Workmanship standards
IPC/WHMA-A-620 classes 1, 2 and 3, explained for buyers
IPC/WHMA-A-620, Requirements and Acceptance for Cable and Wire Harness Assemblies, is the standard most cable assemblies are built and inspected to. The class you choose sets how strict that inspection is.
What IPC/WHMA-A-620 does
The standard, published jointly by IPC and the Wiring Harness Manufacturer's Association, describes what an acceptable crimp, solder joint, splice, shield termination, lacing, marking and finished harness look like. It sets out criteria for each, usually with photographs and drawings, so that a buyer and a manufacturer can agree on what "good" means without arguing about it at receiving inspection.
The standard is revised every few years. Revision F was published in 2025; earlier revisions (D and E) are still named on many drawings and contracts. The revision on your drawing is the one that applies, so state it, and say whether a later revision is acceptable.
The criteria are graded into three product classes. The class is chosen by the user (the buyer or design authority), not by the manufacturer, and belongs on the drawing or purchase order.
The three classes
| Class | Name in the standard | Typical use | What it means in practice |
|---|---|---|---|
| Class 1 | General Electronic Products | Consumer goods, toys, non-critical appliances | The assembly must work. Cosmetic imperfections are broadly accepted. |
| Class 2 | Dedicated Service Electronic Products | Industrial controls, commercial equipment, most automotive and communications work | Continued performance and an extended life are required. Uninterrupted service is desired but not critical. |
| Class 3 | High Performance / Harsh Environment Electronic Products | Aerospace, defense, medical life-support, critical infrastructure | Downtime cannot be tolerated and the assembly must function when required. Acceptance criteria are the tightest. |
A separate space addendum adds further requirements for space-flight hardware. If your program is space-related, call it out explicitly.
Target, acceptable, process indicator, defect
Within each class, the standard describes conditions an inspector can find:
- Target: close to perfect. Desirable, but not required.
- Acceptable: not perfect, but it will keep working in its environment.
- Process indicator: not a defect, but a sign the process needs attention. Good suppliers track these.
- Defect: fails the criteria for the class and must be reworked, repaired or dispositioned (for example "use as is") by the customer.
The same feature can be acceptable at Class 2 and a defect at Class 3. That is why an unstated class produces arguments at receiving inspection.
How to choose a class
- Start from the consequence of failure. If a failed harness grounds an aircraft, stops a vehicle or harms a person, you are in Class 3 territory.
- Check your customer's flowdowns. Aerospace and defense primes usually specify Class 3 and may add their own requirements on top.
- Price the difference honestly. Class 3 means tighter inspection and more rework, which costs more. Specifying Class 3 on a part that does not need it is a real cost with no benefit.
- Write it down. Put "IPC/WHMA-A-620, Class X, revision Y" on the drawing notes, and state whether a later revision is acceptable.
Related standards you will meet
IPC/WHMA-A-620 sits beside J-STD-001 (requirements for soldered electrical and electronic assemblies) and IPC-A-610 (acceptability of electronic assemblies, which covers boards rather than harnesses). For aerospace vehicle wiring installation, SAE AS50881 is common. In automotive work, OEM and USCAR specifications often apply alongside or instead of IPC criteria.
What the class changes in practice
The class affects more than the inspector's checklist. It changes how a supplier plans and prices the work:
- Inspection time. Tighter criteria take longer to inspect, and more features need magnification.
- Rework and scrap. Conditions acceptable at Class 2 must be reworked at Class 3, and some cannot be reworked at all.
- Operator skill. Class 3 work needs operators and inspectors trained and current on the standard.
- Process control. Crimp set-up, stripping and soldering controls matter more when the acceptance window is narrower. See crimp pull testing.
- Records. Class 3 programs usually come with fuller inspection and test records.
That is why two quotes for the same drawing can differ when no class is stated: one supplier has priced Class 2, the other Class 3.
Mixed classes on one part
A drawing can call out a class for the whole assembly and a different class for specific features, but this is easy to misread. If you do it, make each exception explicit in the notes, and check that the supplier's quote reflects it. See what to put on a harness drawing.
Building to a class is not the same as being certified. A manufacturer can build to Class 3 criteria. Individual people hold IPC/WHMA-A-620 training certificates. Ask for both, and read the supplier qualification checklist for how to check.
Common questions
Who decides the class, the buyer or the manufacturer?
The buyer, or the design authority. The standard places the choice with the user. If no class is stated, suppliers will make their own assumption.
Is Class 3 always the safer choice?
It is the stricter choice, not automatically the right one. It adds inspection and rework cost. Use it where failure is unacceptable, and where your customer requires it.
What is the difference between IPC/WHMA-A-620 and IPC-A-610?
IPC/WHMA-A-620 covers cable and wire harness assemblies. IPC-A-610 covers the acceptability of electronic assemblies such as printed circuit boards. A product with both boards and harnesses may call out both.
How long is an IPC/WHMA-A-620 training certificate valid?
Operator, inspector and trainer certificates are valid for two years, after which the holder must recertify.
Does IPC/WHMA-A-620 cover testing?
It includes electrical and mechanical test requirements, but the tests you need and their parameters should still be written on your drawing. See cable assembly testing.
Last reviewed 2026-09-17