KR101896226B1 - Flexible printed circuit board and method for manufacturing the same - Google Patents

Abstract

A flexible circuit board and a method of manufacturing the same are provided. The flexible circuit board includes a metal foil layer formed on at least one of the one surface or the other surface of the substrate, a first wiring layer formed on the metal foil layer, the top surface of the first wiring layer including a convex portion, and a second wiring layer formed on the first wiring layer A second wiring layer formed to cover the upper surface, and an upper surface of the second wiring layer includes a substantially second wiring layer.

Description

TECHNICAL FIELD [0001] The present invention relates to a flexible printed circuit board (FPC)

The present invention relates to a flexible circuit board and a manufacturing method thereof.

BACKGROUND ART [0002] In recent years, a chip on film (COF) package technology using a flexible circuit board has been used in electronic devices in accordance with the miniaturization trend. The flexible circuit board and the COF package technology using the flexible circuit board are used for a flat panel display (FPD) such as a liquid crystal display (LCD), an organic light emitting diode do.

The flexible circuit board includes a wiring pattern formed on one surface or both surfaces of a flexible flexible insulating layer. The wiring pattern can be formed in a semi additive manner, for example, plating using a metal underlying layer formed on an insulating layer. The level of the upper surface of the pad around the through hole that conducts the wiring pattern formed on the upper surface or the both surfaces of the wiring pattern formed in the semi-permanent manner is not uniform, which may cause a problem of product failure due to contact failure or the like .

SUMMARY OF THE INVENTION The present invention provides a flexible circuit board including a pad and a wiring pattern having a flat level on the upper surface using a two-stage plating layer.

Another aspect of the present invention is to provide a method of manufacturing a flexible circuit board including a pad and a wiring pattern having a flat upper surface using a two-step plating layer.

The technical objects of the present invention are not limited to the technical matters mentioned above, and other technical subjects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a flexible circuit board comprising: a metal foil layer formed on at least one surface of a substrate; a metal foil layer formed on the metal foil layer, A second wiring layer formed on the first wiring layer and the first wiring layer so as to cover the upper surface of the first wiring layer and the upper surface of the second wiring layer includes a substantially second wiring layer.

In some embodiments of the present invention, the semiconductor device further includes a through hole penetrating the substrate and a pad overlapping the through hole on one side of the substrate, the pad including a first metal layer filling the through hole, Wherein the first metal layer on the through hole includes a first metal layer having a concave portion whose upper surface faces the other surface of the substrate and a second metal layer formed on the first metal layer and filling the concave portion can do.

In some embodiments of the present invention, the top surface of the second metal layer may be substantially planar.

In some embodiments of the present invention, the first wiring layer may be connected to the first metal layer, and the second wiring layer may be connected to the second metal layer.

In some embodiments of the present invention, the first wiring layer and the first metal layer are formed at the same level, and the second wiring layer and the second metal layer are formed at the same level.

In some embodiments of the present invention, the pad may further include a conductive layer between the inner wall of the through hole and the first metal layer.

In some embodiments of the present invention, at least one intermediate layer interposed between the first wiring layer and the second wiring layer, and between the first metal layer and the second metal layer may be further included.

According to another aspect of the present invention, there is provided a method of fabricating a flexible circuit board, comprising: providing a substrate having a metal foil layer formed on one surface or another surface thereof; forming a plating resist pattern on the one surface or the other surface of the substrate; Forming a conductive wiring on the metal foil layer exposed between the plating resist patterns, removing the plating resist pattern, and removing the metal foil layer exposed between the conductive wirings, Forming a second wiring layer covering the upper surface of the first wiring layer by using a second plating solution, wherein the first wiring layer is formed by using a first plating solution, the upper surface of the first wiring layer including a convex portion, The upper surface of the second wiring layer includes a substantially flat one.

In some embodiments of the present invention, the substrate may include through holes penetrating both sides.

In some embodiments of the present invention, a first metal layer filling the through hole is formed using the first plating solution, and a second metal layer covering the first metal layer is formed using the second plating solution Wherein an upper surface of the first metal layer includes a concave portion, and an upper surface of the second metal layer may be substantially flat.

In some embodiments of the present invention, the first wiring layer and the first metal layer are simultaneously formed, and the second wiring layer and the second metal layer may be formed at the same time.

In some embodiments of the present invention, before forming the first metal layer, forming the conductive layer on the inner wall of the through hole may be further included.

In some embodiments of the present invention, the first plating liquid is composed of a carrier and a leveler mainly composed of a plating promoter, and the second plating liquid is plated with a plating inhibitor as a main component, An accelerator, and a carrier.

According to the flexible circuit board according to the embodiments of the present invention, the level of the upper surface of the pad and the conductive wiring is plated uniformly to improve the adhesion between the electronic component and the ACF (anisotropic conductive film) The problem of lowering the reliability of the inspection at the time of contact inspection can be improved.

Further, according to the method of manufacturing a flexible circuit board according to the embodiments of the present invention, it is possible to simultaneously perform the function of filling a dimple phenomenon in which a groove is formed in a through hole region or a surface of a conductive wiring, And secondary plating for eliminating unevenness in the upper surface level of the conductive wiring can be performed to improve the product reliability.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

1 is a top view of a flexible circuit board according to an embodiment of the present invention.
2 is a cross-sectional view taken along line A-A 'in Fig.
3 is a cross-sectional view taken along the line B-B 'in Fig.
4 to 5 are sectional views of a flexible circuit board according to another embodiment of the present invention.
6 to 10 are intermediate views showing a method of manufacturing a flexible circuit board according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. The dimensions and relative sizes of the components shown in the figures may be exaggerated for clarity of description. Like reference numerals refer to like elements throughout the specification and "and / or" include each and every combination of one or more of the mentioned items.

It is to be understood that when an element or layer is referred to as being "on" or " on "of another element or layer, All included. On the other hand, a device being referred to as "directly on" or "directly above " indicates that no other device or layer is interposed in between.

The terms spatially relative, "below", "beneath", "lower", "above", "upper" May be used to readily describe a device or a relationship of components to other devices or components. Spatially relative terms should be understood to include, in addition to the orientation shown in the drawings, terms that include different orientations of the device during use or operation. For example, when inverting an element shown in the figures, an element described as "below" or "beneath" of another element may be placed "above" another element. Thus, the exemplary term "below" can include both downward and upward directions. The elements can also be oriented in different directions, so that spatially relative terms can be interpreted according to orientation.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. The terms " comprises "and / or" comprising "used in the specification do not exclude the presence or addition of one or more other elements in addition to the stated element.

Although the first, second, etc. are used to describe various elements or components, it is needless to say that these elements or components are not limited by these terms. These terms are used only to distinguish one element or component from another. Therefore, it is needless to say that the first element or the constituent element mentioned below may be the second element or constituent element within the technical spirit of the present invention.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

FIG. 1 is a top view of a flexible printed circuit board according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line A-A 'of FIG. 1, and FIG. 3 is a cross- Fig.

Referring to FIG. 1, a flexible circuit board according to an embodiment of the present invention may include a substrate 10, a pad P, a through hole 30, and a conductive wiring 70.

The substrate 10 may be formed of a flexible material and the flexible circuit board including the substrate 10 may be bent or folded. The substrate may be, for example, a polyimide film. Alternatively, the base film may be a plastic film such as a PET film, a polyethylene naphthalate film, a polycarbonate film, or an insulating metal foil. In the flexible circuit board according to the embodiment of the present invention, the substrate 10 is described as a polyimide film.

The through hole 30 may be formed through the substrate 10. As shown in FIG. 2, the through hole 30 may have a trapezoidal shape in which the width of the upper portion is larger than the width of the lower portion, but the present invention is not limited thereto. That is, the through hole 30 may have a trapezoidal width lower than the upper width, or may have a rectangular or square shape having the same width as the upper width and the lower width.

As shown in Fig. 1, the shape of the cross section of the through hole 30 on the substrate 10 may be circular, but the present invention is not limited thereto. The cross section of the through hole 30 may include any other shape depending on the designer's intention, such as a square shape.

The pad P may be formed on one side of the substrate 10. In the flexible circuit board according to the embodiment of the present invention, the pad P may be formed on one surface and the other surface of the substrate 10. [ The pad P may be formed to overlap with the through hole 30 on one surface of the substrate 10. The pads P can electrically connect the conductive wires formed on both surfaces of the substrate 10. The pad P may be connected to the conductive wiring 70 and the pad P may have a shape in which the width of the conductive wiring 70 is extended.

Regarding the shape of the pad P, it will be described in more detail with reference to FIG.

The pad P may include a first metal layer 20, a second metal layer 40, and a conductive layer 50.

The first metal layer 20 may be formed to fill the through hole 30. The first metal layer 20 may extend from the through hole 30 on one side or both sides of the substrate 10. The upper surface of the first metal layer 20 may include a concave portion 35 facing the other surface which is the opposite surface of the one surface of the substrate 10. The concave portion 35 can be vertically overlapped with the through hole 30 because the concave portion 35 is located at the center of the upper surface of the pad P. [ The height of the upper surface of the first metal layer 20 may be higher than the height of the upper surface of the substrate 10. Therefore, the height of the upper surface of the concave portion 35 may be higher than the height of the upper surface of the substrate 10. A metal foil layer 15 may be interposed between the first metal layer 20 and the upper surface of the substrate 10. The metal foil layer 15 may comprise, for example, a nickel, chromium or copper foil layer.

The first metal layer 20 may be formed by plating the inside of the through hole 30 to form the pad P so as to fill the through hole 30. [ The first metal layer 20 is formed from the conductive layer 50 on both sidewalls of the through hole 30 and the first metal layer 20 grown from the conductive layer 50 reaches the through hole 30 can be charged. A level difference occurs between the first metal layer 20 on the through hole 30 and the upper surface of the first metal layer 20 other than the first metal layer 20 so that the upper surface of the first metal layer 20 is covered with the recess 35 ).

The second metal layer 40 may be formed on the first metal layer 20. The second metal layer 40 may be formed to cover the upper surface of the first metal layer 20. The second metal layer 40 may be formed to fill the concave portion 35 of the first metal layer 20. The upper surface of the second metal layer 40 may be substantially parallel to one surface of the substrate 10. That is, the level of the second metal layer 40 may be substantially planar. The reason why the level of the second metal layer 40 is substantially flat is that the height of the upper surface of the second metal layer 40 depends on the yield of the plating process for forming the second metal layer 40, As shown in Fig. The height difference between the uppermost portion and the lowermost portion of the upper surface of the second metal layer 40 due to such unevenness may be about 1.5 탆 or less. However, in spite of this difference, the formation of the second metal layer 40 may diminish the dimple phenomenon of the pad P and thereby the top surface level unevenness. In this regard, the level of the second metal layer 40 May be substantially planar.

As described above, in the process of forming the first metal layer 20 formed to fill the inside of the through hole 30, the concave portion 35 is formed on the upper surface of the first metal layer 20, The level of the upper surface of the layer 20 may not be uniform. A convex portion 36 may be formed between the concave portion 35 and the edge of the pad P. [ That is, the convex portion 36 may be formed so as to surround the concave portion 35. In the test of the flexible circuit board according to the embodiment of the present invention, the test is interrupted such that the probe slides along the upper surface of the first metal layer 20 which is not planar, P may not be easy to test. The second metal layer 40 having the substantially same level as the upper surface is formed so as to cover the upper surface of the first metal layer 20 so that electrical testing of the pad P and the flexible circuit board can be relatively easy .

The first metal layer 20 and the second metal layer 40 may each include a conductive material such as copper, but the present invention is not limited thereto. Specifically, the first metal layer 20 and the second metal layer 40 may be made of an electrically conductive material such as gold, silver, aluminum, or an alloy thereof. When the first metal layer 20 and the second metal layer 40 include a material having electrical conductivity, the respective composition materials may be different from each other. That is, the plating solution used for forming the first metal layer 20 and the plating solution used for forming the second metal layer 40 may have different compositions. Hereinafter, a method of manufacturing the pad P will be described in more detail.

The conductive layer 50 may be formed on the side wall of the through hole 30. The conductive layer 50 may be formed so as to cover all or a part of both side walls of the through hole 30. The conductive layer 50 may be formed, for example, by plating or sputtering a material such as palladium, nickel, chromium, copper, gold, or an alloy of these metals.

Referring again to FIG. 1, the conductive wiring 70 may be formed on one side of the substrate 10. The conductive wiring 70 can electrically connect circuit elements mounted on the flexible circuit board. Although not shown in Fig. 1, the conductive wiring 70 may be formed on the other surface of the substrate 10 as well. The conductive wiring 70 will be described in more detail with reference to FIG.

The conductive wiring 70 may include a metal foil layer 15, a first wiring layer 120, and a second wiring layer 140. The first wiring layer 120 may be formed on the metal foil layer 15. The upper surface of the first wiring layer 120 may include a convex portion formed in a direction away from the upper surface of the substrate 10. The second wiring layer 140 may be formed to cover the upper surface of the first wiring layer 120. The upper surface of the second wiring layer 140 may be substantially parallel to the upper surface of the substrate 10. That is, the upper surface of the second wiring layer 140 may be substantially planar.

The first wiring layer 120 and the first metal layer 20 may be connected to each other. More specifically, the first wiring layer 120 and the first metal layer 20 may be at the same level. Here, the same level means that the same level is formed by the same manufacturing process.

That is, the first wiring layer 120 may be formed at the same time by performing a plating process of forming the first metal layer 20 to fill the through hole 30. [ The first wiring layer 120 may be formed by forming a resist pattern on the substrate 10 and forming a first wiring layer 120 between the resist patterns by plating.

Meanwhile, the second wiring layer 140 and the second metal layer 40 may be connected to each other. More specifically, the second wiring layer 140 and the second metal layer 40 may be at the same level. That is, the second wiring layer 140 may be formed at the same time by the plating process of forming the second metal layer 40 so as to cover the first metal layer 20.

On the other hand, when the first metal layer 20 and the first wiring layer 120 are formed by the same plating process, the top surface of the first wiring layer 120 may not be uniform and a convex portion may be formed. The formation of the first metal layer 20 may be performed by a plating solution containing a plating promoter to rapidly fill the through hole 30. The first wiring layer 120 formed at the same time may be formed with a convex portion on the upper surface of the first wiring layer 120 as the center portion is rapidly plated by the plating promoter.

The conductive wiring 70 may be connected to an electronic device such as a display panel through an anisotropic conductive film (ACF). At this time, if the convex portion is formed on the upper surface of the conductive wiring 70, the connection quality may be deteriorated due to the contact failure occurring between the ACF and the conductive wiring 70.

In addition, due to the top surface shape of the conductive wiring 70 on which the convex portions are formed, the image obtained through the optical tester is unclear depending on the difference in focus depth between the central portion and the outermost portion of the upper surface of the conductive wiring 70 during optical inspection of the flexible circuit board The reliability of the contact inspection may deteriorate due to the poor contact occurring due to the bending of the probe pin along the convex portion of the conductive wire 70 during the contact inspection using the probe pin.

In the flexible substrate circuit according to the embodiment of the present invention, the second wiring layer 140 covering the convex portion formed on the first wiring layer 120 is formed, and the level of the upper surface of the second wiring layer 140 is substantially planar have. Therefore, problems of poor contact between the ACF and the conductive wiring 70 and deterioration of the inspection reliability at the time of optical inspection and contact inspection of the conductive wiring 70 can be improved.

On the other hand, the metal foil layer 15 may be formed on the surface of the substrate 10. The metal foil layer 15 may function as a seed layer for forming the first metal layer 20 and the first wiring layer 120 by a plating process.

4 to 5 are sectional views of a flexible circuit board according to another embodiment of the present invention.

4 and 5, a flexible circuit board according to another embodiment of the present invention includes a first metal layer 20 and a second metal layer 40, a first wiring layer 120 and a second wiring layer 140). The intermediate layer (45) may include at least one intermediate layer (45). The intermediate layer 45 may be formed along the upper surface level shape of the first metal layer 20 or may be formed so that the shape of the convex portion 36 of the first metal layer 20 is relaxed.

4 and 5, the intermediate layer 45 may be composed of a single layer, but may also be composed of two or more composite layers. The intermediate layer 45 may be formed, for example, by plating one or more metal layers on the first metal layer 20.

FIGS. 6 to 10 are intermediate views illustrating a method of manufacturing a flexible circuit board according to an embodiment of the present invention.

Referring to Fig. 6, a substrate 10 having a metal foil layer 15 formed thereon is provided, and a through hole 30 is formed in the substrate 10. The metal foil layer 15 may be formed on the substrate 10 by sputtering, plating, or the like. The formation of the through hole 30 may be such that CNC or a metal mold is used on the substrate 10 on which the metal foil layer 15 is formed or laser is irradiated to penetrate the substrate 10.

The conductive layer 50 may be formed on the inner wall of the through hole 30 by plating or sputtering a material such as palladium, nickel, chromium, copper, or gold or an alloy of these metals.

Referring to FIG. 7, a plating process may be performed to form the first metal layer 20 filling the through hole 30. The first plating solution used in the plating process for forming the first metal layer 20 includes a plating promoter (brightener B) as a main component and includes a carrier C and a plating inhibitor (leveler L) . The plating promoter, carrier and plating inhibitor may be organic additives included in the plating solution. The plating promoter (B) serves to promote the growth of a part having a high plating level, and the carrier (C) serves to uniformly grow the plating surface irrespective of the plating level, and the plating inhibitor (L) It plays a role of suppressing the growth of the high level part.

The first plating solution used in the plating process for forming the first metal layer 20 may have a strong property of the plating promoter (B). That is, the first metal layer 20 can be formed to quickly fill the through hole 30 by using a first plating solution having a high plating characteristic (B) to fill the through hole 30 quickly. The plating promoter (B) is adsorbed on the sidewall of the through hole (30) and the metal foil layer (15), and the generation and precipitation of the metal crystal can be promoted. The growth of the first metal layer 20 on the side wall of the through hole 30 and the metal foil layer 15 is promoted by the plating promoter B and the first metal layer 20 grown from both side walls of the through- The through hole 30 may be filled with the first metal layer 20 while the first metal layer 20 meets each other.

The plating rate at the boundary between the substrate 10 and the through hole 30 is slower than that of both side walls of the through hole 30 in which the plating promoter B is adsorbed or the upper surface of the metal foil layer 15, The recess (35 in Fig. 2) on the first metal layer can be formed according to the relative difference.

Referring to FIG. 8, a second metal layer 40 is formed on the first metal layer 20. The second metal layer 40 is formed on the first metal layer 20 having the concave portion 35 formed thereon and the second metal layer 40 on the second metal layer 40 formed on the substrate 10, Or may be formed on both sides.

The second plating solution used for forming the second metal layer 40 may have a strong property of the plating inhibitor L. That is, the second plating solution may be one comprising the plating inhibitor (L) as a main component and containing the plating promoter (B) and the carrier (C). The plating inhibitor (L) particles are first adsorbed to a portion having a high level of the plating surface to suppress the plating on the adsorption surface, thereby relatively increasing the plating amount at the low level of the plating surface. That is, the plating inhibitor (L) particles are adsorbed on the surface of the convex portion 36 to make the plating speed of the surface of the concave portion 35 relatively faster than the convex portion 36, and the surface of the second metal layer 40 Can act to be substantially planar.

9, a substrate 10 having a metal foil layer 15 formed on its surface is provided, and a resist 60 is formed on the metal foil layer 15. The plating for forming the first wiring layer 120 is performed using the metal foil layer 15 exposed between the resists 60 as a seed layer.

The plating process for forming the first wiring layer 120 is performed simultaneously with the plating process for forming the first metal layer 20 described above. Therefore, the first wiring layer 120 is formed by using a first plating solution having a high plating promoter (B) property.

The growth of the plating crystal in the central portion of the first wiring layer 120 can be promoted due to the characteristics of the plating promoter (B) in the first plating solution. Therefore, the upper surface of the first wiring layer 120 can be formed with a convex portion.

Referring to FIG. 10, a plating process for forming a second wiring layer 140 on the first wiring layer 120 is performed. The plating process for forming the second wiring layer 140 is performed simultaneously with the plating process for forming the second metal layer 40 described above. Therefore, to form the second wiring layer 140, a second plating solution having a plating inhibitor (L) characteristic is used as the plating solution.

The plating inhibitor L particles are first attracted to the center of the upper surface of the first wiring layer 120 so that the plating rate on the outer surface of the first wiring layer 120 is relatively faster than the center of the first wiring layer 120, Can be formed to be substantially planar.

After the second wiring layer 140 is formed, the resist 60 can be removed. Removing the resist 60 may include removing the metal foil layer 15 between the resist 60 and the substrate 10 together.

As a result, the first metal layer 20 included in the pad P and the first wiring layer 120 included in the conductive wiring 70 are electrically connected to each other by the method of manufacturing the flexible circuit board according to the embodiment of the present invention. It is possible to simultaneously perform the primary plating for forming the flexible circuit board, thereby reducing the manufacturing time of the flexible circuit board. In addition, in order to reduce product defects due to level imbalance that may occur on the top surfaces of the first metal layer 20 and the first wiring layer 120, a second plating may be performed using a plating solution having a different combination characteristic from the plating solution used for the first plating The second metal layer 40 and the second wiring layer 140 having substantially uniform upper surface levels can be formed to improve the product characteristics.

On the other hand, as an embodiment of the present invention, the total thickness T1 and T2 of the pad P and the conductive wiring 70 on one surface of the substrate 10 may be 4 to 20 μm from the surface of the substrate 10. The thickness of the first metal layer 20 and the first wiring layer 120 may be varied depending on the degree of filling of the through holes and the thickness of the first metal layer 20 and the first wiring layer 120 may be 50% 90%. ≪ / RTI >

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is to be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

10: substrate 15: metal foil layer
20: first metal layer 40: second metal layer
P: Pad 30: Through hole
120: first wiring layer 140: second wiring layer

Claims (12)

An insulating substrate including a first surface and a second surface;
A metal foil layer formed on at least one surface of the substrate;
A first wiring layer formed on the metal foil layer and having an upper surface including a convex portion;
A wiring layer formed on the first wiring layer so as to cover the upper surface of the first wiring layer, the second wiring layer having a substantially flat upper surface;
A through hole passing through the substrate;
A metal layer filling the through hole, wherein the upper surface of the through hole includes a concave portion; And
A second metal layer formed to fill the recesses on the first metal layer and having a substantially flat upper surface,
And a flexible circuit board. The method according to claim 1,
Wherein the first metal layer and the second metal layer overlap with the through hole on one side of the substrate,
Further comprising:
Wherein the pad is wider than the conductive wiring including the first wiring layer and the second wiring layer. The method according to claim 1,
The first wiring layer is connected to the first metal layer,
And the second wiring layer is connected to the second metal layer. The method of claim 3,
The first wiring layer and the first metal layer are formed at the same level,
Wherein the second wiring layer and the second metal layer are formed at the same level. 3. The method of claim 2,
The pad includes:
A conductive layer interposed between the inner wall of the through hole and the first metal layer,
Further comprising a flexible circuit board. The method according to claim 1,
And a second metal layer interposed between the first wiring layer and the second wiring layer and between the first metal layer and the second metal layer,
Further comprising a flexible circuit board. Providing an insulating substrate having a metal foil layer formed on one surface or the other surface;
Forming a plating resist pattern on the one surface or the other surface of the substrate, when the substrate is provided;
Forming a first wiring layer having a convex upper surface by using a first plating solution on the metal foil layer exposed between the plating resist patterns and forming an upper surface of the first wiring layer by using a second plating solution; Forming a second wiring layer having a substantially flat top surface as a covering;
Forming a first metal layer having an upper surface including a concave portion by filling the through holes passing through both surfaces of the substrate using the first plating liquid, when the substrate is provided;
Forming a second metal layer covering the first metal layer using the second plating liquid and having a substantially flat upper surface;
Removing the plating resist pattern; And
Removing the metal foil layer exposed between the conductive wirings
Wherein the flexible printed circuit board includes a flexible printed circuit board. delete delete 8. The method of claim 7,
The first wiring layer and the first metal layer are formed at the same time,
Wherein the second wiring layer and the second metal layer are simultaneously formed. 8. The method of claim 7,
Forming a conductive layer on the inner wall of the through hole before forming the first metal layer,
Wherein the flexible printed circuit board further comprises a flexible printed circuit board. 8. The method of claim 7,
The first plating solution is composed of a plating promoter (brightener) as a main component and a carrier and a plating leveler,
Wherein the second plating solution comprises a plating inhibitor as a main component and a plating promoter and a carrier.

Images