Adhesion and contact resistance in an electrostatic MEMS microswitch

A multi-asperity model of the contact resistance in a MEMS microswitch has been developed which includes the effects of elastic and plastic deformation, adhesion, and constrictive resistance. The number of asperities in contact is small enough that a discrete distribution of asperity heights is used. Adhesion produces significant hysteresis in the contact resistance vs. contact force characteristics. Due to the combined effects of plasticity and adhesion, the surface profile changes during the first load/unload cycle. Measurements of the contact resistance as a function of actuation voltage show good qualitative agreement with the model.