What is IPC/WHMA-A-620?
IPC/WHMA-A-620, Requirements and Acceptance Criteria for Cable and Wire Harness Assemblies, is the industry standard for workmanship quality in cable and wire harness manufacturing. Published by IPC (Association Connecting Electronics Industries) and WHMA (Wire Harness Manufacturers Association), it establishes a common language for quality expectations across the entire manufacturing ecosystem.
The standard defines how assemblies should be built, what constitutes acceptable work at each step, and how to inspect the finished product. It removes ambiguity. It makes quality auditable. It ensures consistency whether you're sourcing from a shop in Kansas City or across the country.
Why IPC/WHMA-A-620 matters when sourcing wire harnesses
When you specify IPC/WHMA-A-620, you're not asking a manufacturer to guess what "quality" means to you. You're referencing a detailed, industry-recognized standard that defines workmanship criteria, inspection protocols, and acceptance limits.
It's auditable
You can verify that your supplier is building to the standard through third-party certification and regular audits. No guessing — documented proof of compliance.
It eliminates surprises
A Class 2 or Class 3 assembly built in Kansas City will meet the same criteria as one built anywhere else. The standard is the standard.
It protects your customer relationships
If your customers require IPC/WHMA-A-620, sourcing from a manufacturer who builds to the standard is non-negotiable. We have the documentation to back it up.
It reduces risk
By building to a recognized standard, you reduce the likelihood of field failures and warranty claims. Quality isn't a marketing claim — it's a documented process.
Class 1, 2, and 3: understanding the differences
IPC/WHMA-A-620 defines three classes of workmanship. Each has different acceptance criteria and inspection rigor. Most industrial and commercial manufacturers require Class 2. Life-critical applications require Class 3.
Class 1
General applications
No critical requirements. Consumer electronics, non-critical industrial applications. Lowest cost, appropriate when failures have minimal impact. Not typically specified for industrial or commercial electronics.
Class 2
General & industrial
High reliability and extended life required, but not life-critical. Industrial equipment, commercial devices, transportation applications. This is the most common class for industrial manufacturers.
Class 3
High-performance & life-critical
Zero tolerance for workmanship defects. Medical devices, aerospace, military, and any application where failure could result in injury, death, or loss of critical function. Strictest inspection criteria, highest cost.
How to choose your class
Think about the consequences of failure. Would a defective harness cause downtime or revenue loss? Class 2. Could it cause injury or death? Could the system fail completely? Class 3. When in doubt, we can help you make the right call based on your application and customer requirements.
Questions to ask before you specify a class
- What are the consequences of failure? Downtime? Revenue loss? Injury? Death?
- Is this assembly involved in a safety-critical function? Medical, aerospace, and military applications almost always require Class 3.
- What does your customer require? If you're supplying to a Tier-1 aerospace contractor or medical OEM, they will likely mandate Class 3.
- What does the industry standard for your market dictate? Automotive and industrial typically default to Class 2. Aerospace and medical default to Class 3.
- What's your risk tolerance? Even if your application doesn't strictly require Class 3, building to a higher standard can be a competitive advantage and risk mitigation strategy.
Frequently asked questions
IPC certification means the manufacturer has demonstrated competency in the standard, maintains processes that comply with it, and has trained inspectors who enforce it. For a manufacturer without formal certification, look for demonstrated workmanship consistency, in-process inspection, and documented test procedures — the practices that certification is designed to verify.
Yes. QCS builds to both Class 2 and Class 3 depending on your application requirements. The key is having the processes, training, and inspection rigor to execute both standards consistently — and we maintain both capabilities.
Ask these questions: Do you build to IPC/WHMA-A-620? What classes can you build to? Who are your certified inspectors? Can you provide documentation of your first article inspection and testing procedures? Can you maintain traceability for all materials and workmanship? These answers will tell you whether a supplier can meet your quality requirements.
IPC/WHMA-A-620 is periodically revised as manufacturing techniques and materials evolve. Updates typically occur every few years. A certified manufacturer stays current with the latest revision and updates their processes accordingly. When sourcing, it's worth asking which revision your supplier builds to, especially if you're comparing shops.
IPC/WHMA-A-620 specifically covers wire harnesses and cable assemblies. However, the principles of workmanship quality and rigorous inspection that underpin A-620 apply to box builds as well. Many manufacturers apply Class 2 and Class 3 concepts to box assembly work to maintain consistent quality standards across all manufacturing activities.
Class 3 is typically 15–30% more expensive than Class 2 due to stricter inspection requirements, more frequent testing, and higher defect rejection rates. However, the difference in cost is often worth it when you consider the cost of a field failure, recalls, and reputational damage. We can give you an exact quote once we understand your application and volume requirements.
Ready to source a Class 2 or Class 3 assembly?
QCS builds to IPC/WHMA-A-620 workmanship standards — both Class 2 and Class 3. We can help you determine which class your application requires and deliver assemblies built to specification, on time, with full traceability and documentation.
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