JPH0967684A - Pretreatment of ferrous metallic material to be etched - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ameliorate the adhesion of a photoresist and to improve the etching property by chemically polishing the surface of a ferrous metallic material to be etched with a specified-concn. aq. soln. of the liq. mixture of NH4 HF2 and H2 O2 in a specified ratio. SOLUTION: The surface of a ferrous metallic material such as Fe-Ni alloy to be etched is chemically polished with a 5-30wt.% aq. soln. of the liq. mixture prepared by mixing NH4 HF2 with H2 O2 in 1:2 to 7 weight ratio before a pretreatment is applied for etching. In this case, the soln. is preferably kept at 25-40 deg.C, and the treating time is controlled to 1-5 min. The polished surface of the material is preferably neutralized with an alkaline soln., the fine ruggednesses on the polished surface are decreased by the chemical polishing, the surface is smoothed, an oxide film on the surface is dissolved, and the surface is activated. Consequently, the adhesion of the photoresist to the material is remarkably ameliorated, and the material is etched finely, precisely and stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the adhesion between a processing material and a photoresist when manufacturing an electronic component such as a lead frame or a shadow mask by etching an iron-based metal. It relates to a pretreatment method.

[0002]

2. Description of the Related Art The etching method is a processing technique utilizing the corrosion phenomenon of metals, and is currently a means for finely processing complicated-shaped products such as printed wiring boards, shadow masks for cathode ray tubes, and IC lead frames. Has become an indispensable technology.

FIG. 1 is a schematic explanatory view of this etching process. In FIG. 1, the material to be etched (metal plate)
Is first subjected to surface contaminant removal, and then subjected to a pretreatment for the purpose of enhancing the adhesion to the photoresist film. Next, the surface of the material to be etched is covered with a photoresist film, an exposure mask master plate is further overlaid, and ultraviolet rays are irradiated. Here, as the photoresist, a polymer substance of a type (negative type) that becomes insoluble by irradiation with light is mainly used. Next, after removing the exposure mask original plate and treating the material coated with the photoresist with a developing solution, the photoresist of the portion not irradiated with the ultraviolet rays is melted and removed, and the metal surface of the portion is exposed.

Therefore, if the material in this state is treated with an etching solution such as a ferric chloride solution (which is applicable to both copper-based materials and iron-based materials), the above-mentioned exposed portion of the metal is dissolved. When the remaining photoresist film is peeled off and removed, a product etched in the same pattern as the exposure original plate can be obtained.

Incidentally, in industrial production, the above etching step is generally carried out by an etching facility of the type shown in FIG. That is, in the etching equipment shown in FIG. 2, after the etching tank 2 for spraying the etching solution (ferric chloride solution or the like), a plurality of spray-washing tanks 3 for cleaning the etching solution are provided. There is. In this etching equipment, the portion where the etching liquid is sprayed from the etching liquid spray nozzle 4 onto the surface of the material to be etched 1 that has been continuously fed to the etching tank 2 after finishing the pretreatment, and is exposed from the photoresist film. Is removed by etching. Then, the cleaning water (liquid) is sprayed from the water spray nozzle 5 onto the surface of the material to be etched after being etched in the subsequent multiple stages of spray water washing tank 3 so that chlorides that cause corrosion do not remain on the product surface. Sufficient cleaning is performed.

As described above, a number of steps must be taken to obtain a product by etching, but the pretreatment of the material, which is carried out for the purpose of enhancing the adhesion between the photoresist film and the material to be processed, is also very difficult. This is an important process and has a great impact on product quality.

That is, if the pretreatment of the material is inappropriate, sufficient adhesion between the photoresist film and the material cannot be obtained, and the photoresist film peels off during the etching process, causing undesired dissolution of the material at that portion. As a result, the desired product shape cannot be obtained. Even if the photoresist film is not peeled off, the etching solution may penetrate into the interface between the photoresist film and the surface of the material to cause crevice corrosion, which means that lateral etching proceeds from the crevice corrosion portion. Therefore, fine etching becomes difficult.

FIG. 3 is a schematic view of a cross section of the processing material after the etching processing. However, when the adhesion between the processing material and the photoresist film is low, the etching liquid permeates the interface between the material and the photoresist to form a gap. Corrosion occurs, and as a starting point, etching progresses in the side direction (side etching), so the etching cross section becomes undesired as shown by the broken line, making fine punching impossible. Become.

By the way, as a pretreatment of the material conventionally performed for the purpose of enhancing the adhesion between the photoresist film and the processed material, the degreasing treatment such as alkali degreasing, solvent degreasing, electrolytic degreasing and the like is performed, and then washing The method of performing drying was adopted. However, this method alone cannot be said to have a sufficient effect of improving the adhesion to the photoresist film, and this dissatisfaction was particularly remarkable when the processing material was an iron-based metal.

Therefore, for iron-based metals, a method of pickling or chemical polishing with an aqueous solution of dilute nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or the like (see JP-A-1-259183) or a mixture of chromic acid and sulfuric acid There has been proposed a method of forming an oxide film on the surface using an aqueous solution or an alkaline oxidizing solution (a mixed aqueous solution of sodium hydroxide and sodium nitrate, etc.) (see JP-A-55-122876). However, not only can not be obtained sufficient adhesion between the photoresist film in this method, the metal surface after etching Cl ^- or causing the rusting ions remain, also alone sulfuric acid and nitric acid It has been pointed out that when used or when a mixed acid of nitric acid and hydrofluoric acid is used, the metal surface is discolored and the appearance of the product is impaired.

In view of the above, the object of the present invention is to significantly improve the photoresist adhesiveness of the iron-based metal material to be subjected to etching processing, and to perform fine and accurate etching processing stably. Was to provide.

[0012]

The present invention has been completed based on the results of research conducted by the inventors of the present invention, which were earnestly carried out to achieve the above-mentioned object. Prior to the photoresist coating step, the surface of the iron-based metal material to be treated is mixed with 5 to 5 parts of a mixed solution in which "hydrogen peroxide is mixed with hydrogen difluoride in a ratio of 1 to 2 to 7 in weight ratio.
By chemical polishing with a 30% by weight aqueous solution,
The feature is that the adhesiveness with the photoresist can be remarkably improved ".

The term "iron-based metal" as used herein means not only iron but also steel such as carbon steel and stainless steel, and further Fe--Ni.
It is a general term for metallic materials such as alloys whose main component is Fe.

[0014]

When carrying out the method of the present invention, first, a degreasing treatment is performed to remove oil and contaminants adhering to the surface of the iron-based metal material as the material to be etched. The degreasing method may be any of solvent degreasing, alkaline degreasing, electrolytic degreasing and the like. Then, following this degreasing treatment, the chemical polishing treatment according to the present invention is performed.

In the chemical polishing treatment, first, a mixed solution is prepared by mixing ammonium hydrogen difluoride and hydrogen peroxide in a weight ratio of "ammonium hydrogen difluoride: hydrogen peroxide = 1: 2 to 7". This is carried out using a solution diluted with water to a concentration of 5 to 30% by weight.

In this case, if the mixing ratio of hydrogen peroxide to ammonium hydrogen difluoride is less than 2 by weight, not only the adhesiveness of the photoresist cannot be obtained, but also the metal surface is roughened and the appearance is deteriorated. Unfavorably, on the other hand,
If the ratio is more than 7, the metal surface is passivated and the effect of chemical polishing cannot be obtained, resulting in poor adhesiveness of the photoresist. Further, if the concentration of the "ammonium hydrogen difluoride-hydrogen peroxide mixture" in the aqueous solution is lower than 5% by weight, the effect of chemical polishing will not be exhibited, the photoresist adhesion will be poor, and sufficient chemical resistance will be obtained. It takes a long time to obtain the effect of polishing, resulting in poor productivity. On the other hand, if the concentration is higher than 30% by weight, chemical polishing becomes excessive and the thickness is reduced.

The chemical polishing of the iron-based metal material using the above aqueous solution is preferably carried out by immersing the material to be treated in the aqueous solution or by spraying the aqueous solution onto the surface of the material to be treated. At this time, if the chemical polishing is excessive, the thickness of the material to be treated will be reduced and the product specifications will be exceeded.Therefore, it is necessary to appropriately select the concentration and temperature of the treatment aqueous solution and further the treatment time. is there. The temperature of the treatment solution is 2
It is preferably about 5 to 40 ° C., and the treatment time is usually 1 to 5 minutes, although it varies depending on the treatment method. If necessary, it is preferable that the surface of the material to be treated is neutralized with an alkaline solution such as caustic soda after the chemical polishing.

When the chemical polishing treatment as described above is performed, fine irregularities on the surface of the material to be treated are dissolved to obtain a smooth surface, and at the same time, the oxide film on the surface is also dissolved and the active metal surface is exposed. . As a result of these effects and the like being combined, it is considered that excellent adhesion with the photoresist film is imparted. Then, due to the effect of improving the adhesiveness with the photoresist film, the penetration of the etching solution into the interface between the material to be processed and the photoresist film at the time of etching is eliminated, and the lateral etching progress (side etching) is suppressed.
Therefore, the etching width W shown in FIG. 3 can be made smaller than in the conventional case, and fine etching processing can be performed. In addition, the chemical polishing treatment according to the present invention does not cause discoloration on the surface of the material to be treated, and thus does not impair the appearance.

After the chemical polishing treatment or, if necessary, the neutralization treatment which is subsequently performed, the surface of the material to be treated is thoroughly washed with water and dried, and then a photoresist is applied.
At this time, the photoresist may be either a negative type or a positive type, and may be a water-based type, a solvent type or a dry film.

Next, the present invention will be described with reference to examples.

Example A Fe-Ni-based 42 nickel alloy plate (0.15 mm thick) was prepared as a material to be processed. Then, first, the material to be processed is immersed in a 10% aqueous solution of caustic soda held at 70 ° C. to degrease its surface, and then ammonium hydrogen difluoride (mixed in various proportions (weight proportion) ( NH ₄ HF ₂ )
The chemical polishing process was performed using an aqueous solution prepared by diluting a mixed solution of hydrogen peroxide and hydrogen peroxide (H ₂ O ₂ ) to various concentrations. Two
It was implemented by a method of dipping for a minute. 2 after chemical polishing
% Aqueous solution of caustic soda was used to neutralize the residue of the chemical polishing solution on the surface of the material to be processed, which was then thoroughly washed with water and dried.

Subsequently, a photoresist having a film thickness of 10 μm was applied on the surface of the pre-processed material to be processed, and thereafter, exposure and development were performed in a usual process. Development pattern at this time
The photoresist aperture width (width indicated by symbol ω in FIG. 3) of the photoresist was 50 μm.

Next, using the apparatus shown in FIG. 2, the material to be processed which has been subjected to the above processing was subjected to etching processing by a spray-etching method. At this time, the etching solution is 4
A 7-borate ferric chloride solution was used and the liquid temperature was 48 ° C.

After the etching process, the photoresist film is peeled off and removed, and the side etch width (reference numeral a in FIG. 3) is removed.
The width) and the crevice corrosion width (width indicated by symbol b in FIG. 3) were measured. This result is a separate comparative example (example in which the processing conditions before the photoresist coating process are different)
It is shown in Table 1 in comparison with.

[0024]

[Table 1]

As is clear from the results shown in Table 1, the 42 nickel alloy plate subjected to the pretreatment according to the conditions specified in the present invention exhibits excellent photoresist adhesion, and as a result, the material / photoresist bond It can be seen that precise etching can be performed with a side etch width as small as possible without causing crevice corrosion.

[0026]

[Summary of Effects] As described above, according to the present invention, the photoresist adhesion of the iron-based metal material can be remarkably improved by the relatively simple pretreatment, and the fine etching process can be properly performed. To be able to carry out,
It has a very useful effect on the industry.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of an etching process.

FIG. 2 is an explanatory view of an example of an industrially productive etching facility.

FIG. 3 is a schematic view showing a cross section of a processing material after etching processing.

[Explanation of symbols]

 1 material to be etched 2 etching tank 3 spray-rinsing tank 4 etching liquid spray nozzle 5 spray nozzle for washing a side etch width b crevice corrosion width D etching depth W etching width ω photoresist opening width

Claims (1)

[Claims] 1. The surface of the iron-based metal material to be treated is treated with "1 hydrogen 2" before the photoresist coating step in the etching process.
Chemically polishing with an aqueous solution of 5 to 30% by weight of a mixed solution in which ammonium fluoride is mixed in a weight ratio of 1 to 2 and hydrogen peroxide is 2 to 7. Pretreatment method for improving adhesion.