Direct answer: IPC/WHMA-A-620[1] is the acceptance standard for cable and wire harness assemblies, defining three workmanship classes—Class 1, Class 2, and Class 3—with progressively stricter inspection and documentation requirements (for related inspection guidance, see What Is a Cable Tester? Function and Quality Inspection Uses), used to judge whether crimp, solder, and insulation displacement terminations can be released for volume production.
At a Glance
IPC/WHMA-A-620 is not a single pass/fail threshold. It is a condition-based acceptance standard that sorts each observed solder, crimp, or insulation displacement condition into target, acceptable, defect, or process indicator categories. Before approving any first-article cable assembly, the buyer must fix the applicable class and demand measured evidence, not a verbal compliance claim.
Do Either of These First-Article Scenarios Sound Familiar?
A procurement manager is looking at a first-article cable assembly shipment where three crimp terminals show visibly different barrel forms. The supplier’s cover letter says only “IPC/WHMA-A-620 compliant.” A design engineer is reviewing a first-article report where pull force is listed as “pass” with no measured value, and must decide whether that is enough to release tooling.
Both decision-makers are being asked to approve a production order today against an acceptance boundary that was never stated as a class, a condition category, or a measured result. For OEM buyers evaluating a custom cable assembly, this gap between supplier claims and documented acceptance evidence is common. The standard does not resolve the question by itself; what matters is whether the buyer has tied the inspection to a specific class and required the right evidence.
Which IPC/WHMA-A-620 Class Should Apply to This Wire Harness or Cable Assembly?
IPC/WHMA-A-620, published by IPC and WHMA, is not a single pass/fail threshold. It defines Class 1, Class 2, and Class 3 acceptance requirements that change with end-use risk. The same crimp condition can be acceptable under Class 1 and rejectable under Class 2 or Class 3, so the class must be written into the drawing, purchase order, or first-article checklist before inspection.
The decision step is straightforward: ask whether the assembly goes into general-purpose equipment, high-reliability industrial equipment, or an application where field failure creates unacceptable risk. Do not let the supplier default silently to Class 1. When a wire harness manufacturer receives a drawing without a class callout, the supplier may use the least demanding class, which can leave higher-risk applications under-specified.
Buyers must also avoid a common trap in electrical testing: under IPC/WHMA-A-620 Section 18, dielectric withstanding voltage (DWV) and insulation resistance (IR) testing are not automatically mandated by class alone—they must be explicitly specified on the engineering drawing or purchase order. Once specified without custom parameters, IPC/WHMA-A-620 provides default test levels that scale from Class 2 to Class 3 based on conductor clearance distance and cable construction. These parameters should be locked into the drawing callout rather than left to vendor discretion.
Is That Crimp Condition Target, Acceptable, Defect, or a Process Indicator?
IPC/WHMA-A-620 operates as a condition-based system. An observed condition is categorized as target, acceptable, defect, or process indicator, not merely “passed” or “failed.” A crimp termination condition in one of these categories carries a different disposition requirement.
A process indicator can pass go/no-go inspection while still requiring corrective action because it reveals drift in tooling, operator practice, or material handling (see How Manufacturers Ensure Consistent Cable Assembly Quality). Examples of process indicators include minor bellmouth asymmetry, crimp flash within limits, uneven insulation support wings, or partial conductor brush retention; these should be documented and trended before volume production. By contrast, a crimp height or indentation outside the terminal manufacturer’s specified range, missing bellmouth, or severed strands beyond class limits is a defect and must be rejected through the nonconformance process, not treated as a process indicator. Accepting “passed” without knowing whether the condition was target or process indicator leaves the production order exposed to systematic variation.
Go/No-Go Acceptance Table for Cable Assemblies
The table below maps class, termination type, and IPC/WHMA-A-620 condition categories to practical first-article disposition and required evidence. While IPC/WHMA-A-620 classifies both Target and Acceptable conditions as passable without restriction—and treats Process Indicators as non-rejectable conditions that signal process drift—buyers during first-article inspection (FAI) should hold volume tooling release if a Process Indicator appears until root cause and Cpk stability are verified.
| Termination Type | Class | Target (IPC Pass) | Acceptable (IPC Pass) | Defect (IPC Reject) | Process Indicator (IPC Pass / FAI Hold) | Required FAI Evidence |
|---|---|---|---|---|---|---|
| Crimp termination | Class 1 | Approve | Approve | Reject (NCR required) | Pass lot; log & trend before volume | Measured pull force or crimp height vs. terminal spec |
| Crimp termination | Class 2 | Approve | Approve | Reject (NCR required) | Pass unit; require tooling adjustment & re-sample | Measured pull force and crimp height / Bellmouth check; insulation support check |
| Crimp termination | Class 3 | Approve | Approve | Reject (NCR required) | Hold volume release; corrective action & Cpk verification | Measured pull force, crimp height, cross-section micrograph (if specified), and strain relief verification |
| Solder termination | Class 1 | Approve | Approve | Reject (NCR required) | Pass lot; log & trend | Visual inspection of solder fillet, wetting, and insulation clearance |
| Solder termination | Class 2 | Approve | Approve | Reject (NCR required) | Pass unit; adjust thermal profile & re-sample | Fillet shape and circumferential wetting photos; insulation clearance check |
| Solder termination | Class 3 | Approve | Approve | Reject (NCR required) | Hold volume release; documented corrective action | High-magnification fillet wetting, birdcaging/wicking check, and clearance data |
| Insulation displacement (IDC) | Class 1 | Approve | Approve | Reject (NCR required) | Pass lot; log & trend | Conductor seating, end-stop position, and displacement depth vs. connector spec |
| Insulation displacement (IDC) | Class 2 | Approve | Approve | Reject (NCR required) | Pass unit; check arbor press depth & re-sample | Termination height/depth measurement, conductor alignment, and strain relief check |
| Insulation displacement (IDC) | Class 3 | Approve | Approve | Reject (NCR required) | Hold volume release; full tool qualification | Displacement depth measurement, conductor retention, and dual-slot seating verification |
When electrical testing is specified on the drawing or purchase order without custom customer parameters, IPC/WHMA-A-620 Section 18 defines the following default dielectric withstanding voltage (DWV) and insulation resistance (IR) test levels by class:
| Test (When Specified) | Class 1 Default | Class 2 Default | Class 3 Default | Standard Parameter Notes (IPC Section 18) |
|---|---|---|---|---|
| Dielectric withstanding voltage (DWV) | Not established (User specifies) | Applied when specified (critical if clearance < 2.0 mm or coaxial/triaxial) | Applied when specified across all assemblies | Class 2 default: 1000 VDC (or VAC rms equiv.), max leakage 1.0 mA, min dwell 0.1 s. Class 3 default: 1500 VDC, max leakage 1.0 mA, min dwell 1.0 s. Below 0.58 mm clearance, user and manufacturer must agree on de-rated voltage. |
| Insulation resistance (IR) | Not established (User specifies) | Applied when specified (critical if clearance < 2.0 mm) | Applied when specified across all assemblies | Test voltage: At or above DC DWV voltage (or tester default). Min resistance: 100 MΩ (≤ 3 m length), 10 MΩ (> 3 m length), 500 MΩ (coaxial any length). Max dwell 10 s, measured below 80% RH. |
Which Acceptance Evidence Should You Require for Crimp, Solder, and IDC Terminations?
Crimp termination first-article review should compare crimp height or cross-section against the terminal manufacturer’s specification. Visual continuity alone is not enough to release a crimp. A measured pull force value tied to the selected class is the minimum evidence for load-bearing performance.
Solder termination acceptance evidence should focus on wetting, fillet shape, and insulation clearance, not only electrical continuity after soldering. A solder joint can pass continuity while exhibiting cold wetting or insufficient fillet coverage that fails later under thermal or mechanical stress.
Insulation displacement connection review should verify conductor placement and insulation displacement depth against the connector’s specified range. An IDC can pass continuity while still having a weak gas-tight joint because the conductor was not fully seated or the insulation was not displaced to the required depth.
This comparative view prevents using the same two-line continuity report for all three termination technologies. Each termination type demands different objective evidence, and a supplier that does not distinguish them has not performed a real first-article review.
What Documentation Should You Demand Before Approving the Production Order?
Replace the supplier proof line “IPC/WHMA-A-620 compliant” with a first-article report that states the class level, measured pull-force values, termination method, and condition disposition. If the report says “pull test: passed” without a measured value, treat it as incomplete evidence and request the measured values and pass/fail limits tied to the selected class.
Required items before approval include:
- Drawing revision with the stated IPC/WHMA-A-620 class.
- Measured pull force values for each crimp termination, not a pass/fail note.
- Crimp height or cross-section data for each terminal type on the assembly.
- Solder fillet inspection records with photos and insulation clearance measurements where applicable.
- IDC conductor placement and displacement depth verification.
- Photographs or measurements for any process-indicator condition, with a supplier response for each defect.
- Dielectric withstanding voltage and insulation resistance records for Class 2 and Class 3 assemblies when required by the clearance condition.
At EDOM Electronics, every custom cable assembly and wire harness prototype is backed by measurable inspection records rather than generic compliance statements. Whether you are an OEM engineering team or a regional distributor sourcing custom interconnects, our engineering team reviews your drawing for IPC/WHMA-A-620 class callouts during DFM, matches original or cost-optimized equivalent connectors, and delivers rapid prototypes in 3–5 days complete with measured crimp height logs, pull-force test data, and 100% continuity/Hi-Pot test reports before volume tooling release.
What Nobody Tells You About First-Article Cable Assemblies
Golden samples are often built by senior staff, so a clean first article can hide crimp height drift, tooling wear, and operator variation that appear only in volume lots. The most common first-article risks are not outright defects but process indicators: uneven insulation support, partial brush retention, crimp flash, or a pull-force report that lists “passed” without a value.
Accepting “passed” without measured data means the boundary between acceptable and defect was never tied to a specific class, so later drift is discovered only after production has shipped. That is why the acceptance table above treats process indicators as action triggers, not as reasons to approve. The standard is clear that condition categories are not equal, and a pass on go/no-go can still require documentation, trending, or corrective action.
Before You Release Tooling: The Approval Decision Checklist
- Confirm the IPC/WHMA-A-620 class level is written into the drawing, purchase order, and first-article report.
- Tie the golden sample and any process indicators to a specific condition category, not to a verbal “compliant” claim.
- Require measured evidence for each termination type on the assembly—crimp, solder, and IDC—and reject any report that substitutes “pass” for a value.
- Verify that Class 2 or Class 3 dielectric withstanding voltage and insulation resistance records are present when required by clearance distance or assembly type.
- If a process indicator is open, do not release tooling for volume production until corrective action and a follow-up sample disposition are agreed.
Frequently Asked Questions
What does IPC/WHMA-A-620 actually define?
IPC/WHMA-A-620 defines acceptance criteria for cable and wire harness assemblies, including three workmanship classes—Class 1, Class 2, and Class 3—that set increasing inspection and documentation rigor. It covers crimp, solder, and insulation displacement terminations, among other assembly conditions.
Why is the class level the first thing I should confirm?
The class level changes the acceptance boundary for the same physical condition. A crimp condition that is acceptable under Class 1 may be rejectable under Class 2 or Class 3. Without a stated class, the supplier can default to the least demanding level, leaving the buyer with no defined quality boundary.
What is a process indicator in cable assembly inspection?
A process indicator is a condition that passes go/no-go inspection but still requires corrective action because it reveals drift in tooling, operator practice, or material handling. Examples include uneven insulation support, partial brush retention, or crimp flash. Process indicators should be documented and trended before volume release.
Is a report that says “pull test: passed” enough for first-article approval?
No. The report must include the measured pull force value and the pass/fail limit tied to the selected class. A pass note without a value does not establish where the sample fell relative to the acceptance boundary and cannot support production release.
Can a supplier such as EDOM Electronics help with first-article documentation?
Yes. A supplier such as EDOM Electronics can support OEM buyers by preparing documentation that includes the class level, measured pull-force values, crimp height or cross-section data, condition dispositions, and export-ready packaging records for custom cable assemblies and wire harnesses. The buyer still defines the class and the required evidence before review.
Key Takeaways
- IPC/WHMA-A-620 is a condition-based acceptance standard with three classes; the applicable class must be written into the drawing, purchase order, and first-article report.
- A condition is categorized as target, acceptable, defect, or process indicator—not merely “passed” or “failed.” A process indicator requires corrective action even if it passes go/no-go.
- Each termination type—crimp, solder, and IDC—requires different measured evidence. Continuity alone is insufficient for any of them.
- Reject any first-article report that substitutes “pass” for a measured value, and treat a missing class callout as an open decision item before tooling release.
- Suppliers such as EDOM Electronics can support the inspection and documentation process, but the buyer must set the class and the objective acceptance boundary.
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