A method for preparing a high-performance ceramic substrate

Abstract

The present invention discloses a method for preparing a high-performance ceramic substrate, comprising the following steps: ball-milling and granulating silicon nitride powder, a sintering aid, activated carbon, a crosslinking agent, and ethanol to obtain a mixed powder; dry-pressing the mixed powder to obtain a green body; and sintering the green body to obtain a high-performance ceramic substrate. This method effectively overcomes the problems of poor thermal conductivity and weak mechanical strength of existing silicon nitride ceramics. By adding a crystalline crosslinking agent to effectively reduce oxygen impurity defects, the prepared ceramic substrate has a low open porosity and few internal defects, ensuring the integrity, density, and surface smoothness of the ceramic structure while also exhibiting good thermal conductivity and mechanical strength.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic substrates, and in particular to a method for preparing a high-performance ceramic substrate. Background Art

[0002] With the continuous development of power device technology, especially with the rise of third-generation semiconductor technology, the application areas and demand of ceramic substrates are constantly expanding due to their good thermal conductivity, insulation, resistance to electrical breakdown, heat resistance, mechanics, high strength and high reliability.

[0003] Currently, the main ceramic substrate materials include Si3N4, silicon dioxide, silicon nitride, AlN, BeO, and BN. Si3N4 substrates offer exceptional mechanical properties among various structural ceramics, including flexural strength, high strength, and high-temperature resistance. However, their thermal conductivity still needs to be further improved. Factors affecting the thermal conductivity of silicon nitride ceramics include internal defects and impurities in the silicon nitride lattice, grain boundary thickness, crystal orientation, and crystal size.

[0004] A Chinese invention patent (application number: 202111137630.X) discloses a high-thermal conductivity, high-quality silicon nitride ceramic substrate and its preparation method. It is prepared from silicon nitride powder or silicon nitride powder and aluminum nitride, rare earth oxide, magnesium powder, plasticizer and organic solvent. Method: 1. Weighing; 2. Grinding, mixing and granulating; 3. Dry pressing; 4. Gas pressure sintering. The present invention mainly prepares a silicon nitride ceramic substrate with high thermal conductivity by using β-silicon nitride and aluminum nitride as raw materials and rare earth oxide and magnesium powder as sintering aids. Nitrogen The present invention still has the problem of introducing oxygen impurities by using some rare earth oxides as sintering aids, which occupy the vacancies in the silicon nitride lattice and affect the thermal conductivity of the silicon nitride ceramic substrate. Therefore, the present invention makes improvements to the problem that oxygen impurities affect the thermal conductivity of silicon nitride ceramics, and is used to solve the problem that the thermal conductivity of silicon nitride ceramic substrates is poor due to the presence of oxygen impurities during the sintering process. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing a high-performance ceramic substrate.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for preparing a high-performance ceramic substrate comprises the following steps:

[0008] (1) Under a nitrogen environment, 80-120 parts by weight of silicon nitride powder, 3-8 parts by weight of a sintering aid, 1-5 parts by weight of activated carbon, 20-30 parts by weight of a cross-linking agent, and 200-350 parts by weight of anhydrous ethanol are weighed and mixed uniformly to obtain a mixture; the mixture is added to a ball mill and ball milled for 3-5 hours at a ball mill speed of 300-500 rpm, with silicon nitride balls of 6-10 mm in diameter as the grinding medium, and a ball-to-material ratio of (3-7): (1-3), spray granulated, and passed through an 800-120 mesh sieve to obtain a mixed powder;

[0009] (2) The mixed powder is placed in a hydraulic press at a pressure of 20-40 MPa and dry-pressed to obtain a green body with a thickness of 2-5 mm; the green body is placed in a vacuum sintering furnace, heated to 600-700°C at a rate of 3-6°C / min, and kept warm for 4-8 hours; then transferred to a gas pressure sintering furnace, and when the pressure in the sintering furnace is 0.005-0.05 Pa, heating is started, and the temperature is increased to 1000-1300°C at a rate of 6-12°C / min, and nitrogen is introduced until the pressure in the furnace is 1-3 MPa; then the temperature is increased to 1750-2000°C at a rate of 6-12°C / min, sintered for 12-24 hours, and then cooled to 1000-1400°C at a rate of 10-20°C / min, and finally cooled to room temperature with the furnace to obtain a high-performance ceramic substrate.

[0010] Silicon nitride powder obtained in industrial production often contains impurities such as Fe, Ca, and Al. These impurities will occupy the silicon nitride lattice during the ceramic sintering process. The impurities in the lattice are often accompanied by structural defects such as vacancies, point defects, and dislocations. These structural defects change the local mass or density of the lattice, and the lattice vibration changes, causing phonon scattering, reducing the phonon mean free path, and leading to a decrease in thermal conductivity and mechanical properties. Therefore, the preparation of high-purity silicon nitride powder is the key to preparing high thermal conductivity silicon nitride ceramics.

[0011] Preferably, the silicon nitride powder is pretreated silicon nitride powder; the preparation process of the pretreated silicon nitride powder is as follows: adding silicon nitride powder to an acidic solution at 70-90°C, the mass ratio of the silicon nitride powder to the acidic solution is 1:(4-8); ultrasonicating at an ultrasonic power of 300-500W and an ultrasonic frequency of 30-50kHz for 2-5h, filtering, and then placing in a 0.05-0.2mol / L sodium hydroxide aqueous solution, stirring at 600-1000rpm for 1-3h, the mass ratio of the silicon nitride powder to the sodium hydroxide aqueous solution is 1:(3-5), filtering, and drying to obtain pretreated silicon nitride powder; the acidic solution is mixed by 5-15wt% sulfuric acid and 3-8wt% hydrochloric acid in a mass ratio of (4-7): (0.5-2).

[0012] The sintering aid is composed of the following raw materials in parts by weight: 5-8 parts by weight of silicon dioxide, 3-5 parts by weight of magnesium fluoride, 1-3 parts by weight of scandium oxide, 1-3 parts by weight of aluminum boride, and 1-3 parts by weight of yttrium fluoride.

[0013] The present invention simultaneously uses oxides, fluorides, and a ternary carbide composition as sintering aids during the sintering of a silicon nitride ceramic substrate to improve the thermal conductivity and mechanical strength of the ceramic substrate. Aluminum boride is added to achieve densification. Aluminum boride not only reduces the ratio of silicon nitride grain boundary energy to surface energy, enhancing the driving force for diffusion, but also activates the crystal lattice in a solid solution manner, promoting densification. Fluoride, as a sintering aid, not only promotes silicon nitride densification but also effectively improves the thermal conductivity of silicon nitride ceramics. The ternary carbide Al4SiC4, as a sintering aid for silicon nitride materials, can simultaneously achieve silicon nitride densification and grain refinement under vacuum.

[0014] The introduction of oxide additives lowers the sintering temperature of silicon nitride, shifting the material's fracture from transgranular to intergranular, improving its fracture toughness. However, this is accompanied by certain defects, including the presence of oxygen impurities, which are a major factor affecting its thermal conductivity. Once dissolved within the grains of silicon nitride, oxygen impurities form lattice oxygen, which in turn causes lattice defects. These lattice defects, in turn, lead to phonon scattering, resulting in a decrease in thermal conductivity. Therefore, improving the thermal conductivity of silicon nitride ceramics is essentially a matter of reducing their lattice oxygen content.

[0015] The crosslinking agent is at least one of a silane polymerization product, a hydrosilane crosslinking agent or a crystalline phase crosslinking agent; the crystalline phase crosslinking agent is formed by mixing a silane polymerization product and a hydrosilane crosslinking agent.

[0016] The present invention adds a certain amount of cross-linking agent as a deoxidizer while adding a sintering aid. First, using a silane polymerization product as a cross-linking agent can achieve in-situ growth of highly active and uniform carbon at different high temperatures, and ultimately distribute it in-situ in the silicon nitride ceramic, thereby removing oxygen at the grain boundaries, reducing the oxygen content in the silicon nitride ceramic, hindering the generation of lattice oxygen, effectively reducing the lattice oxygen content and lattice defects of the silicon nitride, and reducing phonon scattering, thereby making the prepared high-performance ceramic substrate have higher thermal conductivity; second, while reducing the oxygen content, the N / O atomic ratio increases, which is conducive to the nucleation, precipitation and growth of β-Si3N4 grains, further purifying the β-Si3N4 lattice, reducing the glass phase, promoting the α→β phase transformation rate, and reducing the problems of ceramic body deformation and cracking, limited lattice oxygen removal effect, and uneven structure caused by the uneven distribution of deoxidizers such as carbon and carbon black directly added.

[0017] The preparation method of the silane polymerization product is as follows: in an ice-water bath environment, 8-12 parts by weight of 4-methoxyphenylmagnesium chloride, 3-6 parts by weight of alkenylchlorosilane and 25-40 parts by weight of tetrahydrofuran are mixed, stirred at 400-600 rpm for 2-5 minutes, and then returned to room temperature, 1-4 parts by weight of p-tert-butylcatechol are added, stirring is continued for 8-12 hours, and the solvent is recovered by reduced pressure distillation to obtain a polymerization monomer; and in a nitrogen environment, 30-60 parts by weight of isopropanol and 0.01-0.1 parts by weight of a Custer catalyst are added to the above polymerization monomer, stirred at 50-70° C. and 500-700 rpm for 8-12 hours, the solvent is recovered by reduced pressure distillation, and dried to obtain the silane polymerization product.

[0018] The addition of a hydrosilane crosslinker effectively bonds the various components of the silicon nitride ceramic together, improving the internal bonding and compactness of the ceramic substrate, thereby effectively increasing the density and mechanical strength of the ceramic substrate. The present invention effectively combines a hydrosilane crosslinker with a silane polymerization product. This can, on the one hand, effectively reduce the oxygen content in the ceramic substrate, promote the α→βSi3N4 phase transformation rate, increase the growth of the β-Si3N4 lattice, and maximize the thermal conductivity of the ceramic substrate. Furthermore, the hydrosilane crosslinker effectively increases the density of the ceramic substrate, thereby improving its mechanical strength.

[0019] The preparation method of the hydrosilane crosslinking agent is as follows: in an ice-water bath and nitrogen environment, 2-5 parts by weight of tetraallylsilane, 15-22 parts by weight of chlorodimethylsilane, 0.005-0.05 parts by weight of Custer's catalyst, and 30-50 parts by weight of isopropyl alcohol are mixed, and the mixture is stirred at 60-80° C. and 500-700 rpm for 8-12 hours to obtain a solution A; the solution A is added to 10-18 parts by weight of a 5-8 wt% lithium aluminum tetrahydride ether solution at a rate of 0.8-1.5 mL / min; after the addition is complete, the mixture is heated to 30-40° C., stirred at 500-700 rpm for 6-12 hours, and the solvent is recovered by reduced pressure distillation to obtain the hydrosilane crosslinking agent;

[0020] Preferably, the crosslinking agent is a crystalline crosslinking agent; the crystalline crosslinking agent is obtained by mixing the silane polymerization product and the hydrosilane crosslinking agent in a mass ratio of (1-3):1.

[0021] The alkenyl chlorosilane is butenyldichloromethylsilane and / or ((E)-3-chloro-1-methylpropenyl)trimethylsilane; preferably, the alkenyl chlorosilane is composed of butenyldichloromethylsilane and ((E)-3-chloro-1-methylpropenyl)trimethylsilane in a mass ratio of (2-6): (1-3).

[0022] The present invention utilizes the different boiling points of butenyldichloromethylsilane and ((E)-3-chloro-1-methylpropenyl)trimethylsilane to form silane polymerization products with relatively large boiling point differences. The silane polymerization products with different boiling points are decomposed at different temperatures during the sintering process by utilizing the synergistic effect. The oxygen content in the sintering aid can be removed at different time periods, thereby hindering the generation of lattice oxygen, effectively reducing the lattice oxygen content and lattice defects of silicon nitride, and reducing phonon scattering, so that the prepared high-performance ceramic substrate has higher thermal conductivity.

[0023] A high-performance ceramic substrate is prepared by adopting the above method.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention adds a certain amount of cross-linking agent as an oxygen scavenger while adding a sintering aid. First, the cross-linking agent causes in-situ growth of highly active and uniform carbon at different high temperatures, which is ultimately distributed in-situ in the silicon nitride ceramic, thereby removing oxygen from the grain boundaries. This reduces the oxygen content in the silicon nitride ceramic, hinders the generation of lattice oxygen, effectively reduces the lattice oxygen content and lattice defects of silicon nitride, and reduces phonon scattering, thereby making the prepared high-performance ceramic substrate have higher thermal conductivity.

[0026] Secondly, while reducing the oxygen content, the N / O atomic ratio increases, which is beneficial to the nucleation, precipitation and growth of β-Si3N4 grains, can further purify the β-Si3N4 lattice, reduce the glass phase, promote the α→β phase transformation rate, and reduce the problems of ceramic body deformation and cracking, limited lattice oxygen removal effect, and uneven structure caused by the uneven distribution of direct addition of scavengers such as carbon and carbon black.

[0027] 2. The present invention uses pretreated silicon nitride powder as a raw material for preparing silicon nitride ceramics, which effectively reduces impurities in silicon nitride ceramics, reduces structural defects such as vacancies, point defects, and dislocations in the ceramic lattice, improves the local quality or density of the lattice, and ultimately improves thermal conductivity and mechanical properties.

[0028] 3. The ceramic substrate prepared by the present invention has good thermal conductivity and mechanical strength, low open porosity, few internal defects, and can ensure the integrity, density and surface smoothness of the ceramic structure. DETAILED DESCRIPTION

[0029] Introduction of some raw materials in this application:

[0030] Silicon nitride powder was purchased from Yumu (Ningbo) New Materials Co., Ltd., item number: 800N.

[0031] Activated carbon was purchased from Hongzhiyuan Water Purification Materials Co., Ltd., model: MZ11.

[0032] Custer catalyst was purchased from Shenzhen Kejunchi Technology Co., Ltd., model: KJC-PT5000.

[0033] ((E)-3-Chloro-1-methylpropenyl)trimethylsilane, CAS number: 116399-78-1.

[0034] Example 1

[0035] A method for preparing a high-performance ceramic substrate comprises the following steps:

[0036] (1) Under nitrogen atmosphere, 100 parts by weight of silicon nitride powder, 5 parts by weight of sintering aid, 2 parts by weight of activated carbon, 25 parts by weight of crystalline crosslinking agent and 300 parts by weight of anhydrous ethanol were weighed and mixed uniformly to obtain a mixture; the mixture was added to a ball mill and ball milled for 4 h, wherein the ball milling speed was 400 rpm, the grinding medium was silicon nitride balls with a ball diameter of 8 mm, and the ball-to-material ratio was 5:2; spray granulation was performed and passed through a 100-mesh sieve to obtain a mixed powder;

[0037] (2) The mixed powder was placed in a hydraulic press at a pressure of 30 MPa and dry-pressed to obtain a green body with a thickness of 3 mm; the green body was placed in a vacuum sintering furnace, heated to 650°C at a rate of 5°C / min, and kept warm for 6 hours; then transferred to a gas pressure sintering furnace, and heating was started when the pressure in the sintering furnace was 0.01 Pa, and the temperature was increased to 1200°C at a rate of 10°C / min, and nitrogen was introduced until the pressure in the furnace was 1.5 MPa; then the temperature was increased to 1850°C at a rate of 10°C / min and sintered for 16 hours, and then the temperature was decreased to 1200°C at a rate of 15°C / min, and finally cooled to room temperature with the furnace to obtain a high-performance ceramic substrate.

[0038] The preparation method of the crystalline crosslinker is as follows: in an ice-water bath and a nitrogen environment, 3 parts by weight of tetraallylsilane, 18 parts by weight of chlorodimethylsilane, 0.01 parts by weight of Custer's catalyst and 40 parts by weight of isopropanol are mixed, and stirred at 70° C. and 600 rpm for 10 hours to obtain solution A; the above solution A is added to 15 parts by weight of 6wt% lithium aluminum tetrahydride ether solution at a rate of 1 mL / min, and after the addition is completed, the temperature is raised to 35° C., stirred at 600 rpm for 8 hours, and the solvent is recovered by reduced pressure distillation to obtain a crystalline crosslinker.

[0039] The sintering aid is composed of the following raw materials in parts by weight: 6 parts by weight of silicon dioxide, 4 parts by weight of magnesium fluoride, 2 parts by weight of scandium oxide, 2 parts by weight of aluminum boride, and 2 parts by weight of yttrium fluoride.

[0040] Example 2

[0041] A method for preparing a high-performance ceramic substrate comprises the following steps:

[0042] (1) Under nitrogen atmosphere, 100 parts by weight of pretreated silicon nitride powder, 5 parts by weight of sintering aid, 2 parts by weight of activated carbon, 25 parts by weight of crystalline crosslinking agent and 300 parts by weight of anhydrous ethanol were weighed and mixed uniformly to obtain a mixture; the mixture was added to a ball mill and ball milled for 4 h, wherein the ball milling speed was 400 rpm, the grinding medium was silicon nitride balls with a ball diameter of 8 mm, and the ball-to-material ratio was 5:2; spray granulation was performed and passed through a 100-mesh sieve to obtain a mixed powder;

[0043] (2) The mixed powder was placed in a hydraulic press at a pressure of 30 MPa and dry-pressed to obtain a green body with a thickness of 3 mm; the green body was placed in a vacuum sintering furnace, heated to 650°C at a rate of 5°C / min, and kept warm for 6 hours; then transferred to a gas pressure sintering furnace, and heating was started when the pressure in the sintering furnace was 0.01 Pa, and the temperature was increased to 1200°C at a rate of 10°C / min, and nitrogen was introduced until the pressure in the furnace was 1.5 MPa; then the temperature was increased to 1850°C at a rate of 10°C / min and sintered for 16 hours, and then the temperature was decreased to 1200°C at a rate of 15°C / min, and finally cooled to room temperature with the furnace to obtain a high-performance ceramic substrate.

[0044] The preparation process of the pretreated silicon nitride powder is as follows: adding the silicon nitride powder to an acidic solution at 80° C., wherein the mass ratio of the silicon nitride powder to the acidic solution is 1:5; ultrasonicating for 3 hours at an ultrasonic power of 400 W and an ultrasonic frequency of 40 kHz, filtering, and then placing in a 0.1 mol / L sodium hydroxide aqueous solution, stirring at 800 rpm for 2 hours, wherein the mass ratio of the silicon nitride powder to the sodium hydroxide aqueous solution is 1:4, filtering, and drying to obtain the pretreated silicon nitride powder; the acidic solution is prepared by mixing 10 wt% sulfuric acid and 5 wt% hydrochloric acid in a mass ratio of 5:1.

[0045] The preparation method of the crystalline crosslinker is as follows: in an ice-water bath and a nitrogen environment, 3 parts by weight of tetraallylsilane, 18 parts by weight of chlorodimethylsilane, 0.01 parts by weight of Custer's catalyst, and 40 parts by weight of isopropanol are mixed, and stirred at 70° C. and 600 rpm for 10 hours to obtain a solution A; the above solution A is added to 15 parts by weight of a 6wt% lithium aluminum tetrahydride ether solution at a rate of 1 mL / min, and after the addition is completed, the temperature is raised to 35° C., stirred at 600 rpm for 8 hours, and the solvent is recovered by reduced pressure distillation to obtain a crystalline crosslinker.

[0046] The sintering aid is composed of the following raw materials in parts by weight: 6 parts by weight of silicon dioxide, 4 parts by weight of magnesium fluoride, 2 parts by weight of scandium oxide, 2 parts by weight of aluminum boride, and 2 parts by weight of yttrium fluoride.

[0047] Example 3

[0048] A method for preparing a high-performance ceramic substrate comprises the following steps:

[0049] (1) Under nitrogen atmosphere, 100 parts by weight of pretreated silicon nitride powder, 5 parts by weight of sintering aid, 2 parts by weight of activated carbon, 25 parts by weight of crystalline crosslinking agent and 300 parts by weight of anhydrous ethanol were weighed and mixed uniformly to obtain a mixture; the mixture was added to a ball mill and ball milled for 4 h, wherein the ball milling speed was 400 rpm, the grinding medium was silicon nitride balls with a ball diameter of 8 mm, and the ball-to-material ratio was 5:2; spray granulation was performed and passed through a 100-mesh sieve to obtain a mixed powder;

[0050] (2) The mixed powder was placed in a hydraulic press at a pressure of 30 MPa and dry-pressed to obtain a green body with a thickness of 3 mm; the green body was placed in a vacuum sintering furnace, heated to 650°C at a rate of 5°C / min, and kept warm for 6 hours; then transferred to a gas pressure sintering furnace, and heating was started when the pressure in the sintering furnace was 0.01 Pa, and the temperature was increased to 1200°C at a rate of 10°C / min, and nitrogen was introduced until the pressure in the furnace was 1.5 MPa; then the temperature was increased to 1850°C at a rate of 10°C / min and sintered for 16 hours, and then the temperature was decreased to 1200°C at a rate of 15°C / min, and finally cooled to room temperature with the furnace to obtain a high-performance ceramic substrate.

[0051] The preparation process of the pretreated silicon nitride powder is as follows: adding the silicon nitride powder to an acidic solution at 80° C., wherein the mass ratio of the silicon nitride powder to the acidic solution is 1:5; ultrasonicating for 3 hours at an ultrasonic power of 400 W and an ultrasonic frequency of 40 kHz, filtering, and then placing in a 0.1 mol / L sodium hydroxide aqueous solution, stirring at 800 rpm for 2 hours, wherein the mass ratio of the silicon nitride powder to the sodium hydroxide aqueous solution is 1:4, filtering, and drying to obtain the pretreated silicon nitride powder; the acidic solution is prepared by mixing 10 wt% sulfuric acid and 5 wt% hydrochloric acid in a mass ratio of 5:1.

[0052] The preparation method of the crystalline crosslinker is as follows: in an ice-water bath environment, 10 parts by weight of 4-methoxyphenylmagnesium chloride, 5 parts by weight of butenyldichloromethylsilane and 30 parts by weight of tetrahydrofuran are mixed, stirred at 500 rpm for 3 minutes, and then returned to room temperature, 3 parts by weight of p-tert-butylcatechol are added, stirring is continued for 10 hours, and the solvent is recovered by reduced pressure distillation to obtain a polymerized monomer; in a nitrogen environment, 50 parts by weight of isopropanol and 0.05 parts by weight of a Custer catalyst are added to the above polymerized monomer, stirred at 60° C. and 600 rpm for 10 hours, the solvent is recovered by reduced pressure distillation, and dried to obtain a crystalline crosslinker.

[0053] The sintering aid is composed of the following raw materials in parts by weight: 6 parts by weight of silicon dioxide, 4 parts by weight of magnesium fluoride, 2 parts by weight of scandium oxide, 2 parts by weight of aluminum boride, and 2 parts by weight of yttrium fluoride.

[0054] Example 4

[0055] A method for preparing a high-performance ceramic substrate comprises the following steps:

[0056] (1) Under nitrogen atmosphere, 100 parts by weight of pretreated silicon nitride powder, 5 parts by weight of sintering aid, 2 parts by weight of activated carbon, 25 parts by weight of crystalline crosslinking agent and 300 parts by weight of anhydrous ethanol were weighed and mixed uniformly to obtain a mixture; the mixture was added to a ball mill and ball milled for 4 h, wherein the ball milling speed was 400 rpm, the grinding medium was silicon nitride balls with a ball diameter of 8 mm, and the ball-to-material ratio was 5:2; spray granulation was performed and passed through a 100-mesh sieve to obtain a mixed powder;

[0057] (2) The mixed powder was placed in a hydraulic press at a pressure of 30 MPa and dry-pressed to obtain a green body with a thickness of 3 mm; the green body was placed in a vacuum sintering furnace, heated to 650°C at a rate of 5°C / min, and kept warm for 6 hours; then transferred to a gas pressure sintering furnace, and heating was started when the pressure in the sintering furnace was 0.01 Pa, and the temperature was increased to 1200°C at a rate of 10°C / min, and nitrogen was introduced until the pressure in the furnace was 1.5 MPa; then the temperature was increased to 1850°C at a rate of 10°C / min and sintered for 16 hours, and then the temperature was decreased to 1200°C at a rate of 15°C / min, and finally cooled to room temperature with the furnace to obtain a high-performance ceramic substrate.

[0058] The preparation process of the pretreated silicon nitride powder is as follows: adding the silicon nitride powder to an acidic solution at 80° C., wherein the mass ratio of the silicon nitride powder to the acidic solution is 1:5; ultrasonicating for 3 hours at an ultrasonic power of 400 W and an ultrasonic frequency of 40 kHz, filtering, and then placing in a 0.1 mol / L sodium hydroxide aqueous solution, stirring at 800 rpm for 2 hours, wherein the mass ratio of the silicon nitride powder to the sodium hydroxide aqueous solution is 1:4, filtering, and drying to obtain the pretreated silicon nitride powder; the acidic solution is prepared by mixing 10 wt% sulfuric acid and 5 wt% hydrochloric acid in a mass ratio of 5:1.

[0059] The preparation method of the crystalline phase crosslinking agent is as follows:

[0060] S1. In an ice-water bath, 10 parts by weight of 4-methoxyphenylmagnesium chloride, 5 parts by weight of butenyldichloromethylsilane, and 30 parts by weight of tetrahydrofuran were mixed, stirred at 500 rpm for 3 minutes, and then returned to room temperature. 3 parts by weight of p-tert-butylcatechol were added, and stirring was continued for 10 hours. The solvent was recovered by distillation under reduced pressure to obtain a polymerized monomer; under a nitrogen environment, 50 parts by weight of isopropanol and 0.05 parts by weight of Custer's catalyst were added to the above polymerized monomer, and the mixture was stirred at 60° C. and 600 rpm for 10 hours. The solvent was recovered by distillation under reduced pressure and dried to obtain a silane polymerization product;

[0061] S2. In an ice-water bath and nitrogen environment, 3 parts by weight of tetraallylsilane, 18 parts by weight of chlorodimethylsilane, 0.01 parts by weight of Custer's catalyst, and 40 parts by weight of isopropanol were mixed, and stirred at 70° C. and 600 rpm for 10 hours to obtain a solution A; the above solution A was added to 15 parts by weight of a 6 wt% lithium aluminum tetrahydride ether solution at a rate of 1 mL / min. After the addition was completed, the temperature was raised to 35° C., stirred at 600 rpm for 8 hours, and the solvent was recovered by distillation under reduced pressure to obtain a hydrosilane crosslinker;

[0062] S3. Evenly mix the above-mentioned silane polymerization product and the hydrosilane crosslinking agent in a mass ratio of 2:1 to obtain a crystalline crosslinking agent.

[0063] The sintering aid is composed of the following raw materials in parts by weight: 6 parts by weight of silicon dioxide, 4 parts by weight of magnesium fluoride, 2 parts by weight of scandium oxide, 2 parts by weight of aluminum boride, and 2 parts by weight of yttrium fluoride.

[0064] Example 5

[0065] A method for preparing a high-performance ceramic substrate comprises the following steps:

[0066] (1) Under nitrogen atmosphere, 100 parts by weight of pretreated silicon nitride powder, 5 parts by weight of sintering aid, 2 parts by weight of activated carbon, 25 parts by weight of crystalline crosslinking agent and 300 parts by weight of anhydrous ethanol were weighed and mixed uniformly to obtain a mixture; the mixture was added to a ball mill and ball milled for 4 h, wherein the ball milling speed was 400 rpm, the grinding medium was silicon nitride balls with a ball diameter of 8 mm, and the ball-to-material ratio was 5:2; spray granulation was performed and passed through a 100-mesh sieve to obtain a mixed powder;

[0067] (2) The mixed powder was placed in a hydraulic press at a pressure of 30 MPa and dry-pressed to obtain a green body with a thickness of 3 mm; the green body was placed in a vacuum sintering furnace, heated to 650°C at a rate of 5°C / min, and kept warm for 6 hours; then transferred to a gas pressure sintering furnace, and heating was started when the pressure in the sintering furnace was 0.01 Pa, and the temperature was increased to 1200°C at a rate of 10°C / min, and nitrogen was introduced until the pressure in the furnace was 1.5 MPa; then the temperature was increased to 1850°C at a rate of 10°C / min and sintered for 16 hours, and then the temperature was decreased to 1200°C at a rate of 15°C / min, and finally cooled to room temperature with the furnace to obtain a high-performance ceramic substrate.

[0068] The preparation process of the pretreated silicon nitride powder is as follows: adding the silicon nitride powder to an acidic solution at 80° C., wherein the mass ratio of the silicon nitride powder to the acidic solution is 1:5; ultrasonicating for 3 hours at an ultrasonic power of 400 W and an ultrasonic frequency of 40 kHz, filtering, and then placing in a 0.1 mol / L sodium hydroxide aqueous solution, stirring at 800 rpm for 2 hours, wherein the mass ratio of the silicon nitride powder to the sodium hydroxide aqueous solution is 1:4, filtering, and drying to obtain the pretreated silicon nitride powder; the acidic solution is prepared by mixing 10 wt% sulfuric acid and 5 wt% hydrochloric acid in a mass ratio of 5:1.

[0069] The preparation method of the crystalline phase crosslinking agent is as follows:

[0070] S1. In an ice-water bath, 10 parts by weight of 4-methoxyphenylmagnesium chloride, 5 parts by weight of ((E)-3-chloro-1-methylpropenyl)trimethylsilane, and 30 parts by weight of tetrahydrofuran were mixed, stirred at 500 rpm for 3 minutes, and then returned to room temperature. 3 parts by weight of p-tert-butylcatechol were added, and stirring was continued for 10 hours. The solvent was recovered by distillation under reduced pressure to obtain a polymerized monomer; under a nitrogen environment, 50 parts by weight of isopropanol and 0.05 parts by weight of Custer's catalyst were added to the above-mentioned polymerized monomer, and the mixture was stirred at 60° C. and 600 rpm for 10 hours. The solvent was recovered by distillation under reduced pressure and dried to obtain a silane polymerization product;

[0071] S2. In an ice-water bath and nitrogen environment, 3 parts by weight of tetraallylsilane, 18 parts by weight of chlorodimethylsilane, 0.01 parts by weight of Custer's catalyst, and 40 parts by weight of isopropanol were mixed, and stirred at 70° C. and 600 rpm for 10 hours to obtain a solution A; the above solution A was added to 15 parts by weight of a 6 wt% lithium aluminum tetrahydride ether solution at a rate of 1 mL / min. After the addition was completed, the temperature was raised to 35° C., stirred at 600 rpm for 8 hours, and the solvent was recovered by distillation under reduced pressure to obtain a hydrosilane crosslinker;

[0072] S3. Evenly mix the above-mentioned silane polymerization product and the hydrosilane crosslinking agent in a mass ratio of 2:1 to obtain a crystalline crosslinking agent.

[0073] The sintering aid is composed of the following raw materials in parts by weight: 6 parts by weight of silicon dioxide, 4 parts by weight of magnesium fluoride, 2 parts by weight of scandium oxide, 2 parts by weight of aluminum boride, and 2 parts by weight of yttrium fluoride.

[0074] Example 6

[0075] A method for preparing a high-performance ceramic substrate comprises the following steps:

[0076] (1) Under nitrogen atmosphere, 100 parts by weight of pretreated silicon nitride powder, 5 parts by weight of sintering aid, 2 parts by weight of activated carbon, 25 parts by weight of crystalline crosslinking agent and 300 parts by weight of anhydrous ethanol were weighed and mixed uniformly to obtain a mixture; the mixture was added to a ball mill and ball milled for 4 h, wherein the ball milling speed was 400 rpm, the ball milling medium was silicon nitride balls with a ball diameter of 8 mm, and the ball-to-material ratio was 5:2; spray granulation was performed and passed through a 100-mesh sieve to obtain a mixed powder;

[0077] (2) The mixed powder was placed in a hydraulic press at a pressure of 30 MPa and dry-pressed to obtain a green body with a thickness of 3 mm; the green body was placed in a vacuum sintering furnace, heated to 650°C at a rate of 5°C / min, and kept warm for 6 hours; then transferred to a gas pressure sintering furnace, and heating was started when the pressure in the sintering furnace was 0.01 Pa, and the temperature was increased to 1200°C at a rate of 10°C / min, and nitrogen was introduced until the pressure in the furnace was 1.5 MPa; then the temperature was increased to 1850°C at a rate of 10°C / min and sintered for 16 hours, and then the temperature was decreased to 1200°C at a rate of 15°C / min, and cooled to room temperature with the furnace to obtain a high-performance ceramic substrate.

[0078] The preparation process of the pretreated silicon nitride powder is as follows: adding the silicon nitride powder to an acidic solution at 80° C., wherein the mass ratio of the silicon nitride powder to the acidic solution is 1:5; ultrasonicating for 3 hours at an ultrasonic power of 400 W and an ultrasonic frequency of 40 kHz, filtering, and then placing the powder in a 0.1 mol / L sodium hydroxide aqueous solution, stirring at 800 rpm for 2 hours, wherein the mass ratio of the silicon nitride powder to the sodium hydroxide aqueous solution is 1:4, filtering, and drying to obtain the pretreated silicon nitride powder; the acidic solution is prepared by mixing 10 wt% sulfuric acid and 5 wt% hydrochloric acid in a mass ratio of 5:1.

[0079] The preparation method of the crystalline phase crosslinking agent is as follows:

[0080] S1. In an ice-water bath, 10 parts by weight of 4-methoxyphenylmagnesium chloride, 3 parts by weight of butenyldichloromethylsilane, 2 parts by weight of ((E)-3-chloro-1-methylpropenyl)trimethylsilane, and 30 parts by weight of tetrahydrofuran were mixed, stirred at 500 rpm for 3 minutes, and then returned to room temperature. 3 parts by weight of p-tert-butylcatechol were added, and stirring was continued for 10 hours. The solvent was recovered by distillation under reduced pressure to obtain a polymerized monomer; under a nitrogen environment, 50 parts by weight of isopropanol and 0.05 parts by weight of Custer's catalyst were added to the above-mentioned polymerized monomer, and the mixture was stirred at 60° C. and 600 rpm for 10 hours. The solvent was recovered by distillation under reduced pressure and dried to obtain a silane polymerization product.

[0081] S2. In an ice-water bath and nitrogen environment, 3 parts by weight of tetraallylsilane, 18 parts by weight of chlorodimethylsilane, 0.01 parts by weight of Custer's catalyst, and 40 parts by weight of isopropanol were mixed, and stirred at 70° C. and 600 rpm for 10 hours to obtain a solution A; the above solution A was added to 15 parts by weight of a 6 wt% lithium aluminum tetrahydride ether solution at a rate of 1 mL / min. After the addition was completed, the temperature was raised to 35° C., stirred at 600 rpm for 8 hours, and the solvent was recovered by distillation under reduced pressure to obtain a hydrosilane crosslinker;

[0082] S3. Evenly mix the above-mentioned silane polymerization product and the hydrosilane crosslinking agent in a mass ratio of 2:1 to obtain a crystalline crosslinking agent.

[0083] The sintering aid is composed of the following raw materials in parts by weight: 6 parts by weight of silicon dioxide, 4 parts by weight of magnesium fluoride, 2 parts by weight of scandium oxide, 2 parts by weight of aluminum boride, and 2 parts by weight of yttrium fluoride.

[0084] Test Example 1

[0085] Thermal conductivity testing: The room-temperature thermal conductivity of the material was measured using the laser flash method, using an LFA-427 laser thermal conductivity meter (Netzsch, Germany). The principle is to heat the sample with a short laser pulse, and then measure the temperature change of the back of the sample over time using an infrared detector to obtain the thermal diffusivity of the sample. The test size was Ø: 12mm x 2.5mm. Each sample was measured five times, and the average value was taken. The results are shown in Table 1. The thermal conductivity of the material was calculated according to the following formula: λ = ραCp

[0086] Where λ refers to thermal conductivity (Wm -1 K -1 ); ρ refers to the sample density (gcm -3 ); α refers to the thermal diffusivity ((mm 2 s -1 ); Cp refers to specific heat capacity (Jg -1 K -1 ).

[0087] Table 1 Thermal conductivity test results

[0088]

[0089]

[0090] From the above results, it can be seen that the high performance ceramic substrate prepared by the present invention has good thermal conductivity, which is higher than the existing technology (less than 160W.m -1 K -1) in the thermal conductivity of the silicon nitride ceramic substrate. After the silicon nitride powder is pretreated, the thermal conductivity is obviously effectively improved. The reason is that before sintering, the impurities such as Fe, Ca, Al that will occupy the lattice of silicon nitride are removed, which effectively reduces the impurities that affect structural defects such as lattice vacancies, point defects, dislocations, etc., improves the local quality or density of the lattice, and improves the thermal conductivity of the material by increasing the density of the ceramic. In Example 4, a crystal phase crosslinker is added to effectively organically combine the cross-linking hydrogenated silane crosslinker and the silane polymerization product of the crystal phase transition aid, and utilize the synergistic effect of the two to jointly improve the thermal conductivity of the ceramic substrate. The reason is that on the one hand, the silane polymerization product can effectively reduce the oxygen content in the ceramic substrate, promote the α→βSi3N4 phase transition rate, improve the growth of the β-Si3N4 lattice, and maximize the thermal conductivity of the ceramic substrate; on the other hand, the hydrogenated silane crosslinker can effectively improve the density of the ceramic substrate through the hydrogenated crosslinker. Example 6 utilizes the different boiling points of butenyldichloromethylsilane and ((E)-3-chloro-1-methylpropenyl)trimethylsilane to form silane polymerization products with large differences in boiling points. By utilizing the synergistic effect of the silane polymerization products with different boiling points, they decompose at different temperatures during the sintering process, and the oxygen content in the sintering aid can be removed at different time periods, thereby hindering the generation of lattice oxygen, effectively reducing the lattice oxygen content and lattice defects of silicon nitride, and reducing phonon scattering, so that the prepared high-performance ceramic substrate has higher thermal conductivity.

[0091] Test Example 2

[0092] Bending strength test: The three-point bending strength of the material at room temperature was measured using an Instron-5569 universal testing machine. The test specimen size was 3mm×4mm×20mm, and the indenter movement rate was 0.5mm / min. -l , span 16mm. Before testing, the sample surface needs to be ground and polished and chamfered 45°. Each sample is tested 5 times and the average value is taken. The test results are shown in Table 2.

[0093] Table 2 Bending strength test

[0094]

[0095]

[0096] The above results demonstrate that the high-performance ceramics prepared by the present invention exhibit excellent flexural strength. The addition of a hydrosilane crosslinker effectively bonds the various components of the silicon nitride ceramic, improving the internal bonding and compactness of the ceramic substrate, thereby effectively increasing the density and mechanical strength of the ceramic substrate.

Claims

1. A method for preparing a high-performance ceramic substrate, characterized in that: It consists of the following steps: (1) Under a nitrogen environment, 80-120 parts by weight of silicon nitride powder or pretreated silicon nitride powder, 3-8 parts by weight of a sintering aid, 1-5 parts by weight of activated carbon, 20-30 parts by weight of a crystalline crosslinker, and 200-350 parts by weight of anhydrous ethanol are mixed, ball milled, and spray granulated to obtain a mixed powder; the crystalline crosslinker is a mixture of a silane polymerization product and a hydrosilane crosslinker; (2) dry-pressing the mixed powder to obtain a green body; placing the green body into a vacuum sintering furnace and a gas pressure sintering furnace in turn for sintering to obtain a high-performance ceramic substrate.

2. The method for preparing a high-performance ceramic substrate according to claim 1, wherein: The preparation process of the pretreated silicon nitride powder is as follows: adding the silicon nitride powder to an acidic solution at 70-90° C., wherein the mass ratio of the silicon nitride powder to the acidic solution is 1:(4-8); ultrasonicating for 2-5 hours, filtering, and then placing in a 0.05-0.2 mol / L sodium hydroxide aqueous solution and stirring for 1-3 hours, wherein the mass ratio of the silicon nitride powder to the sodium hydroxide aqueous solution is 1:(3-5), filtering, and drying to obtain the pretreated silicon nitride powder.

3. The method for preparing a high-performance ceramic substrate according to claim 2, wherein: The acidic solution is prepared by mixing 5-15 wt % sulfuric acid and 3-8 wt % hydrochloric acid in a mass ratio of (4-7): (0.5-2).

4. The method for preparing a high-performance ceramic substrate according to claim 1, wherein: The preparation method of the silane polymerization product is as follows: 4-methoxyphenylmagnesium chloride, alkenylchlorosilane and tetrahydrofuran are mixed and stirred to obtain a polymerization monomer; isopropyl alcohol and Custer catalyst are added and stirred to obtain a silane polymerization product.

5. The method for preparing a high-performance ceramic substrate according to claim 4, wherein: The mass ratio of the 4-methoxyphenylmagnesium chloride, alkenylchlorosilane and tetrahydrofuran is (8-12): (3-6): (25-40).

6. The method for preparing a high performance ceramic substrate according to claim 1, wherein: The preparation method of the hydrosilane crosslinking agent is as follows: tetraallylsilane, chlorodimethylsilane, Custer catalyst and isopropyl alcohol are mixed for reaction to obtain solution A; the solution A is added to lithium aluminum tetrahydride ether solution and stirred to obtain the hydrosilane crosslinking agent.

7. The method for preparing a high-performance ceramic substrate according to claim 6, wherein: The mass ratio of tetraallylsilane, chlorodimethylsilane and isopropyl alcohol is (2-5): (15-22): (30-50); the concentration of lithium aluminum hydride in the lithium aluminum hydride ether solution is 5-8 wt%.

8. The method for preparing a high-performance ceramic substrate according to claim 4 or 5, wherein: The alkenyl chlorosilane is butenyldichloromethylsilane and / or ((E)-3-chloro-1-methylpropenyl)trimethylsilane.

9. The method for preparing a high performance ceramic substrate according to claim 1, wherein: The ball milling speed of the ball milling medium is 300-500 rpm, and the ball milling time is 3-5 hours; the temperature of the vacuum sintering furnace is 600-700° C., and the sintering time is 4-8 hours; the temperature of the gas pressure sintering is 1000-2000° C., and the sintering time is 12-24 hours.

10. A high-performance ceramic substrate prepared by the method according to any one of claims 1 to 9.

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