Circuit board, preparation method for circuit board, and electronic assembly and electronic device

Abstract

Provided in the present application are a circuit board, a preparation method for a circuit board, and an electronic assembly and an electronic device. The circuit board comprises a transmission area and a connection area, wherein the connection area comprises a bending area and a pin area, and the division of the pin area, the bending area and the transmission area is performed from the perspective of a plane; and the connection area comprises a plurality of pins, which are connected to signal lines. Specifically, the pins are arranged in the pin area and are used for being connected to other electronic assemblies. The thickness of the bending area is less than that of the transmission area, such that the bending area has good flexibility; and the insertion loss and impedance of the whole circuit board are balanced, such that the circuit board in the present application can take into account a plurality of performance indexes such as insertion loss, impedance and flexibility.

Description

Circuit board, method for preparing circuit board, electronic component and electronic equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on November 2, 2023, with application number 202311458533.X and invention name "Circuit boards, electronic components and electronic equipment", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the technical field of electronic equipment, and in particular to a circuit board, a method for preparing a circuit board, an electronic component, and an electronic device. Background Art

[0004] Flexible circuit boards (FPCs) have the advantages of high density and thinness. FPCs can be soldered to printed circuit boards (PCBs) to connect the FPCs to the PCBs and realize signal transmission on the boards.

[0005] With technological advancements, signal transmission rates are increasing, and system density is also increasing. To meet these high-speed and high-density system requirements, signal transmission path losses must be minimized. As a crucial carrier in signal transmission paths, reducing insertion loss in flexible printed circuits (FPCs) is a key development direction. Furthermore, the flexibility of FPCs in the flex zone is a crucial performance indicator, significantly impacting the reliability of connections within these zones.

[0006] Summary of the Invention

[0007] The present application provides a circuit board, a method for preparing a circuit board, an electronic component, and an electronic device. The circuit board in the present application can take into account multiple performance indicators such as insertion loss, impedance, and flexibility.

[0008] In a first aspect, the present application provides a circuit board. The circuit board includes a transmission area and a connection area. The connection area includes a bending area and a pin area, and the division of the pin area, bending area, and transmission area is based on a planar perspective. From a layer structure perspective, the circuit board includes a signal layer and a dielectric layer. The signal layer is located between two dielectric layers, so that the dielectric layer can protect the signal layer and achieve insulation between different signal layers. The signal layer includes multiple signal lines, and the signal lines extend from the transmission area to the connection area. Each connection area includes multiple pins, which are connected to signal lines. The signal lines connect the pins between the two connection areas, thereby achieving signal transmission between the two connection areas. The pins are specifically arranged in the pin area for connecting to other electronic components; in other words, the pin area is used to set pins. The thickness of the bending area is less than that of the transmission area, which makes the bending area more flexible and balances the insertion loss and impedance of the entire circuit board. Therefore, the circuit board of the present application can take into account multiple performance indicators such as insertion loss, impedance, and flexibility.

[0009] In one technical solution, the cross-sectional area of ​​a signal line in the connection zone is smaller than the cross-sectional area of ​​the same signal line in the transmission zone. Therefore, the signal line is thinner in the connection zone and thicker in the transmission zone. The thinner signal line in the connection zone occupies less space, allowing for a denser pin density on the circuit board pinmap. This helps reduce the area of ​​the connection zone, the size of the electronic device, and improves its integration. While thinner signal lines in the connection zone have higher insertion loss and higher impedance, thicker signal lines in the transmission zone have lower insertion loss and lower impedance. This optimizes the insertion loss and impedance of the entire signal line, resulting in lower insertion loss and lower impedance overall.

[0010] In one technical solution, the spacing between adjacent signal lines on the same layer in the transmission area is greater than the spacing in the connection area. This makes the signal lines denser in the connection area, so that the density of the pins of the circuit board in the pinmap is set higher, which is conducive to reducing the area of ​​the second connection area, reducing the volume of the electronic device, and improving the integration of the electronic device. The spacing between the signal lines is small, especially the spacing between the same pair of differential signal lines is small, which makes the signal lines tightly coupled, resulting in large insertion loss. The spacing between adjacent signal lines in the transmission area is larger and sparser, which can reduce the insertion loss and make the overall insertion loss of the signal lines lower. This embodiment further optimizes the relationship between the area and insertion loss of the connection area of ​​the circuit board, so as to obtain lower insertion loss when the circuit board has a smaller connection area, and improve the rate at which the circuit board transmits signals to meet the high-density and high-speed requirements of electronic equipment.

[0011] The length of the bending zone along the direction from the pin area to the transmission area is greater than or equal to a preset value. The bending zone is relatively thin and has a certain length, allowing the circuit board to be easily bent in the bending zone, meeting bending requirements. The preset value is selected based on the bending requirements of the circuit board in the direction toward the connection area and the flexibility of the circuit board in the connection area.

[0012] In a specific technical solution, the above-mentioned preset value includes 60mm, which can meet the bending requirements of more electronic components.

[0013] In one possible technical solution, the pin area and the bending area of ​​the circuit board are all flexible circuit boards. Specifically, the pin area, the bending area and the transmission area are all flexible circuit boards, and the preparation process is relatively simple.

[0014] In another possible solution, the pin area of ​​the circuit board comprises a rigid circuit board, while the bending and transmission areas are flexible circuit boards, resulting in a rigid-flexible structure. This solution provides sufficient flexibility in the bending area for bending, and facilitates a denser arrangement of pins in the pin area, achieving both high density and flexible bending characteristics.

[0015] In one possible technical solution, the pin area of ​​the circuit board includes a rigid circuit board, which is connected to two flexible circuit boards. One flexible circuit board includes a first bending zone and a first transmission zone, which are connected to the rigid circuit board. The other flexible circuit board includes a second bending zone and a second transmission zone, which are also connected to the rigid circuit board. The first and second transmission zones are stacked with a gap. This solution allows for more wiring space, thereby increasing the number of signals transmitted by the circuit board. Furthermore, the two independent layers of flexible circuit boards provide for greater flexibility.

[0016] From the perspective of layer structure, the circuit board of the present application also includes a first ground layer and a second ground layer, and the signal layer is located between the first and second ground layers. The first and second ground layers serve as the ground layer or as a shielding layer of the circuit board to increase the signal transmission rate of the signal layer.

[0017] In another possible technical solution, the signal layer of the circuit board of the present application includes a first signal layer and a second signal layer, with the first and second signal layers located on either side of a dielectric layer. In this embodiment, the circuit board has a large number of signal layers, so the signal layer area used to prepare signal lines is larger, thereby increasing the number of signal lines. This solution can improve the integration of the circuit board, allowing the circuit board to transmit a large number of signals.

[0018] To increase the signal transmission rate of the circuit board, the signal layer includes a third signal layer and a fourth signal layer, with a third ground layer disposed between the third and fourth signal layers. The third ground layer serves as a shielding layer between the third and fourth signal layers to reduce crosstalk between the third and fourth signal layers, thereby increasing the signal transmission rate of the circuit board.

[0019] The circuit board includes a first side and a second side that face away from each other in the thickness direction. There are multiple options for achieving a thinner thickness in the bending zone than in the transmission zone. In one option, on the first side of the circuit board, the surfaces of the bending zone and the transmission zone are located in different planes, while on the second side, the surfaces of the bending zone and the transmission zone are located in the same plane. This simplifies the circuit board manufacturing process by thinning the connection zone only on one side of the bending zone.

[0020] In one option, on the first side of the circuit board, the surface of the bending region and the surface of the transmission region are located in different planes; on the second side of the circuit board, the surface of the bending region and the surface of the transmission region are located in different planes. This allows the circuit board to be more symmetrical in the thickness direction, and the symmetry of the transmitted signal is also improved, which helps improve the quality of the circuit board's transmitted signals.

[0021] The dielectric layer can be made of a variety of materials. For example, the dielectric layer can be made of at least one of modified polyimide, liquid crystal polymer, fluorinated ethylene propylene copolymer, and polytetrafluoroethylene. These materials offer excellent flexibility and low signal loss, further reducing insertion loss in circuit board signal transmission.

[0022] In a second aspect, the present application also provides a method for preparing a circuit board. The circuit board prepared by the method for preparing a circuit board may be the circuit board provided in the first aspect above. The circuit board includes a transmission area and a connection area, and the transmission area and the connection area are connected. The above preparation method includes: forming a signal circuit pattern on the first metal layer on the surface of a first flexible metal-clad plate, and the surface of the first flexible metal-clad plate facing away from the first metal layer has a second metal layer; pressing the third metal layer, the first adhesive layer and the first flexible metal-clad plate stacked in sequence, and the third metal layer is located on the side of the first metal layer facing away from the second metal layer; preparing conductive holes, and the conductive holes connect at least two layers of the first metal layer, the second metal layer and the third metal layer; pressing the second flexible metal-clad plate, the second adhesive layer and the third metal layer stacked in sequence; the second flexible metal-clad plate includes a fourth metal layer, and the fourth metal layer is located on the surface facing away from the third metal layer, and the second flexible metal-clad plate and the second adhesive layer cover part of the transmission area. The thickness of the transmission area of ​​the circuit board prepared by this preparation method is greater than the thickness of the connection area, so that the connection area has better flexibility and can take into account multiple performance indicators of the circuit board such as insertion loss, impedance and flexibility.

[0023] Furthermore, the lamination process includes sequentially stacking the second flexible metal-clad sheet, the second adhesive layer, and the third metal layer; the second flexible metal-clad sheet includes a fourth metal layer, which is located on a surface facing away from the third metal layer; and the second flexible metal-clad sheet and the second adhesive layer cover a portion of the transmission area. The process includes: providing a blocking member on the surface of the first metal layer; and removing the blocking member. This facilitates more accurate and reliable coverage of the second flexible metal-clad sheet and the second adhesive layer over the transmission area.

[0024] In a specific technical solution, the signal circuit pattern includes signal lines. The cross-sectional area of ​​the signal lines in the connection area is smaller than the cross-sectional area of ​​the same signal lines in the transmission area. The spacing between adjacent signal lines in the connection area is smaller than the spacing in the transmission area. This reduces the insertion loss of the circuit board and optimizes the impedance of the circuit board, thereby improving the density and rate of signal transmission on the circuit board.

[0025] In the third aspect, the present application also provides a method for preparing a circuit board. The circuit board prepared by the method for preparing a circuit board may be the circuit board provided in the first aspect above. The circuit board includes a transmission area and a connection area, and the transmission area and the connection area are connected. The above preparation method includes: forming a signal circuit pattern on the first metal layer on the surface of the first flexible metal-clad plate, and the surface of the first flexible metal-clad plate facing away from the first metal layer has a second metal layer; pressing the third metal layer, the first adhesive layer and the first flexible metal-clad plate stacked in sequence, and the third metal layer is located on the side of the first metal layer facing away from the second metal layer; preparing conductive holes, and the conductive holes connect at least two layers of the first metal layer, the second metal layer and the third metal layer; pressing the fourth metal layer, the second adhesive layer and the second metal layer stacked in sequence, and the fourth metal layer covers part of the transmission area.

[0026] Furthermore, the lamination process of the fourth metal layer, the second adhesive layer and the second metal layer, wherein the fourth metal layer covers the portion of the transmission area, includes: setting a blocking member on the surface of the first metal layer; and then removing the blocking member. This facilitates the second flexible metal-clad plate and the second adhesive layer to cover the transmission area more accurately and reliably.

[0027] In a specific technical solution, the signal circuit pattern includes signal lines. The cross-sectional area of ​​the signal lines in the connection area is smaller than the cross-sectional area of ​​the same signal lines in the transmission area. The spacing between adjacent signal lines in the connection area is smaller than the spacing in the transmission area. This reduces the insertion loss of the circuit board and optimizes the impedance of the circuit board, thereby improving the density and rate of signal transmission on the circuit board.

[0028] In a fourth aspect, the present application further provides a method for manufacturing a circuit board. The circuit board manufactured by the method can be the circuit board provided in the first aspect. The circuit board includes a transmission area and a connection area, wherein the transmission area and the connection area are connected. The above-mentioned preparation method includes: forming signal circuit patterns on the first metal layer and the second metal layer on both side surfaces of the first flexible metal clad plate, respectively, and the first metal layer and the second metal layer are respectively located on both side surfaces of the first flexible metal clad plate; pressing the third metal layer, the first adhesive layer, the first flexible metal clad plate, the second adhesive layer and the fourth metal layer stacked in sequence; preparing conductive holes to connect at least two layers of the first metal layer, the second metal layer, the third metal layer and the fourth metal layer; pressing the second flexible metal clad plate, the third adhesive layer, the third metal layer, the first adhesive layer, the first flexible metal clad plate, the second adhesive layer, the fourth metal layer, the fourth adhesive layer and the third flexible metal clad plate stacked in sequence; the second flexible metal clad plate and the third flexible metal clad plate respectively cover parts of the transmission area; the second flexible metal clad plate includes a fifth metal layer, and the fifth metal layer is located on the side away from the first flexible metal clad plate; the third flexible metal clad plate includes a sixth metal layer, and the sixth metal layer is located on the side away from the first flexible metal clad plate.

[0029] Furthermore, the above lamination sequentially stacks the second flexible metal-clad plate, the third adhesive layer, the third metal layer, the first adhesive layer, the first flexible metal-clad plate, the second adhesive layer, the fourth metal layer, the fourth adhesive layer, and the third flexible metal-clad plate; the second flexible metal-clad plate and the third flexible metal-clad plate respectively cover portions of the transmission area, and before that, includes: setting a blocking member on the surface of the first metal layer; and after that, includes: removing the blocking member. This facilitates the second flexible metal-clad plate and the second adhesive layer to more accurately and reliably cover the transmission area.

[0030] In a specific technical solution, the signal circuit pattern includes signal lines. The cross-sectional area of ​​the signal lines in the connection area is smaller than the cross-sectional area of ​​the same signal lines in the transmission area. The spacing between adjacent signal lines in the connection area is smaller than the spacing in the transmission area. This reduces the insertion loss of the circuit board and optimizes the impedance of the circuit board, thereby improving the density and rate of signal transmission on the circuit board.

[0031] In a fifth aspect, the present application also provides a method for preparing a circuit board. The circuit board prepared by the method for preparing a circuit board may be the circuit board provided in the first aspect above. The circuit board includes a transmission area and a connection area, and the transmission area and the connection area are connected. The above preparation method includes: forming a signal circuit pattern on the first metal layer of the first flexible metal-clad plate and the second metal layer of the second flexible metal-clad plate respectively, forming a circuit pattern on the third metal layer of the first flexible metal-clad plate, the first metal layer and the third metal layer are respectively located on the two side surfaces of the first flexible metal-clad plate, and the surface of the second flexible metal-clad plate facing away from the second metal layer has a fourth metal layer; pressing the fifth metal layer, the first adhesive layer, the first flexible metal-clad plate, the second adhesive layer and the second flexible metal-clad plate stacked in sequence, the first metal layer is adjacent to the first adhesive layer, and the second metal layer is adjacent to the second adhesive layer; preparing conductive holes to connect at least two layers of the first metal layer, the second metal layer, the third metal layer, the fourth metal layer and the fifth metal layer; pressing the sixth metal layer, the third adhesive layer and the second flexible metal-clad plate stacked in sequence, and the sixth metal layer covers part of the transmission area.

[0032] Furthermore, the sixth metal layer, the third adhesive layer, and the second flexible metal-clad plate are laminated in sequence, and the sixth metal layer covers the portion of the transmission area. The process includes: setting a blocking member on the surface of the first metal layer; and removing the blocking member. This facilitates the second flexible metal-clad plate and the second adhesive layer to cover the transmission area more accurately and reliably.

[0033] In a specific technical solution, the signal circuit pattern includes signal lines. The cross-sectional area of ​​the signal lines in the connection area is smaller than the cross-sectional area of ​​the same signal lines in the transmission area. The spacing between adjacent signal lines in the connection area is smaller than the spacing in the transmission area. This reduces the insertion loss of the circuit board and optimizes the impedance of the circuit board, thereby improving the density and rate of signal transmission on the circuit board.

[0034] In a sixth aspect, the present application also provides an electronic assembly. This electronic assembly includes a printed circuit board and the circuit board provided in the first aspect above, wherein at least one connection area of ​​the circuit board is electrically connected to the printed circuit board. The area of ​​the circuit board near the printed circuit board has good flexibility, and the connection between the circuit board and the printed circuit board is relatively reliable. The circuit board can also balance multiple performance indicators such as insertion loss, impedance, and flexibility, thereby improving the signal transmission rate of the electronic assembly.

[0035] In a seventh aspect, the present application further provides an electronic device. The electronic assembly includes a housing and the electronic assembly provided in the sixth aspect, wherein the electronic assembly is disposed in the housing. The electronic device has a relatively fast signal transmission rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a schematic structural diagram of an electronic device according to an embodiment of the present application;

[0037] FIG2 is a schematic structural diagram of an electronic component in an embodiment of the present application;

[0038] FIG3 is another schematic diagram of the structure of the electronic component in the embodiment of the present application;

[0039] FIG4 is another schematic diagram of the structure of the electronic component in the embodiment of the present application;

[0040] FIG5 is another schematic diagram of the structure of the electronic component in the embodiment of the present application;

[0041] FIG6 is another schematic diagram of the structure of the electronic component in the embodiment of the present application;

[0042] FIG7 is another schematic diagram of the structure of the electronic component in the embodiment of the present application;

[0043] FIG8 is another schematic diagram of the structure of the electronic component in the embodiment of the present application;

[0044] FIG9 is another schematic diagram of the structure of the electronic component in the embodiment of the present application;

[0045] FIG10 is a schematic structural diagram of a circuit board in an embodiment of the present application;

[0046] FIG11 is a schematic diagram of a top view of a circuit board in an embodiment of the present application;

[0047] FIG12 is a schematic diagram of a top view of a circuit board in an embodiment of the present application;

[0048] FIG13 is a schematic structural diagram of a circuit board in an embodiment of the present application;

[0049] FIG14 is a schematic diagram of a top view of a circuit board in an embodiment of the present application;

[0050] FIG15 is a schematic diagram of a top view of a circuit board in an embodiment of the present application;

[0051] FIG16 is a schematic diagram of a top view of a circuit board in an embodiment of the present application;

[0052] FIG17 is a schematic structural diagram of a circuit board in an embodiment of the present application;

[0053] FIG18 is another schematic diagram of the structure of the circuit board in the embodiment of the present application;

[0054] FIG19 is a schematic structural diagram of a circuit board in an embodiment of the present application;

[0055] FIG20 is a schematic structural diagram of a circuit board in an embodiment of the present application;

[0056] FIG21 is a schematic diagram of a top view of a circuit board in an embodiment of the present application;

[0057] FIG22 is a schematic structural diagram of a circuit board in an embodiment of the present application;

[0058] FIG23 is a schematic structural diagram of a circuit board in an embodiment of the present application;

[0059] FIG24 is a schematic structural diagram of a circuit board in an embodiment of the present application;

[0060] FIG25 is a schematic structural diagram of a circuit board in an embodiment of the present application.

[0061] Reference numerals: 100 - housing; 200 - electronic component; 1 - printed circuit board; 2 - circuit board; 21 - transmission area; 211 - first transmission area; 212 - second transmission area; 22 - connection area; 221 - first connection area; 222 - second connection area; 223 - pin area; 224 - bending area; 2241 - first bending area; 2242 - second bending area; 23 - pin; 24 - signal layer; 241 - signal line; 242 - first signal layer; 243 - second signal layer; 244 - third signal layer; 245 - fourth signal layer; 25 - dielectric layer; 26 - first ground layer; 27 - second ground layer; 28 - third ground layer; 29 - first side; 210 - second side; 3 - connector; 4 - packaging structure; L1 - first metal layer; L2 - second metal layer; L3 - third metal layer; L4 - fourth metal layer; L5 - fifth metal layer; L6 - sixth metal layer; BS1 - first adhesive layer; BS2 - second adhesive layer; BS3 - third adhesive layer; BS4 - fourth adhesive layer; FL1 - first flexible metal-clad laminate; FL2 - second flexible metal-clad laminate;FL3 - third flexible metal cladding plate; 5 - barrier. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solutions and advantages of this application clearer, this application will be further described in detail below with reference to the accompanying drawings.

[0063] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and appended claims of this application, the singular expressions "a", "an", "said", "above", "the", and "this" are intended to also include expressions such as "one or more", unless the context clearly indicates otherwise.

[0064] References in this specification to "one embodiment" or "a specific embodiment" mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. The terms "including," "comprising," "having," and their variations all mean "including but not limited to," unless otherwise specifically stated.

[0065] To facilitate understanding of the circuit board, circuit board manufacturing method, electronic component, and electronic device provided in the embodiments of the present application, the application scenarios thereof are first introduced below.

[0066] The electronic devices in the embodiments of the present application may be electronic devices such as information and communications technology (ICT) devices, communication devices (such as routers), computing devices (such as servers), network devices (such as switches), or storage devices (such as storage arrays), or may be electronic devices such as optical modules, vehicle-mounted devices, or terminal devices. The present application does not limit the specific type of electronic device; as long as the electronic device includes electronic components that use circuit boards to transmit signals, the technical solutions provided in the present application may be used.

[0067] For ease of description, the electronic device is described as a server in the embodiment of the present application. Figure 1 is a structural diagram of an electronic device in the embodiment of the present application. As shown in Figure 1, the above-mentioned electronic device may include a housing 100, and an electronic component 200 arranged in the housing 100. Specifically, when the above-mentioned electronic device is a cabinet server, the above-mentioned housing 100 can be understood as a cabinet of the cabinet server, and the electronic component 200 may include a node. As shown in Figure 1, the above-mentioned electronic component 200 specifically includes a printed circuit board 1 and a circuit board 2. The printed circuit board 1 is welded to the circuit board 2 to realize the electrical connection between the printed circuit board 1 and the circuit board 2, and further the physical connection and signal connection between the printed circuit board 1 and the circuit board 2 can be realized.

[0068] Specifically, there are many options for connecting the printed circuit board 1 and the circuit board 2, such as laser welding, hard connection, crimping, sintering, conductive adhesive bonding, hot bar welding, connector connection or surface mounted technology (SMT).

[0069] The above-mentioned circuit board 2 can be applied to different application scenarios, or the electronic component 200 can include different component forms. For example, Figure 2 is a structural schematic diagram of an electronic component in an embodiment of the present application. As shown in Figure 2, in a specific embodiment, the circuit board 2 in the above-mentioned electronic component 200 is used to realize a single-board jumper of a printed circuit board 1. Specifically, both ends of the circuit board 2 are soldered to the same printed circuit board 1 to realize the transmission of signals of devices at two positions in the printed circuit board 1. Figure 3 is another structural schematic diagram of an electronic component in an embodiment of the present application. As shown in Figure 3, in another specific embodiment, the above-mentioned electronic component 200 may include two printed circuit boards 1, and the two printed circuit boards 1 are roughly located in the same plane. The two ends of the circuit board 2 are respectively soldered to the two printed circuit boards 1, so that the circuit board 2 is connected between the two printed circuit boards 1, so that the signals between the two printed circuit boards 1 can be transmitted through the circuit board 2 to realize inter-board interconnection. Figure 4 is another structural schematic diagram of an electronic component in an embodiment of the present application. As shown in Figure 4, in another specific embodiment, the above-mentioned electronic component 200 may also include two printed circuit boards 1. The two printed circuit boards 1 in this embodiment are located in different planes. The two ends of the circuit board 2 are respectively welded to the two printed circuit boards 1, so that the circuit board 2 is connected between the two printed circuit boards 1, so that the signals between the two printed circuit boards 1 can be transmitted through the circuit board 2 to realize cross-board connection. Figure 5 is another structural schematic diagram of the electronic component in the embodiment of the present application. As shown in Figure 5, in another specific embodiment, one end of the circuit board 2 in the electronic component 200 is welded to the printed circuit board 1, and the other end is connected to the connector 3, so that the connector 3 and the printed circuit board 1 can be transmitted through the circuit board 2, and then the printed circuit board 1 can be connected to the external device through the connector 3, and the printed circuit board 1, the circuit board 2 and the connector 3 form an electronic module. Figure 6 is another structural schematic diagram of the electronic component in the embodiment of the present application. As shown in Figure 6, in another specific embodiment, the circuit board 2 realizes the connection between the packaging structure 4 and the printed circuit board 1, so that signals can be transmitted between the packaging structure 4 and the printed circuit board 1. Specifically, one end of the circuit board 2 is connected to the packaging structure 4, and the other end is connected to the printed circuit board 1.

[0070] FIG7 is another schematic diagram of the structure of an electronic assembly in an embodiment of the present application. As shown in FIG7 , in another specific embodiment, a circuit board 2 can be welded to the surface of a printed circuit board 1. FIG8 is another schematic diagram of the structure of an electronic assembly in an embodiment of the present application. As shown in FIG8 , in another specific embodiment, a plurality of stacked circuit boards 2 can be welded to the surface of a printed circuit board 1. In addition, a circuit board 2 can be connected to a single side of a printed circuit board 1, as shown in FIG7 and FIG8 . Alternatively, FIG9 is another schematic diagram of the structure of an electronic assembly in an embodiment of the present application. As shown in FIG9 , in another specific embodiment, circuit boards 2 can be connected to both sides of a printed circuit board 1.

[0071] FIG10 is a schematic diagram of a structure of a circuit board in an embodiment of the present application, and FIG11 is a schematic diagram of a top view of a structure of a circuit board in an embodiment of the present application. As shown in FIG10 and FIG11, in one embodiment, the circuit board 2 includes a transmission area 21 and at least two connection areas 22. The connection areas 22 are used to connect with other electronic devices, for example, at least one connection area 22 is used to electrically connect with a printed circuit board 1. Specifically, each connection area 22 includes a plurality of pins 23. The plurality of pins 23 are arranged in the connection area 22 of the circuit board 2 to form a pinmap. The pins 23 are welded with other electronic devices to achieve the connection between the circuit board 2 and other electronic devices, for example, the pins 23 of the connection area 22 are welded with the printed circuit board 1. The above specifically includes a bending area 224 and a pin area 223. The pins 23 are specifically arranged in the pin area 223, and the bending area 224 is located between the pin area 223 and the transmission area 21. For ease of description, it is considered that the at least two connection areas 22 include a first connection area 221 and a second connection area 222, and the transmission area 21 is located between the bending area 224 and the second connection area 222. For ease of description, this application only uses the first connection area as an example for illustration. The bending area 224 and the pin area 223 in the embodiments of this application refer to adjacent bending areas 224 and pin areas 223. It is worth noting that the transmission area 21 and the connection area 22 of the circuit board 2 are merely for the convenience of describing the areas where the circuit board 2 is divided. The actual structure of the circuit board 2 does not necessarily have a clear boundary to distinguish the transmission area 21 from the connection area 22. The main difference between the connection area 22 and the transmission area 21 is that the connection area 22 includes a plurality of pins 23 for connecting to other electronic devices, and its main function is to connect to other electronic devices.

[0072] Continuing with Figures 10 and 11 , from a layer structure perspective, the circuit board 2 includes a signal layer 24 and a dielectric layer 25, with one signal layer 24 positioned between two adjacent dielectric layers 25. Specifically, the signal layer 24 includes a signal line 241 for transmitting signals; the dielectric layer 25 is primarily an insulator, used to separate and protect the different signal layers 24. Specifically, the signal line 241 is connected to the pin 23 of the connection area 22. For example, one end of the signal line 241 is connected to the pin 23 of the bending area 224, and the other end of the signal line 241 is connected to the pin 23 of the second connection area 222.

[0073] In a specific embodiment, the signal layer 24 may be a copper layer, a silver layer, or a gold layer to reduce signal loss during signal transmission via the signal layer 24 and improve signal transmission speed. The dielectric layer 25 may be a low-loss dielectric, for example, the dielectric layer 25 may be made of at least one of modified polyimide (PI), liquid crystal polymer (LCP), fluorinated ethylene propylene (FEP), and polytetrafluoroethylene (PTFE). These materials are flexible and produce low signal loss, further reducing insertion loss during signal transmission on the circuit board 2.

[0074] In the embodiment provided herein, the thickness of the aforementioned bend region 224 is less than that of the transmission region 21. The thinner bend region 224 of the circuit board 2 can reduce impedance. However, a thinner bend region 224 can also result in higher insertion loss, while a thicker transmission region 21 can reduce insertion loss, resulting in lower insertion loss for the entire signal transmission path of the circuit board 2. Accordingly, a thicker transmission region 21 can also result in higher impedance, but the lower impedance of the bend region 224 can reduce the impedance for the entire signal transmission path of the circuit board 2. Furthermore, the flexibility of the circuit board 2 is strongly correlated with its thickness. During use, high flexibility is generally required at the bend 22 of the circuit board 2. In this embodiment, the thinner bend region 224 provides greater flexibility, making the circuit board 2 more flexible during use. Therefore, the circuit board 2 of the present invention balances multiple performance indicators, including insertion loss, impedance, and flexibility, offering significant advantages, particularly for high-density, high-speed electronic devices, such as those with speeds above 112G.

[0075] In an optional embodiment, the thickness of the bending zone 224 of all connection areas 22 of the circuit board 2 can be smaller than the thickness of the transmission area 21, or the thickness of the bending zone 224 of some connection areas 22 can be smaller than the thickness of the transmission area 21.

[0076] Continuing with Figure 11, the cross-sectional area of ​​the signal line 241 in the connection region 22 is smaller than the cross-sectional area of ​​the same signal line 241 in the transmission region 21. That is, the signal line 241 in the connection region 22 is thinner than the cross-sectional area of ​​the same signal line 241 in the transmission region 21. In one embodiment, the cross-sectional area of ​​the signal line 241 in the connection region 22 is smaller than the cross-sectional area of ​​the same signal line 241 in the transmission region 21. The thinner signal line 241 in the connection region 22 occupies less space, allowing for a higher density of pins 23 on the pinmap of the flexible circuit board 2. This helps reduce the area of ​​the connection region 22, minimizing the size of the electronic device and increasing its integration. While the thinner signal line 241 in the connection region 22 results in higher insertion loss and higher impedance, the thicker signal line 241 in the transmission region 21 results in lower insertion loss and lower impedance. This optimizes the insertion loss and impedance of the entire signal line 241, resulting in lower insertion loss and lower impedance overall.

[0077] In a specific embodiment, when the thickness of the circuit board 2 is constant, the cross-sectional area of ​​the signal line 241 is primarily affected by the line width. Therefore, it can be understood that the line width of the signal line 241 in the bending region 224 is smaller than the line width of the same signal line 241 in the transmission region 21. The line width of the signal line 241 in the second connection region 222 is smaller than the line width of the same signal line 241 in the transmission region 21.

[0078] Continuing with Figure 11, the spacing between adjacent signal lines 241 on the same layer in the transmission area 21 is greater than the spacing in the connection area 22. That is, the signal lines 241 are denser in the connection area 22 and more sparse in the transmission area 21. In a specific embodiment, the spacing between adjacent signal lines 241 on the same layer in the transmission area 21 is greater than the spacing in the connection area 22. When multiple signal lines 241 on the same layer are arranged in the connection area 22, the spacing between adjacent signal lines 241 is smaller, occupying less space. This allows for a higher density of pins 23 on the pinmap of the circuit board 2, which helps reduce the area of ​​the connection area 22, the size of the electronic device, and improves the integration of the electronic device. The smaller spacing between signal lines 241, especially between a pair of differential signal lines, results in tight coupling between the signal lines 241, resulting in higher insertion loss. However, larger spacing between adjacent signal lines 241 in the transmission area 21 can reduce insertion loss, resulting in lower overall insertion loss for the signal lines 241. This embodiment further optimizes the relationship between the area of ​​the connection region 22 of the circuit board 2 and insertion loss. This reduces insertion loss even when the circuit board 2 has a smaller connection region 22, thereby increasing the signal transmission rate of the circuit board 2 to meet the high-density and high-speed requirements of electronic devices. In one embodiment, the density of adjacent signal lines 241 on the same layer in the transmission region 21 is lower than in the bending region 224.

[0079] In the embodiment provided herein, the cross-sectional area of ​​a signal line 241 in the connection region 22 is smaller than the cross-sectional area of ​​the same signal line 241 in the transmission region 21. Adjacent signal lines 241 on the same layer are spaced farther apart in the transmission region 21 than in the connection region 22. The signal lines 241 in the connection region 22 are arranged thinner and denser, facilitating a denser arrangement of pins 23 there, reducing the area of ​​the connection region 22 and, in turn, the area of ​​the circuit board 2. In this embodiment, the signal lines 241 in the connection region 22 are tightly coupled with thin wire widths, resulting in higher impedance in the connection region 22. The thin thickness of the connection region 22 reduces impedance, however. However, the thin thickness of the connection region 22 also results in higher insertion loss. The thicker thickness of the transmission region 21 of the circuit board 2 reduces insertion loss, resulting in lower insertion loss for the entire signal transmission path of the circuit board 2. Accordingly, the thicker thickness of the transmission region 21 of the circuit board 2 also results in higher impedance, but the lower impedance of the bend region 224 reduces impedance for the entire signal transmission path of the circuit board 2. In addition, the transmission area 21 has a larger area for routing than the connection area 22. Therefore, the signal lines 241 are arranged thicker and with larger spacing in the transmission area 21. The thick lines in the transmission area 21 are loosely coupled, which can reduce the impedance of the circuit board 2 in the connection area 22. In addition, the thickness of the connection area 22 in the present application is relatively thin, so it is more flexible, making the circuit board 2 more flexible during use. Therefore, the circuit board 2 in the technical solution of the present application takes into account multiple performance indicators such as insertion loss, impedance and flexibility, and has obvious advantages, especially for high-density and high-speed electronic devices, such as electronic devices with speeds above 112G.

[0080] The embodiment of the present application realizes the division of different areas on the same low-loss circuit board 2. The connection area 22 at the end of the circuit board 2 can support a tight coupling design with thin traces. By setting a thinner bending area 224, the connection area 22 can maintain a low target impedance requirement even when the signal lines 241 are thin and dense. The design of a loose coupling design with thick traces in the middle transmission area 21 can ensure lower loss performance in the longer transmission area 21. This solution solves both the impedance problem of the connection area 22 and the overall insertion loss problem.

[0081] Please continue to refer to Figure 11. In one embodiment, the connection area 22 includes a pin area 223 and a bending area 224. The pins 23 of the circuit board are arranged in the pin area 223, and a pinmap is formed in the pin area 223. The bending area 224 is arranged between the pin area 223 and the transmission area 21. In other words, with respect to the side of the circuit board facing a connection area 22, the transmission area 21, the bending area 224, and the pin area 223 are arranged in sequence. The length of the bending area 224 along the direction from the pin area 223 to the transmission area 21 is greater than or equal to a preset value. The length of the bending area 224 along the extension direction of the circuit board 2 is greater than or equal to a preset value. Since the connection area 22 is relatively thin and has good flexibility, it is convenient to adjust the shape of the circuit board 2 according to the actual product position. The pins 23 are fixed to other components, and only the area outside the pins 23 can be bent, that is, only the bending area 224 can be bent. The length of the bending zone 224 along the direction of the pin zone 223 toward the transmission zone 21 is greater than or equal to the preset value, so that the circuit board 2 can bend in the bending zone 224 to meet the bending requirement. The preset value is selected specifically based on the bending requirement of the circuit board 2 in the direction close to the connection zone 22 and the flexibility of the circuit board 2 in the bending zone 224. For example, the stronger the bending requirement, the larger the bending angle, or the longer the bending distance, the larger the preset value is set; conversely, the weaker the bending requirement, the smaller the preset value is set. For example, the worse the flexibility of the connection zone 22, the larger the preset value is set; conversely, the better the flexibility of the connection zone 22, the smaller the preset value is set.

[0082] In an optional embodiment, the above-mentioned preset value can be 60 mm, and the length of the bending zone 224 along the extension direction of the circuit board 2 is greater than or equal to 60 mm, which can meet the bending requirements of most electronic components, so that the circuit board 2 can be applied to a variety of application scenarios.

[0083] In one embodiment of the present application, the bending region 224, the pin region 223, and the transmission region 21 of the circuit board are all flexible circuit boards. The flexibility of the circuit board 2 is relatively uniform in the connection region 22, and the flexibility of the connection region 22 is consistent, indicating good flexibility. Specifically, the thickness of the bending region 224 is the same as that of the pin region 223.

[0084] Figure 12 is a schematic diagram of a top view of the circuit board in an embodiment of the present application, and Figure 13 is a schematic diagram of a structure of the circuit board in an embodiment of the present application. As shown in Figures 12 and 13, in one embodiment, the rigidity of the above-mentioned pin area 223 is greater than the rigidity of the bending area 224, and the above-mentioned pin area 223 includes a rigid circuit board. The circuit board 2 is a soft and hard combination circuit board, most of which is flexible, and the pin areas 223 at both ends have a certain rigidity. This soft and hard combination circuit board is also applicable to the technical solution provided in this application. Providing a rigid circuit board in the pin area 223 is conducive to preparing relatively dense pins in the pin area 223, thereby increasing the density of the circuit board signal transmission. In a possible embodiment, the above-mentioned pin area 223 includes a rigid circuit board layer, and the rigid circuit board layer is sandwiched on both sides of the flexible circuit board. When preparing the above-mentioned circuit board, the flexible pin area 223, the bending area 224 and the transmission area 21 are first prepared, and then the rigid circuit board layers on both sides are prepared.

[0085] FIG14 is a schematic diagram of the structure of a circuit board according to an embodiment of the present application. As shown in FIG14 , the bending region 224 includes a first bending region 2241 and a second bending region 2242, and the transmission region 21 includes a first transmission region 211 and a second transmission region 212. The first bending region 2241 is connected to the first transmission region 211. Specifically, the first bending region 2241 and the first transmission region 211 can be an integral structure, forming a flexible circuit board. The second bending region 2242 is connected to the second transmission region 212. Specifically, the second bending region 2242 and the second transmission region 212 are an integral structure, forming a flexible circuit board. The first transmission region 211 and the second transmission region 212 are stacked and have a gap, so the two flexible circuit boards are stacked and have a gap. The pin region 223 of the circuit board includes a rigid circuit board, and the pin region 223 is connected to the first bending region 2241 and the second bending region 2242, respectively, that is, one rigid circuit board connects two layers of flexible circuit boards. The circuit board in this solution can have more routing space, thereby increasing the number of signals transmitted by the circuit board. In addition, the two independent layers of flexible circuit boards make the circuit board more flexible.

[0086] Continuing with FIG10 , in one embodiment, the circuit board 2 further includes a first ground layer 26 and a second ground layer 27, with the signal layer 24 located between the first ground layer 26 and the second ground layer 27. A dielectric layer 25 is located between the first ground layer 26 and the signal layer 24, and a dielectric layer 25 is also located between the second ground layer 27 and the signal layer 24. The first ground layer 26 and the second ground layer 27 serve as ground layers or shielding layers for the circuit board 2.

[0087] The specific form of the pinmap of the circuit board 2 in the pin area 223 of the present application has multiple options. For example, as shown in Figure 11, in one embodiment, the pins 23 of the above-mentioned pinmap of the circuit board 2 in the connection area 22 are arranged in a matrix (box). Figure 15 is a schematic diagram of the top structure of the circuit board in the embodiment of the present application. As shown in Figure 15, in one embodiment, the pins 23 of the above-mentioned pinmap of the circuit board 2 in the pin area 223 are staggered (stagger) arranged. Figure 16 is a schematic diagram of the top structure of the circuit board in the embodiment of the present application. As shown in Figure 16, in one embodiment, the pins 23 of the above-mentioned pinmap of the circuit board 2 in the pin area 223 are irregularly arranged. In this embodiment, the spacing (Pin pitch) of the pins 23 in the pinmap of the pin area 223 is 0.4mm~1mm, and the density of the pins 23 is relatively large. Specifically, the above-mentioned Pin pitch refers to the distance between the centers of two adjacent pins 23.

[0088] There are multiple options for the specific form of the circuit board 2 in the embodiment of the present application. Figure 17 is a structural schematic diagram of the circuit board in the embodiment of the present application, and Figure 18 is another structural schematic diagram of the circuit board in the embodiment of the present application. In one possible embodiment, as shown in Figure 18, the above-mentioned circuit board 2 can be a one-to-one type circuit board 2, that is, the circuit board 2 is used to realize signal transmission between two points. In this embodiment, the circuit board 2 can only include two connection areas 22, a first connection area 221 and a second connection area 222, and the first connection area 221 and the second connection area 222 are respectively located at the two ends of the circuit board 2. As shown in Figure 18, in one possible embodiment, the above-mentioned circuit board 2 can be a one-to-many type circuit board 2, that is, the circuit board 2 is used to realize signal transmission between one point and multiple points. In this embodiment, the circuit board 2 includes multiple connection areas 22, one of which is located at one end of the circuit board 2, and at least two connection areas 22 are located at the other end of the circuit board 2.

[0089] FIG19 is a schematic diagram of the structure of a circuit board according to an embodiment of the present application. As shown in FIG19 , in one embodiment, the signal layer 24 of the circuit board 2 includes a first signal layer 242 and a second signal layer 243, which are located on either side of a dielectric layer 25. In this embodiment, the circuit board 2 has a large number of signal layers 24, so the area of ​​the signal layers 24 used to prepare the signal lines 241 is large, thereby increasing the number of signal lines 241. This solution can improve the integration of the circuit board 2, enabling the circuit board 2 to transmit a large number of signals.

[0090] FIG20 is a schematic structural diagram of a circuit board according to an embodiment of the present application. As shown in FIG20 , in one embodiment, the signal layer 24 of the circuit board 2 includes a third signal layer 244 and a fourth signal layer 245, and a third ground layer 28 is provided between the third signal layer 244 and the fourth signal layer 245. Specifically, a dielectric layer 25 is provided between the third signal layer 244 and the third ground layer 28, and a dielectric layer 25 is provided between the fourth signal layer 245 and the third ground layer 28. The third ground layer 28 can serve as a reference ground layer for the third signal layer 244 and / or the fourth signal layer 245. More importantly, the third ground layer 28 can serve as a shielding layer between the third signal layer 244 and the fourth signal layer 245 to reduce crosstalk between the third signal layer 244 and the fourth signal layer 245, thereby improving the signal transmission rate of the circuit board 2.

[0091] Please continue to refer to Figures 19 and 20. There are many options for achieving the solution of making the thickness of the connection area 22 smaller than the thickness of the transmission area 21. For example, as shown in Figure 19, the thickness of the connection area 22 can be reduced on both sides of the circuit board 2, so that the surface of the connection area 22 and the surface of the transmission area 21 on one side of the circuit board 2 are located in different planes, and the surface of the connection area 22 and the surface of the transmission area 21 on the other side are also located in different planes; or, as shown in Figure 20, the thickness of the connection area 22 can also be reduced on one side of the circuit board 2, so that the surface of the connection area 22 and the surface of the transmission area 21 on one side of the circuit board 2 are located in different planes, and the surface of the connection area 22 and the surface of the transmission area 21 on the other side are also located in the same plane.

[0092] As shown in Figures 19 and 20, in a specific embodiment, for ease of description, the circuit board 2 is considered to include a first side 29 and a second side 210 that are spaced apart along the thickness direction. As shown in Figure 19, in an optional implementation, on the first side 29 of the circuit board 2, the surface of the connection area 22 and the surface of the transmission area 21 are located in different planes; on the second side 210 of the circuit board 2, the surface of the connection area 22 and the surface of the transmission area 21 are located in different planes. Specifically, the distance between the surface of the connection area 22 on the first side 29 and the surface of the transmission area 21 on the second side 210 is smaller than the distance between the surface of the transmission area 21 on the first side 29 and the surface of the transmission area 21 on the second side 210; and the distance between the surface of the connection area 22 on the second side 210 and the surface of the transmission area 21 on the first side 29 is smaller than the distance between the surface of the transmission area 21 on the second side 210 and the surface of the transmission area 21 on the first side 29. Specifically, the two sides of the circuit board 2 can be symmetrical along the thickness direction. In this embodiment, the circuit board 2 is symmetrical along the thickness direction, and the signal transmission is also symmetrical, which helps improve the signal transmission quality of the circuit board 2.

[0093] As shown in Figure 20 , in an optional implementation, the thickness of the connection area 22 is reduced on one side of the circuit board 2. Specifically, on the first side 29 of the circuit board 2, the surface of the connection area 22 and the surface of the transmission area 21 are located in different planes; on the second side 210 of the circuit board 2, the surface of the connection area 22 and the surface of the transmission area 21 are located in the same plane. Specifically, the distance between the surface of the connection area 22 on the first side 29 and the surface of the circuit board 2 on the second side 210 is smaller than the distance between the surface of the transmission area 21 on the first side 29 and the surface of the circuit board 2 on the second side 210.

[0094] In a specific embodiment, the thickness h1 of the above-mentioned circuit board 2 in the above-mentioned connection area 22 is less than or equal to 0.3 mm, that is, h1≤0.3 mm. The thickness h2 of the above-mentioned circuit board 2 in the above-mentioned transmission area 21 is greater than or equal to 0.5 mm, that is, h2≥0.5 mm. In a specific embodiment, the thickness difference △h between the above-mentioned circuit board 2 in the connection area 22 and the transmission area 21 is less than or equal to 0.5 mm, that is, △h≤0.5 mm. The line width w1 of the signal line 241 in the connection area 22 is less than or equal to 50 μm, that is, w1≤50 μm. The line width w2 of the signal line 241 in the transmission area 21 is greater than or equal to 250 μm, that is, w1≥250 μm.

[0095] In the embodiment of the present application, the connection area 22 of the circuit board 2 covers the pinmap of the circuit board 2. However, along the width direction of the circuit board 2, the connection area 22 may or may not extend through the circuit board 2. Figure 21 is a schematic top view of the circuit board structure in the embodiment of the present application. As shown in Figures 16 and 21, the circuit board 2 includes an extension direction X, a width direction Y, and a thickness direction Z. The first direction X, the second direction Y, and the thickness direction are perpendicular to each other.

[0096] As shown in Figure 16 , in one embodiment, the connection region 22 extends through the width of the circuit board 2, which helps simplify the manufacturing process of the circuit board 2 and improves the flexibility of the circuit board 2 in the connection region 22. As shown in Figure 21 , in one embodiment, the connection region 22 does not extend through the circuit board 2 in the width direction. That is, the circuit board 2 further includes an additional region along the edge of the connection region 22 in the thickness direction. The thickness of the additional region is greater than that of the connection region 22. In a specific embodiment, the thickness of the additional region can be the same as that of the transmission region 21. This embodiment helps improve the strength of the circuit board 2.

[0097] Based on the same concept, the present application also provides a method for preparing a circuit board 2. FIG22 is a schematic diagram of the structure of a circuit board in an embodiment of the present application. The preparation method provided in this embodiment is used to prepare the circuit board 2 shown in FIG22. Referring to FIG22, the circuit board 2 includes a transmission area 21 and a connection area 22, and the transmission area 21 is connected to the connection area 22. The preparation method of the circuit board 2 provided in the present application includes the following steps:

[0098] S101, forming a signal circuit pattern on a first metal layer L1 on a surface of a first flexible metal-clad plate FL1, and a second metal layer L2 on a surface of the first flexible metal-clad plate FL1 facing away from the first metal layer L1;

[0099] The flexible metal-clad laminate in the present application includes a stacked metal layer and a dielectric layer, and the metal layer can specifically be a metal foil layer. The flexible metal-clad laminate can specifically include a single-sided metal-clad laminate and a double-sided metal-clad laminate. The single-sided metal-clad laminate is a laminate having a metal layer covering one surface of the dielectric layer, and the double-sided metal-clad laminate is a laminate having metal layers covering both surfaces of the dielectric layer. The connection between the metal layer and the dielectric layer in the flexible metal-clad laminate is more reliable, and the use of the flexible metal-clad laminate to prepare the circuit board 2 is conducive to simplifying the preparation process of the circuit board 2. The above-mentioned first flexible metal-clad laminate FL1 is a double-sided metal-clad laminate. In a specific embodiment, the flexible metal-clad laminate in the present application can specifically be a flexible copper clad laminate (FCCL). In addition, the metal layer in the present application can be a copper layer, an aluminum layer, a silver layer, etc.

[0100] S102 , laminating the third metal layer L3 , the first adhesive layer BS1 , and the first flexible metal-clad plate FL1 stacked in sequence, wherein the third metal layer L3 is located on a side of the first metal layer L1 facing away from the second metal layer L2 ;

[0101] The third metal layer L3 is fixed to the surface of the first flexible metal-clad substrate FL1 having the first metal layer L1 through the first adhesive layer BS1.

[0102] S103, preparing a conductive via, wherein the conductive via connects at least two layers among the first metal layer L1, the second metal layer L2, and the third metal layer L3;

[0103] The steps of preparing the conductive holes may specifically include two steps: processing the holes and electroplating the metal layer. The step of processing the holes may be completed by mechanical drilling or laser drilling. For example, the conductive holes are formed by mechanical drilling, and the aperture of the conductive holes is between 4mil and 10mil; the conductive holes are formed by laser drilling, and the aperture of the conductive holes is between 2mil and 4mil. In addition, the conductive holes may specifically be through holes or blind holes. In the process of electroplating the metal layer in the hole, the metal layer may also be electroplated on the surface of the metal layer to thicken the metal layer. Which metal layers the conductive holes are specifically connected to is prepared according to the actual routing requirements.

[0104] S104, forming a circuit pattern on the third metal layer L3;

[0105] Specifically, the circuit pattern may be formed by an etching process. For example, the circuit pattern may be connected to the pin 23 and may also be connected to the signal circuit pattern through a conductive hole.

[0106] S105. Laminating the second flexible metal-clad plate FL2, the second adhesive layer BS2, and the third metal layer L3 stacked in sequence; the second flexible metal-clad plate FL2 includes a fourth metal layer L4, which is located on a surface facing away from the third metal layer L3. The second flexible metal-clad plate FL2 and the second adhesive layer BS2 cover a portion of the transmission area 21.

[0107] The second flexible metal-clad sheet FL2 is a single-sided metal-clad sheet. The fourth metal layer L4 of the second flexible metal-clad sheet FL2 is located on the surface of the circuit board 2. The second flexible metal-clad sheet FL2 and the second adhesive layer BS2 only cover a portion of the transmission area 21, making the circuit board 2 thicker in the transmission area 21 than in the connection area 22.

[0108] S106 , forming a circuit pattern on the fourth metal layer L4 .

[0109] Specifically, the circuit pattern may be formed by an etching process.

[0110] Before the above step S105 , the method includes: providing a blocking member 5 on the surface of the first metal layer L1 ;

[0111] The barrier 5 may be a gasket or a blocking block. The barrier 5 blocks the second adhesive layer BS2, preventing it from flowing into the connection area 22. In particular, a thicker second adhesive layer BS2 improves the adhesion of the second flexible metal-clad sheet FL2 and reduces the impact of the second adhesive layer BS2 on the third metal layer L3 in the connection area 22.

[0112] After the above step S105 , the following steps are performed: removing the blocking member 5 .

[0113] Specifically, controlled depth drilling and milling technology can be used to remove the blocking member 5. This solution is conducive to the second flexible metal-clad plate and the second adhesive layer covering the transmission area more accurately and reliably.

[0114] In a specific embodiment, the signal line pattern formed in step S101 includes signal lines 241. The cross-sectional area of ​​the signal lines 241 in the connection area 22 is smaller than the cross-sectional area of ​​the same signal lines 241 in the transmission area 21. The spacing between adjacent signal lines 241 in the connection area 22 is smaller than the spacing in the transmission area 21. This reduces the insertion loss of the circuit board and optimizes the impedance of the circuit board, thereby improving the density and rate of signal transmission on the circuit board.

[0115] Based on the same inventive concept, the present application also provides a method for preparing a circuit board 2. FIG23 is a schematic diagram of the structure of a circuit board in an embodiment of the present application. The preparation method provided in this embodiment is used to prepare the circuit board 2 shown in FIG23. Referring to FIG23, the circuit board 2 includes a transmission area 21 and a connection area 22, and the transmission area 21 is connected to the connection area 22. The preparation method of the circuit board 2 provided in the present application includes the following steps:

[0116] Step S201: forming a signal circuit pattern on the first metal layer L1 on the surface of the first flexible metal-clad plate FL1; and forming a second metal layer L2 on the surface of the first flexible metal-clad plate FL1 away from the first metal layer L1;

[0117] Step S202 , laminating the third metal layer L3 , the first adhesive layer BS1 , and the first flexible metal-clad plate FL1 stacked in sequence, wherein the third metal layer L3 is located on a side of the first metal layer L1 facing away from the second metal layer L2 ;

[0118] Step S203: preparing a conductive via, wherein the conductive via connects at least two layers among the first metal layer L1, the second metal layer L2, and the third metal layer L3;

[0119] Step S204: forming a circuit pattern on the second metal layer L2 of the first flexible metal-clad substrate FL1;

[0120] Step S205 , laminating the fourth metal layer L4 , the second adhesive layer BS2 , and the second metal layer L2 stacked in sequence, wherein the fourth metal layer L4 covers a portion of the transmission area 21 ;

[0121] Step S206: forming a circuit pattern on the fourth metal layer L4.

[0122] In a specific embodiment, the signal line pattern formed in step S201 includes signal lines 241. The cross-sectional area of ​​the signal lines 241 in the connection area 22 is smaller than the cross-sectional area of ​​the same signal lines 241 in the transmission area 21. The spacing between adjacent signal lines 241 in the connection area 22 is smaller than the spacing in the transmission area 21. This reduces the insertion loss of the circuit board and optimizes the impedance of the circuit board, thereby improving the density and rate of signal transmission on the circuit board.

[0123] Based on the same inventive concept, the present application also provides a method for preparing a circuit board 2. FIG24 is a schematic diagram of a structure of a circuit board in an embodiment of the present application. The preparation method provided in this embodiment is used to prepare the circuit board 2 shown in FIG24. Referring to FIG24, the circuit board 2 includes a transmission area 21 and a connection area 22, and the transmission area 21 is connected to the connection area 22. The preparation method of the circuit board 2 provided in the present application includes the following steps:

[0124] Step S301: forming signal circuit patterns on the first metal layer L1 and the second metal layer L2 on both sides of the first flexible metal-clad plate FL1, respectively. The first metal layer L1 and the second metal layer L2 are located on both sides of the first flexible metal-clad plate FL1;

[0125] Step S302 , laminating the third metal layer L3 , the first adhesive layer BS1 , the first flexible metal-clad plate FL1 , the second adhesive layer BS2 and the fourth metal layer L4 stacked in sequence;

[0126] Step S303: preparing conductive vias to connect at least two layers among the first metal layer L1, the second metal layer L2, the third metal layer L3 and the fourth metal layer L4;

[0127] Step S304: forming circuit patterns on the third metal layer L3 and the fourth metal layer L4;

[0128] Step S305: Laminating the second flexible metal-clad plate FL2, the third adhesive layer BS3, the third metal layer L3, the first adhesive layer BS1, the first flexible metal-clad plate FL1, the second adhesive layer BS2, the fourth metal layer L4, the fourth adhesive layer BS4, and the third flexible metal-clad plate FL3, which are stacked in sequence; the second flexible metal-clad plate FL2 and the third flexible metal-clad plate FL3 respectively cover portions of the transmission area 21;

[0129] Step S306: The second flexible metal-clad plate FL2 includes a fifth metal layer L5, which is located on a side away from the first flexible metal-clad plate FL1; the third flexible metal-clad plate FL3 includes a sixth metal layer L6, which is located on a side away from the first flexible metal-clad plate FL1;

[0130] Step S307 : forming circuit patterns on the fifth metal layer L5 and the sixth metal layer L6 , respectively.

[0131] In a specific embodiment, the signal line pattern formed in step S301 includes a signal line 241, the cross-sectional area of ​​the signal line 241 in the connection area 22 is smaller than the cross-sectional area of ​​the same signal line 241 in the transmission area 21, and the spacing between adjacent signal lines 241 in the connection area 22 is smaller than the spacing in the transmission area 21;

[0132] Based on the same inventive concept, the present application also provides a method for preparing a circuit board 2. FIG25 is a schematic diagram of a structure of a circuit board in an embodiment of the present application. The preparation method provided in this embodiment is used to prepare the circuit board 2 shown in FIG25. Referring to FIG25, the circuit board 2 includes a transmission area 21 and a connection area 22, and the transmission area 21 is connected to the connection area 22. The preparation method of the circuit board 2 provided in the present application includes the following steps:

[0133] Step S401: Signal circuit patterns are formed on the first metal layer L1 of the first flexible metal-clad plate FL1 and the second metal layer L2 of the second flexible metal-clad plate FL2, respectively. A circuit pattern is formed on the third metal layer L3 of the first flexible metal-clad plate FL1. The first metal layer L1 and the third metal layer L3 are respectively located on two side surfaces of the first flexible metal-clad plate FL1. A fourth metal layer L4 is provided on a surface of the second flexible metal-clad plate FL2 facing away from the second metal layer L2.

[0134] Step S402: Laminating the fifth metal layer L5, the first adhesive layer BS1, the first flexible metal-clad sheet FL1, the second adhesive layer BS2, and the second flexible metal-clad sheet FL2 stacked in sequence, wherein the first metal layer L1 is adjacent to the first adhesive layer BS1, and the second metal layer L2 is adjacent to the second adhesive layer BS2;

[0135] Step S403: preparing conductive vias to connect at least two layers among the first metal layer L1, the second metal layer L2, the third metal layer L3, the fourth metal layer L4 and the fifth metal layer L5;

[0136] Step S404: forming a circuit pattern on the fourth metal layer L4;

[0137] Step S405 , laminating the sixth metal layer L6 , the third adhesive layer BS3 , and the second flexible metal-clad plate FL2 stacked in sequence, wherein the sixth metal layer L6 covers a portion of the transmission area 21 ;

[0138] Step S406: forming a circuit pattern on the sixth metal layer L6.

[0139] In a specific embodiment, the signal line pattern formed in step S401 includes signal lines 241. The cross-sectional area of ​​the signal lines 241 in the connection area 22 is smaller than the cross-sectional area of ​​the same signal lines 241 in the transmission area 21. The spacing between adjacent signal lines 241 in the connection area 22 is smaller than the spacing in the transmission area 21. This reduces the insertion loss of the circuit board and optimizes the impedance of the circuit board, thereby improving the density and rate of signal transmission on the circuit board.

[0140] In the above embodiments, the several methods for preparing the circuit board 2 shown in Figures 23, 24 and 25 may also include the process of setting and removing the blocking member 5, and some related details can refer to the method for preparing the circuit board 2 shown in Figure 22.

[0141] Obviously, those skilled in the art may make various changes and modifications to the present application without departing from the scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include these modifications and variations.

Claims

1. A circuit board, characterized in that: It includes a transmission area and a connection area, the connection area includes a bending area and a pin area, the bending area is located between the pin area and the transmission area, and the pin area is provided with a plurality of pins, wherein: The bending area is a flexible circuit board, and the thickness of the bending area is smaller than the thickness of the transmission area.

2. The circuit board according to claim 1, characterized in that The circuit board includes a signal line, and the cross-sectional area of ​​the signal line in the connection area is smaller than the cross-sectional area of ​​the same signal line in the transmission area.

3. The circuit board according to claim 1 or 2, characterized in that: The distance between adjacent signal lines located in the same layer in the transmission area is greater than the distance in the connection area.

4. The circuit board according to any one of claims 1 to 3, characterized in that: A length of the bending area along a direction from the pin area to the transmission area is greater than or equal to a preset value.

5. The circuit board according to claim 4, characterized in that: The preset value includes 60 mm.

6. The circuit board according to any one of claims 1 to 5, characterized in that: The pin area is a flexible circuit board.

7. The circuit board according to any one of claims 1 to 5, characterized in that: The pin area includes a rigid circuit board.

8. The circuit board according to claim 7, characterized in that: The bending zone includes a first bending zone and a second bending zone, the transmission zone includes a first transmission zone and a second transmission zone, the first bending zone is connected to the first transmission zone, the second bending zone is connected to the second transmission zone, the first transmission zone and the second transmission zone are stacked and have a gap; the pin zone is connected to the first bending zone and the second bending zone respectively.

9. The circuit board according to any one of claims 1 to 8, characterized in that: The circuit board includes a first side and a second side which are opposite to each other in the thickness direction; on the first side, the surface of the bending zone and the surface of the transmission zone are located in different planes; on the second side, the surface of the bending zone and the surface of the transmission zone are located in the same plane.

10. The circuit board according to any one of claims 1 to 8, characterized in that: The circuit board includes a first side and a second side which are opposite to each other in the thickness direction; on the first side, the surface of the bending zone and the surface of the transmission zone are located in different planes; on the second side, the surface of the bending zone and the surface of the transmission zone are located in different planes.

11. The circuit board according to any one of claims 1 to 10, characterized in that: The material of the dielectric layer includes at least one of modified polyimide, liquid crystal polymer, fluorinated ethylene propylene copolymer and polytetrafluoroethylene.

12. A method for preparing a circuit board, characterized in that: The circuit board comprises a transmission area and a connection area, the transmission area and the connection area are connected, and the preparation method comprises: A signal circuit pattern is formed on the first metal layer on the surface of the first flexible metal-clad plate, and a second metal layer is formed on the surface of the first flexible metal-clad plate away from the first metal layer; Laminating a third metal layer, a first adhesive layer and a first flexible metal-clad plate which are stacked in sequence, wherein the third metal layer is located on a side of the first metal layer away from the second metal layer; preparing a conductive hole, wherein the conductive hole connects at least two layers among the first metal layer, the second metal layer and the third metal layer; The second flexible metal-clad plate, the second adhesive layer and the third metal layer are laminated in sequence; the second flexible metal-clad plate includes a fourth metal layer, the fourth metal layer is located on the surface away from the third metal layer, and the second flexible metal-clad plate and the second adhesive layer cover part of the transmission area.

13. The preparation method according to claim 12, characterized in that: The second flexible metal-clad plate, the second adhesive layer and the third metal layer are sequentially laminated by lamination; the second flexible metal-clad plate includes a fourth metal layer, the fourth metal layer is located on a surface away from the third metal layer, and the second flexible metal-clad plate and the second adhesive layer cover a portion of the transmission area, and the prior includes: Disposing a blocking member at the connection area on the surface of the first metal layer; After that include: The blocking member is removed.

14. The preparation method according to claim 12 or 13, characterized in that: The signal line pattern includes a signal line, the cross-sectional area of ​​the signal line in the connection area is smaller than the cross-sectional area of ​​the same signal line in the transmission area, and the spacing between adjacent signal lines in the connection area is smaller than the spacing between adjacent signal lines in the transmission area.

15. A method for preparing a circuit board, characterized in that: The circuit board comprises a transmission area and a connection area, the transmission area and the connection area are connected, and the preparation method comprises: A signal circuit pattern is formed on the first metal layer on the surface of the first flexible metal-clad plate, and a second metal layer is formed on the surface of the first flexible metal-clad plate away from the first metal layer; Laminating the third metal layer, the first adhesive layer and the first flexible metal-clad plate stacked in sequence, wherein the third metal layer is located on a side of the first metal layer facing away from the second metal layer; preparing a conductive hole, wherein the conductive hole connects at least two layers among the first metal layer, the second metal layer and the third metal layer; The fourth metal layer, the second adhesive layer and the second metal layer stacked in sequence are laminated, and the fourth metal layer covers a portion of the transmission area.

16. The preparation method according to claim 15, characterized in that: The signal line pattern includes a signal line, the cross-sectional area of ​​the signal line in the connection area is smaller than the cross-sectional area of ​​the same signal line in the transmission area, and the spacing between adjacent signal lines in the connection area is smaller than the spacing between adjacent signal lines in the transmission area.

17. A method for preparing a circuit board, characterized in that: The circuit board comprises a transmission area and a connection area, the transmission area and the connection area are connected, and the preparation method comprises: Signal circuit patterns are formed on the first metal layer and the second metal layer on both side surfaces of the first flexible metal-clad plate, respectively, and the first metal layer and the second metal layer are respectively located on both side surfaces of the first flexible metal-clad plate; Laminating the third metal layer, the first adhesive layer, the first flexible metal-clad plate, the second adhesive layer and the fourth metal layer stacked in sequence; Prepare conductive holes to connect at least two of the first metal layer, the second metal layer, the third metal layer and the fourth metal layer; Laminating the second flexible metal-clad plate, the third adhesive layer, the third metal layer, the first adhesive layer, the first flexible metal-clad plate, the second adhesive layer, the fourth metal layer, the fourth adhesive layer and the third flexible metal-clad plate which are stacked in sequence; the second flexible metal-clad plate and the third flexible metal-clad plate respectively cover parts of the transmission area; The second flexible metal clad laminate includes a fifth metal layer, and the fifth metal layer is located on a side away from the first flexible metal clad laminate; the third flexible metal clad laminate includes a sixth metal layer, and the sixth metal layer is located on a side away from the first flexible metal clad laminate.

18. The preparation method according to claim 17, characterized in that: The signal line pattern includes a signal line, the cross-sectional area of ​​the signal line in the connection area is smaller than the cross-sectional area of ​​the same signal line in the transmission area, and the spacing between adjacent signal lines in the connection area is smaller than the spacing between adjacent signal lines in the transmission area.

19. A method for preparing a circuit board, characterized in that: The circuit board comprises a transmission area and a connection area, the transmission area and the connection area are connected, and the preparation method comprises: Signal circuit patterns are formed on the first metal layer of the first flexible metal clad plate and the second metal layer of the second flexible metal clad plate, respectively; a circuit pattern is formed on the third metal layer of the first flexible metal clad plate, the first metal layer and the third metal layer are respectively located on both side surfaces of the first flexible metal clad plate, and the surface of the second flexible metal clad plate away from the second metal layer has a fourth metal layer; Laminating the fifth metal layer, the first adhesive layer, the first flexible metal-clad plate, the second adhesive layer and the second flexible metal-clad plate stacked in sequence, wherein the first metal layer is adjacent to the first adhesive layer, and the second metal layer is adjacent to the second adhesive layer; Prepare conductive holes to connect at least two layers among the first metal layer, the second metal layer, the third metal layer, the fourth metal layer and the fifth metal layer; The sixth metal layer, the third adhesive layer and the second flexible metal-clad plate stacked in sequence are laminated, and the sixth metal layer covers a portion of the transmission area.

20. The preparation method according to claim 19, characterized in that: The signal line pattern includes a signal line, the cross-sectional area of ​​the signal line in the connection area is smaller than the cross-sectional area of ​​the same signal line in the transmission area, and the spacing between adjacent signal lines in the connection area is smaller than the spacing between adjacent signal lines in the transmission area.

21. An electronic component, characterized in that: The invention comprises a printed circuit board and the circuit board as claimed in any one of claims 1 to 11, wherein at least one connection area of ​​the circuit board is electrically connected to the printed circuit board.

22. An electronic device, characterized in that: It comprises a housing and the electronic component as claimed in claim 21, wherein the electronic component is arranged in the housing.

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