Hardware Engineer's Guide
CONNECTORS & CABLES
ByShimiCohen
Connectors and Cables
Connector Type Pins Pinout
1 USB Type-C 24
2 HDMI A 19
3 RJ45 8P8C 8
4 PWR Jack 5.5/2.1 2–3
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Connectors and Cables
Conn Type Pins Pinout
5 Audio Jack TRS 2-4
6 DisplayPort STD 24
7 SWD 20p 20
8 SMA SMA 1
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Connectors and Cables
Conn Type Pins Pinout
9 SD Mini/Micro 8-9
10 SATA Molex 5
11 BNC 50Ω/75Ω 2
12 RS232 D-SUB 9
DB-9
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Connectors and Cables
INTERCONNECT BASICS
Electrical interconnects serve as the circulatory system of electronic hardware.
They enable power distribution, signal transmission, and data transfer between
discrete components, PCBs, and subsystems.
PRIMARY FUNCTIONS:
• Signal path establishment between processing units
• Power delivery from sources to loads
• Grounding and EMI management
• Mechanical support and positioning
• Environmental protection of electrical connections
SYSTEM IMPACT ANALYSIS:
• Interconnects directly affect system reliability
• Signal integrity degradation increases with poor interconnect design
• Cost optimization requires balanced connector selection strategies
• Maintenance accessibility depends on interconnect architecture
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Connectors and Cables
BOARD-TO-WIRE CONFIGURATIONS:
• Direct PCB termination for fixed installations
• Removable connectors for serviceable systems
• Mixed architectures for modular designs
• Hybrid power/signal distribution schemes
BOARD-TO-BOARD CONFIGURATIONS:
• Parallel PCB stacking with vertical connectors
• Perpendicular board mounting with right-angle interfaces
• Flexible circuit interconnection for dynamic assemblies
• Backplane architectures for scalable systems
WIRE-TO-WIRE CONFIGURATIONS:
• In-line splicing for harness extensions
• Junction boxes for multi-branch distribution
• Sealed connectors for harsh environment applications
• Quick-disconnect systems for field maintenance
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Connectors and Cables
LEVEL 1: COMPONENT LEVEL
• IC package interconnects (BGA, QFP, LGA)
• Passive component terminations
• Test point accessibility
• Thermal management interfaces
LEVEL 2: PCB LEVEL
• On-board trace routing optimization
• Via placement and sizing strategies
• Layer stack-up for signal integrity
• Ground plane continuity maintenance
LEVEL 3: SYSTEM LEVEL
• Inter-PCB connection planning
• Cable harness architecture design
• Connector placement optimization
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Connectors and Cables
CONNECTOR STANDARDS
D-SUB CONNECTORS:
• Standard: DA-15, DB-25, DC-37, DD-50, DE-9
• Applications: Serial, parallel, control
• Current ratings: 5A (per), 13A (max)
• Voltage ratings: 250VAC/350VDC standard
USB CONNECTORS:
• USB-A: Host-side standard connector
• USB-B: Device-side square connector
• USB-C: Reversible, HP capable (100W)
• Micro-USB: Mobile device standard
• Mini-USB: Legacy mobile applications
HIROSE CONNECTORS:
• DF Series: 7.92mm pitch, 30A rating
• GT Series: 3.0mm pitch, 3A rating
• FX Series: 1.25mm pitch, 1A rating
• HR Series: 1-2.5mm pitch, 2-3A rating
MOLEX CONNECTOR SYSTEMS:
• Mini-Fit: 4.2mm pitch (8.5A)
• Micro-Fit: 3.0mm pitch (5A)
• KK: 2.54mm pitch (3A)
• Pico-Blade: 1.25mm pitch (1A)
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Connectors and Cables
SIGNAL CONNECTORS:
• Low-level analog signals (<1V)
• Digital logic levels (3.3V, 5V, 12V)
• High-speed differential pairs
• RF and microwave applications
POWER CONNECTORS:
• DC power distribution (12V, 24V, 48V systems)
• AC mains connections (120VAC, 240VAC)
• High-current applications (>10A per contact)
• Battery interconnections
HYBRID CONNECTORS:
• Combined power and signal in single housing
• Ethernet with PoE (Power over Ethernet)
• USB with power delivery capability
• Multi-function automotive connectors
HIGH-FREQUENCY CONNECTORS:
• Coaxial connectors (SMA, BNC, N-type)
• Board-mount RF connectors
• Millimeter-wave applications
• Impedance-controlled designs (50Ω, 75Ω)
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Connectors and Cables
IP RATING SYSTEM:
IP Code Dust Protection Water Protection Typical Applications
IP44 Protected against 1mm objects Splash resistant Indoor electronics
IP65 Dust tight Water jet resistant Outdoor equipment
IP67 Dust tight Immersion to 1m Marine applications
IP68 Dust tight Continuous immersion Underwater systems
MIL-STD ENVIRONMENTAL CLASSIFICATIONS:
• MIL-STD-810: Environmental testing procedures
• MIL-DTL-38999: Circular connector specifications
• MIL-DTL-83723: Rectangular connector standards
• MIL-STD-1344: Connector reliability testing
• Mating force: 10-50N typical for manual connections
• Insertion cycles: 10-10,000 depending on application
• Vibration resistance: 10-2000Hz, 20G acceleration
• Shock resistance: 50-100G peak acceleration
• Temperature cycling: -55°C to +125°C for military applications
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Connectors and Cables
CABLE TYPES
COAXIAL CABLES:
• Single center conductor with concentric shield
• Controlled impedance (50Ω, 75Ω standard)
• Applications: RF signals, high-speed digital, video
• Construction: Center conductor → Dielectric → Shield → Jacket
Common Coaxial Types:
Cable Type Impedance Center Conductor Dielectric Applications
RG-58 50Ω 20 AWG solid Polyethylene General purpose RF
RG-6 75Ω 18 AWG solid Foam PE Cable TV, satellite
RG-213 50Ω 13 AWG stranded Polyethylene High-power RF
TWISTED PAIR CABLES:
• Balanced transmission line
• Cat5e, Cat6, Cat6A, Cat7, Cat8
• Ethernet, telephony, industrial
Twisted Pair Performance:
Category Bandwidth Max Length Crosstalk (NEXT) Applications
Cat5e 100 MHz 100m 35.3 dB @ 100MHz 1 Gigabit Ethernet
Cat6 250 MHz 100m 39.9 dB @ 100MHz 1 Gigabit Ethernet
Cat6A 500 MHz 100m 42.4 dB @ 500MHz 10 Gigabit Ethernet
Cat7 600 MHz 100m 62.1 dB @ 600MHz 10 Gigabit Ethernet
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Connectors and Cables
SHIELDED CABLES:
• Overall shield (OS): Single shield around conductors
• Individual shield (IS): Shield per conductor pair
• Combined (S/FTP): Overall + individual shields
RIBBON CABLES:
• Multiple parallel conductors in flat configuration
• Standard pitches: 0.05", 0.1", 1.27mm, 2.54mm
• Internal computer connections, test equipment
FLEXIBLE FLAT CABLES & PCB(FFC&FPC):
• Ultra-thin profile (0.1-0.3mm typical)
• High conductor density (0.5mm pitch common)
• Construction: Copper traces on polyimide
IMPEDANCE CHARACTERISTICS:
• Characteristic impedance (Z₀): Function of conductor geometry & dielectric
• Coaxial cable: 𝑍₀ = 60 × 𝑙𝑛(𝐷/𝑑) / √𝜀ᵣ
• Twisted pair: 𝑍₀ = 120 × 𝑙𝑛(2𝑆/𝑑) / √𝜀ᵣ
CONDUCTOR SIZING:
AWG Size Diameter (mm) Resistance (Ω/km) Current Rating (A) Typical Applications
30 0.255 339 0.5 Signal wires
28 0.321 213 0.8 Signal wires
26 0.405 134 1.3 Signal wires
24 0.511 84.2 2.1 Signal/low power
22 0.644 53.0 3.3 Low power
20 0.812 33.3 5.2 Medium power
18 1.024 21.0 8.2 Medium power
16 1.291 13.2 13 High current
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Connectors and Cables
INSULATION MATERIALS:
• PVC: General purpose, -10°C to +70°C, low cost
• Polyethylene: Low dielectric loss, -40°C to +80°C
• PTFE (Teflon): Chemical resistance, -200°C to +260°C
• Polyimide: High temperature, -269°C to +400°C
• XLPE: Cross-linked polyethylene, improved thermal properties
JACKETING MATERIALS:
• PVC: Indoor applications, flame retardant options
• Polyurethane: Flexibility, abrasion resistance
• TPE (Thermoplastic Elastomer): Oil resistance, flexibility
• Fluoropolymers: Chemical resistance, low smoke generation
SHIELDING EFFECTIVENESS:
• Braided shield: 85-95% coverage, 20-40 dB attenuation
• Foil shield: 100% coverage, 10-30 dB attenuation
• Combination: 90-95% braid over foil, 40-80 dB attenuation
• Spiral wrap: 60-80% coverage, 10-20 dB attenuation
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Connectors and Cables
SIGNAL INTEGRITY
PROPAGATION DELAY CALCULATION:
• Velocity of propagation (𝑉𝑝) = 𝑐 / √𝜀ᵣ
• Propagation delay = 𝐿𝑒𝑛𝑔𝑡ℎ / 𝑉𝑝
• Typical values: 1.5-2.0 ns/ft for common cables
• Critical for high-speed digital systems and timing analysis
REFLECTION ANALYSIS:
• Occurs at impedance discontinuities
• Reflection coefficient: 𝜌 = (𝑍₂ − 𝑍₁) / (𝑍₂ + 𝑍₁)
• Standing wave ratio: 𝑆𝑊𝑅 = (1 + |𝜌|) / (1 − |𝜌|)
• Target: 𝑆𝑊𝑅 < 1.5 for good signal quality
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Connectors and Cables
VOLTAGE DROP CALCULATION:
• Vₐᵣₒₚ = I × R × 2 (for DC circuits, round trip)
• R = ρ × L / A (resistance calculation)
• Where: ρ = resistivity, L = length, A = cross-sectional area
CURRENT DERATING FACTORS:
Condition Derating Factor Typical Applications
Single conductor in free air 1.0 Reference condition
Cable bundle (3-6 conductors) 0.8 Harness assemblies
Cable bundle (7-24 conductors) 0.7 Multi-conductor cables
Elevated temperature (+40°C) 0.82 Engine compartments
Elevated temperature (+60°C) 0.71 Industrial ovens
POWER DELIVERY DESIGN EXAMPLE:
• Load: 5V @ 10A
• Cable length: 3 meters
• Voltage drop budget: 2% (0.1V)
• Required wire resistance: 0.1V / 10A = 0.01Ω
• 18 AWG copper: 21.0 Ω/km × 0.006km = 0.126Ω (too high)
• 14 AWG copper: 8.29 Ω/km × 0.006km = 0.050Ω (too high)
• 12 AWG copper: 5.21 Ω/km × 0.006km = 0.031Ω (marginal)
• 10 AWG copper: 3.28 Ω/km × 0.006km = 0.020Ω (acceptable)
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Connectors and Cables
SIGNAL RISE TIME IMPACT:
• Transmission line effects become significant when:
• Cable length > Vp × tᵣᵢₛₑ / 6
• For 2ns rise time: Critical length ≈ 0.3m
• Faster signals require more careful cable design
DIFFERENTIAL PAIR IMPLEMENTATION:
• Common mode rejection improves EMI immunity
• Skew matching: <10% of rise time
• Impedance matching: 100Ω ±10% typical
• Length matching: <5mm for Gbps signals
HIGH-SPEED DESIGN GUIDELINES:
Data Rate Max Skew Impedance Tolerance Length Matching
100 Mbps 1ns ±20% ±10mm
1 Gbps 100ps ±10% ±5mm
10 Gbps 10ps ±5% ±1mm
25 Gbps 4ps ±3% ±0.5mm
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Connectors and Cables
PINOUT & POLARIZATION
POWER PIN PLACEMENT:
• Corner pins for mechanical strength
• Adjacent pins for high current (parallel paths)
• Center pins for sensitive analog supplies
• Separate analog and digital supply pins
GROUND PIN STRATEGY:
• Multiple ground pins for low impedance
• Ground pins adjacent to high-speed signals
• Separate analog and digital grounds
• Shield connection to chassis ground
SIGNAL PIN ASSIGNMENT:
• Differential pairs on adjacent pins
• High-speed signals away from power switching
• Critical signals with dedicated ground returns
• Test points for key signals
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Connectors and Cables
ASYMMETRIC HOUSING DESIGN:
• Trapezoidal profiles prevent 180° rotation
• Chamfered corners indicate proper orientation
• Color coding for visual confirmation
• Tactile feedback for blind mating
DEDICATED KEY FEATURES:
• Plastic keys in connector housing
• Metal guide pins for alignment
• Threaded fasteners for retention
• Bayonet locks for quick connection
KEYING IMPLEMENTATION METHODS:
Keying Type Advantages Disadvantages Applications
Housing shape Low cost, Limited config Simple 2-wire connections
Removable Multiple coding Additional part Modular systems
Pin presence Many combos Manufacturing complexity High-density connectors
size Obvious diff. Space requirements Power vs signal
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Connectors and Cables
PIN 1 IDENTIFICATION:
• Square pin vs round pins
• Colored pin (red for positive)
• Larger pin diameter
• Corner pin designation
HOUSING POLARIZATION:
• Chamfered corners
• Molded alignment features
• Color-coded housings
• Arrow indicators
PCB FOOTPRINT POLARIZATION:
• Silkscreen indicators
• Square pad for pin 1
• Asymmetric hole patterns
• Reference designator placement
CABLE ASSEMBLY POLARIZATION:
• Keyed connectors on both ends
• Wire color coding standards
• Cable marking every meter
• Unique connector types per function
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Connectors and Cables
BOARD-TO-WIRE DESIGN
TERMINAL BLOCKS:
• Screw terminals for field wiring
• Spring clamps for maintenance-free operation
• Rising clamps for solid/stranded wire versatility
• Push-in terminals for quick assembly
TERMINAL BLOCK SPECIFICATIONS:
Terminal Type Wire Range Current Rating Voltage Rating Applications
Screw 2.5mm² 0.2-2.5mm² 17A 300V Control panels
Spring 4mm² 0.2-4.0mm² 32A 500V Industrial automation
Push-in 1.5mm² 0.2-1.5mm² 13A 250V Building automation
PCB mount 6mm² 0.5-6.0mm² 41A 630V Power distribution
WIRE-TO-BOARD CONNECTORS:
• Crimp contacts for reliable connections
• Insulation displacement (IDC) for mass production
• Solderless terminals for prototyping
• Combination power/signal connectors
DIRECT PCB TERMINATION:
• Through-hole solder connections
• Surface mount pad termination
• Wire bonding for fine pitch
• Mechanical strain relief requirements
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Connectors and Cables
MECHANICAL CONSIDERATIONS:
• Component height clearance
• Mating direction accessibility
• PCB thickness compatibility
• Mounting hole placement
ELECTRICAL FOOTPRINT REQUIREMENTS:
• Pad size optimization for soldering
• Thermal relief connections
• Via placement for signal routing
• Ground plane continuity
STANDARD FOOTPRINT DIMENSIONS:
Connector Family Pin Pitch Pad Size Drill Size Applications
Terminal blocks 5.0-7.5mm 2.0mm diam 1.3mm Power connections
Molex KK 2.54mm 1.6mm diam 1.0mm General purpose
JST XH 2.5mm 1.4mm diam 0.9mm Signal connections
Phoenix COMBICON 5.08mm 2.2mm diam 1.4mm Industrial control
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Connectors and Cables
PCB MOUNTING METHODS:
• Through-hole mounting for mechanical strength
• Surface mount for automated assembly
• Mixed mounting for optimal performance
• Mechanical support posts
STRESS RELIEF IMPLEMENTATION:
• Strain relief boots at cable entry
• Cable tie mounting points
• Flexible service loops
• Mechanical decoupling from PCB
MOUNTING HARDWARE:
• Threaded standoffs for panel mounting
• Snap-fit clips for enclosure assembly
• Adhesive mounting for non-critical applications
• Vibration isolation considerations
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Connectors and Cables
BOARD-TO-BOARD DESIGN
HEADERS AND SOCKETS:
• Standard 2.54mm pitch for prototyping
• 2.0mm and 1.27mm for higher density
• Single and double row configurations
• Right-angle variants for space constraints
STACKING CONNECTOR SPECIFICATIONS:
Connector Type Pitch Current Rating Height Range Applications
Standard header 2.54mm 3A per pin 8-25mm Development boards
Mini header 2.0mm 2A per pin 6-20mm Compact systems
Micro header 1.27mm 1A per pin 4-15mm High-density boards
Board-to-board 0.8mm 0.5A per pin 2-10mm Mobile devices
EDGE CONNECTORS:
• Card edge design for easy insertion
• Gold-plated contacts for reliability
• Keying slots for proper orientation
• Retention mechanisms for security
MEZZANINE CONNECTORS:
• High-density parallel connection
• Controlled impedance design
• Power and signal in single connector
• Low-profile configurations available
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Connectors and Cables
MATING CYCLE RATINGS:
• Development/prototyping: 50-100 cycles
• Production testing: 100-500 cycles
• Field service: 500-1,000 cycles
• High-reliability: 10,000+ cycles
INSERTION FORCE CONSIDERATIONS:
• Manual insertion: 2-10N per contact
• Tool-assisted: 10-50N per contact
• Automatic assembly: Force feedback control
• Extraction force: 50-80% of insertion force
FORCE CALCULATION:
• Total force = Contact force × Number of contacts
• Example: 50-pin @ 5N = 250N total
• Consider connector housing friction
• Design for available insertion equipment
CONTACT DENSITY OPTIMIZATION:
• 0.4-0.8mm pitch for high-density applications
• Area array contacts for maximum density
• Multi-row configurations
• Micro-miniature contact technology
SIGNAL INTEGRITY IN HIGH-DENSITY DESIGNS:
• Controlled impedance pathways
• Ground contact placement strategy
• Power distribution architecture
• EMI containment methods
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Connectors and Cables
HARNESS DESIGN
CABLE BUNDLING STRATEGY:
• Group by function (power, signal, data)
• Separate high-current from sensitive signals
• Maintain consistent bundle diameter
ROUTING OPTIMIZATION:
• Minimize cable length while maintaining service access
• Avoid sharp bends and stress concentrations
• Provide strain relief at all termination points
HARNESS ARCHITECTURE TYPES:
Architecture Advantages Disadvantages Applications
Point-to-point Simple, reliable Many individual cables Small systems
Star topology Centralized control Single point of failure Automotive body control
Bus topology Efficient wiring Protocol complexity Industrial fieldbus
Hybrid design Optimized Design complexity Complex systems
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Connectors and Cables
MINIMUM BEND RADIUS GUIDELINES:
• Single conductor: 4 × cable diameter
• Multi-conductor: 6 × cable diameter
• Coaxial cable: 5 × cable diameter
• Fiber optic: 10 × cable diameter
DYNAMIC BEND RADIUS (FLEXING APPLICATIONS):
• Continuous flexing: 10-20 × static bend radius
• Cycle life dependent on bend radius
• Temperature effects on flexibility
• Stress concentration at bend points
STRAIN RELIEF IMPLEMENTATION:
• Boot-style strain reliefs for standard cables
• Cord grips for panel-mount applications
• Service loops for equipment movement
• Mechanical decoupling from connectors
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Connectors and Cables
HARNESS DOCUMENTATION REQUIREMENTS:
• Schematic diagram with pin assignments
• Assembly drawing with routing details
• Cable schedule with specifications
• Test procedures and acceptance criteria
WIRE IDENTIFICATION SYSTEMS:
• Color coding per application standards
• Printed markers at regular intervals
• Heat-shrink labels for permanent marking
• Cable tags for individual identification
STANDARD WIRE COLOR CODES:
Function IPC Standard Aerospace Industrial
Power (+) Red Red Brown
Power (-) Black Black Blue
Ground Green Green Green
Signal Various Various Various
MANUFACTURING SPECIFICATIONS:
• Strip length, strand count
• Crimp specifications, pull tests
• Routing sequence, bundle diameter
• Test Continuity, isolation etc.
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Connectors and Cables
TERMINATION TECHNIQUES
CRIMPING SPECIFICATIONS:
Gauge Length Force Pull Contacts
30 AWG 2-3mm 200-400N 4.5kg Micro-miniature
26 AWG 3-4mm 400-800N 6.8kg Signal
22 AWG 4-5mm 800-1200N 11.3kg Power
18 AWG 5-6mm 1200-2000N 18.1kg Hi-Current
QUALITY FACTORS:
• Wire preparation: Proper strip length, strand control
• Crimp tool calibration: Force and dimensional control
• Contact selection: Wire gauge compatibility
• Inspection criteria: Visual and dimensional checks
SOLDERING TECHNIQUES:
• Thermal connection with metallurgical bond
• Flux selection for oxidation prevention
• Temperature and time control
• Joint inspection and rework procedures
SOLDER JOINT QUALITY:
• Wetting angle: <90°
• Fillet formation: Concave profile
• Intermetallic layer: 1-3μm thickness
• Void content: <25% for reliability
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Connectors and Cables
CONNECTOR SELECTION
VOLTAGE RATINGS:
• Working voltage: Maximum continuous operating voltage
• Withstand voltage: Short-term overvoltage capability
• Breakdown voltage: Insulation failure threshold
• Altitude derating: Voltage reduction at high altitude
CURRENT RATINGS AND DERATING:
• Continuous current: Steady-state capability
• Peak current: Short-term overload capability
• Temperature derating: Current reduction at elevated temperature
• Contact resistance: Voltage drop at rated current
CURRENT DERATING FACTORS:
Ambient Temperature Derating Factor Altitude Derating Factor
+23°C 1.00 Sea level 1.00
+40°C 0.90 3,000m 0.95
+60°C 0.75 6,000m 0.85
+80°C 0.60 10,000m 0.70
INSULATION RESISTANCE:
• Minimum values: 1000 MΩ for low-voltage applications
• Environmental effects: Humidity, contamination
• Measurement conditions: Standard test voltage and time
• Aging effects: Degradation over time
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Connectors and Cables
TEMPERATURE PERFORMANCE:
• Operating temperature range
• Storage temperature range
• Thermal shock resistance
• Thermal cycling endurance
VIBRATION AND SHOCK RESISTANCE:
• Sine wave vibration: Frequency and amplitude
• Random vibration: Power spectral density
• Shock resistance: Peak acceleration and duration
• Mechanical resonance considerations
CHEMICAL RESISTANCE:
• Fluid compatibility: Oils, solvents, cleaning agents
• Corrosion resistance: Salt spray, acidic environments
• Outgassing: Space and medical applications
• UV resistance: Outdoor applications
ENVIRONMENTAL TEST STANDARDS:
Test Parameter Test Standard Typical Requirements
Temperature cycling IEC 60068-2-14 -40°C to +85°C, 100 cycles
Humidity IEC 60068-2-78 85°C, 85% RH, 1000 hours
Vibration IEC 60068-2-6 10-2000Hz, 10G, 2 hours
Shock IEC 60068-2-27 50G, 11ms duration
Salt spray IEC 60068-2-11 5% NaCl, 96 hours
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