Formation of Sn dendrites and SnAg eutectics in a SnAgCu solder

The formation behaviour of grains and their components, including Sn dendrites, Cu6Sn5 and Ag3Sn intermetallic compounds (IMCs), in a SnAgCu alloy is investigated in an experiment in which it was possible to obtain the solid reactants directly from the liquid solder during the liquid–solid phase transformation. The results show that Cu6Sn5 IMCs are formed first in a grain; then large Sn dendrites; fibre-like Ag3Sn IMCs are formed ahead of the β-Sn matrix in the coupling process, generating eutectics.