| Ohmic contact, or contact-type, Microelectromechanical Systems (MEMS) switches employ two separable metal electrodes as a contact. In the switch environment, the switch contact may experience either of two switching modes. Cold switching refers to the application of an electrical signal across the switch only when the contact is fully closed. On the other hand, hot switching refers to the application of a signal while the switch is being opened and closed. Compared to cold switching, hot switching leads to shorter contact lifetimes.;This work explores the effect of multi-domain coupling on the behavior of an electrical contact, what makes hot switching damaging, the making of contact under bias as it compares to the breaking of contact under bias (leading versus trailing edge hot switching), and the specific mechanisms that could be responsible for hot switching damage.;Theoretically, it was found that for a contact operating under displacement control, such as an asperity on the surface of a contact bump, thermal-electrical-mechanical coupling has a significant effect. Generalized (non-dimensional) equations are presented to describe the behavior of the contact in this situation.;Experimentally, a specially built micro-contact testing system and microfabricated contact pairs were used to conduct hot switching tests to characterize hot switching damage. It was found that hot switching damage mechanisms are active on both the leading (closing) and trailing (opening) edges, resulting in directional material transfer damage of roughly the same volume at 4400 microm/s approach/separation rate. Furthermore, the direction of the material transfer damage is shown to be polarity-dependent, from the anode to the cathode. Polarity dependent damage mechanisms were found to be active at separations of less than 10 nm and in time periods on the order of hundreds of nanoseconds. Additionally, thermo-mechanical contact damage mechanism comprised of joule heating and thermal geometry was identified that transfers material away from the contact bump with strong separation rate dependence.;This work makes significant progress toward defining the specific mechanisms responsible for the additional damage associated with hot switching, thereby helping to solve a problem that has plagued the microswitch and inhibited it from significant commercial market penetration. |
