Microstructure, Resistivity, and Strength of Pressureless Sintered Silver Joints: Effect of Powder Formulation

This study formulates an organic vehicle system using triethylene glycol monobutyl ether as the solvent, ethyl cellulose as the binder, and oleic acid as the dispersant to investigate the low‐temperature pressureless sintering of silver paste. The effects of sintering temperature and the composite ratios of silver powders with different sizes and morphologies (400 nm spherical silver powder, 2 μm flake silver powder, and 300 nm flake silver powder) on the electrical and mechanical properties of the sintered bodies were systematically studied. Results indicate that increasing the sintering temperature reduced the number of pores while increasing their size, leading to improved densification that approached the compact structure of bulk silver, thereby optimizing performance. The morphology and size of the silver powders significantly influenced the sintering behavior. Flake powders reduced interfacial resistance through two‐dimensional planar contacts, whereas spherical powders enhanced electrical performance and shear strength by forming more sintering necks. A synergistic effect was achieved by combining spherical and flake powders. Notably, when spherical silver powder was blended with 300 nm flake silver powder at a ratio of 1:3, a minimum porosity of 1.658% was achieved, along with a shear strength of 63.34 MPa and a volume resistivity of 4.85 × 10 ⁻⁶  Ω cm. Furthermore, comparative analysis revealed the distinct advantages of the smaller flake powder over its larger counterpart (2 μm) in enhancing sintered quality, providing experimental basis for the material selection of silver paste.