The interrelation between adhesion, contact creep, and roughness on the life of gold contacts in radio-frequency microswitches

Abstract

With repeated actuation, an increasing adhesive force develops between the gold contacts of radio-frequency microswitches until failure eventually occurs by stiction. Detailed characterization of the contact forces and the contact surfaces as a function of actuation cycles for “cold-switched” devices indicates that the increase in adhesive forces in air is attributed to mechanical creep of the polycrystalline gold contacts. The increase in adhesion is observed to be associated with an increase in contact area and depth of contact impression as well as asperity flattening. These morphological observations are related to the propensity for stiction using two nondimensional numbers, the plasticity index ψ and the adhesion parameter θ. Trajectories of the evolution of contact roughness in terms of these two numbers provide insight into the design of contacts to resist stiction.