Investigation On Characteristics Of Sliding Electrical Contacts

Sliding wear is one of important reasons leading to failure of electrical contacts in electronic devices. In order to improve performance of sliding electrical contacts and reduce the cost, characteristics of goid plated contacts and palladium-nickel plated contacts is investigated by sliding simulation on two aspects:wear property and resistance property, which has significance in designing electrical contacts.1000mΩwas defined as a failure resistance within 20000 sliding cycles in this paper. It was found that, when the coupon was plated with Ni, no matter the probe was plated by Au finish or not, contacts must fail. The failure mechanism was that the gold finish was worn out and the base metal copper and substrate nickel was exposed in the air, so their oxides generated to increase contact resistance. When the coupon had gold plating, the contact resistance must be eligible.The effects of thickness of gold plating and contact force on sliding contact characteristic were investigated in this paper. It was concluded that gold on coupon not only improved resistance characteristic, but also enhanced wear characteristic. But gold on probes could not effectively improve sliding characteristic. This was mainly because wear area of coupon was bigger than that of probe, and gold on coupon provided sufficient gold left in the contact area. On one hand, this remained gold could protect base metal from being oxidized, on the other hand, gold was a good solid lubricant and it lubricated the contacts during sliding. But wear area on probes was smaller than that on coupon, and gold plating made its initial hardness low, so that it increased wear of the contacts, exposed the base metal, made the resistance increased. The pressure could influence the wear characteristics more than the contact resistance characteristics. So, when we select the contact materials, in order to reduce the amount of gold and cost, we can only plate gold on the coupon.1000mΩis defined as a failure resistance to investigate the palladium-nick el contact characteristics.0.5Au-PdNi-50gand 1.0Au-PdNi-150g were failed. The cause was that, palladium-nickel coating wore seriously, and exposed the base metal to form oxide. On the other hand, palladium was a good catalyst, absorbing organic gases to generate polymer on the surface of the coating in the process of sliding. So the contact resistance was increased. Palladium Nickel contact resistance characteristics was much better than that of bright nickel contacts. This was because the palladium-nickel alloy could protect the base metal very well. Wear characteristics of Pd-Ni probe was better than that of bright nickel probe. Wear characteristics of palladium nickel coupon was much worse than that of the bright nickel coupon.