Pre-adjustment-free carbon-based via metallization process and printed wiring board

Abstract

This disclosure provides a carbon-based via metallization process and printed circuit board without pre-adjustment. The aforementioned carbon-based via metallization process involves drilling holes in a copper-clad resin board; using an inorganic small-molecule oxide cleaning solution to roughen and clean the hole walls of the drilled copper-clad resin board; rinsing the cleaned copper-clad resin board with water; immersing the rinsed copper-clad resin board in an aqueous conductive carbon material; and then drying the soaked copper-clad resin board; micro-etching the dried copper-clad resin board; and finally electroplating the micro-etched copper-clad resin board to obtain a carbon-based via metallized copper-clad resin board. This process, while meeting high conductivity requirements, simplifies the process, improves production efficiency, reduces the amount of cleaning solution used and the amount of waste water to be treated, reduces the energy consumption of the first drying step, and decreases yellowing and deformation rates, better meeting the requirements of high-electrical-performance printed circuit boards.

Description

Technical Field

[0001] This disclosure relates to the field of printed circuit board manufacturing technology, and in particular to a carbon-based hole metallization process and a printed circuit board that does not require pre-adjustment. Background Technology

[0002] Printed circuit boards (PCBs) include various types such as rigid copper-clad laminates (CCLs), flexible CCLs, and rigid-flexible CCLs. They typically consist of at least two layers of copper-clad resin, separated by insulating material. Therefore, in many PCB manufacturing processes, a hole-metallization process is required to achieve conductivity between the copper-clad resin layers, ensuring the proper functioning of the PCB.

[0003] Early hole metallization processes typically involved drilling holes in a copper-clad resin board, followed by metallization treatment inside the holes to form a conductive layer on the inner wall—a process known as electroless copper plating. However, early electroless copper plating suffered from unstable bonding between the conductive layer and the insulating material, as well as high costs. Therefore, carbon-based hole metallization processes emerged, using carbon materials, such as carbon black or graphite, as the core conductive medium. This carbon film is physically adsorbed onto the hole walls of the printed circuit board, and then thickened through electroplating to obtain a thick and reliable conductive layer.

[0004] However, in practical applications, traditional carbon-based pore metallization processes generally require the use of macromolecular cleaning agents. For example, patent US5476580 uses a polymeric cleaning agent containing quaternary ammonium compounds and other cationic polymers, and patent CN106653141B uses a weakly alkaline solution with a weakly compounded agent. However, due to the poor water solubility and weak adhesion to the pore walls of traditional macromolecular cleaning agents, traditional carbon-based pore metallization processes require multiple cycles of cleaning and conditioning, water washing, conductive slurry immersion, and micro-etching. Figure 1 As shown. However, the traditional multi-step cyclic process not only has the problems of cumbersome operation and low production efficiency, but also results in large amounts of cleaning fluid consumption and a lot of waste water. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a carbon-based hole metallization process and printed circuit board that, while meeting the requirements of high conductivity, simplifies the process, improves production efficiency, reduces the amount of polymer cleaning liquid and water washing waste liquid, reduces the energy consumption of one drying cycle, and reduces yellowing rate and deformation rate, without the need for pre-adjustment.

[0006] The purpose of this disclosure is achieved through the following technical solution: A carbon-based pore metallization process without pre-adjustment includes the following steps: A drilling operation is performed on the copper-clad resin board; wherein the copper-clad resin board has multiple through holes. The copper-clad resin board after drilling was roughened and cleaned with an inorganic small molecule oxidation cleaning solution to form multiple coarse holes. The copper-clad resin board, after roughening and cleaning the hole walls, is then rinsed with water once. The copper-clad resin board after a single water wash is immersed in an aqueous conductive carbon material to form a pure carbon-based conductive layer in the corresponding coarse pores; wherein, by mass parts, the aqueous conductive carbon slurry is composed of 0.01-25 parts conductive carbon material, 70-98.5 parts water and 0.01-3 parts dispersant. The conductive carbon material includes at least one of carbon black, nano-graphite, graphene, and carbon nanotubes. The copper-clad resin board after soaking is dried once. Micro-etching is performed on the copper-clad resin board after it has been dried once. The copper-clad resin board after micro-etching is subjected to electroplating to form a metal plating layer on the pure carbon-based conductive layer, thereby obtaining a carbon-based metallized copper-clad resin board.

[0007] In one embodiment, the conditions for roughening and cleaning the pore wall are: temperature 30℃-50℃ and time 30s-80s.

[0008] In one embodiment, the inorganic small molecule oxidizing cleaning solution is an acidic inorganic oxidizing cleaning solution, which includes one of the following: sulfuric acid-hydrogen peroxide mixture, sulfuric acid-persulfate mixture, fluorosulfonic acid-hydrogen peroxide mixture, sulfuric acid-potassium permanganate mixture, sulfuric acid-potassium dichromate mixture, and sulfuric acid-sodium dichromate mixture; or, The inorganic small molecule oxidizing cleaning solution is an alkaline system inorganic oxidizing cleaning solution, which includes at least one of sodium hydroxide-potassium permanganate mixture, sodium hydroxide-sodium permanganate mixture, sodium hypochlorite-sodium hydroxide mixture, and sodium hypochlorite-potassium hydroxide mixture.

[0009] In one embodiment, the particle size range of the aqueous conductive carbon slurry is 10 nm to 3000 nm.

[0010] In one embodiment, the dispersant includes at least one of capped propylene glycol block polyether, modified polyacrylic acid, and sodium lignosulfonate.

[0011] In one embodiment, the copper-clad resin board after roughening and cleaning the hole walls is rinsed once for 10s-40s with deionized water with a conductivity of <10μs / cm and a temperature of 10℃-60℃.

[0012] In one embodiment, the soaking conditions are: temperature 25℃-35℃, time 20s-60s, and soaking method is soaking and shaking.

[0013] In one embodiment, the temperature of the first drying is 50°C-80°C; the time is 20s-80s.

[0014] In one embodiment, after the step of micro-etching the copper-clad resin board after drying, and before the step of electroplating the micro-etched copper-clad resin board, the following step is further included: The copper-clad resin board after micro-etching is then subjected to a second water wash. The copper-clad resin board, after being washed twice, is then dried a second time.

[0015] A printed circuit board is prepared using a carbon-based via metallization process without pre-adjustment as described in any of the above embodiments.

[0016] Compared with the prior art, this disclosure has at least the following advantages: Because inorganic small molecule oxidizing cleaning solutions possess excellent water solubility and oxidizing properties, when used to roughen and clean the hole walls of the copper-clad resin board after drilling, the strong oxidizing inorganic groups of the solution can oxidize and hydrolyze the resin molecular structure and organic pollutant molecular structure within the through-holes. This promotes the spontaneous formation of polar functional groups at the fracture ends on the inner wall of the through-holes, creating an uneven adsorption surface on the inner wall of the rough holes. This not only forms adsorption sites for polar functional groups on the inner wall of the rough holes but also improves the overall performance of the inner wall of the rough holes. The hydrophilicity of the surface allows the water-based conductive carbon material to spread and penetrate quickly and fully onto the inner wall of the coarse pores, facilitating the formation of a dense and uniform pure carbon-based conductive layer. Furthermore, the adsorption sites of polar functional groups formed on the inner wall of the coarse pores enable strong hydrogen bond adsorption between the inner wall and the water-based conductive carbon material, thereby increasing the connection strength between the inner wall and the pure carbon-based conductive layer. It also increases the surface roughness of the inner wall, achieving mechanical interlocking between the inner wall and the water-based conductive carbon material, further enhancing the connection strength. In addition, the added inorganic small-molecule oxidation cleaning solution effectively removes oil stains and resin debris from the inner wall of the coarse pores. This eliminates the need for high-molecular-weight organic cleaning agents and multiple cleaning and adjustment steps; a single-step pore wall roughening cleaning process achieves both cleaning and roughening effects on the copper-clad resin board. This simplifies the operation, improves production efficiency, and reduces the amount of cleaning agent used and the volume of wastewater, thus reducing the amount of wastewater to be treated.

[0017] By performing a single water wash on the copper-clad resin board after roughening and cleaning the pore walls, impurities or inorganic small-molecule oxidation cleaning solution remaining on the inner walls of the coarse pores are effectively removed. On the one hand, this allows for a more comprehensive exposure of the adsorption sites of polar functional groups on the inner walls of the coarse pores, increasing the contact area between the inner walls of the coarse pores and the water-based conductive carbon material. On the other hand, it provides good pre-wetting of the inner walls of the coarse pores. When the copper-clad resin board is immersed in the water-washed copper-clad resin board, the water-based conductive carbon material, using water and dispersant as the dispersion medium, can quickly spread and penetrate on the pre-wetted inner walls of the coarse pores, which is beneficial for forming a dense and uniform pure carbon-based conductive layer on the inner walls of the coarse pores. Furthermore, due to the good water solubility of the inorganic small-molecule oxidation cleaning solution, fewer water washes are needed to effectively remove the inorganic small-molecule oxidation cleaning solution remaining on the inner walls of the coarse pores, further reducing the amount of washing waste liquid generated.

[0018] The copper-clad resin board, after soaking, undergoes a primary drying process. This allows the water-based conductive carbon slurry to dry and solidify at a relatively low primary drying temperature, forming a pure carbon-based conductive layer. This pure carbon-based conductive layer is then firmly adsorbed onto the inner wall of the coarse pores. Subsequently, the copper-clad resin board after the primary drying process undergoes micro-etching. This removes carbon-based residues adhering to the surface of the outer copper-clad resin board and excess water-based conductive carbon material within the coarse pores. Furthermore, the micro-etching step slightly etches the outer copper layer of the copper-clad resin board, providing a good adhesion substrate for the electroplating process and ensuring the deposition of a uniform, dense, and complete metal plating layer on the pure carbon-based conductive layer. In this way, the prepared carbon-based porous metallized copper-clad resin board not only meets the requirements for high conductivity but also simplifies the process, improves production efficiency, reduces the amount of polymer cleaning solution and water washing wastewater treatment, lowers the energy consumption of the primary drying process, and reduces yellowing and deformation rates, thus better meeting the requirements of high-performance printed circuit boards. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 Flowchart of a traditional carbon-based pore metallization process including cleaning and adjustment steps; Figure 2 This is a physical image of the aqueous conductive carbon black slurry of Embodiment 1 of the present invention; Figure 3 This is a physical image of the aqueous conductive graphite slurry of Embodiment 2 of the present invention; Figure 4 This is a physical image of the aqueous conductive carbon nanotube slurry of Embodiment 3 of the present invention; Figure 5 This is a physical image of the aqueous conductive graphene slurry of Embodiment 4 of the present invention; Figure 6 This is a physical image of the Zhaoxin rectifier RXN305D used in the testing of this invention; Figure 7 This is a photograph of the FLUKE F15 digital multimeter used in the testing of this invention. Figure 8 This is a photograph of the Sunny BK200M metallurgical microscope used in the testing of this invention. Figure 9 This is a photograph of the metallographic polishing machine used in the testing of this invention. Figure 10 This is a photograph of the 10,000-hole test plate used in the present invention. Figure 11 This is a metallographic polished surface view of the printed circuit board of Embodiment 1 of the present invention; Figure 12 This is a metallographic polished surface image of the printed circuit board after hot stamping test in Embodiment 1 of the present invention; Figure 13 This is a metallographic polished surface view of the printed circuit board of Embodiment 2 of the present invention; Figure 14 This is a metallographic polished surface image of the printed circuit board after hot stamping test in Embodiment 2 of the present invention; Figure 15 This is a metallographic polished surface view of the printed circuit board of Embodiment 3 of the present invention; Figure 16 This is a metallographic polished surface image of the printed circuit board after hot stamping test in Embodiment 3 of the present invention; Figure 17 This is a metallographic polished surface view of the printed circuit board of Embodiment 4 of the present invention; Figure 18 This is a metallographic polished surface image of the printed circuit board after hot stamping test in Embodiment 4 of the present invention; Figure 19 This is a metallographic polished surface view of the printed circuit board of Embodiment 5 of the present invention; Figure 20 This is a metallographic polished surface view of the printed circuit board of Embodiment 6 of the present invention; Figure 21 This is a metallographic polished surface view of the printed circuit board of Embodiment 7 of the present invention; Figure 22 This is a metallographic polished surface image of the printed circuit board after hot stamping test in Embodiment 7 of the present invention; Figure 23 This is a metallographic polished surface view of the printed circuit board of Comparative Example 1 of the present invention. Figure 24This is a metallographic polished surface image of the printed circuit board after hot stamping test in Comparative Example 1 of the present invention. Detailed Implementation

[0021] To facilitate understanding of this disclosure, a more complete description will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the present disclosure. However, this disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0022] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] To better understand the technical solution and beneficial effects of this disclosure, the following detailed description is provided in conjunction with specific embodiments. One embodiment of the carbon-based pore metallization process without pre-adjustment includes some or all of the following steps: S101. Drilling operation is performed on the copper-clad resin board; wherein, the copper-clad resin board has multiple through holes.

[0025] In one embodiment, the copper-clad resin board includes a substrate and a copper layer, with at least one copper layer disposed on one side of the substrate.

[0026] In one embodiment, the copper-clad resin board includes either a rigid resin copper-clad board or a flexible resin copper-clad board. The main difference between rigid and flexible resin copper-clad boards lies in the material of the interposed substrate.

[0027] In one embodiment, the substrate of the rigid resin copper-clad laminate includes at least one selected from epoxy resin substrate, polyimide substrate, polyetheretherketone substrate, polyethylene substrate, polytetrafluoroethylene substrate, polyvinyl chloride substrate, polycarbonate substrate, polyacrylonitrile substrate, polybutylene terephthalate substrate, urea-formaldehyde resin substrate, melamine-formaldehyde resin substrate, phenolic resin substrate, polyoxymethylene substrate, polystyrene substrate, and styrene-acrylonitrile copolymer polyacrylate substrate. Further, the substrate thickness is 0.1 mm to 3 mm. The copper layer thickness is 0.05 mm to 2 mm.

[0028] In one embodiment, the substrate of the flexible resin copper-clad laminate includes at least one selected from polyester substrate, polyurethane substrate, polypropylene substrate, polyamide-imide resin board, and flexible perforated board. Further, the substrate thickness is 0.1 mm to 0.5 mm. The copper layer thickness is 0.03 mm to 0.15 mm.

[0029] In one embodiment, the diameter of the through hole is 0.05mm-5mm, which is beneficial for preparing a thicker multilayer circuit board with a suitable hole diameter.

[0030] S102. Use an inorganic small molecule oxidation cleaning solution to roughen and clean the hole walls of the copper-clad resin board after drilling to form multiple coarse holes.

[0031] It is understandable that, due to the water solubility and strong oxidizing properties of inorganic small molecule oxidizing cleaning solutions, when used to roughen and clean the hole walls of the copper-clad resin board after drilling, the strong oxidizing inorganic groups of the inorganic small molecule oxidizing cleaning solution can oxidize and hydrolyze the resin molecular structure and organic pollutant molecular structure within the through-holes. This promotes the spontaneous formation of polar functional groups at the fracture ends on the inner wall of the through-holes, thus forming an uneven adsorption surface on the inner wall of the coarse pores. In this way, not only are adsorption sites for polar functional groups formed on the inner wall of the coarse pores, but this also helps to improve the adsorption capacity of the coarse pores. The hydrophilicity of the inner wall surface allows the water-based conductive carbon material to spread and penetrate quickly and fully onto the surface of the coarse pores, facilitating the formation of a dense and uniform pure carbon-based conductive layer. Furthermore, the adsorption sites of polar functional groups formed on the inner wall of the coarse pores enable strong hydrogen bond adsorption between the inner wall and the water-based conductive carbon material, thereby increasing the connection strength between the inner wall and the pure carbon-based conductive layer. It also increases the surface roughness of the inner wall, achieving mechanical interlocking between the inner wall and the water-based conductive carbon material, further enhancing the connection strength. In addition, the added inorganic small-molecule oxidizing cleaning solution effectively removes oil stains and resin debris from the inner wall of the coarse pores. This eliminates the need for high-molecular-weight organic cleaning agents and multiple cleaning and adjustment steps; a single-step pore wall roughening cleaning step achieves both cleaning and roughening effects on the copper-clad resin board. This simplifies the process, improves production efficiency, and reduces the amount of cleaning agent used and the volume of wastewater, thus reducing the amount of wastewater to be treated.

[0032] In one embodiment, the inorganic small molecule oxidative cleaning solution includes at least one of an acidic inorganic oxidative cleaning solution and an alkaline inorganic oxidative cleaning solution.

[0033] In one embodiment, the acidic inorganic oxidizing cleaning solution includes one of the following: sulfuric acid-hydrogen peroxide mixture, sulfuric acid-persulfate mixture, fluorosulfonic acid-hydrogen peroxide mixture, sulfuric acid-potassium permanganate mixture, sulfuric acid-potassium dichromate mixture, and sulfuric acid-sodium dichromate mixture, to achieve a better roughening and cleaning effect on the hole walls of rigid resin copper clad laminates.

[0034] In one embodiment, the alkaline inorganic oxidizing cleaning solution includes at least one of sodium hydroxide-potassium permanganate mixture, sodium hydroxide-sodium permanganate mixture, sodium hypochlorite-sodium hydroxide mixture, and sodium hypochlorite-potassium hydroxide mixture, to achieve a better roughening and cleaning effect on the hole walls of the flexible resin copper clad laminate.

[0035] In one embodiment, the inorganic small molecule oxidation cleaning solution further includes a small molecule polyol stabilizer to ensure that the addition of the small molecule polyol stabilizer not only delays the ineffective decomposition of the effective components in the inorganic small molecule oxidation cleaning solution, but also improves the wettability and permeability of the inorganic small molecule oxidation cleaning solution to the pore wall, and is easy to wash with water without residue, simplifying the difficulty of waste liquid treatment.

[0036] In one embodiment, the small molecule polyol stabilizer includes at least one of ethylene glycol, propylene glycol, and glycerol.

[0037] In one embodiment, the mass concentration of the acid-base agent is 2%-8%, the mass concentration of the oxidant is 3%-6%, the mass concentration of the small molecule polyol stabilizer is 0.1%-2%, and the balance is water.

[0038] In one embodiment, the mass concentration of the acid is 4%, the mass concentration of the oxidant is 6%, the mass concentration of the small molecule polyol stabilizer is 1%, and the balance is water. Further, the acid is sulfuric acid, the oxidant is hydrogen peroxide, and the small molecule polyol stabilizer is ethylene glycol.

[0039] In one embodiment, the conditions for roughening and cleaning the pore walls are: temperature 30℃-50℃, time 30s-80s, especially with the use of an acid-base agent with a mass concentration of 2%-8%, an oxidant with a mass concentration of 3%-6%, a small molecule polyol stabilizer with a mass concentration of 0.1%-2%, and the remainder being water. This forms an uneven adsorption surface with a thickness of 0.1mm-0.7mm on the inner wall of the coarse pores, ensuring that the height of the formed uneven adsorption surface is suitable. In this way, while ensuring that the connection strength between the inner wall of the coarse pores and the pure carbon-based conductive layer is improved, it also ensures that the water-based conductive carbon material can flow, spread, and penetrate well on the inner wall of the coarse pores. This effectively avoids the uneven adsorption surface being too high, which would affect the subsequent flow, spreading, and penetration of the water-based conductive carbon material, and effectively avoids the uneven adsorption surface being too low, which would fail to improve the connection strength between the inner wall of the coarse pores and the pure carbon-based conductive layer.

[0040] In one embodiment, the step of roughening and cleaning the hole walls of the copper-clad resin board after drilling using an inorganic small molecule oxidation cleaning solution includes the following specific steps: the copper-clad resin board after drilling is completely immersed in a mixed solution at a temperature of 30℃-50℃, and then the copper-clad resin board is immersed and shaken for 30s-80s to allow the inorganic small molecule oxidation cleaning solution to fully penetrate into the multiple through holes of the copper-clad resin board, thereby achieving better roughening and cleaning of the inner walls of each through hole. On the one hand, it forms an uneven adsorption surface with a roughness of 0.3μm-0.6μm on the inner wall of the coarse hole, and on the other hand, it effectively removes impurities such as oil and resin debris from the inner wall of the coarse hole. There is no need to add high molecular organic cleaning agents or perform multiple cleaning and adjustment steps. The hole wall roughening and cleaning step alone achieves the dual effect of cleaning and roughening of the copper-clad resin board, which not only simplifies the operation process, but also improves production efficiency and reduces the amount of cleaning agent used and the amount of water washing waste liquid, thereby reducing the amount of water washing waste liquid to be treated.

[0041] In one embodiment, the soaking and shaking conditions are as follows: the board is placed vertically and shaken left and right with a left and right amplitude of 5cm-10cm and a frequency of 20 times / min-60 times / min. Under the action of external shaking, the mixture can fully enter the multiple through holes of the copper-clad resin board, thereby achieving rapid and comprehensive roughening and cleaning of the inner wall of each through hole.

[0042] S103. The copper-clad resin board after roughening and cleaning the hole walls is rinsed once with water to effectively remove impurities or inorganic small molecule oxidation cleaning solution remaining on the inner wall of the rough holes. On the one hand, this allows the adsorption sites of polar functional groups on the inner wall of the rough holes to be fully exposed, increasing the contact area between the inner wall of the rough holes and the water-based conductive carbon material. On the other hand, it provides good pre-wetting of the inner wall of the rough holes. When the copper-clad resin board after the first water rinse is immersed in water-based conductive carbon material, the water-based conductive carbon material, using water and dispersant as the dispersion medium, can quickly spread and penetrate on the pre-wetted inner wall of the rough holes, which is conducive to forming a dense and uniform pure carbon-based conductive layer on the inner wall of the rough holes. Furthermore, due to the good water solubility of the inorganic small molecule oxidation cleaning solution, fewer water rinses are needed to effectively remove the inorganic small molecule oxidation cleaning solution remaining on the inner wall of the rough holes, further reducing the amount of water rinse waste liquid generated.

[0043] In one embodiment, the copper-clad resin board after roughening and cleaning the hole walls is rinsed once for 10s-40s with deionized water with a conductivity of <10μs / cm and a temperature of 10℃-60℃ to quickly and thoroughly remove the inorganic small molecule oxidation cleaning liquid, resin impurities and metal impurities remaining on the inner wall of the rough holes.

[0044] In one embodiment, the number of water washes is ≤3, to ensure that the inorganic small molecule oxidizing cleaning liquid, resin impurities and metal impurities remaining on the inner wall of the coarse pores can be effectively removed with fewer water washes.

[0045] In one embodiment, a single wash can be performed by any one of soaking, agitation, or spraying.

[0046] In one embodiment, the water washing method is a spray method, with a spray angle of 30°-90°, a spray flow rate of 0.5m / s-10m / s, and a spray frequency of 1-3 times. This ensures that fewer spray times are needed to effectively remove the inorganic small molecule oxidizing cleaning liquid, resin impurities, and metal impurities remaining on the inner wall of the coarse pores, providing a better adhesion substrate for subsequent water-based conductive carbon materials.

[0047] S104. The copper-clad resin board after one water wash is immersed in water-based conductive carbon material to form a pure carbon-based conductive layer in the corresponding coarse pores; wherein, by mass parts, the water-based conductive carbon slurry is composed of 0.01-25 parts conductive carbon material, 70-98.5 parts water and 0.01-3 parts dispersant.

[0048] It should be noted that since hole wall roughening is a common pretreatment method for circuit boards, some researchers have attempted to combine the water-soluble graphene-calcium carbonate slurry (patent CN117377234A) and the water-soluble nano-silver solution (patent CN106653141B) into conventional hole wall roughening operations. However, because traditional conductive carbon slurries are generally doped with calcium and silver ions, the dispersion of calcium and silver ions with conductive carbon particles is poor, leading to agglomeration. This makes it impossible to form a uniform, dense, and complete carbon-based metal conductive layer within the hole wall. The agglomeration problem is particularly severe when the size of the conductive carbon particles is smaller. Furthermore, the doped calcium and silver ions have poor adhesion to the hole wall and are costly, resulting in the carbon-based metal conductive layer being prone to detachment and high production costs.

[0049] To address the aforementioned issues, some scholars have attempted to incorporate technologies such as ultrasound during immersion, but this requires additional ultrasound equipment, leading to high costs. Alternatively, they have tried introducing various surfactants, such as the simultaneous use of wetting agents, penetrants, dispersants, polymeric barrier agents, and thixotropic agents in patent CN106653141B. However, this results in a more complex composition of the washing wastewater, making it more difficult to treat.

[0050] Therefore, in this disclosure, by setting the aqueous conductive carbon slurry to consist of 0.01-25 parts conductive carbon material, 70-98.5 parts water, and 0.01-3 parts dispersant, the solid content of the aqueous conductive carbon slurry is ensured to be between 0.01% and 15%, ensuring good fluidity. This allows the aqueous conductive carbon slurry to flow, spread, and penetrate within the coarse pores, facilitating the formation of a uniform, dense, and complete pure carbon-based conductive layer within the coarse pores. Furthermore, the solid content of the aqueous conductive carbon slurry is between 0.05% and 10%.

[0051] It is also understood that, since the water-based conductive carbon material includes at least one of carbon black, nano-graphite, graphene, and carbon nanotubes, this ensures that the water-based conductive carbon material of this disclosure is not doped with metal ions, i.e., it is a pure carbon water-based conductive carbon material. On the one hand, this reduces the cost of traditional water-based conductive carbon materials. On the other hand, because the pure carbon water-based conductive carbon material has good fluidity, it can quickly and comprehensively spread and penetrate into the inner wall of the coarse pores. In particular, in conjunction with the concave and convex adsorption surface of the inner wall of the coarse pores, the concave and convex adsorption surface can better adsorb the water-based conductive carbon material of this disclosure, thereby forming a uniform, dense, complete, continuous, and high-strength pure carbon material on the inner wall of the coarse pores. The carbon-based conductive layer; on the other hand, because the inner wall of the coarse pores can be well pre-wetted after a single water wash, the surface energy of the inner wall of the coarse pores is reduced, ensuring that the water-based conductive carbon material of this disclosure can be quickly and completely covered on the inner wall of the coarse pores with a small amount of dispersant. This is conducive to forming a complete, uniform, dense, and continuous high-strength pure carbon-based conductive layer on the inner wall of the coarse pores. No auxiliary ultrasonic equipment or multiple different surfactants are required, thereby reducing production costs and operating procedures, and improving production efficiency. It also avoids the problem of complex composition of the water washing waste liquid, thereby reducing the difficulty of water washing waste liquid treatment.

[0052] It is also understandable that, since the formed pure carbon-based conductive layer has no metal doping, it has high chemical stability and does not release impurity ions into the electroplating solution, ensuring the purity of the electroplating solution and maintaining stable deposition efficiency. This is conducive to forming a complete, uniform, dense, continuous, and high-strength metal coating on the pure carbon-based conductive layer.

[0053] In one embodiment, when the waterborne conductive carbon material is carbon black, the solid content of the waterborne conductive carbon slurry is 1%-4%.

[0054] In one embodiment, when the aqueous conductive carbon material is nano-graphite, the solid content of the aqueous conductive carbon slurry is 2%-10%.

[0055] In one embodiment, when the aqueous conductive carbon material is graphene, the solid content of the aqueous conductive carbon slurry is 0.05%-0.5%.

[0056] In one embodiment, when the aqueous conductive carbon material is carbon nanotubes, the solid content of the aqueous conductive carbon slurry is 0.02%-0.2%.

[0057] In one embodiment, the dispersant includes at least one of capped propylene glycol block polyether, modified polyacrylic acid, and sodium lignosulfonate.

[0058] In one embodiment, the particle size of the aqueous conductive carbon slurry ranges from 10 nm to 3000 nm. This ensures that the particle size of the aqueous conductive carbon slurry (10 nm to 3000 nm) can form good adsorption and intercalation with the uneven adsorption surface with a surface roughness of 0.3 μm to 0.6 μm. This ensures the formation of a complete, uniform, dense, and continuous high-strength pure carbon-based conductive layer on the inner wall of the coarse pores, providing a good adhesion substrate for subsequent metal plating. It is worth mentioning that because the aqueous conductive carbon slurry with a particle size of 10 nm to 3000 nm can stack on the inner wall of the coarse pores to form a porous pure carbon-based conductive layer, it ensures that metal ions can be well deposited and embedded within the pores of the pure carbon-based conductive layer during electroplating, thereby improving the connection strength between the pure carbon-based conductive layer and the metal plating layer.

[0059] In one embodiment, the preparation method of the aqueous conductive carbon slurry includes the following specific steps: First, the aqueous conductive carbon material, water and dispersant are mixed to obtain a primary mixture. Then, the primary mixture is ball-milled to obtain an aqueous conductive carbon slurry with good dispersibility and a particle size range of 10nm-3000nm.

[0060] In one embodiment, when mixing the aqueous conductive carbon material, water, and dispersant, the stirring speed is 300 r / min-5000 r / min and the stirring time is 20 min-30 min, so as to achieve the initial dispersion of the aqueous conductive carbon material, water, and dispersant, which is beneficial to the subsequent ball milling to obtain an aqueous conductive carbon slurry with good dispersibility and a particle size range of 10 nm-3000 nm.

[0061] In one embodiment, the ball milling operation conditions are: a rotation speed of 3000 r / min to 5000 r / min and a time of 2 h to 12 h.

[0062] In one embodiment, the soaking conditions are: temperature 25℃-35℃, time 20s-60s, and soaking method is soaking and shaking, to ensure that the water-based conductive carbon material can fully enter the inner wall of the coarse pores and completely cover the inner wall of the coarse pores.

[0063] In one embodiment, the specific steps of soaking and shaking are as follows: the plate is placed vertically and shaken left and right with an amplitude of 5cm-10cm and a frequency of 20 times / min-60 times / min, so as to ensure that the water-based conductive carbon material can quickly and fully enter the inner wall of the coarse pores and completely cover the inner wall of the coarse pores.

[0064] S105. The copper-clad resin board after soaking is dried once, so that the water-based conductive carbon slurry is dried and cured at a lower temperature during the first drying to form a pure carbon-based conductive layer, so that the pure carbon-based conductive layer can be firmly adsorbed into the inner wall of the coarse pores.

[0065] In one embodiment, the thickness of the pure carbon-based conductive layer is 20nm-100nm.

[0066] It should be noted that traditional non-pure carbon-based conductive layers have low porosity due to the presence of metal, which is not conducive to heat penetration. As a result, the drying temperature of traditional non-pure carbon-based conductive layers is usually high, such as above 80°C. However, high drying temperatures can easily cause deformation or yellowing of copper-clad resin boards, especially for flexible resin copper-clad boards, where this is now more pronounced.

[0067] Therefore, in one embodiment, by utilizing the high porosity of the pure carbon-based conductive layer, the heat from the water-based conductive carbon slurry can quickly penetrate into the interior of the pure carbon-based conductive layer when the temperature of the first drying is 50℃-80℃. This ensures that the water-based conductive carbon slurry can be completely dried and cured in 20s-80s, forming a complete, uniform, dense, and continuous high-strength pure carbon-based conductive layer. It also reduces the probability of deformation or yellowing of the copper-clad resin board and lowers the energy consumption of the first drying.

[0068] In one embodiment, the drying temperature is 50°C-60°C and the drying time is 20s-60s.

[0069] In one embodiment, the specific steps of the drying process are: wind speed of 5m / s-10m / s and temperature of 25-70℃, so as to achieve rapid and low-temperature drying and curing of water-based conductive carbon slurry.

[0070] In one embodiment, steps S104 and S106 are repeated 1 to 3 times.

[0071] S106. Micro-etching is performed on the copper-clad resin board after the first drying. On the one hand, it removes carbon-based residues and excess water-based conductive carbon material adhering to the surface of the outer copper-clad resin board and in the coarse pores. On the other hand, the micro-etching step can slightly etch the outer copper layer of the copper-clad resin board, thereby providing a good adhesion substrate for the electroplating operation to deposit copper metal. This ensures that a uniform, dense and complete metal plating layer is deposited on the pure carbon-based conductive layer to better meet the requirements of high electrical performance printed circuit boards.

[0072] In one embodiment, the copper-clad resin board after one drying is sprayed or soaked in a micro-etching solution at a temperature of 10℃-30℃ for 40s-80s.

[0073] In one embodiment, the micro-etching solution is an acidic buffered persulfate micro-etching solution.

[0074] In one embodiment, the acid-buffered persulfate microetching solution comprises, by mass concentration, 2%-6% acid solvent, 2%-6% persulfate, 0.1%-0.8% buffer, and the balance being water.

[0075] In one embodiment, the acid solvent is sulfuric acid.

[0076] In one embodiment, the persulfate is sodium persulfate.

[0077] In one embodiment, the buffer is glacial acetic acid.

[0078] In one embodiment, the steps of the oscillating soaking method are as follows: the plate is placed vertically and oscillated left and right with an amplitude of 5cm-10cm and a frequency of 20 times / min-60 times / min.

[0079] In one embodiment, after the step of micro-etching the copper-clad resin board after drying and before the step of electroplating the micro-etched copper-clad resin board, the following steps are further included: performing a second water wash on the micro-etched copper-clad resin board to effectively remove residual micro-etching solution and copper ions; then, performing a second drying on the copper-clad resin board after the second water wash to remove moisture and facilitate entry into the electroplating process.

[0080] In one embodiment, the conditions for the secondary water washing are: water with a conductivity of <10 μs / cm, a temperature of 10℃-60℃, a washing time of 10s-40s, and a spray method. Further, the spray angle is 30°-90°, the spray velocity is 0.5m / s-10m / s, and the number of sprays is 1-3 times.

[0081] In one embodiment, the conditions for secondary drying are: temperature of 50°C-80°C and time of 50s-150s.

[0082] S107. Electroplating is performed on the micro-etched copper-clad resin board to form a metal plating layer on the pure carbon-based conductive layer, thereby obtaining a carbon-based hole-metallized copper-clad resin board.

[0083] In one embodiment, when electroplating the micro-etched copper-clad resin board with an electroplating solution, the electroplating solution is set at 1 A / dm³. 2 -4A / dm 2 At current densities, metal coatings with thicknesses of 5µm to 30µm can be formed.

[0084] In one embodiment, the electroplating solution includes an electroplating base, an electroplating brightener, and water. The added electroplating brightener helps to improve the uniformity and smoothness of the metal coating.

[0085] In one embodiment, the electroplating main solution comprises, by mass concentration, 200 g / L-250 g / L of acid and 60 g / L-70 g / L of copper salt, and 15 g / L-25 g / L of electroplating brightener.

[0086] In one embodiment, the electroplating brightener is a sulfuric acid-copper sulfate type electroplating brightener. The sulfuric acid-copper sulfate type electroplating brightener is the commercially available type 830 sulfuric acid-copper sulfate type electroplating brightener.

[0087] The aforementioned carbon-based hole metallization process uses an inorganic small-molecule oxide cleaning solution to roughen and clean the hole walls of the copper-clad resin board after drilling. This single-step hole wall roughening and cleaning process achieves both cleaning and roughening of the copper-clad resin board, eliminating the need for high-molecular-weight organic cleaning agents and multiple cleaning adjustment steps. This simplifies the process, improves production efficiency, and reduces the amount of cleaning agent used and the volume of washing wastewater, thus reducing the amount of washing wastewater to be treated. Especially when combined with a single water wash and immersion in a pure carbon-based water-based conductive carbon material, it ensures that fewer single water washes are needed to effectively remove residues. The inorganic small-molecule oxidizing cleaning solution on the inner wall of the coarse pores further reduces the amount of water washing waste liquid generated. Furthermore, the high porosity of the formed pure carbon-based conductive layer ensures that the copper-clad resin board, after immersion, dries and solidifies at a lower primary drying temperature to form the pure carbon-based conductive layer. This not only reduces the energy consumption of the primary drying process but also decreases the probability of deformation or yellowing of the copper-clad resin board. It also provides a better substrate for subsequent electroplating of metal ions, allowing them to be uniformly deposited within the pores of the pure carbon-based conductive layer. This ensures a uniform, dense, and complete metal plating layer, better meeting the requirements of high-performance printed circuit boards.

[0088] This disclosure also provides a printed circuit board, which is prepared using the carbon-based via metallization process without pre-adjustment described in any of the above embodiments, to ensure that the prepared printed circuit board has excellent conductivity, so as to better meet the requirements of high electrical performance printed circuit boards.

[0089] In one embodiment, a plurality of through holes are formed in the printed circuit board, and each through hole is provided with a metal plating layer and a pure carbon-based conductive layer in sequence from the outside to the inside, so as to ensure the high conductivity and high connectivity of the through hole.

[0090] In one embodiment, a pure carbon-based conductive layer is embedded in the inner wall of the through hole, and a metal plating layer is embedded in the pure carbon-based conductive layer, thereby ensuring high connection strength and high conductivity between the pure carbon-based conductive layer and the inner wall of the through hole.

[0091] Compared with the prior art, this disclosure has at least the following advantages: 1) Due to the water solubility and strong oxidizing properties of inorganic small molecule oxidizing cleaning solution, when used to roughen and clean the hole walls of the copper-clad resin board after drilling, the strong oxidizing inorganic groups of the inorganic small molecule oxidizing cleaning solution can oxidize and hydrolyze the resin molecular structure and organic pollutant molecular structure within the through-hole, promoting the spontaneous formation of polar functional groups at the fracture ends of the through-hole inner wall. This creates an uneven adsorption surface on the inner wall of the coarse hole, thus forming adsorption sites for polar functional groups on the inner wall of the coarse hole, which is beneficial for improving the adsorption capacity of the coarse hole. The hydrophilicity of the wall surface allows the water-based conductive carbon material to spread and penetrate quickly and fully onto the surface of the coarse pore inner wall, facilitating the formation of a dense and uniform pure carbon-based conductive layer. Furthermore, the adsorption sites of polar functional groups formed on the coarse pore inner wall enable strong hydrogen bond adsorption between the coarse pore inner wall and the water-based conductive carbon material, thereby increasing the connection strength between the coarse pore inner wall and the pure carbon-based conductive layer. It also increases the surface roughness of the coarse pore inner wall, achieving mechanical interlocking between the coarse pore inner wall and the water-based conductive carbon material, further enhancing the connection strength. In addition, the added inorganic small-molecule oxidation cleaning solution effectively removes oil stains and resin debris from the coarse pore inner wall. This eliminates the need for high-molecular-weight organic cleaning agents and multiple cleaning adjustment steps; a single-step pore wall roughening cleaning step achieves both cleaning and roughening effects on the copper-clad resin board. This simplifies the operation process, improves production efficiency, and reduces the amount of cleaning agent used and the volume of washing wastewater, thus reducing the amount of washing wastewater to be treated.

[0092] 2) By performing a single water wash on the copper-clad resin board after roughening and cleaning the pore walls, impurities or inorganic small-molecule oxidation cleaning solution remaining on the inner wall of the coarse pores are effectively removed. On the one hand, this allows the adsorption sites of polar functional groups on the inner wall of the coarse pores to be fully exposed, increasing the contact area between the inner wall of the coarse pores and the water-based conductive carbon material. On the other hand, it provides good pre-wetting of the inner wall of the coarse pores. When the copper-clad resin board after the single water wash is immersed in the water-based conductive carbon material, the water-based conductive carbon material, using water and dispersant as the dispersion medium, can quickly spread and penetrate on the pre-wetted inner wall of the coarse pores, which is conducive to forming a dense and uniform pure carbon-based conductive layer on the inner wall of the coarse pores. Furthermore, due to the good water solubility of the inorganic small-molecule oxidation cleaning solution, fewer water washes are needed to effectively remove the inorganic small-molecule oxidation cleaning solution remaining on the inner wall of the coarse pores, further reducing the amount of water wash waste liquid generated.

[0093] 3) The copper-clad resin board after soaking is dried once, so that the water-based conductive carbon paste is dried and cured at a lower temperature to form a pure carbon-based conductive layer, which can be firmly adsorbed into the inner wall of the coarse pores. Then, the copper-clad resin board after the first drying is micro-etched. On the one hand, the carbon-based residues adhering to the surface of the outer copper-clad resin board and the excess water-based conductive carbon material in the coarse pores are removed. On the other hand, the micro-etching step can slightly etch the outer copper layer of the copper-clad resin board, thereby providing a good adhesion substrate for the electroplating operation to deposit copper metal. This ensures that a uniform, dense and complete metal plating layer is deposited on the pure carbon-based conductive layer to better meet the requirements of high electrical performance printed circuit boards.

[0094] The following are some specific examples. When %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively list all possible scenarios, and unless otherwise specified, the materials used in the examples are commercially available.

[0095] 1) Test materials ①Test materials: FR4 porous board (through hole diameter is 0.1mm-4mm), polyamide-imide resin porous board (through hole diameter is 0.05mm-0.2mm), flexible perforated board (through hole diameter is 0.1mm).

[0096] ②Inorganic small molecule oxidizing cleaning solution: Prepared by mass concentration, sulfuric acid 4%, hydrogen peroxide 6%, ethylene glycol stabilizer 1%, and the balance is water.

[0097] ③ Micro-etching solution: Prepared by mass concentration, with 4% sulfuric acid, 4% sodium persulfate, 0.5% glacial acetic acid, and the remainder being water.

[0098] ④ Electroplating solution: Prepared by mass concentration. The main electroplating solution consists of 230 g / L sulfuric acid and 65 g / L copper sulfate; 20 g / L of commercial 830 type sulfuric acid-copper sulfate electroplating brightener, with the remainder being water.

[0099] Electroplating anode: The anode material used is commercially available phosphorus copper plate.

[0100] ⑤ The formulation of the water-based conductive carbon paste is shown in Table 1: Table 1 Formulation of Waterborne Conductive Carbon Paste 2) Main testing equipment: Micro-etching equipment (manual beaker test), water washing equipment (sprayer), conductive material covering (manual beaker test) and small sprayer (self-made), Zhaoxin rectifier RXN305D, FLUKE digital multimeter F15, etc.

[0101] ① Zhaoxin rectifier RXN305D, such as Figure 6 As shown.

[0102] ②FLUKE digital multimeter F15, such as Figure 7 As shown.

[0103] ③ Sunny BK200M metallurgical microscope, such as Figure 8 As shown.

[0104] ④ Zhixing MP-2A metallographic polishing machine, such as Figure 9 As shown.

[0105] 3) Test Items ① Resistance test The purpose of resistance testing is to test the quality of interlayer conductivity bonding of carbon materials. The shape of the multi-hole test plate is as follows: Figure 10 As shown, a multi-hole test board with interconnected holes on both sides is designed on a double-sided FCCL. The resistance at both ends of the interconnected multi-hole test board is measured. Test criteria: a higher resistance indicates a less reliable connection; generally, the resistance value should be less than or equal to 50 ohms. The resistance test uses a multi-hole test board. The purpose of the resistance test is to assess the continuity and capability of the interlayer circuitry. The resistance test is repeated three times.

[0106] ②Metallographic analysis After the electroplating process is completed, a grinding and polishing machine is used to analyze the cross-section of the inner wall of the hole to observe the circuit connection between the layers inside the hole.

[0107] ③ Thermal shock test Thermal shock test, referring to standard ICP-TM650, using lead-tin furnace immersion, 288℃, 10s, 3 times, and then metallographic observation of interlayer separation. Example 1

[0108] The water-based conductive carbon paste was tested on an FR4 rigid board and was found to be a self-made water-based conductive carbon black paste.

[0109] (1) The process steps and process conditions are shown in Table 2 below: Table 2 (2) Aqueous conductive carbon slurry: Add 0.1 kg of commercial dispersant (sodium lignosulfonate) and 0.29 kg of high conductive carbon black (model Yihuilong T-60) to 10 kg of aqueous solution and stir (500 / min) for 30 min to obtain a primary mixture. Then, after grinding with a nanoball mill (speed of 3000 r / min) for 4 h, a stable aqueous conductive carbon black slurry with a particle size range of 15 nm-50 nm and a solid content of 3% is prepared. Example 2

[0110] The test was conducted using a rigid porous plate, and the conductive material was a self-made water-based conductive graphite slurry.

[0111] (1) The process steps and process conditions are shown in Table 3 below: Table 3 (2) Aqueous conductive carbon slurry: Add 0.05 kg of commercial dispersant (modified polyacrylic acid) and 2.95 kg of ultrapure conductive graphite (model LG-6301) to 10 kg of aqueous solution and stir (3000 r / min) for 30 min to obtain a primary mixture. Then, after grinding with a nanoball mill (speed of 500 r / min) for 8 h, a stable aqueous conductive graphite slurry with a particle size range of 50 nm-600 nm and a solid content of 3% is prepared. Example 3

[0112] The test was conducted using a rigid porous plate, and the conductive material was a self-made water-based conductive carbon nanotube slurry.

[0113] (1) The process steps and process conditions are shown in Table 4 below: Table 4 (2) Aqueous conductive carbon slurry: 0.05 kg of commercial dispersant (terminated propylene glycol block polyether) and 2.95 kg of carbon nanotubes (model Deco Island Gold CNT204) were added to 10 kg of aqueous solution and ultrasonicated for 1 h to obtain a primary mixture. After grinding with a nanoball mill (speed of 4000 r / min) for 6 h, a stable aqueous conductive carbon slurry with a particle size range of 20 nm-120 nm and a solid content of 3% was prepared. Example 4

[0114] The test was conducted using a rigid porous plate, and the conductive material was a self-made water-based conductive graphene slurry.

[0115] (1) The process steps and process conditions are shown in Table 5 below: Table 5 (2) Aqueous conductive carbon slurry: Add 0.01 kg of commercial dispersant (terminated propylene glycol block polyether) and 0.19 kg of sheet graphene (model LG5301) to 10 kg of aqueous solution and stir (500 r / min) for 30 min to obtain a primary mixture. Then, grind it in a nanoball mill (speed 5000 r / min) and disperse it for 8 h to prepare a stable aqueous conductive carbon black slurry with a particle size range of 5 nm-100 nm and a solid content of 0.2%. Example 5

[0116] Testing of polyamide-imide (PI) flexible sheets: self-made conductive carbon black solution was used as the conductive material.

[0117] (1) The process steps and process conditions are shown in Table 6 below: Table 6 (2) Aqueous conductive carbon slurry: Add 0.1 kg of commercial dispersant (sodium lignosulfonate) and 0.29 kg of high conductive carbon black (model Yihuilong T-60) to 10 kg of aqueous solution and stir (500 / min) for 30 min to obtain a primary mixture. Then, after grinding with a nanoball mill (speed of 3000 r / min) for 4 h, a stable aqueous conductive carbon black slurry with a particle size range of 15 nm-50 nm and a solid content of 3% is prepared. Example 6

[0118] The test board was a flexible polyamide-imide (PI) board, and the water-based graphite conductive paste was self-made.

[0119] (1) The process steps and process conditions are shown in Table 7 below: Table 7 (2) The preparation method of the water-based conductive carbon slurry is the same as that in Example 5. Example 7

[0120] The test was conducted using phenolic resin porous plates, and the conductive material was a self-made water-based conductive graphite slurry. (1) The process steps and process conditions are shown in Table 8 below: Table 8 (2) Aqueous conductive carbon slurry: Aqueous conductive carbon slurry: Add 0.3 kg of commercial dispersant (sodium lignosulfonate) and 0.37 kg of high conductive carbon black (model Yihuilong T-60) to 10 kg of aqueous solution and stir (500 / min) for 30 min to obtain a primary mixture. Then, after grinding with a nanoball mill (speed of 3000 r / min) for 4 h, a stable aqueous conductive carbon black slurry with a particle size range of 15 nm-50 nm and a solid content of 4% is prepared.

[0121] Comparative Example 1 Board material: FR4 hardboard with perforated surface, after drilling and degumming.

[0122] (1) Process flow: It is manufactured using a process that includes cleaning and adjustments, such as... Figure 1 As shown: The process steps and process conditions are shown in Table 9 below: Table 9 (2) Aqueous conductive carbon slurry: Aqueous conductive carbon slurry: Add 0.1 kg of commercial dispersant (sodium lignosulfonate) and 0.29 kg of high conductive carbon black (model Yihuilong T-60) to 10 kg of aqueous solution and stir (500 / min) for 30 min to obtain a primary mixture. Then, after grinding with a nanoball mill (speed of 3000 r / min) for 4 h, a stable aqueous conductive carbon black slurry with a particle size range of 15 nm-50 nm and a solid content of 3% is prepared.

[0123] (3) Cleaning and pore-forming materials: mass concentration meter, cationic polyacrylamide 0.5%, sodium carbonate 2%, EDTA2Na 0.5%, ethylenediaminetetramethylenephosphonic acid 0.8%, the balance is prepared by deionized water.

[0124] The carbon-based porous metallized copper-clad resin boards prepared in each embodiment and Comparative Example 1 were subjected to resistance testing, and the experimental data in Table 10 below were obtained. Table 10 Summary of Resistances As can be seen from Table 10 above, the resistance of the carbon-based through-hole metallized copper-clad resin boards prepared by the combination of hole wall roughening and cleaning, one-time water washing, and water-based conductive carbon slurry immersion in Examples 1-7 is not significantly different from the resistance of the carbon-based through-hole metallized copper-clad resin boards prepared by Comparative Example 1 with the cleaning and adjustment process. Among them, the resistance of the carbon-based through-hole metallized copper-clad resin boards of Examples 2, 5, and 7 is significantly better.

[0125] Metallographic analysis and thermal shock testing were performed on the carbon-based porous metallized copper-clad resin boards prepared in each embodiment and Comparative Example 1. For details, please refer to [link to relevant documentation]. Figure 11-24 .from Figure 11-24 It can be seen that the conductivity, water-based conductive carbon paste coverage, and electroplating coverage of the carbon-based through-hole metallized copper-clad resin boards in Examples 1-7 are not significantly different from those in Comparative Example 1.

[0126] The experimental data in Table 11 were obtained by statistically analyzing the amount of water used for washing, the amount of waste water, the composition of the waste water, and the amount of detergent used in the preparation process of each embodiment and Comparative Example 1.

[0127] Table 11 Summary Table As can be seen from Table 11 above, since all Examples 1-7 used inorganic small molecule oxidation cleaning solution to roughen and clean the hole walls of the copper-clad resin board after drilling, it ensured that Examples 1-7 could complete the metallization process of carbon-based holes with a smaller amount of inorganic small molecule oxidation cleaning solution. This effectively reduced the large amount of cleaning solution used and the amount of water washing waste liquid to be treated. Moreover, the water washing waste liquid has relatively few components, making it easier to treat. Thus, the comprehensive indicators of Examples 1-7 are significantly better than those of Comparative Example 1, with the comprehensive indicators of Example 7 being better.

[0128] Furthermore, as can be seen from the single-drying process of Examples 1-7 and Comparative Example 1, by using the inorganic small-molecule oxidation cleaning liquid in combination with the water-based conductive carbon slurry with a particle size range of 10nm-3000nm, the pure carbon-based conductive layer formed in Examples 1-7 has a high porosity. This ensures that the water-based conductive carbon slurry can be fully dried and cured using a lower single-drying temperature, which not only reduces the energy consumption of the single-drying process but also reduces the deformation rate or yellowing rate of the copper-clad resin board. The energy consumption, deformation rate, and yellowing rate of the single-drying process in Examples 1-7 are significantly lower than those in Comparative Example 1. In addition, Examples 1-7 can achieve rapid and comprehensive coverage of the coarse-pore inner wall of the water-based conductive carbon material using fewer soaking cycles.

[0129] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A carbon-based pore metallization process without pre-adjustment, characterized in that, Includes the following steps: A drilling operation is performed on the copper-clad resin board; wherein the copper-clad resin board has multiple through holes. The copper-clad resin board after drilling was roughened and cleaned with an inorganic small molecule oxidation cleaning solution to form multiple coarse holes. The copper-clad resin board, after roughening and cleaning the hole walls, is then rinsed with water once. The copper-clad resin board after a single water wash is immersed in an aqueous conductive carbon material to form a pure carbon-based conductive layer in the corresponding coarse pores; wherein, by mass parts, the aqueous conductive carbon slurry is composed of 0.01-25 parts conductive carbon material, 70-98.5 parts water and 0.01-3 parts dispersant. The conductive carbon material includes at least one of carbon black, nano-graphite, graphene, and carbon nanotubes. The copper-clad resin board after soaking is dried once. Micro-etching is performed on the copper-clad resin board after it has been dried once. The copper-clad resin board after micro-etching is subjected to electroplating to form a metal plating layer on the pure carbon-based conductive layer, thereby obtaining a carbon-based metallized copper-clad resin board.

2. The carbon-based pore metallization process without pre-adjustment according to claim 1, characterized in that, The conditions for roughening and cleaning the pore wall are: temperature 30℃-50℃ and time 30s-80s.

3. The carbon-based pore metallization process without pre-adjustment according to claim 1, characterized in that, The inorganic small molecule oxidizing cleaning solution is an acidic inorganic oxidizing cleaning solution, which includes one of the following: sulfuric acid-hydrogen peroxide mixture, sulfuric acid-persulfate mixture, fluorosulfonic acid-hydrogen peroxide mixture, sulfuric acid-potassium permanganate mixture, sulfuric acid-potassium dichromate mixture, and sulfuric acid-sodium dichromate mixture; or... The inorganic small molecule oxidizing cleaning solution is an alkaline system inorganic oxidizing cleaning solution, which includes at least one of sodium hydroxide-potassium permanganate mixture, sodium hydroxide-sodium permanganate mixture, sodium hypochlorite-sodium hydroxide mixture, and sodium hypochlorite-potassium hydroxide mixture.

4. The carbon-based pore metallization process without pre-adjustment according to claim 1, characterized in that, The particle size range of the aqueous conductive carbon slurry is 10nm-3000nm.

5. The carbon-based pore metallization process without pre-adjustment according to claim 1, characterized in that, The dispersant includes at least one of capped propylene glycol block polyether, modified polyacrylic acid, and sodium lignosulfonate.

6. The carbon-based pore metallization process without pre-adjustment according to claim 1, characterized in that, The copper-clad resin board, after roughening and cleaning the hole walls, is rinsed once for 10s-40s with deionized water with a conductivity of <10μs / cm and a temperature of 10℃-60℃.

7. The carbon-based pore metallization process without pre-adjustment according to claim 1, characterized in that, The soaking conditions are: temperature 25℃-35℃, time 20s-60s, and soaking method is soaking and shaking.

8. The carbon-based pore metallization process without pre-adjustment according to claim 1, characterized in that, The temperature for the first drying cycle is 50℃-80℃; the time is 20s-80s.

9. The carbon-based pore metallization process without pre-adjustment according to claim 1, characterized in that, After the step of micro-etching the copper-clad resin board after drying, and before the step of electroplating the micro-etched copper-clad resin board, the following steps are also included: The copper-clad resin board after micro-etching is then subjected to a second water wash. The copper-clad resin board, after being washed twice, is then dried a second time.

10. A printed circuit board, characterized in that, It is prepared using the carbon-based pore metallization process without pre-adjustment as described in any one of claims 1-9.

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