KR101144281B1 - Method for fabricating flexible circuit board - Google Patents

Abstract

A method of manufacturing a flexible circuit board is provided. The method of manufacturing the flexible circuit board may include providing a base film having a base layer formed on at least one surface thereof; Forming a resist pattern on the underlayer; Performing an electroplating to form a wiring pattern on the underlayer exposed by the resist pattern; Removing the resist pattern; And removing the underlayer exposed by the wiring pattern, and before the wiring pattern forming step, by the resist pattern using a pickling solution including one or more of a plating liquid component used for the electrolytic plating. Pickling the exposed surface layer further comprises.

Flexible Circuit Board, Base Layer, Wiring, Pickling, Electroplating

Description

Method for fabricating a flexible circuit board {Method for fabricating flexible circuit board}

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

Recently, a thin and flexible flexible circuit board has been in the spotlight as a next-generation substrate suitable for weight reduction of electronic products. Flexible circuit boards are used in various electronic products. For example, it is used in a flat panel display (FPD) such as a liquid crystal display (LCD), a plasma display panel (PDP), or the like.

The flat panel display requires a screen display unit for displaying an image and a driving printed circuit board for transmitting an electrical signal to the screen display unit. The driving printed circuit board and the screen display unit may be connected by a flexible circuit board. Such a flexible circuit board includes a plurality of wiring patterns, and mounts a driver IC for transmitting a plurality of signals generated from the driving printed circuit board to the screen display unit.

Recently, as electronic components such as driving integrated circuits mounted on flexible circuit boards have been highly integrated, wirings of flexible circuit boards have also been densified, and the width of wirings and the spacing between wirings have been rapidly reduced.

As the wires of the flexible circuit board are miniaturized as described above, it is limited to reduce the wiring width and the space between the wires of the flexible circuit board by the conventional etching method. In order to overcome this limitation, a semi-additive method has been proposed, and the process generally proceeds in the following order.

First, a photosensitive resist is applied to a base film having a base layer formed on at least one surface, and then a resist pattern is formed through an exposure and development process. Here, the underlayer is formed on the insulating base film so that a current can be applied in the electrolytic plating process described later.

Subsequently, after electrolytic plating is performed to form a wiring pattern on the underlying layer exposed by the resist pattern, the resist pattern is peeled off.

Subsequently, the underlayer exposed by the wiring pattern is removed by etching or the like to mutually insulate the wiring pattern, thereby completing wiring formation of the flexible circuit board.

That is, in the semi-additive process, after the plating process for forming the pattern is completed, the wiring is finally formed by removing the underlying layer which serves to supply current in the electrolytic plating.

In this semi-additive process, the pretreatment using acid, that is, pickling, is generally performed before forming the wiring pattern by electroplating after forming the resist pattern. This is to increase the plating adhesion with the underlying layer in the subsequent electroplating. This pickling process is generally carried out with sulfuric acid solution.

On the other hand, the wiring pattern formed by electroplating has a physicochemically weak characteristic as the portion is closer to the lower portion than the upper portion, that is, the portion closer to the underlayer where the wiring pattern is formed. Accordingly, in the process of etching the underlayer exposed by the wiring pattern during the semi-additive process, an undercut phenomenon occurs in which the lower portion of the wiring pattern is excessively etched so that the wiring width at this portion becomes relatively narrow. (See Figure 1).

When the undercut phenomenon occurs as described above, the reliability of the wiring pattern cannot be secured, and in particular, it is difficult to realize the wiring pattern having a fine pitch.

The problem to be solved by the present invention is a method of manufacturing a flexible circuit board that can prevent the undercut phenomenon of the lower wiring pattern while increasing the adhesion to the base layer surface by performing a pickling treatment before the plating for forming the wiring pattern To provide.

Problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

According to one or more exemplary embodiments, a method of manufacturing a flexible circuit board includes: providing a base film having an underlayer formed on at least one surface thereof; Forming a resist pattern on the underlayer; Performing an electroplating to form a wiring pattern on the underlayer exposed by the resist pattern; Removing the resist pattern; And removing the underlayer exposed by the wiring pattern, and before the wiring pattern forming step, by the resist pattern using a pickling solution including one or more of a plating liquid component used for the electrolytic plating. Pickling the exposed surface layer further comprises.

Other specific details of the invention are included in the detailed description and drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Although the first, second, etc. are used to describe various elements, components and / or sections, these elements, components and / or sections are of course not limited by these terms. These terms are only used to distinguish one element, component or section from another element, component or section. Therefore, the first device, the first component, or the first section mentioned below may be a second device, a second component, or a second section within the technical spirit of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms "comprises" and / or "made of" means that a component, step, operation, and / or element may be embodied in one or more other components, steps, operations, and / And does not exclude the presence or addition thereof.

Unless otherwise defined, all terms used in the present specification (including technical and scientific terms) may be used in a sense that can be commonly understood by those skilled in the art. In addition, the terms defined in the commonly used dictionaries are not ideally or excessively interpreted unless they are specifically defined clearly.

2 to 6 are cross-sectional views illustrating a method of manufacturing a flexible circuit board according to an embodiment of the present invention.

First, referring to FIG. 2, a base film 200 is prepared. Here, the base film 200 may be made of an insulating material having a thickness of, for example, 20 ~ 100㎛. In addition, the base film 200 is, for example, polyimide (PI), polyester (PE; polyester), polyethylene terephthalate (PET), and polyethylene naphthalene (PEN; poly ethylene napthalene), polycarbonate It may be made of a material selected from the group of polymers including (PC; poly carbonate) and the like.

Subsequently, the seed layer 210 is formed on the base film 200. The seed layer 210 may be made of, for example, a material including any one of nickel (Ni), chromium (Cr), or an alloy thereof. In addition, the seed layer 210 may be formed by, for example, a sputtering method.

Subsequently, an underlayer 220 is formed on the seed layer 210. The base layer 220 serves to supply current in the electroplating process described later. The base layer 220 may be made of a metal such as copper, for example. In addition, as an example of forming the base layer 220, a thin film of copper or a copper alloy may be formed on the seed layer 210 by a sputtering method, and then may be formed by an electroplating method.

In the drawing, a base layer 220 is formed on the seed layer 210, but the present invention is not limited thereto, and the seed layer 210 forming step may be omitted.

Next, referring to FIG. 3, a resist pattern 230 is formed on the underlayer 220 to expose a region where the wiring pattern is to be formed. Specifically, after the photosensitive resist is formed on the base layer 220, the resist pattern 230 may be formed by performing exposure and development. The base layer 220 is exposed in the region where the wiring pattern is to be formed by the resist pattern 230.

Subsequently, a pickling process is performed on the surface of the underlying layer 220 exposed by the resist pattern 230. This pickling process is for enhancing the adhesion between the wiring pattern 240 and the base layer 220 which will be described later. In this case, the wiring pattern 240 to be described later may be formed by an electroplating method using the base layer 220 as a current supply layer.

In this case, the pickling process on the surface of the base layer 220 is performed using a pickling solution including one or more of the plating liquid components used when the wiring pattern 240 is to be described later. For example, when the plating solution used to form the wiring pattern 240 includes copper sulfate, an pickling treatment liquid containing copper sulfate may be used. The pickling liquid further contains sulfuric acid, or more preferably sulfuric acid and chlorine.

In addition, the pickling process may be performed in a dip manner in which the base film 200 on which the seed layer 210, the base layer 220, and the resist pattern 230 are formed is immersed in the pickling treatment liquid, or the seed layer 210, the base layer 220, and the resist pattern 230 may be performed by a shower method injecting pickling liquid into the base film 200.

The pickling process is described in more detail with reference to the following experimental examples, but these experimental examples do not limit the present invention.

As an experimental example, the pickling process was performed using a pickling solution containing copper sulfate, sulfuric acid and chlorine. Here, the concentration of copper sulfate is 20 to 100 g / L, the concentration of sulfuric acid is 5 to 10 vol.%, And the concentration of chlorine is 50 ppm or less. In addition, the pickling process was supplied with a pickling solution in a shower, it was performed for 20 to 60 seconds using a pickling solution having a temperature of 20 ~ 40 ℃.

A flexible circuit board manufactured by performing the pickling process according to the present experimental example is shown in FIG. 7. Referring to FIG. 7, it can be seen that the wiring pattern has a uniform width at the bottom and the top. That is, it can be seen that no undercut (see FIG. 1) occurring in the wiring pattern of the conventional flexible circuit board has occurred.

As described above, when the pickling treatment process is performed on the surface of the underlayer 220 using a pickling liquid including a plating solution used to form the wiring pattern 240 to be described later, the underlayer 220 and the wiring pattern 240 are formed. This is because the adhesion between the layers is increased and thus the physical and chemical properties of the lower portion of the wiring pattern 240 are reinforced.

After performing the pickling process, referring to FIG. 4, the wiring pattern 240 is formed on the underlayer 220 exposed by the resist pattern 230.

As described above, the wiring pattern 240 may be formed by an electroplating method using the base layer 220 as a current supply layer.

In addition, the wiring pattern 240 may be made of a metal such as copper. When the wiring pattern 240 is made of copper, the wiring pattern 240 forming process may be performed using a plating solution containing copper sulfate.

5, the resist pattern 230 is peeled off and removed. As a result, the underlayer 220 of the region where the wiring pattern 240 is not formed is exposed.

Subsequently, referring to FIG. 6, the wiring pattern 240 is mutually insulated by removing the exposed underlayer 220 and removing the exposed seed layer 210.

Removal of the base layer 220 and the seed layer 210 may be performed by etching or the like. Specifically, the underlayer 220 and the seed layer 210 may be removed by a wet etching method using an etchant such as a mixed solution of hydrogen peroxide / sulfuric acid solution.

Even if the present process, that is, the removal process of the underlayer 220 and the seed layer 210 is performed, the wiring pattern 240 and the underlayer 220 below the same may be formed by the above-described pickling process (see FIG. 3). Since the adhesion between them increases, the lower portion of the wiring pattern 240 does not have a weak characteristic, so undercut does not occur in the wiring pattern 240 in this process.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1 is a photograph showing a flexible circuit board formed according to the prior art.

2 to 6 are cross-sectional views illustrating a method of manufacturing a flexible circuit board according to an embodiment of the present invention.

7 is a photograph illustrating a flexible circuit board formed according to an embodiment of the present invention.

 <Description of the symbols for the main parts of the drawings>

200: base film 210: seed layer

220: base layer 230: resist pattern

240: wiring pattern

Claims (7)

Providing a base film having an underlayer formed on at least one surface; Forming a resist pattern on the underlayer; Pickling the underlying layer surface exposed by the resist pattern using a pickling solution; Performing a plating process using a plating solution to form a wiring pattern on the underlayer exposed by the resist pattern; Removing the resist pattern; And Removing the underlying layer exposed by the wiring pattern; The pickling solution comprises a sulfuric acid and at least one component other than sulfuric acid in the plating liquid component. The method according to claim 1, The plating liquid comprises copper sulfate, The pickling liquid is a method for producing a flexible circuit board containing copper sulfate. The method of claim 2, The pickling liquid further comprises chlorine. The method of claim 3, The concentration of the copper sulfate contained in the pickling solution is 20 ~ 100g / L, the concentration of sulfuric acid is 5 ~ 10vol.%, The concentration of the chlorine is 50ppm or less. 5. The method of claim 4, The pickling step, the method of manufacturing a flexible circuit board is performed for 20 to 60 seconds using the pickling solution having a temperature of 20 ~ 40 ℃. The method according to claim 1, The base layer further includes a seed layer at the bottom, Removing the underlayer further includes removing the seed layer. delete

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