The Ni/ solder /Cu sandwich solder joints were prepared with four kinds of mixed soldering alloys with different Pb contents (0, 4.67%, 22.46%, 37%), and the effects of Pb content and aging time on the microstructure, the evolution of intermetallic compounds (IMC), and mechanical properties were investigated by putting the solders into the -196℃ liquid nitrogen with different times of 10 days, 20 days and 30 days, respectively. The results indicate that Pb element accumulates gradually with the increase of Pb content in solder, moreover, the Pb-rich phase continuously coarsens with the increase of aging time. The nominal chemical composition in IMC layer does not alter during ultra-low temperature aging treatment, while some microcracks and holes will occur gradually by accompanied with the transformation of the scallop-like IMC into lamellar IMC. At the same time, the Pb element accumulates alone the IMC interface near the solder, and a Pb-rich layer will be formed, even some Pb-rich phases extend inside the IMC layer. With the prolongation of aging time, the fracture mode of the solder joint is transformed from ductile fracture to ductile-brittle mixed fracture. The shear strength will be improved with appropriate increased of Pb element, however, it will be decreased as exceeding to 22.46% of Pb content.