Circuit board and electronic device

Abstract

This disclosure relates to a circuit board and an electronic device, wherein the circuit board includes: a first metal layer, a substrate layer, a second metal layer, and an electromagnetic shielding layer sequentially stacked. The electromagnetic shielding layer includes a conductive adhesive layer and a third metal layer stacked together, the third metal layer being connected to the second metal layer via the conductive adhesive layer. The second metal layer is used for data transmission; the impedance between the second metal layer and the first metal layer is less than the impedance between the second metal layer and the third metal layer, and the conductivity of the first metal layer is greater than the conductivity of the third metal layer. Signal return will select the path of lowest impedance; since the impedance between the second metal layer and the first metal layer is lower, the first metal layer can serve as a reference layer to provide a return path. Furthermore, the first metal layer has higher conductivity than the electromagnetic shielding layer to reduce signal insertion loss and improve signal quality.

Description

Technical Field

[0001] This disclosure relates to the field of electrical component technology, and more particularly to a circuit board and electronic device. Background Technology

[0002] In related technologies, electronic devices often use circuit boards for data transmission. To prevent high-speed signals from interfering with other components inside the electronic device, electromagnetic shielding films are attached to the circuit boards to block electromagnetic waves. However, the layered structure of the circuit board and the electromagnetic shielding film can affect signal quality. Utility Model Content

[0003] To overcome the problems existing in the related technologies, this disclosure provides a circuit board and an electronic device.

[0004] According to some embodiments of this disclosure, a circuit board is provided, comprising: a first metal layer, a substrate layer, a second metal layer, and an electromagnetic shielding layer stacked sequentially; the electromagnetic shielding layer includes a conductive adhesive layer and a third metal layer stacked together, the third metal layer being connected to the second metal layer through the conductive adhesive layer; the second metal layer is used for data transmission, the impedance value between the second metal layer and the first metal layer is less than the impedance value between the second metal layer and the third metal layer, and the conductivity of the first metal layer is greater than the conductivity of the third metal layer.

[0005] In some embodiments, the thickness of the conductive adhesive layer is greater than a first preset thickness.

[0006] In some embodiments, the thickness of the substrate layer is less than the second preset thickness.

[0007] In some embodiments, the second metal layer includes a trace area and a ground area;

[0008] The wiring area is electrically isolated from the grounding area. The wiring area is used for data transmission, and the grounding area is used to provide a reference point. The electromagnetic shielding layer is electrically connected to the grounding area.

[0009] In some embodiments, the circuit board further includes a first cover film layer; the first cover film layer is disposed between the second metal layer and the electromagnetic shielding layer, the first cover film layer has a plurality of through holes, and the electromagnetic shielding layer is electrically connected to the grounding area through the through holes.

[0010] In some embodiments, the formed area of ​​the through hole is greater than a preset area.

[0011] In some embodiments, the circuit board further includes a second cover film layer; the second cover film layer is disposed on the side of the first metal layer opposite to the substrate layer.

[0012] In some embodiments, the circuit board further includes a reinforcing plate; the substrate layer is made of a flexible material, the reinforcing plate is disposed on the side of the second cover film layer away from the first metal layer, and the reinforcing plate covers at least a portion of the second cover film layer.

[0013] In some embodiments, the circuit board further includes connectors; the connectors are electrically connected to the first metal layer and the second metal layer respectively, and there are at least two connectors.

[0014] According to some embodiments of this disclosure, an electronic device is provided, including the circuit board described in any of the above embodiments.

[0015] The technical solutions provided by the embodiments of this disclosure can include the following beneficial effects: By providing a substrate layer between the second metal layer and the first metal layer, a certain impedance value is achieved between the second metal layer and the first metal layer. By providing a conductive adhesive layer between the second metal layer and the third metal layer, a certain impedance value is achieved between the second metal layer and the third metal layer. Signal return will select the path of lowest impedance. Since the impedance value between the second metal layer and the first metal layer is lower, the first metal layer can serve as a reference layer to provide a return path. Furthermore, the first metal layer has higher conductivity than the electromagnetic shielding layer, thereby reducing signal insertion loss and improving signal quality.

[0016] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0018] Figure 1 This is a cross-sectional view of a circuit board shown according to some embodiments of the present disclosure.

[0019] Figure 2 This is a front view of a circuit board shown according to some embodiments of the present disclosure.

[0020] Figure 3 This is a block diagram illustrating an electronic device according to some embodiments of the present disclosure. Detailed Implementation

[0021] Some embodiments of this disclosure will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. Various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will become apparent upon understanding this disclosure. For example, the order of operations described herein is merely illustrative and is not limited to those orders set forth herein, but can be changed as will become apparent upon understanding this disclosure, except for operations that must be performed in a particular order. Furthermore, for clarity and brevity, descriptions of features known in the art may be omitted.

[0022] The embodiments described in the following examples of this disclosure are not representative of all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0023] In related technologies, electronic devices often use circuit boards for data transmission. For example, when using USB 3.0 signals for data transmission, the high signal rate generates electromagnetic waves on the circuit board traces, which can interfere with other components inside the electronic device. Typically, circuit boards are fitted with electromagnetic shielding films to block electromagnetic interference (EMI). However, the low conductivity of these shielding films, when used as a reference layer for the signal return path, can cause degradation of the USB 3.0 signal rise edge, resulting in excessive insertion loss and affecting signal quality.

[0024] In view of this, some embodiments of the present disclosure provide a circuit board and an electronic device that utilize a metal layer with high conductivity as a reference layer for the signal return path to reduce signal insertion loss and improve signal quality.

[0025] Figure 1 This is a cross-sectional view of a circuit board according to some embodiments of the present disclosure. Figure 2 This is a front view of a circuit board shown according to some embodiments of the present disclosure. Figure 1 and Figure 2 As shown, the circuit board includes: a first metal layer 3, a substrate layer 1, a second metal layer 2, and an electromagnetic shielding layer 5, which are stacked sequentially. The electromagnetic shielding layer 5 includes a conductive adhesive layer 51 and a third metal layer 52, which are stacked together. The third metal layer 52 is connected to the second metal layer 2 through the conductive adhesive layer 51. The second metal layer 2 is used for data transmission. The impedance between the second metal layer 2 and the first metal layer 3 is less than the impedance between the second metal layer 2 and the third metal layer 52, and the conductivity of the first metal layer 3 is greater than the conductivity of the third metal layer 52.

[0026] Specifically, a substrate layer 1 is disposed between the second metal layer 2 and the first metal layer 3, creating a certain impedance value between them. A conductive adhesive layer 51 is disposed between the second metal layer 2 and the third metal layer 52, creating a certain impedance value between them. Signal return current will choose the path of lowest impedance. Since the impedance value between the second metal layer 2 and the first metal layer 3 is lower, the first metal layer 3 can serve as a reference layer to provide a return path. Furthermore, the first metal layer 3 has higher conductivity than the electromagnetic shielding layer 5, reducing signal insertion loss and improving signal quality.

[0027] The circuit board of this disclosure embodiment is used for transmitting high-speed signals, such as USB 3.0 signals.

[0028] In some embodiments, the thickness of the conductive adhesive layer 51 is greater than a first preset thickness. By increasing the thickness of the conductive adhesive layer 51, the second metal layer 2 used for data transmission is moved away from the third metal layer 52 of the electromagnetic shielding layer 5, thereby increasing the impedance value between the second metal layer 2 and the third metal layer 52. This prevents signals with low inductive return current from using the third metal layer 52 as the main return path.

[0029] For example, the first preset thickness is 1 to 3 micrometers.

[0030] Taking a 15mm long circuit board as an example, when the thickness of the conductive adhesive layer 51 is 3 micrometers, the insertion loss of the USB 3.0 signal at a frequency of 2.5GHz is -10dB. Increasing the thickness of the conductive adhesive layer 51 by 5 micrometers reduces the insertion loss of the USB 3.0 signal at a frequency of 2.5GHz to -7dB, thus reducing the signal insertion loss by 3dB.

[0031] In some embodiments, the thickness of the substrate layer 1 is less than a second preset thickness. By reducing the thickness of the substrate layer 1, the second metal layer 2 used for data transmission is brought closer to the first metal layer 3, thereby reducing the impedance between the second metal layer 2 and the first metal layer 3. This allows signals with low inductive return current to use the first metal layer 3 as the primary return path.

[0032] For example, the second preset thickness is 36 to 100 micrometers.

[0033] Taking a 15mm long circuit board as an example, when the substrate thickness is 36 micrometers, the insertion loss of the USB 3.0 signal at a frequency of 2.5GHz is -10dB. When the substrate thickness is 25 micrometers, the insertion loss of the USB 3.0 signal at a frequency of 2.5GHz is -8dB, which reduces the signal insertion loss by 2dB.

[0034] In other embodiments of this disclosure, a second metal layer 2 and a first metal layer 3 are provided on one side of the substrate layer 1, and the second metal layer 2 and the first metal layer 3 are electrically isolated from each other. An electromagnetic shielding layer 5 is provided on one side of the substrate layer 1, and the electromagnetic shielding layer 5, i.e., the third metal layer 52, is connected to the substrate layer 1 through a conductive adhesive layer 51. The second metal layer 2 and the first metal layer 3 are electrically isolated, so that the second metal layer 2 and the first metal layer 3 have a certain impedance value. A conductive adhesive layer 51 and a substrate layer 1 are stacked between the second metal layer 2 and the third metal layer 52, so that the second metal layer 2 and the third metal layer 52 have a certain impedance value. And the impedance value between the second metal layer 2 and the first metal layer 3 is less than the impedance value between the second metal layer 2 and the third metal layer 52. The second metal layer 2 is used for data transmission, and the first metal layer 3 is used to provide a reference location and to provide a return path as a reference layer.

[0035] Alternatively, a second metal layer 2 and a first metal layer 3 are provided on one side of the substrate layer 1, and the second metal layer 2 and the first metal layer 3 are electrically isolated from each other. An electromagnetic shielding layer 5 covers the second metal layer 2 and the first metal layer 3, meaning the third metal layer 52 is connected to both the second metal layer 2 and the first metal layer 3 via a conductive adhesive layer 51. Electrical isolation between the second metal layer 2 and the first metal layer 3 creates a certain impedance value between them. A conductive adhesive layer 51 is provided between the second metal layer 2 and the third metal layer 52, creating a certain impedance value between them. Furthermore, the impedance value between the second metal layer 2 and the first metal layer 3 is less than the impedance value between the second metal layer 2 and the third metal layer 52. The second metal layer 2 is used for data transmission, and the first metal layer 3 is used to provide a reference location and, as a reference layer, to provide a return path.

[0036] In some embodiments, the second metal layer 2 includes a trace area 21 and a ground area 22. The trace area 21 and the ground area 22 are electrically isolated; the trace area 21 is used for data transmission, and the ground area 22 is used to provide a reference point. The electromagnetic shielding layer 5 is electrically connected to the ground area 22. Although the first metal layer 3 can serve as a reference layer to provide a return path by increasing the thickness of the conductive adhesive layer 51 and / or by decreasing the thickness of the substrate layer 1, some return current still passes through the electromagnetic shielding layer 5. Therefore, by electrically connecting the electromagnetic shielding layer 5 to the ground area 22, the electromagnetic shielding layer 5 is grounded, thereby improving the return current performance of the electromagnetic shielding layer 5.

[0037] In some embodiments, the first metal layer 3 is used to provide a reference location, and the electromagnetic shielding layer 5 is electrically connected to the first metal layer 3 to ground the electromagnetic shielding layer 5.

[0038] In some embodiments, the circuit board further includes a first cover film layer 41. The first cover film layer 41 is disposed between the second metal layer 2 and the electromagnetic shielding layer 5. The first cover film layer 41 has multiple through holes 411, through which the electromagnetic shielding layer 5 is electrically connected to the grounding region 22. The method of electrically connecting the electromagnetic shielding layer 5 to the grounding region 22 is relatively simple, thereby reducing the manufacturing cost of the circuit board. Furthermore, by providing multiple through holes 411, the grounding effect of the electromagnetic shielding layer 5 is improved.

[0039] In some embodiments, the area of ​​the through hole 411 is larger than a preset area. By increasing the area of ​​a single hole, the grounding effect of the electromagnetic shielding layer 5 is further improved.

[0040] For example, the preset area is 0.1 to 0.5 square millimeters.

[0041] Taking a circuit board with a length of 15 mm as an example, when the first cover film layer 41 has four through holes 411, the insertion loss of the USB 3.0 signal at a frequency of 2.5 GHz is -10 dB. When the first cover film layer 41 has eight through holes 411, the insertion loss of the USB 3.0 signal at a frequency of 2.5 GHz is -9.5 dB, and the signal insertion loss can be reduced by 0.5 dB.

[0042] In some embodiments, the circuit board further includes a second cover film layer 42. The second cover film layer 42 is disposed on the side of the first metal layer 3 facing away from the substrate layer 1. By providing the second cover film layer 42, the first metal layer 3 is prevented from being affected by external factors, thereby improving the safety and stability of the circuit board.

[0043] In some embodiments, the circuit board further includes a reinforcing plate 6. The substrate layer 1 is made of a flexible material, meaning the circuit board in this embodiment can be a flexible circuit board. The reinforcing plate 6 is disposed on the side of the second cover film layer 42 facing away from the first metal layer 3, and the reinforcing plate 6 covers at least a portion of the second cover film layer 42. By providing the reinforcing plate 6, the strength of the corresponding position is improved, thereby extending the service life of the circuit board.

[0044] In some embodiments, the circuit board further includes connectors 7. Connectors 7 are electrically connected to the first metal layer 3 and the second metal layer 2, respectively, and at least two connectors 7 are provided. The connectors 7 facilitate electrical connection of the circuit board to other electrical components.

[0045] Connector 7 can be a board-to-board connector (BTB).

[0046] In some embodiments, such as Figure 2As shown, the grounding area 22 is located around the trace area 21, and the connectors 7 are located at opposite ends of the trace area 21 along its length. Multiple through holes 411 are arranged along the length of the trace area 21 and are located on opposite sides of the trace area 21 along its width to improve the grounding effect of the electromagnetic shielding layer 5.

[0047] The circuit board of this embodiment has the following advantages: 1. By using a thickened conductive adhesive layer 51, the second metal layer 2 is moved away from the third metal layer 52 of the electromagnetic shielding layer 5, effectively solving the problem of excessive signal insertion loss caused by the electromagnetic shielding layer 5, reducing signal loss, and avoiding the cost problem caused by replacing high-frequency electromagnetic shielding materials. 2. By using a thinner substrate layer 1, the first metal layer 3 has a higher signal reference conductivity, thereby reducing signal insertion loss. 3. By opening a through-hole 411 in the first cover film layer 41, the electromagnetic shielding layer 5 can be effectively grounded, thereby reducing signal insertion loss.

[0048] According to some embodiments of this disclosure, an electronic device is provided, including the circuit board described in any of the above embodiments.

[0049] Figure 3 This is a block diagram illustrating an electronic device 800 according to some embodiments of the present disclosure. For example, the electronic device 800 may be a mobile phone, computer, digital broadcasting terminal, messaging device, game console, tablet device, medical device, fitness equipment, personal digital assistant, etc.

[0050] Reference Figure 3 The electronic device 800 may include one or more of the following components: processing component 802, memory 804, power supply component 806, multimedia component 808, audio component 810, input / output (I / O) interface 812, sensor component 814, and communication component 816.

[0051] Processing component 802 typically controls the overall operation of electronic device 800, such as operations associated with display, telephone calls, data communication, camera operation, and recording operations. Processing component 802 may include one or more processors 820 to execute instructions to complete all or part of the steps of the methods described above. Furthermore, processing component 802 may include one or more modules to facilitate interaction between processing component 802 and other components. For example, processing component 802 may include a multimedia module to facilitate interaction between multimedia component 808 and processing component 802.

[0052] Memory 804 is configured to store various types of data to support the operation of electronic device 800. Examples of this data include instructions for any application or method operating on electronic device 800, contact data, phonebook data, messages, pictures, videos, etc. Memory 804 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0053] Power supply component 806 provides power to various components of electronic device 800. Power supply component 806 may include a power management system, one or more power supplies, and other components associated with generating, managing, and distributing power to electronic device 800.

[0054] Multimedia component 808 includes a screen that provides an output interface between the electronic device 800 and the user. In some embodiments, the screen may include a liquid crystal display (LCD) and a touch panel (TP). If the screen includes a touch panel, the screen may be implemented as a touchscreen to receive input signals from the user. The touch panel includes one or more touch sensors to sense touches, swipes, and gestures on the touch panel. The touch sensors may sense not only the boundaries of the touch or swipe action but also the duration and pressure associated with the touch or swipe operation. In some embodiments, multimedia component 808 includes a front-facing camera and / or a rear-facing camera. When the electronic device 800 is in an operating mode, such as a shooting mode or a video mode, the front-facing camera and / or the rear-facing camera may receive external multimedia data. Each front-facing camera and rear-facing camera may be a fixed optical lens system or have focal length and optical zoom capabilities.

[0055] Audio component 810 is configured to output and / or input audio signals. For example, audio component 810 includes a microphone (MIC) configured to receive external audio signals when electronic device 800 is in an operating mode, such as call mode, recording mode, and voice recognition mode. The received audio signals may be further stored in memory 804 or transmitted via communication component 816. In some embodiments, audio component 810 also includes a speaker for outputting audio signals.

[0056] I / O interface 812 provides an interface between processing component 802 and peripheral interface modules, such as keyboards, click wheels, buttons, etc. These buttons may include, but are not limited to, home buttons, volume buttons, power buttons, and lock buttons.

[0057] Sensor assembly 814 includes one or more sensors for providing state assessments of various aspects of electronic device 800. For example, sensor assembly 814 can detect the on / off state of electronic device 800, the relative positioning of components such as the display and keypad of electronic device 800, changes in position of electronic device 800 or a component of electronic device 800, the presence or absence of user contact with electronic device 800, orientation or acceleration / deceleration of electronic device 800, and temperature changes of electronic device 800. Sensor assembly 814 may include a proximity sensor configured to detect the presence of nearby objects without any physical contact. Sensor assembly 814 may also include a light sensor, such as a CMOS or CCD image sensor, for use in imaging applications. In some embodiments, sensor assembly 814 may also include an accelerometer, gyroscope, magnetometer, pressure sensor, or temperature sensor.

[0058] Communication component 816 is configured to facilitate wired or wireless communication between electronic device 800 and other devices. Electronic device 800 can access wireless networks based on communication standards, such as WiFi, 3G, 4G, 5G, other communication standards, or combinations thereof. In some embodiments of this disclosure, communication component 816 receives broadcast signals or broadcast-related information from an external broadcast management system via a broadcast channel. In some embodiments of this disclosure, communication component 816 further includes a near-field communication (NFC) module to facilitate short-range communication. For example, the NFC module may be implemented based on radio frequency identification (RFID) technology, Infrared Data Association (IrDA) technology, ultra-wideband (UWB) technology, Bluetooth (BT) technology, and other technologies.

[0059] In the above detailed description, reference has been made to the accompanying drawings, which illustrate specific aspects of this disclosure by way of illustration. In this regard, terms indicating direction or positional relationship, such as “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential,” are used with reference to the orientation of the described figures. Since components of the described device can be positioned in multiple different orientations, directional terms are used for illustrative purposes and not for limitation. It should be understood that other aspects can be utilized and structural or logical changes can be made without departing from the concept of this disclosure. Therefore, the following detailed description should not be considered limiting.

[0060] It should be understood that, unless otherwise specifically indicated, features of various embodiments of this disclosure described herein can be combined with each other. As used herein, the term "and / or" includes any of the associated listed items and any combination of any two or more; it should be understood that, unless otherwise expressly specified and limited, the terms "joining," "attaching," "mounting," "connecting," "linking," "fixing," etc., used in the embodiments of this disclosure should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral part; as a mechanical connection, an electrical connection, or a communicative connection; as a direct connection or an indirect connection through an intermediate medium; as a connection within two elements or an interaction between two elements, unless otherwise expressly limited. Those skilled in the art will understand the specific meaning of the above terms herein according to the specific circumstances.

[0061] Furthermore, the term "above" as used herein with respect to components, elements, or material layers formed or located "above" a surface may be used to indicate that the component, element, or material layer is "indirectly" positioned (e.g., placed, formed, deposited, etc.) on the surface such that one or more additional components, elements, or layers are arranged between the surface and the component, element, or material layer. However, the term "above" as used with respect to components, elements, or material layers formed or located "above" a surface may also optionally have a specific meaning: that the component, element, or material layer is "directly" positioned (e.g., placed, formed, deposited, etc.) on the surface, for example, in direct contact with the surface.

[0062] It should be understood that spatial relative terms, such as “above,” “upper,” “below,” and “lower,” are used herein to describe the relationship between one element and another shown in the figures. In addition to the orientation depicted in the figures, these spatial relative terms are also intended to encompass different orientations of the device in use or operation. For example, if the device in the figures is flipped, an element described as “above” or “upper” relative to another element would be “below” or “lower” relative to that other element. Thus, depending on the spatial orientation of the device, the term “above” encompasses both above and below orientations. Devices may have other orientations (e.g., rotated 90 degrees or in other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0063] Although terms such as “first,” “second,” and “third” may be used herein to describe various components, parts, regions, layers, or sections, these components, parts, regions, layers, or sections are not limited to these terms. Rather, these terms are used only to distinguish one component, part, region, layer, or section from another. Therefore, without departing from the teachings of the examples described herein, a first component, part, region, layer, or section mentioned in the examples may also be referred to as a second component, part, region, layer, or section. Furthermore, the terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first” or “second” may explicitly or implicitly include at least one of that feature.

[0064] It is further understood that the terms "first," "second," etc., are used to describe various types of information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another, and do not indicate a specific order or degree of importance. In fact, the expressions "first," "second," etc., are completely interchangeable. For example, without departing from the scope of this disclosure, first information can also be referred to as second information, and similarly, second information can also be referred to as first information.

[0065] In this description, "multiple" means at least two, referring to two or more, such as two, three, etc., unless otherwise explicitly specified. Other quantifiers are similar. The singular forms "a," "the," and "the" are also intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, unless otherwise specified or clearly indicated from the context, the articles "a" and "an" as used in this application and the appended claims are generally understood to mean "one or more."

[0066] It should be understood that, unless otherwise specifically indicated, features of various embodiments of this disclosure described herein can be combined with each other. As used herein, the term "and / or" includes any one of the related listed items and any combination of two or more; "and / or" describes the association relationship between related objects, indicating that three relationships may exist, for example, A and / or B can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. Similarly, "at least one of..." includes any one of the related listed items and any combination of two or more.

[0067] Furthermore, the term "exemplary" is used herein to indicate that it serves as an example, instance, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as advantageous compared to other aspects or designs. Rather, the use of the term "exemplary" is intended to present concepts in a concrete manner. As used herein, the term "or" is intended to indicate an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified or clear from the context, "X applies A or B" is intended to indicate any of the natural inclusive permutations. That is, if X applies A; X applies B; or X applies both A and B, then applying A or B satisfies the condition under any of the foregoing instances.

[0068] Similarly, although this disclosure has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art upon reading and understanding the specification and drawings. This disclosure includes all such modifications and variations and is limited only by the scope of the claims. In particular, with respect to the various functions performed by the components described above (e.g., elements, resources, etc.), unless otherwise indicated, the terminology used to describe such components is intended to correspond to any component (functionally equivalent) that performs the specific function of the described component, even if it is not structurally equivalent to the disclosed structure. Furthermore, although specific features of this disclosure may have been disclosed with respect to only one of several implementations, such features may be combined with one or more other features of other implementations, as may be desired and advantageous to any given or particular application. Moreover, with regard to the terms “comprising,” “owning,” “having,” “having,” or variations thereof as used in this disclosure, such terms are intended to be inclusive in a manner similar to the term “including.”

[0069] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the utility model disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein.

[0070] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A circuit board, characterized by, include: A first metal layer, a substrate layer, a second metal layer, and an electromagnetic shielding layer are stacked sequentially. The electromagnetic shielding layer includes a conductive adhesive layer and a third metal layer stacked together, and the third metal layer is connected to the second metal layer through the conductive adhesive layer. The second metal layer is used for data transmission. The impedance between the second metal layer and the first metal layer is less than the impedance between the second metal layer and the third metal layer, and the conductivity of the first metal layer is greater than the conductivity of the third metal layer.

2. The circuit board of claim 1, wherein The thickness of the conductive adhesive layer is greater than the first preset thickness.

3. The circuit board of claim 1, wherein The thickness of the substrate layer is less than the second preset thickness.

4. The circuit board according to any one of claims 1 to 3, characterized by The second metal layer includes a trace area and a ground area; The wiring area is electrically isolated from the grounding area. The wiring area is used for data transmission, and the grounding area is used to provide a reference location. The electromagnetic shielding layer is electrically connected to the grounding area.

5. The circuit board of claim 4, wherein, The circuit board also includes a first cover film layer; The first cover film layer is disposed between the second metal layer and the electromagnetic shielding layer. The first cover film layer has a plurality of through holes, and the electromagnetic shielding layer is electrically connected to the grounding area through the through holes.

6. The circuit board of claim 5, wherein, The area of ​​the through hole is greater than the preset area.

7. The circuit board of claim 4, wherein The circuit board also includes a second cover film layer; The second cover film layer is disposed on the side of the first metal layer opposite to the substrate layer.

8. The circuit board of claim 7, wherein, The circuit board also includes a reinforcing plate; The substrate layer is made of a flexible material, and the reinforcing plate is disposed on the side of the second cover film layer away from the first metal layer, and the reinforcing plate covers at least a portion of the second cover film layer.

9. The circuit board of claim 4, wherein, The circuit board also includes a connector; The connectors are electrically connected to the first metal layer and the second metal layer respectively, and there are at least two connectors.

10. An electronic device, comprising: The circuit board includes any one of claims 1 to 9.

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