The electrical and mechanical performance of corroded products on gold plating after long term indoor air exposure

The corroded products formed on gold plating after long term indoor air exposure appear as a set of concentric black rings surrounding a large corroded core on top of a pore. A visible stain is frequently observed between and even beyond the rings. Dust particles also distribute on the exposed coupons. All of these insulated products cause high probability of static contact failure. Concentration of the corroded composition increases and decreases as the morphology is changed from the core to the rings. The contact resistance also goes up and down the same way as the composition alternates, which is high on both the core and the concentric rings, but low on the stained areas among the core and the rings. The contact resistance on the dark stains also fails, which seriously increases the failure probability. It is found that the wearing out of the products which reduces the contact resistance depends on the normal force, geometry of the contact pairs and shearing strength of the corroded products. The effect of pores on contact reliability is much more serious than was predicted previously, especially in low signal applications.