DD223725A1 - AGENT FOR MASK CLEANING - Google Patents

Abstract

The invention relates to an etching agent for mask cleaning, which serves to eliminate metallic deposits that are formed in the production of structured Metallflaechen, such as Elektrodenflaechen on electronic components. The invention has for its object to provide an etching agent for mask cleaning, which is in use over a period of at least 6 months insensitive to accumulation of Stoerionen and thus with stable low chemical consumption and easy handling of the regeneration allows a consistently high etching rate. According to the invention, the object is achieved by the fact that the known copper etchant sulfuric acid / peroxide, in addition to possible additives for accelerating etching, an N-N-dialkylaminomethanediphosphonic acid and / or its water-soluble salt, for. B. N-N-Dimethylaminomethandiphosphonsaeure in a constant concentration of 0.1 g / l to the maximum solution concentration, contains.

Description

Field of application of the invention

The invention relates to an etchant for mask cleaning, which serves to eliminate metallic deposits that arise in the production of structured metal surfaces, such as electrode surfaces on electronic components. The electrode surfaces are u.a. made of copper or its alloys in conjunction with an adhesive layer z. As an alloy of chromium with nickel or iron. The masks used consist for. B. stainless steel.

Characteristic of the known technical solutions

As cleaning agents for the masks described, it is possible to use those etchants which remove the layer systems used at a satisfactory etching rate and in this case do not attack the mask material. The regeneration of the cleaning agent must be simple and may require little effort.

Furthermore, the criteria of toxicity and wastewater treatment should be taken into account when selecting the etching agent.

The above requirements are met by the known copper etchants, e.g. used in printed circuit board production, only conditionally or not fulfilled. A portion of these etchants, eg. As iron (III) chloride, hydrochloric acid / peroxide or copper chloride / peroxide attacks the mask material, cyanide systems have the disadvantage of high toxicity and a complex wastewater treatment.

As conditionally suitable, the system has proven sulfuric acid / peroxide. It is advantageous if, as explained in DE-AS 2700265, the base system an accelerator based on molybdenum ions and an additional stabilizer is added. This stabilizer, preferably an aromatic sulfonic acid, compensates for the decomposing effect of the molybdenum ions

on the peroxide. The etching system described has the disadvantage, in particular in the case of accelerator addition, that after a few days, the etching power decreases during the cleaning of the masks after initially low peroxide consumption and high etching power, and at the same time the peroxide consumption increases. This deterioration of the etch effect is obviously related to a proven accumulation of the etchant with other ions, e.g. B. iron ions.

It is known that special complexing agents can be used to eliminate interfering ions.

Usually used as a complexing agent in heavy metals compounds, eg. As phosphoric acid, tartaric acid, citric acid or fluorides proved to be unsuitable, since no stabilization effect or even reduced etching power or additional decomposition was observed in particular in the existing high concentration of copper ions or in addition to accelerator ions. For other complexing agents, for. B. in chelate compounds no satisfactory resistance to the etching system could be detected.

Object of the invention

It is the object of the invention to overcome the deficiencies of the known etchants set forth in order to perform mask cleaning with high productivity at a low cost.

Explanation of the essence of the invention

The invention has for its object to provide an etchant for mask cleaning, which is insensitive to accumulation of interfering ions in use over a period of at least 6 months and thus with stable low chemical consumption and easy handling of the regeneration allows a consistently high Atzrate. According to the invention the object is achieved in that the known copper etchant sulfuric acid / peroxide addition to possible additives to accelerate the etching of an N-N-Diaikylaminomethandiphosphonsäure and / or their water-soluble salt, eg. B. N-N-Dimethylaminomethandiphosphonsäure in a constant concentration of 0.1 g / l to the maximum solution concentration contains.

Ausführungsbeispiefe

The solution according to the invention will be explained with reference to exemplary embodiments.

These embodiments refer to the stationary operation of the cleaning bath, in which the concentration of copper ions by crystallization of copper sulfate in the range of about 40g /! up to 80g /! lies.

In the Ausführungsöispieien is therefore assumed in each case by the following Grundzusarnmensetzung the cleaning bath:

- sulfuric acid 3 η.

Hydrogen peroxide 10% by volume of a 35% solution

Copper ion concentration 40 g / l

example 1

Example 1 shows the improvement in the storage stability of the detergent at a bath temperature of 40 ^: C. The composition of the solutions and the change in the peroxide concentration are shown in Table 1. The effect of the composition of the cleaning bath according to the invention is demonstrated against an iron ion addition, wherein this concentration of iron ions may correspond to the concentration in the stationary state of the cleaning bath. ',

Table 1 Storage stability of the cleaning agents

Addition of iron ions Phosphonic acid additive Peroxide initial value Peroxide decrease

after 5 days

- 100% 2.6% 0.4 g / l - 100% 90.9% 0.4 g / l 3 g / l. 100% 3.4%

Example 2

Example 2 demonstrates the effect of the improved etchant in a particular application. The following solutions are compared:

Solution A: new formulation according to basic composition

Solution B: 'with interfering ions z. B. iron ions in a concentration of 0.5 g / l enriched approach, resulting from solution A.

Solution C: reaction regenerated with 3.0 g / l phosphonic acid resulting from solution B. ,

The parameters etch rate and the peroxide consumption per etched mass unit were determined in each case at the same temperature for the same temperature of 45 ° C ± 5K and at the same starting concentration of the components according to the base composition over a period of 5 hours by means of coating masks and by analytical control. It was found that in the enriched with interfering ions approach B an average etching rate of about

55% of the etching rate of the solution A is reached, while at the same time the peroxide consumption per kg of mass removal increases to about 190% compared to solution A. By adding the stated amount of phosphonic acid, both the

Etching rate increases to the value of the solution Ä as well as the specific peroxide consumption about 105% of consumption

lowered at solution A. ,

Claims (1)

-1- 255 729 Invention claim. · Etchants for mask cleaning, in particular stainless steel masks with deposits of copper or its alloys and an adhesive layer alloy consisting of the known copper etchant sulfuric acid / peroxide.And possible additives, characterized in that the said etching system additionally a NN-dialkylaminomethanediphosphonic acid and / or its water-soluble salt, z. B. N-N-Dimethylaminomethandiphosphonsäure in a constant concentration of 0.1 g / 1 to the maximum solution concentration contains.