Effect of the reflow process on IMC growth for different devices and complex components

Abstract

Intermetallic compound (IMC), as an inevitable part between pad and solder, has a severe effect on the strength and reliability of microelectronic interconnection. Here, an investigation was carried out on IMC growth for different devices and complex components. The device-level experiments were conducted with five factors: peak temperature, time duration above solder liquidus temperature, the thickness of solder paste, surface finish types, and package types including ball grid array (BGA) and quad flat package (QFP). Meanwhile, four complex components with the same reflow profile were conducted and compared for component-level experiments. A scanning electron microscopy (SEM) was used to measure the thickness and determine the spatial distribution of the elements through the IMC. The multivariate analysis of the formation and growth of IMC during reflow soldering was studied based on Nernst–Shchukarev’s equation and the results of the experiments. The difference in IMC thickness between BGA and QFP with different factors was discussed and compared separately. The results showed that the peak temperature and time above liquidus played a vital role in the IMC growth and the solder paste thickness and different pad metallization could not be ignored. SEM pictures of the solder and statistical results were revealed that the surface finish type has a marked impact on the formation of the IMC. For printed circuit board (PCB) with numbers of components, the IMC thickness and uniformity of solder joints at corner and center positions showed some regularity differences. Meanwhile, the bump shape (Cu1−x Ni x )6Sn5 IMC was observed for small size BGA with electroless nickel and immersion gold during the reflow process. The results have a significant meaning to optimize its reflow process parameters for complex components, to improve the interconnection reliability in engineering.