Microstructural analysis of lead-free solder joint under thermo-mechanical loading

The influences of thermo-mechanical loadings on BGA´s solder joint are discussed in this paper. Since the thermo-mechanical loading caused by mismatch of coefficient of thermal expansion between different materials is a very common and unavoidable phenomenon in electronic packaging. Many products like mobile phones, PC suffer from this loading. It goes without saying that it´s a problem, especially in a rapid changing temperature cycle, needed to be solved and conquered. The major objectives of this paper is to build up an analytic thermo-mechanical model which is capable of analyzing solder joint´s behaviors such as forces, bending moments and present the results from this model in an effort to provide design reference. The comprehension of solder joint can contribute to make assembly more reliable. The finite element model (FEM) program is chosen as the computational method. What´s more, the method of simulation is equipped with the advantages, including saving time, low costs and so on. We can even predict the reliability of products by a proper model prior to mass production. In general, the solder joint is the key aspect in the whole packaging´s structure. In addition, the difference between lead and lead-free solder joint are also discussed and compared in this paper due to the fact that the demand of environment concerns has been highly considered for the past decades. In this paper, through using the finite element analysis, the model has been established, and the results acquired from analytical model should be applied to FEM predictions.