JPS61144092A - Circuit formation for printed wiring board by heat transfer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to the production of printed wiring boards by etching, and relates to a method for forming circuits on printed wiring boards using a heat-sensitive transfer layer of a heat-sensitive string-type laminated film as an etching resist. Regarding.

(Prior Art) Printed wiring boards are usually manufactured by selectively removing the copper layer on a copper-clad laminate using an etching solution to leave copper wiring portions in a desired pattern.

As a selective removal method, it is generally practiced to cover the desired copper wiring portions with an organic or inorganic material called an etching resist, which is essentially insoluble in the etching solution, and thereby prevent contact with the etching solution.

As a method of covering a desired copper wiring portion, a screen printing wash-liquid resist method, a dry film method, etc. are well known. However, the screen printing method has limitations in printing accuracy, and also has problems such as the need to make screen plates each time in low-volume, high-mix production. On the other hand, although the liquid resist method and the dry film method have sufficient accuracy, they require a step in which the circuit pattern of the etching resist must be washed out by a development process.

(Objective of the Invention) An object of the present invention is to manufacture a printed wiring board having a highly accurate wiring pattern without the need for development by using a heat-sensitive transfer layer of a heat-sensitive transfer type laminated film as an etching resist.

(Structure of the Invention) In the present invention, after the heat-sensitive transfer layer surface of a laminated film having a heat-sensitive transfer layer on a support is brought into close contact with the metal surface of a circuit-forming laminate, high-density energy light is emitted from the transparent support side in a pattern. This is a method for forming circuits on printed wiring boards using a thermal transfer method, which is characterized by providing an etching resist layer transferred onto the metal surface by exposing the metal surface to light.

The present invention will be explained in detail below.

The heat-sensitive transfer layer of the present invention is obtained by laminating on a support a composition comprising an inorganic substance or an organic substance having heat-sensitive (photo) properties, or both, and a binder resin having film-forming ability and etching resistance. It is obtained by

Inorganic or organic substances that have heat-sensitive (light) properties include:
It is desirable to have an effective absorption range in the radiation range of the high-density energy light to be irradiated (exposed).

Furthermore, it must be able to efficiently convert light energy into thermal energy.

Examples of such inorganic substances include fine powder carbon, fine powder graphite, etc., and organic substances include so-called heat ray absorbers, pigments, dyes, etc. It is appropriately selected in relation to the wavelength of energy light.

As the organic binder resin, in addition to synthetic polymers such as acrylic resins, vinyl chloride resins, styrene resins, and modified polyester resins, natural polymers such as cellulose resins can also be used.

The thickness of the heat-sensitive transfer layer made of the composition described above is selected depending on the output of the high-density energy light used, the type of the composition, etc., but it is usually 5 microns or less, and the minimum thickness is the etching solution, Although it depends on etching conditions etc., it is usually about 0.1 micron. Note that a protective layer made of an organic resin or the like can also be provided on this heat-sensitive transfer layer.

The support does not necessarily need to be transparent to the high-density energy light used, but it is preferably transparent, and it must be inert so that it does not decompose or deteriorate. No. Examples of such materials include polyethylene terephthalate film and polystyrene film.

As the high-density energy light of the present invention, it is preferable to use a laser light with extremely good convergence.

Examples of laser light include YAG laser and argon laser.

The circuit forming method of the present invention will be explained by taking a copper-clad laminate as an example. First, the heat-sensitive transfer layer surface of the laminated film of the present invention is placed so as to face the copper surface of the copper-clad laminate.

Next, a circuit pattern mask film, a mask film, a laminate film, and a copper-clad laminate are respectively brought into close contact with the support side of the laminate film.

Adhesion is achieved by mechanical adhesion, vacuum adhesion, suction adhesion, or other means.

Next, well-focused high-density energy light is scanned over the mask to transfer the mask pattern onto the copper-clad laminate.

Alternatively, the wiring pattern can be directly transferred without using a mask film by mechanically or optically moving high-density energy light.

Etching is performed using the thermal transfer layer thus formed on the copper surface as an etching resist.

As the etching solution, a ferric chloride-based etching solution, an ammonium persulfate-based etching solution, a copper chloride-based etching solution, an alkaline etching solution, etc. can be used, but the etching solution is not limited to these.

Stripping of the resist after etching varies depending on the organic binder resin component, but from the viewpoint of safety, it is preferable to use a nonflammable solvent as the stripping liquid.

(Effects of the Invention) As explained above, according to the method for forming a circuit on a printed wiring board according to the present invention, the printed wiring board can be formed with high precision and does not require any development process and in some cases does not require a mask film. It becomes possible to manufacture plates. In addition, by selecting high-density energy light and a heat-sensitive (photo) substance for it, complete open nitridation, which is difficult with ordinary photosensitive resists, becomes possible, and the working environment is significantly improved.

Example 1 A graphite dispersion consisting of 100 parts of graphite, 30 parts of ethyl cellulose, and 1170 parts of isopropyl alcohol was coated on a polyethylene terephthalate film (thickness: 70μ) using a dip coater to form a dry film with a thickness of 0.
Coat 35μ and further coat with modified polyester 100μ.
A solution consisting of 900 parts of ethyl acetate was coated with a dip coater to a dry film thickness of 0.15 μm to prepare a heat-sensitive transfer film. Copper-clad laminate with polished copper surface (
The above film was pasted onto copper foil (thickness: 35μ) so that the coated side was in close contact with the polished copper surface, and 12ff! from the polyethylene terephthalate film side. A wiring pattern was drawn using a V YAG laser beam, and the heat-sensitive transfer layer was transferred onto the copper surface. The state of transfer to the copper surface was +-2 good.

This was applied with an alkaline etching solution (manufactured by Shitsukun Metal Finishing Co., Ltd.; Knee Process, I-temperature S.

Etching was carried out by spraying at 10°C to form a wiring circuit.

Example 2 A heat-sensitive transfer film prepared in the same manner as in Example 1 was laminated with a flexible copper-clad substrate made of polished polyind film (copper foil thickness: 35 μm, substrate film thickness: 50 μm),
The wiring patterns (turns) were transferred. The distribution was good. Similarly, when etching was performed using an alkaline etching solution, a highly accurate wiring circuit was formed.

Claims (2)

[Claims] (1) After the heat-sensitive transfer layer surface of a laminated film having a heat-sensitive transfer layer on a support is brought into close contact with the metal surface of a circuit-forming laminate, high-density energy light is irradiated in a pattern from the transparent support side. A method for forming a circuit on a printed wiring board by a thermal transfer method, which comprises providing a transferred etching resist layer on the metal surface. (2) The circuit forming method according to claim 1, wherein the high-density energy light is a laser light.