Abstract
A three-dimensional solder liquid formation model is developed for predicting the geometry, the restoring force and the reliability of solder joints in an area array type of interconnects (e.g., ball grid array (BGA), flip chip) under various pad configurations. In general, the restoring force and the reliability of the solder joints depend on the thermal-mechanical behaviors of the solder, the geometry configuration of the solder ball, and the geometry layout/material properties of the package. A good solder pad configuration could lead to a larger restoring force along the gravitational direction (a higher standoff height and a blunter contact angle) with a better reliability characteristic achieved. In this research, a 2 nd -reflow-process approach is applied for the reliability enhancement of typical BGA assemblies, including PBGA and SuperBGA assemblies. The results show that the 2 nd -reflow-process approach could significantly increase the fatigue life of the solder joint.