Method for manufacturing flexible circuit board and flexible circuit board

Abstract

This application provides a method for fabricating a flexible circuit board and the flexible circuit board itself. The method includes: forming dry films on two opposing surfaces of a first substrate, wherein the thickness of the dry films is greater than or equal to 40 μm and less than or equal to 100 μm, and the exposure resolution of the dry films is less than or equal to 10 μm; patterning the dry films to obtain patterned dry films; electroplating metal onto the patterned dry films to obtain two first circuit layers, which are respectively located on two opposing surfaces of the first substrate; and peeling off the dry films. The method for fabricating a flexible circuit board according to this application can prepare high-density flexible circuit boards.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to a method for manufacturing a flexible circuit board and the flexible circuit board itself. Background Technology

[0002] With the development of display technology, display modules need to have more functions. For example, in foldable screen phones, the display module requires the foldable screen to be able to switch freely between the main screen and the secondary screen. In this case, the flexible printed circuit (FPC) in the display module also needs to have more functions.

[0003] However, conventional flexible circuit boards are insufficient to meet the functional requirements of display modules. Summary of the Invention

[0004] To address the aforementioned issues, this application provides a method for manufacturing a flexible circuit board and a flexible circuit board in its embodiments.

[0005] In a first aspect, embodiments of this application provide a method for manufacturing a flexible circuit board, comprising: forming dry films on two opposing surfaces of a first substrate, wherein the thickness of the dry films is greater than or equal to 40 μm and less than or equal to 100 μm, and the exposure resolution of the dry films is less than or equal to 10 μm; performing patterning processing on the dry films to obtain patterned dry films; electroplating metal on the patterned dry films to obtain two first circuit layers, wherein the two first circuit layers are respectively located on two opposing surfaces of the first substrate; and peeling off the dry films.

[0006] In conjunction with the first aspect, patterning the dry film to obtain a patterned dry film includes: partially exposing the dry film to obtain an exposed portion and an unexposed portion; removing the exposed portion of the dry film using a developing solution to obtain the patterned dry film; preferably, the dry film includes a resin-type dry film, and the developing solution includes an organic developing solution; preferably, the resin-type dry film includes a photosensitive material and a polymer resin; preferably, partially exposing the dry film to obtain an exposed portion and an unexposed portion includes: placing a circuit film of a first circuit layer on the surface of the dry film facing away from the first substrate; irradiating the dry film on which the circuit film is placed with ultraviolet light to obtain the exposed portion and the unexposed portion of the dry film.

[0007] In conjunction with the first aspect, metal is electroplated on the patterned dry film to obtain two first circuit layers, including: electroplating the patterned dry film with a first copper plating solution to obtain the first circuit layer; wherein the true copper salt alkalinity of the first copper plating solution is greater than or equal to 200% and less than or equal to 300%.

[0008] In conjunction with the first aspect, metal is electroplated on the patterned dry film to obtain two first circuit layers, including: using a second copper plating solution to perform multiple electroplatings on the patterned dry film to obtain the first circuit layers; wherein, the true copper salt alkalinity of the second copper plating solution is greater than or equal to 90% and less than or equal to 120%.

[0009] In conjunction with the first aspect, the first substrate includes a first insulating layer and a first copper layer disposed on two opposing surfaces of the first insulating layer; preferably, the material of the first insulating layer includes polyimide; preferably, after stripping the dry film, the method further includes: removing at least a portion of the first copper layer; preferably, removing at least a portion of the first copper layer by wet etching; preferably, after removing the first copper layer, the method further includes: forming a first protective layer on the surface of the first circuit layer opposite to the first substrate; preferably, the material of the first protective layer includes polyimide.

[0010] In conjunction with the first aspect, the method for manufacturing the flexible circuit board further includes: sequentially forming a first adhesive layer and a second substrate on at least one surface of the first circuit layer away from the first substrate; electroplating copper on the surface of the second substrate away from the first substrate and performing patterning treatment to form the second circuit layer; preferably, the material of the first adhesive layer includes at least one of polyester, acrylic, epoxy, or modified epoxy; preferably, the second substrate includes a second insulating layer and a second copper layer disposed on the surface of the second insulating layer away from the first substrate; preferably, the material of the second insulating layer includes polyimide; preferably, when preparing the second circuit layer, the method further includes: etching away at least a portion of the second copper layer; preferably, after removing at least a portion of the second copper layer, the method further includes: forming a second protective layer on the surface of the second circuit layer away from the first substrate; preferably, the material of the second protective layer includes polyimide.

[0011] In conjunction with the first aspect, before electroplating copper on the surface of the second substrate away from the first substrate, the method further includes: forming at least one through hole on the first adhesive layer and the second substrate; electroplating copper on the surface of the second substrate away from the first substrate, including: electroplating copper on the surface of the second substrate away from the first substrate and inside the through hole, to obtain a second circuit layer and a conductive pillar.

[0012] Secondly, embodiments of this application also provide a flexible circuit board, comprising: a first insulating layer; two first circuit layers located on opposite surfaces of the first insulating layer; at least one first adhesive layer located on the surface of the first circuit layer facing away from the first insulating layer; a second insulating layer located on the surface of the first adhesive layer facing away from the first insulating layer; and a second circuit layer located on the surface of the second insulating layer facing away from the first insulating layer; wherein the linewidth of the first circuit layer is smaller than the linewidth of the second circuit layer; and / or, the thickness of the first circuit layer is greater than the thickness of the second circuit layer.

[0013] In conjunction with the second aspect, the linewidth of the first circuit layer is greater than or equal to 8 μm and less than or equal to 50 μm; the linewidth of the second circuit layer is greater than or equal to 50 μm and less than or equal to 500 μm; preferably, the thickness of the first circuit layer is greater than or equal to 30 μm and less than or equal to 70 μm; the thickness of the second circuit layer is greater than or equal to 15 μm and less than or equal to 30 μm; preferably, the material of the first insulating layer and / or the second insulating layer includes polyimide, and the material of the first adhesive layer includes at least one of polyester, acrylic, epoxy, or modified epoxy; preferably, the thickness of the first insulating layer and / or the second insulating layer is greater than or equal to 12.5 μm and less than or equal to 50 μm; the thickness of the first adhesive layer is greater than or equal to 15 μm and less than or equal to 25 μm; preferably, the flexible circuit board further includes a second protective layer located on the side of the second circuit layer opposite to the first insulating layer; preferably, the material of the second protective layer includes polyimide; preferably, the flexible circuit board further includes at least one conductive post, the conductive post penetrating the first adhesive layer and the second insulating layer, and the conductive post being connected to the first circuit layer and the second circuit layer respectively.

[0014] Thirdly, embodiments of this application also provide a display device, including a flexible circuit board manufactured by the above method, or including the above flexible circuit board.

[0015] Through the above technical solution, a first circuit layer with a fine line width and a large line thickness can be prepared using resin-based dry film. The resulting flexible circuit board can meet the requirements for wiring space and circuit layer thickness. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart illustrating a method for manufacturing a flexible circuit board according to an embodiment of this application.

[0017] Figures 2A to 2E This is a structural schematic diagram of the fabrication process of a flexible circuit board provided in an embodiment of this application.

[0018] Figure 3 This is a flowchart illustrating a method for manufacturing a flexible circuit board according to another embodiment of this application.

[0019] Figures 4A to 4F This is a structural schematic diagram of the fabrication process of a flexible circuit board according to another embodiment of this application.

[0020] Figure 5 This is a schematic diagram of the structure of a flexible circuit board provided in an embodiment of this application.

[0021] Figure 6 This is a schematic diagram of the structure of a flexible circuit board provided in another embodiment of this application.

[0022] Figure 7This is a schematic diagram of the structure of a display device provided in an embodiment of this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] Currently, when display modules are used in foldable screen phones, the flexible printed circuit boards (FPCs) within the display modules are also required to have more functions. Conventional double-layer FPCs are limited by wiring space and cannot meet the needs of foldable screen phones. Therefore, multi-layer FPCs are needed to increase wiring space. However, multi-layer FPCs are much more expensive than conventional double-layer FPCs, increasing costs. The inventors discovered that by reducing the width of the lines on the FPC and increasing the thickness of the lines, wiring space can be increased (i.e., increasing line density). However, FPC manufacturing processes include primary etching and modified semi-additive process (MSAP), both of which are difficult to use to produce high-density flexible printed circuit boards.

[0025] To address the aforementioned technical problems, in a first aspect, embodiments of this application provide a method for manufacturing a flexible circuit board, comprising: forming dry films on two opposing surfaces of a first substrate, wherein the thickness of the dry films is greater than or equal to 40 μm and less than or equal to 100 μm, and the exposure resolution of the dry films is less than or equal to 10 μm; patterning the dry films to obtain patterned dry films; electroplating metal onto the patterned dry films to obtain two first circuit layers, the two first circuit layers being located on two opposing surfaces of the first substrate; and peeling off the dry films. The method of this application embodiment can prepare fine lines and high copper thickness (first) circuit layers, i.e., prepare high-density flexible circuit boards, which can meet the requirements for wiring space and circuit layer thickness.

[0026] Figure 1 This is a schematic flowchart illustrating a method for manufacturing a flexible circuit board according to an embodiment of this application. Figures 2A to 2E This is a schematic diagram illustrating the fabrication process of a flexible circuit board according to an embodiment of this application. Figure 1 As shown, the method includes the following steps.

[0027] Step S110: Dry films are formed on the two opposing surfaces of the first substrate.

[0028] In this embodiment, a dry film is bonded to two opposing surfaces of a first substrate, and then the dry film is fixed to the first substrate by heat pressing.

[0029] like Figure 2A As shown, dry films 20 are formed on two opposing surfaces of a first substrate 10. The first substrate 10 includes a first insulating layer 110 and a first copper layer 120 disposed on two opposing surfaces of the first insulating layer 110. That is, the first substrate 10 includes a flexible copper clad laminate (FCCL). Optionally, the material of the first insulating layer 110 includes polyimide (PI). In the embodiments of this application, the thickness of the first insulating layer 110 is greater than or equal to 12.5 μm and less than or equal to 50 μm. For example, the thickness of the first insulating layer 110 is 12.5 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. The thickness of the first copper layer 120 on each side is greater than or equal to 1 μm and less than or equal to 3 μm. For example, the thickness of the first copper layer 120 on each side is 1μm, 1.5μm, 2μm, 2.5μm, or 3μm.

[0030] In this embodiment, the thickness of the dry film is greater than or equal to 40 μm and less than or equal to 100 μm. Exemplarily, the thickness of the dry film can be 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm. It is understood that the thickness of the dry film is greater than or equal to the thickness of the subsequently formed first circuit layer. In this embodiment, the dry film has a high exposure resolution. Exposure resolution refers to the fineness of the image formed by the dry film after exposure during dry film fabrication, i.e., the optimal effect of the dry film. The higher the exposure resolution, the finer the lines or spacing formed by the dry film. Optionally, the exposure resolution of the dry film is less than or equal to 10 μm. Exemplarily, the exposure resolution of the dry film is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0031] Step S120: Pattern the dry film to obtain a patterned dry film.

[0032] Figure 2BThe image shows the patterned dry film 20. Optionally, the patterning process of the dry film includes: partially exposing the dry film to obtain exposed portions and unexposed portions. Specifically, a circuit film of the first circuit layer is placed on the surface of the dry film facing away from the first substrate, and the dry film on which the circuit film is placed is irradiated with ultraviolet light to obtain exposed portions and unexposed portions. The exposed portions of the dry film are removed using a developing solution to obtain the patterned dry film. That is, exposure is performed in a negative film manner. In the embodiments of this application, the dry film includes a resin-type dry film, specifically, the resin-type dry film includes a photosensitive material and a polymer resin. The photosensitive material includes a photoresist. The developing solution includes an organic developing solution, such as propylene glycol methyl ether acetate (PGMEA).

[0033] Step S130: Electroplating metal onto the patterned dry film to obtain two first circuit layers.

[0034] like Figure 2C As shown, the first circuit layer 310 is located on two opposite surfaces of the first substrate 10. Optionally, the first circuit layer is obtained by electroplating on the patterned dry film using a first copper plating solution; wherein the true copper salinity of the first copper plating solution is greater than or equal to 200% and less than or equal to 300%. For example, the true copper salinity of the first copper plating solution is 200%, 210%, 220%, 250%, 270%, 290%, or 300%. That is, the first copper plating solution is a fast copper plating solution, which can carry a high current density and has a fast copper deposition rate, requiring only one electroplating to obtain the first circuit layer. In the embodiments of this application, by using a resin-type dry film, an organic developer, and a first copper plating solution (one-time copper plating), a first circuit layer with fine lines and high copper thickness can be prepared, meeting the requirements of flexible circuit boards for copper thickness and wiring space.

[0035] Optionally, a first circuit layer is obtained by multiple electroplating processes on the patterned dry film using a second copper plating solution; wherein the copper salinity of the second copper plating solution is greater than or equal to 90% and less than or equal to 120%. For example, the copper salinity of the second copper plating solution is 90%, 100%, 110%, or 120%. Because the copper salinity of the second copper plating solution is low, its deposition rate is slow, and a single electroplating process cannot obtain the required thickness of the first circuit layer. Therefore, multiple electroplating processes are used to obtain the required thickness of the first circuit layer. In this embodiment, by using a resin-based dry film, an organic developer, and a second copper plating solution (multiple electroplating processes), a first circuit layer with fine lines and high copper thickness can be prepared, meeting the requirements of flexible circuit boards for copper thickness and wiring space.

[0036] Step S140: Peel off the dry film.

[0037] In this embodiment, a stripping solution is used to peel off the dry film. Exemplarily, the stripping solution includes strongly alkaline solutions such as sodium hydroxide solution and potassium hydroxide solution. Optionally, after peeling off the dry film, the method further includes removing at least a portion of the first copper layer. Specifically, at least a portion of the first copper layer is removed using wet etching to obtain the desired result. Figure 2D The structure shown. In Figure 2D In the process, the first copper layer 120, which is not covered by the first line layer 310, is removed.

[0038] Optionally, after removing at least a portion of the first copper layer, the method further includes: forming a first protective layer on the surface of the first circuit layer opposite to the first substrate. This results in a flexible circuit board as shown in Figure 2E. Figure 2E In this configuration, the first circuit layer 310 is covered by a first protective layer 410. Optionally, the material of the first protective layer 410 includes polyimide. The first protective layer 410 can protect the first circuit layer 310 and prevent damage to it.

[0039] In this embodiment, a first circuit layer with a finer line width and a larger line thickness can be prepared by using a resin-type dry film combined with an electroplating copper process (one-time electroplating with a fast copper plating solution or multiple electroplating with a regular copper plating solution). The resulting flexible circuit board can meet the wiring space requirements and the circuit layer thickness requirements.

[0040] Figure 3 This is a flowchart illustrating a method for manufacturing a flexible circuit board according to another embodiment of this application. Figures 4A to 4F This is a structural schematic diagram of the fabrication process of a flexible circuit board according to another embodiment of this application. Figure 3 The difference between the manufacturing method shown in Figure 2 and the manufacturing method shown in Figure 2 is that... Figure 3 The manufacturing method shown also includes the following steps.

[0041] In step S150, a first adhesive layer and a second substrate are sequentially formed on at least one surface of the first circuit layer that is opposite to the first substrate.

[0042] Optionally, such as Figure 4A As shown, a first adhesive layer 50 and a second substrate 60 are sequentially formed on two opposing surfaces of the first circuit layer 310 away from the first substrate 10. Alternatively, as... Figure 4B As shown, a first adhesive layer 50 and a second substrate 60 are sequentially formed on any surface of the first circuit layer 310 opposite to the first substrate 10. Figure 4AAs shown in 4B, the second substrate 60 includes a second insulating layer 610 and a second copper layer 620 disposed on the surface of the second insulating layer 610 facing away from the first substrate 10. That is, the second substrate 60 includes a single-sided copper-clad laminate (FCCL). Optionally, the material of the second insulating layer 610 includes polyimide (PI). In the embodiments of this application, the thickness of the second insulating layer 610 is greater than or equal to 12.5 μm and less than or equal to 50 μm. For example, the thickness of the second insulating layer 610 is 12.5 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. The thickness of the second copper layer 620 is greater than or equal to 1 μm and less than or equal to 3 μm. For example, the thickness of the second copper layer 620 is 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm.

[0043] In this embodiment, the material of the first adhesive layer 50 includes at least one of polyester, acrylic, epoxy, or modified epoxy. The thickness of the first adhesive layer 50 is greater than or equal to 15 μm and less than or equal to 25 μm. Exemplarily, the thickness of the first adhesive layer 50 is 15 μm, 17 μm, 20 μm, 22 μm, or 25 μm.

[0044] In step S160, copper is electroplated on the surface of the second substrate away from the first substrate, and patterning is performed to form a second circuit layer.

[0045] Copper is electroplated on the surface of the second substrate opposite to the first substrate, and a portion of the copper is etched to form a second circuit layer. Optionally, when preparing the second circuit layer, the method further includes: etching away at least a portion of the second copper layer. That is, the electroplated copper layer and the second copper layer are etched simultaneously to obtain the desired result. Figure 4C and Figure 4D The second line layer 320 is shown.

[0046] Optionally, before copper electroplating, the method further includes: forming at least one through-hole on the first adhesive layer and the second substrate; during copper electroplating, the method includes: electroplating copper on the surface of the second substrate opposite to the first substrate and within the through-hole to obtain a second circuit layer and conductive pillars. Figure 4C and Figure 4D As shown, the conductive post 330 is used to realize the electrical connection between the first circuit layer 310 and the second circuit layer 320.

[0047] Optionally, after removing at least a portion of the second copper layer 620, the method further includes: forming a second protective layer 420 on the surface of the second circuit layer 320 facing away from the first substrate 10, such as... Figure 4E and Figure 4F As shown.

[0048] In this embodiment, the inner circuit layer (i.e., the first circuit layer) employs a modified semi-additive method, while the outer circuit layer (i.e., the second circuit layer) employs an etching method. This ensures high yield rates for both inner and outer circuit layers and reduces the number of layers in the flexible circuit board, thereby lowering costs. In this embodiment, the modified semi-additive method for the inner layer ensures a smooth surface on the first substrate, which does not affect the growth of the dry film, resulting in a high-quality dry film and a highly refined circuit layer.

[0049] Secondly, embodiments of this application also provide a flexible circuit board, comprising: a first insulating layer; two first wiring layers located on opposite surfaces of the first insulating layer; at least one first adhesive layer located on the surface of the first wiring layer facing away from the first insulating layer; a second insulating layer located on the surface of the first adhesive layer facing away from the first insulating layer; and a second wiring layer located on the surface of the second insulating layer facing away from the first insulating layer; wherein the linewidth of the first wiring layer is smaller than the linewidth of the second wiring layer; and / or, the thickness of the first wiring layer is greater than the thickness of the second wiring layer. In embodiments of this application, the inner and outer layers are respectively provided with wiring layers of different linewidths, and the inner layer is provided with finer lines, increasing the wiring space while meeting the copper thickness requirements of the flexible circuit board.

[0050] Figure 5 This is a schematic diagram of the structure of a flexible circuit board provided in an embodiment of this application. Figure 5 As shown, the flexible circuit board includes a first insulating layer 110, two first wiring layers 310, two first adhesive layers 50, two second insulating layers 610, and two second wiring layers 320. The two first wiring layers 310 are located on opposite surfaces of the first insulating layer 110. The two first adhesive layers 50 are located on the surfaces of the first wiring layers 310 facing away from the first insulating layer 110. The second insulating layers 610 are located on the surfaces of the first adhesive layers 50 facing away from the first insulating layer 110. The second wiring layers 320 are located on the surfaces of the second insulating layers 610 facing away from the first insulating layer 110. The linewidth of the first wiring layer 310 is smaller than the linewidth of the second wiring layer 320; and / or, the thickness of the first wiring layer 310 is greater than the thickness of the second wiring layer 320. In this embodiment, the inner and outer layers are provided with wiring layers of different linewidths, and the inner layer has finer lines, increasing the wiring space while meeting the copper thickness requirements of the flexible circuit board.

[0051] Optionally, the linewidth of the first circuit layer 310 is greater than or equal to 8 μm and less than or equal to 50 μm. Exemplarily, the linewidth of the first circuit layer 310 is 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. The thickness of the first circuit layer 310 is greater than or equal to 30 μm and less than or equal to 70 μm. Exemplarily, the thickness of the first circuit layer 310 is 30 μm, 40 μm, 50 μm, 60 μm, or 70 μm. Optionally, the linewidth of the second circuit layer 320 is greater than or equal to 50 μm and less than or equal to 500 μm. For example, the linewidth of the second circuit layer 320 is 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, or 500μm. Optionally, the thickness of the second circuit layer 320 is greater than or equal to 15μm and less than or equal to 30μm. For example, the thickness of the second circuit layer 320 is 15μm, 20μm, 25μm, or 30μm.

[0052] Optionally, the material of the first insulating layer 110 and / or the second insulating layer 610 includes polyimide. Optionally, the thickness of the first insulating layer 110 and / or the second insulating layer 610 is greater than or equal to 12.5 μm and less than or equal to 55 μm. For example, the thickness of the first insulating layer 110 and / or the second insulating layer 610 is 12.5 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

[0053] Optionally, the material of the first adhesive layer 50 includes at least one of polyester, acrylic, epoxy, or modified epoxy. The thickness of the first adhesive layer 50 is greater than or equal to 15 μm and less than or equal to 25 μm. Optionally, the thickness of the first adhesive layer 50 is 15 μm, 20 μm, or 25 μm.

[0054] Optionally, the flexible circuit board further includes a second protective layer 420, which is located on the side of the second circuit layer 320 opposite to the first insulating layer 110. The material of the second protective layer 420 includes polyimide.

[0055] Optionally, the flexible circuit board further includes at least one conductive post 330, which penetrates the first adhesive layer 50 and the second insulating layer 610, and is connected to the first circuit layer 310 and the second circuit layer 320 respectively.

[0056] Optionally, the flexible circuit board further includes a first copper layer 120, located between the first insulating layer 110 and the first circuit layer 310, wherein the orthographic projection of the first copper layer 120 onto the first insulating layer 110 overlaps with the orthographic projection of the first circuit layer 310 onto the first insulating layer 110. The flexible circuit board also includes a second copper layer 620, located between the second insulating layer 610 and the second circuit layer 320, wherein the orthographic projection of the second copper layer 620 onto the first insulating layer 110 overlaps with the orthographic projection of the second circuit layer 320 onto the first insulating layer 110. It should be noted that the first copper layer 120 and / or the second copper layer 620 are provided for copper electroplating, and the thickness of the first copper layer 120 and / or the second copper layer 620 is greater than or equal to 1 μm and less than or equal to 3 μm. Since the first copper layer 120 and the second copper layer 620 are relatively thin, optionally, the first copper layer 120 and the second copper layer 620 can be ignored.

[0057] Figure 6 This is a schematic diagram of the structure of a flexible circuit board provided in another embodiment of this application. Figure 6 The flexible circuit board shown is Figure 5 The difference in the flexible circuit board shown is that it only includes a first adhesive layer 50, a second insulating layer 610, and a second wiring layer 320. That is, the second wiring layer 320 is formed only on one side of the first wiring layer 310. This flexible circuit board is suitable for situations with relatively low wiring requirements.

[0058] Thirdly, embodiments of this application provide a display device, which includes the flexible circuit board in the above embodiments, or a flexible circuit board manufactured according to the method in the above embodiments.

[0059] Figure 7 This is a schematic diagram of the structure of a display device provided in an embodiment of this application. Figure 7 As shown, display device 700 is a product with image display function. For example, display device 700 can be used to display static images, such as pictures or photographs. Display device 700 can also be used to display moving images, such as videos.

[0060] Display device 700 can be a laptop, mobile phone, handheld or portable computer, camera, camcorder, in-vehicle smart central control screen, calculator, smartwatch, GPS navigator, electronic photo, electronic billboard or sign, projector, etc.

[0061] The display device 700 includes a display panel and a flexible circuit board provided in any of the above embodiments. The display panel may be an organic light-emitting diode (OLED) display panel or a quantum dot electroluminescent display panel.

[0062] In addition, the display device 700 can also perform functions such as taking photos, recording videos, fingerprint recognition, and facial recognition. Accordingly, the display device 700 also includes at least one functional module for implementing the above functions, such as an under-display camera or an under-display fingerprint recognition sensor.

[0063] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0064] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0065] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0066] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0067] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for manufacturing a flexible circuit board, characterized in that, include: A dry film is formed on two opposing surfaces of a first substrate, wherein the thickness of the dry film is greater than or equal to 40 μm and less than or equal to 100 μm, and the exposure resolution of the dry film is less than or equal to 10 μm. The dry film is patterned to obtain a patterned dry film; Metal is electroplated onto the patterned dry film to obtain two first circuit layers, which are respectively located on two opposite surfaces of the first substrate. Peel off the dry film.

2. The method for manufacturing a flexible circuit board according to claim 1, characterized in that, The process of patterning the dry film to obtain a patterned dry film includes: The dry film is partially exposed to obtain an exposed portion and an unexposed portion of the dry film; The exposed portion of the dry film is removed using a developing solution to obtain the patterned dry film; Preferably, the dry film comprises a resin-type dry film, and the developing solution comprises an organic developing solution; Preferably, the resin-type dry film comprises a photosensitive material and a polymer resin; Preferably, the step of partially exposing the dry film to obtain an exposed portion and an unexposed portion of the dry film includes: placing a circuit film of the first circuit layer on the surface of the dry film opposite to the first substrate; and irradiating the dry film on which the circuit film is placed with ultraviolet light to obtain the exposed portion and the unexposed portion of the dry film.

3. The method for manufacturing a flexible circuit board according to claim 1, characterized in that, The process involves electroplating metal onto the patterned dry film to obtain two first circuit layers, including: Electroplating is performed on the patterned dry film using a first copper plating solution to obtain the first circuit layer; wherein the true copper salinity of the first copper plating solution is greater than or equal to 200% and less than or equal to 300%.

4. The method for manufacturing a flexible circuit board according to claim 1, characterized in that, The process involves electroplating metal onto the patterned dry film to obtain two first circuit layers, including: The first circuit layer is obtained by electroplating multiple times on the patterned dry film using a second copper plating solution; wherein the true copper salinity of the second copper plating solution is greater than or equal to 90% and less than or equal to 120%.

5. The method for manufacturing a flexible circuit board according to claim 1, characterized in that, The first substrate includes a first insulating layer and a first copper layer disposed on two opposite surfaces of the first insulating layer; Preferably, the material of the first insulating layer includes polyimide; Preferably, after stripping the dry film, the method further includes: removing at least a portion of the first copper layer; Preferably, at least a portion of the first copper layer is removed using wet etching; Preferably, after removing at least a portion of the first copper layer, the method further includes: forming a first protective layer on the surface of the first circuit layer opposite to the first substrate; Preferably, the material of the first protective layer includes polyimide.

6. The method for manufacturing a flexible circuit board according to claim 1, characterized in that, Also includes: A first adhesive layer and a second substrate are sequentially formed on at least one surface of the first circuit layer that is opposite to the first substrate; Copper is electroplated on the surface of the second substrate opposite to the first substrate, and patterning is performed to form a second circuit layer; Preferably, the material of the first adhesive layer includes at least one of polyester, acrylic, epoxy, or modified epoxy. Preferably, the second substrate includes a second insulating layer and a second copper layer disposed on the surface of the second insulating layer opposite to the first substrate; Preferably, the material of the second insulating layer includes polyimide; Preferably, when preparing the second circuit layer, the method further includes: etching away at least a portion of the second copper layer; Preferably, after removing at least a portion of the second copper layer, the method further includes: forming a second protective layer on the surface of the second circuit layer opposite to the first substrate; Preferably, the material of the second protective layer includes polyimide.

7. The method for manufacturing a flexible circuit board according to claim 6, characterized in that, Before electroplating copper on the surface of the second substrate away from the first substrate, the method further includes: forming at least one through hole on the first adhesive layer and the second substrate; The step of electroplating copper on the surface of the second substrate away from the first substrate includes: electroplating copper on the surface of the second substrate away from the first substrate and inside the through hole to obtain the second circuit layer and conductive pillar.

8. A flexible circuit board, characterized in that, include: First insulating layer; Two first circuit layers are located on two opposite surfaces of the first insulating layer, respectively; At least one first adhesive layer is located on the surface of the first circuit layer opposite to the first insulating layer; The second insulating layer is located on the surface of the first adhesive layer that is opposite to the first insulating layer; The second circuit layer is located on the surface of the second insulating layer that is opposite to the first insulating layer; Wherein, the line width of the first line layer is smaller than the line width of the second line layer; And / or, the thickness of the first circuit layer is greater than the thickness of the second circuit layer.

9. The flexible circuit board according to claim 8, characterized in that, The linewidth of the first circuit layer is greater than or equal to 8 μm and less than or equal to 50 μm; the linewidth of the second circuit layer is greater than or equal to 50 μm and less than or equal to 500 μm. Preferably, the thickness of the first circuit layer is greater than or equal to 30 μm and less than or equal to 70 μm; the thickness of the second circuit layer is greater than or equal to 15 μm and less than or equal to 30 μm. Preferably, the material of the first insulating layer and / or the second insulating layer includes polyimide, and the material of the first adhesive layer includes at least one of polyester, acrylic, epoxy, or modified epoxy. Preferably, the thickness of the first insulating layer and / or the second insulating layer is greater than or equal to 12.5 μm and less than or equal to 50 μm; the thickness of the first adhesive layer is greater than or equal to 15 μm and less than or equal to 25 μm. Preferably, the flexible circuit board further includes a second protective layer located on the side of the second circuit layer opposite to the first insulating layer; Preferably, the material of the second protective layer includes polyimide; Preferably, the flexible circuit board further includes at least one conductive post, which penetrates the first adhesive layer and the second insulating layer, and is connected to the first circuit layer and the second circuit layer respectively.

10. A display device comprising a flexible circuit board manufactured by the method of any one of claims 1 to 7, or comprising the flexible circuit board of claim 8 or 9.

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