A Self-Adaptive Stiffness Approach to Improving the Robustness of Electrostatic Switches Against Parameter Variations

The “soft-landing” effect during the closure of RF-MEMS switches is crucial for improving their reliability. However, the rebound suppression effectiveness has rather poor robustness against the dimension deviations and waveform distortions resulting from micro-fabrication tolerance, wear and tear, and circuit aging in the device's life-cycle. In contrast to the traditional constant stiffness system, this letter proposes a novel self-adaptive stiffness approach, whereby the system's stiffness increases markedly with increasing displacement so that its elastic potential energy against the electrostatic energy is mainly concentrated in the region near the closing position for a better rebound suppression. Our experiments show that, for an ensemble of fabricated devices subjected to the unified dual-pulse actuation waveform, the reliable working gap range of the new approach (1.4 μm) in which the switches can be closed completely, is 4.6 times larger than that of the constant stiffness scheme (0.3 μm). In addition, for the actuation voltage and pulse time with variations of up to ±10%, this new approach shows significantly reduced closure time and bounce.