Mechanically tri-stable, true single-pole-double-throw (SPDT) switches

• Published in: Journal of micromechanics and microengineering Vol. 16; no. 11; pp. 2251 - 2258
• Main Authors: Oberhammer, J, Tang, M, Liu, A-Q, Stemme, G
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.11.2006; Institute of Physics
• Subjects: actuators; Applied sciences; design; Electronics; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; low-voltage; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Microelectronic fabrication (materials and surfaces technology); Micromechanical devices and systems; Physics; Precision engineering, watch making; rf mems switch; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transducers; Gold; Input-output; Input signal; Stiction; Capacitive transducer; Switches; Sog; Adhesion; Curvature; Electrostatic actuators; Cantilever beam; Electric motors
• ISSN: 0960-1317; 1361-6439; 1361-6439
• DOI: 10.1088/0960-1317/16/11/001

This paper reports on a mechanically tri-stable switch mechanism based on laterally moving electrostatic curved-electrode actuators. The switch is configured in a 'true'single-pole-double-throw configuration (SPDT), i.e. a single-switch mechanism allows for the input signal to be switched between two output ports. The switch has three stable states: (1) input to first output; (2) switch off; (3) input to second output. Because of a latching mechanism, these states are mechanically stable, i.e. they are maintained without applying external actuation energy. The fabrication of the switches is done by a single photolithographical step and deep etching of a silicon-on-glass wafer which is subsequently coated with sputtered gold. The switch design features active opening, and the contact force is created passively by the deflected cantilevers. The curved-electrode actuators are utilized close to their end position where they develop their maximum force to guarantee a very large opening force which makes the switch less susceptible for contact stiction. The actuation voltages for different designs and functions of the switches are between 30 and 85 V.