Date of Award
Master of Science in Electrical Engineering
Department of Electrical and Computer Engineering
Ronald A. Coutu Jr., PhD.
Reliable microelectromechanical systems (MEMS) switches are critical for developing high performance radio frequency circuits like phase shifters. Engineers have attempted to improve reliability and lifecycle performance using novel contact metals, unique mechanical designs and packaging. Various test fixtures including: MEMS devices, atomic force microscopes (AFM) and nanoindentors have been used to collect resistance and contact force data. AFM and nanoindentor test fixtures allow direct contact force measurements but are severely limited by low resonance sensors, and therefore low data collection rates. This thesis reports the contact resistance evolution results and fabrication of thin film micro-contacts dynamically tested up to 3kHz. The contacts consisted of a lower contact of evaporated Au and a thin film upper contact, consisting of sputtered Au, Ru or RuO2, with an Au electroplated structural layer. The fixed-fixed beam was designed with sufficient restoring force to overcome adhesion. The hemisphere-upper and planar-lower contacts are mated with a calibrated, external load resulting in approximately 200muN of contact force and are cycled in excess of 10 to the 7th power times or until failure. In addition, Au-Au contact pairs with a hemispherical upper an engineered lower contact were tested. These lower engineered contacts were constructed using gray-scale lithography. Contact resistance was measured, in situ, using Holm's a cross-bar configuration and the entire apparatus was isolated from external vibration and housed in an enclosure to minimize contamination due to the ambient environment. Additionally, contact cycling and data collection are automated using a computer, integrated lab equipment and LabVIEW. Results include contact resistance measurements of Au, Ru and RuO2 samples and lifetime testing up to 323.6 million cycles.
DTIC Accession Number
Stilson, Christopher L., "Contact Resistance Evolution and Degradation of Highly Cycled Micro-Contacts" (2014). Theses and Dissertations. 627.