Manufacturing method and structure of flexible circuit board for display module connecting line

Abstract

The invention relates to the technical field of flexible circuit board manufacturing, and discloses a flexible circuit board manufacturing method and structure for a display module connecting line, and the method is characterized in that the method comprises the steps: S100, arranging a false finger region and a pair of golden finger regions on a flexible copper-clad plate, and enabling the false finger region to be connected between the two golden finger regions; s200, a circuit is manufactured in the golden finger area to form golden fingers, meanwhile, a circuit is manufactured in the false finger area to form false fingers, and the false fingers are used for connecting the two golden fingers; s300, covering the artificial finger area and the golden finger area with an insulating layer; and step S400, cutting off an excess material area in the false finger area to prepare a finished product, wherein the excess material area is connected with a non-golden finger part in the golden finger area. According to the design, the golden fingers on the left side and the right side form unified expansion and contraction changes, and the situation that the fingers on the left side and the right side are inconsistent in expansion and contraction size or direction in the FPC production process or the Bonding process is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible circuit board manufacturing, and in particular to a flexible circuit board manufacturing method and structure for display module connecting lines. BACKGROUND

[0002] In the manufacturing process of FPC (flexible circuit board) for display modules, the total width of the product is usually more than 100 mm and the width of the gold finger needs to be controlled below 0.065 mm, which is prone to deformation when applied to the connecting lines of the display module. Specifically, when the flexible circuit board in the display module connecting line is bonded with the display screen, the left and right gold fingers need to be aligned with the display screen lines through the bonding equipment CCD (i.e. using machine vision to achieve high-precision alignment of key electrical connection points in display screen assembly), and after alignment, the left and right gold fingers of the flexible circuit board and the lines of the display screen are connected through the ACF glue, which makes the material characteristics of the upper and lower conductive and the left and right non-conductive, so that the gold finger and the display screen line are connected in one-to-one correspondence. This requires that the spacing tolerance between the leftmost and rightmost gold fingers must be strictly controlled within ±0.05 mm. However, due to the uneven stress of the FPC material during the process, the left and right gold fingers are prone to independent expansion and contraction deformation, which ultimately leads to unstable key spacing size and seriously affects the bonding yield.

[0003] In the existing technology, methods such as increasing reinforcing structures or optimizing material parameters are mainly used to improve the size stability, but these schemes have obvious shortcomings: reinforcing structures will reduce the flexibility of FPC, and material optimization often cannot meet various performance indicators. In particular, for large-size FPC with ultra-fine lines, the existing technology still cannot effectively solve the spacing tolerance problem caused by the independent deformation of the left and right areas. SUMMARY

[0004] The main purpose of the present application is to provide a flexible circuit board manufacturing method for display module connecting lines, which aims to solve the technical problem that the left and right fingers are prone to left or right expansion and contraction deformation during the production and bonding process of FPC.

[0005] In order to achieve the above object, the application provides a flexible circuit board manufacturing method for display module connection line, characterized in that it comprises the following steps: S100, setting a false finger area and a pair of gold finger areas on a flexible copper-clad plate, the false finger area being connected between the two gold finger areas; S200, manufacturing a line on the gold finger area to form a gold finger, and manufacturing a line on the false finger area to form a false finger, the false finger being used to connect the two gold fingers; S300, covering an insulating layer in the false finger area and the gold finger area; S400, cutting off a surplus area inside the false finger area to manufacture a finished product, the surplus area being connected with a non-gold finger part in the gold finger area.

[0006] Optionally, the width ratio between the false finger and the gold finger ranges from 0.8 to 1.2, and the length ratio between the false finger and the true finger ranges from 0.8 to 1.2.

[0007] Optionally, in step S200, a layer of photosensitive dry film is laminated on the gold finger area and the false finger area, and the operations of imaging, developing, etching and removing the photosensitive dry film are sequentially performed to form a plate surface line, the gold finger and the false finger, wherein the gold finger is not connected with the false finger.

[0008] Optionally, in step S300, the insulating layer exposes the line, the false finger and the gold finger, the insulating layer material comprises polyimide, modified epoxy resin coating and solder mask ink, and the thickness ratio between the insulating layer covering the false finger area and the insulating layer covering the gold finger area ranges from 0.8 to 1.2.

[0009] Optionally, between step S100 and step S200, step S110 is further included, a through hole is arranged in the gold finger part network line according to wiring requirements, an initial copper layer or conductive carbon powder with a thickness of 0.3-1 μm is formed in the through hole, and electroplating is performed based on the initial copper layer or conductive carbon powder.

[0010] Optionally, between step S300 and step S400, step S310 is further included, nickel plating or gold plating is performed on the gold finger and the false finger.

[0011] Optionally, in step S200, a pair of limit marks are etched on the left and right ends of the gold finger, the limit marks comprise T-shaped, cross-shaped and circular shapes, and the spacing between the limit marks and the false finger ranges from 0.2 to 0.5 mm.

[0012] Optionally, in step S400, the excess material region is located between the limiting marks near the two ends of the dummy finger, the edge of the excess material region is punched based on the limiting marks using a laser cutting machine, the excess material region is in the shape of a whole rectangle, and transition fillets are arranged around the excess material region, and the radius of the transition fillets is 0.5-1.0 mm.

[0013] Optionally, in step S200, a component area for mounting various circuit components and corresponding circuits is prepared on one side of the flexible copper-clad plate; and step S320 is further included between step S310 and step S400, in which a reinforcing sheet is hot-pressed on the other side of the flexible copper-clad plate.

[0014] The application further provides a flexible circuit board structure for display module connection lines, comprising: a flexible copper-clad plate; a pair of gold fingers arranged on one side of the flexible copper-clad plate; a dummy finger connected between the two gold fingers; and an insulating layer arranged on one side or both sides of the flexible copper-clad plate, the insulating layer exposing the gold fingers and the dummy finger.

[0015] In the technical solution provided by the application, due to the influence of immersion in chemical solution and environmental temperature and humidity, the FPC has swelling and shrinkage changes. The dummy finger has the same structure as the left and right gold fingers, and has no signal connection function and only has a physical connection function. In this structure, the left and right gold fingers are restrained, so that the left and right gold fingers have uniform swelling and shrinkage changes. In the production process or the Bonding process, the left and right gold fingers will not have inconsistent swelling and shrinkage sizes or directions. As described above, the dummy finger only has a physical connection function, but is manufactured in the same way as the gold finger for connecting with the display device. Therefore, unnecessary electrical paths need to be cut off to avoid signal crosstalk or short circuit risk in the final product. Therefore, the excess material region needs to be cut off. After cutting off, the signal crosstalk or short circuit risk is eliminated, and residual stress caused by the insulating layer covering is also eliminated, so that the dummy finger is prevented from being broken due to stress concentration when the FPC is subsequently bent. BRIEF DESCRIPTION OF DRAWINGS

[0016] One or more embodiments are illustrated by way of example in the accompanying drawings that are not intended to be limiting of the embodiments, in which like references numbers refer to like elements in the various figures, unless otherwise indicated. The figures in the drawings are not necessarily to scale, with emphasis being placed on illustrating the principles of the embodiments.

[0017] Figure 1 A flowchart of an embodiment of the method for manufacturing a flexible circuit board for display module connection lines of the application; Figure 2Front view structure diagram of one embodiment of the flexible circuit board structure for display module connecting line of the present application; Figure 3 Front view structure diagram of one embodiment of the flexible circuit board structure for display module connecting line of the present application; Figure 4 Magnified view of the golden finger area; Figure 5 Magnified view of the dummy finger area.

[0018] In the figure: 1, flexible copper clad plate; 2, golden finger area; 21, golden finger; 22, limiting mark; 3, dummy finger area; 31, dummy finger; 32, excess material area; 321, transition round corner; 4, insulating layer; 5, component area; 51, reinforcing sheet. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of the present application, the present application will be described in more detail below in conjunction with the drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on the other element or one or more intervening elements can be present therebetween. When an element is described as "connected to" another element, it can be directly connected to the other element or one or more intervening elements can be present therebetween. The terms "vertical", "horizontal", "left", "right", "inner", "outer" and similar expressions used in the present specification are for illustrative purposes only. In the description of the present application, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating relative importance or implying the number of the technical features indicated. Therefore, unless otherwise specified, the features defined with "first", "second" can explicitly or implicitly include one or more of the features; the meaning of "multiple" is two or more. The term "comprising" and any variation thereof means non-exclusive inclusion, and one or more other features, integers, steps, operations, units, components and / or combinations thereof can be present or added.

[0020] In addition, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. All technical and scientific terms used in the present specification have the same meaning as understood by the person skilled in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not used to limit the present application. The term "and / or" used in the present specification includes any and all combinations of one or more related listed items.

[0021] In addition, the technical features involved in the different embodiments of the application described below can be combined with each other as long as they do not conflict with each other.

[0022] Please refer to Figures 1 to 5 The application provides a flexible circuit board manufacturing method for display module connecting lines, characterized by comprising the following steps: S100, a dummy finger area 3 and a pair of gold finger areas 2 are arranged on a flexible copper-clad plate 1, and the dummy finger area 3 is connected between the two gold finger areas 2; S200, lines are formed in the gold finger areas 2 to form gold fingers 21, and lines are formed in the dummy finger area 3 to form a dummy finger 31, and the dummy finger 31 is used for connecting the two gold fingers 21; S300, an insulating layer 4 is covered in the dummy finger area 3 and the gold finger areas 2; and S400, a remaining area 32 in the dummy finger area 3 is cut off to obtain a finished product, and the remaining area 32 is connected with a part of the gold finger areas 2 which is not the gold fingers 21.

[0023] In the technical scheme provided by the application, due to the influence of immersion in chemical solution and environmental temperature and humidity, the FPC has expansion and contraction changes. The dummy finger 31 has the same structure as the left and right fingers, and has no signal connection function and only has a physical connection function. In this structure, the left and right gold fingers 21 are restricted, the left and right fingers have uniform expansion and contraction changes, and the left and right fingers will not have inconsistent expansion and contraction sizes or directions in the production process or the Bonding process. As described above, the dummy finger 31 only has a physical connection function, but is manufactured by the same method as the gold fingers 21 used for connecting the display device. Therefore, unnecessary electrical paths need to be cut off to avoid signal crosstalk or short circuit risk in the final product. Therefore, the remaining area 32 needs to be cut off. After cutting off, the signal crosstalk or short circuit risk is eliminated, and residual stress generated by the covering of the insulating layer 4 is also eliminated, so that the dummy finger 31 is prevented from being broken due to stress concentration when the FPC is subsequently bent.

[0024] Please refer to Figures 1 to 5 In the embodiment, the width ratio between the dummy finger 31 and the gold finger 21 is 0.8-1.2, and the length ratio between the dummy finger 31 and the real finger is 0.8-1.2. The width ratio between the dummy finger 31 and the gold finger 21 is controlled, so that the dummy finger 31 has a transverse rigidity comparable to that of the gold finger 21. When the FPC is affected by immersion in chemical solution or changes in temperature and humidity, the dummy finger 31 and the gold finger 21 have synchronous expansion and contraction deformation, so that the stress transmission efficiency can be maximized, and the spacing fluctuation between the two gold fingers 21 is reduced from ±0.05 mm to ±0.03 mm. The length ratio between 0.8 and 1.2 can provide sufficient bending moment resistance without increasing the thickness, so that the size deformation and fluctuation of the left and right gold finger areas 2 caused by chemical solution or changes in environmental temperature and humidity are reduced.

[0025] Please refer to Figures 1 to 5 In this embodiment, in step S200, a photosensitive dry film is thermally pressed and attached to the gold finger area 2 and the dummy finger area 3 as a pattern transfer medium for etching; and imaging, developing, etching and film removal operations are sequentially performed to form the board surface circuit, the gold finger 21 and the dummy finger 31. In the imaging process, the design pattern is transferred to the dry film by ultraviolet light irradiation, the gold finger 21 and the dummy finger 31 are synchronously exposed, and after exposure, a photopolymerization reaction occurs to harden the circuit area; in the developing process, the unexposed dry film is dissolved to expose the copper layer to be etched; in the etching process, the exposed copper foil is removed to form a conductive circuit and the gold finger 21 and the dummy finger 31; in the film removal process, a 3-5% sodium hydroxide solution is used to remove the hardened photosensitive dry film. There is no signal connection between the gold finger 21 and the dummy finger 31. The gold finger 21 and the dummy finger 31 are synchronously manufactured using the same process flow to ensure that they are highly consistent in structural strength and reduce the expansion and contraction amplitude.

[0026] Please refer to Figures 1 to 5 In this embodiment, in step S300, the insulating layer 4 exposes the circuit, the dummy finger 31 and the gold finger 21, and the insulating layer 4 material includes polyimide, modified epoxy resin coating and solder resist ink. The thickness ratio between the insulating layer 4 covering the dummy finger area 3 and the insulating layer 4 covering the gold finger area 2 is in the range of 0.8-1.2, which can thin the solder resist ink thickness of the dummy finger area 3 to enhance flexibility and release more deformation, and the thin insulating layer 4 of the dummy finger area 3 can adapt to high-frequency bending, and the thick insulating layer 4 of the gold finger area 2 can maintain interface stability.

[0027] Please refer to Figures 1 to 5 In this embodiment, between step S100 and step S200, step S110 is also included, that is, a through hole is drilled in the gold finger area 2. The through hole position is designed according to the actual project wiring and pad position design needs, and is set in part of the network circuit. An initial copper layer or conductive carbon powder of 0.3-1 μm is formed in the through hole, and electroplating is performed based on the initial copper layer or conductive carbon powder. The through hole not only ensures the conduction of each layer of circuit in the flexible copper-clad plate 1, but also provides a physical fulcrum for stress balance of the dummy finger 31.

[0028] Please refer to Figures 1 to 5In the embodiment, between step S300 and step S400, step S310 is further included, in which nickel plating or gold plating is performed on the gold fingers 21 and the dummy fingers 31, and only the gold fingers 21 and the dummy finger area 3 are exposed in the process to avoid unnecessary gold plating. The dummy fingers 31 are plated synchronously with the nickel plating layer of the gold fingers 21, and the thickness of the nickel plating layer of the dummy fingers 31 is controlled within the range of 0.9-1.1 times that of the gold fingers 21, so as to ensure that the thermal expansion behaviors of the two are consistent in the subsequent lamination and bonding process, and the fpc warping caused by stress is inhibited.

[0029] Please refer to Figures 1 to 5 In the embodiment, in step S200, a pair of limiting marks 22 are etched on the left and right ends of the gold fingers 21. The limiting marks 22 are etched and formed synchronously with the gold finger 21 / dummy finger 31 circuit, and the limiting marks 22 have shapes including T-shaped, cross-shaped and circular-shaped, which can be used as positioning points in the punching of the excess material area 32 and the bonding, and can be switched among the three shapes to adapt to different optical detection and positioning systems to achieve the best positioning effect. The spacing between the limiting marks 22 and the dummy fingers 31 is 0.2-0.5 mm, which can control the design length of the dummy fingers 31.

[0030] Please refer to Figures 1 to 5 In the embodiment, in step S400, the excess material area 32 is located between the limiting marks 22 near the two ends of the dummy fingers 31, and the limiting marks 22 are used as the positioning reference of the laser path to control the punching deviation of the edge of the excess material area 32 in the punching process. The excess material area 32 is in the shape of a whole rectangle, and is connected to the gold finger area 2 on both sides; the excess material area 32 is provided with a transition fillet 321 around the periphery, and the radius of the transition fillet 321 is 0.5-1.0 mm, so that no cracks occur in the process of laser cutting the transition fillet 321.

[0031] Please refer to Figures 1 to 5 In the embodiment, in step S200, the component area 5 for mounting various circuit components and the corresponding circuit are prepared on one side of the flexible copper-clad plate 1; between step S310 and step S400, step S320 is further included, in which a reinforcing sheet 51 is hot-pressed on the other side of the flexible copper-clad plate 1 for the component area 5, and the reinforcing sheet 51 provides rigid support for the component area 5, while the uncovered area remains flexible to meet the dynamic bending requirements of the folding screen and the like.

[0032] Please refer to Figures 1 to 5 Figures 1 to 5 Figures 2 to 5The application further provides a flexible circuit board structure for display module connecting lines, characterized in that comprising: a flexible copper-clad plate 1; a pair of gold fingers 21 arranged on one side of the flexible copper-clad plate 1; a dummy finger 31 connected between the two gold fingers 21; and an insulating layer 4 arranged on one side or both sides of the flexible copper-clad plate 1, the insulating layer 4 exposing the gold fingers 21 and the dummy finger 31. The structure connects the left and right gold fingers 21 through the dummy finger 31, the dummy finger 31 itself has no signal connection function and only plays a physical connection role, and in this structure, the left and right gold fingers 21 are formed in a restraint effect, so that the left and right fingers form a unified expansion and contraction change, and the FPC does not appear the expansion and contraction size or direction inconsistency in the production process or the bonding process.

[0033] The above examples are only used to illustrate the technical solutions of the present application, but not limit it; under the idea of the present application, the technical features in the above examples or different examples can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above, which are not provided in details for simplicity; although the present application is described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for manufacturing a flexible circuit board for display module connection lines, characterized in that, include: Step S100: A fake finger area (3) and a pair of gold finger areas (2) are provided on the flexible copper clad laminate (1), wherein the fake finger area (3) is connected between the two gold finger areas (2); Step S200: A circuit is fabricated in the gold finger area (2) to form a gold finger (21), and a circuit is fabricated in the fake finger area (3) to form a fake finger (31). The fake finger (31) is used to connect the two gold fingers (21). Step S300: Cover the artificial finger area (3) and the gold finger area (2) with an insulating layer (4); Step S400: Remove the excess material area (32) inside the fake finger area (3) to make a finished product, and connect the excess material area (32) to the non-gold finger (21) part inside the gold finger area (2).

2. The method for manufacturing a flexible circuit board for display module connection lines according to claim 1, characterized in that, The width ratio between the artificial finger (31) and the gold finger (21) is in the range of 0.8-1.2, and the length ratio between the artificial finger (31) and the real finger is in the range of 0.8-1.

2.

3. The method for manufacturing a flexible circuit board for display module connection lines according to claim 2, characterized in that, In step S200, a photosensitive dry film is laminated on the gold finger area (2) and the fake finger area (3), and imaging, development, etching and removal of the photosensitive dry film are performed in sequence to form board surface circuits, the gold finger (21) and the fake finger (31), wherein there is no signal connection between the gold finger (21) and the fake finger (31).

4. The method for manufacturing a flexible circuit board for display module connection lines according to claim 3, characterized in that, In step S300, the insulating layer (4) exposes the circuit, the dummy finger (31) and the gold finger (21). The insulating layer (4) material includes polyimide, modified epoxy resin coating and solder resist ink. The thickness ratio between the insulating layer (4) covering the dummy finger area (3) and the insulating layer (4) covering the gold finger area (2) is in the range of 0.8-1.

2.

5. The method for manufacturing a flexible circuit board for display module connection lines according to claim 4, characterized in that, Between steps S100 and S200, there is also step S110, in which, according to the wiring requirements, a via is set in the network line of the gold finger area (2), and an initial copper layer or conductive carbon powder of 0.3-1μm is formed in the via, and electroplating is performed based on the initial copper layer or conductive carbon powder using an electroplating process.

6. The method for manufacturing a flexible circuit board for display module connection lines according to claim 5, characterized in that, Between steps S300 and S400, there is also step S310, in which nickel plating or immersion nickel plating is performed on the gold finger (21) and the fake finger (31).

7. The method for manufacturing a flexible circuit board for display module connection lines according to claim 6, characterized in that, In step S200, a pair of limiting marks (22) are etched on the left and right ends of the gold finger (21). The shape of the limiting marks (22) includes T-shape, cross shape and circle. The distance between the limiting marks (22) and the fake finger (31) is 0.2-0.5mm.

8. The method for manufacturing a flexible circuit board for display module connection lines according to any one of claims 1 to 7, characterized in that, In step S400, the excess material area (32) is located between the limiting marks (22) near both ends of the fake finger (31). The edge of the excess material area (32) is punched based on the limiting marks (22). The excess material area (32) is rectangular in shape. The excess material area (32) is provided with transition rounded corners (321) around its perimeter. The radius of the transition rounded corners (321) is 0.5-1.0 mm.

9. The method for manufacturing a flexible circuit board for display module connection lines according to claim 8, characterized in that, In step S200, a component area (5) for mounting various circuit components and corresponding lines are made on one side of the flexible copper-clad laminate (1); Between step S310 and step S400, step S320 is also included, in which a reinforcing sheet (51) is hot-pressed on the other side of the flexible copper-clad laminate (1) in the component area (5).

10. A flexible circuit board structure for connecting lines of a display module, characterized in that, include: Flexible copper clad laminate (1); A pair of gold fingers (21) are disposed on the same side of the flexible copper-clad laminate (1); A prosthetic finger (31) is connected between the two gold fingers (21); An insulating layer (4) is disposed on one or both sides of the flexible copper-clad laminate (1), and the insulating layer (4) exposes the gold finger (21) and the fake finger (31).

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