Characterisation of the fabrication process of freestanding SU-8 microstructures integrated in printing circuit board in microelectromechanical systems

Abstract

The characterisation of the fabrication process to develop freestanding SU-8 structures integrated in printing circuit board in microelectromechanical systems (PCBMEMS) technology is presented. SU-8 microcantilevers, microbridges, microchannels and micromembranes have been fabricated following the described procedure. Adherence between FR4 substrate and SU-8 has been examined using the destructive blister method, evaluating the surface energy. Residual thermal stress has also been analysed for this integration and compared when using other substrates. Moreover, an estimation of the copper wet etching with cupric chloride has been performed in order to understand how this isotropic etching affects the geometry of the copper structures. Finally, stiction has been observed and examined, estimating the adhesion energy responsible for this effect.