An alumina ceramic slurry, its preparation method and application

Abstract

This invention belongs to the field of ceramic slurry technology, specifically disclosing an alumina ceramic slurry, its preparation method, and its application. The alumina ceramic slurry comprises the following components by mass percentage: 5-8% acrylic resin composition, 0.1-0.3% dispersant, 8-14% resin solvent, 11-17% solvent, 0.93-1.42% inorganic sintering aid, and 59.28-74.97% alumina. The acrylic resin composition contains polydopamine-modified graphene material, acrylic resin, and ethyltoluenesulfonamide. The alumina ceramic slurry of this invention exhibits excellent stability, uniform dispersion, and casting performance. It does not crack or break during casting and can be matched with existing casting preparation processes. Its stability is 85-95%, its flowability is 120-140s, and its absolute Zeta potential is 30-33mV.

Description

Technical Field

[0001] This invention belongs to the field of ceramic slurry technology, specifically relating to an alumina ceramic slurry, its preparation method, and its application. Background Technology

[0002] Alumina ceramic paste is the core material for preparing alumina ceramic substrates, and its properties directly determine the physical, chemical, and mechanical properties of the final ceramic substrate. After years of development, the performance of pastes has been significantly improved, and they are widely used in electronic ceramics, semiconductor packaging, and high-temperature structural components. However, existing technologies still face many challenges in practical applications: (1) Poor dispersibility and easy agglomeration and sedimentation: Alumina powder (especially nano-sized) is prone to agglomeration due to its high surface energy, which leads to a sharp increase in slurry viscosity (>20000mPa·s) and difficulty in increasing solid content, directly affecting the process efficiency of tape casting and ultimately affecting the sintering densification process and product performance.

[0003] (2) High risk of cracking during casting: When alumina ceramic slurry with acrylic resin as binder is cast, the compatibility between the binder and alumina powder is poor and the three-dimensional network structure formed is brittle, resulting in insufficient green strength and easy cracking during drying. Summary of the Invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide an alumina ceramic slurry.

[0005] The second objective of this invention is to provide a method for preparing alumina ceramic slurry.

[0006] The third objective of this invention is to provide an alumina ceramic substrate.

[0007] The fourth objective of this invention is to provide the application of the above-mentioned alumina ceramic slurry in the fields of electronic ceramics, semiconductor packaging, or high-temperature structural components.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides an alumina ceramic slurry comprising the following components in weight percentages: 5-8% acrylic resin composition, 0.1-0.3% dispersant, 8-14% resin solvent, 11-17% solvent, 0.93-1.42% inorganic sintering aid, and 59.28-74.97% alumina; The acrylic resin composition contains polydopamine-modified graphene material, acrylic resin, and ethyltoluenesulfonamide.

[0009] The alumina ceramic slurry of this invention uses an acrylic resin composition as a binder. Polydopamine-modified graphene material is introduced into the acrylic resin composition. Polydopamine modification charges the graphene surface, generating electrostatic repulsion that effectively prevents particle attraction and agglomeration, thus improving the stability of the slurry. The interaction between the polydopamine-modified graphene material and the acrylic resin improves the rheological properties of the slurry and slows particle sedimentation. Simultaneously, the sheet-like polydopamine-modified graphene material interweaves in the slurry to form a stable three-dimensional network structure, effectively supporting the particles and preventing sedimentation. Furthermore, the hydroxyl and amino groups in polydopamine form hydrogen bonds with the carboxyl and hydroxyl groups in the acrylic resin, enhancing interfacial bonding. The combination of the flexibility of polydopamine and the mobility of the acrylic resin molecular chains causes physical entanglement at the interface. This strong interfacial bonding effectively enhances the binding force of the slurry during casting, significantly reducing the cracking rate of the green body.

[0010] In some embodiments of the present invention, the resin solvent includes at least one of ketone solvents and ester solvents.

[0011] In some embodiments of the present invention, the ketone solvent includes at least one of methyl ethyl ketone, acetone, 2-butanone, and methyl isobutyl ketone.

[0012] In some embodiments of the present invention, the ester solvent includes at least one selected from ethyl acetate, butyl acetate, and methyl acetate. In some embodiments of the present invention, the alumina ceramic slurry is composed of the following components in weight percentages: 5-8% acrylic resin composition, 0.1-0.3% dispersant, 8-14% resin solvent, 11-17% solvent, 0.93-1.42% inorganic sintering aid, and the balance being alumina.

[0013] In some embodiments of the present invention, the mass percentage of the acrylic resin composition can be any value or a range formed by any two of the following: 5%, 5.2%, 5.4%, 5.5%, 5.6%, 5.8%, 6%, 6.2%, 6.4%, 6.5%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.5%, 7.6%, 7.8%, and 8%. In some embodiments of the present invention, the mass percentage of the acrylic resin composition is 5.5% to 7%. The acrylic resin composition acts as a binder in this system, and its core function is to optimize the formability of the slurry and ensure that the resulting ceramic green body has sufficient strength to guarantee the integrity of subsequent processing operations.

[0014] When the content of the acrylic resin composition is less than 5 wt%, the following problems may occur: (a) Insufficient green strength: Insufficient acrylic resin composition cannot form sufficient bonding bridges between particles, resulting in a significant decrease in the mechanical strength of the green body. It is prone to breakage or cracking during handling or subsequent processing, leading to an increase in scrap rate. (b) Molding difficulties: Insufficient acrylic resin composition reduces the bonding ability of the slurry. During molding, problems such as delamination, cracks, and edge detachment may occur, seriously affecting the dimensional accuracy and structural integrity of the product, resulting in a decrease in production efficiency and yield. (c) Poor sintering performance: Insufficient acrylic resin composition results in loose particle packing and excessive initial porosity. During sintering, the material migration and densification driving force are insufficient, and these pores cannot be effectively filled, resulting in an increase in the porosity of the sintered body and a significant decrease in density, ultimately deteriorating its key properties such as mechanical strength, thermal conductivity, and electrical properties. (d) Inhomogeneous microstructure: Insufficient acrylic resin composition weakens the bonding force between particles, which may lead to uneven particle distribution in the sintered body. The inhomogeneity of the microstructure will cause abnormal grain growth, eventually forming a sintered body with inconsistent grain size and many structural defects, which seriously affects the overall performance of the product. (e) Uneven distribution of acrylic resin composition: Too low an acrylic resin composition content may cause uneven distribution in the slurry, resulting in significant fluctuations in the mechanical properties of different parts of the sintered body, affecting the consistency of product performance.

[0015] When the content of the acrylic resin composition exceeds 8 wt%, the following problems may occur: (a) Increased porosity of the sintered body: Excess acrylic resin composition decomposes or volatilizes during sintering, leaving behind a large number of pores, resulting in a significant increase in the porosity of the sintered body. Increased porosity reduces the density of the sintered body, deteriorating its mechanical strength, thermal conductivity, and electrical properties. (b) Increased shrinkage: Excessive acrylic resin composition content leads to a significant increase in volume loss during the sintering thermal decomposition stage, resulting in a sharp increase in product shrinkage, causing loss of dimensional accuracy and accompanied by deformation or dimensional deviation. The resulting uneven shrinkage generates huge internal stress in the green body, significantly increasing the risk of cracking of the sintered body. (c) Deterioration of thermal properties: Increased porosity reduces the thermal conductivity of the sintered body, weakening its heat dissipation performance, which is particularly detrimental to applications requiring high thermal conductivity. On the other hand, if excess acrylic resin composition remains and forms carbon traces or other thermal decomposition products, it will damage the microstructure of the material, directly leading to a decrease in its thermal stability and service performance under high-temperature environments. (d) Decreased electrical performance: The presence of porosity and residues can impair the insulation of the sintered body, increasing the risk of leakage. Simultaneously, excessive binder can lead to uncontrolled dielectric constant. These two factors combined severely affect the signal integrity and long-term operational reliability of the ceramic substrate in electronic applications.

[0016] In some embodiments of the present invention, the dispersant includes at least one of sodium hexametaphosphate, polyacrylic acid, polycarboxylate, polyvinylpyrrolidone, sodium citrate, and polyethylene glycol.

[0017] In some embodiments of the present invention, the mass percentage of the dispersant may be any value or a range formed by any two of 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, and 0.3%; in some embodiments of the present invention, the mass percentage of the dispersant is 0.15 to 0.25%.

[0018] The role of dispersants is to ensure the dispersion stability and uniformity of alumina ceramic slurries. When the content of dispersant is less than 0.1 wt%, the following problems may occur: (a) Particle agglomeration: One of the main functions of dispersants is to prevent powder particles from agglomerating. If the amount of dispersant is insufficient, a complete adsorption layer cannot be formed on the particle surface, and effective electrostatic repulsion or steric hindrance effect cannot be provided. Powder particles are prone to agglomeration, which not only leads to a decrease in slurry stability but also damages the performance of the final product. (b) Increased slurry viscosity: Particle agglomeration increases the internal frictional resistance of the slurry, resulting in increased slurry viscosity and poor flowability. This rheological deterioration makes it impossible for the film layer to spread evenly during casting, and the defect rate increases accordingly, ultimately affecting the production yield. (c) Obvious sedimentation: Agglomerated particles have a higher density and settle rapidly under gravity, causing slurry stratification, with the upper part clear and the lower part sedimented, seriously damaging the uniformity and stability of the system. (d) Widened particle size distribution: Agglomeration of some particles leads to an expansion of the overall particle size distribution range. Uneven particle distribution during sintering can lead to defects such as pores and cracks, reducing the material's mechanical strength and electrical insulation properties.

[0019] When the dispersant content exceeds 0.3 wt%, the following problems may occur: (a) Over-dispersion induces flocculation: On the one hand, excessive dispersant molecules will simultaneously adsorb onto multiple particles, forming a "bridging" effect that forces the particles to agglomerate; on the other hand, excessive dispersant will form bridges between particles, which will cause flocculation, leading to particle re-agglomeration and reducing the dispersion effect. Excessive dispersant will also change the charge distribution on the particle surface, weakening the electrostatic repulsion. These two effects together lead to a significant decrease in slurry stability. (b) Abnormally high slurry viscosity: Excessive dispersant will increase the viscosity of the slurry, significantly reducing its fluidity. This makes casting and spreading difficult and directly leads to molding defects such as bubble retention and cracking, seriously affecting production yield. (c) Bubble defects: Excessive dispersant will significantly reduce the surface tension of the slurry and may form a rigid adsorption layer on the surface of the bubble liquid film, thereby stabilizing the bubbles and preventing their escape and merging. These stabilized bubbles remain in the green body and will form pores after sintering, directly damaging the density, uniformity, and final mechanical strength of the product. (d) Increased production costs: Excessive dispersant not only fails to improve dispersion but also wastes raw materials, increasing production costs. (e) Impact on sintering performance: Excessive dispersant may leave residues during sintering, reducing the purity, density, and mechanical properties of alumina ceramics; on the other hand, these residues can disrupt normal sintering shrinkage behavior, leading to loss of control over product dimensional accuracy.

[0020] In some embodiments of the present invention, the mass percentage of the resin solvent in the alumina ceramic slurry is any value or a range formed by any two of 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, and 14%; in some embodiments of the present invention, the mass percentage of the resin solvent in the alumina ceramic slurry is 8.5% to 13%.

[0021] In some embodiments of the present invention, the solvent in the alumina ceramic slurry is selected from at least one of methanol, ethanol, propanol, isopropanol, and butanol.

[0022] In some embodiments of the present invention, the mass percentage of the solvent in the alumina ceramic slurry is any value or a range formed by any two of 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, and 17%; in some embodiments of the present invention, the mass percentage of the solvent in the alumina ceramic slurry is 12.5% ​​to 16%.

[0023] In some embodiments of the present invention, the inorganic sintering aid in the alumina ceramic slurry is any one of 0.93%, 0.95%, 0.98%, 1.0%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, or 1.42%, or a range formed by any two of these values. In some preferred embodiments of the present invention, the inorganic sintering aid in the alumina ceramic slurry is 1.15% to 1.35% by mass.

[0024] The main function of inorganic sintering aids is to reduce sintering temperature and energy consumption, and promote diffusion and bonding between particles, thereby resulting in uniform grain growth and a smooth surface. If the content of inorganic sintering aids is less than 0.93 wt%, the following problems may occur: (a) Increased sintering temperature: Due to insufficient inorganic sintering aid content, a higher temperature is required to achieve the same density during the sintering process. (b) Insufficient density: Insufficient inorganic sintering aid content may lead to increased porosity inside the sintered body, resulting in decreased density and thus deteriorating the mechanical properties of the material. (c) Uneven grain growth: Due to insufficient inorganic sintering aid content, it cannot effectively inhibit grain boundary migration, leading to abnormal growth of a few grains during the sintering process. This uneven microstructure will reduce the mechanical strength and reliability of the material. (d) Deterioration of surface quality: Due to insufficient inorganic sintering aid content, the densification and surface smoothing mechanisms during the sintering process are hindered, leading to increased surface roughness of the green blank and easy generation of defects such as microcracks, which seriously affects the appearance and service performance of the finished product. (e) Extended sintering cycle: In order to compensate for the slowed densification kinetics due to insufficient additives, the sintering time is forced to be extended in the process. This not only directly increases energy consumption and production costs, but may also lead to grain coarsening, affecting production efficiency and overall product performance.

[0025] If the content of inorganic sintering aids exceeds 1.42 wt%, the following problems may occur: (a) Reduced sintering temperature: Excessive inorganic sintering aids will significantly reduce the sintering temperature. Although this can reduce energy consumption, the excessively low sintering temperature may lead to insufficient density of the sintered body, deteriorating the material's performance. (b) Excessive liquid phase: Inorganic sintering aids usually form a liquid phase at high temperatures. Excessive inorganic sintering aids will lead to an excessive liquid phase, resulting in structural defects such as pores and cracks inside and on the surface of the sintered body, significantly reducing the material's mechanical strength and durability. (c) Abnormal grain growth: Excessive inorganic sintering aids may lead to abnormal grain growth, forming large-sized or abnormal grains. Such structures will severely deteriorate the material's mechanical strength and negatively impact its electrical conductivity and thermal stability. (d) Increased chemical reaction complexity: Excessive inorganic sintering aids may undergo complex chemical reactions with the matrix material, generating new compounds or phases. These new phases may adversely affect the material's performance. (e) Deterioration of surface quality: Excessive liquid phase may cause sagging and depressions on the surface of the sintered body, affecting the surface smoothness and appearance quality.

[0026] In some embodiments of the present invention, the inorganic sintering aid includes at least one of magnesium oxide, calcium oxide, and silicon dioxide. In some preferred embodiments of the present invention, the inorganic sintering aid includes magnesium oxide, calcium oxide, and silicon dioxide. In some preferred embodiments of the present invention, based on the total mass of the alumina ceramic slurry, the inorganic sintering aid comprises the following components in mass percentage: 0.6-0.9% magnesium oxide, 0.25-0.4% calcium oxide, and 0.08-0.12% silicon dioxide.

[0027] In some embodiments of the present invention, the mass percentage of magnesium oxide, based on the total mass of the alumina ceramic slurry, is any one of 0.6%, 0.7%, 0.8%, 0.9%, or a range formed by any two of these values.

[0028] In some embodiments of the present invention, the mass percentage of calcium oxide, based on the total mass of the alumina ceramic slurry, is any one of 0.25%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.35%, 0.36%, 0.38%, 0.4%, or a range formed by any two of these values.

[0029] In some embodiments of the present invention, the mass percentage of silicon dioxide, based on the total mass of the alumina ceramic slurry, is any one of 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, or a range formed by any two of these values.

[0030] In some embodiments of the present invention, the mass percentage of the alumina is any one of 59.28%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 74.97% or a range formed by any two of them.

[0031] In some embodiments of the present invention, the acrylic resin composition comprises the following components by mass percentage, based on the total mass of the acrylic resin composition: 0.1-0.5% polydopamine-modified graphene material, 27-30% resin solvent, 40-43% solvent, 4-5% ethyltoluenesulfonamide, and 21.5-28.9% acrylic resin.

[0032] The role of polydopamine-modified graphene material (PDA-C) in acrylic resin compositions is as follows: (1) Enhance mechanical properties and toughness: Graphene has extremely high strength and modulus. As a nanofiller, it is uniformly dispersed in acrylic resin, which can effectively enhance the resin network, thereby significantly improving the overall tensile strength and toughness of the green body. (2) Reduce cracking during green body casting: (a) Stress dispersion: PDA-C can more effectively disperse and transfer external stress, alleviate stress concentration, and thus reduce the risk of cracking caused by stress concentration during casting. (b) Improve thermal stability: The high thermal conductivity of graphene can help dissipate heat, suppress the generation of thermal stress caused by temperature changes during casting, ensure the stability of the casting process and prevent cracking. (c) The polydopamine (PDA) layer formed on the graphene surface has good interfacial adhesion and can enhance the interfacial bonding force between graphene and acrylic resin matrix. At the same time, the PDA layer is rich in active functional groups such as amino and hydroxyl groups. These functional groups can undergo hydrogen bonding or chemical reaction with functional groups (such as carboxyl and hydroxyl groups) in the acrylic resin matrix, further strengthening the interfacial bonding. This strong interfacial bonding effectively reduces interfacial defects and significantly improves the structural integrity of the green body, thereby fundamentally reducing the risk of cracking during the casting process. (3) Promote uniform dispersion and stability: The PDA layer prevents graphene agglomeration by introducing steric hindrance and electrostatic repulsion, ensuring its uniform distribution in the resin. The dispersed graphene then constructs a three-dimensional network, intertwines with the resin molecular chains, supports the particles, prevents sedimentation, and improves the stability of the slurry. (4) Improve rheological properties: An appropriate amount of PDA-C can adjust the viscosity of the acrylic resin, giving the slurry better fluidity. The fluidity is suitable during the casting process, avoiding uneven casting or cracking defects caused by excessive viscosity.

[0033] The role of ethyltoluenesulfonamide in acrylic resin compositions is to improve the flexibility and ductility of the resin composition and enhance its processing performance. When the content of ethyltoluenesulfonamide is within the range defined in this invention, it is beneficial to improve the flexibility and ductility of the acrylic resin, thereby optimizing the viscosity, dispersion uniformity, and casting stability of the slurry. These improvements are ultimately transferred to the alumina ceramic substrate, significantly enhancing its flexibility and impact resistance, making it less prone to cracking or breaking under stress.

[0034] In some embodiments of the present invention, the mass percentage of the acrylic resin is any one of 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 28.9%, or a range formed by any two of these values.

[0035] In some embodiments of the present invention, the acrylic resin is selected from at least one of polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, and polyisobutyl methacrylate.

[0036] In some embodiments of the present invention, the acrylic resin has a weight-average molecular weight of 0.5 × 10⁻⁶. 5 ~5×10 5 .

[0037] In some embodiments of the present invention, the acrylic resin has a weight-average molecular weight of 0.5 × 10⁻⁶. 5 1×10 5 1.5×10 5 2×10 5 2.5×10 5 3×10 5 3.5×10 5 4×10 5 4.5×10 5 5×10 5 The value is any value in the range formed by any two of them. When the molecular weight of the acrylic resin is within the range defined in this invention, it is beneficial to improve the storage and thermal stability and casting performance of the ceramic slurry, as well as to improve the mechanical strength of the ceramic substrate made from the ceramic slurry, making it less prone to breakage and cracking, and ensuring the smooth progress of subsequent processing.

[0038] In some embodiments of the present invention, the mass percentage of the resin solvent in the acrylic resin composition is any value selected from 27%, 28%, 29%, and 30%, or a range formed by any combination of these values. The role of the resin solvent in the present invention is to dissolve the acrylic resin, adjust its viscosity, and improve its processing performance. When the mass percentage of the resin solvent is within the range defined in the present invention, the acrylic resin can be fully dissolved, and the viscosity of the acrylic resin composition can be adjusted to a suitable range, forming a uniform acrylic resin solution, thereby improving the uniformity, stability, and flowability of the alumina ceramic slurry.

[0039] In some embodiments of the present invention, the solvent in the acrylic resin composition is any one of 40%, 41%, 42%, or 43% by mass, or a range formed by any two of these values. The role of the solvent in the acrylic resin composition is to dissolve the acrylic resin, adjust its viscosity and flowability, and improve its processing performance. Controlling the solvent content within the range defined in this invention ensures complete dissolution of the acrylic resin and precisely adjusts the system viscosity, forming a uniform and stable solution. This characteristic ensures the uniformity of the casting process, resulting in a more uniform alumina ceramic substrate in terms of thickness and particle distribution, ultimately achieving higher mechanical strength and effectively preventing deformation and cracking.

[0040] In some embodiments of the present invention, the solvent in the acrylic resin composition is selected from at least one of methanol, ethanol, propanol, isopropanol, and butanol.

[0041] In some embodiments of the present invention, the mass percentage of the polydopamine-modified graphene material is any value or a range formed by any two of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%. When the mass percentage of the polydopamine-modified graphene material is within the range defined by the present invention, it can effectively suppress the agglomeration, sedimentation, and stratification of particles in the slurry, which is beneficial to improving the dispersion uniformity, storage stability, and casting process performance of the slurry. These improvements ultimately ensure that the alumina ceramic substrate has a highly uniform microstructure and macroscopic thickness, exhibits high mechanical strength, and eliminates defects such as breakage, cracking, and micropores.

[0042] In some embodiments of the present invention, the polydopamine-modified graphene material includes graphene and a polydopamine coating layer; the graphene surface is provided with a polydopamine coating layer.

[0043] In some embodiments of the present invention, the polydopamine-modified graphene material comprises the following raw materials in the indicated mass percentages: dopamine hydrochloride 2-5%, alkali 0.01-0.05%, graphene 4.9-13%, and water 82-93%.

[0044] In some embodiments of the present invention, the alkali is selected from at least one of sodium hydroxide and potassium hydroxide.

[0045] In some embodiments of the present invention, the acrylic resin composition is prepared by a method comprising the following steps: The acrylic resin composition is prepared by mixing resin solvent, solvent, ethyl toluenesulfonamide, and acrylic resin, and then mixing it with polydopamine-modified graphene material.

[0046] In some embodiments of the present invention, the mixing rate is 700-1000 rpm when preparing the acrylic resin composition.

[0047] In some embodiments of the present invention, the mixing time for preparing the acrylic resin composition is 180-360 min.

[0048] In some embodiments of the present invention, the mixing temperature during the preparation of the acrylic resin composition is 20~40°C.

[0049] In some embodiments of the present invention, the polydopamine-modified graphene material is prepared by a method comprising the following steps: Dopamine hydrochloride, alkali, and water are mixed to obtain solution A; then solution A is mixed with graphene, causing dopamine hydrochloride to polymerize on the surface of the graphene to obtain solution B; Solution B was spray-dried to obtain the polydopamine-modified graphene material.

[0050] Dopamine hydrochloride can undergo a self-polymerization reaction under alkaline conditions, thereby forming a polydopamine (PDA) layer on the graphene surface, which is uniformly coated on the graphene surface. The PDA layer can effectively fill the defects and gaps on the graphene surface, forming a continuous and stable coating structure, and avoiding direct contact and aggregation of graphene sheets.

[0051] In some embodiments of the present invention, the mixing is performed by mechanical stirring.

[0052] In some embodiments of the present invention, the mixing stirring rate is 500~1000 rpm.

[0053] In some embodiments of the present invention, the mixing time is 20-35 minutes.

[0054] In some embodiments of the present invention, the polymerization reaction takes 20 to 24 hours.

[0055] In some embodiments of the present invention, the inlet air temperature during spray drying is 100~150°C.

[0056] In some embodiments of the present invention, the outlet air temperature during spray drying is 60~110°C.

[0057] In some embodiments of the present invention, the spray flow rate during spray drying is 0.1~1.5L / h.

[0058] In some embodiments of the present invention, the nozzle pressure during spray drying is 0.1~0.3 MPa.

[0059] The second aspect of the present invention provides a method for preparing the alumina ceramic slurry described in the first aspect of the present invention, comprising the following steps: The alumina ceramic slurry is prepared by mixing the raw materials.

[0060] In some embodiments of the present invention, the method for preparing the alumina ceramic slurry includes the following steps: Raw materials including resin solvent, solvent, dispersant, alumina, and inorganic sintering aid are mixed and then mixed with an acrylic resin composition to obtain the alumina ceramic slurry.

[0061] In some embodiments of the present invention, the mixing speed in the preparation method of the alumina ceramic slurry is 100~200 rpm.

[0062] In some embodiments of the present invention, the mixing temperature in the preparation method of the alumina ceramic slurry is 20~50℃.

[0063] In some embodiments of the present invention, the mixing and stirring time in the preparation method of the alumina ceramic slurry is 120~360 min.

[0064] A third aspect of the present invention provides an alumina ceramic substrate prepared from the alumina ceramic slurry described in the first aspect of the present invention.

[0065] The fourth aspect of the present invention provides the application of the alumina ceramic slurry described in the first aspect of the present invention in the fields of electronic ceramics, semiconductor packaging or high-temperature structural components.

[0066] The beneficial effects of this invention are as follows: An acrylic resin composition is introduced into the alumina ceramic slurry of this invention, wherein polydopamine-modified graphene material is introduced into the acrylic resin composition. Polydopamine modification charges the graphene surface, generating electrostatic repulsion to prevent particle attraction and agglomeration, thus improving the stability of the slurry. Simultaneously, the sheet-like polydopamine-modified graphene material interweaves in the slurry to form a stable three-dimensional network structure, effectively supporting the particles and preventing particle sedimentation. Furthermore, the hydroxyl and amino groups in dopamine form hydrogen bonds with the carboxyl and hydroxyl groups of the acrylic resin, enhancing interfacial bonding and effectively preventing cracking during the casting process.

[0067] The alumina ceramic slurry of the present invention has excellent stability, uniform dispersion and casting performance. It does not crack or break during casting and can be matched with existing casting preparation processes.

[0068] The alumina ceramic substrate prepared by the ceramic slurry of the present invention has uniform thickness, no cracks, and high mechanical strength and dielectric constant, specifically: dielectric constant of 9.3~9.7 and breakdown strength of 41~44kV / mm. Detailed Implementation

[0069] The following examples provide a more detailed description of the specific implementation of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described below are methods that can be implemented or understood by those skilled in the art by referring to existing technology. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0070] This example provides an alumina ceramic slurry, which is composed of the following components by mass percentage: 6% acrylic resin composition, 0.21% dispersant (i.e., polyethylene glycol), 9% methyl ethyl ketone, 14% methanol, 1.1% inorganic sintering aid, and 69.69% alumina. The specific formulation is shown in Table 1 below. The acrylic resin composition is composed of the following components by mass percentage: 25.7% acrylic resin, 0.3% polydopamine-modified graphene material (i.e., PDA-C, designated P2), 28% methyl ethyl ketone, 42% methanol, and 4% ethyl toluenesulfonamide; the formulation of the acrylic resin composition is shown in Table 2 below, corresponding to the formulation designated R3. PDA-C is made from the following raw materials in the indicated mass percentages: graphene 9.98%, dopamine hydrochloride 3%, sodium hydroxide 0.02%, and pure water 87%. The formula of PDA-C is shown in Table 3 below, corresponding to formula number P2. Based on the total mass of the alumina ceramic slurry, the inorganic sintering aid is composed of the following components by mass percentage: 0.6% magnesium oxide, 0.4% calcium oxide, and 0.1% silicon dioxide. The formulation of the inorganic sintering aid is shown in Table 4 below, corresponding to the formulation numbered W1.

[0071] The alumina ceramic slurry in this example was prepared using a method that includes the following steps: (1) Preparation of PDA-C Step a: Weigh the pure water, dopamine hydrochloride, and sodium hydroxide according to the formula, and then use a stirrer to stir evenly to ensure that the dopamine hydrochloride and sodium hydroxide are completely dissolved to form a uniform and transparent mother liquor. Stirring speed: 700 rpm; stirring time: 30 min.

[0072] Step b: Add the prescribed amount of sheet graphene to the above mother liquor, and then stir with a stirrer to form a stable PDA-C emulsion. Stirring speed: 700 rpm; stirring time: 22h.

[0073] Step c: Spray drying. The above emulsion is spray dried using a spray dryer. Appropriate temperature and pressure are set to ensure the PDA-C is fully dried before collection, but not damaged by excessive temperature. Inlet air temperature: 120℃; Outlet air temperature: 80℃; Spray flow rate: 1.0L / h; Nozzle pressure: 0.3 MPa.

[0074] (2) Preparation of acrylic resin composition Step 1): Mix methyl ethyl ketone, methanol, ethyl toluenesulfonamide, and acrylic resin in the specified proportions using a stirrer until the acrylic resin is completely dissolved, forming a uniform and transparent gel-like solution. Stirring speed: 700 rpm; stirring time: 30 min.

[0075] Step 2): After the acrylic resin is completely dissolved, add PDA-C at a rate of 0.2 g / min. After the addition is complete, stir at a speed of 700 rpm for 300 min and at a temperature of 35℃.

[0076] (3) Preparation of alumina ceramic slurry Step 1): Add methyl ethyl ketone, methanol, polyethylene glycol, alumina, magnesium oxide, calcium oxide, and silicon dioxide to a ball mill jar in the specified proportions and stir. The stirring speed is 120 rpm, the stirring time is 150 min, and the temperature is controlled at 40℃.

[0077] Step 2): After the above materials are mixed evenly, add the acrylic resin composition. After the addition is complete, stir at a stirring speed of 120 rpm for 300 min and a temperature of 43°C to obtain the alumina ceramic slurry in this example.

[0078] Examples 2-54 The formulations of the alumina ceramic slurry in Examples 2-54 are shown in Table 1 below. The formulations corresponding to the numbers of the acrylic resin compositions in Table 1 are shown in Table 2 below. The formulations corresponding to the numbers of the PDA-C used in the acrylic resin compositions are shown in Table 3 below. The formulations corresponding to the numbers of the inorganic sintering aids in Table 1 are shown in Table 4 below.

[0079] Comparative Examples 1-10 The formulations of the alumina ceramic slurries in Comparative Examples 1 to 10 are shown in Table 1 below. The formulations corresponding to the numbers of the acrylic resin compositions in Table 1 are shown in Table 2 below. The formulations corresponding to the numbers of the PDA-C used in the acrylic resin compositions are shown in Table 3 below. The formulations corresponding to the numbers of the inorganic sintering aids in Table 1 are shown in Table 4 below.

[0080] The alumina ceramic slurries in Examples 2-54 and Comparative Examples 1-10 were all prepared according to the preparation method in Example 1.

[0081] Table 1 Formulation of alumina ceramic slurry (unit: mass percentage)

[0082] Table 2 Formulations corresponding to different acrylic resin compositions (unit: mass percentage)

[0083] The acrylic resins listed in Table 2 are all polymethacrylic resins.

[0084] Table 3. Formulas corresponding to different PDA-C numbers (unit: mass percentage)

[0085] Table 4. Formulations corresponding to different inorganic sintering aids (unit: mass percentage)

[0086] Performance testing: The stability, particle size distribution, flowability, and Zeta potential of the alumina ceramic slurries in Examples 1-54 and Comparative Examples 1-10 were tested respectively. Then, the casting properties of the ceramic slurries and the breakdown strength and dielectric constant of the alumina ceramic substrates made from the ceramic slurries were tested. The specific test methods are as follows: (1) Stability test Test principle: Observe the settling behavior of particles in slurry by using gravity.

[0087] Step (a) Pour the slurry into a transparent container and let it stand for 30 minutes.

[0088] Step (b) Observe and record the height of the settling layer and the clarity of the supernatant.

[0089] Evaluation: The slower the settling speed and the clearer the supernatant, the better the stability of the slurry.

[0090] (2) Particle size distribution test Test principle: The particle size and distribution affect the stability of the slurry.

[0091] The particle size distribution of the diluted slurry was tested using a laser particle size analyzer. The narrow and uniform particle size distribution indicates good dispersibility and high stability.

[0092] (3) Cotton-4 cup flowability test Principle: The flowability test of the Coat-4 cup is based on the principle of kinematic viscosity. At a specific temperature, the flowability is determined by measuring the time required for a given sample to flow out of the nozzle of the Coat-4 cup.

[0093] Test steps: Step a: Set the test temperature to 30℃ and clean the Cotton Cup 4.

[0094] Step b: Block the nozzle with your finger and slowly pour the sample into the Cotton Cup 4 until the liquid level is flush with the rim of the cup. Use a scraper to smooth the liquid level.

[0095] Step c: Quickly remove your finger and start the stopwatch simultaneously. Observe the sample flowing out of the leak. When the first short line appears in the flowing liquid, immediately stop the stopwatch and record the outflow time.

[0096] Evaluation: The slurry with moderate thixotropy can prevent sedimentation when left to stand and is easier to cast. Analyzing the rheological curve can help understand the bonding force and dispersion state between particles.

[0097] (4) Surface charge test - Zeta potential test Principle: The zeta potential reflects the surface charge of particles and affects the electrostatic interaction forces between particles. A high absolute value of the zeta potential means that the repulsive force between particles is large and the binding force is weak.

[0098] The zeta potential of particles in alumina ceramic slurry was measured using a zeta potential meter. The larger the absolute value of the zeta potential, the weaker the interparticle bonding force.

[0099] (5) Casting performance: The alumina ceramic slurries from Examples 1-54 and Comparative Examples 1-10 were cast in a casting machine. The slurry flowed from the casting hopper and was coated onto a film tape at a certain thickness by a doctor blade. After drying and curing, an alumina ceramic substrate was formed. During the casting process, it was observed whether the slurry would crack. If no cracking occurred during the casting process, the casting performance of the slurry was considered to be good.

[0100] (6) Breakdown strength: The breakdown strength is tested using DC voltage; (7) Dielectric constant: The dielectric constant is tested using the parallel plate capacitance method.

[0101] The test results obtained according to the above test method are shown in Table 5 below.

[0102] Table 5 Performance test results of alumina ceramic slurry

[0103] As shown in Table 5, the alumina ceramic slurries in Examples 1-54 of this invention exhibit a stability of 85-95%, a flowability of 120-140 s, an absolute Zeta potential of 30-33 mV, do not crack during casting, have a dielectric constant of 9.3-9.7, and a breakdown strength of 41-44 kV / mm. Compared with Comparative Examples 1-10, the alumina ceramic slurries of this invention have higher absolute potential, dielectric constant, and breakdown strength, demonstrating excellent comprehensive performance. Furthermore, they do not crack during casting and can be matched with existing casting processes.

[0104] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An alumina ceramic slurry, characterized in that: The composition comprises the following components by mass percentage: 5-8% acrylic resin composition, 0.1-0.3% dispersant, 8-14% resin solvent, 11-17% solvent, 0.93-1.42% inorganic sintering aid, and 59.28-74.97% alumina; The acrylic resin composition contains polydopamine-modified graphene material, acrylic resin, and ethyltoluenesulfonamide.

2. The alumina ceramic slurry according to claim 1, characterized in that: Based on the total mass of the acrylic resin composition, the acrylic resin composition comprises the following components in mass percentage: 0.1-0.5% polydopamine-modified graphene material, 27-30% resin solvent, 40-43% solvent, 4-5% ethyltoluenesulfonamide, and 21.5-28.9% acrylic resin.

3. The alumina ceramic slurry according to claim 2, characterized in that: The acrylic resin is selected from at least one of polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, and polyisobutyl methacrylate; And / or, the weight-average molecular weight of the acrylic resin is 0.5 × 10⁻⁶. 5 ~5×10 5 .

4. The alumina ceramic slurry according to claim 2, characterized in that: The polydopamine-modified graphene material comprises graphene and a polydopamine coating layer; the graphene surface is provided with a polydopamine coating layer; And / or, the polydopamine-modified graphene material comprises the following raw materials in the following mass percentages: dopamine hydrochloride 2-5%, alkali 0.01-0.05%, graphene 4.9-13%, and water 82-93%.

5. The alumina ceramic slurry according to claim 4, characterized in that: The polydopamine-modified graphene material is prepared using a method comprising the following steps: Dopamine hydrochloride, alkali, and water are mixed to obtain solution A; then solution A is mixed with graphene, causing dopamine hydrochloride to polymerize on the surface of the graphene to obtain solution B; Solution B was spray-dried to obtain the polydopamine-modified graphene material.

6. The alumina ceramic slurry according to claim 1, characterized in that: The inorganic sintering aid includes at least one of magnesium oxide, calcium oxide, and silicon dioxide. And / or, the dispersant includes at least one of sodium hexametaphosphate, polyacrylic acid, polycarboxylate, polyvinylpyrrolidone, sodium citrate, and polyethylene glycol.

7. The alumina ceramic slurry according to claim 1, characterized in that: Based on the total mass of the alumina ceramic slurry, the inorganic sintering aid comprises the following components by mass percentage: 0.6-0.9% magnesium oxide, 0.25-0.4% calcium oxide, and 0.08-0.12% silicon dioxide.

8. The method for preparing the alumina ceramic slurry according to any one of claims 1 to 7, characterized in that: Includes the following steps: The alumina ceramic slurry is prepared by mixing the raw materials.

9. An alumina ceramic substrate, characterized in that: It is prepared from the alumina ceramic slurry according to any one of claims 1 to 7.

10. The application of the alumina ceramic slurry according to any one of claims 1 to 7 in the fields of electronic ceramics, semiconductor packaging or high-temperature structural components.

Images