Abstract: Single shear lap SnAgCu/Cu solder joints with different thicknesses (0.1, 0.2, 0.3, 0.6 mm) were tested at various loading rates (0.001, 0.01, 0.1, 1 mm/s) with an Instron5948 Micro Tester. The results show that the shear strength of solder joints increased with the increase of loading rates, and increased with the decrease of solder thickness, showing an apparent size effect. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS) were used to analyze the morphology of shear fracture and the crack initiation on the surface of solder joints, the crack initiation location gradually shifted to IMC layer from the solder with the decrease of solder thickness. The fracture morphology of solder joints had elongated dimples and shear planes, and the failure mechanism was micro-void aggregation/pure shear hybrid fracture.