AbstractThe microstructures resulting from the reaction between gold and Pb–Sn solder at temperatures of 80, 125, 140, and 160°C have been studied in the scanning electron microscope and measurements have been made of the reaction kinetics. In the initial stages, the growth rate of the layers of Au–Sn intermetal1ic product was found to be proportional to t1/2with an activation energy of (0·84±0·02) eV. At longer times, the growth rate fell below the t1/2dependence. This was thought to be owing to a restriction in the supply of gold to the reaction.MST/1599a