IPC/WHMA-A-620E: Cable & Wire Harness Guide
IPC/WHMA-A-620E represents the internationally recognized technical consensus standard titled 'Requirements and Acceptance for Cable and Wire Harness Assemblies'. Jointly published by the Association Connecting Electronics Industries (IPC) and the Wiring Harness Manufacturer's Association (WHMA), Revision E (released in late 2022) establishes comprehensive visual acceptance criteria, mechanical specifications, and electrical testing protocols for manufactured cable and wire harnesses across aerospace, defense, automotive, medical, and industrial electronics.
Full Form and Architecture: IPC/WHMA-A-620 Revision E Overview
The full form of the standard encapsulates its institutional origins: IPC (historically the Institute for Printed Circuits, now known as the Association Connecting Electronics Industries) and WHMA (Wiring Harness Manufacturer's Association). Designated as Revision 'E', this current edition serves as the universal contractual benchmark between original equipment manufacturers (OEMs) and cable harness sub-contractors worldwide, establishing clear visual definitions for Acceptable, Target, Defect, and Process Indicator assembly conditions.
The standard structures all manufacturing tolerances around three distinct product end-use classes. Class 1 (General Electronic Products) covers everyday consumer electronics and toys where primary cosmetic perfection is secondary to basic functional operation. Class 2 (Dedicated Service Electronic Products) covers commercial computing, communications, and industrial machinery where uninterrupted service and extended life are required. Class 3 (High Performance / Harsh Environment Electronic Products) governs mission-critical aerospace, military avionics, automotive safety, and life-support medical systems where zero downtime is tolerated and equipment must withstand extreme vibration, thermal shock, and mechanical stress.
Review the detailed comparison and breakdown in the table below:
| IPC Product Class | Industry Classification | End-Use Equipment Examples | Acceptance Philosophy |
|---|---|---|---|
| Class 1 | General Electronic Products | Consumer appliances, toys, everyday electronics | Cosmetic flaws permitted; functional survival prioritized |
| Class 2 | Dedicated Service Products | Telecom, commercial servers, industrial tools | High reliability required; uninterrupted service needed |
| Class 3 | High Performance / Harsh Environment | Military avionics, space exploration, medical implants | Zero failure allowed; harsh vibration and thermal survival |
| Space Addendum | Spaceflight Hardware (-S) | Satellites, space station launch payloads | Extremely stringent vibration, outgassing, & radiation rules |
Classification Tiers: Class 1, Class 2, and Class 3 Performance Mandates
Mechanical crimp termination represents one of the most rigorously detailed sections of IPC/WHMA-A-620E. The standard dictates precise geometric criteria for open-barrel stamped and closed-barrel machined crimps. Inspectors examine conductor brush length (the bare wire strands extending forward past the crimp barrel), insulation support crimp wrap, bellmouth flare dimensions on both the front and rear edges of the conductor crimp, and verify that zero wire strands are severed, folded back, or caught outside the crimp wings.
Soldered terminations and ultrasonic wire welding are governed by exacting metallurgical standards. The standard outlines acceptable solder fillet wicking heights, mandatory 100% visual wetting angles, and strict limits on cold solder joints, fractured fillets, or excessive insulation burning caused by soldering iron dwell times. For ultrasonic wire splices—ubiquitous in modern automotive battery harnesses—Revision E specifies strict weld nugget consolidation, ensuring individual copper strands are fused into a solid, void-free metal matrix without over-compression cracks.
Examine the key benchmarks and metrics outlined in the table below:
| Inspection Feature | Target Condition (Optimal) | Acceptable (Class 3) | Defect Condition (Class 3) |
|---|---|---|---|
| Conductor Brush Extension | Strands extend flush to 1.0mm past barrel | Strands visible past barrel; do not impede mating | Strands do not extend past barrel or block latch |
| Rear Bellmouth Flare | Visible bellmouth on wire entry edge | Bellmouth depth 1x to 2x sheet metal thickness | Zero bellmouth; sharp edge cuts wire strands |
| Insulation Clearance | 1 wire diameter clearance from crimp | Insulation visible before crimp barrel | Insulation crimped inside conductor barrel |
| Cut Strand Count (Class 3) | Zero severed wire strands | Zero cut or damaged strands allowed | Any severed strand on Class 3 is a mandatory defect |
| Solder Wetting Angle | Concave fillet with wetting angle < 90° | Fillet covers 75% of terminal contour | De-wetting, balling, or cold solder fracture |
Inspection Criteria: Crimp Quality, Insulation Clearance, and Soldering
Finally, IPC/WHMA-A-620E mandates rigorous non-destructive electrical verification and environmental testing. Assembled harnesses must undergo 100% electrical continuity testing, pin-to-pin wiring diagram verification, short-circuit isolation checks, and high-voltage dielectric withstand testing (Hi-Pot) up to 1,500VDC to detect microscopic insulation pinholes. The standard also provides formal training and workforce certification pathways—Certified IPC Trainer (CIT) and Certified IPC Specialist (CIS)—ensuring technicians maintain verified competency.
Consult the specifications and reference data in the table below:
| Test Type | Test Parameter | Failure Criteria | Mandatory Class |
|---|---|---|---|
| Electrical Continuity | Point-to-point connection verification | Open circuits or resistance > specified limit | 100% Mandated (Classes 1, 2, and 3) |
| Short Circuit / Miswire | Pin-to-pin isolation check | Crossed wires, shorts, high-resistance leakage | 100% Mandated (Classes 1, 2, and 3) |
| Dielectric Withstand (Hi-Pot) | 500V to 1,500V applied potential | Arcing or dielectric insulation breakdown | Mandated on high-voltage and Class 3 lines |
| Mechanical Pull-Force Test | Tensile pull test on crimped terminal | Wire pulls out below ASTM B913 pull-force | Destructive lot sample testing |
| Crimp Cross-Sectioning | Microsection polish & etch under microscope | Internal voids, loose strands, cracked barrel | Mandated for automated crimp tool validation |
How to Inspect a Wire Crimp to IPC-A-620E Standards
A step-by-step quality control inspection procedure to evaluate a crimped wire terminal against IPC/WHMA-A-620E criteria.
Verify Correct Wire Gauge and Terminal Match
Confirm that the American Wire Gauge (AWG) matches the manufacturer terminal crimp specification and approved tooling dies.
Inspect Conductor Strip Length and Strands
Ensure the insulation strip length is correct, wire strands are straight without excessive twist, and zero strands are severed or frayed.
Examine Rear Bellmouth Flare
Under an illuminated 10x inspection loupe, verify that a visible bellmouth flare exists at the wire entry edge to prevent sharp strand cutting.
Check Conductor Brush Extension
Confirm that bare conductor strands extend visibly past the front edge of the wire crimp barrel without obstructing the terminal mating interface.
Measure Crimp Height with a Blade Micrometer
Measure the finished conductor crimp height using a calibrated digital crimp micrometer to confirm it falls within engineering tolerances.
Frequently Asked Questions (8 Questions Answered)
Q1: What does IPC/WHMA-A-620E stand for?
It stands for Association Connecting Electronics Industries / Wiring Harness Manufacturer's Association Standard A-620 Revision E: 'Requirements and Acceptance for Cable and Wire Harness Assemblies'.
Q2: What is the difference between Revision D and Revision E of IPC-620?
Revision E (released in 2022) updated ultrasonic welding criteria, expanded lead-free soldering rules, clarified overmolding criteria, and aligned Class 3 requirements for harsh environments.
Q3: What are the three product classes in IPC/WHMA-A-620E?
Class 1 is General Electronic Products (consumer), Class 2 is Dedicated Service Products (commercial/telecom), and Class 3 is High Performance Products (aerospace, defense, medical).
Q4: Can any cut strands be accepted in a Class 3 wire crimp?
No. Under IPC/WHMA-A-620E Class 3 criteria, zero cut, severed, or damaged wire strands are permitted during wire stripping and crimping.
Q5: What is a 'bellmouth' on a crimp terminal?
A bellmouth is a slight outward flare at the edge of the crimp barrel that acts like a trumpet horn, preventing the sharp edge of the metal barrel from nicking or shearing wire strands.
Q6: What is the conductor brush in IPC-620?
The conductor brush refers to the ends of the bare wire strands that must extend visibly forward past the conductor crimp wings without interfering with the contact mating area.
Q7: What certifications are available for IPC/WHMA-A-620?
The two primary certifications are Certified IPC Specialist (CIS) for assembly technicians and Certified IPC Trainer (CIT) for instructors who train internal corporate staff.
Q8: Is electrical testing mandatory under IPC/WHMA-A-620E?
Yes, 100% electrical testing for continuity and pin-to-pin shorts is mandatory across all classes to guarantee the finished cable harness functions correctly.
Final Thoughts & Key Takeaways
In conclusion, understanding ipc/whma-a-620e: cable & wire harness guide provides essential clarity, practical strategies, and actionable advice. By incorporating these foundational insights, adhering to verified safety guidelines, and following structured best practices, you ensure reliable, long-term outcomes while preventing common mistakes. Stay informed, consult certified professionals when needed, and maintain consistent quality care.