A Nanoindenter Based Investigation of Gold-Ruthenium Alloy Microcontact Behavior under Cyclic Condition

摘要

A nanoindenter based experimental setup was used to characterize gold-ruthenium (Au5%Ru) microcontact behavior under cycling and hot-switching conditions where a cantilever beam with a contact bump was cycled in and out of physical contact with a flat plate to simulate the action of MEMS ohmic contact switches. Cantilever beam and flat plate were fabricated from silicon, and then sputter coated with 300 nm of Au5%Ru as the contact material. All contacts failed in adhesion with either shorter fatigue life (about 1-2 million cycles) or longer life (about 6 million cycles). The smoother contact surface had shorter fatigue life. The Au5%Ru contact material had longer life and higher resistance than gold. Further, contact resistance was constant during cycling up to failure. Different contact parameters: adhesion force, threshold force, strain hardening/softening and plastic deformation were monitored during cycling. Adhesion force in Au5%Ru microcontact was smaller than in gold. Threshold force was larger in Au5%Ru than in gold. Time-dependent and plastic deformations as well as cyclic softening were observed in Au5%Ru. Thus, elastic-viscoplastic material model(s) with strain softening capability are needed for the analysis of Au5%Ru microcontact behavior.