First-principles study on anisotropy of elastic modulus of α-CoSn₃ IMC

While the solder joints are miniaturized, the proportion of interface IMC in the entire solder joints has increased significantly, and the micro solder joints become more sensitive to the orientation of the interface IMC during the service process. Therefore, this work is based on density functional theory to calculate the lattice constant and elastic modulus anisotropy of α-CoSn₃, and compares the anisotropy indices of common IMCs. The results show that the resistance to linear compression in the 100 direction is less than that of the other two main crystal axes; the (100) shear plane is more resistant to shear deformation than the other two main crystal planes. According to the differential electron density map, the specific contribution of the bonding orbital is analyzed. The three-dimensional graphs and projection graphs of the three-dimensional elastic modulus of α-CoSn₃ varying with crystal orientation intuitively show their anisotropic properties. The anisotropy index of α-CoSn₃ was calculated, and compared with other common IMCs in brazing, the anisotropy degree of α-CoSn₃ was found to be in the middle.