Flame-retardant layer-adding film with high copper peel strength and low dielectric constant and loss and preparation method of flame-retardant layer-adding film

Abstract

The invention discloses a flame-retardant layer-adding film with high copper peel strength and low dielectric constant and loss and a preparation method of the flame-retardant layer-adding film, and belongs to the technical field of resin composite materials. By designing components of the layer-adding film, a pyrazole ring is introduced into epoxy resin to synthesize a novel pyrazole modified epoxy resin material, and the interaction between the layer-adding film and a copper foil is enhanced by adding the novel epoxy resin, so that the copper peel strength is improved; a tertiary amine structure exists in the novel epoxy resin structure, and curing of a layer-adding film can be promoted. The layer-adding film is composed of epoxy resin, a curing agent, an accelerant, filler, a flame retardant and the like, and the problems that an existing layer-adding film material is poor in copper adhesive force, large in dielectric constant and loss and poor in flame retardant property can be effectively solved.

Description

Technical Field

[0001] The present invention relates to a flame-retardant build-up film with high copper peel strength, low dielectric constant and loss, and a preparation method thereof, belonging to the technical field of resin composite materials. Background Art

[0002] With the development of information technology, 3D packaging has become the mainstream means of chip packaging. Chips are developing towards miniaturization and high integration. Chip packaging is mainly achieved through packaging substrates. The key raw material used in the substrate preparation process is the build-up film material, which is used to construct a multi-layer interconnection structure, playing the roles of electrical insulation, mechanical support, auxiliary heat dissipation, maintaining signal integrity, and improving the high-frequency signal transmission performance. Therefore, high-performance build-up film materials have become a current research hotspot.

[0003] Currently, the existing packaging substrates are prone to copper foil delamination under the action of thermal stress. Therefore, it is necessary to improve the copper binding force of the build-up film material and reduce the thermal expansion coefficient of the build-up film to ensure the reliability of chip use. In addition, the build-up film is usually a flammable epoxy resin, and the safety of epoxy is insufficient under high-temperature environments, so it is necessary to improve the flame-retardant performance. With the increase in the wiring density of integrated circuits, the resistance of the metal interconnection wires in electronic components and the capacitance of the interlayer dielectrics are likely to form an RC delay effect, which in turn causes adverse effects such as signal transmission delay, noise interference, and power loss. Therefore, developing insulating dielectric materials with low dielectric constant and loss constant is of great value for reducing interconnect delay, energy consumption, and crosstalk. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a flame-retardant build-up film with high copper peel strength, low dielectric constant and loss. In the present invention, through the design of the build-up film components and further by using pyrazole-modified epoxy resin, the prepared insulating adhesive film has strong copper binding force, excellent dielectric properties and flame-retardant properties, and can meet the requirements of the high-speed and high-integration development of electronic components.

[0005] The present invention includes the following contents: A flame-retardant build-up film with high copper peel strength, low dielectric constant and loss, which contains components such as (A) epoxy resin, (B) curing agent, (C) accelerator, (D) filler, (E) flame retardant, and (F) other additives; The (A) epoxy resin is a combination of (G) a novel pyrazole-modified epoxy resin and (J) an electronic-grade epoxy resin (usually one or several of glycidyl ester type epoxy resin, biphenyl type epoxy resin, bisphenol A type epoxy resin, naphthalene type epoxy resin, phenolic resin type epoxy resin, and dicyclopentadiene type epoxy resin), and the mass ratio of the (G) novel pyrazole-modified epoxy resin to the total mass of the (A) epoxy resin is 20% - 100%.

[0006] The described novel pyrazole-modified epoxy resin synthesis method is obtained by reacting the epoxy groups in a bifunctional epoxy resin with a polypyrazole compound.

[0007] The described bifunctional epoxy resin (H) can be bisphenol A epoxy resin, bisphenol F epoxy resin, biphenyl-type epoxy resin, naphthalene-type epoxy resin, etc.

[0008] The described polypyrazole compound (I) has the following structure:

[0009] R1 can be , , , one or several of them, where the wavy line represents the part connected to the molecular chain; R2 is a hydrogen atom or an alkyl group.

[0010] Its preparation method is as follows: Dissolve pyrazole in DMSO and then add an excessive amount of fine KOH powder. Stir vigorously at 60 °C for 1 h and then dropwise add dibromo compound. After reacting for 4 h, filter off the excessive KOH in the reaction mixture by suction filtration, and then distill off most of the DMSO under reduced pressure. Subsequently, pour the reactant into water, extract with chloroform, and remove the solvent to obtain product 1. Dissolve product 1 in an aqueous HBr solution to convert it into a hydrobromide salt. After removing the solvent, transfer the obtained hydrobromide salt to a sealed glass tube and heat it to 200 °C for 2 h. Finally, dissolve the obtained solid in water and gradually add 50% aqueous NaOH solution until the pH of the solution reaches 12 to form a precipitate. After drying, obtain the dipyrazole compound product. The reaction equation is as follows: .

[0011] The described novel pyrazole-modified epoxy resin synthesis method: The mass ratio of the bifunctional epoxy resin (H) to the polypyrazole compound (I) is 1:10 to 10:1, the reaction temperature is 100 °C - 200 °C, the reaction time is 5 - 10 h, the catalyst is: one or several of 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, triethanolamine, and o-hydroxybenzyl dimethylamine, and the reaction solvent can be one or several of methanol, ethanol, ethylene glycol, propanol, isopropanol, isopentane, pentane, petroleum ether, hexane, cyclohexane, cyclopentane, carbon tetrachloride, ethyl acetate, ether, isopropyl ether, tetrahydrofuran, chloroform, dioxane, benzene, toluene, dichloromethane, acetone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide or a solvent-free system.

[0012] The described curing agent (B) can be: phenolic resin, cyanate ester, etc.

[0013] The promoter (C) described above can be one or more of amine-based curing promoters, imidazole-based curing promoters, and phosphine-based curing promoters.

[0014] The filler (D) described above is spherical silica with an average particle size of 0.1 - 5 μm, and its surface is modified to improve the interfacial compatibility between the filler and the epoxy resin.

[0015] The flame retardant (E) described above can be one or more of organophosphorus flame retardants, organophosphorus compounds containing nitrogen, organosilicon flame retardants, and metal hydroxides, etc.

[0016] The other additives (F) described above can be any one or a combination of at least two of organic solvents, thickeners, defoamers, homogenizers, leveling agents, adhesion improvers, and colorants.

[0017] For the described build-up film, when the non-volatile components are set to 100% by mass, the content of component (A) is 10 - 50% by mass.

[0018] For the described build-up film, when the non-volatile components are set to 100% by mass, the content of component (B) is 10 - 50% by mass.

[0019] For the described build-up film, when the non-volatile components are set to 100% by mass, the content of component (C) is 0.1 - 1% by mass.

[0020] For the described build-up film, when the non-volatile components are set to 100% by mass, the content of component (D) is 20 - 80% by mass.

[0021] For the described build-up film, when the non-volatile components are set to 100% by mass, the content of component (E) is 0.1 - 5% by mass.

[0022] For the described build-up film, when the non-volatile components are set to 100% by mass, the content of the organic solvent in component (F) is 20 - 200% by mass, and the content of the additives other than the organic solvent is 1 - 10% by mass. The organic solvent can be any one or a combination of at least two of toluene, xylene, methyl ethyl ketone, methyl ethyl ketone, cyclohexanone, ethyl acetate, or N,N-dimethylformamide.

[0023] The thickness of the described build-up film is 10 - 100 μm.

[0024] The preparation method of the described build-up film includes the following steps: After mixing each component evenly, it is coated on a substrate and dried to obtain a film material.

[0025] Among them, the thickness of the base material is 10-150 μm, more preferably 25-50 μm; the drying temperature is 20-130 °C; the drying time is 0.1-12 hours; finally, a protective film is covered on the build-up film.

[0026] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, by designing the composition of the build-up film, and further by using a novel pyrazole-modified epoxy resin, pyrazole can enhance the bonding force between the build-up film and the copper foil and improve the copper peel strength; the pyrazole ring in the novel pyrazole-modified epoxy resin can play a catalytic role in the epoxy reaction and promote the complete curing of the build-up film; by controlling the ratio of the epoxy resin, curing agent and filler, the dielectric constant and loss can be effectively reduced, and the problem of excessive signal transmission loss during use can be solved. In addition, the build-up film has good flame retardant properties to ensure the safety of use. Description of the Drawings

[0027] Figure 1 is the 1H NMR spectrum of 4,4'-methylenedipyrazole; Figure 2 is the 1H NMR spectrum of pyrazole-modified epoxy resin; Figure 3 is the digital photo of the build-up film of Example 4; Figure 4 is the DMA curve of Example 4; Figure 5 is the copper peel strength curve of Example 4. Detailed Embodiments

[0028] The present invention will be described in detail below with suitable embodiments of the present invention.

[0029] The present invention provides a flame retardant build-up film with high copper peel strength and low dielectric constant and loss and a preparation method thereof. By adopting a pyrazole-modified epoxy resin, the build-up film can effectively improve its bonding force with the copper foil. At the same time, due to the addition of a low-polarity pyrazole ring, the content of polar groups is reduced, and the dielectric constant and loss can be effectively reduced.

[0030] According to some embodiments of the present invention, in the build-up film, it is composed of (A) epoxy resin, (B) curing agent, (C) accelerator, (D) filler, (E) flame retardant, and (F) other additives; (A) epoxy resin is a combination of (G) novel pyrazole-modified epoxy resin and common electronic-grade epoxy resins (one or more of glycidyl ester-type epoxy resin, biphenyl-type epoxy resin, bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, naphthalene-type epoxy resin, naphthyl ether-type epoxy resin, and dicyclopentadiene-type epoxy resin), where the mass ratio of (G) novel pyrazole-modified epoxy resin to the total mass of (A) epoxy resin is 20% - 100%. When the non-volatile components are set to 100% by mass, the content of component (A) is 10 - 50% by mass, the content of component (B) is 10 - 50% by mass, the content of component (C) is 0.1 - 1% by mass, the content of component (D) is 20 - 70% by mass, the content of component (E) is 0.1 - 5% by mass, the content of organic solvent in component (F) is 20 - 200% by mass, and the content of additives other than the solvent is 1 - 10% by mass.

[0031] By using the resin composition of components (A) to (F) in the above specific proportions, it is found that the problems of low copper foil peel strength, flammability, and large dielectric loss of the build-up film can be solved. The use of the novel pyrazole-modified epoxy resin in the present invention effectively improves the copper peel strength of the build-up film, reduces the usage amount of the accelerator, and simultaneously effectively reduces the problems of dielectric constant and loss tangent.

[0032] (A) Epoxy resin Its components are a combination of (G) novel pyrazole-modified epoxy resin and (J) electronic-grade epoxy resin.

[0033] The novel pyrazole-modified epoxy resin is obtained by reacting (H) bifunctional liquid or solid epoxy resin with (I) polypyrazole compound; The said (I) polypyrazole compound has the following structure:

[0034] R1 can be , , , one or more of them, where the wavy line represents the part connected to the molecular chain; R2 is a hydrogen atom or an alkyl group.

[0035] The reaction equation is as follows:

[0036] where the value of n is an integer between 5 and 20.

[0037] As (H) bifunctional liquid or solid epoxy resins, examples of the liquid epoxy resins include, for example, bisphenol A epoxy resins.

[0038] Synthesis of (G) novel pyrazole-modified epoxy resins: The mass ratio of the bifunctional liquid or solid epoxy resin to the polypyrazole compound is 1:10 to 10:1, the reaction temperature is 100°C - 200°C, the reaction time is 5 - 10 h, the catalyst is one or more of 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, triethanolamine, and o-hydroxybenzyldimethylamine, and the reaction solvent can be one or more of methanol, ethanol, ethylene glycol, propanol, isopropanol, isopentane, pentane, petroleum ether, hexane, cyclohexane, cyclopentane, carbon tetrachloride, ethyl acetate, ether, isopropyl ether, tetrahydrofuran, chloroform, dioxane, benzene, toluene, dichloromethane, acetone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide, or a solvent-free system.

[0039] As (J) electronic-grade epoxy resins, examples include, for example, bisphenol A epoxy resins; bisphenol F epoxy resins; naphthalene-type epoxy resins; glycidyl ester-type epoxy resins; glycidylamine-type epoxy resins; o-cresol novolac epoxy resins; phenol novolac epoxy resins; dicyclopentadiene phenol-type epoxy resins; XYLOK phenol novolac resins; trifunctional phenol novolac epoxy resins; phenol biphenyl-type epoxy resins; tetrafunctional epoxy resins; BPA phenol novolac epoxy resins. These substances can be used alone or in combination of two or more.

[0040] (B) Curing agents The curing agent can be a phenol resin, cyanate ester, etc., and the curing agent can be used alone or in combination of two or more.

[0041] Examples of the phenol resin curing agent include, for example, linear phenol formaldehyde resin; linear bisphenol A formaldehyde resin; biphenyl aralkyl phenol resin; XYLOK phenol novolac resin; linear o-cresol formaldehyde resin; nitrogen-containing phenol resin; dicyclopentadiene phenol resin; trifunctional phenol novolac resin.

[0042] Examples of the cyanate ester curing agent include, for example, bifunctional cyanate ester resins such as bisphenol A dicyanate ester, triphenylmethane triisocyanate, 4,4'-methylenebis(2,6-dimethylphenyl cyanate ester), 4,4'-ethylenediphenyl dicyanate ester, hexafluorobisphenol A dicyanate ester, 1,1-bis(4-cyanate phenylmethane), 2,2-bis(4-cyanate group)phenylpropane, bis(4-cyanate group-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylene))benzene, bis(4-cyanate phenyl) sulfide, and bis(4-cyanate phenyl) ether.

[0043] The mass ratio of component (A) to component (B) in the build-up film, calculated based on the ratio of the total number of epoxy groups in component (A) to the total number of reactive groups in component (B), is such that the total number of epoxy groups in component (A) : the total number of reactive groups in component (B) is 1:3 to 3:1.

[0044] (C)Accelerator The accelerators are mainly amines, imidazoles, and organic phosphines. Since the pyrazole-modified epoxy resin has a promoting effect on the curing reaction, the amount of the accelerator can be reduced compared to the case where pyrazole-modified epoxy resin is not used. The accelerator can be used alone or in combination of two or more, and even the use of an accelerator may not be required.

[0045] Examples of amine accelerators include: triethylamine, tributylamine, 4-dimethylaminopyridine (DMAP), benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-undecene (DBU), etc.

[0046] Examples of imidazole accelerators include: 1H-imidazole, 2-methylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, etc.

[0047] Examples of organic phosphine accelerators include: triphenylphosphine, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, butyltriphenylphosphonium sulfate, etc.

[0048] (D)Filler The filler used in the build-up film is spherical silica with an average particle size of 0.1 - 5 μm. The content of spherical silica, when the non-volatile components in the resin composition are set to 100% by mass, is preferably 20% by mass or more. However, if the content of silica is too high, it will affect the mechanical properties of the build-up film. Therefore, considering the mechanical strength, when the non-volatile components in the resin composition are set to 100% by mass, the content of silica is preferably 80% by mass or less.

[0049] In order to improve the compatibility between the resin and silica, spherical silica can be surface-treated with one or more coupling agents such as amino-silane coupling agents, epoxy-silane coupling agents, mercapto-silane coupling agents, etc. Examples of silane coupling agents include 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, etc. The addition amount of the silane coupling agent is 0.1-5% of the mass of silica.

[0050] (E)Flame retardant The flame retardant can be one or several of organic phosphorus-based flame retardants, organic nitrogen-containing phosphorus compounds, organosilicon-based flame retardants, metal hydroxides, etc. When the non-volatile components are set to 100% by mass, its content is 0.1-5% by mass.

[0051] (F)Other additives Other additives include any one or a combination of at least two of organic solvents, thickeners, defoamers, homogenizers, leveling agents, adhesion-imparting agents, and colorants. The content of the organic solvent is 20-200% by mass, and the content of the additives other than the solvent is 1-10% by mass. The organic solvent can be any one or a combination of at least two of toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, or N,N-dimethylformamide.

[0052] The thickness of the described laminated film is 10-100 μm. Its preparation method includes the following steps: After mixing each component evenly, it is coated on a substrate and dried to obtain a film material. The substrate can be polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), etc., preferably polyethylene terephthalate glycol, and more preferably a PET film with a release agent; the substrate thickness is 10-150 μm, further preferably 25-50 μm; the drying temperature is 20-130 °C; the drying time is 0.1-12 hours; finally, a protective film is covered on the laminated film, and the protective film can be a polypropylene film, etc.

[0053] Example 1

[0054] Synthesis of novel pyrazole-modified epoxy resin Synthesis of 4,4'-methylenedipyrazole: 5.00 g of pyrazole was dissolved in 30 mL of DMSO, and 16.46 g of fine powder KOH was added. After the suspension was vigorously stirred at 60 °C for 1 h, 6.40 g of dibromomethane was added dropwise. After continuing to stir for 4 h, the undissolved KOH in the reaction mixture was removed by suction filtration, and then most of the DMSO was removed by vacuum distillation at 90 °C. Subsequently, it was poured into 300 mL of water, and the solvent was removed by chloroform extraction to obtain 1,1'-methylenedipyrazole. 1,1'-methylenedipyrazole was dissolved in an aqueous HBr solution to be converted into a hydrobromide salt. After the solvent was removed, the obtained hydrobromide salt was transferred to a sealed glass tube and heated to 200 °C for 2 h. The obtained brown solid was dissolved in water, and 50% aqueous NaOH solution was gradually added until the pH of the solution reached 12, forming an off-white precipitate. After drying, the product 4,4'-methylenedipyrazole was obtained, and the NMR was as Figure 1 shown.

[0055] Synthesis of pyrazole-modified bisphenol A epoxy resin: 5 g of 328D bisphenol A epoxy resin (epoxy value: 0.55 - 0.60), 1.5 g of 4,4'-methylenedipyrazole, and 0.02 g of 2,4,6-tris(dimethylaminomethyl)phenol were mixed evenly and heated at 140 °C for 8 h to obtain pyrazole-modified epoxy resin (328D-Py). The structure of the modified epoxy resin was as Figure 2 shown.

[0056] Determination of epoxy value: The hydrochloric acid-acetone method was used to measure the epoxy value of the pyrazole-modified resin. 0.5 g of the resin sample was weighed into a 250 mL conical flask, and 20 mL of acetone-hydrochloric acid solution (2 mL of concentrated hydrochloric acid dissolved in 80 mL of acetone) was added to the conical flask with a pipette. After standing for 30 min, 2 drops of 0.1% methyl red indicator were added, and it was titrated with 0.1 mol / L sodium hydroxide standard solution until the color changed from red to yellow. A blank test was also performed. The epoxy value E was calculated by the following method: E = (V0 - V1) * N / 1000 / W * 100 where V0 and V1 represent the volumes of NaOH solution consumed in the blank and sample tests (mL), N represents the concentration of the NaOH solution (mol / L), and W represents the mass of the resin (g); The epoxy value of the modified epoxy resin obtained was: 0.125 mol / 100g.

[0057] Example 2

[0058] Synthesis of pyrazole-modified biphenyl epoxy resin: 5 g of SQE-101 epoxy resin (epoxy equivalent: 186.78 g / eq), 1.5 g of 4,4'-methylenedipyrazole and 0.02 g of 2,4,6-tris(dimethylaminomethyl)phenol were mixed evenly and heated at 140 °C for 8 h to obtain pyrazole-modified epoxy resin (SQE101-Py). The epoxy value of the modified epoxy resin obtained by titration was: 0.115 mol / 100g.

[0059] Example 3

[0060] Preparation of the interlayer film material Preparation of the resin varnish: 20 g of the 328D-Py epoxy resin synthesized in Example 1, 6.89 g of NC3000 (epoxy equivalent 276 g / eq), 7.56 g of biphenyl aralkyl resin SH-5095 (hydroxyl equivalent: 212.7 g / eq), 1.0 g of DOPO-HQ and 25.0 g of spherical silica (SC-2500SQ) were uniformly dispersed in 100 mL of methyl ethyl ketone solvent to prepare the resin varnish.

[0061] Coating of the resin varnish: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent, dried at 80 °C for 1 h to obtain a resin film with a thickness of 0.05 mm, and then a 0.015 mm thick polypropylene film was covered on the resin film to obtain the interlayer film material.

[0062] Example 4

[0063] Preparation of the interlayer film material Preparation of the resin varnish: 20 g of the SQE101-Py epoxy resin synthesized in Example 2, 6.89 g of NC3000 (epoxy equivalent 276 g / eq), 7.56 g of biphenyl aralkyl resin SH-5095 (hydroxyl equivalent: 212.7 g / eq), 1.0 g of DOPO-HQ and 25.0 g of spherical silica (SC-2500SQ) were uniformly dispersed in 100 mL of methyl ethyl ketone solvent to prepare the resin varnish.

[0064] Coating of the resin varnish: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent, dried at 80 °C for 1 h to obtain a resin film with a thickness of 0.05 mm, and then a 0.015 mm thick polypropylene film was covered on the resin film to obtain the interlayer film material, and its digital photo is as Figure 3 shown. And its glass transition temperature and copper peel strength were tested as Figure 4 and Figure 5 shown.

[0065] Example 5

[0066] Preparation of the multi-layer film material Preparation of the resin varnish: 20 g of the SQE101-Py epoxy resin synthesized in Example 2, 6.89 g of NC3000 (epoxy equivalent: 276 g / eq), 5.90 g of the biphenyl aralkyl resin SH-5095 (hydroxyl equivalent: 212.7 g / eq), 1.2 g of bisphenol A dicyanate, 1.0 g of DOPO-HQ, and 25.0 g of spherical silica (SC-2500SQ) were uniformly dispersed in 100 mL of methyl ethyl ketone solvent to prepare the resin varnish.

[0067] Coating of the resin varnish: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent, dried at 80 °C for 1 h to obtain a resin film with a thickness of 0.05 mm, and then a 0.015 mm thick polypropylene film was covered on the resin film to obtain the multi-layer film material.

[0068] Comparative Example 1 Preparation of the multi-layer film material Preparation of the resin varnish: 3.11 g of SQE-101 epoxy resin (epoxy equivalent: 186.78 g / eq), 6.89 g of NC3000 (epoxy equivalent: 276 g / eq), 0.1 g of 2-ethyl-4-methylimidazole, 7.56 g of the biphenyl aralkyl resin SH-5095 (hydroxyl equivalent: 212.7 g / eq), 1.0 g of DOPO-HQ, and 25.0 g of spherical silica (SC-2500SQ) were uniformly dispersed in 100 mL of methyl ethyl ketone solvent to prepare the resin varnish.

[0069] Coating of the resin varnish: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent, dried at 80 °C for 1 h to obtain a resin film with a thickness of 0.05 mm, and then a 0.015 mm thick polypropylene film was covered on the resin film to obtain the multi-layer film material.

[0070] Comparative Example 2 Preparation of the multi-layer film material Preparation of the resin varnish: 3 g of 328D epoxy resin (epoxy equivalent: 173.9 / eq), 6.89 g of NC3000 (epoxy equivalent: 276 g / eq), 0.1 g of 2-ethyl-4-methylimidazole, 7.56 g of the biphenyl aralkyl resin SH-5095 (hydroxyl equivalent: 212.7 g / eq), 1.0 g of DOPO-HQ, and 25.0 g of spherical silica (SC-2500SQ) were uniformly dispersed in 100 mL of methyl ethyl ketone solvent to prepare the resin varnish.

[0071] Resin varnish coating: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent, dried at 80 °C for 1 h to obtain a resin film with a thickness of 0.05 mm, and then a 0.015 mm thick polypropylene film was covered on the resin film to obtain a laminated film material.

[0072] Dielectric property test: After curing the laminated films of the above examples and comparative examples at 180 °C for 2 hours, the PET film was peeled off to obtain a pre-cured insulating adhesive film; the pre-cured insulating adhesive film was cut into test pieces of 70×70 mm, and then a vector network analyzer (Keysight N5227B) was used to measure the dielectric constant and dielectric loss at 25 °C and a frequency of 10 GHz using a cavity.

[0073] Flame retardancy test: The cured laminated film was cut into 12.7 mm×127 mm splines and tested according to the UL-94V standard, and the test results were recorded.

[0074] Curing property determination: Take 10 mg of the laminated film material without the protective film, measure the DSC curve heated from room temperature to 250 °C at a rate of 10 °C / min, and record the starting curing temperature.

[0075] Peel strength determination: According to the method of peel strength test on IPC-TM650. After the laminated film and the inner substrate were vacuum-pressed and formed by a vacuum hot press and then thermally cured to obtain a substrate with an insulating layer, the insulating layer on the substrate was roughened. The roughened substrate was successively subjected to degreasing adjustment, micro-etching cleaning, pre-impregnation, activation, reduction, electroless copper plating, water washing and baking, pickling, electroplating, etc., and then heated at 180 °C for 120 min to obtain a substrate for evaluation; a universal mechanical testing machine was used to evaluate the copper peel strength of the substrate. A 10×100 mm cut was made on the copper layer, one end was clamped to the fixture of the tester, and the load when peeled vertically at a rate of 50 mm / min for 35 mm was measured, and the peel strength (N / mm) was calculated.

[0076] Glass transition temperature: The glass transition temperature of the film was measured by DMA using a tensile die and a heating rate of 3 °C / min.

[0077] The performance summaries of the above examples and comparative examples are shown in the following table

[0078] It can be seen that the above-mentioned examples and comparative examples all react under the conditions of equal epoxy groups and equal hydroxyl groups (where the molar ratio of epoxy groups to hydroxyl groups is 1:1). Through the performance comparison of each group, it can be known that the peel strength of the interlayer film material obtained from the pyrazole-modified epoxy resin is significantly improved, and the initial curing temperature is basically similar to that of Comparative Examples 1 and 2. The interaction force between the pyrazole ring and the copper foil increases the copper peel strength, indicating that the pyrazole-modified epoxy resin has certain self-promoting properties, can promote the curing reaction of the resin system, and can be cured smoothly without adding a curing accelerator. However, when using unmodified epoxy resin, a curing accelerator needs to be added, otherwise the temperature required for the curing reaction will be greatly increased, and even the curing cannot be carried out smoothly. For example, in Comparative Example 1, if the curing accelerator 2-ethyl-4-methylimidazole is not added, its initial curing temperature reaches 178.0 °C, and the corresponding initial curing temperature in Comparative Example 2 reaches 170.0 °C, both of which are significantly increased. In addition, it can also be seen that the dielectric constant and dielectric loss of the interlayer film material also decrease with the addition of the pyrazole-modified epoxy resin. Especially when using a cyanate ester curing agent, the dielectric properties of the interlayer film can be significantly improved.

[0079] The above-mentioned examples are only some preferred solutions of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A flame-retardant build-up film with high copper peel strength, low dielectric constant and loss, characterized in that, The flame-retardant interlayer film contains a pyrazole-modified epoxy resin component, and the pyrazole-modified epoxy resin is obtained by reacting a bifunctional epoxy resin with a polypyrazole compound, wherein the polypyrazole compound is ， R1 is , , , one or more of; R2 is a hydrogen atom or an alkyl group.

2. The flame-retardant reinforced film with high copper peel strength, low dielectric constant and loss according to claim 1, characterized in that The bifunctional epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, biphenyl-type epoxy resin, and naphthalene-type epoxy resin.

3. The flame-retardant reinforcing film with high copper stripping strength, low dielectric constant and loss according to claim 1, characterized in that The preparation method of the pyrazole-modified epoxy resin includes: reacting the bifunctional epoxy resin with the polypyrazole compound in the presence of a catalyst in a reaction solvent or in a solvent-free system, and the mass ratio of the bifunctional epoxy resin to the polypyrazole compound is 1:10 to 10:1, the reaction temperature is 100°C - 200°C, the reaction time is 5 - 10 h, the catalyst is one or several of 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, triethanolamine, and o-hydroxybenzyl dimethylamine, and the reaction solvent is one or several of methanol, ethanol, ethylene glycol, propanol, isopropanol, isopentane, pentane, petroleum ether, hexane, cyclohexane, cyclopentane, carbon tetrachloride, ethyl acetate, diethyl ether, isopropyl ether, tetrahydrofuran, chloroform, dioxane, benzene, toluene, dichloromethane, acetone, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

4. The flame-retardant reinforced film with high copper peel strength, low dielectric constant and loss according to claim 1, characterized in that The flame-retardant interlayer film contains the following components: epoxy resin, curing agent, accelerator, filler, flame retardant, and other additives, wherein the epoxy resin is composed of the pyrazole-modified epoxy resin or a combination thereof with electronic-grade epoxy resin.

5. The flame-retardant build-up film with high copper peel strength, low dielectric constant and loss according to claim 4, characterized in that, The pyrazole-modified epoxy resin accounts for 20% - 100% of the total mass of the epoxy resin.

6. The flame-retardant reinforcing film with high copper peel strength, low dielectric constant and low loss according to claim 4, characterized in that The electronic-grade epoxy resin is one or several combinations of glycidyl ester-type epoxy resin, biphenyl-type epoxy resin, bisphenol A-type epoxy resin, naphthalene-type epoxy resin, phenolic resin-type epoxy resin, and dicyclopentadiene-type epoxy resin.

7. The flame-retardant laminated film with high copper peel strength, low dielectric constant and loss according to claim 4, characterized in that, The curing agent is phenolic resin or cyanate ester, the accelerator is one or several of amine-based curing accelerators, imidazole-based curing accelerators, and phosphine-based curing accelerators, the filler is spherical silica with an average particle size of 0.1 - 5 μm, and its surface is modified to improve the interfacial compatibility between the filler and the epoxy resin. The flame retardant is one or several of organophosphorus flame retardants, organonitrogen-containing phosphorus compounds, organosilicon flame retardants, and metal hydroxides. The other additives are any one or at least two combinations of organic solvents, thickeners, defoamers, homogenizers, leveling agents, adhesion imparting agents, and colorants.

8. The flame-retardant reinforcing film with high copper peel strength, low dielectric constant and loss according to claim 4, characterized in that, Assuming the mass of non-volatile components in the interlayer film is 100%, the mass ratio of epoxy resin in the interlayer film is 10 - 50%, the curing agent is 10 - 50%, the accelerator is 0.1 - 1%, the filler is 20 - 80%, the flame retardant is 0.1 - 5% by mass, and for the other additives, the organic solvent is 20 - 200%, and the additives other than the organic solvent are 1 - 10%; the organic solvent is any one or at least two combinations of toluene, xylene, butanone, methyl ethyl ketone, cyclohexanone, ethyl acetate, or N,N-dimethylformamide.

9. The flame-retardant build-up film with high copper peel strength, low dielectric constant and loss according to claim 4, characterized in that, Its thickness is 10 - 100 μm.

10. The preparation method of the flame-retardant reinforced film with high copper stripping strength, low dielectric constant and loss according to any one of claims 1-9, characterized in that, Including: After uniformly mixing the components of the additional layer film, coat it on a substrate and dry it.

Images