Use of Water Soluble Lanthanide Compounds As Stabilizer In Electrolytes For Electroless Metal Deposition

Abstract

The present invention relates to the use of water soluble lanthanide compounds as stabilizer in electrolytes for electroless metal deposition, an electrolyte as well as a method for the electroless deposition of metals, particularly layers of nickel, copper, cobalt, boron, silver, palladium or gold, as well as layers of alloys comprising at least one of the aforementioned metals as alloying metal.

Claims

1. An aqueous electrolyte composition for the electroless deposition of a metal layer on a substrate, comprising a metal ion source for the metal to be deposited, a reducing agent, a complexing agent, an accelerator, and a stabilizer, characterized in that the electrolyte comprises as stabilizer a water-soluble lanthanide compound.

2. The aqueous electrolyte composition according to claim 1, wherein the water-soluble lanthanide compound is comprised in a concentration between ≧0.05 mg/L and ≦100 mg/L.

3. The aqueous electrolyte composition according to claim 1, wherein the metal to be deposited comprises at least one metal selected from the group consisting of nickel, copper, cobalt, boron, silver, and gold.

4. The aqueous electrolyte composition according to claim 3, wherein the accelerator is at least one accelerator of selected from the group consisting of saccharine, hydantoin, rhodanine, carbamide and carbamide derivates.

5. The aqueous electrolyte composition according to claim 3, wherein the electrolyte is essentially free of inorganic stabilizers.

6. The aqueous electrolyte composition according to claim 3, wherein the composition is essentially free of cyanides, selenium compounds and sulfur compounds comprising sulfur in an oxidation state between −2 and +5.

7. The aqueous electrolyte composition according to claim 3, further comprising at least one additional carboxylic acid and/or at least one salt of a carboxylic acid.

8. The aqueous electrolyte composition according to claim 7, wherein the carboxylic acid is a compound of the group consisting of acrylic acids, aromatic carboxylic acids, fatty acids, aliphatic carboxylic acids, keto acids, dicarboxylic acids, tricarboxylic acids, straight chained carboxylic acids, heterocyclic carboxylic acids, saturated carboxylic acids, unsaturated carboxylic acids, and α-hydroxy acids.

9. The aqueous electrolyte composition according to claim 3, wherein the pH-value of the composition is in the range of between pH 4 and pH 7.

10. The aqueous electrolyte composition according to claim 3, wherein the reducing agent is at least one compound of the group consisting of sodium hypophosphite, formaldehyde, dimethyl aminoborane, amino borane, and other organic boranes.

11. The aqueous electrolyte composition according to claim 3, wherein the complexing agent is at least one compound of the group consisting of 2-hydroxy propionic acid, propanedioic acid, EDTA and amino acetic acid.

12. A method for the electroless deposition of a metal layer on a substrate comprising the steps of contacting the substrate to be plated with an electrolyte comprising a metal ion source for the metal to be deposited, a reducing agent, a complexing agent, an accelerator, and a stabilizer, characterized in that the electrolyte comprises as stabilizer a water-soluble lanthanide compound.

13. The method according to claim 12, wherein the substrate is contacted with the electrolyte at a temperature within the range of between ≧20° C. and 85° C.

14. The method according to claim 12, wherein the substrate is contacted with the electrolyte for a time between ≧1 s and ≦180 min.

15. (canceled)

16. The method according to claim 12, wherein the water-soluble lanthanide compound is comprised in a concentration between ≧0.05 mg/L and ≦100 mg/L.

17. The method according to claim 12, wherein the metal to be deposited comprises at least one metal selected from the group consisting of nickel, copper, cobalt, boron, silver, and gold.

18. The method according to claim 17, wherein the accelerator is at least one accelerator of the group consisting of saccharine, hydantoin, rhodanine, carbamide and carbamide derivates.

19. The method according to claim 17, wherein the electrolyte is essentially free of inorganic stabilizers.

20. The method according to claim 17, wherein the composition is essentially free of cyanides, selenium compounds and sulfur compounds comprising sulfur in an oxidation state between −2 and +5.

21. The method according to claim 17, further comprising at least one additional carboxylic acid and/or at least one salt of a carboxylic acid.

22. The method according to claim 21, wherein the carboxylic acid is a compound of the group consisting of acrylic acids, aromatic carboxylic acids, fatty acids, aliphatic carboxylic acids, keto acids, dicarboxylic acids, tricarboxylic acids, straight chained carboxylic acids, heterocyclic carboxylic acids, saturated carboxylic acids, unsaturated carboxylic acids, and α-hydroxy acids.

23. The aqueous electrolyte composition according to claim 2, wherein the water-soluble lanthanide compound is comprised in a concentration between ≧0.1 mg/L and ≦25 mg/L.

24. The aqueous electrolyte according to claim 23, wherein the water-soluble lanthanide compound is comprised in a concentration between ≧0.5 mg/L and 10 mg/L.

25. The aqueous electrolyte composition according to claim 1, wherein the electrolyte is essentially free of lead, bismuth, zinc and/or tin.

26. The method according to claim 13, wherein the substrate is contacted with the electrolyte at a temperature within the range of between ≧25° C. and ≦70° C.

27. The method according to claim 14, wherein the substrate is contacted with the electrolyte for a time between ≧10 s and ≦60 min.

Description

EXAMPLE 1

[0064] In a preferred embodiment of the invention the electrolyte according to the present invention comprises: [0065] 13.03 g/l nickel sulfate; [0066] 1.925 mg/L potassium iodide [0067] 17.27 g/l lactic acid; [0068] 5.94 g/l malic acid; [0069] 40.2 g/l sodium hypophosphite; [0070] 9.81 g/l sodium hydroxide; and [0071] 10.00 mg/L neodymium acetate
wherein the pH is in a range of pH 4 to pH 7.

EXAMPLE 2

[0072] At a temperature between 80° C. and 94° C. a substrate (steel sheet) was brought into contact with an electrolyte comprising: [0073] 8.8 g/l nickel acetate tertahydrat; [0074] 0.2 g/L potassium iodide [0075] 30 g/L lactic acid; [0076] 2.5 g/L saccharine, sodium salt [0077] 16 g/l sodium hydroxide solution, 33% by weight; [0078] 30 g/L sodium acetat [0079] 35 g/L sodium hypophosphite dihydrate [0080] 20.0 mg/l samarium (M) sulfate
wherein the pH is in a range of pH 4 to pH 5 at a temperature between 80 and 94° C. an aluminum panel was plated in an electrolyte with the above mentioned composition. The aluminum was treated according to the standard pre-treatment cycle before plating in the electroless nickel bath. A glossy nickel deposit without nodules could be plated from this electrolyte with a plating speed of 6-8 μm/h with a composition of 88-89% by weight nickel and 11-12% by weight of phosphorous.

EXAMPLE 3

[0081] In another preferred embodiment of the invention the electrolyte according to the present invention comprises: [0082] 8.8 g/L nickel acetate tertahydrat; [0083] 0.2 g/L potassium iodide [0084] 30 g/L lactic acid; [0085] 2.5 g/L saccharine, sodium salt [0086] 16 g/L sodium hydroxide solution, 33% by weight; [0087] 35 g/L sodium hypophosphite dihydrate [0088] 5 mg/L neodymium acetate [0089] 15 mg/L potassium antimony tartrate
wherein the pH is in a range of pH 4.0 to pH 5 at a temperature between 80° C. and 94° C. a steel panel was plated in an electrolyte with the above mentioned composition. A glossy nickel deposit could be plated from this electrolyte with a plating speed of 8-10 μm/h with a composition of 88-89% by weight nickel and 10-11.5% by weight of phosphorous

EXAMPLE 4

[0090] In another preferred embodiment of the invention the electrolyte according to the present invention comprises: [0091] 8.8 g/L nickel sulfate; [0092] 0.1 mg/L potassium iodate [0093] 25 g/L lactic acid; [0094] 1.0 g/L saccharine [0095] 2 g/L β-alanin [0096] 15.5 g/l sodium hydroxide solution, 33% by weight; [0097] 20 g/L sodium acetat [0098] 35 g/L sodium hypophosphite dihydrate [0099] 40.00 mg/l cerium (III) iodide [0100] 18 mg/L potassium antimony tartrate
wherein the pH is in a range of pH 4.0 to pH 5 at a temperature between 80° C. and 94° C. an ABS plaque was plated in an electrolyte with the above mentioned composition. The ABS plaque was pre-treated in a standard POP (plating-on-plastic) pretreatment cycle before plating. A glossy nickel deposit could be plated from this electrolyte with a plating speed of 8-10 μm/h with a composition of 90-91% by weight nickel and 9-10% by weight of phosphorous.