Study On The Process And Mechanism Of Diffusion Welding Between Contact And Solder

Electrical contact also called contact or contact junction, is the contact component of electric switch, instruments and meters and so on, which takes on the task of current on or off. Therefore its performance affects the running reliability of electric switch directly. Ag-W contact possesses good thermal and electrical conductivity, abradability, fusion welding resistance, and oxidation resistance. Ag-Cu-Zn solder based on Ag matrix has been widely used, with the characteristics of low melting point, good wetting property and caulking property, and high contact strength and so on. So the research on diffusion connection of contact solder has important theoretical meaning and practical application to enlarge the application of contact and solder.XRD, SEM, micro hardness instrument, and digital electric bridge are used to analyze the microscopic structure, electrical property, phase structure, fractography and the distribution of elements near the interface in this paper. It is also analyzed the effect of processing parameters such as heating temperature, time, and pressure on the electrical property and linear percentage in bonding pad area by used of orthogonal experiments. The processing parameters are optimized. According to Fick secondly law, error function and energy spectrum results are introduced to calculate the diffusion of Cu atom in Ag matrix when the contact solder is welded. The diffusion factor D0 and diffusion activation energy Q under the condition of this experiment are obtained, which are utilized to calculate the diffusion distance of Cu atom at a certain concentration, compared to actual measurement.The results indicate that in investigative test, when the heating temperature is lower than 700℃and little pressure, the diffusion ability of atom is deficiency and it cannot be diffused effectively. And in orthogonal test, the results are different when electrical resistivity and linear percentage of bonding interface are used as index mark. The ratio of electrical resistivity and linear percentage of bonding interface is 3:1 and the optimum processing parameters under the condition of this experiment are obtained. They are 675℃×2h, 0.09MPa and temperature is most important, pressure is second important, time is third important. The better properties both electrical resistivity and linear percentage are obtained by the optimum technology condition. The content of Ag mesosphere has great effect on the electrical property of contact solder when welding by pressure diffusion. The better the performance is, the more the Ag mesosphere is.