Development of Evaluation methods for mechanical properties in micro-sized components for MEMS devices

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Firstly, bending tests were developed using micro-sized bending specimens made of SU-8 photo resist to clarify the bending properties of a micro-sized polymer. A digital microscope was used for the in situ observation of elastic and plastic deformation of cantilever type bend specimens, which had been cut from sheets using a laser cutting system. Loads were applied to these cantilevers using a mechanical testing machine, which was developed by us for micro-sized materials for Micro-electro mechanical systems (MEMS). Load-displacement curve under bending load conditions in micro-sized SU-8 specimens clearly shows ductile manner, although SU-8 is usually brittle material. Shear band like deformation was appeared near root of the specimens after maximum load, and then this plastic deformation area was expanded during loading. The ductile behavior in a micro-sized SU-8 may be caused by regional shear band deformation near the root.Secondly, micro-sized bending tests were performed using epoxy type photo-resist, SU-8, to clarify effects of a processing condition, UV exposure, Post baking and heat curing conditions on bending properties. Form the results in the first year, photo-masks for micro-sized bending specimens were planed. Load-displacement curves of most microsized SU-8 specimens show in an extremely ductile manner and all the specimens were failed by root of the beam. Young's modulus, Yield point and bending strength of SU-8 specimens remarkably increase with increasing exposure dose and heat curing. All the results clarify that bending properties of microsized photoresist are strongly affected by UV exposure and heat curing.