Circuit board to which 3D-molded electromagnetic shielding film is attached, 3D-molded electromagnetic shielding film, and 3D-molded electromagnetic shielding film

Abstract

The invention relates to a circuit board attached with a 3D-formed electromagnetic shielding film, the 3D-formed electromagnetic shielding film, the 3D-formed electromagnetic shielding film and a method for attaching the electromagnetic shielding film to the circuit board. The circuit board comprises electronic components, the 3D molded electromagnetic shielding film comprises a molding layer, a shielding layer and an adhesive film, the molding layer and the adhesive film are arranged in a stacked mode, the shielding layer is a conductive non-woven layer, the conductive non-woven layer is embedded in the adhesive film, and the adhesive film is arranged between the molding layer and the shielding layer. And the ratio of the surface area S2 deducted from the upper surface area of the electronic component after the electromagnetic shielding film is formed to the surface area S1 deducted from the upper surface area of the electronic component before the electromagnetic shielding film is formed is 1.5-17. The electromagnetic shielding film is attached to an electronic component of the system-in-package module through a 3D forming process, and has good electromagnetic shielding performance. The circuit board attached with the 3D formed electromagnetic shielding film is suitable for a wave soldering or reflow soldering process in the subsequent production process, and the electromagnetic shielding film cannot be damaged by the reflow soldering process.

Description

[0001] This application is a divisional application of National Application No. 202011523926.0, entitled "Circuit board with 3D-molded electromagnetic shielding film attached, 3D-molded electromagnetic shielding film and 3D-molded electromagnetic shielding film". Technical Field

[0002] This invention relates to the technical field of electromagnetic shielding films. Specifically, this invention provides a circuit board with a 3D-molded electromagnetic shielding film attached, a 3D-molded electromagnetic shielding film, and a 3D-molded electromagnetic shielding film that can be used in system-in-package (SIP) modules. Background Technology

[0003] Electronic components, especially electronic devices, are highly sensitive to electromagnetic interference (EMI). EMI sources are numerous and can originate from the electronic device itself. EMI interference generated between different devices on an integrated circuit board often affects the operational stability of electronic components, and in severe cases, can lead to device failure. EMI becomes more pronounced when the main circuit is small and the components are close together, and when the electronic device operates at higher frequencies. To ensure the proper functioning of electronic devices, it is essential to shield against unwanted electromagnetic interference.

[0004] As electronic device designs shrink and the number of electronic components integrated on printed circuit boards increases, the industry has begun to see the integration of one or more electronic components and passive elements into a single package system, known as System-in-Package (SIP). Compared to traditional packaging processes, device-level packaging offers electromagnetic shielding that can be applied to the entire device or to individual components within the device. With the advancement of device miniaturization and highly integrated processes, electromagnetic shielding for system-in-packages has remained a hot research topic.

[0005] However, in the packaging stage, the spacing between SIP components is very narrow. SIP components are typically rectangular or square with sides ranging from 1000 to 50000 µm, with a spacing of 200-1000 µm between two components and a depth of 400-1600 µm. For electromagnetic shielding of this component, a continuous and effective conductive layer needs to be formed on the outermost layer of the device. This conductive layer is connected to the ground wire of the circuit board, thus forming a Faraday cage to achieve the shielding effect. The grounding point of the SIP device is often located at the lower third of the device height, i.e., on a multi-layer circuit board; therefore, the electromagnetic shielding layer must achieve effective conductivity with the multi-layer circuit board.

[0006] Electromagnetic shielding for System-in-Package (SIP) typically employs methods such as magnetron sputtering, spraying, and electroplating / chemical plating. There are also reports of using 3D-molded conductive adhesive (WO2018147355). All methods aim to achieve effective conductive layer coverage, interconnectivity of the conductive layers, and good grounding with the circuit board as key technical indicators. Magnetron sputtering is costly and complex. Spraying is inefficient and has a high defect rate. Electroplating / chemical plating causes significant environmental pollution and lacks effective coating protection.

[0007] In summary, there is currently a significant demand for electromagnetic shielding films that possess good plasticity, are easy to 3D mold, and are suitable for lead-free reflow soldering processes. Therefore, developing an electromagnetic shielding film that is easy to 3D mold, suitable for lead-free reflow soldering processes after 3D molding, and possesses good electromagnetic shielding performance is of great importance. Summary of the Invention

[0008] Based on the technical problems described above, the purpose of this invention is to provide a circuit board with a 3D-molded electromagnetic shielding film and a 3D-molded electromagnetic shielding film for circuit boards. According to the technical solution of this invention, the electromagnetic shielding film for system-in-package circuit boards is easily thermoformed, possesses good electromagnetic shielding performance, good plasticity, and can withstand reflow soldering processes. The molding layer not only provides good conformal properties during molding but also adds extra physical protection to the shielding layer, effectively improving the reliability of the device.

[0009] The inventor completed this invention through in-depth and meticulous research.

[0010] According to one aspect of the present invention, a circuit board with a 3D-molded electromagnetic shielding film attached is provided. The circuit board includes electronic components. The 3D-molded electromagnetic shielding film includes a molding layer, a shielding layer, and an adhesive film. The molding layer and the adhesive film are stacked. The shielding layer is a conductive nonwoven layer embedded in the adhesive film. The ratio of the surface area S2 of the electromagnetic shielding film after molding (excluding the surface area of ​​the electronic components) to its surface area S1 before molding (excluding the surface area of ​​the electronic components) is 1.5 to 17. The surface resistance of the electromagnetic shielding film is less than or equal to 10Ω, and its loss factor (i.e., damping value) tan δ is less than or equal to 0.2 in a temperature range of 180-250°C.

[0011] The electromagnetic shielding film, after 3D molding, deducts the surface area of ​​the electronic components ( The surface area S2 of the electronic components is less than the surface area of ​​the components before molding. The formula for calculating the ratio of the surface area S1 of the surface area ...

[0012]

[0013] Where l1 is the side length of the electronic component along the x-axis, l2 is the side length of the electronic component along the y-axis, d1 is the width of the slit between the two electronic components along the x-axis, d2 is the width of the slit between the two electronic components along the y-axis, and h is the height of the electronic component along the z-axis. (For reference) Figure 3 When the electronic components are irregularly shaped, the area of ​​the electromagnetic shielding film before molding, the upper surface area of ​​the electronic components, and the side surface area of ​​the electronic components are all replaced with the area actually measured by laser 3D scanning.

[0014] According to another aspect of the present invention, a 3D-formable electromagnetic shielding film is provided, the 3D-formable electromagnetic shielding film comprising a thermoplastic layer, a shielding layer, and an adhesive film, wherein the thermoplastic layer and the adhesive film are stacked, the shielding layer is a conductive nonwoven layer, the conductive nonwoven layer is partially embedded in the adhesive film, wherein the 3D-formable electromagnetic shielding film has a loss factor value (i.e., damping value) tan δ that is greater than or equal to 0.5 at at least one temperature point within a temperature range of 50-200°C.

[0015] According to another aspect of the present invention, a 3D-molded electromagnetic shielding film is provided, wherein the electromagnetic shielding film comprises any of the 3D-molded electromagnetic shielding films provided in the present invention.

[0016] According to another aspect of the present invention, a method for attaching an electromagnetic shielding film to a circuit board is provided, comprising attaching any 3D-formable electromagnetic shielding film of the present invention to the circuit board and performing 3D forming. The 3D-formable electromagnetic shielding film, after 3D forming, comprises: a molding layer, a shielding layer, and an adhesive film, wherein the molding layer and the adhesive film are stacked, the shielding layer is a conductive nonwoven layer, and the conductive nonwoven layer is embedded in the adhesive film. The ratio of the surface area S2 of the electromagnetic shielding film after forming (excluding the surface area of ​​electronic components) to its surface area S1 before forming (excluding the surface area of ​​electronic components) is 1.5 to 17. The surface resistance of the electromagnetic shielding film is less than or equal to 10Ω, and its loss factor (i.e., damping value) tan δ is less than or equal to 0.2 within a temperature range of 180-250°C. Attached Figure Description

[0017] The accompanying drawings, which are incorporated herein and form part of this specification, illustrate exemplary embodiments of the invention and, together with the general description provided above and the detailed description provided below, serve to explain the features of the invention.

[0018] Figure 1This is a cross-sectional view of a 3D-molded electromagnetic shielding film formed on multiple electronic devices on a system-in-package (SIP) circuit board according to an embodiment of the present invention; wherein 101 is the electromagnetic shielding film, 102 is the SIP component, and 103 is the circuit board;

[0019] Figure 2 This is a cross-sectional view of a 3D-molded electromagnetic shielding film on a single electronic device according to yet another embodiment of the present invention; wherein 204 is a molding layer; 205, 207 and 208 are adhesive layers; and 206 is a conductive nonwoven fabric.

[0020] Figure 3 This is a schematic diagram of the system-in-package (SIP) device in this invention; where 302 is a SIP device, 303 is a circuit board; the length of the SIP device along the x-axis is l1, the width of the SIP device along the y-axis is l2, the height is h, the distance between two adjacent devices along the x-axis is d1, and the distance between them along the y-axis is d2; and

[0021] Figure 4 This is a test fixture for testing the surface resistance of an electromagnetic shielding film in this invention. Detailed Implementation

[0022] It should be understood that, without departing from the scope or spirit of this disclosure, those skilled in the art can conceive of various other embodiments and can modify them based on the teachings of this specification. Therefore, the following specific embodiments are not intended to be limiting.

[0023] Unless otherwise specified, all figures used in this specification and claims to indicate feature dimensions, quantities, and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired characteristics using the teachings disclosed herein. The use of numerical ranges indicated by endpoints includes all numbers within that range and any range within that range; for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0024] According to the technical solution of the present invention, the term "thermoplasticity" refers to the property of a material that can soften and deform when heated and retain a certain shape after cooling. In the softened state, it can be molded or extruded.

[0025] According to the technical solution of the present invention, the term "thermoplastic" refers to a plastic that is plastic at a certain temperature, solidifies upon cooling, and can repeat this process. Its molecular structure is characterized by linear polymer compounds, generally lacking active groups, and does not undergo linear intermolecular cross-linking upon heating. Such materials can be molded using amorphous plastics, with high-temperature induction of crystallization and cooling to solidify, thus improving the material's plasticity.

[0026] According to the technical solution of the present invention, the term "thermosetting plastic," also known as thermosetting plastic, has a chain structure like thermoplastic plastic before molding. During the molding process, thermosetting plastic undergoes a thermal or chemical polymerization reaction to form a cross-linked structure. Once the reaction is complete, the polymer molecules bond to form a three-dimensional network structure. These cross-linked bonds prevent the sliding between molecular chains, resulting in the thermosetting plastic becoming a non-melting and insoluble solid.

[0027] According to the technical solution of the present invention, the term "thermoplastic elastomer (TPE)" refers to a type of elastomer that has the elasticity of rubber at room temperature and can be plasticized and molded at high temperatures. This type of polymer is typically a block copolymer containing hard and soft segments. The soft segments and the uncrystallized hard segments form an amorphous phase, providing elasticity, while some hard segments crystallize to form crystalline microregions, acting as physical crosslinking points and providing plasticity.

[0028] According to the technical solution of the present invention, the term "thermosetting elastomer (TSE)" refers to a cross-linked thermoplastic elastomer. "Cross-linked thermoplastic elastomer" refers to a thermoplastic elastomer used in the manufacture of thermoplastic layers that has undergone chemical cross-linking or electron beam treatment to form a chemically cross-linked thermoplastic elastomer. The chemical cross-linking treatment creates chemical cross-linking points within the thermoplastic elastomer through chemical bonding, forming a cross-linked network structure. Therefore, the cross-linked thermoplastic elastomer no longer possesses thermoplasticity. That is, a cross-linked thermoplastic elastomer is not a thermoplastic elastomer in the traditional sense. Cross-linked elastomers are rubbers in the conventional sense, such as heat-cured silicone rubber and heat-cured nitrile rubber.

[0029] According to the technical solution of the present invention, the term "3D-formed electromagnetic shielding film" refers to an electromagnetic shielding film that can be 3D formed on a circuit board through molding, air pressure and vacuum forming and other shaping methods.

[0030] Molding layer

[0031] In order to meet the basic purpose of electromagnetic shielding film, the “shaping layer” of electromagnetic shielding film in this invention may include one or more of thermoplastic plastics, thermosetting plastics, thermoplastic elastomers and thermosetting elastomers after shaping.

[0032] Preferred thermoplastic materials include polycarbonate (such as Sabic and Lexan series resins from SABIC), polyetheretherketone (such as Victrex APTIV series), polyaryletherketone (such as PEAK from Changchun Jida Special Plastics Engineering Research Co., Ltd.), polyetherimide (such as Sabic and Ultem series resins from SABIC), and polyphenylene sulfide (such as Fortron series resins from Polyplastics Japan). More preferably, non-crystalline or low-crystallinity thermoplastic films are used, allowing the non-crystalline or low-crystallinity plastic to undergo a crystallization heat setting process during 3D molding.

[0033] Thermosetting plastics include phenolic resins (such as AICA BRG series resins from Japan), unsaturated polyesters, epoxy resins (such as Ashland's UPR series resins), silicone resins (such as Wacker's SILRES series resins), polyurethanes (such as Covestro's CPU series), and thermosetting elastomers such as liquid silicone rubber (such as Momentive LIM LSR), thermoplastic polyurethane elastomers (such as COIM LARIPUR series), thermoplastic polyester elastomers (such as DSM TPC-EM series resins), and thermoplastic vulcanized ester elastomers (such as Mitsui TPV series). Products resulting from the chemical crosslinking of any of these thermoplastic elastomers also exhibit shaped characteristics before chemical curing and can therefore be used in this invention. These resins are preferably high-melting-point resins (e.g., greater than 50 degrees Celsius), which soften during molding to achieve conformal shaping and then undergo a curing reaction for final shaping.

[0034] The preferred thermoplastic elastomer material is one or more of thermoplastic polyurethane elastomers, thermoplastic polyester elastomers, and thermoplastic vulcanizate elastomers. The specific type of thermoplastic elastomer used in this invention is not particularly limited, as long as its molecule has a chemically crosslinkable structure (including structures with crosslinkable groups such as unsaturated double bonds, isocyanates, etc., or structures that can be broken and crosslinked by radiation, such as carbon-hydrogen bonds, unsaturated double bonds, etc.). The thermoplastic elastomer used in this invention can be prepared according to known methods in existing art literature or is commercially available. Commercially available thermoplastic polyester elastomer (TPE) products suitable for this invention include DSM's TPC series materials, such as TPC-EM740, TPC-EM550, and TPC-EM400. DuPont's HYTREL series TPEE products are also suitable for this invention, such as HYTREL 5556, HYTREL 6356, HYTREL 7246, and HYTREL 8238. These polyester elastomers comprise block copolymers consisting of crystalline hard segments of polybutylene terephthalate (PBT) and soft segments of polyether based on long-chain polytetrahydrofuran (PTMG). Commercially available polyurethane elastomers (TPUs) suitable for this invention include LPR 9060, LPR2203-93, etc., from COIM, Italy. These materials preferably use high-melting-point polymer resins that can be shaped between 50 and 200 degrees Celsius through a crystalline heat-setting process. To further improve the thermal stability while maintaining good thermoforming properties, the thermoplastic elastomer constituting the electromagnetic shielding film is preferably chemically crosslinked. There are no particular limitations on the method used for chemically crosslinking the thermoplastic elastomer, and conventional physicochemical methods can be employed, such as electron beam radiation crosslinking, microwave radiation crosslinking, ultraviolet radiation crosslinking, and chemical crosslinking. Preferably, the thermoplastic elastomer is cured by electron beam radiation crosslinking. The electron beam radiation includes irradiating the thermoplastic elastomer with an electron beam energy of 100 to 300 kV to a dose of 3 to 16 Mrad, in order to break down weak points in the thermoplastic elastomer molecules and induce cross-linking through chemical bonds.

[0035] Preferred thermosetting elastomer materials include cross-linked thermoplastic polyurethane elastomers, cross-linked thermoplastic polyester elastomers, and hot-vulcanized rubber. Cross-linked thermoplastic polyurethane elastomers and cross-linked thermoplastic polyester elastomers, due to further chemical cross-linking, exhibit infusible and non-melting properties at high temperatures, making them more suitable for the application of this invention. Hot-vulcanized rubber materials are easier to mold within a specific temperature range and then further vulcanize at high temperatures to form an insoluble and infusible solid.

[0036] The shaping layer is in the form of a thin film. Due to the limited spacing between devices, the thickness of the film is 5µm to 100µm, or 5µm to 50µm, or 5µm to 20µm.

[0037] conductive nonwoven layer

[0038] The conductive nonwoven layer applicable to the present invention includes a polymer nonwoven fiber material and a conductive material, wherein the melting point of the polymer nonwoven fiber material is greater than or equal to 220°C.

[0039] Polymer nonwoven fiber materials include one or more of liquid crystal polymer nonwoven fiber materials and polyethylene terephthalate nonwoven fiber materials.

[0040] Conductive nonwoven materials use polymer fiber materials as the nonwoven fabric substrate. One or more conductive metal layers, such as one or more layers of nickel, copper, silver, or gold, are formed on the surface of the polymer fibers through electroplating, chemical plating, magnetron sputtering, or other methods, thus achieving conductivity. Polymer nonwoven fiber materials with a melting point of 220℃ or higher are preferred to ensure the thermal stability of the product.

[0041] In this invention, the conductive nonwoven material provides shielding and grounding. Therefore, it is not necessary for the adhesive layer to contain a high content of conductive particles to achieve good shielding and grounding effects.

[0042] The conductive material in the polymer nonwoven fiber material at least partially covers the surface of the polymer nonwoven fiber material.

[0043] The thickness of the conductive nonwoven layer is 10–50 µm, and the thickness of the coating is typically 0.5–5 µm.

[0044] Adhesive film

[0045] The 3D-molded electromagnetic shielding film applicable to this invention includes an adhesive film. The adhesive film can be an organosilicon pressure-sensitive adhesive film or a structural adhesive film.

[0046] In the electromagnetic shielding film 3D-molded according to the present invention, the adhesive film and the molding layer are stacked. Before 3D molding, the conductive nonwoven shielding layer is partially embedded in the adhesive film; after 3D molding, the conductive nonwoven shielding layer is completely embedded in the adhesive film. The adhesive film serves to bond the molding layer and the conductive nonwoven layer.

[0047] According to some preferred embodiments of the present invention, the adhesive film may also contain no more than 40 wt.% conductive filler to improve the shielding performance and grounding performance of the 3D-molded electromagnetic shielding film.

[0048] Silicone pressure-sensitive adhesives are adhesive layers composed primarily of polydimethylsiloxane, with added silicone resin as a tackifying resin. They are typically crosslinked using peroxides. Silicone pressure-sensitive adhesives containing vinyl groups often employ noble metal-catalyzed silicon-hydrogen bond addition for crosslinking; some examples even utilize electron beam or UV radiation crosslinking. To further improve the temperature resistance of silicone pressure-sensitive adhesives, the use of phenyl-containing polymethylsiloxanes is also a common industry practice.

[0049] When the adhesive film according to the present invention is an organosilicon pressure-sensitive adhesive film, the storage modulus of the organosilicon pressure-sensitive adhesive film at 25°C and 1Hz is 40,000–2,000,000 Pa. It has good adhesion and moldability, and this parameter hardly changes before and after 3D molding.

[0050] When the adhesive film according to the present invention is a structural adhesive film, the structural adhesive film is a cured product of epoxy resin and a hardener. The epoxy resin includes one or more of phenolic epoxy resin, cresol-type epoxy resin, epoxy resin containing a dicyclopentadiene structure and its derivatives, and epoxy resin containing a 9,9-diphenylfluorene structure and its derivatives. The hardener includes one or more of diaminodiphenyl sulfone, dicyandiamide, linear phenolic resin, and linear cresol-type phenolic resin. The epoxy adhesive film is a non-stick adhesive layer prepared by solvent or hot-melt coating of epoxy resin, hardener, and optionally accelerator.

[0051] The adhesive film suitable for this invention may be free of conductive particles, or contain conductive filler of less than or equal to 40 wt.% of the total weight of the adhesive film. That is, the electromagnetic shielding film provided in this invention can achieve shielding or grounding without relying on conductive filler in the adhesive film. In this invention, the conductive particles in the adhesive film enhance the shielding and grounding function of the conductive nonwoven layer. Even without conductive particles, the adhesive film can still achieve shielding and grounding through the conductive nonwoven layer. If no conductive nonwoven layer is present, and only no more than 40 wt.% of conductive filler is used in the adhesive film, the surface resistance of the electromagnetic shielding film may exceed 10 ohms, but effective grounding and shielding functions cannot be achieved.

[0052] In the 3D-formable electromagnetic shielding film provided by this invention, a conductive nonwoven layer is partially embedded in the adhesive film; in the 3D-formable electromagnetic shielding film provided by this invention, a conductive nonwoven layer is embedded in the adhesive film. This invention uses a conductive nonwoven layer, which can improve the cohesive strength of the electromagnetic shielding film and enhance product reliability by controlling the interpenetration between the adhesive film and the conductive nonwoven layer.

[0053] The molding layer can be thermoformed to effectively constrain the conductive nonwoven layer and the adhesive film, resulting in an ideal 3D shape. This invention is particularly suitable for circuit boards with high electronic component height and small spacing. Simultaneously, the molding layer provides mechanical protection to the inner shielding layer (conductive nonwoven layer) during wave soldering or reflow soldering processes. Through interpenetration with the adhesive film, some fibers of the conductive nonwoven layer are exposed on the surface after thermoforming, providing interconnection with the device's grounding point. In some embodiments of this invention, adding an appropriate amount of conductive particles to the adhesive film can further improve the grounding performance of the 3D-formed electromagnetic shielding film.

[0054] The 3D-molded electromagnetic shielding film of this invention comprises a laminated structure consisting of a molding layer, an adhesive layer, and a conductive non-woven fabric layer. This laminated structure can be prepared by independently preparing single-layer materials and then bonding them together (using appropriate temperature and pressure). Alternatively, it can be prepared by coating the adhesive layer onto the molding layer and then bonding it to the non-woven fabric layer. It can also be prepared by coating the non-woven fabric, controlling the amount of adhesive tape penetration, and then bonding it to the molding layer.

[0055] This invention also provides a method for preparing a 3D-formed electromagnetic shielding film, wherein a 3D-formable electromagnetic shielding film according to any embodiment of the invention is attached to a circuit board and 3D-formed to obtain a 3D-formed electromagnetic shielding film. The 3D-formation method includes any of the following: molding, air pressure, and vacuum forming.

[0056] Hot pressing molding refers to preparing a mold with the same recessed shape as the electronic component, placing the electromagnetic shielding film preheated to the molding temperature horizontally on the surface of the electronic component, and pressing the electromagnetic shielding film into the groove between the electronic components by heating the mold.

[0057] Pneumatic molding refers to the process of using high-temperature, high-pressure gas to place an electromagnetic shielding film preheated to the molding temperature horizontally on the surface of an electronic component, and then injecting high-pressure gas into the mold cavity to pressurize and complete the molding process.

[0058] Vacuum forming refers to the process of creating air holes at the connection points of electronic components and then applying a vacuum force in the opposite direction to mold a preheated electromagnetic shielding film onto the device.

[0059] If epoxy film is used, the 3D-molded electromagnetic shielding film still needs to be further cured at high temperature to obtain the final product.

[0060] The following list of embodiments further illustrates various exemplary embodiments of the invention, which should not be construed as unduly limiting the invention:

[0061] Specific implementation scheme 1 is a circuit board with a 3D-molded electromagnetic shielding film attached. The circuit board includes electronic components. The 3D-molded electromagnetic shielding film includes a molding layer, a shielding layer, and an adhesive film. The molding layer and the adhesive film are stacked. The shielding layer is a conductive nonwoven layer embedded in the adhesive film. The surface area S2 of the electromagnetic shielding film after molding (excluding the surface area of ​​the electronic components) is 1.5 to 17 compared with the surface area S1 of the electromagnetic shielding film before molding (excluding the surface area of ​​the electronic components). The surface resistance of the electromagnetic shielding film is less than or equal to 10Ω, and its loss factor value (i.e., damping value) tan δ is less than or equal to 0.2 in the temperature range of 180-250℃.

[0062] Specific implementation scheme 2 is the circuit board according to specific implementation scheme 1, wherein the conductive nonwoven layer includes a polymer nonwoven fiber material and a conductive material, and the melting point of the polymer nonwoven fiber material is greater than or equal to 220°C.

[0063] Specific implementation scheme 3 is the circuit board according to specific implementation scheme 2, wherein the polymer nonwoven fiber material includes at least one of liquid crystal polymer nonwoven fiber material and polyethylene terephthalate nonwoven fiber material.

[0064] Specific implementation scheme 4 is the circuit board according to specific implementation scheme 2, wherein the conductive material at least partially covers the polymer nonwoven fiber material.

[0065] Specific implementation scheme 5 is the circuit board according to specific implementation scheme 1, wherein the adhesive film includes pressure-sensitive adhesive film or structural adhesive film.

[0066] Specific implementation scheme 6 is based on the circuit board described in specific implementation scheme 5, wherein when the adhesive film is an organosilicon pressure-sensitive adhesive film, the energy storage modulus of the organosilicon pressure-sensitive adhesive film at 25°C and 1Hz is 40,000-2,000,000Pa.

[0067] Specific implementation scheme 7 is based on the circuit board described in specific implementation scheme 5, wherein when the adhesive film is a structural adhesive film, the structural adhesive film is a cured product of epoxy resin and hardener.

[0068] Specific implementation scheme 8 is the circuit board according to specific implementation scheme 7, wherein the epoxy resin includes one or more of phenolic epoxy resin, cresol type epoxy resin, epoxy resin containing dicyclopentadiene structure and its derivatives, and epoxy resin containing 9,9-diphenylfluorene structure and its derivatives.

[0069] Specific implementation scheme 9 is the circuit board according to specific implementation scheme 7, wherein the hardener comprises one or more of diaminodiphenyl sulfone, dicyandiamide, linear phenolic resin and linear cresol phenolic resin.

[0070] Specific implementation scheme 10 is the circuit board according to specific implementation scheme 5, wherein the adhesive film further comprises conductive filler, and the content of the conductive filler is less than or equal to 40 wt.% of the total weight of the adhesive film.

[0071] Specific implementation scheme 11 is the circuit board according to specific implementation scheme 1, wherein the molding layer comprises one or more of thermoplastic plastics, thermosetting plastics, thermoplastic elastomers and thermosetting elastomers after molding and shaping.

[0072] Specific implementation scheme 12 is the circuit board according to specific implementation scheme 11, wherein the thermoplastic plastic comprises one or more of polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide and polyphenylene sulfide.

[0073] Specific implementation scheme 13 is the circuit board according to specific implementation scheme 11, wherein the thermosetting plastic comprises one or more of phenolic resin, unsaturated polyester, epoxy resin, silicone resin and polyurethane.

[0074] Specific implementation scheme 14 is the circuit board according to specific implementation scheme 11, wherein the thermoplastic elastomer includes one or more of thermoplastic polyurethane elastomer, thermoplastic polyester elastomer and thermoplastic vulcanized ester elastomer.

[0075] Specific implementation scheme 15 is the circuit board according to specific implementation scheme 11, wherein the thermosetting elastomer comprises one or more of the following products after chemical crosslinking: vulcanized silicone rubber, vulcanized nitrile rubber, thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, and thermoplastic vulcanized ester elastomer.

[0076] Specific implementation scheme 16 is a 3D-formable electromagnetic shielding film, which includes a thermoplastic layer, a shielding layer, and an adhesive film. The thermoplastic layer and the adhesive film are stacked. The shielding layer is a conductive nonwoven layer, which is partially embedded in the adhesive film. The loss factor (i.e., damping value) tan δ of the 3D-formable electromagnetic shielding film is greater than or equal to 0.5 at at least one temperature point within the temperature range of 50-200℃.

[0077] Specific implementation scheme 17 is a 3D-formable electromagnetic shielding film according to specific implementation scheme 16, wherein the conductive nonwoven layer includes a polymer nonwoven fiber material and a conductive material, and the melting point of the polymer nonwoven fiber material is greater than or equal to 220°C.

[0078] Specific implementation scheme 18 is a 3D-formable electromagnetic shielding film according to specific implementation scheme 17, wherein the polymer nonwoven fiber material includes at least one of liquid crystal polymer nonwoven fiber material and polyethylene terephthalate nonwoven fiber material.

[0079] Specific implementation scheme 19 is a 3D-formable electromagnetic shielding film according to specific implementation scheme 17, wherein the conductive material at least partially covers the polymer nonwoven fiber material.

[0080] Specific implementation scheme 20 is a 3D-formable electromagnetic shielding film according to specific implementation scheme 16, wherein the film comprises a pressure-sensitive adhesive film or a structural adhesive film.

[0081] Specific implementation scheme 21 is an electromagnetic shielding film that can be 3D molded according to specific implementation scheme 20, wherein when the adhesive film is an organosilicon pressure-sensitive adhesive film, the storage modulus of the organosilicon pressure-sensitive adhesive film at 25°C and 1Hz is 40,000–2,000,000 Pa.

[0082] Specific implementation scheme 22 is the 3D-formable electromagnetic shielding film according to specific implementation scheme 20, wherein when the adhesive film is a structural adhesive film, the structural adhesive film contains epoxy resin and a hardener.

[0083] Specific implementation scheme 23 is a 3D-formable electromagnetic shielding film according to specific implementation scheme 22, wherein the epoxy resin includes one or more of phenolic epoxy resin, cresol type epoxy resin, epoxy resin containing dicyclopentadiene structure and its derivatives, and epoxy resin containing 9,9-diphenylfluorene structure and its derivatives.

[0084] Specific implementation scheme 24 is a 3D-formable electromagnetic shielding film according to specific implementation scheme 22, wherein the curing agent comprises one or more of diaminodiphenyl sulfone, dicyandiamide, linear phenolic resin and linear cresol-type phenolic resin.

[0085] Specific implementation scheme 25 is a 3D-formable electromagnetic shielding film according to specific implementation scheme 16, wherein the film further comprises conductive filler, and the content of the conductive filler is less than or equal to 40 wt.% of the total weight of the film.

[0086] Specific embodiment 26 is a 3D-molded electromagnetic shielding film, wherein the 3D-molded electromagnetic shielding film comprises the 3D-molded electromagnetic shielding film as described in any one of embodiments 1 to 15.

[0087] Specific embodiment 27 is a method for attaching an electromagnetic shielding film to a circuit board, comprising attaching a 3D-formable electromagnetic shielding film as described in any one of embodiments 16 to 25 to the circuit board and performing 3D forming.

[0088] Specific implementation scheme 28 is a method for attaching an electromagnetic shielding film to a circuit board according to specific implementation scheme 27. The 3D-formable electromagnetic shielding film, after 3D forming, comprises: a molding layer, a shielding layer, and an adhesive film. The molding layer and the adhesive film are stacked. The shielding layer is a conductive nonwoven layer embedded in the adhesive film. The ratio of the surface area S2 of the electromagnetic shielding film after forming (excluding the surface area of ​​the electronic components) to its surface area S1 before forming (excluding the surface area of ​​the electronic components) is 1.5 to 17. The surface resistance of the electromagnetic shielding film is less than or equal to 10Ω, and its loss factor value (i.e., damping value) tan δ is less than or equal to 0.2 in the temperature range of 180-250℃.

[0089] The present invention will now be described in more detail with reference to embodiments. It should be noted that these descriptions and embodiments are intended to facilitate understanding of the invention and are not intended to limit the invention. The scope of protection of the present invention is defined by the appended claims.

[0090] Example

[0091] In this invention, unless otherwise specified, all reagents used are commercially available products and are used directly without further purification.

[0092]

[0093] Test methods

[0094] Surface resistance

[0095] Test fixtures and dimensions as follows Figure 4 As shown, the test fixture weighs 250g in total. It consists of two 25.4mm x 5mm gold-plated conductive blocks on either side and an insulating plastic block in the middle. Prepare a 25.4mm electromagnetic shielding film, with the molding layer facing down and the adhesive layer facing up. Place the test fixture shown in the diagram on the electromagnetic shielding film. Figure 4 As shown, 401 is an electromagnetic shielding film; 409 is a gold-plated conductive block; 410 is an insulating plastic block; D1 is the length of the gold-plated conductive block on the x-axis; D2 is the vertical distance between two parallel gold-plated conductive blocks; D3 is the thickness of the insulating plastic block; and D4 is the length of the gold-plated conductive block on the y-axis. Then, a direct current is applied, and the DC resistance is recorded after 15 seconds. From 15 to 60 seconds, a resistance value is recorded every 5 seconds. The average of the recorded resistance values ​​is recorded as the surface resistance.

[0096] Dynamic Mechanical Testing (DMA) Curve

[0097] The rheological properties of the electromagnetic shielding film samples prepared in Examples 1-4 were measured by the following methods to determine the degree of change in their loss factor.

[0098] Specifically, a DMA Q800 manufactured by TA Instruments (USA) was used in a tensile mode. Samples were prepared to be 10mm x 5mm and held in a tensile fixture. Rheological measurements were then performed at different temperature points with a heating rate of 5℃ / min and a testing frequency of 1Hz to obtain the storage modulus G' and loss modulus G''. The loss factor (i.e., damping value) tan δ was then calculated from the storage modulus G' and loss modulus G'' using the following formula:

[0099] tan δ=G'' / G'.

[0100] Rheology curves

[0101] The rheological properties of the organosilicon pressure-sensitive adhesive of the electromagnetic shielding film samples prepared in Examples 1-4 were measured by the following methods to determine the degree of change in their damping properties.

[0102] Specifically, rheological curves were measured using an Ares G2 rotational rheometer manufactured by TA Instruments, Inc. First, a 1 mm thick pressure-sensitive adhesive film sample was clamped using an 8-inch parallel plate clamp. Then, rheological measurements were performed at different temperature points under conditions of a heating rate of 5 °C / min, a testing frequency of 1 Hz, and a strain of less than or equal to 1%, to obtain the storage modulus G' and loss modulus G''. The loss factor (i.e., damping value) tan δ was then calculated from the storage modulus G' and loss modulus G'' using the following formula:

[0103] tan δ=G'' / G'.

[0104] Example

[0105] Example 1

[0106] Take 500g of silicone pressure-sensitive adhesive PSA6574, dilute the solid content to 30% with toluene, add 7.5g of Luperox A75 (Sigma-Aldrich), and coat a 10µm thick adhesive film onto a release film (fluoroplastic release film, Siliconature 1R82001) using a slot extrusion coating method. After curing in an oven at 150℃ for 2 minutes, heat-bond a 15µm conductive nonwoven fabric and a 9µm APTIV 2000 PEEK film onto the adhesive surface of the adhesive film at a temperature of 80℃ and a pressure of 1MPa. This yields a 3D-formable electromagnetic shielding film.

[0107]

[0108] The 3D-formable electromagnetic shielding film was measured using DMA stretching mode at a fixed frequency of 1 Hz, with a heating rate of 5 ℃ / min from 25 to 250℃. The curve showed tan δ > 0.5 in the range of 135–180℃, with a maximum value of 1.8 at 150℃.

[0109] This 3D-formable electromagnetic shielding film can be thermoformed, such as by using air pressure at 150℃, to achieve a good 3D shape. This 3D-formable electromagnetic shielding film can then be applied to electronic components on circuit boards (such as...). Figure 3 On the surface, a hot-pressed film is formed at 150℃, then heated to 180℃ and held for 30 seconds, before being cooled to 50℃ and the mold opened. The APTV2000 film undergoes further crystallization transformation to obtain a 3D-formed electromagnetic shielding film. Measurements were performed using DMA stretching mode at a fixed frequency of 1Hz, with temperatures ranging from 150℃ to 250℃ at a rate of 5℃ / min. Within the temperature range of 180℃ to 250℃, tan δ was less than 0.2. The maximum tan δ value occurred at 250℃, reaching 0.14. The measured surface resistivity was 150mΩ.

[0110] The device structure used in Example 1 is as follows: Figure 3 As shown in the table below, the corresponding dimensions are as follows. The ratio of the surface area S2 after molding to the surface area S1 before molding is 2.9697.

[0111]

[0112] *The above measurements can be taken using laser 3D scanning, or by embedding the sample in resin, slicing it, and then measuring it under a microscope.

[0113] Example 2

[0114] Epoxy resin DIC 7200HH was dissolved in methyl ethyl ketone (MEK) with a solid content of 70%. Linear phenolic resin AICA BRG-557 was also dissolved in MEK with a solid content of 70%. 100g of the dissolved DIC 7200HH resin solution and 30g of AICA BRG-557 resin solution were mixed thoroughly, and then 3g of 2M4Z was added. The solution was allowed to dissolve until clear and transparent. The epoxy adhesive was coated onto a 10µm conductive PET nonwoven fabric using a slot extrusion coating method, and the solvent was dried at 90℃. The resulting conductive nonwoven fabric with adhesive had a total thickness of 12µm. A 9µm PEEK APTIV2000 PEEK film was then thermally bonded onto the adhesive-coated conductive nonwoven fabric. This yielded a 3D-formable electromagnetic shielding film.

[0115] The 3D-formable electromagnetic shielding film was measured using DMA stretching mode at a fixed frequency of 1 Hz, with a heating range of 25–250 °C and a heating rate of 5 °C / min. The curve showed tan δ > 0.5 in the range of 80–180 °C, with a maximum value of 2.4 at 130 °C.

[0116] This 3D-formable electromagnetic shielding film is attached to a circuit board and can be thermoformed. For example, molding at 150℃ using a die-cutting method can produce a 3D shape that fits well with the electronic components on the circuit board. The film is formed at 150℃, then heated to 180℃ and held for 10 minutes, before being cooled to 50℃ and the die is opened. The resulting product is further cured in a 120℃ oven for 30 minutes to obtain the final electromagnetic shielding film. Measurements were performed using DMA stretching mode at a fixed frequency of 1Hz, with a heating rate of 5℃ / min from 150℃ to 250℃. Within the temperature range of 180℃ to 250℃, tan δ was less than 0.2. The maximum tan δ value occurred at 220℃, reaching 0.05. The surface resistivity was measured to be 500mΩ.

[0117] The device structure used in Example 2 is as follows: Figure 3 As shown in the table below, the corresponding dimensions are as follows. The ratio of the surface area S2 after molding to the surface area S1 before molding is 10.8684.

[0118]

[0119] The other device structure used in Example 2 is also as follows. Figure 3 As shown in the table below, the corresponding dimensions are as follows. The ratio of the surface area S2 after molding to the surface area S1 before molding is 8.8843.

[0120]

[0121] Example 3

[0122] A 10µm thermoplastic polyester elastomer film was prepared by casting and stretching using DuPont Hytrel 7246 particles, and then crosslinked by 180KV 9Mrad electron beam radiation to obtain a crosslinked thermoplastic polyester elastomer film.

[0123] Epoxy resin NPCN 702H was dissolved in methyl ethyl ketone (MEK) with a solid content of 70%. Linear phenolic resin NPEH 710 was also dissolved in MEK with a solid content of 70%. 100g of the dissolved NPCN 702H resin solution and 25g of NPEH 710 resin solution were mixed thoroughly, and then 3g of 2MZ-A was added. After the solution dissolved until clear and transparent, 5g of nickel powder with a particle size D90 of 10µm was added. The adhesive was coated onto a 10µm thick conductive PET nonwoven fabric using a bar coating method, and the solvent was dried at 90℃. The resulting conductive nonwoven fabric with adhesive had a total thickness of 12µm. A 10µm thick self-made cross-linked thermoplastic polyester elastomer film was then thermally bonded onto the conductive nonwoven fabric with adhesive. This yielded a 3D-formable electromagnetic shielding film.

[0124] The 3D-formable electromagnetic shielding film was measured using DMA stretching mode at a fixed frequency of 1 Hz, with a heating range of 25–250 °C and a heating rate of 5 °C / min. The curve showed tan δ > 0.5 in the range of 80–180 °C, with a maximum value of 2.2 at 120 °C.

[0125] This 3D-formable electromagnetic shielding film can be hot-pressed, and a good 3D shape can be obtained by molding at 120℃ using a mold-closing method. The film is molded at 120℃, held at that temperature for 10 minutes, and then cooled to 50℃ before mold opening. The resulting product is further cured in a 120℃ oven for 30 minutes to obtain the final electromagnetic shielding film. Measurements were performed using DMA stretching mode at a fixed frequency of 1Hz, with a heating rate of 5℃ / min from 150 to 250℃. Within the temperature range of 180–250℃, tan δ was less than 0.2. The maximum tan δ value occurred at 220℃, reaching 0.05. The tested surface resistivity was 200mΩ.

[0126] The device structure used in Example 3 is also as described. Figure 3 As shown in the table below, the corresponding dimensions are as follows. The ratio of the surface area S2 after molding to the surface area S1 before molding is 4.0896.

[0127]

[0128] Example 4

[0129] A 15µm film was prepared using Coim LPR 9060 particles through a casting and stretching process, and then crosslinked with a 180KV 16Mrad electron beam to obtain a crosslinked thermoplastic polyurethane elastomer film.

[0130] Epoxy resin DIC 7200 was dissolved in methyl ethyl ketone (MEK) to a solid content of 70%. 100g of the dissolved Nan Ya NPCN 702H resin solution was taken, and 8g of dicyandiamide (DDA 5) was added and mixed thoroughly. Then, 10g of silver-coated copper powder with a particle size of 5µm was added and dispersed evenly. The adhesive was coated onto a 15µm thick self-made cross-linked thermoplastic polyurethane elastomer film using a wire-bar coating method. A 10µm thick conductive PET nonwoven fabric was then attached to one side of the uncured adhesive layer to obtain a 3D-formable electromagnetic shielding film.

[0131] The 3D-formable electromagnetic shielding film was measured using DMA stretching mode at a fixed frequency of 1 Hz, with a heating range of 25–250 °C and a heating rate of 5 °C / min. The curve showed tan δ > 0.5 in the range of 80–180 °C, with a maximum value of 2.5 at 100 °C.

[0132] This 3D-formable electromagnetic shielding film can be hot-pressed, and a good 3D shape can be obtained by molding at 120℃ using a mold-closing method. The film is molded at 120℃, held at that temperature for 10 minutes, and then cooled to 50℃ before mold opening. The resulting product is further cured in a 120℃ oven for 30 minutes to obtain the final electromagnetic shielding film. Measurements were performed using DMA stretching mode at a fixed frequency of 1Hz, with a heating rate of 5℃ / min from 150 to 250℃. Within the temperature range of 180–250℃, tan δ was less than 0.2. The maximum tan δ value occurred at 180℃, reaching 0.17. The tested surface resistivity was 300mΩ.

[0133] The device structure used in Example 4 is as follows: Figure 3 As shown in the table below, the corresponding dimensions are as follows. The ratio of the surface area S2 after molding to the surface area S1 before molding is 4.0896.

[0134]

[0135] Although specific embodiments have been shown and described herein, those skilled in the art will understand that various alternative and / or equivalent embodiments can be used instead of the shown and described specific embodiments without departing from the scope of the invention. This application is intended to include any improvements or modifications to the specific embodiments discussed herein. Therefore, the invention is limited only to the claims and their equivalents.

[0136] Those skilled in the art will understand that various modifications and alterations can be made without departing from the scope of the invention. Such modifications and alterations are intended to fall within the scope of the invention as defined in the appended claims.

Claims

1. A circuit board with a 3D-molded electromagnetic shielding film attached, the circuit board comprising electronic components, wherein the 3D-molded electromagnetic shielding film comprises a molding layer, a shielding layer, and an adhesive film, the molding layer and the adhesive film being stacked, the shielding layer being a conductive nonwoven layer, the conductive nonwoven layer being embedded in the adhesive film, wherein... The ratio of the surface area S2 of the electromagnetic shielding film after molding (excluding the surface area of ​​the electronic components) to the surface area S1 of the electromagnetic shielding film before molding (excluding the surface area of ​​the electronic components) is 1.5 to 17. The surface resistance of the electromagnetic shielding film is less than or equal to 10Ω, and its loss factor value (i.e., damping value) tan δ is less than or equal to 0.2 in the temperature range of 180-250℃. The loss factor value (i.e., damping value) tan δ is measured by rheological curves, which are determined using DMA stretching mode under the conditions of a heating rate of 5℃ / min and a test frequency of 1Hz.

2. The circuit board according to claim 1, wherein, The conductive nonwoven layer comprises a polymer nonwoven fiber material and a conductive material, wherein the melting point of the polymer nonwoven fiber material is greater than or equal to 220°C.

3. The circuit board according to claim 2, wherein, The polymer nonwoven fiber material includes at least one of liquid crystal polymer nonwoven fiber material and polyethylene terephthalate nonwoven fiber material.

4. The circuit board according to claim 2, wherein, The conductive material at least partially covers the polymer nonwoven fiber material.

5. The circuit board according to claim 1, wherein, The adhesive film includes pressure-sensitive adhesive film or structural adhesive film.

6. The circuit board according to claim 5, wherein, When the adhesive film is an organosilicon pressure-sensitive adhesive film, the storage modulus of the organosilicon pressure-sensitive adhesive film at 25°C and 1Hz is 40,000-2,000,000 Pa.

7. The circuit board according to claim 5, wherein, When the adhesive film is a structural adhesive film, the structural adhesive film is a cured product of epoxy resin and hardener.

8. The circuit board according to claim 7, wherein, The epoxy resin comprises one or more of the following: phenolic epoxy resin, cresol-type epoxy resin, epoxy resin containing a dicyclopentadiene structure and its derivatives, and epoxy resin containing a 9,9-diphenylfluorene structure and its derivatives.

9. The circuit board according to claim 7, wherein, The hardener comprises one or more of diaminodiphenyl sulfone, dicyandiamide, linear phenolic resin, and linear cresol-type phenolic resin.

10. The circuit board according to claim 5, wherein, The film also contains conductive filler, the content of which is less than or equal to 40 wt.% of the total weight of the film.

11. The circuit board according to claim 1, wherein, The molding layer comprises one or more of thermoplastic, thermosetting, thermoplastic elastomer and thermosetting elastomer products after molding and shaping.

12. The circuit board according to claim 11, wherein, The thermoplastic comprises one or more of polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, and polyphenylene sulfide.

13. The circuit board according to claim 11, wherein, The thermosetting plastic comprises one or more of phenolic resin, unsaturated polyester, epoxy resin, silicone resin, and polyurethane.

14. The circuit board according to claim 11, wherein, The thermoplastic elastomer includes one or more of thermoplastic polyurethane elastomers, thermoplastic polyester elastomers, and thermoplastic vulcanized ester elastomers.

15. The circuit board according to claim 11, wherein, The thermosetting elastomer comprises one or more of the following: vulcanized silicone rubber, vulcanized nitrile rubber, thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, and thermoplastic vulcanized ester elastomer, which are chemically cross-linked products.

16. A 3D-formable electromagnetic shielding film, the 3D-formable electromagnetic shielding film comprising a thermoplastic layer, a shielding layer, and an adhesive film, wherein the thermoplastic layer and the adhesive film are stacked, the shielding layer is a conductive nonwoven layer, and the conductive nonwoven layer is partially embedded in the adhesive film, wherein... The 3D-formable electromagnetic shielding film has a loss factor (i.e., damping value) tan δ that is greater than or equal to 0.5 at at least one temperature point within the temperature range of 50-200℃. The loss factor (i.e., damping value) tan δ is measured by rheological curves using DMA stretching mode at a heating rate of 5℃ / min and a test frequency of 1Hz.

17. The 3D-formable electromagnetic shielding film according to claim 16, wherein, The conductive nonwoven layer comprises a polymer nonwoven fiber material and a conductive material, wherein the melting point of the polymer nonwoven fiber material is greater than or equal to 220°C.

18. The 3D-formable electromagnetic shielding film according to claim 17, wherein, The polymer nonwoven fiber material includes at least one of liquid crystal polymer nonwoven fiber material and polyethylene terephthalate nonwoven fiber material.

19. The 3D-formable electromagnetic shielding film according to claim 17, wherein, The conductive material at least partially covers the polymer nonwoven fiber material.

20. The 3D-formable electromagnetic shielding film according to claim 16, wherein, The adhesive film includes pressure-sensitive adhesive film or structural adhesive film.

21. The 3D-formable electromagnetic shielding film according to claim 20, wherein, When the adhesive film is an organosilicon pressure-sensitive adhesive film, the storage modulus of the organosilicon pressure-sensitive adhesive film at 25°C and 1Hz is 40,000–2,000,000 Pa.

22. The 3D-formable electromagnetic shielding film according to claim 20, wherein, When the adhesive film is a structural adhesive film, the structural adhesive film contains epoxy resin and a hardener.

23. The 3D-formable electromagnetic shielding film according to claim 22, wherein, The epoxy resin comprises one or more of the following: phenolic epoxy resin, cresol-type epoxy resin, epoxy resin containing a dicyclopentadiene structure and its derivatives, and epoxy resin containing a 9,9-diphenylfluorene structure and its derivatives.

24. The 3D-formable electromagnetic shielding film according to claim 22, wherein, The hardener comprises one or more of diaminodiphenyl sulfone, dicyandiamide, linear phenolic resin, and linear cresol-type phenolic resin.

25. The 3D-formable electromagnetic shielding film according to claim 16, wherein, The film also contains conductive filler, the content of which is less than or equal to 40 wt.% of the total weight of the film.

26. A 3D-molded electromagnetic shielding film, wherein the 3D-molded electromagnetic shielding film comprises the 3D-molded electromagnetic shielding film as claimed in any one of claims 1 to 15.

27. A method for attaching an electromagnetic shielding film to a circuit board, comprising attaching a 3D-formable electromagnetic shielding film as described in any one of claims 16 to 25 to the circuit board and performing 3D forming.

28. The method for attaching an electromagnetic shielding film to a circuit board according to claim 27, wherein the 3D-formable electromagnetic shielding film, after 3D forming, comprises: a molding layer, a shielding layer, and an adhesive film, wherein the molding layer and the adhesive film are stacked, the shielding layer is a conductive nonwoven layer, and the conductive nonwoven layer is embedded in the adhesive film, wherein... The ratio of the surface area S2 of the electromagnetic shielding film after molding (excluding the surface area of ​​the electronic components) to the surface area S1 of the electromagnetic shielding film before molding (excluding the surface area of ​​the electronic components) is 1.5 to 17. The surface resistance of the electromagnetic shielding film is less than or equal to 10Ω, and its loss factor value (i.e., damping value) tan δ measured by rheological curve is less than or equal to 0.2 in the temperature range of 180-250℃.

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