JPS5942997B2 - Method for forming etching-resistant film in printed board manufacturing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention applies an etching-resistant film to a metal foil plate in a predetermined pattern in the production of printed boards used in electronic devices.

It relates to a method of forming according to turns. In the manufacture of printed circuit boards, it is necessary to form an etching solution-resistant film on a metal foil plate in accordance with a predetermined pattern before obtaining a predetermined wiring pattern on the board through an etching process.

For this purpose, a photosensitive resist resin whose solubility in a developing solution changes when exposed to light is applied onto a metal foil plate, and then the resist resin is exposed to light through a film (mask) showing a predetermined pattern in black and white. This process forms an etchant-resistant film on the metal foil plate in accordance with the circuit's turn. The photosensitive resists used in this method include those that become insoluble in developing solutions when exposed to light (so-called photocurable resists or negative/positive resists), and those that become insoluble in developing solutions when exposed to light. There are two types of resists: so-called photo-softening resists and positive-positive resists. However, in the method described above, a resist film is obtained on a metal foil plate by exposing through a mask and developing it. If both are miniaturized, the influence of dust adhering to the mask cannot be avoided. That is, when a photocurable resin is used as a resist, light does not pass through the mask in dusty areas, so the resin in those areas does not remain during development and the metal foil is exposed, eliminating defects such as missing patterns during etching.
Since this defect cannot be corrected, the yield of printed board manufacturing deteriorates. On the other hand, when a photo-softening resin is used, dusty parts are not exposed to light and are therefore insoluble in the developer, and during etching, metal foil remains in spots other than the pattern depending on the dusty parts. This defect is different from the pattern chipping described above,
Recently, photosoftening resins have been more frequently used than photocurable resins because they can be corrected in subsequent steps. However, such correction work is time-consuming and complicated. SUMMARY OF THE INVENTION In view of the drawbacks of the prior art, it is an object of the present invention to provide a method for forming a photosensitive resist film that can obtain a pattern with a complete shape without being affected by dust even if it remains on the mask. It is in.

The method of the present invention will be explained below with reference to the accompanying drawings.

In the method according to the present invention, first, as shown in FIG. 1, a photocurable resist (i.e., a negative-positive type resist) 3 which becomes insoluble in a developer (i.e., a solvent) when exposed to light is placed on a metal foil plate 1. Form by applying.

Next, a mask film 5 is applied on top of this. In this master 5, portions 7a and 7b corresponding to the pattern are transparent, and other portions are opaque. Thereafter, when the metal foil 1 is exposed to light through the mask 5, the light passes only through the transparent parts 7a and 7b, and the resist 3 in the transparent parts is hardened and becomes insoluble in the developer. When this forming image process is completed, the resist film 3 is formed in the area corresponding to the pattern as shown in FIG.
a and 3b are obtained, and the rest of the surface of the metal foil plate 1 is exposed. If dust P adheres to the surface of the mask 5 in the exposure step shown in FIG. 1, the light will not pass through the mask 5 in this area and the photocuring resist 3 will not be cured in the corresponding location, so in the developing step shown in FIG. Part of the pattern 3a is missing as shown by 9, and when this is directly transferred to the etching process, the missing part 9 is removed.
The metal foil on the surface of the metal foil plate 1 is dissolved in the etching solution, resulting in pattern chipping. In order to solve this problem, in the present invention, after the development process is completed, a photo-softening resist (i.e., positive-positive type resist) 10, which becomes soluble in the developer when exposed to light, is placed on top of the one obtained in FIG. It is applied in layers (Figure 3).

Next, a mask 11 (black and white) whose black and white are reversed from the mask 5 in FIG.
That is, parts 13a and 13b corresponding to the pattern are opaque and the other parts are transparent) are applied onto the photo-softening resist 10 on the metal foil plate 1. Then mask 11
When exposed to light, the pattern parts 13a and 13b are not softened and remain insoluble in the developer because no light passes through them.
Therefore, when the development step is completed, a photosoftening resist film 15 is formed on the photocurable resist films 3a and 3b obtained in FIG.
a and 15b are formed in an overlapping manner. The resist films 15a and 15b formed in this way are attached to the defect 9 shown in FIG.
is effectively covered. Therefore, in the next etching process, it fully plays the role of an etching-resistant film and provides a perfectly shaped pattern. As described above, according to the present invention, by using a photocurable resist resin and a photosoftening resin in combination, defects such as pattern chipping can be prevented even if dust is attached to the mask surface. No method provided.

[Brief explanation of the drawing]

1 to 4 are schematic illustrations of a method for forming a photosensitive resist film according to the present invention. 1...Metal foil plate, 3...Photo-curing resist, 5...To mass 10...Photo-softening resist, 11... ·mask.

Claims (1)

[Claims] 1. A method of forming an etching-resistant film according to a wiring pattern on a metal foil plate during the production of a printed board; after applying a photocurable resist agent on the metal foil plate, a predetermined wiring pattern is exposed and developed, and then A method for forming an etching-resistant film on a metal foil plate by applying a photo-softening resist onto the developed metal foil plate, exposing and developing a black and white reverse pattern to the wiring pattern.