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Material Characterization and FE Analysis of Electroplated Microrelays

: Vogel, J.; Sommer, J.-P.; Faust, W.; Kieselstein, E.; Michel, B.

Materials Week 2000. Proceedings
Frankfurt: Werkstoffwoche-Partnerschaft GbRmbH, 2000
8 pp.
Materials Week <2000, München>
Conference Paper
Fraunhofer IZM ()

In comparison to semiconductor relays electromechanical relays are often favoured due to their electrical isolation of control and load circuit, mechanical separation of current lines and EMC-requirements. In extension of traditional relay techniques based on driven electromagnetic coils, MEMS relays are developed for low power and high frequency applications. The driven motivation of the work are the reduction of size and materials applying microforming techniques, the SMD-compatibility, the integration of microelectronics and the improvement of cost-effectiveness of switching technologies, of lifetime and of electromechanical reliability. Both the thermomechanical compatibility (TMC) and the electromechanical reliability become more and more important in microfabrication process under the point of view of new microtechnologies, design and optimised materials. For that reason, the hybrid procedure applied consists of Z the finite element analysis (FEA), which is used for design optimisation and finally leads to general design rules, and Z different material testing techniques to analyse the material behaviour during microfabrication and to determine selected electromechanical properties. Different design variants of electrostatically actuated microrelays have been simulated by 2d- as well 3d-FEA in order to characterise the mechanical response to switching on-and-off processes. The main target was to find an optimised relationship between voltage and contact forces. The material characterisation was focused on the analysis of mechanical parameters and the measurement of applied force contact resistance curves. Suitable measurement techniques were used, among them laser scanning microscopy for surface roughness analysis, the universal hardness for EHU-determination and X-ray diffraction for texture and residual stress analysis. Furthermore, a new kind of load resistance measuring system was virtually prototyped using 3D-CAD software I-DEAS. Based on an innovative kinematic solution the forces of the closed contacts can be measured with an accuracy of better than 50 µN. For different coatings like Ag, PdNi or AuNi the applied load contact resistance curves will be given and discussed.