Abstract:In order to get solder information of thermal fatigue state, shear force test method and nonlinear least
square method are used. A lead-free solder joint with 1210 chip resistor is the research object. A solder joint thermal
fatigue life prediction method based on the solder joint shear strength test is put forward. The test of shear force-thermal
fatigue life is done. According to 0, 300, 600, 900, 600, 1500 cycle data, Gauss-Newton of nonlinear least
square method is used to fit curves based on Matlab programming. By using the shear force value fell by 30% failure
criteria defined, the solder joint failure cycle number is 1439. 04. The method can be used to solder joint shear
strength of solder joint fatigue state monitoring, estimates, the same to the other kinds of solders.