Electroplating solutions
The invention relates to an aqueous electroplating solution for alkaline electroplating, comprising: [M(NH3)4]2+ ions, wherein M is selected from the group consisting of Pd or Pt; and organic anions selected from the group consisting of bicarbonate, carbonate, or a mixture thereof; wherein the following species, if present, are present in the following amounts: alkali metals in an amount of less than 5 g/L; compounds comprising phosphorus in an amount of less than 5 g/L; compounds comprising boron in an amount of less than 5 g/L. The invention also relates to an electroplating bath comprising the electroplating solution, and a method of forming a metal layer on a substrate by electroplating using the electroplating solution.
1. An electroplating bath comprising a cathode and an anode which are both at least partially submerged in an electrolyte, wherein the electrolyte is an aqueous electroplating solution comprising
[Pt(NH 3 ) 4 ] 2+ ions; and organic anions selected from the group consisting of bicarbonate, carbonate, or a mixture thereof;
wherein the molar ratio of Pt: (bicarbonate+carbonate) is approximately 1:2; and
wherein the following species, if present, are present in the following amounts:
alkali metals in an amount of less than 5 g/L;
compounds comprising phosphorus in an amount of less than 5 g/L;
compounds comprising boron in an amount of less than 5 g/L.
2. The electroplating bath as claimed in claim 1 , wherein the concentration of Pt in the solution is 1 to 30 g/litre, on a metal basis.
3. The electroplating bath as claimed in claim 1 , wherein the pH of the solution is 8 to 14.
4. The electroplating bath as claimed in claim 1 , wherein the solution comprises a pH adjusting agent selected from the group consisting of ammonia, urea, an alkylammonium hydroxide, ammonium hydroxide, ammonium bicarbonate and ammonium carbonate.
5. The electroplating bath as claimed in claim 1 , wherein the content of alkali metals in the solution is less than 0.1 g/L.
6. A method of forming a metal layer on a substrate by electroplating, wherein electroplating is carried out using a bath comprising a cathode and an anode which are both at least partially submerged in an electrolyte, wherein the electrolyte is an aqueous electroplating solution comprising
[Pt(NH 3 ) 4 ] 2+ ions; and organic anions selected from the group consisting of bicarbonate, carbonate, or a mixture thereof;
wherein the molar ratio of Pt: (bicarbonate+carbonate) is approximately 1:2; and
wherein the following species, if present, are present in the following amounts:
alkali metals in an amount of less than 5 g/L;
compounds comprising phosphorus in an amount of less than 5 g/L;
compounds comprising boron in an amount of less than 5 g/L.
7. The method as claimed in claim 6 , wherein electroplating is carried out at a temperature of 80° C. or more.
8. The method as claimed in claim 6 , wherein electroplating is carried out at a temperature of 60 to 100° C. or more and a pH of 8 to 14.
9. The method as claimed in claim 6 , wherein the bath is replenished with fresh electroplating solution as required.
10. The method as claimed in claim 6 , wherein a pH adjusting agent is added to the bath as required.
11. The method as claimed in claim 6 , wherein the cathode provides the substrate to be coated.
12. The method as claimed in claim 6 , comprising a step of pausing electroplating and increasing the temperature of the electrolyte in order to purge the bath of residual organic anion.
13. The method as claimed in claim 6 , wherein the cathode acts as the substrate and is selected from jewellery, a medical component or an aviation component.
14. The method as claimed in claim 6 , wherein the concentration of Pt in the solution is 1 to 30 g/litre, on a metal basis.
15. The method as claimed in claim 6 , wherein the pH of the solution is 8 to 14.
16. The method as claimed in claim 6 , wherein the solution comprises a pH adjusting agent selected from the group consisting of ammonia, urea, an alkylammonium hydroxide, ammonium hydroxide, ammonium bicarbonate and ammonium carbonate.
17. The method as claimed in claim 6 , wherein the content of alkali metals in the solution is less than 0.1 g/L.