Interlayer bonding sheet for multilayer board and preparation method thereof

Abstract

The invention discloses an interlayer bonding sheet for a multilayer board and a preparation method of the interlayer bonding sheet, the bonding sheet comprises a middle PTFE-based core layer and hydrocarbon resin surface layers bonded on the upper surface and the lower surface of the PTFE-based core layer, the PTFE-based core layer takes polysiloxane containing double bonds as a supporting base film, and the surface of the PTFE-based core layer is coated with FEVE / PTFE resin. The core layer constructs an interpenetrating network with the help of double-bond-containing FEVE resin and PTFE resin and is chemically bonded with the double-bond-containing polysilane supporting film, a traditional glass fiber cloth reinforcing material is abandoned, the glass fiber effect is eliminated, the interface bonding force between the PTFE resin and the supporting film is improved, and the thermal expansion coefficient of the PTFE resin is reduced; the hydrocarbon resin surface layer adopts octavinyl POSS as a cross-linking agent and a reinforcing phase, the nanocage structure of the hydrocarbon resin surface layer is favorable for reducing the overall dielectric constant, and the resistance material in the resistance copper foil is not easy to damage in the pressing process. The bonding sheet prepared by the invention has uniform and stable dielectric properties, and can meet the requirements of high-frequency signal transmission on the stability and reliability of a multilayer board.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electronic communication materials, and relates to the preparation of a bonding sheet for a copper-clad plate, in particular to a multilayer plate interlayer bonding sheet without glass cloth, uniform and stable dielectric properties, and high mechanical strength, and a preparation method thereof. BACKGROUND

[0002] The bonding sheet plays a role in interlayer bonding and medium in the multilayer circuit board, and is a key material for ensuring stable and reliable signal transmission of the multilayer circuit board. Fluororesin, especially polytetrafluoroethylene (PTFE), is widely used in the preparation of bonding sheets due to its excellent dielectric properties and chemical stability. With the continuous increase of communication frequency, electronic products are developing towards miniaturization, integration, high speed and low power consumption. The accumulation of heat in a small space with large power is inevitable. Therefore, the bonding sheet is required to have stable and uniform low dielectric properties and low thermal expansion coefficient.

[0003] The existing PTFE bonding sheet production is mainly by continuous glass fiber cloth impregnation process, which is easy to cause "glass fiber effect". This phenomenon is mainly caused by the anisotropy of the glass fiber cloth due to the warp and weft knitting structure, resulting in differences in dielectric constant, dielectric loss and thermal expansion coefficient of the copper-clad plate at different positions, thereby seriously affecting the consistency and stability of high-frequency circuit signal transmission. In addition, in order to reduce the thermal expansion coefficient of the bonding sheet and maintain a low dielectric constant, a large amount of silica needs to be added to the PTFE resin. The hard micron-sized silica is easy to be pressed in the multilayer pressing process, thereby causing the resistance value in the circuit to change beyond the standard. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application aims to provide a multilayer plate interlayer bonding sheet and a preparation method thereof. The present application uses polysiloxane containing double bonds as a support film, and coats a reactive FEVE / PTFE resin on the surface of the support film to form a PTFE-based core layer. Then, a hydrocarbon resin reinforced by octavinyl POSS is coated on the upper and lower surfaces of the core layer, and finally the required interlayer bonding sheet is obtained. The bonding sheet has the advantages of uniform and stable dielectric properties, low thermal expansion coefficient, and high mechanical strength, and can meet the stringent requirements of high-frequency signal transmission on the stability and reliability of the multilayer plate.

[0005] The present application is achieved by the following technical solutions: An interlayer adhesive sheet for multi-layer board, the adhesive sheet comprising a middle PTFE-based core layer and carbon-hydrogen resin surface layers bonded to the upper and lower surfaces of the PTFE-based core layer, the middle PTFE-based core layer having a thickness of 70-100 μm; the carbon-hydrogen resin surface layers on the upper and lower sides each having a thickness of 20-40 μm; the PTFE-based core layer having a double-bond-containing polysiloxane as a supporting base film, and a reactive FEVE / PTFE resin coated on the surface thereof, the double-bond-containing polysiloxane as a supporting base film having a thickness of 40-60 μm.

[0006] Further improvements of the present application are: The double-bond-containing polysiloxane is composed of 100 parts of α, ω-dihydroxy polysiloxane, 5-10 parts of white carbon black, 7-20 parts of methyl triethoxysilane, 0.22-1.2 parts of dibutyl tin dilaurate, 10-20 parts of alkenyl triethoxysilane, dibutyl tin dilaurate, and 80-90 parts of ethanol. And / or, the alkenyl triethoxysilane is allyl triethoxysilane or vinyl triethoxysilane or a mixture of both. And / or, the viscosity of the α, ω-dihydroxy polysiloxane is 2000-20000 mPa·s. And / or, the white carbon black is white carbon black produced by a gas phase method, and has a particle size of 20-200 nm.

[0007] Further, the FEVE / PTFE resin is composed of 100 parts of the PTFE dispersion liquid, 0.3-1.2 parts of OP-10 emulsifier, 6-16 parts of FEVE resin containing carbon-carbon double bonds, 0.5-2.5 parts of octavinyl POSS, 0.1-0.8 parts of dicumyl peroxide, and 0.3-1 part of leveling agent BYK333.

[0008] Further, the FEVE resin containing carbon-carbon double bonds is composed of 100 parts of FEVE resin containing hydroxyl groups, 60-150 parts of xylene, 5-15 parts of 3-isopropyl-dimethyl benzyl isocyanate, and 0.05-0.25 parts of dibutyl tin dilaurate. And / or, the FEVE resin containing hydroxyl groups is a fluoroethylene / vinyl ether alternating copolymer.

[0009] Further, the carbon-hydrogen resin surface layer is composed of 100 parts of carbon-hydrogen resin, 5-15 parts of octavinyl POSS, 0.5-3 parts of dicumyl peroxide, and 100-150 parts of xylene. And / or, the carbon-hydrogen resin is one or a mixture of two or more of polybutadiene, polyisoprene, butadiene-styrene copolymer, and terpolymer ethylene-propylene rubber.

[0010] Still further improvement of the present application is: The preparation method of the interlayer bonding sheet for the multilayer board comprises the following steps: (1) Preparation of PTFE-based core layer S1: Stir α, ω-dihydroxy polysiloxane and white carbon black in a blender for 15-30 min, then vacuumize, heat and stir, cool to room temperature, add methyl triethoxysilane, vacuumize and stir for 15-30 min, finally add part of dibutyltin dilaurate, vacuumize and stir for 15-30 min, then pour into a mold, and solidify at room temperature to obtain a polysiloxane support film; S2: Add alkenyl triethoxysilane and the remaining dibutyltin dilaurate into ethanol, stir until uniform to obtain a mixed solution. Spray the mixed solution onto the upper and lower surfaces of the polysiloxane support film obtained in S1, and solidify at room temperature to obtain a polysiloxane support film containing double bonds; S3: Dissolve the hydroxyl-containing FEVE resin in dimethylbenzene, add 3-isopropyl-dimethylbenzyl isocyanate and dibutyltin dilaurate, stir for 2-4 h, pour the solution into methanol to settle, and obtain a FEVE resin containing carbon-carbon double bonds; S4: Add OP-10 emulsifier to a PTFE dispersion liquid with a solid content of 30-40%, stir for 30-60 min, then slowly add the FEVE resin containing carbon-carbon double bonds obtained in S3, stir for 1-2 h, then slowly add octavinyl POSS, dicumyl peroxide and leveling agent BYK333, stir for 1-2 h, and obtain a fluorocarbon resin slurry; S5: Uniformly coat the fluorocarbon resin slurry obtained in S4 on the upper and lower surfaces of the polysiloxane support film containing double bonds obtained in S2, dry, heat and react, then heat and vacuum sinter to obtain a PTFE-based core layer film; S6: Place the PTFE-based core layer film obtained in S5 in a plasma generating device, and treat for 3-10 min in a mixed gas atmosphere with a frequency of 2.45 GHz, a vacuum degree of 10-500 Pa, a radio frequency power of 200-1200 W, and a volume ratio of Ar and H2 of 1-5:1 to obtain a PTFE-based core layer film subjected to surface activation treatment; (2) Preparation of upper and lower carbon-hydrogen resin surface layers S7: Add carbon-hydrogen resin, octavinyl POSS and dicumyl peroxide into dimethylbenzene solvent respectively, and stir for 1-2 h to obtain a mixed glue solution; S8: Blade coat the mixed glue solution obtained in S7 on the upper and lower surfaces of the PTFE-based core layer film subjected to surface activation treatment obtained in S6, and then dry to obtain an interlayer bonding sheet for a multilayer board.

[0011] Still further improvement of the present application is: The temperature of the heating and stirring in S1 is 100-110 DEG C, and the time is 1-2 hours.

[0012] Further, the temperature of the drying in S5 is 105-120 DEG C, the time is 2-5 minutes; the temperature of the heating reaction is 160-180 DEG C, the time is 2-5 minutes; the temperature of the vacuum sintering is 360-380 DEG C, the time is 3-10 minutes.

[0013] Further, the temperature of the drying in S8 is 110-130 DEG C, the time is 1-5 minutes.

[0014] Further, the humidity of the solidification in S1 is 50-70%, the time is 10-24 hours; the humidity of the solidification in S2 is 50-70%, the time is 2-4 hours.

[0015] Further, the mass ratio of the dibutyl tin dilaurate in S1 to the dibutyl tin dilaurate in S2 is 5-20:1.

[0016] Compared with the prior art, the present application has the following beneficial effects: I. The present application discards the traditional glass fiber cloth reinforcing material, uses polysiloxane containing double bonds as a support film, and constructs a low dielectric layer on the surface thereof, which is composed of double bond-containing FEVE resin, PTFE resin and octavinyl POSS, to obtain a bonding core layer, thereby effectively solving the "glass fiber effect" problem. In this process, the FEVE resin and the PTFE form an interpenetrating network structure during sintering, combined with the reinforcing effect of the POSS, the thermal expansion coefficient of the PTFE-based core layer is significantly reduced; more importantly, the double bond-containing FEVE resin can be chemically bonded with the double bond-containing polysiloxane support film during cross-linking and solidification, thereby enhancing the interfacial bonding force between the support film and the resin layer, and improving the stability and size uniformity of the overall structure.

[0017] II. The present application is different from the prior art technology of preparing a core layer by physically blending silicon powder and PTFE resin and then sintering (the strength of the core layer is limited by the weak interfacial bonding force between PTFE and the filler, which easily leads to stress concentration and interfacial debonding). The present application uses a three-dimensional polysiloxane network formed by cross-linking of hydroxyl-terminated PDMS and methyl triethoxysilane, with high-strength Si-O-Si covalent bonds as the main body, as a support skeleton, which itself has excellent mechanical strength. The addition of fumed silica further realizes the nano-reinforcing effect, and the silicon hydroxyl groups on the surface can form strong interaction with the polysiloxane network, efficiently transfer and disperse stress, and improve the mechanical strength of the support film. This composite reinforcement mechanism combined with the surface low dielectric functional layer makes the entire core layer have excellent comprehensive performance.

[0018] Thirdly, in the design of the adhesive sheet surface layer, the eight vinyl POSS is used as the crosslinking agent and the reinforcing phase of the hydrocarbon resin. The unique nano-cage structure introduces uniform nano-cavities in the cured resin, which can effectively reduce the dielectric constant of the adhesive sheet. More importantly, compared with the hard fillers such as micron-sized silicon powder commonly used in the existing process, the nano-sized POSS is not easy to damage the precision resistance material in the resistive copper foil in the multilayer board pressing process, thereby improving the reliability and yield of the product. DETAILED DESCRIPTION

[0019] The application will be described in detail below in combination with specific examples.

[0020] Example 1

[0021] S1: 100g of α, ω-dihydroxyl polysiloxane with a viscosity of 10000mPa·s, 10g of white carbon black with a particle size of 100nm were stirred in a blender for 30min, then vacuumized, heated to 110℃, stirred for 2h, cooled to room temperature, then 15g of methyl triethoxysilane was added, vacuumized and stirred for 15min, finally 0.5g of dibutyltin dilaurate was added, vacuumized and stirred for 15min, then poured into a mold, and cured for 24h at room temperature and humidity of 50%, to obtain a polysiloxane support film with a thickness of 40μm; S2: 10g of allyl triethoxysilane and 0.05g of dibutyltin dilaurate were added to 90g of ethanol, stirred uniformly to obtain a mixed solution. The mixed solution was sprayed onto the upper and lower surfaces of the above-mentioned polysiloxane support film, and cured for 2h at room temperature and humidity of 50%, to obtain a polysiloxane support film containing double bonds; S3: 100g of FEVE resin containing hydroxyl groups was dissolved in 100g of dimethylbenzene, 10g of 3-isopropyl-dimethylbenzyl isocyanate and 0.1g of dibutyltin dilaurate were added, stirred for 2h, the solution was poured into methanol for sedimentation, to obtain FEVE resin containing carbon-carbon double bonds; S4: 1g of OP-10 emulsifier was added to 100g of PTFE dispersion liquid with a solid content of 30%, stirred for 60min, then 9g of the above-mentioned FEVE resin containing carbon-carbon double bonds was slowly added, stirred for 2h, then 2g of octavinyl POSS, 0.5g of dicumyl peroxide and 0.5g of leveling agent BYK333 were slowly added, stirred for 1h, to obtain fluorocarbon resin slurry; S5: the above-mentioned fluorocarbon resin slurry was uniformly coated on the upper and lower surfaces of the above-mentioned polysiloxane support film containing double bonds, dried at 110℃ for 5min, reacted at 180℃ for 2min, and vacuum heat treated at 365℃ for 5min, to obtain a PTFE-based core layer film with a thickness of 100μm; S6: The PTFE-based core layer film was placed in a plasma generating device, and was treated for 3 min in a mixed gas atmosphere with a frequency of 2.45 GHz, a vacuum degree of 10 Pa, a radio frequency power of 500 W, and a volume ratio of Ar and H2 of 1:1, to obtain a surface-activated treated PTFE-based core layer film.

[0022] S7: 70 g of 1, 2-polybutadiene, 30 g of butadiene-styrene copolymer, 10 g of octavinyl POSS, and 2 g of dicumyl peroxide were respectively added into 100 g of xylene solvent, and stirred for 1 h to obtain a mixed glue solution; S8: The mixed glue solution was coated on the upper and lower surfaces of the surface-activated treated PTFE-based core layer film, and then dried at 110°C for 2 min to obtain an interlayer bonding sheet for a multilayer plate with a thickness of 160 μm.

[0023] Example 2:

[0024] This example is substantially the same as Example 1, except that the thickness of the polysiloxane support film in this example is 50 μm.

[0025] In addition, this example is completely the same as Example 1, and thus no further description is given herein.

[0026] Example 3:

[0027] This example is substantially the same as Example 1, except that the thickness of the polysiloxane support film in this example is 60 μm.

[0028] In addition, this example is completely the same as Example 1, and thus no further description is given herein.

[0029] Example 4:

[0030] This example is substantially the same as Example 1, except that the amount of the FEVE resin containing carbon-carbon double bonds in this example is 12 g.

[0031] Example 5:

[0032] This example is substantially the same as Example 1, except that the amount of the FEVE resin containing carbon-carbon double bonds in this example is 15 g.

[0033] In addition, this example is completely the same as Example 1, and thus no further description is given herein.

[0034] Comparative Example 1: 100 g of a PTFE dispersion liquid with a solid content of 30% and 30 g of silicon powder with an average particle size D50 of 3 μm were mixed uniformly and coated on the surface of a peelable support, and then dried at 110°C for 5 min and vacuum heat-treated at 365°C for 5 min to obtain a PTFE core layer film with a thickness of 100 μm. The PTFE core layer film was placed in a plasma generating device, treated in a mixed atmosphere of Ar and H2 with a volume ratio of 1:1 at a frequency of 2.45 GHz, a vacuum degree of 10 Pa, and a radio frequency power of 500 W for 3 min, to obtain a surface-activated treated PTFE core layer film.

[0035] 70 g of 1, 2-polybutadiene, 30 g of butadiene-styrene copolymer, 10 g of octavinyl POSS, and 2 g of dicumyl peroxide were respectively added to 100 g of xylene solvent, stirred for 1 h to obtain a mixed glue solution; The mixed glue solution was coated on the upper and lower surfaces of the surface-activated treated PTFE core layer film, and then dried at 110°C for 2 min to obtain an interlayer bonding sheet for a multi-layer plate with a thickness of 160 μm.

[0036] Comparative Example 2: 100 g of α, ω-dihydroxypolydimethylsiloxane with a viscosity of 10,000 mPa·s and 10 g of white carbon black with a particle size of 100 nm were stirred in a blender for 30 min, then vacuumized, heated to 110°C, and stirred for 2 h. After cooling to room temperature, 15 g of methyltriethoxysilane was added, vacuumized and stirred for 15 min. Finally, 0.5 g of dibutyltin dilaurate was added, vacuumized and stirred for 15 min, and then poured into a mold. The mold was cured at room temperature and 50% humidity for 24 h to obtain a polysiloxane support film with a thickness of 40 μm. A PTFE dispersion liquid with a solid content of 30% was coated on the upper and lower surfaces of the polysiloxane support film, dried at 110°C for 5 min, and vacuum heat treated at 365°C for 5 min to obtain a PTFE-based core layer film with a thickness of 100 μm. The PTFE-based core layer film was placed in a plasma generating device, treated in a mixed atmosphere of Ar and H2 with a volume ratio of 1:1 at a frequency of 2.45 GHz, a vacuum degree of 10 Pa, and a radio frequency power of 500 W for 3 min, to obtain a surface-activated treated PTFE-based core layer film.

[0037] 70 g of 1, 2-polybutadiene, 30 g of butadiene-styrene copolymer, 10 g of octavinyl POSS, and 2 g of dicumyl peroxide were respectively added to 100 g of xylene solvent, stirred for 1 h to obtain a mixed glue solution; The mixed glue solution was coated on the upper and lower surfaces of the surface-activated treated PTFE-based core layer film, and then dried at 110°C for 2 min to obtain an interlayer bonding sheet for a multi-layer plate with a thickness of 160 μm.

[0038] Comparative Example 3: The comparative example is substantially the same as example 1, except that in the comparative example, the octavinyl POSS is replaced by a silica powder with an average particle size D50 of 3 μm.

[0039] The materials prepared in the above examples and comparative examples were subjected to relevant performance tests, and the results are shown in Table 1.

[0040] The dielectric performance test standard refers to the IPC-TM-650 2.5.5.5 standard, the test method is split resonant cavity method, the test condition is room temperature, and the resonant frequency is 10 GHz; the tensile strength test standard refers to the IPC-TM-650 2.4.8 standard; the Z-axis coefficient of thermal expansion (CTE) is tested by TMA thermal analysis method; the thermal stress test standard refers to the IPC-TM-650 2.4.13.1 standard, and the test condition is 288°C, 10s, 6 times.

[0041] Table 1 Performance test results of examples 1-5 and comparative examples 1-3

[0042] By comparing the performance results of the bonding sheet materials provided by examples 1-5 and comparative example 1 of the present application, it can be seen that the bonding sheet material obtained by using a three-dimensional polysiloxane network as a support skeleton has high tensile strength and low dielectric performance.

[0043] By comparing the performance results of comparative examples 1, 4, 5 and comparative example 2, it can be seen that by treating the surface of the polysiloxane support skeleton to improve the interfacial bonding force with the fluorocarbon resin, the heat resistance of the bonding sheet can be improved, and the bonding sheet does not appear delamination phenomenon during the thermal stress test. The interpenetrating network structure formed by FEVE and PTFE resin can significantly reduce the Z-axis CTE value of the bonding sheet, and the Z-axis CTE value of the bonding sheet gradually decreases with the increase of the content of FEVE resin.

[0044] By comparing the performance results of examples 1 and comparative example 3, it can be seen that the bonding sheet prepared by using octavinyl POSS as a reinforcing phase has higher tensile strength and lower dielectric performance.

[0045] The above description of the embodiments is only for the purpose of illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it. Those skilled in the art can obviously easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without having to go through creative labor, therefore, the above embodiments cannot limit the protection scope of the present application. Any improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application shall be covered within the protection scope of the present application.

Claims

1. An interlayer bonding sheet for multilayer boards, the bonding sheet comprising a central PTFE core layer and hydrocarbon resin surface layers bonded to the upper and lower surfaces of the PTFE core layer, characterized in that, The thickness of the PTFE core layer is 70~100μm; the thickness of the hydrocarbon resin surface layer is 20~40μm; the PTFE core layer uses a polysiloxane containing double bonds as a supporting base film, and a reactive FEVE / PTFE resin is coated on its surface, wherein the thickness of the polysiloxane containing double bonds as a supporting base film is 40~60μm.

2. The interlayer bonding sheet for multilayer boards according to claim 1, characterized in that: The polysiloxane containing double bonds is composed of the following raw materials in parts by weight: 100 parts α,ω-dihydroxypolysiloxane, 5-10 parts silica, 7-20 parts methyltriethoxysilane, 0.22-1.2 parts dibutyltin dilaurate, 10-20 parts alkenyltriethoxysilane, and 80-90 parts ethanol; And / or, the alkenyltriethoxysilane is allyltriethoxysilane or vinyltriethoxysilane or a mixture thereof; And / or, the viscosity of the α,ω-dihydroxypolysiloxane is 2000~20000 mPa·s; And / or, the silica is silica produced by the gas phase method, with a particle size of 20~200 nm.

3. The interlayer bonding sheet for multilayer boards according to claim 1, characterized in that: The FEVE / PTFE resin is composed of the following raw materials in parts by weight: 100 parts of the PTFE dispersion, 0.3 to 1.2 parts of OP-10 emulsifier, 6 to 16 parts of FEVE resin containing carbon-carbon double bonds, 0.5 to 2.5 parts of octavinyl POSS, 0.1 to 0.8 parts of dicumyl peroxide, and 0.3 to 1 part of leveling agent BYK333.

4. The interlayer bonding sheet for multilayer boards according to claim 3, characterized in that: The carbon-carbon double bond-containing FEVE resin is composed of the following raw materials in parts by weight: 100 parts of hydroxyl-containing FEVE resin, 60-150 parts of xylene, 5-15 parts of 3-isopropyl-dimethylbenzyl isocyanate, and 0.05-0.25 parts of dibutyltin dilaurate; And / or, the hydroxyl-containing FEVE resin is a fluorinated ethylene / vinyl ether alternating copolymer.

5. The interlayer bonding sheet for multilayer boards according to claim 1, characterized in that: The hydrocarbon resin surface layer is composed of the following raw materials in parts by weight: 100 parts hydrocarbon resin, 5-15 parts octavinyl POSS, 0.5-3 parts dicumyl peroxide, and 100-150 parts xylene. And / or, the hydrocarbon resin is one or a mixture of two or more of polybutadiene, polyisoprene, butadiene-styrene copolymer or ethylene propylene diene monomer (EPDM) rubber.

6. A method for preparing an interlayer bonding sheet for multilayer boards as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Preparation of PTFE core layer S1: Stir α,ω-dihydroxypolysiloxane and silica in a mixer for 15-30 min, then vacuum, heat and stir, cool to room temperature, add methyltriethoxysilane, vacuum and stir for 15-30 min, finally add some dibutyltin dilaurate, vacuum and stir for 15-30 min, pour into a mold, and cure at room temperature to obtain a polysiloxane support film; S2: Add alkenyltriethoxysilane and the remaining dibutyltin dilaurate to ethanol and stir until homogeneous to obtain a mixed solution. Spray the mixed solution onto the upper and lower surfaces of the polysiloxane-supported film obtained in S1 and cure at room temperature to obtain a polysiloxane-supported film containing double bonds; S3: Dissolve hydroxyl-containing FEVE resin in xylene, add 3-isopropyl-dimethylbenzyl isocyanate and dibutyltin dilaurate, stir for 2-4 hours, pour the solution into methanol to precipitate, and obtain FEVE resin containing carbon-carbon double bonds. S4: Add OP-10 emulsifier to a PTFE dispersion with a solid content of 30-40% and stir for 30-60 minutes. Then slowly add the FEVE resin containing carbon-carbon double bonds obtained in S3 and stir for 1-2 hours. Then slowly add octavinyl POSS, dicumyl peroxide and leveling agent BYK333 and stir for 1-2 hours to obtain fluorocarbon resin slurry. S5: The fluorocarbon resin slurry obtained in S4 is uniformly coated on the upper and lower surfaces of the polysiloxane support film containing double bonds obtained in S2. After drying, heating and reaction, and then heating and vacuum sintering, a PTFE-based core layer film is obtained. S6: The PTFE-based core layer film obtained in S5 is placed in a plasma generator and treated for 3 to 10 minutes in a mixed atmosphere with a frequency of 2.45 GHz, a vacuum degree of 10 to 500 Pa, a radio frequency power of 200 to 1200 W, and an Ar to H2 volume ratio of 1 to 5:1 to obtain a surface-activated PTFE-based core layer film. (2) Preparation of hydrocarbon resin surface layers on both the top and bottom surfaces S7: Add hydrocarbon resin, octavinyl POSS and dicumyl peroxide to xylene solvent respectively, stir for 1-2 hours to obtain a mixed adhesive solution; S8: The mixed adhesive obtained in S7 is scraped onto the upper and lower surfaces of the surface-activated PTFE-based core film obtained in S6, and then dried to obtain an interlayer bonding sheet for multilayer boards.

7. The method for preparing an interlayer bonding sheet for multilayer boards according to claim 6, characterized in that: The heating and stirring temperature in S1 is 100~110℃, and the time is 1~2h; And / or, the mass ratio of dibutyltin dilaurate in S1 to dibutyltin dilaurate in S2 is 5~20:

1.

8. The method for preparing an interlayer bonding sheet for multilayer boards according to claim 6, characterized in that: The drying temperature in S5 is 105~120℃, and the time is 2~5 min; the heating reaction temperature is 160~180℃, and the time is 2~5 min; the vacuum sintering temperature is 360~380℃, and the time is 3~10 min.

9. The method for preparing an interlayer bonding sheet for multilayer boards according to claim 6, characterized in that: The drying temperature in S8 is 110~130℃, and the time is 1~5min.

10. The method for preparing an interlayer bonding sheet for multilayer boards according to claim 6, characterized in that: The curing humidity in S1 is 50-70%, and the curing time is 10-24 hours; the curing humidity in S2 is 50-70%, and the curing time is 2-4 hours.

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