Flexible circuit board and electronic device

Abstract

The application provides a flexible circuit board and an electronic device, and relates to the technical field of electronic devices. The flexible circuit board comprises a main body, the main body comprises a first cover layer, a first conductive layer, a first support layer, an adhesive layer, a second support layer, a second conductive layer and a second cover layer which are sequentially arranged along the thickness direction of the main body; the main body has a bending area, the first support layer and the second support layer located in the bending area have a hollow structure, and the hollow structure is used for separating the first support layer and the second support layer at the position of the bending area.

Description

Technical Field

[0001] This application relates to the field of electronic equipment technology, and more particularly to a flexible circuit board and electronic equipment. Background Technology

[0002] Flexible printed circuit boards (FPCs) are widely used inside foldable phones and laptops, allowing direct circuitry between the screen and the device through the hinge. However, the hinge rotates periodically during the opening and closing of foldable electronic devices, requiring the FPC to be repeatedly bent along with the hinge's movement. This prolonged, high-frequency bending action can cause fatigue cracks or even breakage of the copper foil conductors inside the FPC, leading to circuit connection failure. Utility Model Content

[0003] This application provides a flexible circuit board, comprising: a main body, the main body including a first cover layer, a first conductive layer, a first support layer, an adhesive layer, a second support layer, a second conductive layer, and a second cover layer disposed sequentially along its thickness direction; the main body has a bending region, and a hollow structure is provided between the first support layer and the second support layer located in the bending region, the hollow structure being used to separate the first support layer and the second support layer at the location of the bending region.

[0004] In some embodiments of this application, the hollow structure is a rectangular cavity structure adapted to the size of the bending area.

[0005] In some embodiments of this application, the flexible circuit board further includes a shielding material filled within the hollow structure for electromagnetic shielding between the first conductive layer and the second conductive layer.

[0006] In some embodiments of this application, the shielding material is silver particle material, which is covered on the inner wall surface of the hollow structure in a membrane structure.

[0007] In some embodiments of this application, the adhesive layer surrounds the periphery of the hollow structure.

[0008] In some embodiments of this application, the flexible circuit board further includes: a pair of reinforcing structures, the main body including a first panel and a second panel, the first panel and the second panel being connected through the bending area, and the pair of reinforcing structures being respectively connected to the first panel and the second panel; wherein the range of the hollow structure does not exceed the range formed between the pair of reinforcing structures.

[0009] In some embodiments of this application, the flexible circuit board further includes: a first type of line and a second type of line, disposed on the first conductive layer or the second conductive layer; the first type of line and the second type of line are respectively symmetrically disposed on the first panel and the second panel with respect to the bending area.

[0010] In some embodiments of this application, the first category of lines includes a plurality of first lines, which are centrally symmetrically arranged along the center line of the length direction of the first category of lines; the second category of lines includes a plurality of second lines, which are centrally symmetrically arranged along the center line of the length direction of the second category of lines.

[0011] In some embodiments of this application, the first category of lines are power lines for transmitting power signals; the second category of lines are radio frequency lines for transmitting radio frequency signals.

[0012] This application also provides an electronic device, including: a first body, a second body, and a rotating device, wherein the first body and the second body are rotatably connected via the rotating device; a flexible circuit board, wherein the flexible circuit board passes through the rotating device and is connected to the first body and the second body respectively, comprising: a main body, the main body including a first cover layer, a first conductive layer, a first support layer, an adhesive layer, a second support layer, a second conductive layer, and a second cover layer arranged sequentially along its thickness direction; the main body has a bending region, the bending region being disposed opposite to the rotating device, wherein a hollow structure is provided between the first support layer and the second support layer located in the bending region, the hollow structure being used to separate the first support layer and the second support layer at the position located in the bending region. Attached Figure Description

[0013] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein:

[0014] Figure 1 A schematic cross-sectional view of the flexible circuit board provided in an embodiment of this application is shown.

[0015] Figure 2 A top view of the flexible circuit board provided in an embodiment of this application is shown schematically;

[0016] Figure 3 The schematic diagram illustrates the structure of a first type of circuit or a second type of circuit in a flexible circuit board provided in the embodiments of this application;

[0017] Explanation of icon numbers:

[0018] 1. Main body; 101. First covering layer; 102. First conductive layer; 103. First support layer; 104. Adhesive layer; 105. Second support layer; 106. Second conductive layer; 107. Second covering layer; 108. Hollow structure; 2. Shielding material; 3. Reinforcing structure; 4. First type of circuit; 401. First circuit; 5. Second type of circuit; 501. Second circuit. Detailed Implementation

[0019] Exemplary embodiments of this application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art.

[0020] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application pertains.

[0021] Example 1

[0022] This application provides a flexible circuit board, such as Figure 1 As shown, it includes: a main body 1, which includes a first cover layer 101, a first conductive layer 102, a first support layer 103, an adhesive layer 104, a second support layer 105, a second conductive layer 106, and a second cover layer 107 arranged sequentially along its thickness direction; the main body 1 has a bending region, and a hollow structure 108 is provided between the first support layer 103 and the second support layer 105 located in the bending region, the hollow structure 108 being used to separate the first support layer 103 and the second support layer 105 at the position located in the bending region.

[0023] Flexible circuit boards can be applied to foldable phones and foldable computers. The main body 1 of the flexible circuit board can adopt a multi-layer stacked structure, consisting of, from the thickness direction, a first cover layer 101, a first conductive layer 102, a first support layer 103, an adhesive layer 104, a second support layer 105, a second conductive layer 106, and a second cover layer 107. The first cover layer 101 and the second cover layer 107 can be made of materials with good flexibility and insulation, such as polyimide (PI), to protect the internal conductive layers. The first conductive layer 102 and the second conductive layer 106 can be made of materials with good conductivity, such as copper foil, on which the required circuit traces can be etched. The first support layer 103 and the second support layer 105 can be made of materials with certain rigidity and elasticity (such as polyimide PI, polyvinyl naphthol PEN, or stainless steel sheets) to provide support strength for the conductive layers. The adhesive layer 104 can be made of a suitable adhesive, such as epoxy resin or acrylic thermosetting adhesive, to bond the upper and lower parts together.

[0024] In the bending areas where the flexible circuit board requires frequent bending, a cavity, namely a hollow structure 108, is formed in the adhesive layer 104. The hollow structure 108 can be achieved by directly slotting in the adhesive layer 104 or by controlling the adhesive application area. Due to the presence of the hollow structure 108, the first support layer 103 and the second support layer 105 are not bonded by adhesive between the bending areas, thus forming a separated or relatively movable state.

[0025] In related technologies, traditional FPCs require repeated bending at the hinges or other rotating mechanisms of foldable electronic devices, making their internal copper foil conductors prone to fatigue cracking or even breakage. This application addresses this issue by providing a hollow structure 108 between the first support layer 103 and the second support layer 105 in the bending area. This allows the first and second support layers 103 and 105 to deform independently and freely, preventing them from sticking or pulling against each other in the bending area. This reduces the bending stiffness of the flexible circuit board's bending area, making it easier to bend. This effectively solves the problem in related technologies where copper foil conductors are prone to fatigue breakage due to long-term, high-frequency bending, leading to circuit connection failure.

[0026] Furthermore, traditional multilayer FPCs are repeatedly bent as a single thick sheet at the hinge. Their total thickness is relatively large. According to the principles of material mechanics, bending stress is proportional to the material thickness, which easily leads to excessive stretching of the outer copper foil and excessive compression of the inner copper foil, causing the copper foil conductors to easily crack or even break due to fatigue. This application addresses this by providing a hollow structure 108, so the flexible circuit board is no longer bent as a whole in the bending area. The hollow structure 108 allows the first support layer 103, the first conductive layer 102, the first cover layer 101, and the second support layer 105, the second conductive layer 106, and the second cover layer 107 to be bent as two thinner, independent sheets in the bending area. Therefore, by reducing the overall thickness of the flexible circuit board in the bending area into two independent parts, the stress generated can be reduced proportionally to the thickness, reducing the tensile and compressive stress on each part and thus alleviating the fatigue problem. The flexible circuit board of this application embodiment can improve its durability and bending life so as to meet the opening and closing requirements of foldable mobile phones and other electronic devices for tens of thousands or even hundreds of thousands of times.

[0027] In some embodiments, such as Figure 1 As shown, the hollow structure 108 is a rectangular cavity structure adapted to the size of the bending area.

[0028] The hollow structure 108 is a rectangular cavity, meaning that its outline is rectangular in the direction perpendicular to the surface of the flexible circuit board. The dimensions of the hollow structure 108 are adapted to the dimensions of the bending area. For example, along the length of the bending area (i.e., the direction parallel to the bending axis), the length of the rectangular cavity can be equal to or slightly greater than the length of the bending area. Along the width of the bending area (i.e., the direction perpendicular to the bending axis), the width of the rectangular cavity can be equal to or slightly less than the width of the bending area.

[0029] The rectangular cavity can be fabricated using a mask with a rectangular cutout pattern. Adhesive is applied only to the non-bending areas, leaving the bending areas unadhesive. After lamination, a rectangular hollow cavity is naturally formed. Alternatively, adhesive can be applied evenly and pre-laminated first, and then the adhesive layer 104 material in the bending areas can be removed using a laser or mechanical tool to form a rectangular cavity.

[0030] By designing the hollow structure 108 as a rectangular cavity that matches the size of the bending area, the structure of the bending area can be kept symmetrical, which is conducive to the uniform distribution of stress and improves bending performance. On the other hand, the rectangular shape is regular, easy to process, and has low process difficulty, which helps to reduce manufacturing costs.

[0031] In some embodiments, the flexible circuit board further includes a shielding material 2, which is filled within the hollow structure 108 for electromagnetic shielding between the first conductive layer 102 and the second conductive layer 106.

[0032] Shielding material 2 can be a special material with fluidity and conductivity. Examples include conductive gels or conductive silicone containing conductive materials such as silver powder, silver-coated copper powder, carbon nanotubes, and graphene, conductive foam, liquid metal, or conductive ink. Shielding material 2 can completely fill the entire hollow cavity or partially fill it, for example, completely covering the inner wall surface of the hollow cavity. Shielding material 2 can be filled into the hollow cavity through methods such as dispensing, printing, electroplating deposition, or preforming. The filled shielding material 2 needs to establish a good electrical connection with the conductive layers on the upper and lower sides.

[0033] Because the removal of the adhesive layer 104 in the bending area forms a hollow structure 108, the signal lines on the first conductive layer 102 and the second conductive layer 106 may generate electromagnetic radiation or mutual interference when the flexible circuit board is in operation. By providing the shielding material 2, these electromagnetic waves can be absorbed or reflected, effectively blocking the electromagnetic coupling between the first conductive layer 102 and the second conductive layer 106, significantly reducing crosstalk, and improving the integrity and stability of signal transmission. Simultaneously, the shielding material 2 is a post-filling layer located between the first support layer 103 and the second support layer 105, so the portion above the first support layer 103 and the portion below the second support layer 105 can still deform independently and freely. This effectively reduces the stress borne by each part during bending, thereby effectively alleviating fatigue problems caused by stress concentration.

[0034] In some embodiments, the shielding material 2 is a silver particle material, which is covered on the inner wall surface of the hollow structure 108 in a membrane structure.

[0035] The shielding material 2 is a thin film covering the inner wall surface of the hollow structure 108, forming a conductive film layer surrounding the internal space of the cavity. The shielding material 2 can be formed into a continuous silver film through physical vapor deposition, deposited on the inner wall surface through chemical silver plating, or coated onto the inner wall of the cavity through spraying, dipping, or printing. The shielding material 2 is made of silver particles, which can be composed of micron- or nano-sized silver particles. Silver has excellent conductivity.

[0036] By using silver particles as a shielding layer to cover the inner wall of the hollow structure 108 with a membrane structure, not only can the conductivity of silver be used to achieve electromagnetic shielding, but also, thanks to its ultra-thin membrane morphology, the hollow structure 108 retains the effect of low bending stress in the bending area of ​​the flexible circuit board, thereby effectively alleviating fatigue problems.

[0037] In some embodiments, the adhesive layer 104 surrounds the periphery of the hollow structure 108.

[0038] In the bending region, the adhesive layer 104 forms a closed annular or frame-shaped area around the hollow structure 108. This allows the adhesive layer 104 to bond the first support layer 103 and the second support layer 105 on both sides of the hollow structure 108 together, preventing interlayer separation, warping, or accidental peeling caused by the hollow structure 108. Simultaneously, the adhesive layer 104 forms a sealing ring, effectively preventing the shielding material 2 from overflowing or migrating during processing or use, ensuring that the shielding material 2 remains stably positioned in the predetermined location, maintaining its shielding effectiveness and structural integrity.

[0039] In some embodiments, such as Figure 1 As shown, the flexible circuit board also includes: a pair of reinforcing structures 3, the main body 1 includes a first panel and a second panel, the first panel and the second panel are connected by a bending area, and the pair of reinforcing structures 3 are respectively connected to the first panel and the second panel; wherein the range of the hollow structure 108 does not exceed the range formed between the pair of reinforcing structures 3.

[0040] Taking a foldable phone as an example, the flexible circuit board includes a first part on the left and a second part on the right, which are connected by a bending area in the middle. The first part can be used to connect to the display module, and the second part can be used to connect to the mainboard. The foldable phone also includes a rotating device, through which the flexible circuit board can pass and connect to the foldable phone. The bending area of ​​the flexible circuit board corresponds to the rotating area of ​​the rotating device.

[0041] The flexible circuit board also includes a pair of reinforcing structures 3, respectively disposed on the first part and the second part. The reinforcing structures 3 can be made of rigid or semi-rigid materials, such as FR4 material or steel plate. The first part and the second part can be fixedly connected to the housing of the rotating device through the pair of reinforcing structures 3, thereby realizing the synchronous folding and unfolding of the flexible circuit board and the body with the rotating device.

[0042] The hollow structure 108 of the flexible circuit board does not extend beyond the area between the pair of reinforcing structures 3; that is, the projection of the hollow structure 108 on the plane of the flexible circuit board lies entirely between the two reinforcing structures 3. This avoids the rigid reinforcing structures 3 compressing the hollow structure 108 when the flexible circuit board is assembled and fixed with the rotating device, prevents electromagnetic interference between the first conductive layer 102 and the second conductive layer 106 due to pressure, and effectively reduces the risk of cracks in the copper foil circuit of the bending area due to stress concentration, thereby improving product reliability.

[0043] In some embodiments, such as Figure 2 As shown, the flexible circuit board further includes: a first type of line 4 and a second type of line 5, disposed on the first conductive layer 102 or the second conductive layer 106; the first type of line 4 and the second type of line 5 are respectively symmetrically disposed on the first panel and the second panel with respect to the bending area.

[0044] Metal lines for transmitting signals or power are etched or printed on the first conductive layer 102 and the second conductive layer 106 of the flexible circuit board, respectively, which are classified as first category line 4 and second category line 5. The first category line 4 can be a high-speed signal line, such as a display screen drive signal line, a camera data line, a power signal line, etc. The second category line 5 can be a radio frequency line for transmitting radio frequency signals, a low-speed control signal line, or other auxiliary signal lines, etc.

[0045] The layout of the first category line 4 and the second category line 5 on the first and second panels is symmetrical with respect to the central bending area. That is, taking the bending axis of the bending area as the axis of symmetry, the layout characteristics of the first category line 4 on the first panel, such as its direction, length, and distance from the edge of the flexible circuit board, are mirror-symmetrical with the corresponding layout characteristics of the first category line 4 on the second panel. Similarly, the second category line 5 is also symmetrically laid out.

[0046] When the flexible circuit board opens and closes with the rotating device, the bending area undergoes bending deformation. If the circuit distribution is asymmetrical, the stiffness of the conductive layers on both sides will be inconsistent. Especially on the side with denser circuitry, due to the higher proportion and stiffness of the copper foil, deformation is more difficult, resulting in localized stress concentration during bending and easily causing copper foil fatigue cracking. This application, by symmetrically arranging the first type of circuitry 4 and the second type of circuitry 5 on the first and second panels, ensures a balanced stiffness distribution of the circuitry on both sides, making the mechanical stress borne by the first and second panels more uniform during bending. This effectively avoids premature fatigue caused by asymmetrical layout, thus significantly improving the bending life and reliability of the entire flexible circuit board.

[0047] In some embodiments, such as Figure 3 As shown, the first category line 4 includes multiple first lines 401, which are arranged symmetrically along the center line of the length direction of the first category line 4; the second category line 5 includes multiple second lines 501, which are arranged symmetrically along the center line of the length direction of the second category line 5.

[0048] Category 1 Line 4 consists of a group of lines with the same or related functions. The multiple first lines 401 are centrally symmetrically distributed along the centerline of the overall length of the group. Category 2 Line 5 also consists of multiple lines, and the multiple second lines 501 are also centrally symmetrically distributed along the centerline of their respective group's length.

[0049] By setting multiple lines inside the first category line 4 and the second category line 5 to be centrally symmetrical along their length centerline, local fatigue caused by asymmetrical layout inside the first category line 4 and the second category line 5 is effectively avoided, thereby significantly improving the bending life and reliability of the entire flexible circuit board.

[0050] In some embodiments, the first category of lines are power lines for transmitting power signals; the second category of lines are radio frequency lines for transmitting radio frequency signals.

[0051] The first category of lines, 4, is a power line, used to transmit DC power signals and provide the necessary power for the display screen, camera module, or other components. The second category of lines, 5, is a radio frequency (RF) line, used to transmit high-frequency RF signals. By defining the first category of lines, 4, as power lines and the second category of lines, 5, as RF lines, and arranging them in the aforementioned symmetrical manner, the mechanical reliability of the flexible circuit board can be improved by balancing stress, and the stable transmission of high-power power and the purity of high-sensitivity RF signals can be effectively enhanced.

[0052] Example 2

[0053] This application also provides an electronic device, including: a first body, a second body, and a rotating device, wherein the first body and the second body are rotatably connected by the rotating device; a flexible circuit board, which passes through the rotating device and is connected to the first body and the second body respectively, including: a main body 1, the main body 1 including a first cover layer 101, a first conductive layer 102, a first support layer 103, an adhesive layer 104, a second support layer 105, a second conductive layer 106, and a second cover layer 107 arranged sequentially along its thickness direction; the main body 1 has a bending region, the bending region being disposed opposite to the rotating device, wherein a hollow structure 108 is provided between the first support layer 103 and the second support layer 105 located in the bending region, the hollow structure 108 being used to separate the first support layer 103 and the second support layer 105 at the position located in the bending region.

[0054] The electronic device can be a foldable phone, a foldable laptop, a rollable display, or similar device. The electronic device comprises a first body and a second body. The first body can be the upper half of the device housing the display screen, and the second body can be the lower half of the device or a base housing the motherboard and battery. The first and second bodies are rotatably connected via a rotating mechanism, which can be a multi-link hinge, a flexible rotating shaft mechanism, or similar structure, thereby enabling the first and second bodies to switch between folded and unfolded states.

[0055] The flexible circuit board can pass through the internal channel of the rotating device, with one end electrically connected to the first body and the other end electrically connected to the second body, thereby realizing the electrical connection between the first and second bodies. When the electronic device is opened and closed, the flexible circuit board can move synchronously with the rotating device, and its bending area located inside the rotating device or in the corresponding area will repeatedly bend and flatten. The flexible circuit board has a multi-layer structure, and in the bending area opposite to the rotating device, there is a hollow structure 108 between the first support layer 103 and the second support layer 105, which makes the first support layer 103 and the second support layer 105 physically separated in the bending area.

[0056] By using the flexible circuit board of Example 1, the support layer can be separated by utilizing the hollow structure 108 in the bending area. This can significantly reduce the stress and strain borne by the copper foil conductors during repeated bending, enabling the flexible circuit board to withstand tens of thousands or even hundreds of thousands of high-frequency opening and closing cycles throughout the entire life cycle of the electronic device, thus meeting the long-term reliability requirements of the rotating device.

[0057] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A flexible circuit board, characterized by, include: The main body includes a first cover layer, a first conductive layer, a first support layer, an adhesive layer, a second support layer, a second conductive layer, and a second cover layer arranged sequentially along its thickness direction; The main body has a bending area, and a hollow structure is provided between the first support layer and the second support layer located in the bending area. The hollow structure is used to separate the first support layer and the second support layer at the location of the bending area.

2. The flexible circuit board according to claim 1, characterized in that, The hollow structure is a rectangular cavity structure adapted to the size of the bending area.

3. The flexible circuit board of claim 1, wherein, Also includes: A shielding material is filled within the hollow structure for electromagnetic shielding between the first conductive layer and the second conductive layer.

4. The flexible circuit board according to claim 3, characterized in that, The shielding material is silver particle material, which is covered on the inner wall surface of the hollow structure in a membrane structure.

5. The flexible circuit board according to claim 1, characterized in that, The adhesive layer surrounds the periphery of the hollow structure.

6. The flexible circuit board of claim 1, wherein, Also includes: A pair of reinforcing structures, the main body including a first panel and a second panel, the first panel and the second panel being connected through the bending area, and the pair of reinforcing structures being respectively connected to the first panel and the second panel; The hollow structure is located within the area formed between the pair of reinforcing structures.

7. The flexible circuit board according to claim 6, characterized in that, Also includes: The first type of circuit and the second type of circuit are disposed on the first conductive layer or the second conductive layer; The first type of line and the second type of line are respectively symmetrically arranged on the first panel and the second panel with respect to the bending area.

8. The flexible circuit board according to claim 7, characterized in that, The first category of lines includes a plurality of first lines, which are arranged in a centrally symmetrical manner along the centerline of the length direction of the first category of lines; The second category of lines includes multiple second lines, which are arranged in a centrally symmetrical manner along the centerline of the length direction of the second category of lines.

9. The flexible circuit board according to claim 7, characterized in that, The first category of lines are power lines used for transmitting power signals. The second category of lines are radio frequency (RF) lines used for transmitting RF signals.

10. An electronic device, comprising: include: The system comprises a first body, a second body, and a rotating device, wherein the first body and the second body are rotatably connected via the rotating device. A flexible circuit board, which passes through the rotating device and is connected to the first body and the second body respectively, includes: a main body, the main body including a first cover layer, a first conductive layer, a first support layer, an adhesive layer, a second support layer, a second conductive layer, and a second cover layer arranged sequentially along its thickness direction; the main body has a bending region, the bending region being disposed opposite to the rotating device, wherein a hollow structure is provided between the first support layer and the second support layer located in the bending region, the hollow structure being used to separate the first support layer and the second support layer at the position located in the bending region.

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