Fretting Performance Comparison between PFPE and PAO Based Lubricants for Lightly-Loaded Gold-Plated Electrical Contacts

Organic lubricants, such as perfluoropolyether (PFPE)- and polyalphaolefin (PAO)-based oils, have previously been found to reduce fretting wear in gold-plated electrical contacts operating at loads higher than 50 cN. A film of such lubricants might negatively affect the contact performance in applications, such as RF electromechanical switches, in which contact loads are only several centiNewtons. This study compared two PFPE- and a PAO-based lubricant in terms of the fretting performance of lubricated, lightly loaded gold-plated contacts. No failures were observed for unlubricated contacts or PAO-lubricated contacts, whereas PFPE-lubricated contacts experienced failures in 4 out of 6 tests. While both the PFPE-based lubricants resulted in failure from the formation of insulating film, one PFPE-based lubricant also showed failure owing to hydrodynamic lift caused by the lubricant film. Unlubricated contacts sustained a low coefficient of friction of around 0.1 for only about 1% of the total number of fretting cycles achieved by PAO- or PFPE-lubricated contacts at that level of friction. PAO-lubricated contacts performed better than both the unlubricated and PFPE-lubricated contacts when surface wear and contact life are considered.