Composite reinforced FPC and manufacturing method of windowed structure

Abstract

The application relates to a composite reinforced FPC and a manufacturing method of a window structure, which provides a soft board core layer, sets a first window area on the surface of the soft board core layer, then removes the copper layer in the first window area, takes a cover film layer, sets a window group on the cover film layer, and then bonds the cover film layer on the surface of the soft board core layer to form an integrated structure with the soft board core layer. By setting the first window area on the surface of the soft board core layer and removing the copper layer, combining the window design of the cover film layer and the reinforcing layer, and using the UV laser cutting and fast pressing process to integrally bond the cover film layer, the reinforcing layer (polyimide material) and the ceramic layer, the mechanical strength and structural stability of the FPC are effectively improved.

Description

Technical Field

[0001] This application relates to the field of circuit board processing technology, and more specifically, to a method for manufacturing a composite reinforced FPC and a windowed structure. Background Technology

[0002] Flexible printed circuit boards (FPCs) are widely used in consumer electronics, automotive, medical, and high-end equipment due to their thinness, flexibility, and bendability. However, traditional pure flexible boards have low mechanical strength, making them prone to warping, deformation, and pad detachment during SMT assembly, soldering, and component placement. Especially in connector insertion / removal and stress-bearing areas, the substrate alone cannot meet the requirements for pressure resistance and deformation resistance, affecting product yield and reliability.

[0003] To meet the requirements of heat dissipation and recessed assembly of adapter components, partial openings are often made in FPCs. However, openings reduce structural strength and make it difficult to balance flexibility and mechanical support. Therefore, there is an urgent need for a composite structure and its fabrication method that can enhance the mechanical strength of FPCs while enabling recessed assembly of components and heat dissipation. Summary of the Invention

[0004] The purpose of this application is to provide a method for manufacturing a window structure, which solves the problem that opening windows in circuit boards can lead to a decrease in structural strength.

[0005] To achieve the above objectives, a method for fabricating a composite reinforced FPC and a window structure is proposed, wherein: A method for manufacturing a window structure, the method comprising the following steps: S1: Provide a flexible core board layer, and set a first window area on the surface of the flexible core board layer, and then remove the copper layer in the first window area; S2: Take the cover film layer, set the window group on the cover film layer, then attach the cover film layer to the surface of the flexible board core layer and press it quickly to form an integral structure with the flexible board core layer; S3: Take the reinforcing layer, design a second window area on the reinforcing layer, and attach the side of the reinforcing layer with adhesive to the flexible core board layer and press quickly to cover the reinforcing area of ​​the flexible core board layer. Then remove the reinforcing layer in the first window area. S4: Take the pure adhesive layer and ceramic layer in the reinforcing layer, remove the pure adhesive layer in the first window area, place the pure adhesive layer between the reinforcing layer and the ceramic layer and bond them separately, and realize the integrated structure of the flexible core board layer, reinforcing layer and ceramic layer by fast pressing.

[0006] In one embodiment, a release protective layer is attached to the initial cover film layer. When the release protective layer is attached to the surface of the cover film layer, a window group is set on the cover film layer by laser cutting. After the release protective layer is separated from the cover film layer, the cover film layer is then bonded to the surface of the flexible board core layer and quickly pressed.

[0007] In one embodiment, the copper layer in the first window area is removed by acid etching.

[0008] In one embodiment, when the ceramic layer is bonded to the surface of the reinforcing layer using a pure adhesive layer, the pure adhesive layer also needs to be preheated to enhance the adhesion of the pure adhesive layer to the ceramic layer and the reinforcing layer.

[0009] In one embodiment, the preheating temperature of the pure adhesive layer is 60°C.

[0010] In one embodiment, both the reinforcing layer and the supplementary layer are made of polyimide.

[0011] In one embodiment, the surface of the flexible board core layer is browned before the reinforcing layer is bonded to the flexible board core layer.

[0012] A composite reinforced FPC, manufactured using the window structure fabrication method described above; comprising: A flexible core board layer, wherein a first window area is formed on the flexible core board layer, extending through its thickness direction; A covering film layer is attached to the surface of the flexible board core layer; A reinforcing layer is attached to the surface of the flexible core board layer; And a ceramic layer, which is attached to the surface of the reinforcing layer and covers the first window area.

[0013] In one embodiment, the composite reinforced FPC further includes an assembly area that is directly opposite the first window area.

[0014] In one embodiment, the composite-reinforced FPC further includes a pure adhesive layer, on which the ceramic layer is adhered.

[0015] Compared with the prior art, the method for manufacturing a windowed structure described in this application has the following advantages: By setting a first windowed area on the surface of the flexible circuit board core layer and removing the copper layer, combined with the windowed design of the cover film layer and the reinforcing layer, and using UV laser cutting and fast pressing processes to integrate the cover film layer, the reinforcing layer (polyimide material), and the ceramic layer, the mechanical strength and structural stability of the FPC are effectively improved. This method not only achieves the space reservation required for module sinking assembly, but also forms a heat dissipation channel through the synergistic windowed design of the cover film, core board, and PI reinforcement, enhancing heat dissipation conductivity. At the same time, the use of a pure adhesive layer to bond the ceramic layer and the reinforcing layer improves the interlayer bonding force and overall durability, avoiding the structural strength reduction problem caused by traditional windowed processes. This technology retains the thin and flexible characteristics of FPC while taking into account the rigid support and heat dissipation requirements, optimizing the manufacturing process, improving assembly yield and product reliability, and is suitable for high-end electronic equipment fields with high precision, high integration, and high reliability requirements.

[0016] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the method for fabricating a window structure provided in this application embodiment; Figure 2 This is a schematic diagram of the flexible circuit board core layer provided in the embodiments of this application; Figure 3 A schematic diagram illustrating the installation process of the cover film layer provided in an embodiment of this application; Figure 4 A schematic diagram of the covering film layer provided in the embodiments of this application; Figure 5 A schematic diagram showing the installation location of the reinforcing layer as provided in an embodiment of this application; Figure 6 This is a schematic diagram showing the installation position of the ceramic layer in an embodiment of this application.

[0019] Icons: 100-Flexible core board layer; 101-Copper layer; 102-Reinforcement layer; 200-First window area; 300-Gold finger area; 301-Solder pad area; 302-Assembly area; 400-Cover film layer; 401-Release protection layer; 500-Reinforcing layer; 600-Ceramic layer; 601-Pure adhesive layer. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for 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. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" 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 direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] This application provides a method for manufacturing a window structure, applied to composite reinforced FPC, with reference to... Figure 1 The manufacturing method includes the following steps: S1: Provide a flexible core board layer 100, and set a first window area 200 on the surface of the flexible core board layer 100, and then remove the copper layer in the first window area 200; S2: Then take the cover film layer 400, set the window group on the cover film layer 400, and then attach the cover film layer 400 to the surface of the flexible core board layer 100 to form an integral structure with the flexible core board layer 100. S3: Take the reinforcing layer 500 again, design a second window area on the reinforcing layer 500 and remove the window area reinforcement by UV laser cutting, and attach the side of the reinforcing layer 500 with adhesive to the flexible core board layer 100 and press it quickly to cover the reinforcing area of ​​the flexible core board layer 100. Then remove the reinforcing layer 102 in the first window area 200. S4: Finally, a pure adhesive layer 601 is set on the surface of the reinforcing layer 500, and then a ceramic layer 600 is set on the surface of the pure adhesive layer 601. Then, under the action of the fast press, the flexible core board layer 100, the reinforcing layer 500 and the ceramic layer 600 are integrated into a single structure.

[0024] The manufacturing method of this window structure includes the following steps: First, a flexible core board layer 100 is provided, and a first window area 200 is set on its surface, removing the copper layer in this area; then, a cover film layer 400 is taken, and a window assembly is pre-set on this film layer, which is then adhered to the surface of the flexible core board layer 100 and quickly pressed to form an integrated structure; subsequently, a reinforcing layer 500 is taken, and a second window area is designed on it by laser cutting, and the reinforcing layer in the first window area is removed; then, the adhesive surface of the reinforcing layer 500 is adhered to the reinforcing area of ​​the flexible core board layer 100 and quickly pressed, referring to... Figure 5 Then remove the reinforcement layer 102 within the first window area 200; finally, refer to Figure 6 A pure adhesive layer 601 is placed on the surface of the reinforcing layer 500, and a ceramic layer 600 is then placed on top. Through the pressing action of a high-speed press, the flexible core board layer 100, the reinforcing layer 500, and the ceramic layer 600 are combined to form a single integrated structure. It should be noted that... Figure 6 The middle arrow points in the direction of heat dissipation.

[0025] This structure enhances the mechanical strength of the flexible board core layer 100 around the module assembly area through the coordinated design of flexible board windowing, PI reinforcement windowing and ceramic reinforcement. It provides a stable stress area for subsequent FPC component mounting and SMT soldering, effectively solving the problems of board warping and local deformation caused by mechanical stress.

[0026] Meanwhile, the structure also provides the necessary space and support for the sinking assembly of modules (devices), which helps to improve assembly accuracy and reliability. The window design forms a heat dissipation channel, which improves the heat dissipation performance of the circuit board and meets the dual requirements of heat dissipation and structural strength for the assembly of highly integrated and high-density devices.

[0027] In some embodiments, refer to Figure 3 Initially, a release protective layer 401 is attached to the cover film layer 400. When the release protective layer 401 is attached to the surface of the cover film layer 400, a window group is set on the cover film layer 400 by laser cutting. After the release protective layer 401 is separated from the cover film layer 400, the cover film layer 400 is then bonded to the surface of the flexible board core layer 100.

[0028] In some embodiments, a release liner 401 is attached to the initial cover film layer 400. This release liner prevents the cover film layer from being contaminated or damaged during processing. While the release liner 401 is still attached to the surface of the cover film layer 400, the required window groups are formed on the cover film layer 400 by UV laser cutting. After the release liner 401 separates from the cover film layer 400, the cover film layer 400 can be cleanly and precisely bonded to the surface of the flexible core board layer 100 to form an integrated structure. This process effectively protects the integrity of the cover film layer before cutting, ensures the accuracy and edge quality of the windowing, and improves the process controllability and yield of subsequent bonding processes.

[0029] Before the cover film layer 400 is bonded to the surface of the copper layer 101, the copper surface of the flexible circuit board core layer 100 needs to undergo chemical browning treatment. Browning is a commonly used surface treatment process. Its purpose is to form an oxide layer with a micro-uneven structure on the surface of the copper layer through a chemical reaction, thereby increasing the roughness of the copper surface. This increased roughness helps to improve the adhesion between the copper layer and the cover film layer 400, enabling them to form a stronger and more stable bond during subsequent bonding processes, and preventing peeling or delamination during subsequent processing or use.

[0030] After the browning process is completed, the cover film layer 400 is then UV laser-cut to precisely create windows for the gold finger area 300, the solder pad area 301, and the assembly area 302. The windowed cover film layer 400 and the flexible board core layer 100 are then rapidly pressed together using a high-speed press (pressure 120 kg, temperature 180°C, time 120 seconds) to ensure the cover film layer adheres firmly to the browned copper surface, enhancing the overall structural stability.

[0031] After the cover film 400 is bonded to the surface of the copper layer 101, the copper layer corresponding to the windowed area of ​​the cover film on the flexible core board layer 100 needs to be treated. Specifically, the browning layer of the copper layer in this area is removed by chemical methods. This operation usually involves chemical etching or cleaning of the copper surface in the windowed area under the action of specific chemical agents (such as acidic solutions) to remove the oxide layer formed after the browning treatment, thereby exposing the original copper surface, which facilitates subsequent process steps (such as immersion nickel-palladium-gold plating) to be carried out more efficiently and reliably.

[0032] In some embodiments, refer to Figure 4 The window assembly includes: a gold finger area 300, a solder pad area 301, and an assembly area 302, wherein the assembly area 302 is directly opposite the first window area 200.

[0033] In some embodiments, the window assembly includes a gold finger area 300, a solder pad area 301, and an assembly area 302. The gold finger area 300 is used for electrical connection with a plug or connector and serves as the interface portion of the circuit board. The solder pad area 301 is used for soldering to other circuit boards or components, providing both electrical connection and mechanical fixation. The assembly area 302 is the area for mounting other electronic components, typically requiring good conductivity and support to ensure component stability and connection reliability. Notably, the assembly area 302 is directly opposite the first window area 200. This means that in the structural design, the assembly area and the first window area have a clear spatial alignment, allowing for precise subsequent assembly and connection processes, improving assembly efficiency and product yield.

[0034] In some embodiments, the copper layer within the first window area 200 is removed by acid etching.

[0035] In some embodiments, the copper layer within the first window area 200 is removed by acid etching. The removal of the copper layer within the first window area 200 may also include chemical methods such as film exposure and development. The purpose of this operation is to ensure that residual copper layers do not affect the bonding effect or cause short circuits during the bonding process of subsequent layers (such as reinforcing layers or ceramic layers), thereby improving the stability and functionality of the entire FPC structure.

[0036] In some embodiments, when the ceramic layer 600 is bonded to the surface of the reinforcing layer 500 using the pure adhesive layer 601, the pure adhesive layer 601 needs to be preheated to enhance its adhesion to both the ceramic layer 600 and the reinforcing layer 500. The preheating temperature of the pure adhesive layer 601 is 60°C. The reinforcing layer 500 is positioned and bonded to the flexible core board layer 100 through the second window area, and then quickly pressed using a high-speed press (pressure 120KG; temperature 180°C; time 50s) to enhance the structural strength of the corresponding area of ​​the flexible core board layer 100.

[0037] In some embodiments, when the ceramic layer 600 is bonded to the surface of the reinforcing layer 500 using the pure adhesive layer 601, the pure adhesive layer 601 needs to be preheated to enhance the adhesion. The preheating temperature is set to 60°C, which promotes the softening of the pure adhesive material, making it easier for it to form a good bond between the ceramic layer 600 and the reinforcing layer 500.

[0038] After the pure adhesive layer 601 has been preheated, it is used to bond the ceramic layer 600 to the surface of the reinforcing layer 500. This method improves the strength of interlayer bonding during rapid pressing and avoids displacement of the ceramic reinforcement position caused by human shaking or mechanical vibration.

[0039] Furthermore, to ensure the reinforcing layer 500 is accurately bonded to the flexible core layer 100, it needs to be positioned using a second window area. This window area design facilitates precise positioning of the reinforcing layer 500, ensuring its alignment and structural stability on the flexible core layer 100. Subsequently, a fast-press bonding process is performed using a high-pressure press under the following conditions: pressure 120 kg, temperature 180 °C, and time 50 seconds. This bonding method effectively combines the reinforcing layer 500 with the flexible core layer 100, enhancing the structural strength and bending resistance of this area, which is of great significance for improving the overall performance and reliability of the flexible board.

[0040] In some embodiments, the reinforcing layer 500 is made of polyimide (PI). Polyimide is a high-performance organic polymer material with excellent high-temperature resistance, chemical corrosion resistance, good mechanical strength, and dielectric properties, making it suitable for structural reinforcement of flexible printed circuit boards (FPCs). The reinforcing layer 500 is used to enhance the structural strength and bending resistance of critical areas to ensure stable and reliable electrical connection performance in these areas during use. The selection of polyimide material allows for better compatibility with the FPC substrate, improves overall thermal stability and process adaptability, thereby enhancing the durability and functionality of the flexible printed circuit board.

[0041] Embodiments of this application also propose a composite reinforced FPC, manufactured using the above-described method for creating a windowed structure; comprising: Reference Figure 2 The flexible core board layer 100 has a first window area 200 that extends through its thickness direction. A cover film layer 400 is attached to the surface of the flexible core board layer 100, and the cover film layer is provided with window groups; The reinforcing layer 500 is attached to the surface of the flexible core board layer 100; And a ceramic layer 600, which is attached to the surface of the reinforcing layer 500 and covers the first window area 200.

[0042] In some embodiments, the window group includes: a gold finger area 300, a pad area 301 and an assembly area 302, and a first window area 200 is formed on the circuit board, with the assembly area 302 facing the first window area 200.

[0043] In some embodiments, the ceramic layer 600 is installed in a position that covers the first window area 200.

[0044] In some embodiments, the ceramic layer 600 is designed to cover the first windowed area 200. The first windowed area 200 is the copper layer area exposed by laser opening on the cover film layer 400, typically used for electrical connection with plugs or connectors, or as a solder pad area for connecting other circuit boards or components. Placing the ceramic layer 600 under this area effectively provides additional physical support and protection, while improving the insulation, heat resistance, and resistance to mechanical damage of this area. This design helps prevent the copper layer from shifting or being damaged by external forces or environmental factors during subsequent processing, thereby improving the stability, reliability, and overall performance of the circuit board. Furthermore, the addition of the ceramic layer 600 can also provide material support for certain functional requirements (such as thermal management, electromagnetic shielding, etc.), further optimizing the overall performance of the circuit board.

[0045] In existing technologies, FPCs (Flexible Printed Circuit Boards) are prone to defects such as board warping, localized deformation, and even pad detachment during SMT assembly and reflow soldering processes due to insufficient substrate rigidity and low mechanical strength. Furthermore, to meet the requirements of component heat dissipation and recessed assembly, FPCs typically require localized windowing, which significantly compromises the structural integrity of the board surface, leading to a substantial decrease in localized mechanical strength. Traditional reinforcement solutions often involve bonding PI or ceramic reinforcement plates to the back of the flexible circuit board's circuit area. Such a single structure struggles to simultaneously address multiple requirements, including mechanical reinforcement of the gold finger and pad areas, recessed assembly space for modules, and heat dissipation for recessed modules.

[0046] To address the aforementioned technical problems, this invention proposes a composite reinforced FPC structure. This structure retains the original reinforcing layer 500 for the gold finger area 300 and the solder pad area 301, and attaches a ceramic layer 600 to the first window area 200 opposite the assembly area 302, forming a composite reinforcement system. This effectively improves the mechanical structural strength of the gold finger area 300 and the solder pad area 301. Simultaneously, the first window area 200 and the assembly area 302 together constitute a recessed cavity for accommodating the module, with the ceramic layer 600 covering the bottom of this cavity. When the module is installed in this cavity, the heat generated can be conducted outwards through the upper surface of the cavity or via the ceramic layer 600 on the lower surface of the cavity. This design not only perfectly realizes the recessed assembly of the module but also constructs an efficient heat conduction path, meeting the module's heat dissipation requirements.

[0047] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0048] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for manufacturing a window structure, characterized in that, Includes the following steps: S1: Provide a flexible core board layer (100), and set a first window area (200) on the surface of the flexible core board layer (100), and then remove the copper layer in the first window area (200); S2: Take the cover film layer (400), set the window group on the cover film layer (400), then attach the cover film layer (400) to the surface of the flexible core board layer (100) and press it quickly to form an integral structure with the flexible core board layer (100); S3: Take the reinforcing layer (500), design a second window area on the reinforcing layer (500), and attach the side of the reinforcing layer (500) with adhesive to the flexible core board layer (100) and press quickly to cover the reinforcing area of ​​the flexible core board layer (100). Then remove the reinforcing layer (102) in the first window area (200). S4: Take the pure adhesive layer (601) and the ceramic layer (600) in the reinforcing layer (500), remove the pure adhesive layer (601) in the first window area, and place the pure adhesive layer (601) between the reinforcing layer (500) and the ceramic layer (600) and bond them together. A flexible core board layer (100), reinforcing layer (500) and ceramic layer (600) are integrated into a single structure by fast pressing.

2. The method for manufacturing the window structure according to claim 1, characterized in that, The initial cover film layer (400) is attached with a release protective layer (401). When the release protective layer (401) is attached to the surface of the cover film layer (400), a window group is set on the cover film layer (400) by laser cutting. After the release protective layer (401) is separated from the cover film layer (400), the cover film layer (400) is then bonded to the surface of the flexible core board layer (100) and quickly pressed.

3. The method for manufacturing the window structure according to claim 1, characterized in that, The copper layer in the first window area (200) is removed by acid etching.

4. The method for manufacturing the window structure according to claim 1, characterized in that, When bonding the ceramic layer (600) to the surface of the reinforcing layer (500) using the pure adhesive layer (601), the pure adhesive layer (601) also needs to be preheated to enhance the adhesion of the pure adhesive layer (601) to the ceramic layer (600) and the reinforcing layer (500).

5. The method for manufacturing the window structure according to claim 4, characterized in that, The preheating temperature of the pure adhesive layer (601) is 60°C.

6. The method for manufacturing the window structure according to claim 1, characterized in that, Both the reinforcing layer (102) and the supplementary layer (500) are made of polyimide.

7. The method for manufacturing the window structure according to claim 1, characterized in that, Before the reinforcing layer (500) is bonded to the flexible core board layer (100), the surface of the flexible core board layer (100) is browned.

8. A composite reinforced FPC, characterized in that, The window structure is manufactured using the method described in any one of claims 1-7, comprising: A flexible core board layer (100) is provided with a first window area (200) extending through its thickness direction. A cover film layer (400) is attached to the surface of the flexible core board layer (100); A reinforcing layer (500) is attached to the surface of the flexible core board layer (100); And a ceramic layer (600) is attached to the surface of the reinforcing layer (500) and the ceramic layer (600) covers the first window area (200).

9. The composite-reinforced FPC according to claim 8, characterized in that, The composite reinforced FPC also includes an assembly area (302) which is directly opposite the first window area (200).

10. The composite-reinforced FPC according to claim 8, characterized in that, The composite reinforced FPC also includes a pure adhesive layer (601), on which the ceramic layer (600) is bonded.

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