A Nanoindenter Based Method for Studying MEMS Contact Switch Microcontacts

Physical and electrical processes involved in the lifecycle failure of metal contacts in MEMS RF cantilever beam contact switches are of a great interest to switch designers. The main failure of MEMS contact switches occurs at the metal contacts. This paper describes a specially designed nanoindenter based experimental setup for characterizing the physics and mechanics of MEMS scale electrical contacts when they are being cycled. The setup uses silicon cantilevers with contact bumps which are cycled mechanically to simulate the action of a MEMS contact switch. The cantilevers were sputter deposited with 300 nm of gold. Gold was investigated as the initial material of interest, as many current MEMS contact switches employ gold as a contact metal. The setup allows the physical evolution of the contact to be visually tracked and provides data on resistance, material property (e.g. strain hardening), and other changes in the contact behavior. Test data collected during a typical test includes contact adhesion force, contact stiffness change, resistance vs. cycles, and resistance vs. contact force relationships as a function of applied contact cycles. This paper provides details of this unique set-up and typical test results.