High-thermal-conductivity aluminum nitride ceramic and preparation method thereof

Abstract

The invention provides high-thermal-conductivity aluminum nitride ceramic and a preparation method thereof, and belongs to the technical field of aluminum nitride ceramic. Comprising the following raw materials: aluminum nitride powder, a sintering aid, absolute ethyl alcohol, a dispersing agent and a binder. The specific formula comprises the following raw materials: 100 parts of aluminum nitride powder, 3-5 parts of a sintering aid, 100 parts of absolute ethyl alcohol, 1-2 parts of a dispersant and 2-5 parts of a binder. Preferably, the aluminum nitride ceramic material is prepared from the following raw materials: 100 parts of aluminum nitride powder, 4 parts of a sintering aid, 100 parts of absolute ethyl alcohol, 1.2 parts of a dispersing agent and 3 parts of a binding agent. Through research test and improvement on sintering aids, forming, glue discharging and sintering processes, the heat conductivity of the aluminum nitride ceramic structural part can be effectively improved, the green body is high in strength and small in sintering shrinkage deformation, crystal lattices are further purified, crystal grains are promoted to grow up, the porosity is remarkably reduced by properly prolonging the heat preservation time, and the service life of the aluminum nitride ceramic structural part is prolonged. Therefore, the heat conductivity is improved and can reach more than 200W / (m.K), and batch production can be better carried out.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum nitride ceramics, and in particular to a high thermal conductivity aluminum nitride ceramic and a preparation method thereof. Background Art

[0002] Aluminum nitride ceramics have excellent properties such as high thermal conductivity, low dielectric constant, chemical stability, insulation, high temperature resistance and excellent corrosion resistance. They are widely used in integrated circuits, microelectronics, optics, 5G communications, semiconductor devices and other fields. With the development of the industry, the requirements are getting higher and higher. Power electronic devices are increasingly developing in the direction of high power, high integration and miniaturization. Effective heat dissipation is the basic guarantee for the safe and efficient operation of power electronic devices. The theoretical thermal conductivity of aluminum nitride can reach 320W / mk, but due to the influence of multiple factors such as grain boundary phase, impurities, pores, etc., the thermal conductivity of commercial AlN ceramic structural parts is generally in the range of 170-180 W / (m·K), which is far lower than its theoretical value, and there is still a lot of room for improvement. It is usually used to optimize the microstructure of AlN ceramics to reduce or even eliminate structural defects such as grain boundary phase, impurities, pores, etc. as much as possible. This is the key to the development and preparation of high thermal conductivity AlN ceramic structural parts. Among all impurities, oxygen is the main factor affecting the thermal conductivity of AlN, which limits the wider application of AlN ceramics.

[0003] At present, the common method is to dope aluminum nitride with one or more rare earth metal oxides such as Y2O3, La2O3, CeO2 as sintering aids. The sintering aids react with the surface Al2O3 to form liquid yttrium aluminate, which can form a liquid phase at a lower temperature, wet the AlN grains, expel pores, and promote the dense sintering of aluminum nitride ceramics. At the same time, the thermal conductivity of AlN ceramics is highly sensitive to oxygen content. Choosing a reasonable sintering aid can promote the dissolution of lattice oxygen atoms and the migration of grain boundary oxide phases to the outside of the green body, thereby reducing the oxygen content in the sintered AlN ceramics as much as possible. However, this method does not improve the thermal conductivity of aluminum nitride ceramics much. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a high thermal conductivity aluminum nitride ceramic and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: A high thermal conductivity aluminum nitride ceramic, comprising the following raw materials: Aluminum nitride powder, sintering aid, anhydrous ethanol, dispersant, binder; The specific formula includes the following raw materials: 100 parts of aluminum nitride powder, 3-5 parts of sintering aid, 100 parts of anhydrous ethanol, 1-2 parts of dispersant, and 2-5 parts of binder.

[0006] Preferably, the high thermal conductivity aluminum nitride ceramic comprises the following raw materials: 100 parts of aluminum nitride powder, 4 parts of sintering aid, 100 parts of anhydrous ethanol, 1.2 parts of dispersant, and 3 parts of binder.

[0007] Preferably, the D50 of the aluminum nitride powder is 1-1.5 um, the oxygen content of the aluminum nitride powder is below 1.0%, the sintering aid is Y2O3, and the binder is PVB binder.

[0008] Preferably, the dispersant is any one of castor oil, ammonium polyacrylate, and phosphate dispersants.

[0009] Preferably, the PVB adhesive is prepared by mixing polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral by ultrasonic stirring, the weight ratio of the polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral is 6:1.2:1.5, the weight average molecular weight of the polyphenoloxy resin is 35000-80000, the epoxy value of the epoxy-terminated polysiloxane is 0.5-0.7eq / 100g, and the solid content of the polyvinyl butyral emulsion is 35%.

[0010] The present invention also provides a method for preparing high thermal conductivity aluminum nitride ceramics, comprising the following steps: Step 1: Mix aluminum nitride powder, sintering aid and dispersant in anhydrous ethanol by ball milling to obtain a mixed slurry; Step 2: Add a binder to the mixed slurry, mix evenly by ball milling, spray granulate, dry and sieve with a sieve to obtain aluminum nitride granulated powder; Step 3: Use isostatic pressing to press the aluminum nitride granulated powder into a ceramic body, and then set the molding pressure according to the size of the pressed body. Generally, the molding pressure is 70-150 MPa. Step 4: Place the ceramic body into a binder removal furnace for binder removal, control the heating rate at 0.2-0.6°C / min, and keep the temperature at a maximum temperature of 500-550°C for 5-6 hours to remove the binder and control the carbon content of the body; Step 5: Place the debinding green body into a vacuum graphite furnace and fill it with nitrogen for sintering. The heating rate is controlled at 5-10°C / min before 800°C, and at 1-2°C / min from 800 to 1600°C, and multiple stages of heat preservation are performed. The heating rate is controlled at 0.4-0.6°C / min from 1600 to 1800°C. The green body is kept at the highest temperature for 30-50 hours, and then cooled to room temperature to obtain a sintered high thermal conductivity aluminum nitride ceramic green body. Finally, the sintered high thermal conductivity aluminum nitride ceramic green body is post-processed to meet the required requirements.

[0011] Preferably, in the step 1, anhydrous ethanol is added into the ball mill, and the anhydrous ethanol covers the aluminum nitride powder, the sintering aid and the dispersant.

[0012] Preferably, in step three, when the ceramic green body is placed in a debinding furnace for debinding, a layer of BN powder is applied between the ceramic green body and the firing plate, which is beneficial to debinding at the bottom of the green body.

[0013] Preferably, in the step 4, the temperature is kept at 150°C, 200°C, 300°C and 400°C for 1H respectively, and the carbon content of the green body after debinding is controlled at 450-550ppm. When cooling in the step 5, the temperature is slowly reduced to 800°C at a rate of 0.5-3°C / min, and then cooled to room temperature at a cooling rate of 5-10°C.

[0014] Preferably, before the step 5 of filling with nitrogen for sintering and heating, the vacuum graphite furnace is evacuated to below 100Pa and filled with 105KPa nitrogen to reduce the oxygen content in the furnace. The flow rate of nitrogen introduced during the heating and sintering process is 50L / min.

[0015] The high thermal conductivity aluminum nitride ceramics prepared by the present invention and the preparation method thereof are characterized in that the optimal ratio of the sintering aid is studied and tested to find the optimal addition amount. If the sintering aid is added too little, the effect of the sintering aid cannot be achieved, and if it is added too much, the impurity content will be increased, affecting the thermal conductivity. Thus, the addition of oxygen impurities is reduced by a suitable ratio of the sintering aid, and a suitable ratio of the dispersant and the binder can make the powder after spray granulation have good sphericity, uniform particle size, good fluidity, uniform and dense density distribution of the formed green body, and the carbon content of the green body is controlled by a debinding process. The appropriate carbon content can effectively reduce the grain boundary oxides during the sintering process and reduce the oxygen impurity content in the AlN ceramic. The heating and cooling rates are reduced by the sintering process, and the insulation time is appropriately extended, which is conducive to more complete development of the AlN ceramic grains, close contact of the grains, clear interfaces, and no lattice defects.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention adjusts the debinding temperature curve in the debinding process to control the carbon content of the green body after debinding. Appropriate C remaining in the AlN green body during the sintering process can effectively reduce the grain boundary oxide, reduce the oxygen impurity content in the AlN ceramic, and help improve the thermal conductivity of the AlN ceramic. Finally, in the sintering process, the heating rate is reduced to find the optimal sintering temperature. If the sintering temperature is too high, the grains grow abnormally, the grain boundary phase increases, the density decreases, and it is not conducive to the improvement of thermal conductivity. By appropriately extending the heat preservation time, it is helpful to further purify the lattice, promote the growth of the grains, and significantly reduce the porosity, thereby improving the thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable those skilled in the relevant art to make and use the present disclosure.

[0018] Figure 1 It is a schematic diagram of the process structure of high thermal conductivity aluminum nitride ceramics and its preparation method. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The present invention of this embodiment provides a high thermal conductivity aluminum nitride ceramic, including the following raw materials: aluminum nitride powder, sintering aid, anhydrous ethanol, dispersant, binder; The specific formula includes the following raw materials: 100 parts of aluminum nitride powder, 3-5 parts of sintering aid, 100 parts of anhydrous ethanol, 1-2 parts of dispersant, and 2-5 parts of binder.

[0021] The high thermal conductivity aluminum nitride ceramic of this embodiment includes the following raw materials: 100 parts of aluminum nitride powder, 4 parts of sintering aid, 100 parts of anhydrous ethanol, 1.2 parts of dispersant, and 3 parts of binder.

[0022] The D50 of the aluminum nitride powder of this embodiment is 1-1.5 um, the oxygen content of the aluminum nitride powder is below 1.0%, the sintering aid is Y2O3, and the binder is PVB binder.

[0023] The dispersant of this embodiment is any one of castor oil, ammonium polyacrylate, and phosphate dispersants.

[0024] The PVB adhesive of this embodiment is prepared by mixing polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral by ultrasonic stirring, wherein the weight ratio of polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral is 6:1.2:1.5, the weight average molecular weight of polyphenoloxy resin is 35000-80000, the epoxy value of epoxy-terminated polysiloxane is 0.5-0.7eq / 100g, and the solid content of polyvinyl butyral emulsion is 35%; In the PVB adhesive, if too much polyphenol oxide resin is added, the bonding strength and heat resistance will increase. If too much terminal epoxy polysiloxane is added, the storage time will be extended, but the adhesion to the aluminum nitride granulated powder will decrease. If too much polyvinyl butyral is added, the bonding property is better, but its heat resistance will be affected. When the weight ratio of polyphenol oxide resin, terminal epoxy polysiloxane and polyvinyl butyral is 6:1.2:1.5, the prepared PVB adhesive has excellent heat resistance and bonding property, and is better for bonding and molding, so that the prepared aluminum nitride ceramics have better comprehensive performance.

[0025] A method for preparing a high thermal conductivity aluminum nitride ceramic in this embodiment includes the following steps: Step 1: Mix aluminum nitride powder, sintering aid and dispersant in anhydrous ethanol by ball milling to obtain a mixed slurry; Step 2: Add a binder to the mixed slurry, mix evenly by ball milling, spray granulate, dry and sieve with a sieve to obtain aluminum nitride granulated powder; Step 3: Use isostatic pressing to press the aluminum nitride granulated powder into a ceramic body, and then set the molding pressure according to the size of the pressed body. Generally, the molding pressure is 70-150 MPa. Step 4: Place the ceramic body into a binder removal furnace for binder removal, control the heating rate at 0.2-0.6°C / min, and keep the temperature at a maximum temperature of 500-550°C for 5-6 hours to remove the binder and control the carbon content of the body; Step 5: Place the debinding green body into a vacuum graphite furnace and fill it with nitrogen for sintering. The heating rate is controlled at 5-10°C / min before 800°C, and at 1-2°C / min from 800 to 1600°C, and multiple stages of heat preservation are performed. The heating rate is controlled at 0.4-0.6°C / min from 1600 to 1800°C. The green body is kept at the highest temperature for 30-50 hours, and then cooled to room temperature to obtain a sintered high thermal conductivity aluminum nitride ceramic green body. Finally, the sintered high thermal conductivity aluminum nitride ceramic green body is post-processed to meet the required requirements.

[0026] In step 1 of this embodiment, anhydrous ethanol is added into a ball mill, and the anhydrous ethanol covers the aluminum nitride powder, the sintering aid and the dispersant.

[0027] In step three of this embodiment, when the ceramic green body is placed in the debinding furnace for debinding, a layer of BN powder is applied between the ceramic green body and the firing plate, which is beneficial to debinding at the bottom of the green body.

[0028] In step 4 of this embodiment, the temperature is kept at 150°C, 200°C, 300°C and 400°C for 1H respectively, and the carbon content of the green body after debinding is controlled at 450-550ppm. When cooling in step 5, it is slowly reduced to 800°C at a rate of 0.5-3°C / min, and then cooled to room temperature at a cooling rate of 5-10°C.

[0029] In step 5 of this embodiment, before nitrogen is filled for sintering and heating, the vacuum graphite furnace is evacuated to below 100Pa and filled with 105KPa nitrogen to reduce the oxygen content in the furnace. The flow rate of nitrogen introduced during the heating and sintering process is 50L / min. Example 1

[0030] The present invention of this embodiment provides a high thermal conductivity aluminum nitride ceramic, including the following raw materials: aluminum nitride powder, sintering aid, anhydrous ethanol, dispersant, binder; The specific formula includes the following raw materials: 100 parts of aluminum nitride powder, 3 parts of sintering aid, 100 parts of anhydrous ethanol, 1 part of dispersant, and 2 parts of binder.

[0031] The D50 of the aluminum nitride powder of this embodiment is 1 um, the oxygen content of the aluminum nitride powder is below 1.0%, the sintering aid is Y2O3, and the binder is PVB binder.

[0032] The dispersant of this embodiment is any one of castor oil, ammonium polyacrylate, and phosphate dispersants.

[0033] The PVB adhesive of this embodiment is prepared by mixing polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral by ultrasonic stirring, wherein the weight ratio of polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral is 6:1.2:1.5, the weight average molecular weight of polyphenoloxy resin is 35000, the epoxy value of epoxy-terminated polysiloxane is 0.5eq / 100g, and the solid content of polyvinyl butyral emulsion is 35%.

[0034] A method for preparing a high thermal conductivity aluminum nitride ceramic in this embodiment includes the following steps: Step 1: Mix aluminum nitride powder, sintering aid and dispersant in anhydrous ethanol by ball milling to obtain a mixed slurry; Step 2: Add a binder to the mixed slurry, mix evenly by ball milling, spray granulate, dry and sieve with a sieve to obtain aluminum nitride granulated powder; Step 3: Use isostatic pressing to press the aluminum nitride granulated powder into a ceramic body, and then set the molding pressure according to the size of the pressed body. Generally, the molding pressure is 70 MPa. Step 4: Place the ceramic body into a binder removal furnace for binder removal, control the heating rate at 0.2°C / min, and keep the temperature at a maximum temperature of 500°C for 5 hours to remove the binder and control the carbon content of the body; Step 5: Place the debinding green body into a vacuum graphite furnace and fill it with nitrogen for sintering. The heating rate is controlled at 5°C / min before 800°C and at 1°C / min at 800°C, and multiple stages of heat preservation are performed. The heating rate at 1600°C is controlled at 0.4°C / min. The green body is kept at the highest temperature for 30 hours, and then cooled to room temperature to obtain a sintered high thermal conductivity aluminum nitride ceramic green body. Finally, the sintered high thermal conductivity aluminum nitride ceramic green body is post-processed to meet the required requirements.

[0035] In step 1 of this embodiment, anhydrous ethanol is added into a ball mill, and the anhydrous ethanol covers the aluminum nitride powder, the sintering aid and the dispersant.

[0036] In step three of this embodiment, when the ceramic green body is placed in the debinding furnace for debinding, a layer of BN powder is applied between the ceramic green body and the firing plate, which is beneficial to debinding at the bottom of the green body.

[0037] In step 4 of this embodiment, the temperature is kept at 150°C, 200°C, 300°C and 400°C for 1H respectively to control the carbon content of the green body after debinding at 450ppm. When cooling in step 5, the temperature is slowly reduced to 800°C at a rate of 0.5°C / min, and then cooled to room temperature at a cooling rate of 5°C.

[0038] In step 5 of this embodiment, before nitrogen is filled for sintering and heating, the vacuum graphite furnace is evacuated to below 100Pa and filled with 105KPa nitrogen to reduce the oxygen content in the furnace. The flow rate of nitrogen introduced during the heating and sintering process is 50L / min. Example 2

[0039] The present invention of this embodiment provides a high thermal conductivity aluminum nitride ceramic, including the following raw materials: aluminum nitride powder, sintering aid, anhydrous ethanol, dispersant, binder; The specific formula includes the following raw materials: 100 parts of aluminum nitride powder, 4 parts of sintering aid, 100 parts of anhydrous ethanol, 1.2 parts of dispersant, and 3 parts of binder.

[0040] The D50 of the aluminum nitride powder of this embodiment is 1.2 um, the oxygen content of the aluminum nitride powder is below 1.0%, the sintering aid is Y2O3, and the binder is PVB binder.

[0041] The dispersant of this embodiment is any one of castor oil, ammonium polyacrylate, and phosphate dispersants.

[0042] The PVB adhesive of this embodiment is prepared by mixing polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral by ultrasonic stirring, wherein the weight ratio of polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral is 6:1.2:1.5, the weight average molecular weight of polyphenoloxy resin is 35000-80000, the epoxy value of epoxy-terminated polysiloxane is 0.7eq / 100g, and the solid content of polyvinyl butyral emulsion is 35%.

[0043] A method for preparing a high thermal conductivity aluminum nitride ceramic in this embodiment includes the following steps: Step 1: Mix aluminum nitride powder, sintering aid and dispersant in anhydrous ethanol by ball milling to obtain a mixed slurry; Step 2: Add a binder to the mixed slurry, mix evenly by ball milling for 20 hours, spray granulate, dry and sieve with an 80-mesh screen to obtain aluminum nitride granulated powder; Step 3: Use isostatic pressing to press the aluminum nitride granulated powder into a ceramic body, and then set the molding pressure according to the size of the pressed body. Generally, the molding pressure is 80 MPa. Step 4: Place the ceramic body into a binder removal furnace for binder removal, control the heating rate at 0.3°C / min, and keep the temperature at a maximum temperature of 500°C for 6 hours to remove the binder and control the carbon content of the body; Step 5: Place the debinding green body into a vacuum graphite furnace and fill it with nitrogen for sintering. The heating rate is controlled at 8°C / min before 800°C, and at 2°C / min at 1200°C, and multiple stages of heat preservation are performed. The heating rate at 1800°C is controlled at 0.4°C / min. The green body is kept at the highest temperature for 36 hours, and then cooled to room temperature to obtain a sintered high thermal conductivity aluminum nitride ceramic green body. Finally, the sintered high thermal conductivity aluminum nitride ceramic green body is post-processed to meet the required requirements.

[0044] In step 1 of this embodiment, anhydrous ethanol is added into a ball mill, and the anhydrous ethanol covers the aluminum nitride powder, the sintering aid and the dispersant.

[0045] In step three of this embodiment, when the ceramic green body is placed in the debinding furnace for debinding, a layer of BN powder is applied between the ceramic green body and the firing plate, which is beneficial to debinding at the bottom of the green body.

[0046] In step 4 of this embodiment, the temperature is kept at 150°C, 200°C, 300°C and 400°C for 1H respectively to control the carbon content of the green body after debinding at 500ppm. When cooling in step 5, the temperature is slowly reduced to 800°C at 2°C / min, and then cooled to room temperature at a cooling rate of 7°C.

[0047] In step 5 of this embodiment, before nitrogen is filled for sintering and heating, the vacuum graphite furnace is evacuated to below 100Pa and filled with 105KPa nitrogen to reduce the oxygen content in the furnace. The flow rate of nitrogen introduced during the heating and sintering process is 50L / min. Example 3

[0048] The present invention of this embodiment provides a high thermal conductivity aluminum nitride ceramic, including the following raw materials: aluminum nitride powder, sintering aid, anhydrous ethanol, dispersant, binder; The specific formula includes the following raw materials: 100 parts of aluminum nitride powder, 5 parts of sintering aid, 100 parts of anhydrous ethanol, 2 parts of dispersant, and 5 parts of binder.

[0049] The D50 of the aluminum nitride powder of this embodiment is 1.5 um, the oxygen content of the aluminum nitride powder is below 1.0%, the sintering aid is Y2O3, and the binder is PVB binder.

[0050] The dispersant of this embodiment is any one of castor oil, ammonium polyacrylate, and phosphate dispersants.

[0051] The PVB adhesive of this embodiment is prepared by mixing polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral by ultrasonic stirring, wherein the weight ratio of polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral is 6:1.2:1.5, the weight average molecular weight of polyphenoloxy resin is 80,000, the epoxy value of epoxy-terminated polysiloxane is 0.7 eq / 100 g, and the solid content of polyvinyl butyral emulsion is 35%.

[0052] A method for preparing a high thermal conductivity aluminum nitride ceramic in this embodiment includes the following steps: Step 1: Mix aluminum nitride powder, sintering aid and dispersant in anhydrous ethanol by ball milling to obtain a mixed slurry; Step 2: Add a binder to the mixed slurry, mix evenly by ball milling, spray granulate, dry and sieve with a sieve to obtain aluminum nitride granulated powder; Step 3: Use isostatic pressing to press the aluminum nitride granulated powder into a ceramic body, and then set the molding pressure according to the size of the pressed body. Generally, the molding pressure is 150 MPa. Step 4: Place the ceramic body into a binder removal furnace for binder removal, control the heating rate at 0.6°C / min, and keep the temperature at a maximum temperature of 550°C for 6 hours to remove the binder and control the carbon content of the body; Step 5: Place the debinding green body into a vacuum graphite furnace and fill it with nitrogen for sintering. The heating rate is controlled at 10°C / min before 800°C, and at 2°C / min at 1600°C, and multiple stages of heat preservation are performed. The heating rate at 1800°C is controlled at 0.6°C / min. The green body is kept at the highest temperature for 30-50h, and then cooled to room temperature to obtain a sintered high thermal conductivity aluminum nitride ceramic green body. Finally, the sintered high thermal conductivity aluminum nitride ceramic green body is post-processed to meet the required requirements.

[0053] In step 1 of this embodiment, anhydrous ethanol is added into a ball mill, and the anhydrous ethanol covers the aluminum nitride powder, the sintering aid and the dispersant.

[0054] In step three of this embodiment, when the ceramic green body is placed in the debinding furnace for debinding, a layer of BN powder is applied between the ceramic green body and the firing plate, which is beneficial to debinding at the bottom of the green body.

[0055] In step 4 of this embodiment, the temperature is kept at 150°C, 200°C, 300°C and 400°C for 1H respectively to control the carbon content of the blank after debinding at 550ppm. When cooling in step 5, the temperature is slowly reduced to 800°C at 3°C / min, and then cooled to room temperature at a cooling rate of 10°C.

[0056] In step 5 of this embodiment, before nitrogen is filled for sintering and heating, the vacuum graphite furnace is evacuated to below 100Pa and filled with 105KPa nitrogen to reduce the oxygen content in the furnace. The flow rate of nitrogen introduced during the heating and sintering process is 50L / min.

[0057] Comparative Example 1. The difference from Example 3 is that aluminum nitride ceramics are prepared using a common formulation method.

[0058] Comparative Example 2. The difference from Example 3 is that the aluminum nitride ceramics are prepared by using a common debinding method.

[0059] Comparative Example 3. The difference from Example 3 is that the aluminum nitride ceramic is fired at a normal sintering temperature.

[0060] The products of Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests; 30 aluminum nitride ceramic samples were prepared and divided into 6 groups with 5 samples in each group. Each group corresponded to Examples 1-3 and Comparative Examples 1-3 and were numbered A / B / C / D / E / F. Finally, the aluminum nitride ceramic samples in groups A / B / C / D / E / F were tested respectively. The test results are shown in the following table.

[0061] It can be seen from Examples 1-3 and Comparative Examples 1-3 that the high thermal conductivity aluminum nitride ceramics prepared by the present invention and the preparation method thereof can effectively improve the thermal conductivity of aluminum nitride ceramic structural parts by conducting research, testing and improving sintering aids, molding, debinding and sintering processes. The green body has high strength, small sintering shrinkage deformation, and the thermal conductivity can reach more than 200W / (m·K), which is better for mass production.

[0062] The innovation of the present invention is: The present invention studies and tests the optimal ratio of the sintering aid to find the optimal addition amount. If the sintering aid is added too little, the effect of the sintering aid cannot be achieved, and if it is added too much, the impurity content will be increased, affecting the thermal conductivity. Therefore, the addition of oxygen impurities is reduced through the appropriate sintering aid ratio. The appropriate ratio of the dispersant and the binder can make the powder after spray granulation have good sphericity, uniform particle size, good fluidity, uniform and dense density distribution of the formed green body, and the carbon content of the green body is controlled through the debinding process. The appropriate carbon content can effectively reduce the grain boundary oxides during the sintering process and reduce the oxygen impurity content in the AlN ceramic. The heating and cooling rates are reduced through the sintering process, and the insulation time is appropriately extended, which is conducive to more complete development of the AlN ceramic grains, close contact of the grains, clear interfaces, and no lattice defects.

[0063] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0064] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A high thermal conductivity aluminum nitride ceramic, characterized in that: Including the following ingredients: Aluminum nitride powder, sintering aid, anhydrous ethanol, dispersant, binder; The specific formula includes the following raw materials (by mass): 100 parts of aluminum nitride powder, 3-5 parts of sintering aid, 100 parts of anhydrous ethanol, 1-2 parts of dispersant, and 2-5 parts of binder.

2. A high thermal conductivity aluminum nitride ceramic according to claim 1, characterized in that: Including the following ingredients: 100 parts of aluminum nitride powder, 4 parts of sintering aid, 100 parts of anhydrous ethanol, 1.2 parts of dispersant, and 3 parts of binder.

3. A high thermal conductivity aluminum nitride ceramic according to claim 2, characterized in that: The D50 of the aluminum nitride powder is 1-1.5 um, the oxygen content of the aluminum nitride powder is below 1.0%, the sintering aid is Y2O3, and the binder is PVB binder.

4. A high thermal conductivity aluminum nitride ceramic according to claim 3, characterized in that: The dispersant is any one of castor oil, ammonium polyacrylate and phosphate dispersants.

5. The high thermal conductivity aluminum nitride ceramic according to claim 4, characterized in that: The PVB adhesive is prepared by mixing polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral through ultrasonic stirring, wherein the weight ratio of the polyphenoloxy resin, epoxy-terminated polysiloxane and polyvinyl butyral is 6:1.2:1.5, the weight average molecular weight of the polyphenoloxy resin is 35000-80000, the epoxy value of the epoxy-terminated polysiloxane is 0.5-0.7eq / 100g, and the solid content of the polyvinyl butyral emulsion is 35%.

6. A method for preparing the high thermal conductivity aluminum nitride ceramic according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Mix aluminum nitride powder, sintering aid and dispersant in anhydrous ethanol by ball milling to obtain a mixed slurry; Step 2: Add a binder to the mixed slurry, mix evenly by ball milling, spray granulate, dry and sieve with a sieve to obtain aluminum nitride granulated powder; Step 3: Use isostatic pressing to press the aluminum nitride granulated powder into a ceramic body, and then set the molding pressure according to the size of the pressed body. Generally, the molding pressure is 70-150 MPa. Step 4: Place the ceramic body into a binder removal furnace for binder removal, control the heating rate at 0.2-0.6°C / min, and keep the temperature at a maximum temperature of 500-550°C for 5-6 hours to remove the binder and control the carbon content of the body; Step 5: Place the debinding green body into a vacuum graphite furnace and fill it with nitrogen for sintering. The heating rate is controlled at 5-10°C / min before 800°C, and at 1-2°C / min from 800 to 1600°C. Multi-stage heat preservation is performed. The heating rate is controlled at 0.4-0.6°C / min from 1600 to 1800°C. The green body is kept at the highest temperature for 30-50 hours, and then cooled to room temperature to obtain a sintered high thermal conductivity aluminum nitride ceramic green body.

7. The method for preparing a high thermal conductivity aluminum nitride ceramic according to claim 6, characterized in that: In the step 1, anhydrous ethanol is added into the ball mill, and the anhydrous ethanol covers the aluminum nitride powder, the sintering aid and the dispersant.

8. The method for preparing a high thermal conductivity aluminum nitride ceramic according to claim 7, characterized in that: In the step 3, when the ceramic body is placed in the debinding furnace for debinding, a layer of BN powder is applied between the ceramic body and the firing plate.

9. The method for preparing a high thermal conductivity aluminum nitride ceramic according to claim 8, characterized in that: In the step 4, the temperature is kept at 150°C, 200°C, 300°C and 400°C for 1H respectively to control the carbon content of the green body after debinding to be 450-550ppm. When cooling in the step 5, the temperature is slowly reduced to 800°C at a rate of 0.5-3°C / min, and then cooled to room temperature at a cooling rate of 5-10°C.

10. The method for preparing a high thermal conductivity aluminum nitride ceramic according to claim 9, characterized in that: In the step 5, before nitrogen is charged for sintering and heating, the vacuum graphite furnace is evacuated to below 100Pa and filled with 105KPa nitrogen to reduce the oxygen content in the furnace. The flow rate of nitrogen introduced during the heating and sintering process is 50L / min.

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