Photochemical reduction of Fe(III) for electroless or electrodeposition of iron alloys
View Patent ↗A method of photochemically reducing iron(III) species in an iron or iron alloy plating solution by adding an additive to the electroplating solution; contacting the additive with iron(III) species to form an iron(III)-additive species; and irradiating the electroplating solution, wherein the radiation is of sufficient energy to reduce the iron(III) in the iron(III)-additive species to iron(II). The additive comprises hydroxycarboxylic acids and their lactones.
1. A method of photochemically reducing iron(III) species in an iron or iron alloy electroplating solution comprising:
adding an additive to the electroplating solution;
contacting the additive with an iron(III) species to form an iron(III)-additive species; and
irradiating the electroplating solution, wherein the radiation is of sufficient energy to reduce the iron(III) in the iron(III)-additive species to iron(II),
wherein the additive is saccharic acid or a salt or lactone thereof.
2. The method according to claim 1 , wherein irradiating the electroplating solution oxidizes the additive.
3. The method according to claim 2 , further comprising adding the additive to the electroplating solution to replace the oxidized additive.
4. The method according to claim 1 , wherein the additive is air stable.
5. The method according to claim 1 , wherein the pH of the electroplating solution is less than about 7.
6. The method according to claim 5 , wherein the pH of the electroplating solution is less than about 5.
7. The method according to claim 6 , wherein the pH of the electroplating solution is less than about 3.5.
8. The method according to claim 7 , wherein the pH of the electroplating solution is less than about 3.1.
9. The method according to claim 1 , wherein the salt is a monopotassium salt of saccharic acid.
10. A method of electroplating iron or an iron alloy onto a substrate in an electroplating cell comprising:
contacting a substrate with an electroplating solution, wherein the electroplating solution comprises:
iron present as iron(II) and iron(III) species, and
an additive to substantially limit the concentration of the iron(III) species in the electroplating solution, wherein the additive is saccharic acid or a salt or lactone thereof;
applying a voltage across an anode and a cathode in contact with the electroplating solution in an electroplating cell;
irradiating the electroplating solution; and
depositing the iron or iron alloy onto the substrate.
11. The method according to claim 10 , wherein the concentration of the iron(III) species is substantially limited by its contact with the additive to form an iron(III)-additive species.
12. The method according to claim 11 , wherein the irradiating comprises exposing the electroplating solution to radiation of sufficient energy to reduce the iron(III) present in the iron(III)-additive species to iron(II).
13. The method according to claim 12 , wherein the irradiating oxidizes the additive.
14. The method according to claim 13 , further comprising a step of adding the additive to the electroplating solution to replace the oxidized additive.
15. The method according to claim 10 , wherein the additive is air stable.
16. The method according to claim 10 , wherein the pH of the electroplating solution is less than about 7.
17. The method according to claim 16 , wherein the pH of the electroplating solution is less than about 5.
18. The method according to claim 17 , wherein the pH of the electroplating solution is less than about 3.5.
19. The method according to claim 18 , wherein the pH of the electroplating solution is less than about 3.1.
20. The method according to claim 10 , wherein the salt is a monopotassium salt of saccharic acid.