We present the design of a micro-electro-mechanical-system(MEMS)-based power disconnect for use with the proposed 42-V automotive power systems. High-voltage power systems are prone to arcing, which occurs during power disconnections. The high arcing current may lead to severe damage on the systems and may expose electric shock hazards to humans. The objective of the MEMS-based power disconnect we propose is to eliminate arcing occurrence in the systems. To eliminate arcing, one alternative is to electronically terminate the power supply to the system prior to the physical disconnection. The integrated MEMS force sensor on the power disconnect will be activated as a service technician disconnects the connector. The power supply to the system will be electronically shut off to prevent arcing during the physical interruption. The MEMS force sensor on the disconnect has an overall dimension of 3600 μm××1000 μm×10 μm and is fabricated with the Micragem fabrication process. A displacement reduction mechanism is incorporated into the sensor design to increase the sensitivity of the force sensor. Results show that the sensor is capable of measuring a maximum force input of 10.7 mN, resulting from a 20-μm displacement on the sensing structure.
This paper focuses on the design and development of a novel MEMS based force sensor for use in a smart electrical switch which can be used to sense forces applied during the disconnection/connection of the switch. Sensed forces will permit the power to the switch to be turned on/off electronically to prevent arcing at 42 Volts, which would otherwise damage the switch electrical contacts. This paper focuses on the design of a packaging cover for the switch incorporated with a meso-structure, for input force reduction, using a Stereolithography fabrication process. This packaging cover will be installed on a standard ceramic pin grid array (PGA) package to which a MEMS force sensor will be wire-bonded. The complete sensor is proposed for use in smart electrical connectors within automobiles. The purpose of the packaging cover is to transform the macroscopic input force imparted by a technician during disconnection or connection of the switch into a grasping action on the sensor. The macroscopic input force is estimated to be 60N at maximum. To prevent potential damage on the MEMS sensor, the cover converts the applied force to a smaller force in the milli-Newton scale. Since the sensor is to be operated under the harsh environment of the automobile, transverse comb-drive capacitors are
selected as the force sensing technique. The capacitive MEMS sensor will be fabricated using PolyMUMPs surface micromachining. To ensure linearity, the displacement of the comb drive is limited to 1 &mgr;m for a net capacitance change of 0.013 pF. Principles of strain energy and Castigliano's Theorem are used to model the proposed cover design. It is found that for a 60 N input force, the design is capable of converting that force to a lateral displacement of 30.86 &mgr;m, which is equivalent to a 0.01 N force onto the sensor. Design analysis, and results from Finite Element Method (FEM) simulation of the cover design will be presented in this paper.
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