The influence of Copper and Bismuth element in Sn-Ag solders and ENIMAG substrate

Abstract The addition of copper and bismuth elements in Sn-Ag solders on interfacial reaction during reflow soldering and isothermal aging of SA25 and SACB25051 was investigated. The growth of intermetallic compound (IMC) was characterized by using scanning electron microscopy (SEM), optical microscope (OM) and energy dispersive x-ray (EDX). The results show the irregular circle shapes of (Cu,Ni)6Sn5 IMC at the interface of solder joint for SA25 while rod-like shape for SACB25051 during both reflow soldering process and isothermal aging. The SACB25051 solder showed the thinner IMC thickness compared to SA25 solder for both conditions. The Cu and Bi element in Sn-Ag solder promotes a slower growth rate of IMC formation during interaction. The thickness and morphology of the IMC for both solders increase gradually with increasing of aging time.