Preparation method of 96 aluminum oxide ceramic substrate

Abstract

The invention relates to the technical field of ceramic manufacturing processes, and particularly discloses a preparation method of a 96 aluminum oxide ceramic substrate, which comprises the following steps: slurry preparation: carrying out ball milling treatment on high-purity aluminum oxide powder, a sintering aid, a binder, a plasticizer, an organic solvent and a dispersing agent, and fully mixing to obtain tape casting slurry; forming a green body, coating a carrier film with the tape casting slurry through a tape casting machine with a wet film which is uniform in thickness and flat in surface, and drying the carrier film through a drying box in a partitioned manner to obtain a cured green body; and sintering densification treatment: carrying out glue removal treatment on the green body, and carrying out stepped heating sintering to obtain the 96 aluminum oxide ceramic substrate. According to the 96 aluminum oxide ceramic substrate prepared by the scheme, a large number of uniform crystal cores can be formed, small crystal grains can be dissolved, large crystal grains grow at a constant speed, and the uniformity of the crystal grain size is ensured, so that scattering of phonons on a crystal boundary can be reduced, and a structural foundation is laid for improvement of heat conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic manufacturing process, in particular to a preparation method of 96 alumina ceramic substrate. BACKGROUND

[0002] Alumina (Al2O3) ceramics are widely used in the fields of electronic packaging, integrated circuit substrate, power module, sensor and high-temperature structural parts, etc. due to its excellent electrical insulation, high thermal conductivity, good mechanical strength, chemical stability and compatibility with metal co-firing. Among them, 96% alumina ceramic (i.e. Al2O3 content is about 96wt%, the rest is mainly SiO2, CaO, MgO and other sintering aids, hereinafter referred to as 96 alumina ceramic) has a good balance between cost, performance and process maturity, and the 96 alumina ceramic substrate made of it has become one of the mainstream materials of medium and high-end electronic ceramic substrates.

[0003] Currently, the preparation of 96 alumina ceramic substrate usually adopts the process route of tape casting or dry pressing combined with high-temperature sintering. Specifically, first, high-purity α-Al2O3 powder is mixed with sintering aids, organic binders, dispersants and solvents to prepare slurry or powder, and then formed into a green body by tape casting, film rolling or die pressing; then the organic components are removed by degassing treatment, and finally sintered and densified in an air atmosphere at 1500°C-1650°C.

[0004] The Chinese invention patent with publication number CN103435358A discloses a kind of before and after adding organic composition in preparation tape casting slurry, and the former adding organic composition includes solvent and dispersant, solvent is at least one of reagent such as ethanol, dispersant is at least one of reagent such as tributyl phosphate;The latter adding organic composition includes solvent, organic binder and plasticizer, solvent is at least one of reagent such as ethanol, plasticizer is at least one of reagent such as polyethylene glycol, and organic binder is mainly polyvinyl butyral. The organic composition can be applied in tape casting process, specifically, ceramic powder, inorganic bonding phase and former adding organic composition are mixed and ball milled, then latter adding organic composition is added for secondary ball milling;Stirring and defoaming obtain tape casting slurry;Adjust the gap of knife edge of casting machine, the casting speed, and make wet blank, after drying, it is peeled off from the carrier tape, and green ceramic tape is prepared. The preparation process of the invention is simple, the preparation period is short, and the quality of the prepared green blank film is stable and not easy to break.

[0005] However, the above patent application scheme and similar technical solutions still have the following disadvantages: due to the fact that the existing preparation process cannot accurately control the key links such as raw material dispersion, molding and sintering, it is easy to cause the sintered body to have inherent defects such as wide grain size distribution, impurity phase enrichment at grain boundaries, and more micropores, and these inherent defects as main scattering centers seriously hinder the phonon heat transfer of lattice vibration, so that the theoretical thermal conductivity potential cannot be released, thereby limiting its application in iterative high-power LED, semiconductor laser and IGBT module and other high-end electronic packaging fields. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of 96 alumina ceramic substrate to solve the problems raised in the background art.

[0007] To achieve the above purpose, the present application provides a preparation method of 96 alumina ceramic substrate, comprising: S1, slurry preparation: high-purity alumina powder with purity not less than 3N grade, sintering aid, binder, plasticizer, organic solvent and dispersant are ball milled and mixed according to the preset proportion to obtain casting slurry, including the following steps: S1.1, raw material pretreatment: high-purity magnesium oxide, silicon dioxide and calcium oxide nano-powder with a mass ratio of 2:1:0.5 are mixed and treated to obtain a mixed powder; The high-purity alumina powder is dried and pretreated, and is divided into two parts, which are the first part of high-purity alumina powder and the second part of high-purity alumina powder; The mixed powder and the first part of high-purity alumina powder are ball milled, and anhydrous ethanol is added for mixing, and the mass ratio of the total amount of the mixed powder and the first part of high-purity alumina powder to anhydrous ethanol is 10:7-10:10, to obtain a sintering aid; S1.2, mixing preparation: the second part of high-purity alumina powder, sintering aid, binder, plasticizer, organic solvent and dispersant are mixed to obtain the initial mixed slurry; S1.3, slurry post-treatment: the initial mixed slurry is vacuum degassed to obtain an intermediate mixed slurry, and the casting slurry viscosity of the intermediate mixed slurry is determined, and the casting slurry viscosity is compared with the preset viscosity threshold range to obtain the casting slurry, specifically: When the casting slurry viscosity is less than the lower threshold value of the preset viscosity threshold range, then the standing time is increased until the casting slurry viscosity is within the preset viscosity threshold range; when the casting slurry viscosity is within the preset viscosity threshold range, then the intermediate mixed slurry is the casting slurry; when the casting slurry viscosity is greater than the upper threshold value of the preset viscosity threshold range, then the organic solvent is added dropwise to the intermediate mixed slurry, and the low-speed stirring is continued until the casting slurry viscosity is within the preset viscosity threshold range; The organic solvent adopts anhydrous ethanol and dimethylbenzene in a mass ratio of 7:3; S2, green body forming: the casting slurry is coated on a carrier film through a casting machine to form a wet film, the thickness of the wet film is uniform and the surface is flat, then the carrier film is dried through a drying box in a partitioned manner to obtain a solidified green body; S3, sintering densification treatment: the green body is subjected to degassing treatment, and the degassed green body is subjected to sintering treatment through stepwise temperature rising sintering to obtain a 96 alumina ceramic substrate.

[0008] Further, in the step S1.1, the raw material pretreatment further includes drying treatment of the high-purity alumina powder at a temperature of 115-125 DEG C for at least 4 hours, and the high-purity alumina powder is divided into two parts, i.e., a first part of high-purity alumina powder and a second part of high-purity alumina powder; The mixed powder, the first part of high-purity alumina powder and anhydrous ethanol are subjected to ball milling treatment for 2-4 hours to fully mix to obtain a sintering aid.

[0009] Further, in the step S1.2, the initial mixed slurry is obtained, including: S1.2.1, main material mixing: the second part of high-purity alumina powder after drying pretreatment and the sintering aid are mixed in a mass ratio of 191:9-193:7 to form a main material, then an organic solvent and a dispersing agent are added and stirred uniformly to form a main material slurry; S1.2.2, secondary ball milling: the binder and the plasticizer are gradually added to the main material slurry, and ball milling treatment is performed for 4-8 hours to obtain the initial mixed slurry.

[0010] Further, the mass ratio of the organic solvent to the main material is 3:10-4:10, and the mass ratio of the dispersing agent to the main material is 0.5:100-1:100; The dispersing agent adopts herring oil or phosphate ester.

[0011] Further, the mass ratio of the binder to the main material slurry is 3:100-5:100; The binder adopts polyvinyl butyral; The plasticizer adopts polyethylene glycol or dibutyl phthalate, and the mass ratio of the plasticizer to the main material slurry is 1:100-2:100.

[0012] Further, a surface drying area, a main drying area and a curing area are sequentially arranged in the drying box, the carrier film is sequentially sent into the surface drying area, the main drying area and the curing area for partition drying, the length ratio between the surface drying area, the main drying area and the curing area is set as 1:2:1, meanwhile, the temperature of the surface drying area is set as 25-30 DEG C, the temperature of the main drying area is set as 40-45 DEG C, and the temperature of the curing area is set as 45-50 DEG C.

[0013] Further, the sintering densification treatment in the step S3 comprises: S3.1, glue removal treatment: the green body is placed in a sintering furnace, the inside of the sintering furnace is pumped to a vacuum degree of 10-100 Pa, high-purity hydrogen is introduced, and the vacuum degree is maintained at 10-100 Pa, then the sintering furnace is gradually heated from room temperature to 600 DEG C, and the temperature is maintained at 600 DEG C for at least 2 hours, high-purity hydrogen is continuously introduced during the heat preservation process, and the inside of the sintering furnace is repeatedly washed at least 2 times; S3.2, step sintering: the temperature of the inside of the sintering furnace is increased to 1150 DEG C, the green body after the glue removal treatment is sintered at 1150 DEG C for at least 1 hour, then the temperature is continuously increased to 1720 DEG C, and sintering treatment is carried out at 1720 DEG C for 3-4 hours, finally natural cooling is carried out, and a 96 alumina ceramic substrate is obtained.

[0014] Compared with the prior art, the present application has the following beneficial effects: Firstly, a small amount of high-purity alumina powder (i.e. the first part of high-purity alumina powder) is added in the sintering aid, which ensures that it is highly uniformly distributed in the initial mixed slurry, provides a consistent chemical environment for uniform grain growth, and the green body after glue removal treatment is subjected to step sintering, which not only forms a large number of uniform crystal cores, but also makes small grains dissolve and large grains grow uniformly, further ensuring the uniformity of grain size, thereby reducing the scattering of phonons on the grain boundary, and laying a structural foundation for the improvement of thermal conductivity. Secondly, the sintering aid is prepared by high-purity magnesium oxide, silicon dioxide and calcium oxide nano powder, which not only forms an appropriate amount of liquid phase with appropriate fluidity during sintering, but also promotes densification while avoiding excessive glass phase residue. Thirdly, the inside of the sintering furnace is repeatedly washed by high-purity hydrogen, which can reduce the trace amount 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 boundary. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Figure 1 is a microstructure diagram of a traditional process; Figure 2 Figure 2 is a microstructure diagram of a process corresponding to the preparation method in the present application; Figure 3 Figure 3 is a comparison diagram of thermal conductivity of a substrate in the present application. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0017] The present embodiment provides a preparation method of a 96 alumina ceramic substrate, which specifically comprises the following steps: S1, slurry preparation: high-purity alumina powder with a purity not less than 3N grade, sintering aid, binder, plasticizer, organic solvent and dispersant are ball milled and fully mixed according to a preset ratio to form a uniform and stable casting slurry. It is worth noting that during the process of fully mixing the raw materials (i.e. high-purity alumina powder, sintering aid, binder, plasticizer, solvent and dispersant), all the raw materials are ball milled for a long time, and the ball milling time is not less than 12 hours.

[0018] S2, green body forming, i.e. the casting slurry obtained in step S1 is processed by a casting process to obtain a corresponding green body. Specifically, the casting process comprises: The obtained casting slurry is slowly poured into the storage tank of the casting machine, and slowly stirred in the storage tank to prevent the casting slurry from settling. At the same time, the casting machine is started to make the carrier film (not shown in the figure, but those skilled in the art should understand the installation method and installation position of the carrier film and the casting machine) connected with the casting machine move at a constant speed, and the casting slurry forms a corresponding slurry dam in front of the casting knife head of the casting machine. Through the movement of the carrier film below the casting knife head, the casting slurry will be scraped by the knife edge of the casting knife head to form a wet film on the carrier film, and the wet film has uniform thickness and smooth surface. In the present embodiment, the thickness of the wet film is determined according to the gap between the knife edge of the casting knife head and the carrier film.

[0019] Then, the carrier film is dried by a drying box to obtain a solidified green body. Specifically, during the drying process, the carrier film is sequentially dried by a surface drying area, a main drying area and a solidification area in the drying box. The length ratio of the surface drying area, the main drying area and the solidification area is set to 1:2:1, and the temperature of the surface drying area is set to 25-30°C, the temperature of the main drying area is set to 40-45°C, and the temperature of the solidification area is set to 45-50°C.

[0020] Step S3: sintering and densification treatment, that is, after the green body obtained in step S2 is subjected to degreasing treatment, the degreasing treated green body is subjected to sintering treatment by stepwise temperature rising sintering, to obtain a 96 alumina ceramic substrate.

[0021] In this embodiment, all raw materials (i.e. high-purity alumina powder, sintering aid, binder, plasticizer, solvent and dispersant) are mixed by ball milling for no less than 12 hours to obtain the corresponding casting slurry.

[0022] The step S1 specifically includes the following steps: Step S1.1: raw material pretreatment: mixing high-purity magnesium oxide, silicon dioxide and calcium oxide nano-powder with a mass ratio of 2:1:0.5 to obtain a mixed powder; The high-purity alumina powder is dried and pretreated and divided into two parts, i.e. a first part of high-purity alumina powder and a second part of high-purity alumina powder; The mixed powder and the first part of high-purity alumina powder are ball milled with a mass ratio of 1:1.5, and anhydrous ethanol is added for mixing, and the mass ratio of the total amount of the mixed powder and the first part of high-purity alumina powder to anhydrous ethanol is 10:7-10:10, to obtain a sintering aid.

[0023] In the step S1.1, the raw material pretreatment further includes drying the high-purity alumina powder at a temperature of 115-125°C for at least 4 hours.

[0024] The high-purity alumina powder drying method is: high-purity alumina powder is dried by a forced air drying oven. In this embodiment, the high-purity alumina powder is evenly laid on the drying tray of the forced air drying oven, and the thickness of the laid high-purity alumina powder layer is not more than 2 cm, then the drying tray is placed in the forced air drying oven which has been preheated to 115-125℃, to carry out drying and dehumidification treatment in the forced air drying oven. Specifically, the forced air drying oven is used to dry the high-purity alumina powder at a temperature of 115-125℃ for at least 4 hours. After the drying treatment is completed, the high-purity alumina powder is naturally cooled in the forced air drying oven until the temperature is not higher than 50℃, so that the dried high-purity alumina powder is taken out of the forced air drying oven, and the dried high-purity alumina powder is stored by sealing through a desiccator.

[0025] S1.2: Mixing preparation: the second part of high-purity alumina powder, sintering aid, binder, plasticizer, organic solvent and dispersant are mixed to obtain an initial mixed slurry, specifically as follows: S1.2.1: Main material mixing: the second part of high-purity alumina powder after drying pretreatment and the sintering aid are mixed in a mass ratio of 191:9-193:7 to form a main material, then the organic solvent and the dispersant are added and stirred uniformly to form a main material slurry; S1.2.2: Secondary ball milling: the binder and the plasticizer are gradually added to the main material slurry, and ball milling treatment is carried out for 4-8 hours to obtain an initial mixed slurry.

[0026] The mass ratio of the organic solvent to the main material is 3:10-4:10, and the mass ratio of the dispersant to the main material is 0.5:100-1:100, and the dispersant is herring oil or phosphate ester.

[0027] Through the adsorption between the dispersant and the surfaces of various powders (including high-purity alumina powder, high-purity magnesium oxide, silicon dioxide and calcium oxide nano-powder) in the initial mixed main material, a double electric layer or a steric hindrance effect can be formed to prevent the agglomeration of the powders in the initial mixed main material, so that the powders in the initial mixed main material can be fully dispersed in the organic solvent.

[0028] The binder in this embodiment is set to polyvinyl butyl, and the mass ratio of the binder to the main material slurry is 3:100-5:100.

[0029] The plasticizer in this embodiment is set to polyethylene glycol or dibutyl phthalate, and the mass ratio of the plasticizer to the main material slurry is 1:100-2:100.

[0030] Step S1.3: slurry post-processing: the initial mixed slurry is subjected to vacuum degassing treatment to obtain an intermediate mixed slurry, and the casting slurry viscosity of the intermediate mixed slurry is determined, and the casting slurry viscosity is compared with a preset viscosity threshold range to obtain a casting slurry, specifically: When the casting slurry viscosity is less than the lower threshold value of the preset viscosity threshold range, the standing time is increased until the casting slurry viscosity is within the preset viscosity threshold range; when the casting slurry viscosity is within the preset viscosity threshold range, the intermediate mixed slurry is the casting slurry; when the casting slurry viscosity is greater than the upper threshold value of the preset viscosity threshold range, an organic solvent is added to the intermediate mixed slurry, and low-speed stirring is continued until the casting slurry viscosity is within the preset viscosity threshold range.

[0031] It is worth noting that the intermediate mixed slurry obtained is subjected to viscosity measurement at a rotational speed of 20 revolutions / minute by a rotary viscometer to obtain the casting slurry viscosity of the intermediate mixed slurry. Specifically, the obtained casting slurry viscosity is compared with a preset viscosity threshold range (which can be specifically set according to actual needs, so it is not specifically described in this embodiment, for example, 1500 mPa·s-2500 mPa·s) to obtain the final mixed slurry, i.e. the casting slurry. Specifically: When the obtained casting slurry viscosity is less than the lower threshold value (i.e. 1500 mPa·s) of the preset viscosity threshold range, the standing time is increased until the obtained casting slurry viscosity is within the preset viscosity threshold range. When the obtained casting slurry viscosity is 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 obtained casting slurry viscosity is greater than the upper threshold value (i.e. 2500 mPa·s) of the preset viscosity threshold range, an organic solvent is added to the intermediate mixed slurry, and low-speed stirring is continued until the obtained casting slurry viscosity is within the preset viscosity threshold range.

[0032] In the step S3, the sintering densification treatment includes the following steps: S3.1, degassing treatment: the green body is placed in a sintering furnace, the inside of the sintering furnace is pumped to a vacuum degree of 10 Pa-100 Pa, high-purity hydrogen is introduced, and the vacuum degree is maintained at 10 Pa-100 Pa, then the sintering furnace is gradually heated from room temperature to 600°C, and the temperature is maintained at 600°C for at least 2 hours, and high-purity hydrogen is continuously introduced during the heat preservation process. The inside of the sintering furnace is repeatedly washed at least 2 times.

[0033] It should be noted that the gap between two adjacent green bodies is greater than 5mm, and the green body should be placed in the effective temperature zone of the sintering furnace for degassing treatment.

[0034] More specifically, in the effective temperature zone of the sintering furnace, the temperature of the effective temperature zone is raised from room temperature to 300℃ at a rate of 0.5℃ / min-1℃ / min, and then the temperature of the effective temperature zone is raised from 300℃ to 600℃ at a rate of 1℃ / min-2℃ / min.

[0035] In addition, the rate of high-purity hydrogen gas entering the sintering furnace is 0.5L / min-1L / min.

[0036] S3.2, step sintering: the internal temperature of the sintering furnace is raised to 1150℃ at a rate of at least 4℃ / min, and then the degassed green body is sintered at a temperature of 1150℃ for at least 1 hour; then continue to raise the temperature at a rate of at most 1℃ / min to 1720℃, and sinter at a temperature of 1720℃ for 3-4 hours; finally, natural cooling is carried out to obtain a 96 alumina ceramic substrate.

[0037] Reference Figure 1 and Figure 2 It can be seen that: The alumina grain size distribution of the 96 alumina ceramic substrate prepared by the traditional process is wide, ranging from 0.3μm to 1.5μm. The alumina grain size distribution of the 96 alumina ceramic substrate obtained by the preparation method is uniform, ranging from 0.5μm to 0.8μm. Therefore, compared with the traditional process, the preparation method in this embodiment optimizes the alumina grain size distribution index and improves the uniformity of the alumina grain. At the same time, the porosity is reduced from more than 1% in the traditional process to less than 1%, greatly reducing the defect density. Similarly, the number of grain boundary impurity phases is also reduced, achieving the effect of grain boundary purification and improving the grain boundary quality.

[0038] Reference Figure 3 It can be seen that the thermal conductivity of the preparation method in this embodiment is improved from 24.5W / m·K-25W / m·K in the traditional process to 28.5W / m·K, achieving a performance improvement of about 16.3%, thereby successfully breaking through the technical bottleneck that the thermal conductivity of 96 alumina ceramic has been long stagnant at 24W / m·K-25W / m·K.

[0039] Although embodiments of the present application 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 therein without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing a 96 alumina ceramic substrate, characterized by, Comprise: S1, slurry preparation: high purity alumina powder with purity not less than 3N level and sintering aid, binder, plasticizer, organic solvent and dispersant are ball milled and mixed according to the preset proportion, and the tape casting slurry is obtained, comprising the following steps: S1.1, raw material pretreatment: high purity magnesium oxide, silicon dioxide and calcium oxide nano powder with mass ratio of 2:1:0.5 are mixed to obtain mixed powder; The high-purity alumina powder is dried and pretreated, and is divided into two parts, which are the first part of high-purity alumina powder and the second part of high-purity alumina powder; And the mixed powder and the first part of high-purity alumina powder are ball milled, and anhydrous ethanol is added for mixing, the mass ratio of the mixed powder, the first part of high-purity alumina powder and anhydrous ethanol is 10:7-10:10, to obtain sintering aid; S1.2, mixing preparation: the second part of high-purity alumina powder, sintering aid, binder, plasticizer, organic solvent and dispersant are mixed to obtain the initial mixed slurry; S1.3, slurry post-treatment: the initial mixed slurry is vacuum degassed to obtain the intermediate mixed slurry, and the tape casting slurry viscosity of the intermediate mixed slurry is determined, and the tape casting slurry viscosity is compared with the preset viscosity threshold range to obtain the tape casting slurry, specifically: When the tape casting slurry viscosity is less than the lower limit threshold of the preset viscosity threshold range, the standing time is increased until the tape casting slurry viscosity is within the preset viscosity threshold range; When the tape casting slurry viscosity is within the preset viscosity threshold range, the intermediate mixed slurry is the tape casting slurry; When the tape casting slurry viscosity is greater than the upper limit threshold of the preset viscosity threshold range, organic solvent is added to the intermediate mixed slurry, and low-speed stirring is continued until the tape casting slurry viscosity is within the preset viscosity threshold range; The organic solvent is anhydrous ethanol and dimethylbenzene with a mass ratio of 7:3; S2, green body forming: the tape casting slurry is coated on the carrier film by the flow coater to form a wet film, the thickness of the wet film is uniform and the surface is flat, then the carrier film is dried by the drying oven to obtain the solidified green body; S3, sintering and densification treatment: the green body is degassed, and the degassed green body is sintered by stepwise temperature rising to obtain the 96 alumina ceramic substrate.

2. The preparation method of the 96 alumina ceramic substrate according to claim 1, wherein: In step S1.1, the raw material pretreatment further comprises drying the high-purity alumina powder at a temperature of 115-125℃ for at least 4 hours, and dividing it into two parts, which are 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 the sintering aid.

3. The method of claim 1, wherein the 96 alumina ceramic substrate is prepared by the steps of: In step S1.2, the initial mixed slurry is obtained, which comprises: ​ S1.2.1, main material mixing: the mass ratio of the second part of the dried pretreated high-purity alumina powder to the sintering aid is 191:9-193:7, then the organic solvent and the dispersant are added and stirred uniformly to form a main material slurry; S1.2.2, secondary ball milling: the binder and the plasticizer are gradually added to the main material slurry and ball milled for 4-8 hours to obtain an initial mixed slurry.

4. The preparation method of the 96 alumina ceramic substrate according to claim 3, characterized in that: The mass ratio of the organic solvent to the main material is 3:10-4:10, and the mass ratio of the dispersant to the main material is 0.5:100-1:100; The dispersant is herring oil or phosphate ester.

5. The preparation method of the 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 binder is polyvinyl butyral; The plasticizer is polyethylene glycol or dibutyl phthalate, and the mass ratio of the plasticizer to the main material slurry is 1:100-2:

100.

6. The preparation method of the 96 alumina ceramic substrate according to claim 1, characterized in that: The drying box is sequentially provided with a surface drying zone, a main drying zone and a curing zone, and the carrier film is sequentially sent into the surface drying zone, the main drying zone and the curing zone for partition drying, the length ratio between 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℃.

7. The method of claim 1, wherein the 96 alumina ceramic substrate is prepared by the steps of: In step S3, the sintering densification treatment includes: ​ S3.1, degassing treatment: the green body is placed in a sintering furnace, the inside of the sintering furnace is pumped to a vacuum degree of 10-100 Pa, high-purity hydrogen is introduced, and the vacuum degree is maintained at 10-100 Pa, then the temperature in the sintering furnace is gradually increased from room temperature to 600℃, and the temperature is maintained at 600℃ for at least 2 hours, and high-purity hydrogen is continuously introduced during the temperature maintaining process, and the inside of the sintering furnace is repeatedly washed at least 2 times; S3.2, step sintering: the temperature in the inside of the sintering furnace is increased to 1150℃, then the green body after the degassing treatment is sintered at 1150℃ for at least 1 hour, then the temperature is continuously increased to 1720℃, and sintered at 1720℃ for 3-4 hours, and finally naturally cooled to obtain a 96 alumina ceramic substrate.

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