Short answer: IPC-A-610 class 2 is the correct choice for most industrial, IoT, energy and automation electronics: it defines dedicated service products where uninterrupted operation is desired but not critical. Class 3 is for high-performance or harsh-environment products where failure is not acceptable: life-support medical devices, aerospace, safety-critical marine and rail systems. Class 3 tightens hole fill, solder fillet, component alignment and cleanliness limits and typically adds 10–30 % to assembly cost. Specify the class on the assembly drawing and purchase order; without it, class 2 is the industry default.
What IPC-A-610 classes mean
| Class | Definition (IPC-A-610) | Typical products |
|---|---|---|
| Class 1 | General electronic products; function is the main requirement | Consumer electronics, toys, disposable devices |
| Class 2 | Dedicated service products; continued performance and extended life required, uninterrupted service desired | Industrial controls, IoT, telecom, HVAC, instruments, most B2B electronics |
| Class 3 | High-performance/harsh-environment; continued performance critical, downtime not tolerated | Life-support medical, aerospace, military, safety-critical marine and rail |
What changes between class 2 and class 3
- Plated through-hole fill: class 3 requires ≥ 75 % vertical fill; class 2 accepts 50 %.
- Component alignment: class 3 allows less side overhang and end overhang on chip components.
- Solder fillets and wetting: class 3 requires evidence of wetting on all terminations and larger minimum fillets.
- Voiding and cleanliness: tighter limits, and class 3 usually comes with ionic cleanliness testing and coating.
- Documentation: first-article inspection, traceability and process records are expected, not optional.
What class 3 costs
Expect 10–30 % higher assembly cost from slower placement parameters, additional inspection (AOI plus X-ray on BGAs), cleaning and higher rework and scrap. The bare PCB may also need tighter tolerances. For a product whose failure is a safety issue that is money well spent; for a fieldbus module in a cabinet it usually is not.
Key facts
- Industry default when nothing is specified: class 2.
- Class 3 typically adds 10–30 % to assembly cost.
- The class must be stated on the drawing and PO to be contractual.
- Comtec Labs builds to class 2 as standard and to class 3 on request, with IPC-trained inspectors and AOI on every board.
How to write the requirement
On the assembly drawing: “Assemble and inspect to IPC-A-610 current revision, class 2” (or 3). Add IPC J-STD-001 for the soldering process, the coating specification if any, and whether ionic cleanliness testing is required. If only a sub-assembly is safety-critical, specify class 3 for that board only.
Frequently asked questions
Is class 3 always better quality?
It is stricter, not necessarily better for your product. A class 2 board built with a stable process is highly reliable; class 3 adds cost for margins that only critical applications need.
Can a class 2 line build class 3?
Yes, with the same equipment but tighter parameters, more inspection and documented process control. Comtec Labs does both.
What is the difference between IPC-A-610 and J-STD-001?
J-STD-001 defines the soldering process and materials requirements; IPC-A-610 defines the acceptability of the finished assembly. Specify both.
Do medical devices always need class 3?
No. Non-life-support medical devices are commonly built to class 2 with the device's risk analysis (IEC 60601, ISO 14971) driving any tighter requirements.
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