A method for enhancing the interfacial bonding between metal and insulating substrate and its application

Abstract

This invention discloses a method for enhancing the interfacial bonding force between a metal and an insulating substrate. The substrate includes a surface and a porous structure recessed on the surface. The method comprises: (1) pretreating the surface and / or porous structure of the insulating substrate; (2) coating the prepared graphene dispersion onto the charged surface and / or porous structure of the insulating substrate in step (1), and drying to form a conductive layer suitable for metal electroplating; (3) the graphene in the conductive layer forming a physically interpenetrating network structure with the electroplated metal. The insulating substrate treated by the method for enhancing interfacial bonding force achieves a firm connection with the metal using graphene as the bonding medium. Furthermore, depending on the variation of the graphene treatment method, the conductive layer also possesses the flexibility of micromorphology and adjustable position, making it suitable for widespread use.

Description

Technical Field

[0001] This invention belongs to the field of electroplating technology, specifically, it relates to a method for enhancing the cross-sectional bonding force between metal and insulating substrate and its application. Background Art

[0002] Printed Circuit Boards (PCBs) are the most important interconnects for electronic components, often referred to as the "mother of electronic systems." Their manufacturing technology largely reflects the development level of the electronics industry. Hole metallization, the process of creating a metal layer on the walls of insulating holes, is a crucial step in PCB manufacturing. This metal layer needs to possess excellent conductivity to achieve electrical interconnections between PCB layers, and also needs sufficient bonding strength with the insulating substrate to withstand the mechanical and thermal shocks experienced during PCB manufacturing and use. In recent years, with the development of PCBs towards higher frequencies and higher speeds (such as in 5G products), PCBs also require excellent thermal conductivity. Therefore, achieving PCB hole metallization processes with high conductivity, thermal conductivity, and excellent interfacial bonding strength is one of the key research trends.

[0003] Traditional methods for PCB hole metallization involve first depositing a very thin layer of copper as a conductive interface layer on the insulating substrate inside the PCB hole using chemical copper plating, followed by electroplating to thicken the copper layer and achieve hole metallization. Chemical copper plating has advantages such as simplicity and ease of operation, but it also has the following disadvantages: 1) Significant environmental pollution, as formaldehyde used is a carcinogen; 2) Difficult wastewater treatment, as the complexing agents in the plating solution require specialized complex-breaking treatment to reduce their impact on wastewater treatment, placing significant pressure on wastewater treatment systems; 3) Poor stability and short lifespan of the chemical copper plating solution; 4) Long operation process (process flow diagram shown in...). Figure 1 As shown), the production cost is high and the efficiency is low; 5) the interface bonding strength with the low surface energy substrate is poor, and the bonding force between the chemically plated copper layer and the high-frequency PCB polytetrafluoroethylene material with extremely low surface tension is extremely poor.

[0004] Graphene is a two-dimensional carbon nanomaterial composed of carbon atoms arranged in a hexagonal honeycomb lattice with sp2 hybrid orbitals. This unique two-dimensional structure endows graphene with outstanding electronic effects, superior thermal properties, optical properties, and excellent mechanical properties. The graphene pore metallization process—a direct electroplating technology using graphene layers as the conductive dielectric layer—has attracted widespread attention. Due to graphene's extremely high electrical and thermal conductivity, the graphene pore metallization process has the potential to overcome the shortcomings of traditional black-pore direct electroplating technology in terms of insufficient conductivity and heat dissipation, thereby greatly promoting the development of the direct electroplating field and potentially compensating for the deficiencies of traditional chemical copper plating processes.

[0005] Chinese Patent Application No. 201811009256.3 discloses a graphene metallization solution, its preparation method, and its application. The graphene metallization solution is prepared from the following raw materials in the following mass percentages: 0.5-5.0% graphene or graphene oxide; 1-3% film-forming agent; 1-6% dispersant; 0.01-0.2% anionic surfactant; an alkaline solution adjusted to pH 4-14; and the balance being water. This invention uses low-concentration graphene or low-oxidation-degree graphene oxide as the basic conductive material. Through simple and efficient pretreatment, the graphene metallization solution can be effectively adsorbed onto the surface or pore walls of a non-metallic substrate. After simple drying, copper can be directly electroplated. However, this invention does not address the key performance characteristic of metallized products—interfacial bonding strength and its improvement methods, limiting the applicability of this application.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a method and its application for enhancing the interfacial bonding force between metal and insulating substrate. The method involves coating a pretreated insulating substrate with a graphene dispersion to form a composite film structure with controllable thickness and morphology. The provided graphene dispersion contains a binding agent, which enhances the covalent bonding between the conductive layer and the electroplated metal during electroplating and simultaneously interacts with hydrogen bonds of the surface groups of the insulating substrate, greatly enhancing the bonding force between the conductive layer formed by the graphene dispersion and the insulating substrate. Furthermore, the graphene layer and the electroplated metal layer form an interpenetrating network structure, enhancing the interfacial bonding ability between graphene and the electroplated layer, further improving the good bonding performance and scratch resistance between the metallized layer and the insulating substrate.

[0008] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0009] This invention provides a method for enhancing the interfacial bonding force between a metal and an insulating substrate, wherein the substrate includes a surface and a porous structure recessed in the surface, comprising:

[0010] (1) Pretreatment of the surface and / or pore structure of the insulating substrate;

[0011] (2) The prepared graphene dispersion is coated onto the surface and / or pore structure of the insulating substrate that has been charged in step (1), and dried to form a conductive layer that can be electroplated with metal.

[0012] (3) The graphene in the conductive layer forms a physical interpenetrating network structure with the electroplated metal;

[0013] The graphene dispersion comprises water, graphene, a binding agent, and a water-soluble conductive polymer. The binding agent enhances the covalent bond between the conductive layer and the electroplated metal during electroplating and interacts with groups on the surface and / or porous structure of the pretreated insulating substrate.

[0014] In the above scheme, the insulating substrate includes, but is not limited to, epoxy resin glass cloth reinforcement materials, polyimide glass cloth reinforcement materials, polytetrafluoroethylene glass cloth reinforcement materials, polyimide films, acrylic films, hydrocarbon resins, etc. Based on the chemical composition and charge type of the substrate surface (e.g., epoxy glass cloth surface contains hydroxyl groups, imine surfaces contain amino groups), corresponding binding agents are added to the graphene solution. For example, binding agents containing sulfonic acid groups and amino groups can form hydrogen bond interactions with these groups, improving the interfacial energy between graphene and the substrate. Furthermore, these binding agents can also form covalent bonds with the electroplated metal, and the multilayer structure of graphene itself can form an interpenetrating network structure with the electroplated metal under certain physical processing methods and drying processes, enhancing the bonding ability between the two. Specifically, the binding agent performs non-covalent surface modification on graphene, resulting in π-π interactions between the binding agent and graphene. The functional groups in the binding agent improve the surface activity of graphene, allowing graphene to be uniformly dispersed in the dispersion system. The electroplating can be performed using conventional electroplating metals in the art, preferably copper.

[0015] According to the above method, the graphene dispersion further includes a water-soluble polymer, wherein the mass ratio of graphene to water-soluble polymer is 1:0 to 40, preferably 1:0.01 to 5; the water-soluble polymer is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, polyethylene glycol, polyacrylate, polymaleic anhydride, polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl sulfonic acid, polyvinylphosphonic acid, polyvinylamine, and polyvinylpyridine.

[0016] In the above scheme, the conjugated system formed between the additives, water-soluble conductive polymer, and graphene improves the compatibility with the subsequent composite with the water-soluble polymer. This maintains the properties of graphene within the formed conductive layer, enhances the conductivity of the conductive layer, and facilitates the formation of the electroplated metal layer. This application allows the graphene dispersion to be free of water-soluble polymers; therefore, the mass ratio of graphene to water-soluble polymers can be 1:0.

[0017] According to the above method, the graphene dispersion is prepared by the following method:

[0018] The binding agent and water-soluble conductive polymer were dissolved in deionized water, and then graphene was added to the modification solution. The graphene dispersion with graphene surface modification was obtained by physical treatment.

[0019] The physical method is selected from one or both of grinding and ultrasonic treatment;

[0020] Preferably, the method for preparing the graphene dispersion further includes: mixing the mixture obtained by physical treatment of graphene and binding agent with an aqueous solution of water-soluble polymer to obtain the graphene dispersion.

[0021] More preferably, the pH value of the graphene dispersion is 3 to 11.

[0022] In the above scheme, the binding agent and water-soluble conductive polymer are first dissolved into a modification solution before graphene is added. Compared with adding the binding agent and graphene to the solution simultaneously, this largely avoids the self-agglomeration effect of graphene, making it easier for the binding agent to form non-covalent bonds with the graphene surface, thereby improving the dispersibility of graphene in water. The surface-treated insulating material carries a negative or positive charge. Correspondingly, a pH adjuster known in the art is used to adjust the pH value of the graphene solution. When the pH range of the graphene dispersion is 3-11, a stronger electrostatic interaction can be formed between the graphene and the substrate.

[0023] According to the above method, the average number of graphene layers in the graphene dispersion is no more than 10, preferably 1 to 5 layers.

[0024] In the above scheme, the graphene is peeled off under physical action, so that the graphene in the dispersion keeps the interlayer open. This makes the surface of the coated and dried conductive layer have several interpenetrating gaps that can form with the electroplated metal, which greatly improves the bonding strength between the electroplated metal and the conductive layer.

[0025] According to the above method, the mass ratio of graphene, binding agent, and water-soluble conductive polymer is 1:0.05-20:0.01-20, preferably 1:0.1-3:0.05-3; the mass fraction of graphene in the graphene dispersion is 0.05-10%, preferably 0.1-5%, more preferably 5%; the binding agent is an oligomer with sulfonic acid groups, sulfonyl groups, or carboxyl groups, and its molecular weight ranges from 400 to 4000; the water-soluble conductive polymer is selected from one or more of water-soluble polyaniline, water-soluble polythiophene, and polyepoxychloropropane quaternary ammonium salt.

[0026] In the above scheme, the binding agent is selected from poly-2-acrylamide-2-methylpropanesulfonic acid, waterborne epoxy, waterborne polyurethane, etc.

[0027] According to the above method, the grinding speed is 100-5000 rpm, preferably 300-1000 rpm; the grinding time is 1 min-3 h, preferably 10 min-1 h.

[0028] According to the above method, the frequency of the ultrasound is 25-100kHz, preferably 40-75kHz; the duration of the ultrasound is 30min-24h, preferably 4-12h.

[0029] According to the above method, the grinding and ultrasonication are preferably performed simultaneously. When both are performed simultaneously, the running time of grinding and ultrasonication tends to be selected for the longer step. In some implementations, grinding can be stopped after the grinding time is completed and ultrasonication can continue.

[0030] According to the above method, in step (2), the drying process includes: drying temperature of 40 to 100°C and drying air velocity of 0.3 to 10 m / s.

[0031] In the above scheme, the drying can be carried out by a forced-air drying method.

[0032] According to the above method, in step (1), the substrate is selected from hydrophilic materials or non-hydrophilic materials, wherein the surface and / or pore structure of the non-hydrophilic material is hydrophilic after pretreatment; the pretreatment includes prewashing and / or charge adjustment, and the charge adjustment includes: plasma treatment of the substrate surface and / or pore structure, treatment of the substrate surface and / or pore structure with cationic surfactants or anionic surfactants, or friction treatment of the substrate surface and / or pore structure to make the substrate surface and / or pore structure positively or negatively charged.

[0033] In the above scheme, the friction treatment can be performed simultaneously with drilling the substrate surface.

[0034] The hydrophilic material includes, but is not limited to, polyamide, polyvinyl acetate, epoxy resin, acrylate, or composites thereof; the non-hydrophilic material includes, but is not limited to, polyimide, polycarbonate, polylactic acid, polyurethane, polycaprolactone, polymethyl methacrylate, polyhydroxyethyl methacrylate, poly(β-hydroxybutyrate), polybutylene terephthalate, polyethylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, polystyrene, polypropylene, polyethylene, poly-1-butene, poly-4-methyl-1-pentene, or composites thereof; the substrate is preferably epoxy resin / glass fiber composite, polyimide, polyethylene terephthalate, polyimide / glass fiber composite, acrylate, etc.

[0035] When the substrate is a hydrophilic material, the pre-washing includes: ultrasonically cleaning the substrate with a 1% NaOH solution for 0.5 to 5 minutes.

[0036] When the substrate is a non-hydrophilic material, the pre-washing includes: immersing the substrate in a 10% NaOH solution for 20-40 minutes, then removing it, washing off the alkaline solution, and drying it. After treatment, the substrate surface becomes a hydrophilic surface.

[0037] According to the above surface treatment method, the coating in step (2) includes immersion, scraping, or spraying; the immersion includes: immersing the substrate in an ultrasonically dispersed graphene dispersion for 5s to 5min, preferably 30 to 60s; the scraping includes: scraping a film with a thickness of 0.05 to 100μm onto the surface of the substrate to be electroplated using an ultrasonically dispersed graphene dispersion, preferably 0.1 to 10μm; the spraying includes: spraying a film with a thickness of 0.05 to 100μm onto the surface of the substrate to be electroplated using an ultrasonically dispersed graphene dispersion; preferably 0.1 to 10μm; preferably, the substrate is repeatedly scraped or sprayed multiple times; more preferably, the coating is stopped when the surface resistance of the substrate is below 100Ω, preferably below 20Ω.

[0038] In the above scheme, when the substrate itself is uneven, it is preferable to use a spraying method to coat it.

[0039] The substrate surface treatment method specifically includes the following steps:

[0040] (1) Substrate pretreatment: Pre-washing and / or charge adjustment are performed according to the material of the substrate; when the substrate is a hydrophilic material, the pre-washing includes: ultrasonically cleaning the surface of the substrate to be electroplated with a 1% NaOH solution for 0.5 to 5 minutes; when the substrate is a non-hydrophilic material, the pre-washing includes: immersing the surface of the substrate to be electroplated in a 10% NaOH solution for 20 to 40 minutes, then removing it, washing off the alkaline solution, and drying it; the charge adjustment includes: performing plasma treatment on the substrate surface, treating the substrate surface with a cationic surfactant or anionic surfactant, or performing friction treatment on the substrate surface to make the substrate surface positively or negatively charged; the pretreatment makes the non-hydrophilic surface become a hydrophilic surface;

[0041] (2) Preparation of graphene dispersion: The binding agent and water-soluble conductive polymer are dissolved in deionized water and treated by physical methods to obtain a graphene-modified solution. Graphene is then added to the modification solution and treated by physical methods to obtain a graphene dispersion with a mass ratio of graphene, binding agent, and water-soluble conductive polymer of 1:0.05-20:0.01-20. The mass fraction of graphene in the graphene dispersion is 0.05-10%, preferably 0.1-5%. The physical method is selected from one or both of grinding and ultrasonic treatment. The grinding speed is 100-5000 rpm, preferably 1000-3000 rpm. The grinding time is 1 min-3 h, preferably 10 min-1 h. The ultrasonic frequency is 25-100 kHz, preferably 40-75 kHz. The ultrasonic time is 30 min-6 h, preferably 1-2 h.

[0042] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate pretreated in step (1) to form a conductive layer suitable for direct electroplating; the coating includes immersion, scraping, or spraying; the immersion includes immersing the substrate in an ultrasonically dispersed graphene dispersion for 5s to 5min; the scraping includes scraping a film with a thickness of 0.05 to 100μm onto the surface of the substrate to be electroplated using the ultrasonically dispersed graphene dispersion; Selectively, the thickness of the film liquid applied by scraping is 0.1–10 μm; the spraying includes: spraying a graphene dispersion that has been ultrasonically dispersed onto the surface of the substrate to be electroplated with a film liquid thickness of 0.05–100 μm; preferably, the thickness of the sprayed film liquid is 0.1–10 μm; preferably, the substrate is repeatedly scraped or sprayed multiple times, and a drying treatment is performed between each scraping or spraying; the drying treatment includes: a drying temperature of 40–100°C and a drying air velocity of 0.3–10 m / s.

[0043] The present invention also provides an application of the method for enhancing interfacial adhesion as described above in the electroplating of flexible circuit boards.

[0044] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0045] 1. The dispersion provided by the present invention uses graphene with a certain number of layers as the main raw material. The graphene layers are partially opened by physical methods. With the improvement of the drying process, the graphene coated and dried on the surface of the insulating substrate contains a large number of interpenetrating voids that can form with the electroplated metal, which greatly improves the bonding strength between the electroplated metal and the conductive layer.

[0046] 2. The graphene dispersion provided by this invention contains a binding agent, which enhances the covalent bond between the conductive layer and the electroplated metal during electroplating and interacts with hydrogen bonds of the surface groups of the insulating substrate. This greatly enhances the interfacial bonding ability between the conductive layer formed by the graphene dispersion and the insulating substrate and electroplated metal, resulting in good bonding performance and scratch resistance between the electroplated layer formed by subsequent surface treatment and the insulating substrate. In addition, the binding agent can also stabilize the dispersion of graphene.

[0047] 3. In the surface treatment method provided by the present invention, the solvent used to prepare the dispersion by physical means such as grinding and / or ultrasound is mainly water. At the same time, the solvent abandons the organic reagents commonly used in the prior art and mainly uses water, which is environmentally friendly, thus reducing the environmental burden of the treatment method and greatly reducing the treatment cost.

[0048] 4. The surface treatment method provided in this application offers a feasible technical solution for obtaining circuits from flexible circuit boards using additive electroplating.

[0049] 5. This application uses a graphene coating to replace a chemical plating coating. Graphene has higher electrical and thermal conductivity, which can provide a new direction for improving the performance of the circuit board itself.

[0050] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0051] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings:

[0052] Figure 1 This is a schematic diagram of the bonding structure between the electroplated metal, graphene, and substrate provided by the present invention.

[0053] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0055] Example 1

[0056] In this embodiment, the substrate surface treatment is performed using the following method:

[0057] (1) Substrate pretreatment: The substrate is polyamide. Drill holes on its surface to achieve friction treatment. Then, use 1% NaOH solution to ultrasonically clean the surface of the substrate to be electroplated and the drilled holes. The pre-cleaning time is 0.5 min. After that, take it out and dry it for later use.

[0058] (2) Preparation of graphene dispersion: Poly(2-acrylamide-2-methylpropanesulfonic acid) with a molecular weight of 2000 and water-soluble conductive polymer (water-soluble polyaniline) were dissolved in deionized water and ground at 2000 rpm for 10 min to obtain a modification solution. Graphene was then added to the modification solution and ground at 3000 rpm for 1 h to obtain a mixture of graphene, poly(2-acrylamide-2-methylpropanesulfonic acid) and water-soluble polyaniline in a mass ratio of 1:0.05:0.05. The mixture was then further mixed with an aqueous solution of polyvinyl alcohol to obtain a graphene dispersion. The mass ratio of graphene to polyvinyl alcohol in the graphene dispersion was 1:0.01, and the mass fraction of graphene in the graphene dispersion was 10%. The pH of the graphene dispersion was adjusted according to the substrate.

[0059] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from immersion, the substrate is immersed in the ultrasonically dispersed graphene dispersion for 5s, and then taken out and dried; the drying includes: drying at 60℃ for 15min with a drying air velocity of 0.3m / s.

[0060] Example 2

[0061] In this embodiment, the substrate surface treatment is performed using the following method:

[0062] (1) Substrate pretreatment: The substrate is polyethylene terephthalate. Its surface is subjected to plasma treatment, and then the surface of the substrate to be electroplated is immersed in 10% NaOH solution for 20 minutes. After that, it is taken out, the alkaline solution is washed off and dried.

[0063] (2) Preparation of graphene dispersion: Poly(2-acrylamide-2-methylpropanesulfonic acid) with a molecular weight of 400 and water-soluble conductive polymer (water-soluble polythiophene) were dissolved in deionized water and subjected to ultrasonic treatment at 25 kHz for 4 h to obtain a modified solution. Graphene was then added to the modified solution and subjected to ultrasonic treatment at 75 kHz for 24 h to obtain a mixture of graphene, poly(2-acrylamide-2-methylpropanesulfonic acid) and water-soluble polythiophene in a mass ratio of 1:20:20. The mixture was then further mixed with an aqueous solution of polyvinylpyrrolidone to obtain a graphene dispersion. The mass ratio of graphene to polyvinylpyrrolidone in the graphene dispersion was 1:40, and the mass fraction of graphene in the graphene dispersion was 0.05%. The pH of the graphene dispersion was adjusted according to the substrate.

[0064] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from scraping, the ultrasonically dispersed graphene dispersion is repeatedly scraped onto the substrate surface several times, dried after each scraping, and then scraped a second time and dried, and repeated several times, the thickness of the film liquid in each scraping is 10μm, and finally dried to obtain the desired conductive layer; the drying includes: drying at 70℃ for 10min with a drying air velocity of 10m / s.

[0065] Example 3

[0066] In this embodiment, the substrate surface treatment is performed using the following method:

[0067] (1) Substrate pretreatment: The substrate is an epoxy resin / glass fiber composite. The surface of the substrate is cleaned by spraying deionized water with a high-pressure water gun, and then the surface of the substrate to be electroplated is ultrasonically cleaned with 1% NaOH solution for 5 minutes. After that, it is taken out and dried for later use.

[0068] (2) Preparation of graphene dispersion: Poly(2-acrylamide-2-methylpropanesulfonic acid) with a molecular weight of 4000 and polyepoxychloropropane quaternary ammonium salt with a water-soluble conductive polymer were dissolved in deionized water. The mixture was ground at 100 rpm and sonicated at 40 kHz for 1 h to obtain a modified solution. Graphene was then added to the modified solution and ground at 1000 rpm and sonicated at 100 kHz for 4 h to obtain a mixture of graphene, poly(2-acrylamide-2-methylpropanesulfonic acid) and polyepoxychloropropane quaternary ammonium salt with a mass ratio of 1:3:0.01. The mixture was then further mixed with an aqueous solution of polyethyleneimine to obtain a graphene dispersion. The mass ratio of graphene to polyethyleneimine in the graphene dispersion was 1:5, the mass fraction of graphene in the graphene dispersion was 2%, and the pH of the graphene dispersion was adjusted according to the substrate.

[0069] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from spraying, the ultrasonically dispersed graphene dispersion is sprayed onto the substrate surface to form a film with a thickness of 0.5 μm, and after drying, a film with a thickness of 0.5 μm is sprayed again and dried, and this process is repeated several times until the conductive layer is finally dried; the drying includes: drying at 80°C with forced air for 5 minutes, and the drying air velocity is 3 m / s.

[0070] Example 4

[0071] In this embodiment, the substrate surface treatment is performed using the following method:

[0072] (1) Substrate pretreatment: The substrate is polyethylene terephthalate with a surface with a pitted pore structure. The surface and pore structure of the substrate to be electroplated are immersed in 10% NaOH solution for 30 minutes, and then the substrate is taken out, the alkaline solution is washed off and dried.

[0073] (2) Preparation of graphene dispersion: A waterborne epoxy resin with a molecular weight of 1000 and a water-soluble conductive polymer, water-soluble polyaniline, were dissolved in deionized water and ground at 100 rpm for 1 min to obtain a modification solution. Graphene was then added to the modification solution and ground at 1000 rpm for 30 min to obtain a mixture of graphene, waterborne epoxy resin, and water-soluble polyaniline in a mass ratio of 1:10:3. The mixture was then mixed with an aqueous solution of polyethylene glycol to obtain a graphene dispersion. The mass ratio of graphene to polyethylene glycol in the graphene dispersion was 1:0.1, and the mass fraction of graphene in the graphene dispersion was 0.1%. The pH of the graphene dispersion was adjusted according to the substrate.

[0074] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from immersion, the substrate is immersed in the ultrasonically dispersed graphene dispersion for 60s, and then taken out and dried; the drying includes: drying at 85°C for 4 minutes with a drying air velocity of 5m / s.

[0075] Example 5

[0076] In this embodiment, the substrate surface treatment is performed using the following method:

[0077] (1) Substrate pretreatment: The substrate is polyvinyl acetate. The substrate surface is subjected to plasma treatment, and then the surface of the substrate to be electroplated is ultrasonically cleaned with 1% NaOH solution for 1 minute. After that, it is taken out and dried for later use.

[0078] (2) Preparation of graphene dispersion: Poly(2-acrylamide-2-methylpropanesulfonic acid) with a molecular weight of 3000 and water-soluble conductive polymer (water-soluble polyaniline) were dissolved in deionized water and subjected to ultrasonic treatment at 60 kHz for 2 h to obtain a modified solution. Graphene was then added to the modified solution and subjected to ultrasonic treatment at 40 kHz for 12 h to obtain a mixture of graphene, poly(2-acrylamide-2-methylpropanesulfonic acid) and water-soluble polyaniline in a mass ratio of 1:0.15:0.1. The mixture was then further mixed with an aqueous solution of polyvinyl alcohol to obtain a graphene dispersion. The mass ratio of graphene to polyvinyl alcohol in the graphene dispersion was 1:1.2, the mass fraction of graphene in the graphene dispersion was 0.7%, and the pH of the graphene dispersion was adjusted according to the substrate.

[0079] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from scraping coating, and the thickness of the film liquid scraped onto the substrate surface to be electroplated using ultrasonically dispersed graphene dispersion is 100 μm, and the conductive layer is obtained after drying; the drying includes: drying at 90°C for 3 min with a drying air velocity of 0.3 m / s.

[0080] Example 6

[0081] In this embodiment, the substrate surface treatment is performed using the following method:

[0082] (1) Substrate pretreatment: The substrate is polycarbonate with a recessed pore structure on the surface. The substrate surface and pore structure are subjected to plasma treatment, and then the surface of the substrate to be electroplated is immersed in 10% NaOH solution for 40 minutes. After that, it is taken out, the alkaline solution is washed off and dried.

[0083] (2) Preparation of graphene dispersion: Poly(2-acrylamide-2-methylpropanesulfonic acid) with a molecular weight of 2500 and water-soluble conductive polymer (water-soluble polythiophene) were dissolved in deionized water. The mixture was then ground at 500 rpm and sonicated at 40 kHz for 1 h to obtain a modified solution. Graphene was then added to the modified solution and ground at 3000 rpm and sonicated at 100 kHz for 3 h. The mixture was then sonicated at 100 kHz for 1 h to obtain a mixture of graphene, poly(2-acrylamide-2-methylpropanesulfonic acid) and water-soluble polythiophene in a mass ratio of 1:1.5:1.5. The mixture was then mixed with an aqueous solution of polyvinylpyrrolidone to obtain a graphene dispersion. The mass ratio of graphene to polyvinylpyrrolidone in the graphene dispersion was 1:0.8, and the mass fraction of graphene in the graphene dispersion was 5%. The pH of the graphene dispersion was adjusted according to the substrate.

[0084] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from immersion, the substrate is immersed in the ultrasonically dispersed graphene dispersion for 5 minutes, and then taken out and dried; the drying includes: drying at 90°C with forced air for 5 minutes, and the drying air velocity is 10 m / s.

[0085] Example 7

[0086] In this embodiment, the substrate surface treatment is performed using the following method:

[0087] (1) Substrate pretreatment: The substrate is polylactic acid. The surface of the substrate to be electroplated is soaked in 10% NaOH solution for 30 minutes, then removed, washed off the alkaline solution and dried.

[0088] (2) Preparation of graphene dispersion: A waterborne polyurethane with a molecular weight of 800 and a water-soluble conductive polymer, water-soluble polythiophene, were dissolved in deionized water. The mixture was then ground at 1000 rpm and sonicated at 25 kHz for 1 h to obtain a modified solution. Graphene was then added to the modified solution and ground at 3500 rpm and sonicated at 40 kHz for 2 h to obtain a mixture of graphene, waterborne polyurethane, and water-soluble polythiophene in a mass ratio of 1:1:0.5. The mixture was then further mixed with an aqueous solution of polyethyleneimine and polyvinyl alcohol to obtain a graphene dispersion. The graphene dispersion had a high molecular weight ratio of graphene, polyethyleneimine, and polyvinyl alcohol of 1:0.5:0.4, and the mass fraction of graphene in the dispersion was 4%. The pH of the graphene dispersion was adjusted according to the substrate.

[0089] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from spraying, and the ultrasonically dispersed graphene dispersion is repeatedly sprayed onto the substrate surface several times, with a film thickness of 1 μm each time, followed by drying. The conductive layer is obtained after repeated spraying and drying; the drying includes: drying at 80°C with forced air for 5 min, and the drying air velocity is 1 m / s.

[0090] Example 8

[0091] In this embodiment, the substrate surface treatment is performed using the following method:

[0092] (1) Substrate pretreatment: The substrate is polypropylene. Drill holes on its surface to achieve friction treatment. Then, soak the surface of the substrate to be electroplated and the drilled holes in 10% NaOH solution for 30 minutes. After that, take it out, wash off the alkali solution and dry it.

[0093] (2) Preparation of graphene dispersion: Poly(2-acrylamide-2-methylpropanesulfonic acid) with a molecular weight of 3000 and water-soluble conductive polymer (water-soluble polyaniline) were dissolved in deionized water. The mixture was then ground at 1000 rpm and sonicated at 75 kHz for 1 h to obtain a modified solution. Graphene was then added to the modified solution and ground at 5000 rpm and sonicated at 100 kHz for 2 h. After that, it was sonicated at 100 kHz for 22 h to obtain a mixture of graphene, poly(2-acrylamide-2-methylpropanesulfonic acid) and water-soluble polyaniline in a mass ratio of 1:1.5:1.5. The mixture was then mixed with an aqueous solution of polyvinylpyrrolidone to obtain a graphene dispersion. The mass ratio of graphene to polyvinylpyrrolidone in the graphene dispersion was 1:1.6, and the mass fraction of graphene in the graphene dispersion was 5%. The pH of the graphene dispersion was adjusted according to the substrate.

[0094] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from immersion, the substrate is immersed in the ultrasonically dispersed graphene dispersion for 30s, and then taken out and dried; the drying includes: drying at 80℃ for 5min with a drying air velocity of 1m / s.

[0095] Example 9

[0096] In this embodiment, the substrate surface treatment is performed using the following method:

[0097] (1) Substrate pretreatment: The substrate is polyurethane. The surface of the substrate to be electroplated is immersed in 10% NaOH solution for 25 minutes, then removed, washed off the alkaline solution and dried.

[0098] (2) Preparation of graphene dispersion: Poly(2-acrylamide-2-methylpropanesulfonic acid) with a molecular weight of 3500 and water-soluble conductive polymer (water-soluble polyaniline) were dissolved in deionized water. The mixture was then ground at 300 rpm and sonicated at 25 kHz for 10 min to obtain a modified solution. Graphene was then added to the modified solution and ground at 1000 rpm and sonicated at 75 kHz for 1 h to obtain a mixture of graphene, poly(2-acrylamide-2-methylpropanesulfonic acid) and water-soluble polyaniline in a mass ratio of 1:1.5:2. The mixture was then further mixed with an aqueous solution of polyvinylpyrrolidone to obtain a graphene dispersion. The mass ratio of graphene to polyvinylpyrrolidone in the graphene dispersion was 1:1.2, and the mass fraction of graphene in the graphene dispersion was 5%. The pH of the graphene dispersion was adjusted according to the substrate.

[0099] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from scraping coating, and the thickness of the film liquid coated on the substrate surface using the ultrasonically dispersed graphene dispersion is 0.5 μm, then dried, and after repeated scraping and drying several times, the conductive layer is finally dried; the drying includes: drying at 90°C with forced air for 5 min, and the drying air velocity is 0.3 m / s.

[0100] Example 10

[0101] In this embodiment, the substrate surface treatment is performed using the following method:

[0102] (1) Substrate pretreatment: The substrate is polyimide. The surface of the substrate is rinsed with deionized water and then soaked in 10% NaOH solution for 30 minutes. After that, it is taken out, the alkaline solution is washed off and dried.

[0103] (2) Preparation of graphene dispersion: Poly(2-acrylamide-2-methylpropanesulfonic acid) with a molecular weight of 4000 and water-soluble conductive polymer (water-soluble polythiophene) were dissolved in deionized water. The mixture was then ground at 300 rpm and sonicated at 25 kHz for 10 min to obtain a modified solution. Graphene was then added to the modified solution and ground at 1000 rpm and sonicated at 75 kHz for 1 h to obtain a mixture of graphene, poly(2-acrylamide-2-methylpropanesulfonic acid) and water-soluble polythiophene in a mass ratio of 1:1.5:3. The mixture was then further mixed with an aqueous solution of polyvinylpyrrolidone to obtain a graphene dispersion. The mass ratio of graphene to polyvinylpyrrolidone in the graphene dispersion was 1:0.4, and the mass fraction of graphene in the graphene dispersion was 5%. The pH of the graphene dispersion was adjusted according to the substrate.

[0104] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from spraying, and the ultrasonically dispersed graphene dispersion is repeatedly sprayed onto the surface of the substrate, with a film thickness of 10 μm each time, followed by drying, and repeated spraying and drying, and finally forming a conductive layer after drying; the drying includes: drying at 80°C with forced air for 5 min, and the drying air velocity is 0.5 m / s.

[0105] Example 11

[0106] In this embodiment, the substrate surface treatment is performed using the following method:

[0107] (1) Substrate pretreatment: The substrate is an epoxy resin / glass fiber composite. Its surface is subjected to friction treatment, and then the surface of the substrate to be electroplated is ultrasonically cleaned with 1% NaOH solution for 5 minutes.

[0108] (2) Preparation of graphene dispersion: Poly-2-acrylamide-2-methylpropanesulfonic acid with a molecular weight of 4000 and water-soluble conductive polymer water-soluble polythiophene were dissolved in deionized water. The mixture was ground at 500 rpm and sonicated at 25 kHz for 1 h to obtain a modified solution. Graphene was then added to the modified solution and ground at 5000 rpm and sonicated at 60 kHz for 3 h. After that, it was sonicated at 60 kHz for 3 h to obtain a graphene dispersion with a mass ratio of graphene, poly-2-acrylamide-2-methylpropanesulfonic acid and water-soluble polythiophene of 1:3:1. The mass fraction of graphene in the graphene dispersion was 2%. The pH of the graphene dispersion was adjusted according to the substrate.

[0109] (3) Coating to form a conductive layer: The graphene dispersion obtained in step (2) is coated onto the surface of the substrate that has been pre-washed in step (1) to form a conductive layer that can be directly electroplated; the coating is selected from spraying, and the thickness of the film liquid sprayed on the substrate surface using the ultrasonically dispersed graphene dispersion is 0.5 μm. After drying, the spraying and drying are repeated multiple times until the conductive layer is finally formed; the drying includes: drying at 70°C with forced air for 10 min, and the drying air velocity is 2 m / s.

[0110] Comparative Example 1

[0111] This comparative example is based on Example 10, except that the drying method in step (3) is changed to natural drying at room temperature (25°C). Other implementation methods of this comparative example are the same as those in Example 10.

[0112] Comparative Example 2

[0113] This comparative example is based on Example 11, except that the friction treatment step in the pretreatment of step (1) is removed, and the pH adjustment of the graphene dispersion in step (2) is also removed accordingly. Other embodiments of this comparative example are the same as in Example 11.

[0114] Experimental Example 1

[0115] To better illustrate the technical effects of the surface treatment in this invention, the conductive layers obtained in Examples 1-11 and Comparative Examples 1-2 were electroplated with copper under the following conditions: the electroplating current density was 2 A / dm². 2 The electroplating time was 30 minutes. The relevant properties of the plating layer were tested, and the results are shown in the table below:

[0116]

[0117] As shown in the table above, the embodiments of the present invention pre-treated the surface and / or pore structure of the substrate based on its chemical composition and charge type, making the surface negatively or positively charged. Correspondingly, the pH of the graphene dispersion was adjusted to enhance the electrostatic bonding between the two. Furthermore, the present invention adjusted the drying method, utilizing the morphological characteristics of graphene during high-temperature drying to form an interlocking microstructure with the subsequent electroplated metal, thereby improving the scratch resistance of the electroplated layer. Specifically, Examples 1-11 provided by the present invention all exhibit high scratch resistance. However, Comparative Example 1, due to the use of conventional room-temperature natural air drying, resulted in a relatively flat microstructure formed by the graphene on its surface, insufficient to form an interlocking structure with the metal plating layer, leading to a significant decrease in the scratch resistance of the plating layer. Comparative Example 2, by omitting the charge adjustment in the substrate pre-treatment and the pH adjustment of the graphene dispersion, resulted in a decrease in the electrostatic bonding between the substrate and the formed graphene layer, specifically manifested in a decrease in the scratch resistance of the subsequent plating layer.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for enhancing the interfacial bonding force between a metal and an insulating substrate, wherein the substrate comprises a surface and a porous structure recessed in the surface, characterized in that, include: (1) Pre-treatment of the surface and / or pore structure of the insulating substrate, the pre-treatment including pre-washing and / or charge adjustment; (2) The prepared graphene dispersion is coated on the surface and / or pore structure of the insulating substrate that has been charged in step (1), and dried to form a conductive layer that can be electroplated with metal; the drying temperature is 40 to 100°C. (3) The graphene in the conductive layer forms a physical interpenetrating network structure with the electroplated metal; The graphene dispersion comprises water, graphene, a binding agent, and a water-soluble conductive polymer. The mass ratio of graphene, binding agent, and water-soluble conductive polymer is 1:0.05-20:0.01-20. The mass fraction of graphene in the graphene dispersion is 0.05-10%. The binding agent enhances the covalent bond between the conductive layer and the electroplated metal during electroplating and interacts with groups on the surface and / or porous structure of the pretreated insulating substrate. In step (2), the pH value of the graphene dispersion is 3 to 11; The graphene dispersion is prepared by the following method: a binding agent and a water-soluble conductive polymer are dissolved in deionized water, and then graphene is added to the modification solution. The surface-modified graphene dispersion is obtained by physical treatment. The binding agent is selected from one or more of poly(2-acrylamide-2-methylpropanesulfonic acid), waterborne epoxy, and waterborne polyurethane. The water-soluble conductive polymer is selected from one or more of water-soluble polyaniline, water-soluble polythiophene, and polyepoxychloropropane quaternary ammonium salt.

2. The method for enhancing the interfacial bonding force between metal and insulating substrate according to claim 1, characterized in that, The graphene dispersion further includes a water-soluble polymer, wherein the mass ratio of graphene to water-soluble polymer is 1:0 to 40; the water-soluble polymer is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, polyethylene glycol, polyacrylate, polymaleic anhydride, polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, polyvinyl sulfonic acid, polyvinylphosphonic acid, polyvinylamine, and polyvinylpyridine.

3. The method for enhancing the interfacial bonding force between metal and insulating substrate according to claim 2, characterized in that, The mass ratio of graphene to water-soluble polymer is 1:0.01 to 5.

4. The method for enhancing the interfacial bonding force between metal and insulating substrate according to claim 1, characterized in that, The physical method is selected from one or both of grinding and ultrasonic treatment.

5. The method for enhancing the interfacial bonding force between metal and insulating substrate according to claim 2, characterized in that, The method for preparing the graphene dispersion further includes: mixing the mixture obtained by physical treatment of graphene and binding agent with an aqueous solution of water-soluble polymer to obtain the graphene dispersion.

6. The method for enhancing the interfacial bonding force between metal and insulating substrate according to claim 1, characterized in that, In the graphene dispersion, the average number of graphene layers is no more than 10.

7. The method for enhancing the interfacial bonding force between metal and insulating substrate according to claim 6, characterized in that, The graphene dispersion has an average number of graphene layers of 1 to 5.

8. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 1, characterized in that, The mass ratio of graphene, binding agent and water-soluble conductive polymer is 1:0.1-3:0.05-3; the mass fraction of graphene in the graphene dispersion is 0.1-5%.

9. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 4, characterized in that, The grinding speed is 100-5000 rpm; the grinding time is 1 min-3 h; the ultrasonic frequency is 25-100 kHz; and the ultrasonic time is 30 min-24 h.

10. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 9, characterized in that, The grinding speed is 1000-3000 rpm.

11. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 9, characterized in that, The grinding time is 10 minutes to 1 hour.

12. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 9, characterized in that, The frequency of the ultrasound is 40–75 kHz.

13. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 9, characterized in that, The duration of the ultrasound is 4 to 12 hours.

14. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to any one of claims 1-13, characterized in that, In step (2), the drying process includes: the drying air velocity is 0.3 to 10 m / s.

15. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to any one of claims 1-13, characterized in that, In step (1), the substrate is selected from hydrophilic or non-hydrophilic materials, wherein the non-hydrophilic material is hydrophilic on the surface and / or in the pore structure after pretreatment; the charge adjustment includes: plasma treatment of the substrate surface and / or pore structure, treatment of the substrate surface and / or pore structure with cationic or anionic surfactants, or friction treatment of the substrate surface and / or pore structure to make the substrate surface and / or pore structure positively or negatively charged.

16. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to any one of claims 1-13, characterized in that, The coating in step (2) includes immersion, scraping, or spraying; the immersion includes immersing the substrate in an ultrasonically dispersed graphene dispersion for 5 seconds to 5 minutes; the scraping includes scraping a film with a thickness of 0.05 to 100 μm onto the substrate surface using an ultrasonically dispersed graphene dispersion; the spraying includes spraying a film with a thickness of 0.05 to 100 μm onto the substrate surface using an ultrasonically dispersed graphene dispersion.

17. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 16, characterized in that, The substrate is repeatedly coated by scraping or spraying.

18. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 16, characterized in that, Soaking time is 30-60 seconds.

19. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 16, characterized in that, The thickness of the film solution applied by scraping is 0.1–10 μm.

20. The method for enhancing the interfacial bonding force between a metal and an insulating substrate according to claim 16, characterized in that, The thickness of the sprayed film is 0.1–10 μm.

21. The application of a method for enhancing the interfacial bonding force between a metal and an insulating substrate as described in any one of claims 1 to 20 in electroplating technology.

22. The application according to claim 21, characterized in that, Used for metallization of flexible circuit boards and non-metallic surfaces.

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