JPH0636466B2 - Positive image forming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a positive image forming method, and more specifically, to a positive type resist film formed by electrodeposition coating on a circuit board having a conductive film, followed by exposure. The present invention relates to a positive-type image forming method characterized by performing a heat treatment after the above.

[Prior Art] Conventionally, a printed wiring board for an integrated circuit or the like is generally a photosensitive board formed by applying copper plating to a board having an insulating material such as copper foil or a board having a through hole. It is formed by laminating a film, exposing and developing a photographic negative, superposing the film on the film, and then etching unnecessary copper foil other than the circuit pattern, and then removing the photosensitive film. However, since this photosensitive film is generally as thick as 50 μm, the circuit pattern formed by exposure and development is not sharp, and furthermore, it is difficult to uniformly laminate it on the copper foil surface, and particularly the through hole portion is covered. Is almost impossible.

In addition, etching resist ink is screen-printed on the copper-clad substrate with through-holes, then copper is removed from the unprinted parts by etching, and the resist ink in the printed parts is removed to print. A method of forming a wiring circuit pattern is also known. However, since it is difficult to apply the ink to the through holes by this method, the copper in the through holes is often removed by the etching process. For this reason, it is possible to form a circuit board by previously burying an organic material in the through holes, protecting the copper in the through holes from being removed by an etching process, and finally removing the organic materials. However, this method has the drawback that the cost of the circuit board finally obtained is high and the sharpness of the circuit pattern is also poor.

As a method of improving these conventional drawbacks, a positive type photosensitive resin resist film is formed on the substrate by electrodeposition coating, a positive type mask is laid over it, and exposed, and then the exposed portion is removed with an alkaline aqueous solution. A method of obtaining an etching resist by the above is proposed. (JP-A-6
0-207139, JP-A-61-206293, etc.). This method is a method in which a film can be easily formed on the through-hole portion by electrodeposition coating and the unexposed portion remains as a resist film, so that a printed wiring board having excellent resolution can be obtained.

The positive photosensitive resin used in the above method is generally shown below.

A water-soluble or water-dispersible resin containing a benzoquinonediazide unit or a naphthoquinonediazide unit represented by the above formula and capable of electrodeposition coating.

The action of the quinonediazide group in the positive-type photosensitive resin on actinic rays is such that the introduced quinonediazite group is decomposed by exposure to change to indenecarboxylic acid. Therefore, the solubility of the exposed portion in the alkaline aqueous solution (developing solution) is improved. On the other hand, it is presumed that the quinonediazide group in the unexposed portion will become more insoluble in an alkali developing solution by causing a coupling reaction with an aromatic ring, naphthene ring, etc. in the photosensitive resin by contact with an alkaline aqueous solution. .

[Problems to be Solved by the Invention] However, when a positive image is formed using the positive photosensitive resin described above, there are the following problems. That is, since a polar group such as a carboxyl group or an amino group is introduced into the photosensitive resin in order to make it water-soluble or water-dispersible, the insolubilizing means based on the contact between the quinonediazide group in the unexposed portion and the alkaline aqueous solution. By itself, the difference in solubility in the alkaline developer between the exposed and unexposed areas of the photosensitive resin resist film will not be sufficient, and as a result, high resolution images with no image breaks or distortion will be printed. It is difficult to form on a plate.

[Means for Solving the Problem] As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a positive photosensitive resin resist film formed on a substrate is transferred through a positive mask. By further heating after exposure, it is possible to significantly improve the poor solubility of the unexposed area in the alkaline developer without impairing the solubility of the exposed area in the alkaline developer. Therefore, the inventors have found that a stable image having high resolution can be formed on a printed wiring board, and have completed the present invention.

Thus, according to the present invention, a positive resist film containing a quinonediazide compound as a photosensitive component is formed on a circuit board having a conductive film by electrodeposition coating, exposed through a positive mask, and then developed. There is provided a positive type image forming method characterized by performing a heat treatment before.

In the present invention, as the positive electrodeposition coating composition used for forming the positive type resist coating film, a conventionally known composition mainly composed of a water-soluble or water-dispersible resin having a quinonediazide group can be used. Specific examples include those containing a resin containing a benzoquinonediazide unit or a naphthoquinonediazide unit as a main component, and these may be of anionic or cationic type (for example, JP-A- 60-20713
No. 9, JP 61-206293, JP 6
3-6070, Japanese Patent Application No. 62-157841, Japanese Patent Application No. 62-157842, Japanese Patent Application No. 62-245840.
And Japanese Patent Application No. 62-279288).

The positive image forming method of the present invention is carried out as follows, using an anionic electrodeposition coating as an example.

An electrodeposition coating bath containing a neutralized product of an anionic resin having a quinonediazide group as a main component has a pH of 5 to 10, a bath concentration (solid content) of 3 to 30% by weight, preferably 5 to 15% by weight, and a bath temperature of 15 to 40. C., preferably 15 to 30.degree. Then, the conductive substrate is immersed as an anode in this electrodeposition coating bath, and a direct current of 20 to 400 V is applied to carry out the process. A suitable energization time is 30 seconds to 5 minutes, and the dry film thickness is 2 to 100 μm, preferably 3 to 20 μm.
Is desirable.

After electrodeposition coating, after pulling the object to be coated from the electrodeposition bath and washing with water, as it is or after removing water contained in the electrodeposition coating film with hot air or the like, the surface of the photosensitive electrodeposition coating film thus formed A pattern mask (photo positive) is overlaid on the surface, and only the unnecessary portions other than the conductor circuit (circuit pattern) are exposed to actinic rays such as ultraviolet rays.

Thereafter, the article to be coated preferably has a surface temperature of 100 ° C. to 18 ° C.
After heat treatment at a temperature of 0 ° C. (more preferably 120 ° C. to 160 ° C.), the exposed portion is developed with a developing solution such as an alkaline aqueous solution to form a high-resolution rotated image.

The heat treatment time varies depending on the temperature, but is usually 1 second to 30 seconds.
Minutes, preferably 5 seconds to 15 minutes.

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

In the present invention, the actinic rays used for exposure are 3000 to 4
A light ray having a wavelength of 500Å is preferable. These light sources include sunlight, mercury lamps, xenon lamps, arc lamps and the like. Irradiation with actinic radiation is usually performed for 1 second to 20 minutes.

Further, the heat treatment is not particularly limited, and conventionally known means can be used, for example, hot air drying, infrared ray drying, induction heating drying, microwave drying, etc. are used alone or in combination.

The developing treatment is carried out by spraying alkaline water on the surface of the coating film to wash away the photosensitive portion of the coating film. Alkaline water used is usually caustic soda, sodium carbonate, caustic potash, ammonia water, sodium metasilicate, organic amine aqueous solution having a pH of 8 to 14 that can neutralize the free carboxylic acid contained in the coating film to give water solubility. It is possible.

Then, in the developing treatment, the conductive foil portion (non-circuit portion) exposed on the substrate is removed by a usual etching treatment using, for example, ferric chloride solution. Thereafter, the unexposed coating film on the circuit pattern is also ethyl cellosolve, a cellosolve solvent such as ethyl cellosolve acetate: an aromatic hydrocarbon solvent such as toluene or xylene: a ketone solvent such as methyl ethyl ketone or methyl isobutyl ketone: ethyl acetate, Acetate ester solvent such as butyl acetate: Chlorine solvent such as tolchlorethylene or 3 to
It is dissolved and removed by an aqueous solution of 10% caustic soda, caustic potash, etc. to form a printed circuit on the substrate.

[Function and Effect] According to the method of the present invention, a positive type photosensitive electrodeposition coating composition can be easily electrodeposition coated on a copper foil, and when the photosensitive film is irradiated with light through a positive film, the exposed portion is exposed to the quinonediazide compound as described above. Changes to indene carboxylic acid to improve solubility in a developing solution, and subsequent heat treatment promotes insolubilization of the unexposed area due to the di-azo coupling reaction, resulting in development with an alkaline developing solution. A high-resolution image with a line and space of 40 μm can be obtained.

In particular, the method of the present invention is most suitable for manufacturing a printed circuit board having a through hole, and the solder plating step and the like are eliminated as compared with the case of using a photosensitive dry film, and the printed circuit board manufacturing step can be shortened. In the process of manufacturing a circuit board using a photo-curable electrodeposition coating (negative type), a cured film must be formed in the through hole,
Although it is difficult to apply to the production of a circuit board having a small through hole diameter of φ or less, the present invention is suitable for the production of a printed circuit board having a small diameter because the unexposed portion remains as a resist film.

[Examples] Next, examples of the present invention will be described.

Production Example of Positive-Type Photosensitive Resin A four-necked flask was charged with 269 parts of orthonaphthoquinone diazide sulfonic acid chloride and 1345 parts of dioxane,
While stirring at room temperature, N-methylethanolamine 15
0 part was added dropwise in 1 hour. After completion of the dropping, stirring was continued for about 3 hours, and after confirming that absorption of amino groups near 3300 cm ^-1 in IR spectrum disappeared, the reaction was terminated.

Next, this solution was put into deionized water to remove the quaternary amine that trapped hydrochloric acid generated during the reaction. Next, the product was extracted with isobutyl acetate, the solvent was distilled off, and the product was placed in a vacuum dryer and dried to obtain a hydroxyl group-containing orthoquinonediazide compound.

In addition, 290 parts of diethylene glycol dimethyl ether was placed in another 4-necked flask and stirred at 110 ° C.
After the temperature was raised to 202 parts, n-butyl methacrylate 202 parts,
A mixed solution of 24 parts of acrylic acid, 92 parts of m-isopropenyl-α, α-dimethylbenzyl isocyanate and 20 parts of azobisbutyrovaleronitrile was added dropwise over 3 hours, and 1 part was added.
After maintaining for a period of time, a mixed solution of 14 parts of methyl isobutyl ketone and 3 parts of azobisbutyrovaleronitrile was added dropwise over 1 hour and maintained for 2 hours. Then, the temperature was lowered to 50 ° C., 142 parts of the hydroxyl group-containing orthoquinonediazide compound obtained earlier and 4.6 parts of dibutyltin diacetate were added, and the mixture was kept for 3 hours, then, 2250 cm ^{−1 of} infrared spectrum was obtained.
It was confirmed that the absorption of the isocyanate group in the vicinity had disappeared, and a positive photosensitive resin (acid value 40.7, viscosity E, molecular weight 7,000) was obtained. Then, 33 parts of triethylamine was added to the photosensitive resin solution to sufficiently neutralize it, and then deionized water was added so that the solid content became 10%, and an electrodeposition coating bath (p
H8.0).

Examples 1 to 9 A copper clad laminate for printed wiring (240 × 170 ×) having a through hole of 0.3 mmφ in the electrodeposition coating bath obtained in the above Production Example.
1.5mm) as an anode and immersed at a bath temperature of 25 ℃ at 50mA / dm
A direct current of ² was applied for 3 minutes for electrodeposition coating. The coating film was washed with water and dried at 50 ° C. for 5 minutes to form a non-adhesive smooth photosensitive film having a thickness of 8 μm. Then, a positive film was brought into close contact with this electrodeposition coated surface by a vacuum device, and both sides were irradiated with 150 mJ / cm ² using a 3 KW ultra-high pressure mercury lamp. Next, after heating under the predetermined heating conditions shown in Table-1, development is carried out with a 1% sodium carbonate aqueous solution, and after washing with water, the copper foil is removed by etching with a ferric chloride solution. % Aqueous solution of caustic soda to remove and form an image. The performance test results are shown in Table 1 below.

Comparative Example 1 An image was formed in the same manner as in Example 1 except that heating after exposure was not performed. The performance test results are shown in the table below.
Shown in 1.

Test method Resolution: An image was formed by the method described in the example using a positive film having a test pattern of a predetermined line and space, and then observed with a microscope, and each width of the line and space had a predetermined value. The minimum line and space where an image is formed is set as the resolution value.

Remaining scum: The inside of the through-hole of the image made in the same way as the resolution was observed with a microscope, and there was no case where dust-like foreign matter was observed in the through-hole, and there were many cases.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Junichi Higashi 4-17-1, Higashi-Hachiman, Hiratsuka City, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Naozumi Iwasawa 4-17-1, Higashi-Hachiman, Hiratsuka City, Kanagawa Prefecture Nishi Paint Co., Ltd. (72) Inventor Kenji Seko 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Toshio Kondo 4-1-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Incorporated (72) Inventor Jun Akui 4-17-1, Higashi-Hachiman, Hiratsuka, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Masao Ogawa 4-1-1, Higashi-Hachiman, Hiratsuka, Kanagawa Kansai Paint Co., Ltd. (56) Reference JP-A 63-43393 (JP, A) JP-A 50-6401 (JP, A) JP-A 50-139692 (JP, A) JP-A-49-62086 (JP, A) JP-A-53-68169 (JP, A)

Claims (1)

[Claims] 1. A circuit board having a conductive film, a positive resist film containing a quinonediazide compound as a photosensitive component is formed by electrodeposition coating, exposed through a positive mask, and then heated before development processing. A positive type image forming method characterized by performing processing.