Friction force reduction for electrical terminals using graphene coating

Multi-layer graphene, serving as a conductive solid lubricant, is coated on the metal surface of electrical terminals. This graphene layer reduces the wear and the friction between two sliding metal surfaces while maintaining the same level of electrical conduction when a pair of terminals engage. The friction between the metal surfaces was tested under dry sliding in a cyclical insertion process with and without the graphene coating. Comprehensive characterizations were performed on the terminals to examine the insertion effects on graphene using scanning electron microscopy, four-probe resistance characterization, lateral force microscopy, and Raman spectroscopy. With the thin graphene layers grown by plasma enhanced chemical vapor deposition on gold (Au) and silver (Ag) terminals, the insertional forces can be reduced by 74 % and 34 % after the first cycle and 79 % and 32 % after the 10(th)cycle of terminal engagement compared with pristine Au and Ag terminals. The resistance of engaged terminals remains almost unchanged with the graphene coating. Graphene stays on the terminals to prevent wear-out during the cyclic insertional process and survives the industrial standardized reliability test through high humidity and thermal cycling with almost no change.