Effects Of Bi On The Interface Layer Between Sn-Based Alloy And Cu Substrate Under Microgravity Conditions

The wetting behavior of Sn-3.5Ag and Sn-17Bi-0.5 Cu alloy solder on the Cu substrate under the condition of space microgravity were carried on SJ-10 satellite. This paper discussed the influence of the effects of Bi in the alloy on the growth of the intermetallic compounds layer. The experiment result shows that double layer of rod-like crystal was formed inside the Sn-based solder with Cu3Sn on the inside and Cu6Sn5 on the outside. A double interface layer was formed at the interface layer, with Cu3Sn layer near the Cu substrate and Cu6Sn5 layer near the solder. With the addition of Bi alloy solder, the growth of interface layer is inhibited, preventing the transition formation of interface layer. Bi elements gather at the edge of the interface layer near the solder body.