The growth kinetics of intermetallic layers at the interface of a solid metal and a liquid solder

Abstract

During soldering, intermetallic layers can occur at the interface of a solid metal and the saturated or undersaturated solder melt. In systems with a considerable solubility in the liquid state, dissolution causes a manifold drop in layer thickness. Mathematical equations are proposed to evaluate the thickness of any intermetallic layer formed under conditions of simultaneous dissolution in the undersaturated solder melt. The main features of reactive phase formation at the solid metalliquid solder interface are illustrated using the Co-Sn couple with the growing CoSn3 (250°C) and CoSn2 (350°C and 450°C) layers as examples.