Effect of lubricant on sliding conditions in Au-plated slip-ring system for small electric power transfer

The authors have been investigating the sliding quality and the deterioration process of the system of Au plated slip-ring and Ag-Pd brush, which is used mainly in the chip-mounter, to realize stable long life time. Through the past tests, it can be made clear that lubricant is very important for long lifetime, because it can not only make ring wear decrease, but also protect the ring from oxidation. In this paper deterioration process of ring and brush is examined in details, and the followings can be obtained. Usually contact voltage drops have fluctuation. The fluctuation is found to be two types; one is a component which is dependent on rotation speed and the other comes from surface deterioration, such as oxidation. The details are investigated by using Fourier analysis of contact voltage waveforms. Generally, during the test the contact resistance of a ring increases suddenly and the ring reaches end of life, mainly because the lubricant disappears from the contact surface. In this test a temporary decrease of the contact resistance is observed just before the sudden increase of resistance. Further, a supply of lubricant to the ring which became high in resistance, is found to be useful to decrease its resistance. In addition Fourier transform is carried out on the contact voltage waveforms.