This literature review deals with the properties of tin as coating material for (automotive) connectors. Tin-coated contacts have a fairly low and stable contact resistance even in rather aggressive atmosphere, since large oxide free contact spots are easily obtained during insertion. However, tin coated connectors need particular attention with regard to four properties: the wear of the soft tin coating caused by insertion/withdrawal, sensitivity to fretting, diffusion of copper into the tin layer during long term operation, and finally, the relatively high insertion/withdrawal force. Pure tin coating with an effective supply of lubricant to the contact spots seems to have superior properties compared with other tin alloy systems available on the market, if the overall properties of a connector are considered. Improved lubrication may be obtained by co-deposition of a solid lubricant during electroplating of the tin layer. A model is proposed to estimate the required contact force and the achieved insertion/withdrawal force for a tin-coated connector.
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