Abstract
Finite-element analysis (FEA) of solder joints for ultrahigh-density packages must be conducted with an accurate understanding of the deformation characteristics of the Cu/Sn intermetallic compounds (IMCs): Cu3Sn and Cu6Sn5. Therefore, the authors proposed a method to estimate the tensile characteristics of these IMCs in the previous work. The method provided two new findings. One is that the breaking elongation of the Cu/Sn IMCs is approximately 1.4%. The other is that the stress-strain relation of the Cu/Sn IMCs shows nonlinearity. Since the Cu/Sn IMCs have been regarded as elastic materials for a long time, the latter finding should be verified in some way. Then, in this study, we conducted FEAs which simulate the shear tests using the copper-solder joint specimen whose solder joint has the Cu/Sn IMCs layers. The FEA for a loading condition was conducted in two different ways; i.e., two different constitutive models of an elastic model and an elastic-plastic model were employed to describe the deformation behavior of the IMCs for a loading condition. Actual shear tests were also conducted in the same loading conditions as the FEAs. Comparing the FEAs with the actual tests, we discussed the presence or absence of the material nonlinearity of the Cu/Sn IMCs. The result suggested that the Cu/Sn IMCs should have material nonlinearity.
