High heat dissipation coating for aluminum cover plate and preparation method thereof

Abstract

The present application relates to a kind of high heat dissipation coating materials for aluminum cover plate and its preparation method and application, belong to functional coating technical field.The coating material includes the following components: modified polyester resin, curing agent, lubricant and auxiliary agent.The coating material is introduced by chemical reaction into the polyester main chain with biphenyl dihydroxy monomer as key structural unit, can form local order area by π-π stacking, conducive to phonon conduction, so as to significantly improve the heat conduction and heat dissipation performance of coating;At the same time, by regulating the carbon chain length of raw material dihydric alcohol, the flexibility and rigidity of molecular chain can be balanced, and the comprehensive performance of coating can be optimized.The coating material is made into powder after melting extrusion, crushing and screening, and is applied to the surface of aluminum cover plate by electrostatic spraying, and can be cured to form high heat dissipation coating.The coating has excellent thermal conductivity, heat resistance, hardness and lubricity, and can effectively solve the problems of drill bit wear and poor hole wall quality caused by poor heat dissipation during PCB drilling.

Description

Technical Field

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

[0002] With the rapid development of electronic devices towards miniaturization, high integration, and high frequency and speed, the wiring density and number of layers on printed circuit boards (PCBs) continue to increase, placing almost stringent requirements on the processing precision and reliability of their micro-vias. Drilling, as a key process for forming electrical interconnect channels, directly determines the integrity of signal transmission and the service performance of the final product. Against this backdrop, aluminum-based cover plates, possessing excellent rigidity, flatness, and thermal conductivity, have become an indispensable process material supporting high-quality, high-efficiency drilling operations.

[0003] The core performance of aluminum cover plates depends not only on the aluminum substrate but also on the functional coating applied to its surface. This coating plays multiple roles during drilling: it acts as a buffer before the drill bit contacts the copper foil / substrate, reducing drilling impact; it is also a highly efficient lubricant at the friction interface, reducing wear on the drill bit's side edges; simultaneously, as a key pathway for heat conduction and diffusion, its heat dissipation capacity directly affects the drill bit's operating temperature and stability; furthermore, the coating must facilitate the smooth removal of drill cuttings, preventing their adhesion or blockage. Therefore, the quality of the coating becomes a systematic factor affecting hole wall smoothness, hole position accuracy, drill bit life, and even production efficiency.

[0004] However, conventional powder coatings (such as pure epoxy or general-purpose polyester resin coatings) widely used in aluminum cover plates suffer from inherent limitations in thermal conductivity due to the disordered arrangement of their organic polymer molecular chains. Under extreme conditions of high-speed drilling generating instantaneous high temperatures, these coatings cannot quickly conduct the accumulated heat to the highly thermally conductive aluminum substrate and dissipate it, leading to a rapid accumulation of temperature at the drill bit-coating interface. This easily causes the coating resin itself to soften, thermally decompose, or even carbonize, causing drill chips to clump together and entangle the drill bit, resulting in severe hole blockage and in-hole residue defects. Furthermore, the high temperature significantly accelerates drill bit wear and passivation, directly affecting the dimensional accuracy and hole position consistency of the drilled holes. This has become a key technical bottleneck restricting the improvement of yield and efficiency in the manufacturing of high-end PCBs, especially high-multilayer boards and HDI boards.

[0005] Therefore, developing a novel high-performance coating material that can significantly improve the intrinsic thermal conductivity while maintaining good adhesion to the substrate and necessary mechanical properties, thereby synergistically achieving excellent heat dissipation efficiency, superior heat resistance, and stable lubrication characteristics, has become an urgent need in the industry. This invention addresses this core technical problem by proposing a novel solution that fundamentally improves the thermal conductivity of resin-based coatings through molecular structure design. Summary of the Invention

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a high heat dissipation coating material for aluminum cover plates, comprising the following components by weight: 100 parts modified polyester resin, 5-20 parts curing agent, 5-10 parts lubricant, and 1-8 parts additives.

[0008] Furthermore, the curing agent is TGIC triglycidyl isocyanurate.

[0009] Furthermore, the lubricant is at least one of molybdenum disulfide and graphite.

[0010] Furthermore, the additives include leveling agents and degassing agents.

[0011] Preferably, the leveling agent is selected from GLP588 and Modaflow6000; the degassing agent includes one or two of ethylene bis-stearamide and hydrogenated castor oil.

[0012] Furthermore, the preparation method of the modified polyester resin includes the following steps:

[0013] S1. Dissolve p-4-toluenesulfonyl chloride in dichloromethane. Under stirring in an ice-water bath, add aliphatic straight-chain diol and triethylamine dropwise. After reacting for 12 hours, wash the reaction mixture three times with saturated sodium carbonate solution and distilled water, respectively. After drying, remove dichloromethane by rotary evaporation. Recrystallize using ethanol as solvent and dry to obtain a diol p-toluenesulfonate condensate, wherein the molar ratio of p-toluenesulfonyl chloride to aliphatic straight-chain diol is 2:1.

[0014] The specific reaction process of step S1 is as follows:

[0015]

[0016] HO-(CH2) n -OH is the general structural formula for aliphatic straight-chain diols, where n is an integer greater than or equal to 3 and less than or equal to 6;

[0017] S2. The diol p-toluenesulfonate condensate obtained in step S1 and 4,4'-biphenol are dissolved in tetrahydrofuran and mixed evenly. Then, potassium carbonate and potassium iodide catalysts are added, and the mixture is reacted at 80°C for 48 hours. After filtration, the tetrahydrofuran is removed by washing and spin coating to finally obtain the biphenyl dihydroxy monomer, wherein the molar ratio of the diol p-toluenesulfonate condensate condensate to 4,4'-biphenol is 1:2.

[0018] The specific reaction process in step S2 is shown below:

[0019]

[0020] S3. Add the biphenyl dihydroxy monomer, terephthalic acid and esterification catalyst obtained in step S2 into the reactor, purge with nitrogen, raise the temperature to 250°C and keep it at that temperature. When the acid value of the resin is 10-20 mg KOH / g, add isophthalic acid as an acid hydrolysate to de-end the resin. Then, perform vacuum polycondensation. When the acid value of the polyester is controlled to be within the range of 15-40 mg KOH / g, add an antioxidant and keep it at that temperature for 20 minutes before discharging to obtain the modified polyester resin. The molar ratio of biphenyl dihydroxy monomer to terephthalic acid is 1:1-3.

[0021] The specific reaction process in step S3 is as follows:

[0022]

[0023] Preferably, the aliphatic straight-chain diol includes 1,4-butanediol or 1,5-pentanediol.

[0024] Furthermore, the antioxidant is one or more of antioxidant 168, antioxidant 1076, and antioxidant 1010, and the esterification catalyst is dibutyltin oxide.

[0025] The present invention also discloses a method for preparing a high heat dissipation coating material for aluminum cover plates, characterized by comprising the following steps: S1, preparing a modified polyester resin, then weighing each raw material component of the coating material according to the formula, adding each raw material component to a high-speed mixer and mixing evenly to obtain a mixture;

[0026] S2. The mixture is added to an extruder for melt extrusion. The feed temperature of the melt extrusion is 100-140℃ and the discharge temperature is 105-115℃. The melt-extruded material is fed into a tablet press for tableting. The tableted product is fed into a pulverizer for pulverization and then sieved to select particles with a particle size of 30-50μm to obtain the powdered high heat dissipation coating material for the aluminum cover plate.

[0027] The present invention also provides an application of a high heat dissipation coating material for aluminum cover plates, characterized in that: the high heat dissipation coating material for aluminum cover plates is applied to the surface of the aluminum cover plate substrate by electrostatic spraying and cured at 160-220℃ for 5-15 minutes to obtain a high heat dissipation coating.

[0028] Compared with the prior art, the present invention has the following advantages and technical effects:

[0029] 1. The core of this invention lies in introducing biphenyl dihydroxy monomer as a key structural unit into the polyester backbone through a chemical reaction. The biphenyl structure possesses a rigid planar structure, with two benzene rings connected by a single bond. Its conjugated plane exhibits high rigidity and geometric stability, making it resistant to bending or twisting. This rigid planar structure, during polymer melting and solidification, more easily overcomes the disordered tendency of chain segment thermal motion, driving the molecular chains to achieve localized directional alignment and orderly stacking. The introduced biphenyl structure, together with the benzene rings from terephthalic acid, creates ordered microregions through π-π stacking interactions. Within these microregions, the vibrational modes of the molecular chains are more consistent, creating lattice-like efficient channels for phonon propagation and significantly reducing phonon scattering caused by structural disorder. Heat can be conducted more smoothly and rapidly along these ordered molecular chains, thereby intrinsically breaking through the thermal conductivity limit of traditional resins and improving heat dissipation.

[0030] 2. In this invention, aliphatic diols with specific carbon chain lengths (C3-C6) are selected as flexible spacers. Appropriate molecular chain flexibility helps to stabilize ordered regions kinetically. However, if the flexible segments are too long, they can easily lead to disordered molecular chain orientation, hindering the formation of ordered regions and affecting the efficient conduction of phonons. Experimental results show that when the total carbon number of the aliphatic straight-chain diol used is in the range of 3-6, the prepared coating film has a relatively ideal thermal conductivity. On the other hand, it also ensures processability and film-forming properties. An appropriate amount of flexible segments ensures that the resin has suitable melt flowability and adhesion to the substrate. Appropriate flexibility helps to alleviate the internal stress of the polymer kinetically, allowing the rigid ordered microregions formed during curing to exist more stably, rather than cracking or developing defects due to excessive rigidity. Detailed Implementation

[0031] To further illustrate the technical means and effects of the present invention in achieving its 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.

[0032] The main products used in the following implementation methods are as follows: GLP588 leveling agent was purchased from Ningbo Nanhai Co., Ltd.; hydrogenated castor oil was purchased from Rongsheng New Material Technology (Nantong, Jiangsu) Co., Ltd., CAS No. 8001-78-3; molybdenum disulfide was purchased from Shandong Haoyao New Material Co., Ltd. (1250 mesh molybdenum disulfide); graphite was purchased from Zhengzhou Aoyu Chemical Co., Ltd.; and TGIC was purchased from Changzhou Niutang Chemical Plant.

[0033] Example 1

[0034] This embodiment provides a high heat dissipation coating material for aluminum cover plates, which, by weight, includes the following components: 100 parts modified polyester resin, 13 parts curing agent, 2 parts graphite, 5 parts molybdenum disulfide, 1 part GLP588 leveling agent, and 3 parts hydrogenated castor oil.

[0035] The method for preparing the modified polyester resin includes the following steps:

[0036] S1. Dissolve 0.2 mol of p-4-toluenesulfonyl chloride in 210 mL of dichloromethane. Add 0.1 mol of 1,3-propanediol and 35 mL of triethylamine dropwise under stirring in an ice-water bath. After reacting for 12 hours, wash the reaction mixture three times with saturated sodium carbonate solution and distilled water, respectively. After drying, remove dichloromethane by rotary evaporation. Recrystallize using ethanol as solvent and dry to obtain the diol p-toluenesulfonate condensate.

[0037] S2. Dissolve 0.1 mol of the diol p-toluenesulfonate condensate obtained in step S1 and 0.2 mol of 4,4'-biphenyl in tetrahydrofuran and mix well. Then add 20 g of potassium carbonate and 5 g of potassium iodide as catalysts. React at 80°C for 48 hours. Filter, wash and spin coat to remove tetrahydrofuran, and finally obtain biphenyl dihydroxy monomer.

[0038] S3. Add 0.1 mol of biphenyl dihydroxy monomer, 0.15 mol of terephthalic acid and 5 g of dibutyltin oxide obtained in step S2 into a reactor, purge with nitrogen, raise the temperature to 250°C and keep it at that temperature. When the acid value of the resin is about 13 mg KOH / g, add 0.05 mol of isophthalic acid to de-block the end, then perform vacuum polycondensation. When the acid value of the polyester is controlled to be about 25 mg KOH / g, add an antioxidant and keep it at that temperature for 20 minutes before discharging to obtain the modified polyester resin.

[0039] This embodiment also provides a method for preparing a high heat dissipation coating material for aluminum cover plates, including the following steps: S1, after preparing the modified polyester resin, weigh each raw material component of the coating material according to the formula, add each raw material component to a high-speed mixer and mix evenly to obtain a mixture;

[0040] S2. The mixture is added to an extruder for melt extrusion. The feed temperature of the melt extrusion is 120°C and the discharge temperature is 105°C. The melt-extruded material is fed into a tablet press for tableting. The tableted product is fed into a pulverizer for pulverization and then sieved to select particles with a particle size of 30-50μm to obtain the powdered high heat dissipation coating material for the aluminum cover plate.

[0041] Example 2

[0042] This embodiment provides a high heat dissipation coating material for aluminum cover plates and its preparation method. Compared with Example 1, the aliphatic straight-chain diol used in the preparation of the modified polyester resin is 1,6-hexanediol, while the other components, preparation steps and parameters are the same.

[0043] Example 3

[0044] This embodiment provides a high heat dissipation coating material for aluminum cover plates and its preparation method. Compared with Example 1, the aliphatic straight-chain diol used in the preparation of the modified polyester resin is 1,4-butanediol, while the other components, preparation steps and parameters are the same.

[0045] Comparative Example 1

[0046] This comparative example provides a high heat dissipation coating material for aluminum cover plates and its preparation method. Compared with Example 1, the aliphatic linear diol used in the preparation of the modified polyester resin is ethylene glycol, while the other components, preparation steps and parameters are the same.

[0047] Comparative Example 2

[0048] This comparative example provides a high heat dissipation coating material for aluminum cover plates and its preparation method. Compared with Example 1, the aliphatic straight-chain diol used in the preparation of the modified polyester resin is 1,8-octanediol, and the other components, preparation steps and parameters are the same.

[0049] Comparative Example 3

[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 polyester resin is prepared by the following method: 0.1 mol of 1,3-propanediol, 0.15 mol of terephthalic acid, and 5 g of dibutyltin oxide are added to a reaction vessel, nitrogen gas is introduced, the temperature is raised to 250°C and maintained at this temperature. When the acid value of the resin is about 13 mg KOH / g, 0.05 mol of isophthalic acid is added for acid desealing, followed by vacuum polycondensation. When the acid value of the polyester is controlled to be about 25 mg KOH / g, an antioxidant is added and the mixture is kept at this temperature for 20 minutes before being discharged to obtain the polyester resin. The remaining components, preparation steps, and parameters are the same as in Example 1.

[0051] Coating preparation and performance testing

[0052] Powder coating was applied to the aluminum cover plate substrate using an electrostatic spray gun to a thickness of 60-80 μm. After curing at 200℃ for 15 min, the following performance tests were conducted:

[0053] Thermal conductivity test: according to ISO 22007-2 transient plane heat source method;

[0054] Heat dissipation effect: The temperature difference between the coated substrate and the uncoated substrate after 15 minutes of natural cooling from 180℃ was measured by the furnace temperature tester. The larger the difference, the better the heat dissipation effect.

[0055] Heat resistance test: according to GB / T 1735 test standard;

[0056] Hardness: Pencil hardness test according to GB / T 6739-2022 standard.

[0057] Table 1: Performance Test Results

[0058]

[0059] A comparison of the experimental results of Comparative Examples 1-3 and Examples 1-3 shows that the carbon chain length of the aliphatic linear diol affects the ratio of flexible to rigid segments in the polyester resin film-forming process. Appropriate molecular chain flexibility helps to stabilize the ordered regions kinetically, thus facilitating phonon conduction on the basis of the formed π-π stack, significantly improving the coating's thermal conductivity and heat dissipation. Furthermore, the introduction of a rigid structure further enhances the coating's heat resistance and mechanical properties.

[0060] 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 coating material for aluminum cover plates, characterized in that, The product comprises, by weight, the following components: 100 parts modified polyester resin, 5-20 parts curing agent, 5-10 parts lubricant, and 1-8 parts additives; the preparation method of the modified polyester resin includes the following steps: S1. Dissolve p-toluenesulfonyl chloride in dichloromethane. Under stirring in an ice-water bath, add an aliphatic straight-chain diol and triethylamine dropwise. After reacting for 12 hours, wash the reaction mixture three times with saturated sodium carbonate solution and distilled water, respectively. After drying, remove dichloromethane by rotary evaporation. Recrystallize using ethanol as solvent and dry to obtain a diol p-toluenesulfonate condensate, wherein the molar ratio of p-toluenesulfonyl chloride to the aliphatic straight-chain diol is 2:1; the general structural formula of the aliphatic straight-chain diol is HO-(CH2). n -OH, where n is an integer greater than or equal to 3 and less than or equal to 6; S2. The diol p-toluenesulfonate condensate obtained in step S1 and 4,4'-biphenol are dissolved in tetrahydrofuran and mixed evenly. Then, potassium carbonate and potassium iodide catalysts are added, and the mixture is reacted at 80°C for 48 hours. After filtration, the tetrahydrofuran is removed by washing and spin coating to finally obtain the biphenyl dihydroxy monomer, wherein the molar ratio of the diol p-toluenesulfonate condensate condensate to 4,4'-biphenol is 1:

2. S3. Add the biphenyl dihydroxy monomer, terephthalic acid and esterification catalyst obtained in step S2 to the reactor, purge with nitrogen, raise the temperature to 250°C and keep it at that temperature. When the acid value of the resin is 10-20 mg KOH / g, add isophthalic acid as an acid hydrolysate to de-seal the end. Then, perform vacuum polycondensation. When the acid value of the polyester is controlled to be within the range of 15-40 mg KOH / g, add an antioxidant and keep it at that temperature for 20 minutes before discharging to obtain the modified polyester resin. The molar ratio of biphenyl dihydroxy monomer to terephthalic acid is 1:1-3.

2. The high heat dissipation coating material for aluminum cover plates according to claim 1, characterized in that, The curing agent is TGIC triglycidyl isocyanurate.

3. The high heat dissipation coating material for aluminum cover plates according to claim 1, characterized in that, The lubricant is at least one of molybdenum disulfide and graphite.

4. The high heat dissipation coating material for aluminum cover plates according to claim 1, characterized in that, The additives include leveling agents and degassing agents.

5. The high heat dissipation coating material for aluminum cover plates according to claim 4, characterized in that, The leveling agent is selected from GLP588 and Modaflow6000.

6. The high heat dissipation coating material for aluminum cover plates according to claim 4, characterized in that, The degassing agent includes one or both of ethylene bis-stearamide and hydrogenated castor oil.

7. A method for preparing a high heat dissipation coating material for aluminum cover plates as described in any one of claims 1-6, characterized in that, The process includes the following steps: S1, preparing a modified polyester resin, then weighing each raw material component of the coating material according to the formula, adding each raw material component to a high-speed mixer and mixing them evenly to obtain a mixture; S2. The mixture is added to an extruder for melt extrusion. The feed temperature of the melt extrusion is 100-140℃ and the discharge temperature is 105-115℃. The melt-extruded material is fed into a tablet press for tableting. The tableted product is fed into a pulverizer for pulverization and then sieved to select particles with a particle size of 30-50μm to obtain the powdered high heat dissipation coating material for the aluminum cover plate.

8. The application of a high heat dissipation coating material for aluminum cover plates as described in any one of claims 1-6, characterized in that: The high heat dissipation coating material is applied to the surface of the aluminum cover plate substrate by electrostatic spraying and cured at 160-220℃ for 5-15 minutes to obtain the high heat dissipation coating.

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