Analysis And Investigation On Fretting Parameters Affecting The Fretting Characteristics For Non-Noble Metal Plated Contacts

Fretting is one of the main reasons to cause the failure of the electrical contacts. In this paper, the fretting parameters influence the fretting characteristics of non-noble metal plated contacts (SnPb, Ni) were studied, including fretting amplitude, fretting frequency, the thickness of plating and contact probe material.The effect of fretting amplitude on fretting behavior for contact pairs is monotone. When the fretting amplitude is increased, it needs less fretting cycle numbers for resistance to reach the given value. The longer the fretting amplitude means that the fretting velocity is faster under the condition of fretting frequency is constant, the higher the wear rate becomes, the more wear debris are generated. During the repeated fretting motion, large quantity of oxide debris are produced inside and on the ends of the track due to the oxidation, crush, push away and accumulation of metal debris. Therefore, the contact resistance increases quickly. The impact of the larger fretting amplitude should be avoided in the application.The effect of fretting frequency on the fretting characteristics is not monotone, there exists the frequency easiest to cause failure. This result is proved through the experiment of tin-lead alloy contact pairs and nickel plated contact pairs, the frequency between 0.01Hz and 0.1Hz is fastest to cause failure. On the one hand, as fretting frequency increases, metal debris that can be oxidized increases, contact resistance rises. On the other hand, higher frequency reduces the oxidation and the accumulation of oxide, which causes contact resistance rises slowly. The two effects together produce the harmful fretting frequency that causes the fastest failure. So, in the actual design, we should pay attention to avoid this frequency band to improve the reliability of product.For the different thickness of nickel plating, the fretting failure mechanism is same, the accumulation of oxide debris causes contact resistance increases. As the plating thickness increases, the contact resistance rises.The contact resistance changes to be stable if the probe is gold plated, which can delay the fretting failure of contacts compare to the non-noble metal.