Core-Shell Nanoparticle Solder Composition for Thermal Cycle Reliability

The patent employs composite nanoparticles consisting of a metal oxide core (such as CeO2, TiO2, or SiO2) coated with a metal shell (such as Ag, Au, or Cu). This composite structure prevents phase separation of nanoparticles during thermal cycling while maintaining or enhancing shear strength. The core-shell configuration allows the nanoparticles to remain dispersed in the solder matrix without aggregating, thus resolving the contradiction between strength and reliability over thermal cycles.

The patent modifies the physical and chemical parameters of the nanoparticles by controlling their size (10-100 nm diameter), composition (metal oxide core with metal shell), and surface properties. These parameter changes ensure that the nanoparticles remain stable and do not phase separate during thermal cycling, thereby maintaining both shear strength and reliability over time.

The patent applies preliminary action by pre-synthesizing the core-shell structured nanoparticles before incorporating them into the solder paste. The nanoparticles are prepared in advance with controlled size, composition, and surface properties, which simplifies the subsequent mixing and manufacturing processes. This pre-preparation ensures that the nanoparticles are ready for direct incorporation without requiring complex in-situ synthesis or additional processing steps.

The patent uses a surfactant or coupling agent as an intermediary substance to facilitate the uniform dispersion of the core-shell nanoparticles in the solder paste matrix. This intermediary prevents agglomeration and ensures homogeneous distribution, thereby simplifying the manufacturing process while maintaining the reliability benefits of the high-performance nanoparticles.