Three-dimensional interface and property of SnPb solder joint under extreme thermal shocking

To meet the demand of cryogenic reliability on the electronic packaging for deep space satellite, the three-dimensional interfacial morphology and property of eutectic SnPb solder joint under an extreme thermal shocking of 77-423 K were investigated. After thermal shocking, Cu-Sn IMC layers coarsened in the cross-sectional observation and micro-cracks formed in Cu6Sn5 layer. The rough Cu6Sn5 layer in the top view gradually smoothed, with broken Cu6Sn5 particles and exposed Cu3Sn. In the bottom-view observation, the Cu6Sn5 layer of as-soldered joint was overlapped by Cu3Sn layer. But no defects were generated in Cu3Sn layer. The shear force of solder joint was greatly reduced due to broken Cu6Sn5 with the changing fracture characteristics from the solder-controlled mode to the solder/IMC mixed mode.

Automated summary

This study investigated the three-dimensional interfacial morphology and properties of eutectic SnPb solder joint under extreme thermal shocking conditions of 77-423 K to meet the cryogenic reliability requirements of electronic packaging for deep space satellites. The results showed that after thermal shocking, the Cu-Sn IMC layers coarsened and micro-cracks formed in the Cu6Sn5 layer. The rough Cu6Sn5 layer gradually smoothed in the top view, with broken Cu6Sn5 particles and exposed Cu3Sn. In the bottom-view observation, the Cu6Sn5 layer of the as-soldered joint was overlapped by the Cu3Sn layer. However, no defects were generated in the Cu3Sn layer. The shear force of the solder joint was greatly reduced due to the broken Cu6Sn5, with the fracture characteristics shifting from solder-controlled mode to solder/IMC mixed mode.