Nanoindentation characteristics of Cu6Sn5 formed in lead free solder joints

A new structural effect that was developed based on the concepts of the cantilever beams has been proposed in order to illustrate the measurement divergence of nanoindentation test for Cu₆Sn₅ IMCs. Cu₆Sn₅ IMCs were fabricated in Sn3.5Ag/Cu solder joints by wetting reaction at 250°C and subsequent thermal aging, and measured by nanoindentation. In this study, the extra displacement created by the cantilever-like beam structural effect were investigated and discussed through the experimental initial and boundary conditions of Cu₆Sn₅ IMCs. The results showed that the variations of the loading procedures, sample shape, indent positions and indent directions would change the strain gradients on the matrixes, and thus cause the extra displacement. Moreover, through the study of the two-dimensional finite element analysis, the data divergence is minor in the top-view direction. In light of the results obtained from this study, we believe that structural effect would influence measurement accuracy for nanoindentation and test in the top-view direction would have great potential for future applications.