Mechanical properties and microstructure of Sn-based solder joints at cryogenic temperature

This work was designed for low-temperature mechanical properties of the solder joints, the temperature is 293K, 223K, 173K, and 123K, in order to get the mechanical strength and mechanism of fracture at low temperature; Cryogenic temperature (77K) storage experiment is applied to get microstructure of internal solder joint, and the evolution of IMC and other microstructures, as well as solder joints' mechanical properties, failure modes and failure mechanisms The results show that tensile strength of the solder joints increases first and then decreases along with the decreasing temperature, 63Sn37Pb/Cu and 62Sn36Pb2Ag/Ag joints reach their maximum strength at 173K and 223K respectively. Cryogenic temperature storage has no effect on IMC growing, but tin whisker is found in some parts of 63Sn37Pb/Cu and 62Sn36Pb2Ag/Cu solder joints stored for 10 days, without appearance in solder joints that stored for 20 days and those lead-free solder jonits. Sn whisker is random and unpredictable.