US2437865A - Method of electrodepositing copper and baths and compositions therefor - Google Patents

Method of electrodepositing copper and baths and compositions therefor Download PDF

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Publication number
US2437865A
US2437865A US503846A US50384643A US2437865A US 2437865 A US2437865 A US 2437865A US 503846 A US503846 A US 503846A US 50384643 A US50384643 A US 50384643A US 2437865 A US2437865 A US 2437865A
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United States
Prior art keywords
copper
pyrophosphate
bath
baths
composition
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Expired - Lifetime
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US503846A
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English (en)
Inventor
Jesse E Stareck
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United Chromium Inc
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United Chromium Inc
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Filing date
Publication date
Application filed by United Chromium Inc filed Critical United Chromium Inc
Priority to US503846A priority Critical patent/US2437865A/en
Priority to CH255708D priority patent/CH255708A/de
Priority to FR942779D priority patent/FR942779A/fr
Application granted granted Critical
Publication of US2437865A publication Critical patent/US2437865A/en
Priority to DEP29718D priority patent/DE852633C/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

  • Patented is, 1948 STATES PATENT OFFICE METHOD OF ELECTRODEPOSITING COPPER AND BATHS AND COMPOSITIONS THERE- FOR No Drawing. Application September 25, 1943, Serial No. 503,846
  • This invention relates to the eleotrodeposition of copper, and to baths and compositions therefor, and provides improvements therein,
  • the advantages obtained by the aioresaid patented invention are retained, together with additional advantages of great importance; a higher speed of deposition is obtained (the speed is something like doubled), a more ductile deposit is obtained, a better covering power is obtained than with any other known copper plating process, better adherence of the deposited copper on aluminum and stainless steel is obtained, and a better process and bath for barrel plating than any other is obtained.
  • the invention can also be used to good advantage for obtaining strike deposits of copper.
  • the low operating pH makes the process particularly favorable for plating over the more difficult metals, such as, magnesium, aluminum, Zinc, lead, stainless steel and certain alloy steels and castings.
  • the bath is like that of Patent #2,250,566, in that it contains the complex copper pyrophosphate ion, Cu(P2O'z)2; according to the present invention the bath contains the nitrate ion, N03, and has a pH between 6.5 and 7.5, with the optimum at about 7.2 (measured by a glass electrode pH meter).
  • N03 radical inhibits the formation of hydrogen at the cathode, thereby enabling higher operating current densities and voltages to be used.
  • the higher current densities give a faster plating speed, while the higher voltages decrease the tendency of Cu2O formation at the cathode, thus producing a better bond between the deposit and the base metal.
  • the quantity of N03 which is used is from 5 to 20 g./l.
  • concentrations of the bath constituents may be varied widely to give satisfactory plating baths.
  • An example of a bath according to the present invention is one containing in solution from 7.5 to 45 g./1. of metallic copper, with a pyrophosphate content from that necessary to convert the copper to the complex C11(P2O7)2 to an excess limited by saturation.
  • the copper may be conveniently added in the form of copper pyrophosphate, copper sulphate (blue vitriol), or other common cupric compounds of copper.
  • the pyrophosphate radical may be added in the form of an alkali metal pyrophosphate salt either in the hydrated or anhydrous state. From the standpoint of economy of solution cost, the sodium pyrophosphate may be used.
  • alkali metal pyrophosphates notably the potassium salt
  • the potassium salt when used can produce baths which are more concentrated, and which, in turn, permit a corresponding increase in plating current densities at the cathode to be attained.
  • the bath is advantageously made by dissolving a prepared solid composition in warm water, all as more fully hereinafter set forth.
  • the pyrophosphate radical may be said to combine with the copper in the molecular Weight ratio of 2 to 1 to form a pyrophosphate copper complex radical having the formula Cu(PzO'z)2 (see Jour, American Chemical Society 1936, pp. 1412-1429).
  • the proportion of the pyrophosphate radical to copper may vary considerably, but it is advantageous when electrodepo'siting copper on iron, steel, and other less noble metals, to have an excess of pyrophosphate dissolved in the bath beyond that necessary to give the molecular-weight ratioof 2 to 1 between P207 and Cu.
  • the baths given in the specific examples contain such an excess of pyrophosphate radicals.
  • the free pyrophosphate content of the bath decreases the tendency for the deposition of copper by immersion on the less noble metals. It also tends to prevent the formation of traces of insoluble salts in the bath and promotes anode corrosion.
  • Citric acid or a salt thereof, especially an al- Kali-metal salt; is often advantageously added to increase the permissible cathode current density range, to increase the conductivity of the bath, and to increase the brightness of the cathode deposit. It also increases the tolerance of the bath to impurities and aids in anode corrosion.
  • citric acid other organic hydroxy acids which are capable of forming alkali-heavy-metal complexes, such as lactic acid, tartaric acid, glycollic acid, malic acid, or soluble salts thereof, may be used.
  • the pH of the bath is adjusted by adding a suitable acid such as pyrophosphoric acid, or citric acid, or nitric acid, when a test shows that the pH of the bath is higher than the pH desired, or by adding a suitable alkali such as sodium hydroxide for a sodium bath, or potassium hydroxide for a potassium bath, when the test shows that the pH of the bath is lower than the pH desired.
  • a suitable acid such as pyrophosphoric acid, or citric acid, or nitric acid
  • the baths herein described are stable at temperatures up to the boiling point of the solution. No poisonous fumes are evolved. The operating current efliciency is nearly 100%. The throwing power of the baths is excellent. Under ordinary operating conditions, temperatures from 120 to 150 F. are usually preferred. For a strike solution, temperatures of about 70 to 80 F. are preferred.
  • Agitation of the solution is desirable. Air agitation is generally used because it is simple, convenient, and causes no buildup of carbonates in this bath. Mechanical agitation or combinations thereof are also satisfactory. Agitation of the solution increases the operable current density range. The operable current density range also increases with rising temperature and decreases with increasing free pyrophosphate content of the bath.
  • Electrolytic or rolled copper anodes are Ordinarily used.
  • the operating voltage between anode (soluble) and cathode is usually between 2 and 5 volts when bright plating current densities are used.
  • Composition for ordinary tank plating Optimum range 24 to 36 Cu, 30 g./l P207, 200 g./l 150 to 250 Citrate, 15 g./l 5 to 25 N03, g./l 5 to 20 pH, 7.2 6.8 to 7.5 Temperature, 135 F 120 F. to 150 F.
  • Composition for maximum plating speeds Range Cu, 35 g./1 33 to 38 P207, 230 g./l 190 to 250 Citrate, g./l 5 to 25 N03, 10 g./1 5 to pH, 7 6.8 to 7.5 Temperature, 150 F 140 F. to 160 F.
  • Composition for barrel plating Optimum range Cu, g./l 15 to P207, 225 g./l 180 to 250 Citrate, l0 g./l 5 to 20 N03, 10 g./l 5 to 20 pH, 7.5 7 to 8 Temperature, 120 F 100 F. to 130 F.
  • Composition for strike plating Cu 15 g./l 7.5 to 22.5 P201, 150 g./] 100 to 225 Citrate, 7.5 g./l 5 to 10 N03, 7.5 g./l 5 to 10 pH, 7.5 7.0 to 8.0
  • current densities of 100 amperes per square foot and more may be used; with rotating cathodes the current density per square foot may be 300 amperes per square foot,
  • the above described process gives deposits which are smooth, fine grained, dense, ductile and relatively bright. Being fine grained and dense, the deposit is particularly good as a stopofi for carburizing, often requirin less thickness than usual to prevent carbon penetration.
  • a composition of matter consisting of soluble bivalent copper, pyrophosphate (P207), citrate (CsHsO'I), and nitrate (N03) compounds, and for maintaining the baths, a similar composition usually omitting the bivalent copper compound is used.
  • P207 pyrophosphate
  • CsHsO'I citrate
  • N03 nitrate
  • the percentages may be varied about 25%, plus or minus.
  • the percentages may be varied about 25%, plus or minus.
  • the ingredients are pulverized and intimately mixed.
  • the mixing of the bath is troublesome when the ingredients are added separately.
  • the cop-- per pyrophosphate cakes on the bottom of the tank and requires undue stirring and hoeing to bring it into solution.
  • the copper pyrophosphate is readily soluble, requiring only a few minutes from the time the admixture is placed into water until copper plating operations can be started.
  • potassium nitrate being classified as an explosive, it must be shipped under an explosive license" and requires special handling in packaging and shipping; in admixture with the other ingredients given above it is so dispersed and diluted that no special precautions are needed or required.
  • baths and compositions may have other embodiments than those herein specifically described, and the process may be practiced in other modes than that specifically described.
  • a composition of matter for making up a copper plating bath consisting of a soluble bivalcnt copper compound, a soluble pyrophosphate compound, and a soluble nitrate compound, in intimate admixture, the composition consisting of, by weight, 7.5 to 45 parts bivalent copper, 150 to 250 parts pyrophosphate (P207), and 5 to 29 parts nitrate (N03) 2.
  • composition of matter for making up a copper plating bath according to claim 1 furthercontaining 5 to 25 parts citrate (Cal-I501).
  • a composition of matter for replenishing a pyrophosphate copper plating bath consisting of a soluble alkali metal pyrophosphate and a soluble nitrate compound in intimate admixture, in amounts by weight of 150 to 250 parts pyrophosphate (P201) and 5 to parts nitrate (N03).
  • composition of matter for replenishing a pyrophosphate copper plating bath according to claim 4 further containing 5 to 25 parts citrate (6611507) by weight.
  • a method of depositing dense and adherent copper characterized by the bath having a pH between 6.5 and 7.5, and in which the bath consists essentially of 7.5 to g./1. bivalent copper, to 250 g./l. pyrophosphate (P207), and 5 to 20 g./l. nitrate (N03).

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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)
US503846A 1943-09-25 1943-09-25 Method of electrodepositing copper and baths and compositions therefor Expired - Lifetime US2437865A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US503846A US2437865A (en) 1943-09-25 1943-09-25 Method of electrodepositing copper and baths and compositions therefor
CH255708D CH255708A (de) 1943-09-25 1945-05-07 Verfahren zur elektrolytischen Abscheidung von Kupfer.
FR942779D FR942779A (fr) 1943-09-25 1945-11-10 Perfectionnements apportés aux procédés de dépôt électrolytique de cuivre et aux bains permettant leur mise en oeuvre
DEP29718D DE852633C (de) 1943-09-25 1949-01-01 Verfahren zur elektrolytischen Abscheidung von dichten, gut haftenden Kupferueberzuegen aus Baedern

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US503846A US2437865A (en) 1943-09-25 1943-09-25 Method of electrodepositing copper and baths and compositions therefor

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US2437865A true US2437865A (en) 1948-03-16

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CH (1) CH255708A (de)
DE (1) DE852633C (de)
FR (1) FR942779A (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2493092A (en) * 1946-01-11 1950-01-03 United Chromium Inc Method of electrodepositing copper and baths therefor
DE1034946B (de) * 1953-05-09 1958-07-24 Degussa Bad und Verfahren zur elektrolytischen Abscheidung von Kupfer und seinen Legierungen
US2871171A (en) * 1956-05-10 1959-01-27 Atkinson James Thomas Nesbitt Method of electroplating copper on aluminum
US2871172A (en) * 1955-11-02 1959-01-27 James T N Atkinson Electro-plating of metals
US2891896A (en) * 1956-01-30 1959-06-23 Fred I Nobel Improved cyanide copper plating baths
US3460953A (en) * 1966-05-27 1969-08-12 Pennsalt Chemicals Corp Process for depositing brasslike coatings and composition therefor
US3674660A (en) * 1967-05-01 1972-07-04 Albright & Wilson Electrodeposition of copper
US3775268A (en) * 1971-12-30 1973-11-27 Us Navy Use of lead in a nonorganic-containing copper pyrophosphate bath
JPS4843535B1 (de) * 1969-01-09 1973-12-19
JPS5054534A (de) * 1973-09-14 1975-05-14

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL123240C (de) * 1960-07-23
NL131369C (de) * 1961-07-14

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2493092A (en) * 1946-01-11 1950-01-03 United Chromium Inc Method of electrodepositing copper and baths therefor
DE1034946B (de) * 1953-05-09 1958-07-24 Degussa Bad und Verfahren zur elektrolytischen Abscheidung von Kupfer und seinen Legierungen
US2871172A (en) * 1955-11-02 1959-01-27 James T N Atkinson Electro-plating of metals
US2891896A (en) * 1956-01-30 1959-06-23 Fred I Nobel Improved cyanide copper plating baths
US2871171A (en) * 1956-05-10 1959-01-27 Atkinson James Thomas Nesbitt Method of electroplating copper on aluminum
US3460953A (en) * 1966-05-27 1969-08-12 Pennsalt Chemicals Corp Process for depositing brasslike coatings and composition therefor
US3674660A (en) * 1967-05-01 1972-07-04 Albright & Wilson Electrodeposition of copper
JPS4843535B1 (de) * 1969-01-09 1973-12-19
US3775268A (en) * 1971-12-30 1973-11-27 Us Navy Use of lead in a nonorganic-containing copper pyrophosphate bath
JPS5054534A (de) * 1973-09-14 1975-05-14

Also Published As

Publication number Publication date
CH255708A (de) 1948-07-15
DE852633C (de) 1952-10-16
FR942779A (fr) 1949-02-17

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