Selecting metal alloy electric contact materials for MEMS switches

This paper presents a method for selecting metal alloys as the electric contact materials for microelectromechanical systems (MEMS) metal contact switches. This procedure consists of reviewing macro-switch lessons learned, utilizing equilibrium binary alloy phase diagrams, obtaining thin film material properties and, based on a suitable model, predicting contact resistance performance. After determining a candidate alloy material, MEMS switches were designed, fabricated and tested to validate the alloy selection methodology. Minimum average contact resistance values of 1.17 and 1.87 Omega were measured for micro-switches with gold (Au) and gold-platinum (Au-(6.3%)Pt) alloy electric contacts, respectively. In addition, 'hot-switched' life cycle test results of 1.02 x 10(8) and 2.70 x 10(8) cycles were collected for micro-switches with Au and Au-(6.3%)Pt contacts, respectively. These results indicate increased wear with a small increase in contact resistance for MEMS switches with metal alloy electric contacts.