阅读说明：本技术 一种氮化铝陶瓷基板及其制备方法 (Aluminum nitride ceramic substrate and preparation method thereof ) 是由 王群 吴心如 金鑫 李晓冬 于 2020-06-28 设计创作，主要内容包括：本发明属于陶瓷材料技术领域,具体涉及一种氮化铝陶瓷基板及其制备方法。所述制备方法包括制浆、真空除泡、流延成型、排胶和烧结,所述排胶包括以下三段过程：第一段排胶过程：升温到350℃-450℃,保温50min-90min；第二段排胶过程：升温到650℃-750℃,保温25min-45min；第三段排胶过程：降温至400℃-500℃,保温80min-100min。本发明得到的氮化铝陶瓷更致密,三段式排胶法排胶后得到的氮化铝坯片完好平整不含碳杂质,性能更优良。(The invention belongs to the technical field of ceramic materials, and particularly relates to an aluminum nitride ceramic substrate and a preparation method thereof. The preparation method comprises pulping, vacuum defoaming, tape casting, binder removal and sintering, wherein the binder removal comprises the following three processes: the first stage of glue discharging process: heating to 350-450 deg.c and maintaining for 50-90 min; and a second rubber discharge process: heating to 650-750 ℃, and keeping the temperature for 25-45 min; the third rubber discharge process: cooling to 400-500 deg.c and maintaining for 80-100 min. The aluminum nitride ceramic obtained by the method is more compact, and the aluminum nitride blank obtained by glue discharging through a three-stage glue discharging method is perfect, flat and free of carbon impurities, and has better performance.)

1. The preparation method of the aluminum nitride ceramic substrate is characterized by comprising the following three processes of pulping, vacuum defoaming, tape casting, binder removal and sintering:

the first stage of glue discharging process: heating to 350-450 deg.c and maintaining for 50-90 min;

and a second rubber discharge process: heating to 650-750 ℃, and keeping the temperature for 25-45 min;

the third rubber discharge process: cooling to 400-500 deg.c and maintaining for 80-100 min.

2. The preparation method according to claim 1, wherein the rubber discharge comprises the following three processes:

the first stage of glue discharging process: under the condition of inert atmosphere, heating to 350-450 ℃, and preserving heat for 50-90 min;

and a second rubber discharge process: under the condition of vacuum or inert atmosphere, heating to 650-750 ℃, and preserving heat for 25-45 min;

the third rubber discharge process: cooling to 400-500 deg.c and maintaining in air or oxygen atmosphere for 80-100 min.

3. The preparation method according to claim 1 or 2, characterized in that in the first stage of glue discharging process, the temperature is raised to 350-450 ℃ at a heating speed of 3-5 ℃/min;

and/or, in the second stage of glue discharging process, heating to 650-750 ℃ at a heating speed of 8-10 ℃/min;

and/or, in the third stage of rubber discharging process, the temperature is reduced to 400-500 ℃ at the speed of 5-8 ℃/min.

4. A method according to any one of claims 1-3, characterized in that said pulping comprises the steps of:

(1) mixing aluminum nitride powder, a sintering aid and a ball milling medium, carrying out primary ball milling treatment, and drying to obtain aluminum nitride powder containing the sintering aid;

(2) dissolving a dispersing agent, a binder and a plasticizer in a solvent to obtain casting sol;

(3) and (3) mixing the aluminum nitride powder containing the sintering aid obtained in the step (1) with the casting sol obtained in the step (2), and performing secondary ball milling treatment to obtain casting slurry.

5. The preparation method according to claim 4, wherein the mass ratio of the aluminum nitride powder to the sintering aid to the solvent to the dispersant to the binder to the plasticizer is 40-45: 1.5-2.5: 40-45: 1.5-2.5: 7-8: 2 to 3.

6. The method of claim 4 or 5, wherein the ball milling medium is absolute ethanol.

7. The production method according to any one of claims 4 to 6, wherein in the step (2), the dispersant, the binder and the plasticizer are dissolved in the solvent at 35 ℃ to 45 ℃.

8. The production method according to any one of claims 4 to 7, wherein in the step (2), the solvent is a mixed solution of n-butanol and cyclohexanone.

9. The preparation method according to claim 8, wherein the mass ratio of n-butanol to cyclohexanone is 40-45: 60-55.

10. An aluminum nitride ceramic substrate produced by the production method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of ceramic materials, and particularly relates to an aluminum nitride ceramic substrate and a preparation method thereof.

Background

AlN is a covalent crystal having a wurtzite structure, hexagonal system, and a crystal thereof is a covalent bond compound having [ AlN4] tetrahedra as a structural unit, in which c-axis N — Al bonds are slightly long, and the lattice constant α is 0.3110nm, and c is 0.4978 nm. Pure aluminum nitride is blue-white, typically gray or off-white. The aluminum nitride has the advantages of low atomic mass, strong interatomic bonding, simple crystal structure, low dissonance, high room temperature strength, slow strength reduction along with temperature rise and the like.

AlN has the advantages of low atomic mass, strong interatomic bonding, simple crystal structure, low non-harmonicity and the like, has extremely high thermal conductivity, and has excellent performances of low dielectric constant, low dielectric loss, thermal expansion coefficient matched with silicon, insulation, no toxicity, good high-frequency characteristics, high strength and the like, and has very wide application prospect.

The most fundamental requirements of integrated circuits for packaging substrates are high electrical resistivity, high thermal conductivity and low dielectric constant. The substrate for packaging also has the characteristics of good thermal matching with the silicon wafer, easy molding, high surface flatness, easy metallization, easy processing, low cost and the like, and certain mechanical properties. Most ceramics are materials with extremely strong ionic bonds or covalent bonds, have excellent comprehensive performance, are substrate materials commonly used in electronic packaging, have higher insulating property and excellent high-frequency characteristic, have very similar linear expansion coefficient to electronic components, have very stable chemical properties and high thermal conductivity. For a long time, A1 has been used as the substrate material for most high-power hybrid integrated circuits₂O₃And BeO ceramics, but A1₂O₃The thermal conductivity of the substrate is low, and the thermal expansion coefficient is not matched with that of Si; although BeO has excellent comprehensive performance, the application and popularization of BeO are limited by the defects of high production cost and high toxicity. The theoretical thermal conductivity of the aluminum nitride can reach 320W/(m.K), and the aluminum nitride has the excellent characteristics of good electrical insulation, low dielectric constant and dielectric loss, thermal expansion coefficient matched with silicon, stable chemical properties, no toxicity and the like. Therefore, aluminum nitride ceramics are the most ideal substrate material and electronic device packaging material nowadays.

Disclosure of Invention

The invention provides an aluminum nitride ceramic substrate and a preparation method thereof.

Specifically, the invention provides the following technical scheme:

a preparation method of an aluminum nitride ceramic substrate comprises pulping, vacuum bubble removal, tape casting, glue removal and sintering, wherein the glue removal comprises the following three processes:

the first stage of glue discharging process: heating to 350-450 deg.c and maintaining for 50-90 min;

and a second rubber discharge process: heating to 650-750 ℃, and keeping the temperature for 25-45 min;

the third rubber discharge process: cooling to 400-500 deg.c and maintaining for 80-100 min.

Preferably, in the above preparation method, the rubber discharge comprises the following three processes:

the first stage of glue discharging process: under the condition of inert atmosphere, heating to 350-450 ℃, and preserving heat for 50-90 min; the micromolecule organic matter in the base band volatilizes in the heating process and the first section heat preservation process, the macromolecule organic matter starts to crack when the temperature reaches 350 ℃, and micromolecules formed after cracking are easier to remove, so the first section heat preservation temperature of the glue discharging is set to be 350-450 ℃. The heat preservation time is 50min-90min, and sufficient time is enough to completely carry out the volatilization and the cracking process;

and a second rubber discharge process: under the condition of vacuum or inert atmosphere, heating to 650-750 ℃, and preserving heat for 25-45 min; macromolecular organic matters such as the adhesive are completely cracked into carbon or micromolecules at the temperature of 650-750 ℃. After the first glue discharging process, the volatile organic matters in the base band are completely volatilized, and a small amount of macromolecular organic matters such as the binder and the like are remained, so that the macromolecular organic matters are completely cracked into carbon impurities and micromolecular organic matters at the high temperature of 650-750 ℃ for subsequent removal, and the blank sheet without the carbon impurities is obtained. At the temperature of 650-750 ℃, the aluminum nitride can be oxidized in the oxidizing atmosphere, so that the second stage glue discharging process needs to be carried out in the inert atmosphere or vacuum atmosphere. If inert gas is introduced into the furnace tube, the inert gas can protect the aluminum nitride from being oxidized, and carbon impurities and other small molecules generated on the base band due to cracking can be taken away by airflow; if the furnace tube is in a vacuum state, the oxide is absent in the vacuum atmosphere, the aluminum nitride can be protected from being oxidized, and the vacuum state can promote carbon impurities and other small molecules generated by decomposition to migrate to the surface of the base band from the inside of the base band, so that the third-stage glue removing process is facilitated. At the high temperature, a small amount of macromolecular organic matters of the binder are remained, and the temperature is kept for 20-40 min to be sufficient for complete cracking;

the third rubber discharge process: cooling to 400-500 deg.c and maintaining in air or oxygen atmosphere for 80-100 min. After the second stage of rubber discharge process, a large amount of residual carbon impurities generated after cracking of organic matters on the base band need to be completely oxidized into gas in an oxidizing atmosphere and then discharged. Under the oxidizing atmosphere, the aluminum nitride can generate oxidation reaction at the high temperature of over 700 ℃, so that the glue discharging and heat preservation temperature of the third section under the oxidizing atmosphere needs to be carried out at the temperature lower than 700 ℃; the carbon reacts in the oxidizing atmosphere to be oxidized into carbon dioxide or carbon monoxide, and the required temperature is in the range of 300-500 ℃, so that the temperature can be set to be 400-500 ℃ in order to fully and thoroughly oxidize the carbon and the small molecular organic matters on the baseband into the carbon monoxide or the carbon dioxide. The heat preservation time is 80min-100min, sufficient time is needed to ensure that carbon or other organic matters are completely oxidized and removed, and carbon impurities are not contained in the blank sheet after the glue is removed. After the step is finished, a pure aluminum nitride blank which is free of impurities and is smooth and intact can be obtained.

Preferably, in the preparation method, in the first stage of glue discharging process, the temperature is increased to 350-450 ℃ at the heating speed of 3-5 ℃/min. The organic matter in the base band can form carbon impurities in the subsequent sintering process, the performance of the ceramic is influenced, and the pure aluminum nitride blank sheet is obtained after the organic matter in the base band needs to be removed before sintering. In the air, when the temperature is higher than 700 ℃, the aluminum nitride can be oxidized, the inert atmosphere is introduced into the furnace tube to protect the aluminum nitride from being oxidized at high temperature, and the blank sheet obtained after glue discharging is the aluminum nitride blank sheet which is not oxidized at all. The heating speed is controlled within the range of 3 ℃/min-5 ℃/min, so that the temperature is slowly and stably increased, the micromolecule organic matter can be slowly volatilized, the base band can keep the original shape in the process, the base band is intact, the phenomena of deformation, cracks or bubbling and the like do not occur, and the intact and deformation-free aluminum nitride blank sheet is obtained after glue discharging.

Preferably, in the preparation method, in the second stage of glue discharging process, the temperature is increased to 650-750 ℃ at a heating speed of 8-10 ℃/min. The organic matters such as the solvent and the like in the base band at the stage are completely volatilized, the shape of the base band is basically fixed, the deformation is not easy to occur, the temperature is increased to the required temperature at a higher temperature increasing speed of 8-10 ℃/min, and the time is saved.

Preferably, in the preparation method, in the third stage of the rubber discharging process, the temperature is reduced to 400-500 ℃ at the speed of 5-8 ℃/min.

Preferably, in the above preparation method, the pulping comprises the following steps:

(1) mixing aluminum nitride powder, a sintering aid and a ball milling medium, carrying out primary ball milling treatment, and drying to obtain aluminum nitride powder containing the sintering aid;

(2) dissolving a dispersing agent, a binder and a plasticizer in a solvent to obtain casting sol;

(3) and (3) mixing the aluminum nitride powder containing the sintering aid obtained in the step (1) with the casting sol obtained in the step (2), and performing secondary ball milling treatment to obtain casting slurry.

Preferably, in the preparation method, the mass ratio of the aluminum nitride powder, the sintering aid, the solvent, the dispersant, the binder and the plasticizer is 40-45: 1.5-2.5: 40-45: 1.5-2.5: 7-8: 2 to 3.

Preferably, in the above preparation method, the ball milling medium is absolute ethyl alcohol. The aluminum nitride powder is easy to contact with water to generate hydrolysis reaction, so that absolute ethyl alcohol is selected as a solvent during wet ball milling to prevent the aluminum nitride from hydrolyzing and introducing oxygen impurities to influence the performance of the ceramic. The powder is uniformly mixed after ball milling, the sintering aid is uniformly distributed in the powder, the densification of ceramic sintering can be promoted by the sintering aid, and the prepared ceramic has uniform and dense components under the condition that the sintering aid is uniformly distributed. Before preparing the casting slurry, the aluminum nitride powder and the sintering aid powder are required to be fully mixed, and compared with the casting slurry prepared after mixing the aluminum nitride powder and the sintering aid by using a small amount of solution in the casting formula, the aluminum nitride powder and the sintering aid are mixed before preparing the slurry, and finally the obtained casting slurry has more uniform components and is more beneficial to sintering of aluminum nitride ceramics.

Preferably, in the above preparation method, in the step (2), the dispersant, the binder and the plasticizer are dissolved in the solvent at 35 to 45 ℃. Dispersing agent, adhesive and plasticizer are dissolved in solvent to form casting sol needed by preparing casting slurry, at normal temperature, the dissolving process needs a lot of time, and the rising temperature can promote molecular motion, accelerate the dissolving process and save time. The excessive temperature can cause a large amount of volatilization of the solution, which affects the progress of the dissolving process and the viscosity of the final casting slurry, so the heating temperature is controlled to be 35-45 ℃, and the solvent volatilization is avoided while the dissolution is promoted. All solvents in the casting formulation are used to dissolve the dispersant, binder and plasticizer, and compared with a small amount of solution in the casting formulation used to dissolve the dispersant, binder and plasticizer, the components are more fully dissolved, and the obtained sol is more uniform.

Preferably, in the above production method, in the step (2), the solvent is a mixed solution of n-butanol and cyclohexanone.

Preferably, in the preparation method, the mass ratio of n-butyl alcohol to cyclohexanone is 40-45: 60-55.

The invention also provides an aluminum nitride ceramic substrate prepared by the preparation method.

The invention has the following beneficial effects:

(1) according to the invention, before the tape casting slurry is prepared, the aluminum nitride powder and the sintering aid are mixed by a ball milling method, so that the aluminum nitride powder and the sintering aid are mixed more fully and uniformly, the ceramic powder with uniform components is obtained, then the tape casting slurry is prepared, the aluminum nitride powder and the sintering aid in the obtained slurry are distributed uniformly, and the obtained aluminum nitride ceramic is more compact;

(2) according to the invention, three sections of heating and following three atmospheres are selected in the glue discharging stage, each section of temperature corresponds to different temperature changing speeds and different atmospheres, the aluminum nitride substrate can be protected to be complete and undamaged, all organic matters in the aluminum nitride substrate are promoted to be completely removed, a pure aluminum nitride blank sheet is obtained, and the aluminum nitride ceramic obtained after sintering has better performance;

(3) the non-aqueous tape casting and the binder removal method for preparing the aluminum nitride ceramic provided by the invention have the advantages of simple process, lower cost, higher practicability and industrial utilization value.

Drawings

FIG. 1 is a thermogravimetric plot of the cast sheet of example 1.

FIG. 2 shows the aluminum nitride green sheet after the binder removal in example 1.

FIG. 3 is a xrd diagram of an aluminum nitride blank after stripping in example 1.

FIG. 4 shows the aluminum nitride green sheet after the binder removal in comparative example 1.

FIG. 5 shows the aluminum nitride green sheet after the binder removal in comparative example 2.

FIG. 6 shows the aluminum nitride green sheet after the binder removal in comparative example 3.

FIG. 7 is a xrd graph of the aluminum nitride green sheet after binder removal in comparative example 4.

FIG. 8 is a xrd graph of the aluminum nitride green sheet after binder removal in comparative example 5.

FIG. 9 shows the aluminum nitride green sheet after the binder removal in comparative example 6.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the scope of the present invention is not limited thereto.

The experimental procedures used in the following examples are conventional unless otherwise specified. The experimental raw materials and the related equipments used in the following examples are commercially available unless otherwise specified.