Evaluation Method of Thermal Fatigue Life for Surface-Mount Solder Joints by Mechanical Fatigue Test.

Abstract

In this study, we attempt to develop a more efficient method of thermal fatigue life evaluation for solder joints than the thermal cycle test. The mechanical fatigue tests for solder joints of surface mount devices are performed under several temperature and cyclic frequency conditions. In addition, thermal cycle tests are carried out in order to compare the results with the mechanical fatigue test. On the other hand, the strain range of solder joint in the mechanical fatigue and thermal cycles tests is evaluated by using the elasto-plastic finite element method, considering the effects of temperature and strain rate on the stress-strain curve of solder. From the experimental and analytical investigations, it is found that the relation between the elasto-plastic strain range and the fatigue life of the mechanical fatigue test agrees well with that of the thermal cycle test. Furthermore, an evaluation method of thermal fatigue life employing the mechanical fatigue test is proposed on basis of the investigations mentioned above.