Polyimide film with low dielectric constant and low moisture absorption and preparation method thereof

Abstract

The invention provides a polyimide film with low dielectric constant and low moisture absorption. The polyimide film comprises aliphatic polyimide resin; an aromatic polyimide resin; an aliphatic and aromatic copolyimide resin; and nano mesoporous microspheres; the aliphatic polyimide resin contains at least one of a chain aliphatic hydrocarbon group or a cyclic aliphatic hydrocarbon group. According to the low-dielectric polyimide prepared by the method, the dielectric constant can be effectively reduced by air in the low-dielectric nano mesoporous microspheres, and the problem of poor compatibility between the nano mesoporous microspheres and a polyimide matrix does not occur, so that the dielectric property is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of thin films, and in particular relates to a polyimide film with low dielectric constant and low moisture absorption and a preparation method thereof. Background Art

[0002] In recent years, electronic devices have been moving towards miniaturization, multifunctionality, and lightweighting. Against this backdrop, high-performance dielectric materials have become a focus of industry attention and sparked a widespread research boom. The development of such materials is of great significance for further improving the performance of electronic devices, and therefore has received widespread attention from the industry. Low-dielectric materials can effectively alleviate the attenuation problem caused by weak diffraction ability, reduce the power consumption of integrated circuits, improve the performance of electronic devices, and reduce the dielectric constant of materials, which has become a key research focus. Polyimide (PI) is an important dielectric material.

[0003] Polyimide (PI) film, with its excellent properties such as low dielectric constant, good thermal and chemical stability, and low moisture absorption, is an ideal material for interlayer insulation. However, the dielectric constant of common PI films (such as Kapton) currently ranges from 3.1 to 3.6, which no longer meets demand. Therefore, the development of polyimide materials with lower dielectric constants is urgently needed.

[0004] Currently, the methods for reducing the dielectric constant of polyimide in the prior art mainly include:

[0005] Patent application number 201710574815.4 discloses a method for preparing highly transparent and low-dielectric polyimide films. The patent uses fluorine-containing monomers to reduce the dielectric constant of the film. However, the introduction of fluorine elements will lead to a decrease in the bonding strength, glass transition temperature and mechanical strength of the polyimide, and an increase in the thermal expansion coefficient. In addition, the high price of fluorine-containing monomers will increase the production cost of PI films.

[0006] Patent application number 201510225007.8 discloses a method for preparing a porous low-dielectric polyimide film. The patent uses calcium carbonate as a pore-forming agent raw material and removes the calcium carbonate with dilute hydrochloric acid to obtain a porous structure, thereby reducing the dielectric constant of the film. However, the pores prepared by this method are unevenly distributed and poorly sealed, which is prone to stress concentration and collapse.

[0007] Patent application number 201911148544.1 discloses a low-dielectric polyimide film, its preparation method, and application. This patent uses fluorinated silane to modify the outer surface of hollow microspheres, then blends them with polytetrafluoroethylene powder and a polyamic acid solution. Following imidization, the low-dielectric polyimide film is produced. The poor compatibility of fluorinated silane with polyimide molecules in this method can lead to decreased mechanical properties.

[0008] In existing processes, method (3) for reducing the dielectric constant of polyimide has received much attention and has been a research hotspot in recent years. However, due to the influence of the properties of the selected porous material and the uneven dispersion of the porous material, the effect of improving the dielectric properties of the polyimide material is not very ideal.

[0009] With the rapid development of 5G, the Internet of Things, and other fields, microelectronics, as a key technology, has become a hotbed of global high-tech competition, but the requirements for material performance are also becoming increasingly stringent. Polyimide, a key material currently used in microelectronics, typically has a dielectric constant between 3.0 and 3.6. However, facing the current demand for high-frequency and high-speed signal transmission, traditional polyimide materials are no longer able to meet the current dielectric material requirements, gradually becoming a bottleneck restricting the development of microelectronics technology.

[0010] Polyimide (PI), a high-performance polymer material, is widely used in various fields, particularly in microelectronics. Its thin film products, as key interlayer dielectrics (ILDs) in flexible copper-clad laminates (FCCLs), provide fundamental support for the overall performance and functionality of flexible printed circuit boards (FPCBs). However, the relatively high dielectric constant of traditional PI films cannot fully meet the urgent demand for low dielectric constants in current and future integrated circuit designs, which are demanding requirements.

[0011] Based on this, the present invention provides a polyimide film with low dielectric constant and low moisture absorption and a preparation method thereof. Summary of the Invention

[0012] In order to overcome the defects in the prior art, a polyimide film with low dielectric constant and low moisture absorption and a preparation method thereof are provided.

[0013] In order to achieve the above object, the present invention provides the following technical solutions:

[0014] A polyimide film having a low dielectric constant and low moisture absorption, comprising:

[0015] Aliphatic polyimide resin;

[0016] Aromatic polyimide resin;

[0017] Aliphatic and aromatic copolymer polyimide resin; and nano-mesoporous microspheres;

[0018] The aliphatic polyimide resin includes at least one of a chain aliphatic hydrocarbon group and a cyclic aliphatic hydrocarbon group.

[0019] Preferably, the aliphatic polyimide resin is derived from an aliphatic polyamic acid polymerized from an aliphatic diamine monomer and an aliphatic dianhydride monomer;

[0020] Aromatic polyimide resins are derived from aromatic polyamic acid polymerized from aromatic diamine monomers and aromatic dianhydride monomers;

[0021] Aliphatic / aromatic polyimide resins are aliphatic and aromatic copolymer polyimide resins derived from the polymerization of aliphatic / aromatic diamine monomers and aliphatic / aromatic dianhydride monomers;

[0022] The polyimide film is prepared by imidizing a precursor composition, wherein the precursor composition comprises the aliphatic polyamic acid, the aromatic polyamic acid, the aliphatic / aromatic polyamic acid and the nano-mesoporous microspheres.

[0023] Preferably, the aromatic polyamic acid is included in an amount of 5 to 50 wt % relative to the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid.

[0024] Preferably, the chain aliphatic hydrocarbon group comprises at least one aliphatic organic group selected from the group consisting of a C1 to C30 alkyl group, a C2 to C30 alkenyl group, a C2 to C30 alkynyl group, a C1 to C30 alkylene group, a C2 to C30 alkenylene group, and a C2 to C30 alkynylene group;

[0025] The cyclic aliphatic hydrocarbon group includes at least one alicyclic organic group selected from the group consisting of a C3 to C30 cycloalkyl group, a C3 to C30 cycloalkenyl group, a C3 to C30 cycloalkynyl group, a C3 to C30 cycloalkylene group, a C6 to C30 cycloalkenylene group, and a C3 to C30 cycloalkynylene group.

[0026] Preferably, the aliphatic diamine monomer is at least one selected from the group consisting of cyclohexanediamine, 1,4-cyclohexanebis(methylamine), 2,2-bis[(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxyphenyl)]hexafluoropropane, 4,4'-methylenebiscyclohexylamine, 4,4'-methylenebis(2-methylcyclohexylamine), 1,3-adamantanediamine, and 3,3'-diamino-1,1'-diamantane;

[0027] The aliphatic dianhydride monomer is at least one selected from the group consisting of 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]malonic dianhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and cyclobutane-1,2,3,4-tetracarboxylic dianhydride.

[0028] Preferably, the aromatic diamine monomer is at least one selected from the group consisting of 1,4-phenylenediamine, 4,4'-diphenylamine oxide, 3,4'-diphenylamine oxide, 4,4'-dimethyldiphenylamine and 1,3-bis(4-aminophenoxy)benzene;

[0029] The aromatic dianhydride monomer is at least one selected from the group consisting of pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic anhydride (ODPA), and benzophenonetetracarboxylic dianhydride (BTDA).

[0030] Preferably, the nano-mesoporous microspheres exist in at least one of the following states:

[0031] The first state (A) of nano-mesoporous microspheres coated on the surface;

[0032] a second state (B) in which the nano-mesoporous microspheres are physically bound to the polymer chains of the polyimide resin;

[0033] and a third state (C) in which the nano-mesoporous microspheres are chemically bonded to the polymer chains of the polyimide resin;

[0034] The nano-mesoporous microspheres are nano-scale, and the particle size is usually between 1 and 1000 nanometers.

[0035] Mesoporous structure: pore diameter ranges from 2 to 50 nanometers.

[0036] Preferably, the microspheres are included in an amount of 1 wt % to 10 wt % relative to the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid.

[0037] Preferably, the nano-mesoporous microspheres comprise at least one selected from the group consisting of silica, alumina, titania, zeolite, boron oxide and glass.

[0038] The present invention also provides a method for preparing a polyimide film with low dielectric constant and low moisture absorption, comprising the following steps:

[0039] a step of adding an aliphatic diamine monomer or an aromatic diamine monomer and an aliphatic dianhydride monomer or an aromatic dianhydride monomer in proportion to an organic polar solvent to prepare a polyamic acid solution;

[0040] The step of adding microspheres to a polyamic acid solution to prepare a polyamic acid nano-mesoporous microsphere dispersion;

[0041] After forming the polyamic acid nano-mesoporous microsphere precursor composition into a film on a support and drying it to prepare a gel film, heat treatment is performed at a temperature of 200° C. to 450° C. to prepare a polyimide film in which the polyamic acid precursor is imidized.

[0042] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0043] The polyimide film of the present invention is prepared by comprising an aliphatic polyimide resin containing at least one of a chain aliphatic hydrocarbon group, a cyclic aliphatic hydrocarbon group, or a polymerized aromatic hydrocarbon group, and nano-mesoporous microspheres. The aliphatic polyimide resin effectively suppresses the dielectric constant and moisture absorption rate. The inclusion of nano-mesoporous microspheres results in a polyimide film with a lower dielectric constant, thereby providing a method for preparing a polyimide film with improved production, application, and storage stability.

[0044] (1) The low-dielectric polyimide prepared by the present invention and the air inside the low-dielectric nano-mesoporous microspheres can effectively reduce the dielectric constant. There is no compatibility problem between the nano-mesoporous microspheres and the polyimide matrix, so that the dielectric properties are significantly improved.

[0045] (2) Low dielectric nano-mesoporous microspheres are nano-scale microspheres with a highly ordered or disordered pore network ranging from 2 to 50 nanometers inside the microspheres, which allows these particles to be evenly dispersed in the solvent. During storage in the solution, they have good storage stability and will not separate from the polyimide resin precursor.

[0046] (3) The preparation method of the present invention is simple and can be easily industrialized. DETAILED DESCRIPTION

[0047] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0048] In the present application, a polyimide film with low dielectric constant and low moisture absorption comprises:

[0049] Aliphatic polyimide resin;

[0050] Aromatic polyimide resin;

[0051] Aliphatic and aromatic copolymer polyimide resin; and nano-mesoporous microspheres;

[0052] The aliphatic polyimide resin includes at least one of a chain aliphatic hydrocarbon group and a cyclic aliphatic hydrocarbon group.

[0053] The aliphatic polyimide resin of this embodiment is derived from an aliphatic polyamic acid formed by polymerization of an aliphatic diamine monomer and an aliphatic dianhydride monomer;

[0054] Aromatic polyimide resins are derived from aromatic polyamic acid polymerized from aromatic diamine monomers and aromatic dianhydride monomers;

[0055] Aliphatic / aromatic polyimide resins are aliphatic and aromatic copolymer polyimide resins derived from the polymerization of aliphatic / aromatic diamine monomers and aliphatic / aromatic dianhydride monomers;

[0056] The polyimide film is prepared by imidizing a precursor composition, wherein the precursor composition comprises the aliphatic polyamic acid, the aromatic polyamic acid, the aliphatic / aromatic polyamic acid and the nano-mesoporous microspheres.

[0057] The present embodiment includes 5 wt % to 50 wt % of the aromatic polyamic acid relative to the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid.

[0058] The chain aliphatic hydrocarbon group of this embodiment comprises at least one aliphatic organic group selected from the group consisting of C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C1 to C30 alkylene, C2 to C30 alkenylene, and C2 to C30 alkynylene;

[0059] The cyclic aliphatic hydrocarbon group includes at least one alicyclic organic group selected from the group consisting of a C3 to C30 cycloalkyl group, a C3 to C30 cycloalkenyl group, a C3 to C30 cycloalkynyl group, a C3 to C30 cycloalkylene group, a C6 to C30 cycloalkenylene group, and a C3 to C30 cycloalkynylene group.

[0060] The aliphatic diamine monomer of this embodiment is at least one selected from the group consisting of cyclohexanediamine, 1,4-cyclohexanebis(methylamine), 2,2-bis[(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxyphenyl)]hexafluoropropane, 4,4'-methylenebiscyclohexylamine, 4,4'-methylenebis(2-methylcyclohexylamine), 1,3-adamantanediamine, and 3,3'-diamino-1,1'-diamantane.

[0061] The aliphatic dianhydride monomer is at least one selected from the group consisting of 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]malonic dianhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and cyclobutane-1,2,3,4-tetracarboxylic dianhydride.

[0062] Preferably, the aromatic diamine monomer is at least one selected from the group consisting of 1,4-phenylenediamine, 4,4'-diphenylamine oxide, 3,4'-diphenylamine oxide, 4,4'-dimethyldiphenylamine and 1,3-bis(4-aminophenoxy)benzene;

[0063] The aromatic dianhydride monomer is at least one selected from the group consisting of pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic anhydride (ODPA), and benzophenonetetracarboxylic dianhydride (BTDA).

[0064] The nano-mesoporous microspheres of this embodiment exist in at least one of the following states:

[0065] The first state (A) of nano-mesoporous microspheres coated on the surface;

[0066] a second state (B) in which the nano-mesoporous microspheres are physically bound to the polymer chains of the polyimide resin;

[0067] and a third state (C) in which the nano-mesoporous microspheres are chemically bonded to the polymer chains of the polyimide resin;

[0068] The nano-mesoporous microspheres are nano-scale, and the particle size is usually between 1 and 1000 nanometers.

[0069] Mesoporous structure: pore diameter ranges from 2 to 50 nanometers.

[0070] In this embodiment, the microspheres are included in an amount of 1 wt % to 10 wt % relative to the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid.

[0071] The nano-mesoporous microspheres of this embodiment include at least one selected from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, zeolite, boron oxide, and glass.

[0072] The method for preparing a polyimide film with low dielectric constant and low moisture absorption of this embodiment includes the following steps:

[0073] a step of adding an aliphatic diamine monomer or an aromatic diamine monomer and an aliphatic dianhydride monomer or an aromatic dianhydride monomer in proportion to an organic polar solvent to prepare a polyamic acid solution;

[0074] The step of adding microspheres to a polyamic acid solution to prepare a polyamic acid nano-mesoporous microsphere dispersion;

[0075] After forming the polyamic acid nano-mesoporous microsphere precursor composition into a film on a support and drying it to prepare a gel film, heat treatment is performed at a temperature of 200° C. to 450° C. to prepare a polyimide film in which the polyamic acid precursor is imidized.

[0076] The present application is further described below with reference to specific embodiments, comparative examples, and analytical tests:

[0077] Example 1-1:

[0078] Preparation Example 1-1: Preparation of aliphatic and aromatic copolymer polyamic acid solution

[0079] At room temperature, under the protection of nitrogen, 450g of N-methylpyrrolidone (NMP) as a polar solvent, 14.53g of 1,3-cyclohexanediamine (CHDA) as an aliphatic diamine monomer, and 2.80g of 4,4'-diphenylamine oxide (ODA) as an aromatic diamine monomer were added to a 1L reactor and stirred for about 30 minutes. After confirming that the diamine monomer was dissolved in the solvent, 28.51g of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) as an aliphatic dianhydride monomer and 4.16g of biphenyltetracarboxylic dianhydride (BPDA) as an aromatic dianhydride monomer were gradually added, and the addition amount was adjusted so that the final viscosity was 500cP to 1000cP.

[0080] After the addition was completed, the mixture was stirred for 4 hours while maintaining the temperature, thereby preparing a polymerized aliphatic and aromatic copolymerized polyamic acid solution having a final viscosity of 800 CP.

[0081] Preparation Example 1-2: Preparation of Nano-mesoporous Microsphere Dispersion

[0082] CTAB is the abbreviation of Cetyltrimethylammonium Bromide, which is a cationic surfactant. CTAB is used as a template or surfactant. During the synthesis process, CTAB can form micellar structures through self-assembly, providing a template for the growth of nanomaterials or controlling their morphology and size. CTAB micelles can act as templates during the hydrolysis and polycondensation of silicon sources, guiding the formation of silica nanospheres with a regular mesoporous structure. The surface of silica exhibits a negative charge through the interaction of its oxide functional groups, such as hydroxyl and silicate groups, with water molecules. This charge characteristic promotes the loading of SiO2 on the surface of the micelles formed by CTAB self-assembly, forming silica nanospheres with a mesoporous structure. 3.2g of CTAB, 400ml of anhydrous ethanol, 40ml of distilled water, and 8ml of ammonia were weighed and added to a 1L beaker. The mixture was stirred for 30 minutes, followed by 6.4ml of TEOS. CTAB served as a template, surfactant, and porogen, while a mixture of ethanol and water served as the solvent, ammonia served as the base catalyst, and TEOS served as the silicon source. After stirring at room temperature for 24 hours and then calcining at high temperature, silica nanospheres with a mesoporous structure were successfully prepared.

[0083] Preparation Example 1-3: Preparation of polyamic acid precursor composition

[0084] Using a high shear mixer, 1 wt % of nano-mesoporous microspheres were added to 100 g of the aliphatic and aromatic co-polyamic acid solution prepared in Preparation Example 1-1 and mixed at 0° C. for 10 minutes to prepare a polyamic acid precursor composition.

[0085] Example 1-2

[0086] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the added amount was changed so as to include 5 wt % of nano-mesoporous microspheres.

[0087] Examples 1-3

[0088] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the added amount was changed so as to include 10 wt % of nano-mesoporous microspheres.

[0089] Examples 1-4

[0090] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1 except that the added amount was changed so as to contain 25 wt % of the aromatic hydrocarbon-based polyamic acid.

[0091] Examples 1-5

[0092] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 5 wt % of nano-mesoporous microspheres and 25 wt % of aromatic hydrocarbon polyamic acid.

[0093] Examples 1-6

[0094] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amounts were changed to include 10 wt % of nano-mesoporous microspheres and 25 wt % of aromatic hydrocarbon-based polyamic acid.

[0095] Examples 1-7

[0096] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1 except that the added amount was changed so as to contain 50 wt % of the aromatic hydrocarbon-based polyamic acid.

[0097] Examples 1-8

[0098] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 5 wt % of nano-mesoporous microspheres and 50 wt % of aromatic hydrocarbon-based polyamic acid.

[0099] Examples 1-9

[0100] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 10 wt % of nano-mesoporous microspheres and 50 wt % of aromatic hydrocarbon-based polyamic acid.

[0101] Comparative Example 1-1

[0102] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amounts were changed to include 0 wt % of nano-mesoporous microspheres and 10 wt % of aromatic hydrocarbon-based polyamic acid.

[0103] Comparative Example 1-2

[0104] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amounts were changed to include 15 wt % of nano-mesoporous microspheres and 10 wt % of aromatic hydrocarbon-based polyamic acid.

[0105] Comparative Examples 1-3

[0106] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 0 wt % of nano-mesoporous microspheres and the addition amount was changed to include 25 wt % of aromatic hydrocarbon-based polyamic acid.

[0107] Comparative Examples 1-4

[0108] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amounts were changed to include 15 wt % of nano-mesoporous microspheres and 25 wt % of aromatic hydrocarbon-based polyamic acid.

[0109] Comparative Examples 1-5

[0110] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 0 wt % of nano-mesoporous microspheres and the addition amount was changed to include 50 wt % of aromatic hydrocarbon-based polyamic acid.

[0111] Comparative Examples 1-6

[0112] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 15 wt % of nano-mesoporous microspheres and 50 wt % of aromatic hydrocarbon-based polyamic acid.

[0113] Comparative Examples 1-7

[0114] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 5 wt % of mesoporous microspheres with an average particle size of 2000 nm and the addition amount was changed to include 25 wt % of aromatic hydrocarbon-based polyamic acid.

[0115] Comparative Examples 1-8

[0116] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 5 wt % of mesoporous microspheres with an average particle size of 5000 nm and the addition amount was changed to include 25 wt % of aromatic hydrocarbon-based polyamic acid.

[0117] Comparative Examples 1-9

[0118] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 5 wt % of nano-mesoporous microspheres and 75 wt % of aromatic hydrocarbon-based polyamic acid.

[0119] Comparative Examples 1-10

[0120] As shown in Table 1 below, a polyamic acid precursor composition was prepared in the same manner as in Example 1-1, except that the addition amount was changed to include 5 wt % of nano-mesoporous microspheres and 100 wt % of aromatic hydrocarbon-based polyamic acid.

[0121] Table 1

[0122]

[0123]

[0124]

[0125] The polyamic acid precursor compositions prepared in Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-10 were respectively cast on a glass plate to a thickness of 500 μm using a doctor blade, and then dried at 100° C. for 2 minutes to prepare a gel film, which was then heat-cured in an oven at 300° C. for 30 minutes to prepare a 50 μm polyimide film.

[0126] The moisture absorption rate and dielectric constant of the polyimide film thus prepared were measured in the following manner, and the film-forming property was visually observed. The results are shown in Table 2 below.

[0127] 1) Moisture absorption rate measurement

[0128] According to the ASTM D570 method, a polyimide film is cut into a square of 5 cm × 5 cm to prepare a sample, and the cut sample is dried in an oven at 50°C for more than 24 hours and then the weight is measured. Then, the sample whose weight has been measured is immersed in water at 23°C for 24 hours and then the weight is measured again, and the difference in the obtained weights is expressed in % to measure the moisture absorption rate.

[0129] 2) Dielectric constant measurement

[0130] The dielectric constant of the sample was measured at 10 GHz using a high resistance meter and dielectric meter from Keysight.

[0131] Table 2

[0132]

[0133]

[0134] As shown in Table 2, it can be confirmed that the moisture absorption rate and dielectric constant of the polyimide film according to the embodiment of the present invention are significantly low, and the film forming performance is also excellent;

[0135] This result is achieved by the combination of the aliphatic hydrocarbon groups in the polyimide resin and the nano-mesoporous microspheres. It can be seen that the content of the aliphatic hydrocarbon groups in the polyimide resin and the nano-mesoporous microspheres plays a key role.

[0136] The polyamic acid aliphatic hydrocarbon groups contained in the polyimide film of the present invention can be effectively used to suppress the dielectric constant and moisture absorption rate, and the dielectric constant can be further reduced by realizing the electrical properties of air through the nano-microspheres having mesopores. Such nano-mesoporous microspheres form a network with the polyamic acid aliphatic hydrocarbon groups, thereby not only improving the stability but also preventing the layer separation of the nano-mesoporous microspheres and the polyimide precursor solution even if the precursor composition solution is stored for a long time.

[0137] Therefore, an electronic device for high-speed transmission including the polyimide film according to the present invention can achieve high-speed communication at a high frequency of 10 GHz.

[0138] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A polyimide film having low dielectric constant and low moisture absorption, characterized in that Include: Aliphatic polyimide resin; Aromatic polyimide resin; Aliphatic and aromatic copolymer polyimide resin; and nano-mesoporous microspheres; The aliphatic polyimide resin includes at least one of a chain aliphatic hydrocarbon group and a cyclic aliphatic hydrocarbon group.

2. The polyimide film with low dielectric constant and low moisture absorption according to claim 1, wherein: Aliphatic polyimide resins are derived from aliphatic polyamic acid formed by polymerization of aliphatic diamine monomers and aliphatic dianhydride monomers; Aromatic polyimide resins are derived from aromatic polyamic acid polymerized from aromatic diamine monomers and aromatic dianhydride monomers; Aliphatic / aromatic polyimide resins are aliphatic and aromatic copolymer polyimide resins derived from the polymerization of aliphatic / aromatic diamine monomers and aliphatic / aromatic dianhydride monomers; The polyimide film is prepared by imidizing a precursor composition, wherein the precursor composition comprises the aliphatic polyamic acid, the aromatic polyamic acid, the aliphatic / aromatic polyamic acid and the nano-mesoporous microspheres.

3. The polyimide film with low dielectric constant and low moisture absorption according to claim 2, characterized in that: The aromatic polyamic acid is included in an amount of 5 to 50 wt % relative to the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid.

4. The polyimide film with low dielectric constant and low moisture absorption according to claim 3, characterized in that: The chain aliphatic hydrocarbon group comprises at least one aliphatic organic group selected from the group consisting of a C1 to C30 alkyl group, a C2 to C30 alkenyl group, a C2 to C30 alkynyl group, a C1 to C30 alkylene group, a C2 to C30 alkenylene group, and a C2 to C30 alkynylene group; The cyclic aliphatic hydrocarbon group includes at least one alicyclic organic group selected from the group consisting of a C3 to C30 cycloalkyl group, a C3 to C30 cycloalkenyl group, a C3 to C30 cycloalkynyl group, a C3 to C30 cycloalkylene group, a C6 to C30 cycloalkenylene group, and a C3 to C30 cycloalkynylene group.

5. The polyimide film with low dielectric constant and low moisture absorption according to claim 4, characterized in that: The aliphatic diamine monomer is at least one selected from the group consisting of cyclohexanediamine, 1,4-cyclohexanebis(methylamine), 2,2-bis[(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxyphenyl)]hexafluoropropane, 4,4'-methylenebiscyclohexylamine, 4,4'-methylenebis(2-methylcyclohexylamine), 1,3-adamantanediamine, and 3,3'-diamino-1,1'-diamantane; The aliphatic dianhydride monomer is at least one selected from the group consisting of 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]malonic dianhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and cyclobutane-1,2,3,4-tetracarboxylic dianhydride.

6. The polyimide film with low dielectric constant and low moisture absorption according to claim 5, characterized in that: The aromatic diamine monomer is at least one selected from the group consisting of 1,4-phenylenediamine, 4,4'-diphenylamine oxide, 3,4'-diphenylamine oxide, 4,4'-dimethyldiphenylamine and 1,3-bis(4-aminophenoxy)benzene; The aromatic dianhydride monomer is at least one selected from the group consisting of pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic anhydride (ODPA), and benzophenonetetracarboxylic dianhydride (BTDA).

7. The polyimide film with low dielectric constant and low moisture absorption according to claim 6, characterized in that: The nano-mesoporous microspheres exist in at least one of the following states: The first state (A) of nano-mesoporous microspheres coated on the surface; a second state (B) in which the nano-mesoporous microspheres are physically bound to the polymer chains of the polyimide resin; and a third state (C) in which the nano-mesoporous microspheres are chemically bonded to the polymer chains of the polyimide resin; The nano-mesoporous microspheres are nano-scale, and the particle size is usually between 1 and 1000 nanometers. Mesoporous structure: pore diameter ranges from 2 to 50 nanometers.

8. The polyimide film with low dielectric constant and low moisture absorption according to claim 7, characterized in that: The microspheres are included in an amount of 1 wt % to 10 wt % relative to the total solid weight of the aliphatic polyamic acid and the aromatic polyamic acid.

9. The polyimide film with low dielectric constant and low moisture absorption according to claim 8, characterized in that: The nano-mesoporous microspheres include at least one selected from the group consisting of silica, alumina, titania, zeolite, boron oxide and glass.

10. A method for preparing a polyimide film having low dielectric constant and low moisture absorption, characterized in that: The following steps are involved: a step of adding an aliphatic diamine monomer or an aromatic diamine monomer and an aliphatic dianhydride monomer or an aromatic dianhydride monomer in proportion to an organic polar solvent to prepare a polyamic acid solution; The step of adding microspheres to a polyamic acid solution to prepare a polyamic acid nano-mesoporous microsphere dispersion; After forming the polyamic acid nano-mesoporous microsphere precursor composition into a film on a support and drying it to prepare a gel film, heat treatment is performed at a temperature of 200° C. to 450° C. to prepare a polyimide film in which the polyamic acid precursor is imidized.

Images