Survey of Contact Fretting in Electrical Connectors

Fretting in mated electronic connectors can lead to unacceptable increases of contact resistance. Although this phenomenon has been known for many years, it was not until interest developed in replacing gold by certain low-cost contact materials, such as tin-lead solder plate, that the incidence of fretting problems rose dramatically. Over the past 10 years there has been considerable research on the origins of this contact resistance instability, on methods for its measurement, and on finding ways to avoid the problem. This paper is a critical review of fretting based on published work by the author and by other investigators. Included are a discussion of mechanisms of transfer, wear, oxidation, and frictional polymerization which apply to the fretting of contacts; the effect of operational parameters such as cycle rate and force on contact resistance change; a survey of materials whose fretting behavior has been determined; and an analysis of the different roles which lubricants play in controlling fretting according to the contact materials that are involved. Connector design, the particular conditions of field use, expected connector lifetimes, and their reliability requirements determine whether contact materials will be satisfactory. Hardware tests which tend to cause fretting, such as shock and vibration, should be employed before new contact materials and designs are incorporated in connectors.