An electronic device is composed of IC chip, substrate, solder ball, semiconductor package and filling resin. The thermal stress in solder joint parts of the electronic device and warp deformation of the substrate will be generated, when thermal load is applied to it during the manufacturing process and the environment. Especially, when a large thermal stress was generated in the solder joint parts, the solder will be fractured. In this report, thermal expansion coefficient and transition temperature of filling resin were variously changed, and thermal stress in the solder joint parts was analyzed by FEM. As a result, the optimum design manual of the filling resin was obtained.
