Low-dielectric polyimide film material as well as preparation method and application thereof

Abstract

The invention discloses a low-dielectric polyimide film material and a preparation method and application thereof, and relates to the technical field of film material preparation, and the molecular structure of a polyimide copolymer in the polyimide film material comprises structural units shown in general formulas (1) and (2), the polyimide copolymer comprises aromatic ether, fluorine atoms or fluorine-containing groups and siloxane units, at least one of C and D in the structural units contains fluorine atoms or fluorine-containing groups, and the molar ratio of the content of the copolymerization components x: y: z is (1-90%): (1-50%): (1-30%). According to the preparation method, a batch feeding synthesis mode is adopted, molecular chain growth of polyamide acid is controlled through the feeding ratio, the salt forming effect of silicon-containing diamine and polyamide acid is avoided, and high-molecular-weight polyimide is obtained. The polyimide film prepared by the method has the characteristics of low dielectric constant and dielectric loss, low water absorption, good adhesion and the like, and can be applied to the fields of high-frequency and high-speed integrated circuits and the like.

Description

Technical Field

[0001] The present invention relates to a film material, a preparation method and an application thereof, and in particular to a low-dielectric polyimide film material, a preparation method and an application thereof. Background Art

[0002] In integrated circuit and microelectronic packaging applications, substrate and dielectric materials with low dielectric constants and low dielectric loss factors are often required to improve circuit signal transmission speeds and reduce signal transmission delays, crosstalk, and parasitic resistance effects between metal layers. With the miniaturization and high integration of electronic devices and the increasing speed of signal transmission, especially with the increasing popularity of fifth-generation mobile communications (5G), the delay time and transmission loss of signals between devices and wires have increased significantly. This delay time is directly related to the dielectric constant (Dk) and dielectric loss factor (Df) of the substrate medium. Generally speaking, signal transmission rate is inversely proportional to the square root of the dielectric constant of the material. High dielectric constants can easily cause signal transmission delays, while dielectric loss primarily affects signal transmission quality. Lower dielectric loss results in lower signal loss. Therefore, the increasing frequency of electronic devices (frequencies > 1 GHz) increasingly requires materials with low dielectric constants and dielectric loss factors.

[0003] Currently, fluorine-based resins such as polytetrafluoroethylene (PTFE) and liquid crystal polymer (LCP) are commonly used in high-frequency circuit board substrates. These materials share excellent dielectric properties and low water absorption at high frequencies, but their disadvantages include insufficient heat resistance, poor machinability, and weak adhesion to copper foil. Polyimide (PI), due to its high mechanical strength, excellent thermal stability, outstanding insulation properties, and chemical resistance, is widely used in flexible circuit boards, microelectronics, aerospace, and other fields, serving as a key flexible substrate and interlayer insulation material. Traditional polyimide film materials typically have a dielectric constant above 3.0, a high dielectric loss factor at high frequencies, and high water absorption (>2%), far from meeting the development needs of the integrated circuit and microelectronics industries. Therefore, reducing the dielectric constant, dielectric loss, and water absorption are key goals in the application of polyimide film. Furthermore, as a substrate material for multilayer flexible circuit boards, polyimide film requires bonding and lamination with copper foil. Good adhesion greatly facilitates interfacial bonding and helps mitigate the impact of interface roughness on signal transmission loss. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a low-dielectric polyimide film material having low dielectric constant and dielectric loss, low water absorption, and good adhesion; another purpose of the present invention is to provide a method for preparing a low-dielectric polyimide film material with high adjustability; another purpose of the present invention is to provide an application of the low-dielectric polyimide film material in integrated circuits, electronics or microelectronics.

[0005] In order to achieve the above technical objectives and meet the above technical requirements, the technical solution adopted by the present invention is: a low dielectric polyimide film material, the polyimide film material includes a polyimide copolymer, the polyimide copolymer includes aromatic ether, fluorine atoms or fluorine-containing groups, and siloxane units, and the structure of the polyimide copolymer includes structural units represented by general formula (1) and general formula (2): (1) (2) The molar ratio of the copolymer components in general formula (1) and (2) is (1-90%): (1-50%): (1-30%). The molar ratio of the copolymer components has two effects: on the one hand, it helps to maintain a high content of hydrophobic fluorine atoms or fluorine-containing groups and siloxane structures in the molecular structure of the polyimide film, thereby reducing the water absorption rate of the film; on the other hand, the polyimide main chain contains a certain amount of flexible aromatic ether and siloxane structure, which effectively improves the dielectric properties of the film at high frequencies. Unit A is a structural unit formed from an aromatic or alicyclic tetracarboxylic dianhydride; Unit B is a structural unit formed from an aromatic or alicyclic diamine; at least one of C and D contains a fluorine atom or a fluorine-containing group, and C is selected from a hydrogen atom, a methyl group, an ethyl group, a propyl group, a fluorine atom, and a trifluoromethyl group; and D is selected from one of the following structural groups: .

[0006] Furthermore, the tetracarboxylic dianhydride component in the A unit is selected from the group consisting of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyl ether dianhydride, 2,3,3',4-biphenyl ether dianhydride, 3,3',4,4'-biphenyl ketone dianhydride, 3,3',4,4'-biphenyl sulfone dianhydride, 2,2-diphenyl One or more of propane-3,3',4,4'-tetracarboxylic dianhydride, 1,4-diphenoxybenzene-3,3',4,4'-tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), cyclobutanetetracarboxylic dianhydride, hydrogenated pyromellitic dianhydride, and hydrogenated biphenyltetracarboxylic dianhydride.

[0007] Furthermore, the diamine component in the B unit is selected from the group consisting of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,4-bis(3'-aminophenoxy)benzene, 1,3-bis(3'-aminophenoxy)benzene, 1,3-bis(4'-aminophenoxy)benzene, 2,2'-bis(methyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, tetrafluoro-p-phenylenediamine, and one or more of 4,4'-diaminooctafluorobiphenyl.

[0008] Furthermore, the polyimide film has a glass transition temperature greater than 320° C., a dielectric constant less than or equal to 3.0 at 10 GHz, and a dielectric loss factor less than or equal to 0.005.

[0009] On the other hand, the method for preparing the polyimide film of the present invention comprises the following preparation steps: (1) adding aromatic diamine and aromatic ether-containing diamine to a first organic solvent, dissolving them, and then adding dianhydride at a first temperature; (2) then adding the silicon-containing diamine and the second organic solvent, and adding the dianhydride at the second temperature; (3) finally adding a capping agent and reacting at a third reaction temperature to obtain a capped polyamic acid solution; (4) The polyamic acid solution is coated to form a film, and then heated and dried to obtain a polyimide film.

[0010] Furthermore, in step (1), the general structural formula of the aromatic ether-containing diamine is as shown in (3): (3) At least one of C and D contains a fluorine atom or a fluorine-containing group. C is selected from a hydrogen atom, a methyl group, an ethyl group, a propyl group, a fluorine atom, or a trifluoromethyl group; and D is selected from one of the following structural groups: .

[0011] Preferably, the aromatic diamine is one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,4-bis(3'-aminophenoxy)benzene, 1,3-bis(3'-aminophenoxy)benzene, 1,3-bis(4'-aminophenoxy)benzene, 2,2'-bis(methyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, tetrafluoro-p-phenylenediamine, and 4,4'-diaminooctafluorobiphenyl.

[0012] Furthermore, in step (1) and / or (2), the dianhydride is pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyl ether dianhydride, 2,3,3',4-biphenyl ether dianhydride, 3,3',4,4'-biphenyl ketone dianhydride, 3,3',4,4'-biphenyl sulfone dianhydride, 2,2- One or more of phenylpropane-3,3',4,4'-tetracarboxylic dianhydride, 1,4-diphenoxybenzene-3,3',4,4'-tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), cyclobutanetetracarboxylic dianhydride, hydrogenated pyromellitic dianhydride, and hydrogenated biphenyltetracarboxylic dianhydride.

[0013] Furthermore, the total molar amount of dianhydride is the sum of the molar amounts of the aromatic diamine, aromatic ether-containing diamine, and silicon-containing diamine in steps (1) and (2), wherein the amount of dianhydride used in step (1) is 40% to 80% of the sum of the molar amounts of the aromatic diamine and aromatic ether-containing diamine; the amount of dianhydride used in step (2) is the remainder of the total amount of dianhydride; this end-capping method is beneficial to improving the adhesion between the polyimide film and materials such as copper foil. Excessive addition of the end-capping agent will affect the heat resistance of the film, while too little addition will affect the adhesion of the film.

[0014] Furthermore, in step (1) and / or (2), the first organic solvent and / or the second organic solvent is one or a mixture of N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran; wherein the mass ratio of the first organic solvent to the second organic solvent is (6-9): (1-4).

[0015] Furthermore, in step (1), the first reaction temperature is -5~15°C; in step (2), the second reaction temperature is 25~80°C; and in step (3), the third reaction temperature is 25~35°C.

[0016] Furthermore, in the preparation step (3), the end-capping agent is 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and the amount of the end-capping agent is 2% to 10% of the total molar amount of diamine or the total molar amount of dianhydride.

[0017] In another aspect, the present invention provides a use of a polyimide film in integrated circuits, electronics or microelectronics.

[0018] The present invention provides a method for preparing a polyimide film. The polyimide is first synthesized into a low-molecular-weight polyamic acid by using a diamine and a dianhydride in unequal molar ratios. A silicon-containing diamine and a dianhydride are then added to synthesize a high-molecular-weight polyamic acid, which is then end-capped with the silicon-containing diamine. The method employs a batch-feeding synthesis method, controls the molecular chain growth of the polyamic acid by adjusting the feed ratio, effectively improves the solubility of the precursor during the silicon-containing diamine reaction, avoids the salt-forming effect between the silicon-containing diamine and the polyamic acid, and solves the problem of difficulty in polycondensation of aliphatic diamines, ultimately producing a high-molecular-weight polyimide.

[0019] By varying the ratio of copolymer components, the present invention achieves low water absorption through a specific amount of hydrophobic fluorine and silicon, while the flexible aromatic ether and siloxane structures improve the film's dielectric properties at high frequencies. Furthermore, the introduction of the siloxane component and the capping of the molecular chains significantly enhance the film's adhesion, addressing the issues of traditional polyimide films such as high water absorption, high dielectric constant and dielectric loss, and poor adhesion.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) It has the characteristics of low dielectric constant and dielectric loss, low water absorption, good adhesion, etc. The dielectric constant at 10GHz is ≤3.0, the dielectric loss factor is ≤0.005, and the water absorption rate at 25℃ is <0.8%. It can be used in high-frequency and high-speed integrated circuits and other fields; (2) The preparation method is highly controllable. Through three-component copolymerization, aromatic ether, fluorine atoms or fluorine-containing groups, siloxane structures and other copolymer units are simultaneously introduced into the polyimide molecular structure, which can flexibly adjust the dielectric constant and dielectric loss, water absorption, adhesion, etc. of the film. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below.

[0022] Example 1: Preparation of polyimide PI-a film (1) Under nitrogen protection and at room temperature, 120.14 g (0.6 mol) of 4,4'-diaminodiphenyl ether and 151.33 g (0.3 mol) of 4,4'-bis([4-amino-2-trifluoromethyl]phenoxy)biphenyl were added to 2445 g of N,N-dimethylacetamide and stirred vigorously until dissolved; 98.15 g (0.45 mol) of 1,2,4,5-pyromellitic dianhydride was added at 0°C and stirred vigorously for 12 hours to obtain polyamic acid (PAA-1) with lower viscosity.

[0023] (2) At 35°C, 24.85 g (0.1 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 611 g of N,N-dimethylacetamide were added to the PAA-1 solution. After dissolution, 119.97 g (0.55 mol) of 1,2,4,5-pyromellitic dianhydride was added. The mixture was stirred vigorously and reacted for 12 hours to obtain a viscous polyamic acid (PAA-2).

[0024] (3) At room temperature, 24.85 g (0.1 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was added to the PAA-2 solution and the mixture was stirred vigorously for 8 hours to obtain an end-capped polyamic acid (PAA-3) with a viscosity of 186,000 centipoise at 25°C.

[0025] (4) The PAA-3 solution was evenly coated on a dry glass substrate and baked using the following procedure: 60°C / 1 hour, 120°C / 1 hour, 200°C / 1 hour, and 350°C / 1 hour. After cooling to room temperature, the glass plate was placed in water and peeled off to obtain a PI-a film.

[0026] Example 2: Preparation of polyimide PI-b film (1) Under nitrogen protection and at room temperature, 120.14 g (0.6 mol) of 4,4'-diaminodiphenyl ether and 50.44 g (0.1 mol) of 4,4'-bis([4-amino-2-trifluoromethyl]phenoxy)biphenyl were added to 392 g of N,N-dimethylacetamide and stirred vigorously until dissolved; 11.81 g (0.42 mol) of 1,2,4,5-pyromellitic dianhydride was added at 5°C and stirred vigorously for 12 hours to obtain polyamic acid (PAA-1) with lower viscosity.

[0027] (2) At 45°C, 74.55 g (0.3 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 1061 g of N,N-dimethylacetamide were added to the PAA-1 solution. After dissolution, 126.51 g (0.58 mol) of 1,2,4,5-pyromellitic dianhydride was added. The mixture was stirred vigorously for 12 hours to obtain a viscous polyamic acid (PAA-2).

[0028] (3) At room temperature, 4.97 g (0.02 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was added to the PAA-2 solution and the mixture was stirred vigorously for 10 hours to obtain an end-capped polyamic acid (PAA-3) with a viscosity of 123,000 centipoise at 25°C.

[0029] (4) The PAA-3 solution was evenly coated on a dry glass substrate and baked using the following procedure: 60°C / 1 hour, 120°C / 1 hour, 200°C / 1 hour, and 350°C / 1 hour. After cooling to room temperature, the glass plate was placed in water and peeled off to obtain the PI-b film.

[0030] Example 3: Preparation of polyimide PI-c film (1) Under nitrogen protection and at room temperature, 54.07 g (0.5 mol) of 1,4-p-phenylenediamine and 155.54 g (0.3 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane were added to 2484 g of N,N-dimethylacetamide and stirred vigorously until dissolved; at 10°C, 69.82 g (0.32 mol) of 1,2,4,5-pyromellitic dianhydride was added and stirred vigorously for 16 hours to obtain polyamic acid (PAA-1) with lower viscosity.

[0031] (2) At 45°C, 49.70 g (0.2 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 277 g of N,N-dimethylacetamide were added to the PAA-1 solution. After dissolution, 148.32 g (0.68 mol) of 1,2,4,5-pyromellitic dianhydride was added. The mixture was stirred vigorously and reacted for 20 hours to obtain a viscous polyamic acid (PAA-2).

[0032] (3) At room temperature, 9.94 g (0.04 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was added to the PAA-2 solution and the mixture was stirred vigorously for 12 hours to obtain an end-capped polyamic acid (PAA-3) with a viscosity of 146,000 centipoise at 25°C.

[0033] (4) The PAA-3 solution was evenly coated on a dry glass substrate and baked using the following procedure: 60°C / 1 hour, 120°C / 1 hour, 200°C / 1 hour, and 350°C / 1 hour. After cooling to room temperature, the glass plate was placed in water and peeled off to obtain a PI-c film.

[0034] Example 4: Preparation of polyimide PI-d film (1) Under nitrogen protection and at room temperature, 21.63 g (0.2 mol) of 1,4-p-phenylenediamine and 362.92 g (0.7 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane were added to 2840 g of N,N-dimethylacetamide and stirred vigorously until dissolved; 211.84 g (0.72 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added at 15°C and stirred vigorously for 24 hours to obtain polyamic acid (PAA-1) with lower viscosity.

[0035] (2) At 65°C, 24.85 g (0.1 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 1217 g of N,N-dimethylacetamide were added to the PAA-1 solution. After dissolution, 82.38 g (0.28 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added. The mixture was stirred vigorously and reacted for 12 hours to obtain a viscous polyamic acid (PAA-2).

[0036] (3) At room temperature, 12.43 g (0.05 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was added to the PAA-2 solution and the mixture was stirred vigorously for 10 hours to obtain an end-capped polyamic acid (PAA-3) with a viscosity of 154,000 centipoise at 25°C.

[0037] (4) The PAA-3 solution was evenly coated on a dry glass substrate and baked using the following procedure: 60°C / 1 hour, 120°C / 1 hour, 200°C / 1 hour, and 350°C / 1 hour. After cooling to room temperature, the glass plate was placed in water and peeled off to obtain a PI-d film.

[0038] Example 5: Preparation of polyimide PI-e film (1) Under nitrogen protection and at room temperature, 54.07 g (0.5 mol) of 1,4-p-phenylenediamine and 155.54 g (0.3 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane were added to 1782 g of N,N-dimethylacetamide and stirred vigorously until dissolved; at 8 °C, 74.16 g (0.34 mol) of 1,2,4,5-pyromellitic dianhydride and 68.25 g (0.22 mol) of 3,3',4,4'-biphenyl ether dianhydride were added and stirred vigorously for 20 hours to obtain polyamic acid (PAA-1) with lower viscosity.

[0039] (2) At 50°C, 49.70 g (0.2 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 1188 g of N,N-dimethylacetamide were added to the PAA-1 solution. After dissolution, 56.71 g (0.26 mol) of 1,2,4,5-pyromellitic dianhydride and 55.84 g (0.18 mol) of 3,3',4,4'-biphenyl ether dianhydride were added. The mixture was stirred vigorously and reacted for 18 hours to obtain a viscous polyamic acid (PAA-2).

[0040] (3) At room temperature, 9.94 g (0.04 mol) of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was added to the PAA-2 solution and the mixture was stirred vigorously for 10 hours to obtain end-capped polyamic acid (PAA-3) with a viscosity of 132,000 centipoise at 25°C.

[0041] (4) The PAA-3 solution was evenly coated on a dry glass substrate and baked using the following procedure: 60°C / 1 hour, 120°C / 1 hour, 200°C / 1 hour, and 350°C / 1 hour. After cooling to room temperature, the glass plate was placed in water and peeled off to obtain a PI-e film.

[0042] The polyimide films prepared in Examples 1 to 5 were subjected to performance tests, and the test results are summarized in Table 1. The testing methods for the polyimide film samples are as follows: water absorption is tested by immersion method according to ASTM D750; dielectric constant and dielectric loss factor are tested by cavity resonance method according to ASTM D150; peel strength is tested by comparing with commercial electrolytic copper foil at 330°C and 100 kgf / cm 2 The film was hot pressed and laminated under certain conditions, and the adhesion between the film and the copper foil was evaluated according to the IPC-TM-650-2.4.9 method.

[0043] Table 1 Performance data of polyimide films in Examples 1-5 serial number Thickness (μm) Water absorption rate (%) Dielectric constant (10GHz) Dielectric loss factor (10GHz) Peel strength (N / mm) Example 1 (PI-a) 36 0.73 2.92 0.0048 1.12 Example 2 (PI-b) 34 0.61 2.87 0.0041 1.19 Example 3 (PI-c) 37 0.57 2.83 0.0039 1.08 Example 4 (PI-d) 33 0.45 2.93 0.0036 1.13 Example 5 (PI-e) 35 0.64 2.84 0.0044 1.16 As can be seen from Table 1, the polyimide film prepared by the preparation method of the present invention has the characteristics of low dielectric constant and dielectric loss, low water absorption, good adhesion, etc. The dielectric constant at 10 GHz is ≤3.0, the dielectric loss factor is ≤0.005, and the water absorption is <0.8%. It solves the problems of high water absorption, large dielectric constant and dielectric loss, and poor adhesion of traditional polyimide films; and can be applied to fields such as high-frequency and high-speed integrated circuits.

[0044] The above embodiments of the present invention are merely examples to clearly illustrate the present invention, but are not intended to limit the scope of protection of the present invention. All equivalent technical solutions also fall within the scope of the present invention. The scope of patent protection of the present invention should be defined by the claims.

Claims

1. A low dielectric polyimide film material, characterized in that: The polyimide film material includes a polyimide copolymer, the polyimide copolymer includes an aromatic ether, a fluorine atom or a fluorine-containing group, and a siloxane unit, and the structure of the polyimide copolymer includes structural units represented by general formula (1) and general formula (2). （1） （2） The molar ratio of the copolymer components in general formula (1) and general formula (2) is (1-90%): (1-50%): (1-30%); the A unit is a structural unit generated from an aromatic or alicyclic tetracarboxylic dianhydride; the B unit is a structural unit generated from an aromatic or alicyclic diamine; at least one of C and D contains a fluorine atom or a fluorine-containing group, and C is selected from one of a hydrogen atom, a methyl group, an ethyl group, a propyl group, a fluorine atom, and a trifluoromethyl group; and D is selected from one of the following structural groups: ； The invention discloses an application of a low dielectric polyimide film material in integrated circuits, electronics or microelectronics.

2. The low dielectric polyimide film material according to claim 1, wherein: The tetracarboxylic dianhydride component in the A unit is selected from the group consisting of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyl ether dianhydride, 2,3,3',4-biphenyl ether dianhydride, 3,3',4,4'-biphenyl ketone dianhydride, 3,3',4,4'-biphenyl sulfone dianhydride, 2,2-diphenylpropane One or more of -3,3',4,4'-tetracarboxylic dianhydride, 1,4-diphenoxybenzene-3,3',4,4'-tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), cyclobutanetetracarboxylic dianhydride, hydrogenated pyromellitic dianhydride, and hydrogenated biphenyltetracarboxylic dianhydride.

3. The low dielectric polyimide film material according to claim 1, wherein: The diamine component in the B unit is selected from the group consisting of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,4-bis(3'-aminophenoxy)benzene, 1,3-bis(3'-aminophenoxy)benzene, 1,3-bis(4'-aminophenoxy)benzene, 2,2'-bis(methyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, tetrafluoro-p-phenylenediamine, and one or more of 4,4'-diaminooctafluorobiphenyl.

4. The low dielectric polyimide film material according to claim 1, wherein: The polyimide film has a glass transition temperature greater than 320° C., a dielectric constant less than or equal to 3.0 at 10 GHz, and a dielectric loss factor less than or equal to 0.

005.

5. A method for preparing a low dielectric polyimide film material according to any one of claims 1 to 4, characterized in that: The method comprises the following preparation steps: (1) adding aromatic diamine and aromatic ether-containing diamine to a first organic solvent, dissolving them, and then adding dianhydride at a first temperature; (2) then adding the silicon-containing diamine and the second organic solvent, and adding the dianhydride at the second temperature; (3) finally adding a capping agent and reacting at a third reaction temperature to obtain a capped polyamic acid solution; the capping agent is 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and the amount of the capping agent is 2% to 10% of the total molar amount of diamine or the total molar amount of dianhydride; (4) The polyamic acid solution is coated to form a film, and then heated and dried to obtain a polyimide film.

6. The method for preparing a low dielectric polyimide film material according to claim 5, wherein: The general structural formula of the aromatic ether-containing diamine is shown in (3): （3） Wherein, at least one of C and D contains a fluorine atom or a fluorine-containing group, C is selected from one of a hydrogen atom, a methyl group, an ethyl group, a propyl group, a fluorine atom, and a trifluoromethyl group; and D is selected from one of the following structural groups: ； The aromatic diamine is one or more of p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,4-bis(3'-aminophenoxy)benzene, 1,3-bis(3'-aminophenoxy)benzene, 1,3-bis(4'-aminophenoxy)benzene, 2,2'-bis(methyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, tetrafluoro-p-phenylenediamine, and 4,4'-diaminooctafluorobiphenyl.

7. The method for preparing a low dielectric polyimide film material according to claim 5, wherein: In step (1) and / or (2), the dianhydride is pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyl ether dianhydride, 2,3,3',4-biphenyl ether dianhydride, 3,3',4,4'-biphenyl ketone dianhydride, 3,3',4,4'-biphenyl sulfone dianhydride, 2,2-diphenyl One or more of propane-3,3',4,4'-tetracarboxylic dianhydride, 1,4-diphenoxybenzene-3,3',4,4'-tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), cyclobutanetetracarboxylic dianhydride, hydrogenated pyromellitic dianhydride, and hydrogenated biphenyltetracarboxylic dianhydride.

8. The method for preparing a low dielectric polyimide film material according to claim 5, wherein: The total molar amount of dianhydride is the sum of the molar amounts of the aromatic diamine, aromatic ether-containing diamine, and silicon-containing diamine in steps (1) and (2), wherein the amount of dianhydride used in step (1) is 40% to 80% of the sum of the molar amounts of the aromatic diamine and aromatic ether-containing diamine; the amount of dianhydride used in step (2) is the remainder of the total amount of dianhydride.

9. The method for preparing a low dielectric polyimide film material according to claim 5, wherein: In steps (1) and / or (2), the first organic solvent and / or the second organic solvent is one or a mixture of N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran; wherein the mass ratio of the first organic solvent to the second organic solvent is (6-9): (1-4).

10. The method for preparing a low dielectric polyimide film material according to claim 5, wherein: In step (1), the first reaction temperature is -5~15°C; in step (2), the second reaction temperature is 25~80°C; in step (3), the third reaction temperature is 25~35°C.

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