Time-dependent Contact Resistance in a Multi-scale Surface Model

For a number of applications, the time-dependent electrical resistance of contact regions is of great practical importance. For small time scales on the order of microseconds, MEMS switches are impacted by contact resistance transients, while for longer time scales of weeks and months, electrical switchgear contacts show time-dependent contact resistance. Abinitio analysis of contact geometry and contact resistance between two macroscopic bodies can help in understanding and optimizing the electrical contact behavior. In this context, several authors have recently described the time-dependent behavior of metallic contacts using a multi-scale surface description. In such an approach, the contact geometry is analyzed using the multiscale geometric properties of most naturally occurring surfaces, while attributing the time-dependent properties to creep, or timedependent plasticity, of the roughness peaks (asperities). In this paper, the MIMEAC (micromechanical asperity creep) multi-scale contact model is used to analyze the dwell timedependent behavior of an electrical contact. For this analysis, it is assumed that fresh contacts are instantaneously placed into contact, and the resistance is observed under a constant contact force and constant overall bulk temperature. Functional relationships are derived for the dependence of time-dependent contact resistance on the bulk material creep parameters and temperature. The results are interpreted in light of contact material optimization.