US2770587A

US2770587A - Bath for plating bright copper

Info

Publication number: US2770587A
Application number: US588986A
Authority: US
Inventors: Barnet D Ostrow
Original assignee: Elechem Corp
Current assignee: Elechem Corp
Priority date: 1956-06-04
Filing date: 1956-06-04
Publication date: 1956-11-13
Anticipated expiration: 1973-11-13

Description

United States Patent BATH FOR PLATING BRIGHT COPPER Barnet D. Ostrow, North Bellmore, N. Y., assignor to Elechem Corp., Jersey City, N. J., a corporation of New Jersey No Drawing. Application June 4, 1956, Serial No. 588,986

14 Claims. (Cl. 204-52) This invention relates to electroplating from cyanide baths, more particularly to a bath composition which is particularly adapted to produce bright coatings of soft, ductile electroplates of copper.

Numerous attempts to obtain such bright coatings have been made. For instance, it has been proposde to use alkali metal selenite as an addition agent to an electrolytic bath in relatively large amounts. Such baths had a number of disadvantages in that the selenites tended to break down with a resultant adverse effect on the bright plating range. the selenites, the anodes became blackened, forming insoluble compounds which were loosened from the anodes and tended to co-deposit with the plated metal, resulting in rough deposits which were commercially unusable. Also During the electrolysis because of breakdown of r 3 in commercial operation, due to the resulting very narrow 7 bright plating range, non-uniform appearance of the deposits resulted, and the deposits were in many cases insufficiently bright so that buffing was necessary.

The present invention is intended and adapted to overcome the difiiculties and disadvantages inherent in prior baths of the type described, it being among the objects of the present invention to provide a bath composition into which a relatively small amount of addition agents is introduced and which results in greatly increased brightness of the plated surface, with a wider, more uniform and bright plating range. t

It is also among the objects of the present invention to provide a bath composition which results in a plating which is brilliant, soft and ductile and which may be readily buffed if desired to cause the coating to flow, as for example, on steel.

It is further among the objects of the present invention to provide a bath in which there is no breakdown even after long use.

The invention is based upon the discovery that the addition to a copper plating bath of very small amounts of selenium in the form of soluble compounds has a beneficial effect in the operation of the bath in order to give bright deposits. The selenium compounds according to the invention all have a valence of 2 and they may be either organic or inorganic compounds of selenium. The amount of such selenium compounds added is extremely small, ranging from .0001 to .01 gram per liter based upon the selenium metal present in the compounds. The invention includes selenides of alkali metals and such other selenides which are soluble in the bath. Various other inorganic selenium compounds having a valence of -2 which are soluble in the bath may be used. The organic selenium compounds may be the alkali metal selenocyanates, selenoureas, selenazoles and the like. Also included in the invention are compounds of the formula RSeI-I wherein R is an organic radical having 1 to 6 carbon atoms when the radical is alkyl and having 6 to 12 carbon atoms when the radical is aryl.

Listed below are typical classes of compoundswhich are included in the present invention, illustrating the broad nature thereof:

Selencyanides (selenocyanates):

Na seleno-isocyanate K-selenocyanide NOz-phenyl selenocyanide Se dissolved in alkali metal cyanides.

Selenides:

Na and K monoand di-selenides Diamino-diphenyl-di-selenide Nazsee NazSe Selenoacids and salts (organic):

Selenoacetic Selenopropionic Selenoglycollic Selenobenzoic Diselenobenzoic Selenotartaric Selenocitric Seleno oxalic Selenoacids and salts (inorganic):

Na selenophosphite K selenostannate Na selenopersulphate K monoselenothiosulphite K seleno diphosphite Selenoamines and amides:

Ethylamineethyl-diselenocarbama1e Selenourea K-selenoamide Diquinoline selenide Seleno xanthates:

K-selenoxanthate Selenols (alcohols):

Ethyl selenol Ethylene selenoglycol Selenophene:

Selenophene Z-sulphonic acid Selenophene 2-selenic acid Selenoazoles:

2-selenoth-iazoline 2-seleno selanazoline Z-methylbenzo selenazole Example 1 There is provided a cop-per cyanide plating bath containing sodium diselen-ide and having the following compositions:

CuCN

Total KCN Free KCN Dipotassiurn tartrate 45.0 KOH 1-5.0 NazSez .0003 (Se) Example 2 The bath containing potassium selenocy-anate has the following composition:

CuCN 60.0 Total KCN 84.0

KOH 30.0 Free KCN -15 KCNSe .001 (Se) Example 3 In the following composition the addition of the selenium is in the form of selenophenol.

CuCN

Total NaON 90.0 Rochelle salts 45.0

KOH 15.0 Free NaCN 7.5 Selenophenol .002 (Se) Example 4 The following composition contains potassium selenide and an amino acid compound.

Example 6 The selenium present in the bath may be an organic s-elenocyana'te, the bath having the following composition:

Copper cyanide 45 Total KCN 72 Free KCN 9-12 KOH Rochelle salts 45 o-Nitro-phenyl selenocyanate .008 (Se) Example 7 The fol-lowing bath contains the selenium in the form of quaternary selenazol.

Copper cyanide 45 Free NaCN 10 Rochelle salts 45 KOH 15 Z-methylbenzoselenazole ethiodide .01 (Se) Example 8 Various inorganic selenium compounds are suitable for the purpose as in the following composition, which contains the selenium in the form of a thiosulphite of the formula KzSeSOs.

Copper cyanide 75 KCN 105 K tartra te 40 Free KCN 8 KOH 15 K Monoselenothiosulphite .005 se Example 9 The following composition illustrates the use of a selenide in organic form:

Copper cyanide 60 Total KCN 84 KOH 30 Free KCN 12 0,0'-Diamino-diphenyl-diselenide .007 (Se) Example 10 The selenium may be in the form of a phosphite, for instance, having the formula 2K2Se.P2Se3, as illustrated in the following composition:

Copper cyanide 45 Total KON 71 Free KCN 8 Rochelle salts 20 KzCOs 30 K selenodiphosphite .002 (Se) Example 1] Baths containing relatively larger amounts of the selenium compounds may be used as, for instance, the following bath:

CuCN 56.0 Total KCN 82.0 Free KCN 28.0 Selenobenzoic acid .04 (Se) Example 12 The following bath contains a substantial amount of an inorganic complex selenium salt.

CuCN 60.0

Total KCN 94.0 K carbonate 30.00 Free KCN 10.0 Rochelle salts 20.0 Na selenostannate .02 (Se) Example 13 A typical bath containing a Selene-alcohol is the following:

CuCN 45.0 Total KCN 72.00 Free KCN 9-12 KOH 15.0 Rochelle salts 45.0 Ethyl selenol .05 (Se) Example 14 The following is a similar bath in which the selenium is in the form of a xanthate:

CuCN 75.0 Total KCN 105.0 Free KCN 8.0 KOH 15.0 K tartrate 40.0 Na selenoxanthate .04 (Se) Example 15 Selenium in the form of thiazole compounds are also suitable as illustrated by the following formula:

CnCN 45 .0 Free NaCH 10.0 Rochelle salts 45 .0 KOH l5 .0 -selenothiazoline 01 (Se) Example 16 Sulphonic acids and their soluble salts containing selenium are satisfactory as shown by the following composition:

CuCN 55.0 Total KCN 80.0 Free KCN 12.0 KOH 28.0 Selenophene-2-sulphonic acid Na salt .007 (Se) In the preferred form of the invention the amount of selenium is generally not over .01 gram per liter and sufficient to give a brightening effect. But larger amounts may be used as shown in Examples 1114; however such larger amounts do not usually contribute sufficiently to the brightening effects to warrant the added cost involved, so that ordinarily the smaller amounts have been found to be most satisfactory.

The effectiveness of the above baths continues over long periods of time as to stability and bright ranges. in contrast to baths containing the selenium having valences of +4 or +6, such as selenites or selenates, which have a narrow bright range and rapidly lose their effectiveness in the bath under normal operating conditions. They are unstable compounds which darken the anode, cause the cathode to become non-uniformly dull, have a narrow bright range and tend to give rough deposits, whereas those selenium compounds having a valence of 2 do not show such defects.

Although the invention has been described setting forth several specific examples of the operation thereof, the invention is not to be limited thereto as many changes may be made in the details thereof. For instance, the composition of the baths may be considerably altered and other substances may be added thereto, such as alkyl polyamines, including ethylene diamine, diethylene triamine, triethylene tetramine, and others up to alkyl groups having 5 carbon atoms, the number of amino groups being from 2 to 5, in amounts of about .25 to 50 grams per liter, although preferably smaller amounts up to 10.0 are used.

There may be added to the bath a surface active agent which is the condensation product of ethylene oxide and an organic hydroxy compound. Such an agent has the general formula RO(C2H4O)H wherein R is a hydrocarbon radical having 5 to carbon atoms and x is a numeral from 10 to 80. The conditions of operation of the plating bath may be varied within usual practice. Larger amounts of the additive may be used, even above the maxima stated herein. However, such excess does not usually give beneficial effects.

The present application is a contimiation-in-part of my copending application Ser. No. 479,871 filed January 4, 1955, which is a continuation-impart of my application Ser. No. 349,935, filed April 20, 1953, Patent No. 2,732,336, said patent being a continuation-impart'of application Ser. No. 126,679, now Patent No. 2,694,677,

dated November 16, 1954, entitled Bright Copper Plating Bath, which in turn is a continuation-in-part of abandoned application Ser. No. 6,354, filed February 4, 1949, and entitled Electro-Deposition of a Bright Copper.

I claim:

1. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper, and a soluble selenium compound in which the selenium has a valence of 2 in amount sufficient to exert a brightening effect on the copper deposit.

2. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper, and a soluble selenium compound in which the selenium has a valence of 2 in amount sufficient to exert a brightening effect on the copper deposit, the amount being from .0001 to .05 gram per liter of elemental selenium.

3. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper, and a soluble selenium compound in which the selenium has a valence of 2. said selenium compound being present in an amount from .0001 to .01 gram per liter of elemental selenium.

4. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper, and a. soluble inorganic selenium compound in which the selenium has a valence of 2, said selenium compound being present in an amount from .0001 to .01 gram per liter of elemental selenium.

5. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper, and a soluble organic selenium compound in which the selenium has a valence of -2, said selenium compound being present in an amount from .0001 to .01 gram per liter of elemental selenium.

6. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper, and a soluble inorganic selenium compound in which the selenium has a valence of 2, said selenium compound being present in an amount from .0001 to .01 gram per liter of elemental selenium, said compound being taken from the class consisting of inorganic selenides, selenocyanates, selenophosphites and selenothiosulphites.

7. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper, and a soluble organic selenium compound in which the selenium has a valence of 2, said selenium compound being present in an amount from .0001 to .01 gram per liter of elemental selenium, said compound being taken from the class consisting of organic selenonreas, selenocyanates, selenoazoles, selenides, and compounds of the formula RSeH wherein R is an organic radical having 1 to 6 carbon atoms when said radical is alkyl and having 6 to 12 carbon atoms when said radical is aryl.

8. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper containing from .0001 to .01 gram per liter of elemental selenium in the form of selenourea.

9. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper containing from .0001 to .01 gram per liter of elemental selenium in the form of alkali metal selenocyanate.

10. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper containing from .0001 to .01 gram per liter of elemental selenuim in the form of alkali metal selenide.

11. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper containing from .0001 to .01 gram per liter of elemental selenuim in the form of an organic selenide.

12. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper containing from .0001 to .01 gram per liter of elemental selenium in the form of a compound selected from the group consisting of a selenol and the soluble salt thereof.

13. An electrolytic bath comprising an aqueous alkaline solution of a cyanide of copper, and a soluble selenium compound in which the selenium has a valence of 2, said selenium compound being present in an amount from .0001 to .05 gram per liter of elemental selenium, and an alkyl polyamine.

14. An electrolytic bath comprising an aqueous all aline solution of a cyanide of copper, and a soluble selenium compound in which the selenium has a valence of 2, said selenium compound being present in an amount from .0001 to .05 gram per liter of elemental selenium, and a polyethylene glycol ether.

References Cited in the file of this patent UNITED STATES PATENTS 2,384,300 Harford Sept. 4, 1945 2,582,233 Chester et a1 Ian. 15, 1952 ,677 Ostrow Nov. 16, 1954

Claims

1. AN ELECTROLYTIC BATH COMPRISING AN AQUEOUS ALKALINE SOLUTION OF A CYANIDE OF COPPER, AND A SOLUBLE SELENIUM COMPOUND IN WHICH THE SELENIUM HAS A VALENCE OF -2 IN AMOUNT SUFFICIENT TO EXERT A BRIGHTENING EFFECT ON THE COPPER DEPOSIT.