Circuit board, display module and electronic equipment

Abstract

The embodiment of the invention provides a circuit board, a display module and electronic equipment, the electronic equipment comprises the display module and the circuit board, the display module comprises a display screen and the circuit board, the circuit board is divided into a binding area, a multilayer board area and a bending part, the binding area is used for being electrically connected with the display screen, the bending part is used for being electrically connected with the circuit board after being bent, and the multilayer board area is used for being electrically connected with the circuit board after being bent. The metal layer where the binding area is located and the metal layer where the bending part is located are electrically connected in the multilayer board area, the grain size of the metal layer where the binding area is located and the grain size of the metal layer where the first bending part is located are different, for example, the metal layer where the binding area is located adopts electro-coppering, the metal layer where the first bending part is located adopts rolled copper, and the electric connection performance of electro-coppering is good. And the bending performance of the rolled copper is better, so that the electric connection performance and the bending performance of the circuit board can be considered, and the electric connection stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor, in particular to a circuit board, a display module and an electronic device. BACKGROUND

[0002] With the development of mobile terminal and other electronic devices towards light and thin, high reliability, long endurance, the compact design of terminal electronic device monomer module can greatly release the whole machine design space.

[0003] The multi-layer compact circuit board design can be used in the terminal display module, which can reduce the width of the flexible circuit board and increase the architecture battery space capacity.

[0004] In the display module, the bending position of the circuit board will face a relatively harsh bending fatigue pressing scene, and the reliability requirement is higher. SUMMARY

[0005] The embodiments of the present application provide a circuit board, a display module and an electronic device, which improve the reliability of the circuit board.

[0006] To achieve the above purpose, the embodiments of the present application adopt the following technical solutions:

[0007] In a first aspect, the present application provides a circuit board, comprising: a first substrate, a first metal layer, a second substrate and a second metal layer; the first metal layer is arranged on the first substrate, the first metal layer comprises a first part and a first bending part; the second metal layer is arranged on the second substrate, the first metal layer comprises a first binding area and a first part; the binding area is used for electrically connecting with the display screen, the first part and the second part are arranged in layers, and the grain size of the second metal layer is greater than the grain size of the first metal layer. Wherein, the grain size of the second metal layer is larger, so that the bending performance of the second metal layer is better than that of the first metal layer, so that the electrical connection performance of the first metal layer is better, the first metal layer is used for electrical connection with the display screen in the present application, and electrical connection can be realized without bending, the bending performance of the second metal layer is better, the first bending part can be arranged on the second metal layer, and the second metal layer can be used for electrical connection after bending, which improves the bending performance of the circuit board. The circuit board in the present application comprises at least two metal layers, so that the two metal layers are arranged in layers, and different structures of metal are used in the metal layer corresponding to the first bending part and the metal layer corresponding to the binding area, so that the electrical connection performance and the bending performance can be considered, and the electrical connection reliability is improved.

[0008] In an optional implementation, the material of the first metal layer includes copper, the second metal layer adopts rolled copper, and the first metal layer adopts electrolytic copper. In this way, the internal structures of the second metal layer and the first metal layer are different, the first metal layer adopts electrolytic copper, the electrical connection performance of the first metal layer is improved, the second metal layer adopts rolled copper, the bending performance of the second metal layer is improved, and the performance requirements of the first metal layer and the second metal layer can be met.

[0009] In an optional implementation, the first bending part includes a first connecting part and a second connecting part connected in sequence, and the first connecting part is connected with the first part. In this way, in the case where the display screen is connected with the circuit board through the circuit board, the first connecting part of the first bending part is bent to the surface of the circuit board away from the display screen, and is connected with the electronic device arranged on the surface of the circuit board away from the display screen through the second connecting part.

[0010] In an optional implementation, the circuit board further includes a third metal layer arranged above the second metal layer, the third metal layer includes a third part and a third connecting part, the third part of the third metal layer and the second part are arranged in layers, the third connecting part of the third metal layer and the second connecting part are arranged in layers, and the third metal layer adopts electrolytic copper. In this way, by arranging electrolytic copper on the second connecting part and the second part, the electrical connection performance of the second part and the second connecting part is improved, and at the same time, the first connecting part only adopts rolled copper, and the first bending part adopts a local non-electroplating design, so that the electrical connection performance and the bending performance can be met.

[0011] In an optional implementation, the second metal layer includes a first metal line and a plurality of second metal lines, the first metal line is connected with the plurality of second metal lines, the first metal line is arranged on the second part, the second metal lines are arranged on the bending area, and the line width of the second metal lines is smaller than the line width of the first metal line. In this way, part of the relatively thick wires in the first bending part are split into a plurality of relatively thin wires, so that the wire width of the first bending part is uniform, and then the stress of the first bending part is uniformly distributed, and the bending reliability of the circuit board is further improved.

[0012] In an optional implementation, the circuit board further includes a first protective film arranged above the first bending part. In this way, by arranging the first protective film, the third connecting part and the first connecting part can be better protected.

[0013] In an optional implementation, the length direction of the second metal line is perpendicular to the width direction of the first metal line. In this way, the extension directions of the first metal line and the second metal line are perpendicular, so that the stress distribution of the first bending part is more uniform, and the bending reliability of the circuit board is further improved.

[0014] In an alternative implementation, the circuit board further comprises a fourth metal layer disposed below the second substrate, the fourth metal layer comprising a fourth portion and a second bending portion, the fourth portion and the second portion being stacked, and the second bending portion and the first bending portion being stacked, wherein the fourth metal layer is made of rolled copper. Thus, both sides of the second substrate are provided with metal layers, and both sides of the second substrate are provided with rolled copper, which has better bending performance.

[0015] In an alternative implementation, the circuit board further comprises a first connecting layer, and the fourth portion is connected to the second portion through the first connecting layer. Thus, the fourth portion and the second portion can be connected through the first connecting layer to form a stacked structure.

[0016] In an alternative implementation, the circuit board further comprises a second protective film disposed below the second bending portion. Thus, the second bending portion can be better protected by the protective film.

[0017] In an alternative implementation, the circuit board further comprises a fifth metal layer disposed below the first substrate, the fifth metal layer comprising a fifth portion and a second binding area, the fifth portion and the first portion being stacked, the second binding area and the first binding area being stacked, and the fifth metal layer being made of electrolytic copper. Thus, both sides of the first substrate are provided with metal layers, and both sides of the second substrate are provided with electrolytic copper, which has better electrical conductivity.

[0018] In an alternative implementation, the circuit board further comprises a third protective film disposed below the second binding area. Thus, the second binding area can be better protected.

[0019] In an alternative implementation, the circuit board further comprises a third substrate disposed below the first substrate, and a sixth metal layer disposed below the third substrate, the sixth metal layer comprising a sixth portion, the sixth portion and the first portion being stacked. Thus, more layers can be provided in the multi-layer board area, which can increase the wiring area and improve the electrical connection performance of the circuit board.

[0020] In an alternative implementation, the circuit board further comprises a fourth substrate disposed above the second substrate, and a seventh metal layer disposed on the fourth substrate, the seventh metal layer comprising a seventh portion, the seventh portion and the second portion being stacked. Thus, more layers can be provided in the multi-layer board area, which can increase the wiring area and improve the electrical connection performance of the circuit board.

[0021] In a second aspect, the present application provides a display module, comprising a display screen and a circuit board as described above; the binding area of the circuit board is electrically connected to the display screen. Thus, the display module uses the circuit board described above, and the electrical connection performance and the bending performance can be considered, and the reliability of the circuit board is improved.

[0022] In a third aspect, the present application provides an electronic device, comprising a circuit board and a display module as described above; the bending area of the circuit board is connected to the circuit board. Thus, the electronic device uses the circuit board described above, and the electrical connection reliability is improved.

[0023] In a fourth aspect, the present application provides an etching method, comprising: forming a first metal layer on a substrate. The first metal layer comprises a first part and a second part connected to each other. The substrate can be the second substrate in the above-mentioned embodiments, and the first metal layer can be the second metal layer in the above-mentioned embodiments. The first part of the first metal layer can be the second part and the second connecting part in the above-mentioned embodiments, and the second part of the first metal layer can be the first connecting part in the above-mentioned embodiments. A second metal layer is formed on the first part of the first metal layer. The second metal layer can be the third metal layer in the above-mentioned embodiments. The third metal layer comprises a third part and a third connecting part. The second metal layer is formed on the first part of the first metal layer, which can be that the third part is arranged on the second part, and the third connecting part is arranged on the second connecting part. The first mask part of the mask plate is arranged on the second metal layer, and the second mask part of the mask plate is arranged on the second part of the first metal layer. The width of the first mask part is smaller than the width of the second mask part. The first mask part of the mask plate is arranged on the third part and the third connecting part of the third metal layer. The second mask part of the mask plate is arranged on the second part of the first metal layer. The first metal layer and the second metal layer are etched to obtain a metal line. The first metal layer and the second metal layer are etched, which can be that the metal layer and the region where the mask plate is not arranged are etched to obtain the metal line. The metal line comprises a double-layer metal line and a single-layer metal line. The metal line is double-layer in the stacked part of the first metal layer and the second metal layer, and the metal line is single-layer in the second part of the first metal layer. Since the mask plate is designed for etching compensation in the single-layer metal layer part, the width of the single-layer metal layer part is wider, so that the line width of the single-layer part of the first metal layer is close to the line width of the double-layer part of the second metal layer, and the etching precision is improved. Thus, the line width of the local non-electroplating area is compensated and designed, the bending part is designed to be greater than the partial line width, so as to avoid the error caused by the photoetching precision, so that the line width of the local non-electroplating area is close to the partial line width after etching, and the line break caused by over-etching is avoided.

[0024] The embodiment of the present application provides a circuit board, a display module and an electronic device, the electronic device comprises: a display module and a circuit board, the display module comprises: a display screen and a circuit board, the circuit board is divided into: a binding area, a multilayer board area and a bending part, the binding area is used for electrically connecting with the display screen, the bending part is used for electrically connecting with the circuit board after being bent, the metal layer where the binding area is located and the metal layer where the bending part is located are electrically connected in the multilayer board area, the grain size of the metal layer where the binding area is located and the metal layer where the first bending part is located is different, for example, the metal layer where the binding area is located adopts electroplated copper, and the metal layer where the first bending part is located adopts rolled copper, the electroplated copper has better electrical connection performance, and the rolled copper has better bending performance, so that the electrical connection performance and the bending performance of the circuit board can be considered, and the electrical connection stability is improved.

[0025] In some embodiments, a layer of electroplated copper metal layer can be arranged in the binding area of the metal layer where the bending part is located, and the electrical connection stability is improved.

[0026] In some embodiments, the relatively wide wire in the multilayer board area of the metal layer where the bending part is located can be split into a plurality of relatively narrow wires in the first bending part, so that the wire width of the bending part is uniform, and then the stress of the bending part is uniformly distributed, and the bending reliability of the circuit board is further improved. In addition, the line width of the local non-electroplating area can be compensated and designed, the wire width design value of the bending part is set to be greater than the partial wire width of the multilayer board area, so as to avoid the error caused by the photoetching precision, make the wire width of the local non-electroplating area close to the partial wire width of the multilayer board area after etching, and avoid the wire breakage caused by over-etching. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A disassembly structure schematic diagram of an electronic device provided by the embodiment of the present application;

[0028] Figure 2 A structure schematic diagram of an electronic device provided by the embodiment of the present application;

[0029] Figure 3 A structure schematic diagram of another electronic device provided by the embodiment of the present application;

[0030] Figure 4 A structure schematic diagram of still another electronic device provided by the embodiment of the present application;

[0031] Figure 5 A Figure 4 N-N cross-sectional view of an electronic device;

[0032] Figure 6 A structure schematic diagram of a circuit board provided by the embodiment of the present application;

[0033] Figure 7Another schematic structural diagram of a circuit board provided by the embodiment of the present application;

[0034] Figure 8 A working state schematic diagram of a circuit board provided by the embodiment of the present application;

[0035] Figure 9 A flow chart of an etching method provided by the embodiment of the present application;

[0036] Figure 9A 、 Figure 9B 、 Figure 9C 、 Figure 9D are respectively schematic structural diagrams of products obtained after each step in Figure 9 is performed;

[0037] Figure 10 A top view of a circuit board provided by the embodiment of the present application;

[0038] Figure 11 Another schematic structural diagram of a circuit board provided by the embodiment of the present application;

[0039] Figure 12 A schematic diagram of a second metal layer trace provided by the embodiment of the present application;

[0040] Figure 13 Another schematic structural diagram of a circuit board provided by the embodiment of the present application;

[0041] Figure 14 Another schematic structural diagram of a circuit board provided by the embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings.

[0043] Hereinafter, the terms “first”, “second”, and the like are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with “first”, “second”, and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of “a plurality of” is two or more.

[0044] In addition, in the present application, the orientation terms such as “up”, “down”, and the like are defined with respect to the orientation in which the components in the drawings are placed, and it should be understood that these directional terms are relative concepts, which are used for relative description and clarification, and can be changed accordingly according to the change of the orientation in which the components are placed in the drawings.

[0045] Embodiments of the present application provide an electronic device. The electronic device can be a product with a display interface, such as a mobile phone, a display, a tablet computer, a vehicle-mounted computer, and the like. Embodiments of the present application do not specially limit the specific form of the electronic device.

[0046] Embodiments of the present application provide an electronic device. The electronic device can be a product with a display interface, such as a tablet computer, a mobile phone, an e-book reader, a remote controller, a personal computer (PC), a notebook computer, a personal digital assistant (PDA), a vehicle-mounted device, a network television, a wearable device, a television, and the like, and a smart watch, a smart bracelet, and the like. Embodiments of the present application do not specially limit the form of the electronic device. The following embodiments are exemplarily described by taking a mobile phone as an example.

[0047] As shown in Figure 1 , the electronic device 1 includes a display module 10, a middle frame 11, and a shell 12. The middle frame 11 is located between the display module 10 and the shell 12.

[0048] The display module 10 is configured to display an image.

[0049] The display module 10, the middle frame 11, and the shell 12 can be respectively arranged at different layers in the thickness direction of the electronic device. The layers can be parallel to each other, and the plane where each layer is located can be referred to as an X-Y plane, and the direction perpendicular to the X-Y plane can be referred to as a Z direction. For example, the display module 10, the middle frame 11, and the shell 12 can be distributed in layers in the Z direction.

[0050] The display module 10 can include a display screen and a flexible printed circuit (FPC). The display screen can be electrically connected to a printed circuit board (PCB) arranged on the middle frame 11 through the FPC as shown in Figure 1 . Thus, the PCB can transmit display data to the display module 10 to control the display module 10 to display an image.

[0051] The middle frame 11 is located between the display module 10 and the shell 12, and the surface of the middle frame 11 away from the display module 10 is configured to mount internal components such as a battery, a printed circuit board (PCB), a camera, an antenna, and the like. After the shell 12 is covered with the middle frame 11, the above-mentioned internal components are located between the shell 12 and the middle frame 11.

[0052] The shell 12 is connected with the middle frame 11 to form a containing cavity for containing the above-mentioned electronic devices such as the PCB, the camera, and the battery. Thus, the invasion of external water vapor and dust into the containing cavity can be prevented, and the performance of the above-mentioned electronic devices can be affected.

[0053] The embodiments of the present application do not limit the structure of the mobile phone. In some embodiments of the present application, as shown in Figure 2 , the mobile phone can be a straight mobile phone.

[0054] Alternatively, as shown in Figure 3 , the mobile phone can also be a folding screen mobile phone. When the folding screen mobile phone is in a folded state, the display screen 100 of the folding screen mobile phone is located inside the device, for example, the mobile phone can be an inner folding mobile phone. In other embodiments, when the folding screen mobile phone is in a folded state, the display screen 100 of the folding screen mobile phone is located outside the device, for example, the mobile phone can be an outer folding mobile phone.

[0055] In some embodiments, as shown in Figure 4 , the folding screen mobile phone includes a first display screen 200 and a second display screen 300, a middle frame 11 (or a support) and a shell 12 as shown in Figure 5 .

[0056] As shown in Figure 4 , the first display screen 200 includes a first part A and a second part B. When the folding screen mobile phone is in a folded state (the first part A and the second part B of the first display screen 200 are 0°), the first display screen 200 is located inside, the second display screen 300 is located outside, and the first part A of the first display screen 200 is opposite to the second part B of the first display screen 200.

[0057] The first part A of the first display screen 200 and the second display screen 300 are stacked, the second part B of the first display screen 200 and the shell 12 are stacked, and the second display screen is arranged opposite to the first part A of the first display screen 200.

[0058] Taking the mobile phone as shown in Figure 4 , Figure 5 is a N-N cross-sectional view of the mobile phone as shown in Figure 4 . As shown in Figure 5 , the PCB can include a main circuit board 102 and a secondary circuit board 103.

[0059] For example, the main circuit board 102 can be used to integrate electronic devices such as control chips. The control chips include, but are not limited to, system on chip (SOC), charging management chip, power management unit (PMU), radio frequency (RF), display chip, application processor (AP), double data rate (DDR), and universal flash storage (UFS), etc. Among them, the radio frequency chip can also be referred to as a radio frequency power amplifier chip (RF PA).

[0060] The main circuit board 102 can be fixed between the shell 12 and the second part B of the first display screen 200 by screw connection, clamping, gluing, etc. The side of the shell 12 away from the first display screen 200 is provided with a camera 14, for example.

[0061] For example, the sub-circuit board 103 can integrate electronic devices such as universal serial bus (USB) devices, subscriber identity modules (SIM), gravity sensors, acceleration sensors, hall sensors, smart power amplifiers (smart PA), finger prints (FP), and digital monolithic integrated circuits (DMIC). The USB device can be a USB type-C interface device, a USB type-A interface device, a USB type Micro-B interface device, or a USB type-B interface device. The position corresponding to the USB device on the frame is provided with a socket. Accessories such as chargers, earphones, and data lines can be electrically connected to the USB device through the socket to realize power, signal, and data transmission.

[0062] The sub-circuit board 103 can also be fixed between the first part A and the second display screen 300 of the first display screen 200 by screw connection, clamping, gluing, or welding. The battery 13 and the rotating shaft 15 are arranged between the sub-circuit board 103 and the main circuit board 102.

[0063] The display screen 100 has an opposite light-out side and a non-light-out side. The light-out side refers to a side where a display surface of the display screen 100 is located (for example, the left side of the display module 10 in FIG. 1), and the non-light-out side refers to a side opposite to the light-out side (for example, the right side of the display module 10 in FIG. 1). The PCB can be located on the non-light-out side of the display screen 100. Figure 1 The display screen 100 has an opposite light-out side and a non-light-out side. The light-out side refers to a side where a display surface of the display screen 100 is located (for example, the left side of the display module 10 in FIG. 1), and the non-light-out side refers to a side opposite to the light-out side (for example, the right side of the display module 10 in FIG. 1). The PCB can be located on the non-light-out side of the display screen 100. Figure 1

[0064] As shown in FIG. 1, the circuit board 101 can be connected to the secondary circuit board and the first display screen 200. The circuit board 101 can be connected to a driving circuit or a power supply circuit in the display screen 100 to drive the display module to display images or to supply power to the display module. Figure 5

[0065] Referring to FIG. 1, the circuit board 101 includes a hard board area 111 and a soft board area 112. Figure 5 The hard board area 111, for example, includes a part of the circuit board 101 with a higher hardness, and can be provided with a solder pad, a pin, or the like to be electrically connected to an electronic device, the display screen 100, or the like. The soft board area 112 refers to a part of the circuit board 101 with a lower hardness, and is provided with a trace to electrically connect the two hard board areas 111, thereby electrically connecting different electronic devices. The soft board area 112 can be bent so that the circuit board 101 can adapt to different application scenarios.

[0066]

[0067] Referring to FIG. 1, in a case where the first display screen 200 is connected to the secondary circuit board 103 through the circuit board 101, one end of the circuit board 101 is connected to the first display screen 200, and the other end is bent to a surface of the secondary circuit board 103 away from the first display screen 200 and is connected to an electronic device located on the surface of the secondary circuit board 103 away from the first display screen 200. Figure 5 After the electronic device is assembled, a terminal user presses the module, which causes a slight elastic deformation of a part of the bent circuit board 101. The long-term and repeated elastic deformation can cause the circuit board 101 to break and fail.

[0068] For example, in a case where a finger repeatedly presses the first display screen 200, the circuit board 101 connected to the first display screen 200 is subjected to an elastic stress substantially perpendicular to the first display screen 200, so that the circuit board 101 is repeatedly slightly moved in a direction substantially perpendicular to the first display screen 200, thereby easily causing the junction between the non-bent part 100A and the bent part 100B with a large hardness difference and a large thickness difference to break.

[0069]

[0070] ​​​​In addition, some production lines of the electronic device 100 also perform bending, folding, rework and the like on the circuit board 101, which can cause damage to relatively weak positions of the circuit board 101 (for example, the junction between the non-bending part 100A and the bending part 100B), resulting in problems such as disconnection or cracking of the circuit board 101.

[0071] The embodiment of the present application also provides an improved circuit board.

[0072] Figure 6 A structural schematic diagram of a circuit board provided by the embodiment of the present application is shown in FIG. 1. As shown in the figure, the circuit board includes a first substrate 1012, a first metal layer 1011, a second substrate 1023 and a second metal layer 1021 which are stacked from bottom to top. Figure 6

[0073] The first metal layer 1011 is arranged on the first substrate 1012, and the first metal layer 1011 includes a first binding area 101A and a first part 101C which are connected in sequence.

[0074] The second metal layer 1021 is arranged on the second substrate 1023, and the second metal layer 1021 includes a second part 101D and a first bending part 101B which are connected in sequence. The first part 101C and the second part 101D are stacked.

[0075] The shape and size of the first metal layer 1011 and the first substrate 1012 are the same, and the shape and size of the second metal layer 1021 and the second substrate 1023 are the same.

[0076] The embodiment of the present application does not limit the structure of the first substrate 1012. In some embodiments, the first substrate 1012 is made of insulating material, and the material of the first substrate 1012 includes a Polyimide (PI) substrate layer.

[0077] The material of the second substrate 1023 can refer to the description of the first substrate 1012, which will not be repeated here.

[0078] In the case where the display screen is connected to the circuit board through the circuit board 101, the first binding area 101A of the circuit board 101 can be connected to the display screen, the first part 101C and the second part 101D are stacked between the display screen and the circuit board, the first bending part 101B is bent to the surface of the circuit board away from the display screen, and is connected to the electronic device arranged on the surface of the circuit board away from the display screen.

[0079] The first binding area 101A can be electrically connected to the display screen without bending, and the first bending part 101B needs to be bent to be electrically connected to the circuit board.

[0080] ​The circuit board in this application includes at least two metal layers: a first metal layer and a second metal layer. The first metal layer is electrically connected to the display screen through a first bonding area 101A. The first bonding area 101A can achieve electrical connection without bending. The metal layer where the first bonding area 101A is located (first metal layer 1011) can be made of a material with good electrical connection performance. The second metal layer is electrically connected to the circuit board through a first bending portion 101B. The metal layer where the first bending portion 101B is located (second metal layer 1021) can be made of a material with good bending performance.

[0081] In some embodiments, reference is then made to Figure 6 Both the first metal layer 1011 and the second metal layer 1021 can be made of copper, and the grain size of the second metal layer 1021 is larger than that of the first metal layer 1011. Thus, the bending performance of the second metal layer 1021 is superior to that of the first metal layer 1011.

[0082] For example, the material of the first metal layer 1011 includes copper. The first metal layer 1011 can be made of electrolytic copper, and the second metal layer 1021 can be made of rolled copper.

[0083] Electrolytic copper can be produced through copper electrolysis. Its internal structure is a vertical needle-like crystal structure, resulting in relatively low production costs, high purity, very low resistivity, and excellent conductivity. Rolled copper, on the other hand, utilizes the principle of plastic processing, involving repeated rolling and annealing of copper material. Rolled copper has a lamellar crystal structure, with larger grain sizes than electrolytic copper, leading to better ductility and bending performance. Thus, the first metal layer 1011 and the second metal layer 1021 have different internal structures. The first metal layer 1011 uses electrolytic copper, improving its electrical connectivity, while the second metal layer 1021 uses rolled copper, improving its bending performance. This approach balances the performance requirements of both metal layers.

[0084] The circuit board provided in this application includes at least two metal layers. One metal layer is electrically connected to the display screen without bending, and this metal layer is made of electrolytic copper, which improves the electrical connection performance. The other metal layer needs to be bent before it can be electrically connected to the circuit board. A bending area can be provided. This metal layer is made of rolled copper, which has better bending performance, thus improving the bending performance of the circuit board. By dividing the circuit board into two metal layers and staggering the two layers, and using metals with different structures for the metal layers corresponding to the bending area and the bonding area, this application can balance electrical connection performance and bending performance.

[0085] In some embodiments, such as Figure 7As shown, the first bending part 101B includes: a first connecting part 101a and a second connecting part 101b connected in sequence, and the first connecting part 101a is connected with the second part 101D. The first connecting part 101a is arranged between the second part 101D and the second connecting part 101b. The second connecting part 101b is used to connect electronic devices. The electronic devices include: a gravity sensor, an acceleration sensor, a user identification card, a USB device, etc.

[0086] As shown in the drawings, Figure 8 In the case where the display screen is connected with the circuit board through the circuit board 101, the first binding area 101A of the circuit board 101 can be connected with the display screen 200, the first part 101C and the second part 101D are arranged in layers between the display screen and the circuit board, the first connecting part 101a of the first bending part 101B is bent to the surface of the circuit board away from the display screen, and the second connecting part 101b is connected with the electronic devices arranged on the surface of the circuit board away from the display screen.

[0087] In order to improve the electrical connection performance of the second connecting part 101b, in some embodiments, as shown in the drawings, Figure 7 、 Figure 8 The circuit board further includes: a third metal layer 1022, which can be arranged on the second metal layer 1021. The third metal layer 1022 can be arranged on the second part 101D and the second connecting part 101b. The third metal layer 1022 can be made of electrolytic copper. The electrical connection performance of the electrolytic copper is better, and the electrical connection performance is better through the electrical connection between the third metal layer 1022 and the circuit board.

[0088] As shown in the drawings, Figure 7 、 Figure 8 The third metal layer 1022 includes: a third part 1022a and a third connecting part 1022b. The third part 1022a of the third metal layer is arranged on the second part 101D, and the third connecting part 1022b of the third metal layer is arranged on the second connecting part 101b. The third metal layer is made of electrolytic copper. The circuit board provided by the embodiments of the present application improves the electrical connection performance of the multi-layer board area and the connecting part by arranging electrolytic copper on the multi-layer board area and the connecting part of the second metal layer. At the same time, the bending part is only made of rolled copper, and the bending part does not arrange electrolytic copper. The first bending part 101B adopts a local non-electroplating design, which can balance the electrical connection performance and the bending performance.

[0089] The above-mentioned embodiments adopt a local non-electroplating design in the first bending part 101B, which can make the metal layer thickness of the local non-electroplating layer in the multi-layer board area greater than the metal layer thickness of the local non-electroplating area. During the etching of the wiring, due to the difference in the thickness of the metal layer, the wiring in the local non-electroplating area may be over-etched, and the width of the wiring is smaller than the width of the wiring in the multi-layer board area.

[0090] To this end, the embodiment of the present application provides a new etching method. The line width of the local non-electroplating area can be compensated and designed, and the line width of the bending part is designed to be larger than that of the multilayer board area, so as to avoid the error caused by the photoetching precision, and make the line width of the local non-electroplating area close to that of the multilayer board area after etching, thereby avoiding the line break caused by over-etching.

[0091] For example, in the photoetching process, the etching process can include the steps of forming photoresist, exposing and developing the photoresist, and etching.

[0092] For example, after depositing the layer to be etched, a mask can be formed on the layer to be etched, wherein, as shown in Figure 12 the width of the mask 1021D corresponding to the metal line of the bending part is larger than that of the mask 1021C corresponding to the metal line of the multilayer board area, and the layer to be etched is etched under the protection of the mask to obtain the metal line. Then, the mask can be removed to expose the metal line. The width of the metal line of the bending part after etching is consistent with that of the metal line of the multilayer board area.

[0093] For example, the present application also provides an etching method, as shown in Figure 9 the method comprises the following steps:

[0094] S1. As shown in Figure 9A a first metal layer 202 is formed on a substrate 201.

[0095] The first metal layer 201 comprises a first part and a second part connected to each other.

[0096] In this embodiment, the substrate can be the substrate 1023 in the above-mentioned embodiments, and the first metal layer can be the metal layer 1021 in the above-mentioned embodiments. The first part of the first metal layer can be the second part 101D and the second connecting part 101b in the above-mentioned embodiments, and the second part of the first metal layer can be the first connecting part 101a in the above-mentioned embodiments.

[0097] S2. As shown in Figure 9B a second metal layer 203 is formed on the first part of the first metal layer 202.

[0098] The second metal layer can be the metal layer 1022 in the above-mentioned embodiments. The metal layer 1022 comprises a third part 1022a and a third connecting part 1022b.

[0099] The second metal layer is formed on the first part of the first metal layer, which can be that the third part 1022a is arranged on the second part 101D, and the third connecting part 1022b is arranged on the second connecting part 101b.

[0100] S3. For example Figure 9C As shown, the first mask portion 301 of the mask 300 is disposed on the second metal layer 203, and the second mask portion 302 of the mask 300 is disposed on the second portion of the first metal layer 202.

[0101] The width of the first mask portion 301 is smaller than the width of the second mask portion 302.

[0102] The first mask portion 301 of the mask is disposed on the second metal layer 203, which can be done on the metal layer 1022 in the above embodiment.

[0103] The second mask portion 302 of the mask plate is disposed on the second part of the first metal layer 202, which can be done on the first connecting portion 101a of the metal layer 1021 shown in the above embodiment.

[0104] S4. Etch the first metal layer 202 and the second metal layer 203 to obtain the following... Figure 9D The metal wire shown is 400.

[0105] Etching the first metal layer 202 and the second metal layer 203 can be done by etching the areas of metal layers 1022 and 1021 where no mask is provided, to obtain the metal line.

[0106] For example, see Figure 9D The metal line 400 includes a first sub-section 401, a second sub-section 402, and a third sub-section 403. The first sub-section 401 is formed by etching a first portion of a first metal layer 202, the second sub-section 402 is formed by etching a second metal layer 203, and the third sub-section 403 is formed by etching a second portion of the first metal layer 202. The first sub-section 401 and the second sub-section 402 are stacked. The widths of the first sub-section 401, the second sub-section 402, and the third sub-section 403 are all equal.

[0107] In this embodiment, the metal line includes a double-layer metal line and a single-layer metal line. The first metal line is double-layered in the stacked portion of the first metal layer and the second metal layer, and the metal line is single-layered in the second portion of the first metal layer. Since the mask adopts an etching compensation design in the single-layer metal layer portion, the width of the single-layer metal layer portion is wider, making the linewidth of the single-layer portion of the first metal layer close to the linewidth of the double-layer portion of the second metal layer, thereby improving the etching accuracy.

[0108] The line width of the local non-electroplating area is compensated, the line width design value of the bending part is set to be greater than the partial line width, so as to avoid the error caused by the photoetching accuracy, so that the line width of the local non-electroplating area is close to the partial line width after etching, and the line break caused by over-etching is avoided.

[0109] Therefore, the line width design value of the bending part is set to be greater than the line width of the multilayer board area, so that the line width of the local non-electroplating area is close to the line width of the multilayer board area after etching, and the reliability of the circuit board is improved.

[0110] The etching method can be used for etching the second metal layer and the third metal layer to obtain metal lines with uniform width, and can also be used for etching lines in other scenarios where the thickness of the metal layer is inconsistent, which all belong to the protection scope of the present application and will not be repeated here.

[0111] The present application does not limit the size of each part of the circuit board. In some embodiments, as shown in Figure 10 , the width (the size along the x direction as shown in Figure 10 ) of the first binding area 101A is equal to the width (the size along the x direction of the first part 101C or the size along the x direction of the second part 101D) of the multilayer board area, and the width (the size along the x direction of the first bending part 101B) of the first bending part 101B is less than the width (the size along the x direction of the first part 101C or the size along the x direction of the second part 101D) of the multilayer board area.

[0112] The circuit board provided by the present application has a smaller width of the first bending part 101B, and the line is more flexible.

[0113] As shown in Figure 11 , the second metal layer 1021 and the third metal layer 1022 are wiring layers, and the second metal layer 1021 and the third metal layer 1022 include a plurality of metal lines 10220.

[0114] The present application does not limit the wiring mode of the second metal layer 1021. As shown in Figure 12 , in some embodiments, the second metal layer 1021 includes a first metal line 1021A and a plurality of second metal lines 1021B connected to the first metal line 1021A, the first metal line 1021A is arranged in the second part 101D, the second metal line 1021B is arranged in the first bending part 101B, and the line width of the second metal line 1021B is less than the line width of the first metal line 1021A.

[0115] Next, refer to Figure 12The second metal line 1021B includes: a metal line B1, a metal line B2 and a metal line B3, and the metal line B1, the metal line B2 and the metal line B3 are all connected with one first metal line 1021A. Wherein, the line widths of the metal line B1, the metal line B2 and the metal line B3 are the same, and the line widths of the metal line B1, the metal line B2 and the metal line B3 are all smaller than the line width of the first metal line 1021A.

[0116] Wherein, the metal line B1, the metal line B2 and the metal line B3 and the first metal line 1021A are arranged in a comb tooth shape, the width direction of the first metal line 1021A is a first direction (x direction in Figure 12 ), the length direction of the metal line B1, the metal line B2 and the metal line B3 is a second direction (y direction in Figure 12 ), and the first direction and the second direction are perpendicular. In an example, the relatively thick power supply lines in the bending area can be split into multiple relatively thin power supply lines, so that the line width in the bending area is uniform, and the stress in the bending area is uniformly distributed, thereby further improving the bending reliability of the circuit board.

[0117] The present embodiment does not limit the types of the first metal line and the second metal line. In some embodiments, the first metal line and the second metal line are both power supply lines.

[0118] The present embodiment designs the relatively thick power supply lines in the bending area in a comb tooth shape, that is, splits the relatively thick power supply lines into multiple relatively thin power supply lines, so as to ensure that the line width in the bending area is uniform, to realize uniform distribution of stress in the bending area, and to further improve the bending reliability of the circuit board.

[0119] In some embodiments, as shown in Figure 13 The second substrate 1023 includes opposite first and second surfaces, the first surface of the second substrate 1023 is away from the first metal layer 1011, and the second surface of the second substrate 1023 is close to the first metal layer 1011. The second metal layer 1021 is arranged on the first surface (upper surface) of the second substrate 1023, for example, the second metal layer 1021 is arranged on the side of the second substrate 1023 away from the first metal layer 1011.

[0120] In the present embodiment, the second metal layer 1021 can be a copper clad layer of the second substrate 1023. In some embodiments, the circuit board further includes: a metal layer 1024 arranged on the second surface (lower surface) of the second substrate 1023, and the metal layer 1024 adopts rolled copper.

[0121] In an example, as shown in Figure 13As shown, the metal layer 1024 includes a fourth portion 1024a and a second bending portion 1024b, the fourth portion 1024a is arranged below the second portion 101D, and the second bending portion 1024b is arranged below the first bending portion 101B, wherein the metal layer 1024 is made of rolled copper.

[0122] In this embodiment, the second metal layer 1021 and the metal layer 1024 cover the multi-layer board area and the bending area of the second substrate 1023, the second metal layer 1021 and the metal layer 1024 are both made of rolled copper, and the third metal layer 1022 (electrolytic copper) only covers the multi-layer board area and the connecting portion of the second metal layer 1021. As an example, the metal layers on both sides of the first connecting portion 101a for bending in the circuit board are made of rolled copper, which improves the bending performance, and the binding area is provided with electrolytic copper, which improves the electrical connection performance, and both the electrical connection performance and the bending performance can be considered.

[0123] In some embodiments, as shown in Figure 13 , the circuit board further includes a protective film 1025 and a protective film 1026, both of which are arranged in the bending area 101B, the protective film 1025 is arranged on the side of the third metal layer 1022 away from the second metal layer 1021, and the protective film 1026 is arranged on the side of the metal layer 1024 away from the second substrate 1023.

[0124] As an example, referring to Figure 13 , the protective film 1025 is arranged above the first bending portion 101B, and the protective film 1026 is arranged below the second bending portion 1024b.

[0125] The embodiments of the present application do not limit the connection mode of the protective film and the metal layer. As an example, referring to Figure 13 , the protective film 1025 is connected to the third metal layer 1022 through the connecting layer 1002A, and the protective film 1026 is connected to the metal layer 1024 through the connecting layer 1002B.

[0126] In this embodiment, the bending area of the circuit board is buckled on the circuit board through the connector after bending, protective films can be arranged on both sides of the bending area, which can better protect the circuit board.

[0127] In some embodiments, as shown in Figure 13 , the circuit board further includes a metal layer 1013 arranged below the first substrate 1012.

[0128] The metal layer 1013 includes a second binding area 1013a and a fifth portion 1013b, the fifth portion 1013b and the first portion 101C are arranged in layers, and the second binding area 1013a and the first binding area 101A are arranged in layers.

[0129] The metal layer 1013 can be electrolytic copper. In this way, the electrical connection performance of the circuit board can be further improved.

[0130] In some embodiments, the lower surface of the first substrate 1012 is further provided with a copper clad layer, the copper clad layer is formed on the lower surface of the first substrate 1012, and the metal layer 1013 is formed on the lower surface of the copper clad layer.

[0131] In some embodiments, the first metal layer 1011 can be a copper clad layer. The copper clad layer can be electrolytic copper. In this way, the electrical connection performance of the circuit board can be improved.

[0132] The circuit board provided by the embodiments of the present application can be electrically connected to the display screen through the binding area, and the first metal layer 1011 and the metal layer 1013 do not need to be bent. Therefore, the first metal layer 1011 and the metal layer 1013 can both be electrolytic copper, thereby improving the electrical connection performance of the first metal layer 1011 and the metal layer 1013.

[0133] In order to better protect the metal layer 1013, in some embodiments, as shown in Figure 13 The circuit board further includes a protective film 1015, and the first protective film 1015 is arranged below the second binding area 1013a.

[0134] The first metal layer 1011 is electrically connected to the display screen, and the metal layer 1013 is exposed to the air. By arranging the first protective film 1015, the impurities in the external air can be prevented from contacting the metal layer 1013, and the metal layer 1013 can be better protected.

[0135] The embodiments of the present application do not limit the connection mode of the first protective film 1015 and the metal layer 1013. In some embodiments, referring next to Figure 13 The circuit board further includes a connecting layer 1014, and the first protective film 1015 is connected to the metal layer 1013 through the connecting layer 1014.

[0136] The material of the connecting layer 1014 includes one or more of a double-sided adhesive layer or a PP (Polypropylene) adhesive layer.

[0137] In this way, by arranging the connecting layer 1014, the first protective film 1015 and the metal layer 1013 can be better connected, and the protection of the metal layer 1013 can be further improved.

[0138] The embodiments of the present application do not limit the connection mode of the fourth part 1024a and the first part 101C. In some embodiments, as shown in Figure 6 , Figure 7 , Figure 8 , Figure 11 ,Figure 13 As shown in FIG. 1, the circuit board further comprises a connecting layer 100A, which is exemplarily connected between the first portion 101C and the fourth portion 1024a. Figure 13 As shown in FIG. 1, the circuit board further comprises a connecting layer 100A, which is exemplarily connected between the first portion 101C and the fourth portion 1024a.

[0139] The number of metal layers of the circuit board is not limited in the embodiments. In some embodiments, as shown in FIG. 1, the circuit board further comprises a third substrate 1031 and a metal layer 1032, the metal layer 1032 is connected to the third substrate 1031, and the third substrate 1031 is connected to the metal layer 1013. The metal layer 1032 comprises a sixth portion 101E, and the sixth portion 101E is stacked with the first portion 101C and the second portion 101D. Figure 14 As shown in FIG. 1, the circuit board further comprises a connecting layer 100A, which is exemplarily connected between the first portion 101C and the fourth portion 1024a.

[0140] The third substrate 1031 comprises opposite first and second surfaces, the first surface of the third substrate 1031 is close to the metal layer 1013, and the second surface of the third substrate 1031 is away from the metal layer 1013.

[0141] The structure of the third substrate 1031 is not limited in the embodiments. In some embodiments, the third substrate 1031 is made of an insulating material, and the material of the third substrate 1031 comprises a polyimide (PI) substrate layer.

[0142] In some embodiments, a copper cladding layer is arranged on the second surface of the third substrate 1031, and the copper cladding layer is directly formed on the second surface of the third substrate 1031. The copper cladding layer can be made of electrolytic copper. In this way, the electrical connection performance of the circuit board can be improved.

[0143] In some embodiments, the circuit board further comprises a metal layer 1032, which is arranged on the surface of the copper cladding layer away from the third substrate 1031. The metal layer 1032 is made of electrolytic copper. In this way, the electrical connection performance of the circuit board can be further improved.

[0144] The connection mode of the third substrate 1031 and the metal layer 1013 is not limited in the embodiments, and in some embodiments, the third substrate 1031 can be connected to the metal layer 1013 through the connecting layer 100B.

[0145] In some embodiments, in order to better protect the metal layer 1032, a protective film 1034 can also be arranged on the metal layer 1032. The protective film can be connected to the metal layer 1032 through the connecting layer 1033, and the metal layer 1032 can be better protected.

[0146] In some embodiments, referring back to Figure 14The circuit board 101 further comprises a fourth substrate 1041 and a seventh metal layer 1042 connected with the fourth substrate 1041, the fourth substrate 1041 is further connected with the third metal layer 1022, and the seventh metal layer 1042 comprises a seventh part 101F, the seventh part 101F is arranged in a stack with the first part 101C and the second part 101D.

[0147] In some embodiments, the fourth substrate 1041 comprises opposite first and second surfaces, the first surface of the fourth substrate 1041 is away from the third metal layer 1022, and the second surface of the fourth substrate 1041 is close to the third metal layer 1022.

[0148] The embodiments of the present application do not limit the structure of the fourth substrate 1041. In some embodiments, the fourth substrate 1041 is made of an insulating material, and the material of the fourth substrate 1041 comprises a polyimide (PI) substrate layer.

[0149] In some embodiments, a copper cladding layer is arranged on the first surface of the fourth substrate 1041, and the copper cladding layer is directly formed on the first surface of the fourth substrate 1041. The copper cladding layer can be made of electrolytic copper. In this way, the electrical connection performance of the circuit board can be improved. The metal layer 1042 is arranged on the surface of the copper cladding layer away from the fourth substrate 1041. The metal layer 1042 is made of electrolytic copper. In this way, the electrical connection performance of the metal layer 1042 can be further improved.

[0150] The embodiments of the present application do not limit the connection mode of the third metal layer 1022 and the fourth substrate 1041. In some embodiments, the third metal layer 1022 is connected with the fourth substrate 1041 through a connecting layer 100C.

[0151] In some embodiments, in order to better protect the metal layer 1042, a protective film 1044 can also be arranged on the metal layer 1042. The protective film can be connected with the metal layer 1042 through a connecting layer 1043, and the metal layer 1042 can be better protected.

[0152] In the embodiments of the present application, the first metal layer and the second metal layer are used to electrically connect the display screen and the circuit board, the first substrate and the second substrate adopt a double-layer metal layer structure, the electrical connection performance is improved, and the third substrate and the fourth substrate are only provided with a metal layer on one side. In this way, the circuit board comprises six metal layers in total, and the circuit board adopts a 1+2+2+1 stack design, wherein the third substrate, the first substrate, the second substrate and the fourth substrate are arranged in a stack, the metal layer of the third substrate is in the first layer (L1 layer) in the stack, is made of electrolytic copper, the metal layer of the second substrate is in the second layer (L2 layer) and the third layer (L3 layer) in the stack, and is made of electrolytic copper. Figure 14 Figure 14 Figure 14 ​​The L3 layer (in the image) has its bonding area located on the third layer, bonding the FPC to the display panel (FPC on Panel bonding, FOP bonding). The second and third metal layers use electrolytic copper to control the expansion and contraction of the bonding area (gold finger area), ensuring it meets the process capability index (CPK) requirements. The metal layer of the third substrate is located on the fourth layer (…). Figure 14 L4 layer and the fifth layer (in the middle) Figure 14 The L5 layer (in the circuit board) has a bending area located between the fourth and fifth metal layers. This area is used to achieve electrical connection between the circuit board and the circuit board. The fourth and fifth metal layers are made of rolled copper, and a partial electroplating-free design is used in the fifth metal layer to ensure the reliability of the circuit board during bending. The metal layer of the third substrate is located in the sixth layer (…). Figure 14 The L6 layer (in the middle) uses electrolytic copper and adopts a single-layer design, which reduces production costs.

[0153] The stacked structure provided in this application is merely an example. The arrangement order of the stacked structures can also be adjusted. For example, the second substrate and the metal layer on the second substrate can be disposed below the first substrate and the metal layer on the first substrate. This is only necessary so that when the display screen is connected to the circuit board via the circuit board 101, the bonding area of ​​the circuit board 101 can be connected to the display screen, and the bent portion can be bent to the surface of the circuit board away from the display screen, and connected to electronic devices disposed on the surface of the circuit board away from the display screen. These are all within the scope of protection of this application and will not be elaborated further here.

[0154] This application provides a circuit board, a display module, and an electronic device. The electronic device includes a display module and a circuit board. The display module includes a display screen and a circuit board. The circuit board is divided into a bonding area, a multilayer board area, and a bending section. The bonding area is used for electrical connection with the display screen, and the bending section is used for electrical connection with the circuit board after bending. The metal layer where the bonding area is located and the metal layer where the bending section is located are electrically connected in the multilayer board area. The grain size of the metal layer where the bonding area is located and the metal layer where the bending section is located are different. For example, the metal layer where the bonding area is located is made of electroplated copper, and the metal layer where the bending section is located is made of rolled copper. Electroplated copper has better electrical connection performance, while rolled copper has better bending performance. In this way, the electrical connection performance and bending performance of the circuit board can be balanced, and the electrical connection stability can be improved.

[0155] In some embodiments, an electroplated copper metal layer can be provided in the bonding area of ​​the metal layer where the bend is located, which improves the stability of the electrical connection.

[0156] In some embodiments, the metal layer where the bending part is located can be split into multiple narrower traces in the first bending part in the wider trace area of the multilayer board, so that the bending part trace width is uniform, and the bending part stress is uniformly distributed, further improving the bending reliability of the circuit board. In addition, the line width of the local non-electroplating area can also be compensated and designed, and the bending part trace width design value is set to be greater than the partial trace width of the multilayer board area, so as to avoid the error caused by the photoetching precision, so that the trace width of the local non-electroplating area is close to the partial trace width of the multilayer board area after etching, and the trace breakage caused by over-etching is avoided.

[0157] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A circuit board, characterized in that, The circuit board includes: a first substrate, a first metal layer, a second substrate, and a second metal layer stacked together; The first metal layer is disposed on the first substrate, and the first metal layer includes a first bonding area and a first portion; The second metal layer is disposed on the second substrate, and the second metal layer includes a second portion and a first bent portion; The bonding area is used for electrical connection with the display screen. The first part and the second part are stacked, and the grain size of the second metal layer is larger than the grain size of the first metal layer.

2. The circuit board according to claim 1, characterized in that, The second metal layer is made of rolled copper, and the first metal layer is made of electrolytic copper.

3. The circuit board according to claim 1 or 2, characterized in that, The first bending portion includes: a first connecting portion and a second connecting portion connected in sequence, wherein the first connecting portion is connected to the second portion.

4. The circuit board according to claim 3, characterized in that, The circuit board further includes a third metal layer, which includes a third portion and a third connection portion. The third portion of the third metal layer is disposed above the second portion, and the third connection portion of the third metal layer is disposed on the second connection portion. The third metal layer is made of electrolytic copper.

5. The circuit board according to any one of claims 1-4, characterized in that, The second metal layer includes: a first metal wire and a second metal wire, wherein the first metal wire is connected to a plurality of second metal wires, the first metal wire is disposed in a second portion, the second metal wire is disposed in the first bend portion, and the line width of the second metal wire is smaller than the line width of the first metal wire.

6. The circuit board according to any one of claims 1-5, characterized in that, The circuit board further includes a first protective film, which is disposed above the first bend.

7. The circuit board according to any one of claims 1-6, characterized in that, The circuit board further includes a fourth metal layer disposed below the second substrate. The fourth metal layer includes a fourth portion and a second bending portion, wherein the fourth portion and the second portion are stacked, and the second bending portion and the first bending portion are stacked. The fourth metal layer is made of rolled copper.

8. The circuit board according to claim 7, characterized in that, The circuit board further includes a connection layer, through which the fourth part is connected to the first part.

9. The circuit board according to claim 7 or 8, characterized in that, The circuit board further includes a second protective film, which is disposed below the second bend.

10. The circuit board according to any one of claims 1-8, characterized in that, The circuit board further includes a fifth metal layer disposed below the first substrate. The fifth metal layer includes a fifth portion and a second bonding area, wherein the fifth portion and the first portion are stacked, and the second bonding area and the first bonding area are stacked. The fifth metal layer is made of electrolytic copper.

11. The circuit board according to claim 10, characterized in that, The circuit board further includes a third protective film, which is disposed below the second bonding area.

12. The circuit board according to any one of claims 1-11, characterized in that, The circuit board further includes: a third substrate, and a sixth metal layer disposed below the third substrate. The third substrate is disposed below the first substrate, and the sixth metal layer includes: a sixth portion, which is stacked with the first portion.

13. The circuit board according to any one of claims 1-12, characterized in that, The circuit board further includes: a fourth substrate, and a seventh metal layer disposed on the fourth substrate, the fourth substrate being disposed above the second substrate, and the seventh metal layer comprising: a seventh portion, the seventh portion and the second portion being stacked.

14. A display module, characterized in that, include: The display screen, and the circuit board as described in any one of claims 1-13; The bonding area of ​​the circuit board is electrically connected to the display screen.

15. An electronic device, characterized in that, include: The circuit board and the display module as described in claim 14; the first bent portion of the circuit board is connected to the circuit board.

16. An etching method, characterized in that, include: A first metal layer is formed on a substrate; wherein the first metal layer includes: a first portion and a second portion connected to each other; A second metal layer is formed on a first portion of the first metal layer; A first mask portion of a photomask is disposed on the second metal layer, and a second mask portion of a photomask is disposed on a second portion of the first metal layer, wherein the width of the first mask portion is smaller than the width of the second mask portion; The first metal layer and the second metal layer are etched to obtain a metal line.

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