Micromachined Pt–Rh and stainless steel relays for high power DC applications

This paper explores the viability of bulk metal foils, in particular platinum–rhodium (Pt–Rh), for use in high power micromechanical relays. The electrical and thermal response of electrostatically actuated three-terminal micro-relays is evaluated. The micro-relays have a footprint of 6.5 mm2 and an actuation area of 1.32 mm2. A stacked double cantilever structure isolates the actuation electrode from the current path. A micromachined heat sink is located on the upper cantilever. The devices are fabricated by micro-electrodischarge machining and directly assembled on power rated printed circuit boards. The impact of contact materials, and forced cooling is addressed. Preliminary results suggest that the Pt–Rh devices have total on-state resistances of 1.25 Ω and can handle currents substantially in excess of 1 A, and potentially in excess of 2.6 A.