CN115196975A - Preparation method of high-thermal-conductivity silicon nitride substrate - Google Patents
Preparation method of high-thermal-conductivity silicon nitride substrate Download PDFInfo
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- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 58
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 58
- 239000000758 substrate Substances 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000000843 powder Substances 0.000 claims abstract description 61
- 238000005245 sintering Methods 0.000 claims abstract description 24
- 238000010438 heat treatment Methods 0.000 claims abstract description 23
- 238000002156 mixing Methods 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims abstract description 16
- 239000002184 metal Substances 0.000 claims abstract description 16
- 238000005096 rolling process Methods 0.000 claims abstract description 15
- 229910021332 silicide Inorganic materials 0.000 claims abstract description 15
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000011065 in-situ storage Methods 0.000 claims abstract description 12
- 239000007789 gas Substances 0.000 claims abstract description 11
- 238000003825 pressing Methods 0.000 claims abstract description 10
- 239000000463 material Substances 0.000 claims abstract description 9
- 238000000462 isostatic pressing Methods 0.000 claims abstract description 8
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 8
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 8
- 238000001125 extrusion Methods 0.000 claims abstract description 7
- 238000000465 moulding Methods 0.000 claims abstract description 7
- 239000011863 silicon-based powder Substances 0.000 claims abstract description 5
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000011261 inert gas Substances 0.000 claims abstract description 4
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 4
- 239000011777 magnesium Substances 0.000 claims abstract description 4
- 238000010345 tape casting Methods 0.000 claims abstract description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 21
- 239000001301 oxygen Substances 0.000 claims description 21
- 229910052760 oxygen Inorganic materials 0.000 claims description 21
- 238000000498 ball milling Methods 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 17
- 239000002994 raw material Substances 0.000 claims description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 6
- 238000009694 cold isostatic pressing Methods 0.000 claims description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 3
- 229910018251 LaSi 2 Inorganic materials 0.000 claims description 3
- 229910008484 TiSi Inorganic materials 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims description 3
- 239000011268 mixed slurry Substances 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- -1 polytetrafluoroethylene Polymers 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 238000007873 sieving Methods 0.000 claims description 3
- 238000001291 vacuum drying Methods 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 239000012535 impurity Substances 0.000 abstract description 5
- 229910052710 silicon Inorganic materials 0.000 abstract description 2
- 239000012752 auxiliary agent Substances 0.000 description 7
- 239000000919 ceramic Substances 0.000 description 7
- 229910052582 BN Inorganic materials 0.000 description 5
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 5
- 239000012071 phase Substances 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000005219 brazing Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
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- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
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Abstract
The invention discloses a preparation method of a high-thermal-conductivity silicon nitride substrate, which comprises the following steps: s1, mixing materials: mixing in a weight percent ratio, wherein, 80-95wt% Si 3 N 4 powder/Si powder, 1-10wt% of metal silicide, 1-10wt% of magnesium-containing powder; s2, forming: molding the powder by utilizing tape casting, dry pressing, isostatic pressing, extrusion and film rolling; s3, heat treatment: heating the formed product to 900-1350 ℃ in vacuum/inert gas atmosphere for heat treatment for 1-20h to fully decompose the metal silicide and the SiO on the surface of the silicon nitride powder 2 Fully reacting to generate metal oxide on the surface of the silicon nitride powder in situ; s4, sintering: introducing high-purity N with the purity of more than or equal to 99.999 percent 2 And NH 3 The mixed gas is heated to 0.4-10Mpa, then is heated to 1800-1950 ℃, and is heated for 2-60h to be sintered; the invention does not introduce elements outside the system, and avoids generating new elements caused by a carbothermic methodProblems with impurity phases; in situ generated Yb 2 O 3 The contact area of the silicon nitride powder is increased, and the phase change driving force of the silicon nitride is improved.
Description
Technical Field
The invention belongs to the related technical field of preparation methods of high-thermal-conductivity silicon nitride substrates, and particularly relates to a preparation method of a high-thermal-conductivity silicon nitride substrate, which can solve the problem that a high-thermal-conductivity substrate is difficult to prepare due to the fact that the oxygen content of raw material powder is high and the dispersing of an auxiliary agent is not uniform, and lattice oxygen and an air hole structure are formed in a sintering process.
Background
An active brazing (AMB) copper-clad ceramic substrate is one of the most important packaging materials of a high-power semiconductor module, a high-thermal-conductivity silicon nitride ceramic substrate is one of the most optimal parent metals in the manufacturing process of the AMB copper-clad ceramic substrate,the cost of the product accounts for more than 50 percent of the whole product; the silicon nitride substrate is mainly prepared by processing the procedures of mixing, molding, sintering, surface treatment and the like, and MgO and Y are commonly used at present 2 O 3 The metal oxide such as (yttrium oxide) is used as a sintering aid, new oxygen impurities are introduced into a sintering system, and the oxygen impurities finally form lattice oxygen in the sintering process to influence heat conduction, so that the high-heat-conductivity silicon nitride substrate is difficult to sinter.
In order to solve the problems, some people add a small amount of carbon to perform carbothermic reduction treatment on a product at 1450 ℃, so that the oxygen content in a liquid phase is reduced, and the silicon nitride substrate with the initial high thermal conductivity is prepared.
In addition, the method for preparing the silicon nitride substrate in the prior art also has the following disadvantages:
1. at present, substrate raw material powder Si 3 N 4 The oxygen content of the powder or the Si powder is too high, so that the high-heat-conductivity substrate is difficult to prepare;
2. due to the fact that the phase change degree of crystal grains is different due to uneven dispersion of the auxiliary agent, air holes are increased due to the fact that abnormally grown crystal grains are large in appearance, and a high-thermal-conductivity substrate is difficult to prepare;
3. yb in the raw material powder 2 O 3 With Si 3 N 4 The contact area is small, resulting in weak phase-change driving force.
Therefore, a preparation method of the high-thermal-conductivity silicon nitride substrate is developed, which can solve the problem that the high-thermal-conductivity substrate is difficult to prepare due to the fact that the oxygen content of raw material powder is high and the dispersing of the auxiliary agent is not uniform, and lattice oxygen and an air hole structure are formed in the sintering process.
Disclosure of Invention
The invention aims to provide a preparation method of a high-thermal-conductivity silicon nitride substrate, which can solve the problem that a high-thermal-conductivity substrate is difficult to prepare due to the fact that the oxygen content of raw material powder is high and the dispersing of an auxiliary agent is not uniform, and lattice oxygen and an air hole structure are formed in the sintering process.
In order to achieve the purpose, the invention provides the following technical scheme: a preparation method of a high-thermal-conductivity silicon nitride substrate comprises the following steps:
s1, mixing materials: mixing in weight percent, wherein, 80-95wt% Si 3 N 4 powder/Si powder, 1-10wt% of metal silicide and 1-10wt% of magnesium-containing powder;
s2, forming: molding the powder by utilizing tape casting, dry pressing, isostatic pressing, extrusion and film rolling;
s3, heat treatment: heating the formed product to 900-1350 ℃ in vacuum/inert gas atmosphere for heat treatment for 1-20h to fully decompose the metal silicide and the SiO on the surface of the silicon nitride powder 2 Fully reacting to generate metal oxide on the surface of the silicon nitride powder in situ;
s4, sintering: introducing high-purity N with the purity of more than or equal to 99.999 percent 2 And NH 3 The mixed gas is heated to 0.4-10Mpa, then is heated to 1800-1950 ℃, and is heated for 2-60h to be sintered.
Preferably, the metal silicide is Si 2 Yb、TiSi 2 、LaSi 2 One or more powders of (a).
Preferably, the high purity N 2 And NH 3 NH in the mixed gas of 3 The content of (B) is 5-15vol%.
Preferably, the method for preparing the silicon nitride substrate with high thermal conductivity comprises the following steps:
s1, preparing materials: mixing the raw material powder by adopting a ball milling mode: 90wt% of Si 3 N 4 、6wt% YbSi 2 And 4wt% MgSiN 2 Mixing the powder, transferring the powder into a ball milling tank of polytetrafluoroethylene, and adding absolute ethyl alcohol as a medium; sealing the ball milling tank, vacuumizing and filling nitrogen for cleaning the tank through a vent valve, wherein the cleaning frequency is more than or equal to 3 times, a planetary ball milling method is adopted until no residual oxygen and water vapor exist in the ball milling tank, the rotating speed is 300 r/min, the ball milling is carried out for 4 hours, and the powder is mixed;
s2, dry pressing and forming: placing the uniformly mixed slurry in a vacuum drying oven, drying at 60 ℃ for more than 12h, and then sieving by a 100-mesh sieve; dry pressing the obtained powder under the pressure of 20MPa for forming, and then carrying out cold isostatic pressing under the pressure of 180 MPa; then the powder is formed by extrusion and film rolling;
s3, heat treatment of the product: transferring the formed product into a BN crucible, and transferring the BN crucible into a pneumatic sintering furnace; firstly, vacuumizing a pressure sintering furnace until the vacuum degree is 0.1-0.01 Pa, then heating to 900-1350 ℃, the heating rate is 1-600 ℃/h, and the heat preservation time is 1-20h; so that the metal silicide is fully decomposed and is connected with SiO on the surface of the silicon nitride powder 2 Fully reacting to generate metal oxide on the surface of the silicon nitride powder in situ;
s4, sintering of products: followed by charging of high purity N 2 And NH 3 Mixed gas of (2), wherein NH 3 The content is 5-15vol%; raising the pressure to 0.4-10Mpa, raising the temperature to 1910 ℃, wherein the heating rate is 100-600 ℃/h, and the heat preservation time is 2-60h; and then cooling to normal temperature at a cooling rate of 10-900 ℃/min to obtain the high-thermal-conductivity silicon nitride substrate.
Compared with the prior art, the invention provides the preparation method of the high-thermal-conductivity silicon nitride substrate, which has the following beneficial effects:
the preparation method of the high-thermal-conductivity silicon nitride substrate can solve the technical problem that the high-thermal-conductivity substrate is difficult to prepare due to the fact that the oxygen content of the raw material powder is high and the dispersing of the auxiliary agent is not uniform, and lattice oxygen and air hole structures are formed in the sintering process; meanwhile, no elements outside the system are introduced, so that the problem of generating a new impurity phase caused by a carbothermic method is avoided; also, yb generated in situ 2 O 3 The contact area of the silicon nitride powder is increased, the phase-change driving force of the silicon nitride is improved, and the phase-change speed of the silicon nitride is accelerated.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
A preparation method of a high-thermal-conductivity silicon nitride substrate comprises the following steps:
1. mixing materials: mixing in a weight ratio of 80-95wt% of Si 3 N 4 powder/Si powder, 1-10wt% of metal silicide, 1-10wt% of magnesium-containing powder; the metal silicide is Si 2 Yb、TiSi 2 、LaSi 2 A mixture of one or more powders of (a);
2. molding: molding the powder by utilizing tape casting, dry pressing, isostatic pressing, extrusion and film rolling; specifically, casting: the slurry with uniform mixing viscosity of 1700mPa.s flows down from a hopper of a casting machine, is scraped and coated on a special base band by a scraper with the thickness of 0.19mm, is dried and cured at room temperature to obtain a silicon nitride ceramic green body, and then the green body is cut, laminated and subjected to isostatic pressing treatment according to the size and the shape of a required finished product to obtain a green body material of the silicon nitride ceramic substrate;
extruding: pugging the mixed material for 2-3h by a kneader, putting the obtained pug into a vacuum pug mill for further pugging, removing bubbles in the pug and further ensuring the uniformity of the pug, then aging the extruded pug for 24-30h, finally extruding a silicon nitride ceramic green body by a vacuum extruder, and cutting the green body according to the size of a required finished product;
rolling a film: putting the slurry after the pugging is finished between two rollers of a film rolling machine for rolling for multiple times to obtain a film strip; taking down the film belt, folding in half, rolling the film again, and finishing rough rolling of the silicon nitride ceramics with the film rolling direction of 90 degrees with the film rolling direction of the last time; then adjusting the gap between the two rollers, and rolling the film belt from thick to thin until the thickness of the film belt meets the requirements of the product;
3. and (3) heat treatment: heating the formed product to 900-1350 ℃ in vacuum/inert gas atmosphere for heat treatment for 1-20h to fully decompose the metal silicide and to react with SiO on the surface of the silicon nitride powder 2 Fully reacting to generate metal oxide on the surface of the silicon nitride powder in situ;
4. and (3) sintering: introducing high-purity N with the purity of more than or equal to 99.999 percent 2 And NH 3 The mixed gas raises the gas pressure toContinuously heating to 1800-1950 ℃ after 0.4-10Mpa, and preserving heat for 2-60h for sintering; said high purity N 2 And NH 3 NH in the mixed gas of 3 The content of (B) is 5-15vol%.
The second embodiment:
a preparation method of a high-thermal-conductivity silicon nitride substrate comprises the following steps:
s1, preparing materials: mixing the raw material powder in a ball milling mode: by weight percent, 90wt% of Si 3 N 4 、6wt%YbSi 2 And 4wt% of MgSiN 2 Mixing the powder, transferring the powder into a ball milling tank of polytetrafluoroethylene, and adding absolute ethyl alcohol as a medium; sealing the ball milling tank, vacuumizing and filling nitrogen for cleaning the tank through a vent valve, wherein the cleaning time is more than or equal to 3 times, ball milling for 4 hours at a rotating speed of 300 r/min by adopting a planetary ball milling method after residual oxygen and water vapor do not exist in the ball milling tank, and mixing the powder;
s2, dry pressing and forming: placing the uniformly mixed slurry in a vacuum drying oven, drying at 60 ℃ for more than 12h, and then sieving by a 100-mesh sieve; dry pressing the obtained powder under the pressure of 20MPa for forming, and then carrying out cold isostatic pressing under the pressure of 180 MPa; then the powder is formed by extrusion and film rolling; the molding is explained in the first embodiment, and will not be described again; cold isostatic pressing is one of isostatic pressing, and warm isostatic pressing is another, the difference being the temperature of the isostatic pressing medium;
s3, heat treatment of the product: transferring the formed product into a BN (boron nitride) crucible, and transferring the BN crucible into a pneumatic sintering furnace; firstly, vacuumizing an air pressure sintering furnace until the vacuum degree is 0.1Pa-0.01Pa, then heating to 900-1350 ℃, wherein the heating rate is 1-600 ℃/h, and the heat preservation time is 1-20h; make the metal silicide fully decomposed and contact with SiO on the surface of the silicon nitride powder 2 Fully reacting to generate metal oxide on the surface of the silicon nitride powder in situ;
s4, sintering of the product: then high-purity N with the purity more than or equal to 99.999 percent is filled in 2 And NH 3 Mixed gas of (2), wherein NH 3 The content is 5-15vol%; raising the pressure to 0.4-10Mpa, raising the temperature to 1910 ℃, wherein the temperature raising rate is 100-600 ℃/h, and the heat preservation time is 2-60h; then at 10-900 deg.C/miAnd reducing the temperature reduction rate of n to normal temperature to obtain the high-thermal-conductivity silicon nitride substrate.
The preparation method of the high-thermal-conductivity silicon nitride substrate provided by the invention introduces MgSiN 2 And metal silicide YbSi 2 As a sintering aid, not only is the introduction of oxygen element isolated in the raw material section, ybSi 2 Si generated during pyrolysis can also be mixed with SiO on the surface of silicon nitride 2 The reaction plays a role in further reducing the oxygen content of the powder raw material, and meanwhile, high-activity Yb generated by decomposition and SiO on the surface of the silicon nitride powder 2 Reaction to form Yb in situ on the surface 2 O 3 (ii) a The scheme thoroughly isolates the oxygen element introduced by an auxiliary agent system, and Yb is generated in situ 2 O 3 The contact area with the surface of the silicon nitride is larger, the phase-change driving force of the silicon nitride is enhanced, and the high-thermal-conductivity silicon nitride substrate is finally prepared.
Compared with the prior art, the invention has the following beneficial effects:
the preparation method of the high-thermal-conductivity silicon nitride substrate can solve the technical problem that the high-thermal-conductivity substrate is difficult to prepare due to the fact that the oxygen content of raw material powder is high and the dispersing of the auxiliary agent is not uniform, and lattice oxygen and an air hole structure are formed in the sintering process; meanwhile, no elements outside the system are introduced, so that the problem of generating a new impurity phase caused by a carbothermic method is avoided; also, yb generated in situ 2 O 3 The contact area between the silicon nitride powder and the silicon nitride powder is increased, the phase change driving force of the silicon nitride is improved, and the phase change speed of the silicon nitride is accelerated.
The above-mentioned embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention by this, and all equivalent changes or modifications made according to the spirit of the present invention should be covered in the protection scope of the present invention.
Claims (4)
1. A preparation method of a high-thermal-conductivity silicon nitride substrate is characterized by comprising the following steps:
s1, mixing materials: mixing in percentage by weight, whichMiddle, 80-95wt% of Si 3 N 4 powder/Si powder, 1-10wt% of metal silicide and 1-10wt% of magnesium-containing powder;
s2, forming: molding the powder by utilizing tape casting, dry pressing, isostatic pressing, extrusion and film rolling;
s3, heat treatment: heating the formed product to 900-1350 ℃ in vacuum/inert gas atmosphere for heat treatment for 1-20h to fully decompose the metal silicide and the SiO on the surface of the silicon nitride powder 2 Fully reacting to generate metal oxide on the surface of the silicon nitride powder in situ;
s4, sintering: introducing high-purity N with the purity of more than or equal to 99.999 percent 2 And NH 3 The mixed gas is heated to 0.4-10Mpa, then is heated to 1800-1950 ℃, and is heated for 2-60h to be sintered.
2. The method of claim 1, wherein the metal silicide is Si 2 Yb、TiSi 2 、LaSi 2 One or more powders of (a).
3. The method for preparing a silicon nitride substrate with high thermal conductivity as claimed in claim 1, wherein the high purity N is 2 And NH 3 NH in the mixed gas 3 The content of (B) is 5-15vol%.
4. The method for preparing a silicon nitride substrate with high thermal conductivity as claimed in claim 1, comprising the steps of:
s1, preparing materials: mixing the raw material powder by adopting a ball milling mode: 90wt% of Si 3 N 4 、6wt% YbSi 2 And 4wt% MgSiN 2 Mixing the powder, transferring the powder into a ball milling tank of polytetrafluoroethylene, and adding absolute ethyl alcohol as a medium; sealing the ball milling tank, vacuumizing and filling nitrogen for cleaning the tank through a vent valve, wherein the cleaning time is more than or equal to 3 times, ball milling for 4 hours at a rotating speed of 300 r/min by adopting a planetary ball milling method after residual oxygen and water vapor do not exist in the ball milling tank, and mixing the powder;
s2, dry pressing and forming: placing the uniformly mixed slurry in a vacuum drying oven, drying at 60 ℃ for more than 12h, and then sieving by a 100-mesh sieve; dry pressing the obtained powder under the pressure of 20MPa for forming, and then carrying out cold isostatic pressing under the pressure of 180 MPa; then the powder is formed by extrusion and film rolling;
s3, heat treatment of the product: transferring the formed product into a BN crucible, and transferring the BN crucible into a pneumatic sintering furnace; firstly, vacuumizing an air pressure sintering furnace until the vacuum degree is 0.1Pa-0.01Pa, then heating to 900-1350 ℃, wherein the heating rate is 1-600 ℃/h, and the heat preservation time is 1-20h; so that the metal silicide is fully decomposed and is connected with SiO on the surface of the silicon nitride powder 2 Fully reacting to generate metal oxide on the surface of the silicon nitride powder in situ;
s4, sintering of products: followed by charging of high purity N 2 And NH 3 Mixed gas of (2), wherein NH 3 The content is 5-15vol%; raising the pressure to 0.4-10Mpa, raising the temperature to 1910 ℃, wherein the temperature raising rate is 100-600 ℃/h, and the heat preservation time is 2-60h; and then reducing the temperature to normal temperature at the cooling rate of 10-900 ℃/min to obtain the high-thermal-conductivity silicon nitride substrate.
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