Circuit board and display module

Abstract

According to the circuit board provided by the invention, the conductive layer comprises the first modified polyimide layer, so that the first modified polyimide layer has the characteristic of low DF, delay and loss of signals during transmission in the metal layer can be reduced, and the transmission rapidness of the signals in the metal layer can be guaranteed; in addition, the low dielectric constant is also beneficial to reducing stray capacitance generated by the via hole, and is beneficial to improving signal integrity and reducing signal distortion. Besides, the covering film in the circuit board comprises the second modified polyimide layer, and the second modified polyimide layer with low dielectric loss factor is beneficial to reducing interference and noise in the signal transmission process, so that the protection effect on the main signal is realized, and the penetration resistance in the signal transmission process is reduced. In conclusion, according to the circuit board provided by the embodiment of the invention, the modified polyimide layers are arranged in the conductive layer and the covering film, so that the purposes of improving the signal transmission speed of the circuit board and reducing the signal transmission loss are achieved.

Description

TECHNICAL FIELD

[0001] The present specification relates to the technical field of semiconductor technology, in particular, to the technical field of circuit board under semiconductor technology, and more particularly, to a circuit board and a display module. BACKGROUND

[0002] A printed circuit board (PCB) is an important electronic component that provides electrical connections for electronic components. A flexible printed circuit (FPC) is a printed circuit board made of a flexible insulating substrate, which can be bent, folded and twisted to adapt to various complex three-dimensional space installation requirements. Various circuit boards such as flexible circuit boards are widely used in the technical field of display modules.

[0003] With the increase of the amount of data to be transmitted by the circuit board, it is necessary to improve the performance of the circuit board to meet the performance requirements of the circuit board in various application scenarios. CONTENT OF THE INVENTION

[0004] The embodiments of the present specification provide a circuit board to achieve the purpose of improving the signal transmission speed of the circuit board and reducing the signal transmission loss.

[0005] To achieve the above technical purpose, the embodiments of the present specification provide the following technical solutions:

[0006] In a first aspect, a circuit board is provided, comprising:

[0007] A conductive layer, the conductive layer comprising a first modified polyimide layer and a metal layer located on at least one side of the first modified polyimide layer;

[0008] A cover film located on at least one side of the conductive layer, the cover film comprising a second modified polyimide layer;

[0009] An electromagnetic shielding layer located on a side of the cover film away from the conductive layer.

[0010] In combination with the first aspect, in some embodiments of the first aspect, the cover film further comprises:

[0011] A low-loss adhesive layer located on a side of the second modified polyimide layer facing the conductive layer.

[0012] In combination with the first aspect, in some embodiments of the first aspect, the low-loss adhesive layer comprises an adhesive layer with a dielectric loss factor less than or equal to 0.0002;

[0013] Optionally, the low-loss adhesive layer comprises a bisphenol AD epoxy resin layer.

[0014] With reference to the first aspect, in some embodiments of the first aspect, the first modified polyimide layer comprises a modified polyimide layer with a dielectric loss factor less than or equal to 0.0002.

[0015] The second modified polyimide layer comprises a modified polyimide layer with a dielectric loss factor less than or equal to 0.0002.

[0016] With reference to the first aspect, in some embodiments of the first aspect, the modified polyimide layer comprises: a fluorine-containing polyimide layer or a polyimide layer containing inorganic nano-filler.

[0017] Optionally, the inorganic nano-filler comprises: at least one of silica, mica and zinc oxide.

[0018] With reference to the first aspect, in some embodiments of the first aspect, the electromagnetic shielding layer comprises: a high-frequency electromagnetic shielding layer.

[0019] With reference to the first aspect, in some embodiments of the first aspect, the high-frequency electromagnetic shielding layer comprises: a silver-plated polyimide layer.

[0020] With reference to the first aspect, in some embodiments of the first aspect, the number of the cover films is two, and the two cover films are respectively located on two sides of the conductive layer.

[0021] Optionally, the number of the electromagnetic shielding layers is two, and the two electromagnetic shielding layers are respectively located on sides of the cover films away from the conductive layer.

[0022] With reference to the first aspect, in some embodiments of the first aspect, the metal layer comprises a copper foil layer.

[0023] A second aspect provides a display module, comprising:

[0024] A display panel, the display panel comprising a first display area and a second display area;

[0025] A drive circuit, the drive circuit being electrically connected to the display panel through the circuit board as described in any one of the above aspects, and the drive circuit being configured to provide a drive signal for the first display area and / or the second display area.

[0026] With reference to the second aspect, in some embodiments of the second aspect, the drive circuit is electrically connected to the display panel through one of the circuit boards.

[0027] A third aspect provides a computing device comprising the display module as described in any one of the above aspects.

[0028] From the above technical solution, the circuit board provided by the embodiment of the present specification includes a first modified polyimide layer in the conductive layer. Thus, the first modified polyimide layer has the characteristics of low dissipation factor (DF) and low dielectric constant, which is beneficial to reduce the delay and loss of signal transmission in the metal layer, and to ensure the rapidity of signal transmission in the metal layer. In addition, the low dielectric constant also helps to reduce the parasitic capacitance generated by the via hole, which is beneficial to improve the integrity of the signal and reduce signal distortion. In addition, the cover film in the circuit board includes a second modified polyimide layer. The second modified polyimide layer with low dissipation factor helps to reduce interference and noise in the signal transmission process, realizes the protection effect of the main signal, and is beneficial to reduce the penetration resistance in the signal transmission process. In summary, the circuit board provided by the embodiment of the present specification realizes the purpose of improving the signal transmission speed of the circuit board and reducing the signal transmission loss by arranging the modified polyimide layer in the conductive layer and the cover film. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present specification or the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present specification, and those skilled in the art can also obtain other drawings according to the provided drawings without creative labor.

[0030] Figure 1 It is a schematic view of a display module;

[0031] Figure 2 It is a schematic view of another display module;

[0032] Figure 3 It is a schematic view of the cross-sectional structure of a circuit board provided by an embodiment of the present specification;

[0033] Figure 4 It is a schematic view of the cross-sectional structure of another circuit board provided by an embodiment of the present specification;

[0034] Figure 5 It is a schematic view of the cross-sectional structure of another circuit board provided by an embodiment of the present specification;

[0035] Figure 6 It is a schematic view of the top structure of a display module provided by an embodiment of the present specification;

[0036] Figure 7 It is a schematic view of the structure of a display module in a folded state provided by an embodiment of the present specification;

[0037] Figure 8A structural schematic diagram of a display module in a folded state according to an embodiment of the present specification is shown in FIG. 1.

[0038] Figure 9 A structural schematic diagram of an electronic device according to an embodiment of the present specification is shown in FIG. 2.

[0039] Explanation of Reference Numerals

[0040] 10 - conductive layer; 11 - metal layer; 12 - first modified polyimide layer; 20 - cover layer; 21 - low-loss adhesive layer; 22 - second modified polyimide layer; 30 - electromagnetic shielding layer.

[0041] 100 - display panel; 200 - electronic device; 101 - first display area; 102 - second display area; 103 - folding area; 104 - support; 105 - folding structure. DETAILED DESCRIPTION

[0042] Unless otherwise defined, technical terms or scientific terms used in the embodiments of the present specification shall be understood as having the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the present specification belong. The terms "first", "second", and the like used in the embodiments of the present specification do not denote any order, quantity, or importance, but are used to avoid confusion among elements.

[0043] Unless otherwise required by context, "plurality" in the specification means "at least two", and "comprising" is to be interpreted as open, inclusive meaning, i.e. "including but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" are intended to mean that the specific feature, structure, material or characteristic associated with that embodiment or example is included in at least one embodiment or example of the specification. The illustrative representation of the above terms does not necessarily refer to the same embodiment or example.

[0044] The technical solutions in the embodiments of the present specification will be described clearly and completely below in conjunction with the drawings in the embodiments of the present specification. Obviously, the described embodiments are only some of the embodiments of the present specification, not all the embodiments. Based on the embodiments in the present specification, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present specification.

[0045] First, it should be noted that spatial relation terms, such as "front" and "back," are intended to refer to the two opposing first and second surfaces of a device or element. The use of "front" and "back" here is for the purpose of conforming to the orientation of the accompanying drawings and facilitating description. When the orientation of the drawings changes, the spatial relation terms should also be interpreted accordingly; for example, if the device or element in the drawings is flipped, then "front" should be understood as "back."

[0046] SUMMARY

[0047] Circuit boards are widely used in various electronic devices. Taking mobile phones as an example, the display module of a mobile phone usually needs to use circuit boards (especially flexible circuit boards) to realize the electrical connection between the screen and the driving circuit. The driving circuit provides driving signals to the screen through the circuit board (such as TP signal (Touch Panel Signal), MIPI (Mobile Industry Processor Interface) signal, power signal, etc.).

[0048] With the continuous development of mobile phones and other electronic devices, new types of electronic devices have emerged, such as foldable screen phones (which can be called foldable screen phones). Taking foldable screen phones as an example, for instance... Figure 1 As shown, traditional foldable phones are mostly designed with a main and secondary screen setup. This means the main screen and the secondary screen are two completely independent screens, each with its own display area and functions. The two screens are connected by a folding mechanism, allowing them to display different content separately or work together. Both the main and secondary screens have their own driving circuits and circuit boards. The independent operation of these circuit boards ensures the independent operation and rapid response of both screens.

[0049] To reduce the number of hardware components in the device, improve integration, optimize display effects, avoid display differences between the main screen and the secondary screen, and provide users with a seamless display experience, refer to... Figure 2 This technology was developed for foldable phones with extended screen designs. In these phones, the main screen and the extended screen can be connected to a driving circuit via a single driving circuit board. The driving circuit provides driving signals to both the main screen and the extended screen through the driving circuit board. In this design, the driving circuit and the driving circuit board need to meet the functions of zone control and simultaneous driving of two screens. However, in this structure, the number of signals that the driving circuit board needs to transmit increases, leading to higher power consumption. To ensure the fast response of the driving circuit board, it is necessary to guarantee the stability, speed, and low loss characteristics of the various signals transmitted by the driving circuit board.

[0050] Based on this, the circuit board provided by the embodiment of the present specification has the first modified polyimide layer in the conductive layer, so that the first modified polyimide layer has the characteristics of low dissipation factor (DF) and low dielectric constant, which is beneficial to reduce the delay and loss of signal transmission in the metal layer, and ensure the rapidity of signal transmission in the metal layer. In addition, the low dielectric constant also helps to reduce the parasitic capacitance generated by the via hole, which is beneficial to improve the integrity of the signal and reduce signal distortion. In addition, the cover film in the circuit board includes a second modified polyimide layer, and the second modified polyimide layer with low dissipation factor helps to reduce interference and noise in the signal transmission process, realizes the protection effect of the main signal, and is beneficial to reduce the penetration resistance in the signal transmission process. In summary, the circuit board provided by the embodiment of the present specification realizes the purpose of improving the signal transmission speed of the circuit board and reducing the signal transmission loss by arranging the modified polyimide layer in the conductive layer and the cover film.

[0051] Based on the above idea, the circuit board provided by the embodiment of the present specification will be described exemplarily in combination with the accompanying drawings.

[0052] Exemplary circuit board

[0053] One embodiment of the present specification provides a circuit board, as shown in Figure 3 comprising:

[0054] a conductive layer, the conductive layer comprising a first modified polyimide layer and a metal layer located on at least one side of the first modified polyimide layer;

[0055] a cover film located on at least one side of the conductive layer, the cover film comprising a second modified polyimide layer;

[0056] an electromagnetic shielding layer located on the side of the cover film away from the conductive layer.

[0057] In the circuit board, the conductive layer can be used to transmit signals. In some embodiments, when the metal layer is a copper foil, the conductive layer can be referred to as a flexible copper clad laminate (FCCL). The first modified polyimide layer in the conductive layer serves as a substrate to provide the necessary mechanical strength and flexibility for the circuit board, so that it can be bent and deformed in various applications. The metal layer can be used to form a circuit pattern and is the main carrier for transmitting signals. In some embodiments, the conductive layer has high heat resistance, good electrical performance and low dielectric constant to support high-speed signal transmission.

[0058] Cover lay (CVL) can provide physical protection for the circuit board, preventing mechanical damage, dust, moisture and chemical erosion of the circuit. Cover lay has good insulation performance, which can effectively prevent circuit short circuit and electromagnetic interference. In some embodiments, the cover lay can resist environmental factors such as extreme temperature, humidity and ultraviolet light, ensuring the reliability of the circuit board under various conditions. In addition, the surface of the cover lay can be printed with marks, labels or symbols for easy identification, assembly and troubleshooting.

[0059] Electromagnetic interference layer (Electromagnetic Interference Layer) can provide shielding function for circuit board to protect the reliable transmission of signals in the circuit board. Electromagnetic interference layer can effectively prevent the propagation of electromagnetic waves, reduce the influence of electromagnetic interference on the circuit, and help maintain the integrity and stability of the signal by shielding external electromagnetic interference and suppressing internal signal radiation.

[0060] In this specification, the first modified polyimide layer and the second modified polyimide layer can refer to modified polyimide layers with low dielectric loss factor characteristics. The types of the first modified polyimide layer and the second modified polyimide layer can be the same or different.

[0061] In the circuit board provided in this embodiment, the conductive layer includes a first modified polyimide layer. The first modified polyimide layer has low dielectric loss factor (Dissipation Factor, DF) and low dielectric constant characteristics, which is beneficial to reduce the delay and loss of signal transmission in the metal layer, and ensure the rapidity of signal transmission in the metal layer. In addition, low dielectric constant also helps to reduce the parasitic capacitance generated by the via, which is beneficial to improve the integrity of the signal and reduce signal distortion. In addition, the cover lay in the circuit board includes a second modified polyimide layer. The second modified polyimide layer with low dielectric loss factor helps to reduce interference and noise in the signal transmission process, realizes the protection effect of the main signal, and is beneficial to reduce the penetration resistance in the signal transmission process. In summary, the circuit board provided in this embodiment realizes the purpose of improving the signal transmission speed of the circuit board and reducing the signal transmission loss by setting the modified polyimide layer in the conductive layer and the cover lay.

[0062] Reference Figure 4 In some embodiments, according to the design requirements of the circuit board, the metal layer is located on one side of the first modified polyimide layer, and the electromagnetic shielding layer is located on the side of the cover lay away from the conductive layer. The number of metal layers, cover lays and electromagnetic shielding layers in the circuit board is not limited in this specification, and is determined according to the actual situation.

[0063] In order to reduce the penetration resistance in the signal transmission process of the circuit board, in one embodiment, as shown inFigure 5 As shown, the cover film further comprises:

[0064] a low-loss adhesive layer located on the side of the second modified polyimide layer facing the conductive layer.

[0065] In the present embodiment, the low-loss adhesive layer can refer to an adhesive layer with a dielectric loss factor lower than a loss threshold, which can be determined according to the current technology development. For example, in some embodiments, the loss threshold can be 0.0025, i.e., the dielectric loss factor of the low-loss adhesive layer is less than or equal to 0.0025. In some embodiments, the loss threshold can be 0.002, i.e., the dielectric loss factor of the low-loss adhesive layer is less than or equal to 0.002. In other embodiments, the loss threshold can be 0.001, i.e., the dielectric loss factor of the low-loss adhesive layer is less than or equal to 0.002.

[0066] The low-loss adhesive layer in cooperation with the second modified polyimide layer can play a certain protective role for the main signal transmitted by the metal layer, while reducing the penetration resistance in the signal transmission process, which is conducive to improving the overall electrical performance of the circuit board.

[0067] In some embodiments, in order to weaken the loss of the low-loss adhesive layer to the signal as much as possible, the loss threshold can be 0.0002, i.e., the low-loss adhesive layer comprises an adhesive layer with a dielectric loss factor less than or equal to 0.0002. In the present embodiment, by selecting an adhesive layer with a dielectric loss factor less than or equal to 0.0002, the loss of the low-loss adhesive layer to the signal is weakened as much as possible, which is conducive to improving the overall performance of the circuit board in cooperation with the second modified polyimide layer.

[0068] Optionally, in some embodiments, the low-loss adhesive layer comprises a bisphenol AD epoxy resin layer. The bisphenol AD epoxy resin layer can provide lower dielectric loss and node constant in high-frequency application scenarios, which helps to improve the stability of signal transmission. The bisphenol AD epoxy resin layer also has excellent electrical insulation performance and is suitable for use as an insulating adhesive material for electronic and electrical equipment. In addition, the bisphenol AD epoxy resin layer has excellent mechanical strength and can withstand greater mechanical stress. Compared with traditional bisphenol A epoxy resin layers, the bisphenol AD epoxy resin layer has better toughness while maintaining high strength.

[0069] In one embodiment, the first modified polyimide layer comprises a modified polyimide layer with a dielectric loss factor less than or equal to 0.0002.

[0070] The second modified polyimide layer comprises a modified polyimide layer with a dielectric loss factor less than or equal to 0.0002.

[0071] In the present embodiment, the dielectric loss factor of the first modified polyimide layer and the second modified polyimide layer are both less than or equal to 0.0002, which reflects the degree of energy loss of the material in an alternating electric field. Therefore, in the present embodiment, the low dielectric loss factor of the first modified polyimide layer and the second modified polyimide layer means that the material absorbs and dissipates less energy during signal transmission, thereby reducing signal loss and improving the integrity and stability of the signal. In addition, in signal transmission, power loss is proportional to the dielectric loss factor. A low dielectric loss factor helps to reduce power loss and improve the energy efficiency of the system. The lower the dielectric loss factor, the less the signal is delayed during transmission, thereby improving the transmission speed of the signal. Based on this, in the present embodiment, the modified polyimide layer with a dielectric loss factor less than or equal to 0.0002 greatly improves the signal transmission performance of the circuit board.

[0072] In one embodiment, the modified polyimide layer comprises: a fluorine-containing polyimide layer or a polyimide layer containing inorganic nano-filler;

[0073] In the fluorine-containing polyimide layer, the fluorine element has a high electronegativity, which can effectively reduce the electronic polarizability in the polyimide molecule. The reduction of electronic polarizability reduces the polarization response of the material in an alternating electric field, thereby reducing the dielectric loss factor. In addition, the fluorine-containing group (such as -CF3) has a large volume, which can effectively increase the free volume between polyimide molecules. The larger free volume reduces the close packing between molecules and reduces the intermolecular interaction force, further reducing the dielectric loss. Further, the fluorine-containing polyimide has a lower water absorption, and the reduction of water absorption helps to maintain the dielectric performance stability of the material in different environments and reduce the increase of dielectric loss caused by water absorption.

[0074] In the polyimide layer containing inorganic nano-filler, the inorganic nano-filler generally has a lower dielectric polarization loss. When these fillers are uniformly dispersed in the polyimide matrix, they can effectively reduce the overall dielectric polarization loss of the material. In addition, the inorganic nano-filler can form a three-dimensional interconnected network structure in the polyimide matrix, which can prevent the collective polarization of the dielectric material, thereby reducing the energy consumed by polarization. Further, there is a certain interface effect between the inorganic nano-filler and the polyimide matrix, which can improve the dielectric properties of the material and reduce the dielectric loss.

[0075] Optionally, in one embodiment, the inorganic nano-filler comprises: at least one of silica, mica and zinc oxide. Inorganic nano-filler such as silica, mica and zinc oxide has a lower dielectric loss, which can effectively reduce the dielectric constant and dielectric loss factor of the modified polyimide layer when added to polyimide as a filler.

[0076] In one implementation, reference Figure 5 The number of the covering film is two layers, and the two covering films are respectively located on both sides of the conductive layer;

[0077] Optionally, the electromagnetic shielding layer consists of two layers, with each layer located on the side of the cover film away from the conductive layer.

[0078] In this embodiment, the double-layer cover film and the double-layer electromagnetic shielding layer can improve the mechanical strength and electromagnetic shielding performance of the circuit board, which is beneficial to improving the reliability of the circuit board.

[0079] Optionally, in one embodiment, the metal layer comprises a copper foil layer. Copper has very high conductivity, enabling efficient current transmission, reducing resistance and power loss, and has the advantage of low cost compared to precious metals such as silver.

[0080] In one embodiment, the electromagnetic shielding layer includes a high-frequency electromagnetic shielding layer.

[0081] In this embodiment, the high-frequency electromagnetic shielding layer can refer to a film layer used to suppress high-frequency electromagnetic interference. High-frequency electromagnetic interference can refer to electromagnetic interference in the frequency range of GHz and above. Of course, with the improvement of application scenarios or technologies, high-frequency electromagnetic interference can refer to electromagnetic interference in the frequency range of 10 GHz or even higher. This specification does not limit this, and it depends on the actual situation. In a specific embodiment, the high-frequency electromagnetic shielding layer can refer to an electromagnetic shielding layer with a shielding performance of greater than 70 dB for electromagnetic interference of 10 GHz.

[0082] In this embodiment, the high-frequency electromagnetic shielding layer helps to ensure the stability and integrity of long-distance signal transmission and helps to avoid interference from stray signals to signals such as MIPI.

[0083] Optionally, the high-frequency electromagnetic shielding layer includes a polyimide layer with a silver-plated surface. Silver, as a conductor, has high electrical conductivity and will produce a strong reflection effect when it encounters incident electromagnetic waves, so that most of the electromagnetic energy is blocked from penetrating into the internal circuit. The composite structure formed by the combination of silver and polyimide layer can convert electromagnetic energy into heat energy to a certain extent, thus absorbing part of the electromagnetic waves.

[0084] Exemplary module

[0085] In one implementation, such as Figure 6 As shown, a display module is also provided, including:

[0086] The display panel includes a first display area and a second display area;

[0087] A driving circuit is electrically connected to the display panel via a circuit board as described in any of the above embodiments, and the driving circuit is used to provide driving signals for the first display area and / or the second display area.

[0088] In this embodiment, both the first display area and the second display area can be used for display. The first display area and the second display area can display different images independently, or they can display the same image together. This specification does not limit this.

[0089] In this embodiment, the conductive layer of the circuit board includes a first modified polyimide layer. The low dissipation factor (DF) and low dielectric constant of the first modified polyimide layer help reduce signal delay and loss during transmission in the metal layer, ensuring fast signal transmission. Furthermore, the low dielectric constant helps reduce parasitic capacitance at vias, improving signal integrity and reducing signal distortion. Additionally, the cover film in the circuit board includes a second modified polyimide layer. The low DF of the second modified polyimide layer helps reduce interference and noise during signal transmission, protecting the main signal and reducing penetration resistance. In summary, the circuit board provided in this embodiment achieves the goal of increasing signal transmission speed and reducing signal transmission loss by incorporating modified polyimide layers in the conductive layer and cover film.

[0090] In one embodiment, the display module is a foldable display module, meaning that there may be a bending area between the first display area and the second display area, and the first and second display areas can be folded inward or outward along the bending area, such as... Figure 7 As shown, Figure 7 A schematic diagram showing the first display area and the second display area folded outward along the bending area is shown. (Refer to...) Figure 8 , Figure 8 A schematic diagram is shown showing the first display area and the second display area folded inward along the bending area. Figure 7 and Figure 8 The diagram also shows structures such as a support member 104 and a bending mechanism 105 for the display module. The support member 104 can provide support for the display panel, and the bending mechanism can assist the display panel in bending. It can also provide support for the bending area of ​​the display panel when it is in a bent state, so as to avoid the bending area from being bent.

[0091] Still referencing Figure 6The driving circuit is electrically connected to the display panel via a circuit board. Because the circuit board incorporates a modified polyimide layer in its conductive layer and cover film, it achieves improved signal transmission speed and reduced signal transmission loss, allowing a single circuit board to meet the low-loss requirements when transmitting signals from the driving circuit to the first display area and / or the second display area. Of course, in some embodiments, the number of circuit boards in the display module can be two or more; this specification does not limit this, and the specific number depends on the actual situation.

[0092] Exemplary device

[0093] In one embodiment of this specification, an electronic device is also provided, such as... Figure 9 As shown, the electronic device includes a display module as described in any of the above embodiments.

[0094] The display module includes a circuit board as described in any of the above embodiments. The conductive layer of the circuit board includes a first modified polyimide layer. The low dissipation factor (DF) and low dielectric constant of the first modified polyimide layer help reduce signal delay and loss during transmission in the metal layer, ensuring fast signal transmission. Furthermore, the low dielectric constant helps reduce parasitic capacitance at vias, improving signal integrity and reducing signal distortion. Additionally, the cover film in the circuit board includes a second modified polyimide layer. The low DF of the second modified polyimide layer helps reduce interference and noise during signal transmission, protecting the main signal and reducing penetration resistance. In summary, the circuit board provided in this specification, by incorporating modified polyimide layers in the conductive layer and cover film, achieves the goal of increasing signal transmission speed and reducing signal transmission loss.

[0095] In one implementation, the electronic device may be referred to as user equipment (UE), access terminal, user unit, user station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication equipment, user agent, or user device. By way of example and not limitation, the terminal device may be a mobile phone, tablet computer, computer with wireless transceiver capabilities, virtual reality (VR) terminal device, augmented reality (AR) terminal device, wireless terminal in industrial control, wireless terminal in self-driving, wireless terminal in remote medical care, wireless terminal in smart grid, wireless terminal in transportation safety, wireless terminal in smart city, wireless terminal in smart home, etc.

[0096] Electronic devices can also be network devices, which can be any device with wireless transceiver capabilities. These devices include, but are not limited to: evolved node B (eNB), radio network controller (RNC), node B (NB), base station controller (BSC), base transceiver station (BTS), home base station (e.g., home evolved node B, or home node B, HNB), building base band unit (BBU), access point (AP), wireless relay node, wireless backhaul node, transmission point (TP), or transmission and reception point (TRP) in a wireless fidelity (WIFI) system. They can also be gNBs in 5G, such as NR, or transmission points (TRPs or TPs), one or a group of antenna panels (including multiple antenna panels) of a base station in a 5G system, or network nodes constituting a gNB or transmission point, such as BBUs or distributed units (DUs).

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The embodiments described above are merely illustrative of several implementations of this specification, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the solutions provided in this specification. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this specification, and these all fall within the scope of protection of this specification. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A circuit board, characterized in that, include: A conductive layer, the conductive layer comprising a first modified polyimide layer and a metal layer located on at least one side of the first modified polyimide layer; A cover film located on at least one side of the conductive layer, the cover film comprising a second modified polyimide layer; An electromagnetic shielding layer located on the side of the cover film opposite to the conductive layer.

2. The circuit board according to claim 1, characterized in that, The covering film also includes: A low-loss adhesive layer located on the side of the second modified polyimide layer facing the conductive layer.

3. The circuit board according to claim 2, characterized in that, The low-loss adhesive layer includes an adhesive layer with a dielectric loss factor less than or equal to 0.0002; Optionally, the low-loss adhesive layer includes a bisphenol A (BPA) epoxy resin layer.

4. The circuit board according to claim 1, characterized in that, The first modified polyimide layer includes a modified polyimide layer with a dielectric loss factor less than or equal to 0.0002; The second modified polyimide layer includes a modified polyimide layer with a dielectric loss factor less than or equal to 0.0002.

5. The circuit board according to claim 4, characterized in that, The modified polyimide layer includes: a fluorinated polyimide layer or a polyimide layer containing inorganic nanofillers; Optionally, the inorganic nanofiller includes at least one of silica, mica, and zinc oxide.

6. The circuit board according to claim 1, characterized in that, The electromagnetic shielding layer includes: a high-frequency electromagnetic shielding layer; Optionally, the high-frequency electromagnetic shielding layer includes a polyimide layer with a silver-plated surface.

7. The circuit board according to any one of claims 1 to 6, characterized in that, The number of the covering film is two layers, and the two layers of the covering film are respectively located on both sides of the conductive layer; Optionally, the electromagnetic shielding layer consists of two layers, with each layer located on the side of the cover film away from the conductive layer.

8. The circuit board according to any one of claims 1 to 6, characterized in that, The metal layer includes a copper foil layer.

9. A display module, characterized in that, include: The display panel includes a first display area and a second display area; A driving circuit, which is electrically connected to the display panel via a circuit board as described in any one of claims 1 to 8, is used to provide driving signals for the first display area and / or the second display area.

10. The display module according to claim 9, characterized in that, The driving circuit is electrically connected to the display panel via a circuit board.

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