Circuit board and electronic device

Abstract

A circuit board, relating to the technical field of signal transmission, and being used for solving the problem of signal crosstalk between different channels in a circuit board. A signal layer (41) of the circuit board may comprise a first dielectric layer (411), two adjacent signal channels, a first grounding part (4311) and a second grounding part (4312). The signal channels may comprise transmission lines (421) arranged on the first dielectric layer (411), the transmission lines (421), the first grounding part (4311) and the second grounding part (4312) being located on the same side surface of the first dielectric layer (411) so as to form a coplanar waveguide (4001). The first grounding part (4311) and the second grounding part (4312) are located between the two adjacent signal channels and are spaced apart from each other. The first grounding part (4311) and the second grounding part (4312) are used for providing different backflow paths for backflow signals of the two adjacent signal channels to pass through, so as to reduce crosstalk between the different backflow signals. Also provided is an electronic device (01) comprising the circuit board.

Description

Circuit board and electronic equipment

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 29, 2023, with application number 202311636526.4 and invention name “A circuit board and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of signal transmission technology, and in particular to a circuit board and an electronic device. Background Art

[0003] With the continuous development of communication technology, the requirements for signal transmission are getting higher and higher. At present, circuit boards are widely used to electrically connect electronic components. Signal transmission lines are provided in the circuit board, and the signal transmission lines can transmit signals between multiple electronic components electrically connected to the circuit board. The above-mentioned signal transmission lines can be microstrip lines, coplanar waveguides (CPW) or strip lines, etc. In order to improve the transmission efficiency of signals, multiple signal transmission lines can be provided in the circuit board to realize multi-channel signal transmission. However, crosstalk occurs between signals in different channels, thereby affecting the transmission quality of the signal.

[0004] Summary of the Invention

[0005] The present application provides a circuit board and an electronic device for solving the problem of signal crosstalk between different channels in a circuit board.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] In one aspect of the present application, a circuit board is provided, which may include a signal layer. The signal layer may include a first dielectric layer, two adjacent signal channels, and a first ground portion and a second ground portion. The signal channel may include a transmission line, which is disposed on the first dielectric layer. The first ground portion is disposed on the first dielectric layer, and the first ground portion and the transmission line are located on the same side surface of the first dielectric layer. The second ground portion is disposed on the first dielectric layer, and the second ground portion and the transmission line are located on the same side surface of the first dielectric layer. In addition, the first ground portion and the second ground portion are located between the two adjacent signal channels, and the first ground portion and the second ground portion are spaced apart.

[0008] In summary, the circuit board provided in the embodiment of the present application, such as the signal layer of the above-mentioned flexible circuit board, includes multiple signal channels formed on the same side of the first dielectric layer and a first ground portion and a second ground portion located between two adjacent signal channels, so that the first ground portion and the second ground portion can form a coplanar waveguide with the transmission line in the signal channel, and the first ground portion and the second ground portion in the above-mentioned coplanar waveguide are used to provide different return paths for the return signals flowing through the two adjacent signal channels. Based on this, the above-mentioned two adjacent signal channels can be the first signal channel and the second signal channel, and the return signal of the first signal channel and the return signal of the second signal channel can be returned to the reference ground through the first ground portion and the second ground portion respectively. Since the first ground portion and the second ground portion are arranged at intervals, the return signal of the first ground portion and the return signal on the second ground portion can be separated, so that the return paths of the return signals of different signal channels are decoupled from each other, reducing the crosstalk between the above-mentioned two return signals, thereby achieving the purpose of reducing coupling noise and improving signal transmission quality.

[0009] In an optional embodiment, the circuit board also includes a reference layer, which is stacked with the signal layer, and the reference layer includes a second dielectric layer and a metal spacer layer. The metal spacer layer is arranged on the second dielectric layer, and a second opening is provided on the metal spacer layer, which penetrates the metal spacer layer, and the second opening exposes the transmission line, the first ground portion, and the second ground portion. The above-mentioned metal spacer layer may include a transmission line for transmitting low-speed signals and a block-shaped adjacent layer reference ground. In addition, by providing a second opening on the metal spacer layer. The first ground portion and the second ground portion in the coplanar waveguide can be equivalent to the signal line for transmitting the return signal. Therefore, in order to maintain the stability of the impedance of the coplanar waveguide (including the transmission line, the first ground portion and the second ground portion), it is necessary to consider not only the influence of the metal layer in the reference layer on the impedance of the transmission line, but also the influence of the metal layer in the reference layer on the impedance of the first ground portion and the second ground portion. Therefore, the second opening provided on the metal spacer layer in the reference layer needs to expose the transmission line, the first ground portion, and the second ground portion at the same time. In this way, on the one hand, the signal transmitted by the coplanar waveguide can be mainly referenced to the first ground portion and the second ground portion in the coplanar waveguide, so that the return signal of the coplanar waveguide mainly flows back through the first ground portion and the second ground portion, thereby reducing the adjacent layer reference ground (located in the metal spacer layer) as the reference ground for the coplanar waveguide transmission signal, resulting in a phenomenon of reduced characteristic impedance of the coplanar waveguide. On the other hand, when there is no metal layer covering the top and bottom of the coplanar waveguide, the above-mentioned metal limiter and the coplanar waveguide can be isolated by the above-mentioned insulating dielectric layer, such as the third dielectric layer, the fourth dielectric layer and the second dielectric layer. In this way, when the electronic device is bent, when the flexible circuit board abuts the metal limiter, the influence of the metal limiter on the impedance stability of the coplanar waveguide in the flexible circuit board can be reduced.

[0010] In one optional embodiment, the first end of the first ground portion and the first end of the second ground portion are located on the same side and electrically connected, and the second end of the first ground portion and the second end of the second ground portion are located on the same side and electrically connected. In this way, adjacent first and second ground portions can be electrically connected to each other, so that the return signals on the first and second ground portions can be combined and transmitted to the ground layer.

[0011] In an optional embodiment, the signal layer further includes a first lead and a second lead. The first lead is provided on the first dielectric layer, the first lead is electrically connected to the transmission line, and the metal spacer layer covers the first lead. For example, one end of the first lead can be electrically connected to the transmission line, and the other end of the first lead can be electrically connected to the above-mentioned signal source for providing high-speed signals, so that the high-speed signal can be transmitted to the transmission line in the coplanar waveguide through the first lead. The second lead is provided on the first dielectric layer, and the first ground portion and the second ground portion that are electrically connected to each other can be electrically connected to the same second lead, and the metal spacer layer covers the second lead, so that the first return signal of the first signal channel and the second return signal of the second signal channel can pass through the first ground portion and the second ground portion respectively, and then return to the reference ground through the second lead, thereby simplifying the structure of the circuit board.

[0012] In one optional embodiment, the width of the transmission line is greater than the width of the first lead. This improves coplanar coupling between the transmission line and the first and second ground portions, thereby reducing insertion loss. For example, the width of the transmission line can be 50 μm, 100 μm, 150 μm, 200 μm, 240 μm, or 250 μm.

[0013] In an optional implementation, a line width of at least one of the first ground portion and the second ground portion is greater than a line width of the second lead, thereby reducing resistance on the return signal path.

[0014] In an optional embodiment, the first dielectric layer and the second dielectric layer are flexible dielectric layers. In this case, the circuit board can be a flexible circuit board.

[0015] In an optional embodiment, the signal layer further includes a third dielectric layer stacked with the first dielectric layer, with the transmission line, the first ground portion, and the second ground portion located between the first and third dielectric layers. The reference layer further includes a fourth dielectric layer stacked with the second dielectric layer, with the metal spacer layer located between the second and fourth dielectric layers. The third and fourth dielectric layers are flexible dielectric layers. The first and third dielectric layers can prevent the transmission line, the first and second ground portions from short-circuiting with metal portions in the reference layer. Similarly, the second and fourth dielectric layers can prevent the metal spacer layer from short-circuiting with other reference layers or metal portions in the signal layer.

[0016] In one optional embodiment, an air gap is provided between the signal layer and the reference layer. This air gap can, on the one hand, increase the distance between the metal stopper and the coplanar waveguide, thereby reducing the metal stopper's impact on the impedance stability of the coplanar waveguide within the flexible circuit board. Furthermore, the air gap can provide sufficient room for deformation during bending of the flexible circuit board, reducing the likelihood of contact between the deformed signal layer and the reference layer in the bending region. This makes the flexible circuit board more easily bendable in the bending region, thereby increasing its flexibility.

[0017] In an optional embodiment, the circuit board also includes an insulating support portion, which is located in the air gap and connected to the signal layer and the reference layer, so that the signal layer and the reference layer adjacent to the signal layer are supported by the insulating support portion to form the above-mentioned air gap.

[0018] In one optional embodiment, the circuit board includes at least two stacked reference layers, namely a first reference layer and a second reference layer, with the signal layer located between the first and second reference layers. The metal spacer layer within any of the reference layers can include signal lines for transmitting low-speed signals and an adjacent reference ground for grounding, thereby increasing the diversity of signal transmission capabilities of the circuit board.

[0019] In an optional implementation, the signal channel includes two transmission lines, and the signal channel can transmit differential signals.

[0020] In an optional embodiment, the reference layer includes a second dielectric layer and a metal spacer layer. The metal spacer layer is disposed on the second dielectric layer, and a second opening is provided on the metal spacer layer, penetrating the metal spacer layer, exposing the transmission line, the first ground portion, and the second ground portion. The metal spacer layer in the first reference layer can be located between the third dielectric layer and the second dielectric layer, with the metal spacer layer in the first reference layer and the coplanar waveguide sharing the third dielectric layer. Furthermore, the metal spacer layer in the second reference layer can be located between the first dielectric layer and the second dielectric layer, such that the metal spacer layer in the second reference layer and the coplanar waveguide share the first dielectric layer. This can reduce the number of dielectric layers in the circuit board, facilitating a reduction in the thickness of the electronic device.

[0021] Another aspect of the present application provides an electronic device, which may include a hinge mechanism, any of the circuit boards described above, and a first circuit board and a second circuit board. The circuit board may be a flexible circuit board. A portion of the flexible circuit board passes through the hinge mechanism. In addition, one end of the flexible circuit board is electrically connected to the first circuit board. The first circuit board and the second circuit board are respectively arranged on either side of the hinge mechanism, and the other end of the flexible circuit board is electrically connected to the second circuit board. A portion of the flexible circuit board passes through the hinge mechanism, and the flexible circuit board can be referred to as a through-shaft flexible circuit board. The above-mentioned electronic device has the same technical effects as the aforementioned embodiment, which will not be repeated here.

[0022] In an optional embodiment, the electronic device further includes a metal limiter. At least a portion of the metal limiter is stacked with the flexible circuit board. When the electronic device is in a flattened state, there is a gap between the metal limiter and the flexible circuit board; when the electronic device is in a folded state, the metal limiter abuts against the flexible circuit board. When the metal limiter abuts against the flexible circuit board, the metal limiter faces the side surface of the flexible circuit board and has a first distance L1 with the transmission line, and L1 ≥ 100 μm. In this way, when the flexible circuit board abuts against the metal limiter during the bending process of the electronic device, the distance between the metal limiter and the coplanar waveguide can be far enough, thereby reducing the influence of the metal limiter on the impedance stability of the coplanar waveguide in the flexible circuit board.

[0023] In one optional embodiment, the electronic device includes an insulating layer disposed on the side of the metal stopper facing the flexible circuit board. This insulating layer ensures that the first distance L1 between the metal stopper and the coplanar waveguide satisfies L1 ≥ 100 μm, thereby reducing the impact of the metal stopper on the impedance stability of the coplanar waveguide in the flexible circuit board to approximately 1%.

[0024] In an optional embodiment, the electronic device includes a middle frame and a rear shell. The middle frame is connected to the hinge mechanism. A accommodating cavity is formed between the rear shell and the middle frame. The first circuit board or the second circuit board is located in the accommodating cavity, and a portion of the flexible circuit board is located in the accommodating cavity and is electrically connected to the first circuit board or the second circuit board. At least one of the middle frame or the rear shell is a metal limiter. When the electronic device is in a folded state, the portion of the flexible circuit board in the bending area may be deformed (for example, bent). The bent portion of the flexible circuit board may abut against the rear shell so that the rear shell can limit further deformation of the flexible circuit board. Alternatively, in other embodiments, the bent portion of the flexible circuit board may also abut against the middle frame so that the middle frame can limit further deformation of the flexible circuit board.

[0025] In an optional embodiment, the electronic device further includes a display screen, and the hinge mechanism includes a hinge body and a door panel. The hinge body is disposed on the back of the display screen. The door panel is disposed on the back of the display screen and is connected to the hinge body and the middle frame. The flexible circuit board is located on the side of the door panel facing away from the display screen, and the door panel serves as a metal stop. When the electronic device is folded, the bent portion of the flexible circuit board can abut against the door panel, thereby limiting further deformation of the flexible circuit board.

[0026] In one optional embodiment, the first and second ground portions, along with a transmission line within the same signal channel, form a coplanar waveguide. When the electronic device moves from a flattened state to a folded state, the impedance change rate ΔZ of the coplanar waveguide satisfies the range: -10% ≤ ΔZ ≤ +10%. This reduces the impact of the metal stopper on the impedance stability of the coplanar waveguide within the flexible circuit board when the flexible circuit board abuts against the metal stopper.

[0027] In an optional embodiment, the flexible circuit board includes a reference layer and an insulating support portion. The reference layer and the signal layer are stacked, with an air gap between them, and the air gap is located in the bending zone. The insulating support portion is located within the air gap, and the insulating support layer is connected to the signal layer and the reference layer. The insulating support layer is located in the fixed zone. The insulating support portion can be located within the air gap and connected to the signal layer and the reference layer, thereby supporting the signal layer and the reference layer adjacent to the signal layer via the insulating support portion to form the aforementioned air gap. As can be seen from the above, the flexible circuit board needs to bend in the bending zone, while the fixed zone of the flexible circuit board does not need to be bent. Therefore, the insulating layer support portion can be located in the fixed zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic structural diagram of an electronic device provided in an embodiment of the present application;

[0029] FIG2 is a schematic diagram of an exploded structure of the electronic device in FIG1 ;

[0030] FIG3 is a schematic diagram of the electronic device in FIG1 in a folded state;

[0031] FIG4 is a cross-sectional view taken along the dotted line A1-A2 in FIG3;

[0032] FIG5 is another schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0033] Figure 6 is an enlarged view of point B in Figure 4;

[0034] FIG7 is another schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0035] FIG8A is a top view taken along the direction C in FIG7 ;

[0036] FIG8B is a top view taken along the direction C in FIG7 ;

[0037] FIG9 is a cross-sectional view taken along the dotted line D1-D2 in FIG8A;

[0038] FIG10 is another top view taken along the direction C in FIG7 ;

[0039] FIG11 is another top view taken along the direction C in FIG7 ;

[0040] FIG12 is a schematic diagram of a circuit board structure provided by the related art;

[0041] FIG13A is another top view taken along the direction C in FIG7 ;

[0042] FIG13B is another top view taken along the direction C in FIG7 ;

[0043] FIG14A is another top view taken along the direction C in FIG7 ;

[0044] FIG14B is another top view taken along the direction C in FIG7 ;

[0045] FIG15 is another schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0046] FIG16 is a schematic structural diagram of a signal layer provided in an embodiment of the present application;

[0047] FIG17 is a schematic structural diagram of a flexible circuit board provided in an embodiment of the present application;

[0048] FIG18 is a top view taken along the direction E in FIG17 ;

[0049] FIG19 is another top view taken along the direction E in FIG17 ;

[0050] FIG20 is a cross-sectional view taken along the dotted line F1-F2 in FIG17;

[0051] FIG21 is a graph showing the impedance of a coplanar waveguide according to an embodiment of the present application, which changes with the distance between the flexible circuit board and the coplanar waveguide;

[0052] FIG22 is another schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0053] FIG23 is another schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0054] FIG24 is another schematic diagram of the structure of a flexible circuit board provided in an embodiment of the present application;

[0055] Figure 25 is a structural schematic diagram of the circuit board provided in an embodiment of the present application.

[0056] Figure numerals: 01-electronic device; 10-display screen; 20-rotating shaft mechanism; 30a-first middle frame; 30b-second middle frame; 31a-first rear shell; 31b-second rear shell; 201a-first door panel; 201b-second door panel; 202-rotating shaft body; 300a-first accommodating cavity; 300b-second accommodating cavity; 40-flexible circuit board; 51-first circuit board; 52-second circuit board; 401-bending area; 402-fixing area; 301-metal limiter; 41-signal layer; 411-first dielectric layer; 421-transmission line; 420a-first Signal channel; 420b-second signal channel; 430-ground line; 4301-first opening; 4311-first grounding portion; 4312-second grounding portion; 441-first lead; 442-second lead; 443-via; 400-adjacent layer reference ground; 413-third dielectric layer; 61-first reference layer; 62-second reference layer; 410-metal spacer layer; 4101-second opening; 412-second dielectric layer; 414-fourth dielectric layer; 70-insulating layer; 71-air gap; 72-insulating support portion; 4001-coplanar waveguide. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0058] In the following, the terms "first," "second," etc., are used for descriptive convenience only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first," "second," etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0059] In this application, unless otherwise expressly specified or limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed mechanical connection, a detachable mechanical connection, or an integral connection; or, "connection" can be a direct connection or an indirect connection through an intermediate medium. In addition, "transmission connection" refers to a connection relationship that can achieve mechanical transmission, such as rotation, movement, and other movements. This "transmission connection" includes but is not limited to fixed mechanical connections, detachable connections (e.g., snap connections, threaded connections), and surface contact abutment and meshing.

[0060] In addition, unless otherwise clearly specified and limited, the term "electrical connection" should be understood in a broad sense. For example, "electrical connection" can be a direct electrical connection, for example, physical contact and electrical conduction between two components. It can also be understood as the electrical connection between different components in the circuit structure through physical lines such as printed circuit board (PCB) copper foil or wires that can transmit electrical signals to transmit electrical signals; or, "electrical connection" can be an indirect electrical connection between two components through an intermediate medium; or, "electrical connection" can be an electrical connection between two components in an air / non-contact manner, for example, two components are electrically connected by capacitive coupling to transmit electrical signals.

[0061] "Communication connection" can refer to the transmission of electrical signals, including wireless communication connections and wired communication connections. Wireless communication connections do not require physical media and do not constitute a connection relationship that limits the product structure.

[0062] In the embodiments of the present application, the descriptions "vertical" and "parallel" respectively indicate approximately vertical and approximately parallel within a certain error range, and the error range may be a range in which the deviation angle relative to absolute vertical and absolute parallel is less than or equal to 5°, 8° or 10°, respectively, and no specific limitation is made here.

[0063] In the embodiments of the present application, directional terms such as "up", "down", "left" and "right" may be defined including but not limited to the orientation relative to the components schematically placed in the drawings. It should be understood that these directional terms may be relative concepts, which are used for relative description and clarification, and may change accordingly according to changes in the orientation of the components in the drawings.

[0064] In the drawings of the embodiments of the present application, components are represented by guide lines with arrows; parts are represented by guide lines only; openings, holes and the like are represented by guide lines with wavy lines at the ends.

[0065] The present application provides an electronic device that can be applied to various communication systems or communication protocols, such as Bluetooth (BT) communication technology, global positioning system (GPS) communication technology, global system of mobile communication (GSM) communication technology, wireless fidelity (WiFi) communication technology, wideband code division multiple access wireless (WCDMA) communication technology, long term evolution (LTE), 5G communication technology, and other future communication technologies. The electronic device in the embodiment of the present application can be a mobile phone, a tablet computer (pad), a laptop computer, a smart home, a smart wearable device (e.g., a smart watch, a smart bracelet, smart glasses, a smart helmet), a virtual reality (VR) electronic device, an augmented reality (AR) electronic device, etc. The electronic device can also be a handheld device with wireless communication function, a computing device or other processing device connected to a wireless modem, an in-vehicle device, an electronic device in a 5G network, or an electronic device in a future public land mobile network (PLMN), etc., and the present application embodiment is not limited to this.

[0066] In some embodiments, the electronic device may have a display function, in which case the electronic device may include a display screen and a processor electrically connected to the display screen. The processor may provide display data to the display screen to drive the display screen to display images. For example, the processor may include one or more processing units, for example, the processor may include an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural-network processing unit (NPU), etc. Among them, different processing units may be independent devices or integrated into one or more processors.

[0067] In addition, the electronic device 01 may further include an external memory interface electrically connected to the processor, an internal memory, a universal serial bus (USB) interface, a charging management module, a power management module, a battery, an antenna, a mobile communication module, a wireless communication module, an audio module, a speaker, a receiver, a microphone, an earphone interface, a sensor module, buttons, and a camera, etc. The sensor module may include a pressure sensor, a gyroscope sensor, an air pressure sensor, a magnetic sensor, an acceleration sensor, a distance sensor, a proximity light sensor, a fingerprint sensor, a temperature sensor, a touch sensor, an ambient light sensor, and a bone conduction sensor, etc.

[0068] For example, for the sake of convenience, the following examples are all taken as an example of the electronic device 01 being a folding mobile phone. In this case, the electronic device 01 may include a display screen 10 as shown in Figure 1, and the display screen 10 may be a flexible screen. In some embodiments of the present application, the display screen 10 may be a self-luminous display screen, such as an organic light emitting diode (OLED) display screen, a micro (micro or mini) light-emitting diode (light-emitting diode) display screen, or a quantum dot light emitting diode (QLED) display screen. Alternatively, in other embodiments of the present application, the display screen 10 may also be a liquid crystal display (LCD) that requires a backlight source.

[0069] In addition, in order to support the display screen 10 during the folding or flattening process of the electronic device 01, the electronic device 01 may further include a hinge mechanism 20, two middle frames (for example, the two middle frames may be a first middle frame 30a and a second middle frame 30b), and two rear shells (for example, the two rear shells may be a first rear shell 31a and a second rear shell 31b) as shown in FIG2 , which are arranged on the back side of the display screen 10 (the surface arranged opposite the display surface of the display screen 10). The first rear shell 31a is arranged on the side of the first middle frame 30a facing away from the display screen 10, and the first rear shell 31a is connected to the first middle frame 30a. Similarly, the second rear shell 31b is arranged on the side of the second middle frame 30b facing away from the display screen 10, and the second rear shell 31b is connected to the second middle frame 30b. The first rear shell 31a and the second rear shell 31b are respectively arranged on both sides of the hinge mechanism 20, and either of the first rear shell 31a and the second rear shell 31b can be rotatably connected or slidably connected to the hinge mechanism 20.

[0070] Based on this, the display screen 10 can be connected to the hinge mechanism 20, the first middle frame 30a, and the second middle frame 30b. When the electronic device 01 is initially in the flattened state as shown in Figure 1, the user can hold the electronic device 01 and apply external force to the first middle frame 30a and the second middle frame 30b as shown in Figure 2 to fold the first middle frame 30a and the second middle frame 30b in half, causing the first middle frame 30a and the second middle frame 30b to rotate or slide relative to the hinge mechanism 20, thereby causing the display screen 10 to bend as shown in Figure 3, thereby placing the electronic device 01 in the folded state shown in Figure 3.

[0071] For example, in an embodiment of the present application, the flattened state of the electronic device 01 may refer to that, in the display screen 10, the angle between the two parts respectively connected to the first middle frame 30a and the second middle frame 30b may be equal to or approximately equal to 180°. The folded state of the electronic device 01 may refer to that, in the display screen 10, the angle between the two parts respectively connected to the first middle frame 30a and the second middle frame 30b may be less than 180°. In order to illustrate the positional relationship of the various components in the electronic device 01 below, an XYZ coordinate system as shown in Figure 2 can be established, wherein the XY plane is parallel to the display surface of the display screen 10 in the flattened state of the electronic device 01, the X direction is the direction from the first middle frame 30a to the second middle frame 30b, and the Y direction is parallel to the rotation center of the hinge mechanism 20. In addition, the Z direction is the stacking direction of the display screen and the middle frame (for example, the first middle frame 30a and the second middle frame 30b).

[0072] On this basis, as shown in FIG4 (a cross-sectional view obtained by cutting along the dotted line A1-A2 in FIG3 ), a storage cavity can be formed between the first middle frame 30a and the first rear shell 31a, such as the first storage cavity 300a, and a storage cavity can be formed between the second middle frame 30b and the second rear shell 31b, such as the second storage cavity 300b. In addition, the electronic device 01 can further include a flexible printed circuit (FPC) 40, a first circuit board 51, and a second circuit board 52. The first circuit board 51 and the second circuit board 52 can be printed circuit boards (PCBs). In order to avoid multiple circuit boards occupying more layout space in the same storage cavity, the first circuit board 51 and the second circuit board 52 can be respectively arranged on both sides of the hinge mechanism 20, so that the first circuit board 51 is located in the first storage cavity 300a and the second circuit board 52 is located in the second storage cavity 300b.

[0073] For example, the functions of the first circuit board 51 and the second circuit board 52 can be the same or different, and this application is not limited to this. For example, at least one of the first circuit board 51 and the second circuit board 52 can be a mainboard, an interface circuit board (e.g., a Type-C interface circuit board or a Type-A interface circuit board), or a circuit board for transmitting control signals.

[0074] Based on this, as shown in Figure 4 , in order for the flexible circuit board 40 to electrically connect the first circuit board 51 and the second circuit board 52, which are located in different accommodating cavities, a portion of the flexible circuit board 40 passes through the aforementioned hinge mechanism 20. This flexible circuit board 40 can be referred to as a through-axis FPC. One end of the flexible circuit board 40 extends into the first accommodating cavity 300a and is electrically connected to the first circuit board 51. The other end of the flexible circuit board 40 extends into the second accommodating cavity 300b and is electrically connected to the second circuit board 52. For example, the ends of the flexible circuit board 40 can be soldered to the first circuit board 51 and the second circuit board 52, respectively, to achieve electrical connection between the flexible circuit board 40 and the first circuit board 51 and the second circuit board 52.

[0075] In some embodiments of the present application, as shown in FIG5 , a first circuit board 51 can be disposed on the first middle frame 30a. This first circuit board 51 can be the mainboard of the electronic device 01. A second circuit board 52 can be disposed on the second middle frame 30b. This second circuit board 52 can be an interface circuit board. By interposing the flexible circuit board 40 through the axis, the first circuit board 51 and the second circuit board 52 located in different display units can be electrically connected, thereby enabling signal transmission between the mainboard and the interface circuit board via the flexible circuit board 40.

[0076] As can be seen from the above, as shown in Figure 5 , the ends of the flexible circuit board 40 are respectively connected to the first circuit board 51 and the second circuit board 52. Furthermore, the portion of the flexible circuit board 40 that passes through the hinge mechanism 20 can also be connected to the hinge mechanism 20, for example, by bonding the flexible circuit board 40 to the hinge mechanism 20. Therefore, the portions of the flexible circuit board 40 that are respectively connected to the first circuit board 51, the second circuit board 52, and the hinge mechanism 20 will not deform during the bending of the electronic device 01. The portions of the flexible circuit board 40 other than those connected to the aforementioned components (the first circuit board 51, the second circuit board 52, and the hinge mechanism 20) may deform during the bending of the electronic device 01.

[0077] In this case, the flexible circuit board 40 may include a bending region 401 and a fixed region 402. The portions of the flexible circuit board 40 that are respectively connected to the first circuit board 51, the second circuit board 52, and the hinge mechanism 20 (as shown in FIG. 4 ) are located within the fixed region 402. Therefore, the portion of the flexible circuit board 40 located within the fixed region 402 will not, or will nearly not, deform during the bending of the electronic device 01. Furthermore, the portion of the flexible circuit board 40 other than the fixed region 402 may serve as the aforementioned bending region 401. Therefore, the portion of the flexible circuit board 40 located within the bending region 401 may deform during the bending of the electronic device 01.

[0078] The above description uses the example of the flexible circuit board 40 being connected to the first circuit board 51, the second circuit board 52, and the hinge mechanism 20 (as shown in FIG4 ) as an example to illustrate the arrangement of the bending region 401 and the fixing region 402 of the flexible circuit board 40. In other embodiments of the present application, the flexible circuit board 40 may be connected to the first circuit board 51 and the second circuit board 52, while there may be no connection between the flexible circuit board 40 and the hinge mechanism 20. In this case, the portion of the flexible circuit board 40 that passes through the hinge mechanism 20 may be located in the bending region 401. For the sake of convenience, the following description uses the example of the flexible circuit board 40 being connected to the first circuit board 51, the second circuit board 52, and the hinge mechanism 20 (as shown in FIG4 ).

[0079] Based on this, when the electronic device is in a folded state, the portion of the flexible circuit board 40 in the bending area 401 can deform (e.g., bend) as shown in Figure 4. The bent portion of the flexible circuit board 40 can abut against the rear shell (e.g., the first rear shell 31a and the second rear shell 31b) so that the rear shell can limit further deformation of the flexible circuit board 40. Alternatively, in other embodiments, the bent portion of the flexible circuit board 40 can also abut against the middle frame (e.g., the first middle frame 30a and the second middle frame 30b) so that the middle frame can limit further deformation of the flexible circuit board 40. Alternatively, the bent portion of the flexible circuit board 40 can abut against both the rear shell and the middle frame. For example, the rear shell and the middle frame can be made of metal material. Therefore, at least one of the rear shell (e.g., the first rear shell 31a and the second rear shell 31b) and the middle frame (e.g., the first middle frame 30a and the second middle frame 30b) can be referred to as the metal limiter 301 shown in Figure 6 (enlarged view of point B in Figure 4).

[0080] Alternatively, as shown in FIG4 , the hinge mechanism 20 may include a hinge body 202 and two door panels (e.g., a first door panel 201a and a second door panel 201b). The door panels may be disposed on the back of the display screen 10 (as shown in FIG2 ), and the flexible circuit board 40 may be located on the side of the door panels (e.g., the first door panel 201a and the second door panel 201b) facing away from the display screen 10 (as shown in FIG2 ). The first door panel 201a and the second door panel 201b may be disposed on either side of the hinge body 202, respectively, and either the first door panel 201a or the second door panel 201b may be connected to the hinge body 202. Furthermore, the first door panel 201a may be connected to the first middle frame 30a, and the second door panel 201b may be connected to the second middle frame 30b. Among them, the door panel and any one of the hinge body 202 and the middle frame can be rotatably connected, slidably connected or fixedly connected, so that when the electronic device 01 is bent, the display bending portion 103 of the display screen 10 can undergo a bending deformation as shown in Figure 3, thereby making the electronic device 01 in the folded state shown in Figure 3.

[0081] Based on this, as shown in Figure 4 , when the electronic device is in the folded state, the bent portion of the flexible circuit board 40 can abut against the door panels (e.g., the first door panel 201a and the second door panel 201b), so that the door panels can limit further deformation of the flexible circuit board 40. For example, the above-mentioned door panels can be made of metal materials. Therefore, the door panels (e.g., the first door panel 201a and the second door panel 201b) can be referred to as the metal limiter 301 shown in Figure 6.

[0082] In this case, as shown in FIG6 , at least a portion of the metal stopper 301 can be stacked with the flexible circuit board 40. In this way, when the electronic device is in a folded state, the metal stopper 301 can abut against the flexible circuit board 40 to limit further deformation of the flexible circuit board 40 through the metal stopper 301. In addition, when the electronic device 01 is in the flattened state shown in FIG7 , a gap, such as a gap h1 or a gap h2, can be provided between the metal stopper 301 and the flexible circuit board 40. The gap h1 or the gap h2 can represent the gap between the flexible circuit board 40 and different metal stoppers 301, and the gap h1 or the gap h2 provides the flexible circuit board 40 with a certain amount of space for bending and deformation.

[0083] Based on this, the circuit board provided in the embodiments of the present application may be the flexible circuit board 40 described above. The structure of the flexible circuit board 40 is described in detail below. In some embodiments of the present application, the flexible circuit board 40 may include a signal layer 41 as shown in FIG8A (a top view taken along the direction C in FIG7 ). The signal layer 41 may include a first dielectric layer 411, two adjacent signal channels (for example, the two signal channels may be a first signal channel 420a and a second signal channel 420b), and a first ground portion 4311 and a second ground portion 4312. The first ground portion 4311 and the second ground portion 4312 are located between the two adjacent signal channels (for example, the first signal channel 420a and the second signal channel 420b). Furthermore, the first ground portion 4311 and the second ground portion 4312 are spaced apart. Either of the first signal channel 420a and the second signal channel 420b may include a transmission line 421. The present application does not limit the number of signal channels; FIG8A only illustrates two adjacent signal channels, for example, the first signal channel 420a and the second signal channel 420b. In addition, the signals transmitted by different signal channels may be the same or different, and this application does not limit this.

[0084] In some embodiments of the present application, as shown in Figure 8A, the first grounding portion 4311 and the second grounding portion 4312 between two adjacent signal channels (for example, the first signal channel 420a and the second signal channel 420b) can be set independently of each other, and the above-mentioned first grounding portion 4311 and the second grounding portion 4312 can be grounded respectively.

[0085] Alternatively, in some other embodiments of the present application, the first end a1 of the first grounding portion 4311 and the first end b1 of the second grounding portion 4312 located on the same side can be electrically connected, and the second end a2 of the first grounding portion 4311 and the second end b2 of the second grounding portion 4312 located on the same side can be located on the same side and electrically connected, so that the first grounding portion 4311 and the second grounding portion 4312 electrically connected to each other constitute the grounding wire 430 as shown in Figure 8B.

[0086] For example, during the process of manufacturing the above-mentioned grounding line 430, a metal film pattern layer can be formed on the first dielectric layer 411, and then a first opening 4301 as shown in Figure 8B can be formed in the metal film layer through a photolithography (masking) process, thereby separating the above-mentioned metal film pattern layer into a first grounding portion 4311 and a second grounding portion 4312 through the first opening 4301. Alternatively, for another example, independent and spaced-apart first and second grounding portions 4311, 4312 can be formed on the first dielectric layer 411. Then, a metal layer for connecting the first and second grounding portions 4311, 4312 is formed at the ends of the first and second grounding portions 4311, 4312, thereby forming the grounding line 430 shown in Figure 8B. This application does not limit the manufacturing process of the first and second grounding portions 4311, 4312. For the convenience of description, the following examples are based on the example of electrically connecting two adjacent first and second grounding portions 4311, 4312 as shown in Figure 8B to form the grounding line 430.

[0087] Furthermore, as shown in FIG9 (a cross-sectional view taken along line D1-D2 in FIG8A ), transmission line 421 and ground line 430 can be disposed on first dielectric layer 411, and can be located on the same side surface of first dielectric layer 411. In this manner, transmission line 421 and ground line 430, which are adjacent to transmission line 421, can form a coplanar waveguide. Coplanar waveguides offer advantages such as high transmission speed, long transmission distance, and strong anti-interference capabilities.

[0088] Therefore, in some embodiments of the present application, the transmission line 421 can be used to transmit high-speed signals. For example, the transmission distance of the high-speed signal can be greater than 1 / 6λ. Wherein, λ is the wavelength of the high-speed signal. The high-speed signal can be a high-speed digital signal or a radio frequency signal. In some embodiments of the present application, the high-speed digital signal can include a differential signal. In this case, as shown in Figure 10 (a top view obtained along the direction C in Figure 7), the same signal channel, such as the first signal channel 420a (or the second signal channel 420b), can have two transmission lines 421. For example, the high-speed digital signal can be stored or read data, interface data, or screen control data.

[0089] For example, the first dielectric layer 411 may be a substrate made of a polymer material. A metal layer, such as a copper layer, is formed on the first dielectric layer 411. A patterning process such as photolithography or printing is then performed to retain a portion of the copper layer to form the transmission line 421 and the ground line 430, while the remaining portion is removed.

[0090] On this basis, it can be seen from the above that, as shown in FIG8B or FIG10 , the first ground portion 4311 and the second ground portion 4312 are spaced apart between two adjacent signal channels (e.g., the first signal channel 420a and the second signal channel 420b). Therefore, the return signal of the high-speed signal transmitted on the first signal channel 420a can flow back to the reference ground after passing through the first ground portion 4311. Furthermore, the return signal of the high-speed signal transmitted on the second signal channel 420b can flow back to the reference ground through the second ground portion 4312. These two return signals can be isolated by the gap between the first ground portion 4311 and the second ground portion 4312, such as the first opening 4301.

[0091] The following examples illustrate the return paths of return signals for different signal channels on the first ground portion 4311 and the second ground portion 4312. For example, as shown in FIG11 , a first ground portion 4311 is provided between the first signal channel 420a and the first opening 4301. A second ground portion 4312 is provided between the second signal channel 420b and the first opening 4301. In this case, a first return signal (indicated by a solid arrow in the figure) of the high-speed signal transmitted on the first signal channel 420a can flow back to the reference ground from right to left (i.e., from the first end a1 to the second end a2) through the first ground portion 4311. In addition, a second return signal (indicated by a dotted arrow in the figure) of the high-speed signal transmitted on the second signal channel 420b can flow back to the reference ground from left to right (i.e., from the second end b2 to the first end b1) through the second ground portion 4312.

[0092] 11 illustrates an example in which the return signals of the first signal channel 420a and the second signal channel 420b are transmitted in opposite directions on the first ground portion 4311 and the second ground portion 4312, respectively. In other embodiments of the present application, the return signals of the first signal channel 420a and the second signal channel 420b can be transmitted in the same direction on the first ground portion 4311 and the second ground portion 4312, respectively.

[0093] In summary, the circuit board provided in the embodiments of the present application, such as the signal layer 41 of the flexible circuit board 40 (as shown in FIG. 4 ) as shown in FIG. 11 , includes multiple signal channels formed on the same side of the first dielectric layer 411 and a first ground portion 4311 and a second ground portion 4312 located between two adjacent signal channels (e.g., a first signal channel 420a and a second signal channel 420b). The first ground portion 4311 and the second ground portion 4312 can form a coplanar waveguide with the transmission line 421 in the signal channel. The coplanar waveguide can be used to transmit high-speed signals, such as high-speed digital signals or radio frequency signals. For the high-speed signals, the high-speed signals need to be recirculated through the first ground portion 4311 or the second ground portion 4312 in the coplanar waveguide.

[0094] Based on this, the first return signal of the first signal channel 420a (indicated by a solid arrow in FIG11 ) and the second return signal of the second signal channel 420b (indicated by a dotted arrow in FIG11 ) can respectively return to the reference ground through the first ground portion 4311 and the second ground portion 4312. The first ground portion 4311 serves as the return path for the first return signal, and the second ground portion 4312 serves as the return path for the second return signal. Since the first ground portion 4311 and the second ground portion 4312 are spaced apart, the first return signal on the first ground portion 4311 and the second return signal on the second ground portion 4312 can be spaced apart, so that the return paths of the return signals from different signal channels are decoupled from each other, reducing the crosstalk between the two return signals, thereby reducing coupling noise and improving signal transmission quality.

[0095] On this basis, as shown in Figure 11, when the first return signal on the first ground portion 4311 and the second return signal on the second ground portion 4312 have opposite directions, the mutual cancellation effect between the first return signal and the second return signal can be reduced, thereby improving signal transmission efficiency. In comparison, in the circuit board with a coplanar waveguide provided by the related art, as shown in Figure 12, the return signals of adjacent transmission signal lines S1 and S2 have opposite directions and flow into the same ground line GND. The return signals of the above two transmission signal lines are not isolated in the ground line GND, resulting in mutual cancellation, which in turn generates coupling noise.

[0096] On this basis, in order to transmit the high-speed signal from the signal source to the transmission line 421 shown in FIG11 and to return the return signal of the high-speed signal to the reference ground via the first ground portion 4311 or the second ground portion 4312, the signal layer 41 may further include a first lead 441 and a second lead 442. The first lead 441 may be disposed on the first dielectric layer 411, one end of the first lead 441 may be electrically connected to the transmission line 421, and the other end of the first lead 441 may be electrically connected to the signal source for providing the high-speed signal, thereby enabling the high-speed signal to be transmitted to the transmission line 421 in the coplanar waveguide via the first lead 441.

[0097] In addition, the second lead 442 is arranged on the first dielectric layer 411, and the first ground portion 4311 and the second ground portion 4312 that are electrically connected to each other can be electrically connected to the same second lead 442, so that the first return signal of the first signal channel 420a (indicated by a solid arrow in Figure 11) and the second return signal of the second signal channel 420b (indicated by a dotted arrow in Figure 11) can pass through the first ground portion 4311 and the second ground portion 4312 respectively, and then return to the reference ground through the same second lead 442, which can simplify the structure of the flexible circuit board.

[0098] In some embodiments of the present application, in order to allow the return signal on the first ground portion 4311 and the second ground portion 4312 to flow back to the reference ground via the second lead 442, as shown in FIG13A , the flexible circuit board 40 further includes an adjacent layer reference ground 400 stacked with the signal layer 41. The flexible circuit board 40 may further include a via 443 that penetrates the first dielectric layer 411, thereby electrically connecting the second lead 442 to the adjacent layer reference ground 400 through the via 443, so that the adjacent layer reference ground 400 serves as the reference ground for the second lead 442. For example, the adjacent layer reference ground 400 may be a block-shaped metal layer structure (e.g., a block-shaped metal copper leakage area).

[0099] Figure 13A illustrates an example in which adjacent first grounding portions 4311 and second grounding portions 4312 are electrically connected to each other and then electrically connected to the adjacent layer reference ground 400 via the same second lead 442 and the same conductive via 443. In other embodiments of the present application, as shown in Figure 13B , when the first grounding portion 4311 and the second grounding portion 4312 are independently provided, the first grounding portion 4311 and the second grounding portion 4312 can be electrically connected to the adjacent layer reference ground 400 via different conductive vias 443, respectively.

[0100] In addition, in some embodiments of the present application, as shown in Figure 11, the line width (dimension along the Y direction, i.e., perpendicular to the extension direction of the signal line) of the transmission line 421 constituting the coplanar waveguide can be greater than the line width of the first lead 441. For example, the line width of the transmission line 421 can be between 50-250um. In this way, the coplanar coupling between the transmission line 421 and the ground line 430 can be improved, and the insertion loss can be reduced. For example, the line width of the transmission line 421 can be 50μm, 100μm, 150μm, 200μm, 240μm or 250μm.

[0101] In addition, since the adjacent layer reference ground 400 shown in Figure 13A can be a block-shaped metal layer structure, the adjacent layer reference ground 400 has a low resistance characteristic. Therefore, the line width (dimension along the Y direction) of the second lead 442 used to electrically connect the first ground portion 4311 and the second ground portion 4312 to the adjacent layer reference ground 400 can be smaller than the line width (dimension along the Y direction) of the ground line 430, thereby reducing the resistance on the return signal path.

[0102] On this basis, as shown in Figure 13A, when the distance between the ground line 430 and the adjacent transmission line 421 is relatively far, it is not easy for the transmission line 421 and the ground line 430 to generate coplanar coupling. In addition, when the distance between the ground line 430 and the adjacent transmission line 421 is relatively close, since the ground line 430 is conductive, the ground line 430 will pull down the impedance of the transmission line 421, thereby causing the impedance of the transmission line 421 to be unstable. Based on this, the spacing H1 between the above-mentioned ground line 430 and the adjacent transmission line 421 can be in the range of 20μm to 100μm. In this way, coplanar coupling can be achieved between the transmission line 421 and the ground line 430, and the impedance of the transmission line 421 can be stabilized. For example, the spacing H1 between the ground line 430 and the adjacent transmission line 421 can be 20μm to 100μm. For example, H1 may be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, and 100 μm.

[0103] As can be seen from the above, the flexible circuit board 40 has a bending region 401 and a fixed region 402, as shown in Figure 5 . The portions of the flexible circuit board 40 that are connected to the first circuit board 51, the second circuit board 52, and the hinge mechanism 20 (shown in Figure 4 ) are located within the fixed region 402. The portion of the flexible circuit board 40 other than the fixed region 402 constitutes the bending region 401. Therefore, the bending region 401 occupies the majority of the area of ​​the flexible circuit board 40. Based on this, as shown in Figure 14A , the transmission line 421 and ground line 430 that constitute the coplanar waveguide can be located within the bending region 401, enabling the flexible circuit board 40 to transmit high-speed data. Furthermore, the first lead 441 and the second lead 442 can be disposed in the fixed region 402.

[0104] FIG14A illustrates an example in which the flexible circuit board 40 is connected to the first circuit board 51, the second circuit board 52, and the hinge mechanism 20 shown in FIG4 . In other embodiments of the present application, the flexible circuit board 40 is connected to the first circuit board 51 and the second circuit board 52, and the flexible circuit board 40 may not be connected to the hinge mechanism 20. In this case, as shown in FIG14B , the ends of the flexible circuit board may be located in the aforementioned fixed areas 402, so that the ends of the flexible circuit board are respectively connected to the first circuit board 51 and the second circuit board 52 shown in FIG4 . The portion of the flexible circuit board located between the two fixed areas 402 is the bending area 401. For ease of explanation, the following description uses the arrangement of the bending area 401 and the fixed area 402 of the signal layer 41 of the flexible circuit board as shown in FIG14A . As can be seen from the above, the coplanar waveguide formed by the transmission line 421 and the ground line 430 in the signal layer 41 is used to transmit high-speed signals, such as high-speed digital signals or radio frequency signals. In some embodiments of the present application, in the signal layer 41 of the same flexible circuit board, different transmission channels, for example, the first signal channel 420a and the second signal channel 420b in FIG. 10 , can transmit the above-mentioned high-speed digital signals and radio frequency signals, respectively.

[0105] Alternatively, in other embodiments of the present application, as shown in FIG15 , electronic device 01 may include two flexible circuit boards, namely flexible circuit board 40a and flexible circuit board 40b, with both ends of each flexible circuit board electrically connected to first circuit board 51 and second circuit board 52. The coplanar waveguide formed by transmission line 421 and ground line 430 in flexible circuit board 40a can transmit high-speed digital signals, while the coplanar waveguide formed by transmission line 421 and ground line 430 in flexible circuit board 40b can transmit radio frequency signals. The above is merely an example of the number of flexible circuit boards in electronic device 01 and the signals transmitted, and does not constitute a limitation on the number of flexible circuit boards or the signals transmitted.

[0106] The above description is based on an example in which the signal layer 41 shown in FIG14A includes a dielectric layer, such as the first dielectric layer 411. In other embodiments of the present application, as shown in FIG16 , the signal layer 41 may further include a third dielectric layer 413. The third dielectric layer 413 may be stacked with the first dielectric layer 411, with the transmission line 421 and the ground line 430 located between the first dielectric layer 411 and the third dielectric layer 413. For example, the transmission line 421 and the ground line 430 may be fabricated on the first dielectric layer 411. Alternatively, for another example, the transmission line 421 and the ground line 430 may be fabricated on the surface of the third dielectric layer 413 facing the first dielectric layer 411. The third dielectric layer 413 and the first dielectric layer 411 may be made of the same material, and both the third dielectric layer 413 and the first dielectric layer 411 may be flexible dielectric layers.

[0107] On this basis, any flexible printed circuit board in the electronic device 01 can transmit not only the aforementioned high-speed signals but also low-speed signals or non-high-speed signals such as ground signals. To enable the flexible printed circuit board to transmit the aforementioned non-high-speed signals, in some embodiments of the present application, the flexible printed circuit board may further include at least one reference layer. For example, as shown in FIG17 , the flexible printed circuit board 40 may be provided with two reference layers, namely a first reference layer 61 and a second reference layer 62.

[0108] The first reference layer 61 and the second reference layer 62 can be stacked with the signal layer 41, and the signal layer 41 can be located between the first reference layer 61 and the second reference layer 62. In some embodiments of the present application, either the first reference layer 61 or the second reference layer 62 can include a second dielectric layer 412, a metal spacer layer 410, and a fourth dielectric layer 414, with the metal spacer layer 410 stacked between the second dielectric layer 412 and the fourth dielectric layer 414. The second dielectric layer 412 can be located on a side of the fourth dielectric layer 414 facing away from the signal layer 41. For example, the metal spacer layer 410 can be disposed on the second dielectric layer 412. Alternatively, the metal spacer layer 410 can be disposed on the fourth dielectric layer 414, which is not limited in this application.

[0109] The second dielectric layer 412 and the fourth dielectric layer 414 can be flexible dielectric layers. For example, the material of the second dielectric layer 412 and the fourth dielectric layer 414 can be the same as that of the first dielectric layer 411. The metal spacer layer 410 can include signal lines for transmitting the non-high-speed signals and a block-shaped reference ground (hereinafter referred to as an adjacent layer reference ground). In this way, the metal spacer layer 410 in either the first reference layer 61 or the second reference layer 62 can include signal lines for transmitting low-speed signals and an adjacent layer reference ground for grounding, thereby increasing the diversity of signal transmission on the flexible circuit board 40. The first dielectric layer 411 and the third dielectric layer 413 can prevent the transmission line 421, the first ground portion 4311, and the second ground portion 4212 from shorting with metal components in the reference layers (e.g., the first reference layer 61 and the second reference layer 62). Similarly, the second dielectric layer 412 and the fourth dielectric layer 414 can prevent the metal spacer layer 410 from shorting with metal components in other reference layers or the signal layer 41.

[0110] As can be seen from the above, as shown in FIG18 (a top view taken along the direction E in FIG17 ), the metal spacer layer 410 may be provided with a second opening 4101 that passes through the metal spacer layer 410 . The second opening 4101 is used to expose the transmission line 421 and the ground line 430 in the signal layer 41 shown in FIG17 . Since the transmission line 421 and the ground line 430 are provided in the bending region 401 , as shown in FIG18 , the second opening 4101 in the metal spacer layer 410 is located in the bending region 401 , and the portion of the metal spacer layer 410 not provided with the second opening 4101 may be located in the fixed region 402 .

[0111] Based on this, the second opening 4101 exposing the transmission line 421 and the ground line 430 can mean that, as shown in FIG19 (a top view taken along the direction E in FIG17 ), the vertical projections of the transmission line 421 and the ground line 430 on the metal spacer layer 410 can be located within the second opening 4101. Furthermore, the first lead 441 electrically connected to the transmission line 421 and the second lead 442 electrically connected to the ground line 430 are located in the fixed area 402. Therefore, the metal spacer layer 410 can cover the first lead 441 and the second lead 442. In other words, the vertical projections of the first lead 441 and the second lead 442 on the metal spacer layer 410 overlap with the portion of the metal spacer layer 410 where the second opening 4101 is not provided.

[0112] As can be seen above, the ground line 430 in the coplanar waveguide 4001 is provided with a first opening (as shown in FIG11 ). Therefore, the ground line 430 is no longer a blocky metal reference ground, but rather a signal line for transmitting return signals. Therefore, to maintain the impedance stability of the coplanar waveguide 4001, it is necessary not only to consider the effect of the metal layers in the reference layers (e.g., the first reference layer 61 or the second reference layer 62 ) on the impedance of the transmission line 421, but also to consider the effect of the metal layers in the reference layers on the impedance of the ground line 430. Therefore, in either the first reference layer 61 or the second reference layer 62 , the second opening 4101 defined in the metal spacer layer 410 must expose both the transmission line 421 and the ground line 430.

[0113] In this case, as shown in FIG20 (a cross-sectional view taken along the dashed line F1-F2 in FIG17 ), there is no metal layer covering the upper and lower portions of the coplanar waveguide 4001 (including the transmission line 421 and the ground line 430 shown in FIG17 ). This allows the signal transmitted by the coplanar waveguide 4001 to primarily use the ground line 430 in the coplanar waveguide 4001 as a reference ground, thereby allowing the return signal of the coplanar waveguide 4001 to primarily flow back through the ground line 430. This reduces the use of the adjacent layer reference ground (located in the metal spacer layer 410) as a reference ground for the signals transmitted by the coplanar waveguide 4001, resulting in a decrease in the characteristic impedance of the coplanar waveguide 4001.

[0114] On the other hand, as shown in FIG4 , during the bending process of the electronic device 01, at least one of the first door panel 201a, the second door panel 201b, the first and second rear shells 31a, 31b, the first middle frame 30a, or the second middle frame 30b can function as a metal stopper 301, abutting against the flexible circuit board 40. In this case, because the metal stopper 301 is a conductor, when the metal stopper 301 abuts against the flexible circuit board 40, it pulls down the impedance of the coplanar waveguide 4001 (as shown in FIG20 ) in the flexible circuit board 40, causing a sudden change in the impedance of the coplanar waveguide 4001 and reducing the impedance stability of the coplanar waveguide.

[0115] For example, as shown in Figure 21, the horizontal axis represents the various positions on the flexible circuit board along the extension direction of the flexible circuit board (for example, the X direction in Figure 20), and the vertical axis represents the impedance of the coplanar waveguide. The four curves in the figure represent four different distances between the flexible circuit board and the coplanar waveguide when the metal stopper abuts the flexible circuit board. Among them, among all the curves, the distance between the flexible circuit board and the coplanar waveguide represented by curve ① is the largest. For example, when the flexible circuit board abuts the first rear shell 31a and the second rear shell 31b in Figure 4 at position G1 and position G2 respectively, the impedance of the coplanar waveguide at position G1 is A1, and the impedance of the coplanar waveguide at position G2 is B1.

[0116] Furthermore, of all the curves, curve ④ represents the smallest distance between the flexible circuit board and the coplanar waveguide. For example, when the flexible circuit board abuts the first rear housing 31a and the second rear housing 31b in Figure 4 at positions G1 and G2, respectively, the impedance of the coplanar waveguide at position G1 instantly decreases from point A1 on curve ① to point A2 on curve ②. At position G2, the impedance of the coplanar waveguide instantly decreases from point B1 on curve ① to point B2 on curve ②.

[0117] In addition, curves ③ and ④ represent the distance between the flexible circuit board and the coplanar waveguide when the metal stopper abuts the flexible circuit board, which is located between curves ① and ②. Based on this, when there is no metal layer covering the top and bottom of the coplanar waveguide 4001 (including the transmission line 421 and the ground line 430 shown in FIG17 ), as shown in FIG22 , the metal stopper 301 and the coplanar waveguide 4001 can be isolated by the insulating dielectric layers, such as the third dielectric layer 413, the fourth dielectric layer 414, and the second dielectric layer 412. In this way, when the electronic device 01 is bent and the flexible circuit board 40 abuts the metal stopper 301, the distance between the flexible circuit board and the coplanar waveguide can be increased, so that at position G1, the impedance of the coplanar waveguide is between points A1 and A2, and at position G2, the impedance of the coplanar waveguide is between points B1 and B2. In this way, it is possible to avoid a large instantaneous change in the impedance of the flexible circuit board, thereby reducing the influence of the metal stopper 301 on the impedance stability of the coplanar waveguide in the flexible circuit board 40 .

[0118] On this basis, to stabilize the impedance of the coplanar waveguide, in some embodiments of the present application, as further shown in FIG. 22 , when the metal stopper 301 abuts the flexible circuit board 40, a first distance L1 is provided between the surface of the metal stopper 301 facing the flexible circuit board 40 and the coplanar waveguide 4001 (including the transmission line 421 and the ground line 430 shown in FIG. 17 ), where L1 is ≥ 100 μm. In this way, when the flexible circuit board 40 abuts the metal stopper 301 during bending of the electronic device 01, the distance between the metal stopper 301 and the coplanar waveguide 4001 is sufficiently large, thereby reducing the impact of the metal stopper 301 on the impedance stability of the coplanar waveguide in the flexible circuit board 40.

[0119] For example, continuing with FIG21 , when the flexible circuit board 40 shown in FIG22 abuts the metal retainer 301, the first distance L1 between the metal retainer 301 and the coplanar waveguide 4001, as represented by curve ③, is greater than the first distance L1 between the metal retainer 301 and the coplanar waveguide 4001, as represented by curve ④, when the flexible circuit board 40 abuts the metal retainer 301, as shown in FIG22 . Therefore, it can be seen that when the flexible circuit board 40 abuts the metal retainer 301, the greater the first distance L1 between the metal retainer 301 and the coplanar waveguide 4001, the smaller the reduction in the impedance of the coplanar waveguide, and the greater the impedance stability.

[0120] For example, when the flexible circuit board 40 abuts the metal stopper 301, and the first distance L1 between the metal stopper 301 and the coplanar waveguide 4001 satisfies L1 ≥ 100 μm, the impedance change rate ΔZ of the coplanar waveguide 4001 from the flat state to the folded state of the electronic device 01 may be within the range of -10% ≤ ΔZ ≤ +10%. This reduces the impact of the metal stopper 301 on the impedance stability of the coplanar waveguide in the flexible circuit board 40 when the flexible circuit board 40 abuts the metal stopper 301.

[0121] In other embodiments of the present application, to ensure that a first distance L1 between the metal stopper 301 and the coplanar waveguide 4001 satisfies L1 ≥ 100 μm when the flexible circuit board 40 abuts the metal stopper 301, as shown in FIG. 23 , the electronic device may further include an insulating layer 70. The insulating layer 70 may be disposed on the side of the metal stopper 301 facing the flexible circuit board 40. For example, a layer of non-conductive material, such as a polymer material such as Teflon, may be applied to the surface of the metal stopper 301 facing the flexible circuit board 40 by bonding or spraying. This reduces the effect of the metal stopper 301 on the impedance stability of the coplanar waveguide in the flexible circuit board 40 to approximately 1%.

[0122] The above description of the first distance L1 between the metal stopper 301 and the coplanar waveguide 4001 is based on the example of a metal stopper 301 disposed above the flexible circuit board 40. In other embodiments of the present application, the metal stopper 301 may also be disposed below the flexible circuit board 40. In this case, the method for setting the first distance L1 between the metal stopper 301 and the coplanar waveguide 4001 is the same as described above and will not be repeated here.

[0123] In other embodiments of the present application, in order to improve the flexibility characteristics of the entire flexible circuit board 40 on the basis of ensuring that the first distance L1 between the metal limiter 301 and the coplanar waveguide 4001 satisfies L1 ≥ 100 μm when the flexible circuit board 40 abuts the metal limiter 301, so that the flexible circuit board 40 can meet dynamic bending conditions of tens of thousands of times, for example, more than 50,000 times, as shown in FIG. 20 , an air gap 71 can be set between the signal layer 41 and any one of the first reference layer 61 and the second reference layer 62.

[0124] In this manner, on the one hand, the air gap 71 can increase the first distance L1 between the metal stopper 301 and the coplanar waveguide 4001, thereby ensuring that the first distance L1 satisfies L1 ≥ 100 μm. Furthermore, during the bending process of the flexible circuit board 40, the air gap 71 can provide a certain amount of deformation space, thereby reducing the probability of contact between the deformed signal layer 41 and either the first reference layer 61 or the second reference layer 62 in the bending region 401. This makes it easier for the flexible circuit board 40 to bend in the bending region 401, thereby improving the flexibility of the flexible circuit board.

[0125] On this basis, to form the aforementioned air gap 71 between the signal layer 41 and either the first reference layer 61 or the second reference layer 62, the flexible circuit board further includes an insulating support portion 72, as shown in FIG20 . The insulating support portion 72 can be located within the air gap 71 and connected to the signal layer 41 and the reference layer (either the first reference layer 61 or the second reference layer 62). Thus, the insulating support portion 72 supports the signal layer 41 and the reference layer adjacent to the signal layer 41 to form the aforementioned air gap 71. As can be seen from the above, the flexible circuit board 40 needs to be bent in the bending region 401, while the fixed region 402 of the flexible circuit board 40 does not need to be bent. Therefore, the insulating layer support portion 70 can be disposed in the fixed region 402.

[0126] The above description uses the example of a flexible circuit board 40 including two reference layers, for example, a first reference layer 61 and a second reference layer 62. In other embodiments of the present application, as shown in FIG24 , the flexible circuit board 40 may include at least three reference layers, for example, at least two first reference layers 61 disposed above the signal layer 41, and at least two second reference layers 62 disposed below the signal layer 41. In this flexible circuit board 40, the aforementioned air gap 71 may be provided between any two adjacent reference layers. The arrangement and technical effects of this air gap 71 are the same as those described above and will not be further elaborated here.

[0127] Alternatively, in other embodiments of the present application, the flexible circuit board 40 may further include a reference layer stacked with the signal layer 41, and the reference layer may be disposed above or below the flexible circuit board 40. The above is an example of the number of reference layers in the flexible circuit board 40 and does not constitute a limitation on the number of reference layers.

[0128] The above description uses the flexible printed circuit board 40 as an example of the circuit board provided in the embodiment of the present application. In other embodiments of the present application, the circuit board may also be a PCB. In this case, the PCB may include the signal layer 41. The arrangement and technical effects of the transmission lines 421 and ground layer 430 in the signal layer 41 are the same as those described above and will not be further described here. In addition, the PCB may also include a reference layer stacked with the signal layer 41. The arrangement of the reference layer is the same as those described above and will not be further described here.

[0129] Alternatively, in other embodiments of the present application, as shown in FIG25 , any reference layer in the PGB, such as the first reference layer 61 or the second reference layer 62, may have only one dielectric layer, namely, the second dielectric layer 412. In this case, the metal spacer layer 410 in the first reference layer 61 may be located between the third dielectric layer 413 and the second dielectric layer 412, so that the metal spacer layer 410 in the first reference layer 61 and the coplanar waveguide 4001 share the third dielectric layer 413. Furthermore, the metal spacer layer 410 in the second reference layer 62 may be located between the first dielectric layer 411 and the second dielectric layer 412, so that the metal spacer layer 410 in the second reference layer 62 and the coplanar waveguide 4001 share the first dielectric layer 411. This reduces the number of dielectric layers in the PCB, thereby facilitating a reduction in the thickness of the electronic device 01.

[0130] The above is only a specific embodiment of the present application, but the scope of protection of this application is not limited to this. Any changes or substitutions within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A circuit board, characterized in that: Comprising a signal layer, the signal layer comprising: a first dielectric layer; Two adjacent signal channels, the signal channels comprising transmission lines, and the transmission lines are arranged on the first dielectric layer; A first grounding portion is disposed on the first dielectric layer, and the first grounding portion and the transmission line are located on the same side surface of the first dielectric layer; The second grounding portion is arranged on the first dielectric layer, and the second grounding portion and the transmission line are located on the same side surface of the first dielectric layer; the first grounding portion and the second grounding portion are located between the two adjacent signal channels, and the first grounding portion and the second grounding portion are arranged at intervals.

2. The circuit board according to claim 1, characterized in that: The circuit board further includes a reference layer, which is stacked with the signal layer, and the reference layer includes: a second dielectric layer; The metal spacer layer is disposed on the second dielectric layer. The metal spacer layer is provided with a second opening penetrating the metal spacer layer. The second opening exposes the transmission line, the first grounding portion and the second grounding portion.

3. The circuit board according to claim 1 or 2, characterized in that: The first end of the first grounding portion and the first end of the second grounding portion are located on the same side and are electrically connected, and the second end of the first grounding portion and the second end of the second grounding portion are located on the same side and are electrically connected.

4. The circuit board according to claim 3, characterized in that: The signal layer also includes: A first lead is disposed on the first dielectric layer, the first lead is electrically connected to the transmission line, and the metal spacer layer covers the first lead; A second lead is arranged on the first dielectric layer; the first grounding portion and the second grounding portion electrically connected to each other are electrically connected to the same second lead, and the metal spacer layer covers the second lead.

5. The circuit board according to claim 4, characterized in that: The line width of the transmission line is greater than the line width of the first lead line.

6. The circuit board according to claim 4, characterized in that: A line width of at least one of the first ground portion and the second ground portion is greater than a line width of the second lead line.

7. The circuit board according to any one of claims 2 to 6, characterized in that: The first dielectric layer and the second dielectric layer are flexible dielectric layers.

8. The circuit board according to claim 7, characterized in that: The signal layer further includes a third dielectric layer, the third dielectric layer is stacked with the first dielectric layer, and the transmission line, the first grounding portion and the second grounding portion are located between the first dielectric layer and the third dielectric layer; The reference layer further comprises a fourth dielectric layer, the fourth dielectric layer is stacked with the second dielectric layer, and the metal spacer layer is located between the second dielectric layer and the fourth dielectric layer; Wherein, the third dielectric layer and the fourth dielectric layer are flexible dielectric layers.

9. The circuit board according to claim 7, characterized in that: An air gap is provided between the signal layer and the reference layer.

10. The circuit board according to claim 9, characterized in that: The circuit board further includes an insulating support portion, wherein the insulating support portion is located in the air gap and is connected to the signal layer and the reference layer.

11. The circuit board according to any one of claims 2 to 10, characterized in that: The circuit board comprises at least two stacked reference layers, namely a first reference layer and a second reference layer; the signal layer is located between the first reference layer and the second reference layer.

12. The circuit board according to any one of claims 1 to 11, characterized in that: The signal channel includes two transmission lines.

13. An electronic device, characterized in that: include: Rotating shaft mechanism; The circuit board according to any one of claims 1 to 12, wherein the circuit board is a flexible circuit board; a portion of the flexible circuit board passes through the rotating shaft mechanism; a first circuit board, one end of the flexible circuit board being electrically connected to the first circuit board; The second circuit board, the first circuit board and the second circuit board are respectively arranged on both sides of the rotating shaft mechanism; the flexible circuit board The other end is electrically connected to the second circuit board.

14. The electronic device according to claim 13, characterized in that: The electronic device further comprises: a metal stopper, at least a portion of which is stacked with the flexible circuit board; when the electronic device is in a flattened state, there is a gap between the metal stopper and the flexible circuit board; when the electronic device is in a folded state, the metal stopper abuts against the flexible circuit board; When the metal stopper is in contact with the flexible circuit board, a first distance L1 is formed between the metal stopper and the transmission line on one side of the surface of the flexible circuit board, and L1 is ≥ 100 μm.

15. The electronic device according to claim 13 or 14, characterized in that: The electronic device comprises: The insulating layer is arranged on a side of the metal stopper facing the flexible circuit board.

16. The electronic device according to claim 14 or 15, characterized in that: The electronic device comprises: A middle frame connected to the rotating shaft mechanism; A rear shell and the middle frame form a receiving cavity; the first circuit board or the second circuit board is located in the receiving cavity, and a part of the flexible circuit board is located in the receiving cavity and is electrically connected to the first circuit board or the second circuit board; Wherein, at least one of the middle frame or the rear shell is the metal limiting component.

17. The electronic device according to claim 14 or 15, characterized in that: The electronic device further comprises a display screen; the shaft mechanism comprises: The rotating shaft body is arranged on the back of the display screen; A door panel is arranged on the back of the display screen, and the door panel is connected to the rotating shaft body and the middle frame; the flexible circuit board is located on the side of the door panel away from the display screen, and the door panel serves as the metal stopper.

18. The electronic device according to any one of claims 14 to 17, characterized in that: The first ground portion, the second ground portion and the transmission line in the same signal channel form a coplanar waveguide; When the electronic device changes from the flattened state to the folded state, the impedance change rate ΔZ of the coplanar waveguide satisfies the range: -10％≤△Z≤+10％。

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