Contact Resistance in Flat-on-Flat and Sphere-on-Flat Thin Films

The dependence of contact resistance on force between flat, thin-films is thought to be different than that in bulk materials. Multiple mathematical and finite element models have attempted to model this dependence but have been limited in the ranges over which they are valid. Experimental results have shown that the contact resistance between flat, thin films is greater than that predicted by Holm theory when the Holm equivalent radius is greater than the film thickness for gold films of thicknesses between 0.1 and 0.5 μm. This paper fits an equation to the FEM results presented in and the experimental results presented in. New experimental results between gold sphere-on-flat contacts of film thickness 1 μm and contact radii of 20 and 40 μm are presented and the results are compared to those predicted by the equation fitted to the previous FEM and experimental flat-on-flat contact results. As with the thin film flat-on-flat contacts, the thin film sphere-on-flat contacts also have a contact resistance higher than that predicted by Holm in the region where the Holm equivalent radius is greater than the film thickness. Also examined is the transition in the force v. contact resistance relationship at the point where the Hertz radius of contact becomes greater than the Holm equivalent radius of contact.