抄録
In was deposited onto the joint interface of a Cu/Sn joint to examine the effect of the filler metal on the tensile strength of the joint and on the reduction of the bonding temperature. Observations were carried out using Scanning Electron Microscopy (SEM) to observe the interfacial microstructures and fracture surfaces. After the In filler was deposited onto the joint surface, liquid-phase diffusion bonding was carried out. Compared to a specimen that did not have the In filler, a specimen with the In filler could be joined with an approximately 30% lower degree of deformation and at a temperature that was approximately 30 K lower. At the same time, the achieved tensile strength was comparable to that of the base metal on which the In was deposited. Two possible reasons were considered for the increase in the tensile strength. First, when heated to 393 K, In and Sn react with each other and turn into a liquid phase. This layer of liquid then covers the entire bonding surface and increases the area of contact between the bonding surfaces, which in turn causes the increase in the bonding strength. Second, because In is easier to oxidize than Cu and Sn, the metallic In becomes In oxide, which is formed by the In taking oxygen from the native oxide films of the Cu and Sn. Subsequently, the intimate contact that is achieved between the metallic Cu and metallic Sn increases the bonding strength.
