Low-temperature ceramic substrate and method for manufacturing the same

Abstract

The application discloses a low-temperature ceramic substrate and a preparation method thereof. The method comprises the following processing steps: S1, mixing alumina powder and multi-element glass dry gel to obtain ceramic powder; S2, adding a solvent and a dispersing agent to the ceramic powder and performing mixing ball milling to obtain ceramic slurry; S3, adding a plasticizer and a binder to the ceramic slurry prepared in S2 and performing ball milling and defoaming to obtain casting slurry; S4, performing casting forming on the defoamed casting slurry through a casting machine to obtain green ceramic tape, and obtaining green ceramic sheet after low-temperature drying and cutting; S5, stacking and hot-pressing the green ceramic sheet according to required layers, placing the pressed body in a glue removal furnace to perform glue removal, placing the glue-removed body into a sintering furnace to perform calcination, and controlling the highest sintering temperature at 1500 DEG C, so that the ceramic substrate is obtained after furnace cooling. The low-temperature ceramic substrate preparation method provided by the application can significantly reduce the sintering temperature, save energy and reduce cost, and can also simplify the process, improve the efficiency, and has a very good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of inorganic non-metallic material preparation and microelectronic packaging technology, specifically relating to a low-temperature ceramic substrate and its preparation method. Background Technology

[0002] Ceramic substrates are widely used in high-power electronic components, semiconductor lighting (LED), aerospace, and new energy vehicle electronics due to their excellent mechanical strength, good chemical stability, high insulation, and thermal expansion coefficient that matches electronic chips. Currently, the mainstream process for preparing ceramic substrates typically involves preparing ceramic powder into a slurry, then casting or dry pressing it, followed by high-temperature sintering to achieve densification.

[0003] However, traditional methods for preparing ceramic substrates suffer from technical drawbacks such as high sintering temperatures and enormous energy consumption. Taking the most widely used alumina ceramic as an example, due to the extremely strong covalent or ionic bonds between its atoms, its melting point is as high as approximately 2050℃. To achieve complete densification through sintering, the temperature typically needs to be above 1600℃. This extremely high sintering temperature not only leads to huge consumption of electricity or gas during the production process, significantly increasing manufacturing costs, but also places stringent requirements on the high-temperature resistance and lifespan of heating elements in production equipment such as sintering kilns.

[0004] To lower the sintering temperature, industrial processes often employ the addition of low-melting-point sintering aids (such as glass powder containing silicon, calcium, and magnesium) to promote liquid-phase sintering. Traditional physical mixing methods combine various oxide powders, but these methods suffer from uneven mixing and localized enrichment, leading to increased porosity and weakened grain boundary bonding in the ceramic substrate, severely degrading its thermal conductivity, mechanical strength, and dielectric properties. While some patents (such as CN117303868A) disclose sol-gel methods for preparing low-temperature sintering aids, these methods often involve extremely complex processes, long synthesis times, and difficulty in achieving good compatibility with tape casting systems. Therefore, developing a method that can significantly reduce the sintering temperature while ensuring high density and excellent mechanical and electrical properties of the ceramic substrate has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0005] Given the shortcomings of existing ceramic substrate preparation technologies, such as high energy consumption and the tendency of traditional cooling methods to lead to performance degradation, the technical problem to be solved by this invention is to provide a method for preparing ceramic substrates at low temperatures. This method significantly reduces the sintering temperature of the ceramic substrate by introducing a specific ratio of multi-component glass desiccant sintering aid, thereby achieving the goals of energy saving, consumption reduction, and lower kiln hardware costs. Simultaneously, by optimizing the composite and casting processes of the desiccant and alumina powder, the method effectively improves the defects of high porosity and insufficient density that easily occur in low-temperature sintering, ensuring that the product still possesses excellent thermal conductivity, mechanical strength, and electrical insulation properties.

[0006] To achieve the above objectives, the present invention provides the following technical solution: S1. Preparation of ceramic powder: Micron-sized alumina powder is mixed with a prepared multi-element glass dry gel sintering aid to obtain a mixed ceramic powder; wherein the particle size of the micron-sized alumina powder is 0.5~3μm. The ceramic powder contains 90%~98% micron-sized alumina powder by mass and 2%~10% multi-element glass dry gel sintering aid by mass. In the multi-element glass dry gel sintering aid, the mass ratio of silicon source (Si), calcium salt (Ca), and magnesium salt (Mg) ranges from 50%~70%:15%~25%:15%~25%; S2. Preparation of ceramic slurry: Add solvent (50% to 80% of the powder mass) and dispersant trioleic acid glyceride (1% to 5% of the powder mass) to the above mixed ceramic powder, and perform ball milling to obtain a uniformly dispersed ceramic slurry. S3. Preparation of casting slurry: Plasticizer and binder are added to the ceramic slurry prepared in S2 at a ratio of 1% to 4% of the powder mass, and binder at a ratio of 7% to 11% of the powder mass. After thorough ball milling and vacuum degassing, casting slurry is obtained. S4. Casting and preparation of green ceramic sheets: The degassed casting slurry is placed in a casting machine for casting to obtain a green ceramic strip; the green ceramic strip is then placed in a dryer for low-temperature drying, and after drying, it is cut according to the required size to obtain green ceramic sheets. S5. Debinding and Sintering: Green ceramic sheets are stacked according to the required number of layers and then tightly bonded together using a hot press to form a green body. The hot pressing temperature is 60℃~85℃, the hot pressing pressure is 10~30 MPa, and the holding time is 10~20 minutes. The pressed green body is placed in a debinding furnace for debinding, and then transferred to a sintering furnace for firing. The maximum sintering temperature is controlled at 1500℃. After holding at this temperature, it is cooled in the furnace to obtain a dense ceramic substrate.

[0007] Furthermore, as a preferred embodiment of the present invention: The silicon source (Si) in the multi-element glass dry gel sintering aid is one or more of tetraethyl orthosilicate, organochlorosilane, or sodium silicate; the calcium salt (Ca) is one or more of calcium nitrate, calcium acetate, calcium chloride, or calcium formate; and the magnesium salt (Mg) is one or more of magnesium nitrate, magnesium acetate, magnesium chloride, or magnesium formate.

[0008] The specific preparation method of the multi-element glass dry gel sintering aid is as follows: dissolve metal salts (calcium salts and magnesium salts) in deionized water, stir thoroughly, and place in an oven at 80°C until the solute is completely dissolved; then mix a certain amount of ethanol and tetraethyl orthosilicate at a volume ratio of about 1:1, and add dilute nitric acid to adjust the pH of the system to 3 to form a clear solution; then place the solution in an oven and keep it at 100°C for 12 hours to form a dry gel.

[0009] In steps S2 and S3: the solvent is a mixture of ethanol and isopropanol in a volume ratio of approximately 1:1; the dispersant is one or more of triolein, polyacrylamide, polyacrylic acid, polyethylene glycol, N-methylpyrrolidone, and polyvinylpyrrolidone; the binder is one or more of PVB, polymethyl acrylate, ethyl cellulose, and polymethacrylic acid; and the plasticizer is one or more of dibutyl phthalate, diethyl oxalate, glycerol, polyethylene glycol, and dioctyl phthalate. The material is ball-milled for 24 hours to obtain a uniform cast slurry.

[0010] In step S5, the integrated heating process for debinding and sintering is as follows: (1) Heat to 200℃ at a rate of 5℃ / min and hold for 0.5 h to remove physically adsorbed water and residual solvents such as ethanol; (2) Heat to 400℃ at a rate of 5℃ / min and hold for 1.5h to remove organic groups (-OR, -OH), condense and release gas, and fully discharge the polymer binder to prevent bubbling and cracking; (3) Heat the glass transition temperature (600~800℃) at a heating rate of 5℃ / min and hold for 1.5h to soften the glass phase, fill the gaps between ceramic particles, and achieve bonding and densification under capillary force. (4) The temperature is raised to 1500℃ at a heating rate of 5℃ / min and held for 3 hours to promote liquid phase sintering and bonding of alumina particles, improve density and mechanical strength, and finally cool with the furnace.

[0011] Compared with the prior art, the beneficial effects of the present invention are: (1) Significantly reduced sintering temperature, saving energy and reducing costs; the multi-component glass dry gel prepared by the sol-gel method has extremely high chemical homogeneity and surface activity, and can form a uniform liquid phase earlier during the sintering process. Compared with the traditional physical mixed oxides that require a sintering temperature of 1600℃ or even higher, this invention significantly reduces the sintering temperature to 1500℃. Under the same sintering conditions, sintering at 1500℃ saves 15%~20% of energy compared to sintering at 1600℃. This invention not only greatly reduces energy consumption, but also extends the kiln life.

[0012] (2) Optimize the microstructure and improve the overall performance; multi-component dry gel in T g The material softens near a specific temperature and uniformly fills the gaps between alumina particles, eliminating agglomeration and localized micropores that are common in traditional powder mixing. This results in a significantly reduced porosity of 10.9% for the final ceramic substrate, leading to a substantial increase in density. Its flexural strength can reach up to 412 MPa, and its thermal conductivity reaches 24.2 W·(m·K). -1 Its overall performance surpasses that of traditional high-temperature sintered substrates.

[0013] (3) Simplify the process and improve efficiency; the dry gel sintering aid of the present invention can be directly mixed with alumina powder to prepare casting slurry, which solves the defects of long slurry preparation time and complicated steps in the existing low temperature liquid phase sintering aid process. It has good casting adaptability and is suitable for large-scale industrial mass production. Attached Figure Description

[0014] Figure 1 This is a diagram showing the bending strength.

[0015] Figure 2 This is a diagram showing the thermal conductivity.

[0016] Figure 3 This is a dielectric constant diagram.

[0017] Figure 4 This is a porosity diagram. Detailed Implementation

[0018] The following embodiments illustrate the present invention in detail. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent changes or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the protection scope of the present invention.

[0019] Example 1 S1. 90g of micron-sized alumina powder (0.5-3μm) is mixed with 10g of prepared multi-component glass dry gel sintering aid to obtain ceramic powder. The multi-component glass dry gel sintering aid is prepared by using tetraethyl orthosilicate (5.2g), calcium nitrate (2.5g), and magnesium nitrate (2.3g). First, 2.5g of calcium nitrate and 2.3g of magnesium nitrate are dissolved in 10g of deionized water. After thorough stirring, the mixture is placed in an oven at 80℃ until the solute is completely dissolved. Then, a certain amount of ethanol and tetraethyl orthosilicate (5.2g) are thoroughly mixed at a volume ratio of approximately 1:1, and dilute nitric acid is added to adjust the pH to 3 to form a clear solution. The solution is then placed in an oven and kept at 100℃ for 12 hours to form a dry gel.

[0020] S2. Add solvents ethanol and isopropanol (mass ratio of 1:1) to the ceramic powder, which is 70% of the powder mass, and dispersant trioleic acid glyceride, which is 4% of the powder mass, and stir thoroughly.

[0021] S3. Polyvinyl butyral (binder) at 9% of powder mass and dibutyl phthalate (plasticizer) at 3% of powder mass are added, and the mixture is ball-milled for 24 hours to obtain a uniform cast slurry.

[0022] S4. The degassed casting slurry is cast to obtain green ceramic tape, which is then dried at low temperature and cut into green ceramic sheets. S5. Five layers of green ceramic sheets are stacked and hot-pressed. The hot-pressing temperature is 80℃. The hot pressing pressure was 25 MPa and the holding time was 15 minutes. Following this, debinding and sintering were performed, with the following temperature regime: (1) Increase the temperature to 200℃ at a rate of 5℃ / min and maintain the temperature for 0.5h; (2) Increase the temperature to 400℃ at a rate of 5℃ / min and maintain for 1.5 h; (3) Increase T at a rate of 5℃ / min g =700℃ for 1.5 h; (4) Finally, raise the temperature to 1500℃ and hold for 3 hours, then cool with the furnace.

[0023] Example 2 Except that the mass fraction of alumina in S1 is 92% (92g), and the amount of multi-element glass dry gel is 8% and 8g (using 59wt% tetraethyl orthosilicate, 21wt% calcium nitrate, and 20wt% magnesium nitrate), the other steps are the same as in Example 1.

[0024] Example 3 Except that the mass fraction of alumina in S1 is 94% (94g), and the amount of multi-element glass dry gel is 6% and 6g (using 64wt% tetraethyl orthosilicate, 19wt% calcium nitrate, and 17wt% magnesium nitrate), the other steps are the same as in Example 1.

[0025] Example 4 Except that the mass fraction of alumina in S1 is 98% (98g), and the amount of multi-element glass dry gel is 2% and 2g (using 68wt% tetraethyl orthosilicate, 17wt% calcium nitrate, and 15wt% magnesium nitrate), the other steps are the same as in Example 1.

[0026] Comparative Examples 1-4 Traditionally physically mixed silica, calcium carbonate, and magnesium oxide were used as sintering aids to replace the dry gel in Examples 1-4. The total amount and elemental ratio of the sintering aids in each comparative example remained consistent with the corresponding examples. Due to the low activity of physically mixed powders, the maximum sintering temperature in the comparative examples was increased to 1600℃ to achieve densification.

[0027] Performance comparison test The ceramic substrates prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to performance tests, and the results are shown in the table below: ; By comparing the above charts, it can be found that, compared with Examples 1-4, to obtain a ceramic substrate with performance similar to that of Examples 1-4, the sintering temperature needs to be increased to 1600 degrees. Therefore, the preparation method of the present invention greatly reduces energy consumption and saves a lot of costs. Figures 1-4 This is a bar chart showing the performance parameters of the embodiments and comparative embodiments of the present invention.

[0028] The ceramic substrates prepared by this method can significantly reduce sintering temperature, save energy and reduce costs, optimize the microstructure of the ceramic substrates, and improve overall performance. It has significant economic benefits and is suitable for widespread use.

[0029] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing ceramic substrates at low temperatures, characterized in that, The following processing steps are included: S1. Preparation of ceramic powder: Micron-sized alumina powder is mixed with the prepared multi-element glass dry gel sintering aid to obtain ceramic powder; S2. Preparation of ceramic slurry: Add solvent and dispersant to ceramic powder. The amount of solvent added is 50% to 80% of the powder mass, and the amount of dispersant added is 1% to 5% of the powder mass. Mix and ball mill to obtain ceramic slurry. S3. Prepare casting slurry; add plasticizer (1%~4% of powder mass) and binder (7%~11% of powder mass) to the ceramic slurry prepared in S2, and then ball mill to degas the mixture to obtain casting slurry; S4. Casting and preparation of green ceramic sheets: The degassed casting slurry is cast into green ceramic strips by casting machine, and then dried at low temperature and cut to obtain green ceramic sheets. S5. Lamination, debinding, and sintering: Lay the green ceramic sheets in the required number of layers and hot press them. The hot pressing temperature is 60℃~85℃, the hot pressing pressure is 10~30 MPa, and the holding time is 10~20 minutes. Place the pressed green body in a debinding furnace for debinding. After debinding, place the green body in a sintering furnace for calcination. The maximum sintering temperature is controlled at 1500℃~1520℃. After cooling in the furnace, a ceramic substrate is obtained.

2. The method for preparing a ceramic substrate at low temperature according to claim 1, characterized in that, In step S1, the ceramic powder contains 90%-98% by mass of micron-sized alumina powder and 2%-10% by mass of a prepared multi-element glass dry gel sintering aid.

3. The method for preparing a ceramic substrate at low temperature according to claim 1 or 2, characterized in that: The central particle size of the micron-sized alumina powder is 0.5-3 μm.

4. The method for preparing a ceramic substrate at low temperature according to claim 2, characterized in that, In the multi-component glass dry gel sintering aid, the mass ratio range of each starting material is: silicon source 50%-70%, calcium salt 15%~25%, magnesium salt 15%-25%.

5. The method for preparing a ceramic substrate at low temperature according to claim 4, characterized in that, The silicon source in the multi-component glass dry gel sintering aid is one or more of tetraethyl orthosilicate, organochlorosilane, or sodium silicate; the calcium salt is one or more of calcium nitrate, calcium acetate, calcium chloride, or calcium formate; and the magnesium salt is one or more of magnesium nitrate, magnesium acetate, magnesium chloride, or magnesium formate.

6. The method for preparing a ceramic substrate at low temperature according to claim 1, characterized in that, The preparation method of the multi-component glass dry gel sintering aid includes: Calcium and magnesium salts were dissolved in a certain amount of deionized water at a mass ratio of 1.2:

1. After thorough stirring, the solution was placed in an oven at 80°C until the solutes were completely dissolved. Then, ethanol and tetraethyl orthosilicate were thoroughly mixed and added at a volume ratio of approximately 1:

1. Dilute nitric acid was added to adjust the pH to 3 to form a clear solution. The solution was then kept at 100°C for 12 hours to form a dry gel.

7. The method for preparing a ceramic substrate at low temperature according to claim 1, characterized in that, In steps S2 and S3, the solvent is a mixture of ethanol and isopropanol in a volume ratio of approximately 1:1, and the dispersant is one or more of triolein, polyacrylamide, polyacrylic acid, polyethylene glycol, N-methylpyrrolidone, and polyvinylpyrrolidone. The binder is one or more of PVB, polymethyl acrylate, ethyl cellulose, and polymethacrylic acid. The plasticizer is one or more of dibutyl phthalate, diethyl oxalate, glycerin, polyethylene glycol, and dioctyl phthalate.

8. The method for preparing a ceramic substrate at low temperature according to claim 1, characterized in that, In step S5, the heating steps for debinding and sintering are as follows: (1) Heat to 200 °C at a heating rate of 5 °C / min and hold for 0.5 h to desorb water and ethanol; (2) Heat to 400 °C at a rate of 5 °C / min and hold for 1.5 h to remove -OR and -OH, condense and release gas, and prevent bubbling and cracking; (3) Heat the glass to 600-800℃ at a heating rate of 5℃ / min and keep it for 1.5 h to soften the glass, fill the gaps between the particles, and achieve the purpose of bonding. (4) Heat to 1500℃ at a heating rate of 5℃ / min and hold for 3h, then cool with the furnace.

9. A low-temperature ceramic substrate prepared by the method according to any one of claims 1-8.

10. A low-temperature ceramic substrate according to claim 8, characterized in that, The low-temperature ceramic substrate has a porosity of ≤12.2%, a flexural strength of ≥389 MPa, and a thermal conductivity of ≥22.7 W·(m·K). -1 Dielectric constant ≥ 9.72.

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