A Comparison of Micro-Switch Analytic, Finite element, and Experimental Results

Abstract

Electrostatically actuated, metal contact, micro-switches depend on having adequate contact force to achieve desired, low contact resistance. In this study, higher contact forces resulted from overdriving cantilever beam style switches, after pull-in or initial contact, until the beam collapsed onto the drive or actuation electrode. The difference between initial contact and beam collapse was defined as the useful contact force range. Micro-switch pull-in voltage, collapse voltage, and contact force predictions, modeled analytically and with the CoventorWare finite element software package, were compared to experimental results. Contact resistance was modeled analytically using Maxwellian spreading resistance theory. Contact resistance and contact force were further investigated by varying the width of the drive electrode. A minimum contact resistance of 0.26 Ω role= presentation style= box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; font-style: normal; font-weight: normal; line-height: normal; font-size: 14.4px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative; \u3eΩ was measured on micro-switches with 150 μm-wide drive electrodes. The useful contact force range for these devices was between 22.7 and 58.3 V. Contributions of this work include: a contact force equation useful for initial micro-switch designs, a detailed pull-in voltage, collapse voltage, and contact force investigation using CoventorWare, a direct comparison of measured results with analytic and finite element predictions, and a means of choosing a micro-switch operating point for optimized contact resistance performance