Limits of high density, low-force pressure contacts

The prosaic pressure contact is a source of unreliability not only in completed systems but more seriously in testing of ICs prior to packaging. Using a custom-built apparatus, pressure contacts are characterized with applied forces down to a few nN and contact areas down to 10^-11 cm². Nominally clean gold-gold and iridium-gold contacts in air exhibit resistivities higher than that predicted from a simple model based on the plastic deformation of the gold. Interfacial films appear to be a source of unreliability. The surface film on gold in air appears to disrupt conduction to a similar degree