JPH0239050A - Method for forming positive type photoresist - Google Patents

Abstract

PURPOSE:To obtain a printed wiring board which does not generate entirely the defects about a picture due to a waterdrop mark at the time of washing the board with water by forming a positive type photoresist film on the board by subjecting the board to two times of electrodeposition coatings. CONSTITUTION:A positive type photoresist film is formed on a copper-plated laminate substrate by applying the electrodeposition coating on the substrate, and then the electrodeposition coating is subjected on the obtd. film by applying an electrodeposition coating composition contg. a water soluble or a water dispersible resin as a main component on the film. The usable positive type electrodeposition coating composition is mainly composed of a resin etc. contg. a polyoxymethylene polymer, O-nitrocarbinol ester, O-nitrophenyl acetal and a benzo (or naphtho)quinone diazide units which have a salt forming group or a photosensitive group to make the composition to the water soluble or the water dispersible. Thus, the defects about the printed wiring board due to the waterdrop mark which generates on the resist film, are prevented.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method for forming a positive photoresist, and more specifically, it relates to a method for forming a positive photoresist, and more specifically, to coat a copper-clad laminate with a two-coat electrodeposition coating method to form a smooth, non-tacky surface. The present invention also relates to a method for forming a positive photoresist film, which allows an image to be easily formed by irradiating actinic light such as ultraviolet rays through a positive mask.

[Prior art 1] Conventionally, printed wiring boards with through-holes for integrated circuits, etc., are generally made by applying copper plating to a substrate having through-holes covered with copper foil on an insulator. A dry film that consists of laminating resist film, overlapping a photographic negative, exposing and developing it, etching/etching unnecessary copper foil other than the circuit pattern, and then removing the photosensitive resist film. It is formed by a method called law. However, the photosensitive resist film used in this method generally has a film thickness of 5.
Because it is relatively thick at 0 μm, the circuit pattern formed by exposure and development is not sharp, and it is difficult to laminate it uniformly on the copper foil surface, and in particular, it is almost impossible to cover through-hole areas. There are some drawbacks.

Another method is to screen print etching resist ink on a copper-clad substrate having through holes, then perform etching to remove the copper in the unprinted areas, and then remove the resist ink in the printed areas. A method of forming a circuit pattern for printed wiring by a method called a printing method is also known. However, in this method, it is difficult to apply the ink to the through-hole portions, so the copper in the through-hole portions is often removed by etching. For this reason, it is also possible to form a circuit board by embedding an organic material in the through-hole section in advance to protect it from being removed by the copper in the through-hole section during the machining/sawching process, and then finally removing the organic material. However, this method has disadvantages in that the cost of the circuit board finally obtained is high and the dyeability of the circuit pattern is poor.

As a method to improve these conventional drawbacks, a positive photosensitive resin resist film is formed on the substrate by electrodeposition coating, a positive mask is layered on top of the resist film, exposed to light, and then the exposed areas are developed with an alkaline aqueous solution. A method has been proposed in which a cutting resist is obtained by removing the cutting resist (
JP-A-60-207139, JP-A-61-206
(See Publication No. 293, etc.). With this method, a resist film can be easily formed even on small-diameter through-hole parts by electrodeposition coating, and since the unexposed parts remain as a resist film, it is possible to easily form a resist film inside the through-hole as in the case of negative type 7 photoresist. There is no need to cure the resist film by exposure to light, and a perfectly parallel light beam can be used as a light source, making it possible to create printed wiring boards that have high resolution and completely protect conductors such as copper in through holes. It has the advantage of being obtainable.

[Problems to be Solved by the Invention] In the above-mentioned improved method, the development step usually involves photolysis of the photosensitive groups of the positive photoresist film in the exposed area, cleavage of the main chain of the film-forming polymer, etc. using alkali or acid. This is carried out using solubilization development in an aqueous developer.

However, in the case of electrodeposited positive photoresist coatings, the unexposed areas of the coating also have polar groups such as carboxyl groups or amino groups, so they are water-soluble and solvent-based. There is a problem in that the difference in solubility in the developer between the exposed and unexposed areas is smaller than that of the positive resist film. Therefore, in order to obtain a good printed wiring board using an electrodeposited positive photoresist film, it is necessary to adjust the solubility of the film in the developer and to make the film thickness uniform. needs to be strictly controlled.

Furthermore, when forming a photoresist film by electrodeposition, the electrodeposited photoresist film is usually washed with water, so water drop marks remain on the film. however,
In actual industrial lines, it is difficult to completely remove traces of water droplets during the process. For this reason, the film thickness in areas where water droplets have formed is thinner than in areas where there are no traces of water droplets, so the resist film does not act as a sufficient protective film during the development and etching processes, and as a result, there are no traces on the printed wiring board. Defects such as cuts and line thinning, where the drawing line becomes thinner than the installed width, often occur.

On actual industrial lines, various measures are taken to prevent water drop marks, such as air blowing after washing and devising conveying devices, but they are not perfect and equipment and operating costs are high. There are other problems.

[Means for Solving the Problem 1] As a result of intensive research to find a technical means to solve the above-mentioned problem, the present inventors have now decided to form a 7-otoresist film by two electrodeposition processes. It was discovered that the above problem could be solved by painting, and the present invention was completed.

Thus, according to the present invention, a positive type 7 photoresist film is formed on a copper clad laminate by electrodeposition coating, and an electrodeposition coating composition containing a water-soluble or water-dispersible resin as a main component is further applied on the film. Provided is a method for forming a positive photoresist characterized by electrodeposition coating.

In the present invention, the positive electrodeposition coating composition used to form the positive photoresist film can be one conventionally known in the art, for example, to make it water-soluble or water-dispersible. Polyoxymethylene polymers having salt-forming groups and photosensitive groups, ○-nitrocarbinol esters, O-nitrophenyl acetals, resins containing benz (or natu) quinone diazide units, etc. can be mentioned ( For example, JP-A No. 60-207139, JP-A No. 61-2062
Publication No. 93, Japanese Unexamined Patent Publication No. 63-6070, Patent Application No. 1983
(See Japanese Patent Application No. 157841, Japanese Patent Application No. 157842-1982, Japanese Patent Application No. 245840-1982, Japanese Patent Application No. 279288-1988, etc.).

In addition, the electrodeposition coating composition used for applying a second electrodeposition coating on the positive photoresist coating formed by electrodeposition coating includes the electrodeposition coating composition used for forming the positive photoresist coating. It is also possible to use a resin whose main component is a conventionally known salt-forming group-containing resin that does not have a photosensitive group. The glass transition temperature (Tg) of the resin used in the latter electrodeposition coating composition is 20°C or higher, preferably 30 to 120°C.
It is preferable that the Tg is within the range of , and more preferably designed so that the Tg is at least 5° C. higher than the Tg of the resin used in the former positive electrodeposition coating composition. Designing the Tg of the resin used in the electrodeposition coating composition as described above is advantageous because it is possible to completely avoid the problem of the photoresist film and positive film exhibiting stickiness and sticking together when they are exposed in close contact with each other. .

The electrodeposition coating composition used in the present invention may be either anionic or cationic, but generally the first electrodeposition coating is performed using an anionic electrodeposition coating composition. If this is done, the second electrodeposition coating is also carried out using an anionic electrodeposition coating composition, and if the former first electrodeposition coating is carried out using a cationic electrodeposition coating composition, the second electrodeposition coating is performed using a cationic electrodeposition coating composition. It is also convenient to carry out this process using a cationic electrodeposition coating composition.

Formation of the positive photoresist coating of the present invention and manufacture of the printed wiring board are carried out in a conventional manner.

An electrodeposition paint bath consisting of a positive electrodeposition paint composition has a pH of 5 to l.
O1 bath concentration (solid content) 3-30% by weight, preferably 5-30% by weight
15% by weight, and a bath temperature of 15-40°C, preferably 15
Control at ~30°C. Next, a printed wiring board made of an insulator covered with copper foil and plated with copper is placed in this electrodeposition paint bath as an anode if the electrodeposition paint is an anionic type, or as a cathode if the electrodeposition paint is a cationic type. Soak, 20-40
Electrodeposition coating is performed by applying a 0V direct current. The appropriate current application time is usually 30 seconds to 5 minutes, and the dry film thickness is generally 2 to 50 μm, preferably 3 to 20 μm.
It is desirable that it be within the range of .

After electrodeposition coating, the object to be coated is taken out of the electrodeposition bath, washed with water, and then dried as is or, if necessary, drained and dried using an air cleaner, hot air, or the like.

Next, this object to be coated is immersed in an electrodeposition coating bath controlled under the same conditions as above using an electrodeposition composition containing a water-soluble or water-dispersible resin as a main component, and a second coat is applied under the same conditions as above. Perform electrodeposition coating. However, the electrodeposition time is usually preferably within the range of 10 seconds to 3 minutes. After removing the object to be coated from the electrodeposition bath and washing it with water, it can be left as is, or if necessary, it can be blown with air.
Drain and dry using hot air. Thus, a positive photoresist according to the present invention is formed on the substrate.

Next, a pattern mask (photo positive) is placed on the surface of the formed positive photoresist film, and only unnecessary parts other than the conductor circuit (circuit pattern) are exposed to active light such as ultraviolet rays.

Thereafter, the object to be coated may be left as is or at a surface temperature of lOO°O-
After performing heat treatment at a temperature of 180°C1, more preferably 120°C to 160°C, for 1 second to 30 minutes, a high resolution circuit image is formed by developing the exposed area with a developer such as an alkaline aqueous solution. be done.

The positive image thus created has a high resolution with a minimum line width of 40 μm (line and space).

In the present invention, the active light rays used for exposure are 3000 to 4
A light beam with a wavelength of 500 people is good. As a light source containing the light beam, for example, sunlight, a mercury lamp, a xenon lamp, an arc lamp, etc. can be used. Irradiation with actinic rays is usually carried out for a period of 1 second to 20 minutes.

Furthermore, the heat treatment is not particularly limited and can be carried out using conventionally known means, such as hot air drying, infrared drying, induction heating drying, microwave drying, etc. alone or in appropriate combinations. It can be done.

Further, when an anionic electrodeposition paint is used, the development treatment can be carried out by spraying alkaline water onto the surface of the paint film, thereby washing away the exposed areas of the paint film. Alkaline water is usually made of caustic soda with a pH of 8 to 14.
It is possible to use substances that can neutralize free carboxylic acids present in the coating film to impart water solubility, such as soda carbonate, caustic potash, aqueous ammonia, sodium metasilicate, and aqueous organic amine solutions. On the other hand, when a cationic electrodeposition coating material is used, development treatment can be carried out in the same manner using an acid aqueous solution having a pH of 5 or less.

Next, the exposed copper foil portion (
Non-circuit portions) can be removed, for example, by a conventional etching process using a ferric chloride solution or the like. After that, the unexposed mi on the circuit pattern is treated with cellosolve solvents such as ethyl cellosolve and ethyl cellosolve acetate; aromatic hydrocarbon solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ethyl acetate and acetic acid. Acetate-based solvents such as butyl, chlorine-based solvents such as nitrichloroethylene, or 3-10% aqueous solutions such as caustic soda and caustic potash (
In the case of cationic electrodeposition paint, it can be dissolved and removed using an acid aqueous solution to form a printed circuit on the substrate.

[Operations and Effects j Regarding the operation of obtaining a printed wiring board that does not produce any image defects caused by water drop marks during washing by forming a positive photoresist film by two electrodeposition coatings as in the present invention. It is not clear exactly 1, but due to the heat generated during the second electrodeposition coating, the 1
It is assumed that this is because the positive type odresist film formed by the second electrodeposition coating reflows and repairs the water drop marks.

Therefore, by forming a positive photoresist film based on the method of the present invention, defects in printed wiring boards caused by water droplets formed on the resist film, which are a serious problem in industrial lines, can be completely solved. It has the effect of being able to.

Furthermore, the exposed areas of the resist film formed by the method of the present invention can be developed in a short time with a developer such as an alkaline aqueous solution, and the unexposed areas have excellent etching resistance and can be developed using a strong alkali or other remover. It can be easily dissolved and removed in a short time.

[Examples] Next, the present invention will be described in more detail based on Examples. In the examples, "part" and "1%" represent "part by weight" and "% by weight," respectively.

Production Example 1 of Electrodeposition Coating Bath 290 parts of diethylene glycol dimethyl ether was placed in a four-bottle flask, and the temperature was raised to 110°C while stirring;
After that, a mixed solution of 202 parts of n-butyl methacrylate, 24 parts of acrylic acid, 92 parts of m-impropenyl-σσ-dimethylbenzylisocyanate, and 20 parts of azobisbutyloberonitrile was added dropwise over 3 hours. After the mixture was kept for 1 hour, a mixed solution of 14 parts of methyl isobutyl ketone and 3 parts of azobisbutyloberonitrile was added dropwise over 1 hour, and the mixture was kept for an additional 2 hours. Thereafter, the temperature was lowered to 50°C, 142 parts of the following hydroxyl group-containing orthoquinone diazide compound and 4.6 parts of dibutyltin diacetate were added, and after keeping it for 3 hours, the infrared (TR,) spectrum of 250 cm-
' Confirm that the absorption of the isocyanate group in the vicinity has disappeared, and confirm that the positive photosensitive resin (acid value 40.7; viscosity E; molecule!
7,000) (viscosity is based on Gardner at 25°C. The same applies hereinafter).

Next, 33 parts of triethylamine was added to this photosensitive resin solution to sufficiently neutralize it, and then deionized water was added so that the solid content was 10% to prepare an electrodeposition coating bath (pH 08.0).

Preparation of hydroxyl group-containing orthoquinonediazide compound 269 parts of orthonaphthoquinonediazide sulfonic acid chloride and 1345 parts of dioxane were placed in a four-sided flask, and while stirring at room temperature, 150 parts of N-methylethanolamine was added in 1 cup.
It dripped in time.

After the dropwise addition was completed, stirring was continued for about 3 hours, and after confirming that the absorption of amino groups around 3300 cm-' of the IR spectrum disappeared, the reaction was terminated.

This solution was then placed in deionized water to remove the quaternary amine that trapped the hydrochloric acid generated during the reaction.

Next, the product was extracted with isobutyl acetate, the solvent was distilled off, and the product was dried in a vacuum dryer to obtain a hydroxyl group-containing orthoquinonediazide compound.

Production Example 2 of Electrodeposition Coating Bath 290 parts of diethylene glycol dimethyl ether was placed in a four-loaf flask, and the temperature was raised to 60°C with stirring, followed by 185 parts of n-butyl acrylate, 41 parts of acrylic acid, and 233 parts of the following unsaturated compound. A mixed solution of 28 parts of ambismethoxydimethylvaleronitrile and 28 parts of ambismethoxydimethylvaleronitrile was added dropwise over 3 hours, kept for 1 hour, and a mixed solution of 15 parts of diethylene glycol dimethyl ether and 3 parts of ambismethoxydimethylvaleronitrile was added dropwise over 1 hour. Keep it for another 2 hours.Positive photosensitive resin (acid value: 69.6 parts, viscosity: N;
A molecular weight of 7,000) was obtained.

Next, 57 parts of triethylamine was added to this photosensitive resin solution to sufficiently neutralize it, and then deionized water was added so that the solid content was 10% to prepare an electrodeposition coating bath (pH-8.2).

Production of unsaturated compounds 1535 parts of methyl isobutyl ketone and 307 parts of a hydroxyl group-containing orthoquinonediazide compound were placed in a four-bottle flask, and after heating to 50°C, m-isopropenyl-α,σ-
201 parts of dimethylbenzyl isocyanate was added dropwise over 2 hours, and the mixture was kept as it was for 8 hours to obtain an unsaturated compound.

Production Example 3 of Electrodeposition Coating Bath 450 parts of ethylene glycol monobutyl ether was charged in a four-bottle flask, and heated to IIOoC without stirring, followed by 350 parts of methyl methacrylate and 50 parts of styrene.
parts, 1.53 parts of ethyl methacrylate, 47 parts of acrylic acid
A mixture of 1 part and 30 parts of (-butylperoxyoctoate) was added dropwise over 3 hours, and after keeping at 110°C for 1 hour,
A mixed solution of 3 parts of L-butyl peroxyoctoate and 50 parts of ethylene glycol monobutyl ether was added dropwise over 1 hour, and kept at 110°C for another 2 hours to form a high acid value acrylic resin solution (resin acid value: 73; viscosity: U). ;Molecular weight 7.5
00) was obtained.

Next, 50 parts of benzyl alcohol and 36 parts of triethylamine were added to 1000 parts of this solution to sufficiently neutralize it, and then
Deionized water was added so that the solid content was 10% to prepare an electrodeposition coating bath (pH 7.6).

Example 1 A copper-clad laminate for printed wiring (240 x 170 x 1.5 mm) with through holes was immersed as an anode in the electrodeposition coating bath obtained in Production Example 1, and a DC current of 100 V was applied for 3 minutes at a bath temperature of 25°C. It was electrodeposited.

The resulting coating film was washed with water at a water pressure of 1.5 kg/cm'' for 10 seconds, dried at 50°C for 5 minutes, and then the coating film was observed and water drop traces were marked.

The copper-clad laminate thus obtained was used as an anode and immersed in the electrodeposition coating bath obtained in Production Example 3, which was adjusted to 25°C.
A second electrodeposition coating was carried out by applying a direct current of 3 minutes for 3 minutes, and the coating film was washed with water and dried in the same manner as above.

Next, a positive film was brought into close contact with the electrodeposited surface using a vacuum device, and a 3KW ultra-high pressure mercury lamp was used to heat both sides to 150%
mJ/am". Next, the exposed areas were washed with a 1% sodium metasilicate aqueous solution and developed. After washing with water (ferric chloride solution), the copper foil was etched and removed, and then the unexposed areas were was removed with caustic soda to obtain a printed circuit board.

Example 2 A first electrodeposition coating was performed on a copper-clad substrate in the same manner as in Example 1 except that the electrodeposition coating bath of Production Example 2 was used, followed by washing with water,
Dry.

Then, a second electrodeposition coating was performed in the same manner as in Example 1 except that the same electrodeposition coating bath was used and a voltage of 130 V was used, followed by washing and drying. Using the thus obtained substrate, the same steps as in Example 1 including the exposure step were performed to obtain a printed circuit board.

Comparative Example 1 A printed circuit board was obtained in the same manner as in Example 1 except that the second electrodeposition coating was not performed.

Comparative Example 2 A printed circuit board was obtained in the same manner as in Example 2, except that the second electrodeposition coating was not performed.

The performance of the printed circuit boards obtained in the above Examples and Comparative Examples is shown in Table 1 below.

Performance evaluation was performed based on the ratio of occurrence of image breaks, defects, etc. in water droplet traces previously marked on the substrate (number of image abnormalities due to water droplet traces/number of waterdrop traces x 100).

Twenty printed circuit boards were tested on each side.

Table-1

Claims (1)

[Claims] A positive photoresist film is formed on a copper-clad laminate by electrodeposition, and an electrodeposition coating composition containing a water-soluble or water-dispersible resin as a main component is further electrodeposited onto the film. A method for forming a positive photoresist.