"Build it to IPC Class 3" gets typed onto RFQs constantly — often when Class 2 would have shipped a perfectly good product for 20–30% less. Class 3 is not a badge of quality; it is a specific set of acceptance criteria for products where failure can hurt someone or end a mission. If your product does not need it, you are paying for inspection time and rework rules that add cost without adding reliability.
Here is what actually changes between IPC-A-610 Class 2 and Class 3, and how to pick the right one.
The three classes, briefly
IPC-A-610 defines three product classes:
- Class 1 — General Electronic Products. Consumer goods where the primary requirement is function. Toys, some appliances.
- Class 2 — Dedicated Service Electronic Products. Products where continued performance and extended life is required, but not critical. Most industrial equipment, telecom, commercial products.
- Class 3 — High Performance Electronic Products. Products where continued high performance is critical, downtime cannot be tolerated, and end-use may be a harsh environment. Medical life-support, avionics, defense, spaceflight.
The vast majority of commercial PCBAs ship as Class 2. Class 3 is the exception, not the default.
What actually changes at Class 3
The requirements chapter of IPC-A-610 has hundreds of criteria. The ones that most affect cost and yield:
Solder joint fill
- Class 2 plated through-hole: vertical fill of 75% acceptable.
- Class 3 plated through-hole: vertical fill of 75% required and additional criteria for wetting on top side.
Annular ring
- Class 2: breakout up to 90° of the ring is acceptable on internal layers.
- Class 3: no breakout allowed. Minimum external annular ring is larger.
This one alone can force a PCB redesign or a tighter fab process.
Component alignment
- Class 2: allows 50% side overhang on chip components.
- Class 3: allows only 25%.
Solder ball and residue
- Class 2: solder balls allowed if they do not violate minimum spacing.
- Class 3: essentially no solder balls in the vicinity of conductors.
Cleanliness
- Class 2: visual cleanliness plus process controls.
- Class 3: ionic contamination testing (ROSE or ion chromatography) is standard practice.
Rework
- Class 2: most rework allowed with standard limits on reflow cycles.
- Class 3: stricter limits on reflow cycles for gold-plated leads, ceramic parts, and BGA rework. Rework of blind/buried vias is often prohibited.
Where the cost comes from
Class 3 adds cost in four places:
- PCB fab: tighter annular ring and impedance tolerances mean higher fab pricing and lower fab yield.
- Component placement: tighter alignment tolerances slow the placement program.
- Inspection: more AOI escapes get flagged; more parts go to X-ray; more time in visual inspection.
- Documentation: traveler, first-article inspection reports, and lot traceability paperwork are required.
Rule of thumb: expect 20–30% higher unit price on the same design at Class 3 versus Class 2, at moderate volume.
When to actually spec Class 3
Spec Class 3 if any of these are true:
- End product has a regulatory requirement (FDA Class II/III medical, DO-254 avionics, MIL-PRF).
- Downtime or field failure risks life or a multi-million-dollar mission.
- Customer contract explicitly requires it.
Do not spec Class 3 just because it "sounds better." It will not make a Class 2 design more reliable — it will make it more expensive.
The realistic middle path
Many customers land at Class 2 with selected Class 3 requirements — for example, Class 2 workmanship overall with Class 3 cleanliness testing, or Class 2 with 100% X-ray on BGAs. IPC-A-610 explicitly supports flowing down individual Class 3 requirements without demanding the whole class.
Call that out on your RFQ and drawing. It is the cheapest way to buy the reliability you actually need.
What to put on your RFQ
- IPC class (2 or 3), or the hybrid callouts.
- IPC-A-610 revision (latest is J).
- IPC J-STD-001 revision if you require it (workmanship for the assembly process itself).
- Test level (AOI, X-ray, ICT, functional).
Send it with your Gerbers and BOM and we will quote it both ways so you can see the delta.