An ultra-low dielectric constant ltcc material and a preparation method thereof

Abstract

This invention discloses an ultra-low dielectric constant (LTCC) material and its preparation method, which is composed of a glass phase and a ceramic filler phase. The glass phase consists of Li2O, La2O3, SiO2, ZrO2, P2O5, MgF2, and Al2O3. The ceramic filler phase includes BaB2O4 and a modifier, wherein the modifier is at least one of Al2O3, SiO2, or cordierite. This invention achieves co-firing with silver / copper electrodes at low temperatures by combining Li-La-Si glass with BaB2O4 filler in a specific ratio, and exhibits excellent thermal stability and environmental friendliness, meeting the requirements of high-frequency communication applications such as 5G millimeter wave for high-performance substrate materials.

Description

Technical Field

[0001] This invention relates to the field of electronic ceramic materials technology, specifically to an ultra-low dielectric constant (LTCC) material and its preparation method. Background Technology

[0002] With the rapid development of 5G communication, satellite communication, and autonomous driving technologies, high-frequency communication technologies are placing higher demands on signal transmission speed and quality. The application of millimeter-wave bands has made signal attenuation a more prominent issue, making ultra-low dielectric constant materials a research hotspot due to their ability to reduce signal delay and loss. Low-temperature co-fired ceramics (LTCC) technology is a multilayer ceramic preparation technique that co-fires ceramic materials with metal conductors at low temperatures (typically below 900℃), and it is widely used in microwave devices and electronic packaging. Traditional LTCC materials, such as alumina (Al2O3), while possessing high mechanical strength, have high sintering temperatures (1500℃) and relatively high dielectric constants (approximately 9-10), making them unsuitable for high-frequency applications.

[0003] In existing technologies, porous silica is typically used to introduce an air phase (air dielectric constant ≈ 1) to reduce the dielectric constant. However, porous structures exhibit high moisture absorption and poor corrosion resistance, affecting device reliability. While pure silica has a low dielectric constant (≈ 3.8), other oxides need to be added to achieve low-temperature co-firing, which often leads to a significant increase in the dielectric constant. Furthermore, some existing systems suffer from high high-frequency losses, poor thermal stability, or complex manufacturing processes.

[0004] Therefore, developing an LTCC material that combines low dielectric constant, ultra-low loss, good thermodynamic stability, and suitability for low-temperature co-firing has become an urgent need for the development of high-frequency electronic devices. Summary of the Invention

[0005] In view of this, the present invention provides an ultra-low dielectric constant LTCC material and its preparation method to solve the problems mentioned in the background art. By combining Li-La-Si system glass with BaB2O4 filler in a specific ratio, it is possible to co-fire with silver / copper electrodes at low temperature and has excellent thermal stability and environmental friendliness, thus meeting the demand for high-performance substrate materials for high-frequency communication applications such as 5G millimeter wave.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, this invention discloses an ultra-low dielectric constant (LTCC) material, which is composed of a glass phase and a ceramic filler phase, wherein...

[0008] The glass phase is composed of Li2O, La2O3, SiO2, ZrO2, P2O5, MgF2, and Al2O3.

[0009] The ceramic filler phase includes BaB2O4 and a modifier, wherein the modifier is at least one of Al2O3, SiO2, or cordierite.

[0010] A further embodiment: the glass phase accounts for 56-65% of the total mass of the material.

[0011] A further embodiment: the glass phase is composed of Li2O 12-22%, La2O3 19-29%, SiO2 42-64%, ZrO2 0.5-1.2%, P2O5 0.2-1.0%, MgF2 0-4.0%, and Al2O3 0%-2.0% by mass percentage.

[0012] A further embodiment: In the ceramic filler phase, the mass percentage of BaB2O4 is 75-85 wt%, with the balance being a regulator.

[0013] A further proposed solution has a sintering temperature of 840℃-900℃, a dielectric constant of 3.5-4.5 at frequencies of 20GHz-40GHz, and a dielectric loss of no more than 0.005.

[0014] Secondly, this invention discloses a method for preparing the ultra-low dielectric constant LTCC material as described above, comprising the following steps:

[0015] S1. The glass phase raw materials are mixed, melted, and quenched in water, then crushed and ground to obtain glass powder;

[0016] S2. BaCO3 and H3BO3 are mixed in a molar ratio of 1:2, calcined, and then ground to obtain BaB2O4 powder;

[0017] S3. Mix the glass powder, BaB2O4 powder and regulator, add solvent and dispersant and grind twice to obtain a uniform slurry;

[0018] S4. Add binder and plasticizer to the slurry, mix evenly, dry, granulate, and then press into green body;

[0019] S5. After debinding the green blank, it is held at a sintering temperature of 840-900℃ for 0.5-2 hours, and after cooling, the ultra-low dielectric constant LTCC material is obtained.

[0020] A further approach: In step S2, the melting temperature is 1250-1350℃, and the melting time is 0.5-1 hour; the glass powder particle size D50 is controlled at 1.5-2.5μm.

[0021] Further proposed solution: In step S3, the calcination temperature is 700-800℃ and the time is 4-4.5 hours; the particle size D50 of BaB2O4 powder is controlled at 1.5μm.

[0022] A further step: In step S5, the binder is a PVA solution with a concentration of 8-10wt%, and its addition amount is -25wt% of the total mass of the powder; the pressing pressure is 5-10MPa.

[0023] Further steps: In step S6, the debinding process specifically involves placing the green compact in an environment where the temperature is raised to 200-450°C at a rate of 2-5°C / min and held for 1-4 hours; the sintering temperature is raised at a rate of 2-5°C / min.

[0024] The primary function of the glass phase is to provide low-temperature sintering characteristics. Its composition includes Li₂O, La₂O₃, SiO₂, ZrO₂, P₂O₅, MgF₂, and Al₂O₃. SiO₂ acts as a glass network forging body, providing the main skeletal structure and ensuring mechanical strength. La₂O₃ is a network intermediate that strengthens the glass network, contributing to the formation of a stable crystalline phase and improving the glass's dielectric properties and chemical stability. Li₂O acts as a network modifier, used to lower the glass melting temperature and improve its chemical stability. Furthermore, adding small amounts of ZrO₂, P₂O₅, and MgF₂ as nucleating agents promotes glass crystallization, thereby reducing dielectric loss. Adding an appropriate amount of Al₂O₃ increases the glass viscosity, which is beneficial for glass melting.

[0025] The ceramic fillers mainly include: BaB2O4: a low dielectric constant (4.2) filler that effectively reduces the overall dielectric constant of the composite material. A (A = Al2O3, SiO2, cordierite, etc.): adjusts dielectric properties, coefficient of thermal expansion and sintering behavior.

[0026] aSiO2-bLa2O3-cLi2O-dZrO2-eP2O5-fMgO-gAl2O3 glass + (xBaB2O4+yA) filler, where a, b, c, d, e, f, and g represent the mass percentage of the glass component, satisfying a+b+c+d+e+f+g=100%, and x and y represent the mass percentage of the filler component, satisfying x+y=100%.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. Ultra-low dielectric constant and loss: Through an optimized glass-filler composite system, the material performs excellently in the millimeter-wave band, with a dielectric constant as low as 3.5-4.5 (20GHz~40 GHz) and a dielectric loss as low as tanδ ≤ 0.005 (20GHz~40GHz), significantly reducing signal transmission loss and delay.

[0029] 2. Excellent low-temperature sintering characteristics: The material has a low sintering temperature (840℃~900℃), which allows it to be well co-fired with low-cost, high-conductivity metal internal electrodes such as silver (Ag) and copper (Cu), avoiding the use of expensive and high-resistance refractory metals.

[0030] 3. Excellent thermodynamic stability and reliability: The material is highly water-resistant, acid and alkali-resistant, has a good matching coefficient of thermal expansion, and high thermal stability, making it suitable for harsh environments.

[0031] 4. Environmentally friendly: The formula avoids the use of harmful substances such as lead (Pb), making production and post-processing more environmentally friendly.

[0032] 5. In terms of process and cost, this invention exhibits significant practical advantages. The sintering temperature window of the material is 840-900℃. This low-temperature characteristic allows it to be well co-fired with low-cost, high-conductivity silver (Ag) or copper (Cu) metal internal electrodes, avoiding the problem that traditional high-temperature co-fired ceramics must use expensive and high-resistivity refractory metals such as molybdenum (Mo) and tungsten (W). This not only reduces raw material costs but also simplifies the process, making it more conducive to manufacturing high-performance, highly integrated passive devices. Detailed Implementation

[0033] To facilitate understanding of the present invention, a more comprehensive description will be provided below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0034] 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 the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0035] It is understood that the above-mentioned raw materials and reagents are merely examples of some specific embodiments of the present invention, making the technical solution of the present invention clearer, and do not mean that the present invention can only use the above-mentioned reagents. The specific scope shall be determined by the claims. In addition, unless otherwise specified, "parts" in the examples and comparative examples refer to parts by weight.

[0036] Any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0037] Example 1

[0038] This embodiment provides an ultra-low dielectric constant LTCC material with a glass phase composition of 50.8SiO2-25La2O3-21Li2O-1ZrO2-0.8P2O5-0.5MgF2-0.9Al2O3 and a filler phase composition (wt%) of 75BaB2O4-25Al2O3.

[0039] The preparation method is as follows:

[0040] (1) Weigh the corresponding raw materials according to Table 1. The lithium source is Li2CO3, the phosphorus source is NH4H2PO4, and the other raw materials are their corresponding oxyfluorides. Mix them by planetary ball milling for 6 hours to obtain powder.

[0041] Table 1 Glass proportions in Example 1

[0042]

[0043] (2) The powder was melted at 1250°C for 3 hours, quenched in water, crushed, and ground to obtain glass powder with D50=1.5-2.0μm.

[0044] (3) Mix glass powder and filler at a mass ratio of 56:44, add deionized water, and ball mill for 12 hours.

[0045] (4) Add 20wt% of 10% PVA solution to granulate, and press into round green blanks under 10MPa pressure.

[0046] (5) Place the round blank in a container, heat it to 500°C at 3°C / min and keep it at 500°C for 2 hours to remove the glue, then heat it to 860°C at 5°C / min and sinter for 2 hours. After cooling, the ultra-low dielectric constant LTCC material is obtained.

[0047] Example 2

[0048] This embodiment provides an ultra-low dielectric constant LTCC material with a glass phase composition of 55.7SiO2-20La2O3-19Li2O-1ZrO2-0.8P2O5-1.5MgF2-2Al2O3 and a filler phase composition (wt%) of 80BaB2O4-20SiO2.

[0049] The preparation method is as follows:

[0050] (1) Weigh the corresponding raw materials according to Table 2, mix them in a planetary ball mill for 6 hours to obtain powder.

[0051] Table 2 Glass proportions in Example 2

[0052]

[0053] (2) The powder was melted at 1250°C for 3 hours, quenched in water, crushed, and ground to obtain glass powder with D50=1.5-2.0μm.

[0054] (3) Mix glass powder and filler at a mass ratio of 60:40, add deionized water, and ball mill for 12 hours.

[0055] (4) Add 20wt% of 10% PVA solution to granulate, and press into round green blanks under 10MPa pressure.

[0056] (5) Place the round blank in a container, heat it to 500°C at 3°C / min and keep it at 500°C for 2 hours to remove the glue, then heat it to 880°C at 5°C / min and sinter for 2 hours. After cooling, the ultra-low dielectric constant LTCC material is obtained.

[0057] Example 3

[0058] This embodiment provides an ultra-low dielectric constant LTCC material with a glass phase composition of 57.3SiO2-19La2O3-16.5Li2O-1ZrO2-0.8P2O5-1.5MgF2-1Al2O3 and a filler phase composition (wt%) of 85BaB2O4-15cordierite.

[0059] The preparation method is as follows:

[0060] (1) Weigh the corresponding raw materials according to Table 3, mix them in a planetary ball mill for 6 hours to obtain powder.

[0061] Table 3 Glass ratio in Example 3

[0062]

[0063] (2) The powder was melted at 1250°C for 3 hours, quenched in water, crushed, and ground to obtain glass powder with D50=1.5-2.0μm.

[0064] (3) Mix glass powder and filler at a mass ratio of 65:35, add deionized water, and ball mill for 12 hours.

[0065] (4) Add 20wt% of 10% PVA solution to granulate, and press into round green blanks under 10MPa pressure.

[0066] (5) Place the round blank in a container, heat it to 500°C at 3°C / min and keep it at 500°C for 2 hours to remove the glue, then heat it to 900°C at 5°C / min and sinter for 2 hours. After cooling, the ultra-low dielectric constant LTCC material is obtained.

[0067] Comparative Example 1

[0068] Compared with Example 1, the only difference is that the mass ratio of glass powder to filler is 50:50. The resulting material has a low density after sintering at 900°C, and its dielectric loss is relatively high due to excessive porosity. The test performance results are shown in Table 4.

[0069] Comparative Example 2

[0070] Compared with Example 1, the only difference is that the mass ratio of glass powder to filler is 70:30. Due to the high glass phase content, the prepared ceramics sintered and melted at 900°C, resulting in over-firing. It can be sintered at 850°C, but due to the high glass content and the large dielectric constant of the glass, its dielectric constant is also large. The test performance results are shown in Table 4.

[0071] Comparative Example 3

[0072] Compared to Example 1, the only difference is that the filler phase composition is Al2O3. When there is only one component, Al2O3, the dielectric constant of the final material is relatively high due to the large dielectric constant of Al2O3, which cannot meet the material performance requirements of ultra-low dielectric.

[0073] Test case

[0074] The LTCC materials obtained in the examples and comparative examples were subjected to performance tests, and the test results are shown in Table 4.

[0075] Table 4. Test results of dielectric constant and dielectric loss of the examples and comparative examples

[0076]

[0077] Comparative analysis of the performance data of the examples and comparative examples shows that the present invention successfully achieves a balance between ultra-low dielectric constant and ultra-low loss by precisely controlling the ratio and composition of the glass phase and the ceramic filler phase. When the glass / filler mass ratio is in a wide range of 56:44 to 65:35 (Examples 1-3), and the filler phase is mainly low-dielectric BaB2O4 (75-85wt%), the material exhibits excellent comprehensive performance at 40GHz, with a stable dielectric constant of 3.8-4.2 and a low dielectric loss ( As low as (1.8-2.5)×10 -3 Conversely, if the ratio of the two phases is imbalanced, such as in Comparative Example 1 (50:50), excessive filler and insufficient densification lead to a surge in losses (7.8 × 10⁻⁶). -3In contrast, Comparative Example 2 (70:30) showed an increased dielectric constant (5.4) due to the excessive glass phase. Furthermore, if the filler is not properly selected, such as in Comparative Example 3 which only uses high-dielectric Al2O3, even with a suitable ratio, the dielectric constant will significantly increase to 6.8. This fully demonstrates that the synergistic effect of BaB2O4-based composite filler and a specific glass phase at an optimized ratio is key to achieving the high-performance indicators of this invention.

[0078] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0079] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. An ultra-low dielectric constant (LTCC) material, characterized in that, It is composed of a glassy phase and a ceramic filler phase, wherein, The glass phase accounts for 56-65% of the total mass of the material; The glass phase is composed of Li2O 12-22%, La2O3 19-29%, SiO2 42-64%, ZrO2 0.5-1.2%, P2O5 0.2-1.0%, MgF2 0-4.0%, and Al2O3 0%-2.0% by mass percentage. The ceramic filler phase includes BaB2O4 and a modifier, wherein the modifier is at least one of Al2O3, SiO2 or cordierite; wherein the mass percentage of BaB2O4 is 75-85 wt%, and the balance is a modifier.

2. The ultra-low dielectric constant LTCC material according to claim 1, characterized in that, Its sintering temperature is 840℃-900℃, its dielectric constant is 3.5-4.5 at frequencies of 20GHz-40GHz, and its dielectric loss is no greater than 0.

005.

3. A method for preparing the ultra-low dielectric constant LTCC material as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. The glass phase raw materials are mixed, melted, and quenched in water, then crushed and ground to obtain glass powder; S2. BaCO3 and H3BO3 are mixed in a molar ratio of 1:2, calcined, and then ground to obtain BaB2O4 powder; S3. Mix the glass powder, BaB2O4 powder and regulator, add solvent and dispersant and grind again to obtain a uniform slurry; S4. Add binder and plasticizer to the slurry, mix evenly, dry, granulate, and then press into green body; S5. After debinding the green blank, it is held at a sintering temperature of 840-900℃ for 0.5-2 hours, and after cooling, the ultra-low dielectric constant LTCC material is obtained.

4. The preparation method according to claim 3, characterized in that, In step S2, the melting temperature is 1250-1350℃ and the melting time is 0.5-1 hour; the glass powder particle size D50 is controlled at 1.5-2.5μm.

5. The preparation method according to claim 3, characterized in that, In step S3, the calcination temperature is 700-800℃ and the time is 4-4.5 hours; the particle size D50 of BaB2O4 powder is controlled at 1.5μm.

6. The preparation method according to claim 3, characterized in that, In step S5, the binder is a PVA solution with a concentration of 8-10 wt%, and its addition amount is -25 wt% of the total mass of the powder; the pressing pressure is 5-10 MPa.

7. The preparation method according to claim 3, characterized in that, In step S5, the debinding process specifically involves placing the green blank in an environment where the temperature is raised to 200-450°C at a heating rate of 2-5°C / min and held for 1-4 hours; the heating rate for sintering is 2-5°C / min.

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