Optimization of a Cantilever Microswitch with Piezoelectric Actuation

Abstract

This paper considers MEMS microswitches with piezoelectric-film actuation. A mathematical actuator model is established that accounts for normal stress at the piezo-substrate interface, in addition to shear stress. This model gives more accurate predictions for relatively thicker piezoelectric layers.

Maintaining adequate contact force between switch electrodes is important in ohmiccontact switches, but parallel contact geometry is also important in switches that provide capacitive coupling between the signal lines. Furthermore, ‘off-state’ isolation is governed by electrode gap when open. The presented mathematical model demonstrates the relationships between these factors and the switch geometry. Optimum conditions are derived.

Keywords

MEMS microswitches piezoelectric actuation optimization

References

Alzahrani, B.A. and Alghamdi, A.A.A. 2003. ‘‘Review of the Mechanics of Materials Models for One-dimensional Surfacebonded Piezoelectric Actuators,’’ Smart Materials and Structures, 12: N1-N4 .

Crawley, E.F. and Luis, J. de. 1987. ‘‘Use of Piezoelectric Actuators as Elements in Intelligent Structures,’’ AIAA Journal, 25(10): 1373-1385 .

Crawley, E.F. and Anderson, E.H. 1989. Detailed Models of Piezoceramic Actuation of Beams, American Institute of Aeronautics and Astronautics , Vol. 89-1388-CP, pp. 2000-2011.

Fox, C.H.J. , Chen, X. , Hong, W. , Kirby, P.B. and McWilliam, S. 2002. ‘‘Development of Micromachined RF Switches with Piezofilm Actuation,’’ In: Proc. SPIE Conference on Smart Structures and Materials: Smart Electronics, MEMS and Nanotechnology, pp. 40-49 .

Hiltmann, K. , Keller, W. and Lang, W. 1999. ‘‘Micromachined Switches for Low Electric Loads,’’ Sensors and Actuators, A Physical, 74: 203-206 .

Hyman, D. and Mehregany, M. 1999. ‘‘Contact Physics of Gold Microcontacts for MEMS Switches,’’ IEEE Transactions on Components and Packaging Technology, 22(3): 357-364 .

Lee, J.Y. and Kang, S.W. 1999. ‘‘A Characterisation of the Thermal Parameters of Thermally Driven Polysilicon Microbridge Actuators using Electrical Impedance Analysis,’’ Sensors and Actuators, 75: 86-92 .

Petersen, K. 1979. ‘‘Micromechanical Membrane Switches on Silicon,’’ IBM Journal of Research and Development, 23: 376-385 .

Ren, H. and Gerhard, E. 1997. ‘‘Design and Fabrication of a Currentpulse-excited Bi-stable Magnetic Microactuator,’’ Sensors and Actuators, A58: 259-264 .

10.

Smits, J.G. and Choi, W. 1991. ‘‘The Constitutive Equations of Piezoelectric Heterogenous Bimorphs,’’ IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 38(3): 256-271 .

11.

Steel, M.R. , Harrison, F. and Harper, P.G. 1978. ‘‘The Piezoelectric Bimorph: An Experimental and Theoretical Study of Its Quasistatic Response,’’ Journal of Physics, D: Applied Physics, 11: 979-989 .

12.

Schimkat, J. 1999. ‘‘Contact Measurements Providing Basic Design Data for Microrelay Actuator,’’ Sensors and Actuators, A Physical, 73: 138-143 .

13.

Wang, Qing-Ming and Eric, C.L. 1998. ‘‘Performance Analysis of Piezoelectric Cantilever Bending Actuators,’’ Ferroelectrics, 215: 187-213 .

14.

Wood, R. et al. 1998. ‘‘MEMS Microrelays,’’ Mechatronics, 8: 535-547 .

15.

Yao, J. Jason and Chang, M. Frank 1995. ‘‘A Surface Microtmachined Miniature Switch for Telecommunications Applications with Signal Frequencies from DC up to 4 GHz,’’ In: Transducers’ 95, (Proc. 8th International Conference on Solid-State Sensors and Actuators, and Eurosensors IX), June 25-29.