Aln / si3n4 composite ceramic substrate, preparation method and application thereof

Abstract

The application belongs to the technical field of material production, and discloses an AlN / Si3N4 composite ceramic substrate and a preparation method and application thereof. The composite ceramic substrate is prepared by the following steps: Si powder and sintering aids EuO2-HfO2-MgO-Yb2O3 are used to prepare Si-based ceramic substrates by tape casting and n*m matrix cylindrical molds; Al2O3 powder, C powder and Yb2O3 powder are used to prepare Al2O3-C tape casting slurry, the Al2O3-C tape casting slurry is filled into the circular holes of the Si-based ceramic substrates, and Si-Al2O3-C composite ceramic substrates are obtained; and the Si-Al2O3-C composite ceramic substrates are subjected to nitriding treatment at 1320-1380 DEG C, and then are subjected to reaction sintering at 1600-1800 DEG C. The composite ceramic substrate has excellent heat conduction performance and mechanical properties, and AlN ceramic is used as a heat conduction path, and Si3N4 ceramic is used as mechanical support. The application is stable and efficient in production, and can be used in the fields of automobile electronics, aerospace and the like.

Description

Technical Field

[0001] This invention belongs to the field of materials production technology, and more specifically, relates to an AlN / Si3N4 composite ceramic substrate, its preparation method, and its application. Background Technology

[0002] Currently, ceramic substrates are widely used in various fields such as new energy vehicles, high-speed railways, robotics, and aerospace to more effectively control and utilize electricity. However, the power systems in these fields are developing towards higher integration, miniaturization, and intelligence, which places more stringent requirements on ceramic substrates as supporting components and heat sinks, especially on their mechanical and thermal conductivity properties. Therefore, there is an urgent need for a method to efficiently produce ceramic substrates that balance mechanical and thermal conductivity properties.

[0003] Silicon nitride ceramics, due to their excellent mechanical properties such as high strength and high toughness, as well as corrosion resistance, wear resistance, excellent dielectric constant, and chemical stability, have long been used in aerospace, automotive, chemical, and civilian fields. Aluminum nitride ceramics, with their excellent thermal conductivity and electrical insulation, are widely used in electronic device substrates, heat sinks, and lasers. How to combine the mechanical advantages of silicon nitride with the excellent thermal conductivity of aluminum nitride to prepare high-strength and high-thermal-conductivity composite ceramic substrates is a technical problem worthy of in-depth research. Summary of the Invention

[0004] To address the shortcomings and drawbacks of the existing technology, the primary objective of this invention is to provide an AlN / Si3N4 composite ceramic substrate. This composite ceramic exhibits excellent mechanical properties and thermal conductivity.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned AlN / Si3N4 composite ceramic substrate.

[0006] Another object of the present invention is to provide the application of the above-mentioned AlN / Si3N4 composite ceramic substrate.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] An AlN / Si3N4 composite ceramic substrate is prepared by ball milling and mixing Si powder, EuO2-HfO2 powder, MgO powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol, and anhydrous ethanol to obtain a Si-based casting slurry; ball milling and mixing Al2O3 powder, C powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol, and anhydrous ethanol to obtain an Al2O3-C casting slurry; and casting the Si-based casting slurry in a mold to obtain a Si-based ceramic substrate with an n×m matrix of circular holes. Al2O3-C casting slurry was filled into the circular holes of a Si-based ceramic sheet to obtain a Si-Al2O3-C composite ceramic sheet. The composite ceramic sheet was placed in a pressure sintering furnace, and a mixture of N2 and H2 gas was introduced at 800-1000℃ under vacuum. Then, nitriding treatment was carried out at 1320-1380℃, followed by the introduction of flowing N2 at 4-6 MPa. The temperature was raised to 1600-1800℃ and held, and then cooled to 800-1000℃. After natural cooling to room temperature, the product was obtained.

[0009] Preferably, the purity of the Si powder, EuO2 powder, HfO2 powder, MgO powder, Yb2O3 powder, Al2O3 powder, and C powder is all above 99.9%, the particle size of the Si powder is 0.5-1 μm, the particle size of the EuO2 powder, HfO2 powder, MgO powder, and C powder is all <100 nm, and the particle size of the Yb2O3 powder and Al2O3 powder is all 1-2 μm.

[0010] Preferably, the mass ratio of Si powder:EuO2-HfO2 powder:MgO powder:Yb2O3 powder:polyethylene glycol butyral:polyethylene glycol:anhydrous ethanol is (88-92):(2-6):2:4:10:10:200, wherein the mass ratio of EuO2 powder and HfO2 powder is 1:1; the mass ratio of Al2O3 powder:C powder:Yb2O3 powder:polyethylene glycol butyral:polyethylene glycol:anhydrous ethanol is (76-80):(16-20):4:10:10:200.

[0011] Preferably, the mold is an n×m matrix. A cylinder, where n = [a / 30], m = [b / 30], a is the total length of the composite ceramic substrate, and b is the total width of the composite ceramic substrate; 100mm ≤ a ≤ 300mm, 50mm ≤ b ≤ 200mm.

[0012] Preferably, the volume ratio of N2 to H2 in the mixed gas is (93-97):(3-7).

[0013] Preferably, the AlN / Si3N4 composite ceramic substrate has a relative density of 97% or higher, a flexural strength of 687–860 MPa, and a fracture toughness of 6.4–8 MPa·m. 1 / 2Its hardness is 15.6–17 GPa, and its thermal conductivity is 86–116 W / m. -1 K -1 .

[0014] The method for preparing the AlN / Si3N4 composite ceramic substrate includes the following steps:

[0015] S1. Si powder, EuO2-HfO2 powder, MgO powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol and anhydrous ethanol are ball-milled and mixed to obtain Si-based casting slurry;

[0016] S2. Al2O3 powder, C powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol and anhydrous ethanol are ball-milled and mixed to obtain Al2O3-C casting slurry;

[0017] S3. After the Si-based casting slurry is cast in a mold, an n×m matrix is ​​obtained. Si-based ceramic substrate with circular holes; Al2O3-C casting slurry is filled into the circular holes of the Si-based ceramic substrate to obtain a Si-Al2O3-C composite ceramic substrate;

[0018] S4. Place the Si-Al2O3-C composite ceramic sheet into a pressure sintering furnace, maintain a vacuum state and heat to 800-1000℃, then introduce a mixed gas of N2 and H2, then heat to 1320-1380℃ and hold for 2-3 hours for nitriding treatment, then introduce flowing N2 at 4-6 MPa, heat to 1600-1800℃ and hold for 3-4 hours, then cool down to 800-1000℃ and allow it to cool naturally to room temperature to obtain the AlN / Si3N4 composite ceramic substrate.

[0019] Preferably, the casting process conditions in step S3 are as follows: casting belt speed is 0.3-3 m / min; green body thickness is 0.3-0.7 mm; drying temperature is 60-80℃; drying time is 3-5 h.

[0020] Preferably, in step S4, the heating rate to 800-1000°C is 18-25°C / min, the heating rate to 1320-1380°C is 15-18°C / min, and the heating rate to 1600-1800°C is 8-12°C / min.

[0021] Applications of the AlN / Si3N4 composite ceramic substrate in the automotive electronics or aerospace fields.

[0022] This invention involves placing Si-Al2O3-C composite ceramic sheets in a pressure sintering furnace under vacuum. After raising the temperature to 800–1000°C, a mixed atmosphere of N2 (95 vol%) and H2 (5 vol%) is introduced. The temperature is then raised to 1320–1380°C and held for 2–3 hours. During this process, EuO2-HfO2 powder in the Si-Al2O3-C composite ceramic sheet acts as a catalyst, promoting the nitridation of Si powder to α-Si3N4, ensuring nitridation quality and shortening the nitriding time. Then, the temperature is raised to 1600–1800°C and held for 3–4 hours. On one hand, α-Si3N4 undergoes liquid-phase sintering, and the α→β-Si3N4 phase transformation occurs simultaneously with the growth of β-Si3N4 grains, forming an interlocked, dense, bimodal microstructure. On the other hand, at 1600–1800°C, Al2O3 powder undergoes a carbothermic reduction reaction.

[0023] Al₂O₃(s) + C(s) → AlN(s) + CO(g)

[0024] The removal of carbon in the circular hole region and the preparation of AlN ceramics were achieved. Notably, at the interface between the circular holes of AlN and Si3N4 in the AlN / Si3N4 composite ceramic substrate, the following reaction occurs under a holding temperature of 1600–1800℃:

[0025] 3Al2O3(s)+3C(s)+4Si3N4(s)+N2(g)→3Si4Al2O3N6(s)+3CO(g)

[0026] A 0.3–0.5 mm annular β-Sialon phase transition region was generated, which further tightly connected AlN and Si3N4 ceramics, while also balancing the thermal stress caused by the difference in thermal expansion coefficients of AlN and Si3N4, ensuring the formation and density of the composite ceramic substrate, and producing a high-performance AlN / Si3N4 composite ceramic substrate.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. In this invention, the Si3N4 ceramic forms an interlocked, dense, bimodal microstructure, which ensures that the AlN / Si3N4 composite ceramic substrate has excellent mechanical properties; at the same time, the formation of the matrix AlN ceramic provides the composite ceramic substrate with a thermally conductive pathway with good thermal conductivity, thereby achieving optimized overall performance.

[0029] 2. In the AlN / Si3N4 composite ceramic substrate of the present invention, a 0.3-0.5 mm annular β-Sialon phase transition region is formed at the junction of the circular holes of AlN and Si3N4. This not only further tightly connects AlN and Si3N4 ceramics, but also balances the thermal stress caused by the difference in thermal expansion coefficients of AlN and Si3N4, thus ensuring the molding and compactness of the composite ceramic substrate.

[0030] 3. This invention promotes Si powder nitriding by introducing Si powder into EuO2-HfO2 powder, ensuring nitriding quality, shortening nitriding time, and simplifying the preparation process. It eliminates the need for separate debinding and carbon removal steps, saving time and costs. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the production process of the AlN / Si3N4 composite ceramic substrate of the present invention.

[0032] Figure 2 This is a schematic diagram of the mold for the cylinder with an n×m matrix according to the present invention.

[0033] Figure 3 This invention contains an n×m matrix. A schematic diagram of the casting process for Si-based ceramic substrates with circular holes. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0035] The following powders are used in this invention: Si powder (purity above 99%, particle size 0.5-1 μm), EuO2 powder (purity above 99.99%, particle size <100 nm), HfO2 powder (purity above 99.99%, particle size <100 nm), MgO powder (purity 99.9%, particle size <100 nm), Yb2O3 powder (purity above 99.99%, particle size 1-2 μm), Al2O3 powder (purity above 99.99%, particle size 1-2 μm), C powder (purity above 99.99%, particle size <100 nm), and Yb2O3 powder (purity above 99.99%, particle size 1-2 μm).

[0036] Example 1

[0037] 1. A mixture of Si powder, EuO2-HfO2 powder (EuO2 powder and HfO2 powder in a mass ratio of 1:1), MgO powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol, and anhydrous ethanol in a mass ratio of 90:4:2:4:10:10:200 is ball-milled to obtain a Si-based casting slurry.

[0038] 2. Place the Si-based casting slurry into an interior containing a (15-20)×(9-12) matrix. Cylinder mold (e.g.) Figure 2 After undergoing a casting process (casting belt speed 0.3–3 m / min; green body thickness 0.3–0.7 mm; drying temperature 60–80 °C; drying time 3–5 h), the material is cut and separated to obtain a 5×3 matrix. The process for a Si-based ceramic substrate with a circular hole (150mm × 90mm) is as follows: Figure 3 As shown;

[0039] 3. Mix and ball-mill the Al2O3 powder:C powder:Yb2O3 powder:polyethylene glycol butyral:polyethylene glycol:anhydrous ethanol in a mass ratio of 78:18:4:10:10:200 to obtain Al2O3-C casting slurry; fill the circular holes of Si-based ceramic wafers with Al2O3-C casting slurry to obtain Si-Al2O3-C composite ceramic wafers;

[0040] 4. The Si-Al2O3-C composite ceramic sheet was placed in a pressure sintering furnace. Under vacuum, the temperature was increased to 800℃ at a rate of 20℃ / min. A mixed gas of N2 (95 vol%) and H2 (5 vol%) was introduced, and the temperature was increased to 1340℃ at a rate of 16℃ / min and held for 3 hours for nitriding treatment. Then, the temperature was increased to 1800℃ at a rate of 12℃ / min and held for 3 hours. The N2 pressure during the holding process was 5 MPa. After holding, the temperature was reduced to 800℃ and allowed to cool naturally to room temperature to obtain the AlN / Si3N4 composite ceramic substrate. Figure 1 As shown.

[0041] The AlN / Si3N4 composite ceramic substrate prepared in this embodiment has a relative density of 98.2%, a flexural strength of 860 MPa, and a fracture toughness of 8.7 MPa·m. 1 / 2 Its hardness is 16.4 GPa and its thermal conductivity is 112 W / m. -1 K -1 This AlN / Si3N4 composite ceramic substrate possesses excellent mechanical properties (Si3N4 ceramic matrix) and thermal conductivity (AlN ceramic pathway).

[0042] Example 2

[0043] The difference from Example 1 is that in step 1, the mass ratio of Si powder, EuO2-HfO2 powder (mass ratio of EuO2 powder to HfO2 powder is 1:1), MgO powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol, and anhydrous ethanol is 92:2:2:4:10:10:200, which are mixed and ball-milled to obtain Si-based casting slurry.

[0044] The AlN / Si3N4 composite ceramic substrate prepared in this embodiment has a relative density of 97.6%, a flexural strength of 780 MPa, and a fracture toughness of 7.2 MPa·m. 1 / 2 Its hardness is 16.8 GPa and its thermal conductivity is 110 W / m. -1 K -1 .

[0045] Example 3

[0046] The difference from Example 1 is that in step 1, the mass ratio of Si powder, EuO2-HfO2 powder (the mass ratio of EuO2 powder to HfO2 powder is 1:1), MgO powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol, and anhydrous ethanol is 88:6:2:4:10:10:200, which are mixed and ball-milled to obtain Si-based casting slurry.

[0047] The AlN / Si3N4 composite ceramic substrate prepared in this embodiment has a relative density of 97.4%, a flexural strength of 756 MPa, and a fracture toughness of 7.18 MPa·m. 1 / 2 Its hardness is 16.6 GPa and its thermal conductivity is 106 W / m. -1 K -1 .

[0048] Example 4

[0049] The difference from Example 1 is that in step 2, the mass ratio of Al2O3 powder:C powder:Yb2O3 powder:polyethylene glycol butyral:polyethylene glycol:anhydrous ethanol is 76:20:4:10:10:200, which are mixed and ball-milled to obtain Al2O3-C casting slurry.

[0050] The AlN / Si3N4 composite ceramic substrate prepared in this embodiment has a relative density of 98.1%, a flexural strength of 801 MPa, and a fracture toughness of 7.8 MPa·m. 1 / 2 It has a hardness of 16.6 GPa and a thermal conductivity of 114 W / m. -1 K -1 .

[0051] Example 5

[0052] The difference from Example 1 is that in step 2, the mass ratio of Al2O3 powder:C powder:Yb2O3 powder:polyethylene glycol butyral:polyethylene glycol:anhydrous ethanol is 80:16:4:10:10:200, which are mixed and ball-milled to obtain Al2O3-C casting slurry.

[0053] The AlN / Si3N4 composite ceramic substrate prepared in this embodiment has a relative density of 97.9%, a flexural strength of 764 MPa, and a fracture toughness of 7.2 MPa·m. 1 / 2 Its hardness is 15.8 GPa and its thermal conductivity is 86 W / m. -1 K -1 .

[0054] Example 6

[0055] The difference from Example 1 is that in step 3, the Si-based casting slurry is placed inside a matrix containing (15-20) × (9-12). After being cast in a cylindrical mold (casting speed 0.3–3 m / min; green thickness 0.3–0.7 mm; drying temperature 60–80 °C; drying time 3–5 h), a 5×3 matrix is ​​obtained by cutting and separating. A Si-based ceramic sheet with circular holes (150mm×90mm); Al2O3-C casting slurry is filled into the circular holes of the Si-based ceramic sheet to obtain a Si-Al2O3-C composite ceramic sheet.

[0056] The AlN / Si3N4 composite ceramic substrate prepared in this embodiment has a relative density of 97.4%, a flexural strength of 687 MPa, and a fracture toughness of 6.8 MPa·m. 1 / 2 Its hardness is 16.8 GPa and its thermal conductivity is 116 W / m. -1 K -1 .

[0057] Example 7

[0058] The difference from Example 1 is that in step 4, the Si-Al2O3-C composite ceramic sheet is placed in a pressure sintering furnace and heated to 800°C at a rate of 20°C / min under vacuum. A mixed gas of N2 (95 vol%) and H2 (5 vol%) is then introduced, and the temperature is further increased to 1340°C at a rate of 16°C / min and held for 3 hours for nitriding treatment. Then, the temperature is increased to 1600°C at a rate of 12°C / min and held for 3 hours, with the N2 pressure at 5 MPa during the holding process. After holding, the temperature is reduced to 800°C and allowed to cool naturally to room temperature to obtain the AlN / Si3N4 composite ceramic substrate.

[0059] The AlN / Si3N4 composite ceramic substrate prepared in this embodiment has a relative density of 97.2%, a flexural strength of 723 MPa, and a fracture toughness of 6.9 MPa·m. 1 / 2 It has a hardness of 17 GPa and a thermal conductivity of 91 Wm. -1 K -1 .

[0060] Example 8

[0061] The difference from Example 1 is that in step 4, the Si-Al2O3-C composite ceramic sheet is placed in a pressure sintering furnace and heated to 800°C at a rate of 20°C / min under vacuum. A mixed atmosphere of N2 (95 vol%) and H2 (5 vol%) is then introduced, and the temperature is further increased to 1340°C at 16°C / min and held for 3 hours for nitriding. Then, the temperature is increased to 1700°C at 12°C / min and held for 3 hours, with the N2 pressure at 5 MPa during the holding process. After holding, the temperature is reduced to 800°C and allowed to cool naturally to room temperature to obtain the AlN / Si3N4 composite ceramic substrate.

[0062] The AlN / Si3N4 composite ceramic substrate prepared in this embodiment has a relative density of 97.9%, a flexural strength of 749 MPa, and a fracture toughness of 7.3 MPa·m. 1 / 2 Its hardness is 16.1 GPa and its thermal conductivity is 103 W / m. -1 K -1 .

[0063] The AlN / Si3N4 composite ceramic substrate prepared by this invention has a relative density of over 97%, a flexural strength of 687–860 MPa, and a fracture toughness of 6.4–8.7 MPa·m. 1 / 2 The thermal conductivity is 86–116 W / m. -1 K -1 This indicates that the AlN / Si3N4 composite ceramic substrate has excellent mechanical properties (flexural strength and fracture toughness) and thermal conductivity, and can be applied in the fields of automotive electronics or aerospace.

[0064] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An AlN / Si3N4 composite ceramic substrate, characterized in that, The composite ceramic substrate is prepared by ball milling and mixing Si powder, EuO2-HfO2 powder, MgO powder, Yb2O3 powder, polyethylene butyral, polyethylene glycol, and anhydrous ethanol to obtain a Si-based casting slurry; ball milling and mixing Al2O3 powder, C powder, Yb2O3 powder, polyethylene butyral, polyethylene glycol, and anhydrous ethanol to obtain an Al2O3-C casting slurry; casting the Si-based casting slurry in a mold to obtain a Si-based ceramic sheet with an n×m matrix of circular holes; filling the circular holes of the Si-based ceramic sheet with Al2O3-C casting slurry to obtain a Si-Al2O3-C composite ceramic sheet; placing the composite ceramic sheet in a pressure sintering furnace, maintaining a vacuum state, introducing a mixture of N2 and H2 gas at 800~1000 ℃, then holding at 1320~1380 ℃ for 2~3 h for nitriding treatment, and then introducing 4~6 The N2 flowing at MPa is heated to 1600~1800 ℃ and held at that temperature, then cooled to 800~1000 ℃ and allowed to cool naturally to room temperature to obtain the product. The mass ratio of Si powder: EuO2-HfO2 powder: MgO powder: Yb2O3 powder: polyethylene glycol butyral: polyethylene glycol: anhydrous ethanol is (88~92): (2~6): 2:4:10:10:200, wherein the mass ratio of EuO2 powder and HfO2 powder is 1:1; the mass ratio of Al2O3 powder: C powder: Yb2O3 powder: polyethylene glycol butyral: polyethylene glycol: anhydrous ethanol is (76~80): (16~20): 4:10:10:

200. The mold is a cylinder with an n×m matrix and a diameter of Ø10~15 mm, where n=[a / 30], m=[b / 30], a is the total length of the composite ceramic substrate, and b is the total width of the composite ceramic substrate; 100mm≤a≤300mm, 50mm≤b≤200mm.

2. The AlN / Si3N4 composite ceramic substrate according to claim 1, characterized in that, The purity of the Si powder, EuO2 powder, HfO2 powder, MgO powder, Yb2O3 powder, Al2O3 powder, and C powder is all above 99.9%. The particle size of the Si powder is 0.5~1μm; the particle size of the EuO2 powder, HfO2 powder, MgO powder, and C powder is all <100nm; and the particle size of the Yb2O3 powder and Al2O3 powder is 1~2μm.

3. The AlN / Si3N4 composite ceramic substrate according to claim 1, characterized in that, The volume ratio of N2 to H2 in the mixed gas is (93~97):(3~7).

4. The AlN / Si3N4 composite ceramic substrate according to claim 1, characterized in that, The AlN / Si3N4 composite ceramic substrate has a relative density of over 97%, a flexural strength of 687~860 MPa, and a fracture toughness of 6.4~8 MPa·m. 1 / 2 Its hardness is 15.6~17 GPa, and its thermal conductivity is 86~116 W / m. -1 K -1 .

5. The method for preparing the AlN / Si3N4 composite ceramic substrate according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Si powder, EuO2-HfO2 powder, MgO powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol and anhydrous ethanol are ball-milled and mixed to obtain Si-based casting slurry; S2. Al2O3 powder, C powder, Yb2O3 powder, polyethylene glycol butyral, polyethylene glycol and anhydrous ethanol are ball-milled and mixed to obtain Al2O3-C casting slurry; S3. After the Si-based casting slurry is cast in a mold, a Si-based ceramic sheet with Ø10~15 mm circular holes containing an n×m matrix is ​​obtained; Al2O3-C casting slurry is filled into the circular holes of the Si-based ceramic sheet to obtain a Si-Al2O3-C composite ceramic sheet. S4. Place the Si-Al2O3-C composite ceramic sheet into a pressure sintering furnace, maintain a vacuum state and heat to 800~1000℃, then introduce a mixed gas of N2 and H2, then heat to 1320~1380℃ and hold for 2~3h for nitriding treatment, then introduce 4~6MPa of flowing N2, heat to 1600~1800℃ and hold for 3~4h, then cool down to 800~1000℃ and let it cool naturally to room temperature to obtain the AlN / Si3N4 composite ceramic substrate.

6. The method for preparing the AlN / Si3N4 composite ceramic substrate according to claim 5, characterized in that, The casting process conditions described in step S3 are as follows: casting belt speed is 0.3~3m / min; green body thickness is 0.3~0.7mm; drying temperature is 60~80℃; drying time is 3~5h.

7. The method for preparing the AlN / Si3N4 composite ceramic substrate according to claim 5, characterized in that, In step S4, the heating rate to 800~1000 ℃ is 18~25 ℃ / min, the heating rate to 1320~1380 ℃ is 15~18 ℃ / min, and the heating rate to 1600~1800 ℃ is 8~12 ℃ / min.

8. The application of the AlN / Si3N4 composite ceramic substrate according to any one of claims 1-4 in the fields of automotive electronics or aerospace.

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