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

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

[1]  Tennyson Smith,et al.  The hydrophilic nature of a clean gold surface , 1980 .

[2]  Hiroshi Hosaka,et al.  Electromagnetic microrelays: concepts and fundamental characteristics , 1993, [1993] Proceedings IEEE Micro Electro Mechanical Systems.

[3]  J. Fluitman,et al.  Electrostatic curved electrode actuators , 1995, Proceedings IEEE Micro Electro Mechanical Systems. 1995.

[4]  S. Majumder,et al.  Study of contacts in an electrostatically actuated microswitch , 1998, Electrical Contacts - 1998. Proceedings of the Forty-Fourth IEEE Holm Conference on Electrical Contacts (Cat. No.98CB36238).

[5]  Y. Hirai,et al.  Study of large bending and low voltage drive electrostatic actuator with novel shaped cantilever and electrode , 1998, MHA'98. Proceedings of the 1998 International Symposium on Micromechatronics and Human Science. - Creation of New Industry - (Cat. No.98TH8388).

[6]  M. Mehregany,et al.  Contact physics of gold microcontacts for MEMS switches , 1998, Electrical Contacts - 1998. Proceedings of the Forty-Fourth IEEE Holm Conference on Electrical Contacts (Cat. No.98CB36238).

[7]  J. Schimkat,et al.  Contact materials for microrelays , 1998, Proceedings MEMS 98. IEEE. Eleventh Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems (Cat. No.98CH36176.

[8]  K. Pister,et al.  Lateral MEMS microcontact considerations , 1999 .

[9]  J. Schimkat,et al.  Contact measurements providing basic design data for microrelay actuators , 1999 .

[10]  Bernd Hillerich,et al.  Comparison of lateral and vertical switches for application as microrelays , 1999 .

[11]  Adele E. Schmitz,et al.  Surface-micromachined RF MEMs switches on GaAs substrates , 1999 .

[12]  Y. Komura.  Micro Machined Relay for High Frequency Application , 1999 .

[13]  Ernst Obermeier,et al.  Microactuators and their technologies , 2000 .

[14]  Thomas R. Ohnstein,et al.  Factors enhancing the reliability of touch-mode electrostatic actuators , 2000 .

[15]  Gabriel M. Rebeiz,et al.  RF MEMS switches and switch circuits , 2001 .

[16]  Helmut F. Schlaak.  Potentials and limits of micro-electromechanical systems for relays and switches : invited paper , 2002 .

[17]  L. L. Mercado,et al.  A mechanical approach to overcome RF MEMS switch stiction problem , 2003, 53rd Electronic Components and Technology Conference, 2003. Proceedings..

[18]  Richard H. Morrison,et al.  MEMS switches , 2003 .

[19]  J. Maciel,et al.  A packaged, high-lifetime ohmic MEMS RF switch , 2003, IEEE MTT-S International Microwave Symposium Digest, 2003.

[20]  K. Leedy,et al.  Selecting metal alloy electric contact materials for MEMS switchesThe views expressed in this paper , 2004 .

[21]  S. Majumder,et al.  Adhesion and contact resistance in an electrostatic MEMS microswitch , 2005, 18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005..

[22]  J. Oberhammer,et al.  Numerical algorithm for quasi-static nonlinear simulation of touch-mode actuators with complex geometries and pre-stressed materials , 2005, The 13th International Conference on Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05..

[23]  J. Oberhammer,et al.  Mechanically Tri-Stable In-Line Single-Pole-Double-Throw All-Metal Switch , 2006, 19th IEEE International Conference on Micro Electro Mechanical Systems.

[24]  N. McGruer,et al.  Mechanical, Thermal, and Material Influences on Ohmic-Contact-Type MEMS Switch Operation , 2006, 19th IEEE International Conference on Micro Electro Mechanical Systems.