A near-zero sintering shrinkage alumina-based glass-ceramic and a method of making the same
By controlling the sintering process of alumina-based glass ceramics, utilizing the oxidation expansion of metallic aluminum powder and the reduction of temperature by glass powder, the problem of large sintering shrinkage rate is solved, achieving near-zero sintering and good microwave dielectric properties, which is suitable for low-temperature co-fired ceramic technology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHWESTERN POLYTECHNICAL UNIV
- Filing Date
- 2024-05-09
- Publication Date
- 2026-07-31
AI Technical Summary
In the prior art, alumina-based glass ceramics have a large shrinkage rate during sintering, which limits the preparation and application of large-size glass ceramics.
Alumina powder, aluminum powder, glass powder, dispersant and water are mixed and ball-milled to form a slurry. After adding a curing agent, the mixture is defoamed, shaped, dried and sintered. The sintering temperature and heating rate are controlled. The expansion generated by the oxidation of aluminum powder offsets the sintering shrinkage. The glass powder is combined to reduce the sintering temperature and increase the density.
Near-zero sintering shrinkage of alumina-based glass ceramics was achieved, which have good microwave dielectric properties, are suitable for low-temperature co-firing of complex shapes, and have a simple, environmentally friendly and low-cost preparation method, making them suitable for large-scale production.
Smart Images
Figure CN118459204B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of special ceramics technology, specifically relating to an alumina-based glass ceramic and its preparation method. Background Technology
[0002] With the rapid development of electronic information technology, electronic components are moving towards integration and high stability. The importance of Low Temperature Cofired Ceramics (LTCC) technology, suitable for high-density integration and assembly of electronic components, is becoming increasingly prominent. As a key component of LTCC technology, the LTCC substrate must meet requirements such as low dielectric constant, low dielectric loss, and high bending strength to adapt to the demands of efficient signal transmission and high wiring density.
[0003] Currently, domestic research on LTCC substrate materials mainly focuses on microcrystalline glass systems, with relatively insufficient research on glass-ceramic systems. Among glass-ceramic systems, alumina-based glass-ceramics have attracted widespread attention due to their low dielectric constant, low dielectric loss, and high strength. However, glass-ceramics are prone to significant shrinkage during sintering, which restricts the preparation and application of large-size glass-ceramics. Controlling the sintering shrinkage rate to obtain near-zero sintering shrinkage alumina-based glass-ceramics remains a challenge. Summary of the Invention
[0004] In view of this, the object of the present invention is to provide an alumina-based glass ceramic and a method for preparing the same. The alumina-based glass ceramic provided by the present invention has a low sintering shrinkage rate.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0006] This invention provides a method for preparing alumina-based glass ceramics, comprising the following steps:
[0007] Alumina powder, metallic aluminum powder, glass powder, dispersant, and water are mixed and ball-milled to obtain a slurry;
[0008] After mixing the slurry and curing agent, the mixture is defoamed and shaped. The resulting wet blank is then dried and sintered sequentially to obtain the alumina-based glass ceramic.
[0009] Preferably, the mass of the aluminum powder is 5-15% of the mass of the alumina powder.
[0010] Preferably, the mass of the glass powder is 15-40% of the mass of the alumina powder.
[0011] Preferably, the dispersant is a copolymer of isobutylene and maleic anhydride.
[0012] Preferably, the amount of dispersant added is 0.3% to 0.8% of the total mass of alumina powder, metallic aluminum powder, and glass powder.
[0013] Preferably, the curing agent is ethylene glycol diglycidyl ether.
[0014] Preferably, the amount of curing agent added is 100-300% of the mass of the dispersant.
[0015] Preferably, the sintering temperature is 850–1000℃, and the holding time is 2–5 hours.
[0016] Preferably, the heating process to the sintering temperature includes: heating from room temperature to 600°C at a first heating rate, and then heating from 600°C to the sintering temperature at a second heating rate; the first heating rate is 0.1 to 0.5°C / min, and the second heating rate is 1 to 3°C / min.
[0017] The present invention also provides alumina-based glass-ceramics prepared by the preparation method described above, with a sintering shrinkage of -0.5% to 1.0% and a resistivity of 4 to 12 × 10⁻⁶. 13 Ω·cm, dielectric constant of 5.3 to 8.6, dielectric loss of 0.001 to 0.008, quality factor of 53800 to 82700 GHz, and temperature coefficient of -38 to -16 ppm / ℃.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] This invention provides a method for preparing near-zero sintering shrinkage alumina-based glass ceramics, comprising the following steps: ball milling alumina powder, aluminum powder, glass powder, dispersant, and water to obtain a slurry; mixing the slurry with a curing agent, removing bubbles, and molding; and sequentially drying and sintering the resulting wet blank to obtain the alumina-based glass ceramic. This invention introduces low-melting-point glass powder, which lowers the sintering temperature. Simultaneously, the introduction of aluminum powder, which oxidizes and expands during sintering, offsets the sintering shrinkage, achieving near-zero sintering shrinkage in the alumina-based glass ceramic. Furthermore, the liquid phase generated by the glass powder during sintering increases the sintering density and improves the microwave dielectric properties of the alumina-based glass ceramic.
[0020] The alumina-based glass ceramic prepared by this invention has a low sintering temperature and low shrinkage rate. The resulting alumina-based glass ceramic has good microwave dielectric properties and can realize low-temperature co-firing of complex-shaped alumina-based glass ceramics with metal electrodes.
[0021] Moreover, the preparation method of the present invention is simple, environmentally friendly, low in cost, and easy to mass-produce. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 The image shows a SEM image of the alumina-based glass-ceramic prepared in Example 1. Detailed Implementation
[0024] This invention provides a method for preparing alumina-based glass ceramics, comprising the following steps:
[0025] Alumina powder, metallic aluminum powder, glass powder, dispersant, and water are mixed and ball-milled to obtain a slurry;
[0026] After mixing the slurry and curing agent, the mixture is defoamed and shaped. The resulting wet blank is then dried and sintered sequentially to obtain the alumina-based glass ceramic.
[0027] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.
[0028] This invention involves mixing alumina powder, metallic aluminum powder, glass powder, dispersant, and water in a ball mill to obtain a slurry.
[0029] In this invention, the mass of the aluminum powder is preferably 5-15% of the mass of the alumina powder, more preferably 8-12%, and even more preferably 10%. The amount of aluminum powder added in this invention can reduce the sintering shrinkage rate. If the aluminum powder content is too low, the sintering shrinkage rate will be large; while if the aluminum powder content is too high, sintering expansion will occur.
[0030] In this invention, the glass powder is preferably 15-40% of the mass of the alumina powder, more preferably 20-32%, and even more preferably 24%. The glass powder is preferably a zinc-borosilicate system, and its melting point is preferably 900-1000°C. The amount of glass powder added in this invention can lower the sintering temperature and increase the density of the ceramic.
[0031] In this invention, the dispersant is preferably a copolymer of isobutylene and maleic anhydride, with a molecular weight preferably of 55,000 to 65,000. The amount of dispersant added is preferably 0.3% to 0.8% of the total mass of alumina powder, metallic aluminum powder, and glass powder, more preferably 0.4% to 0.5%. The dispersant is used to disperse ceramic slurry, which can increase the solid content of the slurry, reduce drying and sintering shrinkage, and promote densification.
[0032] In this invention, the ball milling speed is preferably 200-400 r / min, more preferably 250-300 r / min, and the time is preferably 5-12 h, more preferably 6-10 h, and even more preferably 8 h; the ball-to-material ratio of the ball milling is preferably 2:1.
[0033] In this invention, the solid content of the slurry is preferably 80-85%.
[0034] After obtaining the slurry, the present invention mixes the slurry and curing agent, removes bubbles, and shapes the slurry. The resulting wet blank is then dried and sintered sequentially to obtain the alumina-based glass ceramic.
[0035] In this invention, the curing agent is preferably ethylene glycol diglycidyl ether, and the amount of the curing agent added is preferably 100-300% of the mass of the dispersant, more preferably 112-200%.
[0036] The present invention does not have special requirements for the defoaming and molding methods; methods commonly used by those skilled in the art can be adopted, such as injection molding.
[0037] In this invention, the drying temperature is preferably 100°C and the drying time is preferably 24 hours.
[0038] In this invention, the sintering temperature is preferably 850–1000°C, more preferably 880–950°C, and even more preferably 920°C, with a holding time preferably 2–5 hours. The heating procedure to the sintering temperature preferably includes: heating from room temperature to 600°C at a first heating rate, and then heating from 600°C to the sintering temperature at a second heating rate. The first heating rate is preferably 0.1–0.5°C / min, more preferably 0.3–0.4°C / min; the second heating rate is preferably 1–3°C / min, more preferably 2°C / min. During the sintering process, the aluminum powder oxidizes and expands, which can offset the sintering shrinkage rate, achieving near-zero sintering shrinkage in the preparation of alumina-based glass ceramics.
[0039] The present invention also provides alumina-based glass-ceramics prepared by the preparation method described above, with a sintering shrinkage of -0.5% to 1.0% and a resistivity of 4 to 12 × 10⁻⁶. 13 Ω·cm, dielectric constant of 5.3 to 8.6, dielectric loss of 0.001 to 0.008, quality factor of 53800 to 82700 GHz, and temperature coefficient of -38 to -16 ppm / ℃.
[0040] To further illustrate the present invention, the alumina-based glass ceramics and their preparation methods provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.
[0041] Example 1
[0042] 500g of alumina powder, 25g of metallic aluminum powder, 75g of glass powder, 2g of a copolymer of isobutylene and maleic anhydride (isobutylene-maleic anhydride copolymer) and 150g of water were ball-milled at a ball-to-material ratio of 2:1, a ball milling speed of 200r / min, and a ball milling time of 12h to obtain a slurry with a solid content of 80%.
[0043] Add 2g of ethylene glycol diglycidyl ether to the slurry; defoam the slurry and pour it into a mold, then demold to obtain a wet blank;
[0044] The wet blank is dried at 100°C for 24 hours to obtain a dry blank; the dry foam (dry blank) is heated to 600°C at a rate of 0.5°C / min, and then heated to 1000°C at a rate of 3°C / min, and held at that temperature for 2 hours to obtain alumina-based glass ceramic.
[0045] The alumina-based glass-ceramic prepared in this embodiment has a sintering shrinkage rate of 1.0% and a resistivity of 12 × 10⁻⁶. 13 Ω·cm, dielectric constant is 8.6, dielectric loss is 0.001, quality factor is 82700 GHz, and temperature coefficient is -38 ppm / ℃.
[0046] Figure 1 The image shows an SEM image of the alumina-based glass-ceramic prepared in Example 1, indicating that the alumina-based glass-ceramic is relatively dense and has no obvious pores.
[0047] Example 2
[0048] 500g of alumina powder, 75g of metallic aluminum powder, 200g of glass powder, 6.2g of a copolymer of isobutylene and maleic anhydride, and 137g of water were ball-milled at a ball-to-material ratio of 2:1, a ball milling speed of 400r / min, and a ball milling time of 5h to obtain a slurry with a solid content of 85%.
[0049] Add 18.6g of ethylene glycol diglycidyl ether to the slurry; defoam the slurry and pour it into a mold, then demold to obtain a wet blank;
[0050] The wet blank is dried at 100°C for 24 hours to obtain a dry blank; the dry foam is heated to 600°C at a rate of 0.1°C / min, and then heated to 950°C at a rate of 1°C / min, and held at that temperature for 5 hours to obtain alumina-based glass ceramic.
[0051] The alumina-based glass-ceramic prepared in this embodiment has a sintering shrinkage rate of -0.5% and a resistivity of 4×10⁻⁶. 13Ω·cm, dielectric constant is 5.3, dielectric loss is 0.008, quality factor is 53800 GHz, and temperature coefficient is -16 ppm / ℃.
[0052] Example 3
[0053] 500g of alumina powder, 50g of metallic aluminum powder, 100g of glass powder, 2.6g of a copolymer of isobutylene and maleic anhydride, and 162.5g of water were ball-milled at a ball-to-particle ratio of 2:1, a ball milling speed of 300r / min, and a ball milling time of 6h to obtain a slurry with a solid content of 85%.
[0054] Add 5.2g of ethylene glycol diglycidyl ether to the slurry; defoam the slurry and pour it into a mold, then demold to obtain a wet blank;
[0055] The wet blank is dried at 100°C for 24 hours to obtain a dry blank; the dry foam is heated to 600°C at a rate of 0.3°C / min, and then heated to 950°C at a rate of 2°C / min, and held at that temperature for 5 hours to obtain alumina-based glass ceramic.
[0056] The alumina-based glass-ceramic prepared in this embodiment has a sintering shrinkage rate of 0.3% and a resistivity of 8 × 10⁻⁶. 13 Ω·cm, dielectric constant is 7.1, dielectric loss is 0.002, quality factor is 74600 GHz, and temperature coefficient is -28 ppm / ℃.
[0057] Example 4
[0058] 500g of alumina powder, 40g of metallic aluminum powder, 160g of glass powder, 3.5g of a copolymer of isobutylene and maleic anhydride, and 175g of water were ball-milled at a ball-to-material ratio of 2:1, a ball milling speed of 250r / min, and a ball milling time of 10h to obtain a slurry with a solid content of 80%.
[0059] Add 7g of ethylene glycol diglycidyl ether to the slurry; defoam the slurry and pour it into a mold, then demold to obtain a wet blank;
[0060] The wet blank is dried at 100°C for 24 hours to obtain a dry blank; the dry foam is heated to 600°C at a rate of 0.4°C / min, and then heated to 880°C at a rate of 3°C / min, and held at that temperature for 2 hours to obtain alumina-based glass ceramic.
[0061] The alumina-based glass-ceramic prepared in this embodiment has a sintering shrinkage rate of 0.8% and a resistivity of 5 × 10⁻⁶. 13 Ω·cm, dielectric constant is 5.9, dielectric loss is 0.006, quality factor is 58200 GHz, and temperature coefficient is -19 ppm / ℃.
[0062] Example 5
[0063] 500g of alumina powder, 60g of metallic aluminum powder, 120g of glass powder, 3.4g of a copolymer of isobutylene and maleic anhydride, and 170g of water were ball-milled at a ball-to-material ratio of 2:1, a ball milling speed of 300r / min, and a ball milling time of 8h to obtain a slurry with a solid content of 85%.
[0064] Add 3.8g of ethylene glycol diglycidyl ether to the slurry; defoam the slurry and pour it into a mold, then demold to obtain a wet blank;
[0065] The wet blank is dried at 100°C for 24 hours to obtain a dry blank; the dry foam is heated to 600°C at a rate of 0.4°C / min, and then heated to 920°C at a rate of 2°C / min, and held at that temperature for 5 hours to obtain alumina-based glass ceramic.
[0066] The alumina-based glass-ceramic prepared in this embodiment has a sintering shrinkage rate of -0.1% and a resistivity of 6 × 10⁻⁶. 13 Ω·cm, dielectric constant is 6.6, dielectric loss is 0.005, quality factor is 65900 GHz, and temperature coefficient is -23 ppm / ℃.
[0067] Comparative Example 1
[0068] 560g of alumina powder, 120g of glass powder, 3.4g of a copolymer of isobutylene and maleic anhydride, and 170g of water were ball-milled at a ball-to-material ratio of 2:1, a ball milling speed of 300r / min, and a ball milling time of 8h to obtain a slurry with a solid content of 85%.
[0069] Add 3.8g of ethylene glycol diglycidyl ether to the slurry; defoam the slurry and pour it into a mold, then demold to obtain a wet blank;
[0070] The wet blank is dried at 100°C for 24 hours to obtain a dry blank; the dry foam is heated to 600°C at a rate of 0.4°C / min, and then heated to 920°C at a rate of 2°C / min, and held at that temperature for 5 hours to obtain alumina-based glass ceramic.
[0071] The alumina-based glass-ceramic prepared in this comparative example had a sintering shrinkage of 18.2% and a resistivity of 3 × 10⁻⁶. 13 Ω·cm, dielectric constant is 6.4, dielectric loss is 0.004, quality factor is 65600GHz, and temperature coefficient is -24ppm / ℃.
[0072] Comparative Example 2
[0073] 620g of alumina powder, 60g of metallic aluminum powder, 3.4g of a copolymer of isobutylene and maleic anhydride, and 170g of water were ball-milled at a ball-to-material ratio of 2:1, a ball milling speed of 300r / min, and a ball milling time of 8h to obtain a slurry with a solid content of 85%.
[0074] Add 3.8g of ethylene glycol diglycidyl ether to the slurry; defoam the slurry and pour it into a mold, then demold to obtain a wet blank;
[0075] The wet blank is dried at 100°C for 24 hours to obtain a dry blank; the dry foam is heated to 600°C at a rate of 0.4°C / min, and then heated to 1550°C at a rate of 2°C / min, and held at that temperature for 5 hours to obtain alumina ceramic.
[0076] The alumina ceramic prepared in this comparative example had a sintering shrinkage of -0.2% and a resistivity of 5 × 10⁻⁶. 13 Ω·cm, dielectric constant is 9.7, dielectric loss is 0.003, quality factor is 92800 GHz, and temperature coefficient is -45 ppm / ℃.
[0077] The sintering shrinkage rate of Comparative Example 1 was significantly higher than that of Example 5; Comparative Example 2 required a temperature of 1550°C to form ceramics, which was significantly higher than the 920°C of Example 5. This invention lowers the sintering temperature and increases the sintering density by introducing glass powder, thereby improving the microwave dielectric properties of alumina-based glass ceramics; simultaneously, the introduction of aluminum powder achieves near-zero sintering shrinkage for alumina-based glass ceramics.
[0078] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method of making an alumina-based glass-ceramic, characterized in that, The steps are as follows: 500g of alumina powder, 25g of metallic aluminum powder, 75g of glass powder, 2g of a copolymer of isobutylene and maleic anhydride, and 150g of water were ball-milled at a ball-to-particle ratio of 2:1, a ball milling speed of 200r / min, and a ball milling time of 12h to obtain a slurry with a solid content of 80%. Add 2g of ethylene glycol diglycidyl ether to the slurry, defoam the slurry and pour it into the mold. After demolding, a wet blank is obtained. The wet blank is dried at 100°C for 24 hours to obtain a dry blank; the dry blank is heated to 600°C at a rate of 0.5°C / min, and then heated to 1000°C at a rate of 3°C / min, and held at that temperature for 2 hours to obtain alumina-based glass ceramic.
2. The alumina-based glass ceramic obtained by the preparation method according to claim 1.