Abstract: The influence of reflow temperature on the shear mechanical properties of three kinds of solders(Sn3.0Ag0.5Cu, Sn0.3Ag0.7Cu and Sn0.3Ag0.7Cu-0.07La-0.05Ce) under veneer structure and board-level structure was studied by shear experiments. Results shown that the shear strength of the high silver solder joints under veneer structure increased with the increase of reflow temperature, while the shear strength of the low silver solder joints under veneer structure increased firstly and then decreased with the increase of reflow temperature. The shear strength of solder joints under board -level structure increased first and then decrease with the increase of reflow temperature, and the shear strength of low silver solder joints with rare earth elements was the highest. The fracture displacement of solder joints under veneer structure and board-level structure decreased with the increase of reflow temperature. The fracture mode of high silver solder joints under board-level structure are changed from ductile fracture to brittle fracture with the increase of reflow temperature. The fracture mode of low silver solder joints under board-level structure always were ductile fractures with the increase of reflow temperature. The fracture position of low silver solder joints under board-level structure shifted to the direction of the IMC with the increase of reflow temperature.