Rheology-Engineered Non-Aqueous Si3N4/Si Slurries for High-Performance Ceramic Substrates with Enhanced Thermal Management Capability

Thin, thermally conductive Si3N4 ceramic substrates are promising candidates for electronic packaging applications, but their fabrication requires precise control of slurry dispersion, rheological behavior, and green-tape uniformity to minimize processing defects. In this work, a non-aqueous Si3N4/Si reactive slurry system is optimized via rheology control for tape casting and reaction bonding. The effects of dispersant type, content, and solid loading on slurry flow behavior and green tape quality are systematically investigated. Dispersant 421 provides the most favorable rheological and dispersion behavior, enabling uniform tape casting at 41 vol % solid loading. The optimized slurry yields green tapes with high thickness uniformity (RSD 0.46%) and homogeneous particle packing. After nitridation and gas-pressure sintering, dense Si3N4 ceramic substrates with a thickness of 0.25 mm are obtained, exhibiting a flexural strength of 815 ± 27 MPa and a thermal conductivity of 81.84 ± 0.64 W/(m·K). The resulting ceramics show a dense microstructure with noticeable translucency, suggesting good structural uniformity. These results establish rheological control as a practical approach for fabricating thin Si3N4 substrates for electronic thermal management.