Preparation method of low-dielectric polyimide, low-dielectric polyimide film and flexible flexible printed circuit board thereof

Abstract

The present invention discloses a preparation method of a low-dielectric polyimide, a low-dielectric polyimide film and a flexible flexible board thereof, which relates to the technical field of organic polymer materials, and its technical key points are as follows: including the following steps: Step S1, synthesize a phenolic hydroxyl group-containing monobasic anhydride monomer with a clear sequence structure; Step S2, synthesize a halogenated monoamine with a clear sequence structure; Step S3, prepare a novel PI resin with a clear sequence structure through imidization and aromatic nucleophilic substitution reactions, optimize the synthesis process, and establish a new strategy for PI resin synthesis. The present invention provides a new strategy for preparing a polyimide resin with low dielectric, low loss and low moisture absorption, enabling the PI resin to be prepared into a polyimide film by means of solution casting, casting, blown film, melt extrusion, etc., without high-temperature thermal imidization, with diverse processing methods and energy saving.

Description

Technical Field

[0001] The present invention relates to the technical field of organic polymer materials, and specifically relates to a preparation method of a low-dielectric polyimide, a low-dielectric polyimide film and a flexible printed circuit board thereof. Background Art

[0002] As an important high-performance polymer material, polyimide resin has broad application prospects in the fields of microelectronics, communication, aerospace, etc. Its low dielectric constant and low loss characteristics make it an ideal material in high-frequency electronic devices, radio frequency microwave circuits and optical communication systems. However, traditional polyimide resins often have relatively high dielectric constants and loss factors, which limit their application in high-frequency, high-speed and high-density electronic devices.

[0003] In view of the deficiencies of traditional polyimide resins in dielectric properties and loss properties, in recent years, researchers have proposed a series of modification methods and new synthesis methods. These methods include introducing functional groups with low dielectric constants and low losses into the molecular structure of polyimide resins; modifying and improving the dielectric properties of resins by adding nanomaterials or fillers; adopting new polymerization processes or catalysts to improve the synthesis efficiency and product quality of polyimide resins. However, these modification methods are often limited in practical applications. For example, the increase of modifiers may affect the mechanical properties and processing properties of materials. Therefore, finding a simple and effective preparation method and modification means to obtain polyimide resins with excellent low-dielectric and low-loss properties has become one of the important research directions at present.

[0004] Analysis shows that the reason for the deficiencies of traditional polyimide (PI) resins in dielectric properties and loss properties is the existence of the intrinsic imide ring structure. The imide ring structure with a permanent dipole moment endows PI resins with excellent mechanical properties and thermal properties while increasing the dielectric constant and dielectric loss of PI; in addition, the easy moisture absorption of the imide ring structure can also lead to further deterioration of dielectric properties. At the same time, traditional polyimide resins are all prepared by high-temperature imidization of polyamic acid, and the forming and processing means are relatively single. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems and provide a preparation method of a low-dielectric polyimide, a low-dielectric polyimide film and a flexible printed circuit board thereof.

[0006] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0007] A preparation method of a low-dielectric polyimide, comprising the following steps:

[0008] Step S1, synthesize a phenolic hydroxyl group-containing monobasic anhydride monomer with a clear sequence structure;

[0009] Step S2: Synthesize halogenated monoamines with a clear sequence structure;

[0010] Step S3: Prepare a novel PI resin with a clear sequence structure through imidization and aromatic nucleophilic substitution reactions, optimize the synthesis process, and establish a new strategy for PI resin synthesis.

[0011] Further in the present invention: The sub-steps of the said Step S1 are as follows:

[0012] Step S11: Purchase relevant raw materials and synthesize intermediates A1 and A2;

[0013] Step S12: Directly prepare the target monomer PMAs through Suzuki coupling reaction;

[0014] Step S13: Through structure regulation, obtain a series of monoacid anhydride monomers containing phenolic hydroxyl groups with different sequence structures; characterize the monomer structures by means of nuclear magnetic resonance, infrared, mass spectrometry, and elemental analysis, and optimize the reaction conditions by combining liquid chromatography and gas chromatography research methods to obtain a general preparation method for such monomers;

[0015] The synthesis route diagram is as follows:

[0016]

[0017] Further in the present invention: The sub-steps of the said Step S2 are as follows:

[0018] Step S21: Through Suzuki coupling reaction, couple intermediate B1 with B2 to synthesize halogenated nitrobenzene B3;

[0019] Step S22: Reduce the nitro group to an amino group to obtain halogenated monoamines FMAs;

[0020] Step S23: Through structure regulation, obtain a series of halogenated monoamine monomers with different sequence structures; characterize the monomer structures by means of nuclear magnetic resonance, infrared, mass spectrometry, and elemental analysis, and optimize the reaction conditions by combining liquid chromatography and gas chromatography research methods to obtain a convenient preparation technology for such monomers;

[0021] The synthesis route diagram is as follows:

[0022]

[0023] Further in the present invention: The sub-steps of the said Step S3 are as follows:

[0024] Step S31: Using the PMAs and the series of halogenated monoamine FMAs monomers as building units, obtain polyimide precursor FPPIs through solution condensation reaction and imidization. One end of the FPPIs is a phenolic hydroxyl group and the other end is a fluorine;

[0025] Step S32: Using the FPPIs as polymerization monomers, a novel PI resin with a well-defined sequence structure is prepared by high-temperature solution polymerization via aromatic nucleophilic substitution reaction; ether bonds, methylene groups, isopropylidene groups, and ester bonds are selected as bridges to connect benzene rings, and novel PI resins with different sequence structures are prepared by regulating the type, quantity, and bonding mode of the groups.

[0026] The synthesis route diagram is as follows:

[0027]

[0028] A preparation method of a low-dielectric polyimide film includes the following steps:

[0029] Step A1: Dissolve the novel PI resin prepared in claim 4 in an organic solvent to prepare a casting solution; the organic solvent is one or more of aprotic organic solvents such as NMP, DMF, DMAc, DMSO, and chloroform, and the concentration of the casting solution is measured by the mass fraction of the novel PI resin, specifically 10 - 20%.

[0030] Step A2: Pour the prepared casting solution onto a flat plate to prepare a PI film. The flat plate is a glass plate or a silicon wafer, and the drying process during the film preparation is drying at 80°C for 4 hours and drying at 120°C for 12 hours.

[0031] A preparation method of a low-dielectric polyimide flexible printed circuit board is as follows:

[0032] Step B1: Dissolve the novel PI resin prepared in claim 4 in an organic solvent to prepare a casting solution; the organic solvent is one or more of aprotic organic solvents such as NMP, DMF, DMAc, DMSO, and chloroform, and the concentration of the casting solution is measured by the mass fraction of the novel PI resin, specifically 10 - 20%.

[0033] Step B2: Pour the prepared casting solution onto a copper foil to prepare a flexible printed circuit board. The drying process for preparing the flexible printed circuit board is drying at 80°C for 4 hours and drying at 180°C for 6 hours under vacuum conditions.

[0034] Compared with the prior art, the beneficial effects of this solution are as follows: A new strategy for preparing a low-dielectric, low-loss, and low-moisture-absorption polyimide resin is provided, enabling the PI resin to be used to prepare polyimide films by means such as solution casting, casting, blown film, and melt extrusion, without high-temperature thermal imidization, with diverse processing methods and energy conservation. Description of the Drawings

[0035] Figure 1 It is the synthesis and preparation route diagram of FPPI-Ph in the embodiment of the present invention;

[0036] Figure 2It is the infrared spectrum of FPAA-Ph in the embodiments of the present invention. Detailed implementation manners

[0037] To enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the embodiments and drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0039] Embodiment:

[0040] (1) Synthesis of the phenolic hydroxyl group-containing monobasic acid anhydride monomer PMA-Ph, and the specific operation is as follows: First, weigh 27.6 g of 4-hydroxyphenylboronic acid, 45.4 g of 3-bromophthalic anhydride, 4.8 g of Pd(PPh 3 ) 4 , 80 g of anhydrous potassium carbonate, and 500 ml of 1,4-dioxane, and add them successively to a 1 L three-necked flask equipped with a magnetic stirrer. Under nitrogen protection, reflux and react for 12 hours; then, cool the reaction system to room temperature, and dilute it with 1000 ml of tetrahydrofuran, and filter to remove the catalyst Pd(PPh 3 ) 4 ; finally, concentrate the filtrate under reduced pressure and pour it into 2000 ml of methanol, filter, wash with water, and dry to obtain 42.4 g of the target product PMA-Ph.

[0041] (2) Synthesis of the fluorinated monobasic amine monomer FMA-Ph, and the specific operation is as follows: First, weigh 28 g of 4-fluorophenylboronic acid, 40 g of p-bromonitrobenzene, 4.8 g of Pd(PPh 3 ) 4 , 80 g of anhydrous potassium carbonate, and 500 ml of 1,4-dioxane, and add them successively to a 1 L three-necked flask equipped with a magnetic stirrer. Under nitrogen protection, reflux and react for 12 hours; then, cool the reaction system to room temperature, and dilute it with 1000 ml of tetrahydrofuran, and filter to remove the catalyst Pd(PPh 3 ) 4, the filtrate was concentrated under reduced pressure and then poured into 2000 ml of methanol. After filtration, washing with water, and drying, approximately 40 g of the intermediate could be obtained. Finally, the intermediate and 5.4 g of palladium-carbon (10%) catalyst were dispersed in 250 ml of ethyl acetate, and the reaction was carried out at room temperature for 2 h under the atmosphere of high-pressure hydrogen. After filtration to remove the palladium-carbon catalyst, rotary evaporation gave 30.8 g of the reduced product FMA-Ph.

[0042] (3) Preparation of the novel PI-Ph: First, 24 g of PMA-Ph and 18 g of FMA-Ph prepared above were weighed and placed in 200 ml of N-methylpyrrolidone (NMP), and the reaction was carried out at room temperature for 10 h. Then, a certain amount of the mixed solution of acetic anhydride and pyridine was slowly added dropwise to the reaction system, and the reaction was continued for 5 h. Finally, the reaction system was poured into 1000 ml of ethanol, stirred, filtered, and dried to obtain the target product PI-Ph. The results of the thermal performance test showed that the glass transition temperature of the prepared novel PI resin was 274 °C, and the 5% thermal weight loss temperature was 526 °C, showing excellent thermal stability.

[0043] Table 1 Summary of the properties of FPPI-Ph

[0044]

[0045]

[0046] (4) Preparation of the novel PI-Ph film: First, the PI-Ph prepared above was dissolved in NMP to prepare a 15% (by mass) PI-Ph casting solution. Then, the PI-Ph casting solution was poured onto a clean glass plate that could be heated, and a doctor blade was used to assist the leveling of the casting solution. Finally, the solvent was removed by drying to obtain the PI film. The specific heating process was drying at 80 °C for 4 h and then at 120 °C for 12 h. The prepared film was flexible with good mechanical properties. The tensile strength of the film was 115 MPa, the tensile modulus was 3.2 GPa, and the elongation at break was 8%. In addition, the dielectric constant of the film was 2.8 @ 10 GHz, the dielectric loss was 0.008 @ 10 GHz, and the water absorption rate was 0.8%, all of which were superior to those of commercial PI.

[0047] (5) Preparation of the flexible printed circuit board (FCCL): First, the PI-Ph casting solution prepared above was coated on a special copper foil, and a doctor blade was used to assist the leveling of the casting solution. Then, the system was placed at 80 °C for drying treatment for 5 h to obtain a preliminarily dried flexible printed circuit board. Finally, it was transferred to a vacuum oven and treated at 180 °C for 6 h to obtain the flexible printed circuit board. The adhesion between PI and the copper foil was strong, the dimensional stability was good, and the solder resistance performance was excellent.

[0048] The above specific embodiments are only explanations of the present invention, and they are not limitations on the present invention. After reading this specification, those skilled in the art can make modifications to these embodiments that do not contribute creatively as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for preparing a low dielectric polyimide, characterized in that: The following steps are involved: Step S1, synthesizing a phenolic hydroxyl group-containing monobasic acid anhydride monomer with a clear sequence structure; Step S2, synthesizing a halogenated monoamine with a clear sequence structure; Step S3, preparing a novel PI resin with a clear sequence structure through imidization and aromatic nucleophilic substitution reaction, optimizing the synthesis process, and establishing a new strategy for PI resin synthesis; The sub-steps of step S1 are as follows: Step S11, purchasing relevant raw materials and synthesizing intermediates A1 and A2; Step S12, directly preparing the target monomer PMAs through Suzuki coupling reaction; Step S13, obtaining a series of phenolic hydroxyl-containing monoanhydride monomers with different sequence structures through structural regulation; characterizing the monomer structure by means of nuclear magnetic resonance, infrared, mass spectrometry and elemental analysis, and optimizing the reaction conditions in combination with liquid chromatography and gas chromatography research methods, to obtain a universal preparation method for this type of monomer; The synthetic route is as follows: The sub-steps of step S2 are as follows: Step S21, coupling the intermediate B1 and B2 to synthesize the halogenated nitrobenzene B3 through a Suzuki coupling reaction; Step S22, reducing the nitro group to an amino group to obtain a halogenated monoamine FMAs; Step S23, obtaining a series of halogenated monoamine monomers with different sequence structures through structural regulation; characterizing the monomer structure by means of nuclear magnetic resonance, infrared, mass spectrometry and elemental analysis, and optimizing the reaction conditions in combination with liquid chromatography and gas chromatography research methods, to obtain a convenient preparation technology for such monomers; The synthetic route is as follows: The sub-steps of step S3 are as follows: Step S31, using the PMAs and halogenated monoamine FMAs series monomers as building units, obtaining polyimide precursor FPPIs through solution condensation reaction and imidization, wherein one end of the FPPIs is a phenolic hydroxyl group and the other end is a fluorine; Step S32, using the FPPIs as polymerization monomers, adopting high temperature solution polymerization to prepare a novel PI resin with a clear sequence structure through an aromatic nucleophilic substitution reaction; selecting methylene, isopropylidene and ester bonds as bridges to connect benzene rings, and preparing novel PI resins with different sequence structures by regulating the group type, number and bonding method; The synthetic route is as follows:

2. A method for preparing a low dielectric polyimide film, characterized in that: The specific steps are as follows: Step A1, dissolving the novel PI resin prepared in claim 1 in an organic solvent to prepare a casting solution; the organic solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide and chloroform aprotic organic solvents, and the concentration of the casting solution is measured by the mass fraction of the novel PI resin, specifically 10-20%; Step A2, pouring the above-configured casting solution onto a flat plate to prepare a PI film, wherein the flat plate is a glass plate or a silicon wafer, and the drying process of the film preparation process is drying at 80° C. for 4 hours and drying at 120° C. for 12 hours.

3. A method for preparing a low dielectric polyimide flexible board, characterized in that: The specific steps are as follows: Step B1, dissolving the novel PI resin prepared in claim 1 in an organic solvent to prepare a casting solution; the organic solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide and chloroform aprotic organic solvents, and the concentration of the casting solution is measured by the mass fraction of the novel PI resin, specifically 10-20%; Step B2, pouring the above-prepared casting solution onto copper foil to prepare a flexible soft board, wherein the drying process for preparing the flexible board is drying at 80° C. for 4 hours and drying at 180° C. for 6 hours under vacuum conditions.

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