An electronic device is composed of IC chip, substrate, solder ball, QFP package and filling resin. When the electronic device is heated, large thermal stress and warp deformation will be generated in electronic device during the solder joint process and temperature cycling test. In this report, the thermal stress generated in solder joint parts of the electronic device was clarified by Finite Element Analysis. And dangerous parts of fracture in the solder joints were forecasted from the value of the thermal stress caused in each solder joint parts. The result of the calculated values was good agreement with the experimental result.
