An intrinsic high thermal conductivity-low dielectric polyimide film and its preparation method and application

Abstract

The present invention relates to an intrinsically high thermal conductivity-low dielectric polyimide film, its preparation method, and applications. The polyimide is composed of polyimide A and polyimide B through blending or grafting. The polyimide film of the present invention has intrinsically high thermal conductivity, low dielectric constant and loss, and excellent heat resistance and mechanical properties. It has broad application prospects in integrated circuits, electronic packaging, and other fields.

Description

Technical Field

[0001] The present 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 other fields due to its outstanding 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 new generation products. At the same time, its generally low thermal conductivity limits its application in high-power electronic devices and microelectronics.

[0003] Currently, the main method for improving the thermal conductivity of polyimide is to introduce thermally conductive fillers such as carbon nanotubes, graphene, and boron nitride into the polyimide matrix. For example, CN119220170A discloses a method for improving the thermal conductivity of polyimide films by filling them with boron nitride nanosheets. However, due to difficulties in dispersing the filler, poor interfacial compatibility, and a high dielectric constant, the mechanical and dielectric properties of the resulting thermally conductive composite materials are unsatisfactory. Research on intrinsically high thermal conductivity has primarily focused on achieving it through molecular design and chain structure improvements. By adjusting the polyimide monomer structure, for example, by introducing rigid segments or highly conjugated structures, the thermal conductivity of the material can be improved to a certain extent. For example, CN113105658A describes a liquid crystal polyimide film containing a large number of ether bonds. The regular arrangement of the liquid crystal molecules can enhance phonon conduction, thereby improving its thermal conductivity. However, the introduction of a large number of polar ether groups in the structure results in a relatively high dielectric constant and dielectric loss of the film. At present, a large number of studies have shown that (e.g., Macromolecules, 1991, 24(5): 1011-1016., Journal of AppliedPolymer Science, 2017, 134(18) (DOI: 10.1002 / app.44774), Journal of PolymerScience Part A: Polymer Chemistry, 1999, 37(2): 211-218.) that the rigid ester structure is conducive to the regular arrangement of molecular chains, and its introduction 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 regular crystalline structure and the presence of hydrophobic ester groups; however, the dielectric constant of the prepared film was relatively high (>3.2). Similarly, simply increasing the proportion of ester-containing structures can further reduce the dielectric constant and dielectric loss of the material, such as ACS Applied Polymer Materials, 2022, 4(6): 4234-4243. In this 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 also has low dielectric loss. However, due to the high proportion of low-polarity polyarylate structures (weak intermolecular interaction), the temperature resistance of the material is insufficient, and its glass transition temperature is ≤220℃.Similarly, 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 its preparation method and application, 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 intrinsically high thermal conductivity and low dielectric polyimide film, comprising the following steps:

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

[0010] (3) forming the blended or segmented polyamic acid solution into a film, and then drying the solvent to obtain a blended or segmented 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 includes one of the following structures:

[0025] .

[0026] Preferably, the raw material of polyamic acid A in step (1) 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 must be ≥25, the temperature is 25°C~50°C, and the stirring time is 4~8 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 segmented polyamic acid film in step (3) is less than 35%.

[0032] Preferably, the conditions for the cyclization reaction and crystallization in step (4) are: under 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 and 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:

[0035] 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 phenylaniline, aromatic ester, and aromatic sulfone).

[0036] 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).

[0037] Beneficial effects

[0038] (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 with the low dielectric properties of the fluorine-containing structure. Compared with traditional thermally conductive composite materials containing thermally conductive inorganic or metal fillers, its mechanical properties have obvious advantages.

[0039] (2) Based on the difference in surface tension or solubility parameters between the two phases, the present invention controls the phase separation of the two phases through block or blending methods and solvent evaporation processes; 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.

[0040] (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 phase separation morphology prepared 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, providing a complete heat conduction path for phonons in the heat conduction process, which can further improve the thermal conductivity of the material.

[0041] (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

[0042] Figure 1 This is a photo of the polyimide film in Comparative Example 2.

[0043] Figure 2 This is a cross-sectional morphology diagram of the polyimide film in Example 2.

[0044] Figure 3 This is a polarizing microscope image of polyimide in Example 2.

[0045] Figure 4 This is the X-ray diffraction curve of the polyimide film in Example 2.

[0046] Figure 5 This is a cross-sectional morphology diagram of the polyimide film in Example 3. DETAILED DESCRIPTION

[0047] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, 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 equally within the scope limited by the appended claims of the application.

[0048] Comparative Example 1

[0049] 6FDA-TFMB homopolymer: To a 150 ml three-necked flask, add 85 g of N,N-dimethylacetamide (DMAC) as the solvent. Under nitrogen, add 6.44 g (20 mmol) of 2,2'-bis(trifluoromethyl)diaminobenzidine (TFMB) and stir at room temperature until completely dissolved. Then, gradually add 8.88 g (20 mmol) of hexafluorodianhydride (6FDA) while stirring continuously to promote the reaction. The solids content is controlled at 15 wt%. The entire process typically lasts approximately 12 hours, resulting in a 6FDA-TFMB polyamic acid solution.

[0050] The above solution was cast onto 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 at each temperature to obtain a 6FDA-TFMB polyimide film. The film is consistent with other studies (Acta Polymerica Sinica, 2023, 54(8): 1219-1228.), with no crystallization and a dielectric constant of 2.7 (@10 6 Hz), thermal conductivity of 0.28 W / m·K, tensile strength of 87 MPa, and modulus of 1.2 GPa.

[0051] Comparative Example 2

[0052] TAHQ-ABHQ homopolymer: 85 g of DMAC was added to a 150 ml three-necked flask as a solvent under a nitrogen atmosphere to prevent oxidation. 6.62 g (19 mmol) of [4-(4-aminobenzoyl)oxyphenyl]-4-aminobenzoate (ABHQ) was then added to the solution and stirred with a magnetic stirrer until completely dissolved. Next, 8.71 g (19 mmol) of p-phenylene trimellitic dianhydride (TAHQ) was slowly added, maintaining a solids content of 15 wt%. Stirring was continued for approximately 12 hours to obtain a TAHQ-ABHQ polyamic acid solution.

[0053] 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 conditions 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.

[0054] Example 1

[0055] 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 amounts and stirred thoroughly. 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.

[0056] Example 2

[0057] Amine-terminated 6FDA-TFMB-60: In a 150 ml three-necked flask, add 85 g of DMAC as solvent and accurately weigh 6.44 g (20 mmol) of TFMB under nitrogen. Stir the solution at room temperature using a magnetic stirrer until TFMB completely dissolves into a homogeneous, transparent solution. Then, add 8.74 g (19.67 mmol) of 6FDA in three batches, stirring the solution continuously to ensure thorough mixing and promote the reaction. The entire reaction typically lasts approximately 10 hours while maintaining a solids content of 15 wt%. This yields an amine-terminated 6FDA-TFMB polyamic acid solution with a degree of polymerization of 60.

[0058] Anhydride-terminated TAHQ-ABHQ-30: In a 150 ml three-necked flask, accurately add 93 g of DMAC as the solvent. Ensure that the entire operation is carried out under a nitrogen atmosphere to prevent any possible oxidation reaction. Subsequently, weigh 6.97 g (20 mmol) of ABHQ and add it to the solvent. Stir the mixture with a magnetic stirrer at room temperature until the ABHQ is completely dissolved, forming a homogeneous solution. Next, gradually add 9.47 g (20.67 mmol) of TAHQ, ensuring a solid content of 15 wt%. Continue stirring the mixed solution for approximately 12 hours to prepare an anhydride-terminated TAHQ-ABHQ polyamic acid solution with a degree of polymerization of 30.

[0059] 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 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.

[0060] 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 "sea-island" structure. Figure 3 The polarizing microscope photo of the film shows that the continuous "sea" phase is covered with spherulites with typical Maltese black crosses, while the "island" phase is translucent and no crystallization occurs. Figure 4The XRD curve of the film shows that the block copolymer polyimide film prepared in Example 2 exhibits a distinct crystalline peak. Therefore, the polyimide film prepared in Example 2 exhibits a phase separation phenomenon with an "island-in-the-sea" structure. Furthermore, the continuous "sea" phase exhibits high crystallinity, providing a smooth thermal conductivity pathway for the preparation of intrinsically high thermal conductivity films.

[0061] Example 3

[0062] Amine-terminated 6FDA-TFMB-30: In a 150 ml three-necked flask, add 85 g of DMAC as solvent and accurately weigh 6.44 g (20 mmol) of TFMB under nitrogen. Stir the solution at room temperature using a magnetic stirrer until TFMB completely dissolves into a homogeneous, transparent solution. Then, gradually add 8.60 g (19.36 mmol) of 6FDA, continuing to stir the solution to ensure thorough mixing and promote the reaction. The entire reaction typically lasts approximately 10 hours while maintaining a solids content of 15 wt%. The resulting amine-terminated 6FDA-TFMB polyamic acid solution with a degree of polymerization of 30 is prepared.

[0063] Anhydride-terminated TAHQ-ABHQ-20: 94 g of DMAC (DMAC) was added to a 150 ml three-necked flask under nitrogen to prevent oxidation. 6.97 g (20 mmol) of ABHQ was then 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 bring the solid content to 15 wt%. The mixed solution was stirred for approximately 24 hours to prepare an anhydride-terminated TAHQ-ABHQ polyamic acid solution with a degree of polymerization of 20.

[0064] Preparation of block copolymer polyimide film: After mechanically stirring equal molar amounts of amino-terminated 6FDA-TFMB polyamic acid solution and anhydride-terminated TAHQ-ABHQ polyamic acid solution at 40°C for 10 hours, a block polyamic acid solution was obtained, which was then cast onto a glass plate to form a film. The film was then heated to 60°C at a rate of 3°C / min, dried under vacuum conditions for 8 hours, and finally heated to 200°C, 300°C, and 350°C at a 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 internal structure of the film is not dense; 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.

[0065] Example 4

[0066] Anhydride-terminated 6FDA-ABTFMB-60: In a 150 ml three-necked flask, 85 g of DMAC was added as solvent. Under nitrogen, 8.38 g (15 mmol) of 2,2'-bis(trifluoromethyl)-4,4'-bis(4-aminophenylcarbonylamino)biphenyl (ABTFMB) was accurately weighed. The solution was mechanically stirred at 30°C until ABTFMB completely dissolved into a homogeneous, transparent solution. Then, 6.77 g (15.25 mmol) of 6FDA was added in three batches, with continued stirring to ensure thorough mixing and promote the reaction. The entire reaction typically lasted approximately 12 hours, maintaining a solids content of 15 wt%. This yielded an anhydride-terminated 6FDA-TFMB polyamic acid solution with a degree of polymerization of 60.

[0067] Amine-terminated TAHQ-DABA-30: 85 g of DMAC was added to a 150 ml three-necked flask under nitrogen to prevent oxidation. 4.55 g (20 mmol) of 4,4'-diaminobenzanilide (DABA) was then 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 to maintain a solids content of 15 wt%. The mixed solution was stirred for approximately 20 hours to prepare an anhydride-terminated TAHQ-DABA polyamic acid solution with a degree of polymerization of 30.

[0068] Preparation of block copolymer polyimide film: Equal molar amounts 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. The above solution was cast on a glass plate to form a film, then heated to 80°C at a rate of 5°C / min, dried under vacuum conditions for 10 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 block polyimide film with 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.

[0069] Example 5

[0070] Amine-terminated 6FAP-BPADA-30: In a 150 ml three-necked flask, 79 g of DMAC was added as solvent. Under nitrogen, 6.42 g (15 mmol) of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP) was accurately weighed. The solution was stirred at room temperature using a magnetic stirrer until 6FAP completely dissolved, forming a homogeneous, transparent solution. Next, 7.56 g (14.52 mmol) of bisphenol A diether dianhydride (BPADA) was gradually added, with continued stirring to ensure thorough mixing and promote the reaction. The entire reaction typically lasted approximately 18 hours, maintaining a solids content of 15 wt%. This yielded an amine-terminated 6FAP-BPADA polyamic acid solution with a degree of polymerization of 30.

[0071] Anhydride-terminated APAB-BPDA-10: In a 150 ml three-necked flask, add 70 g of DMAC as solvent. Ensure that the entire operation is carried out under a nitrogen atmosphere to prevent any possible oxidation. Subsequently, weigh 5.71 g (25 mmol) of p-aminophenyl para-aminobenzoate (APAB) and add it to the solvent. Stir 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 to ensure a solid content of 15 wt%. Stir the mixed solution continuously for approximately 10 hours to prepare an anhydride-terminated APAB-BPDA polyamic acid solution with a degree of polymerization of 10.

[0072] Preparation of block copolymer polyimide film: Equal molar amounts 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. 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 conditions for 10 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 block polyimide film with 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 intrinsically high thermal conductivity and low dielectric polyimide film, characterized in that: The preparation method of the polyimide film comprises 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; Ester-containing aromatic diamines include 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: Fluorinated aromatic diamines include one or more of the following structures: Fluorinated anhydrides include one of the following structures: The flexible structure of the flexible aromatic diamine and the flexible acid anhydride includes one of the following structures: (2) subjecting polyamic acid A and polyamic acid B to a blending reaction or a polymerization reaction to obtain a blended or blocked polyamic acid solution; (3) forming the blended or segmented polyamic acid solution into a film, and then drying the solvent to obtain a blended or segmented 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.

2. A method for preparing an intrinsically 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) subjecting polyamic acid A and polyamic acid B to a blending reaction or a polymerization reaction to obtain a blended or blocked polyamic acid solution; (3) forming the blended or segmented polyamic acid solution into a film, and then drying the solvent to obtain a blended or segmented 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, wherein: 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% to 40wt%.

4. The preparation method according to claim 2, wherein: 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.

5. The preparation method according to claim 2, wherein: The polymerization reaction conditions in step (2) are as follows: the polymerization degrees of polyamic acid A and polyamic acid B are greater than or equal to 5 and greater than or equal to 1, respectively; polyamic acid A and polyamic acid B are 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.

6. The preparation method according to claim 2, wherein: 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.

7. 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.

8. 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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