STABILIZER FOR ACIDIC, METAL-CONTAINING POLISHING BATHS

Abstract

The present invention relates to the use of a mixture of urea and one or more alkane-diphosphonic acids, optionally substituted with one or more hydroxyl or amino groups, or salts thereof for the stabilization of an acidic, metal- and peroxide-containing polishing solution. The invention also relates to peroxide-containing solutions that are suitable for the stabilization of acidic, metal- and peroxide-containing polishing baths, and acidic, peroxide-containing polishing solutions that contain the stabilizer mixture according to the invention. A method of chemical polishing of metal surfaces using the stabilizer according to the invention is also described.

Description

EXAMPLE 1

Chemical Polishing Baths for the Treatment of Carbon Steel C 45

A—Polishing bath according to the state of the art:

Composition (wt. %):
Ammonium hydrogen difluoride  0.8%
Urea                          1.8%
Oxalic acid                   0.5%
Hydrogen peroxide (35%)       10.0%
Water                         remainder
Parameters:
Temperature                   30° C.
Iron removal rate (activity): 50 mg/(dm2 min)

Result:

The surfaces were shiny, and the edges had been deburred.

Working range up to a concentration of 20 g/l of dissolved iron, at higher concentration there was a sharp increase in consumption of hydrogen peroxide. Beyond 30 g/l the bath was no longer serviceable and had to be regenerated by partial replacement. Starting at 25 g/l iron in solution there was increasing precipitation of sparingly soluble deposits (salt coatings).

It was possible to increase the activity by increasing the concentration of ammonium hydrogen difluoride up to an activity of 80 mg/(dm² min). At higher activity the surfaces became matt and rough.

B—Polishing bath according to the invention

Composition (wt. %):
Hydrofluoric acid                0.7%
Urea                             0.7%
1-Hydroxyethane-1,1-diphosphonic acid 0.02%
Hydrogen peroxide (35%)          20.0%
Water                            remainder
Parameters:
Temperature:                     30° C.
Activity:                        200 mg/(dm2 min)

Result:

Smooth, shiny surfaces, edges deburred.

It was possible to increase the activity by increasing the concentration of HF and stabilizer up to 600 mg/(dm² min) without any loss of quality. Moreover, no precipitates were found in the bath. The consumption of hydrogen peroxide did not increase. The bath was serviceable up to an iron concentration of 60 g/l.

The activity of bath (B) relative to bath (A) was up to 8 times higher, with correspondingly shorter times of action and 3 times longer service life. Furthermore, the costs for the chemicals were far lower for bath (B) than for bath (A).

EXAMPLE 2

Chemical Polishing Baths for the Treatment of Copper

A—Polishing bath according to the state of the art

Composition (wt. %):
Sulfuric acid (96%)              1.0%
Hydrogen peroxide (35%)          14.0%
Stabilizer (commercially available) 1.0%
Water                            remainder
Parameters:
Temperature:                     35° C.
Removal rate:                    0.1 g/(dm2 min)

Result:

Good shine, edges deburred. Starting from a content of 10 g/l copper, increasing consumption of hydrogen peroxide. Above a copper content of 20 g/l there was a marked decline in quality of the surfaces and sharply increasing consumption of hydrogen peroxide.

B—Bath according to the invention

Composition (in wt. %):
Sulfuric acid (96%)              1.0%
Hydrogen peroxide (35%)          14.0%
Urea                             0.4%
1-Hydroxyethane-1,1-diphosphonic acid 0.01%
Water                            remainder
Parameters:
Temperature:                     35° C.
Removal rate:                    0.1 g/(dm2 min)

Result

Shiny surfaces up to a copper content of 50 g/l. Up to a copper content of 30 g/l in the solution, the consumption of hydrogen peroxide remains constant. At higher concentration there is a slight increase in consumption per hour of operation. This corresponds to a 2.5- to 3-fold service life of the bath according to the invention.

Claims

1. Use of a mixture of urea and one or more alkane-diphosphonic acids, optionally substituted with one or more hydroxyl or amino groups, or salts thereof for the stabiliztion of an acidic, metal- and peroxide-containing polishing solution.

2. The use as claimed in claim 1, wherein the weight ration or urea to alkane-diphosphonic acid is in the range from 100:1 to 20:1.

3. The use as claimed in claim 1, wherein the alkane-diphosphinic acid comprises 1-hydroxyethane-1,1-diphosphonic acid.

4. The use as claimed in claim 1, wherein the acidic, metal- and peroxide-containing polishing solution has a pH value from 0 to 3.

5. A peroxide-containing solution suitable for the stabilization of acidic, metal- and peroxide-containing polishing baths, comprising a mixture of urea and one or more alkane-diphosphonic acids, optionally substituted with one or more hydroxyl or amino groups, or salts thereof.

6. The solution as claimed in claim 5, wherein the alkane-diphosphonic acid comprises 1-hydroxyethane-1,1-diphosphonic acid.

7. The peroxide-containing solution as claimed in claim 5, wherein the weight ratio of urea to alkane-diphosphonic acids is between 60:1 and 35:1.

8. An acidic, peroxide-containing polishing solution, comprising as stabilizer a mixture of urea and one or more alkane-diphosphonic acids, optionally substituted with one or more hydroxyl or amino groups, or salts thereof.

9. The polishing solution as claimed in claim 8, characterized in that the concentration of the stabilizer in the solution is from 0.1 to 3.0 wt. %.

10. The solution as claimed in claim 8, wherein the weight ratio or urea to alkane-diphosphonic acids is in the range from 100:1 to 20:1.

11. The solution as claimed in claim 8, wherein the solution contains one or more other acids.

12. The solution as claimed in claim 11, wherein the solution contains hydrofluoric acid.

13. The solution as claimed in claim 11, wherein the solution contains sulphuric acid.

14. A method of chemical polishing of metal surfaces with an acidic, peroxide-containing solution at a pH value from 0 to 3, wherein a peroxide-containing solution is used together with a mixture of urea and one or more alkane-diphosphonic acids, optionally substituted with one or more hydroxyl or amino groups, or salts thereof.

15. The method as claimed in claim 14, wherein iron-containing metal surfaces are chemically polished.

16. The method as claimed in claim 15, wherein the aqueous peroxide-containing solution contains hydrofluoric acid.

17. The method as claimed in claim 14, wherein copper-containing metal surfaces are chemically polished.

18. The method as claimed in claim 16, wherein the aqueous peroxide-containing solution contains sulphuric acid.