MEMS Mechanical Fatigue: Experimental Results on Gold Microbeams

This paper proposes a new strategy for detecting material strength loss under mechanical fatigue on the basis of the pull-in voltage of the test device. Gold microbeam specimens are tested for mechanical fatigue using an electrostatically actuated dedicated device. The design of the fatigue device is discussed, providing the analysis of stress distribution inside the specimen. The finite-element method is used to simulate the electromechanical coupling. The fatigue limit is estimated through the ldquostaircaserdquo method, and a Wohler curve is obtained from experiments. The surface topography evolution is monitored by scanning electron microscope images; specimen failure modes and material degradation are discussed, revealing the local yield of the material on the upper surface of the beam. The type of degradation appears to be in agreement with the established literature as a consequence of fatigue.