Contact:

IPC
3000 Lakeside Drive, Suite 105N
Bannockburn, Illinois
60015-1219
Tel 847 615.7100
Fax 847 615.7105
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March 2017 IPC-7530A

Acknowledgment
Any document involving a complex technology draws material from a vast number of sources across many continents. While
the principal members of the Thermal Profiling Guide Task Group (5-22h) of the Assembly & Joining Committee (5-20) are
shown below, it is not possible to include all of those who assisted in the evolution of this standard. To each of them, the
members of the IPC extend their gratitude.

Assembly & Joining Thermal Profiling Guide Technical Liaison of the

Committee Task Group IPC Board of Directors
Vice Chair Chair
Karen A. Tellefsen Ray Prasad Bob Neves
Alpha Addembly Solutions Ray Prasad Consultancy Group Microtek (Changzhou) Laboratories
Co-Chairs Vice Chair
Daniel L. Foster Robert Rowland
Missile Defense Agency Axiom Electronics, LLC
Leo P. Lambert
EPTAC Corporation

Thermal Profiling Guide Task Group

Wallace Ables, Dell Inc. Gerd Fischer, NASA Goddard Space Michael Moore, U.S. Army -
Heriberto Alanis, The Chamberlain Flight Center AMRDEC
Group, Inc. Tim Gallagher, BAE Systems Miles Moreau, KIC
Dudi Amir, Intel Corporation Ognyan Georgiev, Centillion Matthew Park, ZF TRW
Raiyo Aspandiar, Intel Corporation Electronics Ltd. Ray Prasad, Ray Prasad Consultancy
Paul Austen, Electronic Controls Constantino Gonzalez, ACME Group
Design Inc. Training & Consulting Jagadeesh Radhakrishnan, Intel
Frederick Beltran, L-3 Gaston Hidalgo, Samsung Electronics Corporation
Communications America Ivan Rashev, Centillion Electronics
Erik Bjerke, BAE Systems Mitchell Holtzer, Alpha Assembly Ltd
Solutions Christopher Robbat, Raytheon
Gerald Leslie Bogert, Bechtel Plant
Machinery, Inc. Ife Hsu, Intel Corporation Company
Mumtaz Bora, Peregrine Bruce Hughes, AMRDEC MS&T Robert Rowland, Axiom Electronics,
Semiconductor EPPT LLC
Lance Brack, Raytheon Missile Jennie Hwang, H-Technologies Luis Saldivar, The Chamberlain
Systems Group Group, Inc.
Dock Brown, DfR Solutions Rick Iodice, Raytheon Company Keith Sellers, NTS - Baltimore
Rich Burke, Fluke Process Paul Jarski, John Deere Electronic Jose Servin Olivares, Continental
Instruments Solutions Temic SA de CV
Luis Bustamante, Grupo Chamberlain Gildardo Jimenez-Mungia, The Chris Smith, Plexus Corp.
Chamberlain Group, Inc. Vern Solberg, Solberg Technical
Eric Carmden, Foresite, Inc.
Michael Johnson, M/A-COM Consulting
Alejandro Cruz, ACME Inc.
Technology Solutions, Inc. Udo Welzel, Robert Bosch GmbH
James Daggett, Raytheon Company
Milea Kammer, Honeywell Aerospace P. Gil White
Gerjan Diepstraten, Vitronics Soltec
Leo Lambert, EPTAC Corporation Etienne Witte, Axiom Electronics,
Miguel Dominguez, Continental
Kyle Loomis, Kester LLC
Temic SA de CV
Ursula Marquez de Tino, Plexus
Corporation

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IPC-7530A March 2017

Special Recognition

Dudi Amir, Intel Corporation Ife Hsu, Intel Corporation Jagadeesh Radhakrishnan, Intel
Raiyomand Aspandiar, Intel Jennie Hwang, H-Technologies Corporation
Corporation Group Robert Rowland, Axiom Electronics,
Paul Austen, Electronic Controls Michael Johnson, M/A-COM LLC
Design Inc. Technology Solutions, Inc. Chris Smith, Plexus Corp.
Gerald Leslie Bogert, Bechtel Plant Milea Kammer, Honeywell Aerospace Vern Solberg, Solberg Technical
Machinery, Inc. Leo Lambert, EPTAC Corporation Consulting
Gerd Fischer, NASA Goddard Space Ursula Marquez de Tino, Plexus Udo Welzel, Robert Bosch GmbH
Flight Center Corporation
Mitchell Holtzer, Alpha Assembly Ray Prasad, Ray Prasad Consultancy
Solutions Group

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March 2017 IPC-7530A

Table of Contents
1 SCOPE ...................................................................... 1 3.3 Reflow Soldering .............................................. 14
1.1 Purpose ................................................................ 1 3.3.1 True Time Above Liquidus (True TAL) .......... 15
1.2 Background ......................................................... 1 3.4 Equipment Settings ........................................... 16
1.3 Terms and Definitions ........................................ 1 3.4.1 Reflow Oven Selection ..................................... 16
1.3.1 Thermal Profile ................................................... 1 3.4.2 IR vs. Convection ............................................. 16
1.3.2 Recipe ................................................................. 2 3.4.3 Heating Zone Selection .................................... 16
1.3.3 Pasty Range ........................................................ 2 3.4.4 Clearance Height, Conveyor Belt Type/
1.3.4 Ramp Rate .......................................................... 3 Width and Edge-Rail Support .......................... 17
1.3.5 Soak (Dwell) ....................................................... 3 3.4.5 Cover Gas ......................................................... 17
1.3.6 Peak ..................................................................... 3 3.4.6 Profiling ............................................................ 17
1.3.7 Melting Point ...................................................... 3 3.4.7 Product Trackers ............................................... 17
1.3.8 Liquidus .............................................................. 3 4 VAPOR-PHASE REFLOW PROFILING ................. 17
1.3.9 Solidus ................................................................ 3 4.1 Vapor-Phase Reflow ......................................... 19
1.3.10 Eutectic ............................................................... 3
5 WAVE SOLDERING PROFILING ........................... 19
1.3.11 Time Above Liquidus (TAL) ............................. 3
5.1 Machine Considerations ................................... 20
1.3.12 True TAL ............................................................ 4
5.2 Conveyor Considerations ................................. 20
1.3.13 Delta T (Profile or Equipment) .......................... 4
5.3 Preheat Considerations ..................................... 21
1.3.14 Phase Diagram .................................................... 4
5.4 Solder Pot Considerations ................................ 21
1.3.15 Superheat ............................................................ 4
5.5 Profile Development Steps ............................... 21
1.3.16 Cooldown ............................................................ 4
5.6 Design for Mass Wave Soldering
1.3.17 Preheat ................................................................ 4 Considerations .................................................. 22
1.3.18 Class 1 Radiant IR-Dominant Systems ............. 4
6 SELECTIVE SOLDERING PROFILING .................. 22
1.3.19 Class 2 Convection/IR Systems ......................... 4
6.1 Solder Pot ......................................................... 22
1.3.20 Class 3 Convection-Dominant Systems ............. 4
6.1.1 Machine Considerations ................................... 23
1.3.21 Profile Zones ....................................................... 4 6.1.2 Preheat Considerations ..................................... 23
1.3.22 Reflow Program .................................................. 4 6.1.3 Solder Pot and Nozzle Considerations ............ 23
1.3.23 Liquidus Time Delay (LTD) .............................. 4 6.1.4 Profile Development Steps ............................... 23
2 APPLICABLE DOCUMENTS .................................... 4 6.1.5 Design for Manufacturing (DfM) for
Selective Soldering ........................................... 24
2.1 IPC ...................................................................... 4
6.1.6 Thermocouple Attachment for Wave and
2.2 Joint Industry Standards ..................................... 5 Selective Soldering ........................................... 24
2.3 JEDEC ................................................................ 5 6.2 Alternatives to Selective Soldering .................. 25
3 CONVECTION REFLOW PROFILING ..................... 5 6.2.1 Paste-in-Hole Soldering .................................... 25
3.1 Thermal Profiles ................................................. 5 6.2.2 Laser Soldering ................................................. 25
3.1.1 Thermocouple Attachment ............................... 10 7 TEMPERATURE PROFILING TOOLS .................... 26
3.1.2 Preheat Zone ..................................................... 13 7.1 Product Thermal Profilers ................................ 26
3.1.3 Soak Zone ......................................................... 13 7.1.1 Thermal Profiler Usage Recommendations ..... 27
3.1.4 Reflow Zone ..................................................... 13 7.1.2 Thermal Profiler Specifications ........................ 27
3.1.5 Cooling Zone .................................................... 13 7.1.3 Thermal Barrier ................................................ 27
3.1.6 Thermal Profile for Backward Compatibility .. 13 7.1.4 Statistical Process Control (SPC) .................... 27
3.1.7 Unique Profile for Each PWBA ....................... 14 7.2 Machine Profilers .............................................. 27
3.1.8 Flux ................................................................... 14 7.2.1 Purpose .............................................................. 27
3.2 Material Issues .................................................. 14 7.2.2 Measurement Parameters .................................. 28

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IPC-7530A March 2017

7.2.3 Machine Verification ......................................... 28 Figure 3-7 Recommended Locations of Thermocouples

on a BGA ........................................................ 10
7.2.4 Continuous Real-Time Convection
Oven Profilers ................................................... 29 Figure 3-8 First Example of Thermocouple on Inner
and Outer Rows – Drilling From Bottom
7.3 Thermocouple Types and Selection ................. 29 of BGA and Other Components ...................... 11
7.3.1 Thermocouple Type .......................................... 29 Figure 3-9 Second Example of Thermocouple on Inner
7.3.2 Thermocouple Wire Gauge .............................. 29 and Outer Rows – Drilling From Bottom of
BGA and Other Components ......................... 12
7.3.3 Insulation .......................................................... 29
Figure 3-10 Curing Profile .................................................. 15
7.3.4 Wire Length ...................................................... 30 Figure 3-11 Role of Liquidus Time Delay (LTD) in
7.4 Thermocouple Junction .................................... 30 Head on Pillow ............................................... 15
7.5 Calibration and Test ......................................... 30 Figure 3-12 TAL vs. True TAL ............................................ 15
7.6 Thermocouple Attachment ............................... 30 Figure 4-1 VPS Profile Showing Wicking and Opens ..... 18

7.6.1 High-Temperature Solder ................................. 30 Figure 4-2 Profile for VPS With Preheat Resembles
Convection Profile (Time in Minutes) ............. 18
7.6.2 Adhesives .......................................................... 30
Figure 5-1 Dual-Wave Solder Profile ............................... 20
7.6.3 Aluminum/Copper Tape ................................... 30 Figure 5-2 Peak Topside Preheat Temperature ............... 21
7.6.4 Embedded Thermocouple ................................. 31 Figure 5-3 Mass Wave Soldering Thermal Profile
7.6.5 Thermally Conductive Adhesive ...................... 31 Illustration for a Single-Wave Solder Pot ....... 21
7.6.6 Mechanical Attachment .................................... 31 Figure 5-4 Mass Wave Soldering Thermal Profile
Illustration for a Dual-Wave Solder Pot .......... 21
8 TROUBLESHOOTING ............................................ 31 Figure 6-1 Selective Soldering Thermal Profile
8.1 Solder Reflow Defects ...................................... 31 Illustration for Selective Soldering .................. 24
Figure 6-2 Thermocouple Attachment for Wave and
8.1.1 Voids ................................................................. 31
Selective Soldering ......................................... 24
8.1.2 Head on Pillow (HoP) ...................................... 32 Figure 7-1 Typical Thermal Profiler, Thermocouples,
8.1.3 Bridging ............................................................ 32 Thermal Barrier and Carrier ........................... 26
8.1.4 Solder Balls ...................................................... 33 Figure 7-2 Thermocouple Attachment
(Solder Method) .............................................. 30
8.1.5 Cold Solder/Incomplete Solder ........................ 33
Figure 7-3 Thermocouple Attachment
8.1.6 Solder Beading (Squeeze Balls) ...................... 34 (Adhesive Method) ......................................... 30
8.1.7 Grainy Solder .................................................... 34 Figure 7-4 Thermocouple Attachment (Tape Method) ..... 30
8.1.8 Tombstoning ..................................................... 34 Figure 8-1 Reflow Defects – Voids .................................. 31
8.1.9 Solder Wicking ................................................. 35 Figure 8-2 Reflow Defects – Head on Pillow ................... 32
8.1.10 Blow Holes/Pin Holes ...................................... 35 Figure 8-3 Reflow Defects – Bridging .............................. 32
Figure 8-4 Reflow Defects – Solder Balls ........................ 33
8.1.11 Additional Root Causes of Defects ................. 36
Figure 8-5 Reflow Defects – Cold Solder/
8.2 Solder Joint Accept/Reject Criteria .................. 36 Incomplete Solder ........................................... 33
8.3 Control of Wave Soldering Defects ................. 36 Figure 8-6 Reflow Defects – Solder Beading .................. 34
Figure 8-7 Reflow Defects – Grainy Solder ..................... 34
Figures Figure 8-8 Reflow Defects – Tombstoning ....................... 34
Figure 1-1 Phase Diagram for SnPb Solder ...................... 2 Figure 8-9 Reflow Defects – Solder Wicking ................... 35
Figure 1-2 Pasty Range of SAC Solder ............................. 3 Figure 8-10 Reflow Defects – Blow Holes/Pin Holes ........ 35

Figure 3-1 Thermal Profile Schematic ............................... 7

Figure 3-2 SnPb Profile With Multiple Thermocouples ...... 8 Tables
Figure 3-3 SAC 305 Profile for a Single-Sided
Table 3-1 Profile Comparison Between SnPb,
PWBA (Belt Speed for Single-Sided
SAC 305 and Mixed Alloys ................................. 6
PWBA 24 Inches per Minute) ........................... 8
Table 3-2 Profile Comparison Between SAC Alloy,
Figure 3-4 Example of a SAC 305 Profile for a SnBi (Low-Temperature) Alloys and
Double-Sided Board (Speed 21 Inches Resin-Containing SnBi Solder Pastes ................ 7
per Minute) ....................................................... 9
Table 5-1 Mass Wave Soldering Parameter Summary ..... 22
Figure 3-5 Example of Ramp to Peak (RP) Profile (Left)
Ramp to Soak to Peak (RSP) Profile (Right) ... 9 Table 6-1 Selective Soldering Parameter Summary ......... 24
Figure 3-6 Locations of Thermocouples on a Board with Table 8-1 Additional Root Causes of Defects in
Large and Small Components ........................ 10 Solder Joints ..................................................... 36

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March 2017 IPC-7530A

Guidelines for Temperature Profiling for

Mass Soldering Processes (Reflow and Wave)

1 SCOPE
This standard describes thermal profile guidelines and practical guidelines to meet requirements to produce acceptable sol-
der joints in mass soldering processes, including but not limited to reflow and wave soldering.
Thermal profile is a unique temperature vs. time plot for each fully populated printed wiring board assembly (PWBA), using
thermocouples attached with high-temperature solder or copper or aluminum tapes to selected representative components of
the PWBA as it travels at a given belt speed (i.e., transport speed) through various temperature zones of an oven or solder-
ing system.

1.1 Purpose The purpose of this standard is to provide useful and practical information for developing thermal profiles to
produce acceptable SnPb and Pb-free electronics assemblies. This standard is for managers, design and process engineers
and technicians who deal with mass soldering processes.

1.2 Background During mass soldering, it is important that all solder joints reach the minimum soldering temperature.
Minimum soldering temperature is the minimum temperature necessary to ensure metallurgical bonding of the solder alloy
and the base metals to be soldered. Metallurgical bonding requires that the surfaces to be soldered and the solder reach this
minimum soldering temperature for a sufficient time to allow wetting of the solder surfaces and the formation of a layer(s)
of intermetallic compound(s) of some of the base metal(s) with one or more constituents of the solder alloy.
As a practical matter, minimum soldering temperature is somewhat (~ 25 °C) above the liquidus temperature of the solder
alloy. The solder joint on a given PWBA that is the last to reach minimum soldering temperature (typically on or underneath
one of the components with the highest thermal mass) determines the temperature profile setting for a given PWBA and sol-
dering process/machine. Developing a good profile is a balancing act for the process engineer, who also needs to make sure
smaller and temperature-sensitive components do not overheat or become damaged.
Reflow soldering requires controlled rates of heating and subsequent cooling; however, too rapid a heating rate can damage
PWBAs and components. High cooling rates can also damage components and result in temperature gradients of sufficient
magnitude to warp PWBAs and larger components and also fracture solder joints. Because of this, appropriate temperature
profiling is essential for ensuring high-quality solder joints.
Even though different products, based on their thermal mass, require different amounts of thermal input, all products must
achieve the minimum temperature (temperature above liquidus) without exceeding the maximum temperature (without dam-
age to any components) within a defined time period (thermal profile). This is the key reason for developing a unique profile
for each product.
Thermal input is determined by temperature/gas flow settings in each zone, the number of zones and the belt speed, which
stays the same in each zone. Establishing minimum temperature, maximum temperature and duration in a zone ensures for-
mation of intermetallic bonding between the component leads and their corresponding footprint or land patterns on those
pads. All components, even though their thermal masses are different, must meet the same minimum and maximum tem-
perature requirements. This is the biggest challenge for developing a profile, so developing a thermal profile for a PWBA
with very large thermal mass components (e.g., a large ball grid array (BGA)) and small thermal mass components (e.g.,
0201 or smaller chip resistors and capacitors) is a balancing act. In addition, different heating and cooling rates will have
various effects on a variety of defects, adding more complexity to the balancing act. For example, a slower heating rate will
help reduce voids in a BGA, but it will increase the potential for head on pillow (HoP) in the same BGA.

1.3 Terms and Definitions Other than those terms listed below, the definitions of terms used in this standard are in accor-
dance with IPC-T-50.

1.3.1 Thermal Profile A unique temperature vs. time plot for each fully populated PWBA, using thermocouples attached
with high-temperature solder or copper or aluminum tapes to selected representative components of the PWB as it travels
at a given belt speed through various temperature zones of an oven or soldering system. Each product requires unique oven
settings and belt speed (recipe) to achieve the desired profile on the PWBA.

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IPC-7530A March 2017

Thermal profile may also be known as reflow profile, wave profile, selective profile, laser profile or other soldering profiles.

1.3.2 Recipe A combination of oven settings and conveyor speed based on the thermal profile of a product. Sometimes
also known as reflow program.

1.3.3 Pasty Range The semiliquid state between liquidus and solidus, as solder begins to solidify but is not yet completely
solid and also when solder begins to melt but is not yet completely molten.
Figure 1-1 shows eutectic temperature, superheat and pasty range. Eutectic temperature is the lowest melting point possible
for the alloy and is lower than the melting point of any of the metals in the alloy. Even though eutectic is an alloy, it behaves
like a metal because it has only one melting point, just like a metal. The range can be very small or very large depending
on the composition of the alloy. As seen in Figure 1-1, either to the left or right of eutectic temperature, the pasty range is
very small, but it grows as the composition changes in either direction with changes in Sn or Pb content.

400
327 ºC (621 ºF)
700 G
A H
350

600
300
260 ºC (500 ºF)
500
250
231 ºC (448 ºF)
210 ºC – 240 ºC (410 ºF – 464 ºF)
K 400 200
α β
183 ºC (361 ºF)
J
300 150

C
100
200
B
50
100

10 20 30 40 50 60 70 80 90
D F
E IPC-7530a-1-1

Figure 1-1 Phase Diagram for SnPb Solder

A– Liquid solder F – Tin
B– Solid solder G – Reflow soldering temperatures
C– Eutectic composition SN63Pb37 H – Wave soldering temperatures
D– Lead J – Temperature °C
E– Composition weight % tin K – Temperature °F

Figure 1-2 shows a SnAgCu (SAC) phase diagram. Since SAC alloy has an affinity for copper, this changes the total copper
percentages in the diagram. The diagram addresses copper content from 0 % to 3 % by weight on the X-axis and silver con-
tent from 0 % to 8 % on the Y-axis. Due to the dissolution rate of copper in this alloy composition, the analysis has to be
constantly monitored to verify good process controls. Typical SAC alloys are within the zone of < 1 % copper and 3.5 %
to 4 % silver. However, SAC 305 with silver content of 3.5 % is the most commonly used alloy. It is rare to use 4 % silver
due to higher cost and potential reliability concerns. Some mobile applications use 1 % silver to achieve better mechanical
shock and vibration reliability.

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March 2017 IPC-7530A

8
290
280 270
7
260
Ag 3Sn
6
250 C
5 240

5
6 n
A 4

Cu S
21
22 8
3 0
22
2
22
2 4
22 (Sn)
6
1 22
8

280
23

290

300

310
0
0
0 0.4 0.8 1.2 1.6 2.0 2.4 2.8

D B IPC-7530a-1-2

Figure 1-2 Pasty Range of SAC Solder

A– wt % Ag
B– wt % Cu
C– Composition region industry is using - Silver 3.5 % to 4 %, Copper 0.5 % to 0.7 %, remainder tin
D– Sn

1.3.4 Ramp Rate The net change in temperature divided by total time in that zone.
During soldering, the ramp rate is different in different zones (e.g., preheat zone, soak zone, reflow zone and cooling zone).
Ramp rate is very high in the preheat zone and is very low in the soak zone.

1.3.5 Soak (Dwell) The time/temperature an assembly is held at a very low ramp rate in the reflow soldering process to
allow all components to reach a desired stable temperature. In a reflow operation, the soak (dwell) also ensures the solder
paste is fully dried before reaching reflow temperatures, and it acts as a flux activation zone for solder pastes.

1.3.6 Peak The maximum allowable temperature of the entire process. A portion of the reflow process where the tempera-
ture is raised sufficiently to cause the solder paste to reflow.

1.3.7 Melting Point The temperature at which a solder alloy starts to become liquid.

1.3.8 Liquidus The lowest temperature at which an alloy is completely liquid.

1.3.9 Solidus The highest temperature at which an alloy is completely solid.

1.3.10 Eutectic The temperature at which solidus and liquidus are the same. There is not a plastic range (material is mal-
leable but not liquidus or solidus).

1.3.11 Time Above Liquidus (TAL) The time above liquidus (TAL) for solder, expressed at different liquidus temperatures.
The higher the temperature, the shorter the TAL. When a specific temperature is not mentioned, TAL is assumed to be the
time above melting point for solder.

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In cases of eutectic alloys, TAL and time above melting point are the same. In cases of noneutectic alloys, TAL is less than
time above melting point.

1.3.12 True TAL The solder joint on a PWBA that is above melting point for the shortest amount of time, or also known
as the duration of time where all solder joints are above liquidus of solder.
True TAL is less than TAL of component(s) that are smaller in thermal mass. In the case of BGAs, True TAL is less than
TAL of BGA balls on the periphery, which are in molten condition longer than BGA balls in the center of the package.

1.3.13 Delta T (Profile or Equipment) The largest temperature difference between two or more measurement points at a
given point in time.

1.3.14 Phase Diagram An equilibrium diagram depicting thermodynamically distinct phases, with each phase possessing
its own distinct physical, mechanical and electrical properties. In a metallurgical system (e.g., alloy), a phase diagram rep-
resents the relationship between temperature and composition.

1.3.15 Superheat The temperature difference between the peak reflow temperature and the liquidus of the alloy. Super-
heat is generally near 25 °C in SAC Pb-free and near 30 °C to 40 °C in SnPb or low-temperature Pb-free alloys.

1.3.16 Cooldown The amount of time necessary for a PWBA to return to ambient temperature after a soldering operation.

1.3.17 Preheat The section of the soldering equipment which establishes the ramp rate for an assembly before soak. It is
a profile zone where the assembly is heated from room temperature to the beginning of the soak zone temperature and is
characterized by the ramp slope measurement.

1.3.18 Class 1 Radiant IR-Dominant Systems Heating a PWBA predominantly by infrared (IR) radiation with little or no
convection.

1.3.19 Class 2 Convection/IR Systems Heating a PWBA by a combination of IR radiation and convection in varying
ratios.

1.3.20 Class 3 Convection-Dominant Systems Heating a PWBA predominantly by convection with little or no IR.

1.3.21 Profile Zones The profile is divided into distinct time periods which represent portions of the thermal process.
Each zone is characterized by one or more measurements extracted from each zone (e.g., temperature, slope or time value).

1.3.22 Reflow Program See Recipe (1.3.2).

1.3.23 Liquidus Time Delay (LTD) The time difference between inner and outer balls becoming liquidus.

2 APPLICABLE DOCUMENTS

2.1 IPC1

IPC-T-50 Terms and Definitions for Interconnecting and Packaging Electronic Circuits

IPC-A-610 Acceptability of Electronic Assemblies

IPC-CA-821 General Requirements for Thermally Conductive Adhesives

IPC-2222 Sectional Design Standard for Rigid Organic Printed Boards

IPC-7095 Design and Assembly Process Implementation for BGAs

IPC-7801 Reflow Oven Process Control Standard

1. www.ipc.org

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2.2 Joint Industry Standards2

J-STD-001 Requirements for Soldered Electrical and Electronic Assemblies

J-STD-006 Requirements for Electronic Grade Solder Alloys and Fluxed and Non-Fluxed Solid Solders for Electronic Sol-
dering Applications

J-STD-020 Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices

J-STD-075 Classification of Non-IC Electronic Components for Assembly Processes

2.3 JEDEC3

JEP 140 Beaded Thermocouple Temperature Measurement of Semiconductor Packages

3 CONVECTION REFLOW PROFILING

3.1 Thermal Profiles A solder profile, also known as a thermal profile, is a key variable in the manufacturing process that
significantly impacts product yield, quality and reliability. Conveyor speed and zone temperature are two variables in sol-
der profile development. Solder profile is not only product specific; it is also flux and solder alloy dependent. Different pastes
require different profiles for optimum performance, so it is important to consult the paste manufacturer before developing
the solder profile.
To develop the profile, a loaded PWBA is needed for which the profile is being developed. Begin with a given belt speed
and then monitor the top-side PWBA temperature using thermocouples. Most new reflow ovens have built-in thermocouples
and software packages to record the thermal profile. Also, commercial hardware and software packages make thermal pro-
file development an easy task.
Use of such profilers has been important in SnPb and Pb-free assemblies. It is critical that such profilers be used on each
product to achieve good yield without exceeding the temperature constraints imposed by different types of components.
Table 3-1 provides key thermal profiles for SnPb, Pb-free and mixed-alloy assemblies (backward and forward compatibil-
ity profiles). Note that profiles for Pb-free and forward compatibility are the same. Table 3-2 provides profiles for SAC and
low-temperature Pb-free alloys containing bismuth. Profiles for other alloys can be found in J-STD-006.
With SnPb, there has been general industry consensus about the composition of solder to be used: eutectic Sn63Pb37 with
a melting point of 183 °C. With this composition, there is a big difference between melting point (183 °C) and peak tem-
perature (210 °C to 220 °C). This difference, also known as superheat, varies from 30 °C to 40 °C, so it provides a very
wide window (30 °C to 40 °C), and thermal profile development is much easier.
In Pb-free assembly, the commonly used SAC (SnAgCu) solders contain 3 % to 4 % silver, 0.5 % to 0.7 % copper and the
remainder tin. These alloys have a melting point near 220 °C. A few components, such as some aluminum electrolytic
capacitors, put restrictions on the maximum temperature and duration above 230 °C to which they can be subjected. Addi-
tional constraints will be dictated by low-cost laminates, plastic connectors and moisture-sensitive components.
To accommodate such constraints, the peak temperature in Pb-free assemblies should be maintained between 230 °C and
245 °C, a variation of only 15 °C, which is a tight process window. This is nearly a 60 % drop from the 35 °C variation
with SnPb assemblies mentioned earlier. The difficulty in achieving a thermal profile to meet the defined process window
is further increased if large components with high thermal mass are used on the same board with smaller, temperature-
sensitive components. The reasons are simple. Large components with high thermal mass require a larger heat input to meet
the process window requirements for peak temperature and TAL. However, this large heat input may result in smaller,
temperature-sensitive components falling outside the process window requirements. To resolve this issue, very tight process
control and narrow temperature bandwidth across the PWBA are necessary.
The problem can be further compounded by backward-compatibility issues in which some Pb-free components are used on
a primarily SnPb PWBA. In such cases, the profile must accommodate both SnPb and Pb-free package requirements.

2. www.ipc.org
3. www.jedec.org

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Table 3-1 Profile Comparison Between SnPb, SAC 305 and Mixed Alloys
Pb-Free Alloy (SAC
Mixed/Backward 305)/Forward Mixed SAC Alloy (SAC
Profile Topic SnPb Alloy Profile Compatibility Profile Compatibility Profile 305/SAC 105) Profile
Alloy solidus 183 °C 183 °C 217 °C to 220 °C 217 °C to 227 °C1
temperature
Target alloy peak 210 °C to 220 °C 228 °C to 232 °C2 235 °C to 245 °C 240 °C to 245 °C
temp range
Absolute minimum peak 205 °C 228 °C2 230 °C 235 °C
reflow temperature3
Component ramp-up 2 °C to 4 °C 2 °C to 4 °C 2 °C to 4 °C 2 °C to 4 °C
rate per second4 per second4 per second4 per second4
Component ramp-down 2 °C to 6 °C 2 °C to 6 °C 2 °C to 6 °C 2 °C to 6 °C
rate per second4 per second4 per second4 per second4
Soak or preheat 100 °C to 150 °C4 100 °C to 150 °C4 150 °C to 200 °C4 150 °C to 200 °C4
activation temperature
Soak or preheat 60 to 120 seconds4 60 to 120 seconds4 60 to 150 seconds4 60 to 150 seconds4
activation time
Dwell time above 60 to 90 seconds 60 to 90 seconds 60 to 90 seconds 60 to 90 seconds
liquidus
Dwell time at peak 20 seconds max 20 seconds min 20 seconds max 20 seconds min
temperature
Solder paste used SnPb SnPb Pb-free (SAC 305) Pb-free (SAC 305)
SMT component types All SMT type SnPb and All SMT type SnPb All components, All components,
Pb-free, but not Pb-free and Pb-free, including including BGAs, including BGAs, are
BGA balls SAC Pb-free BGA balls are Pb-free, including Pb-free, but BGAs
BGAs with SAC 305 with SAC 105 Pb-free
Pb-free BGA balls BGA balls, not SAC
305 BGA Balls
Reason for peak Pb-free surface finishes A compromise All components are All components are
temperatures on BGA parts have temperature is Pb-free and can take Pb-free and can take
no problem melting needed so SnPb higher heat higher heat
at 205 °C parts do not overheat Too high a peak Pb-free SAC BGAs
All SnPb surface Pb-free SAC BGAs temperature may with melting point
finishes have 90 % tin; with melting point of cause BGA ball drops, of 227 °C can melt,
Pb-free finishes have 217 °C to 220 °C can opens, dewetting and collapse and fully mix
nearly 100 % tin with melt, collapse and fully PWBA warpage with SAC 305 paste
some other Pb-free mix with SnPb paste Large BGAs are Lower peak
elements like bismuth Lower peak tested for maximum temperatures will
temperatures will of 245 °C for MSL- cause SAC 105
cause SAC BGA level rating BGA balls to partially
balls to not melt melt, increasing the
or to partially melt, incidence of HoP,
increasing the opens and poor
incidence of HoP, reliability
opens and poor Too high a peak
reliability temperature may
cause BGA ball
drops, opens,
dewetting and
PWBA warpage
Large BGAs are
tested for maximum
of 245 °C for MSL-
level rating
Note 1. When using SAC 105 BGA balls with melting point of 227 °C with SAC 305 solder paste with melting point of 217 °C to 220 °C.
Note 2. See IPC-7095 for details regarding mixed-alloy/backward compatibility soldering.
Note 3. Coolest temperature on the PWBA.
Note 4. Verify with component and/or solder paste supplier.

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Table 3-2 Profile Comparison Between SAC Alloy, SnBi

(Low-Temperature) Alloys and Resin-Containing SnBi Solder Pastes
Resin-Containing SnBi
SAC 305 Solder SnBi Low-Temperature Low-Temperature
Profile Topic PasteProfile Solder Paste Profile Solder Paste Profile
Alloy solidus temperature 217 °C to 220 °C 139 °C to 140 °C 139 °C to 140 °C
Target alloy peak 235 °C to 245 °C 160 °C to 200 °C 160 °C to 180 °C
temperature range
Absolute minimum peak 230 °C 160 °C 160 °C
reflow temperature1
Component ramp-up rate 2 °C to 4 °C per second2 1 °C to 3 °C per second2 2 °C to 4 °C per second2
Component ramp-down rate 2 °C to 6 °C per second2 2 °C to 6 °C per second2 2 °C to 6 °C per second2
2 2
Soak or preheat activation 150 °C to 200 °C 100 °C to 120 °C None (to avoid premature curing of
temperature resin)
Soak or preheat activation 60 to 120 seconds2 30 to 90 seconds2 None (to avoid premature curing of
time resin)
Dwell time above liquidus 60 to 90 seconds 30 to 90 seconds2 60 to 210 seconds2
2
Dwell time at peak 20 seconds max 20 seconds max Varies3
temperature
Post-reflow resin-cure N/A N/A 125 °C to 130 °C3
temperature
Post-reflow resin-cure time N/A N/A 130 to 240 seconds3
Solder paste used Pb-free (SAC 305) paste SnBi (eutectic or noneutectic) low- SnBi (eutectic or non-eutectic)
temperature paste without resin low-temperature paste with resin
SMT component types All components, All components, including BGAs, All components, including BGAs,
including BGAs, are are Pb-free, including BGAs with are Pb-free, including BGAs with
Pb-free, including BGAs SAC 305 Pb-free BGA balls SAC alloy Pb-free BGA balls
with SAC 305 Pb-free Do not use BGAs with SnPb Do not use BGAs with SnPb
BGA balls solder balls solder balls
Note 1. The coolest component on PWBA.
Note 2. Verify with component and/or solder paste supplier.
Note 3. Some resin-containing solder pastes require extended time after the reflow phase in the thermal profile to cure the resin; others use TAL phase in the
thermal profile to cure the resin.

Figure 3-1 shows a profile schematic. Figure 3-2 shows a

real-world example for a SnPb profile. Figure 3-3 shows an
example of a SAC 305 profile for a single-sided PWBA mov-
ing at 24 inches per minute. Figure 3-4 shows a profile for the
same PWBA in Figure 3-3, but it is double-sided. Note almost F
the same oven temperature but a slower belt speed of 21 G
C
inches per minute.
A
E

D
B IPC-7530a-3-1

Figure 3-1 Thermal Profile Schematic

A – Temperature
B – Time
C – Alloy liquidus temperature
D – Preheat slope = temperature ramp rate
E – Preheat dwell = soak time
F – Time above liquidus
G – Peak temperature = maximum assembly temperature

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Figure 3-2 SnPb Profile With Multiple Thermocouples

Figure 3-3 SAC 305 Profile for a Single-Sided PWBA (Belt Speed for Single-Sided PWBA 24 Inches per Minute)

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Figure 3-4 Example of a SAC 305 Profile for a Double-Sided Board (Speed 21 Inches per Minute)

There are two major types of profiles:

• Ramp to soak to peak (RSP) (Figure 3-5, right)
• Ramp to peak (RP) (Figure 3-5, left)
The key difference between them is the absence of the soak zone in the RP profile. Use of a soak zone in an RSP profile
allows more uniform temperature across the PWBA, and it is very useful in achieving uniform temperature in a PWBA with
a large variation in thermal masses of different components. RSP profiles also make it easier to achieve lower voids in sol-
der joints, especially in BGAs. RP profiles may increase the incidence of voids in solder joints, but they minimize the inci-
dence of HoP in BGAs, which is a serious defect. The presence of voids, especially below IPC-A-610 limits, is not a serious
concern for product reliability.

300 300

250 250

200 200

A 150 A 150

100 100

50 50

0 0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

B B IPC-7530a-3-5

Figure 3-5 Example of Ramp to Peak (RP) Profile (Left) Ramp to Soak to Peak (RSP) Profile (Right)
A – Temperature
B – Time

There are four major zones in a thermal profile, which are discussed in 3.1.2 through 3.1.5.

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3.1.1 Thermocouple Attachment Figure 3-6 shows recom-

mended locations of thermocouples on a PWBA. It is impor-
tant that thermocouples be attached to small and large compo-
nents at the solder joints. For BGAs, it is important to attach
a thermocouple to the top of the package.
In developing any profile, it is very important to use the cor-
rect thermocouple. Type K thermocouples with wire gauge of
36 American wire gauge (AWG) should be used. Thicker ther-
mocouple wires can act as a heatsink and affect temperature
readings. For good accuracy, thermocouple wire length should Figure 3-6 Locations of Thermocouples on a Board with
not exceed 91 cm [35.8 in]. To ensure accuracy, thermocouple Large and Small Components
junctions must be welded. Twisting, crimping or soldering
should not be used.
Care should be exercised when using high-temperature tapes such as polyimide or aluminum. Tapes tend to come loose dur-
ing reflow, and the system will then measure the temperature of the air in the oven and not the temperature of the solder
joints. It is important to ensure good contact of the tape; alternately, a high-temperature solder or thermally conductive
adhesive can be used to attach thermocouples to the solder joints. One benefit of tape is that thermocouples can be reused
repeatedly without being damaged.
Peak temperature readings should be extracted from thermo-
couples placed at or near the center of the package for an
assembly that is in a live-bug orientation. In some cases, drill-
ing a hole into a package may be necessary for advanced con-
structions (2D/3D assemblies or assemblies with an integrated
heat spreader or heatsink). For a dead-bug orientation, verifi-
cation of peak temperature within ± 2 °C of the live-bug ref-
erence is recommended. Refer to JEP 140 for thermocouple
use. Four to six thermocouples should be attached at various IPC-7530a-3-7

component locations to represent the lowest to highest thermal Figure 3-7 Recommended Locations of Thermocouples
mass areas, including at least two thermocouples for BGAs. on a BGA
Figure 3-7 shows thermocouples locations on a BGA.
Use of high-temperature solder or thermally conductive adhesive to attach thermocouples to solder joints is a very good
approach. If high-temperature soldering is not an option because of material availability or soldering difficulties, aluminum
or copper tape work well.
In cases of BGAs, as shown in Figure 3-8 and Figure 3-9, drill holes in the inner and outer rows of the BGA pads from the
bottom of the board and push the thermocouples almost to the top surface to correctly measure BGA ball temperatures. BGA
ball temperatures of inner and outer rows should be within 2 °C.
Proper thermocouple attachment is critical to ensuring accurate temperature measurement. There are various methods for
attaching thermocouples to assemblies for profiling.

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IPC-7530a-3-8

Figure 3-8 First Example of Thermocouple on Inner and Outer Rows – Drilling From Bottom of BGA and Other
Components

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IPC-7530a-3-8

Figure 3-9 Second Example of Thermocouple on Inner and Outer Rows – Drilling From Bottom of BGA and Other
Components

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3.1.2 Preheat Zone The temperature in the preheat zone can range from 30 °C to 175 °C. Many component suppliers
generally recommend a 2 °C to 4 °C per second ramp rate to avoid thermal shock to sensitive components. Such guidelines
are considered conservative since some capacitors are wave soldered and go from a preheat temperature of nearly 120 °C
to a wave pot temperature of 260 °C. A high ramp rate increases the potential for solder balls, so it should be kept as low
as feasible, with consideration given to the acceptable ramp rate of the most sensitive component on the assembly.

3.1.3 Soak Zone The soak zone is intended to raise the temperature of the entire PWBA to a uniform temperature. The
ramp rate in this zone (100 °C to 180 °C for SnPb and 140 °C to 220 °C for SAC Pb-free) is much slower. The soak zone
also acts as the flux activation zone for solder paste. The consequences of having too high a temperature in the soak zone
can include:
• Solder balls
• Solder splatter due to excessive oxidation of paste
• Spent flux activation capability
The purpose of a long soak zone is to minimize voids, especially in BGAs. It is also common practice to not use a soak
zone but to steadily ramp the temperature from preheat zone to peak reflow. However, the likelihood of voids may increase
when ramping steadily to peak reflow temperature.

3.1.4 Reflow Zone The peak temperature in the reflow zone should be high enough to obtain good wetting and to create
a strong metallurgical bond. It should not be so high as to cause component or PWBA damage or discoloration or, in the
worst case, delamination or charring of the PWBA.
A temperature that is too low may result in cold and grainy solder joints, nonmelted solder or poor intermetallic bonding.
As shown in Table 3-1, the peak temperature in this zone should be maintained between 210 °C to 220 °C for SnPb and
230 °C to 245 °C for Pb-free solder alloy. Time above liquidus (TAL) should be 60 to 90 seconds but closer to 60 seconds.
Extended duration above the solder melting point, or TAL, will damage temperature-sensitive components. It also will result
in excessive intermetallic growth, which makes the solder joint brittle and reduces solder joint fatigue resistance.

3.1.5 Cooling Zone The typical cooling rate for most assemblies has been 4 °C to 6 °C per second. This is driven primar-
ily by throughput and SnPb intermetallic thickness concerns. With the transition to Pb-free solders, pad cratering defects
have become more common due to the increased stiffness of SAC solders and the reduction in the flexure resistance and
fracture toughness of laminates. Pad cratering has been identified directly following the reflow process, which has resulted
in several experiments designed to understand the effects of cooling rate. Among other defects such as package warpage,
pad cratering is one of the reasons why many companies use lower-temperature Pb-free solders containing bismuth (see
Table 3-1).
During the cooling phase, various materials will cool at different rates. The BGA package typically will cool faster than the
solder joint and much faster than the PWB. This differential cooling can create mechanical strain on the weakest spot in the
interconnection, which is the laminate below the BGA pad. By significantly slowing the cooling rate, to as low as 1.5 °C
per second, all of the materials will cool more slowly and reduce the strain placed on the laminate.
Experimental work performed by consortia has shown that slowing the cooling rate does not appear to negatively impact
solder joint intermetallics or the grain structure of the joint. If pad cratering is found immediately following reflow or if the
assembly is determined to be at risk for cratering, the cooling rate of the PWBA should be slowed to reduce strain.

3.1.6 Thermal Profile for Backward Compatibility Developing a thermal profile is difficult when dealing with backward
compatibility issues, in which Pb-free components are used on a SnPb PWBA. Such a scenario arises in cases in which it
may not be economical for a component supplier to manufacture SnPb and Pb-free versions of the same component. Most
SnPb components have 85 % tin surface finish with about 15 % Pb.
This is not an issue when using leaded components such as small outline integrated circuits (SOICs), plastic-leaded chip
carriers (PLCCs) or fine-pitch components with Pb-free surface finishes. Problems occur when using Pb-free BGAs on a
primarily SnPb PWBA. If the SnPb profile with a maximum peak temperature of 220 °C is used, the Pb-free BGA balls will
not reflow at all or will only partially reflow, creating a serious solder joint reliability problem.
If SnPb components are soldered along with Pb-free BGAs in the same oven (since SnPb versions are not available), a peak
temperature must be used that will not damage all the SnPb components but will be sufficient to reflow the Pb-free BGAs.
Using SnPb solder paste is appropriate, since most of the components on the PWBA are SnPb. As shown in Table 3-1, a

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peak temperature of 210 °C to 220 °C is adequate for SnPb but inadequate for Pb-free BGA balls with a melting point of
217 °C to 221 °C. A peak temperature of 228 °C to 232 °C with 60 to 90 seconds TAL will be sufficient to reflow Pb-free
BGAs without seriously damaging all the SnPb components on the same board.
If it is difficult to achieve a tight reflow temperature band of 228 °C to 232 °C for soldering SnPb and Pb-free BGAs in
backward compatibility scenarios, consider selective laser soldering the Pb-free BGAs after SnPb components have been
soldered in a convection reflow oven, or find an alternative source for BGAs with SnPb balls.

3.1.7 Unique Profile for Each PWBA Each unique PWBA needs to be profiled to show that all locations on the PWBA
meet the various requirements for creating acceptable solder joints. A single program will produce very different profiles for
different, unique PWBAs. There is some misunderstanding that one oven profile will work for all PWBAs, so there is no
need to develop unique profiles for each PWBA. This is not true, because each PWBA has a unique thermal mass or dif-
ferent loading patterns (distance between PWBAs as they are loaded in the oven). A double-sided PWBA, depending on
component placement and distribution of copper planes, will require a separate profile for each side. Profiles may look the
same for many PWBAs but will generally require different machine programs to create similar profiles. It is common to
have a small number of standard machine programs, but the specific program must be proven to produce an acceptable pro-
file. For additional details on mixed-alloy BGA soldering (backward and forward compatibility), see IPC-7095.
Once the program has been optimized to create the desired profile, it is recommended to create an actual production PWBA
with solder paste and components for reflow. Following reflow, inspect the quality of the solder joints to verify that the sol-
der joints across all of the various components meet the requirements of IPC-A-610 and any customer-specific requirements.
A random problem only in a specific section of the PWBA may be related to solderability. A consistent problem in a given
section may be related to the solder profile due to nonuniform heating (wide bandwidth), paste quality and land pattern
design.
Once the program is found to give the desired results (assuming design and other material variables have been optimized),
document the program. After doing this, no changes should be allowed in the program and the resulting profile.

3.1.8 Flux Flux has two key functions:

• It must remove contamination and oxides from the PWBA and component surfaces and create a suitable nonoxidized metal
surface.
• It must protect the metal surface from reoxidation during heating.
A common mistake that occurs is using a thermal profile that consumes the flux before the solder melts. Ideally, the flux
would be activated just as the solder begins to melt. The activation time should range from 90 to 120 seconds, and flux usu-
ally becomes active at near 130 °C for SnPb solder pastes. Typically, solder paste activation for Pb-free solder will be higher
(in the 150 °C range); however, it is recommended to review the solder paste supplier’s data sheet. It is important to select
a flux and solder alloy that work well with the lead finish.

3.2 Material Issues Components can be damaged by the incorrect application of heat. All components have a heat
exposure limit. Most SnPb SMT components should tolerate a peak temperature of 220 °C for up to 60 seconds. Pb-free
BGAs should be rated to a higher temperature (approximately 240 °C to 260 °C), but the user should verify the rating of
the BGAs. Thermal shock, caused by the rapid application of heat, can crack certain components. However, since the peak
temperature of reflow ovens varies, the intent is to heat the solder in a controlled, established profile to a solder joint tem-
perature of 210 °C to 220 °C for SnPb products and 235 °C to 245 °C for Pb-free products.
Refer to J-STD-020 and J-STD-075 for further information on reflow sensitivity of moisture-sensitive devices.
The component lead finish will affect solderability. There are a number of finishes used, including SnPb, gold, tin and pal-
ladium, so it is important to select a flux and solder alloy that work well with the component lead finish.

3.3 Reflow Soldering When profiling assemblies for solder reflow and adhesive cure, the following should be monitored
(as shown in Figure 3-1 for solder paste):
• Ramp: This is the part of the profile where the PWBA is heated from ambient temperature at a predetermined rate. Con-
trolling ramp is necessary for preventing component damage. It also allows flux solvents to evaporate prior to the flux
being fully active.
• Soak Time: This is monitored to ensure temperature equilibrium across the PWBA. This part of the profile also allows
time to drive off volatile ingredients within the solder paste and to activate the paste’s flux to remove oxides.

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Caution – Use of a soak zone in a thermal profile is helpful for reducing voids in BGA solder joints, but it may increase
the incidence of HoP in BGAs. An RP profile should be considered to minimize HoP.
• TAL: This is the time in which the solder alloy is liquidus. The PWBA must spend enough time in this state to ensure all
areas reach soldering temperature. TAL for eutectic solder may be shorter than TAL for noneutectic solder since noneutec-
tic alloys have both solidus and liquidus temperatures, but eutectic solders have the same solidus and liquidus tempera-
tures.
• Peak/Spike Temperature: Peak temperature is the maximum temperature recorded by the thermocouple for the monitored
location. Excessive temperatures could result in component and PWBA damage.
• Cure period: Cure period is monitored to ensure proper curing of the adhesive.

Note: Figure 3-10 shows an example of a curing profile for

adhesive, underfill or other material. D
E
3.3.1 True Time Above Liquidus (True TAL) It is important
to understand the difference between TAL and True TAL to
minimize incidence of HoP in BGAs (see Figure 3-11 and A
Figure 3-12). When attaching thermocouples to the inner and
outer balls of a BGA, it is common for the temperature of the
outer row of BGA balls to be higher than the temperature of
the inner row of balls, resulting in LTD (see Figure 3-11)
between the melting of outer and inner balls. C
Another way to describe True TAL is the time at which the B IPC-7530a-3-10
solder joint of every component, no matter how large, is
above the melting point of solder. True TAL is also the time Figure 3-10 Curing Profile
when all points of measure are above liquidus at the same A– Temperature
time, or the smaller number. This is critical, especially with B– Time
C– Preheat slope = temperature ramp rate
large BGAs, in which outer balls have higher TAL and inner D– Cure period
balls may have lower TAL. E– Peak temperature = maximum assembly temperature

C
235 ºC – 245 ºC
A
220 ºC B
217 ºC D
dT E
B
A

C
F G H J
IPC-7530A-3-12

Figure 3-11 Role of Liquidus Time Delay (LTD) in Head Figure 3-12 TAL vs. True TAL
on Pillow Note: True TAL is less than TAL.
A – Outer BGA ball temperature
Note: True TAL (in green) is less than TAL. LTD is the amount of
B – Inner BGA ball temperature
time some balls were not above liquidus temperature.
A – Outer ball C – 60 to 90 seconds
B – Inner ball D – TAL
E – True TAL
C – LTD
F – Preheat
G – Soak
H – Reflow
J – Cooling

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It is only during this time that the component is free to self-align. Any single location’s TAL does not measure the actual
time the entire component is free to self-align, which demonstrates the need for True TAL measurement.
Making True TAL sufficiently large (60 seconds) helps to avoid HoP. Another way to minimize HoP is to avoid too long a
soak and ensure minimum 235 °C peak for all balls. When dealing with backward compatibility, strive for 232 °C minimum
peak. To minimize HoP, use an RP profile instead of an RSP profile, but understand that an RP profile may result in more
voids in BGAs. It is important to keep in mind voids are not serious defects, but HoP is a serious defect. The peak
temperature range of 228 °C to 232 °C recommended in Table 3-1 for backward compatibility should be ignored in favor
of a 232 °C peak when dealing with HoP issues.
The following are some specific Pb-free reflow guidelines for peak temperature and TAL:
• Peak Temperature: Target range 235 °C to 245 °C, but aim for 240 °C ± 2 °C
• TAL: Time above 220 °C (solder melting temperature) should be 60 to 90 seconds (ideally 70 seconds)
• TAL: Time at 240 °C (target peak temperature) should be five to 15 seconds (ideally 10 seconds)
• True TAL: Target 60 seconds for all BGA balls

Note: It is understood that in areas of large components not all locations of those components will reach liquidus at the
same time. Some will reach liquidus later than others.

3.4 Equipment Settings

3.4.1 Reflow Oven Selection Reflow ovens are available in various sizes and configurations. When selecting the most
appropriate reflow oven for a particular purpose, many variables should be taken into account in terms of types of devices
being assembled and configurations/options.
Such options that should be reviewed in terms of a product application include:
• Size of product
• Desired throughput
• Types of solders
• Types of fluxes
• Cost of assembly
Such options to be considered regarding ovens include:
• IR or convection number of heating zones
• Clearance height
• Cover gas
• Conveyor belt type
• Belt width
• On-board profiling ability
• Product tracking
• Edge-rail or center-support capability
Some of these options are discussed in 3.4.2 through 3.4.7.

3.4.2 IR vs. Convection Reflow ovens are typically IR or convection reflow. In an IR oven, ceramic heaters transfer heat
to the assembly using radiation. In a convection reflow process, fans force heated air to the assembly. Recent advances in
reflow processes and oven configurations have evolved the use of vacuum reflow. Vacuum reflow helps in applications which
require very low levels of solder voiding in the attachment of a device.

3.4.3 Heating Zone Selection The number of heating zones in standard reflow ovens range from seven to 12 or more.
The minimum number of zones for Pb-free applications should be seven.
Top and bottom heaters typically can be set independently when setting up a thermal profile. For reflow ovens in line with
other pieces of equipment, throughput may be another consideration, in terms of oven length and the number of heating
zones needed to balance throughput with an optimal thermal profile.

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3.4.4 Clearance Height, Conveyor Belt Type/Width and Edge-Rail Support Oven clearance height is normally kept to a
minimum to maintain consistent heating within and between zones. The height of the product also needs to be considered
when defining the clearance height required for a particular oven.
The type of product being assembled affects whether or not the conveyor belt is fine-mesh. If a device is fairly small, a fine-
mesh belt may be needed to eliminate the use of added fixturing to transfer the part through the oven. The size of the assem-
bly passing through the oven will also determine the necessary belt width.
If a PWBA is double-sided, edge rails can be added to the oven so additional fixturing may not be required to support the
assembly above the conveyor belt and to allow for better airflow around the PWBA.

3.4.5 Cover Gas Standard reflow ovens can be configured in such a way that the oven is run in an open-atmosphere envi-
ronment or by using a cover gas such as nitrogen during reflow. The need for nitrogen gas depends on the type of flux in
the solder paste for a particular application, the plating on the PWBA and the terminals of the ICs being assembled.
Nitrogen helps to slow oxidation or prevent reoxidation on metal surfaces. It also promotes better wetting during the reflow
process, especially when soldering to NiAu and bare-copper lands. Advances in solder paste have reduced the need for
nitrogen, especially if an aggressive flux is used in the solder paste. This, however, can be a trade-off on whether a clean-
ing process is needed to remove flux residues.
The major drawback of adding a nitrogen package to an oven is not only the initial cost of adding the feature but also the
long-term cost of ownership of having house gas plumbed to the oven.

3.4.6 Profiling In most cases, reflow ovens are configured such that on-board reflow profiling can be accomplished. In this,
one end of a thermocouple is attached to the oven, and the other end is attached to the product traveling through the oven.
This eliminates the need for purchasing an added data recorder for profiling capability.

3.4.7 Product Trackers Ovens can also be configured with product trackers to allow for traceability of parts through a
reflow oven. These trackers have sensors mounted at the entrance and exit of an oven to sense when a product enters and
exits the oven.

4 VAPOR-PHASE REFLOW PROFILING

There are many forces driving the use of vapor-phase soldering (VPS), also known as condensation soldering:
• Fixed peak temperature (215 °C or 230 °C)
– Includes very large and small components with wide variances in thermal mass
– Large and small components achieve almost the same peak temperature
• Temperature-sensitive components
• Pb-free alloys with higher melting points
• Excellent heat transfer capability
• Inert environment
• Vacuum capability (in some machines)
• Preheat as an integral part of the machine
• Possibility for lower intermetallic thickness due to lower peak temperature
• Potential for lower voids if vacuum capability is used
• Better PWBA cleanliness
• Higher surface insulation values
Even with these driving forces, VPS has gone through changes in popularity. It was the process of choice in the early 1980s,
but its use declined considerably for several reasons, including problems with the VPS process itself and improvements in
IR processes. Convection-dominant IR systems have been known to provide efficient heating without the inherent problems
of VPS.
By the late 1980s, VPS almost disappeared due to excessive incidences of wicking on leads of J-wing and gull-wing devices,
which led to solder opens. This wicking was caused by the lead and the land heating at different rates during VPS; it was

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exacerbated by noncoplanarity (the failure of the lead to touch the land). The surface of the lead reached the solder melt-
ing point a few seconds before the surface of the land. This caused the solder paste to melt, wet and wick up the lead before
the land became hot enough for the molten solder to wet it. By the time the land reached the melting point of the solder
paste, there was not enough solder remaining on the land to form a good solder joint. In addition to wicking in leaded parts,
especially J-lead devices, VPS has also been known to cause tombstoning with chip components.
Figure 4-1 demonstrates a VPS profile showing the leads reaching melting point temperature before the pads. This time delay
in reaching melting point for J-lead components caused wicking and opens in solder joints. Newer VPS systems with built-in
preheat have made this wicking less of a concern (see Figure 4-2). Additionally, superheat (temperature between melting
point and peak reflow) is significantly reduced in Pb-free processes to nearly 40 °C in SnPb alloys and nearly 20 °C in SAC
Pb-free alloys.

220

200
C
180

160 D
140

ºC 120
B
100

80

60

40

20
0 20 40 60 80 100 120 140 160 180 200 220

A IPC-7530a-4-1

Figure 4-1 VPS Profile Showing Wicking and Opens

A – Time (seconds) C – Lead temperature
B – Land temperature D – Sixteen-second lag at 183 °C

LP
250

200

150
ºC
100

50

0
00:01,0
00:19,0
00:37,0
00:55,0
01:13,0
01:31,0
01:49,0
02:07,0
02:25,0
02:43,0
03:01,0
03:19,0
03:37,0
03:55,0
04:13,0
04:31,0
04:49,0
05:07,0
05:25,0
05:43,0
06:01,0

IPC-7530a-4-2

Figure 4-2 Profile for VPS With Preheat Resembles Convection Profile (Time in Minutes)

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VPS uses the latent heat of liquid vaporization to provide heat for soldering. This latent heat is released as the vapor of the
inert liquid condenses on component leads and PWB lands. This liquid produces a dense, saturated vapor that displaces air
and moisture. The temperature of the saturated vapor zone is the same as the boiling point of the vapor-phase liquid. This
fluid does not present any environmental concerns.
4.1 Vapor-Phase Reflow Vapor-phase reflow can be operated as a single- or two-fluid system, utilizing primary and sec-
ondary fluids. The process was developed using the two-fluid approach in batch equipment; but modern in-line systems nor-
mally operate with only one fluid. Whichever system is used, the maximum temperature reached by assemblies in vapor-
phase reflow depends on the choice of the primary fluid. Primary vapor-phase fluids are available in temperature ranges that
support SnPb (210 °C to 220 °C) and Pb-free (235 °C to 245 °C) soldering. While all primary fluids can be classed as per-
fluorocarbons, the basic structure (amine, cyclic or ether) will determine the key properties of in-use stability, solder paste
chemicals solubility and overall process economics. The choice of fluid is normally based on the melting point of the sol-
der alloy to be reflowed.
For the range cited, lower temperatures are suitable for typical SnPb or SnPbAg alloys used for standard attachment pro-
cesses. The upper end of the range will permit reflow of high-Pb alloys, which are used to attach pins to PGA packages.
Users faced with reflow of a specialty alloy have been successful in mixing two primary fluids to tailor a vapor-phase sys-
tem for a specific stable boiling point. Higher temperatures will permit shorter times, which may be advantageous with some
solder pastes.
The primary vapor phase should be inert and should not introduce contaminants that must be removed later. Solder paste
chemicals that dissolve in the fluid are carried in the high-boiling vapor and then deposited onto the surface of the board.
Such residues tend to be difficult to remove. Minimizing solder paste residue in the primary fluid will maximize the lifetime
of the fluid, prevent boiling point elevation due to dissolved paste ingredients and simplify cleaning.
The secondary vapor blanket was originally CFC-113, a lower-boiling fluorinated material which formed a low-cost sacri-
ficial cover over the costlier primary fluid. The constant exposure to the high-boiling primary fluid at the interface of the
two fluids would cause the secondary fluid to undergo thermal decomposition at the interface, generating hydrochloric (HCl)
and hydrofluoric (HF) acid vapors. These corrosive vapors often attack the soldering equipment over time. While the vapors
could be absorbed into flux residues and cause problems for high-reliability products, this was rare in comparison to attacks
on equipment. With the phase-out of CFC-113, industry introduced a low-boiling perfluorocarbon to replace it. This second-
generation secondary blanket fluid was more stable than CFC-113 for prolonged exposure to high-boiling vapor-phase fluids.
As SMT technology grew, most users converted to higher-throughput in-line machines which use a single-fluid approach.
Defluxing after vapor-phase reflow should be done with either a polar solvent formulation or include an aqueous cleaning
formulation that can ensure removal of all solder paste residues, with the choice of cleaning process based on the composi-
tion of the solder paste. Secondary factors influencing this decision are compatibility and component-to-PWBA surface
spacing. In addition, most companies gave serious consideration to the potential chemical loss as a result of using this type
of equipment, since many perfluorinated compounds are very long-lived global warming compounds.
5 WAVE SOLDERING PROFILING
By definition, mass wave soldering implies creating many solder connections simultaneously in a semiautomated or auto-
mated process. Equipment designed for this task generally has four basic characteristics:
• Product conveyance
• Fluxing capability
• Preheating capability
• Molten pot of solder with a nozzle
A key feature of the wave soldering machine is the type of wave nozzle used. This will determine the quality of solder for
both through-hole and SMT components. Solder waves commonly used are single-wave, dual-wave, in which the first wave
is turbulent, and oscillating-wave. Another key feature of a solder wave is whether the solder falls back into the solder pot
in one or both directions. In general, the number of defects (e.g., icicles, bridging, etc.) is much lower in waves in which
the solder falls only in one direction-backward.
The differences between manufacturers are in the application of these basic concepts and the equipment controls. Each
machine has unique characteristics that need to be taken into account when developing a thermal profile. Traditional wave
soldering machines are used for mass soldering of through-hole and some SMT components (typically chip resistors and
capacitors). When bottom-side SMT components are soldered, they are secured in place with a cured adhesive prior to
soldering.

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The wave soldering system automatically performs the soldering process:

1. Flux application
2. Heating of the area to be soldered
3. Application of molten solder
4. Solidification
All of these characteristics act together to ensure proper soldering. A solder recipe is developed by recording the optimum
process parameters selected for conveyor speed, flux application, preheaters and solder temperature.
When profiling assemblies for wave soldering, the following areas should be monitored:
• Preheat: Control the rate of temperature increase to ensure the PWBA, components and flux have sufficient time to reach
soldering temperatures without degradation.
• Thermal shock/Peak temperature: Measure thermal shock and peak temperature to ensure components are not exposed to
excessive shock and/or temperature, which can result in damage.
• Dwell time: Measure dwell time to ensure excessive time in the solder does not occur. This could result in damage to com-
ponents.
• Peak topside temperature: Monitor peak topside temperature to ensure solder joints formed by reflow do not revert to a
liquid state.
See Figure 5-1 for an example of a dual-wave soldering profile.

C D
280
270
260
250
240
230
220
210
200
190
180
170
ºC 160
150
140
130
B
120
110
100
90
80
70
60
50
40
15 30 45 60 75 90 105 120 135 150 165 180 195

A
IPC-7530a-5-1

Figure 5-1 Dual-Wave Solder Profile

A– Time (seconds)
B– Too rapid heating rate
C– First wave
D– Second wave

5.1 Machine Considerations Each part of a wave soldering machine has a unique function, but each function must be
considered as a whole system because of the interrelationships and dependencies of the fluxer, preheaters and solder pot.
Correlation of time and temperature should be a particular concern. Molten solder temperature is usually a constant; the
variables are preheater temperatures, conveyor speed and preheat/solder pot dwell times. Dwell time in preheat and over the
solder pot are the prime thermal profile variables.
For a given PWBA, final soldering results are a function of effectiveness of flux application, conveyor speed, preheat tem-
perature and solder pot temperature.
5.2 Conveyor Considerations The conveyor in a wave soldering machine is a transport and control device. Conveyor
speed controls the time and temperature relationships during preheat as well as solder contact and the amount of time the
component leads remain in the solder. The conveyor also controls the distance and angle between the PWBA and the fluxer,
preheaters and solder pot.

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5.3 Preheat Considerations PWBAs are preheated during wave soldering for various reasons including:
• Dry-off of volatile solvents in the flux
• Achieving optimum flux activity level A
• Reducing thermal shock to the PWBA when it passes over
the solder wave
• Reducing the amount of heat required from the solder pot to
raise the temperature of the metals being joined to soldering
temperature B C D
• Permitting the use of a higher conveyor speed to minimize IPC-7530a-5-2
cycle time
Figure 5-2 Peak Topside Preheat Temperature
• Reducing the incidence of icicle and bridging formation Note: Topside PWBA temperature when it exits preheat is
100 °C to 120 °C for SnPb and 110 °C to 130 °C for Pb-free.
During preheat, thermal energy is generated and transferred to
PWB is moving left to right.
the PWBA by several different methods (e.g., IR lamps, IR A – Measure topside preheat temperature here
panels, radiant heaters and forced-hot-air convection heaters). B – Flux application
Whichever method is used, it is important to have consistent C – Preheat (top and bottom)
D – Solder pot
and repeatable temperature control. Peak preheat temperature
is usually measured on the top side of the PWBA as the
PWBA exits the preheat area (see Figure 5-2). For SnPb D E F
soldering, the peak topside preheat temperature is typically
100 °C to 120 °C. For Pb-free soldering, the peak topside pre-
heat temperature is typically 110 °C to 130 °C. C
A
5.4 Solder Pot Considerations The solder pot contains one
or two waves that contact and transfer solder to the PWBA.
Solder pots must be able to maintain a constant temperature B IPC-7530a-5-3

and create a wave shape that efficiently transfers solder to the

Figure 5-3 Mass Wave Soldering Thermal Profile
PWBA without creating defects (e.g., bridging, icicles or Illustration for a Single-Wave Solder Pot
opens). Wave shape and width are important variables to keep A– Temperature
in mind when creating a thermal profile because they also will B– Time
influence defects such as icicles and bridging and to some C– Solder contact
D– Preheat
extent dwell time, which is also determined by the conveyor E– Soldering
speed. F– Cooldown

5.5 Profile Development Steps A wave soldering profile

consists of three phases: preheat, soldering and cooldown (see D E F
Figures 5-3 and Figure 5-4). The development of a wave sol-
dering thermal profile should include the following actions: C
• Select solder alloy and flux; identify key limitations A
• Review component specifications; identify key limitations
• Review substrate specifications; identify key limitations
B IPC-7530a-5-4
• Determine web width; calculate conveyor speed
• Select preheat zone temperature settings Figure 5-4 Mass Wave Soldering Thermal Profile
Illustration for a Dual-Wave Solder Pot
• Select solder pot temperature setting A– Temperature
• Select cooldown settings (if available) B– Time
C– Solder contact
See Table 5-1 for a summary of common mass wave solder- D– Preheat
E– Soldering
ing parameters (based on flux/alloy type variation).
F– Cooldown

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Table 5-1 Mass Wave Soldering Parameter Summary

Profile Topic SnPb Alloy Pb-free Alloy (SAC SnCu Alloys)
Alloy melting temperature 183 °C 217 °C (SAC) to 227 °C (SnCu)
Solder pot temperature 250 °C to 260 °C 255 °C to 270 °C
Topside peak preheat temperature 100 °C to 120 °C 110 °C to 130 °C
Flux activation time 60 to 120 seconds 60 to 120 seconds
Dwell time (board thickness 1.5 mm to
2 to 4 seconds 3 to 5 seconds
2.25 mm [0.060 in to 0.090 in])
Dwell time (board thickness > 2.25 mm
4 to 8 seconds 5 to 10 seconds
[0.090 in])

5.6 Design for Mass Wave Soldering Considerations PWB design is a critical factor that affects the solderability, reli-
ability and quality of the soldered PWBA. For successful mass wave soldering, carefully consider the following:
• Ratio of the size of a PWBA hole to the diameter of a through-hole lead (IPC-2222)
• Distance from solder connections to the edge of a PWBA
• Rigidity of the PWBA at peak soldering temperature
• Retention of large components (e.g., connectors, sockets, etc.) to prevent movement during soldering
• Thermal relief of large metal planes (e.g., ground planes) to minimize heat-sinking effects
• Adequate clearance for proper solder wetting when using selective wave solder pallets
When wave soldering SMT components that are glued to the bottom of a PWBA, align them parallel to the wave to pre-
vent solder skips.
In selective pallet wave soldering of through-hole components, when SMT components are reflow soldered on the top and
bottom sides, adequate space is necessary between SMT and through-hole components. This space allows the wave fixture
to hide SMT components from the wave while selectively soldering through-hole components.

6 SELECTIVE SOLDERING PROFILING

6.1 Solder Pot By definition, selective soldering implies creating multiple solder connections sequentially or in mass in a
semiautomated or automated process.
Equipment designed for this task generally has four basic characteristics:
• PWBA conveyance (if PWBA moves)
• Pot and fluxer conveyance (if PWBA is stationary)
• Fluxing capability
• Preheating capability
• Pot of molten solder with a single nozzle (sequential soldering)
• Pot of molten solder with a nozzle fixture (mass soldering)
The differences between manufacturers are in the application of these basic concepts and the equipment controls. Each
machine has unique characteristics that need to be taken into account when developing a thermal profile.
Selective soldering systems automatically perform the soldering process, which is flux application, preheating of the area to
be soldered, application of molten solder and solidification. All of these characteristics act together to ensure proper solder-
ing. The operator can develop a solder recipe by recording the optimum process parameters selected for conveyance speed,
flux application, preheaters and solder temperature.
Sequential selective soldering machines solder through-hole components in a sequence. The advantage of sequential selec-
tive soldering is that it can solder through-hole components on PWBAs with bottom-side SMT components without PWBA
fixturing and masking. Its disadvantage is speed because the process uses sequential soldering instead of mass soldering
(e.g., wave soldering).
Mass selective soldering machines solder through-hole components simultaneously using a custom nozzle fixture. As with
sequential selective soldering, mass selective soldering also has the advantage of soldering through-hole components on
PWBAs with bottom-side SMT components without PWBA fixturing and masking. Its disadvantage is the need for a cus-
tom nozzle fixture for each PWB.

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6.1.1 Machine Considerations Each part of a selective soldering machine has a unique function to perform, but the func-
tions must be considered as a whole system because of the interrelationships and dependencies of the fluxer, preheaters,
nozzles and solder pot. Of particular concern is the correlation of the time/temperature/volume relationships. Molten solder
temperature is typically a constant, so the variables are preheater temperatures, preheat/solder pot dwell times and volume
of solder over the nozzle. Dwell time in preheat and over the solder pot are the prime thermal profile variables.

6.1.2 Preheat Considerations PWBAs are preheated during selective soldering for various reasons including:
• Dry-off the volatile solvents in the flux
• Achieve optimum flux-activity level
• Reduce thermal shock to the PWBA during soldering
• Reduce the amount of heat required from the solder pot to raise the temperature of the metals being joined to soldering
temperature
• Permit the use of higher conveyance speeds to minimize cycle time
• Reduce the incidence of icicle and bridging formation
During preheat thermal energy is generated and transferred to the PWBA by several different methods (e.g., IR lamps, IR
panels, radiant heaters and forced-hot-air convection heaters). Whichever method is used, it is important to have consistent
and repeatable temperature control. The best control of preheat will be with machines that have closed-loop control. Peak
preheat temperature is typically measured on the top side of the PWBA before soldering. The peak topside preheat tempera-
ture for SnPb soldering is typically 100 °C to 120 °C, whereas the peak for Pb-free is typically 110 °C to 130 °C.

6.1.3 Solder Pot and Nozzle Considerations Solder pots use a nozzle to transfer solder to the PWBA, so solder pots must
maintain constant temperatures and pump speeds to efficiently transfer the solder to the PWBA without creating defects (e.g.,
bridging, icicles or opens). Different nozzle sizes can be used depending on the clearance the nozzle has to adjacent com-
ponents. Some nozzles can create different solder wave shapes. Increasing or decreasing the pump speed can also change
the shape and height of the solder wave over the nozzle.
Solder pot temperature for SnPb and Pb-free may vary depending on the design of the selective soldering machine. Some
suppliers recommend using a pot temperature higher than typically used for wave soldering because the solder volume com-
ing in contact with the PWBA is considerably smaller than in wave soldering. The molten solder temperature may be a few
degrees higher to 20 °C to 30 °C higher than wave soldering.
For selective soldering, 270 °C is preferable to 290 °C (255 °C to 270 °C for wave soldering) to minimize oxidation in the
solder pot. However, if the system includes a nitrogen inerting option, 290 °C is acceptable.

6.1.4 Profile Development Steps The development of a selective soldering thermal profile should include the following:
• Select solder alloy and flux; identify key limitations
• Review component specifications; identify key limitations
• Review substrate specifications; identify key limitations
• Determine conveyance speed (machine or PWBA)
• Select preheat zone temperature settings
• Select solder pot temperature setting
• Select cooldown settings
See Table 6-1 for a summary of selective soldering parameters.

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Table 6-1 Selective Soldering Parameter Summary

Profile Topic SnPb Alloy Pb-Free Alloy
Alloy melting temperature 183 °C 217 °C (SAC 305), 227 °C (SnCu)
Solder pot temperature (varies between machine manufacturers) 280 °C to 310 °C 280 °C to 310 °C
PWBA preheat (topside) 100 °C to 120 °C 110 °C to 130 °C
Component ramp-down rate Ambient cooling Ambient cooling
Dwell time (board thickness 1.5 mm to 2.3 mm) 2 to 4 seconds 3 to 5 seconds
Dwell time (board thickness > 2.3 mm) 4 to 8 seconds 5 to 10 seconds

A selective soldering profile consists of three phases: preheat,

soldering and cooldown (see Figure 6-1). D E F

6.1.5 Design for Manufacturing (DfM) for Selective Solder-

ing PWB design is a critical factor that affects the solderabil- C
ity, reliability and quality of the soldered PWBA. In selective A
soldering of through-hole components, when SMT compo-
nents are reflow soldered on both top and bottom sides,
adequate space is necessary between SMT and through-hole B IPC-7530a-6-1
components for nozzle clearance. The following should be
Figure 6-1 Selective Soldering Thermal Profile Illustration
carefully considered for successful selective soldering:
for Selective Soldering
• Ratio of the size of a PWBA hole to the diameter of a A – Temperature D – Preheat
through-hole lead (see IPC-2222) B – Time E – Soldering
C – Solder contact F – Cooldown
• Distance from solder connections to the edge of a PWBA
• Rigidity of the PWBA at peak soldering temperature
• Retention of large components (e.g., connectors, sockets, etc.) to prevent movement during soldering
• Thermal relief of large metal planes (e.g., ground planes) to minimize heat-sinking effects

6.1.6 Thermocouple Attachment for Wave and Selective Soldering Figure 6-2 shows recommended locations of ther-
mocouples on a PWBA. It is important that thermocouples be attached to small and large components at the solder joints.
In Figure 6-2, thermocouples 1, 2, 3, 4 and 5 are secured to the top side (component side), whereas thermocouple 6 goes
through the PWBA to measure the bottom side temperature as it is being soldered.

2 4

IPC-7530a-6-2

Figure 6-2 Thermocouple Attachment for Wave and Selective Soldering

Note: See 6.1.6 for explanation of numbers.

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6.2 Alternatives to Selective Soldering

6.2.1 Paste-in-Hole Soldering Paste-in-hole is an alternative to wave and selective soldering through-hole components.
When through-hole components are soldered using paste-in-hole processing, additional spacing around the through-hole
component is necessary to allow the desired volume of solder paste around the through-hole pads to achieve desired hole
fill. In addition, it is important to allow the correct gap between the lead and the hole. For example, the plated through-hole
(PTH) diameter should be about 3 mm larger than the lead diameter to allow capillary action to fill solder in the PTH. If
the gap is too large, paste-in-hole processing may not provide acceptable solder fillets.

6.2.2 Laser Soldering Laser soldering is performed at a very high temperature for a very short period of time. Laser sol-
dering time for through-hole leads is about one second. Some laser soldering systems require 0.25 to 0.5 seconds or less per
joint for selective soldering SMT leads.
Lasers can be used to solder exposed solder joints such as the leads of through-hole and gull wing devices and also to sol-
der hidden solder joints of packages such as BGAs and micro-BGAs.
In laser soldering for though-hole components, solder is applied as wire; for SMT components, solder paste is dispensed or
printed.
Laser soldering uses diode lasers to heat the component lead and PTH pad while automatically feeding solder wire (with
flux inside its core) to achieve the desired fillet. Laser soldering for through-hole components is a point-to-point soldering
process similar to hand soldering, but it is faster and produces consistent quality, which can be a key concern in hand sol-
dering.
Since laser soldering time is very short, the potential for solder ball formation is very high when using solder paste. It is
very important to find a paste supplier that can formulate paste specifically for laser soldering.
Laser soldering can also be beneficial in situations requiring transitions from SnPb to Pb-free soldering. The transition will
only require operators to replace the solder wire spool, which will not take a long period of time (typically a matter of min-
utes).
The key elements of a laser solder profile are laser power that varies from 20 watts to 100 watts, soldering time that can
vary from as fast as 200 milliseconds to as long as four to five minutes for large BGAs with hidden solder joints under the
package. Heat is applied by laser in a defocused manner which heats the entire package, transferring the heat to the balls
(as is the case in hot-air soldering). Preheat is highly recommended to achieve better solder joints and in a shorter period
of time.

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7 TEMPERATURE PROFILING TOOLS

7.1 Product Thermal Profilers A product thermal profiler, also called a remote pass-through thermal profiler, is a
hardware/software kit that can travel with the PWBA through the soldering equipment. It records temperatures measured
using temperature sensors affixed to the PWBA.
In this process, temperature sensors are attached to a thermal profiler, which is inserted into a thermal barrier to protect it
from the process temperatures, and then mounted to the PWBA using a carrier. After the pass-through, the temperature data/
profile are downloaded to a PC for analysis. Figure 7-1 shows an example of a thermal profiler kit with a profiler, thermo-
couples, a thermal barrier and a carrier.

Figure 7-1 Typical Thermal Profiler, Thermocouples, Thermal Barrier and Carrier

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7.1.1 Thermal Profiler Usage Recommendations A thermal profiler must be programmed using its software or hardware
settings. It is recommended to set the profiler recording rate to once per second, which is most common for most mass-
soldering processes. Recording more often than once per second is acceptable, but it is really not necessary for most mass-
soldering processes. The profiler may also need to be set to, or at least to verify, the number of channels (thermocouple
inputs) to be used, the profiler’s date and time and the profiler’s start and stop parameters. Some thermal profilers can accept
several thermocouple types, so ensure it is set for the correct thermocouple type. Consult and follow the thermal profiler’s
user manual for a complete description of its function and proper use.
Most thermal profilers use type K thermocouples as temperature sensor because they:
• Are very rugged
• Can be made almost any size and shape
• Can be attached to the point of interest with solder, tape or glue
• Are relatively low cost

7.1.2 Thermal Profiler Specifications The following are some recommended profiler specifications:
• Accuracy: < ± 2 °C
• Recording frequency: One recording per second or faster
• Input channels: Minimum of three
• Sensor type: Thermocouple (type K is most common)
• Sensor insulation: Teflon® for Pb solder; glass for Pb-free solder
Weak batteries are the biggest cause of profiling failures, so confirm batteries are fully charged. If they are not rechargeable
batteries, confirm they have sufficient capacity.

7.1.3 Thermal Barrier All thermal profilers must be protected from process temperatures using thermal barriers, which
will be provided by the manufacturer. The barrier must be large enough to provide protection for the thermal profiler and
yet small enough to fit through the equipment. Thermal profilers are insulated with many materials. The most common
materials for mass soldering are glass fiber, Teflon® or Kapton®.
Make sure the profiler and barrier are cooled to room temperature before use. Failure to start the profiling equipment at a
cool temperature, typically < 40 °C, can cause the thermal profiler to overheat during soldering.
Do not shortcut the cooling process by using compressed air, freezers or other rapid cooling. The rate at which the barrier
and profiler can cool and become equally thermal throughout depends on the insulation used. The better the insulation, the
longer it takes to release the heat from its core. The best way to cool the profiling equipment after a profile run is to use a
common room air fan with the barrier open and its contents removed and in the fan’s air flow. This will cool the equipment
in about 15 to 20 minutes. Failure to completely cool the profiler and its barrier is the second-largest cause of profiling fail-
ures or the damage to the profiling equipment.
A thermal barrier with an internal thermal profiler will need to be conveyed with the assembly being profiled. It can be
placed on the conveyor belt (if the equipment has one), a blank PWB or a carrier made by the profiler manufacture. It must
ride the conveyor at least 500 mm (20 in) behind the PWBA so as not to influence the thermal environment of the equip-
ment as the PWBA progresses through the equipment.

7.1.4 Statistical Process Control (SPC) The software may offer a means to collect statistical process control (SPC) val-
ues for repeated runs of the same assembly using the same equipment settings over time. This is done so SPC values can
be compared to each other to show consistency.

7.2 Machine Profilers

7.2.1 Purpose The main purpose of machine profilers is to verify proper machine settings or performance. While prod-
uct profilers record product temperatures that are the result of machine settings and product physical properties, machine
profilers eliminate most of the product and solder chemistry variables and focus on machine parameters. Once proper
machine settings are determined using a product profiler, a machine profiler can be used to verify conformance to the
settings. This can be done on a shift basis and at process changeover time. This eliminates the need to sacrifice good assem-
blies for machine performance verification.

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7.2.2 Measurement Parameters Machine profilers are designed to measure machine parameters, which will vary depend-
ing on machine type. Reflow oven profilers may record conveyor speeds, zone sizes, zone air temperatures or heat flow. Heat
flow is the product of zone temperature and air flow or the ability of the oven to deliver heat to the assembly. Some machine
profiling equipment measures airflow in the oven or even ultraviolet (UV) and infrared (IR) radiation.
Wave solder profilers record conveyor speeds, preheat temperatures and a number of chip and main solder wave parameters.
Wave parameters may include contact length, wave height, wave parallelism, wave temperature and change in temperature
at the wave. Wave machine profilers may also measure top- and bottom-side board temperatures as measured on a coupon
designed to simulate a typical PWBA. Some wave solder machine profilers can provide a digitized representation of the
contact area between the board and the wave.
7.2.3 Machine Verification Thermal profiling must be performed on equipment that first has been verified for proper
function. The equipment first must be powered and set to the desired settings and allowed to reach thermal stability. Most
equipment can inform the operator when it has reached its settings. In general, this will take 20 to 30 minutes. Do not
attempt to shortcut this process by forced venting of heat or by altering the equipment’s acceptable limits. Give the equip-
ment enough time to reach thermal stability.
Verification of the equipment’s function is typically done using thermally stable materials that have been instrumented with
thermocouples and then passed through the equipment, in the same manner as a PWBA, to verify the equipment produces
the same thermal profile. There are several commercially available verification tools specifically designed to perform equip-
ment verification.
The operator may also develop a tool using thermally stable materials like aluminum, stainless steel or titanium, which is
machined into plates or blocks suspended in a fixture or pallet that allows some thermal isolation between measurements
points.
Thermocouples should be permanently attached by welding, brazing or mechanically securing into the core of or on the sur-
face of the plate or block. A material 2 mm to 4 mm thick typically will produce verification profile zone values similar to
assembly profiles. Thicker materials may not reach the same temperatures as assembly profiles, but they can be equally as
useful for equipment verification profiles.
Measurement points must cover the width of the conveyor in at least three locations, evenly spaced across the conveyor
width. The equipment being verified (e.g., reflow, wave, selective, vapor phase rework, etc.) will dictate the basic shape of
the verification fixture and the number of measurement points. All must be able to withstand the process temperatures and
to cover the processing area of the equipment. It does not matter the exact shape or size of this fixture as long as it fits the
equipment, can withstand the temperatures and is used in a consistent and repeatable manner.
Verification must be done using the same equipment settings as the previous verification. These settings may be a specific
set used only for a particular equipment verification profile or the same settings planned for a specific PWBA. Whichever
setting is used does not matter as long as the operator has a previous verification profile at these settings for comparison,
unless this will be the first verification at these equipment settings. Using the same settings planned for use for a PWBA
profile will save time since there will be no need to wait for the equipment to reach two different settings: for the verifica-
tion profile and then for the assembly profile.
The equipment settings used for verification should include the measurement values from the same profile zones used for
the desired assembly profile. For reflow, these zones include:
• Preheat: Slope to a temperature
• Soak: Time between the end of the preheat and the liquidus temperature
• Reflow: Time above the liquidus temperature
• Cooling: Slope from peak temperature and the liquidus temperature
Verifying the values for each of these profile zones are consistent with the previous verification profile will confirm the
equipment is consistent and ready to profile the PWBA or production run. Additional values may be taken from the verifi-
cation profile, depending on the process or equipment type.
Verification profile zone values should meet the following tolerance:
• Temperature values: ± 2 °C
• Slope values: ± 0.5 °C per second
• Time values: ± 5 seconds

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The exact values from each profile zone do not matter. Consistency and repeatability with each verification profile run mat-
ter. As verification profiles at the same equipment settings are taken, SPC can be used to verify process control using con-
trol charts (e.g., XbarR) and other process quality measures (e.g., process capability (Cp and CpK)). Most profiling software
offer these SPC process quality tools.
Although it is recommended to use aluminum plate to check for repeatability in oven functions (i.e., no heating elements
have burned out), some users may choose to use a sample PWBA that was originally used to develop the profile. The life
expectancy of a standard thermocouple and sample PWBA can be anywhere from 15 to 30 profiles. The sample PWBA’s
life is dependent on the PWBA thickness and laminate type. Discontinue the use of the sample PWBA when discoloration
of the laminate is apparent.
When the thermocouple is reattached to multiple assemblies, life expectancy is reduced to three to five profiles.
For further information on equipment verification, refer to IPC-7801.

7.2.4 Continuous Real-Time Convection Oven Profilers For reflow ovens, an alternative to the use of a standard pass-
through thermal profiler for process verification is real-time thermal profiling. Real-time thermal profiling continually and
automatically monitors the soldering process, generating an alarm in case of process drift. While real-time thermal profil-
ing requires the initial establishment of a product profile with a pass-through profiler, real-time profiling may reduce the need
for routine profiles on a once-per-shift, daily or weekly basis by calculating a simulated product profile to confirm the pro-
cess is in specification.
Real-time thermal profilers utilize a series of thermocouples that are permanently mounted just above the oven conveyor.
The thermocouple probes are mounted close enough to the PWBA to provide representative temperatures, but far enough
from the oven rails to not to be influenced by the thermal mass of the rails themselves. Though the system does not actu-
ally measure the PWBA temperatures, it provides a measurement of the process temperatures at the conveyor as the PWBA
passes through the reflow oven. Real-time thermal profiling can also automatically output process data to quality control and
SPC programs.
The user should assess the cost benefits of using a continuous real-time thermal machine profiling feature in the reflow oven.

7.3 Thermocouple Types and Selection

7.3.1 Thermocouple Type The thermocouple must match the input requirement of the profiler to be used. See 7.3.1.1
through 7.3.1.4 for recommended common thermocouple types.

7.3.1.1 Type K Type K (nickel-chromium vs. nickel-aluminum) is the most commonly used thermocouple wire, having a
wide operating range of - 200 °C to 1,250 °C and an accuracy of ± 1.5 °C. This material is difficult to solder; so other meth-
ods of attachment are recommended.

7.3.1.2 Type T Type T (copper vs. copper-nickel) has an operating range of - 200 °C to 350 °C and good solderability,
making it easy to attach by soldering. The copper arm has high thermal conductivity; so thinner wire gauges are preferred.
It has an accuracy of ± 0.5 °C.

7.3.1.3 Type J Type J (iron vs. copper-nickel) has an operating range from 0 °C to 750 °C and an accuracy of ± 1.5 °C.
This material is difficult to solder; so other methods of attachment are recommended. It is prone to rusting in humid atmo-
spheres, which will shorten its working life.

7.3.1.4 Type N Type N (nickel-14.2 % chromium-1.4 % silicon vs. nickel-4.4 % silicon-0.1 % magnesium) has an oper-
ating range of - 270 °C to 1,300 °C. This material is difficult to solder; so other methods of attachment are recommended.
It is one of the most stable thermocouple materials and is available with an accuracy of ± 1.1 °C or 0.4 %.

7.3.2 Thermocouple Wire Gauge Thirty-six AWG is the most commonly used wire for profiling. Thirty-eight AWG may
offer greater sensitivity, but it is more fragile and will have a shorter operational life. Thirty-four AWG offers greater opera-
tional life, but it may affect the temperature of the measurement site by conducting heat into or from the thermocouple wire.

7.3.3 Insulation Insulation of the thermocouple is dependent on the environment and temperature extremes to which it
will be exposed. For most soldering applications, glass-braid insulation is used.

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Note: Glass braid offers good high-temperature stability, but it has poor flexibility, which may make handling more diffi-
cult. Polytetrafluoroethylene (PTFE) offers better flexibility, but it will degrade faster with repeated heat cycles.

7.3.4 Wire Length It is recommended that thermocouple lengths not exceed approximately 1 m [39.4 in], because long
thermocouple wires can introduce measurement errors. The thermocouple wire should be as short as practical to reduce the
effects of noise and resistance and to prevent mechanical damage.

7.4 Thermocouple Junction The formation of the thermocouple should be a welded junction. It is recommended that the
thermocouple be replaced when the original junction weld is broken. In the event that the weld or a wire are broken, it is
recommended to never consider twisting the thermocouple wires together to form a junction. This can result in an incorrect
temperature measurement.

7.5 Calibration and Test Calibration of the data logger

A
should be performed as required by the OEM or in accordance
with equipment manufacturer specifications. In the absence of
an OEM or manufacturer’s recommendation, calibration and
B
testing every six months of operation may be established. A
noncalibrated data logger should never be used.
C
Thermocouples should be verified for proper operation when
they have been used more than once. This can be achieved by
using a calibrated data logger to compare temperature mea- IPC-7530a-7-2

surements of the used thermocouple to a calibrated thermo- Figure 7-2 Thermocouple Attachment (Solder Method)
couple. A – High-temperature solder
B – Land
7.6 Thermocouple Attachment C – Thermocouple bead

7.6.1 High-Temperature Solder High-temperature solder

A
attachment should be considered for a sample PWBA that will
be profiled multiple times, because it provides a consistent
reproducible thermal connection. Figure 7-2 shows solder
attachment of a thermocouple. Care should be taken not to use B
a high-temperature solder attachment too close to the melting
point of the solder.
C
7.6.2 Adhesives There are many types of adhesives used
for thermocouple attachment, all of which have different cur- IPC-7530a-7-3
ing mechanisms (e.g., heat, air and UV). It is important that
Figure 7-3 Thermocouple Attachment (Adhesive Method)
the adhesive being used be thermally conductive. More infor- A – Adhesive
mation about thermally conductive adhesive can be obtained B – Land
from IPC-CA-821. This method of attachment should be con- C – Thermocouple bead
sidered for a sample PWBA and will be profiled multiple
times, but the process temperatures are too high for high-
temperature solder. Attachment of a thermocouple using adhe-
B
sive is shown in Figure 7-3.
A
7.6.3 Aluminum/Copper Tape Aluminum/copper tape pro-
vides a securely connected thermocouple with good thermal C
conductivity, is nondestructive and leaves no scars or residu-
als. Using aluminum/copper tape reduces the amount of effort
IPC-7530a-7-4
and expense required to obtain an accurate thermal profile.
This method of thermocouple attachment has been found to be Figure 7-4 Thermocouple Attachment (Tape Method)
reliable and repeatable (see Figure 7-4). Care needs be taken A – Land
B – Tape
when handling the PWBAs, and the secure attachment of the
C – Thermocouple bead
thermocouples should be verified before each use.

Note: Polyimide tapes are not recommended, but if polyimide tapes are used, extreme care should be taken because the
tapes are likely to peel off during their time in the oven.

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7.6.4 Embedded Thermocouple The thermocouple can be embedded in the actual solder joint (see 3.1.1). This is particu-
larly advantageous for BGAs.

To embed a thermocouple, drill a hole through the PWBA, centered in a solder land prior to mounting the component. The
hole should be just large enough to accommodate the thermocouple (approximately 0.4 mm [0.016 in] for a 36 AWG
thermocouple).

The component should then be soldered in place. From the bottom side, use the same drill bit and drill approximately
0.5 mm [0.020 in] into the solder joint, insert the thermocouple into the solder joint and then secure with tape.

7.6.5 Thermally Conductive Adhesive A thermocouple can also be attached using a thermally conductive adhesive. If
using this process, it is recommended to not use too much conductive adhesive.

7.6.6 Mechanical Attachment Spring-loaded thermocouples use mechanical pressure to position the thermocouple against
the measuring point. These may be used on production PWBAs to be shipped.

8 TROUBLESHOOTING

Various types of solder joint defects can occur during the soldering process. The root causes of these defects can vary
depending on the type of defect. Some defects can be caused by factors such as material selection, cleanliness/solderability
considerations or PWB design issues. Some defects can also be caused by implementation of nonoptimum soldering ther-
mal profiles. This section offers insights on common solder defects, their potential root causes and whether or not these
defects can be mitigated by adjusting soldering thermal profile parameters.

Note: These troubleshooting guidelines are associated with soldering defects caused only by thermal profiling. Please refer
to other documents if these defects are attributable to other root causes.

8.1 Solder Reflow Defects

8.1.1 Voids

Defect Voids within the solder joint

description
Reflow Incorrect reflow soldering profile leaves too much flux and
possible volatiles to outgas during reflow
cause Preheat rate is too high
Soak temperature is too low
Reflow Increase soak time to evaporate flux
potential Increase soak temperature
solution Decrease preheat slope
Use N2 environment
Other Solder balls in solder paste have oxidized
possible Outgassing of volatiles (solder paste is not low voiding)
cause Contaminated BGA solder balls
Excessive oxidation on BGA solder balls
Excessive solder paste
Figure 8-1 Reflow Defects – Voids Presence of foreign material on PWB pads
PWB/PWBA pad defects (cavities)

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8.1.2 Head on Pillow (HoP)

Defect Type of open joint that is comprised of two metallurgical distinct

description masses
One formed from the BGA ball and the other from the reflowed
solder paste
They have incomplete or no coalescence
Reflow Incorrect reflow soldering profile
possible High temperature differential (dT) on a component
cause Inadequate support during reflow
Reflow Use N2 environment
potential Decrease flux activation time (soak time)
solution Increase time above liquidus
Increase peak temperature
Check that the pallet does not constrain the PWBA from
expansion
Use PWBA support in the reflow for thin PWBAs < 1.0 mm
Figure 8-2 Reflow Defects – Head on Adjust conveyer speed
Pillow Other Component and PWBA warpage
possible Solder paste activity is too low
cause Insufficient solder paste volume
Solder balls in the solder paste have oxidized
Localized warpage of PWBA
Insufficient flux
Component coplanarity issue
Contaminated BGA solder balls
Excessive oxidation on BGA solder balls

8.1.3 Bridging

Defect Adjacent solder joints coalesce into one large mass, causing a
description short
Reflow Incorrect reflow soldering profile
possible Conveyor vibration
cause Preheat ramp-up rate is too high
Reflow Decrease time above liquidus
potential Decrease peak temperature
solution Decrease preheat ramp-up rate
Check conveyors for smooth movement
Other Misaligned component due to improper placement
possible Excess solder deposited
cause Contamination on component or PWBA
Solder paste viscosity is too low or paste is slumping
Figure 8-3 Reflow Defects – Bridging No solder mask separation between the component leads
Solder paste printing is misaligned or bad
Flux separation
Placement pressure too high
Hot slumping

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8.1.4 Solder Balls

Defect Small solder spheres adhere to the solder mask, component or

description area surrounding the solder joint
Reflow Incorrect reflow soldering profile causes the flux vehicle to carry
possible solder particles away from the solder joint
cause Heating rate is too high, causing evaporation of the flux
Preheat ramp rate is too high
Preheat temperature is too high
Reflow Increase preheat to evaporate flux
potential Reduce preheat ramp rate
solution
Other Solder particles in the solder paste have oxidized
possible Solder paste viscosity is too low, resulting in slumping onto the
cause mask
Misalignment of paste print on the solder mask
Solder paste is contaminated with oxidized particles
Solder paste misprint
PWB not properly cleaned
Insufficient flux content in solder paste
Solder paste stencils are dirty
Small solder particles
Excess pressure pushing solder paste onto the mask
Entrapped volatiles, causing solder splattering
Figure 8-4 Reflow Defects – Solder Balls

8.1.5 Cold Solder/Incomplete Solder

Defect Solder looks grainy and incomplete

description
Reflow Incorrect thermal profile - the solder did not reach the required
possible temperature and time to create a joint
cause Cooling rate is too fast
Peak temperature is too low
TAL is too low
Conveyor speed is too fast
Reflow Increase peak temperature
potential Increase TAL
solution Check for heat-sinking area near the defect
Slow down conveyor speed
Other PWBA disturbed during cooling
possible Excessive heat sinking due to thick copper planes in the PWBA
cause

Figure 8-5 Reflow Defects – Cold Solder/

Incomplete Solder

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8.1.6 Solder Beading (Squeeze Balls)

Defect Trapped solder balls under chip components

description
Reflow Incorrect reflow soldering profile
possible Too much paste under small components
cause Stencil is too thick
Poor land pattern design
Reflow Minimize paste volume on land patterns
potential
solution
Other Poor paste quality
possible
cause

Figure 8-6 Reflow Defects – Solder

Beading

8.1.7 Grainy Solder

Defect Solder joint surface looks grainy and dull

description
Reflow Large delta T due to mass differential, causing some areas to be
possible above liquidus too long
cause Cooldown rate is too slow
Reflow temperature is too low
Reflow Reduce dT by using soak profile
potential Increase conveyor speed
solution
Other Solder joint contamination
possible PWBs or components are contaminated
cause

Figure 8-7 Reflow Defects – Grainy Solder

8.1.8 Tombstoning

Defect Component has been lifted on one end and is soldered on the
description other end
Reflow Wetting force larger on one side than the other
possible Thermal delta exists between the component pads
cause Heating rate is too high
Reflow Reduce dT by using soak profile
potential Reduce preheat ramp
solution Reduce heating rate
Change PWBA travel direction
Other Land pattern area size mismatch
possible Component coplanarity issue
cause Improper placement, resulting in component offset
Solder paste alignment problem
PWB copper ground plane difference
Nonsymmetrical component metallization

Figure 8-8 Reflow Defects – Tombstoning

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8.1.9 Solder Wicking

Defect Solder climbs up the component lead; the pad has little or no
description solder
Reflow Component terminations are hotter than the land areas
possible Peak temperature is too high
cause
Reflow Reduce peak temperature
Potential Slow down conveyor speed
Solution Check for heat-sinking area near the defect
Other Solderability problem with the PWB pads
Possible Component termination coplanarity error
Cause Contaminated components
Excessive solder paste volume

Figure 8-9 Reflow Defects – Solder

Wicking

8.1.10 Blow Holes/Pin Holes

Defect Hole formed in the solder

description
Reflow Moisture outgassing during soldering usually related to thin
possible copper plating or voids in copper plating
cause Reflow temperature is too low
Preheat ramp-up rate is too high
Reflow Increase reflow temperature
potential Decrease ramp-up rate
solution
Other Contamination present
possible Excess volatile content in solder paste
cause
Figure 8-10 Reflow Defects – Blow Holes/
Pin Holes

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8.1.11 Additional Root Causes of Defects Table 8-1 details some additional defects in solder joints, their solder profil-
ing root causes or other root causes.
Table 8-1 Additional Root Causes of Defects in Solder Joints
Type of Defect Soldering Profile-Related Root Causes Other Root Causes
Preheat ramp-up rate too high
Hot slumping None identified
Reflow cycle time too long
Bad components
Improper profile settings, resulting in thermal
Component placement pressure too high
Cracked components shock to the components
Improper PWBA supports
Preheat ramp-up rate too high
Bad feeders/shutter jam
Cooling rate too fast
Improper profile settings, resulting in thermal CTE mismatch
Cracked solder joints shock to components Poor handling
TAL too high or peak temperature too high, Localized PWBA warpage
resulting in excessive intermetallic growth
Preheat ramp-up rate too high
Components absorb moisture due to improper
Improper profile settings, resulting in thermal
Popcorn delamination storage or failure to bake components prior to
shock to components
soldering
Reflow temperature too high
Preheat temperature and time too low Solder paste oxidized
Soak temperature too high, resulting in flux drying PWBA or components contaminated or oxidized
Nonwetting
too soon Improper storage of PWBA or components
Reflow temperature too low Too little flux and flux activation
Reflow temperature too high
Dewetting Contaminated PWBA
Heating rate excessive

8.2 Solder Joint Accept/Reject Criteria Consult J-STD-001 and IPC-A-610 to determine whether or not the visual
appearance of completed solder joints is acceptable.

8.3 Control of Wave Soldering Defects Wave soldering defects are generally either are attributable to the process or are
beyond wave soldering system control (i.e., they are inherent in the components, PWBs and assembly design). With proper
process control and the use of well-designed PWBAs and PWBs and components with good solderability, a modern well-
controlled wave soldering process will be virtually defect-free.

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ANSI/IPC-T-50 Terms and Definitions for

Interconnecting and Packaging Electronic Circuits
Definition Submission/Approval Sheet
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Fax: 847 615.7105 Date:
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• Choice of one registration to IPC TechSummit or two registrations to other IPC conferences
events are bundled into your
• One registration to IPC’s annual Capitol Hill event
membership, you can enjoy the
• One copy of IPC International Technology Roadmap for Electronic Interconnections
convenience of going through
• One registration to an IPC management/business conference
the budgetary approval process
• Two registrations to IPC technology webinars
only one time instead of
• One copy of a Fast Facts market research study
several times a year.
Enterprise Package Even if your membership
For companies that recognize the importance of giving multiple company locations access to IPC anniversary is months away,
membership benefits, the Enterprise Package provides Classic Membership to all employees at you can take advantage of
select locations, plus:
the added value of IPC’s new
• Additional membership discounts beyond Classic Membership membership packages today!
• Unlimited complimentary admission to quarterly webinars Your current membership will
• 50% registration discount to all official IPC events in North America and Europe be prorated and applied to your
Put the resources of the entire industry behind your company by joining IPC today! new membership package.
Learn more at www.ipc.org/membership.
 SINGLE USER LICENSE - NOT FOR USE ON A NETWORK OR ONLINE

Use this helpful chart to compare the features of IPC’s membership bundles; then select the best one for your company.

Features Classic Technology Business Business &

Membership Package Package Technology
Package
24/7 online access to members-only resources x x x x
One single-user download of each new or revised x x x x
IPC standard within 90 days of publication
(with approximately 50 standards documents
developed annually, that represents an average
savings of more than $2,400 each year)
50% discount on IPC standards x x x x
Significant discounts on IPC publications and x x x x
training materials
Significant discount on exhibiting at IPC events, x x x x
including IPC APEX EXPO
Reduced registration rates on IPC conferences x x x x
and other educational events
Access to participate in IPC market research x x x x
studies (along with complimentary report for
each study in which company participates)
One All Access Package registration to x x Includes two
IPC APEX EXPO registrations
Your choice of one registration to IPC TechSummit x x
or two registrations to other IPC technical
conferences
One registration to IPC’s annual Capitol Hill event x x
One copy of IPC International Technology x x
Roadmap for Electronic Interconnections
One registration to an IPC management/business x x
conference
Two registrations to IPC technology webinars x x
One copy of a Fast Facts market research study x x

Enterprise Package — For companies that recognize the importance of giving multiple company sites access to IPC membership benefits,
the Enterprise Package provides Classic Membership to employees at select locations, plus additional discounts, unlimited complimentary
admission to quarterly webinars and 50% registration discount to all official IPC events in North America and Europe
For more information about IPC’s membership options and packages, visit www.ipc.org/membership or contact the Member Success team at
membership@ipc.org.

“Juki gets tremendous value from our IPC membership

… we get quarterly market data which would cost us
thousands of dollars if we commissioned it on our own.
The industry standards generated by IPC committees
allow us to design our equipment with certainty that
it will meet industry requirements. The returns for our
IPC — Association Connecting Electronics Industries® Headquarters
3000 Lakeside Drive, Suite 105 N, Bannockburn, IL 60015
company are so great, they are beyond calculable.”
www.ipc.org Bob Black
+1 847-615-7100 tel President and CEO
+1 847-615-7105 fax Juki Automation Systems Inc.

Visit www.IPC.org/offices for the locations of IPC offices worldwide.

 SINGLE USER LICENSE - NOT FOR USE ON A NETWORK OR ONLINE

Application for Site Membership

Association Connecting Electronics Industries

®
www.ipc.org/membership

Thank you for your decision to join IPC. Membership is site specific, which means that IPC member benefits are available to
all individuals employed at the site designated on this application.

Company Name Company URL

Address 1

Address 2/Mail Stop City State/Province Zip Code Country

Company Phone

Name of Primary Contact Phone

Title E-mail address

Number of Employees at this Site Number of Employees Corporate-Wide

Billing Contact (if different from Primary above)

Address 1

Address 2

Title Phone

E-mail address

To best serve your specific needs, please indicate the most appropriate member category for your facility. (Check one box only.)

c Board Fabricator/Manufacturer
What products do you make for sale? (check all that apply)
c Rigid boards c Flexible circuits c Rigid flex c Printed electronics c Other ________________________________________________

c EMS/Assembly/Contract Manufacturer/ODM
c Aerospace c Automotive c Communications c Computer & Business equipment c Consumer
c Defense/military c Industrial c Medical/Instrument c Other______________________________________________

c Wire Harness Manufacturer

c OEM
c Aerospace c Automotive c Communications c Computer & Business equipment c Consumer
c Defense/military c Industrial c Medical/Instrument c Other
What is your company's primary product line?_______________________________________________________________________
c Supplier
Which industry segment(s) do you supply?
c Supplier to Board Fabricator industry: materials or equipment
c Supplier of assembly materials or equipment
c Supplier – Services and Other
What products do you supply?___________________________________________________________________________________
c Other
c Government c Military c Media c Academia c Non-profit c Associations
 SINGLE USER LICENSE - NOT FOR USE ON A NETWORK OR ONLINE
Association Connecting Electronics Industries

®
Application for Site Membership

Membership Packages and Dues

Membership will begin the day the application and dues payment are received, and will continue for one or two years (savings of 10%) based on the
choice indicated below. All fees are quoted in U.S. dollars.
Please check one:
Classic Membership Enterprise Package
One year Two years
Primary Facility/site: The first site of an organization to join IPC membership c $1,250 c $2,250
Additional Facility/site: Membership for a facility of an organization that has a different c $1050 c $1,890
location than its Primary Facility membership
Please call for a quote
Company with annual revenue of less than $5 million c $725 c $1,305

Government agency, academic institution or nonprofit organization c $375 c $675

Consulting firm (employing fewer than six individuals) c $725 c $1,305

Explanation of Packages

Classic Membership — IPC’s classic membership provides core benefits to all employees at a company site/facility:

• 24/7 online access to members-only resources

• One single-user download of each new or revised IPC standard within 90 days of publication
• Significant discount on IPC standards
• Significant discounts on IPC publications and training materials
• Significant discount on exhibiting at IPC events, including the industry’s flagship event IPC APEX EXPO
• 25% discount on registration rates on IPC conferences and other educational events
• Access to participate in IPC market research studies (along with a complimentary report for each study in which company participates)

Enterprise Package — For companies that recognize the importance of giving multiple company locations access to IPC membership
benefits, the Enterprise Package provides Classic Membership to employees at select locations.

Payment Information (Purchase orders not accepted as a form of payment)

Enclosed is a check for $_________________________ Bill credit card: (check one)
❏❏MasterCard ❏❏American Express ❏❏Visa ❏❏Diners Club

Card No. Expiration Date Security Code

Authorized Signature
Please attach b­ usiness card
Mail application with check *Fax/Mail application with credit card payment to: of primary contact here
or money order to: IPC
IPC 3000 Lakeside Drive, Suite 105 N
3491 Eagle Way Bannockburn, IL 60015
Chicago, IL 60678-1349 Tel: +1 847-615-7100
www.ipc.org Fax: +1 847-615-7105
*Overnight deliveries to this address only.
Contact membership@ipc.org for wire transfer details. 02/17
 SINGLE USER LICENSE - NOT FOR USE ON A NETWORK OR ONLINE

Standard Improvement Form IPC-7530A

The purpose of this form is to provide the Individuals or companies are invited to If you can provide input, please complete
Technical Committee of IPC with input submit comments to IPC. All comments this form and return to:
from the industry regarding usage of will be collected and dispersed to the IPC
the subject standard. appropriate committee(s). 3000 Lakeside Drive, Suite 105N
Bannockburn, IL 60015-1249
Fax 847 615.7105
E-mail: answers@ipc.org

1. I recommend changes to the following:

Requirement, paragraph number
Test Method number , paragraph number

The referenced paragraph number has proven to be:

Unclear Too Rigid In Error
Other

2. Recommendations for correction:

3. Other suggestions for document improvement:

Submitted by:

Name Telephone

Company E-mail

Address

City/State/Zip Date
 SINGLE USER LICENSE - NOT FOR USE ON A NETWORK OR ONLINE

Association Connecting Electronics Industries

3000 Lakeside Drive, Suite 105 N

Bannockburn, IL 60015
847-615-7100 tel
847-615-7105 fax
www.ipc.org

ISBN #978-1-61193-303-1