FPC high-frequency material for improving signal transmission efficiency and preparation method thereof

Abstract

The invention relates to the technical field of polymer composite materials, in particular to an FPC high-frequency material for improving signal transmission efficiency and a preparation method of the FPC high-frequency material. According to the invention, the fluorine-containing diamine monomer of polyimide is designed to prepare a block polymerization type macromolecule containing tert-butyl and benzotrifluoride as the fluorine-containing diamine monomer to participate in the synthesis process of polyimide, so that the formed polyimide molecular chain contains a large amount of fluorine element; the dielectric constant and dielectric loss of the polyimide material are reduced, and the high-frequency signal transmission efficiency is improved. Chemical crosslinking of the modified mesoporous silica and a polyimide matrix is realized by adopting a chemical bond connection mode, so that the modified mesoporous silica is uniformly dispersed in the form of chemical crosslinking points, and a hollow structure can be introduced into the polyimide material, so that the dielectric constant of the polyimide material and the dielectric loss can be further reduced; and the high-frequency signal transmission efficiency and the water resistance are improved.

Description

Technical Field

[0001] This application relates to the technical field of polymer composite materials, and particularly relates to an FPC high-frequency material for improving signal transmission efficiency and a preparation method thereof. Background Art

[0002] Flexible Printed Circuit Board (FPC) is also known as "FPC circuit board", which is a printed circuit board made of a flexible polymer film as the base material and covering layer. Therefore, in addition to high wiring density and light weight, it can be freely bent, wound or even folded, with very strong adaptability to spatial layout. Using FPC circuit boards to replace traditional rigid printed circuit boards can greatly reduce the volume and weight of various electronic products, and it is an important material for the current development of electronic products towards high density, miniaturization, thinness and lightness.

[0003] The composition of FPC circuit boards mainly includes four major types of materials: polymer base materials, copper foils, adhesives and polymer covering films. Currently, the polymer materials used as base materials and covering films in FPC are mainly polyester films (PET) and polyimide films (PI). Among them, polyimide films are the most widely used. However, due to the disadvantages of large dielectric constant and loss factor, high hygroscopicity and uncontrollable thermal expansion coefficient of polyimide films, the performance of FPC circuit boards based on polyimide is not stable enough, and the delay and loss of high-frequency transmission are very serious, and it can no longer meet the requirements of high-frequency and high-speed information transmission in the current 5G era. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, this application provides an FPC high-frequency material for improving signal transmission efficiency and a preparation method thereof. The FPC high-frequency material prepared in this application has low hygroscopicity, low dielectric constant and dielectric loss, high temperature resistance, and excellent mechanical properties. It is suitable for application in automotive electronic systems, especially in communication equipment with strict requirements for high-frequency signals, to improve signal quality and reduce electromagnetic interference.

[0005] In the first aspect, this application provides a preparation method for an FPC high-frequency material for improving signal transmission efficiency, and adopts the following technical scheme: A preparation method for an FPC high-frequency material for improving signal transmission efficiency, comprising the following steps: S1. According to the mass parts, add fluorinated diamine monomers and hydrophobic monomers into N,N-diethylformamide, mechanically stir evenly, fill nitrogen as the protective gas, and react for 3 - 4 h under continuous stirring to obtain a precursor solution; S2. According to the parts by mass, add the modified mesoporous silica and the coupling agent into the precursor solution, ultrasonically disperse for 50 - 60 min, then continue to add the phase transfer catalyst tetrabutylammonium chloride into the dispersion, control the temperature at 60 - 65 °C, keep warm and stir for 3 - 4 h, and discharge to obtain the polyimide composite slurry; S3. Let the polyimide composite slurry stand for 30 - 40 min, remove bubbles under vacuum, then uniformly coat it on the surface of the copper foil, control the coating thickness to be 23 - 27 μm, then place the whole copper foil in a vacuum drying oven, start the heating program for thermal imidization, take it out, and peel off the substrate to obtain the FPC high-frequency material for improving signal transmission efficiency.

[0006] By adopting the above technical solution, the fluorinated diamine monomer and the hydrophobic monomer: these two monomers are used to prepare the precursor solution through mechanical stirring and reaction. The fluorinated diamine monomer helps to reduce the dielectric constant and dielectric loss of the polyimide material. At the same time, the introduced tert-butyl and trifluoromethylbenzene block polymerized macromolecules improve the hydrophobicity of the material. The modified mesoporous silica and the coupling agent: the modified mesoporous silica is combined with the polyimide matrix in the form of chemical cross-linking points, improving the mechanical properties and thermal stability of the material. At the same time, the uniform dispersion of the modified mesoporous silica can introduce a hollow structure, further reducing the dielectric constant and dielectric loss. The phase transfer catalyst tetrabutylammonium chloride: adding the phase transfer catalyst during the reaction helps to improve the reaction efficiency and the uniformity of the product. Step S1: Through mechanical stirring and reaction under nitrogen protection, ensure that the fluorinated diamine monomer and the hydrophobic monomer react fully to form a stable precursor solution. Step S2: Add the modified mesoporous silica and the coupling agent into the precursor solution, and ensure the uniform distribution of the materials through ultrasonic dispersion. At the same time, add the phase transfer catalyst tetrabutylammonium chloride and control the reaction temperature to further improve the reaction efficiency and product quality. Step S3: Ensure the uniformity and stability of the polyimide composite slurry through standing and vacuum defoaming. Coat it on the surface of the copper foil and conduct thermal imidization treatment to finally obtain the FPC high-frequency material with low hygroscopicity, low dielectric constant and dielectric loss, high temperature resistance and excellent mechanical properties. Through the synergistic effect of these steps and components, the FPC high-frequency material prepared in this application can effectively improve the signal transmission efficiency, and at the same time has good water resistance and mechanical properties, and is applicable to fields such as automotive electronic systems and communication equipment.

[0007] Preferably, in step S1, the mass ratio of the fluorinated diamine monomer, the hydrophobic monomer and N,N-diethylformamide is 15:3.5 - 4:500.

[0008] Preferably, in step S1, the preparation method of the fluorinated diamine monomer is as follows: Add tert-butyl diethanolamine and xylene into a polymerization kettle filled with nitrogen, start stirring, and after forming a uniform reaction solution, add a sodium hydroxide solution with a mass fraction of 30%. Stir at 60-65 °C for 2-3 h, then add 3,5-dibromobenzotrifluoride into the polymerization kettle. After adding, raise the temperature to 80-85 °C, keep warm and stir for 4.5-5 h. Then add a capping agent, 2-chloroethylamine hydrochloride, into the polymerization kettle, keep warm for 70-80 min, evaporate the solvent, cool down and discharge to obtain the fluorinated diamine monomer.

[0009] By adopting the above technical solution, in the process of preparing the fluorinated diamine monomer in step S1, tert-butyl diethanolamine and xylene first form a uniform reaction solution. Subsequently, a sodium hydroxide solution is added for reaction, and this step is mainly to introduce fluorine elements and tert-butyl structures. The addition of 3,5-dibromobenzotrifluoride is to further introduce fluorine elements and form the required fluorinated diamine structure. The finally added capping agent, 2-chloroethylamine hydrochloride, is to complete the polymerization reaction and ensure the structure and performance of the final product. The functions of the prepared fluorinated diamine monomer in the polyimide synthesis process are mainly reflected in the following aspects: 1) Reducing the dielectric constant and dielectric loss: The fluorine elements in the fluorinated diamine monomer can significantly reduce the dielectric constant of the polyimide material and reduce the dielectric loss, which is crucial for improving the high-frequency signal transmission efficiency. 2) Improving the hydrophobicity: The tert-butyl and benzotrifluoride block copolymer macromolecules in the fluorinated diamine monomer can make the polyimide material exhibit extremely strong hydrophobicity, improving the problem of reduced water resistance caused by the introduction of fluorine elements. 3) Improving the mechanical properties: The polymeric structure of the fluorinated diamine monomer reduces the content of imide heterocycles in the prepared polyimide molecular chain, affecting its mechanical properties. By chemically cross-linking the modified mesoporous silica and the polyimide matrix through chemical bond connection methods, the mechanical properties of the polyimide material can be improved. 4) Improving the water resistance and thermal stability: The uniform dispersion of the modified mesoporous silica can introduce a hollow structure into the polyimide material, further reducing the dielectric constant and dielectric loss of the polyimide material, while improving the water resistance and thermal stability. In summary, the synergistic effect of the fluorinated diamine monomer in the whole preparation process is multi-faceted. It not only improves the high-frequency signal transmission efficiency but also improves the hydrophobicity, mechanical properties and water resistance of the material. This is crucial for improving the performance of FPC high-frequency materials.

[0010] Preferably, the mass ratio of tert-butyl diethanolamine, xylene, 30% sodium hydroxide solution, 3,5-dibromobenzotrifluoride and 2-chloroethylamine hydrochloride is 5:40-50:55:8-8.5:2-2.3.

[0011] Preferably, in step S1, the hydrophobic monomer is one of perfluorohexyl dianhydride and 4,4'-(hexafluoroisopropanol) benzophenone tetracarboxylic dianhydride.

[0012] Preferably, in step S2, the mass ratio of the modified mesoporous silica, coupling agent, precursor solution and tetrabutylammonium chloride is 6-7:0.2-0.3:100:0.4-0.5.

[0013] Preferably, in step S2, the preparation method of the hydrophobic modified mesoporous silica includes the following steps: S71. According to the mass parts, add 100 parts of mesoporous silica into a solution composed of 300 parts of absolute ethanol and 50 parts of deionized water, ultrasonically disperse for 30-40 min, then mechanically stir and mix at a speed of 1500-1800 rpm for 50-60 min to obtain a mixed solution. Slowly drop 3-4 parts of γ-aminopropyltriethoxysilane into the mixed solution, react at 40-45 °C for 5-6 h, centrifuge, wash, and vacuum dry to obtain silane-modified mesoporous silica; S72. According to the mass parts, heat a dimethylformamide solution of 200 parts of trifluoroacetic anhydride with a mass concentration of 2% to 90 °C, add 100 parts of silane-modified mesoporous silica, and adjust the pH of the dispersion to 9-10 with a 10% sodium hydroxide aqueous solution, react at a constant temperature for 3-4 h, filter, wash with water, and dry to obtain hydrophobic modified mesoporous silica.

[0014] By adopting the above technical solutions, the functions of the prepared modified mesoporous silica are as follows: 1) Chemical cross-linking: The modified mesoporous silica forms chemical cross-linking points with the polyimide matrix through chemical bonds, which helps to improve the mechanical properties and thermal stability of the material. 2) Introduction of hollow structure: The dispersion of mesoporous silica helps to introduce a hollow structure into the polyimide material, which can further reduce the dielectric constant of the material and reduce dielectric loss. 3) Hydrophobic property: The fluorine-containing groups introduced through chemical modification form a hydrophobic layer, improving the water resistance of the material. The coupling agent helps to enhance the interfacial interaction between the modified mesoporous silica and the polyimide matrix, thereby improving the overall performance of the material. The addition of the modified mesoporous silica and the coupling agent act together on the polyimide matrix, and significantly improve the mechanical properties of the material through chemical cross-linking and interfacial strengthening. The hollow structure introduced by the modified mesoporous silica and the hydrophobic property of the fluorine-containing groups act together to reduce the dielectric constant of the material and reduce dielectric loss, thereby optimizing the dielectric properties of the material. The hydrophobic property of the fluorine-containing groups combined with the structural characteristics of the modified mesoporous silica further improves the water resistance of the material. In summary, the modified mesoporous silica plays a key role in the preparation process of FPC high-frequency materials. They act synergistically through various means such as chemical cross-linking, interfacial strengthening, introduction of hollow structure and hydrophobic property, and jointly improve the mechanical properties, dielectric properties and water resistance of the material. This is of great significance for the development of high-performance FPC high-frequency materials.

[0015] Preferably, in step S2, the coupling agent is composed of vinyltriethoxysilane and tetra-isopropyl bis(dioctylphosphite) titanate in a mass ratio of 3:4. By adopting the above technical solution, a coupling agent is a substance that can chemically react with two substances with different properties or states simultaneously, and is used to improve the interfacial properties between these two substances. Vinyltriethoxysilane can react with the hydroxyl groups on the surface of silica to form chemical bonds, thereby improving the bonding strength between silica and the polyimide matrix. At the same time, vinyltriethoxysilane can undergo a cross-linking reaction under the action of ultraviolet light or heat to form a stable polymer network structure, further enhancing the mechanical properties and heat resistance of the material. Tetra-isopropyl bis(dioctylphosphite) titanate is an organic titanate coupling agent. It can react with the hydroxyl groups on the surface of silica to form chemical bonds, and can also react with the imide groups in the polyimide matrix to form chemical bonds. This coupling agent can not only improve the bonding strength between silica and the polyimide matrix, but also improve the heat resistance and mechanical properties of the material. The synergistic effect between vinyltriethoxysilane and tetra-isopropyl bis(dioctylphosphite) titanate is mainly reflected in the following aspects: 1) Interface enhancement: The two act together between the surface of silica and the polyimide matrix, and can form stable chemical bond connections to improve the bonding strength of the interface. 2) Cross-linking network formation: Vinyltriethoxysilane can form a cross-linking network structure under the action of ultraviolet light or heat, while tetra-isopropyl bis(dioctylphosphite) titanate can further enhance this cross-linking effect, thereby improving the mechanical properties and heat resistance of the material. 3) Hydrophobicity improvement: Tetra-isopropyl bis(dioctylphosphite) titanate can react with fluorine-containing groups to form a hydrophobic layer, while vinyltriethoxysilane can react with the hydroxyl groups on the surface of silica to form chemical bonds, and they act together to improve the hydrophobic property of the material and reduce the dielectric constant and dielectric loss. In summary, the synergistic effect of vinyltriethoxysilane and tetra-isopropyl bis(dioctylphosphite) titanate is crucial for improving the performance of FPC high-frequency materials.

[0016] Preferably, in step S3, the heating program is to keep the temperature at 150 °C for 2 h, 230 °C for 1 h, and 310 °C for 1.3 h respectively.

[0017] In a second aspect, the present application provides an FPC high-frequency material for improving signal transmission efficiency, adopting the following technical solution: As a general technical concept, the present application also provides the above-mentioned FPC high-frequency material for improving signal transmission efficiency, which is prepared by using the preparation method of the above-mentioned FPC high-frequency material for improving signal transmission efficiency.

[0018] In summary, the beneficial technical effects of the present application: 1. Optimization of material properties: By designing the structures of fluorinated diamine monomers and modified mesoporous silica, the present application successfully prepared FPC high-frequency materials with low hygroscopicity, low dielectric constant and dielectric loss, high temperature resistance, and excellent mechanical properties. These characteristics are particularly important for high-frequency signal transmission as they directly affect the signal quality and transmission efficiency.

[0019] 2. Improvement of signal transmission efficiency: Due to the strong electronegativity and low polarizability of fluorine elements, the introduction of fluorinated diamine monomers significantly reduces the dielectric constant and dielectric loss of polyimide, thereby optimizing the high-frequency signal transmission efficiency. At the same time, the introduction of modified mesoporous silica further reduces the dielectric constant and dielectric loss.

[0020] 3. Improvement of water resistance: By introducing tert-butyl chain segments and fluorine-containing groups into the polyimide molecular chain, the present application improves the hydrophobicity of the material and solves the problem of reduced water resistance caused by the introduction of fluorine elements.

[0021] 4. Enhancement of mechanical properties: The chemical crosslinking between modified mesoporous silica and the polyimide matrix improves the mechanical properties of the material. At the same time, the uniform dispersion of modified mesoporous silica can also introduce a hollow structure into the polyimide material, further enhancing the mechanical properties.

[0022] 5. Enhancement of thermal stability: The modification treatment of mesoporous silica enhances the thermal stability of FPC high-frequency materials, which is particularly important for applications in high-temperature environments such as automotive electronic systems.

[0023] 6. Solution to the signal attenuation problem: The insulation and thermal stability of modified mesoporous silica solve the problem of severe signal attenuation of traditional FPC materials in high-frequency environments and improve the signal transmission efficiency. Detailed implementation manners

[0024] The following will describe the implementation schemes of the present application in detail in combination with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the examples, they are carried out under conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0025] In the following examples and preparation examples, 1 part represents 300 g.

[0026] Preparation Example 1 Preparation of fluorinated diamine monomer The preparation method of the fluorine-containing diamine monomer is as follows: Add 5 parts of tert-butyl diethanolamine and 45 parts of xylene into a polymerization kettle filled with nitrogen. Start stirring. After forming a uniform reaction solution, add 55 parts of a sodium hydroxide solution with a mass fraction of 30%. Stir at 63°C for 2.3 h, then add 8.3 parts of 3,5-dibromobenzotrifluoride into the polymerization kettle. After adding, raise the temperature to 83°C and continue to keep warm and stir for 4.8 h. Then add 2.1 parts of a capping agent, 2-chloroethylamine hydrochloride, into the polymerization kettle, keep warm for 75 min, evaporate the solvent, cool down and discharge to obtain the fluorine-containing diamine monomer.

[0027] Preparation Example 2 Preparation of Hydrophobically Modified Mesoporous Silica The preparation method of hydrophobically modified mesoporous silica includes the following steps: S71: According to the mass parts, add 100 parts of mesoporous silica with an average pore diameter of 20 nm into a solution composed of 300 parts of absolute ethanol and 50 parts of deionized water, ultrasonically disperse for 35 min, and then mechanically stir and mix at a speed of 1700 rpm for 55 min to obtain a mixed solution. Slowly add 3.4 parts of γ-aminopropyltriethoxysilane to the mixed solution, react at 43°C for 5.5 h, centrifuge, wash, and vacuum dry to obtain silane-modified mesoporous silica; S72: According to the mass parts, heat 200 parts of a dimethylformamide solution of trifluoroacetic anhydride with a mass concentration of 2% to 90°C, add 100 parts of silane-modified mesoporous silica, and adjust the pH of the dispersion to 9.4 with a sodium hydroxide aqueous solution with a mass concentration of 10%. React at a constant temperature for 3.5 h, filter, wash with water, and dry to obtain hydrophobically modified mesoporous silica.

[0028] Example 1 A preparation method of an FPC high-frequency material for improving signal transmission efficiency includes the following steps: S1: According to the mass parts, add 15 parts of fluorine-containing diamine monomer and 3.5 parts of perfluorohexyl dianhydride into 500 parts of N,N-diethylformamide, mechanically stir evenly, fill with nitrogen as a protective gas, and react for 3 h under continuous stirring to obtain a precursor solution; S2: According to the mass parts, add 6 parts of hydrophobically modified mesoporous silica and 0.2 part of coupling agent into 100 parts of the precursor solution, ultrasonically disperse for 50 min, continue to add a phase transfer catalyst, tetrabutylammonium chloride, to the dispersion, and control the temperature at 60°C, keep warm and stir for 4 h, and discharge to obtain a polyimide composite slurry; the coupling agent is composed of vinyltriethoxysilane and tetra-isopropyl di(dioctylphosphite acyloxy) titanate in a mass parts ratio of 3:4; S3. Let the polyimide composite slurry stand for 30 min, remove air bubbles under vacuum, then evenly coat it on the surface of the copper foil, control the coating thickness to be 23 μm. Then place the whole copper foil in a vacuum drying oven and keep it at 150 °C for 2 h, 230 °C for 1 h, and 310 °C for 1.3 h respectively. After taking it out, peel off the substrate to obtain the FPC high-frequency material for improving signal transmission efficiency.

[0029] Example 2 A preparation method of an FPC high-frequency material for improving signal transmission efficiency includes the following steps: S1. According to mass parts, add 15 parts of fluorinated diamine monomer and 4 parts of 4,4'-(hexafluoroisopropanol) benzophenone tetracarboxylic dianhydride into 500 parts of N,N-diethylformamide, mechanically stir evenly, fill nitrogen as the protective gas, and react for 4 h under continuous stirring to obtain a precursor solution. S2. According to mass parts, add 7 parts of modified mesoporous silica and 0.3 part of coupling agent into 100 parts of the precursor solution, ultrasonically disperse for 60 min, continue to add the phase transfer catalyst tetrabutylammonium chloride to the dispersion liquid, and control the temperature at 65 °C, keep stirring for 3 h, and discharge to obtain the polyimide composite slurry; the coupling agent is composed of vinyltriethoxysilane and tetraisopropyl bis(dioctylphosphite acyloxy) titanate in a mass part ratio of 3:4. S3. Let the polyimide composite slurry stand for 40 min, remove air bubbles under vacuum, then evenly coat it on the surface of the copper foil, control the coating thickness to be 27 μm. Then place the whole copper foil in a vacuum drying oven and keep it at 150 °C for 2 h, 230 °C for 1 h, and 310 °C for 1.3 h respectively. After taking it out, peel off the substrate to obtain the FPC high-frequency material for improving signal transmission efficiency.

[0030] Example 3 A preparation method of an FPC high-frequency material for improving signal transmission efficiency includes the following steps: S1. According to mass parts, add 15 parts of fluorinated diamine monomer and 4 parts of 4,4'-(hexafluoroisopropanol) benzophenone tetracarboxylic dianhydride into 500 parts of N,N-diethylformamide, mechanically stir evenly, fill nitrogen as the protective gas, and react for 3.4 h under continuous stirring to obtain a precursor solution. S2. According to mass parts, add 6.5 parts of modified mesoporous silica and 0.25 part of coupling agent into 100 parts of the precursor solution, ultrasonically disperse for 55 min, continue to add the phase transfer catalyst tetrabutylammonium chloride to the dispersion liquid, and control the temperature at 63 °C, keep stirring for 3.5 h, and discharge to obtain the polyimide composite slurry; the coupling agent is composed of vinyltriethoxysilane and tetraisopropyl bis(dioctylphosphite acyloxy) titanate in a mass part ratio of 3:4. S3. Let the polyimide composite slurry stand for 35 min, remove bubbles under vacuum, and then uniformly coat it on the surface of the copper foil. Control the coating thickness to be 25 μm. Then, place the entire copper foil in a vacuum drying oven and keep it at 150 °C for 2 h, 230 °C for 1 h, and 310 °C for 1.3 h respectively. After taking it out, peel off the substrate to obtain the FPC high-frequency material for improving signal transmission efficiency.

[0031] Comparative Example 1 Same as Example 3, except that an equimolar amount of 1,4-cyclohexanediamine is used instead of the fluorinated diamine monomer.

[0032] Comparative Example 2 Same as Example 3, except that mesoporous silica with an average pore diameter of 20 nm in an equal mass fraction is used instead of the modified mesoporous silica.

[0033] Comparative Example 3 Same as Example 3, except that the coupling agent is vinyltriethoxysilane.

[0034] Comparative Example 4 Same as Example 3, except that the coupling agent is tetra-isopropyl di(dioctylphosphite) titanate.

[0035] Performance Test Take samples of the FPC high-frequency materials prepared in Examples 1 - 3 and Comparative Examples 1 - 4 respectively for the following tests. Each group of test samples is tested 3 times, and the results are averaged; the results are shown in Table 1.

[0036] Tensile property test: Test according to GB / T1040.3—2006; Dielectric constant: Use a WK65120B high-precision impedance analyzer to test the dielectric constant of the samples; Dielectric loss: Use the split cylinder resonator 10GHz CR-710 (manufactured by EM Lab) as the measuring device; measurement frequency: 60 GHz.

[0037] Water resistance: Weigh the sample and record the weight as X. Then immerse the sample in pure water, take it out after keeping it at 80 °C for 72 h, dry the water on the surface of the sample, and weigh it again, denoted as Y. Use the formula [(Y - X) / X]×100% to calculate the water absorption rate of the sample and evaluate the water resistance of the sample; Table 1 Test Results Project Tensile strength / MPa Dielectric constant Dielectric loss Water absorption rate / % Example 1 288.5 2.53 0.0021 0.05 Example 2 292.4 2.41 0.0017 0.04 Example 3 289.3 2.35 0.0013 0.04 Comparative example 1 297.7 3.12 0.0045 0.28 Comparative example 2 257.8 2.96 0.0034 0.22 Comparative example 3 275.3 2.68 0.0022 0.07 Comparative example 4 281.2 2.57 0.0019 0.08 Analyzing the data in Table 1, it can be seen that: 1) The FPC high-frequency materials prepared in Examples 1-3 for improving signal transmission efficiency have low hygroscopicity, low dielectric constant and dielectric loss, and excellent mechanical properties. They are suitable for applications in automotive electronic systems, especially in communication devices with strict requirements for high-frequency signals, to improve signal quality and reduce electromagnetic interference.

[0038] 2) Combining the performance comparative analysis of the FPC high-frequency materials prepared in Example 3 and Comparative Example 1 shows that the fluorinated diamine monomer prepared in this application has the following effects: 1) Reducing dielectric constant and dielectric loss: The fluorine element in the fluorinated diamine monomer can significantly reduce the dielectric constant of the polyimide material and reduce dielectric loss, which is crucial for improving the high-frequency signal transmission efficiency. 2) Improving hydrophobicity: The tert-butyl and trifluorotoluene block polymerized macromolecules in the fluorinated diamine monomer can make the polyimide material exhibit extremely strong hydrophobicity, improving the problem of reduced water resistance caused by the introduction of fluorine elements. 3) Improving mechanical properties: The polymerized structure of the fluorinated diamine monomer reduces the content of imide heterocycles in the prepared polyimide molecular chain, affecting its mechanical properties. By chemically cross-linking the modified mesoporous silica with the polyimide matrix through chemical bond connection methods, the mechanical properties of the polyimide material can be improved. 4) Improving water resistance and thermal stability: The uniform dispersion of the modified mesoporous silica can introduce a hollow structure into the polyimide material, further reducing the dielectric constant and dielectric loss of the polyimide material, while improving the water resistance and thermal stability. In summary, the synergistic effect of the fluorinated diamine monomer in the entire preparation process is multi-faceted, not only improving the high-frequency signal transmission efficiency, but also improving the hydrophobicity, mechanical properties and water resistance of the material. This is crucial for improving the performance of FPC high-frequency materials.

[0039] 3) Combining the performance comparative analysis of the FPC high-frequency materials prepared in Example 3 and Comparative Example 2 shows that the modified mesoporous silica prepared in this application forms chemical cross-linking points with the polyimide matrix through chemical bonds, which helps to improve the mechanical properties and thermal stability of the material. The dispersion of mesoporous silica helps to introduce a hollow structure into the polyimide material, which can further reduce the dielectric constant of the material and reduce dielectric loss. The fluorine-containing groups introduced through chemical modification form a hydrophobic layer, improving the water resistance of the material. The hollow structure introduced by the modified mesoporous silica and the hydrophobic characteristics of the fluorine-containing groups work together to reduce the dielectric constant of the material and reduce dielectric loss, thereby optimizing the dielectric properties of the material. In summary, the modified mesoporous silica plays a key role in the preparation process of FPC high-frequency materials. They work together through multiple methods such as chemical cross-linking, interface strengthening, introducing hollow structures and hydrophobic characteristics to jointly improve the mechanical properties, dielectric properties and water resistance of the material.

[0040] 4) Comparative analysis of the performance of the FPC high-frequency materials prepared in combination with Example 3 and Comparative Examples 3-4 for improving signal transmission efficiency shows that the coupling agent is composed of vinyltriethoxysilane and tetraisopropyl bis(dioctylphosphite) titanate in a mass ratio of 3:4. Utilizing their synergistic effect, the two act together between the silica surface and the polyimide matrix, capable of forming stable chemical bond connections and improving the interfacial adhesion strength. Vinyltriethoxysilane can form a cross-linked network structure under the action of ultraviolet light or heat, while tetraisopropyl bis(dioctylphosphite) titanate can further enhance this cross-linking effect, thereby improving the mechanical properties and heat resistance of the material. Tetraisopropyl bis(dioctylphosphite) titanate can react with fluorine-containing groups to form a hydrophobic layer, while vinyltriethoxysilane can react with the hydroxyl groups on the silica surface to form chemical bonds, jointly acting to improve the hydrophobic properties of the material and reduce the dielectric constant and dielectric loss.

[0041] The above embodiments are only used to explain the technical solutions of the present application rather than limit them. Although the above embodiments have specifically described the present application, those skilled in the art should understand that the specific implementation manners of the present application can still be modified or equivalently replaced. Any modification and equivalent replacement without departing from the spirit and scope of the present application shall be covered by the protection scope of the present application.

Claims

1. A preparation method of an FPC high-frequency material for improving signal transmission efficiency, characterized in that, It includes the following steps: S1. According to the mass parts, add the fluorinated diamine monomer and the hydrophobic monomer into N,N-diethylformamide, mechanically stir evenly, charge nitrogen as the protective gas, and react for 3-4 h under continuous stirring to obtain a precursor solution; S2. According to the mass parts, add the modified mesoporous silica and the coupling agent into the precursor solution, ultrasonically disperse for 50-60 min, continue to add the phase transfer catalyst tetrabutylammonium chloride into the dispersion, control the temperature at 60-65 °C, keep warm and stir for 3-4 h, and discharge to obtain a polyimide composite slurry; S3. Let the polyimide composite slurry stand for 30-40 min, remove bubbles under vacuum, then evenly coat it on the surface of the copper foil, control the coating thickness to be 23-27 μm, then place the whole copper foil in a vacuum drying oven, start the heating program for thermal imidization, take it out, and peel off the substrate to obtain an FPC high-frequency material for improving signal transmission efficiency.

2. The preparation method of an FPC high-frequency material for improving signal transmission efficiency according to claim 1, characterized in that, In step S1, the mass parts ratio of the fluorinated diamine monomer, the hydrophobic monomer and N,N-diethylformamide is 15:3.5-4:

500.

3. The preparation method of an FPC high-frequency material for improving signal transmission efficiency according to claim 1, characterized in that, In step S1, the preparation method of the fluorinated diamine monomer is as follows: add tert-butyl diethanolamine and xylene into a polymerization kettle filled with nitrogen, start stirring, after forming a uniform reaction solution, add a sodium hydroxide solution with a mass fraction of 30%, stir at 60-65 °C for 2-3 h, then add 3,5-dibromobenzotrifluoride into the polymerization kettle, after adding, raise the temperature to 80-85 °C, keep warm and stir for 4.5-5 h, then add the capping agent 2-chloroethylamine hydrochloride into the polymerization kettle, keep warm for 70-80 min, evaporate the solvent, cool down and discharge to obtain the fluorinated diamine monomer.

4. The preparation method of an FPC high-frequency material for improving signal transmission efficiency according to claim 2, characterized in that, The mass parts ratio of tert-butyl diethanolamine, xylene, 30% sodium hydroxide solution, 3,5-dibromobenzotrifluoride and 2-chloroethylamine hydrochloride is 5:40-50:55:8-8.5:2-2.

3.

5. The preparation method of an FPC high-frequency material for improving signal transmission efficiency according to claim 1, characterized in that, In step S1, the hydrophobic monomer is one of perfluorohexyl dianhydride and 4,4'-(hexafluoroisopropanol) diphenylmethane tetracarboxylic dianhydride.

6. The preparation method of an FPC high-frequency material for improving signal transmission efficiency according to claim 1, characterized in that, In step S2, the mass parts ratio of the modified mesoporous silica, the coupling agent, the precursor solution and tetrabutylammonium chloride is 6-7:0.2-0.3:100:0.4-0.

5.

7. The preparation method of an FPC high-frequency material for improving signal transmission efficiency according to claim 1, characterized in that, In step S2, the preparation method of the hydrophobic modified mesoporous silica includes the following steps: S71. According to the mass parts, add 100 parts of mesoporous silica into a solution composed of 300 parts of absolute ethanol and 50 parts of deionized water, ultrasonically disperse for 30-40 min, then mechanically stir and mix at a speed of 1500-1800 rpm for 50-60 min to obtain a mixed solution, slowly drop 3-4 parts of γ-aminopropyltriethoxysilane into the mixed solution, react at 40-45 °C for 5-6 h, centrifuge, wash, and vacuum dry to obtain silane-modified mesoporous silica; S72. According to the mass parts, after heating 200 parts of a dimethylformamide solution of trifluoroacetic anhydride with a mass concentration of 2% to 90 °C, 100 parts of silane-modified mesoporous silica is added, and the pH of the dispersion is adjusted to 9 - 10 with an aqueous sodium hydroxide solution with a mass concentration of 10%, and the reaction is carried out at a constant temperature for 3 - 4 h, followed by filtration, washing with water, and drying to obtain hydrophobically modified mesoporous silica.

8. The preparation method of an FPC high-frequency material for improving signal transmission efficiency according to claim 1, characterized in that, In step S2, the coupling agent is composed of vinyltriethoxysilane and tetra-isopropyl di(dioctylphosphite) titanate in a mass parts ratio of 3:

4.

9. The preparation method of an FPC high-frequency material for improving signal transmission efficiency according to claim 1, characterized in that, In step S3, the heating program is to keep the temperature at 150 °C for 2 h, 230 °C for 1 h, and 310 °C for 1.3 h respectively.

10. An FPC high-frequency material for improving signal transmission efficiency, characterized in that, The FPC high-frequency material for improving signal transmission efficiency is prepared by using the preparation method of the FPC high-frequency material for improving signal transmission efficiency according to any one of claims 1 - 9.