Phase structure of Cu3Sn/Cu and formation of monoclinic Cu grain at this interface during aging

Abstract

The phase structure and composition of the Cu/Cu3Sn interface were investigated during aging at 150 °C via transmission electron microscopy. The newly formed Cu3Sn phase was hexagonal, and the Cu substrate was cubic. However, the fine Cu grains that formed at the Cu/Cu3Sn interface were monoclinic. The structure of the Cu3Sn/Cu interface exhibited special crystallographic relationships after aging, that is [21‾1‾6]Cu3Sn//[1‾01]Cu and (02‾20)Cu3Sn//(404)Cu. The mismatch of the crystal plane spacing between the (02‾20)Cu3Sn and (404)Cu crystal planes was 0.959%. In this study, monoclinic Cu precipitated at the Cu/Cu3Sn interface in the form of particles but did not produce a layered structure.