KR100867889B1 - Method for forming embedded capacitor in flexible printed circuit board - Google Patents

Abstract

A method of forming a capacitor by corroding a flexible insulator is disclosed. (a) forming a first photoresist film on the upper conductor and the lower conductor; (b) exposing and developing an unnecessary portion of the first photoresist film formed on the upper conductor to form a necessary pattern; (C) etching the exposed upper conductor by removing the unnecessary first photoresist film; (d) peeling off the first photoresist film; (e) etching the exposed flexible dielectric by removing the upper conductor (F) forming a plating layer by electroless or electrolytic copper plating the printed circuit board; (g) forming a second photoresist film on the plating layer; (h) a circuit configuration of the second photoresist film. Exposing and developing a portion other than the necessary portion to form a necessary pattern; (i) removing the unnecessary second photoresist film to etch the exposed plating layer and the upper and lower conductors; (J) peeling off the second photoresist film. By such a configuration, the dielectric thickness of the printed circuit board can be made thin to realize a high capacity capacitor, and the printed circuit board can be made thinner, smaller and lighter.

Printed Circuit Board, Capacitor, Formation Method

Description

METHODS FOR FORMING EMBEDDED CAPACITOR IN FLEXIBLE PRINTED CIRCUIT BOARD}

1 is a flowchart illustrating a method of forming an embedded capacitor of a flexible printed circuit board according to an exemplary embodiment of the present invention; And

2A to 2K are schematic views illustrating a method of forming a built-in capacitor of a flexible printed circuit board according to the present invention.

<Description of the code | symbol about the principal part of drawing>

10: printed circuit board 12: flexible dielectric

13: upper conductor 14: lower conductor

20: first photoresist film 30: plating layer

40: second photoresist film 50: capacitor

S101: Cutting Step S102: Forming the First Photoresist Film

S103: Exposure and Developing Step S104: Etching Step

S105: Peeling Step S106: Soft Dielectric Corrosion Step

S107: plating layer forming step S108: second photoresist film forming step

S109: Exposure and Developing Step S110: Etching Step

S111: Peeling Step S112: Finishing

The present invention relates to a method of forming a built-in capacitor of a flexible printed circuit board, and more particularly, to reduce the thickness of the dielectric material, which is a raw material of the flexible printed circuit board, to realize a high capacity capacitor, thereby making the flexible printed circuit board thin, small, and light. The present invention relates to a method of forming a built-in capacitor of a flexible printed circuit board.

Recently, the demand for highly integrated passive devices for high performance of electronic devices has increased. However, it has been recognized that various passive elements mounted on flexible printed circuit boards act as a big obstacle in miniaturizing electronic devices. In particular, as semiconductor active devices are increasingly embedded and the number of input / output terminals thereof increases, space for more passive devices is required around the active devices.

A typical passive element is a capacitor. The capacitor is advantageously disposed closest to the input terminal in order to reduce the inductance according to the higher frequency of the operating frequency, the larger the area of the opposite electrode, the higher the dielectric constant of the dielectric between the electrodes, the thinner the dielectric thickness. The higher the capacitance.

In response to these demands, researches for embedding capacitors inside flexible printed circuit boards have been actively conducted. The built-in capacitor is embedded in a printed circuit board used for a memory card, a PC main board, and various RF modules, and can significantly reduce the size of the product. In addition, since it can be disposed in close proximity to the input terminal of the active element, the inductance can be greatly reduced by minimizing the lead length, and is also advantageous for removing high frequency noise.

Meanwhile, a method of forming a capacitor in a flexible printed circuit board can be largely classified into three methods, which will be described in detail below.

First, there is a method of embedding a capacitor directly in a flexible printed circuit board. In this method, a capacitor is inserted into a capacitor mounting portion formed on a flexible printed circuit board, and the gap remaining after the capacitor insertion is filled with an insulator or adhesive to be deposited to form a capacitor.

Second, a capacitor is formed by coating or screen printing a dielectric material on the flexible printed circuit board. Among these methods, the screen printing method is to apply a dielectric material to the flexible printed circuit board and dry it, and then to print a metal paste to form an electrode to form a capacitor, the coating method is to coat the dielectric material on the printed circuit board, copper foil The upper electrode and the lower electrode are formed by laminating, and then a pattern is formed to form a capacitor.

Third, a method of forming a capacitor by laminating tantalum barium, metal powder, or semiconducting filler, which is a ferroelectric having a capacitor characteristic, on a flexible printed circuit board, or by stacking a dielectric such as copper-clad laminate (FR-4), Aramid, and Polylmide. to be. This method forms a power distribution type decoupling capacitor by stacking a dielectric layer consisting of a power electrode and a ground electrode on an inner layer of a flexible printed circuit board.

However, in the case of forming the capacitor by the above method, the first problem is that the thickness of the flexible printed circuit board becomes thick in order to install a relatively thick capacitor on the printed circuit board.

Secondly, coating or screen printing a dielectric material on a flexible printed circuit board has a problem in that the printing accuracy and the thickness of the dielectric are limited.

Third, the method of stacking a dielectric on an inner layer of a flexible printed circuit board has a problem in that a raw material of the flexible printed circuit board has a relatively low dielectric constant and thus cannot realize a high capacity capacitor.

The present invention has been made to solve the problems of the prior art as described above, the technical problem of the present invention is to reduce the thickness of the dielectric material, the raw material of the flexible printed circuit board to realize a high-capacitance capacitor, thin printed circuit board, The present invention provides a method of forming a built-in capacitor of a flexible printed circuit board that can be miniaturized and lightweight.

In order to achieve the above object, the present invention,

In the method of forming a capacitor in the inner layer of the flexible printed circuit board formed by forming the upper conductor and the lower conductor on the upper and lower portions of the flexible dielectric,

Forming a first photoresist film on the upper conductor and the lower conductor;

Exposing and developing an unnecessary portion of the first photoresist film formed on the upper conductor to form a necessary pattern;

Etching the exposed upper conductor by removing the unnecessary first photoresist film;

Peeling off the first photoresist film;

Etching the flexible dielectric exposed by removing the upper conductor to reduce thickness;

Electroless copper plating and electrolytic copper plating the flexible printed circuit board to form a plating layer;

Forming a second photoresist film on the plating layer;

Exposing and developing a portion of the second photoresist film except for a portion necessary for circuit construction to form a necessary pattern;

Etching the plating layer and the upper and lower conductors exposed by removing the unnecessary second photoresist film; And

It is to provide a method of forming a built-in capacitor of a flexible printed circuit board comprising the step of peeling the second photoresist film.

When described in detail with reference to the accompanying drawings a preferred embodiment of the present invention having the features as described above.

1 is a flowchart illustrating a method of forming a built-in capacitor of a flexible printed circuit board according to a preferred embodiment of the present invention, and FIGS. 2A to 2K are schematic views illustrating a method of forming a built-in capacitor of a flexible printed circuit board according to the present invention.

1 and 2A to 2K, a method of forming a built-in capacitor according to a preferred embodiment of the present invention is as follows.

First, the flexible dielectric 12 is introduced to cut a flexible printed circuit board (hereinafter, referred to as a “printed circuit board”) to a working size (S101). At this time, the printed circuit board 10 is a state in which the upper conductor 13 and the lower conductor 14 are formed on the upper and lower surfaces of the flexible dielectric 12 (see FIG. 2A). Here, the upper conductor 13 and the lower conductor 14 may be Cu, and other metals may be used.

A first photoresist film 20 is formed on the upper conductors 13 and the lower conductors 14 of the printed circuit board 10 that have undergone the cutting step (S101) (S102) (see FIG. 2B).

After the step of forming the first photoresist film (S102), an unnecessary pattern of the first photoresist film 20 formed on the upper conductor 13 is exposed and developed to form a necessary pattern (S103) ( 2c).

When the unnecessary first photoresist film 20 is removed through the exposure and development step S103, a portion of the first photoresist film 20 is removed to etch and remove the exposed portion of the upper conductor 13. (S104) (see FIG. 2D).

When the upper conductor 13 exposed by the etching step S104 is corroded and removed, all of the first photoresist film 20 is peeled off (S105) (see Fig. 2E).

When all of the first photoresist film 20 is peeled off by the peeling step S105, the exposed portion of the flexible dielectric 12 is etched to lower the thickness (S106) (FIG. 2F).

When the flexible dielectric 12 exposed by the flexible dielectric corrosion step S106 is corroded and has a low thickness, the plating layer 30 is formed by electroless copper plating and electrolytic copper plating so that electricity can be conducted to the printed circuit board 10. It forms (S107) (FIG. 2G).

After the plating layer forming step S107, the second photoresist film 40 is formed on the plating layer 30 (S108) (FIG. 2H).

After passing through the second photoresist film forming step (S108), a portion of the second photoresist film 40 is exposed and developed so as to remove a portion of the second photoresist film 40 except for a circuit configuration (S109) (FIG. 2I). Reference).

When the unnecessary second photoresist film 40 is removed through the exposing and developing step S109, a portion of the second photoresist film 40 is removed to expose the plating layer 30 and the upper conductor 13. The lower conductor 14 portion is etched and removed (S110) (see FIG. 2J).

When the plating layer 30, the upper conductor 13, and the lower conductor 14 exposed by the etching step S110 are removed by corrosion, all the second photoresist film 40 is peeled off (S111) (FIG. 2k). At this time, the upper conductive plate 51 and the lower conductive plate 52 of the capacitor 50 are formed through the peeling step S111.

When the second photoresist film 40 is completely peeled off by the peeling step S111, the printed circuit board 10 is finished by outer layer processing or the like (S112).

Meanwhile, in the present invention, the flexible printed circuit board has been described as an example, but is not limited thereto. The flexible printed circuit board may be applied to the flexible printed circuit board.

As described in detail above, according to the method of forming a built-in capacitor of a flexible printed circuit board of the present invention, the dielectric material, which is a raw material of the flexible printed circuit board, is thinned by corrosion to realize a high capacity capacitor, and the printed circuit board is thinned and miniaturized. And invention which has the effect which can be reduced in weight.

Although the above has been described with reference to a preferred embodiment of the present invention, the present invention is not limited to the above-described embodiments, those skilled in the art without departing from the gist of the invention described in the claims below It will be readily understood that various modifications are possible within.

Claims (1)

In the method of forming a capacitor in the inner layer of the flexible printed circuit board formed by forming the upper conductor and the lower conductor on the upper and lower portions of the flexible dielectric, Forming a first photoresist film on the upper conductor and the lower conductor; Exposing and developing an unnecessary portion of the first photoresist film formed on the upper conductor to form a necessary pattern; Etching the exposed upper conductor by removing the unnecessary first photoresist film; Peeling off the first photoresist film; Etching the flexible dielectric exposed by removing the upper conductor to reduce thickness; Electroless copper plating and electrolytic copper plating the flexible printed circuit board to form a plating layer; Forming a second photoresist film on the plating layer; Exposing and developing a portion of the second photoresist film except for a portion necessary for circuit construction to form a necessary pattern; Etching the plating layer and the upper and lower conductors exposed by removing the unnecessary second photoresist film; And Peeling the second photoresist film; and forming an embedded capacitor of a flexible printed circuit board.

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