Preparation of metal substrate surfaces for electroplating in ionic liquids

Patent metadata

Field	Value
Publication number	US-9758888-B2
Application number	US-201414271371-A
Country	US
Kind code	B2
Filing date	May 6, 2014
Priority date	May 6, 2014
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Metal surface pretreatments using ionic liquids prior to electroplating are disclosed. The surface treatments include forming an activated metal substrate surface by removing any naturally formed metal oxide layers formed on the surfaces of the metal substrates. According to some embodiments, the surface treatments include exposing the metal substrate to a non-aqueous ionic liquid. In some embodiments, an electrical current is applied to the metal substrate to assist removal of the metal oxide layer. The electrical current can be a pulsed anodic current. After activating the surface, a metal layer can be deposited on the activated surface. In some embodiments, the metal layer is electrodeposited in the same ionic liquid used to form the activated surface. The resultant metal coating is resistant to scratching and peeling.

First claim

What is claimed is:

1. A method of depositing an aluminum metal layer on a surface of an aluminum alloy substrate having an aluminum oxide layer, the method comprising:
while the aluminum alloy substrate is immersed in an ionic liquid:
activating the surface of the aluminum alloy substrate by removing a portion of the aluminum oxide layer by:
(i) applying only a positive current to the aluminum alloy substrate, and
(ii) applying a series of current pulses including an anodic pulse and a reverse pulse to the aluminum alloy substrate; and

forming the aluminum metal layer by electro-depositing aluminum metal on the activated surface of the aluminum alloy substrate.

2. The method of claim 1 , wherein the reverse pulse includes using a current density ranging between about −50 mA/cm 2 and about −400 mA/cm 2 , and the anodic pulse includes using a current density ranging between about 50 mA/cm 2 and about 400 mA/cm 2 .

3. The method of claim 2 , wherein the reverse pulse is applied for at least the same time period as the anodic pulse.

4. The method of claim 1 , wherein the aluminum metal layer is an aluminum alloy layer composed of greater than 50 percent by weight of aluminum.

5. The method of claim 1 , wherein the ionic liquid includes a manganese compound such that manganese is co-deposited with aluminum to form an aluminum alloy layer.

6. The method of claim 1 , wherein the anodic pulse includes using a current density of about −240 mA/cm 2 , and the reverse pulse includes using a current density of about 120 mA/cm 2 .

7. The method of claim 6 , wherein a current density amplitude of the anodic pulse is greater than a current density amplitude of the reverse pulse.

8. The method of claim 1 , wherein a duration of each of the anodic and reverse pulses ranges between about 5 milliseconds and about 50 milliseconds.

9. The method of claim 1 , wherein the aluminum metal layer is substantially free of copper, the method further comprising converting at least a portion of the aluminum metal layer to an oxide layer in an anodizing solution that is substantially free of copper.

10. The method of claim 1 , wherein the series of current pulses is applied metal over a period of time of around 5 minutes.

11. The method of claim 1 , further comprising anodizing the aluminum metal layer.

12. The method of claim 1 , wherein the aluminum metal layer has a thickness ranging between about one micrometer and about 50 micrometers.

13. A method of depositing an aluminum alloy layer on a surface of an aluminum alloy substrate, the method comprising:
activating the surface of the aluminum alloy substrate by immersing the aluminum alloy substrate within an ionic liquid configured to remove at least a portion of a metal oxide layer formed on the aluminum alloy substrate, wherein the activating includes: applying only a positive current to the aluminum alloy substrate, and applying an anodic pulse and a reverse pulse to the aluminum alloy substrate, wherein a current density amplitude of the anodic pulse is greater than a current density amplitude of the reverse pulse; and
depositing the aluminum alloy layer on the activated surface using an electrodeposition process while the aluminum alloy substrate is immersed within the ionic liquid.

14. The method of claim 13 , wherein the reverse pulse includes using a current density ranging between about −50 mA/cm 2 and about −400 mA/cm 2 , and the anodic pulse includes using a current density ranging between about 50 mA/cm 2 and about 400 mA/cm 2 .

15. The method of claim 13 , further comprising converting at least a portion of the aluminum alloy layer to an aluminum oxide using an anodizing solution, wherein the anodizing solution is substantially free of copper.

16. The method of claim 13 , wherein the ionic liquid includes an alloy metal that is co-deposited with aluminum to form the aluminum alloy layer.

17. The method of claim 16 , wherein the alloy metal is manganese.

Assignees

• Xtalic Corp
• Apple Inc

Inventors

• Freydina Evgeniya
• Ruan Shiyun
• Schuh Christopher A
• Lund Alan C

Classifications

• C25D5/44

  Aluminium · CPC title

• C25F1/04

  in solution · CPC title

• Y10T428/1259

  Oxide · CPC title

• C25D5/48

  After-treatment of electroplated surfaces · CPC title

• C25F1/12

  in melts · CPC title