Design, simulation and characterization of an inertia micro-switch fabricated by non-silicon surface micromachining

A multilayer structural inertia micro-switch with conjoined snake springs has been designed and successfully fabricated based on non-silicon surface micromachining technology. The micro-switch consists mainly of a suspended thick proof mass as a movable electrode that is located above the supporting layer, and an elastic beam with holes as a fixed electrode that is some distance above the proof mass. The designed proof mass is much thicker than the conjoined snake spring section. This conformation benefits the improvement of its sensitivity and the contact effect, while protecting the switch against severe shock damage from intensive impact of the switch contacts. The fabricated prototype micro-switch has been tested and characterized. The result indicates that the response time and the contact time of the micro-switch are about 0.40 ms and 12 µs, respectively, when a 100g acceleration is applied, which shows relatively better sensitivity and contact effect. This result agrees with that of dynamics finite-element contact simulation about the designed micro-switch. Besides, no severe plastic deformation occurs to springs or elastic beams after over 10 000 dropping tests in the optical profiling characterization. The fabricated micro-switch shows satisfactory mechanical behavior.

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