MEMS micromirror is used as optical switching or scanning devices, etc. Since the device is made from single crystalline silicon, the fracture stress involves large scattering. Therefore, reliability-based design procedure is indispensable. We propose a method to detect the design stress of both static and fatigue strengths.
As for static strength, a method to determine design stress by using Bayesian inference is proposed, where the design stress is determined by combining a few number of strength data of actual product and prior distribution based on sufficient experimental data. The proposed method is verified by simulated data through the comparison with conventional maximum likelihood method. It is found that the proposed method is especially effective when there is not sufficient strength data. As for the design stress for fatigue strength, a method to evaluate fatigue life in general working environment by extrapolating the experimental data of accelerated fatigue life tests is proposed. As a result, the fatigue design chart based on 99% prediction interval is shown.
