Wear, Fretting and the Role of Lubricants in Edge Card Connectors

We describe the wear process which occurs when a P.C. card with copper/nickel/solder metallization is inserted into an edge card connector that has a contacting pin with a spherical gold alloy dot and a normal force of about 300 gms. The presence of a lubricant delayed the successive wear processes and reduced the amount of solder displaced during a single pass by minimizing the cold welding of solder to the gold dot. Fretting corrosion experiments were made using a simple test jig which permits the use of actual production cards and connector parts. The fretting test fixture provides a way of comparing and evaluating actual connector designs, as well as a means of comparing the effectiveness of various lubricant formulations.