Washing hole-plugging resin composition, preparation method thereof, circuit board and preparation method thereof

Abstract

The invention discloses a washing hole-plugging resin composition and a preparation method thereof, and a circuit board and a preparation method thereof. The composition includes a structural resin including a polymer having a repeating unit derived from vinyl alcohol, a binder resin including a phenolic and epoxy system resin material, and an inorganic filler whose surface is modified with a functional group. The protective film formed by the composition can effectively prevent burrs and line picking in milling and other machining processes, can be quickly and nondestructively removed by hot water after machining, and solves the technical contradiction that the existing protective material is insufficient in protective capability and difficult to remove.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and in particular to a water-washable via-plugging resin composition and its preparation method, as well as a circuit board and its preparation method. Background Technology

[0002] In the PCB manufacturing process, drilling, milling, and other machining processes are typically required to achieve electrical interconnection between multiple layers or to shape the circuit board. To ensure machining accuracy and protect the circuit board itself from damage, auxiliary protective measures are usually employed.

[0003] In existing technologies, a common method is to place a cover plate, such as wood pulp board or phenolic resin board, under the PCB to provide support as the drill bit exits the PCB, thereby preventing burrs or flash at the hole exit. However, this cover plate mainly provides vertical support and cannot provide effective protection for lateral milling operations. Specifically, during milling, lateral cutting forces can easily cause the metal electrodes on the PCB surface to be "picked up" from the substrate, or burrs to form at the edges of metallized through-holes or blind holes. These defects severely affect the yield and electrical reliability of high-end circuit boards.

[0004] Therefore, how to provide a temporary protection solution that can provide comprehensive and effective protection for the PCB surface and holes during machining processes such as drilling and milling to avoid defects such as burrs and trace lifting has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The main objective of this invention is to propose a water-washable plugging resin composition, which aims to solve the problem that existing protection methods cannot effectively prevent burrs and line lifting from printed circuit boards during transverse machining such as milling.

[0006] To achieve the above objectives, the present invention provides a water-washed pore-plugging resin composition comprising a polymeric resin and an inorganic filler, wherein,

[0007] The polymer resin includes:

[0008] Structural resin, the structural resin comprising a polymer having repeating units derived from vinyl alcohol;

[0009] The adhesive resin comprises phenolic resin and epoxy resin;

[0010] The surface of the inorganic filler is modified with one or more functional groups selected from the group consisting of aniline, alkyl, nitrogen-containing functional groups on the main chain or branches, double-bonded functional groups, and epoxy groups.

[0011] In one embodiment, the polymer having repeating units derived from vinyl alcohol is polyvinyl alcohol, and the degree of alcoholysis of the polyvinyl alcohol is between 78% and 100%.

[0012] In one embodiment, the molecular weight of the polyvinyl alcohol is between 10,000 g / mol and 300,000 g / mol.

[0013] In one embodiment, the epoxy resin is selected from at least one of glycidylamine epoxy resin, polyfunctional o-cresol glycidyl ether epoxy resin, phenol-biphenyl epoxy resin, bisphenol F solid epoxy resin, isocyanate modified epoxy resin, naphthol epoxy resin, phenol-formaldehyde epoxy resin, semi-crystalline epoxy resin, liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, liquid bisphenol A-bisphenol F composite epoxy resin, liquid bisphenol S epoxy resin, liquid phenolic epoxy resin, and liquid phenolic resin.

[0014] In one embodiment, the phenolic resin is selected from at least one of linear phenol-formaldehyde resin and linear BPA-formaldehyde resin.

[0015] In one embodiment, the ratio of the content of the phenolic resin to the content of the epoxy resin satisfies the following formula:

[0016] Phenolic resin content = (hydroxyl equivalent of phenolic resin / epoxy equivalent of epoxy resin) × epoxy resin content.

[0017] In one embodiment, the water-washed pore-sealing resin composition further includes a solvent selected from at least one of water, N-methylpyrrolidone, ethanol, acetone, ethyl acetate, n-butyl ether, methyl tert-butyl ether, dimethyl phthalate, butanone, dimethyl sulfoxide, n-butyl ketone, cyclohexanone, toluene, and xylene.

[0018] In one embodiment, the water-washed pore-filling resin composition further includes an additive selected from at least one of leveling agents, dispersants, and defoamers.

[0019] In one embodiment, the inorganic filler is selected from at least one of silicon dioxide, aluminum oxide, aluminum hydroxide, calcium carbonate, magnesium carbonate, magnesium silicate, silicon carbide, titanium carbide, titanium oxide, magnesium oxide, calcium oxide, boron nitride, or aluminum nitride.

[0020] In one embodiment, the polymeric resin further comprises a toughening resin selected from at least one of polyvinyl butyral, polyimide, poly(p-phenylenebenzodioxazole), polybenzimidazole, polyamic acid, polyethylene glycol, and rubber-based polymers.

[0021] In one embodiment, the rubber polymer is selected from at least one of natural rubber, nitrile rubber, styrene-butadiene rubber, chloroprene rubber, ethylene propylene diene monomer (EPDM) rubber, modified EPDM rubber, thermoplastic EPDM rubber, acrylic rubber, fluororubber, EPDM rubber, polyurethane rubber, and silicone rubber.

[0022] In one embodiment, the toughening resin accounts for 1% to 30% of the total weight of the structural resin and the toughening resin.

[0023] In one embodiment, the polymer resin comprises, by weight percentage:

[0024] 5% to 50% of the adhesive resin; and

[0025] A combination of 50% to 95% of the structural resin and the toughening resin.

[0026] In one embodiment, the polymer resin comprises, by weight percentage:

[0027] 5% to 50% of the adhesive resin; and

[0028] 50% to 95% of the structural resin.

[0029] In one embodiment, the water-washed pore-plugging resin composition comprises, by weight percentage:

[0030] 5% to 50% of polymer resin; and

[0031] The inorganic filler comprises 50% to 95%.

[0032] In one embodiment, the water-washed pore-plugging resin composition further comprises, by weight percentage:

[0033] Solvents ranging from 1% to 20%; and

[0034] 0.5% to 5% of adjuvants.

[0035] The present invention also provides a method for preparing a water-washed pore-plugging resin composition, for preparing the water-washed pore-plugging resin composition described in any of the preceding claims, the method comprising the following steps:

[0036] Preparation of resin slurry: The polymer resin is mixed in a first solvent to obtain a resin slurry;

[0037] Preparation of filler slurry: The inorganic filler is mixed in a second solvent to obtain a filler slurry; and

[0038] Mixing: The filler slurry is added to the resin slurry being stirred and mixed to obtain a water-washed pore-plugging resin composition mixed slurry.

[0039] In one embodiment, the polymeric resin comprises a structural resin, a binding resin, and a toughening resin.

[0040] In one embodiment, in the step of preparing the resin slurry, at least one additive selected from dispersants, defoamers, and leveling agents is pre-dissolved in the first solvent; and / or

[0041] In the step of preparing the filler slurry, at least one additive selected from dispersants, defoamers and leveling agents is pre-dissolved in the second solvent.

[0042] In one embodiment, the mixing conditions of the preparation method include at least one of the following:

[0043] The mixing speed during the preparation of the resin slurry is between 3600 rpm and 7200 rpm, the slurry temperature is not higher than 45°C, and the duration is between 20 minutes and 40 minutes.

[0044] The mixing speed during the preparation of the filler slurry is between 3600 rpm and 7200 rpm, the slurry temperature is not higher than 45°C, and the duration is between 20 minutes and 40 minutes; and

[0045] The mixing speed of the filler slurry and the resin slurry is between 3600 rpm and 7200 rpm, the slurry temperature is not higher than 45°C, and the duration is between 60 minutes and 120 minutes.

[0046] In one embodiment, after the mixing step, the preparation method further includes the following steps:

[0047] Desolventization: The water-washed pore-filling resin composition mixture is subjected to desolventization treatment to obtain a water-washed pore-filling resin composition ink with a solid content between 64% and 98% and a viscosity between 10000 Pa·s and 50000 mPa·s.

[0048] In one embodiment, the solvent removal process includes:

[0049] The water-washed plugging resin composition mixture is continuously stirred for 5 minutes to 3 hours at a temperature of 20°C to 50°C and a vacuum degree of less than 0.1 MPa.

[0050] This invention also provides a method for manufacturing a circuit board, comprising the following steps:

[0051] Provide substrate: Provide a circuit board substrate having a protected area, wherein the protected area has a hole structure;

[0052] Forming a protective layer: After applying the water-washable plugging resin composition described in any one of the preceding claims to the area to be protected on the circuit board substrate and filling the hole structure, a curing process is performed to form a protective layer;

[0053] Machining: Machining the printed circuit board on which the protective layer is formed; and

[0054] Remove the protective layer: After the machining, the protective layer is removed using a water washing solution.

[0055] In one embodiment, a water-washable via-sealing resin composition ink is applied to the area to be protected on the circuit board substrate by at least one of screen printing, pad printing, stencil printing, spraying, and squeegee printing.

[0056] In one embodiment, the thickness of the protective layer is between 10 μm and 20 μm.

[0057] In one embodiment, the curing process includes drying the water-washed pore-filling resin composition ink at a temperature range of 50°C to 120°C for 3 to 30 minutes.

[0058] In one embodiment, the curing process includes:

[0059] First stage baking: Bake at a temperature range of 40℃ to 60℃ for 10 minutes;

[0060] Second stage baking: Bake at a temperature range of 90℃ to 110℃ for 10 minutes; and

[0061] Third stage baking: Bake at a temperature range of 140℃ to 160℃ for 10 minutes.

[0062] In one embodiment, the machining is selected from at least one of milling and drilling.

[0063] The step of removing the protective layer is carried out using hot water at a temperature between 50°C and 95°C as the washing solution.

[0064] In one embodiment, the washing solution further comprises one selected from acidic solutes, basic solutes, surfactants, and mixtures of the surfactants with the acidic or basic solutes, wherein the acidic solute is selected from at least one of sulfuric acid and hydrochloric acid, and the basic solute is selected from at least one of potassium hydroxide and sodium hydroxide.

[0065] In one embodiment, if the water washing solution contains the acidic solute, the weight percentage of the acidic solute is between 1% and 20%.

[0066] If the water washing solution contains the alkaline solute, the weight percentage of the alkaline solute is between 1% and 20%.

[0067] If the washing solution contains the surfactant, the surfactant has a weight percentage between 0.5% and 3%.

[0068] In one embodiment, the acidic solute comprises between 1% and 10% by weight; and / or

[0069] The weight percentage of the alkaline solute is between 1% and 10%.

[0070] The present invention also provides a circuit board, which is prepared by any of the circuit board preparation methods described above.

[0071] The water-washed pore-plugging resin composition provided by this invention has the following significant beneficial effects:

[0072] 1. This invention provides strong and effective protection against transverse milling, fundamentally avoiding defects such as burrs and wire lifting: The inorganic filler with surface-modified functional groups in the composition of this invention enables the cured protective layer to have extremely high hardness and mechanical strength, acting as a temporary "reinforced ceramic layer" to effectively resist and disperse the impact and cutting stress of the milling cutter. The phenolic and epoxy binder resin forms a dense, high-strength three-dimensional cross-linked network during curing. This network not only firmly "bonds" the high-content inorganic filler particles together to form a robust whole, but also enables the entire protective layer to have extremely strong adhesion to the copper surface and substrate of the printed circuit board. Therefore, based on the combination of inorganic filler and binder resin, the protective layer formed by this invention is hard, dense, and has strong adhesion, sufficient to provide rigid support for the wires and hole walls during milling, thus solving the problems of burrs and wire lifting that cannot be solved by existing technologies.

[0073] 2. This invention provides a mild, efficient, and environmentally friendly removal method, avoiding damage to the substrate and chemical pollution: The structural resin of the polymer containing repeating units derived from vinyl alcohol, which forms the main framework of the polymer system, imparts water-sensitive properties to the entire protective layer due to the densely distributed hydrophilic groups (hydroxyl groups) on its molecular chains. Thus, although there is a cross-linked, water-insoluble adhesive resin network in the protective film, the structural resin, as the main framework, still retains channels for water molecule penetration and attack. Under hot water conditions (e.g., 50℃-95℃), water molecules can effectively penetrate, swell, and destroy the framework of the structural resin, thereby causing the entire cross-linked network structure to rapidly disintegrate and peel off. This process does not require the use of any strong acids, strong alkalis, or other chemical solvents, making it not only simple, fast, and residue-free, but more importantly, it causes no damage to the circuit board substrate and is very environmentally friendly.

[0074] In summary, this invention cleverly solves the seemingly contradictory technical requirements of "protection" and "removal" through the synergistic effect of structural resin, binding resin and inorganic filler. Attached Figure Description

[0075] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0076] Figure 1 This is a schematic flowchart of an embodiment of the preparation method of the water-washed pore-plugging resin composition of the present invention;

[0077] Figure 2 This is a schematic flowchart of an embodiment of the circuit board manufacturing method of the present invention.

[0078] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0079] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0080] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0081] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0082] This invention proposes a water-washable pore-filling resin composition. In an embodiment of this invention, the water-washable pore-filling resin composition comprises a polymer resin and an inorganic filler. The polymer resin provides the composition with basic core functions such as film-forming properties, adhesion, and removability, while the inorganic filler acts as a reinforcing phase, significantly improving the mechanical strength and abrasion resistance of the cured protective film.

[0083] Specifically, polymer resins include structural resins and adhesive resins.

[0084] The structural resin mainly plays the role of the skeleton in the composition. Its core function is to provide a water-soluble basis for the protective film that is eventually cured, so that it can be quickly and non-destructively removed by a water washing solution after machining.

[0085] In some embodiments of the present invention, the structural resin comprises a polymer having repeating units derived from vinyl alcohol. The densely distributed hydroxyl functional groups on the main chain of this polymer endow it with excellent water solubility. Specifically, a polymer having repeating units derived from vinyl alcohol refers to a class of polymers whose main polymer chain contains the chemical structural unit -[CH2-CH(OH)]-. It is the presence of the hydroxyl (-OH) functional groups on these repeating units that gives the polymer molecular chain strong polarity, enabling it to form hydrogen bonds with water molecules, thereby endowing the polymer with excellent water solubility, allowing the protective layer formed by the water-washed pore-filling resin composition to be easily removed by the washing solution after its function has been completed.

[0086] The bonding resin, as a key modifying and reinforcing component, functions primarily to significantly improve the crosslinking density, hardness, heat resistance, chemical resistance, and adhesion to the substrate of the protective resin composition by forming an effective chemical or physical bond with the structural resin and the surface of the protected substrate (such as a copper surface). This overcomes the shortcomings of single-structure resins, such as insufficient mechanical properties and easy moisture absorption and softening.

[0087] In some embodiments of the present invention, the bonding resin comprises a phenolic and epoxy resin material. By introducing this bonding resin system, it can undergo a cross-linking reaction with the hydroxyl groups in the structural resin to form a more stable network structure, thereby significantly improving the overall protective performance of the material.

[0088] Inorganic fillers are mainly used as mechanical property enhancers in compositions, significantly improving the mechanical properties (such as hardness, modulus), heat resistance, and dimensional stability of the protective layer formed by the composition. In this application, in order to improve the interfacial compatibility between the inorganic filler and the polymer resin matrix, prevent their agglomeration at high contents, and ensure that the two can effectively bond to transfer stress, the surface of the inorganic filler has undergone specific functional group modification.

[0089] In some embodiments of the present invention, the surface of the inorganic filler is modified with one or more functional groups selected from the group consisting of aniline, alkyl, nitrogen-containing functional groups on the main chain or branches, double-bonded functional groups, and epoxy groups. These functional groups can react with or form strong interactions with active groups (such as hydroxyl, epoxy, etc.) in the polymer resin, thereby tightly anchoring the inorganic filler in the resin matrix. This results in a protective layer with higher hardness, Young's modulus, and flexural modulus, effectively resisting impacts and cutting stresses during machining.

[0090] In one specific embodiment, the polymer having repeating units derived from vinyl alcohol is polyvinyl alcohol (PVA), with the structural formula as follows:

[0091] Polyvinyl alcohol (PVA) is typically produced from polyvinyl acetate via alcoholysis, and its structure contains both vinyl alcohol units and residual vinyl acetate units. Therefore, the molar percentage of vinyl alcohol units in the polymer, known in the industry as the degree of alcoholysis, can be precisely controlled by adjusting the extent of the alcoholysis reaction.

[0092] In a preferred embodiment of the invention, the degree of hydrolysis of polyvinyl alcohol is any value between 78% and 100%, such as 78%, 80%, 90%, 100%, etc. The degree of hydrolysis is a core parameter determining the performance of this resin structure. A higher degree of hydrolysis means that the polymer chain contains a higher proportion of hydroxyl groups, which not only enhances its dissolution rate in hot water but also facilitates its cross-linking reaction with functional groups (such as epoxy groups) in the bonding resin system, thereby increasing the cross-linking density and mechanical strength of the final protective film. When the degree of hydrolysis is below 78%, the hydrophilicity of the polymer decreases, which may lead to residues in the removal step, affecting the process effect.

[0093] Furthermore, the molecular weight of polyvinyl alcohol (PVA) is another key parameter affecting the performance of the composition. In a preferred embodiment of the present invention, the molecular weight of PVA is any value between 10,000 g / mol and 300,000 g / mol, such as 100,000 g / mol, 200,000 g / mol, 3,000,000 g / mol, etc. The molecular weight directly affects the viscosity, film-forming properties, and toughness and strength of the cured protective film of the composition. If the molecular weight is too low (e.g., below 100,000), the formed protective film may be too fragile and unable to effectively resist the stress of mechanical processing; if the molecular weight is too high (e.g., above 300,000), it may lead to excessive viscosity of the composition, which is not conducive to coating processes such as screen printing, and may reduce its dissolution rate in hot water. Therefore, the present invention selects the above-mentioned molecular weight range to ensure that the protective film has sufficient mechanical strength while taking into account the processability and final removability of the material.

[0094] It is understandable that by selecting polyvinyl alcohol with a specific degree of hydrolysis and molecular weight range as the structural resin, the contradictory technical requirements of mechanical protective performance and water-soluble removal performance of the protective film can be precisely balanced, thereby achieving the desired technical effect.

[0095] In some embodiments, the resin material of the phenolic-epoxy system includes epoxy resin and phenolic resin. The core function of this system lies in the ring-opening addition reaction between the epoxy groups of the epoxy resin and the phenolic hydroxyl groups of the phenolic resin, forming a dense and stable three-dimensional cross-linked network structure. This structure significantly improves the cohesive strength of the entire composition, its adhesion to substrates such as copper, its heat resistance, and its resistance to chemical attack.

[0096] To achieve precise control over the final performance, the epoxy resin used in this invention can be one or a combination of various types of epoxy resins. In one specific embodiment, the epoxy resin may be selected from at least one of the following: glycidylamine epoxy resin, polyfunctional o-cresol glycidyl ether epoxy resin, phenol-biphenyl epoxy resin, bisphenol F solid epoxy resin, isocyanate modified epoxy resin, naphthol epoxy resin, phenol-formaldehyde epoxy resin, semi-crystalline epoxy resin, liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, liquid bisphenol A-bisphenol F composite epoxy resin, liquid bisphenol S epoxy resin, liquid phenolic epoxy resin, and liquid phenolic resin.

[0097] Specifically, the structural formula of glycidylamine epoxy resin is: Its epoxy equivalent is between 93 and 150 g / eq, its hydrolytic chlorine content is less than 200 ppm, and its viscosity at 25°C is between 0.5 and 5 Poise.

[0098] The structural formula of the multifunctional o-cresol formaldehyde glycidyl ether epoxy resin is: Its epoxy equivalent ranges from 195 to 230 g / eq, its hydrolytic chlorine at 120℃ ranges from 470 to 1000 g / eq, its ICI viscosity at 150℃ ranges from 0.9 to 60 Poise, and its softening point ranges from 45 to 96℃.

[0099] The structural formula of phenol-biphenyl epoxy resin is: Its epoxy equivalent ranges from 261 to 280 g / eq, hydrolytic chlorine content is less than 100 ppm, viscosity at 25°C is between 0.1 and 4.5 poise, and softening point is 45 to 75°C. Adding it to PVB and its hydroxyl groups in copolymerization can effectively improve the glass strength, Tg, and impact resistance of copper.

[0100] The structural formula of bisphenol F solid epoxy resin is: Its epoxy equivalent ranges from 450 to 1000 g / eq, hydrolytic chlorine content is less than 300 ppm, viscosity at 25°C is <1000 Poise, and softening point is 50–88°C. Solid bisphenol F epoxy resin is characterized by low viscosity and flexibility. The properties of its cured product are almost identical to those of bisphenol A epoxy resin. Adding it to PVB for copolymerization with its hydroxyl groups can effectively improve its corrosion resistance.

[0101] The structural formula of isocyanate (MDI) modified epoxy resin is:

[0102] Its epoxy equivalent ranges from 280 to 380 g / eq, hydrolytic chlorine content is less than 300 ppm, viscosity at 25°C is between 0.5 and 3 Poise, and softening point is 50 to 88°C. Solid bisphenol F epoxy resin is characterized by low viscosity and flexibility. The properties of its cured product are almost identical to those of bisphenol A epoxy resin. Adding it to PVB for copolymerization with its hydroxyl groups can effectively improve bond strength and peel strength.

[0103] The structural formula of naphthol-type epoxy resin is: Its epoxy equivalent ranges from 280 to 380 g / eq, its hydrolytic chlorine content is less than 300 ppm, its viscosity at 25°C is between 0.5 and 3 Poise, and its softening point is between 50 and 88°C. Its curing properties, heat resistance, and mechanical properties are superior to traditional bisphenol A. Furthermore, due to its lower internal stress, it exhibits higher Tg and better adhesive properties. When added to structural resins and copolymerized with their hydroxyl groups, it can effectively improve the Tg point, bond strength, and peel strength.

[0104] The structural formula of phenolic epoxy resin is: Its epoxy equivalent ranges from 165 to 200 g / eq, its hydrolytic chlorine content is less than 250 ppm, its viscosity at 25°C is between 1.1 and 12.5 Poise, and its softening point is 25 to 86°C. Because its molecular structure contains two or more epoxy groups, when added to structural resins and copolymerized with their hydroxyl groups, the resulting product has a high crosslinking density and excellent adhesive strength, heat resistance, and chemical resistance. The presence of two or more epoxy groups in its molecular structure leads to a high crosslinking density in the cured product, resulting in excellent adhesive strength, heat resistance, and chemical resistance.

[0105] The structural formula of semi-crystalline epoxy resin is:

[0106] The structural formulas of liquid bisphenol A type epoxy resin and liquid bisphenol F type epoxy resin are as follows:

[0107]

[0108] The structural formula of liquid bisphenol A-bisphenol F composite epoxy resin is:

[0109] The structural formula of liquid phenolic epoxy resin is:

[0110] The structural formula of liquid phenolic resin is

[0111] Among these, semi-crystalline epoxy resin, liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, liquid bisphenol A-bisphenol F composite epoxy resin, liquid bisphenol S epoxy resin, liquid phenolic epoxy resin, and liquid phenolic resin have low epoxy equivalent (between 140 g / eq and 214 g / eq), low hydrolytic chlorine (less than 250 ppm), and low room temperature viscosity (between 1300 mPa·s and 4500 mPa·s at 25°C). They have low viscosity, high crosslinking density, and excellent adhesive strength, heat resistance, and chemical resistance. When compounded as part of an adhesive resin, they can effectively improve the fluidity of the entire composition at low temperatures and its adhesion to the substrate while ensuring high crosslinking density, excellent adhesive strength, heat resistance, and chemical resistance of the cured product.

[0112] In one specific embodiment, the phenolic resin serves as a curing agent for the epoxy resin, and its type and purity significantly influence the progress of the curing reaction and the properties of the final product. The phenolic resin can be selected from at least one of linear phenol-formaldehyde resin and linear BPA-formaldehyde resin. Choosing these phenolic resins, especially those with low free phenol content and low electrical conductivity, is beneficial for ensuring the stability of the curing reaction and the electrical insulation properties of the final protective film.

[0113] Specifically, the structural formula of linear phenol-formaldehyde resin is: Its free phenol content is <0.6%, softening point is 96-123℃, hydroxyl equivalent is between 105-119 g / eq, and electrical conductivity is less than 8 μS / cm.

[0114] The structural formula of linear BPA formaldehyde resin is: Its free phenol content is 1-45%, softening point is 90-140℃, hydroxyl equivalent is between 112-130 g / eq, and electrical conductivity is less than 20 μS / cm.

[0115] It is understood that by selectively combining and compounding the above-mentioned epoxy resins and phenolic resins, the present invention can flexibly adjust the various performance indicators of the water-washable plugging resin composition to meet the diverse protection needs of printed circuit boards of different specifications under specific processing techniques.

[0116] In some embodiments, the ratio of phenolic resin content to epoxy resin content satisfies the following formula:

[0117] Phenolic resin content = (hydroxyl equivalent of phenolic resin / epoxy equivalent of epoxy resin) × epoxy resin content.

[0118] The fundamental reason for using the above formula to determine the amount of the two resins is that it follows the stoichiometric principle in chemical reactions, aiming to achieve an ideal balance in the quantity of the two core functional groups participating in the reaction—the phenolic hydroxyl groups (-OH) on the phenolic resin molecular chain and the epoxy groups on the epoxy resin molecular chain—so as to obtain the curing product with the best performance.

[0119] Specifically, the curing process of the adhesive resin mainly involves a ring-opening addition reaction between phenolic hydroxyl groups and epoxy groups, forming a highly cross-linked three-dimensional network structure. Ideally, for this reaction to proceed most completely and efficiently, one phenolic hydroxyl functional group should react with exactly one epoxy functional group. Therefore, the ideal feed ratio should be such that the total molar ratio of phenolic hydroxyl groups to epoxy groups in the formulation is as close to 1:1 as possible.

[0120] Here, "Epoxy Equivalent Weight (EEW)" refers to the number of grams of epoxy resin containing 1 mole of epoxy groups, while "Hydroxyl Equivalent Weight (EEW)" refers to the number of grams of phenolic resin containing 1 mole of phenolic hydroxyl groups. These two values ​​are key parameters for measuring the reactivity of resins. Therefore, the essence of the above formula is a mathematical conversion of the chemical equilibrium relationship of "moles of phenolic hydroxyl groups ≈ moles of epoxy groups." By using this formula, the amount of phenolic resin containing an equal number of reaction sites can be accurately calculated based on the amount of epoxy resin used and its epoxy equivalent weight.

[0121] Using this stoichiometric method to determine the proportions ensures the full progress of the crosslinking reaction, preventing the presence of excessive amounts of any one component that could result in a large number of unreacted functional groups remaining in the cured network. This leads to the highest crosslinking density in the final cured adhesive resin, resulting in superior heat resistance, chemical resistance, and the strongest mechanical strength and adhesion to the substrate.

[0122] In some embodiments, the inorganic filler is selected from at least one of silicon dioxide, aluminum oxide, aluminum hydroxide, calcium carbonate, magnesium carbonate, magnesium silicate, silicon carbide, titanium carbide, titanium oxide, magnesium oxide, calcium oxide, boron nitride, or aluminum nitride.

[0123] Incorporating these inorganic fillers into a high proportion of the polymer resin matrix serves as a reinforcing framework and functional core, significantly improving the overall performance of the cured protective layer. On one hand, these rigid inorganic filler particles form a dense physical support network within the polymer matrix, thereby substantially enhancing the mechanical properties of the composite material, such as hardness, Young's modulus, tensile modulus, and flexural modulus, strengthening its resistance to physical scratches and its ability to maintain its shape under high-temperature and high-pressure processes. On the other hand, by introducing a high content of inorganic fillers with extremely low coefficients of thermal expansion, the overall coefficient of thermal expansion (CTE) of the composition can be effectively reduced, and its thermal conductivity improved, thus enhancing the heat dissipation efficiency and reliability of the protective layer.

[0124] Furthermore, a diverse selection of inorganic fillers is available, allowing for optimization of the resin composition's specific properties based on application requirements during practical operation. For instance, selecting high-hardness fillers such as silicon carbide and alumina can maximize wear resistance; while selecting high-thermal-conductivity fillers such as boron nitride and aluminum nitride helps to significantly improve the heat dissipation capability of the protective layer at high temperatures.

[0125] To further optimize and adjust the overall properties of the composition to meet more demanding application scenarios, in some embodiments of the present invention, the polymer resin also includes a toughening resin. The introduction of the toughening resin is intended to enhance specific properties of the protective layer, such as improving its chemical resistance, glass transition temperature (Tg), film-forming properties, or flexibility.

[0126] In one specific embodiment, the toughening resin may be selected from at least one or a mixture of the following high-performance polymers: polyvinyl butyral, polyimide, poly(p-phenylenebenzodioxazole), polybenzimidazole, polyamic acid, polyethylene glycol, and rubber polymers.

[0127] These include polyvinyl butyral (PVB), polyimide (PI), poly(p-phenylenebenzodioxazole) (PBO), polybenzimidazole (PBI), or polyamic acid. These polymers are known for their excellent heat resistance, superior chemical resistance, and good film-forming properties. Adding small amounts of them to polymeric resin systems can significantly improve the stability of the final protective film in harsh chemical environments such as strong acids and alkalis, and enhance its dimensional stability at high temperatures.

[0128] Specifically, the structural formulas of polyvinyl butyral and polyimide are as follows:

[0129] The structural formula of poly(p-phenylenebenzodioxazole) is:

[0130] The structural formula of polybenzimidazole is:

[0131] The structural formula of polyamic acid is:

[0132] Polyethylene glycol (PEG) is a polymer with good water solubility and a certain degree of flexibility. When it is necessary to adjust the flexibility of the protective film to accommodate certain easily deformable substrates, or when it is necessary to further accelerate its dissolution rate in water, polyethylene glycol can be added in appropriate amounts. In some embodiments of the present invention, the molecular weight of the polyethylene glycol used can be between 200 g / mol and 20000 g / mol.

[0133] Specifically, the structural formula of polyethylene glycol (PEG) is:

[0134] It is understood that by selectively adding one or more of the toughening resins mentioned above and adjusting their ratio with the structural resin, the present invention can achieve fine customization of the final protective film performance, thereby giving it additional specific advantages in addition to its core protection and removal functions to meet diverse industrial application needs.

[0135] Furthermore, the rubber polymer is selected from at least one of natural rubber, nitrile rubber, styrene-butadiene rubber, chloroprene rubber, ethylene propylene diene monomer (EPDM) rubber, modified EPDM rubber, thermoplastic EPDM rubber, acrylic rubber, fluororubber, EPDM rubber, polyurethane rubber, and silicone rubber.

[0136] Specifically, the structural formula of natural rubber is:

[0137] The structural formula of nitrile rubber is:

[0138] The structural formula of styrene-butadiene rubber is:

[0139] The structural formula of chloroprene rubber is:

[0140] The structural formulas of binary ethylene propylene rubber, modified ethylene propylene rubber, and thermoplastic ethylene propylene rubber are as follows:

[0141] The structural formula of acrylic rubber is:

[0142] The structural formula of fluororubber is:

[0143] The structural formula of ethylene propylene diene monomer (EPDM) rubber is:

[0144] The structural formula of polyurethane rubber is:

[0145] The structural formula of silicone is:

[0146] In some preferred embodiments of the present invention, the amount of toughening resin added is further limited to ensure that while enhancing specific properties, the basic function of the composition is not affected. Specifically, when the composition contains toughening resin, the weight of the toughening resin can account for 1% to 30% of the total weight of the structural resin and the toughening resin, for example, 1%, 5%, 10%, 20%, 30%, etc. This range of proportions is set based on a balance between "performance enhancement" and "core function preservation." Specifically:

[0147] The lower limit of 1% is set because when the content of toughening resin is too low, its effect on improving the performance of the overall polymer resin system (such as improving heat resistance, chemical resistance or flexibility) will not be significant enough to reflect its technical value.

[0148] The 30% upper limit is set to ensure that the core function of this invention—water-soluble removal—is not compromised. Since the structural resin is the primary source of water solubility, and most high-performance toughening resins (such as polyvinyl butyral and polyimide) are not inherently water-soluble, an excessively high proportion would disrupt the hydrophilic continuity of the polymer matrix, making it difficult to completely and quickly remove the final protective film in hot water, thus contradicting the original intent of this invention.

[0149] Therefore, by precisely controlling the content of toughening resin within the range of 1% to 30%, the present invention can effectively enhance the specific properties of the protective film without sacrificing ease of removal, thus achieving a higher level of performance balance.

[0150] In some embodiments, the relative amounts of the major components in the composition are defined to achieve an optimal balance of various performance indicators. Specifically, the water-washed pore-plugging resin composition may contain 5% to 50% (e.g., 5%, 10%, 20%, 30%, 40%, 50%, etc.) of a polymeric resin by weight percentage, and 50% to 95% (e.g., 50%, 60%, 70%, 80%, 90%, 95%, etc.) of an inorganic filler.

[0151] Specifically, inorganic fillers are the core component that imparts high hardness, high wear resistance, and high mechanical strength to the final protective film. By controlling their content within a relatively high range of 50% to 95%, it can be ensured that the protective film formed after curing has sufficient rigidity and strength, acting like a temporary "ceramic" coating to effectively resist the cutting forces and impacts generated during machining processes such as milling or drilling, thereby fundamentally preventing burrs on the copper surface or the circuitry from being lifted. If the content of inorganic fillers is less than 50%, the hardness and strength of the protective film will be insufficient, and the protective effect will be greatly reduced.

[0152] The polymer resin acts as a continuous phase matrix, tightly binding the high-content inorganic filler particles together and ensuring the protective film adheres firmly to the circuit board substrate. Simultaneously, the structural resin (such as PVA) within the polymer resin is fundamental to achieving the final water-soluble removal function. If the polymer resin content is below 5%, it is insufficient to form a continuous and complete resin network to encapsulate and bond the large amount of inorganic filler, potentially leading to poor film formation, a loose film layer, and insufficient adhesion. Conversely, if the polymer resin content exceeds 50%, the relative content of inorganic fillers decreases, making the protective film overall too "soft," with reduced hardness and mechanical strength, failing to meet the protection requirements of high-intensity machining.

[0153] Therefore, by controlling the weight percentages of polymer resin and inorganic filler to within the ranges of 5% to 50% and 50% to 95% respectively, the optimal balance between adhesive film-forming properties and mechanical protection is achieved, ensuring that the composition can form a uniform, highly adhesive protective layer and provide sufficient hardness and strength after curing to cope with subsequent machining operations.

[0154] In some embodiments of the present invention, the polymer resin comprises 50% to 95% (e.g., 50%, 60%, 70%, 80%, 90%, 95%, etc.) of structural resin and 5% to 50% (e.g., 5%, 10%, 20%, 30%, 40%, 50%, etc.) of binding resin by weight. This internal proportion is designed to precisely balance the two core properties sought in the resin composition of the present invention: excellent protective capabilities and convenient removability.

[0155] As mentioned earlier, the structural resin is the functional component that provides the final protective film's water solubility. To ensure that the protective film can be quickly and thoroughly removed without residue under mild hot water conditions after fulfilling its purpose, the structural resin must dominate the entire polymer system. By controlling its content within a relatively high range of 50% to 95%, sufficient hydrophilic groups and water-soluble segments are retained in the entire polymer network after curing and crosslinking, providing ample channels for water molecule penetration and disruption, thus ensuring excellent "mild removal" characteristics. If the structural resin content is below 50%, the proportion of the crosslinked hydrophobic network will be too high, potentially leading to difficulties in film removal.

[0156] The bonding resin (phenolic and epoxy system) is key to providing protective performance. It forms strong chemical bonds through a cross-linking reaction with the structural resin, significantly improving the hardness, adhesion, and chemical resistance of the protective film. If the content of the bonding resin is less than 5%, its cross-linking modification effect will be insignificant, resulting in a softer protective film that cannot provide sufficient mechanical strength to withstand processing stresses such as milling. Conversely, if its content is higher than 50%, it will lead to excessively high cross-linking density and overly strong hydrophobicity of the entire polymer system. This will severely affect the water solubility of the structural resin, making the protective film difficult to remove effectively in hot water, thus defeating the purpose of this invention.

[0157] Therefore, by controlling the content of the adhesive resin within the range of 5% to 50%, sufficient mechanical strength and adhesion are ensured for the protective film without sacrificing its final water solubility and removability.

[0158] In some embodiments of the present invention that include toughening resin, the relative content of each component within the polymer resin is further defined. Specifically, the polymer resin may contain 5% to 50% by weight of a binding resin and 50% to 95% of a combination of structural resin and toughening resin. This ratio is designed to maintain the critical balance between the two core characteristics of the present invention—"strong protection" and "gentle removal"—while optimizing performance through the introduction of toughening resin.

[0159] In this technical solution, a combination of structural resin and toughening resin constitutes the functional matrix of the polymer system. The structural resin provides the basic water-soluble framework, while the toughening resin reinforces this framework with specific properties. To ensure that the entire polymer matrix maintains excellent hydrophilicity and removability after cross-linking and curing, this functional matrix combination must constitute a dominant proportion of the entire polymer resin, i.e., 50% to 95%. This high proportion ensures that water can effectively penetrate and disrupt the film structure during the removal process, achieving rapid and residue-free film removal.

[0160] The binder resin acts as a high-performance crosslinking agent and reinforcing agent. Its role is to react with the active groups in the functional matrix (structural resin and toughening resin) to form a tough, highly adhesive three-dimensional network. If the binder resin content is less than 5%, the degree of crosslinking is insufficient, and the hardness and adhesion of the protective film will not meet the requirements of machining. Conversely, if its content is higher than 50%, it will form an overly dense hydrophobic crosslinking network, severely weakening the water solubility of the functional matrix, making the protective film difficult to remove.

[0161] Therefore, by precisely controlling the ratio of the bonding resin to the (structural resin + toughening resin) combination, this invention achieves the best balance between the two core characteristics of "strong protection" and "gentle removal" while introducing toughening resin to optimize specific properties.

[0162] To further improve the processing performance and final film quality of the water-washed plugging resin composition, in some embodiments of the present invention, the composition further includes an auxiliary agent. This auxiliary agent may be selected from at least one of leveling agents, dispersants, and defoamers. Examples of suitable auxiliary agents include, but are not limited to, products such as dispersant BYK2152, defoamer BYK530, and leveling agent BYK333.

[0163] In some embodiments, the total weight percentage of the adjuvant in the composition may be from 0.5% to 5%.

[0164] The addition of these additives is intended to optimize the physicochemical behavior of the composition during preparation, storage, and application.

[0165] Specifically, the main function of the dispersant is to improve and stabilize the dispersion of high-content inorganic fillers in the resin matrix. Because the inorganic filler content in the composition of this invention is very high (up to 95%), the dispersant can wet and coat the surface of the inorganic filler particles, effectively preventing particle aggregation and sedimentation through electrostatic repulsion or steric hindrance, thereby ensuring the uniformity and storage stability of the slurry.

[0166] The main function of leveling agents is to improve the surface appearance of the composition during the coating and film-forming process. They can reduce the surface tension of the slurry, promote its flow and spread on the substrate, and eliminate surface defects such as brush marks, orange peel, and pinholes that may occur during construction, resulting in a smoother and more even surface of the final cured protective film.

[0167] The main function of defoamers is to eliminate air bubbles introduced into the slurry during preparation and application due to high-speed mixing or shearing. If these air bubbles remain in the final film layer, they will form pinholes or voids, which not only affect the appearance but also severely weaken the density and mechanical strength of the protective film, reducing its protective effect.

[0168] The total content of additives is controlled within the range of 0.5% to 5% because if the additive content is less than 0.5%, the above-mentioned improvement effect will not be obvious; if the content is higher than 5%, the excessive additives may have an adverse effect on the performance of the final protective film, such as reducing adhesion, affecting curing speed, or reducing film hardness.

[0169] It is understood that by introducing these functionally specific additives and controlling their dosage within an optimal range, the present invention can ensure the stability and reliability of its resin composition during preparation and application, thereby providing a strong guarantee for the final formation of a high-quality, high-performance protective film. In some specific embodiments, examples of additives that can be used include, but are not limited to, products such as BYK530, BYK 2152, and BYK333.

[0170] In some embodiments of the present invention, a solvent is also included in the composition to adjust its viscosity and rheological properties for suitability for different coating processes (such as screen printing, spraying, etc.). This solvent may be selected from at least one or a mixture of water, N-methylpyrrolidone, ethanol, acetone, ethyl acetate, n-butyl ether, methyl tert-butyl ether, dimethyl phthalate, butanone, dimethyl sulfoxide, n-butyl ketone, cyclohexanone, toluene, and xylene. Furthermore, in some embodiments, the total weight percentage of the solvent in the final composition to be applied may be from 1% to 20%.

[0171] The solvent primarily acts as a carrier medium in the composition, its core function being to dissolve the polymeric resin (including structural and binding resins) and uniformly disperse inorganic fillers and other additives, forming a homogeneous, stable liquid or paste system with a suitable application viscosity. This invention is called a "water-washed" pore-filling resin because water is the primary solvent for dissolving structural resins (such as PVA). Simultaneously, considering that binding resins (such as epoxy / phenolic resins) may require specific organic solvents to achieve better solubility and compatibility, a mixed solvent system consisting of water and one or more organic solvents can be used. This flexibility allows the invention to adapt to a wider variety of polymeric resin combinations.

[0172] Maintaining the solvent content within the range of 1% to 20% is crucial for achieving a balance between good processability and efficient production. If the solvent content is below 1%, the composition will have excessively high viscosity and poor flowability, leading to mixing difficulties and hindering uniform application via screen printing, spraying, or other methods. If the solvent content is above 20%, the composition will have excessively low solids content, which not only prolongs the subsequent baking and curing time for solvent removal and reduces production efficiency, but may also cause significant volume shrinkage during solvent evaporation, thus affecting the density, smoothness, and adhesion of the final protective film. Therefore, by controlling the solvent content within this optimized range, this invention ensures that its resin composition possesses both excellent workability and forms a high-quality protective film after curing.

[0173] As can be seen from the above embodiments, the water-washed pore-plugging resin composition provided by the present invention has the following significant beneficial effects:

[0174] 1. This invention provides strong and effective protection against transverse milling, fundamentally avoiding defects such as burrs and wire lifting: The inorganic filler with surface-modified functional groups in the composition of this invention enables the cured protective layer to have extremely high hardness and mechanical strength, acting as a temporary "reinforced ceramic layer" to effectively resist and disperse the impact and cutting stress of the milling cutter. The phenolic and epoxy binder resin forms a dense, high-strength three-dimensional cross-linked network during curing. This network not only firmly "bonds" the high-content inorganic filler particles together to form a robust whole, but also enables the entire protective layer to have extremely strong adhesion to the copper surface and substrate of the printed circuit board. Therefore, based on the combination of inorganic filler and binder resin, the protective layer formed by this invention is hard, dense, and has strong adhesion, sufficient to provide rigid support for the wires and hole walls during milling, thus solving the problems of burrs and wire lifting that cannot be solved by existing technologies.

[0175] 2. This invention provides a mild, efficient, and environmentally friendly removal method, avoiding damage to the substrate and chemical pollution: The structural resin of the polymer containing repeating units derived from vinyl alcohol, which forms the main framework of the polymer system, imparts water-sensitive properties to the entire protective layer due to the densely distributed hydrophilic groups (hydroxyl groups) on its molecular chains. Thus, although there is a cross-linked, water-insoluble adhesive resin network in the protective film, the structural resin, as the main framework, still retains channels for water molecule penetration and attack. Under hot water conditions (e.g., 50℃-95℃), water molecules can effectively penetrate, swell, and destroy the framework of the structural resin, thereby causing the entire cross-linked network structure to rapidly disintegrate and peel off. This process does not require the use of any strong acids, strong alkalis, or other chemical solvents, making it not only simple, fast, and residue-free, but more importantly, it causes no damage to the circuit board substrate and is very environmentally friendly.

[0176] In summary, this invention cleverly solves the seemingly contradictory technical requirements of "protection" and "removal" through the synergistic effect of structural resin, binding resin and inorganic filler.

[0177] The present invention also provides a method for preparing a water-washed pore-plugging resin composition, for preparing the water-washed pore-plugging resin composition as described in any of the preceding embodiments.

[0178] like Figure 1 As shown, in some embodiments, the method for preparing the water-washed pore-plugging resin composition includes the following steps:

[0179] S1. Preparation of resin slurry: The polymer resin is mixed in the first solvent to obtain the resin slurry.

[0180] This step aims to obtain a homogeneous, gel-free resin slurry.

[0181] Specifically, if the polymeric resin water-washed plugging resin composition contains a toughening resin, the toughening resin, structural resin, and binding resin are mixed together in a first solvent; if the polymeric resin does not contain a toughening resin, the structural resin and binding resin are mixed in a first solvent.

[0182] In a preferred embodiment, to improve the mixing effect in subsequent steps, additives such as dispersants, defoamers, and leveling agents can be pre-dissolved or dispersed in the first solvent before adding the polymer resin component. Examples of additives that can be used include, but are not limited to, products such as BYK530, BYK 2152, and BYK333.

[0183] Specifically, the mixing process for preparing resin slurry can be achieved using high-speed mixing equipment such as a homogenizer. Of course, the homogenizer can be replaced by an emulsifier, a high-speed mixer, or a collider.

[0184] Furthermore, the mixing speed can be from 3600 rpm to 7200 rpm. To prevent the resin stability from being affected by heat generated by high-speed shearing, the entire process can be carried out in a reactor with a cooling jacket to ensure that the slurry temperature does not exceed 45°C. The mixing time can be any value between 20 minutes and 40 minutes, for example, 30 minutes, to ensure the formation of a homogeneous and stable resin slurry (also referred to as slurry A).

[0185] S2. Preparation of filler slurry: Inorganic fillers are mixed in a second solvent to obtain filler slurry.

[0186] The goal of this step is to prepare a highly dispersed, non-agglomerated inorganic slurry. Specifically, a surface-modified inorganic filler (such as aniline-modified silica) is mixed in a second solvent. The inorganic filler provides mechanical reinforcement, while the surface-modified functional groups improve interfacial compatibility.

[0187] In a preferred embodiment, the dispersant or other additives can be pre-dissolved or dispersed in a second solvent before adding the inorganic filler to improve the dispersion efficiency of the filler. This process can employ similar equipment and process parameters as step S1, for example, using a homogenizer at a rotation speed of 3600 rpm to 7200 rpm and a temperature not exceeding 45°C. The mixing time can be any value between 20 minutes and 40 minutes, such as 30 minutes, to ensure that the inorganic filler particles are fully wetted and uniformly dispersed, forming a non-agglomerated filler slurry (also referred to as slurry B).

[0188] It is worth noting that the first solvent and the second solvent can be the same or different. Specifically, the first solvent and the second solvent can be selected from at least one of water, N-methylpyrrolidone, ethanol, acetone, ethyl acetate, n-butyl ether, methyl tert-butyl ether, dimethyl phthalate, butanone, dimethyl sulfoxide, n-butyl ketone, cyclohexanone, toluene, and xylene.

[0189] S3. Mixing: The filler slurry is added to the resin slurry being stirred and mixed to obtain a water-washed pore-plugging resin composition mixed slurry.

[0190] Specifically, the prepared filler slurry (slurry B) is slowly added to the stirred resin slurry (slurry A) to prevent filler agglomeration due to excessively high local concentrations. After the addition is complete, thorough mixing is continued using equipment such as a homogenizer to ensure that the filler particles achieve optimal dispersion in the final resin composition. The process parameters for this final mixing step can be a rotation speed of 3600 rpm to 7200 rpm, a temperature not exceeding 45°C, and a duration of any value between 60 minutes and 120 minutes, such as 90 minutes, to obtain the final water-washed pore-plugging resin composition.

[0191] In some embodiments, in order to precisely control the workability (especially solid content and viscosity) of the final composition to suit different application requirements, the preparation method may further include a post-processing step S4 after step S3:

[0192] S4. Desolventization: The water-washed pore-filling resin composition mixture is desolventized to obtain a water-washed pore-filling resin composition ink with a solid content between 64% and 98% and a viscosity between 10000 Pa·s and 50000 mPa·s.

[0193] Specifically, this step can be achieved using specialized equipment, such as a vacuum mixer or a vacuum-heated mixer. The slurry mixture obtained in step S3 is placed in the equipment, and while continuously stirring, the system is evacuated to a gauge pressure below 0.1 MPa. The vacuum environment significantly lowers the boiling point of the solvent, allowing it to evaporate efficiently at lower temperatures, thus avoiding premature reaction or degradation of the resin components that might occur during high-temperature processing.

[0194] To further improve the desolventizing efficiency, the composition can be gently heated, for example, by controlling the temperature within the range of 20°C to 50°C. The vacuum stirring process is continued for 5 minutes to 3 hours, by monitoring the viscosity of the composition or measuring its solid content by sampling, until the performance indicators of the composition reach the preset values.

[0195] It is understood that by adding this controllable desolventizing step, the preparation method of the present invention has greater flexibility and can produce a series of products with different solid contents and viscosity specifications according to the downstream application requirements, thereby enhancing the process adaptability and market application range of the composition.

[0196] This invention also proposes a method for manufacturing a circuit board, which uses the water-washed plugging resin composition described in any of the foregoing embodiments as a temporary protective material to protect the circuit board from damage during machining. (Refer to...) Figure 2 In one specific embodiment, the preparation method may include the following steps:

[0197] S10. Provide a substrate: Provide a circuit board substrate with a protected area, the protected area having a hole structure.

[0198] First, a circuit board substrate to be processed is provided. This substrate can be a conventional printed circuit board (PCB), semiconductor chip carrier board, etc. The substrate has areas requiring temporary protection, such as fine copper traces, epoxy green varnish surfaces, and vias and blind vias that require special protection. Before proceeding to the next step, it must be ensured that the surfaces of the areas to be protected on the substrate are clean and dry to guarantee the adhesion of the subsequent protective layer.

[0199] S20. Forming a protective layer: The water-washable plugging resin composition as described in any of the foregoing embodiments is applied to the area to be protected on the circuit board substrate and the hole structure is filled, and then cured to form a protective layer.

[0200] Specifically, this step includes two stages: application and curing.

[0201] Application: The water-washable via-filling resin composition in ink form as described in any of the foregoing embodiments is applied to the area to be protected on the circuit board substrate using a suitable coating method. The application method can be at least one of screen printing, pad printing, stencil printing, spraying, and squeegee printing. During operation, it should be ensured that the composition not only uniformly covers the planar area to be protected but also completely fills the interior of the via structure without leaving any gaps.

[0202] In a preferred embodiment, the final dry film thickness of the protective layer can be controlled between 10 μm and 20 μm. The core objective of precisely controlling the dry film thickness within this range is to achieve a balance between "adequate protective capability" and "efficient process feasibility." This is an optimized process window; too thin or too thick a layer will not achieve the desired technical effect.

[0203] Specifically, if the thickness of the protective film is less than 10μm, its protective performance will be greatly reduced, mainly in the following aspects:

[0204] Insufficient mechanical strength and wear resistance: The core function of the protective film is to provide rigid support for the copper surface and hole walls during high-intensity machining processes such as milling and drilling. If the film layer is too thin, it is too fragile and can be easily penetrated or worn away instantly under the high-speed rotation and cutting force of the milling cutter. It cannot effectively disperse and resist stress, thus losing its fundamental function of preventing burrs and line lifting.

[0205] Poor film integrity and coverage uniformity: At the microscopic level, the circuit board surface is not absolutely flat, and there are microscopic undulations caused by lines, etching, etc. An excessively thin coating is difficult to form a uniform and defect-free protective film, and it is easy to produce weak points such as pinholes and breaks in low-lying areas or rough surfaces. These weak points will become the source of defects in subsequent processing.

[0206] Ineffective filling and support of pore structures: As a "pore-filling resin," filling and supporting pore structures is one of its important functions. Films with a thickness of less than 10μm are difficult to form effective support at the pore openings, especially for larger pore diameters, which may form a fragile "drum skin" that is easily broken during processing and cannot protect the pore edges.

[0207] If the protective film thickness exceeds 20μm, although the protection may be stronger, it will bring a series of process and cost problems:

[0208] Curing difficulties: A thicker film layer means that more time and higher energy are needed to completely remove the internal solvent and allow the resin to fully cure. If curing is incomplete, the film layer will be too soft and lack hardness, which will actually affect the protective effect.

[0209] Removal difficulties: In the removal process, hot water needs to penetrate the entire membrane layer to break down its structure. The thicker the membrane layer, the longer the penetration path, and the longer the processing time required, which significantly reduces the overall efficiency of the production line.

[0210] Increased material costs: While meeting protection requirements, a thicker membrane layer means higher material consumption per unit area, which directly leads to an increase in production costs.

[0211] Thicker coatings increase curing stress and adhesion risks: During solvent evaporation and curing, they experience greater volume shrinkage, leading to the accumulation of higher internal stress. Excessive internal stress can cause film cracking, decreased adhesion, or even warping and peeling from the substrate.

[0212] Further, curing: The circuit board coated with the composition is placed in a heating device such as a hot air furnace for curing treatment to remove the solvent in the composition and crosslink it to form a hard, dense protective layer.

[0213] In one embodiment, the curing process involves drying the water-washed pore-filling resin composition ink at a temperature range of 50°C to 120°C for 3 to 30 minutes. The reason for setting the temperature and time parameters for the above curing process is as follows:

[0214] First, the composition of this invention is washable and contains water and other possible organic solvents. Baking at a specific temperature is necessary to provide sufficient energy for the solvent molecules to overcome surface tension and escape from the coating. If the temperature is below 50°C, the solvent evaporation rate will be too slow, significantly extending production time and potentially causing solvent residue to remain inside the film. Residual solvent will severely affect the hardness and adhesion of the protective film, preventing it from forming an effective protective layer.

[0215] Furthermore, the substrate material of printed circuit boards (such as FR-4) itself has its temperature limit (usually characterized by the glass transition temperature Tg). Controlling the upper limit of the curing temperature to 120°C is a safe temperature that is far below the Tg of most commonly used substrates, which can effectively avoid irreversible damage such as substrate warping, delamination, or performance degradation caused by overheating.

[0216] Meanwhile, the cross-linking and curing reaction of the bonding resin (epoxy / phenolic system) needs to be initiated and carried out under certain energy conditions. A temperature of 120°C is sufficient to drive the reaction to proceed fully within a reasonable time, but not so high as to cause the reaction rate to run away. An excessively rapid reaction will generate huge internal stress, which may lead to the protective film becoming brittle, cracking, or having reduced adhesion.

[0217] Secondly, it takes time for the solvent to completely evaporate from the film. Even at a suitable temperature, if the baking time is less than 3 minutes, the solvent deep within the film may not have enough time to escape, resulting in incomplete curing. Similarly, the chemical cross-linking reaction also requires time. Insufficient curing time will lead to insufficient cross-linking density, resulting in a soft protective film that cannot achieve the hardness required to resist machining.

[0218] Furthermore, from an industrial production perspective, time equals cost. The formulation of this invention is designed to achieve the ideal curing state within 30 minutes. Beyond this time, the improvement in protective film performance becomes insignificant, while significantly reducing production line efficiency and increasing energy consumption and production costs.

[0219] In addition, prolonged heating may lead to over-curing, which may not only make the protective film too brittle, but may also have a potential impact on the molecular structure of the structural resin (PVA), thereby reducing its final solubility in hot water and making the final removal step difficult.

[0220] In another preferred embodiment, a staged heating baking process can be used to cure the water-washed pore-filling resin composition ink. For example, baking can be performed first at 40°C to 60°C for 10 minutes, then at 90°C to 110°C for 10 minutes, and finally at 140°C to 160°C for 10 minutes to ensure gentle solvent evaporation and sufficient film curing. The core purpose of this staged heating baking process is to systematically and stepwise control two key physicochemical changes that occur during the curing process: solvent evaporation and resin crosslinking reaction.

[0221] Directly applying a single high-temperature baking process will cause these two changes to occur simultaneously and drastically, leading to a series of film defects. The staged heating method provides optimal conditions for each change process, ultimately resulting in a dense, uniform, defect-free, and high-performance protective film.

[0222] Specifically, when a liquid resin composition is applied to a substrate, it contains a large amount of solvent. If immediately placed in a high-temperature environment, the film surface will rapidly heat up and begin to solidify, forming a dense "skin." This skin acts like a lid, trapping the solvent deep within the film. As the temperature continues to rise, the trapped solvent will boil or evaporate violently, but unable to escape, eventually forming defects such as bubbles and pinholes within the film, or leaving crater-like marks when it breaks through the skin. Therefore, by performing the first stage of baking at a lower temperature of 40°C to 60°C, it is ensured that the entire film is heated gently and uniformly. This allows the solvent to evaporate and escape slowly and orderly from the inside out, without causing premature surface solidification, thus preventing defect formation and ensuring the uniformity of the film.

[0223] After most of the solvent has been removed in the first stage, the temperature needs to be increased to provide sufficient activation energy for the chemical crosslinking reaction of the bonding resin (epoxy / phenolic system). However, this crosslinking process, accompanied by the movement of molecular chains and the formation of chemical bonds, will generate a certain amount of volume shrinkage and internal stress. If the temperature is increased too quickly or too high, the crosslinking reaction will proceed too violently, causing internal stress to accumulate rapidly and not be released. This may eventually make the protective film brittle and crack, or reduce its adhesion to the substrate due to excessive stress. By performing the second stage of baking at a moderate temperature of 90°C to 110°C, the crosslinking reaction can be started smoothly and proceed in an orderly manner, thereby effectively releasing the internal stress generated during the curing process, enhancing the final adhesion between the film layer and the substrate, and avoiding the risk of cracking due to excessive brittleness of the film layer.

[0224] Finally, to ensure the protective film achieves its ultimate and optimal mechanical properties (such as hardness and abrasion resistance) and chemical properties (chemical resistance), the crosslinking reaction must be ensured to proceed as completely as possible. This requires a high temperature to provide sufficient energy to overcome steric hindrance in the later stages of the reaction, driving all reactive functional groups to fully react and form a highly crosslinked, dense, and stable three-dimensional network structure. The crosslinking reaction can be pushed to its extreme by performing a final baking stage at a high temperature of 140°C to 160°C. This allows the protective film to achieve the highest hardness, abrasion resistance, and Young's modulus that its formulation can provide, enabling it to perfectly withstand subsequent high-intensity machining processes such as milling and drilling; and ensuring that the various properties of the protective film (including heat resistance and chemical resistance) remain stable and unchanged during subsequent processing and cleaning.

[0225] S30. Machining: Machining printed circuit boards with a protective layer.

[0226] Specifically, the circuit board with the protective layer already formed is subjected to the required machining, such as milling with a milling cutter or mechanical drilling. During this process, the high-hardness, high-adhesion protective layer formed by the curing of the composition of the present invention can provide effective rigid support for the copper foil and hole walls in the machining area, thereby preventing defects such as burrs, flash, or line lifting caused by cutting stress.

[0227] S40. Remove the protective layer: After machining, use a water washing solution to remove the protective layer.

[0228] After machining, the circuit board is cleaned to remove the temporary protective layer. Specifically, the water-soluble properties of the protective layer can be utilized by immersing it in hot water for washing. In a preferred embodiment, hot water at a temperature between 50°C and 95°C can be used for rinsing or soaking, with hot water at around 80°C achieving particularly good removal results. To improve removal efficiency, ultrasonic vibration can also be used.

[0229] In some preferred embodiments, to further improve the removal efficiency of the protective layer, specific additives may be added to the water washing solution used in the removal step. These additives, through chemical or physical action, synergistically accelerate the breakdown and peeling of the protective film with hot water. Specifically, the water washing solution may contain a selection of acidic solutes, basic solutes, surfactants, and mixtures of surfactants with acidic or basic solutes.

[0230] Specifically, acidic solutes (in one embodiment, at least one of sulfuric acid and hydrochloric acid) or alkaline solutes (in one embodiment, at least one of potassium hydroxide and sodium hydroxide) primarily act as chemical peeling aids. This chemical peeling effect is multifaceted: on the one hand, they catalyze the hydrolysis of ester bonds, ether bonds, and other chemical bonds formed during the curing process of the bonding resin (epoxy / phenolic system), thereby accelerating the chemical attack and destruction of the water-insoluble cross-linked network structure. On the other hand, when the inorganic filler in the protective layer contains, for example, aluminum hydroxide, because aluminum hydroxide is an amphoteric substance that reacts with both acids and strong bases, it can also be rapidly dissolved by hot acidic or alkaline water, thus significantly and effectively removing the protective layer. This chemical degradation, combined with the swelling and dissolution of the structural resin by hot water, creates a "double attack" effect, greatly shortening the removal time.

[0231] In one embodiment, when the washing solution contains acidic or alkaline solutes, their weight percentage can be between 1% and 20%, preferably less than 10%. This is because if the concentration of the acidic or alkaline solute is below 1%, its chemical stripping effect is not significant; if the concentration is above 20%, it may pose an unnecessary risk of corrosion to exposed metal traces (such as copper) on the circuit board, while also increasing the cost and environmental burden of the treatment. Therefore, 1% to 20% is an optimized balance range between ensuring efficient removal and protecting the substrate. Furthermore, a concentration of acidic or alkaline solutes below 10% can greatly avoid damage to other materials.

[0232] Specifically, the surfactant (in one embodiment, the surfactant can be a product with alkyl-terminated fatty alcohol polyoxyethylene ether) primarily improves removal efficiency through physical action. First, it significantly reduces the surface tension of water, acting as an excellent wetting agent, allowing the washing solution to penetrate more quickly into the interface between the protective film and the substrate, as well as into the micro-cracks within the film layer. Second, after the protective film begins to break down, the surfactant emulsifies and encapsulates the detached resin and filler fragments, preventing them from re-depositing onto the already cleaned circuit board surface, ensuring thorough cleaning.

[0233] In one embodiment, when the washing solution contains a surfactant, its weight percentage can be between 0.5% and 3%. This is because if the concentration of the surfactant is below 0.5%, its wetting and emulsifying effects are limited; if the concentration is above 3%, it will not only cause unnecessary cost waste and foaming problems, but its effect improvement will also be insignificant.

[0234] It is understood that by selectively adding one or more of the above-mentioned additives to the hot water removal process and controlling their concentration within the optimal range, the method of the present invention can flexibly meet different production needs and achieve the most efficient, economical and safest protective layer removal process for products.

[0235] Finally, after the protective layer is completely removed, the circuit board can be rinsed with deionized water and then dried to obtain a high-quality finished circuit board with a clean surface, no damage, and no processing defects.

[0236] It is worth noting that the method and composition described in this invention achieve excellent technical results after completing the entire temporary protection process. This is reflected not only in the effective suppression of defects such as burrs and protrusions during processing, but also in the perfect preservation of the circuit board substrate after processing. Specifically:

[0237] 1. Excellent removal cleanliness with no surface residue: After cleaning with hot water or a water-washing solution containing additives, the cured protective film can be completely and cleanly removed, leaving no resin, filler, or other residue on the surface of the circuit board substrate (including the copper and green paint surfaces). This is crucial for subsequent PCB manufacturing processes. A clean, uncontaminated substrate surface is fundamental to the successful implementation of subsequent processes (such as applying solder resist, performing electrical testing, chemical plating, or electroplating). Any minute residue can cause serious functional defects such as poor solder resist adhesion, probe contact failure, or poor adhesion of subsequent plating layers, leading to the scrapping of the entire circuit board. This invention ensures absolute surface cleanliness, providing a reliable guarantee for the success of all subsequent processes and significantly improving the overall yield and long-term reliability of the product.

[0238] 2. Gentle Process, No Damage to the Original Substrate Structure: The entire process of this invention (including the curing and removal of the protective layer) is completely non-destructive to the circuit board substrate itself. A key metric is that the adhesion between the original metal traces (such as copper foil) on the circuit board and its substrate remains intact after the protective layer is removed. In some embodiments, after treatment by the method of this invention, the peel strength of the plugged via area or the protected trace area meets industry standards, for example, not less than 4 N / cm. This metric strongly demonstrates that the process of this invention is a non-invasive, non-destructive, and gentle process. Neither the curing process of the composition nor the subsequent hot water removal process has a negative impact on the materials of the circuit board substrate (such as epoxy resin, BT resin, etc.) or the interfacial bonding between the metal traces and the substrate. This solves the problem of excessive etching or substrate attack that may occur with some traditional chemical peeling methods, ensuring that the intrinsic quality and reliability of circuit boards, especially high-frequency high-speed boards or flexible boards, which have extremely high requirements for material performance and structural integrity, are not compromised.

[0239] The present invention also proposes a circuit board, which is prepared using the circuit board preparation method of any of the foregoing embodiments.

[0240] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A water-washed pore-plugging resin composition, characterized in that, Including polymer resins and inorganic fillers, among which, The polymer resin includes: Structural resin, the structural resin comprising a polymer having repeating units derived from vinyl alcohol; The adhesive resin comprises phenolic resin and epoxy resin; The surface of the inorganic filler is modified with one or more functional groups selected from the group consisting of aniline, alkyl, nitrogen-containing functional groups on the main chain or branches, double-bonded functional groups, and epoxy groups.

2. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The polymer having repeating units derived from vinyl alcohol is polyvinyl alcohol, and the degree of alcoholysis of the polyvinyl alcohol is between 78% and 100%.

3. The water-washed pore-plugging resin composition according to claim 2, characterized in that, The molecular weight of the polyvinyl alcohol is between 10,000 g / mol and 300,000 g / mol.

4. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The epoxy resin is selected from at least one of the following: glycidylamine epoxy resin, polyfunctional o-cresol glycidyl ether epoxy resin, phenol-biphenyl epoxy resin, bisphenol F solid epoxy resin, isocyanate modified epoxy resin, naphthol epoxy resin, phenol-formaldehyde epoxy resin, semi-crystalline epoxy resin, liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, liquid bisphenol A-bisphenol F composite epoxy resin, liquid bisphenol S epoxy resin, liquid phenolic epoxy resin, and liquid phenolic resin.

5. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The phenolic resin is selected from at least one of linear phenol-formaldehyde resin and linear BPA-formaldehyde resin.

6. The water-washed pore-plugging resin composition according to claim 1, characterized in that, In the bonding resin, the ratio of the content of phenolic resin to the content of epoxy resin satisfies the following formula: Phenolic resin content = (hydroxyl equivalent of phenolic resin / epoxy equivalent of epoxy resin) × epoxy resin content.

7. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The water-washed pore-sealing resin composition further includes a solvent selected from at least one of water, N-methylpyrrolidone, ethanol, acetone, ethyl acetate, n-butyl ether, methyl tert-butyl ether, dimethyl phthalate, butanone, dimethyl sulfoxide, n-butyl ketone, cyclohexanone, toluene, and xylene.

8. The water-washed pore-plugging resin composition according to claim 7, characterized in that, The water-washed pore-filling resin composition further includes an additive selected from at least one of leveling agents, dispersants, and defoamers.

9. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The inorganic filler is selected from at least one of silicon dioxide, aluminum oxide, aluminum hydroxide, calcium carbonate, magnesium carbonate, magnesium silicate, silicon carbide, titanium carbide, titanium oxide, magnesium oxide, calcium oxide, boron nitride, or aluminum nitride.

10. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The polymeric resin further includes a toughening resin, which is selected from at least one of polyvinyl butyral, polyimide, poly(p-phenylenebenzodioxazole), polybenzimidazole, polyamic acid, polyethylene glycol, and rubber polymers.

11. The water-washed pore-plugging resin composition according to claim 10, characterized in that, The rubber polymer is selected from at least one of natural rubber, nitrile rubber, styrene-butadiene rubber, chloroprene rubber, ethylene propylene diene monomer (EPDM) rubber, modified EPDM rubber, thermoplastic EPDM rubber, acrylic rubber, fluororubber, EPDM rubber, polyurethane rubber, and silicone rubber.

12. The water-washed pore-plugging resin composition according to claim 11, characterized in that, The toughening resin accounts for 1% to 30% of the total weight of the structural resin and the toughening resin.

13. The water-washed pore-plugging resin composition according to claim 12, characterized in that, The polymer resin contains, by weight percentage: 5% to 50% of the adhesive resin; and A combination of 50% to 95% of the structural resin and the toughening resin.

14. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The polymer resin contains, by weight percentage: 5% to 50% of the adhesive resin; and 50% to 95% of the structural resin.

15. The water-washed pore-plugging resin composition according to any one of claims 1 to 14, characterized in that, The water-washed pore-plugging resin composition comprises, by weight percentage: 5% to 50% of polymer resin; and The inorganic filler comprises 50% to 95%.

16. The water-washed pore-plugging resin composition according to claim 15, characterized in that, The water-washed pore-plugging resin composition further comprises, by weight percentage: Solvents ranging from 1% to 20%; and 0.5% to 5% of adjuvants.

17. A method for preparing a water-washed pore-plugging resin composition, used to prepare the water-washed pore-plugging resin composition according to any one of claims 1 to 16, characterized in that, The preparation method includes the following steps: Preparation of resin slurry: The polymer resin is mixed in a first solvent to obtain a resin slurry; Preparation of filler slurry: The inorganic filler is mixed in a second solvent to obtain a filler slurry; and Mixing: The filler slurry is added to the resin slurry being stirred and mixed to obtain a water-washed pore-plugging resin composition mixed slurry.

18. The method for preparing the water-washed pore-plugging resin composition according to claim 17, characterized in that, The polymeric resin includes structural resin, bonding resin, and toughening resin.

19. The method for preparing the water-washed pore-plugging resin composition according to claim 17, characterized in that, In the step of preparing the resin slurry, at least one additive selected from dispersants, defoamers, and leveling agents is pre-dissolved in the first solvent; and / or In the step of preparing the filler slurry, at least one additive selected from dispersants, defoamers and leveling agents is pre-dissolved in the second solvent.

20. The method for preparing the water-washed pore-plugging resin composition according to claim 17, characterized in that, The mixing conditions of the preparation method include at least one of the following: The mixing speed during the preparation of the resin slurry is between 3600 rpm and 7200 rpm, the slurry temperature is not higher than 45°C, and the duration is between 20 minutes and 40 minutes. The mixing speed during the preparation of the filler slurry is between 3600 rpm and 7200 rpm, the slurry temperature is not higher than 45°C, and the duration is between 20 minutes and 40 minutes; and The mixing speed of the filler slurry and the resin slurry is between 3600 rpm and 7200 rpm, the slurry temperature is not higher than 45°C, and the duration is between 60 minutes and 120 minutes.

21. The method for preparing the water-washed pore-plugging resin composition according to any one of claims 17 to 20, characterized in that, Following the mixing step, the preparation method further includes the following steps: Desolventization: The water-washed pore-filling resin composition mixture is subjected to desolventization treatment to obtain a water-washed pore-filling resin composition ink with a solid content between 64% and 98% and a viscosity between 10000 Pa·s and 50000 mPa·s.

22. The method for preparing the water-washed pore-plugging resin composition according to claim 21, characterized in that, The solvent removal process includes: The water-washed pore-filling resin composition mixture was stirred for 5 minutes to 3 hours at a temperature of 20°C to 50°C and a vacuum degree of less than 0.1 MPa.

23. A method for manufacturing a circuit board, characterized in that, Includes the following steps: Provide substrate: Provide a circuit board substrate having a protected area, wherein the protected area has a hole structure; Forming a protective layer: After applying the water-washable plugging resin composition of any one of claims 1 to 16 to the area to be protected on the circuit board substrate and filling the hole structure, a curing process is performed to form a protective layer; Machining: Machining the printed circuit board on which the protective layer is formed; and Remove the protective layer: After the machining, the protective layer is removed using a water washing solution.

24. The method for manufacturing a circuit board as described in claim 23, characterized in that, The water-washable via-sealing resin composition ink is applied to the area to be protected on the circuit board substrate by at least one of screen printing, pad printing, stencil printing, spraying, and squeegee printing.

25. The method for manufacturing a circuit board as described in claim 24, characterized in that, The curing process includes drying the water-washed pore-filling resin composition ink at a temperature range of 50°C to 120°C for 3 to 30 minutes.

26. The method for manufacturing a circuit board as described in claim 24, characterized in that, The curing process includes: First stage baking: Bake at a temperature range of 40℃ to 60℃ for 10 minutes; Second stage baking: Bake at a temperature range of 90℃ to 110℃ for 10 minutes; and Third stage baking: Bake at a temperature range of 140℃ to 160℃ for 10 minutes.

27. The method for manufacturing a circuit board as described in claim 23, characterized in that, The step of removing the protective layer is carried out using hot water at a temperature between 50°C and 95°C as the washing solution.

28. The method for manufacturing a circuit board as described in claim 23, characterized in that, The washing solution further comprises one of the following: an acidic solute, an alkaline solute, a surfactant, and a mixture of the surfactant and the acidic or alkaline solute, wherein the acidic solute is selected from at least one of sulfuric acid and hydrochloric acid, and the alkaline solute is selected from at least one of potassium hydroxide and sodium hydroxide.

29. The method for manufacturing a circuit board as described in claim 28, characterized in that, If the water washing solution contains the acidic solute, the weight percentage of the acidic solute is between 1% and 20%. If the water washing solution contains the alkaline solute, the weight percentage of the alkaline solute is between 1% and 20%. If the washing solution contains the surfactant, the surfactant has a weight percentage between 0.5% and 3%.

30. The method for manufacturing a circuit board as described in claim 29, characterized in that, The weight percentage of the acidic solute is between 1% and 10%; and / or The weight percentage of the alkaline solute is between 1% and 10%.

31. A circuit board, characterized in that, The circuit board is prepared using the method described in any one of claims 23 to 30.

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