The role of microstructure and surface topography in the electrical behavior of Sn-coated Cu contacts

Abstract:
An electrical connector must present low and stable contact resistance while being highly resistant against mechanical wear. In order to achieve this we explore the effect of laser surface texturing (LST) on the static resistance of Sn-plated Cu contacts. We study the evolution of the electrical resistance between textured contacts and an Au-coated hemispherical tip under normal loading. The microstructure and topography of the contact surface was analyzed using white light interferometry (WLI), focused ion beam (FIB), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). LST induces surface softening and reduced electrical contact resistance under loading. The resistance vs load behavior of the laser-textured contact follows the Holm model, indicating that plastic deformation governs the electrical resistance. We claim that avoiding surface material pile-up and that insulating layer collapse reduces the resistance hysteresis during operational mating and unmating cycles.