Improvement on the mechanical properties of eutectic Sn58Bi alloy with porous Cu addition during isothermal aging

A comparison of the microstructure, interfacial IMC layer, shear behavior and hardness of the Sn58Bi, SnBi@110P-Cu/Cu and SnBi@500P-Cu/Cu solder joints was carried out during isothermal aging in this study. Experimental results reveal that the regions enclosed by Cu frames in SnBi@110P-Cu/Cu exhibit more refined microstructure and higher hardness before and after aging. In contrast, the hardness of the aged SnBi@500P-Cu solder bulk is closer to the SnBi eutectic solder due to their similar microstructure. With the aging time prolonging, beta-Sn and Bi-rich phases do not only coarsen in solder joints, but also lead to the rise of the thickness of the interfacial IMC layers. The addition of porous Cu can suppress the formation of voids at the soldering interface and improves the shear strength of the SnBi/Cu solder joints during the aging process. The shear strength of the SnBi@500P-Cu/Cu solder joint is higher than the other two before and after aging.

Automated summary

The study compared the microstructure, interfacial IMC layer, shear behavior, and hardness of Sn58Bi, SnBi@110P-Cu/Cu, and SnBi@500P-Cu/Cu solder joints during isothermal aging. The addition of porous Cu can suppress void formation at the soldering interface and improve shear strength during aging, with SnBi@500P-Cu/Cu joints showing the highest shear strength before and after aging.