Compositions and Methods for Electrodepositing Tin-Bismuth Alloys on Metallic Substrates

Patent metadata

Field	Value
Publication number	US-2020032409-A1
Application number	US-201816045211-A
Country	US
Kind code	A1
Filing date	Jul 25, 2018
Priority date	Jul 25, 2018
Publication date	Jan 30, 2020
Grant date	—

Abstract

A method for depositing a tin-bismuth alloy on a substrate, the method including steps of (1) immersing the substrate and an anode in an electrolyte solution that includes water, a stannous salt, a bismuth salt, and at least one of sulfuric acid and sulfamic acid, the anode including tin and, optionally, bismuth, and (2) passing an electric current between the substrate and the anode to form a deposit on the substrate.

First claim

What is claimed is:

1 . An electrolyte solution comprising:
water; a stannous salt; a bismuth salt; and at least one of sulfuric acid and sulfamic acid.

2 . The electrolyte solution of claim 1 wherein the stannous salt comprises at least one of stannous sulfate, stannous chloride and stannous fluoride.

3 . The electrolyte solution of claim 1 wherein the stannous salt comprises stannous sulfate.

4 . The electrolyte solution of claim 1 wherein the stannous salt is present at a concentration ranging from about 15 grams per liter to about 200 grams per liter, based on a total volume of the electrolyte solution.

5 . The electrolyte solution of claim 1 wherein the stannous salt is present at a concentration ranging from about 20 grams per liter to about 100 grams per liter, based on a total volume of the electrolyte solution.

6 . The electrolyte solution of claim 1 wherein the bismuth salt comprises at least one of bismuth sulfate, bismuth oxide, bismuth nitrate, bismuth chloride and bismuth trifluoride.

7 . The electrolyte solution of claim 1 wherein the bismuth salt comprises bismuth sulfate.

8 . The electrolyte solution of claim 1 wherein the bismuth salt is present at a concentration ranging from about 0.25 grams per liter to about 10 grams per liter, based on a total volume of the electrolyte solution.

9 . The electrolyte solution of claim 1 wherein the bismuth salt is present at a concentration ranging from about 0.4 grams per liter to about 4 grams per liter, based on a total volume of the electrolyte solution.

10 . The electrolyte solution of claim 1 wherein the at least one of sulfuric acid and sulfamic acid is present at a concentration ranging from about 50 milliliters per liter to about 150 milliliters per liter, based on a total volume of the electrolyte solution.

11 . The electrolyte solution of claim 1 wherein the at least one of sulfuric acid and sulfamic acid is present at a concentration ranging from about 75 milliliters per liter to about 125 milliliters per liter, based on a total volume of the electrolyte solution.

12 . The electrolyte solution of claim 1 comprising stannous sulfate, bismuth sulfate and sulfuric acid.

13 . The electrolyte solution of claim 1 further comprising at least one of a surfactant, methacrylic acid and dipropylene glycol methyl ether.

14 . A method for manufacturing the electrolyte solution of claim 1 , the method comprising:
mixing the at least one of sulfuric acid and sulfamic acid with at least a portion of the water to yield an acidic solution; dissolving the stannous salt in the acidic solution; and dissolving the bismuth salt in the acidic solution.

15 . An electrodeposition system comprising:
a current source having a first terminal and a second terminal; a bath comprising the electrolyte solution of claim 1 ; a substrate immersed in the electrolyte solution, the substrate being electrically coupled with the first terminal of the current source; and an anode comprising tin, the anode being immersed in the electrolyte solution and being electrically coupled with the second terminal of the current source.

16 . The electrodeposition system of claim 15 wherein the anode further comprises bismuth.

17 . The electrodeposition system of claim 15 wherein the anode further comprises about 2 percent by weight to about 5 percent by weight bismuth, and wherein the substantial balance of the anode is the tin.

18 . A method for depositing a tin-bismuth alloy on a substrate, the method comprising:
immersing the substrate and an anode in the electrolyte solution of claim 1 , the anode comprising tin; and passing an electric current between the substrate and the anode to form a deposit on the substrate.

19 . The method of claim 18 wherein the anode further comprises about 2 percent by weight to about 5 percent by weight bismuth, and wherein the substantial balance of the anode is the tin.

20 . The method of claim 18 wherein the electric current has a current density of about 10 amperes per square foot to about 50 amperes per square foot, based on a surface area of the substrate.

21 . The method of claim 18 wherein the electric current has a current density of about 15 amperes per square foot to about 30 amperes per square foot, based on a surface area of the substrate.

22 . The method of claim 18 wherein the electric current is passed for a duration of time, and wherein the duration of time is between about 5 minutes to about 120 minutes.

23 . The method of claim 18 wherein the electric current is passed for a duration of time, and wherein the duration of time is between about 10 minutes to about 20 minutes.

24 . The method of claim 18 further comprising activating the substrate prior to the immersing and the passing.

25 . The method of claim 24 wherein the activating comprises immersing the substrate into an activation solution for a predetermined period of time, the activation solution comprising water, an ammonium salt comprising a fluorine-containing anion, and sulfuric acid.

26 . The method of claim 24 wherein the activating comprises immersing the substrate into an activation solution for a predetermined period of time, the activation solution comprising water, a fluoride salt, hydrofluoric acid, and sulfuric acid.

27 . The method of claim 24 wherein the activating comprises subjecting the substrate to an anodic sulfuric acid process.

28 . The method of claim 18 further comprising strike plating the substrate prior to the immersing and the passing.

29 . The method of claim 28 wherein the strike plating comprises nickel strike plating.

30 . The method of claim 28 wherein the strike plating comprises:
immersing the substrate and a nickel anode in a strike plating electrolyte solution comprising nickel chloride, hydrochloric acid, and water; and
passing an electric current between the substrate and the nickel anode.

31 . The method of claim 30 wherein the strike plating electrolyte solution comprises:
about 100 grams per liter to about 300 grams per liter of the nickel chloride, based on total volume of the strike plating electrolyte solution; and
about 50 milliliters per liter to about 250 milliliters per liter of the hydrochloric acid, based on total volume of the strike plating electrolyte solution.

Assignees

• Boeing Co

Inventors

• Subramaniaraja Sakurjayaram R
• Brondo Edgardo Reyes

Classifications

• C25D5/38

  of refractory metals or nickel · CPC title

• C25D3/60 Primary

  containing more than 50% by weight of tin · CPC title

• C25D17/10

  Electrodes {, e.g. composition, counter electrode} · CPC title