Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/62—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of gold
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/48—Electroplating: Baths therefor from solutions of gold

Definitions

• This invention has to do with the electrodeposition of gold and more specifically with the electrodeposition of bright gold.
• Bright gold deposits can be obtained from gold electrolytes containing alkali metal gold cyanide at a pH of about 3.0 to about 5.0 by adding base metal compounds such as nickel citrate, cobalt sulfate, etc., to the bath (see U.S. 2,905,601).
• base metal compounds such as nickel citrate, cobalt sulfate, etc.
• One theory explains that such baths produce bright gold because they provide the base metal in the cathode film in a condition to codeposit with the gold.
• the plating specification calls for 24 karat gold, in other cases the base metal present may be deleterious to a solidstate device to be gold plated.
• Among the objects of the invention is to provide a process and electroplating bath for electroplating bright 24 karat gold without the codeposition of other metals with the gold.
• This invention is based on the discovery that excellent bright gold deposits can be obtained by adding small amounts of piperazine or piperazine substitution compounds to acid electrolytes containing alkali metal gold cyanide even in the absence of codepositing metals.
• substituted piperazine will be understood to include those fairly simple substitution compounds obtained by substituting alkyl groups for one or more of the hydrogens of the piperazine ring so that the compound does not lose its essential piperazine characteristics.
• Conducting salts which are preferably alkali metal or ammonium salts may be added to said baths as such or may be formed in the bath by the addition of the corresponding hydroxide or carbonate, etc., to react with a portion of the acid of said baths.
• Such salts also provide efiective buiiering for the solution, especially when the acids employed are weak acids.
• Table I indicates the acid used, which in each case was neutralized to the pH listed with KOH or NaOH to provide the conducting and buffer salts (since the acids employed in these examples are weak acids).
• citric acid When citric acid is added as the acid preferably 5-150 g./I. is employed.
• Bright panels were obtained in all cases.
• the standard practice being to plate 10 x 2.5 cm. brass panels between two platinum cathodes in a liter beaker.
• Current densities from 0.1 to 5 amp./dm. were used, depending upon the temperature selected and the degree of agitation employed.
• Example 10 A bath containing potassium gold cyanide, 12 g./l.; copper ethylenediamine tetraacetate, 4 g./l.; antimony tartrate, 3 g./l.; potassium dihydrogen phosphate, 50 g./l.; and ethylenediamine tetraacetic acid, 20 g./l.; adjusted to a pH of 5.0, yielded deposits with a slight haze at 15 a.s.f. Upon the addition of dimethyl piperazine the deposits were fully bright.
• An electroplating bath for producing bright gold deposits comprising an aqueous solution of alkali metal gold cyanide and as a brightening agent a compound selected from the group consisting of piperazine and alkyl substituted piperazine in an amount sufficient to produce a bright gold deposit, said bath having a pH below about 6.0.
• An electroplating bath according to claim 1 comprising in addition a suflicient amount of conducting salts to substantially lower the voltage required for deposition of the gold.
• An electroplating bath according to claim 4 in which at least one conducting salt is a buffer and is present in an amount sufficient to maintain a stable pH.
• An electroplating bath according to claim 1 containing in addition base metal compounds of such a nature that at least one base metal is present in the cathode film in the condition necessary to co-deposit with the gold.
• An electroplating bath for producing bright gold deposits comprising an aqueous solution of an alkali metal gold cyanide, at least one water soluble compound selected from the class consisting of alkali metal and ammonium salts of organic and inorganic acids to provide a pH below about 6 and as a brightening agent a compound selected from the group consistinng of piperazine and alkyl substituted piperazine in an amount suflicient to produce a bright gold deposit.
• water-soluble compounds are the alkali metal and ammonium salts selected from the class of acids consisting of weak, stable, organic and inorganic acids.
• a method of electrodepositing bright gold which comprises electrolyzing an aqueous solution consisting essentially of a soluble alkali metal gold cyanide and piperazine in the amount of 0.5 to 5.0 grams per liter, said bath having a pH of about 3.0 to 6.0.
• a method of electrodepositing bright gold which comprises electrolyzing at a current density of 0.1 to 5 I amp./dm. an aqueous solution comprising soluble alkali metal gold cyanide and as a brightening agent a compound selected from the group consisting of piperazine and alkyl substituted piperazine in a amount sutficient to produce a bright gold deposit, said bath having a pH of about 3 to 6.
• a method as claimed in claim 14 wherein said added brightening agent is dimethyl piperazine.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

Family

ID=27013831

Family Applications (2)

Family Applications After (1)

Country Status (6)

Cited By (1)

Families Citing this family (1)

Citations (5)

• 1965
  • 1965-10-18 US US497454A patent/US3373094A/en not_active Expired - Lifetime
  • 1965-10-18 US US373094D patent/USB373094I5/en active Pending
• 1966
  • 1966-10-14 CH CH1487766A patent/CH468474A/fr unknown
  • 1966-10-17 DE DE19661521013 patent/DE1521013A1/de active Pending
  • 1966-10-18 FR FR976A patent/FR1497810A/fr not_active Expired
  • 1966-10-18 BE BE688412D patent/BE688412A/xx unknown
  • 1966-10-18 NL NL6614654A patent/NL6614654A/xx unknown

Patent Citations (5)

Also Published As

Similar Documents

Legal Events