Abstract: The mechanical behavior of Sn62Pb36Ag2 solder joints was studied using systematic shear performance tests and fracture morphology analyses from cryogenic (-196 ℃) to ambient (25 ℃) conditions. The results demonstrate that the shear strength exhibits a continuous increase with decreasing temperatures. A pronounced ductile-to-brittle transition was observed near -100 ℃. Below this critical temperature, fractures propagated predominantly along the intermetallic compound (IMC) layer, exhibiting transgranular cleavage facets and pronounced brittleness. In contrast, ductile fractures featuring shear bands dominated above -100 ℃. Further analysis revealed that restricted dislocation mobility and inhibited thermal activation under cryogenic conditions fundamentally account for the enhanced brittleness. These findings provide critical insights for material selection of aerospace interconnects under extreme environments. Specifically, solder alloys with superior low-temperature ductility (e.g., In-based systems) are strongly recommended to ensure reliability in T≤ -100 ℃ applications.