Recently, surface mount technology has lately been put on practical use. Although mechanical loads are small, they lead to the large deformation in solder joint wit small scale. Iteration of this large strain raise up low cycle fatigue. Elements to influence on fatigue of solder joint are vibration, deformation of constructure by difference of thermal coefficient and so on. The latter is an immediate cause to failure of solder joint.
This study is to apply the theory of fatigue frature to solder joint under thermal cycle and anticipate life of solder joint to failure. First, 62Sn-36Pb-2Ag solder is used in this study. Tension test under temperature of 15℃, 50℃, 85℃ is executed to find out the mechanical properties of solder. Secondly, crack growth rate is expressed in terms of crack length "a" and plastic strain range $"\Delta\epsilon_p"$. Thirdly, Solder joint between PCB and capacitor under thermal cycle is analyzed by FEM. Finally this together with crack growth rate will provide the fatigue life prediction of solder joints in electronic packaging.
