Influence of Grafting Properties of Organic Thin Films for Low Level Electrical Contacts Protection

Thin layers of hard gold can act as good "lubricants" for separable connectors, but because of corrosion and wear mechanisms, additional protection is necessary. Organic thin films can be used in many different forms, from liquid to solid and many studies have been reported in the past. The present work shows the major influence of three properties: - the grafting of the film on the substrate, - the film "cohesion" and packing, - the film surface energy, on the friction behaviour and the electrical characteristics of ball on plane contacts. Usual dedicated devices were used to measure friction and contact resistance values. The molecular properties of the films were analysed with several physico-chemical analysis tools (XPS, contact angle, IR, AFM). Liquid films grafted by functional groups were compared to non grafted ones. Thin solid films of different types (poly(methacrylates) and poly(phenylene)-like) were studied and their friction and electrical properties were analysed in relation to their grafting, surface energy and cohesion characteristics. The results of this study should help tailoring the properties of solid films for electrical contacts protection.