Silver Coated Copper Flakes and Methods of Their Manufacture

Patent metadata

Field	Value
Publication number	US-2018264548-A1
Application number	US-201615542174-A
Country	US
Kind code	A1
Filing date	Jan 6, 2016
Priority date	Jan 9, 2015
Publication date	Sep 20, 2018
Grant date	—

Abstract

Compositions having copper flakes coated with silver, where the silver is present as a hermetically closed metal shell around the copper, are described. The hermetically closed metal shell can limit oxidation of copper for at least 365 days at a temperature of less than 100° C. The composition can also contain palladium in an amount of about 1% or less by weight of silver in the shell. Palladium limits the migration of copper from the core flakes to the silver shell at temperatures below 250° C. Methods of manufacturing copper flakes coated can include the steps of treating copper flakes with an acid to form acid treated copper flakes, treating the acid treated copper flakes with a polyamine to form polyamine treated copper flakes, depositing silver on the polyamine treated copper flakes to form copper flakes comprising silver deposits, and depositing silver onto the copper flakes comprising silver deposits.

First claim

1 . A composition comprising one or more copper flakes coated with silver, wherein the silver is present in a hermetically closed metal shell around the copper.

2 . The composition of claim 1 , wherein the grain size of silver in the deposited layer is about 40 nm or less, as measured by Field Emission Scanning Electron Microscopy (FESEM).

3 . The composition of claim 1 , wherein the grain size of silver in the deposited layer is about 15 nm or less, as measured by Field Emission Scanning Electron Microscopy (FESEM).

4 . The composition of claim 1 , further comprising palladium in an amount of about 1 % or less by weight of silver in the shell.

5 . The composition of claim 1 , wherein the hermetically closed metal shell limits the oxidation of copper over a period of at least 365 days at a temperature of less than 100° C.

6 . The composition of claim 1 , wherein the copper flakes do not oxidize until they reach a temperature of at least 200° C.

7 . The composition of claim 1 , wherein the hermetically closed metal shell limits the migration of copper from the core flakes to the silver shell at temperatures below 250° C.

8 . A method of manufacturing copper flakes coated with silver, the method comprising treating copper flakes with an acid to form acid treated copper flakes, treating the acid treated copper flakes with a polyamine to form polyamine treated copper flakes, depositing silver on the polyamine treated copper flakes to form copper flakes comprising silver deposits, and depositing silver onto the copper flakes comprising silver deposits wherein the polyamine is a mixture of linear polyamines with short and long chain lengths.

9 . The method of claim 8 , wherein the step of depositing silver on the polyamine treated copper flakes to form copper flakes comprising silver deposits is performed by electrodisplacement.

10 . The method of claim 8 , wherein the step of depositing silver onto the copper flakes comprising silver deposits is performed by electroless plating.

11 . The method of claim 10 , wherein the step of depositing silver onto the copper flakes comprising silver deposits by electroless plating uses a silver solution comprising a silver diamine complex.

12 . The method of claim 10 , wherein the step of depositing silver onto the copper flakes comprising silver deposits by electroless plating uses a sugar as a reducing agent.

13 . The method of claim 11 , wherein the step of depositing silver onto the copper flakes comprising silver deposits by electroless plating uses a sugar as a reducing agent.

14 . The method of claim 12 , wherein the sugar is dextrose or glucose.

15 . The method of claim 13 , wherein the sugar is dextrose or glucose.

16 . The method of claim 8 , wherein the polyamine is a mixture of triethylenetetramine (TETA) and ethylenediamine (EDA).

17 . The method of claim 10 , wherein the polyamine is a mixture of triethylenetetramine (TETA) and ethylenediamine (EDA).

18 . The method of claim 13 , wherein the polyamine is a mixture of triethylenetetramine (TETA) and ethylenediamine (EDA).

19 . The method of claim 16 , where the mixture of TETA/EDA is in a ratio 80/20 by weight.

20 . The method of claim 18 , where the mixture of TETA/EDA is in a ratio 80/20 by weight.

21 . The method of claim 8 , wherein the step of treating copper flakes with an acid to form acid treated copper flakes is performed in alcohol.

22 . The method of claim 8 , wherein the step of depositing silver on the polyamine treated flakes is performed in the presence of one or more dispersing agents.

23 . The method of claim 22 , wherein the dispersing agent comprises DAXAD 11D, Arabic gum, polyvinylpyrrolidone/PVP or sodium alginate.

24 . The method as claimed in claim 22 , wherein the step of depositing silver on the polyamine treated flakes is performed by adding an aqueous solution of silver salt to a mixture comprising the copper flakes, the polyamine and the dispersing agent.

25 . The method as claimed in claim 24 wherein the silver salt is silver nitrate.

26 . The method as claimed in claim 25 wherein the silver nitrate solution comprises 0.1 to 1.0% by weight palladium nitrate.

27 . The method as claimed in claim 10 wherein the electroless plating comprises adding solutions of silver ammonia and dextrose separately, but at the same time, to a mixture comprising the copper flakes comprising silver deposits.

28 . The method as claimed in claim 27 wherein the solutions of silver ammonia and dextrose are added to the mixture comprising the copper flakes comprising silver deposits over a period of about 2 hours at a temperature of approximately 75° C.

29 . The method as claimed in claim 8 which is a method of manufacturing copper flakes coated with silver wherein the grain size of the silver in the deposited layer is about 40 nm or less, as measured by Field Emission Scanning Electron Microscopy (FESEM).

30 . The method as claimed in claim 29 wherein the grain size of the silver in the deposited layer is about 15 nm or less, as measured by Field Emission Scanning Electron Microscopy (FESEM).

Assignees

• Univ Clarkson

Inventors

• Goia Dan V
• Goia Corina
• Njagi John I

Classifications

• B22F1/068

  Flake-like particles · CPC title

• B22F1/145

  Chemical treatment, e.g. passivation or decarburisation · CPC title

• B22F1/102

  Metallic powder coated with organic material · CPC title

• B22F1/17

  Metallic particles coated with metal · CPC title

• H01B1/026

  Alloys based on copper · CPC title