A low-temperature co-fired ceramic material and its preparation method

Abstract

This invention discloses a low-temperature co-fired ceramic material and its preparation method. The low-temperature co-fired ceramic material comprises a multiphase ceramic powder, which is composed of a mixture of La2O3-MgO-B2O3 microcrystalline glass, a ceramic filler phase, and a dopant phase. The ceramic filler phase is a microwave dielectric ceramic, and the dopant phase is CuO. This low-temperature co-fired ceramic material exhibits low dielectric loss and excellent flexural strength and microwave dielectric properties, making it suitable for applications in high-frequency packaging substrates.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, specifically relating to a low-temperature co-fired ceramic material and its preparation method. Background Technology

[0002] In the microwave and millimeter-wave frequency bands, LTCC (Low-Temperature Ceramic) multilayer ceramic packaging substrates are widely used. They not only serve as packaging for RF chips, digital chips, and power chips, but their unique multilayer structure also allows for the embedding of passive components such as resistors, capacitors, and inductors. Compared to traditional PCB circuits, they offer superior heat dissipation, smaller size, and excellent high-frequency performance. As the frequencies used on these substrates and the density of packaged active / passive components increase, LTCC substrate materials are required to possess high strength, low dielectric constant, and low loss characteristics.

[0003] Currently, commonly used LTCC materials include A6M and DuPont 951. Among them, A6M has a low flexural strength of about 150 MPa, which cannot meet the application requirements of high-density packaging for substrate materials. DuPont 951 uses Si-Pb-B glass as a low-sintering agent and alumina as a ceramic filler phase to prepare low-dielectric-loss LTCC material. However, Si-Pb-B glass cannot crystallize during sintering, resulting in high dielectric loss (dielectric loss: 0.006@3GHz), which also makes it unsuitable for high-frequency packaging substrates. Summary of the Invention

[0004] In view of this, the primary objective of the present invention is to provide a low-temperature co-fired ceramic material that has the characteristics of low dielectric loss and excellent flexural strength and microwave dielectric properties, and can be applied in the field of high-frequency packaging substrates.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of this invention discloses a low-temperature co-fired ceramic material, which includes a multiphase ceramic powder. The multiphase ceramic powder is composed of a mixture of La2O3-MgO-B2O3 microcrystalline glass, a ceramic filler phase, and a doped phase. The ceramic filler phase is a microwave dielectric ceramic, and the doped phase is CuO.

[0007] This invention uses La2O3-MgO-B2O3 microcrystalline glass as the glass phase and microwave dielectric ceramic as the ceramic filler phase. In the early stage of sintering, the La2O3-MgO-B2O3 glass plays a fluxing role, and in the later stage of sintering, it crystallizes into a low-loss phase, thereby reducing the dielectric loss of the material.

[0008] The lanthanide glass-ceramics used in this paper not only possess excellent softening points—their low softening point matches the sintering densification process of the silver conductor paste, ensuring compatibility with the silver conductor co-firing—but also readily crystallize into low-loss phases (such as LaBO3 and Ca3La(BO3)4), thus guaranteeing the material's low-loss characteristics. Doping the lanthanum-boron glass system with MgO not only allows the softening point of the glass-ceramics to be tunable over a wide temperature range (Tg: 620℃~680℃), but also adjusts the grains of the crystalline phase to a dendritic shape, reducing dielectric loss and significantly improving flexural strength. Furthermore, doping CuO into the multiphase ceramic not only acts as a liquid phase to promote sintering during sintering but also promotes the crystallization of La2O3-MgO-B2O3 glass.

[0009] In a further embodiment, the microwave dielectric ceramic is Al2O3, SiO2, or Zn2SiO4. By selecting different microwave dielectric ceramics, low-temperature co-fired ceramic materials with different dielectric constants can be obtained. The specific selection can be made according to actual needs.

[0010] In a further embodiment, the chemical composition of the multiphase ceramic powder is (1-xy)R+xLMB(La2O3-MgO-B2O3)+yCuO, where R represents the ceramic filler phase, x and y represent the mass percentages, 0.40≤x≤0.55, and 0≤y≤0.1.

[0011] In a further embodiment, the composition of each raw material in the La2O3-MgO-B2O3 microcrystalline glass, calculated by mass fraction, is as follows:

[0012] La2O3: 17% ~ 28%, MgO: 10 ~ 21%, B2O3: 45% ~ 65%, ZrO2: 0.5% ~ 1.2%, TiO2: 0.2% ~ 1.0%, Na2O: 0% ~ 2.0%, Al2O3: 0% ~ 2.0%.

[0013] Preferably, the composition is as follows: La2O3: 17%–25%, MgO: 15%–21%, B2O3: 54.2%–64.3%, ZrO2: 0.5%–1.0%, TiO2: 0.2%–0.5%, Na2O: 0%–2.0%, and Al2O3: 0%–1.0%.

[0014] Preferably, the composition is as follows: La2O3: 17%–20%, MgO: 15%–21%, B2O3: 58%–64.3%, ZrO2: 0.5%–1.0%, TiO2: 0.2%–0.5%, Na2O: 0%–2.0%, and Al2O3: 0.5%–1.0%.

[0015] Preferably, it is prepared from La2O3: 20%, MgO: 15%, B2O3: 64.3%, ZrO2: 0.5%, and TiO2: 0.2%.

[0016] A second aspect of the present invention provides a method for preparing a low-temperature co-fired ceramic material as described in the first aspect of the present invention, comprising the following steps:

[0017] Preparation of La2O3-MgO-B2O3 microcrystalline glass;

[0018] La2O3-MgO-B2O3 microcrystalline glass, ceramic filler phase and doped phase are mixed to prepare multiphase ceramic powder;

[0019] The multiphase ceramic powder is subjected to a casting process to obtain LTCC green ceramic tape.

[0020] A further embodiment of the preparation of the La2O3-MgO-B2O3 microcrystalline glass includes the following steps:

[0021] Glass melting: Weigh the raw materials according to the proportions and mix them thoroughly to form a mixture; melt the mixture into glass slag;

[0022] Glass ball milling: After coarse grinding of glass slag, ball milling is performed to obtain LMB glass powder.

[0023] In a further embodiment, the temperature for melting the glass is 1200℃~1300℃, and the time is 0.5h~1.0h.

[0024] In a further embodiment, the rotational speed of the ball mill is 350 r / min to 400 r / min.

[0025] The third aspect of the present invention provides the application of the low-temperature co-fired ceramic material as described in the first aspect of the present invention, or the low-temperature co-fired ceramic material prepared by the preparation method described in the second aspect of the present invention, in the preparation of low-temperature co-fired ceramic substrates.

[0026] The fourth aspect of the present invention provides a low-temperature co-fired ceramic substrate containing the low-temperature co-fired ceramic material as described in the first aspect of the present invention or the low-temperature co-fired ceramic material prepared by the preparation method described in the second aspect of the present invention.

[0027] It is understood that the casting process described in this article is not particularly limited, and conventional casting formulations and processes in the field can be used.

[0028] The beneficial effects of this invention are:

[0029] (1) La2O3-MgO-B2O3 glass has a low softening point. In the early stage of sintering, it forms a liquid phase to promote the flow and mass transfer of particles and reduce the porosity of sintered ceramics. In the later stage of sintering, it crystallizes into the LaBO3 phase. The dielectric constant of the LaBO3 phase is about 7.5 and Q×f is about 70000 GHz. It has the characteristics of low dielectric loss and can significantly reduce the dielectric loss of the glass system, thus making this glass-ceramic composite system have the characteristics of low dielectric loss and low loss.

[0030] (2) During the sintering process of the (1-xy)R+xLMB(La2O3-MgO-B2O3)+yCuO ceramic glass, the addition of a small amount of CuO will reduce the sintering temperature of the multiphase ceramic and promote the crystallization of LMB microcrystalline glass, further reducing the loss of the ceramic glass system.

[0031] (3) By controlling the proportion of LMB glass in the ceramic glass system, the sintering temperature of the multiphase system can be effectively reduced. Moreover, LMB-based microcrystalline glass is prone to precipitate dendritic LaBO3 phase. The dendritic grains act as reinforcements in the multiphase ceramic, which significantly improves the flexural strength of the multiphase ceramic while also providing excellent microwave dielectric properties.

[0032] (4) The (1-xy)R+xLMB(La2O3-MgO-B2O3)+yCuO glass-ceramic material prepared by this invention is sintered in the range of 850℃~900℃. Its dielectric constant is 6.9~7.8 (30GHz) and dielectric loss is 0.0008~0.0013 (30GHz). It can also be co-fired with Ag conductors. It is a new type of low dielectric LTCC substrate material. Attached Figure Description

[0033] Figure 1 This is an SEM image of the ceramic surface in Example 3.

[0034] Figure 2 The images show the XRD patterns of the multiphase ceramics in Examples 1-4. Detailed Implementation

[0035] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, unless otherwise specified, methods not specifically describing conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0037] In the following examples and comparative examples, the flexural strength of the ceramic plates was tested using the three-point bending test method, specifically referring to GB / T6569-2006 Test Method for Bending Strength of Fine Ceramics. The size of the ceramic strip was >40mm×30mm×3mm.

[0038] Table 1. Raw material composition and mass percentage of LMB glass powder in Examples 1-4

[0039] Example 1 20 15 61.8 0.5 0.2 1.5 1.0 Example 2 18 18 60 1.0 0.5 1.5 1.0 Example 3 17 21 58 1.0 0.5 1.5 1.0 Example 4 25 18 55 1.0 0.5 0 0.5

[0040] Table 2. LTCC green ceramic tape casting ingredients in Examples 1-4

[0041] Multiphase ceramic powder 60％ Ethyl acetate 15％ xylene 10％ Butanone 6％ BYK110 1.5％ Dibutyl phthalate 1.5％ B60H 6％

[0042] Example 1

[0043] Preparation of La2O3-MgO-B2O3 microcrystalline glass

[0044] (1) Glass powder melting: Weigh 20% La2O3, 15% MgO, 61.8% B2O3, 0.5% ZrO2, 0.2% TiO2, 1.5% Na2O and 1.0% Al2O3 as raw materials according to mass fraction. After dry mixing and ball milling for 12 hours, a mixture is formed. The mixture is then kept at 1200℃ for 0.75 hours for glass melting. The molten glass is poured into deionized water and quenched to form glass slag.

[0045] (2) Glass ball milling: After the glass slag is coarsely ground by a roller mill, it is finely ground in a planetary ball mill at a speed of 400 r / min for 4 hours to obtain LMB glass powder.

[0046] Preparation of LTCC green ceramic belt

[0047] (1) Preparation of multiphase ceramic powder: Al2O3 ceramic powder, LMB glass powder and CuO powder are prepared according to the following composition expression: 0.45Al2O3+0.50(La2O3-MgO-B2O3)+0.05CuO.

[0048] (2) Preparation of LTCC green ceramic tape: The prepared multiphase ceramic powder is mixed with ethyl acetate, xylene, methyl ethyl ketone, BYK110 dispersant, dibutyl phthalate and B48N binder in the proportions of Table 2. The slurry is ball-milled in a ball mill jar for 24 hours at a speed of 60 r / min. After degassing, the slurry is cast in a casting machine to form a green ceramic tape with a thickness of 125 μm ± 5 μm.

[0049] (3) Lamination sintering: After cutting 20 pieces of green ceramic strips prepared in step (2), they are laminated into green blanks of 75mm×75mm×2.5mm. The green blanks are then debonded at 450℃ and sintered at 850℃ to make ceramic plates.

[0050] The ceramic plate in this embodiment was tested for performance. Its dielectric constant at 30 GHz was ~7.2, dielectric loss was ~0.0009, and flexural strength was approximately ~260 MPa.

[0051] Example 2

[0052] Preparation of La2O3-MgO-B2O3 microcrystalline glass

[0053] (1) Glass powder melting: Weigh 18% La2O3, 18% MgO, 60% B2O3, 1.0% ZrO2, 0.5% TiO2, 1.5% Na2O and 1.0% Al2O3 as raw materials according to mass fraction. After dry mixing and ball milling for 12 hours, a mixture is formed. The mixture is then kept at 1200℃ for 0.75 hours for glass melting. The molten glass is poured into deionized water and quenched to form glass slag.

[0054] (2) Glass ball milling: After the glass slag is coarsely ground by a roller mill, it is finely ground in a planetary ball mill at a speed of 400 r / min for 4 hours to obtain LMB glass powder.

[0055] Preparation of LTCC green ceramic belt

[0056] (1) Preparation of multiphase ceramic powder: Al2O3 ceramic powder, LMB glass powder and CuO powder are prepared according to the following composition expression: 0.40Al2O3+0.55(La2O3-MgO-B2O3)+0.05CuO.

[0057] (2) Preparation of LTCC green ceramic tape: The prepared multiphase ceramic powder is mixed with ethyl acetate, xylene, methyl ethyl ketone, BYK110 dispersant, dibutyl phthalate and B48N binder in the proportions of Table 2. The slurry is ball-milled in a ball mill jar for 24 hours at a speed of 60 r / min. After degassing, the slurry is cast in a casting machine to form a green ceramic tape with a thickness of 125 μm ± 5 μm.

[0058] (3) Lamination sintering: After cutting 20 pieces of green ceramic strips prepared in step (2), they are laminated into green blanks of 75mm×75mm×2.5mm. The green blanks are then debonded at 450℃ and sintered at 850℃ to make ceramic plates.

[0059] The ceramic plate in this embodiment was tested for performance. Its dielectric constant at 30 GHz was ~7.6, dielectric loss was ~0.0011, and flexural strength was approximately ~280 MPa.

[0060] Example 3

[0061] Preparation of La2O3-MgO-B2O3 microcrystalline glass

[0062] (1) Glass powder melting: Weigh 17% La2O3, 21% MgO, 58% B2O3, 1.0% ZrO2, 0.5% TiO2, 1.5% Na2O and 1.0% Al2O3 as raw materials according to mass fraction. After dry mixing and ball milling for 12 hours, a mixture is formed. The mixture is then kept at 1250℃ for 1.0 hour for glass melting. The molten glass is poured into deionized water and quenched to form glass slag.

[0063] (2) Glass ball milling: After the glass slag is coarsely ground by a roller mill, it is finely ground in a planetary ball mill at a speed of 400 r / min for 5 hours to obtain LMB glass powder.

[0064] Preparation of LTCC green ceramic belt

[0065] (1) Preparation of multiphase ceramic powder: Al2O3 ceramic powder, LMB glass powder and CuO powder are prepared according to the following composition expression: 0.40Al2O3+0.50(La2O3-MgO-B2O3)+0.10CuO.

[0066] (2) Preparation of LTCC green ceramic tape: The prepared multiphase ceramic powder is mixed with ethyl acetate, xylene, methyl ethyl ketone, BYK110 dispersant, dibutyl phthalate and B48N binder in the proportions of Table 2. The slurry is ball-milled in a ball mill jar for 24 hours at a speed of 60 r / min. After degassing, the slurry is cast in a casting machine to form a green ceramic tape with a thickness of 125 μm ± 5 μm.

[0067] (3) Lamination sintering: After cutting 20 pieces of green ceramic strips prepared in step (2), they are laminated into green blanks of 75mm×75mm×2.5mm. The green blanks are then debonded at 450℃ and sintered at 850℃ to make ceramic plates.

[0068] The surface morphology of the sintered multiphase ceramic in this embodiment was analyzed, such as... Figure 1 As shown, dendritic LaBO3 phase precipitates on the surface. The dendritic grains have a reinforcing effect in the multiphase ceramic structure, which can significantly improve the flexural strength of the ceramic.

[0069] The ceramic plate in this embodiment was tested for performance. Its dielectric constant at 30 GHz was ~7.8, dielectric loss was ~0.0008, and flexural strength was approximately ~300 MPa.

[0070] Example 4

[0071] Preparation of La2O3-MgO-B2O3 microcrystalline glass

[0072] (1) Glass powder melting: Weigh 25% La2O3, 18% MgO, 55% B2O3, 1.0% ZrO2, 0.5% TiO2 and 0.5% Al2O3 as raw materials according to mass fraction. After dry mixing and ball milling for 12 hours, a mixture is formed. The mixture is then heated at 1250℃ for 1.0 hour for glass melting. The molten glass is then poured into deionized water and quenched to form glass slag.

[0073] (2) Glass ball milling: After the glass slag is coarsely ground by a roller mill, it is finely ground in a planetary ball mill at a speed of 400 r / min for 6 hours to obtain LMB glass powder.

[0074] Preparation of LTCC green ceramic belt

[0075] (1) Preparation of multiphase ceramic powder: Al2O3 ceramic powder, LMB glass powder and CuO powder are prepared according to the following composition expression: 0.37Al2O3+0.53(La2O3-MgO-B2O3)+0.10CuO.

[0076] (2) Preparation of LTCC green ceramic tape: The prepared multiphase ceramic powder is mixed with ethyl acetate, xylene, methyl ethyl ketone, BYK110 dispersant, dibutyl phthalate and B48N binder in the proportions of Table 2. The slurry is ball-milled in a ball mill jar for 24 hours at a speed of 60 r / min. After degassing, the slurry is cast in a casting machine to form a green ceramic tape with a thickness of 125 μm ± 5 μm.

[0077] (3) Lamination sintering: After cutting 20 pieces of green ceramic strips prepared in step (2), they are laminated into green blanks of 75mm×75mm×2.5mm. The green blanks are then debonded at 450℃ and sintered at 850℃ to make ceramic plates.

[0078] The ceramic plate in this embodiment was tested for performance. Its dielectric constant at 30 GHz was ~7.6, dielectric loss was ~0.0012, and flexural strength was approximately ~250 MPa.

[0079] in, Figure 2 The image shows the XRD patterns of the multiphase ceramic powders in Examples 1-4. Figure 2 It can be seen that after sintering different La2O3-MgO-B2O3 glasses with Al2O3 and CuO components at 850℃, the main crystalline phase structure is Al2O3 and LaBO3. This indicates that partial crystallization of the glass occurred during sintering, forming the LaBO3 phase, while the main crystalline phase of the composite ceramic is still the Al2O3 phase.

[0080] Example 5

[0081] In this embodiment, the preparation of the multiphase ceramic powder follows the same method as in Example 1, except that the ceramic filler phase used is SiO2. All other steps and conditions, as well as the preparation of the LTCC green ceramic belt, are the same as in Example 1.

[0082] The ceramic plate in this embodiment was tested for performance. Its dielectric constant at 30 GHz was ~5.3, dielectric loss was ~0.0037, and flexural strength was approximately ~170 MPa.

[0083] Comparative Example 1

[0084] In this comparative example, the multiphase ceramic powder is produced using the same implementation method as in Example 4, except that the proportion of the microcrystalline glass phase is x = 0.35, the proportion of the alumina ceramic phase is y = 0.55, and the proportion of copper oxide is 0.1%. All other steps and conditions are the same as in Example 4.

[0085] The ceramic plate in this comparative example was tested for performance. Its dielectric constant at 30 GHz was ~5.7, dielectric loss was ~0.0044, and flexural strength was approximately ~160 MPa. The glass content was too low, resulting in incomplete sintering of the ceramic.

[0086] Comparative Example 2

[0087] This comparative example uses the same implementation method as Example 4, except that in the multiphase ceramic powder, the LMB glass powder is replaced with an equal mass of La2O3-ZnO-B2O3 microcrystalline glass. All other steps and conditions are the same as in Example 4. The composition of the La2O3-ZnO-B2O3 microcrystalline glass is: La2O3: 20%, ZnO: 15%, B2O3: 64.3%, ZrO2: 0.5%, and TiO2: 0.2%.

[0088] The ceramic plate in this comparative example was tested for performance. Its dielectric constant at 30 GHz was ~7.7, its dielectric loss was ~0.0026, and its flexural strength was approximately ~220 MPa.

[0089] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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.

[0090] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A low-temperature co-fired ceramic material, characterized in that, It includes a multiphase ceramic powder, which is composed of a mixture of La2O3-MgO-B2O3 microcrystalline glass, a ceramic filler phase, and a doped phase. The chemical composition of the multiphase ceramic powder is (1-xy)R+xLMB(La2O3-MgO-B2O3)+yCuO, where R represents the ceramic filler phase, x and y represent the mass percentages, and 0.40≤x≤0.55, 0≤y≤0.

1. The composition of each raw material in the La2O3-MgO-B2O3 microcrystalline glass, by mass fraction, is as follows: La2O3: 17%~28%, MgO: 10~21%, B2O3: 45%~65%, ZrO2: 0.5%~1.2%, TiO2: 0.2%~1.0%, Na2O: 0%~2.0%, Al2O3: 0%~2.0%; The ceramic filling phase is microwave dielectric ceramic, and the doped phase is CuO.

2. The low-temperature co-fired ceramic material as described in claim 1, characterized in that, The microwave dielectric ceramic is Al2O3, SiO2, or Zn2SiO4.

3. A method for preparing a low-temperature co-fired ceramic material as described in any one of claims 1 to 2, characterized in that, Includes the following steps: Preparation of La2O3-MgO-B2O3 microcrystalline glass; La2O3-MgO-B2O3 microcrystalline glass, ceramic filler phase and doped phase are mixed to prepare multiphase ceramic powder; The multiphase ceramic powder is subjected to a casting process to obtain LTCC green ceramic tape.

4. The preparation method according to claim 3, characterized in that, The preparation of the La2O3-MgO-B2O3 microcrystalline glass includes the following steps: Glass melting: Weigh the raw materials according to the proportions and mix them thoroughly to form a mixture; melt the mixture into glass slag; Glass ball milling: After coarse grinding of glass slag, ball milling is performed to obtain LMB glass powder.

5. The preparation method according to claim 4, characterized in that, The temperature for melting the glass is 1200℃~1300℃, and the time is 0.5h~1.0h.

6. The preparation method according to claim 4, characterized in that, The ball mill rotates at a speed of 350 r / min to 400 r / min.

7. The application of the low-temperature co-fired ceramic material as described in any one of claims 1 to 2, or the low-temperature co-fired ceramic material prepared by the preparation method as described in any one of claims 3 to 6, in the preparation of low-temperature co-fired ceramic substrates.

8. A low-temperature co-fired ceramic substrate, characterized in that, The material contains the low-temperature co-fired ceramic material as described in any one of claims 1 to 2 or the low-temperature co-fired ceramic material prepared by the preparation method described in any one of claims 3 to 6.

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