Electromigration study of SnCu0.7 solder joints with Ag added by different methods

Electromigration problem under current stressing has challenged the reliability of electronic products for a long time, which is more serious as the current applied is increasing. Adding nanoparticles have been proved to be effective in improving the mechanical and electrical properties of solder joints. This work studied the impact of Ag element on electromigration behavior of SnCu0.7 solder joints. SnCu0.7Ag0.3 solder is made by element alloying, while SnCu0.7+0.3Ag solder is made by doping Ag nanoparticles into SnCu0.7 solder paste. It is found that Ag3Sn in Ag incorporated solder joints helps lower the dissolution rate of Cu-Ni-Sn IMCs at cathode by impeding Cu diffusion in bulk solder. The rate of void formation and growth at cathode is remarkably inhibited. Compared to SnCu0.7+0.3Ag solder, SnCu0.7Ag0.3 solder has smaller-sized Ag3Sn IMCs particles, and be more effective in lowering the depletion rate of cathode IMCs. Through this study, we compared the performance of element alloying and nano-doping, and concluded that element alloying is more effective than nano-doping in improving solder joints' electromigration resistance under the same composition.