Flexible circuit board and electronic device

Abstract

The embodiments of the present application relate to the technical field of signal transmission. Provided are a flexible circuit board (FPC) and an electronic device, which are used for alleviating the problem of large signal loss of an FPC caused by electromagnetic shielding. The FPC may have a first region and a second region. A reference layer of the FPC is located in the first region, and the reference layer and a signal layer are stacked. A first shielding layer is located in the first region, and the first shielding layer is stacked on the side of the signal layer away from the reference layer. A second shielding layer is located in the second region, and the second shielding layer and the signal layer are stacked. A first ground trace is electrically connected to the first shielding layer and the reference layer, and the first ground trace is also electrically connected to the second shielding layer. A return signal of a signal transmitted by a signal trace in the signal layer may flow from the second shielding layer located in the second region, passes through the first ground trace, and then respectively flows into the first shielding layer and the reference layer located in the first region.

Description

Flexible circuit board and electronic device

[0001] The present application claims priority to the Chinese Patent Application No. 202410875170.8, filed on June 29, 2024, and entitled "Flexible circuit board and electronic device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

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

[0003] With the continuous development of electronic products, flexible printed circuit boards (FPCs) are widely used in consumer electronic products with bending and flexing requirements and ultra-thin requirements, such as folding mobile phones, folding tablets, and notebook computers, due to their advantages of being bendable and occupying less space. In addition, as the integration of electronic devices becomes higher and higher, it is necessary to effectively shield the signals transmitted by the FPC, such as high-speed signals. However, the above electromagnetic shielding will cause a large signal loss, especially in the dynamic bending part of the FPC, which will further reduce the signal quality margin. SUMMARY

[0004] The present application provides a flexible circuit board and an electronic device to alleviate the problem of large signal loss caused by electromagnetic shielding.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] In one aspect of the present application, a flexible circuit board is provided, which can have a first region and a second region. The flexible circuit board includes a signal layer, a reference layer, a first shielding layer, and a second shielding layer. The signal layer is located in the first region and the second region, and the signal layer includes a first ground trace. The reference layer is located in the first region, and the reference layer is stacked with the signal layer. The first shielding layer is located in the first region, and the first shielding layer is stacked on the side of the signal layer away from the reference layer. The second shielding layer is located in the second region. The first end of the first ground trace is located in the first region and is electrically connected to the first shielding layer and the reference layer. The second end of the first ground trace is located in the second region and is electrically connected to the second shielding layer.

[0007] In summary, the powder reference layer is located in the first area, and the second area is not provided with the reference layer, so the number of film layers of the second area of the flexible circuit board can be less than the number of film layers of the first area, and thus the thickness of the second area can be less than the thickness of the first area. Based on this, when the flexible circuit board is applied to a folding electronic device, the second area in the flexible circuit board can be used as an area where the flexible circuit board is dynamically bent, so that the flexible circuit board has good bending resistance. In addition, the part of the signal layer located in the first area can be covered by the first shielding layer, so that the signal in the first area can be electromagnetically shielded by the first shielding layer. And the part of the signal layer located in the second area can be covered by the second shielding layer, so that the signal in the second area can be electromagnetically shielded by the second shielding layer. On this basis, since the first ground trace in the signal layer is electrically connected to the second shielding layer at the second end of the second area, and the first ground trace is electrically connected to the first shielding layer and the reference layer at the first end of the first area. Therefore, the return signal of the signal transmitted by the signal trace in the signal layer can flow through the first ground trace from the second shielding layer located in the second area, and flow into the first shielding layer and the reference layer located in the first area, respectively, so that the return path of the second area and the first area in the flexible circuit board is continuous. This can reduce the impedance fluctuation of the flexible circuit board, thereby reducing the signal loss (especially high-frequency signal loss) caused by the second shielding layer and the first shielding layer.

[0008] In an alternative embodiment, the flexible circuit board further comprises a second dielectric layer, a first conductive adhesive and a second conductive adhesive. The second dielectric layer is located between the first shielding layer and the signal layer, and the second dielectric layer is also located between the second shielding layer and the signal layer. The second dielectric layer has a first opening and a second opening. The first opening exposes the first end of the first ground trace, and the second opening exposes the second end of the first ground trace. In addition, the first conductive adhesive is located in the first opening, and the first conductive adhesive is connected to the first end of the first ground trace and the first shielding layer. The second conductive adhesive is located in the second opening, and the second conductive adhesive is connected to the second end of the first ground trace and the second shielding layer. In this case, the second shielding layer located in the second area can be electrically connected to the second end of the first ground trace in the signal layer through the second conductive adhesive. The first end of the first ground trace is electrically connected to the first shielding layer through the first conductive adhesive. In this way, the second shielding layer can be electrically connected to the first shielding layer through the first ground trace, the first conductive adhesive and the second conductive adhesive.

[0009] In an alternative embodiment, the flexible circuit board further comprises a third dielectric layer and a via. The third dielectric layer is located between the signal layer and the reference layer. The via penetrates the third dielectric layer, and the two ends of the via are electrically connected to the first end of the first ground trace and the reference layer, respectively. In this case, the first ground trace in the signal layer can be electrically connected to the reference layer through the via. Since the first shielding layer is electrically connected to the first ground trace, the first shielding layer can be electrically connected to the reference layer through the first ground trace and the via.

[0010] In an alternative embodiment, the flexible circuit board comprises two second shielding layers, i.e., a second upper shielding layer and a second lower shielding layer. The signal layer is located between the second upper shielding layer and the second lower shielding layer. In this way, the part of the signal layer located in the second region is covered by the second upper shielding layer and the second lower shielding layer from above and below, respectively, so that the electromagnetic shielding effect can be improved.

[0011] In an alternative embodiment, the first shielding layer and the second shielding layer have a first gap H1, 0.2mm≤H1≤6mm. In this case, when H1<0.2mm, the size of the first gap H1 is small, and the installation tolerance of the first shielding layer and the second shielding layer attached to the second dielectric layer is high. Alternatively, when H1>6mm, the size of the first gap H1 is too large, so that the signal line in the signal layer has a large area without electromagnetic shielding at the position corresponding to the first gap H1, thereby reducing the shielding effect on the signal. Therefore, when 0.2mm≤H1≤6mm, the first shielding layer and the second shielding layer can be conveniently attached to the second dielectric layer side by side along the extension direction of the flexible circuit board, and the electromagnetic shielding effect can meet the design requirements.

[0012] In an alternative embodiment, the signal layer further comprises a first signal trace, a second signal trace, and a second ground trace. The second signal trace is arranged apart from the first signal trace. The first signal trace and the second signal trace are located between the first ground trace and the second ground trace. The first end of the second ground trace is located in the first region and is electrically connected to the first shielding layer and the reference layer. The second end of the second ground trace is located in the second region and is electrically connected to the second shielding layer. In this case, the first signal trace and the second signal trace described above can be used to transmit differential signals. When the first signal trace and the second signal trace transmit differential signals, the return signal of the first signal trace can flow through the first ground trace close to the first signal trace from the second shielding layer, and then flow into the first shielding layer and the reference layer. Similarly, the return signal of the second signal trace can flow through the second ground trace close to the second signal trace from the second shielding layer, and then flow into the first shielding layer and the reference layer. Since the first signal trace and the second signal trace are arranged apart between the first ground trace and the second ground trace, the noise coupling between the first ground trace and the second ground trace can be reduced.

[0013] In an optional embodiment, the first signal trace includes a first portion, a second portion and a third portion; the first shielding layer covers the first portion, and the second shielding layer covers the third portion. The second portion is located in the first gap H1. The first portion has a first line width L1, the second portion has a second line width L2, and the third portion has a third line width L3; L2>L1, L2>L3. Since the second portion is located in the first gap H1, no electromagnetic shielding layer is arranged at the position of the second portion. By increasing the line width of the second portion to the second line width, the second line width is greater than the first line width L1 of the first portion and the third line width L3 of the third portion, so that the second portion can be more easily referenced to the first signal trace located on one side of the second portion. In this way, the impedance fluctuation of each portion in the entire first signal trace can be reduced, and the purpose of reducing signal loss caused by electromagnetic shielding can be achieved.

[0014] In an optional embodiment, the material of the first shielding layer is the same as that of the signal layer, so that the manufacturing process of the flexible circuit board can be simplified.

[0015] In an optional embodiment, the conductivity of the first shielding layer can be greater than that of the second shielding layer. Based on this, in order to make the conductivity of the first shielding layer greater than that of the second shielding layer, for example, the first shielding layer and the second shielding layer can both be metal layers, wherein the first shielding layer can be a metal layer with a relatively large thickness, and the second shielding layer can be a metal foil with a relatively small thickness. At this time, the electromagnetic shielding effect of the first shielding layer can be greater than that of the second shielding layer. In addition, since the second shielding layer has a relatively small thickness and is located in the second area, when the second area of the flexible circuit board is used as a dynamic bending area, the flexibility of the dynamic bending area can be improved. Alternatively, in order to make the conductivity of the first shielding layer greater than that of the second shielding layer, for another example, the first shielding layer can be a metal layer, and the second shielding layer can be a dielectric layer doped with metal particles (or conductive powder). The conductive powder can be metal powder or powder made of non-metal conductive material. At this time, since the second shielding layer has higher flexibility and bending resistance than the first shielding layer composed of a metal film, the second area of the flexible circuit board having the second shielding layer can be used as a dynamic bending area of the flexible circuit board.

[0016] In another aspect of the present application, an electronic device is provided, which can include the above-mentioned circuit board and any one of the above-mentioned flexible circuit boards, and the flexible circuit board can be electrically connected with the circuit board. The electronic device has the same technical effects as the flexible circuit board provided in the foregoing embodiments, and details are not repeated here.

[0017] In an optional implementation, the electronic device can include two circuit boards, which are a first circuit board and a second circuit board. In addition, the electronic device can further include a first housing and a second housing that are rotationally connected. The flexible circuit board includes two first regions, and a second region of the flexible circuit board is located between the two first regions. The first circuit board is arranged on the first housing to be connected with the first housing. The first circuit board can be electrically connected with one of the two first regions. For example, the first circuit board can be electrically connected with one of the two first regions through a board-to-board connector, so that the first region electrically connected with the first circuit board can be relatively fixed with the position of the first housing. The second circuit board is arranged on the second housing to be connected with the second housing. The second circuit board can be electrically connected with the other of the two first regions. For example, the second circuit board can be electrically connected with the other of the two first regions through a board-to-board connector, so that the first region electrically connected with the second circuit board can be relatively fixed with the position of the second housing. In this way, the two first regions will not be dynamically bent during rotation of the first housing and the second housing, so as to ensure the reliability of the electrical connection between the flexible circuit board and the first circuit board and the second circuit board.

[0018] In an optional implementation, the electronic device further includes a rotation shaft mechanism located between the first housing and the second housing, and the first housing and the second housing are rotationally connected with the rotation shaft mechanism. The part of the flexible circuit board located in the second region passes through the rotation shaft mechanism. The part of the flexible circuit board passing through the rotation shaft mechanism can be used as a dynamically bent region of the flexible circuit board.

[0019] In yet another aspect of the present disclosure, an electronic device is provided. The electronic device includes a first housing, a second housing, a first circuit board, a second circuit board, and a hinge mechanism. The first circuit board is connected to the first housing, and the second circuit board is connected to the second housing. The hinge mechanism is located between the first housing and the second housing, and the first housing and the second housing are rotatably connected to the hinge mechanism. The hinge mechanism includes a first metal shaft cover. The flexible circuit board has a third region, a fourth region, and a fifth region, and the third region is located between the fourth region and the fifth region. The fourth region is connected to the first housing, and the fifth region is connected to the second housing. The flexible circuit board includes a signal layer, a reference layer, and a third shielding layer. In an example, the third shielding layer can be a metal layer with high electrical conductivity and high thickness. In another example, the third shielding layer can be a metal foil with low electrical conductivity and low thickness, or the third shielding layer can be a structure in which conductive powder or metal particles are combined with a dielectric material. The signal layer is located in the third region, the fourth region, and the fifth region. The reference layer is located in the fourth region and the fifth region and is stacked with the signal layer. The third shielding layer is located in the fourth region and the fifth region and is stacked on a side of the signal layer away from the reference layer. The first circuit board is electrically connected to the fourth region, and the second circuit board is electrically connected to the fifth region. The first metal shaft cover covers at least a portion of the flexible circuit board located in the third region. The first metal shaft cover is electrically connected to the reference layer. As described above, the portions of the signal layer located in the fourth region and the fifth region are covered by the third shielding layer. The third shielding layer located in the fourth region can electromagnetically shield the signal traces of the signal layer located in the fourth region. Similarly, the third shielding layer located in the fifth region can electromagnetically shield the signal traces of the signal layer located in the fifth region. In addition, the first metal shaft cover covers the portion of the signal layer located in the third region. Furthermore, the first metal shaft cover can be electrically connected to the reference layer, such that the first metal shaft cover is grounded to the reference layer. In this case, the first metal shaft cover can electromagnetically shield the signal traces of the signal layer located in the third region, so that the third region of the flexible circuit board can be electromagnetically shielded by the first metal shaft cover in the electronic device. In addition, the third region, the fourth region, and the fifth region of the flexible circuit board can all achieve electromagnetic shielding. On this basis, since the first metal shaft cover can electromagnetically shield the signal traces of the signal layer located in the third region, the portion of the flexible circuit board located in the third region does not need to be provided with the above-mentioned electromagnetic shielding layer. In this way, on the one hand, since the first housing and the second housing are rotatably connected to the hinge mechanism, the portion of the flexible circuit board located in the third region can serve as a region where the flexible circuit board is dynamically bent. In this case, since the portion of the flexible circuit board located in the third region does not need to be provided with the above-mentioned shielding layer, the thickness of the flexible circuit board in the third region can be reduced, and the bending resistance of the flexible circuit board in the third region can be improved.On the other hand, the electromagnetic shielding layer is not arranged in the third area of the flexible circuit board, and the signal loss caused by the electromagnetic shielding layer can be reduced, so that the contradiction between the electromagnetic shielding and the signal loss can be solved.

[0020] In an alternative embodiment, the signal layer further comprises a third signal trace, the third signal trace comprising a fourth portion and a fifth portion; the third shielding layer covers the fourth portion, and the fifth portion passes through the accommodating cavity. The fourth portion has a fourth line width L4, and the fifth portion has a fifth line width L5; L5>L4. As known from the above, the first metal shaft cover covers the fifth portion of the third signal trace, and the third area of the flexible circuit board covered by the first metal shaft cover is not provided with the electromagnetic shielding layer. Therefore, by increasing the line width of the fifth portion to the fifth line width L5, the fifth line width L5 is greater than the fourth line width L4 of the fourth portion, so that the fifth portion can be more easily referenced to the third signal trace located on one side of the fifth portion. In this way, the impedance fluctuation of each portion in the entire third signal trace can be reduced, so as to reduce the signal loss caused by the electromagnetic shielding.

[0021] In an alternative embodiment, the third ground trace is electrically connected with the reference layer and the third shielding layer. The first metal shaft cover is further electrically connected with the third ground trace. In this way, the first metal shaft cover can be grounded to the reference layer through the third ground trace.

[0022] In an alternative embodiment, the first metal shaft cover is electrically connected with the third ground trace. The first metal shaft cover comprises a first shaft cover body, a first metal pressing sheet and a second metal pressing sheet. The first metal pressing sheet is located on the side of the first shaft cover body facing the first circuit board, the first metal pressing sheet is connected with the first shaft cover body and is electrically connected with the third ground trace. The second metal pressing sheet is located on the side of the first shaft cover body facing the second circuit board, the second metal pressing sheet is connected with the first shaft cover body and is electrically connected with the third ground trace. The first shaft cover body can be a metal shaft cover, when the first shaft cover body is connected with the first metal pressing sheet and the second metal pressing sheet located on both sides of the first shaft cover body, the first shaft cover body, the first metal pressing sheet and the second metal pressing sheet can be electrically connected with each other. At this time, when the first metal pressing sheet and the second metal pressing sheet are electrically connected with the third ground trace and the fourth ground trace, the entire first metal shaft cover can be electrically connected with the third ground trace. In this case, the first metal pressing sheet and the second metal pressing sheet can be prepared separately, and then the first metal pressing sheet and the second metal pressing sheet are assembled with the first shaft cover body, so that the first metal shaft cover can be obtained without changing the preparation process of the first shaft cover body, thereby simplifying the manufacturing process of the first metal shaft cover.

[0023] In an alternative embodiment, the electronic device further comprises a third conductive glue and a fourth conductive glue. The third conductive glue is located between the first metal plate and the third ground trace, and the third conductive glue is connected with the first metal plate and the third ground trace. The third conductive glue can be connected with the first metal plate and the third ground trace, so that the first metal plate is electrically connected with the third ground trace through the third conductive glue. The fourth conductive glue is located between the second metal plate and the third ground trace, and the fourth conductive glue is connected with the second metal plate and the third ground trace. Similarly, the fourth conductive glue can be connected with the second metal plate and the third ground trace, so that the second metal plate is electrically connected with the third ground trace through the fourth conductive glue.

[0024] In an alternative embodiment, the signal layer further comprises a fourth signal trace and a fourth ground trace. The third signal trace and the fourth signal trace are arranged in a spaced manner, and the third signal trace and the fourth signal trace are located between the third ground trace and the fourth ground trace. The fourth ground trace is electrically connected with the reference layer and the third shielding layer, and the first metal shaft cover is also electrically connected with the fourth ground trace. In this case, the signal channel formed by the third signal trace and the fourth signal trace can be used to transmit differential signals. In addition, the first metal shaft cover can be electrically connected with both the third ground trace and the fourth ground trace, which can improve the electromagnetic shielding effect of the third shielding layer.

[0025] In an alternative embodiment, the flexible circuit board further has a sixth region and a seventh region. The sixth region is located between the third region and the fourth region, and the seventh region is located between the third region and the fifth region. The signal layer is further located in the sixth region and the seventh region. The flexible circuit board further comprises a fourth shielding layer and a fifth shielding layer. The fourth shielding layer is located in the sixth region, and the fourth shielding layer is stacked with the signal layer. The fifth shielding layer is located in the seventh region, and the fifth shielding layer is stacked with the signal layer. In addition, the signal layer comprises a fifth ground trace and a sixth ground trace. The first end of the fifth ground trace is located in the fourth region, and is electrically connected with the third shielding layer and the reference layer in the fourth region. The second end of the fifth ground trace is located in the sixth region, and is electrically connected with the fourth shielding layer. The first end of the sixth ground trace is located in the fifth region, and is electrically connected with the third shielding layer and the reference layer in the fifth region. The second end of the sixth ground trace is located in the seventh region, and is electrically connected with the fifth shielding layer. In this case, the fourth shielding layer and the fifth shielding layer have better bending resistance relative to the third shielding layer. In this case, when the distance between the board-to-board connector and the first metal axle cover is relatively long, the portions of the flexible circuit board located in the sixth region and the seventh region, and the portion covered by the first metal axle cover can all serve as dynamic bending regions, thereby improving the bending resistance of the entire flexible circuit board. In addition, the shielding effect of the fourth shielding layer and the fifth shielding layer, the electrical connection of the third shielding layer, the reference layer, and the fourth shielding layer through the fifth ground trace, the electrical connection of the third shielding layer, the reference layer, and the fifth shielding layer through the sixth ground trace, and the technical effect of reducing signal loss of the flexible circuit board are as described above, and will not be repeated here.

[0026] In an alternative embodiment, the electrical conductivity of the third shielding layer is greater than at least one of the fourth shielding layer or the fifth shielding layer. For example, in order to make the electrical conductivity of the third shielding layer greater than at least one of the fourth shielding layer or the fifth shielding layer, the third shielding layer can be a metal layer with a relatively large thickness. At least one of the fourth shielding layer or the fifth shielding layer can be a metal foil with a relatively small thickness, or at least one of the fourth shielding layer or the fifth shielding layer can be a structure composed of conductive powder or metal particles and a dielectric material. The technical effects of the fourth shielding layer or the fifth shielding layer are as described above for the second shielding layer, and will not be repeated here.

[0027] In an alternative embodiment, the electrical conductivity of the third shielding layer is less than or equal to 5 x 10 7 S / m. For example, the third shielding layer can be a metal foil with a relatively small thickness, or the third shielding layer can be a structure composed of conductive powder or metal particles and a dielectric material.

[0028] In an alternative embodiment, the rotating shaft mechanism further comprises a second metal shaft cover, which is arranged opposite to the first metal shaft cover and is electrically connected to the reference layer. In this case, a receiving cavity can be formed between the first metal shaft cover and the second metal shaft cover, and the part of the flexible circuit board at least in the third region can pass through the receiving cavity. Since the first metal shaft cover and the second metal shaft cover are both electrically connected to the reference layer, the upper and lower parts of the third region of the flexible circuit board are covered with the grounded first metal shaft cover and the second metal shaft cover respectively, so that the electromagnetic shielding effect can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a structural schematic diagram of an electronic device according to an embodiment of the present application;

[0030] FIG. 2 is a structural schematic diagram of another electronic device according to an embodiment of the present application;

[0031] FIG. 3 is a structural schematic diagram of still another electronic device according to an embodiment of the present application;

[0032] FIG. 4 is a sectional view along the dashed line A1-A2 in FIG. 2;

[0033] FIG. 5 is a structural schematic diagram of the electronic device in a closed state according to an embodiment of the present application;

[0034] FIG. 6 is a sectional view of a flexible circuit board along the dashed line A3-A4 in FIG. 3;

[0035] FIG. 7 is a top view of a signal layer along the direction B in FIG. 6;

[0036] FIG. 8 is a structural schematic diagram of a second shielding layer in FIG. 6;

[0037] FIG. 9 is another sectional view of the flexible circuit board along the dashed line A3-A4 in FIG. 3;

[0038] FIG. 10 is still another sectional view of the flexible circuit board along the dashed line A3-A4 in FIG. 3;

[0039] FIG. 11 is another top view of the flexible circuit board along the direction B in FIG. 6;

[0040] FIG. 12 is an exploded structural schematic diagram of a flexible circuit board according to an embodiment of the present application;

[0041] FIG. 13 is a sectional view along the dashed line A5-A6 in FIG. 11;

[0042] FIG. 14 is a top view along the direction C in FIG. 13;

[0043] FIG. 15 is another top view along the direction C in FIG. 13;

[0044] Fig. 16 is a structural schematic diagram of the first signal trace in Fig. 15;

[0045] Fig. 17 is a structural schematic diagram of a flexible circuit board provided by an embodiment of the present application;

[0046] Fig. 18 is another cross-sectional view obtained by cutting along the dashed line A3-A4 in Fig. 3;

[0047] Fig. 19 is a structural schematic diagram of another electronic device provided by an embodiment of the present application;

[0048] Fig. 20 is a structural schematic diagram of another flexible circuit board provided by an embodiment of the present application;

[0049] Fig. 21 is another cross-sectional view obtained by cutting along the dashed line A1-A2 in Fig. 2;

[0050] Fig. 22 is a structural schematic diagram of another electronic device provided by an embodiment of the present application;

[0051] Fig. 23 is a structural schematic diagram of another electronic device provided by an embodiment of the present application;

[0052] Fig. 24 is a top view obtained in the direction D in Fig. 23;

[0053] Fig. 25 is a structural schematic diagram of another flexible circuit board provided by an embodiment of the present application;

[0054] Fig. 26 is a structural schematic diagram of another electronic device provided by an embodiment of the present application;

[0055] Fig. 27 is a cross-sectional view obtained in the direction E in Fig. 26;

[0056] Fig. 28 is a structural schematic diagram of another electronic device provided by an embodiment of the present application;

[0057] Fig. 29 is a top view obtained in the direction F in Fig. 28;

[0058] Fig. 30 is another top view obtained in the direction F in Fig. 28.

[0059] Reference signs: 01-electronic device; 10-display screen; 11-first housing; 12-second housing; 101-first circuit board; 102-second circuit board; 111-first electronic component; 112-second electronic component; 30-flexible circuit board; 301-first area; 302-second area; 31-signal layer; 32-reference layer; 33-first shielding layer; 34-second shielding layer; 42-second dielectric layer; 43-third dielectric layer; 300-signal channel; 311-first signal trace; 312-second signal trace; 41-third dielectric layer; 340-metallic particles; 313-first ground trace; 314-second ground trace; 51-first conductive adhesive; 52-second conductive adhesive; 421-first opening; 422-second opening; 431-via hole; 3111-first part; 3112-second part; 3113-third part; 341-second upper shielding layer; 342-second lower shielding layer; 20-rotation shaft mechanism; 201-first metal shaft cover; 202-second metal shaft cover; 1101-first back cover; 1102-first middle frame; 1201-second back cover; 1202-second middle frame; 3114-fourth part; 3115-fifth part; 315-third signal trace; 316-fourth signal trace; 317-third ground trace; 318-fourth ground trace; 303-third area; 304-fourth area; 305-fifth area; 2011-first shaft cover body; 2012-first metal pressing sheet; 2013-second metal pressing sheet; 53-third conductive adhesive; 54-fourth conductive adhesive; 50-third shielding layer; 344-fourth shielding layer; 345-fifth shielding layer; 306-sixth area; 307-seventh area; 319-fifth ground trace; 320-sixth ground trace. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments.

[0061] Hereinafter, the terms "first", "second", and the like are only used for description convenience and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0062] In the present application, unless otherwise explicitly specified and limited, the term "connection" should be understood broadly, for example, the "connection" can be a fixed mechanical connection, or a detachable mechanical connection, or integrated; or the "connection" can be direct connection, or indirect connection through an intermediate medium. In addition, "transmission connection" refers to a connection relationship that can realize mechanical transmission, such as rotation, movement and the like. The "transmission connection" includes but is not limited to fixed mechanical connection, detachable connection (for example, clamping connection, threaded connection), and surface contact abutment, engagement and the like.

[0063] In addition, unless otherwise explicitly specified and limited, the term "electrical connection" should be understood broadly, for example, the "electrical connection" can be a direct electrical connection, for example, physical contact and electrical conduction between two components, or can be understood as electrical connection between different components through a physical line that can transmit electrical signals, such as copper foil or wire of a printed circuit board (PCB), for transmission of electrical signals; or the "electrical connection" can be indirect electrical connection between two components through an intermediate medium; or the "electrical connection" can be electrical connection between two components through a non-contact / empty space mode, for example, electrical connection between two components through capacitive coupling for transmission of electrical signals.

[0064] "Communication connection" can refer to electrical signal transmission, including wireless communication connection and wired communication connection. Wireless communication connection does not require a physical medium and is not a connection relationship that defines the product structure.

[0065] In the embodiments of the present application, "vertical" and "parallel" respectively represent approximately vertical and approximately parallel within a certain error range, which can be a range of less than or equal to 5°, 8° or 10° of deviation angle with respect to absolute vertical and absolute parallel, which is not limited here.

[0066] In the embodiments of the present application, the orientation terms such as "upper", "lower", "left", "right" and the like can include but are not limited to the orientation defined relative to the orientation of the components shown in the drawings. It should be understood that these directional terms can be relative concepts, which are used for relative description and clarification, and can change accordingly according to the change of the orientation of the components shown in the drawings. In the drawings of the embodiments of the present application, the components are represented by arrows; the components are only represented by arrows.

[0067] The electronic device in the embodiments of the present application can be a mobile phone, a pad, a notebook computer, a smart home, a smart wearable device (for example, a smart watch, a smart bracelet, smart glasses, a smart helmet), a virtual reality (VR) electronic device, an augmented reality (AR) electronic device, and the like. The electronic device can also be a handheld device, a computing device, or other processing device connected to a wireless modem having a wireless communication function, a vehicle-mounted device, an electronic device in a 5G network, or an electronic device in a future evolved public land mobile network (PLMN), and the like, and the embodiments of the present application are not limited thereto.

[0068] In some embodiments, the electronic device described above can have a display function, in which case the electronic device can include a display screen and a processor electrically connected to the display screen. The processor can provide display data to the display screen to drive the display screen to display images. For example, the processor described above can include one or more processing units, such as: the processor can include a system on a chip (SoC), 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. Different processing units can be independent devices or integrated into one or more processors.

[0069] In addition, the electronic device described above can also include an external memory interface, 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, a key, and a camera, etc. electrically connected to the processor. The sensor module can include a pressure sensor, a gyroscope sensor, a barometric 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.

[0070] The electronic device described above is a foldable electronic device, for example, the foldable electronic device can be a foldable mobile phone, a foldable tablet computer, or a foldable notebook computer. In order to facilitate the description, the electronic device is taken as a foldable tablet computer for example. In this case, the electronic device 01 can include a display screen 10 as shown in FIG. 1, and the display screen 10 can be a flexible screen. In some embodiments of the present application, the display screen 10 can be a self-luminous display screen, for example, an organic light emitting diode (OLED) display screen, a micro or mini light-emitting diode display screen, or a quantum dot light emitting diode (QLED) display screen, etc. Alternatively, in some other embodiments of the present application, the display screen 10 can also be a liquid crystal display (LCD) that needs a backlight source, and the present application does not limit this.

[0071] In addition, in order to support the display screen 10 during folding or unfolding of the electronic device 01, the electronic device 01 can further include at least two housings (for example, the at least two housings can be a first housing 11 and a second housing 12 respectively) arranged on the back surface (a surface arranged opposite to the display surface of the display screen 10) of the display screen 10. The first housing 11 and the second housing 12 can be rotationally connected.

[0072] The present application does not limit the included angle between the first housing 11 and the second housing 12 when the electronic device 01 is in an unfolded state. For example, the unfolded state of the electronic device 01 can mean that, as shown in FIG. 1, the included angle between the two parts of the display screen 10 connected with the first housing 11 and the second housing 12 respectively can be equal to or approximately equal to 180°. Alternatively, for another example, the unfolded state of the electronic device 01 can mean that, as shown in FIG. 2, the maximum included angle between the two parts of the display screen 10 connected with the first housing 11 and the second housing 12 respectively can be less than 180°.

[0073] In order to describe the positional relationship of each component in the electronic device 01, an XYZ coordinate system as shown in FIG. 2 can be established, wherein the X direction is the direction in which the first housing 11 points to the second housing 12, or the direction in which the second housing 12 points to the first housing 11. The Y direction is parallel to the rotation center of the first housing 11 and the second housing 12. In addition, the Z direction is the stacking direction of the display screen and the first housing 11 (or the second housing 12).

[0074] In addition, the above is exemplified by taking the electronic device 01 having two rotationally connected housings (the first housing 11 and the second housing 12) as an example. In this case, the electronic device 01 is a two-fold electronic device. In other embodiments of the present application, the electronic device 01 can also be a multi-fold electronic device, in which case the electronic device can have three or more housings, and adjacent two housings can be rotationally connected. For the convenience of description below, the electronic device is exemplified by taking the above two-fold electronic device as an example.

[0075] On this basis, as shown in FIG. 3, the electronic device 01 can further include a flexible circuit board 30, a first circuit board 101, and a second circuit board 102. In addition, the electronic device 01 can further include at least one first electronic component 111 and at least one second electronic component 112. The first circuit board 101 can be disposed on and connected to the first housing 11. The second circuit board 102 can be disposed on and connected to the second housing 12. The two ends of the flexible circuit board 30 can be electrically connected to the first circuit board 101 and the second circuit board 102, respectively. The first circuit board 101 and the second circuit board 102 can be PCBs.

[0076] For example, the two ends of the flexible circuit board 30 can be electrically connected to the first circuit board 101 and the second circuit board 102, respectively, through a board-to-board (BTB) connector, so that the first electronic component 111 disposed on the first circuit board 101 can be electrically connected to the second electronic component 112 on the second circuit board 102 through the flexible circuit board 30, and signal transmission between the first electronic component 111 and the second electronic component 112 can be achieved. The type of the first electronic component 111 or the second electronic component 112 is not limited in the present application. For example, high-speed signals such as USB signals, display port (DP) signals, embedded display port (eDP) signals, mobile industry processor interface (MIPI) signals, radio frequency (RF) signals, etc. can be transmitted between the first electronic component 111 and the second electronic component 112, so that signals related to antennas, cameras, and display screens can be transmitted across screens.

[0077] In some embodiments of the present application, as shown in FIG. 4 (a cross-sectional view taken along the dashed line A1-A2 in FIG. 2), the first housing 11 can be rotationally connected with the second housing 12. The first circuit board 101 can be arranged on the first housing 11, and the second circuit board 102 can be arranged on the second housing 12. In this case, when the first housing 11 rotates counterclockwise along the arc arrow direction, the included angle between the first housing 11 and the second housing 12 can be the maximum included angle. At this time, the electronic device 01 can be in an unfolded state. In addition, as shown in FIG. 5, when the first housing 11 rotates clockwise along the arc arrow direction, the included angle between the first housing 11 and the second housing 12 decreases. And in the case that the included angle between the first housing 11 and the second housing 12 is approximately 0°, the electronic device 01 can be in a closed state.

[0078] As can be seen from FIG. 4 and FIG. 5, in the process of relative rotation between the first housing 11 and the second housing 12, a part of the flexible circuit board 30, for example, the part of the flexible circuit board 30 between the first circuit board 101 and the second circuit board 102, will be dynamically bent. The structure of the flexible circuit board 30 is described below to enable the flexible circuit board 30 to electromagnetically shield the signal traces in the flexible circuit board 30 and alleviate the problem of large signal loss of the flexible circuit board 30 caused by electromagnetic shielding while meeting the dynamic bending performance requirements.

[0079] In some embodiments of the present application, as shown in FIG. 6 (a cross-sectional view of the flexible circuit board taken along the dashed line A3-A4 in FIG. 3), the flexible circuit board 30 can have a second region 302 and at least one first region 301. FIG. 6 is an example of the flexible circuit board 30 having one first region 301. In addition, the flexible circuit board 30 can include a signal layer 31, a reference layer 32, a first shielding layer 33, and a second shielding layer 34.

[0080] Based on this, as shown in FIG. 6, the signal layer 31 can be located in the first region 301 and the second region 302. The signal layer 31 can include signal traces for transmitting signals (e.g., high-speed signals described above). As an example, as shown in FIG. 7 (a top view of the signal layer along direction B in FIG. 6), the signal layer 31 can include at least one signal channel 300. When the signal channel 300 is used to transmit a differential signal, the signal channel 300 can include two signal traces, such as a first signal trace 311 and a second signal trace 312 arranged in a spaced manner. Alternatively, as another example, when the signal channel 300 is used to transmit a non-differential signal, the signal channel described above can include only one signal trace. The number of signal traces in the signal channel 300 is not limited in the present application, and the following is an example of a signal channel 300 including a first signal trace 311 and a second signal trace 312 for ease of illustration.

[0081] The traces in the signal layer 31 described above can be formed by patterning a metal layer, such as a same layer, through a photolithography process. As shown in FIG. 6, the reference layer 32 can be located in the first region 301, and the reference layer 32 can be arranged in a stacked manner with the signal layer 31. The reference layer 32 can have a block-shaped ground metal pattern, and the reference layer 32 can provide a return path for return signals of the signal traces in the signal layer 31.

[0082] In order to isolate the signal layer 31 and the reference layer 32, as shown in FIG. 6, the flexible circuit board 30 can further include a third dielectric layer 43 located between the signal layer 31 and the reference layer 32, and the third dielectric layer 43 can be located in the first region 301 and the second region 302. The third dielectric layer 43 described above can be a thin film of a high-molecular insulating material with a certain flexibility. For example, a polyimide film or a polyester film.

[0083] In addition, as shown in FIG. 6, the first shielding layer 33 is located in the first region 301, and the first shielding layer 33 is arranged in a stacked manner on a side of the signal layer 31 away from the reference layer 32. As an example, the first shielding layer 33 described above can be a metal film layer with a relatively large thickness, such as a copper layer or a silver layer. The first shielding layer 33 can conduct electricity through free electrons inside the first shielding layer 33 to achieve a shielding effect of electromagnetic interference (EMI).

[0084] In some embodiments of the present application, the material of the first shielding layer 33 can be the same as the material of the signal layer 31, so that the manufacturing process of the flexible circuit board 30 can be simplified. For example, the material of the first shielding layer 33 and the material of the signal layer 31 can both be metal copper. In this case, among the traces in the signal layer 31 (e.g., the first signal trace 311 and the second signal trace 312 shown in FIG. 7), the portions located in the first region 301 can be covered by the first shielding layer 33, so that the signals in the first region 301 can be shielded from EMI by the first shielding layer 33.

[0085] On this basis, as shown in FIG. 6, the second shielding layer 34 can be located in the second region 302, and the second shielding layer 34 can be arranged in a stack with the signal layer 31. FIG. 6 is an example in which the second shielding layer 34 and the first shielding layer 33 are located on the same side of the signal layer 31. In other embodiments of the present application, the second shielding layer 34 can be located on the same side of the signal layer 31 as the reference layer 32.

[0086] In addition, the electrical conductivity of the first shielding layer 33 can be greater than the electrical conductivity of the second shielding layer 34. For example, in order to make the electrical conductivity of the first shielding layer 33 greater than the electrical conductivity of the second shielding layer 34, the second shielding layer 34 can be a thin metal layer, such as a metal foil. When the first shielding layer 33 is a metal layer, the thickness of the second shielding layer 34 can be less than the thickness of the first shielding layer 33. In this case, the electromagnetic shielding effect of the first shielding layer 33 can be greater than the electromagnetic shielding effect of the second shielding layer 34. In addition, since the second shielding layer 34 is thin and is located in the second region 302, the second region 302 of the flexible circuit board 30 can be used as a region of the flexible circuit board 30 that is dynamically bent, so as to improve the flexibility of the dynamically bent region.

[0087] Alternatively, in order to make the electrical conductivity of the first shielding layer 33 greater than that of the second shielding layer 34, the first shielding layer 33 is a metal film layer, and the second shielding layer 34 is a dielectric layer doped with metal particles (or conductive powder). That is, the second shielding layer 34 is a structure in which the conductive powder or metal particles are compounded with the dielectric material. For example, as shown in FIG. 8, the second shielding layer 34 can include a first dielectric layer 41 and metal particles 340 (or conductive powder) doped in the first dielectric layer 41. The conductive powder can be metal powder or powder made of non-metal conductive material. The material of the metal particles 340 can include copper, silver, or aluminum, etc. The second shielding layer 34 can conduct electricity by positive and negative ions in the metal particles 340 to achieve the EMI shielding effect. In this case, among the traces in the signal layer 31 (for example, the first signal trace 311 and the second signal trace 312 shown in FIG. 7), the part located in the second area 302 can be covered by the second shielding layer 34, so that the signals in the second area 302 can be shielded by the second shielding layer 34.

[0088] In addition, since the second shielding layer 34 has the first dielectric layer 41 and the metal particles 340 for conducting electricity are dispersed in the first dielectric layer 41, the second shielding layer 34 has higher flexibility and bending resistance than the first shielding layer 33 composed of a metal film. Therefore, when the flexible circuit board 30 is applied to a folding electronic device, the first area 301 having the second shielding layer 34 in the flexible circuit board 30 can be located in the area where the flexible circuit board is dynamically bent, so as to ensure that the flexible circuit board 30 has good bending resistance during folding of the electronic device, and reduce the probability of failure of the function of the flexible circuit board 30.

[0089] Continuing as shown in FIG. 6, in order to isolate the first shielding layer 33 from the signal layer 31 and isolate the second shielding layer 34 from the signal layer 31, the flexible circuit board 30 can further include a second dielectric layer 42. The second dielectric layer 42 can be located in the first area 301 and the second area 302. Moreover, the part of the second dielectric layer 42 located in the second area 302 can be located between the second shielding layer 34 and the signal layer 31. The part of the second dielectric layer 42 located in the first area 301 can be located between the first shielding layer 33 and the signal layer 31. The materials of the second dielectric layer 42 and the first dielectric layer 41 can be the same as or different from the material of the third dielectric layer 43, which is not limited in the present application.

[0090] In some embodiments of the present application, a first gap H1 as shown in FIG. 6 can be provided between the first shielding layer 33 and the second shielding layer 34. For example, the first gap H1 can satisfy: 0.2mm≤H1≤6mm. In this case, when H1<0.2mm, the size of the first gap H1 is small, and the installation tolerance of the first shielding layer 33 and the second shielding layer 34 attached to the second dielectric layer 42 is high. Alternatively, when H1>6mm, the size of the first gap H1 is too large, and the signal line in the signal layer 31 has a large area at the position corresponding to the first gap H1 without EMI shielding, thereby reducing the shielding effect on the signal.

[0091] Therefore, when 0.2mm≤H1≤6mm, the first shielding layer 33 and the second shielding layer 34 can be conveniently attached side by side to the second dielectric layer 42 along the extension direction (i.e., the X direction) of the flexible circuit board 30, and the EMI shielding effect can meet the design requirements. For example, H1 can be 0.2mm, 0.3mm, 0.5mm, 0.8mm, 1mm, 3mm, 5mm, or 6mm.

[0092] Alternatively, in some other embodiments of the present application, as shown in FIG. 9 (another cross-sectional view of the flexible circuit board obtained by cutting along the dashed line A3-A4 in FIG. 3), the first shielding layer 33 and the second shielding layer 34 can be spliced together along the extension direction (i.e., the X direction) of the flexible circuit board 30. Alternatively, as shown in FIG. 10 (another cross-sectional view of the flexible circuit board obtained by cutting along the dashed line A3-A4 in FIG. 3), a portion of the first shielding layer 33 and the second shielding layer 34 can be stacked along the extension direction (i.e., the X direction) of the flexible circuit board 30. For example, FIG. 10 illustrates the case where the second shielding layer 34 is stacked above the first shielding layer 33. In some other embodiments, the first shielding layer 33 can be stacked above the second shielding layer 34.

[0093] The present application does not limit the arrangement of the first shielding layer 33 and the second shielding layer 34 along the extension direction (i.e., the X direction) of the flexible circuit board 30. For convenience of description, the following description is based on the example shown in FIG. 9, where the first shielding layer 33 and the second shielding layer 34 have the first gap H1 therebetween.

[0094] As described above, as shown in FIG. 11 (another top view of the flexible circuit board 30 obtained along the direction B in FIG. 6), the second region 302 in the flexible circuit board 30 is provided with the second shielding layer 34 for realizing EMI shielding, and the first region 301 in the flexible circuit board 30 is provided with the first shielding layer 33 for realizing EMI shielding. Based on this, in order to reduce the loss (for example, the loss of high-speed signals) generated on the signal lines (for example, the first signal line 311 and the second signal line 312) due to the second shielding layer 34 and the first shielding layer 33, the signal layer 31 can further include at least one ground line for electrically connecting the second shielding layer 34 and the first shielding layer 33. The following illustrates the arrangement of the ground line.

[0095] For example, as shown in FIG. 11, in the case where the signal layer 31 has the first signal line 311 and the second signal line 312, the signal layer 31 can further include two ground lines for electrically connecting the second shielding layer 34 and the first shielding layer 33, which are the first ground line 313 and the second ground line 314. The first signal line 311 and the second signal line 312 can be located between the first ground line 313 and the second ground line 314. The first signal line 311, the second signal line 312, the first ground line 313, and the second ground line 314 can be formed by the same metal layer through a photolithography process.

[0096] Here, the extension direction of the first signal line 311 and the second signal line 312 can be the same as the extension direction (i.e., the X direction) of the flexible circuit board 30, and the first signal line 311 and the second signal line 312 can be located in the first region 301, the second region 302, and the gap (i.e., the first gap H1) between the first region 301 and the second region 302.

[0097] On this basis, as shown in FIG. 11, the first end a1 of the first ground line 313 can be located in the first region 301. Moreover, the first end a1 of the first ground line 313 can be electrically connected to the first shielding layer 33 and the reference layer 32 as shown in FIG. 12. The second end a2 of the first ground line 313 can be located in the second region 302. Moreover, the second end a2 of the first ground line 313 can be electrically connected to the second shielding layer 34.

[0098] In addition, the first end b1 of the second ground trace 314 can be located in the first region 301. Moreover, the first end b1 of the second ground trace 314 can be electrically connected with the first shielding layer 33 and the reference layer 32 as shown in FIG. 12. The second end b2 of the second ground trace 314 can be located in the second region 302. Moreover, the second end b2 of the second ground trace 314 can be electrically connected with the second shielding layer 34. In this case, the second shielding layer 34 located in the second region 302 can be electrically connected with the first shielding layer 33 and the reference layer 32 (as shown in FIG. 12) through the first ground trace 313 and the second ground trace 314.

[0099] The following takes the first ground trace 313 as an example to illustrate the way that the first ground trace 313 electrically connects the second shielding layer 34 with the first shielding layer 33 and the reference layer 32. In some embodiments of the present application, as shown in FIG. 12 (which is an exploded view of the flexible circuit board), the second dielectric layer 42 can be provided with a first opening 421 and a second opening 422. The first opening 421 can expose the first end a1 of the first ground trace 313, and the second opening 422 can expose the second end a2 of the first ground trace 313.

[0100] In addition, as shown in FIG. 12, the above-mentioned flexible circuit board 30 can further include a first conductive adhesive 51 and a second conductive adhesive 52. The first conductive adhesive 51 can be located in the first opening 421, and the first conductive adhesive 51 can be connected with the first end a1 of the first ground trace 313 and the first shielding layer 33. The second conductive adhesive 52 can be located in the second opening 422, and the second conductive adhesive 52 can be connected with the second end a2 of the first ground trace 313 and the second shielding layer 34.

[0101] In this case, as shown in FIG. 13 (which is a cross-sectional view obtained by cutting along the dashed line A5-A6 in FIG. 11), the second shielding layer 34 located in the second region 302 can be electrically connected with the second end a2 of the first ground trace 313 (as shown in FIG. 14) in the signal layer 31 through the second conductive adhesive 52. The first end a1 of the first ground trace 313 is electrically connected with the first shielding layer 33 through the first conductive adhesive 51. In this way, the second shielding layer 34 can be electrically connected with the first shielding layer 33 through the first ground trace 313, the first conductive adhesive 51 and the second conductive adhesive 52. In addition, the way that the second shielding layer 34 is electrically connected with the first shielding layer 33 through the second ground trace 314 is the same, and thus will not be described here.

[0102] On this basis, as shown in FIG. 12, a via 431 is disposed on the third dielectric layer 43 between the signal layer 31 and the reference layer 32. The via 431 can pass through the third dielectric layer 43, and the two ends of the via 431 can be electrically connected to the first end al of the first ground trace 313 and the reference layer 32, respectively. In this case, the first ground trace 313 in the signal layer 31 can be electrically connected to the reference layer 32 through the via 431 shown in FIG. 13. Since the first shielding layer 33 is electrically connected to the first ground trace 313, the first shielding layer 33 can be electrically connected to the reference layer 32 through the first ground trace 313 and the via 431. In addition, since the first shielding layer 33 is electrically connected to the second shielding layer 34 through the first ground trace 313 described above, the second shielding layer 34 can be electrically connected to the reference layer 32 through the first shielding layer 33.

[0103] In this case, as shown in FIG. 13, the second shielding layer 34, the second conductive adhesive 52, the first ground trace 313 in the signal layer 31 (as shown in FIG. 14), the first conductive adhesive 51 and the first shielding layer 33, the via 431, and the reference layer 32 can form a signal return path. For example, as shown in FIG. 14 (which is a top view in the direction C in FIG. 13), in the case where the first signal trace 311 and the second signal trace 312 in the signal layer 31 transmit signals from left to right, for example, the above-mentioned high-speed signals (represented by solid arrows in FIGS. 13 and 14), the return signals of the above-mentioned high-speed signals (represented by dashed arrows in FIGS. 13 and 14) will be from right to left, first passing through the second shielding layer 34 in the second region 302.

[0104] Next, as shown in FIG. 13, the return signals from the second shielding layer 34 flow downward into the first ground trace 313 (shown in FIG. 14) in the signal layer 31 through the second conductive adhesive 52 electrically connected to the second shielding layer 34. The return signals on the first ground trace 313 can flow upward into the first shielding layer 33 in the first region 301 through the first conductive adhesive 51 shown in FIG. 13. In addition, the return signals on the first ground trace 313 can also flow downward into the reference layer 32 in the first region 301 through the via 431 shown in FIG. 13.

[0105] In summary, as shown in FIG. 13, the reference layer 32 is located in the first area 301, and the second area 302 is not provided with the reference layer 32, so the number of film layers of the second area 302 of the flexible circuit board 30 can be less than that of the first area 301, and thus the thickness (dimension along the Y direction) of the second area 302 can be less than that of the first area 301. When the flexible circuit board 30 is applied to a foldable electronic device, the second area 302 in the flexible circuit board 30 can serve as an area where the flexible circuit board 30 is dynamically bent, so that the flexible circuit board 30 has good bending resistance.

[0106] In addition, as shown in FIG. 14, since the first ground trace 313 in the signal layer 31 is electrically connected to the second shielding layer 34 at the second end a2 of the second area 302, and the first ground trace 313 is electrically connected to the first shielding layer 33 and the reference layer 32 (as shown in FIG. 13) at the first end a1 of the first area 301. Therefore, the return signal of the signal transmitted by the signal trace in the signal layer 31 can flow through the first ground trace 313 from the second shielding layer 34 in the second area 302 to the first shielding layer 33 and the reference layer 32 in the first area 301, respectively, so that the return paths of the second area 302 and the first area 301 in the flexible circuit board 30 are continuous. This can reduce the impedance fluctuation of the flexible circuit board 30, thereby reducing the signal (especially high-frequency signal) loss caused by the second shielding layer 34 and the first shielding layer 33.

[0107] In addition, as shown in FIG. 14, in the case where the signal layer 31 further includes a second ground trace 314, by analogy, since the second ground trace 314 is electrically connected to the second shielding layer 34 at the second end b2 of the second area 302, and the second ground trace 314 is electrically connected to the first shielding layer 33 and the reference layer 32 (as shown in FIG. 13) at the first end b1 of the first area 301. Therefore, the return signal of the signal transmitted by the signal trace in the signal layer 31 can flow through the second ground trace 314 from the second shielding layer 34 in the second area 302 to the first shielding layer 33 and the reference layer 32 in the first area 301, respectively, so that the return paths of the second area 302 and the first area 301 in the flexible circuit board 30 are continuous.

[0108] In this case, when the first signal trace 311 and the second signal trace 312 in the signal layer 31 transmit differential signals, the return signal of the first signal trace 311 can flow through the first ground trace 313 closer to the first signal trace 311 from the second shielding layer 34, and then flow into the first shielding layer 33 and the reference layer 32. Similarly, the return signal of the second signal trace 312 can flow through the second ground trace 314 closer to the second signal trace 312 from the second shielding layer 34, and then flow into the first shielding layer 33 and the reference layer 32. Since the first signal trace 311 and the second signal trace 312 are spaced apart between the first ground trace 313 and the second ground trace 314, the noise coupling between the first ground trace 313 and the second ground trace 314 can be reduced.

[0109] As described above, by respectively arranging the first shielding layer 33 and the second shielding layer 34 in different regions of the flexible circuit board 30, such as the first region 301 and the second region 302, the different regions of the flexible circuit board 30 can be shielded from EMI. In addition, since the signal return paths of the first region 301 and the second region 302 are continuous, the signal loss caused by EMI shielding can be reduced. On this basis, in order to further reduce the signal loss caused by EMI shielding, as shown in FIG. 15 (another plan view obtained in the direction C in FIG. 13), the first signal trace 311 can include a first portion 3111, a second portion 3112, and a third portion 3113. The first shielding layer 33 covers the first portion 3111, the second shielding layer 34 covers the third portion 3113, and the second portion 3112 is located in the first gap H1.

[0110] On this basis, as shown in FIG. 16, the first portion 3111 has a first line width L1, the second portion 3112 has a second line width L2, and the third portion 3113 has a third line width L3. Among them, L2>L1, L2>L3. Since the second portion 3112 is located in the first gap H1, no EMI shielding layer is arranged at the position of the second portion 3112. By increasing the line width of the second portion 3112 to the above-mentioned second line width L2, the second line width L2 is greater than the first line width L1 of the first portion 3111 and the third line width L3 of the third portion 3113, so that the second portion 3112 can more easily take the first signal trace 313 on one side of the second portion 3112 as the reference ground (GND). In this way, the impedance fluctuation of each portion in the entire first signal trace 311 can be reduced, achieving the purpose of reducing the signal loss caused by EMI shielding.

[0111] In addition, in the first signal trace 311, the first portion 3111 is covered by the first shielding layer 33 and the reference layer 32 (as shown in FIG. 13), and the first portion 3111 can take the first shielding layer 33 and the reference layer 32 as reference ground, so that the backflow signal flows through the first shielding layer 33 and the reference layer 32. Similarly, in the first signal trace 311, the third portion 3113 is covered by the second shielding layer 34, and the third portion 3113 can take the second shielding layer 34 as reference ground, so that the backflow signal flows through the second shielding layer 34. Based on this, the size of the first line width L1 and the third line width L3 can be determined by the distance between the first portion 3111 and the first shielding layer 33 (the size along the Z direction in FIG. 13), and the distance between the third portion 3113 and the second shielding layer 34 (the size along the Z direction in FIG. 13).

[0112] For example, when the thickness of the second dielectric layer 42 in FIG. 13 is uniform, in the case where the thickness (the size along the Z direction) of the second shielding layer 34 is less than the thickness of the first shielding layer 33, the distance between the first portion 3111 and the first shielding layer 33 shown in FIG. 15 can be greater than the distance between the third portion 3113 and the second shielding layer 34. In this case, the first line width L1 of the first portion 3111 can be greater than the third line width L3 of the third portion 3113, so that the first portion 3111 is more likely to take the first shielding layer 33 as reference ground, thereby reducing the impedance fluctuation of each portion in the entire first signal trace 311, and achieving the purpose of reducing signal loss caused by EMI shielding. For example, by adjusting the first line width L1, the second line width L2, and the third line width L3, the impedance variation rate ΔZ of the first signal trace 311 can satisfy the range of -10%≤ΔZ≤+10%. In addition, the setting mode of the second signal trace 312 in FIG. 15 is the same as that of the first signal trace 311, and details are not repeated here.

[0113] FIGS. 14, 15, and 16 are examples taking the signal layer 31 including the first signal trace 311 and the second signal trace 312, and the first ground trace 313 and the second ground trace 314 located on both sides of the first signal trace 311 and the second signal trace 312 as examples. In other embodiments of the present application, the signal layer 31 can not be used to transmit differential signals, at this time, one signal channel 300 (as shown in FIG. 7) of the signal layer 31 can include one signal trace, for example, the first signal trace 311 shown in FIG. 17. At this time, the signal layer 31 can further include the first ground trace 313 arranged apart from the first signal trace 311. The electrical connection mode of the first ground trace 313 with the second shielding layer 34, the first shielding layer 33, and the reference layer 32 (as shown in FIG. 13), and the setting mode of the backflow path of the backflow signal flowing through the first ground trace 313 are described above, and details are not repeated here.

[0114] In addition, the above is described by way of example with the flexible circuit board 30 having one second shielding layer 34. In other embodiments of the present application, in order to improve the EMI shielding effect of the second region 302 of the flexible circuit board 30, the flexible circuit board 30 can include two second shielding layers in the second region 302, namely a second upper shielding layer 341 and a second lower shielding layer 342 as shown in FIG. 18 (which is another cross-sectional view taken along the dashed line A3-A4 in FIG. 3). The signal layer 31 can be located between the second upper shielding layer 341 and the second lower shielding layer 342.

[0115] Similarly, as shown in FIG. 18, the second lower shielding layer 342 can be electrically connected to the ground trace (for example, the first ground trace 313) in the signal layer 31 through the via hole 431 formed in the third dielectric layer 43, so that the backflow signal on the second lower shielding layer 342 flows back to the first shielding layer 33 and the reference layer 32 in the first region 301 through the ground trace. In this way, the part of the signal layer 31 in the second region 302 is covered by the second upper shielding layer 341 and the second lower shielding layer 342 on the top and bottom respectively, so that the EMI shielding effect can be improved. Moreover, the backflow signal on the second upper shielding layer 341 and the second lower shielding layer 342 can flow back to the first shielding layer 33 and the reference layer 32 in the first region 301, so that the backflow paths of the second region 302 and the first region 301 of the flexible circuit board 30 are continuous, thereby reducing the signal loss caused by EMI shielding and achieving the purpose of alleviating the contradiction between EMI shielding and signal loss.

[0116] As described above, the second shielding layer (for example, the second upper shielding layer 341 and the second lower shielding layer 342) has a higher bending resistance than the first shielding layer 33. Therefore, when the flexible circuit board 30 is applied to a foldable electronic device, the second region 302 of the flexible circuit board 30 having the second shielding layer (for example, the second upper shielding layer 341 and the second lower shielding layer 342) can be the region of the flexible circuit board that is dynamically bent.

[0117] As shown in FIG. 19, the first housing 11 in the electronic device 01 can rotate relative to the second housing 12. In the flexible circuit board 30, the first region 301 provided with the first shielding layer 33 can be fixedly connected with and electrically connected to the first circuit board 101 on the first housing 11. In addition, in the flexible circuit board 30, the second region 302 provided with the second shielding layer 34 can span the first housing 11 and the second housing 12, so that the second shielding layer 34 can serve as a region where the flexible circuit board is dynamically bent, thereby ensuring that the electronic device has good bending resistance during folding, and reducing the probability of failure of the function of the flexible circuit board 30. In addition, as shown in FIG. 19, the end of the second region 302 of the flexible circuit board 30 away from the first region 301 can be fixedly connected with and electrically connected to the second circuit board 102 on the second housing 12. In this way, the circuit boards on different housings can be electrically connected through the flexible circuit board 30.

[0118] The above is an example of the flexible circuit board 30 having one second region 302 and one first region 301. In other embodiments of the present application, as shown in FIG. 20, the flexible circuit board 30 can include one second region 302 and two first regions. The two first regions can be first region 301a and first region 301b, respectively. The second region 302 can be located between the first region 301a and the first region 301b. As described above, the first circuit board 101 is arranged on the first housing 11 so that the first circuit board 101 can be connected with the first housing 11. Moreover, the first circuit board 101 is electrically connected with one of the two first regions, i.e., the first region 301a. For example, the first circuit board 101 can be electrically connected with the first region 301a through a BTB connector, and the first circuit board 101 is connected with the first housing 11, so the first region 301a can be relatively fixed in position with the first housing 11. In addition, the second circuit board 102 is arranged on the second housing 12 so that the second circuit board 102 can be connected with the second housing 12. Moreover, the second circuit board 102 is electrically connected with the other of the two first regions, i.e., the first region 301b. For example, the second circuit board 102 can be electrically connected with the first region 301b through a BTB connector, and the second circuit board 102 is connected with the second housing 12, so the first region 301b can be relatively fixed in position with the second housing 12. In this case, in some embodiments of the present application, as shown in FIG. 21 (another cross-sectional view taken along the dashed line A1-A2 in FIG. 2), since the first region 301a of the flexible circuit board is relatively fixed in position with the first housing 11, and the first region 301b of the flexible circuit board is relatively fixed in position with the second housing 12, in the case of rotational connection between the first housing 11 and the second housing 12, the first region 301a and the first region 301b do not undergo dynamic bending, thereby ensuring the reliability of the electrical connection between the flexible circuit board and the first circuit board 101 and the second circuit board 102.

[0119] Alternatively, in other embodiments of the present application, as shown in FIG. 22, the electronic device 01 can further include a hinge mechanism 20. The hinge mechanism 20 can be located between the first housing 11 and the second housing 12, and the first housing 11 and the second housing 12 are rotationally connected with the hinge mechanism 20. In addition, the first circuit board 101 can be electrically connected with the first region 301a. The second circuit board 102 can be electrically connected with the first region 301b.

[0120] For example, as shown in FIG. 22, the first housing 11 can include a first rear shell 1101 and a first middle frame 1102 connected with each other. The first circuit board 101 is connected with the first middle frame 1102, so that the first circuit board 101 and the first area 301a are relatively fixed in position with the first housing 11. Similarly, the second housing 12 can include a second rear shell 1201 and a second middle frame 1202 connected with each other. The second circuit board 102 is connected with the second middle frame 1202, so that the second circuit board 102 and the first area 301b are relatively fixed in position with the second housing 12.

[0121] In addition, as shown in FIG. 22, any one of the first rear shell 1101 and the second rear shell 1201 can be rotatably connected or slidably connected with the rotation shaft mechanism 20, so that the first housing 11 and the second housing 12 are respectively rotatably connected with the rotation shaft mechanism 20. The part of the flexible circuit board 30 located in the second area 302 can pass through the rotation shaft mechanism 20, so that the second area 302 with the second shielding layer 34 (as shown in FIG. 20) can be located in the area where the flexible circuit board 30 is dynamically bent.

[0122] The above is an example of partitioning the flexible circuit board 30 and providing different EMI shielding layers in different areas of the flexible circuit board 30 to achieve the purpose of EMI shielding. In other embodiments of the present application, on the basis of partitioning the flexible circuit board 30, other components in the electronic device with the flexible circuit board 30 can also be used to shield the part of the flexible circuit board 30, which will be described in detail below.

[0123] For example, as shown in FIG. 23, some embodiments of the present application provide an electronic device 01, which can include a first housing 11, a second housing 12, a first circuit board 101, a second circuit board 102, a rotation shaft mechanism 20 and a flexible circuit board 30. In the case where the first housing 11 includes a first rear shell 1101 and a first middle frame 1102, and the second housing 12 includes a second rear shell 1201 and a second middle frame 1202, the first circuit board 101 is connected with the first housing 11, and the second circuit board 102 is connected with the second housing 12, which are the same as described above, and will not be described here again. In addition, the first housing 11 and the second housing 12 are respectively rotatably connected with the rotation shaft mechanism 20, which is the same as described above, and will not be described here again.

[0124] On this basis, as shown in FIG. 23, the rotating shaft mechanism 20 can include a first metal shaft cover 201 and a second metal shaft cover 202 arranged oppositely. The first metal shaft cover 201 and the second metal shaft cover 202 form an accommodating cavity 200 therebetween. In addition, the flexible circuit board 30 can have a third region 303, a fourth region 304, and a fifth region 305. The third region 303 can be located between the fourth region 304 and the fifth region 305. For example, the portion of the flexible circuit board 30 located at the fourth region 304 can be electrically connected to the first circuit board 101 and connected to the first housing 11 through the first circuit board 101 arranged on the first housing 11. The portion of the flexible circuit board 30 located at the fifth region 305 can be electrically connected to the second circuit board 102 and connected to the second housing 12 through the second circuit board 102 arranged on the second housing 12.

[0125] In addition, as shown in FIG. 23, the flexible circuit board 30 can include a signal layer 31, a reference layer 32, and a third shielding layer 50. The signal layer 31 can be located at the third region 303, the fourth region 304, and the fifth region 305. The reference layer 32 can be located at the fourth region 304 and the fifth region 305, and the reference layer 32 can be arranged in a stack with the signal layer 31. In addition, the third shielding layer 50 can be located at the fourth region 304 and the fifth region 305, and the third shielding layer 50 can be arranged on the side of the signal layer 31 away from the reference layer 32. At least the portion of the flexible circuit board 30 located at the third region 303 passes through the accommodating cavity 200, so that the first metal shaft cover 201 or the second metal shaft cover 202 can cover at least the portion of the flexible circuit board 30 located at the third region 303. In addition, at least one of the first metal shaft cover 201 or the second metal shaft cover 202 can be electrically connected to the reference layer 32.

[0126] For example, the third shielding layer 50 can be a metal layer with high electrical conductivity and high thickness. At this time, the third shielding layer 50 and the first shielding layer 33 have the same material and the same conduction mode, which will not be described here again. Alternatively, for another example, the third shielding layer 50 has low electrical conductivity, for example, the electrical conductivity is less than or equal to 5 x 10 7 S / m. Based on this, in some embodiments, the third shielding layer 50 can be a metal foil with thin thickness, or a structure composed of conductive powder or metal particles and dielectric material. At this time, the third shielding layer 50 can have the same material and the same conduction mode as the second shielding layer 34, which will not be described here again. For the convenience of description below, the third shielding layer 50 is taken as an example of a metal layer with high thickness and high electrical conductivity.

[0127] As shown in FIG. 23, the signal layer 31 in the fourth area 304 and the part of the signal layer 31 in the fifth area 305 are both covered by the third shielding layer 50. The third shielding layer 50 in the fourth area 304 can shield the signal lines in the signal layer 31 in the fourth area 304 from EMI. Similarly, the third shielding layer 50 in the fifth area 305 can shield the signal lines in the signal layer 31 in the fifth area 305 from EMI.

[0128] In addition, the part of the signal layer 31 in the third area 303 passes through the accommodating cavity 200 formed between the first metal shaft cover 201 and the second metal shaft cover 202. At least one of the first metal shaft cover 201 or the second metal shaft cover 202 can be electrically connected to the reference layer 32, so that at least one of the first metal shaft cover 201 or the second metal shaft cover 202 is grounded to the reference layer 32. In this case, the shaft cover grounded to the reference layer 32 among the first metal shaft cover 201 or the second metal shaft cover 202 can shield the signal lines in the signal layer 31 in the third area 303 from EMI, so that the third area 303 of the flexible circuit board 30 can be shielded from EMI by the first metal shaft cover 201 or the second metal shaft cover 202 in the electronic device 01. In this way, the third area 303, the fourth area 304 and the fifth area 305 in the flexible circuit board 30 can all be shielded from EMI.

[0129] On this basis, as shown in FIG. 23, since the shaft cover grounded to the reference layer 32 among the first metal shaft cover 201 or the second metal shaft cover 202 can shield the signal lines in the signal layer 31 in the third area 303 from EMI, the part of the flexible circuit board 30 in the third area 303 does not need to be provided with the above-mentioned EMI shielding layer. In this way, on the one hand, since the first shell 11 and the second shell 12 are rotationally connected to the shaft mechanism 20, the part of the flexible circuit board 30 in the third area 303 can serve as the area where the flexible circuit board 30 is dynamically bent. In this case, since the part of the flexible circuit board 30 in the third area 303 does not need to be provided with the above-mentioned EMI shielding layer, the thickness (dimension along the Z direction) of the flexible circuit board 30 in the third area 303 can be reduced, and the bending resistance of the flexible circuit board 30 in the third area 303 can be improved. On the other hand, since the part of the flexible circuit board 30 in the third area 303 does not need to be provided with the above-mentioned EMI shielding layer, the signal loss caused by the EMI shielding can be reduced, and the contradiction between EMI shielding and signal loss can be alleviated.

[0130] The above is an example of the rotation shaft mechanism 20 including the first metal shaft cover 201 and the second metal shaft cover 202 arranged oppositely. When the first metal shaft cover 201 and the second metal shaft cover 202 are both electrically connected to the reference layer 32, the upper and lower parts of the third region 303 of the flexible circuit board 30 are covered with the first metal shaft cover 201 and the second metal shaft cover 202, respectively, which are grounded, thereby improving the EMI shielding effect. Alternatively, in other embodiments of the present application, the rotation shaft mechanism 20 can have only one of the first metal shaft cover 201 or the second metal shaft cover 202, which is grounded in the same manner and has the same technical effect as described above, which will not be described herein again. For the convenience of description, the following is an example of the rotation shaft mechanism 20 including the first metal shaft cover 201 and the second metal shaft cover 202, and at least one of the first metal shaft cover 201 or the second metal shaft cover 202 being electrically connected to the reference layer 32.

[0131] As described above, in FIG. 23, at least one of the first metal shaft cover 201 or the second metal shaft cover 202 can be electrically connected to the reference layer 32. The following describes the manner in which the first metal shaft cover 201 or the second metal shaft cover 202 is electrically connected to the reference layer 32. In some embodiments of the present application, as shown in FIG. 24 (which is a top view in the direction D in FIG. 23), the signal layer 31 of the flexible circuit board 30 can include a third signal trace 315, a fourth signal trace 316, a third ground trace 317, and a fourth ground trace 318. The third signal trace 315 and the fourth signal trace 316 are arranged at intervals, and can be located between the third ground trace 317 and the fourth ground trace 318.

[0132] In this case, the signal channel formed by the third signal trace 315 and the fourth signal trace 316 can be used to transmit differential signals. The third ground trace 317 and the fourth ground trace 318 can be electrically connected to the reference layer 32 shown in FIG. 23 through the via hole provided on the dielectric layer, so as to achieve the grounding of the third ground trace 317 and the fourth ground trace 318. The manner of providing the via hole on the dielectric layer is as described above, which will not be described herein again. In addition, in order to improve the EMI shielding effect of the third shielding layer 50, the third ground trace 317 and the fourth ground trace 318 can also be electrically connected to the third shielding layer 50 through the conductive adhesive, so that the third shielding layer 50 is grounded to the reference layer 32 through the third ground trace 317 and the fourth ground trace 318. The manner of electrically connecting the third shielding layer 50 to the ground trace through the conductive adhesive is as described above, which will not be described herein again.

[0133] Based on this, at least one of the first metal shaft cover 201 or the second metal shaft cover 202 can be electrically connected with the third ground trace 317 and the fourth ground trace 318. Since the third ground trace 317 and the fourth ground trace 318 are electrically connected with the reference layer 32 and the third shielding layer 50, the shaft cover, which is electrically connected with the third ground trace 317 and the fourth ground trace 318, in the first metal shaft cover 201 or the second metal shaft cover 202 can be electrically connected with the reference layer 32, so as to realize the grounding of the shaft cover as described above.

[0134] In some embodiments, when the first metal shaft cover 201 and the second metal shaft cover 202 shown in FIG. 23 are both electrically connected with the reference layer, the signal layer 31 covers the first metal shaft cover 201 and the second metal shaft cover 202 respectively on the upper and lower surfaces of the part of the third region 303, so as to improve the effect of EMI shielding.

[0135] On this basis, as shown in FIG. 24, the third signal trace 315 can include a fourth part 3114 and a fifth part 3115. The fourth part 3114 can be located in the fourth region 304, so that the third shielding layer 50 (as shown in FIG. 23) in the fourth region 304 can cover the fourth part 3114 of the third signal trace 315. In addition, the fifth part 3115 of the third signal trace 315 can pass through the accommodating cavity 200 shown in FIG. 23, that is, the fifth part 3115 can be covered by the first metal shaft cover 201 and the second metal shaft cover 202. In addition, as shown in FIG. 25, the fourth part 3114 can have a fourth line width L4, and the fifth part 3115 can have a fifth line width L5; L5>L4.

[0136] As described above, the fifth part 3115 of the third signal trace 315 passes through the accommodating cavity 200 shown in FIG. 23, and the part of the flexible circuit board 30 passing through the accommodating cavity 200 is not provided with the EMI shielding layer. Therefore, by increasing the line width of the fifth part 3115 to the fifth line width L5 described above, the fifth line width L5 is greater than the fourth line width L4 of the fourth part 3114, so that the fifth part 3115 can more easily take the third signal trace 315 located on one side of the fifth part 3115 as a reference ground (GND). In this way, the impedance fluctuation of each part in the entire third signal trace 315 can be reduced, so as to reduce the signal loss caused by EMI shielding. The fourth signal trace 316 is set in the same way as described above, and will not be described here.

[0137] On this basis, in order to make the first metal shaft cover 201 electrically connected with the third ground trace 317 and the fourth ground trace 318, as shown in FIG. 26, the first metal shaft cover 201 can include a first shaft cover body 2011, a first metal pressing sheet 2012 and a second metal pressing sheet 2013. The first metal pressing sheet 2012 can be located on the side of the first shaft cover body 2011 facing the first circuit board 101, the first metal pressing sheet 2012 is connected with the first shaft cover body 2011, and the first metal pressing sheet 2012 is electrically connected with the third ground trace 317 and the fourth ground trace 318 (as shown in FIG. 24). In addition, the second metal pressing sheet 2013 is located on the side of the first shaft cover body 2011 facing the second circuit board 102, the second metal pressing sheet 2013 is connected with the first shaft cover body 2011, and the second metal pressing sheet 2013 is electrically connected with the third ground trace 317 and the fourth ground trace 318.

[0138] The first shaft cover body 2011 can be a metal shaft cover, when the first shaft cover body 2011 is connected with the first metal pressing sheet 2012 and the second metal pressing sheet 2013 located on both sides of the first shaft cover body 2011, the first shaft cover body 2011, the first metal pressing sheet 2012 and the second metal pressing sheet 2013 can be electrically connected with each other. At this time, when the first metal pressing sheet 2012 and the second metal pressing sheet 2013 are electrically connected with the third ground trace 317 and the fourth ground trace 318, the entire first metal shaft cover 201 can be electrically connected with the third ground trace 317 and the fourth ground trace 318. In this case, the first metal pressing sheet 2012 and the second metal pressing sheet 2013 can be prepared separately, and then the first metal pressing sheet 2012 and the second metal pressing sheet 2013 are assembled with the first shaft cover body 2011, that is, the first metal shaft cover 201 can be obtained, without changing the preparation process of the first shaft cover body 2011, thereby simplifying the manufacturing process of the first metal shaft cover 201. In addition, the structure of the second metal shaft cover 202 is the same, and will not be described here. For example, the cross-sectional shape of the first metal pressing sheet 2012 and the second metal pressing sheet 2013 in the Z direction can be L-shaped.

[0139] On this basis, as shown in FIG. 26, the electronic device 01 can further include a third conductive adhesive 53 and a fourth conductive adhesive 54. The third conductive adhesive 53 can be located between the first metal pressing sheet 2012 and the third ground trace 317 or the fourth ground trace 318 (as shown in FIG. 24) in the signal layer 31. The third conductive adhesive 53 can be connected with the first metal pressing sheet 2012 and the third ground trace 317, so that the first metal pressing sheet 2012 is electrically connected with the third ground trace 317 (or the fourth ground trace 318) through the third conductive adhesive 53. For example, a through hole can be formed in the part of the flexible circuit board 30 located in the fourth area 304, and the bottom of the through hole can be exposed to the third ground trace 317 (or the fourth ground trace 318). The third conductive adhesive 53 described above can be located in the through hole.

[0140] Similarly, the fourth conductive adhesive 54 can be located between the second metal pressing sheet 2013 and the third ground trace 317 or the fourth ground trace 318 (as shown in FIG. 24) in the signal layer 31, and the fourth conductive adhesive 54 can be connected with the second metal pressing sheet 2013 and the third ground trace 317 (or the fourth ground trace 318). For example, a through hole can be formed in the part of the flexible circuit board 30 located in the fifth area 305, and the bottom of the through hole can be exposed to the third ground trace 317 (or the fourth ground trace 318). The fourth conductive adhesive 54 described above can be located in the through hole.

[0141] The above is an example in which the signal layer 31 includes the third signal trace 315, the fourth signal trace 316, the third ground trace 317, and the fourth ground trace 318 shown in FIG. 24. In other embodiments of the present application, the signal layer 31 can not be used to transmit differential signals. In this case, one signal channel 300 (as shown in FIG. 7) of the signal layer 31 can include one signal trace, for example, the third signal trace 315. In this case, the signal layer 31 can further include a third ground trace 317 arranged apart from the third signal trace 315. The third ground trace 317 is electrically connected with at least one of the first metal shaft cover 201 and the second metal shaft cover 202 in the manner described above, and will not be described again here.

[0142] In addition, FIG. 26 is an example of the flexible circuit board 30 in which the third region 303, which is a dynamic bending region, is adjacent to the fourth region 304 and the fifth region 305, which are non-bending regions, on both sides. For example, the side on which the third shielding layer 50 is located faces the BTB, and the side on which the reference layer 32 is located faces the first circuit board 101 or the second circuit board 102. In this case, as shown in FIG. 27 (which is a cross-sectional view along the direction E in FIG. 26), the portion of the flexible circuit board 30 that extends beyond the first metal shaft cover 201 is electrically connected to the BTB, and the distance (dimension in the X direction) between the BTB and the first metal shaft cover 201 is short. Therefore, the dynamic bending region of the flexible circuit board 30 is substantially located in the region covered by the first metal shaft cover 201 (i.e., the third region 303 shown in FIG. 26).

[0143] For example, the side on which the third shielding layer 50 is located faces the BTB, and the side on which the reference layer 32 is located faces the first circuit board 101 or the second circuit board 102. Alternatively, for another example, the side on which the third shielding layer 50 is located can face the first circuit board 101 or the second circuit board 102, and the side on which the reference layer 32 is located can face the BTB.

[0144] In some embodiments of the present application, as shown in FIG. 28, the flexible circuit board 30 can also have a sixth region 306 and a seventh region 307. The sixth region 306 can be located between the third region 303 and the fourth region 304, and the seventh region 307 can be located between the third region 303 and the fifth region 305.

[0145] In this case, in order to improve the bending resistance of the flexible circuit board 30, as shown in FIG. 28, the signal layer 31 can also be located in the sixth region 306 and the seventh region 307. In addition, the flexible circuit board 30 can further include a fourth shielding layer 344 and a fifth shielding layer 345. The fourth shielding layer 344 can be located in the sixth region 306, and the fourth shielding layer 344 can be stacked with the signal layer 31. The fifth shielding layer 345 is located in the seventh region 307, and the fifth shielding layer 345 is stacked with the signal layer 31. The electrical conductivity of the third shielding layer 50 can be greater than that of at least one of the fourth shielding layer 344 or the fifth shielding layer 345. At least one of the fourth shielding layer 344 or the fifth shielding layer 345 can be a metal foil with a relatively small thickness, or a structure in which conductive powder or metal particles are compounded with a dielectric material. At this time, at least one of the fourth shielding layer 344 or the fifth shielding layer 345 can be the same as the material and the conductive method of the second shielding layer 34 described above, and will not be described again here.

[0146] The shielding effects of the fourth shielding layer 344 and the fifth shielding layer 345 are the same as described above, and will not be repeated here. In addition, compared with the third shielding layer 50, the fourth shielding layer 344 and the fifth shielding layer 345 have better bending resistance. In this case, when the distance between the BTB and the first metal shaft cover 201 is relatively long, the portions of the flexible circuit board 30 shown in FIG. 29 (which is a top view obtained in the direction of F in FIG. 28) located in the sixth region 306 and the seventh region 307, and covered by the first metal shaft cover 201, can all be used as dynamic bending regions, thereby improving the bending resistance of the entire flexible circuit board 30.

[0147] In other embodiments, another shielding layer located away from the fourth shielding layer 344 can also be provided in the sixth region 306, and the material and conductive manner of the shielding layer can be the same as those of the fourth shielding layer 344. Similarly, another shielding layer located away from the fifth shielding layer 345 can also be provided in the seventh region 307, and the material and conductive manner of the shielding layer can be the same as those of the fifth shielding layer 345.

[0148] On this basis, in order to reduce the signal loss caused by the EMI shielding effect of the fourth shielding layer 344 and the fifth shielding layer 345, as shown in FIG. 30 (which is another top view obtained in the direction of F in FIG. 28), the signal layer 31 can further include a fifth ground trace 319 and a sixth ground trace 320. The first end c1 of the fifth ground trace 319 is located in the fourth region 304, and the first end c1 of the fifth ground trace 319 can be electrically connected to the third shielding layer 50 and the reference layer 32 (as shown in FIG. 28) in the fourth region 304. The second end c2 of the fifth ground trace 319 is located in the sixth region 306, and the second end c2 of the fifth ground trace 319 can be electrically connected to the fourth shielding layer 344. The technical effects of electrically connecting the third shielding layer 50, the reference layer 32, and the fourth shielding layer 344 by the fifth ground trace 319 and reducing the signal loss of the flexible circuit board 30 are the same as described above, and will not be repeated here.

[0149] In addition, the first end d1 of the sixth ground trace 320 is located in the fifth region 305, and the first end d1 of the sixth ground trace 320 can be electrically connected to the third shielding layer 50 and the reference layer 32 (as shown in FIG. 28) in the fifth region 305. The second end d2 of the sixth ground trace 320 is located in the seventh region 307, and the second end d2 of the sixth ground trace 320 can be electrically connected to the fifth shielding layer 345. The technical effects of electrically connecting the third shielding layer 50, the reference layer 32, and the fifth shielding layer 345 by the sixth ground trace 320 and reducing the signal loss of the flexible circuit board 30 are the same as described above, and will not be repeated here.

[0150] The above is an example of the third shielding layer 50 being a metal layer with a relatively large thickness and a relatively high conductivity in FIG. 27 or FIG. 28. In other embodiments of the present application, the third shielding layer 50 in FIG. 27 or FIG. 28 can be a metal foil with a relatively low conductivity and a relatively small thickness, or the third shielding layer 50 can be a structure in which conductive powder or metal particles are compounded with a dielectric material. Based on this, since a metal layer with a relatively large thickness does not need to be provided as a shielding layer in the flexible circuit board 30, the flexible circuit board 30 can have good bending resistance.

[0151] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any change or replacement within the technical scope disclosed in the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A flexible circuit board, characterized in that, The flexible circuit board has a first region and a second region; the flexible circuit board includes: A signal layer is located in the first region and the second region; the signal layer includes a first ground trace; A reference layer is located in the first region and is stacked on top of the signal layer; A first shielding layer is located in the first region and is stacked on the side of the signal layer opposite to the reference layer; The second shielding layer is located in the second region and is stacked on top of the signal layer; Wherein, the first end of the first grounding trace is located in the first region and is electrically connected to the first shielding layer and the reference layer; the second end of the first grounding trace is located in the second region and is electrically connected to the second shielding layer.

2. The flexible circuit board according to claim 1, characterized in that, The flexible circuit board also includes: A second dielectric layer is located between the first shielding layer and the signal layer, and the second dielectric layer is also located between the second shielding layer and the signal layer; a first opening and a second opening are formed on the second dielectric layer; the first opening exposes a first end of the first grounding trace, and the second opening exposes a second end of the first grounding trace; The first conductive adhesive is located inside the first opening, and the first conductive adhesive is connected to the first end of the first grounding trace and the first shielding layer. The second conductive adhesive is located inside the second opening, and the second conductive adhesive is connected to the second end of the first grounding trace and the second shielding layer.

3. The flexible circuit board according to claim 2, characterized in that, The flexible circuit board also includes: A third dielectric layer is located between the signal layer and the reference layer; A via is provided, penetrating the third dielectric layer, with its two ends electrically connected to the first end of the first ground trace and the reference layer, respectively.

4. The flexible circuit board according to any one of claims 1-3, characterized in that, The flexible circuit board includes two second shielding layers, namely a second upper shielding layer and a second lower shielding layer; the signal layer is located between the second upper shielding layer and the second lower shielding layer.

5. The flexible circuit board according to any one of claims 1-4, characterized in that, There is a first gap H1 between the first shielding layer and the second shielding layer, where 0.2mm≤H1≤6mm.

6. The flexible circuit board according to claim 5, characterized in that, The signal layer also includes: First signal routing; The second signal trace is spaced apart from the first signal trace; The second grounding trace; the first signal trace and the second signal trace are located between the first grounding trace and the second grounding trace; the first end of the second grounding trace is located in the first region and is electrically connected to the first shielding layer and the reference layer; the second end of the second grounding trace is located in the second region and is electrically connected to the second shielding layer.

7. The flexible circuit board according to claim 6, characterized in that, The first signal trace includes a first part, a second part, and a third part; the first shielding layer covers the first part, and the second shielding layer covers the third part; the second part is located within the first gap H1; The first part has a first line width L1, the second part has a second line width L2, and the third part has a third line width L3; L2 > L1 and L2 > L3.

8. The flexible circuit board according to any one of claims 1-7, characterized in that, The conductivity of the first shielding layer is greater than that of the second shielding layer.

9. The flexible circuit board according to claim 8, characterized in that, Both the first shielding layer and the second shielding layer are metal layers; the thickness of the first shielding layer is greater than the thickness of the second shielding layer.

10. The flexible circuit board according to claim 8, characterized in that, The first shielding layer is a metal layer; The second shielding layer is a dielectric layer doped with metal particles.

11. An electronic device, characterized in that, include: Circuit board; The flexible circuit board as described in any one of claims 1-10, wherein the flexible circuit board is electrically connected to the circuit board.

12. The electronic device according to claim 11, characterized in that, The flexible circuit board includes two first regions; a second region of the flexible circuit board is located between the two first regions; the electronic device includes two circuit boards, namely a first circuit board and a second circuit board; the electronic device also includes a first housing and a second housing rotatably connected. The first circuit board is disposed on the first housing; the first circuit board is electrically connected to one of the two first regions; The second circuit board is disposed on the second housing; the second circuit board is electrically connected to another of the two first regions.

13. The electronic device according to claim 12, characterized in that, The electronic device also includes: A rotating shaft mechanism is located between the first housing and the second housing, and the first housing and the second housing are rotatably connected to the rotating shaft mechanism respectively; the portion of the flexible circuit board located in the second region passes through the rotating shaft mechanism.

14. An electronic device, characterized in that, include: First shell; Second shell; A first circuit board is connected to the first housing. The second circuit board is connected to the second housing. A rotating shaft mechanism is located between the first housing and the second housing, and the first housing and the second housing are rotatably connected to the rotating shaft mechanism; the rotating shaft mechanism includes a first metal shaft cover; A flexible circuit board having a third region, a fourth region, and a fifth region, wherein the third region is located between the fourth region and the fifth region; The fourth region is connected to the first housing, and the fifth region is connected to the second housing; the flexible circuit board includes: a signal layer, a reference layer, and a third shielding layer; the signal layer is located in the third region, the fourth region, and the fifth region; the reference layer is located in the fourth region and the fifth region, and is stacked with the signal layer; the third shielding layer is located in the fourth region and the fifth region, and is stacked on the side of the signal layer opposite to the reference layer; The first circuit board is electrically connected to the fourth region, and the second circuit board is electrically connected to the fifth region; the first metal cap covers at least the portion of the flexible circuit board located in the third region; the first metal cap is electrically connected to the reference layer.

15. The electronic device according to claim 14, characterized in that, The signal layer further includes a third signal trace, which includes a fourth part and a fifth part; the third shielding layer covers the fourth part, and the first metal shaft cover covers the fifth part; The fourth part has a fourth line width L4, and the fifth part has a fifth line width L5; L5 > L4.

16. The electronic device according to claim 15, characterized in that, The third grounding trace is electrically connected to the reference layer and the third shielding layer; The first metal shaft cover is also electrically connected to the third grounding trace.

17. The electronic device according to claim 16, characterized in that, The first metal shaft cover includes: First shaft cover body; The first metal pressure plate is located on the side of the first shaft cover body facing the first circuit board. The first metal pressure plate is connected to the first shaft cover body and is electrically connected to the third grounding trace. The second metal pressure plate is located on the side of the first shaft cover body facing the second circuit board. The second metal pressure plate is connected to the first shaft cover body and electrically connected to the third grounding trace.

18. The electronic device according to claim 17, characterized in that, The electronic device also includes: The third conductive adhesive is located between the first metal plate and the third grounding trace, and the third conductive adhesive is connected to the first metal plate and the third grounding trace; The fourth conductive adhesive is located between the second metal plate and the third grounding trace, and the fourth conductive adhesive is connected to the second metal plate and the third grounding trace.

19. The electronic device according to any one of claims 15-18, characterized in that, The signal layer further includes a fourth signal trace and a fourth ground trace; the third signal trace and the fourth signal trace are spaced apart, and the third signal trace and the fourth signal trace are located between the third ground trace and the fourth ground trace; The fourth grounding trace is electrically connected to the reference layer and the third shielding layer, and the first metal shaft cover is also electrically connected to the fourth grounding trace.

20. The electronic device according to any one of claims 14-19, characterized in that, The flexible circuit board further has a sixth region and a seventh region; the sixth region is located between the third region and the fourth region, and the seventh region is located between the third region and the fifth region; the signal layer is also located in the sixth region and the seventh region; The flexible circuit board also includes: The fourth shielding layer is located in the sixth region and is stacked on top of the signal layer; The fifth shielding layer is located in the seventh region and is stacked on top of the signal layer; The signal layer includes: The fifth grounding trace has its first end located in the fourth region and electrically connected to the third shielding layer and the reference layer within the fourth region; the second end of the fifth grounding trace is located in the sixth region and electrically connected to the fourth shielding layer. The sixth grounding trace has its first end located in the fifth region and electrically connected to the third shielding layer and the reference layer within the fifth region; the second end of the sixth grounding trace is located in the seventh region and electrically connected to the fifth shielding layer.

21. The electronic device according to any one of claims 14-20, characterized in that, The rotating shaft mechanism further includes a second metal shaft cover, which is disposed opposite to the first metal shaft cover; the second metal shaft cover is electrically connected to the reference layer.

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