IMC's growth behavior and the characterization of its size during isothermal aging

This study was concerned on the growth behavior and the size characteristics of the interfacial intermetallic compounds (IMCs) between solder and Cu substrates during isothermal aging. Through the analysis of the 3D volume, 2D area, and the thickness of the IMC, a scientific method of characterization of the IMC's thickness size was found. That is using the image analysis software to calculate areas(S) of the cross-section at the thickness direction from a certain volume IMC, find out the whole IMC's average thickness(x). In this paper, the SnAgCu/Cu specimens were aged at 150°C for 24h, 48h, 120h, 240h, 480h. The above method was used to measure the thickness at different aging time. The quantitative relationship between IMC's thickness(x) and aging time(t) can be obtained on condition of above experiment by IMC's growth curve fitting. With the increase of aging time, the grain size of the interfacial Cu6Sn5 increased and the morphology of the interfacial Cu6Sn5 was changed from scallop-like to needle-like and then to rod-like. In this study, we also use the method to measure the solder IMC's thickness from other references. It was found that the measured data was more fitting with the index growth low and the curve fit. Key words: IMC; isothermal aging; lead-free solder