JPH0841656A - Pretreatment of material to be etched - Google Patents

Abstract

PURPOSE:To improve the adhesion of a photosensitive resist and to etch a material with high accuracy in size by uniformly forming a thin oxide film on the material surface. CONSTITUTION:A material to be etched such as a lead frame material is sent to an oxidizing, recovering and washing device 5 before sending it to a photosensitive resist coating machine 7, and an oxide film is formed on the material surface by using a liq. mixture of chromic acid and phosphoric acid when being used in the oxidation in This device 5. The liq. mixture contains 10-80g/l of chromic acid and 40-100g/l. of phosphoric acid, and the oxidation is preferably conducted at normal temps. to 50 deg.C for 30 to 120sec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment method for an etching material, and more particularly to a method suitable for etching a lead frame material.

[0002]

2. Description of the Prior Art Generally, etching materials such as iron, stainless steel, iron-nickel alloy (42% Ni-remaining F
For e), copper, copper alloys, etc., after pretreatment such as degreasing-water washing-pickling-water washing, an aqueous or oily photosensitive resist is applied. However, in this method, even if degreasing and pickling are complete, the adhesiveness of the photosensitive resist is inferior, so "waviness" occurs on the end surface after etching, or it becomes "rounded" and the specified dimension is It often happens that you cannot get it.

By the way, if the surface of the material is oxidized,
It is said that since the hydroxyl group (OH) in the resist and the oxygen in the oxide film are bonded, the adhesiveness of the photosensitive resist is improved. Therefore, conventionally, various methods of forming an oxide film before coating a photosensitive resist have been proposed.

For example, one in which a metal film is heat-treated (JP-A-5-44062), one in which an iron oxide layer having a thickness of 95 to 1000 angstroms is formed on the surface of an iron-based metal by heat treatment (JP-A-63-63). -489 publication),
Heat treatment is performed in an oxidizing atmosphere to form a thin metal oxide film on the surface of the metal film (JP-A-49-11184).
No. 0), an aqueous solution of an alkali sulfonic acid, a surfactant and an oxidizing agent (JP-A-4-218686).
Japanese Laid-Open Patent Publication No. 1989-242242), a steel material is dipped in a mixed solution of chromic acid and sulfuric acid to form an oxide film on the surface of the steel material (JP-A-55)
-122876).

[0005]

However, the above-mentioned conventional method has the following drawbacks.

In the case of heat treatment as described above, since the etching material has a wide width and a long length, a uniform film cannot be formed and etching becomes difficult. In the case of using the above aqueous solution, the main purpose is to clean the surface of the material, and since the treatment for improving the adhesiveness of the resist is not performed, the adhesiveness of the photosensitive resist cannot be expected to be improved. Further, the method of using the mixed solution is a general method for improving the corrosion resistance of the steel material, and since the film is formed quickly, the film on the surface becomes too thick and is not suitable as a pretreatment for the steel material for etching.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, improve the adhesiveness of the photosensitive resist, and finish the etching processing dimension with high accuracy by forming a thin oxide film uniformly on the surface. It is an object of the present invention to provide a pretreatment method of an etching material capable of achieving the above.

[0008]

The pretreatment method for an etching material according to the present invention forms an oxide film using a mixed liquid of chromic acid and phosphoric acid before applying a photosensitive resist to the etching material. To do.

[0009]

When an oxide film is formed by using a mixed solution of chromic acid and phosphoric acid, the film is formed slowly, so that the oxidizability is slow, and an angstrom-order oxide film is uniformly formed. Therefore, the adhesion of the photosensitive resist to the etching material can be significantly improved without impairing the etching property, and the etching becomes easy.

The etching material of the present invention includes iron, stainless steel, iron-nickel alloy (42% Ni-remaining Fe).
There are copper and copper alloys. The photosensitive resist may be water-based or oil-based.

As a result of various studies on the mixed liquid composition of chromic acid and phosphoric acid used in the present invention, the chromic acid concentration was 10 to 80 g / l and the phosphoric acid concentration was 40 to 100 g / l.
1, the temperature of the liquid used is room temperature to 50 ° C., and the treatment time is 30
It has been found preferable to use in the range of 120 seconds. The optimum condition within this usage range is chromic acid 5
0 g / l + phosphoric acid 80 g / l, liquid temperature 30 ° C., treatment time 30 seconds.

[0012]

EXAMPLES Examples of the pretreatment method for the etching material of the present invention will be described below. FIG. 1 is an overall view of a pretreatment process when a lead frame material is used as an etching material. The lead frame material unwound from the material unwinder 1 is degreased-recovered-water washing device 3 via the accumulator 2.
, Degreasing, collecting, and washing with water. further,
Pickling-Recovery-Sending to the washing device 4 for pickling, collecting and washing.

Then, it is sent to the oxidation-recovery-water washing device 5 which constitutes the pretreatment device which is the main part of this embodiment. The oxidation treatment in the oxidation-recovery-water washing device 5 is performed by forming an oxide film on the surface of the lead frame material using a mixed liquid of chromic acid and phosphoric acid.

The lead frame material on which the oxide film is formed is sent to the photosensitive resist coating machine 7 through the warm water machine 6 and is coated with the photosensitive resist there. After coating, the resist is dried by being sent to the hot air drier 8, and the material winder 9 winds up the lead frame material with resist.

The lead frame material with resist wound by the winder 9 is then exposed and etched using a mask pattern of a predetermined shape to form a lead frame of a predetermined shape.

As described above, since the oxide film is formed before applying the photosensitive resist to the lead frame material, the adhesion of the photosensitive resist is improved. Further, since a mixed liquid of chromic acid and phosphoric acid is used to form the oxide film, the oxidizability is slow and the oxide film of angstrom order is uniformly formed.

As a result, the etching is improved and the yield of the etching products is greatly improved. In addition, the dimensional accuracy of the lead frame is significantly improved. In addition, the appearance of the product is improved, and lead chips, pinholes, etc. are eliminated. Further, since the treatment is performed with the mixed liquid of chromic acid and phosphoric acid before the application of the photosensitive resist, the deterioration of the photosensitive resist is eliminated.

(Specific example) 42% N with a plate thickness of 0.15 mmt
i-remaining Fe alloy strip is used to etch 160
When manufacturing the lead frame of the pin, the method of the above-described example was applied to the pretreatment of the material for the lead frame, and the photosensitive resist was applied. The conditions are as follows.

Degreasing (30 g / l caustic soda, 40 ° C., 30 seconds immersion) ↓ Pickling (10 g / l hydrochloric acid, room temperature, 30 seconds immersion) ↓ Oxidation treatment (30 g / l chromic anhydride + 50 g / l phosphoric acid, 50 ° C. For 30 seconds) For comparison, using the same alloy strip, degreasing → pickling →
The conventional method of oxidation treatment (20 g / l chromic anhydride + 600 g / l sulfuric acid, 85 ° C., 30 seconds immersion) was also applied to apply the photosensitive resist. Table 1 shows the results of the adhesion, dimensional accuracy, yield, and appearance of the resist applied to the alloy strip by applying these two methods.

[0020]

[Table 1]

As is clear from Table 1, the adhesiveness of the resist was measured by the cellotape peeling test method. In the conventional method, peeling of the resist was recognized, but in the case of this example, all were sound.

Further, the dimensional accuracy of the round hole and the lead width is ± 0.02 mm in the present embodiment, but is ± 0.05 mm in the conventional method, which often deviates from the standard value of the dimension. there were.

As is clear from Table 1, the yield is 97% in the case of this embodiment, while it is 7 in the case of the conventional method.
It is 0%, which shows that the method of the present example is remarkably excellent. The appearance of the lead shape was linear in this example, and "waviness", chipping, and pinholes were hardly recognized, whereas those of the conventional method were recognized.

[0024]

According to the present invention, since the oxide film is formed by using the mixed liquid of chromic acid and phosphoric acid, a thin oxide film can be uniformly formed on the surface, and the photosensitive resist of The adhesiveness is improved, and the dimensional accuracy of the etching product can be significantly improved.

[Brief description of drawings]

FIG. 1 is an overall view of an etching pretreatment process for a lead frame material for explaining an example of a pretreatment method for an etching material according to the present invention.

[Explanation of symbols]

 1 Material Unwinder 2 Accumulator 3 Degreasing-Recovery-Water Washing Device 4 Pickling-Recovery-Water Washing Device 5 Oxidation-Recovery-Water Washing Device 6 Hot Water Machine 7 Photosensitive Resist Coating Machine 8 Hot Air Dryer 9 Material Winding Machine

Claims (3)

[Claims] 1. A pretreatment method for an etching material, which comprises forming an oxide film by using a mixed solution of chromic acid and phosphoric acid before applying a photosensitive resist to the etching material. 2. The composition of the mixed solution of chromic acid and phosphoric acid has a chromic acid concentration of 10 to 80 g / l and a phosphoric acid concentration of 40 to
It is 100 g / l, The pretreatment method of the etching material of Claim 1 characterized by the above-mentioned. 3. The pretreatment method for an etching material according to claim 1, wherein the mixed liquid of chromic acid and phosphoric acid is used at room temperature to 50 ° C. for a treatment time of 30 to 120 seconds. .