RF-MEMS beam components : FEM modelling and experimental identification of pull-in in presence of residual stress

TL;DR

This paper validates FEM models for RF-MEMS microbeams, incorporating residual stress effects, and demonstrates their accuracy in predicting pull-in voltage through experimental comparison, enabling residual stress identification.

Contribution

It introduces an integrated FEM modeling approach that accounts for residual stress and initial curvature in out-of-plane microbeams, validated by experimental results.

Findings

FEM models accurately predict pull-in voltage considering residual stress.

Experimental validation shows good agreement with numerical predictions.

Models enable residual stress estimation via reverse analysis of pull-in voltage.

Abstract

In this paper an experimental validation of numerical approaches aimed to predict the coupled behaviour of microbeams for out-of-plane bending tests is performed. This work completes a previous investigation concerning in plane microbeams bending. Often out-of-plane microcantilevers and clamped-clamped microbeams suffer the presence of residual strain and stress, which affect the value of pull-in voltage. In case of microcantilever an accurate modelling includes the effect of the initial curvature due to microfabrication. In double clamped microbeams a preloading applied by tensile stress is considered. Geometrical onlinearity caused by mechanical coupling between axial and flexural behaviour is detected and modelled. Experimental results demonstrate a good agreement between FEM approaches proposed and tests. A fairly fast and accurate prediction of pull-in condition is performed, thus numerical models can be used to identify residual stress in microbridges by reverse analysis from the measured value of pull-in voltage.