Effect of Cu concentration, solder volume, and temperature on the reaction between SnAgCu solders and Ni

The interfacial reaction between SnAgCu and Ni is influenced by three important factors, namely, the Cu concentration in solder, solder volume, and temperature. In our previous studies, the first two factors had been investigated individually. In this study, the effects of these three factors are studied concurrently. Three different sizes of solder spheres (300, 500, and 760 μm in diameter) with three different Cu concentrations (0.3, 0.5, and 0.7 wt.%) are used. The aging temperatures are 160 and 180 °C. It is found that as the residual apparent Cu concentration in the solder decreases and the solder volume reduces, the type of intermetallic compound changes from (Cu,Ni) 6Sn 5 to (Ni,Cu) 3Sn 4. This study confirms that the critical Cu concentration decreases as the temperature decreases. In addition, the massive spalling phenomenon, which tends to occur in a liquid–solid reaction, is not observed in the solid-solid reaction.