Ceramic substrate and preparation method thereof

Abstract

The invention discloses a ceramic substrate and a preparation method thereof, and the preparation method comprises the following steps: S1, mixing raw materials of the ceramic substrate to obtain mixed material powder; s2, carrying out compression molding on the mixed material powder to obtain a ceramic substrate green body; s3, the ceramic substrate green body is placed under the conditions of normal pressure P0 and normal temperature T0, the temperature is increased and increased to reach the pressure P1 and the temperature T1, P1 / T1 = 1.80-5.10 kPa / DEG C, and the conditions are kept for glue discharging treatment; and S4, continuously increasing the pressure and the temperature of the ceramic substrate green body to reach the pressure intensity P2 and the temperature T2, simultaneously carrying out ultrasonic oscillation treatment with the frequency of V, enabling the ratio of P2 to T2 to V to be (0.6-1.5) MPa to 600 DEG C to (2-4) Hz, and keeping for sintering treatment to obtain the ceramic substrate. The ceramic substrate prepared by the preparation method has high density, high breaking strength and low porosity.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic devices, and more specifically, to a ceramic substrate and a preparation method thereof. Background Art

[0002] Ceramic materials can be made into precision ceramic devices such as ceramic substrates due to their advantages such as good insulation, high strength and wear resistance. They are widely used in semiconductor power devices, integrated circuit packaging, automotive batteries, aerospace and military electronics.

[0003] The sintering process of ceramic materials is a key step to achieve internal particle densification and enable the ceramic substrate to obtain good mechanical strength. Since the sintering temperature of the ceramic material itself is relatively high, sintering aids or other components are generally added to enhance the sintering of the ceramic material or to achieve the purpose of improving corresponding properties such as thermal conductivity. Mixtures of different formulations and particle size ratios often have defects such as local agglomerates, microcracks or pores after normal pressure sintering, which reduces the mechanical strength and reliability of the obtained ceramic substrate, ultimately resulting in the prepared ceramic substrate having low density, high porosity and low flexural strength.

[0004] Therefore, it is of great significance to develop a method for preparing a ceramic substrate to improve the density and flexural strength of the ceramic substrate and reduce the porosity of the ceramic substrate. Summary of the invention

[0005] The object of the present invention is to solve the deficiencies of the prior art and to provide a ceramic substrate and a method for preparing the same.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a method for preparing a ceramic substrate, the method comprising the following steps:

[0008] S1. Mixing raw materials of a ceramic substrate to obtain a mixed material powder;

[0009] S2. The mixed material powder is pressed to obtain a green ceramic substrate;

[0010] S3. The ceramic substrate green body is placed under normal pressure P0 and normal temperature T0, and the pressure and temperature are increased to a pressure of P1 and a temperature of T1, and △P1 / △T1=(P1-P0) / (T1-T0)=1.80-5.10kPa / ℃, and maintained for debinding treatment;

[0011] S4. Continue to increase the pressure and temperature of the ceramic substrate green body treated in step S3 to a pressure of P2 and a temperature of T2, and simultaneously perform ultrasonic oscillation treatment at a frequency of V, and make △P2:△T2:V=(P2-P1):(T2-T1):V=(0.6-1.5)MPa:600℃:(2-4)Hz, and maintain it for sintering treatment to obtain a ceramic substrate.

[0012] The present invention can control △P1 / △T1 and △P2:△T2:V, so that the ceramic substrate green body can timely decompose and discharge organic matter during the preparation process, and the internal grains can grow uniformly and controllably as the temperature rises, and the pressure change trend is synchronously controlled to prevent the problem of local defects caused by abnormal crystal structure, and promote grain rearrangement with the vibration treatment to eliminate the pores generated by the debinding treatment, thereby improving the stacking density, timely filling the gaps generated inside the ceramic substrate green body, reducing the porosity inside the ceramic substrate, and improving the density and flexural strength of the prepared ceramic substrate.

[0013] Specifically, during the high-temperature preparation process of the ceramic substrate, closed pores and a small number of small pores are usually difficult to expel. At this time, the oscillation force combined with the pressure change provides a greater sintering driving force for the powder sintering, which is more conducive to promoting grain sliding, plastic deformation and diffusion mass transfer in the sintered body. By synchronously adjusting the temperature, pressure and oscillation frequency, the isolated pores diffuse to the grain boundaries and are eliminated, allowing the densification process to continue. At the same time, the alumina grains continue to grow under the action of high temperature, thereby completely eliminating the closed pores in the material, reducing material defects and internal stresses, and thereby increasing the overall strength performance and reliability after porcelain formation.

[0014] When the △P1 / △T1 value is too large, that is, the pressure change per unit temperature is too large or the temperature change per unit pressure is too small, the density inside the ceramic substrate green body will be too low or the pore distribution will be uneven, thereby generating internal stress, reducing the density and flexural strength of the ceramic substrate and increasing the porosity of the ceramic substrate; and when the △P1 / △T1 value is too small, that is, the pressure change per unit temperature is too small or the temperature change per unit pressure is too large, the organic matter in the debinding process will be decomposed and discharged too quickly, and the gaps generated inside the ceramic substrate green body cannot be filled in time, thereby reducing the density and flexural strength of the ceramic substrate and increasing the porosity of the ceramic substrate.

[0015] For △P2:△T2:V, when △P2:V and / or △T2:V are too low, grain growth cannot be promoted, which is not conducive to improving the density and flexural strength of the prepared ceramic substrate and reducing the porosity of the ceramic substrate; when △P2:V and / or △T2:V are too high, the grains grow abnormally, and the liquid phase enters the interior of the grains, which is easy to cause crystal structure defects, which is not conducive to improving the density and flexural strength of the prepared ceramic substrate and reducing the porosity of the ceramic substrate; when V in the ratio is too low or is 0 (i.e., no ultrasonic oscillation treatment), the pores generated by the debinding treatment cannot be eliminated, which is not conducive to improving the density and flexural strength of the prepared ceramic substrate and reducing the porosity of the ceramic substrate; when V in the ratio is too high, it will affect the normal progress of the sintering process, and in severe cases, the green body cannot be sintered into shape.

[0016] In addition, the preparation method of the ceramic substrate of the present invention can not only improve the degree of densification of particles inside the ceramic material, but also the required sintering temperature and pressure are low, and the time for pressing and molding the ceramic substrate raw materials is short. It will not affect the process of pressing and densifying the powder particles of the ceramic material to form a green body, nor will it hinder the growth of grains and affect the discharge of volatile gases during the debinding process due to excessively high pressing densification, which helps to improve the overall strength performance of the ceramic substrate.

[0017] Preferably, in step S3, the ΔP1 / ΔT1 may be any one of 1.80 kPa / °C, 1.81 kPa / °C, 2.0 kPa / °C, 2.07 kPa / °C, 2.50 kPa / °C, 3.0 kPa / °C, 3.26 kPa / °C, 3.30 kPa / °C, 4.30 kPa / °C, 4.5 kPa / °C, 5.04 kPa / °C, 5.10 kPa / °C, or a range between any two of them.

[0018] Preferably, in step S3, ΔP1 / ΔT1=1.81-5.04 kPa / °C.

[0019] Preferably, in step S3, the ΔP2:ΔT2:V=(P2-P1):(T2-T1):V=(0.6-1.0)MPa:600℃:(3-4)Hz.

[0020] In the present invention, the normal pressure P0 in step S3 is 0.1 MPa and the normal temperature T0 is 25°C.

[0021] Preferably, in step S3, the P1 is 1.5-3.0 MPa, and the T1 is 600-800°C.

[0022] Preferably, in step S3, the time required for the pressure and temperature increase is 20-60 minutes, and the pressure and temperature increase linearly with time during the pressure and temperature increase process.

[0023] Preferably, in step S3, the holding time for the debinding treatment is 60-120 minutes.

[0024] Preferably, in step S4, the ΔP2:ΔT2:V may be specifically 0.6MPa:600℃:2Hz, 0.7MPa:600℃:2Hz, 0.8MPa:600℃:2Hz, 0.9MPa:600℃:2Hz, 1.0MPa:600℃:2Hz, 1.1MPa:600℃:2Hz, 1.2MPa:600℃:2Hz, 1.3MPa:600℃:2Hz, 1.4MPa:600℃:2Hz, 1.5MPa:600℃:2Hz, 0.6MPa:600℃:3Hz, 0.7MPa:600℃:3Hz, 0.8MPa:600℃:3Hz, 0.9MPa:600℃:3Hz, 1.0MPa:600℃:3Hz :3Hz, 1.1MPa:600℃:3Hz, 1.2MPa:600℃:3Hz, 1.3MPa:600℃:3Hz, 1.4MPa:600℃:3Hz, 1.5MPa:600℃:3Hz, 0.6MPa:600℃:4Hz, 0.7MPa:600℃:4Hz, 0.8MPa:600℃:4Hz, 0.9MPa:600℃:4Hz, 1.0MPa:600℃:4Hz, 1.1MPa:600℃:4Hz, 1.2MPa:600℃:4Hz, 1.3MPa:600℃:4Hz, 1.4MPa:600℃:4Hz, 1.5MPa:600℃:4Hz, any one of them or the range between any two of them.

[0025] Preferably, in step S4, the P2 is 3.0-3.6 MPa, the T2 is 1200-1400° C., and the V is 2-4 Hz.

[0026] Preferably, in step S4, the time required for the pressure and temperature increase is 20-100 min, and the pressure and temperature increase linearly with time during the pressure and temperature increase process.

[0027] Preferably, in step S4, the holding time for sintering is 120-240 minutes.

[0028] Preferably, in step S4, after the sintering process, a pressure reduction and temperature reduction process is also included.

[0029] More preferably, the pressure reduction and temperature reduction treatment refers to reducing the pressure to normal pressure P0 and the temperature to normal temperature T0.

[0030] Preferably, in step S1, the raw materials of the ceramic substrate include, by weight: 30-50 parts of alumina powder, 0-2 parts of sintering aid, 5-10 parts of dispersant, and 38-64 parts of solvent.

[0031] The preparation method of the ceramic substrate of the present invention can improve the density and flexural strength of the prepared ceramic substrate and reduce the porosity of the ceramic substrate with or without a sintering aid.

[0032] More preferably, the alumina powder is at least two of alumina A, alumina B, and alumina C with different particle sizes, the D50 particle size of the alumina A is 5-10 μm, the D50 particle size of the alumina B is 50-100 μm, the D50 particle size of the alumina C is 100-200 μm, and the mass ratio of the alumina A, alumina B, and alumina C is (0-9):(0-8):(0-2).

[0033] More preferably, the sintering aid is at least one of silicon dioxide, calcium oxide and magnesium oxide.

[0034] More preferably, the dispersant is at least one of polycarboxylate ammonium salt and polyacrylate ammonium salt.

[0035] More preferably, the solvent is at least one of ethanol, methanol, acetone and water.

[0036] Preferably, the raw materials of the mixed ceramic substrate are prepared by wet ball milling.

[0037] More preferably, the wet ball milling time is 20-30 hours.

[0038] Preferably, after mixing the raw materials of the ceramic substrate, the process further comprises drying at 80-120°C.

[0039] Preferably, in step S2, the pressing pressure is 100-400 MPa and the time is 10-25 min.

[0040] In a second aspect, the present invention provides a ceramic substrate prepared by the preparation method described in the first aspect.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention can control △P1 / △T1 and △P2:△T2:V, so that the ceramic substrate green body can timely decompose and discharge organic matter during the preparation process, and the internal grains can grow uniformly and controllably as the temperature rises, and the pressure change trend is synchronously controlled to prevent the problem of local defects caused by abnormal crystal structure, and promote grain rearrangement with the vibration treatment to eliminate the pores generated by the debinding treatment, thereby improving the stacking density, timely filling the gaps generated inside the ceramic substrate green body, reducing the porosity inside the ceramic substrate, and improving the density and flexural strength of the prepared ceramic substrate. DETAILED DESCRIPTION

[0043] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0044] The experimental methods in the following examples without specifying specific conditions are generally based on conventional conditions in the art; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets.

[0045] Example 1

[0046] This embodiment provides a ceramic substrate, and the preparation method thereof includes the following steps:

[0047] S1. Alumina ceramic balls were added to the raw materials of the ceramic substrate at a ball-to-material ratio of 3:1, and the raw materials of the ceramic substrate were wet-milled for 25 h in a ball mill and dried at 100 ° C to obtain a mixed material powder;

[0048] S2. The mixed powder was pressed and molded at a pressure of 300 MPa for 20 min to obtain a green ceramic substrate;

[0049] S3. The ceramic substrate green body is placed under normal pressure P0 (0.1MPa) and normal temperature T0 (25°C), and the pressure and temperature are increased to pressure P1 = 2.3MPa, temperature T1 = 700°C, and △P1 / △T1 = (P1-P0) / (T1-T0) = 3.26kPa / °C, and maintained for 80min for debinding treatment;

[0050] S4. The green ceramic substrate processed in step S3 is further pressurized and heated to a pressure of P2 = 3.3 MPa and a temperature of T2 = 1300 ° C. At the same time, an ultrasonic oscillation treatment with a frequency of V = 3 Hz is performed, and △P2:△T2:V = (P2-P1): (T2-T1): V = 1.0 MPa: 600 ° C: 3 Hz is maintained for 180 min for sintering, and then the temperature and pressure are reduced to 0.1 MPa and the temperature is reduced to 25 ° C to obtain a ceramic substrate;

[0051] Wherein, in step S1, the raw materials of the ceramic substrate, calculated by weight, include: 40 parts of alumina powder, 2 parts of sintering aid, 8 parts of dispersant, and 50 parts of solvent; the alumina powder is alumina A, alumina B, and alumina C in a mass ratio of 6:3:1;

[0052] The D50 particle size of the aluminum oxide A is 5 μm, the D50 particle size of the aluminum oxide B is 100 μm, and the D50 particle size of the aluminum oxide C is 200 μm; the sintering aid is calcium oxide, the dispersant is polycarboxylate ammonium salt (5027), and the solvent is anhydrous ethanol;

[0053] In step S3, the time required for the pressure and temperature increase is 40 minutes, and the pressure and temperature increase linearly with time during the pressure and temperature increase process;

[0054] In step S4, the time required for the pressure and temperature increase is 20 minutes, and the pressure and temperature increase linearly with time during the pressure and temperature increase process.

[0055] Examples 2-3 and Comparative Examples 1-6

[0056] Embodiments 2-3 and comparative examples 1-6 provide different ceramic substrates, which differ from embodiment 1 in that the experimental parameters in step S3 and step S4 are different, and the rest are consistent with embodiment 1, as shown in the following table:

[0057] Table 1 Experimental parameters in step S3 and step S4 of Examples 1-3 and Comparative Examples 1-6

[0058]

[0059] In the above table, V=0 Hz in Comparative Example 5, indicating that in step S4 of Comparative Example 5, no ultrasonic oscillation treatment is performed while the sintering treatment is performed.

[0060] Embodiment 4-9

[0061] Embodiments 4-9 provide different ceramic substrates. The difference between them and Embodiment 3 is that the composition and amount of the ceramic substrate raw material in step S1 are different. The rest are consistent with Embodiment 3, as shown in the following table:

[0062] Table 2 Composition and amount of ceramic substrate raw materials in step S1 of Example 3-9

[0063]

[0064]

[0065] Performance Testing

[0066] The performance tests of the ceramic substrates of the embodiments and comparative examples are as follows:

[0067] (1) Density test

[0068] Using a solid density meter, the ceramic substrate (3 cm × 5 cm, length × width) of each embodiment or comparative example was washed with water and dried at 100°C to constant weight. At this time, the mass of the ceramic substrate was M1. Then, the ceramic substrate was immersed in water to obtain the mass of the ceramic substrate in water as M2. At this time, the formula [ρ 陶瓷基片 =M1 / (M1-M2)×ρ 水 , ρ 水 =1g / cm 3 ] to obtain the density of the ceramic substrate, the density of the ceramic substrate (ρ 陶瓷基片 )≥3.75g / cm 3 is qualified;

[0069] (2) Flexural strength test

[0070] The ceramic substrate (24 mm × 40 mm × 1 mm, length × width × height) of each embodiment or comparative example was tested by a three-point flexural tester, and laser scribing was used to prepare the sample, with a span of 30 mm and a test speed of 0.5 mm / min. The flexural strength of the ceramic substrate was measured, and the flexural strength of the ceramic substrate was ≥450 MPa, which was qualified.

[0071] (3) Porosity test

[0072] Take the ceramic substrate (5 mm×5 mm, length×width) of each embodiment or comparative example, perform surface polishing, then use FE-SEM (field emission scanning electron microscope) to photograph the pores on the surface of the ceramic substrate, and use ImageJ image area processing software to calculate the porosity of the ceramic substrate (i.e., the percentage of the area of ​​the pores to the surface area of ​​the ceramic substrate). The porosity of the ceramic substrate is ≤2.0%, which is qualified;

[0073] The experimental results are shown in the following table:

[0074] Table 3 Performance test results of ceramic substrates of various embodiments and comparative examples

[0075]

[0076]

[0077] It can be seen from Table 4 that the ceramic substrates prepared in Examples 1-9 of the present invention by controlling the value ranges of △P1 / △T1 and △P2:△T2:V in the debinding treatment and sintering treatment have density, flexural strength and porosity that meet the standards, and can be adapted to alumina powder raw materials of different particle sizes and mass ratios, and have good overall strength performance and reliability.

[0078] The ceramic substrates prepared in Comparative Examples 1-6 that do not meet the value range of △P1 / △T1 or the value range of △P2:△T2:V have at least one of density, flexural strength and porosity that does not meet the standards, and ceramic substrates with good overall performance cannot be prepared.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a ceramic substrate, characterized in that: The preparation method comprises the following steps: S1. Mixing raw materials of a ceramic substrate to obtain a mixed material powder; S2. The mixed material powder is pressed to obtain a green ceramic substrate; S3. The ceramic substrate green body is placed under normal pressure P0 and normal temperature T0, and the pressure and temperature are increased to a pressure of P1 and a temperature of T1, and △P1 / △T1=(P1-P0) / (T1-T0)=1.80-5.10kPa / ℃, and maintained for debinding treatment; S4. Continue to increase the pressure and temperature of the ceramic substrate green body treated in step S3 to a pressure of P2 and a temperature of T2, and simultaneously perform ultrasonic oscillation treatment at a frequency of V, and make △P2:△T2:V=(P2-P1):(T2-T1):V=(0.6-1.5)MPa:600℃:(2-4)Hz, and maintain it for sintering treatment to obtain a ceramic substrate.

2. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S3, ΔP1 / ΔT1=1.81-5.04 kPa / °C.

3. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S3, the ΔP2:ΔT2:V=(P2-P1):(T2-T1):V=(0.6-1.0)MPa:600℃:(3-4)Hz.

4. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S3, the P1 is 1.5-3.0 MPa, and the T1 is 600-800°C.

5. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S4, the P2 is 3.0-3.6 MPa, the T2 is 1200-1400° C., and the V is 2-4 Hz.

6. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S3, the holding time for the debinding treatment is 60-120 minutes.

7. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S4, the holding time for the sintering treatment is 120-240 minutes.

8. The method for preparing a ceramic substrate according to claim 1, characterized in that: In step S1, the raw materials of the ceramic substrate include, by weight, 30-50 parts of alumina powder, 0-2 parts of sintering aid, 5-10 parts of dispersant, and 38-64 parts of solvent.

9. The method for preparing a ceramic substrate according to claim 8, characterized in that: Including at least one of the following (1)-(4): (1) The alumina powder is at least two of alumina A, alumina B, and alumina C with different particle sizes, the D50 particle size of the alumina A is 5-10 μm, the D50 particle size of the alumina B is 50-100 μm, the D50 particle size of the alumina C is 100-200 μm, and the mass ratio of the alumina A, alumina B, and alumina C is (0-9):(0-8):(0-2); (2) The sintering aid is at least one of silicon dioxide, calcium oxide and magnesium oxide; (3) The dispersant is at least one of polycarboxylic acid ammonium salt and polyacrylic acid ammonium salt; (4) The solvent is at least one of ethanol, methanol, acetone and water.

10. A ceramic substrate, characterized in that: The product is prepared by the preparation method described in any one of claims 1 to 9.

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