Deformation behavior of (Cu, Ag)-Sn intermetallics by nanoindentation

Nanoindentation is an important technique for probing the mechanical behavior of materials at small length scales. In this study, nanoindentation was used to extract the elastic and plastic properties of Cu, Sn-3.5Ag solder, Ag3Sn, and intermetallics in Cu/Sn-Ag solder joints including Cu6Sn5, and Cu3Sn. The elastic and plastic properties of Cu, Sn-3.5Ag solder, Ag3Sn, Cu6Sn5, and Cu3Sn were measured and where possible, compared to limited data available in the literature. Finite element analysis was used to simulate the indentation behavior from elastic-plastic properties of the intermetallics. The predicted values matched very well with experimental results. Finite element analysis also showed that pile-up took place in indentation of Cu and solder, while indentation sink-in was observed in Ag3Sn, Cu6Sn5, and Cu3Sn. The relative degree of pile-up/sink-in was shown to be a function of the work hardening exponent of the phase and the ratio of yield stress to Young's modulus. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.