The study of the growth behavior of Cu<inf>6</inf>Sn<inf>5</inf> at the Sn/Cu interface during the heating preservation stage

Abstract

In this study, Sn/Cu soldering interface and the growth characteristics of IMC grains were in-situ investigated. High-pressure air (0.8MPa) was used to blow away the residual liquid solder on the Cu substrate at different soldering temperatures (250 ° C, 275 ° C, 300 ° C) and different soldering time (10s,30s,60s,120s), thereby obtaining the unobstructed view for growth morphology of IMC in the heating preservation phase. The top-view and cross-section view of solder joints were observed under scanning electron microscopy (SEM). With these observations, in-depth analyses of the morphology and thickness of IMC were made. It was observed that IMC grains in heating preservation all presented scalloped or oval structured morphology with the increase of soldering temperature and soldering time. Scalloped IMC grains appeared at heating preservation, then became larger and the amount of IMC grains decreased with the increasing of soldering temperature and time, which can be explained in accordance to the ripening theory. The grain size in heating preservation illustrated a nearly uniform fashion, resulting from large swallowing up of small grains during the soldering process. By calculating the thickness of IMC layer in different soldering time, it was found that the increase of IMC thickness obeyed the t1/3 law, which means IMC growth is controlled by GB during heating preservation.