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
  • C25D3/58—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of copper
• • 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

Definitions

• This invention relates to an electrolyte as well as a method for the electrolytic deposition of a gold-copper alloy on a substrate surface.
• alloy layers which can be varied in respect of their physical properties like brightness, hardness, wear resistance or colour. These properties are influenced by the composites of the alloys, e. g. the metals co-plated, as well as by the composition of the bath used for the deposition of the alloy, e. g. the electrolyte. Further, also the method and the plating parameters like temperature and current density are influencing the plating result in important ways.
• U.S. patent 5;006,208 discloses a galvanic gold alloying bath which contains beneath gold and copper in form of cyanide compounds a selenium compound.
• the deposit achieved from this galvanic bath is soft, light yellow and matt.
• the gold-alloy containing is constituted by 14 - 18 carat.
• European patent EP 0 384 679 B1 discloses a bath for the electrolytic deposition of gold-copper alloy as well as a method for electroplating articles using such a bath.
• An electrolyte is disclosed which contains gold in form of a cyanide compound, copper in the form of a cyanide compound as well as tellurium or bismuth in the form of water soluble compounds.
• European patent application 0 566 054 A1 discloses a solution for electroplating gold-copper alloys.
• an electrolyte comprising a soluble gold compound present as a gold cyanide complex, a soluble copper compound present as a copper cyanide complex as well as a soluble divalent sulfur compound in an amount sufficient to brighten the alloys.
• the brightening additive may be a thiocyanate, thiomalic acid, imidazolidinethione, a sulfite or thiobarbituric acid.
• an electrolyte for the electrolytic deposition of a gold-copper alloy on a substrate surface wherein the electrolyte comprises beneath a source of gold and copper potassium cyanide (KCN) in a concentration capable to maintain a copper to KCN ratio in the range of 3 to 7, and at least one complexing agent of the group consisting of ethylenediamine tetraacetic acid [EDTA], diethylenetriamine pentaacetic acid and nitrilo-triacetic acid [NTA] hydroxyethyl imino diacetic acid [HEIDA], nitrilo propionic diacetic acid [NPDA], imino diacetic acid [IDA], nitrilo trimethylphosphoric acid [NTMA, Dequest 2000], triethanol amine [TEA].
• EDTA ethylenediamine tetraacetic acid
• NDA nitrilo-triacetic acid
• HEIDA hydroxyethyl imino diacetic acid
• NPDA nitri
• the electrolyte according to the invention can comprise gold in a concentration between 2 to 20 g/I and copper in a concentration between 10 to 50 g/I.
• the at least one complexing agent of the group mentioned above is comprised in the inventive electrolyte in a concentration between 0,05 to 0,6 mol/l. It is believed that the strong chelating agents beneath functioning as complexing agent will contribute to the conductivity of the electrolyte.
• the inventive electrolyte may further comprise one of at least one metal of the group consisting of Sb, Se, Ag, Pt, Ni and Zn.
• selenium functions as brightener for the deposit. The same is true for tellurium and antimony.
• Zinc and nickel can function as grain refiner as well as stabilizer to the free KCN.
• Gold is believed to function as efficiency booster to yield in higher plating velocity and carat.
• the metals mentioned above can be comprised in the inventive electrolyte in an amount between 0,1 mg/l and 10 g/l. It is within the scope of the invention that the electrolyte can comprise further additive metals to influence the physical properties of the deposit.
• the inventive electrolyte can further comprise a surface active agent or wetting agent which will function as brightener.
• a capable surface active agent which can be comprised in the electrolyte is for example sodium-lauryl-etherphosphate.
• commercially available products known by name of nonionic, cationic, or amphoteric surfactants can be employed single or in combinations.
• the amount of the surface active agent in the inventive electrolyte may vary in a range of 0,1 ti 5 ml/l.
• the electrolyte can comprise secondary brightener and/or stabilizing agents.
• secondary brightener and/or stabilizing agents are pyridin sulfonic acid and ammonium hydrogene difluoride.
• the amount of these secondary brightener and/or stabilizing agents may vary in a range between 0,1 g/l to 10 g/l.
• the pH-value of the inventive electrolyte may vary in a range of pH 8 to pH 13, with a preferred pH-value of about 11.
• the inventive electrolyte may comprise alkaline hydroxide or alkaline earth hydroxide.
• the current density conducted between the substrate and the anode may vary in a range of 0,2 to 2 A/dm 2 .
• the temperature of the electrolyte is in the range of 70° C to 90° C.
• the inventive electrolyte together with the inventive method permits to produce a large range of carat suitable for plating and electroforming producing accurate value of carat between 18 and 14.
• the value of carat can be controlled by measurement of efficiency in Mg/A.nm. According to the relationship of temperature and current density disclosed above, the right efficiency for an adequate value of carat is obtained by tuning the current density and temperature respectively.
• a further advantage of the deposit yield by the inventive electrolyte and the inventive method is the possibility to heat-treat the deposited alloys in order to get an optimum ductility for a gold alloy. This is advantageously for both decorative and functional applications.
• heat-treating the alloys deposited a relatively high hardness is achieved. Relatively high in these terms means higher than that of the metallurgical alloy.
• the hardness rises from 280 HV to 380 HV while the aspect of surface isn't changed by oxidation.
• a further advantage of the deposits obtained from the inventive electrolyte is the good solder ability of the alloys. This characteristic is especially important in electroforming when it is necessary to close holes done to empty the mandrels and for further artistic work.
• the electrolyte Due to the strong complexing power of the complexing agent used according to this invention, the electrolyte is relatively none-sensitive to possible contaminations from various metals like Sn, Zn, Ag, Ni or Cr coming from different sources like drag ins from pre-treatment, mandrels composition or replenishment products. Generally, such types of contamination create an instability of the relation between current density and efficiency which may cause problems during electroforming processes. So, the non-sensity of the electrolyte to this contaminations is a further advance of this invention.
• gold-copper alloy deposits on substrate surfaces are obtainable showing a thickness of > 20 microns and a carat in the range of 12 to 19 carat.
• gold-copper alloy deposits on substrate surfaces are obtainable showing a thickness of > 20 microns and a carat in the range of 12 to 19 carat.
• electroforming at a thickness of 200 microns and more is possible.
• inventive electrolyte is also of high economic interest since it shows a minimum turn-over of 0,25 kg/l.

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• 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)

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• 2007
  • 2007-04-19 EP EP07007963.7A patent/EP1983077B1/fr not_active Ceased
  • 2007-04-19 EP EP16197251.8A patent/EP3170924A1/fr not_active Withdrawn
• 2008
  • 2008-04-21 CN CN2008100934716A patent/CN101289756B/zh not_active Expired - Fee Related

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