Q: How to design PCB for IPC-A-610 Class 3 high-reliability electronics?
Answer
IPC-A-610 Class 3 (High Performance Electronic Products) requires tighter tolerances than Class 2: (1) Minimum annular ring: 0.05 mm vs 0.025 mm for Class 2. (2) Solder joint acceptance criteria: inspect for wetting voids fillet shape. (3) Component placement: +-0.05 mm position tolerance for SOIC and larger. (4) Trace width tolerance: +-20% for Class 3 vs +-30% for Class 2. (5) All components must have date/lot codes. (6) X-ray inspection for BGA and QFN packages. (7) Conformal coating required for boards in harsh environments. Use gold-plated (ENIG) finish for boards with fine-pitch components. Include ICT fixture holes for in-circuit test.
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