A reusable high-frequency, low-dielectric, and low-loss polyimide film and its preparation method and application

Abstract

The present invention belongs to the technical field of polyimide preparation, and specifically relates to a reusable high-frequency, low-dielectric, and low-loss polyimide film, and a preparation method and application thereof. The preparation method of the polyimide film comprises the steps of: subjecting a dianhydride monomer and a polyamine compound to a condensation reaction in the presence of a solvent to obtain a polyamic acid solution; wherein the polyamine compound contains one or more trifluoromethyl groups; molding the polyamic acid solution to obtain a polyamic acid film; subjecting the polyamic acid film to a thermal imidization reaction to obtain a reusable high-frequency, low-dielectric-loss polyimide film. The present invention improves the dielectric properties, hydrophobic properties, and solubility properties of the polyimide film by introducing a trifluoromethyl group and adjusting the number of substitutions of the trifluoromethyl group, thereby obtaining a reusable high-frequency, low-dielectric, and low-loss polyimide film.

Description

Technical Field

[0001] The invention belongs to the technical field of polyimide preparation, and in particular relates to a reusable high-frequency, low-dielectric, and low-loss polyimide film and a preparation method and application thereof. Background Art

[0002] With the development of science and technology in recent years, the number of transistors on integrated circuit (IC) chips has continued to increase. While the device integration continues to increase, the device size is also shrinking, which directly leads to an increase in the resistance and capacitance of the device, and then leads to an increase in power consumption, signal transmission lag and crosstalk.

[0003] Currently, some common devices (such as wearable devices, unmanned driving, and smart homes) require lower signal delay times, and effectively reducing the dielectric constant of materials can be considered the most effective and direct way to solve these problems. Therefore, reducing the dielectric constant and dielectric loss of materials has become a hot topic for many researchers.

[0004] Polyimide (PI) is a high-performance engineering polymer material, named after the imide structure in the main chain. Although the polyimide molecule contains polar groups (such as carbonyl), the carbonyl group in the conjugated imide ring is symmetrical, so the mobility of free electrons is greatly limited, which gives polyimide excellent electrical insulation properties. At the same time, polyimide also has excellent thermal stability, radiation resistance, low water absorption, chemical stability and mechanical properties, so polyimide is an ideal choice for use as ILD (internal layer dielectric material). However, in recent years, with the rapid development of electronic devices, higher requirements have been put forward for polyimide materials used in electronic devices: that is, how to have a lower dielectric constant, dielectric loss and better solubility at high frequencies.

[0005] Reducing the molar polarizability or increasing the molar volume of the molecule is an effective way to reduce the dielectric constant of the polymer. Therefore, in order to prepare polyimide materials with low dielectric constant and dielectric loss, researchers often increase the free volume of the polymer molecular chain and introduce air (the dielectric constant of air is 1) to further reduce the dielectric constant and dielectric loss of polyimide. The increase in free volume is indeed very helpful in improving the dielectric properties of polyimide, but the increase in the gap between molecules will further lead to an increase in the thermal expansion coefficient, making it difficult for polyimide to be effectively composited with carriers such as copper. In addition, the introduction of too much rigid structure into polyimide will also affect the mechanical properties and water absorption of polyimide.

[0006] Using organic and inorganic nanoparticles to introduce holes in polyimide is also one of the common ways to reduce its dielectric constant. The introduction of holes can effectively introduce air into the polyimide. The dielectric constant of air is 1, thereby reducing the dielectric constant. Specifically, in the design of amino monomers, large side groups (such as benzene, biphenyl, etc.) are introduced to increase the spacing of molecular chains, and holes at the angstrom level are introduced to introduce air. However, this method will have a great negative impact on the mechanical properties of polyimide, and it is difficult to prepare polyimide with high performance.

[0007] With the development of economy, the concept of environmental protection has become more deeply rooted in people's minds, and the demand for environmentally friendly materials is also increasing. Therefore, the demand for reusable polyimide is also increasing. However, most PIs have the problem of poor solubility and need further improvement.

[0008] Therefore, it is necessary to find a suitable method to regulate the preparation of reusable high-frequency, low-dielectric, and low-loss polyimide. Summary of the invention

[0009] In view of the above-mentioned deficiencies in the prior art, the present invention provides a reusable high-frequency, low-dielectric, and low-loss polyimide film, and a preparation method and application thereof. The reusable high-frequency, low-dielectric, and low-loss polyimide film provided by the present invention can have a lower dielectric constant and lower dielectric loss at high frequency, and the polyimide film can be reused, which is economical, environmentally friendly, and conducive to sustainable development.

[0010] In a first aspect, the present invention provides a method for preparing a reusable high-frequency low dielectric loss polyimide film, which comprises the following steps:

[0011] A dianhydride monomer and a polyamine compound are subjected to a polycondensation reaction in the presence of a solvent to obtain a polyamic acid solution; wherein the polyamine compound contains one or more trifluoromethyl groups;

[0012] forming the polyamic acid solution to obtain a polyamic acid film;

[0013] The polyamic acid film is subjected to a thermal imidization reaction to obtain a polyimide film which is reusable, has a high frequency and low dielectric loss.

[0014] Optionally, based on the total molar amount of the dianhydride monomer and the polyamine compound, the molar fraction of the polyamine compound is 0.01-10%.

[0015] Optionally, the conditions of the polycondensation reaction include: reacting under an inert atmosphere, a reaction temperature of -5°C-30°C, and a reaction time of 6-24h.

[0016] Optionally, the polyamic acid film is subjected to a thermal imidization reaction using the following heating program: heating to 30-90°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120min, heating to 90-150°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120min, heating to 150-200°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120min, heating to 200-250°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120min, heating to 250-400°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120min.

[0017] In a second aspect, the present invention provides a method for preparing a reusable high-frequency low dielectric loss polyimide film, which comprises the following steps:

[0018] A dianhydride monomer and a polyamine compound are subjected to a polycondensation reaction in the presence of a solvent to obtain a polyamic acid solution; wherein the polyamine compound contains one or more trifluoromethyl groups;

[0019] Adding pyridine and a catalyst to the polyamic acid solution to carry out a chemical imidization reaction to obtain polyimide;

[0020] The polyimide is formed into a film to obtain a polyimide film which is reusable at high frequency and has low dielectric loss.

[0021] Optionally, the addition ratio of the polyamine compound, the dianhydride monomer, the catalyst and the pyridine is 1 mol:1 mol:(1-3) ml:(0.5-2) ml.

[0022] Optionally, the catalyst is selected from one or more of acetic anhydride, quinoline, and isoquinoline.

[0023] Optionally, the conditions of the polycondensation reaction include: reacting under an inert atmosphere, a reaction temperature of -5°C-30°C, and a reaction time of 6-24h.

[0024] Optionally, the conditions of the chemical imidization reaction include: reaction temperature of 60-190° C., and reaction time of 12-24 h.

[0025] Optionally, the polyamine compound is a diamine compound, and the diamine compound is selected from one or more of the following structural formulas:

[0026]

[0027] The value of n is an integer ranging from 1 to 10.

[0028] Optionally, the dianhydride monomer is selected from one or more of the following structural formulas:

[0029]

[0030] Optionally, the solvent is selected from one or more of anhydrous DMF, anhydrous NMP, anhydrous DMAC, and γ-butyrolactone.

[0031] In a third aspect, the present invention provides a reusable high-frequency low dielectric loss polyimide film prepared by the preparation method as described above.

[0032] In a fourth aspect, the present invention provides a use of the aforementioned reusable high-frequency and low dielectric loss polyimide film in electronic packaging materials and circuit substrates.

[0033] Beneficial effects:

[0034] (1) The present invention can effectively reduce the dielectric constant of the polyimide film, improve the dielectric properties of the polyimide film, and reduce the water absorption of the polyimide film by introducing a trifluoromethyl group and controlling the number of substitutions of the trifluoromethyl group.

[0035] (2) The polyimide film obtained by the preparation method of the present invention has good solubility, so that the obtained polyimide film can be reused.

[0036] (3) The polyimide film prepared by the present invention can be used at high frequencies and fully meets the usage requirements of existing 5G technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a diagram showing infrared test results of the polyimide films prepared in Examples 1 and 2 of the present invention.

[0038] Figure 2 This is a diagram showing the DSC test results of the polyimide films prepared in Examples 1 and 2 of the present invention.

[0039] Figure 3 This is a graph showing the TGA test results of the polyimide films prepared in Examples 1 and 2 of the present invention.

[0040] Figure 4 The figure is a UV test result diagram of the polyimide film prepared in Example 1 and Example 2 of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] The embodiment of the present invention provides a method for preparing a reusable high-frequency low-dielectric-loss polyimide film, which comprises the following steps:

[0043] S10, subjecting the dianhydride monomer and the polyamine compound to a condensation polymerization reaction in the presence of a solvent to obtain a polyamic acid solution; wherein the polyamine compound contains one or more trifluoromethyl groups;

[0044] S11, molding the polyamic acid solution to obtain a polyamic acid film;

[0045] S12, subjecting the polyamic acid film to a thermal imidization reaction to obtain a reusable high-frequency and low-dielectric-loss polyimide film.

[0046] In the present embodiment, fluorine atom has the characteristics of strong electronegativity and low polarizability, and the polarizability at high frequency is low. By introducing trifluoromethyl, the dielectric properties of polyimide film are greatly improved. Fluorine atom is also a hydrophobic group at the same time. After introduction, there will be a kind of aggregation phenomenon on the surface of polyimide film, which can effectively hinder water molecules from entering polyimide film, thereby reducing the water absorption of polyimide film. Trifluoromethyl not only has low polarizability and hydrophobicity, but also has a large free volume. Introducing trifluoromethyl in polyimide film increases the free volume of polyimide film, and the dielectric properties of polyimide film can be further improved. At the same time, the dielectric properties and hydrophobicity of polyimide film can be further improved by increasing the content of trifluoromethyl. In addition, due to the strong electronegativity of trifluoromethyl, the transparency of polyimide film can be improved, and the most important thing is that the solubility of polyimide film is also greatly improved with the introduction of trifluoromethyl. Therefore, in this embodiment, the volume of the polyimide structure is increased by introducing a trifluoromethyl group, so that the dielectric properties, hydrophobic properties and solubility properties of the polyimide film can be improved, thereby preparing a polyimide film with excellent performance.

[0047] In this embodiment, the dielectric properties of the polyimide film are improved by using a polyamine compound and a dianhydride monomer containing different numbers of trifluoromethyl side groups. The free volume expansion brought by the trifluoromethyl group is used to reduce its dielectric constant without causing a significant reduction in mechanical properties and an increase in thermal expansion coefficient that would make it difficult to use. At the same time, as the number of introduced trifluoromethyl groups increases, not only does the water absorption rate of the polyimide film continue to decrease, but the solubility of the polyimide film also continues to increase, ultimately obtaining a reusable polyimide film.

[0048] In this embodiment, by controlling the number of introduced trifluoromethyl groups, a reusable polyimide film with low water absorption, low dielectric and low loss is produced.

[0049] In some implementations, step S10 specifically includes:

[0050] S101, dissolving the polyamine compound in a solvent, then adding a dianhydride monomer, and adjusting the solid content of the system to 20-30% (adjusted by adding a solvent);

[0051] S102, performing polycondensation reaction under an inert atmosphere (such as a nitrogen atmosphere) to obtain a polyamic acid solution.

[0052] In this embodiment, the linear polyamic acid is obtained by polycondensation of the dianhydride monomer and the polyamine compound. The viscosity of the polyamic acid solution formed by the polycondensation of the dianhydride monomer and the polyamine compound increases, which is beneficial to the subsequent curing and film-forming step.

[0053] In step S101, in one embodiment, the molar fraction of the polyamino compound in the dianhydride monomer and the diamine monomer has a significant effect on the formation of the thin film. If the molar fraction is too large, the polymer concentration will be too high and it will not spread, while if the molar fraction is too low, it will lead to the failure of film formation. Therefore, the present invention limits the molar amount of the polyamino compound to the total molar amount of the dianhydride monomer and the polyamino compound, and the molar fraction of the polyamino compound is 0.01-10%.

[0054] In some embodiments, the solvent can be selected from one or more of anhydrous DMF, anhydrous NMP, anhydrous DMAC, and γ-butyrolactone.

[0055] In step S102, in some embodiments, the conditions of the polycondensation reaction include: reaction temperature of -5°C-30°C, and reaction time of 6-24h.

[0056] In some implementations, step S11 specifically includes:

[0057] Filtering the polyamic acid solution to obtain a filtered polyamic acid solution;

[0058] The filtered polyamic acid solution is subjected to vacuum treatment to remove bubbles, thereby obtaining a defoamed polyamic acid solution;

[0059] The defoamed polyamic acid solution is coated on a substrate (such as a glass plate) and then heated and dried to obtain a polyamic acid film.

[0060] In some implementations, step S12 specifically includes:

[0061] The polyamic acid film (located on the substrate) is subjected to a thermal imidization reaction by using programmed temperature increase;

[0062] After the thermal imidization reaction is completed, the film is cooled to room temperature and then immersed in a separation aid. The film on the substrate is naturally detached to obtain a reusable high-frequency and low-dielectric-loss polyimide film.

[0063] In some embodiments, the separation aid may be, but is not limited to, water (such as deionized water, cold water, or hot water) or toluene.

[0064] In some embodiments, the polyamic acid film is subjected to a thermal imidization reaction using the following heating program: heating to 30-90°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120 min, heating to 90-150°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120 min, heating to 150-200°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120 min, heating to 200-250°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120 min, heating to 250-400°C at a heating rate of 1.0-20°C / min, and then keeping warm for 5-120 min.

[0065] Another embodiment of the present invention provides a method for preparing a reusable high-frequency low dielectric loss polyimide film, which comprises the following steps:

[0066] S20, subjecting the dianhydride monomer and the polyamine compound to a condensation polymerization reaction in the presence of a solvent to obtain a polyamic acid solution; wherein the polyamine compound contains one or more trifluoromethyl groups;

[0067] S21, adding pyridine and a catalyst to the polyamic acid solution to carry out a chemical imidization reaction to obtain polyimide;

[0068] S22, forming the polyimide into a film to obtain a polyimide film that can be reused at high frequency and has low dielectric loss.

[0069] In the present embodiment, fluorine atom has the characteristics of strong electronegativity and low polarizability, and the polarizability at high frequency is low. By introducing trifluoromethyl, the dielectric properties of polyimide film are greatly improved. Fluorine atom is also a hydrophobic group at the same time. After introduction, there will be a kind of aggregation phenomenon on the surface of polyimide film, which can effectively hinder water molecules from entering polyimide film, thereby reducing the water absorption of polyimide film. Trifluoromethyl not only has low polarizability and hydrophobicity, but also has a large free volume. Introducing trifluoromethyl in polyimide film increases the free volume of polyimide film, and the dielectric properties of polyimide film can be further improved. At the same time, the dielectric properties and hydrophobicity of polyimide film can be further improved by increasing the content of trifluoromethyl. In addition, due to the strong electronegativity of trifluoromethyl, the transparency of polyimide film can be improved, and the most important thing is that the solubility of polyimide film is also greatly improved with the introduction of trifluoromethyl. Therefore, in this embodiment, by introducing a trifluoromethyl group, the dielectric property, hydrophobic property and solubility property of the polyimide film can be improved, thereby preparing a polyimide film with excellent performance.

[0070] In this embodiment, the dielectric properties of the polyimide film are improved by using a polyamine compound and a dianhydride monomer containing different numbers of trifluoromethyl side groups. The free volume expansion brought by the trifluoromethyl group is used to reduce its dielectric constant without causing a significant reduction in mechanical properties and an increase in thermal expansion coefficient that would make it difficult to use. At the same time, as the number of introduced trifluoromethyl groups increases, not only does the water absorption rate of the polyimide film continue to decrease, but the solubility of the polyimide film also continues to increase, ultimately obtaining a reusable polyimide film.

[0071] In some implementations, step S20 specifically includes:

[0072] S201, dissolving the polyamine compound in a solvent, then adding a dianhydride monomer, and adjusting the solid content of the system to 15-20% (adjusted by adding a solvent);

[0073] S202, performing polycondensation reaction under an inert atmosphere (such as a nitrogen atmosphere) to obtain a polyamic acid solution.

[0074] In this embodiment, the linear polyamic acid is obtained by polycondensation of the dianhydride monomer and the polyamine compound. The viscosity of the polyamic acid solution formed by the polycondensation of the dianhydride monomer and the polyamine compound increases, which is beneficial to the subsequent curing and film-forming step.

[0075] In some embodiments, the solvent may be selected from one or more of anhydrous DMF, anhydrous NMP, anhydrous DMAC, γ-butyrolactone, and the like.

[0076] In step S202, in some embodiments, the conditions of the polycondensation reaction include: reaction temperature of -5°C-30°C, and reaction time of 6-24h.

[0077] In some implementations, step S21 specifically includes:

[0078] Adding pyridine and a catalyst to the polyamic acid solution to carry out a chemical imidization reaction, and obtaining polyimide by filtering;

[0079] The polyimide is dried and then dissolved in a solvent (such as NMP, etc.) to obtain a polyimide solution;

[0080] The polyimide solution is coated on a substrate (such as a glass plate), vacuum dried at 100-200°C to remove the solvent, cooled to room temperature, and then immersed in a separation aid. The film on the glass plate falls off naturally to obtain a reusable high-frequency low dielectric loss polyimide film.

[0081] In some embodiments, the separation aid may be, but is not limited to, water (such as deionized water, cold water, or hot water) or toluene.

[0082] In some embodiments, the catalyst may be selected from one or more of acetic anhydride, quinoline, isoquinoline, and the like.

[0083] In some embodiments, the addition ratio of the polyamine compound, dianhydride monomer, catalyst, and pyridine is 1 mol:1 mol:(1-3) ml:(0.5-2) ml. The catalyst within the above range can accelerate the process of imidization, and pyridine as a dehydrating agent can accelerate dehydration and accelerate imidization.

[0084] In this embodiment, in addition to forming the polyimide into a film, different molding methods can be used to form a strip or other forms according to actual use requirements.

[0085] In this embodiment, the polyamine compound may be a compound containing two or more amine groups. In some embodiments, the polyamine compound is a diamine compound, and the diamine compound may be selected from one or more of the following structural formulas, but is not limited thereto:

[0086]

[0087]

[0088] The value of n is an integer ranging from 1 to 10.

[0089] In some embodiments, the dianhydride monomer may be selected from one or more of the following structural formulas, but is not limited thereto:

[0090]

[0091] The embodiment of the present invention also provides a reusable high-frequency low-dielectric-loss polyimide film prepared by the above-mentioned preparation method.

[0092] The embodiment of the present invention also provides a use of the aforementioned reusable high-frequency and low-dielectric-loss polyimide film in electronic packaging materials and circuit substrates.

[0093] The present invention will be further described below by means of specific examples.

[0094] Example 1

[0095] This embodiment adopts thermal imidization to prepare the polyimide film, which specifically includes the following steps:

[0096] Weigh 2 g of diamine monomer PBAP3F, add it to a three-necked flask filled with nitrogen, and add an appropriate amount of anhydrous DMAC. After the diamine monomer is completely dissolved, add 2.5676 g of anhydride BPADA, and add DMAC again to adjust the solid content of the system to 20%. After stirring and reacting at room temperature for 8 hours under a nitrogen atmosphere, filter out insoluble impurities. Vacuum the filtered filtrate for 3 hours to remove bubbles, and obtain a defoamed polyamic acid solution. Use a 750μm scraper to scrape the defoamed polyamic acid solution onto a glass plate to form a thin film, then put it into an oven to remove the solvent, and finally put the glass plate loaded with the polyamic acid film into a muffle furnace for thermal imidization using the following heating program: heat to 45°C at a rate of 1°C / min and keep warm for 50 minutes, then heat to 120°C at a rate of 1°C / min and keep warm for 50 minutes, then heat to 175°C at a rate of 1°C / min and keep warm for 50 minutes, then heat to 225°C at a rate of 1°C / min and keep warm for 50 minutes, and finally heat to 275°C at a rate of 1°C / min and keep warm for 50 minutes to complete the thermal imidization. After the thermal imidization is completed, cool to room temperature, soak the glass plate in cold water, and wait for the film to fall off naturally, so as to obtain a reusable high-frequency, low-dielectric-loss polyimide film.

[0097] The reaction route involved in this embodiment is as follows:

[0098]

[0099] Example 2

[0100] This embodiment adopts thermal imidization to prepare the polyimide film, which specifically includes the following steps:

[0101] Weigh 2g of diamine monomer PBAP6F, add it to a three-necked flask filled with nitrogen, and add an appropriate amount of anhydrous DMAC. After the diamine monomer is completely dissolved, add 2.1988g of anhydride BPADA, and add DMAC again to adjust the solid content of the system to 20%. After stirring and reacting at room temperature for 8h under a nitrogen atmosphere, filter out insoluble impurities. Vacuum the filtered filtrate for 3h to remove bubbles, and obtain a defoamed polyamic acid solution. Use a 750μm scraper to scrape the defoamed polyamic acid solution onto a glass plate to form a thin film, then put it into an oven to remove the solvent, and finally put the glass plate loaded with the polyamic acid film into a muffle furnace, and use the following heating program for thermal imidization: heat to 75°C at a rate of 1°C / min and keep warm for 50 minutes, then heat to 135°C at a rate of 1°C / min and keep warm for 50 minutes, then heat to 175°C at a rate of 1°C / min and keep warm for 50 minutes, then heat to 230°C at a rate of 1°C / min and keep warm for 50 minutes, and finally heat to 300°C at a rate of 1°C / min and keep warm for 50 minutes to complete the thermal imidization. After the thermal imidization is completed, cool to room temperature, soak the glass plate in cold water, and wait for the film to fall off naturally, so as to obtain a reusable high-frequency, low-dielectric-loss polyimide film.

[0102] The reaction route involved in this embodiment is as follows:

[0103]

[0104] The polyimide films prepared in Example 1 and Example 2 were subjected to infrared, DSC, TGA, UV and solubility tests, and the results were as follows: Figure 1-Figure 4 , and as shown in Table 1. As shown in Table 1, the polyimide films prepared in Example 1 and Example 2 exhibit good solubility in DMAC and NMP, and also have certain solubility in THF and DMF but are insoluble in ethyl acetate and toluene. It can be seen that the polyimide films prepared in Example 1 and Example 2 have good solubility in most organic solvents.

[0105] Table 1

[0106]

[0107] "--" poorly soluble, "-" slightly soluble, "+" soluble, "++" easily soluble

[0108] The dielectric constant, dielectric loss and other performance tests of the polyimide films prepared in Example 1 and Example 2 were performed at a frequency of 10 GHz. The results are shown in Table 2:

[0109] Table 2

[0110]

[0111] It can be seen from Table 2 that the polyimide films prepared in Example 1 and Example 2 still have a smaller dielectric constant and lower dielectric loss at a frequency of 10 Hz.

[0112] Example 3

[0113] This embodiment adopts chemical imidization to prepare the polyimide film, which specifically includes the following steps:

[0114] Weigh 2g of diamine monomer PBAP6F, add it to a three-necked flask filled with nitrogen, and add an appropriate amount of anhydrous DMAC. After the diamine monomer is completely dissolved, add 2.1988g of anhydride BPADA, and add DMAC again to adjust the solid content of the system to 15%. After stirring and reacting for 8 hours at room temperature under a nitrogen atmosphere, a uniform polyamic acid solution is obtained. Add 2ml of acetic anhydride and 1ml of pyridine to the polyamic acid solution, and heat and stir at 60°C for 24h. Pour the solution obtained after stirring into 300ml of ethanol and filter to obtain a yellow polyimide powder.

[0115] The obtained polyimide powder was placed in a vacuum oven and dried at 200°C for 24 hours to obtain a solvent-free polyimide powder. Weigh 2g of solvent-free polyimide powder, add 8g of anhydrous NMP, stir at room temperature for 5 hours to obtain a uniform polyimide solution, filter out insoluble impurities, and vacuum the filtered polyimide solution for 3 hours to remove bubbles. Use a 750μm scraper to scrape a thin film on a glass plate from the polyimide solution after removing bubbles, then place it in a vacuum oven and dry it at 200°C for 24 hours to remove the solvent. After drying, soak the glass plate in cold water and wait for the film to fall off naturally to obtain a multiplexed high-frequency, low-dielectric-loss polyimide film.

[0116]

[0117] In summary, the present invention synergistically utilizes polyamine compounds containing different numbers of trifluoromethyl side groups and dianhydride monomers to improve the dielectric properties of the polyimide film, and while utilizing the free volume expansion brought by the trifluoromethyl group to reduce its dielectric constant, it will not cause a significant reduction in mechanical properties and an increase in thermal expansion coefficient that would make it difficult to use; at the same time, as the number of introduced trifluoromethyl groups increases, not only the water absorption rate of the polyimide film continues to decrease, but also the solubility of the polyimide film continues to increase, and finally a reusable polyimide film is obtained.

[0118] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a reusable high-frequency low dielectric loss polyimide film, characterized in that: The following steps are involved: The dianhydride monomer and the polyamine compound are subjected to a polycondensation reaction in the presence of a solvent, wherein the polycondensation reaction conditions include: reacting in an inert atmosphere, the reaction temperature is -5°C-30°C, and the reaction time is 6-24h to obtain a polyamic acid solution; wherein the polyamine compound is The dianhydride monomer is Based on the total molar amount of the dianhydride monomer and the polyamine compound, the molar fraction of the polyamine compound is 0.01-10%; forming the polyamic acid solution to obtain a polyamic acid film; The polyamic acid film is subjected to a thermal imidization reaction using the following heating program: heating to 30-90°C at a heating rate of 1.0-20°C / min and then keeping the temperature for 5-120min, heating to 90-150°C at a heating rate of 1.0-20°C / min and then keeping the temperature for 5-120min, heating to 150-200°C at a heating rate of 1.0-20°C / min and then keeping the temperature for 5-120min, heating to 200-250°C at a heating rate of 1.0-20°C / min and then keeping the temperature for 5-120min, heating to 250-400°C at a heating rate of 1.0-20°C / min and then keeping the temperature for 5-120min, to obtain a reusable high-frequency and low dielectric loss polyimide film.

2. A method for preparing a reusable high-frequency low dielectric loss polyimide film, characterized in that: The following steps are involved: The dianhydride monomer and the polyamine compound are subjected to a polycondensation reaction in the presence of a solvent, wherein the polycondensation reaction conditions include: reacting in an inert atmosphere, the reaction temperature is -5°C-30°C, and the reaction time is 6-24h to obtain a polyamic acid solution; wherein the polyamine compound is The dianhydride monomer is Adding pyridine and acetic anhydride to the polyamic acid solution to carry out a chemical imidization reaction, wherein the conditions of the chemical imidization reaction include: a reaction temperature of 60-190° C. and a reaction time of 12-24 hours to obtain polyimide; Forming the polyimide into a film to obtain a polyimide film with high frequency and low dielectric loss that can be reused; The addition ratio of the polyamine compound, the dianhydride monomer, the acetic anhydride and the pyridine is 1 mol:1 mol:(1-3) ml:(0.5-2) ml.

3. The method for preparing a reusable high-frequency low dielectric loss polyimide film according to claim 1 or 2, characterized in that: The solvent is selected from one or more of anhydrous DMF, anhydrous NMP, anhydrous DMAC, and γ-butyrolactone.

4. A reusable high-frequency low dielectric loss polyimide film prepared by the preparation method according to claim 1 or 2.

5. Use of the reusable high-frequency and low-dielectric-loss polyimide film according to claim 4 in electronic packaging materials and circuit substrates.

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