Strength Analysis of MEMS Micromirror Devices - Effects of Loading Mode and Etching Damage

Strength evaluation method for MEMS micromirror has been proposed. Pure bending and combined loading tests have been performed and torsion strength has been estimated from those results. Two-parameter Weibull distribution was used to evaluate the fractured stresses estimated from FEM model. There exists the difference in strength between pure bending and combined loading. From the load factor analysis, it is found that both geometry and stress distribution have to be considered to estimate the strength of MEMS since flaw population is non-uniformly distributed. It is also found torsional strength can be estimated on the safe side by using the result of combined loading test. From the comparison between two kinds of specimen fabricated by different etching conditions, it is found that the fracture strength is greatly affected by the amount of etching damage (notching).