JPH04335593A - Manufacture of flexible double-sided wiring board - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method which can form a fine circuit pattern by using a liquid photoresist and an organic film. CONSTITUTION:Photoresist films 8 by a negative-circuit pattern are formed on both faces of a conductive thin-film clad film 3 in which conductive thin films have been applied to both faces of a resin film 1 and which is provided with a through hole 4 and double-sided conductive thin films 5; after that, organic films 9 by a positive-circuit pattern including the through hole 4 are formed by an organic aqueous solution bath; and an etching operation is performed by making use of the organic films 9 as etching masks. Thereby, wiring patterns are formed.

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 flexible printed double-sided wiring board.

0002

[Prior art] Flexible printed double-sided wiring board is
After forming a through hole in a predetermined position of a conductive thin film coated with a conductive thin film such as copper on both sides of the resin film and having a thickness of about 100 μm, copper etc. are applied to the upper surface of the conductive thin film and the inner peripheral surface of the through hole. It is manufactured by providing a double-sided conductive thin film made of the following, and then forming a wiring pattern made of the conductive thin film and the double-sided conductive thin film by photolithography. In this photolithography, it was necessary to use a photoresist and cover the double-sided conductive thin film and through holes corresponding to the circuit pattern with the photoresist film. However, if a liquid photoresist is used for a conductive thin film with through holes formed, the openings of the through holes on both sides of the conductive thin film will be affected by the surface tension and viscosity of the photoresist liquid. The periphery and the inner peripheral surface of the through hole could not be completely covered with photoresist, and this portion was etched.

[0003] Therefore, a method called a tenting method using a dry film photoresist was adopted. This method will be explained using FIGS. 5 and 6. first,
A conductive thin film 3 having a conductive thin film 2 of copper or the like adhered to both sides of a resin film 1 is prepared. A through hole 4 is formed at a predetermined location on the conductive thin film 3, and the inner peripheral surface of the through hole 4 and the upper surface of the conductive thin film 2 (both sides of the conductive thin film) are plated with copper or the like by electrolytic plating or electroless plating. A double-sided conductive thin film 5 is formed. Next, a dry film photoresist 6 with a thickness of about 50 μm is applied.
is laminated on both sides of the conductive thin film 3, and exposed through a predetermined mask. Subsequently, development is performed to leave a dry film photoresist 6 corresponding to the circuit pattern. This state is shown in FIG. Subsequently, the double-sided conductive thin film 5 and the conductive thin film 2 are etched using an acidic etching solution containing cupric chloride or the like to form double-sided conductive wiring as shown in FIG. If such a method is adopted, the conductive thin film 5 inside the through hole 4 and around the opening thereof will surely remain without being etched.

0004

However, in the conventional manufacturing method described above, since the thickness of the dry film photoresist is about 50 μm, the resolution during pattern formation is also about 50 μm. As a result,
There is a problem in that a high resolution of 50 μm or less cannot be obtained and a fine circuit pattern cannot be formed. This invention was made in view of the above-mentioned circumstances,
The purpose is to provide a method for manufacturing a flexible printed double-sided wiring board that can form fine circuit patterns.

[0005]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a method for manufacturing a flexible printed double-sided wiring board, which includes a through hole penetrating both sides, and a conductive thin film on the inner surface and the through hole. forming a photoresist film with a negative circuit pattern on the upper surface of the conductive thin film of the conductive thin film-covered film provided with the conductive thin film; a step of forming an organic film in an aqueous solution bath; a step of peeling off the photoresist film and etching the conductive thin film located under the photoresist film using the organic film as an etching mask; and removing the organic film. process and
The main point is to include.

[0006]

[Operation] First, a double-sided conductive thin film is formed by plating or other method on the inner circumferential surface of the through-hole of a conductive thin-film-covered film in which a conductive thin film is adhered to both sides and a through-hole is formed, and on the upper surface of the conductive thin film. Subsequently, a negative circuit pattern photoresist film is formed using liquid photoresist on both sides of the conductive thin film, except for the through-hole portion. Since this photoresist film is formed from liquid photoresist, it can be formed into a fine pattern. Next, an organic aqueous solution bath is performed. Then, an organic film is formed on the portion of the negative circuit pattern where the photoresist film is not present, that is, on the upper surface of the double-sided conductive thin film corresponding to the circuit pattern including the inner peripheral surface of the through hole and the periphery of its opening. Ru. Since this organic film is formed in areas where there is no photoresist film, it can be formed into a fine pattern as well. Subsequently, the photoresist film of the negative circuit pattern is peeled off, and the double-sided conductive thin film and the conductive thin film located under the photoresist film are etched using the organic film as an etching mask. When this organic film is removed, the double-sided conductive thin film and the conductive thin film appear in a positive circuit pattern, completing a flexible printed double-sided wiring board.

[0007]

[Embodiment] FIGS. 1 to 4 illustrate the manufacturing process of an embodiment of the present invention. In each figure, the same parts as in FIGS. is omitted. First, a through hole 4 is formed in a conductive thin film 3 formed by coating a conductive thin film 2 of copper or the like on both sides of a resin film 1, and then electrolytic plating or electroless plating is applied to the upper surface of the conductive thin film 2 on both sides. A double-sided conductive thin film 5 made of copper or the like is formed on the inner peripheral surface of the through hole 4. Next, a liquid photoresist is applied to both sides of the conductive thin film 3 to a thickness of, for example, 5 μm using a spinner or a roll coater.
Apply the film to a certain thickness. Next, a mask with a predetermined pattern is placed on both sides of the conductive thin film 3, exposed to light, and developed to form a photoresist film 8 with a reverse pattern (negative circuit pattern) as shown in FIG. At this time, if the photoresist is a positive type, a mask with a negative circuit pattern is used, and if the photoresist is a negative type, a mask with a positive circuit pattern is used.

Next, it is immersed in an organic aqueous solution such as an alkylimidazole aqueous solution. Alkylimidazole has the following structural formula.

[Chemical structural formula]

Alkylimidazole is an organic compound with the above structure, but it is almost insoluble in water at room temperature, but becomes soluble in water when ionized in an acidic atmosphere. Ionized alkylimidazole exhibits strong chemical reactivity with copper, etc., forms a complex with copper, etc., and forms a monomolecular film (
organic film). On the monomolecular film formed in this way, the alkylimidazoles aggregate one after another due to the van der Waals bonding force of the long-chain alkyl groups, and the film grows, and the hydrogen bonding force between the imidazoles forms a firm film. grow up.

When the conductive thin film 3 is immersed in an organic aqueous solution having such properties, the inner peripheral surface of the through hole 4 and the periphery of its opening, as well as the area other than the photoresist film 8 of the negative circuit pattern, are removed. On the upper surface of the exposed inner conductive thin film 5, an organic film 9 is formed as a positive circuit pattern, as shown in FIG. Next, using this positive circuit pattern organic film 9 as an etching mask, the photoresist film 8 is peeled off with an alkaline etching solution, and the inner conductive thin film 5 and the conductive thin film 2 located under the photoresist film 8 are further etched. do. Then, a positive circuit pattern formed by the organic film 9 remains on both sides of the conductive thin film 3 as shown in FIG. Next, by removing this organic film 9 with hydrochloric acid or the like, only the double-sided conductive wiring of the positive circuit pattern consisting of the inner conductive thin film 5 and the conductive thin film 2 remains as shown in FIG. 4, and the flexible printed double-sided wiring board is completed. do.

As described above, according to the method for manufacturing a flexible printed double-sided wiring board described above, a fine negative circuit pattern with a thin film thickness is produced using a liquid photoresist without using a thick dry film photoresist. After forming the photoresist film 8, an organic film 9 with a fine positive circuit pattern is formed using an organic aqueous solution, and etching is performed using the organic film as an etching mask. can be formed.

[0011]

[Effects of the Invention] As explained above, according to the present invention, as a flexible printed double-sided wiring board manufacturing method,
forming a photoresist film with a negative circuit pattern on the upper surface of the conductive thin film of a conductive thin film-covered film having through holes penetrating both sides and provided with a conductive thin film on the inner surface and the through holes; forming an organic film in a portion where the photoresist film is not present, including the through hole, using an organic aqueous solution bath;
A manufacturing method is adopted that includes the steps of peeling off the photoresist film and etching the conductive thin film located under the photoresist film using the organic film as an etching mask, and removing the organic film. Therefore, a liquid photoresist can be used, a thin photoresist film can be formed, and an extremely fine circuit pattern can be formed.

[Brief explanation of drawings]

[Figure 1] ~

FIG. 4 is a manufacturing process diagram illustrating a method for manufacturing a flexible printed double-sided wiring board according to an embodiment of the present invention.

[Figure 5]

FIG. 6 is a manufacturing process diagram illustrating a conventional method for manufacturing a flexible printed double-sided wiring board.

[Explanation of symbols]

1 Resin film 2 Conductive thin film 3 Conductive thin film 4 Through hole 5 Double-sided conductive thin film 8 Photoresist film 9 Organic film

Claims (1)

[Claims] [Claim 1] Having a through hole penetrating both sides,
forming a photoresist film with a negative circuit pattern on the upper surface of the conductive thin film of a conductive thin film-covered film having a conductive thin film on the inner surface and the through holes; A step of forming an organic film in a non-existing part using an organic aqueous solution bath, and a step of peeling off the photoresist film and etching the conductive thin film located under the photoresist film using the organic film as an etching mask. A method for manufacturing a flexible printed double-sided wiring board, comprising the steps of: and removing the organic film.