Printed circuit board and method for manufacturing printed circuit board

Abstract

An insulating layer made of an insulator film or the like is prepared. Then, a thin metal film and a thin copper film are formed in sequence on the insulating layer. The thin copper film is subsequently laminated with a dry film or the like, and exposed and developed to form a plating resist thereon that have patterns opposite to conductor patterns which are formed in a subsequent step. This is followed by forming conductor patterns made of copper, by electrolytic plating using an electrolytic copper sulfate plating solution, on the surfaces of the thin copper film where the plating resist is not formed. The plating resist is then removed by, for example, stripping. After this, the thin copper film is held at a temperature of not less than 200° C. and not more than 300° C. for approximately an hour to be thermally treated. Then, the thin copper film and the thin metal film are removed by chemical etching except the portions under the conductor patterns.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to printed circuit boards and a method for manufacturing such printed circuit boards. [0003] 2. Description of the Background Art [0004] Printed circuit boards such as flexible printed circuit boards are widely used in a variety of electrical and electronic devices. A printed circuit board includes, for example, an insulating layer of, e.g., polyimide, having on one side or both sides thereof conductor layers of, e.g., a copper foil with prescribed patterns. [0005] Conventionally, conductor layers having prescribed patterns in printed circuit boards such as flexible printed circuit boards are formed by the known methods such as the semi-additive, substractive, and full-additive methods (refer to JP 2002-176259, for example). [0006] The above-mentioned semi additive method is now described with reference to the drawings. [0007] FIGS. 4 (a), 4 (b), 4 (c), 4 (d), 4 (e), and 4 (f) are schem...

AI Technical Summary

Benefits of technology

[0053] Now, advantageous effects provided by the above-described thermal treatment of the thin copper film 3 will be described.

[0054]FIG. 3 is a magnified view of the region A in FIG. 2 (f). As shown in FIG. 3, thermally treating the thin copper layer 3 allows the size of grains contained in the thin copper layer 3 to be increased.

[0055] That is, in this embodiment, the thermally treated thin copper film 3 contains a grain 21 of such size as to extend between one surface of the thin copper film 3 in contact with the insulating layer 1 and the other surface of the thin copper film 3 in contact with the conductor pattern 5. That is, the thin copper film 3 has a point where only a single grain 21 is present in the thickness direction V. This reduces or prevents the incidence of side etching of the thin copper film 3 under the conductor pattern 5 during the removal of the thin copper film 3 except the portion on which the conductor pattern 5 is formed. This ensures a sufficient adhesion area of the thin copper film 3 to the insulating layer 1 to improve the adhesion. Where the thin metal film 2 is present between the insulating layer 1 and the thin copper film 3, a sufficient adhesion area of the thin copper film 2 to the thin metal film 2 is ensured to improve the adhesion.

[0056] Although in this embodiment, the use of polyimide, polyester, or the like as the material of the insulating layer 1 is described, any other highly insulating films of plastics may also be used as the insulating layer 1. For example, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyether nitril film, polyethersulfone film, a polyvinyl chloride film or the like may be used.

[0057] It is preferred to use, in particular, a polyimide film, a polyethylene terephthalate film, or a polyethylene naphthalate film, since they are superior in such properties as thermal resistance, dimensional stability, electrical properties, mechanical properties, and chemical resistant properties. EXAMPLES Inventive Example

[0058] A printed circuit board according to Inventive Example and the method for manufacturing the printed circuit board will be described below. The manufacturing method according to Inventive Example is based upon the manufacturing method according to the above-described embodiment, and therefore the

Problems solved by technology

This results in a deterioration of the adhesion of the conductor layer 14 to the thin conductive film 12.

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