Aluminum nitride ceramic substrate and preparation method thereof
By introducing boron nitride dispersion into the preparation of aluminum nitride ceramic substrate, a silicon nitride reinforcing phase is generated, which solves the problem of improving thermal conductivity and mechanical properties and meets the requirements of high-power electronic packaging.
Patent Information
- Application Number
- CN202511720116.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-02-10
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The existing aluminum nitride ceramic substrates have difficulty simultaneously improving thermal conductivity and mechanical properties during the fabrication process, which limits their application in high-power electronic packaging.
Boron nitride dispersion, containing hydroxylated boron nitride nanosheets and hyperbranched polysilazane, is mixed by ball milling, then cast and cold isostatic pressing. Combined with specific sintering temperature and cooling process, a silicon nitride reinforcing phase is generated, which promotes densification and improves tensile strength and thermal conductivity.
Simultaneous optimization of the tensile strength and thermal conductivity of aluminum nitride ceramic substrates was achieved, improving the substrate's mechanical load-bearing capacity and heat dissipation capacity, making it suitable for high-power electronic packaging.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of ceramic substrate technology, specifically relating to an aluminum nitride ceramic substrate and its preparation method. Background Technology
[0002] AlN ceramics possess excellent comprehensive properties, including high thermal conductivity, low dielectric constant, good electrical insulation, good mechanical properties, and safety and non-toxicity. Furthermore, AlN ceramics have a thermal expansion coefficient that matches that of silicon and gallium arsenide. Simultaneously, AlN ceramics overcome the thermal mismatch between the substrate and Si wafer caused by the thermal expansion coefficient mismatch between BeO and Al2O3 and Si. Therefore, AlN ceramics have become the most ideal electronic packaging material for hybrid integrated circuits, microwave power devices, semiconductor devices, and large-scale integrated systems, and can be used as a high-performance ceramic substrate material for assembling ultra-large-scale integrated circuits.
[0003] As semiconductor chips continue to evolve towards higher power and higher integration, the input power of chips is constantly increasing, leading to a sharp increase in heat density. This places more stringent demands on the heat dissipation capacity and structural reliability of packaging substrates. Against this backdrop, the flexural strength and thermal conductivity of aluminum nitride ceramic substrates have become two key indicators determining their practical application performance. High thermal conductivity ensures that the substrate can quickly conduct the heat generated by the chip to the heat dissipation system, avoiding performance degradation or failure caused by heat accumulation. High flexural strength, on the other hand, ensures that the substrate has sufficient mechanical load-bearing capacity and dimensional stability during packaging processes and service, resisting deformation or fracture caused by external forces and thermal stress. Therefore, how to further optimize the AlN ceramic structure during the fabrication process and simultaneously improve its thermal conductivity and mechanical properties is crucial to promoting its wider application in high-power electronic packaging. Summary of the Invention
[0004] The purpose of this invention is to provide an aluminum nitride ceramic substrate and its preparation method, so as to simultaneously improve its thermal conductivity and mechanical properties.
[0005] The objective of this invention can be achieved through the following technical solutions: The first aspect of this application provides a method for preparing an aluminum nitride ceramic substrate, comprising the following steps: Step 1: According to weight parts, aluminum nitride powder, sintering aid, boron nitride dispersion, dispersant, binder, plasticizer, and solvent are mixed and ball-milled to obtain a slurry. The boron nitride dispersion includes hydroxylated boron nitride nanosheets and hyperbranched polysilazane, with a mass ratio of hyperbranched polysilazane to boron nitride of 0.8-1:1. The amount of modified boron nitride added is 0.8% to 1.2% of the mass of aluminum nitride powder. The second step is to cast the slurry into a blank and then cold isostatically press it at 20 MPa to obtain a blank. The blank is then debonded and sintered to obtain an aluminum nitride ceramic substrate.
[0006] In some possible implementations, the sintering aid is one of yttrium oxide and yttrium fluoride.
[0007] In some possible implementations, the oxygen content in the aluminum nitride powder is 0.8% to 2.5%. Conventional methods for preparing aluminum nitride powder (e.g., AlN hydrolyzes upon contact with humid air to form Al(OH)3, which is then heated to Al2O3) inevitably introduce oxygen, and the smaller the particle size, the higher the proportion of surface oxides. In the method for preparing the aluminum nitride ceramic substrate provided by this invention, a boron nitride dispersion is added to introduce hyperbranched polysilazane and boron nitride. The hyperbranched polysilazane undergoes in-situ pyrolysis at high temperature to generate nanoscale silicon nitride. This phase undergoes a eutectic reaction with the oxygen-containing impurities inherent in the AlN raw material (e.g., alumina) and added rare earth oxides (e.g., Y2O3) to form a Y-Si-Al-O liquid phase. This liquid phase can wet AlN grains at a lower temperature, promoting particle rearrangement and dissolution-reprecipitation, accelerating the densification process, reducing the sintering temperature, and improving sintering efficiency.
[0008] In some possible implementations, the boron nitride dispersion is prepared by the following steps: Hydroxylated boron nitride nanosheets and hyperbranched polysilazane were added to ethanol and ultrasonically dispersed for 1-3 hours to obtain a dispersion. The mass fraction of hyperbranched polysilazane in the dispersion was 5%–10%.
[0009] In some possible implementations, the hydroxylated boron nitride nanosheets are obtained by treating boron nitride with a high-temperature alkali. Specifically, the hydroxylated boron nitride nanosheets are prepared through the following steps: Boron nitride powder was added to an alkaline solution and subjected to a hydroxylation reaction at a temperature of 120-140℃ for 18-24 hours. After the reaction was completed, the product was centrifuged, washed, and dried to obtain hydroxylated boron nitride nanosheets.
[0010] The alkaline solution is a 5-8 mol / L sodium hydroxide aqueous solution.
[0011] In some possible implementations, the hyperbranched polysilazane is prepared by hydrosilylation reaction of bis(N,N-diallylamino)methylsilane as a reactant in the presence of a catalyst.
[0012] Specifically, the hyperbranched polysilazane is prepared through the following steps: Diallylamine and triethylamine were added to n-hexane. Under nitrogen protection and an ice-water bath, a n-hexane solution containing methyldichlorosilane was added. The dropping rate was controlled to maintain the system temperature at (10±5)℃. After the dropping was completed, the reaction was continued at room temperature for 2 hours to obtain bis(N,N-diallylamino)methylsilane. The ratio of diallylamine, triethylamine, and methyldichlorosilane is 0.4-0.5 mol: 0.4 mol: 0.2 mol; hexane is used as a solvent, and the amount can be adjusted according to the actual reaction volume. Bis(N,N-diallylamino)methylsilane was added to toluene, and Karstedt catalyst was added. The reaction was carried out at 70-80℃ for 36-72 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain hyperbranched polysilazane. The ratio of bis(N,N-diallylamino)methylsilane, Karstedt catalyst, and toluene was 2 g: 5 mg: 10-20 mL.
[0013] In some possible implementations, the mass ratio of aluminum nitride powder to sintering aid is 100:2-5; The ratio of aluminum nitride powder, dispersant, binder and plasticizer is 100:1-3:10-15:6-8; the mass fraction of solvent in the slurry is adjusted to 40% to 50%.
[0014] In some possible implementations, the dispersant is one of castor oil, sodium succinate, and dibutyl phosphate; The adhesive is one of polyvinyl butyral and polymethyl methacrylate; The plasticizer is one of dibutyl phthalate and glyceryl triacetate.
[0015] The solvent is one of ethanol, n-butanol, isopropanol, and ethyl acetate.
[0016] In some possible implementations, the ball milling speed in the first step is 300 r / min, and the ball milling time is 1-2 h; In the third step, the adhesive is discharged at 550-600℃ for 3-5 hours, and then held at 1700-1800℃ for 3-5 hours.
[0017] In some possible implementations, during the sintering process: the temperature is increased at 10°C / min between room temperature and 1300°C, and then increased at 5°C / min after reaching 1300°C. After reaching the set sintering temperature, the temperature is held. After the holding period, the temperature is cooled to 1300°C at a rate of 5°C / min. After reaching 1300°C, the product is cooled with the furnace.
[0018] The second aspect of this application provides an aluminum nitride ceramic substrate, which is prepared by the above-described preparation method.
[0019] The beneficial effects of this invention are: This invention provides an aluminum nitride ceramic substrate and its preparation method. In the preparation process of the aluminum nitride ceramic substrate, a boron nitride dispersion is added. This dispersion mainly consists of hydroxylated boron nitride nanosheets and hyperbranched polysilazane. Hyperbranched polysilazane can act as a highly efficient dispersant; its three-dimensional branched molecular structure effectively inhibits the aggregation of hydroxylated boron nitride nanosheets. Through steric hindrance, it significantly improves the dispersion stability of hydroxylated boron nitride nanosheets in the slurry and subsequent preform, thus laying the foundation for performance optimization.
[0020] During sintering, hyperbranched polysilazane undergoes pyrolysis, generating silicon nitride in situ. This in-situ generated silicon nitride acts as a reinforcing phase, directly improving the tensile strength of the substrate. The newly formed silicon nitride is highly reactive, further promoting the densification of the ceramic body during sintering. Simultaneously, the hyperbranched polysilazane and its pyrolysis products consume the inherent alumina impurities in the aluminum nitride powder and react with added rare earth oxides (such as yttrium oxide) sintering aids to generate a low-melting-point liquid phase. This liquid phase, through a liquid-phase sintering mechanism, significantly reduces the sintering temperature of the system, improves sintering efficiency, and further promotes grain rearrangement and porosity elimination, which is beneficial for increasing the density of the aluminum nitride ceramic substrate.
[0021] Uniformly dispersed hydroxylated boron nitride nanosheets introduced into the dispersion effectively bear and disperse loads in the aluminum nitride ceramic substrate through mechanisms such as pull-out, bridging, and crack deflection, becoming a key reinforcement to improve the tensile strength of the substrate. Boron nitride itself is an excellent thermal conductor, which helps to optimize the in-plane thermal conductivity of the substrate.
[0022] In this invention, hydroxylated boron nitride nanosheets and hyperbranched polysilazane exhibit a significant synergistic reinforcement effect: the hyperbranched polysilazane ensures the uniform dispersion of the hydroxylated boron nitride nanosheets and generates a silicon nitride reinforcing phase in situ, promoting densification; while the hydroxylated boron nitride nanosheets serve as the core reinforcing material, enhancing both mechanical strength and thermal conductivity. Together, they successfully achieve simultaneous optimization of the tensile strength and thermal conductivity of the aluminum nitride ceramic substrate. Detailed Implementation
[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0024] The following is a detailed description of an aluminum nitride ceramic substrate and its preparation method according to an embodiment of this application.
[0025] The following is a detailed description with reference to specific examples.
[0026] Example 1
[0027] This embodiment provides a method for preparing an aluminum nitride ceramic substrate, comprising the following steps: Step 1: According to weight parts, aluminum nitride powder, sintering aid, boron nitride dispersion, dispersant, binder, plasticizer, and solvent are mixed and ball-milled to obtain a slurry. The ball milling speed is 300 r / min, and the ball milling time is 2 h. The sintering aid is yttrium oxide, the dispersant is castor oil, the binder is polyvinyl butyral, the plasticizer is dibutyl phthalate, and the solvent is ethanol. The boron nitride dispersion includes hydroxylated boron nitride nanosheets and hyperbranched polysilazane. The mass ratio of hyperbranched polysilazane to boron nitride is 1:1, and the amount of modified boron nitride added is 1% of the mass of aluminum nitride powder. The oxygen content in the aluminum nitride powder is 1%. The mass ratio of aluminum nitride powder to sintering aid is 100:2. The ratio of aluminum nitride powder, dispersant, binder, and plasticizer is 100:1:10:6. The mass fraction of solvent in the slurry is adjusted to 45%.
[0028] The second step involves casting the slurry and then cold isostatically pressing it at 20 MPa to obtain a blank. The blank is then debonded at 600°C for 5 hours and sintered to obtain an aluminum nitride ceramic substrate. During the sintering process, the temperature is increased at 10°C / min between room temperature and 1300°C, and then increased at 5°C / min after reaching 1300°C. After reaching the set sintering temperature of 1800°C, the temperature is held for 5 hours. After the holding period, the temperature is cooled to 1300°C at a rate of 5°C / min. After reaching 1300°C, the product is cooled with the furnace.
[0029] The boron nitride dispersion was prepared by the following steps: Boron nitride powder was added to an alkaline solution and subjected to a hydroxylation reaction at 120°C for 24 hours. After the reaction, the product was centrifuged, washed, and dried to obtain hydroxylated boron nitride nanosheets. The alkaline solution was a 5 mol / L sodium hydroxide aqueous solution.
[0030] Diallylamine and triethylamine were added to n-hexane. Under nitrogen protection and an ice-water bath, a n-hexane solution containing methyldichlorosilane was added. The dropping rate was controlled to maintain the system temperature at (10±5)℃. After the addition was complete, the reaction was continued at room temperature for 2 hours to obtain bis(N,N-diallylamino)methylsilane. The ratio of diallylamine, triethylamine, and methyldichlorosilane was 0.5 mol: 0.4 mol: 0.2 mol. The amount of n-hexane used as a solvent could be adjusted according to the actual reaction volume. Bis(N,N-diallylamino)methylsilane was added to toluene, and Karstedt catalyst was added. The reaction was carried out at 80℃ for 36 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain hyperbranched polysilazane. The ratio of bis(N,N-diallylamino)methylsilane, Karstedt catalyst and toluene was 2 g: 5 mg: 20 mL.
[0031] Hydroxylated boron nitride nanosheets and hyperbranched polysilazane were added to ethanol and ultrasonically dispersed for 2 hours to obtain a dispersion. The mass fraction of hyperbranched polysilazane in the dispersion was 8%; the hydroxylated boron nitride nanosheets were obtained by high-temperature alkali treatment of boron nitride.
[0032] Example 2
[0033] The difference between this embodiment and Example 1 is that the boron nitride dispersion includes hydroxylated boron nitride nanosheets and hyperbranched polysilazane, the mass ratio of hyperbranched polysilazane to boron nitride is 0.8:1, and the amount of modified boron nitride added is 0.8% of the mass of aluminum nitride powder; the remaining raw materials and preparation methods are the same as in Example 1.
[0034] Step 1: According to weight parts, aluminum nitride powder, sintering aid, boron nitride dispersion, dispersant, binder, plasticizer, and solvent are mixed and ball-milled to obtain a slurry. The ball milling speed is 300 r / min, and the ball milling time is 2 h. The sintering aid is yttrium oxide, the dispersant is castor oil, the binder is polyvinyl butyral, the plasticizer is dibutyl phthalate, and the solvent is ethanol. The boron nitride dispersion includes hydroxylated boron nitride nanosheets and hyperbranched polysilazane. The mass ratio of aluminum nitride powder to sintering aid is 100:2. The ratio of aluminum nitride powder, dispersant, binder, and plasticizer is 100:1:10:6. The mass fraction of solvent in the slurry is adjusted to 45%.
[0035] The second step involves casting the slurry and then cold isostatically pressing it at 20 MPa to obtain a blank. The blank is then debonded at 600°C for 5 hours and sintered to obtain an aluminum nitride ceramic substrate. During sintering, the temperature is increased at a rate of 10°C / min from room temperature to 1300°C, and then increased at a rate of 5°C / min after reaching 1300°C. The substrate is held at this temperature for 5 hours, and then cooled to 1300°C at a rate of 5°C / min after reaching the set sintering temperature of 1800°C. After reaching this temperature, the substrate is held at this temperature for 5 hours, and then cooled to 1300°C at a rate of 5°C / min. After reaching 1300°C, the product is cooled with the furnace. The boron nitride dispersion is the same as in Example 1.
[0036] Example 3
[0037] This embodiment provides a method for preparing an aluminum nitride ceramic substrate. Compared with Example 1, the mass ratio of aluminum nitride powder to sintering aid is 100:5; the remaining raw materials and preparation methods are the same as in Example 1.
[0038] Step 1: According to weight parts, aluminum nitride powder, sintering aid, boron nitride dispersion, dispersant, binder, plasticizer, and solvent are mixed and ball-milled to obtain a slurry. The ball milling speed is 300 r / min, and the ball milling time is 2 h. The sintering aid is yttrium oxide, the dispersant is castor oil, the binder is polyvinyl butyral, the plasticizer is dibutyl phthalate, and the solvent is ethanol. The boron nitride dispersion includes hydroxylated boron nitride nanosheets and hyperbranched polysilazane. The mass ratio of hyperbranched polysilazane to boron nitride is 1:1, and the amount of modified boron nitride added is 1% of the mass of aluminum nitride powder. The oxygen content in the aluminum nitride powder is 1%. The ratio of aluminum nitride powder, dispersant, binder, and plasticizer is 100:1:10:6. The mass fraction of solvent in the slurry is adjusted to 45%.
[0039] The second step involves casting the slurry and then cold isostatically pressing it at 20 MPa to obtain a blank. The blank is then debonded at 600°C for 5 hours and sintered to obtain an aluminum nitride ceramic substrate. During sintering, the temperature is increased at a rate of 10°C / min from room temperature to 1300°C, and then increased at a rate of 5°C / min after reaching 1300°C. The substrate is held at this temperature for 5 hours, and then cooled to 1300°C at a rate of 5°C / min after reaching the set sintering temperature of 1800°C. After reaching this temperature, the substrate is held at this temperature for 5 hours, and then cooled to 1300°C at a rate of 5°C / min. After reaching 1300°C, the product is cooled with the furnace. The boron nitride dispersion is the same as in Example 1.
[0040] Example 4
[0041] This embodiment provides a method for preparing an aluminum nitride ceramic substrate. Compared with Example 1, the ratio of aluminum nitride powder, dispersant, binder and plasticizer in this embodiment is 100:2:10:7; the remaining raw materials and preparation methods are the same as in Example 1.
[0042] Step 1: According to weight parts, aluminum nitride powder, sintering aid, boron nitride dispersion, dispersant, binder, plasticizer, and solvent are mixed and ball-milled to obtain a slurry. The ball milling speed is 300 r / min, and the ball milling time is 2 h. The sintering aid is yttrium oxide, the dispersant is castor oil, the binder is polyvinyl butyral, the plasticizer is dibutyl phthalate, and the solvent is ethanol. The boron nitride dispersion includes hydroxylated boron nitride nanosheets and hyperbranched polysilazane. The mass ratio of hyperbranched polysilazane to boron nitride is 1:1, and the amount of modified boron nitride added is 1% of the mass of aluminum nitride powder. The oxygen content in the aluminum nitride powder is 1%. The mass ratio of aluminum nitride powder to sintering aid is 100:2. The mass fraction of solvent in the slurry is adjusted to 45%.
[0043] The second step involves casting the slurry and then cold isostatically pressing it at 20 MPa to obtain a blank. The blank is then debonded at 600°C for 5 hours and sintered to obtain an aluminum nitride ceramic substrate. During sintering, the temperature is increased at a rate of 10°C / min from room temperature to 1300°C, and then increased at a rate of 5°C / min after reaching 1300°C. The substrate is held at this temperature for 5 hours, and then cooled to 1300°C at a rate of 5°C / min after reaching the set sintering temperature of 1800°C. After reaching this temperature, the substrate is held at this temperature for 5 hours, and then cooled to 1300°C at a rate of 5°C / min. After reaching 1300°C, the product is cooled with the furnace. The boron nitride dispersion is the same as in Example 1.
[0044] Example 5
[0045] This embodiment provides a method for preparing an aluminum nitride ceramic substrate. Compared with Example 1, the oxygen content in the aluminum nitride powder used in this embodiment is 1.5%; the remaining raw materials and preparation methods are the same as in Example 1.
[0046] Example 6
[0047] This embodiment provides a method for preparing an aluminum nitride ceramic substrate. Compared with the previous embodiment, the oxygen content in the aluminum nitride powder used in this embodiment is 2%; the remaining raw materials and preparation methods are the same as in Example 1.
[0048] Example 7
[0049] This embodiment provides a method for preparing an aluminum nitride ceramic substrate. Compared with Example 1, the oxygen content in the aluminum nitride powder used in this embodiment is 2.5%; the remaining raw materials and preparation methods are the same as in Example 1.
[0050] Example 8
[0051] This embodiment provides a method for preparing an aluminum nitride ceramic substrate. Compared with Example 1, the preparation process of the boron nitride dispersion differs. Specifically, the boron nitride dispersion is prepared through the following steps: Boron nitride powder was added to an alkaline solution and subjected to a hydroxylation reaction at 140℃ for 18 hours. After the reaction was completed, the product was centrifuged, washed, and dried to obtain hydroxylated boron nitride nanosheets. The alkaline solution was an 8 mol / L sodium hydroxide aqueous solution.
[0052] Diallylamine and triethylamine were added to n-hexane. Under nitrogen protection and an ice-water bath, a n-hexane solution containing methyldichlorosilane was added. The dropping rate was controlled to maintain the system temperature at (10±5)℃. After the addition was complete, the reaction continued at room temperature for 2 hours to obtain bis(N,N-diallylamino)methylsilane. The ratio of diallylamine, triethylamine, and methyldichlorosilane was 0.4-0.5 mol: 0.4 mol: 0.2 mol. The amount of n-hexane used as a solvent could be adjusted according to the actual reaction volume. Bis(N,N-diallylamino)methylsilane was added to toluene, and Karstedt catalyst was added. The reaction was carried out at 70°C for 72 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain hyperbranched polysilazane. The ratio of bis(N,N-diallylamino)methylsilane, Karstedt catalyst and toluene was 2 g: 5 mg: 20 mL.
[0053] Hydroxylated boron nitride nanosheets and hyperbranched polysilazane were added to ethanol and ultrasonically dispersed for 2 hours to obtain a dispersion. The mass fraction of hyperbranched polysilazane in the dispersion was 10%; the hydroxylated boron nitride nanosheets were obtained by high-temperature alkali treatment of boron nitride.
[0054] The remaining raw materials and preparation methods are the same as in Example 1.
[0055] Comparative Example 1
[0056] The difference between this comparative example and Example 1 is that boron nitride dispersion is not added; the other raw materials and preparation methods are the same as in Example 1.
[0057] Comparative Example 2
[0058] The difference between this comparative example and Example 7 is that hyperbranched polysilazane is not added to the boron nitride dispersion, while the other raw materials and preparation process remain the same as in Example 7.
[0059] Comparative Example 3
[0060] The difference between this comparative example and Example 7 is that boron nitride dispersion was not added; the other raw materials and preparation methods are the same as in Example 7.
[0061] Test example: Performance tests were performed on Examples 1-8 and Comparative Examples 1-3; Bending strength was determined in accordance with GB / T6569-2006; The thermal conductivity of ceramic samples was measured using laser thermal conductivity method. The sample surface was ground and polished to remove surface defects. The specific heat capacity and thermal diffusivity of the sample were tested and calculated. Thermal conductivity = α·ρ·C, the unit of thermal conductivity is W / (m·K). In the formula: α is the thermal diffusivity, mm 2 / s; ρ is the density of the sample, in g / cm³. 2 ; C is the specific heat capacity, J / (g·K).
[0062] The results are shown in Table 1: Table 1
[0063] As shown in Table 1, the aluminum nitride ceramic substrates prepared according to the conditions in Examples 1-8 all exhibit high tensile strength and thermal conductivity. A comparison between Example 1 and Comparative Example 1 reveals that the absence of boron nitride dispersion and the lack of introduction of hydroxylated boron nitride nanosheets and hyperbranched polysilazane results in lower tensile strength. Examples 1 and 5-6 show that increasing the oxygen content of the aluminum nitride powder in the raw materials leads to a decrease in thermal conductivity. This is because increased oxygen content facilitates the reaction of sintering aids to generate a liquid phase, which promotes sintering densification. However, further increases in oxygen content inhibit the growth of aluminum nitride grains. The increased contact area between aluminum nitride grains leads to a decrease in the thermal conductivity of the ceramic substrate sample due to the increased interfacial thermal resistance. However, to a certain extent, refining the grains and strengthening the interfacial strength are beneficial to improving the bending strength of the aluminum nitride substrate. According to the comparison of Examples 1, 7 and Comparative Examples 1-2, only hydroxylated boron nitride nanosheets were added without introducing hyperbranched polysilazane. The system only had physical doping, and there was a lack of strong interfacial bonding between the components. Moreover, the hydroxylated boron nitride nanosheets had poor dispersion, which affected the densification degree and easily formed stress concentration points and thermal resistance points that were difficult to eliminate, resulting in a decrease in tensile strength and thermal conductivity.
[0064] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing an aluminum nitride ceramic substrate, characterized in that, Includes the following steps: Step 1: According to weight parts, aluminum nitride powder, sintering aid, boron nitride dispersion, dispersant, binder, plasticizer, and solvent are mixed and ball-milled to obtain a slurry; the boron nitride dispersion includes hydroxylated boron nitride nanosheets and hyperbranched polysilazane, with a mass ratio of hyperbranched polysilazane to boron nitride of 0.8-1:1, and the amount of modified boron nitride added is 0.8% to 1.2% of the mass of aluminum nitride powder; The second step is to cast the slurry into a blank and then cold isostatically press it to obtain a blank. The blank is then debonded and sintered to obtain an aluminum nitride ceramic substrate.
2. The method for preparing an aluminum nitride ceramic substrate according to claim 1, characterized in that, The sintering aid is one of yttrium oxide and yttrium fluoride.
3. The method for preparing an aluminum nitride ceramic substrate according to claim 1, characterized in that, The oxygen content in aluminum nitride powder is 0.8% to 2.5%.
4. The method for preparing an aluminum nitride ceramic substrate according to claim 1, characterized in that, The boron nitride dispersion was prepared by the following steps: Hydroxylated boron nitride nanosheets and hyperbranched polysilazane were added to ethanol and ultrasonically dispersed for 1-3 hours to obtain a dispersion; the mass fraction of hyperbranched polysilazane in the dispersion was 5%-10%.
5. The method for preparing an aluminum nitride ceramic substrate according to claim 4, characterized in that, The hydroxylated boron nitride nanosheets are obtained by treating boron nitride with a high temperature and an alkaline solution.
6. The method for preparing an aluminum nitride ceramic substrate according to claim 1, characterized in that, The hyperbranched polysilazane is prepared by hydrosilylation reaction of bis(N,N-diallylamino)methylsilane as the reactant monomer under the action of a catalyst.
7. The method for preparing an aluminum nitride ceramic substrate according to claim 1, characterized in that, The mass ratio of aluminum nitride powder to sintering aid is 100:2-5; The ratio of aluminum nitride powder, dispersant, binder and plasticizer is 100:1-3:10-15:6-8; the mass fraction of solvent in the slurry is adjusted to 40% to 50%.
8. The method for preparing an aluminum nitride ceramic substrate according to claim 1, characterized in that, The dispersant is one of castor oil, sodium succinate, and dibutyl phosphate; The adhesive is one of polyvinyl butyral and polymethyl methacrylate; The plasticizer is one of dibutyl phthalate and glyceryl triacetate; The solvent is one of ethanol, n-butanol, isopropanol, and ethyl acetate.
9. The method for preparing an aluminum nitride ceramic substrate according to claim 1, characterized in that, In the first step, the ball milling speed is 300 r / min, and the ball milling time is 1-2 h; In the third step, the adhesive is discharged at 550-600℃ for 3-5 hours, and then held at 1700-1800℃ for 3-5 hours. During the sintering process, the temperature is increased at 10℃ / min between room temperature and 1300℃, and then increased at 5℃ / min after reaching 1300℃. After reaching the set sintering temperature, the temperature is held. After the holding period, the temperature is cooled to 1300℃ at a rate of 5℃ / min. After reaching 1300℃, the product is cooled with the furnace.
10. An aluminum nitride ceramic substrate, characterized in that, Prepared by the preparation method according to any one of claims 1-9.