Micro-contact performance and reliability under low frequency, low amplitude, alternating current (AC) test conditions

This paper presents an experimental investigation of micro-contact performance (i.e. contact resistance) and reliability (i.e. successful cycles) evaluated under time-varying, low frequency, low amplitude, alternating current (AC) test conditions. Previous research efforts have focused on either on direct current (DC) or high frequency, radio frequency (RF) test conditions. This works attempts to bridge the gap in prior work by generating knowledge related to frequency, phase, and amplitude effects on micron-sized electrical contacts. Contact support structures, micromachined with gold on gold micro-contacts, were actuated using an externally applied contact load of approximately 200 μN and tested in dry, nitrogen ambient environments to minimize pre-test contact surface contamination. Contact resistances measured were comparable to those obtained using a DC. However, reliability is drastically reduced with AC signals between 100 to 100 kHz. Device failure typically occurred prior to 10k cycles on devices proven to last beyond 100M cycles or more under DC conditions. Phase of the AC appeared to have some influence on the manner of failure, as did AC signals that persisted through contact opening. In all cases examined, noticeable physical damage in the form of material migration was observed using a scanning electron microscope.