Electrical performance of contaminated rough surfaces in contact

The inevitable presence of thin insulating films at the contact interface of electrical contacts has an adverse effect on their performances. An attempt is made to study the electrical performance of degraded electrical contacts where insulating films reside at the contact interface of conductive rough surfaces. The degradation mechanism is based on gradual growth of an insulating film and the characteristics of the insulating film are assumed to be known without considering details regarding the physical and chemical origins of the growth mechanisms. The present study relies on recently developed theories for electrical contact resistance of clean and fully contaminated rough surfaces, thus bridging the gap between these two extreme cases. For thick insulating films no current flow occurs across contaminated asperity contacts, whereas for thin insulating films tunneling currents are taken into account. A relationship is obtained between the degraded electrical contact resistance and the metallic conductance area. The effect of tunneling currents on the performance of partially contaminated surfaces is negligible due to the considerable current flow across the metallic asperity contacts. The electrical performance of fully contaminated surfaces is sensitive to the thickness and integrity of the insulating films and, therefore, can be exploited to study the durability of thin insulating films.