KR20060066971A - Manufacturing method for double side flexible printed circuit board - Google Patents

Abstract

The present invention relates to a method for manufacturing a double-sided flexible circuit board capable of realizing fine wiring patterns and improving product reliability.

Such a double-sided flexible circuit board manufacturing method,

A preparation step of providing a film disc having a conductive layer of a thin film formed on both sides of the insulating base film;

A wiring pattern forming step of processing the conductor layers of the base film into predetermined circuit patterns, respectively;

A perforation process for drilling through-holes for electrically connecting the wiring patterns formed on both sides of the base film for the necessary circuit conduction;

An electroless plating process of forming a conductive layer of a thin film for plating the through-holes of the base film;

Applying a photosensitive layer (photoresist) made of a photosensitive film or ink onto the conductive layer;

An exposure step of placing a predetermined mask pattern on the photosensitive layer applied in the above step and irradiating light to cure only a portion of the through hole, which is a part of the conductive layer, and a hole pad portion around the conductive layer to serve as a resist;

A developing step of dissolving and removing the photoresist layer of the through-hole and the hole pad portion around the unsaturated through hole by exposure to ultraviolet light in the exposure step;

Forming a plating layer in the through hole of the portion where the photosensitive layer is removed in the process and the conductive layer exposed to the periphery thereof;

A peeling step of removing the photosensitive resin remaining in the developing step;

An etching step of removing the conductive layer remaining in the base film other than the plating layer formed above;

It provides a double-sided flexible circuit board manufacturing method comprising a.

Flexible Circuit Board, Through Hole, Conductive Layer, Plating Layer,

Description

MANUFACTURING METHOD FOR DOUBLE SIDE FLEXIBLE PRINTED CIRCUIT BOARD

1 is a process chart showing a manufacturing method of a double-sided flexible printed circuit board according to the present invention.

2 is a cross-sectional view sequentially illustrating a process of manufacturing a double-sided flexible circuit board according to the process of FIG.

The present invention relates to a method for manufacturing a double-sided flexible printed circuit board, and more particularly, to a method for manufacturing a double-sided flexible printed circuit board capable of realizing fine wiring patterns and improving reliability of a product.

In general, as electronic devices become more complicated, much of the wiring has been replaced by printed circuit boards in the wires, which saves labor due to internal space, weight, and assembly of the product, and compared to wires. It is known to have high reliability.

This printed circuit board is one of the basic parts that are used almost all of the electronic equipment, and the electronic devices produced in recent years are manufactured in a precise and lightweight small and small type, the flexible printed circuit board in the existing printed circuit board It has been replaced by (Flexible Printed Circuit Board). In particular, such flexible circuit boards are more frequently used in mobile phones, notebook computers, camcorders, liquid crystal displays, and the like.

Such flexible printed circuit boards have excellent flexibility and flexibility, and have the advantage of being able to freely connect two non-adjacent circuits or components while serving as a printed circuit board, and are widely used in general industrial machines as well as electronic devices. .

There are many types of flexible circuit boards, such as single layer, double sided, and multilayer type, depending on the circuit pattern layer of the wiring structure. The flexible circuit board is designed and manufactured according to the structure and function of the electronic device and applied to the product.

Among the flexible printed circuit boards, a typical method for manufacturing a double-sided flexible printed circuit board is a double-sided CCL (Copper) in which Cu thin films are laminated on both sides of an insulating film such as a polyimide film or a polyester film. After preparing a clad laminate film, through holes are formed in a predetermined position of the CCL film by using a drill or the like to electrically connect the portion where the circuit pattern of the Cu layer is to be formed. The holes are plated so that the Cu layers are electrically connected to each other.

Then, a double-sided flexible circuit board is fabricated by using a photosensitive film on both sides of the CCL film or by applying a liquid to process each Cu layer into a predetermined circuit pattern through exposure, development, etching, and peeling process. do.

 However, in the manufacture of such a conventional double-sided flexible printed circuit board, when the through-hole is formed in the double-sided CCL film, the plating layer is formed not only on the through-hole but also on the Cu layer when plating the hole. When processing the circuit pattern, there is a problem in that the wiring pattern can not be minutely implemented because the spacing of the pitches cannot be made compact.

The present invention has been made to solve the conventional problems as described above, the object of the present invention is to first form a wiring pattern on both sides of the insulating base film, and then through-holes so as to electrically connect these wiring patterns Perforations, and selectively plating only the through-hole and the pad portion around the through hole, thereby minimizing the thickness of the wiring pattern to the thickness of the original state, thereby implementing a fine wiring pattern. It is to provide a double-sided flexible circuit board manufacturing method that can improve the reliability of the product by improving the flexibility by having a.

The manufacturing method of the double-sided flexible circuit board proposed by the present invention,

A preparation step of providing a film disc having a conductive layer of a thin film formed on both sides of the insulating base film;

A wiring pattern forming step of processing the conductor layers of the base film into predetermined circuit patterns, respectively;

A perforation process for drilling through-holes for electrically connecting the wiring patterns formed on both sides of the base film for the necessary circuit conduction;

An electroless plating process of forming a conductive layer of a thin film for plating the through-holes of the base film;

Applying a photosensitive layer (photoresist) made of a photosensitive film or ink onto the conductive layer;

An exposure step of placing a predetermined mask pattern on the photosensitive layer applied in the above step and irradiating light to cure only a portion of the through hole, which is a part of the conductive layer, and a hole pad portion around the conductive layer to serve as a resist;

A developing step of dissolving and removing the photoresist layer of the through-hole and the hole pad portion around the unsaturated through hole by exposure to ultraviolet light in the exposure step;

Forming a plating layer in the through hole of the portion where the photosensitive layer is removed in the process and the conductive layer exposed to the periphery thereof;

A peeling step of removing the photosensitive resin remaining in the developing step;

An etching step of removing the conductive layer remaining in the base film other than the plating layer formed above;

It provides a double-sided flexible circuit board manufacturing method comprising a.

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

1 is a process diagram showing a method for manufacturing a double-sided flexible printed circuit board according to the present invention, Figure 2 is a cross-sectional view sequentially showing a process for manufacturing a double-sided flexible printed circuit board according to the process of Figure 1, manufacturing a flexible circuit board of the present invention One embodiment of the method first has a preparatory process P1 of preparing a raw material for producing the double-sided flexible circuit board of the present invention.

The raw material prepared in the preparation step (P1) is a double-sided CCL (Copper Clad Laminate) film in which conductor layers 4a and 4b made of thin Cu are laminated on both sides of the insulating base film 2 as shown in FIG. 2A. This can be used.

The base film 2 may be made of an insulating film such as a polyimide film or a polyester film.

When a raw material made of a double-sided CCL film is prepared as described above, each conductor layer 4a is subjected to a pretreatment step, a photosensitive material laminating step of applying a film or a photosensitive ink, etc. to both conductor layers 4a and 4b of the CCL film. A circuit pattern forming step (P2) is performed in which a) 4b is formed into a predetermined circuit pattern as shown in Fig. 2B through an exposure, development, etching, and peeling process.

In the circuit pattern forming process P2, since the exposure, development, etching, and peeling processes may be applied to a method commonly used in manufacturing a flexible circuit board, detailed description thereof will be omitted.

When this process is completed, the through hole drilling process P3 is performed by using a drill or the like for the necessary circuit conduction of the conductor layers 4a and 4b constituting the circuit patterns on both sides, and as shown in FIG. The through hole 6 is formed through the 4b) and the base film 2.

When the above process is completed, the conductor layers 4a and 4b located in the through hole 6 are separated on both sides by the base film 2, and the electroless plating process (P4) is performed to plate the primary to conduct it. As shown in FIG. 2D, a thin conductive layer 8 is formed on the surfaces of the conductor layers 4a and 4b and the base film 2 including the through holes 6.

This electroless plating process P4 is formed with a considerably thin thickness, which can also be performed by a vacuum deposition process.

When the process is completed, as shown in FIG. 2E, a process P5 of applying a photosensitive layer (photoresist) 10 made of photosensitive film or ink to the surfaces of both conductive layers 4 is performed. The foreign matter on the surface of the conductive layer 4 may be removed so that the photosensitive layer 10 may adhere to the surface well, and the surface may be heated to a predetermined temperature, and then the film may be laminated or ink may be applied.

When the process is completed, an exposure process of placing a mask pattern (not shown) processed into a predetermined shape on the applied photosensitive layer 10 and irradiating light (UV) to cure only a predetermined portion of the photosensitive layer 10. (P6) is performed.

In the exposure process P6, as shown in FIG. 2F, the partial exposure is performed such that only the hole pad portion around the through hole 6 is developed. When the process is completed, the development process P7 is performed. ) Is a step of dissolving and removing the photosensitive layer 10 that is not exposed to light in the exposure step P6, that is, the photosensitive layer that is not photocured with a developer.

When the developing process P7 is completed, as shown in FIG. 2G, the photosensitive layer 10 is photocured, that is, the photosensitive layer 10 around the through hole 6 is removed and the remaining part remains.

When this process is completed, the plating process P8 is performed. At this time, since only the photosensitive layer 10 of the periphery of the through hole 6 is removed in the above process, the through hole 6 and its periphery are conducted as shown in FIG. 2H. As the plating layer 12 is formed only on the layer 8, the conductor layers 4a and 4b are in an electrically connected state. This plating step (P8) can be carried out by a conventional electroplating step.

In this case, the plating layer 12 formed may be formed to have a predetermined thickness by using a metal material such as Cu. In the plating process P8, the plating layer 12 is formed only at the through hole 6 and its periphery, and both conductors are formed. Since the layers 4a and 4b have the original thickness, the overall thickness of the circuit board can be reduced and the flexibility of the circuit board can be improved.

When the plating step P8 is completed, a peeling step P9 is performed to remove the photosensitive layer 10 remaining in the photocured state on both conductor layers 4a and 4b with a peeling solution. Upon completion, all remaining photosensitive layer 10 as shown in FIG. 2I is removed.

When the above process is completed, the plated conductive layer 8 appears in the lower portion of the removed photosensitive layer 10. If the conductive layer 8 is removed by the etching process P10, as shown in FIG. 2J. As the conductive layer 8 between the plating layers 12 is removed, the plating layers 12 formed in the through holes 6 are electrically connected to the respective conductor layers 4a and 4b on both sides of the base film 2. The manufacture of the double-sided flexible circuit board is completed, constituting each circuit pattern.

In the etching process P10 as described above, the soft etching method may be used to remove only the conductive layer 8 without removing the conductive layers 4a and 4b formed on the base film 2.

The plated layer 12 of the double-sided flexible printed circuit board manufactured as described above may be further subjected to a coverlay or silicon coating process to protect the surface circuit from the external environment, or may be plated with gold to improve corrosion resistance.

In the above-described practical example, manufacturing a double-sided flexible circuit board has been described as an example. For example, when a plurality of circuit boards on which a circuit pattern forming step (P2) is completed are laminated and the next process is performed, the multilayer flexible circuit board is performed as described above. The same can be produced.

As described above, in the method of manufacturing a double-sided flexible circuit board according to the present invention, after forming wiring patterns on both sides of the base film, the through holes are drilled to electrically connect these wiring patterns so that the through holes and the surroundings thereof are formed. Since only the pad part is selectively plated, the thickness of the wiring pattern can be maintained at the thickness of the original raw material, thereby realizing a fine wiring pattern.                     

In addition, since the thickness of the circuit board maintains the state of the raw materials, it is possible to maintain good flexibility and improve the reliability of the product.

Claims (3)

A preparation step of providing a film disc having a conductive layer of a thin film formed on both sides of the insulating base film; A wiring pattern forming step of processing the conductor layers of the base film into predetermined circuit patterns, respectively; A perforation process for drilling through-holes for electrically connecting the wiring patterns formed on both sides of the base film for the necessary circuit conduction; An electroless plating process of forming a conductive layer of a thin film for plating the through-holes of the base film; Applying a photosensitive layer (photoresist) made of a photosensitive film or ink onto the conductive layer; An exposure step of placing a predetermined mask pattern on the photosensitive layer applied in the above step and irradiating light to cure only a portion of the through hole, which is a part of the conductive layer, and a hole pad portion around the conductive layer to serve as a resist; A developing step of dissolving and removing the photoresist layer of the through-hole and the hole pad portion around the unsaturated through hole by exposure to ultraviolet light in the exposure step; Forming a plating layer in the through hole of the portion where the photosensitive layer is removed in the process and the conductive layer exposed to the periphery thereof; A peeling step of removing the photosensitive resin remaining in the developing step; An etching step of removing the conductive layer remaining in the base film other than the plating layer formed above; Duplex flexible circuit board manufacturing method comprising a. The method of manufacturing a double-sided flexible circuit board as set forth in claim 1, wherein the exposure step is performed in a partial exposure step so that only the through-hole and the hole pad portion around the hole pad are developed. The method of claim 1, wherein the etching process is performed by a soft etching process to remove only the conductive layer without removing the conductive layers formed on the base film.

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