Preparation method of ceramic substrate and ceramic substrate

Abstract

The invention discloses a preparation method of a ceramic substrate and the ceramic substrate. The preparation method comprises the following steps: S1, providing a tape casting raw material, and preparing the tape casting raw material into a substrate green body by adopting a tape casting method; s2, the substrate green body obtained in the step S1 is subjected to flash memory freezing treatment, and a substrate biscuit is obtained; comprising the steps of pretreatment, flash memory freezing treatment and vacuum drying treatment, the operation of flash memory freezing treatment and vacuum drying treatment is taken as a cycle, multiple times of cycle operation are carried out, so that a nanocrystalline sponge structure is formed on the surface of a substrate blank, and then a substrate biscuit is obtained; and S3, sintering treatment. The preparation method of the ceramic substrate is high in production efficiency and low in production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a preparation method of a ceramic substrate and the ceramic substrate. Background Art

[0002] In the preparation method of ceramic substrates in the prior art, in order to make the green body obtained by molding have good integrity and strength, it is often necessary to add dispersants, binders, plasticizers, etc. to the raw materials. These additives need to be removed thoroughly to avoid defects in the sintering stage, such as cracks or insufficient strength, caused by failure to effectively remove the binder. Therefore, debinding is one of the necessary processes. For ceramic materials, debinding is thermal debinding, that is, the green body is placed in a temperature-controlled environment and gradually heated to decompose and evaporate various additives, mainly binders. The debinding process is generally as follows: starting from room temperature, the temperature is increased to 200°C at a rate of 0.5°C / minute. This stage is mainly used to remove moisture; then, the temperature is continued to be increased to 600°C at a rate of 1°C / minute. After reaching 600°C, the temperature is maintained for 2 to 4 hours to ensure that the binder is fully decomposed and volatilized; after the insulation is completed, the sample is allowed to cool naturally to room temperature, which helps to reduce thermal stress and cracks caused by a sudden drop in temperature. However, this method has a long processing time and high cost.

[0003] Therefore, it is very necessary to provide a method for preparing a ceramic substrate with high production efficiency and low production cost, and a ceramic substrate. Summary of the invention

[0004] The object of the present invention is to solve the above problems and provide a method for preparing a ceramic substrate and a ceramic substrate. The method for preparing the ceramic substrate has high production efficiency and low production cost.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a ceramic substrate, comprising the steps of:

[0007] S1, providing a tape casting raw material, and using a tape casting method to make a substrate green body from the tape casting raw material;

[0008] S2, subjecting the substrate green body obtained in step S1 to flash memory freezing treatment to obtain a substrate green body; comprising the steps of:

[0009] S21, pretreatment: placing the substrate green body obtained in step S1 in a sample chamber frozen by liquid nitrogen, and adjusting the temperature of the substrate green body to 25-30° C.;

[0010] S22, flash freezing treatment: placing the green substrate processed in step S21 in a liquid nitrogen tank for rapid freezing treatment;

[0011] S23, vacuum drying treatment: transferring the substrate blank treated in step S22 from the liquid nitrogen tank to a vacuum drying chamber for heating and drying;

[0012] The operation of step S22 and step S23 is regarded as one cycle, and the cycle operation is repeated multiple times, so that a nanocrystalline sponge structure is formed on the surface of the substrate blank, thereby obtaining the substrate blank;

[0013] S3, sintering treatment: the substrate blank obtained in step S2 is sintered to obtain a ceramic substrate.

[0014] Optionally, during the flash freezing treatment, when the substrate processed in step S21 is green, the entire sample cavity is vertically placed into a liquid nitrogen tank; the temperature of the rapid freezing treatment is -196°C, and the time is 30-60s.

[0015] Optionally, in step S23, the vacuum degree in the vacuum drying chamber is ≤10Pa, and the heating drying is performed at a heating rate of 1-2°C / min, the temperature is increased to between -20°C and -50°C, and maintained for 10±2min.

[0016] Optionally, step S22 and step S23 are looped 4-6 times.

[0017] Optionally, the casting raw materials include ceramic powder, flux, dispersant, binder, plasticizer, organic solvent and water.

[0018] Optionally, the casting raw material includes, by weight, 95-97 parts of ceramic powder and 3-5 parts of flux; the amount of dispersant added is 1%-3% of the total weight of the inorganic powder in the raw material, the amount of binder added is 5%-8% of the total weight of the inorganic powder in the raw material, the amount of plasticizer added is 3%-5% of the total weight of the inorganic powder in the raw material, and the amount of solvent added is 25%-40% of the total weight of the inorganic powder in the raw material; the mass ratio between the organic solvent and water is (2-4):(6-8).

[0019] Optionally, the organic solvent comprises ethanol and toluene in a mass ratio of 1:1.

[0020] Optionally, the ceramic powder includes alumina ceramic powder, the dispersant includes phosphate ester, the binder includes polyvinyl butyral, and the plasticizer includes dioctyl phthalate.

[0021] Optionally, in step S3, the temperature rising curve of the sintering treatment is: heating from room temperature to 1200±5°C at a heating rate of 5°C / min; heating from 1200±5°C to 1600±5°C at a heating rate of 2°C / min, and keeping warm for 6 hours; after the insulation is completed, the ceramic substrate is taken out after cooling with the furnace.

[0022] Second aspect: The present invention provides a ceramic substrate, which is prepared by the above-mentioned method for preparing a ceramic substrate.

[0023] The beneficial effects produced by the present invention include at least:

[0024] In the preparation method of the ceramic substrate described in the present invention, the substrate green body formed by laminating the multi-layer cast film is synergistically processed through multiple cycles of flash freezing and vacuum drying, which optimizes the ceramic particle arrangement of the ceramic substrate, completely removes organic matter, improves the performance consistency of the substrate green body, and improves the performance of the prepared ceramic substrate; the substrate green body after the multiple cycles of flash freezing and vacuum drying is directly sintered, which omits the debinding process compared with the prior art, reduces the production links, and improves production efficiency. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of the present invention, the preferred embodiments of the present invention are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in the present invention. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0026] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. Unless otherwise specified. The raw materials used in the present invention can be derived from suppliers known in the art, or prepared by known methods.

[0027] In a first aspect, the present invention provides a method for preparing a ceramic substrate, comprising the steps of:

[0028] S1, providing a tape casting raw material, and using a tape casting method to make a substrate green body from the tape casting raw material;

[0029] S2, subjecting the substrate green body obtained in step S1 to flash memory freezing treatment to obtain a substrate green body; comprising the steps of:

[0030] S21, pretreatment: placing the substrate green body obtained in step S1 in a sample chamber frozen by liquid nitrogen, and adjusting the temperature of the substrate green body to 25-30° C.; within the temperature range selected by the present invention, the organic solvent in the substrate green body has good rheology and plasticity, which is conducive to removing tiny bubbles that may exist on the green body, especially on the surface of the green body, and ensuring that the film surface is flat and smooth without bubbles; at the same time, within the temperature range selected by the present invention, the organic molecules can be in a quasi-stable state, the intermolecular interaction force is moderate, and the surface tension of the cast film is moderate, which is conducive to the formation of a microstructure in the subsequent freezing process;

[0031] S22, flash freezing treatment: placing the substrate green body processed in step S21 in a liquid nitrogen tank for rapid freezing treatment; during the rapid freezing treatment, various organic substances in the substrate green body are instantly frozen into a polymer glass phase, and the ceramic particles are quickly fixed, blocking the movement of each component and between components;

[0032] S23, vacuum drying treatment: transferring the substrate blank treated in step S22 from the liquid nitrogen tank to a vacuum drying chamber for heating and drying;

[0033] The operation of step S22 and step S23 is regarded as one cycle, and the cycle operation is repeated multiple times, so that a nanocrystalline sponge structure is formed on the surface of the substrate blank, thereby obtaining the substrate blank;

[0034] S3, sintering treatment: the substrate blank obtained in step S2 is sintered to obtain a ceramic substrate.

[0035] After repeated rapid freezing (below its glass transition temperature Tg) and heating (above its glass transition temperature Tg), the chain segments of polymer-i move and rearrange, causing some of the originally ordered crystalline regions to transform into amorphous regions, forming more amorphous regions. The increase in the proportion of amorphous regions usually leads to a decrease in the phase transition temperature of the polymer (because the existence of amorphous regions makes the movement of polymer chains more free, and the molecular arrangement of amorphous regions is looser, so that phase transition can occur at lower temperatures), and sublimation occurs between -20°C and -50°C.

[0036] The polymer glass phase is formed instantly by flash cooling, and then the solvent water is crystallized by slowly heating up, and sublimates in a vacuum environment. The sublimation process drives other organic matter to move to the surface or near the surface of the blank to form a crystalline film. Due to the hindrance of the glass phase, the organic crystals cannot grow after nucleation, forming nanocrystals. The nanocrystals undergo phase change during the continued heating process and are volatilized, leaving a porous structure on the surface of the blank. After repeated rapid freezing and heating, a sponge structure is formed on the surface of the blank. The existence of the sponge structure helps to maintain the structural stability of the blank and avoid collapse.

[0037] Because the organic matter has been extracted to the surface of the green body, and the ceramic particles are rearranged during the freezing process to form a denser green body. The green body density at this time can reach the level of compacted green body after the pressing process, and because the organic matter has been removed, it does not need to go through the debinding process and can be directly sintered. Therefore, compared with the general method, the green body needs to be debinded to remove the organic matter before sintering into porcelain. This solution omits the debinding process through improvement, and the ceramic substrate prepared has a higher yield than the general method.

[0038] Optionally, during flash freezing, when the green substrate processed in step S21 is placed in the sample cavity as a whole vertically into a liquid nitrogen tank, a cold air layer may form on the surface of the sample during the cooling process, which will reduce the cooling efficiency. Placing the whole vertically into the liquid nitrogen tank can reduce the thickness of the gas layer, increase the cooling rate, prevent the formation of large ice crystals during the cooling process, and help maintain the structural integrity of the sample; the temperature of the rapid freezing treatment is -196°C, and the time is 30-60s.

[0039] Optionally, in step S23, the vacuum degree in the vacuum drying chamber is ≤10Pa, and the heating drying is carried out at a heating rate of 1-2°C / min, and the temperature is raised to between -20°C and -50°C, and maintained for 10±2min. During the vacuum drying process in step S23, the molecular thermal motion rate is controlled by slowly increasing the temperature, providing sufficient time for the solvent molecules to precipitate. Due to the obstruction of the glass crystals, uniform and fine nanocrystals (10-50nm) are formed on the surface of the blank, and are eventually removed by sublimation; slow heating helps to fully release thermal stress, stabilize molecular rearrangement, and create conditions for the next cycle.

[0040] Optionally, step S22 and step S23 are cycled 4-6 times. During the flash freezing process of step S22, the ceramic particles are rearranged again, and the structure tends to be dense; the organic molecules tend to be released completely during repeated heating. During the cycle of step S22 and step S23, from a microscopic point of view, the first cycle initially destroys the molecular clustering phenomenon, the 2-3 cycles generate crystal nuclei in an orderly manner, and the 4-5 cycles further refine the crystals. Therefore, multiple cycles are a process of gradually fine-tuning the microstructure, accumulating the crystal nucleation effect, optimizing the arrangement of ceramic particles and realizing the densification of the blank. The time used to transfer the substrate blank treated in step S22 to the vacuum drying oven described in step S23 is 5 minutes.

[0041] Optionally, the casting raw material includes ceramic powder, flux, dispersant, binder, plasticizer, organic solvent and water. In the casting raw material, in parts by weight, the casting raw material includes 95-97 parts of ceramic powder and 3-5 parts of flux; the amount of dispersant added is 1%-3% of the total weight of inorganic powder in the raw material, the amount of binder added is 5%-8% of the total weight of inorganic powder in the raw material, the amount of plasticizer added is 3%-5% of the total weight of inorganic powder in the raw material, and the amount of solvent added is 25%-40% of the total weight of inorganic powder in the raw material; the mass ratio between the organic solvent and water is (2-4): (6-8). The organic solvent includes ethanol and toluene in a mass ratio of 1:1.

[0042] Optionally, the ceramic powder includes alumina ceramic powder, the dispersant includes phosphate, the binder includes polyvinyl butyral, and the plasticizer includes dioctyl phthalate. The substrate green body obtained by the present invention contains dispersant phosphate, binder polyvinyl butyral, plasticizer dioctyl phthalate and organic solvent (ethanol and toluene with a mass ratio of 1:1) and water, etc. Phosphate, polyvinyl butyral, water and ethanol are polar compounds, dioctyl phthalate and toluene are non-polar compounds. According to the principle of "like dissolves like", water and ethanol can better dissolve dispersants and binders, while toluene can dissolve plasticizers. During this dissolution process, some plasticizers and binders undergo esterification reaction. The above mutually soluble organic matter and water form a polymer with a network structure in the green body.

[0043] Optionally, in step S3, the temperature rising curve of the sintering treatment is: heating from room temperature to 1200±5°C at a heating rate of 5°C / min; heating from 1200±5°C to 1600±5°C at a heating rate of 2°C / min, and keeping warm for 6 hours; after the insulation is completed, the ceramic substrate is taken out after cooling with the furnace.

[0044] Second aspect: The present invention provides a ceramic substrate, which is prepared by the above-mentioned method for preparing a ceramic substrate.

[0045] Specific examples 1 to 15 respectively use the preparation method of the present invention to prepare ceramic substrates. In examples 1 to 15, the ratio of organic solvent to water, the green body temperature during pre-freezing pretreatment, the freezing treatment temperature, the freezing treatment time, the heating rate and the maximum temperature during vacuum drying treatment, and the number of freezing-heating cycles are used as variables to prepare the substrate. In examples 1 to 15, except for the conditions listed in Table 1, the other preparation conditions are the same.

[0046] Comparative Example 1: Compared with Example 1, the difference of Comparative Example 1 is that no organic solvent is used, only water is used as the solvent; the number of flash memory freezing-warming cycle operations is 3 times.

[0047] Comparative Example 2: Compared with Example 4, the difference of Comparative Example 2 is that the maximum temperature during vacuum drying treatment is 10°C, and the number of flash freezing-heating cycle operations is 3 times.

[0048] Comparative Example 3: Compared with Example 1, the difference of Comparative Example 3 is that the number of flash memory freezing-warming cycle operations is 2 times.

[0049] Comparative Example 4: Compared with Example 14, the difference of Comparative Example 4 is that the heating rate during vacuum drying treatment is 1.5°C / min and the maximum temperature is -35°C, and the number of freezing-heating cycles is 3 times.

[0050] Comparative Example 5: Compared with Example 1, the difference of Comparative Example 5 is that after pretreatment before freezing, the substrate green body is pressed at a pressure of 10 MPa for 30 seconds.

[0051] Comparative Example 6: Compared with Examples 5 and 14, the difference of Comparative Example 6 is that after pretreatment before freezing, the substrate green body is pressed at a pressure of 10 MPa for 30 seconds.

[0052] Comparative Example 7: Compared with Example 3, the difference of Comparative Example 7 is that after pretreatment before freezing, the substrate green body is pressed at a pressure of 10 MPa for 30 seconds.

[0053] The specific parameters of the variable parameters in Examples 1 to 15 and Comparative Examples 1-7 are shown in Table 1.

[0054] Table 1. Parameter setting table of preparation conditions in Examples 1 to 15 and Comparative Examples 1-7.

[0055]

[0056] Table 2. Performance test table of the ceramic substrates prepared in Examples 1 to 15 and Comparative Examples 1-7.

[0057]

[0058] The performance of the ceramic substrates prepared in Examples 1 to 15 and Comparative Examples 1-7 was tested; the performance test included the mass difference before and after heat treatment, the volume density of the green body after flash freeze-vacuum drying cycle treatment, the density of the ceramic substrate, and the three-point bending strength, wherein in Examples 1 to 15 and Comparative Examples 1 to 4, the mass difference before and after heat treatment refers to the difference in mass of the substrate green body before and after flash freeze-vacuum drying cycle treatment; the specific test results are shown in Table 2.

[0059] As shown in Table 2, the volume density of the substrate blank prepared by the preparation method of the present invention reaches 2.8±0.1 g / cm 3 The density of the green body obtained after debinding treatment in the prior art is 2.6±0.1g / cm 3 , indicating that compared with the prior art, the density of the substrate blank obtained by the preparation method of the present invention is increased by 7-8%; indicating that the performance consistency of the substrate blank obtained by the preparation method of the ceramic substrate of the present invention is good; the density of the ceramic substrate obtained after sintering in the present invention is as high as 3.89g / cm 3 , indicating that the preparation method of the ceramic substrate of the present invention is beneficial to improving the mechanical and dielectric properties of the ceramic substrate; the three-point bending strength of the ceramic substrate obtained by the present invention is above 500 MPa, and the highest is up to 530 MPa, which is much higher than the ceramic substrate obtained in the comparative example.

[0060] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0061] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a ceramic substrate, characterized in that: Includes steps: S1, providing a tape casting raw material, and using a tape casting method to make a substrate green body from the tape casting raw material; S2, subjecting the substrate blank obtained in step S1 to a flash memory freezing process to obtain a substrate blank; Includes steps: S21, pretreatment: placing the substrate green body obtained in step S1 in a sample chamber frozen by liquid nitrogen, and adjusting the temperature of the substrate green body to 25-30° C.; S22, flash freezing treatment: placing the green substrate processed in step S21 in a liquid nitrogen tank for rapid freezing treatment; S23, vacuum drying treatment: transferring the substrate blank treated in step S22 from the liquid nitrogen tank to a vacuum drying chamber for heating and drying; The operation of step S22 and step S23 is regarded as one cycle, and the cycle operation is repeated multiple times, so that a nanocrystalline sponge structure is formed on the surface of the substrate blank, thereby obtaining the substrate blank; S3, sintering treatment: the substrate blank obtained in step S2 is sintered to obtain a ceramic substrate.

2. The method for preparing a ceramic substrate according to claim 1, characterized in that: During the flash freezing treatment, when the substrate processed in step S21 is green, the sample cavity is vertically placed in a liquid nitrogen tank; the temperature of the rapid freezing treatment is -196°C and the time is 30-60s.

3. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S23, the vacuum degree in the vacuum drying chamber is ≤10Pa, and the temperature is increased to between -20°C and -50°C at a heating rate of 1-2°C / min and maintained for 10±2min.

4. The method for preparing a ceramic substrate according to claim 1, characterized in that: Step S22 and step S23 are cycled 4-6 times.

5. The method for preparing a ceramic substrate according to claim 1, characterized in that: The casting raw materials include ceramic powder, flux, dispersant, binder, plasticizer, organic solvent and water.

6. The method for preparing a ceramic substrate according to claim 5, characterized in that: The casting raw material comprises, by weight, 95-97 parts of ceramic powder and 3-5 parts of flux; the added amount of dispersant is 1%-3% of the total weight of inorganic powder in the raw material, the added amount of binder is 5%-8% of the total weight of inorganic powder in the raw material, the added amount of plasticizer is 3%-5% of the total weight of inorganic powder in the raw material, and the added amount of solvent is 25%-40% of the total weight of inorganic powder in the raw material; the mass ratio between the organic solvent and water is (2-4):(6-8).

7. The method for preparing a ceramic substrate according to claim 6, characterized in that: The organic solvent includes ethanol and toluene in a mass ratio of 1:

1.

8. The method for preparing a ceramic substrate according to claim 1, characterized in that: The ceramic powder includes alumina ceramic powder, the dispersant includes phosphate ester, the binder includes polyvinyl butyral, and the plasticizer includes dioctyl phthalate.

9. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S3, the temperature rise curve of the sintering treatment is: heating from room temperature to 1200±5°C at a heating rate of 5°C / min; heating from 1200±5°C to 1600±5°C at a heating rate of 2°C / min, and keeping warm for 6 hours; after the insulation is completed, the ceramic substrate is taken out after cooling with the furnace.

10. A ceramic substrate, characterized in that: The ceramic substrate is prepared by the method for preparing a ceramic substrate according to any one of claims 1 to 9.

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