Electrical and tribological properties of tin plated copper alloy for electrical contacts in relation to intermetallic growth

many studies have been performed on reliability and accelerated testing of tinned contacts. The major contact resistance failure mechanism has been assigned to fretting by many authors. From a material point of view, one way to postpone or minimize the phenomenon is to select a coating presenting the best properties for the application. It is well known that the performances of an electroplated coating are determined by a broad variety of variables: metal or alloy, underlayer, layer finish, thickness and deposition process. The work undertaken here concerns tin electroplating processes. It is part of a large program aimed at determining an improved coating for connector type electrical contacts. The electrical and tribological properties of various coatings are analyzed and their behavior is correlated to physico-chemical and morphological characteristics of the layers. The thickness of the tin electroplate and the influence of an underlayer are examined for two tinning processes. Intermetallic formation is found to strongly influence the results.