Effects of Hot Switching and Contamination on Contact Reliability of Pt-Coated Microswitches

Abstract

Hot switching and hydrocarbon-induced contact activation limit the lifetimes and exacerbate the surface erosion/damage in switches. However, the relative effects of voltage and contamination have not been studied. We report on these effects in Pt-coated microswitches. Long lifetime, as determined from electrical contact resistance (ECR) data versus switch cycle count, was observed under cold switching conditions. Cycling under hot switching conditions was performed at different contact voltage levels $V_{c}$ in: 1) a clean, hydrocarbon-free environment and 2) the presence of 40 ppm benzene (C6H6) in N2 gas. In the clean environment, carbon-induced contact activation did not occur, but the switches exhibited an ECR increase in as little as 100 times less than under cold switching conditions. The degree of erosion increased with $V_{c}$ in both environments. In the contaminated environment, substantial amount of tribopolymer (TP) was generated and contact activation increased as $V_{c}$ increased. For the conditions tested, this work shows that minimizing environmental contamination is the strongest factor in minimizing contact erosion in microswitches, while lowering $V_{c}$ also plays an important role.