A nanocrystalline high-strength alumina ceramic substrate material and its preparation method

Abstract

The present invention discloses a preparation method of an alumina ceramic substrate material. By using nano-scale alumina powder and designing and optimizing the powder mixture in different particle size ranges, the problems of low strength and insufficient mechanical properties of medium grain size alumina ceramic substrates are solved. This application utilizes the synergistic effect of multiple dispersants and surfactants to solve the problems of easy agglomeration and difficult dispersion of nano-crystals. By designing the composition and powder particle size ratio of the sintering aid, the sintering temperature of the alumina ceramic is effectively reduced. On the premise of ensuring the sintering density of the material, the sintering temperature is effectively reduced, thereby effectively suppressing the growth of nano-crystals, and thus improving the strength of the alumina ceramic substrate material. The alumina substrate material prepared by the present invention has a grain size of 100-300 nm, a density ≥ 3.95 g / cm 3 , a surface roughness ≤ 0.2 μm, a warpage ≤ 0.1 mm, a flexural strength ≥ 600 MPa, and no appearance defects such as cracking and breakage.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and specifically discloses a nanocrystalline high-strength alumina ceramic substrate material and a preparation method thereof. Background Art

[0002] With the development of information technology, the electronics industry has become one of the most dynamic, innovative and important industries in the world economy today. Electronic packaging technology plays a crucial role in the electronics industry and is the guarantee for the normal and stable operation of semiconductor chips. Among them, electronic packaging materials are the top priority of electronic packaging technology. Ceramic material packaging has attracted much attention due to its good chemical stability, high thermal conductivity, high mechanical strength, low thermal expansion coefficient, low dielectric constant and low dielectric loss. Alumina ceramic packaging substrate materials have excellent electrical, mechanical and chemical stability, are superior to most oxide ceramics in physical properties such as mechanical, thermal and electrical properties, and have rich raw material sources and low costs. They are currently the most commonly used substrate materials in integrated circuits in the electronics industry, accounting for more than 80% of the total amount of ceramic substrate materials. At present, alumina ceramic substrates are widely used in thick film circuits, thin film circuits, hybrid integrated circuits, multi-chip modules and high-power IGBT modules and other fields.

[0003] With the development of 5G and 6G communication technologies, and the rise of third-generation semiconductors such as GaN, AlN, and SiC, power devices have developed rapidly, and the demand for alumina ceramic packaging has increased sharply. In some harsh operating environments, such as aerospace, space exploration, deep sea drilling, etc., higher performance requirements are also put forward for alumina packaging ceramics. To meet the requirements of high-power, high-density packaging and long life of devices, alumina substrates need to have higher physical and mechanical properties, especially higher requirements are put forward for the flexural strength of alumina substrate materials. At present, the performance of medium-grained (1-4 μm) alumina ceramic materials used cannot fully meet the needs of the new generation of electronic packaging technology. Fine grain refinement is the main way to improve the performance of alumina substrates. The microstructure of fine-grained alumina ceramics is more uniform, and the mechanical properties are significantly improved. However, most of the existing relatively mature technologies can only refine the alumina grain size to the submicron level (0.8-1.0 μm), and cannot refine the grains to the nanometer level below 0.5 μm. Because alumina generally has low sintering activity and high sintering temperature, sintering at too high a temperature will cause excessive grain growth, resulting in weakening of mechanical properties. In addition, problems such as easy agglomeration, difficult dispersion and low sintering density of nanoscale alumina powder have not been solved.

[0004] Therefore, the preparation of high-performance nanocrystalline alumina substrate materials faces severe challenges. Summary of the Invention

[0005] In view of the above-mentioned deficiencies, the present invention adopts nano-scale alumina powder, and solves the problems of low strength and insufficient mechanical properties of medium-grained alumina ceramic substrates by designing and optimizing the combination of powders in different particle size ranges. The present application utilizes the synergistic effect of multiple dispersants and surfactants to solve the problems of easy agglomeration and difficulty in dispersion of nano-grains. The present application effectively reduces the sintering temperature of alumina ceramics by designing the composition of sintering aids and the powder particle size ratio. Under the premise of ensuring the sintering density of the material, the sintering temperature is effectively reduced, and the growth of nano-grains is effectively inhibited, thereby improving the strength of the alumina ceramic substrate material. The alumina substrate material obtained in the present application has a grain size of 100-300nm and a density of ≥3.95g / cm 3 , surface roughness ≤0.2μm, warpage ≤0.1mm, bending strength ≥600MPa, no cracking, breakage and other appearance defects.

[0006] The present invention is achieved by the following technical means:

[0007] The present invention first discloses a method for preparing an alumina ceramic substrate material, comprising:

[0008] (1) Batching and mixing

[0009] Weigh 3-6wt% of sintering aid, 0.5-2.0wt% of rare earth additive and the balance of alumina powder, mix them and add them into a ball mill to obtain a first mixture;

[0010] Take the first mixture, add a solvent and a dispersant, add 40-100 ml of the solvent and 30-80 ml of the dispersant to every 100 g of the first mixture, to obtain a second mixture;

[0011] The second mixture is added to alumina ceramic grinding balls and ground and dispersed for 10-15 hours, the mass ratio of the grinding balls to the second mixture is 2:1-5:1, and the ball mill speed is 600-1000 r / min to obtain a dispersed slurry;

[0012] Add 10-20% of the first mixture by mass percentage of the binder to the dispersed slurry, then add 5-20% of the first mixture by mass percentage of the plasticizer, perform secondary ball milling, the speed is 600-800r / min, the ball milling time is 8-15h, and finally the speed is reduced to 200-400r / min and mixed for 1-3h. When pouring out the slurry, filter the slurry with a 200-mesh screen to remove the binder blocks, large particles of powder and other residues to obtain a stable and uniform casting slurry.

[0013] (2) Defoaming

[0014] The obtained casting slurry is defoamed on a vacuum defoaming machine, with a vacuum degree of less than -0.1 MPa, the temperature controlled at 30 - 45 °C, the time being 1 - 3 h, and the viscosity of the finally obtained defoamed slurry being 2000 - 4000 mPa·s.

[0015] (3) Casting forming

[0016] The defoamed slurry is cast on a casting forming machine to obtain a green sheet. The temperature for casting forming is 50 - 90 °C, the casting forming speed is 0.2 - 0.5 m / min, and the doctor blade gap is 300 - 600 μm. Then, it is dried at 80 - 150 °C for 1 - 3 h to obtain a green sheet of alumina substrate.

[0017] (4) Debinding

[0018] The formed green sheet is put into a debinding furnace for debinding. The debinding temperature is 700 - 800 °C, the debinding time is 3 - 6 h, under the condition of nitrogen or argon, with a gas flow rate of 5 - 10 L / min. The heating rate is from room temperature to 300 °C at 0.5 - 1.0 °C / min, and from 300 °C to the debinding temperature at a rate of 1.0 - 1.5 °C / min to obtain a debound alumina material.

[0019] (5) Sintering

[0020] The debound alumina material is transferred to a low - pressure sintering furnace for pressure sintering. It is heated at a heating rate of 1 - 3 °C / min to 1320 - 1420 °C, the sintering time is 2 - 3 h, the sintering atmosphere is nitrogen or argon, and the sintering pressure is 2 - 6 MPa, finally obtaining an alumina ceramic substrate material.

[0021] Furthermore, the alumina powder in step (1) is nano - and sub - micron alumina powder with a mass fraction > 99.9 wt%, where:

[0022] The powder with a particle size of 40 - 80 nm accounts for 5 - 8 wt%, the powder with a particle size of 80 - 150 nm accounts for 20 - 25 wt%, the powder with a particle size of 150 - 200 nm accounts for 30 - 40 wt%, the powder with a particle size of 200 - 250 nm accounts for 15 - 24 wt%, and the balance is the powder with a particle size of 250 - 300 nm.

[0023] Furthermore, the rare - earth additive is made by mixing nano - sized CeO2 and La2O3 with a particle size of 50 - 100 nm, and the mass ratio of CeO2 to La2O3 is 2:1 - 4:1.

[0024] Furthermore, the solvent is prepared by mixing ethyl acetate, butyl acetate, acetone and absolute ethanol, where:

[0025] Ethyl acetate 30 - 40 wt%, butyl acetate 20 - 30 wt%, acetone 10 - 20 wt%, and the balance is absolute ethanol.

[0026] Furthermore, the dispersant described in step (1) is prepared by mixing glyceryl trioleate, castor oil, and polymethacrylic acid, where:

[0027] Glyceryl trioleate 30 - 40 wt%, castor oil 20 - 30 wt%, and the balance is polymethacrylic acid.

[0028] Furthermore, the binder described in step (1) is polyvinyl butyral, and the plasticizer is dibutyl phthalate.

[0029] Furthermore, the alumina ceramic grinding balls added to the second mixture in step (1) include grinding balls with diameters of 1 mm, 2 mm, 4 mm, and 6 mm, where:

[0030] The grinding balls with a diameter of 1 mm account for 10 - 20 wt%, the grinding balls with a diameter of 2 mm account for 30 - 40 wt%, the grinding balls with a diameter of 4 mm account for 20 - 30 wt%, and the balance is the grinding balls with a diameter of 6 mm.

[0031] Furthermore, the sintering aid used in the sintering in step (5) is a mixture of CaO + SiO2 + MgO + B2O3, where:

[0032] The particle size of CaO powder is 50 - 100 nm, accounting for 10 - 20 wt%; the particle size of SiO2 powder is 50 - 100 nm, accounting for 30 - 40 wt%; the particle size of MgO powder is 50 - 100 nm, accounting for 10 - 20 wt%; the particle size of B2O3 powder is 50 - 100 nm, and the balance is B2O3 powder.

[0033] The present invention also discloses an alumina ceramic substrate material prepared by any of the above preparation methods.

[0034] Furthermore, the grain size of the alumina substrate material is 100 - 300 nm, the density ≥ 3.95 g / cm 3 , the surface roughness ≤ 0.2 μm, the warpage ≤ 0.1 mm, and the flexural strength ≥ 600 MPa.

[0035] The beneficial effects of the present invention are as follows:

[0036] The present invention prepares a nanocrystalline ceramic substrate material by using nanoscale alumina powders with different particle size ranges, designs the composition ratios and contents of various dispersants, and combines with the ball milling and dispersion process to effectively overcome the agglomeration problem of nanoscale powders, significantly improve the dispersion effect of nanoscale powders. Further, by designing and regulating the composition ratios and particle size ranges of sintering aids, the sintering temperature of alumina ceramics is effectively reduced, and with the grain growth inhibition effect of rare earth oxides, the growth behavior of nanoscale alumina grains during sintering is effectively inhibited. Finally, an alumina ceramic substrate material with excellent performance is prepared, and the flexural strength of the alumina ceramic material is significantly improved. The performance of the alumina substrate material obtained by the present invention is compared with that of conventional medium grain size alumina as shown in the following table, and it can be seen that the flexural strength, density, warpage degree, etc. of the alumina material in this application are significantly improved. Detailed Embodiments

[0037] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0039] Example 1

[0040] A high-strength ultra-nanocrystalline alumina ceramic substrate material and its preparation method include:

[0041] Using nano- and sub-micron alumina powders with a mass fraction higher than 99.9 wt%, wherein the powder with a particle size of 40 - 80 nm is 5 wt%, the powder with a particle size of 80 - 150 nm is 25 wt%, the powder with a particle size of 150 - 200 nm is 40 wt%, the powder with a particle size of 200 - 250 nm is 15 wt%, and the powder with a particle size of 250 - 300 nm is 15 wt%.

[0042] Using CaO + SiO2 + MgO + B2O3 as sintering aids, wherein the CaO powder is 50 - 100 nm, the SiO2 powder is 50 - 100 nm, the MgO powder is 50 - 100 nm, the B2O3 powder is 50 - 100 nm, wherein the CaO powder is 20 wt%, the MgO powder is 20 wt%, the SiO2 powder is 40 wt%, and the B2O3 powder is 20 wt%.

[0043] CeO2 and La2O3 with a particle size of 50-100 nm are used as rare earth additives, wherein the mass ratio of CeO2 to La2O3 is 2:1.

[0044] The solvents used are ethyl acetate, butyl acetate, acetone and anhydrous ethanol, wherein ethyl acetate is 40wt%, butyl acetate is 30wt%, acetone is 10wt% and anhydrous ethanol is 20wt%.

[0045] The dispersants used are triolein, castor oil and polymethacrylic acid, wherein the triolein is 30 wt %, the castor oil is 30 wt % and the polymethacrylic acid is 40 wt %.

[0046] The adhesive used is polyvinyl butyral, and the plasticizer used is dibutyl phthalate.

[0047] (1) Batching and mixing

[0048] Weigh alumina powder, sintering aid and rare earth additive, wherein the content of solvent is 3wt%, the content of rare earth additive is 1.0wt%, and the content of alumina powder is 96wt%. Add the weighed alumina powder, solvent and rare earth additive into a ball mill, and add solvent, the amount of solvent added is 100g (solid powder): 60ml. Add dispersant, the amount of dispersant added is 100g (solid powder): 60ml. Then add alumina ceramic grinding balls (10wt% for 1mm diameter grinding balls, 40wt% for 2mm diameter grinding balls, 30wt% for 4mm diameter grinding balls, 20wt% for 6mm diameter grinding balls), the mass ratio of grinding balls to solid powder is 3:1, the ball mill speed is 800r / min, and the ball milling dispersion is carried out for 10h to give the slurry fluidity.

[0049] Add 15% of the solid powder mass binder to the slurry after ball milling, and then add 10% of the solid powder mass plasticizer, and perform secondary ball milling at a speed of 600r / min for 10h, and finally reduce the speed to 200r / min and mix for 2h. When pouring out the slurry, filter the slurry with a 200-mesh screen to remove the binder blocks, large particles of powder and other residues to obtain a stable and uniform casting slurry.

[0050] (2) Defoaming

[0051] The obtained slurry was defoamed in a vacuum defoamer with a vacuum degree of less than -0.1 MPa and a temperature controlled at 35°C for 1 h. The viscosity of the final slurry was about 3500 mPa·s.

[0052] (3) Tape casting

[0053] The defoamed slurry is cast on a casting machine to obtain a green sheet. The casting temperature is 65 °C, the casting speed is 0.3 m / min, and the doctor blade gap is 450 μm. Then, it is dried at 120 °C for 1.5 h to obtain a green sheet of alumina substrate.

[0054] (4) Debinding

[0055] The green sheet after casting is put into a debinding furnace for debinding. The debinding temperature is 700 °C, the debinding time is 5 h, under nitrogen or argon conditions, and the gas flow rate is 5 L / min. The heating rate is from room temperature to 300 °C at 0.5 °C / min, and the temperature is raised from 300 °C to 700 °C at a rate of 1.0 °C / min.

[0056] (5) Sintering

[0057] The debound alumina material is transferred to a low-pressure sintering furnace for pressure sintering. It is heated to 1400 °C at a heating rate of 2 °C / min, the sintering time is 2 h, the sintering atmosphere is nitrogen or argon, and the sintering pressure is 3 MPa. Finally, a high-performance alumina substrate material is obtained.

[0058] The grain size of the alumina substrate material obtained in this example is 200 - 400 nm, the density is 3.99 g / cm 3 , the relative density is 99%, the surface roughness is ≤0.2 μm, the warpage is ≤0.1 mm, the flexural strength is 640 MPa, and there are no appearance defects such as cracking and breakage.

[0059] Example 2

[0060] A high-strength ultra-nano-crystalline alumina ceramic substrate material and its preparation method include:

[0061] Nano- and sub-micron alumina powders with a mass fraction higher than 99.9 wt% are used, among which the powder with a particle size of 40 - 80 nm is 5 wt%, the powder with a particle size of 80 - 150 nm is 25 wt%, the powder with a particle size of 150 - 200 nm is 40 wt%, the powder with a particle size of 200 - 250 nm is 15 wt%, and the powder with a particle size of 250 - 300 nm is 15 wt%.

[0062] CaO + SiO2 + MgO + B2O3 is used as a sintering aid, among which the CaO powder is 50 - 100 nm, the SiO2 powder is 50 - 100 nm, the MgO powder is 50 - 100 nm, the B2O3 powder is 50 - 100 nm, among which the CaO powder is 20 wt%, the MgO powder is 20 wt%, the SiO2 powder is 40 wt%, and the B2O3 powder is 20 wt%.

[0063] Nano-CeO2 and La2O3 with a particle size of 50 - 100 nm are used as rare earth additives, and the mass ratio of CeO2 to La2O3 is 2:1.

[0064] The solvents used are ethyl acetate, butyl acetate, acetone and absolute ethanol, among which ethyl acetate is 40 wt%, butyl acetate is 30 wt%, acetone is 10 wt%, and absolute ethanol is 20 wt%.

[0065] The dispersants used are glyceryl trioleate, castor oil and polymethacrylic acid, among which glyceryl trioleate is 30 wt%, castor oil is 30 wt%, and polymethacrylic acid is 40 wt%.

[0066] The binder used is polyvinyl butyral, and the plasticizer used is dibutyl phthalate.

[0067] (1) Batching and mixing

[0068] Weigh alumina powder, sintering aids and rare earth additives, among which the content of the cosolvent is 6 wt%, the rare earth additive is 1.2 wt%, and the alumina powder is 93.8 wt%. Add the weighed alumina powder, cosolvent and rare earth additives into the ball mill tank, and add the solvent. The addition amount of the solvent is 100 g (solid powder): 60 ml. Add the dispersant, and the addition amount of the dispersant is 100 g (solid powder): 60 ml. Then add alumina ceramic grinding balls (10 wt% of 1-mm-diameter grinding balls, 40 wt% of 2-mm-diameter grinding balls, 30 wt% of 4-mm-diameter grinding balls, 20 wt% of 6-mm-diameter grinding balls). The mass ratio of the grinding balls to the solid powder is 3:1, the ball mill rotation speed is 800 r / min, and ball milling and dispersion are carried out for 10 h to endow the slurry with fluidity.

[0069] Add 15% of the binder based on the mass of the solid powder to the slurry after ball milling and dispersion, then add 10% of the plasticizer based on the mass of the solid powder, and carry out secondary ball milling at a rotation speed of 600 r / min for 10 h. Finally, reduce the rotation speed to 200 r / min and mix for 2 h. When pouring out the slurry, filter the slurry through a 200-mesh sieve to remove residues such as binder blocks and large-particle powders to obtain a stable and uniform casting slurry.

[0070] (2) Defoaming

[0071] The obtained slurry is defoamed on a vacuum defoaming machine. The vacuum degree is less than -0.1 MPa, the temperature is controlled at 35 °C, and the time is 1 h. The viscosity of the finally obtained slurry is about 3500 mPa·s.

[0072] (3) Tape casting

[0073] The defoamed slurry is tape cast on a tape casting machine to obtain a green sheet. The temperature of tape casting is 65 °C, the speed of tape casting is 0.3 m / min, and the doctor blade gap is 450 μm. Then, it is dried at 120 °C for 1.5 h to obtain a green sheet of alumina substrate.

[0074] (4) Debinding

[0075] Put the green sheet after tape casting into a debinding furnace for debinding. The debinding temperature is 700 °C, the debinding time is 5 h, under the condition of nitrogen or argon, and the gas flow rate is 5 L / min. The heating rate is from room temperature to 300 °C at 0.5 °C / min, and from 300 °C to 700 °C at 1.0 °C / min.

[0076] (5) Sintering

[0077] Transfer the debound alumina material to a low-pressure sintering furnace for pressure sintering. Heat it up to 1320 °C at a heating rate of 2 °C / min, the sintering time is 2 h, the sintering atmosphere is nitrogen or argon, and the sintering pressure is 5 MPa. Finally, a high-performance alumina substrate material is obtained.

[0078] The grain size of the alumina substrate material obtained in this example is 100 - 300 nm, the density is 3.95 g / cm 3 , the relative density is 98.5%, the surface roughness is ≤0.2 μm, the warpage is ≤0.1 mm, the flexural strength is 610 MPa, and there are no appearance defects such as cracking and breakage.

[0079] Example 3

[0080] A high-strength ultra-nano-crystalline alumina ceramic substrate material and its preparation method include:

[0081] Using nano- and sub-micron alumina powders with a mass fraction higher than 99.9 wt%, among which the powder with a particle size of 40 - 80 nm is 8 wt%, the powder with a particle size of 80 - 150 nm is 20 wt%, the powder with a particle size of 150 - 200 nm is 40 wt%, the powder with a particle size of 200 - 250 nm is 24 wt%, and the powder with a particle size of 250 - 300 nm is 8 wt%.

[0082] Using CaO + SiO2 + MgO + B2O3 as sintering aids, among which the CaO powder is 50 - 100 nm, the SiO2 powder is 50 - 100 nm, the MgO powder is 50 - 100 nm, the B2O3 powder is 50 - 100 nm, where the CaO powder is 20 wt%, the MgO powder is 20 wt%, the SiO2 powder is 40 wt%, and the B2O3 powder is 20 wt%.

[0083] Using nano-CeO2 and La2O3 with a particle size of 50 - 100 nm as rare earth additives, and the mass ratio of CeO2 to La2O3 is 2:1.

[0084] Using ethyl acetate, butyl acetate, acetone and absolute ethanol as solvents, among which ethyl acetate is 40 wt%, butyl acetate is 30 wt%, acetone is 10 wt%, and absolute ethanol is 20 wt%.

[0085] The dispersants used are glycerol trioleate, castor oil and polymethacrylic acid, among which glycerol trioleate is 30 wt%, castor oil is 30 wt%, and polymethacrylic acid is 40 wt%.

[0086] The binder used is polyvinyl butyral, and the plasticizer used is dibutyl phthalate.

[0087] (1) Batching and mixing

[0088] Weigh alumina powder, sintering aids and rare earth additives, where the content of the cosolvent is 5 wt%, the rare earth additive is 1.5 wt%, and the alumina powder is 94.5 wt%. Add the weighed alumina powder, cosolvent and rare earth additives into the ball mill tank, and add a solvent. The addition amount of the solvent is 100 g (solid powder): 100 ml. Add the dispersant, and the addition amount of the dispersant is 100 g (solid powder): 80 ml. Then add alumina ceramic grinding balls (10 wt% of 1 mm diameter grinding balls, 40 wt% of 2 mm diameter grinding balls, 30 wt% of 4 mm diameter grinding balls, 20 wt% of 6 mm diameter grinding balls). The mass ratio of the grinding balls to the solid powder is 3:1, the ball mill rotation speed is 800 r / min, and ball milling and dispersion are carried out for 10 h to endow the slurry with fluidity.

[0089] Add a binder of 15% of the mass of the solid powder to the slurry after ball milling and dispersion, then add a plasticizer of 10% of the mass of the solid powder, and carry out secondary ball milling at a rotation speed of 600 r / min for a ball milling time of 10 h. Finally, reduce the rotation speed to 200 r / min and mix for 2 h. When pouring out the slurry, filter the slurry through a 200-mesh sieve to remove residues such as binder blocks and large particle powders, and obtain a stable and uniform tape-casting slurry.

[0090] (2) Defoaming

[0091] Defoam the obtained slurry on a vacuum defoamer. The vacuum degree is less than -0.1 MPa, the temperature is controlled at 35 °C, and the time is 1 h. The viscosity of the finally obtained slurry is about 4000 mPa·s.

[0092] (3) Tape casting

[0093] The defoamed slurry is tape-cast on a tape casting machine to obtain a green sheet. The temperature of tape casting is 65 °C, the tape casting speed is 0.3 m / min, and the doctor blade gap is 450 μm. Then, dry it at 120 °C for 1.5 h to obtain a green sheet of the alumina substrate.

[0094] (4) Debinding

[0095] Put the green sheet after tape casting into a debinding furnace for debinding. The debinding temperature is 700 °C, the debinding time is 5 h, under nitrogen or argon conditions, and the gas flow rate is 5 L / min. The heating rate is from room temperature to 300 °C at 0.5 °C / min and from 300 °C to 700 °C at 1.0 °C / min.

[0096] (5) Sintering

[0097] Transfer the debound alumina material to a low-pressure sintering furnace for pressure sintering. Heat it up to 1380 °C at a heating rate of 2 °C / min, the sintering time is 2 h, the sintering atmosphere is nitrogen or argon, and the sintering pressure is 5 MPa. Finally, a high-performance alumina substrate material is obtained.

[0098] The grain size of the alumina substrate material obtained in this example is 100 - 500 nm, and the density is 3.95 g / cm 3 , the relative density is higher than 98.5%, the surface roughness is ≤ 0.2 μm, the warpage is ≤ 0.1 mm, the flexural strength is 630 MPa, and there are no appearance defects such as cracking and breakage.

[0099] Table 1

[0100]

[0101] According to the results in Table 1, the sintering temperature of the alumina ceramic substrate material in the present invention is reduced to below 1400 °C. The significantly reduced sintering temperature effectively reduces the growth trend of nano-alumina grains during sintering, making the alumina grain size less than 500 nm. At the same time, the sintering relative density of the alumina ceramic is not reduced (higher than 98.5%). The surface roughness of the alumina ceramic substrate obtained in the present invention is less than 0.2 μm, significantly lower than that of a normal alumina substrate (usually higher than 0.35 μm), and the sintering warpage of the ceramic substrate is significantly reduced. At the same time, the present invention greatly improves the flexural strength of the alumina ceramic substrate material to above 600 MPa, which is much higher than that of normal alumina ceramic materials.

[0102] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0103] The above-described embodiments merely represent several implementation manners of the present invention, which are convenient for understanding the technical solutions of the present invention specifically and in detail, but should not be construed as limiting the protection scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all fall within the protection scope of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the technical solutions provided by the present invention are all within the protection scope of the appended claims of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing an alumina ceramic substrate material, comprising: (1) Batching and mixing Weigh 3-6wt% of sintering aid, 0.5-2.0wt% of rare earth additive and the balance of alumina powder, mix them and add them into a ball mill to obtain a first mixture; Take the first mixture, add a solvent and a dispersant, add 40-100 ml of the solvent and 30-80 ml of the dispersant to every 100 g of the first mixture, to obtain a second mixture; The second mixture is added to alumina ceramic grinding balls and ground and dispersed for 10-15 hours, the mass ratio of the grinding balls to the second mixture is 2:1-5:1, and the ball mill speed is 600-1000 r / min to obtain a dispersed slurry; Add 10-20% of the binder by mass percentage of the first mixture to the dispersed slurry, then add 5-20% of the plasticizer by mass percentage of the first mixture, perform secondary ball milling, the speed is 600-800r / min, the ball milling time is 8-15h, and finally the speed is reduced to 200-400r / min and mixed for 1-3h, and the ground slurry is passed through a 200-mesh screen to obtain a casting slurry; (2) Defoaming The casting slurry is defoamed on a vacuum defoamer with a vacuum degree of less than -0.1MPa and a temperature of 30-45°C for 1-3h to obtain a defoamed slurry; (3) Tape casting The defoamed slurry is tape-casted on a tape-casting machine to obtain a green sheet, the tape-casting temperature is 50-90° C., the tape-casting speed is 0.2-0.5 m / min, and the scraper gap is 300-600 μm to obtain a formed green sheet; (4) Debonding The formed green sheet is placed in a debinding furnace for debinding, the debinding temperature is 700-800°C, the debinding time is 3-6h, nitrogen or argon conditions, the gas flow rate is 5-10L / min, the heating rate is 0.5-1.0°C / min from room temperature to 300°C, and the heating rate is 1.0-1.5°C / min from 300°C to the debinding temperature to obtain a debinding alumina material; (5) Sintering The debinding alumina material is transferred into a low-pressure sintering furnace for pressure sintering, and the temperature is raised to 1320-1420°C at a heating rate of 1-3°C / min, the sintering time is 2-3h, the sintering atmosphere is nitrogen or argon, and the sintering pressure is 2-6MPa, and finally an alumina ceramic substrate material is obtained; wherein: The alumina powder in step (1) is nano and submicron alumina powder with a mass fraction of >99.9wt%, comprising: Powder with a particle size of 40-80nm accounts for 5-8wt%, powder with a particle size of 80-150nm accounts for 20-25wt%, powder with a particle size of 150-200nm accounts for 30-40wt%, powder with a particle size of 200-250nm accounts for 15-24wt%, and the remainder is powder with a particle size of 250-300nm; The rare earth additive in step (1) is prepared by mixing CeO2 and La2O3 with a particle size of 50-100 nm, and the mass ratio of CeO2 to La2O3 is 2:1-4:1; The second mixture added in step (1) to the alumina ceramic grinding balls includes grinding balls with diameters of 1 mm, 2 mm, 4 mm, and 6 mm, wherein: the grinding balls with a diameter of 1 mm account for 10-20 wt%, the grinding balls with a diameter of 2 mm account for 30-40 wt%, the grinding balls with a diameter of 4 mm account for 20-30 wt%, and the balance is the grinding balls with a diameter of 6 mm.

2. The preparation method according to claim 1, wherein: The solvent in step (1) is prepared by mixing ethyl acetate, butyl acetate, acetone, and absolute ethanol, wherein: ethyl acetate 30-40 wt%, butyl acetate 20-30 wt%, acetone 10-20 wt%, and the balance is absolute ethanol.

3. The preparation method according to claim 1, wherein: The dispersant in step (1) is prepared by mixing glyceryl trioleate, castor oil, and polymethacrylic acid, wherein: glyceryl trioleate 30-40 wt%, castor oil 20-30 wt%, and the balance is polymethacrylic acid.

4. The preparation method according to claim 1, wherein: The binder in step (1) is polyvinyl butyral, and the plasticizer is dibutyl phthalate.

5. The preparation method according to claim 1, wherein: The sintering aid used in step (5) for sintering is a mixture of CaO + SiO2 + MgO + B2O3, wherein: the particle size of CaO powder is 50-100 nm, accounting for 10-20 wt%; the particle size of SiO2 powder is 50-100 nm, accounting for 30-40 wt%; the particle size of MgO powder is 50-100 nm, accounting for 10-20 wt%; the particle size of B2O3 powder is 50-100 nm, and the balance is B2O3 powder.

6. An alumina ceramic substrate material prepared by the preparation method according to any one of claims 1 to 5.

7. The alumina ceramic substrate material according to claim 6, wherein: The grain size of this alumina ceramic substrate material is 100 - 300 nm, and the density is ≥ 3.95 g / cm 3 , the surface roughness is ≤ 0.2 μm, the warpage is ≤ 0.1 mm, and the flexural strength is ≥ 600 MPa.

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