  The recent development of electric and electronic devices has been
remarkable. The miniaturization of electronic devices and high integration are
progressing by advances in mounting technology. As a result, the reliability of
fatigue life has been prioritized as an important concern, since the thermal
expansion difference between a package and printed circuit board causes thermal
fatigue. It is demanded a long-life product which has short development time.
However, it is difficult because of interaction between each design factor. The
authors have investigated the influence of various design factors on the
reliability of soldered joints in BGA model by using response surface method
and cluster analysis. By using these techniques, the interaction of all design
factors was clarified. Based upon the analytical results, design engineers can
rate each factor's effect on reliability and assess the reliability of their
basic design plan at the concept design stage.
