JPH03192792A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To improve a resist film in releasability and to form a circuit pattern of high density by a method wherein light exposure, development, and etching are successively carried out, then a full-face light exposure is executed once, and a resist is separated. CONSTITUTION:A positive type photosensitive resin composition is electrodeposited on a board provided with a conductive coating to form a photosensitive resist film on the board, which is exposed to light, developed, and etched, then the board is fully exposed to light once, and then the resist film is separated off. As mentioned above, a resist is fully exposed to light by irradiating it with an active light beam as a pre-treatment for a separation process, whereby a photosensitive group contained in the resist is turned alkali-soluble to improve the resist in solubility to a stripping solution, and in result the resist can be easily separated with a strong alkali by the pre-treatment concerned. By this setup, a resist film can be improved in releasability and a circuit pattern of high density can be formed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a printed wiring board.

(Conventional technology) Conventionally, when manufacturing printed wiring boards.

First, a layer of a photocurable resin composition is formed on a substrate.

Next, actinic light is irradiated in an imagewise manner, and uncured portions are developed and removed to form a resist pattern.

In this process, nine different methods are employed to form the layer of the photocurable resin composition. For example, methods using a photocurable resin composition solution (coating liquid) such as dip coating, roll coating, and curtain coating.

Alternatively, a method is known in which films of photocurable resin compositions (photosensitive films) are laminated. Among these methods, the method of laminating photosensitive films is currently adopted as the mainstream method because it can easily form a layer of a photocurable resin composition with a uniform thickness.

Recently, as printed wiring boards have become more dense and precise, higher quality resist patterns have become necessary. That is, it is desired that the resist pattern be free of pinholes and that is in close contact with the surface of the underlying substrate. It is known that the currently mainstream method of laminating photosensitive films has limitations in meeting such demands.

This method has poor ability to follow irregularities on the substrate surface caused by dents during substrate manufacturing, non-uniform polishing, pits of copper plating on the surface of the mesh 9 of the glass cloth in the inner layer of the substrate, etc. , it is difficult to obtain sufficient adhesion. This difficulty is solved by laminating the film under reduced pressure (% Kosho 5
9-3740), but this requires special and expensive equipment.

For these reasons, solution coating methods such as dip coating, roll coating, and curtain coating have been reconsidered in recent years.

However, these coating methods have problems such as difficulty in controlling the film thickness, insufficient uniformity of the film thickness, and occurrence of pinholes.

Recently, a new method of forming a photosensitive resist film by electrodeposition coating has been proposed (Japanese Unexamined Patent Application Publication No. 1983-1989-1).
(See Publication No. 235496). According to this method, (1) the adhesion of the resist is improved;

■Good ability to follow irregularities on the substrate surface. ■Able to form a photoresist film with uniform thickness in a short time. ■ Since the coating liquid is an aqueous solution, it can prevent contamination of the work environment and has the advantage of not causing any problems in terms of disaster prevention.It can be said to be an epoch-making method that solves the problems of the conventional methods mentioned above.

In this electrodeposition method, copper plating is applied to the surface of a copper-clad laminate having through holes and the through hole area, and a photosensitive resist film (negative After forming a mold (either a positive mold or a positive mold), exposing and developing.

Etch unnecessary copper foil other than the circuit pattern.

Finally, the resist film is peeled off to obtain a printed wiring board.

In particular, if the photosensitive resin composition is positive type, it is convenient for manufacturing printed wiring boards having through holes.

(Problem to be Solved by the Invention) However, when manufacturing a printed wiring board using a positive photosensitive resin, in order to obtain a sharp resist pattern after development, the photosensitive resin is used to cover the photosensitive resist in unexposed areas. Since the film is designed to have high developer resistance, there is a problem in that when the resist film is peeled off after development, the peelability is poor and the resist film tends to remain on the substrate. This problem has arisen the more we try to form high-density circuit patterns, which have been in increasing demand recently, and no good means have been found to resolve this contradiction.

(Means for Solving the Problems) As a result of intensive study by the present inventors, the conventional problems were solved. We have discovered an excellent method for manufacturing printed wiring boards.

That is, the present invention provides a substrate K having a conductive film.

A photosensitive resist film is formed by electrodepositing a positive photosensitive resin composition, followed by exposure and development.

The present invention relates to a method for manufacturing a printed wiring board, which is characterized in that after etching, the entire surface is once exposed to light, and then the resist is peeled off.

The following nine inventions will be described in detail.

In the present invention, photosensitive groups in the resist are changed to alkali-soluble by irradiating the resist with actinic rays and exposing the entire surface as a pretreatment for the stripping process.

It is characterized by improving solubility in a stripping solution, and by performing such pretreatment, resist stripping with a strong alkali is facilitated.

Examples of active light sources include those that emit light with a wavelength of 300 to 450 nm9, such as a water scissor vapor arc.

Carbon arc, xenon arc, metal halide arc, etc. are preferably used.

In addition, the exposure amount for full surface exposure is 50 to 10100O/
al is appropriate. 50 J/ar? If it is less than 1000 J/cm", the effect of improving solubility is small, and if it exceeds 1000 J/cm", the solubility tends to worsen.

On the other hand, peeling is usually carried out by spraying an aqueous alkaline solution such as sodium hydroxide, sodium carbonate, potassium hydroxide, or sodium metasilicate, or by immersing it in an aqueous alkaline solution. This alkaline aqueous solution has a pH of 9 to 14.
Preferably.

It is possible to use one that can be neutralized as a free carboxylic acid present in the resist film after the entire surface is exposed to give water solubility.

(Example) The present invention will be explained below with reference to Examples.

Example 1 Dioxane solution 5009 (resin content 50 wt %) of acrylic resin (acid value 65.Mw about 35,000).

Ion-exchanged water was slowly added to a solution containing 75 g of an ester of 2-ethylhexyl gallate and 1,2-naphthoquinonediazide-5-sulfonic acid and 239 triethylamine while stirring.

An anionic electrodeposition bath (pH 8.2) with a solid content of 10 wt% was prepared.

Next, a copper-clad laminate (M made by Hitachi Chemical Co., Ltd.) was placed on the anode in the electrodeposition bath.
A copper-plated substrate with through holes formed in CL-E-61) was connected to a stainless steel plate (SUS-304) to the cathode, and a DC voltage of 150 V was applied for 3 minutes. This substrate was taken out from the anode, washed with water, and dried at 80° C. for 5 minutes. A positive photosensitive resist film with a uniform thickness was formed on the obtained substrate.

A photomask was applied to this substrate on which a positive photosensitive resist film was formed, and the exposure amount was 300 with an ultra-high voltage mercury lamp.
mJ/cm'') e After developing with a 1% aqueous sodium carbonate solution, unnecessary portions of copper were etched with an aqueous ferric chloride solution.Then, the entire surface of the resist film was exposed using an ultra-high pressure mercury lamp at an exposure dose of 500 mJ/cJ112>.

Finally, when the remaining resist film was peeled off with an aqueous solution of sodium trihydroxide, the resist film was completely peeled off and a good printed wiring board was obtained.

Comparative Example 1 A photomask was applied to a substrate on which a positive photosensitive resist film was formed in the same electrodeposition bath and under the same conditions as in Example, and exposed with an ultra-high pressure mercury lamp (exposure amount: 300 mJ/cm), 1% sodium carbonate. After developing with an aqueous solution.

Etch the unnecessary parts of the copper using a ferric chloride aqueous solution.

When the remaining resist film was peeled off with a 3% aqueous sodium hydroxide solution, the resist film was not completely peeled off, and there was particularly significant residual peeling in areas where the line spacing was narrow.

(Effects of the Invention) The present invention has excellent removability of a resist film and is effective in forming a high-density circuit pattern.

Claims (1)

[Claims] 1. A photosensitive resist film is formed by electrodepositing a positive photosensitive resin composition on a substrate having a conductive film, and then exposed, developed, and etched, and then the entire surface is exposed, and then the resist is removed. A method for manufacturing a printed wiring board characterized by peeling.