Shear strength and fracture behavior of locally-melted hybrid Cu/Sn3.0Ag0.5Cu/Sn58Bi/Cu joints under different loading rates

Abstract

With the increasing demand for low temperature reflow processes in electronic packaging, SnBi-based solders have been increasingly explored to replace partially SnAgCu solders (typically Sn3.0Ag0.5Cu, i.e., SAC305) in the board-level BGA packaging due to their features of low thermal effects on devices and PCBs. In order to verify whether the hybrid Cu/SnAgCu/SnBi/Cu joints, in which SnBi solder exhibits the significant phase segregation, are suitable for mobile electronic packaging, the fracture behavior of locally-melted hybrid Cu/SAC305/Sn58Bi/Cu joints under different loading rates ranging from 100 to 5000 μm/s were studied systematically. It is found that the shear strength of hybrid joints increases significantly with increasing loading rate. Meanwhile, due to different loading rate sensitivities of Sn58Bi solder and SAC305 solder, the deformation behavior, fracture position (path) and fracture mode of the hybrid Cu/SAC305/Sn58Bi/Cu joints are significantly different when subjected to shear stress with different loading rates.