A low-loss temperature-stable microwave composite dielectric material, its preparation method and application

Abstract

The present invention provides a low-loss temperature-stable microwave composite dielectric material, a preparation method thereof and an application. The preparation method is as follows: first, strontium titanate, barium titanate or calcium titanate ceramic particles are uniformly mixed into a polymer resin through ultrasonic and high-speed mechanical stirring treatment to obtain a mixed solution, and a three-dimensional woven spacer fabric is used as a reinforcement to be compounded and molded with the polymer resin mixed solution, and its resonance frequency temperature coefficient is adjusted, so as to obtain a low-loss temperature-stable microwave composite dielectric material. The microwave composite dielectric material prepared by the present invention has a high hollow degree, can effectively reduce the dielectric loss of the structure, and realizes low density, low dielectric constant, low dielectric loss and low resonance frequency temperature coefficient, and can be widely used in the manufacture of microwave devices such as resonators, antennas, filters, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave dielectric materials, and specifically provides a low-loss temperature-stable microwave composite dielectric material, a preparation method thereof, and an application thereof. Background Art

[0002] Microwave dielectric materials are widely used in filters, resonators, and microwave dielectric substrates. With the development of communication technologies towards high frequency and high speed, it is required that microwave dielectric materials have a low dielectric constant ( ), to ensure the signal transmission rate, and a low temperature coefficient of resonant frequency ( ) to reduce or control the change in dielectric properties caused by temperature in the circuit operating characteristics and ensure the frequency stability of the device during operation. Therefore, microwave dielectric materials with low dielectric constant, low dielectric loss, and high temperature stability have always been a research hotspot in recent years. However, when reducing the dielectric constant, it is difficult for the temperature coefficient of resonant frequency to approach zero.

[0003] Microwave dielectric ceramics are ideal microwave dielectric materials due to the designability of their temperature coefficient of resonant frequency and the diversity of their dielectric constants. In recent years, researchers have adjusted by adding multiple ceramic materials with opposite temperature coefficients of resonant frequency to achieve microwave dielectric materials with a low temperature coefficient of resonant frequency. However, the high dielectric constant of ceramics results in a low signal transmission rate, high brittleness, low dielectric breakdown strength, and more stringent processing conditions, which hinder their application adaptability. The ceramic-polymer composite materials prepared by combining microwave dielectric ceramics with polymers can combine the advantages of both and adjust the dielectric properties of the composite materials. However, this method requires filling a large volume content of ceramics, resulting in problems such as low strength, poor fluidity, and poor flexibility of the composite materials.

[0004] Therefore, microwave dielectric materials that can simultaneously meet the requirements of high strength, low dielectric constant, and low temperature coefficient of resonant frequency still need to be developed. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a low-loss temperature-stable microwave composite dielectric material, a preparation method thereof, and an application thereof, solving the problems raised in the above background art.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0007] According to the first aspect of the present invention, a preparation method of a low-loss temperature-stable microwave composite dielectric material is provided. The ceramic material is uniformly mixed into the polymer resin through ultrasonic and high-speed mechanical stirring treatment to obtain a mixed solution, and a three-dimensional woven spacer fabric is used as a reinforcement to be compounded with the polymer resin mixed solution to obtain the microwave composite dielectric material.

[0008] In existing microwave composite dielectric materials, ceramic materials and short fibers are filled into polymers. Although the preparation method is simple, the obtained microwave composite dielectric materials cannot simultaneously meet the market requirements in terms of dielectric constant, dielectric loss, and resonant frequency temperature. The preparation method of the temperature-stable microwave composite dielectric material provided by the present invention first uniformly disperses ceramic materials into a resin, and then uniformly coats a mixed solution containing ceramic materials and the resin on the surface of reinforcing fibers with a three-dimensional woven spacer structure. While the resin cures, it combines with the reinforcing fibers and wraps the reinforcing fibers. The added ceramic materials are also uniformly dispersed on the surface of the reinforcing fibers, reducing the phenomenon of local electric field concentration. As a result, the obtained microwave composite dielectric material is light in weight, has a low dielectric constant, a low dielectric loss, and a resonant frequency temperature coefficient close to zero.

[0009] Preferably, the raw material of the three-dimensional woven spacer fabric is selected from at least one of glass fiber, aramid fiber, polyethylene fiber, basalt fiber, polyphenylene sulfide fiber, and polytetrafluoroethylene fiber.

[0010] Preferably, the ceramic material is selected from at least one of strontium titanate, barium titanate, and calcium titanate.

[0011] Preferably, the polymer resin is selected from thermosetting resins or thermoplastic resins.

[0012] Specifically, the polymer resin is selected from at least one of epoxy resin, polyimide resin, phenolic resin, polytetrafluoroethylene resin, vinyl resin, and polypropylene resin.

[0013] Preferably, in the mixed solution, the ceramic material accounts for 5-15 wt% of the mixed solution.

[0014] Preferably, the composite molding process is selected from one of resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM), or hand lay-up molding process.

[0015] According to the second aspect of the present invention, there is provided a low-loss temperature-stable microwave composite dielectric material obtained by the above preparation method. The resonant frequency temperature coefficient of the microwave composite dielectric material is -30 ppm / °C to +30 ppm / °C; the dielectric constant of the microwave composite dielectric material is 1.3 to 2, and the dielectric loss ≤ 0.008.

[0016] Preferably, the tensile strength of the panel is 100-200 MPa, and the flat compressive strength is 4-10 MPa.

[0017] According to the third aspect of the present invention, there is provided an application of a low-loss temperature-stable microwave composite dielectric material in filters, resonators, and microwave dielectric substrates.

[0018] The present invention provides a low-loss temperature-stable microwave composite dielectric material, a preparation method thereof, and an application thereof, having the following beneficial effects:

[0019] A preparation method of a low-loss temperature-stable microwave composite dielectric material provided by this solution is as follows: First, ceramic materials are evenly dispersed in a resin, and then a mixed solution containing ceramic materials and the resin is evenly coated on the surface of a three-dimensional woven spacer structure fabric with a hollow structure. While the resin cures, it combines with the reinforcing fibers and wraps the reinforcing fibers, and the added ceramic materials are also evenly dispersed on the surface of the reinforcing fibers. By adopting a three-dimensional woven spacer structure, the internal electric field distribution of the microwave composite dielectric material is optimized, the dielectric constant and dielectric loss of the overall material are reduced, and at the same time, ceramic materials are introduced to regulate the dielectric temperature stability of the overall material. Thus, a low-loss temperature-stable microwave composite dielectric material is obtained, which can simultaneously meet the characteristics of light weight, low dielectric constant, low dielectric loss, and a resonance frequency temperature coefficient close to zero. Specific embodiments

[0020] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] The present invention discloses a preparation method of a low-loss temperature-stable microwave composite dielectric material, comprising the following steps:

[0022] Step 1: First, a three-dimensional woven spacer fabric with a hollow structure is prepared by three-dimensional weaving;

[0023] Step 2: Mix ceramic materials with a polymer resin, and fully stir through ultrasonic and mechanical stirring treatments to obtain a uniformly mixed mixed solution containing ceramic materials and the resin;

[0024] Step 3: Adopt a hand lay-up molding, VARTM or RTM molding process to composite the reinforcing fibers with the mixed solution to obtain a low-loss temperature-stable microwave composite dielectric material.

[0025] This application uses a three-dimensional hollow structure composite material to eliminate most of the lossy materials while maintaining the integrity and mechanical properties of the material, effectively reducing the dielectric constant and dielectric loss of the overall material; ceramics have a large resonance frequency temperature coefficient. Introducing ferroelectric phase ceramics into the material enables the material to have the intrinsic dielectric response of ceramics. Therefore, the dielectric temperature stability of the overall material can be regulated, thereby obtaining a temperature-stable microwave composite dielectric material.

[0026] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0027] Example 1

[0028] (1) 1500 denier aramid fibers were used to obtain a 6 mm thick three-dimensional woven spacer aramid fabric as the reinforcing aramid fibers through three-dimensional weaving technology;

[0029] (2) Strontium titanate ceramics with a particle size of 5 μm were mixed with polyimide resin and fully stirred by ultrasonic treatment and a high-speed mixer to obtain a mixed solution with strontium titanate ceramics accounting for 10 wt% of the total content;

[0030] (3) By using the hand lay-up molding method, the mixed solution was evenly coated on the surface of the reinforcing aramid fibers, allowing the mixed solution to fully penetrate into the fabric. It was pre-cured at 160 °C for 30 minutes, pre-cured at 260 °C for 40 minutes, and cured at 310 °C for 40 minutes. An imidization reaction occurred during the curing process to obtain a microwave composite dielectric material.

[0031] Example 2

[0032] (1) 300 tex glass fibers were used to obtain a 6 mm thick three-dimensional woven spacer glass fabric as the reinforcing glass fibers through three-dimensional weaving technology;

[0033] (2) Strontium titanate ceramics with a particle size of 5 μm were mixed with epoxy resin and fully stirred by ultrasonic treatment and a high-speed mixer to obtain a mixed solution with strontium titanate ceramics accounting for 10 wt% of the total content;

[0034] (3) The VARTM molding process was used to fill the mixed solution into the reinforcing glass fibers, controlling the vacuum degree to be -0.1 MPa. It was pre-cured at 50 °C for 3 h and cured at 70 °C for 7 h to obtain a microwave composite dielectric material.

[0035] Example 3

[0036] (1) 300 tex basalt fibers were used to obtain a 6 mm thick woven spacer structure as the reinforcing basalt fibers through three-dimensional weaving technology;

[0037] (2) Strontium titanate ceramics with a particle size of 5 μm were mixed with vinyl resin, curing agent (methyl ethyl ketone), and catalyst (cobalt isooctoate) and fully stirred by ultrasonic treatment and a high-speed mixer to obtain a mixed solution with strontium titanate ceramics accounting for 15 wt% of the total content;

[0038] (3) The mixed solution was filled into the reinforcing glass fiber through the VARTM molding process, the vacuum degree was controlled at -0.1 MPa, and it was completely cured at room temperature for 4 to 8 hours to obtain a ceramic-filled basalt fiber / vinyl resin temperature-stable microwave composite dielectric material.

[0039] Example 4

[0040] The preparation method of this embodiment is the same as that of embodiment 1, except that the strontium titanate ceramic accounts for 5 wt % of the mixed solution.

[0041] Example 5

[0042] The preparation method of this embodiment is the same as that of embodiment 1, except that the strontium titanate ceramic accounts for 15 wt % of the mixed solution.

[0043] Comparative Example 1

[0044] 10wt% of strontium titanate ceramic, 15wt% of aramid fiber powder and 65wt% of epoxy resin and curing agent are fully mixed by ultrasonic treatment and high-speed mechanical stirring to obtain a mixed solution; the mixed solution is placed in a mold for pre-curing at 50°C for 2 hours, and then cured at 80°C for 6 hours to obtain a microwave dielectric composite material.

[0045] Comparative Example 2

[0046] The preparation method of this comparative example is the same as that of Example 1, except that in this comparative example, the strontium titanate ceramic accounts for 0wt% of the mixed solution.

[0047] Comparative Example 3

[0048] The preparation method of this comparative example is the same as that of Example 1, except that in this comparative example, strontium titanate ceramic accounts for 20 wt % of the mixed solution.

[0049] The performance tests of the microwave dielectric composite materials prepared in Examples 1-5 and Comparative Examples 1-3 were respectively carried out, as shown in Table 1.

[0050] Table 1

[0051]

[0052] From the comparison between Examples 1 to 3 and Comparative Example 1, it can be seen that by adding ceramic particles to the composite material, the temperature coefficient of resonance frequency of the material can be regulated to achieve a microwave composite dielectric material with a low temperature coefficient of resonance frequency. However, the traditional solid structure has an insignificant effect on the regulation of dielectric properties at low ceramic filling contents. The temperature coefficient of resonance frequency of the microwave dielectric material satisfies the mixing rule. Therefore, by adding materials with different temperature coefficients of resonance frequency, the overall temperature coefficient of resonance frequency can be regulated. The present invention combines a three-dimensional woven spacer structure composite material. Since most of the lossy and dielectrically unstable parts are eliminated, a temperature-stable microwave composite dielectric material can be obtained by modifying with a small amount of ceramic particles ( ), while ensuring that the composite material has a low dielectric loss. In addition, for the traditional method of improving the mechanical properties of ceramic-polymer materials, a microwave dielectric composite material prepared by adding short fibers to the ceramic-polymer resin has a tensile strength of up to 80 MPa, but the improvement effect of short fibers on the mechanical properties of the composite material is not significant. The present invention combines the excellent mechanical and electrical comprehensive properties of fiber-reinforced composite materials and the dielectric property regulation effect of ceramic materials to achieve a ceramic-modified fiber-reinforced composite material with high strength.

[0053] From the comparison between Example 1, Examples 4 - 5 and Comparative Examples 2 - 3, it can be seen that when the strontium titanate ceramic filling content is between 5 wt% and 15 wt%, a microwave composite dielectric material with a low temperature coefficient of resonance frequency can be achieved. By incorporating ceramic particles into the resin matrix of the fiber-reinforced composite material, the composite material has the intrinsic dielectric response of strontium titanate ceramics, thereby regulating the stability of the dielectric properties of the composite material. When the strontium titanate content is 10 wt%, the temperature coefficient of resonance frequency of the composite material is close to zero, having good temperature stability and can be applied to environments with extremely high requirements for temperature stability. When the strontium titanate content exceeds 10 wt%, the temperature coefficient of resonance frequency of the composite material continuously increases in the positive direction. Therefore, by regulating the content of strontium titanate ceramics, the overall dielectric temperature stability of the composite material can be regulated, thereby preparing a temperature-stable microwave composite dielectric material.

[0054] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a low-loss temperature-stable microwave composite dielectric material, characterized in that: The ceramic material is uniformly mixed into the polymer resin by ultrasonic and high-speed mechanical stirring to obtain a mixed solution, and a three-dimensional woven spacer fabric is used as a reinforcement to perform composite molding with the polymer resin mixed solution to obtain the microwave composite dielectric material; In the mixed solution, strontium titanate accounts for 10 wt % of the mixed solution.

2. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: The three-dimensional woven spacer fabric is made of at least one of glass fiber, aramid fiber, polyethylene fiber, basalt fiber, polyphenylene sulfide fiber and polytetrafluoroethylene fiber.

3. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: The polymer resin is selected from thermosetting resins or thermoplastic resins.

4. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: The polymer resin is selected from at least one of epoxy resin, polyimide resin, phenolic resin, polytetrafluoroethylene resin, vinyl resin and polypropylene resin.

5. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: The composite molding process is selected from resin transfer molding or hand lay-up molding, wherein the resin transfer molding is selected from vacuum assisted resin transfer molding.

6. A low-loss, temperature-stable microwave composite dielectric material obtained by the preparation method according to any one of claims 1 to 5, characterized in that: The resonant frequency temperature coefficient of the microwave composite dielectric material is -30ppm / °C to +30ppm / °C; the dielectric constant of the microwave composite dielectric material is 1.3 to 2, and the dielectric loss is ≤0.

008.

7. The low-loss temperature-stable microwave composite dielectric material according to claim 6, characterized in that: The panel tensile strength of the temperature-stable microwave composite dielectric material is 100-200 MPa, and the flat compressive strength is 4-10 MPa.

8. Use of the low-loss, temperature-stable microwave composite dielectric material according to claim 6 or 7 in filters, resonators and microwave dielectric substrates.

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