An alumina ceramic substrate, its preparation method and application

Abstract

This disclosure provides an alumina ceramic substrate, its preparation method, and its application, belonging to the technical field of ceramic circuit boards. The preparation method of the alumina ceramic substrate includes the following steps: mixing abrasive and a grinding solvent, performing a first ball milling, mixing the resulting first mixture with a binder, performing a second ball milling, adding a defoamer to the resulting second mixture, and performing defoaming and aging treatments to obtain a slurry; wherein the abrasive is alumina powder and a dispersant, and the dispersant is polyvinyl acetate and sodium silicate; casting the obtained slurry on a casting machine to form an alumina green body, and then forming an alumina ceramic blank; sintering the obtained alumina ceramic blank to obtain the alumina ceramic substrate. The preparation method of the alumina ceramic substrate disclosed herein can significantly improve the toughness and strength of the alumina green body.

Description

Technical Field

[0001] This disclosure relates to the field of ceramic circuit board technology, specifically to an alumina ceramic substrate, its preparation method, and its application. Background Technology

[0002] Alumina electronic ceramic substrates possess high mechanical strength and are suitable for high pressure, high temperature, wear resistance, and strong corrosion resistance, making them widely applicable in various fields such as machinery, chemical industry, medical, and industrial electronics. The main methods for preparing alumina electronic ceramic substrates include dry pressing, extrusion molding, gel casting, slip casting, and isostatic pressing.

[0003] Currently, industrial methods for preparing alumina green bodies with a thickness of 200-500μm have certain drawbacks. These drawbacks include difficulty in controlling the strength and toughness, making it inconvenient to adjust them; the resulting green bodies have low strength, and the density and uniformity of the green bodies are relatively poor. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an alumina ceramic substrate, its preparation method, and its application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing an alumina ceramic substrate, comprising the following steps:

[0006] Preparation of slurry: The grinding material and grinding solvent are mixed and ball-milled for the first time. The resulting first mixture is mixed with the binder and ball-milled for the second time. The resulting second mixture is mixed with a defoamer and subjected to defoaming and aging treatments to obtain the slurry. The grinding material is alumina powder and a dispersant, and the dispersant is polyvinyl acetate and sodium silicate.

[0007] The obtained slurry is cast into alumina green on a casting machine, and then made into alumina ceramic blanks;

[0008] The obtained alumina ceramic blank is sintered to obtain the alumina ceramic substrate.

[0009] In this disclosure, during the preparation of the slurry, alumina powder, dispersant, and grinding solvent are first ball-milled. The specific dispersant can effectively disperse the particles or powder uniformly in the liquid, thereby forming a stable suspension or emulsion, and can increase the surface activity of the particles or powder, effectively preventing them from settling or agglomerating in the liquid, thus allowing the alumina powder to be uniform in the slurry and improving the slurry's fluidity, enabling the powder and colloid to better combine during the molding process, thereby improving the strength and toughness of the alumina green body. In addition, the dispersant can also promote film formation on the surface of the green body, improve the smoothness of the green body surface, thereby further improving the strength and toughness of the alumina ceramic green body. Adding defoamers during the degassing process has two main benefits. First, defoamers easily spread on the solution surface and automatically expand on the foam surface, carrying away a layer of solution from adjacent surfaces. This causes the liquid film to thin locally, reaching a critical thickness where the liquid film ruptures and the foam is destroyed. Defoamers also inhibit the formation of bubbles in the slurry, significantly reducing the number of bubbles inside the slurry during the molding process and increasing the density of the green body. Second, defoamers can also increase the viscosity of the slurry during the preparation process. These two aspects work together to improve the strength and toughness of the alumina ceramic green body without the need to add sintering aids.

[0010] In one embodiment, the mass of the dispersant is 0.01-0.4% of the mass of the alumina powder; preferably 0.1-0.2%.

[0011] In this disclosure, the amount of dispersant added affects the dispersibility of alumina powder and the compatibility of alumina powder with other components. If the amount of dispersant added is too small, the alumina powder will not be uniformly dispersed in the slurry, resulting in a decrease in the toughness and strength of the alumina green body. If the amount of dispersant added is too large, the defoamer in the degassing process will not be able to effectively degas, thereby increasing the porosity of the alumina green body and decreasing its toughness and strength. When the mass of the dispersant is 0.4-0.8% of the mass of the alumina powder, the resulting alumina ceramic green body has high strength and toughness.

[0012] In one embodiment, the viscosity of the polyvinyl acetate is 5000 mPa·s-7000 mPa·s; for example, it can be 5000 mPa·s, 5500 mPa·s, 6000 mPa·s, 6500 mPa·s, or 7000 mPa·s, but is not limited to the listed values, and other resins in this range are also applicable.

[0013] The viscosity of the sodium silicate is 6000-8000 mPa·s, for example, it can be 5000 mPa·s, 5500 mPa·s, 6000 mPa·s, 6500 mPa·s, 7000 mPa·s, 7500 mPa·s, or 8000 mPa·s, but it is not limited to the listed values. Other resins in this range are also applicable.

[0014] In one embodiment, the polyvinyl acetate has a pH of 4-5, and the sodium silicate has a pH of 11-13;

[0015] Specifically, this disclosure uses polyvinyl acetate and sodium silicate to adjust the viscosity and pH of the first mixture. When the viscosity and pH of polyvinyl acetate and sodium silicate are within the above range, alumina green embryos with better strength and toughness can be obtained.

[0016] In one embodiment, the mass ratio of polyvinyl acetate to sodium silicate is (1-3):1; for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, or 3:1, but is not limited to the listed values, and other resins within this range are also applicable. In this disclosure, when the mass ratio of polyvinyl acetate to sodium silicate is (1-3):1, alumina green blanks with higher strength and toughness can be obtained.

[0017] In one embodiment, the mass of the binder is 20-35% of the mass of the alumina powder; and / or, the mass of the defoamer is 0.01-0.1% of the mass of the alumina powder.

[0018] In one embodiment, the adhesive is at least one of polyacrylate and polyurethane; the defoamer is polyether-modified polysiloxane.

[0019] In one implementation, the conditions for the first ball milling are as follows:

[0020] The mass ratio of abrasive to grinding balls is 1:(1-2).

[0021] And / or, the diameter of the grinding balls is 5-20 mm; further, the grinding balls are composed of grinding balls with diameters of 10 mm, 15 mm, and 20 mm, and the mass ratio of grinding balls with diameters of 10 mm, 15 mm, and 20 mm is 1:1:1. Selecting grinding balls of different diameters for ball milling can further improve the dispersibility of alumina powder, reduce the generation of agglomerated particles in the slurry, and improve the fluidity of the slurry.

[0022] And / or, the mass of the grinding solvent is 40-50% of the grinding material;

[0023] And / or, the grinding balls are zirconia balls;

[0024] And / or, the ball mill speed is 150-300 rpm;

[0025] And / or, the ball milling time is 9-12 hours;

[0026] And / or, the volume of the grinding solvent, abrasive, and grinding balls is 50-70% of the volume of the grinding jar.

[0027] In one embodiment, the grinding solvent is at least one selected from ethanol, propanol, isopropanol, ethylene glycol, n-butanol, isobutanol, tert-butanol, and toluene.

[0028] In one embodiment, the conditions for the second ball milling are as follows: the ball milling time is 14-16 hours; the ball milling speed is 200-400 rpm.

[0029] In one embodiment, the degassing treatment conditions are as follows: the degassing time is 30 min to 2 h, and the degassing pressure is less than -0.09 MPa.

[0030] In one embodiment, the aging conditions are as follows: the aging time is 2-6 hours.

[0031] In one embodiment, the casting conditions are as follows: the casting temperature is 40-80℃, the casting speed is 0.2-0.5M / min, the scraper height is 550-750μm, and the filter accuracy is 0.5-5μm.

[0032] In one embodiment, the thickness of the embryo is 200 μm-500 μm; more preferably, the thickness of the embryo is 300 μm-400 μm.

[0033] In the sintering process of the alumina ceramic substrate preparation method, the heating rate is 0.2-1℃ / min. When the heating rate is less than 0.2℃ / min, the heating rate is too slow, which easily leads to the formation of impurity phases; when the heating rate is greater than 1℃ / min, the heating rate is too fast, resulting in undercooked grains, large grain size differences, and poor uniformity. More preferably, in the sintering process of the alumina ceramic substrate preparation method, the heating rate is 0.4-0.7℃ / min.

[0034] Specifically, in the sintering process of the alumina ceramic substrate preparation method, the sintering temperature is 1400-1600℃. When the sintering temperature is less than 1400℃, the sintering temperature is too low, resulting in more fragmented grains in the ceramic, low strength, and poor density. When the sintering temperature is greater than 1600℃, the sintering temperature is too high, leading to local over-burning and the formation of abnormally large grains, resulting in decreased density and strength.

[0035] Specifically, in the sintering process of the alumina ceramic substrate preparation method, the holding time at the sintering temperature is 4-7 hours. Too short a holding time will result in insufficient sintering; too long a holding time will easily lead to over-firing. Therefore, a holding time of 4-7 hours is a suitable range.

[0036] Preferably, in the sintering process of the alumina ceramic substrate preparation method, the cooling rate is 0.2-1.5℃ / min. When the cooling rate is greater than 1.5℃ / min, the cooling rate is too fast, resulting in uneven sintering and ceramic breakage; when the cooling rate is less than 0.2℃ / min, the cooling rate is too slow, leading to high energy consumption and high cost. More preferably, in the sintering process of the alumina ceramic substrate preparation method, the cooling rate is 0.4-0.5℃ / min.

[0037] On the other hand, an alumina ceramic substrate is provided, which is prepared by the method for preparing the alumina ceramic substrate.

[0038] In one aspect, the application of the aforementioned alumina ceramic substrate in thin-film integrated circuits is provided.

[0039] Specifically, the ceramic substrate is used in the fabrication of MOSFETs, IGBTs, transistors, chips, electronic heaters, or high-frequency switching power supplies.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. The alumina ceramic base provided in this disclosure has high strength and toughness. Its preparation process is simple and easy to operate and control, and its application prospects are very broad.

[0042] 2. This disclosure selects specific dispersants and defoamers and controls the amount of dispersants and defoamers added to improve the density, uniformity, strength and toughness of alumina green blanks through casting molding. Attached Figure Description

[0043] Figure 1 This is a scanning electron microscope image of the plane of the alumina green embryo obtained in Example 1;

[0044] Figure 2 Scanning electron microscope image of a cross-section of alumina green embryo;

[0045] Figure 3 This is a scanning electron microscope image of the alumina green ceramic substrate obtained in Example 1;

[0046] Figure 4 This is a scanning electron microscope (SEM) image of a cross-section of an alumina ceramic substrate. Detailed Implementation

[0047] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0048] Example 1

[0049] This embodiment provides a method for preparing an alumina ceramic substrate, including the following steps:

[0050] (1) Ball milling: 1.75 kg toluene, 1.4 kg anhydrous ethanol, 0.004 kg polyvinyl acetate, 0.004 kg sodium silicate, and 7 kg alumina powder were added sequentially to a 15L ball milling jar. Then, 6 kg of zirconia balls were added. The zirconia balls were composed of zirconia balls with diameters of 10 mm, 15 mm, and 20 mm in a mass ratio of 1:1:1. The mixture was ball milled at 250 rpm for 12 hours. The first mixture was then mixed with 2.45 kg of acrylic polyester and ball milled at 400 rpm for 16 hours to obtain the second mixture.

[0051] (2) Degassing and aging: In a 20L degassing reactor, the second mixture and 0.0008 kg of polyether modified polysiloxane were added. Degassing was carried out for 1 hour under the conditions of a stirring speed of 20Hz and a vacuum pressure of -0.09Mpa. The vacuum pump was then turned off, and the mixture was aged for 4 hours under the conditions of a stirring speed of 5Hz and a temperature of 22℃ to obtain the slurry.

[0052] (3) Casting: After the aging process is completed, the negative pressure is removed, the degassing reactor is pressurized to 0.08 MPa, and the slurry is added to the casting machine hopper for discharge. The filter uses two types of filters with a precision of 0.5 μm and 1 μm to filter impurities. Then the casting machine drying tunnel adopts a three-stage drying mode with temperatures of 40℃, 50℃ and 60℃. The casting film belt is turned on and the speed is adjusted to 0.3 M / Min for casting. The scraper height is adjusted to 600 to produce a uniform alumina green blank with a thickness of 230 μm.

[0053] (4) Molding: The green blank is cut to obtain a sheet green blank with a width of 160mm. The obtained sheet green blank is dried at 120℃ for 5h in a flat manner; then cooled, the obtained product is placed in a mold and punched into blanks with a size of 140*140mm.

[0054] (5) Sintering: The blanks are stacked in 8 layers on the ceramic refractory firing plate and then placed in the integrated grate firing furnace. The temperature is raised to 1500℃ at a heating rate of 0.62℃ / min and held for 5 hours. After the holding period, the temperature is lowered to 600℃ at a cooling rate of 0.4℃ / min and then naturally cooled to room temperature to obtain the alumina ceramic substrate.

[0055] Example 2

[0056] This embodiment provides a method for preparing an alumina ceramic substrate, including the following steps:

[0057] (1) Ball milling: 1.75 kg toluene, 1.4 kg anhydrous ethanol, 0.004 kg polyvinyl acetate, 0.004 kg sodium silicate, and 7 kg alumina powder were added sequentially to a 15L ball milling jar. Then, 6 kg of zirconia balls were added. The zirconia balls were composed of zirconia balls with diameters of 10 mm, 15 mm, and 20 mm in a mass ratio of 1:1:1. The mixture was ball milled at 300 rpm for 9 hours. The first mixture was then mixed with 1.4 kg of acrylic polyester and ball milled at 200 rpm for 14 hours to obtain the second mixture.

[0058] (2) Degassing and aging: In a 20L degassing reactor, the second mixture and 0.007kg of polyether-modified polysiloxane were added. Degassing was carried out for 2 hours under the conditions of a stirring speed of 20Hz and a vacuum pressure of -0.09Mpa. The vacuum pump was then turned off, and the mixture was aged for 2 hours under the conditions of a stirring speed of 5Hz and a temperature of 26℃ to obtain the slurry.

[0059] (3) Casting: After the aging process is completed, the negative pressure is removed, the degassing reactor is pressurized to 0.08 MPa, and the slurry is added to the casting machine hopper for discharge. The filter uses two types of filters with a precision of 0.5 μm and 1 μm to filter impurities. Then the casting machine drying tunnel adopts a three-stage drying mode with temperatures of 40℃, 50℃ and 60℃. The casting film belt is turned on and the speed is adjusted to 0.5 M / Min for casting. The scraper height is adjusted to 600 to produce a uniform alumina green blank with a thickness of 500 μm.

[0060] (4) Molding: The green blank is cut to obtain a sheet green blank with a width of 160mm. The obtained sheet green blank is dried at 120℃ for 5h in a flat manner; then cooled, the obtained product is placed in a mold and punched into blanks with a size of 140*140mm.

[0061] (5) Sintering: The blanks are stacked in 4 layers on the ceramic refractory firing plate and then placed in the integrated grate furnace. The temperature is raised to 1600℃ at a heating rate of 0.62℃ / min and held for 4 hours. After the holding period, the temperature is lowered to 600℃ at a cooling rate of 0.4℃ / min and then naturally cooled to room temperature to obtain the alumina ceramic substrate.

[0062] Example 3

[0063] This embodiment provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that: in step (1), the mass of polyvinyl acetate is 0.007 kg and the mass of sodium silicate is 0.007 kg, while the other components and steps are the same as in Example 1.

[0064] Example 4

[0065] This embodiment provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that: in step (1), the mass of polyvinyl acetate is 0.014 kg and the mass of sodium silicate is 0.014 kg, while the other components and steps are the same as in Example 1.

[0066] Example 5

[0067] This embodiment provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that: in step (1), the mass of polyvinyl acetate is 0.00035 kg and the mass of sodium silicate is 0.00035 kg, while the other components and steps are the same as in Example 1.

[0068] Example 6

[0069] This embodiment provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that: in step (1), the mass of polyvinyl acetate is 0.006 kg and the mass of sodium silicate is 0.002 kg, while the other components and steps are the same as in Example 1.

[0070] Example 7

[0071] This embodiment provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that: in step (1), the mass of polyvinyl acetate is 0.0064 kg and the mass of sodium silicate is 0.0016 kg, while the other components and steps are the same as in Example 1.

[0072] Comparative Example 1

[0073] This comparative example provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that step (1) is different. Step (1) in this comparative example is as follows: 1.75 kg toluene, 1.4 kg anhydrous ethanol, 0.008 kg polyvinyl acetate, and 7 kg alumina powder are added sequentially to a 15 L ball mill jar, followed by 6 kg of zirconia balls. The zirconia balls are composed of zirconia balls with diameters of 10 mm, 15 mm, and 20 mm in a mass ratio of 1:1:1. The mixture is ball-milled at 300 rpm for 9 h. The first mixture is then mixed with 1.4 kg of acrylic polyester and ball-milled at 200 rpm for 14 h to obtain the second mixture. All other steps are the same as in Example 1.

[0074] Comparative Example 2

[0075] This comparative example provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that step (1) is different. Step (1) in this comparative example is as follows: 1.75 kg toluene, 1.4 kg anhydrous ethanol, 0.008 kg sodium silicate, and 7 kg alumina powder are added sequentially to a 15 L ball mill jar, followed by 6 kg of zirconia balls. The zirconia balls are composed of zirconia balls with diameters of 10 mm, 15 mm, and 20 mm in a mass ratio of 1:1:1. The mixture is ball-milled at 300 rpm for 9 h. The first mixture is then mixed with 1.4 kg of acrylic polyester and ball-milled at 200 rpm for 14 h to obtain the second mixture. All other steps are the same as in Example 1.

[0076] Comparative Example 3

[0077] This comparative example provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that step (1) is different. Step (1) in this comparative example is as follows: 1.75 kg of toluene, 1.4 kg of anhydrous ethanol, and 7 kg of alumina powder are added sequentially to a 15 L ball mill jar, followed by 6 kg of zirconia balls. The zirconia balls are composed of zirconia balls with diameters of 10 mm, 15 mm, and 20 mm in a mass ratio of 1:1:1. The mixture is ball-milled at 300 rpm for 9 h. 1.4 kg of acrylic polyester is added to the first mixture, and the mixture is ball-milled at 200 rpm for 14 h to obtain the second mixture. All other steps are the same as in Example 1.

[0078] Comparative Example 4

[0079] This comparative example provides a method for preparing an alumina ceramic substrate, which differs from the alumina ceramic substrate in Example 1 only in that step (2) is different. In this comparative example, step (2) does not involve the addition of polyether-modified polysiloxane, while the other steps are the same as in Example 1.

[0080] Performance testing

[0081] The viscosity of the slurry obtained in Examples 1-7 and Comparative Examples 1-4, the density, flatness, flexural strength, compressive strength and microstructure of the green body and alumina ceramic substrate were tested.

[0082] The testing method is as follows:

[0083] Viscosity: Rotational viscometer method;

[0084] Density: by displacement method;

[0085] Flatness: measured by micrometer;

[0086] Bending strength: GB / T 6569-2006 Four-point bending method;

[0087] Compressive strength: GB / T4740-1999 Ceramic materials, compressive strength test method;

[0088] Microstructure: Scanning electron microscope.

[0089] The test results are shown in Table 1-2 and Figure 1-4 As shown.

[0090] Table 1. Test results of slurry viscosity and green embryo properties.

[0091]

[0092] Table 2 Performance test results of alumina ceramic substrates

[0093]

[0094] As can be seen from the data in Tables 1 and 2, the alumina green and alumina ceramic substrate prepared in this disclosure have high density, high strength and high toughness.

[0095] Comparing Examples 1 and 2-5, it can be seen that when the mass of the dispersant is 0.01-0.4% of the mass of alumina powder, the resulting alumina green and alumina ceramic substrate have better overall performance. When the mass of the dispersant is 0.1-0.2% of the mass of alumina powder, the resulting alumina green and alumina ceramic substrate have even better overall performance.

[0096] Comparing Examples 1 and 6-7, it can be seen that when the mass ratio of polyvinyl acetate to sodium silicate is (1-3):1, the resulting alumina green and alumina ceramic substrate have better overall performance.

[0097] Comparing Example 1 and Comparative Examples 1-3, it can be seen that polyvinyl acetate and sodium silicate in this disclosure have an interaction that can significantly improve the overall performance of alumina green and alumina ceramic substrate.

[0098] Comparing Examples 1 and 4, it can be seen that when no defoamer is used during the degassing process, the overall performance of the resulting alumina green and alumina ceramic substrate is significantly reduced.

[0099] Figure 1 This is a scanning electron microscope image of the plane of the alumina green embryo obtained in Example 1. Figure 2 Scanning electron microscope image of a cross-section of alumina green embryo; Figure 3 This is a scanning electron microscope image of the alumina green ceramic substrate obtained in Example 1. Figure 4 A scanning electron microscope (SEM) image of a cross-section of an alumina ceramic substrate; from Figure 1 and Figure 3 It can be seen that the alumina green and the alumina ceramic substrate have smooth and flat surfaces; from Figure 2 It can be seen that the bonding density between alumina powders in the alumina green is high; from Figure 4 It can be seen that the alumina ceramic substrate has no pores and has high density.

[0100] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an alumina ceramic substrate, characterized in that, Includes the following steps: The grinding material and grinding solvent are mixed and subjected to a first ball milling. The resulting first mixture is mixed with a binder and subjected to a second ball milling. The resulting second mixture is then treated with a defoamer, followed by degassing and aging to obtain a slurry. The grinding material consists of alumina powder and a dispersant, which is polyvinyl acetate and sodium silicate. The obtained slurry is cast into a green body on a casting machine and then made into alumina ceramic blanks; The obtained alumina ceramic blank is sintered to obtain the alumina ceramic substrate; The mass of the dispersant is 0.01-0.4% of the mass of the alumina powder; The mass ratio of polyvinyl acetate to sodium silicate is (1-3):1; The mass of the defoamer is 0.01-0.1% of the mass of the alumina powder.

2. The preparation method according to claim 1, characterized in that, The mass of the dispersant is 0.1-0.2% of the mass of the alumina powder.

3. The preparation method according to claim 1, characterized in that, The viscosity of the polyvinyl acetate is 5000 mPa·s-7000 mPa·s; and / or the viscosity of the sodium silicate is 6000-8000 mPa·s.

4. The preparation method according to claim 1, characterized in that, The mass of the binder is 20-35% of the mass of the alumina powder.

5. The preparation method according to claim 1, characterized in that, The adhesive is at least one of polyacrylate and polyurethane; the defoamer is polyether-modified polysiloxane.

6. The preparation method according to claim 1, characterized in that, The conditions for the first ball milling are as follows: The mass ratio of abrasive to grinding balls is 1:1 to 1:

2. And / or, the diameter of the grinding balls is 5-20mm; And / or, the mass of the grinding solvent is 40-50% of the grinding material; And / or, the grinding balls are zirconia balls; And / or, the ball mill speed is 150-300 rpm; And / or, the ball milling time is 9-12 hours.

7. The preparation method according to claim 1, characterized in that, The conditions for the second ball milling are as follows: the ball milling time is 14-16 hours; the ball milling speed is 200-400 rpm. And / or, the degassing treatment conditions are as follows: the degassing time is 30 min to 2 h, and the degassing pressure is less than -0.09 MPa; And / or, the aging conditions are as follows: the aging time is 2-6 hours; And / or, the casting conditions are as follows: the casting temperature is 40-80℃, the casting speed is 0.2-0.5m / min, the scraper height is 550-750μm, and the filter accuracy is 0.5-5μm; And / or, the sintering conditions are as follows: the sintering temperature is 1400-1600℃, and the sintering time is 4-7h.

8. An alumina ceramic substrate, characterized in that, It is prepared by the method of any one of claims 1-7.

9. The application of the alumina ceramic substrate as described in claim 8 in thin-film integrated circuits.

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