Flexible circuit boards, mid-frame assemblies, electronic devices

Abstract

This application provides an FPC, a mid-frame assembly, and an electronic device, relating to the field of electronic technology. The FPC includes three conductor layers and a shielding layer on the surface. Air gaps exist between the first and second conductor layers, and between the second and third conductor layers; however, there is no air gap between the first conductor layer and the shielding layer. Signal lines in the FPC extend from the second conductor layer, reach the gap region, and then extend to the first conductor layer via vias. After crossing the gap region, they return to the second conductor layer. Therefore, the distance from the signal line to the shielding layer in the gap region does not change with the bending of the flexible circuit board; only the distance from the signal line to the second and third conductor layers changes with the bending of the FPC. This one-sided distance change reduces the characteristic impedance fluctuations of the signal lines caused by delamination at the gaps, thereby improving signal quality, with a more significant improvement in signal quality for high-speed signals.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a flexible circuit board, a mid-frame assembly, and an electronic device. Background Technology

[0002] With the continuous development of display technology, foldable electronic devices are gradually becoming a trend in future mobile electronic products. When unfolded, foldable electronic devices offer a larger display area, enhancing the viewing experience. When folded, they have a smaller size, making them easy for users to carry.

[0003] Foldable electronic devices typically include multiple circuit boards and flexible printed circuits (FPCs) mounted along a hinge. Signal transmission between these circuit boards usually relies on the FPC. Therefore, the signal transmission quality of the FPC is directly linked to the performance of the electronic device, and the stability of the characteristic impedance of the signal lines within the FPC has a direct impact on signal transmission quality. Summary of the Invention

[0004] This application provides a flexible circuit board, a mid-frame assembly, and an electronic device to improve the stability of the characteristic impedance of signal lines, thereby improving the signal transmission quality of the flexible circuit board.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] A first aspect of this application provides a flexible circuit board, which can be used, for example, as a through-axis flexible circuit board in a foldable electronic device. The flexible circuit board includes a first conductor layer, a second conductor layer, and a third conductor layer, with the second conductor layer located between the first and third conductor layers. The flexible circuit board also includes a first connection layer and a first shielding layer. The first connection layer is located between the first and second conductor layers and has a first gap. The first shielding layer is located on the side of the first conductor layer away from the second conductor layer and is coupled to the first conductor layer. The flexible circuit board also includes at least one signal line, which includes a first sub-signal line, two second sub-signal lines, and two first connection portions. The first sub-signal line is located in the first conductor layer and opposite to the first gap; for example, along the thickness direction, the first sub-signal line is located above the first gap. Two second sub-signal lines are located in the second conductor layer and along the extension direction of the signal lines, and the two second sub-signal lines are respectively located on both sides of the first gap; the first connection portion penetrates the first connection layer along the thickness direction of the first connection layer; the two ends of the first sub-signal line are respectively coupled to the two second sub-signal lines through the two first connection portions, that is, the first end of the first sub-signal line is coupled to one second sub-signal line through one first connection portion, and the second end of the first sub-signal line is coupled to another second sub-signal line through another first connection portion.

[0007] In the flexible circuit board provided in this embodiment, the first sub-signal line of the signal line is located in the first conductor layer, and the first sub-signal line, together with the first shielding layer and the second conductor layer, forms a stripline structure. Since there is no gap structure between the first shielding layer and the first conductor layer, there is no delamination between them during the bending process of the flexible circuit board. The third distance from the first shielding layer to the first sub-signal line remains unchanged during dynamic bending; only the fourth distance from the first sub-signal line to the second conductor layer undergoes a sudden delamination. During the bending process of the flexible circuit board, compared to changes in the distance from the signal line to both sides, a change in distance on only one side can significantly reduce the characteristic impedance fluctuation caused by delamination at the first gap (e.g., impedance fluctuation can be reduced by about 50%), thereby reducing signal reflection and improving signal quality. Furthermore, the second sub-signal line is located in the second conductor layer, and signal transmission is performed using the standard stripline structure formed by the second sub-signal line and the first conductor layer, eliminating the need for the first shielding layer to participate in signal return. This reduces the loss and far-end crosstalk caused by the first shielding layer for high-speed signals, providing a better shielding effect. That is, the flexible circuit board provided in this application, through a specific wiring structure, can achieve high-quality signal transmission while satisfying the bending performance of the through-axis flexible circuit board of foldable electronic devices, and can also take into account the loss problem.

[0008] In one possible implementation, the flexible circuit board further includes at least one ground wire, which is arranged side-by-side with the signal wire. The ground wire includes a first sub-ground wire, two second sub-ground wires, and two second connecting portions. The first sub-ground wire is located in a first conductor layer and opposite to a first gap; for example, along the thickness direction, the first sub-ground wire is located above the first gap. The two second sub-ground wires are located in a second conductor layer and along the extension direction of the signal wire, with the two second sub-ground wires located on opposite sides of the first gap. The second connecting portions penetrate the first connecting layer along its thickness direction. The two ends of the first sub-ground wire are correspondingly coupled to the two second sub-ground wires through the two second connecting portions.

[0009] In the flexible circuit board provided in this embodiment, a first sub-signal line, two second sub-ground lines, a first shielding layer, and a second conductor layer form a ground-coplanar waveguide structure. The characteristic impedance of the first sub-signal line is affected by four parts: a fifth distance from the first sub-signal line to the left second sub-ground line, a sixth distance from the first sub-signal line to the right second sub-ground line, a third distance from the first sub-signal line to the first shielding layer, and a fourth distance from the first sub-signal line to the second conductor layer. During the bending process of the flexible circuit board, the third, fifth, and sixth distances remain unchanged, while only the fourth distance changes abruptly due to delamination. Therefore, the impact of the abrupt change in the fourth distance on the characteristic impedance of the first sub-signal line can be significantly reduced, further improving the stability of the characteristic impedance of the first sub-signal line.

[0010] In one possible implementation, the first sub-signal line includes a first segment, a second segment, and a third segment connected sequentially. The second segment faces the first gap; for example, the projection of the second segment onto the first connection layer lies within the first gap. The first and third segments are located on opposite sides of the first gap; for example, the projections of the first and third segments onto the first connection layer lie on opposite sides of the first gap. The first and third segments are coupled to the first connection portion. The first and third segments of the first sub-signal line essentially serve as transition sections, allowing the first connection portion to pass through the first connection layer from a location other than the first gap, instead of passing through the first gap, thereby reducing the manufacturing difficulty and precision requirements of the first connection portion.

[0011] In one possible implementation, the first sub-ground wire includes a fourth segment, a fifth segment, and a sixth segment connected in sequence; the fifth segment faces the first gap, for example, the projection of the fifth segment on the first connection layer lies within the first gap. The fourth and sixth segments are located on opposite sides of the first gap, for example, the projections of the fourth and sixth segments on the first connection layer lie on opposite sides of the first gap, and the fourth and sixth segments are coupled to the second connection portion. The fourth and sixth segments in the first sub-ground wire essentially serve as transition sections, allowing the second connection portion to pass through the first connection layer from a location other than the first gap instead of through the first gap, thereby reducing the manufacturing difficulty and precision requirements of the second connection portion.

[0012] In one possible implementation, the spacing between the second and fifth segments is smaller than the spacing between the first and fourth segments. At the location corresponding to the first gap, the second and fifth segments are brought closer together (i.e., the signal line and ground line are close together), which alters the electromagnetic field distribution of the second segment, fully utilizing the field distribution characteristics of the ground-coplanar waveguide structure to reduce impedance fluctuations during bending. At the locations on either side of the first gap, the flexible circuit board does not delaminate during bending, resulting in a reduced thickness compared to the first gap. Therefore, the thickness of the first segment to its adjacent layer is smaller, while the thickness of the second segment to its adjacent layer is larger, meaning the characteristic impedance of the first segment is lower than that of the second segment. By moving the first and fourth segments relatively apart, the characteristic impedance of the first segment can be increased, thus maintaining a stable balance between the characteristic impedances of the first and second segments.

[0013] In one possible implementation, the spacing between the first and fourth segments is 60µm to 200µm. By setting the spacing between the first and fourth segments to 60µm to 200µm, the characteristic impedance of the first segment can be optimized.

[0014] In one possible implementation, the spacing between the second and fifth segments is 50µm to 100µm. By setting the spacing between the second and fifth segments to 50µm to 100µm, the second segment can have better anti-interference capability, lower common mode, and smaller RE.

[0015] In one possible implementation, the spacing between the second sub-signal line and the second sub-ground line is smaller than the spacing between the first and fourth segments. By reducing the spacing between the second sub-signal line and the second sub-ground line, more space is available to increase the width of the second sub-signal line. Increasing the width of the second sub-signal line increases the volume of the effective conductor used to propagate electromagnetic waves, thereby reducing the loss of the second sub-signal line.

[0016] In one possible implementation, the spacing between the second sub-signal line and the second sub-ground line is 60µm to 200µm. By limiting the spacing between the second sub-signal line and the second sub-ground line to 60µm to 200µm, the width of the second sub-signal line can be increased while reducing process complexity and ensuring process yield.

[0017] In one possible implementation, the width of the second segment is greater than the width of the first segment. At the locations on either side of the first gap, the flexible circuit board does not delaminate during bending, resulting in a reduced thickness compared to the first gap. Therefore, the thickness of the first segment to the adjacent layer is smaller, while the thickness of the second segment to the adjacent layer is larger, meaning the characteristic impedance of the first segment is lower than that of the second segment. By increasing the width of the second segment, the characteristic impedance of the second segment can be reduced, thus maintaining a stable balance between the characteristic impedances of the first and second segments.

[0018] In one possible implementation, the width of the first segment is 30µm to 60µm. By setting the width of the first segment to 30µm to 60µm, various factors such as conductor loss, fabrication process, and characteristic impedance can be optimized.

[0019] In one possible implementation, the width of the second segment is 40µm to 70µm. By setting the width of the second segment to 40µm to 70µm, various factors such as conductor loss, fabrication process, and characteristic impedance can be optimized.

[0020] In one possible implementation, the width of the first segment is smaller than the width of the second sub-signal line. By increasing the width of the second sub-signal line, the volume of the effective conductor used to propagate electromagnetic waves can be increased, thereby reducing the loss of the second sub-signal line.

[0021] In one possible implementation, the width of the second sub-signal line is 45µm to 80µm. By setting the width of the second sub-signal line to 45µm to 80µm, various factors such as conductor loss, fabrication process, and characteristic impedance can be optimized.

[0022] In one possible implementation, the width of the fifth segment is greater than the width of the fourth segment. By increasing the width of the fifth segment, it can be placed closer to the second segment of the signal line, thereby altering the electromagnetic field distribution of the second segment and fully utilizing the field distribution characteristics of the ground coplanar waveguide structure to reduce impedance fluctuations generated during bending.

[0023] In one possible implementation, the width of the fourth segment is equal to the width of the second sub-ground wire. This simplifies the fabrication process and layout of the ground wire.

[0024] In one possible implementation, at least one signal line comprises two adjacent signal lines; the differential characteristic impedance of the two signal lines is 80 ohms to 100 ohms. By setting the differential characteristic impedance of the two signal lines to 80 ohms to 100 ohms, the flexible circuit board can be adapted to the signal transmission of various chips.

[0025] In one possible implementation, the spacing between the first segments of the two signal lines is greater than the spacing between the second segments. By bringing the second segments of the differential pair signal lines closer together, the differential lines are more tightly coupled, resulting in less radiation and less crosstalk with the outside. By moving the first segments of the differential pair signal lines further apart, the characteristic impedance of the differential pair signal lines can be increased.

[0026] In one possible implementation, the spacing between the first segments of the two signal lines is 60µm to 150µm. By setting the spacing between the first segments of the differential pair signal lines to 60µm to 150µm, the characteristic impedance transition of the first sub-signal line in the signal line can be reduced.

[0027] In one possible implementation, the spacing between the second segments of the two signal lines is 50µm to 100µm. By setting the spacing between the second segments of the differential pair signal lines to 50µm to 100µm, the performance of the differential pair signal lines can be balanced, and the impact of layering on the characteristic impedance can be reduced.

[0028] In one possible implementation, the spacing between the first segments of the two signal lines is greater than the spacing between the second sub-signal lines. By reducing the spacing between the second sub-signal lines in the differential pair signal lines, leeway can be provided to increase the width of the second sub-signal lines, thereby increasing the width of the second sub-signal lines and reducing their losses.

[0029] In one possible implementation, the spacing between the second sub-signal lines in the two signal lines is 60µm to 150µm. By setting the spacing between the second sub-signal lines in the differential pair signal lines to 60µm to 150µm, the width of the second sub-signal lines can be increased while reducing process complexity and ensuring process yield.

[0030] In one possible implementation, the fifth segment includes a first end near the fourth segment and a second end near the sixth segment. The width of the first end decreases from the center towards the first end, and the width of the second end decreases from the center towards the second end. The width of the fifth segment gradually decreases to be equal to the widths of the fourth and sixth segments, thus achieving a smooth transition in the linewidth of the first sub-ground line and reducing the risk of bending and breakage of the first sub-signal line.

[0031] In one possible implementation, the second conductor layer further includes a cutout region, with the first sub-signal line opposite to this cutout region. For example, the projection of the first sub-signal line onto the second conductor layer lies within the cutout region. By cutting out the projection area of ​​the first sub-signal line on the second conductor layer, no ground signal is generated in the projection area, thus no magnetic field is produced. This does not affect the characteristic impedance of the first sub-signal line, further reducing the impact of changes in distance between the first and second conductor layers on the characteristic impedance of the first sub-signal line.

[0032] In one possible implementation, the distance from the first connector to the first gap is 0.5mm to 2mm. Setting the distance from the first connector to the first gap to 0.5mm to 2mm can improve process yield, reduce process difficulty, and optimize the characteristic impedance of the first sub-signal line.

[0033] In one possible implementation, the signal rate transmitted via the signal line is greater than or equal to 10 Gbps. In scenarios involving high-speed signal transmission, the flexible circuit board provided in this application offers a more significant improvement in signal transmission quality.

[0034] In one possible implementation, signal lines are used to transmit radio frequency (RF) signals. The flexible circuit board provided in this application can also be used to transmit RF signals.

[0035] In one possible implementation, the flexible circuit board further includes a second connection layer, multiple insulating layers, and a second shielding layer; the second connection layer is located between the second conductor layer and the third conductor layer, and the second connection layer has a second gap, the projection of the second gap on the first connection layer overlapping with the first gap; the two opposite surfaces of the first conductor layer, the second conductor layer, and the third conductor layer are respectively covered with insulating layers; the second shielding layer is located on the side of the third conductor layer away from the second conductor layer.

[0036] In one possible implementation, the dielectric constant of the material of the first connecting layer or insulating layer is 2.8 to 3.5. By adjusting the dielectric constant of the materials of the first connecting layer and insulating layer, the characteristic impedance of the signal line can be further optimized.

[0037] In one possible implementation, the flexible circuit board further includes a second shielding layer located on the side of the third conductor layer away from the second conductor layer.

[0038] In one possible implementation, the thickness of the first shielding layer is 6µm to 14µm. This can further optimize the problem of abrupt changes in the characteristic impedance of the signal line.

[0039] In one possible implementation, the thickness of the first, second, or third conductor layer is 6µm to 15µm. This can further optimize the problem of abrupt changes in the characteristic impedance of the signal line.

[0040] In one possible implementation, the thickness of the first or second interconnect layer is 10µm to 20µm. This can further optimize the problem of abrupt changes in the characteristic impedance of the signal line.

[0041] In one possible implementation, the distance between the first conductor layer and the first shielding layer is 30µm to 55µm. This can further optimize the problem of abrupt changes in the characteristic impedance of the signal line.

[0042] In one possible implementation, the distance between the first conductor layer and the first interconnect layer is 6µm to 18µm. This can further optimize the problem of abrupt changes in the characteristic impedance of the signal line.

[0043] In one possible implementation, the distance between the first interconnect layer and the second conductor layer is 15µm to 30µm. This can further optimize the problem of abrupt changes in the characteristic impedance of the signal line.

[0044] In one possible implementation, the distance from the second interconnect layer to the second conductor layer or the distance from the third conductor layer is 6µm to 18µm. This can further optimize the problem of abrupt changes in the characteristic impedance of the signal line.

[0045] A second aspect of the embodiments of this application provides a mid-frame assembly, the mid-frame assembly including a first frame, a second frame, a pivot mechanism, and a flexible circuit board, the first frame and the second frame being connected by the pivot mechanism, the flexible circuit board extending from the side where the first frame is located through the pivot mechanism to the side where the second frame is located, the flexible circuit board including any of the flexible circuit boards of the first aspect.

[0046] A third aspect of the present application is an electronic device, including a mid-frame assembly and a display screen, the display screen being disposed on the mid-frame assembly, the mid-frame assembly including the mid-frame assembly of the second aspect. Attached Figure Description

[0047] Figure 1A A schematic diagram of an electronic device in an unfolded state provided in an embodiment of this application;

[0048] Figure 1BA schematic diagram of the folded state of an electronic device provided in an embodiment of this application;

[0049] Figure 2A A layout diagram of an electronic device provided in an embodiment of this application;

[0050] Figure 2B This is a structural schematic diagram of a mid-frame component provided in an embodiment of this application;

[0051] Figure 3A An embodiment of this application provides a method for... Figure 2B A sectional view along the A1-A2 direction;

[0052] Figure 3B A schematic diagram of an FPC at a first gap position in a flattened state, provided for an embodiment of this application;

[0053] Figure 3C A schematic diagram of an FPC at a first gap position in a bent state, provided for an embodiment of this application;

[0054] Figure 3D A schematic diagram of electromagnetic field distribution along a stripline provided in this application embodiment;

[0055] Figure 4A An embodiment of this application provides a method for... Figure 2B A sectional view along the A1-A2 direction;

[0056] Figure 4B An electromagnetic field distribution diagram of a stripline provided in an embodiment of this application;

[0057] Figure 5A An embodiment of this application provides a method for... Figure 2B A sectional view along the A1-A2 direction;

[0058] Figure 5B A ground-coplanar waveguide magnetic field distribution diagram provided in this application embodiment;

[0059] Figure 6 This application provides a schematic diagram of the wiring layout in an FPC.

[0060] Figure 7A This application provides a schematic diagram of the wiring layout in an FPC.

[0061] Figure 7B A ground-coplanar waveguide magnetic field distribution diagram provided in this application embodiment;

[0062] Figure 7C A ground-coplanar waveguide magnetic field distribution diagram provided in this application embodiment;

[0063] Figure 8A This application provides a schematic diagram of the structure of signal lines and ground lines of an FPC.

[0064] Figure 8B This is a schematic diagram of the structure of the signal line and ground line of an FPC provided in an embodiment of this application. Detailed Implementation

[0065] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0066] Hereinafter, the terms "second," "first," etc., are used for descriptive convenience only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "second," "first," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0067] Furthermore, in the embodiments of this application, directional terms such as "upper," "lower," "left," and "right" may be defined relative to the orientation in which the components are schematically placed in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly based on the orientation of the components in the accompanying drawings.

[0068] In the embodiments of this application, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled connection" can be a direct electrical connection or an indirect electrical connection through an intermediate medium. The term "contact" can be direct contact or indirect contact through an intermediate medium.

[0069] In this embodiment of the application, "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0070] This application provides an electronic device, which may be, for example, a foldable electronic device. The electronic device may be, for example, a consumer electronics product, a home electronics product, an in-vehicle electronics product, or a financial electronics product. Consumer electronics products include mobile phones, tablets, laptops, e-readers, personal computers (PCs), personal digital assistants (PDAs), desktop monitors, smart wearable products (e.g., smartwatches, smart bracelets), virtual reality (VR) electronic devices, augmented reality (AR) electronic devices, drones, etc. Home electronics products include smart door locks, televisions, refrigerators, and rechargeable small household appliances (e.g., soymilk makers, robot vacuum cleaners), etc. In-vehicle electronics products include in-vehicle navigation systems, in-vehicle DVDs, etc. Financial electronics products include ATMs, self-service electronic devices, etc.

[0071] Figure 1A This is a schematic diagram of an electronic device in its unfolded state, provided as an embodiment of this application. Figure 1B This is a schematic diagram of the folded state of an electronic device provided in an embodiment of this application.

[0072] To facilitate understanding of the electronic equipment provided in the embodiments of this application, in conjunction with the accompanying drawings... Figure 1A The following is a description of an existing electronic device:

[0073] like Figure 1A As shown, the electronic device 1 includes a screen protective layer 10, a display screen 20, a mid-frame 30, and a back cover (or rear shell, battery cover, etc.) 40. The screen protective layer 10 is disposed on the display screen 20 and located on the light-emitting side of the display screen 20. The display screen 20 is disposed on the mid-frame 30, which supports the display screen 20. The back cover 40 is disposed on the mid-frame 30, forming a receiving space with the side of the mid-frame 30 away from the display screen 20.

[0074] For example, electronic device 1 is a foldable electronic device, and display screen 20 is a flexible display screen. Display screen 20 is a self-emissive display screen, eliminating the need for a backlight module (BLM). Display screen 20 can be a self-emissive display screen such as an organic light-emitting diode (OLED) display screen, an active-matrix organic light-emitting diode (AMOLED) display screen, a mini organic light-emitting diode (Mini-OLED) display screen, a micro light-emitting diode (Micro-LED) display screen, a micro organic light-emitting diode (Micro-OLED) display screen, or a quantum dot light-emitting diode (QLED) display screen.

[0075] The middle frame 30 includes a first frame 301, a second frame 302, and a pivot mechanism 303. The first frame 301 and the second frame 302 are disposed on both sides of the pivot mechanism 303, and the pivot mechanism 303 is connected to the first frame 301 and the second frame 302 respectively. The first frame 301 and the second frame 302 can be used to support the flexible display screen 20, so that the flexible display screen 20 remains as flat as possible during use and protects the non-display surface of the flexible display screen 20. For example, a portion of the flexible display screen 20 is fixed to the first frame 301 by an adhesive layer, and a portion is fixed to the second frame 302 by an adhesive layer. The adhesive layer can be a thin film layer formed after applying glue, and the specific form of the adhesive layer is not limited in this embodiment.

[0076] In some embodiments, the display screen 20 may include a first display area 201 corresponding to the first frame 301, a second display area 202 corresponding to the second frame 302, and a bendable display area 203 corresponding to the pivot mechanism 303. The bendable display area 203 may be connected between the first display area 201 and the second display area 202. The first display area 201 may be connected to the first frame 301, and the second display area 202 may be connected to the second frame 302.

[0077] In addition, other electronic components may be disposed on the side of the first frame 301 and the second frame 302 away from the display screen 20, such as a printed circuit board (PCB), a battery, a receiver, a speaker, and a camera. The PCB can integrate electronic components such as the main controller, storage unit, antenna module, and power management module of the electronic device, while the battery can power the display screen 20, the circuit board, the receiver, the speaker, and the camera. Of course, the embodiments of this application do not limit the electronic components disposed on the first frame 301 and the second frame 302.

[0078] The back cover 40 includes a first housing 401 and a second housing 402. The first housing 401 is fastened to the first frame 301, and the second housing 402 is fastened to the second frame 302.

[0079] Under the action of the pivot mechanism 303, the first frame 301 and the second frame 302 can move closer to each other or further away from each other. Correspondingly, the first display area 201 and the second display area 202 of the display screen 20 can move closer to each other or further away from each other, so that the display screen 20 can be folded or unfolded.

[0080] In the unfolded state, the angle between the first frame 301 and the second frame 302 can be approximately 180°, and the display screen 20 is in the unfolded state.

[0081] In the folded state, the angle between the first frame 301 and the second frame 302 can be rotated from 180° to a state where the first frame 301 and the second frame 302 are parallel and opposite to each other, and the distance between the first frame 301 and the second frame 302 is minimized. At this time, the first display area 201 and the second display area 202 can be considered to be positioned on different planes. For example... Figure 1B As shown, when the electronic device 1 is folded, the display screen 20 faces inward, and the first display area 201 and the second display area 202 face each other (folding inward). Similarly, the electronic device 1 can also be illustrated with the display screen 20 facing outward and the first housing 401 and the second housing 402 facing each other (folding outward) when folded.

[0082] Of course, electronic device 1 is not limited to a two-fold electronic device 1; electronic device 1 can also be a multi-fold electronic device 1. This application embodiment does not limit this.

[0083] Figure 2A This is a layout diagram of an electronic device provided in an embodiment of this application. Figure 2B This is a structural schematic diagram of a mid-frame component provided in an embodiment of this application.

[0084] In some embodiments, such as Figure 2AAs shown, foldable electronic devices typically include multiple circuit boards, and signal transmission between these circuit boards is accomplished by a flexible printed circuit (FPC) provided by the pivot mechanism 303.

[0085] In some electronic devices, a centralized layout is often used, placing the system-on-chip (SOC) and radio frequency integrated circuit (RFIC) on the same circuit board to reduce communication losses between them.

[0086] In other electronic devices, such as Figure 2A As shown, placing the SOC and part of the RFIC on different circuit boards increases the usable antenna area and isolates the heat-generating components of the RF system, resulting in better overall heat dissipation. In this layout, data communication between the first circuit board containing the SOC and the second circuit board containing the RFIC requires a high-speed signal (e.g., a rate > 10Gbps). This high-speed signal needs to be transmitted from the first circuit board to the second circuit board. For example, as... Figure 2B As shown, signal transmission from the first circuit board to the second circuit board can be achieved through an FPC with a through-shaft. The FPC extends from the side where the first frame 301 is located through the rotating shaft mechanism 303 to the side where the second frame 302 is located. Both ends of the FPC are provided with pads, and the FPC is coupled to the first circuit board and the second circuit board through the pads.

[0087] Figure 3A An embodiment of this application provides a method for... Figure 2B A sectional view along the A1-A2 direction.

[0088] In some embodiments, such as Figure 3A As shown, the FPC sequentially includes a first shielding layer 51, a first insulating cover film 61, a first conductor layer 71, a first insulating substrate 62, a first connecting layer 81, a first insulating film 63, a second conductor layer 72, a second insulating film 64, a second connecting layer 82, a second insulating substrate 65, a third conductor layer 73, a second insulating cover film 66, and a second shielding layer 52.

[0089] The first conductor layer 71 is a ground layer, the second conductor layer 72 is a signal line layer, the second conductor layer 72 includes, for example, a signal line 721 and ground lines 722 disposed on both sides of the signal line 721, and the third conductor layer 73 is a ground layer.

[0090] In some embodiments, such as Figure 3AAs shown, the first connecting layer 81 has a first air gap 811, and the second connecting layer 82 has a second air gap 821. When the FPC is applied in the above-mentioned electronic device 1, the positions of the first air gap 811 and the second air gap 821 correspond to the positions of the pivot mechanism 303, and the first air gap 811 and the second air gap 821 are located below the bendable display area 203 in the display screen 20.

[0091] By setting a first gap 811 on the first connecting layer 81 and a second gap 821 on the second connecting layer 82, the original structure of three conductor layers laminated and bonded together can be locally separated into three independent structures to release bending stress, thereby enabling the FPC to meet the reliability requirements of multiple dynamic bending in foldable electronic device application scenarios.

[0092] Figure 3B This is a schematic diagram of an FPC at a first gap position in a flattened state, provided as an embodiment of this application. Figure 3C This is a schematic diagram of an FPC at a first gap position in a bent state, provided as an embodiment of this application.

[0093] However, for the FPC at the first gap 811 position, as Figure 3B As shown, when the electronic device is in a flattened state, the three conductor layers in the FPC are in a pressed and bonded state. However, as... Figure 3C As shown, during the bending process of the electronic device, when the FPC follows the bending of the electronic device, irregular delamination will occur in local locations of the three conductor layers depending on the bending angle of the FPC. This delamination causes drastic and irregular changes in the distance between the second conductor layer 72 and the first conductor layer 71 and the third conductor layer 73 (the two lower ground layers) in the stripline structure. Furthermore, due to the introduction of air layers of varying thickness, the equivalent dielectric constant of the dielectric between the second conductor layer 72 and the first conductor layer 71, and between the second conductor layer 72 and the third conductor layer 73, will decrease.

[0094] Figure 3D This is a schematic diagram of an electromagnetic field distribution along a stripline, provided as an embodiment of this application.

[0095] like Figure 3D As shown, an FPC comprising three conductor layers is equivalent to constructing a stripline transmission structure. Here, a stripline structure refers to a transmission line structure consisting of signal conductors on a dielectric substrate and grounding metal plates located on opposite sides. One side of the conductor line is bonded to the substrate, while the other side is exposed to air or other dielectric materials.

[0096] Stripline transmission schemes are characterized by simple manufacturing, convenient installation, low cost, low loss, low radiation, and low far-end crosstalk, making the FPC structure a high-speed signal transmission scheme with good electrical performance.

[0097] In actual products, considering the need to thicken the signal line 721 (to reduce loss and improve bending resistance) and to simplify the manufacturing process, the ground lines 722 on both sides of the signal line 721 are usually designed to be far away from the signal line 721. Therefore, the influence of the ground lines 722 on the magnetic field of the signal line 721 is usually not considered. Figure 3D As can be seen from the above, the first distance H1 from the signal line 721 to the first conductor layer 71 and the second distance H2 from the signal line 721 to the second conductor layer 72 have a direct influence on the magnetic field, thereby affecting the characteristic impedance of the signal line 721.

[0098] Typically, the first distance H1 from signal line 721 to the first conductor layer 71 and the second distance H2 from signal line 721 to the third conductor layer 73 are proportional to the characteristic impedance of signal line 721. Therefore, the greater the separation between the second conductor layer 72 and the first and third conductor layers 71 and 73, the higher the characteristic impedance of signal line 721. The existence of separation causes abrupt differences in the characteristic impedance of high-speed signals traveling in the second conductor layer 72 at the locations of the first gap 811 and the second gap 821 compared to other locations, thereby causing signal reflection and affecting signal quality.

[0099] Characteristic impedance (or simply impedance): This refers to the characteristic impedance of a transmission line. During signal transmission, the signal level inversion generates a momentary electric field between the signal line conductor and the reference plane. This electric field produces a corresponding instantaneous current. When the transmission line is isotropic (uniform), a stable current I always exists as long as the signal is transmitting. However, if the signal output level is V, during signal transmission, the transmission line will be equivalent to a resistor of magnitude V / I. This equivalent resistance is called the characteristic impedance of the transmission line.

[0100] Based on this, embodiments of this application provide an FPC for reducing impedance fluctuations in signal lines and improving signal quality.

[0101] Figure 4A An embodiment of this application provides a method for... Figure 2B Sectional view along line A1-A2. Figure 4B An electromagnetic field distribution diagram of a stripline provided in an embodiment of this application.

[0102] like Figure 4A As shown, the FPC includes a first conductor layer 71, a second conductor layer 72, and a third conductor layer 73, with the second conductor layer 72 located between the first conductor layer 71 and the third conductor layer 73. This application embodiment is not limited to an FPC comprising three conductor layers; an FPC may also include more conductor layers. This application embodiment is merely illustrative using a three-conductor-layer example.

[0103] In some embodiments, each of the first conductor layer 71, the second conductor layer 72, and the third conductor layer 73 has an insulating layer covering both sides of its surface. For example, such as... Figure 4A As shown, along Figure 4A From a certain perspective, a first insulating cover film 61 covers the top of the first conductor layer 71, and a first insulating substrate 62 covers the bottom of the first conductor layer 71. A first insulating film 63 covers the top of the second conductor layer 72, and a second insulating film 64 covers the bottom of the second conductor layer 72. A second insulating substrate 65 covers the top of the third conductor layer 73, and a second insulating cover film 66 covers the bottom of the third conductor layer 73.

[0104] In some embodiments, the dielectric constant of the insulating layer material included in the FPC is 2.8 to 3.5. For example, the dielectric constants of the insulating layer material are 2.8, 2.9, 3.0, 3.12, 3.2, 3.3, 3.4, and 3.5. For instance, when the frequency of the transmitted signal is 5 GHz, the dielectric constant of the insulating layer material is 3. By adjusting the dielectric constant of the insulating layer material, the characteristic impedance of the signal line 721 can be further optimized.

[0105] Dielectric constant: It is the main parameter reflecting the dielectric properties or polarization properties of piezoelectric materials under the action of an electrostatic field. It is usually represented by ε. Different applications of piezoelectric elements have different requirements for the dielectric constant of piezoelectric materials.

[0106] like Figure 4A As shown, the FPC also includes a first bonding layer 81, which is located between the first conductor layer 71 and the second conductor layer 72. For example, the first bonding layer 81 is located between the first insulating substrate 62 and the first insulating film 63. The first bonding layer 81 serves as an interlayer bonding layer between the first conductor layer 71 and the second conductor layer 72; for example, the first bonding layer 81 can be a bonding sheet.

[0107] For example, the first connection layer 81 has a first gap 811, which is located below the bendable display area 203 when the FPC is applied in the electronic device 1. (The last part, "along the perpendicular to...", appears to be a typo and can be left as is.) Figure 4A The direction of the viewing angle (the extension direction of the signal line 721) and the first gap 811 may, for example, penetrate the first connection layer 81. The first gap 811 may be, for example, an air gap, or a vacuum gap, etc.

[0108] The FPC may also include a second connecting layer 82 located between the second conductor layer 72 and the third conductor layer 73. For example, the second connecting layer 82 is located between the second insulating film 64 and the second insulating substrate 65. The second connecting layer 82 serves as an interlayer bonding layer between the second conductor layer 72 and the third conductor layer 73; for example, the second connecting layer 82 may be an adhesive sheet.

[0109] For example, the second connection layer 82 has a second gap 821, which is located below the bendable display area 203 when the FPC is applied in the electronic device 1. (The last part, "along the perpendicular to...", appears to be a typo and can be left as is.) Figure 4A The direction of the viewing angle (the extension direction of the signal line 721) allows the second gap 821 to penetrate the second connection layer 82, for example. The second gap 821 can be an air gap, a vacuum gap, or the like. When the FPC is in a flattened state, the projection of the first gap 811 onto the second connection layer 82 can overlap (e.g., coincide) with the second gap 821.

[0110] By setting a first gap 811 on the first connecting layer 81 and a second gap 821 on the second connecting layer 82, the bending performance of the FPC can be improved.

[0111] In some embodiments, the dielectric constant of the materials of the first interconnect layer 81 and / or the second interconnect layer 82 is 2.8 to 3.5. For example, the dielectric constants of the materials of the first interconnect layer 81 and / or the second interconnect layer 82 are 2.8, 2.9, 3.0, 3.12, 3.2, 3.3, 3.4, and 3.5. For instance, when the frequency of the transmitted signal is 5 GHz, the dielectric constant of the materials of the first interconnect layer 81 and / or the second interconnect layer 82 is 3. The materials of the first interconnect layer 81 and the second interconnect layer 82 may be the same or different, and this embodiment does not limit this.

[0112] The characteristic impedance of the signal line 721 can be further optimized by adjusting the dielectric constant of the materials of the first interconnect layer 81 and / or the second interconnect layer 82.

[0113] In some embodiments, the FPC further includes a first shielding layer 51 located on the surface of the FPC. The first shielding layer 51 is located on the side of the first conductor layer 71 away from the second conductor layer 72 and is coupled to the first conductor layer 71. For example, the first shielding layer 51 covers an insulating layer located on the surface of the first conductor layer 71 and is coupled to the first conductor layer 71 through the insulating layer. For example, the first shielding layer 51 covers a first insulating cover film 61 and is coupled to the first conductor layer 71 through the first insulating cover film 61.

[0114] The first shielding layer 51 is attached above the surface of the first conductor layer 71 of the FPC, which can shield against electromagnetic interference (EMI) generated by high-speed signals, reducing interference to the radio frequency system in electronic devices, and simultaneously reducing interference from the radio frequency system to high-speed signals. Furthermore, with the first shielding layer 51 on the FPC surface, the signal line 721 will not be in close contact with the metal layer in the rotating mechanism 303 when it moves with the rotating mechanism 303. Therefore, the signal line 721 will not form a stripline structure with the rotating mechanism 303, avoiding the influence of the stripline structure on the characteristic impedance of the signal line 721 and improving transmission performance.

[0115] The first shielding layer 51 passes through the first insulating cover film 61 and is coupled to the first conductor layer 71, providing a return current for the signal of the first conductor layer 71.

[0116] In some embodiments, the third conductor layer 73 has a planar structure, and the third conductor layer 73 itself can act as a shielding layer. No shielding layer is required on the side of the third conductor layer 73 away from the second conductor layer 72.

[0117] In other embodiments, the third conductor layer 73 has a linear structure, and the FPC further includes a second shielding layer 52 located on another surface of the FPC, on the side of the third conductor layer 73 away from the second conductor layer 72. For example, the second shielding layer 52 covers an insulating layer located on the surface of the third conductor layer 73. For instance, the second shielding layer 52 covers a second insulating cover film 66.

[0118] In some embodiments, such as Figure 4A As shown, the FPC includes a signal line 721, which includes a first sub-signal line 7211, two second sub-signal lines 7212, and two first connecting portions 7213.

[0119] The first sub-signal line 7211 is located in the first conductor layer 71 and is opposite to the first gap 811. Two second sub-signal lines 7212 are located in the second conductor layer 72 and are respectively located on both sides of the first gap 811. A first connecting portion 7213 penetrates the first connecting layer 81 along its thickness direction, and the two ends of the first sub-signal line 7211 are correspondingly coupled to the two second sub-signal lines 7212 through the two first connecting portions 7213.

[0120] from Figure 4AFrom a visual perspective, the first sub-signal line 7211 is located above the first gap 811, and its projection on the first connection layer 81 overlaps with the first gap 811. For example, along the extension direction of the first sub-signal line 7211, the size of the first sub-signal line 7211 is greater than or equal to the size of the first gap 811. Two second sub-signal lines 7212 are located on the left and right sides of the first gap 811. The second sub-signal line 7212 on the left is coupled to the left end of the first sub-signal line 7211 through one or more first connection portions 7213, and the second sub-signal line 7212 on the right is coupled to the right end of the first sub-signal line 7211 through one or more first connection portions 7213.

[0121] Of course, considering process and yield issues, the embodiments of this application do not limit the end of the first sub-signal line 7211 to be exactly coupled to the first connection portion 7213. A certain amount of redundancy can be set to reduce process difficulty and improve coupling yield. Similarly, a certain amount of redundancy can also be set at the end of the second sub-signal line 7212.

[0122] In this embodiment, the signal line 721 first extends in the second conductor layer 72, then jumps to the first conductor layer 71 at the first gap 811, and after crossing the first gap 811, jumps back to the second conductor layer 72. Instead of the signal line 721 always extending in the second conductor layer 72.

[0123] In the FPC provided in the embodiments of this application, such as Figure 4B As shown, the first sub-signal line 7211 of signal line 721 is located in the first conductor layer 71, forming a stripline structure with the first shielding layer 51 and the second conductor layer 72. Since there is no delamination between the first shielding layer 51 and the first conductor layer 71 during FPC bending, the third distance H3 from the first shielding layer 51 to the first sub-signal line 7211 remains unchanged during dynamic bending; only the fourth distance H4 from the first sub-signal line 7211 to the second conductor layer 72 undergoes a sudden delamination. Compared to the situation where both the first distance H1 and the second distance H2 undergo sudden changes, a change in distance on only one side can reduce the characteristic impedance fluctuation of the first sub-signal line 7211 caused by delamination at the first gap 811 (for example, impedance fluctuation can be reduced by about 50%), thereby reducing signal reflection and improving signal quality. Furthermore, the second sub-signal line 7212 is located in the second conductor layer 72, and signal transmission is performed using the standard stripline structure formed by the second sub-signal line 7212 and the first conductor layer 71, eliminating the need for the first shielding layer 51 to participate in signal return. This can reduce the loss and far-end crosstalk of the first shielding layer 51 to high-speed signals, providing a better shielding effect. That is, the FPC provided in this application, through a specific wiring structure, can achieve high-quality signal transmission while meeting the bending performance requirements of the through-axis FPC of foldable electronic devices, and can also take into account the loss problem.

[0124] To meet bending performance requirements, the thickness of the first shielding layer 51 typically needs to be less than 1 μm. In this case, for the first shielding layer 51 to function effectively, the shielding metal layer, which primarily provides shielding, needs to connect with the ground signal of the FPC, and the actual signal return path will be transmitted through the shielding metal layer. To maintain the flexibility and bending resistance of the first shielding layer 51, the thickness of the shielding metal layer generally does not exceed 0.5 μm. This thickness is less than the skin depth of the electrical signal transmitted by the FPC within the metal. When the conductor thickness is less than the signal skin depth, the conductor loss during signal transmission increases significantly. Therefore, in this application, when the first shielding layer 51 is no longer needed for signal return, the loss and far-end crosstalk caused by the first shielding layer 51 to high-speed signals can be reduced, providing a better shielding effect.

[0125] Skin depth refers to the uneven current distribution within a conductor when it carries alternating current or an alternating electromagnetic field. The current concentrates in the conductor's "skin," meaning a thin layer on its outer surface. The closer to the surface, the higher the current density, while the current inside the conductor is relatively low. This increases the conductor's resistance and consequently, its power loss. This phenomenon is called the skin effect. The skin depth is defined as the thickness from the surface to a point where the current density decreases to 0.368 (1 / e) of the surface current density.

[0126] Figure 5A An embodiment of this application provides a method for... Figure 2B Sectional view along line A1-A2. Figure 5B This is a ground-coplanar waveguide magnetic field distribution diagram provided for an embodiment of this application.

[0127] In some embodiments, such as Figure 5A As shown, the FPC also includes at least one ground wire (or associated ground wire) 722, which is arranged side by side with the signal wire 721, and the ground wire 722 and the signal wire 721 extend in the same direction. Figure 5A The following is an example of an FPC that includes two ground wires 722 and two ground wires 722 on both sides of a signal line 721.

[0128] By adding an accompanying ground line 722 to at least one side of the signal line 721, better signal isolation can be provided, and a more flexible impedance control scheme can be provided by adjusting the distance between the ground line 722 and the signal line 721.

[0129] The ground wire 722 includes a first sub-ground wire 7221, two second sub-ground wires 7222, and two second connecting portions 7223. The first sub-ground wire 7221 is located in the first conductor layer 71 and is opposite to the first gap 811. The two second sub-ground wires 7222 are located in the second conductor layer 72, and the two second sub-ground wires 7221 are respectively located on both sides of the first gap 811. The second connecting portions 7223 penetrate the first connecting layer 81 along its thickness direction, and the two ends of the first sub-ground wire 7221 are correspondingly coupled to the two second sub-ground wires 7222 through the second connecting portions 7223.

[0130] That is, the ground lines 722 on both sides of the signal line 721, like the signal line 721, jump from the second conductor layer 72 to the first conductor layer 71 at the first gap 811. The structure of the ground line 722 will not be described in detail here; please refer to the above description of the signal line 721.

[0131] like Figure 5B As shown, signal line 721, ground line 722, first shielding layer 51 and second conductor layer 72 constitute a coplanar waveguide ground (CPWG) structure.

[0132] In this process, a central conductor strip is fabricated on one side of the dielectric substrate. Figure 5B The first sub-signal line 7211 in the middle, and conductor planes are made on both sides adjacent to the center conductor strip ( Figure 5B The two second sub-ground lines (7221) in the middle form a coplanar waveguide. Based on the coplanar waveguide, a complete conductor plane is attached to the other side (thickness side) of the dielectric substrate. Figure 5B The first shielding layer 51 and the second conductor layer 72 are connected to the two side conductor surfaces (second sub-ground wires 7221) through vertical holes to form the return ground of the central conductor. This structure is called a strip-ground coplanar waveguide structure. Alternatively, it can be understood as a stripline waveguide with two additional conductors added to both sides of the signal conductor, close to each other. These two additional conductors are connected to the ground plane below through metal holes, achieving a more complete grounding effect. The difference between the stripline and ground coplanar waveguide structures is the addition of two side conductors as extra return surfaces. Aside from material influences, such as... Figure 4B As shown, the characteristic impedance of the stripline structure is primarily determined only by the distances between the ground planes (H3, H4). However, as... Figure 5B As shown, the characteristic impedance of the ground coplanar waveguide structure is determined by the distance between the two ground wires (H5, H6) and the distance between the ground planes (H3, H4). Moreover, compared with the stripline structure, the electromagnetic field of the ground coplanar waveguide structure is more distributed near the two conductors (the two second sub-ground wires 7221), and the ground coplanar waveguide has a more robust grounding structure, thus exhibiting lower surface wave leakage and radiation loss.

[0133] In the FPC provided in the embodiments of this application, such as Figure 5B As shown, the first sub-signal line 7211, together with the two second sub-ground lines 7221, the first shielding layer 51, and the second conductor layer 72, forms a ground-coplanar waveguide structure. The characteristic impedance of the first sub-signal line 7211 is affected by four distances: the fifth distance H5 from the first sub-signal line 7211 to the left second sub-ground line 7221, the sixth distance H6 from the first sub-signal line 7211 to the right second sub-ground line 7221, the third distance H3 from the first sub-signal line 7211 to the first shielding layer 51, and the fourth distance H4 from the first sub-signal line 7211 to the second conductor layer 72. During the bending process of the FPC, the third distance H3, the fifth distance H5, and the sixth distance H6 remain unchanged, while only the fourth distance H4 changes abruptly due to delamination. Therefore, the impact of the abrupt change in the fourth distance H4 on the characteristic impedance of the first sub-signal line 7211 can be significantly reduced, further improving the stability of the characteristic impedance of the first sub-signal line 7211.

[0134] Figure 6 This is a schematic diagram of the wiring layout in an FPC provided in an embodiment of this application.

[0135] In some embodiments, such as Figure 6 As shown, signal line 721 is a single-ended signal line. For example, signal line 721 is an radio frequency signal line. The distance from the first sub-signal line 7211 to the second sub-ground line 7221 on one side is... Figure 5B The fifth distance H5 in the diagram refers to the distance from the first sub-signal line 7211 to the second sub-ground line 7221 on the other side. Figure 5B The sixth distance H6 in the equation.

[0136] Figure 7A This is a schematic diagram of the wiring layout in an FPC provided in an embodiment of this application. Figure 7B and Figure 7C This is a ground-coplanar waveguide magnetic field distribution diagram provided for an embodiment of this application.

[0137] In other embodiments, such as Figure 7A As shown, the FPC includes two adjacent signal lines 721, which together form a pair of differential signal lines.

[0138] For example, the differential characteristic impedance of the two signal lines 721 is 80 ohms to 100 ohms. For instance, the differential characteristic impedance of the two signal lines 721 may be 80 ohms, 83 ohms, 85 ohms, 87 ohms, 90 ohms, 93 ohms, 95 ohms, 97 ohms, or 100 ohms. Fluctuations in characteristic impedance within the range of process tolerance (±10%) are all within the protection scope of this application's embodiments.

[0139] By setting the differential characteristic impedance of the two signal lines 721 to 80 ohms to 100 ohms, the FPC can be adapted to the signal transmission of various chips.

[0140] In this embodiment, the characteristic impedance of the signal line 721 can be kept near the calibrated value by adjusting the line width of the multiple signal lines 721, the spacing between the signal lines 721, and the spacing between the signal lines 721 and the ground line 722.

[0141] In some embodiments, signal line 721 is used to transmit high-speed signals. For example, the signal rate transmitted by signal line 721 is greater than or equal to 10Gbps. For instance, the signal rate transmitted by signal line 721 is 10Gbps, 16Gbps, 20Gbps, 23.4Gbps, 32Gbps, etc.

[0142] In scenarios involving the transmission of high-speed signals, the FPC provided in this application demonstrates a more significant improvement in signal transmission quality.

[0143] In some embodiments, such as Figure 7A As shown, the first sub-signal line 7211 of signal line 721 includes a first segment 701, a second segment 702 and a third segment 703 connected in sequence.

[0144] The second segment 702 is directly opposite the first gap 811, and its projection on the first connecting layer 81 lies within the first gap 811. For example, the length of the second segment 702 is the same as the size of the first gap 811, and the end of the second segment 702 is located on the boundary of the first gap 811. The first segment 701 and the third segment 703 are located on opposite sides of the second segment 702 and the first gap 811, respectively. For example, the projections of the first segment 701 and the third segment 703 on the first connecting layer 81 lie on opposite sides of the first gap 811, and the first segment 701 and the third segment 703 are coupled to the first connecting portion 7213 to achieve coupling between the first sub-signal line 7211 and the first connecting portion 7213.

[0145] "Directly opposite" can be understood as follows: along the extension direction of signal line 721, the boundary line between the second segment 702 and the first segment 701, as well as the boundary line between the second segment 702 and the third segment 703, coincides with the boundary line of the first gap 811.

[0146] The first segment 701 and the third segment 703 can be symmetrically arranged on both sides of the second segment 702 to improve the symmetry of the FPC bending force. Alternatively, the first segment 701 and the third segment 703 can be asymmetrically arranged on both sides of the second segment 702 to improve the flexibility of the FPC layout.

[0147] The first segment 701 and the third segment 703 in the first sub-signal line 7211 are equivalent to transition parts, so that the first connection part 7213 does not need to pass through the first gap 811, but passes through the first connection layer 81 from a place other than the first gap 811, thereby reducing the process difficulty and process precision requirements of the first connection part 7213.

[0148] For example, the distance from the first connecting portion 7213 to the first gap 811 is 0.5mm to 2mm. This distance refers to the distance from the side of the first connecting portion 7213 away from the first gap 811 to the boundary of the first gap 811 near the first connecting portion 7213. Alternatively, it can be understood as the lengths of the first segment 701 and the third segment 703 being 0.5mm to 2mm. The length of the first segment 701 refers to the dimension from the end of the first segment 701 to the junction of the first segment 701 and the second segment 702.

[0149] For example, the distance from the first connecting part 7213 to the first gap 811 is 0.5mm, 0.75mm, 1.0mm, 1.25mm, 1.5mm, 1.75mm, or 2mm.

[0150] Setting the distance from the first connection 7213 to the first gap 811 to 0.5mm to 2mm can improve the process yield, reduce the process difficulty, and optimize the characteristic impedance of the first sub-signal line 7211.

[0151] In some embodiments, such as Figure 7A As shown, the first sub-ground wire 7221 of ground wire 722 includes a fourth segment 704, a fifth segment 705 and a sixth segment 706 connected in sequence.

[0152] The fifth segment 705 is directly opposite the first gap 811, and its projection on the first connecting layer 81 lies within the first gap 811. For example, the end of the fifth segment 705 is located on the boundary of the first gap 811. The fourth segment 704 and the sixth segment 706 are located on either side of the fifth segment 705, and on either side of the first gap 811. For example, their projections on the first connecting layer 81 lie on either side of the first gap 811. The fourth segment 704 and the sixth segment 706 are coupled to the second connecting portion 7223 to achieve coupling between the first sub-ground wire 7221 and the second connecting portion 7223.

[0153] "Directly opposite" can be understood as follows: along the extension direction of signal line 721, the boundary line between the fifth segment 705 and the fourth segment 704, and the boundary line between the fifth segment 705 and the sixth segment 706, coincide with the boundary position of the first gap 811.

[0154] The fourth segment 704 and the sixth segment 706 can be symmetrically arranged on both sides of the fifth segment 705 to improve the symmetry of the FPC bending force. Alternatively, the fourth segment 704 and the sixth segment 706 can be asymmetrically arranged on both sides of the fifth segment 705 to improve the flexibility of the FPC layout.

[0155] The fourth segment 704 and the sixth segment 706 in the first sub-ground wire 7221 are equivalent to transition parts, so that the second connection part 7223 does not need to pass through the first gap 811, but passes through the first connection layer 81 from a point other than the first gap 811, thereby reducing the process difficulty and process precision requirements of the second connection part 7223.

[0156] For ease of explanation, the structure of the first paragraph 701 and the fourth paragraph 704 will be explained below. The structure of the third paragraph 703 and the sixth paragraph 706 can be referred to the relevant explanations of the first paragraph 701 and the fourth paragraph 704.

[0157] In some embodiments, such as Figure 7A As shown, the distance h1 between the second segment 702 and the fifth segment 705 is less than the distance h2 between the first segment 701 and the fourth segment 704.

[0158] At the location corresponding to the first gap 811, the second segment 702 and the fifth segment 705 are brought closer together (reducing the spacing h1, i.e., the signal line 721 and the ground line 722 are brought closer together). This changes the electromagnetic field distribution of the second segment 702, fully utilizing the field distribution characteristics of the ground coplanar waveguide structure to reduce impedance fluctuations generated during bending. At the location of the first gap 811, delamination occurs during the bending of the FPC. At the locations on both sides of the first gap 811, delamination does not occur during the bending of the FPC. Figure 7B As shown, during the bending process of the FPC, the fourth distance H4 between the second segment 702 and the second conductor layer 72 will change (increase). Figure 7C As shown, during the bending process of the FPC, the fourth distance H4 between the first segment 701 and the second conductor layer 72 does not change. Therefore, the fourth distance H4 between the first segment 701 and the second conductor layer 72 is smaller, while the fourth distance H4 between the second segment 702 and the second conductor layer 72 is larger, which means that the characteristic impedance of the first segment 701 is lower than that of the second segment 702. By making Figure 7C The fifth distance H5 and the sixth distance H6 (spacing h2) between the first segment 701 and its adjacent fourth segment 704 are greater than, Figure 7B The fifth distance H5 and the sixth distance H6 (spacing h1) between the second segment 702 and the adjacent fifth segment 705 can increase the characteristic impedance of the first segment 701 so that the characteristic impedances of the first segment 701 and the second segment 702 remain stable and balanced.

[0159] For example, the spacing h1 between the second segment 702 and the fifth segment 705 is 50um to 100um. For instance, the spacing h1 between the second segment 702 and the fifth segment 705 is 50um, 60um, 70um, 80um, 90um, or 100um.

[0160] By setting the spacing h1 between the second segment 702 and the fifth segment 705 to 50um to 100um, the second segment 702 can have better anti-interference ability, lower common mode and smaller electromagnetic radiation.

[0161] For example, the spacing h2 between the first segment 701 and the fourth segment 704 is 60um to 200um. For instance, the spacing h2 between the first segment 701 and the fourth segment 704 is 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, 160um, 170um, 180um, 190um, and 200um.

[0162] By setting the spacing h2 between the first segment 701 and the fourth segment 704 to 60um to 200um, the characteristic impedance of the first segment 701 can be optimized.

[0163] In some embodiments, such as Figure 7A As shown, the distance h3 between the second sub-signal line 7212 and the second sub-ground line 7222 is less than the distance h2 between the first segment 701 and the fourth segment 704.

[0164] By reducing the spacing h3 between the second sub-signal line 7212 and the second sub-ground line 7222, space can be provided to increase the width of the second sub-signal line 7212. Increasing the width of the second sub-signal line 7212 increases the volume of the effective conductor used to propagate electromagnetic waves, thereby reducing the loss of the second sub-signal line 7212.

[0165] For example, the spacing h3 between the second sub-signal line 7212 and the second sub-ground line 7222 is 60um to 200um. For instance, the spacing h3 between the second sub-signal line 7212 and the second sub-ground line 7222 is 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, 150um, 160um, 170um, 180um, 190um, or 200um.

[0166] By limiting the spacing h3 between the second sub-signal line 7212 and the second sub-ground line 7222 to 60um to 200um, the width of the second sub-signal line 7212 can be increased while reducing the difficulty of the process and ensuring the yield of the process.

[0167] In some embodiments, such as Figure 7A As shown, the width w1 of the second segment 702 is greater than the width w2 of the first segment 701.

[0168] For example, the width w1 of the second segment 702 is 40um to 70um. For instance, the width w1 of the second segment 702 is 40um, 50um, 60um, or 70um.

[0169] For example, the width w2 of the first segment 701 is 30um to 60um. For instance, the width w2 of the first segment 701 is 30um, 40um, 50um, or 60um.

[0170] At the locations on both sides of the first gap 811, the FPC does not delaminate during bending, resulting in a reduced thickness compared to the area at the first gap 811. Therefore, the thickness of the first segment 701 to the adjacent layer is smaller, while the thickness of the second segment 702 to the adjacent layer is larger, meaning the characteristic impedance of the first segment 701 is lower than that of the second segment 702. By increasing the width w1 of the second segment 702, the characteristic impedance of the second segment 702 can be reduced, thus maintaining a stable and balanced characteristic impedance between the first and second segments 701.

[0171] In some other embodiments, the width w1 of the second segment 702 is equal to the width w2 of the first segment 701.

[0172] This simplifies the fabrication process of the first sub-signal line 7211 and reduces the risk of breakage at the junction of the first segment 701 and the second segment 702.

[0173] In some other embodiments, the width w1 of the second segment 702 is smaller than the width w2 of the first segment 701. This allows for thickness variation in the film layer below the first segment 701 and the film layer below the second segment 702. The characteristic impedance of the first segment 701 and the second segment 702 can be adjusted by coordinating the linewidth and spacing.

[0174] In some embodiments, such as Figure 7A As shown, the width w2 of the first segment 701 is smaller than the width w3 of the second sub-signal line 7212.

[0175] By increasing the width w3 of the second sub-signal line 7212, the volume of the effective conductor used to propagate electromagnetic waves can be increased, thereby reducing the loss of the second sub-signal line 7212. In addition, by reducing the width of the first segment 701 and the second segment 702, the characteristic impedance fluctuation caused by the change in distance to ground after the first sub-signal line 7211 jumps to the first conductor layer 71 can be compensated.

[0176] For example, the width w3 of the second sub-signal line 7212 is 45um to 80um. For instance, the width w3 of the second sub-signal line 7212 is 45um, 50um, 60um, 70um, or 80um.

[0177] By setting the width w3 of the second sub-signal line 7212 to 45um to 80um, various factors such as conductor loss, fabrication process, and characteristic impedance can be optimized.

[0178] In some embodiments, such as Figure 7A As shown, the width w4 of the fifth segment 705 is greater than the width w5 of the fourth segment 704.

[0179] By increasing the width w4 of the fifth segment 705, the fifth segment 705 can be made closer to the second segment 702 of the signal line 721, thereby changing the electromagnetic field distribution of the second segment 702 and making full use of the field distribution characteristics of the ground coplanar waveguide structure to reduce the impedance fluctuations generated during bending.

[0180] For example, the width of the fifth segment 705 is wider in the middle and narrower at both ends. For instance, the fifth segment 705 includes a first end near the fourth segment 704 and a second end near the sixth segment 706, with the width of the first end decreasing towards the middle. Similarly, the width of the second end decreases towards the middle (e.g., tapering) to ensure a smooth transition in the linewidth of the first sub-ground line 7221, reducing the risk of bending and breakage of the first sub-signal line 7211.

[0181] In some embodiments, such as Figure 7A As shown, the width w5 of the fourth segment 704 is equal to the width w6 of the second sub-ground line 7222. This simplifies the fabrication process and layout of the ground line 722.

[0182] In some embodiments, such as Figure 7A As shown, in the two signal lines 721, the spacing h4 between the first segment 701 is greater than the spacing h5 between the second segment 702.

[0183] By bringing the second segments 702 of the differential pair signal lines 721 closer together, the differential lines are more tightly coupled, resulting in less radiation and less crosstalk with the outside. By moving the first segments 701 of the differential pair signal lines 721 further apart, the characteristic impedance of the differential pair signal lines 721 can be increased.

[0184] For example, in two signal lines 721, the spacing h4 between the first segments 701 is 60um to 150um. For instance, in two signal lines 721, the spacing h4 between the first segments 701 is 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, or 150um.

[0185] By setting the spacing h4 between the first segments 701 of the differential pair signal line 721 to 60um to 150um, the characteristic impedance jump of the first sub-signal line 7211 in the signal line 721 can be reduced.

[0186] For example, in two signal lines 721, the spacing h5 between the second segments 702 is 50um to 100um. For instance, in two signal lines 721, the spacing h5 between the second segments 702 is 50um, 60um, 70um, 80um, 90um, or 100um.

[0187] By setting the spacing h5 between the second segments 702 of the differential pair signal line 721 to 50um to 100um, the various performance characteristics of the differential pair signal line 721 can be balanced, and the impact of layering on the characteristic impedance can be reduced.

[0188] In some embodiments, such as Figure 7A As shown, in the two signal lines 721, the spacing h4 between the first segment 701 is greater than the spacing h6 between the second sub-signal lines 7212.

[0189] By reducing the spacing h6 between the second sub-signal lines 7212 in the differential pair signal line 721, space can be provided to increase the width of the second sub-signal lines 7212, thereby increasing the width of the second sub-signal lines 7212 and reducing the loss of the second sub-signal lines 7212.

[0190] For example, in two signal lines 721, the spacing h6 between the second sub-signal lines 7212 is 60um to 150um. For instance, in two signal lines 721, the spacing h6 between the second sub-signal lines 7212 is 60um, 70um, 80um, 90um, 100um, 110um, 120um, 130um, 140um, or 150um.

[0191] By setting the spacing h6 between the second sub-signal lines 7212 in the differential pair signal line 721 to 60um to 150um, the width of the second sub-signal line 7212 can be increased while reducing the process difficulty and ensuring the process yield.

[0192] In some embodiments, the thickness of the first shielding layer 51 is 6um to 14um. For example, the thickness of the first shielding layer 51 is 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, or 14um.

[0193] In some embodiments, the thickness of the first conductor layer 71, the second conductor layer 72, or the third conductor layer 73 is 6 μm to 15 μm. Taking the first conductor layer 71 as an example, the thickness of the first conductor layer 71 is 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm.

[0194] In some embodiments, the thickness of the first connection layer 81 or the second connection layer 81 is 10um to 20um. Taking the first connection layer 81 as an example, the thickness of the first connection layer 81 is 10um, 11um, 12um, 13um, 14um, 15um, 16um, 17um, 18um, 19um, or 20um.

[0195] In some embodiments, the distance between the first conductor layer 71 and the first shielding layer 51 is 30 μm to 55 μm. For example, the thickness of the first insulating cover film 61 is 30 μm to 55 μm. For example, the distance between the first conductor layer 71 and the first shielding layer 51 is 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, and 55 μm.

[0196] In some embodiments, the distance between the first conductor layer 71 and the first connecting layer 81 is 6 μm to 18 μm. For example, the thickness of the first insulating substrate 62 is 6 μm to 18 μm. For example, the distance between the first conductor layer 71 and the first connecting layer 81 is 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, or 18 μm.

[0197] In some embodiments, the distance between the first connecting layer 81 and the second conductor layer 72 is 15µm to 30µm. For example, the thickness of the first insulating film 63 is 15µm to 30µm. Examples of distances between the first connecting layer 81 and the second conductor layer 72 are 15µm, 16µm, 17µm, 18µm, 19µm, 20µm, 21µm, 22µm, 23µm, 24µm, 25µm, 26µm, 27µm, 28µm, 29µm, and 30µm.

[0198] In some embodiments, the distance between the second connecting layer 82 and the second conductor layer 72 is 6 μm to 18 μm. For example, the thickness of the second insulating film 64 is 6 μm to 18 μm. Examples of distances between the second connecting layer 82 and the second conductor layer 72 are 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, and 18 μm.

[0199] In some embodiments, the distance between the second connecting layer 82 and the third conductor layer 73 is 6 μm to 18 μm. For example, the thickness of the second insulating substrate 65 is 6 μm to 18 μm. For example, the distance between the second connecting layer 82 and the third conductor layer 73 is 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, or 18 μm.

[0200] The embodiments of this application do not limit the thickness of the second shielding layer 52 and the second insulating cover film 66, and can be reasonably set according to the application scenario of FPC.

[0201] By adjusting the thickness of each film layer in the FPC, the characteristic impedance of signal line 721 can be further optimized, reducing the impact of delamination on signal transmission quality.

[0202] Figure 8A and Figure 8B This is a schematic diagram of the structure of the signal line and ground line of an FPC provided in an embodiment of this application.

[0203] In some embodiments, such as Figure 8A and Figure 8B As shown, the second conductor layer 72 also includes a cutout region 723, with the first sub-signal line 7211 opposite to the cutout region 723. For example, the projection of the first sub-signal line 7211 onto the second conductor layer 72 overlaps with the cutout region 723. Alternatively, the projection of the first sub-signal line 7211 onto the second conductor layer 72 may be located within the cutout region 723.

[0204] The embodiments of this application do not limit the outline shape of the hollow area 723. The outline of the hollow area 723 may coincide with the projected outline of the first sub-signal line 7211, or the outline of the hollow area 723 may be a concentric pattern with the projected outline of the first sub-signal line 7211, or the outline of the hollow area 723 may be different from the projected outline shape of the first sub-signal line 7211.

[0205] The projection area of ​​the first sub-signal line 7211 is hollowed out on the second conductor layer 72. Since there is no ground signal in the projection area and no magnetic field is generated, it will not affect the characteristic impedance of the first sub-signal line 7211. This can further reduce the impact of the distance change between the first conductor layer 71 and the second conductor layer 72 on the characteristic impedance of the first sub-signal line 7211.

[0206] In some embodiments, the third conductor layer 73 further includes a cutout region, wherein the projection of the first sub-signal line 7211 of the signal line 721 onto the third conductor layer 73 overlaps with the cutout region. For example, the projection of the first sub-signal line 7211 onto the third conductor layer 73 is located within the cutout region.

[0207] This application also provides a mid-frame component, such as... Figure 2B As shown, the mid-frame assembly includes a first frame 301, a second frame 302, a hinge mechanism 303, and an FPC. The first frame 301 and the second frame 302 are located on both sides of the hinge mechanism 303 and are connected by the hinge mechanism 303. The FPC extends from the side where the first frame 301 is located through the hinge mechanism 303 to the side where the second frame 302 is located. The mid-frame assembly provided in this application embodiment can be applied to the electronic device provided in this application embodiment. In this case, the side where the first conductor layer 71 of the FPC is located faces the display screen 20, and the side where the third conductor layer 73 is located faces away from the display screen 20.

[0208] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope 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 in that, include: A first conductor layer, a second conductor layer, and a third conductor layer, wherein the second conductor layer is located between the first conductor layer and the third conductor layer; A first connecting layer is located between the first conductor layer and the second conductor layer; the first connecting layer has a first gap; The first shielding layer is located on the side of the first conductor layer away from the second conductor layer and is coupled to the first conductor layer; At least one signal line, the signal line including a first sub-signal line, two second sub-signal lines and two first connecting portions; The first sub-signal line is located in the first conductor layer and is opposite to the first gap; the two second sub-signal lines are located in the second conductor layer and are respectively located on both sides of the first gap; the first connection portion penetrates the first connection layer along the thickness direction of the first connection layer; the two ends of the first sub-signal line are respectively coupled to the two second sub-signal lines through the two first connection portions.

2. The flexible circuit board according to claim 1, characterized in that, The flexible circuit board also includes at least one ground line, which is arranged side by side with the signal line; The ground wire includes a first sub-ground wire, two second sub-ground wires, and two second connecting portions; the first sub-ground wire is located in the first conductor layer and is opposite to the first gap; the two second sub-ground wires are located in the second conductor layer and are respectively located on both sides of the first gap; the second connecting portions penetrate the first connecting layer along the thickness direction of the first connecting layer; the two ends of the first sub-ground wire are correspondingly coupled to the two second sub-ground wires through the two second connecting portions.

3. The flexible circuit board according to claim 1 or 2, characterized in that, The first sub-signal line includes a first segment, a second segment, and a third segment connected in sequence; the second segment is directly opposite the first gap, the first segment and the third segment are located on both sides of the first gap, and the first segment and the third segment are respectively coupled to the first connecting portion.

4. The flexible circuit board according to claim 2, characterized in that, The first sub-ground wire includes a fourth segment, a fifth segment, and a sixth segment connected in sequence; the fifth segment is directly opposite the first gap, the fourth segment and the sixth segment are located on both sides of the first gap, and the fourth segment and the sixth segment are respectively coupled to the second connecting part.

5. The flexible circuit board according to claim 4, characterized in that, In the case where the first sub-signal line comprises a first segment, a second segment, and a third segment connected in sequence. The distance between the second segment and the fifth segment is less than the distance between the first segment and the fourth segment; And / or, The spacing between the second sub-signal line and the second sub-ground line is less than the spacing between the first segment and the fourth segment.

6. The flexible circuit board according to claim 5, characterized in that, The spacing between the first segment and the fourth segment is 60µm to 200µm; And / or, The spacing between the second segment and the fifth segment is 50µm to 100µm; And / or, The spacing between the second sub-signal line and the second sub-ground line is 60um to 200um.

7. The flexible circuit board according to any one of claims 4-6, characterized in that, In the case where the first sub-signal line comprises a first segment, a second segment, and a third segment connected in sequence. The width of the second segment is greater than the width of the first segment; And / or, The width of the first segment is less than the width of the second sub-signal line.

8. The flexible circuit board according to claim 7, characterized in that, The width of the first segment is 30um to 60um; And / or, The width of the second segment is 40um to 70um; And / or, The width of the second sub-signal line is 45um to 80um.

9. The flexible circuit board according to any one of claims 4-6, characterized in that, The width of the fifth segment is greater than the width of the fourth segment; And / or, The width of the fourth segment is equal to the width of the second sub-ground wire.

10. The flexible circuit board according to any one of claims 4-6, characterized in that, The at least one signal line includes two adjacent signal lines; the differential characteristic impedance of the two signal lines is 80 ohms to 100 ohms.

11. The flexible circuit board according to claim 10, characterized in that, In the case where the first sub-signal line comprises a first segment, a second segment, and a third segment connected in sequence. In the two signal lines, the spacing between the first segments is greater than the spacing between the second segments; And / or, Of the two signal lines, the spacing between the first segments is greater than the spacing between the second sub-signal lines.

12. The flexible circuit board according to claim 11, characterized in that, In the two signal lines, the spacing between the first segments is 60um to 150um; And / or, In the two signal lines, the spacing between the second segments is 50µm to 100µm; And / or, In the two signal lines, the spacing between the second sub-signal lines is 60um to 150um.

13. The flexible circuit board according to any one of claims 4-6, characterized in that, Along the direction from the middle to the end, the width of the end of the fifth segment tends to decrease.

14. The flexible circuit board according to any one of claims 1, 2, 4-6, characterized in that, The second conductor layer also includes a cutout area, with the first sub-signal line opposite to the cutout area.

15. The flexible circuit board according to any one of claims 1, 2, 4-6, characterized in that, The distance from the first connecting part to the first gap is 0.5mm to 2mm.

16. The flexible circuit board according to any one of claims 1, 2, 4-6, characterized in that, The signal transmitted by the signal line has a rate greater than or equal to 10Gbps; or, The signal line is used to transmit radio frequency signals.

17. The flexible circuit board according to any one of claims 1, 2, 4-6, characterized in that, The flexible circuit board further includes a second connection layer, multiple insulating layers, and a second shielding layer; The second connecting layer is located between the second conductor layer and the third conductor layer, and the second connecting layer has a second gap, the projection of the second gap onto the first connecting layer overlapping the first gap; The insulating layer is respectively covered on two opposing surfaces of the first conductor layer, the second conductor layer, and the third conductor layer; The second shielding layer is located on the side of the third conductor layer away from the second conductor layer.

18. A mid-frame component, characterized in that, The device includes a first frame, a second frame, a pivot mechanism, and a flexible circuit board. The first frame and the second frame are connected by the pivot mechanism. The flexible circuit board extends from the side where the first frame is located, through the pivot mechanism, to the side where the second frame is located. The flexible circuit board includes the flexible circuit board according to any one of claims 1-17.

19. An electronic device, characterized in that, It includes a mid-frame assembly and a display screen, the display screen being disposed on the mid-frame assembly, the mid-frame assembly including the mid-frame assembly of claim 18.

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