Interfacial Reactions in Sn-Pb/Ni-8.0 at.%V Couples

Abstract

The Ni-8.0 at.%V (Ni-7.0 wt.%V) substrate is an important diffusion barrier layer material in flip-chip technology. This study examines interfacial reactions in couples prepared using Ni-8.0 at.%V substrate and Sn-6.0 at.%Pb, Sn-27.6 at.%Pb, and Sn-83.8 at.%Pb solders, at temperatures between 210°C and 450°C. In the Sn-27.6 at.%Pb/Ni-8.0 at.%V and Sn-83.8 at.%Pb/Ni-8.0 at.%V couples, the reaction products are the Ni3Sn4 phase and a T phase with limited Pb solubility, being similar to those in the Sn/Ni-8.0 at.%V couples. However, the Ni3Sn4 phase is formed at an earlier stage and the T phase is formed later. The phase formation sequences are different from those in Sn/Ni-8.0 at.%V couples. In Sn-6.0 at.%Pb/Ni-8.0 at.%V couples, a “Pb-rich” phase is formed, in addition to the T phase and the Ni3Sn4 phase, and the T phase and Ni3Sn4 phase are formed almost simultaneously. Although Pb does not participate actively in the interfacial reactions, the phase formation sequences are changed when Pb alloys in the solder, due to the reduced Sn flux from the solder into the Ni-8.0 at.%V substrate.