Meaning
An electroplated noble metal layer alloyed with trace cobalt or nickel provides low contact resistance and high wear tolerance on separable electrical connectors. A surface finish utilizing hard gold overplate protects mating contacts from oxidation and friction-induced wear during repeated insertion cycles. Its functional boundary ends where excessive deposit thickness causes solder joint embrittlement during board assembly.
Alloy Composition
Co-deposited metallic elements increase the micro-hardness of pure gold from soft levels up to two hundred Knoop hardness units. Application of hard gold overplate requires precise control of bath temperature, current density, and cobalt concentration.
Wear Resistance
High mating cycle demands require durable surface coatings to prevent exposure of underlying nickel barrier layers. When hard gold overplate undergoes sliding contact, the hard deposit maintains low friction coefficients and prevents galling between contact members. Base metal exposure leads to rapid atmospheric oxidation and passive intermodulation distortion in high-frequency signal paths, resulting in permanent signal degradation across radio module interfaces.
Cross-sectional optical microscopy measures wear tracks after durability cycling tests.
Plating Specification
Inspection protocols mandate minimum deposit thickness requirements based on expected connector mating operations. Standard hard gold overplate specifications require zero point seven five micrometers of gold over a nickel underplate. Certificate of conformance documents confirm deposit hardness and plating adhesion before component release.
