If you've ever received a spec sheet requiring "IPC Class 2" or wondered what makes an aerospace harness different from a consumer product, you've encountered IPC/WHMA-A-620. This standard—formally titled "Requirements and Acceptance for Cable and Wire Harness Assemblies"—is the global benchmark for wire harness quality.
Understanding A-620 isn't just about compliance checkboxes. It's about speaking a common language with customers, setting clear quality expectations, and building harnesses that perform reliably in their intended applications. Let's break it down.
What is IPC/WHMA-A-620?
IPC/WHMA-A-620 is a joint standard developed by IPC (Association Connecting Electronics Industries) and WHMA (Wire Harness Manufacturers Association). First published in 2002 and regularly updated (current version is A-620D), it provides visual and measurable criteria for evaluating wire harness quality.
A-620 Covers:
Wire Preparation
Cutting, stripping, tinning requirements
Crimping
Terminal crimps, splice crimps, insulation crimps
Soldering
Hand soldering, pot tinning, heat shrink
Assembly
Connector assembly, lacing, bundling, labeling
Protection
Sleeving, molding, potting, strain relief
Testing
Electrical test requirements and documentation
The standard defines three product classes, each with progressively stricter requirements. Your customer's specification determines which class applies—and that drives every quality decision from design through inspection.
Class 1 vs Class 2 vs Class 3: Which Do You Need?
The three classes aren't about "good, better, best"—they're about matching quality requirements to product end-use. Applying Class 3 criteria to a Class 1 product wastes money; applying Class 1 criteria to a Class 3 product invites failure.
| Aspect | Class 1 | Class 2 | Class 3 |
|---|---|---|---|
| Description | General Electronic Products | Dedicated Service Products | High Performance Products |
| Typical Applications | Consumer electronics, toys, appliances | Industrial, automotive, commercial | Aerospace, military, medical life support |
| Failure Consequence | Inconvenience | Equipment damage, downtime | Safety critical, life-threatening |
| Inspection Level | Sampling acceptable | Increased sampling | 100% inspection typical |
| Documentation | Basic | Detailed | Complete traceability |
| Cost Impact | Baseline | +15-25% | +40-80% |
"I often see customers request Class 3 because they think it means 'highest quality.' But for a commercial HVAC controller, Class 3 adds cost without benefit—Class 2 provides the right reliability level. Match the class to the application, not to your aspirations."
Hommer Zhao
Quality Engineering Manager
Key Inspection Criteria
A-620 uses three acceptance levels for each criteria: Target (ideal), Acceptable (meets requirements), and Defect (reject). The strictness increases from Class 1 to Class 3—what's acceptable in Class 1 might be a defect in Class 3.
Wire Stripping Criteria
| Criteria | Class 1 | Class 2 | Class 3 |
|---|---|---|---|
| Nicked strands | <20% of strands | <10% of strands | No nicked strands |
| Severed strands | <10% of strands | None visible | None allowed |
| Insulation damage | Minor acceptable | No exposed conductor | Pristine required |
Connector Pin/Socket Criteria
| Criteria | Class 1 | Class 2 | Class 3 |
|---|---|---|---|
| Terminal seating | Functional | Flush ± tolerance | Perfect seating |
| Pin damage | Minor bends OK | No functional impact | No damage visible |
| Retention force | Per spec | Per spec + margin | 100% verified |
Crimping Requirements by Class
Crimping is where A-620 gets very specific. The standard defines measurable criteria for crimp height, bellmouth, conductor visibility, and insulation support. These are the numbers your quality team checks daily.
| Crimp Attribute | Class 1 & 2 | Class 3 |
|---|---|---|
| Crimp Height | Within manufacturer spec | Within tighter tolerance (typically ±0.05mm) |
| Bellmouth (Front) | Visible, protects strands | Required, measurable per spec |
| Conductor Visibility | Strands visible in inspection window | Full conductor engagement verified |
| Insulation Crimp | Grips insulation, no conductor damage | Defined gap from conductor crimp |
| Pull Force Testing | Sampling per AQL | 100% or destructive sample from each setup |
Critical: Crimp Cross-Section Analysis
Class 3 often requires cross-section analysis of crimps to verify proper conductor compression and void-free termination. This destructive test is performed on samples from production runs, adding time and cost but ensuring absolute reliability.
For detailed crimping techniques, see our crimping best practices guide.
Soldering Standards
While crimping dominates modern harness manufacturing, soldering still applies to PCB connections, shielding terminations, and specialty applications. A-620 references IPC J-STD-001 for soldering workmanship, with class-specific requirements.
Class 1
- Solder wetting visible
- Minor voids acceptable
- Touch-up allowed
- Visual inspection only
Class 2
- Good wetting required
- Limited voids
- Controlled touch-up
- Magnification inspection
Class 3
- Excellent wetting required
- No visible voids
- Restricted rework
- 100% magnified inspection
Harness Assembly Requirements
Beyond individual connections, A-620 specifies how the complete harness should look and function. These assembly-level requirements cover wire routing, bundling, and protection.
Wire Routing & Bundling
Wires should follow natural paths without excessive tension or sharp bends. Minimum bend radius is typically 10× wire diameter for solid wire, 6× for stranded.
Lacing & Tie Wraps
Lacing patterns must be consistent and tight. Cable ties must not cut into insulation. Class 3 typically requires lacing over tie wraps in critical areas.
Strain Relief
Every connector must have appropriate strain relief to prevent wire stress at termination points. Boot molding or backshells required for Class 2/3.
Labeling & Marking
Wire labels must be legible, permanent, and positioned per drawing. Class 3 requires lot traceability on labels.
Protective Covering
Sleeving, conduit, and spiral wrap must be properly secured and provide specified coverage. No gaps exposing wires in Class 2/3.
Documentation & Traceability
Documentation requirements escalate dramatically from Class 1 to Class 3. What's optional for consumer products becomes mandatory for aerospace applications.
| Document Type | Class 1 | Class 2 | Class 3 |
|---|---|---|---|
| Inspection Records | Optional | Required | Detailed per unit |
| Material Certs | On request | Maintained | Lot traceable |
| Test Reports | Summary | Per lot | Per serial number |
| Operator Training | Basic | Certified | Certified + recurrent |
| Record Retention | 1-2 years | 5+ years | Product lifetime |
"For Class 3 aerospace harnesses, we can tell you exactly which spool of wire, which lot of terminals, and which operator built any harness we've ever shipped. When an aircraft is in service for 30+ years, that traceability isn't paperwork—it's a safety requirement."
Hommer Zhao
Quality Engineering Manager
Getting IPC/WHMA-A-620 Certified
Certification demonstrates your facility and personnel meet A-620 requirements. IPC offers multiple certification paths:
CIS - Certified IPC Specialist
Operators and inspectors who apply A-620 criteria daily. Training covers visual inspection, measurement techniques, and acceptance decisions.
- 3-day training course
- Written and practical exams
- 2-year certification validity
CIT - Certified IPC Trainer
Master trainers who can certify CIS candidates in-house. Reduces ongoing training costs for larger operations.
- 5-day intensive training
- Must pass CIS first
- Can certify unlimited CIS
View our certifications page to see our current IPC certifications and quality credentials.
Frequently Asked Questions
Is A-620 certification mandatory?
No, A-620 is a voluntary consensus standard. However, many customers—especially in automotive, aerospace, and medical—require it contractually. Without certification, you may be excluded from certain markets.
What's the difference between A-620 and J-STD-001?
A-620 covers wire harness/cable assembly workmanship, while J-STD-001 covers soldering to PCBs. They overlap where harnesses connect to boards, and A-620 references J-STD-001 for those requirements.
Can we self-certify to A-620?
You can train to the standard and implement its requirements, but formal certification requires IPC-authorized training. Self-declaration without certified personnel may not satisfy customer audits.
How often do we need recertification?
CIS certification is valid for 2 years. CIT must recertify when new standard revisions are released (typically every 3-5 years). Many companies recertify annually to maintain proficiency.
Related Resources
About the Author
Hommer Zhao is a Quality Engineering Manager with IPC-A-620 CIT certification. He has trained over 200 operators and inspectors in A-620 standards and led quality systems development for automotive and aerospace harness programs. His practical approach helps manufacturers achieve compliance without unnecessary complexity.
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