Manufacturing method of flexible circuit board for golden finger high-fidelity signal transmission

Abstract

The invention discloses a method for manufacturing a flexible circuit board for high-fidelity signal transmission of a golden finger, which comprises the following steps of: taking a double-sided flexible copper-clad plate, manufacturing a blind hole, manufacturing circuit patterns on two sides, enabling the blind hole to communicate a golden finger circuit on the front side with a back reinforcing circuit on the back side, manufacturing a dry film pattern on the front side, and manufacturing the dry film pattern on the back side. A conductive film is attached to the back face, covers the back face reinforcing circuit and partially covers the board edge conducting circuit, electrogilding processing is carried out, the conductive film is removed, resin ink is printed on the back face in a silk-screen mode, baking curing and film stripping are carried out, and the flexible circuit board is formed through post-process processing; a back reinforcing circuit is designed, a blind hole is used for being communicated with a golden finger circuit on the front face, a conductive film is connected to a plate edge conducting circuit on the plate edge, a gold plating lead is replaced, high-precision machining of a golden finger with the four sides wrapped with gold is achieved, the back reinforcing circuit is used for achieving the reinforcing layer effect, resin ink is manufactured, and the manufacturing cost is reduced. And the strength and the reinforcing integrity of the reinforcing layer are improved.

Description

Technical Field

[0001] The invention relates to the field of circuit boards and flexible circuit board manufacturing, and in particular to a method for manufacturing a flexible circuit board for gold finger high-fidelity signal transmission. Background Art

[0002] Flexible circuit boards used in some high-precision video or medical fields require higher processing accuracy and signal transmission accuracy. For flexible circuit boards with gold finger designs, a "four-sided gold coating" process is generally required, that is, the surface, top and two sides of the gold finger need to be covered with a gold layer, which can ensure signal stability and improve the reliability of the gold finger. When the gold finger is electroplated, it is necessary to use leads to extend to the edge of the board. The copper layer pattern on the edge of the board is clamped by an electroplating fixture to generate current conduction, conduct electricity to the gold finger area, and realize the electroplating process. After the electroplating process is completed, the leads need to be removed to prevent the gold finger from short-circuiting.

[0003] At the same time, for some flexible circuit boards that require small area and high precision, the gold fingers will be designed as "offset gold fingers" to achieve the effect of arranging more gold fingers in a smaller space. Therefore, the distance between the gold fingers of the "offset gold fingers" and the circuit graphics on the board is closer, making it more difficult to set the leads.

[0004] In addition, the body of the flexible circuit board is relatively soft, and a reinforcement layer is generally required on the back of the gold finger to increase the supporting strength of the gold finger.

[0005] At present, for this type of flexible circuit boards that require "gold coating on all four sides" and "offset gold fingers", the method of designing the leads at the rear end of the circuit and extending them to the copper layer pattern at the edge of the board is generally adopted to make the leads and form circuit conduction. The reinforcement layer is generally realized by independently attached reinforcement sheets.

[0006] The current production method for making leads has problems such as complex lead design and greater difficulty in processing when removing the leads due to the small board space and high precision requirements; the thickness of the independently attached reinforcement sheet is relatively thick, which affects the use effect of the small space, and there is a problem that the reinforcement sheet is easy to fall off.

[0007] Therefore, in view of the above background and problems, it is necessary to provide a method for manufacturing a flexible circuit board with high-fidelity signal transmission of gold fingers. Summary of the invention

[0008] The present invention aims to provide a method for manufacturing a flexible circuit board with high-fidelity signal transmission of gold fingers for high-precision flexible circuit boards with "four-sided gold coating" and "misaligned gold fingers". The method includes the following steps:

[0009] S10: taking a double-sided flexible copper-clad board, the double sides being divided into a front side and a back side, making a blind hole on the back side to form a blind hole circuit board;

[0010] S20: making circuit patterns on both sides of the blind hole circuit board, the circuit pattern on the front side includes a gold finger circuit, and the circuit pattern on the back side includes a back side reinforcement circuit; the plurality of blind holes are respectively located within the graphic range of the plurality of back side reinforcement circuits, and connect the gold finger circuits with the back side reinforcement circuits; the circuit pattern on the back side also includes a board edge conduction circuit located at one edge of the double-sided flexible copper clad board; the whole is processed to form a circuit pattern board;

[0011] S30: making a dry film pattern on the front side to expose the gold finger circuit, attaching a conductive film to the back side, covering the back side reinforcement circuit with the conductive film, and partially covering the board edge conductive circuit, performing electroplating gold processing, forming the gold finger circuit into a gold finger, and forming a gold finger board as a whole;

[0012] S40: peeling off the conductive film, screen printing resin ink on the range of the back reinforcement circuit, and baking and curing to form a resin layer reinforcement plate;

[0013] S50: performing a film stripping process on the resin layer reinforcement plate, attaching a cover film layer to the front surface and the back surface respectively, and performing a molding process according to a molding line of a finished product to form the flexible circuit board.

[0014] Furthermore, the blind hole is made by pasting dry film on both sides of the double-sided flexible copper clad laminate to make a dry film pattern, exposing the pattern of the blind hole on the back side, and performing etching, laser drilling and electroplating in sequence to form the blind hole.

[0015] Furthermore, adjacent gold finger circuits are staggered in vertical arrangement to form staggered gold finger circuits.

[0016] Furthermore, the back side reinforcement circuit corresponds to the gold finger circuit distribution.

[0017] Furthermore, an open circuit pattern is formed between adjacent circuits of the back reinforcement circuit corresponding to the gold finger circuit, and the edge extends to the forming line.

[0018] Furthermore, the conductive film is a double-layer film of a carbon black micro-adhesive film and an insulating protective film, and the material of the insulating protective film is one of PP, PE, PET, and PTFE.

[0019] Furthermore, attaching the conductive film to the back side includes: screen printing an adhesive layer on the area outside the molding line on the back side, the adhesive layer is an acrylic adhesive layer or an epoxy resin adhesive layer, and the adhesive layer avoids the board edge conductive circuit; attaching the conductive film to the back side.

[0020] Optionally, attaching the conductive film to the back side is: taking a single-sided flexible copper-clad laminate, and making a whole board pattern on it by punching or milling to form a single-sided copper-clad laminate pattern; taking a micro-mucous film, the area of ​​which is larger than that of the single-sided copper-clad laminate pattern on one side, and attaching the insulating dielectric layer of the single-sided copper-clad laminate pattern to one side of the adhesive layer of the micro-mucous film to form the conductive film; attaching one side of the adhesive layer of the conductive film to the back side, and one end of the whole board pattern contacts the board edge conduction circuit, and the other end contacts the back reinforcement circuit.

[0021] Furthermore, the back reinforcement circuit corresponds to the resin ink in the top direction of the gold finger and extends to the molding line.

[0022] Furthermore, the covering film layer attached to the front surface is a window covering film layer for making windows corresponding to the gold fingers.

[0023] The technical solution of the present invention designs a back reinforcement circuit on the back side, and connects it with the gold finger circuit on the front side through a blind hole, and then uses a conductive film attached to the back side to connect to the board edge conductive circuit on the board edge to form a conductive circuit network. During the electroplating gold processing, the clamp of the electroplating line clamps the board edge conductive circuit, conducts to the back reinforcement circuit through the conductive film, and then conducts to the gold finger circuit through the blind hole to form the electroplating gold processing process of the gold finger circuit. After the electroplating gold processing is completed, the conductive film is removed, and the back process is completed, effectively realizing the production of high-precision flexible circuit boards with "four-sided gold coating" and "misaligned gold fingers". The method of designing the back reinforcement circuit, making blind holes and using conductive film for conduction replaces the direct design of gold finger leads on the front, effectively avoiding the problems of complex lead design, difficult processing and difficult removal, and improving the processing accuracy and processability of the circuit board; at the same time, the back reinforcement circuit is used to play the role of a reinforcement layer, and resin ink is further produced to improve the strength of the reinforcement layer and the integrity of the reinforcement, replacing the method of independently attaching reinforcement sheets to form a reinforcement layer effect with thinner thickness and higher precision; the overall processing process has the matching of the front and back processes, forming an effective and feasible overall processing flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0025] Figure 1 It is a key process flow chart of an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a planar structure for forming a blind hole on the back side of an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the planar structure of the front side of a circuit pattern board formed in accordance with an embodiment of the present invention;

[0028] Figure 4 A schematic diagram of the planar structure of the back side of the circuit pattern board formed in the embodiment of the present invention;

[0029] Figure 5 Embodiments of the present invention Figure 4 Schematic diagram of the AA cross-section structure;

[0030] Figure 6 It is a schematic diagram of the planar structure of the back side of the gold finger board formed in the embodiment of the present invention;

[0031] Figure 7 Embodiments of the present invention Figure 6 Schematic diagram of BB cross-section structure;

[0032] Figure 8 It is a schematic diagram of the planar structure of another method for manufacturing the back side of the gold finger board according to the embodiment of the present invention;

[0033] Fig. 9 Embodiments of the present invention Figure 8 Schematic diagram of CC cross-section structure;

[0034] Fig.10 It is a schematic diagram of the planar structure of the back side of the resin layer reinforcement plate formed in the embodiment of the present invention;

[0035] Fig.11 Embodiments of the present invention Fig.10 Schematic diagram of DD cross-section structure;

[0036] Fig.12 A schematic diagram of the planar structure of the back side of a flexible circuit board formed in accordance with an embodiment of the present invention;

[0037] Fig.13Embodiments of the present invention Fig.12 Schematic diagram of EE cross-sectional structure;

[0038] Fig.14 It is a schematic diagram of the planar structure of the front side of a flexible circuit board formed in accordance with an embodiment of the present invention.

[0039] Description of Figure Numbers:

[0040] Label name Label name 10 Blind hole circuit board 310B Conductive film 100B Back copper layer 320 Molding line 110 Blind Via 330A Front dry film graphic layer 120A Front line 330B Micro mucosa 120B Back reinforcement line 340B Single-sided copper clad laminate graphics 130B Board edge conduction line 40 Resin layer reinforcement plate 20 Circuit board 410 Resin layer 100J Insulation dielectric layer 420 Gold plating layer 110A Gold Finger Line 50 Flexible circuit board 30 Gold Finger Board 510 Back cover film 310A Front dry film graphic layer 520 Window covering film

[0041] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, inside, outside...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0044] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0045] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0046] See also Figure 1 , Figure 1 The key process flow chart of the implementation mode of the present invention.

[0047] A method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers according to an embodiment of the present invention comprises: Figure 1The key production process is described in detail step by step as follows.

[0048] See also Figure 2 , Figure 2 It is a schematic diagram of the planar structure of forming a blind hole 110 on the back side of an embodiment of the present invention.

[0049] Step S10:

[0050] A double-sided flexible copper-clad board is taken, the double sides are divided into a front side and a back side, and include an insulating dielectric layer 100J, and a blind hole 110 is made toward the back side to form a blind hole circuit board 10.

[0051] In this embodiment, the blind hole 110 is made by affixing dry film to both sides of the double-sided flexible copper clad laminate to make a dry film pattern, exposing the pattern of the blind hole 110 on the back side, that is, making the blind hole 110 pattern on the back copper layer 100B, and sequentially performing etching, laser drilling, and electroplating to form the blind hole 110.

[0052] First, a blind hole 110 is made on the board surface for connecting the back reinforcement circuit with the front gold finger circuit 110A. Since the thickness of the high-precision circuit board is generally thin, the blind hole 110 can be formed by direct electroplating.

[0053] See also Figures 3 to 5 , Figure 3 A schematic diagram of the planar structure of the front side of a circuit pattern board formed in accordance with an embodiment of the present invention; Figure 4 A schematic diagram of the planar structure of the back side of the circuit pattern board formed in the embodiment of the present invention; Figure 5 Embodiments of the present invention Figure 4 Schematic diagram of the AA cross-section structure.

[0054] Step S20:

[0055] Circuit patterns are made on both sides of the blind hole circuit board 10, the circuit pattern on the front side includes a gold finger circuit 110A and a front circuit 120A. The gold finger circuit 110A in this embodiment is a staggered gold finger circuit 110A, that is, adjacent gold finger circuits 110A are staggered up and down, and the circuit pattern on the back side includes a back side reinforcement circuit; a plurality of blind holes 110 are respectively located within the graphic range of a plurality of back side reinforcement circuits, and connect the gold finger circuit 110A with the back side reinforcement circuit; the gold finger circuit 110A corresponding to each back side reinforcement circuit must be distributed with more than or equal to one blind hole 110 to ensure the conduction between the back side reinforcement circuit and the front side gold finger circuit 110A during the electroplating gold processing; after the circuit pattern is formed, the insulating dielectric layer 100J is exposed in the area where the copper layer is etched away.

[0056] The circuit pattern on the back also includes a board edge conductive circuit 130B located at one of the edges of the double-sided flexible copper clad board; the board edge conductive circuit 130B is a necessary design. Generally, according to the distribution of the electroplating wire clamps, the corresponding board edge conductive circuit 130B that can be clamped is designed to achieve effective conduction of the current of the electroplating wire clamps to the board edge conductive circuit 130B.

[0057] The above overall processing forms the circuit pattern board 20.

[0058] In one embodiment, the back reinforcement circuit corresponds to the distribution of the gold finger circuit 110A. The corresponding distribution can effectively achieve the effect of conduction through the blind hole 110, and prevent the misalignment or size difference between the gold finger pattern and the back reinforcement circuit pattern, which may cause the insulating medium layer of the flexible circuit board to be damaged during processing or application. Optionally, the single side of each back reinforcement circuit corresponding to the gold finger circuit 110A is smaller than the gold finger circuit 110A, that is, each back reinforcement circuit completely falls within the range of each gold finger circuit 110A, which can also form the effect of conduction and preventing the insulating medium layer from being damaged.

[0059] In one embodiment, an open circuit pattern is made between adjacent circuits of the back reinforcement circuit corresponding to the gold finger circuit 110A, and the edge extends to the molding line; that is, the back reinforcement circuit patterns corresponding to the gold finger circuit 110A area are disconnected from each other to prevent short circuits, while other areas extend to the molding line, forming a larger area of ​​reinforcement layer to support the gold finger, which is convenient for the insertion of the gold finger during application.

[0060] See also Figures 6 to 9 , Figure 6 It is a schematic diagram of the planar structure of the back side of the gold finger board formed in the embodiment of the present invention; Figure 7 Embodiments of the present invention Figure 6 Schematic diagram of BB cross-section structure; Figure 8 It is a schematic diagram of the planar structure of another method for manufacturing the back side of the gold finger board according to the embodiment of the present invention; Fig. 9 Embodiments of the present invention Figure 8 Schematic diagram of the CC cross-section structure.

[0061] Step S30:

[0062] A dry film pattern is made on the front side to expose the gold finger circuit 110A, a dry film layer is attached to the front side and a dry film pattern is made to form a front dry film pattern layer 310A, a conductive film 310B is attached to the back side, the same conductive film 310B covers the back reinforcement circuit and partially covers the board edge conductive circuit 130B, and electroplating gold is performed to form an electroplated gold layer 420, and the gold finger circuit 110A forms a gold finger 420A, and the whole is processed to form a gold finger board 30.

[0063] In this embodiment, the conductive film 310B is used to form an electrical connection between the back reinforcement circuit and the board edge conductive circuit 130B (further forming an electrical connection between the back reinforcement circuit and the gold finger circuit 110A through the blind hole 110), instead of directly making the electroplated gold lead on the circuit pattern. On the one hand, it avoids the problem of complex design and production of leads due to excessive circuit density and high circuit precision requirements. On the other hand, after the electroplating gold processing is completed, the conductive film 310B can be easily removed, and there is no need to use graphic etching (dry film application → exposure → development → etching → film removal) to remove the leads, which greatly simplifies the process and avoids the large expansion and contraction effect of multiple graphic etching on the board.

[0064] In this embodiment, the conductive film 310B is a double-layer film composed of a carbon black micro-adhesive film and an insulating protective film, and the material of the insulating protective film is one of PP, PE, PET, and PTFE.

[0065] The carbon black micro-adhesive film has good electrical conductivity and can ensure the current transmission during the gold electroplating process. The insulating protective film is used to protect the surface, which effectively prevents the carbon black micro-adhesive film from being plated with gold during gold electroplating.

[0066] As an optional method, the conductive film 310B is attached to the back side by screen printing an adhesive layer on the area outside the molding line on the back side, wherein the adhesive layer is an acrylic adhesive layer or an epoxy resin adhesive layer, and the adhesive layer avoids the board edge conductive line 130B; and attaching the conductive film 310B to the back side.

[0067] In order to make the conductive film 310B more firmly bonded to the back side (or when the conductive film 310B has no adhesion performance), a glue layer is made in the invalid area outside the molding line, and the conductive film 310B is bonded to the board edge area on the back side by the glue layer, so as to form the effect of the conductive film 310B contacting the back side reinforcement line on the back side. The conductive film 310B can be removed later by using a laser controlled depth milling plate to mill to the thickness of the conductive film 310B, or in the subsequent molding process, the conductive film 310B can be directly removed by punching or milling (it is worth noting that if the laser controlled depth milling plate is used to remove the conductive film 310B, the main processing flow is: laser controlled depth milling → removal Conductive film 310B → silk screen resin ink on the back → cover film attached on both sides → overall molding; if the conductive film 310B is removed by subsequent direct molding, the main processing flow is: first attach the cover film on one side of the gold finger, then mold, and then make the silk screen resin ink on the back and attach the cover film on the back); the method of adhering the conductive film 310B with an adhesive layer requires extending the board edge conductive line 130B, and the board edge conductive line 130B needs to form three areas in sequence: exposed area (contact with the electroplating wire clamp for conductivity), bonding area, and conductive film 310B contact area to ensure that both the sealing of the bonding and the contact conductivity of the conductive film 310B are met.

[0068] As an optional method, attaching a conductive film to the back side is as follows: first, make a conductive film: take a single-sided flexible copper-clad board, and use punching or milling to make a whole board pattern on it to form a single-sided copper-clad board pattern 340B; take a micro-mucous film 330B, the area of ​​the micro-mucous film 330B is larger than the single-sided copper-clad board pattern 340B, and the insulating dielectric layer of the single-sided copper-clad board pattern 340B is attached to one side of the adhesive layer of the micro-mucous film 330B to form a conductive film; secondly, attach the conductive film: attach one side of the adhesive layer of the conductive film to the back side, one end of the whole board pattern contacts the board edge conductive circuit 130B, and the other end contacts (partially covers) the back reinforcement circuit.

[0069] A "conductive film" is made by using a single-sided flexible copper clad laminate and a micro-adhesive film 330B, and a single-sided copper clad laminate pattern 340B is formed using the single-sided flexible copper clad laminate to form the conduction between the back reinforcement circuit and the board edge conduction circuit 130B. On the one hand, it makes the production of the conductive circuit pattern more flexible and meets the conduction requirements of the distribution of different gold finger circuits 110A, that is, it can be understood as forming an auxiliary lead network independent of the flexible circuit board itself. On the other hand, it can form batch automated processing, making the attachment of the conductive film more accurate, efficient and reliable.

[0070] See also Fig.10 and Fig.11 , Fig.10 It is a schematic diagram of the planar structure of the back side of the resin layer reinforcement plate formed in the embodiment of the present invention; Fig.11 Embodiments of the present invention Fig.10 Schematic diagram of the DD cross-section structure.

[0071] Step S40:

[0072] The conductive film 310B is peeled off, and resin ink is screen-printed on the area of ​​the back reinforcement circuit, and then baked and cured to form a resin layer 410 , and the entire process is processed to form a resin layer reinforcement plate 40 .

[0073] In this embodiment, the back reinforcement circuit corresponds to the resin ink in the top direction of the gold finger and extends to the molding line.

[0074] The resin ink is screen-printed and baked to form further support for the front gold finger area from the back, and to improve the integrity of the support performance of the back reinforcement circuit to prevent the problem of tearing of the insulating dielectric layer of the flexible circuit board due to insufficient reinforcement support; the resin ink extends to the molding line, which can increase the support area and reduce the "steps" formed by each layer.

[0075] See also Figure 12 to Figure 14 , Fig.12 A schematic diagram of the planar structure of the back side of a flexible circuit board formed in accordance with an embodiment of the present invention; Fig.13 Embodiments of the present invention Fig.12 Schematic diagram of EE cross-sectional structure; Fig.14 It is a schematic diagram of the planar structure of the front side of a flexible circuit board formed in accordance with an embodiment of the present invention.

[0076] Step S50:

[0077] The resin layer reinforcement plate 40 is subjected to a film stripping process, and a cover film layer is attached to the front and back sides respectively, and is subjected to a molding process according to a molding line of a finished product to form a flexible circuit board 50 .

[0078] In this embodiment, a back cover film layer 510 is attached to the back surface, and a cover film layer attached to the front surface is a window cover film layer 520 for making windows corresponding to the gold fingers.

[0079] The front cover film has windows to expose the gold fingers, and with the support of the back reinforcement circuit and the resin layer 410, a gold finger with high reliability is formed on the front side.

[0080] It is worth noting that due to the actual design and processing of circuit boards, the actual structure diagram and the thickness of each layer, line width and other dimensions are all in the micron level. For example, the thickness of each layer is generally 5μm to 50μm. If the drawings in the specification are made according to the actual proportion, there will be a problem of unclear drawings. Therefore, in order to more clearly show the implementation process of the manufacturing method, the drawings of this embodiment are all schematic diagrams that enlarge the technical features, which do not represent the size of the actual structure diagram, nor do they represent enlarged views of the actual structure diagram in proportion.

[0081] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing a flexible circuit board with high-fidelity signal transmission of gold fingers, characterized in that: The production method comprises the following steps: S10: taking a double-sided flexible copper-clad board, the double sides being divided into a front side and a back side, making a blind hole on the back side to form a blind hole circuit board; S20: making circuit patterns on both sides of the blind hole circuit board, wherein the circuit pattern on the front side includes a gold finger circuit, and the circuit pattern on the back side includes a back side reinforcement circuit; The plurality of blind holes are respectively located within the graphic range of the plurality of back reinforcement circuits, and connect the gold finger circuit with the back reinforcement circuit; The circuit pattern on the back side also includes a board edge conductive circuit located at one edge of the double-sided flexible copper clad board; The whole is processed to form a circuit pattern board; S30: making a dry film pattern on the front side to expose the gold finger circuit, attaching a conductive film to the back side, covering the back side reinforcement circuit with the conductive film, and partially covering the board edge conductive circuit, performing electroplating gold processing, forming the gold finger circuit into a gold finger, and forming a gold finger board as a whole; S40: peeling off the conductive film, screen printing resin ink on the range of the back reinforcement circuit, and baking and curing to form a resin layer reinforcement plate; S50: performing a film stripping process on the resin layer reinforcement plate, attaching a cover film layer to the front surface and the back surface respectively, and performing a molding process according to a molding line of a finished product to form the flexible circuit board.

2. The method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers as claimed in claim 1, characterized in that: The blind hole making method is as follows: Dry films are pasted on both sides of the double-sided flexible copper-clad laminate to produce dry film patterns, the patterns of the blind holes are exposed on the back side, and etching, laser drilling and electroplating are performed in sequence to form the blind holes.

3. The method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers as claimed in claim 1, characterized in that: The adjacent gold finger circuits are staggered up and down to form staggered gold finger circuits.

4. The method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers as claimed in claim 1, characterized in that: The back side reinforcement circuit corresponds to the gold finger circuit distribution.

5. The method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers as claimed in claim 1, characterized in that: An open circuit pattern is formed between adjacent circuits of the back reinforcement circuit corresponding to the gold finger circuit, and the edge extends to the forming line.

6. The method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers as claimed in claim 1, characterized in that: The conductive film is a double-layer film composed of a carbon black micro-adhesive film and an insulating protective film, and the material of the insulating protective film is one of PP, PE, PET, and PTFE.

7. A method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers as claimed in claim 1 or 6, characterized in that: The method of attaching the conductive film to the back side includes: screen printing a glue layer on the area outside the molding line on the back side, wherein the glue layer is an acrylic glue layer or an epoxy resin glue layer, and the glue layer avoids the board edge conductive circuit; and attaching the conductive film to the back side.

8. The method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers as claimed in claim 1, characterized in that: The step of attaching a conductive film to the back side is as follows: Take a single-sided flexible copper-clad laminate, and use punching or milling to make a whole board pattern on it to form a single-sided copper-clad laminate pattern; Taking a micro-mucose film, the area of ​​which is larger than that of the single-sided copper-clad board pattern on one side, and attaching the insulating dielectric layer of the single-sided copper-clad board pattern to one side of the adhesive layer of the micro-mucose film to form the conductive film; One side of the adhesive layer of the conductive film is attached to the back side, one end of the whole board pattern contacts the board edge conductive circuit, and the other end contacts the back side reinforcement circuit.

9. The method for manufacturing a flexible circuit board for high-fidelity signal transmission with gold fingers as claimed in claim 1, characterized in that: The back reinforcement circuit corresponds to the resin ink in the top direction of the gold finger and extends to the molding line.

10. The method for manufacturing a flexible circuit board for high-fidelity signal transmission of a gold finger as claimed in claim 1, characterized in that: The covering film layer attached to the front side is a window covering film layer for making windows corresponding to the gold fingers.

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