Preparation method of silicon nitride ceramic substrate

The invention discloses a preparation method of a silicon nitride ceramic substrate. The preparation method comprises steps as follows: silica powder, silicon nitride powder, a sintering aid and a dispersing agent are mixed, a solvent is added, all components are subjected to ball milling for the first time, then an adhesive and a plasticizer are added, all components are subjected to the ball milling the second time and subjected to vacuum defoamation, slurry is obtained, and a mass ratio of the silica powder to the silicon nitride powder is (1:10)-(10:1); the slurry is subjected to tape casting and dried, a biscuit is obtained and subjected to vacuum adhesive discharging, and a green body is obtained; the green body is sintered, and the silicon nitride ceramic substrate is obtained. The silicon nitride powder and the cheap silica powder are adopted as main raw materials, the silicon nitride ceramic substrate is prepared with a tape casting technology, and the silicon nitride ceramic substrate with low cost