Micro-Arc Assisted Electroless Plating Methods

• US 20090223829A1
• Filed: 12/20/2006
• Published: 09/10/2009
• Est. Priority Date: 12/20/2005
• Status: Abandoned Application

• Current Assignee: Auckland UniServices Limited (Auckland University)
• Original Assignee: Auckland UniServices Limited (Auckland University)
• Inventors: Liu, Zhenmin, Gao, Wei
• Application Number:
  US12/158,535
• Publication Number:
  US 20090223829A1
• Time in Patent Office: Days
• US Class Current: 205/200
• CPC Class Codes: C23C 18/1834 Use of organic or inorganic compounds other than metals, e.g. activation, sensitisation with polymers
• CPC Class Codes: C23C 18/1848 by electrochemical pretreatment
• CPC Class Codes: C23C 18/32 Coating with nickel, cobalt or mixtures thereof with phosphorus or boron C23C18/50 takes precedence
• CPC Class Codes: C23C 18/36 using hypophosphites
• CPC Class Codes: C25D 11/026 Anodisation with spark discharge
• CPC Class Codes: C25D 11/04 of aluminium or alloys based thereon
• CPC Class Codes: C25D 11/18 After-treatment, e.g. pore-sealing
• CPC Class Codes: C25D 11/26 of refractory metals or alloys based thereon
• CPC Class Codes: C25D 11/30 of magnesium or alloys based thereon
• CPC Class Codes: C25D 11/34 of metals or alloys not provided for in groups C25D11/04 - C25D11/32

Abstract

A method for electorless plating of a substrate such as magnesium, aluminium, titanium or an alloy, comprises the steps of forming a very thin film of oxide on the substrate by plasma electrolytic oxidation before depositing a layer comprising nickel on the substrate by electroless nickel deposition.

Claims

1. A method for electroless plating of a substrate comprising the steps of:

forming a layer of oxide on the substrate by plasma electrolytic oxidation (PEO), and depositing a layer comprising nickel on the substrate by electroless nickel (EN) deposition.

2. A method according to claim 1 wherein the substrate is selected from magnesium, aluminium, titanium and their alloys, and iron alloys.

3. A method according to claim 1 wherein the substrate consists essentially of magnesium, a magnesium alloy, aluminium, an aluminium alloy, titanium, or a titanium alloy.

4. A method according to claim 1 wherein the substrate is magnesium or a magnesium alloy.

5. A method according to claim 1 wherein the substrate is copper or a copper alloy.

6. A method according to claim 1 comprising carrying out PEO to a voltage between electrodes up to about 450 Volts.

7. A method according to claim 1 comprising carrying out PEO for a time of at least two minutes.

8. A method according to claim 1 comprising carrying out PEO for a time of up to 10 minutes.

9. A method according to claim 1 comprising carrying out PEO with a current density of up to about 1000 A/m⁻

2.

10. A method according to claim 1 comprising carrying out PEO at an electrolyte temperature at or below about 45°

C.

11. A method according to claim 1 comprising carrying out PEO at an concentration of major electrolyte constituents of up to 5 g/litre.

12. A method according to claim 1 comprising carrying out PEO in an electrolyte which includes phosphate ions.

13. A method according to claim 1 comprising carrying out PEO to form said layer of oxide as a very thin film of oxide on the substrate.

14. A method according to claim 1 wherein depositing a layer which includes nickel on the substrate by EN deposition comprises depositing a layer of substantially pure nickel metal on the substrate.

15. A method according to claim 1 comprising carrying out EN deposition in an electrolyte which includes nickel sulphate as a nickel source.

16. A method according to claim 1 comprising carrying out EN deposition in an electrolyte which includes nickel carbonate as a nickel source.

17. A method according to claim 1 comprising depositing a layer comprising nickel deposition by EN at an electrolyte pH of between about 4.5 and about 8.

18. A method according to claim 1 comprising depositing a layer comprising nickel deposition by EN at an electrolyte pH of between about 6 and about 8.

19. A method according to claim 1 comprising depositing a layer comprising nickel by EN deposition at an electrolyte temperature of about 80°

C.

20. A method according to claim 1 also including chemically depositing metal onto the substrate between the PEO and the EN deposition.

21-23. -23. (canceled)

24. A method for electroless plating of a substrate which consists essentially of magnesium, a magnesium alloy, aluminium, and aluminium alloy, titanium or a titanium alloy, comprising the steps of forming a very thin film of oxide on the substrate by plasma electrolytic oxidation (PEO), and depositing a layer comprising nickel on the substrate by electroless nickel (EN) deposition in an electrolyte which includes nickel sulphate or nickel carbonate as a nickel source.

25-28. -28. (canceled)