Water-washable plug hole resin composition and method for preparing the same, circuit board and method for processing the same

Abstract

This invention discloses a water-washable via-plugging resin composition and its preparation method, as well as a circuit board and its processing method. The water-washable via-plugging resin composition comprises a polymeric resin and an inorganic filler. The polymeric resin includes a structural resin and a reinforcing resin. The structural resin comprises a polymer having repeating units derived from at least one of vinyl alcohol and vinylpyrrolidone. The reinforcing resin comprises an alkali-soluble resin. The surface of the inorganic filler is modified with at least one functional group selected from the group consisting of aniline, alkyl, nitrogen-containing functional groups on the main chain or branches, and double-bonded functional groups. This invention achieves rigid protection of the circuit and via edges during the machining stage, effectively preventing burrs and circuit lifting defects, while ensuring rapid, gentle, and zero-residue peeling during the film removal stage.

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 processing method. Background Technology

[0002] In the advanced manufacturing process of printed circuit boards (PCBs), drilling, milling, and other machining processes are typically required to achieve electrical interconnection between multiple layers or to cut the PCB's outline. To ensure machining accuracy and protect the PCB surface and internal structure from physical damage, auxiliary protective measures are usually necessary.

[0003] In existing technologies, a common protection method is to place a cover plate (such as wood pulp board or phenolic resin board) under the PCB to provide support when the drill bit penetrates the PCB. However, this traditional cover plate can only provide vertical support. For lateral milling operations, the cover plate cannot provide effective lateral rigidity protection. Specifically, during high-speed milling, the strong lateral cutting forces and shear stresses can easily cause the metal electrodes on the PCB surface to be "picked up" from the substrate, or cause severe "burr" defects at the edges of metallized through holes and blind holes. These irreversible physical damages severely reduce the yield and electrical reliability of high-end circuit boards.

[0004] To compensate for the shortcomings of cover plates, the industry has attempted to introduce temporary protective filler materials. However, these materials face an extremely severe inherent contradiction: to effectively resist the cutting force of high-speed milling cutters, the protective material must possess extremely high mechanical modulus and hardness; but after machining, overly hard and dense materials are often extremely difficult to peel off, requiring prolonged removal using highly corrosive chemical solvents, which can easily cause secondary chemical damage and residual contamination to the PCB's insulating substrate and metal circuitry. Conversely, if easily cleanable soft materials are used, they simply cannot provide the necessary rigid support during milling.

[0005] Therefore, how to provide a temporary protection solution that can provide high-rigidity lateral and vertical protection during machining processes such as drilling and milling to completely prevent burrs and line lifting, while also enabling rapid, gentle, and residue-free removal of the film after machining, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The main objective of this invention is to propose a water-washable plugging resin composition, which aims to solve the technical problem in existing circuit board machining protection schemes that it is difficult to simultaneously achieve high rigidity and anti-cutting protection while ensuring safe and damage-free film removal after processing.

[0007] 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,

[0008] The polymer resin includes:

[0009] Structural resin, the structural resin comprising a polymer having repeating units derived from at least one of vinyl alcohol and vinylpyrrolidone;

[0010] The reinforcing resin comprises an alkali-soluble resin;

[0011] The surface of the inorganic filler is modified with at least one functional group selected from the group consisting of aniline, alkyl, nitrogen-containing functional groups on the main chain or branches, and double-bonded functional groups.

[0012] In one embodiment, the polymer resin further includes a binding resin, which comprises phenolic resin and epoxy resin.

[0013] In one embodiment, the structural resin comprises a polymer having repeating units derived from vinyl alcohol, wherein 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%.

[0014] In one embodiment, the molecular weight of the polyvinyl alcohol is between 10,000 g / mol and 300,000 g / mol.

[0015] In one embodiment, the structural resin comprises a polymer having repeating units derived from vinylpyrrolidone, wherein the polymer having repeating units derived from vinylpyrrolidone is polyvinylpyrrolidone, and the molecular weight of the polyvinylpyrrolidone is between 2,500 g / mol and 1,200,000 g / mol.

[0016] 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 epoxy resin, liquid bisphenol F epoxy resin, liquid bisphenol A-bisphenol F composite epoxy resin, liquid bisphenol S epoxy resin, and liquid phenolic epoxy resin.

[0017] In one embodiment, the phenolic resin is selected from at least one of linear phenol-formaldehyde resin, linear BPA-formaldehyde resin, and liquid phenolic resin.

[0018] In one embodiment, the ratio of the content of phenolic resin to the content of epoxy resin in the bonding resin satisfies the following formula:

[0019] Phenolic resin content = (hydroxyl equivalent of phenolic resin / epoxy equivalent of epoxy resin) × epoxy resin content.

[0020] In one embodiment, the alkali-soluble resin is selected from at least one of the first type of resin and polyimide precursor;

[0021] The first type of resin is a monomer and / or prepolymer containing at least one functional group selected from carboxyl groups, ester bonds and acrylate groups.

[0022] In one embodiment, the acid value of the first type of resin is between 5 mgKOH / g and 300 mgKOH / g, and the molecular weight is between 50 g / mol and 50,000 g / mol; and / or

[0023] The molecular weight of the polyimide precursor is between 1000 g / mol and 100000 g / mol.

[0024] In one embodiment, the first type of resin is selected from at least one of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, carboxyl-functionalized acrylate resin, modified epoxy acrylate resin, modified polyurethane acrylate resin, and modified polyester acrylate resin; and / or

[0025] The polyimide precursor is selected from at least one of polyamic acid and polyisoimide.

[0026] 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, barium sulfate, and aluminum nitride.

[0027] In one embodiment, the polymeric resin further comprises a toughening resin selected from at least one of polyvinyl butyral, polyimide, poly(p-phenylenebenzodioxazole), polybenzimidazole, polyethylene glycol, and rubber polymers.

[0028] 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.

[0029] In one embodiment, the toughening resin accounts for 1% to 30% of the total weight of the structural resin and the toughening resin.

[0030] In one embodiment, the polymer resin comprises, by weight percentage:

[0031] A combination of 30% to 70% consisting of the structural resin and the toughening resin;

[0032] 30% to 65% of the reinforcing resin.

[0033] In one embodiment, the adhesive resin in the polymer resin has a weight percentage of no more than 5%.

[0034] In one embodiment, the water-washed pore-plugging resin composition comprises, by weight percentage:

[0035] 20% to 70% of the aforementioned polymeric resin; and

[0036] The inorganic filler comprises 30% to 80%.

[0037] In one embodiment, the water-washed pore-plugging resin composition further comprises, by weight percentage:

[0038] Solvents ranging from 1% to 20%; and

[0039] 0.5% to 5% of adjuvants.

[0040] In one embodiment, the solvent is 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, N,N-dimethylformamide, N,N-dimethylacetamide, propylene glycol monomethyl ether acetate, toluene, and xylene; and / or

[0041] The additive is selected from at least one of leveling agents, dispersants, and defoamers.

[0042] 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 claims, the preparation method comprising the following steps:

[0043] Preparation of resin slurry: The polymer resin is mixed in a first solvent to obtain a resin slurry;

[0044] Preparation of filler slurry: The inorganic filler is mixed in a second solvent to obtain a filler slurry; and

[0045] 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.

[0046] 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

[0047] 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.

[0048] In one embodiment, the mixing conditions of the preparation method include at least one of the following:

[0049] 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.

[0050] 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

[0051] 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.

[0052] In one embodiment, after the mixing step, the preparation method further includes the following steps:

[0053] 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 10,000 mPa.s and 50,000 mPa.s.

[0054] In one embodiment, the solvent removal process includes:

[0055] 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.

[0056] The present invention also proposes a circuit board processing method using a water-washable via-plugging resin composition as described in any of the preceding claims, the circuit board processing method comprising the following steps:

[0057] Circuit board provided: A circuit board is provided that defines a processing area, on which a target hole to be filled is pre-formed;

[0058] Hole plugging: The water-washed hole plugging resin composition is applied to the processing area of ​​the circuit board and filled into the target hole to be plugged;

[0059] Curing: The water-washed plugging resin composition is heat-treated to form a cured protective film on the circuit board;

[0060] Processing: Machining the circuit board to which the cured protective film has been formed; and

[0061] Film removal: The processed circuit board is cleaned with a water washing solution to remove the cured protective film.

[0062] In one embodiment, the water-washable plugging resin composition is applied to the processing area of ​​the circuit board by at least one of screen printing, pad printing, stencil printing, spraying, and squeegee printing.

[0063] In one embodiment, the heat treatment includes drying the water-washed pore-blocking resin composition for 3 to 30 minutes at a temperature range of 50°C to 120°C.

[0064] In one embodiment, the heat treatment includes stepped baking, which sequentially includes:

[0065] First stage baking: Bake at a temperature range of 40℃ to 60℃ for 10 minutes;

[0066] Second stage baking: Bake at a temperature range of 90℃ to 110℃ for 10 minutes; and

[0067] Third stage baking: Bake at a temperature range of 140℃ to 160℃ for 10 minutes.

[0068] In one embodiment, during the film removal step, the temperature of the washing solution is between 50°C and 95°C.

[0069] In one embodiment, the washing solution further comprises:

[0070] The solute comprises, by weight, between 1% and 20%, wherein the solute is selected from at least one of acidic and basic solutes; and / or

[0071] Surfactants ranging from 0.5% to 3% by weight.

[0072] In one embodiment, the acidic solute is selected from at least one of sulfuric acid and hydrochloric acid; and / or

[0073] The alkaline solute is selected from at least one of potassium hydroxide and sodium hydroxide.

[0074] The present invention also proposes a circuit board prepared using the circuit board processing method described in any of the preceding claims.

[0075] The water-washed pore-plugging resin composition of this application has the following beneficial effects:

[0076] 1. It breaks the inherent technical contradiction between "high-rigidity protection" and "high-cleanliness film removal".

[0077] This invention successfully constructs an interpenetrating polymer network that is both rigid and flexible, and is sensitive to both water and alkali, through deep microscopic physical block and chemical synergy of structural resin (providing hydrophilic permeation channels), reinforcing resin (providing alkali response and a high-modulus framework), and inorganic filler (providing rigid support). This composition exhibits extremely strong physical support under high-intensity machining conditions, while achieving instantaneous controlled disintegration upon contact with specific stripping solutions, thus solving the industry pain points of traditional PCB temporary protective materials: "hard and difficult to wash, easy to wash but not wear-resistant."

[0078] 2. Provides superior dynamic mechanical protection, eliminating burrs and line damage.

[0079] By utilizing a high proportion of inorganic fillers (30% to 80%) and surface modification with specific functional groups (such as those containing double bonds and nitrogen-containing groups), an extremely robust "resin-filler" stress transmission network is formed within the composition. The addition of microscopic elastic buffer centers constructed with a specific proportion of toughening resin gives the cured protective film excellent compressive modulus and impact toughness. When dealing with high-power drilling or high-speed transverse milling, this protective layer effectively disperses cutting kinetic energy and locks in edge displacement of metal traces, eliminating the fatal defects of burrs at the hole openings and "picking up" traces that are very common in high-end circuit board processing.

[0080] 3. Achieve a fast, gentle, and residue-free green film removal process.

[0081] The polymer resin system of this invention incorporates a multi-dimensional aqueous phase disintegration mechanism (such as high-density hydrogen-bonded water washing channels constructed from polyvinyl alcohol / polyvinylpyrrolidone, and the instantaneous acid-base neutralization driving force provided by acrylic resins). In the film removal process, highly corrosive and hazardous organic chemical solvents are eliminated; only hot water or slightly alkaline aqueous solutions are needed to trigger a dramatic surge in osmotic pressure and disentanglement of the polymer chains within the film layer. The protective film swells as a whole at an extremely high rate and peels off completely in sheets, significantly shortening the process time and eliminating secondary chemical contamination of high-precision circuitry and insulating substrates by microscopic adhesive residues.

[0082] 4. Possesses excellent processing rheology and high aspect ratio void filling rate.

[0083] By precisely proportioning low-dosage (≤5%) or even omitting the binder resin that acts as a thermosetting hard point, and supplementing it with a carefully designed solvent boiling point gradient and specialized modifying agents (leveling agents, defoamers, dispersants), the composition of this invention exhibits excellent thixotropic flowability and hole wall wetting ability in its uncured state. Even when faced with micron-sized blind holes or dense fine circuit trenches with high aspect ratios, the composition can achieve extremely full filling without pinholes or bubbles, and the volume shrinkage rate during the curing process is extremely low, providing a perfectly flat physical support substrate for subsequent precision mechanical alignment and smooth cutting. Attached Figure Description

[0084] 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.

[0085] 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;

[0086] Figure 2 This is a schematic flowchart of an embodiment of the circuit board processing method of the present invention.

[0087] 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

[0088] 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.

[0089] 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.

[0090] 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.

[0091] This invention proposes a water-washable pore-filling resin composition comprising a polymeric resin and an inorganic filler. The polymeric resin, by constructing a continuous matrix network, provides physical encapsulation and interfacial anchoring for the composition, thereby achieving core functions such as film-forming properties, adhesion, and removability. The inorganic filler, dispersed within the polymeric matrix, acts as a reinforcing phase, effectively dispersing and absorbing external mechanical cutting stresses, significantly improving the mechanical strength and wear resistance of the cured protective film.

[0092] Specifically, polymer resins include structural resins, binding resins, and reinforcing resins.

[0093] Specifically, the structural resin comprises a polymer having repeating units derived from at least one of vinyl alcohol and vinylpyrrolidone. In terms of material configuration, the polymer may be a homopolymer containing only vinyl alcohol repeating units, a homopolymer containing only vinylpyrrolidone repeating units, a copolymer formed by copolymerization of the two, or a physical blend of the aforementioned polymers.

[0094] In detail, repeating units derived from vinyl alcohol refer to the presence of the chemical structural unit -[CH2-CH(OH)]- in the polymer backbone structure. It is the high density of hydroxyl (-OH) functional groups on this repeating unit that gives the polymer molecular chain strong polarity, enabling it to form a dense hydrogen bond network with water molecules in the stripping solution, thereby endowing the polymer with excellent hydrophilicity and substrate adhesion.

[0095] On the other hand, repeating units derived from vinylpyrrolidone refer to chemical structural units containing strongly polar lactam rings (pyrrolidone side groups) in their polymer chains. These lactam ring groups not only form strong hydrogen bonds with water molecules to provide excellent water sensitivity, but their large steric hindrance effect also effectively prevents the tight crystallization of the polymer chain, creating a large number of amorphous regions (free volumes) within the cross-linked protective network.

[0096] The specific hydrophilic framework constructed by the aforementioned hydroxyl and / or lactam rings allows the water-washed pore-filling resin composition to retain abundant water molecule permeation channels at the microscopic level even after crosslinking and curing. In the final stripping process, these channels guide the washing solution to rapidly penetrate deep into the protective film layer, triggering intense hydration and deentanglement of the polymer chains. This causes the protective layer, which originally provided strong mechanical support, to rapidly swell and disintegrate, ensuring that the protective film, after fulfilling its mission of resisting machining cutting forces, can be easily, thoroughly, and without physical / chemical residue by the aqueous system.

[0097] In some embodiments, the polymer having repeating units derived from vinyl alcohol is polyvinyl alcohol (PVA), with the structural formula shown below. Polyvinyl alcohol (PVA) is typically produced from polyvinyl acetate via alcoholysis, and its structure contains both ethylene alcohol units and residual vinyl acetate units. Therefore, the molar percentage of ethylene alcohol units in the polymer, commonly referred to in the industry as the degree of alcoholysis, can be precisely controlled by adjusting the extent of the alcoholysis reaction.

[0098] Optionally, the degree of alcoholysis of polyvinyl alcohol ranges from 78% to 100%. The degree of alcoholysis refers to the molar percentage of acetyl groups replaced by hydroxyl groups in the polyvinyl alcohol molecular chain. From a microscopic molecular configuration perspective, limiting the degree of alcoholysis to this specific range of 78% to 100% is to establish a dynamic equilibrium between the "mechanical rigidity" of the protective film and the "aqueous phase disintegration kinetics."

[0099] When the degree of alcoholysis is at the high end of this range (such as 98% to 100% complete alcoholysis), the extremely high density of hydroxyl groups on the molecular chain can induce strong intermolecular hydrogen bonds and form highly regular crystalline regions. This high crystallinity endows the cured protective film with extremely high physical cohesive strength and surface hardness, enabling it to work synergistically with inorganic fillers to provide tough rigid support when facing the high-speed impact of mechanical drilling or transverse milling, thereby fundamentally eliminating defects such as burrs at the hole edges or lines being picked up.

[0100] When the degree of alcoholysis is at the lower end of this range (e.g., 78% to 90% partial alcoholysis), the large acetate groups remaining in the molecular chain act as internal plasticizers, effectively breaking the regular arrangement of polymer chain segments, reducing crystallinity, and increasing the free volume between molecular chains. During the decoction stage, these amorphous regions become "entry windows" for water molecules, significantly reducing the energy barrier for water molecules to penetrate the resin matrix. This structural feature allows the protective film to generate instantaneous osmotic pressure and swelling stress when exposed to hot water at 50℃-95℃, causing the polymer network to rapidly undergo solvation and disintegrate, achieving efficient, zero-residue removal in the absence of strong chemical additives.

[0101] In some embodiments, the molecular weight of polyvinyl alcohol is between 10,000 g / mol and 300,000 g / mol. Molecular weight, as a key indicator of polymer chain length, directly determines the degree of chain entanglement in the structural resin during the curing process and the microscopic cohesion of the final protective film.

[0102] Specifically, limiting the molecular weight of polyvinyl alcohol to the aforementioned specific range allows the water-washed plugging resin composition to achieve a balance between processing rheology and physical protective properties. If the molecular weight is below 10,000 g / mol, the molecular chain segments are too short, making it difficult to construct a sufficiently strong physical cross-linked network between the polymers. This results in a protective film with high brittleness and low cohesive strength. When faced with the instantaneous shear stress generated by mechanical drilling or milling, the film layer is prone to brittle fracture or local peeling, thereby losing its protective effect on the circuit board surface and hole walls.

[0103] If the molecular weight is higher than 300,000 g / mol, on the one hand, it will cause the viscosity of the water-washed plugging resin composition to surge in the uncured state, significantly increasing the application resistance of coating processes such as screen printing and spraying, making it difficult to ensure the fullness and surface smoothness of the plugging; on the other hand, due to the extremely long and densely entangled polymer chains, the rate of water molecule immersion and chain disentanglement will decrease significantly in the subsequent film removal process, thereby significantly reducing the dissolution or swelling rate of the protective film in hot water and increasing the film removal time.

[0104] By controlling the molecular weight of polyvinyl alcohol to between 10,000 g / mol and 300,000 g / mol, this invention ensures that the protective film has a high mechanical modulus to resist cutting stress, while also taking into account the process applicability of the composition ink and the efficient peeling characteristics in the final film removal stage.

[0105] In some embodiments, the polymer having repeating units derived from vinylpyrrolidone is polyvinylpyrrolidone.

[0106] Microscopic molecular structure analysis reveals that polyvinylpyrrolidone (PVP) contains highly polar lactam rings within its repeating units. This structural feature endows PPVP with extremely high surface free energy, enabling strong physical adsorption and interfacial anchoring with the metal layer or substrate on the circuit board surface. This ensures the stable adhesion of the protective film formed by the water-washable plugging resin composition during machining, preventing film detachment due to cutting vibrations. Furthermore, the lactam rings possess significant steric hindrance, effectively disrupting the regular arrangement of chain segments within the polymer system and forming abundant amorphous regions. These regions act as "hydrophilic pumps" for water molecules in the cured matrix, rapidly guiding water molecule penetration and promoting network volume swelling during the film removal process, thereby significantly improving overall cleaning efficiency.

[0107] In some embodiments, the molecular weight of polyvinylpyrrolidone is between 2,500 g / mol and 1,200,000 g / mol. Limiting the molecular weight of polyvinylpyrrolidone to this specific range is based on a deep synergistic consideration of the composition's "initial rheology" and "later defilming kinetics".

[0108] Specifically, if the molecular weight of polyvinylpyrrolidone is less than 2500 g / mol, due to the extremely short molecular chain and insufficient cohesion, the composition is prone to exhibiting excessive hygroscopicity and tackiness after drying. This is not only detrimental to the handling of plates during processing, but may also lead to an excessively low mechanical modulus of the protective film, which cannot provide sufficient rigid support during milling.

[0109] If the molecular weight of polyvinylpyrrolidone is higher than 1,200,000 g / mol, on the one hand, it will cause the viscosity of the ink composition to increase non-linearly, which will easily produce defects such as stringing, bubbles or incomplete filling during the printing process, seriously affecting the quality of via plugging; on the other hand, the ultra-high molecular weight chain segments are too densely entangled in the cured network. When washing with hot water, the deentanglement activation energy required for the polymer chains to detach from the matrix will increase significantly, which will cause incomplete film removal or microscopic residues, affecting the subsequent electroplating or mounting process of the circuit board.

[0110] By controlling the molecular weight of polyvinylpyrrolidone within the range of 2500 g / mol to 1200000 g / mol, this invention utilizes its wide-range distribution characteristics to ensure both the excellent wetting and adhesion capabilities of the protective film to the PCB interface and excellent process applicability and instant water washing removal characteristics even at extremely high filler contents.

[0111] Specifically, the bonding resin includes phenolic resin and epoxy resin.

[0112] As a thermosetting component in the composition, the main function of the bonding resin is to construct a dense three-dimensional network framework within the cured protective film through a chemical cross-linking reaction. Specifically, the epoxy groups in the epoxy resin molecule can undergo a ring-opening addition reaction with the active hydroxyl groups in the phenolic resin under heating conditions to form a thermosetting matrix with extremely high cohesive strength and excellent interfacial adhesion.

[0113] The introduction of this system is crucial for improving the cutting resistance of the protective film. The strong interfacial bonding provided by the epoxy resin ensures that the protective film can be tightly anchored to the copper surface and hole walls of the circuit board, preventing peeling or delamination of the film from the substrate even under the enormous lateral shear forces generated by high-speed milling. Simultaneously, the hard network formed by the cross-linking of phenolic resin significantly improves the film's heat distortion temperature (Tg) and modulus, enabling it to work synergistically with the reinforcing resin to support the edges of the metal circuitry during machining, thereby effectively suppressing burrs and preventing the circuitry from being lifted.

[0114] 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 some embodiments, 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 type 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, and liquid phenolic epoxy resin.

[0115] Specifically, the structural formula of glycidylamine epoxy resin is: Its epoxy equivalent is between 93 and 150 g / eq, hydrolyzed chlorine should be less than 200 ppm, and viscosity at 25℃ is between 0.5 and 5 Poise.

[0116] 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℃.

[0117] 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 copolymerization can effectively improve the glass strength, Tg, and impact resistance of copper.

[0118] 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 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 its corrosion resistance.

[0119] The structural formula of isocyanate (MDI) modified epoxy resin is:

[0120] 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.

[0121] The structural formula of naphthol-type epoxy resin is: 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. 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 its hydroxyl groups, it can effectively improve the Tg point, bond strength, and peel strength.

[0122] 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.

[0123] The structural formula of semi-crystalline epoxy resin is: .

[0124] The structural formulas of liquid bisphenol A type epoxy resin and liquid bisphenol F type epoxy resin are as follows: .

[0125] The structural formula of liquid bisphenol A-bisphenol F composite epoxy resin is: .

[0126] The structural formula of liquid phenolic epoxy resin is: or .

[0127] 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, and liquid phenolic epoxy 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 also have low viscosity, high product crosslinking density, and excellent bonding strength, heat resistance, and chemical resistance.

[0128] By selecting and combining specific types of epoxy resins, the crosslinking density and physical skeleton strength of the protective film can be precisely controlled according to different application scenarios. Specifically, glycidylamine-type or multifunctional o-cresylaldehyde-type epoxy resins, due to their high functionality, can form an extremely high-density three-dimensional network during curing, significantly improving the hardness and heat distortion temperature of the protective film, thereby maintaining dimensional stability during high-intensity milling. Phenolic-biphenyl-type or naphthol-type epoxy resins, by introducing rigid aromatic ring structures, improve the mechanical modulus of the film layer while reducing water absorption, ensuring reliability in complex process environments. The use of liquid bisphenol A, bisphenol F, or their composite systems is mainly used to adjust the rheological properties of the composition in the uncured state, ensuring that the ink has excellent printing penetration and hole-filling depth. In addition, the introduction of semi-crystalline or isocyanate-modified epoxy resins can further optimize the bonding force between the film layer and the metal interface of the circuit board, enhancing the resistance to vibration and shear.

[0129] In some embodiments, phenolic resin is used as a curing agent for epoxy resin, and its type and purity have a significant impact on the progress of the curing reaction and the performance of the final product. The phenolic resin can be selected from at least one of linear phenol-formaldehyde resin, linear BPA-formaldehyde resin, and liquid phenolic resin. In the system, the phenolic resin acts as a hardener, and its active hydroxyl groups on its molecular chain chemically crosslink with epoxy groups. The use of linear phenol-formaldehyde resin (Novolac) imparts excellent chemical stability and rigidity to the cured matrix, ensuring that the protective film does not soften or become sticky under the instantaneous high temperatures generated by mechanical cutting, thereby effectively preventing drill bit slag buildup. Linear BPA-formaldehyde resin improves the toughness of the film while maintaining strength, mitigating the risk of brittleness caused by high filler loading. The combined use of liquid phenolic resin can synergistically regulate the thixotropy of the ink while ensuring the activity of the crosslinking reaction, enabling the composition applied to the circuit board processing area to form a protective layer with uniform thickness and no pinholes.

[0130] Specifically, the structural formula of linear phenol-formaldehyde resin is: Its free phenol content is <0.6%, and its softening point is 96~123. oC, with a hydroxyl equivalent between 105 and 119 g / eq and an electrical conductivity less than 8 μS / cm.

[0131] The structural formula of linear BPA formaldehyde resin is: Its free phenol content is 1-45%, and its softening point is 90-140°C. o C, hydroxyl equivalent between 112 and 130 g / eq, and conductivity less than 20 μS / cm.

[0132] The structural formula of liquid phenolic resin is .

[0133] It is understood that, through the synergistic combination of the epoxy system and the phenolic system, the water-washed pore-filling resin composition of the present invention constructs a thermosetting skeleton with multi-level modulus gradients at the microscopic level, providing a stable supporting matrix for inorganic fillers and supporting a "rigid barrier" that can resist extreme mechanical processing stress.

[0134] In some embodiments, the ratio of phenolic resin content to epoxy resin content satisfies the following formula:

[0135] Phenolic resin content = (hydroxyl equivalent of phenolic resin / epoxy equivalent of epoxy resin) × epoxy resin content.

[0136] 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 number 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.

[0137] 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.

[0138] 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 equimolar number of reaction sites can be accurately calculated based on the amount of epoxy resin used and its epoxy equivalent weight.

[0139] By designing the components according to the above stoichiometric ratio formula, a near-complete chemical reaction between the epoxy groups and hydroxyl groups can be ensured. This precise stoichiometric matching minimizes the amount of unreacted small molecules remaining in the film, thereby avoiding the problem of decreased film strength due to insufficient crosslinking.

[0140] It is worth noting that in some embodiments, the polymer resin may not include the binding resin. That is, in this embodiment, the polymer resin is composed of a structural resin and a reinforcing resin.

[0141] From a physicochemical perspective, the system after removing the binding resin constitutes a pure, fully controllable swelling protective framework. In this system, the structural resin (such as polyvinyl alcohol and / or polyvinylpyrrolidone) provides the basic film-forming continuous phase and water-sensitive permeation network, while the reinforcing resin (such as alkali-soluble resin) interacts strongly with the structural resin through polar functional groups (such as carboxyl groups, ester bonds, or acrylate groups) on its molecular chain, thereby endowing the film with rigidity sufficient to withstand general-strength machining.

[0142] The core advantage of this resin-free formulation lies in eliminating the physical shielding effect of thermosetting cross-linked networks on water molecules. Specifically, because there are no irreversible three-dimensional thermosetting hard points constructed from epoxy and phenolic resins in the system, the entire protective film exhibits extremely high uniform swelling consistency during the film removal process. When exposed to hot water or slightly alkaline aqueous solutions, water molecules can penetrate unimpeded into every microscopic level of the protective film, triggering comprehensive molecular chain de-entanglement and acid-base neutralization reactions.

[0143] This design allows the protective film to disintegrate and peel off in sheets at an extremely high rate after processing, completely eliminating microscopic residues that may result from excessive local cross-linking. Therefore, this implementation method is particularly suitable for high-precision circuit board manufacturing processes with stringent surface cleanliness requirements, achieving a gentle, rapid, and zero-pollution green film removal process while ensuring necessary physical protection.

[0144] Specifically, the reinforcing resin includes an alkali-soluble resin. This reinforcing resin performs both physical reinforcement and chemical sensing functions in the composition. Specifically, during the machining stage, the reinforcing resin, through its high-rigidity molecular chain framework, increases the overall modulus of the protective film, providing a stable support for the inorganic filler to resist the lateral shearing force generated by the milling cutter; during the stripping stage, it acts as a "chemical sensitizer," capable of instantaneously responding to alkaline solutes in the stripping solution, triggering the overall disintegration of the film layer.

[0145] In some embodiments, the alkali-soluble resin is selected from at least one of a first type of resin and a polyimide precursor; wherein the first type of resin is a monomer and / or prepolymer containing at least one functional group selected from carboxyl groups, ester bonds and acrylate groups.

[0146] Specifically, from the perspective of processing rheology and curing kinetics, monomers refer to reactive small molecules with low molecular weight. In water-washed pore-filling resin compositions, they act as reactive diluents, effectively adjusting the thixotropy and printing viscosity of the ink by utilizing their low molecular volume, ensuring that the resin can deeply fill the target pores with high aspect ratios. On the other hand, during the curing process, monomers participate in free radical or thermal crosslinking reactions through their highly active functional groups, which can significantly increase the crosslinking density of the polymer network and enhance the surface hardness of the protective film.

[0147] Prepolymers, on the other hand, are oligomers that have undergone partial polymerization and have a certain molecular weight distribution. Prepolymers provide the basic film-forming framework and viscoelasticity for the protective film before curing, which can effectively improve the ink's adhesion performance. More importantly, the macromolecular chain structure of prepolymers helps to absorb and buffer the volume shrinkage stress during the curing process, thereby ensuring excellent stress matching between the cured protective film and the circuit board interface and preventing edge cracking during machining.

[0148] Furthermore, the first type of resin is essentially acrylic acid and acrylate compounds. The carboxyl groups (-COOH) carried on the molecular chains of these acrylic acid and acrylate compounds are key to achieving efficient water washing. During the film stripping process, when the alkaline aqueous solution comes into contact with the protective film, the carboxyl groups can rapidly undergo an acid-base neutralization reaction with the alkaline solute in the aqueous solution, generating highly hydrophilic carboxylate groups. This process generates a dramatic surge in osmotic pressure, forcing a large number of water molecules to rush into the polymer matrix, resulting in significant controlled swelling of the originally dense film layer. At the same time, the presence of ester bonds and acrylate groups not only helps maintain the toughness of the film layer during processing, but also allows for bond breaking under specific alkaline hydrolysis, further accelerating the disintegration of the polymer network, thereby achieving instantaneous peeling of the protective film.

[0149] Polyimide precursors (such as polyamic acid or polyisoimide) provide the polyimide backbone with extremely high physical modulus and thermal stability after curing. More ingeniously, compared to traditional polyimides that are completely closed-ring and difficult to dissolve and melt, these precursor molecules carry a large number of polar groups (such as free carboxyl groups in polyamic acid), which endows the resin with specific swelling and neutralization / disintegration capabilities under alkaline conditions. In some embodiments, the acid value of the first type of resin is between 5 mgKOH / g and 300 mgKOH / g, and the molecular weight is between 50 g / mol and 50,000 g / mol.

[0150] Specifically, limiting the acid value to between 5 mgKOH / g and 300 mgKOH / g is to precisely control the permeation kinetics of the stripping solution. If the acid value is below 5 mgKOH / g, there are too few hydrophilic sensing sites on the molecular chains, which will result in insufficient swelling stress generated by the neutralization reaction to overcome the entanglement forces between the polymer chains, causing slow stripping speed or even residue. If the acid value is above 300 mgKOH / g, the composition will be too sensitive to environmental humidity, and will easily soften due to moisture absorption during production and storage, reducing its rigid support effect during milling. Limiting the molecular weight to between 50 g / mol and 50,000 g / mol ensures that the reinforcing resin, while possessing excellent alkali solubility, can achieve molecular-level compatibility with the aforementioned structural resin at the microscopic level, constructing a uniform and dense protective layer.

[0151] In some embodiments, the polyimide precursor is selected from at least one of polyamic acid and polyisoimide, and its molecular weight is between 1,000 g / mol and 100,000 g / mol.

[0152] Specifically, the inherent polar structure within the polyimide precursor's polymer backbone enables it to exhibit excellent solubility switching capabilities in alkaline aqueous solutions. During composition formulation and via plugging, the precursor morphology ensures good solubility and processing flowability. In the subsequent thermosetting stage, the precursor undergoes controlled dehydration cyclization (i.e., imidization). This in-situ generated rigid polyimide crosslinked backbone provides the protective film with superior thermal stability and extremely high physical hardness. During the stripping stage, thanks to the polar sites remaining in the network, this component can undergo a direct acid-base neutralization reaction with the alkaline stripping solution, rapidly causing a polarity shift and deentanglement of the macromolecular chains. By controlling the molecular weight between 1000 g / mol and 100000 g / mol, this component maintains both extremely high rigidity and support modulus while ensuring excellent stripping cleanliness, making it particularly suitable for microscopic protection of high-precision circuit hole edges, effectively preventing hole tearing or edge chipping under extreme processing stress.

[0153] In some embodiments, the first type of resin is selected from at least one of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, carboxyl-functionalized acrylate resin, modified epoxy acrylate resin, modified polyurethane acrylate resin, and modified polyester acrylate resin.

[0154] By precisely screening and compounding the aforementioned monomers and prepolymers, the comprehensive performance optimization of the protective film under complex machining environments can be achieved. Specifically, acrylic acid and methacrylic acid, as high acid value monomers, mainly provide the core alkali-responsive sensitive points for the system through the high density of carboxyl units in their molecular structure, ensuring that a strong acid-base neutralization driving force can be triggered during the film removal stage. Ester monomers such as methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate are mainly used to adjust the glass transition temperature (Tg) and flexibility of the protective film. Among them, long-chain butyl acrylate can introduce an internal plasticizing effect, alleviate the internal stress of the high-filling system, and prevent edge chipping during processing, while methyl methacrylate helps to improve the surface hardness of the film layer.

[0155] Furthermore, carboxyl-functionalized acrylate resins, modified epoxy acrylate resins, modified polyurethane acrylate resins, and modified polyester acrylate resins, as prepolymers with specific functional skeletons, can significantly enhance the bonding stability between the protective film and the anisotropic interfaces of the circuit board (such as the copper surface, solder resist surface, and substrate surface). Modified epoxy acrylate resins utilize their residual epoxy skeleton and hydroxyl groups to improve the heat resistance and shear strength of the film; modified polyurethane acrylate resins, through the hydrogen bond network formed by urethane bonds, endow the film with excellent impact toughness, preventing brittle fracture under high-speed drilling impact; modified polyester acrylate resins balance cost and film-forming properties. These prepolymers, interpenetrating and coupled with the aforementioned structural resins, construct a continuous phase with multi-level modulus distribution, achieving a balance between mechanical protective strength and chemical delamination rate.

[0156] Specifically, inorganic fillers are mainly used as mechanical property enhancers in the composition, which can significantly improve the mechanical properties (such as hardness, modulus), heat resistance, and dimensional stability of the protective film 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 combine to transfer stress, the surface of the inorganic filler has undergone specific functional group modification.

[0157] In some embodiments, 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.

[0158] The surface modification of the aforementioned specific functional groups is the core to achieving "uniform dispersion under high load" and "efficient stress transfer." Specifically:

[0159] Nitrogen-containing functional groups on the aniline group, main chain, or side chain: Due to the lone pair of electrons in nitrogen atoms, they can form strong hydrogen bonds or coordination effects with the aforementioned structural resins (such as the lactam ring in polyvinylpyrrolidone) or polar groups in reinforcing resins. This intermolecular adsorption force significantly enhances the interfacial adhesion between the inorganic filler and the polymer matrix, forming an extremely stable "resin-filler" interface layer. Under mechanical cutting forces, this interface layer can guide stress to be rapidly transferred from the flexible resin matrix to the rigid filler particles, preventing film brittleness caused by stress concentration.

[0160] Alkyl groups: Primarily used to adjust the wettability of filler surfaces. By introducing alkyl groups with specific chain lengths, the surface energy of filler particles can be reduced, preventing self-aggregation of fine powders under high-filling conditions. This ensures that the filler is monodisperse in the ink composition, thereby guaranteeing the isotropic physical properties of the cured protective film and avoiding weak points in protection caused by uneven filler distribution.

[0161] Containing double-bond functional groups: This endows inorganic fillers with "reactive enhancement" properties. During thermosetting, the double bonds on the filler surface can covalently bond with the reinforcing resin (such as acrylate compounds), achieving a qualitative change from simple "physical encapsulation" to "chemical anchoring." This covalent network greatly enhances the dynamic mechanical modulus of the protective film, enabling it to maintain perfect edge integrity even under the severe shearing of high-speed milling, and to detach uniformly during the defilming stage as the polymer network swells, without producing microscopic residues.

[0162] 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, barium sulfate, and aluminum nitride.

[0163] Incorporating these inorganic fillers into a high proportion of a polymer resin matrix can significantly improve the overall performance of the cured protective layer. On one hand, these rigid inorganic filler particles can form a dense physical support network within the polymer matrix, thereby greatly enhancing the mechanical properties of the composite material, such as hardness, Young's modulus, tensile modulus, and flexural modulus, and 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 increased, thereby improving the heat dissipation efficiency and reliability of the protective layer.

[0164] 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.

[0165] In some embodiments, the polymeric resin further comprises a toughening resin selected from at least one of polyvinyl butyral, polyimide, poly(p-phenylenebenzodioxazole), polybenzimidazole, polyethylene glycol, and rubber polymers.

[0166] Specifically, the introduction of toughening resin aims to construct elastic buffer centers or high-strength, tough fibrous networks within the polymer matrix to enhance the fracture energy of the protective film under extreme machining loads. In particular, because the water-washed plugging resin composition contains a high proportion of inorganic fillers, although the cured protective film possesses high hardness, it is highly susceptible to micro-stress concentration and microcrack induction when subjected to the instantaneous impact stress of high-speed drilling or milling. The toughening resin, through its unique molecular chain flexibility or strong interactions, can effectively absorb and dissipate impact kinetic energy, acting as a crack passivation agent, thereby preventing brittle fracture or edge chipping of the protective film.

[0167] Furthermore, the specific reinforcing mechanisms of toughening resins with different chemical skeletons are as follows:

[0168] Polyimide, poly(p-phenylenebenzodioxazole) (PBO), and polybenzimidazole (PBI): These high-performance polymers possess highly ordered, rigid aromatic heterocyclic backbones. In polymer resin systems, they can form a molecular-level reinforcing framework. Through extremely strong intermolecular forces and thermal stability, they enhance the modulus retention of the protective film under cutting heat conditions, ensuring excellent mechanical integrity even in processing areas under high heat loads.

[0169] Polyvinyl butyral (PVB), polyethylene glycol (PEG), and rubber-based polymers: These components possess low glass transition temperatures and excellent flexibility. They are typically uniformly dispersed in the resin matrix in a microscopic phase-separated form, creating a "core-shell" structure or flexible island-like regions. When external stress is transmitted to these regions, localized shear yielding or crimping processes forcefully alter the crack propagation path and absorb energy, thereby significantly enhancing the impact resistance and flexibility of the protective film. This ensures that the protective film can conform to the microscopic undulations of the circuit board surface without blistering or peeling.

[0170] Specifically, the structural formulas of polyvinyl butyral and polyimide are: and .

[0171] The structural formula of poly(p-phenylenebenzodioxazole) is: .

[0172] The structural formula of polybenzimidazole is: .

[0173] The structural formula of polyamic acid is: .

[0174] 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.

[0175] Specifically, the structural formula of polyethylene glycol (PEG) is: .

[0176] It is understood that by integrating the aforementioned toughening resin into the polymer matrix, this invention constructs a multiphase composite network with both rigidity and flexibility. This network not only supports the rigid inorganic filler to resist milling and shearing, but also alleviates the internal stress caused by crosslinking shrinkage or thermal mismatch at the microscopic level. From a physical mechanism perspective, it completely solves the technical pain point of high-hardness protective films being prone to brittleness and ensures perfect precision of the circuit edges after processing.

[0177] 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.

[0178] The aforementioned rubber-like polymers construct an effective stress dissipation mechanism by forming microscopically discrete elastic centers within the polymeric resin matrix. Specifically, because the water-washed pore-filling resin composition of the present invention has a high crosslinking density and filler loading after curing, the introduction of rubber-like microparticles can absorb and offset kinetic energy before the machining stress is transmitted to the matrix defects through localized shear yielding, thereby significantly inhibiting the initiation and propagation of macroscopic cracks.

[0179] The synergistic effects of rubber components with different chemical properties in the system are as follows:

[0180] Nitrile rubber, acrylic rubber, and polyurethane rubber: These rubbers contain highly polar groups such as cyano, ester, or urethane groups in their molecular chains. These polar groups can generate significant dipole-dipole interactions or hydrogen bonds with the hydroxyl or lactam rings in the aforementioned resin structures, greatly enhancing the interfacial bonding between the rubber microphase and the continuous phase. This excellent compatibility ensures that the toughening components are highly uniformly dispersed in the cured protective film, thus providing isotropic impact protection during machining.

[0181] Ethylene propylene diene monomer (EPDM), ethylene propylene diene monomer (EPDM), modified ethylene propylene diene monomer (EPDM), and thermoplastic ethylene propylene diene monomer (EPDM): These rubbers possess excellent heat resistance and low-temperature flexibility. During high-speed drilling or milling of circuit boards, the high-frequency friction between the tool and the material generates instantaneous localized high temperatures. The ethylene propylene diene monomer (EPDM) system can maintain a constant elastic modulus under this thermal load, effectively preventing the protective film from softening due to heat, which could lead to a decrease in rigidity or tool sticking defects.

[0182] Fluororubber and silicone: These high-performance elastomers possess extremely low surface energy and extremely high chemical stability. Their introduction not only significantly improves the wear resistance life of the protective film, but their unique low surface tension characteristics also help regulate the rheological behavior of the composite ink, improve the wetting quality of the hole walls during the plugging process, and reduce the adhesion work between resin residues and the metal circuit interface during the film removal stage, ensuring a highly clean surface after washing.

[0183] Natural rubber, styrene-butadiene rubber, and chloroprene rubber: These general-purpose rubbers mainly utilize the entanglement effect of their long chain segments to provide basic elongation at break and vibration resistance, ensuring that the overall structure remains intact and does not experience large-area physical peeling when the protective film is subjected to the mechanical stress of a high-power milling machine.

[0184] By screening and compounding the aforementioned rubber polymers, this invention achieves precise control over the micromechanical behavior of the protective film, enabling it to maintain excellent dynamic anti-cutting ability even with extremely high filler content, thereby completely eliminating the circuit damage and burr problems commonly encountered in high-end circuit board mechanical manufacturing processes.

[0185] In some embodiments, the toughening resin accounts for 1% to 30% of the total weight of the structural resin and the toughening resin, for example, 1%, 5%, 10%, 20%, 30%, etc. Limiting the addition ratio of the toughening resin to this specific micro-proportioning range is to construct an ideal microphase separation structure (such as an "island" structure) within the polymer matrix, thereby achieving a precise balance between the rigid support of the protective film, its impact toughness, and the final water washing and removal kinetics.

[0186] Specifically, if the toughening resin accounts for less than 1% of the weight, the density of the micro-elastic buffer centers formed within the system is too low. When the protective film is subjected to instantaneous high-energy impact from a drill bit or milling cutter during processing, the extremely limited flexible phase region cannot effectively absorb and dissipate the enormous mechanical deformation stress, leading to the failure of the crack passivation mechanism. Under this extreme stress concentration, the protective film is still prone to brittle microcrack propagation or localized chipping.

[0187] Conversely, if the toughening resin accounts for more than 30% of the total weight, the microstructure of the system is prone to phase inversion or excessive overlap, causing the structural resin, which is originally a hydrophilic continuous phase, to be severely fragmented by the flexible macromolecular network. On the one hand, this will significantly weaken the overall macroscopic mechanical modulus and yield strength of the membrane, causing it to soften and yield when faced with the shear force of high-speed milling, and thus failing to provide a strong rigid support base for the high-load inorganic filler, thereby losing its anti-burr function; on the other hand, excessive toughening macromolecules (especially rubber-like components with a certain degree of hydrophobicity) will block the water-sensitive permeation channels constructed by the structural resin and reinforcing resin over a large area, significantly increasing the physical resistance to water molecule penetration and the energy barrier for chain segment disentanglement during the membrane removal stage, resulting in a precipitous drop in cleaning efficiency.

[0188] Therefore, by strictly controlling the relative weight ratio of toughening resin to structural resin to 1% to 30%, this invention ensures that flexible nodes with high stress absorption capacity are appropriately embedded in the continuous polymer skeleton, which not only endows the material with excellent shock absorption performance, but also perfectly retains the high rigidity and instantaneous aqueous phase disintegration characteristics required to resist cutting forces.

[0189] 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-filling resin composition may comprise 20% to 70% by weight of a polymeric resin and 30% to 80% by weight of the inorganic filler. Strictly limiting the macroscopic ratio of the polymeric resin to the inorganic filler within the aforementioned range is to establish an optimal engineering balance between the composition's "processing rheology / demolding kinetics" and "post-curing mechanical rigidity".

[0190] Specifically, the polymer resin, as the continuous phase of the system, is responsible for encapsulating the inorganic filler and providing physical anchoring to the circuit board interface, while also constructing aqueous permeation channels during film removal. If the weight percentage of the polymer resin is less than 20% (i.e., the relative weight of the inorganic filler is greater than 80%), the system will lack sufficient polymer matrix to fully wet and encapsulate the massive amount of filler particles. This will not only lead to a sharp deterioration in the rheological properties of the ink composition (such as an exponential increase in system viscosity and loss of thixotropic flowability), making it extremely easy to generate gaps or internal voids during printing of vias, but will also cause a significant decrease in the cohesive bonding of the cured protective film, resulting in severe brittleness and easy powdering and detachment. In addition, too low a resin content also means a lack of sufficient water-sensitive components, which will significantly increase the cleaning difficulty during the film removal stage.

[0191] Conversely, if the weight percentage of polymer resin is higher than 70% (i.e., the relative weight of inorganic filler is lower than 30%), although it can impart excellent coating leveling and demolding rates to the composition, the low loading of inorganic powder as the physical reinforcing phase prevents the curing film from forming a sufficiently dense and rigid load-bearing skeleton. When faced with the intense mechanical impact and lateral shear force generated by high-power high-speed drilling or transverse milling, this "resin-rich" protective film has severely insufficient compressive modulus and surface hardness, making it prone to softening, shrinkage, or plastic deformation. Consequently, it cannot provide rock-solid physical support and completely loses its core function as a temporary protective layer: "preventing burrs and suppressing line picking."

[0192] Therefore, by controlling the relative weight ratios of polymeric resin and inorganic filler to 20% to 70% and 30% to 80% respectively, the water-washable pore-filling resin composition of the present invention successfully constructs a highly dense and uniformly stress-distributed "organic-inorganic" composite penetration network in its microstructure. This formulation ensures excellent printability and instant water-washable film removal characteristics while maximizing its dynamic anti-cutting ability.

[0193] In some embodiments, the polymer resin comprises, by weight percentage: 30% to 70% of a combination of structural resin and toughening resin, and 30% to 65% of reinforcing resin. Precisely controlling the proportions of each component within the polymer matrix within the above range is to construct an ideal "rigid-flexible" and "water / alkali-sensitive" co-continuous phase network or interpenetrating polymer network at the microscopic level.

[0194] Specifically, the combination of the structural resin and the toughening resin primarily provides basic hydrophilic washing channels and stress-buffering flexibility within the system. If the weight percentage of this combination is less than 30%, a continuous hydrophilic network cannot be formed within the system, resulting in significant interruption of the water molecule penetration pathways during the defilming stage, significantly delaying the overall disintegration of the membrane. Simultaneously, the extreme scarcity of flexible segments makes the entire polymer matrix highly brittle, easily inducing tearing and fragmentation of the microscopic phase interfaces when subjected to the instantaneous impact of high-speed machining. Conversely, if the weight percentage of this combination is greater than 70%, the system will be over-plasticized, macroscopically manifested as a softer membrane and a lower glass transition temperature (Tg). This excessive flexibility significantly weakens the effective support of the membrane for the inorganic filler, making it prone to tool sticking or plastic yielding under the strong shearing of milling tools, failing to protect the edges of the circuit from picking or burrs.

[0195] On the other hand, the reinforcing resin is mainly responsible for providing a high-modulus rigid framework and a specific chemical response to the stripping solution (such as acid-base neutralization). If the weight percentage of the reinforcing resin is less than 30%, the density of rigid aromatic rings or cross-linked networks within the polymer matrix is ​​insufficient, resulting in a lack of necessary mechanical hardness and heat distortion resistance in the cured protective film. Furthermore, the sharp reduction in the number of chemically responsive sites (such as carboxyl groups) in the system directly leads to insufficient chemical driving force (osmotic pressure) during alkaline washing and stripping, easily resulting in incomplete peeling and residual adhesive. However, if the weight percentage of the reinforcing resin is higher than 65%, the excessively high proportion of rigid segments will severely restrict the segment mobility of the entire polymer network. This extreme rigidity not only increases the internal stress of the film layer but also generates strong physical steric hindrance, severely compressing or blocking the hydrophilic channels provided by the structural resin. The physical consequence is a dramatic increase in the diffusion barrier of water molecules, causing the film layer to only undergo surface swelling in the stripping solution and failing to achieve deep disintegration, ultimately slowing down the cleaning efficiency.

[0196] Therefore, by limiting the proportions of the "combination of structural resin and toughening resin" and the "reinforcing resin" to 30% to 70% and 30% to 65%, respectively, the polymer resin system of the present invention achieves perfect engineering self-consistency in microscopic thermodynamics and kinetics. This ratio ensures that the protective film exhibits "rock-solid" mechanical support during machining, while achieving instantaneous "melting and disintegration" with zero residue in hot water or alkaline solutions at specific temperatures.

[0197] In some embodiments, the weight percentage of the binder resin in the polymer resin is no more than 5%. Specifically, the weight percentage of the binder resin can be any value between 0 and 5% (e.g., 1%, 2%, 3%, 4%, 5%). It is worth noting that the weight percentage can also be 0, which corresponds to the specific embodiment where the aforementioned polymer resin does not include the binder resin.

[0198] Strictly limiting the binder resin, which is a thermosetting crosslinking component, to a low doping level of 5% or less is the key engineering boundary for balancing the core contradiction between "extreme mechanical protection" and "rapid water washing and film removal" in the micro-network design of this invention.

[0199] Specifically, if the weight percentage of the bonding resin exceeds 5%, the thermosetting three-dimensional network formed by the reaction of epoxy resin and phenolic resin within the system will become excessively dense and prone to abrupt changes in the permeation threshold within the polymer matrix, transforming from a microscopic "discrete phase" into a "continuous phase" that permeates the entire system. Due to the significant hydrophobic properties and irreversible chemical bonding structure of this thermosetting network, it forms a robust and dense physical barrier within the protective membrane, severely blocking the water-sensitive permeation channels constructed by the structural and reinforcing resins. This directly leads to water molecules and alkaline solutes in the stripping solution having difficulty penetrating deep into the membrane layer, causing a precipitous decline in the membrane's swelling kinetics, ultimately resulting in a significant increase in stripping time, making stripping operations difficult, and even producing stubborn residues that cannot be completely washed away in micropores or along the edges of complex circuits.

[0200] When the amount of adhesive resin added is controlled to be greater than 0 and not greater than 5% (e.g., 1% to 5%), a small amount of epoxy and phenolic crosslinking products can form discrete, high-strength, rigid anchoring nodes in the hydrophilic polymer matrix. These locally present chemical crosslinking points are sufficient to increase the overall heat distortion temperature of the film layer at critical moments and strengthen its initial adhesion to the metal interface of the circuit board, effectively resisting the local high-frequency frictional heat and instantaneous lateral tearing force brought about by high-power mechanical cutting. More importantly, its discontinuous micro-island distribution perfectly avoids blocking the water molecule penetration path, ensuring the efficient disintegration and peeling of the polymer network in hot water or weak alkaline solutions.

[0201] Furthermore, the addition of the binding resin helps improve the hardness stability of the protective film in the post-film-forming environment, effectively resisting the problem of moisture absorption and softening during long-term storage. From a microscopic physical mechanism perspective, due to the strong hydrophilicity of the structural resin, under conditions of high humidity or prolonged storage, water molecules easily penetrate into the macromolecular chains, causing a plasticizing effect and resulting in an uncontrolled decrease in film hardness. However, by introducing a trace amount (no more than 5%) of binding resin (such as an epoxy resin and phenolic resin system), the formed hydrophobic thermosetting crosslinking nodes act like stable "structural interlocks" embedded in the hydrophilic matrix. These crosslinking points effectively limit the excessive stretching and rearrangement of polymer chains by water molecules, thereby significantly enhancing the film's physical shielding ability against environmental moisture.

[0202] This structure ensures that after the protective film has been plugged and cured, even after a long period of turnover or storage, its macroscopic hardness remains within the preset process parameters. It prevents insufficient support during cutting due to environmental moisture absorption, thus guaranteeing the consistency and stability of machining accuracy. When the weight percentage of the binder resin is 0, as in the aforementioned example without binder resin, the protective system eliminates irreversible thermosetting crosslinking points, relying purely on physical entanglement between macromolecular chain segments, hydrogen bonding interactions, and acid-base neutralization effects to provide processing support. This extreme formulation design, which completely eliminates the physical shielding effect, pushes the film removal and peeling response rate to the extreme, particularly meeting the stringent "zero residue" processing requirements of high-end printed circuit boards with ultra-high aspect ratio blind vias or micron-level fine line spacing.

[0203] In some embodiments, the water-washed plugging resin composition of this application further comprises 1% to 20% solvent and 0.5% to 5% additives by weight.

[0204] Specifically, the solvent system in the composition primarily plays a crucial role in dissolving the polymer, adjusting the initial rheological properties of the ink, and controlling the curing evaporation rate. Strictly limiting the solvent content to between 1% and 20% is to achieve a balance between "printability" and "curing dimensional stability." Specifically, if the solvent content is below 1%, the initial viscosity of the composition will be too high, leading to a surge in flow resistance during screen printing or squeegee application, making it difficult to fully fill the high aspect ratio micropores with resin. Conversely, if the solvent content is above 20%, the evaporation of a large amount of solvent during the subsequent thermosetting baking stage will cause severe volume shrinkage of the protective film. This excessive shrinkage not only creates severe depressions at the pore openings (i.e., incomplete pore filling) but also induces enormous internal stress within the film layer, causing microcracks to form in the protective film before mechanical processing.

[0205] In some embodiments, the solvent is 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, N,N-dimethylformamide, N,N-dimethylacetamide, propylene glycol monomethyl ether acetate, toluene, and xylene.

[0206] The solvents listed above encompass polar solvents, non-polar solvents, low-boiling-point fast-drying solvents, and high-boiling-point slow-drying solvents. By selecting and compounding solvents with different evaporation rates from the above list, an ideal "boiling point gradient" can be constructed during the curing process. For example, low-boiling-point solvents (such as acetone, ethanol, and ethyl acetate) evaporate rapidly in the early stages of baking, promoting rapid surface drying and setting of the film layer; while high-boiling-point polar solvents (such as N-methylpyrrolidone, dimethyl sulfoxide, and cyclohexanone) can effectively dissolve the macromolecular resin in the system and slowly escape in the middle and later stages of baking, thus reserving sufficient time for the expulsion of internal bubbles and effectively avoiding "plate bursting" or micropore bubbling defects caused by premature skinning of the surface.

[0207] Furthermore, although the amount of additives added is extremely low (0.5% to 5%), they are key enabling components for eliminating microscopic process defects in highly filled resin systems. If the total content of additives is less than 0.5%, they cannot effectively cover the filler surface or change the surface tension of the system, thus losing their modifying significance; if it is higher than 5%, the small molecule additives that do not participate in the binding will produce a serious plasticizing effect in the cured film, significantly weakening the mechanical compressive modulus of the protective film, and even contaminating the stripping solution during the stripping stage.

[0208] In some embodiments, the additive is selected from at least one of leveling agents, dispersants, and defoamers. Examples of possible additives include, but are not limited to, products such as dispersant BYK2152, defoamer BYK530, and leveling agent BYK333.

[0209] Specifically, dispersants mainly adsorb onto the surface of a large number of inorganic filler particles through steric hindrance or electrostatic repulsion, preventing secondary agglomeration of micropowders during static or shearing processes, thus ensuring the uniformity of the composition during long-term storage and printing. Defoamers, with their extremely low surface tension and insolubility, can quickly penetrate and destroy the microbubble liquid film trapped inside the ink during high-speed stirring or screen printing extrusion, causing the bubbles to burst and be expelled, fundamentally eliminating stress concentration and mechanical weaknesses caused by pores in the cured film. Leveling agents, by forming a monomolecular oriented layer on the coating surface, dynamically adjust the surface tension of the composition, eliminating defects such as mesh, orange peel, or pinholes caused by printing squeegees, ensuring that the surface of the cured protective layer has excellent smoothness, providing a reliable surface foundation for subsequent high-precision mechanical positioning and smooth cutting.

[0210] In summary, the water-washed pore-plugging resin composition of this application has the following beneficial effects:

[0211] 5. It breaks the inherent technical contradiction between "high-rigidity protection" and "high-cleanliness film removal".

[0212] This invention successfully constructs an interpenetrating polymer network that is both rigid and flexible, and is sensitive to both water and alkali, through deep microscopic physical block and chemical synergy of structural resin (providing hydrophilic permeation channels), reinforcing resin (providing alkali response and a high-modulus framework), and inorganic filler (providing rigid support). This composition exhibits extremely strong physical support under high-intensity machining conditions, while achieving instantaneous controlled disintegration upon contact with specific stripping solutions, thus solving the industry pain points of traditional PCB temporary protective materials: "hard and difficult to wash, easy to wash but not wear-resistant."

[0213] 6. Provides superior dynamic mechanical protection, eliminating burrs and line damage.

[0214] By utilizing a high proportion of inorganic fillers (30% to 80%) and surface modification with specific functional groups (such as those containing double bonds and nitrogen-containing groups), an extremely robust "resin-filler" stress transmission network is formed within the composition. The addition of microscopic elastic buffer centers constructed with a specific proportion of toughening resin gives the cured protective film excellent compressive modulus and impact toughness. When dealing with high-power drilling or high-speed transverse milling, this protective layer effectively disperses cutting kinetic energy and locks in edge displacement of metal traces, eliminating the fatal defects of burrs at the hole openings and "picking up" traces that are very common in high-end circuit board processing.

[0215] 7. Achieve a fast, gentle, and residue-free green film removal process.

[0216] The polymer resin system of this invention incorporates a multi-dimensional aqueous phase disintegration mechanism (such as high-density hydrogen-bonded water washing channels constructed from polyvinyl alcohol / polyvinylpyrrolidone, and the instantaneous acid-base neutralization driving force provided by acrylic resins). In the film removal process, highly corrosive and hazardous organic chemical solvents are eliminated; only hot water or slightly alkaline aqueous solutions are needed to trigger a dramatic surge in osmotic pressure and disentanglement of the polymer chains within the film layer. The protective film swells as a whole at an extremely high rate and peels off completely in sheets, significantly shortening the process time and eliminating secondary chemical contamination of high-precision circuitry and insulating substrates by microscopic adhesive residues.

[0217] 8. Possesses excellent processing rheology and high aspect ratio void filling rate.

[0218] By precisely proportioning low-dosage (≤5%) or even omitting the binder resin that acts as a thermosetting hard point, and supplementing it with a carefully designed solvent boiling point gradient and specialized modifying agents (leveling agents, defoamers, dispersants), the composition of this invention exhibits excellent thixotropic flowability and hole wall wetting ability in its uncured state. Even when faced with micron-sized blind holes or dense fine circuit trenches with high aspect ratios, the composition can achieve extremely full filling without pinholes or bubbles, and the volume shrinkage rate during the curing process is extremely low, providing a perfectly flat physical support substrate for subsequent precision mechanical alignment and smooth cutting.

[0219] 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.

[0220] like Figure 1 As shown, in some embodiments, the method for preparing the water-washed pore-plugging resin composition includes the following steps:

[0221] S1. Preparation of resin slurry: The polymer resin is mixed in a first solvent to obtain a resin slurry.

[0222] In some embodiments, during the preparation of the resin slurry, at least one additive selected from dispersants, defoamers, and leveling agents is pre-dissolved in the first solvent. From a physicochemical perspective, pre-dissolving the additive in the first solvent allows for molecular-level pre-distribution of the additive molecules within the system by utilizing the solvent's dilution effect. This pretreatment effectively avoids the risk of "agglomeration" or "precipitation" caused by excessively high local concentrations of the additive when it is directly added to a thick resin system. This ensures that the dispersant can wet the subsequently added polymer chains immediately, while the defoamer can pre-reduce the surface tension to suppress the entrainment of air bubbles during the initial stirring stage.

[0223] Specifically, the mixing speed during resin slurry preparation 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.

[0224] Limiting the mixing speed to the high-shear range of 3600 rpm to 7200 rpm is to provide sufficient mechanical shear energy to quickly break up the swollen particles formed in the early stage of dissolution of polymer resins (especially polyvinyl alcohol, alkali-soluble resins, etc.), forcibly stretch and untangle the physical entanglement between macromolecular chains, and promote their full hydration with the first solvent molecules, thereby constructing a homogeneous and transparent polymer solution.

[0225] Meanwhile, strictly controlling the slurry temperature to no higher than 45°C is a critical process limit. On the one hand, high-shear mixing generates a large amount of mechanical heat; if left uncontrolled, excessively high temperatures can lead to excessive evaporation of the first solvent and disrupt the solid content balance of the system. On the other hand, excessively high temperatures may trigger microscopic pre-crosslinking reactions of the active components in the system (especially when containing binder resins or acrylate monomers), resulting in abnormal viscosity fluctuations in the slurry and even the formation of gel particles, severely impairing the storage stability and pore-filling performance of the final ink composition. By executing the above-mentioned high-shear temperature control process within a time window of 20 to 40 minutes, this invention can obtain a continuous resin phase matrix with extremely uniform molecular distribution and stable rheological properties.

[0226] S2. Preparation of filler slurry: The inorganic filler is mixed in a second solvent to obtain a filler slurry.

[0227] In this step, by pre-dispersing a high-load inorganic powder in a second solvent, the aim is to construct a filler precursor phase with high fluidity and uniform composition, thereby laying the physical foundation for subsequent molecular-level composite with the resin matrix.

[0228] In some embodiments, during 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.

[0229] From an interfacial chemistry perspective, pre-dissolving dispersants and other additives in a second solvent is of crucial process significance. This "additive-first" strategy ensures that, upon the addition of inorganic fillers, dispersant molecules can rapidly achieve saturation adsorption on the filler particle surface using their solubilophilic segments, forming an extremely thin and uniform wetting coating. This not only significantly reduces the surface free energy of the filler powder, preventing instantaneous "coarsening" or agglomeration of ultrafine powders due to van der Waals forces, but also constructs effective charge repulsion or steric hindrance barriers between particles. Simultaneously, the pre-dissolved defoamer can instantly break up trace amounts of air adsorbed on the powder surface, ensuring perfect interfacial wetting between the filler and solvent, thereby significantly improving the micro-dispersion quality of the slurry.

[0230] Specifically, 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 rpm and 40 rpm.

[0231] The mixing speed is limited to 3600 rpm to 7200 rpm to generate a high-intensity fluid shear field. Since inorganic fillers (such as silica or aluminum nitride) generally exhibit physical agglomeration in their dry state, conventional stirring alone cannot completely break them up. The strong shear force generated in the aforementioned high-speed range effectively overcomes the attraction between filler particles, forcing the physical disintegration of the agglomerates and allowing the powder to be distributed in a monodisperse state in the second solvent.

[0232] Meanwhile, the slurry temperature is strictly controlled to not exceed 45℃, primarily for the sake of interfacial stability. If the mechanical heat generated by stirring causes the slurry to heat up too quickly, it will significantly alter the adsorption-desorption balance of chemical additives on the filler surface, leading to thinning or even detachment of the dispersed film and causing secondary agglomeration of the filler. Furthermore, excessively high temperatures will exacerbate the uncontrolled volatilization of the second solvent, causing a sharp increase in slurry viscosity, which in turn affects the metering accuracy and mixing efficiency of subsequent mixing steps. By executing this temperature-controlled shearing process within a time range of 20 to 40 minutes, excellent storage stability and rheological consistency of the filler slurry can be ensured.

[0233] 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.

[0234] In this step, a specific feeding sequence and mixing strategy of "adding filler slurry to resin slurry under stirring" is adopted. This aims to utilize the "shear dilution" effect in fluid dynamics to achieve a smooth transition and deep fusion of the two-phase interface. Because the resin slurry has high viscoelasticity, adding pre-dispersed filler slurry under stirring ensures that the filler particles are rapidly coated by the flowing polymer chains upon contact with the continuous resin matrix phase. This effectively avoids interfacial instability phenomena such as "filler flocculation" or "resin precipitation" caused by excessive local concentration gradients.

[0235] Specifically, the mixing speed when mixing 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.

[0236] Maintaining the mixing speed within the high-energy shear range of 3600 rpm to 7200 rpm has the physical significance of maintaining an extremely high shear rate within the system to overcome the flow resistance caused by viscosity differences in the initial stage of mixing between the two phases. This strong mechanical shear field can forcibly stretch the entangled segments of resin molecules, causing them to collide and interface with modified functional groups (such as aniline groups and nitrogen-containing groups) on the filler surface more frequently, thereby forming a highly homogeneous system on a macroscopic scale without stratification or sedimentation.

[0237] Meanwhile, strictly limiting the slurry temperature to no higher than 45℃ is the core defense to ensure the chemical stability of the mixed system. During the high-intensity mixing process that lasts for 1 to 2 hours, the internal energy accumulation due to the conversion of mechanical energy is very significant. If the temperature is not suppressed below 45℃ through external temperature control measures, it is very easy for highly active additives in the system to undergo effective thermal degradation, or to trigger a microscopic thermosetting reaction between the polymer resin and the reinforcing resin, resulting in a "false coagulation" phenomenon in the slurry.

[0238] Setting the mixing time to 60 to 120 minutes is a necessary physical process to achieve "interface wetting saturation." Compared to steps S1 and S2, step S3 involves a more complex process of adsorption and rearrangement of macromolecular chain segments on the filler surface. Within this longer time window, the polymer resin can fully penetrate into the microscopic voids on the surface of the filler particles through Brownian motion and shear convection, completely eliminating residual microbubbles, thereby constructing an "organic-inorganic" composite structure with high cohesive strength. This process ensures that the final mixed slurry exhibits excellent thixotropic properties and cutting resistance toughness in subsequent hole-filling processing.

[0239] S4. 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 10,000 mPa.s and 50,000 mPa.s.

[0240] In this step, a controlled desolventizing process physically removes excess solvent used in the previous steps to aid dispersion and mixing, aiming to precisely transform the composition from a low-viscosity "slurry state" to an "ink state" suitable for specific processes. Limiting the solid content to 64% to 98% ensures extremely low volume shrinkage during the subsequent pore-filling curing process, preventing cracks or voids within the pores due to excessive solvent residue. Controlling the viscosity to 10,000 mPa·s to 50,000 mPa·s imparts ideal thixotropy and wall-hanging ability to the ink, ensuring excellent filling flow under screen printing or squeegee pressure, while remaining firmly within the pores without leakage or sagging when stationary.

[0241] 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.

[0242] In some embodiments, the solvent removal process includes: continuously stirring and washing the pore-filling resin composition mixture slurry at a temperature of 20°C to 50°C and a vacuum environment with a vacuum degree of less than 0.1 MPa for 5 minutes to 3 hours.

[0243] Specifically, limiting the temperature to the lower range of 20°C to 50°C is to promote solvent evaporation while strictly avoiding thermal damage to the polymer matrix caused by high temperatures. Since the composition contains heat-sensitive structural and reinforcing resins, excessively high desolventizing temperatures can easily induce trace amounts of free radical polymerization or condensation reactions within the system prematurely, leading to an abnormally long "thermal history" of the ink. This not only causes its initial viscosity to deviate from the preset range but also severely shortens the ink's effective shelf life.

[0244] Secondly, the setting of a vacuum level below 0.1 MPa (i.e., a high vacuum negative pressure environment) effectively reduces the vaporization energy barrier of solvent molecules. Driven by this pressure gradient, solvent molecules can achieve rapid phase transition migration under medium and low temperature conditions, thereby achieving efficient desolvation without destroying the chemical structure of the system.

[0245] Finally, the continuous stirring process constantly renews the surface boundary layer of the slurry through forced convection, preventing surface crusting caused by excessive local solvent evaporation, and promoting the rapid rise and collapse of microbubbles accumulated within the system under vacuum. By adjusting the processing time from 5 minutes to 3 hours, the boiling point characteristics of different solvent components can be tailored to achieve micron-level precision control over the final ink solid content and viscosity, thereby ensuring that the prepared water-washable plugging resin composition ink perfectly matches the high-precision machining protection requirements of high-end circuit boards.

[0246] 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 embodiment, the preparation method may include the following steps:

[0247] S10. Provide a circuit board: Provide a circuit board with a defined processing area, wherein a target hole to be filled is pre-formed on the processing area.

[0248] In this step, the circuit board can be a single-sided board, a double-sided board, or a multilayer high-density interconnect (HDI) board, and its substrate can cover epoxy resin glass cloth laminate (such as FR-4), polyimide (PI) film, or other high-frequency microwave substrates.

[0249] The term "machining area" refers to a specific area where secondary drilling, shaping milling, or edge cutting will be performed in subsequent processes. "Target holes to be filled" include, but are not limited to, through holes, blind holes, or buried holes that have already undergone preliminary hole formation (such as mechanical drilling or laser drilling) and hole plating. From a physical protection perspective, these target holes and their surrounding fine lines are the weakest points where machining stress is most likely to concentrate. When a high-speed milling cutter performs transverse cutting, the hole edges, lacking sufficient support, are highly susceptible to metal tearing or burr defects.

[0250] S20, Hole plugging: The water-washed hole plugging resin composition is applied to the processing area of ​​the circuit board and filled into the target hole to be plugged.

[0251] In this step, the excellent rheological properties and wettability of the water-washed plugging resin composition prepared in the aforementioned steps are utilized, enabling it to accurately cover the designated area of ​​the circuit board and completely fill the target hole to be processed under the drive of external mechanical pressure.

[0252] Specifically, the water-washable plugging resin composition can be applied to the processing area of ​​the circuit board by at least one of screen printing, pad printing, stencil printing, spraying, and squeegee printing.

[0253] Through the above application method, the present invention ensures that the water-washable via-filling resin composition can form a perfect mechanical interlock with the copper layer, solder mask layer, and via wall interface on the circuit board surface. This highly dense filling state completely eliminates residual air in the vias, effectively preventing local collapse of mechanical support caused by the presence of "micro-voids" after curing. This, in turn, ensures the perfect support performance of the "rigid protective layer" for the circuit edges and via edges during subsequent milling processes at the physical level.

[0254] S30. Curing: The water-washed plugging resin composition is heat-treated to form a cured protective film on the circuit board.

[0255] In this step, controlled thermal energy input triggers the removal of solvents from the composition and the rearrangement and initial cross-linking of polymer segments, thereby transforming the liquid or paste-like filler into a solid protective layer with high mechanical strength, providing rigid support for subsequent mechanical cutting.

[0256] In some embodiments, the heat treatment includes drying the water-washed pore-plugging resin composition for 3 to 30 minutes at a temperature range of 50°C to 120°C.

[0257] Specifically, setting a lower limit of 50°C during the heat treatment stage is to ensure that the first and second solvents in the system have sufficient vapor pressure to achieve effective phase change evaporation. If the temperature is below 50°C, the solvent residue rate will be too high, causing the film layer to appear "mud-like," which will easily lead to tool sticking or protection failure due to insufficient strength during subsequent milling.

[0258] Setting an upper limit of 120°C is to protect the composition from "washing sensitivity." Since the system contains a large amount of structural and reinforcing resins, if the curing temperature exceeds 120°C, it will, on the one hand, cause excessive thermal degradation or uncontrolled deep oxidation of the polymer chains, leading to the deactivation of active groups (such as carboxyl and hydroxyl groups) originally used for hydrolysis. On the other hand, excessive heat will accelerate the cross-linking reaction of the binding resin (such as epoxy / phenolic systems), forming an overly dense and irreversible thermosetting network, thereby blocking the permeation channels of water molecules and making final film removal difficult. Furthermore, a gradient temperature increase from 50°C to 120°C helps achieve uniform solvent migration from the inside out, effectively avoiding film cracking or internal pore defects caused by surface skinning.

[0259] Furthermore, controlling the drying time between 3 and 30 minutes is to balance production efficiency and film density. In the initial 3-minute stage, the film surface initially loses its stickiness (surface drying) and forms a preliminary physical framework. As the time extends to 30 minutes, a stable interfacial bond (i.e., "interfacial anchoring") is established between the polymer matrix and the inorganic filler through surface-modified functional groups. If the time is less than 3 minutes, the film will not cure evenly inside and outside, making it difficult to withstand the lateral stress generated by high-speed cutting. If the time is more than 30 minutes, it will not only waste energy but also cause the film to become brittle due to thermal aging, reducing its flexibility against vibration and impact.

[0260] Through the aforementioned precise heat treatment process, the cured protective film obtained by this invention exhibits a highly interwoven physical state of "hard filler - rigid substrate - flexible nodes" at the microscopic level. This film not only forms excellent interfacial adhesion with the circuit board processing area, but also retains sensitive chemical delamination sensing points.

[0261] In some embodiments, the heat treatment includes stepped baking, which aims to induce the orderly migration of solvents within the composition according to their boiling points through segmented, controlled thermal gradients, thereby achieving a stepwise rearrangement of polymeric chain segments. The stepped baking sequentially includes:

[0262] First stage baking: Bake at a temperature range of 40℃ to 60℃ for 10 minutes.

[0263] This stage falls within the initial kinetic range of solvent evaporation, and its core purpose is to remove low-boiling-point solvents (such as acetone, ethanol, and ethyl acetate) from the system. By maintaining a low-temperature environment of 40°C to 60°C, it is ensured that solvent molecules escape smoothly from the protective film surface at a slower rate, avoiding the "bumping" phenomenon caused by violent vaporization due to instantaneous high temperature. This eliminates pinhole or crater-like morphological defects inside the film layer from the source, achieving the initial "shaping" of the film layer.

[0264] Second stage baking: Bake at a temperature range of 90℃ to 110℃ for 10 minutes.

[0265] Upon entering the intermediate temperature stage, medium-to-high boiling point solvents (such as methyl ethyl ketone and propylene glycol monomethyl ether acetate) begin to migrate on a large scale. At this time, the polymer matrix undergoes microscopic volume expansion due to heating, enhancing chain segment mobility and facilitating the expulsion of residual air at the interface between the inorganic filler and the resin. Locking the temperature between 90°C and 110°C ensures that the protective film maintains a certain degree of viscoelasticity while losing most of the solvent, thereby alleviating the initial internal stress caused by curing shrinkage at the molecular level and preventing brittle cracking of the film layer during subsequent processing.

[0266] Third stage baking: Bake at a temperature range of 140℃ to 160℃ for 10 minutes.

[0267] This stage is the "final reinforcement stage." Although high temperatures may pose a challenge to water washability, within an extremely short timescale of 10 minutes, temperatures of 140°C to 160°C can instantly stimulate deep physical / chemical anchoring of the reinforcing resin and binder resin (if present). This instantaneous high energy input causes the mechanical modulus and surface hardness of the protective film to reach their peak, constructing a "rigid barrier" sufficient to withstand extreme high-power milling stress. Through this "short-time high-energy" process strategy, this invention cleverly avoids excessive thermal cross-linking or carbonization of polymer chains caused by prolonged high temperatures while ensuring the film layer possesses ultimate physical protective strength, thus perfectly preserving the alkali-sensitive disintegration activity of the system during the film removal stage.

[0268] This three-stage, gradient-progressive curing process results in a protective film that exhibits extremely high density and interfacial bonding on a macroscopic level, while maintaining clear water molecule permeation channels on a microscopic level. This process arrangement represents the best practice for achieving a high degree of engineering harmony between the seemingly contradictory parameters of "extreme mechanical protection" and "rapid alkaline water removal."

[0269] In some preferred embodiments, the final cured protective film thickness can be controlled between 10 μm and 20 μm. The core objective of precisely controlling the dry film thickness within this range of 10 μm to 20 μm 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 film will not achieve the desired technical effect.

[0270] S40. Processing: Machining the circuit board on which the cured protective film has been formed.

[0271] In this step, the cured protective film, as a temporary high-performance rigid support medium, directly participates in and intervenes in the stress distribution during the machining process, thereby protecting the delicate structure of the circuit board from damage.

[0272] Specifically, machining includes at least one of drilling, form milling, cutting, and grinding. During these high-energy, high-stress machining operations, the cured protective film performs the following core physical functions:

[0273] 1. Lateral Stress Support and "Stress Locking" Mechanism: Taking form milling as an example, when the milling cutter cuts laterally into the circuit board substrate and copper foil layer at a high speed of tens of thousands of revolutions per minute, it generates severe local shear stress. Because the cured protective film tightly fills the target hole and covers the surface of the processing area, its high content of inorganic fillers and strong polymer skeleton construct an extremely high-modulus physical barrier. This barrier can "lock" the degree of freedom of the metal circuit edges at the microscopic level, preventing the copper foil from undergoing upward or outward tearing displacement under the cutting force. This strong physical support fundamentally eliminates the generation of burrs at the hole opening, ensuring a highly flat and perpendicular cutting surface.

[0274] 2. Thermomechanical Stability: During machining, the intense friction between the cutting tool and the material generates instantaneous high temperatures. Thanks to the stable cross-linked network formed by the aforementioned heat treatment process and the introduction of high-performance toughening resins (such as polyimide, PBO, etc.), the cured protective film maintains high elastic modulus and dimensional stability even under the temperature rise of the machining process. This non-thermoplastic characteristic effectively prevents the film layer from softening at high temperatures or "sticking" to the tool, ensuring that cutting chips can be smoothly removed and avoiding tool wear or machining accuracy deviations caused by residue accumulation.

[0275] 3. Load Dispersion and Shock Absorption: The micro-elastic nodes formed by toughening resin within the protective film effectively absorb and buffer the vibration energy generated by drilling impacts, preventing shock waves from inducing micro-cracks on brittle insulating substrates or fragile fine circuits. This "rigid-flexible" structure allows the circuit board to withstand higher power and higher efficiency machining conditions without worrying about interlayer peeling or circuit detachment due to excessive processing stress.

[0276] By implementing this step, the curing protective film transforms the originally vulnerable "open" processing environment of the circuit board into a physically supported "closed" processing environment, thereby enabling the processed hole size, line spacing and edge consistency to achieve extremely high process precision indicators.

[0277] S50, Film Removal: The processed circuit board is cleaned with a water washing solution to remove the cured protective film.

[0278] In this step, through the synergistic effect of physical penetration, chemical degradation and interface stripping, the cured protective film that has fulfilled its mechanical protection mission is completely removed from the surface of the circuit board and the target holes, restoring the circuit board to its original, highly clean, ready-to-assemble state.

[0279] Specifically, in the film removal step, the temperature of the washing solution is between 50°C and 95°C. Alternatively, the washing solution can be hot water with a temperature between 50°C and 95°C.

[0280] Limiting the temperature to a high-temperature range of 50℃ to 95℃ has clear kinetic significance. From a polymer physics perspective, temperatures above 50℃ provide sufficient energy to cause significant thermal motion in the polymer chains within the cured protective film, leading to the relaxation of the originally dense physical cross-linked network. If the temperature is below 50℃, the water molecule penetration barrier is too high, resulting in low film removal efficiency. Setting the upper limit at 95℃ ensures an extremely high penetration rate while effectively preventing the mechanical impact of violent solvent boiling on precision circuitry and protecting the circuit board substrate (such as FR-4) from delamination due to excessive heating.

[0281] In some embodiments, the washing solution further comprises, by weight, a solute ranging from 1% to 20%, the solute being selected from at least one of acidic and basic solutes.

[0282] Specifically, when the washing solution is alkaline, hydroxide ions in the solution can rapidly penetrate and undergo a transient acid-base neutralization reaction with the carboxyl functional groups on the molecular chains of the reinforcing resin (such as acrylic resins). This reaction transforms the hydrophobic macromolecular chains into highly hydrophilic carboxylate structures, thereby generating a huge surge in osmotic pressure inside the membrane. This osmotic pressure, as an endogenous driving force, forces a large influx of water molecules into the polymer framework, causing the membrane to undergo violent, controlled swelling within a very short time and ultimately disintegrate into tiny fragments that detach.

[0283] Acidic solutes, on the other hand, are mainly targeted at resin systems with specific acid-sensitive groups or easily hydrolyzed chain segments (such as ester bonds, amide bonds, etc.). By accelerating the breaking of chemical bonds, they achieve a qualitative change in the polymer network from a "macroscopic continuous state" to a "microscopic discrete state".

[0284] By limiting the solute content to 1% to 20%, sufficient chemical driving force is ensured to achieve rapid film removal, while avoiding excessive concentrations of chemicals that could cause micro-corrosion of the copper surface circuitry or create an environmental processing burden.

[0285] Preferably, the solute content is limited to between 1% and 10%. Specifically, further narrowing the solute (acidic or alkaline) content and preferably limiting it to the specific concentration range of 1% to 10% is to achieve the most stringent "near-zero damage" protection to the circuit board substrate and sensitive metal layer while ensuring "extremely rapid peeling kinetics".

[0286] Specifically, when the solute content is between 1% and 10%, the washing solution possesses sufficient ionic strength to stimulate a chemical response within the protective film. Taking alkaline solutes as an example, within this concentration range, hydroxide ions can create a constant diffusion pressure difference within the micropores of the cured protective film, inducing a moderate acid-base neutralization reaction in the reinforcing resin and generating osmotic pressure sufficient to expand the polymer chains. A concentration of 1% to 10%, combined with a heat input of 50°C to 95°C, is sufficient to completely disintegrate a protective film of conventional thickness within 30 to 120 seconds, fully meeting the high-cycle requirements of automated production lines. Achieving excellent material compatibility and metal interface protection: If the solute content exceeds 10% (i.e., in the high range of 10% to 20%), although the removal time can be further shortened, the surge in strong electrolyte concentration significantly increases the chemical corrosiveness of the solution. For exposed copper surfaces, nickel-gold pads, or cured permanent solder resist inks on circuit boards, excessively high concentrations of acid and alkali solutions can easily cause micro-erosion or surface fading defects.

[0287] By limiting the concentration to less than 10%, this invention cleverly restricts the chemical reaction to a selective reaction range "only targeting the protective film substrate," ensuring that the surface of the metal circuit after film removal maintains perfect flatness and original wettability, effectively avoiding the risk of electrochemical migration.

[0288] Furthermore, limiting the optimal solute content to 1% to 10% significantly reduces the cost of alkali / acid neutralization in wastewater treatment and decreases chemical consumption during the stripping process. Because the solution viscosity is lower within this concentration range, less residue remains on the circuit board surface, making subsequent water rinsing more efficient and ensuring the final circuit board exhibits extremely high ionic cleanliness. Therefore, a solute content of 1% to 10% is not only the core technology for achieving "fast washing," but also a process guarantee for ensuring that high-precision, high-value-added circuit boards achieve an "ultra-clean surface" after machining.

[0289] In some embodiments, the acidic solute is selected from at least one of sulfuric acid and hydrochloric acid; the basic solute is selected from at least one of potassium hydroxide and sodium hydroxide.

[0290] Specifically, the selection of the aforementioned strong inorganic acid or strong inorganic base is intended to provide extremely high ionic strength and chemical reactivity for the film stripping process, thereby achieving instantaneous peeling of the protective film through efficient "polarity conversion".

[0291] Specifically, potassium hydroxide and sodium hydroxide, as strong electrolytes, can dissociate into highly reactive hydroxide ions in aqueous solution. When the stripping solution comes into contact with the cured protective membrane, these ions can rapidly penetrate the microscopic channels constructed by the structural resin and undergo an instantaneous neutralization reaction with the carboxyl groups (-COOH) on the molecular chains of the reinforcing resin (such as acrylic resins), generating potassium or sodium carboxylate salts with extremely high hydrophilicity. This chemical transformation process is accompanied by a huge release of free energy, which not only breaks the hydrogen bond network between molecular chains but also generates a dramatic surge in osmotic pressure inside the membrane. This endogenous driving force forces water molecules to rush into the polymer matrix at a geometric rate, causing the protective membrane to undergo overall swelling and disintegration from the inside out, ultimately achieving clean stripping with zero residue.

[0292] Specifically, sulfuric acid or hydrochloric acid provides protons ( This is primarily used to catalyze protective systems containing acid-sensitive crosslinking points (such as ester bonds, amide bonds, or specific modified prepolymer segments). Under thermodynamic conditions ranging from 50°C to 95°C, a strong acid environment accelerates the hydrolytic breakage of these chemical bonds, shearing the originally continuous three-dimensional macromolecular network into low-molecular-weight soluble fragments. Choosing sulfuric acid or hydrochloric acid allows the strong electrolyte properties to ensure a constant chemical driving force at low concentrations (1% to 20%). While rapidly peeling off the protective film, adjusting the pH balance minimizes electrochemical attack on sensitive metal layers (such as nickel / gold layers) on the circuit board surface, ensuring the electrical properties and pad wettability of the circuit board surface after peeling.

[0293] The introduction of this specific acid-base solute enables the water-washed plugging resin composition of this invention to exhibit an "inert solid" characteristic during machining, while displaying an "active instant dissolution" characteristic under specific chemical conditions. This rapid switching of properties ensures that even protective films filled in micropores with a high aspect ratio of 20:1 or higher can be completely removed within tens of seconds, significantly improving the process yield and production efficiency of high-end circuit boards.

[0294] In some embodiments, the washing solution further comprises 0.5% to 3% by weight of a surfactant.

[0295] Specifically, surfactants act as "interface penetrators" in the film stripping process. Due to the strong mechanical anchoring force between the cured protective film and the metal surface or hole walls of the circuit board, surfactants significantly enhance the wetting ability of the washing solution to extremely fine gaps by reducing the surface tension of the solution. This ensures that the washing solution can quickly penetrate to the contact interface between the protective film and the circuit board, forming an extremely thin water film at this interface and reducing the adhesion work between the film and the metal. Combined with a concentration limit of 0.5% to 3%, excellent penetration and stripping effects are guaranteed while preventing foam overflow caused by excessive surfactant, ultimately achieving "zero dead angles and zero residue" clean stripping in complex circuits and high aspect ratio pores.

[0296] In some embodiments, the surfactant may be a product with alkyl-terminated fatty alcohol polyoxyethylene ether.

[0297] It is worth noting that the solute in the washing solution can be either an acidic solute or a basic solute, or a combination of both. Furthermore, the solute in the washing solution can also be a combination of either an acidic solute or a basic solute and a surfactant. Alternatively, the solute in the washing solution can be a combination of an acidic solute, a basic solute, and a surfactant.

[0298] 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.

[0299] It is understood that the circuit board processing method of this application, by transforming a high-modulus, water / alkali-sensitive resin composition into a complete industrial process, achieves a "reductionist" effect on the mechanical processing and subsequent cleaning of circuit boards, with the following specific beneficial effects:

[0300] 1. Physical "rigid locking" completely eliminates manufacturing defects.

[0301] The circuit board processing method of this application constructs a temporary rigid entity in the area to be processed on the circuit board through high-density via plugging and stepped curing. In this way, during milling or drilling, the protective film physically "holds" the edges of the metal lines, preventing tearing displacement under high-speed cutting forces. Simultaneously, even with extremely narrow linewidths or extremely high aspect ratios, the "mechanical interlocking" effect of the protective film ensures the lines remain rock-solid, greatly improving processing yield.

[0302] 2. Thermal stress management at the process level ensures the film layer remains undamaged.

[0303] The stepped baking process effectively avoids defects such as bubbles, pinholes, or "boiling over" caused by instantaneous solvent vaporization. At the same time, the volume shrinkage force during the cross-linking process is released in stages, ensuring that the protective film does not spontaneously crack or blister before processing.

[0304] 3. "Instantaneous disintegration" at the chemical level achieves ultimate cleanliness.

[0305] By utilizing the endogenous "osmotic pressure" generated by alkali neutralization, the high-modulus film layer undergoes complete disintegration in a very short time, rather than slow dissolution. This ensures that even holes with a high aspect ratio of 20:1 or higher can be cleaned with "zero dead angles." Furthermore, the low-concentration (1%-10%) acid-base system, while breaking down the film layer, hardly undergoes any electrochemical reaction with the surfaces of metals such as copper and gold, perfectly preserving the original electrical properties of the circuit board and the wettability of the solder pads.

[0306] 4. Green production and increased efficiency

[0307] The entire process utilizes a water-based film removal system, completely eliminating expensive, highly volatile, and toxic organic solvents, significantly reducing wastewater treatment costs and environmental risks. Simultaneously, the fast film removal rate and high cleanliness drastically shorten turnaround time between processes, enabling the entire production line to maintain an extremely high operating cycle time.

[0308] The present invention also proposes a circuit board, which is prepared using the circuit board preparation method of any of the foregoing embodiments.

[0309] 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, The water-washed pore-plugging resin composition comprises a polymeric resin and an inorganic filler, wherein... The polymer resin includes: Structural resin, the structural resin comprising a polymer having repeating units derived from at least one of vinyl alcohol and vinylpyrrolidone; The reinforcing resin comprises an alkali-soluble resin; The surface of the inorganic filler is modified with at least one functional group selected from the group consisting of aniline, alkyl, nitrogen-containing functional groups on the main chain or branches, and double-bonded functional groups.

2. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The polymer resin also includes a bonding resin, which comprises phenolic resin and epoxy resin.

3. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The structural resin comprises a polymer having repeating units derived from vinyl alcohol, wherein 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%.

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

5. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The structural resin comprises a polymer having repeating units derived from vinylpyrrolidone, wherein the polymer having repeating units derived from vinylpyrrolidone is polyvinylpyrrolidone, and the molecular weight of the polyvinylpyrrolidone is between 2500 g / mol and 1200000 g / mol.

6. The water-washed pore-plugging resin composition according to claim 2, 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 epoxy resin, liquid bisphenol F epoxy resin, liquid bisphenol A-bisphenol F composite epoxy resin, liquid bisphenol S epoxy resin, and liquid phenolic epoxy resin.

7. The water-washed pore-plugging resin composition according to claim 2, characterized in that, The phenolic resin is selected from at least one of linear phenol-formaldehyde resin, linear BPA-formaldehyde resin, and liquid phenolic resin.

8. The water-washed pore-plugging resin composition according to claim 2, 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.

9. The water-washed pore-plugging resin composition according to claim 1, characterized in that, The alkali-soluble resin is selected from at least one of the first type of resin and polyimide precursor; The first type of resin is a monomer and / or prepolymer containing at least one functional group selected from carboxyl groups, ester bonds and acrylate groups.

10. The water-washed pore-plugging resin composition according to claim 9, characterized in that, The first type of resin has an acid value between 5 mgKOH / g and 300 mgKOH / g, and a molecular weight between 50 g / mol and 50,000 g / mol; and / or The molecular weight of the polyimide precursor is between 1000 g / mol and 100000 g / mol.

11. The water-washed pore-plugging resin composition according to claim 9, characterized in that, The first type of resin is selected from at least one of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, carboxyl-functionalized acrylate resin, modified epoxy acrylate resin, modified polyurethane acrylate resin, and modified polyester acrylate resin; and / or The polyimide precursor is selected from at least one of polyamic acid and polyisoimide.

12. 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, barium sulfate, and aluminum nitride.

13. 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, polyethylene glycol, and rubber polymers.

14. The water-washed pore-plugging resin composition according to claim 13, 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.

15. The water-washed pore-plugging resin composition according to claim 13, characterized in that, The toughening resin accounts for 1% to 30% of the total weight of the structural resin and the toughening resin.

16. The water-washed pore-plugging resin composition according to claim 13, characterized in that, The polymer resin contains, by weight percentage: A combination of 30% to 70% consisting of the structural resin and the toughening resin; 30% to 65% of the reinforcing resin.

17. The water-washed pore-plugging resin composition according to claim 2, characterized in that, In the polymer resin, the weight percentage of the bonding resin is no more than 5%.

18. The water-washed pore-plugging resin composition according to any one of claims 1 to 17, characterized in that, The water-washed pore-plugging resin composition comprises, by weight percentage: 20% to 70% of the aforementioned polymeric resin; and The inorganic filler comprises 30% to 80%.

19. The water-washed pore-plugging resin composition according to claim 1, 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.

20. The water-washed pore-plugging resin composition according to claim 19, characterized in that, The solvent is 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, N,N-dimethylformamide, N,N-dimethylacetamide, propylene glycol monomethyl ether acetate, toluene, and xylene; and / or The additive is selected from at least one of leveling agents, dispersants, and defoamers.

21. 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 20, 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.

22. The method for preparing the water-washed pore-plugging resin composition according to claim 21, 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.

23. The method for preparing the water-washed pore-plugging resin composition according to claim 21, 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.

24. The method for preparing the water-washed pore-plugging resin composition according to any one of claims 21 to 23, 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 10,000 mPa∙s and 50,000 mPa∙s.

25. The method for preparing the water-washed pore-plugging resin composition according to claim 24, characterized in that, The solvent removal process includes: 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.

26. A circuit board processing method using the water-washed via-plugging resin composition according to any one of claims 1 to 20, characterized in that, The circuit board processing method includes the following steps: Circuit board provided: A circuit board is provided that defines a processing area, on which a target hole to be filled is pre-formed; Hole plugging: The water-washed hole plugging resin composition is applied to the processing area of ​​the circuit board and filled into the target hole to be plugged; Curing: The water-washed plugging resin composition is heat-treated to form a cured protective film on the circuit board; Processing: Machining the circuit board to which the cured protective film has been formed; and Film removal: The processed circuit board is cleaned with a water washing solution to remove the cured protective film.

27. The circuit board processing method as described in claim 26, characterized in that, The water-washable plugging resin composition is applied to the processing area of ​​the circuit board by at least one of screen printing, pad printing, stencil printing, spraying, and squeegee printing.

28. The circuit board processing method as described in claim 26, characterized in that, The heat treatment includes drying the water-washed pore-blocking resin composition for 3 to 30 minutes at a temperature range of 50°C to 120°C.

29. The circuit board processing method as described in claim 26, characterized in that, The heat treatment includes stepped baking, which sequentially 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.

30. The circuit board processing method as described in claim 26, characterized in that, In the film removal step, the temperature of the washing solution is between 50°C and 95°C.

31. The circuit board processing method as described in claim 26, characterized in that, The washing solution further comprises: The solute comprises, by weight, between 1% and 20%, wherein the solute is selected from at least one of acidic and basic solutes; and / or Surfactants ranging from 0.5% to 3% by weight.

32. The circuit board processing method as described in claim 31, characterized in that, The acidic solute is selected from at least one of sulfuric acid and hydrochloric acid; and / or The alkaline solute is selected from at least one of potassium hydroxide and sodium hydroxide.

33. A circuit board, characterized in that, The circuit board is prepared using the processing method described in any one of claims 26 to 32.

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