The impact of Ni and Zn doping on the stability, electrical and thermal conductivity of intermetallic compounds between Sn solder and Cu substrate

Abstract

First-principles calculations, grounded in density functional theory and augmented by the Boltzmann transport theory, have been conducted to scrutinize the influence of Ni and Zn doping on Cu-Sn IMC interfaces. These calculations, which factor in a radius parameter, shed light on the effects to interfacial stability, electronic structure, bonding properties, and the conductive behaviors—both electrical and thermal. The doping of Ni elements increases the absolute value of the interfacial formation enthalpy, enhancing its stability, while the doping of Zn elements reduces the absolute value of the formation enthalpy, decreasing its stability. The calculation results of the ideal adhesion work Wad indicate that all Cu-Sn-X (X: Ni, Zn)/Cu interface models are stable, with Wad >0. Due to the transfer of electrons and the hybridization of electronic orbitals at the Cu-Sn-X (X: Ni, Zn)/Cu interface, chemical bonds with both covalent and ionic characteristics are formed. Doping the Cu-Sn IMC/Cu system with Ni and Zn in place of Cu and Sn atoms leads to a reduction in the quantity of free electrons, consequently lowering the system's electrical and thermal conductivities.