Integrated protection and shielding structure for FPC (Flexible Printed Circuit) and preparation method of integrated protection and shielding structure

Abstract

The invention relates to an integrated protection and shielding structure for an FPC (Flexible Printed Circuit) and a preparation method of the integrated protection and shielding structure. The method comprises the following steps: processing a pre-prepared layer-adding insulating film to enable the shape of the layer-adding insulating film to be matched with the shape of a flexible board substrate; the processed layer-adding insulating film is attached to the surface of the outer layer of the flexible board substrate, so that the layer-adding insulating film covers the flexible board substrate; manufacturing a metal shielding layer on the partial layer-adding insulating film of the to-be-shielded part of the flexible substrate in a printing, silk-screen printing or magnetron sputtering mode; and synchronously manufacturing an insulation protection layer on the metal shielding layer through an ink printing mode, and manufacturing a solder mask protection layer on a part of the layer-adding insulation film of the part to be subjected to solder mask protection of the flexible substrate, so as to obtain the integrated protection and shielding structure for the FPC. According to the invention, the problems of complex working procedures, complex materials and high cost of laminating a protective film, printing solder resist ink and laminating an electromagnetic shielding film on the outer layer of the flexible substrate in the prior art can be solved.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, and in particular to an integrated protection and shielding structure for FPC and its preparation method. Background Technology

[0002] In the fabrication of flexible printed circuits (FPCs), after the copper-clad laminate (CCL) has completed circuit processing and hole metallization, a protective film needs to be laminated onto the outer layer of the FPC substrate, solder resist ink needs to be printed, and an electromagnetic shielding film needs to be laminated. Traditionally, the processes for completing these steps are extremely complex: the protective film requires punching, laminating, hot pressing, and curing / baking; the ink requires printing, exposure, development, and curing / baking; and the electromagnetic shielding film requires punching, laminating, hot pressing, and curing / baking. Furthermore, the materials are complex and costly: the protective film (generally consisting of a PI (Polyimide) layer, semi-cured pure adhesive, and release paper / film), ink, and shielding film (generally consisting of an insulating protective layer, a metal shielding layer, a conductive adhesive layer, and release paper / film) is required. Summary of the Invention

[0003] This invention provides an integrated protection and shielding structure for FPC and its preparation method, which can solve the problems of complex processes, complex materials and high costs in traditional technologies, such as laminating protective films, printing solder resist ink and laminating electromagnetic shielding films on the outer layer of flexible board substrates.

[0004] To address the aforementioned technical problems, this invention provides a method for fabricating an integrated protection and shielding structure for FPCs, comprising: The pre-prepared extension insulating film is processed so that the shape of the extension insulating film matches the shape of the flexible substrate. The processed extended insulating film is bonded to the surface of the outer layer of the flexible board substrate, so that the extended insulating film covers the surface of the flexible board substrate; A metal shielding layer is fabricated on the additional insulating film at the portion of the flexible substrate to be shielded by printing, screen printing, or magnetron sputtering. An insulating protective layer is simultaneously fabricated on the metal shielding layer by ink printing, and a solder resist protective layer is fabricated on the additional insulating film at the portion of the flexible board substrate to be protected by solder resist, thereby obtaining an integrated protection and shielding structure for FPC.

[0005] Optionally, processing the pre-prepared extension insulating film to match its shape with the shape of the flexible substrate includes: Pre-preparation of the added insulating film; The added insulating film is punched to make its shape correspond to the shape of the flexible substrate. The protective layer opening, the insulating film opening, and the shielding layer grounding hole are processed on the added insulating film by steel die punching or laser cutting, so that the surface shape of the added insulating film corresponds to the surface shape of the outer layer of the flexible board substrate.

[0006] Optionally, the step of bonding the processed extension insulating film to the surface of the outer layer of the flexible substrate includes: The processed laminated insulating film is bonded to the surface of the outer layer of the flexible board substrate using a vacuum press; The laminated reinforcing insulating film is hot-pressed using a laminator to solidify and form the reinforcing insulating film on the outer surface of the flexible substrate.

[0007] Optionally, when the extended insulating film is laminated using a vacuum press, the lamination pressure is 0.2-1.0 MPa, the lamination time is 0.5-3 min, and the lamination temperature is 60-150℃. When the laminated insulating film is hot-pressed and cured using a laminator, the pressing temperature is 160-250℃, the pressing time is 30-120min, and the pressing pressure is 2-5MPa.

[0008] Optionally, the step of simultaneously forming an insulating protective layer on the metal shielding layer and forming a solder resist protective layer on a portion of the additional insulating film at the solder resist protection location on the flexible substrate by ink printing includes: Insulating ink is printed on the metal shielding layer and the extended insulating film on the flexible substrate using an ink printing machine to obtain printed material; The printed material after the insulating ink has been printed is exposed using an LDI or film exposure machine to obtain the exposed material; The exposed material is developed using a developer to form an insulating protective layer on the metal shielding layer, and a solder resist protective layer is formed on the additional insulating film at the portion of the flexible substrate to be protected against solder resist. The insulating protective layer and the solder resist protective layer are cured and baked using a nitrogen oven to cure the ink.

[0009] Optionally, when printing insulating ink, the stencil used for printing is an 80-400 mesh stencil, and the printing thickness is 5-20 μm; During exposure, the exposure wavelength is 355-436nm, and the exposure energy is 100-1500mJ / cm². 2 ; During curing and baking, the baking temperature is 150-200℃ and the baking time is 30-120 minutes.

[0010] Optionally, the fabrication of the metal shielding layer by screen printing includes: The surface treatment is performed on the added insulating film that is bonded to the flexible board substrate; Copper paste is printed on the surface of the added insulating film at the areas where a shielding layer needs to be formed by screen printing. The printed copper paste was dried using a nitrogen oven. After the printed copper paste dries, it is sintered into a copper layer by pulse or microwave sintering to form a metal shielding layer.

[0011] Optionally, the fabrication of the metal shielding layer by printing includes: The surface treatment is performed on the added insulating film that is bonded to the flexible board substrate; Using a piezoelectric inkjet printer, nano-copper paste is printed on the surface of the added insulating film at the locations where a shielding layer needs to be formed. The printed nano-copper paste was dried using a nitrogen oven. After the printed nano-copper paste dries, it is sintered into a copper layer by pulse or microwave sintering to form a metal shielding layer.

[0012] Optionally, the fabrication of the metal shielding layer by magnetron sputtering includes: The surface treatment is performed on the added insulating film that is bonded to the flexible board substrate; The added insulating film is covered with a mask, exposing the parts of its surface where the shielding layer needs to be set. A copper layer is sputtered onto the parts where the shielding layer needs to be set using a target sputtering method to form a metal shielding layer.

[0013] Furthermore, the present invention also proposes an integrated protection and shielding structure for FPC, wherein the integrated protection and shielding structure for FPC is prepared by the preparation method of the integrated protection and shielding structure for FPC described above.

[0014] The beneficial effects of the technical solution provided by this invention include: An additional insulating film, which has been punched and processed, can be directly applied to the flexible board substrate to cover and protect the areas to be shielded, the areas to be protected against solder resist, and other parts of the flexible board substrate. Moreover, a metal shielding layer can be directly processed on the areas to be shielded on the additional insulating film (corresponding to the areas to be shielded on the flexible board substrate). Then, an insulating protective layer and a solder resist protective layer can be printed on the areas to be protected against solder resist on the metal shielding layer and the additional insulating film (corresponding to the areas to be protected against solder resist on the flexible board substrate) to protect the areas to be protected against solder resist on the metal shielding layer and the additional insulating film.

[0015] Compared to traditional techniques, the preparation method proposed in this invention eliminates the need for punching, laminating, hot pressing, curing, and baking of the protective film, as well as for the electromagnetic shielding film, greatly simplifying the process. Furthermore, unlike traditional methods, the method eliminates the need for a protective film composed of a PI (Polyimide) layer, semi-cured pure adhesive, and release paper / film, and also eliminates the need for a shielding film composed of an insulating protective layer, a metal shielding layer, a conductive adhesive layer, and release paper / film, reducing the types of materials used and lowering costs. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a simplified schematic diagram illustrating the steps of the integrated protection and shielding structure method for FPC described in an embodiment of the present invention; Figure 2 This is a simplified flowchart illustrating the integrated protection and shielding structure method for FPC as described in an embodiment of the present invention. Figure 3 This is a schematic diagram of the cross-sectional structure when an additional insulating film is laminated on a flexible substrate in the integrated protection and shielding structure method for FPC described in an embodiment of the present invention. Figure 4 This is a schematic diagram of the cross-sectional structure of the integrated protection and shielding structure method for FPC described in the embodiments of the present invention when a metal shielding layer is fabricated on the added insulating film; Figure 5 This is a cross-sectional structural diagram of the integrated protection and shielding structure method for FPC described in this embodiment of the invention, in which an insulating protective layer is fabricated on a metal shielding layer and a solder resist protective layer is fabricated on an additional insulating film.

[0018] In the diagram: 100, flexible board substrate; 200, additional insulating film; 202, opening in insulating film; 204, grounding hole in shielding layer; 206, opening in protective layer; 300, metal shielding layer; 400, insulating protective layer; 600, solder resist protective layer. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In traditional technologies, the processes of laminating a protective film, printing solder resist ink, and laminating an electromagnetic shielding film on the outer layer of a flexible printed circuit board (FPC) are very complex, resulting in low production efficiency and high material costs. To address these technical problems, this invention proposes an integrated protection and shielding structure for FPCs and its fabrication method.

[0021] like Figures 1 to 2 As shown, the integrated protection and shielding structure method for FPC may include the following steps: S100: Process the pre-prepared extended insulating film 200 so that the shape of the extended insulating film 200 matches the shape of the flexible substrate 100. S200: The processed extended insulating film 200 is attached to the surface of the outer layer of the flexible board substrate 100 so that the extended insulating film 200 covers the surface of the flexible board substrate 100. S300: A metal shielding layer 300 is fabricated on a portion of the insulating film 200 on the area to be shielded of the flexible substrate 100 by means of printing, screen printing, or magnetron sputtering. S400, by means of ink printing, an insulating protective layer 400 is simultaneously formed on the metal shielding layer 300, and a solder resist protective layer 600 is formed on the partial additional insulating film 200 of the flexible board substrate 100 to be protected by solder resist, thereby obtaining an integrated protection and shielding structure for FPC.

[0022] An additional insulating film 200, which has been punched and processed, can be directly attached to the flexible board substrate 100 to cover and protect the areas to be shielded, the areas to be protected against solder resist, and other areas of the flexible board substrate 100. Moreover, a metal shielding layer 300 can be directly processed and fabricated on the areas to be shielded on the additional insulating film 200 (corresponding to the areas to be shielded on the flexible board substrate 100). Then, an insulating protective layer 400 and a solder resist protective layer 600 can be printed and fabricated simultaneously on the metal shielding layer 300 and the areas to be protected against solder resist on the additional insulating film 200 (corresponding to the areas to be protected against solder resist on the flexible board substrate 100) to protect the areas to be protected against solder resist on the metal shielding layer 300 and the additional insulating film 200.

[0023] Compared to traditional techniques, the preparation method proposed in this invention eliminates the need for punching, laminating, hot pressing, curing, and baking of the protective film, as well as for the electromagnetic shielding film, greatly simplifying the process. Furthermore, unlike traditional methods, the method eliminates the need for a protective film composed of a PI (Polyimide) layer, semi-cured pure adhesive, and release paper / film, and also eliminates the need for a shielding film composed of an insulating protective layer, a metal shielding layer, a conductive adhesive layer, and release paper / film, reducing the types of materials used and lowering costs.

[0024] Further, in step S100, the pre-prepared extension insulating film 200 is processed to match the shape of the extension insulating film 200 with the shape of the flexible substrate 100, which may include the following steps: S110, Pre-prepared layered insulating film 200.

[0025] The build-up film 200 is a high-performance insulating film made of materials such as epoxy resin or polyimide, with inorganic fillers and coupling agents added to adjust its mechanical and processing properties. This facilitates subsequent shaping via laser engraving or mechanical punching, and allows for complete bonding and curing to the flexible substrate 100 via hot pressing. Furthermore, the thickness of the build-up film 200 can range from 10-55 μm.

[0026] S120. The shape of the added insulating film 200 is punched to make the shape of the added insulating film 200 correspond to the shape of the flexible substrate 100.

[0027] Since the added insulating film 200 needs to be attached to the surface of the outer layer of the flexible board substrate 100, that is, to cover the surface of the outer layer of the flexible board substrate 100, the outline of the added insulating film 200 needs to correspond to the outline of the outer layer of the flexible board substrate 100. Therefore, the added insulating film 200 needs to be punched to make its shape correspond to the shape of the flexible board substrate 100, so as to fully cover the flexible board substrate 100 with the added insulating film 200.

[0028] S130. Protective layer opening 206, insulating film opening 202, and shielding layer grounding hole 204 are processed on the added insulating film 200 by steel die punching or laser cutting, so that the surface shape of the added insulating film 200 corresponds to the surface shape of the outer layer of the flexible substrate 100.

[0029] Furthermore, when attaching the extended insulating film 200 to the surface of the outer layer of the flexible substrate 100, it is also necessary to process protective layer openings 206 corresponding to the solder resist protection area of ​​the flexible substrate 100, insulating film openings 202 and shielding layer grounding holes 204 corresponding to the shielding area of ​​the flexible substrate 100, so that the surface shape of the extended insulating film 200 corresponds to the surface shape of the outer layer of the flexible substrate 100.

[0030] In addition, such as Figure 3 As shown, in step S200, the processed extended insulating film 200 is bonded to the surface of the outer layer of the flexible substrate 100, which may further include the following steps: S210. The processed extended insulating film 200 is bonded to the outer surface of the flexible board substrate 100 using a vacuum press. That is, the air and volatiles at the bonding interface are eliminated by the vacuum environment, and the constant temperature and pressure system of the vacuum press is used to soften, flow and wet the resin layer of the extended insulating film 200 to the surface (including the circuit layer) of the flexible board substrate 100. Finally, a dense and highly adhesive insulating layer is formed by thermosetting.

[0031] Specifically, the surface of the outer layer of the flexible substrate 100 and the added insulating film 200 can be pre-treated, including cleaning (such as plasma cleaning), roughening and drying the surface of the outer layer of the flexible substrate 100, and warming, cutting (i.e. processing the added insulating film 200 in step S100) and peeling off the protective film.

[0032] Then, the flexible substrate 100 can be positioned in the press chamber of the vacuum press using a clamp, and the extension insulating film 200 can be laid on the outer surface of the flexible substrate 100, aligning the two. The press chamber of the vacuum press can then be evacuated, placing the flexible substrate 100 and the extension insulating film 200 in a vacuum environment. During evacuation, the air in the press chamber can be purged first, followed by the air and resin volatiles at the interface between the flexible substrate 100 and the extension insulating film 200.

[0033] Then, the flexible substrate 100 and the reinforcing insulating film 200 in the press chamber can be heated and pressurized, including three steps: gradually increasing the temperature (to fully soften the resin in the reinforcing insulating film 200), gradually increasing the pressure (to avoid instantaneous pressure causing displacement of the reinforcing insulating film 200 or deformation of the flexible substrate 100), and maintaining the temperature and pressure (to allow the resin in the reinforcing insulating film 200 to fully flow, wet the flexible substrate 100, and initially cure). Then, the flexible substrate 100 and the reinforcing insulating film 200 in the press chamber can be cooled and depressurized, with gradual cooling (to avoid rapid cooling causing thermal stress warping) and gradual pressure reduction (to avoid sudden pressure changes causing peeling of the reinforcing insulating film 200). Finally, the laminated flexible substrate 100 and reinforcing insulating film 200 can be removed.

[0034] Furthermore, in step S210, when the laminated insulating film 200 is bonded using a vacuum press (mainly referring to the heating and pressurization stage), the bonding pressure can be 0.2-1.0 MPa, the bonding time can be 0.5-3 min, and the bonding temperature can be 60-150℃.

[0035] S220. The laminated reinforcing insulating film 200 is hot-pressed using a laminator to solidify and form the reinforcing insulating film 200 onto the surface of the outer layer of the flexible substrate 100 (e.g., ...). Figure 3 (As shown). The laminator uses a heated platen and uniform pressure to soften and flow the incompletely cured resin in the laminated insulating film 200 (which was in a semi-cured stage after the initial vacuum bonding), allowing it to fully wet the surface of the flexible substrate 100 (including the line gaps). A cross-linking reaction occurs at high temperature, ultimately forming a dense, high-hardness, and highly adhesive cured insulating layer. Simultaneously, the hot-pressing process further eliminates residual micro-bubbles at the interface, improving the dielectric properties and heat resistance stability of the laminated insulating film 200.

[0036] Specifically, the flexible substrate 100 and the added insulating film 200 can be pre-treated, including inspecting the appearance of the added insulating film 200 (no obvious bubbles, wrinkles, or resin overflow) and positioning (confirming that the added insulating film 200 is aligned with the flexible substrate 100).

[0037] Then, the flexible substrate 100 and the added insulating film 200 are fed and positioned using a laminator, and then both are subjected to heating treatment, including preheating treatment (to slowly soften the resin in the added insulating film 200 to avoid interface delamination caused by temperature shock) and curing heating treatment (to promote the resin crosslinking reaction). Moreover, during the heating treatment, pressure treatment is performed simultaneously, including applying low pressure during preheating to fix the flexible substrate 100 and the added insulating film 200 and prevent displacement; during the curing heating, the pressure is gradually increased to the target pressure to ensure that the resin fully wets the circuit gaps under pressure and removes micro-air bubbles; and the temperature and pressure are maintained at the target temperature and target pressure until the resin is completely cured.

[0038] Then, the fully cured laminated insulating film 200 and flexible substrate 100 can be gradually cooled and depressurized, and then discharged.

[0039] Furthermore, in step S220, when the laminated insulating film 200 is hot-pressed and cured by a laminator (mainly referring to the heating and pressurizing stage), the pressing temperature can be 160-250℃, the pressing time can be 30-120min, and the pressing pressure can be 2-5MPa.

[0040] In addition, such as Figure 4 As shown, in step S300, the metal shielding layer 300 is fabricated by screen printing, which may further include the following steps: S310a, Surface treatment is performed on the added insulating film 200 bonded to the flexible substrate 100.

[0041] Specifically, the shielded portion (i.e., the location where the shielding layer needs to be applied) of the extended insulating film 200 bonded to the flexible substrate 100 can be treated with oxygen plasma using a vacuum plasma cleaner or an atmospheric pressure plasma treatment device to increase its surface energy, thereby facilitating the printing of a metal shielding layer 300 at that location. Furthermore, the power during oxygen plasma treatment can be 500-2000W, and the treatment time can be 2-10 minutes.

[0042] S320a. Copper paste is printed on the surface of the reinforcing insulating film 200 at the areas where a shielding layer needs to be set by screen printing.

[0043] Specifically, nano-copper paste can be printed on the reinforcing insulating film 200 at the locations where the shielding layer needs to be set and at the locations of the shielding layer grounding holes 204 using a printing screen. Moreover, the nano-copper paste has a particle size of less than 100nm and a solid content between 40% and 80%; the printing screen is a 200-500 mesh screen, and the printing thickness can be 4-10um.

[0044] S330a. Use a nitrogen oven to dry the printed copper paste.

[0045] Specifically, a nitrogen oven can be used to dry the copper paste printed on the reinforcing insulating film 200, allowing it to dry and partially cure. The drying temperature can be 60-120℃, and the drying time can be 2-20 minutes.

[0046] S340a. After the printed copper paste dries, it is sintered into a copper layer by pulse or microwave sintering to form a metal shielding layer 300 (e.g., Figure 4 (As shown).

[0047] Specifically, the copper paste printed on the pre-dried layer of the reinforcing insulating film 200 can be sintered by pulse or microwave sintering to form a copper layer. Moreover, the sintering temperature can be 150-250℃, the sintering time can be 10-60min, and the thickness of the copper layer can be 2-5um.

[0048] Furthermore, in step S300, the metal shielding layer 300 is fabricated by printing, which may further include the following steps: S310b, Surface treatment is performed on the added insulating film 200 bonded to the flexible substrate 100.

[0049] Similarly, the shielded portion (i.e., the location where the shielding layer needs to be applied) of the extended insulating film 200 bonded to the flexible substrate 100 can be treated with oxygen plasma using a vacuum plasma cleaner or an atmospheric pressure plasma treatment device to increase its surface energy, thereby facilitating the printing of a metal shielding layer 300 at that location. Furthermore, the power during oxygen plasma treatment can be 500-2000W, and the treatment time can be 2-10 minutes.

[0050] S320b: Using a piezoelectric inkjet printer, print nano-copper paste on the areas of the surface of the reinforcing insulating film 200 where a shielding layer needs to be set.

[0051] Specifically, a piezoelectric inkjet printer can be used to print nano-copper paste on the positions where a shielding layer needs to be set on the added insulating film 200, as well as at the positions where the shielding layer grounding hole 204 is located. The nano-copper paste has a particle size of less than 100nm, a solid content of 40%-80%, and a printing thickness of 4-10um.

[0052] S330b: Use a nitrogen oven to dry the printed nano-copper paste.

[0053] Similarly, a nitrogen oven can be used to dry the copper paste printed on the reinforcing insulating film 200, allowing it to dry and partially cure. The drying temperature can be 60-120℃, and the drying time can be 2-20 minutes.

[0054] S340b: After the printed nano-copper paste dries, it is sintered into a copper layer by pulse or microwave sintering to form a metal shielding layer 300 (e.g., Figure 4 (As shown).

[0055] Similarly, the pre-dried printed copper paste on the reinforcing insulating film 200 can be sintered using pulse or microwave sintering to form a copper layer. Furthermore, the sintering temperature can be 150-250℃, the sintering time can be 10-60 minutes, and the thickness of the copper layer can be 2-5 μm.

[0056] Furthermore, in step S300, the fabrication of the metal shielding layer 300 by magnetron sputtering may further include the following steps: S310c, Surface treatment is performed on the added insulating film 200 bonded to the flexible substrate 100.

[0057] Specifically, the areas to be shielded (where a shielding layer needs to be set) or the entire surface of the added insulating film 200 can be cleaned for 5-10 minutes each using acetone, ethanol, and deionized water ultrasonic cleaning methods in sequence to keep the surface of the added insulating film 200 clean.

[0058] S320c, using a mask to cover the additional insulating film 200, exposing the areas on its surface where the shielding layer needs to be applied, sputtering a copper layer onto the areas where the shielding layer needs to be applied to form a metal shielding layer 300 (e.g., ...). Figure 4 (As shown).

[0059] After cleaning the surface of the augmentation insulating film 200, a mask can be used to cover the areas of the augmentation insulating film 200 where the shielding layer needs to be formed. Then, using a target sputtering method, a high-purity copper target (purity ≥ 99.99%) is sputtered onto the areas of the augmentation insulating film 200 where the shielding layer needs to be formed. The target sputtering equipment can use high-purity argon gas (purity ≥ 99.99%) as the working gas, with a sputtering power of 50-300W and a sputtering time of 20-60 minutes, resulting in a copper layer thickness of 2-5 μm.

[0060] In addition, such as Figure 5 As shown, in step S400, by means of ink printing, an insulating protective layer 400 is simultaneously formed on the metal shielding layer 300, and a solder resist protective layer 600 is formed on the partial additional insulating film 200 of the flexible substrate 100 to be protected against solder resist. This may further include the following steps: S410. Insulating ink is printed on the metal shielding layer 300 and the reinforcing insulating film 200 on the flexible substrate 100 using an ink printing machine to obtain printed material.

[0061] Specifically, before printing insulating ink on the extended insulating film 200 and the metal shielding layer 300, the surfaces of both are first cleaned. Then, the flexible substrate 100 can be positioned on the worktable of the ink printing machine, and the insulating ink can be printed on the metal shielding layer 300 and the extended insulating film 200 on the flexible substrate 100 using a printing stencil.

[0062] Furthermore, when printing insulating ink, the stencil is 80-400 mesh, and the ink thickness is 5-20µm. Also, the insulating ink can be a UV-sensitive type.

[0063] S420. Use an LDI (Laser Direct Imaging) or film exposure machine to expose the printed material after printing insulating ink to obtain exposed material.

[0064] Exposure and development are key patterning processes for UV photosensitive insulating inks (after stencil printing). By selectively exposing and curing and developing to remove uncured parts, insulating protection patterns (including the insulating protection layer 400 on the metal shielding layer 300 and the solder resist protection layer 600 on the reinforcing insulating film 200) are precisely formed on the surface of the metal shielding layer 300 and the reinforcing insulating film 200.

[0065] Specifically, the exposure steps may include: After printing insulating ink on the reinforcing insulating film 200 and the metal shielding layer 300, the printed insulating ink is pretreated. That is, after printing on the stencil, the printed material is allowed to stand, so that the printed insulating ink flows naturally and levels. The leveled insulating ink can also be pre-dried to prevent the ink from falling off during subsequent development.

[0066] The flexible substrate 100 is clamped and positioned. The insulating ink on the extension insulating film 200 and the metal shielding layer 300 is exposed using an exposure device (i.e., LDI or film exposure machine). This exposure (i.e., UV light initiates cross-linking and polymerization of ink molecules, forming a solid curing layer insoluble in the developer) to form an insulating protective layer 400. Specifically, the insulating ink on the metal shielding layer 300 is exposed and cured to form an insulating protective layer 400, and the insulating ink on the areas of the extension insulating film 200 requiring solder resist protection is exposed and cured to form a solder resist protective layer 600. Furthermore, the insulating ink at other locations on the extension insulating film 200 is not exposed, ensuring that the insulating ink at these locations does not undergo cross-linking and remains in a liquid / semi-solid state soluble in the developer, facilitating subsequent removal by development.

[0067] Moreover, during exposure, the exposure wavelength of the exposure equipment can be 355-436nm, and the exposure energy can be 100-1500mJ / cm2.

[0068] S430. Develop the exposed material using a developer to form an insulating protective layer 400 on the metal shielding layer 300, and form a solder resist protective layer 600 on a portion of the additional insulating film 200 of the flexible substrate 100 to be protected against solder resist (e.g., ...). Figure 5 (As shown).

[0069] After exposing the insulating ink on the metal shielding layer 300 and the insulating ink on the solder resist protection area of ​​the reinforcing insulating film 200, it is necessary to remove the unexposed insulating ink from other areas of the reinforcing insulating film 200 by developing. Specifically, this may include: Prepare an alkaline developer (such as a 1-2% sodium carbonate aqueous solution or a 0.8-1.5% sodium bicarbonate aqueous solution). Then, the alkaline developer can be sprayed onto the unexposed insulating ink on other parts of the reinforcing insulating film 200 to remove the unexposed insulating ink, leaving only the insulating protective layer 400 on the exposed metal shielding layer 300 and the solder resist protective layer 600 on the reinforcing insulating film 200 corresponding to the solder resist protection area of ​​the flexible substrate 100.

[0070] S440. Use a nitrogen oven to cure and bake the insulating protective layer 400 and the solder resist protective layer 600 to cure the ink.

[0071] The insulating protective layer 400 and the solder resist protective layer 600 formed by printing insulating ink can be baked and cured in a nitrogen-protected environment, which can improve the crosslinking degree, adhesion, heat resistance and insulation performance of the insulating ink (the degree of curing after development is about 70-80%, and the degree of curing after baking can be greater than or equal to 95%).

[0072] Furthermore, during the curing and baking process, the baking temperature is 150-200℃ and the baking time is 30-120 minutes.

[0073] Furthermore, the present invention also proposes an integrated protection and shielding structure for FPC, wherein the integrated protection and shielding structure for FPC is prepared by the preparation method of the integrated protection and shielding structure for FPC described above.

[0074] The solution provided by this invention simplifies the traditional complex process, reducing the original processing of protective film (die-cutting, pre-applying, pressing, and curing), electromagnetic shielding film (die-cutting, suction application, pressing, and curing), and ink printing to a simple process of graphic fabrication of the layered insulating film 200 and its bonding and hot pressing, shielding layer fabrication, and ink printing. It also reduces material costs and types. Traditional technologies require protective film (generally including a PI layer, semi-cured pure adhesive, and release paper / film), ink, and shielding film (generally including an insulating protective layer, a metal shielding layer, conductive adhesive, and release paper / film). This invention only requires the layered insulating film 200, copper paste or copper target material, and ink.

[0075] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0076] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A method for fabricating an integrated protection and shielding structure for FPC, characterized in that, include: The pre-prepared extension insulating film is processed so that the shape of the extension insulating film matches the shape of the flexible substrate. The processed extended insulating film is bonded to the surface of the outer layer of the flexible board substrate, so that the extended insulating film covers the surface of the flexible board substrate; A metal shielding layer is fabricated on the additional insulating film at the portion of the flexible substrate to be shielded by printing, screen printing, or magnetron sputtering. An insulating protective layer is simultaneously fabricated on the metal shielding layer by ink printing, and a solder resist protective layer is fabricated on the additional insulating film at the portion of the flexible board substrate to be protected by solder resist, thereby obtaining an integrated protection and shielding structure for FPC.

2. The method for fabricating an integrated protection and shielding structure for FPC according to claim 1, characterized in that, The process of processing the pre-prepared extension insulating film to match the shape of the extension insulating film with the shape of the flexible substrate includes: Pre-preparation of the added insulating film; The added insulating film is punched to make its shape correspond to the shape of the flexible substrate. The protective layer opening, the insulating film opening, and the shielding layer grounding hole are processed on the added insulating film by steel die punching or laser cutting, so that the surface shape of the added insulating film corresponds to the surface shape of the outer layer of the flexible board substrate.

3. The method for fabricating an integrated protection and shielding structure for FPC according to claim 2, characterized in that, The step of bonding the processed extended insulating film to the surface of the outer layer of the flexible substrate includes: The processed laminated insulating film is bonded to the surface of the outer layer of the flexible board substrate using a vacuum press; The laminated reinforcing insulating film is hot-pressed using a laminator to solidify and form the reinforcing insulating film on the outer surface of the flexible substrate.

4. The method for fabricating an integrated protection and shielding structure for FPC according to claim 3, characterized in that, When the added insulating film is laminated using a vacuum press, the lamination pressure is 0.2-1.0 MPa, the lamination time is 0.5-3 min, and the lamination temperature is 60-150℃. When the laminated insulating film is hot-pressed and cured using a laminator, the pressing temperature is 160-250℃, the pressing time is 30-120min, and the pressing pressure is 2-5MPa.

5. The method for fabricating an integrated protection and shielding structure for FPC according to claim 1, characterized in that, The method of simultaneously fabricating an insulating protective layer on the metal shielding layer and a solder resist protective layer on the portion of the additional insulating film to be protected by solder resist on the flexible substrate via ink printing includes: Insulating ink is printed on the metal shielding layer and the extended insulating film on the flexible substrate using an ink printing machine to obtain printed material; The printed material after the insulating ink has been printed is exposed using an LDI or film exposure machine to obtain the exposed material; The exposed material is developed using a developer to form an insulating protective layer on the metal shielding layer, and a solder resist protective layer is formed on the additional insulating film at the portion of the flexible substrate to be protected against solder resist. The insulating protective layer and the solder resist protective layer are cured and baked using a nitrogen oven to cure the ink.

6. The method for fabricating an integrated protection and shielding structure for FPC according to claim 5, characterized in that, When printing insulating ink, the stencil used for printing is an 80-400 mesh stencil, and the printing thickness is 5-20µm; During exposure, the exposure wavelength is 355-436nm, and the exposure energy is 100-1500mJ / cm². 2 ; During curing and baking, the baking temperature is 150-200℃ and the baking time is 30-120 minutes.

7. The method for fabricating an integrated protection and shielding structure for FPC according to claim 1, characterized in that, The process of fabricating the metal shielding layer by screen printing includes: The surface treatment is performed on the added insulating film that is bonded to the flexible board substrate; Copper paste is printed on the surface of the added insulating film at the areas where a shielding layer needs to be formed by screen printing. The printed copper paste was dried using a nitrogen oven. After the printed copper paste dries, it is sintered into a copper layer by pulse or microwave sintering to form a metal shielding layer.

8. The method for fabricating an integrated protection and shielding structure for FPC according to claim 1, characterized in that, The process of fabricating the metal shielding layer by printing includes: The surface treatment is performed on the added insulating film that is bonded to the flexible board substrate; Using a piezoelectric inkjet printer, nano-copper paste is printed on the surface of the added insulating film at the locations where a shielding layer needs to be set. The printed nano-copper paste was dried using a nitrogen oven. After the printed nano-copper paste dries, it is sintered into a copper layer by pulse or microwave sintering to form a metal shielding layer.

9. The method for fabricating an integrated protection and shielding structure for FPC according to claim 1, characterized in that, The fabrication of the metal shielding layer by magnetron sputtering includes: The surface treatment is performed on the added insulating film that is bonded to the flexible board substrate; The added insulating film is covered with a mask, exposing the parts of its surface where the shielding layer needs to be set. A copper layer is sputtered on the parts where the shielding layer needs to be set using a target sputtering method, thus forming a metal shielding layer.

10. An integrated protection and shielding structure for FPC, characterized in that, The integrated protection and shielding structure for FPC is prepared by the preparation method of the integrated protection and shielding structure for FPC as described in any one of claims 1-9.

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