A modified polyimide resin composition and a method for preparing the same

Abstract

The application discloses a modified polyimide resin composition and a preparation method thereof, and belongs to the technical field of high-frequency high-speed printed circuit board substrates. The composition comprises a bismaleimide resin, a diallyl bisphenol A curing agent, a copper foil interface modifier, a latent curing accelerator and an inorganic filler. The copper foil interface modifier is a monofunctional maleimide containing a benzimidazole structure. A benzimidazole group of the copper foil interface modifier forms a coordination bond with a copper foil, and a maleimide double bond participates in resin crosslinking to form a double-bonding interface. The resin and the curing agent are pre-polymerized to form a soluble prepolymer soluble in acetone. The modified polyimide resin composition and the preparation method thereof are used, and the obtained composition has excellent high-temperature and high-humidity interface reliability, low dielectric loss and high glass transition temperature after curing, and meets the long-term reliable operation requirement of high-frequency high-speed PCBs in harsh environments.

Description

Technical Field

[0001] This invention relates to the field of high-frequency and high-speed printed circuit board substrate technology, and in particular to a modified polyimide resin composition and its preparation method. Background Technology

[0002] With the rapid development of 5G communication, artificial intelligence servers, and high-speed computing, high-frequency and high-speed printed circuit boards (PCBs) are facing increasingly stringent requirements regarding the dielectric properties, heat resistance, and long-term reliability of the substrate. Bismaleimide (BMI) resin, due to its excellent heat resistance, dimensional stability, and good mechanical properties, has become one of the key substrates for high-frequency and high-speed PCBs. However, traditional BMI resin systems still face the following core challenges in practical applications: First, under harsh operating environments with high temperature and humidity (such as 85℃ / 85% relative humidity), the interfacial bonding between BMI resin and copper foil will significantly deteriorate. This is mainly because the weak chemical bond between the resin and copper foil relies primarily on physical adsorption or conventional coupling agents. Water molecules can easily penetrate along the interface and trigger hydrolysis, leading to a significant decrease in the peel strength of the copper foil and severely affecting the long-term operational reliability of the PCB.

[0003] Secondly, traditional BMI resins are only soluble in highly toxic, high-boiling-point solvents such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc), and cannot be dissolved in low-toxicity, low-cost conventional solvents such as acetone and methyl ethyl ketone. This not only increases the environmental and health risks during the production process, but also requires high-temperature solvent removal during prepreg preparation, which easily introduces air bubbles, leading to large fluctuations in resin content and affecting the dielectric uniformity of the substrate and the yield.

[0004] Furthermore, in high-frequency and high-speed applications, simultaneously achieving low dielectric loss, high heat resistance, high peel strength, and low water absorption has always been a technical challenge in the modification of BMI resins. Existing technologies often only optimize a single property, making it difficult to achieve synergistic improvements in multiple properties.

[0005] Therefore, developing a modified bismaleimide resin composition that is soluble in low-toxicity solvents and exhibits excellent interfacial reliability under high temperature and high humidity conditions is of great significance for meeting the application requirements of next-generation high-frequency and high-speed PCBs. Summary of the Invention

[0006] The purpose of this invention is to provide a modified polyimide resin composition and its preparation method to solve the above-mentioned problems.

[0007] This invention provides a modified polyimide resin composition comprising the following components: Bismaleimide resin, 100 parts by weight; Diallyl bisphenol A curing agent, 30-60 parts by weight; Copper foil interface modifier, 2-5 parts by weight; Latent curing accelerator, 0.1-1 parts by weight; and Inorganic filler, 0-30 parts by weight; The main active ingredient of the copper foil interface modifier is a monofunctional maleimide containing a benzimidazole structure. Its molecule contains only one maleimide double bond and one benzimidazole group. The benzimidazole group is connected to the nitrogen atom of the maleimide through a methylene or ether bond. The bismaleimide resin is pre-reacted with diallyl bisphenol A curing agent to form a soluble prepolymer, which is dissolved in acetone at 25°C to form a clear solution with a solid content of not less than 50%.

[0008] Preferably, the bismaleimide resin is a mixture of a first bismaleimide containing an alicyclic group and a second bismaleimide containing a fluorinated substituent, wherein the molar ratio of the first bismaleimide to the second bismaleimide is 3:7 to 5:5.

[0009] Preferably, the ratio of the amount of allyl group in the diallyl bisphenol A curing agent to the amount of maleimide group in the bismaleimide resin is 0.9:1 to 1.1:1.

[0010] Preferably, the monofunctional maleimide containing a benzimidazole structure is N-(2-benzimidazolylmethyl)maleimide with a purity ≥98%.

[0011] Preferably, the latent curing accelerator is 2-ethyl-4-methylimidazole encapsulated in microcapsules, with a DSC peak exothermic temperature of 160℃-180℃.

[0012] Preferably, the inorganic filler is selected from one or more of spherical silica, alumina, and boron nitride, with an average particle size of 0.1 μm-5 μm.

[0013] A method for preparing the modified polyimide resin composition as described above is provided, comprising the following steps: (1) The bismaleimide resin, diallyl bisphenol A curing agent and copper foil interface modifier are mixed and prepolymerized at 120-140°C for 30-60 minutes to form a soluble prepolymer. (2) Cool the prepolymer obtained in step (1) to room temperature, add the latent curing accelerator and inorganic filler, and stir until uniform; (3) Dissolve the mixture obtained in step (2) in acetone to prepare a resin solution with a solid content of 50-60%, thereby obtaining the modified bismaleimide resin composition.

[0014] Preferably, the temperature of the prepolymerization reaction in step (1) is 130-135°C and the time is 40-50 minutes.

[0015] Preferably, the resin solution in step (3) is used to impregnate the surface-modified glass fiber cloth to prepare copper-clad laminate; the surface-modified glass fiber cloth is a glass fiber cloth grafted with N-phenylmaleimide after being primed with silane coupling agent.

[0016] Preferably, the surface-modified glass fiber cloth is prepared by the following method: a. Dissolve γ-methacryloxypropyltrimethoxysilane in an ethanol-water mixture to prepare a silane treatment solution with a mass concentration of 0.5-2%, adjust the pH value to 4-5, and hydrolyze for 30 minutes. b. Immerse the fiberglass cloth in the silane treatment solution for 5-10 minutes, then remove it and dry it at 120°C for 15 minutes. c. Dissolve N-phenylmaleimide in acetone to prepare an N-phenylmaleimide treatment solution with a mass concentration of 3-8%; d. Immerse the silane-treated glass fiber cloth in the N-phenylmaleimide treatment solution for 5-15 minutes. e. Take out the glass fiber cloth and dry it at 120-150℃ for 10-20 minutes to obtain the surface-modified glass fiber cloth.

[0017] Therefore, the present invention, employing the above-mentioned modified polyimide resin composition and its preparation method, has the following beneficial effects: (1) By introducing maleimide with a monofunctional group containing benzimidazole structure as a copper foil interface modifier, the benzimidazole group in its molecular structure can form a stable chemical coordination bond with the copper foil surface, while the maleimide double bond participates in the curing and cross-linking reaction of the resin matrix, forming a double-bonded interface of "covalent bond to resin and coordination bond to anchor copper foil". Compared with the physical modification of traditional silane coupling agents, this chemically bonded interface can effectively inhibit the penetration and hydrolysis of water molecules along the interface, and significantly improve the interface stability under high temperature and high humidity conditions.

[0018] (2) By pre-conducting a controlled prepolymerization reaction between bismaleimide resin and diallyl bisphenol A curing agent to form a low molecular weight soluble prepolymer, the composition can be completely dissolved in low-toxicity, low-cost conventional solvents such as acetone and methyl ethyl ketone at room temperature to form a clear resin solution with a solid content of not less than 50%. This not only avoids the use of highly toxic solvents such as DMF and DMAc from the source, reducing environmental and health risks, but also, due to the low boiling point of acetone, it can be quickly removed at a lower temperature when preparing prepreg, effectively reducing bubble defects. The resin content fluctuation can be controlled within 3%, significantly improving production efficiency and product qualification rate.

[0019] (3) Through the synergistic combination of alicyclic groups and fluorinated substituents in bismaleimide resin, and the optimized functional group ratio, the inherent high heat resistance (glass transition temperature T) of BMI resin is maintained. g While achieving a temperature of ≥250℃, it also achieves excellent dielectric properties and low water absorption.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a comparative graph showing the experimental data of Example 1 and Comparative Examples 1-4 in the present invention's modified polyimide resin composition and its preparation method, where (a) is a comparison graph of peel strength retention rate, and (b) is a comparison graph of D... f (10GHz) Comparison chart, (c) represents T g Comparison chart. Detailed Implementation

[0022] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0024] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0025] This invention provides a modified polyimide resin composition comprising the following components: Bismaleimide resin, 100 parts by weight; the bismaleimide resin is a mixture of a first bismaleimide containing an alicyclic group and a second bismaleimide containing a fluorine substituent, wherein the molar ratio of the first bismaleimide to the second bismaleimide is 3:7 to 5:5; Diallyl bisphenol A curing agent, 30-60 parts by weight; the molar ratio of the allyl group of the diallyl bisphenol A curing agent to the molar ratio of the maleimide group of the bismaleimide resin is 0.9:1 to 1.1:1; Copper foil interface modifier, 2-5 parts by weight; Latent curing accelerator, 0.1-1 parts by weight; the latent curing accelerator is 2-ethyl-4-methylimidazole microencapsulated with a DSC peak exothermic temperature of 160℃-180℃; Inorganic filler, 0-30 parts by weight; the inorganic filler is selected from one or more of spherical silica, alumina, and boron nitride, with an average particle size of 0.1μm-5μm; The main active ingredient of the copper foil interface modifier is a monofunctional maleimide containing a benzimidazole structure. Its molecule contains only one maleimide double bond and one benzimidazole group. The benzimidazole group is connected to the nitrogen atom of the maleimide through a methylene or ether bond. The monofunctional maleimide containing a benzimidazole structure is N-(2-benzimidazole methyl)maleimide, with a purity ≥98%. Bismaleimide resin is pre-reacted with diallyl bisphenol A curing agent to form a soluble prepolymer, which is dissolved in acetone at 25°C to form a clear solution with a solid content of not less than 50%.

[0026] Specifically, bismaleimide (BMI) resin forms the basic framework of the composition of this invention, providing the main network structure of the cured resin matrix. The maleimide double bonds at both ends of the BMI molecule are highly reactive, capable of undergoing olefin-allyl addition reactions (Ene reaction) and Diels-Alder cycloaddition reactions with the diallylbisphenol A (DBA) curing agent to form a highly cross-linked three-dimensional network. The cured BMI resin exhibits excellent heat resistance, dimensional stability, and mechanical strength, making it ideal for achieving high glass transition temperatures (T0). g The basic guarantee is ≥250℃. A mixture of alicyclic bismaleimide and fluorinated bismaleimide is preferred. Specifically: Bismaleimide with alicyclic groups (e.g., N,N'-(4,4'-methylenedicyclohexyl)bismaleimide): The alicyclic structure has a large molecular volume and low polarizability, effectively increasing the free volume between molecular chains and reducing the number of polarizing groups per unit volume, thereby reducing the dielectric constant and dielectric loss of the resin. Simultaneously, the alicyclic structure does not contain aromatic ring conjugated systems, further reducing the adverse effects of π-electron cloud interactions on dielectric properties. Bismaleimide with fluorinated substituents (e.g., fluorinated aliphatic or aromatic bismaleimides): Fluorine atoms have the strongest electronegativity and extremely low molar polarizability. The introduction of CF bonds can significantly reduce the polarization ability of the molecular chain, thereby greatly reducing the dielectric constant and dielectric loss factor of the resin system. Furthermore, the hydrophobicity of fluorine atoms helps reduce the water absorption rate of the cured resin. The molar ratio of the two BMIs, from 3:7 to 5:5, was determined through experimental optimization. When the first BMI molar ratio was below 30%, the improvement in the dielectric properties of the resin system was not significant; when the first BMI molar ratio was above 50%, the crosslinking density of the system decreased, and T... g The mechanical properties decrease. An optimal balance between dielectric properties and heat resistance can be achieved within the range of 3:7 to 5:5.

[0027] Diallylbisphenol A (DBA) is the most commonly used co-curing agent for BMI resin. Its molecule contains an allyl group at each end. Under heating conditions, the allyl groups react with the maleimide double bonds of BMI to form an intermediate, which then undergoes a Diels-Alder reaction and rearrangement aromatization to form a highly cross-linked cured network. The introduction of DBA not only reduces the self-polymerization tendency of BMI, improving the resin's toughness and processability, but also enhances the material's impact resistance by extending the chain segment length between cross-linking points. The molar ratio of the allyl groups in the DBA curing agent to the maleimide groups in the BMI resin is controlled between 0.9:1 and 1.1:1. This ratio range is determined based on the following: when the ratio is below 0.9:1, there is an excess of maleimide groups in the system, resulting in excessively high cross-linking density and increased brittleness after curing. Furthermore, the remaining unreacted maleimide groups increase water absorption and deteriorate dielectric properties. When the ratio is higher than 1.1:1, there is an excess of allyl groups, resulting in too many unreacted allyl groups remaining in the cured network, leading to insufficient crosslinking density. g And the heat resistance decreases. In the range of 0.9:1 to 1.1:1, the two reactive groups react in close equivalence, the cross-linked network structure is the most complete, and the overall performance is the best.

[0028] In specific calculations, the amount of allyl groups in the DBA curing agent = (DBA mass / DBA molecular weight) × 2; the amount of maleimide groups in the BMI resin = (first BMI mass / first BMI molecular weight) × 2 + (second BMI mass / second BMI molecular weight) × 2.

[0029] The copper foil interface modifier's molecular structure contains both a benzimidazole group and a maleimide double bond, exhibiting a "dual-function" characteristic: The benzimidazole group's role: The imine nitrogen atom on the benzimidazole ring contains a lone pair of electrons, enabling it to form stable coordinate bonds with copper atoms on the copper foil surface. The bond energy of this chemical coordination bond is much higher than the hydrogen bonds or physical adsorption forces formed by conventional silane coupling agents, and it is not easily destroyed by water molecule hydrolysis, making it the core mechanism for ensuring interface stability under high temperature and high humidity conditions. The maleimide double bond's role: This double bond undergoes a co-crosslinking reaction with maleimide or allyl groups in the BMI-DBA curing system, allowing the interface modifier to be covalently embedded in the resin crosslinking network, achieving a dual interface bonding of "covalent bond to resin, coordinate bond anchoring of copper foil."

[0030] N-(2-benzimidazolylmethyl)maleimide is preferred as the copper foil interface modifier. Its benzimidazol group is linked to the nitrogen atom of maleimide via a methylene group. The molecular structure is optimized to maintain an appropriate spatial distance between the two functional groups, maximizing their bonding function without affecting reactivity due to steric hindrance. The dosage is controlled at 2-5 parts by weight (based on 100 parts by weight of BMI resin). Below 2 parts, the coordination bond density on the copper foil surface is insufficient, the interface reinforcement effect is not significant, and the peel strength retention rate after aging remains low. Above 5 parts, excessive monofunctional modifier occupies crosslinking points, reducing crosslinking density and leading to reduced T... g And mechanical properties decrease. Within the range of 2-5 parts, the optimal interface reinforcement effect can be achieved without sacrificing heat resistance.

[0031] The latent curing accelerator utilizes microencapsulation technology to encapsulate the active accelerator (2-ethyl-4-methylimidazole) within the polymer capsule wall. At room temperature, the capsule wall remains intact, isolating the accelerator from the resin matrix, resulting in a longer pot life and shelf life for the resin. When the temperature rises to the capsule wall's release temperature (160-180°C), the capsule wall ruptures or softens, releasing the imidazole accelerator, which catalyzes the crosslinking reaction between BMI and DBA, accelerating the curing process. Microencapsulated 2-ethyl-4-methylimidazole is preferred, with a DSC peak exothermic temperature of 160-180°C. Below 160°C, the accelerator begins to release during the initial stages of prepreg drying and lamination, leading to premature resin gelation and a narrow processing window. Above 180°C, the release temperature is too high, causing the curing reaction to start too late, resulting in insufficient curing or excessively long curing times, reducing production efficiency. The release temperature of 160℃-180℃ matches the temperature rise curve of gradient hot pressing, ensuring that the resin cures rapidly after sufficient flow and wetting. The dosage should be controlled between 0.1-1 parts by weight. Too little will result in insignificant promoting effect; too much will lead to an overly vigorous reaction, easily generating internal stress, and residual imidazole groups may increase dielectric loss.

[0032] The main function of inorganic fillers is to reduce the coefficient of thermal expansion (CTE) of the resin system, improve dimensional stability, and enhance thermal conductivity. Spherical silica is the most commonly used filler, effectively reducing resin curing shrinkage and improving substrate rigidity. Alumina and boron nitride have high thermal conductivity, improving heat dissipation. Spherical silica with a particle size of 0.1μm-5μm is preferred. Spherical fillers facilitate the wetting and penetration of the resin into the fiberglass cloth, reducing system viscosity. If the particle size is too small (<0.1μm), the filler is prone to agglomeration and difficult to disperse; if the particle size is too large (>5μm), it will affect the surface smoothness of the prepreg and the copper foil peel strength. The dosage is controlled between 0-30 parts by weight to adapt to the different requirements of CTE and processability in various applications. Formulations without fillers are suitable for thin PCBs with high processing fluidity requirements; formulations with fillers are suitable for multilayer boards with high dimensional stability requirements.

[0033] The formation mechanism of soluble prepolymers: The principle of achieving low-toxicity solvent solubility by pre-conducting a controlled prepolymerization reaction between bismaleimide resin and diallyl bisphenol A curing agent is as follows: Traditional direct mixtures of BMI and DBA have small molecular weights, short chains, high density of polar maleimide groups, and strong intermolecular forces, making them soluble only in highly polar solvents such as DMF and DMAc. Through controlled prepolymerization, BMI and DBA undergo partial Ene reactions and chain elongation to form a prepolymer with a medium molecular weight (approximately 1500-3000). In this prepolymer, the local density of maleimide groups decreases, and the flexibility of the molecular chain increases, lowering the solvent polarity threshold required for solvation. This allows it to dissolve in moderately polar, low-toxicity solvents such as acetone at room temperature.

[0034] A method for preparing the modified polyimide resin composition as described above is provided, comprising the following steps: (1) The bismaleimide resin, diallyl bisphenol A curing agent and copper foil interface modifier are mixed and prepolymerized at 120-140°C for 30-60 minutes to form a soluble prepolymer; preferably, the temperature of the prepolymerization reaction is 130-135°C and the time is 40-50 minutes. Specifically, by controlling the degree of prepolymerization, sufficient reactive groups are retained, allowing the prepolymer to fully crosslink during the subsequent hot-pressing curing stage, thus ensuring the heat resistance and mechanical properties of the final cured product. The prepolymerization reaction temperature is 120-140℃, and the time is 30-60 minutes. Below 120℃, the reaction rate is too slow, resulting in low prepolymerization efficiency; above 140℃, the reaction is too vigorous, easily leading to excessive crosslinking and gelation, resulting in loss of solubility. A reaction time of 30-60 minutes allows for sufficient prepolymerization while controlling the molecular weight within the target range.

[0035] (2) Cool the prepolymer obtained in step (1) to room temperature, add the latent curing accelerator and inorganic filler, and stir until uniform; (3) Dissolve the mixture obtained in step (2) in acetone to prepare a resin solution with a solid content of 50-60%, thereby obtaining the modified bismaleimide resin composition.

[0036] In step (3), the resin solution is used to impregnate the surface-modified glass fiber cloth to prepare copper-clad laminate; the surface-modified glass fiber cloth is a glass fiber cloth grafted with N-phenylmaleimide after being primed with silane coupling agent.

[0037] Surface-modified glass fiber cloth is prepared by the following method: a. Dissolve γ-methacryloxypropyltrimethoxysilane in an ethanol-water mixture to prepare a silane treatment solution with a mass concentration of 0.5-2%, adjust the pH value to 4-5, and hydrolyze for 30 minutes. b. Immerse the fiberglass cloth in the silane treatment solution for 5-10 minutes, then remove it and dry it at 120°C for 15 minutes. c. Dissolve N-phenylmaleimide in acetone to prepare an N-phenylmaleimide treatment solution with a mass concentration of 3-8%; d. Immerse the silane-treated glass fiber cloth in the N-phenylmaleimide treatment solution for 5-15 minutes. e. Take out the glass fiber cloth and dry it at 120-150℃ for 10-20 minutes to obtain the surface-modified glass fiber cloth.

[0038] Surface modification mechanism of fiberglass cloth: Two-step modification principle: Step 1: Applying a silane coupling agent as a base. γ-Methacryloxypropyltrimethoxysilane (such as KH-570) hydrolyzes in water to generate silanol groups, which then undergo a condensation reaction with the silanol groups on the glass fiber surface, covalently anchoring the silane to the glass fiber surface. Simultaneously, the methacryloyloxy group at the other end of the silane provides a polymerizable double bond site for subsequent grafting.

[0039] Step 2: N-Phenylmaleimide (N-PMI) grafting. Under heating conditions (120-150℃), the maleimide double bond of N-PMI undergoes free radical copolymerization or thermal polymerization with the methacryloyloxy double bond introduced by silane, thereby introducing a layer of maleimide groups onto the glass fiber surface.

[0040] Synergistic effect: After the surface-modified glass fiber cloth is immersed in the resin solution, the maleimide groups on the glass fiber surface participate in the curing and cross-linking reaction of the BMI-DBA resin system, so that the glass fiber and resin are connected by covalent bonds, forming a uniform and consistent cured network, which completely eliminates the voids and weak boundary layers present at the traditional glass fiber-resin interface. This mechanism is an important guarantee for reducing the water absorption rate of the substrate and improving the long-term stability of dielectric properties.

[0041] To provide a clearer and more detailed description of the modified polyimide resin composition and its preparation method provided in the embodiments of the present invention, specific examples will be described below.

[0042] The following examples describe the raw materials used: The first bismaleimide containing an alicyclic group is N,N'-(4,4'-methylenedicyclohexyl)bismaleimide, with a molecular weight of 358.4 g / mol. The second bismaleimide containing a fluorine substituent is N,N'-(4,4'-methylenedi(2-fluorobenzene))bismaleimide, with a molecular weight of 394.3 g / mol. Diallyl bisphenol A curing agent (DBA) has a molecular weight of 308.4 g / mol. The copper foil interface modifier is N-(2-benzimidazolylmethyl)maleimide, with a purity ≥98%. The latent curing accelerator is microencapsulated 2-ethyl-4-methylimidazole, with a DSC peak exothermic temperature of 165℃. The inorganic filler is spherical silica with an average particle size of 1 μm.

[0043] The glass fiber cloth is a surface-modified glass fiber cloth, which is prepared by dissolving γ-methacryloxypropyltrimethoxysilane in an ethanol-water mixture to prepare a 1% (w / w) silane treatment solution, adjusting the pH to 4.5, and hydrolyzing for 30 minutes; immersing the glass fiber cloth in the treatment solution for 8 minutes, and then drying it at 120°C for 15 minutes; dissolving N-phenylmaleimide in acetone to prepare a 5% (w / w) N-PMI treatment solution; immersing the silane-treated glass fiber cloth in the N-PMI treatment solution for 10 minutes, and then drying it at 135°C for 15 minutes to obtain the surface-modified glass fiber cloth.

[0044] Example 1 The composition is formulated as follows: 30 parts by weight of the first bismaleimide, 70 parts by weight of the second bismaleimide, 45 parts by weight of diallyl bisphenol A curing agent, 3 parts by weight of N-(2-benzimidazolylmethyl)maleimide, 0.5 parts by weight of microcapsule-encapsulated 2-ethyl-4-methylimidazole, and 15 parts by weight of spherical silica. The molar ratio of the first bismaleimide to the second bismaleimide is 3:7.

[0045] Preparation method of the composition: First bismaleimide, second bismaleimide, diallyl bisphenol A curing agent, and N-(2-benzimidazolylmethyl)maleimide were added to a reaction vessel, stirred, and heated to 130°C for a prepolymerization reaction for 45 minutes to form a soluble prepolymer. After cooling to room temperature, 2-ethyl-4-methylimidazole microcapsules and spherical silica were added and stirred until homogeneous. The resulting mixture was dissolved in acetone to prepare a resin solution with a solid content of 55%, which was a clear solution at 25°C.

[0046] Example 2 The composition is formulated as follows: 40 parts by weight of the first bismaleimide, 60 parts by weight of the second bismaleimide, 40 parts by weight of diallyl bisphenol A curing agent, 4 parts by weight of N-(2-benzimidazolylmethyl)maleimide, 0.3 parts by weight of microcapsule-encapsulated 2-ethyl-4-methylimidazole, and 0 parts by weight of spherical silica. The molar ratio of the first bismaleimide to the second bismaleimide is 4:6.

[0047] Preparation method of the composition: First bismaleimide, second bismaleimide, diallyl bisphenol A curing agent, and N-(2-benzimidazolylmethyl)maleimide were added to a reaction vessel, stirred, and heated to 135°C for a prepolymerization reaction for 40 minutes to form a soluble prepolymer. After cooling to room temperature, 2-ethyl-4-methylimidazole was added and microcapsules were added and stirred until homogeneous. The resulting mixture was dissolved in acetone to prepare a resin solution with a solid content of 55%, which was a clear solution at 25°C.

[0048] Example 3 The composition is formulated as follows: 50 parts by weight of a first bismaleimide, 50 parts by weight of a second bismaleimide, 50 parts by weight of diallyl bisphenol A curing agent, 5 parts by weight of N-(2-benzimidazolylmethyl)maleimide, 0.8 parts by weight of microcapsule-encapsulated 2-ethyl-4-methylimidazole, and 20 parts by weight of spherical silica. The molar ratio of the first bismaleimide to the second bismaleimide is 5:5.

[0049] Preparation method of the composition: First bismaleimide, second bismaleimide, diallyl bisphenol A curing agent, and N-(2-benzimidazolylmethyl)maleimide were added to a reaction vessel, stirred, and heated to 120°C for a prepolymerization reaction for 60 minutes to form a soluble prepolymer. After cooling to room temperature, 2-ethyl-4-methylimidazole microcapsules and spherical silica were added and stirred until homogeneous. The resulting mixture was dissolved in acetone to prepare a resin solution with a solid content of 55%, which was a clear solution at 25°C.

[0050] Comparative Example 1 The difference between this comparative example and Example 1 is that it does not contain a copper foil interface modifier.

[0051] The composition is formulated as follows: 30 parts by weight of the first bismaleimide, 70 parts by weight of the second bismaleimide, 45 parts by weight of diallyl bisphenol A curing agent, 0.5 parts by weight of microcapsule-encapsulated 2-ethyl-4-methylimidazolium, and 15 parts by weight of spherical silica. It does not contain N-(2-benzimidazolylmethyl)maleimide.

[0052] The composition was prepared using the same method as in Example 1. The resulting prepolymer was soluble in acetone and formed a clear solution with a solid content of 55% at 25°C.

[0053] Comparative Example 2 The difference between this comparative example and Example 1 is that all the bismaleimide resins used are first bismaleimides containing alicyclic groups, and do not contain second bismaleimides with fluorine substituents.

[0054] The composition is formulated as follows: 100 parts by weight of first bismaleimide, 45 parts by weight of diallyl bisphenol A curing agent, 3 parts by weight of N-(2-benzimidazolylmethyl)maleimide, 0.5 parts by weight of microcapsule-encapsulated 2-ethyl-4-methylimidazole, and 15 parts by weight of spherical silica.

[0055] The composition was prepared using the same method as in Example 1. The resulting prepolymer has slightly poor solubility in acetone and requires prolonged stirring to achieve clarity.

[0056] Comparative Example 3 The difference between this comparative example and Example 1 is that no prepolymerization reaction is performed.

[0057] The composition formulation is the same as in Example 1. The composition is prepared by directly mixing all components and dissolving them in acetone without a prepolymerization reaction. The resulting mixture has poor solubility in acetone and cannot form a clear and homogeneous resin solution; it separates into layers after standing.

[0058] Comparative Example 4 The difference between this comparative example and Example 1 is that the amount of copper foil interface modifier used exceeds the selected range.

[0059] The composition is formulated as follows: 30 parts by weight of the first bismaleimide, 70 parts by weight of the second bismaleimide, 45 parts by weight of diallyl bisphenol A curing agent, 8 parts by weight of N-(2-benzimidazolylmethyl)maleimide, 0.5 parts by weight of microencapsulated 2-ethyl-4-methylimidazole, and 15 parts by weight of spherical silica. The amount of copper foil interface modifier is 8 parts by weight, which exceeds the selected range of 2-5 parts by weight.

[0060] The composition was prepared using the same method as in Example 1. The resulting prepolymer was soluble in acetone and formed a clear solution with a solid content of 55% at 25°C.

[0061] Performance testing: The resin solutions of each embodiment and comparative example were impregnated with surface-modified glass fiber cloth (comparative example 3 could not be prepared as a sample could not be formed due to the inability to form a uniform resin solution) to prepare copper-clad laminate samples for performance testing.

[0062] The test methods are as follows: peel strength is tested according to IPC-TM-650; peel strength is tested and retention rate is calculated after aging at 85℃ / 85%RH for 1000 hours; dielectric properties are tested at 10GHz according to IPC-TM-650 (separated dielectric resonator method); glass transition temperature is tested according to IPC-TM-650 (DMA method); water absorption rate is tested according to IPC-TM-650.

[0063] The test results are shown in Table 1 and Figure 1 As shown.

[0064] Table 1 Performance test results of each embodiment and comparative example

[0065] As can be seen from the data in Table 1: Compared with Comparative Example 1, the initial peel strength of Example 1 increased from 1.05 N / mm to 1.62 N / mm, an increase of 54%; after aging at 85℃ / 85%RH for 1000 hours, the peel strength retention rate increased significantly from 40.0% to 93.2%. This fully demonstrates that N-(2-benzimidazolylmethyl)maleimide significantly enhances interfacial bonding and hydrolysis resistance through benzimidazole-copper coordination bonds.

[0066] Compared with Comparative Example 2, in Example 1, after introducing a second bismaleimide with a fluorinated substituent, D k It decreased from 3.12 to 2.82, a drop of 9.6%; D f It decreased from 0.0032 to 0.0016, a drop of 50%. Meanwhile, T... g The temperature drop of only 6°C indicates that the synergistic effect of alicyclic BMI and fluorinated BMI can significantly improve dielectric properties while maintaining high heat resistance.

[0067] Comparative Example 3 did not undergo a prepolymerization reaction; the components were directly mixed in acetone, which failed to form a homogeneous adhesive. This verifies that the prepolymerization reaction is a key process step in achieving low-toxicity solvent solubility.

[0068] The amount of interface modifier used in Comparative Example 4 was 8 parts by weight, exceeding the range of 2-5 parts. Although the peel strength retention rate remained good after aging (91.4%), T... g The temperature dropped from 262℃ to 238℃, a decrease of 24℃. This is because excessive monofunctional modifiers occupy crosslinking sites, reducing the crosslinking density.

[0069] As can be seen, the compositions in the examples, through the combined technical solution of benzimidazole copper foil interface modifier, synergistic combination of alicyclic and fluorinated BMI, and the formation of soluble prepolymers from prepolymers, have achieved comprehensive optimization of the compositions in terms of acetone solubility, interface reliability, dielectric properties and heat resistance. Compared with each comparative example, they all show significant advantages in key performance indicators.

[0070] Therefore, this invention employs the aforementioned modified polyimide resin composition and its preparation method. By introducing maleimide, a monofunctional group containing a benzimidazole structure, as a copper foil interface modifier, the benzimidazole group in its molecular structure can form stable chemical coordination bonds with the copper foil surface, while the maleimide double bonds participate in the curing and crosslinking reaction of the resin matrix, forming a dual-bonded interface of "covalently bonded resin and coordinately bonded copper foil." Compared with traditional physical modification using silane coupling agents, this chemically bonded interface effectively inhibits the penetration and hydrolysis of water molecules along the interface, significantly improving interface stability under high temperature and high humidity conditions. Experimental data show that the copper-clad laminate prepared using the composition of this invention retains over 90% of its copper foil peel strength after aging at 85℃ / 85% relative humidity for 1000 hours, far exceeding the typically less than 60% level in existing technologies.

[0071] By pre-polymerizing bismaleimide resin with diallyl bisphenol A curing agent in a controlled manner to form a low-molecular-weight soluble prepolymer, the composition can be completely dissolved in low-toxicity, low-cost conventional solvents such as acetone and methyl ethyl ketone at room temperature, forming a clear resin solution with a solid content of not less than 50%. This not only avoids the use of highly toxic solvents such as DMF and DMAc from the source, reducing environmental and health risks, but also, due to the low boiling point of acetone, it can be quickly removed at lower temperatures during the preparation of prepreg, effectively reducing bubble defects. The resin content fluctuation can be controlled within 3%, significantly improving production efficiency and product qualification rate.

[0072] Through the synergistic combination of alicyclic groups and fluorinated substituents in bismaleimide resin, and the optimized functional group ratio, the inherent high heat resistance (glass transition temperature T0) of BMI resin is maintained. g While achieving a temperature of ≥250℃, it also achieves excellent dielectric properties and low water absorption. The copper-clad laminate prepared using the composition of this invention exhibits a dielectric loss factor D at a frequency of 10 GHz. f It can achieve a dielectric constant as low as 0.0018, a water absorption rate of less than 0.15%, and an initial copper foil peel strength of more than 1.5 N / mm, realizing a synergistic improvement of multiple performance characteristics such as low dielectric loss, high heat resistance, high peel strength and low water absorption.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A modified polyimide resin composition, characterized in that, It contains the following components: Bismaleimide resin, 100 parts by weight; Diallyl bisphenol A curing agent, 30-60 parts by weight; Copper foil interface modifier, 2-5 parts by weight; Latent curing accelerator, 0.1-1 parts by weight; and Inorganic filler, 0-30 parts by weight; The main active ingredient of the copper foil interface modifier is a monofunctional maleimide containing a benzimidazole structure. Its molecule contains only one maleimide double bond and one benzimidazole group. The benzimidazole group is connected to the nitrogen atom of the maleimide through a methylene or ether bond. The bismaleimide resin is pre-reacted with diallyl bisphenol A curing agent to form a soluble prepolymer, which is dissolved in acetone at 25°C to form a clear solution with a solid content of not less than 50%.

2. The modified polyimide resin composition according to claim 1, characterized in that, The bismaleimide resin is a mixture of a first bismaleimide containing an alicyclic group and a second bismaleimide containing a fluorinated substituent, wherein the molar ratio of the first bismaleimide to the second bismaleimide is 3:7 to 5:

5.

3. The modified polyimide resin composition according to claim 1, characterized in that, The ratio of the amount of allyl group in the diallyl bisphenol A curing agent to the amount of maleimide group in the bismaleimide resin is 0.9:1 to 1.1:

1.

4. The modified polyimide resin composition according to claim 1, characterized in that, The monofunctional maleimide containing a benzimidazole structure is N-(2-benzimidazolylmethyl)maleimide, with a purity ≥98%.

5. The modified polyimide resin composition according to claim 1, characterized in that, The latent curing accelerator is 2-ethyl-4-methylimidazole encapsulated in microcapsules, with a DSC peak exothermic temperature of 160℃-180℃.

6. The modified polyimide resin composition according to claim 1, characterized in that, The inorganic filler is selected from one or more of spherical silica, alumina, and boron nitride, with an average particle size of 0.1 μm-5 μm.

7. A method for preparing a modified polyimide resin composition according to any one of claims 1-6, characterized in that, Includes the following steps: (1) The bismaleimide resin, diallyl bisphenol A curing agent and copper foil interface modifier are mixed and prepolymerized at 120-140°C for 30-60 minutes to form a soluble prepolymer. (2) Cool the prepolymer obtained in step (1) to room temperature, add the latent curing accelerator and inorganic filler, and stir until uniform; (3) Dissolve the mixture obtained in step (2) in acetone to prepare a resin solution with a solid content of 50-60%, thereby obtaining the modified bismaleimide resin composition.

8. The method for preparing the modified polyimide resin composition according to claim 7, characterized in that, The temperature of the prepolymerization reaction in step (1) is 130-135℃ and the time is 40-50 minutes.

9. The method for preparing the modified polyimide resin composition according to claim 7, characterized in that, The resin solution mentioned in step (3) is used to impregnate the surface-modified glass fiber cloth to prepare copper-clad laminate; the surface-modified glass fiber cloth is a glass fiber cloth grafted with N-phenylmaleimide after being primed with silane coupling agent.

10. The method for preparing the modified polyimide resin composition according to claim 9, characterized in that, The surface-modified glass fiber cloth is prepared by the following method: a. Dissolve γ-methacryloxypropyltrimethoxysilane in an ethanol-water mixture to prepare a silane treatment solution with a mass concentration of 0.5-2%, adjust the pH value to 4-5, and hydrolyze for 30 minutes. b. Immerse the fiberglass cloth in the silane treatment solution for 5-10 minutes, then remove it and dry it at 120°C for 15 minutes. c. Dissolve N-phenylmaleimide in acetone to prepare an N-phenylmaleimide treatment solution with a mass concentration of 3-8%; d. Immerse the silane-treated glass fiber cloth in the N-phenylmaleimide treatment solution for 5-15 minutes. e. Take out the glass fiber cloth and dry it at 120-150℃ for 10-20 minutes to obtain the surface-modified glass fiber cloth.

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