Effects of laser soldering speed on mechanical properties of SOP micro-joints

SOP(small outline package)devices were soldered by diode-laser soldering and IR reflow soldering method respectively and the tensile strengths of soldered joints were measured by Microjoints Tester(STR-1000), and the effects of laser soldering speed on mechanical properties of SOP micro-joints were studied and the characteristics of fracture microstructures of micro-joints were also analyzed by SEM.The results indicate that the tensile strength of soldered joints is influenced remarkably by laser soldering speed, and the mechanical properties of the joints soldered with Sn -Ag -Cu solder are more sensitive to soldering speed than that with Sn -Pb solder, and there is an optimal speed of laser soldering according to the best mechanical property.There are some micropores and shallow dimples when the speed is lower, which is called micropore aggregation fracture.There are plenty of dimples in the fracture and some sidesteps in the local zone of the fracture when the speed is higher, which the fracture includes dimple and cleavage fracture, and when the speed is moderate, there are lots of big and deep dimples in the fracture, which is the ductile fracture.