A repairable protective coating for circuit board surfaces and methods of making and using the same

Abstract

This invention discloses a repairable protective coating for circuit board surfaces, prepared from a low-viscosity hyperbranched thermoplastic acrylic resin, fluorescent powder, solvent 1, leveling agent, and defoamer. The low-viscosity hyperbranched thermoplastic acrylic resin is prepared from a hyperbranched vinyl prepolymer, monomers, dispersant, initiator, chain transfer agent, and solvent 2. The hyperbranched vinyl prepolymer is prepared from a polyhydroxy compound, a bifunctional NCO monomer, a hydroxyl acrylic monomer, a polymerization inhibitor, and solvent 3. Using the self-made hyperbranched thermoplastic acrylic resin as the film-forming material for the repairable protective coating on circuit board surfaces, with the addition of appropriate amounts of solvent and additives, the prepared circuit board protective coating possesses excellent "three-proof" properties (waterproof, dustproof, and shockproof), impact resistance, flexibility, high and low temperature impact resistance, insulation properties, and dielectric properties, while also exhibiting repairability and easy removal characteristics.

Description

Technical Field

[0001] This invention belongs to the field of coating technology for circuit boards, specifically relating to a repairable protective coating for the surface of circuit boards, its preparation method, and its application method. Background Technology

[0002] Circuit board protective coatings are specially formulated coatings used to protect circuit boards and related equipment from environmental corrosion, thereby improving and extending their service life and ensuring safety and reliability. Under real-world conditions, such as chemical environments (fuels, coolants, etc.), vibration, high dust, salt spray, humidity, and high temperatures, circuit boards may experience corrosion, softening, deformation, and mold growth, leading to circuit failures. Circuit board protective coatings can be applied to the surface of circuit boards, forming a light and flexible film approximately 25-80 μm thick. This protects the circuit board from damage under these harsh conditions. Based on the main material, circuit board protective coatings can be classified into acrylic, polyurethane, silicone, epoxy, and polyxylene types. To meet special construction and application scenarios, some circuit boards need to be repaired and reused. For these types of circuit boards, thermoplastic acrylic protective coatings must be used to ensure their repairability.

[0003] Acrylic circuit board protective coatings primarily use high-molecular-weight thermoplastic acrylic resins, the vast majority of which are currently imported, with only a very small portion using domestically produced resins. However, domestically produced resins present two main problems. Firstly, when the molecular weight of domestic resins is the same as that of imported products, the viscosity of domestic resins is significantly higher, leading to stringing during spraying and severely impacting application quality and efficiency. Secondly, domestically produced resins have a wider molecular weight distribution and contain more small molecules, which cannot meet the requirements of some environments with high vacuum requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a repairable protective coating for circuit board surfaces, as well as its production and application methods. Using a self-made low-viscosity, hyperbranched, high-molecular-weight thermoplastic acrylic resin as the film-forming substance, this invention solves problems such as low solids content, thin single-coat thickness, and stringing caused by the high viscosity of the resin during application, thus improving the repairability, application performance, and temperature resistance of this type of circuit board protective coating.

[0005] This invention provides a technical solution for a repairable protective coating for circuit board surfaces.

[0006]

[0007]

[0008] Further, the leveling agent is one or more of BYK-300, BYK-306, BYK-307, BYK-310, BYK-323, BYK-331, BYK-333, BYK-346, BYK-348, BYK-354, BYK-358N, BYK-361N, BYK-370, and BYK-371; the defoamer is BYK-141, BYK-370, BYK-371, etc. The phosphor is one or more of the following: K-077, BYK-066N, BYK-065, BYK-088, BYK-037, BYK-024, BYK-021, BYK-019, BYK-018, and BYK-017; the phosphor is one of commercially available inorganic or organic phosphors; and the solvent 1 is one or more of the following: butanone, toluene, xylene, trifluorotoluene, butyl acetate, and cyclohexanone.

[0009] Furthermore, by mass percentage, the low-viscosity hyperbranched thermoplastic acrylic resin comprises the following components:

[0010]

[0011] The monomer is one or more of the following: n-butyl acrylate, isobutyl acrylate, butyl methacrylate, isobutyl methacrylate, methyl methacrylate, isobornyl methacrylate, and caprolactone acrylate.

[0012] Furthermore, the dispersant is one or more of sodium hydroxide, magnesium chloride, magnesium carbonate, calcium carbonate, barium sulfate, calcium sulfate, calcium phosphate, talc, and kaolin.

[0013] Furthermore, the initiator is one of azobisisobutyronitrile, tert-butyl peroxide, benzoyl peroxide, lauroyl peroxide, and dimethyl azobisisobutyronitrile.

[0014] Furthermore, the chain transfer agent is one or more of dodecyl mercaptan, 2-methylhexyl 3-mercaptoacetate, aliphatic thiols, trichloroethylene, tetrachloromethane, and 2,4-diphenyl-4-methyl-1-pentene.

[0015] Furthermore, the solvent 2 is deionized water.

[0016] Furthermore, by mass percentage, the hyperbranched vinyl prepolymer comprises the following components:

[0017]

[0018]

[0019] Further, the polyhydroxy compound is one or more of polycarbonate polyol, polyester polyol, polyether polyol, polycaprolactone polyol, pentaerythritol, trimethylolpropane, glycerol, dipropylene glycol, and tripropylene glycol; the bifunctional NCO monomer is one or more of IPDI, HDI, HMDI, MDI, and TDI; the acrylic monomer is one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate; the polymerization inhibitor is one or more of benzoquinone, tetrachlorobenzoquinone, hydroquinone, p-tert-butylhydroquinone, 2,6-di-tert-butyl-p-methylphenol, diphenylamine, p-phenylenediamine, phenothiazine, ferric chloride, sodium sulfate, and sodium sulfide; and the solvent 3 is one or more of xylene, toluene, butyl acetate, cyclohexane, and amyl acetate.

[0020] Secondly, this application provides a process for preparing a repairable protective coating for the surface of a circuit board, employing the following technical solution:

[0021] Step 1, Preparation of hyperbranched vinyl prepolymer: Using a reflux dehydration synthesis apparatus, first add all the solvent of the prescribed amount to a three-necked flask, start stirring, and control the stirring speed at 200-400 r / min; add the prescribed amount of polyhydroxy compound to the three-necked flask, heat to reflux, dehydrate for 1 hour, then cool to room temperature. Next, slowly add the prescribed amount of bifunctional NCO monomer to the three-necked flask and stir for 30 minutes. Heat to (50-60)℃ and hold for 1 hour, then heat to (80-85)℃ and hold for 3 hours. Detect N... When the CO content reaches the design value of 2.5%-5.5%, first add the amount of polymerization inhibitor specified in the formula, and then slowly add the hydroxyacrylic acid monomer using a peristaltic pump; keep the reaction at (80-85)℃ for 3 hours. When the NCO content is less than 0.3%, stop heating, connect the distillation apparatus, and after the apparatus is connected, first turn on the vacuum pump and control the vacuum degree to 0.06MPa, and then start heating for distillation until there are no liquid droplets at the tail pipe of the condenser and the system temperature rises rapidly. Then stop heating and vacuuming, cool down and discharge the material for later use.

[0022] Step 2, Preparation of low-viscosity hyperbranched thermoplastic acrylic resin: First, add all of the solvent 2 in the formula to a three-necked flask, start stirring, control the stirring speed at 200-400 r / min, and slowly raise the temperature. When the temperature reaches 60-65℃, slowly add the mixture of hyperbranched vinyl prepolymer and monomer prepared in step (1), and keep it at 60-65℃ for 30 min; then, add all of the dispersant and chain transfer agent, and keep it at 60-65℃ for 30-60 min; after the heat preservation is completed, slowly raise the temperature to 80℃ and add the initiator. The resin was reacted at 80-85℃ for 3 hours, then the temperature was raised to 90℃ and maintained at 90-95℃ for another 3 hours. After the reaction was completed, heating was stopped, and the mixture was allowed to cool naturally to below 35℃. The mixture was then filtered through an 80-mesh sieve to obtain uniform, spherical resin particles. Finally, a sufficient amount of 5% dilute sulfuric acid solution was prepared in a beaker using deionized water and concentrated sulfuric acid. This solution was added to the beaker containing the resin particles, and the mixture was stirred and washed with a glass rod. This process was repeated until the conductivity of the washing solution was approximately the same as that of the deionized water used.

[0023] Step 3: Add solvent 1 to the mixing tank, and slowly add the low viscosity hyperbranched thermoplastic acrylic resin prepared in step (2) under high speed stirring (speed ≥ 1000 r / min). After it is completely dissolved, add fluorescent powder, leveling agent and defoamer respectively under high speed stirring (speed ≥ 1000 r / min). Continue high speed stirring (speed ≥ 1000 r / min) for 20 min, and then filter and package to obtain the repairable protective coating for the surface of the circuit board.

[0024] Thirdly, this application provides a method for applying a repairable protective coating to the surface of a circuit board, which can be applied by spraying, dipping, or brushing. When spraying, the coating needs to be diluted with a special spraying thinner to a viscosity of 50–80 mPa·s, the spraying pressure is 0.3–0.4 MPa, the distance between the spray gun and the board surface is 20–30 cm, and the coating thickness is (20–35) μm. When dipping, the coating needs to be diluted with a special dipping thinner to a viscosity of 100–200 mPa·s, and then the circuit board is vertically immersed in the protective coating. When the coating is in place for 20-25 seconds, and no more air bubbles appear, slowly lift the circuit board out of the coating at a uniform speed of 1-2 seconds per mm. Ensure the coating evenly covers the circuit board surface. After lifting, suspend the circuit board above the coating container or drip tray to allow the coating to drip naturally until most of the excess coating has detached from the surface. Then, place it in an air-circulating drying cabinet to dry. Alternatively, when using a brush, first stir the coating thoroughly, then let it stand until no more air bubbles appear. Use a craft brush for brush application. After brushing, place the circuit board in an air-circulating drying cabinet to dry.

[0025] Beneficial effects

[0026] The low-viscosity hyperbranched thermoplastic acrylic resin prepared by this invention has a molecular weight ≥100,000 and a solubility viscosity of 198 mPa·s when the non-volatile content is 35%, which greatly reduces the solubility viscosity of high molecular weight thermoplastic acrylic resin.

[0027] Using self-made hyperbranched thermoplastic acrylic resin as the film-forming material for a repairable protective coating on circuit board surfaces, and adding appropriate amounts of solvents and additives, the prepared circuit board protective coating has excellent "three-proof" properties, impact resistance, flexibility and other mechanical properties, high and low temperature impact resistance, insulation properties and dielectric properties, while also being repairable and easy to remove. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] Formulation for the synthesis of hyperbranched vinyl prepolymers:

[0031] Raw material name Amount added (g) Polycaprolactone polyol CAPA3050 27.9 IPDI 24.8 Hydroxyethyl acrylate 5.5 hydroquinone 0.55 Xylene: Butyl acetate = 1:1 41.3

[0032] Synthesis process of hyperbranched vinyl prepolymers:

[0033] The reflux dehydration synthesis apparatus was assembled. First, all the xylene and butyl acetate in the prescribed amounts were added to a three-necked flask, and stirring was started, controlling the stirring speed at 200–400 rpm. Then, the prescribed amount of polycaprolactone polyol CAPA3050 was added to the three-necked flask, and the mixture was heated to reflux and dehydrated for 1 hour. After cooling to room temperature, the prescribed amount of IPDI was slowly added to the three-necked flask and stirred for 30 minutes. The temperature was then raised to (50–60) °C and held for 1 hour, followed by raising the temperature to (80–85) °C and holding for 3 hours. NCO was then measured. When the content reaches 3.5%, hydroquinone is added first, and then hydroxyethyl acrylate is slowly added using a peristaltic pump. The reaction is kept at (80-85)℃ for 3 hours. When the NCO content is less than 1.5%, heating is stopped, and the distillation apparatus is connected. After the apparatus is connected, the vacuum pump is turned on first, and the vacuum degree is controlled at 0.06MPa. Then the heating is started for distillation until there are no liquid droplets at the tail end of the condenser and the system temperature rises rapidly. Then the heating and vacuuming are stopped, and the material is cooled and discharged for later use to obtain hyperbranched vinyl prepolymer A.

[0034] Low-viscosity hyperbranched acrylic resin synthesis formulation:

[0035]

[0036]

[0037] Synthesis process of low-viscosity hyperbranched thermoplastic acrylic resin:

[0038] First, add all the deionized water specified in the formula to a three-necked flask, start stirring, and control the stirring speed at 200-400 rpm, while slowly raising the temperature. When the temperature reaches 60-65℃, slowly add the mixture of hyperbranched vinyl prepolymer A and butyl methacrylate, and maintain the temperature at 60-65℃ for 30 minutes. Then, add all of the sodium hydroxide and tetrachloromethane, and maintain the temperature at 60-65℃ for 30-60 minutes. After the temperature maintenance is complete, slowly raise the temperature to 80℃ and add benzoyl peroxide, maintaining the reaction at 80-85℃ for 3 hours. Subsequently, raise the temperature to 90℃ and continue the reaction at 90-95℃ for 3 hours. After the temperature maintenance is complete, stop heating and allow the mixture to cool naturally to below 35℃. Filter the mixture through an 80-mesh sieve to obtain uniform, spherical resin particles. Finally, using deionized water and concentrated sulfuric acid, prepare a sufficient amount of 5% dilute sulfuric acid aqueous solution in a beaker, add it to the beaker containing the resin particles, and stir and wash with a glass rod. Repeat this process until the conductivity of the washing solution is substantially the same as that of the deionized water used, thus obtaining low-viscosity hyperbranched thermoplastic acrylic resin A.

[0039] Circuit board protective coating formulation:

[0040] Raw material name Amount added (g) Low viscosity hyperbranched thermoplastic acrylic resin A 35.0 fluorescent powder 0.2 Xylene: Butyl ketone = 1:1 65.0 BYK 306 0.3 BYK 066N 0.2

[0041] Add xylene and methyl ethyl ketone to the mixing tank, and slowly add the low-viscosity hyperbranched thermoplastic acrylic resin A prepared in step (2) under high-speed stirring (speed ≥ 1000 r / min). After it is completely dissolved, add phosphor, BYK 306 and BYK 066N respectively under high-speed stirring (speed ≥ 1000 r / min). Continue high-speed stirring (speed ≥ 1000 r / min) for 20 min, and then filter and package to obtain the repairable protective coating A for the surface of the circuit board.

[0042] Circuit board protective coating process:

[0043] Dilute the coating with a special dipping thinner to a viscosity of 100–200 mPa·s. Then, vertically immerse the circuit board into the protective coating on its surface and hold for 20–25 seconds. When no air bubbles remain in the coating, slowly remove the circuit board from the coating at a uniform speed of 1–2 seconds / mm, ensuring that the coating evenly covers the surface of the circuit board. After removal, suspend the circuit board above the coating container or drip tray to allow the coating to drip naturally until most of the excess coating has detached from the surface. Then, place it in an air-circulating drying cabinet for drying.

[0044] Key performance characteristics achieved by repairable protective coatings for circuit board surfaces:

[0045] project performance Testing standards Dielectric constant, 1MHz 2.44 GB / T 1409 Insulation resistance, Ω <![CDATA[3.0×10 12 ]]> SJ20671 Suspension viscosity (non-volatile content 35%), mPa·s 186 GB / T 9269 Impact, 50cm No cracks or peeling in the paint film GB / T 1732 Flexible, mm 1 GB / T 1731 Adhesion, cross-cut test Level 1 GB / T 9286 High and low temperature shock (-60℃-120℃, 50 cycles) No cracks or peeling in the paint film GJB 150.5A

[0046] Example 2

[0047] Formulation for the synthesis of hyperbranched vinyl prepolymers:

[0048] Raw material name Amount added (g) Polyether 210 30.0 IPDI 13.2 Hydroxyethyl acrylate 5.5 hydroquinone 0.55 Xylene: Butyl acetate = 1:1 51.0

[0049] Synthesis process of hyperbranched vinyl prepolymers:

[0050] The reflux dehydration synthesis apparatus was assembled. First, all the xylene and butyl acetate in the prescribed amounts were added to a three-necked flask. Stirring was started, and the stirring speed was controlled at 200-400 rpm. The prescribed amount of polyether 210 was added to the three-necked flask, and the mixture was heated to reflux and dehydrated for 1 hour. Then, the mixture was cooled to room temperature. Next, the prescribed amount of IPDI was slowly added to the three-necked flask and stirred for 30 minutes. The temperature was raised to (50-60)℃ and held for 1 hour, then raised to (80-85)℃ and held for 3 hours. When the NCO content reached 2.9%, the prescribed amount of hydroquinone was added first, followed by the slow addition of hydroxyethyl acrylate using a peristaltic pump. The reaction was maintained at (80-85)℃ for 3 hours. When the NCO content was less than 1.0%, heating was stopped, and the distillation apparatus was assembled. After the device is assembled, first turn on the vacuum pump and control the vacuum degree to 0.06MPa. Then start the heating to distill until there are no liquid droplets at the tail end of the condenser and the system temperature rises rapidly. Then stop heating and vacuuming, cool down and discharge the material for later use to obtain hyperbranched vinyl prepolymer B.

[0051] Low-viscosity hyperbranched acrylic resin synthesis formulation:

[0052] Raw material name Amount added (g) Hyperbranched vinyl prepolymer B 6.5 Isobutyl methacrylate 24.0 Sodium hydroxide 2.25 Magnesium chloride 3.25 Benzoyl peroxide 2.0 dodecyl mercaptan 1.85 Deionized water 60.0

[0053] Synthesis process of low-viscosity hyperbranched thermoplastic acrylic resin:

[0054] First, add all the deionized water specified in the formula to a three-necked flask, start stirring, and control the stirring speed at 200-400 rpm, while slowly raising the temperature. When the temperature reaches 60-65℃, slowly add the mixture of hyperbranched vinyl prepolymer B and isobutyl methacrylate, and maintain the temperature at 60-65℃ for 30 minutes. Then, add all of the sodium hydroxide, magnesium chloride, and dodecyl mercaptan, and maintain the temperature at 60-65℃ for 30-60 minutes. After the temperature maintenance is complete, slowly raise the temperature to 80℃ and add benzoyl peroxide, maintaining the reaction at 80-85℃ for 3 hours. Then, raise the temperature to 90℃ and continue the reaction at 90-95℃ for 3 hours. After the temperature maintenance is complete, stop heating and allow the mixture to cool naturally to below 35℃. Filter the mixture through an 80-mesh sieve to obtain uniform, spherical resin particles. Finally, using deionized water and concentrated sulfuric acid, prepare a sufficient amount of 5% dilute sulfuric acid aqueous solution in a beaker, add it to the beaker containing the resin particles, and stir and wash with a glass rod. Repeat this process until the conductivity of the washing solution is substantially the same as that of the deionized water used, thus obtaining low-viscosity hyperbranched thermoplastic acrylic resin B.

[0055] Circuit board protective coating formulation:

[0056]

[0057]

[0058] Add xylene and methyl ethyl ketone to the mixing tank, and slowly add the low viscosity hyperbranched thermoplastic acrylic resin B prepared in step (2) under high speed stirring (speed ≥ 1000 r / min). After it is completely dissolved, add phosphor, BYK 306 and BYK 066N respectively under high speed stirring (speed ≥ 1000 r / min). Continue high speed stirring (speed ≥ 1000 r / min) for 20 min, and then filter and package to obtain the repairable protective coating B for the surface of the circuit board.

[0059] Circuit board protective coating process:

[0060] Dilute the coating with a special dipping thinner to a viscosity of (100-200) mPa·s. Then, vertically immerse the circuit board into the protective coating on its surface and hold for (20-25) s. When there are no air bubbles in the coating, slowly remove the circuit board from the coating at a uniform speed of (1-2) s / mm to ensure that the coating evenly covers the surface of the circuit board. After removal, suspend the circuit board above the coating tank or drip tray to allow the coating to drip naturally until most of the excess coating is removed from the surface. Then, place it in an air-circulating drying cabinet for drying.

[0061] The main performance characteristics achieved by the circuit board protective coating are:

[0062] project performance Testing standards Dielectric constant, 1MHz 2.48 GB / T 1409 Insulation resistance, Ω <![CDATA[1.2×10 12 ]]> SJ20671 Suspension viscosity (non-volatile content 35%), mPa·s 198 GB / T 9269 Impact, 50cm No cracks or peeling in the paint film GB / T 1732 Flexible, mm 1 GB / T 1731 Adhesion, cross-cut test Level 1 GB / T 9286 High and low temperature shock (-60℃-120℃, 50 cycles) No cracks or peeling in the paint film GJB 150.5A

[0063] This disclosure has been described with reference to the foregoing embodiments; however, these embodiments are merely examples for implementing this disclosure. It must be noted that the disclosed embodiments do not limit the scope of this disclosure. On the contrary, any changes and modifications made without departing from the spirit and scope of this disclosure are within the scope of patent protection of this disclosure.

Claims

1. A repairable protective coating for circuit board surfaces, characterized in that: It consists of the following components by mass percentage: Low-viscosity hyperbranched thermoplastic acrylic resin 25%~35% Fluorescent powder 0.2%~5% Solvent 1: 57%~74.6% Leveling agent 0.1%~1% Defoamer 0.1%~2%; The low-viscosity hyperbranched thermoplastic acrylic resin, by weight percentage, comprises the following components: Hyperbranched vinyl prepolymer 2.0%~10.5% Monomer content: 18%~24.5% Dispersant 0.6%~5.5% Initiator 0.3%~3.0% Chain transfer agent 1.0%~3.5% Solvent 2 53.0%~78.1%, The monomer is one or more of the following: n-butyl acrylate, isobutyl acrylate, butyl methacrylate, isobutyl methacrylate, methyl methacrylate, isobornyl methacrylate, and caprolactone acrylate. The hyperbranched vinyl prepolymer, by mass percentage, comprises the following components: Polyhydroxy compounds: 10.0%–32% Bifunctional NCO monomers 7.5%~25.1% Hydroxyacrylate monomer 0.6%~5.5% Polymerization inhibitor 0.06%~0.55% Solvent 3: 40.0%~70.0%; The polyhydroxy compound is one or more of polycarbonate polyol, polyester polyol, polyether polyol, pentaerythritol, trimethylolpropane, glycerol, dimeric glycerol, and trimeric glycerol; the bifunctional NCO monomer is one or more of IPDI, HDI, HMDI, MDI, and TDI; and the hydroxyacrylate monomer is one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

2. The repairable protective coating for circuit board surfaces according to claim 1, characterized in that: The dispersant is one or more of sodium hydroxide, magnesium chloride, magnesium carbonate, calcium carbonate, barium sulfate, calcium sulfate, calcium phosphate, talc, and kaolin; the initiator is one of azobisisobutyronitrile, tert-butyl peroxide, benzoyl peroxide, lauroyl peroxide, and dimethyl azobisisobutyronitrile; the chain transfer agent is one or more of dodecyl mercaptan, 2-methylhexyl 3-mercaptoacetate, aliphatic thiols, trichloroethylene, tetrachloromethane, and 2,4-diphenyl-4-methyl-1-pentene; and the solvent 2 is deionized water.

3. The repairable protective coating for circuit board surfaces according to claim 1, characterized in that: The polymerization inhibitor is one or more of benzoquinone, tetrachlorobenzoquinone, hydroquinone, p-tert-butylcatechol, 2,6-di-tert-butyl-p-methylphenol, diphenylamine, p-phenylenediamine, phenothiazine, ferric chloride, sodium sulfate, and sodium sulfide; the solvent 3 is one or more of xylene, toluene, butyl acetate, cyclohexane, and amyl acetate.

4. The repairable protective coating for circuit board surfaces according to claim 1, characterized in that: The leveling agent is one or more of BYK-300, BYK-306, BYK-307, BYK-310, BYK-323, BYK-331, BYK-333, BYK-346, BYK-348, BYK-354, BYK-358N, BYK-361N, BYK-370, and BYK-371; the defoamer is BYK-141, BYK-077, BYK-066N, BYK-065, BYK-088, BYK-037, BYK-024, BYK-021, BYK-019, BYK-018, and BYK-017. One or more of the following: the phosphor is one of commercially available inorganic or organic phosphors; the solvent 1 is one or more of butanone, toluene, xylene, trifluorotoluene, butyl acetate, and cyclohexanone.

5. A method for preparing a repairable protective coating for a circuit board surface as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Preparation of hyperbranched vinyl prepolymer: Using a reflux dehydration synthesis apparatus, first add all of the formulated amount of solvent 3 to a three-necked flask, start stirring, and control the stirring speed at 200-400 r / min; add the formulated amount of polyhydroxy compound to the three-necked flask, heat to reflux, dehydrate for 1 h, and then cool to room temperature. Then slowly add the formulated amount of bifunctional NCO monomer to the three-necked flask and stir for 30 min. Heat to 50-60℃ and hold for 1 h, then heat to 80-85℃ and hold for 3 h. Detect NC When the O content reaches the design value of 2.5%-5.5%, first add the amount of polymerization inhibitor specified in the formula, and then slowly add the hydroxyacrylic acid monomer using a peristaltic pump; keep the reaction at 80-85℃ for 3 hours. When the NCO content is less than 0.3%, stop heating, connect the distillation apparatus, and after the apparatus is connected, first turn on the vacuum pump and control the vacuum degree to 0.06MPa, and then start heating for distillation until there are no liquid droplets at the tail end of the condenser and the system temperature rises rapidly. Then stop heating and vacuuming, cool down and discharge the material for later use. (2) Preparation of low-viscosity hyperbranched thermoplastic acrylic resin: First, add all of the solvent 2 in the formula to a three-necked flask, start stirring, control the stirring speed at 200-400 r / min, and start slowly heating. When the temperature reaches 60-65℃, slowly add the mixture of hyperbranched vinyl prepolymer and monomer prepared in step (1), and keep it at 60-65℃ for 30 min; then, add all of the dispersant and chain transfer agent, and keep it at 60-65℃ for 30-60 min; after the heat preservation is completed, slowly heat to 80℃ and add The initiator was used to maintain the reaction at 80-85℃ for 3 hours, then the temperature was raised to 90℃ and maintained at 90-95℃ for another 3 hours. After the reaction was completed, heating was stopped, and the mixture was allowed to cool naturally to below 35℃. The mixture was then filtered through an 80-mesh sieve to obtain uniform, spherical resin particles. Finally, a sufficient amount of 5% dilute sulfuric acid solution was prepared in a beaker using deionized water and concentrated sulfuric acid. This solution was added to the beaker containing the resin particles, and the mixture was stirred and washed with a glass rod. This process was repeated until the conductivity of the washing solution was the same as that of the deionized water used. (3) Add solvent 1 to the cylinder according to the formula amount, and slowly add the low viscosity hyperbranched thermoplastic acrylic resin prepared in step (2) at a speed of ≥1000r / min. After it is completely dissolved, add fluorescent powder, leveling agent and defoamer respectively under high speed stirring (speed ≥1000r / min). Continue high speed stirring (speed ≥1000r / min) for 20 minutes, filter and package to obtain the repairable protective coating for the surface of the circuit board.

6. A method of using the repairable protective coating for a circuit board surface as described in any one of claims 1-4, characterized in that: Includes the following steps: The repairable protective coating on the circuit board surface can be applied by spraying, dipping, or brushing. For spraying, dilute with a special spraying thinner to a viscosity of 50-80 mPa·s, spray pressure of 0.3-0.4 MPa, and distance of the spray gun from the board surface of 20-30 cm. For dipping, dilute with a special dipping thinner to a viscosity of 100-200 mPa·s, then vertically immerse the circuit board in the protective coating for 20-25 seconds. When no air bubbles remain in the coating, slowly remove the circuit board from the coating at a uniform speed of 1-2 seconds / mm, ensuring the coating evenly covers the circuit board surface. After removal, suspend the circuit board above the coating container or drip tray to allow the coating to drip naturally until most of the excess coating detaches from the surface. Then, place it in an air-circulating drying cabinet for drying. For brushing, first stir the coating evenly, then let it stand until no air bubbles remain. Use a craft brush for application. After brushing, place the circuit board in an air-circulating drying cabinet for drying.

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