| This research effort examines the physical and electrical processes involved in lifecycle failure of Microelectromechanical (MEMS) Radio-Frequency (RF) cantilever beam ohmic contact switches. Complete details including multiple parameters of microcontact performance are difficult to measure and have not been previously reported. Data of contact parameters, failure and characteristics of failure over contact lifetime are sparse. This study investigated the mechanics of microcontact behavior with the design and construction of a novel experimental setup. Three representative contact materials of varying microstructure were tested and parameters of contact during cycling to failure were measured. Gold, Au5%Ru and Au-4%V2O5 were all tested as possible contact switch materials. Au-4%V2O5, a dispersion strengthened material developed at Lehigh University, showed the most promise of the materials tested with the longest-life contact lasting more than 15.5x106 cycles. Evidence of time-dependent deformation and contact heating during cycling was noted in all materials tested. Material hardness was neither proportional to contact lifetime nor adhesive forces measured during testing. Surfaces of post-cycling contact surfaces were evaluated and failures were categorized by ductile or brittle separation characteristics. Separation characteristics were correlated by contact lifetime. |
