High-temperature-resistant low-dielectric bismaleimide adhesive

Abstract

The invention belongs to the field of advanced functional materials, and particularly relates to a high-temperature-resistant low-dielectric bismaleimide adhesive as well as a preparation method and application thereof. The adhesive is composed of maleic anhydride terminated polyimide resin, a catalyst and aminated polyimide microspheres. Wherein the polyimide resin and the polyimide microspheres have good compatibility, and polar carboxyl side groups in the maleic anhydride-terminated polyimide resin can react with amino groups on the surfaces of the aminated polyimide microspheres under the action of a catalyst to form strong interface compounding, so that uniform dispersion of the porous microspheres is facilitated; therefore, the dielectric constant of the adhesive is reduced; meanwhile, a micro-cross-linked structure formed by the rigid porous microspheres in a cured product can effectively improve the heat-resistant stability of the adhesive, the problem that a traditional modification method is difficult to realize cooperative regulation and control of high temperature resistance and low dielectric constant is solved, and the adhesive has a good application prospect in the fields of chip packaging, information communication and the like.

Description

Technical Field

[0001] This application belongs to the field of advanced functional materials, and specifically relates to a high-temperature resistant, low-dielectric bismaleimide adhesive, its preparation method, and its application. Background Technology

[0002] Bismaleimide adhesives are a class of high-performance adhesives with maleic anhydride as the end-cap unit. Due to their outstanding high-temperature resistance, excellent corrosion resistance, good physical and chemical stability, and excellent electrical insulation and adhesive properties, they have become one of the important types of high-performance adhesives. These properties enable their widespread application in semiconductor packaging, microelectronics, and aerospace composite materials. Today, with the continuous improvement of the integration level of microelectronics technology, higher requirements are placed on the dielectric properties of these adhesives; furthermore, their high-temperature stability is also an important evaluation indicator when applied to harsh environments such as high temperatures.

[0003] Traditional bismaleimide adhesives primarily form a cross-linked network structure through the high-temperature curing reaction of maleic anhydride, with a dielectric constant typically between 3.8 and 3.5, which is increasingly insufficient to meet the application requirements of semiconductor packaging and microelectronics. Therefore, the development of bismaleimide adhesives with low dielectric properties has become a hot topic in this field in recent years. Traditional methods for reducing the dielectric constant of maleimide adhesives mainly involve introducing bulky side groups, flexible structural groups (ether bonds, ester bonds, methylene groups, etc.), and low-polarity fluorine (-F, -CF3, etc.) into the system. However, the introduction of these units often sacrifices the excellent thermal stability of the bismaleimide adhesive itself, especially the introduction of units such as fluorine, which can lead to a decrease in the adhesive's bonding performance. Therefore, how to prepare bismaleimide adhesives with excellent adhesion, low dielectric properties, and high-temperature resistance through macromolecular structure design and relatively simple processes is a crucial foundation for expanding the applications of this type of material and meeting the increasingly demanding needs of different fields. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a bismaleimide adhesive that combines low dielectric properties, high adhesion, and excellent high-temperature resistance.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: In a first aspect, a bismaleimide adhesive comprises: a maleic anhydride-terminated polyimide resin, aminated polyimide microspheres, and an initiator; The preparation method of the maleic anhydride-terminated polyimide resin is to obtain an amino-terminated prepolymer by condensation reaction of dianhydride monomer and diamine monomer, and then by end-capping reaction with maleic anhydride. The dianhydride monomer is selected from one or more of the following: 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA), hexafluorodianhydride (6FDA), bisphenol A type diether dianhydride (BPADA), 3,3,4,4-diphenyl sulfone tetracarboxylic dianhydride (DSDA), and cyclobutane tetracarboxylic dianhydride (CBDA); Preferably, the dianhydride monomer is selected from hexafluorodianhydride (6FDA), bisphenol A diether dianhydride (BPADA), and cyclobutanetetracarboxylic dianhydride (CBDA). The diamine monomer is selected from aromatic diamines containing carboxylic acids; Preferably, the carboxylic acid-containing aromatic diamine is selected from 3,5-diaminobenzoic acid or 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid; Preferably, the molar ratio of dianhydride monomer to diamine monomer in the condensation reaction is 1:(1.1-1.2).

[0006] Aminated polyimide microspheres are synthesized from aromatic dianhydrides and trifunctional aromatic amines via a hydrothermal method. Preferably, the aromatic dianhydride is selected from biphenyltetracarboxylic dianhydride or pyromellitic dianhydride; Preferably, the trifunctional aromatic amine is selected from either 1,3,5-tris(4-aminophenoxy)benzene or 1,3,5-triaminobenzene; Preferably, the aminated polyimide microspheres are synthesized by a hydrothermal method from equimolar amounts of aromatic dianhydride and trifunctional aromatic amine; Preferably, the specific steps of the hydrothermal method are as follows: dissolve equimolar amounts of aromatic dianhydride and trifunctional aromatic amine in a polar aprotic solvent, stir at room temperature for 12-24 hours, then react at 150-200°C for 1-12 hours under sealed conditions, cool to room temperature, filter and wash to obtain aminated polyimide microspheres.

[0007] More preferably, the specific steps of the hydrothermal method are as follows: dissolve equimolar amounts of aromatic dianhydride and trifunctional aromatic amine in a polar aprotic solvent, stir at room temperature for 12-18 hours, then react at 150-200°C for 5-10 hours under sealed conditions, cool to room temperature, filter and wash to obtain amino-modified polyimide microspheres.

[0008] Preferably, the polar aprotic solvent is selected from one or more combinations of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), sulfolane, 1,4-dioxane and tetrahydrofuran; Preferably, the polar aprotic solvent is selected from one or more combinations of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc); Preferably, the average diameter of the aminated polyimide microspheres is 5-20 μm.

[0009] The initiator is selected from organic peroxide initiators; Preferably, the organic peroxide initiator is selected from any one or a combination of tert-butyl hydroperoxide, peroxyacetone, peroxyacid, methyl ethyl ketone peroxide, benzoyl peroxide, cyclohexanone peroxide, and cumene hydroperoxide. Preferably, the organic peroxide initiator is selected from methyl ethyl ketone peroxide.

[0010] Based on the total mass of the adhesive, the initiator added is (2-5) wt% of the bismaleimide adhesive, and the amino-modified polyimide microspheres added are (3-8) wt% of the bismaleimide adhesive.

[0011] Maleic anhydride-terminated polyimide resin, aminated polyimide microspheres and initiator; Secondly, the preparation method of the bismaleimide adhesive mentioned above includes: dispersing maleic anhydride-terminated polyimide resin and aminated polyimide microspheres in a low-boiling-point solvent, adding an initiator to the solution, and preparing a bismaleimide adhesive solution by stirring and dissolving.

[0012] The boiling point of the low-boiling solvent does not exceed 80°C; Preferably, the low-boiling-point solvent is selected from either tetrahydrofuran or ethyl acetate.

[0013] Preferably, the stirring and dissolving time is 1-60 minutes; Preferably, vacuum degassing is performed during the stirring and dissolving process.

[0014] Furthermore, the preparation method of the maleic anhydride-terminated polyimide resin specifically includes the following steps: S1. Under nitrogen protection, the dianhydride monomer and the diamine monomer are dissolved in a polar aprotic solvent and stirred at room temperature for 12-24 h to obtain a viscous solution. S2. Increase the temperature to 180-200℃ and react under nitrogen protection for 12-18 h to synthesize amino-terminated polyimide; S3. Under nitrogen protection, maleic anhydride is added to the amino-terminated polyimide synthesized in step S2, and the mixture is stirred at room temperature for 12-24 h to obtain a viscous solution. The polymer solution is then heated to 180-200℃ and reacted under nitrogen protection for 12-18 h to synthesize maleic anhydride-terminated polyimide resin. S4. Pour the maleic anhydride-terminated polyimide resin synthesized in step S3 into an ethanol solvent to precipitate the resin. After washing with deionized water and drying, the maleic anhydride-terminated polyimide resin is obtained.

[0015] Preferably, the polar aprotic solvent is selected from one or more combinations of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), sulfolane, 1,4-dioxane and tetrahydrofuran; Preferably, the polar aprotic solvent is selected from one or more combinations of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc); Preferably, in step S3, the molar amount of maleic anhydride is twice the molar amount of polyimide.

[0016] Thirdly, the bismaleimide adhesive cured product is obtained by curing the bismaleimide adhesive described above at room temperature to 120°C. Preferably, the bismaleimide adhesive cured product is obtained by curing the above-described bismaleimide adhesive at 50-120°C; Preferably, the cured bismaleimide adhesive has a curing time of 1-10°C. 6 The dielectric constant within Hz is ≤3; Preferably, the dielectric loss of the cured bismaleimide adhesive is ≤0.005. Preferably, the glass transition temperature of the cured bismaleimide adhesive is ≥380°C; Preferably, the initial decomposition temperature of the bismaleimide adhesive cured product under a nitrogen atmosphere is ≥520℃; Preferably, the peel strength of the cured bismaleimide adhesive to copper foil is not less than 3.8 N / cm.

[0017] Fourthly, the above-mentioned bismaleimide adhesive and bismaleimide adhesive cured products are used in the fields of chip packaging and information communication.

[0018] The beneficial effects of the above-mentioned technical solution proposed in this application are as follows: an amino-terminated prepolymer is synthesized by using a carboxylic acid aromatic diamine monomer and a dianhydride monomer, and then reacted with maleic anhydride to synthesize a maleic anhydride-terminated polyimide resin. The resin is then used in combination with aminated polyimide microspheres, and a dense cross-linked network is formed between the amino and carboxyl groups through intermolecular interactions. At the same time, an organic peroxide initiator is selected to cure the bismaleimide adhesive at low temperature to obtain a cured bismaleimide adhesive.

[0019] Bismaleimide adhesive cured products have lower dielectric constants and lowest dielectric losses, effectively reducing material polarization capabilities. They are more suitable for high-frequency, low-loss electronic packaging applications, exhibit stronger adhesion to metals such as copper foil, and have better high-temperature resistance and excellent dimensional stability at high temperatures. Attached Figure Description

[0020] Figure 1 SEM image of the synthesized aminated polyimide microspheres in Example 1; Figure 2 Cross-sectional SEM image of the cured bismaleimide adhesive prepared in Example 1; Figure 3 Example 1: Comparison of dielectric constants of Example 1 with 3 wt% polyimide microspheres and Comparative Example 1 without microsphere binder. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention. It should be noted that the terminology used herein is only for describing specific implementation methods and is not intended to limit the exemplary implementation methods according to the present invention.

[0022] Unless otherwise specified, the experimental conditions used in the examples are generally in accordance with conventional conditions in the art or the conditions recommended by the reagent company. Unless otherwise specified, the materials and reagents used in the examples can be purchased commercially.

[0023] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings: The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0024] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0025] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0026] In this application, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions containing the listed features.

[0027] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0028] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0029] In this application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass-volume percentage.

[0030] All references to documents mentioned in this application are incorporated herein by reference as if each document were individually incorporated herein by reference. Unless they conflict with the inventive purpose and / or technical solution of this application, all cited documents are incorporated herein by reference in their entirety and for all purposes. When citing documents in this application, the definitions of relevant technical features, terms, nouns, phrases, etc., are also incorporated herein by reference. When citing documents in this application, examples and preferred embodiments of the cited technical features may also be incorporated herein by reference, but only to the extent that they enable the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, this application shall prevail or modifications shall be made adaptably to the description in this application.

[0031] In the embodiments of this invention, the dianhydride and diamine monomers were purchased from Tianjin Zhongtai Materials Technology Co., Ltd., the triamine monomers and solvents were purchased from Sinopharm Group, and the peroxide catalysts were purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0032] The bonding performance was tested by the lap shear test (GB / T 33334-2016), with a tensile rate of 50 mm·min. -1 .

[0033] The dielectric constant was measured using a Novocontrol concept 80 broadband dielectric spectrometer with a frequency range of 1-10. 6 Hz, test temperature is 30℃.

[0034] The glass transition temperature was tested using a Q800 DMA device, with a temperature range of 25-500℃.

[0035] The initial decomposition temperature was measured using a Netzsch TG 309 Libra Classic thermogravimetric analyzer, with a temperature range of 30-800℃, and the test atmosphere was nitrogen.

[0036] The peel strength between the bismaleimide adhesive and the copper foil was tested according to the standard GB / T 2790-1995.

[0037] Example 1 Under nitrogen protection, 6FDA and 3,5-diaminobenzoic acid were co-dissolved in N-methylpyrrolidone solvent, with the molar ratio of 6FDA to 3,5-diaminobenzoic acid controlled at 1:1.1 and the reactant mass fraction at 10 wt%. The mixture was stirred at room temperature for 12-24 h to obtain a viscous solution. The polymer solution was then heated to 180-200 °C and reacted under nitrogen protection for 12-18 h to synthesize amino-terminated polyimide. An appropriate amount of maleic anhydride was added to the above polymer solution, with the molar amount of maleic anhydride controlled at twice that of polyimide. The mixture was stirred at room temperature for 12 h to obtain a viscous solution. The solution was then heated to 180 °C and reacted under nitrogen protection for 12 h to synthesize a maleic anhydride-terminated polyimide solution. Under nitrogen protection, equimolar amounts of biphenyl dianhydride and 1,3,5-tris(4-aminophenoxy)benzene were dissolved in N,N-dimethylformamide solvent and reacted with stirring at room temperature for 12 h. The reaction solution was then transferred to an autoclave and reacted at 180°C for 5 h under sealed conditions to synthesize aminated polyimide microspheres. After cooling to room temperature, the microspheres were filtered, washed, and dried for later use. 3% of the aminated polyimide microspheres, 2% of methyl ethyl ketone peroxide, and maleic anhydride-terminated polyimide resin were dissolved in tetrahydrofuran solvent, with the solid mass fraction controlled at 10-20 wt%, and stirred thoroughly at room temperature to prepare a bismaleimide adhesive.

[0038] Example 2 Under nitrogen protection, BPADA and 3,5-diaminobenzoic acid were co-dissolved in N-methylpyrrolidone solvent, with the molar ratio of BPADA to 3,5-diaminobenzoic acid controlled at 1:1.1 and the reactant mass fraction at 10 wt%. The mixture was stirred at room temperature for 12-24 h to obtain a viscous solution. The polymer solution was then heated to 180-200 °C and reacted under nitrogen protection for 12-18 h to synthesize amino-terminated polyimide. An appropriate amount of maleic anhydride was added to the above polymer solution, with the molar amount of maleic anhydride controlled at twice that of polyimide. The mixture was stirred at room temperature for 12 h to obtain a viscous solution. The solution was then heated to 180 °C and reacted under nitrogen protection for 12 h to synthesize a maleic anhydride-terminated polyimide solution. Under nitrogen protection, equimolar amounts of biphenyl dianhydride and 1,3,5-triaminobenzene were dissolved in N,N-dimethylformamide solvent and reacted with stirring at room temperature for 12 h. The reaction solution was then transferred to an autoclave and reacted at 180 °C for 5 h under sealed conditions to synthesize aminated polyimide microspheres. After cooling to room temperature, the microspheres were filtered, washed, and dried for later use. 3% of the aminated polyimide microspheres, 2% of methyl ethyl ketone peroxide, and maleic anhydride-terminated polyimide resin were dissolved in tetrahydrofuran solvent, with the solid mass fraction controlled at 10-20 wt%, and stirred thoroughly at room temperature to prepare a bismaleimide adhesive.

[0039] Example 3 CBDA and 3,5-diaminobenzoic acid were co-dissolved in N-methylpyrrolidone solvent under nitrogen protection, with the molar ratio of CBDA to 3,5-diaminobenzoic acid controlled at 1:1.1 and the reactant mass fraction at 10 wt%. The mixture was stirred at room temperature for 12-24 h to obtain a viscous solution. The polymer solution was then heated to 180-200 °C and reacted under nitrogen protection for 12-18 h to synthesize amino-terminated polyimide. An appropriate amount of maleic anhydride was added to the above polymer solution, with the molar amount of maleic anhydride controlled at twice that of the polyimide. The mixture was stirred at room temperature for 12 h to obtain a viscous solution. The solution was then heated to 180 °C and reacted under nitrogen protection for 12 h to synthesize a maleic anhydride-terminated polyimide solution. Under nitrogen protection, equimolar amounts of biphenyl dianhydride and 1,3,5-tris(4-aminophenoxy)benzene were dissolved in N,N-dimethylformamide solvent and reacted with stirring at room temperature for 12 h. The reaction solution was then transferred to an autoclave and reacted at 180 °C for 5 h under sealed conditions to synthesize aminated polyimide microspheres. After cooling to room temperature, the microspheres were filtered, washed, and dried for later use. 3% of the aminated polyimide microspheres, 2% of methyl ethyl ketone peroxide, and maleic anhydride-terminated polyimide resin were dissolved in tetrahydrofuran solvent, with the solid mass fraction controlled at 10-20 wt%, and stirred thoroughly at room temperature to prepare a bismaleimide adhesive.

[0040] Example 4 Under nitrogen protection, 6FDA and 3,5-diaminobenzoic acid were co-dissolved in N-methylpyrrolidone solvent, with the molar ratio of 6FDA to 3,5-diaminobenzoic acid controlled at 1:1.1 and the reactant mass fraction at 10 wt%. The mixture was stirred at room temperature for 12-24 h to obtain a viscous solution. The polymer solution was then heated to 180-200 °C and reacted under nitrogen protection for 12-18 h to synthesize amino-terminated polyimide. An appropriate amount of maleic anhydride was added to the above polymer solution, with the molar amount of maleic anhydride controlled at twice that of polyimide. The mixture was stirred at room temperature for 12 h to obtain a viscous solution. The solution was then heated to 180 °C and reacted under nitrogen protection for 12 h to synthesize a maleic anhydride-terminated polyimide solution. Under nitrogen protection, equimolar amounts of biphenyl dianhydride and 1,3,5-triaminobenzene were dissolved in N,N-dimethylformamide solvent and reacted with stirring at room temperature for 12 h. The reaction solution was then transferred to an autoclave and reacted at 180 °C for 5 h under sealed conditions to synthesize aminated polyimide microspheres. After cooling to room temperature, the microspheres were filtered, washed, and dried for later use. 3% of the aminated polyimide microspheres, 2% of methyl ethyl ketone peroxide, and maleic anhydride-terminated polyimide resin were dissolved in tetrahydrofuran solvent, with the solid mass fraction controlled at 10-20 wt%, and stirred thoroughly at room temperature to prepare a bismaleimide adhesive.

[0041] Comparative Example 1 Under nitrogen protection, 6FDA and 3,5-diaminobenzoic acid were co-dissolved in N-methylpyrrolidone solvent, with the molar ratio of 6FDA to 3,5-diaminobenzoic acid controlled at 1:1.1 and the reactant mass fraction at 10 wt%. The mixture was stirred at room temperature for 12-24 h to obtain a viscous solution. The polymer solution was then heated to 180-200 °C and reacted under nitrogen protection for 12-18 h to synthesize amino-terminated polyimide. An appropriate amount of maleic anhydride was added to the above polymer solution, with the molar amount of maleic anhydride controlled at twice that of polyimide. The mixture was stirred at room temperature for 12 h to obtain a viscous solution. The solution was then heated to 180 °C and reacted under nitrogen protection for 12 h to synthesize a maleic anhydride-terminated polyimide solution. Maleic anhydride-terminated polyimide resin was dissolved in tetrahydrofuran solvent, and the solid mass fraction was controlled at 10-20 wt% and stirred thoroughly at room temperature to prepare a bismaleimide adhesive.

[0042] Comparative Example 2 Under nitrogen protection, 6FDA and 3,5-diaminobenzoic acid were co-dissolved in N-methylpyrrolidone solvent, with the molar ratio of 6FDA to 3,5-diaminobenzoic acid controlled at 1:1.1 and the reactant mass fraction at 10 wt%. The mixture was stirred at room temperature for 12-24 h to obtain a viscous solution. The polymer solution was then heated to 180-200 °C and reacted under nitrogen protection for 12-18 h to synthesize amino-terminated polyimide. An appropriate amount of maleic anhydride was added to the above polymer solution, with the molar amount of maleic anhydride controlled at twice that of polyimide. The mixture was stirred at room temperature for 12 h to obtain a viscous solution. The solution was then heated to 180 °C and reacted under nitrogen protection for 12 h to synthesize a maleic anhydride-terminated polyimide solution. Under nitrogen protection, equimolar amounts of biphenyl dianhydride and 4,4-diaminodiphenyl ether (ODA) were dissolved in N,N-dimethylformamide solvent and reacted with stirring at room temperature for 12 h. The reaction solution was then transferred to an autoclave and reacted at 180 °C for 5 h under sealed conditions to synthesize amino-free polyimide microspheres. After cooling to room temperature, the microspheres were filtered, washed, and dried for later use. 3% amino-free polyimide microspheres, 2% methyl ethyl ketone peroxide, and maleic anhydride-terminated polyimide resin were dissolved in tetrahydrofuran solvent, with the solid mass fraction controlled at 10-20 wt%, and stirred thoroughly at room temperature to prepare a bismaleimide adhesive.

[0043] The bismaleimide adhesive solutions prepared in Examples 1-4 and Comparative Examples 1-2 were coated onto aluminum foil, dried at 60°C for 2 hours, and then heated to 80°C for 1 hour to obtain a cured layer with a dry film thickness of (25±2) μm.

[0044] The performance of the bismaleimide adhesives prepared in Examples 1-4 and Comparative Examples 1-2 is listed in Table 1.

[0045] Table 1

[0046] right Figure 1 Analysis of the experimental data recorded in the paper showed that the dielectric constant and dielectric loss of Examples 1-4 were lower than those of the comparative examples. Among them, Example 3 had the lowest dielectric constant and dielectric loss, indicating that the introduction of aminated microspheres effectively reduced the polarization ability of the material and made it more suitable for high-frequency, low-loss electronic packaging.

[0047] The peel strength of Examples 1-4 was significantly higher than that of Comparative Examples 1-2, with Example 2 exhibiting the highest peel strength to copper foil. This is because the amino groups on the surface of the microspheres and the carbonyl groups (C=O) in the bismaleimide resin interact through hydrogen bonds and other means to enhance cohesion. Simultaneously, the aminated microspheres also strengthen the bonding force at the resin-metal interface.

[0048] Analysis of thermal properties revealed that the glass transition temperature of Examples 1-4 was significantly increased, which is beneficial to dimensional stability at high temperatures. It also showed that the addition of microspheres did not sacrifice the thermal stability of the bismaleimide adhesive, but instead delayed thermal decomposition.

[0049] Comparative Example 1 did not add microspheres, while Comparative Example 2 synthesized non-amino modified microspheres. The bismaleimide adhesive prepared in this way had higher dielectric constant and dielectric loss, significantly lower peel strength to copper foil, and a lower glass transition temperature. This indicates that the introduction of amino-modified polyimide microspheres can simultaneously improve adhesion, dielectric properties, and thermal stability through interfacial enhancement and crosslinking effects.

[0050] Finally, it should be noted that the above-described embodiments are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be pointed out that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Furthermore, it should be understood that after reading the above teachings of this application, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the scope of protection of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A bismaleimide adhesive, characterized in that, Bismaleimide adhesives include: maleic anhydride-terminated polyimide resin, aminated polyimide microspheres, and initiators; The preparation method of the maleic anhydride-terminated polyimide resin is to obtain an amino-terminated prepolymer by condensation reaction of dianhydride monomer and diamine monomer, and then by end-capping reaction with maleic anhydride. The dianhydride monomer is selected from one or more combinations of 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, hexafluoro dianhydride, bisphenol A type diether dianhydride, 3,3,4,4-diphenyl sulfone tetracarboxylic dianhydride and cyclobutane tetracarboxylic dianhydride. The diamine monomer is selected from aromatic diamines containing carboxylic acids; The aminated polyimide microspheres are synthesized from aromatic dianhydrides and trifunctional aromatic amines via a hydrothermal method. The initiator is selected from organic peroxide initiators; Based on the total mass of the adhesive, the initiator added is (2-5) wt% of the bismaleimide adhesive, and the amino-modified polyimide microspheres added are (3-8) wt% of the bismaleimide adhesive.

2. The bismaleimide adhesive according to claim 1, characterized in that, The specific steps of the hydrothermal method are as follows: dissolve equimolar amounts of aromatic dianhydride and trifunctional aromatic amine in a polar aprotic solvent, stir at room temperature for 12-24 hours, then react at 150-200℃ for 1-12 hours under sealed conditions, cool to room temperature, filter and wash to obtain amino-modified polyimide microspheres. And / or, the aromatic dianhydride is selected from biphenyltetracarboxylic dianhydride or pyromellitic dianhydride; And / or, the trifunctional aromatic amine is selected from any one of 1,3,5-tris(4-aminophenoxy)benzene or 1,3,5-triaminobenzene.

3. The bismaleimide adhesive according to claim 2, characterized in that, The polar aprotic solvent is selected from one or more combinations of N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,4-dioxane, and tetrahydrofuran.

4. The bismaleimide adhesive according to claim 1, characterized in that, The carboxylic acid-containing aromatic diamine is selected from 3,5-diaminobenzoic acid or 4,4'-diaminobiphenyl-2,2'-dicarboxylic acid; And / or, the average diameter of the aminated polyimide microspheres is 5-20 μm; And / or, the organic peroxide initiator is selected from any one or more combinations of tert-butyl hydroperoxide, peroxyacetone, peroxyacid, methyl ethyl ketone peroxide, benzoyl peroxide, cyclohexanone peroxide, and cumene hydroperoxide.

5. The bismaleimide adhesive according to claim 1, characterized in that, The organic peroxide initiator is selected from methyl ethyl ketone peroxide.

6. A method for preparing the bismaleimide adhesive as described in any one of claims 1-5, characterized in that, Maleic anhydride-terminated polyimide resin, aminated polyimide microspheres and initiator are dispersed in a low-boiling-point solvent, and initiator is added to the solution. After stirring and dissolving, a bismaleimide adhesive solution is prepared. The boiling point of the low-boiling solvent does not exceed 80°C.

7. The method for preparing the bismaleimide adhesive according to claim 6, characterized in that, The low-boiling-point solvent is selected from either tetrahydrofuran or ethyl acetate; And / or, the stirring and dissolving time is 1-60 minutes; And / or, vacuum degassing is performed during the stirring and dissolving process.

8. A cured bismaleimide adhesive, characterized in that, It is obtained by curing the bismaleimide adhesive according to any one of claims 1-5 at room temperature to 120°C.

9. The cured bismaleimide adhesive according to claim 8, characterized in that, The bismaleimide adhesive cured product is at 1-10 6 The dielectric constant within Hz is ≤3; And / or, the dielectric loss of the cured bismaleimide adhesive is ≤0.005; And / or, the glass transition temperature of the cured bismaleimide adhesive is ≥380°C; And / or, the initial decomposition temperature of the bismaleimide adhesive cured product under a nitrogen atmosphere is ≥520°C; And / or, the peel strength of the cured bismaleimide adhesive to copper foil is not less than 3.8 N / cm.

10. The application of the bismaleimide adhesive as described in any one of claims 1-5 and the cured bismaleimide adhesive as described in any one of claims 8-9 in the fields of chip packaging and information communication.

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