Silicon nitride ceramic slurry, silicon nitride ceramic substrate, and method for manufacturing the same

Abstract

The present application relates to a kind of silicon nitride ceramic slurry, silicon nitride ceramic substrate and preparation method thereof.The above-mentioned silicon nitride ceramic slurry is water-based slurry system, using specific additive amount of sintering aid, dispersant, film forming aid and water, and using the reasonable collocation and mixing of acrylic resin aqueous solution and water-based acrylic emulsion with different molecular weight as binder, specifically, binder includes the mass ratio of 1: (1-10) acrylic resin aqueous solution and water-based acrylic emulsion, the mass average molecular weight of polymer in acrylic resin aqueous solution is 2000-7000, the mass average molecular weight of polymer in water-based acrylic emulsion is 8000-20000, can obtain high stability, good rheological water-based casting slurry, make green body good and stablely form, and in different temperature stages, binder is gaseous in stages and escapes from green body when degassing, it is favorable to reduce the deformation and cracking and other defects of green body in degassing process.

Description

Technical Field

[0001] This invention relates to the field of ceramic technology, and in particular to a silicon nitride ceramic slurry, a silicon nitride ceramic substrate, and a method for preparing the same. Background Technology

[0002] Ceramic substrates can be produced using tape casting. Tape casting offers broad prospects for the miniaturization of electronic devices and components, as well as the realization of very large-scale integrated circuits. It also provides possibilities for the macroscopic and microscopic structural design of engineering ceramics, offering a new approach to optimizing material performance.

[0003] Currently, the slurries used in tape casting are primarily prepared by mixing organic solvents, binders, additives, and ceramic powders. However, the use of organic solvents presents problems such as environmental pollution, health hazards to production personnel, high fire safety requirements, and high production costs. Water-based tape casting improves upon traditional slurries by using water instead of organic solvents, while also selecting appropriate binders and additives. Because water-based slurries use water as a solvent, they also have some drawbacks, such as high surface tension, poor wettability of the powder, and susceptibility to deformation and cracking of the green body during drying and debinding. Summary of the Invention

[0004] Therefore, it is necessary to provide a silicon nitride ceramic slurry, a silicon nitride ceramic substrate, and a method for preparing the same, in order to solve the problems of easy deformation and cracking of the green body during the drying and degreasing process.

[0005] A silicon nitride ceramic slurry, comprising the following components by weight:

[0006] 100 parts of silicon nitride powder

[0007] 4-10 parts of sintering aid

[0008] Dispersant 0.5-2 parts,

[0009] 1-5 parts of film-forming aid

[0010] 30-40 parts water, and

[0011] 20-40 parts adhesive;

[0012] The adhesive comprises an aqueous acrylic resin solution and an aqueous acrylic emulsion in a mass ratio of 1:(1-10), wherein the mass-average molecular weight of the polymer in the aqueous acrylic resin solution is 2000-7000, and the mass-average molecular weight of the polymer in the aqueous acrylic emulsion is 8000-20000.

[0013] In one embodiment, the polymer in the acrylic resin aqueous solution is obtained by copolymerizing unsaturated carboxylic acids and reacting them with organic amines or ammonia to form salts, wherein the unsaturated carboxylic acids include at least one of acrylic acid and methacrylic acid.

[0014] In one embodiment, the monomer of the aqueous acrylic emulsion polymer includes methyl methacrylate.

[0015] In one embodiment, the sintering aid comprises 2-5 parts of a non-oxide magnesium compound and 2-5 parts of rare earth oxides.

[0016] In one embodiment, the solid content of the acrylic resin aqueous solution is 30% to 40%.

[0017] In one embodiment, the solid content of the aqueous acrylic emulsion is 30% to 50%.

[0018] In one embodiment, the sintering aid comprises a non-oxide magnesium compound;

[0019] In one embodiment, the rare earth oxide is selected from at least one of yttrium oxide, ytterbium oxide, and gadolinium oxide;

[0020] In one embodiment, the dispersant is selected from at least one of polyacrylamide and polyacrylic acid;

[0021] In one embodiment, the film-forming aid is selected from at least one of polyvinylpyrrolidone and 12-ol esters.

[0022] In one embodiment, the silicon nitride ceramic slurry further includes 1-3 parts of plasticizer.

[0023] In one embodiment, the plasticizer is selected from at least one of glycerol and polyethylene glycol.

[0024] In one embodiment, the silicon nitride ceramic slurry further includes 1.2-3.2 parts of a defoaming agent.

[0025] In one embodiment, the defoaming agent is selected from at least one of dimethyl silicone oil, tributyl phosphate, and polyether-modified silicone oil.

[0026] A method for preparing silicon nitride ceramic slurry according to any of the above embodiments includes the following steps:

[0027] Silicon nitride powder, sintering aid, dispersant, film-forming aid, water, and binder are ground and mixed to obtain silicon nitride ceramic slurry.

[0028] In one embodiment, the grinding and mixing process specifically includes:

[0029] The silicon nitride powder, the sintering aid, the dispersant, the film-forming aid, and water are subjected to a first ball milling process to obtain a first mixture;

[0030] The first mixture is subjected to sand milling to obtain the second mixture;

[0031] A binder is added to the second mixture, and a second ball milling process is performed to obtain a silicon nitride ceramic slurry.

[0032] A method for preparing a silicon nitride ceramic substrate includes the following steps:

[0033] The silicon nitride ceramic slurry described in any of the above embodiments is cast into a film and then cut to obtain a green film sheet.

[0034] The green film is subjected to a debinding process to obtain a substrate blank;

[0035] The substrate blank is sintered to obtain the silicon nitride ceramic substrate.

[0036] In one embodiment, the glue removal process specifically includes:

[0037] The green film is placed in the oven cavity, and the oven temperature is increased to 200-250°C at a rate of 0.5-5°C / min and held for 3-10 hours. Then, the temperature is increased to 300-350°C at a rate of 0.5-5°C / min and held for 8-12 hours. Finally, the temperature is increased to 400-450°C at a rate of 0.5-5°C / min and held for 8-12 hours. Then, the temperature is increased to 500-600°C at a rate of 5-10°C / min and held for 2-5 hours. The film is then allowed to cool naturally in air to remove the adhesive.

[0038] A silicon nitride ceramic substrate is prepared by the method for preparing the silicon nitride ceramic substrate.

[0039] Compared with traditional methods, the above-mentioned silicon nitride ceramic slurry, silicon nitride ceramic substrate and their preparation method have the following advantages:

[0040] The aforementioned silicon nitride ceramic slurry uses water as a solvent, avoiding environmental pollution and health hazards associated with organic solvents, and significantly reducing material costs. In the water-based slurry system, specific amounts of sintering aids, dispersants, film-forming aids, and water are added, and acrylic resin aqueous solutions and waterborne acrylic emulsions with different molecular weights are rationally mixed as binders. Specifically, the binder includes an acrylic resin aqueous solution and a waterborne acrylic emulsion in a mass ratio of 1:(1-10). The mass-average molecular weight of the polymer in the acrylic resin aqueous solution is 2000-7000, and the mass-average molecular weight of the polymer in the waterborne acrylic emulsion is 8000-20000. This results in a water-based casting slurry with high stability and good rheological properties, allowing for good and stable green body molding. Furthermore, during binder removal, the binder vaporizes in stages at different temperature stages and escapes from the green body, which helps reduce defects such as deformation and cracking of the green body during the binder removal process. Detailed Implementation

[0041] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] An example of the silicon nitride ceramic slurry of the present invention comprises, by weight, the following components:

[0044] 100 parts of silicon nitride powder

[0045] 4-10 parts of sintering aid

[0046] Dispersant 0.5-2 parts,

[0047] 1-5 parts of film-forming aid

[0048] 30-40 parts water, and

[0049] 20-40 parts of adhesive.

[0050] The binder includes an aqueous acrylic resin solution and an aqueous acrylic emulsion in a mass ratio of 1:(1-10). The mass-average molecular weight of the polymer in the aqueous acrylic resin solution is 2000-7000, and the mass-average molecular weight of the polymer in the aqueous acrylic emulsion is 8000-20000.

[0051] The aforementioned silicon nitride ceramic slurry uses water as a solvent, avoiding environmental pollution and health hazards associated with organic solvents, and significantly reducing material costs. In the water-based slurry system, specific amounts of sintering aids, dispersants, film-forming aids, and water are added, and acrylic resin aqueous solutions and waterborne acrylic emulsions with different molecular weights are rationally mixed as binders. Specifically, the binder includes an acrylic resin aqueous solution and a waterborne acrylic emulsion in a mass ratio of 1:(1-10). The mass-average molecular weight of the polymer in the acrylic resin aqueous solution is 2000-7000, and the mass-average molecular weight of the polymer in the waterborne acrylic emulsion is 8000-20000. This results in a water-based casting slurry with high stability and good rheological properties, allowing for good and stable green body molding. Furthermore, during binder removal, the binder vaporizes in stages at different temperature stages and escapes from the green body, which helps reduce defects such as deformation and cracking of the green body during the binder removal process.

[0052] In one example, the silicon nitride powder in the silicon nitride ceramic slurry has a particle size of 500 nm to 800 nm. The silicon nitride powder can be particles of uniform size, such as particles with a particle size of 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, and 800 nm; it can also be a mixture of particles of multiple sizes, such as a mixture of two or more particle sizes of 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, and 800 nm. It is understood that in other examples, silicon nitride powder outside the aforementioned particle size range may also be used.

[0053] In silicon nitride ceramic slurries, water is used as a solvent, avoiding the environmental pollution and health hazards associated with organic solvents, and significantly reducing material costs. For every 100 parts by weight of silicon nitride powder, 20-40 parts by weight of water are used. In one example, the weight of water is 20-40 parts. In some specific examples, the weight of water can be, but is not limited to, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, or 40 parts, etc.

[0054] In silicon nitride ceramic slurry, 20-50 parts by weight of binder are used for every 100 parts by weight of silicon nitride powder. In one example, the number of parts by weight of binder is 20-50 parts. In some specific examples, the number of parts by weight of binder can be, but is not limited to, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50 parts, etc.

[0055] In one example, the polymer in the aqueous acrylic resin solution is obtained by copolymerization with unsaturated carboxylic acids and reaction with an organic amine or ammonia to form a salt. The unsaturated carboxylic acid includes at least one of acrylic acid and methacrylic acid. Furthermore, the unsaturated carboxylic acid may also include at least one of maleic anhydride, methylene succinic acid, etc. In one example, the monomer of the polymer in the aqueous acrylic emulsion includes methyl methacrylate.

[0056] In one example, the solid content of the acrylic resin aqueous solution is 30% to 40%.

[0057] In one example, the solids content of the aqueous acrylic emulsion is 30% to 50%.

[0058] In silicon nitride ceramic slurry, 4-10 parts by weight of sintering aid are used for every 100 parts by weight of silicon nitride powder. In one example, the weight of sintering aid is 4-7 parts by weight. In some specific examples, the weight of sintering aid can be, but is not limited to, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 9 parts, 9.5 parts, etc.

[0059] The sintering aid is preferably insoluble in water and does not react with water.

[0060] In one example, the sintering aid comprises 2-5 parts of a non-oxide magnesium compound and 2-5 parts of rare earth oxides.

[0061] During the sand milling process for preparing water-based slurries, the surface of fresh silicon nitride powder undergoes micro-hydrolysis and oxidation. This hydrolysis reaction introduces oxygen impurities, leading to a decrease in the thermal conductivity of the ceramic product, which is detrimental to the ceramic substrate. Therefore, in one example, a non-oxide magnesium compound is used as the sintering aid. Compared to traditionally used oxide sintering aids, this reduces the introduction of oxygen impurities from the raw materials, effectively controlling the oxygen content in the sintered body and resulting in ceramic products with higher thermal conductivity.

[0062] Optionally, the non-oxide magnesium compound may be, but is not limited to, at least one of magnesium silicon nitride, magnesium silicon carbide, and magnesium silicide.

[0063] In silicon nitride ceramic slurry, 2-5 parts by weight of rare earth oxides are used for every 100 parts by weight of silicon nitride powder. In one example, the weight of rare earth oxides is 3-4 parts. In some specific examples, the weight of rare earth oxides can be, but is not limited to, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0064] Alternatively, the rare earth oxide may be, but is not limited to, at least one of yttrium oxide, ytterbium oxide, and gadolinium oxide.

[0065] In silicon nitride ceramic slurries, 0.5-2 parts by weight of dispersant are used for every 100 parts by weight of silicon nitride powder. In one example, the dispersant is 1-2 parts by weight. In some specific examples, the dispersant may be, but is not limited to, 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.8 parts, 2 parts, etc.

[0066] In one example, the dispersant includes one or a mixture of two of polyacrylamide (PAA-NH4) and polyacrylic acid (PAA).

[0067] In silicon nitride ceramic slurry, 1-5 parts by weight of film-forming aid are used for every 100 parts by weight of silicon nitride powder. In one example, the weight of film-forming aid is 2-4 parts. In some specific examples, the weight of film-forming aid can be, but is not limited to, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc.

[0068] In one example, polyvinylpyrrolidone (PVP) is used as the film-forming aid. In the aforementioned silicon nitride ceramic slurry, at least one of polyacrylamide and polyacrylic acid is used as a dispersant, supplemented with polyvinylpyrrolidone as a film-forming aid, and acrylic resin and waterborne acrylic emulsion are reasonably matched in proportion as a mixed binder to prepare the slurry. The slurry has a suitable viscosity and high solid content. The film formed by casting has fewer defects, good strength and toughness, the cast film does not stick to the PET release film and is easy to separate, and a thicker green film can be obtained.

[0069] It is understandable that in other examples, film-forming aids may also be alcohol esters such as dodecyl alcohol.

[0070] In one example, adding a specific amount of plasticizer to the silicon nitride ceramic slurry can improve the toughness of the green ceramic belt. 1-3 parts by weight of plasticizer are used for every 100 parts by weight of silicon nitride powder. In one example, the amount of plasticizer is 1.5-2.5 parts by weight. In some specific examples, the amount of plasticizer by weight can be, but is not limited to, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, etc.

[0071] In one example, the plasticizer is selected from at least one of glycerin and polyethylene glycol.

[0072] Because water-based solvents have high surface tension and poor wettability to powders, they easily generate a large number of bubbles, making degassing difficult. Therefore, in silicon nitride ceramic slurries, 0.2-3.2 parts by weight of degassing agent are used for every 100 parts by weight of silicon nitride powder. In one example, the weight of degassing agent is 1.2-2.5 parts by weight. In some specific examples, the weight of degassing agent can be, but is not limited to, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, etc.

[0073] In one example, the defoaming agent used is dimethyl silicone oil, which has low surface tension and is well-suited to the above-mentioned water-based slurry system, effectively eliminating bubbles formed in the water-based slurry system of the present invention.

[0074] It is understandable that in other examples, the defoaming agent may also be at least one of tributyl phosphate and polyether-modified silicone oil.

[0075] The aforementioned silicon nitride ceramic slurry system is stable and has a long aging period, allowing casting to be carried out in air. The viscosity of the casting slurry is adjustable between 3000 cp and 8000 cp, the actual solid content can reach over 50%, and the flatness and thickness of the cast film are adjustable between 100 μm and 600 μm, with uniform thickness.

[0076] Furthermore, the present invention also provides a method for preparing silicon nitride ceramic slurry according to any of the above examples.

[0077] An example method for preparing a silicon nitride ceramic slurry includes the following steps:

[0078] Silicon nitride powder, sintering aid, dispersant, film-forming aid, water, binder, plasticizer and defoamer are ground and mixed to obtain silicon nitride ceramic slurry.

[0079] The grinding and mixing process specifically includes:

[0080] Step S1: The silicon nitride powder, sintering aid, dispersant, film-forming aid and water are subjected to a first ball milling process to obtain a first mixture.

[0081] Step S1 mainly involves preliminary dispersion so that the slurry can smoothly enter the sand mill.

[0082] Step S2: The first mixture is subjected to sand milling to obtain the second mixture.

[0083] The purpose of step S2 is to obtain a monodisperse slurry, which is mainly achieved by breaking up agglomerates through sand milling, further dispersing the slurry and grinding large particles.

[0084] Step S3: Add a binder to the second mixture and perform a second ball milling process to obtain a silicon nitride ceramic slurry.

[0085] Step S3 is the glue application step, where an adhesive is added to further disperse and coat the dispersed particles obtained in step 2, making the slurry system more stable.

[0086] In the example where the silicon nitride ceramic slurry contains a plasticizer, the plasticizer is preferably added in step S3. In the example where the silicon nitride ceramic slurry contains a deaerator, it is preferred that a portion of the deaerator is added in step S1, and the remainder is added in step S3.

[0087] In one example, the process parameters for the first ball milling process include:

[0088] The weight ratio of silicon nitride grinding balls to silicon nitride powder is 2-3:1, the ball milling speed is 280-320 r / min, and the ball milling time is 3-6 h.

[0089] In one example, the sand milling process parameters include:

[0090] The grinding time is 1-2 hours.

[0091] In one example, the process parameters for the second ball milling process include:

[0092] The ball milling speed is 50-100 r / min, and the ball milling time is 4h-8h.

[0093] Furthermore, the present invention also provides a method for preparing a silicon nitride ceramic substrate.

[0094] One embodiment of the method for preparing a silicon nitride ceramic substrate includes the following steps:

[0095] Silicon nitride ceramic slurry is cast into a preform film.

[0096] The green film is debonded to obtain a substrate preform.

[0097] The substrate blank is sintered to obtain a silicon nitride ceramic substrate.

[0098] In one example, the degumming process specifically includes the following steps:

[0099] The preform film is placed in the furnace chamber, and the furnace temperature is increased to 200-250℃ at a rate of 0.5-5℃ / min and held for 3-10 hours. Then, it is increased to 300-350℃ at a rate of 0.5-5℃ / min and held for 8-12 hours. Finally, it is increased to 400-450℃ at a rate of 0.5-5℃ / min and held for 8-12 hours. Then, it is increased to 500-600℃ at a rate of 5-10℃ / min and held for 2-5 hours. Finally, it is allowed to cool naturally in air and the adhesive is removed.

[0100] In one example, the sintering process specifically includes the following steps:

[0101] The substrate blank is placed in the furnace cavity of the sintering furnace. After the furnace cavity is evacuated, the temperature is raised to 1800℃~2000℃, preferably at a rate of 5-10℃ / minute, and then held at the temperature for sintering.

[0102] Furthermore, in one example, the sintering process time is 4-6 hours.

[0103] In one example, the step of evacuating the furnace cavity during the sintering process includes:

[0104] Evacuate the furnace cavity until the pressure drops below 100 Pa, then fill it with a protective gas, such as nitrogen, to raise the pressure inside the furnace cavity to 0.1 MPa to 1 MPa. Repeat the above evacuation and protective gas filling process until the pressure inside the furnace cavity is finally reduced to below 0.01 Pa.

[0105] Furthermore, the present invention also provides a silicon nitride ceramic substrate, which is prepared by the silicon nitride ceramic substrate preparation method of any of the above examples.

[0106] The following description, in conjunction with specific embodiments, provides further details, but the present invention is not limited to the specific embodiments described below.

[0107] Unless otherwise specified, all raw materials and instruments used in the following specific embodiments are commercially available.

[0108] In the following examples, the polymer in the aqueous acrylic resin solution is obtained by copolymerizing acrylic acid, methacrylic acid, maleic anhydride, and methylene succinic acid in a weight ratio of 15:35:25:25 and reacting with ammonia to form a salt, with a solid content of 30%; the monomer of the polymer in the aqueous acrylic emulsion is methyl methacrylate, with a solid content of 30%.

[0109] Example 1

[0110] This embodiment provides a method for preparing a silicon nitride ceramic substrate, including the following steps:

[0111] Step 1: By weight, 100 parts of silicon nitride powder with a particle size D50 of 0.7 micrometers, 3 parts of magnesium silicon nitride (sintering aid 1), 4 parts of yttrium oxide (sintering aid 2), 1 part of PAA-NH4 as a dispersant, 5 parts of PVP, 0.2 parts of dimethyl silicone oil as a defoaming agent, and 40 parts of pure water are mixed and ball-milled until uniformly dispersed to obtain the first mixture. The weight ratio of silicon nitride balls to powder is 2:1, the ball-milling time is 3 hours, and the ball-milling speed is 280 r / min.

[0112] Step 2: Add the first mixture to the sand mill and mill for 1 hour to obtain the second mixture.

[0113] Step 3: Add the second mixture to a ball mill jar, along with 30 parts of an aqueous acrylic resin solution and an aqueous acrylic emulsion (mass ratio of 1:4). Add 2 parts of glycerol plasticizer and 0.2 parts of dimethyl silicone oil as degassing agents. The ball mill is operated at 80 r / min, and the mixture is slowly rotated for 5 hours to obtain a silicon nitride ceramic slurry. The slurry is then degassed under a vacuum of 0.1 Pa to obtain a slurry with a dynamic viscosity of 5000 mPa·s at 25°C.

[0114] Step 4: Cast silicon nitride ceramic slurry to obtain a cast film, cut it to obtain a preform film, and place the preform film into a boron nitride crucible.

[0115] Step 5: Place the boron nitride crucible in the debinding furnace chamber and perform debinding in an air atmosphere. The furnace temperature is increased from room temperature to 200°C at a rate of 1°C / min and held for 3 hours, then increased to 300°C at a rate of 0.5°C / min and held for 8 hours, then increased to 400°C at a rate of 0.5°C / min and held for 8 hours, then increased to 500°C at a rate of 1°C / min and held for 3 hours, and then allowed to cool naturally to obtain the substrate blank.

[0116] Step 6: Place the boron nitride crucible containing the substrate blank into the high-temperature sintering furnace cavity. Evacuate the furnace cavity until the pressure drops below 0.01 Pa, then fill it with nitrogen gas of 99.99% purity or higher to raise the pressure inside the furnace cavity to 0.1 MPa. Repeat the evacuation operation once more, and finally reduce the pressure inside the furnace cavity to below 0.01 Pa. Fill the furnace cavity with high-purity nitrogen gas to 1 MPa, and raise the temperature to 1850°C at a rate of 10°C / min. Hold the temperature for 4 hours. After sintering, the silicon nitride ceramic substrate is obtained.

[0117] The silicon nitride ceramic substrate prepared in this embodiment was tested and found to have a three-point flexural strength of 800 MPa, a thermal conductivity of 82 W / (m·K) measured by laser scintillation, and a density of 3.22 g / cm³ measured by water displacement. 3 .

[0118] Example 2

[0119] This embodiment provides a method for preparing a silicon nitride ceramic substrate, including the following steps:

[0120] Step 1: By weight, 100 parts of silicon nitride powder with a particle size D50 of 0.7 micrometers, 3 parts of magnesium silicon nitride, 5 parts of ytterbium oxide, 1 part of PAA-NH4 as a dispersant, 5 parts of PVP, 0.2 parts of dimethyl silicone oil as a defoaming agent, and 40 parts of pure water are mixed and ball-milled to obtain the first mixture. The weight ratio of silicon nitride balls to powder is 2:1, the ball-milling time is 3 hours, and the ball-milling speed is 280 r / min.

[0121] Step 2: Add the first mixture to the sand mill and mill for 1 hour to obtain the second mixture.

[0122] Step 3: Add the second mixture to a ball mill jar, along with 30 parts of an aqueous acrylic resin solution and an aqueous acrylic emulsion (mass ratio of 1:4). Add 2 parts of glycerol plasticizer and 0.2 parts of dimethyl silicone oil as degassing agents. The ball mill is operated at 80 r / min, and the mixture is slowly rotated for 5 hours to obtain a silicon nitride ceramic slurry. The slurry is then degassed under a vacuum of 0.1 Pa to obtain a slurry with a dynamic viscosity of 5000 mPa·s at 25°C.

[0123] Step 4: Cast silicon nitride ceramic slurry to obtain a cast film, cut it to obtain a preform film, and place the preform film into a boron nitride crucible.

[0124] Step 5: Place the boron nitride crucible in the debinding furnace chamber and perform debinding in an air atmosphere. The furnace temperature is increased from room temperature to 200°C at a rate of 1°C / min and held for 3 hours, then increased to 300°C at a rate of 0.5°C / min and held for 8 hours, then increased to 400°C at a rate of 0.5°C / min and held for 8 hours, then increased to 500°C at a rate of 1°C / min and held for 3 hours, and then allowed to cool naturally to obtain the substrate blank.

[0125] Step 6: Place the boron nitride crucible containing the substrate blank into the high-temperature sintering furnace cavity. Evacuate the furnace cavity until the pressure drops below 0.01 Pa, then fill it with nitrogen gas of 99.99% purity or higher to raise the pressure inside the furnace cavity to 0.1 MPa. Repeat the evacuation operation once more, and finally reduce the pressure inside the furnace cavity to below 0.01 Pa. Fill the furnace cavity with high-purity nitrogen gas to 1 MPa, and raise the temperature to 1900°C at a rate of 10°C / min. Hold the temperature for 5 hours. After sintering, the silicon nitride ceramic substrate is obtained.

[0126] The silicon nitride ceramic substrate prepared in this embodiment has a three-point flexural strength of 750 MPa, a thermal conductivity of 92 W / (m·K) measured by laser scintillation, and a density of 3.25 g / cm³ measured by water displacement. 3 .

[0127] Example 3

[0128] This embodiment provides a method for preparing a silicon nitride ceramic substrate, including the following steps:

[0129] Step 1: By weight, 100 parts of silicon nitride powder with a particle size D50 of 0.7 micrometers, 5 parts of magnesium silicon nitride, 3 parts of yttrium oxide, 1 part of PAA-NH4 as a dispersant, 5 parts of PVP, 0.2 parts of dimethyl silicone oil as a defoaming agent, and 35 parts of pure water are mixed and ball-milled to obtain the first mixture. The weight ratio of silicon nitride balls to powder is 2:1, the ball-milling time is 3 hours, and the ball-milling speed is 280 r / min.

[0130] Step 2: Add the first mixture to the sand mill and mill for 1 hour to obtain the second mixture.

[0131] Step 3: Add the second mixture to a ball mill jar, along with 30 parts of an aqueous acrylic resin solution and an aqueous acrylic emulsion (mass ratio of 1:10). Add 2 parts of polyethylene glycol as a plasticizer and 0.2 parts of dimethyl silicone oil as a defoamer. The ball mill is operated at 80 r / min, and the mixture is slowly rotated for 5 hours to obtain a silicon nitride ceramic slurry. The slurry is then defoamed under a vacuum of 0.1 Pa to obtain a slurry with a dynamic viscosity of 6000 mPa·s at 25°C.

[0132] Step 4: Cast silicon nitride ceramic slurry to obtain a cast film, cut it to obtain a preform film, and place the preform film into a boron nitride crucible.

[0133] Step 5: Place the boron nitride crucible in the debinding furnace chamber and perform debinding in an air atmosphere. The furnace temperature is increased from room temperature to 200°C at a rate of 1°C / min and held for 3 hours, then increased to 300°C at a rate of 0.5°C / min and held for 8 hours, then increased to 400°C at a rate of 0.5°C / min and held for 8 hours, then increased to 500°C at a rate of 1°C / min and held for 3 hours, and then allowed to cool naturally to obtain the substrate blank.

[0134] Step 6: Place the boron nitride crucible containing the substrate blank into the high-temperature sintering furnace cavity. Evacuate the furnace cavity until the pressure drops below 0.01 Pa, then fill it with nitrogen gas of 99.99% purity or higher to raise the pressure inside the furnace cavity to 0.1 MPa. Repeat the evacuation operation once more, and finally reduce the pressure inside the furnace cavity to below 0.01 Pa. Fill the furnace cavity with high-purity nitrogen gas to 1 MPa, and raise the temperature to 1800°C at a rate of 10°C / min. Hold the temperature for 4 hours. After sintering, the silicon nitride ceramic substrate is obtained.

[0135] The silicon nitride ceramic substrate prepared in this embodiment has a three-point flexural strength of 920 MPa, a thermal conductivity of 70 W / (m·K) measured by laser scintillation, and a density of 3.20 g / cm³ measured by water displacement. 3 .

[0136] Example 4

[0137] This embodiment provides a method for preparing a silicon nitride ceramic substrate, including the following steps:

[0138] Step 1: By weight, 100 parts of silicon nitride powder with a particle size D50 of 0.7 micrometers, 2 parts of magnesium silicon nitride, 5 parts of yttrium oxide, 1 part of PAA-NH4 as a dispersant, 5 parts of PVP, 0.2 parts of dimethyl silicone oil as a defoamer, and 35 parts of pure water are mixed and ball-milled to obtain the first mixture. The weight ratio of silicon nitride balls to powder is 2:1, the ball-milling time is 3 hours, and the ball-milling speed is 280 r / min.

[0139] Step 2: Add the first mixture to the sand mill and mill for 1 hour to obtain the second mixture.

[0140] Step 3: Add the second mixture to a ball mill jar, along with 30 parts of an aqueous acrylic resin solution and an aqueous acrylic emulsion (mass ratio of 10:1), 2 parts of polyethylene glycol as a plasticizer, and 0.2 parts of dimethyl silicone oil as a defoaming agent. The ball mill is operated at 80 r / min, and the mixture is slowly rotated for 5 hours to obtain a silicon nitride ceramic slurry. The slurry is then defoamed under a vacuum of 0.1 Pa to obtain a slurry with a dynamic viscosity of 5000 mPa·s at 25°C.

[0141] Step 4: Cast silicon nitride ceramic slurry to obtain a cast film, cut it to obtain a preform film, and place the preform film into a boron nitride crucible.

[0142] Step 5: Place the boron nitride crucible in the debinding furnace chamber and perform debinding in an air atmosphere. The furnace temperature is increased from room temperature to 200°C at a rate of 1°C / min and held for 3 hours, then increased to 300°C at a rate of 0.5°C / min and held for 8 hours, then increased to 400°C at a rate of 0.5°C / min and held for 8 hours, then increased to 500°C at a rate of 1°C / min and held for 3 hours, and then allowed to cool naturally to obtain the substrate blank.

[0143] Step 6: Place the boron nitride crucible containing the substrate blank into the high-temperature sintering furnace cavity. Evacuate the furnace cavity until the pressure drops below 0.01 Pa, then fill it with nitrogen gas of 99.99% purity or higher to raise the pressure inside the furnace cavity to 0.1 MPa. Repeat the evacuation operation once more, and finally reduce the pressure inside the furnace cavity to below 0.01 Pa. Fill the furnace cavity with high-purity nitrogen gas to 1 MPa, and raise the temperature to 1900°C at a rate of 10°C / min. Hold the temperature for 8 hours. After sintering, the silicon nitride ceramic substrate is obtained.

[0144] The silicon nitride ceramic substrate prepared in this embodiment was tested and found to have a three-point flexural strength of 680 MPa, a thermal conductivity of 98 W / (m·K) measured by laser scintillation, and a density of 3.23 g / cm³ measured by water displacement. 3 .

[0145] The relevant experimental parameters for Examples 1-4 are shown in Table 1.

[0146] Table 1. Relevant experimental parameters and performance test results for Examples 1-4

[0147]

[0148] Comparative Example 1

[0149] This comparative example illustrates a method for preparing silicon nitride ceramic substrates using organic solvent casting, with the following steps:

[0150] A: Mix 100g of silicon nitride powder (median particle size 0.7μm), 1.5g of magnesium oxide powder (MgO), and 3.5g of yttrium oxide powder, add 1.68g of castor oil, and then add 100g of anhydrous ethanol-butanone mixed solvent (mass ratio of anhydrous ethanol to butanone is 1:2). Perform the first ball milling using silicon nitride balls as the ball milling medium at a ball milling rate of 200 rpm for 24 hours. Then add 4.2g of binder polyvinyl butyral and 6.72g of plasticizer for the second ball milling at a ball milling rate of 80 rpm for 24 hours. The plasticizer is dioctyl sebacate and diisobutyl phthalate in a mass ratio of 1:1. After ball milling, degas under a vacuum of 0.1 Pa to obtain a slurry with a dynamic viscosity of 3000 mPa·s at 25°C. The dynamic viscosity at 25°C was measured by a rotational viscometer.

[0151] B: The slurry is cast into a blank to obtain a green body. After cutting, it is vacuum debinded in a vacuum debinding furnace. The vacuum degree during the debinding process is 0.06 Pa. During the debinding, the temperature is raised to 600℃ at a rate of 1℃ / min. After holding at 600℃ for 0.5h, it is cooled to room temperature to obtain a green body.

[0152] C: The green blank is placed in a graphite crucible and then placed in a nitrogen atmosphere sintering furnace with a sintering atmosphere of 1 MPa. The temperature is raised to 1400℃ at a heating rate of 10℃ / min and held for 2 hours. Then, the temperature is raised to 1600℃ at a heating rate of 10℃ / min, and then raised to 1800℃ at a heating rate of 5℃ / min. After holding for 4 hours, the temperature is lowered to 1600℃ at a cooling rate of 1℃ / min. After that, the furnace is cooled to obtain a silicon nitride ceramic substrate.

[0153] The silicon nitride ceramic substrate prepared in this comparative example has a three-point bending strength of 720 MPa and a thermal conductivity of 70 W / (m·K) measured by laser scintillation.

[0154] Comparative Example 2

[0155] This comparative example illustrates a method for preparing silicon nitride ceramic substrates using organic solvent casting, with the following steps:

[0156] A: Mix 100g of silicon nitride powder (median particle size 0.7μm), 2g of MgO powder and 8g of Yb2O3 powder, add 2g of castor oil, and then add 130g of anhydrous ethanol-butanone mixed solvent (mass ratio of anhydrous ethanol to butanone is 1:2). Perform the first ball milling with silicon nitride balls as the ball milling medium at a ball milling rate of 200 rpm for 20 h. Then add 14g of binder polyvinyl butyral and 10.5g of plasticizer for the second ball milling at a ball milling rate of 80 rpm for 24 h. The plasticizer is dioctyl sebacate and diisobutyl phthalate in a mass ratio of 1:1. After ball milling, degas under a vacuum of 0.1 Pa to obtain a slurry with a dynamic viscosity of 12000 mPa·s at 25℃. The dynamic viscosity at 25℃ was measured by a rotational viscometer.

[0157] B: The slurry is cast into a blank and cut. After cutting, it is vacuum debinded in a vacuum debinding furnace with a vacuum degree of 0.1 Pa. The temperature is raised to 650℃ at a rate of 0.5℃ / min. After holding at 650℃ for 1 hour, it is cooled to room temperature to obtain the green blank.

[0158] C: The green blank is placed in a graphite crucible and then placed in a nitrogen atmosphere sintering furnace with a sintering atmosphere of 1 MPa. The temperature is raised to 1400℃ at a heating rate of 10℃ / min and held for 2 hours. Then, the temperature is raised to 1600℃ at a heating rate of 10℃ / min, and then raised to 1800℃ at a heating rate of 5℃ / min. After holding for 4 hours, the temperature is lowered to 1600℃ at a cooling rate of 10℃ / min. After that, the furnace is cooled to obtain a silicon nitride ceramic substrate.

[0159] The silicon nitride ceramic substrate prepared in this comparative example has a three-point bending strength of 800 MPa and a thermal conductivity of 65 W / (m·K) measured by laser scintillation.

[0160] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A silicon nitride ceramic slurry, characterized in that, By weight, it includes the following components: 100 parts of silicon nitride powder 4-10 parts of sintering aid Dispersant 0.5-2 parts, 1-5 parts of film-forming aid 30-40 parts water, and 20-40 parts adhesive; The binder comprises an aqueous acrylic resin solution and an aqueous acrylic emulsion in a mass ratio of 1:(1-10), wherein the mass-average molecular weight of the polymer in the aqueous acrylic resin solution is 2000-7000, and the mass-average molecular weight of the polymer in the aqueous acrylic emulsion is 8000-20000; the sintering aid comprises 2-5 parts of a non-oxide magnesium compound and 2-5 parts of rare earth oxides; the dispersant is selected from at least one of ammonium polyacrylate and polyacrylic acid; and the film-forming aid is selected from at least one of polyvinylpyrrolidone and dodecyl alcohol ester.

2. The silicon nitride ceramic slurry as described in claim 1, characterized in that, The silicon nitride ceramic slurry meets one or more of the following characteristics (1) to (4): (1) The polymer in the acrylic resin aqueous solution is obtained by copolymerization of unsaturated carboxylic acids and reaction with organic amines or ammonia to form salts, wherein the unsaturated carboxylic acids include at least one of acrylic acid and methacrylic acid; (2) The monomers of the polymer in the aqueous acrylic emulsion include methyl methacrylate; (3) The solid content of the acrylic resin aqueous solution is 30%~40%; (4) The solid content of the aqueous acrylic emulsion is 30%~50%.

3. The silicon nitride ceramic slurry as described in claim 1 or 2, characterized in that, The silicon nitride ceramic slurry also includes 1-3 parts of plasticizer.

4. The silicon nitride ceramic slurry as described in claim 3, characterized in that, The plasticizer is selected from at least one of glycerol and polyethylene glycol.

5. The silicon nitride ceramic slurry as described in claim 1, 2, or 4, characterized in that, The silicon nitride ceramic slurry also includes 0.2-3.2 parts of defoaming agent.

6. The silicon nitride ceramic slurry as described in claim 5, characterized in that, The defoaming agent is selected from at least one of dimethyl silicone oil, tributyl phosphate, and polyether-modified silicone oil.

7. A method for preparing a silicon nitride ceramic slurry according to any one of claims 1-6, characterized in that, Includes the following steps: The silicon nitride powder, the sintering aid, the dispersant, the film-forming aid, water, and the binder are ground and mixed to obtain a silicon nitride ceramic slurry.

8. The preparation method according to claim 7, characterized in that, The grinding and mixing process specifically includes: The silicon nitride powder, the sintering aid, the dispersant, the film-forming aid, and water are subjected to a first ball milling process to obtain a first mixture; The first mixture is subjected to sand milling to obtain the second mixture; The binder is added to the second mixture, and a second ball milling process is performed to obtain a silicon nitride ceramic slurry.

9. A method for preparing a silicon nitride ceramic substrate, characterized in that, Includes the following steps: The silicon nitride ceramic slurry according to any one of claims 1-6 is cast into a green film and then cut to obtain a green film. The green film is subjected to a debinding process to obtain a substrate blank; The substrate blank is sintered to obtain the silicon nitride ceramic substrate.

10. The preparation method according to claim 9, characterized in that, The specific steps of the adhesive removal process include: The green film is placed in the furnace chamber, and the furnace temperature is increased to 200-250°C at a rate of 0.5-5°C / min and held for 3-10 hours. Then, the temperature is increased to 300-350°C at a rate of 0.5-5°C / min and held for 8-12 hours. Finally, the temperature is increased to 400-450°C at a rate of 0.5-5°C / min and held for 8-12 hours. Then, the temperature is increased to 500-600°C at a rate of 5-10°C / min and held for 2-5 hours. The film is then allowed to cool naturally in air to remove the adhesive.

11. A silicon nitride ceramic substrate, characterized in that, It is prepared by the preparation method described in claim 10.

Images