Flexible printed circuit board, electronic device including same, and method of manufacturing flexible printed circuit board

Abstract

The invention provides a flexible printed circuit board and a manufacturing method thereof. The flexible printed circuit board includes: a base film including a bending region, a first region, and a second region, the bending region being disposed between the first region and the second region; a plurality of first line patterns formed on one surface of the base film; a first plating layer covering the plurality of first line patterns; a first protective layer formed on the bending region of the base film so as to cover the first plating layer; and a second plating layer formed so as to cover the first plating layer on which the first protective layer is not formed, and the first plating layer on the bending region is formed at a thickness of 0.05-0.25 [mu] m.

Description

[0001] This application is a divisional application of the invention patent application with the application number 201780009892.3, titled "Flexible Printed Circuit Board, Electronic Device Comprising the Same, and Method of Manufacturing a Flexible Printed Circuit Board", which was filed on June 20, 2017. Technical Field

[0002] The present invention relates to a flexible printed circuit board, an electronic device comprising the same, and a method of manufacturing a flexible printed circuit board. Background Art

[0003] Recently, with the trend of miniaturization of electronic devices, a Chip On Film (COF) packaging technology using a flexible printed circuit board has been used. The flexible printed circuit board and the COF packaging technology using the same are applicable to flat panel displays (FPDs) such as liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays.

[0004] Since the flexible printed circuit board has flexibility, it is used after being folded or bent when applied to an electronic device. When the flexible printed circuit board is folded and used, there may be a problem of a decrease in the durability of the flexible printed circuit board at the bent portion.

[0005] In particular, in order to protect the circuit pattern or ensure the adhesion to electronic components, after forming the conductive circuit pattern, a plating layer is formed. And, during the plating process or after plating, substances contained in the circuit pattern and the plating layer diffuse into each other to form an intermetallic compound layer (IMC layer). The hardness of the intermetallic compound layer is relatively higher than that of the circuit pattern. Therefore, the flexibility is reduced, which becomes the main cause of cracks occurring when the flexible printed circuit board is bent.

[0006] And, preferably, in order to prevent cracks from occurring at the bent portion of the flexible printed circuit board, a protective layer covering the circuit pattern is formed after forming the circuit pattern, and then a plating layer is formed at the terminal portion. However, there is a problem that a hole portion is formed due to a local battery phenomenon at the boundary portion between the protective layer and the plating layer when plating the terminal portion. To solve the above problem, Korean Patent Publication No. 2000-62154 (hereinafter referred to as 'Prior Art 1'). However, Prior Art 1 is for preventing the local battery phenomenon and does not consider the circuit defect at the bent portion of the flexible printed circuit board. Therefore, there is still a risk of circuit defects. Summary of the Invention

[0007] Technical Problem to be Solved

[0008] The technical problem to be solved by the present invention is a flexible printed circuit board in which a coating layer formed of a thin film is formed in a bending region, and which improves the product reliability, and an electronic device including the same.

[0009] Another technical problem to be solved by the present invention is a method for manufacturing a flexible printed circuit board in which a coating layer formed of a thin film is formed in a bending region, and which improves the product reliability.

[0010] The technical problems of the present invention are not limited to the technical problems mentioned above, and those skilled in the art should clearly understand other technical problems not described.

[0011] Technical solution for solving the problem

[0012] To solve the above technical problems, a flexible printed circuit board according to an embodiment of the present invention includes: a base film including a bending region, a first region, and a second region, the bending region being disposed between the first region and the second region; a plurality of first circuit patterns formed on one surface of the base film; a first coating layer covering the plurality of first circuit patterns; a first protective layer formed to cover the first coating layer on the bending region of the base film; and a second coating layer formed to cover the first coating layer on which the first protective layer is not formed, and the first coating layer on the bending region is formed with a thickness of 0.05 to 0.25 μm.

[0013] In several embodiments of the present invention, the first circuit pattern includes an element connection portion, and the first protective layer is not formed on the element connection portion.

[0014] In several embodiments of the present invention, the second coating layer is formed to cover the element connection portion.

[0015] In several embodiments of the present invention, it further includes: a plurality of second circuit patterns formed on the other surface opposite to the one surface of the base film; a third coating layer covering the second circuit patterns; a second protective layer formed to cover the third coating layer on the bending region of the base film; and a fourth coating layer formed to cover the third coating layer on which the second protective layer is not formed.

[0016] In several embodiments of the present invention, the third coating layer is formed with a thickness of 0.05 to 0.25 μm.

[0017] In several embodiments of the present invention, a via hole for electrically connecting the first circuit pattern and the second circuit pattern is further included inside the base film.

[0018] In several embodiments of the present invention, the second coating layer is formed thicker than the first coating layer.

[0019] The manufacturing method of the flexible printed circuit board of the present invention for solving the above technical problems includes the following steps: forming a base film including a bending area, a first area, and a second area, where the bending area is disposed between the first area and the second area; forming a plurality of first circuit patterns on one surface of the base film; forming a first plating layer covering the plurality of first circuit patterns; forming a first protective layer covering the first plating layer on the bending area of the base film; forming a second plating layer covering the first plating layer where the first protective layer is not formed, and the first plating layer on the bending area is formed with a thickness of 0.05 to 0.25 μm.

[0020] In several embodiments of the present invention, it further includes the following steps: forming a plurality of second circuit patterns on the other surface, which is the opposite surface of the one surface of the base film; forming a third plating layer covering the plurality of second circuit patterns; forming a second protective layer covering the third plating layer on the bending area of the base film; forming a fourth plating layer covering the third plating layer where the second protective layer is not formed.

[0021] In several embodiments of the present invention, when forming the second plating layer, it is formed thicker than the thickness of the first plating layer.

[0022] An electronic device according to an embodiment of the present invention for solving the above technical problems includes: a first circuit element and a second circuit element; and a printed circuit board including: a first area connected to the first circuit element and extending evenly with the connection surface of the first circuit element, a second area connected to the second circuit element and extending evenly with the connection surface of the second circuit element, and a bending area connecting the first area and the second area and bending at an angle of 90° to 180°. And the flexible printed circuit board includes: a base film; a plurality of circuit patterns formed on at least one surface of the base film; a first plating layer formed covering the plurality of circuit patterns; a first protective layer formed covering the first plating layer within the bending area; and a second plating layer formed covering the first plating layer where the first protective layer is not formed, and the first plating layer within the bending area is formed with a thickness of 0.05 to 0.25 um.

[0023] In several embodiments of the present invention, the bending area of the flexible printed circuit board is bent with a radius of curvature of 0.01 mm to 0.49 mm.

[0024] In several embodiments of the present invention, at least a part of the first area and the second area of the flexible printed circuit board are relatively disposed in contact with each other.

[0025] Effects of the Invention

[0026] A flexible printed circuit board according to an embodiment of the present invention and a manufacturing method thereof include a first plating layer formed of a thin film on a circuit pattern within a bending region of the flexible printed circuit board, and prevent cracks occurring on the plating layer or the circuit pattern due to tension when the flexible printed circuit board is bent.

[0027] Moreover, a protective layer is formed on the first plating layer within the bending region, and a second plating layer having a sufficient thickness is formed on the first plating layer where the protective layer is not formed, thereby ensuring the adhesion between the flexible printed circuit board and circuit components or electronic devices.

[0028] The effects of the present invention are not limited to those described above. Those skilled in the art should clearly understand other effects not described through the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A top view for illustrating a flexible printed circuit board according to an embodiment of the present invention;

[0030] Figure 2 For the cross-sectional view along the Figure 1 A - A' line;

[0031] Figure 3 For the cross-sectional view along the Figure 1 B - B' line;

[0032] Figure 4 A graph showing the bending test results of a flexible printed circuit board according to an embodiment of the present invention;

[0033] Figure 5 A cross-sectional view of a flexible printed circuit board according to another embodiment of the present invention;

[0034] Figure 6 A cross-sectional view of an electronic device including a flexible printed circuit board according to an embodiment of the present invention;

[0035] Figure 7 For Figure 6 An enlarged view of the bending region of the flexible printed circuit board included in the electronic device;

[0036] Figures 8 to 10 An intermediate step drawing for illustrating a manufacturing method of a flexible printed circuit board according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The advantages, features, and methods of achieving the present invention will become apparent from the accompanying drawings and the embodiments described in detail below. However, the present invention is not limited to the embodiments disclosed below, but can be embodied in various different forms. These embodiments are only provided to make the disclosure of the present invention more complete and to fully inform those of ordinary skill in the technical field to which the present invention pertains of the scope of the present invention. The present invention is only defined by the scope of the claims. For clarity of illustration, the sizes and relative sizes of the components shown in the drawings may be exaggerated. Throughout the specification, the same reference numerals refer to the same components, and "and / or" includes each and all combinations of the recited items.

[0038] When referring to an element or layer as "on" or "upon" another element or layer, it includes all cases where the other element or layer is directly on top of the different element or layer and where there are other layers or other elements intervening in between. In contrast, when an element is referred to as "directly on" or "directly upon" another element, it means that there are no other elements or layers intervening in between.

[0039] Spatially relative terms such as "below", "beneath", "lower", "above", "upper", etc. are used herein for ease of description to facilitate the relationship between one element or component and another as shown in the figures. Spatially relative terms are to be understood to include different orientations of the elements in addition to the orientation shown in the figures during use or operation. For example, when an element shown in the figures is flipped, an element described as "below" or "beneath" another element may be positioned "above" the other element. Thus, the exemplary term "below" can include both the below and above directions. Elements can also be oriented in different directions, and thus, spatially relative terms can be interpreted according to the orientation.

[0040] The terms used in this specification are for the purpose of describing embodiments and not for limiting the present invention. Unless otherwise specifically stated in the context, the singular forms in this specification also include the plural forms. The terms "comprises" and / or "comprising" used in the specification do not exclude the presence or addition of one or more other components in addition to the recited components.

[0041] Although the first, second, etc. are used to describe various elements or components, the above elements or components are not limited to these terms. These terms are used to distinguish one element or component from another. Thus, the first element or component described below can also be the second element or component within the technical concept of the present invention.

[0042] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification shall be construed in accordance with the common understanding of those of ordinary skill in the technical field to which the present invention pertains. Also, unless explicitly defined otherwise, terms defined in commonly used dictionaries shall not be construed in an abnormal or overly pedantic manner.

[0043] Figure 1 A top view of a flexible printed circuit board according to an embodiment of the present invention is shown; Figure 2 and Figure 3 are cross-sectional views taken along lines A-A' and B-B' of Figure 1 respectively.

[0044] Referring to Figures 1 to 3 , a flexible printed circuit board 1 according to an embodiment of the present invention includes: a base film 10, first circuit patterns 20, 21, first protective layers 30, 31, a first plating layer 40, and a second plating layer 50.

[0045] The base film 10 may be formed of a flexible material and is formed as a base material on the flexible printed circuit board 1 so that the flexible printed circuit board 1 can be bent or folded.

[0046] The base film 10 includes a bending region 100, a first region 101, and a second region 102. The bending region 100 may be disposed between the first region 101 and the second region 102. When the flexible printed circuit board 1 is mounted on an electronic device, the bending region 100 is the region where it is bent for mounting. Conversely, when the flexible printed circuit board 1 is mounted on an electronic device, the first region 101 and the second region 102 are the non-bent regions.

[0047] The base film 10 may be, for example, a polyimide film. Alternatively, the base film 10 may also be an insulating film such as a PET (Polyethylene Terephthalate) film, a polyethylene naphthalate film, a polycarbonate film, or a metal foil such as an aluminum oxide foil. In the flexible printed circuit board 1 according to an embodiment of the present invention, the base film 10 is described by taking a polyimide film as an example.

[0048] The base film 10 may have insulating properties. That is, as will be described below, when circuit patterns 20, 120 are formed on both sides of a flexible printed circuit board ( Figure 4 2) according to another embodiment of the present invention, insulation is formed to block electrical connection between the circuit patterns 20, 120.

[0049] However, the present invention is not limited thereto, and the base film 10 may also have through holes (not shown) formed therein for electrically connecting the circuit patterns 20, 120.

[0050] The base film 10 may include an element configuration area 12. The element configuration area 12 is an area for configuring circuit elements electrically connected to the flexible printed circuit board 1.

[0051] A plurality of first circuit patterns 20 are formed on the base film 10. The first circuit pattern 20 is, for example, a circuit pattern formed by a strip having a predetermined u. The plurality of first circuit patterns 20 may be continuously formed at a predetermined interval on one surface of the base film 10.

[0052] The first circuit pattern 20 may include a conductive material such as metal. Specifically, the first circuit pattern 20 may be a conductive circuit for transmitting an electronic signal or a transparent conductive circuit for transmitting the capacitance according to touch. More specifically, the first circuit pattern 20 may include a conductive substance such as copper, but the present invention is not limited thereto, and the first circuit pattern 20 may also include substances such as gold and aluminum.

[0053] As Figure 2 and Figure 3 shown, the first circuit pattern 20 of the flexible printed circuit board according to an embodiment of the present invention may be formed of one layer, but the present invention is not limited thereto. The flexible printed circuit board 1 may include two or more layers of multilayer printed circuits.

[0054] The first circuit patterns 20, 21 may include element connection portions 15. The element connection portions 15 may overlap with the element configuration area 12 of the base film 10.

[0055] The element connection portions 15 may include terminals electrically connected to the circuit elements arranged on the element configuration area 12. That is, when the circuit elements are mounted in a chip on film (COF) or film on glass (FOG) manner, the element connection portions 15 may be terminals formed on the first circuit pattern 20. The above-mentioned circuit elements may include, for example, a semiconductor chip (IC), a sensor, a light emitting diode (LED), etc., but the present invention is not limited thereto.

[0056] A first plating layer 40 may be formed on the plurality of first circuit patterns 20. The first plating layer 40 may be formed to cover the upper surface and the side surfaces of the first circuit pattern 20. The first plating layer 40 may be formed to have a thickness of 0.05 to 0.25 μm. Regarding the thickness of the first plating layer 40, refer to Figure 4 and Table 1 for description.

[0057] Figure 4 is a graph showing the bending test results of the flexible printed circuit board 1 according to an embodiment of the present invention, and Table 1 is a table showing the bending test results represented by numbers Figure 4 thereof.

[0058]

Table 1

[0059]

[0060]

[0061] In a flexible printed circuit board according to an embodiment of the present invention, after forming the thickness of the first plating layer 40 to be 0.05 to 0.5 μm, a bending test was performed by repeatedly bending a portion of the bending region 100 of the flexible printed circuit board. Then, the number of times of cracks occurring in the circuit pattern 20 for the first time was recorded and is shown in Table 1 and Figure 4 respectively.

[0062] As confirmed in Table 1 and Figure 4 respectively, when the thicknesses of the first plating layer 40 are 0.05, 0.1, 0.15, 0.2, and 0.25 μm, the first occurrences of cracks were observed to be 381, 354, 302, 252, and 179 times, respectively. That is, when the thickness of the first plating layer 40 is 0.05 μm, the durability against the occurrence of cracks on the circuit pattern is the highest in the bending test. When the thickness of the first plating layer 40 increases by 0.05 μm each time, the number of the first occurrences of cracks decreases by about 30 to 50 times.

[0063] However, when the thickness of the first plating layer 40 is 0.3 μm, the number of the first occurrences of cracks sharply decreases to 43 times, and the first occurrences of cracks are 17, 5, 1, and 1 times respectively in 0.35, 0.4, 0.45, and 0.5 μm.

[0064] Therefore, the first plating layer 40 of the flexible printed circuit board 1 according to an embodiment of the present invention can be formed with a thickness of 0.05 to 0.25 μm. When the thickness of the first plating layer 40 is greater than 0.25 μm, as shown in the bending test results in Figure 4 and Table 1, the durability against the bending of the flexible printed circuit board 1 may sharply decrease. On the contrary, when the first plating layer 40 is formed with a thickness less than 0.05 μm, it is difficult to perform electroplating or electroless plating of the first plating layer 40 formed by an electroless plating method.

[0065] Generally, when the first plating layer 40 covers both the upper surface and the side surface of a plurality of first circuit patterns 20, due to the first plating layer 40 formed on the bending region 100 of the base film 10, there may be a problem of hindering the deformation of the first circuit pattern 20 into a required shape. As shown in the above bending test results, the above situation is more prominent when the thickness of the first plating layer is formed to be greater than 0.25 μm, and the possibility of cracks occurring on the circuit pattern or the plating layer increases due to the tensile stress applied to the first circuit pattern 20 in the bending region 100.

[0066] However, the flexible printed circuit board according to the embodiment of the present invention forms the first coating layer 40 with a thickness of 0.05 to 0.25 μm, so that it has a durability of at least 179 bends or more in the bending test. That is, the first coating layer 40 is formed thinner with the above thickness range, so as not to limit the deformation of the first circuit pattern 20 and improve the operation reliability of mounting the bending region 100 on the flexible printed circuit board 1 of the electronic device in a bent state.

[0067] The first coating layer 40 can prevent corrosion of the plurality of first circuit patterns 20 and improve the adhesion between the component connection part 15 and the circuit components connected thereto. The first coating layer 40 may include, for example, metals such as tin (Sn), nickel (Ni), gold (Au), palladium (Pd), and aluminum (Al).

[0068] The first protective layer 30 may be formed to cover a part of the first coating layer 40. More specifically, the first protective layer 30 is formed to cover the first coating layer 40 on the bending region 100 of the base film 10. The first protective layer 30 may be formed up to the boundary between the bending region 100 and the first region 101 or the second region 102 in the bending region 100, but may also be formed by expanding a part inwardly of the first region 101 or the second region 102. And the first protective layer 30 may not be formed on the component connection part 15 of the first circuit pattern 20.

[0069] The first protective layer 30 may include, for example, photoresist ink, but is not limited thereto, and the first protective layer 30 may also include a cover film.

[0070] The first protective layer 30 can protect the first circuit pattern 20 from external impacts or corrosive substances.

[0071] The second coating layer 50 may be formed to cover a part of the first coating layer 40. Specifically, the second coating layer 50 may be formed to cover the upper surface and side surfaces of the first coating layer 40 where the first protective layer 30 is not formed. The second coating layer 50 may include the same substance as the first coating layer 40.

[0072] The second coating layer 50 is formed thicker than the first coating layer 40. That is, the first coating layer 40 is formed with a thickness of 0.05 to 0.25 μm to prevent cracks that may occur on the first circuit pattern 20 in the bending region 100. Thus, due to the relatively thin thickness of the first coating layer 40, the adhesion force with the circuit components or the electronic device may be reduced at the component connection part 15. The second coating layer 50 may be formed thicker than the first coating layer 40, and can improve the adhesion force with the circuit components or the electronic device at the component connection part 15.

[0073] Figure 5 It is a cross-sectional view of a flexible printed circuit board according to another embodiment of the present invention.

[0074] Refer toFigure 5 According to another embodiment of the present invention, the flexible printed circuit board 2 may include: a second circuit pattern 120, a second protective layer 130, a third plating layer 140, and a fourth plating layer 150 formed on the other surface of the base film 10 on which the first circuit pattern 20 is formed, i.e., the opposite surface.

[0075] A plurality of second circuit patterns 120 may be formed on the opposite surface of the base film 10 on which the first circuit pattern 20 is formed. A plurality of second circuit patterns 120 may also be formed at positions corresponding to the plurality of first circuit patterns 20. However, the present invention is not limited thereto, and according to the circuit design, the plurality of second circuit patterns 120 may be arranged in a shape different from that of the plurality of first circuit patterns 20.

[0076] The plurality of second circuit patterns 120 may be continuously formed at a predetermined interval on the other surface of the base film 10, and like the first circuit pattern 20, include a conductive material such as copper.

[0077] The first circuit pattern 20 and the second circuit pattern 120 may be electrically insulated by the base film 10. If necessary, a through hole (not shown) for electrically connecting the first circuit pattern 20 and the second circuit pattern 120 may also be formed in the base film 10.

[0078] The third plating layer 140 may be formed to cover the second circuit pattern 120. The third plating layer 140 may cover the upper surface and the side surface of the second circuit pattern 120. The third plating layer 140 may be formed to have a thickness similar to that of the first plating layer 40. That is, the third plating layer 140 may be formed to have a thickness of 0.05 to 0.25 μm.

[0079] When the third plating layer 140 is formed to be greater than 0.25 μm, when the base film 10 is bent in the bending region 100, the durability against cracks occurring on the circuit pattern may be reduced, which is the same as the description regarding the first plating layer 40.

[0080] The second protective layer 130 is formed in the bending region 100 of the base film 10 and covers the third plating layer 140, and the fourth plating layer 150 may be formed on the third plating layer 140 where the second protective layer 130 is not formed.

[0081] The fourth plating layer 150 is formed to be thicker than the third plating layer 140, and can prevent a reduction in the adhesion of the element connection portion 15 to the circuit element or the electronic device that may occur due to the third plating layer 140 being formed to have a thickness of 0.05 to 0.25 μm.

[0082] Figure 6 It is a cross-sectional view of an electronic device including a flexible printed circuit board according to several embodiments of the present invention.

[0083] Refer to Figure 6, an electronic device 3 according to an embodiment of the present invention may include: a flexible printed circuit board 5, a display 200, a substrate 300, and a driving element 400.

[0084] The display 200 and the substrate 300 may be electrically connected through the flexible printed circuit board 5. The display 200 may display an image, and the substrate 300 generates a signal for driving the display 200. The substrate 300 is a PCB substrate or other flexible printed circuit board.

[0085] The driving element 400 may be disposed on the flexible printed circuit board 5. More specifically, the driving element 400 may be disposed in the component arrangement area ( Figure 1 of 12) of the flexible printed circuit board 5. The driving element 400 is, for example, a DDIC (Display Driver IC) for driving the display.

[0086] Here, the display 200, the substrate 300, the driving element 400, etc. are exemplary circuit elements that can be connected to the flexible printed circuit board 5, and the present invention is not limited thereto. That is, those of ordinary skill in the technical field of the present invention should understand that the electronic device 3 of the present invention can be any situation as long as the flexible printed circuit board 5 is bent at a predetermined angle and connected to the circuit elements.

[0087] The flexible printed circuit board 5 may include a bending area 500, a first area 501, and a second area 502

[0088] The first area 501 is connected to the display 200 and extends evenly with the connection surface of the display 200. Although not shown, the first area 501 may include a terminal portion connected to the display 200.

[0089] The second area 502 is connected to the substrate 300 and extends evenly with the connection surface of the substrate 300. Similarly, the second area 502 may include a terminal portion connected to the substrate 300.

[0090] As shown in the figure, the first area 501 and the second area 502 of the flexible printed circuit board 5 are relatively separated from each other and mounted on the electronic device 3, but the present invention is not limited thereto. That is, at least a part of the first area 501 and the second area 502 may be relatively in contact with each other. That is, the flexible printed circuit board 5 is folded with the bending area 500 as a reference line and mounted on the electronic device 3.

[0091] The bending area 500 connects the first area 501 and the second area 502 and bends at an angle of 90° to 180°.

[0092] The bending area 500, the first area 501, and the second area 502 of the flexible printed circuit board 5 may be respectively connected to the Figure 1corresponds to the bending region 100, the first region 101, and the second region 102 formed on the base film 10 of the flexible printed circuit board 1.

[0093] Figure 7 For expanding the bending region of the flexible printed circuit board to be formed in Figure 6 the electronic device.

[0094] Refer to Figure 7 , the bending region 500 of the flexible printed circuit board is mounted on the electronic device 3 in a state having a predetermined radius of curvature (r).

[0095] When the flexible printed circuit board 5 according to an embodiment of the present invention is mounted on the electronic device 3 in a bent state, the total thickness (D1) of the flexible printed circuit board 5 may be 0.1 mm to 1 mm.

[0096] As an example of the flexible printed circuit board according to an embodiment of the present invention, the total thickness (D1) of the flexible printed circuit board 5 is 0.2 mm, and the thickness D2 of the cross section is 0.071 mm. At this time, the radius of curvature r of the bending region of the flexible printed circuit board 5 is 0.029 mm. The radius of curvature (r) of the above bending region 500 is only an example, and the radius of curvature of the bending region in the flexible printed circuit board according to several embodiments of the present invention may be 0.01 mm to 0.49 mm.

[0097] Figures 8 to 10 It is a drawing of an intermediate step for explaining a manufacturing method of a flexible printed circuit board according to an embodiment of the present invention.

[0098] Refer to Figure 8 , a plurality of first circuit patterns 20 are formed on one surface of the base film 10. When forming the plurality of first formed circuit patterns 20, for example, after forming a conductive material on one surface of the base film 10 by sputtering coating or lamination method and then performing a patterning process, or printing the conductive material on the base film 10 to form.

[0099] Figure 8 Illustrated in is that only a plurality of first circuit patterns 20 are formed on one surface of the base film 10, however, the present invention is not limited thereto. As in the flexible printed circuit board 2 of another embodiment of the present invention described above, a second circuit pattern 120 may also be formed on the other surface, which is the opposite surface of one surface of the base film 10.

[0100] Refer to Figure 9 , a first plating layer 40 is formed to cover the plurality of first circuit patterns 20.

[0101] The first plating layer 40 is formed of a metal material such as tin, nickel, gold plating, gold, palladium, and aluminum with a thickness of 0.05 to 0.25 μm on the first conductive pattern 20 by, for example, electrolytic plating or electroless plating.

[0102] Refer to Figure 10 , a first protective layer 30 is formed to cover the first plating layer 40 on the curved region 100. The first protective layer 30 can be formed by coating a photoresist ink, however, the present invention is not limited thereto, and it can also be formed by laminating a solder resist ink or a cover film.

[0103] Refer to again Figure 3 , a second plating layer 40 is formed on the first plating layer 40 where the first protective layer 30 is not formed. The second plating layer 40 is formed of a metal material such as tin, nickel, gold plating, gold, palladium, and aluminum by electrolytic plating or electroless plating in the same manner as the first plating layer 30. In order to ensure sufficient adhesion to the circuit element at the element connection portion 15, the second plating layer 40 can be formed thicker than the first plating layer 30.

[0104] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited thereto, and it can be manufactured in various different forms. Those of ordinary skill in the art of the present invention should understand that it can be implemented in other detailed forms without changing the technical idea or essential features of the present invention. Therefore, the embodiments described above are exemplary in all aspects and not restrictive.

Claims

1. A flexible printed circuit board, characterized in that, comprising: a base film including a bending region, a first region and a second region, the bending region being disposed between the first region and the second region; a plurality of first circuit patterns formed on one surface of the base film; a first plating layer covering the plurality of first circuit patterns; a first protective layer formed to cover the first plating layer on the bending region of the base film; and a second plating layer formed to cover the first plating layer where the first protective layer is not formed, and the first plating layer has a thickness greater than 0.1 μm and less than or equal to 0.25 μm.

2. The flexible printed circuit board according to claim 1, characterized in that, the first circuit pattern includes a component connection portion, and the first protective layer is not formed on the component connection portion.

3. The flexible printed circuit board according to claim 2, characterized in that, the second plating layer is formed to cover the component connection portion.

4. The flexible printed circuit board according to claim 1, characterized in that, further comprising: a plurality of second circuit patterns formed on the opposite surface of the one surface of the base film, i.e., the other surface; a third plating layer covering the second circuit patterns; a second protective layer formed to cover the third plating layer on the bending region of the base film; and a fourth plating layer formed to cover the third plating layer where the second protective layer is not formed.

5. The flexible printed circuit board according to claim 4, characterized in that, the third plating layer is formed with a thickness of 0.05 - 0.25 μm.

6. The flexible printed circuit board according to claim 4, characterized in that, through holes for electrically connecting the first circuit patterns and the second circuit patterns are further included inside the base film.

7. The flexible printed circuit board according to claim 1, characterized in that, the second plating layer is formed thicker than the first plating layer.

8. A manufacturing method of a flexible printed circuit board, characterized in that, comprising the following steps: forming a base film including a bending region, a first region and a second region, the bending region being disposed between the first region and the second region; forming a plurality of first circuit patterns on one surface of the base film; forming a first plating layer to cover the plurality of first circuit patterns; forming a first protective layer to cover the first plating layer on the bending region of the base film; forming a second plating layer to cover the first plating layer where the first protective layer is not formed, and the first plating layer has a thickness greater than 0.1 μm and less than or equal to 0.25 μm.

9. The manufacturing method of the flexible printed circuit board according to claim 8, characterized in that, further comprising the following steps: forming a plurality of second circuit patterns on the opposite surface of the one surface of the base film, i.e., the other surface; forming a third plating layer to cover the plurality of second circuit patterns; forming a second protective layer to cover the third plating layer on the bending region of the base film; forming a fourth plating layer to cover the third plating layer where the second protective layer is not formed.

10. The manufacturing method of the flexible printed circuit board according to claim 1, characterized in that, The second coating is formed to be thicker than the first coating when the second coating is formed.

11. An electronic device, characterized in that, comprising: a first circuit element and a second circuit element; and a flexible printed circuit board, comprising: a first region connected to the first circuit element and extending evenly from the connection surface of the first circuit element, a second region connected to the second circuit element and extending evenly from the connection surface of the second circuit element, and a bending region connecting the first region and the second region and bending at an angle of 90° to 180°. Moreover, the flexible printed circuit board comprises: a base film; a plurality of circuit patterns formed on at least one surface of the base film; a first coating formed to cover the plurality of circuit patterns; a first protective layer formed to cover the first coating within the bending region; and a second coating formed to cover the first coating where the first protective layer is not formed, and the first coating has a thickness greater than 0.1 μm and less than or equal to 0.25 μm.

12. The electronic device according to claim 11, characterized in that, the bending region of the flexible printed circuit board is bent such that the radius of curvature is 0.01 mm to 0.49 mm.

13. The electronic device according to claim 11, characterized in that, at least a part of the first region and the second region of the flexible printed circuit board face each other in contact.

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