A water-soluble coated aluminum sheet for PCB drilling of M9 material and a preparation method thereof

Abstract

The present application belongs to the technical field of water-soluble coated aluminum sheet, and particularly relates to a water-soluble coated aluminum sheet for PCB drilling of M9 material and a preparation method thereof. The water-soluble coated aluminum sheet for PCB drilling of M9 material comprises an aluminum sheet and a water-soluble coating; the water-soluble coating is formed by coating water-soluble paint on the surface of the aluminum sheet; the water-soluble paint comprises the following components in parts by weight: water-soluble resin 50-100 parts, modified filler 1-15 parts, curing agent 5-20 parts, and auxiliary agent 0.1-3 parts; the water-soluble resin comprises modified epoxy resin and polyurethane resin; and the modified filler comprises at least one of modified carbon nanotube and modified wollastonite. The water-soluble coated aluminum sheet of the present application systematically realizes the synergistic beneficial effects of drill bit protection, efficient heat dissipation, silk entanglement inhibition, easy cleaning, firm coating and the like through the interaction between the components, and effectively solves the problems of reduced service life of the drill bit and reduced drilling accuracy.

Description

Technical Field

[0001] This invention belongs to the field of water-soluble coated aluminum sheet technology, specifically relating to a water-soluble coated aluminum sheet for drilling M9 material PCBs and its preparation method. Background Technology

[0002] PCBs are widely used in medical equipment, industrial equipment, communication equipment, automotive electronics, and home appliances. The drilling process is crucial in PCB manufacturing. To protect the PCB substrate and improve drilling quality, a cover plate is often placed on the copper-clad laminate being processed; this plate is called a "cover plate." Cover plate materials mainly include phenolic resin boards, epoxy glass cloth boards, ordinary aluminum foil boards, and resin-coated aluminum-based cover plates. Among these, resin-coated aluminum-based cover plates have many unique advantages compared to other cover plates. They not only effectively improve the quality of the drilled holes and extend the life of the drill bit, but can also be used in drilling operations that increase the number of stacked boards, greatly improving drilling efficiency.

[0003] M9 material is an ultra-low loss copper-clad laminate designed specifically for next-generation AI servers and high-speed network equipment (such as 1.6T switches). Its core lies in a fundamental restructuring of the material system to meet the extreme requirements for signal integrity at transmission rates of 224Gbps and even higher. To achieve extremely low dielectric constant (Dk) and dielectric loss (Df), M9 material abandons the traditional FR-4 epoxy resin and E-glass fiber cloth system, instead using a special hydrocarbon resin as the main body and introducing high-purity quartz glass fiber cloth (Q-glass) as a reinforcing material. This ensures low signal attenuation while achieving a lower coefficient of thermal expansion (CTE) to match the mechanical and thermal stability requirements of high-performance chips. However, this composite structure optimized for high-frequency performance also brings unprecedented processing challenges: the high hardness of the quartz fiber and the high toughness of the resin system mean that traditional mechanical drilling processes face severe challenges, including a drastic reduction in drill bit life (from thousands of holes to about 200 holes), a surge in the risk of drill bit breakage, and difficulty in controlling hole position accuracy.

[0004] Therefore, there is an urgent need to develop a water-soluble coated aluminum sheet cover plate that can effectively solve problems such as reduced drill bit life and decreased drilling accuracy, specifically targeting the characteristics of M9 material. Summary of the Invention

[0005] To address at least one deficiency in existing technologies, this invention aims to provide a water-soluble coated aluminum sheet specifically for drilling M9 material PCBs and its preparation method. The water-soluble coated aluminum sheet of this invention can systematically achieve six synergistic beneficial effects—precise guidance, drill bit protection, efficient heat dissipation, suppression of wire entanglement, easy cleaning, and strong coating—through the interaction between specific components.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a water-soluble coated aluminum sheet for drilling M9 material PCBs, comprising an aluminum sheet and a water-soluble coating; the water-soluble coating is formed by coating the surface of the aluminum sheet with a water-soluble paint. The water-soluble coating comprises the following components in parts by weight: 50-100 parts water-soluble resin, 1-15 parts modified filler, 5-20 parts curing agent, and 0.1-3 parts additives; The water-soluble resin includes modified epoxy resin and polyurethane resin; The modified filler includes at least one of modified carbon nanotubes and modified wollastonite.

[0007] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the mass ratio of the modified epoxy resin to the polyurethane resin is (1~3):1.

[0008] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the weight-average molecular weight of the modified epoxy resin is 2000~8000 Da.

[0009] In the water-soluble coating of this invention, when the weight-average molecular weight of the modified epoxy resin is below 2,000 Da, the crosslinking density is low, the coating hardness is insufficient, making it difficult to meet the drilling guidance requirements, and the curing shrinkage rate is large, which may lead to stress concentration or cracking in the coating. Conversely, when the weight-average molecular weight of the modified epoxy resin is above 8,000 Da, the viscosity of the coating system of this invention is too high, which is not conducive to coating and leveling, and may lead to poor compatibility with other components in the water-soluble coating, resulting in reduced reactivity and incomplete curing. Selecting a modified epoxy resin with a weight-average molecular weight of 2,000 to 8,000 Da not only maintains a high epoxy group content, ensuring sufficient crosslinking with the curing agent, but also achieves good compatibility with modified fillers and other components, effectively balancing coating hardness, adhesion, and other properties, making it suitable for M9 materials.

[0010] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the molecular weight of the polyurethane resin is 20,000 to 40,000 Da.

[0011] In the water-soluble coating of the present invention, the selected polyurethane resin has a molecular weight that is too low (Mn). <20000 Da) The resulting film is prone to insufficient skeleton strength, affecting the overall mechanical properties of the coating. Furthermore, when combined with modified epoxy resin, macroscopic phase separation easily occurs, leading to decreased impact resistance of the final coated aluminum sheet and easy cracking during drilling. Conversely, when the molecular weight of the polyurethane resin is too high (Mn > 10000 Da), it is prone to problems such as insufficient skeleton strength after film formation, affecting the overall mechanical properties of the coating. (40000 Da) The viscosity of the formulation system is too high, making coating difficult and leveling poor. At the same time, it is easy to cause problems such as decreased compatibility with modified epoxy resin, weak interfacial bonding between the two phases, and narrowing of the processing window.

[0012] In this invention, the weight-average molecular weight of the modified epoxy is controlled at 2000~8000 Da and the number-average molecular weight of the polyurethane is controlled at 20000~40000 Da, which helps to form an interpenetrating polymer network and provides the coating system in this invention with the best balance of hardness, flexibility, adhesion and processability, effectively improving the overall performance.

[0013] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the curing agent may be 810 or polyamide 650.

[0014] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the additives include defoamers and leveling agents.

[0015] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the additives include the following components in parts by weight: 0.1 to 1.5 parts of defoamer and 0.5 to 1.5 parts of leveling agent.

[0016] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the defoamer includes at least one of organosilicon, non-silicone polymer, mineral oil, and polyacrylate defoamers.

[0017] In a preferred embodiment of the water-soluble coated aluminum sheet of the present invention, the defoamer may be at least one of BYK-066N, BYK-066, BYK-141, Tego Airex 900, BYK-354, BYK-052, and Tego Foamex N.

[0018] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the leveling agent includes at least one of silicone leveling agents, polyacrylate leveling agents, and fluorocarbon modified leveling agents.

[0019] In a preferred embodiment of the water-soluble coated aluminum sheet of the present invention, the leveling agent may be at least one of BYK-354, BYK-307, BYK-333, Tego Glide 450, BYK-361N, Modarez, and Eface IF-2066.

[0020] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the preparation method of the modified epoxy resin includes the following steps: mixing epoxy resin with surfactant, stirring, stirring in an oil bath, and distilling under reduced pressure to obtain the modified epoxy resin.

[0021] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the molar ratio of the epoxy resin to the surfactant is (2~5):1.

[0022] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the surfactant is γ-aminopropyltrimethoxysilane (γ-APS).

[0023] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the stirring time is 1-3 hours.

[0024] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the oil bath stirring is carried out in an oil bath at 60~80℃ for 1~3 hours.

[0025] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the modified filler includes modified carbon nanotubes and modified wollastonite.

[0026] In the water-soluble coating of this invention, modified carbon nanotubes and modified wollastonite are selected as modified filler components. The diameter of the modified wollastonite is at the micrometer level, which can serve as a micrometer-level skeleton in the formulation system, providing macroscopic mechanical support and impact resistance. At the same time, the modified carbon nanotubes with a diameter at the nanometer level can further fill the molecular gaps between the formulation components to form a "dual-scale" network, providing nanoscale reinforcement and thermal conductivity network for the water-soluble coating system, improving the dimensional stability under high drilling temperatures, the hardness of the coating, and the wear resistance. In addition, the modified wollastonite and modified carbon nanotubes work together to form thermal conductivity channels in the component system, which can further assist in heat dissipation and reduce the risk of burrs and other defects caused by insufficient heat dissipation during drilling.

[0027] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the preparation method of the modified carbon nanotubes includes the following steps: adding carbon nanotubes and tannic acid to deionized water, stirring, so that the tannic acid is fully adsorbed onto the surface of the carbon nanotubes through π-π stacking, ultrasonically dispersing to promote uniform coating of tannic acid on the surface of the carbon nanotubes, solid-liquid separation, washing to remove unreacted free tannic acid, vacuum drying to obtain modified carbon nanotubes.

[0028] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the mass ratio of the modified carbon nanotubes to the modified wollastonite is (5~20):1.

[0029] In this invention, when the mass ratio of modified carbon nanotubes to modified wollastonite is too high, the content of modified carbon nanotubes in the coating component system is relatively low. Although the cost is lower and the hardness is sufficient, the thermal conductivity of the coating will decrease, the flexibility will weaken, the impact resistance may decrease, and the coating will be prone to brittle cracking. When the mass ratio of the two is too low, the wollastonite "skeleton" is insufficient, the coating rigidity is insufficient, the guiding performance under drilling pressure may deteriorate, the cost will increase significantly, the resin viscosity will increase, which is not conducive to coating leveling, and the resulting water-soluble coating cannot meet the requirements of M9 material well.

[0030] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the carbon nanotubes are multi-walled carbon nanotubes.

[0031] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the mass ratio of the carbon nanotubes to the tannic acid is (1~3):(0.1~0.8).

[0032] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the stirring time is 1 to 2 hours.

[0033] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the ultrasonic dispersion time is 30-50 minutes.

[0034] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the washing involves repeatedly washing with deionized water 3 to 5 times.

[0035] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the vacuum drying temperature is 60~80℃ and the time is 10~15 h.

[0036] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the preparation method of the modified wollastonite includes the following steps: dissolving a silane coupling agent, hydrolyzing it, spraying it onto wollastonite, stirring, drying, grinding and sieving to obtain the modified wollastonite.

[0037] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the wollastonite is 800~1500 mesh fibrous or acicular wollastonite.

[0038] In this invention, 800-1500 mesh wollastonite (aspect ratio 8-15:1) is selected, which can form a perfect complementary reinforcement with nanoscale carbon nanotubes (diameter ~20nm). At the same time, it can retain the reinforcing skeleton function of the fiber and be well dispersed in the coating, further improving the reinforcing effect and thermal conductivity of wollastonite in the coating.

[0039] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the amount of silane coupling agent added is 0.5-3% of the mass of wollastonite.

[0040] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the silane coupling agent includes γ-aminopropyltrimethoxysilane.

[0041] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the solvent used for dissolution is an ethanol / water mixture.

[0042] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the volume ratio of ethanol to water in the ethanol / water mixture is 9:1.

[0043] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the hydrolysis time is 5-10 minutes.

[0044] In one embodiment of the water-soluble coated aluminum sheet of the present invention, the stirring is carried out at 60~80°C for 1-2 hours.

[0045] As one embodiment of the water-soluble coated aluminum sheet of the present invention, the drying is performed at 100-120°C for 1-2 hours.

[0046] This invention also claims protection for a method for preparing the water-soluble coated aluminum sheet, comprising the following steps: S1. Preparation of water-soluble coating: Modified epoxy resin and modified filler are mixed and stirred, polyurethane resin is added, stirring is continued, additives are added, mixed evenly, and vacuum degassing is performed to obtain the water-soluble coating. S2. Apply the water-soluble coating onto the aluminum sheet and dry it to obtain the water-soluble coated aluminum sheet.

[0047] In one embodiment of the method for preparing the water-soluble coated aluminum sheet, the mixing and stirring time is 30-80 min.

[0048] In one embodiment of the method for preparing the water-soluble coated aluminum sheet, the stirring time is 15-30 minutes.

[0049] In one embodiment of the method for preparing the water-soluble coated aluminum sheet, the wet film thickness of the water-soluble coating is 30-50 μm.

[0050] In one embodiment of the method for preparing the water-soluble coated aluminum sheet, the drying temperature is 60~80℃ and the time is 5~30min.

[0051] Compared with the prior art, the present invention has the following beneficial effects: The water-soluble coating of this invention uses an epoxy-polyurethane composite resin to provide moderate hardness to suppress drill bit slippage and improve hole position accuracy. The flexible polyurethane component buffers impact loads and reduces drill bit wear. Modified carbon nanotubes and modified wollastonite are added to the formulation system to construct a "nano + micro" dual-scale reinforcing network, which synergistically improves the thermal conductivity and heat dissipation capacity of the coating, reduces the temperature in the drilling area, and suppresses drill bit thermal deformation. At the same time, the cross-linked network constructed by the water-soluble resin, modified filler, curing agent and other components at room temperature makes the coating tend to be discharged as powder during cutting, reducing the risk of wire entanglement from the source. The resulting coating has excellent adhesion to the aluminum substrate and can effectively ensure firm adhesion and non-peeling under high-speed rotation and high-temperature impact.

[0052] The water-soluble coating formulation of this invention forms a synergistic mechanism of "rigid guidance + flexible buffer + multi-level reinforcement + chemical anchoring" through the interaction between the components, systematically addressing the processing challenges brought by the high hardness and high cutting resistance of M9 material, and significantly improving drilling quality and processing efficiency. Detailed Implementation

[0053] 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.

[0054] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0055] Example 1

[0056] A water-soluble coated aluminum sheet for drilling M9 material PCBs includes an aluminum sheet and a water-soluble coating; the water-soluble coating is formed by coating the surface of the aluminum sheet with a water-soluble paint. The water-soluble coating comprises the following components in parts by weight: 90 parts water-soluble resin, 10 parts modified filler, 18 parts curing agent, 0.5 parts defoamer, and 0.5 parts leveling agent; The water-soluble resin includes modified epoxy resin and polyurethane resin; the mass ratio of the modified epoxy resin to the polyurethane resin is 2:1.

[0057] The modified epoxy resin has a weight-average molecular weight of 8000 Da.

[0058] The polyurethane resin has a molecular weight of 40,000 Da.

[0059] The modified filler includes modified carbon nanotubes and modified wollastonite; the mass ratio of the modified carbon nanotubes to the modified wollastonite is 10:1.

[0060] The curing agent is polyamide 650; The defoamer selected is BYK-066N; The leveling agent used is BYK-354.

[0061] The method for preparing the modified epoxy resin includes the following steps: mixing epoxy resin with a surfactant, stirring vigorously for 1 hour, stirring in an oil bath at 60°C for 3 hours, and distilling under reduced pressure to obtain the modified epoxy resin.

[0062] The molar ratio of epoxy resin to surfactant is 2:1.

[0063] The surfactant is γ-aminopropyltrimethoxysilane.

[0064] The preparation method of the modified carbon nanotubes includes the following steps: adding carbon nanotubes and tannic acid to deionized water, stirring for 1.5 hours to allow tannic acid to be fully adsorbed onto the surface of carbon nanotubes through π-π stacking, ultrasonically dispersing for 40 minutes to promote uniform coating of tannic acid on the surface of carbon nanotubes, solid-liquid separation, washing repeatedly with deionized water 3 times to remove unreacted free tannic acid, and vacuum drying at 60℃ for 12 hours to obtain modified carbon nanotubes.

[0065] The carbon nanotubes are multi-walled carbon nanotubes.

[0066] The mass ratio of the carbon nanotubes to the tannic acid is 1:0.6.

[0067] The preparation method of the modified wollastonite includes the following steps: dissolving the silane coupling agent, hydrolyzing it for 8 minutes and then spraying it onto the wollastonite, stirring it at 80°C for 1.5 hours, drying it at 100°C for 1.5 hours, grinding it and sieving it to obtain the modified wollastonite.

[0068] The wollastonite is 1000-mesh fibrous wollastonite.

[0069] The amount of the silane coupling agent added is 1% of the mass of wollastonite.

[0070] The silane coupling agent includes γ-aminopropyltrimethoxysilane.

[0071] The solvent used for dissolution is an ethanol / water mixture (the volume ratio of ethanol to water is 9:1).

[0072] Preparation method: S1. Preparation of water-soluble coating: Modified epoxy resin and modified filler are mixed and stirred for 60 min, polyurethane resin is added, stirring is continued for 20 min, additives are added, mixed evenly, and vacuum degassing is performed to obtain the water-soluble coating. S2. Apply water-soluble coating to aluminum sheet, with a wet film thickness of 40μm, and dry at 60℃ for 20min to obtain the water-soluble coated aluminum sheet.

[0073] Example 2

[0074] A water-soluble coated aluminum sheet for drilling M9 material PCBs includes an aluminum sheet and a water-soluble coating; the water-soluble coating is formed by coating the surface of the aluminum sheet with a water-soluble paint. The water-soluble coating comprises the following components in parts by weight: 50 parts water-soluble resin, 5 parts modified filler, 8 parts curing agent, 0.1 parts defoamer, and 0.1 parts leveling agent; The water-soluble resin includes modified epoxy resin and polyurethane resin; the mass ratio of the modified epoxy resin to the polyurethane resin is 1:1.

[0075] The modified epoxy resin has a weight-average molecular weight of 2000 Da.

[0076] The polyurethane resin has a molecular weight of 20,000 Da.

[0077] The modified filler includes modified carbon nanotubes and modified wollastonite. The mass ratio of the modified carbon nanotubes to the modified wollastonite is 5:1.

[0078] The curing agent used is 810 curing agent; The defoamer used is Tego Airex 900; The leveling agent used is BYK-333.

[0079] The method for preparing the modified epoxy resin includes the following steps: mixing epoxy resin with a surfactant, stirring vigorously for 1 hour, stirring in an oil bath at 80°C for 1 hour, and distilling under reduced pressure to obtain the modified epoxy resin.

[0080] The molar ratio of epoxy resin to surfactant is 2:1.

[0081] The surfactant is γ-aminopropyltrimethoxysilane.

[0082] The preparation method of the modified carbon nanotubes includes the following steps: adding carbon nanotubes and tannic acid to deionized water, stirring for 1 hour to allow tannic acid to be fully adsorbed onto the surface of carbon nanotubes through π-π stacking, ultrasonically dispersing for 30 minutes to promote uniform coating of tannic acid on the surface of carbon nanotubes, separating solid and liquid, washing repeatedly with deionized water 3 times to remove unreacted free tannic acid, and vacuum drying at 60℃ for 15 hours to obtain modified carbon nanotubes.

[0083] The carbon nanotubes are multi-walled carbon nanotubes.

[0084] The mass ratio of the carbon nanotubes to the tannic acid is 1:0.1.

[0085] The preparation method of the modified wollastonite includes the following steps: dissolving the silane coupling agent, hydrolyzing it for 5 minutes and then spraying it onto the wollastonite, stirring it at 80°C for 1 hour, drying it at 100°C for 1 hour, grinding it and sieving it to obtain the modified wollastonite.

[0086] The wollastonite is 800-mesh acicular wollastonite.

[0087] The amount of the silane coupling agent added is 0.5% of the mass of wollastonite.

[0088] The silane coupling agent includes γ-aminopropyltrimethoxysilane.

[0089] The solvent used for dissolution is an ethanol / water mixture (the volume ratio of ethanol to water is 9:1).

[0090] Preparation method: S1. Preparation of water-soluble coating: Modified epoxy resin and modified filler are mixed and stirred for 30 min, polyurethane resin is added, stirring is continued for 15 min, additives are added, mixed evenly, and vacuum degassing is performed to obtain the water-soluble coating. S2. Apply water-soluble coating to aluminum sheet, with a wet film thickness of 30μm, and dry at 80℃ for 10min to obtain the water-soluble coated aluminum sheet.

[0091] Example 3

[0092] A water-soluble coated aluminum sheet for drilling M9 material PCBs includes an aluminum sheet and a water-soluble coating; the water-soluble coating is formed by coating the surface of the aluminum sheet with a water-soluble paint. The water-soluble coating comprises the following components in parts by weight: 100 parts water-soluble resin, 15 parts modified filler, 20 parts curing agent, 1.5 parts defoamer, and 1.5 parts leveling agent; The water-soluble resin includes modified epoxy resin and polyurethane resin; the mass ratio of the modified epoxy resin to the polyurethane resin is 3:1.

[0093] The modified epoxy resin has a weight-average molecular weight of 5000 Da.

[0094] The polyurethane resin has a molecular weight of 60,000 Da.

[0095] The modified filler includes modified carbon nanotubes and modified wollastonite. The mass ratio of the modified carbon nanotubes to the modified wollastonite is 20:1.

[0096] The curing agent is polyamide 650; The defoamer used is BYK-066; The leveling agent used is BYK-307.

[0097] The preparation method of the modified epoxy resin includes the following steps: mixing epoxy resin with surfactant, stirring vigorously for 3 hours, stirring in an oil bath at 60°C for 3 hours, and distilling under reduced pressure to obtain the modified epoxy resin.

[0098] The molar ratio of epoxy resin to surfactant is 5:1.

[0099] The surfactant is γ-aminopropyltrimethoxysilane.

[0100] The preparation method of the modified carbon nanotubes includes the following steps: adding carbon nanotubes and tannic acid to deionized water, stirring for 2 hours to allow tannic acid to be fully adsorbed onto the surface of carbon nanotubes through π-π stacking, ultrasonically dispersing for 50 minutes to promote uniform coating of tannic acid on the surface of carbon nanotubes, separating solid and liquid, washing repeatedly with deionized water 3 times to remove unreacted free tannic acid, and vacuum drying at 60℃ for 15 hours to obtain modified carbon nanotubes.

[0101] The carbon nanotubes are multi-walled carbon nanotubes.

[0102] The mass ratio of the carbon nanotubes to the tannic acid is 3:0.8.

[0103] The preparation method of the modified wollastonite includes the following steps: dissolving the silane coupling agent, hydrolyzing it for 10 minutes, spraying it onto the wollastonite, stirring it at 80°C for 1 hour, drying it at 120°C for 1 hour, grinding it, and sieving it to obtain the modified wollastonite.

[0104] The wollastonite is 1500 mesh fibrous wollastonite.

[0105] The amount of the silane coupling agent added is 2% of the mass of wollastonite.

[0106] The silane coupling agent includes γ-aminopropyltrimethoxysilane.

[0107] The solvent used for dissolution is an ethanol / water mixture (the volume ratio of ethanol to water is 9:1).

[0108] Preparation method: S1. Preparation of water-soluble coating: Modified epoxy resin and modified filler are mixed and stirred for 80 min, polyurethane resin is added, stirring is continued for 30 min, additives are added, mixed evenly, and vacuum degassing is performed to obtain the water-soluble coating. S2. Apply water-soluble coating to aluminum sheet, with a wet film thickness of 50μm, and dry at 60℃ for 30min to obtain the water-soluble coated aluminum sheet.

[0109] Example 4

[0110] Compared with Example 1, the only difference in this example is that the mass ratio of modified epoxy resin to polyurethane resin is 5:1.

[0111] The other components and preparation methods are the same as in Example 1.

[0112] Example 5

[0113] Compared with Example 1, the only difference in this example is that an equal amount of modified carbon nanotubes are used instead of modified wollastonite.

[0114] The other components and preparation methods are the same as in Example 1.

[0115] Comparative Example 1 Compared with Example 1, the only difference in this comparative example is that polyurethane resin is not added, and an equal amount of modified epoxy resin is used instead.

[0116] For other components and preparation methods, please refer to Example 1.

[0117] Comparative Example 2 Compared with Example 1, the only difference in this comparative example is that an equal amount of acrylic resin is used instead of polyurethane resin.

[0118] For other components and preparation methods, please refer to Example 1.

[0119] Comparative Example 3 Compared with Example 1, the only difference in this comparative example is that the epoxy resin is not modified.

[0120] For other components and preparation methods, please refer to Example 1.

[0121] Comparative Example 4 Compared with Example 1, the only difference in this comparative example is that the fillers (carbon nanotubes, wollastonite) are not modified.

[0122] For other components and preparation methods, please refer to Example 1.

[0123] Experiment 1: Performance Testing The water-soluble coated aluminum sheets with M9 material for PCB drilling prepared in Examples 1, 4-5, and Comparative Examples 1-4 were uniformly cut into 50mm×50mm samples, and the following performance tests were performed on them respectively: (1) Surface hardness: The industry standard "Cover plates for drilling printed circuit boards" (T / CPCA 4402-2010) stipulates that the surface hardness of the cover plate shall be tested in accordance with GB / T 2411-2008. (2) 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). (3) 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). (4) Drilling performance: Drill holes continuously (φ0.3mm, theoretical maximum number of holes is 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, it is determined that the coating has failed. 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 the hole wall has ≥50μm of aluminum powder / coating residue observed by cross-section, wipe the hole wall with isopropanol after drilling and detect the aluminum content in the wiping solution by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0124] The experimental results are shown in Table 1.

[0125] Table 1 Performance Test Results The experimental data in Table 1 show that the water-soluble coated aluminum sheet prepared in this embodiment of the invention has good overall performance. Specifically, the hardness (Shore D) remains within the range of 70-75, which allows for good compatibility with M9 material. It also exhibits high adhesion, effectively preventing coating peeling and failure during drilling. Furthermore, after multiple drilling operations, the drill bit wear is low, and the borehole diameter deviation and aluminum residue are minimal. This indicates that the water-soluble coated aluminum sheet prepared in this embodiment of the invention can effectively overcome the problems of short drill bit life, easy residue buildup during drilling, and wire entanglement present in existing technologies.

[0126] Compared with Example 1, the mass ratio of modified epoxy resin to polyurethane resin in Example 4 was unsuitable, resulting in increased hardness of the water-soluble coated aluminum sheet and a corresponding decrease in drilling performance. In Example 5, only a single type of modified filler was added. Due to the excessive proportion of modified carbon nanotubes, agglomeration easily occurred, thereby reducing the adhesion between the coating and the substrate, decreasing the coating hardness, increasing the direct friction between the drill bit and the cover plate, and failing to provide stable guidance during drilling, which aggravated the drill bit sway and increased the hole diameter deviation. At the same time, the abrasive properties of the modified carbon nanotubes may also exacerbate wear.

[0127] Compared with Example 1, Comparative Example 1 used an equal amount of modified epoxy resin instead of polyurethane resin, and the hardness of the water-soluble coated aluminum sheet increased significantly. Excessive hardness is not suitable for M9 material with the same high hardness. At the same time, excessive coating hardness leads to increased wear of drill bit, increased hole diameter deviation and increased aluminum residue on hole wall. In Comparative Example 2, an equal amount of acrylic resin was used to replace polyurethane resin. The hardness of the resulting water-soluble coating increased. However, due to the lack of interaction between the modified epoxy resin and polyurethane resin and other components, the adhesion of the water-soluble coating decreased significantly, and its drilling performance also deteriorated significantly. In Comparative Example 3, no modification was made to the epoxy resin, and the hardness did not change significantly, but the adhesion decreased. In Comparative Example 4, no modification was made to the filler, and the hardness of the water-soluble coated aluminum sheet decreased, while the adhesion only reached level 2. Drilling performance, such as drilling loss and hole diameter deviation, deteriorated significantly.

[0128] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A water-soluble coated aluminum sheet for drilling M9 material PCBs, comprising an aluminum sheet and a water-soluble coating; characterized in that, The water-soluble coating is formed by coating the surface of the aluminum sheet with water-soluble paint; The water-soluble coating comprises the following components in parts by weight: 50-100 parts water-soluble resin, 1-15 parts modified filler, 5-20 parts curing agent, and 0.1-3 parts additives; The water-soluble resin includes modified epoxy resin and polyurethane resin; The modified filler includes at least one of modified carbon nanotubes and modified wollastonite.

2. The water-soluble coated aluminum sheet as described in claim 1, characterized in that, The mass ratio of the modified epoxy resin to the polyurethane resin is (1~3):1; The weight-average molecular weight of the modified epoxy resin is 2000~8000 Da; The molecular weight of the polyurethane resin is 20,000 to 40,000 Da; The additives include defoamers and leveling agents.

3. The water-soluble coated aluminum sheet as described in claim 1, characterized in that, The method for preparing the modified epoxy resin includes the following steps: mixing epoxy resin with a surfactant, stirring, stirring in an oil bath, and distilling under reduced pressure to obtain the modified epoxy resin.

4. The water-soluble coated aluminum sheet as described in claim 3, characterized in that, The molar ratio of the epoxy resin to the surfactant is 2~5∶1; The surfactant is γ-aminopropyltrimethoxysilane; The stirring time is 1-3 hours; The oil bath stirring is carried out in an oil bath at 60~80℃ for 1~3 hours.

5. The water-soluble coated aluminum sheet as described in claim 1, characterized in that, The method for preparing the modified carbon nanotubes includes the following steps: adding carbon nanotubes and tannic acid to deionized water, stirring, ultrasonically dispersing, solid-liquid separation, washing, and vacuum drying to obtain modified carbon nanotubes.

6. The water-soluble coated aluminum sheet as described in claim 5, characterized in that, The carbon nanotubes are multi-walled carbon nanotubes; The mass ratio of the carbon nanotubes to the tannic acid is (1~3):(0.1~0.8). The stirring time is 1 to 2 hours; The ultrasonic dispersion time is 30-50 minutes; The washing process involves repeatedly washing with deionized water 3 to 5 times. The vacuum drying temperature is 60~80℃, and the time is 10~15 h.

7. The water-soluble coated aluminum sheet as described in claim 1, characterized in that, The preparation method of the modified wollastonite includes the following steps: dissolving the silane coupling agent, hydrolyzing it, spraying it onto the wollastonite, stirring, drying, grinding and sieving to obtain the modified wollastonite.

8. The water-soluble coated aluminum sheet as described in claim 7, characterized in that, The wollastonite is 800-1500 mesh fibrous or acicular wollastonite; The amount of the silane coupling agent added is 0.5-3% of the mass of wollastonite; The silane coupling agent includes γ-aminopropyltrimethoxysilane; The solvent used for dissolution is an ethanol / water mixture; The hydrolysis time is 5-10 minutes; The stirring is carried out at 60~80℃ for 1-2 hours; The drying process involves drying at 100-120℃ for 1-2 hours.

9. A method for preparing a water-soluble coated aluminum sheet as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Preparation of water-soluble coating: Modified epoxy resin and modified filler are mixed and stirred, polyurethane resin is added, stirring is continued, additives are added, mixed evenly, and vacuum degassing is performed to obtain the water-soluble coating. S2. Apply the water-soluble coating onto the aluminum sheet and dry it to obtain the water-soluble coated aluminum sheet.

10. The preparation method according to claim 9, characterized in that, The mixing and stirring time is 30-80 minutes; The stirring time is 15-30 minutes. The wet film thickness of the water-soluble coating is 30-50 μm; The drying temperature is 60~80℃, and the time is 5~30min.

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