Synergistic Modulation of Rheological and Electrical Behavior in W–Cu Pastes via Particle Size Gradient and Ball Milling-Induced Morphology Reconstruction

To develop high-performance W–Cu conductor pastes for high-temperature co-fired ceramics (HTCC), graded particle-size design and ball-milling modification were systematically investigated. The particle-size distribution and powder morphology were changed, resulting in pastes with improved rheological stability and electrical conductivity. Rheological analysis combined with microstructural characterization revealed that powder size and morphology jointly controlled rheological behavior, sintering densification, and electrical conductivity. The optimized pastes exhibited improved flowability and dense sintered films. Electrical testing showed that resistivity decreased significantly, from 57.77 ± 2.41 mΩ·cm for coarse mixed powders to 5.80 ± 0.37 mΩ·cm for ball-milled powder s. Inspired by previous studies on W–Cu bulk composites, ball milling was employed to induce lamellar particle morphologies, which facilitated interparticle contact, promoted the formation of conductive networks. As a result, dense W–Cu films with reduced resistivity were successfully fabricated, demonstrating the feasibility of W–Cu pastes as advanced metallization materials for HTCC.