Coating aluminum sheet for PCB drilling and preparation method thereof

Abstract

The invention belongs to the field of PCB processing, and discloses a coated aluminum sheet for PCB drilling and a preparation method thereof.The coated aluminum sheet for PCB drilling comprises an aluminum foil base material and a water-soluble resin coating on the surface of the base material, and the water-soluble resin coating is obtained by spraying and curing water-soluble resin paint; the water-soluble resin coating is prepared from the following raw materials in parts by weight: water-borne epoxy resin, a cross-linking agent, a defoaming agent, a flatting agent, a wetting agent, modified silicon carbide whiskers, modified graphene and deionized water, and the modified silicon carbide whiskers are prepared by hydroxylating silicon carbide whiskers, grafting zwitterions and then loading nano boron nitride, the modified graphene is obtained by activating graphene oxide, coordinating the activated graphene oxide with ferric iron metal and then performing non-covalent grafting with a polyether chain; according to the coated aluminum sheet for PCB drilling, the modified silicon carbide whiskers and the modified graphene are added into the water-soluble resin coating adopted by the coating, and the performance of the coated aluminum sheet is comprehensively improved through structural complementation and function cooperation.

Description

Technical Field

[0001] This invention belongs to the field of PCB processing technology, specifically relating to a coated aluminum sheet for PCB drilling and its preparation method. Background Technology

[0002] With the rapid development of the electronics and information industry, PCBs (printed circuit boards) are evolving towards higher density, higher precision, and thinner profiles, with hole diameters continuously shrinking (reaching below 0.1mm). Drilling accuracy requirements have increased to ±0.01mm, placing higher demands on PCB drilling processes. In the PCB drilling process, aluminum sheets, used as cover plates, directly affect drilling accuracy, hole wall quality, and processing efficiency. Traditional aluminum sheets suffer from insufficient hardness, poor lubrication, and poor thermal conductivity, leading to defects such as coating peeling, rapid drill wear, and hole wall contamination during drilling, severely impacting PCB product quality and production efficiency.

[0003] Currently, coated aluminum sheets on the market generally suffer from problems such as a single filler modification scheme and insufficient performance synergy, making it difficult to simultaneously meet the comprehensive performance requirements of hardness, lubricity, thermal conductivity, and adhesion. Specifically, this manifests in the following aspects: (1) Single filler modification is insufficient to meet multiple performance requirements; (2) The interface bonding mechanism between the filler and the resin and substrate is imperfect; (3) The thermal conductivity network is discontinuous, resulting in prominent local overheating problems. Existing coated aluminum sheets for PCB drilling cannot meet the performance requirements of high hardness, low friction, high thermal conductivity, and strong adhesion due to limitations in filler modification schemes, weak interface bonding, and discontinuous thermal conductivity networks. There is an urgent need to develop coated aluminum sheets for PCB drilling to provide a reliable cover for high-precision PCB drilling. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a coated aluminum sheet for PCB drilling and its preparation method. The water-soluble resin coating used for the coating incorporates modified silicon carbide whiskers and modified graphene. Through structural complementarity and functional synergy, the hardness, wear resistance, and thermal conductivity of the coating are improved, thereby achieving a comprehensive improvement in the performance of the coated aluminum sheet.

[0005] The objective of this invention can be achieved through the following technical solutions: A coated aluminum sheet for PCB drilling includes an aluminum foil substrate and a water-soluble resin coating on the surface of the substrate. The water-soluble resin coating is obtained by spraying and curing a water-soluble resin coating. The water-soluble resin coating includes the following raw materials in parts by weight: 60-70 parts of water-based epoxy resin, 8-12 parts of crosslinking agent, 0.5-1 part of defoamer, 1-1.5 parts of leveling agent, 1-2 parts of wetting agent, 4-8 parts of modified silicon carbide whiskers, 1-3 parts of modified graphene, and 12-15 parts of deionized water. Modified silicon carbide whiskers are silicon carbide whiskers that have been hydroxylated, grafted with zwitterions, and then loaded with nano-boron nitride. The modified graphene is made by activating graphene oxide, coordinating it with trivalent iron metal, and then non-covalently grafting it with polyether chains.

[0006] Preferably, the waterborne epoxy resin is a water-soluble epoxy resin containing flexible hydrophilic chains obtained by reacting epoxy resin with polyethylene glycol.

[0007] Preferably, the crosslinking agent is an aqueous isocyanate crosslinking agent, the defoamer is an organosilicon defoamer, the leveling agent is an acrylate leveling agent, and the wetting agent is a polycarboxylate wetting and dispersing agent.

[0008] Preferably, the method for preparing modified silicon carbide whiskers includes the following steps: A1. Add silicon carbide whiskers to potassium hydroxide solution, stir and heat to 120°C, reflux for 1.5~2.5h, centrifuge and wash the precipitate with deionized water until the pH of the washing solution is 7, and vacuum dry to obtain activated silicon carbide whiskers. A2. Add activated silicon carbide whiskers to a mixture of ethanol and water and stir to disperse. Then add 3-(dimethylamino)propylmethacrylamide and 1,3-propanesulfonic acid lactone, stir evenly, heat in an oil bath to 60°C, stir and react for 3-5 hours. Centrifuge to separate, wash the precipitate 2-3 times with anhydrous ethanol and deionized water in turn, and vacuum dry to obtain zwitterionic grafted silicon carbide whiskers. A3. Add zwitterionic grafted silicon carbide whiskers to deionized water and ultrasonically disperse to obtain a uniform dispersion. Add hydroxylated boron nitride nanosheets to the dispersion and continue ultrasonication for 0.5-1.5 h. Then add 3-(methacryloyloxy)propyltrimethoxysilane, stir and heat to 55°C for 1-3 h, centrifuge, wash the precipitate 3-5 times with deionized water, and vacuum dry to obtain modified silicon carbide whiskers.

[0009] Preferably, the mass ratio of activated silicon carbide whiskers, 3-(dimethylamino)propylmethacrylamide, and 1,3-propanesulfonic acid lactone is 80:5~8:3~5, and the mass ratio of zwitterionic grafted silicon carbide whiskers, hydroxylated boron nitride nanosheets, and 3-(methacryloyloxy)propyltrimethoxysilane is 60:2~3:1.

[0010] Preferably, the method for preparing modified graphene includes the following steps: B1. Add graphene oxide to deionized water and ultrasonically disperse it to form a uniform dispersion. Slowly add ferric chloride solution to the graphene oxide dispersion while stirring. Then adjust the pH of the mixture to 6.0 with sodium hydroxide solution. Stir and react at 30°C for 1.5~2.5h to form a graphene metal complex. B2. Add polyethylene glycol monomethyl ether to the system, stir and heat to 50°C, react for 2-4 hours, add 3-glycidyl etheroxypropyltrimethoxysilane, raise the temperature to 65°C, continue stirring and react for 1.5-2.5 hours. After the reaction is completed, centrifuge and wash the precipitate 2-3 times with deionized water and anhydrous ethanol in sequence, and vacuum dry to obtain modified graphene.

[0011] Preferably, the mass ratio of graphene oxide, ferric chloride, polyethylene glycol monomethyl ether, and 3-glycidyl etheroxypropyltrimethoxysilane is 10:3:15:5.

[0012] A method for preparing a coated aluminum sheet for PCB drilling includes the following steps: S1. The aluminum foil is cleaned sequentially with sodium hydroxide solution and nitric acid solution to remove surface oil and oxide layer. Then, the aluminum foil is immersed in 2wt% 3-aminopropyltriethoxysilane solution for 8-10 minutes. The aluminum foil is then removed and placed in a forced-air drying oven to dry. S2. Add waterborne epoxy resin, deionized water, defoamer, leveling agent, wetting agent, modified silicon carbide whiskers, and modified graphene to a high-speed disperser in sequence, disperse at 2000 rpm for 20-40 min, slowly add crosslinking agent while stirring at 500 rpm, homogenize for 10-20 min, and finally pour into a ball mill and grind for 1-2 h to obtain water-soluble resin coating. S3. Use a slot coater to evenly coat the coating onto the pretreated aluminum foil surface, controlling the wet film thickness to be 30~40μm. Immediately send the coated aluminum sheet into a programmable oven, first heat to 80℃ and hold for 2~4 minutes, then heat to 120℃ and hold for 1~3 minutes, and finally heat to 180℃ and cure for 4~6 minutes to form a water-soluble resin coating. Cool and roll up to obtain the coated aluminum sheet for PCB drilling.

[0013] The beneficial effects of this invention are: This invention relates to a water-soluble resin coating for PCB drilling aluminum sheets, incorporating modified silicon carbide whiskers and modified graphene. Through structural complementarity and functional synergy, the coating's hardness, wear resistance, and thermal conductivity are improved, resulting in a comprehensive performance enhancement of the coated aluminum sheet. The rigid framework of the modified silicon carbide whiskers resists the mechanical impact of the drill bit, preventing direct wear of the coating. The interlayer slip of graphene and the polyethylene glycol monomethyl ether lubricating film reduce the frictional resistance between the drill bit and the coating, lowering the stress load on the modified silicon carbide whisker framework. Together, these elements achieve a balance between high hardness and wear resistance and low friction and reduced wear. The main network of modified silicon carbide whiskers and the supplementary network of modified graphene form a highly efficient thermal conductivity system, preventing overheating and coating carbonization. The dual anchoring of modified graphene ensures a tight bond between the coating and the substrate, preventing coating peeling caused by overheating.

[0014] This invention utilizes modified silicon carbide whiskers that undergo hydroxyl activation, zwitterionic grafting, and boron nitride nanosheet loading. With a one-dimensional whisker structure at its core, it provides rigid support and an efficient thermal conductivity pathway for the coating, which is fundamental to determining the coating's hardness, wear resistance, and thermal conductivity. The modified silicon carbide whiskers are distributed in a three-dimensional, interwoven pattern within an aqueous epoxy resin matrix, forming a rigid framework structure. On one hand, the silicon carbide whiskers themselves have a Mohs hardness of 9.5, directly resisting the mechanical impact during drill cutting. On the other hand, the zwitterionic graft layer forms strong hydrogen bonds with the resin matrix, and the boron nitride nanosheets are cross-linked with the silicon carbide whiskers and resin via KH570, preventing whisker-matrix interface delamination and further enhancing the coating's resistance to deformation. Meanwhile, the boron nitride nanosheets loaded on the modified silicon carbide crystal surface form a whisker-nanosheet composite thermally conductive unit with the silicon carbide crystal itself. The one-dimensional silicon carbide crystal acts as a thermally conductive channel to connect the dispersed boron nitride nanosheets, constructing a continuous thermally conductive network inside the coating. This rapidly conducts the localized heat generated by the friction between the drill bit and the coating during drilling to the entire coating, preventing heat concentration that could lead to coating carbonization and failure.

[0015] This invention modifies graphene using Fe 3+ Coordination, polyethylene glycol monomethyl ether grafting, and KH560 crosslinking, with a two-dimensional sheet-like structure as the core, focus on optimizing the coating's interfacial properties (adhesion, lubricity), while simultaneously enhancing the thermal conductivity network and improving the overall compatibility of the coating. The interfacial reinforcement effect of modified graphene comes from the dual anchoring of chemical coordination and covalent crosslinking, Fe... 3+ The graphene forms Fe-O-Al coordination bonds with oxygen atoms in the Al2O3 layer on the aluminum foil substrate surface, and simultaneously coordinates with oxygen-containing functional groups on the modified graphene surface, establishing a direct bond between graphene and the substrate. The terminal hydroxyl groups of the polyethylene glycol monomethyl ether grafted layer crosslink with the silanol groups generated by the hydrolysis of KH560, while the epoxy groups at the other end of KH560 react with the aqueous epoxy resin, forming a covalent bond between graphene and the resin matrix. This dual anchoring eliminates interfacial gaps between the coating and the substrate, and within the coating itself, preventing coating detachment due to mechanical vibration during drilling. Simultaneously, the flexible polyethylene glycol monomethyl ether chains grafted onto the modified graphene surface form a lubricating film on the coating surface. The two-dimensional graphene sheets themselves possess excellent interlayer slip characteristics; during drilling, the graphene sheets undergo interlayer slippage upon contact with the coating, and the polyethylene glycol monomethyl ether chains simultaneously undergo elastic deformation, transforming sliding friction into a composite friction mode of interlayer slippage and chain segment deformation. This significantly reduces the coefficient of friction and minimizes mechanical wear on the drill bit edge. Furthermore, the two-dimensional sheet structure of modified graphene can fill the gap regions in the one-dimensional thermally conductive network constructed by modified silicon carbide crystals. Although the three-dimensional interlaced distribution of silicon carbide crystals forms the main channels, there are still micron-level gaps. Graphene sheets can laterally cover these gaps to form a three-dimensional thermally conductive network with one-dimensional channels and two-dimensional coverage, reducing interfacial thermal resistance and further improving the overall thermal conductivity of the coating.

[0016] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 A modified silicon carbide whisker is obtained by hydroxylating silicon carbide whiskers, grafting zwitterions, and then loading boron nitride nanoparticles. The preparation method specifically includes the following steps: A1. Add 100g of silicon carbide whiskers to 500mL of 2mol / L potassium hydroxide solution, stir and heat to 120℃, reflux for 2h, centrifuge and wash the precipitate with deionized water until the pH of the washing solution is 7, and vacuum dry to obtain activated silicon carbide whiskers. A2. Add 80g of activated silicon carbide whiskers to a mixture of 400mL of ethanol and water (volume ratio 1:1) and stir to disperse. Then add 6.5g of 3-(dimethylamino)propylmethacrylamide and 4.0g of 1,3-propanesulfonic acid lactone, stir evenly, heat in an oil bath to 60℃, stir and react for 4h, centrifuge to separate, wash the precipitate 2-3 times with anhydrous ethanol and deionized water in turn, and vacuum dry to obtain zwitterionic grafted silicon carbide whiskers. A3. Add 60g of zwitterionic grafted silicon carbide whiskers to 300mL of deionized water and ultrasonically disperse to obtain a uniform dispersion. Add 2.5g of hydroxylated boron nitride nanosheets to the dispersion and continue ultrasonication for 1h. Then add 1g of 3-(methacryloyloxy)propyltrimethoxysilane, stir and heat to 55℃ for 2h, centrifuge, wash the precipitate 3-5 times with deionized water, and vacuum dry to obtain the modified silicon carbide whiskers.

[0019] Example 2 A modified graphene is prepared by activating graphene oxide, coordinating it with ferric metal, and then non-covalently grafting it with a polyether chain. The specific preparation method includes the following steps: B1. Add 10g of graphene oxide to 100mL of deionized water and ultrasonically disperse to form a uniform dispersion. Slowly add 38mL of 0.5mol / L ferric chloride solution to the graphene oxide dispersion while stirring. Then adjust the pH of the mixture to 6.0 with sodium hydroxide solution and stir at 30℃ for 2h to form a graphene metal complex. B2. Add 15g of polyethylene glycol monomethyl ether to the system, stir and heat to 50℃, react for 3h, add 5g of 3-glycidyl etheroxypropyltrimethoxysilane, raise the temperature to 65℃, continue stirring and react for 2h, after the reaction is completed, centrifuge and wash the precipitate 2-3 times with deionized water and anhydrous ethanol in sequence, and vacuum dry to obtain modified graphene.

[0020] Example 3 A coated aluminum sheet for PCB drilling includes an aluminum foil substrate and a water-soluble resin coating on the surface of the substrate. The water-soluble resin coating is obtained by spraying and curing a water-soluble resin coating. The water-soluble resin coating includes the following raw materials in parts by weight: 60 parts of water-based epoxy resin, 12 parts of crosslinking agent, 0.5 parts of defoamer, 1.5 parts of leveling agent, 1 part of wetting agent, 8 parts of modified silicon carbide whiskers, 1 part of modified graphene, and 15 parts of deionized water. The modified silicon carbide whiskers were prepared in Example 1, the modified graphene was prepared in Example 2, the waterborne epoxy resin was obtained by reacting epoxy resin with polyethylene glycol to obtain a water-soluble epoxy resin containing flexible hydrophilic chains, the crosslinking agent was a waterborne isocyanate crosslinking agent, the defoamer was an organosilicon defoamer, the leveling agent was an acrylate leveling agent, and the wetting agent was a polycarboxylate wetting and dispersing agent.

[0021] The above-mentioned method for preparing coated aluminum sheets for PCB drilling includes the following steps: S1. The aluminum foil is cleaned sequentially with sodium hydroxide solution and nitric acid solution to remove surface oil and oxide layer. Then, the aluminum foil is immersed in 2wt% 3-aminopropyltriethoxysilane solution for 8 minutes. The aluminum foil is then removed and placed in a forced-air drying oven to dry. S2. Add waterborne epoxy resin, deionized water, defoamer, leveling agent, wetting agent, modified silicon carbide whiskers, and modified graphene to a high-speed disperser in sequence, disperse at 2000 rpm for 40 min, slowly add crosslinking agent under low-speed stirring at 500 rpm, homogenize for 10 min, and finally pour into a ball mill and grind for 2 h to obtain water-soluble resin coating. S3. Use a slot coater to evenly coat the coating onto the pretreated aluminum foil surface, controlling the wet film thickness to 30μm. Immediately send the coated aluminum sheet into a programmable oven, first heat to 80℃ and hold for 4 minutes, then heat to 120℃ and hold for 1 minute, and finally heat to 180℃ and cure for 6 minutes to form a water-soluble resin coating. Cool and roll up to obtain a coated aluminum sheet for PCB drilling.

[0022] Example 4 A coated aluminum sheet for PCB drilling includes an aluminum foil substrate and a water-soluble resin coating on the surface of the substrate. The water-soluble resin coating is obtained by spraying and curing a water-soluble resin coating. The water-soluble resin coating includes the following raw materials in parts by weight: 70 parts of water-based epoxy resin, 8 parts of crosslinking agent, 1 part of defoamer, 1 part of leveling agent, 2 parts of wetting agent, 4 parts of modified silicon carbide whiskers, 3 parts of modified graphene, and 12 parts of deionized water. The modified silicon carbide whiskers were prepared in Example 1, the modified graphene was prepared in Example 2, the waterborne epoxy resin was obtained by reacting epoxy resin with polyethylene glycol to obtain a water-soluble epoxy resin containing flexible hydrophilic chains, the crosslinking agent was a waterborne isocyanate crosslinking agent, the defoamer was an organosilicon defoamer, the leveling agent was an acrylate leveling agent, and the wetting agent was a polycarboxylate wetting and dispersing agent.

[0023] The above-mentioned method for preparing coated aluminum sheets for PCB drilling includes the following steps: S1. The aluminum foil is cleaned sequentially with sodium hydroxide solution and nitric acid solution to remove surface oil and oxide layer. Then, the aluminum foil is immersed in 2wt% 3-aminopropyltriethoxysilane solution for 10 minutes. The aluminum foil is then removed and placed in a forced-air drying oven to dry. S2. Add waterborne epoxy resin, deionized water, defoamer, leveling agent, wetting agent, modified silicon carbide whiskers, and modified graphene to a high-speed disperser in sequence, disperse at 2000 rpm for 20 min, slowly add crosslinking agent while stirring at 500 rpm, homogenize for 20 min, and finally pour into a ball mill and grind for 1 h to obtain water-soluble resin coating. S3. Use a slot coater to evenly coat the coating onto the pretreated aluminum foil surface, controlling the wet film thickness to 40μm. Immediately send the coated aluminum sheet into a programmable oven, first heat to 80℃ and hold for 2 minutes, then heat to 120℃ and hold for 3 minutes, and finally heat to 180℃ and cure for 4 minutes to form a water-soluble resin coating. Cool and roll up to obtain a coated aluminum sheet for PCB drilling.

[0024] Example 5 A coated aluminum sheet for PCB drilling includes an aluminum foil substrate and a water-soluble resin coating on the surface of the substrate. The water-soluble resin coating is obtained by spraying and curing a water-soluble resin paint. The water-soluble resin paint includes the following raw materials in parts by weight: 65 parts of water-based epoxy resin, 10 parts of crosslinking agent, 0.8 parts of defoamer, 1.2 parts of leveling agent, 1.5 parts of wetting agent, 6 parts of modified silicon carbide whiskers, 2 parts of modified graphene, and 13.5 parts of deionized water. The modified silicon carbide whiskers were prepared in Example 1, the modified graphene was prepared in Example 2, the waterborne epoxy resin was obtained by reacting epoxy resin with polyethylene glycol to obtain a water-soluble epoxy resin containing flexible hydrophilic chains, the crosslinking agent was a waterborne isocyanate crosslinking agent, the defoamer was an organosilicon defoamer, the leveling agent was an acrylate leveling agent, and the wetting agent was a polycarboxylate wetting and dispersing agent.

[0025] The above-mentioned method for preparing coated aluminum sheets for PCB drilling includes the following steps: S1. The aluminum foil is cleaned sequentially with sodium hydroxide solution and nitric acid solution to remove surface oil and oxide layer. Then, the aluminum foil is immersed in 2wt% 3-aminopropyltriethoxysilane solution for 9 minutes. The aluminum foil is then removed and placed in a forced-air drying oven to dry. S2. Add waterborne epoxy resin, deionized water, defoamer, leveling agent, wetting agent, modified silicon carbide whiskers, and modified graphene to a high-speed disperser in sequence, disperse at 2000 rpm for 30 min, slowly add crosslinking agent while stirring at 500 rpm, homogenize for 15 min, and finally pour into a ball mill and grind for 1.5 h to obtain water-soluble resin coating. S3. Use a slot coater to evenly coat the coating onto the pretreated aluminum foil surface, controlling the wet film thickness to 35μm. Immediately send the coated aluminum sheet into a programmable oven, first heat to 80℃ and hold for 3 minutes, then heat to 120℃ and hold for 2 minutes, and finally heat to 180℃ and cure for 5 minutes to form a water-soluble resin coating. Cool and roll up to obtain a coated aluminum sheet for PCB drilling.

[0026] Comparative Example 1 A coated aluminum sheet for PCB drilling includes an aluminum foil substrate and a water-soluble resin coating on the surface of the substrate. The water-soluble resin coating is obtained by spraying and curing a water-soluble resin paint. The water-soluble resin paint includes the following raw materials in parts by weight: 65 parts of water-based epoxy resin, 10 parts of crosslinking agent, 0.8 parts of defoamer, 1.2 parts of leveling agent, 1.5 parts of wetting agent, 2 parts of modified graphene, and 13.5 parts of deionized water. The modified graphene was prepared in Example 2. The waterborne epoxy resin was obtained by reacting epoxy resin with polyethylene glycol to obtain a water-soluble epoxy resin containing flexible hydrophilic chains. The crosslinking agent was a waterborne isocyanate crosslinking agent. The defoamer was an organosilicon defoamer. The leveling agent was an acrylate leveling agent. The wetting agent was a polycarboxylate wetting and dispersing agent.

[0027] The above-mentioned method for preparing coated aluminum sheets for PCB drilling includes the following steps: S1. The aluminum foil is cleaned sequentially with sodium hydroxide solution and nitric acid solution to remove surface oil and oxide layer. Then, the aluminum foil is immersed in 2wt% 3-aminopropyltriethoxysilane solution for 9 minutes. The aluminum foil is then removed and placed in a forced-air drying oven to dry. S2. Add waterborne epoxy resin, deionized water, defoamer, leveling agent, wetting agent, and modified graphene to a high-speed disperser in sequence. Disperse at 2000 rpm for 30 min. Add crosslinking agent slowly while stirring at 500 rpm. Homogenize for 15 min. Finally, pour into a ball mill and grind for 1.5 h to obtain water-soluble resin coating. S3. Use a slot coater to evenly coat the coating onto the pretreated aluminum foil surface, controlling the wet film thickness to 35μm. Immediately send the coated aluminum sheet into a programmable oven, first heat to 80℃ and hold for 3 minutes, then heat to 120℃ and hold for 2 minutes, and finally heat to 180℃ and cure for 5 minutes to form a water-soluble resin coating. Cool and roll up to obtain a coated aluminum sheet for PCB drilling.

[0028] Comparative Example 2 A coated aluminum sheet for PCB drilling includes an aluminum foil substrate and a water-soluble resin coating on the surface of the substrate. The water-soluble resin coating is obtained by spraying and curing a water-soluble resin coating. The water-soluble resin coating includes the following raw materials in parts by weight: 65 parts of water-based epoxy resin, 10 parts of crosslinking agent, 0.8 parts of defoamer, 1.2 parts of leveling agent, 1.5 parts of wetting agent, 6 parts of modified silicon carbide whiskers, and 13.5 parts of deionized water. The modified silicon carbide whiskers were prepared in Example 1. The waterborne epoxy resin was obtained by reacting epoxy resin with polyethylene glycol to obtain a water-soluble epoxy resin containing flexible hydrophilic chains. The crosslinking agent was a waterborne isocyanate crosslinking agent. The defoamer was an organosilicon defoamer. The leveling agent was an acrylate leveling agent. The wetting agent was a polycarboxylate wetting and dispersing agent.

[0029] The above-mentioned method for preparing coated aluminum sheets for PCB drilling includes the following steps: S1. The aluminum foil is cleaned sequentially with sodium hydroxide solution and nitric acid solution to remove surface oil and oxide layer. Then, the aluminum foil is immersed in 2wt% 3-aminopropyltriethoxysilane solution for 9 minutes. The aluminum foil is then removed and placed in a forced-air drying oven to dry. S2. Add waterborne epoxy resin, deionized water, defoamer, leveling agent, wetting agent, and modified silicon carbide whiskers to a high-speed disperser in sequence, disperse at 2000 rpm for 30 min, slowly add crosslinking agent while stirring at 500 rpm, homogenize for 15 min, and finally pour into a ball mill and grind for 1.5 h to obtain water-soluble resin coating. S3. Use a slot coater to evenly coat the coating onto the pretreated aluminum foil surface, controlling the wet film thickness to 35μm. Immediately send the coated aluminum sheet into a programmable oven, first heat to 80℃ and hold for 3 minutes, then heat to 120℃ and hold for 2 minutes, and finally heat to 180℃ and cure for 5 minutes to form a water-soluble resin coating. Cool and roll up to obtain a coated aluminum sheet for PCB drilling.

[0030] Performance testing The coated aluminum sheets for PCB drilling prepared in Example 4, Comparative Example 1, and Comparative Example 2 were uniformly cut into 50mm×50mm samples, and the following performance tests were performed on them respectively: (1) Coating thickness: Using an eddy current thickness gauge (accuracy ±1μm), 10 points were randomly measured and the average value was taken; (2) Pencil hardness: According to GB / T6739-2022, use a 45° angle pencil hardness tester and apply a force of 1000g to scratch; (3) Adhesion: According to GB / T9286-1998, after dividing the grid with a cross-cutting tool (1mm spacing), test with 3M tape, and rate from 0 to 5 (0 is the best). (4) Friction coefficient: A reciprocating friction testing machine (load 5N, speed 50mm / s) was used, and the mating part was a carbide drill bit (WC-Co). (5) Thermal conductivity: According to ASTM D5470, the hot wire method tester was used (accuracy ±5%). (6) Drilling performance: Drill holes continuously (φ0.3mm, theoretical maximum number of holes about 25, to avoid aluminum foil area limitation) on a PCB CNC drilling machine (speed 30000rpm, feed speed 50mm / min). Stop the machine after drilling 5 holes and check. If any of the following conditions are met, the coating is judged to be in failure. Record the "cumulative effective number of holes" (total number of holes before failure) at this time: ① Coating integrity: Observe the area around the drill hole using a 20x microscope. If the area of ​​coating peeling is ≥0.5mm... 2 Or the coating may expose the substrate (the natural aluminum color is exposed); ② Drill bit condition: Weigh the drill bit with an electronic balance (accuracy 0.1mg). If the drill bit wear after a single drilling operation is ≥0.5mg (drill bit wear caused by aluminum powder / coating adhesion), or if obvious aluminum chips are observed on the drill bit cutting edge under a microscope; ③ Hole wall quality: Measure the hole diameter with a hole gauge (accuracy 0.001mm). If the hole diameter deviation is ≥0.02mm (caused by coating debris clogging the hole wall or substrate deformation), or if cross-section observation shows aluminum powder / coating residue ≥50μm on the hole wall, After drilling, the hole walls were wiped with isopropanol, and the aluminum content in the wiping fluid was detected by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0031] The obtained data is shown in Table 1 below.

[0032] Table 1 Performance test of coated aluminum sheet used for PCB drilling

[0033] As shown in Table 1, the pencil hardness of Example 4 reached 5H, significantly higher than that of Comparative Example 1 (3H) and Comparative Example 2 (4H). This indicates that the rigid framework of the modified silicon carbide whiskers plays a dominant role in improving hardness, while the modified graphene assists in reducing the coefficient of friction (0.14) through interlayer slip. Both work synergistically to extend drilling life. Comparative Example 1, lacking modified silicon carbide whiskers, had insufficient coating resistance to deformation, resulting in the most significant decrease in hardness and drilling life.

[0034] Example 4 showed an adhesion grade of 0, which was superior to the two comparative examples (grade 1), attributed to the Fe of the modified graphene. 3+ - The coordination of Al2O3 and the covalent anchoring of KH560, while the lack of interface reinforcement of modified graphene in Comparative Example 1 and the lack of physical anchoring of silicon carbide whiskers in Comparative Example 2 both resulted in decreased adhesion.

[0035] Example 4 showed a thermal conductivity (1.72 W / (m·K)) that was twice that of Comparative Example 1 and 1.4 times that of Comparative Example 2, confirming that the continuous thermally conductive network constructed by modified silicon carbide whiskers and modified graphene can effectively reduce interfacial thermal resistance. However, a single filler is difficult to form an efficient pathway. Comparative Example 1 lacked modified silicon carbide whiskers, resulting in a broken thermally conductive network. Comparative Example 2 lacked modified graphene, resulting in insufficient interfacial contact area.

[0036] Example 4 demonstrates significant advantages in drilling performance. This is because the modified silicon carbide whiskers (rigid framework) enhance the coating's wear resistance, preventing rapid coating wear and exposure of the substrate during drilling. The modified graphene interlayer slip and thermal conductivity network reduce the friction coefficient between the drill bit and the coating (reducing drill bit wear) while rapidly dissipating drilling heat (preventing coating carbonization and detachment). Therefore, only slight coating exposure to the substrate occurs after 22 holes, with minimal drill bit wear and hole wall residue. Comparative Example 1 exhibits the worst performance, lacking the rigid support of modified silicon carbide whiskers. Its coating hardness is only 3H, making it easily worn down by the drill bit during drilling. Large-area coating detachment occurs after 10 holes, leading to aluminum powder directly adhering to the drill bit (wear amount reaching 2.3 mg). Simultaneously, aluminum powder clogs the hole walls, resulting in a hole diameter deviation exceeding the standard of 0.035 mm (far exceeding the PCB requirement of ≤0.02 mm). Comparative Example 2 had moderate performance. Although modified silicon carbide whiskers improved hardness (4H), it lacked the lubrication and thermal conductivity of modified graphene. The friction coefficient between the drill bit and the coating was relatively high (0.18). After 16 holes, the wear of the drill bit reached 1.5 mg. Furthermore, local overheating caused slight carbonization of the coating. The residual aluminum content on the hole wall (0.5 mg / L) was higher than that of Example 4, demonstrating that a single filler cannot meet the synergistic requirements of "wear resistance + friction reduction + thermal conductivity".

[0037] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A coated aluminum sheet for PCB drilling, characterized in that, The invention includes an aluminum foil substrate and a water-soluble resin coating on the surface of the substrate. The water-soluble resin coating is obtained by spraying and curing a water-soluble resin paint. The water-soluble resin paint comprises the following raw materials in parts by weight: 60-70 parts of water-based epoxy resin, 8-12 parts of crosslinking agent, 0.5-1 part of defoamer, 1-1.5 parts of leveling agent, 1-2 parts of wetting agent, 4-8 parts of modified silicon carbide whiskers, 1-3 parts of modified graphene, and 12-15 parts of deionized water. The modified silicon carbide whiskers are silicon carbide whiskers that have been hydroxylated, grafted with zwitterions, and then loaded with nano-boron nitride. The modified graphene is obtained by activating graphene oxide, coordinating it with trivalent iron metal, and then non-covalently grafting it with polyether chains.

2. The coated aluminum sheet for PCB drilling according to claim 1, characterized in that, The waterborne epoxy resin is a water-soluble epoxy resin containing flexible hydrophilic chains obtained by reacting epoxy resin with polyethylene glycol.

3. The coated aluminum sheet for PCB drilling according to claim 1, characterized in that, The crosslinking agent is an aqueous isocyanate crosslinking agent, the defoamer is an organosilicon defoamer, the leveling agent is an acrylate leveling agent, and the wetting agent is a polycarboxylate wetting and dispersing agent.

4. The coated aluminum sheet for PCB drilling according to claim 1, characterized in that, The method for preparing the modified silicon carbide whiskers includes the following steps: A1. Add silicon carbide whiskers to potassium hydroxide solution, stir and heat to 120°C, reflux for 1.5~2.5h, centrifuge and wash the precipitate with deionized water until the pH of the washing solution is 7, and vacuum dry to obtain activated silicon carbide whiskers. A2. Add activated silicon carbide whiskers to a mixture of ethanol and water and stir to disperse. Then add 3-(dimethylamino)propylmethacrylamide and 1,3-propanesulfonic acid lactone, stir evenly, heat in an oil bath to 60°C, stir and react for 3-5 hours. Centrifuge to separate, wash the precipitate 2-3 times with anhydrous ethanol and deionized water in turn, and vacuum dry to obtain zwitterionic grafted silicon carbide whiskers. A3. Add zwitterionic grafted silicon carbide whiskers to deionized water and ultrasonically disperse to obtain a uniform dispersion. Add hydroxylated boron nitride nanosheets to the dispersion and continue ultrasonication for 0.5-1.5 h. Then add 3-(methacryloyloxy)propyltrimethoxysilane, stir and heat to 55°C for 1-3 h, centrifuge, wash the precipitate 3-5 times with deionized water, and vacuum dry to obtain the modified silicon carbide whiskers.

5. The coated aluminum sheet for PCB drilling according to claim 4, characterized in that, The mass ratio of the activated silicon carbide whiskers, 3-(dimethylamino)propylmethacrylamide, and 1,3-propanesulfonic acid lactone is 80:5~8:3~5, and the mass ratio of the zwitterionic grafted silicon carbide whiskers, hydroxylated boron nitride nanosheets, and 3-(methacryloyloxy)propyltrimethoxysilane is 60:2~3:

1.

6. The coated aluminum sheet for PCB drilling according to claim 1, characterized in that, The method for preparing the modified graphene includes the following steps: B1. Add graphene oxide to deionized water and ultrasonically disperse it to form a uniform dispersion. Slowly add ferric chloride solution to the graphene oxide dispersion while stirring. Then adjust the pH of the mixture to 6.0 with sodium hydroxide solution. Stir and react at 30°C for 1.5~2.5h to form a graphene metal complex. B2. Add polyethylene glycol monomethyl ether to the system, stir and heat to 50°C, react for 2-4 hours, add 3-glycidyl etheroxypropyltrimethoxysilane, raise the temperature to 65°C, continue stirring and react for 1.5-2.5 hours. After the reaction is completed, centrifuge and wash the precipitate 2-3 times with deionized water and anhydrous ethanol in sequence, and vacuum dry to obtain modified graphene.

7. The coated aluminum sheet for PCB drilling according to claim 6, characterized in that, The mass ratio of graphene oxide, ferric chloride, polyethylene glycol monomethyl ether, and 3-glycidyl etheroxypropyltrimethoxysilane is 10:3:15:

5.

8. A method for preparing a coated aluminum sheet for PCB drilling as described in claims 1-7, characterized in that, Includes the following steps: S1. The aluminum foil is cleaned sequentially with sodium hydroxide solution and nitric acid solution to remove surface oil and oxide layer. Then, the aluminum foil is immersed in 2wt% 3-aminopropyltriethoxysilane solution for 8-10 minutes. The aluminum foil is then removed and placed in a forced-air drying oven to dry. S2. Add waterborne epoxy resin, deionized water, defoamer, leveling agent, wetting agent, modified silicon carbide whiskers, and modified graphene to a high-speed disperser in sequence, disperse at 2000 rpm for 20-40 min, slowly add crosslinking agent while stirring at 500 rpm, homogenize for 10-20 min, and finally pour into a ball mill and grind for 1-2 h to obtain water-soluble resin coating. S3. Use a slot coater to evenly coat the coating onto the pretreated aluminum foil surface, controlling the wet film thickness to be 30~40μm. Immediately send the coated aluminum sheet into a programmable oven, first heat to 80℃ and hold for 2~4 minutes, then heat to 120℃ and hold for 1~3 minutes, and finally heat to 180℃ and cure for 4~6 minutes to form a water-soluble resin coating. Cool and roll up to obtain the coated aluminum sheet for PCB drilling.

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