High heat dissipating lubricating coating material for aluminum sheet and preparation method thereof

Abstract

The application belongs to the technical field of functional coating, and particularly relates to a high-heat-dissipation lubricating coating material for coating aluminum sheet and a preparation method thereof. The coating material comprises a polyimide precursor, fillers, a solid lubricant and an organic solvent. The core lies in that a novel polyimide precursor is prepared as a film-forming resin through a specific synthesis process, and the resin introduces rigid structural units containing triazole rings in the molecular chain. The triazole rings and imide bonds synergize to build an effective phonon transmission channel by enhancing the intermolecular hydrogen bond and pi-pi conjugation effect, thereby significantly improving the thermal conductivity of the coating. At the same time, this molecular structure endows the coating with the characteristic of 'easy interlayer sliding', and in combination with the added molybdenum disulfide solid lubricant, excellent lubricating performance is achieved. By adjusting the proportion of rigid triazole rings and flexible chain segments, the application successfully balances the thermal conductivity, lubricating performance and film-forming property and adhesion of the coating. The coating is particularly suitable for PCB drilling aluminum-coated cover plates, and can effectively solve the problems of drill needle overheating, wear and tear and drill dust adhesion, and improve the drilling quality and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of functional coating technology, and specifically relates to a high heat dissipation and lubrication coating material for coating aluminum sheets and its preparation method. Background Technology

[0002] Printed circuit boards (PCBs) are critical components in electronic devices, and the drilling process during their manufacturing is crucial to the precision and reliability of the final product. Hole wall quality and hole position accuracy are core indicators for measuring drilling quality, and these indicators are influenced by a complex interplay of factors, including substrate material, drill bit, and drilling process conditions. To protect the substrate and improve drilling quality, the industry commonly uses cover plate materials, among which coated aluminum sheets are superior to ordinary aluminum sheets due to the synergistic effect of the surface coating and the aluminum substrate.

[0003] However, existing aluminum sheet coating technologies have significant drawbacks. Traditional adhesive resin coatings are insufficient in performance, and the widely used adhesive resin coatings have poor heat dissipation and lubrication properties. This results in the inability to effectively dissipate the high heat generated by the drill bit during drilling, and also fails to reduce friction between the drill bit and the workpiece, leading to drill bit overheating, accelerated wear, and ultimately severely affecting drilling quality and hole position accuracy. This causes drill chips to adhere heavily to the drill bit, aluminum sheet, and PCB substrate, resulting in problems such as wire entanglement, hole blockage, residual drill chips, and dust accumulation. These defects not only cause processing abnormalities such as drill bit breakage and hole position misalignment, but also severely restrict further improvements in drilling efficiency and quality. Therefore, there is an urgent need to develop a high heat dissipation and lubrication coating for aluminum sheets to overcome the above problems simultaneously. Summary of the Invention

[0004] This invention provides a high heat dissipation and lubrication coating material for coating aluminum sheets and its preparation method. The obtained coating has the characteristics of high heat dissipation and lubrication, as well as good film-forming properties and adhesion, which meets the performance requirements of aluminum-clad cover plates in PCB drilling applications.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a high heat dissipation lubricating coating material for coating aluminum sheets, comprising the following components: polyimide precursor, filler, solid lubricant and organic solvent.

[0007] Furthermore, the high heat dissipation lubricating coating material for the coated aluminum sheet, by weight, comprises the following components: 50-70 parts polyimide precursor, 2-5 parts filler, 3-5 parts solid lubricant, and 30-100 parts organic solvent.

[0008] Furthermore, the preparation process of the polyimide precursor includes the following steps:

[0009] S1. Under nitrogen protection, 4 mmol of 4,4'-diaminodiphenylmethane was added to an appropriate amount of deionized water and concentrated hydrochloric acid to form a mixture. The reaction mixture was stirred at 3°C, and 30 mL of sodium nitrite solution was added dropwise. After stirring for 1 h, 10 mL of sodium azide aqueous solution was added dropwise and the reaction was continued for 2 h. After standing for 8 h, the system was filtered to obtain 4,4'-diazidodiphenylmethane.

[0010] The specific reaction process of step S1 is as follows:

[0011]

[0012] S2. Under nitrogen protection, 10 mmol of 4,4'-diazidodiphenylmethane and 20 mmol of 3-aminophenylacetylene prepared in step S1 were dissolved in N,N-dimethylacetamide to form a mixture. Appropriate amounts of CuSO4·5H2O, sodium ascorbate and triethylamine were added successively and stirred evenly. Then the mixture was heated to 60°C and reacted for 6 hours. Subsequently, a saturated solution of disodium ethylenediaminetetraacetate was added to form a precipitate. The precipitate was filtered, washed and vacuum dried to obtain intermediate 1.

[0013] The specific reaction process in step S2 is shown below:

[0014]

[0015] S3. Under nitrogen protection, the intermediate 1,4,4'-diphenyl ether diamine obtained in step S2 is dissolved in N,N-dimethylacetamide to form a mixed solution. Pyromellitic dianhydride is added in batches, and the mixture is stirred at 4°C for 12 hours. Then, a certain amount of acetic anhydride and triethylamine are added for dehydration and cyclization. The product is filtered, washed, and vacuum dried to obtain the polyimide precursor.

[0016] The specific reaction process in step S3 is as follows:

[0017]

[0018] Furthermore, the molar ratio of intermediate 1,4,4'-diphenyl ether diamine in step S3 is 1:1-3.

[0019] Furthermore, the solid lubricant is molybdenum disulfide powder with a particle size of 0.5-1.0 μm.

[0020] Furthermore, the filler is one or more of calcium carbonate, calcined kaolin, mica powder, and silicon dioxide.

[0021] Furthermore, the organic solvent is N,N-dimethylacetamide.

[0022] The present invention also provides a method for preparing a coating material for coating aluminum sheets, the method comprising the following steps: uniformly coating the high heat dissipation and lubrication coating material onto an aluminum sheet substrate after sanding treatment by one of the following methods: brushing, spin coating or dip coating; and then performing a degassing process and a thermal imidization process to obtain the coating.

[0023] The degassing process is as follows: 80℃ for 12 hours, 100℃ for 2 hours, and 120℃ for 12 hours.

[0024] The thermal imidization process is as follows: under a nitrogen atmosphere, maintain at 150°C for 1 hour; maintain at 200°C for 1 hour; maintain at 250°C for 1 hour; maintain at 300°C for 1 hour.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] 1. This invention utilizes a polyimide precursor prepared using a specific process as a film-forming resin for curing. A triazole ring structure is introduced into the polyimide resin. This triazole ring is a five-membered heterocyclic compound containing three nitrogen atoms, exhibiting properties similar to imide bonds in terms of strong dipole moment, hydrogen bond acceptance, and aromaticity. It enhances the π-π conjugation effect and simultaneously forms hydrogen bonds with the carbonyl oxygen atoms in the imide bond. This non-covalent interaction combining hydrogen bonding and π-π conjugation reduces phonon scattering, promotes heat transfer and long-range phonon transport, and ultimately improves the thermal conductivity of the coating. Furthermore, the π-π conjugated stacking effect between molecular chains induces relative slippage between chain segments under shear force. This effect, synergistic with the interlayer slippage of the added molybdenum disulfide solid lubricant, contributes to the coating's excellent macroscopic lubrication properties. In addition, this double non-covalent effect combining π-π stacking and hydrogen bonding also improves the coating's heat resistance.

[0027] 2. This invention also adjusts the amount of raw materials used in the preparation of polyimide precursors, controls the proportion of rigid triazole rings introduced, and connects them with flexible segments to ensure the best balance between node rigidity and spacer flexibility, thereby enabling the coating film to exhibit excellent thermal conductivity and lubricity while also having good film-forming properties and adhesion. Detailed Implementation

[0028] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with embodiments, is provided below.

[0029] The main products used in the following embodiments are as follows: 4,4'-diaminodiphenylmethane was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; sodium azide was purchased from Shanghai Jiachen Chemical Industry Co., Ltd.; 4,4'-diphenyl ether diamine was purchased from Tokyo Kogyo Kasei Corporation; pyromellitic dianhydride was purchased from Tokyo Kogyo Kasei Corporation; N,N-dimethylacetamide was purchased from Shanghai Titan Technology Co., Ltd.; and 3-aminophenylacetylene was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0030] Example 1

[0031] This embodiment provides a high heat dissipation and lubrication coating material for coated aluminum sheets, wherein the amounts of each component by weight are as follows: 70 parts polyimide precursor, 5 parts silicon dioxide, 3 parts molybdenum disulfide powder and 70 parts N,N-dimethylacetamide.

[0032] The preparation process of the polyimide precursor includes the following steps:

[0033] S1. Under nitrogen protection, 4 mmol of 4,4'-diaminodiphenylmethane was added to an appropriate amount of deionized water and concentrated hydrochloric acid to form a mixture. The reaction mixture was stirred at 3°C, and 30 mL of sodium nitrite solution was added dropwise. After stirring for 1 h, 10 mL of sodium azide aqueous solution was added dropwise and the reaction was continued for 2 h. After standing for 8 h, the system was filtered to obtain 4,4'-diazidodiphenylmethane.

[0034] S2. Under nitrogen protection, 10 mmol of 4,4'-diazidodiphenylmethane and 20 mmol of 3-aminophenylacetylene prepared in step S1 were dissolved in N,N-dimethylacetamide to form a mixture. 1 mmol of CuSO4·5H2O, 2 mmol of sodium ascorbate and 10 mmol of triethylamine were added successively and stirred until homogeneous. The mixture was then heated to 60°C and reacted for 6 hours. Subsequently, a saturated solution of disodium ethylenediaminetetraacetate was added to form a precipitate. The precipitate was filtered, washed and vacuum dried to obtain intermediate 1.

[0035] S3. Under nitrogen protection, the intermediate 1,4,4'-diphenyl ether diamine obtained in step S2 is dissolved in N,N-dimethylacetamide to form a mixed solution. Pyromellitic dianhydride is added in batches, and the mixture is stirred at 4°C for 12 hours. Then, a measured amount of acetic anhydride and triethylamine are added for dehydration and cyclization. The product is filtered, washed, and vacuum dried to obtain the polyimide precursor. The molar ratio of the intermediate 1,4'-diphenyl ether diamine is 1:1.

[0036] This embodiment also provides a method for preparing a coating material for coating aluminum sheets. The preparation method includes the following steps: uniformly coating the high heat dissipation and lubrication coating material onto an aluminum sheet substrate that has undergone sanding treatment by brushing, and then performing a degassing process and a thermal imidization process to obtain the coating.

[0037] The degassing process is as follows: 80℃ for 12 hours, 100℃ for 2 hours, and 120℃ for 12 hours.

[0038] The thermal imidization process is as follows: under a nitrogen atmosphere, maintain at 150°C for 1 hour; maintain at 200°C for 1 hour; maintain at 250°C for 1 hour; maintain at 300°C for 1 hour.

[0039] Example 2

[0040] This embodiment provides a high heat dissipation lubricating coating material for coating aluminum sheets and its preparation method. Compared with Example 1, the molar ratio of intermediate 1 and 4,4'-diphenyl ether diamine in step S3 of the polyimide precursor preparation process is 1:2, and the remaining components, preparation steps and parameters are the same.

[0041] Example 3

[0042] This embodiment provides a high heat dissipation lubricating coating material for coating aluminum sheets and its preparation method. Compared with Example 1, the molar ratio of intermediate 1 and 4,4'-diphenyl ether diamine in step S3 of the polyimide precursor preparation process is 1:3, and the remaining components, preparation steps and parameters are the same.

[0043] Comparative Example 1

[0044] This comparative example provides a high heat dissipation lubricating coating material for coating aluminum sheets and its preparation method. Compared with Example 1, the molar ratio of intermediate 1 and 4,4'-diphenyl ether diamine in step S3 of the polyimide precursor preparation process is 1:0.5, and the remaining components, preparation steps and parameters are the same.

[0045] Comparative Example 2

[0046] This comparative example provides a high heat dissipation lubricating coating material for coating aluminum sheets and its preparation method. Compared with Example 1, the molar ratio of intermediate 1 and 4,4'-diphenyl ether diamine in step S3 of the polyimide precursor preparation process is 1:4, and the remaining components, preparation steps and parameters are the same.

[0047] Comparative Example 3

[0048] This comparative example provides a high heat dissipation lubricating coating material for coating aluminum sheets and its preparation method. Compared with Example 1, the molar ratio of intermediate 1 and 4,4'-diphenyl ether diamine in step S3 of the polyimide precursor preparation process is 1:0, and the remaining components, preparation steps and parameters are the same.

[0049] Comparative Example 4

[0050] This comparative example provides a high heat dissipation and lubrication coating material for coating aluminum sheets and its preparation method. Compared with Example 1, the polyimide precursor is prepared by the following method: under nitrogen protection, 4,4'-diphenyl ether diamine is dissolved in N,N-dimethylacetamide to form a mixed solution, pyromellitic dianhydride is added in batches, and the mixture is stirred at 4°C for 12 hours. Then, a certain amount of acetic anhydride and triethylamine are added for dehydration and cyclization. The product is filtered, washed and vacuum dried to obtain the polyimide precursor. The remaining components, preparation steps and parameters are the same.

[0051] The aluminum sheet samples prepared in the above embodiments and comparative examples were subjected to the following performance tests:

[0052] Drilling test: The aluminum sheet sample is drilled with a 0.25mm diameter hole to test the hole wall roughness and hole position accuracy;

[0053] Thermal conductivity test: Tested according to ASTM E1530 standard for thermal conductivity testing of coatings;

[0054] Adhesion test: Adhesion test shall be conducted in accordance with the test standard GB / T 9286-2021.

[0055] Table 1: Performance Test Results

[0056]

[0057] A comparison of the experimental results of Comparative Examples 1-2 and Examples 1-3 shows that by adjusting the relative amounts of intermediate 1 and 4,4'-diphenyl ether diamine, the proportion of the rigid triazole ring introduced into the film-forming resin polyimide can be controlled. When the molar ratio of intermediate 1 to 4,4'-diphenyl ether diamine is in the range of 1:1-3, the coating film can maintain high thermal conductivity while obtaining optimal adhesion and drilling quality (manifested as low pore wall roughness), achieving the best balance of various properties. A comparison of the experimental results of Comparative Examples 3-4 and Examples 1-3 shows that when only intermediate 1 is used as the diamine raw material, the coating film is rigid and the film-forming effect is poor, resulting in poor adhesion to the substrate. When only 4,4'-diphenyl ether diamine is used as the raw material, the thermal conductivity and lubricity of the coating film itself decrease significantly.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high heat dissipation and lubrication coating material for coating aluminum sheets, characterized in that, By weight, the amounts of each component are as follows: 50-70 parts polyimide precursor, 2-5 parts filler, 3-5 parts solid lubricant and 30-100 parts organic solvent. The preparation process of the polyimide precursor includes the following steps: S1. Under nitrogen protection, 4 mmol of 4,4'-diaminodiphenylmethane was added to an appropriate amount of deionized water and concentrated hydrochloric acid to form a mixture. The reaction mixture was stirred at 3°C, and 30 mL of sodium nitrite solution was added dropwise. After stirring for 1 h, 10 mL of sodium azide aqueous solution was added dropwise and the reaction was continued for 2 h. After standing for 8 h, the system was filtered to obtain 4,4'-diazidodiphenylmethane. S2. Under nitrogen protection, 10 mmol of 4,4'-diazidodiphenylmethane and 20 mmol of 3-aminophenylacetylene prepared in step S1 were dissolved in N,N-dimethylacetamide to form a mixture. Appropriate amounts of CuSO4·5H2O, sodium ascorbate and triethylamine were added successively and stirred evenly. Then the mixture was heated to 60°C and reacted for 6 hours. Subsequently, a saturated solution of disodium ethylenediaminetetraacetate was added to form a precipitate. The precipitate was filtered, washed and vacuum dried to obtain intermediate 1. S3. Under nitrogen protection, the intermediate 1,4,4'-diphenyl ether diamine obtained in step S2 is dissolved in N,N-dimethylacetamide to form a mixed solution. Pyromellitic dianhydride is added in batches, and the mixture is stirred at 4°C for 12 hours. Then, a certain amount of acetic anhydride and triethylamine are added for dehydration and cyclization. The product is filtered, washed, and vacuum dried to obtain the polyimide precursor. The molar ratio of intermediate 1,4,4'-diphenyl ether diamine in step S3 is 1:1-3; The solid lubricant is molybdenum disulfide powder with a particle size of 0.5-1.0 μm.

2. The high heat dissipation lubricating coating material for coated aluminum sheets according to claim 1, characterized in that, The filler is one or more of calcium carbonate, calcined kaolin, mica powder, and silicon dioxide.

3. The high heat dissipation lubricating coating material for coated aluminum sheets according to claim 1, characterized in that, The organic solvent is N,N-dimethylacetamide.

4. A method for preparing a high heat dissipation and lubrication coating material for coated aluminum sheets as described in any one of claims 1-3, characterized in that, The process includes the following steps: uniformly coating the high heat dissipation and lubrication coating material onto the frosted aluminum substrate using one of the following methods: brushing, spin coating, or dip coating; followed by a degassing process and a thermal imidization process to obtain the coating. The degassing process is as follows: 80℃ for 12 hours, 100℃ for 2 hours, and 120℃ for 12 hours. The thermal imidization process is as follows: under a nitrogen atmosphere, maintain at 150°C for 1 hour; maintain at 200°C for 1 hour; maintain at 250°C for 1 hour; maintain at 300°C for 1 hour.

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