Corrosion control and lubrication of plated noble metal connector contacts

There is considerable interest in the corrosion control and lubrication of separable electronic connectors and other contact-containing devices. This originates in the desire to minimize the use of costly precious metals, like gold, palladium, and their alloys, without sacrifice in reliability. When the application is in aggressive environments, pore corrosion of the finish limits the reliability of the connector. Also, there may be many engagements and separations of the connector during its lifetime which can result in a wearing out of the noble metal plating. Numerous surface treatments have been proposed for corrosion control, including barrier coatings which restrict access of air to the contact, and chemical modifications of the finish such as chromating. This paper is a study of barrier coatings and a chromating treatment with the objective of identifying those characteristics which improve the performance of the contact finish (An plate and Au flashed Pd, both on a Ni underplate). Polyphenylether-microcrystalline wax mixtures were used in a laboratory modeling study where the oil-wax ratio and the coating thickness were varied. Performances in a corrosive, high-humidity environment, in wear, and during fretting (with the additional variable of surface roughness) were determined. It was found that Au finishes, even as thin as 0.1 mu m, when treated with suitable coatings can approach the corrosion performance of much thicker platings.