Ultrathin polyimide film, preparation method and application

Abstract

The invention belongs to the technical field of polyimide film materials, and particularly relates to an ultrathin polyimide film, a preparation method and application. The preparation method comprises the following steps: S1, in an inert atmosphere, dissolving a diamine monomer in a dianhydride monomer, then adding the dianhydride monomer in multiple batches, and stirring each time of adding so that the diamine monomer and the dianhydride monomer are subjected to a polymerization reaction to obtain a polyamide acid solution; s2, uniformly coating the coating on the surface of the PET film, and drying to form a coating, so as to obtain the PET film attached with the coating; and S3, pouring the polyamide acid solution prepared in the step S1 into a glue tank of a comma scraper, uniformly coating the surface of the PET film attached with the coating, then drying part of the cross-linked film, stripping part of the cross-linked film, clamping the cross-linked film on a bracket with needle plates on the periphery, and carrying out high-temperature imidization treatment to obtain the polyimide film.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyimide film materials, and in particular relates to an ultra-thin polyimide film, a preparation method and applications. Background Art

[0002] Polyimide, an aromatic heterocyclic polymer containing imide groups in its molecular structure, is one of the most comprehensive organic polymer materials. It has a high-performance, high-temperature resistance exceeding 400°C, a long-term operating temperature range of -200°C to 300°C, no distinct melting point, and high insulation properties. Polyimide films, due to their excellent thermal stability, electrical insulation, mechanical properties, and dielectric properties, are widely used in microelectronic integrated circuits, flexible printed circuit substrates, rail transportation, aerospace, and other fields.

[0003] The main methods for forming polyimide films include aluminum foil impregnation, cast film, and cast-stretching. The impregnation method has simple equipment and process, but aluminum powder often sticks to the film surface, and production efficiency is low. The cast film method is the mainstream domestic production process for polyimide films for electrical applications. It has good equipment precision, good film uniformity, and no restrictions on film length. It can be produced continuously, and generally required films can be produced using this method. The performance of films produced by the stretching method is significantly improved, but the process is relatively complex and the equipment investment is large. However, both the cast film method and the cast-stretching method require steel belt casting, which requires high steel belt flatness and no surface defects. Once the steel belt has a poor appearance, the produced PI film will also have a poor appearance. The steel belt surface is difficult to repair, and optical-grade PI film materials cannot be produced. In addition, the production of large-width, highly flat steel belts is difficult, and large-width PI films cannot be produced using the steel belt cast film method.

[0004] In recent years, with the rapid development of microelectronics technology, higher performance requirements have been placed on polyimide films. On the one hand, to accommodate the miniaturization and integration of electronic devices, polyimide films need to become ultra-thin. On the other hand, to ensure the performance of electronic devices, polyimide films also require high flatness. Therefore, developing a method for large-scale production of ultra-thin, highly flat polyimide films is of great practical significance. Ultra-thin, highly flat polyimide films are used in chips in fields such as aviation, aerospace, microelectronics, nanotechnology, liquid crystals, separation membranes, and lasers. High flatness of polyimide films can affect the performance of the chip's copper foil material, thermal conductivity uniformity, and other factors, thereby affecting the accuracy, stability, and safety of the application product. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing an ultrathin polyimide film, comprising the following steps:

[0007] S1. In an inert atmosphere, dissolving a diamine monomer in a dianhydride monomer, and then adding the dianhydride monomer in multiple batches, stirring each time, to allow the diamine monomer and the dianhydride monomer to undergo a polymerization reaction to obtain a polyamic acid solution;

[0008] S2, evenly coating the polyester coating on the surface of the PET film, drying to form a coating to obtain a PET film with the coating;

[0009] S3. Pour the polyamic acid solution obtained in step S1 into the glue groove of the comma scraper and evenly coat it on the surface of the PET film with the coating, then dry the partially cross-linked film, peel off the partially cross-linked film, clamp it on a bracket with needle plates on all sides, and undergo high-temperature imidization treatment to obtain a polyimide film.

[0010] Furthermore, the molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.95-1.05); and the added amount of the dehydrating agent and the accelerator accounts for 1%-3% of the total weight of the solution.

[0011] Furthermore, the diamine monomer is at least one of 4,4'-diaminodiphenyl ether and p-phenylenediamine; the dianhydride monomer is at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, hexafluorodianhydride, and 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride; and the organic solvent is at least one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0012] Furthermore, the dehydrating agent is one or a combination of two or more of acetic anhydride, propionic anhydride and butyric anhydride, and the accelerator is one or a combination of two or more of trimethylamine, triethylamine, tripropylamine, triethanolamine, N-ethylpiperidine, imidazole, pyridine, quinoline and isoquinoline.

[0013] Furthermore, the polyester coating is a pure polyester powder coating or a polyester-epoxy powder coating.

[0014] Furthermore, the polymerization reaction temperature in step S1 is 0-25° C.; the solid content of the polyamic acid solution is 10%-30%, and the viscosity is 3000 cps-40000 cps.

[0015] Furthermore, the drying conditions in step S3 are: temperature of 60-200° C., and drying time of 20-60 min; the high-temperature imidization treatment conditions are: temperature of 200-500° C., and time of 20-60 min.

[0016] Furthermore, the thickness of the ultra-thin polyimide film is 3-15 μm.

[0017] An ultra-thin polyimide film is prepared by the above-mentioned method for preparing an ultra-thin polyimide film.

[0018] The ultra-thin polyimide film described above is used as a raw material in the field of flexible printed circuit boards.

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention adopts a casting method to prepare a polyimide film. It uses a PET film after a special coating treatment as a substrate, and casts a polyamic acid solution on the substrate. Then, after drying, peeling, and high-temperature imidization, an ultra-thin polyimide film is obtained. The ultra-thin polyimide film with a thickness of 3-15 μm can be obtained. The surface of the film has high flatness and can meet the requirements of the microelectronics industry for use as a substrate for flexible printed circuit boards (FPCs), semiconductor packaging materials, and as an interlayer dielectric material for ultra-large-scale integrated circuits. These applications require the film to have high-precision flatness and uniformity to ensure the reliability and performance requirements of the circuit;

[0021] 2. The cast substrate used in the present invention is a PET film, and the width can reach more than 1.5 m. Therefore, the method of the present invention can produce ultra-thin polyimide films with a large width, improve production efficiency, and greatly increase the length of the desolventizing oven, thereby controlling the residual solvent amount and the degree of semi-crosslinking of the coating, increasing the film production speed, improving efficiency, and being suitable for large-scale production. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Example 1

[0024] Preparation of polyamic acid solution:

[0025] In a nitrogen atmosphere, 4,4'-diaminodiphenyl ether was dissolved in N,N-dimethylacetamide. Pyromellitic dianhydride was then added in multiple batches, stirring for 30 minutes between additions. Polymerization was carried out at 10°C. The resulting polyamic acid solution had a solids content of 18% and a viscosity of 2,000-50,000 cps. The molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic dianhydride was 1:1.

[0026] Preparation of ultra-thin polyimide films:

[0027] S1. Apply the coating evenly on the surface of the PET film and dry it to form a coating;

[0028] S2. Pour the polyamic acid solution into the glue groove of the comma scraper, evenly coat it on the coated surface of the PET film, and dry it at a temperature of 60°C-100°C for 20-30 minutes to form a partially cross-linked film with a thickness of 15-25 μm. Then peel off the partially cross-linked film, clamp it on a bracket with needle plates on all sides, and perform high-temperature imidization at 250°C for 20-30 minutes to obtain a polyimide film.

[0029] Example 2

[0030] Preparation of polyamic acid solution:

[0031] 4,4'-diaminodiphenyl ether is dissolved in N,N-dimethylformamide, and then pyromellitic dianhydride is added. A polymerization reaction is carried out at 0°C in a nitrogen atmosphere to obtain a polyamic acid solution with a solid content of 20% and a viscosity of 5000-80000 cps, wherein the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic dianhydride is 1:1.

[0032] Preparation of ultra-thin polyimide films:

[0033] S1. Apply the coating evenly on the surface of the PET film and dry it to form a coating;

[0034] S2. The polyamic acid solution is evenly coated on the coated surface of the PET film, and dried at a temperature of 80-150° C. for 20-30 min to form a partially cross-linked film with a thickness of 15-25 μm. The partially cross-linked film is then peeled off and subjected to high-temperature imidization at 250° C. for 20-30 min to obtain a polyimide film.

[0035] Example 3

[0036] Preparation of polyamic acid solution:

[0037] 4,4'-diaminodiphenyl ether is dissolved in N-methylpyrrolidone, and then pyromellitic dianhydride is added. The polymerization reaction is carried out at 25°C in a nitrogen atmosphere to obtain 25% with a viscosity of 20,000-100,000 cps, wherein the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic dianhydride is 1:1.

[0038] Preparation of ultra-thin polyimide films:

[0039] S1. Apply the coating evenly on the surface of the PET film and dry it to form a coating;

[0040] S2. The polyamic acid solution is evenly coated on the coated surface of the PET film, and dried at a temperature of 80°C-200°C for 15-60 min to form a partially cross-linked film with a thickness of 5-25 μm. The partially cross-linked film is then peeled off and subjected to high-temperature imidization at 400°C for 10-30 min to obtain a polyimide film.

[0041] Comparative Example 1

[0042] Preparation of polyamic acid solution:

[0043] 4,4'-diaminodiphenyl ether is dissolved in N,N-dimethylacetamide, and then pyromellitic dianhydride is added. A polymerization reaction is carried out at 10°C in a nitrogen atmosphere to obtain a polyamic acid solution with a solid content of 15%-30% and a viscosity of 2000cps-40000cps, wherein the molar ratio of 4,4'-diaminodiphenyl ether to pyromellitic dianhydride is 1:1.

[0044] Preparation of ultra-thin polyimide films:

[0045] The polyamic acid solution is evenly coated on the surface of the PET film, dried to form a partially cross-linked film, and then the partially cross-linked film is peeled off and subjected to high-temperature imidization to obtain an ultra-thin polyimide film with a thickness of 1000 Å. In this case, during the first round of drying, film formation is difficult, the coating is prone to shrinkage in the oven, the finished product curls, or the partially cross-linked film dried by the coating has low strength and is easy to break. The peeling force after the semi-finished product is completed is large, which damages the surface of the PET film and makes it impossible to tear it apart.

[0046] Test example

[0047] The performance of the ultra-thin polyimide films prepared in Examples 1-3 was tested, and the results are shown in Table 1:

[0048]

[0049] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0050] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing an ultra-thin polyimide film, characterized in that: The preparation method comprises the following steps: S1. In an inert atmosphere, dissolving a diamine monomer in a dianhydride monomer, and then adding the dianhydride monomer in multiple batches, stirring each time, so that the diamine monomer and the dianhydride monomer undergo a polymerization reaction to obtain a polyamic acid solution; S2, evenly coating the polyester coating on the surface of the PET film, drying to form a coating to obtain a PET film with the coating attached; S3, pouring the polyamic acid solution obtained in step S1 into the glue groove of the comma scraper, evenly coating it on the surface of the PET film with the coating, and then drying the partially cross-linked film, peeling off the partially cross-linked film, clamping it on a bracket with needle plates around it, and subjecting it to high-temperature imidization treatment to obtain a polyimide film.

2. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.95-1.05); the added amount of the dehydrating agent and the accelerator accounts for 1%-3% of the total weight of the solution.

3. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The diamine monomer is at least one of 4,4'-diaminodiphenyl ether and p-phenylenediamine; the dianhydride monomer is at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, hexafluoro dianhydride, and 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride; and the organic solvent is at least one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

4. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The dehydrating agent is one or a combination of two or more of acetic anhydride, propionic anhydride and butyric anhydride, and the accelerator is one or a combination of two or more of trimethylamine, triethylamine, tripropylamine, triethanolamine, N-ethylpiperidine, imidazole, pyridine, quinoline and isoquinoline.

5. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The polyester coating is a pure polyester powder coating or a polyester-epoxy powder coating.

6. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The polymerization reaction temperature in step S1 is 0-25° C.; the solid content of the polyamic acid solution is 10%-30%, and the viscosity is 3000cps-40000cps.

7. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The drying conditions in step S3 are: temperature of 60-200° C., and drying time of 20-60 min; the high-temperature imidization conditions are: temperature of 200-500° C., and time of 20-60 min.

8. The method for preparing an ultra-thin polyimide film according to claim 1, characterized in that: The thickness of the ultra-thin polyimide film is 3-15 μm.

9. An ultra-thin polyimide film prepared by the method for preparing an ultra-thin polyimide film according to any one of claims 1 to 8.

10. The ultra-thin polyimide film as claimed in claim 9 is used as a raw material in the field of flexible printed circuit boards.

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