On the mechanical properties of Cu3Sn intermetallic compound through molecular dynamics simulation and nanoindentation testing

Abstract

Cu3Sn crystal is a well-known intermetallic compound (IMC), which is often observed at the interface of Sn solder and Cu metallization. It is generally recognized as the major cause of the failure of solder bumps and electrodes in microelectronics industry. The aim of the study is to investigate the elastic mechanical properties of orthorhombic Cu3Sn crystal by way of molecular dynamics (MD) simulation and dynamic nanoindentation testing. In the MD simulations, the force field between atoms is modeled with the modified embedded atom method (MEAM). Based on the continuum mechanics assumption, the elastic stiffnesses of the Cu3Sn can be derived from the calculated energy, and then, used in the generalized Hook's law in compliance form to calculate the associated mechanical properties. Further, using the Voigt-Reuss bounds and Voigt-Reuss-Hill approximation these mechanical properties are averaged for facilitating the comparison with experimental data. Besides, the size-dependent effects on the mechanical properties of the crystal are also assessed. The numerical results show that average bulk modulus, Young's modulus, shear modulus and Poisson's ratio of the orthorhombic Cu3Sn crystal are 128.9 GPa, 132.7 GPa, 49.9 GPa and 0.328, and most importantly, they agree very well with our nanoindentation testing results and those published theoretical/experimental data in literature.