Sn-0.7Â wt%Cu-(xNi) alloys: Microstructure-mechanical properties correlations with solder/substrate interfacial heat transfer coefficient

In spite of being barely studied, the prediction of mechanical properties by controlling and monitoring solidification thermal parameters (growth rate - v; cooling rate - Ṫ; solder/substrate interfacial heat transfer coefficient - hi) may be a powerful tool in the pre-programming of optimized final properties in solder alloys. The management of these parameters is fundamental to determine the final as-soldered microstructure, including the morphologies and sizes of phases. Within this scope, the aim of the present investigation is to determine interrelations of thermal parameters (v, Ṫ, hi), microstructure and tensile properties for Sn-0.7 wt%Cu-xNi (0-0.1 wt%Ni) solders solidified under steady-state conditions against a copper water-cooled substrate. It is demonstrated that the ultimate tensile strength can be linearly correlated with hi for Sn-Cu-Ni alloys. The final microstructures are shown to be very responsive to the changes in v as well as in Cu and Ni contents.