Preparation method of 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, comprising the following steps:

• (a) mixing an original powder, a sintering aid, a dispersant, a defoamer, a binder, and a plasticizer in a protective atmosphere to allow vacuum degassing at a vacuum degree of −0.1 kPa to −10 kPa for 6 h to 24 h to obtain a mixed slurry;
• wherein the original powder is at least one selected from the group consisting of a silicon nitride powder and a silicon powder;
• (b) subjecting the mixed slurry to tape casting and drying in a nitrogen atmosphere to obtain a first green body;
• wherein the drying is conducted in a mobile hot N2 atmosphere with a progressively increasing temperature;
• (c) subjecting the first green body to shaping pretreatment to obtain a second green body;
• wherein the shaping pretreatment refers to treating the first green body by cold isostatic pressing;
• (d) subjecting the second green body to debonding at 500° C. to 900° C. for 1 h to 3 h in a micro-positive-pressure nitrogen atmosphere with an atmospheric pressure of 0.12 MPa to 0.2 MPa to obtain a third green body;
• and
• (e) 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;
• wherein a crucible for the gas pressure sintering is selected from the group consisting of a high-purity boron nitride (BN) crucible or a graphite crucible with a high-purity BN isolation layer coated on a surface.