MEMS Mechanical Fatigue: Effect of Mean Stress on Gold Microbeams

In this paper, the reliability of gold components for microelectromechanical systems applications is studied by evaluating the mechanical fatigue behavior. The lifetime of microspecimens under alternate loads with different mean stress conditions is tested with the introduction of an original experimental procedure. Dedicated fatigue test devices are designed and fabricated with the aim of producing an alternate load on the embedded specimen. Electrostatic actuation is used as a driving force. Gold microbeams are tested under tensile variable load with different levels of mean and alternate stresses. FEM models are exploited to estimate the stress level produced in the material under the variable actuation conditions. Experimental results are analyzed to investigate the effects of different mean stress levels on lifetime under mechanical fatigue. The fatigue results are represented by a Goodman-Smith diagram scheme. Surface topography degradation is monitored through scanning electron microscope images. The modes of failure are in agreement with the literature, which is a consequence of fatigue degradation.