Effect of different lubricant films on contact resistance of stationary separable gold-plated electrical contacts

Electromechanical switches use gold-plated contacts that have an expected life of at least one million switching cycles. However, these contacts often fail prematurely from wear of the gold plating. A film of contact lubricant over thin gold plating is an effective alternative to reduce wear and increase contact life. That was the case for contacts that operated at high contact loads, usually greater than 50 gf, but with the miniaturization of all devices electrical contacts are now being used at loads as low as 5 gf. Use of conventional lubricants, which are organic materials and insulating, can affect the performance of electrical contacts operating at low loads. This paper examines the effect on contact resistance of unlubricated and various commercial lubricant films between gold-plated contacts over the load range of 1–35 gf. It was unexpectedly found that 6 out 10 tested lubricants resulted in increased contact resistance, orders of magnitude higher than the unlubricated contact case, for loads up to 7 gf. A critical load was also found, below which the contact resistance was higher than that for the unlubricated case.