Kinetics of intermetallic compound layer growth and interfacial reactions between Sn-8Zn-5In solder and bare copper substrate

The growth kinetics of the intermetallic compound layer formed between Sn-8Zn-5ln solder and bare Cu substrate by solid-state isothermal aging were examined at temperatures between 70 and 150 degrees C for times up to 100 days. Experimental results showed that the intermetallic compound observed on the bare copper substrate was gamma-Cu5Zn8 and its thickness increased with ageing temperature and time. The layer growth of the intermetallic compound in the couple of the Cu/Zn satisfied the parabolic law at the given temperature range. As a whole, because the values of time exponent (n) were approximately 0.5, the layer growth of the intermetallic compound was considered to be mainly controlled by diffusion mechanism over the temperature range studied. The apparent activation energy for growth of the gamma-Cu5Zn8 intermetallic compound was 62 kJ mol(-1).