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.