Mechanical fatigue analysis of gold microbeams for RF-MEMS applications by pull-in voltage monitoring

This work is focused on the reliability of gold microcantilevers under the effect of mechanical fatigue. A dedicated device for testing the material is designed and built; the material degradation is monitored during the tests by means of a novel technique based on the control of the pull-in voltage of the device, which was demonstrated to be related to the loss of mechanical strength. The fatigue effect is produced through the excitation of the device at a frequency near the resonance; the excitation frequency and the time of actuation are used as a counter for the number of cycles. The lifetime of the device is measured under variable levels of vibration amplitudes; the number of cycles to failure is estimated within a specific range of actuation voltages by means of the W?hler diagram obtained by experiments. The fatigue limit is also estimated following the stair-case method.