The Lifetime Prediction for Metal MEMS Cantilever Switch

This is the first reported work using FEM (finite element method) to predict metal MEMS switch reliability operating under stress conditions for over decades. The lifetime of cantilever-based switch is determined by the extent of Vpi (pull in voltage) drop due to the beam creep by continuously operating at the actuated state. A time hardening Norton-Bailey creep law is adopted here to describe the creep behavior of Au alloy beam material. A numerical platform is developed in Ansys workbench [1] to calculate the non-recoverable beam deflection induced by accumulated creep strain upon electro-static hold-down at elevated temperatures with different passing through current levels. The creep lifetime prediction curve sets are generated and validated against the MEMS switch device Vpi drop measurement through 1000hrs accelerated life tests. The reliability plot based on Vpi drop shows that the Au alloy switch can retain an acceptable Vpi voltage degradation for ~200 years at 85°C/0A and ~5 years at 85°C/10A, with ~10% probability of not passing a desired 150V standoff voltage test.