High-performance flexible shielding film, preparation method and application thereof

Abstract

This invention discloses a high-performance flexible shielding film, its preparation method, and its applications. The method includes: roughening the surface of a flexible polymer substrate and laminating a photosensitive dry film onto the surface of the substrate to obtain a pretreated film; patterning and developing the photosensitive dry film to expose a target patterned area on the pretreated film, and then catalytically activating the target patterned area to selectively attach catalytically active components to the target patterned area to obtain an activated film; depositing a metal seed layer on the target patterned area, and then selectively depositing a gradient composite shielding layer on the metal seed layer to obtain an electroplated film; and finally, peeling the electroplated film to remove areas on the photosensitive dry film where no metal deposition has occurred, resulting in a high-performance flexible shielding film. This achieves a flexible shielding film that combines ultra-high shielding efficiency, excellent flexibility, high degree of patterning freedom, and good environmental stability.

Description

Technical Field

[0001] This invention relates to the field of thin film technology, and in particular to a high-performance flexible shielding film, its preparation method, and its application. Background Technology

[0002] Flexible shielding films are key materials widely used in flexible electronics, wearable devices, high-frequency communications, and electromagnetic compatibility protection. As electronic devices become thinner, more flexible, and more integrated, higher demands are being placed on the overall performance of shielding materials.

[0003] However, traditional flexible shielding films are mainly prepared by coating conductive fillers or by integral metal sputtering processes. These methods suffer from poor adhesion between the metal layer and the substrate, making them prone to peeling and detachment. Furthermore, their homogeneous structure makes it difficult to balance high conductivity and magnetic loss characteristics, resulting in limited electromagnetic shielding effectiveness. Additionally, conventional metal shielding layers are prone to cracking under repeated bending and their surfaces are susceptible to oxidation and corrosion, leading to insufficient long-term stability. Summary of the Invention

[0004] This invention provides a high-performance flexible shielding film, its preparation method, and its application, to solve the technical problems of limited electromagnetic effect and insufficient mechanical properties of traditional flexible shielding films.

[0005] In a first aspect, the present invention provides a method for preparing a high-performance flexible shielding film, comprising:

[0006] A pretreated film is obtained by roughening the surface of a flexible polymer substrate and then laminating a photosensitive dry film onto the surface of the flexible polymer substrate.

[0007] The photosensitive dry film is patterned by exposure and development to expose the target pattern area on the pretreated film material, and the target pattern area is catalytically activated to selectively attach catalytically active components to the target pattern area to obtain an activated film material.

[0008] A metal seed layer is deposited in the target pattern area, and a gradient composite shielding layer is sequentially deposited on the metal seed layer through a selective electroplating process to obtain an electroplated film material. The gradient composite shielding layer includes a nickel-based alloy layer directly deposited on the metal seed layer, a highly conductive copper layer deposited on the nickel-based alloy layer, and a silver-graphene composite protective layer deposited on the highly conductive copper layer.

[0009] The electroplated film is peeled off to remove areas on the photosensitive dry film where no metal deposition has occurred, resulting in a high-performance flexible shielding film.

[0010] In some embodiments, the surface roughening treatment of the flexible polymer substrate includes:

[0011] The polymer flexible substrate is loaded onto the unwinding roller of the plasma treatment machine. The unwinding roller is started, and the polymer flexible substrate is passed sequentially through an ultrasonic cleaning tank containing isopropanol and deionized water, and then dried with hot air to obtain a clean substrate.

[0012] The clean substrate is transferred to a sealed plasma reaction chamber, a working gas is introduced into the chamber, and the chamber pressure is maintained at 50 Pa to 150 Pa. The radio frequency power supply is turned on, and the radio frequency power density is controlled at 0.3 W / cm² to 0.8 W / cm² to perform plasma bombardment treatment on the surface of the clean substrate.

[0013] In some embodiments, the step of laminating a photosensitive dry film onto the surface of the flexible polymer substrate to obtain a pretreated film material includes:

[0014] The flexible polymer substrate is loaded onto the worktable of a vacuum laminator, and the photosensitive dry film is aligned and covered onto the surface of the flexible polymer substrate.

[0015] The substrate area covered with the photosensitive dry film is evacuated to a pressure below 100 Pa. Then, the heating roller of the vacuum laminator is controlled to maintain the roller temperature at 80℃~110℃, and the photosensitive dry film is rolled at a uniform speed of 0.3MPa~0.8MPa and 0.5m / min~2.0m / min.

[0016] The laminated film is cooled to cure and shape the photosensitive dry film, resulting in a film without the pretreatment.

[0017] In some embodiments, the step of patterning and developing the photosensitive dry film to expose the target patterned area on the pretreated film material includes:

[0018] The target shielding pattern mask is placed on the photosensitive dry film and exposed with an ultraviolet light source to cause a selective photocrosslinking reaction in the photosensitive dry film corresponding to the target shielding pattern mask.

[0019] The pre-treated film material is sprayed with developing solution using a spray developing machine to remove the unexposed photosensitive dry film, thereby exposing the target pattern area on the pre-treated film material.

[0020] The surface residue of the pretreated film is cleaned with deionized water, and then dried with hot air to complete the patterning exposure and development.

[0021] In some embodiments, the catalytic activation treatment of the target patterned region to selectively attach catalytically active components to the target patterned region to obtain an activated film material includes:

[0022] Using a selective slit coating device, the catalytically active components are coated onto the target pattern area to form a uniform catalytic layer;

[0023] The coated film is transferred to a curing oven for heating and curing to attach the catalytic active component to the target pattern area, thereby obtaining the activated film.

[0024] In some embodiments, depositing a metal seed layer in the target pattern region includes:

[0025] The activated film material is immersed in a chemical nickel plating solution to uniformly deposit a metal seed layer under the action of the catalytically active components in the target pattern area; the chemical nickel plating solution uses nickel sulfate as the main salt, sodium hypophosphite as the reducing agent, and contains complexing agents and stabilizers.

[0026] In some embodiments, the step of selectively depositing a gradient composite shielding layer sequentially on the metal seed layer to obtain an electroplated film material includes:

[0027] The activated film material is used as the cathode and immersed in a nickel-tungsten-phosphorus alloy electroplating bath containing nickel ions, tungstate and hypophosphite. The temperature of the plating bath is controlled at 60℃~70℃ and the cathode current density is 2 A / dm²~5 A / dm². Electroplating is performed for 10min~20min using a pulse power supply to deposit a nickel-tungsten-phosphorus alloy layer with a thickness of 1μm~3μm on the metal seed layer of the activated film material.

[0028] After the activated film material that has completed the electroplating of the nickel-based alloy layer is washed with water, it is immersed in an acidic copper sulfate electroplating bath. The temperature of the plating solution in the acidic copper sulfate electroplating bath is controlled at 20℃~25℃, the cathode current density is 3 A / dm²~8A / dm², and the DC power supply is used for electroplating for 20min~40min, so as to deposit a highly conductive copper layer with a thickness of 8μm~15μm on the nickel-tungsten-phosphorus alloy layer.

[0029] After the activated film material that has completed copper electroplating is washed with water, it is immersed in a silver-graphene composite electroplating bath. The temperature of the plating solution in the acidic copper sulfate electroplating bath is controlled at 25℃~35℃, the cathode current density is 0.5 A / dm²~1.5 A / dm², and DC electroplating is performed for 5min~10min to co-deposit a silver-graphene composite protective layer with a thickness of 0.5μm~1.5μm on the highly conductive copper layer, thus obtaining the electroplated film material. The plating solution in the silver-graphene composite electroplating bath is a cyanide-free complex system of silver plating solution with uniformly dispersed functionalized graphene nanosheets.

[0030] In some embodiments, the step of peeling off the electroplated film to remove areas on the photosensitive dry film where no metal deposition has occurred, to obtain a high-performance flexible shielding film, includes:

[0031] The electroplated film is immersed in an alkaline stripping solution at a temperature of 45℃~60℃ for 2min~5min to dissolve and remove areas on the photosensitive dry film where no metal deposition has occurred. The stripping solution is a mixed aqueous solution containing 1 wt%~3 wt% sodium hydroxide, 0.5 wt%~2 wt% organic amine stripping accelerator, and 0.1 wt%~0.5 wt% silver corrosion inhibitor.

[0032] The electroplated film is sprayed with mild deionized water at a pressure of 0.05 MPa to 0.15 MPa, then immersed in a silver protective solution containing benzotriazole derivatives for 30 to 60 seconds, rinsed with deionized water and dried to obtain the high-performance flexible shielding film.

[0033] Secondly, the present invention also provides a high-performance flexible shielding film, which is prepared based on the above-described method for preparing a high-performance flexible shielding film.

[0034] Thirdly, the present invention also provides an application of the above-mentioned high-performance flexible shielding film in electronic devices.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] By roughening the surface and catalytic activation, a strong mechanical anchor and chemical bond are established on the substrate surface, enabling the subsequently deposited dense metal layer to possess excellent adhesion and bending resistance, maintaining its integrity in repeated bending applications. Arbitrarily complex patterns can be defined on the substrate using photolithography, meeting the needs of high-density integration and specific area shielding in modern electronic devices, avoiding the etching waste and precision loss associated with traditional monolithic metallization. A gradient composite shielding layer structure achieves superior and wide-band electromagnetic shielding performance. The bottom nickel-based alloy provides good magnetic loss and transition bonding, the thick, highly conductive copper layer in the middle forms a low-resistance path, and the top silver-graphene composite layer further enhances surface conductivity. Leveraging the shielding contribution of graphene and the stability of silver, it provides excellent oxidation resistance, corrosion resistance, and additional mechanical reinforcement. This results in a flexible shielding film that combines ultra-high shielding performance, excellent flexibility, high degree of patterning freedom, and good environmental stability. Detailed Implementation

[0037] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0038] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0039] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0040] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity requirement (i.e., the number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] The present invention discloses a method for preparing a high-performance flexible shielding film, comprising steps S101 to S103, which are detailed below:

[0043] Step S101: The surface of the polymer flexible substrate is roughened, and a photosensitive dry film is laminated onto the surface of the polymer flexible substrate to obtain a pretreated film.

[0044] In this step, the flexible polymer substrate can be polyimide, polyethylene terephthalate, polyethylene naphthalate, thermoplastic polyurethane, or liquid crystal polymer, etc.; the photosensitive dry film can be epoxy acrylate, polyester acrylate, or polyurethane acrylate, etc. Due to the common problem of poor adhesion between the metal layer and the polymer material, this step roughens the surface of the flexible polymer substrate to increase the specific surface area and mechanical anchoring points. The photosensitive dry film serves as a patterning carrier to accurately define the metal deposition area, meeting the customized pattern requirements of shielding films for electronic devices.

[0045] In some embodiments, the surface roughening treatment of the polymer flexible substrate in step S101 includes:

[0046] The polymer flexible substrate is loaded onto the unwinding roller of the plasma treatment machine. The unwinding roller is started, and the polymer flexible substrate is passed sequentially through an ultrasonic cleaning tank containing isopropanol and deionized water, and then dried with hot air to obtain a clean substrate.

[0047] The clean substrate is transferred to a sealed plasma reaction chamber, a working gas is introduced into the chamber, and the chamber pressure is maintained at 50 Pa to 150 Pa. The radio frequency power supply is turned on, and the radio frequency power density is controlled at 0.3 W / cm² to 0.8 W / cm² to perform plasma bombardment treatment on the surface of the clean substrate.

[0048] In this embodiment, a rolled flexible polymer substrate is loaded onto the unwinding roller of a plasma treatment machine and passed through a guide roller. The online cleaning section is activated, causing the substrate to pass sequentially through an ultrasonic cleaning tank containing isopropanol and deionized water, followed by hot air drying to obtain a clean substrate. The clean substrate is then transferred to a sealed plasma reaction chamber, into which a mixed gas of argon and oxygen is introduced, with oxygen comprising 20% ​​to 40% of the volume, and the chamber pressure is maintained at 50 Pa to 150 Pa. The radio frequency power supply is turned on, generating glow discharge between the electrodes. The radio frequency power density is controlled at 0.3 W / cm² to 0.8 W / cm², and the surface of the clean substrate is subjected to plasma bombardment treatment for a duration of 30 to 120 seconds. After the plasma-treated substrate is removed from the reaction chamber, its surface water contact angle is detected in real time using an online contact angle measuring instrument. When the contact angle drops below 40°, the roughening effect is deemed satisfactory.

[0049] In this embodiment, argon ions are used to obtain high energy under a radio frequency electric field to physically bombard and etch the substrate surface, increasing the micro-roughness and specific surface area. Oxygen plasma undergoes a chemical reaction on the surface, introducing oxygen-containing polar functional groups such as hydroxyl and carboxyl groups, which significantly enhances the surface energy. This roughened surface provides strong mechanical anchoring points, which, combined with newly generated chemical bonding sites, fundamentally solve the adhesion problem between the metal layer and the flexible substrate, ensuring the reliability of the final product under bending.

[0050] In some embodiments, step S101, which involves laminating a photosensitive dry film onto the surface of the flexible polymer substrate to obtain a pretreated film, includes:

[0051] The flexible polymer substrate is loaded onto the worktable of a vacuum laminator, and the photosensitive dry film is aligned and covered onto the surface of the flexible polymer substrate.

[0052] The substrate area covered with the photosensitive dry film is evacuated to a pressure below 100 Pa. Then, the heating roller of the vacuum laminator is controlled to maintain the roller temperature at 80℃~110℃, and the photosensitive dry film is rolled at a uniform speed of 0.3MPa~0.8MPa and 0.5m / min~2.0m / min.

[0053] The laminated film is cooled to cure and shape the photosensitive dry film, resulting in a film without the pretreatment.

[0054] In this embodiment, the pretreated film material is loaded onto the lower worktable of the vacuum laminator and preheated to 50°C~70°C. A pre-cut sheet of photosensitive dry film is then placed over the preheated pretreated film material. The laminator's optical alignment system is used to align the edges of the photosensitive dry film with the substrate edge reference line. The vacuum system is then activated to evacuate the substrate area covered with the dry film until the pressure is below 100 kJ / m³. Pa is used to remove any trapped gas. Then, the heated rollers on the upper worktable are controlled to roll the photosensitive dry film at a pressure of 0.3MPa to 0.8MPa and a linear speed of 0.5m / min to 2.0m / min, while the roller temperature is maintained at 80 to 110°C. This allows the photosensitive resin layer of the dry film to melt and firmly adhere to the roughened surface of the pretreated substrate. After lamination, the cooling system is immediately activated to rapidly cool the laminated film to below 40°C, allowing the photosensitive dry film to solidify and set, resulting in a bubble-free, wrinkle-free, and firmly bonded pretreated film for subsequent patterning processes.

[0055] Step S102: The photosensitive dry film is patterned by exposure and development to expose the target pattern area on the pretreated film material, and the target pattern area is catalytically activated to selectively attach catalytically active components to the target pattern area to obtain an activated film material.

[0056] In this step, the negative photosensitive dry film is exposed to ultraviolet light, causing cross-linking and curing of the portion outside the target pattern area. Then, alkaline solution development is used to selectively dissolve and remove the unexposed dry film, precisely exposing the target pattern area on the substrate. The exposed area undergoes catalytic activation treatment, ensuring that the catalytically active components are chemically adsorbed only onto the surface of the pattern area. This guarantees that subsequent metal chemical deposition and electroplating are strictly confined to the pattern area, avoiding metal deposition in non-target areas, thus fundamentally ensuring the accuracy of the shape and the sharpness of the edges.

[0057] In some embodiments, step S102, which involves patterning and developing the photosensitive dry film to expose the target patterned area on the pretreated film, includes:

[0058] The target shielding pattern mask is placed on the photosensitive dry film and exposed with an ultraviolet light source to cause a selective photocrosslinking reaction in the photosensitive dry film corresponding to the target shielding pattern mask.

[0059] The pre-treated film material is sprayed with developing solution using a spray developing machine to remove the unexposed photosensitive dry film, thereby exposing the target pattern area on the pre-treated film material.

[0060] The surface residue of the pretreated film is cleaned with deionized water, and then dried with hot air to complete the patterning exposure and development.

[0061] In this embodiment, the pre-treated film material with the photosensitive dry film bonded to it is placed on the vacuum chuck stage of the ultraviolet lithography machine. The mask with the target shielding pattern is precisely aligned with the alignment marks on the film material using an automatic alignment system, with the alignment accuracy controlled within ±5 μm. Under vacuum adsorption and fixation, ultraviolet light is used for exposure, with the dominant wavelength of the exposure spectrum at 365 nm and the exposure energy controlled within the range of 80 mJ / cm² to 150 mJ / cm², causing selective photocrosslinking of the photosensitive dry film in the target pattern area. The exposed film material is then transferred to an online spray developer, where a sodium carbonate aqueous solution with a mass fraction of 0.8% to 1.2% is used as the developing solution, the temperature is maintained at 30±2℃, and the film is developed through a fan-shaped nozzle at a pressure of 0.15 MPa to 0.25 MPa. The film surface is sprayed with MPa pressure for 45s to 90s to dissolve and remove the unexposed photosensitive dry film, thereby exposing a clear target pattern area on the pretreated substrate. After development, the film surface is cleaned with deionized water spray to remove residual developer and dissolved substances, and then dried with hot air at 60℃ to 80℃ to complete the patterning process.

[0062] In some embodiments, the step S102 of performing catalytic activation treatment on the target patterned region to selectively attach catalytically active components to the target patterned region to obtain an activated membrane material includes:

[0063] Using a selective slit coating device, the catalytically active components are coated onto the target pattern area to form a uniform catalytic layer;

[0064] The coated film is transferred to a curing oven for heating and curing to attach the catalytic active component to the target pattern area, thereby obtaining the activated film.

[0065] In this embodiment, a catalytic conductive slurry containing silver nanoparticles or palladium-silver core-shell structured nanoparticles is prepared, with a viscosity of 500 cP to 3000 cP. Using a selective slit coating device, the catalytic slurry is coated onto the exposed membrane surface according to the digital pattern of the target pattern area, forming a uniform catalytic layer with a thickness of 0.5 μm to 5 μm. The coated membrane is immediately transferred to an online curing oven and heated at 80°C to 150°C for 1 min to 5 min, causing the solvent in the catalytic slurry to evaporate and the organic carrier to partially decompose, thereby firmly attaching high-density catalytically active nanoparticles to the surface of the target pattern area, thus obtaining the activated membrane.

[0066] Step S103: Deposit a metal seed layer in the target pattern area, and sequentially deposit a gradient composite shielding layer on the metal seed layer using a selective electroplating process to obtain an electroplated film. The gradient composite shielding layer includes a nickel-based alloy layer directly deposited on the metal seed layer, a highly conductive copper layer deposited on the nickel-based alloy layer, and a silver-graphene composite protective layer deposited on the highly conductive copper layer.

[0067] In this step, a metal seed layer is deposited to serve as the cathode for subsequent selective electroplating, ensuring that the metal material is deposited within the target patterned area. A nickel-based alloy layer serves as the bottom layer, enhancing adhesion to the substrate and providing magnetic loss; a highly conductive copper layer forms the main body, establishing an excellent conductive network for efficient electromagnetic wave reflection shielding; the surface silver-graphene composite layer combines high conductivity, excellent oxidation and corrosion resistance, and the mechanical reinforcement provided by graphene. Ultimately, this results in a shielding film that achieves high performance in terms of adhesion, conductivity, shielding effectiveness (wideband EMI SE), and environmental durability.

[0068] In some embodiments, the deposition of a metal seed layer in the target pattern region in step S103 includes:

[0069] The activated film material is immersed in a chemical nickel plating solution to uniformly deposit a metal seed layer under the action of the catalytically active components in the target pattern area; the chemical nickel plating solution uses nickel sulfate as the main salt, sodium hypophosphite as the reducing agent, and contains complexing agents and stabilizers.

[0070] In this embodiment, the activated film material that has undergone catalytic activation is loaded onto the conveyor fixture of the electroless plating equipment. An acidic electroless nickel plating solution is injected into the electroless nickel plating tank. This solution has nickel sulfate as the main salt, sodium hypophosphite as the reducing agent, and contains complexing agents and stabilizers. The nickel ion concentration is 5 g / L to 8 g / L, the pH value is maintained at 4.5 to 5.0, and the solution temperature is controlled at 85±2℃. The activated film material is immersed in the electroless nickel plating solution for 5 min to 15 min. Under the action of the catalytic active components, the target pattern area undergoes an autocatalytic reduction reaction, uniformly depositing a dense amorphous nickel-phosphorus alloy layer as a conductive metal seed layer. After deposition, the substrate is removed from the plating solution, the surface residual plating solution is cleaned in a water washing tank, and then dried with hot air to complete the preparation of the seed layer.

[0071] In this embodiment, the palladium and other catalytic components in the activated region catalyze the reduction of nickel ions in the sodium hypophosphite solution, causing them to be uniformly reduced and deposited as a metallic nickel layer on the pattern surface. This achieves the selective formation of a uniform, dense, and strongly adherent metallic conductive seed layer on a non-conductive flexible substrate, providing a conductive cathode for subsequent electroplating. At the same time, the nickel seed layer itself is firmly bonded to the substrate, enabling good adhesion to the subsequent nickel-based alloy electroplating layer.

[0072] In some embodiments, step S103, which involves selectively depositing a gradient composite shielding layer onto the metal seed layer to obtain an electroplated film, includes:

[0073] The activated film material is used as the cathode and immersed in a nickel-tungsten-phosphorus alloy electroplating bath containing nickel ions, tungstate and hypophosphite. The temperature of the plating bath is controlled at 60℃~70℃ and the cathode current density is 2 A / dm²~5 A / dm². Electroplating is performed for 10min~20min using a pulse power supply to deposit a nickel-tungsten-phosphorus alloy layer with a thickness of 1μm~3μm on the metal seed layer of the activated film material.

[0074] After the activated film material that has completed the electroplating of the nickel-based alloy layer is washed with water, it is immersed in an acidic copper sulfate electroplating bath. The temperature of the plating solution in the acidic copper sulfate electroplating bath is controlled at 20℃~25℃, the cathode current density is 3 A / dm²~8A / dm², and the DC power supply is used for electroplating for 20min~40min, so as to deposit a highly conductive copper layer with a thickness of 8μm~15μm on the nickel-tungsten-phosphorus alloy layer.

[0075] After the activated film material that has completed copper electroplating is washed with water, it is immersed in a silver-graphene composite electroplating bath. The temperature of the plating solution in the acidic copper sulfate electroplating bath is controlled at 25℃~35℃, the cathode current density is 0.5 A / dm²~1.5 A / dm², and DC electroplating is performed for 5min~10min to co-deposit a silver-graphene composite protective layer with a thickness of 0.5μm~1.5μm on the highly conductive copper layer, thus obtaining the electroplated film material. The plating solution in the silver-graphene composite electroplating bath is a cyanide-free complex system of silver plating solution with uniformly dispersed functionalized graphene nanosheets.

[0076] In this embodiment, a substrate with a metal seed layer is used as the cathode and immersed in a nickel-tungsten-phosphorus alloy electroplating bath containing nickel ions, tungstate, and hypophosphite, using a soluble anode. The plating bath temperature is controlled at 60°C~70°C, and the cathode current density is 2 A / dm²~5 A / dm². Electroplating is performed for 10-20 minutes using a pulsed power supply, depositing a dense nickel-tungsten-phosphorus alloy layer with a thickness of 1 μm~3 μm on the metal seed layer, serving as the bottom layer of the gradient composite shielding layer. After the nickel-based alloy layer electroplating is completed, the substrate is washed with water and then transferred to an acidic copper sulfate electroplating bath. The plating bath temperature is controlled at 20°C~25°C, and the cathode current density is 3 A / dm²~8 A / dm². Electroplating is performed using a DC power supply for 20-40 minutes, depositing a layer with a thickness of 8 μm~15 μm on the nickel-tungsten-phosphorus alloy layer. The highly conductive copper layer with a thickness of μm is formed. After the copper layer electroplating is completed, the substrate is washed and activated with water, and then immersed in a silver-graphene composite electroplating bath. The plating solution is a cyanide-free complex system silver plating solution, in which functionalized graphene nanosheets are uniformly dispersed at a concentration of 0.1 g / L to 0.5 g / L. The temperature of the plating solution is controlled at 25℃ to 35℃, the cathode current density is 0.5 A / dm² to 1.5 A / dm², and DC electroplating is performed for 5 min to 10 min. A silver-graphene composite protective layer with a thickness of 0.5 μm to 1.5 μm and uniform graphene embedding is co-deposited on the highly conductive copper layer to obtain the electroplated film material.

[0077] In this embodiment, a patterned region with a deposited conductive seed layer is used as the cathode. By independently controlling the plating solution system, power supply mode, current density, temperature, and time in stages, the reduction deposition of metal ions (Ni²⁺, Cu²⁺, Ag⁺) in different plating solutions is achieved on the cathode surface. The bottom layer, a nickel-tungsten-phosphorus alloy (Ni-WP), is pulse-plated. Its amorphous / microcrystalline structure has low internal stress, high hardness, and excellent corrosion resistance. As a transition layer, it is firmly bonded to the bottom seed layer and provides an ideal substrate for the upper copper layer. The middle layer, a dense, highly conductive copper layer, constitutes the main body of electromagnetic shielding (mainly for reflection loss). Its sufficient thickness ensures extremely low bulk resistance. The surface layer, a silver-graphene composite layer, features uniformly dispersed functionalized graphene that not only enhances the mechanical strength and wear resistance of the coating, but its own conductivity and shielding properties synergize with silver to further improve surface conductivity and overall shielding effectiveness. At the same time, the silver layer provides excellent oxidation resistance and environmental corrosion resistance, protecting the internal copper layer. This embodiment employs a gradient design of "strong bonding transition layer - high conductivity main layer - composite protective layer" to achieve a balance between adhesion, conductivity, mechanical durability, and environmental stability.

[0078] Step S104: The electroplated film is peeled off to remove the areas on the photosensitive dry film where no metal deposition has occurred, thereby obtaining a high-performance flexible shielding film.

[0079] In this embodiment, after the preceding processes, the unexposed and undeveloped areas on the photosensitive dry film (where no metal deposition has occurred) remain in an uncrosslinked or weakly bonded state, while the patterned areas are covered and locked by a dense metal layer. By selectively removing these unused dry films, a clean, flexible substrate is exposed, while the areas where the metal pattern is firmly attached are completely preserved.

[0080] In some embodiments, step S104 includes:

[0081] The electroplated film is immersed in an alkaline stripping solution at a temperature of 45℃~60℃ for 2min~5min to dissolve and remove areas on the photosensitive dry film where no metal deposition has occurred. The stripping solution is a mixed aqueous solution containing 1 wt%~3 wt% sodium hydroxide, 0.5 wt%~2 wt% organic amine stripping accelerator, and 0.1 wt%~0.5 wt% silver corrosion inhibitor.

[0082] The electroplated film is sprayed with mild deionized water at a pressure of 0.05 MPa to 0.15 MPa, then immersed in a silver protective solution containing benzotriazole derivatives for 30 to 60 seconds, rinsed with deionized water and dried to obtain the high-performance flexible shielding film.

[0083] In this embodiment, a weakly alkaline stripping solution containing corrosion inhibitors is prepared, which selectively swells and dissolves the photosensitive dry film under moderate heating conditions. The organic amine promotes the stripping efficiency, and the special silver corrosion inhibitor preferentially adsorbs onto the silver layer surface to form a protective film, thereby inhibiting the corrosion of the silver-graphene composite protective layer by the alkaline medium while removing the dry film. Gentle spraying assists in mechanical separation, and the benzotriazole protective solution forms a denser and more stable protective layer on the silver layer surface through strong coordination, further enhancing its antioxidant and environmental corrosion resistance.

[0084] For example, using a 25μm thick polyimide (PI) film as the substrate and an epoxy acrylate negative photosensitive dry film as the photosensitive dry film, a high-performance flexible shielding film is prepared based on the preparation method of the present invention. The film has a metal layer adhesion of 5B grade (no peeling), a sheet resistance of <0.01Ω, an electromagnetic shielding effectiveness (plane wave method) of >70 dB, and a sheet resistance change rate of <5% after a bending radius of 3mm and 10,000 dynamic bending cycles.

[0085] Using the same substrate and photosensitive dry film as raw materials, silver conductive paste is printed on the photosensitive dry film using screen printing process and then cured. Then, copper (10μm) is electroplated on the silver conductive layer to obtain a flexible shielding film with metal adhesion of 1B grade, sheet resistance of 0.03Ω, electromagnetic shielding effectiveness (plane wave method) of 40dB, and sheet resistance change rate of >30% after bending radius of 3mm and dynamic bending 10,000 times.

[0086] It is evident that the flexible shielding film prepared according to the present invention has superior performance in terms of adhesion, conductivity, high-frequency shielding effectiveness, and mechanical properties.

[0087] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0088] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for preparing a high-performance flexible shielding film, characterized in that, include: A pretreated film is obtained by roughening the surface of a flexible polymer substrate and then laminating a photosensitive dry film onto the surface of the flexible polymer substrate. The photosensitive dry film is patterned by exposure and development to expose the target pattern area on the pretreated film material, and the target pattern area is catalytically activated to selectively attach catalytically active components to the target pattern area to obtain an activated film material. A metal seed layer is deposited in the target pattern area, and a gradient composite shielding layer is sequentially deposited on the metal seed layer through a selective electroplating process to obtain an electroplated film material. The gradient composite shielding layer includes a nickel-based alloy layer directly deposited on the metal seed layer, a highly conductive copper layer deposited on the nickel-based alloy layer, and a silver-graphene composite protective layer deposited on the highly conductive copper layer. The electroplated film is peeled off to remove areas on the photosensitive dry film where no metal deposition has occurred, resulting in a high-performance flexible shielding film.

2. The method for preparing the high-performance flexible shielding film as described in claim 1, characterized in that, The surface roughening treatment of the flexible polymer substrate includes: The polymer flexible substrate is loaded onto the unwinding roller of the plasma treatment machine. The unwinding roller is started, and the polymer flexible substrate is passed sequentially through an ultrasonic cleaning tank containing isopropanol and deionized water, and then dried with hot air to obtain a clean substrate. The clean substrate is transferred to a sealed plasma reaction chamber, a working gas is introduced into the chamber, and the chamber pressure is maintained at 50 Pa to 150 Pa. The radio frequency power supply is turned on, and the radio frequency power density is controlled at 0.3 W / cm² to 0.8 W / cm² to perform plasma bombardment treatment on the surface of the clean substrate.

3. The method for preparing the high-performance flexible shielding film as described in claim 1, characterized in that, The process of laminating a photosensitive dry film onto the surface of the flexible polymer substrate to obtain a pretreated film material includes: The flexible polymer substrate is loaded onto the worktable of a vacuum laminator, and the photosensitive dry film is aligned and covered onto the surface of the flexible polymer substrate. The substrate area covered with the photosensitive dry film is evacuated to a pressure below 100 Pa. Then, the heating roller of the vacuum laminator is controlled to maintain the roller temperature at 80℃~110℃, and the photosensitive dry film is rolled at a uniform speed of 0.3MPa~0.8MPa and 0.5m / min~2.0m / min. The laminated film is cooled to cure and shape the photosensitive dry film, thus obtaining the pretreated film.

4. The method for preparing the high-performance flexible shielding film as described in claim 1, characterized in that, The step of patterning and developing the photosensitive dry film to expose the target pattern area on the pretreated film material includes: The target shielding pattern mask is placed on the photosensitive dry film and exposed with an ultraviolet light source to cause a selective photocrosslinking reaction in the photosensitive dry film corresponding to the target shielding pattern mask. The pre-treated film material is sprayed with developing solution using a spray developing machine to remove the unexposed photosensitive dry film, thereby exposing the target pattern area on the pre-treated film material. The surface residue of the pretreated film is cleaned with deionized water, and then dried with hot air to complete the patterning exposure and development.

5. The method for preparing the high-performance flexible shielding film as described in claim 1, characterized in that, The step of catalytically activating the target patterned region to selectively attach catalytically active components to the target patterned region to obtain an activated membrane material includes: Using a selective slit coating device, the catalytically active components are coated onto the target pattern area to form a uniform catalytic layer; The coated film is transferred to a curing oven for heating and curing to attach the catalytic active component to the target pattern area, thereby obtaining the activated film.

6. The method for preparing the high-performance flexible shielding film as described in claim 1, characterized in that, The deposition of a metal seed layer in the target pattern region includes: The activated film material is immersed in a chemical nickel plating solution to uniformly deposit a metal seed layer under the action of the catalytically active components in the target pattern area; the chemical nickel plating solution uses nickel sulfate as the main salt, sodium hypophosphite as the reducing agent, and contains complexing agents and stabilizers.

7. The method for preparing the high-performance flexible shielding film as described in claim 1, characterized in that, The process involves selectively depositing a gradient composite shielding layer sequentially onto the metal seed layer to obtain an electroplated film material, comprising: The activated film material is used as the cathode and immersed in a nickel-tungsten-phosphorus alloy electroplating bath containing nickel ions, tungstate and hypophosphite. The temperature of the plating bath is controlled at 60℃~70℃ and the cathode current density is 2 A / dm²~5 A / dm². Electroplating is performed for 10min~20min using a pulse power supply to deposit a nickel-tungsten-phosphorus alloy layer with a thickness of 1μm~3μm on the metal seed layer of the activated film material. After the activated film material that has completed the electroplating of the nickel-based alloy layer is washed with water, it is immersed in an acidic copper sulfate electroplating bath. The temperature of the plating solution in the acidic copper sulfate electroplating bath is controlled at 20℃~25℃, the cathode current density is 3 A / dm²~8A / dm², and the DC power supply is used for electroplating for 20min~40min, so as to deposit a highly conductive copper layer with a thickness of 8μm~15μm on the nickel-tungsten-phosphorus alloy layer. After the activated film material that has completed copper electroplating is washed with water, it is immersed in a silver-graphene composite electroplating bath. The temperature of the plating solution in the acidic copper sulfate electroplating bath is controlled at 25℃~35℃, the cathode current density is 0.5 A / dm²~1.5 A / dm², and DC electroplating is performed for 5min~10min to co-deposit a silver-graphene composite protective layer with a thickness of 0.5μm~1.5μm on the highly conductive copper layer, thus obtaining the electroplated film material. The plating solution in the silver-graphene composite electroplating bath is a cyanide-free complex system of silver plating solution with uniformly dispersed functionalized graphene nanosheets.

8. The method for preparing the high-performance flexible shielding film as described in claim 1, characterized in that, The process of peeling off the electroplated film to remove areas on the photosensitive dry film where no metal deposition has occurred, resulting in a high-performance flexible shielding film, includes: The electroplated film is immersed in an alkaline stripping solution at a temperature of 45°C to 60°C for 2 to 5 minutes to dissolve and remove areas on the photosensitive dry film where no metal deposition has occurred. The stripping solution is a mixed aqueous solution containing 1 wt% to 3 wt% sodium hydroxide, 0.5 wt% to 2 wt% organic amine stripping accelerator, and 0.1 wt% to 0.5 wt% silver corrosion inhibitor. The electroplated film is sprayed with mild deionized water at a pressure of 0.05 MPa to 0.15 MPa, then immersed in a silver protective solution containing benzotriazole derivatives for 30 to 60 seconds, rinsed with deionized water and dried to obtain the high-performance flexible shielding film.

9. A high-performance flexible shielding film, characterized in that, It is prepared according to the preparation method of the high-performance flexible shielding film as described in any one of claims 1 to 8.

10. The application of the high-performance flexible shielding film as described in claim 9 in electronic devices.