Strength Behaviour of Polysilicon Thin Film Flexure Hinge

Abstract

This work reports on strength behaviour of polysilicon thin film flexure hinge. In order to develop a microscopic modelling of thin film flexure hinge for microstructures, in situ test benches have been designed and fabricated. The experiment demonstrated that a deviation between the macroscopic theory value and experimental result. A model similar to that used for rotational stiffness in macroscopic steel is used to fit testing data for polysilicon film flexure hinge. The dynamic characteristic and fatigue behaviour of the thin film flexure hinge were also investigated. The hinge was excited by an integrated electro-thermal microactuator that could be self-heated and driven. Resonant frequency of the polysilicon flexure hinge test benches is 6.5 Hz, and the maximum operating frequency reached 1KHz. When a cyclic loading of 1μN.μm was exerted to the micromachining flexure hinge, the limit stress alternation number exceed 1.0×108. When the stress alternation number exceeded 1.0×109, the polysilicon beam of microactuator would lost its elastic character. If the micro hinge operated at high temperature (exceed 200/), the lifetime would decreased. If the working temperature were too high, the micro hinge would be burned out.