Generation of asymmetric topographic structures in Cu-Sn connectors using extended direct laser interference patterning for the tailoring of insertion and removal forces

The reduction of insertion forces of separable electrical connections has been one of the main demands of the connector industry, and most solutions combine the use of lubricants with a specific connector design. An important challenge here is that there is a need for a solution that requires lower contact forces during mating while still ensuring a stable electrically conductive connection, without compromising the mechanical stability of the connection in operation. Extended direct laser interference patterning (xDLIP) was used here to generate asymmetric saw-tooth structures on Sn-coated Cu connectors. The main objective is generating an anisotropic tribological behavior, in which the insertion force is significantly lower than the removal force. Topographical interlocking is the main mechanism governing the observed anisotropy. The tailored connectors were characterized tribologically and electrically by simulating insertion/removal cycles and determining the evolution of the contact resistance at the end of each insertion motion. Different structural inclinations, counter-electrode geometry, and contact forces were evaluated. For certain combinations, it is possible to observe substantial differences between the insertion and removal forces, of up to 4 times. Summarizing, this work presents a chemistry-free route to influence the insertion and removal forces in connectors, without affecting the electrical characteristics at their contact spot.