JP2872834B2 - Method for manufacturing two-layer flexible printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a two-layer flexible printed circuit board having an opening in a support film layer.

[0002]

2. Description of the Related Art Conventional flexible printed circuit boards are:
As electronic devices have become smaller and lighter, their applications have expanded, and recently, not only as conventional wiring boards,
The use of substrates having holes in a support film such as a carrier tape for TAB is also increasing. As a method of manufacturing a substrate for a flexible printed circuit having a hole formed in the support film layer and having conductor wiring, a hole is formed in the support film layer in advance by punching or the like, and the conductor layer is formed using an adhesive. After laminating, how to form a wiring circuit,
Apply a polyamic acid solution directly to the conductor layer and dry / imidize it, or form a conductor layer on the support film layer by vapor deposition or sputtering to produce a two-layer flexible printed circuit board, and then apply laser or strong A method has been used in which a hole is formed in a support film layer with an alkaline solution, and then a wiring circuit is formed.

In particular, in recent years, applications requiring heat resistance include:
Although a flexible printed circuit board having a two-layer structure manufactured by the latter method is used, there is a problem that processing with a strong alkaline solution takes a very long time depending on the type of a film layer. Therefore, processing by laser is performed, but the fine wire lead is easily bent at the time of pressure contact with the chip or other handling, and may be broken in some cases. Although tie bars have been devised, holes that are processed using a laser have sharp edges, so there are problems such as cracks and breaks in the lead hole edges. In addition, since soot generated during laser processing adheres to the surface of the conductor or the surface of the film, plating cannot be performed or the electrical characteristics of the product deteriorate.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-layer flexible printed circuit board without deteriorating its inherent alkali resistance, solvent resistance, heat resistance, and electrical characteristics, and at the same time, without reducing the circuit pattern. The present invention provides a method for manufacturing a two-layer flexible printed circuit board having a perforated support film, which does not cause cracking or disconnection, can be easily plated, and has no decrease in electrical characteristics due to soot adhesion. .

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for forming a conductive foil using a two-layer flexible printed circuit board without an adhesive layer, which is obtained by directly casting and drying a polyamic acid solution on a conductive foil. A circuit is formed thereon, and then a hole is formed by laser processing while leaving the film layer with a thickness of 0.5 to 5 μm. Thereafter, etching is performed in an alkaline solution to remove the remaining film layer. The method for manufacturing a flexible printed circuit board described above.

According to the present invention, it is possible to prevent cracks and disconnections occurring at the edge portion of a hole and the boundary between circuit patterns when performing laser processing with excellent processing accuracy in order to produce a circuit with higher density. Further, it is possible to prevent plating from becoming difficult due to the adhesion of soot generated at the time of laser processing, and to prevent the electrical characteristics of the product from being deteriorated.

A method for obtaining a two-layer flexible circuit board used in the present invention is described in, for example, JP-A-62-20.
Methods described in JP-A-0795 and JP-A-63-328858 can be used.

[0008] Materials that can be used as the conductor layer include metal foils such as copper, aluminum, constantan, and nickel.

Examples of the type of laser used for drilling include an excimer laser, a carbon dioxide laser, a YAG laser, etc., but there is little damage to the conductor foil, and the processing speed and the processing state are adjusted by adjusting the laser output. Excimer lasers are particularly desirable in that they can be adjusted freely.

[0010] As a method of forming a hole with a laser, a method of fixing a sample and scanning a laser beam, or a method of fixing a laser beam and moving a sample placed on an XY table are used.

In the method of forming a hole while leaving a film layer of 0.5 to 5 μm, first, a resist for alkali etching in the next step is applied to the film surface. As the resist, those used in ordinary alkali etching can be used. Since the resist that is to be the opening portion of the film is also removed by laser processing, the resist may be applied to the entire surface of the film. When the film thickness left after the laser processing is 0.5 to 1 μm, there is no practical problem if alkali etching is performed without applying a resist for alkali etching, but soot adhering to the film surface is completely removed. In order to remove the resist, it is more preferable to apply the resist because the resist is removed together with the resist as well as the cleaning with alkali.

The thickness of the film is adjusted by adjusting the laser irradiation time. That is, in the excimer laser, since the thickness that can be removed by one pulse is constant, the film can be removed to an arbitrary thickness by adjusting the number of irradiation pulses. The thickness which leaves the film layer is preferably 0.5 to 5 μm. 0.5 μm
In the following, it is difficult to control the thickness unless the laser output is reduced, and the processing time is prolonged due to the decrease in the output, which is not preferable. On the other hand, when the thickness is 5 μm or more, it takes a long time for alkali etching in the next step, which is not preferable.

[0013]

According to the present invention, after a conductor wiring is formed on a two-layer flexible circuit board obtained by directly applying and drying a polyamic acid solution on a conductor foil, the film layer is formed to a thickness of 0.5 to 5 μm. Perform hole processing while leaving at the thickness of, reduce the thickness processed by the alkaline solution, and then,
Shortening the alkali processing time by removing the remaining film layer by performing etching in an alkaline solution,
A flexible printed circuit that does not cause cracks or breaks at the boundary between the edge of the hole and the circuit pattern, and does not make plating difficult due to the adhesion of soot that occurs during laser processing or reduce the electrical characteristics of the product A substrate can be manufactured.

[0014]

EXAMPLE A polyamic acid solution was applied on a commercially available electrolytic copper foil having a thickness of 35 μm with a spinner.
The temperature was raised to 2 ° C. over 2 hours and dried to obtain a two-layer flexible circuit board. The thickness of the obtained polyimide layer was 25 μm. After a circuit pattern is formed on the copper foil surface of the two-layer flexible printed circuit board by ordinary etching, a resist for alkali etching is applied to the film surface, and then the film layer is formed into an A by using a KrF excimer laser. (Μm) Hole processing was performed so as to remain. Excimer laser, output 50W, frequency 200H
z, and the energy density was 0.8 J / cm ² . For drilling, fix the flexible printed circuit board on the XY table, fix the laser beam,
This was done by scanning the XY table.
The obtained flexible printed circuit board was subjected to alkali etching in a hydrazine solution to remove the remaining film layer. After washing with water, the resist was removed to obtain a flexible printed circuit board having openings. Table 1 shows the results of processing under different conditions.

[0015]

[Table 1]

[0016]

According to the present invention, laser drilling is performed with high accuracy, and cracks or disconnections occur between the edge of the drilled hole and the boundary between the circuit pattern and soot generated during laser processing. Without making plating difficult or reducing the electrical properties of the product.
A flexible printed circuit board having holes in the support film can be obtained. INDUSTRIAL APPLICABILITY The present invention can be easily applied to a continuous production process of a flexible printed circuit board using a continuous sheet, and is suitable as an industrial method for manufacturing a hole-processed flexible printed circuit board.

Claims (1)

(57) [Claims] When providing a predetermined opening portion by laser processing on a film of a substrate for a two-layer flexible printed circuit, a hole is formed by leaving a film layer with a thickness of 0.5 to 5 μm, and then the film layer is treated with an alkaline solution. And removing the remaining film by etching.