A multilayer polyimide film and a preparation method and application thereof

Abstract

The application discloses a kind of multilayer polyimide film and its preparation method and application, belong to high-performance polyimide technical field, solve the problem that PI film in prior art is not ideal when being applied to flexible PI board Heat stability.The method comprises: ODA, GAPD and DMAc are mixed under ice bath, after mixing BPDA and TAHQ, it is added in batches, to obtain solution B;SiO2 Aerogel is added to anhydrous ethanol, ultrasonic is obtained at room temperature, to obtain solution C;Solution B is coated into thin film, after drying, solution C is coated on it, after drying, solution B is coated on it again, drying is obtained Polyimide film.The multilayer low-dielectric polyimide film prepared by the application has the advantages of low dielectric, high temperature resistance, high interfacial compatibility and low water absorption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-performance polyimide, more particularly to a multilayer polyimide film and a preparation method and application thereof. BACKGROUND

[0002] Polyimide (PI) is a kind of high polymer material with excellent thermal stability, mechanical stability, chemical stability and electrical insulation performance. Due to these characteristics, PI has become one of the most important polymer interlayer insulating materials in the microelectronic industry. However, with the development of integrated circuits, the device size is continuously reduced and the device integration is continuously improved. The traditional aromatic PI film cannot meet the requirements of the microelectronic industry for high-performance insulating materials due to its insufficiently low dielectric constant (Dk) and dielectric loss (Df). Especially in the field of 5G high-frequency communication and flexible printed circuit board (FPCB), the demand for low dielectric constant materials is particularly urgent. Therefore, reducing the dielectric constant and dielectric loss of PI film has become the focus of research.

[0003] Low dielectric material is a material with a dielectric constant less than 3. The application of low dielectric material is mainly to solve the problems of RC delay, crosstalk and increased power consumption caused by parasitic capacitance between lines and layers of super large scale integrated circuits. However, in the application of flexible PI board, the thermal stability of the existing PI film is not ideal. SUMMARY

[0004] The present application provides a multilayer polyimide film and a preparation method and application thereof to solve the problem of insufficient thermal stability of PI film in the prior art when applied to flexible PI board.

[0005] In a first aspect, the present application provides a preparation method of a multilayer polyimide film, comprising the following steps: stirring 4,4'-diamino diphenyl ether, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and dimethylacetamide in an ice bath to obtain solution A; mixing biphenyl tetracarboxylic dianhydride and p-phenylene-bisphenyltricarboxylic dianhydride, and adding the mixture into solution A in multiple times to mix uniformly to obtain solution B; adding hydrophilic SiO2 aerogel into anhydrous ethanol, and ultrasonicating at room temperature to obtain solution C; coating solution B into a film shape, and sequentially performing drying, thermal cyclization in an inert atmosphere, and ultraviolet curing operations to obtain a first film; coating solution C on the first film, and drying to obtain a second film; coating solution B on the second film, and sequentially performing drying and thermal cyclization in an inert atmosphere to obtain the multilayer polyimide film.

[0006] As a possible implementation manner, a mass ratio of the diphenyl tetracarboxylic dianhydride, the p-phenylene-bisbenzimidazole dianhydride, the 4,4'-diaminodiphenyl ether and the 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane is 5:5:7-9:1-3; and / or, a mass fraction of the hydrophilic SiO2 aerogel is 10%-20%; and / or, the solution B is coated into a film shape, and a coating amount is 20-30 μL / cm 2 ; and / or, the solution C is coated on the first film, and a coating amount is 20-30 μL / cm 2 ; and / or, the solution B is coated on the second film, and a coating amount is 20-30 μL / cm 2 .

[0007] As a possible implementation manner, the solution A is added in multiple times, and the adding is performed 2-4 times, and each time interval is 30-60 min; and / or, the mixing is uniformly performed to obtain the solution B, and a mixing temperature is 20-25 ℃, and a mixing time length is 8-12 h; and / or, a drying temperature is 70-80 ℃, and a drying time length is 1-2 h; and / or, the inert atmosphere environment is a nitrogen atmosphere; and / or, a heat cyclization condition is that a temperature is respectively raised to 100 ℃, 150 ℃, 200 ℃, 250 ℃ and 300 ℃ at a temperature raising rate of 2-5 ℃ / min, and each temperature is kept for 60-80 min.

[0008] In a second aspect, the present application provides a multilayer polyimide film prepared according to the preparation method of any possible implementation manner of the first aspect.

[0009] As a possible implementation manner, a dielectric constant is 2-3 under a condition of 1 MHz.

[0010] As a possible implementation manner, a thickness is 10-20 μm.

[0011] In a third aspect, the present application provides an application of the multilayer polyimide film prepared according to the preparation method of any possible implementation manner of the first aspect or the multilayer polyimide film of any possible implementation manner of the second aspect in a flexible polyimide plate.

[0012] In a fourth aspect, a working temperature of the flexible polyimide plate is 25-450 ℃.

[0013] The application introduces a silicon-containing monomer (GAPD, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane) and a bulky monomer (TAHQ, p-phenylene-benzene trimesate dianhydride) into a low dielectric polyimide copolymerized with BPDA (biphenyl tetracarboxylic dianhydride) and ODA (4,4'-oxydianiline) by molecular structure design, effectively reduces the molecular polarity and electronic polarization by introducing low-polarity chemical bonds, thereby reducing the dielectric constant. The dielectric properties of the polyimide are adjusted by regulating the molecular structure and adding inorganic fillers, and a low-dielectric polyimide with excellent thermal stability is obtained to meet the requirements of stability and durability of flexible PI boards, so that it has a wide application prospect in the microelectronic field.

[0014] The multilayer low-dielectric polyimide film prepared by the application has the advantages of low dielectric, high temperature resistance, high interfacial compatibility and low water absorption. The inorganic filler SiO2 aerogel in the second layer is uniformly dispersed in the system and does not agglomerate. The low-dielectric polyimide film with sandwich structure does not delaminate, indicating that the film has excellent interfacial compatibility. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0016] Figure 1 The morphological diagram of the polyimide film provided by the embodiments of the present application is shown, wherein A is polyimide film I, and B is polyimide film V.

[0017] Figure 2 The dielectric constant test results of the polyimide film provided by the embodiments of the present application are shown.

[0018] Figure 3 The FT-IR characterization results of the polyimide film provided by the embodiments of the present application are shown.

[0019] Figure 4 The TGA characterization results of the polyimide film provided by the embodiments of the present application are shown.

[0020] Figure 5 The interfacial compatibility test results of the polyimide film I provided by the embodiments of the present application are shown, wherein A is before peeling, and B is after peeling. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To address the issue of insufficient thermal stability of PI films when applied to flexible PI boards in existing technologies, this invention provides an experimental method for preparing multilayer polyimide films. Figure 1 As can be seen, the embodiments of the present invention successfully prepared a multilayer polyimide film.

[0023] Furthermore, the performance of the multilayer polyimide film prepared in the embodiments of the present invention was characterized. It can be seen that the multilayer polyimide film prepared in the embodiments of the present invention has a dielectric constant of 2 to 3, contains Si-O-Si and Si-C bonds in its molecules, and has better thermal stability.

[0024] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0025] Example 1

[0026] This embodiment provides an experiment for the preparation of a multilayer polyimide film.

[0027] Stir 4,4'-diaminodiphenyl ether (ODA), 1,3-bis(3-aminopropyl)-1,1,3,3- tetramethyldisiloxane (GAPD) and dimethylacetamide (DMAc) in an ice bath for 1 h to obtain solution A-I; mix biphenyltetracarboxylic dianhydride (BPDA) and p-phenylene-bisphenyltricarboxylic dianhydride (TAHQ), add into solution A-I in 3 times with an interval of 30 min, and mix uniformly to obtain solution B-I; wherein the molar ratio of BPDA, TAHQ, ODA and GAPD is 5:5:7:3; add 10% by mass of hydrophilic SiO2 aerogel into anhydrous ethanol, and ultrasonically treat at room temperature to obtain solution C-I; use a pipette to take 100 μL of solution B-I, and coat on a clean glass sheet of 2 cm x 2 cm, which is coated in a thin film shape, and then sequentially perform drying, thermal cyclization in a nitrogen environment, and UV light curing in a UV machine to obtain a first film-I; use the pipette to take 100 μL of solution C-I, and coat on the first film-I, which is dried to obtain a second film-I; take 100 μL of solution B-I, and coat on the second film-I, which is sequentially subjected to drying and thermal cyclization in a nitrogen environment, and then is immersed in deionized water at 100°C, taken off from the glass sheet, and dried in an oven at 100°C to obtain a polyimide film I.

[0028] Stir ODA, GAPD and DMAc in an ice bath for 1 h to obtain solution A-II; mix BPDA and TAHQ, add into solution A-II in 3 times with an interval of 30 min, and mix uniformly to obtain solution B-II; wherein the molar ratio of BPDA, TAHQ, ODA and GAPD is 5:5:7:3; add 10% by mass of hydrophilic SiO2 aerogel into anhydrous ethanol, and ultrasonically treat at room temperature to obtain solution C-II; use a pipette to take 100 μL of solution B-II, and coat on a clean glass sheet of 2 cm x 2 cm, which is coated in a thin film shape, and then sequentially perform drying, thermal cyclization in a nitrogen environment, and UV light curing in a UV machine to obtain a first film-II; use the pipette to take 150 μL of solution C-II, and coat on the first film-II, which is dried to obtain a second film-II; take 100 μL of solution B-II, and coat on the second film-II, which is sequentially subjected to drying and thermal cyclization in a nitrogen environment, and then is immersed in deionized water at 100°C, taken off from the glass sheet, and dried in an oven at 100°C to obtain a polyimide film II.

[0029] The ODA, GAPD and DMAc were stirred in an ice bath for 1 h to obtain solution A-III; BPDA, TAHQ were mixed and added to solution A-III in three times with an interval of 30 min, and mixed uniformly to obtain solution B-III; wherein, the molar ratio of BPDA, TAHQ, ODA and GAPD was 5:5:7:3; 10% by mass of hydrophilic SiO2 aerogel was added to anhydrous ethanol, and ultrasonic was performed at room temperature to obtain solution C-III; 100 μL of solution B-III was sucked by a pipette and coated on a clean glass sheet of 2 cm x 2 cm, and after coating into a thin film, drying, thermal cyclization in a nitrogen environment, and UV light curing in a UV machine were sequentially performed to obtain a first film-III; 200 μL of solution C-III was sucked by a pipette and coated on the first film-III, and dried to obtain a second film-III; 100 μL of solution B-III was sucked and coated on the second film-III, and after sequentially performing drying and thermal cyclization in a nitrogen environment, immersion in deionized water at 100 ℃, removal from the glass sheet, and drying in an oven at 100 ℃, a polyimide film III was obtained.

[0030] The ODA, GAPD and DMAc were stirred in an ice bath for 1 h to obtain solution A-III; BPDA, TAHQ were mixed and added to solution A-III in three times with an interval of 30 min, and mixed uniformly to obtain solution B-III; wherein, the molar ratio of BPDA, TAHQ, ODA and GAPD was 5:5:7:3; 10% by mass of hydrophilic SiO2 aerogel was added to anhydrous ethanol, and ultrasonic was performed at room temperature to obtain solution C-III; 100 μL of solution B-III was sucked by a pipette and coated on a clean glass sheet of 2 cm x 2 cm, and after coating into a thin film, drying, thermal cyclization in a nitrogen environment, and UV light curing in a UV machine were sequentially performed to obtain a first film-III; 200 μL of solution C-III was sucked by a pipette and coated on the first film-III, and dried to obtain a second film-III; 100 μL of solution B-III was sucked and coated on the second film-III, and after sequentially performing drying and thermal cyclization in a nitrogen environment, immersion in deionized water at 100 ℃, removal from the glass sheet, and drying in an oven at 100 ℃, a polyimide film III was obtained.

[0031] Kapton polyimide film was used as a comparison, and its preparation process was as follows: 10 mol of 4,4'-diamino diphenyl ether (ODA) and N,N-dimethylacetamide (DMAc) were added to a 500 mL round-bottom flask, and after ice bath stirring for 1 h, 10 mL of pyromellitic dianhydride (PMDA) was added in batches, and reacted at room temperature for 12 h; after sequentially performing drying and thermal cyclization in a nitrogen environment, immersion in deionized water at 100 ℃, removal from the glass sheet, and drying in an oven at 100 ℃, a polyimide film V was obtained.

[0032] Example 2

[0033] The present embodiment provides a performance characterization experiment of a multi-layer polyimide film.

[0034] The morphology of the polyimide film I and the polyimide film V prepared in Example 1 is shown in Figure 1 As can be seen from the figure, Figure 1 the polyimide film I has a matte surface due to the addition of SiO2 aerogel, and the SiO2 aerogel is uniformly distributed in the film without agglomeration and phase separation.

[0035] The dielectric constant of the polyimide film I to the polyimide film V prepared in Example 1 was tested, and the test conditions were as follows: the film thickness was 10 μm, the length and width were 2 cm x 2 cm, the frequency was 10 2 - 10 7 Hz, and the temperature was room temperature. The results are shown in Figure 2 As can be seen from the figure, Figure 2 the GAPD contains a large number of C-C and C-H bonds, which are low-molecular polarizable groups. The introduction of GAPD can hinder the accumulation of polymer chain segments, reduce molecular polarization, increase free volume, form dielectric confinement effect, and reduce the dielectric constant of polyimide (PI). The introduction of silicon-oxygen bond can increase the flexibility of PI molecular structure. By introducing large-volume monomer TAHQ, the distance between polymer molecular chains can be effectively increased, the intermolecular interaction force can be reduced, and the close accumulation of molecular chains can be reduced. Such structural changes result in an increase in the free volume inside the material, reducing the number of polarized molecules per unit volume, and thus reducing the dielectric constant of the material.

[0036] By physically modifying the SiO2 aerogel interlayer, the introduction of pores in PI can greatly reduce the number of polarized molecules per unit volume, thereby reducing the overall dielectric constant.

[0037] The polyimide film I to the polyimide film V prepared in Example 1 was characterized by FT-IR, and the conditions were as follows: the mode was ATR infrared, the film thickness was 10 μm, the length and width were 2 cm x 2 cm, and the temperature was room temperature. The results are shown in Figure 3 As can be seen from the figure, Figure 3 the C=O bond appears a bending vibration peak at 720 cm -1 , the C-N bond appears a stretching vibration peak at 1368 cm -1 , and the C=O bond appears a stretching vibration peak at 1780 cm -1 and 1720 cm -1 , proving that imine structure is formed in the polymer. The benzene ring appears at 1490 cm -1 and 3095 cm -1characteristic absorption peaks of C-C bond and hydrocarbon C-H bond stretching, indicating that the aromatic structure is complete in the product. At 764 cm -1 , 1056 cm -1 , the stretching vibration peaks of Si-C, Si-O-Si bond can be observed, and gradually increase with the increase of the content of the third monomer. At 2941 cm -1 , the stretching vibration peak of C-H bond can be observed, indicating that GAPD is successfully introduced into the PI molecular structure.

[0038] Example 3

[0039] This example provides a water absorption performance test experiment of a multilayer polyimide film.

[0040] The polyimide film I to polyimide film V prepared in Example 1 are respectively subjected to water absorption performance test, and the test conditions are: the temperature is room temperature, the soaking time in water is 48 h, the film thickness is 10 μm, and the length and width are respectively 2 cm x 2 cm. The results shown in Table 1 are obtained.

[0041] Table 1 Water absorption test results of polyimide film

[0042] Before water absorption / g After water absorption / g Polyimide film I 0.0025 0.0026 Polyimide film II 0.0055 0.0055 Polyimide film III 0.0039 0.0040 Polyimide film IV 0.0022 0.0023 Polyimide film V 0.0031 0.0026

[0043] As shown in Table 1, the water absorption of the polyimide film I to polyimide film IV is significantly lower than that of the polyimide film V. Compared with the polyimide film V, the polyimide film I to polyimide film IV has a lower glass transition temperature (Tg, 285℃), but has a low water absorption rate and excellent hydrolysis resistance. The low water absorption rate is beneficial to the reduction of the dielectric constant. The monomer activity of PMDA and GAPD is high, which leads to easy explosion of the reaction and reduction of the molecular weight. Therefore, the BPDA anhydride is selected as the raw material in the present application.

[0044] Example 4

[0045] This example provides a thermal stability test experiment of a multilayer polyimide film.

[0046] The polyimide film I to polyimide film V prepared in Example 1 are respectively subjected to TGA (thermogravimetric analysis) characterization, and the conditions are: the temperature range is room temperature to 900℃, and the atmosphere is nitrogen atmosphere. The results shown in Table 2 are obtained. Figure 4

[0047] As shown in Table 2, the thermal stability of the polyimide film I to polyimide film IV is significantly higher than that of the polyimide film V. Compared with the polyimide film V, the polyimide film I to polyimide film IV has a lower glass transition temperature (Tg, 285℃), but has a low water absorption rate and excellent hydrolysis resistance. The low water absorption rate is beneficial to the reduction of the dielectric constant. The monomer activity of PMDA and GAPD is high, which leads to easy explosion of the reaction and reduction of the molecular weight. Therefore, the BPDA anhydride is selected as the raw material in the present application. Figure 4 ​It is known that the silicon-containing monomer GAPD is an aliphatic diamine, lacking rigid structures such as benzene rings that provide high-temperature stability. The number of benzene rings in the molecular chain is reduced. Due to the high flexibility of the alkyl chain, the flexibility of the polymer backbone increases, and the high-temperature stability of the PI film gradually decreases. Although the addition of GAPD reduces high-temperature stability, no significant degradation occurs below 450℃. Since polyimide film V itself has excellent thermal stability, and the thermal stability of polyimide films I to IV is not significantly different, it also exhibits excellent thermal stability. The circuit board material is a tin-lead alloy, and the soldering temperature is around 250℃, thus meeting the soldering requirements.

[0048] Example 5

[0049] This embodiment provides an interfacial compatibility test experiment for a multilayer polyimide film.

[0050] This was achieved by rapidly peeling off the 3M pressure-sensitive adhesive tape attached to the sample, resulting in... Figure 5 The results are shown.

[0051] Depend on Figure 5 It can be seen that no significant delamination occurred on the substrate before and after peeling off the 3M pressure-sensitive adhesive. In the use of flexible electronic devices, the adhesion between substrates is crucial. This indicates that polyimide film I possesses excellent interfacial compatibility.

[0052] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0053] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a multilayer polyimide film, characterized in that, Includes the following steps: 4,4'-diaminodiphenyl ether, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and dimethylacetamide were stirred in an ice bath to obtain solution A; Biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltriester dianhydride were mixed and added to solution A in multiple portions, and mixed evenly to obtain solution B. Hydrophilic SiO2 aerogel was added to anhydrous ethanol and sonicated at room temperature to obtain solution C; The solution B was coated into a thin film, and then subjected to drying, thermal cyclization in an inert atmosphere, and ultraviolet curing to obtain the first thin film. The solution C is coated onto the first film and dried to obtain the second film; The solution B is coated onto the second film, and then dried and thermally cyclized in an inert atmosphere to obtain the multilayer polyimide film.

2. The method according to claim 1, characterized in that, The molar ratio of the biphenyltetracarboxylic dianhydride, the p-phenylene-bisphenyltriester dianhydride, the 4,4'-diaminodiphenyl ether, and the 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane is 5:5:7-9:1-3. And / or, the mass fraction of the hydrophilic SiO2 aerogel is 10% to 20%; And / or, the solution B is coated into a thin film at a coating amount of 20–30 μL / cm. 2 ; And / or, the solution C is coated onto the first film at a coating amount of 20–30 μL / cm. 2 ; And / or, the solution B is coated onto the second film at a coating amount of 20–30 μL / cm. 2 .

3. The method according to claim 1, characterized in that, The addition to solution A in multiple portions is to be done in 2 to 4 portions, with an interval of 30 to 60 minutes between each portion. And / or, the uniform mixing yields solution B, with a mixing temperature of 20–25°C and a mixing time of 8–12 h; And / or, the drying step is performed at a temperature of 70-80°C for a duration of 1-2 hours; And / or, the inert atmosphere environment is a nitrogen environment; And / or, the conditions for thermal circulation are: heating to 100, 150, 200, 250, and 300°C respectively at a heating rate of 2–5°C / min, and holding at each temperature for 60–80 min.

4. A multilayer polyimide film, characterized in that, It is prepared according to any one of claims 1 to 3.

5. The multilayer polyimide film according to claim 4, characterized in that, At 1 MHz, its dielectric constant is 2 to 3.

6. The multilayer polyimide film according to claim 4, characterized in that, Its thickness is 10–20 μm.

7. The application of the multilayer polyimide film prepared by the preparation method according to any one of claims 1 to 3 or the multilayer polyimide film according to any one of claims 4 to 6 in a flexible polyimide board.

8. The application according to claim 7, characterized in that, The working temperature of the flexible polyimide sheet is 25~450℃.

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