An aluminum nitride ceramic and its sintering method

Abstract

This invention provides an aluminum nitride ceramic and its sintering method, belonging to the field of aluminum nitride ceramic manufacturing technology. Specifically, through a specific sintering procedure and specific sintering aids, this invention ensures that the secondary phase at the grain boundaries of the obtained aluminum nitride ceramic contains only the YAP and YAM phases, and no YAG phase. This results in the aluminum nitride ceramic phase obtained by sintering according to this invention having higher room temperature thermal conductivity and mechanical strength compared to existing products. It can be widely used in cutting-edge fields such as electrostatic chuck substrates, high-power semiconductor packaging substrates, and high-power laser heat dissipation substrates, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of aluminum nitride ceramic manufacturing technology, and specifically to an aluminum nitride ceramic and its sintering method. Background Technology

[0002] In the semiconductor manufacturing field, aluminum nitride (AlN) ceramics are often used as substrates or dielectric layer materials for electrostatic chucks due to their excellent temperature uniformity. Aluminum nitride has a theoretical room-temperature thermal conductivity as high as 320 W / (m·K). However, in practical applications, oxygen impurities are usually dissolved in the aluminum nitride lattice. These oxygen impurities typically exist in the form of Al-O bonds at grain boundaries and within the lattice, which increases phonon scattering and significantly reduces the room-temperature thermal conductivity of aluminum nitride. This results in the measured room-temperature thermal conductivity of aluminum nitride ceramics typically being only 80–150 W / (m·K). Therefore, how to reduce the adverse effects of oxygen impurities on aluminum nitride ceramics has become a pressing technical problem to be solved in this field.

[0003] Currently, a common method to improve the room-temperature thermal conductivity of aluminum nitride ceramics is to introduce yttrium trioxide (Y₂O₃) into the raw materials. This serves two purposes: firstly, it generates a liquid phase that promotes the densification of the aluminum nitride ceramic; secondly, Y₂O₃ reacts with the alumina in the aluminum nitride, thereby "drawing" the dissolved oxygen from the interior to the grain boundaries to form a second phase. The second phase is mainly yttrium aluminum oxide, including YAG, YAP, and YAM phases, among which the YAG phase (Y₃Al₅O₃) is the most prominent. 12 YAG is an aluminum-rich phase, which is the easiest to form. However, the YAG phase cannot effectively encapsulate aluminum nitride grains and instead tends to form high thermal resistance barriers at grain boundaries, severely hindering the phonon transport network. YAM (Y4Al2O9) is a yttrium-rich phase, which can be formed by the absorption of Y2O3 by the YAG phase to form the YAP phase and then continue to form under high temperature and long-term heat preservation conditions. The YAM phase can spread evenly along the edges of aluminum nitride grains to form a grain boundary network, which can effectively reduce the grain boundary thermal resistance of aluminum nitride.

[0004] However, existing aluminum nitride ceramic sintering processes are relatively crude, resulting in insufficient reaction between Y₂O₃ and the oxides on the aluminum nitride surface. Consequently, the YAG phase cannot undergo a deep transformation to the YAM phase, limiting the improvement in the room-temperature thermal conductivity of aluminum nitride ceramics. Furthermore, commercially available aluminum nitride ceramics often exhibit low flexural strength. Therefore, improving the room-temperature thermal conductivity and mechanical strength of aluminum nitride ceramics is of great significance for the development of the semiconductor industry. Summary of the Invention

[0005] The purpose of this invention is to provide an aluminum nitride ceramic that balances room temperature thermal conductivity and mechanical strength.

[0006] To achieve the above objectives, the first aspect of the present invention provides a sintering method for aluminum nitride ceramics, specifically comprising the following steps: S1: Mix aluminum nitride powder, dopant, solvent, dispersant and binder to obtain a slurry, and grind the slurry to obtain a fine slurry; S2: Spray granulation of the fine slurry to obtain granulated powder; S3: Press the granulated powder into shape to obtain a green body; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

[0007] Preferably, in step S1, by weight, the aluminum nitride powder is 90-110 parts, the dopant is 0.5-12 parts, the solvent is 50-200 parts, the dispersant is 0.5-1 parts, and the binder is 1.5-5 parts.

[0008] Preferably, in step S1, the dopant is selected from any one or more of yttrium oxide, calcium oxide, and magnesium oxide.

[0009] Preferably, the solvent is a low molecular weight alcohol, which is selected from any one or more of methanol, ethanol, propanol, and butanol; The dispersant is selected from any one or more of polyacrylate, ammonium polyacrylate, fish oil, and castor oil; The binder is selected from any one or more of trimethyl phosphate, polyvinyl alcohol, methylcellulose, ethylcellulose, and sodium carboxymethyl cellulose.

[0010] Preferably, the D50 of the granulated powder is 60~80μm.

[0011] Preferably, in step S3, the density of the green body is 1.8~2.0 g / cm³. 3 .

[0012] In the technical solution provided by this invention, a spray granulation process can be used to obtain a D50 of 60~80μm and a bulk density of 0.9~1.1g / cm³. 3 The aluminum nitride powder has good flowability. After being pressed and molded, the aluminum nitride powder can provide a uniform initial microstructure basis for the subsequent densification of aluminum nitride.

[0013] Preferably, the glue removal process includes the following steps: A1: Raise the temperature of the green compact from room temperature to the first discharge temperature at a heating rate of 0.3~0.6℃ / min. The first discharge temperature is 170~190℃. Hold the compact within the first discharge temperature range for 30~45min. A2: Raise the temperature of the green body from the first debinding temperature to the second debinding temperature at a heating rate of 0.2~0.4℃ / min. The second debinding temperature is 390~410℃. Hold the green body within the second debinding temperature range for 230~260min. A3: Raise the temperature of the green body from the second debinding temperature to the third debinding temperature at a heating rate of 0.2~0.4℃ / min. The third debinding temperature is 530~560℃. Hold the green body within the third debinding temperature range for 180~220min. A4: After the heat preservation in step A3 is completed, the green body temperature is reduced from the third debinding temperature to room temperature at a cooling rate of 1~3℃ / min to complete the debinding and obtain the green body.

[0014] Preferably, the sintering process includes: B1: The temperature of the billet is raised to the first sintering temperature at a heating rate of 2~4℃ / min. The first sintering temperature is 595~605℃. The billet is held at the first sintering temperature for 170~185min. B2: The temperature of the green body is raised from the first sintering temperature to the second sintering temperature at a heating rate of 2~3℃ / min. The second sintering temperature is 1095~1105℃. The green body is held at the second sintering temperature for 115~125min. B3: The temperature of the green body is raised from the second sintering temperature to the third sintering temperature at a heating rate of 1.5~2℃ / min, the third sintering temperature is 1295~1305℃, and the green body is held at the third sintering temperature for 175~185min. B4: The temperature of the green body is raised from the third sintering temperature to the fourth sintering temperature at a heating rate of 0.9~1.0℃ / min, the fourth sintering temperature is 1595℃~1605℃, and the green body is held at the fourth sintering temperature for 175~185min. B5: The temperature of the green body is raised from the fourth sintering temperature to the fifth sintering temperature at a heating rate of 0.8~0.85℃ / min, the fifth sintering temperature is 1745℃~1755℃, and the green body is held at the fifth sintering temperature for 115~125min. B6: The temperature of the green body is raised from the fifth sintering temperature to the sixth sintering temperature at a heating rate of 0.4~0.6℃ / min, the sixth sintering temperature is 1805~1815℃, and the green body is held at the sixth sintering temperature for 475~485min. B7: The temperature of the billet is reduced from the sixth sintering temperature to the seventh sintering temperature at a cooling rate of 0.4~0.6℃ / min, the seventh sintering temperature is 1745℃~1755℃, and the billet is held at the seventh sintering temperature for 115~125min. B8: The temperature of the billet is reduced from the seventh sintering temperature to the eighth sintering temperature at a cooling rate of 0.9~1.1℃ / min, the eighth sintering temperature is 1295~1305℃, and the billet is held at the eighth sintering temperature for 115~125min. B9: The temperature of the green body is reduced from the eighth sintering temperature to the ninth sintering temperature at a cooling rate of 1.4~1.6℃ / min, wherein the ninth sintering temperature is 1195~1205℃; B10: The temperature of the billet is naturally cooled to room temperature along with the furnace temperature, and sintering is completed.

[0015] Preferably, step B2 further includes an air intake step, which includes: B21: Gas is introduced at the same time as the heating begins, with an intake rate of 20 L / min. The intake gas is selected from any one or more of nitrogen, helium, argon, and neon.

[0016] In the technical solution provided by this invention, the function of sintering process B1 is to remove adsorbed water and organic binders from the raw materials; the function of sintering process B2 is to introduce inert gas, which, under inert gas protection, removes water and other organic binders while preventing the aluminum nitride powder from oxidizing at high temperatures. Through sintering processes B1 and B2, the grain boundaries of aluminum nitride can be effectively purified, making the surface of aluminum nitride powder clean and laying the foundation for subsequent oxygen removal; sintering process B3 adopts a slow heating strategy of less than 2℃ / min, which allows sintering aids such as Y2O3, CaO, and MgO to fully react with the aluminum nitride grain boundary phase, thereby enriching the dissolved oxygen inside the aluminum nitride lattice towards the grain boundary and drawing in oxygen defects; sintering processes B4 to B6 adopt an ultra-slow heating strategy of less than 1℃ / min, which can precisely control the kinetic process of oxygen defect segregation and purification towards the grain boundary, making the initially generated oxygen-rich... The high thermal resistance of the aluminum YAG phase allows sufficient time for further absorption of sintering aids, thereby transforming the YAG phase into yttrium-rich YAM and YAP phases. In sintering process B6, the green body is held at the sixth sintering temperature for an extended period, providing sufficient thermal driving force for the purification and densification of aluminum nitride oxygen defects, resulting in the densification of aluminum nitride ceramics. The YAM and YAP phases are uniformly spread along the edges of the main aluminum nitride grains, completely eliminating the high thermal resistance barrier at the grain boundaries. Through sintering processes B1 to B6, aluminum nitride ceramics with no YAG phase residue inside the grain boundary phase and composed entirely of YAM and YAP phases can be obtained. To ensure the stability of the grain boundary phase inside the aluminum nitride ceramic, the sintering process of this invention provides B7 to B9. Sintering processes B7 to B9 employ a gradually increasing cooling rate. By controlling the cooling rate, the decomposition of the high-temperature phase of aluminum nitride can be effectively suppressed, maintaining the excellent grain boundary phase composition of aluminum nitride.

[0017] Furthermore, a second aspect of the present invention provides an aluminum nitride ceramic, wherein the secondary phase at the grain boundaries of the aluminum nitride ceramic is composed of a YAM phase and a YAP phase, and the ratio of the YAM phase to the YAP phase is (2.3~2.8):1, and the aluminum nitride ceramic is obtained by sintering using the sintering method described in the first aspect.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The aluminum nitride ceramic preparation method provided by this invention, through the careful selection of raw materials and control of the sintering process, ensures that the final aluminum nitride ceramic contains only YAP and YAM phases in its grain boundary secondary phases, and no YAG phase. Compared with existing aluminum nitride ceramics, the aluminum nitride ceramic prepared by the sintering method provided by this invention has a higher thermal conductivity at room temperature. Simultaneously, the aluminum nitride ceramic prepared by the sintering method provided by this invention has no stress concentration or structural defects caused by isolated agglomeration of grain boundary phases, which results in higher mechanical strength compared with existing aluminum nitride ceramics. Benefiting from these advantages, the aluminum nitride ceramic provided by this invention can be widely used in cutting-edge fields such as electrostatic chuck substrates, high-power semiconductor packaging substrates, and high-power laser heat dissipation substrates, and has broad application prospects. Attached Figure Description

[0019] Figure 1 The XRD results are for the aluminum nitride ceramic in Example 1 of this invention; Figure 2 The XRD results are for the aluminum nitride ceramic in Example 2 of this invention; Figure 3 The XRD results are for the aluminum nitride ceramic in Example 3 of this invention; Figure 4 The XRD results are for the aluminum nitride ceramic in Example 4 of this invention; Figure 5 The XRD results are for the aluminum nitride ceramic in Example 5 of this invention; Figure 6 The XRD results are for the aluminum nitride ceramic in Example 6 of this invention; Figure 7 The XRD results are shown for the aluminum nitride ceramic in Comparative Example 1 of this invention. Detailed Implementation

[0020] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0021] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] As described in the background art, currently, aluminum nitride ceramics have low room temperature thermal conductivity and mechanical strength due to the high proportion of YAG phase in the grain boundaries and the uneven distribution of secondary phases. In view of this, the present invention provides a sintering method for aluminum nitride ceramics that takes into account both room temperature thermal conductivity and mechanical strength.

[0023] Specifically, the sintering method for aluminum nitride ceramics provided by the present invention includes the following steps: S1: Mix aluminum nitride powder, dopant, solvent, dispersant and binder to obtain a slurry, and grind the slurry to obtain a fine slurry; S2: Spray granulation of the fine slurry to obtain granulated powder; S3: Press the granulated powder into shape to obtain a green body; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

[0024] By weight, in step S1 of the above embodiments, the aluminum nitride powder comprises 90-110 parts, the dopant 0.5-12 parts, the solvent 50-200 parts, the dispersant 0.5-1 part, and the binder 1.5-5 parts. In step S1 of the above embodiments, the dopant is selected from any one or more of yttrium trioxide (Y2O3), calcium oxide (CaO), and magnesium oxide (MgO).

[0025] More specifically, in the above embodiments, the dopant should at least include yttrium oxide, and the mass percentage of yttrium oxide relative to aluminum nitride powder is preferably 0.5% to 1.5%, more preferably 0.5% to 1%.

[0026] More specifically, in the above embodiments, to further improve the reaction rate, the dopant may also include calcium oxide and magnesium oxide in addition to yttrium oxide. The total mass of the dopant is preferably 0.4% to 13% of the aluminum nitride powder.

[0027] More specifically, in the above embodiments, the aluminum nitride powder is preferably aluminum nitride powder with an oxygen content of less than or equal to 0.48%.

[0028] In the above embodiments, the solvent is a low molecular weight alcohol, which is selected from any one or more of methanol, ethanol, propanol, and butanol; The dispersant is selected from any one or more of trimethyl phosphate, polyacrylate, ammonium polyacrylate, fish oil, and castor oil; The adhesive is selected from any one or more of polyvinyl alcohol, methylcellulose, ethylcellulose, and sodium carboxymethylcellulose; More specifically, in step S1 of the above embodiments, the grinding method is preferably any one of roller milling, ball milling, air jet milling, disc milling, and planetary milling, with ball milling being the most preferred. When using ball milling, the milling time is 5-12 hours, the milling speed is preferably 380-480 r / min, and the milling medium is preferably alumina balls. Through the above ball milling process, the fine slurry obtained has a D50 of 1.5-4 μm.

[0029] More specifically, in the above embodiments, the centrifugal atomization frequency of spray granulation is preferably 80~100Hz, the inlet air temperature is 85~95℃, preferably 90℃, the outlet air temperature is 65~75℃, preferably 70℃, and the feed rate is 3~8L / h, preferably 5L / h. Through the above spray granulation process, the granulated powder obtained has a D50 of 60~80μm and a bulk density of 0.9~1.1g / cm³. 3 .

[0030] In step S3 of the above embodiment, compression molding refers to die molding, and the molding pressure of die molding is 100~135MPa, preferably 120MPa. The density of the green body obtained by die molding is 1.8~2.0g / cm³. 3 .

[0031] In the above embodiments, the glue removal process includes the following steps: A1: Raise the temperature of the green compact from room temperature to the first discharge temperature at a heating rate of 0.3~0.6℃ / min. The first discharge temperature is 170~190℃. Hold the compact within the first discharge temperature range for 30~45min. A2: Raise the temperature of the green body from the first debinding temperature to the second debinding temperature at a heating rate of 0.2~0.4℃ / min. The second debinding temperature is 390~410℃. Hold the green body within the second debinding temperature range for 230~260min. A3: Raise the temperature of the green body from the second debinding temperature to the third debinding temperature at a heating rate of 0.2~0.4℃ / min. The third debinding temperature is 530~560℃. Hold the green body within the third debinding temperature range for 180~220min. A4: After the heat preservation in step A3 is completed, the green body temperature is reduced from the third debinding temperature to room temperature at a cooling rate of 1~3℃ / min to complete the debinding and obtain the green body.

[0032] In the above embodiments, the sintering process includes: B1: The temperature of the billet is raised to the first sintering temperature at a heating rate of 2~4℃ / min. The first sintering temperature is 595~605℃. The billet is held at the first sintering temperature for 170~185min. B2: The temperature of the green body is raised from the first sintering temperature to the second sintering temperature at a heating rate of 2~3℃ / min. The second sintering temperature is 1095~1105℃. The green body is held at the second sintering temperature for 115~125min. B3: The temperature of the green body is raised from the second sintering temperature to the third sintering temperature at a heating rate of 1.5~2℃ / min, the third sintering temperature is 1295~1305℃, and the green body is held at the third sintering temperature for 175~185min. B4: The temperature of the green body is raised from the third sintering temperature to the fourth sintering temperature at a heating rate of 0.9~1.0℃ / min, the fourth sintering temperature is 1595℃~1605℃, and the green body is held at the fourth sintering temperature for 175~185min. B5: The temperature of the green body is raised from the fourth sintering temperature to the fifth sintering temperature at a heating rate of 0.8~0.85℃ / min, the fifth sintering temperature is 1745℃~1755℃, and the green body is held at the fifth sintering temperature for 115~125min. B6: The temperature of the green body is raised from the fifth sintering temperature to the sixth sintering temperature at a heating rate of 0.4~0.6℃ / min, the sixth sintering temperature is 1805~1815℃, and the green body is held at the sixth sintering temperature for 475~485min. B7: The temperature of the billet is reduced from the sixth sintering temperature to the seventh sintering temperature at a cooling rate of 0.4~0.6℃ / min, the seventh sintering temperature is 1745℃~1755℃, and the billet is held at the seventh sintering temperature for 115~125min. B8: The temperature of the billet is reduced from the seventh sintering temperature to the eighth sintering temperature at a cooling rate of 0.9~1.1℃ / min, the eighth sintering temperature is 1295~1305℃, and the billet is held at the eighth sintering temperature for 115~125min. B9: The temperature of the green body is reduced from the eighth sintering temperature to the ninth sintering temperature at a cooling rate of 1.4~1.6℃ / min, wherein the ninth sintering temperature is 1195~1205℃; B10: The temperature of the billet is naturally cooled to room temperature along with the furnace temperature, and sintering is completed.

[0033] Using the dopant provided in the specific embodiments of this invention, combined with the sintering procedure provided by this invention, the dopant can be used as a sintering aid for aluminum nitride ceramics. During the sintering process, the dopant can react with oxygen-containing impurities such as alumina in the aluminum nitride powder to generate a second phase. Before holding at the sixth sintering temperature, the second phase consists of YAG phase, YAM phase, and YAP phase. During the holding at the sixth sintering temperature, the YAG phase will continuously absorb the dopant and transform into the YAM phase and YAP phase, thereby achieving precise directional control of the grain boundary phase of aluminum nitride ceramics. After the YAG phase is completely transformed into the YAM phase and YAP phase, the room temperature volume resistivity and room temperature thermal conductivity of aluminum nitride ceramics are correspondingly improved.

[0034] The technical solutions of the present invention are further described below through specific embodiments. Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some cases, terms with conventionally understood meanings are limited herein for clarification or ease of reference, and such limitations should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and have been adopted through conventional methods.

[0035] In the following embodiments, unless otherwise specified, the room temperature thermal conductivity was measured by laser flare method using a laser thermal conductivity meter; the bending strength was measured by three-point bending method; the room temperature volume resistivity was measured by ultra-high insulation resistance meter; and the secondary phases at grain boundaries were measured by XRD method.

[0036] Example 1

[0037] Preparation of aluminum nitride ceramics (1% mass fraction dopant) S1: By weight, take 100 parts aluminum nitride powder (oxygen content 0.45%), 0.5 parts Y2O3 powder, 0.5 parts CaO powder, 50 parts anhydrous ethanol, 0.8 parts trimethyl phosphate, and 3 parts sodium carboxymethyl cellulose. Mix thoroughly to obtain a slurry. Ball mill the slurry using alumina balls with a D50 of 70 μm as the milling media. The ball mill speed is 400 r / min, and the milling time is 6 h to obtain a fine slurry with a D50 of 2.0 μm and a bulk density of 1.0 g / cm³. 3 ; S2: The fine slurry is spray-granulated at an inlet air temperature of 70°C, an outlet air temperature of 90°C, and a feed rate of 5 L / h to obtain granulated powder with a D50 of 70 μm and a bulk density of 1.0 g / cm³. 3 ; S3: The granulated powder is molded under a pressure of 120 MPa to obtain a green body with a density of 1.90 g / cm³.3 ; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

[0038] The glue removal process includes the following steps: A1: Raise the temperature of the green compact from room temperature to the first discharge temperature at a heating rate of 0.5℃ / min. The first discharge temperature is 180℃. Hold the compact within the first discharge temperature range for 40 minutes. A2: Raise the temperature of the green body from the first discharge temperature to the second discharge temperature at a heating rate of 0.3℃ / min. The second discharge temperature is 400℃. Hold the green body within the second discharge temperature range for 250 minutes. A3: The temperature of the green compact is raised from the second debinding temperature to the third debinding temperature at a heating rate of 0.3℃ / min. The third debinding temperature is 550℃. The compact is then kept at the third debinding temperature for 200 minutes. A4: After the heat preservation in step A3 is completed, the green body temperature is reduced from the third debinding temperature to room temperature at a cooling rate of 2℃ / min to complete the debinding and obtain the green body.

[0039] The sintering process includes: B1: The temperature of the billet is raised to the first sintering temperature at a heating rate of 3℃ / min. The first sintering temperature is 600℃. The billet is held at the first sintering temperature for 180min. B2: The temperature of the billet is raised from the first sintering temperature to the second sintering temperature at a heating rate of 2.5℃ / min. The second sintering temperature is 1100℃. The billet is held at the second sintering temperature for 120 minutes. B3: The temperature of the green body is raised from the second sintering temperature to the third sintering temperature at a heating rate of 1.67℃ / min, the third sintering temperature is 1300℃, and the green body is held at the third sintering temperature for 180min. B4: The temperature of the green body is raised from the third sintering temperature to the fourth sintering temperature at a heating rate of 1.0℃ / min, the fourth sintering temperature is 1600℃, and the green body is held at the fourth sintering temperature for 180min. B5: The temperature of the green body is raised from the fourth sintering temperature to the fifth sintering temperature at a heating rate of 0.83℃ / min. The fifth sintering temperature is 1750℃. The green body is held at the fifth sintering temperature for 120 minutes. B6: The temperature of the green body is raised from the fifth sintering temperature to the sixth sintering temperature at a heating rate of 0.5℃ / min. The sixth sintering temperature is 1810℃. The green body is held at the sixth sintering temperature for 480 min. B7: The temperature of the billet is reduced from the sixth sintering temperature to the seventh sintering temperature at a cooling rate of 0.5℃ / min. The seventh sintering temperature is 1750℃. The billet is held at the seventh sintering temperature for 120 minutes. B8: The temperature of the billet is reduced from the seventh sintering temperature to the eighth sintering temperature at a cooling rate of 1.0℃ / min, the eighth sintering temperature is 1300℃, and the billet is held at the eighth sintering temperature for 120min. B9: The temperature of the green body is reduced from the eighth sintering temperature to the ninth sintering temperature at a cooling rate of 1.5℃ / min, wherein the ninth sintering temperature is 1200℃. B10: The temperature of the green body is naturally cooled to room temperature along with the furnace temperature, and sintering is completed to obtain aluminum nitride ceramic.

[0040] The room-temperature thermal conductivity, flexural strength, grain boundary phase composition, and room-temperature volume resistivity of the above aluminum nitride ceramics were tested, and the results are shown in Table 1. The XRD results are as follows: Figure 1 As shown.

[0041] Table 1

[0042] Example 2

[0043] Preparation of aluminum nitride ceramics (2.3% mass fraction mixed dopant) S1: By mass, take 100 parts of aluminum nitride powder (oxygen content of 0.42%), 1 part of Y2O3 powder, 0.8 parts of CaO powder, 0.5 parts of MgO, 100 parts of anhydrous ethanol, 0.8 parts of trimethyl phosphate, and 3 parts of sodium carboxymethyl cellulose. Mix them thoroughly to obtain a slurry. Ball mill the slurry, using alumina balls with a D50 of 70 μm as the milling media. The ball mill speed is 420 r / min, and the ball milling time is 7 h to obtain a fine slurry with a D50 of 1.8 μm. S2: The fine slurry is spray-granulated at an inlet air temperature of 70°C, an outlet air temperature of 90°C, and a feed rate of 5 L / h to obtain granulated powder with a D50 of 72 μm and a bulk density of 1.02 g / cm³. 3 ; S3: The granulated powder is molded under a pressure of 120 MPa to obtain a green body with a density of 1.92 g / cm³. 3 ; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

[0044] The glue removal procedure is the same as in Example 1.

[0045] The sintering procedure is the same as in Example 1.

[0046] The room-temperature thermal conductivity, flexural strength, grain boundary phase composition, and room-temperature volume resistivity of the above aluminum nitride ceramics were tested, and the results are shown in Table 2. The XRD results are as follows: Figure 2 As shown.

[0047] Table 2

[0048] Example 3

[0049] Preparation of aluminum nitride ceramics (2.3% mass fraction mixed dopant) S1: By mass, take 100 parts of aluminum nitride powder (oxygen content of 0.42%), 1 part of Y2O3 powder, 0.8 parts of CaO powder, 0.5 parts of MgO, 100 parts of anhydrous ethanol, 0.8 parts of trimethyl phosphate, and 3 parts of sodium carboxymethyl cellulose. Mix them thoroughly to obtain a slurry. Ball mill the slurry, using alumina balls with a D50 of 70 μm as the milling media. The ball mill speed is 420 r / min, and the ball milling time is 7 h to obtain a fine slurry with a D50 of 1.8 μm. S2: The fine slurry is spray-granulated at an inlet air temperature of 70°C, an outlet air temperature of 90°C, and a feed rate of 5 L / h to obtain granulated powder with a D50 of 72 μm and a bulk density of 1.02 g / cm³. 3 ; S3: The granulated powder is molded under a pressure of 120 MPa to obtain a green body with a density of 1.92 g / cm³. 3 ; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

[0050] The glue removal process includes the following steps: A1: Raise the temperature of the green compact from room temperature to the first discharge temperature at a heating rate of 0.3℃ / min. The first discharge temperature is 190℃. Hold the compact within the first discharge temperature range for 45 minutes. A2: Raise the temperature of the green body from the first debinding temperature to the second debinding temperature at a heating rate of 0.4℃ / min. The second debinding temperature is 410℃. Hold the green body within the second debinding temperature range for 240 minutes. A3: The temperature of the green body is raised from the second debinding temperature to the third debinding temperature at a heating rate of 0.2℃ / min. The third debinding temperature is 540℃. The body is then kept at the third debinding temperature for 180 minutes. A4: After the heat preservation in step A3 is completed, the green body temperature is reduced from the third debinding temperature to room temperature at a cooling rate of 3℃ / min to complete the debinding and obtain the green body.

[0051] The sintering process includes: B1: The temperature of the billet is raised to the first sintering temperature at a heating rate of 2.0℃ / min. The first sintering temperature is 605℃. The billet is held at the first sintering temperature for 170min. B2: The temperature of the green body is raised from the first sintering temperature to the second sintering temperature at a heating rate of 2.0℃ / min. The second sintering temperature is 1105℃. The green body is held at the second sintering temperature for 125 minutes. B3: The temperature of the green body is raised from the second sintering temperature to the third sintering temperature at a heating rate of 1.75℃ / min, the third sintering temperature is 1305℃, and the green body is held at the third sintering temperature for 185min. B4: The temperature of the green body is raised from the third sintering temperature to the fourth sintering temperature at a heating rate of 1.0℃ / min. The fourth sintering temperature is 1600℃. The green body is held at the fourth sintering temperature for 185 minutes. B5: The temperature of the green body is raised from the fourth sintering temperature to the fifth sintering temperature at a heating rate of 0.8℃ / min, the fifth sintering temperature is 1750℃, and the green body is held at the fifth sintering temperature for 120min. B6: The temperature of the green body is raised from the fifth sintering temperature to the sixth sintering temperature at a heating rate of 0.4℃ / min. The sixth sintering temperature is 1815℃. The green body is held at the sixth sintering temperature for 485 minutes. B7: The temperature of the billet is reduced from the sixth sintering temperature to the seventh sintering temperature at a cooling rate of 0.5℃ / min. The seventh sintering temperature is 1750℃. The billet is held at the seventh sintering temperature for 120 minutes. B8: The temperature of the billet is reduced from the seventh sintering temperature to the eighth sintering temperature at a cooling rate of 1.0℃ / min, the eighth sintering temperature is 1300℃, and the billet is held at the eighth sintering temperature for 120min. B9: The temperature of the green body is reduced from the eighth sintering temperature to the ninth sintering temperature at a cooling rate of 1.5℃ / min, wherein the ninth sintering temperature is 1200℃. B10: The temperature of the green body is naturally cooled to room temperature along with the furnace temperature, and sintering is completed to obtain aluminum nitride ceramic.

[0052] The room-temperature thermal conductivity, flexural strength, grain boundary phase composition, and room-temperature volume resistivity of the above aluminum nitride ceramics were tested, and the results are shown in Table 3. The XRD results are as follows: Figure 3 As shown.

[0053] Table 3

[0054] Example 4

[0055] Preparation of aluminum nitride ceramics (2.5% mass fraction mixed dopant) S1: By mass, take 100 parts of aluminum nitride powder (oxygen content of 0.42%), 0.5 parts of Y2O3 powder, 1.0 parts of CaO powder, 1.0 parts of MgO, 100 parts of anhydrous ethanol, 0.8 parts of trimethyl phosphate, and 3 parts of sodium carboxymethyl cellulose. Mix them thoroughly to obtain a slurry. Ball mill the slurry, using alumina balls with a D50 of 70 μm as the milling media. The ball mill speed is 450 r / min, and the ball milling time is 8 h to obtain a fine slurry with a D50 of 1.6 μm. S2: The fine slurry is spray-granulated at an inlet air temperature of 70°C, an outlet air temperature of 90°C, and a feed rate of 5 L / h to obtain granulated powder with a D50 of 65 μm and a bulk density of 0.95 g / cm³. 3 ; S3: The granulated powder is molded under a pressure of 120 MPa to obtain a green body with a density of 1.88 g / cm³. 3 ; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

[0056] The glue removal procedure is the same as in Example 3.

[0057] The sintering procedure is the same as in Example 3.

[0058] The room-temperature thermal conductivity, flexural strength, grain boundary phase composition, and room-temperature volume resistivity of the above aluminum nitride ceramics were tested, and the results are shown in Table 4. The XRD results are as follows: Figure 4 As shown.

[0059] Table 4

[0060] Example 5

[0061] Preparation of aluminum nitride ceramics (1.5% by mass single dopant, high oxygen content powder) S1: By mass, take 100 parts of aluminum nitride powder (oxygen content of 0.48%), 1.5 parts of Y2O3 powder, 100 parts of anhydrous ethanol, 0.8 parts of trimethyl phosphate, and 3 parts of sodium carboxymethyl cellulose. Mix them thoroughly to obtain a slurry. Ball mill the slurry, using alumina balls with a D50 of 70 μm as the milling media. The ball mill speed is 450 r / min, and the ball milling time is 8 h to obtain a fine slurry with a D50 of 1.6 μm. S2: The fine slurry is spray-granulated at an inlet air temperature of 70°C, an outlet air temperature of 90°C, and a feed rate of 5 L / h to obtain granulated powder with a D50 of 65 μm and a bulk density of 0.95 g / cm³. 3 ; S3: The granulated powder is molded under a pressure of 120 MPa to obtain a green body with a density of 1.88 g / cm³. 3 ; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

[0062] The glue removal procedure is the same as in Example 3.

[0063] The sintering procedure is the same as in Example 3.

[0064] The room-temperature thermal conductivity, flexural strength, grain boundary phase composition, and room-temperature volume resistivity of the above aluminum nitride ceramics were tested, and the results are shown in Table 5. The XRD results are as follows: Figure 5 As shown.

[0065] Table 5

[0066] Example 6

[0067] Preparation of aluminum nitride ceramics (1.5% by mass single dopant, low oxygen content powder) S1: By mass, take 100 parts of aluminum nitride powder (oxygen content of 0.25%), 1.5 parts of Y2O3 powder, 100 parts of anhydrous ethanol, 0.8 parts of trimethyl phosphate, and 3 parts of sodium carboxymethyl cellulose. Mix them thoroughly to obtain a slurry. Ball mill the slurry, using alumina balls with a D50 of 70 μm as the milling media. The ball mill speed is 450 r / min, and the ball milling time is 8 h to obtain a fine slurry with a D50 of 1.6 μm. S2: The fine slurry is spray-granulated at an inlet air temperature of 70°C, an outlet air temperature of 90°C, and a feed rate of 5 L / h to obtain granulated powder with a D50 of 65 μm and a bulk density of 0.95 g / cm³. 3 ; S3: The granulated powder is molded under a pressure of 120 MPa to obtain a green body with a density of 1.88 g / cm³. 3 ; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

[0068] The glue removal procedure is the same as in Example 3.

[0069] The sintering procedure is the same as in Example 3.

[0070] The room-temperature thermal conductivity, flexural strength, grain boundary phase composition, and room-temperature volume resistivity of the above aluminum nitride ceramics were tested, and the results are shown in Table 6. The XRD results are as follows: Figure 6 As shown.

[0071] Table 6

[0072] Comparative Example 1 Traditional sintering process Traditional aluminum nitride ceramics often use a single sintering curve. In this comparative example, all raw materials are the same as in Example 5, but the sintering program is modified to the program shown in Table 7.

[0073] Table 7

[0074] The room temperature thermal conductivity, flexural strength, grain boundary phase composition, and room temperature volume resistivity of the above samples were tested, and the results are shown in Table 8. The XRD results are as follows: Figure 7 As shown.

[0075] Table 8

[0076] As can be seen from the above embodiments and comparative examples, the sintering method for aluminum nitride ceramics provided by the present invention can effectively improve the room temperature thermal conductivity, mechanical strength, and room temperature volume resistivity of the final aluminum nitride ceramics compared with existing sintering methods.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A sintering method for aluminum nitride ceramics, characterized in that, Includes the following steps: S1: Mix aluminum nitride powder, dopant, solvent, dispersant and binder to obtain a slurry, and grind the slurry to obtain a fine slurry; S2: Spray granulation of the fine slurry to obtain granulated powder; S3: Press the granulated powder into shape to obtain a green body; S4: According to the glue removal procedure, the green body is de-glueed to obtain a green body; S5: The green body is sintered according to the sintering procedure to obtain aluminum nitride ceramic.

2. The sintering method as described in claim 1, characterized in that, By weight, in step S1, the aluminum nitride powder is 90-110 parts, the dopant is 0.5-12 parts, the solvent is 50-200 parts, the dispersant is 0.5-1 parts, and the binder is 1.5-5 parts.

3. The sintering method as described in claim 1, characterized in that, In step S1, the dopant is selected from any one or more of yttrium oxide, calcium oxide, and magnesium oxide.

4. The sintering method as described in claim 1, characterized in that, The solvent is a low molecular weight alcohol, which is selected from any one or more of methanol, ethanol, propanol, and butanol. The dispersant is selected from any one or more of trimethyl phosphate, polyacrylate, ammonium polyacrylate, fish oil, and castor oil; The adhesive is selected from any one or more of polyvinyl alcohol, methylcellulose, ethylcellulose, and sodium carboxymethylcellulose.

5. The sintering method as described in claim 1, characterized in that, The D50 of the granulated powder is 60~80μm.

6. The sintering method as described in claim 1, characterized in that, In step S3, the density of the green body is 1.8~2.0 g / cm³. 3 .

7. The sintering method as described in claim 1, characterized in that, The glue removal process includes the following steps: A1: Raise the temperature of the green compact from room temperature to the first discharge temperature at a heating rate of 0.3~0.6℃ / min. The first discharge temperature is 170~190℃. Hold the compact within the first discharge temperature range for 30~45min. A2: Raise the temperature of the green body from the first debinding temperature to the second debinding temperature at a heating rate of 0.2~0.4℃ / min. The second debinding temperature is 390~410℃. Hold the green body within the second debinding temperature range for 230~260min. A3: Raise the temperature of the green body from the second debinding temperature to the third debinding temperature at a heating rate of 0.2~0.4℃ / min. The third debinding temperature is 530~560℃. Hold the green body within the third debinding temperature range for 180~220min. A4: After the heat preservation in step A3 is completed, the green body temperature is reduced from the third debinding temperature to room temperature at a cooling rate of 1~3℃ / min to complete the debinding and obtain the green body.

8. The sintering method as described in claim 1, characterized in that, The sintering process includes: B1: The temperature of the billet is raised to the first sintering temperature at a heating rate of 2~4℃ / min. The first sintering temperature is 595~605℃. The billet is held at the first sintering temperature for 170~185min. B2: The temperature of the green body is raised from the first sintering temperature to the second sintering temperature at a heating rate of 2~3℃ / min. The second sintering temperature is 1095~1105℃. The green body is held at the second sintering temperature for 115~125min. B3: The temperature of the green body is raised from the second sintering temperature to the third sintering temperature at a heating rate of 1.5~2℃ / min, the third sintering temperature is 1295~1305℃, and the green body is held at the third sintering temperature for 175~185min. B4: The temperature of the green body is raised from the third sintering temperature to the fourth sintering temperature at a heating rate of 0.9~1.0℃ / min, the fourth sintering temperature is 1595℃~1605℃, and the green body is held at the fourth sintering temperature for 175~185min. B5: The temperature of the green body is raised from the fourth sintering temperature to the fifth sintering temperature at a heating rate of 0.8~0.85℃ / min, the fifth sintering temperature is 1745℃~1755℃, and the green body is held at the fifth sintering temperature for 115~125min. B6: The temperature of the green body is raised from the fifth sintering temperature to the sixth sintering temperature at a heating rate of 0.4~0.6℃ / min, the sixth sintering temperature is 1805~1815℃, and the green body is held at the sixth sintering temperature for 475~485min. B7: The temperature of the billet is reduced from the sixth sintering temperature to the seventh sintering temperature at a cooling rate of 0.4~0.6℃ / min, the seventh sintering temperature is 1745℃~1755℃, and the billet is held at the seventh sintering temperature for 115~125min. B8: The temperature of the billet is reduced from the seventh sintering temperature to the eighth sintering temperature at a cooling rate of 0.9~1.1℃ / min, the eighth sintering temperature is 1295~1305℃, and the billet is held at the eighth sintering temperature for 115~125min. B9: The temperature of the green body is reduced from the eighth sintering temperature to the ninth sintering temperature at a cooling rate of 1.4~1.6℃ / min, wherein the ninth sintering temperature is 1195~1205℃; B10: The temperature of the billet is naturally cooled to room temperature along with the furnace temperature, and sintering is completed.

9. The sintering method as described in claim 8, characterized in that, The B2 step further includes an air intake step, which includes: B21: Gas is introduced at the same time as the heating begins, with an intake rate of 20 L / min. The intake gas is selected from any one or more of nitrogen, helium, argon, and neon.

10. An aluminum nitride ceramic, characterized in that, The secondary phase at the grain boundaries of the aluminum nitride ceramic is composed of a YAM phase and a YAP phase, and the ratio of the YAM phase to the YAP phase is (2.3~2.8):

1. The aluminum nitride ceramic is obtained by sintering using any of the sintering methods described in claims 1 to 9.

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