Composite adhesive film for high-frequency copper-clad plate as well as preparation method and application of composite adhesive film

Abstract

The invention provides a composite adhesive film for a high-frequency copper-clad plate as well as a preparation method and application of the composite adhesive film. The preparation method comprises the following steps: (1) sequentially carrying out plasma surface treatment and silane coupling agent modification on polytetrafluoroethylene fiber cloth to obtain modified polytetrafluoroethylene fiber cloth; and (2) mixing the modified polytetrafluoroethylene fiber cloth prepared in the step (1) with the modified polyphenyl ether, and drying to obtain the composite adhesive film for the high-frequency copper-clad plate, the modified polyphenyl ether is polyphenyl ether containing unsaturated double bonds and fluorine substituent groups; the silane coupling agent comprises a silane coupling agent containing a carbon-carbon double bond and / or a silane coupling agent containing a carbon-carbon triple bond. According to the composite adhesive film for the high-frequency copper-clad plate provided by the invention, the interface compatibility of the polytetrafluoroethylene fiber cloth and the resin matrix is good, and the high-frequency copper-clad plate prepared from the composite adhesive film has the characteristics of low dielectric constant, low dielectric loss and good welding resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of copper clad laminate preparation, and particularly relates to a composite adhesive film for high-frequency copper clad laminates, a preparation method thereof, and applications thereof. Background Art

[0002] At present, with the development of high-frequency communications, the requirements for the dielectric properties and thermal conductivity of copper clad laminates are becoming increasingly higher. Conventional epoxy resin and glass fiber cloth reinforcement materials can no longer meet the dielectric material requirements of high-end high-frequency communications due to their large dielectric constant and signal loss.

[0003] Compared with ordinary glass fiber cloth, polytetrafluoroethylene fiber cloth has excellent dielectric, corrosion resistance and insulation properties, and has great application potential in the field of high-frequency and high-speed copper clad laminates.

[0004] CN119261326A discloses an LCP-based copper-clad laminate, a preparation method, and an application thereof. The LCP-based copper-clad laminate comprises a PTFE fiber cloth; and on one surface of the PTFE fiber cloth, a first LCP film, a first metal film, and a first copper layer are sequentially stacked in a direction away from the PTFE fiber cloth; and on the other surface of the PTFE fiber cloth, a second LCP film, a second metal film, and a second copper layer are sequentially stacked in a direction away from the PTFE fiber cloth. This technical solution laminates a PTFE fiber cloth having a low dielectric constant and dielectric loss with the first LCP film and the second LCP film to produce an LCP-based copper-clad laminate having a low dielectric constant and dielectric loss.

[0005] CN115515303A discloses a PTFE low thermal expansion coefficient copper-clad laminate and its preparation method. The PTFE low thermal expansion coefficient copper-clad laminate comprises a fiber-based fabric with a metal layer provided on its upper and / or lower surface, connected to the fiber-based fabric via an adhesive layer. The fiber-based fabric is woven from polytetrafluoroethylene fibers or a combination of polytetrafluoroethylene fibers and a blended fiber. This solution uses polytetrafluoroethylene fiber cloth or a combination of polytetrafluoroethylene fibers and a blended fiber cloth instead of glass fiber cloth, significantly reducing the dielectric constant and dielectric loss of the composite substrate.

[0006] However, the surface energy of polytetrafluoroethylene is low, which makes the interface compatibility of polytetrafluoroethylene fiber cloth with resin matrix, adhesive, etc. poor. When working for a long time, it will affect the comprehensive performance of the copper clad laminate and have poor solder resistance.

[0007] Therefore, it is necessary to develop a high-frequency copper clad laminate with low dielectric constant and dielectric loss, good stability and good solder resistance. Summary of the Invention

[0008] In response to the shortcomings of the prior art, the present invention provides a composite adhesive film for high-frequency copper-clad laminates, a preparation method, and applications thereof. The composite adhesive film for high-frequency copper-clad laminates comprises polytetrafluoroethylene fiber cloth with good interfacial compatibility with the resin matrix, resulting in a high-frequency copper-clad laminate having low dielectric constant, low dielectric loss, and good solder resistance.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a composite adhesive film for a high-frequency copper clad laminate, the preparation method comprising the following steps:

[0011] (1) subjecting a polytetrafluoroethylene fiber cloth to plasma surface treatment and silane coupling agent modification in sequence to obtain a modified polytetrafluoroethylene fiber cloth;

[0012] (2) mixing the modified polytetrafluoroethylene fiber cloth and modified polyphenylene ether obtained in step (1), and drying them to obtain the composite adhesive film for the high-frequency copper clad laminate;

[0013] The modified polyphenylene ether is a polyphenylene ether containing unsaturated double bonds and fluorine-containing substituents;

[0014] The silane coupling agent includes a silane coupling agent containing a carbon-carbon double bond and / or a silane coupling agent containing a carbon-carbon triple bond.

[0015] In the present invention, the composite adhesive film for high-frequency copper-clad laminates is prepared by sequentially subjecting polytetrafluoroethylene fiber cloth to plasma surface treatment and silane coupling agent modification, thereby improving the interfacial compatibility between the polytetrafluoroethylene fiber cloth and the resin matrix-modified polyphenylene ether. The high-frequency copper-clad laminates prepared using the composite adhesive film have low dielectric constant, low dielectric loss, and good solder resistance. The polytetrafluoroethylene fiber cloth is subjected to plasma surface treatment, and hydroxyl groups are grafted onto its surface. The hydroxyl groups on the polytetrafluoroethylene fiber cloth then undergo a shrinkage reaction with the hydroxyl groups generated by hydrolysis of a silane coupling agent containing a carbon-carbon double bond and / or a silane coupling agent containing a carbon-carbon triple bond, thereby grafting the silane coupling agent containing a carbon-carbon double bond and / or a silane coupling agent containing a carbon-carbon triple bond onto the surface of the polytetrafluoroethylene fiber cloth. The modified polyphenylene ether contains unsaturated double bonds. During the preparation of high-frequency copper-clad laminates, the composite adhesive film for high-frequency copper-clad laminates is subjected to vacuum hot pressing, and the unsaturated double bonds in the modified polyphenylene ether undergo an addition reaction with the carbon-carbon double bonds and / or carbon-carbon triple bonds on the surface of the modified polytetrafluoroethylene fiber cloth, thereby significantly improving the interfacial compatibility between the two, reducing interfacial polarity, inhibiting polarization effects, and effectively reducing the generation of charge traps. This helps to reduce the dielectric constant and dielectric loss of the composite adhesive film, improve solder resistance, and enable the copper-clad laminates prepared using the composite adhesive film for high-frequency copper-clad laminates to be applied to more high-frequency fields.

[0016] Preferably, the thickness of the polytetrafluoroethylene fiber cloth in step (1) is 10 to 100 μm (for example, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm or 90 μm, etc.), and more preferably 10 to 50 μm.

[0017] Preferably, the gas used in the plasma surface treatment includes any one of H2, NH3, Ar, N2, O2 or CF4, or a combination of at least two of them.

[0018] Preferably, the gases used in the plasma surface treatment include H2, CF4 and O2.

[0019] Preferably, the volume ratio of H2, CF4 and O2 is (1-3.5):(1-2):1, for example, 1.2:1:1, 1.5:1:1, 1.7:1:1, 2:1:1, 1.2:1:1, 2.5:1:1, 2.7:1:1, 3:1:1, 3.2:1:1, 1.5:1.2:1, 2:1.5:1 or 3:1.8:1, etc., and more preferably (2-2.5):(1-2):1.

[0020] In the present invention, the volume ratio of H2, CF4 and O2 is preferably (1-3.5):(1-2):1. If the proportion of H2 is too high, it will lead to excessive etching of the polytetrafluoroethylene fiber cloth and may introduce unstable free radicals; while if the proportion of H2 is too low, the number of active hydrogen ions and free radicals will be reduced, and sufficient CF bonds cannot be effectively broken, resulting in poor modification effect.

[0021] Preferably, the flow rate of the gas used in the plasma surface treatment is 30 to 80 mL / min, for example, 35 mL / min, 40 mL / min, 45 mL / min, 50 mL / min, 55 mL / min, 60 mL / min, 65 mL / min, 70 mL / min or 75 mL / min, and more preferably 50 to 80 mL / min.

[0022] Preferably, the power of the plasma surface treatment is 300-2000 W, for example, 500 W, 700 W, 900 W, 1100 W, 1300 W, 1500 W, 1700 W or 1900 W.

[0023] Preferably, the absolute vacuum degree of the plasma surface treatment is ≤1×10 -6 Pa, for example 2×10 -7 Pa, 3×10 -7 Pa, 4×10 -7 Pa, 5×10 -7 Pa, 6×10 -7 Pa, 7×10-7 Pa, 8×10 -7 Pa or 9×10 -7 Pa et al.

[0024] Preferably, the temperature of the plasma surface treatment is 70-300°C, such as 100°C, 130°C, 160°C, 190°C, 210°C, 240°C or 270°C, and more preferably 80-160°C.

[0025] Preferably, the plasma surface treatment time is 10 to 60 min, for example, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min or 55 min, and more preferably 10 to 30 min.

[0026] Preferably, the silane coupling agent containing a carbon-carbon double bond includes any one of vinyltrimethoxysilane, methylvinyldiethoxysilane or vinyltri(β-methoxyethoxy)silane, or a combination of at least two thereof.

[0027] Preferably, the silane coupling agent modification in step (1) comprises the following steps: placing the polytetrafluoroethylene fibers after plasma surface treatment in a modification liquid for modification treatment, and drying to obtain the modified polytetrafluoroethylene fiber cloth.

[0028] Preferably, the modifying liquid comprises a silane coupling agent, ethanol and a pH regulator.

[0029] Preferably, the modified liquid is prepared by the following method: after mixing the silane coupling agent and ethanol, a pH regulator is added thereto to obtain a modified liquid with a pH value of 3 to 4 (for example, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8 or 3.9, etc.).

[0030] Preferably, the mass ratio of the silane coupling agent to ethanol is (1-2):100, for example, 1.1:100, 1.2:100, 1.3:100, 1.4:100, 1.5:100, 1.6:100, 1.7:100, 1.8:100 or 1.9:100, etc.

[0031] Preferably, the pH adjuster comprises a hydrochloric acid solution.

[0032] Preferably, the concentration of the hydrochloric acid solution is 0.05-0.20 mol / L, for example, 0.07 mol / L, 0.09 mol / L, 0.11 mol / L, 0.13 mol / L, 0.15 mol / L, 0.17 mol / L or 0.19 mol / L.

[0033] Preferably, the modification treatment is carried out under stirring conditions.

[0034] Preferably, the temperature of the modification treatment is 50-80°C, for example, 53°C, 56°C, 59°C, 62°C, 65°C, 68°C, 71°C, 74°C or 77°C.

[0035] Preferably, the modification treatment time is 1.5 to 2.5 h, for example, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2.0 h, 2.1 h, 2.2 h, 2.3 h or 2.4 h.

[0036] Preferably, the raw materials for preparing the modified polyphenylene ether include polyphenylene ether, fluorine-containing bisphenol compounds and acrylic anhydride compounds.

[0037] Preferably, the fluorine-containing bisphenol compound includes 4,4-(hexafluoroisopropylidene)diphenol (bisphenol AF).

[0038] Preferably, the acrylic anhydride compound includes methacrylic anhydride and / or acrylic anhydride.

[0039] Preferably, the raw materials for preparing the modified polyphenylene ether further include an initiator and / or a catalyst.

[0040] Preferably, the initiator comprises an alkyl peroxide and / or an acyl peroxide.

[0041] Preferably, the alkyl peroxide comprises tert-butyl hydroperoxide and / or dicumyl peroxide.

[0042] Preferably, the acyl peroxide comprises benzoyl peroxide.

[0043] Preferably, the catalyst comprises 4-dimethylaminopyridine.

[0044] Preferably, the raw materials for preparing the modified polyphenylene ether further include non-fluorinated bisphenol compounds;

[0045] Preferably, the non-fluorine-containing bisphenol compound includes 4,4-dihydroxydiphenylmethane (bisphenol F) and / or 2,2-bis(4-hydroxyphenyl)propane (bisphenol A).

[0046] Preferably, the preparation method of the modified polyphenylene ether comprises the following steps:

[0047] (I) Polyphenylene ether, a fluorinated bisphenol compound, a solvent and an optional initiator are mixed and reacted to obtain bishydroxy polyphenylene ether.

[0048] (II) mixing the bishydroxy polyphenylene ether prepared in step (I), an acrylic anhydride compound, a solvent and optionally a catalyst, and reacting them to obtain the modified polyphenylene ether.

[0049] Preferably, the mass ratio of the polyphenylene ether and the fluorinated bisphenol compound in step (I) is (1-5):1, for example, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1 or 4.5:1.

[0050] Preferably, the mass ratio of the polyphenylene ether to the solvent in step (I) is 1:(1.5-3), for example, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6 or 1:2.8.

[0051] Preferably, the solvent in step (I) comprises tetrahydrofuran.

[0052] Preferably, the mass ratio of the polyphenylene ether to the initiator in step (I) is (10-30):1, for example, 12:1, 14:1, 16:1, 18:1, 20:1, 22:1, 24:1, 26:1 or 28:1.

[0053] Preferably, the reaction in step (I) is carried out under a nitrogen atmosphere.

[0054] Preferably, the reaction temperature in step (I) is 90-100°C (e.g., 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C or 99°C, etc.), and the reaction time is 4-6h (e.g., 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, 5.2h, 5.4h, 5.6h or 5.8h, etc.).

[0055] Preferably, the mass ratio of the bishydroxy polyphenylene ether and the acrylic anhydride compound in step (II) is 6:(1-2), for example, 6:1.1, 6:1.2, 6:1.3, 6:1.4, 6:1.5, 6:1.6, 6:1.7, 6:1.8 or 6:1.9.

[0056] Preferably, the mass ratio of the bishydroxy polyphenylene ether to the catalyst in step (II) is 6:(1-2), for example, 6:1.1, 6:1.2, 6:1.3, 6:1.4, 6:1.5, 6:1.6, 6:1.7, 6:1.8 or 6:1.9.

[0057] Preferably, the mass ratio of the bishydroxy polyphenylene ether to the solvent in step (II) is 1:(12-20), for example, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18 or 1:19.

[0058] Preferably, the solvent in step (II) comprises chlorobenzene.

[0059] Preferably, the reaction temperature in step (II) is 60-80°C (e.g., 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C or 78°C, etc.), and the reaction time is 4-6h (e.g., 4.2h, 4.4h, 4.6h, 4.8h, 5.0h, 5.2h, 5.4h, 5.6h or 5.8h, etc.).

[0060] Preferably, the reaction in step (I) and step (II) further comprises the steps of washing with methanol, filtering and drying independently after the reaction.

[0061] Preferably, the mixing of the modified polytetrafluoroethylene fiber cloth and the modified polyphenylene ether in step (2) comprises impregnating the modified polytetrafluoroethylene fiber cloth with a modified polyphenylene ether solution to achieve mixing.

[0062] Preferably, the modified polyphenylene ether solution comprises modified polyphenylene ether and a solvent.

[0063] Preferably, the mass ratio of the modified polyphenylene ether to the solvent in the modified polyphenylene ether solution is 1:(5-10), for example, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9 or 1:9.5.

[0064] Preferably, the solvent in the modified polyphenylene ether solution includes any one of toluene, xylene or N,N-dimethylformamide, or a combination of at least two of them.

[0065] Preferably, the immersion time is 30 to 60 min, for example, 33 min, 36 min, 39 min, 42 min, 45 min, 48 min, 51 min, 54 min or 57 min.

[0066] Preferably, the drying temperature in step (2) is 100-120°C, for example, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C or 118°C.

[0067] Preferably, the drying time in step (2) is 1.5 to 3.0 h, for example, 1.7 h, 1.9 h, 2.1 h, 2.3 h, 2.5 h, 2.7 h or 2.9 h.

[0068] In a second aspect, the present invention provides a composite adhesive film for high-frequency copper clad laminates, which is prepared by the preparation method described in the first aspect.

[0069] In a third aspect, the present invention provides a high-frequency copper clad laminate, comprising the composite adhesive film for high-frequency copper clad laminate as described in the second aspect and copper foil.

[0070] Preferably, the high-frequency copper clad laminate is prepared by the following method: laminating a layer of copper foil on the upper and lower surfaces of a composite adhesive film for the high-frequency copper clad laminate, and vacuum hot pressing to obtain the high-frequency copper clad laminate.

[0071] Preferably, the temperature of the vacuum hot pressing is 190-240°C, for example, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C or 235°C.

[0072] Preferably, the pressure of the vacuum hot pressing is 3-10 MPa, for example, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa or 9 MPa.

[0073] Preferably, the vacuum hot pressing time is 60 to 120 minutes, for example, 70 minutes, 80 minutes, 90 minutes, 100 minutes or 110 minutes.

[0074] In a fourth aspect, the present invention provides a use of the composite adhesive film for high-frequency copper clad laminate as described in the second aspect or the high-frequency copper clad laminate as described in the third aspect in the preparation of a high-frequency circuit board.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] The present invention uses a polyphenylene ether containing unsaturated double bonds and fluorine-containing substituents as the resin matrix and improves the interfacial compatibility between the polytetrafluoroethylene fiber cloth and the resin matrix to achieve the effects of reducing the dielectric constant and dielectric loss and improving solder resistance. The high-frequency copper-clad laminate made of the composite adhesive film has a dielectric constant of ≤2.35, a dielectric loss of ≤0.007, and a solder resistance of >5 minutes at a frequency of 10 GHz. In preferred embodiments, the dielectric constant is ≤2.20, the dielectric loss is ≤0.006, and the solder resistance is >5 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 A schematic structural diagram of the high-frequency copper-clad laminate provided in Example 1;

[0078] Among them, 1-upper copper foil layer; 2-composite adhesive film layer for high-frequency copper clad laminate; 3-lower copper foil layer. DETAILED DESCRIPTION

[0079] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0080] The sources of some components in the following examples and comparative examples are as follows:

[0081] Polyphenylene ether powder: Model: S201, Mn = 12600 g / mol, purchased from Asahi Kasei Industries, Japan;

[0082] Toluene, chlorobenzene, methanol, bisphenol A, benzoyl peroxide, methylvinyldimethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, and ethanol reagents were purchased from Shanghai Aladdin Chemical Reagent Co., Ltd.

[0083] Other reagents and experimental instruments are commercially available in the art.

[0084] Example 1

[0085] This embodiment provides a composite adhesive film for high-frequency copper clad laminates, a preparation method thereof, and a high-frequency copper clad laminate. The preparation method of the composite adhesive film for high-frequency copper clad laminates comprises the following steps:

[0086] (1) Polytetrafluoroethylene fiber cloth (thickness 20 μm) was subjected to plasma surface treatment. The gases used were H2, CF4, and O2 in a volume ratio of 2:1:1. The gas flow rate was 60 mL / min, the power was 1000 W, and the absolute vacuum was 1×10 - 6 Pa, the plasma surface treatment temperature is 120 ° C, the treatment time is 50 minutes, and a polytetrafluoroethylene fiber cloth after plasma surface treatment is obtained; then, 200 parts by weight of ethanol are added, 3.0 parts by weight of methylvinyldimethoxysilane are added, and a hydrochloric acid solution with a concentration of 0.05 mol / L is added dropwise while stirring until the pH of the reaction system reaches 4, and the polytetrafluoroethylene fiber cloth after the plasma surface treatment is added, and heated and stirred, heated and stirred in a water bath at 60 ° C for 2 hours, filtered, and dried to obtain a modified polytetrafluoroethylene fiber cloth;

[0087] (2) 20 parts by weight of modified polyphenylene ether were dissolved in 100 parts by weight of toluene, and the solution was stirred to obtain a uniform modified polyphenylene ether solution. The modified polytetrafluoroethylene fiber cloth obtained in step (1) was immersed in the modified polyphenylene ether solution, and was taken out after immersion for 0.5 h. The cloth was baked at 110° C. for 2.0 h to form a semi-cured adhesive film. The two semi-cured adhesive films were hot-pressed at 160° C. and 3 MPa for 0.5 h to obtain the composite adhesive film for high-frequency copper clad laminate, with a thickness of 60 μm.

[0088] The preparation method of the modified polyphenylene ether comprises the following steps:

[0089] (I) 20 parts by weight of polyphenylene ether was dissolved in 30 parts by weight of tetrahydrofuran, and stirred at 90° C. to form a uniform solution. 4 parts by weight of 4,4-(hexafluoroisopropylidene)diphenol was added in 5 portions. After the solution was completely dissolved, 1.0 parts by weight of benzoyl peroxide was added in 3 portions. The mixture was stirred under a nitrogen atmosphere for 5 hours. After cooling to room temperature (25° C.), the mixture was washed with excess methanol, filtered, and dried at 100° C. for 12 hours to obtain bishydroxy polyphenylene ether.

[0090] (II) 6 parts by weight of the bishydroxy polyphenylene ether prepared in step (I) and 100 parts by weight of chlorobenzene were stirred in an oil bath at 70°C until the bishydroxy polyphenylene ether was completely dissolved, 1.74 parts by weight of methacrylic anhydride was added and mixed, 1.40 parts by weight of 4-dimethylaminopyridine was added, stirred for 5 hours, cooled to room temperature, washed with excess methanol, filtered, and dried at 120°C for 6.0 hours to obtain the modified polyphenylene ether.

[0091] The high-frequency copper clad laminate comprises an upper copper foil layer 1, a composite adhesive film layer 2 for high-frequency copper clad laminates, and a lower copper foil layer 3 which are stacked in sequence.

[0092] The high-frequency copper clad laminate is prepared by the following method: a layer of copper foil (35 μm) is laminated on the upper and lower surfaces of the composite adhesive film for the high-frequency copper clad laminate, and vacuum hot pressing is performed. The process conditions of the vacuum hot pressing are: the hot pressing temperature is 200° C., the pressure is 5 MPa, and the time is 1.5 h, to obtain the high-frequency copper clad laminate.

[0093] Example 2

[0094] This embodiment provides a composite adhesive film for high-frequency copper clad laminates, a preparation method thereof, and a high-frequency copper clad laminate. The preparation method of the composite adhesive film for high-frequency copper clad laminates comprises the following steps:

[0095] (1) Polytetrafluoroethylene fiber cloth (thickness 50 μm) was subjected to plasma surface treatment. The gases used were H2, CF4, and O2 in a volume ratio of 2.5:2:1. The gas flow rate was 70 mL / min, the power was 1000 W, and the absolute vacuum was 1×10 -6 Pa, the plasma surface treatment temperature is 120 ° C, the treatment time is 60 minutes, and the polytetrafluoroethylene fiber cloth after the plasma surface treatment is obtained; then, 200 parts by weight of ethanol are added, 3.0 parts by weight of vinyltrimethoxysilane are added, and a hydrochloric acid solution with a concentration of 0.05 mol / L is added dropwise while stirring until the pH of the reaction system reaches 3, and the polytetrafluoroethylene fiber cloth after the plasma surface treatment is added, and heated and stirred, heated and stirred in a water bath at 50 ° C for 2.5 hours, filtered, and dried to obtain a modified polytetrafluoroethylene fiber cloth;

[0096] (2) 20 parts by weight of modified polyphenylene ether was dissolved in 120 parts by weight of toluene, and the mixture was stirred to obtain a uniform modified polyphenylene ether solution. The modified polytetrafluoroethylene fiber cloth obtained in step (1) was immersed in the modified polyphenylene ether solution, and after immersion for 1.0 h, it was taken out and baked at 120° C. for 1.5 h to form a semi-cured film. A piece of the semi-cured film was hot-pressed at 160° C. and 3 MPa for 0.5 h to obtain the composite film for high-frequency copper clad laminate, with a thickness of 60 μm.

[0097] The preparation method of the modified polyphenylene ether comprises the following steps:

[0098] (I) 20 parts by weight of polyphenylene ether was dissolved in 45 parts by weight of tetrahydrofuran, and stirred at 95° C. to form a uniform solution. 10 parts by weight of 4,4-(hexafluoroisopropylidene)diphenol was added in 5 portions. After the 4,4-(hexafluoroisopropylidene)diphenol was completely dissolved, 2.0 parts by weight of benzoyl peroxide was added in 2 portions. The mixture was stirred and reacted under a nitrogen atmosphere for 5 hours. After cooling to room temperature, the mixture was washed with excess methanol, filtered, and dried at 100° C. for 12 hours to obtain bishydroxy polyphenylene ether.

[0099] (II) 6 parts by weight of the bishydroxy polyphenylene ether prepared in step (I) and 72 parts by weight of chlorobenzene were stirred in an oil bath at 60°C until the bishydroxy polyphenylene ether was completely dissolved, 1.0 parts by weight of methacrylic anhydride was added and mixed, 1.0 parts by weight of 4-dimethylaminopyridine was added, stirred for 4 hours, cooled to room temperature, washed with excess methanol, filtered, and dried at 120°C for 6 hours to obtain the modified polyphenylene ether.

[0100] The high-frequency copper-clad laminate comprises an upper copper foil layer, a composite adhesive film layer for high-frequency copper-clad laminates and a lower copper foil layer which are stacked in sequence.

[0101] The high-frequency copper clad laminate is prepared by the following method: a layer of copper foil (35 μm) is superimposed on the upper and lower surfaces of the composite adhesive film for the high-frequency copper clad laminate, and vacuum hot pressing is performed. The process conditions of the vacuum hot pressing are: the hot pressing temperature is 200° C., the pressure is 5 MPa, and the time is 1.5 h, to obtain the high-frequency copper clad laminate.

[0102] Example 3

[0103] This embodiment provides a composite adhesive film for high-frequency copper clad laminates, a preparation method thereof, and a high-frequency copper clad laminate. The preparation method of the composite adhesive film for high-frequency copper clad laminates comprises the following steps:

[0104] (1) Polytetrafluoroethylene fiber cloth (thickness 40 μm) was subjected to plasma surface treatment. The gases used were H2, CF4, and O2 in a volume ratio of 2.5:1.5:1, with a gas flow rate of 60 mL / min, a power of 900 W, and an absolute vacuum of 1×10 -6Pa, the plasma surface treatment temperature is 120 ° C, the treatment time is 60 minutes, and a polytetrafluoroethylene fiber cloth after plasma surface treatment is obtained; then, 200 parts by weight of ethanol are added, 3.0 parts by weight of vinyl tris (β-methoxyethoxy) silane are added, and a hydrochloric acid solution with a concentration of 0.05 mol / L is added dropwise while stirring until the pH of the reaction system reaches 3.5, and the polytetrafluoroethylene fiber cloth after the plasma surface treatment is added, and heated and stirred, heated and stirred in a water bath at 70 ° C for 1.5 hours, filtered, and dried to obtain a modified polytetrafluoroethylene fiber cloth;

[0105] (2) 20 parts by weight of modified polyphenylene ether was dissolved in 200 parts by weight of toluene, and the solution was stirred to obtain a uniform modified polyphenylene ether solution. The modified polytetrafluoroethylene fiber cloth obtained in step (1) was immersed in the modified polyphenylene ether solution, and after immersion for 0.7 hours, it was taken out and baked at 100°C for 3.0 hours to form a semi-cured film. A piece of the semi-cured film was hot-pressed at 160°C and 3MPa for 0.5 hours to obtain the composite film for high-frequency copper clad laminate, with a thickness of 50μm. The preparation method of the modified polyphenylene ether comprises the following steps:

[0106] (I) dissolving 20 parts by weight of polyphenylene ether in 60 parts by weight of tetrahydrofuran and stirring at 100° C. to form a uniform solution, adding 20 parts by weight of 4,4-(hexafluoroisopropylidene)diphenol in 5 portions, and after the solution is completely dissolved, adding 0.67 parts by weight of benzoyl peroxide in 2 portions, stirring and reacting for 6 hours under a nitrogen atmosphere, and then cooling to room temperature, adding excess methanol for washing, filtering, and drying at 100° C. for 12 hours to obtain bishydroxy polyphenylene ether;

[0107] (II) 6 parts by weight of the bishydroxy polyphenylene ether prepared in step (I) and 120 parts by weight of chlorobenzene were stirred in an 80°C oil bath until the bishydroxy polyphenylene ether was completely dissolved, 3.0 parts by weight of methacrylic anhydride were added and mixed, 2.0 parts by weight of 4-dimethylaminopyridine were added, stirred for 6 hours, cooled to room temperature, washed with excess methanol, filtered, and dried at 120°C for 6 hours to obtain the modified polyphenylene ether.

[0108] The high-frequency copper-clad laminate comprises an upper copper foil layer, a composite adhesive film layer for high-frequency copper-clad laminates and a lower copper foil layer which are stacked in sequence.

[0109] The high-frequency copper clad laminate is prepared by the following method: a layer of copper foil (35 μm) is laminated on the upper and lower surfaces of the composite adhesive film for the high-frequency copper clad laminate, and vacuum hot pressing is performed. The process conditions of the vacuum hot pressing are: the hot pressing temperature is 200° C., the pressure is 5 MPa, and the time is 1.5 h, to obtain the high-frequency copper clad laminate.

[0110] Example 4

[0111] This embodiment provides a composite adhesive film for high-frequency copper-clad laminates, a preparation method thereof, and a high-frequency copper-clad laminate. The only difference between this embodiment and Example 1 is that the volume ratio of the gases H2, CF4, and O2 used in the plasma surface treatment is adjusted to 1:1:1, and other conditions are the same as those in Example 1.

[0112] Example 5

[0113] This embodiment provides a composite adhesive film for high-frequency copper-clad laminates, a preparation method thereof, and a high-frequency copper-clad laminate. The only difference between this embodiment and Example 1 is that the volume ratio of the gases H2, CF4, and O2 used in the plasma surface treatment is adjusted to 3.5:1:1, and other conditions are the same as those in Example 1.

[0114] Example 6

[0115] This embodiment provides a composite adhesive film for high-frequency copper-clad laminates, a preparation method thereof, and a high-frequency copper-clad laminate. The only difference between this embodiment and Example 1 is that the volume ratio of the gases H2, CF4, and O2 used in the plasma surface treatment is adjusted to 5:1:2, and other conditions are the same as those in Example 1.

[0116] Comparative Example 1

[0117] This comparative example provides a polyphenylene ether film, a preparation method thereof, and a high-frequency copper clad laminate. The only difference between the comparative example and Example 1 is that the preparation method of the polyphenylene ether film comprises the following steps: dissolving the modified polyphenylene ether in toluene and pouring the resulting solution into a polytetrafluoroethylene mold, wherein the mass ratio of the modified polyphenylene ether to toluene is 1:5; drying the solution at 110°C; hot pressing the solution at 180°C and 3 MPa for 120 min; and demolding the solution to obtain the polyphenylene ether film having a thickness of 60 μm.

[0118] The high-frequency copper-clad laminate comprises an upper copper foil layer, a polyphenylene ether film layer, and a lower copper foil layer stacked in sequence. The high-frequency copper-clad laminate is prepared by laminating a layer of copper foil (35 μm) above and below the polyphenylene ether film, followed by vacuum hot pressing. The vacuum hot pressing process conditions are: a temperature of 200°C, a pressure of 5 MPa, and a time of 1.5 hours. Other conditions are the same as in Example 1.

[0119] Comparative Example 2

[0120] This comparative example provides a composite adhesive film for high-frequency copper clad laminates, a preparation method thereof, and a high-frequency copper clad laminate. The difference between the comparative example and Example 1 is that the preparation method of the composite adhesive film for high-frequency copper clad laminates does not include step (1), and the modified polytetrafluoroethylene fiber cloth in step (2) is replaced by polytetrafluoroethylene fiber cloth (with a thickness of 20 μm). Other conditions are the same as those in Example 1.

[0121] Comparative Example 3

[0122] This comparative example provides a composite adhesive film for high-frequency copper clad laminates, a preparation method thereof, and a high-frequency copper clad laminate. The difference between the comparative example and Example 1 is that step (1) of the preparation method of the composite adhesive film for high-frequency copper clad laminates does not include a plasma surface treatment step, and other conditions are the same as those in Example 1.

[0123] Comparative Example 4

[0124] This comparative example provides a composite adhesive film for high-frequency copper clad laminates, a preparation method thereof, and a high-frequency copper clad laminate. The difference between the comparative example and Example 1 is that in step (1) of the preparation method of the composite adhesive film for high-frequency copper clad laminates, methylvinyldimethoxysilane is replaced with dimethyldiethoxysilane of the same mass, and other conditions are the same as those in Example 1.

[0125] Comparative Example 5

[0126] This comparative example provides a composite adhesive film for high-frequency copper clad laminates, a preparation method thereof, and a high-frequency copper clad laminate. The difference between the composite adhesive film and the comparative example 1 is that 4,4-(hexafluoroisopropylidene)diphenol is replaced with bisphenol A of the same mass in the preparation method of the modified polyphenylene ether, and the other conditions are the same as those in Example 1.

[0127] The high-frequency copper clad laminates provided in Examples 1 to 8 and Comparative Examples 1 to 5 were subjected to the following tests.

[0128] (1) Dielectric properties: According to IEC 61189-2-721 (2015-04) standard, the dielectric constant and dielectric loss are tested at a frequency of 10 GHz;

[0129] (2) Solder resistance: According to IPC-TM-6502.4.13.1 standard, the copper foil is bubbling in a tinning furnace at 288°C. The criterion is whether the copper foil bubbles. The time when the copper foil bubbles occurs is recorded. The maximum test time is 5 minutes. If the copper foil bubbles do not occur within the test time of 5 minutes, it is recorded as >5 minutes.

[0130] The test results are shown in Table 1 below:

[0131] Table 1

[0132]

[0133] From the contents of Table 1, it can be seen that the high-frequency copper clad laminates made of the composite adhesive films for high-frequency copper clad laminates provided in Examples 1 to 6 have a dielectric constant of ≤2.35, a dielectric loss of ≤0.007, and a soldering resistance of >5 min at a frequency of 10 GHz.

[0134] Compared with Example 1, if the proportion of H2 in the plasma treatment is too low (Example 4), fewer active sites will be formed on the polytetrafluoroethylene fiber cloth, resulting in less silane coupling agent grafted to the surface of the polytetrafluoroethylene fiber cloth, resulting in poor surface modification effect, affecting the bonding between the polytetrafluoroethylene fiber cloth and the modified polyphenylene ether, and thus affecting the performance of the high-frequency copper clad laminate; if the proportion of H2 in the plasma treatment is too high (Example 5), it will cause a high degree of etching on the surface of the polytetrafluoroethylene fiber cloth, destroying its molecular structure, weakening the mechanical strength, and also resulting in a decrease in the modification effect; it can be seen that in the present invention, by controlling the volume ratio of H2, CF4 and O2 during plasma surface treatment, it is preferably (2-2.5): (1-2): 1, and the prepared composite adhesive film for high-frequency copper clad laminate and high-frequency copper clad laminate have better performance.

[0135] Compared with Example 1, if the proportion of H2 and O2 in the plasma treatment is too high (Example 6), the surface of the polytetrafluoroethylene fiber cloth will be over-etched, damaging the performance of the polytetrafluoroethylene fiber cloth itself, which is not conducive to improving the overall dielectric properties of the composite film for high-frequency copper clad laminates. Therefore, it can be seen that in the present invention, by controlling the volume ratio of H2, CF4 and O2 during plasma surface treatment within the range of (1-3.5): (1-2): 1, the composite film for high-frequency copper clad laminates and high-frequency copper clad laminates prepared have better performance.

[0136] Compared with Example 1, if the modified polytetrafluoroethylene fiber cloth is not added (Comparative Example 1), the prepared polyphenylene ether film has no supporting carrier, and the dielectric properties of the film cannot be improved by using polytetrafluoroethylene with better dielectric properties. The dielectric constant and dielectric loss of the prepared high-frequency copper clad laminate are large, and the solder resistance is reduced.

[0137] Compared with Example 1, if the modified polytetrafluoroethylene fiber cloth is replaced with polytetrafluoroethylene fiber cloth (Comparative Example 2), the polytetrafluoroethylene fiber cloth is not modified, and its compatibility with the modified polyphenylene ether is poor. The polytetrafluoroethylene fiber cloth and the modified polyphenylene ether are prone to delamination, the dielectric constant and dielectric loss are large, and the solder resistance is reduced.

[0138] Compared with Example 1, if the polytetrafluoroethylene fiber cloth is not subjected to plasma surface treatment (Comparative Example 3), the compatibility of the polytetrafluoroethylene fiber cloth and the modified polyphenylene ether is improved compared with Comparative Example 2, but still cannot achieve good chemical bonding. Compared with Example 1, the compatibility is still poor, the dielectric constant and dielectric loss of the obtained high-frequency copper clad laminate are large, and the solder resistance is reduced.

[0139] Compared with Example 1, if methylvinyldimethoxysilane is replaced with dimethyldiethoxysilane (Comparative Example 4), since there is no carbon-carbon double bond or carbon-carbon triple bond to bond with the modified polyphenylene ether, the compatibility of the polytetrafluoroethylene fiber cloth and the modified polyphenylene ether cannot be improved by chemical bonding. Compared with Example 1, the compatibility is still poor, the dielectric constant and dielectric loss of the obtained high-frequency copper clad laminate are large, and the solder resistance is reduced.

[0140] Compared with Example 1, if 4,4-(hexafluoroisopropylidene)diphenol is replaced with bisphenol A of the same mass (Comparative Example 5), the dielectric constant and dielectric loss of the obtained high-frequency copper clad laminate are larger. The reason is that compared with bisphenol A, the electronegativity of the fluorine atom in 4,4-(hexafluoroisopropylidene)diphenol is stronger. In the hexafluoroisopropylidene group (-C(CF3)2-), the six fluorine atoms significantly reduce the polarity of the entire molecule through a strong electron-withdrawing effect. At the same time, the symmetry of the hexafluoroisopropylidene group is greater than that of bisphenol A. The isopropylidene group is higher, and the symmetrical structure can offset the local dipole moment and further reduce the polarization effect. The fluorine atom is larger in volume, and the steric hindrance effect of the hexafluoroisopropylidene group limits the flexibility of the molecular chain, reduces the movement of the molecular chain segments at high frequencies, and inhibits dipole rearrangement. Therefore, the modified polyphenylene ether modified with 4,4-(hexafluoroisopropylidene)diphenol has lower dielectric constant and dielectric loss, which ultimately improves the dielectric properties of the composite adhesive film for high-frequency copper clad laminates, making the prepared high-frequency copper clad laminates have better dielectric properties.

[0141] The applicant states that while the above-described embodiments illustrate the process of the present invention, the present invention is not limited to the above-described process steps, nor does it imply that the present invention must rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a composite adhesive film for high-frequency copper-clad laminate, characterized in that: The preparation method comprises the following steps: (1) subjecting a polytetrafluoroethylene fiber cloth to plasma surface treatment and silane coupling agent modification in sequence to obtain a modified polytetrafluoroethylene fiber cloth; (2) mixing the modified polytetrafluoroethylene fiber cloth and modified polyphenylene ether obtained in step (1), and drying them to obtain the composite adhesive film for the high-frequency copper clad laminate; The modified polyphenylene ether is a polyphenylene ether containing unsaturated double bonds and fluorine-containing substituents; The silane coupling agent includes a silane coupling agent containing a carbon-carbon double bond and / or a silane coupling agent containing a carbon-carbon triple bond.

2. The preparation method according to claim 1, characterized in that The thickness of the polytetrafluoroethylene fiber cloth in step (1) is 10 to 100 μm; Preferably, the gas used in the plasma surface treatment includes any one of H2, NH3, Ar, N2, O2 or CF4, or a combination of at least two thereof; Preferably, the gases used in the plasma surface treatment include H2, CF4 and O2; Preferably, the volume ratio of H2, CF4 and O2 is (1-3.5):(1-2):1; Preferably, the flow rate of the gas used in the plasma surface treatment is 30 to 80 mL / min; Preferably, the power of the plasma surface treatment is 300 to 2000W; Preferably, the absolute vacuum degree of the plasma surface treatment is ≤1×10 -6 Pa; Preferably, the temperature of the plasma surface treatment is 70 to 300°C; Preferably, the plasma surface treatment time is 10 to 60 minutes.

3. The preparation method according to claim 1 or 2, characterized in that The silane coupling agent containing a carbon-carbon double bond includes any one of vinyltrimethoxysilane, methylvinyldiethoxysilane or vinyltri(β-methoxyethoxy)silane or a combination of at least two thereof; Preferably, the silane coupling agent modification in step (1) comprises the following steps: placing the polytetrafluoroethylene fiber after plasma surface treatment in a modification liquid for modification treatment, and drying to obtain the modified polytetrafluoroethylene fiber cloth; Preferably, the modification liquid comprises a silane coupling agent, ethanol and a pH regulator; Preferably, the modified liquid is prepared by the following method: after mixing a silane coupling agent and ethanol, a pH regulator is added thereto to obtain a modified liquid with a pH value of 3 to 4; Preferably, the mass ratio of the silane coupling agent to ethanol is (1-2):100; Preferably, the pH adjuster comprises a hydrochloric acid solution; Preferably, the concentration of the hydrochloric acid solution is 0.05 to 0.20 mol / L; Preferably, the modification treatment is carried out under stirring conditions; Preferably, the temperature of the modification treatment is 50-80°C; Preferably, the modification treatment time is 1.5 to 2.5 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that The raw materials for preparing the modified polyphenylene ether include polyphenylene ether, fluorine-containing bisphenol compounds and acrylic anhydride compounds; Preferably, the fluorine-containing bisphenol compound includes 4,4-(hexafluoroisopropylidene)diphenol; Preferably, the acrylic anhydride compound includes methacrylic anhydride and / or acrylic anhydride; Preferably, the raw materials for preparing the modified polyphenylene ether further include an initiator and / or a catalyst; Preferably, the initiator comprises an alkyl peroxide and / or an acyl peroxide; Preferably, the catalyst comprises 4-dimethylaminopyridine; Preferably, the raw materials for preparing the modified polyphenylene ether further include non-fluorinated bisphenol compounds; Preferably, the non-fluorine-containing bisphenol compound includes 4,4-dihydroxydiphenylmethane and / or 2,2-bis(4-hydroxyphenyl)propane.

5. The preparation method according to claim 4, characterized in that The preparation method of the modified polyphenylene ether comprises the following steps: (I) mixing polyphenylene ether, a fluorinated bisphenol compound, a solvent and optionally an initiator, and reacting them to obtain bishydroxy polyphenylene ether; (II) mixing the bishydroxy polyphenylene ether prepared in step (I), an acrylic anhydride compound, a solvent and optionally a catalyst, and reacting them to obtain the modified polyphenylene ether; Preferably, the mass ratio of the polyphenylene ether and the fluorinated bisphenol compound in step (I) is (1-5):1; Preferably, the mass ratio of the polyphenylene ether to the solvent in step (I) is 1:(1.5-3); Preferably, the solvent in step (I) comprises tetrahydrofuran and / or toluene; Preferably, the mass ratio of the polyphenylene ether to the initiator in step (I) is (10-30):1; Preferably, the reaction in step (I) is carried out under a nitrogen atmosphere; Preferably, the reaction temperature in step (I) is 90-100° C. and the reaction time is 4-6 h; Preferably, the mass ratio of the bishydroxy polyphenylene ether and the acrylic anhydride compound in step (II) is 6:(1-2); Preferably, the mass ratio of the bishydroxy polyphenylene ether to the catalyst in step (II) is 6:(1-2); Preferably, the mass ratio of the bishydroxy polyphenylene ether to the solvent in step (II) is 1:(12-20); Preferably, the solvent in step (II) comprises chlorobenzene; Preferably, the reaction temperature in step (II) is 60-80°C; Preferably, the reaction time in step (II) is 4 to 6 hours; Preferably, the reaction in step (I) and step (II) further comprises the steps of washing with methanol, filtering and drying independently after the reaction.

6. The preparation method according to any one of claims 1 to 5, characterized in that The mixing of the modified polytetrafluoroethylene fiber cloth and the modified polyphenylene ether in step (2) comprises impregnating the modified polytetrafluoroethylene fiber cloth with a modified polyphenylene ether solution to achieve mixing; Preferably, the modified polyphenylene ether solution comprises modified polyphenylene ether and a solvent; Preferably, the mass ratio of the modified polyphenylene ether to the solvent in the modified polyphenylene ether solution is 1:(5-10); Preferably, the solvent in the modified polyphenylene ether solution includes any one of toluene, xylene or N,N-dimethylformamide or a combination of at least two thereof; Preferably, the immersion time is 30 to 60 minutes.

7. The preparation method according to any one of claims 1 to 6, characterized in that The drying temperature in step (2) is 100-120° C. The drying time in step (2) is 1.5 to 3.0 hours.

8. A composite adhesive film for high-frequency copper-clad laminate, characterized in that: The composite adhesive film for high-frequency copper clad laminate is prepared by the preparation method according to any one of claims 1 to 7.

9. A high-frequency copper-clad laminate, characterized in that: The high-frequency copper-clad laminate comprises the composite adhesive film for high-frequency copper-clad laminate according to claim 8 and copper foil.

10. Use of the composite adhesive film for high-frequency copper-clad laminate according to claim 8 or the high-frequency copper-clad laminate according to claim 9 in the preparation of a high-frequency circuit board.

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