Electrical Switching Using Compliant Metal Infiltrated Multi-Wall Nanotube Arrays
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1085-T02-05
Electrical Switching Using Compliant Metal Infiltrated Multi-Wall Nanotube Arrays Justin Bult1, W. Gregory Sawyer2, Andrey Voevodin3, Chris Muratore3, Pam Dickrell2, Sunil Pal1, Pulickel Ajayan1, and Linda Schadler1 1 Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180 2 Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL, 32611 3 Air Force Research Laboratory, Wright-Patterson AFB, OH, 45433 ABSTRACT The topology of conventional noble-metal-coated switch counterfaces creates modes of switch failure via fouling, arcing, and local melting when impacted. To avoid these failure phenomena, compliant conductive contact surfaces of vertically aligned multi-wall nanotube arrays grown on conductive substrates have been fabricated. Infiltration of the array by noble metal results in a robust compliant switch contact surface. Cyclic hot-switch testing of the nanotube based switch, via modified nano-indentation, results in performance surpassing conventional designs with stable resistance of 0.4 Ω over 3000 cycles for 25 mN contacting force. Investigating the physical performance of the array shows the array is compacted less than 3% over the first 500 cycles with no observable compaction through the remaining cycles. The improvement in performance of the nanotube based switch is attributed to the ability for the compliant contact surface to conform to the probe tip geometry, increasing the effective contact surface area. INTRODUCTION In metal-metal low-force electrical switch contacts there are a limited number of design variables to be considered. One can look at modifying the contacting configuration, the contacting force, or the contacting materials of the switch counterfaces. The fundamental criteria used to optimize these variables within the design envelope are the contact resistance and functional lifetime of the switch over a given operational range. To improve and prolong the switch operation, the detrimental effects of contamination, oxidation, and local welding must be avoided in the context of the design modifications being undertaken. For the case of switch contact counterface material; the most conventional material is the goldgold contact. Gold exhibits superior performance due to its inert nature, low potential to be oxidized, and low electrical resistance [1]. Yet the nature of the gold-gold contact causes asperity driven failure [2,3]. The true contact area of the counterfaces is considerably lower than would be calculated for theoretically ideal smooth surfaces [4]. This leads to excessive current being passed through asperity created constrictions and to reduced performance both in terms of resistance and switch lifetime [3].
An as yet unexplored avenue for a switch contacting material is a contacting surface with a tailored compliant counterface with conductivity and thermal stability similar to that of the noble metals already in use. To produce such a material, a composite approach is undertaken herein; combining the elastic capabi
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