Investigation of interfacial reactions between Sn–Ag–Bi–In solder and (Cu, electroless Ni–P/Cu) substrate

The growth kinetics of intermetallic compound layers formed between Sn–3Ag–8Bi – 5In solder and (Cu, electroless Ni – P/Cu) substrate were investigated at temperatures between 70 and 170 °C for 1 to 60 days. The layer growth of the intermetallic compounds in the Sn–Ag– Bi – In/Cu and Sn–Ag –Bi – In/electroless Ni –P systems satisfied the parabolic time law. As a whole, because the values of time exponent have approximately 0.5, the layer growth is mainly controlled by diffusion. The apparent activation energies for the growth of the Cu Sn and Ni Sn intermetallic compounds are 81.4 and 67.1 kJ/mol, respectively.