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, capable to obtain the solid reactants directly from the liquid solder during the liquid-to-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.