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Étude expérimentale et modélisation du contact électrique et mécanique quasi statique entre surfaces rugueuses d'or : application aux micro-relais mems

Abstract : The multi scale study of quasi static electrical contact is aimed at understanding those in MEMS microswitches. In this work, an accurate modeling of contact is developed to validate constitutive relations based on measurements obtained through the development of two original experimental set ups: a precision balance, which enables to perform a macroscopic contact between crossed roads coated with thin films of the materials to be tested, and a nanoindenter instrumented for electrical measurements reproducing microswitches contacts. They both allow a comparative study of different samples depending on the force (from μN to N), current (µA to A), surface condition (roughness) or time, while the contact is characterized through its electrical resistance. The measurements are obtained in the first place for gold, the reference contact material for MEMS microswitches applications. The study of large contacts was nevertheless extended to Ru, Rh, Pt and Au-Ni alloy.The results obtained using the precision balance showed the need to take into account the influence of the thin film configuration of contact materials, both in terms of mechanical (roughness) and electrical (distribution of current lines). Their comparison to a statistical model of rough contact gives satisfactory results. This approach also required the development of an image analysis algorithm of topographic maps obtained through atomic force microscopy. It allows quantifying precisely the position, height and radius of curvature of each surface asperity.Measurements made using the nanoindenter showed the effect of the time of closure of the micro contact on electrical resistance values. The creep of asperities may be partly responsible for the observed time decay, leading to limit resistance values comparable to those calculated using a numerical modeling of the contact between discretized asperities and a smooth sphere.
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Pierre-Yves Duvivier. Étude expérimentale et modélisation du contact électrique et mécanique quasi statique entre surfaces rugueuses d'or : application aux micro-relais mems. Autre. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2010. Français. ⟨NNT : 2010EMSE0583⟩. ⟨tel-00740248⟩

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