Increase of Magnetic Sensitivity of Magnetically Controlled MEMS Switches
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Increase of Magnetic Sensitivity of Magnetically Controlled MEMS Switches Sergey M. Karabanov, Dmitry V. Suvorov, Gennady P. Gololobov, Dmitry Y. Tarabrin, Evgeny V. Slivkin Ryazan State Radio Engineering University 59/1 Gagarina St., Ryazan 390005, Russia ABSTRACT The paper presents the research results of influence of various parameters of magnetic field concentrator geometry on sensitivity of magnetically controlled MEMS switches. It is shown that magnetic sensitivity increases with the growth of the magnetic concentrator width and practically does not depend on its length. It is established that dependence of magnetic sensitivity on the overlap length of the ferromagnetic flexible contact-concentrator has a minimum corresponding to 2-3 lengths of the contact gap. Recommendations on sensitivity increase of magnetically controlled MEMS switches are provided. INTRODUCTION Magnetically controlled MEMS switches are the functional analogue of small reed switches and some integrated Hall sensors [1,6,8]. This is a marketable product combining the advantages of reed switches (absence of energy consumption in standby mode, direct load commutation, low contact resistance) and Hall sensors (small size, possibility of SMT assembly). The complex task of simultaneous increase of switches magnetic sensitivity, resistance maintenance to impact force (inertial resistance), and increase of contact pressure force determining the value of contact resistance is critical. There are two main types of magnetically controlled MEMS switches geometry: switches with end fixation of a ferromagnetic flexible contact or its fastening on torsions [3] which mode of operation is based on reorientation of an extended ferromagnetic flexible contact along magnet-like lines; switches with two mobile ferromagnetic flexible contacts or one moving flexible contact and one fixed flexible contact [4, 5] the mode of operation of which is similar to the one of reed switches [3,7,8]. Each design type has its benefits and drawbacks. The general thing is that increase of magnetic sensitivity due to reduction of fastening rigidity of the flexible contact results in decrease of G-force resistance, and accordingly, in essential reduction of field of application of magnetically controlled MEMS switches. The problem of magnetic sensitivity increase of magnetically controlled MEMS switches on condition of keeping G-force resistance is important. The prospective way of this task solution is the use of magnetic concentrators representing a fixed plate of trapezoidal form the narrow end of which is directed to the contact overlap area. The plate can perform simultaneously the functions of the conductor and heat sink, the contact platform is located on the concentrator the narrow end. The use of magnetic concentrators does not effect Gforce resistance of MEMS switches [2,3]. The purpose of the work is the complex detailed calculation of magnetic system of MEMS switches with magnetic concentrators and comparative evaluation according to the magnetic sensitivity criterio
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