Method for preparing flexible circuit board and flexible circuit board

Abstract

The flexible circuit board of the present application includes a flexible substrate and at least one circuit component disposed on the flexible substrate. The flexible substrate is provided with a first bonding portion and at least one metal foil pattern layer. The circuit component is provided with a second bonding portion. Wirebonds are formed between the first and second bonding portions. The metal foil pattern layer includes a first reinforcement portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion and / or a second reinforcement portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion. The present application provides at least one metal foil pattern layer at the wire bonding site of the flexible circuit board to form a permanent reinforcement structure. This ensures that the flatness and strength requirements of the bonding site are met during wire bonding, while also meeting the flexibility requirements of the flexible circuit board.

Description

Technical Field

[0001] The present application relates to the field of flexible electronic technology, and in particular to a method for preparing a flexible circuit board and a flexible circuit board. Background Art

[0002] The rapid development of flexible display and flexible electronic technologies has brought revolutionary changes to electronic products, making electronic products in the fields of wearable devices and electronic terminals show more and more flexible deformation capabilities.

[0003] Currently, flexible electronics packaging is primarily based on traditional semiconductor packaging processes, which are unable to fully adapt to or meet the performance requirements of flexible electronics. For example, in the COB (Chip on Board) process for flexible circuit boards, if wire bonding is performed without adding any reinforcement to the flexible substrate, the bonding pads lack sufficient hardness and rigidity, resulting in low bonding efficiency, poor bonding reliability, and even chip breakage due to uneven force, resulting in a low bond pass rate. Summary of the Invention

[0004] In response to the above technical problems, the present application provides a flexible circuit board that can meet the flatness and strength requirements of the bonding position during wire bonding, while also meeting the flexibility requirements of the flexible circuit board.

[0005] To solve the above technical problems, the present application provides a flexible circuit board, comprising a flexible substrate and at least one circuit component arranged on the flexible substrate, the flexible substrate being provided with a first bonding portion and at least one metal foil pattern layer, the circuit component being provided with a second bonding portion, the first bonding portion and the second bonding portion being wire-bonded, the metal foil pattern layer including a first reinforcement portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion and / or a second reinforcement portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion.

[0006] The metal foil pattern layer includes the first reinforcement portion and the second reinforcement portion, and the first reinforcement portion and the second reinforcement portion are continuous or disconnected from each other.

[0007] The metal foil pattern layer at least includes the second reinforcing portion, and a projection of the second reinforcing portion in the thickness direction of the flexible substrate covers the arrangement area of ​​the circuit components.

[0008] The metal foil pattern layer at least includes the first reinforcement portion, and the pattern of the first reinforcement portion is consistent with the arrangement pattern of the first bonding portion.

[0009] The flexible substrate includes at least one stacked flexible substrate, at least one surface of the flexible substrate is provided with the metal foil pattern layer, and adjacent metal foil pattern layers are insulated from each other.

[0010] Wherein, the metal foil pattern layer also includes the routing pattern of the flexible circuit board.

[0011] Wherein, the thickness of the metal foil pattern layer is 5-25 μm.

[0012] The present application also provides a method for preparing a flexible circuit board, comprising:

[0013] a. Providing a flexible substrate on which a circuit component is to be fabricated, the flexible substrate having a first bonding portion and at least one metal foil pattern layer, the circuit component having a second bonding portion, the metal foil pattern layer including a first reinforcement portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion and / or a second reinforcement portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion;

[0014] b. Producing at least one circuit component on the flexible substrate, wherein the circuit component is provided with the second bonding portion;

[0015] c. Wire-bonding the first bonding portion and the second bonding portion to obtain the flexible circuit board.

[0016] Wherein, step a comprises:

[0017] Providing a flexible substrate, wherein at least one side of the flexible substrate is covered with a metal foil;

[0018] When one side surface of the flexible substrate is covered with the metal foil, the first bonding portion and the second reinforcing portion are etched on the metal foil to obtain the flexible substrate;

[0019] When both opposite surfaces of the flexible substrate are covered with the metal foil, the first bonding portion, or the first bonding portion and the second reinforcing portion are etched on the metal foil on one side, and the first reinforcing portion and / or the second reinforcing portion are etched on the metal foil on the other side to obtain the flexible substrate.

[0020] Wherein, step a comprises:

[0021] a01 providing at least two layers of flexible substrate for laminating to form the flexible substrate, at least one side surface of the flexible substrate is covered with a metal foil;

[0022] a02. Etching the metal foil into a corresponding pattern according to the stacking position corresponding to the flexible substrate to obtain the first bonding portion and at least one metal foil pattern layer, and the metal foil pattern layer includes the first reinforcing portion and / or the second reinforcing portion;

[0023] a03. Stacking at least two layers of the flexible substrates together according to the corresponding stacking positions of the flexible substrates to obtain a flexible substrate.

[0024] Wherein, step a03 includes:

[0025] When the flexible substrate being etched is a top layer and one side surface is covered with the metal foil, a first bonding portion is etched on the metal foil, or the first bonding portion and the second reinforcing portion are etched;

[0026] When the flexible substrate being etched is the top layer and both opposite surfaces thereof are covered with the metal foil, the first bonding portion is etched on the metal foil on one side of the circuit component to be fabricated, or the first bonding portion and the second reinforcing portion are etched, and the first reinforcing portion and / or the second reinforcing portion are etched on the metal foil on the other side;

[0027] When the flexible substrate being etched is a non-top layer, the first reinforcing portion and / or the second reinforcing portion are etched on the metal foil.

[0028] Wherein, the method comprises:

[0029] If the pattern etched on the current metal foil includes the patterns of the first reinforcement portion and the second reinforcement portion, the first reinforcement portion and the second reinforcement portion are made continuous or disconnected from each other;

[0030] If the pattern etched on the current metal foil includes the second reinforcement portion or a pattern including the first reinforcement portion and the second reinforcement portion, the projection of the second reinforcement portion covers the fabrication area of ​​the circuit component;

[0031] If the pattern etched on the current metal foil includes the first reinforcing portion or a pattern including the first reinforcing portion and the second reinforcing portion, the etching pattern of the first reinforcing portion is made consistent with that of the first bonding portion.

[0032] Wherein, the method further includes:

[0033] When etching the metal foil, the wiring pattern of the flexible circuit board is also etched.

[0034] Wherein, the thickness of the metal foil pattern layer is 5-25 μm.

[0035] The present application also provides a flexible circuit board, which is prepared using the above-mentioned method for preparing a flexible circuit board.

[0036] The flexible circuit board of the present application forms a permanent reinforcement structure by setting at least one metal foil pattern layer at the lead bonding point of the flexible circuit board, which can not only meet the flatness and strength requirements of the bonding position during wire bonding, but also support and protect the finished product after the wire bonding is completed, making it easier to store, use and transfer the finished product, while meeting the flexibility requirements of the flexible circuit board.

[0037] The method for preparing a flexible circuit board of the present application provides at least one metal foil pattern layer on a flexible substrate, wherein the metal foil pattern layer includes a first reinforcement portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion and / or a second reinforcement portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion, thereby forming at least one metal foil pattern layer in the flexible circuit board as a permanent reinforcement structure, which can not only meet the flatness and strength requirements of the bonding position during wire bonding, but also support and protect the finished product after wire bonding is completed, thereby facilitating the storage, use and transfer of the finished product, and at the same time meeting the flexibility requirements of the flexible circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a structural schematic diagram of a flexible circuit board according to the first embodiment of the present application;

[0039] Figure 2 1 is a schematic structural diagram of a flexible substrate of a flexible circuit board according to the first embodiment of the present application;

[0040] Figure 3 is a schematic side view of a flexible circuit board according to the first embodiment of the present application;

[0041] Figure 4 is a schematic side view of a flexible circuit board according to a second embodiment of the present application;

[0042] Figure 5 is a schematic structural diagram of a flexible circuit board according to the third embodiment of the present application;

[0043] Figure 6 is a schematic side view of a flexible circuit board according to a third embodiment of the present application;

[0044] Figure 7 is a schematic structural diagram of a flexible circuit board according to a fourth embodiment of the present application, not showing a flexible substrate;

[0045] Figure 8 is a side view schematic diagram of a flexible circuit board according to a fourth embodiment of the present application;

[0046] Figure 9is a side view schematic diagram of a flexible circuit board according to a fifth embodiment of the present application;

[0047] Figure 10 1 is a flow chart of a method for preparing a flexible circuit board according to the sixth embodiment of the present application. DETAILED DESCRIPTION

[0048] The following describes the implementation of the present application through specific embodiments. People familiar with this technology can easily understand other advantages and effects of the present application from the contents disclosed in this specification.

[0049] In the following description, reference is made to the accompanying drawings, which illustrate several embodiments of the present application. It should be understood that other embodiments may also be used, and that mechanical composition, structural, electrical, and operational changes may be made without departing from the spirit and scope of the present application. The following detailed description should not be considered restrictive, and the scope of the embodiments of the present application is limited only by the claims of the published patents. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0050] Although the terms "first", "second", etc. are used herein to describe various elements in some instances, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0051] Furthermore, as used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms "comprise", "include" indicate the presence of the described features, steps, operations, elements, components, items, kinds, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Thus, "A, B, or C" or "A, B, and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B, and C". Exceptions to this definition occur only when the combination of elements, functions, steps, or operations is inherently mutually exclusive in some way.

[0052] A flexible circuit board according to an embodiment of the present application includes a flexible substrate and at least one circuit component disposed on the flexible substrate. The flexible substrate is provided with a first bonding portion and at least one metal foil pattern layer. The circuit component is provided with a second bonding portion. Wire bonding is performed between the first bonding portion and the second bonding portion. The metal foil pattern layer includes a first reinforcement portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion and / or a second reinforcement portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion. "Covering" means that the projection is located directly below the first bonding portion and / or the second bonding portion and that the projection has an area greater than or equal to the area of ​​the first bonding portion and / or the second bonding portion, thereby obscuring the first bonding portion and / or the second bonding portion. Thus, by providing at least one metal foil pattern layer at the wire bonding location of the flexible circuit board, a permanent reinforcement structure is formed. This structure not only meets the flatness and strength requirements of the bonding location during wire bonding, but also provides support and protection for the finished product after wire bonding, facilitating storage, use, and transfer of the finished product. Furthermore, the flexible requirements of the flexible circuit board are met.

[0053] It should be noted that "metal foil pattern layer" broadly refers to a pattern layer formed by etching metal foil, but this application defines the metal foil pattern layer as including a portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion and / or the second bonding portion. Therefore, the "metal foil pattern layer" in this application refers to a pattern layer that includes a portion for supporting the first bonding portion and / or the second bonding portion. As such, it can be understood that since there is no situation where the projection of the first bonding portion itself covers itself or the first bonding portion supports itself, although the pattern layer where the first bonding portion is located can also be obtained by etching metal foil, when the pattern layer where the first bonding portion is located does not include a portion for supporting the second bonding portion, the pattern layer where the first bonding portion is located does not belong to the metal foil pattern layer in this application. Conversely, when the pattern layer where the first bonding portion is located includes a portion for supporting the second bonding portion, the pattern layer where the first bonding portion is located does belong to the metal foil pattern layer in this application.

[0054] The metal foil pattern layer is preferably a copper foil pattern layer. The number of metal foil pattern layers can be one, two, or more. The metal foil pattern layers are insulated from each other. The patterns of different metal foil pattern layers can be the same or different. However, each metal foil pattern layer includes a first reinforcement portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion and / or a second reinforcement portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion. In other words, the projection of a single metal foil pattern layer can cover only the first bonding portion, only the second bonding portion, or both the first and second bonding portions. The area covered by the projection of the metal foil pattern layer is the area where the metal foil pattern layer provides flatness and strength. When the metal foil pattern layer includes the first reinforcement portion, it can improve the flatness and strength during wire bonding on the flexible substrate, thereby improving the wire bonding pass rate. When the metal foil pattern layer includes the second reinforcement portion, it can improve the flatness and strength during wire bonding on the chip, thereby improving the wire bonding pass rate and reducing the probability of chip damage.

[0055] The pattern of the metal foil pattern layer can be optimized according to actual needs. For example, when the metal foil pattern layer includes a first reinforcement portion and a second reinforcement portion, the first reinforcement portion and the second reinforcement portion are continuous or disconnected; when the metal foil pattern layer includes a first reinforcement portion or includes a first reinforcement portion and a second reinforcement portion, the projection of the second reinforcement portion in the thickness direction of the flexible substrate covers the area where the circuit components are arranged; when the metal foil pattern layer includes a first reinforcement portion or includes a first reinforcement portion and a second reinforcement portion, the pattern of the first reinforcement portion is consistent with the layout pattern of the first bonding portion. In actual implementation, when the metal foil pattern layer only includes the first reinforcement portion, no pattern is set at the position corresponding to the second bonding portion, that is, a blank; when the metal foil pattern layer only includes the second reinforcement portion, no pattern is set at the position corresponding to the first bonding portion, that is, a blank. This ensures that the unsupported portion will not be uneven due to the presence of other patterns (such as the trace pattern of the flexible circuit board).

[0056] Typically, flexible circuit boards mostly use flexible copper clad laminate (FCCL) as the processing substrate for their flexible substrates. The flexible copper foil substrate is coated with copper foil on the surface of a polyimide base film. At least one metal foil pattern layer can be obtained by etching the copper foil on the surface of at least one flexible copper foil substrate. Therefore, in addition to the first reinforcement portion and / or the second reinforcement portion, the metal foil pattern layer can also include the routing pattern of the flexible circuit board. Both can be formed simultaneously in the same process, which is simple and mature.

[0057] The flexible circuit board of the present application is described in detail below through different embodiments.

[0058] First embodiment

[0059] Please refer to Figures 1 to 3 The flexible circuit board of this embodiment includes a flexible substrate 22 and at least one circuit component 21 disposed on the flexible substrate 22 .

[0060] The flexible substrate 22 includes a first bonding portion 221 and at least one flexible substrate. A metal foil pattern layer is provided on at least one surface of the flexible substrate. In this embodiment, the first bonding portion 221 is also a gold finger. The flexible substrate has two layers, each of which includes a flexible substrate, namely, a first flexible substrate 222 and a second flexible substrate 224. The metal foil pattern layer has two layers, including a first metal foil pattern layer 223 and a second metal foil pattern layer 225. The first bonding portion 221, the first flexible substrate 222, the first metal foil pattern layer 223, the second flexible substrate 224, and the second metal foil pattern layer 225 are arranged in sequence from top to bottom. In addition, in this embodiment, a protective film 226 is provided below the second metal foil pattern layer 225. The protective film 226 is a PI film. The surface of the first flexible substrate 222 is also provided with a positioning identification mark 25 and an orientation identification mark 26.

[0061] At least one side of each flexible substrate is provided with a metal foil pattern layer, with adjacent metal foil pattern layers being insulated from each other. In this embodiment, the first metal foil pattern layer 223 and the second metal foil pattern layer 225 are respectively etched from the metal foil formed on both sides of the second flexible substrate 224, while the first bonding portion 221 is etched from the metal foil formed on the upper surface of the first flexible substrate 222. An adhesive layer may also be provided between the first metal foil pattern layer 223 and the first flexible substrate 222, thereby forming a three-layer flexible substrate 22, i.e., a flexible substrate 22 having three layers of metal foil, the three layers of metal foil being the metal foil comprising the first metal foil pattern layer 223, the second metal foil pattern layer 225, and the first bonding portion 221.

[0062] The circuit component 21 is provided with a second bonding portion 211. The first bonding portion 221 is electrically connected to the second bonding portion 211 by bonding wires 23. In this embodiment, the circuit component 21 is a flexible bare chip that is attached to the flexible substrate 22 via a die attach film (DAF).

[0063] In this embodiment, the first metal foil pattern layer 223 includes a first reinforcement portion 2231 and a second reinforcement portion 2232 , and the second metal foil pattern layer 225 also includes a first reinforcement portion (located below the first reinforcement portion 2231 ) and a second reinforcement portion (located below the first reinforcement portion 2231 ). The pattern of the first reinforcing portion 2231 in the first metal foil pattern layer 223 is consistent with the pattern of the first reinforcing portion in the second metal foil pattern layer 225. The pattern of the second reinforcing portion 2232 in the first metal foil pattern layer 223 is consistent with the pattern of the second reinforcing portion in the second metal foil pattern layer 225. The projections of the first reinforcing portion 2231 and the second bonding portion 211 in the thickness direction of the flexible substrate 22 cover the areas where the first bonding portion 221 and the second bonding portion 211 are located. The projections of the second reinforcing portions cover the areas where the circuit components 21 are located. The first reinforcing portion and the second reinforcing portion in each metal foil pattern layer are continuously disposed, thereby forming a single piece of metal foil without any hollowing out. All the whole pieces of metal foil corresponding to different circuit components 21 in the same layer together constitute a bonding portion support pattern, which supports the first bonding portion 221 and the second bonding portion 211, improves the yield rate of wire bonding on the circuit components 21 and the flexible substrate 22, and prevents the circuit components 21 from being broken during wire bonding. In the gap between the entire metal foil corresponding to adjacent circuit components 21, the routing pattern of the flexible circuit board is arranged. The bonding portion support pattern and the routing pattern are formed simultaneously when etching the metal foil. The bonding portion support pattern and the routing pattern can be insulated from each other, or the bonding portion support pattern can be electrically connected to part of the routing pattern. At this time, the bonding portion support pattern can play a role in improving the signal of the circuit component 21.

[0064] Second embodiment

[0065] Please refer to Figure 4 The difference between the flexible circuit board of this embodiment and the first embodiment is that the first metal foil pattern layer 223 includes a first reinforcing portion 2231 and a second reinforcing portion 2232, and the second metal foil pattern layer 225 includes a first reinforcing portion 2251 and a second reinforcing portion 2252. The first reinforcing portion 2231 and the second reinforcing portion 2232 are disconnected from each other, and the first reinforcing portion 2251 and the second reinforcing portion 2252 are disconnected from each other. That is, the first reinforcing portion and the second reinforcing portion in each metal foil pattern layer are disconnected from each other.

[0066] For the remaining structures in this embodiment, please refer to the relevant description of the first embodiment and will not be repeated here.

[0067] Third embodiment

[0068] Please refer to Figure 5 and Figure 6The flexible circuit board of this embodiment includes a flexible substrate 32 and at least one circuit component 31 disposed on the flexible substrate 32 .

[0069] The flexible substrate 32 includes a first bonding portion 321 and at least one flexible substrate. A metal foil pattern layer is provided on at least one surface of the flexible substrate. In this embodiment, the flexible substrate comprises two layers, including a third flexible substrate 322 and a fourth flexible substrate 324. The metal foil pattern layers comprise two layers, each layer of the flexible substrate corresponding to a flexible substrate, namely, a third metal foil pattern layer 323 and a fourth metal foil pattern layer 325, respectively. The first bonding portion 321, the third flexible substrate 322, the third metal foil pattern layer 323, the fourth flexible substrate 324, and the fourth metal foil pattern layer 325 are arranged sequentially from top to bottom. In addition, in this embodiment, a protective film 326 is provided below the fourth metal foil pattern layer 325. Positioning identification marks and orientation identification marks are also provided on the surface of the third flexible substrate 322.

[0070] Each flexible substrate has a metal foil pattern layer on at least one side, with adjacent metal foil pattern layers insulated from each other. In this embodiment, the third metal foil pattern layer 323 and the fourth metal foil pattern layer 325 are respectively etched from metal foil formed on both sides of the fourth flexible substrate 324, while the first bonding portion 321 is etched from the metal foil formed on the upper surface of the third flexible substrate 322. An adhesive layer is also provided between the third metal foil pattern layer 323 and the third flexible substrate 322, thereby forming a three-layer flexible substrate 32. In other words, the flexible substrate 32 comprises three layers of metal foil, namely, the metal foil comprising the third metal foil pattern layer 323, the fourth metal foil pattern layer 325, and the first bonding portion 321.

[0071] The circuit component 31 is provided with a second bonding portion 311. The first bonding portion 321 is bonded to the second bonding portion 311 via a wire 33 to achieve electrical connection. In this embodiment, the circuit component 31 is a flexible bare chip, which is attached to the flexible substrate 32 via a die attach film (DAF).

[0072] In this embodiment, the third metal foil pattern layer 323 and the fourth metal foil pattern layer 325 only support the second bonding portion 311, that is, only include the second reinforcement portion. The pattern of the second reinforcement portion in the third metal foil pattern layer 323 and the second reinforcement portion in the fourth metal foil pattern layer 325 are consistent, and the projection in the thickness direction of the flexible substrate 32 covers the setting area of ​​the second bonding portion 311 and covers the entire setting area of ​​the circuit component 31, thereby forming a whole piece of metal foil without hollowing out, which has a better support effect. All the whole pieces of metal foil corresponding to different circuit components in the same layer together constitute the bonding portion support pattern, which plays the role of supporting the second bonding portion 311, improving the qualified rate of wire bonding on the circuit component 31 and preventing the circuit component 31 from being broken during wire bonding. In the gap between the entire metal foil corresponding to adjacent circuit components 31, the routing pattern of the flexible circuit board is arranged. The bonding portion support pattern and the routing pattern are formed simultaneously when etching the metal foil. The bonding portion support pattern and the routing pattern can be insulated from each other, or the bonding portion support pattern can be electrically connected to part of the routing pattern. At this time, the bonding portion support pattern can play a role in improving the signal of the circuit component 31.

[0073] In actual implementation, this embodiment can also provide a whole piece of metal foil on the upper surface of the third flexible substrate 322 at a position corresponding to the circuit component 31, forming a metal foil pattern layer whose projection covers the area where the second bonding portion 311 is provided, and the metal foil pattern layer also includes the pattern of the first bonding portion 321.

[0074] Please refer to Figure 7 and Figure 8 ,in Figure 7 The flexible substrate is not shown in the figure. The flexible circuit board of this embodiment includes a flexible substrate 42 and at least one circuit component 41 disposed on the flexible substrate 42.

[0075] The flexible substrate 42 includes a first bonding portion 421 and at least one flexible substrate. In this embodiment, the flexible substrate comprises two layers, each layer corresponding to a flexible substrate, namely, a fifth flexible substrate 422 and a sixth flexible substrate 424. The metal foil pattern layer comprises two layers, including a fifth metal foil pattern layer 423 and a sixth metal foil pattern layer 425. The first bonding portion 421, the fifth flexible substrate 422, the fifth metal foil pattern layer 423, the sixth flexible substrate 424, and the sixth metal foil pattern layer 425 are arranged in sequence from top to bottom. In addition, in this embodiment, a protective film 426 is provided below the sixth metal foil pattern layer 425. Positioning identification marks and orientation identification marks are also provided on the surface of the fifth flexible substrate 422.

[0076] Each flexible substrate has a metal foil pattern layer on at least one side, with adjacent metal foil pattern layers insulated from each other. In this embodiment, the fifth metal foil pattern layer 423 and the sixth metal foil pattern layer 425 are respectively etched from metal foil formed on both sides of the sixth flexible substrate 424, while the first bonding portion 421 is etched from the metal foil formed on the top surface of the fifth flexible substrate 422. An adhesive layer is also provided between the fifth metal foil pattern layer 423 and the fifth flexible substrate 422, thereby forming a three-layer flexible substrate 42. In other words, the flexible substrate 42 comprises three layers of metal foil, namely, the metal foil comprising the fifth metal foil pattern layer 423, the sixth metal foil pattern layer 425, and the first bonding portion 421.

[0077] The circuit component 41 is provided with a second bonding portion 411. The first bonding portion 421 is electrically connected to the second bonding portion 411 via a wire 43. In this embodiment, the circuit component 41 is a flexible bare chip that is attached to the flexible substrate 42 via a die attach film (DAF).

[0078] In this embodiment, the fifth metal foil pattern layer 423 and the sixth metal foil pattern layer 425 only support the first bonding portion 421, that is, only include the first reinforcement portion. The pattern of the first reinforcement portion of the fifth metal foil pattern layer 423 and the first reinforcement portion of the sixth metal foil pattern layer 425 are the same, and are both consistent with the layout pattern of the first bonding portion 421. Therefore, when the projection in the thickness direction of the flexible substrate 42 covers the first bonding portion 421, a structure of a whole metal foil is not formed, leaving a hollow position, which has better flexibility and can improve the qualified rate of wire bonding on the flexible substrate 42. The first reinforcement portion in the fifth metal foil pattern layer 423 and the sixth metal foil pattern layer 425 constitutes a bonding portion support pattern, which supports the first bonding portion 421. The fifth metal foil pattern layer 423 and the sixth metal foil pattern layer 425 also contain a routing pattern for the flexible circuit board. The bonding portion support pattern and the routing pattern are formed simultaneously during the etching of the metal foil. The bonding portion support pattern and the routing pattern can be insulated from each other, or the bonding portion support pattern can be electrically connected to a portion of the routing pattern. In this case, the bonding portion support pattern can improve the signal transmission of the circuit component 41. Preferably, the projection of the fifth metal foil pattern layer 423 and the sixth metal foil pattern layer 425 in the thickness direction of the flexible substrate 42 is blank in the area where the circuit component 41 is located. That is, there is no metal foil pattern below the circuit component 41, thereby improving the flatness and flexibility of the circuit component 41.

[0079] For a flexible circuit board having at least two layers of metal foil, the structures of the first to fourth embodiments above can be deduced by analogy, and the patterns of different metal foil pattern layers can be the same or different.

[0080] Fifth embodiment

[0081] Please refer to Figure 9 The flexible circuit board of this embodiment includes a flexible substrate 62 and at least one circuit component 61 disposed on the flexible substrate 62 .

[0082] The flexible substrate 62 is provided with a first bonding portion 621 and a layer of flexible substrate. The layer of flexible substrate includes a seventh flexible substrate 622 and a seventh metal foil pattern layer 623 located on the upper surface of the seventh flexible substrate 622. Furthermore, the upper surface of the seventh flexible substrate 622 is further provided with a first bonding portion 621. In other words, the seventh metal foil pattern layer 623 and the first bonding portion 621 are located on the same side of the seventh flexible substrate 622.

[0083] The circuit component 61 is provided with a second bonding portion 611. The first bonding portion 621 is bonded to the second bonding portion 611 via a wire 63 to achieve electrical connection. In this embodiment, the circuit component 61 is a flexible bare chip that is attached to the flexible substrate 62 via a die attach film (DAF).

[0084] In this embodiment, the seventh metal foil pattern layer 623 only supports the second bonding portion 611, that is, it only includes the second reinforcement portion, and the second reinforcement portion covers the entire area where the circuit component 61 is located, thereby forming a solid metal foil without any hollowing out, which provides a better support effect. All the solid metal foils corresponding to different circuit components in the same layer together constitute the bonding portion support pattern, which plays a role in supporting the second bonding portion 611, improving the pass rate of wire bonding on the circuit component 61 and preventing the circuit component 61 from being broken during wire bonding. The routing pattern of the flexible circuit board is arranged in the gap between the solid metal foils corresponding to adjacent circuit components 61. The bonding portion support pattern and the routing pattern are formed simultaneously when etching the metal foil. The bonding portion support pattern and the routing pattern can be insulated from each other, or the bonding portion support pattern can be electrically connected to a portion of the routing pattern. In this case, the bonding portion support pattern can play a role in improving the signal of the circuit component 61.

[0085] In actual implementation, when the flexible substrate has at least two layers, the second reinforcing portion same as that in this embodiment can also be provided on the top layer of the flexible substrate.

[0086] The flexible circuit board of the present application is provided with at least one metal foil pattern layer at the wire bonding position of the flexible circuit board to form a permanent reinforcement structure, which can not only meet the flatness and strength requirements of the bonding position during wire bonding, but also support and protect the finished product after the wire bonding is completed, thereby facilitating the storage, use and transfer of the finished product, and at the same time meeting the flexibility requirements of the flexible circuit board.

[0087] Sixth embodiment

[0088] Figure 10 FIG. 1 is a flow chart of a method for preparing a flexible circuit board according to the sixth embodiment of the present application. Figure 10 As shown, the method for preparing the flexible circuit board of the present application includes:

[0089] Step 510: Provide a flexible substrate on which a circuit component is to be fabricated. The flexible substrate is provided with a first bonding portion and at least one metal foil pattern layer. The circuit component is provided with a second bonding portion. The metal foil pattern layer includes a first reinforcement portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion and / or a second reinforcement portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion.

[0090] The flexible substrate may include one, two or more flexible substrate layers, on which a first bonding portion and a metal foil pattern layer are formed, wherein the pattern of the metal foil pattern layer is designed according to the positions of the first bonding portion and the second bonding portion.

[0091] When the flexible substrate includes a layer of flexible base material, the process of providing the flexible substrate may include:

[0092] Providing a flexible substrate, wherein at least one side of the flexible substrate is covered with a metal foil;

[0093] When one side surface of the flexible substrate is covered with a metal foil, a first bonding portion and a second reinforcing portion are etched on the metal foil to obtain a flexible substrate;

[0094] When both sides of the flexible substrate are covered with metal foil, a first bonding portion or a first reinforcement portion is etched on one side of the metal foil, and a first reinforcement portion and / or a second reinforcement portion is etched on the other side of the metal foil to obtain a flexible substrate.

[0095] The above process involves etching patterns corresponding to the number of metal foils on the flexible substrate, resulting in the corresponding flexible substrate. When only one side of the metal foil is present, both the first bonding portion and the pattern supporting the second bonding portion must be etched simultaneously. When both sides of the flexible substrate are covered entirely with metal foil, the pattern supporting the second bonding portion can be etched on at least one of the two metal foils, or a pattern capable of supporting at least one of the first and second bonding portions can be etched on both sides of the metal foil, depending on the product design.

[0096] When the flexible substrate includes at least two layers of flexible base materials, the process of providing the flexible substrate may include:

[0097] Providing at least two layers of flexible substrates for stacking to form a flexible substrate, wherein at least one side of the flexible substrate is covered with a metal foil;

[0098] Etching each layer of metal foil into a corresponding pattern according to the corresponding stacking position of each flexible substrate to obtain a first bonding portion and at least one metal foil pattern layer, wherein the metal foil pattern layer includes a first reinforcement portion and / or a second reinforcement portion;

[0099] At least two layers of flexible substrates are stacked together according to the corresponding stacking positions of the flexible substrates to obtain a flexible substrate.

[0100] In this embodiment, the process of etching each layer of metal foil into a corresponding pattern according to the corresponding stacking position of each flexible substrate may include:

[0101] When the currently etched flexible substrate is the top layer and one side surface is covered with metal foil, a first bonding portion is etched on the metal foil, or the first bonding portion and the second reinforcing portion are etched;

[0102] When the currently etched flexible substrate is the top layer and the surfaces on both sides are covered with metal foil, a first bonding portion, or a first bonding portion and a second reinforcement portion, is etched on the metal foil on the side of the circuit component to be manufactured, and a first reinforcement portion and / or a second reinforcement portion is etched on the metal foil on the other side;

[0103] When the flexible substrate to be etched is a non-top layer, a first reinforcing portion and / or a second reinforcing portion is etched on the metal foil.

[0104] Among them, when the flexible substrate has at least two layers and at least one side of the flexible substrate is covered with a whole layer of metal foil, while etching the first bonding portion, it is sufficient to ensure that the projection of each metal foil pattern layer in the stacking direction of the flexible substrate can cover the position of the first bonding portion and / or the second bonding portion on the circuit component to be manufactured. According to the different stacking positions corresponding to each flexible substrate, the pattern of the metal foil pattern layer thereon can be adjusted accordingly.

[0105] When etching the metal foil pattern, the following optimizations can be performed on the pattern according to product design requirements:

[0106] If the pattern etched on the current metal foil includes patterns of a first reinforcement portion and a second reinforcement portion, the first reinforcement portion and the second reinforcement portion are made continuous or disconnected from each other;

[0107] If the pattern etched on the current metal foil includes the second reinforcement portion or includes the first reinforcement portion and the second reinforcement portion, the projection of the second reinforcement portion covers the manufacturing area of ​​the circuit components;

[0108] If the pattern etched on the current metal foil includes the first reinforcement portion or includes the first reinforcement portion and the second reinforcement portion, the pattern of the first reinforcement portion is made consistent with the etched pattern of the first bonding portion.

[0109] In actual implementation, when the metal foil pattern layer only includes the part corresponding to the first bonding part, no pattern is set at the position corresponding to the second bonding part. When the metal foil pattern layer only includes the part corresponding to the second bonding part, no pattern is set at the position corresponding to the first bonding part, thereby ensuring that the unsupported part will not be uneven due to the presence of other patterns.

[0110] In this embodiment, when etching each layer of metal foil, the routing pattern of the flexible circuit board is also etched. The thickness of the metal foil pattern layer is 5-25 μm. Therefore, when forming at least one metal foil pattern layer as a permanent reinforcement structure, the flexibility of the flexible circuit board around the circuit components can still be guaranteed.

[0111] When etching a pattern, a layer of photosensitive dry film is first attached to the metal foil to be etched. This photosensitive dry film prepares for subsequent exposure and development. Then, the surface area where no metal is needed is developed and projected onto the substrate attached with the photosensitive dry film to achieve exposure and development. Finally, the developed part is chemically etched using chemicals. After completion, the dry film is removed to obtain the etched pattern.

[0112] When the number of metal foils is at least two layers, before etching the metal foil pattern layer, the process also includes drilling holes in the flexible substrate and plating copper in the inner side of the holes. Electrical conduction between the upper and lower cross-layer routing patterns on the multilayer board is achieved through drilling holes and copper plating in the holes.

[0113] Step 520: fabricate at least one circuit component on the flexible substrate, wherein the circuit component is provided with a second bonding portion.

[0114] A drop of DAF glue is placed on the flexible substrate where the circuit components are to be placed. The components are then placed on the glue in the correct orientation to ensure they are flat and perfectly bonded to the flexible substrate. This process is well known to those skilled in the art and will not be described in detail here.

[0115] Step 530 : Wire-bonding the first bonding portion and the second bonding portion to obtain a flexible circuit board.

[0116] Wire bonding is performed on flexible substrates and circuit components, a common process. The inclusion of metal foil within the flexible substrate to support the bonding positions improves the wire bonding pass rate and product yield. Furthermore, the metal foil within the flexible substrate is a permanent structure that supports and protects the flexible circuit components after wire bonding, facilitating subsequent transfer and testing of finished products.

[0117] The present application also provides a flexible circuit board, which is prepared using the above-mentioned method for preparing a flexible circuit board.

[0118] The method for preparing a flexible circuit board of the present application provides at least one metal foil pattern layer on a flexible substrate, and the projection of the metal foil pattern layer in the thickness direction of the flexible substrate covers the position of the first bonding portion and / or the second bonding portion on the circuit component to be manufactured, thereby forming a metal foil pattern layer in the flexible circuit board as a permanent reinforcement structure, which can not only meet the flatness and strength requirements of the bonding position during wire bonding, but also support and protect the finished product after wire bonding is completed, thereby facilitating the storage, use and transfer of the finished product, and at the same time meeting the flexibility requirements of the flexible circuit board.

[0119] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed in this application shall be covered by the claims of this application.

Claims

1. A flexible circuit board, characterized in that: The present invention comprises a flexible substrate and at least one circuit component arranged on the flexible substrate, wherein the flexible substrate is provided with a first bonding portion and at least one metal foil pattern layer, the circuit component is provided with a second bonding portion, the first bonding portion and the second bonding portion are wire-bonded, the metal foil pattern layer comprises a first reinforcing portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion, and a second reinforcing portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion, wherein the first reinforcing portion and the second reinforcing portion are continuous or disconnected from each other; alternatively, the metal foil pattern layer comprises at least the first reinforcing portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion, wherein the pattern of the first reinforcing portion is consistent with the arrangement pattern of the first bonding portion; the metal foil pattern layer also comprises a routing pattern of the flexible circuit board.

2. The flexible circuit board according to claim 1, wherein: The flexible substrate comprises at least one stacked flexible base material, at least one side surface of the flexible base material is provided with the metal foil pattern layer, and adjacent metal foil pattern layers are insulated from each other.

3. The flexible circuit board according to claim 1, wherein: The thickness of the metal foil pattern layer is 5-25 μm.

4. A method for preparing a flexible circuit board, characterized in that: include: a. Providing a flexible substrate on which a circuit component is to be fabricated, the flexible substrate having a first bonding portion and at least one metal foil pattern layer, the circuit component having a second bonding portion, the metal foil pattern layer comprising a first reinforcing portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion, and a second reinforcing portion whose projection in the thickness direction of the flexible substrate covers the second bonding portion, wherein the first reinforcing portion and the second reinforcing portion are continuous or disconnected; alternatively, the metal foil pattern layer comprising at least the first reinforcing portion whose projection in the thickness direction of the flexible substrate covers the first bonding portion, wherein the pattern of the first reinforcing portion is consistent with the arrangement pattern of the first bonding portion; b. Producing at least one circuit component on the flexible substrate, wherein the circuit component is provided with the second bonding portion; c. Wire-bonding the first bonding portion and the second bonding portion to obtain the flexible circuit board.

5. The method for preparing a flexible circuit board according to claim 4, wherein: Step a includes: Providing a flexible substrate, wherein opposite surfaces of the flexible substrate are both covered with the metal foil; The first bonding portion is etched on the metal foil on one side, and the first reinforcement portion and the second reinforcement portion are etched on the metal foil on the other side, or the first reinforcement portion is etched to obtain the flexible substrate.

6. The method for preparing a flexible circuit board according to claim 4, wherein: Step a includes: a01 providing at least two layers of flexible substrate for laminating to form the flexible substrate, at least one side surface of the flexible substrate is covered with a metal foil; a02. Etching the metal foil into a corresponding pattern according to the stacking position corresponding to the flexible substrate to obtain the first bonding portion and at least one metal foil pattern layer, and the metal foil pattern layer includes the first reinforcing portion and the second reinforcing portion, or includes the first reinforcing portion; a03. Stacking at least two layers of the flexible substrates together according to the corresponding stacking positions of the flexible substrates to obtain a flexible substrate.

7. The method for preparing a flexible circuit board according to claim 6, wherein: Step a03 includes: When the flexible substrate being etched is the top layer and both opposite surfaces thereof are covered with the metal foil, the first bonding portion is etched on the metal foil on the side of the circuit component to be manufactured, and the first reinforcement portion and the second reinforcement portion are etched on the other side of the metal foil, or only the first reinforcement portion is etched; When the flexible substrate being etched is a non-top layer, the first reinforcement portion and the second reinforcement portion are etched on the metal foil, or the first reinforcement portion is etched.

8. The method for preparing a flexible circuit board according to claim 5 or 6, characterized in that: include: If the pattern etched on the current metal foil includes the patterns of the first reinforcement portion and the second reinforcement portion, the first reinforcement portion and the second reinforcement portion are made continuous or disconnected from each other.

9. The method for preparing a flexible circuit board according to claim 5 or 6, characterized in that: include: If the pattern etched on the current metal foil includes the patterns of the first reinforcement portion and the second reinforcement portion, the projection of the second reinforcement portion covers the manufacturing area of ​​the circuit component.

10. The method for preparing a flexible circuit board according to claim 5 or 6, characterized in that: include: If the pattern etched on the current metal foil includes the first reinforcing portion or a pattern including the first reinforcing portion and the second reinforcing portion, the etching pattern of the first reinforcing portion is made consistent with that of the first bonding portion.

11. The method for preparing a flexible circuit board according to claim 5 or 6, characterized in that: The method further comprises: When etching the metal foil, the wiring pattern of the flexible circuit board is also etched.

12. The method for preparing a flexible circuit board according to claim 4, wherein: The thickness of the metal foil pattern layer is 5-25 μm.

13. A flexible circuit board, characterized in that: The flexible circuit board is prepared by the method for preparing the flexible circuit board according to any one of claims 5 to 12.

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