Preparation method of high-thermal-conductivity Si3N4 ceramic substrate

Abstract

The invention discloses a preparation method of a high-thermal-conductivity Si3N4 ceramic substrate, and relates to the field of ceramic material forming. The preparation method comprises the following steps: uniformly mixing silicon powder, a dispersant, a binder, a plasticizer and a composite sintering aid in a solvent, carrying out ball milling to obtain slurry, carrying out defoaming, tape casting and lamination on the prepared slurry, carrying out warm isostatic pressing treatment, nitriding, and sintering to obtain the high-thermal-conductivity Si3N4 ceramic substrate. The prepared high-thermal-conductivity Si3N4 ceramic substrate is high in thermal conductivity, good in compactness, high in bending strength and fracture toughness and suitable for various power electronic devices and integrated circuit devices.

Description

Technical Field

[0001] This invention relates to the field of ceramic material forming, specifically to a method for preparing a high thermal conductivity Si3N4 ceramic substrate. Background Technology

[0002] Traditional ceramic substrate materials, such as alumina ceramic substrates, while possessing certain insulation and mechanical properties, have relatively low thermal conductivity. In applications such as power electronic devices and integrated circuits, if heat dissipation is not timely, it can lead to overheating, affecting the device's performance, reliability, and lifespan. Si3N4 ceramic, with its high theoretical thermal conductivity, has become one of the ideal materials for preparing high thermal conductivity ceramic substrates. However, current processes for preparing high thermal conductivity Si3N4 ceramic substrates suffer from problems such as poor slurry stability, uneven film thickness after molding, and weak lamination. Conventional sintering methods often struggle to simultaneously achieve ideal high density and high thermal conductivity.

[0003] Currently, the thermal conductivity of high-density Si3N4 powder ceramic substrates on the market is limited. This is mainly because although sintering aids can promote densification, excessive amounts can form oxygen-rich grain boundary phases, significantly increasing grain boundary thermal resistance and reducing thermal conductivity. High-purity Si3N4 powder can reduce lattice oxygen content, but completely eliminating oxygen impurities requires hot isostatic pressing sintering, which is costly and easily sacrifices density. Therefore, how to precisely control the process and microstructure, select appropriate additives, and optimize the dosage of additives to achieve a balance between density and thermal conductivity is an urgent problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a high thermal conductivity Si3N4 ceramic substrate, the preparation steps of which are as follows: (1) Mix silicon powder, dispersant, binder, plasticizer, composite sintering aid and solvent ethanol in a weight ratio of 100:(1.5~2):(4.5~5):(3.5~4.5):(4~6):(65~70), ball mill for 4~6 hours to obtain a mixture, and degas in a vacuum degassing machine for 30~60 minutes to obtain a slurry; (2) Pour the slurry into the casting machine. After casting is completed, collect the cast film and check the film thickness. Cut the cast film into sheets using a cutting device to form a laminated sample. Place the laminated sample into the laminator for pre-pressing and then pressurize it. After the laminated sample is processed, cut it and then perform isostatic pressing. (3) The block blank obtained by the above isostatic pressing is first placed in N2 atmosphere and heated to 1400~1500℃, held for 10~12h, and then sintered. It is then embedded in Si3N4 powder doped with boron nitride powder, and heated to 1850~1920℃ in N2 atmosphere with a pressure of 7~10MPa, and held for 6~10h to obtain a high thermal conductivity Si3N4 ceramic substrate.

[0005] Furthermore, the dispersant is one or more of trioleic acid glyceride, polyethyleneimine, and tetramethylammonium hydroxide.

[0006] Furthermore, the adhesive is one or more of polyvinyl butyral, polymethyl methacrylate, nitrocellulose, and petroleum resin.

[0007] Furthermore, the plasticizer is one or more of dibutyl phthalate, butyl benzyl phthalate, and glycerol.

[0008] Furthermore, the composite sintering aid includes a first sintering aid, a second sintering aid, and a third sintering aid; the first sintering aid is carbon powder, the second sintering aid is MgO or MgSiN2, and the third sintering aid is Yb2O3 or Y2O3, with a mass ratio of 3:6:1.

[0009] Furthermore, the slurry in step (1) is subjected to a shear rate of 100 s. -1 The viscosity is 2.1~2.4 Pa·s.

[0010] Furthermore, in step (2), the thickness of the cast film is 210~215 μm, the thickness of the laminated sample is 4.1~4.3 mm, and the area of ​​the laminated sample is 0.004~0.005 m². 2 The area of ​​the laminated sample after cutting is 0.0024~0.0028 m². 2 .

[0011] Furthermore, the parameters for pre-pressing the laminator in step (2) are: pressure of 3 tons, corresponding pressure of 6~7 MPa, temperature of 50~55℃, and holding time of 1~2 min; the parameters for pressurizing the laminator are: pressure of 10 tons, corresponding pressure of 20~22 MPa, temperature of 70~75℃, and holding time of 1~2 min.

[0012] Furthermore, in step (2), the temperature of the isostatic pressing is 50~55℃, and the pressurization is carried out in stages: the first stage is pressurized to 5MPa and the holding time is 100~120s; the second stage is pressurized to 10MPa and the holding time is 100~120s; the third stage is pressurized to 60MPa and the holding time is 580~600s.

[0013] The present invention also provides a high thermal conductivity Si3N4 ceramic substrate, which is prepared by the above-described method for preparing a high thermal conductivity Si3N4 ceramic substrate.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) The present invention promotes silicon powder nitriding, phase transformation and grain growth by high-temperature heat treatment of silicon powder briquettes under nitrogen atmosphere, and then sintersing and densifying them in Si3N4 powder doped with boron nitride powder. During the nitriding and sintering process, the silicon powder is not exposed to air, thereby greatly reducing the oxygen content of impurities and improving the thermal conductivity.

[0015] (2) The composite sintering aid system used in this invention has a multi-component synergistic effect: Mg ions can reduce the sintering temperature of Si3N4, promote the early start of the sintering reaction and promote the generation of liquid phase, and fill the internal pores of the ceramic through the liquid phase sintering mechanism, thereby significantly improving the density of the ceramic; carbon powder can undergo a reduction reaction with silicon dioxide formed by oxidation on the surface of silicon powder to remove the oxide layer, eliminate the interface thermal conduction barrier, and at the same time, precisely control the liquid phase content in the system to avoid excessive glass phase generation; rare earth elements, with their excellent oxygen affinity, can effectively adsorb and remove dissolved oxygen in the Si3N4 lattice, reducing phonon scattering caused by lattice defects; in addition, carbon powder can also induce the formation of a characteristic bimodal microstructure by inhibiting the excessive dissolution of oxygen in the lattice, thus optimizing the heat conduction channel; the above-mentioned multi-effect synergistic effect exerts its power from multiple dimensions such as density improvement, defect elimination and microstructure control, significantly improving the thermal conductivity of Si3N4 ceramic.

[0016] (3) By precisely limiting the parameters of each step of the process, including slurry formulation, mixing process, casting molding, lamination treatment and warm isostatic pressing, this invention effectively improves the stability of the slurry, ensures the uniformity of the thickness of the cast film and the tightness of the bonding of the laminated samples; at the same time, the segmented pressurization warm isostatic pressing process can reduce the internal stress of the sample and further optimize the sample performance; this method has strong process repeatability and is suitable for large-scale production, laying the foundation for the application of high thermal conductivity Si3N4 ceramic products. Attached Figure Description

[0017] Figure 1 Example 2 is a high thermal conductivity Si3N4 ceramic cast film.

[0018] Figure 2 This is a SEM image of the cross-section of the high thermal conductivity Si3N4 ceramic in Example 2 after being etched with molten sodium hydroxide at 450°C for 60 seconds. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1; (1) Mix 100g silicon powder, 1.5g trioleic acid glyceride, 4.5g polyvinyl butyral, 3.5g dibutyl phthalate, 1.2g carbon powder, 2.4g MgSiN2, 0.4g Yb2O3 and 65g solvent ethanol, add Si3N4 grinding balls with a diameter of 10mm, put them in a grinder, the mass ratio of silicon powder to Si3N4 grinding balls is 2:1.5, the grinder speed is 280r / min, and the ball milling is performed for 4h to obtain a mixture. The mixture is then degassed in a vacuum degassing machine for 30min, the vacuum degree is set to 12KPa, and the stirring speed is 1900r / min to obtain a slurry; (2) Pour the slurry into the casting machine. The casting speed of the casting machine is 0.5 m / min, the heating temperature is 50℃, and the heating time is 40 min. After casting is completed, collect the cast film and check the film thickness. Cut the cast film into sheets using a cutting device, take 20 sheets and stack them to form a laminated sample. Put the laminated sample into the laminator and pre-press it. The pressure is 3 tons, the corresponding pressure is 6 MPa, the temperature is 50℃, and the holding time is 1 min. Adjust the parameters of the laminator and proceed. The samples were pressurized to 10 tons (20 MPa), at 70°C for 1 minute. After being cut, the laminated samples were placed in a mold of a warm isostatic pressing (WIP) apparatus at 50°C. The pressurization was performed in stages: the first stage was pressurized to 5 MPa for 100 seconds; the second stage was pressurized to 10 MPa for 100 seconds; and the third stage was pressurized to 60 MPa for 580 seconds. (3) The block blank obtained by the above isostatic pressing is first placed in N2 atmosphere and heated to 1400°C, held for 10h, and then placed in a graphite crucible for sintering. It is then buried in Si3N4 powder doped with boron nitride powder, heated to 1850°C in N2 atmosphere with a pressure of 7MPa, and held for 6h to obtain a high thermal conductivity Si3N4 ceramic substrate.

[0021] Example 2; (1) Mix 100g silicon powder, 1.6g trioleic acid glyceride, 4.7g polyvinyl butyral, 3.6g dibutyl phthalate, 1.5g carbon powder, 3g MgSiN2, 0.5g Yb2O3 and 67g solvent ethanol, add Si3N4 grinding balls with a diameter of 10mm, put them in a grinder, the mass ratio of silicon powder to Si3N4 grinding balls is 2:1.5, the grinder speed is 300r / min, and the ball milling is performed for 5h to obtain a mixture. The mixture is then degassed in a vacuum degassing machine for 60min, the vacuum degree is set to 13KPa, and the stirring speed is 1800r / min to obtain a slurry; (2) Pour the slurry into the casting machine. The casting speed of the casting machine is 0.8 m / min, the heating temperature is 50℃, and the heating time is 50 min. After casting is completed, collect the cast film and check the film thickness. Cut the cast film into sheets using a cutting device, take 20 sheets and stack them to form a laminated sample. Put the laminated sample into the laminator and pre-press it. The pressure is 3 tons, the corresponding pressure is 6.5 MPa, the temperature is 52℃, and the holding time is 1.5 min. Adjust the parameters of the laminator. The samples were pressurized to 10 tons (21 MPa), at 72°C for 1.5 minutes. After being cut, the laminated samples were placed in a mold of a warm isostatic pressing (WIP) apparatus at 52°C. The pressurization was performed in stages: the first stage was pressurized to 5 MPa for 110 seconds; the second stage was pressurized to 10 MPa for 110 seconds; and the third stage was pressurized to 60 MPa for 600 seconds. (3) The block blank obtained by the above isostatic pressing is first placed in N2 atmosphere and heated to 1450°C, held for 12h, and then placed in a graphite crucible for sintering. It is then buried in Si3N4 powder doped with boron nitride powder, heated to 1900°C in N2 atmosphere with a pressure of 8MPa, and held for 8h to obtain a high thermal conductivity Si3N4 ceramic substrate.

[0022] Example 3; (1) Mix 100g silicon powder, 2g trioleic acid glyceride, 5g polyvinyl butyral, 4.5g dibutyl phthalate, 1.8g carbon powder, 3.6g MgSiN2, 0.6g Yb2O3 and 70g solvent ethanol, add Si3N4 grinding balls with a diameter of 10mm, put them in a grinder, the mass ratio of silicon powder to Si3N4 grinding balls is 2:1.5, the grinder speed is 320r / min, and the ball milling is performed for 6h to obtain a mixture. The mixture is then degassed in a vacuum degassing machine for 30min, the vacuum degree is set to 15KPa, and the stirring speed is 1900r / min to obtain a slurry; (2) Pour the slurry into the casting machine. The casting speed of the casting machine is 0.9 m / min, the heating temperature is 55℃, and the heating time is 60 min. After casting is completed, collect the cast film and test the film thickness. Cut the cast film into sheets using a cutting device, take 20 sheets and stack them to form a laminated sample. Place the laminated sample into the laminator and pre-press it. The pressure is 3 tons, the corresponding pressure is 7 MPa, the temperature is 55℃, and the holding time is 2 min. Adjust the parameters of the laminator and proceed. The samples were pressurized to 10 tons (22 MPa), at 75°C for 2 minutes. After being cut, the laminated samples were placed in a mold of a warm isostatic pressing (WIP) apparatus at 55°C. The pressurization was performed in stages: the first stage was pressurized to 5 MPa for 120 seconds; the second stage was pressurized to 10 MPa for 120 seconds; and the third stage was pressurized to 60 MPa for 600 seconds. (3) The block blank obtained by the above isostatic pressing is first placed in N2 atmosphere and heated to 1500°C, held for 10h, and then placed in a graphite crucible for sintering. It is then buried in Si3N4 powder doped with boron nitride powder, heated to 1920°C in N2 atmosphere with a pressure of 10MPa, and held for 10h to obtain a high thermal conductivity Si3N4 ceramic substrate.

[0023] Example 4; (1) Mix 100g silicon powder, 1.7g trioleic acid glyceride, 4.9g polyvinyl butyral, 4g dibutyl phthalate, 1.35g carbon powder, 2.7g MgSiN2, 0.45g Yb2O3 and 65g solvent ethanol, add Si3N4 grinding balls with a diameter of 10mm, put them in a grinder, the mass ratio of silicon powder to Si3N4 grinding balls is 2:1.5, the grinder speed is 300r / min, and the mixture is ball-milled for 4h to obtain a mixture. Degas the mixture in a vacuum degassing machine for 60min, set the vacuum degree to 12KPa, and the stirring speed to 1700r / min to obtain a slurry; (2) Pour the slurry into the casting machine. The casting speed of the casting machine is 0.6 m / min, the heating temperature is 50℃, and the heating time is 60 min. After casting is completed, collect the cast film and test the film thickness. Cut the cast film into sheets using a cutting device, take 20 sheets and stack them to form a laminated sample. Place the laminated sample into the laminator and pre-press it. The pressure is 3 tons, the corresponding pressure is 6 MPa, the temperature is 50℃, and the holding time is 2 min. Adjust the parameters of the laminator and proceed. The samples were pressurized to 10 tons (22 MPa), at 70°C for 2 minutes. After being cut, the laminated samples were placed in a mold of a warm isostatic pressing (WIP) apparatus at 50°C. The pressurization was performed in stages: the first stage was pressurized to 5 MPa for 120 seconds; the second stage was pressurized to 10 MPa for 120 seconds; and the third stage was pressurized to 60 MPa for 580 seconds. (3) The block blank obtained by the above isostatic pressing is first placed in N2 atmosphere and heated to 1400°C, held for 10h, and then placed in a graphite crucible for sintering. It is then buried in Si3N4 powder doped with boron nitride powder, heated to 1900°C in N2 atmosphere with a pressure of 7MPa, and held for 8h to obtain a high thermal conductivity Si3N4 ceramic substrate.

[0024] Example 5; (1) Mix 100g silicon powder, 1.6g trioleic acid glyceride, 3.8g polyvinyl butyral, 4.4g dibutyl phthalate, 1.2g carbon powder, 2.4g MgSiN2, 0.4g Yb2O3 and 68g solvent ethanol, add Si3N4 grinding balls with a diameter of 10mm, put them in a grinder, the mass ratio of silicon powder to Si3N4 grinding balls is 2:1.5, the grinder speed is 320r / min, and the ball milling is performed for 5h to obtain a mixture. Degas the mixture in a vacuum degassing machine for 30min, set the vacuum degree to 15KPa, and the stirring speed to 1900r / min to obtain a slurry; (2) Pour the slurry into the casting machine. The casting speed of the casting machine is 0.45 m / min, the heating temperature is 52℃, and the heating time is 50 min. After casting is completed, collect the cast film and test the film thickness. Cut the cast film into sheets using a cutting device, take 20 sheets and stack them to form a laminated sample. Put the laminated sample into the laminator and pre-press it. The pressure is 3 tons, the corresponding pressure is 6.5 MPa, the temperature is 52℃, and the holding time is 1.5 min. Adjust the parameters of the laminator. The samples were pressurized to 10 tons (21 MPa), at 72°C for 1.5 minutes. After being cut, the laminated samples were placed in a mold of a warm isostatic pressing (WIP) apparatus at 55°C. The pressurization was performed in stages: the first stage increased the pressure to 5 MPa for 110 seconds; the second stage increased the pressure to 10 MPa for 110 seconds; and the third stage increased the pressure to 60 MPa for 600 seconds. (3) The block blank obtained by the above isostatic pressing is first placed in N2 atmosphere and heated to 1450°C, held for 12h, and then placed in a graphite crucible for sintering. It is then buried in Si3N4 powder doped with boron nitride powder, heated to 1900°C in N2 atmosphere with a pressure of 10MPa, and held for 8h to obtain a high thermal conductivity Si3N4 ceramic substrate.

[0025] Example 6; (1) Mix 100g silicon powder, 1.8g trioleic acid glyceride, 5g polyvinyl butyral, 4.2g dibutyl phthalate, 1.5g carbon powder, 3g MgSiN2, 0.5g Yb2O3 and 68g solvent ethanol, add Si3N4 grinding balls with a diameter of 10mm, put them in a grinder, the mass ratio of silicon powder to Si3N4 grinding balls is 2:1.5, the grinder speed is 280r / min, and the mixture is ball-milled for 4h to obtain a mixture. Degas the mixture in a vacuum degassing machine for 60min, set the vacuum degree to 15KPa, and the stirring speed to 1900r / min to obtain a slurry; (2) Pour the slurry into the casting machine. The casting speed of the casting machine is 0.9 m / min, the heating temperature is 55℃, and the heating time is 60 min. After casting is completed, collect the cast film and test the film thickness. Cut the cast film into sheets using a cutting device, take 20 sheets and stack them to form a laminated sample. Place the laminated sample into the laminator and pre-press it. The pressure is 3 tons, the corresponding pressure is 7 MPa, the temperature is 55℃, and the holding time is 2 min. Adjust the parameters of the laminator and proceed. The samples were pressurized to 10 tons (22 MPa), at 75°C for 2 minutes. After being cut, the laminated samples were placed in a mold of a warm isostatic pressing (WIP) apparatus at 50°C. The pressurization was performed in stages: the first stage was pressurized to 5 MPa for 120 seconds; the second stage was pressurized to 10 MPa for 120 seconds; and the third stage was pressurized to 60 MPa for 600 seconds. (3) The block blank obtained by the above isostatic pressing is first placed in N2 atmosphere and heated to 1500°C, held for 12h, and then placed in a graphite crucible for sintering. It is then buried in Si3N4 powder doped with boron nitride powder, heated to 1920°C in N2 atmosphere with a pressure of 10MPa, and held for 10h to obtain a high thermal conductivity Si3N4 ceramic substrate.

[0026] Comparative Example 1; The difference between the high thermal conductivity Si3N4 ceramic substrate of Comparative Example 1 and Example 2 is only in step (1). Step (1) is modified as follows: 100g silicon powder, 1.8g trioleic acid glyceride, 5g polyvinyl butyral, 4.2g dibutyl phthalate, 5g MgO and 68g solvent ethanol are mixed, and Si3N4 grinding balls with a diameter of 10mm are added. The mixture is placed in a grinder with a mass ratio of silicon powder to Si3N4 grinding balls of 2:1.5. The grinder speed is 280r / min. The mixture is ball-milled for 4h to obtain a mixture. The mixture is then degassed in a vacuum degassing machine for 60min with a vacuum degree of 15KPa and a stirring speed of 1900r / min to obtain a slurry. The remaining steps are the same as in Example 6. Comparative Example 2; The difference between the high thermal conductivity Si3N4 ceramic substrate of Comparative Example 2 and Example 2 is only in step (1). Step (1) is modified as follows: 100g silicon powder, 1.8g trioleic acid glyceride, 5g polyvinyl butyral, 4.2g dibutyl phthalate, 4g MgO, 1g Y2O3 and 68g solvent ethanol are mixed, and Si3N4 grinding balls with a diameter of 10mm are added. The mixture is placed in a grinder with a mass ratio of silicon powder to Si3N4 grinding balls of 2:1.5. The grinder speed is 280r / min. The mixture is ball-milled for 4h to obtain a mixture. The mixture is then degassed in a vacuum degassing machine for 60min with a vacuum degree of 15KPa and a stirring speed of 1900r / min to obtain a slurry. The remaining steps are the same as in Example 6.

[0027] Comparative Example 3; The difference between the high thermal conductivity Si3N4 ceramic substrate of Comparative Example 3 and Example 2 is only in step (1). Step (1) is modified as follows: 100g silicon powder, 1.8g polyethyleneimine, 5g polymethyl methacrylate, 4.2g dibutyl phthalate, 1.5g carbon powder, 3g MgSiN2, 0.5g Yb2O3 and 68g solvent ethanol are mixed, and Si3N4 grinding balls with a diameter of 10mm are added. The mixture is placed in a grinder with a mass ratio of silicon powder to Si3N4 grinding balls of 2:1.5. The grinder speed is 280r / min. The mixture is ball-milled for 4h to obtain a mixture. The mixture is then degassed in a vacuum degassing machine for 60min with a vacuum degree of 15KPa and a stirring speed of 1900r / min to obtain a slurry. The remaining steps are the same as in Example 6.

[0028] Comparative Example 4; The difference between the high thermal conductivity Si3N4 ceramic substrate of Comparative Example 4 and Example 2 is only in step (1). Step (1) is modified as follows: 100g Si3N4 powder, 1.8g trioleic acid glyceride, 5g polyvinyl butyral, 4.2g dibutyl phthalate, 1.5g carbon powder, 3g MgSiN2, 0.5g Yb2O3 and 68g solvent ethanol are mixed, and Si3N4 grinding balls with a diameter of 10mm are added. The mixture is placed in a grinder with a mass ratio of silicon powder to Si3N4 grinding balls of 2:1.5. The grinder speed is 280r / min and the mixture is ball-milled for 4h to obtain a mixture. The mixture is then degassed in a vacuum degassing machine for 60min with a vacuum degree of 13KPa and a stirring speed of 1900r / min to obtain a slurry. The remaining steps are the same as in Example 6.

[0029] Comparative Example 5; The difference between the high thermal conductivity Si3N4 ceramic substrate of Comparative Example 5 and Example 2 lies in the difference between steps (1) and (3). Step (1) is modified as follows: 100g Si3N4 powder, 1.8g trioleic acid glyceride, 5g polyvinyl butyral, 4.2g dibutyl phthalate, 1.5g carbon powder, 3g MgSiN2, 0.5g Yb2O3 and 68g solvent ethanol are mixed, and Si3N4 grinding balls with a diameter of 10mm are added. The mixture is placed in a grinder, and the mass ratio of silicon powder to Si3N4 grinding balls is 2:1.5. The ball milling was performed at a speed of 280 r / min for 4 h to obtain a mixture. The mixture was then degassed in a vacuum degassing machine for 60 min. The vacuum degree was set to 13 kPa and the stirring speed was 1900 r / min to obtain a slurry. Step (3) was modified as follows: the block blank obtained by the above isostatic pressing was first placed in a N2 atmosphere and heated to 1500°C and kept at that temperature for 12 h. Then it was placed in a graphite crucible for sintering. In a N2 atmosphere, the pressure was set to 10 MPa and the temperature was heated to 1920°C and kept at that temperature for 10 h to obtain a high thermal conductivity Si3N4 ceramic substrate. The remaining steps were the same as in Example 6.

[0030] Test methods: Porosity was tested using Archimedes' drainage method according to GB / T25995-2010 standard; density was calculated theoretically as (1 - porosity) × 100%; thermal conductivity was calculated as k = Cp·ρ·α, where Cp is the heat capacity of Si3N4 ceramic, with a value of 0.71 J / (g·K), ρ is the bulk density of the sample, tested according to GB / T4100-2015 standard, and α is the thermal diffusivity, measured by laser scintillation method; flexural strength was tested using the three-point bending method with a span of 30 mm and a loading rate of 0.5 mm / min; fracture toughness was tested using the single-sided notched beam method with a span of 20 mm, a loading rate of 0.05 mm / min, a groove depth of 2 mm, and a groove width ≤ 0.2 mm. The test results are shown in Table 1.

[0031] Table 1

[0032] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a high thermal conductivity Si3N4 ceramic substrate, characterized in that, The preparation steps include the following: (1) Mix silicon powder, dispersant, binder, plasticizer, composite sintering aid and solvent ethanol in a weight ratio of 100:(1.5~2):(4.5~5):(3.5~4.5):(4~6):(65~70), ball mill for 4~6 hours to obtain a mixture, and degas in a vacuum degassing machine for 30~60 minutes to obtain a slurry; (2) Pour the slurry into the casting machine. After casting is completed, collect the cast film and check the film thickness. Cut the cast film into sheets using a cutting device to form a laminated sample. Place the laminated sample into the laminator for pre-pressing and then pressurize it. After the laminated sample is processed, cut it and then perform isostatic pressing. (3) The block blank obtained by the above isostatic pressing is first placed in N2 atmosphere and heated to 1400~1500℃, held for 10~12h, and then sintered. It is then embedded in Si3N4 powder doped with boron nitride powder, and heated to 1850~1920℃ in N2 atmosphere with a pressure of 7~10MPa, and held for 6~10h to obtain a high thermal conductivity Si3N4 ceramic substrate.

2. The method for preparing a high thermal conductivity Si3N4 ceramic substrate according to claim 1, characterized in that, The dispersant is one or a mixture of trioleic acid glyceride, polyethyleneimine, and tetramethylammonium hydroxide.

3. The method for preparing a high thermal conductivity Si3N4 ceramic substrate according to claim 1, characterized in that, The adhesive is one or more of polyvinyl butyral, polymethyl methacrylate, nitrocellulose, and petroleum resin.

4. The method for preparing a high thermal conductivity Si3N4 ceramic substrate according to claim 1, characterized in that, The plasticizer is one or a mixture of dibutyl phthalate, butyl benzyl phthalate, and glycerol.

5. The method for preparing a high thermal conductivity Si3N4 ceramic substrate according to claim 1, characterized in that, The composite sintering aid includes a first sintering aid, a second sintering aid, and a third sintering aid; the first sintering aid is carbon powder, the second sintering aid is MgO or MgSiN2, and the third sintering aid is Yb2O3 or Y2O3, with a mass ratio of 3:6:

1.

6. The method for preparing a high thermal conductivity Si3N4 ceramic substrate according to claim 1, characterized in that, The slurry in step (1) is subjected to a shear rate of 100 s. -1 The viscosity is 2.1~2.4 Pa·s.

7. The method for preparing a high thermal conductivity Si3N4 ceramic substrate according to claim 1, characterized in that, In step (2), the thickness of the cast film is 210~215 μm, the thickness of the laminated sample is 4.1~4.3 mm, and the area of ​​the laminated sample is 0.004~0.005 m². 2 The area of ​​the laminated sample after cutting is 0.0024~0.0028 m². 2 .

8. The method for preparing a high thermal conductivity Si3N4 ceramic substrate according to claim 1, characterized in that, The parameters for pre-pressing the laminator in step (2) are: pressure of 3 tons, corresponding pressure of 6~7 MPa, temperature of 50~55℃, and holding time of 1~2 min; the parameters for pressurizing the laminator are: pressure of 10 tons, corresponding pressure of 20~22 MPa, temperature of 70~75℃, and holding time of 1~2 min.

9. The method for preparing a high thermal conductivity Si3N4 ceramic substrate according to claim 1, characterized in that, In step (2), the temperature of the isostatic pressing is 50~55℃, and the pressurization is carried out in stages: the first stage is pressurized to 5MPa and the holding time is 100~120s; the second stage is pressurized to 10MPa and the holding time is 100~120s; the third stage is pressurized to 60MPa and the holding time is 580~600s.

10. A high thermal conductivity Si3N4 ceramic substrate, characterized in that, It is prepared by the method of preparing a high thermal conductivity Si3N4 ceramic substrate according to any one of claims 1-9.

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