Ssza002b 1
Ssza002b 1
SSZA002B – August 2009 – Revised August 2015 Plastic Ball Grid Array (PBGA) 1
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SSZA002B – August 2015
1.0 Introduction:
The Plastic Ball Grid Array or PBGA package, qualified and ramped by Texas Instruments Philippines is a cavity-
up laminate based substrate package in which the die is attached to the substrate in the normal die up manner. The
wire- bonded device and the complete assembly is then overmolded and solder balls attached to form the package.
This package provides a cost-effective packaging solution, offering higher density over traditional leadframe
packages. Texas Instruments’ advanced design and simulation capabilities enable package optimizations needed for
maximum electrical and thermal performance. The PBGA package is offered in a range of sizes from 17mm x 17mm
to 35mm x 35mm, in ball pitch of 0.8mm and 1.0mm, to provide a ball count ranging from 208 to 976 balls. PBGA
packages are available in 2 and 4 layer substrate designs.
Wire Bonds
Conductor Traces
Conventional PBGA
Substrate and Structure
Die
Solder Balls
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SA DIE WIRE
WAFER
Plasma
Clean
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pBGA Package Product Guide
Pitch Package Size (mm)
(mm) 17x17 23x23 27x27 31x31 35x35
352ZDU 484ZED
376ZDW/ZDU 520ZXF
388ZDW 580ZEQ
420ZDQ 632ZXZ
432ZDU
0.8
640ZKK
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A typical package outline with 1mm pitch and appropriate tolerances are shown below.
ZXZ (S-PBGA-N456)
Package Height .......... ranges depending on body size, ball size and layer count.
Package Size ............. Ranging from 17mm x 17mm to 35mm x35mm
Ball Pitch .................... 0.8 mm and 1.0mm
The PBGA package is primarily composed of copper laminated BT substrate. This adds stiffness to the package
and uniform expansion during board mount and board level temperature cycling. Also, because of cavity up
configuration, the solder balls for this package may be placed in a complete array over the entire bottom side.
Therefore, balls immediately under the die may be used as thermal paths to further enhance the thermal performance.
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2.1 PCB Land Pattern and Solder Mask Design
The solder lands on the package side are always Solder Mask Defined (SMD). The land pattern on the PCB
should be designed to correspond with the land pattern on the package. The land on the PCB should be Non-Solder
Mask Defined (NSMD) in order to realize the best board level reliability performance.
For NSMD pads, TI recommends a clearance (typically 3 mils) between the copper pad and solder mask to avoid
overlap between the solder joint and solder mask due to mask registration tolerances.
The diameter of the solder ball land on the PCB should be the same or up to 20% less than that of the package
substrate solder land. The trace leading into the NSMD ball land on the PCB should not exceed more than 50% of the
land diameter. Again, this is to avoid too much solder wetting this lead-in to the ball thereby creating too much ball
collapse and possibly impacting board level reliability.
All measurements in mm Ball size, SMO, Pad Size and Apertures are shown in Diameters
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2.2 Escape routing guidelines
A typical PBGA has four or five rows of solder balls around the periphery of the package. The number of lines routed (N)
between the pads on the PCB is defined by the pad size and trace (width and spacing) fabrication capabilities of the PCB
manufacturer. For NSMD pads, exposure of underlying copper traces is forbidden, so the diameter and tolerance of the
solder mask opening define D. The following relationship is used to define N:
As shown below, 1 mm ball pitch with 4 rows of solder balls can be routed to 4 layers of PCB which uses a 0.125 mm
line width and 0.125 mm line space.
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Solder paste deposition by the stencil-printing process involves the transfer of the solder paste through pre-defined
apertures with the application of pressure. Stencil parameters such as aperture area ratio and the stencil fabrication
method have a significant impact on paste deposition. Inspection of the stencil prior to placement of the BGA package is
highly recommended to improve board assembly yields. Aperture size to PCB pad size is typically 1:1 ratio with 0.100 to
0.125 mm thick stencil.
• Chem-etch
• Laser cut
• Electroform (Metal additive processes)
Nickel-plated electro polished chem-etch or laser cut with tapered aperture walls (5° tapering) is recommended to
facilitate paste release.
BGA packages are placed using standard pick and place equipment with a placement accuracy of ±0.10 mm.
Component pick and place systems are composed of a vision system that recognizes and positions the component and
a mechanical system which physically performs the pick and place operation. Two commonly used types of vision
systems are: (1) a vision system that locates a package silhouette and (2) a vision system that locates individual bumps
on the interconnect pattern. Both methods are valid since the parts align due to self-centering feature of the BGA solder
joint during solder reflow. The latter vision system while providing greater accuracy tends to be more expensive and time
consuming. BGAs have excellent self-alignment during solder reflow if a minimum of 50% of the ball is aligned with the
pad. The 50% accuracy is in both the X and Y direction as determined by the following relation.
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3.6 REFLOW
Finally, successful reflow cycles strike a balance among temperature, timing, and length of cycle. Mistiming may lead
to excessive fluxing activation, oxidation, excessive voiding, or even damage to the package. Heating the paste too
hot, too quickly before it melts can also dry the paste, which leads to poor wetting. Process development is needed
to optimize reflow profiles for each solder paste/flux combination
The BGA may be assembled using standard IR or IR convection SMT reflow processes. As with other packages, the
thermal profile for specific board locations must be determined. The BGA is qualified for up to three reflow cycles at 245°
C peak (J-STD-020). The actual temperature used in the reflow oven is a function of:
• Board density
• Board geometries
• Component location on the board
• Size of surrounding components
• Component mass
• Furnace loading
• Board finish
• Solder paste types
It is recommended that the temperature profile be validated at the ball location of the BGA as well as several other
locations on the PCB surface.
To produce the optimum solder joint, it is important to understand the amount of collapse of the solder balls, and the
overall shape of the joint. These are a function of:
0.50+/-0.1mm
Controlling the collapse, and thus defining the package standoff, is critical to obtaining the optimum joint reliability.
Generally, a larger standoff gives better solder joint fatigue strength, but this should not be achieved by reducing the
board land diameter. Reducing the land diameter will increase the standoff, but will also reduce the minimum cross-
section area of the joint. This, in turn, will increase the maximum shear force at the PCB side of the solder joint.
Therefore, a reduction of land diameter will normally result in a worse fatigue life, and should be avoided unless all the
consequences are well understood
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3.6.1 For Pb Free paste reflow
A DOE (design of experiment) was performed to assemble the board under different assembly conditions.
: Thermocouples were attached to the solder joint through the other side of
the board by drilling through the PCB. Then the components were placed on
the board.
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3.6.1.5 Lead free reflow profile for lead free components using lead free solder paste
An actual reflow profile using no clean paste that produce good board level reliability result.
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3.6.2 Reflow profile for PbSn components using PbSn solder paste
The reflow peak temperature should be kept in the 215°C to 225°C range. An actual reflow profile used to produce good
board level reliability result is shown below (no clean paste):
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Removing BGA packages involves heating the solder joints above the liquidus temperature of the solder and picking
the part off the PCB when the solder melts. The quality of rework is controlled by directing thermal energy to solder
without over-heating the adjacent components. Heating should occur in an encapsulated, inert, gas-purged environment
where the temperature gradients do not exceed ±5° C across the heating zone using a convective bottom side pre-
heater to maximize temperature uniformity. If possible, the PCB area should be preheated through the bottom side of
the board, to 100°C before heating the BGA to ensure a controlled process. Interchangeable nozzles designed with
different geometries will accommodate different applications to direct the airflow path. Once the liquidus temperature is
reached, the nozzle vacuum is automatically activated and the component is removed.
It is recommended that the reflow profile used to reflow the BGA be as close to the PCB mount profile as possible.
Preheat from the bottom side of the board is recommended where possible. Once the liquidus temperature is reached,
the solder will reflow and the BGA will self-align.
Most BGA rework stations will have a pick and place feature for accurate placement and alignment. Manual pick and
place, with only eyeball alignment, is not recommended. It is difficult to achieve consistent placement accuracy.
It is recommended that the reflow profile used to reflow the BGA be as close to the PCB mount profile as possible.
Preheat from the bottom side of the board is recommended where possible. Once the liquidus temperature is reached,
the solder will reflow and the BGA will self-align.
5.0 Reliability
Reliability is one of the first questions designers ask about any new packaging technology. They want to know how
well the package will survive handling and assembly operation, and how long it will last on the board. The elements of
package reliability and system reliability, while related, focus on different material properties and characteristics and are
tested by different methods.
Package reliability focuses on materials of construction, thermal flows, material adherence/ delamination issues,
resistance to high temperatures, moisture resistance and ball/stitch bond reliability. Thorough engineering of the
package is performed to prevent delamination caused by the interaction of the substrate material and the mold
compound. TI subjects each PBGA to rigorous qualification testing before the package is released to production.
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Package-Level Reliability Test Results
Level 4 3 4
Test Environments
THB, 85RH/85°C 168 hrs 0/26 0/78 na
300 hrs 0/26 na na
600hrs 0/26 0/78 na
1000hrs 0/26 0/78 na
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Board-level Reliability Summary
6.1 Trays
Thermally resistant plastic trays are used to ship these packages. Each family of parts with the same package outline
has its own individually designed tray. The trays are designed to be used with pick-and-place machines.
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6.2 Tape-and-Reel
Pkg Pkg Reel
Package Qty per reel
Group Size WIDTH DIAMETER HUB
PBGA 256 GDH
PBGA 256 ZKB
PBGA 256 ZEP
PBGA 491 ZCN
PBGA 491 ZDN
PBGA 256 ZFE
17x17 750 32mm 13 in 4 in
PBGA 208 ZFE
PBGA 1088 CYL
PBGA 208 ZKB
PBGA 754 AAN
PBGA 256 ZDH
PBGA 208 ZDH
PBGA 289 ZEL
PBGA 289 GDY
19x19 500 32mm 13 in 4 in
PBGA 289 ZDY
PBGA 484 ZVK
PBGA 288 GDQ
PBGA 324 GDU
PBGA 324 GDW
PBGA 324 ZKD
PBGA 376 ZKD
PBGA 324 ZDU
PBGA 768 ZDU
PBGA 640 ZKK
PBGA 324 ZDW
23X23 250 44mm 13 in 7 in
PBGA 376 ZDU
PBGA 376 ZDW
PBGA 388 ZDW
PBGA 420 ZDQ
PBGA 484 ZDU
PBGA 376 ZKC
PBGA 324 ZKC
PBGA 484 ZER
PBGA 484 ZDW
PBGA 256 GFN
PBGA 256 ZFN
PBGA 272 GDP
PBGA 272 GFN
PBGA 584 ZEQ
PBGA 580 ZEQ
PBGA 316 GFN
PBGA 352 GPC
PBGA 352 ZPC
PBGA 388 GDS
27x27 250 44mm 13 in 6 in
PBGA 388 GED
PBGA 388 GPC
PBGA 388 ZDS
PBGA 388 ZED
PBGA 388 ZPC
PBGA 456 GXF
PBGA 456 ZXF
PBGA 484 ZED
PBGA 520 ZXF
PBGA 676 GPY
PBGA 352 GFT
PBGA 352 ZFT
PBGA 388 GFW
PBGA 388 GFT
PBGA 420 GDC
PBGA 474 GPJ
PBGA 520 GPJ
PBGA 580 GPA
PBGA 624 GPA 35x35 250 56mm 13 in 6 in
PBGA 624 ZPA
PBGA 676 GXD
PBGA 676 ZXD
PBGA 680 GPA
PBGA 680 ZPA
PBGA 680 ZWZ
PBGA 976 ZWZ
PBGA 729 GXB
7.0 Sockets
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Typical testing of TI pbga packages is done through the use of a pogo pin style contactor. See below for an image of
an actual test socket and contactor. Also note the typical witness marks on the ball after testing.
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A pinch style contact has been used extensively for contacting solder balls in conventional BGAs and is the proposed
method for burn-in of these packages, providing the most reliable solution with less ball deformation at an affordable
cost. Further information on the availability of these sockets can be obtained from your local TI Field Sales
representative.
Picture below showing a typical Texas Instruments burn-in socket and pins
Socket Pins
PBGA socket
Socket Pin Package: 456 ZXF
The contact is designed to grip the solder ball with a pinching action. This not only provides electrical contact to the
solder ball but also helps retain the package in the socket. Each contact incorporates two beams that provide an oxide-
piercing interface with the sides of the balls above the central area—the equator. No contact is made on the bottom of
the solder ball so the original package planarity specifications are unchanged. The contact is shown below:
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Cross-section Magnification:
Ball Contact on
Socket Pin Device
Ball
Horizontal
Socket
Cross Section: Pin
Result: Good
Contact between
the ball and the
socket pin
Cross-section Magnification:
Device
Vertical Cross Ball Socket
Section: Pin Remarks: Good
Ball Contact on the
Ball Contact on socket pin; No
Socket Pin Abnormalities seen
inside the socket
The witness marks left on the solder ball from the contact are shown below. There is no damage to the bottom of the
ball and typical pin contact signature is seen in the ball marking magnification photograph below.
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Frequently Asked Questions
Q What size land diameter for these packages should I design on my board?
A Land size is the key to board-level reliability, and Texas Instruments strongly
recommends following the design rules included in this document.
Revision History
Rev B. August 2015 Changed the “Optium Land Configurations“ table on page 6
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