Flexible printed circuit and preparation method therefor, flexible printed circuit assembly and display device

Abstract

A flexible printed circuit, comprising: a first protective layer, a plurality of electrically conductive layers and a second protective layer, wherein the plurality of electrically conductive layers are disposed on the first protective layer and are stacked in sequence in a direction perpendicular to the first protective layer. The second protective layer is disposed on the side of the plurality of electrically conductive layers away from the first protective layer. Among the plurality of electrically conductive layers, the electrically conductive layer closest to the second protective layer is a first electrically conductive layer, the first electrically conductive layer comprising a plurality of pads; the second protective layer is provided with a plurality of first openings, the plurality of first openings respectively exposing parts of the plurality of pads; and the area of the orthographic projection of each first opening on the first protective layer is smaller than the surface area of each pad.

Description

Flexible circuit board and manufacturing method thereof, flexible circuit board assembly and display device

[0001] This application claims priority to Chinese patent application No. 202311847261.2 filed on December 28, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present disclosure relates to the field of display technology, and in particular to a flexible circuit board and a preparation method thereof, a flexible circuit board assembly, and a display device. Background Art

[0003] Flexible printed circuits (FPCs) are currently widely used in many display devices such as mobile phones, laptops, wearable devices, and tablet computers due to their high wiring density, light weight, thin thickness, and bendability. Summary of the Invention

[0004] In one aspect, a flexible circuit board is provided. The flexible circuit board includes a first protective layer, multiple conductive layers, and a second protective layer. The multiple conductive layers are disposed on the first protective layer and stacked sequentially in a direction perpendicular to the first protective layer. The second protective layer is disposed on a side of the multiple conductive layers away from the first protective layer. The conductive layer closest to the second protective layer is the first conductive layer, and the first conductive layer includes multiple solder pads. The second protective layer has multiple first openings, each of which exposes a portion of the multiple solder pads. The area of ​​the orthographic projection of each first opening on the first protective layer is smaller than the surface area of ​​the solder pad.

[0005] In some embodiments, at least one groove is formed on the exposed surface of the pad.

[0006] In some embodiments, the groove passes through the pad.

[0007] In some embodiments, a bottom wall of the groove is located within the pad.

[0008] In some embodiments, a sidewall of the groove is flush with an edge of the first opening.

[0009] In some embodiments, an orthographic projection of an end of the first opening away from the first protective layer on the first protective layer is located within a range of an orthographic projection of an end of the first opening close to the first protective layer on the first protective layer.

[0010] In some embodiments, the pad includes a sub-portion and at least one branch; the sub-portion includes a first node and a second node spaced apart, and the branch includes a first end and a second end relative to each other, the first end is connected to the first node, and the second end is connected to the second node.

[0011] In some embodiments, the pad includes a plurality of branches located on both sides of the sub-portion, and the plurality of branches are symmetrically arranged with respect to the sub-portion.

[0012] In some embodiments, the conductive layer that is next closest to the second protective layer among the multiple conductive layers is the second conductive layer; the second conductive layer includes a plurality of pad auxiliary parts; the flexible circuit board also includes: an insulating layer arranged between the first conductive layer and the second conductive layer, and a plurality of vias are arranged in the insulating layer; the pads are connected to the pad auxiliary parts through the vias.

[0013] In some embodiments, an orthographic projection of the pad on the first protection layer at least partially overlaps with an orthographic projection of the pad auxiliary portion on the first protection layer.

[0014] In another aspect, a method for preparing a flexible circuit board is provided. The method comprises: providing a copper-clad substrate, the copper-clad substrate comprising a plurality of conductive layers stacked in sequence, wherein a top conductive layer of the plurality of conductive layers is a first conductive layer; forming a plurality of solder pads in the first conductive layer; forming a second protective layer on a side of the first conductive layer away from the other conductive layers; the second protective layer having a plurality of first openings, each of the plurality of first openings exposing a portion of the plurality of solder pads; the area of ​​the orthographic projection of each first opening on the first protective layer being smaller than the surface area of ​​the solder pad; and forming the first protective layer on a side of the plurality of conductive layers away from the second protective layer.

[0015] In some embodiments, the conductive layer next closest to the second protective layer among the multiple conductive layers is the second conductive layer; the copper-clad substrate further includes: an insulating layer arranged between the first conductive layer and the second conductive layer; before forming the first protective layer on the side of the multiple conductive layers away from the second protective layer, the preparation method further includes: forming a plurality of vias in the insulating layer; forming a plurality of pad auxiliary parts in the second conductive layer, and the pads are connected to the pad auxiliary parts through the vias.

[0016] On the other hand, a flexible circuit board assembly is provided, comprising: a flexible circuit board, the flexible circuit board being the flexible circuit board as described in any of the above embodiments; an optical component, the optical component comprising a plurality of pins; a bonding portion located within each first opening of the flexible circuit board; the pins being bonded to the pads of the flexible circuit board through the bonding portion.

[0017] In another aspect, a display device is provided, comprising: the flexible circuit board assembly according to any one of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the technical solutions of the present disclosure, the following briefly introduces the drawings required for use in some embodiments of the present disclosure. Obviously, the drawings described below are only drawings of some embodiments of the present disclosure, and those skilled in the art can also derive other drawings based on these drawings. Furthermore, the drawings described below are schematic diagrams and are not intended to limit the actual dimensions of the products, actual processes of the methods, etc. involved in the embodiments of the present disclosure.

[0019] FIG1 is a structural diagram of a display device according to some embodiments;

[0020] FIG2 is a structural diagram of a flexible circuit board assembly according to some embodiments;

[0021] FIG3A is a structural diagram of yet another flexible circuit board assembly according to some embodiments;

[0022] FIG3B is a top view of yet another flexible circuit board assembly according to some embodiments;

[0023] FIG4A is a structural diagram of a flexible circuit board according to some embodiments;

[0024] FIG4B is a partial top view of a flexible circuit board according to some embodiments;

[0025] FIG5 is a structural diagram of yet another flexible circuit board assembly according to some embodiments;

[0026] FIG6 is a structural diagram of another flexible circuit board according to some embodiments;

[0027] FIG7A is a structural diagram of yet another flexible circuit board assembly according to some embodiments;

[0028] 7B is a top view of yet another flexible circuit board assembly according to some embodiments;

[0029] FIG8 is a structural diagram of another flexible circuit board according to some embodiments;

[0030] FIG9 is a structural diagram of yet another flexible circuit board assembly according to some embodiments;

[0031] FIG10 is a structural diagram of another flexible circuit board according to some embodiments;

[0032] FIG11 is a structural diagram of another flexible circuit board according to some embodiments;

[0033] FIG12 is a flow chart of a method for manufacturing a flexible circuit board according to some embodiments;

[0034] 13A to 13D are structural diagrams corresponding to steps in a method for manufacturing a flexible circuit board according to some embodiments. DETAILED DESCRIPTION

[0035] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present disclosure. Obviously, the embodiments described are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0036] Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and its other forms, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open and inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" are intended to indicate that the particular features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0037] In the following, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0038] When describing some embodiments, the expressions "coupled" and "connected" and their derivatives may be used. The term "connected" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. The term "coupled" indicates, for example, that two or more components are in direct physical or electrical contact. The term "coupled" or "communicatively coupled" may also refer to two or more components that are not in direct contact with each other, but still cooperate or interact with each other. The embodiments disclosed herein are not necessarily limited to the contents of this document.

[0039] “At least one of A, B and C” has the same meaning as “at least one of A, B or C” and both include the following combinations of A, B and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B and C.

[0040] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0041] Additionally, the use of “based on” is meant to be open and inclusive, as a process, step, calculation, or other action “based on” one or more stated conditions or values ​​may, in practice, be based on additional conditions or values ​​beyond those stated.

[0042] It will be understood that when a layer or element is referred to as being on another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may be present therebetween.

[0043] Exemplary embodiments are described herein with reference to cross-sectional and / or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and the area of ​​regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include deviations in shape due to, for example, manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0044] Some embodiments of the present disclosure provide a display device, which can be any display device that displays images, whether in motion (e.g., video) or fixed (e.g., still images), and whether text or images. More specifically, it is expected that the display device of the embodiments described can be implemented in or associated with a variety of electronic devices, such as (but not limited to) mobile phones, wireless devices, personal data assistants (PDAs), handheld or portable computers, GPS receivers / navigators, cameras, MP4 video players, camcorders, game consoles, watches, clocks, calculators, television monitors, flat-panel displays, computer monitors, automotive displays (e.g., odometer displays, etc.), navigation systems, cockpit controls and / or displays, displays of camera views (e.g., displays of rearview cameras in vehicles), electronic photographs, electronic billboards or signs, projectors, architectural structures, packaging, and aesthetic structures (e.g., displays of images of a piece of jewelry), etc.

[0045] In the embodiments of the present disclosure, the display device is taken as a wearable device for illustration, and the device may be a smart watch, a smart bracelet, etc.

[0046] FIG1 is a structural diagram of a display device according to some embodiments. As shown in FIG1 , the display device 1000 includes a frame 100 , a cover 200 , a display panel 300 , a flexible circuit board assembly 400 , and other electronic components.

[0047] As shown in Figure 1, the longitudinal section of the frame 100 is U-shaped, and the display panel 300, the flexible circuit board assembly 400 and other electronic accessories are arranged in the frame 100. The flexible circuit board assembly 400 is located between the display panel 300 and the frame 100, and the cover plate 200 is located on the side of the display panel 300 away from the flexible circuit board assembly 400.

[0048] Exemplarily, the flexible circuit board assembly 400 is located on the non-light-emitting side of the display panel 300 and is coupled to the display panel 300. The flexible circuit board assembly 400 is used to provide a drive signal to the display panel 300, thereby ensuring normal display of the display panel 300. The side of the display panel 300 used to display an image is the light-emitting side, and the non-light-emitting side of the display panel 300 is the side of the display panel 300 opposite to the light-emitting side.

[0049] Exemplarily, the above-mentioned display panel 300 can be: an organic light emitting diode (OLED) display panel, a quantum dot light emitting diode (QLED) display panel, a micro light emitting diode (Micro LED) display panel, etc., and the present disclosure does not make any specific limitations on this.

[0050] In addition, the display panel 300 may be a flexible display panel. In the case where the display panel 300 is a flexible display panel, the display device 1000 is a flexible display device.

[0051] In some examples, referring to FIG. 2 and FIG. 3A , the flexible circuit board assembly 400 includes a flexible circuit board 10 , an optical component 20 , and a bonding portion 30 . The optical component 20 is bonded to the flexible circuit board 10 via the bonding portion 30 .

[0052] Exemplarily, the optical component 20 may be an infrared sensor or an ambient light sensor (ALS device for short).

[0053] For example, if the display device 1000 is a smartwatch, the optical component 20 may be an ALS device. The ALS device is used to detect the light intensity in the smartwatch's usage scenario. The smartwatch adjusts the screen brightness of the display screen based on the ambient light intensity detected by the ALS device to ensure that the user can clearly view the screen information.

[0054] For example, the bonding portion 30 is formed of solder, which is a conductive material, so that the optical component 20 and the flexible circuit board 10 can be fixedly connected and electrically connected at the same time through the bonding portion 30 .

[0055] For example, the solder may include tin-lead solder, binary alloy lead-free solder, or multi-element alloy lead-free solder. Specifically, the material of the solder may include tin-lead alloy (Sn-Pb), tin-silver alloy (Sn-Ag), tin-copper alloy (Sn-Cu), or may be at least one of tin-silver-copper alloy (Sn-Ag-Cu), tin-zinc-bismuth alloy (Sn-Zn-Bi), tin-silver-bismuth-copper alloy (Sn-Ag-Bi-Cu), tin-silver-bismuth-indium alloy (Sn-Ag-Bi-In), and tin-silver-bismuth-copper-germanium alloy (Sn-Ag-Bi-Cu-Ge).

[0056] 2 , the flexible circuit board assembly 400 further includes a connection portion 40 on the flexible circuit board 10. The connection portion 40 is electrically connected to the display panel 300 or other circuit boards via a board-to-board (BTB) connection.

[0057] For example, as shown in FIG3A , a flexible circuit board 10 includes a first protective layer 1, multiple conductive layers 2, and a second protective layer 3. The multiple conductive layers 2 are disposed on the first protective layer 1 and stacked in a direction perpendicular to the first protective layer 1. The second protective layer 3 is disposed on a side of the multiple conductive layers 2 away from the first protective layer 1.

[0058] The first protective layer 1 and the second protective layer 3 can both effectively protect the multiple conductive layers 2 .

[0059] For example, the first protective layer 1 can be a single-layer structure, a double-layer structure, or a multi-layer structure. For example, the first protective layer 1 is a single-layer structure composed of a polyimide (PI) layer. For another example, the first protective layer 1 is a double-layer structure composed of a sequentially stacked adhesive layer and a PI layer. The embodiments of the present disclosure are not limited to this.

[0060] The structure of the second protective layer 3 may be the same as or different from that of the first protective layer 1. For example, the structure of the second protective layer 3 is the same as that of the first protective layer 1. Both the second protective layer 3 and the first protective layer 1 are single-layer structures composed of a PI layer.

[0061] For example, the material of each conductive layer 2 may include a metal material, such as copper (Cu), or other suitable materials. In the case where the material of the conductive layer 2 includes copper, the conductive layer 2 may be a copper foil.

[0062] For example, the number of the conductive layers 2 may be two, three, or more layers, etc. The embodiments of the present disclosure do not limit this.

[0063] It should be noted that an insulating layer is provided between two adjacent conductive layers 2 , and the insulating layer between the adjacent conductive layers 2 is used to electrically insulate the two adjacent conductive layers 2 .

[0064] As shown in FIG. 3A , the conductive layer 2 closest to the second protective layer 3 among the plurality of conductive layers 2 is the first conductive layer 21 . The first conductive layer 21 includes a plurality of pads 211 .

[0065] Exemplarily, as shown in FIG. 3A , the second protection layer 3 has a plurality of first openings 31 , and the plurality of first openings 31 respectively expose a portion of the plurality of pads 211 .

[0066] Exemplarily, the first openings 31 correspond one-to-one to the pads 211 . For example, one first opening 31 is used to expose a portion of one pad 211 .

[0067] It is understood that some of the plurality of pads 211 are used to connect to the optical component 20; some of the plurality of pads 211 may also be connected to other devices. The other devices may be, for example, resistors for controlling current, dividing voltage, or matching impedance, capacitors for storing charge and releasing energy, inductors for storing magnetic energy and resisting current changes, or integrated circuits integrating multiple electronic components, etc., but are not limited thereto.

[0068] For example, as shown in FIG. 3A , the optical component 20 has pins 201 , and the exposed portion of the pad 211 is connected to the pins 201 of the optical component 20 via a bonding portion 30 , thereby achieving electrical connection between the optical component 20 and the flexible circuit board 10 .

[0069] Specifically, the electrical connection between the optical component 20 and the flexible circuit board 10 can be achieved through surface mount technology (SMT).

[0070] Surface mount technology (SMT) refers to a circuit assembly technique in which leadless or short-lead surface mount components are mounted on the surface of a circuit board or other substrate and assembled through soldering methods such as reflow or dip soldering. Specifically, in the embodiment of the present disclosure, optical component 20 is mounted on the surface of flexible circuit board 10 and soldered through methods such as reflow or dip soldering to achieve an electrical connection between optical component 20 and flexible circuit board 10.

[0071] Specifically, when achieving electrical connection between the optical component 20 and the flexible circuit board 10, solder for reflow soldering is first printed on the multiple pins 201 of the optical component 20 or the corresponding pads 211 on the flexible circuit board 10, and the multiple pins 201 of the optical component 20 are aligned and contacted with the pads 211 of the flexible circuit board 10. The solder is heated to melt the solder through a soldering technique such as reflow soldering or dip soldering, and then quickly cooled to solidify the solder to form a bonding portion 30. The bonding portion 30 is located in the first opening 31, and the surface of the bonding portion 30 close to the pad 211 is electrically connected to the pad 211 of the flexible circuit board 10, and the surface of the bonding portion 30 close to the pin 201 is electrically connected to the pin 201. Thus, the electrical connection between the optical component 20 and the flexible circuit board 10 is achieved through the bonding portion 30.

[0072] For example, the number of pads 211 connected to one optical component 20 may be one, two, or more, etc., which is not limited in the embodiments of the present disclosure.

[0073] Exemplarily, as shown in FIG3A , when the optical component 20 has a plurality of pins 201 , the number of pads 211 connected to one optical component 20 is also a plurality, and one pad 211 is connected to one pin 201 of the optical component 20 .

[0074] The multiple pads 211 connected to the same optical component 20 may transmit the same signal or different signals.

[0075] For example, multiple pads 211 connected to the same optical component 20 are used to transmit different signals. Specifically, the multiple pads 211 connected to the optical component 20 are connected to multiple traces provided on the conductive layer 2 for transmitting different signals. When the optical component 20 is connected to the flexible printed circuit board 10, the multiple pads 211 can transmit different signals from the multiple traces to the corresponding multiple pins 201 on the optical component 20.

[0076] In some examples, referring to FIG. 3A and FIG. 3B , a portion of the pad 211 exposed by the first opening 31 is in contact with the bonding portion 30 .

[0077] It is understandable that the portion of the pad 211 exposed by the first opening 31 conforms to the shape of the first opening 31. For example, if the orthographic projection of the first opening 31 on the first protective layer 1 is circular, the orthographic projection of the portion of the pad 211 exposed by the first opening 31 on the first protective layer 1 is also circular. For another example, if the orthographic projection of the first opening 31 on the first protective layer 1 is a square, the orthographic projection of the portion of the pad 211 exposed by the first opening 31 on the first protective layer 1 is also a square. FIG3B illustrates a case where the orthographic projection of the portion of the pad 211 exposed by the first opening 31 on the first protective layer 1 is a square. In this case, the pad 211 can be called a rectangular pad.

[0078] In the thickness direction of the flexible circuit board 10, if the cross-sectional area at different positions of the first opening 31 remains constant, the orthographic projection of the portion of the pad 211 exposed by the first opening 31 on the first protective layer 1 coincides with the orthographic projection of the cross section at any position of the first opening 31 on the first protective layer 1. In other words, the area of ​​the portion of the pad 211 exposed by the first opening 31 is equal to the cross-sectional area at any position of the first opening 31 (i.e., the area of ​​the orthographic projection of the first opening 31 on the first protective layer 1).

[0079] In some implementations, the optical component 20 and the flexible circuit board 10 may easily have a problem of loose welding. In the case of loose welding between the optical component 20 and the flexible circuit board 10, the display device 1000 including the flexible circuit board assembly 400 may be separated from the flexible circuit board 10 due to vibration or collision during assembly or transportation, affecting the connectivity between the optical component 20 and the flexible circuit board 10 and affecting the functional use of the optical component 20.

[0080] Based on this, the present disclosure improves the flexible circuit board 10 . As shown in FIG. 4A to FIG. 6 , in the flexible circuit board 10 provided in the embodiment of the present disclosure, the area of ​​the orthographic projection of each first opening 31 on the first protective layer 1 is smaller than the surface area of ​​the pad 211 .

[0081] In some examples, referring to FIG. 4A and FIG. 4B , the orthographic projection of the first opening 31 on the first protection layer 1 completely falls within the orthographic projection of the pad 211 on the first protection layer 1 .

[0082] It should be noted that the "surface area of ​​the pad 211" mentioned above refers to the sum of the surface areas of the outer surfaces of the pad 211 exposed by the first opening 31. The outer surface refers to the surface exposed to the outside. Specifically, in the embodiments of the present disclosure, the surface area of ​​the pad 211 refers to the sum of the areas of the outer surfaces of the pad 211 exposed by the first opening 31.

[0083] For example, the number of outer surfaces of the pad 211 exposed by the first opening 31 may be one or more, which is not limited in the embodiments of the present disclosure.

[0084] For example, as shown in FIG. 4A and FIG. 6 , the portion of the pad 211 exposed by the first opening 31 includes multiple outer surfaces. In this case, the surface area of ​​the pad 211 is equal to the sum of the areas of the multiple outer surfaces of the pad 211 exposed by the first opening 31 .

[0085] It is understood that when the portion of the pad 211 exposed by the first opening 31 includes multiple side surfaces, the bonding portion 30 contacts all of the side surfaces. In this case, the contact area between the bonding portion 30 and the pad 211 is the surface area of ​​the pad 211 exposed by the first opening 31. The larger the contact area between the bonding portion 30 and the pad 211, the more secure the welding between the optical component 20 and the flexible circuit board 10.

[0086] In the embodiment shown in Figure 3A, in the thickness direction of the flexible circuit board 10, the cross-sectional area at different positions of the first opening 31 remains unchanged, and the surface area of ​​the exposed portion of the pad 211 is equal to the cross-sectional area of ​​the first opening 31 (that is, the area of ​​the positive projection of the first opening 31 on the first protective layer 1). At this time, the contact area between the bonding portion 30 and the pad 211 is equal to the surface area of ​​the portion of the pad 211 exposed by the first opening 31, that is, the cross-sectional area of ​​the first opening 31.

[0087] In this embodiment of the present disclosure, the surface area of ​​the pad 211 exposed by the first opening 31 is made larger than the area of ​​the positive projection of the first opening 31 on the first protective layer 1, that is, the contact area between the pad 211 and the bonding portion 30 is made larger, thereby enhancing the welding strength between the optical component 20 and the flexible circuit board 10, making the welding between the optical component 20 and the flexible circuit board 10 more firm, improving the welding quality between the optical component 20 and the flexible circuit board 10, and reducing the probability of fracture at the welding point between the optical component 20 and the flexible circuit board 10 due to loose welding between the optical component 20 and the flexible circuit board 10 in the event of collision or vibration during transportation, thereby ensuring the effectiveness of the electrical connection between the optical component 20 and the flexible circuit board 10.

[0088] In some embodiments, as shown in FIG. 4A to FIG. 6 , at least one groove A is formed on the exposed surface of the pad 211 .

[0089] For example, the number of grooves A can be one, two, or more. The embodiments of the present disclosure are not limited to this. For example, as shown in Figures 4A and 6, a groove A is provided on the surface of the exposed side of the pad 211.

[0090] For example, the orthographic projection of the groove A on the first protective layer 1 can be any one of a sawtooth shape, a cross shape, or a polygon; wherein the polygon can be any one of a triangle, a pentagon, a hexagon, etc. Of course, the projection of the groove A on the first protective layer 1 can also be any shape. The embodiments of the present disclosure are not limited to this.

[0091] Exemplarily, when at least one groove A is formed on the exposed surface of the pad 211 , the bonding portion 30 includes at least one protrusion extending into the groove A.

[0092] It is understood that the protrusions of the bonding portion 30 and the grooves A of the pad 211 match each other. Specifically, this can include matching in shape, number, and position. The number of protrusions on the bonding portion 30 is the same as the number of grooves A on the pad, and there is a one-to-one correspondence between the protrusions of the bonding portion 30 and the grooves A on the pad. That is, one protrusion of the bonding portion 30 is located within one groove A on the pad.

[0093] Alternatively, if the number of grooves A on the pad 211 is one, the number of protrusions on the bonding portion 30 may also be one; if the number of grooves A on the pad 211 is two, the number of protrusions on the bonding portion 30 may also be two. FIG. 6 illustrates a case where a groove A is provided on the exposed side of the pad 211. In this case, referring to FIG. 6 and FIG. 7A , the bonding portion 30 includes a protrusion that extends into the groove A. In this case, in the cross-sectional view of the flexible circuit board assembly 400, the bonding portion 30 is T-shaped.

[0094] Exemplarily, the protrusion of the bonding portion 30 extends into the groove A of the pad 211 and fits tightly against the bottom wall and side walls of the groove A.

[0095] With the above arrangement, by providing the groove A on the surface of the exposed side of the pad 211, the surface area of ​​the pad 211 exposed by the first opening 31 is increased, thereby increasing the contact area between the bonding portion 30 and the pad 211, thereby improving the welding quality between the optical component 20 and the flexible circuit board 10; at the same time, the area space that can accommodate the bonding portion 30 is increased. When the bonding portion 30 is formed by a welding technique such as reflow soldering or dip soldering, the bonding portion 30 can also be filled in the groove A of the pad 211, thereby further improving the stability and firmness of the welding between the optical component 20 and the flexible circuit board 10, effectively improving the problem of poor welding between the optical component 20 and the flexible circuit board 10, and ensuring the effectiveness of the electrical connection between the optical component 20 and the flexible circuit board 10; at the same time, it can also improve the phenomenon of abnormal transmission between the optical component 20 and the flexible circuit board 10 caused by the fracture of the welding point between the optical component 20 and the flexible circuit board 10 due to collision during transportation.

[0096] It should be noted that there are many specific configuration methods for the groove A, which can be selected according to actual needs.

[0097] In one implementation, as shown in FIG4A , the bottom wall aa of the groove A is located within the pad 211 . That is, the groove A only passes through a portion of the pad 211 . In this case, both the bottom wall aa and the side wall bb of the groove A are located within the pad 211 .

[0098] As shown in Figures 4A and 5, the bonding portion 30 contacts the bottom wall aa and side wall bb of the groove A, thereby increasing the contact area between the solder and the pad 211, ensuring the welding quality between the optical component 20 and the flexible circuit board 10, and improving the product yield; moreover, the bottom wall aa and side wall bb of the groove A are both located within the pad 211, that is, the contact area between the bonding portion 30 and the pad 211 is large, ensuring good connectivity between the bonding portion 30 and the pad 211, thereby ensuring the effectiveness of the electrical connection between the optical component 20 and the flexible circuit board 10.

[0099] Furthermore, as shown in FIG. 4A , when the bottom wall aa of the groove A is located within the pad 211 , the side wall bb of the groove A is flush with the edge of the first opening 31 .

[0100] Exemplarily, as shown in FIG. 4A , the orthographic projection of the groove A on the first protective layer 1 coincides with the orthographic projection of the first opening 31 on the first protective layer 1 .

[0101] In this case, as shown in FIG. 5 , a portion of the bonding portion 30 is located in the groove A, and the orthographic projection of the bonding portion 30 on the first protective layer 1 coincides with the orthographic projection of the groove A on the first protective layer 1 .

[0102] In this embodiment, by making the side wall bb of the groove A flush with the edge of the first opening 31, the space in the groove A for accommodating the bonding portion 30 can be greatly increased, so that the material of the bonding portion 30 is increased, which is beneficial to further improve the welding quality between the optical component 20 and the flexible circuit board 10 and ensure the stability of signal transmission between the optical component 20 and the flexible circuit board 10.

[0103] Furthermore, in combination with Figures 4A and 5, the bottom wall aa of the groove A is fitted with the surface of the bonding portion 30 close to the first protective layer 1. Since the bottom wall aa of the groove A is a flat surface, when the bonding portion 30 is formed by welding techniques such as reflow soldering or dip soldering, the bonding portion 30 and the pad 211 can be tightly combined, further ensuring the welding quality between the optical component 20 and the flexible circuit board 10, and reducing the probability of fracture at the welding point between the optical component 20 and the flexible circuit board 10 due to loose welding between the optical component 20 and the flexible circuit board 10, resulting in collision or vibration during transportation or other environments (for example, the flexible circuit board 10 is bent), thereby greatly improving the product yield.

[0104] In another implementation, as shown in FIG. 6 , the groove A passes through the pad 211 .

[0105] Exemplarily, as shown in FIG6 , the orthographic projection of the groove A on the first protective layer 1 is located within the range of the orthographic projection of the first opening 31 on the first protective layer 1 .

[0106] Exemplarily, as shown in FIG. 6 , the bottom wall aa of the groove A is located in the insulating layer close to the first conductive layer 21 .

[0107] For example, in combination with Figures 6 to 7B, when the groove A passes through the pad 211 and the number of grooves A is one, the shape of the positive projection of the pad 211 on the first protective layer 1 is annular. At this time, the pad 211 is different from the conventional rectangular pad mentioned above and can be called an irregular pad 211.

[0108] In this case, a portion of the bonding portion 30 is located in the groove A and contacts the bottom wall aa and side wall bb of the groove A, thereby increasing the contact area between the bonding portion 30 and the pad 211, thereby improving the welding quality between the optical component 20 and the flexible circuit board 10; moreover, the groove A passes through the pad 211, further increasing the space in the groove A for accommodating the bonding portion 30, thereby increasing the material of the bonding portion 30, thereby further ensuring the welding quality between the optical component 20 and the flexible circuit board 10, and ensuring the stability of signal transmission between the optical component 20 and the flexible circuit board 10.

[0109] In some embodiments, as shown in Figures 8 and 9, the orthographic projection of the end of the first opening 31 away from the first protective layer 1 on the first protective layer 1 is within the range of the orthographic projection of the end of the first opening 31 close to the first protective layer 1 on the first protective layer 1. In other words, the cross-sectional area of ​​the end of the first opening 31 away from the first protective layer 1 is smaller than the cross-sectional area of ​​the end of the first opening 31 close to the first protective layer 1.

[0110] Illustratively, in the cross-sectional view of the flexible circuit board 10 , the first opening 31 has a trapezoidal shape.

[0111] Among them, the end of the first opening 31 close to the first protective layer 1 can expose the entire surface of the pad 211 close to the second protective layer 3; it can also expose a part of the surface of the pad 211 close to the second protective layer 3, and the embodiments of the present disclosure are not limited to this.

[0112] In this example, as shown in FIG9 , the bonding portion 30 is filled within the first opening 31. The sidewalls of the leads 201 of the optical component 20 are in contact with the end of the first opening 31 away from the first protective layer 1, or there is a small gap between them. At this point, the bonding portion 30 is in contact with the bottom surface and part of the side surface of the leads 201 of the optical component 20.

[0113] With the above arrangement, when the bonding portion 30 is formed by a soldering technique such as reflow soldering or dip soldering, since the cross-sectional area of ​​the end of the first opening 31 away from the first protective layer 1 is smaller than the cross-sectional area of ​​the end of the first opening 31 close to the first protective layer 1, when the pin 201 of the optical component 20 extends into the first opening 31, the side surface of the pin 201 does not fit the first opening 31. Therefore, after the solder used to form the bonding portion 30 is liquefied, the liquid solder can climb along the bottom surface of the pin 201 of the optical component 20 close to the pad 211 to both sides of the pin 201, that is, the solder is not only located at the pin 201 of the optical component 20 close to the pad 211, but also at the bottom surface of the pin 201 of the optical component 20 close to the pad 211. The bottom surface of the optical component 20 is also located on both sides of the pin 201 of the optical component 20, further increasing the contact area between the pin 201 of the optical component 20 and the bonding portion 30, thereby improving the welding quality between the optical component 20 and the flexible circuit board 10, effectively avoiding the optical component 20 and the flexible circuit board 10 from being disconnected at the welding position, and increasing the stability between the optical component 20 and the flexible circuit board 10; moreover, by changing the size of the two ends of the first opening 31, a stable connection between the optical component 20 and the flexible circuit board 10 is achieved, the process is simple, the operation is feasible, the processing cost is relatively low, and it can be mass-produced and used.

[0114] In some embodiments, as shown in FIG. 10 , the pad 211 includes a sub-portion 211 a and at least one branch portion 211 b .

[0115] As shown in Figure 10 , the sub-section 211a includes a first node a1 and a second node a2 spaced apart from each other, and the branch 211b includes a first end b1 and a second end b2 opposite each other. The first end b1 is connected to the first node a1, and the second end b2 is connected to the second node a2. In other words, the sub-section 211a and at least one branch 211b are connected in parallel.

[0116] For example, the number of the branches 211 b in the pad 211 may be one, two, or more, which is not limited in the embodiments of the present disclosure.

[0117] It can be understood that the portion of the pad 211 exposed by the first opening 31 is connected to the pin 201 of the optical component 20, and the end of the pad 211 away from the second protective layer 3 is connected to the trace on the flexible circuit board 10, thereby realizing the electrical connection between the optical component 20 and the flexible circuit board 10.

[0118] When the soldering pad 211 includes a sub-portion 211a and at least one branch 211b, the pins 201 of the optical component 20 can be connected to the traces on the flexible printed circuit board 10 via the sub-portion 211a, and the pins 201 of the optical component 20 can also be connected to the traces on the flexible printed circuit board 10 via the branch 211b. If one of the sub-portion 211a and the at least one branch 211b is poorly soldered to the optical component 20, the optical component 20 can still be connected to the traces on the flexible printed circuit board 10 via the other of the sub-portion 211a and the at least one branch 211b. This reduces the likelihood of poor communication between the optical component 20 and the flexible printed circuit board 10, ensuring the effectiveness of the electrical connection between the optical component 20 and the flexible printed circuit board 10.

[0119] As can be seen from the above, the portion of the pad 211 exposed by the first opening 31 is electrically connected to the optical component 20 via the bonding portion 30. As shown in Figure 10, both the sub-portion 211a and the branch 211b of the pad 211 can be electrically connected to the optical component 20. In this case, the first opening 31 can simultaneously expose the sub-portion 211a and the branch 211b of the pad 211. It can be understood that the first opening 31 also exposes the gap between the sub-portion 211a and the branch 211b, and the bonding portion 30 can also fill this gap, thereby increasing the material of the bonding portion 30, thereby increasing the welding strength between the optical component 20 and the flexible circuit board 10, further ensuring the welding quality between the optical component 20 and the flexible circuit board 10, and ensuring the stability of signal transmission between the optical component 20 and the flexible circuit board 10.

[0120] Furthermore, when electrical connection can be achieved between the optical component 20 and the flexible circuit board 10 through the sub-part 211a or any one of the branches 211b, when the bonding part 30 is formed by a welding technique such as reflow soldering or dip soldering, the welding angle between the optical component 20 and the flexible circuit board 10 and the required amount of the bonding part 30 can be independently selected, thereby further improving the welding effect between the optical component 20 and the flexible circuit board 10.

[0121] In some embodiments, the pins of some optical components 20 (for example, ALS devices) are relatively small. When the optical components 20 are mounted on the surface of the flexible circuit board 10 through the SMT process, it is difficult to accurately align the pins of the ALS device with the solder pads 211 of the flexible circuit board 10. When there is a slight misalignment between the pins of the ALS device and the solder pads of the flexible circuit board 10, it will cause poor welding (for example, loose welding) between the ALS device and the flexible circuit board 10, thereby causing abnormal signal transmission between the ALS device and the flexible circuit board 10, affecting the product yield.

[0122] In the above-mentioned embodiment of the present application, the pad 211 includes a sub-portion 211a and at least one branch 211b, and the first opening 31 exposes the sub-portion 211a and the branch 211b of the pad 211 at the same time. The area of ​​the positive projection of the portion of the pad 211 exposed by the first opening 31 on the plane where the first protective layer 1 is located is increased, thereby reducing the difficulty of aligning the pins of the ALS device with the pad 211 of the flexible circuit board 10, reducing the probability of poor welding between the ALS device and the flexible circuit board 10, and ensuring the effectiveness of the electrical connection between the optical component 20 and the flexible circuit board 10.

[0123] In some embodiments, as shown in FIG. 10 , the pad 211 includes a plurality of branches 211 b located on both sides of the sub-portion 211 a , and the plurality of branches 211 b are symmetrically arranged with respect to the sub-portion 211 a .

[0124] For example, the number of branches 211b included in the pad 211 is an even number, and the even number of branches 211b is evenly distributed on both sides of the sub-section 211a. For example, the number of branches 211b included in the pad 211 can be two, four, six, eight, etc. Figure 10 illustrates two branches 211b, which are located on both sides of the sub-section 211a.

[0125] In this embodiment, the multiple branches 211b are independent of each other and can all realize the electrical connection between the optical component 20 and the flexible circuit board 10, thereby improving the effectiveness of the electrical connection between the optical component 20 and the flexible circuit board 10; moreover, the multiple branches 211b are symmetrically arranged about the sub-part 211a. When the bonding part 30 is formed by welding technology such as reflow soldering or dip soldering, different positions of the pad 211 are subjected to uniform force, thereby ensuring the stability of welding and the welding quality between the optical component 20 and the flexible circuit board 10.

[0126] In some embodiments, as shown in Figure 11, the conductive layer 2 that is next closest to the second protective layer 3 among the multiple conductive layers 2 is the second conductive layer 22; the second conductive layer 22 includes a plurality of pad auxiliary portions 221; the flexible circuit board 10 also includes: an insulating layer 4 arranged between the first conductive layer 21 and the second conductive layer 22, and a plurality of vias 41 are provided in the insulating layer 4; the pads 211 are connected to the pad auxiliary portions 221 through the vias 41.

[0127] Exemplarily, the insulating layer 4 can be made of at least one of polyimide (PI) material, polydimethylsiloxane (PDM), liquid crystal polymer (LCP) material, modified polyimide (MPI) material, platinum catalyzed silica gel (ecoflex) material, and hydrogel.

[0128] For example, conductive material may be filled into the via hole 41 by electroplating or other processes, thereby electrically connecting the pad 211 and the pad auxiliary portion 221. In this case, the pad 211 and the pad auxiliary portion 221 form a "double pad" design.

[0129] For example, the end of the pad 211 near the first protective layer 1 is connected to the wire in the flexible circuit board 10 through the pad auxiliary portion 221. The signal in the flexible circuit board 10 is transmitted to the pin of the optical component 20 through the pad 211 and the pad auxiliary portion 221, ensuring the functional use of the optical component 20.

[0130] In this embodiment, by providing a pad auxiliary portion 221, the pad 211 and the pad auxiliary portion 221 located on different conductive layers 2 constitute a "double pad" design, thereby improving the connection strength between the flexible circuit board 10 and the optical component 20 and ensuring the stability of the connection between the flexible circuit board 10 and the optical component 20.

[0131] In some embodiments, as shown in FIG. 11 , the orthographic projection of the pad 211 on the first protection layer 1 at least partially overlaps with the orthographic projection of the pad auxiliary portion 221 on the first protection layer 1 .

[0132] It should be noted that the above-mentioned “the orthographic projection of the solder pad 211 on the first protective layer 1 at least partially overlaps with the orthographic projection of the solder pad auxiliary part 221 on the first protective layer 1” includes two situations: the orthographic projection of the solder pad 211 on the first protective layer 1 partially overlaps with the orthographic projection of the solder pad auxiliary part 221 on the first protective layer 1, and the orthographic projection of the solder pad 211 on the first protective layer 1 completely overlaps with the orthographic projection of the solder pad auxiliary part 221 on the first protective layer 1.

[0133] For example, as shown in FIG11 , the orthographic projection of the pad 211 on the first protective layer 1 completely overlaps with the orthographic projection of the pad auxiliary portion 221 on the first protective layer 1. In this case, the same mask can be used to form the pad 211 and the pad auxiliary portion 221, thereby simplifying the manufacturing process of the flexible circuit board 10 and reducing the manufacturing cost of the flexible circuit board 10.

[0134] The embodiment of the present disclosure further provides a method for preparing a flexible circuit board 10, which is used to prepare the above-mentioned flexible circuit board 10. As shown in FIG12 , the method for preparing the flexible circuit board 10 includes steps S1 to S4.

[0135] S1: As shown in FIG13A , a copper-clad substrate 01 is provided. The copper-clad substrate 01 includes a plurality of conductive layers 2 stacked in sequence. Among the plurality of conductive layers 2 , a conductive layer 2 located at the top layer is a first conductive layer 21 .

[0136] For example, the number of the conductive layers 2 included in the copper-clad substrate 01 may be one, two, or multiple layers, which is not limited in the embodiments of the present disclosure.

[0137] Furthermore, the copper-clad substrate 01 is composed of at least one layer of copper-clad laminate. Copper-clad laminate, also known as copper-clad foil laminate, is a sheet-like material made by impregnating a reinforcing material with resin, coating one or both sides with copper foil, and then hot-pressing. Copper-clad laminates include single-sided and double-sided copper-clad laminates. Single-sided copper-clad laminates include an insulating layer and a conductive layer located on one side of the insulating layer; double-sided copper-clad laminates include an insulating layer and two conductive layers located on either side of the insulating layer.

[0138] When the copper-clad substrate 01 includes a single conductive layer 2, the copper-clad substrate 01 can be composed of a single-sided copper-clad laminate. When the copper-clad substrate 01 includes multiple conductive layers 2, the copper-clad substrate 01 can be composed of multiple double-sided copper-clad laminates; or, it can be composed of multiple single-sided copper-clad laminates; or, it can be composed of multiple single-sided copper-clad laminates and multiple double-sided copper-clad laminates. The embodiments of the present disclosure are not limited to this. For example, as shown in Figure 13A, the copper-clad substrate 01 is composed of a double-sided copper-clad laminate and a single-sided copper-clad laminate. In this case, the copper-clad substrate 01 includes three conductive layers 2.

[0139] S2 : As shown in FIG. 13B , a plurality of pads 211 are formed in the first conductive layer 21 .

[0140] For example, in this step, other conductive layers 2 in the copper-clad substrate 01 can be etched simultaneously, and conductive patterns (e.g., pads 211 and signal traces of the flexible circuit board 10) can be formed simultaneously in multiple conductive layers 2. This simplifies the manufacturing process of the flexible circuit board 10.

[0141] For example, when part of the signal traces of the flexible circuit board 10 are located in the first conductive layer 21 , the part of the signal traces can be formed on the first conductive layer 21 simultaneously when the plurality of pads 211 are formed.

[0142] The above-mentioned step S2 may specifically include: forming a layer of photoresist on the first conductive layer 21, then exposing and developing the photoresist layer to form multiple openings on the photoresist layer, and then using the developed photoresist layer as a mask to etch and remove the portion of the first conductive layer 21 corresponding to the opening to form a pad 211 and part of the signal line.

[0143] Illustratively, after this step, the method may further include: forming an interlayer conductive structure to connect signal traces in different conductive layers 2 , or to connect pads 211 to signal traces in other conductive layers 2 .

[0144] S3: As shown in Figure 13C, a second protective layer 3 is formed on the side of the first conductive layer 21 away from the other conductive layers 2; the second protective layer 3 has a plurality of first openings 31, and the plurality of first openings 31 respectively expose a portion of the plurality of 211; the area of ​​the orthographic projection of each first opening 31 on the first protective layer 1 is smaller than the surface area of ​​the pad 211.

[0145] The surface area of ​​the pad 211 may refer to the description in some of the above embodiments, which will not be repeated here.

[0146] For example, the material of the second protective layer 3 can refer to the description in some of the above embodiments, which will not be repeated here.

[0147] S4: As shown in FIG13D , a first protective layer 1 is formed on a side of the plurality of conductive layers 2 away from the second protective layer 3 .

[0148] For example, the material of the first protective layer 1 can refer to the description in some of the above embodiments, which will not be repeated here.

[0149] It should be noted that some steps of the above-mentioned manufacturing method may be performed simultaneously, or may be performed in an order different from that shown in FIG12. For example, steps S3 and S4 may be performed simultaneously, that is, the second protective layer 3 is formed on the side of the first conductive layer 21 away from the other conductive layers 2, and the first protective layer 1 is formed on the side of the multiple conductive layers 2 away from the second protective layer 3.

[0150] The method for preparing a flexible circuit board 10 provided in some embodiments of the present disclosure can be used to prepare the flexible circuit board 10 of any of the above-mentioned embodiments. In the flexible circuit board 10 prepared by this method, the surface area of ​​the pad 211 exposed by the first opening 31 is larger than the area of ​​the orthographic projection of the first opening 31 on the first protective layer 1. When the optical component 20 and the flexible circuit board 10 are electrically connected via the bonding portion 30, the contact area between the pad 211 and the bonding portion 30 is larger, thereby enhancing the welding strength between the optical component 20 and the flexible circuit board 10, making the welding between the optical component 20 and the flexible circuit board 10 more secure, improving the welding quality between the optical component 20 and the flexible circuit board 10, and reducing the probability of fracture at the weld between the optical component 20 and the flexible circuit board 10 due to a weak welding between the optical component 20 and the flexible circuit board 10 in the event of collision or vibration during transportation, thereby ensuring the effectiveness of the electrical connection between the optical component 20 and the flexible circuit board 10.

[0151] In some embodiments, the conductive layer 2 next closest to the second protective layer 3 among the multiple conductive layers 2 is the second conductive layer 22; the copper-clad substrate 01 further includes an insulating layer 4 disposed between the first conductive layer 21 and the second conductive layer 22. Before forming the first protective layer 1 on the side of the multiple conductive layers 2 away from the second protective layer 3, the above-mentioned preparation method further includes: forming a plurality of vias 41 in the insulating layer 4; and forming a plurality of auxiliary pad portions 221 in the second conductive layer 22, wherein the pads 211 are connected to the auxiliary pad portions 221 through the vias 41.

[0152] The material of the insulating layer 4 can refer to the description in some of the above embodiments and will not be repeated here.

[0153] For example, conductive material may be filled into the via hole 41 by electroplating or other processes, thereby electrically connecting the pad 211 and the pad auxiliary portion 221. In this case, the pad 211 and the pad auxiliary portion 221 form a "double pad" design.

[0154] In this embodiment, a pad auxiliary portion 221 is formed in the second conductive layer 22 close to the first conductive layer 21, so that the pad 211 and the pad auxiliary portion 221 located on different conductive layers 2 constitute a "double pad" design, thereby improving the connection strength between the flexible circuit board 10 and the optical component 20 and ensuring the stability of the connection between the flexible circuit board 10 and the optical component 20.

[0155] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that a person skilled in the art can conceive within the technical scope disclosed in the present disclosure should be included within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A flexible circuit board, comprising: A first protective layer; A plurality of conductive layers disposed on the first protective layer and sequentially stacked in a direction perpendicular to the first protective layer; And A second protective layer disposed on a side of the plurality of conductive layers away from the first protective layer; Wherein, among the plurality of conductive layers, the conductive layer closest to the second protective layer is a first conductive layer, and the first conductive layer includes a plurality of pads; the second protective layer is provided with a first opening at a position corresponding to the pad, and at least a part of the pad is exposed through the first opening; the area of the orthographic projection of each first opening on the first protective layer is smaller than the surface area of the pad.

2. The flexible circuit board according to claim 1, wherein, At least one groove is formed on a surface of the pad where it is exposed.

3. The flexible circuit board according to claim 2, wherein, The groove penetrates through the pad.

4. The flexible circuit board according to claim 2, wherein, The bottom wall of the groove is located within the pad.

5. The flexible circuit board according to claim 4, wherein, The side wall of the groove is flush with the edge of the first opening.

6. The flexible circuit board according to claim 1, wherein, The orthographic projection of the end of the first opening away from the first protective layer on the first protective layer is located within the range of the orthographic projection of the end of the first opening close to the first protective layer on the first protective layer.

7. The flexible circuit board according to claim 1, wherein, The pad includes a sub - part and at least one branch - part; The sub - part includes a first node and a second node arranged at intervals, the branch - part includes an opposite first end and a second end, the first end is connected to the first node, and the second end is connected to the second node.

8. The flexible circuit board according to claim 7, wherein the pad includes a plurality of branch - parts located on both sides of the sub - part, and the plurality of branch - parts are symmetrically arranged with respect to the sub - part.

9. The flexible circuit board according to any one of claims 1 to 8, wherein, Among the plurality of conductive layers, the conductive layer next to the second protective layer is a second conductive layer; the second conductive layer includes a plurality of pad auxiliary parts; The flexible circuit board further includes: an insulating layer disposed between the first conductive layer and the second conductive layer, and a plurality of vias are formed in the insulating layer; The pad is connected to the pad auxiliary part through the via.

10. The flexible circuit board according to claim 9, wherein, The orthographic projection of the pad on the first protective layer and the orthographic projection of the pad auxiliary part on the first protective layer at least partially overlap.

11. A method for manufacturing a flexible circuit board, wherein A copper - clad substrate is provided, the copper - clad substrate includes a plurality of conductive layers sequentially stacked, and one of the conductive layers located at the top layer is a first conductive layer; A plurality of pads are formed in the first conductive layer; A second protective layer is formed on a side of the first conductive layer away from other conductive layers; the second protective layer has a plurality of first openings, and each of the first openings exposes a part of the plurality of pads; the area of the orthographic projection of each first opening on the first protective layer is smaller than the surface area of the pad; A first protective layer is formed on a side of the plurality of conductive layers away from the second protective layer.

12. The preparation method according to claim 11, wherein, Among the plurality of conductive layers, the conductive layer next to the second protective layer is a second conductive layer; the copper - clad substrate further includes: an insulating layer disposed between the first conductive layer and the second conductive layer; before forming the first protective layer on a side of the plurality of conductive layers away from the second protective layer, the manufacturing method further includes: Forming a plurality of vias in the insulating layer; A plurality of pad assisting portions are formed in the second conductive layer, and the pads are connected to the pad assisting portions through vias.

13. A flexible circuit board assembly, comprising: A flexible circuit board, which is the flexible circuit board according to any one of claims 1 to 10; An optical component, which includes a plurality of pins; Bonding portions located in respective first openings of the flexible circuit board; the pins are bonded to the pads of the flexible circuit board through the bonding portions.

14. A display device, comprising: A display panel; A flexible circuit board assembly, located on a non-light-emitting side of the display panel and coupled to the display panel, which is the flexible circuit board assembly according to claim 13.

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