A method for treating the front surface of a metal foil for a laminate

Abstract

The present application relates to the technical field of surface treatment, in particular to a kind of surface treatment method before metal foil material bonding for layer board, it includes the following steps: the surface pretreatment of metal foil material;After dilution, the photosensitive etching ink is coated to the surface to be processed of metal foil material after pretreatment, form continuous photosensitive film on foil surface, then drying;After the negative of preparation is attached to the surface of metal foil material with photosensitive film, metal foil material is sequentially exposed, developed and cured, and form protective film;Under the condition that electrolyte flows at less than set flow rate, metal foil material is electrolytic processed with ultrasonic auxiliary energy field, then remove protective film, form finished metal foil material;Finished metal foil material is sol-gel treated.The purpose of the surface treatment method before metal foil material bonding for layer board is to solve the problems of poor rigidity of foil, difficult to control deformation, large randomness of surface morphology, harsh reaction conditions, poor process reproducibility and insufficient interfacial strength.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and more specifically to a surface treatment method for metal foil materials used in laminates before bonding. Background Technology

[0002] Fiber metal laminates (FMLs) are interlayer hybrid composite materials formed by alternating layers of fiber-reinforced composite materials and metal substrates, which are then cured under certain temperature and pressure conditions. This structure possesses excellent properties such as impact resistance and fatigue resistance, overcoming the fatigue performance of metal materials and the relatively poor impact resistance and toughness of composite materials. Moreover, it is lighter than metal materials, making it an ideal structural material for aircraft and a promising new material in the aerospace field.

[0003] The development of fiber-reinforced metal laminates has undergone four generations of upgrades: the earliest research focused on aramid fiber-reinforced aluminum alloy laminates, Arall. While this laminate offered improved performance compared to single-metal and fiber composites, it suffered from high residual stress, low fatigue resistance, low notch strength, and low peel strength. To address the fiber fracture issue under fatigue loads in Arall laminates, glass fiber reinforced aluminum alloy laminates, Glare, were developed by replacing aramid fibers with glass fibers. While this improved performance, the use of glass fibers reduced the overall stiffness of the laminate, limiting its applications. Finally, to improve the overall stiffness of the laminate, carbon fibers with higher modulus were used instead of glass. The carbon fiber reinforced aluminum alloy laminate Care, developed using fiber, exhibits significantly improved laminate stiffness. However, the large difference in electrical galvanic order between aluminum alloy and carbon fiber leads to severe electrochemical corrosion upon contact. To address this corrosion issue, researchers developed a carbon fiber reinforced titanium alloy laminate, TiGr, using titanium alloy instead of aluminum alloy. Titanium alloy does not exhibit contact corrosion with carbon fiber, demonstrates good material compatibility, has low density, and possesses a series of advantages such as high elastic modulus, high specific strength, high specific stiffness, high temperature resistance, fatigue resistance, and impact resistance. Utilizing its lightweight, temperature-resistant, and corrosion-resistant characteristics, it shows promising application potential in aircraft engine nacelles, wing leading edges, and fuselage undersides.

[0004] The combined use of metallic materials, especially foils with a thickness of less than 0.2 mm, and fiber composite materials can bring considerable benefits to aircraft in terms of weight reduction and performance improvement. However, it also poses significant challenges to the bonding technology. Due to the different molecular structures of the metal and fiber composite layers, their corresponding physical and mechanical properties differ considerably. The interlayer interface between the two is one of the weakest parts of the fiber-metal sheet. The presence of the interlayer interface makes the sheet prone to delamination and cracking during use, affecting the transmission of interfacial stress and thus severely restricting the performance of the sheet. Therefore, improving the interlayer interface bonding strength is a crucial issue that urgently needs to be addressed.

[0005] Therefore, the inventors provide a surface treatment method for metal foil materials used in laminates before bonding. Summary of the Invention

[0006] (1) Technical problems to be solved

[0007] This invention provides a surface treatment method for metal foils used in laminates before bonding, which solves the technical problems of poor foil rigidity leading to difficult deformation control, large randomness of surface morphology, harsh reaction conditions, poor process reproducibility, and insufficient interlayer interface strength.

[0008] (2) Technical solution

[0009] This invention provides a surface treatment method for metal foil materials used in laminates before adhesive bonding, comprising the following steps:

[0010] Surface pretreatment of metal foil;

[0011] Diluted photosensitive etching ink is coated onto the pretreated surface of the metal foil to be processed, forming a continuous photosensitive film on the foil surface, and then the metal foil is dried.

[0012] After the prepared film is attached to the surface of a metal foil with a photosensitive film, the metal foil is exposed, developed and cured in sequence to form a protective film on the photosensitive part of the photosensitive film.

[0013] An ultrasonic vibrating head is placed in a static electrolyte, and a metal foil that has undergone development and curing is immersed in the electrolyte. The metal foil is connected to the positive terminal of the power supply, and the tool cathode is connected to the negative terminal of the power supply. The metal foil is electrolytically processed under the condition that the electrolyte flows at a rate lower than the set flow rate.

[0014] The electrolytically processed metal foil is placed in a film removal solution to remove the protective film and then cleaned to form a finished metal foil with a uniformly distributed, densely arrayed protruding structure on its surface.

[0015] The finished metal foil is subjected to sol-gel treatment to form a gel film on the surface of the finished metal foil.

[0016] Furthermore, the surface pretreatment of the metal foil specifically includes the following steps:

[0017] The surface of the metal foil is polished and cleaned.

[0018] The surface of the metal foil to be processed and the conductive contact parts used for clamping are cleaned after grinding and cleaning.

[0019] Furthermore, the process of producing the negative is as follows:

[0020] A laser photoplotter is used to process the film, and opaque circular areas with a set spacing and a set diameter are drawn on the film.

[0021] Furthermore, the diameter of the circular region is 0.1 to 0.15 mm.

[0022] Furthermore, the center-to-center distance between two adjacent circular regions is 0.2–0.3 mm.

[0023] Furthermore, the step of sequentially exposing, developing, and curing the metal foil to form a protective film on the photosensitive area of ​​the photosensitive film specifically includes the following steps:

[0024] The metal foil is placed in an exposure machine, and the photosensitive part of the photosensitive film is cured by exposure to form the protective film.

[0025] The exposed metal foil is placed in a developing solution, and the unexposed areas on the photosensitive film are dissolved in the developing solution, exposing the metal in the remaining areas of the metal foil except for the circular area.

[0026] After being developed, the metal foil is cleaned and then placed in an oven for curing.

[0027] Furthermore, the step of subjecting the finished metal foil to sol-gel treatment to form a gel film on the surface of the finished metal foil specifically includes the following steps:

[0028] The finished metal foil is immersed in the sol for a first preset time to ensure that the sol is in full contact with the surface of the finished metal foil.

[0029] The finished metal foil is pulled out vertically at a set speed. As the solvent in the sol evaporates, the sol adhering to the surface of the finished metal foil gels to form a gel film. The pulling process is repeated until the gel film on the surface of the finished metal foil reaches the preset thickness.

[0030] The finished metal foil with a gel film of a preset thickness is placed in a drying oven and dried at a preset temperature to form a gel film on its surface.

[0031] Furthermore, after forming a gel film on the surface of the finished metal foil, the process further includes:

[0032] After the gel film dries, apply the primer within the second preset time, and then store it at room temperature for the third preset time until the primer is fully dry.

[0033] Further, the metal foil coated with ink is dried at 60–90°C for 15–60 minutes.

[0034] Further, the developed metal foil is cured at 120–180°C for 60–120 min.

[0035] (3) Beneficial effects

[0036] In summary, this invention fabricates a regularly arranged, densely arrayed columnar structure on the surface of a metal foil using ultrasonic-assisted electrolytic processing under flooded conditions. The columnar structure and the micro-pit-like structures formed between the columns improve the shape characteristics of the metal foil surface, creating a mechanical interlocking effect during bonding. Simultaneously, based on the ultrasonic-assisted electrolytic processing, a sol-gel method is used to coat the metal foil surface with a gel film, chemically modifying the metal surface and forming a transition layer with active functional groups. The microstructure formed by ultrasonic-assisted electrolytic processing and the functional groups introduced by the sol-gel treatment promote the physical interlocking and chemical bond formation between the metal foil and the adhesive, effectively improving the bonding strength at weak interfaces between the metal and the composite material, meeting the requirements of lightweight and high-strength laminate structures. The entire process is simple, environmentally friendly, and applicable to the surface treatment of metal materials of different thicknesses and materials, demonstrating significant application value. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic flowchart of a surface treatment method for metal foil materials used in laminates before adhesive bonding, provided in an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram of the ultrasonic-assisted energy field electrolytic processing of metal foil provided in an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the bonding process of a fiber metal laminate provided in an embodiment of the present invention.

[0041] In the picture:

[0042] 1-Metal foil; 2-Gel film; 3-Thermoplastic resin film; 4-Resin-based carbon fiber prepreg; 5-Tool cathode; 6-Protective film. Detailed Implementation

[0043] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0044] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0046] Figure 1 This is a schematic flowchart of a surface treatment method for metal foil materials used in laminates before adhesive bonding, provided by an embodiment of the present invention. The method may include the following steps:

[0047] S100. Surface pretreatment of metal foil.

[0048] Specifically, the surface of the metal foil is polished and cleaned; the surface of the metal foil to be processed and the conductive contact parts used for clamping are then cleaned. In one specific embodiment, an oilstone or non-woven cloth is used to mechanically polish and clean the metal foil to eliminate sharp edges, burrs, and uneven areas such as burrs and peeling, and to remove oil stains and the natural passivation layer from the titanium alloy surface. The surface of the foil to be processed and the conductive contact parts used for clamping are then cleaned with water and set aside for later use.

[0049] S200: Diluted photosensitive etching ink is applied to the surface of the pretreated metal foil to be processed, forming a continuous photosensitive film on the foil surface, and then the metal foil is dried.

[0050] Specifically, the photosensitive etching ink is diluted with ethanol to give it a certain degree of fluidity. A roller brush is then used to apply the diluted ink evenly to the surface of the foil, forming a continuous photosensitive film. After ink application, the metal foil is placed in an oven to dry at 60–90°C for 15–60 minutes before being removed.

[0051] S300: After the prepared film is attached to the surface of a metal foil with a photosensitive film, the metal foil is exposed, developed and cured in sequence to form a protective film on the photosensitive part of the photosensitive film.

[0052] Specifically, a laser photoplotter is used to process the film, drawing uniformly arranged circles with a certain spacing and diameter on the film. The circular areas are opaque, with a diameter controlled between 0.1 and 0.15 mm and a center-to-center distance controlled between 0.2 and 0.3 mm. The edges of the pattern on the film should be clear and complete. After the film is laminated onto the surface of a foil with a photosensitive film, the foil is placed in an exposure machine. Exposure causes the photosensitive areas of the photosensitive film on the foil (the areas corresponding to the opaque circles on the film) to solidify, forming a strong and insulating protective film 6. The exposed foil is then placed in a developing solution. The unexposed areas of the photosensitive film dissolve in the developing solution, exposing the metal outside the circles on the foil. After development, the foil is rinsed with water and placed in an oven to cure at 120–180°C for 60–120 minutes before being removed.

[0053] S400. Place the ultrasonic vibrating head into the static electrolyte and immerse the metal foil after development and curing in the electrolyte. Connect the metal foil to the positive terminal of the power supply and the tool cathode to the negative terminal of the power supply. Electrolytically process the metal foil under the condition that the electrolyte flows at a rate lower than the set flow rate.

[0054] Specifically, such as Figure 2 As shown, the ultrasonic vibrating head is placed in a static electrolyte solution, and the exposed, developed, and cured metal foil 1 is immersed in the electrolyte solution. The metal foil 1 is connected to the positive terminal of the power supply, and the tool cathode 5 is connected to the negative terminal of the power supply. The gap between the tool cathode 5 and the metal foil 1 is set as the initial processing gap. After processing begins, the tool cathode 5 moves linearly in a certain direction, and the electrolyte flows at a low speed to reach a state of overflow (overflow refers to a state where the electrolyte is relatively slow or nearly stationary during processing. Overflow can reduce the uneven distribution of the flow field across the entire surface area and minimize the impact of the electrolyte flow rate on processing. However, during overflow processing, the difference in ion concentration at the electrode-solution interface is relatively large compared to high-speed scouring, which can easily lead to concentration polarization and is not conducive to uniform removal). The ultrasonic vibrating head outputs ultrasonic frequency vibration shock waves to remove the electrolytic products, bubbles, and heat generated on the surface of the metal foil during electrolysis. After the tool cathode moves a certain distance in a linear direction, the processing is completed. The set flow rate is relatively small, generally 1 to 5 m / s, and can be as low as 2 m / s. No specific limit is set here, and it can be selected according to the actual working conditions.

[0055] The overcurrent electrolyte avoids the problem of uneven metal dissolution rates caused by the high-speed scouring of electrolytes in conventional electrolytic machining, which can lead to fluctuations in the metal foil and inconsistent processing gaps. Simultaneously, the introduced ultrasonic-assisted energy field accelerates ion diffusion, eliminates concentration polarization and passivation films on the metal surface, and effectively removes electrolytic machining products from the gap areas. This process avoids processing deformation and exhibits good consistency, allowing precise control of characteristic dimensions such as column diameter, spacing, and height, thereby increasing the foil surface area and achieving a meshing effect.

[0056] S500: The electrolytically processed metal foil is placed in a film removal solution to remove the protective film and then cleaned to form a finished metal foil with a uniformly distributed, densely arrayed raised structure on the surface.

[0057] Specifically, the electrolytically processed metal foil is placed in a film-removing solution to remove the protective film 6 on the surface, and then rinsed with water to form a metal foil with a regularly arranged, densely arrayed columnar structure on its surface. For example... Figure 2 As shown, the columnar structure and the micro-pit structure (recesses) formed between the columns can improve the shape characteristics of the metal foil surface and form a mechanical interlocking effect during the bonding process, thereby helping to improve the bonding strength.

[0058] S600. The finished metal foil is subjected to sol-gel treatment to form a gel film on the surface of the finished metal foil.

[0059] Specifically, step S600 includes the following steps:

[0060] S601. Immerse the finished metal foil in the sol for a first preset time to ensure that the sol is in full contact with the surface of the finished metal foil.

[0061] S602. The finished metal foil is pulled out vertically at a set speed. As the solvent in the sol evaporates, the sol adhering to the surface of the finished metal foil gels to form a gel film. The pulling process is repeated until the gel film on the surface of the finished metal foil reaches the preset thickness.

[0062] Specifically, the metal foil is slowly and uniformly pulled vertically out at a certain speed. As the solvent in the sol evaporates, the sol adhering to the surface of the metal foil rapidly gels, forming a gel film. After pulling, the foil is placed vertically to avoid uneven distribution of the gel film. The above pulling process is repeated until the gel film on the surface of the metal foil reaches a certain thickness.

[0063] S603. Place the finished metal foil with a gel film of a preset thickness in a drying oven and dry it at a preset temperature to form a gel film on the surface.

[0064] Specifically, a sol-gel method is used to form a transition layer between the metal and the adhesive. This transition layer exhibits strong adhesion, good uniformity, controllable composition, and simple process implementation on the electrolytically processed metal surface. This treatment can improve the chemical properties of the metal foil surface, and the resulting transition layer and adhesive can form chemical bonds during the bonding process, enhancing the cross-linking strength.

[0065] As an optional implementation, after step S603, the method further includes: S604, applying a primer within a second preset time after the gel film dries, and storing the material at room temperature for a third preset time until the primer is fully dried. Specifically, the primer is applied within 24 hours after the sol-gel dries to protect the surface of the aforementioned treated metal foil, and the material is stored after being placed at room temperature for a certain period of time until the primer is fully dried, wrapped in kraft paper.

[0066] This invention utilizes ultrasonic-assisted electrolytic machining to replace traditional methods such as sandblasting, acid washing or alkaline washing, and anodizing, to process uniformly arranged, densely arrayed columnar features on the surface of metal foil. The overcurrent electrolyte avoids the problem of uneven metal dissolution rates caused by the high-speed rinsing of the electrolyte in conventional electrolytic machining, which can lead to fluctuations in the metal foil and inconsistent processing gaps. Simultaneously, the introduced ultrasonic-assisted energy field accelerates ion diffusion, eliminates concentration polarization and passivation films on the metal surface, and effectively removes electrolytic machining products from the gap areas. This process avoids processing deformation and exhibits good consistency, allowing precise control of columnar diameter, spacing, and height, thereby increasing the surface area of ​​the foil and achieving an interlocking effect. Furthermore, a transition layer (i.e., a gel film) is formed between the metal and the adhesive on the surface after ultrasonic-assisted electrolytic machining using a sol-gel method. This transition layer exhibits strong adhesion, good uniformity, controllable composition, and simple process implementation. This treatment can improve the chemical properties of the metal foil surface, and the resulting transition layer (i.e., gel film) can form chemical bonds with the adhesive during the bonding process, thereby increasing the cross-linking strength.

[0067] The microstructure formed by ultrasonic-assisted electrolytic machining and the transition layer functional groups introduced by sol-gel treatment promote the physical interlocking and chemical bonding between the metal foil and the adhesive. This effectively enhances the bonding strength at weak interfaces between the metal and the composite material, facilitating the formation of a laminated structure consisting of metal foil-transition layer-adhesive film-fiber-reinforced prepreg-adhesive film-transition layer-metal foil, meeting the requirements for lightweight and high strength. The entire process is simple, environmentally friendly, and applicable to the surface treatment of metal materials of varying thicknesses and materials, demonstrating significant application value.

[0068] Example 1

[0069] 1) Electrolytic processing

[0070] Mechanical polishing: Use an oilstone or non-woven cloth to mechanically polish and clean the titanium alloy foil with dimensions of 300mm×300mm×0.2mm.

[0071] Cleaning: Clean the surface of the foil to be processed and the conductive contact parts used for clamping with water.

[0072] Coating and Drying: Dilute the photosensitive etching ink with ethanol, with the ethanol volume being 20%–35% of the ink. Use a roller brush to apply the diluted ink evenly to the foil surface. After coating, place the parts in an oven to dry at 60°C for 60 minutes, then remove them.

[0073] Film preparation: A 0.2mm thick film is processed using a laser photoplotter to draw evenly arranged circles on the film. The diameter of the circles is 0.1mm, the distance between the centers of the circles is 0.3mm, and the circular areas are black and opaque.

[0074] Exposure: After the film is attached to the surface of the foil with the photosensitive film, the foil is placed in the exposure machine and exposed for 30 seconds to form a protective film.

[0075] Developing and curing: Place the exposed foil in the developing solution and soak for 15 minutes. Then, gently wipe the surface of the foil with a non-woven cloth. Rinse the foil with water and place it in an oven to cure at 150°C for 60 minutes.

[0076] Ultrasonic-assisted electrolytic machining: Adjust the electrode end face and the titanium alloy foil to the required positions according to the set machining gap. After installation, connect the titanium alloy foil and the tool cathode to the positive and negative terminals of the DC machining power supply, respectively. Place the ultrasonic vibrator and the titanium alloy foil in a static electrolyte. The ultrasonic vibrator generates oscillation waves through high-frequency movement. Select the ultrasonic vibration parameters, electrolytic machining process parameters, and power supply parameters. Apply a certain machining voltage between the positive and negative terminals. The tool cathode moves in a certain direction until the machining is completed and then retracts.

[0077] Optimized processing parameters: ultrasonic vibration frequency of 30kHz, electrolyte of 10% KBr aqueous solution, electrolyte temperature of 25℃; processing voltage of 20V; initial processing gap of 0.3mm, cathode moving speed of 100mm / min, processing stroke of 320mm; after processing is completed, the cathode stops moving, the power is cut off, and the cathode retracts.

[0078] Film removal and cleaning: The foil is placed in a 15% NaOH solution at 60℃ and soaked for 60 minutes to remove the protective film on the surface of the foil. After rinsing with water, a dense array of columnar structures with regular arrangement is formed on the surface. The diameter of the formed cylinder is 0.1 mm, the center-to-center distance is 0.3 mm, and the height of the cylinder is 0.05 mm.

[0079] 2) Sol-gel treatment process

[0080] Immersion: Immerse the electrolytically processed titanium alloy foil in the sol for 10 minutes to ensure full contact between the sol and the surface of the titanium alloy foil.

[0081] Pulling: Pull the titanium alloy foil vertically out at a uniform speed of 100 mm / min, repeat several times, and then place the titanium alloy foil vertically.

[0082] Drying: Place the titanium alloy foil in a drying oven and keep it at 60°C for 1 hour to form a gel film.

[0083] Sealing: Apply a primer to protect the surface of the aforementioned treated foil within 24 hours after the sol-gel dries. After placing at room temperature for 30 minutes, wrap it in kraft paper and store it.

[0084] 3) Adhesive bonding process

[0085] Pretreatment of adhesive film: After cutting the resin-based carbon fiber prepreg 4 and the thermoplastic resin adhesive film 3 of the same material, they are soaked in acetone for cleaning to remove surface oil and impurities. After rinsing with deionized water, they are dried for later use. The cutting size matches the outer size of the titanium alloy foil.

[0086] Material stacking: Resin-based carbon fiber prepreg 4 and thermoplastic resin film 3 are stacked on the surface of titanium alloy foil. The two are stacked multiple times, with 3 to 5 layers of carbon fiber prepreg and 2 to 3 layers of thermoplastic film, forming an interlayer hybrid structure in the form of titanium alloy foil-film-carbon fiber-film-titanium alloy foil combination. The hybrid structure is wrapped with aluminum foil to prevent resin from overflowing.

[0087] Heating and pressurizing: The stacked materials are transferred to an autoclave, and the heating rate is controlled by pneumatic pressurization. Once the target temperature is reached, it is held for a certain period of time. Subsequently, a certain pressure is applied at this temperature, and the holding and pressurization time is controlled to remove air trapped between the layers. Finally, heating is stopped, the pressure is released, and the material is allowed to cool with the furnace temperature to form a layered structure.

[0088] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0089] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A method for treating the front surface of a metal foil for a laminate prior to bonding, characterized by, The method includes the following steps: Surface pretreatment of metal foil; Diluted photosensitive etching ink is coated onto the pretreated surface of the metal foil to be processed, forming a continuous photosensitive film on the foil surface, and then the metal foil is dried. After the prepared film is attached to the surface of a metal foil with a photosensitive film, the metal foil is exposed, developed and cured in sequence to form a protective film on the photosensitive part of the photosensitive film. An ultrasonic vibrating head is placed in a static electrolyte solution, and a metal foil material that has undergone development and curing is immersed in the electrolyte solution. The metal foil material is connected to the positive terminal of the power supply, and the tool cathode is connected to the negative terminal of the power supply. Electrolytic processing is performed on the metal foil material under the condition that the electrolyte flows at a rate lower than the set flow rate. After the processing begins, the tool cathode moves in a straight line in a certain direction, and the electrolyte does not flow at a high speed to achieve a flooded field. The flooded field refers to the electrolyte being in a relatively low-speed scouring or near-static state during the processing. The electrolytically processed metal foil is placed in a film removal solution to remove the protective film and then cleaned to form a finished metal foil with a uniformly distributed, densely arrayed protruding structure on its surface. The finished metal foil is subjected to sol-gel treatment to form a gel film on the surface of the finished metal foil; The process of making the negative is as follows: A laser photoplotter is used to process the film, and opaque circular areas with a set spacing and a set diameter are drawn on the film.

2. The method for treating the front surface of a metal foil for a laminate according to claim 1, characterized in that, The surface pretreatment of the metal foil specifically includes the following steps: The surface of the metal foil is polished and cleaned. The surface of the metal foil to be processed and the conductive contact parts used for clamping are cleaned after grinding and cleaning.

3. The surface treatment method for metal foil before bonding of a laminate according to claim 1, characterized in that, The diameter of the circular region is 0.1 to 0.15 mm.

4. The surface treatment method for metal foil materials used in laminates before adhesive bonding according to claim 1 or 3, characterized in that, The distance between the centers of two adjacent circular regions is 0.2 to 0.3 mm.

5. The surface treatment method for metal foil materials used in laminates before bonding according to claim 1, characterized in that, The step of sequentially exposing, developing, and curing the metal foil to form a protective film on the photosensitive area of ​​the photosensitive film specifically includes the following steps: The metal foil is placed in an exposure machine, and the photosensitive part of the photosensitive film is cured by exposure to form the protective film. The exposed metal foil is placed in a developing solution, and the unexposed areas on the photosensitive film are dissolved in the developing solution, exposing the metal in the remaining areas of the metal foil except for the circular area. After being developed, the metal foil is cleaned and then placed in an oven for curing.

6. The surface treatment method for metal foil before bonding of a laminate according to claim 1, characterized in that, The step of performing sol-gel treatment on the finished metal foil to form a gel film on the surface of the finished metal foil specifically includes the following steps: The finished metal foil is immersed in the sol for a first preset time to ensure that the sol is in full contact with the surface of the finished metal foil. The finished metal foil is pulled out vertically at a set speed. As the solvent in the sol evaporates, the sol adhering to the surface of the finished metal foil gels to form a gel film. The pulling process is repeated until the gel film on the surface of the finished metal foil reaches the preset thickness. The finished metal foil with a gel film of a preset thickness is placed in a drying oven and dried at a preset temperature to form a gel film on its surface.

7. The surface treatment method for metal foil materials used in laminates before bonding according to claim 1, characterized in that, After forming a gel film on the surface of the finished metal foil, the process further includes: After the gel film dries, apply the primer within the second preset time, and then store it at room temperature for the third preset time until the primer is fully dry.

8. The surface treatment method for metal foil materials used in laminates before bonding according to claim 1, characterized in that, The metal foil coated with ink is dried at 60–90°C for 15–60 minutes.

9. The surface treatment method for metal foil materials used in laminates before adhesive bonding according to claim 1, characterized in that, The developed metal foil is cured at 120–180°C for 60–120 min.

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