A preparation method of a high-thermal-conductivity and net-size silicon nitride ceramic substrate includes the following steps: (1) mixing an original powder, a sintering aid, a dispersant, a defoamer, a binder, and a plasticizer in a protective atmosphere to allow vacuum degassing to obtain a mixed slurry; (2) subjecting the mixed slurry to tape casting and drying in a nitrogen atmosphere to obtain a first green body; (3) subjecting the first green body to shaping pretreatment to obtain a second green body; (4) subjecting the second green body to debonding at 500 C. to 900 C. to obtain a third green body; and (5) subjecting the third green body to gas pressure sintering in a nitrogen atmosphere at 1,800 C. to 2,000 C. to obtain the high-thermal-conductivity and net-size silicon nitride ceramic substrate.

A preparation method of a high-thermal-conductivity and net-size silicon nitride ceramic substrate includes the following steps: (1) mixing an original powder, a sintering aid, a dispersant, a defoamer, a binder, and a plasticizer in a protective atmosphere to allow vacuum degassing to obtain a mixed slurry; (2) subjecting the mixed slurry to tape casting and drying in a nitrogen atmosphere to obtain a first green body; (3) subjecting the first green body to shaping pretreatment to obtain a second green body; (4) subjecting the second green body to debonding at 500 C. to 900 C. to obtain a third green body; and (5) subjecting the third green body to gas pressure sintering in a nitrogen atmosphere at 1,800 C. to 2,000 C. to obtain the high-thermal-conductivity and net-size silicon nitride ceramic substrate.