Flexible Printed Circuit Board

Abstract

The present invention relates to a flexible printed circuit board (FPCB) and a manufacturing method thereof, and more particularly to a manufacturing method of a flexible printed circuit board in which a reference mark is formed inside the FPCB during a series of manufacturing processes, and the outer shape is processed using the reference mark as a reference point, thereby minimizing processing tolerances that occur during outer shape processing of the board.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a flexible printed circuit board, and more particularly to a method for manufacturing a flexible printed circuit board that can reduce processing tolerances that occur during contour processing of the flexible printed circuit board. [Background technology]

[0002] The recent growth of electronic devices such as personal computers, notebook computers, and cameras has been remarkable. Accordingly, printed circuit boards are becoming increasingly important as key components in the high integration and packaging of products.

[0003] A printed circuit board (PCB) is a device that connects and supports various components according to the circuit design of electrical wiring on a printed circuit board, and is an essential element in constructing electronic products.

[0004] In recent years, electronic products have become smaller and lighter. Accordingly, flexible printed circuit boards (FPCBs), which are a type of printed circuit board (PCB) that are made from bendable flexible materials and allow for three-dimensional wiring, have been attracting attention and have the advantages of being smaller and lighter. They are now widely used in small and medium-sized electronic products such as smartphones, cameras, notebook computers, and tablet PCs.

[0005] Such flexible printed circuit boards (FPCBs) are generally manufactured through various processes including cutting, drilling, copper plating, roughening, dry film, exposure, etching, photo solder resist (PSR), hot pressing, gold plating, printing, bare board test (BBT), outline processing, and final inspection.

[0006] Among these manufacturing processes, in the contour processing process, the contour of the circuit board is processed to match the shape of the product / device (smartphone, notebook computer, etc.) in which the flexible printed circuit board (FPCB) will ultimately be installed. The guide hole formed on the outside of the circuit board in the printing process is used as a reference point, and the contour processing is performed while correcting the distance accordingly.

[0007] However, even if the flexible printed circuit board (FPCB) is fixed during external processing, there is a risk that the distance from the reference point will be inaccurate due to curl caused by bending due to the flexibility of the board material.

[0008] In such cases, because the reference points do not match when processing the exterior shape, the connector (terminal) part is not in the center but is biased to one side, causing the contact part between the circuit board and the connector part to become misaligned, resulting in the connector part coming into contact with another connector part and causing a short circuit. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent No. 10-1500435 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been devised to solve the above-mentioned problems, and has an object to provide a method for reducing the processing tolerances that occur during the contour processing of a flexible printed circuit board (FPCB). [Means for solving the problem]

[0011] A method for manufacturing a flexible printed circuit board (FPCB) according to an embodiment of the present invention includes a cutting step of cutting a base film having an insulating layer and one or more copper foil layers into a panel shape according to a predetermined standard, a drilling step of drilling holes penetrating both the insulating layer and the copper foil layer of the base film, a copper plating step of plating copper on inner walls of the holes, a circuit and fiducial mark forming step of forming a predetermined circuit pattern and a fiducial mark on the copper foil layer of the base film, a temporary bonding step of temporarily bonding a coverlay to a predetermined region on an upper surface of the copper foil layer on which the circuit and fiducial mark are formed, a complete bonding step of applying a predetermined temperature and pressure to the temporarily bonded coverlay to completely bond it to the base film, a surface plating step of plating a surface of an area excluding a predetermined area not covered by the coverlay, and an outline processing step of processing an outer shape of a panel-shaped board into a predetermined size and shape, wherein the outline processing step is characterized in that the outline processing is performed using the fiducial mark formed inside the flexible printed circuit board (FPCB) as a reference point using the circuit and fiducial mark forming step.

[0012] Specifically, the circuit and fiducial mark forming step includes a roughening step of roughening the surface of the copper foil layer of the base film, a lamination step of adhering a dry film onto the copper foil layer, an exposure step of irradiating ultraviolet (UV) light in the shape of a predetermined circuit pattern and fiducial marks to be formed on the dry film adhered to the copper foil layer, a development step of peeling off the dry film in the portion that has not been exposed to the ultraviolet (UV) light and has not been hardened, an etching step of oxidizing and removing the area on the copper foil layer excluding the circuit pattern and fiducial marks, and a peeling step of peeling off the dry film remaining on the surface of the base film after the etching step to complete the formation of the circuit pattern and fiducial marks.

[0013] According to one embodiment, the reference mark formed using the circuit and reference mark forming step is characterized in that it is located in an area within a predetermined distance from a circuit terminal portion of the board to which the connector is connected.

[0014] According to another embodiment, the reference mark formed using the circuit and reference mark forming step is characterized in that it is located in an area within a circuit terminal portion of the substrate to which the connector is connected.

[0015] More specifically, the reference mark is characterized in that the reference mark is set on an extension portion that extends the area of ​​the pin contact portion with which the connector pin touches within the circuit terminal portion of the board by a predetermined length.

[0016] A flexible printed circuit board (FPCB) according to an embodiment of the present invention includes a circuit terminal portion to which a connector is connected and a reference mark, and the reference mark formed in the board functions as a reference point when processing the exterior of the board.

[0017] According to one embodiment, the reference mark is formed in an area within a predetermined distance from the circuit terminal portion.

[0018] According to another embodiment, the reference mark is formed in an area within the circuit terminal portion.

[0019] Meanwhile, the circuit terminal portion is characterized in that it includes an extension portion which is an area in which the area of ​​the pin contact portion with which the connector pin comes into contact is extended by a predetermined length.

[0020] In this case, the reference mark is set in a region of an extension portion formed in a circuit terminal portion of the substrate. Effect of the Invention

[0021] The present invention takes a reference point inside the flexible printed circuit board (FPCB) and performs external processing to narrow the distance between the reference point and the connector (terminal) portion of the flexible printed circuit board (FPCB), thereby minimizing the possibility of processing tolerances occurring due to curling caused by the flexibility of the board during external processing. [Brief description of the drawings]

[0022] [Figure 1] 1 is a flow chart showing a method for manufacturing a flexible printed circuit board (FPCB) according to the present invention. [Diagram 2] 1A-1C are diagrams showing examples of the overall shape of a flexible printed circuit board (FPCB). [Diagram 3] FIG. 13 is a diagram showing an example of an enlarged state of a circuit terminal portion. [Figure 4] 5 is a diagram showing the positions at which reference marks are formed according to the first embodiment of the present invention. FIG. [Diagram 5] 10 is a diagram showing the positions at which reference marks are formed according to the second embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings so that a person having ordinary skill in the art to which the present invention pertains can easily carry out the present invention. However, the present invention can be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, in order to clearly explain the present invention, parts that are not related to the description are omitted, and similar parts are denoted by similar reference numerals throughout the specification.

[0024] The present invention will now be described in detail with reference to the accompanying drawings.

[0025] 1. Manufacturing method of flexible printed circuit board (FPCB) according to the present invention FIG. 1 is a flow chart showing a method for manufacturing a flexible printed circuit board (FPCB) according to the present invention, and the process steps will be described based on this flow chart.

[0026] 1.1.Cutting step (S10) The cutting step is the first process for producing a flexible printed circuit board (FPCB) product, and involves cutting the base film, which is the raw material of the flexible printed circuit board (FPCB), to meet the work specifications. Here, the base film has an insulating layer (PI, polyimide) and a copper foil layer.

[0027] Here, the base film may have an insulating layer (PI) with a copper foil layer bonded to its upper surface, or may have an insulating layer (PI) with copper foil layers bonded to its upper and lower surfaces. In the former case, a single-sided flexible printed circuit board (FPCB) is manufactured, and in the latter case, a double-sided flexible printed circuit board (FPCB) is manufactured.

[0028] 1.2.Drill step (S20) The drilling step is a step of drilling holes in the base film using a drill so as to penetrate through both the insulating layer (PI) and the copper foil layer of the base film.

[0029] This step does not have to be performed if the base film has a single-sided structure with an insulating layer (PI) and a copper foil layer bonded only to the upper surface thereof.

[0030] 1.3. Copper plating step (S30) The copper plating step is a step of plating the inner walls of the holes drilled in the drilling step with copper, which is a conductor, to provide conductivity.

[0031] This process is a process for electrically connecting the upper and lower copper foils with respect to the insulating layer (PI) when the base film has a double-sided structure, and like the drilling step (S20), this does not need to be performed when the base film has a single-sided structure.

[0032] 1.4. Circuit and Reference Mark Formation Step (S40) The circuit and fiducial mark forming step includes a roughening step (S41) of roughening the surface of the copper foil layer so that a dry film (photosensitive film) can be well attached to the base film; a lamination step (S42) of adhering the dry film to the copper foil layer of the base film using heat and pressure; an exposure step (S43) of irradiating UV (ultraviolet) light in the shape of a predetermined circuit pattern and fiducial mark to be formed on the dry film adhered to the copper foil layer of the base film to form the circuit and fiducial mark; a development step (S44) of peeling off the dry film in the portion not exposed to the UV light and not hardened; an etching step (S45) of treating the developed base film with chemicals to oxidize and remove the exposed portion of the copper foil layer, i.e., the portion not corresponding to the circuit pattern and fiducial mark; and a peeling step (S46) of peeling off the dry film remaining on the surface of the base film to complete the formation of the circuit pattern and fiducial mark.

[0033] At this time, the portion of the dry film that is hardened by irradiation with UV light in the exposure step (S43) acts as a resistance to the chemicals in the etching step (S45) and remains as the circuit and reference marks that the copper foil underneath the dry film is to form.

[0034] Meanwhile, in the manufacturing process of a typical flexible printed circuit board (FPCB), only a circuit pattern is formed on a base film through roughening, lamination, exposure, development, etching and peeling processes. However, in the present invention, as described above, a fiducial mark is further formed in the process of forming the circuit. The fiducial mark formed in this process functions as a reference point during the external processing in the external processing step (S100) described later.

[0035] Here, the position of the reference mark formed using the above-mentioned process can be set according to the following two embodiments.

[0036] <Embodiment 1> FIG. 2 is a diagram showing the overall appearance of a flexible printed circuit board having a circuit terminal portion of a typical flexible printed circuit board (FPCB) to which a connector is connected, and FIG. 3 is a diagram showing an enlarged view of the circuit terminal portion of the flexible printed circuit board (FPCB).

[0037] In the case of the first embodiment, the fiducial mark may be formed so as to be located near the circuit terminal portion of the flexible printed circuit board (FPCB) as shown in Fig. 4. This is because, when UV light is irradiated onto the dry film adhered to the copper foil layer of the base film in the exposure step (S43), the UV light is irradiated onto a shape realized to include, in addition to the predetermined circuit pattern, a fiducial mark set at any one of the regions within a predetermined distance from the circuit terminal portion of the flexible printed circuit board (FPCB), thereby forming the predetermined circuit pattern and the fiducial mark on the copper foil layer of the base film.

[0038] <Embodiment 2> In the second embodiment, the fiducial mark may be formed so as to be located within the circuit terminal portion of the flexible printed circuit board (FPCB). As in the first embodiment, the exposure step (S43) is performed by irradiating UV light to a predetermined circuit pattern and the shape of the fiducial mark, but here, there is a difference in the shape.

[0039] In the first embodiment, the reference mark is realized in a shape that is located near the circuit terminal portion of the flexible printed circuit board (FPCB), whereas in the second embodiment, the reference mark is realized in a shape that is located within the circuit terminal portion of the flexible printed circuit board (FPCB), as shown in FIG.

[0040] In this case, specifically, when realizing a shape having a predetermined circuit pattern and a reference mark, a shape of an extension part may be realized by extending the area of ​​the pin contact part that contacts the terminal pin in the circuit terminal part of the flexible printed circuit board (FPCB) by a predetermined length in the width direction, and this may be set as the reference mark. That is, by irradiating the copper foil layer of the base film with UV light in a shape having the predetermined circuit pattern and the extension part, the predetermined circuit pattern and the reference mark located in the circuit terminal part of the flexible printed circuit board (FPCB) are formed on the copper foil layer.

[0041] In this way, unlike the conventional method in which the reference point during external processing of a flexible printed circuit board (FPCB) was located outside the flexible printed circuit board (FPCB), in the present invention, a reference point is formed in addition to the circuit pattern during the series of processes for forming the circuit pattern on the board, so that the reference point during external processing is located inside the flexible printed circuit board (FPCB).

[0042] Here, in FIG. 4, the reference mark is shown to have a circular shape, however, the present invention is not limited to this in any way, and the reference mark may be formed into various shapes such as a triangle or a rectangle.

[0043] 1.5. Temporary adhesion step (S50) The temporary bonding step is a step of temporarily bonding a coverlay to the flexible printed circuit board (FPCB) product after the circuit and reference mark forming step (S40). Here, the coverlay is a film for protecting the flexible printed circuit board (FPCB) and is used to protect the circuit and form an insulating layer.

[0044] Here, when temporarily bonding the coverlay, a specified area to be gold plated in the surface plating step (S70) described below is excluded in order to expose the circuit, and the specified area refers to the soldering area.

[0045] 1.6. Full adhesion step (S60) The complete adhesion step is a step of applying a predetermined temperature and pressure to the coverlay temporarily adhered in the temporary adhesion step to completely adhere it to the base film. Prior to applying the predetermined temperature and pressure, a normal process (lamination process) is performed in which a slip sheet (paper) is sandwiched between the copper foil corroded using the circuit pattern and reference mark formation step (S40) in order to protect the base film from high temperature and high pressure while the coverlay is temporarily adhered.

[0046] 1.7. Surface plating step (S70) After the complete bonding step (S60), the surface of the area not covered by the coverlay, i.e., the area where the circuit (copper foil) was exposed as the soldering area in the temporary bonding step (S50), is plated with gold.

[0047] 1.8. Printing step (S80) After the gold plating step, the process of printing product information to be written on the flexible printed circuit board (FPCB) product is carried out, such as customer name, final product code, part number, part location, rated capacity, etc.

[0048] 1.9. Abnormality check step (S90) This is a step of checking whether there is an abnormality in the electrical function of the flexible printed circuit board (FPCB) to ensure the electrical signal quality of the board. Since the flexible printed circuit board (FPCB) constitutes a circuit that plays the role of an electric wire, this is a step of checking whether there is an abnormality in the circuit pattern formed using the circuit and reference mark forming step (S40). In the method of checking whether there is an abnormality in the electrical function of the flexible printed circuit board (FPCB), for example, a current can be applied to the flexible printed circuit board (FPCB) to check whether there is an abnormality in the electrical function such as an open (disconnection) or a short (short circuit).

[0049] 1.10. Outline processing step (S100) The outer shape processing step is a step of processing the outer shape of a flexible printed circuit board (FPCB) product, which is currently in the form of a panel, using a mold to give it a predetermined size and shape.

[0050] In the contour processing step of the present invention, unlike the conventional method in which the contour processing is performed using a guide hole formed on the outside of the flexible printed circuit board (FPCB) as a reference point, the contour processing is performed using a reference mark formed inside the flexible printed circuit board (FPCB) as a reference point using the circuit pattern and reference mark formation step (S40).

[0051] In this way, in the course of a series of processes for forming a circuit pattern on a flexible printed circuit board (FPCB), a reference mark is further formed inside the FPCB, specifically, near the circuit terminal portion of the FPCB to which the terminal (connector) is connected, or at a position within that area, and the outer shape of the FPCB product is processed using this as a reference point during the outer shape processing, thereby minimizing the occurrence of tolerances during the outer shape processing and improving the production efficiency of flexible printed circuit board (FPCB) products.

[0052] 2. Flexible Printed Circuit Board (FPCB) of the Present Invention The difference between the flexible printed circuit board (FPCB) of the present invention and a conventional flexible printed circuit board (FPCB) is that, unlike a conventional flexible printed circuit board (FPCB), which has its exterior processed using guide holes formed on its exterior as reference points, the flexible printed circuit board (FPCB) of the present invention has reference marks that function as reference points during exterior processing, which are further formed inside the FPCB using a series of processes for forming a circuit pattern as described above.

[0053] According to the first embodiment, the reference mark formed inside the flexible printed circuit board (FPCB) may be located in an area within a predetermined distance from the circuit terminal portion of the flexible printed circuit board (FPCB) so as to approach the circuit terminal portion of the flexible printed circuit board (FPCB) to which the terminal (connector) is connected, as shown in Fig. 4, and according to the second embodiment, the reference mark may be located within the circuit terminal portion of the flexible printed circuit board (FPCB) as shown in Fig. 5. In the case of the second embodiment, specifically, the reference mark may also be located in an area in the circuit terminal portion of the flexible printed circuit board (FPCB) where the terminal (connector) pin comes into contact.

[0054] The fiducial mark is a portion of the copper foil that is distinguishable from the circuit that was left behind during etching (S45). The fiducial mark may be formed near the circuit terminal portion as shown in FIG. 4, or may be formed within the circuit terminal portion as shown in FIG. 5, through a series of processes, such as irradiating UV light onto the predetermined circuit pattern and fiducial mark shape to be formed on the dry film adhered to the copper foil layer (S43), peeling off the dry film that has not been exposed to UV light and has not hardened (S44), and then oxidizing and removing the areas that do not correspond to the circuit pattern and fiducial mark (S45).

[0055] In this way, the flexible printed circuit board (FPCB) of the present invention is provided with a reference mark that functions as a reference point during external processing, located near or inside the circuit terminal portion of the flexible printed circuit board (FPCB).By narrowing the distance between the flexible printed circuit board (FPCB) product and the reference point more than conventionally, it is possible to minimize the occurrence of processing tolerances caused by various factors, such as the occurrence of curl due to the flexibility of the flexible printed circuit board (FPCB) during external processing.

[0056] Meanwhile, although the technical idea of ​​the present invention has been specifically described based on the above embodiment, it should be noted that the above embodiment is for the purpose of explanation and not for the purpose of limiting the present invention. It should be understood by those skilled in the art that various embodiments are possible within the scope of the technical idea of ​​the present invention. [Explanation of symbols]

[0057] 100: Flexible Printed Circuit Board (FPCB) 110: Circuit terminal section 112: Pin contact part 120: Reference mark

Claims

[Claim 1] A flexible printed circuit board (FPCB) having a circuit terminal portion to which a connector is connected and a reference mark, A reference mark formed in the flexible printed circuit board (FPCB) serves as a reference point during outer shaping of the flexible printed circuit board (FPCB); A flexible printed circuit board (FPCB), characterized in that the reference mark is an extension portion that extends the area of ​​the pin contact portion where the connector pin touches by a predetermined length within the area within the circuit terminal portion of the flexible printed circuit board (FPCB) to which the connector is connected.

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