Polyimide high-thermal-conductivity composite film and preparation method thereof
By adding high thermal conductivity fillers to the polyimide (PI) film and using water-alcohol co-solvent and ultrasonic treatment technology, a polyimide high thermal conductivity composite film with excellent thermal conductivity and mechanical properties was prepared, which solved the problem of using highly toxic solvents and low thermal conductivity PI films in the prior art, and achieved efficient and environmentally friendly preparation of heat dissipation materials.
Patent Information
- Application Number
- CN202510147356.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-11
- Publication Date
- 2025-05-13
AI Technical Summary
The high-boiling point aprotic polar solvent used in the preparation process of existing polyimide (PI) films is highly toxic and has high energy consumption, and the thermal conductivity of PI is low, making it difficult to meet the heat dissipation needs of high-performance electronic devices.
Polyimide high-thermal conductivity composite films were prepared by water alcohol cosolvent and sonication technology. By adding high-thermal conductivity fillers such as boron nitride to the PI matrix, and performing prepolymerization and solid-phase polymerization-thermal imidation reaction under the protection of nitrogen atmosphere, a composite film with excellent thermal conductivity and mechanical properties was prepared.
The preparation of polyimide high-thermal conductivity composite film has been achieved, with significantly improved thermal conductivity, excellent mechanical properties, good thermal stability and flexibility. It is suitable for heat dissipation applications of high-performance electronic devices. It also uses green solvents and simple and easy-to-use processes to meet the requirements of environmental protection and economic benefits.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of polyimide synthesis, and in particular to a polyimide high thermal conductivity composite film and a preparation method thereof. Background Art
[0002] With the rapid development of microelectronic devices towards high integration and miniaturization, the heat generated in such devices may cause serious problems for their performance and durability. Therefore, heat dissipation has become an important consideration in advanced microelectronic devices. Polyimide (PI) has attracted attention as a high-performance heat dissipation material due to its excellent mechanical and electrical insulation properties as well as thermal and chemical stability. However, the thermal conductivity of PI is very low, so it is necessary to add high thermal conductivity fillers to the PI matrix.
[0003] Conventional PI film preparation uses high-boiling-point aprotic polar solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO). These solvents are classified as highly toxic solvents by the European REACH (Registration, Evaluation, Authorization and Restriction of Chemical Substances) regulations, and in addition, they require a large amount of energy during the solvent recovery process. Therefore, it is necessary to develop an environmentally friendly, cost-effective strategy to prepare PI thermally conductive composite films without the use of such harmful and expensive organic solvents. Summary of the invention
[0004] In order to solve the above technical problems, a polyimide high thermal conductivity composite film and a preparation method thereof are provided. The present invention adopts a green solvent to prepare the polyimide high thermal conductivity composite film, which is non-toxic and harmless, and has a safe process. The prepared composite film exhibits excellent in-plane and out-of-plane thermal conductivity, tensile strength, thermal stability and flexibility.
[0005] In order to achieve the above objectives, the present invention is implemented by the following technical solutions:
[0006] A method for preparing a polyimide high thermal conductivity composite film comprises the following steps:
[0007] S1. Adding a thermally conductive filler into a water-alcohol co-solvent, and ultrasonically treating the mixture to prepare a thermally conductive filler suspension;
[0008] Wherein, the water-alcohol co-solvent is a mixed solvent of water and isopropanol, the volume ratio of water to isopropanol is in the range of 1:1.3-1.7, and preferably the volume ratio of water to isopropanol is 2:3;
[0009] S2, adding dianhydride monomer, diamine monomer and catalyst to the thermally conductive filler suspension to obtain a reaction system, and performing a prepolymerization reaction to obtain a polyamic acid composite thermally conductive suspension;
[0010] S3, placing the polyamic acid composite thermal conductive suspension in a mold to carry out solid phase polymerization-thermal imidization reaction, and obtaining a polyimide high thermal conductive composite film after peeling.
[0011] Further, the thermally conductive filler is one or more of spherical thermally conductive materials, fibrous thermally conductive materials, and sheet thermally conductive materials; wherein the spherical thermally conductive material is selected from any one or more of silicon oxide, aluminum oxide, magnesium oxide, and aluminum nitride, and the average particle size of the spherical thermally conductive material is less than 500nm; wherein the fibrous thermally conductive material is selected from one or more of tetrapod-shaped zinc oxide, carbon fiber, metal fiber, and ceramic fiber, and the average fiber diameter of the fibrous thermally conductive material is less than 10μm, and the aspect ratio is in the range of 5-60; wherein the sheet thermally conductive material is selected from one or more of hexagonal boron nitride, graphene, graphite, and silicon micropowder, and the sheet diameter of the sheet thermally conductive material is less than 10μm, and the sheet thickness is in the range of 200-500nm.
[0012] Furthermore, the mass percentage of the thermally conductive filler in the polyimide high thermal conductive composite film is greater than 5%.
[0013] Furthermore, the dianhydride monomer is selected from one or more of pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA); the diamine monomer is selected from one or more of 4,4'-diaminodiphenyl ether (ODA) and p-phenylenediamine (PDA); and the catalyst is selected from one or more of 4-dimethylaminopyridine (DMAP) and 1,2-dimethylimidazole (DMIZ).
[0014] Furthermore, the molar ratio of the diamine monomer, the dianhydride monomer and the catalyst is 1:1-3:1; and the mass concentration of the reaction system is 0.1-0.3 g / mL.
[0015] Furthermore, step S2 is carried out under nitrogen atmosphere protection and stirring, and the stirring speed is 200-500 rpm.
[0016] Furthermore, the ultrasonic treatment time in S1 is 3-5 hours; the order of adding the materials in S2 is: first dissolving the catalyst and diamine monomer in the thermal conductive filler suspension, stirring at room temperature for 20-60 minutes, then adding the dianhydride monomer, and conducting a prepolymerization reaction (nucleophilic reaction) at 60-70°C for 18-30 hours.
[0017] Furthermore, the process parameters of the solid phase polymerization-thermal imidization reaction in S3 are:
[0018] First, heat the temperature from room temperature to 40-50°C at a heating rate of 1-3°C / min and keep it warm for 6h-9h, then keep the heating rate to 70-110°C and keep it warm for 30min;
[0019] Then, the temperature is raised to 140-160°C at a heating rate of 4-10°C / min and kept at this temperature for 30 minutes. The temperature is then raised to 180-220°C at this rate and kept at this temperature for 30 minutes.
[0020] Finally, the temperature is raised to 230-280°C at a heating rate of 4-10°C / min and kept warm for 1 hour.
[0021] Preferably, the process parameters of the solid phase polymerization-thermal imidization reaction in S3 are:
[0022] First, heat the temperature from room temperature to 50°C at a heating rate of 1-3°C / min and keep it warm for 6h-9h, then keep the heating rate to 100°C and keep it warm for 30min;
[0023] Then, the temperature was raised to 150°C at a rate of 4-10°C / min and kept at that temperature for 30 minutes, and the temperature was raised to 200°C at the same rate and kept at that temperature for 30 minutes;
[0024] Finally, the temperature was raised to 250°C at a heating rate of 4-10°C / min and kept at this temperature for 1 hour.
[0025] The second aspect of the present invention provides a polyimide high thermal conductivity composite film obtained by the above preparation method.
[0026] Beneficial technical effects:
[0027] The polyimide high thermal conductivity composite film prepared by the method of the present invention has the following advantages: the thermal conductivity is significantly improved, which can meet the heat dissipation requirements of high-performance electronic devices, the mechanical properties are excellent, the tensile strength and elongation at break are high, and the film is suitable for a variety of application scenarios, and the interface bonding is good, and there are no obvious defects between the thermal conductive material BN and the polyimide matrix, thereby ensuring the overall performance of the composite film; the present invention ultrasonically disperses boron nitride in a water-alcohol system to synthesize a high thermal conductivity composite film, and the preparation method is simple and easy, does not require complex equipment and expensive raw materials, and the entire preparation process is green and environmentally friendly, and no harmful substances are discharged. DETAILED DESCRIPTION
[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0029] Unless otherwise specifically stated, the numerical value set forth in these embodiments does not limit the scope of the present invention. The technology and method known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology and method should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values.
[0030] The experimental methods in the following examples without specifying specific conditions are usually measured in accordance with national standards; if there is no corresponding national standard, the method is carried out in accordance with the general standard requirements or general methods.
[0031] The thermal conductive filler used in the following cases takes hexagonal boron nitride as an example. In order to obtain a better thermal conductive effect, thermal conductive fillers of different dimensions can be added in other embodiments. For example, while using sheet and / or fiber as the main thermal conductive filler to play a thermal conductive role, spherical fillers can be heated to fill the gaps to make the thermal conductive network more complete.
[0032] Example 1
[0033] A method for preparing a polyimide high thermal conductivity composite film comprises the following steps:
[0034] S1, 100 mL of distilled water and 150 mL of isopropanol form a water-alcohol co-solvent, 2.09 g of hexagonal boron nitride powder (BN, flake diameter 5-8 μm, thickness 300-350 nm) is added thereto, and ultrasonic treatment is performed at 45 kHz for 3 hours using a Branson 1510 ultrasonic cleaner (Branson, USA) to prepare a thermal conductive filler suspension;
[0035] S2. Under nitrogen atmosphere protection and stirring speed of 350 rpm, 11.00 g of 1,2-dimethylimidazole as a catalyst (DMIZ, 0.11 mol) and 7.61 g of 4,4'-diaminodiphenyl ether (ODA, 0.038 mol) were added to the above thermally conductive filler suspension and stirred for 1 hour to completely dissolve the catalyst and diamine monomer, then the temperature was raised to 70° C., 11.18 g of 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA, 0.038 mol) was added to form a reaction system, and a prepolymerization reaction was carried out at 70° C. for 18 hours under continuous stirring to obtain a polyamic acid composite thermally conductive suspension (referred to as PAAS / BN composite suspension);
[0036] S3, by using a 50 μm thick casting knife to cast the PAAS / BN composite suspension onto a glass plate at a casting speed of 0.025 m / s, and immediately immersed in deionized water at room temperature, removed from the water bath after 30 minutes and thoroughly washed three times with deionized water, and then subjected to solid phase polymerization-thermal imidization reaction, the specific process parameters are: firstly, the temperature is raised from room temperature to 50°C at a heating rate of 2°C / min and kept warm for 6 hours to remove the solvent, and the heating rate is maintained to 100 ℃ and keep it warm for 30 minutes; then heat it to 150℃ at a heating rate of 8℃ / min and keep it warm for 30 minutes, keep heating it to 200℃ at the same rate and keep it warm for 30 minutes; finally heat it to 250℃ at a heating rate of 10℃ / min and keep it warm for 1 hour; then cool it to room temperature and peel it off to obtain a polyimide high thermal conductive composite film (PI / BN composite film) with a thickness of about 50μm. In this case, the theoretical mass percentage of BN in the composite film is 10%.
[0037] Example 2
[0038] The preparation process of the polyimide high thermal conductivity composite film (PI / BN composite film) in this case is the same as that in Example 1, except that the amount of BN added is 4.70 g. The theoretical mass percentage of BN in the composite film in this case is 20%.
[0039] Example 3
[0040] The preparation process of the polyimide high thermal conductivity composite film (PI / BN composite film) in this case is the same as that in Example 1, except that the amount of BN added is 8.05 g. The theoretical mass percentage of BN in the composite film in this case is 30%.
[0041] Example 4
[0042] The preparation process of the polyimide high thermal conductivity composite film in this case is the same as that in Example 1, except that the amount of BN added is 12.53 g. The theoretical mass percentage of BN in the composite film in this case is 40%.
[0043] Example 5
[0044] The preparation process of the polyimide high thermal conductivity composite film (PI / BN composite film) in this case is the same as that in Example 1, except that the amount of BN added is 18.79 g. The theoretical mass percentage of BN in the composite film in this case is 50%.
[0045] Example 6
[0046] A method for preparing a polyimide high thermal conductivity composite film comprises the following steps:
[0047] S1, 100 mL of distilled water and 150 mL of isopropanol form a water-alcohol co-solvent, 15.89 g of hexagonal boron nitride powder (BN, flake diameter 5-8 μm, thickness 300-350 nm) is added thereto, and ultrasonic treatment is performed at 45 kHz for 5 hours using a Branson 1510 ultrasonic cleaner (Branson, USA) to prepare a thermal conductive filler suspension;
[0048] S2. Under nitrogen atmosphere protection and stirring speed of 500 rpm, 11.00 g of 1,2-dimethylimidazole as a catalyst (DMIZ, 0.11 mol) and 7.61 g of 4,4'-diaminodiphenyl ether (ODA, 0.038 mol) were added to the above thermally conductive filler suspension and stirred for 1 hour to completely dissolve the catalyst and diamine monomer, then the temperature was raised to 70° C., 8.29 g of pyromellitic dianhydride (PMDA, 0.038 mol) was added to form a reaction system, and a prepolymerization reaction was carried out at 70° C. for 18 hours under continuous stirring to obtain a polyamic acid composite thermally conductive suspension (referred to as PAAS / BN composite suspension);
[0049] S3, by using a 50 μm thick casting knife to cast the PAAS / BN composite suspension onto a glass plate at a casting speed of 0.025 m / s, and immediately immersed in deionized water at room temperature, removed from the water bath after 30 minutes and thoroughly washed three times with deionized water, and then subjected to solid phase polymerization-thermal imidization reaction, the specific process parameters are: firstly, the temperature is raised from room temperature to 50°C at a heating rate of 2°C / min and kept warm for 6 hours to remove the solvent, and the heating rate is maintained to 100 ℃ and keep it warm for 30 minutes; then heat it to 150℃ at a heating rate of 8℃ / min and keep it warm for 30 minutes, keep heating it to 200℃ at the same rate and keep it warm for 30 minutes; finally heat it to 250℃ at a heating rate of 10℃ / min and keep it warm for 1 hour; then cool it to room temperature and peel it off to obtain a polyimide high thermal conductive composite film (PI / BN composite film) with a thickness of about 50μm. In this case, the theoretical mass percentage of BN in the composite film is 50%.
[0050] Comparative Example 1
[0051] This case is the preparation of pure polyimide film, and its preparation process is the same as that of Example 5, except that BN is not added.
[0052] Comparative Example 2
[0053] This case is the preparation of pure polyimide film, and its preparation process is the same as that of Example 6, except that BN is not added.
[0054] Comparative Example 3
[0055] This case is the preparation of a polyimide composite film, and its preparation process is the same as that of Example 5, except that BN is not subjected to ultrasonic treatment, and BN is directly dispersed in a water-alcohol co-solvent with mechanical stirring at 1000 rpm to form a suspension.
[0056] Comparative Example 4
[0057] This case is the preparation of a thin film, and its preparation process is the same as that of Example 5, except that the water-alcohol co-solvent is replaced with 250 mL of distilled water. When all distilled water is used as the solvent, water participates in the side reaction, and in the subsequent thermal imidization process, PAA decomposes prematurely, and imidization cannot be completed. It may also cause BN surface oxidation or structural damage, affecting the performance of the composite film, and the performance will not be compared in the subsequent process.
[0058] Comparative Example 5
[0059] This case is the preparation of a thin film, and its preparation process is the same as that of Example 5, except that the water-alcohol co-solvent is replaced with 250 mL. The solubility of the polyimide precursor or the polyimide itself in isopropanol is poor, and it is difficult to form a uniform and stable solution. At the same time, the volatilization rate of isopropanol is fast. During the film formation process, the rapid volatilization of the solvent may cause uneven drying speed of the film, and easily cause defects such as pores and cracks in the film, affecting the density and mechanical properties of the composite film. The performance will not be compared in the following.
[0060] Comparative Example 6
[0061] This case is the preparation of a polyimide composite film, and its preparation process is the same as that of Example 5, except that the water-alcohol co-solvent is replaced with 150 mL of distilled water and 100 mL of isopropanol.
[0062] Comparative Example 7
[0063] This case is the preparation of a polyimide composite film, and its preparation process is the same as that of Example 5, except that the water-alcohol co-solvent is replaced with 108 mL of distilled water and 142 mL of isopropanol.
[0064] Comparative Example 8
[0065] This case is the preparation of a polyimide composite film, and its preparation process is the same as that of Example 5, except that the water-alcohol co-solvent is replaced with 92 mL of distilled water and 158 mL of isopropanol.
[0066] Comparative Example 9
[0067] This case is the preparation of a polyimide composite film, and its preparation process is the same as that of Example 5, except that the alcohol in the water-alcohol co-solvent is anhydrous ethanol.
[0068] Comparative Example 10
[0069] This case is the preparation of a polyimide composite film, and its preparation process is the same as that of Example 5, except that the alcohol in the water-alcohol co-solvent is n-propanol.
[0070] Comparative Example 11
[0071] This case is the preparation of a polyimide composite film, and its preparation process is the same as that of Example 5, except that the catalyst is replaced with triethylamine (TEA). When TEA is used as a catalyst, the viscosity of the PAAS / BN composite suspension obtained is much lower than that of the PAAS / BN composite suspension prepared using DMIZ as a catalyst in Example 5. A brittle film is obtained by drop casting the PAAS / BN composite suspension, and many cracks are formed in the subsequent thermal imidization process. This phenomenon may be attributed to the relatively low molecular weight of PAAS obtained by prepolymerization when TEA is used. The performance is not compared in the subsequent process.
[0072] Comparative Example 12
[0073] This case is the preparation of a polyimide composite film, and its preparation process is the same as that of Example 5, except that the water-alcohol co-solvent is replaced with DMF 250 mL.
[0074] The variables of the above embodiments and comparative examples and their corresponding composite membrane properties are shown in Table 1 below.
[0075] Table 1 Variables of the embodiments and comparative examples and their corresponding composite membrane properties
[0076]
[0077]
[0078] As can be seen from Table 1, a series of PI films were prepared using different solvents, monomers, and boron nitride masses. The results show that the thermally conductive PI / BN composite film was successfully prepared using non-toxic, environmentally friendly and inexpensive co-solvents of water and tert-butyl alcohol. The PI / BN50 film of Example 5 exhibited excellent in-plane and out-of-plane thermal conductivity (15.078 W / mK and 1.138 W / mK, respectively), which was attributed to the effective exfoliation and dispersion of BN in the aqueous solvent. Despite the high BN loading, the PI / BN50 film of Example 5 had high tensile strength and good flexibility. The high BN loading (50 wt%) can provide the resulting PI / BN composite film with the advantages of high thermal conductivity and low cost. The PI / BN50 composite film of Example 5 of the present invention is expected to be used as a heat dissipation material in advanced microelectronic devices.
[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A method for preparing a polyimide high thermal conductivity composite film, characterized in that: The steps include: S1. Adding a thermally conductive filler into a water-alcohol co-solvent and subjecting the mixture to ultrasonic treatment to prepare a thermally conductive filler suspension; Wherein, the water-alcohol co-solvent is a mixed solvent of water and isopropanol, and the volume ratio of water to isopropanol is in the range of 1:1.3-1.7; S2, adding dianhydride monomer, diamine monomer and catalyst to the thermally conductive filler suspension to obtain a reaction system, and performing a prepolymerization reaction to obtain a polyamic acid composite thermally conductive suspension; S3, placing the polyamic acid composite thermal conductive suspension in a mold to carry out solid phase polymerization-thermal imidization reaction, and obtaining a polyimide high thermal conductive composite film after peeling.
2. The method for preparing a polyimide high thermal conductivity composite film according to claim 1, characterized in that: The thermally conductive filler is one or more of spherical thermally conductive materials, fibrous thermally conductive materials, and sheet thermally conductive materials; The spherical thermal conductive material is selected from any one or more of silicon oxide, aluminum oxide, magnesium oxide, and aluminum nitride, and the average particle size of the spherical thermal conductive material is less than 500 nm; The fibrous thermal conductive material is selected from one or more of tetrapod-shaped zinc oxide, carbon fiber, metal fiber, and ceramic fiber, and the average fiber diameter of the fibrous thermal conductive material is less than 10 μm and the aspect ratio is in the range of 5-60; The flaky thermal conductive material is selected from one or more of hexagonal boron nitride, graphene, graphite, and silicon powder. The flaky thermal conductive material has a sheet diameter of less than 10 μm and a sheet thickness in the range of 200-500 nm.
3. The method for preparing a polyimide high thermal conductivity composite film according to claim 2, characterized in that: The mass percentage of the thermally conductive filler in the polyimide high thermally conductive composite film is greater than 5%.
4. The method for preparing a polyimide high thermal conductivity composite film according to claim 1, characterized in that: The dianhydride monomer is selected from one or more of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride; the diamine monomer is selected from one or more of 4,4'-diaminodiphenyl ether and p-phenylenediamine; the catalyst is selected from one or more of 4-dimethylaminopyridine and 1,2-dimethylimidazole.
5. The method for preparing a polyimide high thermal conductivity composite film according to claim 4, characterized in that: The molar ratio of the diamine monomer, the dianhydride monomer and the catalyst is 1:1-3:1; and the mass concentration of the reaction system is 0.1-0.3 g / mL.
6. The method for preparing a polyimide high thermal conductivity composite film according to claim 1, characterized in that: Step S2 is carried out under nitrogen atmosphere protection and stirring, and the stirring speed is 200-500 rpm.
7. The method for preparing a polyimide high thermal conductivity composite film according to claim 1, characterized in that: The ultrasonic treatment time in S1 is 3-5 hours; the order of adding the materials in S2 is: first dissolving the catalyst and diamine monomer in the thermal conductive filler suspension, stirring at room temperature for 20-60 minutes, then adding the dianhydride monomer, and performing prepolymerization at 60-70°C for 18-30 hours.
8. The method for preparing a polyimide high thermal conductivity composite film according to claim 1, characterized in that: The process parameters of the solid phase polymerization-thermal imidization reaction described in S3 are: First, heat the temperature from room temperature to 40-50°C at a heating rate of 1-3°C / min and keep it warm for 6h-9h, then keep the heating rate to 70-110°C and keep it warm for 30min; Then, the temperature is raised to 140-160°C at a heating rate of 4-10°C / min and kept at this temperature for 30 minutes. The temperature is then raised to 180-220°C at this rate and kept at this temperature for 30 minutes. Finally, the temperature is raised to 230-280°C at a heating rate of 4-10°C / min and kept warm for 1 hour.
9. A polyimide high thermal conductive composite film obtained according to the preparation method according to any one of claims 1 to 8.