Pin Header Plating Oxidation: Tarnish, Resistance Rise and Prevention
August 3, 2026Views: 214
排针电镀氧化
The surface film is the problem, not “rusty copper”
Pin stock is copper alloy; air sees tin or gold over nickel. Yellowing, dulling and delayed high resistance are usually tin oxide, sulfide, or nickel exposed after thin gold wears through. Scrapping the lot as “wet incoming metal” often misses the cause.
Field checks
- Yellow, hazy tin: humidity, sulfur, fingerprints, open packs. Solder tails may still wet after flux; mating faces will raise resistance.
- Dark or reddish gold: flash gold too thin, nickel diffusion, or wear-through. Do not sand gold pins.
- Local stain at the heel: flux residue, skin salts, incomplete wash.
- High resistance with decent cosmetics: measure; color is not a spec.
Prevention
| Stage | Action |
|---|---|
| Stores | Keep original seals and desiccant; keep gold away from sulfur-rich rubber and cardboard |
| Spec | Tin for low-cycle power; write gold thickness for signals and harsh air |
| Selective plating | Gold on contact, tin on solder tail |
| Line | Minimize bare-hand contact; dry after wash; do not gouge gold with ICT probes |
If the mating face already oxidized, judge contact resistance and force against the spec. Polishing thins the plating and invites the next film.
Junjia supplies tin, gold and selective plating with tube or foil packs. Qualify resistance against real climate and cycles. See also the plating selection article in this series.