Flexible circuit board manufacturing method and flexible circuit board

Abstract

This invention discloses a method for manufacturing a flexible circuit board and a flexible circuit board, relating to the field of integrated circuit manufacturing technology. The method includes the following steps: providing a flexible copper-clad laminate (CCL) having a pre-processed area; drilling holes in the CCL to form positioning holes, the positioning holes partially overlapping with the pre-processed area and forming a semi-circular notch in the overlapping area; providing a punching die to punch the flexible CCL, the area covered by the projection of the punching die along the punching direction forming a first projection pattern, the first projection pattern partially overlapping with the pre-processed area and forming a pad half-hole in the overlapping area, the pad half-hole completely covering the semi-circular notch, and the sidewall of the pad half-hole forming a sidewall copper-plated area. By forming a larger sidewall copper-plated area formed by the sidewall of the pad half-hole, sufficient and stable solder volume can be provided for soldering, reducing the risk of cold solder joints and improving the yield of integrated circuit manufacturing, production of dedicated lithography machines, and etching machines.

Description

Technical Field

[0001] This invention relates to the field of flexible printed circuit boards, and in particular to a method for manufacturing a flexible printed circuit board and a flexible printed circuit board. Background Technology

[0002] In the electronics manufacturing industry, especially in the manufacturing of specialized equipment for semiconductor devices such as integrated circuit manufacturing, lithography machines, and etching machines, flexible printed circuit boards (PCBs) play a crucial role. Furthermore, the bonding between PCBs and PCBs is a key step in establishing circuit connections within these specialized lithography and etching machines, significantly impacting their performance and stability. However, this bonding process currently faces numerous challenges, severely affecting production efficiency and product quality.

[0003] Generally, flexible printed circuit boards (FPCBs) employ a double-sided substrate structure with a polyimide (PI) layer sandwiched in between. During soldering of the FPCB to the PCB, solder should normally flow smoothly to form a stable solder joint between the upper and lower pads of the FPCB and the PCB pads, achieving a good electrical and mechanical connection. However, the presence of the PI layer interferes with the solder flow path, preventing the solder joint from being fully filled with solder, thus leading to frequent cold solder joints on the FPCB. Cold solder joints can cause a series of problems such as poor circuit contact and signal transmission interruption, seriously affecting the normal use of electronic products.

[0004] The current industry practice is to create semi-circular notches along the edges of the upper and lower pads on flexible circuit boards and then plate them with copper. This copper and tin plating on the sidewalls improves the soldering effect. However, this approach still has significant drawbacks. Firstly, the area covered by the copper and tin plating is limited, failing to provide a sufficient and stable amount of solder for soldering. Secondly, the area around the pads is still constrained by the intermediate PI layer, leaving a risk of cold solder joints during the soldering process, resulting in a significant decrease in production yield. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for manufacturing flexible printed circuit boards (PCBs) that enables the formation of stable solder joints between the upper and lower pads of the flexible PCB and the PCB pads, thereby improving the yield rate of production.

[0006] The present invention also proposes a flexible circuit board manufactured using the above-described flexible circuit board manufacturing method.

[0007] According to a first aspect of the present invention, a method for manufacturing a flexible circuit board includes the following steps:

[0008] A flexible copper-clad laminate is provided, the flexible copper-clad laminate having a pre-processed area, the pre-processed area having a pad area;

[0009] Drilling is performed on the flexible copper-clad laminate to form metal vias and positioning holes. The metal vias completely overlap with the pre-processed area, and the positioning holes are located in the pad area. The positioning holes partially overlap with the pre-processed area and form a semi-circular notch in the overlapping area.

[0010] A punching die is provided to punch the flexible copper-clad laminate. A positioning pin is inserted into the positioning hole and the positioning hole is used as a positioning reference. The area covered by the projection of the punching die along the punching direction forms a first projection pattern. The first projection pattern and the pre-processed area partially overlap and form a pad half-hole in the overlapping area. The pad half-hole completely covers the semi-circular notch, and the sidewall of the pad half-hole forms a sidewall copper-plated area.

[0011] Copper plating is performed on the surface of the copper-plated area on the sidewall and the surface of the sidewall of the metal via to form a conductive copper layer, which is electrically connected to the conductive layer of the flexible copper-clad laminate.

[0012] The surface of the conductive copper layer is tin-plated to form a solderable tin layer on the surface of the copper-plated area of ​​the sidewall.

[0013] A flexible circuit board is punched out along the edge of the pre-processed area, the flexible circuit board retaining the metal vias and the pad half-holes.

[0014] The flexible circuit board manufacturing method according to the first aspect of the present invention has at least the following beneficial effects: by forming metal vias and pad half-holes with specific structures on the flexible copper-clad laminate, and performing copper plating and tin plating on their sidewalls, many problems existing in the traditional flexible circuit board and PCB soldering are solved. In the traditional method, the PI layer interferes with the flow path of solder, resulting in insufficient solder filling at the solder joint and frequent cold solder joints. In the present invention, the design of the metal vias and pad half-holes provides a smoother channel for solder flow. At the same time, the sidewalls of the pad half-holes are formed after the positioning holes are punched, which have a larger area than the sidewalls of the semi-circular notches formed on the flexible circuit board in the original method. Because the sidewalls of the pad half-holes form a wider copper plating area, and the sidewall copper plating area forms a solderable tin layer after tin plating, it can provide sufficient and stable solder for soldering, reduce the risk of cold solder joints, improve the reliability and stability of soldering, thereby improving the performance and stability of electronic products and reducing failures caused by poor circuit contact, signal transmission interruption, and other problems.

[0015] According to some embodiments of the present invention, the blanking die includes a protrusion and a blanking portion, the area covered by the projection of the protrusion along the blanking direction forms a second projection pattern, the second projection pattern completely coincides with the projection of the positioning hole along the axial direction, and the protrusion and the blanking portion are smoothly connected.

[0016] According to some embodiments of the present invention, after providing a punching die to punch the flexible copper-clad laminate, the method further includes the following steps: using a laser to perform micro-hole processing on the pad areas at both ends of the axial direction of the pad half-hole, burning through the insulating substrate and the conductive layer of the flexible copper-clad laminate corresponding to the pad area, so as to form uniformly distributed micro-holes on the insulating substrate.

[0017] According to some embodiments of the present invention, the copper plating of the surface of the sidewall copper plating area and the sidewall surface of the metal via includes the following steps: activating the sidewall copper plating area, the hole wall of the metal via and the hole wall of the micropore to form a catalyst layer in the sidewall copper plating area, the hole wall of the metal via and the hole wall of the micropore.

[0018] According to some embodiments of the present invention, after activating the copper-plated area on the sidewall, the wall of the metal via, and the wall of the micro-hole, the method further includes the following steps: copper plating the copper-plated area on the sidewall, the wall of the metal via, and the wall of the micro-hole; depositing the conductive copper layer on the copper-plated area on the sidewall and the wall of the metal via; and depositing a copper layer on the wall of the micro-hole to form a conductive copper pillar, wherein the upper and lower ends of the conductive copper pillar are respectively connected to the conductive layer of the flexible copper-clad laminate.

[0019] According to some embodiments of the present invention, the copper plating process for the sidewall copper plating area, the hole wall of the metal via, and the hole wall of the microvia includes the following steps:

[0020] The copper-plated area on the sidewall, the wall of the metal via, and the wall of the micro-hole are subjected to a copper plating process to form a copper plating layer of uniform thickness on the activated copper-plated area on the sidewall and the wall of the micro-hole.

[0021] The copper plating layer is subjected to a secondary copper plating process to thicken the copper plating area on the sidewall and the copper plating layer on the wall of the metal via. Simultaneously, the copper plating layer on the wall of the microhole is subjected to a secondary copper plating process to form the conductive copper pillar.

[0022] According to some embodiments of the present invention, the primary copper plating process employs a chemical copper plating process, and the secondary copper plating process employs an electroplating process.

[0023] According to some embodiments of the present invention, after copper plating of the surface of the sidewall copper-plated area and the sidewall surface of the metal via, and before tin plating of the surface of the conductive copper layer, the following steps are further included:

[0024] The flexible copper-clad laminate, on which copper plating has been applied to the sidewall copper plating area, the hole wall of the metal via, and the hole wall of the micro-hole, is subjected to circuit pattern processing to form a conductive circuit pattern including the pad area.

[0025] A cover film is applied to the surface of the flexible copper-clad laminate after the circuit diagram processing is completed, and a window is made in the cover film at the position corresponding to the pad area to expose the pad area.

[0026] According to some embodiments of the present invention, the step of punching out the flexible circuit board along the edge of the pre-processed area includes the following steps: using multiple shaped punching dies to punch out the flexible copper-clad laminate sequentially along the edge of the pre-processed area to punch out the shape of the flexible circuit board.

[0027] According to a second aspect embodiment of the present invention, the flexible circuit board is manufactured using the flexible circuit board manufacturing method described in the first aspect embodiment above. The flexible circuit board has an insulating substrate and a conductive layer. The conductive layer can cover both sides of the insulating substrate. The insulating substrate has a pad area. The edge of the pad area is provided with a pad half-hole. Conductive copper pillars are uniformly distributed in the area of ​​the insulating substrate corresponding to the pad area. The conductive copper pillars pass through the insulating substrate and are connected to the conductive layer to achieve electrical connection. The sidewall of the pad half-hole is a smooth and continuous sidewall and is a copper-plated area of ​​the sidewall.

[0028] It has at least the following beneficial effects: This flexible circuit board has all the beneficial effects brought about by the above-mentioned flexible circuit board manufacturing method, which will not be repeated here.

[0029] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0031] Figure 1 This is a schematic diagram of a flexible circuit board according to a second aspect embodiment of the present invention (the shaded area in the diagram represents the pad area of ​​the flexible circuit board).

[0032] Figure 2 for Figure 1 A schematic diagram of a flexible copper-clad laminate is shown (the dotted area in the diagram represents the pre-processing area).

[0033] Figure 3 for Figure 2 The diagram shows a partially enlarged view of area A in the flexible copper clad laminate (area A is a partial area of ​​the pre-processed area in the flexible copper clad laminate).

[0034] Figure 4 for Figure 3 The diagram shows a partially enlarged view of the pre-processed area A in the case of a flexible copper-clad laminate being punched using a punching die (area A is a partial area of ​​the pre-processed area in the flexible copper-clad laminate).

[0035] Figure 5 for Figure 4 An enlarged schematic diagram of the blanking die is shown;

[0036] Figure 6 for Figure 4 The diagram shows a partially enlarged view of area A after the flexible copper clad laminate has been punched by a punching die (area A is a partial area of ​​the pre-processed area in the flexible copper clad laminate).

[0037] Figure 7 for Figure 1 A schematic diagram showing the flexible copper-clad laminate punched out of the shape of a flexible circuit board;

[0038] Figure 8 This is a cross-sectional view of the pad area of ​​a flexible circuit board according to a second aspect embodiment of the present invention.

[0039] Icon labels:

[0040] 1. Flexible copper clad laminate; 2. Pre-processed area; 3. Metal via; 4. Positioning hole; 5. Pad half hole; 6. Pad area; 7. Conductive layer; 8. Semi-circular notch; 9. Punching die; 91. Protrusion; 92. Punching part; 10. Outer shape punching die; 11. Flexible circuit board; 12. Insulating substrate; 13. Conductive copper pillar; 14. Conductive copper layer. Detailed Implementation

[0041] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0042] In the description of this invention, the use of "first" and "second" is for the purpose of distinguishing technical features only, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0043] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0044] Reference Figure 1 as well as Figure 8 According to a first aspect of the present invention, a method for manufacturing a flexible circuit board includes the following steps:

[0045] A flexible copper clad laminate 1 is provided, the flexible copper clad laminate 1 having a pre-processed area 2, and the pre-processed area 2 having a pad area 6;

[0046] Drilling is performed on the flexible copper clad laminate 1 to form metal vias 3 and positioning holes 4. The metal vias 3 completely overlap with the pre-processed area 2. The positioning holes 4 are located in the pad area 6. The positioning holes 4 partially overlap with the pre-processed area 2 and form a semi-circular notch 8 in the overlapping area.

[0047] A punching die 9 is provided to punch the flexible copper-clad board 1. A positioning pin is inserted into the positioning hole 4 and the positioning hole 4 is used as the positioning reference. The area covered by the projection of the punching die 9 along the punching direction forms a first projection pattern. The first projection pattern and the pre-processed area 2 partially overlap and form a pad half hole 5 in the overlapping area. The pad half hole 5 completely covers the semi-circular notch 8. The side wall of the pad half hole 5 forms a side wall copper plating area.

[0048] Copper plating is performed on the surface of the copper-plated area on the sidewall and the surface of the sidewall of the metal via 3 to form a conductive copper layer 14, which is electrically connected to the conductive layer 7 of the flexible copper-clad laminate 1.

[0049] The surface of the conductive copper layer 14 is tin-plated to form a solderable tin layer on the surface of the copper-plated area of ​​the sidewall.

[0050] A flexible circuit board 11 is punched out along the edge of the pre-processing area 2. The flexible circuit board 11 retains metal vias 3 and pad half-holes 5.

[0051] The following will combine Figures 1 to 8 The method for manufacturing flexible circuit boards according to the present invention will be described in detail.

[0052] Reference Figures 1 to 2A flexible copper-clad laminate 1 is provided: a flexible copper-clad laminate 1 of suitable specifications is selected. The flexible copper-clad laminate 1 has a pre-planned pre-processing area 2 and a pad area 6. The shape and size of the pre-processing area 2 and the pad area 6 are determined according to the design requirements of the actual electronic product. For example, for a small consumer electronic product, the flexible circuit board 11 has an irregular shape, so the pre-processing area 2 can be designed to be irregular in shape, and the shape of the pre-processing area 2 is approximately the same as the shape of the flexible circuit board 11.

[0053] Reference Figure 3 Drilling: Drilling is performed on the flexible copper-clad laminate 1 using drilling equipment. First, a metal via 3 is drilled, ensuring that the metal via 3 completely overlaps with the pre-processing area 2. The diameter of the metal via 3 can be set according to the circuit design requirements, such as a diameter of 0.5 mm. Next, a positioning hole 4 is drilled. The positioning hole 4 is located on the pad area 6 of the flexible circuit board 11, and the positioning hole 4 partially overlaps with the pre-processing area 2. That is, part of the positioning hole 4 falls on the pre-processing area 2, while the other part is outside the pre-processing area 2. Therefore, the area where the two overlap on the pre-processing area 2 forms a semi-circular notch 8. The radius of the semi-circular notch 8 can be determined according to the actual positioning and subsequent punching requirements. For example, it can be determined according to the positioning pin of the matching punching die 9 in the subsequent punching, or it can be determined according to the diameter of the half-hole 5 of the pad on the pad area 6 of the flexible circuit board product. In this embodiment, no specific requirements are required.

[0054] Reference Figure 4 Blanking: Prepare a specially designed blanking die 9, the shape and size of which are related to the pre-processing area 2. Insert the positioning pin of the blanking die 9 into the positioning hole 4, using the positioning hole 4 as the positioning reference to ensure the accurate positioning of the flexible copper-clad laminate 1 during the blanking process. The blanking die 9 presses downward along the blanking direction, and the area covered by the projection of the blanking die 9 along the blanking direction forms a first projection pattern. The first projection pattern partially overlaps with the pre-processing area 2, and a pad half-hole 5 is formed in the overlapping area (the overlapping area is the shaded part in the figure). The pad half-hole 5 completely covers the semi-circular notch 8. The area where the first projected pattern overlaps with the pre-processing area 2 will be punched away by the punching die 9. The outline formed in the pre-processing area 2 is the outline of the pad half-hole 5, and the sidewall of the pad half-hole 5 is the sidewall copper plating area. Since the pad half-hole 5 completely covers the semi-circular notch 8, the outline of the pad half-hole 5 is larger than the outline of the pre-formed semi-circular notch 8. Therefore, the area of ​​the sidewall of the pad half-hole 5, i.e., the sidewall copper plating area, is larger than the area of ​​the sidewall of the semi-circular notch 8. The size of the pad half-hole 5 can be designed according to the actual welding requirements, and this embodiment does not impose specific limitations.

[0055] Copper plating: Copper plating is performed on the surfaces of the copper-plated areas on the sidewalls and the sidewall surfaces of the metal vias 3 using either chemical or electroplating methods. In chemical copper plating, the flexible copper-clad laminate 1 is immersed in a chemical copper plating solution containing copper salts, reducing agents, etc. Under preset temperature and time conditions, copper ions are reduced to copper in the copper-plated areas on the sidewalls and the sidewall surfaces of the metal vias 3, forming a conductive copper layer 14. This conductive copper layer 14 is electrically connected to the original conductive layer 7 of the flexible copper-clad laminate 1. In electroplating, the flexible copper-clad laminate 1 is used as the cathode and placed in an electroplating solution containing copper ions. An electric current is applied to deposit copper ions in the copper-plated areas on the sidewalls and the sidewall surfaces of the metal vias 3, forming the conductive copper layer 14. The thickness of the copper plating can be determined according to the conductivity requirements of the circuit; for example, a copper plating thickness of 10 μm.

[0056] Tin plating: The surface of the conductive copper layer 14 is tin-plated, which can be done by chemical tin plating or electroplating. In chemical tin plating, the flexible copper-clad laminate 1 is immersed in a chemical tin plating solution. Under suitable conditions, tin ions are reduced to tin on the surface of the conductive copper layer 14, forming a tin layer suitable for soldering. In electroplating, the flexible copper-clad laminate 1 is placed as the cathode in an electroplating solution, and an electric current is applied to deposit tin ions on the surface of the conductive copper layer 14 to form a tin layer. The thickness of the tin plating can be determined according to the soldering process requirements; for example, a tin plating thickness of 5 μm.

[0057] Reference Figure 7 The flexible circuit board 11 is punched out using a punching device along the edge of the pre-processing area 2. At this time, the flexible circuit board 11 retains metal vias 3 and solder pad half-holes 5. After the punched flexible circuit board 11 undergoes subsequent processing steps such as cleaning and inspection, it can be used to solder with a PCB to manufacture electronic products.

[0058] The flexible circuit board 11, after being manufactured through the above steps, provides a sufficient and stable amount of solder when soldered to the PCB. This allows the solder to flow smoothly between the pad area 6 of the flexible circuit board 11 and the PCB pads, thereby forming a stable solder joint between the upper and lower pads of the flexible circuit board 11 and the PCB pads. This effectively avoids the occurrence of cold solder joints, improves the yield rate of soldering, and ensures the reliability and stability of electronic products.

[0059] In summary, the flexible circuit board manufacturing method according to the first aspect of the present invention solves many problems existing in the welding performance of traditional flexible circuit boards 11 to PCBs by forming metal vias 3 and solder pad half-holes 5 with specific structures on the flexible copper-clad laminate 1 and performing copper and tin plating on their sidewalls. In the traditional method, the PI layer interferes with the flow path of tin, resulting in insufficient tin filling at the solder joint and frequent occurrence of cold solder joints. In this invention, the design of the metal via 3 and the pad half-hole 5 provides a smoother channel for the flow of solder. At the same time, the positioning hole 4, after being punched, forms the sidewall of the pad half-hole 5. Compared with the sidewall of the semi-circular notch 8 formed on the flexible circuit board 11 in the original conventional method, the area of ​​the sidewall formed by the pad half-hole 5 is larger. Because the copper plating area of ​​the sidewall formed by the sidewall is wider, and the copper plating area of ​​the sidewall is tin-plated to form a solderable tin layer, it can provide sufficient and stable solder for soldering, reduce the risk of cold solder joints, improve the reliability and stability of soldering, thereby improving the performance and stability of electronic products and reducing failures caused by poor circuit contact, signal transmission interruption and other problems.

[0060] Secondly, in terms of production efficiency, the positioning hole 4 and the pre-processing area 2 partially overlap to form a semi-circular notch 8. During punching, the positioning hole 4, i.e., this semi-circular notch 8, serves as the positioning reference, enabling more precise punching operations and improving punching accuracy and efficiency. Simultaneously, after punching, the positioning hole 4 forms the sidewall of the solder pad semi-hole 5. Compared to the sidewall of the semi-circular notch 8 formed on the flexible circuit board 11 in the traditional method, this sidewall has a larger area of ​​copper plating. Because the sidewall of the solder pad semi-hole 5 forms a wider area, it provides sufficient and stable solder for welding, reducing the risk of cold solder joints and improving the reliability and stability of the PCB-flexible circuit board 11 welding, thereby enhancing the performance and stability of electronic products. By reducing the occurrence of defects such as cold solder joints, the rework rate is reduced. Furthermore, because this method is relatively simple to operate, the use of the punching die 9 for hole enlargement further improves overall production efficiency, facilitating large-scale production and reducing production costs.

[0061] Furthermore, in terms of product quality, the flexible circuit board 11 produced by this method can form more stable solder joints during welding, achieving good electrical and mechanical connections and improving the product yield. Moreover, the punching and reasonable structural design ensure the dimensional accuracy and quality stability of the flexible circuit board 11, meeting the demands of electronic products for high-quality flexible circuit boards 11 and enhancing the product's competitiveness in the market.

[0062] Reference Figure 4 as well as Figure 5In some embodiments of the present invention, the blanking die 9 includes a protrusion 91 and a blanking portion 92. The area covered by the projection of the protrusion 91 along the blanking direction forms a second projection pattern. The second projection pattern completely coincides with the projection of the positioning hole 4 along the axial direction. The protrusion 91 and the blanking portion 92 are smoothly connected.

[0063] In the implementation of the flexible circuit board manufacturing method according to the foregoing embodiments, the specific implementation method of the punching die 9 described in this embodiment is as follows:

[0064] First, when designing the blanking die 9, the structure of the protrusion 91 and the blanking part 92 must be planned. The protrusion 91 is a key part of the blanking die 9 used to cooperate with the positioning hole 4 for positioning. It should be noted that the protrusion 91 is the positioning pin part mentioned in the previous embodiment. In the design, it is necessary to ensure that the second projection pattern formed by the area covered by the projection of the protrusion 91 along the blanking direction completely coincides with the projection of the positioning hole 4 along the axial direction. For example, if the positioning hole 4 is circular with a diameter of 1mm, then the projection of the protrusion 91 along the blanking direction should also be a circle with a diameter of 1mm, so as to ensure that the protrusion 91 can be accurately inserted into the positioning hole 4 during the blanking process, providing a stable positioning reference for the flexible copper-clad laminate 1, avoiding positional deviation during blanking, and thus improving blanking accuracy.

[0065] The punching section 92 is a key part used to punch out the shape of the pad area 6 and the pad half-hole 5 of the flexible circuit board 11. The protrusion 91 and the punching section 92 are connected by a smooth transition. From a mechanical point of view, the smooth transition can avoid mold damage caused by stress concentration during the punching process, extending the mold's service life. For example, if the protrusion 91 and the punching section 92 are connected at a right angle, the right angle is prone to cracking or even breakage due to the large impact force during punching; while the smooth transition can evenly distribute stress, reducing local stress concentration. From the perspective of punching effect, the smooth transition makes the punching process more stable, reducing deformation and burr generation of the flexible copper-clad laminate 1 during punching. For example, when punching the pad half-hole 5, the smooth transition mold structure can ensure that the sidewall of the pad half-hole 5 is smoother and neater, improving the quality of the flexible circuit board 11.

[0066] In the actual punching operation, after the positioning pin is inserted into the positioning hole 4 of the flexible copper-clad laminate 1, the protrusion 91 of the punching die 9 is aligned with the positioning hole 4 and slowly pressed down, so that the protrusion 91 is accurately inserted into the positioning hole 4, achieving precise positioning of the flexible copper-clad laminate 1. Then, the punching die 9 is pressed down further, and the punching part 92 punches the flexible copper-clad laminate 1. Due to the smooth transition design between the protrusion 91 and the punching part 92, the punching process is stable and smooth, and finally a flexible circuit board 11 that meets the design requirements is obtained. The metal vias 3 and the pad half-holes 5 on the flexible circuit board 11 have accurate dimensions and good quality.

[0067] Reference Figure 7 as well as Figure 8 In some embodiments of the present invention, after a punching die 9 punches the flexible copper-clad laminate 1, the following steps are also included: using a laser to perform micro-hole processing on the pad areas 6 at both ends of the axial direction of the pad half-hole 5, burning through the insulating substrate 12 and the conductive layer 7 of the flexible copper-clad laminate 1 corresponding to the pad area 6, so as to form uniformly distributed micro-holes in the insulating substrate 12.

[0068] After completing the punching step according to the flexible circuit board fabrication method of the aforementioned embodiment, a micro-hole processing operation is performed on the pad areas 6 at both ends of the pad half-hole 5 using a laser. The specific implementation method is as follows:

[0069] First, considering the processing accuracy and effect on the insulating substrate 12 and conductive layer 7 of the flexible copper-clad laminate 1, a pulsed fiber laser can be selected. This type of laser has advantages such as good beam quality, high processing accuracy, and small heat-affected zone, and can burn through the insulating substrate 12 and conductive layer 7 while minimizing the impact on surrounding conductive layer 7 and other structures. The laser power needs to be adjusted according to the material and thickness of the insulating substrate 12 and conductive layer 7 of the flexible copper-clad laminate 1.

[0070] Secondly, before laser micro-via processing, the flexible copper-clad laminate 1 needs to be positioned. Using the positioning holes 4 and positioning pins used during the previous punching process, the flexible copper-clad laminate 1 can be fixed to the matching laser processing fixture, ensuring that the pad areas 6 at both ends of the axial direction of the pad half-hole 5 are accurately within the working range of the laser processing. Simultaneously, a vision positioning system is used to identify and position the pad areas 6. This system can quickly and accurately capture the positional information of the pad areas 6 and feed the data back to the laser processing equipment, ensuring that the laser can accurately act on the target area.

[0071] Then, when laser processing begins, the laser beam scans the pad area 6 according to a preset path. The scanning trajectory of the laser beam can be designed according to actual needs, and generally a uniformly distributed grid-like scanning path is used to ensure that uniformly distributed micropores are formed on the insulating substrate 12 and the conductive layer 7.

[0072] Finally, after laser scanning, uniformly distributed micropores are formed on the insulating substrate 12 and conductive layer 7 corresponding to the pad area 6. These uniformly distributed micropores increase the contact area between the pad area 6 and the subsequent welding materials, improving the strength and reliability of the weld. They also help to better remove gases during the welding process, reducing welding defects. After the micropore treatment is completed, the flexible copper-clad laminate 1 is cleaned to remove residues generated during laser processing, preparing it for subsequent processing steps.

[0073] Reference Figure 8 In some embodiments of the present invention, copper plating of the surface of the sidewall copper plating area and the sidewall surface of the metal via 3 includes the following steps: activating the sidewall copper plating area, the hole wall of the metal via 3 and the hole wall of the micropore to form a catalyst layer in the sidewall copper plating area, the hole wall of the metal via 3 and the hole wall of the micropore.

[0074] After completing the relevant steps according to the aforementioned flexible circuit board fabrication method, an activation treatment is performed on the copper-plated areas on the sidewalls, the walls of the metal vias 3, and the walls of the microvias to form a catalyst layer. The specific implementation method is as follows:

[0075] First, a suitable activation solution needs to be prepared. Commonly used activation solutions are colloidal solutions containing palladium (Pd) and tin (Sn), such as a palladium chloride-stannous chloride colloidal solution. After preparation, the solution is thoroughly stirred to ensure uniform mixing of components, and then allowed to stand for a period of time to allow the colloidal particles in the solution to reach a stable state. Next, the flexible circuit board 11 is pretreated. The flexible copper-clad laminate 1, after micro-hole treatment, is placed in a cleaning tank and rinsed with deionized water to remove residual impurities and contaminants generated during processing. Then, the flexible circuit board 11 is placed in an acid pickling tank for acid pickling. A commonly used acid pickling solution is dilute sulfuric acid solution, with a concentration controlled between 5% and 10%. The purpose of acid pickling is to further remove the surface oxide layer and impurities, and improve surface activity. The acid pickling time is controlled between 1 and 2 minutes. After acid pickling, the flexible circuit board 11 is rinsed again with deionized water to remove residual acid.

[0076] After pretreatment, the flexible circuit board 11 is immersed in the prepared activation solution. During immersion, palladium and tin ions in the activation solution are adsorbed onto the surface to be plated and form a uniform catalytic layer through a chemical reaction. This catalytic layer has high catalytic activity, providing favorable conditions for the subsequent copper plating reaction. After activation, the flexible circuit board 11 is removed from the activation solution and immediately rinsed with deionized water to remove any residual activation solution. Then, the flexible circuit board 11 is placed in a drying oven to remove surface moisture, preparing it for the subsequent copper plating process. After the above activation treatment steps, a uniform catalytic layer is successfully formed in the copper plating area on the sidewalls, the walls of the metal vias 3, and the walls of the micropores, laying a good foundation for the subsequent copper plating process.

[0077] Therefore, it is understandable that, further, referring to Figure 8 In some embodiments of the present invention, after activating the copper-plated area on the sidewall, the wall of the metal via 3 and the wall of the micro-hole, the following steps are further included: copper plating is performed on the copper-plated area on the sidewall, the wall of the metal via 3 and the wall of the micro-hole; a conductive copper layer 14 is deposited on the copper-plated area on the sidewall and the wall of the metal via 3; and a copper layer is deposited on the wall of the micro-hole to form a conductive copper pillar 13. The upper and lower ends of the conductive copper pillar 13 are respectively connected to the conductive layer 7 of the flexible copper-clad laminate 1.

[0078] After activating the copper-plated area on the sidewall, the wall of the metal via 3, and the wall of the micropore and forming a catalyst layer according to the aforementioned embodiments, the copper plating process is carried out. The specific implementation method is as follows:

[0079] First, prepare a suitable copper plating solution. Fix the activated and dried flexible circuit board 11 onto a specialized copper plating fixture, ensuring its stability during the plating process and preventing shaking or displacement. Then, slowly immerse the fixture containing the flexible circuit board 11 into the pre-prepared copper plating solution. During immersion, carefully control the speed to avoid air bubbles adhering to the surface of the flexible circuit board 11, which would affect the plating quality. During the copper plating process, process parameters such as current density, temperature, and time must be strictly controlled. Current density is one of the key factors affecting the quality and speed of copper plating, generally controlled between 1 and 3 A / dm². A suitable current density allows copper ions to deposit uniformly on the catalyst layer, forming a dense and uniform conductive copper layer 14. If the current density is too high, it will lead to a rough plating layer and scorching; if the current density is too low, the plating speed will be too slow, affecting production efficiency. The temperature of the copper plating solution is usually controlled between 20-30℃. A suitable temperature can improve the diffusion rate and chemical reactivity of copper ions, which is beneficial for obtaining a high-quality plating layer. Meanwhile, the temperature of the copper plating solution should be monitored and adjusted regularly to ensure it remains stable within the set range. The copper plating time is determined based on the required plating thickness, and can generally be determined experimentally for different plating thicknesses. For example, to obtain a conductive copper layer 14 with a thickness of 5-10 μm, the copper plating time can be controlled between 10 and 20 minutes.

[0080] For copper plating on the walls of microvias, the diffusion and deposition of copper ions within the microvias are relatively difficult due to their small size. To ensure uniform copper deposition on the walls of the microvias and the formation of conductive copper pillars 13, pulsed copper plating can be used. Pulsed copper plating, by periodically changing the magnitude and direction of the current, can increase the diffusion rate of copper ions within the microvias, making it easier for copper ions to reach the bottom of the microvias for deposition, thereby forming conductive copper pillars 13 whose upper and lower ends are connected to the conductive layer 7 of the flexible copper-clad laminate 1. The parameters for pulsed copper plating include pulse frequency, pulse width, and duty cycle, which need to be optimized and adjusted according to the size of the microvias and the copper plating requirements. For example, the pulse frequency can be set between 100 and 1000 Hz, the pulse width between 10 and 100 μs, and the duty cycle between 30% and 70%.

[0081] After copper plating, the flexible circuit board 11 is removed from the copper plating solution and rinsed with deionized water to remove any residual copper plating solution. Then, the flexible circuit board 11 is placed in a drying oven for drying. The drying temperature can be controlled between 60-80℃, and the drying time is adjusted appropriately according to the thickness and size of the flexible circuit board 11, generally 10-20 minutes, to remove surface moisture. After the above copper plating steps, a conductive copper layer 14 is successfully deposited on the copper-plated areas of the sidewalls and on the walls of the metal vias 3. A copper layer is deposited on the walls of the microvias to form conductive copper pillars 13, satisfying the electrical connection requirements of the flexible circuit board 11.

[0082] Furthermore, referring to Figure 8 In some embodiments of the present invention, the copper plating process for the sidewall copper plating area, the hole wall of the metal via 3, and the hole wall of the microhole includes the following steps:

[0083] A copper plating process is performed on the copper-plated areas of the sidewalls, the walls of the metal vias 3, and the walls of the micro-holes to form a copper plating layer of uniform thickness on the activated copper-plated areas of the sidewalls and the walls of the micro-holes.

[0084] The copper plating layer is subjected to a secondary copper plating process to thicken the copper plating area on the sidewall and the copper plating layer on the wall of the metal via 3. At the same time, the copper plating layer on the wall of the micro-hole is subjected to a secondary copper plating process to form a conductive copper pillar 13.

[0085] After completing the preliminary preparations according to the aforementioned embodiments, copper plating is performed on the copper-plated areas of the sidewalls, the walls of the metal vias 3, and the walls of the micro-holes. The specific implementation method is as follows:

[0086] Primary copper plating process: The primary copper plating solution is prepared first. An acidic sulfate copper plating system is selected, and copper sulfate, sulfuric acid, and specific additives are mixed in a specific ratio. Copper sulfate serves as the copper ion supply source, with its concentration controlled at 65-85 g / L to ensure sufficient and stable copper ions participate in the reaction during the plating process. The sulfuric acid concentration is set at 190-210 g / L, which not only improves the conductivity of the solution but also effectively inhibits copper ion hydrolysis. The activated and dried flexible circuit board 11 is securely mounted on a dedicated copper plating fixture, ensuring its position remains fixed during the plating process to prevent shaking or displacement from affecting the plating quality. Subsequently, the fixture, along with the flexible circuit board 11, is slowly immersed into the prepared primary copper plating solution at a moderate immersion speed to prevent air bubbles from adhering to the surface. During the primary copper plating process, process parameters are strictly controlled. The current density is controlled between 1.2 and 2.5 A / dm². A suitable current density can enable copper ions to be deposited uniformly on the activated copper plating area of ​​the sidewall and on the walls of the micropores, forming a copper plating layer of uniform thickness.

[0087] Secondary copper plating: After the primary copper plating, the flexible circuit board 11 is removed from the solution, rinsed with deionized water, and dried. Then, the secondary copper plating solution is prepared. The secondary copper plating solution is also based on an acidic sulfate system, but the component ratio can be fine-tuned according to actual needs. For example, the copper sulfate concentration can be appropriately increased to 70-90 g / L to further meet the requirements for a thicker plating layer. The flexible circuit board 11 is then fixed onto the copper plating fixture and immersed in the secondary copper plating solution. During the secondary copper plating, the current density is adjusted to 1.5-3 A / dm². Appropriately increasing the current density can accelerate the copper plating speed while ensuring the plating quality. The solution temperature is maintained at 23-29℃ to provide a good environment for copper ion deposition. For the copper plating areas on the sidewalls and the walls of the metal vias 3, the purpose of secondary copper plating is to thicken the copper plating layer. By extending the copper plating time to 12-20 minutes, the thickness of the copper plating layer in these areas is increased to meet the requirements for electrical connection and mechanical performance. For the walls of micropores, due to their small size, copper ion diffusion and deposition are difficult during the secondary copper plating process. Therefore, a pulsed copper plating method is used. Pulsed copper plating improves the diffusion ability of copper ions within the micropores by periodically changing the magnitude and direction of the current, making it easier for copper ions to reach the bottom of the micropores for deposition. The pulse frequency is set between 200 and 800 Hz, the pulse width is 20 to 80 μs, and the duty cycle is between 40% and 60%. After this pulsed copper plating treatment, copper is further deposited on the existing copper plating layer on the walls of the micropores, forming conductive copper pillars 13 whose upper and lower ends are connected to the conductive layer 7 of the flexible copper-clad laminate 1.

[0088] After the second copper plating is completed, the flexible circuit board 11 is taken out, rinsed with deionized water to remove the residual solution on the surface, and then placed in a drying oven at 60-80℃ for 10-20 minutes to remove moisture. This completes the entire copper plating process, enabling the flexible circuit board 11 to meet the expected electrical connection and performance requirements.

[0089] Specifically, in some embodiments of the present invention, the primary copper plating process employs a chemical copper plating process, and the secondary copper plating process employs an electroplating process.

[0090] When carrying out the copper plating process for the flexible circuit board, a chemical copper plating process is used for the first copper plating process, and an electroplating process is used for the second copper plating process. The specific implementation process is as follows:

[0091] One-step copper plating process (chemical copper plating): First, the chemical copper plating solution is prepared. Each component is added sequentially to deionized water according to the specified proportions, and stirred thoroughly until completely dissolved. Then, the pH of the solution is adjusted to 12-13 with sodium hydroxide solution to obtain a homogeneous and stable chemical copper plating solution. The activated and dried flexible circuit board 11 is then placed into the chemical copper plating solution. During the chemical copper plating process, copper ions in the solution are reduced to copper atoms under the action of the reducing agent, and uniformly deposited on the activated sidewall copper plating areas and the walls of the micropores, forming a copper plating layer of uniform thickness. By real-time monitoring of the copper plating time and observation of the plating layer appearance, the chemical copper plating time is controlled at 20-30 minutes to ensure the copper plating layer reaches the initially required thickness. During the chemical copper plating process, the solution should be gently stirred occasionally to ensure uniform solution composition and avoid uneven plating caused by excessively high or low concentrations in certain areas.

[0092] Secondary copper plating treatment (electroplating copper process): After the first chemical copper plating, the flexible circuit board 11 is removed from the chemical copper plating solution, rinsed with deionized water, and dried. Next, the electroplating copper solution is prepared, using an acidic sulfate copper plating system, mixing copper sulfate, sulfuric acid, and appropriate additives. The prepared electroplating copper solution is poured into the electroplating tank, and the flexible circuit board 11, which has undergone the first copper plating treatment, is mounted on the electroplating fixture, ensuring good contact between the flexible circuit board 11 and the cathode. The anode (usually a phosphor bronze plate) is also correctly installed. After connecting the power supply, the power is turned on for electroplating. During the electroplating process, process parameters such as current density, temperature, and time are controlled to ensure rapid and uniform deposition of copper ions in the sidewall copper plating area and on the walls of the metal vias 3, thickening the copper plating layer. Simultaneously, pulse electroplating is used on the walls of the micro-holes, periodically changing the magnitude and direction of the current to enhance the diffusion ability of copper ions within the micro-holes, promoting the deposition of copper at the bottom of the micro-holes to form conductive copper pillars 13. After electroplating is completed, the flexible circuit board 11 is removed from the electroplating tank, rinsed with deionized water to remove the residual electroplating solution on the surface, and the moisture is removed. Finally, the entire copper plating process is completed, so that the flexible circuit board 11 meets the expected electrical connection and performance requirements.

[0093] In some embodiments of the present invention, after copper plating of the surface of the sidewall copper plating area and the sidewall surface of the metal via 3, and before tin plating of the surface of the conductive copper layer 14, the following steps are further included:

[0094] The flexible copper-clad laminate 1, which has undergone copper plating treatment on the sidewall copper-plated area, the hole wall of the metal via 3 and the hole wall of the micro-hole, is processed into a conductive circuit pattern including the pad area 6.

[0095] A cover film is applied to the surface of the flexible copper-clad laminate 1 after the circuit diagram processing is completed, and a window is made at the position of the cover film corresponding to the pad area 6 to expose the pad area 6.

[0096] After completing the copper plating treatment of the sidewall copper plating area and the sidewall surface of the metal via 3, the following steps must be performed before carrying out the tin plating treatment of the conductive copper layer 14:

[0097] Circuit pattern processing: First, the flexible copper-clad laminate 1, after copper plating, is cleaned. Next, photolithography is used to process the circuit pattern. First, a layer of photoresist is uniformly coated onto the surface of the flexible copper-clad laminate 1. After coating, a pre-baking process is performed. Then, using an exposure device, the designed circuit pattern mask is placed on the photoresist-coated flexible copper-clad laminate 1, and exposure is performed. After exposure, development is performed, followed by rinsing with deionized water to remove residual developer. Next, etching is performed. After etching, it is rinsed with deionized water to remove residual etching solution. Finally, photoresist stripping is performed. Through photoresist stripping, the photoresist remaining on the conductive circuit pattern is removed, resulting in a clear conductive circuit pattern. After photoresist stripping, it is rinsed again with deionized water and dried.

[0098] Cover film application and windowing: Select a suitable cover film material. The cover film is usually composed of a polyimide film and an adhesive layer, possessing good insulation, heat resistance, and flexibility. When applying the cover film to the flexible copper-clad laminate 1, first align the adhesive layer side of the cover film with the surface of the flexible copper-clad laminate 1, and then use a hot press to hot press and bond them together. After the cover film is applied, windowing is performed to expose the pad areas 6. According to the designed pad positions and sizes, use laser cutting equipment or punching equipment to make windows at the positions of the cover film corresponding to the pad areas 6. After windowing, the flexible copper-clad laminate 1 is cleaned again to remove any debris and impurities, preparing it for subsequent tin plating.

[0099] Reference Figure 7 In some embodiments of the present invention, punching out the flexible circuit board 11 along the edge of the pre-processing area 2 includes the following steps: using multiple shaped punching dies 10 to sequentially punch out the flexible copper-clad laminate 1 along the edge of the pre-processing area 2 to punch out the shape of the flexible circuit board 11. After completing a series of operations such as circuit pattern processing, cover film attachment, and windowing processing on the flexible copper-clad laminate 1, the process of punching out the flexible circuit board 11 along the edge of the pre-processing area 2 is then initiated. The specific implementation steps are as follows:

[0100] First, based on the designed dimensions and shape of the flexible circuit board 11, multiple shape-cutting dies 10 are designed and manufactured. The shape and size of these dies must match the shape of each part of the flexible circuit board 11 to ensure that the punched flexible circuit board 11 meets the design requirements. The flexible copper-clad laminate 1, processed in the previous steps, is placed on the worktable of the punching machine, and its position is accurately adjusted so that the pre-processed area 2 of the flexible copper-clad laminate 1 corresponds to the position of the first shape-cutting die 10. The punching machine is started, and the first shape-cutting die 10 punches the flexible copper-clad laminate 1 downwards with appropriate pressure and speed. During the punching process, the cutting edge of the die cuts into the flexible copper-clad laminate 1, punching off its edge portion to form a part of the shape of the flexible circuit board 11. After the first die punching is completed, the flexible copper-clad laminate 1 is moved on the worktable so that the next part of its pre-processed area 2 corresponds to the second shape-cutting die 10. During the movement, the moving distance must be accurate, which can be assisted by a positioning system or marking lines. The punching machine is restarted for a second punching operation, and so on, using multiple shaped punching dies 10 to punch the flexible copper-clad laminate 1 along the edge of the pre-processing area 2. Once all the shaped punching dies 10 have completed their punching operations, the punched flexible circuit board 11 is removed from the worktable. At this point, the shape of the flexible circuit board 11 is basically formed, but there may still be some minor burrs or unevenness. Further finishing processes can be performed, such as gently sanding the edges with sandpaper to remove burrs, making the shape of the flexible circuit board 11 more perfect and meeting the final design requirements.

[0101] Reference Figure 1 as well as Figure 8 According to a second aspect embodiment of the present invention, the flexible circuit board 11 is manufactured using the flexible circuit board manufacturing method of the first aspect embodiment described above. The flexible circuit board 11 has an insulating substrate 12 and a conductive layer 7. The conductive layer 7 can cover both sides of the insulating substrate 12. The insulating substrate 12 has a pad area 6. A pad half-hole 5 is provided on the edge of the pad area 6. Conductive copper pillars 13 are uniformly distributed in the area of ​​the insulating substrate 12 corresponding to the pad area 6. The conductive copper pillars 13 pass through the insulating substrate 12 and are connected to the conductive layer 7 to achieve electrical connection. The sidewall of the pad half-hole 5 is a smooth and continuous sidewall and is a copper-plated sidewall area.

[0102] The flexible circuit board 11 is manufactured using the flexible circuit board manufacturing method provided in the first aspect embodiment. In the initial stage of manufacturing, a suitable insulating substrate 12 is selected according to the method. The insulating substrate 12 is usually made of materials with good insulation, flexibility and heat resistance, such as polyimide.

[0103] During the fabrication process, the insulating substrate 12 is first pretreated to ensure its surface is flat and clean, providing a good foundation for the subsequent adhesion of the conductive layer 7. Next, the conductive layer 7 is formed on both sides of the insulating substrate 12 through chemical deposition or electroplating, ensuring that the conductive layer 7 uniformly and firmly covers both sides of the insulating substrate 12 and guarantees good conductivity.

[0104] The pad area 6 on the insulating substrate 12 is designed during fabrication. A specific drilling process is used to form a half-hole 5 at the edge of the pad area 6. During drilling, drilling parameters, such as drill bit speed and feed rate, are strictly controlled to ensure that the sidewall of the formed half-hole 5 is smooth and continuous, creating favorable conditions for subsequent sidewall copper plating. After sidewall copper plating, this sidewall becomes the copper-plated area, enhancing the conductivity and reliability of the half-hole 5.

[0105] Simultaneously, conductive copper pillars 13 are uniformly distributed in the insulating substrate 12 area corresponding to the pad area 6 using a special process. For example, a process combining photolithography and etching is used. First, photoresist is coated on the surface of the insulating substrate 12. The pattern of conductive copper pillars 13 is formed through exposure, development, and other steps. Then, etching is performed to remove excess material, forming holes with a certain depth and diameter. Copper is then filled into the holes through electroplating or other methods to form conductive copper pillars 13. These conductive copper pillars 13 penetrate the insulating substrate 12 and are tightly connected to the conductive layers 7 on both sides, achieving good electrical connection and ensuring stable current transmission in the flexible circuit board 11.

[0106] After the above series of manufacturing processes, the flexible circuit board 11 is finally obtained. The flexible circuit board 11 not only has the basic structure of insulating substrate 12 and conductive layer 7, but also improves the performance and reliability of the circuit board through the special design of pad half-holes 5 and conductive copper pillars 13, which can meet the requirements of various complex electronic devices for flexible circuit board 11.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] Of course, the present invention is not limited to the above-described embodiments. Those skilled in the art can make equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method for manufacturing a flexible circuit board, characterized in that, Includes the following steps: A flexible copper-clad laminate is provided, the flexible copper-clad laminate having a pre-processed area, the pre-processed area having a pad area; Drilling is performed on the flexible copper-clad laminate to form metal vias and positioning holes. The metal vias completely overlap with the pre-processed area, and the positioning holes are located in the pad area. The positioning holes partially overlap with the pre-processed area and form a semi-circular notch in the overlapping area. A punching die is provided to punch the flexible copper-clad laminate. A positioning pin is inserted into the positioning hole and the positioning hole is used as a positioning reference. The area covered by the projection of the punching die along the punching direction forms a first projection pattern. The first projection pattern and the pre-processed area partially overlap and form a pad half-hole in the overlapping area. The pad half-hole completely covers the semi-circular notch, and the sidewall of the pad half-hole forms a sidewall copper-plated area. Copper plating is performed on the surface of the copper-plated area on the sidewall and the surface of the sidewall of the metal via to form a conductive copper layer, which is electrically connected to the conductive layer of the flexible copper-clad laminate. The surface of the conductive copper layer is tin-plated to form a solderable tin layer on the surface of the copper-plated area of ​​the sidewall. A flexible circuit board is punched out along the edge of the pre-processed area, the flexible circuit board retaining the metal vias and the pad half-holes.

2. The method for manufacturing a flexible circuit board according to claim 1, characterized in that, The blanking die includes a protrusion and a blanking part. The area covered by the projection of the protrusion along the blanking direction forms a second projection pattern. The second projection pattern completely coincides with the projection of the positioning hole along the axial direction. The protrusion and the blanking part are smoothly connected.

3. The method for manufacturing a flexible circuit board according to claim 2, characterized in that, After providing a punching die to punch the flexible copper-clad laminate, the method further includes the following steps: using a laser to perform micro-hole processing on the pad areas at both ends of the axial direction of the pad half-hole, burning through the insulating substrate and the conductive layer of the flexible copper-clad laminate corresponding to the pad area, so as to form uniformly distributed micro-holes on the insulating substrate.

4. The method for manufacturing a flexible circuit board according to claim 3, characterized in that, The copper plating process for the surface of the copper-plated sidewall area and the sidewall surface of the metal via includes the following steps: activating the copper-plated sidewall area, the wall of the metal via, and the wall of the micropore to form a catalytic layer in the copper-plated sidewall area, the wall of the metal via, and the wall of the micropore.

5. A method for manufacturing a flexible circuit board according to claim 4, characterized in that, After activating the copper-plated area on the sidewall, the wall of the metal via, and the wall of the micro-hole, the method further includes the following steps: copper plating is performed on the copper-plated area on the sidewall, the wall of the metal via, and the wall of the micro-hole; a conductive copper layer is deposited on the copper-plated area on the sidewall and the wall of the metal via; and a copper layer is deposited on the wall of the micro-hole to form a conductive copper pillar, wherein the upper and lower ends of the conductive copper pillar are respectively connected to the conductive layer of the flexible copper-clad laminate.

6. The method for manufacturing a flexible circuit board according to claim 5, characterized in that, The copper plating process for the sidewall copper plating area, the hole wall of the metal via, and the hole wall of the microvia includes the following steps: The copper-plated area on the sidewall, the wall of the metal via, and the wall of the micro-hole are subjected to a copper plating process to form a copper plating layer of uniform thickness on the activated copper-plated area on the sidewall and the wall of the micro-hole. The copper plating layer is subjected to a secondary copper plating process to thicken the copper plating area on the sidewall and the copper plating layer on the wall of the metal via. Simultaneously, the copper plating layer on the wall of the microhole is subjected to a secondary copper plating process to form the conductive copper pillar.

7. A method for manufacturing a flexible circuit board according to claim 6, characterized in that, The primary copper plating process employs a chemical copper plating process, while the secondary copper plating process employs an electroplating process.

8. A method for manufacturing a flexible circuit board according to claim 3, characterized in that, After copper plating is performed on the surface of the copper-plated area on the sidewall and the sidewall surface of the metal via, and before tin plating is performed on the surface of the conductive copper layer, the following steps are also included: The flexible copper-clad laminate, on which copper plating has been applied to the sidewall copper plating area, the hole wall of the metal via, and the hole wall of the micro-hole, is subjected to circuit pattern processing to form a conductive circuit pattern including the pad area. A cover film is applied to the surface of the flexible copper-clad laminate after the circuit diagram processing is completed, and a window is made in the cover film at the position corresponding to the pad area to expose the pad area.

9. A method for manufacturing a flexible circuit board according to claim 8, characterized in that, The process of punching out the flexible circuit board along the edge of the pre-processing area includes the following steps: using multiple shaped punching dies to punch out the flexible copper-clad laminate sequentially along the edge of the pre-processing area to punch out the shape of the flexible circuit board.

10. A flexible circuit board, characterized in that, The flexible circuit board is manufactured using the flexible circuit board manufacturing method according to any one of claims 2 to 9. The flexible circuit board has an insulating substrate and a conductive layer. The conductive layer can cover both sides of the insulating substrate. The insulating substrate has a pad area. The edge of the pad area is provided with a pad half-hole. Conductive copper pillars are uniformly distributed in the area of ​​the insulating substrate corresponding to the pad area. The conductive copper pillars pass through the insulating substrate and are connected to the conductive layer to achieve electrical connection. The sidewall of the pad half-hole is a smooth and continuous sidewall and is a copper-plated area of ​​the sidewall.

Images