IPC-A-610 is the standard that defines what an acceptable solder joint looks like. It has three classes, and suppliers quote them interchangeably as if they were grades of quality. They are not. They describe three different sets of customer expectations.
The definitions come from IPC-A-610 itself. Note that the classes are defined by the consequence of failure, not by how difficult the board is to build.
| Class | Defined as | What failure means | Typical products |
|---|---|---|---|
| Class I General electronic products |
The function of the completed assembly is the only criterion. Cosmetic imperfections are not important. | Inconvenience. The product stops working and is repaired or replaced. | Consumer toys, disposable electronics, some accessories |
| Class II Dedicated service products |
Continued functionality and a long service life are desired. Uninterrupted service is not critical. Some cosmetic imperfections are acceptable. | Loss of use. The product has to come out of service, but nothing dangerous happens. | Most consumer and industrial electronics, computers, instruments |
| Class III High performance / harsh environment |
Continued high performance, or performance on demand, is critical. Equipment downtime cannot be tolerated. The end-use environment may be unusually harsh. The assembly must function in that environment. | Failure of the end product. In the cases that matter, this means harm to a person. | Medical life support, aerospace, military, some automotive safety systems |
Class III is not a certificate you hang on the wall. It changes what operators are allowed to accept.
The same machines can build a Class II board and a Class III board. What changes is the acceptance criteria applied to every joint — how much solder fillet is required, how much voiding is permitted in a BGA ball, how much mask encroachment is tolerated, whether a slightly offset component is acceptable or must be reworked. Class III reduces the allowable variation substantially.
Class III work is usually paired with tighter process control: first-article inspection on every new build, more X-ray on hidden joints, stricter traceability of materials and lots, and records that a customer or auditor can review afterwards. That documentation is a large part of what you are paying for.
The counter-intuitive part: a Class III line rejects more boards. Joints that a Class II line would pass get reworked, because the standard does not permit them. A supplier who claims Class III but shows you a low reject rate is either building simple boards or is not applying the criteria.
No, and this is the most common mix-up. IPC-A-610 is a workmanship standard — it defines what an acceptable solder joint looks like. ISO 9001, IATF 16949 and ISO 13485 are management system standards — they define how a company controls its processes, records and suppliers. A factory can hold IATF 16949 and build to Class II, or hold no automotive certification and build to Class III. You normally need to specify both.
It means the workmanship standard is stricter, which removes one category of failure. It does not fix a design problem, a bad component choice, or a thermal issue. Class III is necessary for high-reliability products but it is not sufficient on its own.
You can, but it is usually a waste. Prototypes exist to find design problems; the workmanship grade rarely changes the outcome at that stage. It is more common — and cheaper — to build prototypes to Class II and switch to Class III once the design is frozen and heading for production.
You do, usually from your own regulatory or customer requirements. In medical devices it is often driven by the risk classification of the device; in automotive by the OEM's own specification. A contract manufacturer should ask you which class applies rather than assume — if a supplier never asks, that is worth noticing.
A different standard. Bare board acceptance is governed by IPC-A-600, not IPC-A-610 — IPC-A-610 covers assembly. Hongrong fabricates to IPC-A-600F and assembles to IPC-A-610 Class III.
Setup, stencils, component minimums and test fixtures — and how to keep unit cost sane between 1 and 1,000 pieces.
ENIG, HASL, OSP, immersion silver, immersion tin and ENEPIG compared — cost, shelf life and failure modes.
IATF 16949, ISO 13485, ISO 9001 and IPC-A-610 Class III — and the documents we will send you.
Tell us what the product does and what happens if it fails. We will tell you which class we would build it to — and if the answer is Class II, we will say so rather than sell you the stricter one.
