Ruthenium Alloy Layer and Its Layer Combinations

Abstract

Aqueous electrolyte for deposition of a ruthenium alloy layer on metal surfaces, in particular base metal surfaces, its use and a corresponding electrolytic process, and a correspondingly produced layer sequence.

Claims

1-15. (canceled)

16. An aqueous electrolyte for deposition of ruthenium alloys on metal surfaces, in particular base metal surfaces, comprising: a) ruthenium as a bicyclic, anionic ruthenium nitrido complex compound of the formula [Ru.sub.2N(H.sub.2O).sub.2X.sub.8].sup.3, wherein X is one or more singly or multiply negatively charged counterions, at a concentration of 0.5-20 g/l based on ruthenium as metal; b) one or more alloy metals dissolved in ionic form and selected from the group consisting of: Cu, W, Fe, Co, Ni, In, Zn, Sn, Pd, and Pt, each at a concentration of 0.1-10 g/l based on the metal; c) one or more anions of a di-, tri-, or tetracarboxylic acid at a concentration of 0.05-2 mol per liter; d) one or more anionic surfactants at a concentration of 0.1-500 mg/1; wherein the electrolyte has a pH value of 5.0 to 10.0.

17. The electrolyte according to claim 16, wherein the carboxylic acid is selected from the group consisting of oxalic acid, citric acid, tartaric acid, succinic acid, maleic acid, glutaric acid, adipic acid, malonic acid, and malic acid.

18. The electrolyte according to claim 16, wherein the surfactant is selected from the group consisting of fatty alcohol sulfates, alkyl sulfates, alkyl sulfonates, aryl sulfonates, alkylaryl sulfonates, heteroaryl sulfates salts, and alkoxylated derivatives thereof.

19. The electrolyte according to claim 16, wherein the pH value of the electrolyte is in a range of 7-8.

20. The electrolyte according claim 16, wherein the electrolyte has a buffer system selected from the group consisting of borate, phosphate, and carbonate buffers.

21. The electrolyte according claim 16, wherein the alloy metal is selected from the group of Ni, Pd, Pt, Sn, Zn, and Co.

22. The electrolyte according claim 16, wherein it does not contain sulfur-containing compounds in which the sulfur is present in an oxidation state of +4.

23. A method for producing an article having a metal surface and an alloy metal layer thereon, which comprises electrolytically depositing the alloy metal layer on the metal surface using the aqueous electrolyte according to claim 1.

24. The method according to claim 23, wherein the alloy metal layer has a thickness of 0.05-5 m

25. The method according to claim 23, wherein the alloy metal layer serves as a sublayer for a further electrolytically deposited metal layer of noble metals or alloys thereof, wherein the latter has a thickness of 0.05-5 m.

26. The method according to claim 23, wherein the metal layer(s) produced has/have an abrasion resistance of less than 0.25 m/1000 strokes per the Bosch-Weinmann test.

27. A process for electrolytically depositing an alloy metal layer on metal surfaces, in particular base metal surfaces, in which: a) the metal surface is brought into contact as a cathode with an aqueous electrolyte according to claim 16; b) an anode is brought into contact with the electrolyte; and c) a sufficient current flow is established between the cathode and the anode.

28. The process according to claim 27, wherein the current density in the electrolyte is 0.1-50.0 A/dm.sup.2.

29. The process according to claim 27, wherein the temperature during the electrolysis is between 20 C. and 80 C.

30. A metal layer sequence comprising a substrate provided with a metal surface, in particular a base metal surface, an alloy metal layer which is electrolytically deposited thereon and produced by a process according to claim 27.

Description

EXAMPLES

[0044] 1 liter of the electrolyte specified in the respective exemplary embodiment are heated to the temperature specified in the exemplary embodiment by means of a magnetic stirrer, while being stirred with a cylindrical magnetic stirring rod 60 mm long at at least 200 rpm. This stirring and temperature is also maintained during the coating.

[0045] After the desired temperature has been reached, the pH value of the electrolyte is set using a KOH solution (c=0.5 g/ml) and sulfuric acid (c=25%) to the value specified in the exemplary embodiment.

[0046] Expanded metal sections made of platinized titanium serve as anodes.

[0047] A mechanically polished brass plate with a surface area of at least 0.2 dm.sup.2 serves as cathode. This can be coated beforehand with at least 5 m of nickel from an electrolyte which produces high-gloss layers. A gold layer approximately 0.1 m thick may also be deposited on the nickel layer.

[0048] Prior to introduction into the electrolyte, these cathodes are cleaned with the aid of electrolytic degreasing (5-7 V) and an acid dip containing sulfuric acid (c=5% sulfuric acid). Between each cleaning step and before introduction into the electrolyte, the cathode is rinsed with deionized water.

[0049] The cathode is positioned in the electrolyte between the anodes and moved parallel thereto at at least 5 cm/second. The distance between anode and cathode should not change.

[0050] In the electrolyte, the cathode is coated by applying a direct electric current between anode and cathode. The current intensity is selected such that at least 0.5 A/dm.sup.2 is achieved on the surface area. Higher current densities can be selected if the electrolyte specified in the application example is intended to produce layers that can be used for technical and decorative purposes.

[0051] The duration of the current flow is selected such that a layer thickness of at least 0.5 to 1 m is achieved on average over the surface area. Higher layer thicknesses can be produced if the electrolyte specified in the application example is intended to produce layers of a quality that can be used for technical and decorative purposes.

[0052] After coating, the cathode is removed from the electrolyte and rinsed with deionized water.

[0053] The drying of the cathodes can take place via compressed air, hot air, or centrifugation.

[0054] The surface area of the cathode, the level and duration of the applied current, and the weight of the cathode before and after coating are documented and used to determine the average layer thickness as well as the efficiency of deposition.

Deposition of Ruthenium Alloy Layers

[0055]

TABLE-US-00001 Example no. 1 2 3 4 5 Ru [mol/l] 0.05 0.05 0.08 0.02 0.05 Zn [mol/l] 0.003 Sn [mol/l] 0.016 Co [mol/l] 0.016 Ni [mol/l] 0.06 Pd [mol/l] 0.0009 Dipotassium oxalate [mol/l] 0.3 0.36 0.36 0.18 0.3 Tripotassium citrate [mol/l] 0.032 0.16 0.016 Ammonium sulfate [mol/l] 0.075 0.37 Dipotassium hydrogen 0.43 phosphate [mol/l] pH value 7.0 8.0 7.5 9.0 7.0 Temperature [C.] 65 60 65 55 65 Current density [A/dm.sup.2] 1 2 2 1 2 Alloy [wt. %] 60% 20% 10% 20% 15% Zn Pd Ni Sn Co Cracks none none none none none