PCB Protection: Conformal Coating and Sourcing
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PCB protection for China-built PCBAs usually means conformal coating — acrylic, silicone, urethane, or parylene applied 25-75 microns thick to guard against humidity, salt fog, and condensation. Acrylic (type AR) is the cheapest and most common from Chinese contract manufacturers, but silicone (SR) holds up better in high-temperature or vibration-heavy automotive and outdoor IoT builds. Inspection follows IPC-CC-830B, which sets coverage and thickness acceptance.
When you order conformal coating, specify the material class, dry-film thickness, and keep-out zones for connectors and test points — many Chinese lines coat the whole board unless told otherwise. The common pitfall is bridged connectors or coated programming headers that fail in final assembly.
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FAQ
How much does conformal coating add to PCBA cost in China?
Manual or selective acrylic coating typically adds $0.10-0.50 per board at moderate volume; parylene via vacuum deposition is far more expensive, often several dollars per board and run by specialist subcontractors.
What standard governs conformal coating quality?
IPC-CC-830B defines material qualification and inspection; coverage is checked under UV light since most coatings contain a fluorescing tracer. Ask the factory for UV inspection photos per batch.
Which coating type should I choose for outdoor electronics?
Silicone (SR) handles wide temperature swings and moisture better for outdoor or automotive use; acrylic is fine for indoor consumer products. Match the coating to your operating temperature and humidity spec.
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