Fracture mechanism of lead-free soldered joints of rectangular chip component

Shear strengths of rectangular chip component soldered with Sn-Pb solder and with Sn-Ag-Cu solder were studied by means of STR-1000 micro-joints tester and microscopic fractography by SEM. Fracture appearance of the joints was also analyzed.The results indicate that shear strength of the joints soldered with Sn-AgCu is greater than that with Sn-Pb, but the shear curves of two kinds of joints obviously show that plastic strain appear before joints crack. SEM analysis of the fractures illustrates that cracks are located in two interfaces:one is between solder and component bottom pad, the other is between solder and component side pad, and the performances of the joints soldered with Sn-Ag-Cu solder are better than that with Sn-Pb solder, which illuminate that Sn-Pb solder can be completely replaced by Sn-Ag-Cu solder.