Abnormal Grain Growth of Ni₃Sn₄ at Sn-3.5Ag/Ni Interface

Abstract

By the reaction of molten solder alloy with compositions of 96.5Sn-3.5Ag (compositions are all in weight percent unless specified otherwise) with either the thick Cu or the thick Ni substrate at 250°C, the rounded Cu₆Sn₅ grains formed over Cu and the faceted Ni₃Sn₄ grains precipitated over Ni. As the soldering time changed from 1 min to 60 min, normal grain growth occurred for rounded Cu₆Sn₅ grains while abnormal grain growth (AGG) mode was observed for faceted Ni₃Sn₄ grains. The measured grain size distributions also confirmed the difference between normal grain growth and abnormal grain growth.