Low-temperature co-fired microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a low-temperature co-fired microwave dielectric ceramic material and a preparation method thereof. The low-temperature co-fired microwave dielectric ceramic material comprises a ceramic main material and an auxiliary agent, wherein the ceramic main material is Mg2SiO4; the auxiliary agent comprises CaTiO3 accounting for 14-16 wt% of the ceramic main material, Li2O accounting for 0.5-1 wt% of the ceramic main material, WmOn accounting for 0-2 wt% of the ceramic main material and low-melting-point glass accounting for 0.5-1 wt% of the ceramic main material, and the WmOn comprises one or more of V2O5, CuO, Bi2O3 and B2O3. According to the low-temperature co-fired microwave dielectric ceramic material, CaTiO3, Li2O, WmOn and low-melting-point glass are combined on the basis of Mg2SiO4, the sintering temperature of Mg2SiO4 ceramic is successfully reduced to a low-temperature co-fired ceramic window, meanwhile, the basic requirement for environmental protection is met, the intrinsic advantage of ultralow loss of the Mg2SiO4 ceramic is reserved to the maximum extent, and the low-temperature co-fired microwave dielectric ceramic material is suitable for being used as a low-temperature co-fired microwave dielectric ceramic material. The core problems of low-temperature sintering, low dielectric constant and low loss keeping which are correlated and restricted with one another are solved.

Description

Technical Field

[0001] This invention relates to the field of microwave dielectric ceramic materials, and more particularly to a low-temperature co-fired microwave dielectric ceramic material and its preparation method. Background Technology

[0002] With the rapid development of technologies such as 5G, the Internet of Things, satellite internet, and millimeter-wave radar, microwave and radio frequency front-end devices are evolving towards higher frequencies, wider bandwidths, smaller sizes, lower power consumption, and higher reliability. Against this backdrop, low-temperature co-fired ceramic (LTCC) technology, due to its ability to integrate passive components (such as inductors, capacitors, resistors, filters, and antennas) with three-dimensional interconnects to achieve high-density, high-performance system-in-package, has become an indispensable core process platform for modern wireless communication modules. As the physical carrier of LTCC technology, the performance of microwave dielectric ceramic materials directly determines the electrical performance limits of the entire system.

[0003] Ideal low-temperature co-fired ceramic microwave dielectric materials must simultaneously meet multiple requirements: the sintering temperature is typically no higher than 950℃ (preferably ≤900℃) to ensure compatibility with low-cost, high-conductivity silver or copper electrodes; they must possess excellent microwave dielectric properties, including a moderate and stable dielectric constant and extremely low dielectric loss (manifested as a high quality factor Q×f); and they must also possess excellent frequency-temperature stability, i.e., the resonant frequency temperature coefficient τf should be close to zero (|τf|<10ppm / °C) to ensure reliable operation of the device over a wide temperature range.

[0004] Among numerous candidate materials, magnesium silicate (Mg2SiO4) ceramics stand out due to their low raw material cost, environmental friendliness, and moderate dielectric constant (ε). (≈6~7), especially its intrinsically low dielectric loss, with Q×f values ​​reaching over 150,000 GHz, is considered to have significant application potential in the millimeter-wave band. However, the sintering temperature of pure-phase magnesium silicate ceramics is too high, usually exceeding 1450°C, making co-firing with silver or copper electrodes impossible. Furthermore, high temperatures easily cause component volatilization, leading to deviations in stoichiometry and deterioration of dielectric properties, severely limiting its application in low-temperature co-fired ceramics.

[0005] To reduce the sintering temperature, existing research mainly focuses on two technical routes, but neither has achieved a balanced optimization of performance: One approach is to introduce single oxide or fluoride sintering aids (such as ZnO, CuO, LiF, etc.). For example, LiF can form a liquid phase at lower temperatures, reducing the sintering temperature to below 950°C. However, it poses potential hazards to the environment and human health, and its cooling effect is limited when added in small amounts, while excessive addition leads to increased porosity and decreased reliability. Other oxide aids are often insufficient in cooling effect, still requiring sintering above 1200°C, and typically require larger addition amounts, resulting in a significant increase in material loss and negating their low-loss advantage.

[0006] Secondly, single glass phase additives, such as borosilicate glass and phosphate glass, can be introduced. These additives can significantly reduce the sintering temperature to below 900℃, meeting the process window for low-temperature co-fired ceramics. However, to achieve effective densification, the amount of glass phase added is usually high, leading to a sharp increase in the dielectric loss of the material. The Q×f value can drop from hundreds of thousands of GHz to thousands of GHz, severely degrading high-frequency performance. At the same time, the introduction of the glass phase will also shift the temperature coefficient of the resonant frequency in the negative direction, often requiring the use of composite positive τf materials for compensation, which in turn causes a significant increase in the dielectric constant (>10), affecting its application in specific frequency bands.

[0007] In summary, most existing modification methods for magnesium silicate ceramics are "single-function" additive strategies, which are difficult to synergistically solve the core problem of the mutual constraints between "low-temperature sintering", "maintaining low loss" and "suitable dielectric constant and frequency-temperature stability". Summary of the Invention

[0008] The purpose of this invention is to propose a low-temperature co-fired microwave dielectric ceramic material and its preparation method, so as to solve the problem that existing magnesium silicate ceramics cannot solve the mutual constraints between "low-temperature sintering", "maintaining low loss" and "suitable dielectric constant and frequency temperature stability".

[0009] To achieve this objective, the present invention adopts the following technical solution: This invention provides a low-temperature co-fired microwave dielectric ceramic material, the raw material composition of which includes a ceramic main material of Mg2SiO4 and additives; the additives include 14-16 wt% CaTiO3 and 0-2 wt% W m O n And low-melting-point glass, comprising 0.5 to 1% of the main ceramic material, wherein W m O n It includes one or more of V2O5, CuO, Bi2O3 and B2O3.

[0010] In the low-temperature co-fired microwave dielectric ceramic material, the additives also include 0-1.5 wt% Li2O, which accounts for 0-1.5 wt% of the main ceramic material.

[0011] In the low-temperature co-fired microwave dielectric ceramic material, the low-melting-point glass comprises Li2CO3, MgO, ZnO, H3BO3 and SiO2, and the molar ratio of Li2CO3, MgO, ZnO, H3BO3 and SiO2 is (0.8~1.1):(0.8~1.1):(0.8~1.1):(1.8~2.1):(0.8~1.1).

[0012] This invention also provides a method for preparing a low-temperature co-fired microwave dielectric ceramic material, which includes the following steps: Preparation of Mg2SiO4 ceramic main material: MgO and SiO2 powders are mixed according to the formula to obtain the first mixed powder; the mixed powder is then heated to obtain Mg2SiO4 ceramic main material; Preparation of low-melting-point glass: Li2CO3, MgO, ZnO, H3BO3 and SiO2 powders are mixed according to the formula to obtain a second mixed powder; the second mixed powder is heated to a molten state; then, the molten second mixed powder is water-quenched to form glass; the glass is taken out, ground and dried to obtain low-melting-point glass; Ceramic powder preparation: Ceramic main material and additives are mixed to obtain ceramic powder; Press molding: Ceramic powder is pressed into shape to obtain a ceramic blank; Sintering: The ceramic blank is sintered to obtain microwave dielectric ceramic with low dielectric constant.

[0013] The method for preparing the low-temperature co-fired microwave dielectric ceramic material includes the following steps in the preparation of the Mg2SiO4 ceramic main material: mixing MgO and SiO2 powders with a purity of ≥99.5% in a molar ratio of MgO:SiO2=2:1, drying and grinding, and then holding at 1295~1305℃ for 2.5~3.5h to synthesize Mg2SiO4 powder.

[0014] The method for preparing the low-temperature co-fired microwave dielectric ceramic material includes the following steps in the preparation of low-melting-point glass: Li2CO3, MgO, ZnO, H3BO3, and SiO2 powders with a purity ≥ 99.5% are mixed in a molar ratio of (0.8~1.1):(0.8~1.1):(0.8~1.1):(1.8~2.1):(0.8~1.1), and heated at 1345~1352℃ for 2.5~3.5h to make the powders molten. The molten second mixed powder is then water-quenched to form glass. The glass is then removed, ground, and dried to obtain low-melting-point glass.

[0015] The method for preparing the low-temperature co-fired microwave dielectric ceramic material includes the following steps in the preparation of ceramic powder: mixing Mg2SiO4 ceramic main material, low-melting-point glass and other additives according to the ratio, and then drying and secondary grinding; subsequently, heating to the holding temperature and holding at the temperature, and cooling to obtain the ceramic main material.

[0016] The preparation method of the low-temperature co-fired microwave dielectric ceramic material includes the following steps in the pressing and molding step: adding 10-15 wt% of polyvinyl alcohol as the main ceramic material, mixing evenly, drying, and pressing into a ceramic blank.

[0017] The method for preparing the low-temperature co-fired microwave dielectric ceramic material includes the following steps in the sintering step: placing the ceramic blank at a temperature of 850-950℃ for 2-5 hours to sinter it into ceramic, thereby obtaining the low-temperature co-fired microwave dielectric ceramic material.

[0018] One of the technical solutions in this invention can have the following beneficial effects: The low-temperature co-fired microwave dielectric ceramic material is based on Mg2SiO4 and incorporates CaTiO3, Li2O, and W. m O n By combining low-melting-point glass with Mg2SiO4 ceramics, the sintering temperature of Mg2SiO4 ceramics was successfully reduced to the low-temperature co-fired ceramic window, while meeting the basic requirements of environmental protection and preserving its intrinsic advantage of ultra-low loss to the maximum extent. This solved the three core problems of "low-temperature sintering", "low dielectric constant" and "maintaining low loss" that are interrelated and mutually restrictive. Detailed Implementation

[0019] The technical solution of the present invention will be further illustrated below through specific embodiments. To facilitate understanding of the present invention, a more comprehensive description is provided below. 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.

[0020] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0021] 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 specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] This invention provides a low-temperature co-fired microwave dielectric ceramic material, the raw material composition of which includes a ceramic main material of Mg2SiO4 and additives; the additives include 14-16 wt% CaTiO3 and 0-2 wt% W m O n And low-melting-point glass, comprising 0.5 to 1% of the main ceramic material, wherein W m O n It includes one or more of V2O5, CuO, Bi2O3 and B2O3.

[0023] Mg₂SiO₄, as the main component of ceramics, primarily provides a low dielectric constant and a high Qf value, while CaTiO₃ modifies the temperature coefficient of the material. m O n It acts as a flux. Through CaTiO3 and W... m O n The combination with low-melting-point glass reduces the sintering temperature of Mg2SiO4 ceramic materials while ensuring their good microwave dielectric properties.

[0024] Since silver has a melting point of 961°C, to ensure that the electrodes do not melt, leak, or develop severe spheroidization during co-firing, the sintering temperature of microwave dielectric ceramic materials must be significantly lower than 960°C. In this field, a low sintering temperature should be ≤950°C. In actual production, to allow for a process window and safety margin, the target sintering temperature is set between 850°C and 950°C. In the field of low-temperature co-fired ceramics, a dielectric constant less than 10 is considered low.

[0025] The low-temperature co-fired microwave dielectric ceramic material is based on Mg2SiO4 combined with CaTiO3 and W. m O n By combining low-melting-point glass with Mg2SiO4 ceramics, the sintering temperature of Mg2SiO4 ceramics was successfully reduced to the low-temperature co-fired ceramic window, while meeting the basic requirements of environmental protection and preserving its intrinsic advantage of ultra-low loss to the maximum extent. This solved the three core problems of "low-temperature sintering", "low dielectric constant" and "maintaining low loss" that are interrelated and mutually restrictive.

[0026] Specifically, the additives also include 0-1.5 wt% Li2O in the amount of the ceramic main material.

[0027] In a preferred embodiment of the present invention, Li2O, Li2O-W was also added. m O n - Low-melting-point glass forms a ternary eutectic system to reduce the sintering temperature of the material.

[0028] In this preferred embodiment, Wm O n The actual substance is B2O3, and the ternary eutectic system is Li2O-B2O3-low-melting-point glass. During sintering, when the temperature reaches 450–650℃, it is in the low-temperature start-up and deep wetting stage. B2O3 melts first, forming the first ultra-low viscosity liquid phase. Li2O is usually added in the form of Li2CO3, which decomposes to form Li2O; Li2O rapidly dissolves in the B2O3 melt, forming a Li2O-B2O3 binary eutectic system, which dramatically increases the amount of liquid phase and makes the viscosity extremely low. This low-viscosity, highly active Li2O-B2O3 melt has extremely strong capillary force, which can rapidly penetrate into the smallest pores between ceramic powder particles, and even encapsulate every tiny Mg2SiO4 and CaTiO3 grain, laying the physical contact foundation for the subsequent mass transfer process.

[0029] As the temperature rises to 650–800℃, the glass enters a transitional phase between intermediate temperatures and interfacial activation, at which point the low-melting-point glass begins to soften and gradually melt. However, at this stage, the surface and internal pores of the low-melting-point glass particles are completely wetted by the Li₂O-B₂O₃ liquid phase formed in the first step. This Li₂O-B₂O₃ liquid phase acts as a flux, lowering the energy barrier for the melting of the low-melting-point glass particles themselves, thus promoting the melting process and allowing it to completely transform into a liquid phase at a temperature lower than its softening point. Simultaneously, the highly active Li₂O₃ in the Li₂O-B₂O₃ liquid phase… + and [B4O7] 2- Plasma can undergo a slight, controllable interfacial reaction with the surface of the main crystalline phase Mg2SiO4 particles, dissolving the sharp corners of the Mg2SiO4 particle surface and generating more mobile ions such as Mg2+. 2+ SiO4 2- It significantly activated the particle surface and reduced the activation energy of solid-phase material diffusion through the liquid phase.

[0030] The temperature continues to rise to the sintering temperature, which is 850–950℃, at which point it is in the high-temperature densification and mass transport stage, Li2O-W m O n The low-melting-point glass phases are completely fused, forming a homogeneous, stable, and viscosity-optimized composite liquid phase. This liquid phase exhibits moderate viscosity, high solubility, and a high diffusion coefficient. The viscosity-reducing effect of Li₂O provides good fluidity, while the addition of the low-melting-point glass prevents premature liquid phase loss or preform collapse due to excessively low viscosity. Furthermore, the presence of Li₂O continuously ensures high ion mobility in the liquid phase. Simultaneously, the low-melting-point glass provides Mg... 2+ Zn 2+ [SiO4] 2- Plasma is highly correlated with the composition of the host crystalline phase, making host crystalline phase materials such as Mg...2+ SiO4 2- The solubility and diffusion rate in this composite liquid phase are maximized.

[0031] Specifically, the low-melting-point glass comprises Li2CO3, MgO, ZnO, H3BO3 and SiO2, and the molar ratio of Li2CO3, MgO, ZnO, H3BO3 and SiO2 is (0.8~1.1):(0.8~1.1):(0.8~1.1):(1.8~2.1):(0.8~1.1).

[0032] In a specific embodiment of the present invention, the components of the low melting point glass include Li2CO3, MgO, ZnO, H3BO3 and SiO2, and the molar ratio of Li2CO3, MgO, ZnO, H3BO3 and SiO2 is 1:1:1:2:1.

[0033] This invention also provides a method for preparing a low-temperature co-fired microwave dielectric ceramic material, which includes the following steps: Preparation of Mg2SiO4 ceramic main material: MgO and SiO2 powders are mixed according to the formula to obtain the first mixed powder; the mixed powder is then heated to obtain Mg2SiO4 ceramic main material; Preparation of low-melting-point glass: Li2CO3, MgO, ZnO, H3BO3 and SiO2 powders are mixed according to the formula to obtain a second mixed powder; the second mixed powder is heated to a molten state; then, the molten second mixed powder is water-quenched to form glass; the glass is taken out, ground and dried to obtain low-melting-point glass; Ceramic powder preparation: Ceramic main material and additives are mixed to obtain ceramic powder; Press molding: Ceramic powder is pressed into shape to obtain a ceramic blank; Sintering: The ceramic blank is sintered to obtain microwave dielectric ceramic with low dielectric constant.

[0034] The low-temperature co-fired microwave dielectric ceramic material prepared by this invention has lower preparation requirements than traditional Mg2SiO4-based ceramics, and the sintering temperature and time are significantly reduced. Performance tests show that, compared to Mg2SiO4 microwave ceramics, it can achieve comparable microwave dielectric properties: dielectric constant εr is between 9 and 10, resonant frequency temperature coefficient τf is between -10 and +10 ppm / ℃, and Q×f value is between 60,000 and 100,000 GHz. It is expected to meet the requirements of microwave dielectric ceramic processes for microwave ceramic materials with low sintering temperature, high quality factor, and a wide temperature coefficient range.

[0035] Specifically, the steps in preparing Mg2SiO4 ceramic main material include the following steps: mixing MgO and SiO2 powders with a purity of ≥99.5% in a molar ratio of MgO:SiO2=2:1, drying and grinding, and then holding at 1295~1305℃ for 2.5~3.5h to synthesize Mg2SiO4 powder.

[0036] By adopting the above steps, the solid-state reaction can be effectively driven to generate Mg2SiO4, while avoiding excessive sintering or abnormal grain growth caused by excessively high temperature.

[0037] Specifically, the preparation of low-melting-point glass includes the following steps: mixing Li2CO3, MgO, ZnO, H3BO3, and SiO2 powders with a purity ≥ 99.5% according to a molar ratio of (0.8~1.1):(0.8~1.1):(0.8~1.1):(1.8~2.1):(0.8~1.1), heating at 1345~1352℃ for 2.5~3.5h to make the powders molten, and then water-quenching the molten second mixed powder to form glass. The glass is then removed, ground, and dried to obtain low-melting-point glass.

[0038] By adopting the above steps, it is ensured that the prepared low-melting-point glass can effectively optimize the sintering process of ceramics and guarantee that the low-temperature co-fired microwave dielectric ceramic material has good microwave dielectric properties.

[0039] Specifically, the ceramic powder preparation process includes the following steps: mixing Mg2SiO4 ceramic main material, low melting point glass and other additives according to the specified ratio, and then drying and secondary grinding; subsequently, heating to the holding temperature and holding at that temperature, and then cooling to obtain the ceramic main material.

[0040] The material components are uniformly mixed and the particles are refined through secondary grinding, and the physicochemical stability of the powder is ensured by drying. This significantly improves the uniformity, density and electrical properties of the final ceramic material, while also enhancing the controllability of the process.

[0041] Specifically, the pressing and molding step includes the following steps: adding 10-15 wt% of polyvinyl alcohol as the main ceramic material, mixing evenly, drying, and pressing into a ceramic blank.

[0042] Polyvinyl alcohol (PVA) transforms dry, loose ceramic powder into a green body with sufficient plasticity and mechanical strength. Furthermore, PVA decomposes upon heating, slowly and steadily burning and releasing gases during sintering. Pressing then shapes the ceramic powder into a specific form.

[0043] Specifically, the sintering step includes the following steps: placing the ceramic blank at a temperature of 850-950℃ for 2-5 hours to sinter it into ceramic, thereby obtaining a low-temperature co-fired microwave dielectric ceramic material.

[0044] The high temperature of 850–950℃ promotes the formation, stabilization and optimized growth of the target crystalline phase, while the long-term heat preservation of 3–6 hours ensures that the reaction has enough time to proceed fully.

[0045] Example Group A A method for preparing a low-temperature co-fired microwave dielectric ceramic material includes the following steps: Preparation of Mg2SiO4 ceramic main material: MgO and SiO2 powders with a purity of ≥99.5% were mixed in a molar ratio of MgO:SiO2=2:1, dried and ground, and then kept at 1300℃ for 3h to synthesize Mg2SiO4 powder. Preparation of low melting point glass: Li2CO3, MgO, ZnO, H3BO3 and SiO2 powders with a purity of ≥99.5% were mixed in a molar ratio of 1:1:1:2:1 and heated at 1350℃ for 3 hours to make the powders molten. The molten second mixed powder was then water-quenched to form glass. The glass was then removed, ground and dried to obtain low melting point glass. Ceramic powder preparation: Mg2SiO4 ceramic main material, low melting point glass and other additives are mixed according to the ratio, and then dried and ground twice; subsequently, the mixture is heated to the holding temperature and held at that temperature, and then cooled to obtain the ceramic main material; Pressing and molding: Add 10 wt% polyvinyl alcohol to the ceramic main material, mix evenly, dry, and press into a ceramic blank; Sintering: The ceramic blank is placed at the sintering temperature and kept at that temperature for 3 hours to sinter into ceramic, thus obtaining a low-temperature co-fired microwave dielectric ceramic material.

[0046] The sintering temperature and main components of the microwave ceramic are shown in Table 1.

[0047] Table 1 - Specific Parameters

[0048] Comparative Example 1 The preparation steps of Comparative Example 1 are the same as those of Example 2, except that the main components of the microwave ceramic are Mg2SiO4 + 10wt%CaTiO3 + 3wt%LiF, and the sintering temperature of Comparative Example 1 is the same as that of Example 2, which is 900℃.

[0049] Comparative Example 2 The preparation steps of Comparative Example 2 were the same as those of Example 2, except that the main components of the microwave ceramic were Mg2SiO4 + 10wt%CaTiO3 + 10wt%ZBS low-temperature glass, and the ZBS low-temperature glass had a composition of ZnO:B2O3:SiO2 = 6:2:2. The sintering temperature of Comparative Example 2 was 1000℃.

[0050] Comparative Example 3 The preparation steps of Comparative Example 3 were the same as those of Example 2, except that the main components of the microwave ceramic were Mg2SiO4 + 10wt%CaTiO3 + 1.5wt%LiF + 2wt%ZBS low-temperature glass, and the ZBS low-temperature glass composition was ZnO:B2O3:SiO2 = 6:2:2. The sintering temperature of Comparative Example 3 was the same as that of Example 2, which was 900℃.

[0051] The low-loss microwave ceramics obtained in Examples 1-8 and Comparative Examples 1-3 were subjected to performance tests, including dielectric constant εr, quality factor Q×f, and temperature coefficient of resonant frequency τf. The performance test method and procedure were carried out in accordance with the IEC60089-2-721 standard, and the results are shown in Table 2.

[0052] Table 2 - Test Results

[0053] Compared with Examples 1-8, Comparative Example 1 has a dielectric constant, Q×f value, frequency temperature coefficient, and sintering temperature that are comparable. However, the material that mainly lowers the sintering temperature in Comparative Example 1 is LiF, which poses a significant hazard to human health and the environment, contradicting national environmental protection policies. Furthermore, the formulation of the comparative example is not within the scope of the formulations in the examples.

[0054] Compared with Examples 1-8, Comparative Example 2 has a lower dielectric constant, but its sintering temperature is much higher than 950°C, and its sintering temperature is only Q×f=29222GHz, which is much lower than that of Examples 1-8.

[0055] Compared to Comparative Examples 3 (Examples 1-8), the dielectric constant, Q×f value, and frequency temperature coefficient are comparable to the sintering temperature. However, consistent with the disadvantages of Comparative Example 1, the main material used in this formulation to lower the sintering temperature is LiF, which poses significant risks to human health and the environment, contradicting national environmental protection policies and hindering industrial-scale production. Furthermore, the formulations in the comparative examples are not within the scope of the formulations in the examples.

[0056] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A low-temperature co-fired microwave dielectric ceramic material, characterized in that, Its raw material composition includes a ceramic main material with Mg2SiO4 as the component and additives; the additives include 14-16 wt% CaTiO3 and 0-2 wt% W as the ceramic main material. m O n And low-melting-point glass, comprising 0.5 to 1% of the main ceramic material, wherein W m O n It includes one or more of V2O5, CuO, Bi2O3 and B2O3.

2. The low-temperature co-fired microwave dielectric ceramic material according to claim 1, characterized in that, The additives also include 0-1.5 wt% Li2O, which accounts for 0-1.5 wt% of the main ceramic material.

3. The low-temperature co-fired microwave dielectric ceramic material according to claim 1, characterized in that, The low-melting-point glass comprises Li2CO3, MgO, ZnO, H3BO3 and SiO2, and the molar ratio of Li2CO3, MgO, ZnO, H3BO3 and SiO2 is (0.8~1.1):(0.8~1.1):(0.8~1.1):(1.8~2.1):(0.8~1.1).

4. A method for preparing a low-temperature co-fired microwave dielectric ceramic material, characterized in that, The method for preparing the low-temperature co-fired microwave dielectric ceramic material according to claims 1-3 includes the following steps: Preparation of Mg2SiO4 ceramic main material: MgO and SiO2 powders are mixed according to the formula to obtain the first mixed powder; the mixed powder is then heated to obtain Mg2SiO4 ceramic main material; Preparation of low-melting-point glass: Li2CO3, MgO, ZnO, H3BO3 and SiO2 powders are mixed according to the formula to obtain a second mixed powder; the second mixed powder is heated to a molten state; then, the molten second mixed powder is water-quenched to form glass; the glass is taken out, ground and dried to obtain low-melting-point glass; Ceramic powder preparation: Ceramic main material and additives are mixed to obtain ceramic powder; Press molding: Ceramic powder is pressed into shape to obtain a ceramic blank; Sintering: The ceramic blank is sintered to obtain microwave dielectric ceramic with low dielectric constant.

5. The method for preparing a low-temperature co-fired microwave dielectric ceramic material according to claim 4, characterized in that, The steps in preparing Mg2SiO4 ceramic main material include the following steps: mixing MgO and SiO2 powders with a purity of ≥99.5% in a molar ratio of MgO:SiO2=2:1, drying and grinding, and then holding at 1295~1305℃ for 2.5~3.5h to synthesize Mg2SiO4 powder.

6. The method for preparing a low-temperature co-fired microwave dielectric ceramic material according to claim 4, characterized in that, The preparation of low-melting-point glass includes the following steps: Li2CO3, MgO, ZnO, H3BO3, and SiO2 powders with a purity ≥99.5% are mixed in a molar ratio of (0.8~1.1):(0.8~1.1):(0.8~1.1):(1.8~2.1):(0.8~1.1), and heated at 1345~1352℃ for 2.5~3.5h to make the powders molten. The molten second mixed powder is then water-quenched to form glass. The glass is then removed, ground, and dried to obtain low-melting-point glass.

7. The method for preparing a low-temperature co-fired microwave dielectric ceramic material according to claim 4, characterized in that, The steps in preparing ceramic powder include: mixing Mg2SiO4 ceramic main material, low melting point glass and other additives according to the ratio, and then drying and secondary grinding; subsequently, heating to the holding temperature and holding at that temperature, and then cooling to obtain the ceramic main material.

8. The method for preparing a low-temperature co-fired microwave dielectric ceramic material according to claim 4, characterized in that, The pressing and molding process includes the following steps: adding 10-15 wt% polyvinyl alcohol to the ceramic main material, mixing evenly, drying, and pressing into a ceramic blank.

9. The method for preparing a low-temperature co-fired microwave dielectric ceramic material according to claim 4, characterized in that, The sintering process includes the following steps: placing the ceramic blank at 850-950℃ for 2-5 hours to sinter it into ceramic, thereby obtaining a low-temperature co-fired microwave dielectric ceramic material.

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