Study on interfacial mechanism of Ag–Si immiscible sintering for robust migration inhibition

• Heterogeneous Ag–Si sintered joints are proposed as a promising die-attach solution. • Ag–Si joints exhibit superior resistance to coarsening and electrochemical migration. • The native SiO 2 layer plays a beneficial role in interfacial bonding. • Ag–Si interfacial bonding is promoted by the release of Ag nanoparticles. • The role of Si incorporation is systematically investigated. Sintered Ag interconnects are promising for SiC power devices, but high-temperature grain coarsening, electrochemical migration (ECM), and high-cost limit wider application. To address these issues, Ag–Si composite particles with enhanced functional capabilities have been proposed. In this study, we systematically investigated the underlying mechanisms governing the low-temperature co-sintering behavior of Ag and Si particles, thermally induced coarsening during high-temperature aging, and electrochemical Ag migration under electrical bias. Our results demonstrate that the Si secondary phase becomes uniformly embedded within the Ag matrix without triggering the reaction-driven interdiffusion that is commonly observed in Ag–metal composite systems. As a result, Si serves as a chemically stable and structurally robust geometric constraint, acting as an effective barrier that reliably suppresses both thermally and electrically driven Ag migration. The sintered Ag–Si composite exhibits markedly higher microstructural stability than pure sintered Ag and outperforms Ag–metal composite counterparts under identical high-temperature aging and ECM stress conditions. This superior stability originates from the formation of an immiscible yet tightly consolidated Ag–Si microstructure, which enables durable long-term inhibition of Ag migration. The tight consolidation mainly arises from two coupled non-equilibrium interfacial processes: (i) the release of high-energy Ag nanoparticles that promote interfacial contact and neck formation on SiO 2 layers; (ii) the non-uniform structural evolution (e.g., regrowth or rearrangement) of the SiO 2 interlayer, which further enhances intimate contact and Ag–SiO 2 interfacial interaction. This work clarifies the mechanism of low-temperature Ag/semiconductor interface formation and supports Ag-based immiscible composites for high-temperature SiC packaging.