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
  • C25D3/38—Electroplating: Baths therefor from solutions of copper

Definitions

• the present invention relates to electrolytic deposition of copper from acid electrolytes. More particularly, this invention relates to new and improved electrolytes for use in the electrorefining of copper which will promote smoother and more efiicient plating and to new and improved additive agents to be introduced therein.
• purified cathode copper is obtained by passing an electric current from an impure copper anode through an aqueous acid electrolyte to a pure copper cathode.
• the copper dissolves from the anode and is deposited on the cathode in purified form.
• additives it has been found to be highly advantageous to introduce additives into the electrolyte in order to promote the formation of a smoth, dense deposit of copper on the cathode. Without these additive agents, the copper deposits on the cathode are soft, coarsely crystalline and prone to develop into nodules or trees.
• Another object is to provide new and improved additive agents for copper electrodeposition electrolytes which will improve the quality and physical characteristics of the cathode electrodeposits in the electrorefining of copper.
• An additional object is to provide a new and improved combination of additive agents for use in electrodepositing copper from an aqueous electrolyte which will control the deposition of copper and increase cathode polarization and thus provide electrolytically pure cathode copper which is smooth, dense and substantially nodule-free.
• the method of this invention involves a procedure whereby very pure cathode copper is obtained by electrodeposition techniques and whereby the formation of nodules or trees on the cathode is essentially eliminated.
• Lignosulfonate materials added alone to electrodeposition baths produce a rough cathode deposit with heavy nodules.
• nitrogen compounds and lignosulfonates an outstandingly better copper deposit was produced which was smooth, dense and essentially nodule free.
• quaternary ammonium salts to be employed herein may be represented by the following structural formula:
• R, R R and R are independently selected from the group consisting of alkyl and aryl radicals con taining from 1 to 20 carbon atoms, at least one of the R, R R and R must contain a minimum of 8 carbon atoms, and A- is an inconsequential anion such as Cl, Br: OH and the like.
• Typical quaternary ammonium salts of this class are:
• methyldodecyl-benzyl trimethyl ammonium chloride methyldodecyl xylylene bis (trimethyl ammonium chloride) n-alkyl (C14, C C dimethyl benzyl ammonium chloride p-diisobutyl phenoxy ethoxy benzyl ammonium chloride ethyl hexadecyl dimethyl ammonium bromide diisobutyl-cresoxy-ethoxy ethyl dimethyl benzyl ammonium chloride (or hydroxide) soya trimethyl ammonium chloride 1 di-polyoxyethylene stearyl methyl ammonium chloride octadecyl trimethyl ammonium chloride coco trimethylquaternary ammonium chloride di-hydrogenated tallow dimethyl quaternary ammonium chloride cottonseed trimethyl quaternary ammonium chloride In the above listing of quaternary amomnium salts which may suitably
• polyethylene amines to be employed herein are high molecular weight polyethylene polyamines (also known as polyethylene imines) and may be represented by the following structural formula:
• the polyethylene polyamines to be utilized herein may be characterized as having relative viscosities of at least 1.25 (measured in aqueous solution at C. in comparison with water using a No. 100 Cannon-Fenske viscometer) with a preferred range of from about 1.25 to about 3.00.
• the lignosulfonate component of the additive agent can be lignosulfonate-containing residue from the acid sulfite pulping of wood either in crude form containing wood sugars or in substantially sugar-free refined form, for example, as prepared by the process described in U.S. Pat. No. 3,271,382.
• a lignocellulose material such as wood is generally cooked in a solution of sulfurous acid, part of the sulfurous acid being combined as bisulfite.
• the cation assosciated with the bisulfite ion is generally known as the pulping base. Pulping base cations normally used include sodium, calcium, ammonium, magnesium and the like.
• the spent cooking liquors In acid sulfite pulping of conifer woods, the spent cooking liquors, irrespective of the base used contain approximately 65% lignosulfonates, 25% wood sugars and 10% inorganic salts and miscellaneous lay-products.
• the spent sulfite liquors may be used as such but for economic purposes, the liquor will usually be concentrated to at least about 40-50% concentration. More conveniently, such concentrated liquors would be dried to form water-soluble powders, to facilitate shipment and storage, by a suitable drying process such as spray drying, drum drying and the like.
• the term lignosulfonate covers both dried liquor solids and never-dried spent sulfite liquors.
• the concentration of additive agent to be introduced into any given electrofining bath will vary considerably depending on such factors as the impurities from the impure copper anode present in the electrolyte, the composition of the electrolyte, the temperature of the electrolyte, the current density and the like.
• the ammonium compound and the lignosulfonate should be added separately to the standard acid copper electrolyte in amounts sufficient to provide concentrations therein of from about 0.5 to about 10 milligrams ammonium compound and about -100 milligrams of lignosulfonate per liter of electrolyte, and more preferably about 0.6-1.8 mg.
• ammonium compound and about 50 mg. lignosulfonate per liter of electrolyte When a polyethylene amine is used in conjunction with a lignosulfonate material it is usually preferred to prepare an aqueous solution of both components in the ratio of about 1 part polyethylene amine to about 250 parts lignosulfonate and then dried to form a convenient condensate powder. This condensate powder can then be dissolved in an acid copper electrolyte in a sufficient amount to provide a concentration of about 0.1 to about 0.3 mg. polyethylene amine and about 30- 100 mg. lignosulfonate per liter of electrolyte, and more preferably about 0.18-0.20 mg. polyethylene amine and mg. lignosulfonate per liter of electrolyte.
• the lignosulfonate compone of the additive agent should be introduced into the electrolyte in a concentration about 20 to times that of the quaternary ammonium compound when that component is employed in conjunction with the lignosulfonate, and about 250 times that of the high molecular weight polyethylene polya'mine when such an amine is a component of the additive agent.
• EXAMPLE I A series of copper electrodepositiontests were conducted to determine the effectiveness of the additive agents of the present invention. The tests were conducted under the following electrodeposition conditions which were held constant for all the samples tested:
• the electrolytic apparatus was set up in the same manner for each sample tested. For each sample to be tested, a 32 oz. jar was utilized. The jars were placed in a constant temperature bath. Each jar was equipped with holders for tWo anodes and a cathode, a vertical reciprocating stirring device and a D.C. regulated current supply. The two anodes were positioned one on each side of the oathode and each anode was spaced one inch from the cathode. Prior to testing, the copper anodes and the cathodes were washed 24 hours in carbon tetrachloride for degreasing and the cathodes were pickled one hour in a 5% sulfuric acid chromerge solution. The copper sheet used was electrolytic refined copper.
• the basic electrolyte introduced into each of the jars was prepared from Bakers Analytical Grade cu ric sulfate pentahydrate g./l.), C. P. sulfuric acid (125 g./l.) and hydrochloric acid (10 mg/l.).
• the particular additive agent under test was added to the electrolyte in a given jar and the effect of the additive agent on the electrodeposition of copper was determined by visual observation of the plating at the cathode. The results of this testing are tabulated in the following table:
• the additive agents employed were lignosulfonate materials and quaternary ammonium compounds.
• the lignosulfonate materials employed in the instant testing were spent sulfite liquors from sodium and calcium acid sulfite pulping of predominantly hemlock wood which were concentrated and then spray dried without neutralization.
• other lignosulfonate materials could be employed herein with equally outstanding results.
• the weight of copper transferred was measured in each of the tests and was very consistent at from about 33 to about 33.5 grams, which approximates 100% efiiciency at 600 ma. for 47 hours. Any variations in the weight of copper deposited, which was very small, could not be correlated with the additive used.
• the polyethylene polyamines to be tested were prepared from commercially available low molecular weight polyethylene amines by condensation polymerization reaction with ethylene chloride.
• One such amine was prepared by reacting equal volumes of ethylene chloride and tetraethylene pentamine for 6 hours in a steam bath and is hereinafter referred to as Amine No. 1.
• Another amine was prepared by reacting equal volumes of ethylene chloride and diethylene triamine for 6 hours in a steam bath this product is hereinafter referred to as Amine No. 2.
• a commercially available polyethylene amine (Union Carbide Corporation) having an average molecular weight of 1800 was employed and is referred to hereinafter as Amine No. 3.
• the lignosulfonate material employed herein was spent sulfite liquor from soda acid sulfite pulping of predominantly hemlock wood which was concentrated and then spray dried without neutralizers. As will be recognized by those skilled in the art, other lignosulfonate materials could also have been used herein.
• An aqueous acidic copper electrodeposition electrolyte comprising as its essential ingredients a source of copper ions, a source of hydrogen ions and an amount of an additive agent effective to provide an electrolyte which produces copper electrodeposits which are smooth, dense and essentially free of protrusions, said additive agent comprising a lignosulfonate material and a cation active organic nitrogen compound selected from the group consisting of polyethylene amines and quaternary ammonium compounds having the general formula:
• R, R R and R are independently selected from the group consisting of alkyl and aryl radicals containing from 1 to 20 carbon atoms, at least one of R, R R and R must contain a minimum of 8 carbon atoms, and A" is an anion, and mixtures thereof.
• the electrolyte of claim 1 wherein the lignosulfonate material is the lignosulfonate-containing residue from the acid sulfite pulping of wood.
• a combination of additive agents for copper electrodeposition electrolytes which improve the quality and physical characteristics of the copper electrodeposits comprising: a mixture of a cation active organic nitrogen compound selected from the group consisting of quaternary ammonium compounds, polyethylene amines and mixtures thereof, and a lignosulfonate material; said quaternary ammonium compounds having the general formula:
• R, R R and R are independently selected from the group consisting of alkyl and aryl radicals containing from 1 to 20 carbon atoms, at least one of R, R R and R must contain a minimum of 8 carbon atoms, and A is an anion.
• the electrolyte comprising as its essential ingredients a source of copper ions and a source of hydrogen ions, the steps comprising adding to the electrolyte in an amount effective to provide an electrolyte which produces copper electrodeposits which are smooth, dense and essentially free of protrusions, a cation active organic nitrogen compound selected from the group consisting of quaternary ammonium compounds having the general formula:
• R, R R and R are independently selected from the group consisting of alkyl and aryl radicals containing from 1 to 20 carbon atoms, at least one of R, R R and R must contain a minimum of 8 carbon atoms, and A is an anion, polyethylene amines and mixtures thereof, in conjunction with a lignosulfonate material; and then passing an electric current from an anode through the electrolyte to a cathode to deposit copper thereon.
• polyethylene polyamine has a relative viscosity of at least 1.25 measured in 10% aqueous solution at 25 C. in comparison with water.
• the lignosulfonate material added to the electrolyte comprises a lignosulfonate-containing residue from the acid sulfite pulping of wood.

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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)
• Electrolytic Production Of Metals (AREA)

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Cited By (12)

• 1969
  • 1969-01-23 US US793582*A patent/US3650915A/en not_active Expired - Lifetime
  • 1969-12-08 ZM ZM174/69A patent/ZM17469A1/xx unknown
• 1970
  • 1970-01-23 ES ES375824A patent/ES375824A1/es not_active Expired

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