Reparable high-thermal-conductivity nano-composite three-protection coating, preparation method and application thereof

Abstract

The application relates to the technical field of three-proofing paint, in particular to a repairable high-thermal-conductivity nano-composite three-proofing paint as well as a preparation method and application thereof. The repairable high-thermal-conductivity nano-composite three-proofing paint comprises the following components in parts by weight: 50-60 parts of modified organic silicon-epoxy hybrid resin, 8-12 parts of alkylated nano boron nitride, 5-8 parts of alkylated nano silicon dioxide, 3-5 parts of star-shaped furan-maleimide-furan crosslinking agent, 1-1.5 parts of microcapsule imidazole, 0.1-0.5 parts of sulfonium salt, and high-boiling-point solvent, which is supplemented to 100 parts; the high-boiling-point solvent comprises at least one of propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether. The application realizes breakthrough of the traditional three-proofing paint thickness coating limitation under low thickness through the following mutual cooperation: the modified organic silicon-epoxy hybrid resin forms a dense film, the nano filler is composite and enhanced, and the reversible crosslinking structure is repairable, and the application is suitable for high-reliability protection scenes of precision electronic devices.

Description

Technical Field

[0001] This application relates to the field of conformal coating technology, specifically to a repairable high thermal conductivity nanocomposite conformal coating, its preparation method, and its application. Background Technology

[0002] Organic coating protection technology is one of the effective strategies to improve the reliability of electronic products, and it has the characteristics of low cost, easy processing and excellent protective performance.

[0003] Organic coatings protect circuit boards and related components in electronic products from environmental corrosion, thereby improving and extending their lifespan and ensuring safety and reliability. Under real-world conditions such as chemical environments (fuels, coolants, etc.), vibration, high dust levels, salt spray, humidity, and high temperatures, circuit boards may experience corrosion, softening, deformation, and mold growth, leading to circuit malfunctions. Circuit board protective coatings can be applied to the surface of the circuit board, forming a lightweight and flexible film. This film protects the circuit board from damage under the aforementioned harsh conditions.

[0004] Based on the main material of the circuit board protective coating, it can be divided into acrylic, polyurethane, silicone, epoxy, and polyxylene types. Traditional acrylic, polyurethane, or ordinary silicone conformal coatings only achieve an IP54-IP66 protection level, which is difficult to meet the IP68 requirements of MIL-STD-810G / H or IEC60529. Although epoxy / polyurethane potting compounds can improve the protection level, the adhesive layer thickness is ≥2mm, resulting in high thermal resistance, irreversibility, and the inability to perform local repairs, leading to overall heat dissipation failure and a significant increase in maintenance costs. Summary of the Invention

[0005] To address the technical challenge of achieving high protection levels with low thickness while enabling localized repairs in conformal coatings used on components such as circuit boards, this application provides a repairable, high thermal conductivity nanocomposite conformal coating.

[0006] In the first aspect, this application provides a repairable, high thermal conductivity nanocomposite three-proof coating, which adopts the following technical solution:

[0007] A reworkable, high thermal conductivity nanocomposite three-proof coating comprises the following components in parts by weight: 50-60 parts of modified organosilicon-epoxy hybrid resin, 8-12 parts of alkylated nano-boron nitride, 5-8 parts of alkylated nano-silica, 3-5 parts of star-shaped furan-maleimide-furan crosslinking agent, 1-1.5 parts of microencapsulated imidazole, 0.1-0.5 parts of thioonium salt, and a high-boiling-point solvent to bring the total to 100 parts; wherein the high-boiling-point solvent includes at least one of propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether.

[0008] By employing the above technical solutions, the silicone segments of the modified silicone-epoxy hybrid resin provide hydrophobicity, effectively blocking water vapor penetration; the epoxy groups enhance the chemical bonding with the metal substrate, preventing coating peeling; the hybrid structure forms a dense cross-linked network, reducing molecular gaps and inhibiting the diffusion of corrosive media, which is the basis for achieving high protection in thin layers. The microcapsule imidazole core material is a latent curing agent, released upon heating or mechanical pressure, triggering low-temperature curing of the epoxy groups; the microcapsule shell avoids premature reaction, extends shelf life, and enables localized repair.

[0009] Alkylated boron nitride nanoparticles undergo surface alkylation treatment to improve their dispersibility in resin and prevent agglomeration; the parallel stacking of lamellar structures creates a labyrinth effect, extending the water and oxygen permeation path; high thermal conductivity establishes a heat conduction network, quickly dissipating local hot spots and preventing coating cracking caused by thermal stress. Alkylated nano-silica fills the gaps between boron nitride lamellars, further improving coating density; surface hydrophobic modification enhances capillary resistance, reducing water adsorption rate.

[0010] The star-shaped topology of the star-shaped furan-maleimide-furan crosslinking agent provides multiple reaction sites, forming a three-dimensional network and improving the mechanical strength of the coating; its reversible reaction characteristics (furan / maleimide bond) allow the coating to be repairable at high temperatures and self-heal microcracks at room temperature by dissociating the bonds.

[0011] This application utilizes a modified silicone-epoxy hybrid resin to form a dense film, nanofiller composite to enhance the barrier, and a reversible cross-linked structure to provide repairability. Through these synergistic effects, it achieves a breakthrough in the limitation of traditional conformal coatings requiring thick coatings to provide high protection at a low thickness, making it suitable for high-reliability protection scenarios for precision electronic devices.

[0012] Preferably, the method for preparing the alkylated boron nitride nanoparticles or alkylated silica nanoparticles includes the following steps:

[0013] Nano-boron nitride or nano-silica is added to a high-boiling-point solvent and homogenized. Then, hexamethyldisilazane is added and the mixture is heated to react, thereby obtaining alkylated nano-boron nitride or alkylated nano-silica.

[0014] By employing the above technical solution, the -Si(CH3)3 groups in hexamethyldisilazane react with the -OH groups on the filler surface, replacing the hydroxyl groups to form hydrophobic siloxane bonds, significantly reducing the filler surface energy. Alkylation eliminates hydrogen bonding between fillers, preventing nanoparticle aggregation, ensuring monodispersity in the resin, and reducing local defects (such as micropores and cracks). The modified filler surface has a polarity matching with the resin, enhancing interfacial adhesion through chemical bonding and preventing corrosive media from penetrating along the interface. During solvent homogenization, the alkylated boron nitride layers align parallel to the substrate, forming a dense stacked structure, thus strengthening the "maze effect" of boron nitride. Alkylated silica fills the nanoscale gaps between the boron nitride layers, blocking the ends of the "maze channels," synergistically forming a nano-mortar structure, achieving high protective performance with low thickness.

[0015] Preferably, the mass ratio of the alkylated boron nitride nanoparticles to the alkylated silica nanoparticles is 1.5-2:1.

[0016] By adopting the above technical solutions, when the content of alkylated boron nitride nanoparticles is too low, alkylated boron nitride is the main heat carrier. When its content is insufficient, it is difficult to form a continuous heat-conducting network, and the local heat accumulation of electronic devices accelerates the electrochemical corrosion of the metal substrate. The alkylated boron nitride sheets are the key barrier to block the corrosive medium. The reduction of its content leads to an increase in the interlayer spacing and a shortening of the water / oxygen diffusion path. The alkylated nano-silica is difficult to completely fill the voids and form nanochannels that directly connect to the substrate. When the content of alkylated boron nitride nanoparticles is too high, the van der Waals forces between the sheets increase, making it easy to form clusters and generate pinholes during spraying. The viscosity increases sharply, the thixotropic properties of the coating become unbalanced, and the leveling properties are poor. Excessive rigid alkylated boron nitride nanoparticles weaken the plastic deformation ability of the resin. The stacking interface of alkylated boron nitride nanoparticles increases, and the thermal resistance increases. Therefore, after a lot of research and experimental verification, the applicant finally determined that the mass ratio of alkylated boron nitride nanoparticles to alkylated nano-silica in this application is preferably as described above.

[0017] Preferably, the preparation method of the modified organosilicon-epoxy hybrid resin includes the following steps:

[0018] 100 parts of bisphenol A epoxy resin, 35-45 parts of PDMS-E and 0.2-0.4 parts of triphenylphosphine were mixed, heated and reacted, and then cooled to obtain a modified organosilicon-epoxy hybrid resin.

[0019] By employing the above technical solution, PDMS-E (hydroxyl-terminated polydimethylsiloxane) undergoes a condensation reaction with the hydroxyl groups of bisphenol A epoxy resin, forming a hybrid structure linked by Si-OC bonds, thus improving UV resistance and thermal stability. The catalyst triphenylphosphine precisely controls the reaction rate, avoiding side reactions and ensuring that the siloxane segments are uniformly embedded in the epoxy network, ultimately forming a bicontinuous structure of "organosilicon continuous phase + epoxy dispersed phase," combining the advantages of both. PDMS segments migrate to the coating surface, forming a silicon-enriched layer, enhancing hydrophobicity. The polar groups in PDMS-E enhance chemical bonding with the metal / concrete substrate, strengthening the adhesion strength. The high flexibility of the organosilicon segments offsets the curing shrinkage stress of the epoxy resin, reducing internal stress in the coating and preventing thin-layer cracking.

[0020] Preferably, the preparation method of the star-shaped furan-maleimide-furan crosslinking agent includes the following steps:

[0021] Furan-methanol and maleimide-benzoic acid were mixed and dissolved in toluene, heated to react, and then rotary evaporated to obtain a star-shaped furan-maleimide-furan crosslinking agent.

[0022] By adopting the above technical solution, the star-shaped furan-maleimide-furan crosslinking agent contains multiple furan end groups, which form a high-density crosslinking network with maleimide groups through a Diels-Alder (DA) cycloaddition reaction. The increased crosslinking point density effectively fills the micropores of the coating, preventing water and oxygen penetration. The increased crosslinking point density also ensures sufficient mechanical strength even at low thicknesses.

[0023] The carboxyl groups in maleimide benzoic acid form ionic bonds with the metal / ceramic substrate, increasing adhesion strength and preventing edge delamination of the thin layer. The furan-maleimide bond can reversibly dissociate at high temperatures, releasing active groups that can re-bond and repair microcracks. The heterocyclic structure of maleimide and the aromatic conjugated system of furan provide resistance to acid and alkali corrosion. Star-shaped furan-maleimide-furan crosslinking agents encapsulate alkylated boron nitride nanoparticles or alkylated silica nanoparticles, improving dispersibility and enhancing the thermal conductivity of the coating.

[0024] Secondly, this application provides a method for preparing a repairable, high thermal conductivity nanocomposite three-proof coating, which adopts the following technical solution:

[0025] A method for preparing a repairable high thermal conductivity nanocomposite three-proof coating, comprising the following steps:

[0026] Under light-protected conditions, the modified organosilicon-epoxy hybrid resin, star-shaped furan-maleimide-furan crosslinking agent, microcapsule imidazole, thioonium salt and high-boiling-point solvent in the prescribed amounts are stirred and mixed; then alkylated nano boron nitride and alkylated nano silica are added and stirred and mixed, filtered and degassed to obtain a reworkable high thermal conductivity nanocomposite three-proof coating.

[0027] Thirdly, this application provides an application of a repairable, high thermal conductivity nanocomposite three-proof coating, employing the following technical solution:

[0028] The application of a reworkable, high thermal conductivity nanocomposite three-proof coating includes the following steps:

[0029] A reworkable, high thermal conductivity nanocomposite three-proof coating is applied to the component. First, the 365nm LED is surface-dried for 30 seconds, then initially cured at 80-100℃ for 20-30 minutes, and then further cured at 120-150℃ for 20-30 minutes to obtain the coated component.

[0030] By employing the above technical solution, 365nm ultraviolet light excites a thionium salt photoinitiator, enabling the coating surface to complete photopolymerization within 30 seconds. This rapid increase in viscosity forms a solid framework, preventing sagging / overflow and ensuring uniform layer thickness. This method is particularly suitable for vertical surface coating and the protection of micro-pitch components. During the photocuring stage, only partial cross-linking occurs, reserving space for flexible molecular chain segments to avoid stress concentration caused by direct high-temperature curing, thus preventing layer cracking / peeling.

[0031] Above 80℃, imidazole curing agents are released, catalyzing the deepening cross-linking of the epoxy-organic silicone hybrid resin to form a dense network. At this temperature, the star-shaped furan-maleimide cross-linking agent maintains the stable state of Diels-Alder (DA) bonds, simultaneously constructing a reversible repair network and reserving a structural foundation for rework. Coating peel strength increases, ensuring substrate adhesion. High temperature activates alkylated nano-boron nitride / nano-silica surface groups, forming covalent bonds with the resin and opening thermal pathways. DA bond dissociation and reconstruction, above 120℃, triggers partial DA bond reverse reaction (rDA), releasing free furan / maleimide groups, reconstructing cross-linking points to eliminate micro-stress, and improving coating toughness.

[0032] Preferably, the application of the reworkable high thermal conductivity nanocomposite three-proof coating further includes the following steps:

[0033] Peeling: When the coated component becomes a faulty component, the faulty part of the faulty component is heated to peel off the original repairable high thermal conductivity nanocomposite three-proof coating. After cooling to room temperature, the peeled faulty component is obtained.

[0034] Recoating: Apply a new, repairable, high thermal conductivity nanocomposite three-proof coating to the stripped faulty component. First, surface dry the 365nm LED for 30 seconds, then pre-cur at 80-100℃ for 20-30 minutes, and then further cure at 120-150℃ for 20-30 minutes to obtain a newly coated component.

[0035] By employing the above technical solution, heating the faulty area during repair triggers the reverse reaction (rDA) of the Diels-Alder (DA) bonds in the star-shaped furan-maleimide crosslinking agent, causing the crosslinking network to dissociate into free furan / maleimide monomers, thus softening the coating. Microcapsules that did not fully rupture during the initial curing stage remain on the substrate surface during repair heating. Reheating releases the imidazole curing agent a second time, aiding in the formation of chemical bonds between the new coating and the substrate, ensuring adhesion after repair.

[0036] In summary, this application has the following beneficial effects:

[0037] Because this application achieves high protection at a low thickness by using a modified organosilicon-epoxy hybrid resin to form a dense film, nanofiller composite to enhance the barrier, and a reversible cross-linked structure to provide repairability, it overcomes the limitation of traditional conformal coatings that require thick coatings to achieve high protection. This makes it suitable for high reliability protection scenarios for precision electronic devices.

[0038] When this application is coated onto a component, it needs to undergo initial curing at 80-100℃ and then re-curing at 120-150℃. Initial curing catalyzes the epoxy-organosilicon hybrid resin to deepen cross-linking and form a dense network. Re-curing activates the alkylated nano boron nitride / nano silica surface groups, which form covalent bonds with the resin, thus opening the thermal conductivity path. At the same time, the cross-linking points are reconstructed to eliminate micro-stress and improve the toughness of the coating. Detailed Implementation

[0039] The raw materials in this application include the following:

[0040] Bisphenol A epoxy resin: The commercially available product with CAS number 25085-99-8 is used;

[0041] PDMS-E: Hydroxyl-terminated polydimethylsiloxane, using a commercially available product with CAS number 70131-67-8;

[0042] Triphenylphosphine: Uses commercially available products with CAS number 603-35-0;

[0043] Hexamethyldisilazane: Use commercially available product with CAS number 999-97-3;

[0044] Furan-Methanol: Use commercially available products with CAS number 98-00-0;

[0045] Maleimide benzoic acid: Uses commercially available products with CAS number 17057-04-4;

[0046] Microencapsulated imidazole: The commercially available product ILCA-202 from Guangzhou Beicai Coatings Co., Ltd. is used.

[0047] Thionium salts: including triphenylthionium chloride, triphenylthionium o-trifluorobenzenesulfonate, etc. This application uses the commercially available product triphenylthionium chloride with CAS number 4270-70-6;

[0048] Propylene glycol methyl ether acetate: Use the commercially available product with CAS number 108-65-6;

[0049] Dipropylene glycol dimethyl ether: Use the commercially available product with CAS number 34590-94-8;

[0050] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0051] Example 1

[0052] A method for preparing a repairable, high thermal conductivity nanocomposite three-proof coating includes the following steps:

[0053] Under light-protected conditions, 600g of modified organosilicon-epoxy hybrid resin, 50g of star-shaped furan-maleimide-furan crosslinking agent, 15g of microcapsule imidazole, 5g of thionium salt, and 130g of high-boiling-point solvent were stirred at 500rpm for 30min. Then, 120g of alkylated nano-boron nitride and 80g of alkylated nano-silica were added and stirred at 200rpm for 30min. The mixture was filtered and degassed to obtain a reworkable, high-thermal-conductivity nanocomposite conformal coating. The high-boiling-point solvent was a mixture of propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether in a 7:3 volume ratio. Either propylene glycol methyl ether acetate or dipropylene glycol dimethyl ether can be used as the high-boiling-point solvent.

[0054] A method for preparing alkylated boron nitride nanoparticles or alkylated silica nanoparticles includes the following steps:

[0055] 200g of nano-boron nitride or 200g of nano-silica was added to a high-boiling-point solvent and homogenized using a microfluidic homogenizer (100μm pore size, 200MPa pressure, 4 cycles, and cooling at 30℃ throughout). Then, 4g of hexamethyldisilazane was added, and the mixture was heated at 50℃ for 2 hours to obtain alkylated nano-boron nitride or alkylated nano-silica. The high-boiling-point solvent was a mixture of propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether in a volume ratio of 7:3.

[0056] A method for preparing modified organosilicon-epoxy hybrid resin includes the following steps:

[0057] Mix 1000g of bisphenol A epoxy resin, 400g of PDMS-E (350g-450g is acceptable), and 3g of triphenylphosphine (2-4g is acceptable). Under nitrogen protection, heat and react at 80℃ for 3h. After cooling to 40℃, the modified organosilicon-epoxy hybrid resin is obtained.

[0058] A method for preparing a star-shaped furan-maleimide-furan crosslinking agent includes the following steps:

[0059] 2 mol furan-methanol and 1 mol maleimide-benzoic acid were mixed and dissolved in 3 L of toluene. The mixture was heated at 70 °C for 6 h. After removing the toluene by rotary evaporation, a star-shaped furan-maleimide-furan crosslinking agent was obtained.

[0060] The application of a reworkable, high thermal conductivity nanocomposite three-proof coating includes the following steps:

[0061] A reworkable, high thermal conductivity nanocomposite three-proof coating was applied to the printed circuit board assembly with a thickness of 30±5μm. First, it was surface-dried on a 365nm LED for 30s, then pre-cured at 80℃ for 30min, and then cured again at 120℃ for 30min to obtain the coated component.

[0062] Example 2-3

[0063] Examples 2-3 are based on the preparation method of Example 1, but the content of each component in the reworkable high thermal conductivity nanocomposite three-proof coating is adjusted.

[0064] Comparative Examples 1-2

[0065] Comparative Example 1, based on the application in Example 1, replaced the reworkable high thermal conductivity nanocomposite conformal coating with commercially available acrylic conformal paint with a thickness of 30±5μm.

[0066] Comparative Example 2, based on the preparation method of Example 1, replaced the reworkable high thermal conductivity nanocomposite three-proof coating with irreversible epoxy thermal conductive adhesive, with a thickness of 2.5±0.2mm.

[0067] Performance testing

[0068] The performance of Examples 1-3 and Comparative Examples 1-2 was tested as follows, and the test results are shown in Table 1.

[0069] thermal conductivity

[0070] The thermal conductivity of the material was determined according to ASTM D5470-2006.

[0071] Water vapor transmission rate

[0072] The water vapor transmission rate of the material was determined according to ASTM E96-2014.

[0073] Salt spray test rating

[0074] According to ASTM B117-2019, the salt spray test rating of materials is determined, ranging from level 0 to level 10, and the degree of corrosion ranges from complete corrosion to no corrosion.

[0075] IP Level

[0076] The IP rating of materials is determined according to IEC 60529-2013.

[0077] Vibration conditions

[0078] The integrity of the material under vibration was determined according to MIL-STD-810-2019.

[0079] Table 1. Content of each component (in g) and performance test results for Examples 1-3 and Comparative Examples 1-2.

[0080]

[0081] Referring to Table 1, comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that the addition of modified organosilicon-epoxy hybrid resin, alkylated nano-boron nitride, alkylated nano-silica, star-shaped furan-maleimide-furan crosslinking agent, and microencapsulated imidazole to the conformal coating can effectively improve the performance of the conformal coating. The reason is:

[0082] The modified silicone-epoxy hybrid resin utilizes silicone segments to provide hydrophobicity, effectively blocking water vapor penetration; epoxy groups enhance chemical bonding with the metal substrate, preventing coating peeling; the hybrid structure forms a dense cross-linked network, reducing intermolecular gaps and inhibiting the diffusion of corrosive media, which is the foundation for achieving high protection with thin layers. The microcapsule imidazole core acts as a latent curing agent, released upon heating or mechanical pressure, triggering low-temperature curing of the epoxy groups; the microcapsule shell prevents premature reaction, extends shelf life, and enables localized repair.

[0083] Alkylated boron nitride nanoparticles undergo surface alkylation treatment to improve their dispersibility in resin and prevent agglomeration; the parallel stacking of lamellar structures creates a labyrinth effect, extending the water and oxygen permeation path; high thermal conductivity establishes a heat conduction network, quickly dissipating local hot spots and preventing coating cracking caused by thermal stress. Alkylated nano-silica fills the gaps between boron nitride lamellars, further improving coating density; surface hydrophobic modification enhances capillary resistance, reducing water adsorption rate.

[0084] The star-shaped topology of the star-shaped furan-maleimide-furan crosslinking agent provides multiple reaction sites, forming a three-dimensional network and improving the mechanical strength of the coating; its reversible reaction characteristics (furan / maleimide bond) allow the coating to be repairable at high temperatures and self-heal microcracks at room temperature by dissociating the bonds.

[0085] Comparison revealed that Example 1 showed the best results among Examples 1-3. Therefore, Example 1 is preferred.

[0086] Examples 4-7

[0087] Examples 4-7 are based on the preparation method of Example 1, ensuring that the total mass of alkylated boron nitride nanoparticles and alkylated silica nanoparticles is 200g, and adjusting the mass ratio of alkylated boron nitride nanoparticles and alkylated silica nanoparticles. The specific adjustments are shown in Table 2.

[0088] The reworkable high thermal conductivity nanocomposite three-proof coatings of Examples 4-7 were subjected to the above performance tests, and the test results are shown in Table 2.

[0089] Table 2. Mass ratio and performance test results of alkylated boron nitride nanoparticles and alkylated silica nanoparticles in Examples 1 and 4-7.

[0090]

[0091] Referring to Table 2, a comparison of Examples 1 and 4-7 shows that as the mass proportion of alkylated boron nitride nanoparticles gradually increases, the effectiveness of the reworkable high thermal conductivity nanocomposite conformal coating first increases and then decreases. This is because, as the mass proportion of alkylated boron nitride nanoparticles gradually increases, a continuous thermally conductive network is gradually formed, the interlayer spacing gradually decreases, and the water / oxygen diffusion path gradually lengthens, blocking the corrosive medium. When this range is exceeded, the van der Waals forces between the alkylated boron nitride nanoparticles increase, easily forming clusters, which can easily cause pinholes during spraying; the viscosity increases sharply, the coating's thixotropy becomes unbalanced, and leveling is poor; excessive rigid alkylated boron nitride weakens the resin's plastic deformation ability; the number of alkylated boron nitride nanoparticle stacking interfaces increases, raising the thermal resistance; thus, the effectiveness of the reworkable high thermal conductivity nanocomposite conformal coating decreases.

[0092] Examples 8-9

[0093] Example 8 is an adjustment based on the application of Example 1:

[0094] The application of a reworkable, high thermal conductivity nanocomposite three-proof coating includes the following steps:

[0095] A reworkable, high thermal conductivity nanocomposite three-proof coating was applied to the printed circuit board assembly with a thickness of 30±5μm. First, it was surface-dried on a 365nm LED for 30s, then initially cured at 90℃ for 25min, and then cured again at 135℃ for 25min to obtain the coated component.

[0096] Example 9 is an adjustment based on the preparation method of Example 1:

[0097] The application of a reworkable, high thermal conductivity nanocomposite three-proof coating includes the following steps:

[0098] A reworkable, high thermal conductivity nanocomposite three-proof coating was applied to the printed circuit board assembly with a thickness of 30±5μm. First, it was surface-dried on a 365nm LED for 30s, then pre-cured at 100℃ for 20min, and then cured again at 150℃ for 20min to obtain the coated component.

[0099] Comparative Examples 3-4

[0100] Comparative Example 3 was modified from the preparation method of Example 1 as follows:

[0101] The application of a reworkable, high thermal conductivity nanocomposite three-proof coating includes the following steps:

[0102] A reworkable, high thermal conductivity nanocomposite three-proof coating was applied to the printed circuit board assembly with a thickness of 30±5μm. First, it was surface-dried on a 365nm LED for 30s, and then cured at 80℃ for 60min to obtain the coated component.

[0103] Comparative Example 4 was modified from the preparation method of Example 1 as follows:

[0104] The application of a reworkable, high thermal conductivity nanocomposite three-proof coating includes the following steps:

[0105] A reworkable, high thermal conductivity nanocomposite three-proof coating was applied to the printed circuit board assembly with a thickness of 30±5μm. First, the coating was surface-dried on a 365nm LED for 30s, and then cured at 120℃ for 60min to obtain the coated component.

[0106] The reworkable high thermal conductivity nanocomposite three-proof coatings of Examples 8-9 and Comparative Examples 3-4 were subjected to the above performance tests, and the test results are shown in Table 3.

[0107] Table 3 Application conditions and performance test results for Examples 1, 8-9 and Comparative Examples 3-4

[0108]

[0109] Referring to Table 3, comparing Examples 1, 8-9, and Comparative Examples 3-4, it is evident that the reworkable high thermal conductivity nanocomposite conformal coating is better achieved through a two-step curing process using different temperatures. This is because: initial curing is performed at 80-100℃, catalyzing the deepening cross-linking of the epoxy-silicone hybrid resin to form a dense network. At this temperature, the star-shaped furan-maleimide crosslinking agent maintains the stable state of the Diels-Alder (DA) bonds, simultaneously constructing a reversible repair network and reserving a structural foundation for rework. This increases the coating's peel strength, ensuring substrate adhesion. High temperature activates the alkylated nano-boron nitride / nano-silica surface groups, forming covalent bonds with the resin, thus opening the thermal conductivity path. Further curing at 120-150℃ causes DA bond dissociation and reconstruction. Above 120℃, a partial reverse DA bond reaction (rDA) is triggered, releasing free furan / maleimide groups, reconstructing crosslinking points to eliminate micro-stress, and improving coating toughness.

[0110] If curing is performed at 80℃ throughout the process, solvent residue can easily remain inside the coating, forming micron-sized bubbles or pinholes, leading to decreased coating density and increased water vapor permeability. 80℃ cannot activate the deep cross-linking reaction of the resin, resulting in insufficient reaction of surface modifiers (such as silane coupling agents) on the nanofillers, leading to weak interfacial bonding. Incompletely cross-linked resin molecular chains encapsulate the thermally conductive filler, increasing interfacial thermal resistance. Furthermore, the DA bonds (peelable structures) are not fully formed, requiring strong mechanical peeling during rework, which can damage the components.

[0111] If curing is carried out at 120℃ throughout the process, it will cause a thermal expansion mismatch between the resin and the component. The concentrated high-temperature curing will cause internal stress to accumulate and exceed the material's yield limit. The resin will oxidize and decompose, and the nanofiller interface layer (such as titanate) will desorb at high temperature, leading to filler agglomeration. Excessive cross-linking of DA bonds will increase the peeling force, and the high temperature will cause reversible bonds (such as Diels-Alder bonds) to be converted into irreversible covalent bonds. During rework, strong mechanical peeling is required, which will damage the component.

[0112] Examples 10-11

[0113] Example 10 is an adjustment based on the application of Example 1:

[0114] Peeling: When the coated component becomes a faulty component, the faulty part of the faulty component is heated at 150°C for 10 minutes to peel off the original repairable high thermal conductivity nanocomposite three-proof coating. After cooling to room temperature, the peeled faulty component is obtained.

[0115] Recoating: Apply a new, repairable, high thermal conductivity nanocomposite three-proof coating to the stripped faulty component with a thickness of 30±5μm. First, surface dry the 365nm LED for 30s, then pre-cur at 80℃ for 30min, and then further cure at 120℃ for 30min to obtain a newly coated component.

[0116] Example 11 is an adjustment based on the application of Example 1:

[0117] Peeling: When the coated element becomes a faulty element after one peeling, the faulty part of the faulty element is heated at 150°C for 10 minutes to peel off the original repairable high thermal conductivity nanocomposite three-proof coating. After cooling to room temperature, the peeled faulty element is obtained.

[0118] Recoating: Apply a new, repairable, high thermal conductivity nanocomposite three-proof coating to the stripped faulty component with a thickness of 30±5μm. First, surface dry the 365nm LED for 30s, then pre-cur at 80℃ for 30min, and then further cure at 120℃ for 30min to obtain a newly coated component.

[0119] The reworkable high thermal conductivity nanocomposite three-proof coatings of Examples 10-11 were subjected to the above performance tests, and the test results are shown in Table 4.

[0120] Table 4. Number of repairs and performance test results for Examples 1 and 10-11

[0121]

[0122] Referring to Table 4, a comparison of Examples 1 and 10-11 shows that after a part coated with the reworkable high thermal conductivity nanocomposite three-proof coating prepared in this application fails, the original coating can be peeled off by heating, and a new coating can be applied, maintaining good performance. This is because heating the faulty area during repair triggers the reverse reaction (rDA) of the Diels-Alder (DA) bonds in the star-shaped furan-maleimide crosslinking agent, causing the crosslinking network to dissociate into free furan / maleimide monomers, softening the coating. Microcapsules that are not completely ruptured during the initial curing stage remain on the substrate surface during repair heating. Reheating releases the imidazole curing agent a second time, assisting the new coating in forming chemical bonds with the substrate and ensuring adhesion after repair.

[0123] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A repairable, high thermal conductivity nanocomposite three-proof coating, characterized in that, The product comprises the following components in parts by weight: 50-60 parts of modified organosilicon-epoxy hybrid resin, 8-12 parts of alkylated nano-boron nitride, 5-8 parts of alkylated nano-silica, 3-5 parts of star-shaped furan-maleimide-furan crosslinking agent, 1-1.5 parts of microencapsulated imidazole, 0.1-0.5 parts of thionium salt, and a high-boiling-point solvent to bring the total to 100 parts; wherein the high-boiling-point solvent includes at least one of propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether. The preparation method of the modified organosilicon-epoxy hybrid resin includes the following steps: 100 parts of bisphenol A epoxy resin, 35-45 parts of hydroxyl-terminated polydimethylsiloxane and 0.2-0.4 parts of triphenylphosphine were mixed, heated and reacted, and then cooled to obtain a modified organosilicon-epoxy hybrid resin. The preparation method of the star-shaped furan-maleimide-furan crosslinking agent includes the following steps: Furan-methanol and maleimide-benzoic acid were mixed and dissolved in toluene, heated to react, and then rotary evaporated to obtain a star-shaped furan-maleimide-furan crosslinking agent.

2. The reworkable high thermal conductivity nanocomposite three-proof coating according to claim 1, characterized in that: The preparation method of the alkylated boron nitride nanoparticles or alkylated silica nanoparticles includes the following steps: Nano-boron nitride or nano-silica is added to a high-boiling-point solvent and homogenized. Then, hexamethyldisilazane is added and the mixture is heated to react, thereby obtaining alkylated nano-boron nitride or alkylated nano-silica.

3. The reworkable high thermal conductivity nanocomposite three-proof coating according to claim 1, characterized in that: The mass ratio of the alkylated boron nitride nanoparticles to the alkylated silicon dioxide nanoparticles is 1.5-2:

1.

4. The method for preparing the repairable high thermal conductivity nanocomposite three-proof coating according to any one of claims 1-3, characterized in that, Includes the following steps: Under light-protected conditions, the modified organosilicon-epoxy hybrid resin, star-shaped furan-maleimide-furan crosslinking agent, microcapsule imidazole, thioonium salt and high-boiling-point solvent in the prescribed amounts are stirred and mixed; then alkylated nano boron nitride and alkylated nano silica are added and stirred and mixed, filtered and degassed to obtain a reworkable high thermal conductivity nanocomposite three-proof coating.

5. The application of the repairable high thermal conductivity nanocomposite three-proof coating as described in any one of claims 1-3, characterized in that, Includes the following steps: A reworkable, high thermal conductivity nanocomposite three-proof coating is applied to the component. First, the 365nm LED is surface-dried for 30 seconds, then initially cured at 80-100℃ for 20-30 minutes, and then further cured at 120-150℃ for 20-30 minutes to obtain the coated component.

6. The application of the repairable high thermal conductivity nanocomposite three-proof coating according to claim 5, characterized in that, It also includes the following steps: Peeling: When the coated component becomes a faulty component, the faulty part of the faulty component is heated to peel off the original repairable high thermal conductivity nanocomposite three-proof coating. After cooling to room temperature, the peeled faulty component is obtained. Recoating: Apply a new, repairable, high thermal conductivity nanocomposite three-proof coating to the stripped faulty component. First, surface dry the 365nm LED for 30 seconds, then pre-cur at 80-100℃ for 20-30 minutes, and then further cure at 120-150℃ for 20-30 minutes to obtain a newly coated component.

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