阅读说明：本技术 一种多层板用层间粘结片及其制备方法和应用 (Interlayer bonding sheet for multilayer board and preparation method and application thereof ) 是由 苏民社 周如金 梁伟 郭浩勇 于 2019-09-04 设计创作，主要内容包括：本发明提供一种多层板用层间粘结片及其制备方法和应用,所述多层板用层间粘结片包括改性PTFE基片,以及粘结于所述改性PTFE基片表面的介电树脂层；所述改性PTFE基片为表面经过等离体子和单体接枝聚合处理的改性PTFE基片；等离子体处理和单体接枝聚合处理的协同配合在PTFE基片上形成一层长时效性的活化层,其活化性可以保持30天,充分满足了制造工艺的需求和对产品性能的要求。本发明提供的多层板用层间粘结片通过改性PTFE基片与介电树脂层的协同配合,介电性能、粘结强度、机械性能以及耐性好,包含所述多层板用层间粘结片的多层板在高温下的粘结稳定性高,可以充分满足多层板的信号高频化、稳定性、可靠性需求。(The invention provides an interlayer bonding sheet for a multilayer board, and a preparation method and application thereof, wherein the interlayer bonding sheet for the multilayer board comprises a modified PTFE substrate and a dielectric resin layer bonded on the surface of the modified PTFE substrate; the modified PTFE substrate is a modified PTFE substrate with the surface subjected to plasma and monomer graft polymerization treatment; the plasma treatment and the monomer graft polymerization treatment are cooperated to form a long-time-effect activation layer on the PTFE substrate, the activation property can be maintained for 30 days, and the requirements of the manufacturing process and the product performance are fully met. The interlayer bonding sheet for the multilayer board provided by the invention has good dielectric property, bonding strength, mechanical property and resistance through the synergistic matching of the modified PTFE substrate and the dielectric resin layer, and the multilayer board containing the interlayer bonding sheet for the multilayer board has high bonding stability at high temperature, so that the requirements of the multilayer board on signal high frequency, stability and reliability can be fully met.)

1. An interlayer bonding sheet for a multilayer board, comprising a modified PTFE substrate, and a dielectric resin layer bonded to the surface of the modified PTFE substrate;

the modified PTFE substrate is a modified PTFE substrate with the surface subjected to plasma and monomer graft polymerization treatment.

2. The interlayer bonding sheet for multilayer sheets according to claim 1, wherein the monomer is selected from any one or a combination of at least two of styrene, methyl methacrylate, acrylic acid, glycidyl methacrylate, or a silane coupling agent;

preferably, the silane coupling agent is selected from any one of or a combination of at least two of a silane coupling agent containing a vinyl group, a silane coupling agent containing an acrylate group, or a silane coupling agent containing an epoxy group.

3. The interlayer bonding sheet for multilayer sheets according to claim 1 or 2, wherein the modified PTFE substrate is obtained by a method in which a monomer is graft-polymerized by plasma initiation or after plasma treatment;

preferably, the surface treatment depth of the plasma treatment is 5-15 nm;

preferably, the contact angle after the plasma treatment is 84-98 degrees.

4. The interlayer bonding sheet for a multilayer sheet according to any one of claims 1 to 3, comprising a modified PTFE substrate, and dielectric resin layers bonded to the upper and lower surfaces of the modified PTFE substrate;

preferably, the thickness of the modified PTFE substrate is 0.3-1.5 mm;

preferably, the modified PTFE substrate is a modified glass cloth with a PTFE layer on the surface;

preferably, the glass cloth is electronic-grade glass cloth or once-desized glass cloth;

preferably, the PTFE layer is obtained by soaking glass cloth in PTFE emulsion, and then drying and sintering;

preferably, the PTFE emulsion is a PTFE emulsion containing a powdered filler;

preferably, the powder filler is selected from any one or a combination of at least two of silicon dioxide, titanium dioxide, strontium titanate, barium titanate, boron nitride, aluminum nitride, silicon carbide, alumina, glass fiber, polytetrafluoroethylene, polyphenylene sulfide or polyether sulfone, and is further preferably silicon dioxide;

preferably, the median particle diameter of the powder filler is 1 to 15 μm, and more preferably 1 to 10 μm.

5. The interlayer bonding sheet for multilayer boards according to any one of claims 1 to 4, wherein the thickness of the dielectric resin layer is 5 to 60 μm, preferably 20 to 50 μm;

preferably, the raw materials for preparing the dielectric resin layer comprise the following components in parts by weight: 20-70 parts of polymer matrix material, 0-70 parts of powder filler and 1-3 parts of initiator;

preferably, the polymer matrix material is selected from any one or a combination of at least two of polybutadiene, polyisoprene, butadiene-styrene copolymer, polyphenylene oxide or ethylene propylene rubber;

preferably, the initiator is an organic peroxide initiator;

preferably, the powder filler is selected from any one or a combination of at least two of silicon dioxide, titanium dioxide, strontium titanate, barium titanate, boron nitride, aluminum nitride, silicon carbide, alumina, glass fiber, polytetrafluoroethylene, polyphenylene sulfide or polyether sulfone, and is further preferably silicon dioxide;

preferably, the median particle diameter of the powder filler is 1 to 15 μm, and more preferably 1 to 10 μm.

6. A method for producing an interlayer bonding sheet for a multilayer sheet according to any one of claims 1 to 5, comprising the steps of:

(1) preparing a modified PTFE substrate: the modified PTFE substrate is prepared by one of the following methods:

(1a) treating the PTFE substrate with plasma to obtain a modified PTFE substrate with monomer graft polymerization initiated by the plasma;

(1b) coating a prepolymer on the PTFE substrate subjected to plasma treatment, and carrying out graft polymerization to obtain the modified PTFE substrate;

(2) and (2) coating a dielectric resin layer on the modified PTFE substrate obtained in the step (1), and curing to obtain the interlayer bonding sheet for the multilayer board.

7. The method according to claim 6, wherein the atmosphere of the plasma treatment in the step (1a) or the step (1b) is selected from He, Ne and O independently₂、H₂、N₂、Ar、CO₂、SO₂、NH₃、CH₄Or water vapor or a combination of at least two of the foregoing;

preferably, the plasma treatment of the step (1a) and the step (1b) is independently performed by a low-temperature plasma generating device;

preferably, the voltage of the plasma treatment in the step (1a) and the step (1b) is 500-10000V independently;

preferably, the plasma treatment time in the step (1a) and the step (1b) is 10-600 s, and more preferably 50-600 s;

preferably, the system vacuum degree of the plasma treatment in the step (1a) and the step (1b) is 133-1333 Pa respectively and independently;

preferably, the radio frequency power of the plasma treatment in the step (1a) and the step (1b) is 1-5 kW independently;

preferably, the prepolymer of step (1b) comprises a monomer and an initiator;

preferably, the initiator is dibenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, dicumyl peroxide or azobisisobutyronitrile;

preferably, the concentration of the initiator in the prepolymer in the step (1b) is 0.002-0.006 mol/L;

preferably, the reaction temperature of the graft polymerization in the step (1b) is 85-135 ℃;

preferably, the reaction time of the graft polymerization in the step (1b) is 30-150 min;

preferably, the graft polymerization of step (1b) is carried out in a protective atmosphere, preferably nitrogen;

preferably, the coating method in the step (2) is roller coating;

preferably, the curing temperature in the step (2) is 160-250 ℃, and further preferably 180-230 ℃;

preferably, the curing time in the step (2) is 1-4 h, and more preferably 1.5-3 h.

8. The preparation method according to claim 6 or 7, characterized in that it comprises in particular the steps of:

(1) preparing a modified PTFE substrate: the modified PTFE substrate is prepared by one of the following methods:

(1a) placing the PTFE substrate coated with monomer on the surface in a low-temperature plasma generator, and polymerizing the monomer under the initiation of plasma in the atmosphere selected from He, Ne and O₂、H₂、N₂、Ar、CO₂、SO₂、NH₃、CH₄Or any one or the combination of at least two of water vapor, the voltage is 500-10000V, the system vacuum degree is 133-1333 Pa, the radio frequency power is 1-5 kW, and the time is 10-600 s, so as to obtain the modified PTFE substrate of which the monomer is grafted and polymerized by the initiation of the plasma;

(1b) placing the PTFE substrate in a low-temperature plasma generator for surface plasma treatment in a treatment atmosphere selected from He, Ne and O₂、H₂、N₂、Ar、CO₂、SO₂、NH₃、CH₄Or any one or the combination of at least two of water vapor, the treatment voltage is 500-10000V, the vacuum degree of a system for treatment is 133-1333 Pa, the radio frequency power for treatment is 1-5 kW, and the treatment time is 10-600 s; then coating a prepolymer on the PTFE substrate after plasma treatment, and carrying out graft polymerization for 30-150 min at 85-135 ℃ in a protective atmosphere to obtain the modified PTFE substrate;

(2) and (2) coating a dielectric resin layer on the modified PTFE substrate obtained in the step (1), and curing at 160-250 ℃ for 1-4 h to obtain the interlayer bonding sheet for the multilayer board.

9. A multilayer board comprising at least two PTFE double-sided circuit boards, and the interlayer bonding sheet for multilayer boards according to any one of claims 1 to 5 interposed between the two PTFE double-sided circuit boards.

10. An electronic device, characterized in that it comprises a multilayer board according to claim 9.

Technical Field

The invention belongs to the technical field of copper-clad plates, and particularly relates to an interlayer bonding sheet for a multilayer plate, and a preparation method and application thereof.

Background

Printed Circuit Boards (PCBs) are electrical structural elements formed by insulating matrix materials and conductor wiring, which are used as main support bodies for mounting and plugging electronic components such as transistors, diodes, volume Circuits, passive components and other electronic parts, and have become indispensable components for achieving circuit interconnection in most electronic products. With the wide application of integrated circuits, the high performance of electronic products is continuously promoting the forward development of the PCB industry, and PCBs are inevitably subject to the continuous transition to high frequency and high speed characteristics. In the high-frequency and high-speed development process of electronic circuit base materials, the key point is that a material with excellent electrical performance is selected, the dielectric constant and the dielectric loss tangent of Polytetrafluoroethylene (PTFE) are small, the ageing resistance and the high and low temperature resistance are good, the mechanical strength is high, the processing and application requirements of a PCB (printed circuit board) can be fully met, and the Polytetrafluoroethylene (PTFE) is an ideal base material.

In recent years, the electronic industry based on microelectronic technology has driven the development of electronic products toward miniaturization, multi-functionalization and high performance, and PCBs are also required to realize multi-functionalization and multi-layering as structural elements for circuit interconnection. However, the PTFE resin has low surface energy and very poor flowability and adhesiveness, and cannot meet the bonding requirements of multi-layer PCBs, and is difficult to use as a bonding material between the layers of a multi-layer board. Therefore, the interlayer bonding material for the multilayer board with excellent comprehensive performance is found, and the interlayer bonding material has important significance for the development of the circuit substrate industry.

CN104164087A discloses a low resin fluidity prepreg and a preparation method thereof, wherein the prepreg uses electronic grade glass fiber cloth as a reinforcing material, and the surface of the prepreg is coated with a thermosetting resin composition; the thermosetting resin composition comprises 100 parts of bismaleimide resin, 30-60 parts of allyl compound, 10-30 parts of bisphenol A epoxy resin, 5-20 parts of epoxy resin containing biphenyl structural units, inorganic filler and solvent. The prepreg has higher flexibility and bonding strength, does not flow glue, solves the problem that the reliability of the rigid-flex printed circuit board manufactured by the prepreg is reduced due to the low degree of bonding of the current similar products, has the glass transition temperature of over 200 ℃ after curing, and improves the heat resistance, the processing toughness and the like of the rigid-flex printed circuit board.

CN102731966A discloses a thermosetting epoxy resin composition and a prepreg and a copper-clad laminate prepared by using the same, wherein the resin composition comprises 100 parts of epoxy resin, 2-10 parts of a tetraphenylethane compound, 5-30 parts of a phenol novolac resin, 0.5-2.2 parts of dicyandiamide and 0.05-1.0 part of a curing accelerator; the thermosetting epoxy resin composition has good cohesiveness, can effectively absorb ultraviolet light, and has good heat resistance, toughness and machining performance after curing. The prepreg and the copper clad laminate prepared from the thermosetting epoxy resin composition have high heat resistance, low linear expansion coefficient, good cohesiveness, toughness and machining performance, and can meet the requirement of PCB processing.

CN109760398A discloses a combination mode of a fluorine-containing resin prepreg of a high-frequency copper-clad plate, which specifically comprises the steps of baking glass fiber cloth, preparing fluorine-containing resin impregnation liquid, immersing the glass fiber cloth into the fluorine-containing resin impregnation liquid, performing plasma activation, pressing and the like, and solves the problems that when light and thin copper foils are adopted for pressing, the copper-clad plate prepared by the existing fluorine-containing resin copper-clad plate manufacturing process is high in hygroscopicity, high in dielectric constant, high in transmission loss, high in peeling strength and poor in adhesiveness, and the copper skin is easy to fall off.

However, in the prior art, although the prepreg based on the thermosetting resin such as epoxy has good adhesive property, the dielectric constant and the dielectric loss tangent are high, the high frequency characteristic is insufficient, and the prepreg cannot meet the requirement of signal high frequency; the polyolefin resin has low dielectric loss tangent but poor resistance, and is difficult to meet the process requirements and use requirements for manufacturing printed circuit boards. Although the prepreg of the fluorine-containing resin overcomes the defects of partial dielectric property and tolerance, the bonding property of the fluorine resin and a film material is poor, and the obtained PTFE multilayer board has poor bonding heat-resistant reliability due to the phenomena of layering and foaming at high temperature; plasma treatment can improve the adhesiveness of the PTFE multilayer sheet, but the improvement has poor timeliness, increases the time limitation of the preparation process, and can not meet the subsequent application requirements.

Therefore, the development of an interlayer bonding material for a multilayer board, which has good bonding property, good heat resistance and reliability and is easy for industrial production, so as to meet the preparation process requirements and various performance requirements of a high-frequency multilayer printed circuit board is a research focus in the field.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide an interlayer bonding sheet for a multilayer board, a preparation method and application thereof, wherein the interlayer bonding sheet for the multilayer board comprises a modified PTFE substrate and a dielectric resin layer bonded on the surface of the modified PTFE substrate; the modified PTFE substrate is subjected to plasma and monomer graft polymerization treatment to form a stable and long-time-effect activation layer on the PTFE material, so that the activity time of the modified PTFE substrate is obviously prolonged, and the operability of industrial production is improved; and the modified PTFE substrate and the dielectric resin layer are cooperatively matched, so that the interlayer bonding sheet for the multilayer board has excellent dielectric property, fluidity and bonding strength, and can meet the signal high-frequency requirement, stability and reliability requirement of the multilayer board.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides an interlayer bonding sheet for a multilayer sheet, comprising a modified PTFE substrate, and a dielectric resin layer bonded to a surface of the modified PTFE substrate.

The modified PTFE substrate is a modified PTFE substrate with the surface subjected to plasma and monomer graft polymerization treatment.

The interlayer bonding sheet for the multilayer board comprises a modified PTFE substrate and a dielectric resin layer bonded on the surface of the modified PTFE, wherein the modified PTFE substrate is subjected to plasma and monomer graft polymerization treatment, and an active layer with stability and long timeliness is formed on the surface of the modified PTFE substrate, so that the high-strength stable bonding is realized between the modified PTFE substrate and the dielectric resin layer. The modified PTFE substrate and the dielectric resin layer have excellent dielectric property, low dielectric constant and dielectric loss tangent and sufficient high-frequency property, and can meet the electrical property requirement of a multilayer board.

The PTFE material on the PTFE substrate has the characteristics of high crystallinity, low surface energy and difficult wetting, and meanwhile, the difference between the solubility parameter and the solubility parameter of a common adhesive is large, and the interfaces are difficult to diffuse mutually at will, so the PTFE material is a difficult-to-bond material. The plasma being passed through various gases (e.g. He, Ne, O)₂、H₂、N₂、Ar、CO₂、SO₂、NH₃、CH₄Or water vapor or the combination of at least two of the water vapor) to bombard the surface of the PTFE material, so that the surface of the PTFE material generates free radicals to form active centers, thereby modifying the surface of the material; however, the active centers generated by plasma treatment have short service life and poor timeliness, and generally lose effectiveness within 4-6 hours after treatment. Therefore, the PTFE substrate after the pure plasma treatment must be processed in the next step in a short time, which has a great limitation on the process flow of the whole product. Aiming at the problem, the modified PTFE substrate combines plasma treatment and monomer graft polymerization treatment, and a long-time-effect activation layer is formed on the PTFE substrate through the synergistic cooperation of the plasma treatment and the monomer graft polymerization treatment, so that the activation layer can be stably bonded with a dielectric resin layer in high strength, and has high heat resistance and high-temperature reliability, and the activation property can be maintained for more than 30 days, thereby fully meeting the requirements of the manufacturing process and the product performance.

In addition, the dielectric resin layer in the interlayer bonding sheet for the multilayer board has excellent dielectric property and heat resistance, good chemical resistance and mechanical property, toughness capable of meeting the process requirement of the multilayer board, good fluidity and bonding property, strong interlayer bonding force between circuit boards and high bonding stability.

In conclusion, the interlayer bonding sheet for the multilayer board provided by the invention has excellent dielectric property, fluidity, bonding strength, mechanical property and resistance through the synergistic cooperation of the modified PTFE substrate and the dielectric resin layer, and can fully meet the signal high-frequency requirement, stability and reliability requirement of the multilayer board.

Preferably, the monomer is selected from any one of styrene, methyl methacrylate, acrylic acid, glycidyl methacrylate or a combination of at least two of silane coupling agents.

Preferably, the silane coupling agent is selected from any one of or a combination of at least two of a silane coupling agent containing a vinyl group, a silane coupling agent containing an acrylate group, or a silane coupling agent containing an epoxy group.

Illustratively, the silane coupling agent may be Japanese Beacon KBM-403, KBM-503, KBM-1003, KBM-1403, or the like.

Preferably, the modified PTFE substrate is obtained by plasma-initiated monomer graft polymerization or by plasma treatment followed by monomer graft polymerization.

The modified PTFE substrate of the invention can be obtained by two methods: firstly, the monomer is directly initiated by plasma to carry out graft polymerization on the surface of PTFE, the energy of low-temperature plasma generated by glow discharge is 2-5 eV, which is equivalent to the bond energy of an organic compound, so that the graft polymerization of the monomer on the surface of PTFE can be directly initiated, an initiator is not required to be added, and the modified PTFE substrate with long activation timeliness is obtained. Secondly, treating the surface of the PTFE by using plasma, and breaking chains on the surface of the material by using high-energy-state plasma to generate free radicals to form active sites so as to obtain the surface of the PTFE with transiently activated surface; then, the monomer is initiated by an initiator to perform graft polymerization reaction on the surface of the PTFE to obtain a stable and long-acting modified PTFE substrate; moreover, the monomer should be grafted and polymerized within 1h after plasma treatment, and if the plasma-treated material is left in the air for too long time, active free radicals can be ineffective, and the monomer and the PTFE surface cannot be stably and effectively combined.

Preferably, the plasma treatment has a surface treatment depth of 5-15 nm, such as 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm or 14nm, and the specific values therebetween are not exhaustive for the purpose of space and brevity.

When the surface treatment depth of the plasma treatment is within the range of 5-15 nm, the activating layer and the dielectric resin layer formed after the PTFE material and the monomer are subjected to graft polymerization have the best bonding strength and high bonding stability. When the plasma treatment depth is less than 5nm, the plasma etching depth is shallow, the surface area is low, and ideal bonding cannot be formed; when the plasma treatment depth is more than 15nm, the treatment is excessive, the surface activation is weakened, the improvement of wettability is affected, and an ideal bond cannot be formed.

Preferably, the contact angle after the plasma treatment is 84-98 degrees.

The contact angle after plasma treatment is 84-98 degrees, if the contact angle is larger than 98 degrees, the activation degree of the PTFE material is low, the wettability is poor, the PTFE material is difficult to generate graft polymerization reaction with a monomer, and the PTFE material cannot be tightly adhered to a dielectric resin layer; if the contact angle is less than 84 °, the surface is excessively treated with plasma, which reduces the surface activation, lowers the wettability of the substrate surface, and prevents high-strength adhesion with the dielectric resin layer.

Preferably, the interlayer bonding sheet for a multilayer sheet comprises a modified PTFE substrate, and dielectric resin layers bonded to the upper and lower surfaces of the modified PTFE substrate.

Preferably, the modified PTFE substrate has a thickness of 0.3 to 1.5mm, such as 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, or 1.4mm, and specific values therebetween, not to be limited by space and for the sake of brevity, the present invention is not exhaustive of the specific values included in the ranges.

Preferably, the modified PTFE substrate is a modified glass cloth with a PTFE layer on the surface.

Preferably, the glass cloth is electronic-grade glass cloth or once-desized glass cloth; for example, the electronic grade glass cloth may be 1037, 106, 1080, 1078, and the like.

Preferably, the PTFE layer is obtained by impregnating glass cloth in PTFE emulsion, and then drying and sintering.

The PTFE emulsion of the present invention means an aqueous dispersion containing a PTFE resin.

Preferably, the PTFE emulsion is a PTFE emulsion containing a powdered filler.

Preferably, the powder filler is selected from any one or a combination of at least two of silica, titanium dioxide, strontium titanate, barium titanate, boron nitride, aluminum nitride, silicon carbide, alumina, glass fiber, polytetrafluoroethylene, polyphenylene sulfide or polyether sulfone, and more preferably is silica.

Illustratively, the silica may be any one of crystalline silica, fused silica, or spherical silica, or a combination of at least two thereof.

Preferably, the powder filler has a median particle diameter of 1 to 15 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or 14 μm, and specific values therebetween, which are not intended to limit the disclosure and for the sake of brevity, the present invention is not exhaustive of the specific values included in the range, and more preferably 1 to 10 μm.

Preferably, the thickness of the dielectric resin layer is 5-60 μm, such as 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 33 μm, 35 μm, 37 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 53 μm, 55 μm, 57 μm or 59 μm, and the specific dot values therebetween are limited to the dot value range and for the sake of brevity, the invention does not exhaust the specific dot values included in the range, and more preferably 20-50 μm.

Preferably, the raw materials for preparing the dielectric resin layer comprise the following components in parts by weight: 20-70 parts of polymer matrix material, 0-70 parts of powder filler and 1-3 parts of initiator.

Preferably, the polymer matrix material is selected from any one of polybutadiene, polyisoprene, butadiene-styrene copolymer, polyphenylene oxide or ethylene propylene rubber or a combination of at least two of the same.

The resin compositions disclosed in the prior art to meet the above requirements can be used to prepare the dielectric resin layer of the present invention. Such prior art includes, by way of example and not limitation: CN106867173A discloses a composite material, comprising: (1) 20-70 parts of a thermosetting mixture comprising: (A) a thermosetting resin based on polybutadiene having a molecular weight of 11000 or less and containing 60% or more of vinyl groups or a copolymer resin of polybutadiene and styrene, which is composed of hydrocarbon elements; and (B) an ethylene-propylene rubber which is solid at room temperature and has a weight average molecular weight of more than 10 ten thousand and less than 15 ten thousand and a number average molecular weight of more than 6 ten thousand and less than 10 ten thousand; (2) 10-60 parts of glass fiber cloth; (3) 0-70 parts of powder filler; (4) 1-3 parts of curing initiator. CN102161823A discloses a composite material, which comprises more than one vinyl liquid resin with molecular weight less than 10000 and polar functional groups, a polyphenylene oxide resin with molecular weight less than 5000 and molecular end with unsaturated double bond, glass fiber cloth, powder filler, flame retardant and curing initiator. CN101643565B discloses a composite material, which comprises a resin containing more than 60% of vinyl and consisting of hydrocarbon elements with molecular weight of less than 11000, a medium-low molecular weight solid styrene-based resin with unsaturated double bonds, glass fiber cloth, powder filler, flame retardant and curing initiator. CN102807658A discloses a polyphenylene ether resin composition component comprising a functionalized polyphenylene ether resin, a crosslinking curing agent and an initiator; the functionalized polyphenylene ether resin is polyphenylene ether resin with a number average molecular weight of 500-5000 and an unsaturated double bond at the molecular terminal, and the crosslinking curing agent is olefin resin with a number average molecular weight of 500-10000 and containing 10-50 wt% of styrene structure, and the molecule of the resin contains a 1, 2-bit addition butadiene structure. CN102993683A discloses a modified polyphenylene ether resin, an organic silicon compound containing an unsaturated double bond, and the like.

In the raw material for preparing the polymer matrix material of the present invention, the content of the polymer matrix material may be 22 parts by weight, 25 parts by weight, 28 parts by weight, 30 parts by weight, 32 parts by weight, 35 parts by weight, 38 parts by weight, 40 parts by weight, 42 parts by weight, 45 parts by weight, 48 parts by weight, 50 parts by weight, 52 parts by weight, 55 parts by weight, 58 parts by weight, 60 parts by weight, 62 parts by weight, 65 parts by weight, 68 parts by weight, 69 parts by weight, or the like.

The content of the powder filler may be 2 parts by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 55 parts by weight, 60 parts by weight, 65 parts by weight, 68 parts by weight, or the like.

The initiator may be present in an amount of 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.2 parts by weight, 2.4 parts by weight, 2.6 parts by weight, 2.8 parts by weight, 2.9 parts by weight, or the like.

As a preferred embodiment of the present invention, the polymer matrix material comprises: (A) a thermosetting resin based on polybutadiene or a butadiene-styrene copolymer having a molecular weight of 11000g/mol or less (e.g., 10500g/mol, 10000g/mol, 9800g/mol, 9500g/mol, 9300g/mol, 9000g/mol, 8800g/mol, 8500g/mol, 8300g/mol, or 8000 g/mol), containing 60% or more (e.g., 61%, 63%, 65%, 67%, 69%, 71%, 73%, 75%, or 77% or the like) vinyl groups and composed of hydrocarbon elements, and comprising (B) a thermosetting resin having a weight average molecular weight of 100000 to 150000g/mol (e.g., 105000g/mol, 110000g/mol, 115000g/mol, 120000g/mol, 125000g/mol, 130000g/mol, 135000g/mol, 140000g/mol, or 145000g/mol, or the like), An ethylene-propylene rubber which is solid at room temperature and has a number-average molecular weight of 60000 to 100000g/mol (e.g., 65000g/mol, 70000g/mol, 75000g/mol, 80000g/mol, 85000g/mol, 90000g/mol, or 95000 g/mol).

The molecular weight, the weight average molecular weight and the number average molecular weight data are obtained by testing according to the method specified in GB/T21863-2008 standard, and are measured by gel permeation chromatography based on polystyrene calibration.

Preferably, the initiator is an organic peroxide initiator; illustratively, the organic peroxide initiator includes benzoyl peroxide, dicumyl peroxide, or t-butyl peroxybenzoate, and the like.

Preferably, the powder filler is selected from any one or a combination of at least two of silica, titanium dioxide, strontium titanate, barium titanate, boron nitride, aluminum nitride, silicon carbide, alumina, glass fiber, polytetrafluoroethylene, polyphenylene sulfide or polyether sulfone, and more preferably is silica.

Illustratively, the silica may be crystalline silica, fused silica, or spherical silica, among others.

Preferably, the powder filler has a median particle diameter of 1 to 15 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or 14 μm, and specific values therebetween, which are not intended to limit the disclosure and for the sake of brevity, the present invention is not exhaustive of the specific values included in the range, and more preferably 1 to 10 μm.

In another aspect, the present invention provides a method for producing an interlayer bonding sheet for a multilayer sheet according to the first aspect, comprising the steps of:

(1) preparing a modified PTFE substrate: the modified PTFE substrate is prepared by one of the following methods:

(1a) and treating the PTFE substrate with plasma to obtain the modified PTFE substrate with monomer grafted and polymerized by plasma.

(1b) And coating a prepolymer on the PTFE substrate subjected to plasma treatment, and carrying out graft polymerization to obtain the modified PTFE substrate.

(2) And (2) coating a dielectric resin layer on the modified PTFE substrate obtained in the step (1), and curing to obtain the interlayer bonding sheet for the multilayer board.

Preferably, the plasma of step (1a) and step (1b)The atmosphere for the bulk treatment is selected from He, Ne and O independently₂、H₂、N₂、Ar、CO₂、SO₂、NH₃、CH₄Or water vapor or a combination of at least two thereof.

Preferably, the plasma treatment in step (1a) and step (1b) is performed independently by a low-temperature plasma generator.

Preferably, the plasma treatment voltage of step (1a) and step (1b) is 500-10000V, such as 550V, 600V, 700V, 800V, 900V, 1000V, 1500V, 2000V, 3000V, 4000V, 5000V, 6000V, 7000V, 8000V, 9000V or 9500V, and the specific values therebetween are not exhaustive, and for the sake of brevity, the invention is not exhaustive.

Preferably, the plasma treatment time in step (1a) and step (1b) is 10-600 s, such as 15s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 120s, 150s, 180s, 200s, 220s, 250s, 280s, 300s, 320s, 350s, 380s, 400s, 420s, 450s, 480s, 500s, 520s, 550s, 570s or 590s, and the specific point values between the above point values are limited to space and for the sake of brevity, the invention does not exhaust the specific point values included in the range, and further preferably 50-600 s.

Preferably, the system vacuum degree of the plasma treatment in the steps (1a) and (1b) is 133-1333 Pa, such as 135Pa, 140Pa, 150Pa, 170Pa, 190Pa, 200Pa, 230Pa, 250Pa, 280Pa, 300Pa, 350Pa, 400Pa, 500Pa, 600Pa, 700Pa, 800Pa, 900Pa, 1000Pa, 1100Pa, 1200Pa or 1300Pa, and the specific values therebetween are limited to the space and are not exhaustive, and the invention is not intended to list the specific values included in the range for the sake of brevity.

Preferably, the rf power of the plasma treatment in steps (1a) and (1b) is 1 to 5kW, such as 1.2kW, 1.4kW, 1.6kW, 1.8kW, 2kW, 2.2kW, 2.5kW, 2.8kW, 3kW, 3.2kW, 3.5kW, 3.8kW, 4kW, 4.2kW, 4.5kW, 4.7kW or 4.9kW, and the specific points between the above points are limited to space and for brevity, and the invention is not exhaustive of the specific points included in the range.

Preferably, the prepolymer of step (1b) comprises a monomer and an initiator.

Preferably, the initiator is dibenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, dicumyl peroxide or azobisisobutyronitrile.

Preferably, the concentration of the initiator in the prepolymer in the step (1b) is 0.002-0.006 mol/L, such as 0.0023mol/L, 0.0025mol/L, 0.003mol/L, 0.0035mol/L, 0.004mol/L, 0.0045mol/L, 0.005mol/L, 0.0055mol/L or 0.0059mol/L, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive.

Preferably, the reaction temperature of the graft polymerization in the step (1b) is 85 to 135 ℃, for example, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃ or 133 ℃.

Preferably, the reaction time of the graft polymerization in the step (1b) is 30-150 min, such as 35min, 40min, 45min, 50min, 55min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, 130min, 140min or 145 min.

Preferably, the graft polymerization of step (1b) is carried out in a protective atmosphere, preferably nitrogen.

Preferably, the coating method in the step (2) is roll coating.

Preferably, the curing temperature in step (2) is 160 to 250 ℃, such as 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃, 200 ℃, 205 ℃, 210 ℃, 215 ℃, 220 ℃, 225 ℃, 230 ℃, 235 ℃, 240 ℃ or 245 ℃, and more preferably 180 to 230 ℃.

Preferably, the curing time in the step (2) is 1 to 4 hours, such as 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, 2.3 hours, 2.5 hours, 2.8 hours, 3 hours, 3.5 hours or 3.8 hours, and the like, and further preferably 1.5 to 3 hours.

Preferably, the preparation method specifically comprises the following steps:

(1) preparing a modified PTFE substrate: the modified PTFE substrate is prepared by one of the following methods:

(1a) placing the PTFE substrate coated with monomer on the surface in a low-temperature plasma generator, and polymerizing the monomer under the initiation of plasma in the atmosphere selected from He, Ne and O₂、H₂、N₂、Ar、CO₂、SO₂、NH₃、CH₄Or any one or the combination of at least two of water vapor, the voltage is 500-10000V, the system vacuum degree is 133-1333 Pa, the radio frequency power is 1-5 kW, and the time is 10-600 s, so as to obtain the modified PTFE substrate of which the monomer is grafted and polymerized by the initiation of the plasma;

(1b) placing the PTFE substrate in a low-temperature plasma generator for surface plasma treatment in a treatment atmosphere selected from He, Ne and O₂、H₂、N₂、Ar、CO₂、SO₂、NH₃、CH₄Or any one or the combination of at least two of water vapor, the treatment voltage is 500-10000V, the vacuum degree of a system for treatment is 133-1333 Pa, the radio frequency power for treatment is 1-5 kW, and the treatment time is 10-600 s; and then coating a prepolymer on the PTFE substrate after plasma treatment, and carrying out graft polymerization for 30-150 min at 85-135 ℃ in a protective atmosphere to obtain the modified PTFE substrate.

(2) And (2) coating a dielectric resin layer on the modified PTFE substrate obtained in the step (1), and curing at 160-250 ℃ for 1-4 h to obtain the interlayer bonding sheet for the multilayer board.

In another aspect, the present invention provides a multilayer board comprising at least two PTFE double-sided circuit boards, and an interlayer bonding sheet for a multilayer board according to the first aspect interposed between the two PTFE double-sided circuit boards.

In another aspect, the present invention provides an electronic device including the multilayer board as described above.

Compared with the prior art, the invention has the following beneficial effects:

(1) the interlayer bonding sheet for the multilayer board comprises a modified PTFE substrate and a dielectric resin layer, wherein the surface of the modified PTFE substrate is subjected to plasma and monomer graft polymerization, the dielectric resin layer is bonded on the modified PTFE substrate, the modified PTFE substrate and the dielectric resin layer have excellent dielectric properties, the dielectric constant and the dielectric loss tangent are low, the high-frequency property is sufficient, and the electric property requirement of the multilayer board can be met.

(2) The modified PTFE substrate combines plasma treatment and monomer graft polymerization treatment, and a long-time-effect activation layer is formed on the PTFE substrate through the synergistic cooperation of the plasma treatment and the monomer graft polymerization treatment, so that the activation layer can be stably bonded with a dielectric resin layer in high strength, and has high heat resistance and high-temperature reliability, and the activation property can be maintained for more than 30 days, thereby fully meeting the requirements of a manufacturing process and the performance requirements of products.

(3) The interlayer bonding sheet for the multilayer board provided by the invention has excellent dielectric property, fluidity, bonding strength, mechanical property and tolerance by the synergistic cooperation of the modified PTFE substrate and the dielectric resin layer, the multilayer board containing the interlayer bonding sheet for the multilayer board has no layering and foaming phenomena at 288 ℃ in a high-temperature environment, the bonding stability is high, and the signal high-frequency requirement, the stability and the reliability requirement of the multilayer board can be fully met.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The experimental materials used in the examples and comparative examples of the present invention were as follows:

(1) a PTFE substrate: soaking 1078 type electronic grade glass cloth in PTFE emulsion (average particle size of PTFE is 0.1-0.5 μm) at normal temperature, drying at 150 deg.C, and sintering at 360 deg.C for 30min to obtain the final product; such materials are available from dupont, usa.

(2) Dielectric resin treatment liquid I: 30 parts by weight of ethylene-propylene rubber (number average molecular weight 80000g/mol, lion chemical company, usa), 40 parts by weight of polybutadiene (molecular weight 3200g/mol, japan caoda corporation), 30 parts by weight of silica (median particle diameter 5 μm, new materials of Jiangsu Union Ltd.), and 2 parts by weight of benzoyl peroxide (Shanghai Kanglang Biotech Co., Ltd.) were dissolved in 50 parts by weight of xylene and mixed uniformly to obtain a dielectric resin treatment liquid I;

dielectric resin treatment liquid II: 25 parts by weight of ethylene-propylene rubber (number average molecular weight 80000g/mol, lion chemical company, usa), 35 parts by weight of butadiene-styrene copolymer (number average molecular weight 4500g/mol, sartomer company, usa), 10 parts by weight of polyphenylene ether (weight average molecular weight 1700g/mol, SABIC company, usa), 30 parts by weight of silica (median particle diameter 10 μm, Jiangsu Union Rui New Material Co., Ltd.) and 2 parts by weight of benzoyl peroxide (Shanghai Kanglang Biotech Co., Ltd.) were dissolved in 50 parts by weight of xylene and mixed uniformly to obtain dielectric resin treatment liquid II.

(3) Low-temperature plasma generating device: plasma processor model CD1200 from europlas corporation, belgium.

(4) Monomer (b): glycidyl methacrylate, acrylic acid, methyl methacrylate, styrene were all purchased from Aladdin; silane coupling agent KBM-403 is available from Japan shin-Etsu; graft polymerization initiator: dicumyl peroxide, tert-butyl peroxybenzoate and azobisisobutyronitrile are all available from national pharmaceutical group chemical reagents, ltd; benzoyl peroxide was purchased from Shanghai Kanglang Biotech limited.

(5) Self-made PTFE double-sided circuit board.

Example 1

This example provides an interlayer bonding sheet for a multilayer board, which is prepared by the following steps:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.9mm by using ethanol and drying; then placing the film in a low-temperature plasma generating device, setting the voltage to be 3000V, the system vacuum degree to be 560Pa, the radio frequency power to be 3kW, and the film is placed in Ar and H₂In mixed atmosphere of (Ar, H)₂In a volume ratio of 9:1) for 240 s; standing in the air for 10min, then soaking the substrate in glycidyl methacrylate containing 0.002mol/L dicumyl peroxide, and carrying out graft polymerization at 130 ℃ for 40min under the protection of nitrogen to obtain a modified PTFE substrate;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 28 days, then respectively rolling and coating a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of both the upper surface and the lower surface being 25 mu m, and curing at 180 ℃ for 3 hours to obtain the interlayer bonding sheet for the multilayer board.

Example 2

This example provides an interlayer bonding sheet for a multilayer board, which is prepared by the following steps:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.5mm by using acetone and drying; then placing the plasma in a low-temperature plasma generating device, setting the voltage to be 3000V, the vacuum degree of a system to be 155Pa, the radio frequency power to be 1kW and the plasma in N₂、H₂In a mixed atmosphere of (N)₂、H₂The volume ratio of (1) to (2) for 600 s; standing in the air for 10min, then soaking the substrate in acrylic acid containing 0.004mol/L dibenzoyl peroxide, and carrying out graft polymerization at 90 ℃ for 140min under the protection of nitrogen to obtain a modified PTFE substrate;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 5 days, then respectively rolling a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of both the upper surface and the lower surface being 40 mu m, and curing at 230 ℃ for 2h to obtain the interlayer bonding sheet for the multilayer board.

Example 3

This example provides an interlayer bonding sheet for a multilayer board, which is prepared by the following steps:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 1.3mm by using ethanol and drying; then placing the film in a low-temperature plasma generating device, setting the voltage to be 6000V, the system vacuum degree to be 1224Pa, the radio frequency power to be 5kW, and processing the film for 60s in Ar atmosphere; standing in the air for 10min, then soaking the substrate in methyl methacrylate containing 0.006mol/L dibenzoyl peroxide, and carrying out graft polymerization at 105 ℃ for 70min under the protection of nitrogen to obtain a modified PTFE substrate;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 20 days, then respectively rolling and coating a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of 50 mu m on the upper surface and the lower surface, and curing at 210 ℃ for 3 hours to obtain the interlayer bonding sheet for the multilayer board.

Example 4

This example provides an interlayer bonding sheet for a multilayer board, which is prepared by the following steps:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.8mm by using ethanol and drying; then placing the film in a low-temperature plasma generating device, setting the voltage to be 2000V, the system vacuum degree to be 155Pa, the radio frequency power to be 3kW, the voltage to be in Ar and H₂In mixed atmosphere of (Ar, H)₂In a volume ratio of 9:1) for 360 s; standing in the air for 10min, then immersing the substrate in a silane coupling agent KBM-403 containing 0.002mol/L tert-butyl peroxybenzoate, and carrying out graft polymerization at 115 ℃ for 100min under the protection of nitrogen to obtain a modified PTFE substrate;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 15 days, then respectively rolling and coating a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of both the upper surface and the lower surface being 25 mu m, and curing at 200 ℃ for 2h to obtain the interlayer bonding sheet for the multilayer board.

Example 5

This example provides an interlayer bonding sheet for a multilayer board, which is prepared by the following steps:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.8mm by using acetone and drying; immersing the acrylic acid monomer into the acrylic acid monomer to enable the monomer to be fully adsorbed to form a thin layer; then placing the PTFE substrate adsorbing the monomer in a low-temperature plasma generating device, setting the voltage to be 2000V, the system vacuum degree to be 155Pa and the radio-frequency power to be 3kW, and treating for 600s in Ar atmosphere to obtain a modified PTFE substrate initiated by acrylic acid graft polymerization by plasma;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 28 days, then respectively rolling and coating a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of 25 mu m on the upper surface and the lower surface, and curing at 200 ℃ for 2 hours to obtain the interlayer bonding sheet for the multilayer board.

Example 6

This example provides an interlayer bonding sheet for a multilayer board, which is prepared by the following steps:

(1) preparing a modified PTFE substrate: PT with the thickness of 1.0mmCleaning the FE substrate with ethanol and drying; immersing the monomer into methyl methacrylate monomer to enable the monomer to be fully adsorbed to form a thin layer; then, the PTFE substrate adsorbing the monomer is placed in a low-temperature plasma generating device, the voltage is set to be 500V, the system vacuum degree is 1330Pa, the radio frequency power is 5kW, and the temperature is N₂Treating for 550s in atmosphere to obtain a modified PTFE substrate which is grafted and polymerized by methyl methacrylate initiated by plasma;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 30 days, then respectively rolling and coating a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of both the upper surface and the lower surface being 30 mu m, and curing at 210 ℃ for 1.5h to obtain the interlayer bonding sheet for the multilayer board.

Example 7

This example provides an interlayer bonding sheet for a multilayer board, which is prepared by the following steps:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.5mm by using ethanol and drying; immersing the film in styrene monomer to make the monomer fully adsorb to form a thin layer; then, the PTFE substrate adsorbing the monomer is placed in a low-temperature plasma generating device, the voltage is set to be 8000V, the vacuum degree of the system is 550Pa, the radio frequency power is 3kW, and the temperature is controlled to be H₂Treating for 300s in the atmosphere to obtain a modified PTFE substrate initiated by styrene graft polymerization by plasma;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 28 days, then respectively rolling and coating a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of 50 mu m on the upper surface and the lower surface, and curing at 230 ℃ for 3 hours to obtain the interlayer bonding sheet for the multilayer board.

Example 8

This example provides an interlayer bonding sheet for a multilayer board, which is prepared by the following steps:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 1.2mm by using acetone and drying; then placing the plasma in a low-temperature plasma generating device, setting the voltage to be 1000V, the vacuum degree of a system to be 600Pa, the radio frequency power to be 2kW and the temperature to be O₂Treating in atmosphere for 300 s; standing in air for 10min, and soaking in methyl methacrylate containing 0.005mol/L azobisisobutyronitrileIn ester, under the protection of nitrogen, grafting and polymerizing for 60min at 85 ℃ to obtain a modified PTFE substrate;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 30 days, then respectively rolling and coating dielectric resin treatment liquid II on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of both the upper surface and the lower surface being 25 mu m, and curing at 200 ℃ for 2h to obtain the interlayer bonding sheet for the multilayer board.

Comparative example 1

The comparative example provides an interlayer bonding sheet for a multilayer board, the preparation method comprising:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.8mm by using ethanol and drying; then placing the film in a low-temperature plasma generating device, setting the voltage to be 800V, the system vacuum degree to be 155Pa, the radio frequency power to be 1kW, and processing the film for 20s in Ar atmosphere; standing in the air for 10min, then soaking the substrate in glycidyl methacrylate containing 0.002mol/L dicumyl peroxide, and carrying out graft polymerization at 130 ℃ for 40min under the protection of nitrogen to obtain a modified PTFE substrate;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 5 days, then respectively rolling and coating a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of both the upper surface and the lower surface being 25 mu m, and curing at 180 ℃ for 3 hours to obtain the interlayer bonding sheet for the multilayer board.

Comparative example 2

The comparative example provides an interlayer bonding sheet for a multilayer board, the preparation method comprising:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.8mm by using ethanol and drying; then placing the film in a low-temperature plasma generating device, setting the voltage to be 10000V, the vacuum degree of a system to be 1224Pa, the radio frequency power to be 5kW, and processing the film for 900s in Ar atmosphere; standing in the air for 10min, then immersing the substrate in a silane coupling agent KBM-403 containing 0.002mol/L tert-butyl peroxybenzoate, and carrying out graft polymerization at 115 ℃ for 100min under the protection of nitrogen to obtain a modified PTFE substrate;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 5 days, then respectively rolling and coating a dielectric resin treatment solution I on the upper surface and the lower surface to obtain dielectric resin layers with the thicknesses of both the upper surface and the lower surface being 25 mu m, and curing at 180 ℃ for 3 hours to obtain the interlayer bonding sheet for the multilayer board.

Comparative example 3

The comparative example provides an interlayer bonding sheet for a multilayer board, the preparation method comprising:

(1) cleaning a PTFE substrate with the thickness of 0.9mm by using ethanol and drying;

(2) respectively rolling a dielectric resin treatment solution I on the upper surface and the lower surface of the PTFE substrate obtained in the step (1) to obtain dielectric resin layers with the thickness of 40 mu m on the upper surface and the lower surface, and curing at 200 ℃ for 3h to obtain the interlayer bonding sheet for the multilayer board.

Comparative example 4

The comparative example provides an interlayer bonding sheet for a multilayer board, the preparation method comprising:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.5mm by using ethanol and drying; then placing the film in a low-temperature plasma generating device, setting the voltage to be 3000V, the system vacuum degree to be 560Pa, the radio frequency power to be 3kW, and the film is placed in Ar and H₂In mixed atmosphere of (Ar, H)₂In a volume ratio of 9:1) for 240 s; standing in the air for 1 day, then soaking the substrate in glycidyl methacrylate containing 0.002mol/L dicumyl peroxide, and carrying out graft polymerization at 130 ℃ for 40min under the protection of nitrogen to obtain a modified PTFE substrate;

(2) respectively rolling a dielectric resin treatment solution I on the upper surface and the lower surface of the modified PTFE substrate obtained in the step (1) to obtain dielectric resin layers with the thickness of 25 mu m on the upper surface and the lower surface, and curing at 180 ℃ for 3h to obtain the interlayer bonding sheet for the multilayer board.

Comparative example 5

The comparative example provides an interlayer bonding sheet for a multilayer board, the preparation method comprising:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.5mm by using ethanol and drying; then soaking the substrate in glycidyl methacrylate containing 0.002mol/L dicumyl peroxide, and carrying out graft polymerization at 130 ℃ for 40min under the protection of nitrogen to obtain a modified PTFE substrate;

(2) respectively rolling a dielectric resin treatment solution I on the upper surface and the lower surface of the modified PTFE substrate obtained in the step (1) to obtain dielectric resin layers with the thickness of 25 mu m on the upper surface and the lower surface, and curing at 180 ℃ for 3h to obtain the interlayer bonding sheet for the multilayer board.

Comparative example 6

The comparative example provides an interlayer bonding sheet for a multilayer board, the preparation method comprising:

(1) preparing a modified PTFE substrate: cleaning a PTFE substrate with the thickness of 0.8mm by using ethanol and drying; then placing the film in a low-temperature plasma generating device, setting the voltage to be 500V, the system vacuum degree to be 1120Pa, the radio frequency power to be 3kW, the voltage to be in Ar and H₂In mixed atmosphere of (Ar, H)₂The volume ratio of (1) to (9) is processed for 360s to obtain a modified PTFE substrate;

(2) and (2) standing the modified PTFE substrate obtained in the step (1) for 1 day, then respectively rolling a dielectric resin treatment solution I on the upper surface and the lower surface of the modified PTFE substrate to obtain dielectric resin layers with the thicknesses of both the upper surface and the lower surface being 25 mu m, and curing at 180 ℃ for 3 hours to obtain the interlayer bonding sheet for the multilayer board.

Application example

A multilayer board is prepared by the following steps:

the interlayer bonding sheets for the multilayer boards provided in examples 1 to 8 and comparative examples 1 to 6 were placed between two PTFE double-sided circuit boards with circuit patterns, respectively, pressed in a press at 190 ℃ for 90 minutes, and then cooled and taken out to obtain the multilayer boards.

And (3) performance testing:

(1) surface treatment depth of plasma: a Hitachi S-3400N type scanning electron microscope is adopted to make a section and observe the surface treatment depth of the plasma treatment.

(2) Contact Angle (CA): the static contact angle of the surface of deionized water after plasma treatment was tested using a DSA20 contact angle tester, KRUSS, germany.

(3) Adhesive property: the multilayer board provided in the application example is placed in a soldering tin furnace at 288 ℃ to be soaked for 5 minutes, and is taken out to be sliced and observed, if obvious layering and foaming phenomena occur, the adhesion and the adhesion stability are poor; if no delamination and foaming occurred, the adhesion and adhesion stability were good.

The adhesive properties of the interlayer adhesive sheets for multilayer boards provided in examples 1 to 8 and comparative examples 1 to 6 were measured according to the above-described methods, and the specific data are shown in table 1:

TABLE 1

As can be seen from the data in table 1, in the interlayer bonding sheets for multilayer boards provided in embodiments 1 to 8 of the present invention, after the PTFE substrate is modified by plasma and monomer graft polymerization, a long-acting active layer is formed on the surface of the PTFE substrate, and the PTFE substrate can maintain good activity even after being left in the air for more than 30 days, and is bonded to the dielectric resin layer stably with high strength; the multilayer boards based on the interlayer bonding sheets for multilayer boards described in examples 1 to 8 have good high temperature resistance and excellent bonding stability, and no delamination and foaming phenomenon occurs during high temperature treatment at 288 ℃. The modified PTFE substrate can be prepared by plasma-initiated monomer graft polymerization (examples 5 to 7) or by plasma treatment followed by monomer graft polymerization (examples 1 to 4 and 8).

When the modified PTFE substrate is prepared by a monomer graft polymerization method after plasma treatment, the treatment depth of the plasma treatment is within the range of 5-15 nm defined by the invention, the contact angle is within the range of 84-98 degrees, and the monomer graft polymerization is carried out within 1h after the plasma treatment, so that the modified PTFE substrate with long activation timeliness and good adhesive property can be obtained. If the depth of the plasma treatment is less than 5nm (comparative example 1) or more than 15nm (comparative example 2), the standing time after the plasma treatment is too long (comparative example 4) and then the monomer graft polymerization is carried out, resulting in a decrease in activation aging, adhesive strength of the interlayer adhesive sheet and adhesive stability.

If the PTFE substrate is directly subjected to monomer graft polymerization without surface plasma modification (comparative example 5) or without any modification treatment (comparative example 3), an interlayer bonding sheet for a multilayer board having good bonding properties cannot be obtained, which has low bonding stability under high temperature treatment and has a significant delamination foaming phenomenon in the bonding structure.

If the PTFE substrate is only subjected to surface plasma modification (comparative example 6), the activation aging of the modified PTFE substrate is very short, and the interlayer bonding sheet obtained by coating the dielectric resin layer after standing for 1 day has poor high temperature resistance and also has obvious delamination and foaming phenomena at high temperature.

The applicant states that the present invention is illustrated by the above examples of the interlayer bonding sheet for multilayer boards of the present invention and the preparation method and application thereof, but the present invention is not limited to the above process steps, i.e., it is not meant that the present invention must rely on the above process steps to be carried out. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.