KR20170112814A - Flexible printed circuit board, manufacturing method of the same, and touch panel comprising the same - Google Patents

Abstract

A flexible printed circuit board according to an embodiment includes: a substrate including a through hole; A first metal layer disposed on an upper surface, a lower surface, and an inner surface of the through hole of the substrate; And a second metal layer disposed on an upper surface, a lower surface, and an inner surface of the through hole of the first metal layer.
A method of manufacturing a flexible circuit board according to an embodiment of the present invention includes: preparing a substrate; Forming a through hole on the substrate; Forming a first metal layer on the substrate on which the through hole is formed; And forming a second metal layer on the first metal layer.
A touch panel according to an embodiment includes a flexible printed circuit board, the flexible printed circuit board including a through hole; A first wiring layer disposed on the substrate; And a second wiring layer disposed under the substrate, wherein the first wiring layer and the second wiring layer are electrically connected to a driving chip disposed on the substrate.

Description

TECHNICAL FIELD [0001] The present invention relates to a flexible printed circuit board, a method of manufacturing the same, and a touch panel including the flexible printed circuit board,

The present disclosure relates to a touch panel and a touch device including the touch panel.

A touch panel which inputs an image by touching an input device such as a finger or a stylus to an image displayed on the touch device in various electronic products has been applied.

A circuit board for applying a signal to the touch panel is separately provided.

In recent years, a curved surface display or a flexible display has been used in various electronic products, and a flexible circuit board that can be applied thereto has been developed.

In addition, since a small and slim touch device is required, a multi-layer flexible circuit board on both sides can be energized through the conductive material filled in the through hole and the through hole.

In such a multilayer flexible circuit board, a polyimide substrate having copper foils laminated on both surfaces thereof is prepared, and a through hole is formed through a drill. Next, the conductive material may be disposed on the inner surface of the through hole through plating. As a result, the upper surface and the lower surface of the substrate can be electrically connected through the conductive material disposed in the through hole. Next, a patterned wiring layer can be formed on both surfaces of the flexible circuit board, that is, on the upper and lower surfaces through the exposure, development and etching steps after laminating the dry film.

In such a multilayer flexible circuit board, a copper foil by electroless plating and a copper foil by electrolytic plating are sequentially disposed on a polyimide substrate, the overall thickness thereof may become thick, and the process is complicated.

Further, when the copper foil by electroless plating is disposed on the inner surface of the through hole, the adhesion may be low, and voids may be generated in the region inside the through hole.

Embodiments provide a flexible circuit board having a slim thickness, a manufacturing method thereof, and a touch panel having improved reliability.

A flexible printed circuit board according to an embodiment includes: a substrate including a through hole; A first metal layer disposed on an upper surface, a lower surface, and an inner surface of the through hole of the substrate; And a second metal layer disposed on an upper surface, a lower surface, and an inner surface of the through hole of the first metal layer.

A method of manufacturing a flexible circuit board according to an embodiment of the present invention includes: preparing a substrate; Forming a through hole on the substrate; Forming a first metal layer on the substrate on which the through hole is formed; And forming a second metal layer on the first metal layer.

A touch panel according to an embodiment includes a flexible printed circuit board, the flexible printed circuit board including a through hole; A first wiring layer disposed on the substrate; And a second wiring layer disposed under the substrate, wherein the first wiring layer and the second wiring layer are electrically connected to a driving chip disposed on the substrate.

A second embodiment of the present invention provides a semiconductor device comprising a substrate including a through hole, a first metal layer disposed on an upper surface, a lower surface, and an inner surface of the through hole of the substrate, a second metal layer disposed on the upper surface, Metal layer.

The first metal layer according to the embodiment can be integrally disposed on the upper surface and the lower surface of the substrate and the inner surface of the through hole so that the adhesion of the first metal layer can be improved on the inner surface of the through hole.

In addition, the second metal layer according to the embodiment can be integrally disposed on the upper surface, the lower surface, and the inner surface of the through hole of the substrate, and the adhesion of the second metal layer can be improved on the inner surface of the through hole.

In addition, since the metal layer is disposed on the inner surface of the through hole at the same time as the top and bottom surfaces of the substrate, it is possible to prevent a step from being generated, and a slim and flexible circuit board can be formed.

In addition, in the method of manufacturing a flexible circuit board according to the embodiment, it is possible to omit the step of filling the inner surface of the through hole with a conductive material separately, thereby improving the process efficiency.

In addition, since the flexible circuit board according to the embodiment can prevent the occurrence of voids in the metal layer that can be disposed on the inner side of the through hole, the reliability of the touch panel including the same can be improved.

1 is a view showing a manufacturing process of a flexible circuit board according to a comparative example.
2 is a cross-sectional view of a flexible circuit board according to a comparative example.
3 to 7 are sectional views of a flexible circuit board according to an embodiment.
8 to 12 are views showing a manufacturing process of a flexible circuit board according to an embodiment.

In the description of the embodiments, it is to be understood that each layer (film), area, pattern or structure may be referred to as being "on" or "under / under" Quot; includes all that is formed directly or through another layer. The criteria for top / bottom or bottom / bottom of each layer are described with reference to the drawings.

The thickness or the size of each layer (film), region, pattern or structure in the drawings may be modified for clarity and convenience of explanation, and thus does not entirely reflect the actual size.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The manufacturing process of the flexible circuit board according to the comparative example will be described with reference to Fig. The flexible circuit board according to the comparative example includes a substrate 100, a first metal layer 110 disposed on both surfaces of the substrate 100, and a second metal layer 120 disposed on both surfaces of the first metal layer 110 can do.

The first metal layer 110 may be a metal seed layer formed by sputtering.

The second metal layer 120 may be a metal layer, for example, a copper foil. The second metal layer 120 may be composed of a first Cu layer formed by sputtering and a second Cu layer formed by electrolytic plating disposed on the seed layer.

Next, a through hole may be formed through a drilling or etching process.

Then, a process for electrically conducting the inner surface of the through hole may be performed.

For example, the side surface of the substrate 100 exposed by the through hole can be adsorbed on Pd. At this time, the Pd is for imparting conductivity to the side surface of the through hole, but when placed on Cu, unevenness may occur. In the case where Pd adsorption is performed on the side surface of the through hole by a wet process, it may be difficult to selectively adsorb Pd only on the side surface of the substrate. For example, in the case of adsorbing Pd on the side surface of the substrate by the step of immersing the substrate including the through hole and the metal layer on the liquid phase containing Pd, the Pd adhered to the region except for the side surface of the substrate is removed A separate etching process can be performed.

Then, the conductive material M may be filled in the inside of the through-hole. The conductive material M may be disposed on one or all of the upper surface and the lower surface of the second metal layer 120 extending from the inner surface and the inner surface of the through hole.

Next, the metal layers may be patterned to form a wiring layer. At this time, the wiring layer disposed under the substrate 100 may be electrically connected to the wiring layer disposed above the substrate 100 along the through holes.

At this time, the patterned wiring layer has a problem that the line width is large because the thickness of the copper foil is 2 mu m or more.

In addition, when the first and second metal layers are disposed on the substrate 100 by plating, the overall thickness of the flexible circuit board can be increased, making it difficult to manufacture a slim flexible circuit board, The manufacturing cost of the flexible circuit board may increase.

That is, in the manufacturing method of the flexible circuit board according to the comparative example, since the through holes are formed after the first and second metal layers are disposed on the substrate, in the step of forming the through holes, The conductive material does not come into contact with the side surface of the substrate. Therefore, a process of disposing a separate conductive material on the inner surface of the through hole can be performed. In addition, when the conductive material is disposed in the remaining region except for the inner surface of the substrate 100, the etching process may further proceed.

In addition, copper plating may be disposed on the inner surface of the through hole to improve process efficiency, but the adhesion between the inner surface of the through hole and the copper plating is low.

Referring to FIG. 2, in the flexible circuit board according to the comparative example, voids (V) may be generated on the inner surface of the through hole. Accordingly, the electrical characteristics of the flexible circuit board may be deteriorated, and the reliability of the touch panel including the flexible circuit board may be deteriorated.

The flexible circuit board according to the embodiment of FIGS. 3 to 7 solves the problem of the flexible circuit board according to the comparative example.

The flexible circuit board according to an embodiment may include a substrate 100, a first metal layer 110, and a second metal layer 120.

The substrate 100 may comprise plastic. For example, the substrate 100 may include poly (ethylene terephthalate), PET, polycarbonate (PC), polymethylmethacrylate (PMMA), or polyimide. have.

Preferably, the substrate 100 may be polyimide.

The substrate 100 includes the plastic film so that the flexible circuit board according to the embodiment can be flexibly realized. For example, the substrate 100 may be a highly flexible substrate that can be bent or bent at 180 degrees. Further, the base material 100 may have insulating properties.

The substrate 100 may have a thickness (T1) of 10 mu m to 200 mu m. For example, the substrate 100 may have a thickness (T1) of 10 mu m to 100 mu m. The base material 100 may have a thickness (T1) of 10 [mu] m to 50 [mu] m.

When the thickness (T1) of the base material 100 is more than 200 mu m, the flexible characteristics of the base material 100 may be deteriorated. Further, depending on the thickness of the base material 100, the overall thickness of the flexible circuit board may increase.

The substrate 100 may include an open area by a through hole.

A first metal layer 110 may be disposed on the substrate 100.

The first metal layer 110 may be disposed on the upper and lower surfaces of the substrate 100, and on the inner surfaces of the through holes.

The first metal layer 110 includes a first sub first metal layer 110a disposed on the upper surface of the substrate 100, a second sub first metal layer 110b disposed on the lower surface of the substrate 100, And a third sub first metal layer 110c connecting the first sub first metal layer 110a and the second sub first metal layer 110b to each other.

The first sub first metal layer 110a, the second sub first metal layer 110b, and the third sub first metal layer 110c may be integrally connected to each other.

The first sub first metal layer 110a, the second sub first metal layer 110b, and the third sub first metal layer 110c may be formed at the same time. Therefore, the process time can be shortened and the process can be simplified.

The first sub first metal layer 110a, the second sub first metal layer 110b, and the third sub first metal layer 110c may include materials corresponding to each other.

The first metal layer 110 may include any one of Ni, Cr, Cu, Ti, Pd, and alloys thereof. For example, the first metal layer 110 may be an alloy of Ni and Cr. That is, since the first metal layer 110 uses an alloy of Ni and Cr, adhesion with the through holes can be improved. The first metal layer 110 may be disposed between the second metal layer 120 and the substrate 100 to serve as a seed layer. That is, the first metal layer is excellent in adhesion to the substrate 100, and the adhesion characteristic of the second metal layer 120 can be improved on the first metal layer 110, Can be prepared.

The first metal layer 110 may be in direct contact with the inner surface of the through hole. In detail, since the third sub first metal layer 110c includes an alloy of Ni and Cr, the adhesion or adhesion between the third sub first metal layer 110c and the polyimide substrate 100 on which the through holes are disposed can be improved.

That is, when Cu is directly deposited on the side surface of the polyimide substrate through which the through holes are formed, the adhesiveness may be lowered due to the difference in physical properties between the organic material polyimide and Cu.

Alternatively, when a conductive material such as Pd is directly disposed on the side surface of the polyimide base through which the through hole is formed, a step of disposing a conductive material in contact with the inner side surface of the through hole, a step of providing Pd And a process for disposing a conductive material such as Cu between the step of removing Pd and the Pd disposed on one side of the through hole and the Pd disposed on the opposite side of the one side of the through hole are separately required, And the manufacturing yield of the flexible circuit board can be reduced.

Therefore, by arranging an alloy of Ni and Cr having excellent adhesion properties with polyimide directly on the inner surface of the through hole of the polyimide, the process efficiency can be improved and a flexible circuit board with improved reliability can be formed.

The first metal layer 110 may have a thickness of 0.01 탆 to 0.5 탆. For example, the first metal layer 110 may have a thickness of 0.01 탆 to 0.3 탆. For example, the first metal layer 110 may have a thickness of 0.01 to 0.25 μm.

When the thickness of the first metal layer 110 is less than 0.01 탆, the effect of improving adhesion due to the placement of the first metal layer 110 on the substrate 100 may be degraded.

If the thickness of the first metal layer 110 is more than 0.5 占 퐉, the thickness of the flexible circuit board may increase. In addition, since the first metal layer 110 can be formed by a sputtering process, if the thickness of the first metal layer 110 is more than 0.5 탆, the manufacturing cost of the flexible circuit board may increase.

The thickness T2a of the first metal layer 110 on the upper surface of the base 100 may correspond to the thickness T2b of the first metal layer 110 on the lower surface of the base 100. [ For example, the thickness (T2a) of the first metal layer 110 on the upper surface of the substrate 100 and the thickness T2b of the first metal layer 110 on the lower surface of the substrate 100 are 0.01 Mu] m to 0.5 [mu] m. That is, as the first metal layer 110 is disposed on both sides and side surfaces of the substrate 100 at the same time, the thickness can be uniform and the process efficiency can be improved.

The first metal layer 110 may be disposed on the substrate 100 and the second metal layer 120 may be disposed on the first metal layer 110.

The second metal layer 120 may be disposed on the upper and lower surfaces of the first metal layer 110 and the inner surfaces of the through holes.

The second metal layer 120 includes a first sub second metal layer 120a disposed on an upper surface of the first metal layer 110 and a second sub second metal layer 120b disposed on a lower surface of the first metal layer 110 And a third sub second metal layer 120c connecting the first sub second metal layer 120a and the second sub second metal layer 120b to each other.

The first sub-second metal layer 120a, the second sub-second metal layer 120b, and the third sub-second metal layer 120c may be integrally connected to each other.

The first sub-second metal layer 120a, the second sub-second metal layer 120b, and the third sub-second metal layer 120c may be formed at the same time. Therefore, the process time can be shortened and the process can be simplified.

The first sub-second metal layer 120a, the second sub-second metal layer 120b, and the third sub-second metal layer 120c may include corresponding materials.

The second metal layer 120 may include any one of Cu, Ag, Au, Ni, Pt, Zn and Pb. For example, the second metal layer 120 may be Cu. That is, the second metal layer 120 may be made of Cu having a high conductivity and a lower manufacturing cost than Ag and Au.

The second metal layer 120 may have a thickness of 0.1 탆 to 0.5 탆. For example, the second metal layer 120 may have a thickness of 0.1 탆 to 0.3 탆. For example, the second metal layer 120 may have a thickness of 0.1 μm to 0.25 μm.

If the thickness of the second metal layer 120 is less than 0.1 탆, breakage or cracking may occur due to bending, and electrical connection characteristics of the patterned wiring layer may be deteriorated.

If the thickness of the second metal layer 120 is more than 0.5 mu m, the thickness of the flexible circuit board may increase. In addition, since the second metal layer 120 may be formed by a sputtering process, if the thickness of the second metal layer 120 is more than 0.5 μm, the manufacturing cost of the flexible circuit board may increase.

In addition, when the thickness of the second metal layer 120 is more than 0.5 mu m, the etching factor may be decreased as the etching time of the second metal layer 120 such as Cu increases, And it may be difficult to realize a patterned wiring layer having a minute size.

The thickness T3a of the second metal layer 120 on the upper surface of the substrate 100 may correspond to the thickness T3b of the second metal layer 120 on the lower surface of the substrate 100. [ For example, the thickness T3a of the second metal layer 120 on the upper surface of the substrate 100 and the thickness T3b of the second metal layer 120 on the lower surface of the substrate 100 are 0.1 Mu] m to 0.5 [mu] m. That is, since the second metal layer 120 is disposed on both sides and side surfaces of the substrate 100 at the same time, the thickness can be uniform and the process efficiency can be improved.

That is, in the flexible circuit board according to the embodiment, the thickness of the second metal layer can be 0.1 탆 to 0.5 탆, which is excellent in reliability and can realize a patterned wiring layer having a minute size.

Referring to FIG. 7, a plurality of second metal layers 120 may be formed on the first metal layer 110.

The second metal layer 120 may include a second lower metal layer 121 and a second upper metal layer 122. Since the second lower metal layer 121 is formed earlier than the second upper metal layer 121, the first metal layer 110 may be formed on the first lower metal layer 121, And the second upper metal layer 122 is formed next to the second lower metal layer so that the second metal layer 122 is located closer to the second metal layer 121 than the first metal layer 110 and the second lower metal layer 121, Metal layer.

The second lower metal layer 121 and the second upper metal layer 122 may be formed by different processes.

The second lower metal layer 121 may be formed by sputtering Cu with a thickness of 0.1 탆 to 0.5 탆. At this time, since the thickness of the second lower metal layer 121 is thin, the inner surfaces of the through holes having a size of about 20 mu m may be spaced from each other.

Next, the second upper metal layer 122 may be disposed on an upper surface, a side surface, and an inner surface of the through hole of the second lower metal layer 121. At this time, the second upper metal layer 122 may be entirely filled in the through hole by plating. The thickness of the second upper metal layer 122 may vary depending on the width of the through hole. On the other hand, the width of the through holes may be 5 탆 to 30 탆 and 10 탆 to 20 탆.

That is, since the second lower metal layer 121 is formed by sputtering, the second lower metal layer 121 has a good adhesion with the first metal layer 110, By forming the second upper metal layer 122 by plating, the manufacturing cost can be reduced.

4 and 6, the inner surface of the through hole may have a surface roughness greater than that of the upper surface and the lower surface of the substrate 100. For example, the inner surface of the substrate 100 on which the through holes are formed may have a higher surface roughness than the upper and lower surfaces of the substrate 100 by a drilling process and a desmear process. Accordingly, it is possible to increase the adhesion of the third sub first metal layer 110c that contacts the inner surface of the through hole, thereby improving the reliability of the flexible circuit board.

Referring to FIGS. 3 and 4, the width of the through hole may correspond to the width of the upper surface of the substrate 100 and the width of the lower surface of the substrate 100.

That is, the side surface of the base material 100 on which the through holes are formed may have a similar inclination angle with the upper surface of the base material 100 by 90 degrees. In addition, the side surface of the substrate 100 on which the through holes are formed may have an inclination angle of 90 degrees with the lower surface of the substrate 100, and a similar inclination angle thereof. Accordingly, the through holes may be spaced apart from each other by a predetermined distance from the upper surface to the lower surface of the substrate 100. For example, when the through hole is formed by the etching process, the through hole may have a constant spacing width.

5 and 6, the through holes may have different widths on the upper surface and the lower surface of the substrate 100, respectively.

That is, the side surface of the substrate 100 on which the through holes are formed may have an inclination angle of 90 degrees or more with respect to the upper surface of the substrate 100, that is, an obtuse angle. The side surface of the substrate 100 on which the through holes are formed may have an inclination angle of less than 90 degrees with respect to the lower surface of the substrate 100, that is, an acute angle. As a result, the width from the upper surface to the lower surface of the substrate 100 can be reduced. For example, when the through holes are formed by the laser process, the through holes have different spacing widths, and the inner surface of the substrate on which the through holes are formed may have an inclined surface.

A method of manufacturing a flexible circuit board according to an embodiment will be described with reference to Figs. 8 to 12. Fig.

A method of manufacturing a flexible circuit board according to an embodiment includes: preparing a substrate; Forming a through hole on the substrate; Forming a first metal layer on the substrate on which the through hole is formed; And forming a second metal layer on the first metal layer.

Fig. 8 shows a step of preparing the substrate 100. Fig. For example, a polyimide substrate having excellent flexible characteristics can be prepared.

Fig. 9 shows a step of forming a through-hole H on the substrate 100. Fig. At this time, the through hole H can be formed by a laser drill.

Unlike the comparative example, the manufacturing method of the flexible circuit board according to the embodiment may not include a separate metal material on the upper and lower sides of the substrate 100. That is, since the penetrating substrate 100 is a single material, it is possible to perform precise processing in a desired shape.

In addition, a CO ₂ laser can be used instead of the UV laser as the laser source of the laser drill. As a result, the manufacturing efficiency of the flexible circuit board can be improved and the manufacturing cost can be reduced.

The inner surface of the polyimide substrate on which the through holes H are formed may include a smear of polyimide modified by the laser. Accordingly, the inner surface of the polyimide substrate may have an irregular shape.

Figure 10 shows the desmear step. And a through hole formed by the laser drill is formed, followed by a desmear process.

The desmearing step may be a step of removing the polyimide smear attached to the inner surface of the through hole. By the desmearing process, the inner surface of the polyimide substrate may have a slope similar to a straight line.

The adhesion between the substrate 100 and the first metal layer 110 can be improved by increasing the contact area between the substrate 100 and the first metal layer 110 on the inner surface of the through hole. In addition, it is possible to prevent voids from being generated in the inner surface area of the through hole.

Alternatively, the surface roughness of the inner surface of the through-hole formed by the drilling and desmearing process may be larger than the upper surface and the lower surface of the substrate 100 not subjected to the drilling and desmearing process. Accordingly, the adhesion of the first metal layer 110 to the inner surface of the through hole can be improved.

11, the step of forming the first metal layer 110 on the substrate 100 on which the through holes H are formed will be described.

The first metal layer 110 may be disposed on the upper surface, the lower surface and the side surface of the substrate 100, that is, the inner surface of the through hole. The first metal layer 110 disposed on the upper surface, the lower surface and the side surface of the substrate 100, that is, the inner surface of the through hole may be formed by any one of evaporation, plating, and sputtering Can

For example, the first metal layer 110 may be formed by sputtering. Accordingly, adhesion between the substrate 100 and the first metal layer 110 on the top, bottom, and side surfaces of the substrate 100 can be improved.

Since the embodiment does not require the step of disposing the conductive Pd on the inner surface of the substrate separately, it is possible to improve the process efficiency.

Next, referring to FIG. 12, a second metal layer 120 may be formed on the first metal layer 110.

The second metal layer 120 may be disposed on the upper surface, the lower surface and the side surface of the first metal layer 110, that is, the inner surface of the through hole. The second metal layer 120 disposed on the upper surface, the lower surface and the side surface of the first metal layer 110, that is, the inner surface of the through hole may be formed by any one of evaporation, plating, and sputtering Can be formed

For example, the second metal layer 120 may be formed by sputtering. Accordingly, the adhesion between the first metal layer 110 and the second metal layer 120 on the top, bottom, and side surfaces of the first metal layer 110 can be improved.

Alternatively, the second metal layer 120 may be formed by plating after sputtering. Accordingly, the adhesion between the first metal layer 110 and the second metal layer 120 on the upper surface, the lower surface, and the side surface of the first metal layer 110 can be improved, and the manufacturing cost can be reduced.

Next, a patterned wiring layer may be formed on both sides of the flexible circuit board, that is, on the upper and lower surfaces of the flexible circuit board through the exposure, development, and etching processes after laminating the dry film on the second metal layer 120.

Accordingly, the substrate 100 may include patterned wiring layers on the upper and lower sides.

On the other hand, a driving chip may be disposed on the substrate 100.

That is, the substrate 100 may be a wiring layer and a supporting substrate of a driving chip.

The flexible printed circuit board may include a substrate 100 including through holes, a first wiring layer disposed on the substrate 100, and a second wiring layer disposed on the bottom of the substrate 100.

The first wiring layer and the second wiring layer may be electrically connected to a driving chip disposed on the substrate 100. In detail, the second wiring layer may be connected to the driving chip through a second metal layer 120 disposed inside the through hole.

That is, the first and second wiring layers can be disposed on both sides of the substrate 100, and the thickness of the flexible circuit board can be reduced. In addition, the different wiring layers may be connected to one side of the substrate 100 by one driving chip, and the touch panel including the flexible circuit board according to the embodiment may have a slim thickness.

One end of the flexible circuit board may be disposed on one surface of the touch panel. At this time, one surface of the touch panel and one end of the flexible circuit board may be disposed with the bonding unit interposed therebetween. That is, the touch panel and the flexible circuit board can be connected and fixed through the bonding portion.

The features, structures, effects and the like described in the foregoing embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Further, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments may be modified and implemented. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (13)

A substrate including a through hole;
A first metal layer disposed on an upper surface, a lower surface, and an inner surface of the through hole of the substrate; And
And a second metal layer disposed on an upper surface, a lower surface, and an inner surface of the through hole of the first metal layer. The method according to claim 1,
Wherein the first metal layer is in contact with the through hole. The method according to claim 1,
Wherein the inner surface of the through hole includes a surface roughness higher than that of the upper surface and the lower surface of the substrate. The method according to claim 1,
And the width of the through-hole is reduced from the upper surface to the lower surface of the substrate. The method according to claim 1,
Wherein the substrate is a flexible substrate. The method according to claim 1,
Wherein the first metal layer comprises any one of Ni, Cr, Cu, Ti, Pd and alloys thereof. The method according to claim 1,
Wherein the second metal layer comprises any one of Cu, Ag, Au, Ni, Pt, Zn, and Pb. The method according to claim 1,
Wherein the first metal layer comprises 0.01 占 퐉 to 0.5 占 퐉. Preparing a substrate;
Forming a through hole on the substrate;
Forming a first metal layer on the substrate on which the through hole is formed; And
And forming a second metal layer on the first metal layer. 10. The method of claim 9,
Wherein the first metal layer is formed by any one of vapor deposition, sputtering, and plating. In the flexible printed circuit board,
A substrate including a through hole;
A first wiring layer disposed on the substrate; And
And a second wiring layer disposed under the substrate,
Wherein the first wiring layer and the second wiring layer are electrically connected to a driving chip disposed on an upper portion of the substrate. 12. The method of claim 11,
And the second wiring layer is connected to the driving chip through a second metal layer disposed inside the through hole. 12. The method of claim 11,
And one end of the flexible circuit board is disposed on one surface of the touch panel.

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