DE2007484A1 - Process for the production of a light mask for the photo etching technique - Google Patents

Description

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Process for the production of an exposure mask for the Photo etching technique

The present invention relates to a method of manufacture an exposure mask for photo etching, e.g. for the production of! printed circuit boards, in which on a glass plate a lead sulfide layer is applied and after application An etching mask, e.g. in the form of a photoresist, covers the uncovered part of the lead sulfide layer with chromosulfuric acid to be etched out.

In the manufacture of printed circuit boards using photo-etching technology and when etching moldings, exposure masks are used which consist of glass plates that have a thickness of about 1 / µm have a strong lead sulfide layer with the desired pattern. The production of these glass originals takes place in such a way that an approximately 1 / u thick layer of lead sulfide is applied to a glass plate, over it an etching mask is produced by way of the photo etching technique, whereupon the lead sulfide layer with the help of chromosulfuric acid is etched. During this etching process, the lead sulfide is oxidized to lead chromate and lead sulfate. These reaction products are sparingly soluble and stick to the etched surface as a yellow protective skin, so that the etching through the lead sulfide layer is slowed down. The reaction products can only be removed after etching, e.g. by wiping them off remove with a wet sponge. The contour accuracy The glass originals produced in this way are limited, however, since the edges are undercut during the etching occurs.

The present invention is based on the object To specify the process for the production of glass originals, the

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the production of glass originals with larger contours allowed.

To solve this problem, a method of the type mentioned is proposed, according to the invention, the Etching is carried out in several process stages and after each partial etching the etched parts with complexing agents are treated to remove the formed etching products, whereupon the etching is continued.

The yellow top layer described is removed here. lead sulfide thus exposed is then further etched and the newly formed yellow "top layer in turn with complexing agents worn away. Usually a 4-step process is sufficient to etch a plate.

The use of M-sodium salt has proven to be particularly suitable proved by ethylenediarainetra-acetic acid. Other suitable complexing agents include: ammoniacal tartaric acid solution, neutral solutions of nitrilotriacetic acid and diethylenetriaminepentaacetic acid.

The undercut of the lead sulfide pattern resulting from this process is extremely low. It is therefore possible to produce original rias with very low tolerances.

Embodiment

Glass plates, which had an approximately 1 / U thick layer of lead sulfide, on which a mask covering the parts not to be etched was applied, were first wetted with tap water, placed in a suitable frame and then spray etched with an etching solution of 150 g for 10 seconds per liter of Ohromtrioxyd, 112 ml per liter of concentrated sulfuric acid, 3 ml per liter of concentrated hydrochloric acid at a temperature of about 45 °. The glass plates treated in this way were then rinsed with deionized water and placed in a complex

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Solution of about 150 g of the disodium salt of the Ethylenediarnintetra-KoRigsätr-e in ? 1 exposed to deionized water. At the same time, it was with a soft flat brush O "bez ^v surface of the glass original painted over until the ^ by the Aet en formed yellow Bleiehromatschicht was removed and the gray color of the underlying lead sulfide layer came to light after a further rinsing rait tap water. Varrde etching for a Bauer continued for about 7 to 8 seconds. This was again followed by a treatment in the complex image-xing solution. The etching process is then ended on the cone. If this is not the case, another etching can be carried out, this time only 2 seconds takes erÜLgen. this is followed by a further rinse in tap water, then rinse in deionized "water and then drying the glass originals with compressed air ·. "

4 claims

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Claims (4)

Claims 1. Method of making an exposure mask for the
Photo-etching technique, for example for the production of printed circuit boards, in which a lead sulfide layer is applied to a glass plate and after applying an etching mask, for example in
In the form of a TjOtolackschicbt the uncovered parts of the lead sulfide layer are etched out with chromosulfuric acid, characterized in that the
Etching is carried out in several process steps and that after each partial etching the etched parts with a
Complexing agents are treated to remove the etching products formed, whereupon the etching is continued. Ί . Process according to Claim 1, characterized in that the dinatriura salt of ethylenediaminetetra-acetic acid is used as the complexing agent. 3. The method according to claim 1, characterized net that as a complexing agent ammoniacal tartaric acid is used. 4. The method according to claim 1, characterized in that neutral Lösui ^ n of nitrilotriacetic acid as complexing agent or Mäthylenetriaminepenta-acetic acid is used will. VPA 9/401/89 109838/0782