Size Effect of Interfacial Reaction in Sn-0.7Cu/Cu solder under Multiple Reflow

Abstract

With the development of the miniaturization and the integration of electronic products, the size of solder joints have gradually decreased in the packaging process. In addition, micro solder joints often need to be reflowed during the process of package interconnection due to the development of packaging technology, which greatly reduces the reliability of the solder joints. In this study, Sn-0.7Cu solder balls with the diameter of 200 μm, 500 μm, and 800 μm were employed to react with Cu substrates at 250 °C for 1 minute and reflowed 1 to 20 times. The size effect of the interface reaction at Sn-0.7Cu/Cu was analyzed in this study. The results show that as the number of reflow times rises, the thickness of IMC layer and the size of Cu6Sn5 grains becomes larger. After the 9th reflow, the growth rate of IMCs’ thickness and Cu6Sn5 grains’ average diameter at the interface under multiple reflow gradually decreased. Multiple reflow have little effect on IMC growth which produced by the large-sized solder balls, compared with the smaller-sized solder balls. The size effect of formation and evolution of the intermetallic compound (IMC) obviously under multiple reflow.