Abstract
A three-dimensional (3-D) solder liquid formation model is developed for predicting the geometry, the restoring force and the reliability of solder joints in an area array of interconnects [e.g., ball grid array (BGA), flip chip] with various pad configurations. In general, the restoring force and the reliability of the solder joints depend on the thermal-mechanical behavior of the solder, the geometry 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 better reliability characteristics achieved. In this research, a second-reflow-process approach is applied for the reliability enhancement of typical BGA assemblies, including PBGA and SuperBGA assemblies. The results show that for a typical PBGA assembly, the ratio of the enhancement by application of the second-reflow-process approach is 2.03 based on the Coffin-Manson criterion and 1.4 based on the energy density based method, and more significantly, for a typical SuperBGA assembly, it is 7.17 and 2.422, respectively.