A flame retardant build-up film with high copper peel strength, low dielectric constant and loss, and a preparation method thereof

Abstract

The present invention discloses a flame-retardant build-up film with high copper peel strength and low dielectric constant and loss, and a preparation method thereof, belonging to the technical field of resin composite materials. The present invention introduces pyrazole rings into epoxy resin through the design of the build-up film components to synthesize a new pyrazole-modified epoxy resin material. The addition of the new epoxy resin enhances the interaction between the build-up film and the copper foil, thereby improving the copper peel strength; the presence of tertiary amine structure in the new epoxy resin structure can promote the curing of the build-up film. The build-up film is composed of epoxy resin, curing agent, accelerator, filler, flame retardant and other components, which can effectively solve the problems of poor copper adhesion, large dielectric constant and loss, and poor flame retardant performance of current build-up film materials.

Description

Technical Field

[0001] The invention relates to a flame retardant build-up layer film with high copper peeling 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 method for chip packaging. Chips are moving towards miniaturization and high integration. Chip packaging is mainly achieved through packaging substrates. The key raw material used in the substrate preparation process is build-up film materials. They are used to construct multi-layer interconnect structures, providing electrical insulation, mechanical support, auxiliary heat dissipation, maintaining signal integrity, and improving high-frequency signal transmission performance. Therefore, high-performance build-up film materials have become a current research hotspot.

[0003] Current packaging substrates are prone to copper foil delamination under thermal stress. Therefore, it is necessary to improve the copper bonding strength of the build-up film material and reduce the thermal expansion coefficient of the build-up film to ensure chip reliability. Furthermore, the build-up film is typically made of flammable epoxy resin, which is not safe at high temperatures and needs to have improved flame retardancy. As integrated circuit wiring density increases, the resistance of metal interconnects and the capacitance of interlayer dielectrics within electronic components can easily form RC delay effects, leading to adverse effects such as signal transmission delay, noise interference, and power loss. Therefore, developing insulating dielectric materials with low dielectric constants and dissipation constants is crucial to reducing interconnect delays, energy consumption, and crosstalk. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a flame-retardant build-up film with high copper peel strength, low dielectric constant, and low loss. By designing the build-up film components and further utilizing a pyrazole-modified epoxy resin, the resulting insulating adhesive film exhibits strong copper bonding, excellent dielectric properties, and flame retardancy, meeting the demands of high-speed and high-integration electronic component development.

[0005] The present invention includes the following contents:

[0006] A flame-retardant build-up film with high copper peel strength and low dielectric constant and loss, comprising components such as (A) epoxy resin, (B) curing agent, (C) accelerator, (D) filler, (E) flame retardant, and (F) other additives;

[0007] The epoxy resin (A) is a combination of a novel pyrazole-modified epoxy resin (G) and an electronic-grade epoxy resin (J) (usually one or more of a glycidyl ester epoxy resin, a biphenyl epoxy resin, a bisphenol A epoxy resin, a naphthalene epoxy resin, a phenolic resin epoxy resin, and a dicyclopentadiene epoxy resin), wherein the mass ratio of the novel pyrazole-modified epoxy resin (G) to the total mass ratio of the epoxy resin (A) is 20%-100%.

[0008] The novel pyrazole-modified epoxy resin (G) is synthesized by reacting the epoxy group in the bifunctional epoxy resin (H) with the polypyrazole compound (I).

[0009] The (H) bifunctional epoxy resin may be bisphenol A epoxy resin, bisphenol F epoxy resin, biphenyl epoxy resin, naphthalene epoxy resin, etc.

[0010] The polypyrazole compound (I) has the following structure:

[0011]

[0012] R1 can be 、 、 、 One or more of the following, wherein the wavy line represents the part connected to the molecular chain; R2 is a hydrogen atom or an alkyl group.

[0013] The preparation method is as follows: pyrazole is dissolved in DMSO and then KOH powder is added in excess. After vigorous stirring at 60°C for 1 hour, the dibromo compound is added dropwise. After reacting for 4 hours, the excess KOH in the reaction mixture is removed by filtration, and then most of the DMSO is removed by reduced pressure distillation. The reactant is then poured into water, extracted with chloroform, and the solvent is removed to obtain product 1. Product 1 is dissolved in an aqueous HBr solution and converted into a hydrobromide salt. After the solvent is removed, the obtained hydrobromide salt is transferred to a sealed glass tube and heated to 200°C for 2 hours. Finally, the obtained solid is dissolved in water, and 50% NaOH aqueous solution is gradually added until the pH of the solution reaches 12 to form a precipitate. After drying, the product dipyrazole compound is obtained, and the reaction equation is as follows:

[0014] .

[0015] The (G) novel pyrazole-modified epoxy resin synthesis method comprises the following steps: the mass ratio of the (H) bifunctional epoxy resin to the (I) polypyrazole compound is 1:10 to 10:1, the reaction temperature is 100°C-200°C, the reaction time is 5-10 hours, 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, diethyl 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.

[0016] The (B) curing agent may be phenolic resin, cyanate ester, etc.

[0017] The (C) accelerator may be one or more of an amine curing accelerator, an imidazole curing accelerator, and a phosphine curing accelerator.

[0018] The filler (D) is spherical silica with an average particle size of 0.1-5 μm, and is surface-modified to improve the interface compatibility between the filler and the epoxy resin.

[0019] The flame retardant (E) may be one or more of an organophosphorus flame retardant, an organic nitrogen-containing phosphorus compound, an organosilicon flame retardant, a metal hydroxide, and the like.

[0020] The (F) other additives may be any one or a combination of at least two of an organic solvent, a thickener, a defoaming agent, a leveling agent, a leveling agent, an adhesion-imparting agent, and a colorant.

[0021] In the build-up film, when the non-volatile components are taken as 100% by mass, the content of component (A) is 10-50% by mass.

[0022] In the build-up film, when the non-volatile components are taken as 100% by mass, the content of component (B) is 10-50% by mass.

[0023] In the build-up film, when the non-volatile components are taken as 100% by mass, the content of the component (C) is 0.1-1% by mass.

[0024] In the build-up film, when the non-volatile components are taken as 100% by mass, the content of the component (D) is 20-80% by mass.

[0025] In the build-up film, when the non-volatile components are taken as 100% by mass, the content of the component (E) is 0.1-5% by mass.

[0026] In the build-up film, when the non-volatile component is set to 100% by mass, the organic solvent content in component (F) is 20-200% by mass, and the content of additives other than the organic solvent is 1-10% by mass. The organic solvent can be any one of toluene, xylene, butanone, methyl ethyl ketone, cyclohexanone, ethyl acetate, or N,N-dimethylformamide, or a combination of at least two of them.

[0027] The build-up film has a thickness of 10-100 μm.

[0028] The preparation method of the build-up film comprises the following steps: mixing the components evenly, coating the mixture on a substrate, and drying the mixture to obtain a film material.

[0029] The thickness of the substrate is 10 to 150 μm, more preferably 25 to 50 μm; the drying temperature is 20 to 130° C.; the drying time is 0.1 to 12 hours; and finally, a protective film is covered on the build-up film.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention designs the components of the build-up film and further uses a new pyrazole-modified epoxy resin. Pyrazole can enhance the bonding strength between the build-up film and the copper foil and improve the copper peel strength. The pyrazole ring in the new pyrazole-modified epoxy resin can catalyze the epoxy reaction and promote the complete curing of the build-up film. By controlling the ratio of epoxy resin, curing agent and filler, the dielectric constant and loss can be effectively reduced, solving the problem of excessive signal transmission loss during use. In addition, the build-up film has good flame retardant properties, ensuring safety in use. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the H NMR spectrum of 4,4'-methylenedipyrazole;

[0033] Figure 2 This is the H-NMR spectrum of pyrazole-modified epoxy resin;

[0034] Figure 3 This is a digital photo of the build-up film of Example 4;

[0035] Figure 4 is the DMA curve of Example 4;

[0036] Figure 5 This is the copper peel strength curve of Example 4. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below using preferred embodiments of the present invention.

[0038] 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. The build-up film can effectively improve its bonding strength with copper foil by adopting pyrazole-modified epoxy resin. At the same time, due to the addition of low-polarity pyrazole rings, the content of polar groups is reduced, which can effectively reduce the dielectric constant and loss.

[0039] According to some embodiments of the present invention, the build-up film 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) new pyrazole-modified epoxy resin and common electronic grade epoxy resin (one or more of glycidyl ester epoxy resin, biphenyl epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, naphthalene epoxy resin, naphthylene ether epoxy resin and dicyclopentadiene epoxy resin), wherein (G) new The mass ratio of the pyrazole-modified epoxy resin to the total mass ratio of the epoxy resin (A) is 20%-100%. When the non-volatile component is 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 the organic solvent in component (F) is 20-200% by mass, and the content of auxiliary agents other than the solvent is 1-10% by mass.

[0040] By using a resin composition containing components (A) to (F) in the aforementioned specific ratios, it has been found that the low copper foil peel strength, flammability, and high dielectric loss issues associated with build-up films can be addressed. The use of the novel pyrazole-modified epoxy resin in this invention effectively improves the copper peel strength of the build-up film, reduces the amount of accelerator used, and effectively reduces the dielectric constant and dielectric loss.

[0041] (A) Epoxy resin

[0042] Its components are a combination of (G) a novel pyrazole-modified epoxy resin and (J) an electronic-grade epoxy resin.

[0043] The novel pyrazole-modified epoxy resin is obtained by reacting (H) a bifunctional liquid or solid epoxy resin and (I) a polypyrazole compound;

[0044] The polypyrazole compound (I) has the following structure:

[0045]

[0046] R1 can be 、 、 、 One or more of the following, wherein the wavy line represents the part connected to the molecular chain; R2 is a hydrogen atom or an alkyl group.

[0047] The reaction equation is as follows:

[0048]

[0049] The value of n is an integer between 5 and 20.

[0050] (H) The bifunctional liquid or solid epoxy resin, particularly the liquid epoxy resin, includes, for example, bisphenol A epoxy resin.

[0051] (G) Synthesis of novel pyrazole-modified epoxy resins: The mass ratio of a bifunctional liquid or solid epoxy resin to a 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.

[0052] Examples of the electronic-grade epoxy resin (J) include bisphenol A epoxy resin, bisphenol F epoxy resin, naphthalene-type epoxy resin, glycidyl ester-type epoxy resin, glycidyl amine-type epoxy resin, o-cresol-formaldehyde epoxy resin, phenol novolac epoxy resin, dicyclopentadiene phenol-type epoxy resin, XYLOK novolac epoxy resin, trifunctional novolac epoxy resin, phenol biphenyl-type epoxy resin, tetrafunctional epoxy resin, and BPA novolac epoxy resin. These may be used alone or in combination of two or more.

[0053] (B) Curing agent

[0054] The curing agent may be phenolic resin, cyanate ester, etc., and the curing agent may be used alone or in combination of two or more.

[0055] Examples of the phenolic resin curing agent include linear phenol formaldehyde resin, linear bisphenol A formaldehyde resin, biphenyl aralkylphenol resin, XYLOK phenolic resin, linear o-cresol formaldehyde resin, nitrogen-containing phenolic resin, dicyclopentadiene phenol resin, and trifunctional phenolic resin.

[0056] Examples of the cyanate curing agent include difunctional cyanate resins such as bisphenol A dicyanate, triphenylmethane triisocyanate, 4,4'-methylenebis(2,6-dimethylphenylcyanate), 4,4'-ethylenediphenyl dicyanate, hexafluorobisphenol A dicyanate, 1,1-bis(4-cyanatephenylmethane), 2,2-bis(4-cyanate)phenylpropane, bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylene))benzene, bis(4-cyanatephenyl)sulfide, and bis(4-cyanatephenyl)ether.

[0057] The mass ratio of component (A) to component (B) in the build-up film is calculated as the ratio of the total number of epoxy groups in component (A) to the total number of reactive groups in component (B), with the total number of epoxy groups in component (A) : the total number of reactive groups in component (B) being 1:3 to 3:1.

[0058] (C) Accelerator

[0059] Accelerators are mainly amines, imidazoles, and organic phosphines. Since pyrazole-modified epoxy resins promote the curing reaction, the amount of accelerator used can be reduced compared to the solution without pyrazole-modified epoxy resins. Accelerators can be used alone or in combination of two or more, or even no accelerator is needed.

[0060] Examples of the amine accelerator include triethylamine, tributylamine, 4-dimethylaminopyridine (DMAP), benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diaminobicyclo(5,4,0)-undecene (DBU).

[0061] Examples of the imidazole accelerator 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'-undecylimidazole-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole.

[0062] Examples of the organic phosphine accelerator include triphenylphosphine, tetraphenylphosphine tetraphenylborate, n-butylphosphine tetraphenylborate, tetrabutylphosphine decanoate, (4-methylphenyl)triphenylphosphine thiocyanate, tetraphenylphosphine thiocyanate, and butyltriphenylphosphine sulfate.

[0063] (D) Filler

[0064] The filler used in the build-up film is: spherical silica with an average particle size of 0.1-5μm. The content of spherical silica is preferably above 20% by mass when the non-volatile component in the resin composition is set to 100% by mass. However, too high a silica content will affect the mechanical properties of the build-up film. Therefore, from the perspective of mechanical strength, when the non-volatile component in the resin composition is set to 100% by mass, the silica content is preferably below 80% by mass.

[0065] To improve the compatibility between the resin and silica, the spherical silica can be surface-treated with one or more coupling agents, such as aminosilane coupling agents, epoxysilane coupling agents, and mercaptosilane coupling agents. Examples of silane coupling agents include 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane. The amount of silane coupling agent added is 0.1-5% of the mass of the silica.

[0066] (E) Flame retardant

[0067] The flame retardant may be one or more of an organophosphorus flame retardant, an organic nitrogen-containing phosphorus compound, an organosilicon flame retardant, and a metal hydroxide, and its content is 0.1-5% by mass when the non-volatile component is set to 100% by mass.

[0068] (F) Other additives

[0069] Other additives include: any one or a combination of at least two of an organic solvent, a thickener, a defoaming agent, a leveling agent, a leveling agent, an adhesion-imparting agent, and a colorant. The organic solvent content is 20-200% by mass, and the content of 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, butanone, methyl ethyl ketone, cyclohexanone, ethyl acetate, or N,N-dimethylformamide.

[0070] The build-up film has a thickness of 10-100 μm. Its preparation method includes the following steps: uniformly mixing the components, coating the film on a substrate, and drying to obtain a film material. The substrate can be polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), etc., preferably polyethylene terephthalate, more preferably PET film with a release agent; the substrate thickness is 10-150 μm, more preferably 25-50 μm; the drying temperature is 20-130°C, and the drying time is 0.1-12 hours. Finally, the build-up film is covered with a protective film, which can be, for example, a polypropylene film.

[0071] Example 1

[0072] Synthesis of a Novel Pyrazole-Modified Epoxy Resin

[0073] Synthesis of 4,4'-methylenedipyrazole: 5.00 g of pyrazole was dissolved in 30 mL of DMSO and 16.46 g of finely powdered KOH was added. The suspension was vigorously stirred at 60 °C for 1 h, and 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 filtration, and then most of the DMSO was removed by vacuum distillation at 90 °C. It was then poured into 300 mL of water and the solvent was extracted with chloroform to obtain 1,1'-methylenedipyrazole. 1,1'-methylenedipyrazole was dissolved in HBr aqueous solution and 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% NaOH aqueous solution was gradually added until the pH of the solution reached 12 to form an off-white precipitate. After drying, the product 4,4'-methylenedipyrazole was obtained, and the nuclear magnetic resonance was as follows. Figure 1 shown.

[0074] Synthesis of pyrazole-modified bisphenol A epoxy resin: 5 g 328D bisphenol A epoxy resin (epoxy value: 0.55-0.60), 1.5 g 4,4'-methylenedipyrazole and 0.02 g 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 is as follows: Figure 2 shown.

[0075] Epoxy value determination: The epoxy value of pyrazole-modified resin is measured using the hydrochloric acid acetone method. Weigh 0.5 g of resin sample into a 250 mL conical flask. Use a pipette to add 20 mL of acetone-hydrochloric acid solution (2 mL of concentrated hydrochloric acid dissolved in 80 mL of acetone) to the conical flask. Let it stand for 30 minutes. Add 2 drops of 0.1% methyl red indicator and titrate with 0.1 mol / L sodium hydroxide standard solution until the color turns red to yellow. Perform a blank test. The epoxy value E is calculated using the following method:

[0076] E=(V0-V1)*N / 1000 / W*100

[0077] Wherein, V0 and V1 represent the volume of NaOH solution consumed in blank and sample tests (mL), N represents the concentration of NaOH solution (mol / L), and W represents the mass of resin (g);

[0078] The epoxy value of the modified epoxy resin is 0.125 mol / 100g.

[0079] Example 2

[0080] Synthesis of pyrazole-modified biphenyl epoxy resin: 5 g of SQE-101 epoxy resin (epoxy equivalent weight: 186.78 g / eq), 1.5 g of 4,4'-methylenedipyrazole, and 0.02 g of 2,4,6-tris(dimethylaminomethyl)phenol were mixed and heated at 140°C for 8 h to obtain the pyrazole-modified epoxy resin (SQE101-Py). Titration determined the epoxy value of the modified epoxy resin to be 0.115 mol / 100 g.

[0081] Example 3

[0082] Preparation of build-up film materials

[0083] Preparation of resin varnish: 20 g of the 328D-Py epoxy resin synthesized in Example 1, 6.89 g of NC3000 (epoxy equivalent weight: 276 g / eq), 7.56 g of biphenyl aralkyl resin SH-5095 (hydroxyl equivalent weight: 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 butanone solvent to prepare a resin varnish.

[0084] Resin varnish coating: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent and dried at 80°C for 1 hour to obtain a resin film with a thickness of 0.05 mm. Subsequently, a 0.015 mm thick polypropylene film was covered on the resin film to obtain a build-up film material.

[0085] Example 4

[0086] Preparation of build-up film materials

[0087] Preparation of 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 butanone solvent to prepare a resin varnish.

[0088] Resin varnish coating: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent and dried at 80°C for 1 hour to obtain a resin film with a thickness of 0.05 mm. Subsequently, a 0.015 mm thick polypropylene film was covered on the resin film to obtain a build-up film material, the digital photo of which is shown in FIG. Figure 3 And test its glass transition temperature and copper peel strength as shown in Figure 4 and Figure 5 shown.

[0089] Example 5

[0090] Preparation of build-up film materials

[0091] Preparation of 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 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 butanone solvent to prepare a resin varnish.

[0092] Resin varnish coating: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent and dried at 80°C for 1 hour to obtain a resin film with a thickness of 0.05 mm. Subsequently, a 0.015 mm thick polypropylene film was covered on the resin film to obtain a build-up film material.

[0093] Comparative Example 1

[0094] Preparation of build-up film materials

[0095] Preparation of 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 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 butanone solvent to prepare a resin varnish.

[0096] Resin varnish coating: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent and dried at 80°C for 1 hour to obtain a resin film with a thickness of 0.05 mm. Subsequently, a 0.015 mm thick polypropylene film was covered on the resin film to obtain a build-up film material.

[0097] Comparative Example 2

[0098] Preparation of build-up film materials

[0099] Preparation of 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 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 butanone solvent to prepare a resin varnish.

[0100] Resin varnish coating: The above resin varnish was coated on a 0.04 mm thick PET film with a release agent and dried at 80°C for 1 hour to obtain a resin film with a thickness of 0.05 mm. Subsequently, a 0.015 mm thick polypropylene film was covered on the resin film to obtain a build-up film material.

[0101] Dielectric Properties: The build-up films of the examples and comparative examples were cured at 180°C for 2 hours, and then the PET films were peeled off to obtain pre-cured insulating films. The pre-cured insulating films were cut into 70×70 mm test pieces, and the dielectric constant and dielectric loss at 25°C and a frequency of 10 GHz were measured using a vector network analyzer (Keysight N5227B) in a cavity.

[0102] Flame retardant performance test: Cut the cured build-up film into 12.7mm×127mm strips and test according to the UL-94V standard, and record the test results.

[0103] Curing performance measurement: Take 10 mg of the build-up film material with the protective film removed, measure the DSC curve when heated from room temperature to 250°C at 10°C / min, and record the starting curing temperature.

[0104] Peel strength was measured according to the peel strength test method specified in IPC-TM650. The build-up film and inner substrate were vacuum pressed together using a vacuum hot press and then heat-cured to produce a substrate with an insulating layer. The insulating layer on the substrate was then roughened. The roughened substrate then underwent degreasing, micro-etching, pre-impregnation, activation, reduction, chemical copper coating, water washing and baking, pickling, and chemical plating. The substrate was then heated at 180°C for 120 minutes to obtain an evaluation substrate. The copper peel strength of the substrate was evaluated using a universal mechanical testing machine. A 10×100 mm cut was made in the copper layer, and one end was clamped to the tester's fixture. The load at which a 35 mm vertical peel was applied at a rate of 50 mm / min was used to calculate the peel strength (N / mm).

[0105] Glass transition temperature: DMA was used to test the glass transition temperature of the film using a stretching die at a heating rate of 3°C / min.

[0106] The performance of the above embodiments and comparative examples are summarized in the following table

[0107]

[0108] It can be seen that the above-mentioned embodiments and comparative examples all react under conditions of equal epoxy groups and equal hydroxyl groups (wherein the molar ratio of epoxy groups to hydroxyl groups is 1:1). Through the comparison of the performance of each group, it can be seen that the peel strength of the build-up film material obtained by the pyrazole-modified epoxy resin is significantly improved, and the curing starting temperature is basically similar to that of Comparative Examples 1 and 2. The interaction between the pyrazole ring and the copper foil improves the copper peel strength, indicating that the pyrazole-modified epoxy resin has certain self-promoting properties, which can promote the curing reaction of the resin system and can be smoothly cured without adding a accelerator. If an unmodified epoxy resin is used, a curing accelerator needs to be added, otherwise the temperature required for the curing reaction will be greatly increased, and it may even fail to cure smoothly. For example, in Comparative Example 1, if the curing accelerator 2-ethyl-4-methylimidazole is not added, its curing starting temperature reaches 178.0°C, and the corresponding curing starting temperature in Comparative Example 2 reaches 170.0°C, both of which are significantly improved. In addition, it can be seen that the dielectric constant and dielectric loss of the build-up film material are also reduced by adding pyrazole-modified epoxy resin, especially when using cyanate curing agent, the dielectric properties of the build-up film can be significantly improved.

[0109] The embodiments described above are merely some preferred embodiments of the present invention and are not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A flame retardant build-up layer film with high copper peel strength and low dielectric constant and loss, characterized in that: The flame retardant build-up layer 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 build-up layer film with high copper peel strength and 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 epoxy resin and naphthalene epoxy resin.

3. The flame retardant build-up layer film with high copper peel strength and low dielectric constant and loss according to claim 1, characterized in that: The preparation method of the pyrazole-modified epoxy resin comprises: reacting the bifunctional epoxy resin with the polypyrazole compound in a reaction solvent or in a solvent-free system in the presence of a catalyst, wherein 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 hours, and the catalyst is 2,4,6-tris(dimethylaminomethyl)phenol, triethylamine, triethanolamine, etc. The reaction solvent is 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.

4. The flame retardant build-up layer film with high copper peel strength and low dielectric constant and loss according to claim 1, characterized in that: The flame retardant build-up 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 the pyrazole-modified epoxy resin and electronic-grade epoxy resin.

5. The flame retardant build-up layer film with high copper peel strength and 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 build-up layer film with high copper peel strength and low dielectric constant and loss according to claim 4, characterized in that: The electronic grade epoxy resin is one or a combination of glycidyl ester epoxy resin, biphenyl epoxy resin, bisphenol A epoxy resin, naphthalene epoxy resin, phenolic resin epoxy resin and dicyclopentadiene epoxy resin.

7. The flame retardant build-up layer film with high copper peel strength and low dielectric constant and loss according to claim 4, characterized in that: The curing agent is a phenolic resin or a cyanate ester, the accelerator is one or more of an amine curing accelerator, an imidazole curing accelerator, and a phosphine curing accelerator, the filler is spherical silica with an average particle size of 0.1-5 μm, and the surface is modified to improve the interfacial compatibility between the filler and the epoxy resin, the flame retardant is one or more of an organophosphorus flame retardant, an organic nitrogen-containing phosphorus compound, an organosilicon flame retardant, and a metal hydroxide, and the other auxiliary agents are any one or a combination of at least two of an organic solvent, a thickener, a defoaming agent, a leveling agent, a leveling agent, an adhesion-imparting agent, and a colorant.

8. The flame retardant build-up film with high copper peel strength and low dielectric constant and loss according to claim 4, characterized in that: Assuming that the mass of the non-volatile components in the build-up film is 100%, the mass proportion of the epoxy resin in the build-up 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, the organic solvent among other additives is 20-200%, and the additives other than organic solvents are 1-10%; the organic solvent is any one of toluene, xylene, butanone, methyl ethyl ketone, cyclohexanone, ethyl acetate or N,N-dimethylformamide, or a combination of at least two thereof.

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

10. The method for preparing a flame retardant build-up layer film having high copper peel strength and low dielectric constant and loss according to any one of claims 1 to 9, wherein: include: After the components of the build-up film are evenly mixed, the film is coated on a substrate and dried.

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