Tribological properties of edge card connector spring/tab interface

The influence of multilayer surface coatings on the tribological behavior of an edge-card connector was studied. The card tab had a multilayer structure consisting of a printed circuit board with overplated layers of copper, nickel, hard gold, and soft gold; the thickness of each was found to alter the frictional characteristics of the surface. Dry experimental data were found to agree with Finkin´s theoretical model for solid film lubrication. As the thickness of soft gold increased for both dry and lubricated conditions, the coefficient of friction and wear increased. Surface roughness was observed to increase friction, and the increase of the soft gold-layer thickness had the tendency to increase surface roughness. It was found that the addition of a minimum layer of lubricant can lower the friction on the contact surface and reduce the influence of the layered surface coatings. The coefficient of friction remained relatively constant from thin film to flooded conditions. The difference in wear between dry and thin-film-lubricant conditions was minor