引張応力が重畳された繰返しねじりを受ける銅－はんだ接合体の弾・塑性・クリープ有限要素解析

抄録

The strength reliability of solder joints in electronic products is evaluated by conducting thermal cycling (TC) test. However, the test takes a very long time to complete the evaluation and therefore Highly Accelerated Limit Test (HALT) is expected to be conducted as an accelerated test of TC test. HALT gives a product a severe loading which combines fast thermal change with mechanical vibration until the product fails. To conduct HALT as an alternative for TC test, the correlation between the deformation behavior of solder joints under TC test and that under HALT must be clarified by conducting the FEAs of those tests. Since the solder joint in the electronic product under HALT is subjected to multiaxial loading, the FEA of HALT must employ a constitutive model which can describe the deformation behavior of solder alloys subjected to multiaxial loading accurately. However, the constitutive models prospectively incorporated in commercial FEA software often do not describe such a deformation. Then, in this study, an original constitutive model was implemented into the FEA software ANSYS by writing a user material subroutine ”USERMAT.” Using the USERMAT, the FEAs of the copper-solder joint subjected to cyclic torsion with a superimposed tensile stress were conducted. The analysis results were compared with the experiments to discuss the applicability of the implemented constitutive model to multiaxial loading condition.