Low-loss high-strength LTCC (Low Temperature Co-Fired Ceramic) composite material and preparation method thereof

Abstract

The invention discloses a low-loss high-strength LTCC (Low Temperature Co-Fired Ceramic) composite material and a preparation method thereof, and belongs to the technical field of LTCC composites.The low-loss high-strength LTCC composite material comprises the following components in percentage by weight: 30-50 wt% of Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass, 30-50 wt% of Al2O3, 0-5 wt% of ZrO2 and 0-5 wt% of TiO2; the preparation method comprises the following steps: melting Ca-Ba-Al-Mg-Zn-B-Si multi-component and complex-phase microcrystalline glass at a high temperature, and compounding Al2O3, ZrO2 and TiO2 to prepare an LTCC dielectric material which can be sintered at 880-900 DEG C and is low in dielectric constant, low in loss, high in strength and high in co-firing adaptability; the composite material disclosed by the invention is excellent in comprehensive performance, simple in composition, easy to sinter and convenient to regulate and control, and provides more choices for an LTCC (Low Temperature Co-Fired Ceramic) process.

Description

Technical Field

[0001] This invention belongs to the field of LTCC composite material technology, specifically relating to a low-loss, high-strength LTCC composite material, and also to a method for preparing the low-loss, high-strength LTCC composite material. Background Technology

[0002] Low-temperature co-fired ceramics (LTCC) are multilayer structures formed by co-sintering low-resistivity metallic conductors (such as silver and copper) and ceramic matrix materials at low temperatures (below 1000℃). The material systems can be classified into three categories: ① ceramic-glass systems (microcrystalline glass); ② glass-ceramic filler composite systems; ③ ceramic + sintering aids. Depending on the application and requirements, LTCC substrates and their corresponding ceramic powders are required to possess different properties, such as high strength, low loss, good co-firing performance with metallic conductors, and a low coefficient of thermal expansion. In the LTCC process, glass-ceramic filler composite systems are characterized by simple processing, easy composition control, and a relatively fast sintering shrinkage rate. These materials also typically have a low dielectric constant and a low temperature coefficient.

[0003] Chinese patent CN115557783A discloses a low-expansion, low-dielectric-constant, and low-loss low-temperature co-fired material and its preparation method. The material composition is flake-like Al2O3 (0-10 wt%), BPO4 ceramic (60-80 wt%), and BSMP glass (20-40 wt%). The BSMP glass composition is 10-30 mol% B2O3, 30-50 mol% SiO2, 10-30 mol% MgO, and 20-40 mol% P2O5. The patent provides a low-dielectric-constant (3.5-5), low thermal expansion coefficient (3-4 ppm / K), and flexural strength of 150-242 MPa low-temperature co-fired ceramic material; it basically meets the requirements of most low-temperature co-fired ceramic materials, but the dielectric loss is relatively high (0.003-0.007).

[0004] Chinese Patent Publication No. CN116947322A discloses a high-strength calcium aluminum silicon microcrystalline glass and its preparation method. The composition of the material is: CaO 15-25 wt%, Al2O3 10-15 wt%, SiO2 50-65 wt%, ZnO+BaO 10 wt%. This invention provides a high-strength calcium aluminum silicon microcrystalline glass with wollastonite CaSiO3 as the main crystalline phase, and barium feldspar BaAl2Si2O8 and quartz SiO2 as the secondary crystalline phases. The flexural strength is 193 MPa, the Young's modulus is 79 GPa, the coefficient of thermal expansion is 5.11 ppm / ℃, and the dielectric constant is 6.5-7.3. However, the loss of this microcrystalline glass is relatively large (0.002-0.003).

[0005] Chinese patent CN114671614A discloses a low-dielectric, low-loss calcium aluminum borosilicate-based microcrystalline glass material. Its raw material composition is: 18–28 mol% CaCO3, 18–28 mol% B2O3, 15–20 mol% SiO2, 11–25 mol% Al2O3, 8–12 mol% BaCO3, 5–8 mol% P2O5, and 0–6 mol% trace elements. The trace element percentage is not zero, specifically: 0–3 mol% CeO2, 0–3 mol% La2O3, and / or 0–3 mol% Na2CO3. The material is obtained by sequentially melting, water quenching, granulation, and sintering. Its dielectric constant εr = 4–5, dielectric loss Tanδ < 0.0006, and sintering temperature is 850℃–950℃, basically meeting the requirements of most low-temperature co-fired ceramic materials. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a low-loss, high-strength LTCC composite material and its preparation method, which can be made into a low-dielectric, low-loss, and high-strength LTCC dielectric material that can be sintered at 880-900℃, so as to meet the current industry requirements for low-dielectric, low-loss, and high-strength LTCC materials and provide more options for LTCC processes.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a low-loss, high-strength LTCC composite material, comprising the following components by weight percentage: Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass: 48-68 wt%, Al2O3: 30-50 wt%, ZrO2: 1 wt%, TiO2: 1 wt%.

[0008] Furthermore, the composition of the Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass includes: 50-65 wt% SiO2, 1-10 wt% CaO, 0-5 wt% Al2O3, 0-5 wt% MgO, 0-5 wt% BaO, 0-5 wt% ZnO, and 10-25 wt% B2O3.

[0009] A method for preparing a low-loss, high-strength LTCC composite material, comprising the following steps:

[0010] 1) Ingredients: Select high-temperature molten Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass, Al2O3, TiO2 and ZrO2 according to the formula ratio for batching;

[0011] 2) Ball milling: After the molten high-temperature Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass is crushed by ball milling, it is mixed with Al2O3, TiO2 and ZrO2 in a ball mill. The ball milling parameters are: 250 rpm / 4H, material:ball:anhydrous ethanol = 1:3:1.

[0012] Step 3, Pre-sintering: The ball-milled composite from step 2) is sintered in a high-temperature furnace under air conditions at a sintering temperature of 700℃ for 2 hours.

[0013] The preparation method of Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass includes the following steps:

[0014] (1.1) Raw material selection: SiO2 according to the formula 2、 The raw materials are selected from CaO, Al2O3, ZnO, BaO, B2O3, and MgO; among them, CaO and BaO are calculated from equal amounts of CaCO3 and BaCO3.

[0015] (1.2) Ball milling: Add the selected ingredients in step (1.1) into a ball mill and ball mill. The ball milling parameters are: 250 rpm / 4H, and the ratio of material to ball to anhydrous ethanol is 1:3:1.

[0016] (1.3) Drying: After the ball-milled mixture is naturally air-dried, it is dried at 120℃ for 12 hours;

[0017] (1.4) Glass melting: Place the mixture from step (1.3) into a platinum crucible and melt at the following temperatures: RT → 300 min → 1600 °C → 1 h → 1600 °C.

[0018] (1.5) Water quenching: The molten glass is poured into deionized water to obtain transparent glass particles;

[0019] (1.6) Crushing: The glass particles are crushed using a jaw crusher;

[0020] (1.7) Ball milling: Add the crushed glass to a ball mill for ball milling. Ball milling parameters: 250 rpm / 2h, material:ball:anhydrous ethanol = 1:3:1;

[0021] (1.8) Drying: After the ball-milled Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass is naturally air-dried, it is dried at 120℃ for 12 h.

[0022] The beneficial effects of this invention are as follows: Compared with the prior art, the LTCC material provided by this invention is a low-dielectric, low-loss, high-strength, and co-fired adaptable microcrystalline glass-ceramic composite system based on multi-component, complex-phase Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass + (Al2O3, ZrO2, TiO2). This material is prepared by high-temperature melting of Ca-Ba-Al-Mg-Zn-B-Si multi-component, complex-phase microcrystalline glass, followed by composite formation with Al2O3, ZrO2, and TiO2, resulting in a low-dielectric, low-loss, and high-strength LTCC dielectric material that can be sintered at 880-900℃. The composite material of this invention has excellent comprehensive performance, simple composition, is easy to sinter, and is easy to control, providing more options for LTCC processes. This product has advantages in high-frequency (above 10GHz) LTCC products.

[0023] Analysis of the reasons for high strength: During the sintering process of the Ca-Ba-Al-Mg-Zn-B-Si multi-component, complex-phase microcrystalline glass-ceramic composite system, the glass first forms a liquid glass phase. A very small portion of Al2O3 dissolves in the glass, which hinders the formation of crystal nuclei and inhibits the crystallization of the glass, forming an amorphous glass matrix composite material. At the same time, Al2O3 acts as a filler, distributed in the glass, and plays a filling role, improving the bending strength of the ceramic body.

[0024] The reasons for low dielectric constant and low loss: The dielectric constant of the Ca-Ba-Al-Mg-Zn-B-Si multi-component, complex-phase microcrystalline glass-alumina composite material is related to both the composite formed by the component materials and its material composition. SiO2 has a dielectric constant of 4 and a loss of 0.001-0.002, while alumina has a dielectric constant of 9.8 and a loss of 0.0001-0.0003. In composite material 2 of Comparative Example 2, alumina is the most abundant component, resulting in numerous ceramic pores after sintering, which is equivalent to introducing air (dielectric constant 1) as a component material, leading to a low ceramic dielectric constant. In composite material 4 of Example 2, the sintering density is relatively dense, resulting in a high dielectric constant and a loss of 0.001-0.002, basically meeting the material requirements for LTCC process.

[0025] Analysis of the reasons for the strong adaptability of co-firing: Conventional microcrystalline glass systems suffer from reduced glass phase due to grain precipitation, resulting in poor fluidity, severe shrinkage, and poor compatibility with silver paste. In the sintering process of this invention, a small amount of alumina dissolves, which inhibits grain precipitation, ensures the fluidity of the glass phase, and makes the shrinkage during sintering more gradual. This reduces the mismatch in shrinkage between metal and ceramic sintering, reduces the stress at the interface between the two materials, and makes the sintering shrinkage behavior of ceramics similar to that of silver paste. Attached Figure Description

[0026] Figure 1 Here is a sintered surface view of composite material 2;

[0027] Figure 2 Here is a cross-sectional view of the sintered composite material 2;

[0028] Figure 3 The phase diagram of the sintered sample of composite material 2 is shown.

[0029] Figure 4 The diagram shows the co-firing of composite material 2 with conductive silver paste.

[0030] Figure 5 The image shows the co-firing of composite material 2 with conductive silver paste. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments.

[0032] Terminology Explanation: LTCC: Low Temperature Co-Fired Ceramics;

[0033] Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass: a multi-component, complex-phase microcrystalline glass made from elements such as calcium, barium, aluminum, magnesium, zinc, boron, silicon, and oxygen;

[0034] Conductive silver paste: formulated with silver powder or its oxides, solvents, binders, and diluents. It can be printed onto substrates and, after sintering, possesses the ability to conduct current and dissipate accumulated static charge.

[0035] The overall solution describes a low-loss, high-strength LTCC composite material comprising the following components by weight percentage: Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass: 48-68 wt%, Al2O3: 30-50 wt%, ZrO2: 1 wt%, TiO2: 1 wt%.

[0036] The composition of Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass includes: 50-65 wt% SiO2, 1-10 wt% CaO, 0-5 wt% Al2O3, 0-5 wt% MgO, 0-5 wt% BaO, 0-5 wt% ZnO, and 10-25 wt% B2O3.

[0037] A method for preparing a low-loss, high-strength LTCC composite material, comprising the following steps:

[0038] 1) Ingredients: Select high-temperature molten Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass, Al2O3, TiO2 and ZrO2 according to the formula ratio for batching;

[0039] 2) Ball milling: After the molten high-temperature Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass is crushed by ball milling, it is mixed with Al2O3, TiO2 and ZrO2 in a ball mill. The ball milling parameters are: 250 rpm / 4h, material:ball:anhydrous ethanol = 1:3:1.

[0040] Step 3, Pre-sintering: The ball-milled composite from step 2) is sintered in a high-temperature furnace under air conditions at a sintering temperature of 700℃ for 2 hours.

[0041] The preparation method of Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass includes the following steps:

[0042] (1.1) Raw material selection: SiO2 according to the formula 2、 The raw materials were selected from CaO, Al2O3, ZnO, BaO, B2O3, and MgO.

[0043] (1.2) Ball milling: Add the selected ingredients in step (1.1) into a ball mill and ball mill. The ball milling parameters are: 250 rpm / 4 h, and the ratio of material to ball to anhydrous ethanol is 1:3:1.

[0044] (1.3) Drying: After the ball-milled mixture is naturally air-dried, it is dried at 120℃ for 12 hours;

[0045] (1.4) Glass melting: Place the mixture from step (1.3) into a platinum crucible and melt at the following temperatures: RT → 300 min → 1600 °C → 1 h → 1600 °C.

[0046] (1.5) Water quenching: The molten glass is poured into deionized water to obtain transparent glass particles;

[0047] (1.6) Crushing: The glass particles are crushed using a jaw crusher;

[0048] (1.7) Ball milling: Add the crushed glass to a ball mill for ball milling. Ball milling parameters: 250 rpm / 2H, material:ball:anhydrous ethanol = 1:3:1;

[0049] (1.8) Drying: After the ball-milled Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass is naturally air-dried, it is dried at 120℃ for 12h.

[0050] Examples 1-5 respectively use the five formulations of composite materials 3-7 in Table 1 and their melting temperature and pre-firing temperature in the preparation process (composite material numbers 3-7 correspond to example numbers 1-5, and the formulation of composite material 1-2 is used as comparative example 1-2).

[0051] Table 1 Composite Material Formulation

[0052]

[0053] The preparation methods for the above 7 formulas are as follows:

[0054] 1) Ingredients: Select high-temperature molten Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass, Al2O3, TiO2 and ZrO2 according to the formula ratio for batching;

[0055] 2) Ball milling: After the molten high-temperature Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass is crushed by ball milling, it is mixed with Al2O3, TiO2 and ZrO2 in a ball mill. The ball milling parameters are: 250 rpm / 4h, material:ball:anhydrous ethanol = 1:3:1.

[0056] Step 3, Pre-sintering: The ball-milled composite from step 2) is sintered in a high-temperature furnace under air conditions at a sintering temperature of 700℃ for 2 hours.

[0057] The preparation method of Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass includes the following steps:

[0058] (1.1) Raw material selection: SiO2 according to the formula 2、 The raw materials were selected from CaO, Al2O3, ZnO, BaO, B2O3, and MgO.

[0059] (1.2) Ball milling: Add the selected ingredients in step (1.1) into a ball mill and ball mill. The ball milling parameters are: 250 rpm / 4H, and the ratio of material to ball to anhydrous ethanol is 1:3:1.

[0060] (1.3) Drying: After the ball-milled mixture is naturally air-dried, it is dried at 120℃ for 12 hours;

[0061] (1.4) Glass melting: Place the mixture from step (1.3) into a platinum crucible and melt at the following temperatures: RT → 300 min → 1600 °C → 1 h → 1600 °C.

[0062] (1.5) Water quenching: The molten glass is poured into deionized water to obtain transparent glass particles;

[0063] (1.6) Crushing: The glass particles are crushed using a jaw crusher;

[0064] (1.7) Ball milling: Add the crushed glass to a ball mill for ball milling. Ball milling parameters: 250 rpm / 2h, material:ball:anhydrous ethanol = 1:3:1;

[0065] (1.8) Drying: After the ball-milled Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass is naturally air-dried, it is dried at 120℃ for 12h.

[0066] To verify the performance of the LTCC composite materials prepared in each embodiment, step 3) of the embodiment is followed by:

[0067] 4) Molding: Granulate the sintered powder from step 3) with 5% PVA glue; dry press it under 3T pressure to form a sample with a diameter of 14mm and a height of 4mm; the purpose is to form the sample, which requires the glue to fix the material.

[0068] 5) Sample preparation: Mix the powder from step 3) with the binder, plasticizer, dispersant, and solvent in the specified proportions and ball mill them. The ball milling parameters are: 250 rpm and 14 hours. Cast a 50µm raw tape from the ball-milled mixture. Print an 80*100mm inner electrode (i.e., print the inner electrode pattern on the 50µm raw tape). Stack the electrodes according to a 10-layer electrode plus 10-layer substrate structure. The water pressure conditions are: water temperature 72℃, pressure 5100Psi, duration 300s. Cut the breathable paper with two 100mm cutting edges on the first side and two 100mm cutting edges on the second side.

[0069] 6) Sintering: Remove the binder from the green samples in steps 4) and 5) at 450°C, sinter at 900°C for 2 hours, and then allow to cool naturally.

[0070] 7) Testing: Test dielectric constant, dielectric loss, bending strength, and microstructure.

[0071] The sintering and dielectric properties of the microcrystalline glass-ceramic composite materials prepared in Examples 1-5 and Comparative Examples 1-2 are shown in Table 2 below.

[0072] Table 2 Sintering and Dielectric Properties

[0073]

[0074] Composite material 1 has low sintering density (requirement > 2.70 ± 0.05), low dielectric constant (requirement 6.0 ± 0.2), and bending strength close to the lower limit (requirement > 200 MPa), thus failing to meet the performance requirements.

[0075] Composite material 2 has low sintering density (requirement > 2.70 ± 0.05), low dielectric constant (requirement 6.0 ± 0.2), and flexural strength close to the lower limit (requirement > 200 MPa), thus failing to meet the performance requirements.

[0076] This invention provides a low-dielectric, low-loss, high-strength, and co-fired adaptable glass-ceramic composite material (LTCC) based on a multi-component, complex-phase Ca-Ba-Al-Mg-Zn-B-Si glass-ceramic + (Al2O3, ZrO2, TiO2) system, and its preparation method. The components of each material can be determined by XRF testing using a high-temperature melting method; the phases can be determined by X-ray diffraction analysis.

[0077] Mechanism explanation:

[0078] The reason for the high strength is that during the sintering process of the Ca-Ba-Al-Mg-Zn-B-Si multi-component, complex-phase microcrystalline glass-ceramic composite system, the glass first forms a liquid glass phase, and a very small portion of Al2O3 dissolves in the glass, which hinders the formation of crystal nuclei and inhibits the crystallization of the glass, forming an amorphous glass matrix composite material. At the same time, Al2O3 acts as a filler, distributed in the glass, and plays a filling role, improving the bending strength of the ceramic body.

[0079] The reasons for low dielectric constant and low loss: The dielectric constant of the Ca-Ba-Al-Mg-Zn-B-Si multi-component, complex-phase microcrystalline glass-alumina composite material is related to both the composite formed by the component materials and its material composition. SiO2 has a dielectric constant of 4 and a loss of 0.001-0.002, while alumina has a dielectric constant of 9.8 and a loss of 0.0001-0.0003. In composite material 2 of Comparative Example 2, alumina is the most abundant component, resulting in numerous ceramic pores after sintering, which is equivalent to introducing air (dielectric constant 1) as a component material, leading to a low ceramic dielectric constant. In composite material 4 of Example 2, the sintering density is relatively dense, resulting in a high dielectric constant and a loss of 0.001-0.002, basically meeting the material requirements for LTCC process.

[0080] The strong adaptability of co-firing is due to the fact that conventional microcrystalline glass systems suffer from reduced glass phase due to grain precipitation, resulting in poor fluidity, severe shrinkage, and poor compatibility with silver paste. In this invention, trace amounts of alumina dissolve during the sintering process, inhibiting grain precipitation, ensuring the fluidity of the glass phase, and making the shrinkage during sintering more gradual. This reduces the mismatch in shrinkage during metal-ceramic sintering, decreases the stress at the interface between the two materials, and makes the sintering shrinkage behavior of the ceramic closely resemble that of silver paste.

Claims

1. A low-loss, high-strength LTCC composite material, characterized in that, It includes the following components by weight percentage: Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass: 48-68 wt%, Al2O3: 30-50 wt%, ZrO2: 1 wt%, TiO2: 1 wt%.

2. The low-loss, high-strength LTCC composite material according to claim 1, characterized in that, The composition of Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass includes: 50-65 wt% SiO2, 1-10 wt% CaO, 0-5 wt% Al2O3, 0-5 wt% MgO, 0-5 wt% BaO, 0-5 wt% ZnO, and 10-25 wt% B2O3.

3. The method for preparing a low-loss, high-strength LTCC composite material according to any one of claims 1-2, characterized in that, The method includes the following steps: Step 1, Ingredients: Select Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass, Al2O3, TiO2 and ZrO2 according to the formula ratio for ingredient preparation; Step 2, ball milling: After the molten Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass is crushed by ball milling, it is mixed and ball milled with Al2O3, TiO2 and ZrO2 in a ball mill. The ball milling parameters are: 250 rpm / 4H, material:ball:anhydrous ethanol = 1:3:

1. Step 3, Pre-sintering: The ball-milled composite from step 2) is sintered in a high-temperature furnace under air conditions at a sintering temperature of 700℃ for 2 hours.

4. The method for preparing a low-loss, high-strength LTCC composite material according to claim 5, characterized in that, The preparation method of Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass includes the following steps: (1.1) Raw material selection: SiO2 according to the formula 2、 The raw materials were selected from CaO, Al2O3, ZnO, BaO, B2O3, and MgO. (1.2) Ball milling: Add the selected ingredients in step (1.1) into a ball mill and ball mill. The ball milling parameters are: 250 rpm / 4H, and the ratio of material to ball to anhydrous ethanol is 1:3:

1. (1.3) Drying: After the ball-milled mixture is naturally air-dried, it is dried at 120℃ for 12 hours; (1.4) Glass melting: Place the mixture from step (1.3) into a platinum crucible and melt at the following temperatures: RT → 300 min → 1600 °C → 1 h → 1600 °C. (1.5) Water quenching: The molten glass is poured into deionized water to obtain transparent glass particles; (1.6) Crushing: The glass particles are crushed using a jaw crusher; (1.7) Ball milling: Add the crushed glass to a ball mill for ball milling. The ball milling parameters are: 250 rpm and 2 h. The ratio of material to ball to anhydrous ethanol is 1:3:

1. (1.8) Drying: After the ball-milled Ca-Ba-Al-Mg-Zn-B-Si microcrystalline glass is naturally air-dried, it is dried at 120℃ for 12h.

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