Intrinsic high thermal conductivity-low dielectric polyimide film and preparation method and application thereof

Abstract

The invention relates to an intrinsic high-thermal-conductivity-low-dielectric polyimide film as well as a preparation method and application thereof. Polyimide is prepared from polyimide A and polyimide B through blending or grafting. The polyimide film provided by the invention has intrinsic high thermal conductivity, low dielectric constant and loss and excellent heat resistance and mechanical properties, and has wide application prospects in the fields of integrated circuits, electronic packaging and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of high-performance polymer film materials, and particularly relates to an intrinsic high thermal conductivity-low dielectric polyimide film and a preparation method and application thereof. Background Art

[0002] As an excellent polymer material, polyimide is widely used in aerospace, electronics and electrical fields due to its excellent thermal stability, mechanical strength and electrical insulation properties. However, with the continuous development of technology, the dielectric constant and dielectric loss of traditional polyimide are increasingly unable to meet the performance requirements of the new generation of products; at the same time, its thermal conductivity is generally low, which limits its application in high-power electronic devices and microelectronics.

[0003] At present, the main method for improving the thermal conductivity of polyimide is to introduce thermal conductive fillers such as carbon nanotubes, graphene, boron nitride, etc. into the polyimide matrix. For example, CN119220170A discloses a method for improving the thermal conductivity of polyimide film by filling boron nitride nanosheets. However, due to the difficulty of dispersing the filler, poor interface compatibility, and high dielectric constant of the filler, the mechanical properties and dielectric properties of the prepared thermal conductive composite material are not ideal. The research on intrinsic high thermal conductivity is mainly focused on achieving it through molecular design and chain structure improvement. By adjusting the structure of polyimide monomers, such as introducing rigid segments or highly conjugated structures, the thermal conductivity of the material can be improved to a certain extent. For example, CN113105658A introduces a liquid crystal polyimide film containing a large number of ether bonds. The regular arrangement of liquid crystal molecules can improve the conduction of phonons and thus improve its thermal conductivity; but a large number of polar ether bond groups are introduced into its structure, which makes the dielectric constant and dielectric loss of the film high. At present, a large number of studies have shown (such as Macromolecules, 1991, 24(5): 1011-1016., Journal of Applied Polymer Science, 2017, 134(18) (DOI: 10.1002 / app.44774), Journal of Polymer Science Part A: Polymer Chemistry, 1999, 37(2): 211-218.) that since the rigid ester structure is conducive to the regular arrangement of molecular chains, introducing it into the polyimide structure is conducive to obtaining crystalline polyimide. For example, in Journal of Materials Chemistry C, 2024 (DOI: 10.1039 / d4tc04308a), crystalline polyimide was prepared by using ester-containing polyimide, and the dielectric loss value of the film was significantly reduced due to the presence of regular crystalline structure and hydrophobic ester group; however, the dielectric constant of the prepared film was high (>3.2). Similarly, simply by increasing the proportion of ester-containing structure, the dielectric constant and dielectric loss of the material can be further reduced, such as ACS Applied Polymer Materials, 2022, 4(6): 4234-4243. In the study, polyarylate-polyimide was prepared. Due to the presence of polyarylate units with liquid crystal properties, the dielectric constant of the prepared film can be as low as 2.91, and it has low dielectric loss. However, due to the high proportion of low-polarity polyarylate structure (weak intermolecular interaction), the temperature resistance of the material is insufficient, and its glass transition temperature is ≤220℃.Similarly, in order to reduce the dielectric constant of polyimide, many studies have been conducted to reduce the polarizability by introducing fluorine groups or other low-polarity groups (Polymer Chemistry, 2022, 13(26):3949-3955., Macromolecules, 2003, 36(24): 9122-9127.), thereby reducing the dielectric constant; however, the thermal conductivity of the material cannot be guaranteed.

[0004] Therefore, there is currently no ideal solution for polyimide materials that combine high thermal conductivity, low dielectric properties and excellent mechanical properties. Summary of the invention

[0005] The purpose of the present invention is to provide an intrinsic high thermal conductivity-low dielectric polyimide film and a preparation method and application thereof, which can well solve the contradiction between high thermal conductivity, low dielectric and mechanical properties.

[0006] The invention provides an intrinsic high thermal conductivity and low dielectric polyimide film. The polyimide film is formed by blending or grafting an ester-containing rigid polyimide A and a fluorine-containing flexible polyimide B.

[0007] The present invention also provides a method for preparing an intrinsic high thermal conductivity-low dielectric polyimide film, comprising the following steps:

[0008] (1) subjecting an ester-containing aromatic diamine or a rigid aromatic diamine to a condensation reaction with an ester-containing acid anhydride or a rigid acid anhydride in an organic solvent to obtain polyamic acid A; subjecting a fluorine-containing aromatic diamine or a flexible aromatic diamine to a condensation reaction with a fluorine-containing acid anhydride or a flexible acid anhydride in an organic solvent to obtain polyamic acid B;

[0009] (2) mixing polyamic acid A and polyamic acid B to obtain a blended or block polyamic acid solution;

[0010] (3) forming a film from the blended or block polyamic acid solution, and then drying the solvent to obtain a blended or block polyamic acid film;

[0011] (4) The above-mentioned blended or block polyamic acid film is subjected to cyclization reaction and crystallization to obtain an intrinsic high thermal conductivity and low dielectric polyimide film.

[0012] Preferably, the ester-containing aromatic diamine in step (1) comprises one or more of the following structures:

[0013] ;

[0014] Preferably, the rigid aromatic diamine comprises one or more of the following structures:

[0015] ;

[0016] Preferably, the ester-containing anhydride comprises one or more of the following structures:

[0017] ;

[0018] Preferably, the rigid anhydride comprises one or more of the following structures:

[0019] .

[0020] Preferably, the fluorinated aromatic diamine in step (1) comprises one or more of the following structures:

[0021] ;

[0022] Preferably, the fluorinated anhydride comprises one of the following structures:

[0023] ;

[0024] Preferably, the flexible structure in the flexible aromatic diamine and the flexible acid anhydride comprises one of the following structures:

[0025] .

[0026] Preferably, in step (1), the raw material of polyamic acid A contains at least one ester-containing monomer, and the weight proportion of the ester-containing monomer in polyamic acid A is ≥30%; the raw material of polyamic acid B contains at least one fluorine-containing monomer, and the weight proportion of F atoms in polyamic acid B is 5wt%~40wt%.

[0027] Preferably, the organic solvent in step (1) is N,N-dimethylacetamide (DMAc) or N,N-dimethylformamide (DMF).

[0028] Preferably, the blending reaction conditions in step (2) are as follows: the polymerization degree of polyamic acid A and polyamic acid B should be ≥ 25, the temperature is 25° C. to 50° C., and the stirring time is 4 to 8 hours.

[0029] Preferably, the polymerization reaction conditions in step (2) are as follows: the polymerization degrees of polyamic acid A and polyamic acid B are respectively greater than or equal to 5 and greater than or equal to 1; polyamic acid A and polyamic acid B are respectively polyamic acid oligomers terminated with amine or anhydride, and the molar number of the terminated amine group is equal to the molar number of the anhydride group; the temperature is 40° C. to 80° C., and the stirring time is 8 to 24 hours.

[0030] Preferably, the solvent drying conditions in step (3) are: a heating rate of 1°C / min to 10°C / min, a maximum temperature of 50°C to 160°C, and a maximum temperature residence time of 2 to 24 hours.

[0031] Preferably, the solvent content of the blended or block polyamic acid film in step (3) is less than 35%.

[0032] Preferably, the conditions for the cyclization reaction and crystallization in step (4) are as follows: under a nitrogen atmosphere, the reaction temperature is 200-450° C., the heating rate is 0.1-5° C. / min, and the maximum temperature is maintained for 10-60 min.

[0033] The present invention also provides an application of an intrinsic high thermal conductivity-low dielectric polyimide film in integrated circuits and electronic packaging.

[0034] The above-mentioned "rigidity" and "flexibility" are defined as follows in the present invention: Rigidity refers to the presence of: aromatic structures (such as benzene ring, biphenyl, naphthalene ring), aromatic heterocyclic structures (such as benzimidazole, benzoxazole, pyrimidine), and aromatic structures with restricted rotation (such as benzoylaniline, aromatic esters, and aromatic sulfones).

[0035] Flexibility refers to the presence of: fatty chain structure (such as C1~C12), fatty ring structure (cyclohexane), siloxane structure, flexible aromatic structure (such as ether bond, thioether bond, ketone bond, methylene bond, isopropyl).

[0036] Beneficial Effects

[0037] (1) The present invention simultaneously introduces a crystallizable phase and a fluorine-containing phase into the polyimide film, combining the high thermal conductivity of the crystallized phase and the low dielectric property of the fluorine-containing structure. Compared with traditional thermally conductive composite materials containing thermally conductive inorganic or metal fillers, the mechanical properties of the thermally conductive composite materials have obvious advantages.

[0038] (2) Based on the difference in surface tension or solubility parameters between the two phases, the present invention achieves phase separation of the two phases through block or blending methods and solvent evaporation process control; the interfacial voids generated by phase separation can further reduce the dielectric constant of the material; at the same time, the crystallization of the ester-containing part at high temperature helps to further reduce dielectric loss and improve mechanical properties.

[0039] (3) The present invention adjusts the weight ratio and block length of the rigid ester-containing polyamic acid segment and the flexible fluorinated polyamic acid segment so that the prepared phase separation morphology is an "island" structure, and the rigid ester-containing polyamic acid segment with a higher content and a larger molecular weight is a continuous "sea" phase, and the flexible fluorinated polyamic acid segment with a lower content and a smaller molecular weight is a dispersed "island" phase; the continuous "sea" phase becomes a continuous crystalline "sea" phase after subsequent high-temperature crystallization, which provides a complete heat conduction path for phonons in the heat conduction process, thereby further improving the thermal conductivity of the material.

[0040] (4) The method provided by the present invention is simple to prepare, does not require the introduction of foreign functional fillers, and does not require the synthesis of monomers with complex structures. The process route through polycondensation is relatively simple, has high production efficiency and good economy, and shows the potential for wide application in high-performance electronic devices, meeting the dual requirements of thermal conductivity and low dielectric properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a photo of the polyimide film in Comparative Example 2.

[0042] Figure 2 This is a cross-sectional morphology diagram of the polyimide film in Example 2.

[0043] Figure 3 This is a polarizing microscope image of polyimide in Example 2.

[0044] Figure 4 This is the X-ray diffraction curve of the polyimide film in Example 2.

[0045] Figure 5 This is a cross-sectional morphology diagram of the polyimide film in Example 3. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0047] Comparative Example 1

[0048] 6FDA-TFMB homopolymer: In a 150 ml three-necked flask, add 85 grams of N,N-dimethylacetamide (DMAC) as a solvent. Under nitrogen protection, add 6.44 grams (20 mmol) of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB) and stir at room temperature until completely dissolved. Then, gradually add 8.88 grams (20 mmol) of hexafluorodianhydride (6FDA), continue stirring to promote the reaction, and control the solid content to 15 wt%. The whole process usually lasts about 12 hours, and finally obtains a 6FDA-TFMB polyamide acid solution.

[0049] The above solution was cast on a glass plate to form a film, then heated to 60°C at a rate of 5°C / min, dried under vacuum for 8 hours, and finally heated to 200°C, 300°C, and 350°C at a rate of 2°C / min, and then heated for 30 minutes respectively to obtain a 6FDA-TFMB polyimide film. The film is consistent with other studies (Journal of Polymeric Sciences, 2023, 54(8): 1219-1228.), with no crystallization and a dielectric constant of 2.7 (@10 6 Hz), thermal conductivity 0.28 W / m·K, tensile strength 87 MPa, and modulus 1.2 GPa.

[0050] Comparative Example 2

[0051] TAHQ-ABHQ homopolymer: 85 g of DMAC was added as a solvent in a 150 ml three-necked flask and operated under a nitrogen atmosphere to prevent oxidation. Then 6.62 g (19 mmol) of [4-(4-aminobenzoyl)oxyphenyl] 4-aminobenzoate (ABHQ) was added to the solution and stirred with a magnetic stirrer until completely dissolved. Next, 8.71 g (19 mmol) of p-phenylene-diphenyltriphenylamine dianhydride (TAHQ) was slowly added and the solid content was controlled to 15 wt %. Stirring was continued for about 12 hours to obtain a polyamic acid solution of TAHQ-ABHQ.

[0052] The above solution was cast on a glass plate to form a film, then heated to 60°C at a rate of 5°C / min, dried under vacuum for 8 hours, and finally heated to 200°C, 300°C, and 350°C at a rate of 2°C / min, and then heated for 30 minutes respectively to obtain a TAHQ-ABHQ polyimide film. Figure 1 As shown, the prepared film is translucent, has poor toughness, breaks after bending, and has a dielectric constant of 3.6 (@10 6 Hz), and the in-plane thermal conductivity is 1.82 W / m·K.

[0053] Example 1

[0054] The 6FDA-TFMB polyamic acid solution in Comparative Example 1 and the TAHQ-ABHQ polyamic acid solution in Comparative Example 2 were mixed in equal mass and stirred evenly, and then a blended polyimide film was prepared according to the same film-making process as in Comparative Example 2. The film had obvious haze, excellent mechanical toughness, and a dielectric constant of 2.7 (@10 6 Hz), thermal conductivity of 0.63 W / m·K, tensile strength of 96 MPa, and modulus of 1.5 GPa.

[0055] Example 2

[0056] Amine-terminated 6FDA-TFMB-60: In a 150 ml three-necked flask, add 85 g of DMAC as a solvent, and accurately weigh 6.44 g (20 mmol) of TFMB under nitrogen protection, and stir the solution with a magnetic stirrer at room temperature until TFMB is completely dissolved into a uniform transparent solution. Then, add 8.74 g (19.67 mmol) of 6FDA in three batches, and continue to stir the solution to ensure adequate mixing and promote the reaction. The entire reaction usually lasts about 10 hours while maintaining a solid content of 15 wt%, and finally prepares an amine-terminated 6FDA-TFMB polyamic acid solution with a degree of polymerization of 60.

[0057] Anhydride-terminated TAHQ-ABHQ-30: In a 150 ml three-necked flask, accurately add 93 grams of DMAC as a solvent, and ensure that the entire operation process is carried out under a nitrogen environment to prevent any possible oxidation reaction. Subsequently, weigh 6.97 grams (20 mmol) of ABHQ and add it to the solvent. Use a magnetic stirrer to stir the mixture at room temperature until ABHQ is completely dissolved to form a uniform solution. Next, gradually add 9.47 grams (20.67 mmol) of TAHQ, and ensure that the solid content is 15 wt%. Continue to stir the mixed solution for about 12 hours, and finally prepare an anhydride-terminated TAHQ-ABHQ polyamide acid solution with a degree of polymerization of 30.

[0058] Preparation of block copolymer polyimide film: The same molar amount of amine-terminated 6FDA-TFMB polyamic acid solution and anhydride-terminated TAHQ-ABHQ polyamic acid solution were mechanically stirred at 40°C for 12 hours to obtain a block polyamic acid solution, and then the block polyimide film was prepared according to the same film preparation process as in Comparative Example 1. The block polyimide film has excellent mechanical toughness and a dielectric constant of 3.0 (@10 6 Hz), thermal conductivity of 1.25 W / m·K, tensile strength of 122 MPa, and modulus of 1.6 GPa.

[0059] Performance testing and characterization: Figure 2 This is a scanning electron microscope (SEM) morphology image of the cross section of the block copolymer polyimide film prepared in Example 2. It can be seen from the image that there is obvious phase separation and a clear "island" structure. Figure 3 This is a polarizing microscope photo of the film. It can be clearly seen that the continuous "sea" phase is full of spherulites with typical Maltese black crosses, while the "island" phase is translucent and no crystallization occurs. Figure 4From the XRD curve of the film, it can be seen that the block copolymer polyimide film prepared in Example 2 has an obvious crystallization peak. Therefore, a phase separation phenomenon with an "island" structure appears inside the polyimide film prepared in Example 2, and the continuous "sea" phase has high crystallinity, which provides a smooth heat conduction path for the preparation of the intrinsic high thermal conductivity film.

[0060] Example 3

[0061] Amine-terminated 6FDA-TFMB-30: In a 150 ml three-necked flask, add 85 g of DMAC as a solvent, and accurately weigh 6.44 g (20 mmol) of TFMB under nitrogen protection, and stir the solution with a magnetic stirrer at room temperature until TFMB is completely dissolved into a uniform transparent solution. Then, gradually add 8.60 g (19.36 mmol) of 6FDA, and continue to stir the solution to ensure adequate mixing and promote the reaction. The entire reaction usually lasts for about 10 hours while maintaining a solid content of 15 wt%, and finally prepares an amine-terminated 6FDA-TFMB polyamic acid solution with a degree of polymerization of 30.

[0062] Anhydride-terminated TAHQ-ABHQ-20: In a 150 ml three-necked flask, 94 g of DMAC was accurately added as a solvent, and the entire operation was carried out under a nitrogen atmosphere to prevent any possible oxidation reaction. Subsequently, 6.97 g (20 mmol) of ABHQ was weighed and added to the solvent. After mechanical stirring at 40 °C for 4 hours, 9.62 g (21 mmol) of TAHQ was gradually added to make the solid content 15 wt%. The mixed solution was stirred for about 24 hours, and finally an anhydride-terminated TAHQ-ABHQ polyamic acid solution with a degree of polymerization of 20 was prepared.

[0063] Preparation of block copolymer polyimide film: The same molar amount of amino-terminated 6FDA-TFMB polyamic acid solution and anhydride-terminated TAHQ-ABHQ polyamic acid solution were mechanically stirred at 40°C for 10 hours to obtain a block polyamic acid solution, which was then cast on a glass plate to form a film, then heated to 60°C at 3°C / min, dried under vacuum conditions for 8 hours, and finally heated to 200°C, 300°C, and 350°C at a heating rate of 1°C / min, and then heated for 30 minutes respectively to obtain a block polyimide film. The cross-sectional SEM image of the film is shown in the figure. Figure 5 As shown in the figure, it can be seen that the two phases of the block undergo microphase separation, and because the length of the two blocks is short, the microphase separation size is small, so that the inside of the film is not a dense structure; the film has excellent mechanical toughness and a dielectric constant of 2.9 (@10 6Hz), thermal conductivity of 0.98 W / m·K, tensile strength of 134 MPa, and modulus of 1.8 GPa.

[0064] Example 4

[0065] Anhydride-terminated 6FDA-ABTFMB-60: In a 150 ml three-necked flask, add 85 g of DMAC as a solvent, and accurately weigh 8.38 g (15 mmol) of 2,2'-bis(trifluoromethyl)-4,4'-bis(4-aminophenylcarbonylamino)biphenyl (ABTFMB) under nitrogen protection, and use mechanical stirring solution at 30 ° C until TFMB is completely dissolved into a uniform transparent solution. Then, add 6.77 g (15.25 mmol) of 6FDA in three batches, and continue to stir the solution to ensure adequate mixing and promote the reaction. The entire reaction usually lasts about 12 hours while maintaining a solid content of 15 wt%, and finally prepares an anhydride-terminated 6FDA-TFMB polyamic acid solution with a degree of polymerization of 60.

[0066] Amine-terminated TAHQ-DABA-30: In a 150 ml three-necked flask, 85 g of DMAC was accurately added as solvent, and the entire operation was carried out under nitrogen to prevent any possible oxidation reaction. Subsequently, 4.55 g (20 mmol) of 4,4'-diaminobenzanilide (DABA) was weighed and added to the solvent. After mechanical stirring at 40 °C for 6 hours, 8.87 g (19.36 mmol) of TAHQ was gradually added, and the solid content was ensured to be 15 wt%. The mixed solution was stirred for about 20 hours, and finally an anhydride-terminated TAHQ-DABA polyamic acid solution with a degree of polymerization of 30 was prepared.

[0067] Preparation of block copolymer polyimide film: The same molar amount of anhydride-terminated 6FDA-ABTFMB polyamic acid solution and amine-terminated TAHQ-DABA polyamic acid solution were mechanically stirred at 60°C for 12 hours to obtain a block polyamic acid solution, and the above solution was cast on a glass plate to form a film, then heated to 80°C at 5°C / min, dried under vacuum conditions for 10 hours, and finally heated to 200°C, 300°C, and 350°C at a heating rate of 2°C / min, and then heated for 30 minutes respectively to obtain a block polyimide film, which has excellent mechanical toughness and a dielectric constant of 3.1 (@10 6 Hz), thermal conductivity of 1.11 W / m·K, tensile strength of 158 MPa, and modulus of 2.3 GPa.

[0068] Example 5

[0069] Amine-terminated 6FAP-BPADA-30: In a 150 ml three-necked flask, add 79 g of DMAC as a solvent, and accurately weigh 6.42 g (15 mmol) of 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane (6FAP) under nitrogen protection, and stir the solution with a magnetic stirrer at room temperature until 6FAP is completely dissolved into a uniform transparent solution. Then, gradually add 7.56 g (14.52 mmol) of bisphenol A diether dianhydride (BPADA), and continue to stir the solution to ensure adequate mixing and promote the reaction. The entire reaction usually lasts for about 18 hours while maintaining a solid content of 15 wt%, and finally prepares an amine-terminated 6FAP-BPADA polyamic acid solution with a degree of polymerization of 30.

[0070] Anhydride-terminated APAB-BPDA-10: In a 150 ml three-necked flask, accurately add 70 g of DMAC as solvent, and ensure that the entire operation process is carried out under nitrogen to prevent any possible oxidation reaction. Subsequently, weigh 5.71 g (25 mmol) of p-aminophenyl para-aminobenzoate (APAB) and add it to the solvent, stirring at room temperature for 4 hours. Then add 6.69 g (22.73 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) in three batches, and ensure that the solid content is 15 wt%. Continue to stir the mixed solution for about 10 hours, and finally prepare an anhydride-terminated APAB-BPDA polyamic acid solution with a degree of polymerization of 10.

[0071] Preparation of block copolymer polyimide film: The same molar amount of anhydride-terminated 6FAP-BPADA polyamic acid solution and amine-terminated APAB-BPDA polyamic acid solution were mechanically stirred at 40°C for 12 hours to obtain a block polyamic acid solution, and the above solution was cast on a glass plate to form a film, then heated to 60°C at 5°C / min, dried under vacuum conditions for 10 hours, and finally heated to 200°C, 300°C, and 350°C at a heating rate of 2°C / min, and then heated for 30 minutes respectively to obtain a block polyimide film, which has excellent mechanical toughness and a dielectric constant of 3.0 (@10 6 Hz), thermal conductivity of 0.7 W / m·K, tensile strength of 107 MPa, and modulus of 1.2 GPa.

Claims

1. An intrinsic high thermal conductivity and low dielectric polyimide film, characterized in that: The polyimide film is formed by blending or grafting rigid polyimide A containing ester groups and flexible polyimide B containing fluorine.

2. A method for preparing an intrinsic high thermal conductivity and low dielectric polyimide film, comprising the following steps: (1) subjecting an ester-containing aromatic diamine or a rigid aromatic diamine to a condensation reaction with an ester-containing acid anhydride or a rigid acid anhydride in an organic solvent to obtain polyamic acid A; subjecting a fluorine-containing aromatic diamine or a flexible aromatic diamine to a condensation reaction with a fluorine-containing acid anhydride or a flexible acid anhydride in an organic solvent to obtain polyamic acid B; (2) obtaining a blended or segmented polyamic acid solution by blending or polymerizing polyamic acid A and polyamic acid B; (3) forming a film from the blended or block polyamic acid solution, and then drying the solvent to obtain a blended or block polyamic acid film; (4) The above-mentioned blended or block polyamic acid film is subjected to cyclization reaction and crystallization to obtain an intrinsic high thermal conductivity and low dielectric polyimide film.

3. The preparation method according to claim 2, characterized in that: The ester-containing aromatic diamine in step (1) includes one or more of the following structures: ； Rigid aromatic diamines include one or more of the following structures: ； Ester-containing anhydrides include one or more of the following structures: ； Rigid anhydrides include one or more of the following structures: 。 4. The preparation method according to claim 2, characterized in that: The fluorinated aromatic diamine in step (1) includes one or more of the following structures: ； Fluorinated anhydrides include one of the following structures: ； The flexible structure in the flexible aromatic diamine and the flexible acid anhydride includes one of the following structures: 。 5. The preparation method according to claim 2, characterized in that: In the step (1), the raw material of polyamic acid A contains at least one ester-containing monomer, and the weight proportion of the ester-containing monomer in polyamic acid A is ≥30%; the raw material of polyamic acid B contains at least one fluorine-containing monomer, and the weight proportion of F atoms in polyamic acid B is 5wt%~40wt%.

6. The preparation method according to claim 2, characterized in that: The blending reaction conditions in step (2) are as follows: the polymerization degree of polyamic acid A and polyamic acid B are both ≥ 25, the temperature is 25° C. to 50° C., and the stirring time is 4 to 8 hours.

7. The preparation method according to claim 2, characterized in that: The polymerization reaction conditions in step (2) are as follows: the polymerization degrees of polyamic acid A and polyamic acid B are respectively greater than or equal to 5 and greater than or equal to 1; polyamic acid A and polyamic acid B are respectively polyamic acid oligomers terminated with amine or anhydride, and the molar number of the terminated amine group is equal to the molar number of the anhydride group; the temperature is 40° C. to 80° C., and the stirring time is 8 to 24 hours.

8. The preparation method according to claim 2, characterized in that: The solvent drying conditions in step (3) are: a heating rate of 1°C / min to 10°C / min, a maximum temperature of 50°C to 160°C, and a maximum temperature residence time of 2 to 24 hours.

9. The preparation method according to claim 2, characterized in that: The conditions for the cyclization reaction and crystallization in step (4) are as follows: under a nitrogen atmosphere, the reaction temperature is 200-450° C., the heating rate is 0.1-5° C. / min, and the maximum temperature is maintained for 10-60 min.

10. Use of the intrinsic high thermal conductivity and low dielectric polyimide film according to claim 1 in integrated circuits and electronic packaging.

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