US3129153A - Dissolution of copper - Google Patents

Dissolution of copper Download PDF

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Publication number
US3129153A
US3129153A US51280A US5128060A US3129153A US 3129153 A US3129153 A US 3129153A US 51280 A US51280 A US 51280A US 5128060 A US5128060 A US 5128060A US 3129153 A US3129153 A US 3129153A
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United States
Prior art keywords
copper
persulfate
dissolution
potential
solution
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US51280A
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English (en)
Inventor
Paul H Margulies
William J Tillis
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FMC Corp
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FMC Corp
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Filing date
Publication date
Priority to NL268373D priority Critical patent/NL268373A/xx
Application filed by FMC Corp filed Critical FMC Corp
Priority to US51280A priority patent/US3129153A/en
Priority to GB30165/61A priority patent/GB963365A/en
Priority to FR871457A priority patent/FR1303216A/fr
Application granted granted Critical
Publication of US3129153A publication Critical patent/US3129153A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F3/00—Electrolytic etching or polishing
    • C25F3/02—Etching

Definitions

  • This invention relates to the dissolution of copper and particularly to a method of dissolving metallic copper in an aqueous persulfate (peroxydisulfate) solution.
  • One of such applications for dissolving or etching copper is in the production of copper printing plates by photoengraving. In this process the copper plate is covered with a mask and then exposed to the copper-etching solution. By dissolving the copper in areas not covered by the masking material, a plate having the desired pattern and suitable for printing can be produced.
  • the agents most often used to dissolve copper have been strong mineral acids, e.g., nitric or sulfuric acids, or ferric chloride solutions. These agents all have disadvantages. In the case of the strong acids, their highly corrosive nature requires the use of special process equipment. Additionally, these acids generate noxious fumes and, in general, are difiicult to work with. With respect to the ferric chloride solutions, this agent similarly is quite corrosive so that special equipment is required. Further, it gives rise to noxious fumes. Additionally, ferric chloride solutions must be used at high ferric chloride concentrations, with the result that solid reaction products readily form in them if they become loaded with dissolved copper. This can seriously reduce the precision of etchings, Further, disposal of the exhausted solution presents a serious problem because of the toxicity of the iron contained therein. Additionally, copper recovery from ferric chloride is not feasible, although economically desirable.
  • persulfate solutions dissolve copper at a slow rate. While this disadvantage has been overcome by catalyzing the dissolution reaction by the addition of certain catalysts, for example, mercury (as described in copending patent application Serial No. 633,547, filed January 11, 1957), the resultant solutions are not desirable for etching printing plates, since mercury would be constantly removed with the body of the copper plate and would interfere with subsequent printing operations. Additionally, mercury on the surface of the plates constitutes a health hazard in the printing plate industry.
  • the dissolution rate of copper in persulfate solutions may be increased, in far greater measure than would be expected, by applying an electric potential to the copper higher than the polarizing potential of copper in a persulfate solution but below the deposition potential of copper (i.e., about 1.2 volts).
  • the copper serves as the anode
  • the persulfate solution serves as the electrolyte
  • an inert conductor serves as the cathode.
  • the aqueous persulfate solution employed herein contains about 10 to 50 parts by weight of a dipersulfate and, preferably, about 20 to 30 parts by weight of this ingredient. It is preferred, for present purposes, to employ ammonium persulfate by reason of its ready and high degree of solubility in water, although other persulfate, for example, sodium persulfate or mixtures of persulfate, having the requisite solubility, can be employed.
  • the copper engraving plates are contacted by the persulfate solution and become the anode of an electrolytic cell.
  • An inert material is employed as the cathode, and similarly contacts the persulfate solution, A small electric potential is then applied to the cell.
  • the amount of the electric potential applied must be greater than the polarization potential of copper in the persulfate solution being employed as the etchant; that is, the applied potential must be sufiicient to allow a current to be passed through the cell. When this current flows, it synergistically activates the dissolution of the anodic copper. It has been determined, for example, that applied potentials of 0.1 volt which passed as little as 40 milliamps were sufficient to activate copper dissolution.
  • the maximum electrical potential to be applied should be below the deposition potential of copper in the persulfate solution being employed as etchant, this value being about 1.2 volts. Above this value, the applied potential no longer merely acts as an activating means for dissolving copper but is suificiently high to dissolve copper at the anode and physically plate it out at the cathode. This type of operation is not desired because, in addition to copper plating out at the cathode, persulfate solution is simultaneously reduced at the cathode and converted to the corresponding sulfate with the serious loss of active oxygen. As a result, increased use of electricity and excess loss of persulfate result when the applied potential is above the deposition potential of copper in persulfate.
  • the expected effect is found to be only a small percentage of the over-all increase in the dissolution rate.
  • the increased dissolution rate is so much greater than the sum of the chemical dissolution rate due to the effect of the persulfate on the copper, plus the electrolytic dissolution rate caused by the electrical current, that it can only be described as synergistic.
  • This synergistic dissolution effect appears to reach its peak when the voltage is about 60% of the deposition potential of copper.
  • the preferred range of operation for the present process is between about to about 85% of the deposition potential of copper in the persulfate solution (i.e., about 0.3 to 1.0 volt).
  • the instant process increases the dissolution rate of copper to a point where it is comparable to that obtained when mercury ions are employed as catalysts in the persulfate solutions. This rate is of the same order of magnitude as that obtained with commercial ferric chloride solutions. Therefore by means of this electrolytic activation, the present process can dissolve copper at substantially the same rate as ferric chloride solutions but with none of their disadvantages.
  • the present process works exceptionally well with photoengraving copper which generally contains minor amounts of silver, of the order of 1%, as an alloying constituent.
  • the present process is also applicable to the etching of pure copper.
  • the synergistic effect obtained by activating the dissolution of copper with a small electric potential is not as great when pure copper is used as compared with the alloyed copper employed for photoengraving purposes.
  • EXAMPLE 1 Pure copper panels, 2" x1" X A", were separately immersed in an ammonium persulfate solution having a concentration of 25 by weight. The panels were agitated in the solution by being rotated at 250 r.p.m. Electrical contact to a panel was made by use of a mercury seal and current was supplied by a S-volt rectifier. Various amperages were supplied to the test panels during the copper dissolution and are reported in Table I. The panels were etched in this manner for a 2-minute interval after which the panels were rinsed, dried and weighed. This procedure was repeated two additional times until the total time of immersion was six minutes. Thereafter, the panels were again etched in this same manner for a 4-minute interval after which the panels were rinsed, dried and weighed. This latter procedure was repeated three more times, so that the copper panels had a total etching period of twenty-two minutes.
  • Photoengraving copper panels containing about 1% silver, 2 x 1" x A", were separately immersed in an ammonium persulfate solution having a concentration of 25%.
  • the panels were agitated in the solution by being rotated at 250 r.p.rn. Electrical contact to a panel was made by use of a mercury seal and current was supplied by a S-volt rectifier.
  • Various amperages were supplied to the panels during the copper dissolution and are reported in Table II.
  • the panels were etched in this manner for a 2-minute interval after which the panels were rinsed, dried and weighed. This procedure was repeated two additional times until the total time of immersion was six minutes. Thereafter, the panels were again etched in this same manner for a 4-minute interval after which the panels were rinsed, dried and weighed. This latter procedure was repeated three more times, so that the copper panels had a total etching period of twenty-two minutes.
  • the dissolution rate due to the electrolytic dissolution is 2.3 rug/sq. in./min. Therefore the maximum rate due to the additive chemical and electrolytic dissolution should have been 46.7 Whereas the actual dissolution rate obtained was 62.8, clearly indicating a synergistic effect.
  • EXAMPLE 3 Ammonium persulfate baths, similar to those employed in Example 1, were tested ceriometrically ⁇ for their ammonium persulfate concentration. This was rfound to be 19.04%. Using a carbon anode and a stainless steel cathode, 300 milliarnps of D.-C. current were passed through this solution for 66 minutes. The resultant persulfate concentration was again ceriometrically determined and found to be 18.59%.
  • a method for dissolving copper which comprises contacting the copper with an aqueous solution consisting essentially of about to about 45% of a persulfate while simultaneously applying an electric potential between said copper and an inert conductor, said copper serving as an anode, said persulfate serving as the electrolyte, and said inert conductor serving as the cathode, said electric potential being above the polarizing potential of copper in said persulfate solution and sufficient to permit a substantial current flow through said cell, but below the deposition potential of copper in said persulfate solution.
  • a method for etching photoengraving copper which comprises contacting the photoengraving copper plate with an aqueous solution consisting essentially of about 10 to about of a persulfate while simultaneously applying an electric potential between said photoengraving copper and an inert conductor, said photoengraving copper serving as an anode, said persulfate serving as the electrolyte, and said inert conductor serving as the oathode, said electric potential being above the polarizing potential of photoengraving copper in said persultate solution and suificient to permit a substantial current flow through said cell, but below the deposition potential of photocngnav-ing copper in said persulfate solution.

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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)
  • Electrolytic Production Of Metals (AREA)
  • ing And Chemical Polishing (AREA)
  • Manufacturing Of Printed Circuit Boards (AREA)
US51280A 1960-08-23 1960-08-23 Dissolution of copper Expired - Lifetime US3129153A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL268373D NL268373A (en:Method) 1960-08-23
US51280A US3129153A (en) 1960-08-23 1960-08-23 Dissolution of copper
GB30165/61A GB963365A (en) 1960-08-23 1961-08-22 Improvements in and relating to etching copper plates
FR871457A FR1303216A (fr) 1960-08-23 1961-08-23 Procédé de dissolution du cuivre

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US51280A US3129153A (en) 1960-08-23 1960-08-23 Dissolution of copper

Publications (1)

Publication Number Publication Date
US3129153A true US3129153A (en) 1964-04-14

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US51280A Expired - Lifetime US3129153A (en) 1960-08-23 1960-08-23 Dissolution of copper

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US (1) US3129153A (en:Method)
GB (1) GB963365A (en:Method)
NL (1) NL268373A (en:Method)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4264418A (en) * 1978-09-19 1981-04-28 Kilene Corp. Method for detersifying and oxide coating removal
US5098533A (en) * 1991-02-06 1992-03-24 International Business Machines Corp. Electrolytic method for the etch back of encapsulated copper-Invar-copper core structures
US20050082257A1 (en) * 2001-09-10 2005-04-21 Gust Bierings Method of etching copper on cards

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1082596A (en) * 1912-04-02 1913-12-30 Isidor Kitsee Treating metal-carrying ores.
US2196133A (en) * 1936-09-28 1940-04-02 Robert Laing Bruce Gall Photography
US2361680A (en) * 1941-06-18 1944-10-31 Bell Telephone Labor Inc Method of reducing edge leakage in metal oxide-metal rectifiers
US2558504A (en) * 1946-03-12 1951-06-26 Aller Claes Borge Method of producing a printing form having a bimetallic surface
US2596307A (en) * 1947-11-05 1952-05-13 Charles Litzenberg Process of electrostripping electrodeposited metals
US2647864A (en) * 1952-05-29 1953-08-04 Daniel L Goffredo Etching process
US2843538A (en) * 1954-10-01 1958-07-15 Haugen Ole Wilhelm Electrolytic process for leaching precious metals

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1082596A (en) * 1912-04-02 1913-12-30 Isidor Kitsee Treating metal-carrying ores.
US2196133A (en) * 1936-09-28 1940-04-02 Robert Laing Bruce Gall Photography
US2361680A (en) * 1941-06-18 1944-10-31 Bell Telephone Labor Inc Method of reducing edge leakage in metal oxide-metal rectifiers
US2558504A (en) * 1946-03-12 1951-06-26 Aller Claes Borge Method of producing a printing form having a bimetallic surface
US2596307A (en) * 1947-11-05 1952-05-13 Charles Litzenberg Process of electrostripping electrodeposited metals
US2647864A (en) * 1952-05-29 1953-08-04 Daniel L Goffredo Etching process
US2843538A (en) * 1954-10-01 1958-07-15 Haugen Ole Wilhelm Electrolytic process for leaching precious metals

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4264418A (en) * 1978-09-19 1981-04-28 Kilene Corp. Method for detersifying and oxide coating removal
US5098533A (en) * 1991-02-06 1992-03-24 International Business Machines Corp. Electrolytic method for the etch back of encapsulated copper-Invar-copper core structures
US20050082257A1 (en) * 2001-09-10 2005-04-21 Gust Bierings Method of etching copper on cards
US7767074B2 (en) * 2001-09-10 2010-08-03 Obducat Ab Method of etching copper on cards

Also Published As

Publication number Publication date
GB963365A (en) 1964-07-08
NL268373A (en:Method)

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