IMC growth behavior along c-axis of Sn grain under current stressing
Due to the asymmetric structure of Sn unit cell, the electromigration behaviors of Sn based solder joints were significantly depended on the crystal orientation of Sn grain. The present investigation illustrated the effect of Sn grain c-axis on the intermetallic compounds (IMCs) growth under current stressing. The Cu particles reinforced Sn3.5Ag solder joint was selected to obtain various observed surfaces of the sample after 46 days current stressing. The front side, back side, right side and anode side of the sample represented different phenomena, which reflected and proved the importance of c-axis orientation on Cu atomic migration in three-dimension space. Besides, another composite solder joint was polished severe times on the observed surface which was full of IMCs. It showed that the IMCs were covered on the Sn-based solder, and there was crack at the cathode underneath the front surface after 38 days current stressing. The IMC growth behavior would be well understood by systematic study in this work.
The authors acknowledge the support of this work from Beijing Natural Science Foundation (No. 2172006), and (No. 2172009), the Science and Technology Project of Beijing Municipal Education Commission (SQKM201710005003) and (SQKM201610005024) and National key research and development program of China (2017YFB0305701).