Composite film material for circuit board manufacturing process and preparation method thereof, and selective via hole method for circuit board

Abstract

The application discloses a composite film material for a circuit board process, a preparation method of the composite film material, and a circuit board selective hole plugging method. The composite film material comprises a metal layer, a photosensitive layer arranged on a first surface of the metal layer, and a resin bonding layer arranged on a second surface of the metal layer. The resin bonding layer comprises an alkali-soluble resin and is used for bonding with the circuit board. The application uses the strong support of the metal layer and a specific formula design of the resin bonding layer to ensure that the film material can be cleaned and removed without residues by an alkaline solvent after experiencing an extreme heat process of 150 DEG C to 220 DEG C, and the yield and surface flatness of a selective hole plugging process of a high thickness-diameter ratio circuit board are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and in particular to a composite film material for circuit board manufacturing processes, its preparation method, and a selective via plugging method for circuit boards. Background Technology

[0002] "Resin plugging" is a key process in high-end printed circuit board manufacturing to achieve high-reliability interconnection. It mainly eliminates the risk of electrical short circuits caused by holes and achieves surface smoothing by filling them with resin. As electronic products develop towards higher integration, the aspect ratio of circuit boards continues to rise (e.g., aspect ratio ≥ 8:1 or board thickness greater than 6mm), which places extremely high physical and chemical requirements on the precision and reliability of the "selective resin plugging" process.

[0003] However, existing technologies often struggle to strike a balance between "high-intensity masking under extreme pressure" and "clean peeling after high-temperature curing" when selectively plugging vias in high aspect ratio circuit boards. This is because current solutions typically rely on homogeneous polymer masking materials (such as conventional photosensitive dry films) as the via-covering medium. In complex vacuum via-plugging processes, this single-dimensional material system faces an irreconcilable underlying physicochemical contradiction: on the one hand, to maintain the shape of the via edges and prevent collapse, shrinkage, or cracking under the high-intensity mechanical shearing of the vacuum suction and via-plugging scraper, the masking material must possess extremely high structural rigidity and high-temperature cross-linking resistance; on the other hand, once the material is baked for a long time at high temperatures (e.g., above 150°C), under oxygen, and shear force to form a dense, highly cross-linked network or experience polymer chain breakage, its interface will undergo irreversible deep bonding or carbonization with the circuit board substrate, making complete peeling with conventional stripping solutions impossible in subsequent processes. This compromise based on the upper limit of the physical properties of homogeneous materials makes it easy to form stubborn residues or voids at the edges of tiny apertures, causing fatal defects in subsequent electroplating or circuit interconnection. This makes it impossible for existing technologies to meet the high-yield production requirements of high aspect ratio through holes under extreme processing conditions. Summary of the Invention

[0004] The main objective of this invention is to propose a composite film material for circuit board manufacturing, which aims to solve the technical problem that existing cover hole media cannot simultaneously achieve high-strength mechanical shielding under high pressure and clean peeling without residue after high-temperature curing when facing vacuum via plugging processes for circuit boards with high aspect ratios.

[0005] To achieve the above objectives, the present invention provides a composite film material for circuit board manufacturing processes, comprising:

[0006] Metal layer;

[0007] A photosensitive layer is disposed on the first surface of the metal layer; and

[0008] A resin adhesive layer is disposed on the second surface of the metal layer, the second surface being opposite to the first surface;

[0009] The resin adhesive layer comprises an alkali-soluble resin and is used to bond with the circuit board.

[0010] In one embodiment, the resin adhesive layer further comprises a non-alkali-soluble resin, wherein the non-alkali-soluble resin is selected from at least one of non-alkali-soluble thermoplastic resins and non-alkali-soluble thermosetting resins.

[0011] In one embodiment, the metal layer is made of at least one of silver, copper, nickel, iron, tin, zinc, phosphorus, and aluminum; and / or

[0012] The thickness of the metal layer is from 0.05 micrometers to 5 micrometers; and / or

[0013] The surface roughness Ra of the metal layer is between 0.05 micrometers and 5 micrometers; and / or

[0014] The surface roughness Rz of the metal layer is between 0.2 micrometers and 20 micrometers; and / or

[0015] The thickness of the photosensitive layer is between 2 micrometers and 100 micrometers; and / or

[0016] The resolution of the photosensitive layer is no greater than 1 mm; and / or

[0017] The adhesion strength of the resin adhesive layer is between 0.05 N / cm and 6 N / cm; and / or

[0018] The thickness of the resin adhesive layer is between 5 micrometers and 70 micrometers.

[0019] In one embodiment, 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.

[0020] 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

[0021] 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

[0022] The molecular weight of the polyimide precursor is between 1000 g / mol and 100000 g / mol; and / or

[0023] The polyimide precursor is selected from at least one of polyamic acid and polyisoimide.

[0024] In one embodiment, the non-alkali-soluble thermoplastic resin is selected from at least one of polyamide resin, polyester resin, polystyrene resin, rubber resin, polyvinyl butyral, and polyurethane resin.

[0025] In one embodiment, the molecular weight of the non-alkali-soluble thermoplastic resin is between 3000 g / mol and 400000 g / mol.

[0026] In one embodiment, the rubber resin 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.

[0027] In one embodiment, the non-alkali-soluble thermosetting resin comprises a polymer with an aromatic ring and / or heterocyclic ring in the main chain.

[0028] In one embodiment, the polymer having an aromatic ring and / or heterocyclic ring in its main chain is selected from polyimide resins, epoxy resins, phenolic resins, benzoxazine resins, and bismaleimide resins.

[0029] In one embodiment, the epoxy resin is selected from at least one of glycidylamine epoxy resin, phenoxy 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; and / or

[0030] The benzoxazine resin is selected from at least one of bisphenol A benzoxazine, bisphenol F benzoxazine, MDA benzoxazine, DCPD benzoxazine, phenolic benzoxazine, and DOPO benzoxazine; and / or

[0031] The bismaleimide resin is selected from at least one of diaminodiphenylmethane modified bismaleimide, biphenyl-containing bismaleimide, high-performance thermoplastic resin blended toughened modified bismaleimide, isopropyl-p-phenyl bismaleimide, PI modified bismaleimide, and cyanate ester modified bismaleimide.

[0032] In one embodiment, the glass transition temperature of the polymer is not lower than 130°C.

[0033] In one embodiment, the resin adhesive layer further comprises an initiator, which comprises at least one of a latent accelerator and a latent curing agent.

[0034] In one embodiment, where the non-alkali-soluble resin comprises a non-alkali-soluble thermosetting resin,

[0035] The latent curing agent for curing non-alkali-soluble thermosetting resins is selected from at least one of phenolic resins, benzoxazine, bismaleimide resins, reactive esters, and amine dicyandiamide curing agents; and / or

[0036] The latent accelerator used for curing non-alkali-soluble thermosetting resins is selected from at least one of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methylimidazole.

[0037] In one embodiment, when the latent curing agent comprises phenolic resin and the non-alkali-soluble thermosetting resin comprises epoxy resin, the mass of the phenolic resin and the mass of the epoxy resin satisfy the following formula:

[0038] The mass of phenolic resin = (hydroxyl equivalent of phenolic resin / epoxy equivalent of epoxy resin) × mass of epoxy resin.

[0039] In one embodiment, the mass of the latent curing agent used to cure the non-alkali-soluble thermosetting resin is no more than 10% of the mass of the non-alkali-soluble thermosetting resin; and / or the mass of the latent accelerator used to cure the non-alkali-soluble thermosetting resin is no more than 5% of the mass of the non-alkali-soluble thermosetting resin.

[0040] In one embodiment, the latent curing agent used to cure the alkali-soluble resin is selected from at least one of benzoyl peroxide, tert-butyl peroxide, dicumyl peroxide, cumene hydroperoxide, and hydroxycumene peroxide; and / or

[0041] The latent accelerator used to cure the alkali-soluble resin is selected from at least one of N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-methylaniline, n-butanol-aniline condensate, butyraldehyde-n-butylamine condensate, thiourea, ethylidene thiourea, tetramethylthiourea, cobalt naphthenate, cobalt naphthenate, cobalt acetate, and copper octoate.

[0042] In one embodiment, the mass of the latent curing agent used to cure the alkali-soluble resin is no more than 10% of the mass of the alkali-soluble resin; and / or

[0043] The mass of the latent accelerator used to cure the alkali-soluble resin is no more than 5% of the mass of the alkali-soluble resin.

[0044] In one embodiment, the resin adhesive layer further comprises a filler selected from at least one of silicon dioxide, aluminum oxide, aluminum hydroxide, calcium carbonate, magnesium carbonate, magnesium silicate, silicon carbide, titanium carbide, barium sulfate, magnesium sulfate, titanium oxide, magnesium oxide, calcium oxide, boron nitride, and aluminum nitride.

[0045] In one embodiment, the surface of the filler is modified with at least one surface-modifying group selected from epoxy, aniline, amino, and alkyl groups.

[0046] In one embodiment, the particle size of the filler is between 0.1 micrometers and 50 micrometers.

[0047] In one embodiment, the resin adhesive layer further comprises an additive selected from at least one of leveling agents, defoamers, wetting and dispersing agents, and silane coupling agents.

[0048] In one embodiment, the leveling agent is selected from at least one of polyether-modified polydimethylsiloxane solution, aralkyl-modified polymethylalkylsiloxane, polyacrylate, and nonionic organic surfactant; and / or

[0049] The defoamer is selected from at least one of dimethyl polysiloxane containing fumed silica and organically modified polysiloxane containing fumed silica; and / or

[0050] The wetting and dispersing agent is selected from at least one of polyether-modified silicone, propylene glycol methyl ether acetate, and nonionic organic surfactants; and / or

[0051] The silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane.

[0052] In one embodiment, where the resin adhesive layer contains both a silane coupling agent and a filler, the mass of the silane coupling agent is 0.5% to 30% of the mass of the filler.

[0053] In one embodiment, in the resin adhesive layer:

[0054] The total mass of the resin accounts for 20% to 100% of the total mass of the resin adhesive layer;

[0055] The filler accounts for 0% to 80% of the total mass of the resin adhesive layer.

[0056] In one embodiment, the mass of the additive in the resin adhesive layer accounts for 0.01% to 20% of the total mass of the resin adhesive layer.

[0057] In one embodiment, the mass ratio of the alkali-soluble resin to the non-alkali-soluble resin is from 0.2:0.8 to 1:0.

[0058] In one embodiment, when the non-alkali-soluble resin simultaneously comprises a non-alkali-soluble thermoplastic resin and a non-alkali-soluble thermosetting resin, the mass ratio of the non-alkali-soluble thermoplastic resin to the non-alkali-soluble thermosetting resin is from 0.7:0.3 to 1:0.

[0059] In one embodiment, the composite film material further includes a protective film disposed on the surface of at least one of the photosensitive layer and the resin adhesive layer.

[0060] In one embodiment, the thickness of the protective film is between 3 micrometers and 50 micrometers; and / or

[0061] The release force of the protective film is between 1g and 2000g.

[0062] The present invention also proposes a method for preparing a composite film material for circuit board manufacturing as described in any of the preceding claims, the method comprising:

[0063] Provide a metal layer;

[0064] A photosensitive layer is formed on the first surface of the metal layer; and

[0065] The resin adhesive layer ink is applied to the second surface of the metal layer and dried to form the resin adhesive layer.

[0066] In one embodiment, before applying the resin adhesive layer ink to the second surface of the metal layer, the preparation method further includes preparing the resin adhesive layer ink, the step of preparing the resin adhesive layer ink comprising:

[0067] Alkali-soluble resin and non-alkali-soluble resin are dissolved in a first solvent and mixed in a first process to obtain a resin slurry;

[0068] The filler is dispersed in a second solvent for a second mixing to obtain a filler slurry; and

[0069] The resin slurry and filler slurry are mixed in a third step to obtain the resin adhesive layer ink.

[0070] In one embodiment, the step of preparing the resin slurry further includes: pre-dissolving at least one additive selected from leveling agents, wetting and dispersing agents and defoamers in the first solvent before dissolving the alkali-soluble resin and the non-alkali-soluble resin;

[0071] The step of preparing the filler slurry further includes: pre-dissolving at least one additive selected from leveling agents, wetting and dispersing agents, defoamers and silane coupling agents in the second solvent before dispersing the filler in the second solvent.

[0072] In one embodiment, the first solvent and the second solvent are each independently selected from at least one of ketone solvents, aromatic hydrocarbon solvents and ester solvents with boiling points between 70°C and 200°C.

[0073] In one embodiment, the ketone solvent is selected from at least one of isoflurane, butanone, cyclohexanone, and methyl isobutyl ketone; and / or

[0074] The aromatic hydrocarbon solvent is selected from at least one of toluene, xylene, and trimethylbenzene; and / or

[0075] The ester solvent is selected from at least one of n-butyl acetate, isobutyl acetate, sec-butyl acetate, isopropyl acetate, propylene glycol methyl ether acetate, and dimethyl carbonate.

[0076] In one embodiment, the first mixing speed is 3600 rpm to 7200 rpm, the mixing temperature is not greater than 45°C, and the mixing time is 10 minutes to 60 minutes; and / or

[0077] The second mixing speed is 3600 rpm to 7200 rpm, the mixing temperature is not greater than 45°C, and the mixing time is 10 minutes to 60 minutes; and / or

[0078] The third mixing speed is 3600 rpm to 7200 rpm, the mixing temperature is not greater than 45°C, and the mixing time is 60 minutes to 120 minutes.

[0079] The present invention also proposes a method for selectively plugging vias in a circuit board, using a composite film material for circuit board manufacturing as described in any of the preceding claims, the method comprising the following steps:

[0080] Film application: The composite film material is applied to the surface of the circuit board to be processed, wherein the resin adhesive layer of the composite film material is attached to the circuit board;

[0081] Patterning: The photosensitive layer of the composite film is exposed and developed to selectively expose the metal layer that matches the target hole to be filled on the surface of the circuit board.

[0082] Etching: Etching the exposed metal layer to expose the target holes to be filled on the circuit board;

[0083] First film removal: The remaining photosensitive layer on the composite film is removed using a first alkaline solution;

[0084] Hole plugging: Under vacuum conditions, plugging resin is filled into the target holes of the circuit board;

[0085] Curing: The circuit board is baked to cure the via-sealing resin.

[0086] In one embodiment, after the curing step, the circuit board selective via plugging method further includes:

[0087] First grinding and micro-etching: The circuit board is ground and micro-etched to remove the plugging resin and metal layer on the surface of the circuit board.

[0088] Second film removal: A second alkaline solution is used to remove the residual resin adhesive layer on the surface of the circuit board; and

[0089] Second grinding plate: Grinds and removes the resin that plugs the holes protruding from the surface of the circuit board.

[0090] In one embodiment, prior to the film application step, the circuit board selective via plugging method further includes:

[0091] Pre-treatment: The circuit board is drilled and its surface is roughened.

[0092] In one embodiment, the first alkaline solution and / or the second alkaline solution comprises at least one of sodium carbonate, potassium carbonate, sodium hydroxide, sodium phosphate, sodium pyrophosphate, and organic amine; and / or

[0093] The mass concentration of the first alkaline solution and / or the second alkaline solution is 3% to 8%; and / or

[0094] The temperature of the first alkaline solution and / or the second alkaline solution treatment is 55°C to 70°C, and the treatment time is 30 seconds to 10 minutes.

[0095] In one embodiment, in the curing step, a stepped drying process is used to cure the pore-filling resin, wherein,

[0096] The drying conditions for the first stage are: temperature 110℃, duration 30 minutes;

[0097] The drying conditions for the second stage are: temperature 150℃, duration 45 minutes.

[0098] The composite film material for circuit board manufacturing in this application has the following beneficial effects:

[0099] 1. The composite film material of this application constructs a selective via-plugging physical barrier with high mechanical rigidity and thermal stability, overcoming the technical bottleneck of easy cracking and collapse of the via-plugging medium in the process of high aspect ratio (e.g., ≥8:1) or ultra-thick copper clad laminate (e.g., thickness greater than 6mm). Specifically, the composite film material of this application adopts an integrated stack structure with a metal layer as the core support and photosensitive layer and resin adhesive layer respectively mounted on both sides. Utilizing the high tensile strength and low thermal expansion characteristics of the metal foil, combined with the microscopic physical anchoring of the resin adhesive layer, it provides a solid mechanical barrier and stress buffering mechanism under vacuum negative pressure suction and high temperature thermal cycling environment. Based on this, the composite film material itself can perfectly withstand the reciprocating shear force and pressure difference impact brought by the deep hole plugging scraper, thereby eliminating the risk of leakage of the plugging resin into non-opening areas or the formation of voids at the bottom of the hole during high-pressure filling of deep holes, ensuring the cleanliness of the surface and the flatness of the plugged holes in the selective via-plugging process of ultra-thick copper clad laminate.

[0100] 2. This invention achieves a balance between high-strength adhesion and zero-residue film removal at the end of the process under extreme thermodynamic processing conditions such as high aspect ratio through holes or back-drilled holes. Specifically, facing the need for prolonged high-temperature (e.g., above 150°C) stepped baking and curing after plugging deep holes in ultra-thick boards, the composite film material of this application precisely blends alkali-soluble resin, non-alkali-soluble resin, and trace amounts of inorganic fillers in its resin adhesive layer, and combines this with temperature gradient control of a latent initiator to limit the crosslinking density of the polymer system to a critical state that provides a dense support network while maintaining the activity of acidic functional groups. This allows the residual adhesive layer of the composite film to rapidly swell and peel off in a sheet-like manner in conventional alkaline solutions after enduring prolonged high-temperature thermal stress, thus eliminating the risk of residual adhesive easily generated at the edges of high aspect ratio microholes. This provides a high-yield substrate for subsequent micro-blind hole electroplating and circuit interconnection of ultra-thick copper-clad laminates.

[0101] 3. The composite film material of this application establishes an ultra-high resolution boundary definition mechanism adapted to high-density interconnect ultra-thick boards, breaking through the opening accuracy limit of traditional physical screen printing under high-depth-diameter holes with small pitch. Specifically, the composite film material of this application directly laminates a photosensitive layer with specific resolution onto the surface of a metal layer, utilizing the photosensitive layer's photoresist capability to guide the underlying metal layer to selectively chemically etch, transforming macroscopic physical imprinting masking into a vertical opening definition mechanism based on microscopic photochemical reactions. Furthermore, this composite film material essentially provides a steep and structurally complete physical isolation wall between the hole-filling and non-hole-filling areas on ultra-thick copper-clad laminates. Even when facing dense vias or back-drilled arrays with micro-pitch in ultra-thick boards, it can ensure that each high-depth-diameter-diameter target hole to be filled is accurately positioned, avoiding incomplete filling or ink bleeding at the hole edge caused by opening deformation in traditional processes. Attached Figure Description

[0102] 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.

[0103] Figure 1 This is a schematic diagram of the structure of a composite film material for circuit board manufacturing according to an embodiment of the present invention;

[0104] Figure 2 This is a schematic flowchart of an embodiment of the method for preparing the composite membrane material of the present invention;

[0105] Figure 3 This is a flowchart illustrating an embodiment of the selective via plugging method for circuit boards according to the present invention.

[0106] Explanation of icon numbers:

[0107] 10. Metal layer; 20. Photosensitive layer; 30. Resin adhesive layer; 40. Protective film

[0108] 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

[0109] 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.

[0110] 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.

[0111] 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.

[0112] This invention proposes a composite film material for circuit board manufacturing.

[0113] In embodiments of the present invention, such as Figure 1 As shown, the composite film material used in the circuit board manufacturing process includes a metal layer 10, a photosensitive layer 20, and a resin adhesive layer 30. Specifically, this composite film material integrates the patterning capability of the photosensitive layer 20, the rigid support capability of the metal layer 10, and the alkaline peelability of the resin adhesive layer 30 through the organic combination of the three physical layers, thus constructing an integrated carrier suitable for selective via plugging with high aspect ratios.

[0114] Specifically, the metal layer 10 serves as the mechanical framework and process barrier layer of the entire composite film. Specifically, the metal layer 10 is made of at least one of the following materials: silver, copper, nickel, iron, tin, zinc, phosphorus, and aluminum. More specifically, the metal layer 10 can be made of metal units such as copper, silver, and nickel, or it can be a metal alloy of copper, silver, and nickel.

[0115] In some embodiments, the metal layer 10 can be made of metal monomers such as copper, silver, and nickel. For example, the metal layer 10 can be made of electrolytic copper foil or rolled copper foil. By utilizing the excellent ductility and chemical stability of copper, and in conjunction with subsequent acidic or alkaline etching processes, high-precision aperture openings can be rapidly formed within seconds.

[0116] In other embodiments, the metal layer 10 may be an alloy of metals such as copper, silver, and nickel, for example, a nickel alloy or an aluminum alloy. By adjusting the proportion of different elements in the metal layer 10 (e.g., adding trace amounts of phosphorus or zinc), the physical hardness and coefficient of thermal expansion (CTE) of the metal layer 10 can be precisely adjusted. This multi-material selectivity allows the metal layer 10 to be matched according to the substrate characteristics of the circuit board to be processed, thereby effectively offsetting the internal stress generated by resin shrinkage during the high-temperature baking and curing stage (e.g., at 150°C), avoiding warping or bending of the circuit board after the vias are filled and cured, and ensuring the final flatness of the product.

[0117] In some embodiments, the thickness of the metal layer 10 is from 3 micrometers to 300 micrometers, preferably from 9 micrometers to 18 micrometers.

[0118] Specifically, the thickness of the metal layer 10 depends on the aspect ratio of the circuit board to be processed and the pressure load during vacuum via plugging. When the thickness of the metal layer 10 is within the aforementioned range, it possesses sufficient shear strength to withstand the horizontal thrust generated by the reciprocating motion of the via plugging scraper on the metal surface, thereby ensuring that the resin adhesive layer 30 beneath the metal layer 10 does not shift due to uneven stress. In particular, for ultra-thick circuit boards with a thickness greater than 6 mm, copper foil with a thickness of 9 to 18 micrometers is preferably used as the metal layer 10. Utilizing the excellent longitudinal support force of the metal foil within this thickness range, it can effectively prevent the film material from collapsing or cracking into the via during vacuum suction, ensuring the surface flatness after via plugging.

[0119] In some embodiments, the surface roughness Ra of the metal layer 10 is between 0.05 micrometers and 300 micrometers, and the surface roughness Rz of the metal layer 10 is between 0.2 micrometers and 20 micrometers.

[0120] Specifically, the surface roughness (Ra and Rz) of the metal layer 10 directly affects the interfacial bonding strength through a micro-anchoring mechanism. When the surface roughness of the metal layer 10 is within the aforementioned range, an interlocking effect can be formed between it, the upper photosensitive layer 20, and the lower resin adhesive layer 30. By controlling Ra to be between 0.05 micrometers and 300 micrometers, resin molecules can fully wet the micro-uneven structure of the metal surface, thereby significantly increasing the interfacial contact area.

[0121] This specific roughness design offers dual benefits: firstly, it ensures that the photosensitive layer 20 will not peel or tumble due to insufficient adhesion when the composite film experiences thermal stress fluctuations during the exposure and development process; secondly, because Rz is controlled at an extremely low level of 0.2 to 20 micrometers, this guarantees the flatness of the metal layer 10 surface, allowing the etching solution to uniformly erode the metal along the vertical direction during subsequent etching steps, thereby obtaining patterned openings with steep edges and high resolution. This precise control of the microstructure ultimately achieves accurate definition of the target hole area to be plugged, avoiding quality defects such as resin overflow or incomplete hole plugging caused by edge burrs.

[0122] Specifically, the photosensitive layer 20 is disposed on the first surface of the metal layer 10, which is the glossy surface of the metal layer 10.

[0123] Specifically, the first surface of the metal layer 10 serves as the interface supporting the photosensitive layer 20. The smoothness of its glossy surface ensures the uniformity of the photosensitive layer 20's thickness during coating or lamination. Because the glossy surface has low microscopic undulations, it effectively reduces random reflections of incident light at the metal interface. During the exposure step, this optical correction effect significantly reduces light scattering interference in non-exposed areas, thereby ensuring the fidelity of pattern transfer and providing reliable solder resist and guide boundaries for high-precision selective via plugging.

[0124] In some embodiments, the thickness of the photosensitive layer 20 is between 2 micrometers and 100 micrometers. Preferably, the thickness of the photosensitive layer 20 is between 10 micrometers and 25 micrometers.

[0125] Specifically, the thickness design of the photosensitive layer 20 needs to balance pattern resolution and tolerance to subsequent etching processes. When the thickness of the photosensitive layer 20 is in the range of 2 micrometers to 100 micrometers, it can not only provide sufficient shielding power to resist the lateral erosion of the metal layer 10 by acidic or alkaline etching solutions, but also maintain excellent light transmittance, ensuring that the photochemical reaction can penetrate the entire thickness of the photosensitive layer 20 to reach the metal surface. In addition, when the thickness of the photosensitive layer 20 is preferably between 10 micrometers and 25 micrometers, the composite film can achieve optimal sidewall perpendicularity while maintaining extremely high production efficiency, thereby improving the size consistency of the aperture opening.

[0126] In some embodiments, the resolution of the photosensitive layer 20 is no greater than 1 mm. Preferably, the resolution of the photosensitive layer 20 is no greater than 100 micrometers.

[0127] Specifically, the resolution of the photosensitive layer 20 defines the minimum selective via spacing achievable by the composite film. The technical characteristic of a resolution no greater than 1 mm (e.g., 50 to 100 micrometers) allows the film to meet the precision wiring requirements of ultra-high density interconnect (HDI) circuit boards. By employing a photosensitive layer 20 with a resolution within this range, the present invention can perform "precise positioning, partial opening, and overall via plugging" on dense via arrays on a circuit board.

[0128] This high-resolution capability, combined with the rigid framework of metal layer 10, ensures that even in complex via-plugging processes with extremely small via spacing, the opening edges of metal layer 10 maintain structural integrity without collapse or ink seepage. This fundamentally solves the problems of incomplete or incorrect via plugging and pad contamination caused by insufficient alignment accuracy in traditional via-plugging processes, significantly improving the electrical connection reliability and process yield of precision circuit boards.

[0129] A resin adhesive layer 30 is disposed on the second surface of the metal layer 10, the second surface being opposite to the first surface, and the second surface being the rough surface of the metal layer 10.

[0130] Specifically, the second surface of the metal layer 10, serving as the bonding interface in direct contact with the circuit board, provides abundant microscopic anchoring points for the resin adhesive layer 30 due to its rough surface characteristics. When the resin adhesive layer 30 is coated or pressed onto this rough surface, the resin macromolecular chains can penetrate deep into the microscopic valleys of the metal surface, forming a physical interlocking effect. This interface design ensures that the resin adhesive layer 30 and the metal layer 10 maintain extremely high bonding strength under the subsequent high-pressure environment of vacuum plugging and the thermal shock of baking and curing, effectively preventing interlayer delamination and thus ensuring the structural stability of the composite film as the overall carrier.

[0131] Specifically, the resin adhesive layer 30 is used to bond with the circuit board.

[0132] In some embodiments, the resin adhesive layer 30 serves as a transition layer between the composite film and the circuit board to be treated, its core function being to achieve reliable temporary adhesion. By adjusting the rheological properties of the resin adhesive layer 30, it can fully wet the undulations of the circuit board surface and the edges of the copper foil lines under lamination pressure, thereby venting interfacial air and achieving a bubble-free bonding effect. This tight bonding provides a solid foundation for subsequent selective etching and precise via plugging, preventing the via-plugging resin from leaking into non-via areas through interfacial gaps under pressure, thus ensuring the cleanliness of the circuit board surface.

[0133] Furthermore, the resin adhesive layer 30 comprises an alkali-soluble resin and an alkali-insoluble resin, wherein the alkali-insoluble resin is selected from at least one of an alkali-insoluble thermoplastic resin and an alkali-insoluble thermosetting resin.

[0134] Specifically, by blending alkali-soluble resins with non-alkali-soluble resins, this invention achieves a "performance-tunable" bonding system. The alkali-soluble resin (such as a resin containing carboxyl or phenolic hydroxyl groups) provides crucial "alkali-removable" properties to the bonding layer, ensuring that after the via-closing process, residual film on the board surface can be removed using alkaline solutions such as sodium hydroxide or potassium hydroxide without damaging the underlying circuit copper surface.

[0135] The introduction of non-alkali-soluble resins serves as both a "skeletal support" and a "performance compensation." When the non-alkali-soluble resin is selected from non-alkali-soluble thermoplastic resins, its excellent film-forming properties and toughness can improve the integrity of the composite film during peeling, preventing film breakage. When the non-alkali-soluble resin is selected from non-alkali-soluble thermosetting resins (such as epoxy resins, cyanate ester resins, etc.), the micro-crosslinked network formed during the pre-baking stage can significantly improve the heat resistance and shear strength of the adhesive layer. This synergistic effect of the dual-resin system ensures that the resin adhesive layer 30 not only has sufficient adhesion during the film application stage (e.g., 0.05 N / cm to 6 N / cm), but also maintains good chemical sensitivity after high-temperature curing above 150°C, achieving a perfect balance between "firm adhesion" and "clean peeling."

[0136] Of course, in other embodiments, the resin adhesive layer 30 may also be based solely on an alkali-soluble resin. Specifically, when the resin adhesive layer 30 is composed only of an alkali-soluble resin, the system exhibits extremely high chemical sensitivity and stripping efficiency. Because there is no mechanical obstruction from non-alkali-soluble components within the system, the alkaline stripping solution (such as a 1% to 5% sodium hydroxide solution by mass) can rapidly penetrate and neutralize the acidic functional groups on the resin molecular chains, causing the entire adhesive layer to swell, dissolve, and peel off from the metal surface and circuit board surface in a very short time.

[0137] This single alkali-soluble resin system is particularly suitable for the production of precision circuit boards with short process cycles or extremely high requirements for surface cleanliness. In this embodiment, by selecting alkali-soluble monomers or prepolymers with high film-forming properties and moderate molecular weight distribution, it is possible to ensure that the adhesive layer still possesses sufficient cohesive strength to support the metal layer 10 and the photosensitive layer 20 without adding non-alkali-soluble resins. Simultaneously, this simplified formulation design effectively reduces interlayer interfacial energy, enabling the composite film to achieve "zero residue" clean removal after vacuum plugging, thus providing an excellent surface condition for subsequent circuit plating or surface treatment processes.

[0138] In some embodiments, the adhesion strength of the resin adhesive layer 30 is between 0.05 N / cm and 6 N / cm. Preferably, the adhesion strength of the resin adhesive layer 30 is between 0.1 N / cm and 4 N / cm.

[0139] Specifically, the adhesion of the resin adhesive layer 30 limits the temporary bond strength between the composite film and the circuit board interface. Controlling the adhesion force within the range of 0.05 N / cm to 6 N / cm ensures that the film will not shift or lift at the edges due to mechanical forces during high-pressure spraying or scraping for vacuum via plugging. If the adhesion force is below 0.05 N / cm, the film is highly susceptible to leakage during the hot and humid cycles of exposure and development or the impact of etching solutions, leading to damage to non-via plugging areas.

[0140] Preferably, controlling the adhesion force between 0.1 N / cm and 4 N / cm allows the composite film to maintain excellent bonding stability while possessing good peeling ease. This adhesion force range ensures that after the via-filling curing process (e.g., at temperatures above 150°C), excessive chemical bonding will not occur between the resin adhesive layer 30 and the copper surface of the circuit board. In the final alkaline stripping step, the alkaline solution can penetrate more smoothly to the interface, achieving complete peeling of the film without leaving adhesive residue on the circuit board surface. This protects the surface physical state of the fine lines and avoids potential issues such as incomplete plating or delamination in subsequent electroplating processes.

[0141] In some embodiments, the thickness of the resin adhesive layer 30 is between 5 micrometers and 70 micrometers.

[0142] Specifically, the thickness of the resin adhesive layer 30 directly affects its ability to fill the copper foil lines on the circuit board surface and its stress buffering effect. When the thickness is between 5 micrometers and 70 micrometers, the adhesive layer can act as a "buffer pad" to absorb the thermal stress caused by the mismatch of the coefficient of thermal expansion (CTE) between the circuit board substrate and the metal layer 10.

[0143] If the thickness is less than 5 micrometers, the adhesive layer may not be able to completely cover the undulations of the circuit board (such as 0.5 oz or 1 oz copper-thickness lines), resulting in microbubbles remaining at the interface, which can induce pinholes or ink bleeding during vacuum plugging. If the thickness is greater than 70 micrometers, it will increase the overall longitudinal thermal resistance of the film and may lead to an excessively long lateral dissolution path during alkaline film removal, thereby reducing the removal efficiency. By optimizing the thickness within the above range, this invention achieves a perfect fit to the complex surface morphology of high-density interconnect boards, ensuring the precision and production efficiency of the selective plugging process.

[0144] 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.

[0145] Specifically, the first type of resin, by introducing specific chemical functional groups, endows the resin adhesive layer 30 with excellent chemical reactivity and solubility properties. When the first type of resin contains carboxyl groups (-COOH), the hydrophilic carboxylate generated by the acid-base neutralization reaction between the carboxyl groups and hydroxide ions (OH-) in the alkaline stripping solution can significantly enhance the solubility of the resin in the aqueous phase, thereby achieving rapid and residue-free stripping.

[0146] When the first type of resin contains ester bonds (–COO–) or acrylate groups (CH2=CH–COO–), these functional groups not only enhance the physical adhesion between the adhesive layer and the metal layer 10 and the circuit board surface through intermolecular van der Waals forces and hydrogen bonds, but also endow the resin with crosslinking potential under ultraviolet radiation or hydrolytic properties in an alkaline environment. In particular, the introduction of acrylate groups enables the resin adhesive layer 30 to maintain alkali solubility while possessing good film-forming rigidity, effectively resisting lateral creep caused by plugging pressure.

[0147] For example, 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.

[0148] In some embodiments, the acid value of the first type of resin is from 5 mg KOH / g to 300 mg KOH / g, preferably from 50 mg KOH / g to 140 mg KOH / g.

[0149] Specifically, acid value is a key indicator for measuring the alkali solubility rate of resin. Limiting the acid value to the range of 5 mg KOH / g to 300 mg KOH / g ensures that the resin adhesive layer 30 possesses basic hydrophilicity and chemical reactivity. When the preferred acid value is 50 mg KOH / g to 140 mg KOH / g, the adhesive layer maintains good corrosion resistance in the developer (such as a 1% sodium carbonate solution), but exhibits excellent dissolution and diffusion efficiency in strongly alkaline stripping solutions (such as a 3%–5% sodium hydroxide solution). This precise acid value gradient design effectively avoids accidental dissolution in the early stages of the process, while ensuring efficient and clean stripping at the end of the process.

[0150] In some embodiments, the molecular weight of the first type of resin is from 50 g / mol to 50,000 g / mol, preferably from 50 g / mol to 5,000 g / mol.

[0151] Specifically, molecular weight distribution directly affects the rheological behavior and film quality of the resin adhesive layer 30. When the molecular weight is in the range of 50 g / mol to 50,000 g / mol, the resin system exhibits moderate viscosity during coating, which is beneficial for forming a uniform and dense coating. Preferably, controlling the molecular weight in the lower range of 50 g / mol to 5,000 g / mol can significantly improve the penetration ability and dissolution rate of the resin molecules.

[0152] The introduction of low molecular weight components allows alkaline solutions to penetrate more quickly into the microscopic gaps of the resin adhesive layer 30, accelerating the swelling and peeling process of the molecular chains. This low molecular weight design is particularly crucial when dealing with the edge regions of high aspect ratio holes, effectively reducing the retention of residual adhesive at the micro-hole edges, thereby improving the hole-filling quality of the circuit board and the reliability of subsequent electrical interconnections. Through the synergistic optimization of acid value and molecular weight, this invention successfully solves the technical challenge of difficult film removal from complex circuit board surfaces.

[0153] Furthermore, the polyimide precursor is selected from at least one of polyamic acid and polyisoimide. Specifically, unlike fully closed-ring polyimides, polyamic acid retains a large number of uncyclic free carboxyl groups (-COOH) on its main chain, while polyisoimide has extremely high hydrolytic ring-opening activity in alkaline aqueous solutions and can be rapidly converted into polymer macromolecules with carboxylate structures.

[0154] This inherent microscopic chemical structure endows the resin adhesive layer with excellent intrinsic alkali solubility. In processes involving selective via plugging with high aspect ratios, the composite film must undergo a stepped high-temperature curing process above 150°C and a vacuum process. After this rigorous thermodynamic process, although the polymer network is already highly dense, the densely packed acidic response sites (free carboxyl groups) in the polyimide precursor backbone can still undergo a rapid acid-base neutralization and saponification reaction with the strong alkaline solution (such as sodium hydroxide) at the end of the process (second stripping stage). Utilizing this specific chemical erosion mechanism, the originally highly adhesive resin adhesive layer can rapidly swell in volume, completely destroying its interfacial adhesion to the copper-clad laminate.

[0155] Meanwhile, the rigid aromatic ring structure in the polyimide precursor backbone provides excellent physical support, enabling the composite film to exhibit superior sheet-like peel selectivity during the debonding stage. This means that under strong alkali conditions, the adhesive layer can rapidly detach as a complete sheet, preventing resin gelatinization and the formation of "residual adhesive traps" at the hole wall edges. This fundamentally improves the surface cleanliness and electrical interconnect reliability after plugging high aspect ratio holes. It can be understood that by flexibly proportioning the first type of resin to the polyimide precursor, this application can customize the overall thermodynamic properties and debonding rate of the resin adhesive layer for different circuit board substrates (such as FR-4, polyimide flexible boards, or ceramic substrates).

[0156] In some embodiments, the molecular weight of the polyimide precursor is between 1,000 g / mol and 100,000 g / mol, preferably between 8,000 g / mol and 50,000 g / mol.

[0157] Specifically, the molecular weight of the polyimide precursor directly determines the thermodynamic equilibrium point between its mechanical strength and alkali penetration and dissolution performance. When the molecular weight is in the range of 1000 g / mol to 100000 g / mol, it exhibits good film-forming properties and structural stability after film formation, and can serve as an effective elastic support skeleton to maintain the overall rigidity of the composite membrane and resist the pressure differential shear during the pore-filling process.

[0158] Preferably, the molecular weight of the polyimide precursor is controlled between 8000 g / mol and 50000 g / mol. This specific molecular weight range ensures that the precursor macromolecules possess sufficient heat resistance and tear strength while maintaining excellent dissolution-diffusion kinetics. Experimental studies have shown that excessively low molecular weight (less than 8000 g / mol) leads to insufficient cohesion in the resin adhesive layer during high-temperature curing, potentially causing slight lateral creep and adhesive overflow or resulting in brittle film. Conversely, excessively high molecular weight (greater than 50000 g / mol) leads to excessive physical entanglement of molecular chains, making it difficult for strong alkaline stripping solutions to quickly penetrate into the three-dimensional network, resulting in significantly prolonged stripping time and even the formation of microscopic residues. By precisely optimizing the molecular weight within the aforementioned preferred range, this application perfectly achieves the dual technical benefits of high-pressure mechanical support and efficient, clean stripping, making it particularly suitable for the high-precision via-filling process of ultra-thick copper-clad laminates.

[0159] In some embodiments, the non-alkali-soluble thermoplastic resin is selected from at least one of polyamide resin, polyester resin, polystyrene resin, rubber resin, polyvinyl butyral, and polyurethane resin.

[0160] Specifically, the non-alkali-soluble thermoplastic resin, as a physical modifier in the resin adhesive layer 30, is mainly used to adjust the toughness, film-forming properties, and adhesion to the circuit board substrate of the film material. The introduction of polyamide or polyester resin can significantly improve the mechanical strength of the adhesive layer at room temperature, preventing the composite film material from cracking during winding or slitting. The addition of polyvinyl butyral (PVB) and polyurethane resin, utilizing the abundant polar groups in their molecular chains, enhances the wettability of the film material to the copper surface of the circuit board and the solder mask layer, thereby ensuring reliable, bubble-free bonding before vacuum plugging.

[0161] In some embodiments, the rubber resin 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.

[0162] Specifically, the introduction of rubber-based resins provides the resin adhesive layer 30 with excellent stress buffering and impact resistance. When plugging vias in large-size circuit boards or substrates with complex wiring topologies, the curing process often generates significant internal stress due to the difference in the coefficient of thermal expansion (CTE) between different materials. By adding components such as nitrile rubber or EPDM rubber, their low modulus and high elasticity effectively absorb and release interfacial stress. Furthermore, the introduction of fluororubber or silicone further enhances the chemical resistance of the adhesive layer, ensuring that the edges of the adhesive layer do not swell or permeate during the acid and alkali washing stages of subsequent etching processes, thus maintaining the physical boundary integrity of the selective via plugging area.

[0163] In some embodiments, the molecular weight of the non-alkali-soluble thermoplastic resin is between 3,000 g / mol and 400,000 g / mol, preferably between 5,000 g / mol and 100,000 g / mol.

[0164] Specifically, the molecular weight of the non-alkali-soluble thermoplastic resin directly controls the cohesive strength and thermorheological properties of the resin adhesive layer 30. When the molecular weight is in the range of 3000 g / mol to 400000 g / mol, the resin system exhibits excellent film-forming flexibility, capable of withstanding the deformation of the metal layer 10 during bending or pressing without generating microcracks.

[0165] Preferably, the molecular weight is controlled between 5000 g / mol and 100000 g / mol. This molecular weight range achieves an optimal balance between "film-forming flowability" and "curing dimensional stability." Thermoplastic resins with molecular weights within this range can form a uniform interpenetrating network (IPN) structure with the aforementioned alkali-soluble resin. This microstructure ensures that the adhesive layer will not be bleed-out due to excessively low viscosity during the high-temperature baking stage after plugging, and that during the final alkali removal stage, its moderate molecular chain segment length will not form a dense physical barrier that hinders alkali penetration, thus ensuring complete removal. By precisely controlling the molecular weight of the thermoplastic component, this invention improves the process tolerance of the composite film material in complex manufacturing environments.

[0166] In some embodiments, the non-alkali-soluble thermosetting resin comprises a polymer having an aromatic ring and / or a heterocyclic ring in its main chain.

[0167] Specifically, the non-alkali-soluble thermosetting resin, serving as the thermally stable framework in the resin adhesive layer 30, plays a crucial role in imparting structural stiffness to the composite film during high-temperature processes (such as the pore-filling curing stage at 150°C to 200°C). By introducing aromatic rings (such as benzene rings, naphthalene rings, biphenyl rings, etc.) and / or heterocyclic rings (such as imide rings, triazine rings, oxazole rings, etc.) into the polymer backbone, the extremely high bonding energy and steric hindrance effect of these cyclic structures can significantly increase the glass transition temperature (Tg) and thermal decomposition temperature of the resin molecules.

[0168] In high-pressure spraying or scraping processes for vacuum plugging, thermosetting resins containing aromatic or heterocyclic rings in their main chain can form a highly dense three-dimensional cross-linked network. This micro-network structure has an extremely low free volume, effectively suppressing the free expansion and lateral creep of the resin after heating. The introduction of this specific structure ensures that the rate of change of the physical dimensions of the resin adhesive layer 30 is controlled at an extremely low level (e.g., less than 0.5%) during prolonged high-temperature baking, thereby preventing pore displacement or wrinkling of the metal layer 10 caused by thermal shrinkage of the composite film.

[0169] Furthermore, the hydrophobic properties and chemical inertness of the aromatic or heterocyclic structures enhance the shielding effect of the adhesive layer against etching and developing solutions. Even under continuous impact from strong acids or weak alkalis, these thermosetting resins with rigid backbones maintain interfacial integrity, ensuring precise boundaries of the "selective via plugging" region. By adjusting the density of aromatic and heterocyclic rings, this invention can customize the elastic modulus and thermal gradient of the adhesive layer to meet different aperture requirements with varying aspect ratios, thereby achieving highly reliable protection for precision circuit boards under extreme thermodynamic environments.

[0170] In some embodiments, polymers having aromatic rings and / or heterocycles in their main chain are selected from at least one of polyimide resins, epoxy resins, phenolic resins, benzoxazine resins, and bismaleimide resins.

[0171] Specifically, polymers whose main chain has aromatic rings and / or heterocycles are selected from at least one of polyimide resins, epoxy resins, phenolic resins, benzoxazine resins, and bismaleimide resins.

[0172] Specifically, polymers with aromatic rings and / or heterocyclic rings in their main chains construct a framework system with extremely high thermal stability and mechanical strength for the resin adhesive layer 30 through rigid cyclic structures (such as benzene rings, biphenyl rings, imide rings, etc.) in their main chains.

[0173] When the polymer is selected from polyimide resin (PI), the highly stable imide heterocycles on its main chain can give the membrane excellent heat resistance (Tg can usually reach above 250°C) and extremely low coefficient of thermal expansion, ensuring that the membrane will not be displaced or deformed due to thermal stress during the vacuum plugging curing stage of high aspect ratio holes.

[0174] When the polymer is selected from epoxy resin, its rich aromatic backbone (such as bisphenol A or phenolic resin) and high modulus after crosslinking can significantly improve the anchoring force between the resin adhesive layer 30 and the metal layer 10 and the circuit board surface. In addition, the low shrinkage rate exhibited by epoxy resin during curing effectively prevents cracks or gaps from appearing at the edges of the plugging area, ensuring a sealing effect.

[0175] When the polymer is selected from phenolic resin, its high-density aromatic ring crosslinking network not only improves the chemical resistance of the adhesive layer, making it maintain stable physical properties in complex etching solutions, but also serves as a highly efficient synergistic curing agent to optimize the crosslinking gradient of the overall resin system.

[0176] When the polymer is selected from benzoxazine or bismaleimide (BMI) resins, its unique nitrogen-containing heterocyclic structure, after ring-opening curing upon heating, forms a dense network with extremely high rigidity and excellent dielectric properties. This network structure maintains a very high elastic modulus even at high temperatures (e.g., 150°C to 200°C), effectively resisting the vertical pressure of via plugging on the film material and ensuring the long-term accuracy of the aperture shape in selective via plugging processes. By compounding the above-mentioned high-performance thermosetting resins, this invention can flexibly customize the thermodynamic response characteristics of composite films for different levels of PCB heat resistance requirements (e.g., conventional FR-4 or high-performance ceramic substrates).

[0177] In some embodiments, the epoxy resin is selected from at least one of glycidylamine epoxy resin, phenoxy 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.

[0178] Specifically, the different structures of the epoxy resins mentioned above provide diverse crosslinking network properties and rheological control methods for the resin adhesive layer 30. By introducing glycidylamine epoxy resin or multifunctional o-cresolaldehyde glycidyl ether type epoxy resin, the crosslinking density and glass transition temperature (Tg) of the system can be significantly improved, ensuring that the membrane material has excellent hardness and dimensional stability during the high-temperature curing stage of vacuum plugging.

[0179] In embodiments where high flexibility and adhesion are desired, the initial viscosity and wetting properties of the resin adhesive layer 30 can be effectively adjusted by adding liquid bisphenol A, liquid bisphenol F, or bisphenol A-bisphenol F composite epoxy resin. These liquid components can assist the resin system in rapidly filling the micro-unevennesses on the circuit board surface under lower bonding pressure, eliminating interfacial bubbles.

[0180] In addition, the introduction of components with large-volume rigid structures, such as naphthol-type epoxy resin or phenol-biphenyl epoxy resin, can significantly reduce the moisture absorption rate of the resin and improve its dielectric properties by utilizing the polycyclic aromatic structure in its molecular chain. This is crucial for the via-plugging process of high-frequency and high-speed circuit boards.

[0181] The addition of isocyanate-modified epoxy resin or phenoxy resin focuses on improving the cohesive strength and peel resistance of the adhesive layer, preventing the film edge from cracking due to the shear stress of the grinding wheel during the mechanical grinding step (first or second grinding plate). Through the combined use of the above epoxy resins, a stable base that meets both precision patterning requirements and withstands extreme physical and mechanical processing is achieved, laying the material foundation for high-quality selective via plugging.

[0182] In some embodiments, the phenolic resin may be selected from at least one of linear phenol-formaldehyde resin, linear BPA-formaldehyde resin, and liquid phenolic resin.

[0183] When linear phenol-formaldehyde resin or linear BPA-formaldehyde resin is selected, the rigid aromatic ring structure and high density of active phenolic hydroxyl groups (-OH) in its molecular backbone enable it to undergo efficient ring-opening addition reactions with epoxy groups in the system under the catalysis of a latent accelerator and under heating conditions. This linear macromolecular structure exhibits excellent chemical latency and solvent compatibility at room temperature, ensuring the stability of the composite film during preparation and storage; while in the stepped high-temperature curing stage (e.g., 150℃), it rapidly transforms into a highly dense three-dimensional thermosetting network. The direct benefit of this crosslinking mechanism is that it significantly increases the glass transition temperature (Tg) and shear modulus of the cured resin adhesive layer, enabling it to maintain absolute dimensional stability when subjected to high-pressure impacts from deep-hole plugging and mechanical stress from the subsequent first grinding plate, without interlayer creep or edge collapse. When liquid phenolic resin is selected, it plays a crucial dual role in the resin adhesive layer 30 formulation as both a "processing performance regulator" and a "chemical crosslinking enhancer." Compared to solid powder or flake phenolic resins, liquid phenolic resins have lower initial viscosity and excellent compatibility, enabling them to achieve molecular-level uniform mixing with alkali-soluble resins and the aforementioned epoxy components at room temperature. This high degree of microscopic uniformity ensures that the resin adhesive layer 30 formed after coating and drying of the composite film has extremely high density and surface smoothness.

[0184] In the lamination process, the introduction of liquid phenolic resin significantly reduces the minimum melt viscosity of the resin system. This means that at lower lamination temperatures (e.g., 60°C to 100°C), the resin adhesive layer 30 exhibits quasi-fluid-like spreading properties, rapidly filling the tiny gaps between fine lines on the circuit board and expelling interfacial air. This superior leveling capability provides a physical guarantee against interfacial leakage during vacuum plugging.

[0185] Furthermore, the abundant hydroxyl (-OH) structures in liquid phenolic resin can undergo ring-opening curing reactions with epoxy resin to form stable ether bonds and cross-linking networks. After undergoing a plugging curing process at temperatures above 150°C, the system exhibits excellent chemical resistance and mechanical stability. Even in the deep grinding stage (first grinding stage) of high aspect ratio holes, the adhesive layer containing liquid phenolic resin maintains extremely high cohesion, avoiding interlayer cracking caused by grinding wheel extrusion and ensuring the final yield of the selective plugging process. Simultaneously, its residual polar groups can assist in the physical swelling of alkali molecules during the subsequent alkaline stripping step, thus ensuring thorough stripping while maintaining heat resistance.

[0186] In some embodiments, the benzoxazine resin is selected from at least one of bisphenol A type benzoxazine, bisphenol F type benzoxazine, MDA type (diaminodiphenylmethane type) benzoxazine, DCPD type (dicyclopentadiene type) benzoxazine, phenol type benzoxazine, and DOPO type (phosphorus-containing flame retardant type) benzoxazine.

[0187] Specifically, benzoxazine resin, as a high-performance nitrogen-containing heterocyclic thermosetting resin, exhibits near-zero shrinkage during the heating and curing process, which is the key physical basis for ensuring the accuracy of high aspect ratio hole plugs.

[0188] When benzoxazine is selected from bisphenol A or bisphenol F type benzoxazine, the symmetrical structure of the rigid aromatic ring and oxazine ring in its molecular chain can impart an extremely high glass transition temperature (Tg) of 30°C and excellent mechanical strength to the resin adhesive layer. This ensures that the composite membrane will not experience dimensional creep caused by internal stress when subjected to vacuum plugging curing thermal cycles above 150°C, thereby maintaining the geometric stability of the pore openings.

[0189] When benzoxazine is selected from DCPD or MDA type benzoxazine, the low water absorption of the dicyclopentadiene structure or the high crosslinking density of the diaminodiphenylmethane structure can significantly improve the dielectric stability and solderability of the adhesive layer in humid environments. This is particularly important for the precision manufacturing process of multilayer circuit boards, as it can effectively prevent moisture from penetrating to the film interface during wet processes such as etching and stripping.

[0190] Furthermore, the introduction of DOPO-type benzoxazine resins focuses on imparting inherent flame-retardant properties and thermal oxidation stability to the composite film. The introduction of the DOPO structure enhances the intermolecular cohesive energy without sacrificing the resin's heat resistance, allowing the resin adhesive layer 30 to maintain its surface structural integrity and prevent charring or adhesion even when subjected to high-speed mechanical frictional heat during the first or second grinding process. Through the compounding of these different functionalized benzoxazine resins, this invention achieves comprehensive compatibility with complex circuit board manufacturing environments (high voltage, high temperature, strong chemical polarity).

[0191] In some embodiments, the bismaleimide resin (BMI) is selected from at least one of diaminodiphenylmethane modified bismaleimide, biphenyl-containing bismaleimide, high-performance thermoplastic resin blended toughened modified bismaleimide, isopropylparaben-type bismaleimide, PI (polyimide) modified bismaleimide, and cyanate ester modified bismaleimide.

[0192] Specifically, bismaleimide resin, as a thermosetting system with high crosslinking density and excellent heat resistance, provides extremely high Vickers hardness and modulus to the main chain. By introducing diaminodiphenylmethane (DDM) modification or isopropylparaben-type structure, and utilizing the Michael addition reaction of the modified groups on the maleimide double bonds, the brittleness of BMI resin after curing can be significantly reduced, thereby giving the resin adhesive layer 30 better cohesive toughness. This improved toughness ensures that the composite film does not develop microcracks at the edges when subjected to high-speed mechanical impacts from the first and second grinding plates, thus maintaining the physical sealing of the pore-filling area.

[0193] When the bismaleimide is selected from biphenyl-containing or PI-modified bismaleimides, the rigidity of the biphenyl structure and the high glass transition temperature (Tg) of the PI chain segment enable the film material to maintain an extremely stable elastic modulus even under instantaneous thermal shock above 200°C. This is crucial for the vacuum plugging and curing of multilayer boards, effectively resisting the internal stress caused by thermal expansion and preventing delamination between the metal layer 10 and the resin layer.

[0194] Furthermore, the introduction of high-performance thermoplastic resin blends for toughening modification or cyanate ester-modified bismaleimide focuses on optimizing the dielectric properties and processing rheology of the system. The introduction of cyanate esters can form a triazine ring crosslinking network with BMI, improving heat resistance while reducing the dielectric constant (Dk) and dielectric loss (Df), making it particularly suitable for selective via plugging in high-frequency signal transmission lines. Simultaneously, the blending of thermoplastic resins can adjust the initial peel strength of the resin adhesive layer 30, ensuring that the film can be detached in complete sheets during the final alkaline stripping step, avoiding the residue of fine particles on the circuit board surface and significantly improving the final yield of the precision process.

[0195] In some embodiments, the glass transition temperature (Tg) of the polymer is not lower than 130°C.

[0196] Specifically, the glass transition temperature (Tg) is a core indicator for measuring the thermodynamic stability of the resin adhesive layer 30. Controlling the Tg within a range of not less than 130°C (e.g., 130°C to 280°C) ensures that the composite film maintains a robust physical form under the high-temperature environment of circuit board manufacturing.

[0197] In the vacuum via plugging process, the circuit board needs to undergo prolonged high-temperature baking and curing (typically around 150°C). If the Tg of the resin adhesive layer 30 is below 130°C, the resin molecular chains will undergo a drastic amorphous transformation during heating, leading to a sharp decrease in the modulus of the adhesive layer and an excessively fluid, heat-softened state. This softening can cause severe lateral adhesive overflow, which not only contaminates the non-via plugged areas on the circuit board surface but may also cause the metal layer 10 to shrink or shift after losing its rigid support, thereby compromising the dimensional accuracy of selective via plugging.

[0198] When the glass transition temperature (Tg) is not lower than 130°C, the polymer backbone maintains good creep resistance and dimensional stability near the curing temperature. This allows the resin adhesive layer 30 to act as a stable "rigid pad," maintaining tight anchorage with the metal layer 10 and the circuit board surface even at high temperatures. Furthermore, the high Tg characteristic enhances the film's resistance to mechanical frictional heat generated during subsequent grinding processes, effectively preventing film adhesion or adhesive residue caused by localized overheating. By maintaining a high glass transition temperature, this invention achieves precise control over the quality of high aspect ratio via plugs under extreme thermal stress conditions, ensuring the reliability of precision circuit boards.

[0199] In some embodiments, the resin adhesive layer 30 further comprises an initiator, which includes at least one of a latent accelerator and a latent curing agent.

[0200] Specifically, the initiator plays a crucial role in the formulation of the resin adhesive layer 30 by precisely controlling the reaction kinetics. By introducing a latent chemical structure, this invention achieves high stability of the composite film material at room temperature and efficient crosslinking at a specific process temperature.

[0201] When the initiator contains a latent curing agent, its physical or chemical barrier against the resin matrix (such as epoxy resin) at room temperature significantly extends the shelf life of the composite film, preventing a decrease in adhesion due to premature resin cross-linking. During the baking and curing stage after vacuum plugging (typically 110°C to 150°C), the latent curing agent is instantly activated through thermal depolymerization, melting, or release of encapsulated active groups, guiding the resin system to transform from a viscoelastic state to a rigid network structure in a very short time. This triggered curing behavior ensures that the resin at the edges of the plugged area does not excessively sag, maintaining the integrity of the plugged shape.

[0202] When the initiator contains a latent accelerator, it acts as a catalytic center, significantly reducing the crosslinking activation energy between the main film-forming resins (such as thermosetting resins and alkali-soluble resins). In a stepped baking process, the latent accelerator can control the orderly release of the reaction rate with the temperature gradient, thereby effectively alleviating the internal stress caused by chemical shrinkage.

[0203] The selective application of this initiator enables the resin adhesive layer 30 to withstand repeated thermal fluctuations during the exposure and development stages, and also maintains its specific chemical sensitivity through a controllable degree of crosslinking before the final stripping step. This not only ensures the mechanical stability of the composite film in complex PCB manufacturing processes, but also provides mechanistic support for the subsequent efficient and clean "second stripping" using alkaline solutions.

[0204] In some embodiments, where the non-alkali-soluble resin comprises a non-alkali-soluble thermosetting resin, the latent curing agent used to cure the non-alkali-soluble thermosetting resin is selected from at least one of phenolic resin, benzoxazine, bismaleimide resin, reactive ester, and amine dicyandiamide curing agent.

[0205] Specifically, the selection of latent curing agents aims to construct a chemical framework with "high thermal stability" and "controlled crosslinking rate". When the latent curing agent is selected from phenolic resins, benzoxazine, or bismaleimide resins, these components not only participate in the crosslinking reaction, but also increase the glass transition temperature (Tg) of the system through their own rigid cyclic structure.

[0206] Specifically, when an active ester is used as a curing agent, its low secondary hydroxyl groups generated by the reaction with epoxy groups significantly reduce the moisture absorption of the resin adhesive layer 30 and improve its dielectric properties. The use of an amine-based dicyandiamide curing agent, however, leverages its insolubility at room temperature and explosive activity at high temperatures (above approximately 140°C) to achieve a balance between excellent storage stability (shelf life of over 6 months) and rapid curing of the composite film. This latent characteristic ensures that during the pore-filling process, the resin adhesive layer 30 maintains appropriate viscoelasticity before reaching the trigger temperature to facilitate adhesion, and rapidly cross-links to lock in its shape after reaching the trigger temperature, avoiding voids in the film caused by premature curing.

[0207] Furthermore, the latent accelerator used for curing the non-alkali-soluble thermosetting resin is selected from at least one of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methylimidazole.

[0208] Specifically, imidazole derivatives, as latent accelerators, play a key role in regulating the activation energy of the curing reaction through electronic and steric hindrance effects. By introducing substituents such as methyl, ethyl, or phenyl groups onto the imidazole ring, the activation temperature gradient of the accelerator can be precisely controlled.

[0209] For example, 2-phenylimidazole exhibits superior latency compared to 2-methylimidazole due to the conjugation and steric hindrance effects of the benzene ring. During the stepped baking process in circuit board manufacturing, these accelerators ensure that the resin system maintains a low crosslinking rate at low temperatures (e.g., 110°C) to allow volatiles in the plugging resin to escape fully, preventing porosity. At high temperatures (e.g., 150°C), the reaction is accelerated, enabling the resin adhesive layer 30 to reach the preset hardness and chemical resistance in a very short time. This micro-control of the reaction sequence not only enhances the film's ability to withstand the mechanical stress of the abrasive plate but also ensures that the resin network maintains uniform swelling characteristics in the subsequent "second peeling" step, thereby achieving efficient peeling.

[0210] In some embodiments, where the latent curing agent comprises phenolic resin and the non-alkali-soluble thermosetting resin comprises epoxy resin, the mass of the phenolic resin and the mass of the epoxy resin satisfy the following formula:

[0211] The mass of phenolic resin = (hydroxyl equivalent of phenolic resin / epoxy equivalent of epoxy resin) × mass of epoxy resin.

[0212] Specifically, the above formula follows the principle of stoichiometry and equivalence, aiming to ensure that the active functional groups in the resin adhesive layer 30 system reach a near-perfect reaction equilibrium. Under the catalysis of a latent accelerator, the phenolic hydroxyl groups (-OH) in the phenolic resin and the epoxy groups (epoxypropylene) in the epoxy resin can undergo a ring-opening addition reaction in a 1:1 molar ratio.

[0213] By strictly adhering to this mass ratio formula, this invention achieves precise control over the microstructure of the cross-linked network:

[0214] 1. Eliminate residual active groups: If there is an excess of phenolic resin, the residual hydrophilic phenolic hydroxyl groups will significantly increase the moisture absorption rate of the adhesive layer, resulting in water vapor bursting during the high-temperature curing step after vacuum plugging; if there is an excess of epoxy resin, the unreacted epoxy groups will cause the film layer to undergo slow self-crosslinking during storage, shortening the shelf life of the composite film and causing a decrease in film adhesion.

[0215] 2. Optimized thermodynamic properties: Equivalent proportions enable the construction of a uniform and dense three-dimensional network structure, thereby allowing the resin adhesive layer 30 to achieve the theoretically highest glass transition temperature (Tg) and optimal dimensional stability. This ensures that the interfacial bonding force remains within a stable range of 0.05 N / cm to 6 N / cm under etching solution impact and via plugging pressure.

[0216] 3. Ensuring cleanliness during film removal: The fully reacted resin system exhibits regular swelling behavior in the alkaline stripping solution. Since there are no free small-molecule resin residues, the alkaline solution can uniformly disrupt interfacial adhesion, allowing the film to peel off in its complete physical form during the "second stripping" step, thus solving the problem of residual adhesive at the edges of high aspect ratio holes.

[0217] In some embodiments, the mass of the latent curing agent used to cure the non-alkali-soluble thermosetting resin is no more than 10% of the mass of the non-alkali-soluble thermosetting resin, and the mass of the latent accelerator used to cure the non-alkali-soluble thermosetting resin is no more than 5% of the mass of the non-alkali-soluble thermosetting resin.

[0218] Specifically, the dosage ratio of the initiator (including latent curing agents and accelerators) is the key to controlling the delicate balance between the "storage stability" and "reactivity" of the resin adhesive layer 30 throughout the entire process.

[0219] The latent curing agent is controlled to be no more than 10% of the mass of the non-alkali-soluble thermosetting resin, aiming to construct a semi-cured system with "low internal stress" and "high tolerance". If the amount of curing agent exceeds 10%, it will cause slow micro-crosslinking of the composite film during storage before lamination, making the resin adhesive layer 30 brittle and hard, resulting in the film adhesion force falling below the lower limit of 0.05 N / cm, leading to the risk of leakage during pore plugging. Furthermore, an appropriate amount of curing agent ensures that the resin network maintains a moderate crosslinking density after curing at 150°C. This density of network exhibits good "swelling without dissolving" characteristics in strong alkaline solutions (such as 5% NaOH), allowing the film to be peeled off in a complete sheet during the "second film removal" step, avoiding the generation of fine debris.

[0220] Furthermore, controlling the mass of the latent accelerator to no more than 5% of the mass of the non-alkali-soluble thermosetting resin is primarily aimed at precisely controlling the slope of the exothermic peak. Specifically, excessive accelerator content can trigger a "burst polymerization" phenomenon, causing the resin system to generate a large amount of heat instantaneously, resulting in the violent vaporization of residual first or second solvents, thereby creating microbubbles or voids in the pore-filling region. By limiting the proportion to within 5%, a "stepped drying process" can be used to induce stable cross-linking of the resin. In addition, a low dose of accelerator helps maintain stable adhesion between the resin adhesive layer 30 and the metal layer 10 under the high-temperature environment of the vacuum pore-filling process, preventing interlayer delamination caused by rapid chemical shrinkage.

[0221] In some embodiments, the latent curing agent used to cure the alkali-soluble resin is selected from at least one of benzoyl peroxide (BPO), tert-butyl peroxide (TBPB), dicumyl peroxide (DCP), cumyl hydroperoxide (CHP), and hydroxycumyl peroxide.

[0222] Specifically, peroxide curing agents, acting as free radical initiators, are primarily used to induce cross-linking reactions of acrylate groups or other unsaturated bonds in alkali-soluble resins. By selecting peroxides with different decomposition temperatures (10-hour half-life temperatures), the thermal activation threshold of the resin adhesive layer 30 can be precisely set. For example, using dicumyl peroxide (DCP) ensures that the composite membrane maintains extremely high chemical stability during normal storage and lamination stages (approximately 60°C to 100°C); however, once it enters the high-temperature stage of pore-filling curing (above 130°C), it rapidly decomposes and releases free radicals, triggering the transformation of the resin system from a linear structure to a three-dimensional network structure. This controlled curing behavior effectively improves the compressive strength of the membrane during vacuum pore-filling and prevents ink seepage at the pore edges due to excessive resin softness.

[0223] Furthermore, the latent accelerator used for curing the alkali-soluble resin is selected from at least one of N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-methylaniline, n-butanol-aniline condensate, butyraldehyde-n-butylamine condensate, thiourea, ethylidene thiourea, tetramethylthiourea, cobalt naphthenate, cobalt naphthenate, cobalt acetate, and copper octoate.

[0224] Specifically, the accelerator, through redox systems or complexation, synergistically lowers the activation energy of the reaction with the aforementioned peroxide curing agent. When the accelerator is selected from aromatic amines such as N,N-dimethylaniline or thiourea, it can form a highly unstable intermediate with the peroxide, thereby inducing the generation of free radicals at a lower temperature. This ensures that the alkali-soluble resin can achieve micro-crosslinking in the early stage of the "step-by-step baking process," locking in the initial adhesion between the resin adhesive layer 30 and the metal layer 10.

[0225] When the accelerator is selected from metal salts such as cobalt naphthenate, cobalt naphthenate, or copper octanoate, the valence state change of metal ions catalyzes the decomposition of peroxides, which can significantly shorten the curing time and improve the crosslinking efficiency. This precise kinetic control ensures that the cohesive force of the resin adhesive layer 30 remains in dynamic equilibrium during continuous processes such as "first film removal" and "vacuum plugging". Especially for alkali-soluble resins containing acrylate functional groups, the application of the above-mentioned accelerator ensures that the film layer has sufficient structural integrity before the final "second film removal", allowing it to be peeled off as a whole under the action of alkali, eliminating the sticky residue caused by uneven curing.

[0226] In some embodiments, the mass of the latent curing agent used to cure the alkali-soluble resin is no more than 10% of the mass of the alkali-soluble resin, and the mass of the latent accelerator used to cure the alkali-soluble resin is no more than 5% of the mass of the alkali-soluble resin.

[0227] Specifically, controlling the concentration of the initiator (including curing agent and accelerator) in the alkali-soluble resin system is key to ensuring a balance between "development accuracy" and "thoroughness of film removal" in the composite film.

[0228] Specifically, the curing agent content used in alkali-soluble resins (such as resins containing acrylate groups) is controlled to be no more than 10%, mainly for the purpose of coordinating the crosslinking density and the alkali dissolution rate.

[0229] 1. Maintaining developing performance: The core function of alkali-soluble resins is to achieve patterning under weak alkali conditions (such as 1% sodium carbonate). If the proportion of curing agent is too high, excessive thermal cross-linking may occur during the pre-bake stage of the process, resulting in a significant slowdown in the developing speed or incomplete developing, thereby reducing the resolution of selectively plugged orifices.

[0230] 2. Ensure efficient film removal: In the curing stage after vacuum plugging, an appropriate amount of curing agent (e.g., 5% to 8%) is sufficient to give the resin adhesive layer 30 the necessary resistance to ink penetration. Limiting it to within 10% ensures that the cross-linked resin network can still maintain sufficient physical swelling gaps in the strong alkaline stripping solution, allowing alkali molecules to quickly penetrate and neutralize carboxyl groups, achieving smooth overall film removal.

[0231] Furthermore, the mass of the latent accelerator is controlled to be no more than 5% of the mass of the alkali-soluble resin, with the focus on suppressing the "dark reaction" of the system and improving the process tolerance:

[0232] 1. Improved storage stability: Accelerator content exceeding 5% significantly lowers the activation energy threshold of the curing system, making the composite film material highly susceptible to self-crosslinking (i.e., "curing" too quickly) during room temperature transportation or storage. This can lead to unstable adhesion during film application and even "residual adhesive" during development.

[0233] 2. Controlling the exothermic curve: During the selective plugging baking and curing process, a low concentration of accelerator can guide the free radical polymerization reaction to proceed smoothly. This avoids the formation of microbubbles or thermal stress cracks at the interface between the resin adhesive layer 30 and the metal layer 10 due to localized intense exothermic reactions, thereby ensuring the edge adhesion of the film material in the subsequent first grinding process.

[0234] By limiting the ratio of curing agent to accelerator within the above range, this invention solves the problem of difficult film removal caused by "over-curing" after high-temperature pore plugging of photosensitive film, and achieves the organic unity of high-precision patterning and efficient and clean peeling.

[0235] In some embodiments, the resin adhesive layer 30 further comprises a filler selected from at least one of silicon dioxide, aluminum oxide, aluminum hydroxide, calcium carbonate, magnesium carbonate, magnesium silicate, silicon carbide, titanium carbide, barium sulfate, magnesium sulfate, titanium oxide, magnesium oxide, calcium oxide, boron nitride, and aluminum nitride.

[0236] Specifically, the filler, as an inorganic reinforcing phase in the resin adhesive layer 30, plays a multiple role in regulating the physical strength, coefficient of thermal expansion (CTE), and processing adaptability of the membrane material. By uniformly dispersing the aforementioned inorganic microparticles in the organic resin matrix, this invention achieves high stability of the composite membrane material under complex electrical properties and mechanical stress environments.

[0237] When silica is selected as the filler, its extremely low coefficient of thermal expansion and excellent dielectric properties effectively reduce the thermal shrinkage rate of the resin adhesive layer 30 during vacuum via plugging baking. This ensures that the displacement deviation between the metal layer 10 and the circuit board is minimized when subjected to thermal cycling at temperatures above 150°C, thereby improving the alignment accuracy of selective via plugging.

[0238] When the filler is selected from aluminum hydroxide, calcium carbonate or magnesium oxide, it not only plays the role of volume filling and cost reduction, but also plays a certain role of flame retardant synergy or acid-base buffering when heated, which helps to maintain the physical integrity of the film structure during alkaline film removal.

[0239] When fillers are selected from high thermal conductivity materials such as boron nitride (BN), aluminum nitride (AlN), or alumina, the horizontal and vertical thermal conductivity of the resin adhesive layer 30 can be significantly improved. In continuous plug-and-cure production, high thermal conductivity fillers help heat diffuse evenly within the film, avoiding resin scorching caused by localized overheating or stress warping due to thermal gradients.

[0240] Furthermore, the use of fillers with higher hardness, such as silicon carbide (SiC) or titanium carbide, can enhance the shear strength of the resin adhesive layer 30. During the first or second grinding step, these micro-hard phases support the resin skeleton, preventing "edge curling" or "biting" at the film edges caused by grinding wheel pressure, thus ensuring the smoothness of the edges in the plugging area.

[0241] In some embodiments, the surface of the filler is modified with at least one surface-modifying group selected from epoxy, aniline, amino, and alkyl groups.

[0242] Specifically, surface-modifying groups are anchored to the surface of inorganic fillers through chemical bonding (such as the dealcoholization condensation reaction of silane coupling agents), thereby altering the interfacial compatibility between the filler and the organic resin matrix. Since the surface of inorganic fillers (such as silica and alumina) is usually rich in hydrophilic hydroxyl groups, direct addition can easily lead to agglomeration and interfacial defects.

[0243] When the modifying groups are selected from epoxy or amino groups, these active functional groups can directly participate in the cross-linking and curing process of the thermosetting resin (such as epoxy resin) in the resin adhesive layer 30, forming strong covalent bonds at the organic / inorganic interface. This "molecular bridging" effect significantly improves the cohesive strength of the resin adhesive layer 30, ensuring that the filler will not peel off from the resin matrix under the high-pressure impact of vacuum plugging.

[0244] When the modifying group is selected from aniline or alkyl, the polarity of the filler surface can be effectively reduced, improving its dispersion uniformity in alkali-soluble or non-alkali-soluble thermoplastic resins. This modification can reduce the melt viscosity of the system, improve the rheological properties during film application, and make the resin adhesive layer 30 easier to penetrate and wet the fine gaps in the circuit board.

[0245] In some embodiments, the particle size of the filler is between 0.1 micrometers and 50 micrometers. Preferably, the particle size of the filler is between 0.3 micrometers and 30 micrometers.

[0246] Specifically, the particle size distribution of the filler directly affects the surface roughness, light transmittance, and micropore-filling ability of the resin adhesive layer 30. Specifically, when the filler particle size is between 0.1 micrometers and 10 micrometers, fillers within this range (such as spherical silica) can densely fill the gaps between polymer molecular chains, significantly improving the shear modulus of the membrane. In the first grinding process, the fine-particle filler provides uniform surface hardness, preventing uneven mechanical damage to the membrane edges caused by the grinding wheel, thereby ensuring the sharpness of the selective pore-filling boundaries.

[0247] When the filler particle size is between 10 and 50 micrometers, the larger particle size filler acts as a "support skeleton" in the resin adhesive layer 30, which can effectively control the overall coefficient of thermal expansion (CTE) of the film. For a thicker resin adhesive layer 30 (such as 50 micrometers or more), the appropriate introduction of large particle size filler can prevent substrate warping caused by curing shrinkage.

[0248] By controlling the particle size within the range of 0.1 micrometers to 50 micrometers and employing a gradation design (i.e., mixing different particle sizes), this invention enables the resin adhesive layer 30 to maintain good rheological processability while achieving a high filling capacity. This not only ensures the physical positioning accuracy of the composite membrane in selective pore plugging but also utilizes the "physical barrier" effect of the filler to slow down excessive longitudinal penetration of alkali solution during the defilm removal process, thereby achieving clean peeling with controlled lateral swelling.

[0249] In some embodiments, the resin adhesive layer 30 further includes an additive selected from at least one of leveling agents, defoamers, wetting and dispersing agents, and silane coupling agents.

[0250] Specifically, the additives in the resin adhesive layer 30 act as functional regulators, aiming to optimize the surface physical state, liquid coating performance, and bonding energy between heterogeneous interfaces of the composite film. By adding trace amounts of the above-mentioned additives, the present invention can significantly improve the application tolerance of the resin adhesive layer 30 on the complex surfaces of high-density interconnect (HDI) boards.

[0251] In some embodiments, the leveling agent is selected from at least one of polyether-modified polydimethylsiloxane solution, aralkyl-modified polymethylalkylsiloxane, polyacrylate and nonionic organic surfactant.

[0252] Specifically, leveling agents reduce the surface tension of the resin system, ensuring the elimination of defects such as pinholes, orange peel, and brush marks when coating the metal layer 10 on either a glossy or rough surface. In particular, polyether-modified polydimethylsiloxane or polyacrylate leveling agents can guide the resin adhesive layer 30 to spontaneously form a smooth and dense coating surface during the drying process. This smoothness not only ensures the uniformity of the composite film thickness but also provides a consistent sealing boundary for subsequent "vacuum plugging," preventing pressure leakage due to localized thickness deviations.

[0253] In some embodiments, the defoamer is selected from at least one of dimethyl polysiloxane containing fumed silica and organically modified polysiloxane containing fumed silica.

[0254] Specifically, the defoamer utilizes the high specific surface area of ​​fumed silica and the extremely low surface energy of polysiloxane to rapidly break down microbubbles generated in the resin adhesive layer 30 during stirring, mixing, and continuous coating. Eliminating microbubbles is crucial in processes involving selective pore plugging. If bubbles remain in the adhesive layer, thermal expansion during high-temperature pore plugging curing above 150°C can cause "pore bursting" or form micropores at the pore edges, thereby compromising the electrical insulation reliability of the plugging resin. Using a modified system containing fumed silica not only provides rapid defoaming but also exhibits excellent foam suppression durability, ensuring the long-term quality of the membrane material.

[0255] In some embodiments, the wetting and dispersing agent is selected from at least one of polyether-modified silicone, propylene glycol methyl ether acetate (PMA), and nonionic organic surfactants.

[0256] Specifically, the wetting and dispersing agent is mainly used to optimize the distribution of the aforementioned inorganic fillers (such as silica and alumina) in the organic resin matrix. Through the adsorption of polar functional groups on the filler surface, it prevents the sedimentation and aggregation of micron-sized particles in the resin solution, maintaining the isotropic physical properties of the resin adhesive layer 30. Furthermore, propylene glycol methyl ether acetate, as a solvent-based dispersant, effectively regulates the evaporation rate of the system, ensuring that during the coating and drying stage, the resin molecular chains can fully extend and wet the microstructure of the metal layer 10 surface.

[0257] In some embodiments, the silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane (KH-560), and 3-methacryloyloxypropyltrimethoxysilane (KH-570).

[0258] Specifically, the silane coupling agent acts as an interfacial "molecular bridge," forming chemical bonds with the hydroxyl groups on the surface of the inorganic filler or metal layer 10 through alkoxy hydrolysis products on one end, and chemically crosslinking with the resin matrix through amino, glycidyl ether, or methacryloyl ether.

[0259] Furthermore, when the system contains epoxy resin or alkali-soluble acrylate resin, the use of these coupling agents can enhance the adhesion of the metal / resin interface from physical adsorption to chemical bonding. This qualitative change in bonding energy ensures that the composite film will not peel off from the circuit board surface under the high-intensity mechanical grinding of the "first grinding plate" and "second grinding plate," thus guaranteeing the interface sealing quality of the high aspect ratio hole plugging process.

[0260] In some embodiments, when the resin adhesive layer 30 contains both a silane coupling agent and a filler, the mass of the silane coupling agent is 0.5% to 30% of the filler mass.

[0261] Specifically, silane coupling agents, as bifunctional molecules, carry an alkoxy group at one end that can undergo a condensation reaction with the hydroxyl groups on the surface of fillers (such as silica, alumina, and other inorganic particles), and an active group at the other end that can chemically bond with alkali-soluble or non-alkali-soluble resins (such as epoxy groups and vinyl groups). By strictly controlling the amount of silane coupling agent within a specific range of 0.5% to 30% of the filler mass, a surface modification mechanism at the molecular level is utilized to form a dense monomolecular or multimolecular covering layer on the filler surface. This effectively reduces the surface energy of the filler and eliminates micro-agglomeration, significantly improving the interfacial bonding force and dispersion stability of the resin adhesive layer 30.

[0262] The direct benefit of this specific ratio is that it significantly improves the interfacial compatibility and wettability between the inorganic filler and the organic resin matrix, resulting in excellent shear thinning characteristics and dispersion stability of the composite slurry during preparation. When the proportion of silane coupling agent is within the above range, the cohesive strength of the resin adhesive layer 30 after curing is significantly enhanced, effectively resisting frequent thermal stress impacts during high aspect ratio plugging processes and avoiding voids or cracks caused by interfacial peeling. If the silane coupling agent content is less than 0.5%, it is difficult to achieve complete coating of the filler surface, which can easily lead to filler sedimentation and uneven mixing; if it is higher than 30%, excessive silane molecules may self-polymerize, forming a weak interfacial layer and reducing the overall adhesion and chemical resistance of the membrane.

[0263] It is worth noting that the resin adhesive layer 30 is a multiphase system composed of the total mass of resin (organic continuous phase), the mass of filler (inorganic reinforcing phase), and the mass of additives (functional adjustment components). When the total mass of resin reaches its defined upper limit of 100%, its physical essence means that in this specific embodiment, the resin adhesive layer 30 adopts a "full resin" pure organic formulation design, that is, no inorganic filler is added to the system (the filler content is 0%).

[0264] In this "all-resin" implementation scenario, the limitation of 0.01% to 20% for additives should be understood as trace functional modification within the total resin mass. In other words, when the total resin mass percentage is 100%, this value represents the total amount of film-forming substances in the adhesive layer excluding additives, while additives exist in the organic system as "add-on" or "component substitution." Utilizing the physical property that additives can significantly change interfacial tension at extremely low concentrations (e.g., 0.01%), even in pure resin formulations, only trace amounts of additives are needed to activate the aforementioned leveling, defoaming, and wetting mechanisms, ensuring that the composite membrane material still possesses excellent film-forming quality and bonding accuracy without filler support.

[0265] The logic behind this numerical gradient setting is to ensure that, regardless of whether inorganic fillers are introduced into the resin adhesive layer 30, the additives can act as independent variables to compensate for the process activity of the system. When the total resin mass percentage is at the extreme state of 100%, the introduction of 0.01% additives can effectively solve the orange peel and microbubble problems that are prone to occur in pure resin coatings during the curing process, thereby eliminating the single physical property defect of polymer materials under high-temperature processes. Therefore, the resin content range of "20% to 100%" and the starting additive content of "0.01%" present a "master-slave composite" relationship in engineering practice, jointly constructing the performance envelope of the resin adhesive layer 30 under different complex process environments.

[0266] In some embodiments, the component ratio of the resin adhesive layer 30 is precisely controlled, wherein the total mass of the resin accounts for 20% to 100% of the total mass of the resin adhesive layer 30, and the mass of the filler accounts for 0% to 80% of the total mass of the resin adhesive layer 30.

[0267] Specifically, the total mass of the resin includes the sum of the masses of the aforementioned alkali-soluble resin and non-alkali-soluble resin. As the organic continuous phase of the resin adhesive layer 30, it undertakes the core functions of providing initial adhesion, film-forming properties, and chemical exfoliation activity.

[0268] When the total resin mass is between 20% and 100%, the physical entanglement and chemical cross-linking mechanism of polymer segments ensures that the composite film can fully wet the microstructure of the circuit board surface during the bonding stage, thereby forming a continuous and dense bonding layer at the interface. The direct benefit of this proportion limit is that it ensures that the resin bonding layer 30 has sufficient cohesive strength to withstand the pressure load of the metal layer 10 during the vacuum plugging process, preventing interface cracking or film peeling due to insufficient resin content.

[0269] Meanwhile, by controlling the filler mass within the range of 0% to 80%, the thermodynamic properties of the resin adhesive layer 30 are precisely compensated by utilizing the physical filling and modulus enhancement mechanism of inorganic microparticles in the organic matrix. In practical process applications, when the filler content is within the above range, the coefficient of thermal expansion (CTE) of the resin adhesive layer 30 can be significantly adjusted, achieving a dynamic match with the thermal shrinkage rate of the circuit board substrate to be treated.

[0270] This synergistic design of organic and inorganic components has two advantages. First, the high proportion of resin ensures that the stripping solution can quickly penetrate and induce the swelling and peeling of resin molecules during the final alkaline stripping step, achieving the process goal of "clean stripping". Second, the introduction of an appropriate amount of filler increases the rigidity of the resin adhesive layer 30, effectively suppressing the lateral overflow phenomenon that may occur during high-temperature baking above 150°C, and ensuring the dimensional accuracy and edge cleanliness of the selective plugging area.

[0271] In some embodiments, the mass of the additives in the resin adhesive layer accounts for 0.01% to 20% of the total mass of the resin adhesive layer 30.

[0272] Specifically, the additives include at least one of the aforementioned leveling agents, defoamers, wetting and dispersing agents, and silane coupling agents. As functional regulating components, they are designed to achieve precise modification of the organic / inorganic heterogeneous interface and the coating fluid dynamics state through trace addition.

[0273] When the mass percentage of the additive is between 0.01% and 20%, the surface activity regulation mechanism and chemical bonding bridging mechanism significantly optimize the process adaptability of the resin adhesive layer 30 in the coating preparation and film application stages. Within this proportion range, the additive can effectively reduce the surface tension of the resin system and eliminate micro-defects such as pinholes and orange peel that occur when coating the surface of the metal layer 10, thereby ensuring the formation of a highly uniform and dense coating surface. The direct benefit of this highly smooth surface characteristic is that it can provide a consistent physical sealing boundary for selective vacuum plugging processes, preventing pressure leakage or resin overflow caused by local thickness deviations.

[0274] Meanwhile, the additives, through their unique anti-foaming and kinetic wetting mechanisms, can quickly eliminate microbubbles entrained in the resin adhesive layer 30 during high-speed stirring or continuous coating. By limiting the additive proportions within the aforementioned range, it can be ensured that the composite film does not develop burst holes or microcracks at the interface due to bubble expansion when subjected to high-temperature curing thermal cycles above 150°C, thus guaranteeing the electrical insulation reliability after plugging high aspect ratio holes.

[0275] If the mass percentage of the additive is less than 0.01%, it will be difficult to form an effective molecular coating in the complex resin system, resulting in poor leveling or local agglomeration of fillers. If its percentage is higher than 20%, the excessive additive molecules may produce a "plasticizing effect" or accumulate at the interface to form a weak interface layer, which will weaken the adhesion between the resin adhesive layer 30 and the copper surface of the circuit board, and may even affect the cleanliness of the final alkaline defilming.

[0276] In some embodiments, the mass ratio of alkali-soluble resin to non-alkali-soluble resin is from 0.2:0.8 to 1:0.

[0277] Specifically, alkali-soluble resins serve as the main chemical exfoliation carriers, and the acidic functional groups (such as carboxyl groups) distributed in their molecular chains endow the membrane material with solubility in an alkaline environment; while non-alkali-soluble resins serve as structural reinforcing phases, used to regulate the viscoelasticity, mechanical strength, and crosslinking density of the membrane material after curing.

[0278] When the mass ratio of alkali-soluble resin to non-alkali-soluble resin is in the range of 0.2:0.8 to 1:0, the compatibility balance and network interpenetration mechanism of the polymer blend system ensure that the resin adhesive layer 30 has both excellent adhesion and efficient film removal characteristics. This allows the film material to maintain a moderately loose microstructure after undergoing vacuum plugging pressure with high aspect ratio pores and subsequent high-temperature baking, ensuring that the alkaline stripping solution can quickly diffuse to the interface between the metal layer 10 and the resin, achieving clean peeling without residue.

[0279] Preferably, the mass ratio of alkali-soluble resin to non-alkali-soluble resin is between 0.7:0.3 and 0.9:0.1. Within this preferred range, by increasing the proportion of the alkali-soluble component and utilizing the high reaction rate mechanism of acid-base neutralization, the film removal time at the end of the process is significantly shortened. When the ratio is between 0.7:0.3 and 0.9:0.1, the resin adhesive layer 30 exhibits excellent "lateral swelling controlled" characteristics, meaning that the film material peels off in sheets rather than dissolves in a paste during the film removal process. This not only significantly reduces the risk of accidental corrosion of the resin inside the plugging holes but also effectively avoids secondary contamination of the precision circuit surface by the film removal residue, ensuring the high precision of the selective process.

[0280] Furthermore, this formulation limit also reflects a consideration of physical support performance. While maintaining high alkali sensitivity, a small amount of non-alkali-soluble resin (e.g., 0.1 to 0.3 parts) acts as a "skeleton anchor" at the microscopic level through its unique hydrophobic groups and thermosetting crosslinking network. This allows the composite membrane to maintain stable edge stability during the mechanical grinding process of the first and second grinding plates, preventing softening or peeling of the membrane edges due to excessive alkali-soluble resin ratio, thereby ensuring the dimensional consistency of the selective plugging pattern.

[0281] In some embodiments, where the non-alkali-soluble resin comprises both a non-alkali-soluble thermoplastic resin and a non-alkali-soluble thermosetting resin, the mass ratio of the non-alkali-soluble thermoplastic resin to the non-alkali-soluble thermosetting resin is from 0.7:0.3 to 1:0.

[0282] Specifically, non-alkali-soluble thermoplastic resins (such as polyamides, polyesters, or rubber-based resins) mainly contribute to the film-forming flexibility and initial wetting energy of the system, while non-alkali-soluble thermosetting resins (such as epoxy resins, benzoxazine, or bismaleimide) construct a rigid network through thermally induced crosslinking, providing heat resistance and chemical resistance.

[0283] When the mass ratio is within the range of 0.7:0.3 to 1:0, a deep balance is achieved between the "rheological adaptability" of the resin adhesive layer 30 in the lamination process and the "structural stability" in the curing process by utilizing the long-chain physical entanglement mechanism of the thermoplastic component and the micro-crosslinking strengthening mechanism of the thermosetting component. This ratio limit ensures that the composite film has excellent tear resistance and deformation recovery during the lamination stage, and can conform to the wiring undulations on the circuit board surface without breaking. At the same time, in the subsequent vacuum plugging baking process above 150°C, the appropriate amount of thermosetting component locks in the interface displacement, effectively suppressing the hole position deviation caused by thermal shrinkage.

[0284] Preferably, the mass ratio of non-alkali-soluble thermoplastic resin to non-alkali-soluble thermosetting resin is from 0.95:0.05 to 0.8:0.2. Within this preferred range, by maintaining the dominant position of the thermoplastic component and utilizing its excellent cohesive toughness mechanism, the integrity of the composite film material during peeling is significantly improved, preventing the generation of debris or particle residues during the film removal stage. When the ratio is between 0.95:0.05 and 0.8:0.2, the trace cross-linking points formed in the system can provide an elastic modulus sufficient to resist pore-clogging pressure (vacuum negative pressure) without forming a dense chemical barrier layer due to excessive cross-linking density. This ensures that the alkaline film removal solution can smoothly penetrate and induce physical swelling of the alkali-soluble resin, achieving an organic unity of "efficient support" and "clean film removal".

[0285] If the proportion of non-alkali-soluble thermosetting resin is too high (e.g., mass ratio less than 0.7:0.3), the resin adhesive layer 30 will become more brittle after curing. During the mechanical grinding step of the first or second grinding plate, the shear stress of the grinding wheel can easily cause the film edge to break or chip. Conversely, if there is no thermosetting component at all (i.e., the ratio is 1:0), although the ultimate peel flexibility can be obtained, when facing the extreme baking conditions of high aspect ratio holes, a small amount of lateral creep may occur due to insufficient modulus. Therefore, through the precise control of the above-mentioned preferred ratio, this application achieves maximum coverage of the tolerance of precision circuit board manufacturing processes.

[0286] In some embodiments, the composite film material further includes a protective film 40, which is disposed on the surface of at least one of the photosensitive layer 20 and the resin adhesive layer 30. Specifically, the protective film 40 can be a PE release film, a PP release film, or a PET release film. As an external physical barrier for the composite film material, the core function of the protective film 40 is to isolate environmental pollutants (such as dust and moisture) and prevent the photosensitive layer 20 or the resin adhesive layer 30 from sticking together or being mechanically scratched during winding and transportation.

[0287] In some embodiments, the thickness of the protective film 40 is between 3 micrometers and 50 micrometers. Specifically, the thickness of the protective film 40 is designed to balance the flexibility of the film material with the mechanical protection strength. When the thickness is in the range of 3 micrometers to 50 micrometers, the physical shielding mechanism of the polymer film ensures that the protective film 40 has sufficient puncture resistance, effectively resisting indentation damage from external microparticles on the surface of the photosensitive layer 20 or the resin adhesive layer 30. This thickness limitation ensures smooth transmission and tension control of the composite film material on the automatic laminating machine, while avoiding excessively large overall film roll diameter or insufficient flexibility due to excessive thickness of the protective film 40, thereby ensuring the stability of material loading in the precision circuit board manufacturing process.

[0288] In some embodiments, the release force of the protective film 40 is between 1g and 2000g. Specifically, the release force defines the interaction energy between the interface of the protective film 40 and the photosensitive layer 20 or the resin adhesive layer 30. By controlling the release force within the range of 1g to 2000g, the interfacial wetting and low surface energy isolation mechanism ensures that the protective film 40 can be smoothly peeled from the surface of the composite film material during the pre-lamination process.

[0289] If the release force is less than 1g, the protective film 40 is prone to spontaneous detachment during winding or slitting, resulting in damage to the exposed functional layer. If the release force is greater than 2000g, excessive peeling stress may be generated during automatic peeling, which may cause the photosensitive layer 20 or the resin adhesive layer 30 to peel off locally from the surface of the metal layer 10 or cause stress damage. By finely setting the release force within the above range, the smoothness and uniformity of the peeling process are ensured, eliminating the risk of static electricity accumulation caused by peeling vibration, thereby ensuring the interface cleanliness and molecular-level contact quality when the resin adhesive layer 30 is bonded to the copper surface of the circuit board.

[0290] In summary, the composite film material for circuit board manufacturing in this application has the following beneficial effects:

[0291] 1. The composite film material of this application constructs a selective via-plugging physical barrier with high mechanical rigidity and thermal stability, overcoming the technical bottleneck of easy cracking and collapse of the via-plugging medium in the process of high aspect ratio (e.g., ≥8:1) or ultra-thick copper clad laminate (e.g., thickness greater than 6mm). Specifically, the composite film material of this application adopts an integrated stack structure with a metal layer 10 as the core support and a photosensitive layer 20 and a resin adhesive layer 30 respectively mounted on both sides. Utilizing the high tensile strength and low thermal expansion characteristics of the metal foil, combined with the microscopic physical anchoring of the resin adhesive layer 30, a robust mechanical barrier and stress buffering mechanism is provided under vacuum negative pressure suction and high-temperature thermal cycling environments. Based on this, the composite film material itself can perfectly withstand the reciprocating shear force and pressure difference impact brought by the deep-hole plugging scraper, thereby eliminating the risk of leakage of the plugging resin into non-opening areas or the formation of voids at the bottom of the hole during high-pressure filling of deep holes, ensuring the cleanliness of the surface and the flatness of the plugged holes in the selective via-plugging process of ultra-thick copper clad laminates.

[0292] 2. This invention achieves a balance between high-strength adhesion and zero-residue film removal at the end of the process under extreme thermodynamic processing conditions such as high aspect ratio through holes or back-drilled holes. Specifically, facing the need for prolonged high-temperature (e.g., above 150°C) stepped baking and curing after plugging deep holes in ultra-thick boards, the composite film material of this application precisely blends alkali-soluble resin, non-alkali-soluble resin, and trace amounts of inorganic fillers in its resin adhesive layer 30, and combines this with temperature gradient control of a latent initiator to limit the crosslinking density of the polymer system to a critical state that provides a dense support network while maintaining the activity of acidic functional groups. This allows the residual adhesive layer of the composite film material to rapidly swell and peel off in a sheet-like manner in conventional alkaline solutions after enduring prolonged high-temperature thermal stress, thus eliminating the risk of residual adhesive easily generated at the edges of high aspect ratio microholes. This provides a high-yield substrate for subsequent micro-blind hole electroplating and circuit interconnection of ultra-thick copper-clad laminates.

[0293] 3. The composite film material of this application establishes an ultra-high resolution boundary definition mechanism adapted to high-density interconnect ultra-thick boards, breaking through the opening accuracy limit of traditional physical screen printing under high-depth-diameter holes with small pitch. Specifically, the composite film material of this application directly laminates a photosensitive layer 20 with specific resolution onto the surface of the metal layer 10, and uses the photoresist capability of the photosensitive layer 20 to guide the underlying metal layer 10 to selectively chemically etch, transforming the macroscopic physical imprinting masking into a vertical opening definition mechanism based on microscopic photochemical reactions. Furthermore, this composite film material essentially provides a steep and structurally complete physical isolation wall between the hole-filling area and the non-hole-filling area on the ultra-thick copper-clad board. Even when facing dense vias or back-drilled hole arrays with small pitch in ultra-thick boards, it can ensure that each high-depth-diameter-diameter target hole to be filled is accurately positioned, avoiding the incomplete filling or ink bleeding at the hole edge caused by opening deformation in traditional processes.

[0294] As shown in Figure 2, this application also proposes a method for preparing a composite film material for circuit board manufacturing as described in any of the preceding claims. The method for preparing the composite film material includes the following steps:

[0295] S10, Provides metal layer 10.

[0296] Specifically, this step establishes the rigid mechanical framework of the entire composite film by providing a metal foil (such as electrolytic copper foil or rolled copper foil) with a specific thickness (e.g., 3 micrometers to 300 micrometers) and surface roughness. The microscopic morphology difference between the first surface (bright surface) and the second surface (rough surface) of the metal layer 10 provides a physical anchoring basis for the subsequent attachment of different functional layers on both sides.

[0297] S20, A photosensitive layer 20 is formed on the first surface of the metal layer 10.

[0298] Specifically, depending on the initial physical state of the photosensitive material, the formation process can employ coating or lamination techniques. When the photosensitive material is liquid, it can be directly coated onto the first surface of the metal layer 10 using methods such as comma blade coating, microgravure coating, slot coating, curtain coating, or spraying. When the photosensitive material is in dry film form, it can be laminated using methods such as hot roll bonding, room temperature roll bonding, vacuum hot press bonding, or vacuum room temperature bonding.

[0299] S30. Apply the ink of the resin adhesive layer 30 to the second surface of the metal layer 10 and dry it to form the resin adhesive layer 30.

[0300] Specifically, the aforementioned homogenized and mixed resin adhesive layer 30 ink is applied to the second surface (rough surface) of the metal layer 10 by a coating method (such as comma blade coating, slit coating, etc.).

[0301] Subsequently, the ink in the resin adhesive layer 30 is dried. This drying process aims to controllably remove the solvent from the ink system, causing the resin macromolecular chains to physically entangle without triggering the chemical cross-linking reaction of the initiator, thereby forming a coating in stage B (semi-cured state). This heat treatment transforms the resin adhesive layer 30 from a flowing slurry state to a viscoelastic solid with specific adhesion (0.05 N / cm to 6 N / cm). This not only endows the composite film with physical properties such as non-stickiness at room temperature, easy winding, and long-term storage, but also preserves the latent activity of the resin system, ensuring that when it is finally applied to the circuit board to be processed, it can regain its microrheological filling ability under hot pressing, achieving gapless wrapping of the substrate circuit undulations.

[0302] In some embodiments, before applying the resin adhesive layer 30 ink to the second surface of the metal layer 10, the preparation method further includes preparing the resin adhesive layer ink, the step of preparing the resin adhesive layer ink including:

[0303] S40. Dissolve the alkali-soluble resin and the non-alkali-soluble resin in a first solvent and mix them to obtain a resin slurry.

[0304] This step aims to construct the organic continuous phase matrix of the composite membrane material. Specifically, before dissolving the alkali-soluble and insoluble resins, at least one additive selected from leveling agents, wetting and dispersing agents, and defoamers can be pre-dissolved in a first solvent. By pre-dissolving the above-mentioned surfactants in the solvent system, their amphiphilic molecular structure can significantly reduce the surface tension of the first solvent, thereby providing an excellent physical wetting environment for the subsequent dissolution of the polymer resin.

[0305] In some embodiments, the rotational speed of the first mixing is limited to 3600 rpm to 7200 rpm, the mixing temperature is not greater than 45°C, and the mixing time is 10 minutes to 60 minutes. Utilizing the high-speed shear hydrodynamic mechanism generated within this specific rotational speed range, the initial agglomeration state of solid or high-viscosity resin components in the solvent can be rapidly broken, promoting the full expansion and entanglement of macromolecular chains in the solvent. Simultaneously, strictly controlling the mixing temperature to not exceed 45°C effectively avoids heat accumulation caused by high-speed mechanical friction. This synergy of temperature and shear force ensures highly homogeneous integration of alkali-soluble and non-alkali-soluble resins at the molecular level, while preventing excessive solvent evaporation or premature micro-crosslinking of latent active groups due to localized overheating of the resin system, thereby obtaining a pure resin slurry with highly stable rheological properties.

[0306] S50. Disperse the filler in the second solvent for a second mixing to obtain a filler slurry.

[0307] This step aims to construct an independent, highly dispersible inorganic reinforcing phase system. Specifically, before dispersing the filler in the second solvent, at least one additive selected from leveling agents, wetting and dispersing agents, defoamers, and silane coupling agents is pre-dissolved in the second solvent. Under this operation, utilizing the preferential occupancy and chemical anchoring mechanism of silane coupling agents and dispersants, when high surface energy inorganic filler particles (such as silica and alumina) enter the second solvent, the modified molecules can instantly coat the filler surface, forming a steric barrier layer.

[0308] In some embodiments, the second mixing speed is 3600 rpm to 7200 rpm, the mixing temperature is not greater than 45°C, and the mixing time is 10 minutes to 60 minutes. By forcibly overcoming the van der Waals attraction between filler particles through high-speed shear force, combined with the surface chemical modification of the silane coupling agent, complete deagglomeration of the inorganic filler from a hard agglomerate state to a primary microparticle state is achieved. This independent slurry preparation process eliminates the process pain point of difficulty in dispersing inorganic microparticles in the high viscosity environment of organic resins, forming a nano / micron-scale colloidal filler slurry with extremely high suspension stability, effectively preventing secondary agglomeration during subsequent compounding.

[0309] In some embodiments, the first solvent and the second solvent are each independently selected from at least one of ketone solvents, aromatic hydrocarbon solvents and ester solvents with boiling points between 70°C and 200°C.

[0310] Specifically, the solvent system plays a crucial physical mediating role in the preparation process, dissolving the polymer resin, diluting the binder ink, and facilitating the uniform dispersion of inorganic fillers. By strictly limiting the solvent's boiling point to a specific thermodynamic range of 70°C to 200°C, and utilizing its moderate saturated vapor pressure and volatilization kinetics, it is ensured that the resin binder ink will not experience surface skinning or drastic viscosity changes due to excessively rapid solvent evaporation during high-speed mixing and coating stages. Simultaneously, during the drying process after coating, the solvent within this boiling point range can completely escape from the resin's three-dimensional network at a stable and controllable gradient rate. This parameter limitation effectively prevents pinholes and internal microbubbles in the coating caused by rapid solvent boiling, ensuring that the resin binder layer after film formation possesses a highly dense physical structure and uniform thickness.

[0311] Further, optionally, the ketone solvent is selected from at least one of isophorone, butanone, cyclohexanone, and methyl isobutyl ketone. Utilizing the high polarity and strong dipole moment of ketone solvents, they can efficiently open and dissolve alkali-soluble resins and epoxy polymer chains within the system, providing excellent initial dissolving power for the preparation of resin slurries, completely eliminating the generation of undissolved gel particles, and ensuring the complete expansion of the matrix resin in the liquid phase.

[0312] Optionally, the aromatic hydrocarbon solvent is selected from at least one of toluene, xylene, and trimethylbenzene. Based on the principle of "like dissolves like," aromatic hydrocarbon solvents exhibit excellent affinity for non-alkali-soluble thermosetting resins (such as phenolic resins, benzoxazine, and polyimides) whose main chain contains aromatic rings. Their intervention significantly reduces the entanglement resistance between rigid polymer chains, effectively modulates the overall compatibility of multi-component resin blends, and prevents micro-phase separation or resin precipitation during long-term storage or solvent evaporation film formation.

[0313] Optionally, the ester solvent is selected from at least one of n-butyl acetate, isobutyl acetate, sec-butyl acetate, isopropyl acetate, propylene glycol methyl ether acetate, and dimethyl carbonate. The introduction of ester solvents mainly utilizes their relatively gentle evaporation gradient and excellent surface wetting tension, which can work synergistically with leveling agents in the system to further optimize the spreading and extensibility of the wet film on the metal layer surface. By compounding the above-mentioned ketones, aromatic hydrocarbons, and ester solvents with different solubility parameters (polarity, hydrogen bonding force, dispersion force) and evaporation rates, not only can the filler and resin be extremely uniformly dispersed in the ink during the process, but the rheological performance collapse induced by the mismatch of a single solvent between ink systems is also avoided from a physical and thermodynamic perspective. This gives the resin-bonded ink an extremely stable and wide processing window throughout the entire process from pulping to drying.

[0314] S60. The resin slurry and filler slurry are mixed for the third time to obtain the resin bonding layer 30 ink.

[0315] Specifically, the third mixing speed is 3600 rpm to 7200 rpm, the mixing temperature is no greater than 45°C, and the mixing time is 60 minutes to 120 minutes. By merging the two completely homogenized liquid slurries mentioned above and applying continuous high-speed shearing for 60 minutes to 120 minutes, the convective diffusion and shear emulsification between multiphase fluids are utilized to force the surface-modified inorganic filler particles to uniformly penetrate and distribute within the three-dimensional network voids of the organic polymer.

[0316] Furthermore, strictly controlling the mixing temperature to no more than 45°C is the core safety boundary of this final mixing stage, which can suppress the reactivity of any latent curing agents and accelerators that may exist in the system. This long-duration, high-speed, and low-temperature mixing process enables the final output resin binder layer 30 ink to achieve perfect compatibility of the organic and inorganic phases at the microscale. This not only completely eliminates microbubbles and hard particles inside the ink but also endows the ink with excellent thixotropy and coating tolerance. As a result, when this ink is applied to the surface of the metal layer 10, it can form a resin binder layer 30 with uniform thickness, a smooth surface, and a highly dense structure, providing a zero-defect medium basis for the vacuum plugging process.

[0317] As shown in Figure 3, this application also proposes a selective via plugging method for circuit boards, using a composite film material for circuit board manufacturing as described in any of the foregoing claims. This selective via plugging method includes the following steps:

[0318] S101, Film application: The composite film material is applied to the surface of the circuit board to be processed, wherein the resin adhesive layer 30 of the composite film material is attached to the circuit board.

[0319] Specifically, the circuit board to be processed is a copper-clad laminate. Furthermore, the types of copper-clad laminates include high-density interconnect (HDI) boards, multilayer boards, rigid-flex boards, and ultra-thick boards with a thickness greater than 6mm, which are widely used in aerospace, automotive electronics, high-end smartphones, and server motherboards, where long-term stability and electrical connection accuracy are extremely important.

[0320] Specifically, this step utilizes the viscoelastic characteristics of the resin adhesive layer 30 to achieve molecular-level physical wetting and preliminary bonding between the composite film and the substrate of the circuit board to be treated under certain pressure and temperature conditions. Based on the adhesion force of the resin adhesive layer 30 (0.05 N / cm to 6 N / cm), it ensures the film can adhere firmly during subsequent complex patterning and etching processes, effectively locking the physical coverage position of the via area to be plugged, thus providing a stable carrier foundation for subsequent high-precision selective processes.

[0321] It is worth noting that the composite film can be applied to only one side of the circuit board or to both sides of the circuit board at the same time. The specific application conditions depend on the spatial topology of the target hole to be filled.

[0322] Specifically, when the target hole to be plugged is a back-drilled blind hole or a conventional blind hole with only a single opening, a single-sided lamination process is adopted, that is, the composite film is only laminated to the surface of the circuit board on the side with the hole opening. By utilizing the single-sided physical coverage and barrier mechanism, the opening is effectively closed to perform selective hole plugging, while avoiding redundant material laying, significantly optimizing process efficiency and reducing processing costs.

[0323] When the target hole to be plugged is a through-hole (especially a high aspect ratio through-hole), a double-sided lamination process must be used. This involves simultaneously laminating composite film on both sides of the circuit board and simultaneously performing subsequent patterning, etching, film removal, and grinding operations. Utilizing the simultaneous double-sided sealing and rigid symmetrical support capabilities, not only are the two ends of the hole completely sealed during the high-pressure filling stage of vacuum plugging, preventing resin leakage from the back side or collapse and ensuring absolute fullness of the hole filling, but also a completely symmetrical thermal expansion stress model is constructed on both sides of the copper-clad laminate during the subsequent stepped thermosetting process. This effectively counteracts substrate warping deformation that may be caused by single-sided pressure or single-sided heating, achieving high-precision patterning and stable surface flatness control at both ends of high aspect ratio through-holes.

[0324] S102, Patterning: Expose and develop the photosensitive layer 20 of the composite film material to selectively expose the metal layer 10 that matches the target hole to be filled on the surface of the circuit board to be processed.

[0325] Specifically, the photosensitive layer 20 can be exposed using exposure light with a wavelength between 320 nm and 405 nm. In addition, a development process can be performed using a solution of 3% to 6% sodium carbonate, potassium carbonate, sodium hydroxide, sodium phosphate, sodium pyrophosphate, and organic amines. The conditions for this development process are room temperature (usually 25°C) to 80°C, and the processing time is between 30 seconds and 10 minutes.

[0326] In this step, the dissolution properties of the photosensitive layer 20 are spatially defined through a photochemical reaction mechanism, and the photosensitive material in the uncrosslinked areas is precisely removed using a weakly alkaline solution such as sodium carbonate or potassium carbonate. This allows for the precise mapping of the geometric array of holes to be plugged onto the surface of the metal layer 10. The high resolution of the photosensitive layer 20 (preferably no more than 100 micrometers) ensures the perpendicularity and dimensional consistency of the opening edges, providing a highly reliable shielding boundary for subsequent etching of the metal layer 10.

[0327] S103, Etching: The exposed metal layer 10 is etched to expose the target holes to be filled on the circuit board.

[0328] Specifically, the selective chemical etching mechanism of the etching solution on the metal layer 10 (such as copper foil) is utilized to rapidly peel off the metal portions not protected by the photosensitive layer 20. Specifically, an etching solution containing sulfuric acid or hydrochloric acid in a hydrogen peroxide solution can be used to chemically etch the exposed metal layer. For example, a 10%–30% copper chloride-hydrochloric acid etching solution can be used, with the etching temperature controlled between room temperature (typically 25°C) and 80°C, and the etching time controlled between 30 seconds and 10 minutes.

[0329] Based on the barrier properties of the metal layer 10 as a mechanical skeleton, this step achieves vertical penetration from the composite film to the hole to be plugged on the circuit board. Thus, the physical rigidity of the metal layer 10 ensures the structural integrity of the opening area, effectively preventing hole edge collapse or cracking under vacuum negative pressure due to insufficient strength of traditional dry film, and significantly improving the opening quality of high aspect ratio through holes.

[0330] S104, First film removal: The remaining photosensitive layer 20 on the composite film is removed using a first alkaline solution.

[0331] Specifically, this step aims to completely peel off the photosensitive material that serves as a temporary pattern mask after the etching process is completed, so as to expose a complete and clean boundary of the metal cap aperture medium.

[0332] Specifically, the first alkaline solution contains at least one of sodium carbonate, potassium carbonate, sodium hydroxide, sodium phosphate, sodium pyrophosphate, and organic amines. Utilizing the high concentration of hydroxide ions (OH-) dissociated from the above alkaline substances in aqueous solution, or the high pH environment they create, a strong acid-base neutralization reaction and saponification hydrolysis reaction can occur with the acidic functional groups (such as carboxyl groups) on the cross-linked resin network within the photosensitive layer 20. This chemical deconstruction mechanism can completely destroy the cohesive strength of the photosensitive material and its physical anchoring force with the metal interface, inducing the photosensitive layer 20 to rapidly swell, fragment, and detach from the metal interface.

[0333] Furthermore, the mass concentration of the first alkaline solution is precisely controlled between 3% and 8%. Within this specific mass concentration range, the first alkaline solution possesses sufficient chemical potential energy to penetrate and completely dissolve the stubborn photosensitive resin that has undergone exposure curing and acid-base etching. The direct benefit of this concentration limitation is that, while achieving maximum stripping efficiency, it avoids unintended lateral over-etching of the underlying resin adhesive layer 30 due to excessively strong solution alkalinity, thus achieving a perfect process balance between stripping the photosensitive layer 20 and protecting the underlying resin adhesive layer 30.

[0334] Furthermore, the water temperature for the first alkaline solution treatment is between 55°C and 70°C, and the treatment time is between 30 seconds and 10 minutes. By setting the treatment water temperature within this relatively high thermodynamic range of 55°C to 70°C, the principle of accelerating molecular motion and diffusion through thermodynamics is utilized, significantly increasing the penetration rate of the alkaline solution into the microscopic gaps within the photosensitive polymer. Simultaneously, the controlled treatment time of 30 seconds to 10 minutes ensures that the acid-base neutralization and hydrolytic stripping reactions reach their complete endpoint in all areas of the macroscopic plate surface. This synergistic limitation of time and temperature parameters not only guarantees the high-throughput production efficiency of the automated film removal line but also ensures the absolute physical cleanliness of the metal layer surface and eliminates the potential interference of microscopic residual adhesive on the subsequent vacuum plugging sealing quality.

[0335] S105, Hole plugging: In a vacuum state, the hole plugging resin is filled into the target hole of the circuit board.

[0336] Specifically, after removing the photosensitive layer 20, the via-filling resin can be filled into the target holes of the circuit board under vacuum negative pressure using screen printing and aluminum sheet via filling. Through the strong support of the metal layer 10 in the composite film and the sealing effect of the resin adhesive layer 30, this step can completely eliminate air inside the holes, thus solving the problems of insufficient bottom filling and voids inside the holes caused by surface tension. This achieves dense filling of the via-filling resin within the channels of ultra-thick circuit boards, significantly improving the electrical connection reliability of the product under high-density interconnection.

[0337] S106. Curing: The circuit board is baked to cure the via-sealing resin.

[0338] Specifically, after the resin plugging is completed, the circuit board can be baked to cure the plugging resin in the target holes.

[0339] In this embodiment, a stepped drying process is used to cure the pore-filling resin. The drying conditions for the first stage are: temperature of 110°C and duration of 30 minutes; the drying conditions for the second stage are: temperature of 150°C and duration of 45 minutes.

[0340] The aforementioned stepped drying process allows for the orderly control of resin shrinkage stress and volatile matter removal through segmented temperature control. Specifically, in the first stage at 110°C, low-temperature pre-drying allows the solvent in the resin to slowly escape, preventing the formation of microbubbles due to violent boiling. In the second stage at 150°C, thermal induction activates deep cross-linking of resin molecules. This process design guides the plugging resin and the resin adhesive layer 30 to reach a stable physical state simultaneously. Based on the characteristic that the Tg of the resin adhesive layer 30 is not lower than 130°C, it ensures that no lateral overflow of adhesive occurs during the curing thermal process, thereby locking in the flatness and structural stability of the plugged pores.

[0341] S107, First grinding and micro-etching: The circuit board is ground and micro-etched to remove the via-filling resin and metal layer 10 located on the surface of the circuit board.

[0342] Specifically, the surface treatment equipment performs physical grinding and chemical micro-etching sequentially or simultaneously on the circuit board. The mechanical cutting force of the grinding elements forcibly removes redundant plugging material protruding from the board surface, as well as the metal layer 10 serving as the process carrier. Combined with the chemical oxidation-reduction reaction of the micro-etching solution, it deeply dissolves microscopic metal residues to achieve microscopic roughening of the interface. This composite treatment mechanism completely eliminates the physical step difference between plugged and non-plugged locations, achieving a high degree of flatness on the circuit board surface, while significantly improving the microscopic cleanliness and surface activity of the exposed metal interface.

[0343] During this process, because the metal layer 10 and the resin adhesive layer 30 have a stable adhesion (preferably 0.1 N / cm to 4 N / cm), the film material can withstand the high-speed shearing of the grinding wheel without chipping or premature peeling, thereby protecting the fine lines underneath from wear and ensuring that the surface flatness after grinding is controlled within the micron-level precision range.

[0344] S108, Second film removal: The resin adhesive layer 30 remaining on the surface of the circuit board is removed using a second alkaline solution.

[0345] Specifically, this step aims to completely peel off the resin adhesive layer 30, which serves as a temporary support medium for the hole caps, after completing high-intensity physical and thermodynamic processes such as vacuum plugging, high-temperature stepped curing, and the first grinding plate, in order to restore the initial base surface state of the circuit board.

[0346] Specifically, the second alkaline solution contains at least one of sodium carbonate, potassium carbonate, sodium hydroxide, sodium phosphate, sodium pyrophosphate, and organic amines. The high concentration of hydroxide ions (OH-) dissociated from these strongly alkaline substances in aqueous solution can undergo deep acid-base neutralization and saponification reactions with acidic functional groups such as carboxyl groups on the alkali-soluble resin segments of the resin adhesive layer 30. This specific chemical erosion mechanism completely destroys the interfacial adhesion energy formed between the resin adhesive layer 30 and the copper surface after high-temperature curing, inducing physical swelling of its polymer network.

[0347] Furthermore, the mass concentration of the second alkaline solution is precisely limited to 3% to 8%. Within this specific high concentration range, the solution possesses sufficient chemical potential to penetrate and dismantle the highly cross-linked resin network that has undergone a long thermal process above 150°C. The direct benefit of this concentration limitation is that it can both forcibly peel off the residual adhesive layer with extremely strong adhesion and, thanks to the physical skeletal barrier effect of the non-alkali-soluble resin in the resin adhesive layer 30 formulation, allow the membrane material to detach in large-area sheet-like form rather than dissolve into a paste. This not only significantly reduces the filtration burden on the stripping liquid system but also effectively avoids secondary microscopic contamination of the cured pore-clogging resin by the stripping waste liquid or residue.

[0348] Furthermore, the water temperature for the second alkaline solution treatment is between 55°C and 70°C, and the treatment time is between 30 seconds and 10 minutes. By maintaining the stripping water temperature at a thermodynamically high-activity state of 55°C to 70°C, and utilizing the principle of accelerating molecular motion through thermal activation kinetics, the penetration and diffusion rate of alkaline molecules into the micropores at the interface between the resin and the copper-clad laminate is significantly improved. Combined with a process time of 30 seconds to 10 minutes, this ensures that the stripping reaction in all areas of the complex board surface can be completely and thoroughly performed. Thus, even after facing extremely harsh high aspect ratio vacuum pressure difference and long-term high-temperature baking processes, this application can still achieve "zero residue" clean stripping of the hole edges and fine circuit surfaces, providing a flawless physical substrate for subsequent surface micro-etching and high-density interconnect (HDI) electroplating processes. S109, Second grinding: Grinding away the plugging resin protruding from the board surface.

[0349] Finally, the cured via-plugging resin head is planarized using a fine grinding process to ensure it is completely flush with the copper surface of the circuit board. Based on the strict control over the fullness and positional accuracy within the vias achieved in previous steps, this step ultimately realizes a high-precision, high-reliability selective resin via-plugging structure, providing perfect process support for high-density wiring and surface mounting on circuit boards with high aspect ratios.

[0350] In some embodiments, prior to the film application step, the selective via plugging method for circuit boards of this application further includes a pretreatment step, which specifically involves drilling holes and roughening the surface of the circuit board.

[0351] This pretreatment step aims to provide the optimal initial datum state for the physical mounting and interfacial bonding of the composite film. Specifically, high aspect ratio through-holes and back-drilled holes can be precisely formed on the circuit board to be treated by mechanical drilling or laser drilling, establishing the spatial geometry target for subsequent selective via plugging processes.

[0352] Furthermore, after drilling, a surface roughening treatment (such as browning or micro-etching) is performed. Utilizing chemical oxidation or micro-physical etching mechanisms, a rough micro-morphology with micro- and nano-scale undulations is constructed on the originally smooth copper surface and circuit edges of the circuit board. This physical change in surface morphology significantly increases the free energy and specific surface area of ​​the substrate surface. Consequently, in the subsequent film lamination step, the polymer chains and liquid components (such as liquid phenolic resin or liquid epoxy resin) in the resin adhesive layer 30 can deeply penetrate and anchor in these micro-troughs under hot pressure, forming a high-strength physical interlocking effect. This ensures that during the subsequent high-pressure jetting and high-temperature baking process of vacuum via plugging, the edges of the composite film will not experience lifting, peeling, or micro-displacement, fundamentally eliminating the risk of leakage (side leakage) of the via-plugging resin into non-via areas through interface gaps, thus guaranteeing the ultimate cleanliness of the circuit board surface.

[0353] It is worth noting that the composite film preparation method and the circuit board selective via plugging method of this application use the composite film defined in any of the foregoing embodiments, and therefore have all the technical effects of the composite film in the foregoing embodiments, which will not be repeated here.

[0354] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural transformations made using the contents of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of patent protection of the present invention.

Claims

1. A composite film material for circuit board manufacturing, characterized in that, include: Metal layer; A photosensitive layer is disposed on the first surface of the metal layer; as well as A resin adhesive layer is disposed on the second surface of the metal layer, the second surface being opposite to the first surface; The resin adhesive layer comprises an alkali-soluble resin and is used to bond with the circuit board.

2. The composite film material for circuit board manufacturing as described in claim 1, characterized in that, The resin adhesive layer further comprises a non-alkali-soluble resin, wherein the non-alkali-soluble resin is selected from at least one of non-alkali-soluble thermoplastic resins and non-alkali-soluble thermosetting resins.

3. The composite film material for circuit board manufacturing as described in claim 1 or 2, characterized in that, The metal layer is made of at least one of the following materials: silver, copper, nickel, iron, tin, zinc, phosphorus, and aluminum; and / or The thickness of the metal layer is from 3 micrometers to 300 micrometers; and / or The surface roughness Ra of the metal layer is between 0.05 micrometers and 5 micrometers; and / or The surface roughness Rz of the metal layer is between 0.2 micrometers and 20 micrometers; and / or The thickness of the photosensitive layer is between 2 micrometers and 100 micrometers; and / or The resolution of the photosensitive layer is no greater than 1 mm; and / or The adhesion strength of the resin adhesive layer is between 0.05 N / cm and 6 N / cm; and / or The thickness of the resin adhesive layer is between 5 micrometers and 70 micrometers.

4. The composite film material for circuit board manufacturing as described in claim 1 or 2, characterized in that, The alkali-soluble resin is selected from at least one of the first type of resin and 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.

5. The composite film material for circuit board manufacturing as described in claim 4, 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 50000 g / mol; and / or 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 molecular weight of the polyimide precursor is between 1000 g / mol and 100000 g / mol; and / or The polyimide precursor is selected from at least one of polyamic acid and polyisoimide.

6. The composite film material for circuit board manufacturing as described in claim 2, characterized in that, The non-alkali-soluble thermoplastic resin is selected from at least one of polyamide resin, polyester resin, polystyrene resin, rubber resin, polyvinyl butyral and polyurethane resin.

7. The composite film material for circuit board manufacturing as described in claim 2 or 6, characterized in that, The molecular weight of the non-alkali-soluble thermoplastic resin is between 3000 g / mol and 400000 g / mol.

8. The composite film material for circuit board manufacturing as described in claim 6, characterized in that, The rubber resin 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.

9. The composite film material for circuit board manufacturing as described in claim 2, characterized in that, The non-alkali-soluble thermosetting resin comprises polymers whose main chain has aromatic rings and / or heterocycles.

10. The composite film material for circuit board manufacturing as described in claim 9, characterized in that, The polymer having an aromatic ring and / or heterocyclic ring in its main chain is selected from at least one of polyimide resins, epoxy resins, phenolic resins, benzoxazine resins, and bismaleimide resins.

11. The composite film material for circuit board manufacturing as described in claim 10, characterized in that, The epoxy resin is selected from at least one of glycidylamine epoxy resin, phenoxy 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; and / or The benzoxazine resin is selected from at least one of bisphenol A benzoxazine, bisphenol F benzoxazine, MDA benzoxazine, DCPD benzoxazine, phenolic benzoxazine, and DOPO benzoxazine; and / or The bismaleimide resin is selected from at least one of diaminodiphenylmethane modified bismaleimide, biphenyl-containing bismaleimide, high-performance thermoplastic resin blended toughened modified bismaleimide, isopropyl-p-phenyl bismaleimide, PI modified bismaleimide, and cyanate ester modified bismaleimide.

12. The composite film material for circuit board manufacturing as described in any one of claims 9 to 11, characterized in that, The glass transition temperature of the polymer is not lower than 130°C.

13. The composite film material for circuit board manufacturing as described in claim 2, characterized in that, The resin adhesive layer also includes an initiator, which comprises a latent accelerator and a latent curing agent.

14. The composite film material for circuit board manufacturing as described in claim 13, characterized in that, When the non-alkali-soluble resin includes a non-alkali-soluble thermosetting resin, The latent curing agent for curing non-alkali-soluble thermosetting resins is selected from at least one of phenolic resins, benzoxazine, bismaleimide resins, reactive esters, and amine dicyandiamide curing agents; and / or The latent accelerator used for curing non-alkali-soluble thermosetting resins is selected from at least one of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methylimidazole.

15. The composite film material for circuit board manufacturing as described in claim 14, characterized in that, When the latent curing agent comprises phenolic resin and the non-alkali-soluble thermosetting resin comprises epoxy resin, the mass of the phenolic resin and the mass of the epoxy resin satisfy the following formula: The mass of phenolic resin = (hydroxyl equivalent of phenolic resin / epoxy equivalent of epoxy resin) × mass of epoxy resin.

16. The composite film material for circuit board manufacturing as described in claim 14 or 15, characterized in that, The mass of the latent curing agent used for curing non-alkali-soluble thermosetting resins is no more than 10% of the mass of the non-alkali-soluble thermosetting resins; and / or The mass of the latent accelerator used to cure the non-alkali-soluble thermosetting resin is no more than 5% of the mass of the non-alkali-soluble thermosetting resin.

17. The composite film material for circuit board manufacturing as described in claim 13, characterized in that, The latent curing agent used to cure the alkali-soluble resin is selected from at least one of benzoyl peroxide, tert-butyl peroxide, dicumyl peroxide, cumyl hydroperoxide, and hydroxycumyl peroxide; and / or The latent accelerator used to cure the alkali-soluble resin is selected from at least one of N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-methylaniline, n-butanol-aniline condensate, butyraldehyde-n-butylamine condensate, thiourea, ethylidene thiourea, tetramethylthiourea, cobalt naphthenate, cobalt naphthenate, cobalt acetate, and copper octoate.

18. The composite film material for circuit board manufacturing as described in claim 17, characterized in that, The mass of the latent curing agent used to cure the alkali-soluble resin is no more than 10% of the mass of the alkali-soluble resin; and / or The mass of the latent accelerator used to cure the alkali-soluble resin is no more than 5% of the mass of the alkali-soluble resin.

19. The composite film material for circuit board manufacturing as described in claim 1 or 2, characterized in that, The resin adhesive layer further comprises a filler selected from at least one of silicon dioxide, aluminum oxide, aluminum hydroxide, calcium carbonate, magnesium carbonate, magnesium silicate, silicon carbide, titanium carbide, barium sulfate, magnesium sulfate, titanium oxide, magnesium oxide, calcium oxide, boron nitride, and aluminum nitride.

20. The composite film material for circuit board manufacturing as claimed in claim 19, characterized in that, The surface of the filler is modified with at least one surface-modifying group selected from epoxy, aniline, amino and alkyl groups.

21. The composite film material for circuit board manufacturing as claimed in claim 19, characterized in that, The particle size of the filler is between 0.1 micrometers and 50 micrometers.

22. The composite film material for circuit board manufacturing as described in claim 1 or 2, characterized in that, The resin adhesive layer further comprises an additive selected from at least one of leveling agents, defoamers, wetting and dispersing agents, and silane coupling agents.

23. The composite film material for circuit board manufacturing as described in claim 22, characterized in that, The leveling agent is selected from at least one of polyether-modified polydimethylsiloxane solution, aralkyl-modified polymethylalkylsiloxane, polyacrylate, and nonionic organic surfactant; and / or The defoamer is selected from at least one of dimethylpolysiloxane containing fumed silica and organically modified polysiloxane containing fumed silica; and / or The wetting and dispersing agent is selected from at least one of polyether-modified silicone, propylene glycol methyl ether acetate, and nonionic organic surfactants; and / or The silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane.

24. The composite film material for circuit board manufacturing as described in claim 23, characterized in that, When the resin adhesive layer contains both a silane coupling agent and a filler, the mass of the silane coupling agent is 0.5% to 30% of the mass of the filler.

25. The composite film material for circuit board manufacturing as described in claim 1 or 2, characterized in that, In the resin adhesive layer: The total mass of the resin accounts for 20% to 100% of the total mass of the resin adhesive layer; The filler accounts for 0% to 80% of the total mass of the resin adhesive layer.

26. The composite film material for circuit board manufacturing as described in claim 1 or 2, characterized in that, In the resin adhesive layer, the mass of the additive accounts for 0.01% to 20% of the total mass of the resin adhesive layer.

27. The composite film material for circuit board manufacturing as described in claim 2, characterized in that, The mass ratio of the alkali-soluble resin to the non-alkali-soluble resin is from 0.2:0.8 to 1:

0.

28. The composite film material for circuit board manufacturing as described in claim 2, characterized in that, When the non-alkali-soluble resin simultaneously comprises a non-alkali-soluble thermoplastic resin and a non-alkali-soluble thermosetting resin, the mass ratio of the non-alkali-soluble thermoplastic resin to the non-alkali-soluble thermosetting resin is from 0.7:0.3 to 1:

0.

29. The composite film material for circuit board manufacturing as described in claim 1 or 2, characterized in that, The composite film material further includes a protective film, which is disposed on the surface of at least one of the photosensitive layer and the resin adhesive layer.

30. The composite film material for circuit board manufacturing as described in claim 29, characterized in that, The thickness of the protective film is between 3 micrometers and 50 micrometers; and / or The release force of the protective film is between 1g and 2000g.

31. A method for preparing a composite membrane material, characterized in that, The method for preparing the composite film material for circuit board manufacturing as described in any one of claims 1 to 30 includes: Provide a metal layer; A photosensitive layer is formed on the first surface of the metal layer; and The resin adhesive layer ink is applied to the second surface of the metal layer and dried to form the resin adhesive layer.

32. The method for preparing the composite membrane material as described in claim 31, characterized in that, Before applying the resin adhesive layer ink to the second surface of the metal layer, the preparation method further includes preparing the resin adhesive layer ink, the step of preparing the resin adhesive layer ink comprising: Alkali-soluble resin and non-alkali-soluble resin are dissolved in a first solvent and mixed in a first process to obtain a resin slurry; The filler is dispersed in a second solvent for a second mixing to obtain a filler slurry; and The resin slurry and the filler slurry are mixed for a third time to obtain a resin bonding layer ink.

33. The method for preparing the composite membrane material as described in claim 32, characterized in that, The step of preparing the resin slurry further includes: pre-dissolving at least one additive selected from leveling agents, wetting and dispersing agents and defoamers in the first solvent before dissolving the alkali-soluble resin and the non-alkali-soluble resin; The step of preparing the filler slurry further includes: pre-dissolving at least one auxiliary agent selected from leveling agents, wetting and dispersing agents, defoamers and silane coupling agents in the second solvent before dispersing the filler in the second solvent.

34. The method for preparing the composite membrane material as described in claim 32, characterized in that, The first solvent and the second solvent are each independently selected from at least one of ketone solvents, aromatic hydrocarbon solvents and ester solvents with boiling points between 70°C and 200°C.

35. The method for preparing the composite membrane material as described in claim 34, characterized in that, The ketone solvent is selected from at least one of isoflurane, butanone, cyclohexanone, and methyl isobutyl ketone; and / or The aromatic hydrocarbon solvent is selected from at least one of toluene, xylene, and trimethylbenzene; and / or The ester solvent is selected from at least one of n-butyl acetate, isobutyl acetate, sec-butyl acetate, isopropyl acetate, propylene glycol methyl ether acetate, and dimethyl carbonate.

36. The method for preparing the composite membrane material as described in claim 32, characterized in that, The first mixing speed is 3600 rpm to 7200 rpm, the mixing temperature is not greater than 45°C, and the mixing time is 10 minutes to 60 minutes; and / or The second mixing speed is 3600 rpm to 7200 rpm, the mixing temperature is not greater than 45°C, and the mixing time is 10 minutes to 60 minutes; and / or The third mixing speed is 3600 rpm to 7200 rpm, the mixing temperature is not greater than 45°C, and the mixing time is 60 minutes to 120 minutes.

37. A method for selectively plugging vias in a circuit board, characterized in that, Using the composite film material for circuit board manufacturing as described in any one of claims 1 to 30, the selective via plugging method for the circuit board includes the following steps: Film application: The composite film material is applied to the surface of the circuit board to be processed, wherein the resin adhesive layer of the composite film material is attached to the circuit board; Patterning: The photosensitive layer of the composite film is exposed and developed to selectively expose the metal layer that matches the target hole to be filled on the surface of the circuit board. Etching: Etching the exposed metal layer to expose the target holes to be filled on the circuit board; First film removal: The remaining photosensitive layer on the composite film is removed using a first alkaline solution; Hole plugging: Under vacuum conditions, plugging resin is filled into the target holes of the circuit board; Curing: The circuit board is baked to cure the via-sealing resin.

38. The method for selectively plugging vias in a circuit board as described in claim 37, characterized in that, Following the curing step, the circuit board selective via plugging method further includes: First grinding and micro-etching: The circuit board is ground and micro-etched to remove the plugging resin and metal layer on the surface of the circuit board. Second film removal: A second alkaline solution is used to remove the residual resin adhesive layer on the surface of the circuit board; and Second grinding plate: Grinds and removes the resin that plugs the holes protruding from the surface of the circuit board.

39. The selective via plugging method for a circuit board as described in claim 37 or 38, characterized in that, Prior to the film application step, the circuit board selective via plugging method further includes: Pre-treatment: The circuit board is drilled and its surface is roughened.

40. The method for selectively plugging vias in a circuit board as described in claim 38, characterized in that, The first alkaline solution and / or the second alkaline solution contain at least one of sodium carbonate, potassium carbonate, sodium hydroxide, sodium phosphate, sodium pyrophosphate, and organic amine; and / or The mass concentration of the first alkaline solution and / or the second alkaline solution is 3% to 8%; and / or The water temperature for treatment with the first alkaline solution and / or the second alkaline solution is 55°C to 70°C, and the treatment time is 30 seconds to 10 minutes.

41. The selective via plugging method for a circuit board as described in claim 37 or 38, characterized in that, In the curing step, a stepped drying process is used to cure the pore-filling resin, wherein, The drying conditions for the first stage are: temperature 110℃, duration 30 minutes; The drying conditions for the second stage are: temperature 150℃, duration 45 minutes.

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