Martin Geear, Alan Finlay (Microsaic Systems Ltd.)
We have demonstrated electromechanical circuit breakers based on MEMS structures. The devices use laterally moving thermal actuators to set and trip low-resistance contacts. The actuators are fabricated from electroplated Ni, on Si substrates, with Au-Co contact layers. Trip currents of 300 mA are obtained, with contact resistances below 1 Ohm. Rapid tripping (below 50 ms) is achieved, even for modest over-current levels, and sensitivity to ambient temperature is much less than for positive temperature coefficient (PTC) devices typically used for over-current protection in electronics applications. These MEMS devices offer an ultra-miniature, potentially low cost solution for circuit protection applications at low currents, where a high degree of system control is desired.
Latch region of a prototype circuit breaker
fabricated in electroplated metal on silicon.