If you've ever received a spec sheet requiring "IPC Class 2" or "IPC/WHMA-A-620 Class 3," or wondered what makes an aerospace harness different from a consumer product, you've encountered IPC/WHMA-A-620—often shortened to IPC 620. This standard, formally titled "Requirements and Acceptance for Cable and Wire Harness Assemblies," is the global benchmark for wire harness quality.
This guide is written for buyers and quality engineers who need to specify, source, or verify IPC/WHMA-A-620 compliant wire harnesses without wading through the full 400-page standard. We cover what each class actually requires, the specific crimp, solder, splice, and marking criteria inspectors use, what changed across revisions B through E, how A-620 relates to IPC-A-610 and J-STD-001, and exactly how to confirm a supplier really builds to it. As an assembly partner, our operators work to A-620 acceptance criteria every day—so this is the same framework we use on the shop floor.
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 revised roughly every three to five years, it provides visual and measurable criteria for evaluating the quality of a cable harness. It is the harness-assembly counterpart to the broader family of IPC electronics standards. If your program requires it, see how we document IPC/WHMA-A-620 conformance at our facility.
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.
Revisions: A-620B, C, D & E (Why the Letter Matters)
A common source of confusion in RFQs is the revision letter. IPC/WHMA-A-620 is periodically re-balloted, and each revision refines the acceptance criteria—so an "IPC/WHMA-A-620 Class 3" callout means slightly different things under revision B than under revision E. The letter is not decoration; it defines which acceptance limits your inspector will actually apply.
| Revision | What It Represents |
|---|---|
| A-620 (2002) | Original release—the first industry-consensus acceptance standard dedicated to cable and wire harness assemblies. |
| A-620B | Widely adopted revision still cited on many legacy drawings; if a print says "IPC/WHMA-A-620B," build and inspect to that edition, not a newer one. |
| A-620E / A-620D | Refined crimp, splice, and connector criteria and expanded coverage of newer termination and sealing technologies. |
| A-620E | Latest revision; continues to tighten and clarify acceptance criteria and align with related IPC documents. When a customer specifies "IPC/WHMA-A-620E," confirm your operators are trained to that edition. |
Buyer tip: pin the revision before first article
Write the full callout on your drawing or purchase order—for example "IPC/WHMA-A-620E, Class 3"—rather than a bare "IPC 620." If the revision is left open, agree on it with your supplier before first-article inspection so acceptance limits aren't disputed after parts are built.
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% |
A common issue is 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.
OurPCB Engineering Team
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."
OurPCB Engineering Team
Quality Engineering Manager
A-620 vs IPC-A-610 vs J-STD-001
These three IPC documents are constantly mixed up in specifications, yet they judge different things. Getting the reference right on your drawing prevents a supplier from applying the wrong acceptance criteria.
| Standard | What It Governs | Use It To Judge |
|---|---|---|
| IPC/WHMA-A-620 | Cable and wire harness assembly workmanship | Crimps, splices, connectors, lacing, protection on a harness |
| IPC-A-610 | Acceptability of populated printed circuit boards | Component placement and solder joints on a PCB |
| J-STD-001 | Soldered electrical and electronic assemblies (process requirements) | The soldering process itself, referenced by both A-620 and A-610 |
In short: use A-620 to accept a harness, IPC-A-610 to accept a circuit board, and J-STD-001 for the underlying solder process. All three share the same Class 1/2/3 model, so a "Class 3" program is consistent across them. For a broader look at how these sit alongside product and management-system certifications, see our roundup of the top wire harness certifications and how UL vs CSA vs CE marks differ from workmanship standards.
How to Verify a Supplier Builds A-620 Compliant Wire Harnesses
"We build to IPC/WHMA-A-620" is easy to write on a website. Because A-620 defines workmanship you build to—not a company-wide accreditation like ISO 9001—the burden is on the buyer to confirm it's real. Here's the evidence a genuine A-620 shop can produce on request:
Current CIS / CIT certificates
Ask for Certified IPC Specialist (CIS) or Certified IPC Trainer (CIT) certificates for the operators and inspectors on your job—and check they are still within their validity window.
The specific revision and class
A compliant supplier states exactly what they build to (e.g. "A-620E, Class 3") rather than a vague "IPC compliant." Vagueness here is a red flag.
First-article & crimp cross-section reports
Request a sample first-article inspection report and, for Class 3, crimp cross-section (micro-section) analysis showing proper conductor compression and void-free termination.
Traceability records
For Class 2/3, the shop should show lot traceability linking wire spool, terminal lot, and operator to a finished harness serial number.
A documented quality system behind it
A-620 workmanship lives inside a quality system. Confirm how it is controlled on the floor—our own approach is described on our quality capabilities page.
Want to go deeper on supplier audits? See how we run quality control and inspection, the certifications we hold and follow, and a worked example of an A-620–built JST connector assembly.
Common Misconceptions About IPC 620
Myth: "Class 3 always means better quality."
Reality: Class 3 means tighter acceptance limits for high-performance, safety-critical products—at 40–80% higher cost. For most commercial and industrial harnesses, Class 2 is the correct, more economical target. Higher class ≠ better value.
Myth: "A-620 certifies the company."
Reality: A-620 certifies people (CIS/CIT) and defines how work is accepted. There is no company-wide 'A-620 certified' stamp the way ISO 9001 or IATF 16949 accredit an organization. Judge the operators and the evidence, not a logo.
Myth: "IPC 620 and IPC 610 are interchangeable."
Reality: They are separate standards—A-620 for harnesses, A-610 for circuit boards. Citing the wrong one on a drawing can send your harness to the wrong acceptance criteria.
Myth: "The revision letter doesn't matter."
Reality: It does. Acceptance limits shift between revisions B, C, D and E. A bare 'IPC 620' with no revision or class is an incomplete spec that invites disputes at inspection.
Myth: "Once a crimp looks fine, it passes."
Reality: Visual acceptance is only part of it. A-620—especially Class 3—backs the visual criteria with pull-force testing and crimp cross-section analysis to catch problems the eye can't see.
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.
"IPC/WHMA-A-620 Standards: Class 1 vs Class 2 vs Class 3 only becomes production-ready after measurable validation. That usually means 100% continuity, a defined insulation threshold such as 500 VDC, and one application-specific check tied to IEC 60529, UL, or the customer's own spec."
Frequently Asked Questions
What is IPC/WHMA-A-620 (IPC 620)?
IPC/WHMA-A-620, often shortened to IPC 620, is the joint IPC and WHMA standard titled "Requirements and Acceptance for Cable and Wire Harness Assemblies." It is the industry benchmark that defines target, acceptable, and defect conditions for wire preparation, crimping, soldering, connectorization, and protection of cable and wire harness assemblies.
What is the difference between Class 1, Class 2, and Class 3?
Class 1 (General Electronic Products) prioritizes function for consumer-grade items. Class 2 (Dedicated Service Products) adds reliability for industrial, automotive, and commercial equipment and is the most common default. Class 3 (High Performance Products) is the strictest tier, used for aerospace, military, and life-supporting medical harnesses where failure is safety-critical—it typically requires 100% inspection, tighter crimp tolerances, and full traceability.
What does IPC/WHMA-A-620 Class 3 require?
Class 3 requires the tightest acceptance limits in the standard: no nicked or severed strands, crimps within tighter tolerance (often verified by cross-section analysis), 100% inspection rather than sampling, controlled or restricted rework, magnified solder inspection with no visible voids, and complete lot-level traceability of wire, terminals, and operators for the life of the product.
What's the difference between IPC/WHMA-A-620 and IPC-A-610?
IPC-A-610 covers acceptability of electronic assemblies (populated printed circuit boards), while IPC/WHMA-A-620 covers cable and wire harness assemblies. They share the same three-class model and cross-reference each other, but you use A-620 to judge a harness and A-610 to judge a PCB. Soldering workmanship in both points to IPC J-STD-001.
What changed between IPC/WHMA-A-620 revisions B, C, D and E?
The standard is revised roughly every 3–5 years (…B, C, D, and the latest revision E), each edition refining crimp, splice, and marking criteria and adding coverage for newer connector and sealing technologies. Because acceptance limits can shift between revisions, your drawing or purchase order should state exactly which revision applies (for example "IPC/WHMA-A-620E, Class 3"); if it doesn't, confirm it before first article rather than at inspection.
How do I verify a supplier builds IPC/WHMA-A-620 compliant wire harnesses?
Ask for current CIS or CIT certificates for the operators and inspectors on your job, the specific revision and class they build to, sample first-article inspection and crimp cross-section reports, and their traceability records. A genuine A-620 shop can show these on request. Note that A-620 defines workmanship you build to—it is not a company-wide accreditation like ISO 9001 or IATF 16949.
Is IPC/WHMA-A-620 certification mandatory?
No, A-620 is a voluntary consensus standard. However, many customers—especially in automotive, aerospace, and medical—require it contractually, so building and inspecting to it is effectively mandatory to compete in those markets.
Related Resources
About the Author
OurPCB Engineering Team has trained over 200 operators and inspectors in A-620 standards and led quality systems development for automotive and aerospace harness programs. The team's practical approach helps manufacturers achieve compliance without unnecessary complexity.
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