Batch sintering method for high-property silicon nitride ceramic substrate
The present disclosure relates to a batch sintering method for a high-property silicon nitride ceramic substrate. The batch sintering method includes: (1) silicon nitride ceramic substrate green bodies are stacked and put into a boron nitride crucible, and a layer of boron nitride powder is applied between adjacent silicon nitride ceramic substrate green bodies; (2) after step-by-step vacuumization, debinding is performed in a nitrogen atmosphere or a reducing atmosphere at 500° C. to 900° C.; (3) gas pressure sintering is then performed in a nitrogen atmosphere at 1800° C. to 2000° C., completing the batch preparation of the high-property silicon nitride ceramic substrate.
1 . A batch sintering method for making a high-property silicon nitride ceramic substrate, comprising the following steps:
(1) stacking silicon nitride ceramic substrate green bodies, putting the silicon nitride ceramic substrate green bodies into a boron nitride crucible, and applying a layer of boron nitride powder between adjacent silicon nitride ceramic substrate green bodies;
(2) performing step-by-step vacuumization, and then debinding in a nitrogen atmosphere or a reducing atmosphere at 500° C. to 900° C.; wherein the step-by-step vacuumization is performed in at least two steps or at least three steps; if vacuumization is performed in the at least two steps, parameters of the step-by-step vacuumization include: a first step of 20 to 30 minutes of vacuumization for making a vacuum degree reach 20 kPa to 30 kPa, and a second of 10 to 20 minutes of vacuumization for making a vacuum degree less than 10 Pa; or if vacuumization is performed in the at least three steps, parameters of the step-by-step vacuumization include: a first step of 10 to 15 minutes of vacuumization for making a vacuum degree reach 60 kPa to 80 kPa, a second step of 10 to 15 minutes of vacuumization for making a vacuum degree reach 10 kPa to 30 kPa, and a third step of 10 to 15 minutes of vacuumization for making a vacuum degree less than 10 Pa; and then
(3) performing gas pressure sintering in a nitrogen atmosphere at 1800° C. to 2000° C., thereby completing a batch preparation of the high-property silicon nitride ceramic substrate.
2 . The batch sintering method according to claim 1 , wherein a number of the stacked silicon nitride ceramic substrate green bodies is 5 to 50.
3 . The batch sintering method according to claim 1 , wherein in the boron nitride powder, a content of O is not more than 1%, a content of C is not more than 0.01%, and a content of metal impurity ions is not more than 0.02%; and an average grain size of the boron nitride powder is 1 μm to 5 μm.
4 . The batch sintering method according to claim 3 , wherein the average grain size of the boron nitride powder is 2 μm to 5 μm.
5 . The batch sintering method according to claim 1 , wherein an amount of the boron nitride powder used is 1.0 mg/cm 2 to 2.5 mg/cm 2 .
6 . The batch sintering method according to claim 5 , wherein the amount of the boron nitride powder used is 1.5 mg/cm 2 to 2.5 mg/cm 2 .
7 . The batch sintering method according to claim 1 , wherein in Step (2), a pressure of the nitrogen atmosphere or the reducing atmosphere is 0.05 MPa to 0.2 MPa; wherein the reducing atmosphere is a nitrogen/hydrogen mixed atmosphere with a hydrogen content not higher than 5%; and a duration of debinding is 1 to 3 hours.
8 . The batch sintering method according to claim 7 , wherein in Step (2), the pressure of the nitrogen atmosphere or the reducing atmosphere is 0.1 MPa to 0.2 MPa.
9 . The batch sintering method according to claim 1 , wherein a pressure of the nitrogen atmosphere in Step (3) is 0.5 MPa to 10 MPa; and a duration of the gas pressure sintering is 4 to 12 hours.
10 . The batch sintering method according to claim 1 , further comprising providing a plurality of boron nitride crucibles including the boron nitride crucible, stacking silicon nitride ceramic substrate green bodies, putting stacked silicon nitride ceramic substrate green bodies in each of the plurality of boron nitride crucibles, applying a layer of boron nitride powder between adjacent silicon nitride ceramic substrate green bodies in each of the plurality of boron nitride crucibles, evenly arranging the plurality of boron nitride crucibles in a graphite kiln furniture, and performing gas pressure sintering in the graphite kiln furniture.
11 . The batch sintering method according to claim 10 , wherein the graphite kiln furniture has a multi-layer grid structure.
12 . The batch sintering method according to claim 1 , further comprising preparing each silicon nitride ceramic substrate green body by slurry tape-casting or powder pressing;
wherein the slurry tape-casting comprises the following steps:
(1) mixing at least one of silicon nitride powder and silicon powder as original powder, sintering aids, dispersant, defoamer, binder and plasticizer in a protective atmosphere to form a mixture, degassing the mixture in vacuum to obtain a mixed slurry;
(2) tape-casting and drying the mixed slurry in a nitrogen atmosphere to obtain a first green body; and
(3) performing shaping pretreatment on the first green body to obtain a respective silicon nitride ceramic substrate green body.
13 . The batch sintering method according to claim 12 , wherein if the original powder contains the silicon powder, a weight of the silicon powder is not less than 75% of that of the original powder, wherein a weight of the original powder is a sum of a weight of the silicon nitride powder and a weight of silicon nitride produced after complete nitridation of the silicon powder.
14 . The batch sintering method according to claim 13 , further comprising, before the step of performing gas pressure sintering, nitriding a debound silicon nitride ceramic substrate green body, wherein parameters of the nitriding include: nitrogen atmosphere: nitrogen/hydrogen mixed atmosphere with a hydrogen content not higher than 5%; pressure: 0.1 MPa to 0.2 MPa; nitridation temperature: 1350° C. to 1450° C.; and duration of nitridation: 3 to 6 hours.