In recent years, the development of the electronic device using the semiconductor is remarkable. In current advanced technology, it has succeeded in making the package which size is almost equal to the IC chip. Moreover for miniaturization and high integration of the electronic device, it has been fined in soldered joints divisions. As a result, the strength reliability become an important problem, since the thermal fatigue fracture is generated by thermal expansion difference between package and printed-circuit board. However, it is difficult to guarantee quality during the design stage, because it is hard to know which design factors will prolong the fatigue life. So it is needed that a quantitative evaluation technique of the relation between the design change and the thermal fatigue reliability. The authors introduced a simple approach to help solving the design and development of a package system by using the SDSS (statistical design support system) and FEM (Finite Element Method) analysis. In this study, in order to improve the reliability, evaluations of the influence of various design factors on the reliability of BGA (Ball Grid Array) soldered joints were carried out. By using the total equivalent inelastic strain range obtained by FEM analysis, the sensitivity is calculated and the authors got the influence of each design factor. With the results, the design engineers can know the rate of each factors’ effect on the reliability of solder joints and they can use the results to assess the reliability of their design from the concept design stage. Consequently, it can be expected that almost reliability problems can be avoided at the beginning, and it will lead a great advantage of shortening design period and slashing costs. And this will lead design engineers to come up with more new ideas.
