A method for manufacturing a high-precision flexible circuit board with low signal loss

Abstract

The present invention discloses a method for manufacturing a high-precision flexible circuit board with low signal loss. The flexible circuit board includes a gold finger area and a wire area. A lead auxiliary area is added between the gold finger area and the wire area. A double-sided flexible copper clad board is drilled with via holes, electroplated and patterned in the lead auxiliary area in sequence to form a graphic flexible board. The patterning includes a lead auxiliary circuit on the first side of the graphic flexible board and a lead on the second side. The lead is connected to the lead auxiliary circuit through the via hole, and then the gold fingers are connected to form a conductive circuit. The gold fingers and the pattern are transferred to the graphic flexible board, and a cover film is affixed and pressed to form a high-precision flexible circuit board. The leads are transferred to the back side of the flexible circuit board by designing the via hole, which solves the problem of difficult lead processing of the gold fingers requiring "gold covering on all four sides"; the short circuit problem caused by incomplete etching caused by possible exposure deviation is solved by unilaterally shrinking the exposed non-photocuring area in the longitudinal direction and unilaterally enlarging it in the transverse direction.

Description

Technical Field

[0001] The present invention relates to the field of flexible circuit board manufacturing, and in particular to a method for manufacturing a high-precision flexible circuit board with low signal loss. Background Art

[0002] In some digital AI and medical fields, flexible circuit boards are required to have high precision and low signal loss. When the high-precision flexible circuit boards used in such fields are designed with gold fingers, the gold fingers are required to have a "four-sided gold-wrapped" process, that is, the upper surface, left side, right side, and head end (the tail end connecting the line, covered by a covering film) of the gold finger are all covered with gold to improve the signal fidelity and service life of the gold finger.

[0003] Generally, the process of attaching gold to the copper surface is achieved by electroplating gold on a single-sided copper-clad flexible board. Electroplating gold requires "leads" to provide a conductive carrier for the gold fingers. Generally, the gold finger lead is designed in the epitaxial area at the head end of the gold finger. After the electroplating gold processing is completed, the lead is removed by etching or forming.

[0004] However, for gold fingers with four-sided gold coating, the gold finger lead wire cannot be designed at the head end, so a new lead design is needed to meet the electroplating requirements of the gold fingers with four-sided gold coating.

[0005] For high-precision flexible circuit boards with "four-sided gold-coated" gold fingers, not only are the gold finger guides required to be conductive, but also after removing the gold finger guides, there must be no additional impact on the processing quality and application process of the circuit graphics and gold finger graphics.

[0006] Therefore, in order to solve the problems raised by the above background technology, it is necessary to provide a method for manufacturing a high-precision flexible circuit board with low signal loss. Summary of the Invention

[0007] The present invention aims to solve the problem of flexible circuit boards in the prior art requiring comprehensive performance such as high-fidelity signals and easy processing, and proposes a method for manufacturing a high-precision flexible circuit board with low signal loss. The manufacturing method includes the following steps:

[0008] The design pattern includes a gold finger area and a wire pattern area.

[0009] S10: adding a lead auxiliary area between the gold finger area and the conductor pattern area;

[0010] S20: Take a double-sided flexible copper-clad laminate, drill holes in the lead auxiliary area and perform electroplating to form via holes, thereby forming a flexible laminate with via holes;

[0011] S30: manufacturing a circuit pattern on the flexible board with via holes, wherein the circuit pattern includes a plurality of gold finger circuits and a conductor circuit to form a patterned flexible board;

[0012] The lead auxiliary area on the first surface of the graphic flexible board is provided with a plurality of lead auxiliary circuits, the via holes are located on the lead auxiliary circuits, and the lead auxiliary circuits are connected to the gold finger circuit and the wire circuit;

[0013] A lead is formed on the edge of the second surface of the graphic flexible board, and a lead conductive line is formed between the lead and the conductive hole, and the lead conductive line connects the lead and the conductive hole;

[0014] S40: performing electroplating gold finger processing on the graphic flexible board to form a gold finger flexible board;

[0015] S50: performing pattern transfer processing on the gold finger flexible board to form a pattern transfer flexible board; etching all the circuit patterns on the second surface of the gold finger flexible board;

[0016] S60: affixing a cover film to the pattern-transferred flexible board and laminating the cover film to form a high-precision flexible circuit board.

[0017] Furthermore, a single auxiliary lead circuit connects all of the plurality of gold finger circuits.

[0018] Furthermore, the conductive hole is located between two adjacent gold finger circuits.

[0019] Furthermore, the electroplating gold finger processing includes: applying a dry film to the second surface, exposing, and developing to form a development pattern located on the surface of the lead, and the development pattern corresponds to the electroplating chuck setting.

[0020] Furthermore, the gold finger circuit is distributed longitudinally, and the pattern transfer process includes applying a dry film to the gold finger flexible board and exposing it to light. The non-photocuring area of ​​the lead auxiliary circuit corresponding to the dry film is unilaterally reduced in the longitudinal distribution direction of the gold finger circuit and unilaterally enlarged in the transverse direction.

[0021] Furthermore, the reduced size or the enlarged size is 10 μm to 50 μm.

[0022] Furthermore, the pattern transfer process includes etching the copper of the via hole.

[0023] Furthermore, the applying of the covering film includes applying the covering film to the surface of the pattern transfer flexible board where the gold finger circuit is located or to both sides of the pattern transfer flexible board.

[0024] Furthermore, the pressing is performed using a rigid plate pressing device.

[0025] Furthermore, the pressing parameters are as follows: a heating rate of 2°C / min to 4°C / min, a maximum temperature of 160°C to 170°C, and a pressure of 10 kg / cm 2 Up to 20kg / cm 2 , the cooling rate is 6℃ / min to 10℃ / min.

[0026] The technical solution of the present invention transfers the leads to the back side of the flexible circuit board by adding a lead auxiliary area and a via hole in the lead auxiliary area to the original design pattern. The via hole connects the leads to the gold finger circuit, providing conductive conditions for the subsequent electroplating of the gold finger circuit, thereby solving the problem of difficulty in processing the leads of the gold finger that needs to be "gold-plated on all four sides"; further, by unilaterally reducing the exposed non-photocuring area in the longitudinal direction relative to the longitudinal distribution direction of the gold finger and unilaterally enlarging it in the transverse direction, the short circuit problem caused by incomplete etching caused by exposure deviation is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0028] Figure 1 Schematic diagram of the process flow of an embodiment of the present invention;

[0029] Figure 2 Schematic diagram of the planar structure of a flexible board with via holes according to an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the front planar structure of a graphic flexible board according to an embodiment of the present invention;

[0031] Figure 4 Schematic diagram of the back plane structure of the graphic flexible board according to the embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the planar structure of the dry film pattern on the front side of the graphic flexible board according to an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the planar structure of the dry film pattern on the back of the graphic flexible board according to an embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of the planar structure of the gold finger flexible board according to an embodiment of the present invention;

[0035] Figure 8 This is a schematic diagram of the planar structure of the dry film pattern of the gold finger flexible board according to an embodiment of the present invention;

[0036] Figure 9 This is a schematic diagram of the planar structure of a local dry film pattern on a gold finger flexible board according to an embodiment of the present invention;

[0037] Figure 10 Schematic diagram of the planar structure of the pattern transfer flexible board according to an embodiment of the present invention;

[0038] Figure 11 This is a schematic diagram of the planar structure of a cover film attached to the front side of a pattern transfer flexible board according to an embodiment of the present invention;

[0039] Figure 12 Schematic diagram of the cross-sectional structure of a pattern transfer flexible board according to an embodiment of the present invention.

[0040] Figure 13 This is a schematic diagram of the planar structure of a high-precision flexible circuit board according to an embodiment of the present invention.

[0041] Description of Figure Numbers:

[0042] Label name Label name 20 Through-hole flexible board 370 Developing graphics 210 Gold Finger Area 40 Gold Finger Flexible Board 220 Lead auxiliary area 410 Gold Finger 230 Wire graphics area 420 Developing circuit pattern 240 vias 4210 Vertical single-sided shrinking 250 Flexible board insulation layer 4220 Horizontal single-side enlargement 30 Graphic flexible board 4230 Light curing area 300 Line Graphics 4240 Non-light-cured area 310 Gold Finger Line 430 No copper holes 320 Wire lines 50 Graphic transfer flexible board 330 Lead auxiliary line 60 High-precision flexible circuit boards 340 lead 610 Covering film 350 Lead wire 6110 Cover film PI layer 360 Anti-electrochemical gold dry film pattern 6120 Covering film adhesive layer

[0043] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0045] 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, etc.) are only used to explain the relative position relationship and movement status of the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0046] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0047] 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 this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0048] In the method 10 for manufacturing a high-precision flexible circuit board with low signal loss of this embodiment, the flexible circuit board is manufactured according to a design pattern, and the design pattern includes a gold finger area 210 and a conductor pattern area 230 .

[0049] See also Figure 1 , Figure 1 Schematic diagram of the process flow of an embodiment of the present invention.

[0050] The preparation method comprises the following steps:

[0051] Step S10:

[0052] A lead auxiliary area 220 is added between the gold finger area and the conductor pattern area.

[0053] The common gold finger lead design is at the head end of the gold finger. Due to the "four-sided gold plating" process requirements, the gold finger, including the head end, also needs to be electroplated with gold. In order to make the lead design not affect the normal use of the gold finger area 210 and the wire pattern area 230, a lead auxiliary area 220 is added between the gold finger area 210 and the wire pattern area 230 to add an auxiliary connection and conduction circuit pattern 300 when making electroplated gold.

[0054] See also Figure 2 , Figure 2 Schematic diagram of the planar structure of a flexible board with via holes according to an embodiment of the present invention.

[0055] Step S20:

[0056] A double-sided flexible copper clad board including a flexible board insulation layer 250 is taken, holes are drilled and electroplated in the lead auxiliary area 220 to form a via hole 240, and the entire flexible board 20 with a via hole is formed.

[0057] In this embodiment, the leads 340 are fabricated on the second side of the flexible circuit board, while the gold finger circuits 310 are fabricated on the original first side. Therefore, the flexible circuit board is required to use a double-sided copper clad laminate. When forming the circuit pattern 300, the original gold finger circuits 310 and wire circuits 320 are distributed on the first side, and the leads 340 and related circuit patterns are distributed on the second side.

[0058] See also Figure 3 , Figure 3 This is a schematic diagram of the front planar structure of a graphic flexible board according to an embodiment of the present invention.

[0059] Step S30:

[0060] A circuit pattern 300 is produced on the flexible board 20 with a via hole. The circuit pattern 300 includes a plurality of gold finger circuits 310 and a wire circuit 320 to form a graphic flexible board 30. A plurality of lead auxiliary circuits 330 are produced in the lead auxiliary area 220 on the first surface of the graphic flexible board 30. The via 240 is located on the lead auxiliary circuit 330. The lead auxiliary circuit 330 connects the gold finger circuit 310 and the wire circuit 320.

[0061] In this embodiment, a single lead auxiliary circuit 330 connects all the gold finger circuits 310. On the one hand, the single lead auxiliary circuit 330 is easy to implement during design and processing. On the other hand, when the conductive hole 240 is set in the area between adjacent gold finger circuits 310, the single lead auxiliary circuit 330 can connect the gold finger circuits 310 together to form a complete pattern, which is convenient for the production of the conductive hole 240 and can make the gold finger circuits 310 form a mutually connected conductive effect, thereby preventing the phenomenon of weak current or non-conduction caused by circuit problems.

[0062] In this embodiment, the via 240 is located between two adjacent gold finger circuits 310; the via 240 is made on the lead auxiliary circuit 330 between the two adjacent gold finger circuits 310, so that the signal transmission between the gold finger circuit 310 and the wire circuit 320 is more direct and the transmission effect is better; this is different from distributing the via 240 on the gold finger circuit 310 or the wire circuit 320, in which case the signal transmission needs to bypass the via 240, resulting in poor signal transmission effect.

[0063] See also Figure 4 , Figure 4 Schematic diagram of the back plane structure of the graphic flexible board according to the embodiment of the present invention.

[0064] Leads 340 are formed on the edge of the second surface of the graphic flexible board 30 . Lead conductive wires 350 are formed between the leads 340 and the vias 240 . The lead conductive wires 350 connect the leads 340 and the vias 240 .

[0065] In this embodiment, the conductive hole 240 is connected to the lead conductive line 350, and then connected to the lead 340. The conductive hole 240 is also connected to the lead auxiliary circuit 330 on the first side, and the lead auxiliary circuit 330 is connected to the gold finger circuit 310. All circuits are connected to form a conductive circuit, which is used to contact the external power supply through the lead 340 on the second side of the graphic flexible board 30 during the subsequent electroplating gold plating process, and provide current to the conductive circuit, thereby providing the gold finger circuit 310 with the current required for electroplating, meeting the prerequisite that the gold finger circuit 310 needs to be powered on during the electroplating process.

[0066] See also Figure 5 、 Figure 6 and Figure 7 ; Figure 5 This is a schematic diagram of the planar structure of the dry film pattern on the front side of the graphic flexible board according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the planar structure of the dry film pattern on the back of the graphic flexible board according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the planar structure of the gold finger flexible board according to an embodiment of the present invention.

[0067] Step S40:

[0068] The graphic flexible board 30 is subjected to electroplating gold finger processing, and the gold finger circuit 310 forms the gold finger 410 , thereby forming the gold finger flexible board 40 as a whole.

[0069] like Figure 5 As shown, the electroplating gold finger process includes: applying an anti-electrostatic gold dry film to the first surface of the patterned flexible board 30, performing pattern transfer to form an anti-electrostatic gold dry film pattern 360 on the first surface, performing electroplating gold processing, and then removing the anti-electrostatic gold dry film.

[0070] Optionally, the electroplating gold finger processing includes: sticking blue glue on the first side of the graphic flexible board 30 and making a blue glue pattern, then performing electroplating gold processing, and tearing off the blue glue; the blue glue plays the role of covering and protecting the area that does not require electroplating gold processing.

[0071] like Figure 6 As shown, in this embodiment, the electroplating gold finger processing includes: applying a dry film to the second surface, exposing, and developing to form a development pattern 370 located on the lead surface, and the development pattern 370 corresponds to the electroplating chuck setting.

[0072] Since the lead 340 is formed on the second side, it is necessary to form a developed pattern 370 on the lead 340 so that the electroplating chuck can effectively clamp and contact the lead 340 to form a conductive process during electroplating; while the gold finger electroplating process is being performed on the first side of the graphic flexible board 30, an anti-static gold dry film is attached to the second side of the graphic flexible board 30, and the anti-static gold dry film is exposed and developed in sequence to form an anti-static gold dry film pattern 360 on the second side.

[0073] like Figure 7 As shown, after the above processing, the gold finger flexible board 40 is formed.

[0074] See also Figure 8 、 Figure 9 and Figure 10 , Figure 8 This is a schematic diagram of the planar structure of the dry film pattern of the gold finger flexible board according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the planar structure of a local dry film pattern on a gold finger flexible board according to an embodiment of the present invention; Figure 10 Schematic diagram of the planar structure of a pattern transfer flexible board according to an embodiment of the present invention.

[0075] Step S50:

[0076] The gold finger flexible board 40 is subjected to pattern transfer processing to form a pattern transfer flexible board 50 ; all circuit patterns on the second surface of the gold finger flexible board 40 are completely etched.

[0077] like Figure 8 As shown, in this embodiment, the gold finger circuit 310 is distributed longitudinally, and the pattern transfer process includes applying a dry film to the gold finger flexible board 40 and performing an exposure process, and performing a development process to form a developed circuit pattern 420.

[0078] like Figure 9 As shown, after the dry film is exposed, a photocured area 4230 and a non-photocured area 4240 are formed; the non-photocured area 4240 of the lead auxiliary circuit 330 corresponding to the dry film is unilaterally reduced in the longitudinal distribution direction of the corresponding gold finger circuit 310 to form a longitudinal unilaterally reduced edge 4210, and unilaterally enlarged in the transverse direction to form a transverse unilaterally enlarged edge 4220.

[0079] In one embodiment, film exposure is used, and during exposure, the light-transmitting area of ​​the film corresponds to the light-cured area 4230 of the dry film, and the light-shielding area of ​​the film corresponds to the non-light-cured area 4240 of the dry film.

[0080] In one embodiment, a laser direct imaging (LDI) device is used for exposure, and the laser directly irradiates the photocured area 4230 corresponding to the dry film.

[0081] There is a certain deviation in exposure. If the non-photocured area 4240 deviates to the gold finger circuit 310, the gold finger circuit 310 in the deviated area will be etched away during subsequent etching, which will affect the signal transmission effect. Excessive deviation in a single direction may even cause the gold finger 410 to short-circuit. Therefore, in an embodiment of the present invention, the non-photocured area 4240 after exposure is unilaterally reduced or enlarged to reduce the impact of exposure deviation on the flexible circuit board.

[0082] like Figure 8As shown, when the lead auxiliary circuit 330 is a single circuit, the lead auxiliary circuit 330 that is not connected to the gold finger circuit 310 and the wire circuit 320 needs to be etched away. Therefore, during exposure, the longitudinal direction is unilaterally reduced to reduce the non-connected area, and the formed photocured area 4230 is longitudinally enlarged. After etching, the width of the area of ​​the lead auxiliary circuit 330 connecting the gold finger circuit 310 and the wire circuit 320 is increased to prevent the exposure deviation from causing the etching deviation, which affects the signal transmission effect; and the lateral direction is unilaterally enlarged to increase the non-photocured area 4240, and completely cover the area of ​​the lead auxiliary circuit 330 connecting the gold finger circuit 310 and the wire circuit 320, thereby ensuring that it is completely etched, and preventing the short circuit problem caused by incomplete etching caused by the exposure deviation.

[0083] It is worth noting that the reduced size or the enlarged size is 10 μm to 50 μm.

[0084] like Figure 10 As shown, the pattern transfer process includes etching the copper of the via hole 240 to form a copper-free hole 430; after etching, a film stripping process is performed to form a pattern-transferred flexible board 50.

[0085] See also Figure 11 、 Figure 12 and Figure 13 , Figure 11 This is a schematic diagram of the planar structure of a cover film attached to the front side of a pattern transfer flexible board according to an embodiment of the present invention; Figure 12 Schematic diagram of the cross-sectional structure of a pattern transfer flexible board according to an embodiment of the present invention; Figure 13 This is a schematic diagram of the planar structure of a high-precision flexible circuit board according to an embodiment of the present invention.

[0086] Step S60:

[0087] A cover film is attached to the pattern transfer flexible board 50 and pressed together to form a high-precision flexible circuit board 60 .

[0088] like Figure 11 As shown, in this embodiment, the covering film 610 is applied, including applying the covering film 610 to the surface where the gold finger circuit of the pattern transfer flexible board 50 is located or to both sides of the pattern transfer flexible board 50, as shown in FIG. Figure 12 As shown, the cover film 610 includes a cover film PI layer 6110 and a cover film glue layer 6120 .

[0089] In one embodiment, a covering film 610 is affixed to the surface where the gold finger circuit of the pattern transfer flexible board 50 is located because a double-sided flexible copper-clad laminate is used to replace the single-sided flexible circuit board of the prior art. The double-sided flexible copper-clad laminate includes a flexible board insulation layer 250, and all the circuit patterns 300 on the second side are completely etched away, that is, the flexible board insulation layer 250 on the second side is exposed. The flexible board insulation layer 250 and the covering film 610 are made of the same material, both of which are polyimide (PI) material, which is equivalent to the second side being a covering film layer. Therefore, only a single-sided covering film needs to be affixed (not shown in the accompanying drawings).

[0090] like Figure 12 As shown, in another embodiment, a cover film 610 is attached to both sides of the pattern transfer flexible board 50 and pressed. The cover film adhesive layer 6120 is melted by heat to form a fluid colloidal state. The cover film adhesive layers 6120 on both sides of the pattern transfer flexible board 50 flow into the copper-free holes 430 and fill the copper-free holes 430. If the cover film 610 is attached to one side of the pattern transfer flexible board 50, it is easy for the cover film adhesive layer 6120 in the copper-free holes 430 to overflow from the second side of the pattern transfer flexible board 50 where the cover film is not attached during pressing, causing contamination to the second side of the pattern transfer flexible board 50. In addition, if the thickness of the single-sided cover film adhesive layer 6120 is too thin to fill the copper-free holes 430, it will result in poor filling of the copper-free holes 430, and there will be problems of delamination and blistering at the position of the copper-free holes 430 during subsequent applications. Therefore, attaching a double-sided cover film 610 can form a better flexible circuit board processing effect.

[0091] In this embodiment, the lamination is performed using a rigid plate lamination device, and the lamination parameters are: a heating rate of 2°C / min to 4°C / min, a maximum temperature of 160°C to 170°C, and a pressure of 10kg / cm 2 Up to 20kg / cm 2 , the cooling rate is 6℃ / min to 10℃ / min.

[0092] In this embodiment, the relatively slow heating rate causes the glue layer to gradually heat up and gradually change from a solid state to a fluid state, forming a more sufficient fluid effect, which is more conducive to filling the copper-free hole 430; the maximum temperature is reasonably controlled to meet the pressing and bonding temperature requirements of the flexible circuit board cover film 610; the relatively small pressure forms sufficient flow conditions for the flowing colloid during the slow temperature increase process, and prevents problems such as line deviation caused by excessive pressure; the slow cooling process provides the temperature and time conditions for the board to fully release the internal stress after pressing.

[0093] It is worth noting that due to the relatively precise design and processing of flexible circuit boards, the structure of the actual processing process and the thickness of each layer, line width and other dimensions are all at the micron level. If the drawings are made according to the enlarged ratio of the actual structure, the drawings will be unclear. Therefore, in order to more clearly and intuitively represent the implementation process of the manufacturing method of this embodiment, the drawings of this embodiment are all schematic diagrams that enlarge the technical features, which do not represent the size of the actual structure, nor are they enlarged drawings of the actual structure in proportion.

[0094] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing a high-precision flexible circuit board with low signal loss, wherein the flexible circuit board is manufactured according to a design pattern, wherein the design pattern includes a gold finger area and a conductor pattern area. It is characterized in that The production method comprises the following steps: S10: adding a lead auxiliary area between the gold finger area and the conductor pattern area; S20: Take a double-sided flexible copper-clad laminate, drill holes in the lead auxiliary area and perform electroplating to form via holes, thereby forming a flexible laminate with via holes; S30: manufacturing a circuit pattern on the flexible board with via holes, wherein the circuit pattern includes a plurality of gold finger circuits and a conductor circuit to form a patterned flexible board; The lead auxiliary area on the first surface of the graphic flexible board is provided with a plurality of lead auxiliary circuits, the via holes are located on the lead auxiliary circuits, and the lead auxiliary circuits are connected to the gold finger circuit and the wire circuit; A lead is formed on the edge of the second surface of the graphic flexible board, and a lead conductive line is formed between the lead and the conductive hole, and the lead conductive line connects the lead and the conductive hole; S40: performing electroplating gold finger processing on the graphic flexible board to form a gold finger flexible board; S50: performing pattern transfer processing on the gold finger flexible board to form a pattern transfer flexible board; All the circuit patterns on the second surface of the gold finger flexible board are completely etched; The gold finger circuit is distributed longitudinally, and the pattern transfer process includes applying a dry film to the gold finger flexible board and exposing it to light. The non-photocuring area of ​​the lead auxiliary circuit corresponding to the dry film is unilaterally reduced in the longitudinal distribution direction of the gold finger circuit and unilaterally enlarged in the transverse direction. S60: affixing a cover film to the pattern-transferred flexible board and laminating the cover film to form a high-precision flexible circuit board.

2. The method for manufacturing a high-precision flexible circuit board with low signal loss according to claim 1, characterized in that: A single lead auxiliary circuit connects all of the plurality of gold finger circuits.

3. The method for manufacturing a high-precision flexible circuit board with low signal loss according to claim 2, characterized in that: The conducting hole is located between two adjacent gold finger circuits.

4. The method for manufacturing a high-precision flexible circuit board with low signal loss according to claim 1, wherein: The electroplating gold finger processing includes: applying a dry film to the second surface, exposing, and developing to form a development pattern located on the surface of the lead, and the development pattern corresponds to the electroplating chuck setting.

5. The method for manufacturing a high-precision flexible circuit board with low signal loss according to claim 1, wherein: The reduced size or the enlarged size is 10 μm to 50 μm.

6. The method for manufacturing a high-precision flexible circuit board with low signal loss according to claim 1, wherein: The pattern transfer process includes etching the copper of the via hole.

7. The method for manufacturing a high-precision flexible circuit board with low signal loss according to claim 1, wherein: The applying of the covering film includes applying the covering film to the surface of the pattern transfer flexible board where the gold finger circuit is located or to both surfaces of the pattern transfer flexible board.

8. The method for manufacturing a high-precision flexible circuit board with low signal loss according to claim 1, wherein: The pressing is performed using a rigid plate pressing device.

9. The method for manufacturing a high-precision flexible circuit board with low signal loss according to claim 8, wherein: The pressing parameters are: heating rate of 2℃ / min to 4℃ / min, maximum temperature of 160℃ to 170℃, pressure of 10kg / cm 2 Up to 20kg / cm 2 , the cooling rate is 6℃ / min to 10℃ / min.

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