Microstructure and mechanical behavior of SnBi-xAg and SnBi-xAg@P-Cu solder joints during isothermal aging

To improve the reliability of SnBi solder joints, Ag and porous Cu were used as additives to obtain SnBi-xAg@P-Cu/Cu (x = 0, 0.4, 1 wt%) solder joints. The effect of porous Cu addition on the microstructure, IMC layer, shear behavior and hardness of the solder joints during isothermal aging was studied. The experimental results indicate that there are some areas enclosed by Cu frames in the SnBi-xAg@P-Cu/Cu solder joints. Compared with the SnBi-xAg/Cu solder joints, these areas show a more refined microstructure and higher hardness than the other areas do. After being aged at 100 degrees C for 600 h, the hardness of the solder bulks showed an increasing trend due to the coarsening of the microstructure. The addition of porous Cu improves the shear strength of the SnBi-xAg/Cu solder joints before and after aging. Among them, SnBi-0.4Ag@P-Cu/Cu shows the highest shear strength. After isothermal aging, the shear fracture transferred from the solder bulk to the soldering interface in the SnBi and SnBi-0.4Ag solder joints. The addition of porous Cu has a positive effect on suppressing the crack propagation in the solder joints. Therefore, the fracture position is mainly located in the solder bulks in the SnBi-xAg@P-Cu/Cu solder joint.

Automated summary

The addition of porous Cu improves the microstructure and hardness of the SnBi-xAg@P-Cu/Cu solder joints, leading to an increase in hardness and coarsening of the microstructure after aging. Among them, SnBi-0.4Ag@P-Cu/Cu shows the highest shear strength.