A high-frequency copper-clad plate based on PTFE and a preparation method thereof

Abstract

The application discloses a kind of high frequency copper-clad plate based on PTFE and preparation method thereof, belong to high polymer composite technical field.Its preparation method includes: using sol-gel method to combine polyethylene imine auxiliary preparation high-entropy oxide nanoparticles;Nanofiller with core-shell is prepared by fluorination modification after being coated by polydopamine;Hollow alumina-silica ceramic microspheres are modified by multiple fluorine-containing silane and fluorine shell layer doping;Polytetrafluoroethylene-based nanocomposite dispersion liquid is prepared by compounding fluorinated boron nitride nanosheet and hexagonal boron nitride flake;After gradient fluorinated silane treatment, glass fiber cloth is impregnated with dispersion liquid to prepare prepreg;After multilayer copper foil is stacked, it is formed by staged vacuum hot pressing.The obtained copper-clad plate dielectric layer is composed of fluorinated modified PTFE resin, multi-scale low-dielectric filler and surface fluorinated glass fiber, and has extremely low dielectric constant, extremely low dielectric loss, high peel strength, low water absorption and high thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically, it relates to a PTFE-based high-frequency copper-clad laminate and its preparation method. Background Technology

[0002] Copper clad laminate (CCL) is the core substrate of printed circuit boards (PCBs). It is made by impregnating reinforcing materials (such as fiberglass cloth) with resin and then laminating them with copper foil. It plays a crucial role in the electronics and information industry. With the miniaturization, high performance, and high reliability of electronic products, especially the rapid rise of emerging technologies such as 5G communication, the Internet of Things, millimeter-wave radar, autonomous driving, cloud servers, and artificial intelligence, the demand for high-frequency and high-speed signal transmission has increased dramatically, placing higher demands on the dielectric properties, thermal management performance, and mechanical reliability of CCLs. Traditional epoxy resin-based CCLs suffer from high dielectric loss and severe signal attenuation under high-frequency conditions, making them unsuitable for applications above 10GHz. Therefore, high-frequency and high-speed CCLs have become a key focus of industry development.

[0003] High-frequency and high-speed copper-clad laminates (CCLs) are mainly divided into two categories: high-speed CCLs and high-frequency CCLs. High-speed CCLs primarily emphasize signal transmission rates and are typically used in multilayer high-density interconnect (HDI) boards, servers, and data centers, requiring a low and stable dielectric constant (Dk) and low dielectric loss (Df). High-frequency CCLs, on the other hand, prioritize signal integrity in extremely high-frequency bands (such as millimeter waves) and are commonly used in radio frequency / microwave circuits, such as 5G base station antennas, satellite communications, and radar systems. Currently, mainstream high-frequency material systems include modified epoxy resins, cyanate ester (CE) resins, polyphenylene oxide (PPO / PPE) resins, hydrocarbon resins, and polytetrafluoroethylene (PTFE) resins. Among these, PTFE-based CCLs are widely recognized as the best-performing material in high-frequency and high-speed applications due to their extremely low dielectric constant (Dk typically in the range of 2.0-2.6), extremely low dielectric loss factor (Df can be as low as below 0.0009), excellent heat resistance, and chemical stability.

[0004] However, the production technology of PTFE-based high-frequency copper-clad laminates has extremely high barriers to entry, mainly in the following aspects: First, PTFE resin itself is a non-polar material with low surface energy, resulting in poor adhesion to copper foil and reinforcing materials. Traditional lamination processes easily lead to delamination and insufficient peel strength. Second, PTFE has a high melting point (approximately 327℃), requiring processing under high temperature and high pressure conditions above 350℃. This places stringent demands on equipment precision and process control, easily leading to defects such as dimensional instability, warping, and internal bubbles. Third, to further reduce dielectric loss and improve thermal conductivity, ceramic fillers (such as silica and alumina) or hollow microspheres are typically added. However, the dispersibility and interfacial compatibility of these fillers are significant issues, easily leading to filler agglomeration, fluctuations in dielectric properties, and increased water absorption. In the international market, companies such as Rogers, Taconic, and Park Electrochemical, with decades of technological accumulation, hold leading positions in PTFE formulation design, filler modification, and continuous production equipment. For example, Rogers' TC series products achieve thermal conductivity of 0.8-1.2 W / m·K through high thermal conductivity ceramic filling, while maintaining Dk stability and low loss; Taconic's TLY series improves mechanical strength through optimized fabric structure. However, these imported products are expensive and have long delivery cycles, which seriously restricts cost control and supply chain security for downstream applications.

[0005] The domestic high-frequency, high-speed copper-clad laminate (CCL) industry started relatively late, primarily due to the following reasons: First, core raw materials rely on imports, such as high-purity PTFE dispersions, ultra-thin electronic-grade glass fiber cloth (1080 and 1078 types), RTF / HVLP low-profile copper foil, and special ceramic powders. Second, formulation technology has high barriers to entry; there is a lack of systematic breakthroughs in interface modification of PTFE composite systems, multi-scale filler compounding, and low-loss network construction. Third, manufacturing equipment lacks precision; domestic hot presses, impregnation lines, and other equipment still lag behind international advanced levels in terms of temperature uniformity, pressure control, and vacuum, resulting in poor product consistency and high scrap rates. Fourth, certification cycles are long; downstream end-users have strict verification requirements for domestically produced materials, limiting market penetration. In existing technologies, researchers have proposed various modification methods to improve the performance of PTFE-based CCLs. For example, adding inorganic fillers (such as fused silica and titanium dioxide) can reduce the dielectric constant and improve dimensional stability, but excessive filler content can increase losses and reduce peel strength. Surface chemical etching or plasma treatment can improve the adhesion between PTFE and copper foil, but the process is complex and prone to introducing surface defects. Introducing hollow glass microspheres can reduce density and dielectric constant, but the microspheres are prone to breakage and have high water absorption, affecting damp heat reliability. Using two-dimensional materials such as boron nitrides or graphene can improve thermal conductivity, but dispersion is difficult and the cost is high. In addition, some patents (such as CN115847957A) attempt to improve mechanical strength and thermal conductivity through thermosetting resin hybridization or continuous hot pressing processes, but it is still difficult to achieve both extremely low losses and high reliability, especially in the frequency band above 10 GHz, where signal attenuation and phase stability are still not ideal.

[0006] With the large-scale commercialization of 5G, the pre-research of 6G technology, and the advancement of L4 / L5 autonomous driving in automobiles, the performance requirements for copper-clad laminates (CCLs) are further increasing: dielectric loss must be below 0.001, thermal conductivity above 0.8 W / m·K, water absorption rate below 0.02%, and peel strength above 1.4 N / mm. Simultaneously, they must possess low CTE, high Tg, and excellent resistance to CAF. Existing technologies have significant shortcomings in the synergistic optimization of multiple indicators, particularly regarding the long-term reliability of domestically produced materials under extreme environments, which still needs verification. This not only leaves downstream domestic enterprises dependent on foreign suppliers for core equipment but also hinders the independent control and high-quality development of my country's electronic information industry.

[0007] Therefore, there is an urgent need to develop a new PTFE-based high-frequency copper clad laminate preparation technology. Through innovative filler design, interfacial fluorination modification, and multi-scale structure construction, a comprehensive breakthrough can be achieved in terms of extremely low dielectric loss, high thermal conductivity, low water absorption, and excellent adhesion performance, thereby promoting the domestic substitution of key materials and meeting national strategic needs. Summary of the Invention

[0008] To address the problems of high dielectric loss, insufficient thermal conductivity, high water absorption, low peel strength, poor filler interface compatibility, and reliance on imported key raw materials and core technologies in existing PTFE-based high-frequency copper-clad laminates, this invention provides a PTFE-based high-frequency copper-clad laminate and its preparation method. By introducing high-entropy oxide nanoparticles, multilayer fluorinated core-shell structures, fluorinated modified hollow ceramic microspheres, multi-scale low-dielectric / thermal-conductivity filler networks, glass fiber gradient fluorination interfaces, and optimized hot-pressing processes, synergistic optimization of extremely low dielectric loss, high thermal conductivity, low water absorption, and high adhesive strength is achieved, breaking through the performance bottlenecks of traditional PTFE composite systems and promoting the localization of key materials.

[0009] The present invention adopts the following technical solution: a method for preparing high-frequency copper-clad laminate based on PTFE, which, by weight, includes the following steps: (1) preparing high-entropy oxide nanoparticles: magnesium nitrate (CAS No.: 10377-60-3), cobalt nitrate (CAS No.: 10141-05-6), nickel nitrate (CAS No.: 13478-00-7), copper nitrate (CAS No.: 3251-23-8), and zinc nitrate (CAS No.: 10196-18-6) are prepared in a mass ratio of (1-1.2):(1-1.2):(1-1.2):(1-1.2) (1-1.2) Mix to obtain a mixed salt solution with a total mass of 100 parts; add citric acid (CAS No.: 77-92-9) at 1.5-2.5 times the mass of the mixed salt, stir to dissolve, then add polyethyleneimine (CAS No.: 9002-98-6) at 0.1-0.3 times the mass of the mixed salt, adjust the pH to 7.0-8.0, heat to 80-100℃ and stir for 4-8 hours to form a sol, then vacuum dry and calcine at 800-1000℃ in air for 4-8 hours, and then ball mill to obtain high-entropy oxide nanoparticles with an average particle size of 30-80nm; (2) Preparation of fluorinated polydopamine-coated high-entropy oxide core-shell nanofillers: 100 parts by weight of the high-entropy oxide nanoparticles from step (1) were dispersed in deionized water, and 2-6 parts by weight of dopamine hydrochloride (CAS No.: 62-31-7) were added. The mixture was stirred and reacted for 6-10 hours at pH 8.2-8.8 and 25-35℃ to form a polydopamine coating layer. Subsequently, pentafluorobenzoyl chloride (CAS No.: 2251-50-5) was added at a molar percentage of 120-180 of the dopamine molars, and the mixture was reacted for 3-5 hours in the presence of triethylamine (CAS No.: 121-44-8). Washing and vacuum drying yielded fluorinated polydopamine-high entropy oxide core-shell nanofiller; (3) Preparation of fluorine-modified hollow ceramic microspheres: 100 parts by weight of hollow alumina-silica ceramic microspheres (CAS No.: 1344-28-1 and 14808-60-7 composite, particle size 10-30 micrometers) were added to 400-600 parts by weight of anhydrous ethanol (CAS No.: 64-17-5), and 3-(methacryloyloxy)propyltrimethoxysilane (CAS No.: 2530-85-0) was added dropwise at 5-10% by weight of the microspheres to adjust the pH to 4.0-5.0. Stir for 2-4 hours and dry; then add 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (CAS No.: 83048-65-1) at 2-6% by weight of the microspheres, continue the reaction and dry to obtain fluorine-modified hollow ceramic microspheres; (4) Preparation of polytetrafluoroethylene nanocomposite dispersion: 100 parts by weight of polytetrafluoroethylene aqueous dispersion (solid content 55-65% by weight, CAS No.: 9002-84-0), 8-35 parts by weight of core-shell nanofiller from step (2), and 15-50 parts by weight of fluorine-modified hollow ceramic microspheres from step (3) are added to the same container, and then 1-4 parts by weight of polyoxyethylene nonylphenyl ether (CAS No.: 9014-90-8) and 150-350 parts by weight of deionized water are added. The polytetrafluoroethylene nanocomposite dispersion is obtained by high-speed shearing and ultrasonic dispersion; (5) Surface treatment and impregnation of glass fiber fabric: Select Electronic grade alkali-free glass fiber cloth (CAS No.: 65997-17-3), after calcination to remove the sizing agent, is immersed in a solution containing 1-4% by mass of phenyltriethoxysilane (CAS No.: 780-69-8) and 0.2-1.5% by mass of γ-aminopropyltriethoxysilane (CAS No.: 919-30-2), and then impregnated with the dispersion of step (4), controlling the mass ratio of resin solids to glass fiber cloth to be 50-90. :100, after roller pressing to remove residual liquid, the prepreg is dried step by step to obtain the prepreg; (6) Lamination hot pressing: the prepreg from step (5) is stacked in multiple layers with a total dielectric thickness of 80-350 micrometers, and roughened electrolytic copper foil (CAS No.: 7440-50-8, thickness 8-35 micrometers) is laid on the top and bottom. It is then pressed in a vacuum hot press at a pressure of 1-4 MPa and a temperature of 300-380℃ for 30-90 minutes, and then cooled and depressurized to obtain a high-frequency copper-clad laminate based on PTFE.

[0010] In step (1), the total mass of the mixed salt solution is 100 parts, the mass ratio of nitrate is 1:1:1:1:1, the amount of citric acid added is twice the mass of the mixed salt, the molecular weight of polyethyleneimine is 800-1200, ammonia water (CAS No.: 1336-21-6) is used to adjust the pH, the heating and stirring speed is 200-300 rpm, the calcination temperature is 900℃ and the time is 6 hours, the ball milling uses zirconia balls, the ball-to-material ratio is 10:1, the speed is 400-500 r / min and the time is 8-12 hours, and the specific surface area of ​​the obtained high-entropy oxide nanoparticles is 80-120 m². 2 / g.

[0011] In step (2), the high-entropy oxide nanoparticles are dispersed in 600-900 parts by weight of deionized water, and 4 parts by weight of dopamine hydrochloride is added. After the reaction, pentafluorobenzoyl chloride is added in an acetonitrile (CAS No.: 75-05-8) / water mixture. The amount of triethylamine added is 1.1-1.3 times the molar amount of pentafluorobenzoyl chloride. The drying temperature is 70-90℃ and the time is 10-14 hours. Further, 1-4 parts by weight of trifluoropropyltrimethoxysilane (CAS No.: 429-60-7) are added for co-modification to form a multilayer fluorinated shell.

[0012] In step (3), the hollow ceramic microspheres are further doped with a fluorine-containing shell: after silanization and drying, the microspheres are added to a deionized aqueous solution containing 1-4 parts by weight of silicon tetrafluoride (CAS No.: 7783-61-1) and 2-8 parts by weight of aluminum nitrate nonahydrate (CAS No.: 7784-27-2), and hydrolyzed at pH 2.0-3.0, temperature 50-70℃, and time 2-4 hours, followed by calcination at 500-600℃ for 2-3 hours.

[0013] In step (4), 5-25 parts by weight of boron fluoride nitride nanosheets (the surface of which is modified with perfluorooctyltriethoxysilane CAS No.: 51851-37-7) are further added. The mass ratio of core-shell nanofiller, hollow ceramic microspheres and boron fluoride nitride nanosheets is (10-30):(20-45):(10-20) to construct a multi-scale low dielectric network structure.

[0014] Step (5) further includes a gradient fluorination layer for the surface treatment of the glass fiber cloth: after the bissilane treatment, it is immersed in a solution containing 1-3% by mass of (3,3,3-trifluoropropyl)trimethoxysilane (CAS No.: 429-60-7), and heat-treated at 180-220°C for 10-20 minutes; the impregnation includes 2-5 cycles, with a resin weight gain of 10-20% by mass each time, and the rolling directions are staggered to form an anisotropic structure.

[0015] In step (6), the hot pressing adopts a staged process: initial pressure of 0.5-1.0 MPa, heating to 220-260℃ and holding for 10-20 minutes to remove moisture; increase pressure to 2-4 MPa, heating to 340-370℃ and holding for 40-80 minutes; cooling rate of 2-4℃ / minute to below 80℃.

[0016] In step (4) or (5), 10-30 parts by weight of surface-fluorinated modified hexagonal boron nitride sheets (CAS No.: 10043-11-5, diameter 1-10 micrometers) are further introduced as a planar thermally conductive reinforcing phase, and the in-plane orientation is controlled by rolling.

[0017] Further steps include edge trimming and copper surface micro-etching: the micro-etching solution contains 50-150 g / L of sulfuric acid (CAS No.: 7664-93-9) and 10-40 g / L of hydrogen peroxide (CAS No.: 7722-84-1), with a treatment time of 30-90 seconds and a temperature of 25-35℃.

[0018] A PTFE-based high-frequency copper clad laminate is obtained by the above-described method for preparing a PTFE-based high-frequency copper clad laminate. Its dielectric layer is composed of polytetrafluoroethylene resin, fluorinated polydopamine-high-entropy oxide core-shell nanofiller, fluorine-modified hollow ceramic microspheres, and surface polysilane-modified electronic glass fibers, with roughened electrolytic copper foil on both the top and bottom.

[0019] Compared with the prior art, the present invention has the following significant advantages and innovations: (1) It innovatively introduces high-entropy oxide nanoparticles as the core filler, and utilizes the lattice distortion, configuration entropy stability and slow-release polarization mechanism of the high-entropy effect to significantly reduce the dielectric loss of the composite material, while improving the interfacial compatibility and thermal stability between the filler and the PTFE matrix. Traditional PTFE-based copper clad laminates often use single-component ceramic fillers such as SiO2, Al2O3 or TiO2 to adjust the dielectric properties, but these fillers often produce high dielectric loss (Df usually > 0.0015@10GHz) at high frequencies due to their single crystal structure and strong polarization relaxation, and the difference in interfacial polarity leads to filler agglomeration and uneven dispersion, which in turn causes local electric field concentration and increased loss. The present invention applies rock salt type high-entropy oxide (HEO) nanoparticles to the PTFE composite system for the first time, and prepares an average particle size of 30-80nm and a specific surface area of ​​80-120m² by sol-gel method combined with polyethyleneimine (PEI). 2 / g nanoparticles. The core mechanism of high-entropy oxides lies in their "high configuration entropy" effect: five metal cations (Mg 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+) The random occupancy of lattice sites by moles leads to severe lattice distortion and slow ion / electron migration. This distortion suppresses the fast dipole polarization and interfacial polarization relaxation common in traditional ceramic fillers, causing the polarization response to lag behind the high-frequency electric field change, thereby significantly reducing dielectric loss. According to the effective medium theory and the Debye relaxation model, the high-entropy structure is equivalent to introducing the "cocktail effect", and the multi-element synergy suppresses the leakage conduction loss caused by the Jahn-Teller distortion of a single element or the migration of oxygen vacancies. At the same time, the high configuration entropy makes the phase structure highly stable in a wide temperature range, avoiding the phase transformation or grain coarsening that occurs in traditional fillers at high processing temperatures (>300℃). (2) Construct a multilayer fluorinated core-shell structure and a gradient fluorinated interface. Through the bio-inspired transition layer of polydopamine (PDA), pentafluorobenzoyl chloride acylation and multi-fluorosilane co-modification, the all-round low surface energy matching of filler-resin-glass fiber is achieved, which greatly suppresses water adsorption, reduces water absorption rate and improves interfacial bonding strength and moisture heat resistance reliability. PTFE itself is a strongly hydrophobic material (contact angle >110°), but the inorganic fillers and glass fiber surfaces are rich in hydroxyl groups (-OH), which are highly polar and have a large difference in surface energy compared to non-polar PTFE (PTFE surface energy ~18-20 mN / m, inorganic materials >70 mN / m). This results in poor interfacial wettability and weak adhesion (traditional peel strength <1.2 N / mm), and the easy formation of hydrophilic channels, leading to increased water absorption (>0.03%). In high-humidity environments, this induces a "wicking effect" and deterioration of dielectric properties. This invention innovatively uses PDA coating as a bridge: dopamine undergoes oxidative self-polymerization under weakly alkaline conditions to form a PDA layer rich in catechols and amino groups, similar to mussel adhesive proteins, exhibiting super-strong adhesion to high-entropy oxide surfaces (through hydrogen bonds, π-π stacking, and coordination bonds). At the same time, the active groups on the PDA surface facilitate subsequent fluorination. Subsequently, pentafluorobenzoyl chloride is introduced for acylation, grafting the strongly electron-withdrawing C6F5- group onto the PDA layer to form a low surface energy fluorinated shell. Simultaneously, trifluoropropyltrimethoxysilane is co-modified to further construct a multilayer fluorinated structure. This core-shell design reduces the filler surface energy to <20 mN / m, highly matching PTFE and significantly improving dispersibility and interfacial wetting. For hollow ceramic microspheres and glass fibers, this invention employs multiple fluorinated silanes (including perfluorodecyl and trifluoropropylsilane) and silicon tetrafluoride doping to form a gradient fluorinated layer: the inner silane coupling enhances chemical bonding, while the outer long-chain fluoroalkyl layer provides a hydrophobic barrier. According to the Cassie-Baxter model, the fluorinated surface forms a micro-nano rough structure, further amplifying hydrophobicity (contact angle >150°). Mechanistically, the high bond energy (~485 kJ / mol) and low polarity of the CF bond block the hydrogen bond adsorption pathway of water molecules, inhibiting interfacial moisture migration.(3) Multi-scale low dielectric / thermal conductivity network synergistic design: Combining nanoscale core-shell fillers to regulate local polarization, micron-scale fluorinated hollow microspheres to introduce air phase to reduce overall Dk, two-dimensional boron fluoride nitride (BNNS) nanosheets to bridge the interface, and oriented hexagonal boron nitride (h-BN) sheets to construct in-plane thermal conductivity pathways, the dielectric constant / loss is synergistically reduced and the thermal management capability is significantly improved. Traditional filling systems mostly use single-scale fillers, which are difficult to achieve low Dk, low Df and high thermal conductivity at the same time: solid ceramics have limited Dk reduction and increase density, hollow microspheres introduce air (Dk=1) but are easy to break and absorb water, and two-dimensional materials have good thermal conductivity but are easy to stack, resulting in high thermal resistance in the vertical direction. This invention constructs a multi-scale network: nanoscale fluorinated core-shell high-entropy oxides (8-35 parts) provide local low-polarity regions, utilizing a high-entropy slow-release mechanism to suppress nanoscale relaxation losses; micron-sized fluorinated hollow ceramic microspheres (15-50 parts) introduce a large number of closed air pores, effectively reducing the composite Dk according to Lichtenecker's logarithmic mixing law (the higher the air volume fraction, the more significant the decrease in Dk); fluorinated BNNS (5-25 parts) serve as a bridging phase, and the two-dimensional structure easily bridges nano- and micron-sized fillers under shear force, forming a low-polarity interface network, further suppressing interface polarization; large-size oriented h-BN sheets (10-30 parts) induce in-plane orientation through roll forming, constructing a high-thermal-conductivity percolation pathway (h-BN in-plane thermal conductivity >300 W / m·K). Mechanistically, the multi-scale synergy conforms to the effective medium theory and percolation theory: low-scale fillers fill gaps, improving filling efficiency, while high-scale fillers form a continuous phase, lowering the threshold; fluorination ensures interface compatibility at all scales, avoiding phonon scattering and electric field concentration. In terms of thermal conductivity, the in-plane orientation h-BN forms a "highway" and works in conjunction with BNNS bridging to increase the thermal conductivity from ~0.25W / m·K of traditional PTFE to over 0.85W / m·K. (4) Process optimization and structural control: staged vacuum hot pressing, multi-cycle staggered roller pressing impregnation and post-treatment process ensures precise control of the PTFE melting-flow-crystallization process, achieves thorough bubble removal, uniform filler orientation, optimized crystallinity and enhanced surface micro-etching, and improves the consistency of the board, mechanical strength and copper foil bonding force. Traditional hot pressing often uses single-stage high temperature pressurization, which easily causes PTFE to melt rapidly, resulting in bubble residue, disordered filler and low crystallinity (<50%), causing internal defects and dimensional instability. The present invention uses a staged process: initial pressure at low temperature (220-260℃) dehydration and degassing to avoid moisture-induced bubbles; medium pressure at high temperature (340-370℃) to promote resin flow and filler orientation; slow cooling to control the crystallization rate, improve crystallinity and reduce internal stress. Meanwhile, multiple cyclic impregnations (2-5 times) and staggered rolling induce anisotropic structures, enhancing in-plane strength. Mechanistically, the viscoelasticity and crystallization kinetics of PTFE are controlled in stages: low temperature eliminates low-molecular-weight volatiles, high temperature reduces viscosity to promote wetting, and slow cooling avoids spherulite defects caused by rapid crystallization.Post-etching treatment (H2SO4 / H2O2 system) forms a micron-level coarsening structure on the copper surface, increasing the mechanical anchoring effect and improving peel strength. Comprehensive performance breakthroughs and significance for domestic production: The above-mentioned innovative synergistic effects enable the copper-clad laminate of this invention to achieve Dk≤2.18, Df≤0.0009@10GHz, peel strength≥1.45N / mm, water absorption ≤0.012%, thermal conductivity≥0.85W / m·K, and Td>560℃, comprehensively reaching or surpassing the international advanced levels of Rogers RO3000 series, etc. Simultaneously, by using domestically produced raw materials and equipment, costs are reduced by more than 30%, promoting the independent controllability of high-frequency, high-speed copper-clad laminates. Traditional technologies struggle to coordinate multiple performance indicators (e.g., low thermal conductivity often sacrifices thermal conductivity, while high thermal conductivity easily increases thermal conductivity). This invention achieves comprehensive suppression of polarization loss, conduction loss, interface loss, and thermal resistance through a high-entropy, low-loss core, multi-fluorinated interface barrier, multi-scale network, and precision manufacturing process. It is suitable for scenarios such as 5G / 6G base stations, millimeter-wave radar, and AI servers.

[0020] In summary, this invention achieves a systematic innovation at the mechanistic level, encompassing "filler modification, interface optimization, network construction, and process control," breaking through the performance bottlenecks of existing technologies and possessing significant theoretical value and industrialization prospects. Attached Figure Description

[0021] Figure 1 This is a transmission electron microscope image of the high-entropy oxide nanoparticles prepared in Example 1.

[0022] Figure 2 This is the energy dispersive X-ray spectrum of magnesium in the high-entropy oxide nanoparticles prepared in Example 1.

[0023] Figure 3 This is the energy-dispersive X-ray spectrum of cobalt in the high-entropy oxide nanoparticles prepared in Example 1 (size range same). Figure 2 ).

[0024] Figure 4 This is the energy-dispersive X-ray spectrum of nickel in the high-entropy oxide nanoparticles prepared in Example 1 (size range same). Figure 2 ).

[0025] Figure 5 This is the energy-dispersive X-ray spectrum of copper in the high-entropy oxide nanoparticles prepared in Example 1 (size range same). Figure 2 ).

[0026] Figure 6 This is the energy-dispersive X-ray spectrum of zinc element in the high-entropy oxide nanoparticles prepared in Example 1 (size range same). Figure 2 ).

[0027] Figure 7This is the infrared spectrum of the polytetrafluoroethylene nanocomposite dispersion prepared in Example 1. Detailed Implementation

[0028] The present invention will now be described in detail through specific embodiments. However, these illustrative embodiments are for purposes and uses only to illustrate the invention and do not constitute any limitation on the actual scope of protection of the invention, nor are they intended to restrict the scope of protection of the invention to these embodiments. For parameter ranges not mentioned, intermediate values ​​are selected. Also, for mass ratios not explicitly stated or mentioned, the mass ratio after addition generally refers to the mass ratio. Furthermore, in the present invention, the unit of mass is grams (g).

[0029] Example 1

[0030] The preparation method of high-frequency copper-clad laminate based on PTFE includes the following steps: (1) Preparation of high-entropy oxide nanoparticles: Magnesium nitrate (CAS No.: 10377-60-3), cobalt nitrate (CAS No.: 10141-05-6), nickel nitrate (CAS No.: 13478-00-7), copper nitrate (CAS No.: 3251-23-8), and zinc nitrate (CAS No.: 10196-18-6) are mixed in a mass ratio of 1:1:1:1:1 (i.e., 20g of each is taken, and the total mass is 100g) to obtain a mixed salt solution; citric acid (CAS No.: 77-92- 9) Dissolve 200g (twice the mass of the mixed salt) by stirring, then add 20g (0.2 times the mass of the mixed salt) of polyethyleneimine (CAS No.: 9002-98-6) with a molecular weight of 1000. Adjust the pH to 7.5 using ammonia (CAS No.: 1336-21-6), heat to 90℃, and stir at 250 rpm for 6 hours to form a sol. Then vacuum dry and calcine at 900℃ for 6 hours in air. Finally, ball mill the sol at 450 rpm for 10 hours using zirconia balls (ball-to-material ratio 10:1) to obtain an average particle size of 55nm and a specific surface area of ​​100m². 2 / g of high-entropy oxide nanoparticles, their transmission electron microscopy image is as follows Figure 1 As shown, the energy dispersive X-ray spectra of various metallic elements are respectively as follows: Figures 2 to 6As shown. (2) Preparation of fluorinated polydopamine-coated high-entropy oxide core-shell nanofiller: 100g of high-entropy oxide nanoparticles obtained in step (1) were dispersed in 750g of deionized water, and 4g of dopamine hydrochloride (CAS No.: 62-31-7) was added. The mixture was stirred and reacted for 8 hours at pH 8.5 and 30℃ to form a polydopamine coating layer. Then, 2.4g of pentafluorobenzoyl chloride (CAS No.: 2251-50-5) (approximately 150% of the molar amount of dopamine) was added, and 2.5g of trifluoropropyltrimethoxysilane (CAS No.: 429-60-7) was added for co-modification. The reaction was carried out in an acetonitrile / water mixed system. Triethylamine (CAS No.: 121-44-8) was added as an acid-binding agent (the amount was 1.2 times the molar amount of acyl chloride). The reaction was carried out for 4 hours, and after washing and vacuum drying at 80℃ for 12 hours, a core-shell nanofiller with multiple fluorinated shells was obtained. (3) Preparation of fluorine-modified hollow ceramic microspheres: 100g of hollow alumina-silica ceramic microspheres with a particle size of 20 micrometers (mass ratio of alumina to silica is 2:1) were added to 500g of anhydrous ethanol, and 7.5g of 3-(methacryloyloxy)propyltrimethoxysilane (CAS No.: 2530-85-0) (7.5% of the mass of microspheres) was added dropwise. The pH was adjusted to 4.5, and the mixture was stirred for 3 hours and then dried. 4g of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (CAS No.: 83048-65-1) (4% of the mass of microspheres) was then added, and the reaction was continued and dried. Subsequently, a fluorine-doped shell treatment was performed: the microspheres were added to 500g of deionized water containing 2.5g of silicon tetrafluoride (CAS No.: 7783-61-1) and 5g of aluminum nitrate nonahydrate (CAS No.: 7784-27-2), and hydrolyzed for 3 hours at pH 2.5 and 60℃, followed by calcination at 550℃ for 2.5 hours to obtain fluorine-modified hollow ceramic microspheres.(4) Preparation of polytetrafluoroethylene nanocomposite dispersion: 100g of polytetrafluoroethylene aqueous dispersion (solid content 60%, CAS No.: 9002-84-0), 20g of core-shell nanofiller from step (2), and 32.5g of fluorine-modified hollow ceramic microspheres from step (3) were added to the same container; 15g of boron nitride nanosheets modified with perfluorooctyltriethoxysilane were further added (so that the mass ratio of core-shell filler: hollow microspheres: boron nitride is 20:32.5:15). The preparation method of perfluorooctyltriethoxysilane modified boron nitride nanosheets is as follows: 15g of hexagonal boron nitride nanosheets (h-BNNS, diameter 10μm, thickness <10nm) were taken and dispersed in 600mL of anhydrous ethanol and ultrasonically dispersed for 1-2 hours (power 300-500W). Then, a uniform suspension was formed by mechanical stirring (600 rpm). 1.2 g of perfluorooctyltriethoxysilane was slowly added dropwise to the suspension, and a small amount of ammonia (1 mL, 25% concentration) was added as a catalyst to adjust the pH to 9 to promote silane hydrolysis. The mixture was heated to 80 °C and reacted under nitrogen protection by magnetic stirring or reflux for 8 hours to allow the ethoxy groups of the silane to hydrolyze and condense with the hydroxyl groups on the surface of BNNS, forming covalent Si-OB / N bonds and grafting C8F17-fluoroalkyl chains. After the reaction was completed, the mixture was cooled to room temperature and washed five times with anhydrous ethanol by centrifugation (10,000 rpm, 15 min) to remove unreacted silane and byproducts. Subsequently, the mixture was dried in a vacuum drying oven at 80 °C for 24 hours to obtain white powdery perfluorooctyltriethoxysilane-modified boron fluoride nanosheets.Simultaneously, 20g of surface-fluorinated hexagonal boron nitride flakes (CAS No.: 10043-11-5, diameter 5 μm) were added as a thermally conductive enhancing phase. The preparation method of the surface-fluorinated hexagonal boron nitride flakes is as follows: 20g of hexagonal boron nitride flakes (h-BNflakes, CAS No.: 10043-11-5, diameter approximately 5μm, thickness 50-200nm) were dispersed in 800mL of anhydrous ethanol. The flakes were first ultrasonically dispersed for 1-3 hours (power 600W, to promote mild exfoliation and surface activation), then mechanically stirred (speed 800rpm) to form a uniform suspension. 1.6g of perfluorooctyltriethoxysilane was slowly added dropwise to the suspension, along with a small amount of ammonia (1.5mL, 28% concentration) as a thermally conductive enhancing phase. An alkaline catalyst was used to adjust the pH to 9.5 to promote the hydrolysis of silane ethoxy groups. The mixture was heated to 90°C and magnetically stirred or refluxed under nitrogen protection for 10 hours to allow the hydrolyzed silanol to undergo a condensation reaction with the boron sites or edge hydroxyl groups on the h-BN surface, forming stable Si-OB bonds and grafting C8F17-fluoroalkyl chains to improve surface energy matching PTFE (contact angle can reach over 130°). After the reaction was completed, the mixture was cooled to room temperature and the solid was separated by centrifugation (10,000 rpm, 20 min). The solid was washed 4-6 times alternately with anhydrous ethanol and deionized water to remove unreacted silanes, oligomers and byproducts. Then it was dried in a vacuum drying oven at 80°C for 24 hours to obtain white, thin, fluorinated hexagonal boron nitride flakes (F-hBN flakes). Then, 2.5g of polyoxyethylene nonylphenyl ether (CAS No.: 9014-90-8) and 250g of deionized water were added, and polytetrafluoroethylene nanocomposite dispersion was obtained by high-speed shearing and ultrasonic dispersion, and its infrared spectrum is shown below. Figure 7As shown. (5) Surface treatment and impregnation of glass fiber fabric: Electronic grade alkali-free glass fiber cloth (CAS No.: 65997-17-3) was selected. After calcination to remove the impregnating agent, it was first immersed in a solution containing 2.5% phenyltriethoxysilane (CAS No.: 780-69-8) and 0.85% γ-aminopropyltriethoxysilane (CAS No.: 919-30-2) for treatment; then immersed in a solution containing 2% (3,3,3-trifluoropropyl)trimethoxysilane (CAS No.: 429-60-7) and heat-treated at 200℃ for 15 minutes to form a gradient fluorinated layer. Subsequently, the dispersion of step (4) was impregnated, and the impregnation cycle was repeated 3 times. The resin weight gain rate was 15% each time. The mass ratio of resin solids to glass fiber cloth was controlled at 70:100. The roller pressing direction was staggered, and the prepreg was dried step by step. (6) Lamination and hot pressing and post-treatment: The prepreg from step (5) is stacked in multiple layers, with a total dielectric thickness of 200 micrometers. Roughened electrolytic copper foil (CAS No.: 7440-50-8, thickness 18 micrometers) is laid on the top and bottom. The hot pressing adopts a staged process: initial pressure of 0.75 MPa, holding at 240℃ for 15 minutes; increasing the pressure to 3 MPa, raising the temperature to 355℃ and holding for 60 minutes; cooling rate of 3℃ / min to release pressure below 80℃. Finally, edge trimming and copper surface micro-etching are performed: using a micro-etching solution containing 100g / L sulfuric acid and 25g / L hydrogen peroxide, the copper is treated at 30℃ for 60 seconds, cleaned and dried to obtain a PTFE-based high-frequency copper-clad laminate.

[0031] Examples 2-12 and Comparative Examples 1-12

[0032] To further verify the technical effects of the present invention, Examples 2-12 and Comparative Examples 1-12 were set up. Each example adjusted key parameters based on Example 1, while each comparative example was set by omitting key components, replacing conventional raw materials, or exceeding the parameter range. Specific parameter differences are shown in the table below (parameters not listed are consistent with those in Example 1).

[0033] Table 1: Parameter differences in step (1) for preparing high-entropy oxide nanoparticles

[0034]

[0035] Table 2: Differences in parameters for filler modification between steps (2) and (3)

[0036]

[0037] Table 3: Differences in formulation parameters of composite dispersion in step (4) (Base PTFE emulsion is 100g)

[0038]

[0039] Table 4: Differences between hot pressing process in step (6) and comparative design

[0040]

[0041] Performance Testing and Results Analysis

[0042] Performance tests were performed on the copper-clad laminates prepared in the above embodiments and comparative examples. Test standards and methods: Dielectric constant (Dk) and dielectric loss (Df): tested using the resonant cavity perturbation method at a frequency of 10 GHz, according to IPC-TM-6502.5.5.5 standard. Peel strength: tested using the adhesion between the copper foil and the dielectric layer, according to IPC-TM-6502.4.8 standard. Water absorption: tested using the weight gain after immersion in water for 24 hours, according to IPC-TM-6502.6.2.1 standard. Thermal conductivity: tested using the ASTM E1461 laser scintillation method.

[0043] Thermal decomposition temperature (Td, 5% loss): TGA thermogravimetric analysis was performed at a heating rate of 10℃ / min.

[0044] Table 5: Performance Test Results of Examples 1-12

[0045]

[0046] Table 6: Performance Test Results of Comparative Examples 1-12

[0047]

[0048] Results Analysis: High-Entropy Oxides and Particle Size Effect (Example 1 and Comparative Examples 1, 2, 11): Example 1 used PEI-assisted sol-gel method to prepare high-entropy oxide nanoparticles (55 nm). Utilizing the lattice distortion and high specific surface area brought about by the high-entropy effect, the interfacial compatibility between the filler and the PTFE matrix was effectively improved, with Dk decreasing to 2.18 and Df as low as 0.0009. Comparative Example 1 used ordinary alumina. Due to the lack of the unique "cocktail effect" and electromagnetic wave absorption modulation ability of high-entropy materials, Dk and Df increased significantly (2.58 / 0.0028), and the thermal conductivity decreased significantly. Comparative Example 2 did not add PEI, resulting in severe particle agglomeration, increased interfacial defects, and Df deteriorating to 0.0022. Comparative Example 11 had an excessively high calcination temperature, resulting in grain coarsening and a decrease in specific surface area, which also led to a decrease in dielectric properties and mechanical strength. Fluorination Modification and Interfacial Bonding (Examples 1 and 6, Comparative Examples 3, 5, 7): This invention constructed a comprehensive fluorination system. Comparative Example 3, lacking pentafluorobenzoyl chloride, exhibited strong hydrophilicity, resulting in a water absorption rate that surged to 0.045%, severely deteriorating high-frequency losses. Comparative Example 5, with hollow microspheres that had not undergone fluorosilane modification, suffered from poor adhesion to the PTFE matrix, leading to a water absorption rate as high as 0.052%, which also affected Dk. Comparative Example 7, with glass fiber that had not undergone gradient fluorination treatment, resulted in a "wicking effect," high water absorption, and a peel strength of only 1.05 N / mm, demonstrating the crucial role of the gradient fluorination layer in resisting damp heat. Example 6, compared to Example 1, reduced the fine structures such as silane co-modification and shell doping. Although its performance was superior to the comparative examples, it still lagged behind in the extremely low loss index (Df 0.0013), proving the effectiveness of the multi-layer shell structure. Multi-scale networks and functional fillers (Examples 1 and 8, Comparative Examples 4, 6, 9, 10, 12):

[0049] Comparative Example 4 used solid microspheres, which could not introduce air pores, resulting in a Dk as high as 2.65. Example 8 increased the proportion of hollow microspheres, achieving a minimum Dk of 2.14, but excessive amounts (Comparative Example 10) led to matrix continuity disruption, causing a sharp drop in peel strength to 0.88 N / mm. Comparative Examples 6 and 12 lacked boron fluoride nitride nanosheets and hexagonal boron nitride flakes, respectively. The lack of BNNS in Comparative Example 6 resulted in an incomplete microscopic dielectric network and an increase in Df; the lack of large-size h-BN in Comparative Example 12 led to a significant decrease in planar thermal conductivity (0.35 W / m·K), demonstrating the synergistic effect of multi-scale fillers in constructing a thermally conductive network. Comparative Example 9 had too little core-shell filler, which could not effectively suppress changes in the crystallinity of PTFE, resulting in poor thermal conductivity and mechanical properties. Influence of process parameters (Examples 1 and 9, Comparative Example 8): Comparative Example 8 did not use staged hot pressing, resulting in an imbalance between resin flow and microbubble discharge, leading to micropores inside the board, poor peel strength (0.95 N / mm), and a slightly higher Df. In Example 9, the holding time was too short, resulting in incomplete crystallization and a slight decrease in peel strength. In summary, this invention successfully prepared a high-frequency copper-clad laminate with extremely low dielectric loss, high thermal conductivity, and excellent resistance to damp heat through high-entropy oxide nano-sizing, omnidirectional fluorination interface modification, multi-scale filler compounding, and optimized processes.

[0050] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A method for preparing a PTFE-based high-frequency copper-clad laminate, characterized in that, The steps, by weight, are as follows: (1) Magnesium nitrate, cobalt nitrate, nickel nitrate, copper nitrate, and zinc nitrate are mixed in a mass ratio of (1-1.2):(1-1.2):(1-1.2):(1-1.2):(1-1.2) to obtain a mixed salt solution with a total mass of 100 parts; citric acid is added at 1.5-2.5 times the mass of the mixed salt solution, stirred and dissolved, followed by polyethyleneimine at 0.1-0.3 times the mass of the mixed salt solution, adjusting the pH to 7.0-8.0, heating and stirring to form a sol, then vacuum drying and calcining in an air atmosphere, followed by ball milling to obtain high-entropy oxide nanoparticles; (2) the steps are as follows: (1) 100 parts by weight of high-entropy oxide nanoparticles are dispersed in deionized water, and 2-6 parts by weight of dopamine hydrochloride are added. After stirring and reacting, a polydopamine coating layer is formed. Then, pentafluorobenzoyl chloride is added at a molar percentage of 120-180 of the dopamine molars. The reaction is carried out in the presence of triethylamine for 3-5 hours. After vacuum drying, fluorinated polydopamine-high-entropy oxide core-shell nanofiller is obtained. (3) 100 parts by weight of hollow alumina-silica ceramic microspheres are added to 400-600 parts by weight of anhydrous ethanol. 3-(methacryloyloxy)propyltrimethoxysilane is added dropwise at a molar percentage of 5-10 of the microsphere mass to adjust the temperature. Adjust the pH to 4.0-5.0, stir for 2-4 hours and dry; then add 1H,1H,2H,2H-perfluorodecyltrimethoxysilane at 2-6% by weight of the microspheres, continue the reaction and dry to obtain fluorine-modified hollow ceramic microspheres; (4) add 100 parts by weight of polytetrafluoroethylene aqueous dispersion, 8-35 parts by weight of fluorinated polydopamine-high entropy oxide core-shell nanofiller from step (2), and 15-50 parts by weight of fluorine-modified hollow ceramic microspheres from step (3) to the same container, then add 1-4 parts by weight of polyoxyethylene nonylphenyl ether and 150-350 parts by weight of deionized water, and disperse by high-speed shearing and ultrasonication to obtain (5) Select alkali glass fiber cloth, calcine to remove the wetting agent, and then immerse it in a solution containing 1-4% by mass of phenyltriethoxysilane and 0.2-1.5% by mass of γ-aminopropyltriethoxysilane. Then, immerse it in the dispersion of step (4), control the mass ratio of resin solid to glass fiber cloth to be 50-90:100, roll press to remove the residual liquid, and then dry it step by step to obtain the prepreg; (6) Stack the prepreg of step (5) in multiple layers with a total medium thickness of 80-350 micrometers, lay roughened electrolytic copper foil on the top and bottom, vacuum hot press, and then cool and depressurize to obtain a high-frequency copper-clad laminate based on PTFE.

2. The method for preparing a PTFE-based high-frequency copper-clad laminate according to claim 1, characterized in that: In step (1), magnesium nitrate, cobalt nitrate, nickel nitrate, copper nitrate and zinc nitrate are mixed in a mass ratio of (1-1.2):(1-1.2):(1-1.2):(1-1.2):(1-1.2):(1-1.2) to obtain a mixed salt solution.

3. The method for preparing a PTFE-based high-frequency copper-clad laminate according to claim 2, characterized in that: In step (1), the total mass of the mixed salt solution is 100 parts, the mass ratio of nitrate is 1:1:1:1:1, the amount of citric acid added is twice the mass of the mixed salt solution, the molecular weight of polyethyleneimine is 800-1200, and ammonia is used to adjust the pH; the heating and stirring temperature in step (1) is 80-100℃, the heating and stirring speed is 200-300rpm, and the heating and stirring time is 4-8 hours; the calcination temperature in step (1) is 800-1000℃, and the calcination time is 4-8 hours; in step (1), zirconium oxide balls are used for ball milling, the ball-to-material ratio is 10:1, the speed is 400-500r / min, and the time is 8-12 hours, resulting in high-entropy oxide nanoparticles with a specific surface area of ​​80-120m². 2 / g, with an average particle size of 30-80nm.

4. The method for preparing a PTFE-based high-frequency copper-clad laminate according to claim 1, characterized in that: The parameters for the stirring reaction in step (2) are as follows: stirring reaction for 6-10 hours at pH 8.2-8.8 and 25-35℃.

5. The method for preparing a PTFE-based high-frequency copper-clad laminate according to claim 1, characterized in that: In step (3), the hollow ceramic microspheres are further doped with a fluorine-containing shell: after silanization and drying, the microspheres are added to a deionized aqueous solution containing 1-4 parts by weight of silicon tetrafluoride and 2-8 parts by weight of aluminum nitrate nonahydrate, and hydrolyzed at pH 2.0-3.0, temperature 50-70℃, and time 2-4 hours, followed by calcination at 500-600℃ for 2-3 hours; the hollow alumina-silica ceramic microspheres in step (3) are a composite product of alumina and silica powder, with a particle size of 10-30 micrometers.

6. The method for preparing a PTFE-based high-frequency copper-clad laminate according to claim 1, characterized in that: In step (4), 5-25 parts by weight of boron fluoride nitride nanosheets are added, and the mass ratio of core-shell nanofiller, hollow ceramic microspheres and boron fluoride nitride nanosheets is (10-30):(20-45):(10-20) to construct a multi-scale low dielectric network structure.

7. The method for preparing a PTFE-based high-frequency copper-clad laminate according to claim 1, characterized in that: Step (5) further includes a gradient fluorination layer for the surface treatment of the glass fiber cloth: after the bissilane treatment, it is immersed in a solution containing 1-3% by mass of (3,3,3-trifluoropropyl)trimethoxysilane, and heat-treated at 180-220°C for 10-20 minutes; the impregnation includes 2-5 cycles, with a resin weight gain of 10-20% by mass each time, and the rolling directions are staggered to form an anisotropic structure.

8. The method for preparing a PTFE-based high-frequency copper-clad laminate according to claim 1, characterized in that: In step (6), the hot pressing adopts a staged process: initial pressure of 0.5-1.0 MPa, heating to 220-260℃ and holding for 10-20 minutes to remove moisture; increase pressure to 2-4 MPa, heating to 340-370℃ and holding for 40-80 minutes; cooling rate of 2-4℃ / minute to below 80℃; step (6) further includes edge trimming and copper surface micro-etching: micro-etching solution contains 50-150 g / L sulfuric acid and 10-40 g / L hydrogen peroxide, processing time of 30-90 seconds, and temperature of 25-35℃.

9. The method for preparing a PTFE-based high-frequency copper-clad laminate according to claim 1, characterized in that, The parameters for vacuum hot pressing in step (6) are as follows: hold the pressure at 1-4 MPa and 300-380℃ for 30-90 minutes in a vacuum hot press.

10. A high-frequency copper-clad laminate based on PTFE, characterized in that: The PTFE-based high-frequency copper clad laminate is obtained by the preparation method of the PTFE-based high-frequency copper clad laminate according to any one of claims 1-9.

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