A kind of polytetrafluoroethylene glass cloth high frequency copper clad plate modified by para-aramid nanofiber and its preparation method

Abstract

The application provides a kind of para-aramid nanofiber modified polytetrafluoroethylene glass fabric high-frequency copper-clad plate and a preparation method thereof, comprising the following steps: A) using silane coupling agent to modify the glass fabric, to obtain surface-modified glass fabric;B) the surface-modified glass fabric is immersed in aramid nanofiber modified polytetrafluoroethylene impregnating solution, and after taking out, drying to obtain impregnated glass fabric;C) the impregnated glass fabric is stacked in turn, and drying, impurity removal and sintering are carried out in turn under vacuum environment, to obtain a semi-cured sheet;D) the semi-cured sheet is covered with copper foil, and vacuum hot pressing treatment is carried out, to obtain a para-aramid nanofiber modified polytetrafluoroethylene glass fabric high-frequency copper-clad plate.The para-aramid nanofiber modified polytetrafluoroethylene glass fabric high-frequency copper-clad plate of the application has excellent dielectric properties, and the water absorption, peel strength, ultra-low loss, linear thermal expansion coefficient and other properties meet the index requirements of copper-clad polytetrafluoroethylene glass fabric laminated plate for microwave circuit.

Description

Technical Field

[0001] This invention belongs to the field of copper clad laminate preparation technology, and particularly relates to a high-frequency copper clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth and its preparation method. Background Technology

[0002] 5G communication features high frequency, high-speed transmission, low latency, and large-capacity storage. This necessitates that copper-clad laminates (CCLs) widely used in 5G equipment possess characteristics such as low dielectric constant, low dielectric loss, high thermal conductivity, excellent heat resistance, and high reliability. Polytetrafluoroethylene (PTFE) is a homopolymer of tetrafluoroethylene (TFE) with a very large molecular weight, typically exceeding several million. Furthermore, due to the small radius and extremely high electronegativity of fluorine atoms, the carbon backbone in its molecular structure is almost completely surrounded by fluorine atoms on both sides. This endows PTFE with excellent insulation, dielectric properties, high heat resistance, chemical resistance, and weather resistance, exhibiting extremely low dielectric loss at high frequencies. In the 1950s and 60s, the United States began utilizing the excellent dielectric properties of PTFE to manufacture CCLs for high-frequency micro-applications. Even today, PTFE CCLs remain an indispensable material in the communications field.

[0003] Currently, commercially available PTFE-based high-frequency copper-clad laminates typically use ceramic powder-modified polytetrafluoroethylene (PTFE) emulsions, followed by impregnation of fiberglass cloth with the ceramic powder-modified PTFE solution. However, PTFE emulsions have extremely low surface polarity, while ceramic powders have high surface polarity and a higher density than the emulsion. Ceramic powders tend to settle during impregnation and agglomerate during drying, hindering uniform dispersion within the PTFE particles. This results in variations in dielectric constant and thermal expansion at different locations in the final copper-clad laminate, affecting the stability of its dielectric properties. Furthermore, the relatively high dielectric constant of ceramic powder means that adding a certain amount will further increase the dielectric constant of the copper-clad laminate, failing to meet the low dielectric constant requirement for high-frequency copper-clad laminates. Summary of the Invention

[0004] The purpose of this invention is to provide a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth and its preparation method. The high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth in this invention has a low coefficient of thermal expansion, ultra-low loss (Df < 0.002) and stable dielectric properties.

[0005] This invention provides a method for preparing a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth, comprising the following steps:

[0006] A) Silane coupling agent is used to modify glass fiber cloth to obtain surface-modified glass fiber cloth;

[0007] B) The surface-modified glass fiber cloth is immersed in the aramid nanofiber modified polytetrafluoroethylene impregnation solution, and then dried to obtain the impregnated glass fiber cloth.

[0008] The aramid nanofiber modified polytetrafluoroethylene impregnation solution is obtained by mixing polytetrafluoroethylene aqueous dispersion emulsion and aramid nanofiber slurry;

[0009] C) Stack the resin-impregnated fiberglass cloths in sequence, and dry, remove impurities and sinter them in sequence under vacuum to obtain a semi-cured sheet;

[0010] D) The semi-cured sheet is coated with copper foil and subjected to vacuum hot pressing to obtain a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth.

[0011] Preferably, the modification treatment in step A) is as follows:

[0012] A silane coupling agent, an acidic medium, and water are mixed to obtain a silane coupling agent solution. Then, glass fiber cloth is immersed in the silane coupling agent solution for modification treatment to obtain surface-modified glass fiber cloth.

[0013] Preferably, an acidic medium is added to water to adjust the pH to 3.0–4.0, and then a silane coupling agent is added to obtain a silane coupling agent solution.

[0014] The mass concentration of the silane coupling agent solution is 0.2-0.5%, and the modification treatment time is 5-12 min.

[0015] Preferably, the silane coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane.

[0016] Preferably, the aramid nanofiber slurry is obtained by dispersing para-aramid nanofibers in water, wherein the diameter of the para-aramid nanofibers is 10-300 nm; and the mass ratio of water to para-aramid nanofibers is 300:(3-10).

[0017] Preferably, in the aramid nanofiber modified polytetrafluoroethylene impregnation solution, the mass ratio of polytetrafluoroethylene to para-aramid nanofibers is 1:(0.003-0.08).

[0018] Preferably, the vacuum level of the vacuum environment in step C) is -1 to -0.90 MPa.

[0019] Preferably, the drying temperature in step C) is 80–100°C, and the drying time is 10–30 min;

[0020] The temperature for impurity removal is 220–240℃, and the holding time for impurity removal is 10–20 minutes.

[0021] The sintering temperature is 330–350℃, and the sintering holding time is 60–120s.

[0022] Preferably, the vacuum degree of the vacuum hot pressing process in step D) is -1 to -0.93 MPa, and the hot pressing process curve is as follows:

[0023] First stage: Temperature 80-120℃, heat preservation time 30-60min, hot pressing pressure 0MPa;

[0024] Second stage: Temperature 220~240℃, heat preservation time 10~20min, hot pressing pressure 0MPa;

[0025] The third stage: the temperature is increased from 240℃ to 330℃, and the pressure is increased from 0~0.5MPa to 3~4MPa. The pressure increase is completed during the heating process.

[0026] Fourth stage: The temperature is raised from 330℃ to 350-380℃, and the pressure is gradually increased from 3-4MPa to 9-10MPa. The pressurization is completed during the heating process.

[0027] Fifth stage: Temperature 350~380℃, holding time 40~80min, hot pressing pressure 9~10MPa.

[0028] Stage 6: Allow the temperature to cool naturally to 250-270℃, then turn on water cooling for rapid cooling.

[0029] This invention provides a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth prepared by the preparation method described above.

[0030] This invention provides a method for preparing a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth, comprising the following steps: A) modifying the glass fiber cloth with a silane coupling agent to obtain a surface-modified glass fiber cloth; B) immersing the surface-modified glass fiber cloth in an aramid nanofiber modified polytetrafluoroethylene impregnation solution, removing it and drying it to obtain an impregnated glass fiber cloth; the aramid nanofiber modified polytetrafluoroethylene impregnation solution is obtained by mixing polytetrafluoroethylene aqueous dispersion emulsion and aramid nanofiber slurry; C) stacking the impregnated glass fiber cloth sequentially, and drying, removing impurities and sintering them sequentially under vacuum to obtain a prepreg; D) coating the prepreg with copper foil and performing vacuum hot pressing to obtain a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth. Because of the presence of amide bonds on the molecular chain of para-aramid nanofibers, they can easily combine with hydrogen bonds in water, achieving uniform and stable dispersion in aqueous solutions. This allows for the uniform mixing and stable existence of the para-aramid nanofiber aqueous dispersion and the polytetrafluoroethylene (PTFE) aqueous emulsion. Simultaneously, the para-aramid nanofibers possess low dielectric constant and low coefficient of thermal expansion. The copper-clad laminate obtained using the method of this invention avoids the sedimentation of modified fillers during impregnation. The resulting para-aramid nanofiber modified PTFE fiberglass cloth high-frequency copper-clad laminate exhibits excellent dielectric properties. Its water absorption rate, peel strength, ultra-low loss (Df < 0.002), and X / Y / Z (0℃~100℃) linear coefficient of thermal expansion all meet the requirements for PTFE fiberglass cloth laminates used in microwave circuits, demonstrating broad application prospects in the field of high-frequency copper-clad laminates. Detailed Implementation

[0031] This invention provides a method for preparing a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth, comprising the following steps:

[0032] A) Silane coupling agent is used to modify glass fiber cloth to obtain surface-modified glass fiber cloth;

[0033] B) The surface-modified glass fiber cloth is immersed in the aramid nanofiber modified polytetrafluoroethylene impregnation solution, and then dried to obtain the impregnated glass fiber cloth.

[0034] The aramid nanofiber modified polytetrafluoroethylene impregnation solution is obtained by mixing polytetrafluoroethylene aqueous dispersion emulsion and aramid nanofiber slurry;

[0035] C) Stack the resin-impregnated fiberglass cloths in sequence, and dry, remove impurities and sinter them in sequence under vacuum to obtain a semi-cured sheet;

[0036] D) The semi-cured sheet is coated with copper foil and subjected to vacuum hot pressing to obtain a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth.

[0037] The present invention first heat-treats the glass fiber cloth to remove the paraffin on the fiber surface, and then uses a silane coupling agent to modify the glass fiber cloth to obtain a surface-modified glass fiber cloth.

[0038] Because glass fiber has an overly smooth surface and very low surface free energy, resulting in low chemical reactivity, it cannot bond well with the resin matrix. This invention utilizes a silane coupling agent to modify it, allowing one group in the silane coupling agent to bond with the glass fiber and another group to bond with the matrix resin. This firmly connects the fiber and the matrix, two materials with very different properties, achieving excellent adhesion and improving the strength of the composite material. In this invention, the silane coupling agent is preferably γ-glycidyl etheroxypropyltrimethoxysilane. Specifically, in the embodiments of this invention, Dow Corning OFS-6040 silane coupling agent can be used.

[0039] In this invention, the glass fiber cloth can be a commonly used E-type electronic grade alkali-free glass fiber cloth, such as glass fiber cloth with model numbers 104, 106, 1080, 2116, and 7628.

[0040] The preferred temperature for the heat treatment is 430–450°C, more preferably 435–445°C, such as 430°C, 435°C, 440°C, 445°C, 450°C, and preferably a range of values ​​with the above values ​​as the upper or lower limit; the preferred time for the heat treatment is 20–40 min, more preferably 25–35 min, such as 20 min, 25 min, 30 min, 35 min, 40 min, and preferably a range of values ​​with the above values ​​as the upper or lower limit.

[0041] The specific steps for modifying the glass fiber cloth are as follows:

[0042] An acidic medium is added to water to adjust the pH to 3.0–4.0. Then, a silane coupling agent is added to obtain a silane coupling agent solution. The glass fiber cloth is then soaked in the silane coupling agent solution for a certain period of time to modify it. After being removed, it is naturally air-dried to obtain a surface-modified glass fiber cloth.

[0043] In this invention, the silane coupling agent is preferably Dow Corning OFS-6040, the acidic medium is preferably acetic acid, and the mass concentration of the silane coupling agent solution is preferably 0.2-0.5%, more preferably 0.3-0.4%.

[0044] In this invention, the modification time is preferably 5 to 12 minutes, more preferably 8 to 10 minutes; the drying temperature is preferably 100 to 120°C, more preferably 105 to 110°C; and the drying time is preferably 40 to 60 minutes, more preferably 50 to 55 minutes.

[0045] After obtaining the surface-modified glass fiber cloth, the present invention immerses the surface-modified glass fiber cloth in an aramid nanofiber modified polytetrafluoroethylene impregnation solution. After being immersed in the solution for a certain period of time, the impregnated glass fiber cloth is taken out, the excess solution is squeezed out, and it is naturally air-dried to obtain the impregnated glass fiber cloth.

[0046] In this invention, the aramid nanofiber modified polytetrafluoroethylene impregnation solution is prepared according to the following steps:

[0047] Para-aramid nanofibers were added to water and dispersed using a disperser to obtain a para-aramid nanofiber slurry.

[0048] Aqueous dispersion of polytetrafluoroethylene (PTFE) emulsion was mixed evenly with aramid nanofiber slurry to obtain para-aramid nanofiber modified PTFE impregnation solution.

[0049] In this invention, the diameter of the para-aramid nanofibers is preferably 10-300 nm, more preferably 50-250 nm, such as 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, and preferably within the range of any of the above values ​​as the upper or lower limit; the mass ratio of water to para-aramid nanofibers is preferably 300:(3-10), more preferably 300:(5-8), such as 300:3, 300:4, 300:5, 300:6, 300:7, 300:8, 300:9, 300:10, and preferably within the range of any of the above values ​​as the upper or lower limit.

[0050] The strong polarity of para-aramid nanofiber molecular chains causes their melting temperature to exceed their decomposition temperature upon heating. Further heating leads to decomposition, rendering them ineffective as adhesives that can be melted and bonded by traditional resins. Therefore, if glass fibers and para-aramid nanofibers are impregnated and then pressed together, the glass fibers and aramid nanofibers remain in a phase-separated state. The para-aramid nanofibers are merely physically adsorbed onto the glass fibers by van der Waals forces, failing to form a dense composite material.

[0051] In this invention, the polytetrafluoroethylene (PTFE) resin particles exist in a uniform aqueous dispersion state, sharing the same water solvent as the para-aramid nanofibers. This improves the feasibility of modifying the PTFE resin matrix with para-aramid nanofibers. This invention does not impose any special restrictions on the source of the PTFE aqueous dispersion emulsion; commercially available products containing PTFE aqueous dispersion emulsions well-known to those skilled in the art can be used. The solid content of the PTFE aqueous dispersion emulsion in this invention is preferably 50–80 wt%, more preferably 60–70 wt%, such as 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, preferably within a range where any of the above values ​​is the upper or lower limit.

[0052] In this invention, the mass ratio of polytetrafluoroethylene to para-aramid nanofibers in the aramid nanofiber modified polytetrafluoroethylene impregnation solution is preferably 1:(0.003-0.08), more preferably 1:(0.005-0.05), such as 1:0.003, 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, and preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0053] In this invention, the immersion time of the surface-modified fiberglass cloth in the impregnation solution is preferably 3 to 8 minutes, more preferably 5 to 6 minutes, such as 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, preferably any of the above values ​​as the upper or lower limit; the immersion temperature can be carried out at room temperature.

[0054] In this invention, the natural drying time after impregnation is preferably 1 to 10 hours, more preferably 4 to 6 hours.

[0055] Impregnated fiberglass cloth is stacked in sequence, with release cloth separating the layers. It is placed in a vacuum atmosphere furnace and heated to perform drying, dehydration, impurity removal and sintering in sequence to obtain a semi-cured sheet.

[0056] In this invention, the vacuum degree in the vacuum atmosphere furnace is preferably -1 to -0.90 MPa, more preferably -1 MPa to -0.98 MPa; the drying and dehydration temperature is preferably 80 to 100°C, more preferably 85 to 95°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, preferably within the range of any of the above values ​​as the upper or lower limit; the drying time is preferably 10 to 30 min, more preferably 15 to 25 min.

[0057] The preferred temperature for impurity removal is 220–240°C, more preferably 225–235°C, such as 220°C, 225°C, 230°C, 235°C, 240°C, and preferably any of the above values ​​as the upper or lower limit; the preferred heat preservation time for impurity removal is 10–20 min, more preferably 12–18 min.

[0058] The sintering temperature is preferably 330–350°C, more preferably 335–345°C, such as 330°C, 335°C, 340°C, 345°C, 350°C, and preferably within the range of any of the above values ​​as the upper or lower limit; the sintering holding time is preferably 60–120 s, more preferably 70–100 s, such as 60 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, and preferably within the range of any of the above values ​​as the upper or lower limit.

[0059] After sintering is complete, the temperature is rapidly reduced to below 60°C.

[0060] In this invention, the resin content of the prepreg is calculated by measuring the mass change of the glass fiber cloth before and after impregnation with the adhesive solution. The obtained prepreg is then subjected to repeated impregnation, drying, impurity removal, and sintering steps as needed to increase the resin content until a predetermined resin content is reached. In this invention, the resin content in the prepreg is preferably 40-70%, more preferably 50-60%, such as 40%, 45%, 50%, 55%, 60%, 65%, or 70%, preferably within a range where any of the above values ​​is the upper or lower limit.

[0061] The obtained semi-cured sheets are stacked, and copper foil is applied to the top and bottom surfaces or to one side. Then, vacuum hot pressing is performed to obtain a high-frequency copper-clad laminate of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth.

[0062] In this invention, the vacuum degree of the vacuum hot pressing process is preferably -1 to -0.93 MPa, more preferably -0.98 MPa; the hot pressing process curve is as follows:

[0063] First stage: temperature 80-120℃, preferably 90-110℃, more preferably 90-100℃; holding time 30-60min, preferably 40-50min; hot pressing pressure 0MPa;

[0064] Second stage: temperature 220-240℃, preferably 230-235℃; holding time 10-20min, preferably 15-20min; hot pressing pressure 0MPa;

[0065] The third stage: the temperature is increased from 240℃ to 330℃, and the pressure is increased from 0~0.5MPa to 3~4MPa. The pressure increase is completed during the heating process.

[0066] Fourth stage: The temperature is raised from 330℃ to 350-380℃, and the pressure is gradually increased from 3-4MPa to 9-10MPa. The pressurization is completed during the heating process.

[0067] Fifth stage: Temperature 350~380℃, holding time 40~80min, hot pressing pressure 9~10MPa.

[0068] Stage 6: Allow the temperature to drop naturally to 250-270℃, then turn on water cooling for rapid cooling.

[0069] This invention provides a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth, which is prepared according to the preparation method described above.

[0070] The high-frequency copper-clad laminate modified with para-aramid nanofibers and polytetrafluoroethylene glass fiber cloth in this invention has ultra-low dielectric loss (<0.002).

[0071] This invention provides a method for preparing a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth, comprising the following steps: A) modifying the glass fiber cloth with a silane coupling agent to obtain a surface-modified glass fiber cloth; B) immersing the surface-modified glass fiber cloth in an aramid nanofiber modified polytetrafluoroethylene impregnation solution, removing it and drying it to obtain an impregnated glass fiber cloth; the aramid nanofiber modified polytetrafluoroethylene impregnation solution is obtained by mixing polytetrafluoroethylene aqueous dispersion emulsion and aramid nanofiber slurry; C) stacking the impregnated glass fiber cloth sequentially, and drying, removing impurities and sintering them sequentially under vacuum to obtain a prepreg; D) coating the prepreg with copper foil and performing vacuum hot pressing to obtain a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth. Because of the presence of amide bonds on the molecular chain of para-aramid nanofibers, they can easily combine with hydrogen bonds in water to achieve uniform and stable dispersion in aqueous solution. Therefore, it is possible to achieve uniform mixing and stable existence of para-aramid nanofiber aqueous dispersion and polytetrafluoroethylene aqueous emulsion. At the same time, para-aramid nanofibers have low dielectric constant and low coefficient of thermal expansion. The copper-clad laminate obtained by the method of this invention avoids the sedimentation of modified fillers during impregnation. The high-frequency copper-clad laminate of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth prepared by pressing has a low coefficient of thermal expansion, ultra-low loss (Df < 0.002) and stable dielectric properties.

[0072] To further illustrate the present invention, the following detailed description of the high-frequency copper-clad laminate of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth and its preparation method provided by the present invention is provided in conjunction with the embodiments, but it should not be construed as a limitation on the scope of protection of the present invention.

[0073] Example 1

[0074] (1) Add 5 parts by weight of para-aramid nanofibers with a diameter of 50 nm to 100 nm to 300 parts by weight of water, and disperse by stirring with a dispersant to obtain para-aramid nanofiber slurry.

[0075] (2) The solid content of the polytetrafluoroethylene (PTFE) aqueous dispersion emulsion is 60%. The mass ratio of polytetrafluoroethylene in the polytetrafluoroethylene aqueous dispersion emulsion to the mass ratio of para-aramid nanofiber in the para-aramid nanofiber slurry is 100:4. The para-aramid nanofiber modified polytetrafluoroethylene adhesive is obtained.

[0076] (3) Select a suitable amount of E-type electronic grade alkali-free glass fiber cloth of model 1080, place it in a muffle furnace and heat-treat it at 450℃ for 35 minutes to remove the paraffin on the fiber surface.

[0077] (4) Add acetic acid to deionized water and stir to adjust the pH to 4.0. Then, add the corresponding silane coupling agent according to the mass of deionized water and stir slowly until the solution is clear to obtain a silane coupling agent solution with a content of 0.5%.

[0078] (5) Soak the dewaxed glass fiber cloth in a silane coupling agent solution for 8 minutes, take it out and air dry it naturally, and dry it in an oven at 110°C for 50 minutes for later use to obtain surface-modified glass fiber cloth.

[0079] (6) Place the aramid nanofiber modified polytetrafluoroethylene impregnation solution obtained in step (2) into the impregnation tank, arrange the surface modified glass fiber obtained in step (5) in the impregnation tank, and after the glass fiber cloth is completely immersed in the adhesive solution for 5 minutes, take out the impregnated glass fiber cloth and squeeze out the excess adhesive solution using the extrusion roller, and let it air dry naturally for 4 to 6 hours to obtain the impregnated glass fiber cloth.

[0080] (7) Stack the impregnated fiberglass cloth obtained in step (6) in sequence, with the layers separated by a release cloth, place it in a vacuum atmosphere furnace, evacuate to -1MPa to -0.98MPa, and process it according to the following process:

[0081] First stage: Heat up to 100℃ for dehydration and drying, and keep warm for 20 minutes;

[0082] Second stage: Remove impurities at 230℃ and keep warm for 10 minutes;

[0083] Third stage: Sintering, 350℃, holding for 120s;

[0084] Phase 4: Rapidly cool down to <60℃.

[0085] A semi-cured sheet of polytetrafluoroethylene glass fiber cloth modified with para-aramid nanofibers was obtained.

[0086] (8) Repeat the impregnation process of step (6) and the drying, impurity removal and sintering process of step (7) on the para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth semi-cured sheet obtained in step (7) to increase the resin content of the semi-cured sheet. Repeat this process multiple times until the resin content of the semi-cured sheet reaches 50%.

[0087] (9) Take a high-frequency copper foil with a nominal thickness of 35μm. Stack the copper foil, the multilayer para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth semi-cured sheet obtained in step (8), and the copper foil in sequence. Place them on a steel plate mold, place a gasket of nominal thickness, and then transfer them to a vacuum hot press. The vacuum degree is maintained at -0.98MPa throughout the hot pressing process. Press according to the process in Table 1:

[0088] Table 1. Example 1: Hot pressing process

[0089]

[0090] Comparative Example 1

[0091] The preparation process is the same as in Example 1, except that the modification of the polytetrafluoroethylene aqueous dispersion emulsion with para-aramid nanofiber aqueous dispersion in steps (1) and (2) is omitted. A polytetrafluoroethylene (PTFE) aqueous dispersion emulsion with a solid content of 60% is used directly as the impregnation solution.

[0092] The physical property analysis results of the copper-clad laminate prepared by para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth in Example 1 and the copper-clad laminate prepared by the comparative example are shown in Table 2.

[0093] Table 2. Physical property parameters of the copper-clad laminates prepared in the examples.

[0094]

[0095] As shown in Table 2, the copper-clad laminate modified with para-aramid nanofibers and polytetrafluoroethylene glass fiber cloth prepared by the present invention has stable dielectric properties and a low coefficient of thermal expansion.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth, comprising the following steps: A) A surface-modified glass fiber cloth is obtained by modifying the glass fiber cloth with a silane coupling agent; the silane coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane. B) The surface-modified glass fiber cloth is immersed in the aramid nanofiber modified polytetrafluoroethylene impregnation solution, and then dried to obtain the impregnated glass fiber cloth. The aramid nanofiber modified polytetrafluoroethylene impregnation solution is obtained by mixing polytetrafluoroethylene aqueous dispersion emulsion and aramid nanofiber slurry; the aramid nanofiber slurry is obtained by dispersing para-aramid nanofibers in water, the diameter of the para-aramid nanofibers being 10~100nm; the mass ratio of water to para-aramid nanofibers is 300:(3~10). In the aramid nanofiber modified polytetrafluoroethylene impregnation solution, the mass ratio of polytetrafluoroethylene to para-aramid nanofibers is 1:(0.003~0.08). C) Stack the resin-impregnated fiberglass cloths in sequence, and dry, remove impurities and sinter them in sequence under vacuum to obtain a semi-cured sheet; The drying temperature in step C) is 80~100℃, and the drying time is 10~30min; The temperature for impurity removal is 220~240℃, and the holding time for impurity removal is 10~20min; The sintering temperature is 330~350℃, and the sintering holding time is 60~120s; D) The semi-cured sheet is coated with copper foil and subjected to vacuum hot pressing to obtain a high-frequency copper-clad laminate of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth.

2. The preparation method according to claim 1, characterized in that, The modification process in step A) is as follows: A silane coupling agent, an acidic medium, and water are mixed to obtain a silane coupling agent solution. Then, glass fiber cloth is immersed in the silane coupling agent solution for modification treatment to obtain surface-modified glass fiber cloth.

3. The preparation method according to claim 2, characterized in that, Add an acidic medium to water to adjust the pH to 3.0-4.0, then add a silane coupling agent to obtain a silane coupling agent solution. The mass concentration of the silane coupling agent solution is 0.2~0.5%, and the modification treatment time is 5~12 min.

4. The preparation method according to claim 1, characterized in that, The vacuum level of the vacuum environment in step C) is -1 to -0.90 MPa.

5. The preparation method according to claim 1, characterized in that, The vacuum degree of the vacuum hot pressing process in step D) is -1 to -0.93 MPa, and the hot pressing process curve is as follows: First stage: Temperature 80~120℃, heat preservation time 30~60min, hot pressing pressure 0 MPa; Second stage: Temperature 220~240℃, heat preservation time 10~20min, hot pressing pressure 0MPa; The third stage: the temperature is increased from 240℃ to 330℃, and the pressure is increased from 0~0.5MPa to 3~4MPa. The pressure increase is completed during the heating process. Fourth stage: The temperature is raised from 330℃ to 350~380℃, and the pressure is gradually increased from 3~4MPa to 9~10MPa. The pressurization is completed during the heating process. Fifth stage: Temperature 350~380℃, holding time 40~80min, hot pressing pressure 9~10MPa; Stage 6: Allow the temperature to cool naturally to 250~270℃, then turn on water cooling for rapid cooling.

6. The high-frequency copper-clad laminate made of para-aramid nanofiber modified polytetrafluoroethylene glass fiber cloth by the preparation method according to any one of claims 1 to 5.

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