A low dielectric constant aluminum nitride ceramic substrate and its preparation method

Abstract

The present invention relates to the technical field of ceramic substrates, and provides a low dielectric constant aluminum nitride ceramic substrate and a preparation method thereof. A low dielectric constant aluminum nitride ceramic substrate, the raw materials of which include the following components in parts by weight: 85-105 parts of aluminum nitride, 8-14 parts of sintering aid, 12-16 parts of plasticizer, 6-10 parts of binder, 6-8 parts of dispersant, 14-18 parts of reinforcing agent, and 80-90 parts of solvent; the raw materials of the reinforcing agent include rare earth nitride, rare earth oxide and zinc oxide. Through the above technical solution, the problem of high dielectric constant of aluminum nitride ceramic substrates in the related art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic substrates, and specifically, to a low dielectric constant aluminum nitride ceramic substrate and a preparation method thereof. Background Art

[0002] With the development of electronic devices towards high frequency and high integration, the dielectric properties of packaging materials have become a key factor restricting signal transmission efficiency. Although traditional alumina ceramic substrates have good mechanical strength and insulation, their dielectric constant is relatively high, which easily causes significant energy loss and phase delay in high-frequency signal transmission and is difficult to meet the requirements of fields such as 5G communication and microwave devices. Beryllium oxide ceramics have a relatively low dielectric constant, but their toxicity and high cost limit their wide application. Against this background, aluminum nitride ceramics have become the focus of research due to their inherent advantages.

[0003] The crystal structure of aluminum nitride ceramics endows them with unique electrical properties: the hexagonal wurtzite structure makes their dielectric constant significantly lower than that of alumina, and the dielectric loss is only 1 / 3 to 1 / 2 of that of alumina, showing lower signal attenuation in high-frequency environments. However, there are still bottlenecks in the dielectric properties of aluminum nitride substrates under existing preparation processes. For example, although the sintering aids added during the co-firing process at high temperature can promote densification, they may form high-dielectric phases, resulting in an increase in the overall dielectric constant. In addition, the interaction between conductor materials such as tungsten and molybdenum used in the metallization process and the ceramic interface may introduce parasitic capacitance, further affecting the high-frequency characteristics.

[0004] In summary, although aluminum nitride ceramics perform excellently in terms of thermal conductivity, mechanical properties, etc., their dielectric constant still needs to be further optimized. Therefore, it is of crucial significance to develop an aluminum nitride ceramic substrate that can reduce the dielectric constant. Summary of the Invention

[0005] The present invention provides a low dielectric constant aluminum nitride ceramic substrate and a preparation method thereof, which solve the problem of high dielectric constant of aluminum nitride ceramic substrates in related technologies.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a low dielectric constant aluminum nitride ceramic substrate, and the raw materials include the following components in parts by weight: 85-105 parts of aluminum nitride, 8-14 parts of sintering aid, 12-16 parts of plasticizer, 6-10 parts of binder, 6-8 parts of dispersant, 14-18 parts of reinforcing agent, and 80-90 parts of solvent;

[0008] The raw materials of the reinforcing agent include rare earth nitrides, rare earth oxides, and zinc oxide.

[0009] In the present invention, the rare earth nitride can be any one or more rare earth nitrides, and can be one or more of cerium nitride, scandium nitride, lanthanum nitride, ytterbium nitride, preferably one or two of cerium nitride and scandium nitride.

[0010] In the present invention, the rare earth oxide can be any one or more rare earth oxides, and can be one or more of yttrium oxide, scandium oxide, cerium oxide, samarium oxide, preferably one or two of yttrium oxide and scandium oxide.

[0011] As a further technical solution, the preparation method of the reinforcing agent includes the following steps:

[0012] Mix rare earth nitride, rare earth oxide and zinc oxide, ball mill, and pre-sinter to obtain the reinforcing agent.

[0013] In the present invention, the preparation process of the reinforcing agent forms a precursor composite phase of rare earth nitride, rare earth oxide and zinc oxide through mechanical mixing and pre-sintering. The ball milling process breaks the agglomeration of raw materials, and the pre-sintering promotes the preliminary interaction between components to form an active intermediate phase. The prepared reinforcing agent is more likely to combine with the aluminum nitride matrix during subsequent sintering, avoiding the amorphous high-dielectric layer at the interface. At the same time, the dispersed reinforcing phase effectively hinders the crack propagation, improving the toughness of the material, providing a structural guarantee for the balance of low dielectric constant and high reliability. By mixing and pre-sintering rare earth nitride, rare earth oxide and zinc oxide, the dielectric constant of the aluminum nitride ceramic substrate is further reduced.

[0014] As a further technical solution, the mass ratio of the rare earth nitride, rare earth oxide and zinc oxide is 5 - 7:3:7.

[0015] In the present invention, the mass ratio of the rare earth nitride, rare earth oxide and zinc oxide can be 5.2:3:7, 5.4:3:7, 5.6:3:7, 5.8:3:7, 6:3:7, 6.2:3:7, 6.4:3:7, 6.6:3:7, 6.8:3:7, 7:3:7, preferably 5:3:7, 6:3:7, 7:3:7, and more preferably 6:3:7.

[0016] In the present invention, by adjusting the mass ratio of the rare earth nitride, rare earth oxide and zinc oxide to 5 - 7:3:7, the dielectric constant of the aluminum nitride ceramic substrate is further reduced.

[0017] As a further technical solution, when ball milling, the rotation speed is 600 - 700 rpm and the time is 2 - 3 h;

[0018] When pre-sintering, the temperature is 450 - 550 °C and the time is 4 - 5 h.

[0019] In the present invention, the settings of ball milling and pre-sintering parameters are used to regulate the activity of the reinforcing agent: high-speed ball milling reduces the particle size of the raw materials, and pre-sintering can form a reinforcing agent precursor with a porous structure. The treated reinforcing agent is more easily dispersed in the slurry mixing, and the mixing conditions with the matrix during sintering are milder, avoiding grain coarsening caused by local overheating. At the same time, an appropriate amount of pores are retained to reduce the dielectric constant, achieving the optimization of process controllability and material properties.

[0020] In the present invention, the sintering aid can be any one or more conventional sintering aids, which can be one or more of magnesium oxide, calcium oxide, titanium dioxide, zirconium oxide, silicon dioxide, boron oxide, lithium oxide, and is preferably one or more of magnesium oxide, calcium oxide, zirconium oxide, and titanium dioxide.

[0021] In the present invention, the sintering aid regulates the properties of the ceramic material through multi-dimensional microstructural control. The sintering aid promotes the formation of a liquid phase or enhances atomic diffusion at high temperatures, accelerates the densification process of the green body, reduces pore defects and improves the density of the material. At the same time, the sintering aid can inhibit abnormal grain growth and form a uniform fine-grained structure. This structure not only improves the strength and toughness of the material but also optimizes the thermal expansion coefficient matching and reduces internal stress. In addition, the glass phase or high-melting-point compound formed by the sintering aid can strengthen the grain boundary bonding, block the crack propagation path, and inhibit the oxidation or decomposition reaction of the material at high temperatures, enhancing the long-term stability. The sintering aid can also reduce the sintering temperature, reduce energy consumption and extend the equipment life. At the same time, it cooperates with the binder and dispersant to improve the slurry process performance and enhance the operability of the forming process.

[0022] In the present invention, the plasticizer can be any one or more conventional plasticizers, which can be one or more of polyvinyl alcohol, polyethylene glycol, dioctyl phthalate, dibutyl phthalate, tributyl citrate, acetyl tributyl citrate, and is preferably one or more of dioctyl phthalate, dibutyl phthalate, and polyethylene glycol.

[0023] In the present invention, a plasticizer is added to the raw materials of the low-dielectric-constant aluminum nitride ceramic substrate. When adding the plasticizer, the long-chain molecular structure of the plasticizer unfolds in the solvent and inserts between the ceramic particles and the functional components, reducing the frictional resistance between the particles, significantly improving the slurry fluidity, and ensuring the integrity of the forming of complex shapes. The plasticizer can also form weak interactions with the active sites on the particle surface, enhancing the binding force between the particles, increasing the green body strength, and inhibiting the generation of microcracks during the drying process. Therefore, the introduction of the plasticizer endows the low-dielectric-constant aluminum nitride ceramic substrate with excellent processing performance and mechanical strength.

[0024] In the present invention, the binder can be any one or more conventional binders, and is preferably one or two of polyvinyl butyral and polyvinylpyrrolidone.

[0025] In the present invention, a binder is added to the raw materials of the low dielectric constant aluminum nitride ceramic substrate. When adding the binder, the binder forms a continuous network in the solvent, effectively bonding the ceramic powder and the functional components, ensuring the shape integrity of the green body during the forming process. The binder molecules form chemical adsorption or oxygen bonds with the particle surface, enhancing the bonding force between particles, improving the green body strength, meeting the requirements of subsequent processing. Moreover, the decomposition temperature of the binder and the solvent volatilization characteristics are synergistically regulated to form a gradient pore structure, promoting the discharge of residual organic matter. The decomposition products escape through the microchannels, avoiding the defect of closed pores, ensuring that the density of the sintered material reaches an ideal level, improving the integrity of the green body structure, and preventing the green body from cracking during the drying process.

[0026] In the present invention, the dispersant can be any one or more conventional dispersants, preferably dibutyl phosphate.

[0027] In the present invention, a dispersant is added to the raw materials of the low dielectric constant aluminum nitride ceramic substrate. When the dispersant is dibutyl phosphate, the phosphate group in its molecular structure undergoes coordination adsorption with the surface of aluminum nitride particles, forming an organic coating layer, effectively reducing particle agglomeration, providing a uniform microstructure basis for subsequent sintering. In addition, in the ethanol solvent system, dibutyl phosphate and the plasticizer synergistically optimize the rheological properties of the slurry, ensuring the uniform distribution of components during the forming process, and giving full play to the effect of the enhancer, improving the mechanical strength of the low dielectric constant aluminum nitride ceramic substrate.

[0028] As a further technical solution, the solvent includes one of ethanol and isopropanol.

[0029] As a further technical solution, when the sintering aid is zirconia and titanium dioxide, the zirconia and titanium dioxide are surface-treated zirconia and titanium dioxide;

[0030] The raw materials of the surface-treated zirconia and titanium dioxide include zirconia, titanium dioxide, and 5-hydroxy nicotinic acid.

[0031] As a further technical solution, the preparation method of the surface-treated zirconia and titanium dioxide includes the following steps:

[0032] Add zirconia and titanium dioxide into ethanol, add 5-hydroxy nicotinic acid, stir until uniform, and dry to obtain surface-treated zirconia and titanium dioxide;

[0033] When stirring, the temperature is 40~50 °C.

[0034] In the present invention, the sintering aid is zirconia and titanium dioxide surface-treated with 5-hydroxy nicotinic acid. The surface treatment improves the dispersibility of the sintering aid in the system, prevents the agglomeration of the sintering aid, makes the mixing of the sintering aid and aluminum nitride more uniform. Moreover, the surface treatment process is carried out at 40-50 °C to ensure the full interaction of 5-hydroxy nicotinic acid molecules with zirconia and titanium dioxide. Low-temperature stirring avoids the decomposition of organic substances, and the ethanol solvent promotes molecular diffusion. The formed nano-level organic layer completely volatilizes during debinding, leaving only uniformly dispersed zirconia and titanium dioxide particles. The low-dielectric-constant aluminum nitride ceramic substrate formed by sintering is more compact and evenly distributed, reducing the pores of the low-dielectric-constant aluminum nitride ceramic substrate. Therefore, the flexural strength of the low-dielectric-constant aluminum nitride ceramic substrate is improved.

[0035] As a further technical solution, the mass ratio of zirconia, titanium dioxide, and 5-hydroxy nicotinic acid is 20:70:4-7.

[0036] In the present invention, the mass ratio of zirconia, titanium dioxide, and 5-hydroxy nicotinic acid can be 20:70:4, 20:70:4.2, 20:70:4.4, 20:70:4.6, 20:70:4.8, 20:70:5, 20:70:5.2, 20:70:5.4, 20:70:5.6, 20:70:5.8, 20:70:6, 20:70:6.2, 20:70:6.4, 20:70:6.6, 20:70:6.8, 20:70:7.

[0037] In the present invention, by adjusting the mass ratio of zirconia, titanium dioxide, and 5-hydroxy nicotinic acid to 20:70:4-7, the flexural strength of the low-dielectric-constant aluminum nitride ceramic substrate is further improved. By limiting the proportion of 5-hydroxy nicotinic acid, the surface-treated sintering aid promotes the dispersion of the aid during sintering and avoids carbon residue caused by excessive organic substances, ensuring the insulation and dielectric purity of the final ceramic.

[0038] The present invention also provides a preparation method of a low-dielectric-constant aluminum nitride ceramic substrate for preparing the described low-dielectric-constant aluminum nitride ceramic substrate, comprising the following steps:

[0039] S1. Mix aluminum nitride, a sintering aid, a plasticizer, a dispersant, and a reinforcing agent evenly, add a binder and a solvent, and mix evenly to obtain a slurry.

[0040] S2. Cast and form the slurry, and dry it to obtain a green body.

[0041] S3. Debind and sinter the green body to obtain a low-dielectric-constant aluminum nitride ceramic substrate.

[0042] As a further technical solution, during sintering, the temperature is 1550~1650°C and the time is 2.5~3.5h.

[0043] The working principle and beneficial effects of the present invention are as follows:

[0044] In the present invention, aluminum nitride is selected as the matrix material, and its hexagonal crystal structure endows the material with high thermal conductivity and low dielectric constant characteristics, providing a basic guarantee for signal transmission. The sintering aid forms a liquid phase at high temperature, promoting particle rearrangement and densification, while inhibiting abnormal grain growth and constructing a uniform fine-grained structure to ensure the simultaneous improvement of material density and mechanical strength. The long-chain molecules of the plasticizer are inserted between aluminum nitride particles, reducing the slurry viscosity and increasing the fluidity to ensure the integrity of complex shape forming. The polymer network structure of the binder effectively bonds aluminum nitride particles to form a green body with high strength. Its polar groups combine with the hydroxyl groups on the particle surface, enhancing the interfacial bonding force and reducing the risk of drying cracking. The dispersant is used to promote the dispersion of aluminum nitride particles and inhibit the formation of aggregates, providing a uniform microstructure basis for sintering. The synergy of the binder and the dispersant reduces the closed pore defects; the reinforcing agent composed of rare earth nitrides, rare earth oxides, and zinc oxide reduces the dielectric constant of the aluminum nitride ceramic substrate, enabling low-dielectric-constant ceramics to support the development of optical communication modules towards high speed and high density, and promoting the industrialization of optoelectronic technology. Specific embodiments

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of the present invention.

[0046] In the following embodiments and comparative examples, the particle sizes of scandium nitride and cerium nitride are both 300 mesh, the particle sizes of yttrium oxide and scandium oxide are both 300 mesh, the particle size of zinc oxide is 100nm, polyvinyl butyral is purchased from Hubei Darlie Chemical Co., Ltd. with the product number Darl-1, the model of polyvinylpyrrolidone is K-15, and the particle sizes of zirconia and titanium dioxide are both 20nm.

[0047] Example 1

[0048] A low-dielectric-constant aluminum nitride ceramic substrate, the raw materials include the following components in parts by weight: 105 parts of aluminum nitride, 14 parts of magnesium oxide, 16 parts of dioctyl phthalate, 10 parts of polyvinyl butyral, 8 parts of dibutyl phosphate, 18 parts of reinforcing agent, and 90 parts of ethanol;

[0049] The preparation method of the reinforcing agent includes the following steps:

[0050] Mix scandium nitride, yttrium oxide, and zinc oxide with a mass ratio of 9:3:7, ball mill for 2 h at a rotation speed of 700 rpm, and sinter at 550 °C for 4 h to obtain a reinforcing agent;

[0051] A method for preparing a low dielectric constant aluminum nitride ceramic substrate includes the following steps:

[0052] S1. Mix aluminum nitride, magnesium oxide, dioctyl phthalate, dibutyl phosphate, and the reinforcing agent evenly, add polyvinyl butyral and ethanol, and mix evenly to obtain a slurry;

[0053] S2. Cast the slurry into a film and dry it to obtain a green body;

[0054] S3. Debind the green body and sinter it at 1650 °C for 2.5 h to obtain a low dielectric constant aluminum nitride ceramic substrate.

[0055] Example 2 [[ID=id=16]]

[0056] A low dielectric constant aluminum nitride ceramic substrate, the raw materials of which include the following components in parts by weight: 85 parts of aluminum nitride, 8 parts of calcium oxide, 12 parts of dibutyl phthalate, 6 parts of polyvinylpyrrolidone, 6 parts of dibutyl phosphate, 14 parts of reinforcing agent, and 80 parts of isopropanol;

[0057] The preparation method of the reinforcing agent includes the following steps:

[0058] Mix cerium nitride, lanthanum oxide, and zinc oxide with a mass ratio of 3:3:7, ball mill for 3 h at a rotation speed of 600 rpm, and sinter at 450 °C for 5 h to obtain a reinforcing agent;

[0059] A method for preparing a low dielectric constant aluminum nitride ceramic substrate includes the following steps:

[0060] S1. Mix aluminum nitride, calcium oxide, dibutyl phthalate, dibutyl phosphate, and the reinforcing agent evenly, add polyvinylpyrrolidone and isopropanol, and mix evenly to obtain a slurry;

[0061] S2. Cast the slurry into a film and dry it to obtain a green body;

[0062] S3. Debind the green body and sinter it at 1550 °C for 3.5 h to obtain a low dielectric constant aluminum nitride ceramic substrate.

[0063] Example 3

[0064] A low dielectric constant aluminum nitride ceramic substrate, the raw materials of which include the following components in parts by weight: 95 parts of aluminum nitride, 10 parts of zirconium oxide, 14 parts of polyethylene glycol, 8 parts of polyvinyl butyral, 7 parts of dibutyl phosphate, 16 parts of reinforcing agent, and 85 parts of ethanol;

[0065] The preparation method of the reinforcing agent includes the following steps:

[0066] Mix scandium nitride, scandium oxide and zinc oxide with a mass ratio of 8:3:7, ball-mill at a speed of 650 rpm for 2.5 h, and sinter at 500 °C for 4.5 h to obtain a reinforcing agent;

[0067] A preparation method of a low dielectric constant aluminum nitride ceramic substrate includes the following steps:

[0068] S1. Mix aluminum nitride, zirconium oxide, polyethylene glycol, dibutyl phosphate and the reinforcing agent evenly, add polyvinyl butyral and ethanol, and mix evenly to obtain a slurry;

[0069] S2. Cast and form the slurry, and dry it to obtain a green body;

[0070] S3. Debind the green body and sinter at 1600 °C for 3 h to obtain a low dielectric constant aluminum nitride ceramic substrate.

[0071] Example 4

[0072] The difference between this example and Example 3 is only that the mass ratio of scandium nitride, scandium oxide and zinc oxide in this example is 4:3:7.

[0073] Example 5

[0074] The difference between this example and Example 3 is only that the mass ratio of scandium nitride, scandium oxide and zinc oxide in this example is 5:3:7.

[0075] Example 6

[0076] The difference between this example and Example 3 is only that the mass ratio of scandium nitride, scandium oxide and zinc oxide in this example is 6:3:7.

[0077] Example 7

[0078] The difference between this example and Example 3 is only that the mass ratio of scandium nitride, scandium oxide and zinc oxide in this example is 7:3:7.

[0079] Example 8

[0080] The difference between this example and Example 6 is only that zirconium oxide in this example is replaced with an equal mass of titanium dioxide.

[0081] Example 9

[0082] The difference between this example and Example 6 is only that zirconium oxide in this example is replaced with an equal mass of a sintering aid, and the sintering aid is zirconium oxide and titanium dioxide with a mass ratio of 2:7.

[0083] Example 10

[0084] The difference between this example and Example 6 is only that in this example, zirconia is replaced with an equal mass of sintering aids, and the sintering aids are surface-treated zirconia and titanium dioxide;

[0085] The preparation method of surface-treated zirconia and titanium dioxide includes the following steps:

[0086] Add 20 g of zirconia and 70 g of titanium dioxide to 100 g of ethanol, add 7 g of 5-hydroxy nicotinic acid, stir evenly at 50 °C, and dry to obtain surface-treated zirconia and titanium dioxide.

[0087] Example 11

[0088] The difference between this example and Example 10 is only that the preparation method of surface-treated zirconia and titanium dioxide in this example includes the following steps:

[0089] Add 20 g of zirconia and 70 g of titanium dioxide to 100 g of ethanol, add 4 g of 5-hydroxy nicotinic acid, stir evenly at 40 °C, and dry to obtain surface-treated zirconia and titanium dioxide.

[0090] Example 12

[0091] The difference between this example and Example 3 is only that in this example, the reinforcing agent includes scandium nitride, scandium oxide and zinc oxide with a mass ratio of 8:3:7, and the reinforcing agent is directly used for the preparation of a low-dielectric constant aluminum nitride ceramic substrate without ball milling and sintering.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 3 is only that the raw materials of the reinforcing agent in this comparative example include scandium nitride and scandium oxide with a mass ratio of 8:3.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 3 is only that the raw materials of the reinforcing agent in this comparative example include scandium nitride and zinc oxide with a mass ratio of 8:7.

[0096] Comparative Example 3

[0097] The difference between this comparative example and Example 3 is only that the raw materials of the reinforcing agent in this comparative example include scandium oxide and zinc oxide with a mass ratio of 3:7.

[0098] Comparative Example 4

[0099] The difference between this comparative example and Example 3 is only that this comparative example has no reinforcing agent.

[0100] Experimental Example 1

[0101] The low-dielectric-constant aluminum nitride ceramic substrates prepared in Examples 1-7, Example 12 and Comparative Examples 1-4 were tested for dielectric constant according to the method specified in GB / T 5594.4-2015 "Test Methods for Properties of Structural Ceramic Materials for Electronic Components - Part 4: Test Methods for Dielectric Constant and Dissipation Factor". The test results are shown in Table 1.

[0102] Table 1 Test Results of Dielectric Constant

[0103]

[0104] As can be seen from Table 1, the dielectric constants of the low-dielectric-constant aluminum nitride ceramic substrates prepared in Examples 1-7 and Example 12 reached below 4.1. It can be seen therefrom that in the present invention, the reinforcing agent uses rare earth nitrides, rare earth oxides and zinc oxide, which reduces the dielectric constant of the aluminum nitride ceramic substrate.

[0105] Experimental Example 2

[0106] The low-dielectric-constant aluminum nitride ceramic substrates prepared in Examples 6 and 8-11 were tested for the flexural strength of the samples according to the test method specified in GB / T 6569-2006 "Test Method for Flexural Strength of Fine Ceramics". The test method was three-point bending. The test results are shown in Table 2.

[0107] Table 2 Test Results of Flexural Strength

[0108]

[0109] As can be seen from Table 2, the flexural strengths of the low-dielectric-constant aluminum nitride ceramic substrates in Examples 10-11 reached above 429 MPa. It can be seen therefrom that in the present invention, 5-hydroxy nicotinic acid is used to surface-treat zirconia and titanium dioxide, which improves the flexural strength of the low-dielectric-constant aluminum nitride ceramic substrate.

[0110] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A low dielectric constant aluminum nitride ceramic substrate, characterized in that, The raw materials include the following components in parts by weight: 85 - 105 parts of aluminum nitride, 8 - 14 parts of sintering aid, 12 - 16 parts of plasticizer, 6 - 10 parts of binder, 6 - 8 parts of dispersant, 14 - 18 parts of reinforcing agent, and 80 - 90 parts of solvent; The preparation method of the reinforcing agent includes the following steps: Mix rare earth nitride, rare earth oxide and zinc oxide, ball mill, and pre - sinter to obtain the reinforcing agent; The mass ratio of the rare earth nitride, rare earth oxide and zinc oxide is 5 - 7:3:

7.

2. The low dielectric constant aluminum nitride ceramic substrate according to claim 1, wherein The rare earth nitride includes one or two of cerium nitride and scandium nitride; The rare earth oxide includes one or two of yttrium oxide and scandium oxide.

3. A low dielectric constant aluminum nitride ceramic substrate according to claim 1, characterized in that, During the ball milling, the rotation speed is 600 - 700 rpm and the time is 2 - 3 h; During the pre - sintering, the temperature is 450 - 550 °C and the time is 4 - 5 h.

4. A low dielectric constant aluminum nitride ceramic substrate according to claim 1, characterized in that, The sintering aid includes one or more of magnesium oxide, calcium oxide, zirconia, and titanium dioxide; The plasticizer includes one or more of dioctyl phthalate, dibutyl phthalate, and polyethylene glycol; The binder includes one of polyvinyl butyral and polyvinylpyrrolidone; The dispersant includes dibutyl phosphate; The solvent includes one of ethanol and isopropanol.

5. A low dielectric constant aluminum nitride ceramic substrate according to claim 4, wherein, When the sintering aid is zirconia and titanium dioxide, the sintering aid is a surface - treated sintering aid; The raw materials of the surface - treated sintering aid include zirconia, titanium dioxide, and 5 - hydroxynicotinic acid.

6. The low-dielectric-constant aluminum nitride ceramic substrate according to claim 5, wherein The preparation method of the surface - treated sintering aid includes the following steps: Add zirconia and titanium dioxide into ethanol, add 5 - hydroxynicotinic acid, stir until uniform, and dry to obtain the surface - treated sintering aid; During the stirring, the temperature is 40 - 50 °C.

7. The low dielectric constant aluminum nitride ceramic substrate according to claim 6, wherein, The mass ratio of zirconia, titanium dioxide, and 5 - hydroxynicotinic acid is 20:70:4 - 7.

8. A preparation method of a low dielectric constant aluminum nitride ceramic substrate for preparing a low dielectric constant aluminum nitride ceramic substrate according to any one of claims 1 to 7, characterized in that, It includes the following steps: S1. Mix aluminum nitride, sintering aid, plasticizer, dispersant, and reinforcing agent evenly, add binder and solvent, and mix evenly to obtain a slurry; S2. Cast and form the slurry, and dry to obtain a green body; S3. Debind and sinter the green body to obtain a low - dielectric - constant aluminum nitride ceramic substrate.

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