A possible degeneration mechanism in stationary electrical contacts

Abstract

A mechanism for the degeneration of stationary electrical contacts is proposed. The mechanism derives from Mullins' model (1959) of flattening of free surfaces through the action of capillarity forces. Mass transport for surface deformation is assumed to occur through volume self-diffusion and is calculated on the basis of diffusion constants characteristic of plastically deformed or mechanically stressed aluminium. A simple electrical contact model suggests that the increase in contact resistance stemming from surface flattening in Al at room temperature can become noticeable in a time interval of a few days ( approximately 10/sup 6/ s). This result may explain the deterioration of contaminated Al/Al stationary electrical contacts operated at room temperature, after run-times of 10/sup 5/-10/sup 6/ s. Finally, since many metals are characterized both by rapid volume or surface diffusion and by a large surface energy, the results suggest that asperity flattening can lead to degeneration in all bulk electrical interfaces.<>