Active Opening Force and Passive Contact Force Electrostatic Switches for Soft Metal Contact Materials

• Published in: Journal of microelectromechanical systems Vol. 15; no. 5; pp. 1235 - 1242
• Main Authors: Oberhammer, J., Stemme, G.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.10.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Actuators; Appliances; Applied sciences; Circuit properties; Contact; Contact force; Contact material; Contacts; curved-electrode actuator; Deflection; Design optimization; Electric, optical and optoelectronic circuits; Electronics; Electrostatics; Exact sciences and technology; Gold; Inorganic materials; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical instruments, equipment and techniques; mems switches; Microelectromechanical systems; microelectromechanical systems (MEMS) switch; Micromechanical devices; Micromechanical devices and systems; microswitch; Microswitches; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Physics; RF MEMS; Switches; Actuators; Gold; Microrelays; Contact material; Capacitive transducer; Metals; Switches; Contact resistance; Experimental study; curved-electrode actuator; Adhesion; Cantilever beam; Bistability; RF MEMS; microswitch; microelectromechanical systems (MEMS) switch; Microwave circuits; Force control; Curvature; Microelectromechanical device; Electrostatic force
• ISSN: 1057-7157; 1941-0158; 1941-0158
• DOI: 10.1109/JMEMS.2006.882810

This paper reports on a mechanically bi-stable, electrostatically actuated switch mechanism with a large active opening force and a small passive closing force, designed to fit the contact and opening force requirements of soft contact materials such as gold. So far, most microelectromechanical systems (MEMS) switch designs have been optimized for a large contact force without paying too much attention to the opening force. In the "conventional," most commonly used electrostatic microswitch concept, the force of the actuator is used to close the switch contacts, and the switch is opened by the passive restoring force of the deflected cantilever or membrane. This concept results in a large contact force, but the opening force is typically too small to overcome the contact adhesion force of soft metals, which makes this concept less suitable for contact materials such as gold with its low contact resistance at low contact forces. The switch concept presented in this paper is based on two cantilevers laterally moving by curved electrode actuators. The tips of the cantilevers are endowed with hooks which can be mechanically interlocked. In the latched state, the spring forces of the deflected cantilevers also act as the passive contact force between the switch contacts. The opening force is actively created by the curved-electrode actuators, which are utilized close to their best electromechanical operating point resulting in a maximum contact separation force. The theoretical discussion of the new concept as compared to conventional switch designs is supported by simulation results, measurements on fabricated devices, and by an analysis of exemplary switches published in the literature