Fluid-electrostatic-mechanical modeling of the dynamic response of RF-MEMS capacitive switches

For predicting dynamic responses of electrostatically actuated RF-MEMS it is imperative to be able to include fluid squeeze film effects (air damping) in a directly coupled electrostatic-mechanical model, in an efficient and accurate way. This paper presents the modeling methodology to predict the dynamic response of a capacitive RF-MEMS obtained with implementation of a isothermal non-linear compressible Reynolds equation in a directly coupled fluid-structural element in a pre-release of the Ansys FE software. Multi-physics simulations of harmonic (AC) responses and transient switching cycles, in which the switch closes and non-linear contact is included, were validated with measurements. It is concluded that the presented multi-physics model is a powerful tool for virtual device design and indispensable for predicting functional performance of RF-MEMS. This model provides more accurate transient results than models based on the linearized Reynolds equations.