A method for preparing a 96 alumina ceramic substrate

Abstract

The present application relates to the technical field of ceramic manufacturing process, and specifically discloses a preparation method of 96 alumina ceramic substrate, which comprises the following steps: slurry preparation, ball milling and fully mixing high-purity alumina powder, sintering aids, binders, plasticizers, organic solvents and dispersants to obtain casting slurry; green body forming, coating the casting slurry on a carrier film through a casting machine to form a wet film with uniform thickness and smooth surface, and carrying out partition drying on the carrier film through a drying box to obtain a solidified green body; sintering and densification treatment, carrying out glue removal treatment on the green body, and obtaining the 96 alumina ceramic substrate through stepwise sintering. The 96 alumina ceramic substrate prepared by the present application can form a large number of uniform crystal cores, and can also make small crystal grains dissolve and large crystal grains grow at a uniform speed, thereby ensuring the uniformity of the grain size, reducing the scattering of phonons on the grain boundary, and laying a structural foundation for the improvement of thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of ceramic manufacturing technology, specifically to a method for preparing a 96% alumina ceramic substrate. Background Technology

[0002] Alumina (Al2O3) ceramics are widely used in electronic packaging, integrated circuit substrates, power modules, sensors, and high-temperature structural components due to their excellent electrical insulation, high thermal conductivity, good mechanical strength, chemical stability, and compatibility with metals. Among them, 96% alumina ceramics (i.e., Al2O3 content of approximately 96wt%, with the remainder mainly consisting of sintering aids such as SiO2, CaO, and MgO, hereinafter referred to as 96% alumina ceramics) have become one of the mainstream materials for mid-to-high-end electronic ceramic substrates because they achieve a good balance between cost, performance, and process maturity.

[0003] Currently, the preparation of 96% alumina ceramic substrates typically employs a process route combining tape casting or dry pressing with high-temperature sintering. Specifically, high-purity α-Al₂O₃ powder is first mixed with sintering aids, organic binders, dispersants, and solvents to form a slurry or powder, which is then shaped into a green body through tape casting, rolling, or molding. Subsequently, organic components are removed through debinding, and finally, the substrate is sintered and densified in an air atmosphere at 1500°C–1650°C.

[0004] Chinese invention patent CN103435358A discloses a method for adding organic compositions in the early and late stages of casting slurry preparation. The early stage organic composition includes a solvent and a dispersant, wherein the solvent is at least one of reagents such as ethanol, and the dispersant is at least one of reagents such as tributyl phosphate. The late stage organic composition includes a solvent, an organic binder, and a plasticizer, wherein the solvent is at least one of reagents such as ethanol, the plasticizer is at least one of reagents such as polyethylene glycol, and the organic binder is mainly polyvinyl butyral. This organic composition can be applied in the casting process. Specifically, ceramic powder, inorganic binder phase, and the early stage organic composition are first mixed and ball-milled, and then the late stage organic composition is added for a second ball milling. After stirring and defoaming, a casting slurry is obtained. The blade gap and casting speed of the casting machine are adjusted to form a wet blank, which is then peeled off from the carrier belt after drying to obtain a green ceramic tape. The preparation process of this invention is simple, the preparation cycle is short, and the quality of the resulting green film is stable and not easily broken.

[0005] However, the above-mentioned patent application schemes and similar technical solutions still have the following shortcomings: Since the existing preparation process cannot accurately control key links such as raw material dispersion, molding and sintering, it is easy to cause inherent defects such as wide grain size distribution, impurity phase enrichment at grain boundaries and more micropores in the sintered body. These inherent defects, as the main scattering centers, seriously hinder the phonon heat transfer of lattice vibration, so that the theoretical thermal conductivity potential cannot be released, thus limiting its application in high-end electronic packaging fields such as iterative high-power LEDs, semiconductor lasers and IGBT modules. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a 96 alumina ceramic substrate to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides a method for preparing a 96 alumina ceramic substrate, comprising:

[0008] S1. Slurry preparation: High-purity alumina powder with a purity of not less than 3N is ball-milled and thoroughly mixed with sintering aids, binders, plasticizers, organic solvents, and dispersants according to a preset ratio to obtain a casting slurry, including the following steps:

[0009] S1.1 Raw material pretreatment: High-purity magnesium oxide, silicon dioxide and calcium oxide nanoparticles with a mass ratio of 2:1:0.5 are mixed to obtain mixed powder;

[0010] The high-purity alumina powder is dried and pretreated, and then divided into two parts: the first part of high-purity alumina powder and the second part of high-purity alumina powder.

[0011] The mixed powder with a mass ratio of 1:1.5 was ball-milled with the first part of high-purity alumina powder, and anhydrous ethanol was added and mixed thoroughly. The mass ratio of the total amount of the mixed powder and the first part of high-purity alumina powder to the mass ratio of anhydrous ethanol was 10:7-10:10, thus obtaining a sintering aid.

[0012] S1.2, Mixing preparation: The high-purity alumina powder, sintering aid, binder, plasticizer, organic solvent and dispersant in the second part are mixed to obtain an initial mixed slurry;

[0013] S1.3 Post-processing of slurry: The initial mixed slurry is subjected to vacuum degassing to obtain an intermediate mixed slurry, and the viscosity of the intermediate mixed slurry for casting is determined. Simultaneously, the viscosity of the casting slurry is compared with a preset viscosity threshold range to obtain the cast slurry. Specifically:

[0014] When the viscosity of the cast slurry is less than the lower limit of the preset viscosity threshold range, the settling time is increased until the viscosity of the cast slurry is within the preset viscosity threshold range; when the viscosity of the cast slurry is within the preset viscosity threshold range, the intermediate mixed slurry is the cast slurry; when the viscosity of the cast slurry is greater than the upper limit of the preset viscosity threshold range, an organic solvent is added dropwise to the intermediate mixed slurry, and low-speed stirring continues until the viscosity of the cast slurry is within the preset viscosity threshold range.

[0015] The organic solvent used is anhydrous ethanol and xylene in a mass ratio of 7:3;

[0016] S2. Green body forming: The casting slurry is coated onto a carrier film with a wet film through a casting machine. The wet film has a uniform thickness and a smooth surface. Then, the carrier film is dried in sections through a drying oven to obtain a cured green body.

[0017] S3. Sintering and densification treatment: The green blank is subjected to debinding treatment and sintered by step heating. The debinding green blank is then sintered to obtain a 96 alumina ceramic substrate.

[0018] Furthermore, in step S1.1, the raw material pretreatment also includes drying the high-purity alumina powder at a temperature of 115℃-125℃ for at least 4 hours, and dividing it into two parts, namely the first part of high-purity alumina powder and the second part of high-purity alumina powder.

[0019] The mixed powder, the first part of high-purity alumina powder, and anhydrous ethanol are ball-milled for 2-4 hours to obtain a sintering aid.

[0020] Furthermore, in step S1.2, obtaining the initial mixed slurry includes:

[0021] S1.2.1, Mixing the main material: The second part of high-purity alumina powder after drying and pretreatment with a mass ratio of 191:9-193:7 is mixed with the sintering aid to form the main material, and then organic solvent and dispersant are added and stirred evenly to form the main material slurry;

[0022] S1.2.2 Secondary ball milling: Binder and plasticizer are gradually added to the main material slurry, and the mixture is ball milled for 4-8 hours to obtain the initial mixed slurry.

[0023] Furthermore, the mass ratio of the organic solvent to the main ingredient is 3:10-4:10, and the mass ratio of the dispersant to the main ingredient is 0.5:100-1:100;

[0024] The dispersant is herring oil or phosphate ester.

[0025] Furthermore, the mass ratio of the adhesive to the main material slurry is 3:100-5:100;

[0026] The adhesive is polyvinyl butyral;

[0027] The plasticizer is polyethylene glycol or dibutyl phthalate, and the mass ratio of the plasticizer to the main slurry is 1:100-2:100.

[0028] Furthermore, the drying chamber is sequentially equipped with a surface drying zone, a main drying zone, and a curing zone. The carrier film is sequentially fed into the surface drying zone, the main drying zone, and the curing zone for zoned drying. The length ratio between the surface drying zone, the main drying zone, and the curing zone is set to 1:2:1. At the same time, the temperature of the surface drying zone is set to 25℃-30℃, the temperature of the main drying zone is set to 40℃-45℃, and the temperature of the curing zone is set to 45℃-50℃.

[0029] Furthermore, in step S3, the sintering densification treatment includes:

[0030] S3.1 Debinding treatment: Place the green blank in the sintering furnace, evacuate the inside of the sintering furnace to a vacuum degree of 10Pa-100Pa, introduce high-purity hydrogen gas and maintain the vacuum degree of 10Pa-100Pa, then gradually raise the temperature inside the sintering furnace from room temperature to 600℃, and hold at 600℃ for at least 2 hours. During the holding process, continuously introduce high-purity hydrogen gas and repeat the gas purging process inside the sintering furnace at least twice.

[0031] S3.2 Step sintering: After raising the internal temperature of the sintering furnace to 1150°C, the green body after the debinding treatment is sintered at 1150°C for at least 1 hour; then the temperature is raised to 1720°C and sintered at 1720°C for 3-4 hours; finally, natural cooling is performed to obtain 96 alumina ceramic substrate.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] Firstly, this invention adds a small amount of high-purity alumina powder (i.e., the first part of high-purity alumina powder) to the sintering aid to ensure that the powder is highly uniformly distributed in the initial mixed slurry, providing a consistent chemical environment for uniform grain growth. At the same time, the green body after debinding is subjected to step sintering, which not only forms a large number of uniform crystal nuclei, but also dissolves small grains and allows large grains to grow at a uniform rate, further ensuring the uniformity of grain size. This reduces the scattering of phonons at grain boundaries and lays the structural foundation for improving thermal conductivity.

[0034] Secondly, this invention prepares sintering aids using high-purity magnesium oxide, silicon dioxide, and calcium oxide nanoparticles, which not only form an appropriate amount of liquid phase with suitable fluidity during sintering, but also promote densification while avoiding excessive glass phase residue.

[0035] Thirdly, this invention uses high-purity hydrogen to repeatedly purge the inside of the sintering furnace, which can reduce trace amounts of impurities such as silicon dioxide on the surface of the powder and generate gaseous silicon hydroxide, thereby further improving the purity of the grain boundaries. Attached Figure Description

[0036] Figure 1 Microscopic structure diagram of traditional process;

[0037] Figure 2 This is a microstructure diagram of the process corresponding to the preparation method in this invention;

[0038] Figure 3 This is a comparison chart of the thermal conductivity of the substrate in this invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] This embodiment provides a method for preparing a 96% alumina ceramic substrate, which specifically includes the following steps:

[0041] S1. Slurry Preparation: High-purity alumina powder with a purity of not less than 3N is ball-milled and thoroughly mixed with sintering aids, binders, plasticizers, organic solvents, and dispersants according to a preset ratio to form a uniform and stable cast slurry. It is worth noting that during the thorough mixing of the raw materials (i.e., high-purity alumina powder, sintering aids, binders, plasticizers, solvents, and dispersants), all raw materials are ball-milled for a prolonged period, with a ball-milling time of not less than 12 hours.

[0042] S2: Green body forming, which involves processing the cast slurry obtained in step S1 through a casting process to obtain the corresponding green body. Specifically, the casting process includes:

[0043] The obtained casting slurry is slowly poured into the storage tank of the casting machine and slowly stirred in the tank to prevent sedimentation. Simultaneously, the casting machine is started, causing the carrier film connected to the casting machine (not shown in the figure, but those skilled in the art should understand the installation method and position of the carrier film and casting machine) to move at a uniform speed, forming a slurry dam in front of the casting cutter head. Through the movement of the carrier film below the casting cutter head, the casting slurry is scraped by the cutting edge of the casting cutter head, thereby forming a wet film on the carrier film. The wet film has a uniform thickness and a smooth surface. In this embodiment, the thickness of the wet film is determined based on the gap between the cutting edge of the casting cutter head and the carrier film.

[0044] The carrier film is then dried in a drying oven to obtain a cured green body. Specifically, during the drying process, the carrier film is sequentially dried through a surface drying zone, a main drying zone, and a curing zone within the drying oven. The length ratio of the surface drying zone, the main drying zone, and the curing zone is set to 1:2:1, and the temperature of the surface drying zone is set to 25℃-30℃, the temperature of the main drying zone is set to 40℃-45℃, and the temperature of the curing zone is set to 45℃-50℃.

[0045] Step S3: Sintering densification treatment, that is, after the green blank obtained in step S2 is debinded, the green blank after debinding is sintered by step heating to obtain 96 alumina ceramic substrate.

[0046] In this embodiment, all raw materials (i.e., high-purity alumina powder, sintering aid, binder, plasticizer, solvent and dispersant) are fully mixed by ball milling for no less than 12 hours to obtain the corresponding casting slurry.

[0047] Step S1 specifically includes the following steps:

[0048] Step S1.1: Raw material pretreatment: High-purity magnesium oxide, silicon dioxide and calcium oxide nanoparticles with a mass ratio of 2:1:0.5 are mixed to obtain mixed powder;

[0049] The high-purity alumina powder is dried and pretreated, and then divided into two parts: the first part of high-purity alumina powder and the second part of high-purity alumina powder.

[0050] The mixed powder with a mass ratio of 1:1.5 was ball-milled with the first part of high-purity alumina powder, and anhydrous ethanol was added and mixed thoroughly. The mass ratio of the total amount of the mixed powder and the first part of high-purity alumina powder to the mass ratio of anhydrous ethanol was 10:7-10:10, thus obtaining a sintering aid.

[0051] In step S1.1, the raw material pretreatment also includes drying the high-purity alumina powder at a temperature of 115℃-125℃ for at least 4 hours.

[0052] The method for drying high-purity alumina powder is as follows: The high-purity alumina powder is pre-treated by drying in a forced-air drying oven. In this embodiment, the high-purity alumina powder is evenly spread on a drying tray in the forced-air drying oven, with a powder layer thickness not exceeding 2 cm. The drying tray is then placed in a forced-air drying oven preheated to 115℃-125℃ for drying and dehumidification. Specifically, the high-purity alumina powder is dried in the forced-air drying oven at 115℃-125℃ for at least 4 hours. After drying, the high-purity alumina powder is naturally cooled in the forced-air drying oven until the temperature does not exceed 50℃. The dried high-purity alumina powder is then removed from the forced-air drying oven and sealed for storage using a desiccant.

[0053] S1.2: Mixing Preparation: The high-purity alumina powder, sintering aid, binder, plasticizer, organic solvent, and dispersant from the second part are mixed to obtain an initial mixed slurry, as follows:

[0054] S1.2.1: Main material mixing: The second part of high-purity alumina powder after drying and pretreatment with a mass ratio of 191:9-193:7 is mixed with the sintering aid to form the main material, and then organic solvent and dispersant are added and stirred evenly to form the main material slurry;

[0055] S1.2.2: Secondary ball milling: Binder and plasticizer are gradually added to the main material slurry, and the mixture is ball milled for 4-8 hours to obtain the initial mixed slurry.

[0056] The mass ratio of the organic solvent to the main ingredient is 3:10-4:10, and the mass ratio of the dispersant to the main ingredient is 0.5:100-1:100. The dispersant is herring oil or phosphate ester.

[0057] Through adsorption between the dispersant and the surfaces of various powders (including high-purity alumina powder, high-purity magnesium oxide, silicon dioxide and calcium oxide nanoparticles) in the initial mixed main material, an electric double layer or steric hindrance effect can be formed to prevent the powders in the initial mixed main material from agglomerating, thereby allowing the powders in the initial mixed main material to be fully dispersed in the organic solvent.

[0058] In this embodiment, the binder is set as polyvinyl butyral, and the mass ratio of the binder to the main material slurry is 3:100-5:100.

[0059] In this embodiment, the plasticizer is set as polyethylene glycol or dibutyl phthalate, and the mass ratio of the plasticizer to the main material slurry is 1:100-2:100.

[0060] Step S1.3: Post-processing of slurry: The initial mixed slurry is subjected to vacuum degassing to obtain an intermediate mixed slurry, and the viscosity of the intermediate mixed slurry for casting is determined. Simultaneously, the viscosity of the casting slurry is compared with a preset viscosity threshold range to obtain the cast slurry. Specifically:

[0061] When the viscosity of the cast slurry is less than the lower limit of the preset viscosity threshold range, the settling time is increased until the viscosity of the cast slurry is within the preset viscosity threshold range; when the viscosity of the cast slurry is within the preset viscosity threshold range, the intermediate mixed slurry is the cast slurry; when the viscosity of the cast slurry is greater than the upper limit of the preset viscosity threshold range, an organic solvent is added dropwise to the intermediate mixed slurry, and low-speed stirring continues until the viscosity of the cast slurry is within the preset viscosity threshold range.

[0062] It is worth noting that the viscosity of the obtained intermediate mixed slurry is measured at a rotational viscometer at a speed of 20 rpm to obtain the viscosity of the cast slurry. Specifically, the obtained viscosity of the cast slurry is compared with a preset viscosity threshold range (which can be set according to actual needs, and therefore not specifically described in this embodiment, such as 1500 mPa·s-2500 mPa·s) to obtain the final mixed slurry, i.e., the cast slurry. Specifically:

[0063] When the viscosity of the obtained cast slurry is less than the lower limit of the preset viscosity threshold range (i.e., 1500 mPa·s), the settling time is increased until the viscosity of the obtained cast slurry falls within the preset viscosity threshold range. When the viscosity of the obtained cast slurry falls within the preset viscosity threshold range (i.e., 1500 mPa·s-2500 mPa·s), the obtained intermediate mixed slurry is the final mixed slurry. When the viscosity of the obtained cast slurry is greater than the upper limit of the preset viscosity threshold range (i.e., 2500 mPa·s), an organic solvent is added dropwise to the intermediate mixed slurry, and low-speed stirring continues until the viscosity of the obtained cast slurry falls within the preset viscosity threshold range.

[0064] In step S3, the sintering densification treatment includes the following steps:

[0065] S3.1 Debinding treatment: Place the green blank in the sintering furnace, evacuate the furnace to a vacuum of 10Pa-100Pa, introduce high-purity hydrogen gas, and maintain the vacuum at 10Pa-100Pa. Then, gradually raise the temperature of the furnace from room temperature to 600°C and hold it at 600°C for at least 2 hours. During the holding process, continuously introduce high-purity hydrogen gas and repeat the gas purging process of the furnace at least twice.

[0066] It should be noted that the gap between two adjacent green blanks should be greater than 5 mm, and the green blanks should be placed in the effective uniform temperature zone of the sintering furnace for debinding.

[0067] More specifically, in the effective uniform temperature zone of the sintering furnace, the temperature of the effective uniform temperature zone is raised from room temperature to 300℃ at a heating rate of 0.5℃ / min-1℃ / min, and then raised from 300℃ to 600℃ at a heating rate of 1℃ / min-2℃ / min.

[0068] In addition, the rate at which high-purity hydrogen is introduced into the sintering furnace is 0.5 L / min to 1 L / min.

[0069] S3.2 Step sintering: The internal temperature of the sintering furnace is raised to 1150°C at a rate of at least 4°C / min, and the green body after debinding is sintered at 1150°C for at least 1 hour; then the temperature is raised to 1720°C at a rate of up to 1°C / min, and sintered at 1720°C for 3-4 hours; finally, natural cooling is performed to obtain a 96 alumina ceramic substrate.

[0070] refer to Figure 1 and Figure 2 Therefore, we can conclude that:

[0071] Traditional processes produce 96% alumina ceramic substrates with a wide alumina grain size distribution, ranging from 0.3 μm to 1.5 μm. In contrast, the alumina ceramic substrates prepared using this method exhibit a uniform alumina grain size distribution, ranging from 0.5 μm to 0.8 μm. Therefore, compared to traditional processes, the method described in this embodiment optimizes the alumina grain size distribution index and improves the uniformity of the alumina grains. Simultaneously, it reduces the porosity from greater than 1% in traditional processes to less than 1%, significantly reducing the defect density. Similarly, it reduces the number of grain boundary impurity phases, achieving a grain boundary purification effect and improving grain boundary quality.

[0072] refer to Figure 3As can be seen, the thermal conductivity of the preparation method in this embodiment is increased from 24.5 W / m·K-25 W / m·K in the traditional process to 28.5 W / m·K, achieving a performance improvement of about 16.3%, thus successfully breaking through the technical bottleneck that the thermal conductivity of 96 alumina ceramic has long been stagnant at 24 W / m·K-25 W / m·K.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended embodiments and their equivalents.

Claims

1. A method for preparing a 96% alumina ceramic substrate, characterized in that, include: S1. Slurry preparation: High-purity alumina powder with a purity of not less than 3N is ball-milled and thoroughly mixed with sintering aids, binders, plasticizers, organic solvents, and dispersants according to a preset ratio to obtain a casting slurry, including the following steps: S1.1 Raw material pretreatment: High-purity magnesium oxide, silicon dioxide and calcium oxide nanoparticles with a mass ratio of 2:1:0.5 are mixed to obtain mixed powder; The high-purity alumina powder is dried and pretreated, and then divided into two parts: the first part of high-purity alumina powder and the second part of high-purity alumina powder. The mixed powder with a mass ratio of 1:1.5 was ball-milled with the first part of high-purity alumina powder, and anhydrous ethanol was added and mixed thoroughly. The mass ratio of the total amount of the mixed powder and the first part of high-purity alumina powder to the mass ratio of anhydrous ethanol was 10:7-10:10, thus obtaining a sintering aid. S1.2, Mixing preparation: The high-purity alumina powder, sintering aid, binder, plasticizer, organic solvent and dispersant in the second part are mixed to obtain an initial mixed slurry; S1.3 Post-processing of slurry: The initial mixed slurry is subjected to vacuum degassing to obtain an intermediate mixed slurry, and the viscosity of the intermediate mixed slurry for casting is determined. Simultaneously, the viscosity of the casting slurry is compared with a preset viscosity threshold range to obtain the cast slurry. Specifically: When the viscosity of the cast slurry is less than the lower limit of the preset viscosity threshold range, the settling time is increased until the viscosity of the cast slurry is within the preset viscosity threshold range; when the viscosity of the cast slurry is within the preset viscosity threshold range, the intermediate mixed slurry is the cast slurry; when the viscosity of the cast slurry is greater than the upper limit of the preset viscosity threshold range, an organic solvent is added dropwise to the intermediate mixed slurry, and low-speed stirring continues until the viscosity of the cast slurry is within the preset viscosity threshold range. The organic solvent used is anhydrous ethanol and xylene in a mass ratio of 7:3; S2. Green body forming: The casting slurry is coated onto a carrier film with a wet film through a casting machine. The wet film has a uniform thickness and a smooth surface. Then, the carrier film is dried in sections through a drying oven to obtain a cured green body. S3. Sintering and densification treatment: The green blank is subjected to debinding treatment and sintered by step heating. The debinding green blank is then sintered to obtain a 96 alumina ceramic substrate.

2. The method for preparing a 96% alumina ceramic substrate according to claim 1, characterized in that: In step S1.1, the raw material pretreatment also includes drying the high-purity alumina powder at a temperature of 115℃-125℃ for at least 4 hours, and dividing it into two parts, namely the first part of high-purity alumina powder and the second part of high-purity alumina powder. The mixed powder, the first part of high-purity alumina powder, and anhydrous ethanol are ball-milled for 2-4 hours to obtain a sintering aid.

3. The method for preparing a 96% alumina ceramic substrate according to claim 1, characterized in that, In step S1.2, obtaining the initial mixed slurry includes: S1.2.1, Mixing the main material: The second part of high-purity alumina powder after drying and pretreatment with a mass ratio of 191:9-193:7 is mixed with the sintering aid to form the main material, and then organic solvent and dispersant are added and stirred evenly to form the main material slurry; S1.2.2 Secondary ball milling: Binder and plasticizer are gradually added to the main material slurry, and the mixture is ball milled for 4-8 hours to obtain the initial mixed slurry.

4. The method for preparing a 96% alumina ceramic substrate according to claim 3, characterized in that: The mass ratio of the organic solvent to the main ingredient is 3:10-4:10, and the mass ratio of the dispersant to the main ingredient is 0.5:100-1:

100. The dispersant is herring oil or phosphate ester.

5. The method for preparing a 96% alumina ceramic substrate according to claim 4, characterized in that: The mass ratio of the binder to the main material slurry is 3:100-5:100; The adhesive is polyvinyl butyral; The plasticizer is polyethylene glycol or dibutyl phthalate, and the mass ratio of the plasticizer to the main slurry is 1:100-2:

100.

6. The method for preparing a 96% alumina ceramic substrate according to claim 1, characterized in that: The drying oven is equipped with a surface drying zone, a main drying zone, and a curing zone. The carrier film is sequentially fed into the surface drying zone, the main drying zone, and the curing zone for zoned drying. The length ratio between the surface drying zone, the main drying zone, and the curing zone is set to 1:2:

1. The temperature of the surface drying zone is set to 25℃-30℃, the temperature of the main drying zone is set to 40℃-45℃, and the temperature of the curing zone is set to 45℃-50℃.

7. The method for preparing a 96% alumina ceramic substrate according to claim 1, characterized in that, In step S3, the sintering densification process includes: S3.1 Debinding treatment: Place the green blank in the sintering furnace, evacuate the inside of the sintering furnace to a vacuum degree of 10Pa-100Pa, introduce high-purity hydrogen gas and maintain the vacuum degree of 10Pa-100Pa, then gradually raise the temperature inside the sintering furnace from room temperature to 600℃, and hold at 600℃ for at least 2 hours. During the holding process, continuously introduce high-purity hydrogen gas and repeat the gas purging process inside the sintering furnace at least twice. S3.2 Step sintering: After raising the internal temperature of the sintering furnace to 1150°C, the green body after the debinding treatment is sintered at 1150°C for at least 1 hour; then the temperature is raised to 1720°C and sintered at 1720°C for 3-4 hours; finally, natural cooling is performed to obtain 96 alumina ceramic substrate.

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