Dielectric ceramic substrate and preparation method thereof
By adding additives such as silicon oxide and magnesium carbonate to alumina-based composite ceramics, and combining dry pressing and high-temperature sintering, high-performance alumina-based dielectric ceramic substrates were prepared. This solved the problem of insufficient dielectric properties under high frequency and extreme environments, and achieved ceramic substrates with high density and low dielectric loss, thus improving production efficiency and consistency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-12
- Publication Date
- 2026-04-14
AI Technical Summary
The dielectric performance requirements of existing alumina-based composite ceramics for high-frequency, miniaturized, and extreme environments have not been fully met, and there are gaps in the mass production and performance consistency of high-end ceramics in China.
Using alumina as the main material and adding additives such as silicon oxide, magnesium carbonate, and calcium carbonate, an alumina-based dielectric ceramic substrate is prepared through dry pressing and firing processes. The dielectric constant is controlled at 7.8~8.0, the porosity is <0.1%, and the flexural strength is ≥200MPa.
This technology enables the development of dielectric ceramic substrates with high density, good flatness, and high precision, thereby reducing dielectric loss, improving equipment efficiency and stability, and lowering production costs and temperature control requirements.
Abstract
Description
Technical Field
[0001] This invention relates to a ceramic substrate for dielectrics, and more particularly to a dielectric ceramic substrate and its preparation method. Background Technology
[0002] With the rapid development of electronic information technology, the demand for high-performance dielectric materials in fields such as high-frequency communication, radar systems, microwave circuits, and semiconductor devices is becoming increasingly urgent. Alumina-based composite ceramics, due to their excellent dielectric properties, high mechanical strength, high temperature resistance, and chemical stability, have become one of the core materials in these fields. However, as applications expand towards higher frequencies, miniaturization, and extreme environments (such as high temperatures and radiation), higher requirements are placed on the dielectric properties of composite ceramics, necessitating a systematic study of their performance optimization mechanisms and application potential.
[0003] The dielectric properties of alumina-based composite ceramics are mainly reflected in their low dielectric loss and moderate dielectric constant. This makes them an ideal choice for high-frequency filters, resonators, and microwave circuit boards, effectively reducing energy loss during signal transmission and improving equipment efficiency and stability.
[0004] Current research on the dielectric properties of alumina-based composite ceramics mainly focuses on three aspects: material composition optimization, microstructure control, and innovative fabrication processes. Existing studies have shown that introducing rare earth elements or transition metal oxides can effectively regulate the grain boundary properties of ceramics. For example, by adding a CaO~SiO2~MgO composite flux (SiO2 / CaO=1.8, MgO content 20wt%), the material can achieve a dielectric constant of 9.23 after sintering at 1550℃. In terms of fabrication processes, the application of cold isostatic pressing technology significantly improves the uniformity of ceramics. Combined with 3D printing technology, the porosity of the ceramic substrate can be controlled below 0.5%, and the dielectric constant fluctuation range can be reduced to ±0.05.
[0005] Research on the dielectric properties of alumina composite ceramics is progressing towards higher purity, composite materials, environmental adaptability, and process innovation to meet the needs of cutting-edge fields such as 5G communication, fusion energy, and high-temperature electronics. However, there are still some gaps in China's mass production and performance consistency of high-end ceramics. Summary of the Invention
[0006] To address the above problems, this invention provides a dielectric ceramic substrate, the specific technical solution of which is as follows: A dielectric ceramic substrate includes alumina and additives, said additives including one or more of silicon oxide, magnesium carbonate, calcium carbonate, yttrium oxide, boron nitride, titanium dioxide, and barium carbonate.
[0007] Preferably, the raw materials include the following by mass parts: alumina: 85 parts; silicon dioxide: 2-12 parts; magnesium carbonate: 1-3 parts; calcium carbonate: 0-3 parts; yttrium oxide: 0-1 parts; boron nitride: 0.5-2.5 parts; titanium dioxide: 0-1 parts; barium carbonate: 0-8 parts.
[0008] Preferably, the dielectric constant of the dielectric ceramic substrate is 7.8 to 8.0.
[0009] Preferably, the porosity of the dielectric ceramic substrate is <0.1%.
[0010] Preferably, the dielectric ceramic substrate has a flexural strength ≥200 MPa.
[0011] A method for preparing a dielectric ceramic substrate, used for the dielectric ceramic substrate, includes the following steps: Step 1: Add the silicon dioxide, magnesium carbonate, calcium carbonate, yttrium oxide, titanium dioxide and other additives to the ball flask in proportion, add 99% alumina ceramic balls, the amount of which is 1.5 to 2 times the total powder, add an appropriate amount of deionized water and dispersant, and ball mill for 2 to 6 hours; Step 2: Add an appropriate amount of alumina to the ball mill and continue ball milling for 12-24 hours; Step 3: Add an appropriate amount of adhesive to the ball flask and ball mill for 3-10 minutes; Step 4: The ball-milled slurry is spray-granulated into powder, and then pressed into green body on a dry pressing mold.
[0012] Step 5: Place the green body in a shuttle kiln and fire it.
[0013] Preferably, the dispersant in step one is ammonium polyacrylate, and the amount added is 0.3% of the powder mass.
[0014] Preferably, the adhesive in step three is a PVA aqueous solution with a concentration of 10% and an addition amount of 10-20 wt%.
[0015] Preferably, the firing temperature of the ceramic body in step five is 1640~1660℃.
[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a dielectric ceramic substrate with high density, good flatness and high precision.
[0017] 1. Firing transforms the alumina and silicon dioxide in the green body into the mullite phase, thereby reducing the dielectric constant.
[0018] 2. Generally, when the alumina content in a ceramic green body is about 80% and the silicon content is about 20%, the dielectric constant is 8.0. In the formulation system of this invention, the alumina content is about 85%, which is a significant improvement, resulting in superior performance of the ceramic substrate.
[0019] 3. The formulation of this invention uses a large amount of sintering aids such as calcium oxide and boron nitride, which reduces the amount of silicon oxide used and effectively avoids problems such as sand adhesion.
[0020] 4. The project's design formula takes into account factors such as tunnel kiln production, with a firing temperature of 1640~1660℃. It can share or alternate with other products with high alumina content using tunnel kilns, avoiding the need to adjust the temperature due to inconsistent firing temperatures or use other kiln equipment such as shuttle kilns, thus improving production efficiency and reducing production costs.
[0021] 5. The prepared ceramic substrate has high flatness and precision. When preparing a 50*50mm ceramic substrate, the precision deviation of the four corners after firing is less than 0.05mm. Detailed Implementation
[0022] The present invention will now be further described with reference to the embodiments.
[0023] This application provides a dielectric ceramic substrate with a high alumina content and a dielectric constant of 7.8~8.0, and a method for preparing the same. The ceramic substrate uses alumina as the main material and adds silicon oxide, magnesium carbonate, calcium carbonate and other additives. The substrate is formed by dry pressing to obtain a green body. After debinding, it is fired at 1640~1660℃ to obtain an alumina-based dielectric ceramic substrate with high density, good flatness and high precision.
[0024] The chemical composition of the substrate includes (by weight percentage) 85% aluminum oxide, 2-12% silicon dioxide, 1-3% magnesium carbonate, 0-3% calcium carbonate, 0-1% yttrium oxide, 0.5-2.5% boron nitride, 0-1% titanium dioxide, and 0-8% barium carbonate.
[0025] Example 1
[0026] 210g of silica, 40g of magnesium carbonate, 26g of calcium carbonate, 4g of yttrium oxide, 10g of boron nitride, and 10g of titanium dioxide were added to a spherical flask. 4kg of 995 alumina spherical pellets, 6g of ammonium polyacrylate dispersant, and an appropriate amount of deionized water were added. The mixture was ball-milled for 6 hours. 1700g of alumina was added to the spherical flask and ball-milled for 12 hours. Then, 300g of PVA aqueous solution was added, and the mixture was ball-milled for five minutes. The mixture was then spray-granulated, dry-pressed at 80MPa to obtain a green body, and fired at 1640℃ to obtain a fully dense 50×50mm ceramic substrate with a porosity of <0.1%, a flexural strength of 201.6MPa, a dielectric constant of 8.0, and a corner accuracy deviation of less than 0.05mm.
[0027] Example 2
[0028] 220g of silicon dioxide, 30g of magnesium carbonate, 20g of calcium carbonate, 5g of yttrium oxide, 10g of boron nitride, 5g of titanium dioxide, and 10g of barium carbonate were added to a spherical flask. 4kg of 995 alumina spherical pellets and 6g of ammonium polyacrylate dispersant were added, along with an appropriate amount of deionized water. The mixture was ball-milled for 3 hours. 1700g of alumina was added to the spherical flask and ball-milled for 24 hours. Then, 300g of PVA aqueous solution was added, and the mixture was ball-milled for five minutes. The mixture was then spray-granulated, dry-pressed at 80MPa to obtain a green body, and fired at 1640℃ to obtain a fully dense 50×50mm ceramic substrate with a porosity of <0.1%, a flexural strength of 212MPa, a dielectric constant of 7.9, and a corner accuracy deviation of less than 0.05mm.
[0029] Example 3
[0030] 210g of silicon dioxide, 30g of magnesium carbonate, 30g of calcium carbonate, 5g of yttrium oxide, 10g of boron nitride, 5g of titanium dioxide, and 10g of barium carbonate were added to a spherical flask. 4kg of 995 alumina spherical pellets and 6g of ammonium polyacrylate dispersant were added, along with an appropriate amount of deionized water. The mixture was ball-milled for 3 hours. 1700g of alumina was added to the spherical flask and ball-milled for 24 hours. Then, 300g of PVA aqueous solution was added, and the mixture was ball-milled for five minutes. The mixture was then spray-granulated, dry-pressed at 80MPa to obtain a green body, and fired at 1640℃ to obtain a fully dense 50×50mm ceramic substrate with a porosity of <0.1%, a dielectric constant of 8.0, and a corner accuracy deviation of less than 0.05mm.
[0031] Comparative Example 1 200g of silica, 60g of magnesium carbonate, and 40g of yttrium oxide were added to a spherical flask, along with 4kg of 995 alumina spherical pellets, 6g of ammonium polyacrylate dispersant, and an appropriate amount of deionized water. The mixture was ball-milled for 3 hours. Then, 1700g of alumina was added to the spherical flask and ball-milled for 24 hours. Next, 300g of PVA aqueous solution was added, and the mixture was ball-milled for five minutes. The mixture was then spray-granulated, dry-pressed at 80MPa to obtain a green body, and fired at 1640℃. The resulting green body had a porosity of <0.1% and a dielectric constant of 9.6.
[0032] The content of high-dielectric phase in the ceramic was controlled by adjusting the content of additives such as magnesium carbonate, yttrium oxide, and calcium carbonate. By adding various regulating components such as boron nitride, titanium dioxide, and barium carbonate, a low-dielectric grain boundary phase was formed, reducing the dielectric constant. Furthermore, while Comparative Example 1 only achieved ceramic densification, the examples, based on densification, exhibited a lower dielectric constant and higher dimensional accuracy.
Claims
1. A dielectric ceramic substrate, characterized in that, It includes alumina and additives, wherein the additives include one or more of silicon oxide, magnesium carbonate, calcium carbonate, yttrium oxide, boron nitride, titanium dioxide, and barium carbonate.
2. The dielectric ceramic substrate according to claim 1, characterized in that, The following raw materials are included in parts by weight: Alumina: 85 parts; Silica: 2-12 parts; Magnesium carbonate: 1-3 parts; Calcium carbonate: 0-3 parts; Yttrium oxide: 0-1 part; Boron nitride: 0.5~2.5 parts; Titanium dioxide: 0~1 parts; Barium carbonate: 0-8 parts.
3. The dielectric ceramic substrate according to claim 1, characterized in that, The dielectric constant of the dielectric ceramic substrate is 7.8~8.
0.
4. A dielectric ceramic substrate according to claim 1, characterized in that, The porosity of the dielectric ceramic substrate is <0.1%.
5. A dielectric ceramic substrate according to claim 1, characterized in that, The dielectric ceramic substrate has a flexural strength ≥200 MPa.
6. A method for preparing a dielectric ceramic substrate, used for the dielectric ceramic substrate of claim 1, characterized in that, Includes the following steps: Step 1: Add the silicon dioxide, magnesium carbonate, calcium carbonate, yttrium oxide, titanium dioxide and other additives to the ball flask in proportion, add 99% alumina ceramic balls, the amount of which is 1.5 to 2 times the total powder, add an appropriate amount of deionized water and dispersant, and ball mill for 2 to 6 hours; Step 2: Add an appropriate amount of alumina to the ball mill and continue ball milling for 12-24 hours; Step 3: Add an appropriate amount of adhesive to the ball flask and ball mill for 3-10 minutes; Step 4: The ball-milled slurry is spray-granulated into powder, and then pressed into green bodies on a dry pressing machine; Step 5: Place the green body in a shuttle kiln and fire it.
7. The method for preparing a dielectric ceramic substrate according to claim 6, characterized in that, In step one, the dispersant is ammonium polyacrylate, and the amount added is 0.3% of the powder mass.
8. The method for preparing a dielectric ceramic substrate according to claim 6, characterized in that, The adhesive in step three is a PVA aqueous solution with a concentration of 10% and an addition amount of 10-20 wt%.
9. The method for preparing a dielectric ceramic substrate according to claim 6, characterized in that, The firing temperature of the ceramic body in step five is 1640~1660℃.