On Key Technology Of MEMS Switches

In a micro switch, the adhension force caused by the surface effect exerts great influences on the reliability of the contactors. Based on solid mechanics, elastic-plastic mechanics and adhension mechanics, a micro-nano scale elastic-plastic contact model was built in this paper. A tunnel current theory based on quantum mechanics was given to build the calculation model of tunnel current and contact resistance on a rough surface contactor. A micro permanent magnet switch was designed according to the electromechanical dynamic theory. In this paper, the research contents are as follows.1. Based on Lennard-Jones potential energy theorem and Hamaker hypothesis, the adhension force between a stiff sphere and an elastic surface was obtained. The contact deformation of the surface was calculated through classical elastic theory and the change rules of the contact force, the contact deformation and the contact area were studied through the simulated analysis.2. The contact mechanism between two contaminative contactors was studied in cases of the contamination carbon on the contact surface. The change rules of the contact force, the contact deformation and the contact area were studied.3. The contact stress computing model was built in this paper. The yielding stress of elastic surface was researched to get the plastic area and the plastic deformation.4. The deformation regulations of elastic and plastic area were given. The interval and the contact area between the sphere and the surface were analyzed. Taking gold for example, the stress-strain relationship was studied and the yield limit of gold was obtained.5. The plastic contact model was built in the paper. The contact stress, the deformation and the contact area of the surface were researched on the basis of the plastic contact model to get the attractive and repulsive area, the elastic and plastic deformation area.6. Using the tunnel current density formulas, the computational formulas of the tunnel current through a stiff sphere contactor and a stiff plane were given. The contact resistance was calculated and further the rules that the contraction area and the shrinkage of the contactor area changed with the interval between two contractors were presented. 7. The electric contact model was set up to calculate the contact force, tunnel current and contact resistance between a stiff sphere contactor and an elastic-plastic surface.8. As the micro mounds on the contactors being described according to normal distribution, the electrical contact model of a rough surface was built. The effects of the mounds radius, the mounds height error and the mounds number on the contact resistance were studied. Change laws of contact resistance that transfer with contact force and pressure between the contactors were obtained.9. A new type of micro permanent magnetic acceleration switch was designed. The static design laws were presented. The calculation model of the squeeze damping was built and the analytical formulae of the gas damp force and damp coefficient of the parallel flats in the MEMS devices were derived。10. According to the contact resistance model of the classical rough surface, the contact pressure-resistance and current-voltage curve were given.11. The dynamic model of the switch was built. The dynamic response under an acceleration excitation of the square wave signals was simulated.