Analysis on the thermal fatigue behavior of QFP soldered joints

The creep strain and plastic strain of soldered joints in time history are studied and analyzed with numerical simulation method, which are found to be accumulated as ladder form.Based on Solomon and Shine and Fox models, the fatigue life values of the Sn-Pb and SnAgCu soldered joints are evaluated by equivalent strain, which are about 937 and 1 391 respectively.The experimental results showed both in experiment and simulation results indicate that the tensile force of soldered joints will be decreased with the increase of thermal cycling times, the reliability of SnAgCu after thermal cycling is better than that of Sn-Pb, the fracture mode of the soldered joints transforms from toughness fracture into brittle fracture, and the brittle intermetallic compounds at the interface of soldered joints will grow up gradually with the increase of thermal cycling times during thermal cycling process, which give a strong impact to the reliability of soldered joints and reduce the tensile force of soldered joints at the same time.