Abstract This disclosure relates to a method for preparing alkali metal gold cyanide which has been found to be particularly useful in gold electroplating operations in the semiconductor industry in order to provide electrical contacts to semiconductor devices. In the process, finely divided gold metal particles are reacted with hydrogen peroxide and alkali metal cyanide to produce univalent alkali metal gold cyanide. The alkali metal gold cyanide is then acidified with a mineral acid in order to precipitate out gold cyanide. The gold cyanide is subsequently removed by filtration, washed and redissolved in a solution of alkali metal cyanide thereby yielding the final alkali metal gold cyanide end product in its pure state.
A method for converting finely divided gold particles into an aqueous electroplating solution of pure alkali metal gold cyanide which comprises: reacting said gold particles with hydrogen peroxide and alkali metal cyanide to provide a reaction mixture comprising alkali metal gold cyanide and soluble inorganic by-products; acidifying said reaction mixture with a mineral acid to provide insoluble gold cyanide; removing said soluble gold cyanide from the reaction mixture; and reacting said insoluble gold cyanide with alkali metal cyanide to produce alkali metal gold cyanide.
Claim 2
Independent Claim
84 words
A method for converting finely divided gold particles into an aqueous electroplating solution of pure alkali metal gold cyanide which comprises: reacting said gold particles with hydrogen peroxide and alkali metal cyanide to provide a reaction mixture comprising alkali metal gold cyanide and soluble inorganic by-products; acidifying said reaction mixture with a mineral acid to provide insoluble gold cyanide; removing said soluble gold cyanide from the reaction mixture; and reacting said insoluble gold cyanide with alkali metal cyanide to produce alkali metal gold cyanide.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein potassium gold cyanide is provided by employing potassium cyanide as the alkali metal cyanide.
Claim 4
Dependent Claim
31 words
The method of claim 2 wherein said reaction of gold particles with hydrogen peroxide and alkali metal cyanide is carried out at a temperature between about 55° and about 65° C.
Claim 5
Dependent Claim
14 words
The method of claim 3 wherein sulfuric acid is employed as the mineral acid.
Claim 6
Dependent Claim
35 words
The method of claim 1 wherein said gold particles are reacted with stoichiometric excesses of hydrogen peroxide and alkali metal cyanide to provide the reaction mixture comprising alkali metal gold cyanide and soluble inorganic by-products.