Mechanical properties of soldered joints of QFP devices

Mechanical properties of soldered joints of quad flat packge(QFP) devices are investigated by numerical simulation, and the results of simulation indicate that soldered joints of high density in leads and the lead-free exhibit lower equivalent stress.The results of experiment indicate that the tensile strength of SnAgCu soldered joints is significantly greater than that of SnPb soldered joints, and the tensile strength of devices soldered by laser reflow increases by 25% than that by infrared reflow.The fracture microstructure of QFP for SnPb solder is coarse, but for SnAgCu solder is fine.The dimples in the fracture of joints formed by infrared reflow welding are not uniform, which the fracture includes brittle fracture and toughness fracture;but those by laser soldering are uniform, which fracture is toughness fracture.The experiment results are close to the simulated result.