AVS 46th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Wednesday Sessions
       Session MM-WeA

Paper MM-WeA6
Adhesion Properties of Gold-on-Gold Microswitch Contacts

Wednesday, October 27, 1999, 3:40 pm, Room 620

Session: Micro-Science and Tribology
Presenter: S. Majumder, Northeastern University
Authors: S. Majumder, Northeastern University
N.E. McGruer, Northeastern University
G.G. Adams, Northeastern University
P.M. Zavracky, Northeastern University
R.H. Morrison, Northeastern University
J. Krim, North Carolina State University
Correspondent: Click to Email
Electrostatically actuated microswitches have been developed at Northeastern University. As part of this effort, gold-on-gold microswitch contacts have been studied on the basis of electrical measurements, surface analysis, and an analytical model of the contacts.@footnote 1@ Measurements show that the turn-off voltage of the switch is often substantially smaller than the turn-on voltage, an effect which is not predicted by an electromechanical model of the actuation mechanism. Also, contact stiction is a dominant mode of eventual switch failure. Motivated by these observations, we extend our study of contacts to include adhesive surface forces at the contact interface. We consider the applicability of the JKR and DMT surface force models.@footnote 2@ to our problem. We examine the validity of these models through various measurements. Under typical operating conditions, the contact force is approximately 40 µN, the spring force which returns the switch to the off position is 150 µN, and the adhesion force (minimum spring force required to turn off the switch) usually ranges from 10-50 µN for a major portion of the switch lifetime (10@super 4@ - 10@super 6@ switching cycles). Failure by stiction is preceded by a gradual increase in the adhesion force. The adhesion force has a strong (inverse) correlation with the contact resistance, and some correlation with the maximum applied contact force during the on-cycle. Other results that are compared with the model include the variation of contact resistance with contact force during loading and unloading, the contact resistance when the switch just turns on and off, and the effect of loading history. @FootnoteText@ @footnote 1@ S. Majumder, N.E. McGruer, P.M. Zavracky, G. G. Adams, R. H. Morrison, J. Krim, Transducers '97, Chicago, IL (1997). @footnote 2@ M. D. Pashley, J. B. Pethica, D. Tabor, Wear, vol. 100, pp. 7-31, 1984. .