Development of a new solder joint modeling tool for IC package designers

In an attempt to assist IC package designers, a model for predicting solder meniscus geometries from lead shapes and material parameters is currently under development. Of particular interest, the gull-wing lead is mathematically represented as a horizontal section and two smoothly joined parabolas, allowing close matching of experimental gull-wing solder joints. Solutions are obtained using the public domain Surface Evolver software. This software was designed to solve problems pertaining to equilibrium meniscus geometry and includes routines for calculating wetting forces such as those exerted on component leads by molten solder. Meniscus geometry and force results from these calculations can be used in finite-element modeling programs to determine thermomechanical stresses.