Ceria reinforced nanocomposite solder foils fabricated by accumulative roll bonding process

As one of the key technologies for high performance electronic devices, composite solders have been recently developed to improve thermal and mechanical properties of solder joints. In this study, accumulative roll bonding process was used as an effective alternative method for manufacturing high-strength, finely dispersed, void-free and highly uniform Sn–Ag–Cu/CeO₂ nanocomposite solders. Microstructural investigation of nanocomposite solders revealed that homogenous distribution of CeO₂ nanoparticle has been achieved and the eutectic as-cast morphology of the solder changed to recrystallized fine grained structure. As a result of severe plastic deformation during rolling, brittle and elongated intermetallics crushed into fine particles with an average diameter of a few hundred nanometers and dispersed uniformly in the solder matrix. Mechanical test results showed that the microhardness, 0.2% yield stress, and ultimate tensile strength of the composite solder increased with addition of CeO₂ nanoparticles, while the ductility of the composite was decreased.