IPC/WHMA-A-620 Class 2 vs. Class 3: What Changes for Harness Builders and Inspectors
Nov 03, 2026
Ask a harness inspector what slows them down, and product class is often near the top of the list.
The same crimp, splice or tie-wrap can be acceptable on a Class 2 harness and a defect on a Class 3 harness. Here's what changes between the two, and how to tell which one applies.
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ElectroSpec’s IPC/WHMA-A-620 CIS certification covers all 8 Revision F modules, including how product class changes acceptance.
What the Classes Mean
IPC/WHMA-A-620 uses the same three product classes as other IPC acceptance standards.
- Class 1, General Electronic Products: the main requirement is that the assembly works.
- Class 2, Dedicated Service Electronic Products: continued performance and extended life are required, and uninterrupted service is desired but not critical.
- Class 3, High Performance/Harsh Environment Electronic Products: the product must keep working when needed, with no downtime tolerated.
Class 3 is where you find aerospace, defense, medical and other critical applications.
Who Decides the Class?
The customer does, usually through the drawing, purchase order or contract. Inspectors don't pick the class, and neither do operators.
If the documentation doesn't say, ask. Assuming Class 2 on a Class 3 job is one of the most expensive mistakes a harness shop can make.
What Gets Stricter in Class 3
The standard sets each requirement by class, so the exact criteria are in IPC/WHMA-A-620 itself. In general, moving from Class 2 to Class 3 means:
- Less tolerance for conductor damage. Nicked, cut or broken strands that may be acceptable at Class 2 are more likely to be defects at Class 3.
- Tighter crimp and termination conditions. Conductor and insulation position, bellmouth and related features are judged more strictly.
- Stricter soldered terminations. Wetting, fillet and insulation-clearance conditions narrow.
- More conditions become defects. Some conditions that are acceptable or only process indicators at Class 2 become defects at Class 3.
- More attention to securing and routing. Strain relief, bend radius and protection of the finished harness matter more when failure is not an option.
What Does Not Change
The structure of the standard stays the same. You still judge each condition as target, acceptable, process indicator or defect. Class 3 applies stricter limits to the same features.
That's why knowing how to navigate IPC/WHMA-A-620 quickly matters so much. The answer is usually in the same section, with different criteria for each class.
Where the Space Addendum Fits
Some space and military programs call out the IPC/WHMA-A-620 Space and Military Applications Electronic Hardware Addendum. It adds requirements on top of Class 3. If a drawing references the addendum, base Class 3 knowledge alone is not enough.
Practical Tips for Inspectors
- Confirm the class before you inspect the first piece, not after you find a questionable condition.
- Record the class on the traveler or inspection record.
- When a condition is borderline, check the class-specific criteria rather than relying on memory.
- Escalate conflicts between the drawing and the standard rather than resolving them yourself.
Frequently Asked Questions
Is there a separate certification for Class 3?
No. IPC/WHMA-A-620 CIS covers all three classes. The Space Addendum is a separate path.
Can a Class 3 harness be built by someone certified to Class 2?
Certification isn't issued by class. Your company's quality system and customer requirements decide who may build and inspect Class 3 product.
