Liquid-Solid Reaction between Low Silver Sn-0.45Ag-0.68Cu-xNi-yP Solder and Cu Substrate under Different Temperatures

The effect of soldering time and temperature on the formation of intermetallic compounds (IMCs) between Sn-0.45Ag-0.68Cu-xNi-yP solder liquid and copper base material was investigated. Soldering was carried out at 250°C and 270°C with soldering times for 5, 10, 20, 40, 60, 80, 100, 150, 200, 500, 800, and 900s respectively. In the initial reaction stage, it was observed that typical scallop-shape Cu
6
Sn
5
IMCs form in the interface priority. With soldering time increased, Cu
6
Sn
5
transformed to (Cu,Ni)
6
Sn
5
by atoms diffusion, and the shape changed from fine scalloped to wavy shape, and then change to smooth eventually. Liquid-solid reaction mechanism at soldering less than 60s was different from soldering time for more than 60s.