Flexible circuit board and touch screen

Abstract

The application relates to the technical field of flexible circuit boards, in particular to a flexible circuit board and a touch screen. The flexible circuit board comprises a base material and a wiring layer arranged on the base material, the side of the base material is provided with a laminated layer; the flexible circuit board comprises at least a bending area, in the bending area, the wiring layer is arranged on one side of the base material to form a single-layer wiring structure of the bending area; and in the bending area, the laminated layer on the non-wiring side of the base material is removed completely or partially. The flexible circuit board wiring form is optimized, and the structures of different board layers are improved, so that the bending softness of the flexible circuit board is improved.

Description

Technical Field

[0001] This application relates to the field of flexible circuit board technology, and more specifically, to a flexible circuit board and a touch screen. Background Technology

[0002] In the current laptop industry, the demand for narrower bezels is increasing in pursuit of a more aesthetically pleasing appearance. Narrower bezels require a more compact layout of electronic components on the control circuit boards of various laptop parts. Simultaneously, the space available for wiring such as flexible circuit boards is decreasing, leading to a gradual reduction in the size of flexible circuit boards. Since flexible circuit boards typically need to be bent to the back of the LCD display module, the requirement for their flexibility is also increasing.

[0003] Currently, the stacking design of flexible circuit boards in the industry is often very fixed, and the main factor affecting the bending effect of flexible circuit boards is the middle area of ​​the flexible circuit board. With a fixed stacking structure and thickness, the flexible circuit board has poor bending flexibility and may be difficult to bend. Utility Model Content

[0004] The purpose of this application is to provide a flexible circuit board and a touch screen, which improves the bending flexibility of the flexible circuit board by optimizing the wiring form of the flexible circuit board and improving the structure of different board layers.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a flexible circuit board, including a substrate and a wiring layer disposed on the substrate, wherein a stacked layer is disposed on the side of the substrate; The flexible circuit board includes at least a bending region, and within the bending region, the wiring layer is disposed on one side of the substrate to form a single-layer wiring structure of the bending region. Furthermore, within the bending zone, the stacked layer located on the non-wiring side of the substrate is completely or partially removed.

[0006] In an optional embodiment, the stacked layer includes a grounded copper foil layer, a cover film, and a silver foil layer arranged sequentially from the inside out, wherein the grounded copper foil layer is bonded to the substrate.

[0007] In an optional embodiment, within the bending area, the non-wiring side of the substrate does not have the stacked layer, the substrate surface is fully exposed, and the stacked layer is laid continuously on the side of the substrate wiring side.

[0008] In an optional embodiment, within the bending area, the grounding copper foil layer, the cover film, and the silver foil layer on the non-wiring side of the substrate are all removed to allow the substrate to form a single-layer exposed structure.

[0009] In an optional embodiment, within the bending area, the middle portion of the grounding copper foil layer, the middle portion of the cover film, and the middle portion of the silver foil layer on the non-wiring side of the substrate are removed, and the remaining portions are symmetrically centered.

[0010] In an optional embodiment, within the bending region, the removal sections of the ground copper foil layer, the removal sections of the cover film, and the removal sections of the silver foil layer on the non-wiring side of the substrate are staggered and stacked.

[0011] In an optional embodiment, within the bending zone, the removal area of ​​the grounding copper foil layer, the removal area of ​​the cover film, and the removal area of ​​the silver foil layer gradually increase.

[0012] In an optional embodiment, the grounding copper foil layer has a mesh structure, and the mesh size of the grounding copper foil layer on the substrate wiring side is smaller than the mesh size of the grounding copper foil layer on the substrate non-wiring side.

[0013] In an optional implementation, within the bending area, the wiring routing of the single-layer wiring structure follows the bending direction of the flexible circuit board.

[0014] Secondly, the present invention provides a touch screen, including a touch screen sensor, a main control circuit board, and a flexible circuit board as described in any of the foregoing embodiments, wherein the flexible circuit board is connected between the touch screen sensor and the main control circuit board.

[0015] The flexible circuit board in this application can effectively improve the bending flexibility of the flexible circuit board and avoid damage to the signal lines due to stress concentration.

[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 This is a schematic diagram showing the arrangement of the bending and non-bending areas on a flexible circuit board. Figure 2 This is a schematic diagram of the distribution structure of the grounding copper foil layer and the wiring layer in the prior art; Figure 3 This is a schematic diagram of the distribution structure of the stacked layers and the substrate in the prior art; Figure 4This is a schematic diagram of the distribution structure of the stacked layers and the substrate in Embodiment 1 of this application; Figure 5 This is a schematic diagram of the distribution structure of the stacked layers and the substrate in Embodiment 2 of this application.

[0019] icon: A - Bending area; B - Non-bending area; C - Wiring layer; 1-Substrate; 2-Grounded copper foil layer; 3-Covering film; 4-Silver foil 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] Combination Figures 1-3 This application addresses the problem of insufficient flexibility in bending within narrow spaces caused by the fixed stacked structure and overall thickness of existing flexible circuit boards. By optimizing the stacked structure of the bending area A of the flexible circuit board, the bending performance of the flexible circuit board is significantly improved while ensuring electrical performance.

[0024] By setting a single-layer wiring structure in the bending area A of the flexible circuit board, and removing all or part of the redundant stacked layers on the non-wiring side, the overall thickness of the bending area is fundamentally reduced, thereby achieving a comprehensive improvement in flexibility.

[0025] Meanwhile, by staggering the remaining faults after removing some of the stacked layers, stress concentration is avoided, thus improving bending reliability and product lifespan.

[0026] Based on the fact that the stacked layer on the non-wiring side of the substrate 1 is completely or partially removed in this application, the flexible circuit board with improved bending flexibility in this application will be described below through two different embodiments.

[0027] Example 1 See Figure 4 , combined Figures 1-2 The flexible circuit board provided in this embodiment has a main structure including a substrate 1 and a wiring layer C disposed on the substrate 1, and a stacked layer disposed on the side of the substrate 1.

[0028] Overall, the flexible circuit board includes a non-bending area B and a bending area A. Under normal circumstances, the non-bending area B is located at both ends of the flexible circuit board and can be connected to the motherboard and the display module respectively. The bending area A is the part that needs to be bent.

[0029] The substrate 1 is specifically a flexible substrate 1, which is typically made of polyimide film. On existing conventional flexible circuit boards, symmetrical stacked layers are provided on both sides of the substrate 1, namely the top and bottom surfaces of the substrate 1.

[0030] The stacked layers, from the inside out, include: a grounded copper foil layer 2 directly bonded to the substrate 1; a cover film 3 covering the grounded copper foil layer 2, typically a photosensitive cover film 3 or a polyimide cover film 3; and an outermost silver foil layer 4, which constitutes an electromagnetic shielding layer. In the non-bending region B, the aforementioned symmetrical stacked structure provides the necessary mechanical support, electrical insulation, and electromagnetic shielding for the circuit.

[0031] In this embodiment, within the bending area A, a wiring layer C is disposed on one side of the substrate 1 to form a single-layer wiring structure for the bending area A. The wiring layer C is only arranged on one side of the substrate 1, which can be the top or bottom surface of the substrate 1. This concentrates the traces within the bending area A on the same side and in the same layer of the substrate 1. By abandoning the traditional double-layer wiring mode, the thickness of the wiring layer C can be directly reduced, thus providing a structural foundation for improving the bending flexibility of the flexible circuit board by increasing the angle of the substrate 1.

[0032] In order to achieve better flexibility, the flexible circuit board in this embodiment has all the stacked layers on the non-wiring side of the substrate 1 removed.

[0033] Specifically, in the non-wiring side region of substrate 1 within bending zone A, the grounding copper foil layer 2, the cover film 3, and the silver foil layer 4 are all removed, so that the non-wiring side surface of substrate 1 is completely exposed within bending zone A, forming a single-layer exposed structure.

[0034] Meanwhile, within the bending area A, the stacked layer located on the wiring side of the substrate 1, the grounding copper foil layer 2, the cover film 3, and the silver foil layer 4 maintain their integrity and extend to the non-bending area B, forming a continuous structure of the stacked layer on the wiring side of the substrate 1 to ensure the protection of the signal lines and the continuity of the overall flexible circuit board.

[0035] In this embodiment, because all the stacked layers on the non-wiring side of the bending region A are removed, the total thickness of the bending region A is significantly reduced. Compared to traditional double-layer symmetrical stacked flexible circuit boards, the thickness of the bending region A can be reduced by approximately 40%-50%.

[0036] The reduction in the thickness of the bending zone A enables the flexible circuit board to easily achieve small-radius bending within a narrow frame space, completely solving the technical problem of the difficulty in bending the flexible circuit board.

[0037] In traditional multilayer stacks, all material layers bear stress as a whole during bending, which easily leads to fatigue cracks at the bending axis. However, in this embodiment, the surface of the substrate 1 on the non-wiring side is exposed, allowing the zero-stress layer to be closer to the center of the flexible circuit board during bending, and even potentially adjusted to be inside the substrate 1. This significantly reduces the tensile and compressive stress on the copper foil of the wiring layer C, effectively extending the dynamic bending life of the flexible circuit board.

[0038] Since only the flexible substrate 1 remains on the non-wiring side of the bending area A, the transition between it and the rigid area is smoother, effectively dispersing the bending stress and preventing failure modes such as wrinkling of the cover film 3, copper foil fatigue, or tearing of the substrate 1 caused by stress concentration at the junction.

[0039] Example 2 See Figure 5 , combined Figures 1-2 The flexible circuit board in this application has a similar main structure to that in Embodiment 1. It also includes a substrate 1, a wiring layer C disposed on one side of the substrate 1 in the bending area, and a continuous stacked layer located in the wiring layer C. The difference is that the stacked layer in this embodiment is not completely removed, but partially removed, which takes into account both electromagnetic shielding and structural transition requirements.

[0040] Specifically, the flexible circuit board in this embodiment also includes a non-bending area B and a bending area A. In the bending area A, the ground copper foil layer 2, the cover film 3, and the silver foil layer 4 located on the non-wiring side of the substrate 1 are not completely removed, but only the middle part is removed, and narrow and long parts are retained on both sides. The remaining stacked layers are symmetrically distributed with respect to the center of the bending area A.

[0041] Furthermore, the removal sections of the non-wiring side grounding copper foil layer 2, the removal sections of the cover film 3, and the removal sections of the silver foil layer 4 are staggered and stacked.

[0042] Specifically, on the longitudinal section of the flexible circuit board, the removal section of the outermost silver foil layer 4 is located on the outermost side.

[0043] The removal section of the intermediate cover film 3 is located inside the removal section of the silver foil layer 4.

[0044] The removal section of the innermost grounding copper foil layer 2 is located at the innermost side.

[0045] Preferably, within the bending zone A, the removal area of ​​the grounding copper foil layer 2, the removal area of ​​the cover film 3, and the removal area of ​​the silver foil layer 4 gradually increase.

[0046] This configuration allows the three removal sections at different levels to form a stepped or sloping transition zone.

[0047] This application, by staggering three removal sections, can disperse concentrated stress to different locations and extend stress lines into gentle stress transition zones, allowing stress to be transferred and released, thus significantly improving the reliability of flexible circuit boards during bending.

[0048] Because a portion of the grounded copper foil layer 2 and silver foil layer 4 are retained on the non-wiring side edge of the bending area A, they can absorb and reflect external electromagnetic interference to a certain extent, providing basic protection for the inner single-layer signal line.

[0049] In this application, the grounding copper foil layer 2 has a grid structure. Regardless of the type of stacked layer, the mesh size of the grounding copper foil layer 2 on the wiring side of the substrate 1 is smaller than that on the non-wiring side of the substrate 1. The mesh size of the single or double grounding copper foil layer 2 is relatively sparse, which can improve the size to a certain extent. That is to say, in the bending area A and the non-bending area B on the wiring side, a dense grid with a smaller mesh size is used to provide good grounding and shielding effects.

[0050] On the non-wiring side, whether the area is completely removed or partially retained, the grounding copper foil layer 2 uses a sparse grid with a larger mesh size, which gives the flexible circuit board a certain degree of local flexibility in the non-bending area B, reduces the overall stiffness, and avoids the non-bending area B, which has a large rigidity, from generating excessive tensile stress on the bending area A.

[0051] Within the bending zone A, the routing of the single-layer wiring structure follows the bending direction of the flexible circuit board. This ensures that when the flexible circuit board bends along the predetermined bending line, the copper foil undergoes uniform bending deformation rather than being subjected to severe stretching or compression. This further protects the integrity of the circuit and reduces impedance abrupt changes and signal loss.

[0052] This application also provides a touch screen, including a touch screen sensor, a main control circuit board, and a flexible circuit board as described above. The flexible circuit board is connected between the touch screen sensor and the main control circuit board, which can effectively solve the problem that the flexible circuit board is difficult to bend under the thin and light design, and significantly improve the stability and service life of the device.

[0053] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0054] 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 flexible circuit board, characterized in that, It includes a substrate and a wiring layer disposed on the substrate, wherein a stacked layer is disposed on the side of the substrate; The flexible circuit board includes at least a bending region, and within the bending region, the wiring layer is disposed on one side of the substrate to form a single-layer wiring structure of the bending region. Furthermore, within the bending zone, the stacked layer located on the non-wiring side of the substrate is completely or partially removed.

2. The flexible circuit board according to claim 1, characterized in that, The stacked layer includes a grounded copper foil layer, a cover film, and a silver foil layer arranged sequentially from the inside to the outside, with the grounded copper foil layer being bonded to the substrate.

3. The flexible circuit board according to claim 2, characterized in that, Within the bending zone, the non-wiring side of the substrate does not have the stacked layer, the substrate surface is completely exposed, and the stacked layer is laid continuously on the side of the substrate wiring side.

4. The flexible circuit board according to claim 3, characterized in that, Within the bending zone, the grounding copper foil layer, the cover film, and the silver foil layer on the non-wiring side of the substrate are all removed to allow the substrate to form a single-layer exposed structure.

5. The flexible circuit board according to claim 2, characterized in that, Within the bending zone, the middle portions of the grounding copper foil layer, the middle portions of the cover film, and the middle portions of the silver foil layer on the non-wiring side of the substrate are removed, and the remaining portions are symmetrically centered.

6. The flexible circuit board according to claim 5, characterized in that, Within the bending zone, the removal sections of the grounding copper foil layer, the removal sections of the cover film, and the removal sections of the silver foil layer on the non-wiring side of the substrate are staggered and stacked.

7. The flexible circuit board according to claim 5, characterized in that, Within the bending zone, the removal area of ​​the grounding copper foil layer, the removal area of ​​the covering film, and the removal area of ​​the silver foil layer gradually increase.

8. The flexible circuit board according to claim 5, characterized in that, The grounding copper foil layer has a grid structure, and the mesh size of the grounding copper foil layer on the wiring side of the substrate is smaller than the mesh size of the grounding copper foil layer on the non-wiring side of the substrate.

9. The flexible circuit board according to claim 5, characterized in that, Within the bending zone, the wiring routing of the single-layer wiring structure follows the bending direction of the flexible circuit board.

10. A touchscreen, characterized in that, It includes a touch screen sensor, a main control circuit board, and a flexible circuit board as described in any one of claims 1-9, wherein the flexible circuit board is connected between the touch screen sensor and the main control circuit board.

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