JPH0338086A - Formation of conductor pattern in flexible printed-wiring board - Google Patents

Abstract

PURPOSE:To make it possible to obtain easily highly reliable fine conductor patterns by a method wherein the conductor patterns are formed by plating. CONSTITUTION:A conductive thin film 13 is formed on a film 12 by plating or the like, plating resists 14 are formed on the film 13; then, conductor patterns 11 are formed on the film 13 by plating. Moreover, after the resists 14 are removed, parts which have been covered with the resists 14 of the film 13 are removed by etching. Accordingly, the patterns 11 can be made fine to a width in which the resists 14 can be formed without being limited by the thickness of the patterns 11. Thereby, the highly reliable fine conductor patterns 11 can be easily formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for forming a conductor pattern on a flexible printed wiring board, and particularly to a method for forming a fine conductor pattern that has been required in recent years for flexible printed wiring boards.

(Conventional technology) In recent years, as electronic devices such as calculators, watches, cameras, and radios have become more personal, there has been an increasing demand for them to be smaller, S-shaped, or lighter. As a part of making these electronic devices smaller and lighter, flexible printed wiring boards, which are mounted with electronic components such as IC chips and installed inside the electronic devices, have been widely used. and.

For this type of flexible printed wiring board, there is naturally an increasing demand for further reduction in size and weight, and specifically, there is a growing demand for higher density by making the conductor patterns even finer. .

Conventionally, when forming conductive patterns on flexible printed wiring boards, the following method has been adopted.

First, as shown in FIG. 6, a conductor layer (22) is formed on the film (21) by, for example, adhering copper foil.

Next, as shown in FIG. 7, for example, a try film is pasted on the conductor layer (22), and this dry film is exposed and exposed.
By developing, an etching resist (23) is formed.

Next, as shown in FIG. 8, unnecessary conductor Jl (22) is removed by etching to form a conductor pattern (24).

Finally, as shown in FIG.
3) Remove.

(Problems to be Solved by the Invention) However, the conventional method of forming the conductor pattern (24) by etching away unnecessary portions of the conductor Pa (22) has had the following problems.

When unnecessary portions of the conductor layer (22) are etched, the sidewalls of the portions that will become the conductor pattern (24) are also etched, causing a so-called under-ant effect.

In particular, when the conductor and pattern (24) are made fine, this undercut effect causes the conductor pattern (24) to be fine.
4) became abnormally thin, causing problems such as reliability deterioration.

The amount of erosion of the side wall of the conductor pattern (24) by the underforce/foot action increases as the etching becomes deeper in the vertical direction, that is, as the conductor layer (22) becomes thinner. Undercutting can be reduced by making the conductor M thinner.
If (22) is made too thin.

This also deteriorates the reliability of the conductor pattern (24), so the conductor layer (22) cannot be made very thin.

Therefore, in the conventional method, the conductor pattern (24)
The limit was to reduce the width to the same level as the thickness of the conductor layer (22), which cannot be made very thin.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a method by which highly reliable fine conductor patterns can be easily formed.

(Means and actions for solving the problem) The above a
l! The means taken by the present invention to solve the problem are as follows:
jJ ~ As shown in 5th UA, ``The following (a) ~ (e)
A method for forming a conductor pattern (11) on a flexible printed wiring board (10), the method comprising the steps of:

(a) conductive f! on the film (12); (b) forming a plating resist (14) on the conductive thin film (13) L; (c) forming a plating resist (14) on the conductive thin film (13); (c) forming a plating resist (14) on the conductive thin film (13); Forming the conductor pattern (11) - [8, (d) Step of removing the plating resist (14).

(c) Step 1 of removing the conductive thin film (13) covered with the plating resist (14) by etching.

That is, the flexible printed wiring board (
The method for forming the conductor pattern (11) in 1O) involves various methods such that the conductor pattern (eyes) can be formed by plating instead of forming the conductor pattern (24) by etching as in the conventional method. 1: It is an elaborate version of my husband.

In f culm i), ITO film or chemical copper J? is applied on the film (!2). A conductive thin film 1!11 (13) such as No. 11 is formed by plating. This tlt? 1f1rI
IJ(t:+) is.

When the 4-body pattern (11) is later formed by electroplating, it becomes a 7f pole, and when the conductor pattern (11) is formed later by chemical plating, it is used as a film (
12) and the conductor pattern (11). Therefore, this conductivity 8N(1
3) is to use a highly conductive material when later forming the conductor pattern (1) by electroplating, and to use a film (12) when later forming the conductor pattern (11) by chemical plating. Both of the conductor patterns (11) need to be made as thin as possible using a material with high adhesiveness. because.

After forming the conductive pattern (11), unnecessary parts of the conductive Q film (13) must be removed by etching, and the conductive thin IE! (13) cannot be selectively etched away, that is, a conductive thin film
(13) is removed by etching the conductive pattern (It
) is removed by etching at the same time, if the conductive III (13) is thin, it can be removed without damaging the conductive pattern (eyes). Furthermore, conductivity fIi! 1 (13) may be any material as long as it satisfies the above conditions.

In step (b), the conductive +t formed in step (a)
A plating resist (eye) is formed on 'gM(13)h. This plating resist (14) determines the convergence of the conductor pattern (11) to be formed.

In other words, in the method for forming a conductor pattern (11) according to the present invention, the convergence of the conductor pattern (11) is different from that of the conductor pattern (24), which cannot be made very thin due to reliability concerns. ), but is determined only by the plating resist (14). In other words, in the method for forming a conductor pattern (eye) according to the present invention, the width of the conductor pattern (11) is set to the width that can be formed by the plating resist, regardless of the thickness of the conductor pattern (11). It is now possible to make it as thin as possible.

The plating resist (14) may be of any type as long as it can form a fine pattern, such as a dry film or a liquid resist.

- "In the culm (C), conductive 1:I film (1:I) h
The conductor pattern (eyes) is formed by plating.

The plating method is not specified, such as electrolytic copper plating or oxidized copper plating, but if the conductor pattern (11) is formed by electroplating, It is necessary to form a conductive thin film (1 piece) using a material with a high and conductor pattern (11
) It is necessary to form the tetraelectric M film (13) using a material with high density JRt.

In Step 8(d), the plating resist (14) is removed. Note that the means for removing the plating resist (14) is not particularly limited.

[Change (e) odor-] was covered with plating resist (14): 4 volts + A M (13), that is, 4″ tlt resist C WX4 with no conductor pattern (11) formed on its L. (13), conductivity @II (13
) is removed by etching as an etching resist. At this time, it is sufficient if only the conductive thin film (13) can be selectively etched away, but even if this is not possible, the conductive thin film (13) is formed very thinly compared to the conductive pattern (11). Therefore, when the conductive thin layer 115I (13) is etched away, a portion of the conductive pattern (11) is also etched away to some extent, but it is hardly affected.

(Embodiments) Hereinafter, the invention will be described in detail according to embodiments shown in the drawings.

First, as shown in FIG. 1, a 1 μm thick chemical steel plating was applied to a 35 mm wide polyimide film (12) to form a conductive thin film (13). Further, sprocket holes for conveyance (not shown) were formed by punching.

Next, as shown in FIG. 2, a dry film with a thickness of 25 μm is laminated on the conductive film G (t:+), and this dry film is exposed and developed, so that the distance between the conductor patterns/the width of the conductor pattern is 13/ A plating resist (14) having a thickness of 17 (um) was formed.

Next, as shown in Figure 1ls3, electrolytic copper plating is applied to the conductive thin film (13) to a thickness of 15 μm, and the conductive pattern (
11) was formed.

Next, as shown in FIG. 4, the plating resist (14) was removed.

Finally, plating resist (14) as shown in Figure 1s5
conductive el! with no conductive pattern (11) formed thereon. (13), conductor pattern (1
1) was removed by etching as an etching resist. At this time, the conductor patterns (11) were also etched by 1 .mu.m over the entire surface, and the conductor pattern spacing/conductor pattern width was 15/15 (.mu.m).

The obtained conductor pattern (11) had no variation in width, thickness, etc., and was highly reliable.9 (Effects of the Invention) As described above, the conductor pattern in the flexible printed wiring board according to the present invention was According to the formation method, the width of the conductor pattern is not limited to the thickness of the conductor pattern, which cannot be made very thin in order to maintain reliability, as in the conventional method, and the four-body pattern is formed using a plating resist. It can be narrowed down to a convergence that can be formed. Therefore, it is possible to easily form a fine conductor pattern with high reliability, and it is possible to provide a higher density flexible printed wiring board.

[Brief explanation of drawings]

Figures 1 to 5 are detailed diagrams showing the method of forming a conductor pattern on a flexible printed wiring board according to the present invention, and Figures 6 to 9 are diagrams showing the formation of a conductor pattern on a conventional flexible printed wiring board. It is a sectional view showing the method step by step. Explanation of the symbols 1O... Flexible printed wiring board, 11-... Conductor pattern, 12-... Film, 13... Conductive thin film. 14... Plating resist. that's all

Claims (1)

[Scope of Claims] A method for forming a conductor pattern on a flexible printed wiring board, the method comprising the following steps (a) to (e). (a) forming a conductive thin film on the film; (b)
(c) forming a conductor pattern on the conductive thin film by plating; (d) removing the plating resist; (e) removing the conductive material covered by the plating resist. A process in which the thin film is removed by etching.