Field Performance of Tin Coated Post and Spring Connector System

Field measurements are presented showing the contact resistance stability of a nonlubricated tin coated contact system working in logic level circuitry, in a variety of environments for up to three years. The connector system consists of a hot tin dipped bellows contact that mates to a bright acid tin plated round Post. The resistance of this system was found to be low and stable in normal use, with no evidence of fretting corrosion. Instances of substantially increased resistance were found in some connector systems that had been subjected to unusual use or testing. Failure analysis of these connections indicated that the major cause of degradation was an accumulation of hydrocarbons at the contact interface. The source of these hydrocarbons was determined to be organic acid brightening agents from the bright acid tin plating process that are entrapped within the tin deposit during electroplating. The conclusion is drawn that this contact system provides reliable performance when used within the constraints recommended by the manufacturer.