Intermetallic compound layer growth between SnAgCu solder and Cu substrate in electronic packaging

Abstract

Growth kinetics of intermetallic compound (IMC) layers formed between SnAgCu solder for reflow soldering and Cu substrate by solid state isothermal aging were investigated at temperatures between 100 and 140 °C. For the aged samples, two distinct layers of IMCs of the type Cu6Sn5 and Cu3Sn were identified with the later adjacent to the copper substrate. In the as-soldered samples, only a single layer of interfacial Cu6Sn5 type IMC was formed. Moreover, the apparent activation energies were 96.75 kJ/mol (total IMC), 85.98 kJ/mol (Cu6Sn5 IMC) and 105.92 kJ/mol (Cu3Sn IMC), respectively.