Evolution mechanism of cold adhesion force between electrical contact determined by coating hardness

Micro-Electromechanical-Relay (MER) is one of the most important electric components in electrical equipment. However, cold adhesion failure between electrical contacts in MER usually increases the risk for operating failure of closed contacts. In this letter, Au-Ni composite coatings with different Ni content are deposited on the surface of electrical contact by magnetron sputtering, to investigate the effect of coating quality on the cold adhesion. The relationship between push force and cold adhesion force is built employing mechanical contact theory to evaluate the cold adhesion. The results indicate that the cold adhesion force between electrical contacts remarkably decreases from 13.8 mN to 2.3 mN when the coating hardness gradually increases from 1.6 GPa to 3.8 GPa. The cold adhesion reveals a similar trend even at extreme environmental conditions (high/low temperature cycling in the range of 180 °C–65 °C). This finding provides an innovation strategy for solving the cold adhesion problem.