Flexible circuit board and foldable electronic equipment

Abstract

The invention provides a flexible circuit board and foldable electronic equipment. The flexible circuit board is provided with a bendable area, the flexible circuit board can be bent from the bendable area, and the flexible circuit board comprises a first sub-circuit board, a bonding layer, a second sub-circuit board and an electromagnetic shielding film. The bonding layer is arranged on one side of the first sub-circuit board, and the bonding layer avoids the bendable area; the second sub-circuit board is arranged on one side, deviating from the first sub-circuit board, of the bonding layer, and the second sub-circuit board is provided with a signal transmission line; the electromagnetic shielding film is arranged on the side, away from the first sub-circuit board, of the second sub-circuit board, and the electromagnetic shielding film serves as at least part of the reference surface of the impedance of the signal transmission line. The flexible circuit board provided by the embodiment of the invention is relatively good in reliability and relatively long in bending life, and the impedance change of the signal transmission line is relatively small.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and in particular to a flexible circuit board and a foldable electronic device. Background Art

[0002] With the development of technology and the improvement of people's daily life needs, electronic devices such as mobile phones and PDAs are no longer limited to straight-board designs, but have appeared in folding forms. In other words, foldable electronic devices have emerged. Foldable electronic devices include flexible circuit boards, which are usually arranged corresponding to the bendable parts of the foldable electronic devices. The flexible circuit boards in the related art are prone to breakage and failure when bent, which makes the reliability of the flexible circuit boards low and the lifespan short. Summary of the invention

[0003] In a first aspect, an embodiment of the present application provides a flexible circuit board, wherein the flexible circuit board has a bendable area, the flexible circuit board can be bent from the bendable area, and the flexible circuit board includes:

[0004] a first sub-circuit board;

[0005] An adhesive layer, the adhesive layer is disposed on one side of the first sub-circuit board, and the adhesive layer avoids the bendable area;

[0006] a second sub-circuit board, the second sub-circuit board being disposed on a side of the adhesive layer away from the first sub-circuit board, the second sub-circuit board having a signal transmission line; and

[0007] An electromagnetic shielding film is disposed on a side of the second sub-circuit board facing away from the first sub-circuit board, and the electromagnetic shielding film serves as at least a partial reference surface of the impedance of the signal transmission line.

[0008] In a second aspect, an embodiment of the present application provides a foldable electronic device, the foldable electronic device comprising:

[0009] A first main body, the first main body comprising a first circuit board;

[0010] a second main body portion, the second main body portion comprising a second circuit board;

[0011] a bendable portion, the bendable portion being located between the first main body portion and the second main body portion; and

[0012] As described in the first aspect, the flexible circuit board has one end arranged corresponding to the first main body and electrically connected to the first circuit board, the bendable area of ​​the flexible circuit board is arranged corresponding to the bendable portion, and the other end of the flexible circuit board is arranged corresponding to the second main body and electrically connected to the second circuit board.

[0013] In summary, the flexible circuit board provided in the embodiment of the present application comprises a first sub-circuit board, an adhesive layer and a second circuit board which are sequentially stacked. The flexible circuit board has a bendable area. When the flexible circuit board is bent from the second area, the bending radius of the sub-circuit board located on the outer layer of the flexible circuit board is greater than the bending radius of the sub-circuit board located on the flexible circuit board. Therefore, the sub-circuit board on the outer layer of the flexible circuit board is not easy to break. Further, when the flexible circuit board is bent from the second area, the bending radius of the sub-circuit board located on the inner layer of the flexible circuit board is smaller than the bending radius of the sub-circuit board located on the outer layer of the flexible circuit board. Since the adhesive layer of the flexible circuit board avoids the second area, so that the adjacent two layers of sub-circuit boards form a first gap corresponding to the bendable area, the first gap can release the extrusion force of the sub-circuit board located on the inner layer, so that the sub-circuit board located on the inner layer of the flexible circuit board is not easy to break, thereby improving the reliability and bending life of the flexible circuit board. Wherein, one of the first sub-circuit board and the second sub-circuit board is located on the inner layer of the flexible circuit board compared to the other of the first sub-circuit board and the second sub-circuit board.

[0014] Further, in this embodiment, the electromagnetic shielding film is arranged on the side of the second sub-circuit board away from the first sub-circuit board; and in this embodiment, the electromagnetic shielding film serves as at least a partial reference surface of the impedance of the signal transmission line. The electromagnetic shielding film serves as at least a partial reference surface of the signal transmission line, so when the flexible circuit board is bent, or when the flexible circuit board is used in a foldable electronic device: the distance from the signal transmission line to the electromagnetic shielding film remains unchanged, or the distance from the signal transmission line to the electromagnetic shielding film changes slightly; in addition, the dielectric constant of the film layer between the signal transmission line and the electromagnetic shielding film will not change, or the probability of change is small; therefore, in this embodiment, the electromagnetic shielding film serves as at least a partial reference surface of the impedance of the signal transmission line, which can make the impedance of the signal transmission line of the flexible circuit board change less or even not change, thereby making the impedance of the signal transmission line consistent with the actual required impedance. When the flexible circuit board provided in the embodiment of the present application is used to transmit signals, the signal sent from the source end connected to one end of the flexible circuit board and the signal transmitted to the terminal connected to the other end of the flexible circuit board via the signal transmission line of the flexible circuit board are more matched. When the flexible circuit board is applied to a foldable electronic device, it can be ensured that the performance of the foldable electronic device controlled by the signal transmitted by the flexible circuit board is normal. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the implementation will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A top view of a flexible circuit board provided in one embodiment of the present application;

[0017] Figure 2 For one embodiment Figure 1 A cross-sectional view of the flexible circuit board along line II provided in;

[0018] Figure 3 For one embodiment Figure 2 A detailed identification diagram of the flexible circuit board shown in FIG.

[0019] Figure 4 is a schematic diagram of a flexible circuit board according to a first embodiment of the related art;

[0020] Figure 5 is a schematic diagram of a flexible circuit board according to a second embodiment of the related art;

[0021] Figure 6 for Figure 5 A schematic diagram of a case where the flexible circuit board shown in FIG. is assembled or applied to a foldable electronic device;

[0022] Figure 7 for Figure 5 A schematic diagram of another case where the flexible circuit board shown in is applied to a foldable electronic device;

[0023] Figure 8 for Figure 2 Schematic diagram of thickness of some film layers of the flexible circuit board;

[0024] Fig. 9 A top view of a first conductive layer and a second conductive layer in a flexible circuit board provided in one embodiment;

[0025] Fig.10 for Fig. 9 A schematic diagram of a signal transmission line in a second conductive layer in a flexible circuit board provided in;

[0026] Fig.11 for Fig. 9 A schematic diagram of a first conductive layer in a provided flexible circuit board;

[0027] Fig.12 for Fig. 9 The enlarged schematic diagram of II in the middle;

[0028] Fig.13 For another embodiment Figure 1 A cross-sectional view of the flexible circuit board along line II provided in;

[0029] Fig.14 for Fig.13 A schematic diagram of the thickness of each film layer of the sub-circuit board of the flexible circuit board shown in FIG.

[0030] Fig.15 A schematic diagram of a foldable electronic device in an unfolded state provided by an embodiment of the present application;

[0031] Fig.16 A schematic diagram of a foldable electronic device in a folded state provided by an embodiment of the present application;

[0032] Fig.17 for Fig.15 Schematic diagram of the partial structure of the foldable electronic device shown in. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0035] Reference to "embodiment" or "implementation" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment or implementation may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0036] The embodiment of the present application provides a flexible circuit board 50 and a foldable electronic device 1 including the flexible circuit board 50 . Next, the flexible circuit board 50 and the foldable electronic device 1 including the flexible circuit board 50 provided in the embodiment of the present application are introduced in detail.

[0037] Please also read Figure 1 , Figure 2 and Figure 3 , Figure 1 A top view of a flexible circuit board provided in one embodiment of the present application; Figure 2 For one embodiment Figure 1 A cross-sectional view of the flexible circuit board along line II provided in; Figure 3 For one embodiment Figure 2 Detailed identification schematic diagram of a flexible circuit board shown in . The flexible circuit board 50 has a bendable area (i.e., the second area 500b). The flexible circuit board 50 can be bent from the bendable area, and the flexible circuit board 50 includes a multi-layer sub-circuit board 510 stacked and an adhesive layer 520 located between two adjacent layers of sub-circuit boards 510. Among them, the number Q of sub-circuit boards 510 of the flexible circuit board 50 satisfies: Q ≥ 2, and Q is a positive integer. In the schematic diagram of this embodiment, the flexible circuit board 50 includes two layers of sub-circuit boards 510 stacked as an example, which can be understood that it should not be understood as a limitation on the embodiment of the present application. When the flexible circuit board 50 includes two layers of sub-circuit boards 510, the two layers of sub-circuit boards 510 are named as the first sub-circuit board 510a and the second sub-circuit board 510b respectively. In other words, when the flexible circuit board 50 includes two layers of sub-circuit boards 510, the flexible circuit board 50 includes a first sub-circuit board 510a, an adhesive layer 520, and a second sub-circuit board 510b. In addition, the flexible circuit board 50 also includes an electromagnetic shielding film 540. Next, the flexible circuit board 50 provided in the embodiment of the present application is described in detail. The adhesive layer 520 is arranged on one side of the first sub-circuit board 510a, and the adhesive layer 520 avoids the bendable area. The second sub-circuit board 510b is arranged on the side of the adhesive layer 520 away from the first sub-circuit board 510a, and the second sub-circuit board 510b has a signal transmission line 5121. The electromagnetic shielding film 540 is arranged on the side of the second sub-circuit board 510b away from the first sub-circuit board 510a. In this embodiment, the electromagnetic shielding film 540 serves as at least a partial reference surface of the impedance of the signal transmission line 5121.

[0038] In this embodiment, the flexible circuit board 50 includes a first area 500a, a second area 500b and a third area 500c arranged in sequence. The second area 500b is a bendable area of ​​the flexible circuit board 50. When the flexible circuit board 50 is applied to the foldable electronic device 1, the second area 500b is arranged corresponding to the bendable portion 30 of the foldable electronic device 1.

[0039] In the schematic diagram of this embodiment, when the flexible circuit board 50 includes two sub-circuit boards 510, the first sub-circuit board 510a is the sub-circuit board 510 located at the bottom of the flexible circuit board 50, and the second sub-circuit board 510b is the sub-circuit board 510 located at the top of the flexible circuit board 50. It can be understood that as the placement position of the flexible circuit board 50 is different, the positions of the first sub-circuit board 510a and the second sub-circuit board 510b are also different.

[0040] The adhesive layer 520 is disposed on one side of the first sub-circuit board 510a, and the second sub-circuit board 510b is disposed on the side of the adhesive layer 520 away from the first sub-circuit board 510a; in other words, the first sub-circuit board 510a and the second sub-circuit board 510b are disposed opposite to each other and spaced apart, and the adhesive layer 520 is disposed between the first sub-circuit board 510a and the second sub-circuit board 510b.

[0041] The bonding layer 520 may be, but is not limited to, bonding glue or adhesive. When the bonding layer 520 is bonding glue or adhesive, it is also referred to as Adh glue or Adh glue layer.

[0042] In one embodiment, the adhesive layer 520 includes a first connection portion 521 and a second connection portion 522. The first connection portion 521 is arranged corresponding to the first area 500a, and the first connection portion 521 is used to bond the portion of the first sub-circuit board 510a located in the first area 500a and the portion of the second sub-circuit board 510b located in the first area 500a. The second connection portion 522 is arranged at a distance from the first connection portion 521, and the second connection portion 522 is arranged corresponding to the third area 500c, and the second connection portion 522 is used to bond the portion of the first sub-circuit board 510a located in the third area 500c and the portion of the second sub-circuit board 510b located in the third area 500c. It can be seen that the adhesive layer 520 avoids the bendable area. Therefore, the adhesive layer 520, the first sub-circuit board 510a and the second sub-circuit board 510b in the flexible circuit board 50 cooperate with each other to form a gap corresponding to the bendable area (also called the second area 500b). For the convenience of description, the gap is named the first gap 520a.

[0043] When the bonding layer 520 includes a first connection portion 521 and a second connection portion 522, the first connection portion 521 may be, but not limited to, a bonding glue or an adhesive. The second connection portion 522 may be, but not limited to, a bonding glue or an adhesive. The material of the second connection portion 522 may be the same as that of the first connection portion 521, or the material of the second connection portion 522 may be different from that of the first connection portion 521, and this application does not limit this.

[0044] In the schematic diagram of this embodiment, the number of the signal transmission lines 5121 is two as an example for illustration, which can be understood that it should not be understood as a limitation on the flexible circuit board 50 provided in the embodiment of the present application.

[0045] Since the first gap 520a is provided between the first sub-circuit board 510a and the second sub-circuit board 510b at the bendable area, the adjacent first sub-circuit board 510a and the adjacent second sub-circuit board 510b of the flexible circuit board 50 are not connected together. This structure of the flexible circuit board 50 is also called a delaminated structure.

[0046] In this embodiment, the sub-circuit board 510 includes a base layer 511, a conductive layer 512, a connecting adhesive layer 513 and a coating layer 514 which are stacked in sequence. The thickness d1 of the base layer 511 satisfies: 10 μm ≤ d1 ≤ 18 μm. The thickness d2 of the conductive layer 512 satisfies: 5 μm ≤ d2 ≤ 10 μm. The thickness d3 of the connecting adhesive layer 513 satisfies: 8 μm ≤ d3 ≤ 15 μm, and the thickness of the connecting adhesive layer 513 is greater than the thickness of the conductive layer 512.

[0047] When the multi-layer sub-circuit board 510 includes a first sub-circuit board 510a, the base layer 511 of the first sub-circuit board 510a is also referred to as a first base layer 511a, the conductive layer 512 of the first sub-circuit board 510a is also referred to as a first conductive layer 512a, the connecting adhesive layer 513 of the first sub-circuit board 510a is also referred to as a first connecting adhesive layer 513a, and the coating layer 514 of the first sub-circuit board 510a is also referred to as a first coating layer 514a. The base layer 511, the conductive layer 512, and the connecting adhesive layer 513 of the first sub-circuit board 510a meet the above conditions.

[0048] Correspondingly, when the multi-layer sub-circuit board 510 includes a second sub-circuit board 510b, the base layer 511 of the second sub-circuit board 510b is also referred to as a second base layer 511b, the conductive layer 512 of the second sub-circuit board 510b is also referred to as a second conductive layer 512b, the connecting adhesive layer 513 of the second sub-circuit board 510b is also referred to as a second connecting adhesive layer 513b, and the coating layer 514 of the second sub-circuit board 510b is also referred to as a second coating layer 514b. The base layer 511, the conductive layer 512, and the connecting adhesive layer 513 of the second sub-circuit board 510b meet the above conditions.

[0049] In order to conveniently introduce the beneficial effects of the flexible circuit board 50 provided in the embodiment of the present application, the flexible circuit board 50 in the related art is first introduced. It can be understood that the flexible circuit board 50 in the related art is a solution before the flexible circuit board 50 provided in the embodiment of the present application is improved, and the flexible circuit board 50 in the related art should not be understood as the flexible circuit board 50 in the prior art.

[0050] Next, the flexible circuit board 50 of the first embodiment of the related art is introduced. Figure 4 , Figure 4 Schematic diagram of a flexible circuit board of the first embodiment in the related art. In the first embodiment in the related art, the first gap 520a does not exist in the flexible circuit board 50 at the adjacent first sub-circuit board 510a and the second sub-circuit board 510b corresponding to the second area 500b. In other words, the adhesive layer 520 of the flexible circuit board 50 in the related art is a whole layer structure, that is, the adhesive layer 520 of the flexible circuit board 50 in the related art is arranged corresponding to the first area 500a, the second area 500b, and the third area 500c. Therefore, when the flexible circuit board 50 in the related art is bent from the second area 500b, the bending radius of the sub-circuit board 510 of the flexible circuit board 50 located in the inner layer is smaller than the bending radius of the sub-circuit board 510 of the flexible circuit board 50 located in the outer layer, and the inner sub-circuit board 510 corresponding to the second area 500b is compressed and the pressure has nowhere to be released, which causes the inner sub-circuit board 510 corresponding to the second area 500b to be easily broken and fail. Among them, when the flexible circuit board 50 is bent from the second area 500b, one of the first sub-circuit board 510a and the second sub-circuit board 510b in the flexible circuit board 50 is the sub-circuit board 510 located in the inner layer of the flexible circuit board 50, and the other of the first sub-circuit board 510a and the second sub-circuit board 510b in the flexible circuit board 50 is the sub-circuit board 510 located in the outer layer of the flexible circuit board 50.

[0051] Next, the flexible circuit board 50 of the second embodiment of the related art is introduced. Figure 5 , Figure 5 Schematic diagram of a flexible circuit board of the second embodiment in the related art. The flexible circuit board 50 provided in the second embodiment in the related art has a first gap 520a at the first sub-circuit board 510a and the second sub-circuit board 510b corresponding to the second area 500b. The second sub-circuit board 510b has a signal transmission line 5121. In the flexible circuit board 50 provided in the second embodiment in the related art, the first sub-circuit board 510a of the flexible circuit board 50 includes a first conductive layer 512a, and the second sub-circuit board 510b includes a second conductive layer 512b, wherein the second conductive layer 512b has a signal transmission line 5121, and the first conductive layer 512a is a whole layer of metal sheet. In addition, the flexible circuit board 50 provided in the second embodiment in the related art does not include an electromagnetic shielding film 540. The impedance (also called characteristic impedance) of the signal transmission line 5121 in the flexible circuit board 50 provided in the second embodiment of the related art is designed with the first conductive layer 512a as the reference plane. In the flexible circuit board 50 provided in the second embodiment of the related art, the impedance of the signal transmission line 5121 changes greatly when the flexible circuit board 50 is in a bent state and when the flexible circuit board 50 is in a flattened state. When the impedance (also called characteristic impedance) of the signal transmission line 5121 changes greatly, it will cause reflection of the signal transmitted on the signal transmission line 5121, thereby causing energy loss of the signal transmitted on the signal transmission line 5121. For example, one end of the signal transmission line 5121 is electrically connected to the source end (also called the transmitting end, which can be a circuit board or an electronic device, etc.), and the other end of the signal transmission line 5121 is electrically connected to the terminal (also called the receiving end, which can be a circuit board or an electronic device, etc.). The signal emitted by the source end is transmitted to the terminal via the signal transmission line 5121. When the impedance on the signal transmission line 5121 changes greatly, the signal emitted by the source end and the signal received by the terminal are mismatched, thereby causing the performance of the foldable electronic device 1 to which the flexible circuit board 50 is applied to be abnormal.

[0052] Next, the calculation formula of the characteristic impedance of the signal transmission line 5121 in the flexible circuit board 50 of the second embodiment in the related art is introduced. The calculation formula of the characteristic impedance of the signal transmission line 5121 in the flexible circuit board 50 can be found in the following formula.

[0053]

[0054] In the above formula, Z is the characteristic impedance of the signal transmission line 5121, Er is the dielectric constant of the film layer between the first conductive layer 512a of the first sub-circuit board 510a and the second conductive layer 512b of the second sub-circuit board 510b, H is the distance between the signal transmission line 5121 and the reference plane, W is the width of the signal transmission line 5121, and T is the thickness of the signal transmission line 5121.

[0055] In the related art, the signal transmission line 5121 of the second conductive layer 512b of the second sub-circuit board 510b uses the first conductive layer 512a of the first sub-circuit board 510a as a reference plane. In other words, when the impedance (also called characteristic impedance) of the signal transmission line 5121 of the second conductive layer 512b of the second sub-circuit board 510b is designed, the conductive layer 512 of the first sub-circuit board 510a is used as a reference plane. In the related art, when the impedance (also called characteristic impedance) of the signal transmission line 5121 of the second conductive layer 512b of the second sub-circuit board 510b is designed, using the conductive layer 512 of the first sub-circuit board 510a as a reference plane will cause the impedance of the signal transmission line 5121 to change. Next, the change of the impedance of the signal transmission line 5121 is introduced in two cases.

[0056] In the first case, the distance between the first conductive layer 512a of the first sub-circuit board 510a of the flexible circuit board 50 and the second conductive layer 512b of the second sub-circuit board 510b becomes smaller. Figure 6 , Figure 6 for Figure 5 Schematic diagram of a situation after the flexible circuit board is assembled or applied to a foldable electronic device as shown in FIG.

[0057] Specifically, if the signal transmission line 5121 is designed with a corresponding width (referred to as line width) W and a distance (referred to as line distance) H between the signal transmission line 5121 and the reference plane according to the stacking, then the characteristic impedance of the signal transmission line 5121 is determined when the thickness T of the signal transmission line 5121 is constant. For example, when the signal transmission line 5121 is used to transmit a differential signal, the impedance (also referred to as differential impedance) of the signal transmission line 5121 is 90 ohms (Ω); when the signal transmission line 5121 is used to transmit a single-ended signal, the impedance (also referred to as single-ended impedance) of the signal transmission line 5121 is 50 ohms (Ω). In the first case, the line width W and line distance H of the signal transmission line 5121 are designed and calculated based on the non-bending area of ​​the flexible circuit board 50 and the non-bending area containing the adhesive layer 520. However, in reality, the adhesive layer 520 avoids the bendable area of ​​the flexible circuit board 50, that is, the bendable area of ​​the flexible circuit board 50 does not have the adhesive layer 520. Therefore, in practical applications, after the first sub-circuit board 510a of the flexible circuit board 50 is assembled with the second sub-circuit board 510b, or when the flexible circuit board 50 is applied to the foldable electronic device 1, the first gap 520a between the portion of the first sub-circuit board corresponding to the second area 500b and the portion of the second sub-circuit board 510b corresponding to the second area 500b will be very small, and in some cases, the portion of the first sub-circuit board 510a corresponding to the second area 500b and the portion of the second sub-circuit board 510b corresponding to the second area 500b will be attached together. In the non-bending area (including the first area 500a and the third area 500c) of the flexible circuit board 50 and including the adhesive layer 520, the distance between the first conductive layer 512a of the first sub-circuit board 510a and the second conductive layer 512b of the second sub-circuit board 510b is marked as a spacing H1, and the distance between the first conductive layer 512a of the first sub-circuit board 510a and the second conductive layer 512b of the second sub-circuit board 510b in the bendable area (i.e., the second area 500b) of the flexible circuit board 50 is marked as a spacing H2. In practical applications, after the first sub-circuit board 510a and the second sub-circuit board 510b of the flexible circuit board 50 are assembled or when the flexible circuit board 50 is applied to the foldable electronic device 1, H2 ​

[0058] In the second case, the distance between the first conductive layer 512a of the first sub-circuit board 510a of the flexible circuit board 50 and the second conductive layer 512b of the second sub-circuit board 510b becomes larger. Figure 7 , Figure 7 for Figure 5 Schematic diagram of another case where the flexible circuit board shown in is applied to a foldable electronic device. In the second case, when the flexible circuit board 50 is applied to a foldable electronic device 1, when the foldable electronic device 1 is extended or retracted, or when the hinge in the foldable electronic device 1 slides, the spacing between the first sub-circuit board 510a and the second sub-circuit board 510b corresponding to the second area 500b becomes larger. In other words, the first gap 520a becomes larger. When the first gap 520a becomes larger, air will enter the first gap 520a, and the dielectric constant of the air is less than the dielectric constant of the film layer between the first conductive layer 512a and the second conductive layer 512b. For example, the dielectric constant of the air is 1 or approximately 1, and the dielectric constant of the film layer between the first conductive layer 512a and the second conductive layer 512b is or approximately 3 to 6. It can be seen from the calculation formula of the characteristic impedance of the signal transmission line 5121 in the flexible circuit board 50 introduced above that as the dielectric constant Er decreases, the distance H between the signal transmission line 5121 and the first conductive layer 512a as the reference plane increases, which will cause the impedance Z of the signal transmission line 5121 to increase.

[0059] In summary, in the flexible circuit board 50 provided by the second embodiment of the related art, the signal transmission line 5121 of the second conductive layer 512b of the second sub-circuit board 510b uses the first conductive layer 512a of the first sub-circuit board 510a as a reference plane. In the first case, the impedance Z of the signal transmission line 5121 will be reduced; in the second case, the impedance Z of the signal transmission line 5121 will be increased. It can be seen that in the flexible circuit board 50 provided by the second embodiment of the related art, the signal transmission line 5121 of the second conductive layer 512b of the second sub-circuit board 510b uses the first conductive layer 512a of the first sub-circuit board 510a as a reference plane, which will cause the impedance of the signal transmission line 5121 to be inconsistent with the actual required impedance.

[0060] Next, the flexible circuit board 50 provided in the embodiment of the present application is introduced.

[0061] In the flexible circuit board 50 provided in the embodiment of the present application, when the flexible circuit board 50 is bent from the second area 500b, the bending radius of the sub-circuit boards 510 of each layer of the flexible circuit board 50 is different. Specifically, the bending radius of the sub-circuit board 510 located at the outer layer of the flexible circuit board 50 is greater than the bending radius of the sub-circuit board 510 located at the inner layer of the flexible circuit board 50. Since the bending radius of the sub-circuit board 510 located at the outer layer of the flexible circuit board 50 is greater than the bending radius of the sub-circuit board 510 located at the flexible circuit board 50 when the flexible circuit board 50 is bent from the second area 500b, the sub-circuit board 510 at the outer layer of the flexible circuit board 50 is not easy to break. When the flexible circuit board 50 is bent from the second area 500b, the bending radius of the sub-circuit board 510 located on the inner layer of the flexible circuit board 50 is smaller than the bending radius of the sub-circuit board 510 located on the outer layer of the flexible circuit board 50. Since the adhesive layer 520 of the flexible circuit board 50 avoids the second area 500b, so that the two adjacent layers of sub-circuit boards 510 form a first gap 520a corresponding to the second area 500b, the first gap 520a can release the squeezing force on the sub-circuit board 510 located on the inner layer, so that the sub-circuit board 510 located on the inner layer of the flexible circuit board 50 is not easy to break, thereby improving the reliability and bending life of the flexible circuit board 50.

[0062] In one embodiment, when the second area 500b of the flexible circuit board 50 is bent, the first sub-circuit board 510a is the sub-circuit board 510 located in the inner layer of the flexible circuit board 50, and the second sub-circuit board 510b is the sub-circuit board 510 located in the outer layer of the flexible circuit board 50. It can be understood that in another embodiment, when the second area 500b of the flexible circuit board 50 is bent, the first sub-circuit board 510a is the sub-circuit board 510 located in the outer layer of the flexible circuit board 50, and the second sub-circuit board 510b is the sub-circuit board 510 located in the inner layer of the flexible circuit board 50.

[0063] In addition, the second sub-circuit board 510b has a signal transmission line 5121, and the signal transmission line 5121 is used to transmit signals. The signal transmission line 5121 can be, but is not limited to, a microstrip line.

[0064] The electromagnetic shielding film 540 is used to shield electromagnetic radiation interference to protect the signal transmitted in the flexible circuit board 50 from interference or less interference. In one embodiment, the electromagnetic shielding film 540 includes a metal layer or a film layer containing a metal component that can only shield electromagnetic waves. For example, the electromagnetic shielding film 540 can be, but is not limited to, silver paste, etc.

[0065] In one implementation, the electromagnetic shielding film 540 may be attached to the surface of the first sub-circuit board 510 a facing away from the second sub-circuit board 510 b by glue.

[0066] In one embodiment, the electromagnetic shielding film 540 is resistant to bending and is not easily broken by bending.

[0067] Furthermore, in this embodiment, the electromagnetic shielding film 540 is disposed on a side of the second sub-circuit board 510b away from the first sub-circuit board 510a; and in this embodiment, the electromagnetic shielding film 540 serves as at least a partial reference surface of the impedance of the signal transmission line 5121. The electromagnetic shielding film 540 serves as at least a partial reference surface of the signal transmission line 5121. Therefore, when the flexible circuit board 50 is bent, or the flexible circuit board 50 is applied to the foldable electronic device 1, the distance from the signal transmission line 5121 to the electromagnetic shielding film 540 remains unchanged, or the distance from the signal transmission line 5121 to the electromagnetic shielding film 540 changes slightly. In addition, the dielectric constant of the film layer between the signal transmission line 5121 and the electromagnetic shielding film 540 will not change, or the probability of change is small. Therefore, in this embodiment, the electromagnetic shielding film 540 serves as at least a partial reference surface of the impedance of the signal transmission line 5121, so that the impedance of the signal transmission line 5121 of the flexible circuit board 50 changes little or even does not change, thereby making the impedance of the signal transmission line 5121 consistent with the actual required impedance. For example, the flexible circuit board 50 provided in the embodiment of the present application includes the electromagnetic shielding film 540. Compared with the case where the flexible circuit board 50 is in a flat state, when the flexible circuit board 50 is bent from the bendable area (i.e., the second area 500b), the change amount of the signal transmission line 5121 of the flexible circuit board 50 is less than or equal to a preset threshold value. In one embodiment, the preset threshold value may be, but is not limited to, one tenth of the impedance of the signal transmission line 5121 when the flexible circuit board 50 is in a flat state.

[0068] When the flexible circuit board 50 provided in the embodiment of the present application is used to transmit signals, the signal sent from the source end connected to one end of the flexible circuit board 50 and the signal transmitted to the terminal connected to the other end of the flexible circuit board 50 via the signal transmission line 5121 of the flexible circuit board 50 are relatively matched. When the flexible circuit board 50 is applied to the foldable electronic device 1, the performance of the foldable electronic device 1 controlled by the signal transmitted by the flexible circuit board 50 can be guaranteed to be normal.

[0069] In summary, the flexible circuit board 50 provided in the embodiment of the present application includes a first sub-circuit board 510a, an adhesive layer 520 and a second circuit board 210 which are sequentially stacked. The flexible circuit board 50 has a bendable area. When the flexible circuit board 50 is bent from the second area 500b, the bending radius of the sub-circuit board 510 located on the outer layer of the flexible circuit board 50 is greater than the bending radius of the sub-circuit board 510 located on the flexible circuit board 50. Therefore, the sub-circuit board 510 on the outer layer of the flexible circuit board 50 is not easy to break. Furthermore, when the flexible circuit board 50 is bent from the second area 500b, the bending radius of the sub-circuit board 510 located in the inner layer of the flexible circuit board 50 is smaller than the bending radius of the sub-circuit board 510 located in the outer layer of the flexible circuit board 50. Since the adhesive layer 520 of the flexible circuit board 50 avoids the second area 500b, so that the two adjacent layers of sub-circuit boards 510 form a first gap 520a corresponding to the bendable area, the first gap 520a can release the squeezing force on the sub-circuit board 510 located in the inner layer, so that the sub-circuit board 510 located in the inner layer of the flexible circuit board 50 is not easy to break, thereby improving the reliability and bending life of the flexible circuit board 50. In which, one of the first sub-circuit board 510a and the second sub-circuit board 510b is located in the inner layer of the flexible circuit board 50 compared to the other of the first sub-circuit board 510a and the second sub-circuit board 510b.

[0070] Furthermore, in this embodiment, the electromagnetic shielding film 540 is disposed on a side of the second sub-circuit board 510b away from the first sub-circuit board 510a; and in this embodiment, the electromagnetic shielding film 540 serves as at least a partial reference surface of the impedance of the signal transmission line 5121. The electromagnetic shielding film 540 serves as at least a partial reference surface of the signal transmission line 5121. Therefore, when the flexible circuit board 50 is bent or the flexible circuit board 50 is used in the foldable electronic device 1, the distance from the signal transmission line 5121 to the electromagnetic shielding film 540 remains unchanged, or the distance from the signal transmission line 5121 to the electromagnetic shielding film 540 changes slightly. In addition, the dielectric constant of the film layer between the signal transmission line 5121 and the electromagnetic shielding film 540 does not change, or the probability of change is small. Therefore, in this embodiment, the electromagnetic shielding film 540 serves as at least a partial reference surface of the impedance of the signal transmission line 5121, which can make the impedance of the signal transmission line 5121 of the flexible circuit board 50 change slightly or even not change, thereby making the impedance of the signal transmission line 5121 consistent with the actual required impedance. When the flexible circuit board 50 provided in the embodiment of the present application is used to transmit signals, the signal sent from the source end connected to one end of the flexible circuit board 50 and the signal transmitted to the terminal connected to the other end of the flexible circuit board 50 via the signal transmission line 5121 of the flexible circuit board 50 are more matched. When the flexible circuit board 50 is applied to the foldable electronic device 1, it can be ensured that the performance of the foldable electronic device 1 controlled by the signal transmitted by the flexible circuit board 50 is normal.

[0071] See also Figure 8 , Figure 8 for Figure 2 Schematic diagram of thickness of some film layers of the flexible circuit board in FIG. The thickness d0 of the electromagnetic shielding film 540 satisfies: 3 μm≤d0≤10 μm.

[0072] In one embodiment, the thickness of the electromagnetic shielding film 540 is less than or equal to 10 μm. For example, the thickness d0 of the electromagnetic shielding film 540 satisfies: 3 μm ≤ d0 ≤ 10 μm. For example, the thickness of the electromagnetic shielding film 540 is 3 μm, or 4 μm, or 5 μm, or 6 μm, or 7 μm, or 8 μm, or 9 μm, or 10 μm. The thickness d0 of the electromagnetic shielding film 540 satisfies: 3 μm ≤ d0 ≤ 10 μm, which can make the electromagnetic shielding film 540 have a better shielding effect on the one hand; on the other hand, the electromagnetic shielding film 540 has a better bending performance, is not easy to break, and makes the flexible circuit board 50 have a smaller bending radius.

[0073] Please also read Figure 1 , Figure 2 , and see Fig. 9 , Fig.10 and Fig.11 , Fig. 9 A top view of a first conductive layer and a second conductive layer in a flexible circuit board provided in one embodiment; Fig.10 for Fig. 9 A schematic diagram of a signal transmission line in a second conductive layer in a flexible circuit board provided in; Fig.11 for Fig. 9 A schematic diagram of a first conductive layer in a flexible circuit board is provided. The first sub-circuit board 510a includes a first conductive layer 512a, and the first conductive layer 512a has a plurality of grids 5122. The second sub-circuit board 510b includes a second conductive layer 512b, and the second conductive layer 512b has the signal transmission line 5121.

[0074] The material of the first conductive layer 512a may be, but is not limited to, conductive materials such as copper or silver. The material of the second conductive layer 512b may be, but is not limited to, conductive materials such as copper or silver. The material of the second conductive layer 512b may be the same as or different from that of the first conductive layer 512a, which is not limited in the embodiments of the present application.

[0075] The first conductive layer 512a includes an upper surface and a lower surface disposed opposite to each other. The first conductive layer 512a has a plurality of through holes to form a plurality of grids 5122. The plurality of through holes penetrate the upper surface of the first conductive layer 512a and the lower surface of the first conductive layer 512a.

[0076] The shape of the through hole may be, but is not limited to, circular, or approximately circular, or elliptical, or approximately elliptical, or square, or approximately square, or diamond, or approximately diamond, etc. The embodiment of the present application does not limit the shape of the through hole.

[0077] In the flexible circuit board 50 provided in the embodiment of the present application, the first sub-circuit board 510a includes a first conductive layer 512a, and the first conductive layer 512a has a plurality of grids 5122. Compared with the case where the first conductive layer 512a is a whole metal layer, the first conductive layer 512a of the flexible circuit board 50 provided in the embodiment of the present application has a plurality of grids 5122, so the metal content of the first conductive layer 512a of the flexible circuit board 50 provided in the embodiment of the present application is reduced. When the first conductive layer 512a includes copper, compared with the case where the first conductive layer 512a includes a whole copper layer, when the first conductive layer 512a of the flexible circuit board 50 provided in the embodiment of the present application has a plurality of grids 5122, the copper content of the first conductive layer 512a is reduced. Compared with the case where the first conductive layer 512a is a whole metal layer, the first conductive layer 512a of the flexible circuit board 50 provided in the embodiment of the present application has a plurality of grids 5122, thereby reducing the portion of the signal layer transmission line directly facing the first conductive layer 512a and the second conductive layer 512b. Therefore, in the flexible circuit board 50 provided in the embodiment of the present application, the first conductive layer 512a of the flexible circuit board 50 includes a plurality of grids 5122. Therefore, when the first conductive layer 512a serves as at least a partial reference surface of the signal transmission line 5121, no matter the spacing between the first conductive layer 512a and the second conductive layer 512b is reduced or the spacing between the first conductive layer 512a and the second conductive layer 512b is increased, the first conductive layer 512a has a small influence on the impedance of the signal transmission line 5121 in the second conductive layer 512b. In summary, in the flexible circuit board 50 provided in the embodiment of the present application, the first conductive layer 512a has a plurality of grids 5122, which can weaken the reference effect of the first conductive layer 512a on the signal transmission line 5121 of the second conductive layer 512b, and greatly reduce the influence of the first conductive layer 512a on the impedance of the signal transmission line 5121 of the second conductive layer 512b, thereby improving the signal continuity of the signal transmission line 5121 under various circumstances.

[0078] It can be understood that in this embodiment, the flexible circuit board 50 includes two sub-circuit boards 510, namely the first sub-circuit board 510a and the second sub-circuit board 510b. It can be understood that the first conductive layer 512a of the flexible circuit board 50 includes multiple grids 5122 and can also be combined with the flexible circuit board 50 to include more sub-circuit boards 510. The schematic diagram of the embodiment of the present application should not be understood as a limitation on the embodiment of the present application.

[0079] As can be seen from the above description, in the first case, the distance between the first conductive layer 512a of the first sub-circuit board 510a of the flexible circuit board 50 and the second conductive layer 512b of the second sub-circuit board 510b becomes smaller, which will cause the impedance Z of the signal transmission line 5121 to become smaller; in the second case, the distance between the first conductive layer 512a of the first sub-circuit board 510a of the flexible circuit board 50 and the second conductive layer 512b of the second sub-circuit board 510b becomes larger, which will cause the impedance Z of the signal transmission line 5121 to become larger. It can be seen that in the flexible circuit board 50 provided in the second embodiment of the related art, the signal transmission line 5121 of the second conductive layer 512b of the second sub-circuit board 510b only uses the first conductive layer 512a of the first sub-circuit board 510a as a reference plane, which will cause the impedance of the signal transmission line 5121 to be inconsistent with the actual required impedance. In this embodiment, in addition to using the electromagnetic shielding film 540 as an impedance reference plane, the signal transmission line 5121 of the flexible circuit board 50 also uses the first conductive layer 512a as an impedance reference plane. The flexible circuit board 50 provided in the embodiment of the present application introduces the electromagnetic shielding film 540 as a new reference plane to the signal transmission line 5121, and the first conductive layer 512a has a plurality of grids 5122, which weakens the reference function of the first conductive layer 512a as a reference plane. Therefore, the flexible circuit board 50 provided in the embodiment of the present application has good signal continuity of the signal transmission line 5121 in various situations, whether the first gap 520a becomes smaller or larger, thereby improving the signal continuity of the signal transmission line 5121. In one embodiment, when the flexible circuit board 50 is stationary, the first gap 520a may become smaller, which may cause the impedance of the signal transmission line 5121 to become smaller; when the first sub-circuit board 510a and the second sub-circuit board 510b of the flexible circuit board 50 slide, the impedance of the signal transmission line 5121 may become larger. The flexible circuit board 50 provided in the embodiment of the present application can improve the impedance continuity of the signal transmission line 5121 when the flexible circuit board 50 is stationary and when the first sub-circuit board 510a and the second sub-circuit board 510b of the flexible circuit board 50 slide, thereby improving the impedance continuity of the flexible circuit board 50. In addition, the flexible circuit board 50 provided in the embodiment of the present application has a long bending life, which can meet the design requirements of the flexible circuit board 50 applied to the foldable electronic device 1, and finally provide users with high-quality and high-durability products.

[0080] For further information, please refer to Figures 9 to 11, the signal transmission line 5121 extends along a first direction D1. The first conductive layer 512a includes a plurality of first conductive wires 5123 and a plurality of second conductive wires 5124 arranged at intervals. The first conductive wires 5123 extend along a second direction D2, and the second direction D2 is different from the first direction D1. The plurality of second conductive wires 5124 cross the plurality of first conductive wires 5123 to form the plurality of grids 5122, and the second conductive wires 5124 extend along a third direction D3, and the third direction D3 is different from the first direction D1, and the third direction D3 is different from the second direction D2.

[0081] In this embodiment, the second direction D2 is different from the first direction D1; the third direction D3 is different from the first direction D1, and the third direction D3 is different from the second direction D2. Therefore, the extension direction of the signal transmission line 5121 (i.e., the first direction D1) intersects with the extension direction of the first wire 5123 (i.e., the second direction D2); the extension direction of the signal transmission line 5121 (i.e., the first direction D1) intersects with the extension direction of the second wire 5124 (i.e., the third direction D3); and the extension direction of the first wire 5123 (i.e., the second direction D2) intersects with the extension direction of the second wire 5124 (i.e., the third direction D3).

[0082] The above-mentioned extension direction of the signal transmission line 5121, the first conductive wire 5123, and the second conductive wire 5124 can make the opposing area between the signal transmission line 5121 and the first conductive wire 5123 and the second conductive wire 5124 in the first conductive layer 512a smaller. Therefore, when the first conductive layer 512a serves as at least a partial reference surface of the signal transmission line 5121, no matter the distance between the first conductive layer 512a and the second conductive layer 512b decreases or the distance between the first conductive layer 512a and the second conductive layer 512b increases, the first conductive layer 512a has little effect on the impedance of the signal transmission line 5121 in the second conductive layer 512b. In summary, in the flexible circuit board 50 provided in the embodiment of the present application, the first conductive layer 512a has a plurality of grids 5122, and the above-mentioned extension direction of the signal transmission line 5121, the first conductive wire 5123, and the second conductive wire 5124 can further weaken the reference effect of the first conductive layer 512a on the signal transmission line 5121 of the second conductive layer 512b, and can greatly reduce the influence of the first conductive layer 512a on the impedance of the signal transmission line 5121 of the second conductive layer 512b, thereby improving the signal continuity of the signal transmission line 5121 under various circumstances.

[0083] Please also read Figures 9 to 11 , and see Fig.12 , Fig.12 for Fig. 9 In this embodiment, the angle a between the signal transmission line 5121 and the first conductive line 5123 satisfies: 7°≤a≤83°; the angle b between the signal transmission line 5121 and the second conductive line 5124 satisfies: 7°≤b≤83°.

[0084] For example, the angle a between the signal transmission line 5121 and the first conductive line 5123 may be, but is not limited to, 7°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, or 83°.

[0085] When the angle a between the signal transmission line 5121 and the first conductive wire 5123 is too small, the overlap between the signal transmission line 5121 and the first conductive wire 5123 is large, and the first conductive layer 512a has little effect on improving the impedance of the signal transmission line 5121 of the second conductive layer 512b; when the angle a between the signal transmission line 5121 and the first conductive wire 5123 is too large, the angle between the signal transmission line 5121 and the second conductive wire 5124 may be small, so that the overlap between the signal transmission line 5121 and the second conductive wire 5124 is large, and the first conductive layer 512a has little effect on improving the impedance of the signal transmission line 5121 of the second conductive layer 512b.

[0086] Correspondingly, when the angle b between the signal transmission line 5121 and the second conductive line 5124 is too small, the overlap between the signal transmission line 5121 and the second conductive line 5124 is relatively large, and the first conductive layer 512a has a relatively small effect on improving the impedance of the signal transmission line 5121 of the second conductive layer 512b; when the angle b between the signal transmission line 5121 and the second conductive line 5124 is too large, the angle between the signal transmission line 5121 and the first conductive line 5123 may be relatively small, so that the overlap between the signal transmission line 5121 and the first conductive line 5123 is relatively large, and the first conductive layer 512a has a relatively small effect on improving the impedance of the signal transmission line 5121 of the second conductive layer 512b.

[0087] In the flexible circuit board 50 provided in the embodiment of the present application, the angle a between the signal transmission line 5121 and the first conductive line 5123 satisfies: 7°≤a≤83°; the angle b between the signal transmission line 5121 and the second conductive line 5124 satisfies: 7°≤b≤83°, so that the overlap between the signal transmission line 5121 and the first conductive line 5123 is not much, and the overlap between the signal transmission line 5121 and the second conductive line 5124 is not much, so that the first conductive layer 512a has a better improvement effect on the impedance of the signal transmission line 5121 of the second conductive layer 512b. That is, the impedance of the signal transmission line 5121 of the flexible circuit board 50 provided in the embodiment of the present application has a small change or even no change, so that the impedance of the signal transmission line 5121 is consistent with the actual required impedance. When the flexible circuit board 50 provided in the embodiment of the present application is used to transmit signals, the signal sent from the source end connected to one end of the flexible circuit board 50 and the signal transmitted to the terminal connected to the other end of the flexible circuit board 50 via the signal transmission line 5121 of the flexible circuit board 50 are more matched. When the flexible circuit board 50 is applied to the foldable electronic device 1, it can be ensured that the performance of the foldable electronic device 1 controlled by the signal transmitted by the flexible circuit board 50 is normal.

[0088] See also Fig.12 , the line width W1 of the first conductive line 5123 satisfies: 40 μm≤W1≤100 μm; and the line width W2 of the second conductive line 5124 satisfies: 40 μm≤W2≤100 μm.

[0089] The line width W1 of the first conductive line 5123 may be, but is not limited to, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm.

[0090] When the line width of the first wire 5123 is too small, it is difficult to manufacture the first wire 5123 in terms of technology; when the line width of the first wire 5123 is too large, the impedance improvement of the signal transmission line 5121 is relatively limited. In the flexible circuit board 50 provided in the embodiment of the present application, the line width W1 of the first wire 5123 satisfies: 40μm≤W1≤100μm; on the one hand, the difficulty of manufacturing the first wire 5123 is relatively small, the manufacturing of the first wire 5123 is convenient, and the manufacturing cost of the first wire 5123 is reduced; on the other hand, the impedance improvement of the signal transmission line 5121 by the first wire 5123 is relatively obvious.

[0091] The line width W2 of the second conductive line 5124 may be, but is not limited to, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm.

[0092] When the line width of the second wire 5124 is too small, it is difficult to manufacture the second wire 5124 in terms of technology; when the line width of the second wire 5124 is too large, the impedance improvement of the signal transmission line 5121 is relatively limited. In the flexible circuit board 50 provided in the embodiment of the present application, the line width W2 of the second wire 5124 satisfies: 40μm≤W2≤100μm; on the one hand, the difficulty of manufacturing the second wire 5124 is relatively small, the manufacturing of the second wire 5124 is facilitated, and the manufacturing cost of the second wire 5124 is reduced; on the other hand, the impedance improvement of the signal transmission line 5121 by the second wire 5124 is relatively obvious.

[0093] The line width of the first conductive line 5123 may be the same as or different from the line width of the second conductive line 5124 , which is not limited here.

[0094] See also Fig.11 , a size L1 of the grid 5122 in the second direction D2 satisfies: 40 μm≤L1≤100 μm; a size L2 of the grid 5122 in the third direction D3 satisfies: 40 μm≤L2≤100 μm.

[0095] The size L1 of the grid 5122 in the second direction D2 may be, but is not limited to, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm.

[0096] When the size of the grid 5122 in the third direction D3 is constant, when the size of the grid 5122 in the second direction D2 is too small, the first conductive layer 512a where the grid 5122 is located does not significantly improve the impedance of the signal transmission line 5121; when the size of the grid 5122 in the second direction D2 is too large, the signal transmitted on the signal transmission line 5121 is easily radiated through the grid 5122, thereby interfering with the devices or lines around the flexible circuit board 50, and making the energy of the signal output through the signal transmission line 5121 poor. In addition, the signal transmitted on the signal transmission line 5121 is also easily interfered by the devices or lines around the flexible circuit board 50. In the flexible circuit board 50 provided in the embodiment of the present application, the size L1 of the grid 5122 in the second direction D2 satisfies: 40μm≤L1≤100μm. On the one hand, the impedance of the signal transmission line 5121 can be significantly improved by the first conductive layer 512a where the grid 5122 is located. On the other hand, the signal transmitted by the signal transmission line 5121 is not easily radiated through the grid 5122, thereby reducing interference with devices or lines around the flexible circuit board 50, so that the energy of the signal output through the signal transmission line 5121 is better. In addition, the signal transmitted on the signal transmission line 5121 is not easily interfered by devices or lines around the flexible circuit board 50.

[0097] Accordingly, the size L2 of the grid 5122 in the third direction D3 may be but is not limited to 40 μm, or 45 μm, or 50 μm, or 55 μm, or 60 μm, or 65 μm, or 70 μm, or 75 μm, or 80 μm, or 85 μm, or 90 μm, or 95 μm, or 100 μm.

[0098] When the size of the grid 5122 in the second direction D2 is constant, when the size of the grid 5122 in the third direction D3 is too small, the first conductive layer 512a where the grid 5122 is located does not significantly improve the impedance of the signal transmission line 5121; when the size of the grid 5122 in the third direction D3 is too large, the signal transmitted on the signal transmission line 5121 is easily radiated through the grid 5122, thereby interfering with the devices or lines around the flexible circuit board 50, and making the energy of the signal output through the signal transmission line 5121 poor. In addition, the signal transmitted on the signal transmission line 5121 is also easily interfered by the devices or lines around the flexible circuit board 50. In the flexible circuit board 50 provided in the embodiment of the present application, the dimension L2 of the grid 5122 in the third direction D3 satisfies: 40μm≤L2≤100μm. On the one hand, the impedance of the signal transmission line 5121 can be significantly improved by the first conductive layer 512a where the grid 5122 is located. On the other hand, the signal transmitted by the signal transmission line 5121 is not easily radiated through the grid 5122, thereby reducing interference with devices or lines around the flexible circuit board 50, so that the energy of the signal output through the signal transmission line 5121 is better. In addition, the signal transmitted on the signal transmission line 5121 is not easily interfered by devices or lines around the flexible circuit board 50.

[0099] See also Fig.13 , Fig.13 For another embodiment Figure 1 The cross-sectional view of the flexible circuit board provided in FIG. 5 along the II line. The first sub-circuit board 510a includes a first conductive layer 512a, and the second sub-circuit board 510b includes a second conductive layer 512b, and the second conductive layer 512b has the signal transmission line 5121. The first conductive layer 512a includes a conductive portion 5125, and the conductive portion 5125 avoids the positive projection area of ​​the signal transmission line 5121 on the first conductive layer 512a. The flexible circuit board 50 also includes a third sub-circuit board 510c, and the third sub-circuit board 510c is arranged on the side of the first sub-circuit board 510a away from the second sub-circuit board 510b, and the third sub-circuit board 510c includes a third conductive layer 512c.

[0100] The first conductive layer 512a includes an orthographic projection area and a non-projection area of ​​the signal transmission line 5121. The orthographic projection area is the area where the orthographic projection of the signal transmission line 5121 on the first conductive layer 512a is located. The non-projection area is other areas other than the orthographic projection of the signal transmission line 5121 on the first conductive layer 512a. In the flexible circuit board 50 provided in the embodiment of the present application, the conductive portion 5125 is located in the non-projection area, and the conductive portion 5125 avoids the orthographic projection area. In one embodiment, the non-conductive portion is provided in the orthographic projection area; in another embodiment, the first conductive layer 512a has a gap 5126 that penetrates the upper surface and the lower surface of the first conductive layer 512a in the orthographic projection area.

[0101] Therefore, in the flexible circuit board 50 provided in the embodiment of the present application, the first conductive layer 512a includes a conductive portion 5125, and the conductive portion 5125 avoids the positive projection area of ​​the signal transmission line 5121 on the first conductive layer 512a. The third sub-circuit board 510c is arranged on the side of the first sub-circuit board 510a away from the second sub-circuit board 510b, and the third sub-circuit board 510c includes a third conductive layer 512c. The third conductive layer 512c of the third sub-circuit board 510c serves as a partial reference surface of the signal transmission line 5121. Compared with the related art, the signal transmission line 5121 in the embodiment of the present application uses the electromagnetic shielding film 540 and the third conductive layer 512c as reference surfaces. Therefore, the impedance of the signal transmission line 5121 in the flexible circuit board 50 is consistent with the actual required impedance. When the flexible circuit board 50 provided in the embodiment of the present application is used to transmit signals, the signal sent from the source end connected to one end of the flexible circuit board 50 and the signal transmitted to the terminal connected to the other end of the flexible circuit board 50 via the signal transmission line 5121 of the flexible circuit board 50 are relatively matched. When the flexible circuit board 50 is applied to the foldable electronic device 1, the performance of the foldable electronic device 1 controlled by the signal transmitted by the flexible circuit board 50 can be guaranteed to be normal.

[0102] For further information, see Figure 2 , Fig.13As shown in the drawings, the flexible circuit board 50 has a first area 500a, a second area 500b and a third area 500c arranged in sequence, wherein the second area 500b is the bendable area. The adhesive layer 520 avoids the second area 500b, so that the first sub-circuit board 510a and the second sub-circuit board 510b form a first gap 520a corresponding to the second area 500b. The adhesive layer 520 also avoids the portion of the first area 500a adjacent to the second area 500b, so that the first sub-circuit board 510a and the second sub-circuit board 510b form a second gap 520b corresponding to the portion of the first area 500a adjacent to the second area 500b, and the second gap 520b is connected to the first gap 520a. The adhesive layer 520 also avoids the portion of the third area 500c adjacent to the second area 500b, so that the first sub-circuit board 510a and the second sub-circuit board 510b form a third gap 520c corresponding to the portion of the third area 500c adjacent to the second area 500b, and the third gap 520c is connected to the first gap 520a.

[0103] In one embodiment, the boundary between the first area 500a and the second area 500b is named as the first boundary L1, and the boundary between the third area 500c and the second area 500b is named as the second boundary L2. In other words, the first area 500a and the second area 500b have the first boundary L1, and the third area 500c and the second area 500b have the second boundary L2.

[0104] In an embodiment, the adhesive layer 520 avoids the portion of the first area 500a adjacent to the second area 500b, so the first sub-circuit board 510a and the second sub-circuit board 510b form a second gap 520b corresponding to the portion of the first area 500a adjacent to the second area 500b. In other words, there is a distance between the first connecting portion 521 and the first boundary line L1, so that the first sub-circuit board 510a and the second sub-circuit board 510b and the first connecting portion 521 cooperate to form the second gap 520b.

[0105] In this embodiment, the adhesive layer 520 avoids the portion of the third area 500c adjacent to the second area 500b, so the first sub-circuit board 510a and the second sub-circuit board 510b form a third gap 520c corresponding to the portion of the third area 500c adjacent to the second area 500b. In other words, there is a distance between the second connecting portion 522 and the second boundary line L2, so that the first sub-circuit board 510a and the second sub-circuit board 510b and the second connecting portion 522 cooperate to form the third gap 520c.

[0106] When the flexible circuit board 50 corresponds to the foldable electronic device 1 (see Figures 15 to 17 ) is set, the first area 500a corresponds to the first main body 10 of the foldable electronic device 1, the third area 500c corresponds to the second main body 20 of the foldable electronic device 1, and the second area 500b corresponds to the bendable part 30 of the foldable electronic device 1.

[0107] In this embodiment, in addition to the first gap 520a, the flexible circuit board 50 also has a second gap 520b and a third gap 520c. In the flexible circuit board 50, the second gap 520b is connected to the first gap 520a and the third gap 520c is connected to the first gap 520a to form an overall gap, and the overall gap is larger than the second area 500b.

[0108] In this embodiment, the adhesive layer 520 also avoids the portion of the first area 500a adjacent to the second area 500b, so that the first sub-circuit board 510a and the second sub-circuit board 510b form a second gap 520b corresponding to the portion of the first area 500a adjacent to the second area 500b, and the second gap 520b is connected to the first gap 520a; therefore, the first connecting portion 521 is located in the first area 500a, and the first connecting portion 521 is at a certain distance from the boundary line (first boundary line L1) between the first area 500a and the second area 500b, so that when the second area 500b of the flexible circuit board 50 is bent, the first connecting portion 521 is in a static non-stress state, or a small stress state. Further, the boundary of the first connecting portion 521 adjacent to the second area 500b is also in a static non-stress state, or a small stress state. The first connection portion 521 is in a non-stress state, or a small stress state, so that when the second area 500b of the flexible circuit board 50 is bent, the first connection portion 521 does not squeeze or squeezes with small force the sub-circuit board 510 located in the inner layer of the flexible circuit board 50 at the first boundary line L1, so that the sub-circuit board 510 in the inner layer of the flexible circuit board 50 is not easy to break, thereby improving the reliability and bending life of the flexible circuit board 50.

[0109] Furthermore, the adhesive layer 520 also avoids the portion of the third area 500c adjacent to the second area 500b, so that the first sub-circuit board 510a and the second sub-circuit board 510b corresponding to the portion of the third area 500c adjacent to the second area 500b form a third gap 520c, and the third gap 520c is connected to the first gap 520a; therefore, the second connecting portion 522 is located in the third area 500c, and the second connecting portion 522 is at a certain distance from the boundary line (second boundary line L2) between the third area 500c and the second area 500b, so that when the second area 500b of the flexible circuit board is bent, the second connecting portion 522 is in a static non-stress state, or a small stress state. Further, the second connecting portion 522 adjacent to the boundary of the second area 500b is also in a static non-stress state, or a small stress state. The second connection portion 522 is in a non-stressed state, or a relatively small stress state, so that when the second area 500b of the flexible circuit board 50 is bent, the second connection portion 522 does not squeeze or squeezes relatively small force on the inner sub-circuit board 510 of the flexible circuit board 50 at the second boundary line L2, so that the inner sub-circuit board 510 of the flexible circuit board 50 is not easy to break, thereby improving the reliability and bending life of the flexible circuit board 50.

[0110] For further information, please also refer to Fig.13 and Fig.14 , Fig.14 for Fig.13 Schematic diagram of the thickness of each film layer of the sub-circuit board of the flexible circuit board shown in . The sub-circuit board 510 includes a base layer 511, a conductive layer 512, a connecting adhesive layer 513 and a coating layer 514 stacked in sequence. The thickness d1 of the base layer 511 satisfies: 10μm≤d1≤18μm. The thickness d2 of the conductive layer 512 satisfies: 5μm≤d2≤10μm. The thickness d3 of the connecting adhesive layer 513 satisfies: 8μm≤d3≤15μm, and the thickness of the connecting adhesive layer 513 is greater than the thickness of the conductive layer 512.

[0111] When the multi-layer sub-circuit board 510 includes a first sub-circuit board 510a, the base layer 511 of the first sub-circuit board 510a is also referred to as a first base layer 511a, the conductive layer 512 of the first sub-circuit board 510a is also referred to as a first conductive layer 512a, the connecting adhesive layer 513 of the first sub-circuit board 510a is also referred to as a first connecting adhesive layer 513a, and the coating layer 514 of the first sub-circuit board 510a is also referred to as a first coating layer 514a. The base layer 511, the conductive layer 512, and the connecting adhesive layer 513 of the first sub-circuit board 510a meet the above conditions.

[0112] Correspondingly, when the multi-layer sub-circuit board 510 includes a second sub-circuit board 510b, the base layer 511 of the second sub-circuit board 510b is also referred to as a second base layer 511b, the conductive layer 512 of the second sub-circuit board 510b is also referred to as a second conductive layer 512b, the connecting adhesive layer 513 of the second sub-circuit board 510b is also referred to as a second connecting adhesive layer 513b, and the coating layer 514 of the second sub-circuit board 510b is also referred to as a second coating layer 514b. The base layer 511, the conductive layer 512, and the connecting adhesive layer 513 of the second sub-circuit board 510b meet the above conditions.

[0113] Correspondingly, when the multilayer sub-circuit board 510 includes a third sub-circuit board 510c, the base layer 511 of the third sub-circuit board 510c is also referred to as a third base layer 511c, the conductive layer 512 of the third sub-circuit board 510c is also referred to as a third conductive layer 512c, the connecting adhesive layer 513 of the third sub-circuit board 510c is also referred to as a third connecting adhesive layer 513c, and the coating layer 514 of the third sub-circuit board 510c is also referred to as a third coating layer 514c. The base layer 511, the conductive layer 512, and the connecting adhesive layer 513 of the third sub-circuit board 510c meet the above conditions.

[0114] It can be understood that the thickness of the same film layer in each sub-circuit 510 can be the same or different, and the present application does not impose any limitation on this, as long as the above range is met.

[0115] The material of the base layer 511 may include but is not limited to polyimide (PI). When the material of the base layer 511 includes PI, the base layer 511 is also referred to as PI base. Please refer to the previous description for the conductive layer 512, which will not be repeated here.

[0116] The thickness d1 of the base layer 511 may be, but is not limited to, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, or 18 μm.

[0117] When the thickness of the base layer 511 is too small, the strength of the base layer 511 is weak, and the base layer 511 is easily damaged. When the thickness of the base layer 511 is too large, the bending performance of the base layer 511 is poor, it is easy to break, and the bending radius of the flexible circuit board 50 is large. In the flexible circuit board 50 provided in the embodiment of the present application, in the sub-circuit board 510, the thickness d1 of the base layer 511 satisfies: 10μm≤d1≤18μm, on the one hand, the base layer 511 can have relatively good strength, and the base layer 511 is not easily damaged; on the other hand, the base layer 511 has good bending performance, is not easy to break, and the flexible circuit board 50 has a smaller bending radius. In addition, in the flexible circuit board 50 provided in the embodiment of the present application, the thickness d1 of the base layer 511 satisfies: 10μm≤d1≤18μm, and the cost of the flexible circuit board 50 can also be taken into account, so that the cost of the flexible circuit board 50 is not too high.

[0118] The material of the conductive layer 512 can be found in the previous description and will not be described in detail herein.

[0119] The thickness d2 of the conductive layer 512 may be, but is not limited to, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0120] When the thickness of the conductive layer 512 is too small, the strength of the conductive layer 512 is relatively weak, and the electrical connection performance of the conductive layer 512 is relatively poor. When the thickness of the conductive layer 512 is too large, the bending performance of the conductive layer 512 is poor, it is easy to break, and the bending radius of the flexible circuit board 50 is large. In the flexible circuit board 50 provided in the embodiment of the present application, the thickness d2 of the conductive layer 512 satisfies: 5μm≤d2≤10μm, on the one hand, the conductive layer 512 has relatively good strength and electrical connection performance, and the conductive layer 512 is not easily damaged; on the other hand, the conductive layer 512 has good bending performance, is not easy to break, and the flexible circuit board 50 has a smaller bending radius.

[0121] In one embodiment, the conductive layer 512 has one or more conductive lines. When the conductive layer 512 includes a plurality of conductive lines, there is a gap between two adjacent conductive lines.

[0122] The connecting adhesive layer 513 is used to bond the conductive layer 512 and the coating layer 514. When there is a gap between two adjacent conductive lines in the conductive layer 512, the connecting adhesive layer 513 is used to fill the gap between the two adjacent conductive lines. The thickness of the connecting adhesive layer 513 is greater than the thickness of the conductive layer 512. Therefore, after the connecting adhesive layer 513 fills the gap between the two adjacent conductive lines, it can also be bonded to the coating layer 514, thereby ensuring the integrity of the sub-conductive layer 512.

[0123] The thickness d3 of the connecting adhesive layer 513 may be, but is not limited to, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm.

[0124] When the thickness of the connecting adhesive layer 513 is small, the connection effect of the connecting adhesive layer 513 is not good. When the thickness of the connecting adhesive layer 513 is large, the bending performance of the connecting adhesive layer 513 is poor, which leads to a large bending radius of the flexible circuit board 50. In the flexible circuit board 50 provided in the embodiment of the present application, the thickness d3 of the connecting adhesive layer 513 satisfies: 8μm≤d3≤15μm, which can ensure that the connection effect of the connecting adhesive layer 513 is good on the one hand; on the other hand, it can ensure that the bending performance of the flexible circuit board 50 is good and the bending radius is small.

[0125] The material of the cover layer 514 may be, but is not limited to, polyimide (PI), etc. The cover layer 514 is used to protect the conductive layer 512 .

[0126] For further information, see Figure 3 , the flexible circuit board 50 includes a first surface 50a and a second surface 50b disposed opposite to each other. When the multi-layer sub-circuit board 510 includes a first sub-circuit board 510a and a second sub-circuit board 510b, the multi-layer sub-circuit board 510 includes a first sub-circuit board 510a adjacent to the first surface 50a and a second sub-circuit board 510b adjacent to the second surface 50b. The base layer 511 of the first sub-circuit board 510a is away from the first surface 50a compared to the coating layer 514 of the first sub-circuit board 510a. The base layer 511 of the second sub-circuit board 510b is away from the second surface 50b compared to the coating layer 514 of the second sub-circuit board 510b.

[0127] In this embodiment, the first surface 50a and the second surface 50b of the flexible circuit board 50 are disposed opposite to each other, the first surface 50a is the outermost surface of the flexible circuit board 50, and the second surface 50b is the outermost surface of the flexible circuit board 50. In this embodiment, in the stacking direction of the plurality of sub-circuit boards 510, the first sub-circuit board 510a and the second sub-circuit board 510b are respectively the two outermost sub-circuit boards 510 of the flexible circuit board 50.

[0128] The base layer 511 of the first sub-circuit board 510a is away from the first surface 50a compared to the coating layer 514 of the first sub-circuit board 510a. In other words, the coating layer 514 of the first sub-circuit board 510a is adjacent to the first surface 50a compared to the base layer 511 of the first sub-circuit board 510a, or the surface of the coating layer 514 of the first sub-circuit board 510a away from the base layer 511 of the first sub-circuit board 510a is the first surface 50a. When the flexible circuit board 50 is electrically connected to the circuit of the circuit board or the device of the circuit board, a hole is usually opened in the coating layer 514 and the connecting glue layer 513 of the first sub-circuit board 510a to expose the conductive layer 512 of the first sub-circuit board 510a, so that the conductive layer 512 of the first sub-circuit board 510a is electrically connected to the circuit of the circuit board or the device of the circuit board.

[0129] Correspondingly, the base layer 511 of the second sub-circuit board 510b is away from the second surface 50b compared to the coating layer 514 of the second sub-circuit board 510b. In other words, the coating layer 514 of the second sub-circuit board 510b is adjacent to the second surface 50b compared to the base layer 511 of the second sub-circuit board 510b, or the surface of the coating layer 514 of the second sub-circuit board 510b away from the base layer 511 of the second sub-circuit board 510b is the second surface 50b. When the flexible circuit board 50 is electrically connected to the exposed part of the circuit board or the device of the circuit board, a hole is usually opened in the coating layer 514 and the connecting glue layer 513 of the second sub-circuit board 510b to expose the conductive layer 512 of the second sub-circuit board 510b, so that the conductive layer 512 of the second sub-circuit board 510b is electrically connected to the circuit of the circuit board or the device of the circuit board.

[0130] See also Fig.13 and Fig.14 , when the multi-layer sub-circuit board 510 includes a first sub-circuit board 510a, a second sub-circuit board 510b and a third sub-circuit board 510c, the third sub-circuit board 510c is located on a side of the first sub-circuit board 510a away from the second sub-circuit board 510b.

[0131] It can be understood that in the schematic diagram of the present embodiment, the multilayer sub-circuit board 510 includes the first sub-circuit board 510a, the second sub-circuit board 510b and the third sub-circuit board 510c as an example. It can be understood that when the multilayer sub-circuit board 510 includes the first sub-circuit board 510a and the second sub-circuit board 510b, the respective film layers of the first sub-circuit board 510a and the second sub-circuit board 510b can also satisfy the aforementioned thickness d1 of the base layer 511 that satisfies: 10μm≤d1≤18μm. The thickness d2 of the conductive layer 512 satisfies: 5μm≤d2≤10μm. The thickness d3 of the connecting adhesive layer 513 satisfies: 8μm≤d3≤15μm, and the thickness of the connecting adhesive layer 513 is greater than the thickness of the conductive layer 512.

[0132] Please continue reading Figure 1 , Fig.13 In the drawings, in one embodiment, the number of layers N of the sub-circuit boards 510 included in the flexible circuit board 50 satisfies: N≥3; and the width W of the flexible circuit board 50 satisfies: 10mm≤W≤50mm.

[0133] In one embodiment, the number N of layers of the sub-circuit boards 510 included in the flexible circuit board 50 satisfies 3≤W≤10. For example, the number N of layers of the sub-circuit boards 510 included in the flexible circuit board 50 may be, but is not limited to, 3, 4, 5, 6, 7, 8, 9, or 10.

[0134] The width W of the flexible circuit board 50 may be, but is not limited to, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, or 50 mm.

[0135] The flexible circuit board 50 provided in the embodiment of the present application has a sub-circuit board 510 whose number of layers N satisfies: N ≥ 3; and a width W of the flexible circuit board 50 satisfies: 10 mm ≤ W ≤ 50 mm, so that the flexible circuit board 50 can meet the demand of transmitting electrical signals and makes the width of the flexible circuit board 50 narrower. When the flexible circuit board 50 is applied to a foldable electronic device 1, it is convenient to assemble it in the foldable electronic device 1.

[0136] In one embodiment, the thickness of the portion of the flexible circuit board 50 located in the second area 500b is less than the thickness of the portion of the flexible circuit board 50 located in the first area 500a, and the thickness of the portion of the flexible circuit board 50 located in the third area 500c is less than the thickness of the portion of the flexible circuit board 50 located in the first area 500a. The thickness of the portion of the flexible circuit board 50 located in the first area 500a is equal to or approximately equal to the thickness of the portion of the flexible circuit board 50 located in the third area 500c.

[0137] For example, the flexible circuit board 50 includes a three-layer sub-circuit board 510, the thickness of the flexible circuit board 50 located in the first area 500a is less than 200μm (for example, less than or equal to 195μm), the thickness of the flexible circuit board 50 located in the first area 500a is less than 200μm (for example, less than or equal to 195μm), and the thickness of the portion of the flexible circuit board 50 located in the second area 500b is less than or equal to 165μm. In this embodiment, the bending life of the flexible circuit board 50 can be more than 100,000 times. It should be noted that the thickness of the flexible circuit board 50 is less than 200μm, which means that the thickness of the portion of the flexible circuit board 50 located in the first area 500a is less than 200μm, and the thickness of the portion of the flexible circuit board 50 located in the third area 500c is less than 200μm.

[0138] The flexible circuit board 50 provided in one embodiment of the present application is thin and has a small bending radius. When the flexible circuit board 50 is applied to the foldable electronic device 1, it is beneficial to the miniaturization of the hinge structure corresponding to the bendable portion 30 of the foldable electronic device 1 and the compactness of the overall size of the foldable electronic device 1.

[0139] In addition, the flexible circuit board 50 provided in one embodiment of the present application is thinner and has a smaller bending radius. When the flexible circuit board 50 is applied to the foldable electronic device 1, it is beneficial to the miniaturization of the hinge structure corresponding to the bendable portion 30 of the foldable electronic device 1 and the compactness of the overall size of the foldable electronic device 1.

[0140] The present application provides a foldable electronic device 1, which may be, but is not limited to, a mobile phone, a PDA, a laptop computer, an e-reader, a handheld computer, an electronic display screen, a notebook computer, an ultra-mobile personal computer (UMPC), a netbook, a personal digital assistant (PDA), an augmented reality (AR)\virtual reality (VR) device, a media player, a smart wearable device, and other foldable devices. In the schematic diagram of the present embodiment, the foldable electronic device 1 is illustrated as a foldable mobile phone, which is understandable and should not be understood as a limitation on the foldable electronic device 1 provided in the embodiment of the present application.

[0141] Please also read Fig.15 , Fig.16 and Fig.17 , Fig.15 A schematic diagram of a foldable electronic device in an unfolded state provided by an embodiment of the present application; Fig.16 A schematic diagram of a foldable electronic device in a folded state provided by an embodiment of the present application; Fig.17 for Fig.15 Schematic diagram of a partial structure of a foldable electronic device shown in . The foldable electronic device 1 includes a first main body 10, a second main body 20 and a bendable portion 30. The first main body 10 includes a first circuit board 110. The second main body 20 includes a second circuit board 210. The bendable portion 30 is located between the first main body 10 and the second main body 20. One end of the flexible circuit board 50 is arranged corresponding to the first main body 10 and is electrically connected to the first circuit board 110, the bendable area of ​​the flexible circuit board 50 is arranged corresponding to the bendable portion 30, and the other end of the flexible circuit board 50 is arranged corresponding to the second main body 20 and is electrically connected to the second circuit board 210.

[0142] When the flexible circuit board 50 includes a first area 500a, a second area 500b and a third area 500c arranged in sequence, and the second area 500b is the bendable area, the first area 500a of the flexible circuit board 50 is arranged corresponding to the first main body 10 and is electrically connected to the first circuit board 110, the second area 500b is arranged corresponding to the bendable portion 30, and the third area 500c is arranged corresponding to the second main body 20 and is electrically connected to the second circuit board 210.

[0143] For specific details of the flexible circuit board 50 in the foldable electronic device 1, please refer to the detailed description of the flexible circuit board 50 in the previous embodiments, which will not be repeated here.

[0144] In this embodiment, the first main body portion 10 and the second main body portion 20 are bendably connected via the bendable portion 30. The foldable electronic device 1 of this embodiment has a flattened state and a folded state. The foldable electronic device 1 can be switched from the flattened state to the folded state, and from the folded state to the flattened state. It can be understood that in one embodiment, the foldable electronic device 1 also has a hovering state (also called an intermediate state) between the folded state and the flattened state. In this embodiment, the so-called flattened state refers to the state in which the first main body portion 10 and the second main body portion 20 of the foldable electronic device 1 are flat or approximately flat. The so-called folded state refers to the state in which the first main body portion 10 and the second main body portion 20 of the foldable electronic device 1 are bent and arranged relative to each other.

[0145] In one embodiment, the first main body 10 further includes a first housing 120 , and the first housing 120 is used to carry the first circuit board 110 . The second main body further includes a second housing 220 , and the second housing 220 is used to carry the second circuit board 210 .

[0146] In one embodiment, the foldable electronic device 1 further includes a display screen 60. The display screen 60 may be, but is not limited to, various components with corresponding functions such as a touch screen, a touch display screen 60, or a display screen 60 fixedly attached to a support member, such as a display screen 60 attached to a flexible steel plate, a touch screen, a touch display screen, etc. The display screen 60 may be unfolded or folded along with the first housing 120 and the second housing 220. In other words, the display screen 60 may be unfolded along with the unfolding of the first housing 120 and the second housing 220, and may be folded along with the folding of the first housing 120 and the second housing 220.

[0147] The display screen 60 includes a first display portion 610, a bendable display portion 620, and a second display portion 630. The first display portion 610 is fixed to the first housing 120, and the second display portion 630 is fixed to the second housing 220. The first display portion 610 and the second display portion 630 are respectively connected to two opposite sides of the bendable display portion 620. The display screen 60 includes the first display portion 610, the bendable display portion 620, and the second display portion 630, that is, the first main body 10 also includes the first display portion 610, and the second main body 20 also includes the second display portion 630.

[0148] In one embodiment, the foldable electronic device 1 may be an inward-folding electronic device. That is, when the electronic device 1 is in a folded state, the display screen 60 is located inside the foldable electronic device 1. The inward-folding foldable electronic device 1 can effectively reduce the possibility of the display screen 60 being hit, which is conducive to extending the service life of the display screen 60.

[0149] In another embodiment, the foldable electronic device 1 may be an outward-folding electronic device 1. That is, when the foldable electronic device 1 is in a folded state, the display screen 60 is located outside the foldable electronic device 1. When the foldable electronic device 1 is in a folded state, the outward-folding foldable electronic device 1 still makes it convenient for the user to use the display screen 60.

[0150] The foldable electronic device 1 provided in the embodiment of the present application is an inward-folding electronic device 1. It can be understood that this should not be construed as a limitation on the foldable electronic device 1 provided in the embodiment of the present application.

[0151] In addition, in the embodiment of the present application, the foldable electronic device 1 includes two main bodies (i.e., a first main body 10 and a second main body 20) as an example for illustration. In other words, the foldable electronic device 1 shown in the schematic diagram of the embodiment of the present application is a two-folding electronic device 1. It can be understood that in other embodiments, the foldable electronic device 1 includes three or more main bodies (also called folding blocks). In other words, the foldable electronic device 1 includes multiple main bodies (identified as Q main bodies), where Q is greater than or equal to 2, and Q is a positive integer.

[0152] In one embodiment, taking into account the uniformity of the weight of the foldable electronic device 1 and making full use of the internal space of the foldable electronic device 1, multiple electrical components (such as batteries, circuit modules, etc.) inside the foldable electronic device 1 are distributed in the multiple main body parts. For example, when the foldable electronic device 1 includes two main body parts, namely, a first main body part 10 and a second main body part 20, multiple electrical modules (such as batteries, circuit modules, etc.) inside the foldable electronic device 1 are distributed in the first main body part 10 and the second main body part 20. The multiple electrical modules inside the electronic device 1 need to be electrically connected. Specifically, in this embodiment, the first main body part 10 includes a first circuit board 110, the second main body part 20 includes a second circuit board 210, and the flexible circuit board 50 electrically connects the first circuit board 110 and the second circuit board 210.

[0153] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present application, and these improvements and modifications are also regarded as the scope of protection of the present application.

Claims

1. A flexible circuit board, characterized in that: The flexible circuit board has a bendable area, and the flexible circuit board can be bent from the bendable area. The flexible circuit board includes: A first sub-circuit board; An adhesive layer, the adhesive layer is disposed on one side of the first sub-circuit board, and the adhesive layer avoids the bendable area; a second sub-circuit board, the second sub-circuit board being disposed on a side of the adhesive layer away from the first sub-circuit board, the second sub-circuit board having a signal transmission line; and An electromagnetic shielding film is disposed on a side of the second sub-circuit board facing away from the first sub-circuit board, and the electromagnetic shielding film serves as at least a partial reference surface of the impedance of the signal transmission line.

2. The flexible circuit board according to claim 1, characterized in that: The thickness d0 of the electromagnetic shielding film satisfies: 3 μm≤d0≤10 μm.

3. The flexible circuit board according to claim 1 or 2, characterized in that: The first sub-circuit board comprises a first conductive layer, wherein the first conductive layer has a plurality of grids; The second sub-circuit board includes a second conductive layer, and the second conductive layer has the signal transmission line.

4. The flexible circuit board according to claim 3, characterized in that: The signal transmission line extends along a first direction; the first conductive layer comprises: a plurality of first conductive lines arranged at intervals, wherein the first conductive lines extend along a second direction, and the second direction is different from the first direction; and A plurality of second conductive lines are arranged at intervals, the plurality of second conductive lines cross the plurality of first conductive lines to form the plurality of grids, the second conductive lines extend along a third direction, and the third direction is different from the first direction, and the third direction is different from the second direction.

5. The flexible circuit board according to claim 4, characterized in that: The angle a between the signal transmission line and the first conductor satisfies: 7°≤a≤83°; An angle b between the signal transmission line and the second conductive line satisfies: 7°≤b≤83°.

6. The flexible circuit board according to claim 4, characterized in that: The line width W1 of the first conductive line satisfies: 40 μm≤W1≤100 μm; The line width W2 of the second conductive line satisfies: 40 μm≤W2≤100 μm.

7. The flexible circuit board according to claim 4, characterized in that: The size L1 of the grid in the second direction satisfies: 40 μm≤L1≤100 μm; A size L2 of the grid in the third direction satisfies: 40 μm≤L2≤100 μm.

8. The flexible circuit board according to claim 1 or 2, characterized in that: The first sub-circuit board includes a first conductive layer, the second sub-circuit board includes a second conductive layer, and the second conductive layer has the signal transmission line; The first conductive layer includes a conductive portion, and the conductive portion avoids an orthographic projection area of ​​the signal transmission line on the first conductive layer; The flexible circuit board further includes a third sub-circuit board, which is disposed on a side of the first sub-circuit board away from the second sub-circuit board, and includes a third conductive layer.

9. The flexible circuit board according to claim 1, characterized in that: The flexible circuit board has a first area, a second area and a third area arranged in sequence, wherein the second area is the bendable area; The adhesive layer avoids the second area, so that the first sub-circuit board and the second sub-circuit board form a first gap corresponding to the second area; The adhesive layer also avoids a portion of the first area adjacent to the second area, so that a second gap is formed between the first sub-circuit board and the second sub-circuit board corresponding to a portion of the first area adjacent to the second area, and the second gap is connected to the first gap; The adhesive layer also avoids a portion of the third area adjacent to the second area, so that a third gap is formed between the first sub-circuit board and the second sub-circuit board corresponding to a portion of the third area adjacent to the second area, and the third gap is connected to the first gap.

10. A foldable electronic device, characterized in that: The foldable electronic device comprises: A first main body, the first main body comprising a first circuit board; a second main body portion, the second main body portion comprising a second circuit board; a bendable portion, the bendable portion being located between the first main body portion and the second main body portion; and The flexible circuit board as described in any one of claims 1-9, one end of the flexible circuit board is arranged corresponding to the first main body and electrically connected to the first circuit board, the bendable area of ​​the flexible circuit board is arranged corresponding to the bendable portion, and the other end of the flexible circuit board is arranged corresponding to the second main body and electrically connected to the second circuit board.

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