Flexible Printed Circuit, Circuit Board Assembly, and Electronic Device

Abstract

This application discloses a flexible printed circuit, a circuit board assembly, and an electronic device. The flexible printed circuit includes a bent portion and a soldering portion connected to the bent portion. The flexible printed circuit includes a plurality of conductive layers and a plurality of insulating layers, and the insulating layers are disposed between two adjacent conductive layers. The plurality of conductive layers includes a first soldering layer, a second soldering layer, and a trace layer. Both the first soldering layer and the second soldering layer are located in the soldering portion. The first soldering layer is one surface layer of the soldering portion, and the first soldering layer is formed by a plurality of first pads arranged at intervals from each other. The second soldering layer is the other surface layer of the soldering portion, and the second soldering layer is formed by a plurality of second pads arranged at intervals from each other. The trace layer is located between the first soldering layer and the second soldering layer and extends from the soldering portion to the bent portion. The first pads and the second pads are connected by using through-hole conductors and are connected to the trace layer. The pad pitch in the soldering portion of the flexible printed circuit is relatively small, whereby the surface area of the soldering portion is reduced and miniaturization can be facilitated.

Description

Technical Field

[0001] This application claims priority to Chinese Patent Application No. 202210758071.2, titled "FLEXIBLE PRINTED CIRCUIT, CIRCUIT BOARD ASSEMBLY, AND ELECTRONIC DEVICE", filed with the China National Intellectual Property Administration on June 30, 2022, the entire content of which is incorporated herein by reference.

[0002] This application relates to the field of circuit connection structure technologies, and particularly to flexible printed circuits, circuit board assemblies, and electronic devices.

Background Art

[0003] Currently, with the continuous development of electronic devices such as mobile phones, printed circuit boards (PCBs, also referred to as printed circuit boards) and flexible printed circuits (FPCs) are widely applied in electronic devices. The flexible printed circuit and the printed circuit board can be soldered to each other by using the FPC on board (FOB) technology on the substrate, and signal and / or power transmission can be realized.

[0004] However, conventional flexible printed circuits have a large pad spacing, which requires a large soldering space to be reserved on both the flexible printed circuit and the printed circuit board. As a result, the size of the circuit board assembly becomes large, making it difficult to implement the miniaturization and multifunctionality of electronic devices.

Summary of the Invention

[0005] This application provides a flexible printed circuit. The pad spacing in the soldering portion of the flexible printed circuit is relatively small, whereby the surface area of the soldering portion is reduced, making it possible to facilitate miniaturization. This application further provides a circuit board assembly including the above flexible printed circuit and an electronic device including the above circuit board assembly.

[0006] According to a first aspect, this application provides a flexible printed circuit including a bending portion and a soldering portion connected to the bending portion. The flexible printed circuit includes a plurality of conductive layers and a plurality of insulating layers, and the insulating layers are disposed between two adjacent conductive layers. The plurality of conductive layers includes a first soldering layer, a second soldering layer, and a trace layer. Both the first soldering layer and the second soldering layer are located in the soldering portion. The first soldering layer is one surface layer of the soldering portion, and the first soldering layer is formed by a plurality of first pads arranged at intervals from each other. The second soldering layer is the other surface layer of the soldering portion, and the second soldering layer is formed by a plurality of second pads arranged at intervals from each other. The trace layer is located between the first soldering layer and the second soldering layer and extends from the soldering portion to the bending portion. The first pads and the second pads are connected by using through-hole conductors, and the through-hole conductors are connected to the trace layer.

[0007] In this application, the first soldering layer and the second soldering layer are used as two surface layers of the soldering part. Only the first pads are arranged on the first soldering layer, and no traces are arranged. Only the second pads are arranged on the second soldering layer, and no traces are arranged. Therefore, it is not necessary to arrange a protective layer (also called a solder mask layer) outside the first soldering layer and the second soldering layer, and it is not necessary to arrange a solder mask opening structure. This enables the implementation of a solder maskless design. The pad spacing in the soldering part (i.e., the spacing between two adjacent first pads and the spacing between two adjacent second pads) is not limited by structures such as traces and solder mask openings. Compared with the pad spacing in the prior art, the pad spacing is significantly reduced, whereby the surface area of the soldering part is reduced, and it is possible to facilitate the miniaturization of the flexible printed circuit. In addition, the traces of the flexible printed circuit are arranged on the trace layer, which is the inner layer structure of the flexible printed circuit and is covered by an insulating layer or a protective layer. This helps to improve the circuit reliability of the flexible printed circuit.

[0008] In addition, compared with conventional products, the flexible printed circuit in this application arranges a plurality of pads separately on the soldering layer. The soldering layer may increase the number of conductive layers. However, since the thickness of the conductive layer is extremely small, for example, the current thickness of the copper foil layer is usually 0.25 micrometers, the increase in the overall thickness of the flexible printed circuit in this application is small and controllable, and it does not cause any obvious adverse effects or obvious obstacles to the miniaturization of both the circuit board assembly using the flexible printed circuit and the electronic device.

[0009] The through-hole conductor can be a conductive layer structure formed on the through-hole wall or a conductor pillar structure filled in the through-hole.

[0010] In a possible implementation, the trace layer includes conductor blocks and traces. The conductor blocks are located at the soldering portions. One end of a trace is connected to a conductor block, and the other end of the trace extends to a bent portion. The pads are connected to the conductor blocks by using through-hole conductors. The first pad and the second pad are connected to the conductor blocks by using through-hole conductors. The first pad and the second pad can be electrically connected to another part or another component of the flexible printed circuit by using the conductor blocks and traces.

[0011] In a possible implementation, the shape of the conductor block can be the same as or similar to the shape of the first pad.

[0012] In a possible implementation, the area of the conductor block is the same as the area of the first pad. Compared with the pad pitch in the conventional solution, the pad pitch in the present application can be reduced by about 22%. In a structure where a plurality of pads are arranged in an array, the surface area of the soldering portion of the flexible printed circuit in the present application may be about 40% smaller than the surface area of the soldering portion of the conventional product. The surface area of the soldering portion is significantly reduced, which can facilitate the miniaturization of the flexible printed circuit and the miniaturization of both the circuit board assembly using the flexible printed circuit and the electronic device.

[0013] In a possible implementation, the area of the conductor block is smaller than the area of the first pad. In this implementation, since the first pad and the second pad are connected to the conductor block by using through-hole conductors, the locations of the first pad and the second pad are limited by the arrangement of the conductor block. The area of the conductor block is smaller than the area of the first pad, so that when the internal connection requirement (i.e., the conductor block is connected to the through-hole conductor) is satisfied, the area of the conductor block can be set to a small value. In this way, when the trace layer satisfies the trace arrangement requirement, the distance between two adjacent conductor blocks can be relatively small. In that case, the center-to-center distance between two adjacent first pads is relatively small. Thereby, the pad pitch in the soldering portion can be further reduced, making it possible to facilitate the miniaturization of the flexible printed circuit.

[0014] In a possible implementation, there are multiple trace layers, and the multiple conductor blocks connected to the multiple first pads are located on different trace layers. The conductor blocks connected corresponding to at least two of the multiple first pads can be located on different trace layers.

[0015] The trace layer arranged on the conductor block also needs to arrange traces connected to the conductor block. Therefore, when the multiple conductor blocks connected to the multiple first pads are arranged centrally on a specific trace layer of the flexible printed circuit, the trace layer has relatively high trace arrangement requirements. As a result, the space of the trace layer is insufficient and trace arrangement is difficult. When the conductor blocks connected corresponding to at least two of the multiple first pads are located on different trace layers, the traces connected to the conductor blocks can also be dispersed on different trace layers. This reduces the difficulty of routing the trace layer and improves routing flexibility.

[0016] In a possible implementation, there is one or more trace layers, and a plurality of punctured regions are provided in each trace layer. A plurality of through-hole conductors pass through the plurality of punctured regions of each trace layer in a one-to-one correspondence. Support blocks are disposed in the plurality of punctured regions of each trace layer. The through-hole conductors pass through and are connected to the support blocks. When there is one trace layer, the support block is a conductor block. Alternatively, when there are a plurality of trace layers, the support block is a conductor block or a lower pad.

[0017] In this implementation, since the support blocks (conductor blocks or lower pads) are disposed in the punctured regions of each trace layer of the flexible printed circuit, the overall support structure of each punctured region of the flexible printed circuit is stable and the possibility of collapse is low. In addition, the thicknesses of the plurality of punctured regions of the flexible printed circuit can be made consistent. This facilitates batch drilling and metal filling, and improves the production efficiency and yield of the flexible printed circuit.

[0018] In a possible implementation, the plurality of insulating layers include a first insulating layer and a second insulating layer. The first insulating layer is located between the first soldering layer and an adjacent trace layer, extends from the soldering portion to the bending portion, and a part of the first insulating layer located at the bending portion forms one surface layer of the bending portion. The second insulating layer is located between the second soldering layer and an adjacent trace layer, extends from the soldering portion to the bending portion, and a part of the second insulating layer located at the bending portion forms the other surface layer of the bending portion.

[0019] In a possible implementation, the plurality of conductive layers further include a first routing layer and a second routing layer. Both the first routing layer and the second routing layer are located at the bending portion. The first routing layer and the first soldering layer are disposed on the same layer, and the second routing layer and the second soldering layer are disposed on the same layer. The flexible printed circuit further includes a first protective layer and a second protective layer. Both the first protective layer and the second protective layer are located at the bending portion. The first protective layer is located on the side of the first routing layer away from the trace layer. The second protective layer is located on the side of the second routing layer away from the trace layer. The first protective layer and the second protective layer are the two surface layers of the bending portion.

[0020] In this implementation, the first routing layer and the second routing layer are disposed at the bending portion of the flexible printed circuit. The first routing layer, the second routing layer, and the trace layer can all be configured for trace placement. Therefore, the flexible printed circuit can better meet routing requirements such as a plurality of transmission channels.

[0021] In a possible implementation, at least one insulating layer of the flexible printed circuit forms an air gap at the bending portion. In this way, the structures of the flexible printed circuit located on both sides of the air gap can move relatively independently to improve the bending performance of the bending portion of the flexible printed circuit.

[0022] According to a second aspect, the present application further provides a flexible printed circuit including a bent portion and a soldering portion connected to the bent portion. The flexible printed circuit includes a plurality of conductive layers, a plurality of insulating layers, and a first protective layer. The insulating layers are disposed between two adjacent conductive layers. The plurality of conductive layers includes a soldering layer and a trace layer. The soldering layer is located at the soldering portion. The soldering layer is one surface layer of the soldering portion. The soldering layer is formed by a plurality of pads spaced apart from each other. The trace layer is located on the side of the soldering layer and extends from the soldering portion to the bent portion. The pads are connected to the trace layer by using through-hole conductors. The first protective layer is located on the side of the trace layer away from the soldering layer. The first protective layer extends from the soldering portion to the bent portion. A part of the first protective layer located at the soldering portion forms the other surface layer of the soldering portion. A part of the first protective layer located at the bent portion forms one surface layer of the bent portion.

[0023] In this implementation, the soldering layer is used as one surface layer of the soldering portion, and only pads are disposed on the soldering layer, and no traces are disposed. Therefore, it is not necessary to dispose a protective layer (or a solder mask layer) outside the soldering layer at the soldering portion, and it is not necessary to dispose a solder mask opening structure. This enables the implementation of a solder maskless design, and the pad spacing at the soldering portion is not limited by structures such as traces and solder mask openings. Compared with the pad spacing in the prior art, the pad spacing is significantly reduced, whereby the surface area of the soldering portion is reduced, and it is possible to facilitate the miniaturization of the flexible printed circuit.

[0024] In addition, compared with conventional products, in the flexible printed circuit of the present application, a plurality of pads are separately arranged on the soldering layer. The soldering layer may increase the number of conductive layers. However, since the thickness of the conductive layer is extremely small, the increase in the overall thickness of the flexible printed circuit in the present application is small and controllable, and does not cause any obvious adverse effects or obvious obstacles to the miniaturization of both the circuit board assembly using the flexible printed circuit and the electronic device.

[0025] In a possible implementation, the trace layer includes conductor blocks and traces. The conductor blocks are located at the soldering portions. One end of the trace is connected to the conductor block, and the other end of the trace extends to the bending portion. The pads are connected to the conductor blocks by using through-hole conductors. The pads can be electrically connected to another part or another component of the flexible printed circuit by using the conductor blocks and traces.

[0026] In a possible implementation, the shape of the conductor block can be the same as or similar to the shape of the pad.

[0027] In a possible implementation, the area of the conductor block is the same as the area of the pad. Compared with the pad spacing in the conventional solution, the pad spacing in the present application can be reduced by about 22%. In a structure where a plurality of pads are arranged in an array, the surface area of the soldering portion of the flexible printed circuit in the present application may be about 40% smaller than the surface area of the soldering portion of the conventional product. The surface area of the soldering portion is significantly reduced, which can facilitate the miniaturization of the flexible printed circuit and the miniaturization of both the circuit board assembly using the flexible printed circuit and the electronic device.

[0028] In a possible implementation, the area of the conductor block is smaller than the area of the pad. In this implementation, since the pad and the second pad are connected to the conductor block by using through-hole conductors, the locations of the pad and the second pad are limited by the arrangement of the conductor block. The area of the conductor block is smaller than the area of the pad, so that when the internal connection requirement (i.e., the conductor block is connected to the through-hole conductor) is satisfied, the area of the conductor block can be set to a small value. In this way, when the trace layer meets the trace arrangement requirement, the distance between two adjacent conductor blocks can be relatively small. In that case, the center spacing between two adjacent pads is relatively small. Thereby, the pad spacing in the soldering portion can be further reduced, making it possible to facilitate the miniaturization of the flexible printed circuit.

[0029] In a possible implementation, there are multiple trace layers, and the multiple conductor blocks connected to the multiple pads are located on different trace layers. The conductor blocks connected corresponding to at least two of the multiple pads can be located on different trace layers. The trace layer on which the conductor block is arranged further needs to arrange the traces connected to the conductor block. Therefore, when the multiple conductor blocks connected to the multiple pads are centrally arranged on a specific trace layer of the flexible printed circuit, the trace layer has relatively high trace arrangement requirements. As a result, the space of the trace layer is insufficient and trace arrangement is difficult. When the conductor blocks connected corresponding to at least two of the multiple pads are located on different trace layers, the traces connected to the conductor blocks can also be dispersed on different trace layers. This reduces the difficulty of routing the trace layer and improves routing flexibility.

[0030] In a possible implementation, there is one or more trace layers, and a plurality of punctured regions are provided in each trace layer. A plurality of through-hole conductors penetrate the plurality of punctured regions of each trace layer in a one-to-one correspondence. Support blocks are disposed in the plurality of punctured regions of each trace layer. The through-hole conductors penetrate and are connected to the support blocks. When there is one trace layer, the support block is a conductor block. Alternatively, when there are a plurality of trace layers, the support block is a conductor block or a lower pad.

[0031] In this implementation, since the support blocks (conductor blocks or lower pads) are disposed in the punctured regions of each trace layer of the flexible printed circuit, the overall support structure of each punctured region of the flexible printed circuit is stable and the possibility of collapse is low. In addition, it is possible for the thicknesses of the plurality of punctured regions of the flexible printed circuit to be consistent. This facilitates batch drilling and metal filling, and improves the production efficiency and yield of the flexible printed circuit.

[0032] In a possible implementation, the plurality of insulating layers includes a first insulating layer. The first insulating layer is located between the soldering layer and the adjacent trace layer and extends from the soldering portion to the bending portion. A part of the first insulating layer located in the bending portion forms the other surface layer of the bending portion.

[0033] In a possible implementation, the plurality of conductive layers further includes a routing layer. The routing layer is located in the bending portion, and the routing layer and the soldering layer are disposed on the same layer. The flexible printed circuit further includes a second protective layer. The second protective layer is located on the side of the routing layer away from the trace layer. The second protective layer is located in the bending portion and is the other surface layer of the bending portion.

[0034] In a possible implementation, at least one insulating layer of the flexible printed circuit forms an air gap at the bending portion. In this way, the structures of the flexible printed circuit located on both sides of the air gap can move relatively independently, improving the bending performance of the bending portion of the flexible printed circuit.

[0035] According to a third aspect, the present application further provides a circuit board assembly including a circuit board and a flexible printed circuit in any one of the above descriptions. The soldering portion of the flexible printed circuit is soldered to the circuit board.

[0036] Since the pads of the soldering portion of the flexible printed circuit protrude from the surface, solder paste collapse and short circuits can be avoided in the soldering process, and it is guaranteed that the soldered joint has a specific height. This improves the soldering quality and reliability.

[0037] In a possible implementation, the circuit board assembly includes a first circuit board, a second circuit board, a flexible printed circuit, a first component, and a second component. The flexible printed circuit includes two soldering portions and a bending portion connecting the two soldering portions. The two soldering portions of the flexible printed circuit are respectively soldered to the first circuit board and the second circuit board. The structure of each of the soldering portion and the bending portion of the flexible printed circuit can use any one of the above structures. The first circuit board may be a printed circuit board or a flexible printed circuit, and the second circuit board may be a printed circuit board or a flexible printed circuit. There may be one or more first components, and the first component is fixed to and electrically connected to the first circuit board. There may be one or more second components, and the second component is fixed to and electrically connected to the second circuit board. The flexible printed circuit is configured to realize an electrical connection between the first component and the second component.

[0038] The first circuit board and the second circuit board may be stacked. The bent portion of the flexible printed circuit is bent such that the circuit board assembly forms a sandwich stack structure. The entire circuit board assembly occupies a relatively small space and requires a relatively small installation space. This helps to reduce the difficulty of installation and improve the scope of application. In some other implementations, the first circuit board and the second circuit board may alternatively form another relative positional relationship, for example, a staggered arrangement.

[0039] In some implementations, the circuit board assembly includes a first circuit board, a second circuit board, a flexible printed circuit, a first electrical connector, a second electrical connector, a first component, and a second component. The flexible printed circuit includes a soldering portion, a connection portion, and a bent portion connecting the soldering portion and the connection portion. The structure of each of the soldering portion and the bent portion of the flexible printed circuit can use any one of the above structures. The first circuit board may be a printed circuit board or a flexible printed circuit. There may be one or more first components, and the first components are fixed to and electrically connected to the first circuit board. The soldering portion of the flexible printed circuit is soldered to the first circuit board. There may be one or more second components, and the second components are fixed to and electrically connected to the second circuit board. The first electrical connector and the second electrical connector may be a male connector and a female connector respectively, and the male connector and the female connector are paired with each other. Each of the first electrical connector and the second electrical connector may be a board-to-board electrical connector or the like. The first electrical connector is fixed to and electrically connected to the connection portion of the flexible printed circuit. The second electrical connector is fixed to and electrically connected to the second circuit board. The first electrical connector is fixed to and electrically connected to the second electrical connector. The flexible printed circuit is configured to realize an electrical connection between the first component and the second component.

[0040] The first circuit board and the second circuit board may be stacked. The bent portion of the flexible printed circuit is bent so that the circuit board assembly forms a sandwich stack structure. The entire circuit board assembly occupies a relatively small space and requires a relatively small installation space. This helps reduce the difficulty of installation and improve the scope of application. In some other implementations, the first circuit board and the second circuit board may alternatively form another relative positional relationship, for example, a staggered arrangement.

[0041] In some implementations, the circuit board assembly includes a circuit board, a flexible printed circuit, a first component, and a second component. The flexible printed circuit includes a soldering portion, a mounting portion, and a bent portion connecting the soldering portion and the mounting portion. The structure of each of the soldering portion and the bent portion of the flexible printed circuit can use any one of the above structures. The circuit board may be a printed circuit board or a flexible printed circuit. There may be one or more first components, and the first components are fixedly and electrically connected to the circuit board. The soldering portion of the flexible printed circuit is soldered to the circuit board. There may be one or more second components, and the second components are fixed to and electrically connected to the mounting portion of the flexible printed circuit. The flexible printed circuit is configured to realize an electrical connection between the first component and the second component.

[0042] According to a fourth aspect, the present application further provides an electronic device including a housing and the above circuit board assembly. The circuit board assembly is installed inside the housing.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0044] Hereinafter, with reference to the accompanying drawings, the technical solutions of the embodiments in the present application will be described. In the description of the embodiments of the present application, unless otherwise specified, " / " indicates "or". For example, A / B may indicate A or B. The term "and / or" in this specification only describes the association relationship for describing the associated objects, and indicates that three relationships may exist. For example, A and / or B may indicate the following three cases, that is, only A exists, both A and B exist, and only B exists. In addition, in the description of the embodiments of the present application, "a plurality of" means two or more, in other words, "a plurality of" means at least two.

[0045] It should be noted that in the description of the embodiments of the present application, the terms "installation", "connection", and "arrangement" should be understood in a broad sense unless there are obvious conditions and limitations. For example, "connection" can be a detachable connection, a non-detachable connection, a direct connection, or an indirect connection through an intermediate medium.

[0046] Terms such as "first", "second", etc. are intended only for the purpose of description and should not be understood as an indication of relative importance or an implicit indication of the quantity of the indicated technical features. Therefore, the features limited by "first" or "second" may explicitly indicate or implicitly include one or more such features.

[0047] Please refer to FIGS. 1 to 3. FIG. 1 is a schematic diagram of the structure of a conventional flexible printed circuit 20 used in a flexible printed circuit structure on a substrate. FIG. 2 is a schematic diagram of the cross-sectional structure of the flexible printed circuit 20 shown in FIG. 1 cut along A-A. FIG. 3 is a schematic diagram of a partial structure of the flexible printed circuit 20 shown in FIG. 1.

[0048] The conventional flexible printed circuit 20 includes two soldering portions 20a and a bending portion 20b connecting the two soldering portions 20a. The bending portion 20b can change its shape and, for example, can be bent. The flexible printed circuit 20 includes a first protective layer 201, a first conductive layer 202, an insulating layer 203, a second conductive layer 204, and a second protective layer 205 that are continuously stacked. The first protective layer 201 and the second protective layer 205 are also insulating layers and may also be called solder mask layers. The first protective layer 201 and the second protective layer 205 are the two surface layers of the flexible printed circuit 20. The first conductive layer 202 includes a plurality of pads 2021 and a plurality of traces 2022. The first protective layer 201 is provided with a plurality of openings 2011 to expose the plurality of pads 2021.

[0049] One or more traces 2022 are usually disposed between two adjacent pads 2021. When one trace 2022 is disposed between two adjacent pads 2021, the center-to-center spacing between the two adjacent pads 2021 includes the radius R of the two pads 2021, two distances S between the edge of the opening 2011 of the first protective layer 201 and the pad 2021, two distances S1 and S2 between the edge of the opening 2011 and the trace 2022, and the width W of the trace 2022. In other words, the center-to-center spacing between two adjacent pads 2021 = 2R + 2S + S1 + S2 + W. In some products, considering the current general processing capabilities of flexible printed circuits 20 in the industry, taking the minimum value as an example, R is 0.15 mm, S is 0.075 mm, both S1 and S2 are 0.075 mm, and W is 0.1 mm. In this case, the pad spacing is greater than 0.7 mm. Such a large pad spacing leads to a large surface size of the soldering portion 20a and a large volume of the flexible printed circuit 20.

[0050] This application provides a flexible printed circuit. A soldering layer with only pads arranged and no traces arranged is added to the soldering part of the flexible printed circuit, and a solder maskless design is used. Thereby, the pad pitch of the soldering layer is not limited by structures such as traces and solder mask openings. The pad pitch is significantly reduced, whereby the surface area of the soldering part is reduced, making it possible to easily miniaturize the flexible printed circuit. This application further provides a circuit board assembly including the above flexible printed circuit, and an electronic device including the above circuit board assembly.

[0051] Please refer to FIGS. 4 to 6. FIG. 4 is a schematic diagram of the structure of a flexible printed circuit 1 according to an embodiment of this application in some embodiments. FIG. 5 is a schematic diagram of the cross-sectional structure of the flexible printed circuit 1 shown in FIG. 4 cut along B-B. FIG. 6 is a schematic diagram of a partial structure of the flexible printed circuit 1 shown in FIG. 4.

[0052] In some embodiments, the flexible printed circuit 1 includes a bending part 1a and a soldering part 1b connected to the bending part 1a. The flexible printed circuit 1 may be an integrally formed mechanical part, and the bending part 1a and the soldering part 1b are two parts of the flexible printed circuit 1. The bending part 1a can change its shape. For example, it can be bent, whereby the flexible printed circuit 1 can change its shape. The flexible printed circuit 1 may be soldered to another component (such as a printed circuit board) by using the soldering part 1b. In other words, the soldering part 1b is configured to connect to another component to realize an electrical connection to another component. There may be two soldering parts 1b. The two soldering parts 1b may be respectively connected to two ends of the bending part 1a. The two soldering parts 1b may be respectively soldered to different components. The flexible printed circuit 1 can realize an electrical connection between different components.

[0053] The flexible printed circuit 1 includes a plurality of conductive layers 11 and a plurality of insulating layers 12. The plurality of conductive layers 11 and the plurality of insulating layers 12 are stacked, and the insulating layer 12 is disposed between two adjacent conductive layers 11. The conductive layer 11 is configured to realize a conductive function, and the conductive layer 11 can be manufactured from a conductive material such as copper foil. The insulating layer 12 is configured to realize an insulating function, and the insulating layer 12 can be manufactured from an insulating material such as polyimide (PI). The insulating layer 12 can electrically insulate adjacent conductive layers 11.

[0054] A bonding layer (not shown in the figure) may be disposed between the conductive layer 11 and the insulating layer 12 to achieve mutual fixation, or the bonding layer may not be disposed. It can be understood that the conductive layer 11 and the insulating layer 12 may be in direct contact with each other and fixed. The decision on whether to dispose a bonding layer between the conductive layer 11 and the adjacent insulating layer 12 may be the same or different. The method and structure for fixing the plurality of conductive layers 11 and the plurality of insulating layers 12 are not strictly limited in this embodiment of the present application.

[0055] For example, the plurality of conductive layers 11 include a first soldering layer 111, a second soldering layer 112, and a trace layer 113.

[0056] Both the first soldering layer 111 and the second soldering layer 112 are conductive layers. The first soldering layer 111 and the second soldering layer 112 are configured to solder another component to realize an electrical connection between the flexible printed circuit 1 and this other component. Both the first soldering layer 111 and the second soldering layer 112 are located in the soldering portion 1b. The first soldering layer 111 is one surface layer of the soldering portion 1b, and the first soldering layer 111 is formed by a plurality of first pads 1111 arranged at intervals from each other. In this embodiment of the present application, that two structures are arranged at intervals from each other means that the two structures are separated by a specific distance and a gap is formed between the two structures. The plurality of first pads 1111 may be arranged in an array or in another arrangement manner. The second soldering layer 112 is the other surface layer of the soldering portion 1b, and the second soldering layer 112 is formed by a plurality of second pads 1121 arranged at intervals from each other. The plurality of second pads 1121 may be arranged in an array or in another arrangement manner. In this embodiment of the present application, the surface layer of the soldering portion 1b is a layer structure on the outermost side of the soldering portion 1b, and the "outer side" of the flexible printed circuit 1 is in an orientation close to the external space.

[0057] The trace layer 113 is a conductive layer, and at least traces are arranged in the trace layer 113 to realize electrical signal transmission through the traces. The electrical signal may include, but is not limited to, one or more of a power signal, a ground signal, and a data signal. The trace layer 113 is located between the first soldering layer 111 and the second soldering layer 112 and extends from the soldering portion 1b to the bending portion 1a. There may be one or more trace layers 113. When there are a plurality of trace layers 113, an insulating layer is arranged between two adjacent trace layers 113.

[0058] The first pad 1111 and the second pad 1121 are connected by using a through-hole conductor 13, and the through-hole conductor 13 is connected to the trace layer 113. In this case, the first pad 1111 and the second pad 1121 can be electrically connected by using the through-hole conductor 13, and can also be electrically connected to the trace layer 113 by using the through-hole conductor 13.

[0059] For example, the quantity of the first pads 1111 and the quantity of the second pads 1121 can be the same. A plurality of first pads 1111 and a plurality of second pads 1121 may be arranged in a one-to-one correspondence, and the corresponding first pad 1111 and second pad 1121 are connected by using a through-hole conductor 13. The corresponding first pad 1111 and second pad 1121 can have the same or similar shapes and sizes. The through-hole conductor 13 can be a conductive layer structure formed in the through-hole wall or a conductor pillar structure filled in the through-hole. This is not strictly limited in this embodiment of the present application.

[0060] In some other embodiments, the quantity of the first pads 1111 and the quantity of the second pads 1121 can be different. Some of the first pads 1111 and some of the second pads 1121 are arranged corresponding to each other, or some of the first pads 1111 and all of the second pads 1121 are arranged corresponding to each other, or all of the first pads 1111 and some of the second pads 1121 are arranged corresponding to each other. The corresponding first pad 1111 and second pad 1121 can still be connected by using the through-hole conductor 13.

[0061] For example, the plurality of insulating layers 12 includes a first insulating layer 121 and a second insulating layer 122. The first insulating layer 121 is located between the first soldering layer 111 and the adjacent trace layer 113, and extends from the soldering portion 1b to the bending portion 1a. A part of the first insulating layer 121 located in the soldering portion 1b insulates the first soldering layer 111 from the adjacent trace layer 113. A part of the first insulating layer 121 located in the bending portion 1a forms one surface layer of the bending portion 1a and forms a protective layer configured to protect the internal structure of the bending portion 1a.

[0062] The second insulating layer 122 is located between the second soldering layer 112 and the adjacent trace layer 113, and extends from the soldering portion 1b to the bending portion 1a. A part of the second insulating layer 122 located in the soldering portion 1b insulates the second soldering layer 112 from the adjacent trace layer 113. A part of the second insulating layer 122 located in the bending portion 1a forms the other surface layer of the bending portion 1a and forms a protective layer configured to protect the internal structure of the bending portion 1a.

[0063] Please refer to FIGS. 5 to 7. FIG. 7 is a schematic diagram of a partial structure of the trace layer 113 shown in FIG. 5.

[0064] In some embodiments, the trace layer 113 includes a conductor block 1131 and a trace 1132. The conductor block 1131 is located in the soldering portion 1b. One end of the trace 1132 is connected to the conductor block 1131, and the other end extends to the bending portion 1a. The first pad 1111 and the second pad 1121 are connected to the conductor block 1131 by using through-hole conductors 13. The first pad 1111 and the second pad 1121 can be electrically connected to another part or another component of the flexible printed circuit 1 by using the conductor block 1131 and the trace 1132.

[0065] In this embodiment, when the first soldering layer 111 and the second soldering layer 112 are used as two surface layers of the soldering portion 1b, only the first pad 1111 is disposed on the first soldering layer 111, no traces are disposed, only the second pad 1121 is disposed on the second soldering layer 112, and no traces are disposed. Therefore, the protective layer (or called the solder mask layer) does not need to be disposed outside the first soldering layer 111 and the second soldering layer 112 in the soldering portion 1b, and the solder mask opening structure does not need to be disposed. This enables the implementation of a solder maskless design, and the pad pitch in the soldering portion 1b (that is, the pitch between two adjacent first pads 1111 and the pitch between two adjacent second pads 1121) is not limited by structures such as traces and solder mask openings. Compared with the pad pitch in the prior art, the pad pitch is significantly reduced, whereby the surface area of the soldering portion 1b is reduced, and it is possible to facilitate the miniaturization of the flexible printed circuit 1. In addition, the traces of the flexible printed circuit 1 are disposed on the trace layer 113, which is the inner layer structure of the flexible printed circuit 1 and is covered by the insulating layer 12 or the protective layer. This helps to improve the circuit reliability of the flexible printed circuit 1.

[0066] In addition, compared with conventional products, the flexible printed circuit 1 in the present application separately disposes a plurality of pads on the soldering layer. The soldering layer may increase the number of conductive layers (for example, compared with the structure shown in FIG. 2, one conductive layer is added to the structure in the embodiment shown in FIG. 5). However, since the thickness of the conductive layer 11 is extremely small, for example, the current thickness of the copper foil layer is usually 0.25 micrometers, the increase in the overall thickness of the flexible printed circuit 1 in the present application is small and controllable, and it does not cause an obvious adverse effect or an obvious obstacle to the miniaturization of both the circuit board assembly using the flexible printed circuit 1 and the electronic device.

[0067] Both the conductor block 1131 and the trace 1132 are conductive components. The conductor block 1131 is configured to electrically connect the first pad 1111 and the second pad 1121 by using the through-hole conductor 13, and may be further configured to electrically connect the inner conductive structure (e.g., the trace 1132) of the flexible printed circuit 1. In this case, the flexible printed circuit 1 can be electrically connected to another component by using the first pad 1111 and the second pad 1121.

[0068] In some embodiments, the shape of the conductor block 1131 may be the same as or similar to the shape of the first pad 1111, for example, both are circular. For example, the area of the conductor block 1131 is the same as the area of the first pad 1111. As shown in FIG. 5, the center-to-center spacing between two adjacent first pads 1111 includes the radius R of the two first pads 1111, the width W of the trace 1132, and the two distances S3 and S4 between the first pad 1111 and the trace 1132. In other words, the center-to-center spacing between two adjacent first pads 1111 = 2R + W + S3 + S4. In some products with the same processing power, taking the minimum value as an example, R is 0.15 mm, S is 0.075 mm, both S3 and S4 are 0.075 mm, and W is 0.1 mm. In this case, the pad spacing in the soldering portion 1b is reduced to 0.55 mm. Compared with the pad spacing in the conventional solution, the pad spacing in the present application can be reduced by about 22%. In a structure in which a plurality of pads are arranged in an array, the surface area of the soldering portion 1b of the flexible printed circuit 1 in the present application may be about 40% smaller than the surface area of the soldering portion of the conventional product. The surface area of the soldering portion 1b is significantly reduced, which can facilitate the miniaturization of the flexible printed circuit 1 and the miniaturization of both the circuit board assembly using the flexible printed circuit 1 and the electronic device.

[0069] FIG. 8 is a schematic diagram of the internal structure of the flexible printed circuit 1 according to an embodiment of the present application in some other embodiments. The flexible printed circuit 1 shown in this embodiment may include most of the technical features in the above embodiment. Hereinafter, while skipping the common ones, the differences between the flexible printed circuit 1 in the above embodiment and the one in this embodiment will be mainly described.

[0070] In some embodiments, the area of the conductor block 1131 may be smaller than the area of the first pad 1111. In this embodiment, since the first pad 1111 and the second pad 1121 are connected to the conductor block 1131 by using the through-hole conductor 13, the locations of the first pad 1111 and the second pad 1121 are limited by the arrangement of the conductor block 1131. The area of the conductor block 1131 is smaller than the area of the first pad 1111, so that when the internal connection requirement (that is, the conductor block is connected to the through-hole conductor 13) is satisfied, the area of the conductor block 1131 can be set to a small value. In this way, when the trace layer 113 satisfies the arrangement requirement of the trace 1132, the interval between two adjacent conductor blocks 1131 can be relatively small. In that case, the center-to-center interval between two adjacent first pads 1111 is relatively small. Thereby, the pad interval in the soldering portion 1b can be further reduced, and it is possible to facilitate the miniaturization of the flexible printed circuit 1.

[0071] Please refer to FIGS. 9 and 10. FIG. 9 is a schematic diagram of the internal structure of the flexible printed circuit 1 according to an embodiment of the present application in some other embodiments. FIG. 10 is a schematic diagram of a partial structure of the flexible printed circuit 1 shown in FIG. 9. The flexible printed circuit 1 shown in this embodiment may include most of the technical features in the above embodiment. Hereinafter, while skipping the common ones, the differences between the flexible printed circuit 1 in the above embodiment and the one in this embodiment will be mainly described.

[0072] In some embodiments, there may be a plurality of trace layers 113 of the flexible printed circuit 1, for example, two layers, three layers, or four layers. In this embodiment, two layers are used as an example for explanation and illustration. The plurality of conductor blocks 1131 connected to the plurality of first pads 1111 may be dispersed on different trace layers 113. For example, the conductor blocks 1131 connected corresponding to at least two of the plurality of first pads 1111 may be located on different trace layers 113. For example, the plurality of first pads 1111 includes a first first pad and a second first pad. The first first pad is connected to a first conductor block, and the first conductor block is located on a first trace layer. The second first pad is connected to a second conductor block, and the second conductor block is located on a second trace layer. The above "first" and "second" are for distinguishing two structures and do not constitute a sequence limitation, an importance limitation, or other limitations.

[0073] It can be understood that the trace layer 113 on which the conductor block 1131 is disposed needs to be further provided with a trace 1132 connected to the conductor block 1131. Therefore, when the plurality of conductor blocks 1131 connected to the plurality of first pads 1111 are centrally disposed on a specific trace layer 113 of the flexible printed circuit 1, the trace layer 113 has relatively high trace layout requirements. As a result, the space of the trace layer 113 is insufficient and trace layout is difficult. When the conductor blocks 1131 connected corresponding to at least two of the plurality of first pads 1111 are located on different trace layers 113, the traces 1132 connected to the conductor blocks 1131 can also be dispersed on different trace layers 113. This reduces the difficulty of routing the trace layer 113 and improves routing flexibility.

[0074] In some embodiments, a plurality of punctured regions are provided in the soldering portion 1b of the flexible printed circuit 1, and the plurality of through-hole conductors 13 penetrate the plurality of punctured regions in a one-to-one correspondence. The first soldering layer 111, the second soldering layer 112, and the trace layer 113 are each provided with a plurality of corresponding punctured regions. The punctured regions include the space occupied by the through-hole conductors 13 and the space within a specific range around the through-hole conductors 13. For example, the plurality of first pads 1111 are arranged in the plurality of punctured regions of the first soldering layer 111, the plurality of through-hole conductors 13 penetrate the plurality of first pads 1111 and are connected to the first pads 1111. The plurality of second pads 1121 are arranged in the plurality of punctured regions of the second soldering layer 112, the plurality of through-hole conductors 13 penetrate the plurality of second pads 1121 and are connected to the second pads 1121.

[0075] There may be one or more trace layers 113. Each trace layer 113 is provided with a plurality of punctured regions. The support blocks are arranged in the punctured regions, and a plurality of through-hole conductors 13 penetrate the plurality of punctured regions in a one-to-one correspondence. The through-hole conductors 13 penetrate the support blocks and are connected to the support blocks. For example, as shown in FIG. 5, when there is one trace layer 113 and a plurality of conductor blocks 1131 connected to a plurality of first pads 1111 are all located on the trace layer 113, the support blocks in the punctured regions of the trace layer 113 are the conductor blocks 1131, and the through-hole conductors 13 penetrate the conductor blocks 1131 and are connected to the conductor blocks 1131. As shown in FIG. 9, when there are a plurality of trace layers 113 and a plurality of conductor blocks 1131 connected to a plurality of first pads 1111 are dispersed on different trace layers 113, the support blocks in the plurality of punctured regions of the trace layer 113 can be the conductor blocks 1131 or the lower pads 1133 (target pads). In other words, when there are a plurality of trace layers 113, if the conductor blocks 1131 are not arranged in the punctured regions of the trace layer 113, the lower pads 1133 are arranged. Both the lower pads 1133 and the conductor blocks 1131 are essentially conductor structures. The difference between the lower pads 1133 and the conductor blocks 1131 is that the lower pads 1133 are not connected to the traces and are a suspended structure in the transmission circuit of the flexible printed circuit 1, while the conductor blocks 1131 are connected to the traces 1132 and are part of the transmission circuit. The area of the lower pads 1133 may be larger than, smaller than, or equal to the area of the conductor blocks 1131. This is not strictly limited in this embodiment of the present application.

[0076] In this embodiment, since the support block (conductor block 1131 or lower pad 1133) is disposed in the punctured region of each trace layer 113 of the flexible printed circuit 1, the overall support structure of each punctured region of the flexible printed circuit 1 is stable and the possibility of collapse is low. In addition, the thicknesses of the plurality of punctured regions of the flexible printed circuit 1 can be made consistent. This facilitates batch punching and metal filling, improving the production efficiency and yield of the flexible printed circuit 1.

[0077] In the above embodiment, when the number of trace layers 113 of the flexible printed circuit 1 is relatively small (for example, one layer, two layers, or three layers), the thickness of the bent portion 1a of the flexible printed circuit 1 is extremely small, whereby the bending performance can be guaranteed, and the flexible printed circuit 1 can satisfy various installation environments and is understood to have better reliability. In some other embodiments, the number of trace layers 113 of the flexible printed circuit 1 may alternatively be relatively large in order to meet routing requirements such as a plurality of transmission channels.

[0078] FIG. 11 is a schematic diagram of the internal structure of the flexible printed circuit 1 according to an embodiment of the present application in some other embodiments. The flexible printed circuit 1 shown in this embodiment may include most of the technical features in the above embodiment. Hereinafter, while skipping the common ones, the differences between the flexible printed circuit 1 in the above embodiment and that in this embodiment will be mainly described.

[0079] In some embodiments, the plurality of conductive layers 11 further include a first routing layer 114 and a second routing layer 115. Both the first routing layer 114 and the second routing layer 115 are located at the bending portion 1a. The first routing layer 114 and the first soldering layer 111 are disposed on the same layer. The first routing layer 114 is a conductive layer, and at least one or a plurality of traces are disposed thereon to realize electrical signal transmission through the traces. The second routing layer 115 and the second soldering layer 112 are disposed on the same layer. The second routing layer 115 is a conductive layer, and at least one or a plurality of traces are disposed thereon to realize electrical signal transmission through the traces. The first routing layer 114 and / or the second routing layer 115 may be electrically connected to the trace layer 113.

[0080] The flexible printed circuit 1 further includes a first protective layer 141 and a second protective layer 142. Both the first protective layer 141 and the second protective layer 142 are located at the bending portion 1a. The first protective layer 141 is located on the side of the first routing layer 114 away from the trace layer 113. The second protective layer 142 is located on the side of the second routing layer 115 away from the trace layer 113. The first protective layer 141 and the second protective layer 142 are two surface layers of the bending portion 1a. Both the first protective layer 141 and the second protective layer 142 are insulating layers configured to protect the internal structure of the flexible printed circuit 1. The first protective layer 141 and the second protective layer 142 may also be referred to as a solder mask layer.

[0081] In this embodiment, the first routing layer 114 and the second routing layer 115 are disposed at the bending portion 1a of the flexible printed circuit 1. The first routing layer 114, the second routing layer 115, and the trace layer 113 may all be configured for trace placement. Therefore, the flexible printed circuit 1 can better meet routing requirements such as a plurality of transmission channels.

[0082] FIG. 12 is a schematic diagram of the internal structure of the flexible printed circuit 1 according to an embodiment of the present application in some other embodiments. The flexible printed circuit 1 shown in this embodiment may include most of the technical features in the above embodiment. Hereinafter, while skipping the common ones, the differences between the flexible printed circuit 1 in the above embodiment and the one in this embodiment will be mainly described.

[0083] In some embodiments, when there are two or more conductive layers 11 of the flexible printed circuit 1, at least one insulating layer 12 of the flexible printed circuit 1 may form an air gap in the bent portion 1a. In other words, the bent portion 1a of the flexible printed circuit 1 forms one or more air gaps. In this way, the structures of the flexible printed circuit 1 located on both sides of the air gap can move relatively independently, and the bending performance of the bent portion 1a of the flexible printed circuit 1 can be improved.

[0084] For example, the flexible printed circuit 1 may have a four-layer substrate structure. The plurality of conductive layers 11 of the flexible printed circuit 1 may include a first routing layer 114, a second routing layer 115, and two trace layers 113. The insulating layer 12 located between the two trace layers 113 may form an air gap 121 in the bent portion 1a. The insulating layer 12 located between the two trace layers 113 may include a first insulating sub-layer 122 and a second insulating sub-layer 123. A part of the first insulating sub-layer 122 in the soldering portion 1b and a part of the second insulating sub-layer 123 in the soldering portion 1b may be press-fitted and fixed by using an adhesive on both the first insulating sub-layer 122 and the second insulating sub-layer 123. The adhesive on both a part of the first insulating sub-layer 122 in the bent portion 1a and a part of the second insulating sub-layer 123 in the bent portion 1a may be removed or omitted. The air gap 121 is formed between a part of the first insulating sub-layer 122 in the bent portion 1a and a part of the second insulating sub-layer 123 in the bent portion 1a.

[0085] In some other embodiments, when the plurality of conductive layers 11 of the flexible printed circuit 1 do not include the first routing layer 114 and the second routing layer 115 but include a plurality of trace layers 113, one or more air gaps may be formed at the bending portion 1a, whereby the bending performance of the bending portion 1a of the flexible printed circuit 1 becomes better.

[0086] When there are two or more conductive layers 11 of the flexible printed circuit 1, it may be understood that the stack structure of the flexible printed circuit 1 can be implemented in a plurality of ways. For example, when there are three conductive layers 11, the bending portion 1a can form a single-layer + two-layer stack structure by using one air gap, or a single-layer + single-layer + single-layer stack structure by using two air gaps. When there are four conductive layers 11, the bending portion 1a can form a two-layer + two-layer stack structure by using one air gap, or a single-layer + two-layer + single-layer stack structure by using two air gaps, or a single-layer + single-layer + single-layer + single-layer stack structure by using three air gaps. The quantity of the conductive layers 11 of the flexible printed circuit 1 and the specific stack structure are not strictly limited in this embodiment of the present application.

[0087] FIG. 13 is a schematic diagram of the internal structure of the flexible printed circuit 1 according to an embodiment of the present application in some other embodiments.

[0088] In some embodiments, the flexible printed circuit 1 includes a bent portion 1a and a soldering portion 1b connected to the bent portion 1a. The flexible printed circuit 1 may be an integrally formed mechanical part, and the bent portion 1a and the soldering portion 1b are two parts of the flexible printed circuit 1. The bent portion 1a can change its shape. For example, it can be bent, whereby the flexible printed circuit 1 can change its shape. The flexible printed circuit 1 may be soldered to another component (e.g., a printed circuit board) by using the soldering portion 1b. In other words, the soldering portion 1b is configured to connect to another component to realize an electrical connection to the other component. There may be two soldering portions 1b. The two soldering portions 1b may be respectively connected to two ends of the bent portion 1a. The two soldering portions 1b may be respectively soldered to different components. The flexible printed circuit 1 can realize an electrical connection between these different components.

[0089] In the above embodiment, the surface layers on both sides of the soldering portion 1b of the flexible printed circuit 1 form a soldering structure. In this embodiment, the surface layer on the side of the soldering portion 1b of the flexible printed circuit 1 forms a soldering structure, and the surface layer on the other side does not form a soldering structure. Specifically, it is as follows.

[0090] The flexible printed circuit 1 includes a plurality of conductive layers 15, a plurality of insulating layers 16, and a first protective layer 171. The plurality of conductive layers 15, the plurality of insulating layers 16, and the first protective layer 171 are stacked, and the insulating layer 16 is disposed between two adjacent conductive layers 15. The conductive layer 15 is configured to realize a conductive function, and the conductive layer 15 may be manufactured from a conductive material such as copper foil. The insulating layer 16 is configured to realize an insulating function, and the insulating layer 16 may be manufactured from an insulating material such as polyimide (PI). The insulating layer 16 can electrically insulate the adjacent conductive layers 15.

[0091] The bonding layer (not shown in the figure) may be disposed between the conductive layer 15 and the insulating layer 16 to achieve mutual fixation, or the bonding layer may not be disposed, and it may be understood that the conductive layer 15 and the insulating layer 16 may be in direct contact with each other and fixed. The decision on whether to dispose a bonding layer between the conductive layer 15 and the adjacent insulating layer 16 may be the same or different. The method and structure for fixing the plurality of conductive layers 15 and the plurality of insulating layers 16 are not strictly limited in this embodiment of the present application.

[0092] For example, the plurality of conductive layers 15 include a soldering layer 151 and a trace layer 152.

[0093] The soldering layer 151 is a conductive layer, and the soldering layer 151 is configured to solder another component to realize an electrical connection between the flexible printed circuit 1 and this other component. The soldering layer 151 is located at the soldering portion 1b, and the soldering layer 151 is one surface layer of the soldering portion 1b. The soldering layer 151 is formed by a plurality of pads 1511 arranged at intervals from each other. The plurality of pads 1511 may be arranged in an array or in another arrangement.

[0094] The trace layer 152 is a conductive layer, and at least traces are arranged in the trace layer 152 to realize electrical signal transmission through the traces. The electrical signal may include, but is not limited to, one or more of a power signal, a ground signal, and a data signal. The trace layer 152 is located on the side of the soldering layer 151 and extends from the soldering portion 1b to the bending portion 1a. There may be one or more trace layers 152. When there are a plurality of trace layers 152, the insulating layer is disposed between two adjacent trace layers 152. The pads 1511 are connected to the trace layer 152 by using through-hole conductors 18. The through-hole conductor 18 may be a conductive layer structure formed on the through-hole wall or a conductor pillar structure filled in the through-hole. This is not strictly limited in this embodiment of the present application.

[0095] The trace layer 152 may include a conductor block 1521 and a trace 1522. The conductor block 1521 is located at the soldering portion 1b. One end of the trace 1522 is connected to the conductor block 1521, and the other end extends to the bending portion 1a. The pad 1511 of the soldering layer 151 is connected to the conductor block 1521 by using the through-hole conductor 18, and the pad 1511 can be electrically connected to another part or another component of the flexible printed circuit 1 by using the conductor block 1521 and the trace 1522.

[0096] The first protective layer 171 is located on the side of the trace layer 152 away from the soldering layer 151. The first protective layer 171 extends from the soldering portion 1b to the bending portion 1a. A part of the first protective layer 171 located at the soldering portion 1b forms the other surface layer of the soldering portion 1b. A part of the first protective layer 171 located at the bending portion 1a forms one surface layer of the bending portion 1a. The first protective layer 171 is also an insulating layer and may be called a solder mask layer, and is configured to protect the internal structure of the flexible printed circuit 1. No soldering structure is provided on the side of the soldering portion 1b where the first protective layer 171 is located. There is no need to arrange structures such as traces and solder mask openings on the soldering portion 1b on the first protective layer 171. The first protective layer 171 can be a continuous and complete surface structure.

[0097] The plurality of insulating layers 16 may include a first insulating layer 161. The first insulating layer 161 is located between the soldering layer 151 and the adjacent trace layer 152 and extends from the soldering portion 1b to the bending portion 1a. A part of the first insulating layer 161 located at the bending portion 1a forms the other surface layer of the bending portion 1a. The part of the first insulating layer 161 located at the soldering portion 1b is configured to insulate the soldering layer 151 from the trace layer 152.

[0098] In this embodiment, the soldering layer 151 is used as one surface layer of the soldering portion 1b, and only the pads 1511 are arranged on the soldering layer 151, and no traces are arranged. Therefore, it is not necessary to arrange a protective layer (or a solder mask layer) outside the soldering layer 151 for the soldering portion 1b, and it is not necessary to arrange a solder mask opening structure. This makes it possible to realize a solder maskless design, and the pad pitch in the soldering portion 1b is not limited by structures such as traces and solder mask openings. Compared with the pad pitch in the prior art, the pad pitch is significantly reduced, whereby the surface area of the soldering portion 1b is reduced, and it becomes possible to easily miniaturize the flexible printed circuit 1.

[0099] In addition, compared with conventional products, the flexible printed circuit 1 in the present application separately arranges a plurality of pads on the soldering layer. The soldering layer may increase the number of conductive layers. However, since the thickness of the conductive layer is extremely small, for example, the current thickness of the copper foil layer is usually 0.25 micrometers, the increase in the overall thickness of the flexible printed circuit 1 in the present application is small and controllable, and it does not cause any obvious adverse effects or obvious obstacles to the miniaturization of both the circuit board assembly using the flexible printed circuit 1 and the electronic device.

[0100] In some embodiments, the shape of the conductor block 1521 may be the same as or similar to the shape of the pad 1511. For example, both may be circular. For example, the area of the conductor block 1521 is the same as the area of the pad 1511. As shown in FIG. 13, the center-to-center spacing between two adjacent pads 1511 includes the radius R of the two pads 1511, the width W of the trace, and the two distances S3 and S4 between the pad 1511 and the trace. In other words, the center-to-center spacing between two adjacent pads 1511 = 2R + W + S3 + S4. In some products, for example, the same processing capabilities and minimum values are used. R is 0.15 mm, S is 0.075 mm, both S3 and S4 are 0.075 mm, and W is 0.1 mm. In this case, the pad spacing is reduced to 0.55 mm. Compared with the pad spacing in the conventional solution, the pad spacing in the present application can be reduced by about 22%. In a structure in which a plurality of pads 1511 are arranged in an array, the surface area of the soldering portion 1b of the flexible printed circuit 1 in the present application may be about 40% smaller than the surface area of the soldering portion of the conventional product. The surface area of the soldering portion 1b is significantly reduced, which can facilitate the miniaturization of the flexible printed circuit 1 and the miniaturization of both the circuit board assembly using the flexible printed circuit 1 and the electronic device.

[0101] In some other embodiments, the area of the conductor block 1521 may be smaller than the area of the pad 1511. In this embodiment, since the pad 1511 is connected to the conductor block 1521 by using the through-hole conductor 18, the location of the pad 1511 is limited by the arrangement of the conductor block 1521. The area of the conductor block 1521 is smaller than the area of the pad 1511, so that when the internal connection requirement (i.e., the conductor block 1521 is connected to the through-hole conductor 18) is satisfied, the area of the conductor block 1521 can be set to a small value. In this way, when the trace layer 152 satisfies the trace arrangement, the interval between two adjacent conductor blocks 1521 can be relatively small. In that case, the center-to-center interval between two adjacent pads 1511 is relatively small. As a result, the pad interval in the soldering portion 1b can be further reduced, making it possible to easily miniaturize the flexible printed circuit 1.

[0102] FIG. 14 is a schematic diagram of the internal structure of the flexible printed circuit 1 according to an embodiment of the present application in some other embodiments. The flexible printed circuit 1 shown in this embodiment may include most of the technical features in the above embodiments. In the following, while skipping the common ones, the differences between the flexible printed circuit 1 in the above embodiment and the one in this embodiment will be mainly described.

[0103] In some embodiments, there may be multiple trace layers 152 of the flexible printed circuit 1, for example, two layers, three layers, or four layers. In this embodiment, two layers are used as an example for explanation and illustration. Two conductor blocks 1521 connected corresponding to two adjacent pads 1511 may be located on different trace layers 152. The plurality of conductor blocks 1521 connected to the plurality of pads 1511 may be dispersed on different trace layers 152. For example, the conductor blocks 1521 connected corresponding to at least two of the plurality of pads 1511 may be located on different trace layers 152. For example, the plurality of pads 1511 includes a first pad and a second pad. The first pad is connected to the first conductor block, and the first conductor block is located on the first trace layer. The second pad is connected to the second conductor block, and the second conductor block is located on the second trace layer. The above "first" and "second" are descriptions for distinguishing two structures and do not constitute a sequence limitation, importance limitation, or other limitation.

[0104] It may be understood that the trace layer 152 in which the conductor block 1521 is disposed further needs to dispose a trace 1522 connected to the conductor block 1521. Therefore, when the plurality of conductor blocks 1521 connected to the plurality of pads 1511 are centrally disposed on a specific trace layer 152 of the flexible printed circuit 1, the trace layer 152 has relatively high trace placement requirements. As a result, the space of the trace layer 152 is insufficient and trace placement is difficult. When the conductor blocks 1521 connected corresponding to at least two of the plurality of pads 1511 are located on different trace layers 152, the traces 1522 connected to the conductor blocks 1521 may also be dispersed on different trace layers 152. This reduces the routing difficulty of the trace layer 152 and improves routing flexibility.

[0105] In some embodiments, a plurality of punctured regions are provided in the soldering portion 1b of the flexible printed circuit 1, and the plurality of through-hole conductors 18 penetrate the plurality of punctured regions in a one-to-one correspondence. The soldering layer 151 and the trace layer 152 are each provided with a plurality of corresponding punctured regions. The punctured regions include the space occupied by the through-hole conductors 18 and the space within a specific range around the through-hole conductors 18. For example, the plurality of pads 1511 are arranged in the plurality of punctured regions of the soldering layer 151, and the plurality of through-hole conductors 18 penetrate the plurality of pads 1511 and are connected to the pads 1511.

[0106] There may be one or more trace layers 152. Each trace layer 152 is provided with a plurality of punctured regions. The support block is disposed in the punctured region, and a plurality of through-hole conductors 18 penetrate the plurality of punctured regions in a one-to-one correspondence. The through-hole conductor 18 penetrates the support block and is connected to the support block. For example, as shown in FIG. 13, when there is one trace layer 152 and a plurality of conductor blocks 1521 connected to a plurality of pads 1511 are all located on the trace layer 152, the support block in the punctured region of the trace layer 152 is the conductor block 1521, and the through-hole conductor 18 penetrates the conductor block 1521 and is connected to the conductor block 1521. As shown in FIG. 14, when there are a plurality of trace layers 152 and a plurality of conductor blocks 1521 connected to a plurality of pads 1511 are dispersed on different trace layers 152, the support blocks in the plurality of punctured regions of the trace layer 152 can be the conductor blocks 1521 or the lower pads 1523 (target pads). In other words, when there are a plurality of trace layers 152, if the conductor block 1521 is not disposed in the punctured region of the trace layer 152, the lower pad 1523 is disposed. Both the lower pad 1523 and the conductor block 1521 are essentially conductor structures. The difference between the lower pad 1523 and the conductor block 1521 is that the lower pad 1523 is not connected to the trace and is a suspended structure in the transmission circuit of the flexible printed circuit 1, and the conductor block 1521 is connected to the trace 1522 and is part of the transmission circuit. The area of the lower pad 1523 may be larger than, smaller than, or equal to the area of the conductor block 1521. This is not strictly limited in this embodiment of the present application.

[0107] In this embodiment, since the support blocks (conductor block 1521 or lower pad 1523) are arranged in the punctured regions of each trace layer 152 of the flexible printed circuit 1, the overall support structure of each punctured region of the flexible printed circuit 1 is stable and the possibility of collapse is low. In addition, the thicknesses of the plurality of punctured regions of the flexible printed circuit 1 can be made consistent. This facilitates batch drilling and metal filling, and improves the production efficiency and yield of the flexible printed circuit 1.

[0108] When there are a plurality of trace layers 152, it may be understood that some of the plurality of through-hole conductors 18 do not penetrate all of the trace layers 152 and may penetrate some of the trace layers 152. For example, as shown in FIG. 14, when there are two trace layers 152, some through-hole conductors 18 penetrate the two trace layers 152 and some through-hole conductors 18 penetrate one trace layer 152. In this case, the number of punctured regions of different trace layers 152 may be different, and accordingly, the number of support blocks arranged in the punctured regions may be different. The through-hole conductors 18 do not penetrate all of the trace layers 152. The trace layer 152 not penetrated by the through-hole conductor 18 may include a support region. The support region is arranged corresponding to the punctured regions of the other trace layers 152 penetrated by the through-hole conductor 18. The support blocks are also arranged in the support area, and the support strength of the flexible printed circuit 1 corresponding to the through-hole conductor 18 can be improved.

[0109] In the above embodiment, when the number of trace layers 152 of the flexible printed circuit 1 is relatively small (for example, one layer, two layers, or three layers), the thickness of the bent portion 1a of the flexible printed circuit 1 is extremely small, whereby the bending performance can be guaranteed, the flexible printed circuit 1 can meet various installation environments, and it may be understood that the reliability is better. In some other embodiments, the number of trace layers 152 of the flexible printed circuit 1 may alternatively be relatively large in order to meet routing requirements such as a plurality of transmission channels.

[0110] FIG. 15 is a schematic diagram of the internal structure of the flexible printed circuit 1 according to an embodiment of the present application in some other embodiments. The flexible printed circuit 1 shown in this embodiment may include most of the technical features in the above embodiment. Hereinafter, while skipping the common ones, the differences between the flexible printed circuit 1 in the above embodiment and that in this embodiment will be mainly described.

[0111] In some embodiments, the plurality of conductive layers 15 further includes a routing layer 153, the routing layer 153 is located at the bent portion 1a, and the routing layer 153 and the soldering layer 151 are disposed on the same layer. The routing layer 153 is a conductive layer, and at least one or a plurality of traces are disposed thereon to realize electrical signal transmission through the traces. The routing layer 153 is manufactured from a conductive material such as copper foil. The routing layer 153 may be electrically connected to the trace layer 152.

[0112] The flexible printed circuit 1 further includes a second protective layer 172. The second protective layer 172 is located on the side of the routing layer 153 away from the trace layer 152. The second protective layer 172 is located at the bent portion 1a and is the other surface layer of the bent portion 1a. The second protective layer 172 is an insulating layer configured to protect the internal structure of the flexible printed circuit 1 and may also be called a solder mask layer.

[0113] In this embodiment, the routing layer 153 is disposed at the bent portion 1a of the flexible printed circuit 1. Both the routing layer 153 and the trace layer 152 can be configured for trace placement. Therefore, the flexible printed circuit 1 can better meet routing requirements such as a plurality of transmission channels.

[0114] FIG. 16 is a schematic diagram of the internal structure of the flexible printed circuit 1 according to an embodiment of the present application in some other embodiments. The flexible printed circuit 1 shown in this embodiment may include most of the technical features in the above embodiments. In the following, while skipping the common ones, the differences between the flexible printed circuit 1 in the above embodiment and that in this embodiment will be mainly described.

[0115] In some embodiments, when there are two or more conductive layers 15 of the flexible printed circuit 1, at least one insulating layer 16 of the flexible printed circuit 1 may form an air gap at the bent portion 1a. In other words, the bent portion 1a of the flexible printed circuit 1 forms one or more air gaps. In this way, the structures of the flexible printed circuit 1 located on both sides of the air gap can move relatively independently to improve the bending performance of the bent portion 1a of the flexible printed circuit 1.

[0116] For example, the flexible printed circuit 1 may have a three-layer substrate structure. The plurality of conductive layers 15 of the flexible printed circuit 1 may include a routing layer 153 and two trace layers 152. The insulating layer 16 located between the two trace layers 152 may form an air gap 161 at the bending portion 1a. The insulating layer 16 located between the two trace layers 152 may include a first insulating sub-layer 162 and a second insulating sub-layer 163. A part of the first insulating sub-layer 162 in the soldering portion 1b and a part of the second insulating sub-layer 163 in the soldering portion 1b may be press-fitted and fixed by using an adhesive on both the first insulating sub-layer 162 and the second insulating sub-layer 163. The adhesive on both a part of the first insulating sub-layer 162 in the bending portion 1a and a part of the second insulating sub-layer 163 in the bending portion 1a may be removed or omitted. The air gap 161 is formed between a part of the first insulating sub-layer 162 in the bending portion 1a and a part of the second insulating sub-layer 163 in the bending portion 1a. An air gap may also be formed between the routing layer 153 and the trace layer 152.

[0117] In some other embodiments, when the plurality of conductive layers 15 of the flexible printed circuit 1 do not include a routing layer 153 but include a plurality of trace layers 152, one or more air gaps may be formed at the bending portion 1a, whereby the bending performance of the bending portion 1a of the flexible printed circuit 1 is improved.

[0118] When there are two or more conductive layers 15 of the flexible printed circuit 1, it may be understood that the stack structure of the flexible printed circuit 1 can be implemented in a plurality of ways. For example, when there are three conductive layers 15, the bent portion 1a can form a single layer + two-layer stack structure by using one air gap, or a single layer + single layer + single layer stack structure by using two air gaps. When there are four conductive layers 15, the bent portion 1a can form a two-layer + two-layer stack structure by using one air gap, or a single layer + two-layer + single layer stack structure by using two air gaps, or a single layer + single layer + single layer stack structure by using three air gaps. The quantity of the conductive layers 15 of the flexible printed circuit 1 and the specific stack structure are not strictly limited in this embodiment of the present application.

[0119] In some other embodiments, the flexible printed circuit 1 may include two routing layers 153, for example, it may include a first routing layer and a second routing layer. Both the first routing layer and the second routing layer are located at the bent portion 1a. The first routing layer and the soldering layer 151 are arranged on the same layer. The second routing layer is located on the side of the first protective layer 171 away from the trace layer 152. In this case, the flexible printed circuit 1 may further include a second protective layer and a third protective layer. Both the second protective layer and the third protective layer are located at the bent portion 1a. The second protective layer is located on the side of the first routing layer away from the trace layer 152. The third protective layer is located on the side of the second routing layer away from the trace layer 152. In this embodiment, a part of the first protective layer 171 located at the bent portion 1a is no longer the surface layer of the bent portion 1a, but the internal layer structure of the bent portion 1a.

[0120] In the above-described embodiments, the flexible printed circuit 1 may include two soldering portions 1b and a bending portion 1a. The bending portion 1a is connected between the two soldering portions 1b. The two soldering portions 1b are soldered to different components. The flexible printed circuit 1 realizes electrical connection between these different components.

[0121] In some other embodiments, the flexible printed circuit 1 may alternatively include a soldering portion 1b and a bending portion 1a, and may further include a connection portion. The bending portion 1a may be connected between the soldering portion 1b and the connection portion. The connection portion may be configured to fix an electrical connector. The electrical connector includes, but is not limited to, a board to board (BTB) connector, etc. When the soldering portion 1b and the electrical connector are connected to different components, the flexible printed circuit 1 can realize electrical connection between these different components. The design of the soldering portion 1b and the bending portion 1a of the flexible printed circuit 1 may be the same as or similar to those in the above-described embodiments, and details thereof will not be described again here.

[0122] In some other embodiments, the flexible printed circuit 1 may alternatively include a soldering portion 1b, a bending portion 1a, and an attachment portion. The bending portion 1a may be connected between the soldering portion 1b and the attachment portion. The attachment portion may be configured to attach a component. The component may be a chip and / or an auxiliary component of the chip. When the soldering portion 1b of the flexible printed circuit 1 is fixed to and electrically connected to another component, the component mounted on the attachment portion of the flexible printed circuit 1 is electrically connected to the corresponding component. When the attachment portion of the flexible printed circuit 1 attaches a component, the flexible printed circuit 1 and this component together form a Flexible Printed Circuit Assembly (FPCA) of the flexible printed circuit 1. The design of the soldering portion 1b and the bending portion 1a of the flexible printed circuit 1 may be the same as or similar to those in the above-described multiple embodiments, and for details, they will not be described again here.

[0123] Please refer to FIGS. 17 to 19. FIG. 17 is a schematic diagram of the structure of a circuit board assembly 10 in some embodiments according to an embodiment of the present application. FIG. 18 is a schematic diagram of the structure of the circuit board assembly 10 shown in FIG. 17 from another angle. FIG. 19 is a schematic diagram of a partial structure of the circuit board assembly 10 shown in FIG. 17.

[0124] In some embodiments, the circuit board assembly 10 includes a circuit board 2 and a flexible printed circuit 1. The soldering portion 1b of the flexible printed circuit 1 is soldered to the circuit board 2, and the bending portion 1a can change its shape based on the installation environment. The circuit board 2 may be a printed circuit board or a flexible printed circuit. A plurality of pads 21 are arranged on the circuit board 2. The plurality of pads 21 on the circuit board 2 correspond to the pad structures (i.e., the first pad 1111 and the second pad 1121) of the soldering portion 1b of the flexible printed circuit 1.

[0125] The soldering portion 1b can be fixed to and electrically connected to the circuit board 2 by using surface mount technology (SMT), hot bar soldering technology, or another method. FIG. 19 may be understood as using the structure of the flexible printed circuit 1 shown in FIG. 9 as an example. The flexible printed circuit 1 of the circuit board assembly 10 in this embodiment may alternatively use the structure of another flexible printed circuit in which both surface layers of the soldering portion 1b include the soldering structures shown in the above embodiments, for example, the structures shown in FIGS. 5, 8, 11, or 12.

[0126] When the soldering portion 1b of the flexible printed circuit 1 is fixed to the circuit board 2 through hot press soldering, solder paste and solder flux may be pre-arranged on the pads of the soldering portion 1b (i.e., the first pad 1111 and the second pad 1121) and the pads 21 of the circuit board 2. Then, soldering is performed between the pads by heating using a pulse heat head, and electrical conduction between the flexible printed circuit 1 and the circuit board 2 is realized. When the soldering portion 1b of the flexible printed circuit 1 is fixed to the circuit board 2 by using surface mount technology, the flexible printed circuit 1 can be soldered to the circuit board 2 as a component, or the circuit board 2 can be soldered to the flexible printed circuit 1 as a component, and electrical conduction between the flexible printed circuit 1 and the circuit board 2 is realized.

[0127] In this embodiment, since the pads of the soldering portion 1b of the flexible printed circuit 1 (i.e., the first pad 1111 and the second pad 1121) have a structure protruding from the surface, it is possible to avoid solder paste collapse and short circuits in the soldering process, and it is guaranteed that the soldering joint has a specific height. This improves the soldering quality and reliability.

[0128] Please refer to FIGS. 20 and 21. FIG. 20 is a schematic diagram of the structure of the circuit board assembly 10 according to an embodiment of the present application in some other embodiments. FIG. 21 is a schematic diagram of a partial structure of the circuit board assembly 10 shown in FIG. 20.

[0129] In some embodiments, the circuit board assembly 10 includes a circuit board 2 and a flexible printed circuit 1. The soldering portion 1b of the flexible printed circuit 1 is soldered to the circuit board 2, and the bending portion 1a can change its shape based on the installation environment. The circuit board 2 may be a printed circuit board or a flexible printed circuit. A plurality of pads 21 are arranged on the circuit board 2. The plurality of pads 21 on the circuit board 2 correspond to the structure of the pads 1511 of the soldering portion 1b of the flexible printed circuit 1.

[0130] The soldering portion 1b can be fixed to and electrically connected to the circuit board 2 by using surface mount technology (SMT) or in another way. FIG. 21 may be understood as using the structure of the flexible printed circuit 1 shown in FIG. 14 as an example. In this embodiment, the flexible printed circuit 1 of the circuit board assembly 10 may alternatively use the structure of another flexible printed circuit in which one surface layer of the soldering portion 1b includes a soldering structure and the other surface layer does not include the soldering structure in the above embodiments, for example, the structures shown in FIGS. 13, 15, or 16.

[0131] When the soldering portion 1b of the flexible printed circuit 1 is fixed to the circuit board 2 by using surface mount technology, the flexible printed circuit 1 can be soldered to the circuit board 2 as a component, or the circuit board 2 can be soldered to the flexible printed circuit 1 as a component, and electrical conduction between the flexible printed circuit 1 and the circuit board 2 is realized.

[0132] In some embodiments, in the circuit board assembly 10 shown in FIGS. 17 to 21, the circuit board assembly 10 may further include one or more components, and these one or more components may be soldered to the circuit board 2 and / or soldered to the flexible printed circuit 1. When the circuit board 2 is a printed circuit board and the components are mounted on the circuit board 2, the circuit board 2 and the components may together form a Printed Circuit Board Assembly (PCBA).

[0133] In some embodiments, in the circuit board assembly 10 shown in FIGS. 17 to 21, the circuit board assembly 10 may further include an electrical connector. The electrical connector may be fixed to and electrically connected to the flexible printed circuit 1, whereby the flexible printed circuit 1 can be electrically connected to another component by using the electrical connector.

[0134] Some embodiments of the circuit board assembly 10 will be described below.

[0135] FIG. 22 is a schematic diagram of the structure of the circuit board assembly 10 according to some embodiments of the present application.

[0136] In some embodiments, the circuit board assembly 10 includes a first circuit board 22, a second circuit board 23, a flexible printed circuit 1, a first component 31, and a second component 32. The flexible printed circuit 1 includes two soldering portions 1b and a bending portion 1a connecting the two soldering portions 1b. The two soldering portions 1b of the flexible printed circuit 1 are soldered to the first circuit board 22 and the second circuit board 23 respectively. For the structure of each of the soldering portion 1b and the bending portion 1a of the flexible printed circuit 1, refer to any of the structures in the above embodiments. The first circuit board 22 may be a printed circuit board or a flexible printed circuit, and the second circuit board 23 may be a printed circuit board or a flexible printed circuit. There may be one or more first components 31, and the first component 31 is fixed to and electrically connected to the first circuit board 22. There may be one or more second components 32, and the second component 32 is fixed to and electrically connected to the second circuit board 23. The flexible printed circuit 1 is configured to realize an electrical connection between the first component 31 and the second component 32.

[0137] The first circuit board 22 and the second circuit board 23 may be stacked. The bending portion 1a of the flexible printed circuit 1 is bent so that the circuit board assembly 10 forms a sandwich stack structure. The entire circuit board assembly 10 occupies a relatively small space and requires a relatively small installation space. This helps to reduce the difficulty of installation and improve the application range. In some other embodiments, the first circuit board 22 and the second circuit board 23 may alternatively form another relative positional relationship, for example, a staggered arrangement.

[0138] FIG. 23 is a schematic diagram of the structure of the circuit board assembly 10 according to the embodiment of the present application in some other embodiments.

[0139] In some embodiments, the circuit board assembly 10 includes a first circuit board 22, a second circuit board 23, a flexible printed circuit 1, a first electrical connector 41, a second electrical connector 42, a first component 31, and a second component 32. The flexible printed circuit 1 includes a soldering portion 1b, a connecting portion 1c, and a bending portion 1a that connects the soldering portion 1b and the connecting portion 1c. For the structure of each of the soldering portion 1b and the bending portion 1a of the flexible printed circuit 1, refer to any of the structures in the above embodiments. The first circuit board 22 may be a printed circuit board or a flexible printed circuit. There may be one or more first components 31, and the first component 31 is fixed to and electrically connected to the first circuit board 22. The soldering portion 1b of the flexible printed circuit 1 is soldered to the first circuit board 22. There may be one or more second components 32, and the second component 32 is fixed to and electrically connected to the second circuit board 23. The first electrical connector 41 and the second electrical connector 42 may be a male connector and a female connector, respectively, and the male connector and the female connector are paired with each other. Each of the first electrical connector 41 and the second electrical connector 42 may be a board-to-board electrical connector or the like. The first electrical connector 41 is fixed to and electrically connected to the connecting portion 1c of the flexible printed circuit 1. The second electrical connector 42 is fixed to and electrically connected to the second circuit board 23. The first electrical connector 41 is fixed to and electrically connected to the second electrical connector 42. The flexible printed circuit 1 is configured to realize an electrical connection between the first component 31 and the second component 32.

[0140] The first circuit board 22 and the second circuit board 23 may be stacked. The bent portion 1a of the flexible printed circuit 1 is bent so that the circuit board assembly 10 forms a sandwich stack structure. The entire circuit board assembly 10 occupies a relatively small space and requires a relatively small installation space. This helps reduce the difficulty of installation and improve the scope of application. In some other embodiments, the first circuit board 22 and the second circuit board 23 may alternatively form another relative positional relationship, for example, a staggered arrangement.

[0141] FIG. 24 is a schematic diagram of the structure of the circuit board assembly 10 according to an embodiment of the present application in some other embodiments.

[0142] In some embodiments, the circuit board assembly 10 includes a circuit board 2, a flexible printed circuit 1, a first component 31, and a second component 32. The flexible printed circuit 1 includes a soldering portion 1b, a mounting portion 1d, and a bent portion 1a connecting the soldering portion 1b and the mounting portion 1d. For the structure of each of the soldering portion 1b and the bent portion 1a of the flexible printed circuit 1, refer to any of the structures in the above embodiments. The circuit board 2 may be a printed circuit board or a flexible printed circuit. There may be one or more first components 31, and the first component 31 is fixed to and electrically connected to the circuit board 2. The soldering portion 1b of the flexible printed circuit 1 is soldered to the circuit board 2. There may be one or more second components 32, and the second component 32 is fixed to and electrically connected to the mounting portion 1d of the flexible printed circuit 1. The flexible printed circuit 1 is configured to realize an electrical connection between the first component 31 and the second component 32.

[0143] Embodiments of the present application further provide an electronic device including a housing and a circuit board assembly. The circuit board assembly may use any of the structures in the above embodiments, and the circuit board assembly is installed inside the housing. The electronic device may be an electronic product such as, but not limited to, a mobile phone, a tablet computer (tablet), a portable game console, a palmtop computer (personal digital assistant, PDA), a notebook computer, an ultra-mobile personal computer (UMPC), a handheld computer, a netbook, an in-vehicle media playback device, a wearable electronic device, a virtual reality (VR) terminal device, or an augmented reality (AR) terminal device.

[0144] For example, when the electronic device is a mobile phone or a tablet computer and the circuit board assembly uses the structure of the circuit board assembly 10 shown in FIG. 22 or FIG. 23, the first circuit board 22 and the second circuit board 23 may be a main board and a sub-board respectively, the first component 31 may include a processor or the like, and the second component 32 may include a radio frequency chip or the like.

[0145] For example, when the electronic device is a wearable electronic device, such as a smart watch or a smart band, and the circuit board assembly uses the structure of the circuit board assembly 10 shown in FIG. 23, the first circuit board 22 may be a circuit board of a heart rate module, the first component 31 may include a heart rate detection sensor, the second circuit board 23 may be a main board, and the second component 32 may include a processor or the like.

[0146] For example, when the electronic device is a Bluetooth headset and the circuit board assembly 10 uses the structure of the circuit board assembly 10 shown in FIG. 24, the circuit board 2 may be the main board, the first component 31 may include a processor or the like, and the second component 32 may include a microphone (Microphone, MIC) and / or its auxiliary components.

[0147] It may be understood that the structure of the circuit board assembly is diverse, and the application examples of the circuit board assembly in electronic devices of different forms, different types, and different sizes are also diverse. This is not strictly limited in this embodiment of the present application.

[0148] The above embodiments are only intended to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should still understand that they can modify the technical solutions described in the above embodiments or make equivalent substitutions for some of their technical features without departing from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A flexible printed circuit including a bent portion and a soldering portion connected to the bent portion, wherein the flexible printed circuit includes a plurality of conductive layers and a plurality of insulating layers, and the insulating layers are disposed between two adjacent conductive layers, the plurality of conductive layers include a first soldering layer, a second soldering layer, and a trace layer, both the first soldering layer and the second soldering layer are located in the soldering portion, the first soldering layer is a surface layer on one side of the soldering portion, the first soldering layer is formed by a plurality of first pads arranged at intervals from each other, the second soldering layer is a surface layer on the other side of the soldering portion, and the second soldering layer is formed by a plurality of second pads arranged at intervals from each other, the trace layer is located between the first soldering layer and the second soldering layer and extends from the soldering portion to the bent portion, and the first pads and the second pads are connected using through-hole conductors, and the through-hole conductors are connected to the trace layer, A flexible printed circuit.

2. The trace layer includes a conductor block and a trace, the conductor block is located in the soldering portion, one end of the trace is connected to the conductor block, the other end of the trace extends to the bent portion, and the first pads and the second pads are connected to the conductor block using the through-hole conductors, The flexible printed circuit according to claim 1.

3. The area of the conductor block is smaller than the area of the first pad, The flexible printed circuit according to claim 2.

4. There are a plurality of trace layers, and the plurality of conductor blocks connected to the plurality of first pads are located on different trace layers, The flexible printed circuit according to claim 2 or 3.

5. There is one or more trace layers, a plurality of punctured regions are provided on each trace layer, and a plurality of through-hole conductors penetrate the plurality of punctured regions of each trace layer in a one-to-one correspondence, Support blocks are disposed in the plurality of punctured regions of each trace layer, and the through-hole conductors penetrate the support blocks and are connected to the support blocks, When there is one trace layer, the support block is the conductor block, or when there are multiple trace layers, the support block is the conductor block or the lower pad. The flexible printed circuit according to claim 2 or 3.

6. The plurality of insulating layers include a first insulating layer and a second insulating layer. The first insulating layer is located between the first soldering layer and the adjacent trace layer, and extends from the soldering portion to the bending portion. A part of the first insulating layer located at the bending portion forms one surface layer of the bending portion. The second insulating layer is located between the second soldering layer and the adjacent trace layer, and extends from the soldering portion to the bending portion. A part of the second insulating layer located at the bending portion forms the other surface layer of the bending portion. The flexible printed circuit according to any one of claims 1 to 5.

7. The plurality of conductive layers further include a first routing layer and a second routing layer. Both the first routing layer and the second routing layer are located at the bending portion. The first routing layer and the first soldering layer are arranged on the same layer. The second routing layer and the second soldering layer are arranged on the same layer. The flexible printed circuit further includes a first protective layer and a second protective layer. Both the first protective layer and the second protective layer are located at the bending portion. The first protective layer is located on the side of the first routing layer away from the trace layer. The second protective layer is located on the side of the second routing layer away from the trace layer. The first protective layer and the second protective layer are two surface layers of the bending portion. The flexible printed circuit according to any one of claims 1 to 5.

8. At least one insulating layer of the flexible printed circuit forms an air gap at the bending portion. The flexible printed circuit according to claim 7.

9. A flexible printed circuit including a bending portion and a soldering portion connected to the bending portion. The flexible printed circuit includes a plurality of conductive layers, a plurality of insulating layers, and a first protective layer. The insulating layers are arranged between two adjacent conductive layers. The plurality of conductive layers include a soldering layer and a trace layer. The soldering layer is located at the soldering portion. The soldering layer is one surface layer of the soldering portion. The soldering layer is formed by a plurality of pads arranged at intervals from each other. The trace layer is located on the side of the soldering layer and extends from the soldering portion to the bending portion. The pads are connected to the trace layer using through-hole conductors. The first protective layer is located on the side of the trace layer away from the soldering layer. The first protective layer extends from the soldering portion to the bending portion. A part of the first protective layer located at the soldering portion forms the other surface layer of the soldering portion. A part of the first protective layer located at the bending portion forms one surface layer of the bending portion. Flexible printed circuit.

10. The trace layer includes a conductor block and a trace. The conductor block is located at the soldering portion. One end of the trace is connected to the conductor block. The other end of the trace extends to the bending portion. The pads are connected to the conductor block using the through-hole conductors. The flexible printed circuit according to claim 9.

11. The area of the conductor block is smaller than the area of the pads. The flexible printed circuit according to claim 10.

12. There are a plurality of trace layers. The plurality of conductor blocks connected to the plurality of pads are located on different trace layers. The flexible printed circuit according to claim 10 or 11.

13. There is one or more trace layers. A plurality of punctured regions are provided on each trace layer. A plurality of through-hole conductors penetrate the plurality of punctured regions of each trace layer in a one-to-one correspondence. Support blocks are arranged in the plurality of punctured regions of each trace layer. The through-hole conductors penetrate the support blocks and are connected to the support blocks. When there is one trace layer, the support block is the conductor block. Or when there are a plurality of trace layers, the support block is the conductor block or a lower pad. The flexible printed circuit according to claim 10 or 11.

14. The plurality of insulating layers includes a first insulating layer, the first insulating layer is located between the soldering layer and the adjacent trace layer, and extends from the soldering portion to the bending portion, and a part of the first insulating layer located at the bending portion forms the other surface layer of the bending portion. The flexible printed circuit according to any one of claims 9 to 13.

15. The plurality of conductive layers further includes a routing layer, the routing layer is located at the bending portion, and the routing layer and the soldering layer are arranged on the same layer. The flexible printed circuit further includes a second protective layer, the second protective layer is located on the side of the routing layer away from the trace layer, the second protective layer is located at the bending portion, and is the other surface layer of the bending portion. The flexible printed circuit according to any one of claims 9 to 13.

16. At least one insulating layer of the flexible printed circuit forms an air gap at the bending portion. The flexible printed circuit according to claim 15.

17. A circuit board assembly including a circuit board and the flexible printed circuit according to any one of claims 1 to 16, wherein the soldering portion of the flexible printed circuit is soldered to the circuit board.

18. An electronic device including a housing and the circuit board assembly according to claim 17, wherein the circuit board assembly is installed inside the housing.

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