Gold electroplating solution and method

Patent metadata

Field	Value
Publication number	US-10570525-B2
Application number	US-201614996412-A
Country	US
Kind code	B2
Filing date	Jan 15, 2016
Priority date	Jan 16, 2015
Publication date	Feb 25, 2020
Grant date	Feb 25, 2020

Abstract

A gold electroplating solution includes a gold (III) cyanide compound, a chloride compound, and hydrochloric acid. The gold (III) cyanide compound is potassium gold (III) cyanide, ammonium gold (III) cyanide, or sodium gold (III) cyanide. The chloride compound is potassium chloride, ammonium chloride, or sodium chloride. Various structures may be made with the gold electroplating solution having a gold layer deposited directly on the stainless steel (SST) layer using a photolithography process. Such structures include a gold pattern having a discontinuous pattern, a bond pad region having one or more traces on the opposite side of the dielectric layer, a gimbal having gold bond pads, and a bonding joint having an electrical interface including a gold layer.

First claim

The invention claimed is:

1. A method of producing an electrodeposited gold pattern directly onto a stainless steel surface, the method comprising:
creating a photoresist pattern on the stainless steel surface;
cleaning portions of the stainless steel surface not covered by the photoresist pattern;
immersing the stainless steel surface in a gold electroplating solution, wherein the gold electroplating solution includes:
a gold (III) cyanide compound,
wherein the gold (III) cyanide compound consists of ammonium gold (III) cyanide;
a chloride salt, the chloride salt consists of ammonium chloride;
hydrochloric acid, wherein the hydrochloric acid is supplied in a sufficient amount such that the gold electroplating solution has a pH between about 0 and about 1, and
wherein the gold electroplating solution is free of oxidizing acids and nitrate salts; and
applying a voltage between an anode within the gold electroplating solution and the stainless steel surface to generate a current from the anode to the stainless steel surface to electroplate gold from the gold electroplating solution onto the stainless steel surface.

2. The method of claim 1 , further comprising adding sufficient hydrochloric acid to the gold electroplating solution such that the gold electroplating solution has a pH between about 0.7 and about 0.9.

3. The method of claim 1 , further comprising maintaining a concentration of ammonium gold (III) cyanide in the gold electroplating solution between about 1.0 grams of gold per liter of solution and 3.0 grams of gold per liter of solution, and maintaining a concentration of chloride anions in the gold electroplating solution between about 0.30 moles per liter of solution and 0.60 moles per liter of solution.

4. The method of claim 3 , further comprising maintaining a concentration of ammonium gold (III) cyanide in the gold electroplating solution between about 1.8 grams of gold per liter of solution and 2.2 grams of gold per liter of solution, and maintaining a concentration of chloride anions in the gold electroplating solution between about 0.45 moles per liter of solution and 0.55 moles per liter of solution.

5. The method of claim 1 , wherein cleaning the stainless steel surface includes an oxygen plasma cleaning process.

6. The method of claim 1 , wherein the voltage generates a continuous direct current, and wherein the continuous direct current produces a current density at the stainless steel surface of between 1 ampere per square decimeter and 40 amperes per square decimeter.

7. The method of claim 1 , wherein the voltage generates a pulsed direct current.

8. The method of claim 7 , where the pulsed direct current produces a time averaged current density at the stainless steel surface of between 1 ampere per square decimeter and 40 amperes per square decimeter.

9. The method of claim 1 , wherein the stainless steel surface is one selected from the group consisting of a disk drive head suspension, an optical image stabilization suspension, and a medical device.

10. The method of claim 1 , wherein the gold electroplating solution is free of ethylenediamine hydrochloride.

Assignees

• Hutchinson Technology

Inventors

• Swanson Kurt C
• Riemer Douglas P
• Fank Steven A

Classifications

• C25D5/36

  of iron or steel · CPC title

• C25D3/48 Primary

  of gold · CPC title

• C25D5/02

  Electroplating of selected surface areas · CPC title

• C25D7/00

  Electroplating characterised by the article coated · CPC title

• C25D5/18

  Electroplating using modulated, pulsed or reversing current · CPC title