High-strength and low-dielectric ceramic composite material as well as preparation method and application thereof
The high-strength, low-dielectric ceramic composite material prepared by layered composite structure and low-temperature co-fired ceramic process solves the problems of insufficient strength of low-dielectric materials and difficult processing of high-dielectric materials, and realizes the size adaptability and low loss performance of high-frequency devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING YUAN LIU HONG YUAN ELECTRONIC TECHNOLOGY CO LTD
- Filing Date
- 2026-02-11
- Publication Date
- 2026-05-26
AI Technical Summary
Existing low-dielectric materials have insufficient mechanical strength, making them prone to cracking during high-frequency device processing. Furthermore, high-dielectric-constant materials result in excessively small device sizes, difficulty in controlling processing precision, and increased parasitic parameters at high frequencies, failing to meet the low-loss requirements of millimeter-wave communication.
A high-strength, low-dielectric ceramic composite material with a layered composite structure is prepared by a low-temperature co-fired ceramic process. The dielectric constant and sintering shrinkage rate of the functional layer and the substrate layer are matched to ensure the interfacial bonding strength. The dielectric constant of the functional layer is ≤5.0 and the flexural strength of the substrate layer is ≥200MPa.
It achieves size adaptability and processing precision control of high-frequency devices, reduces parasitic parameters, improves the mechanical strength of materials, and meets the low-loss requirements of millimeter-wave communication.
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Figure CN122079653A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of composite dielectric materials and high-frequency device technology, specifically to a high-strength, low-dielectric ceramic composite material, its preparation method, and its application. Background Technology
[0002] With the rapid development of millimeter-wave communication technology, the operating frequency of devices is constantly increasing (20GHz and above), which places stringent requirements on the dielectric properties of dielectric materials. Conventional LTCC materials (such as systems containing 90-95wt% alumina) have significant drawbacks in high-frequency scenarios due to their high dielectric constant (≥7.0): First, according to the electromagnetic wave wavelength formula, the high dielectric constant leads to excessively small device size (e.g., the overall resonator size in the 20GHz band is ≤0.5mm), making it difficult to control the processing precision; second, parasitic parameters (such as edge capacitance and inter-line coupling) increase significantly, leading to device performance deviations, such as unexpected resonant points appearing out of band; and third, high-frequency signal delay and energy loss are aggravated, making it difficult to meet the low-loss requirements of millimeter-wave communication.
[0003] Against this backdrop, low dielectric constant materials (dielectric constant ≤ 5.0) have become the preferred core dielectric material for high-frequency devices due to their ability to reduce signal delay and energy loss. However, existing low dielectric materials generally suffer from insufficient mechanical strength: commercially available low dielectric composite materials often have a bending strength of less than 100 MPa, making them prone to cracking during device mounting, soldering, and other processing, thus failing to meet practical requirements.
[0004] To address this contradiction, existing technologies attempt to combine high-strength substrates with low-dielectric layers, but two major bottlenecks exist: first, the sintering activity of conventional high-strength LTCC substrates (such as 90% alumina) and low-dielectric materials is mismatched, with shrinkage deviations exceeding 3%, leading to interface delamination; second, thick substrates (>200μm) interfere with the electromagnetic field distribution of the low-dielectric layer, degrading the high-frequency performance of devices. Therefore, there is an urgent need for a ceramic composite material system that can balance low dielectric constant, high strength, and co-firing compatibility to meet the design and mass production requirements of high-frequency devices and solve the aforementioned problems of large signal delay and parasitic parameters. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a high-strength, low-dielectric ceramic composite material and its preparation method, as well as a millimeter-wave filter based on this system, suitable for scenarios such as millimeter-wave communication where high requirements are placed on both material strength and dielectric properties.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] In a first aspect, the present invention provides a high-strength, low-dielectric ceramic composite material, wherein the ceramic composite material is a layered composite structure comprising: a functional layer and at least one substrate layer; the functional layer is prepared using a first composite material, and the dielectric constant of the functional layer at a frequency of 20 GHz is not greater than 5.0; the substrate layer is prepared using a second composite material, and the flexural strength of the substrate layer is ≥200 MPa.
[0008] The substrate layer and the functional layer are integrally sintered using a low-temperature co-fired ceramic process, and the sintering shrinkage rate deviation between the substrate layer and the functional layer is ≤3%.
[0009] Optionally, the number of substrate layers is two, and the functional layer is located between the two substrate layers.
[0010] Optionally, composite material 1 (functional layer) comprises the following raw materials in parts by weight: 70 to 90 parts silicate glass, 5 to 10 parts pore-forming agent, and 12 parts organic binder.
[0011] Optionally, the composite material 2 (substrate layer) includes the following raw materials in parts by weight: 60-80 parts alumina powder, 10-20 parts low melting point glass powder, 2-5 parts sintering aid, and 12 parts organic binder.
[0012] Optionally, the thickness of the substrate layer is 50–200 μm; the thickness of the functional layer is 25–60 μm.
[0013] Optionally, the alumina powder has a particle size of 0.8 to 1.5 μm, and the low-melting-point glass powder has a softening point of 750°C to 850°C.
[0014] Alumina has high material strength and low dielectric loss, which can ensure high strength while maintaining low dielectric loss in the substrate layer. The proportions of the above components directly affect the relevant properties of the material. For example, if the proportion of alumina exceeds the requirements, the product will not be densely sintered. All the above components should be thoroughly mixed during preparation.
[0015] Secondly, the present invention also provides a method for preparing a high-strength, low-dielectric ceramic composite material, comprising the following steps:
[0016] Preparation of functional layer green ceramic tape: Silicate glass, pore-forming agent and organic binder are mixed, and the mixture is ball-milled, cast, and dried to obtain functional layer green ceramic tape;
[0017] Preparation of substrate green ceramic tape: Alumina powder, low melting point glass powder, sintering aid and organic binder are mixed, and the mixture is ball-milled, cast and dried to obtain substrate green ceramic tape;
[0018] Lamination and co-firing: The green ceramic tape of the substrate layer and the green ceramic tape of the functional layer are aligned and laminated, then hot-pressed, debonded, and co-fired. After cooling, a ceramic composite material is obtained.
[0019] Optionally, hot pressing is performed at 10–15 MPa and 70–90°C for 20–40 min; debinding is performed at 320–450°C for 3–5 h; and co-firing is performed at 850–920°C for 1.5–2.5 h. Under these specific conditions, the sintering shrinkage deviation between the substrate layer and the functional layer is ≤3%.
[0020] Thirdly, the present invention also provides a high-frequency filter, including a dielectric substrate, wherein the dielectric substrate is made of the above-mentioned ceramic composite material.
[0021] Optionally, the insertion loss of the high-frequency filter in the 20GHz to 30GHz frequency band is ≤0.8dB.
[0022] Compared with the prior art, the present invention has at least the following beneficial effects:
[0023] Improved high-frequency adaptability: The functional layer dielectric constant of 4.0 allows the size of devices (such as resonators) in the 20GHz band to increase to 0.8–1.2 mm, making the processing accuracy easier to control and reducing parasitic parameters by 30–50%.
[0024] Significantly improved strength: The flexural strength of the substrate layer is ≥200MPa, and the strength of the ceramic composite system reaches 80-90% of that of composite material 2, solving the problem of insufficient strength of low dielectric materials;
[0025] High reliability of co-firing: The substrate layer and the functional layer are integrally sintered through a low-temperature co-firing ceramic process. The sintering shrinkage rate deviation between the substrate layer and the functional layer is ≤3%. The shrinkage of the two composite materials is matched, the interface bonding strength is ≥20MPa, and there is no delamination or cracking.
[0026] Excellent device performance: The high-frequency filter based on this system has an insertion loss of ≤0.8dB in the 20GHz~30GHz frequency band, which meets the low loss requirement of millimeter wave communication. Attached Figure Description
[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.
[0028] Figure 1 This is a schematic diagram of the high-strength, low-dielectric ceramic composite material structure of the present invention.
[0029] Figure 2 This is a schematic diagram of the electrical performance of a millimeter-wave bandpass filter prepared using the high-strength, low-dielectric ceramic composite material of the present invention. Detailed Implementation
[0030] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.
[0031] A high-strength, low-dielectric ceramic composite material, such as Figure 1 As shown, the device comprises a substrate layer 2, a functional layer 1, and a substrate layer 2 bonded together in sequence. The functional layer and the substrate layer are prepared using a low-temperature co-fired ceramic process. The substrate layer is made of composite material 2 (the second composite material), with a dielectric constant of 7.0, containing 60-80 parts of alumina, and an overall flexural strength of over 200 MPa. The functional layer is made of composite material 1 (the first composite material), with a dielectric constant of 4.0, and the main material is a silicate glass system, with a dielectric loss ≤0.003 (20 GHz). The composite material 2 achieves co-firing compatibility with composite material 1 by adjusting the sintering aid formulation, with a sintering shrinkage deviation of ≤3% and an interface bonding strength ≥20 MPa. The thickness of the substrate layer is determined according to the overall thickness of the device, ranging from 50 to 200 μm, while the thickness of the functional layer varies from 25 to 60 μm depending on the design.
[0032] Core design of ceramic composite systems
[0033] This invention addresses the issues of insufficient strength in low-dielectric materials and poor high-frequency compatibility of conventional LTCC materials by constructing a ceramic composite material system through "composition gradient regulation + synergistic formulation optimization," as detailed below:
[0034] 1. Material composition and properties
[0035] Composite material 1 (functional layer):
[0036] Composition: Contains 70-90 parts silicate glass, 5-10 parts pore-forming agent, and 12 parts organic binder. After sintering, a microstructure is formed with silicate glass as the continuous phase and uniform closed pores inside. The average diameter of the pores is ≤0.5μm. This structure can precisely control the overall dielectric constant of the material to 4.0.
[0037] Performance: Dielectric constant 4.0±0.2, dielectric loss ≤0.003 (20GHz), pure layer flexural strength 80~100MPa;
[0038] Function: As a high-frequency functional area, it reduces signal delay and loss, and is suitable for device size design in the 20GHz and above frequency bands.
[0039] Composite material 2 (substrate layer):
[0040] Composition: 60-80 parts alumina (to improve strength), 10-20 parts low melting point glass (softening point 750-850℃, matching co-firing temperature), 2-5 parts ZnO-B2O3-SiO2 sintering aid (to adjust sintering activity); the liquid phase formed during sintering helps to inhibit excessive grain growth, thereby improving the material strength through a fine grain strengthening mechanism (grain size ≤2μm).
[0041] Properties: Dielectric constant 7.0±0.3, flexural strength 290MPa;
[0042] Function: Provides high-strength support and achieves co-firing compatibility with composite material 1 through formula adjustment, avoiding interface delamination.
[0043] 2. Key Design Considerations
[0044] Co-firing compatibility: By reducing the alumina content (60-80 parts) and adding low-melting-point glass, composite material 2 achieves the same co-firing temperature (850-920℃) as composite material 1, with both having a sintering shrinkage rate of 13-14% and a deviation of ≤1%, and an interfacial bonding strength of ≥20MPa.
[0045] Thin-layer high matching: The thickness of the substrate layer is controlled between 50 and 200 μm to ensure the supporting strength of composite material 2, while avoiding interference from excessively thick substrates with the electromagnetic field distribution of the functional layer. The dielectric constant deviation of the functional layer is ≤0.1.
[0046] Strength-High Frequency Synergy: The overall strength of the ceramic composite system reaches 160-270 MPa, which is 80-90% of that of composite material 2. Simultaneously, the functional layer's dielectric constant of 4.0 is suitable for the size design of high-frequency devices, solving the problems of difficult processing and large parasitic parameters associated with conventional LTCC materials. This invention mainly addresses the issues of large signal delay and large parasitic parameters by selecting materials with lower dielectric constants.
[0047] A method for preparing a ceramic composite material system includes the following steps: 1. Preparation of functional layer green ceramic tape: 70-90 parts of silicate glass, 5-10 parts of pore-forming agent and organic binder are mixed and ball-milled, and dried by scraping to obtain a functional layer green ceramic tape with a thickness of 25-60 μm; 2. Preparation of substrate layer green ceramic tape: 60-80 parts of alumina powder (particle size 0.8-1.5 μm), 10-20 parts of low melting point glass powder, 2-5 parts of sintering aid and 12 parts of organic binder are mixed and ball-milled, and dried by scraping to obtain a substrate layer green ceramic tape with a thickness of 50-200 μm; 3. Lamination and co-firing: The two types of functional layer green ceramic tapes and substrate layer green ceramic tapes are aligned and laminated, hot-pressed at 10-15 MPa and 70-90℃ for 20-40 min, debinded at 320-450℃ for 3-5 h, co-fired at 850-920℃ for 1.5-2.5 h, and cooled to obtain a ceramic composite material system.
[0048] The silicate glass is made from self-made glass powder with the composition Ca-Mg-Ti-Al-Li-Ba-Si; the low-melting-point glass is made from self-made glass powder with the composition Li-Mg-Zn-B-Si-Mn; the pore-forming agent is a conventional ceramic pore-forming agent, such as HEC, and the sintering aid is ZnO-B2O3-SiO2; the composition ratio of silicate glass, low-melting-point glass, and sintering aid can be in accordance with the conventional ratio in this field.
[0049] High-frequency filters based on ceramic composite materials
[0050] A high-frequency filter was fabricated based on this ceramic composite material system. Resonators (aperture 0.2–0.4 mm) and feeder structures were formed by laser drilling and metal paste filling. The low dielectric properties of the functional layer were utilized to optimize device size and high-frequency performance. The substrate layer provided mechanical support. The specific design is as follows:
[0051] Structural design: The functional layer is formed by laser drilling (hole diameter 0.05-0.1mm) and filling with electronic paste to form 4-6 half-wavelength resonators (spacing 0.8-1.2mm), which are suitable for frequency bands of 20GHz and above;
[0052] Performance specifications: The filter operates at a frequency of 20–30 GHz, with insertion loss ≤0.8 dB, return loss ≥15 dB, out-of-band suppression >40 dB at 40 GHz, and overall bending strength ≥160 MPa. It solves the problems of excessively small size and difficult manufacturing of conventional LTCC filters.
[0053] Example 1
[0054] A method for preparing a high-strength, low-dielectric ceramic composite material includes the following steps:
[0055] Preparation of green ceramic tape of composite material 1 (functional layer): By weight, 80 parts of silicate glass, 8 parts of pore-forming agent, and 12 parts of organic binder (BM-SZ) were added to 30 parts of n-butanol and mixed evenly. The mixture was then subjected to planetary ball milling for 3 hours with 500 parts of zirconia balls as the ball milling medium at a speed of 250 r / min. The mixture was then cast and dried at a speed of 0.75 m / min to obtain a green ceramic tape of functional layer with a thickness of 40 μm.
[0056] Preparation of green ceramic tape for composite material 2 (substrate layer): By weight, 70 parts of alumina powder (particle size 1.0 μm), 15 parts of low melting point glass powder, 3 parts of ZnO-B2O3-SiO2 sintering aid, 12 parts of organic binder (BM-SZ) were mixed with 30 parts of n-butanol and ball-milled for 4 hours with 500 parts of zirconia balls as the ball milling medium at a speed of 300 r / min; then cast at a speed of 0.75 m / min and dried to obtain a green ceramic tape with a substrate layer thickness of 60 μm.
[0057] Co-firing of ceramic composite system: Align the substrate green ceramic tape, functional layer green ceramic tape, and substrate green ceramic tape in sequence, stack them at 30MPa and 65℃, and hot press at 13MPa and 80℃ for 30min to obtain composite green body; then place it in sintering furnace and sinter according to the following procedure: first heat up to 330℃ at 5℃ / min and hold for 4h to remove binder; then heat up to 880℃ at 3℃ / min and hold for 2h for co-firing; finally cool down to room temperature at 4℃ / min to obtain ceramic composite material.
[0058] Example 2
[0059] A method for preparing a high-strength, low-dielectric ceramic composite material includes the following steps:
[0060] Preparation of green ceramic tape of composite material 1 (functional layer): 70 parts by weight of silicate glass, 5 parts by weight of pore-forming agent and 12 parts by weight of organic binder (BM-SZ) were added to 30 parts by weight of n-butanol and mixed evenly. The mixture was then ball-milled for 3 hours with 500 parts by weight of zirconia balls as the ball milling medium at a speed of 250 r / min. The mixture was then cast and dried at a speed of 0.5 m / min to obtain a green ceramic tape of functional layer with a thickness of 25 μm.
[0061] Preparation of green ceramic tape for composite material 2 (substrate layer): By weight, 60 parts of alumina powder (particle size 1.0 μm), 10 parts of low melting point glass powder, 2 parts of ZnO-B2O3-SiO2 sintering aid, 12 parts of organic binder (BM-SZ) were mixed with 30 parts of n-butanol and ball-milled for 4 hours with 500 parts of zirconia balls as the ball milling medium at a speed of 300 r / min; then cast at a speed of 0.5 m / min and dried to obtain a green ceramic tape with a substrate layer thickness of 50 μm.
[0062] Co-firing of ceramic composite system: The substrate green ceramic tape, functional layer green ceramic tape, and substrate green ceramic tape are aligned sequentially and stacked at 30 MPa and 65℃. The composite green body is then hot-pressed at 10 MPa and 70℃ for 20 min to obtain a composite green body. It is then placed in a sintering furnace and sintered according to the following procedure: First, the temperature is increased to 320℃ at 5℃ / min and held for 3 h to remove the binder; then the temperature is increased to 850℃ at 3℃ / min and held for 1.5 h for co-firing; finally, the temperature is decreased to room temperature at 4℃ / min to obtain the ceramic composite material.
[0063] Example 3
[0064] A method for preparing a high-strength, low-dielectric ceramic composite material includes the following steps:
[0065] Preparation of green ceramic tape of composite material 1 (functional layer): 90 parts by weight of silicate glass, 10 parts by weight of pore-forming agent and 12 parts by weight of organic binder (BM-SZ) were added to 30 parts by weight of n-butanol and mixed evenly. The mixture was then ball-milled for 3 hours with 500 parts by weight of zirconia balls as the ball milling medium at a speed of 250 r / min. The mixture was then cast and dried at a speed of 1 m / min to obtain a green ceramic tape of functional layer with a thickness of 60 μm.
[0066] Preparation of green ceramic tape for composite material 2 (substrate layer): By weight, 80 parts of alumina powder (particle size 1.0 μm), 20 parts of low melting point glass powder, 2 parts of ZnO-B2O3-SiO2 sintering aid, 12 parts of organic binder (BM-SZ) were mixed with 30 parts of n-butanol and ball-milled for 4 hours with 500 parts of zirconia balls as the ball milling medium at a speed of 300 r / min; then cast at a speed of 1 m / min and dried to obtain a green ceramic tape with a substrate layer thickness of 200 μm.
[0067] Co-firing of ceramic composite system: The substrate green ceramic tape, functional layer green ceramic tape, and substrate green ceramic tape are aligned sequentially and stacked at 30 MPa and 65℃. The composite green body is then hot-pressed at 15 MPa and 90℃ for 40 min to obtain a composite green body. It is then placed in a sintering furnace and sintered according to the following procedure: First, the temperature is increased to 450℃ at 5℃ / min and held for 5 h to remove the binder; then the temperature is increased to 920℃ at 3℃ / min and held for 2.5 h for co-firing; finally, the temperature is decreased to room temperature at 4℃ / min to obtain the ceramic composite material.
[0068] The properties of the ceramic composite materials obtained in each embodiment were tested using the following methods:
[0069] The dielectric constant and dielectric loss were determined by preparing cylindrical samples and using a vector network analyzer to test the resonant frequency peak and Q value, thereby inferring the dielectric constant and dielectric loss of the samples.
[0070] The bending strength test involves preparing the material into a long strip sample of 4mm*3mm*40mm and then testing it using a universal testing instrument to obtain the bending strength of the material.
[0071] Performance test results of the ceramic composite material obtained in Example 1:
[0072] Composite material 1 (functional layer): dielectric constant 4.01 (20GHz), dielectric loss 0.003, pure layer flexural strength 90MPa;
[0073] Composite material 2 (substrate): dielectric constant 7.02 (20GHz), flexural strength 290MPa;
[0074] Ceramic composite system: The interfacial bonding strength between the substrate layer and the functional layer is 22 MPa, and the overall flexural strength reaches 230 MPa. The interfacial bonding between the substrate layer and the functional layer is intact, with no delamination. The dielectric constant of the functional layer in the ceramic composite system is stable, with a deviation from the design value (4.0) ≤ 0.1. Co-firing compatibility: The sintering shrinkage rates of both the substrate layer and the functional layer are 13.5 ± 0.5%, and the deviation between the two sintering shrinkage rates is 0.8%, meeting the co-firing requirements.
[0075] Performance test results of the ceramic composite material obtained in Example 2:
[0076] Composite material 1 (functional layer): dielectric constant 3.95 (20GHz), dielectric loss 0.003, pure layer flexural strength 87MPa;
[0077] Composite material 2 (substrate): dielectric constant 7.00 (20GHz), flexural strength 285MPa;
[0078] Ceramic composite system: The interfacial bonding strength between the substrate layer and the functional layer is 23 MPa, and the overall flexural strength reaches 226 MPa. The interfacial bonding between the substrate layer and the functional layer is intact, with no delamination. The dielectric constant of the functional layer in the ceramic composite system is stable, with a deviation from the design value (4.0) ≤ 0.1. Co-firing compatibility: The sintering shrinkage rates of both the substrate layer and the functional layer are 13.5 ± 0.4%, and the deviation between the two sintering shrinkage rates is 0.7%, meeting the co-firing requirements.
[0079] Performance test results of the ceramic composite material obtained in Example 3:
[0080] Composite material 1 (functional layer): dielectric constant 4.02 (20GHz), dielectric loss 0.003, pure layer flexural strength 91MPa;
[0081] Composite material 2 (substrate): dielectric constant 7.03 (20GHz), flexural strength 292MPa;
[0082] Ceramic composite system: The interfacial bonding strength between the substrate layer and the functional layer is 22 MPa, and the overall flexural strength reaches 233 MPa. The interfacial bonding between the substrate layer and the functional layer is intact, with no delamination. The dielectric constant of the functional layer in the ceramic composite system is stable, with a deviation from the design value (4.0) ≤ 0.1. Co-firing compatibility: The sintering shrinkage rates of both the substrate layer and the functional layer are 13.5 ± 0.3%, and the deviation between the two sintering shrinkage rates is 0.6%, meeting the co-firing requirements.
[0083] Application Example 1
[0084] High-frequency filter fabrication:
[0085] Structure Forming: Five resonator holes (0.3 mm diameter, 1.0 mm spacing) were machined on the functional layer green ceramic tape obtained in Example 1 using an ultraviolet laser drilling machine. The laser illumination time was 15 ms and the number of illuminations was 4. Silver paste (90 wt% Ag content, 4000 kcp viscosity) was filled using screen printing to obtain a patterned functional layer green ceramic tape. Input / output feed lines (0.2 mm width) were machined using screen printing with a squeegee speed of 75 mm / s and a squeegee pressure of 175 kPa. After printing, the material was dried at 75°C for 25 s to form a 20 GHz bandpass filter structure. Co-firing: Following the co-firing process of the ceramic composite material system in Example 1, the substrate green ceramic tape and the patterned functional layer green ceramic tape were stacked, hot-pressed, cut, and sintered. Then, an electroplating process was used with nickel and tin-lead plating materials. The plating thickness was 2 µm for nickel, 3 µm for tin, and 10% for lead, completing the filter fabrication.
[0086] Filter performance testing:
[0087] High-frequency performance: Tested using a calibrated vector network analyzer, the filter patch was soldered onto a pin-matched, 50Ω impedance test board. The test board was connected to the vector network analyzer, and the instrument was configured to fully display the S21 and S11 curves. Test results showed an insertion loss of 0.75dB at the 20GHz center frequency, a return loss of 17dB, a passband range of 16–21GHz, and out-of-band rejection of 40dB, with high rejection even at 40GHz. The fabrication accuracy was controlled within ±0.02mm. Due to the functional layer dielectric constant of 4.0, parasitic parameters were reduced by 40% compared to conventional high-dielectric LTCC filters.
[0088] Mechanical properties: Three-point bending test shows a bending strength of 160MPa, which meets the stress requirements of patch processing;
[0089] Reliability: After continuously applying a 1W power signal to the filter at 125℃ for 1000 hours, the insertion loss change was ≤0.1dB, and no cracking was observed. This example verifies the applicability of the ceramic composite material system of this invention in high-frequency devices, solving the problems of difficult design and fabrication of conventional LTCC materials and insufficient strength of low-dielectric materials in the millimeter-wave band.
[0090] Figure 2 The diagram shows the electrical performance of a millimeter-wave bandpass filter made using the high-strength, low-dielectric ceramic composite material of the present invention. The test methods and test results are consistent with those described in the above "Filter Performance Test: High-Frequency Performance". The red curve represents "dB(S(1,1))" and the blue curve represents "dB(S(2,1)".
[0091] This invention discloses a high-strength, low-dielectric ceramic composite material and its preparation method, as well as a high-frequency filter based on this system. The ceramic composite material system consists of two composite materials: composite material 1 (dielectric constant 4.0) serves as the low-dielectric main structural functional layer, and composite material 2 (dielectric constant 7.0) serves as the high-strength substrate layer; both contain alumina. Composite material 2 achieves low-temperature co-firing compatibility with composite material 1 through special formulation adjustments, ensuring good interfacial bonding. The substrate layer thickness of both the upper and lower layers of the ceramic composite material system is 50–200 μm, with an overall flexural strength exceeding 200 MPa, approaching the strength of conventional LTCC (low-temperature co-fired ceramic) products without affecting the electrical performance of the functional layer. The millimeter-wave filter prepared based on this system can operate in the 20 GHz and above frequency bands, with an insertion loss ≤0.8 dB. This solves the problems of excessively small size and difficult design and fabrication caused by the high dielectric constant of conventional LTCC materials in the millimeter-wave band, meeting the requirements of millimeter-wave communication scenarios.
[0092] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the inventive concept of the present invention, can make other changes and modifications to these embodiments, all of which fall within the scope of the present invention.
[0093] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If such modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.
Claims
1. A high-strength, low-dielectric ceramic composite material, characterized in that, The ceramic composite material has a layered composite structure, comprising: a functional layer and at least one substrate layer; the functional layer is made of a first composite material, and the dielectric constant of the functional layer at a frequency of 20 GHz is not greater than 5.0; the substrate layer is made of a second composite material, and the flexural strength of the substrate layer is ≥200 MPa. The substrate layer and the functional layer are integrally sintered using a low-temperature co-fired ceramic process, and the sintering shrinkage rate deviation between the substrate layer and the functional layer is ≤3%.
2. The ceramic composite material according to claim 1, characterized in that, The number of substrate layers is two, and the functional layer is located between the two substrate layers.
3. The ceramic composite material according to claim 1, characterized in that, The second composite material comprises the following raw materials in parts by weight: 60-80 parts alumina powder, 10-20 parts low melting point glass powder, 2-5 parts sintering aid, and 12 parts organic binder.
4. The ceramic composite material according to claim 3, characterized in that, The alumina powder has a particle size of 0.8–1.5 μm, and the low-melting-point glass powder has a softening point of 750°C–850°C.
5. The ceramic composite material according to claim 1, characterized in that, The first composite material comprises the following raw materials in parts by weight: 70-90 parts silicate glass, 5-10 parts pore-forming agent, and 12 parts organic binder.
6. The ceramic composite material according to claim 1, characterized in that, The thickness of the substrate layer is 50–200 μm; the thickness of the functional layer is 25–60 μm.
7. A method for preparing a ceramic composite material according to any one of claims 1 to 6, characterized in that, Includes the following steps: Preparation of functional layer green ceramic tape: Silicate glass, pore-forming agent and organic binder are mixed, and the mixture is ball-milled, cast, and dried to obtain functional layer green ceramic tape; Preparation of substrate green ceramic tape: Alumina powder, low melting point glass powder, sintering aid and organic binder are mixed, and the mixture is ball-milled, cast and dried to obtain substrate green ceramic tape; Lamination and co-firing: The green ceramic tape of the substrate layer and the green ceramic tape of the functional layer are aligned and laminated, then hot-pressed, debonded, and co-fired. After cooling, a ceramic composite material is obtained.
8. The method for preparing the ceramic composite material according to claim 7, characterized in that, Hot pressing is performed at 10–15 MPa and 70–90℃ for 20–40 minutes; debinding is performed at 320–450℃ for 3–5 hours; co-firing is performed at 850–920℃ for 1.5–2.5 hours.
9. A high-frequency filter, comprising a dielectric substrate, characterized in that, The medium matrix is made of the ceramic composite material described in any one of claims 1 to 6.
10. The high-frequency filter according to claim 9, characterized in that, The insertion loss of the high-frequency filter in the 20GHz to 30GHz frequency band is ≤0.8dB.