Polyamide acid, polyimide, and preparation method and application thereof

Abstract

The application discloses polyamide acid, polyimide and a preparation method and application thereof. The polyamide acid and the polyimide both contain at least a structural unit. Through research on a PI material molecular structure, a molecular chain segment arrangement and PI-PI interaction, the application proposes a PI adhesive material with a molecular main chain containing a structure, a side chain containing a high-polarity aliphatic heterocyclic structure and strong interaction with a high-rigidity PI base film. Meanwhile, a non-planar structure of the aliphatic heterocyclic structure provides a large free volume and a large degree of freedom, which is beneficial to forming a high-bonding molecular conformation with the PI base film, so that high bonding strength can be generated without treatment, and the PI adhesive material has very good application value.

Description

Technical Field

[0001] This invention relates to the technical field of polyimide, and more specifically, to polyamic acid, polyimide, its preparation methods and applications. Background Technology

[0002] Polyimide (PI) is a type of polymer containing an imide ring structure in its molecular backbone. It is one of the functional polymer materials with the best overall performance and one of the few polymer materials that can meet the needs of the microelectronics industry.

[0003] PI (polyimide) material has always been one of the most important basic materials in the microelectronics industry. PI films and adhesives are widely used in the manufacturing and packaging of microelectronic devices. Especially in the preparation of flexible copper-clad laminates (FCCLs), the PI adhesive layer must simultaneously possess high bonding strength with both the copper foil and the PI base film, and withstand subsequent high-temperature processes such as soldering without blistering or peeling. Typically, to enhance the bonding strength between the PI adhesive layer and the PI base film, pretreatment methods such as alkaline treatment or plasma / arc treatment are used to increase the surface energy of the PI base film. However, these methods inevitably increase processing steps, and wet chemical treatments such as alkaline treatment generate waste liquid, which can easily pollute the environment.

[0004] Therefore, there is an urgent need to develop PI adhesive materials that can form high adhesion with untreated PI-based films. Summary of the Invention

[0005] To address the problems in existing technologies, this invention proposes polyamic acid, polyimide, their preparation methods, and applications. Based on research into the molecular structure, molecular chain segment arrangement, and PI-PI interactions of PI materials, this invention proposes a method where the molecular backbone contains... The PI adhesive material has a side chain containing highly polar aliphatic heterocyclic structures, which interact strongly with the high-rigidity PI base film. At the same time, the non-planar structure of the aliphatic heterocycles provides a large free volume and degree of freedom, which is conducive to forming a molecular conformation with high adhesion to the PI base film. Thus, it can produce high bonding strength without treatment, and has very good application value.

[0006] One object of the present invention is to provide a polyamic acid, wherein the polyamic acid contains at least Structural unit.

[0007] In the polyamic acid described in this invention, preferably,

[0008] The two -* characters are either in the middle position or in the adjacent position. When they are in the adjacent position, one of the -* characters must be in the middle position. Alignment;

[0009] Preferably,

[0010] The The structural unit is selected from at least one of the following structures:

[0011]

[0012] In the polyamic acid described in this invention, preferably, the polyamic acid has the following structural units:

[0013]

[0014] The Ar1 is selected from tetravalent aromatic residues, the Ar2 is selected from divalent aromatic residues, and the Ar2 contains at least the following structural units:

[0015]

[0016] In the polyamic acid of the present invention, preferably, the Ar1 does not contain fluorine; more preferably, the Ar1 is selected from at least one of the following structures:

[0017]

[0018] In the polyamic acid described in this invention, preferably,

[0019] The Ar2 The molar percentage of Ar2 is not less than 40%, preferably, the Ar2 contains... The molar percentage is not less than 45%; for example The molar percentages are 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc.

[0020] More preferably, the Ar2 does not contain fluorine.

[0021] More preferably, the Ar2 further includes at least one of the following structures:

[0022]

[0023] A second objective of this invention is to provide a method for preparing polyamic acid, comprising the following steps:

[0024] In a protective atmosphere, diamine monomers are dispersed in a solvent and mixed, then dianhydride monomers are added to react and generate a solution containing polyamic acid.

[0025] The diamine monomer contains at least one... diamine compounds with a specific structure;

[0026] The polyamic acid described in this invention is preferably prepared using the method described above.

[0027] In the preparation method of polyamic acid described in this invention, preferably,

[0028] The structural formula of the dianhydride monomer is O(O=C)2-Ar1-(C=O)2O; wherein Ar1 is selected from tetravalent aromatic residues; and / or,

[0029] The diamine monomer has the structural formula H2N-Ar2-NH2; wherein Ar2 is selected from divalent aromatic residues, and Ar2 contains at least Structural unit, in which The two -* characters are either in the middle position or in the adjacent position. When they are in the adjacent position, one of the -* characters must be in the middle position. Alignment;

[0030] Preferably, Ar2 contains The molar percentage of the structural unit is not less than 40%; more preferably, Ar2 contains The molar percentage of structural units is not less than 45%; for example... The molar percentages are 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc.; and / or,

[0031] The solvent is selected from organic solvents; preferably, the organic solvent is selected from at least one of m-cresol, N-methylpyrrolidone, γ-butyrolactone, dimethyl sulfoxide, N,N-dimethylacetamide or N,N-dimethylformamide;

[0032] The protective gas is at least one of nitrogen and inert gas.

[0033] In the preparation method of polyamic acid described in this invention, preferably,

[0034] The Ar1 in the dianhydride monomer does not contain fluorine; preferably, the Ar1 is selected from at least one of the following structures:

[0035]

[0036] In the preparation method of polyamic acid described in this invention, preferably,

[0037] The corresponding diamine monomer is selected from at least one of the following structures:

[0038]

[0039] In the preparation method of polyamic acid described in this invention, preferably,

[0040] The Ar2 in the diamine monomer does not contain fluorine.

[0041] Preferably, the Ar2 further includes at least one of the following structures:

[0042]

[0043] In the preparation method of polyamic acid described in this invention, preferably,

[0044] The molar ratio of the dianhydride monomer to the diamine monomer is (0.85–1.15):1; preferably (0.9–1.1):1; for example, 0.85:1, 0.9:1, 0.95:1, 1:1, 1.05:1, 1.1:1, 1.15:1; and / or,

[0045] The mass ratio of the dianhydride monomer to the solvent is (0.1–0.45):1; preferably (0.13–0.4):1; for example, 0.1:1, 0.13:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1; and / or,

[0046] The reaction temperature is 0–100°C; preferably 4–80°C; for example, 0, 4, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100°C; and / or,

[0047] The reaction time is 4 to 60 hours; preferably 6 to 60 hours; for example, 4, 8, 12, 16, 20, 30, 40, 50, or 60 hours.

[0048] A third objective of this invention is to provide a polyimide having the structural unit shown in formula (I):

[0049]

[0050] in,

[0051] Ar1 in formula (I) corresponds to Ar1 in the polyamic acid described in one of the objectives of this invention or Ar1 in the polyamic acid prepared by the method described in the second objective of this invention;

[0052] The Ar2 in formula (I) corresponds to the Ar2 in the polyamic acid described in one of the objectives of this invention, or the Ar2 in the polyamic acid prepared by the method described in another objective of this invention.

[0053] In the technical solution of the present invention, Ar1 may contain fluorine, but preferably does not contain fluorine; because the introduction of fluorine will reduce the adhesion of polyimide.

[0054] The fourth objective of this invention is to provide a method for preparing polyimide, selected from the following two methods:

[0055] Method 1: This method involves coating a solution containing polyamic acid into a film under a protective atmosphere, heating at low temperature to remove most of the solvent, and then curing at high temperature to complete imidization, thereby obtaining polyimide.

[0056] Method 2: This method includes the steps of adding a dehydrating agent to a solution containing polyamic acid, heating the solution to react, removing the dehydrating agent after the reaction is complete, and obtaining the polyimide material.

[0057] The polyamic acid in this invention is selected from the polyamic acid described in one of the objectives of this invention or the polyamic acid prepared by the method described in another objective of this invention;

[0058] The polyimide described in the third objective of this invention is preferably prepared using the method described above.

[0059] In the method for preparing polyimide according to the present invention, preferably,

[0060] In Method 1,

[0061] The low-temperature heating temperature is 50–160°C; preferably 60–150°C; and / or,

[0062] The high-temperature curing temperature is 180–400℃; preferably 200–350℃; and / or,

[0063] The high-temperature curing time is 1–120 min; preferably 1.5–90 min.

[0064] In method two,

[0065] The dehydrating agent is selected from aromatic hydrocarbons, preferably at least one of toluene or xylene; and / or

[0066] The mass ratio of the dehydrating agent to the polyamic acid-containing solution is 0.05–0.2:1; preferably 0.08–0.18:1; and / or,

[0067] The polyamic acid-containing solution has a polyamic acid mass concentration of 10% to 45%; preferably 13% to 40%; and / or,

[0068] The temperature of the heating reaction is 100–220°C; preferably 120–210°C; and / or,

[0069] The heating reaction time is 0.5 to 6 hours; preferably 1 to 5 hours.

[0070] The dehydrating agent can be removed using the methods commonly used in this field.

[0071] A fifth objective of this invention is to provide an application of the polyimide described in objective three of this invention or the polyimide prepared by the method described in objective four of this invention in the microelectronics industry, preferably as an adhesive layer material in the microelectronics industry. The polyimide material of this invention can be used as an adhesive layer to bond a substrate and / or a conductive material. The substrate is selected from commonly used electronic-grade polyimide substrates such as Kapton H and Uplex; the conductive material is selected from copper foil, aluminum foil, and conductive silver paste.

[0072] The above-mentioned contents of the present invention The polyimide structure allows for high adhesion to untreated PI films such as Kapton. The polyimide material of this invention, after curing, exhibits a peel strength ≥13 N / cm, preferably ≥15 N / cm, to untreated PI film substrates such as Kapton HN and Uplex.

[0073] The polyimide material of the present invention, after curing, has a peel strength ≥15N / cm with conductive materials such as copper foil and semiconductor substrates such as silicon, preferably ≥18N / cm.

[0074] The polyimide material of the present invention, when subjected to a 350°C tin bath treatment for 1 minute with untreated PI film substrates such as Kapton HN and Uplex, exhibits a peel strength ≥11 N / cm, preferably ≥13 N / cm.

[0075] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0076] Compared with the prior art, the present invention has at least the following advantages:

[0077] This invention proposes a molecular backbone containing The PI adhesive material has a side chain containing highly polar aliphatic heterocyclic structures, which interact strongly with the high-rigidity PI base film. Simultaneously, the non-planar structure of the aliphatic heterocycles provides a large free volume and degree of freedom, which is beneficial for forming a molecular conformation with high adhesion to the PI base film, thus achieving high bonding strength without further treatment. Therefore, this invention provides a polyimide (PI) material with high bonding strength that was independently designed and synthesized. Detailed Implementation

[0078] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0079] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0080] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0081] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0082] Example 1

[0083] Preparation of polyamic acid:

[0084] Add 9.5517 g (0.045 mol) to a three-necked flask. 22.5781 g (0.055 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 320 g of N-methyl-2-pyrrolidone (NMP) were dissolved by stirring, and then 31.5785 g (0.098 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. The mixture was stirred and reacted at 50 °C under nitrogen protection for 48 h to obtain a polyamic acid solution.

[0085] Application Example 1

[0086] After coating the polyamic acid solution of Example 1 onto a Kapton HN PI film, most of the solvent was removed at 150°C under nitrogen protection. Then, imidization was completed at 350°C under nitrogen protection for 5 minutes to obtain the PI-Kapton composite film of Example 1. The composite film was then hot-pressed with copper foil to obtain the FCCL of Example 1.

[0087] Example 2

[0088] Preparation of polyamic acid:

[0089] Add 13.6669 g (0.065 mol) to a three-necked flask. 14.3679 g (0.035 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 300 g of m-cresol were dissolved by stirring, and then 30.4006 g (0.098 mol) of 4,4'-oxobisphthalic anhydride (ODPA) was added. The mixture was stirred and reacted at 60 °C under nitrogen protection for 36 h to obtain a polyamic acid solution.

[0090] Application Example 2

[0091] After coating the polyamic acid solution of Example 2 onto a Kapton HN PI film, most of the solvent was removed at 120°C under nitrogen protection. Then, imidization was completed at 330°C under nitrogen protection for 10 minutes to obtain the PI-Kapton composite film of Example 2. The composite film was hot-pressed with copper foil to obtain the FCCL of Example 2.

[0092] Example 3

[0093] Add 21.0260 g (0.1 mol) to a three-necked flask. 300g of dimethylacetamide (DMAc) was stirred and dissolved, and then 11.2908g (0.0384mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) and 29.9802g (0.0576mol) of bisphenol A type diether dianhydride (BPADA) were added. The mixture was stirred and reacted at 40℃ under nitrogen protection for 48h to obtain a polyamic acid solution.

[0094] Application Example 3

[0095] After coating the polyamic acid solution described in Example 3 onto a Kapton HN PI film, most of the solvent was removed at 80°C under nitrogen protection. Then, imidization was completed at 300°C under nitrogen protection for 30 minutes to obtain the PI-Kapton composite film of Example 3. The composite film was then hot-pressed with copper foil to obtain the FCCL of Example 3.

[0096] Example 4

[0097] Add 14.7182 g (0.07 mol) to a three-necked flask. 5.9409 g (0.03 mol) of 4,4'-diaminodiphenylmethane and 350 g of dimethylacetamide (DMAc) were dissolved by stirring, and then 6.4781 g (0.0297 mol) of pyromellitic dianhydride (PMDA) and 36.0700 g (0.0693 mol) of bisphenol A diether dianhydride (BPADA) were added. The mixture was stirred and reacted at 40 °C under nitrogen protection for 48 h to obtain a polyamic acid solution.

[0098] Application Example 4

[0099] After coating the polyamic acid solution of Example 4 onto the Kapton HN PI film, most of the solvent was removed at 60°C under nitrogen protection. Then, imidization was completed at 350°C under nitrogen protection for 30 minutes to obtain the PI-Kapton composite film of Example 4. The composite film was hot-pressed with copper foil to obtain the FCCL of Example 4.

[0100] Example 5

[0101] Add 10.513 g (0.05 mol) to a three-necked flask. 20.5255 g (0.05 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 370 g of N-methylpyrrolidone (NMP) were dissolved by stirring. Then, 31.5785 g (0.098 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. The mixture was stirred and reacted at 40 °C under nitrogen protection for 36 h to obtain a polyamic acid solution.

[0102] Application Example 5

[0103] After coating the polyamic acid solution of Example 5 onto the Kapton HN PI film, most of the solvent was removed at 100°C under nitrogen protection. Then, imidization was completed at 330°C under nitrogen protection for 15 minutes to obtain the PI-Kapton composite film of Example 5. The composite film was hot-pressed with copper foil to obtain the FCCL of Example 5.

[0104] Example 6

[0105] Add 21.026 g (0.1 mol) to a three-necked flask. 350g of N-methylpyrrolidone (NMP) was dissolved by stirring, and then 15.2778g (0.04925mol) of 4,4'-oxydiphthalic anhydride (ODPA) and 15.8698g (0.04925mol) of bisphenol A diether dianhydride (BPADA) were added. The mixture was stirred and reacted at 60℃ under nitrogen protection for 24h to obtain a polyamic acid solution.

[0106] Application Example 6

[0107] After coating the polyamic acid solution of Example 6 onto the Kapton HN PI film, most of the solvent was removed at 100°C under nitrogen protection. Then, imidization was completed at 330°C under nitrogen protection for 15 minutes to obtain the PI-Kapton composite film of Example 6. The composite film was hot-pressed with copper foil to obtain the FCCL of Example 6.

[0108] Example 7

[0109] (ODPA5+6FDA5-meta morpholine)

[0110] Add 21.026 g (0.1 mol) to a three-necked flask. 350g of N-methylpyrrolidone (NMP) was stirred and dissolved, and then 15.2778g (0.04925mol) of 4,4'-oxobisphthalic anhydride (ODPA) and 21.8788g (0.04925mol) of hexafluoroisopropylphthalic anhydride (6FDA) were added. The mixture was stirred and reacted at 60°C under nitrogen protection for 24h to obtain a polyamic acid solution.

[0111] Application Example 7

[0112] After coating the polyamic acid solution of Example 7 onto the Kapton HN PI film, most of the solvent was removed at 100°C under nitrogen protection. Then, imidization was completed at 330°C under nitrogen protection for 15 minutes to obtain the PI-Kapton composite film of Example 7. The composite film was then hot-pressed with copper foil to obtain the FCCL of Example 7.

[0113] Example 8

[0114] Add 7.3591 g (0.035 mol) to a three-necked flask. 26.6832 g (0.065 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 320 g of N-methyl-2-pyrrolidone (NMP) were dissolved by stirring, and then 31.5785 g (0.098 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. The mixture was stirred and reacted at 50 °C under nitrogen protection for 48 h to obtain the polyamic acid solution of Example 8.

[0115] After coating the polyamic acid solution of Example 8 onto a Kapton HN PI film, most of the solvent was removed at 150°C under nitrogen protection. Then, imidization was completed at 350°C under nitrogen protection for 5 minutes to obtain the PI-Kapton composite film of Example 8. The composite film was then hot-pressed with copper foil to obtain the FCCL of Example 8.

[0116] Comparative Example 1

[0117] 41.051 g (0.1 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 320 g of N-methyl-2-pyrrolidone (NMP) were added to a three-necked flask and stirred until dissolved. Then, 31.5785 g (0.098 mol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was added. The mixture was stirred and reacted at 50 °C under nitrogen protection for 48 h to obtain a polyamic acid solution.

[0118] After coating the polyamic acid solution of Comparative Example 1 onto a Kapton HN PI film, most of the solvent was removed at 150°C under nitrogen protection. Then, imidization was completed at 350°C under nitrogen protection for 5 minutes to obtain the PI-Kapton composite film of Comparative Example 2. The composite film was hot-pressed with copper foil to obtain the FCCL of Comparative Example 1.

[0119] Comparative Example 2

[0120] 41.051 g (0.1 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 320 g of N-methyl-2-pyrrolidone (NMP) were added to a three-necked flask and stirred until dissolved. Then, 43.5355 g (0.098 mol) of hexafluoroisopropylphthalic anhydride (6FDA) was added. The mixture was stirred and reacted at 50 °C under nitrogen protection for 48 h to obtain a polyamic acid solution.

[0121] After coating the polyamic acid solution of Comparative Example 2 onto a Kapton HN PI film, most of the solvent was removed at 150°C under nitrogen protection. Then, imidization was completed at 350°C under nitrogen protection for 5 minutes to obtain the PI-Kapton composite film of Comparative Example 2. The composite film was hot-pressed with copper foil to obtain the FCCL of Comparative Example 2.

[0122] It can be seen that the polyamic acid prepared in each of the above embodiments contains at least [missing information]. Structural unit, and The molar percentage of aliphatic heterocyclic structural units in Ar2 is not less than 40%. The specific molar percentages of aliphatic heterocyclic structural units in Ar2 in the polyamic acids prepared in each embodiment are shown in Table 1 below:

[0123] Table 1

[0124]

[0125] According to the IPC-TM-650-2.4.9 standard, the peel strength between the developed PI adhesive material and the PI base film was tested using a Free Wheeling Rotary Drum test fixture. The peel strength between the developed PI adhesive material and the copper foil was also tested. The results are shown in Table 2.

[0126] Table 2

[0127]

[0128] A comparison of the results of Example 8 and Example 1 of the present invention shows that when the polyimide structure Ar2 contains... When the content of structural units decreases, its adhesive strength and heat resistance decrease significantly.

[0129] A comparison of the results of Comparative Examples 1 and 2, and of Examples 5 and 6, shows that the presence of fluorine in the examples of this invention has a relatively small impact on the viscosity of the PI adhesive material; while the presence of fluorine in the comparative examples has a relatively large impact on the viscosity of the PI adhesive material. Therefore, it is evident that the present invention introduces a certain proportion of fluorine... Structural units can not only improve the viscosity of PI adhesive materials, but also reduce the influence of fluorine on the viscosity of PI adhesive materials.

[0130] In summary, this invention introduces a certain proportion of The polyimide prepared by the structure has excellent adhesion to PI-based films / copper foils and heat resistance.

[0131] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0132] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0133] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application’s filing, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0134] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. A polyamic acid, characterized in that: The polyamic acid has the following structural units: ； The Ar1 is selected from tetravalent aromatic residues, the Ar2 is selected from divalent aromatic residues, and the Ar2 contains at least the following structural units: In the Ar2 mentioned The molar percentage is not less than 40%.

2. The polyamic acid according to claim 1, characterized in that: Two of them It is located in the intermediate position or in the adjacent position, and when it is in the adjacent position, one of them To be located The alignment.

3. The polyamic acid according to claim 1, characterized in that: The The structural unit is selected from at least one of the following structures: 、 、 、 。 4. The polyamic acid according to claim 3, characterized in that: Ar1 does not contain fluorine.

5. The polyamic acid according to claim 4, characterized in that: The Ar1 is selected from at least one of the following structures: 、 、 、 。 6. The polyamic acid according to claim 1, characterized in that: The Ar2 The molar percentage is not less than 45%.

7. The polyamic acid according to claim 6, characterized in that: The Ar2 does not contain fluorine.

8. The polyamic acid according to claim 7, characterized in that: The Ar2 also includes at least one of the following structures: 、 、 、 。 9. A method for preparing polyamic acid, comprising the following steps: In a protective atmosphere, diamine monomers are dispersed in a solvent and mixed, then dianhydride monomers are added to react and generate a solution containing polyamic acid. The structural formula of the dianhydride monomer is O(O=C)2-Ar1-(C=O)2O; wherein Ar1 is selected from tetravalent aromatic residues; The diamine monomer contains at least one... A diamine compound with the structure H2N-Ar2-NH2; wherein Ar2 is selected from divalent aromatic residues, and Ar2 contains at least Structural unit; Ar2 contains The molar percentage of structural units is not less than 40%.

10. The method for preparing polyamic acid according to claim 9, characterized in that: The polyamic acid according to any one of claims 2-8 is prepared by the method described above.

11. The method for preparing polyamic acid according to claim 9, characterized in that: The solvent is selected from organic solvents.

12. The method for preparing polyamic acid according to claim 11, characterized in that: The organic solvent is selected from at least one of m-cresol, N-methylpyrrolidone, γ-butyrolactone, dimethyl sulfoxide, N,N-dimethylacetamide, or N,N-dimethylformamide.

13. The method for preparing polyamic acid according to claim 9, characterized in that: The molar ratio of the dianhydride monomer to the diamine monomer is (0.85~1.15):1; and / or, The mass ratio of the dianhydride monomer to the solvent is (0.1~0.45):1; and / or, The reaction temperature is 0~100℃; and / or, The reaction time is 4 to 60 hours.

14. The method for preparing polyamic acid according to claim 13, characterized in that: The molar ratio of the dianhydride monomer to the diamine monomer is (0.9~1.1):1; and / or, The mass ratio of the dianhydride monomer to the solvent is (0.13~0.4):1; and / or, The reaction temperature is 4~80℃; and / or, The reaction time is 6 to 60 hours.

15. A polyimide, characterized in that, The polyimide has the structural unit shown in formula (I): Formula (I); in, The Ar1 in formula (I) corresponds to the Ar1 in the polyamic acid according to any one of claims 1-8 or to the Ar1 in the polyamic acid prepared by the method according to any one of claims 9-14; The Ar2 in formula (I) corresponds to the Ar2 in the polyamic acid according to any one of claims 1-8 or to the Ar2 in the polyamic acid prepared by the method according to any one of claims 9-14.

16. A method for preparing a polyimide, selected from the following two methods: Method 1: This method involves coating a solution containing polyamic acid into a film under a protective atmosphere, removing the solvent by heating at a low temperature, and then curing at a high temperature to obtain polyimide. Method 2: This method includes the steps of adding a dehydrating agent to a solution containing polyamic acid, heating the solution to react, removing the dehydrating agent after the reaction is complete, and obtaining the polyimide material. The polyamic acid is selected from the polyamic acid according to any one of claims 1-8 or the polyamic acid prepared by the method according to any one of claims 9-14; The polyimide of claim 15 is prepared by the method described above.

17. The method for preparing polyimide according to claim 16, characterized in that: In Method 1, The temperature of the low-temperature heating is 50~160℃; and / or, The high-temperature curing temperature is 180~400℃; and / or, The high-temperature curing time is 1~120 min; and / or, In method two, The dehydrating agent is selected from aromatic hydrocarbons; and / or, The mass ratio of the dehydrating agent to the polyamic acid-containing solution is 0.05~0.2:1; and / or, The polyamic acid-containing solution has a mass concentration of 10% to 45%; and / or, The temperature of the heating reaction is 100~220℃; and / or, The heating reaction takes 0.5 to 6 hours.

18. The method for preparing polyimide according to claim 17, characterized in that: In Method 1, The temperature of the low-temperature heating is 60~150℃; and / or, The high-temperature curing temperature is 200~350℃; and / or, The high-temperature curing time is 1.5~90 min; and / or, In method two, The dehydrating agent is selected from at least one of toluene or xylene; and / or The mass ratio of the dehydrating agent to the polyamic acid-containing solution is 0.08~0.18:1; and / or, The polyamic acid-containing solution has a mass concentration of 13% to 40%; and / or, The temperature of the heating reaction is 120~210℃; and / or, The heating reaction takes 1 to 5 hours.

19. The use of a polyimide as described in claim 15 or a polyimide prepared by the method of any one of claims 16-18 in the microelectronics industry.

20. The application according to claim 19, characterized in that: Applications of adhesive layer materials in the microelectronics industry.

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