Abstract: Sn3.0Ag0.5Cu lead-free solder joints of different sizes in the range of 200 μm to 600 μm were multi-reflowed and aged,and then the shear strength of those solder joints were tested by the micro-force tester DAGE4000.The effect of solder volume differences on the shear strength of solder joints was investigated.The results indicated that the shear strength of SnAgCu lead-free solder joints decreased with the increasing of the solder joint volume,showing an apparent volume effect.The effect of aging time and reflow times on the shear strength of solder joints with different sizes were also discussed,and scanning electron microscopy(SEM) was used to analyze the morphology of shear fracture,and the failure mechanism of solder joints were discussed.