The study of cooling process´ effect on the growth of IMC at Sn-3.5Ag/Cu soldering interface

As one of the important factors affecting the quality of soldering joints, the intermetallic compound (IMC) formed at the solder and substrate interface becomes more and more concerned by researchers. However, it´s difficult to study the effect of cooling process on the growth of IMC for the continuity and high temperature of the soldering process. This paper making use of high-pressure air to remove liquid solder in reaction to prevent IMC from continuing grow in the cooling process and achieve the purpose of rapid cooling, meanwhile retaining the growth morphology characteristics of IMC in the process of heating-heat preservation stage, consequently making it possible for studying the effect of cooling process on the growth of IMC independently in soldering process. By comparing the top-view and cross-section of the IMC growth morphology of soldering joints in general air cooling conditions with the high-pressure air cooled soldering at different soldering time (5 s, 10 s, 30 s, 60 s) and different soldering temperature (250 °C, 300 °C), obtained that the grains of IMC in high-pressure air cooled were all presented as scallop structure while the grains in general air cooling were faced, later even prismatic structure, which proved that Cu₆Sn₅ has a secondary growth in the cooling stage, and the Ag₃Sn particles were also formed in cooling stage.