US2609339A - Bright copper plating from cyanide baths - Google Patents

Description

Patented Sept. 2, 1952 faeoasss I FranhPassal, Detroit, Micln, assignor to United Chromium, Incorporated, New York, N. Y., a

corporation of Delaware I Application November 2, 1948,

.No Drawing. 1

. Serial No. 58,026

This invention relates to cyanide bathsior electroplating copper, and to processes Dielectrodepositing smooth and bright copper thereirom, and provides, improvements therein, Ad vanta ges of the bath and process accordingwto the present invention are; H y

1. Wide limits of the free cyanide without detriment to smooth and bright deposits, and to cathode current efficiency;

Z I-Iigh current efficiency. I smooth deposits obtainable at 90 to. 100% cathode current efficiency; l p 3. Pitting'of the electrodeposit is avoided;

4,"Free rinsing properties of the electrodeposit'sf'in'aking' unnecessary aspecial cleaning cycle after' copper plating and priorto bright nickel plating? I. I 1 5. Low "concentration and stability of the brighteners used, making the .bath economical to operatej an and I 1 v 7. softness and easy flow of the copper electro! deposite n buffing. 1

An example of a bath composition, together with ranges for the constituents is given below.

Bath composition v pH approximately 12.5 to 13.5.

' odium salts are -equivalents of the potassium salts. The novel constituent is the substance rhodanine, or substituted rhodanines, or condensation products of rhodanine, or of a substituted rhodanine, with compounds containing an active carbonyl (CO) group such as aromatic or aliphatic aldehyde or aldehydic acids. The particular brightener additive that is chosen should have a solubility in the bath of at least 0.005 gram perlite'rl V v I 4 Claims. (01. 204-52) Anti-pit agents are not required .in the bath when rhodanine, substituted rhodanine, or'a con- 7 densation product of rhodanine, is present.

Rhodanine (2-mercaptothiaaolidone-4) has the following structural formula 'i'mui right and .1

. so 6. Wide latitude iin theopera ting temperature the interaction ofaliphatic or aromatic .isothiocyanates witlithiog'lycollic 'acid' according to the following general reactiornalso' produces a powerful brightening effect."

ph'atic group; or' anaromatic or substituted aro- I .l': 1;';. 1;;f F f "p Examplesof specific substituted rhodanines are the fOIlOWil'ig: 1 3. x 1

eral 1 reactionwherebysuch condensation. products are formed-isthe following: R"f' C'O Li a 7 'R-N- oo ags zip R1 stands 101'; H; an aliphatic. .or substitutedaliphatic-group, or anzaromaticior substituted aromaticgroupl R, stands for. an aliphatic orsube stituted aliphatic group, an. aromatic orasubstituted aromatic :group, a. carboxyl group (.COOI-I) acetald-rhodanine 2. Rhodanine with O--hgz droa'y-m-methozey bent;-;

OH OCH: O-hydroxy-m-methoxy-benzalrhodanine RhQdaui-newi h l zlo alice mew S=L Z'=G'H (G'OH glyoxylal-rhodanine In the foregoing example of a bath composiips a substitut d hedan ne. 9r. arh dan ne or ubst u d ani e m den e ion p oduct; can be used in place of rhodanine, and the amountof the subs ituted rh anineer t "1 9.. inc or substituted rhodanine condensation;; product, when usedin plac of rhodanine, is substantially the same amount and range given in the aforesaid example. 50

Process conditions Range 8-25 21. p. s. f. 5 to 35. 170 F 140 to 180 F. 15 ft./min. 5 to 20.

sh t r/ a l we ente l-tr mpeter 99%, 1.. Nate: e'Ihe bath will give bright depositsat currentfdensities the :low-Lpart oflthe range without, agitation, The higher current densities requireragitationh o l i It'is desirable to continuously :filter the bath.

If ordinary precautions are taken in the operation of the bath, it has been found that there is no tendency toward the formation of gas pits, striations, etc. on the cathode deposits. vHowever, if oils, greases, bufiing compounds etc. are introduced into the bath'in appreciable'quantities,- some pitting may occur in the cathodedeposits; In .such cases, it has been found advantageous toadd to the bath small quantities of compatiblewetting or anti-pitting agents.- Ex- 75 amples of wetting agents which were found to have been effective are proprietary substances known as Cerfak Liquid (a sodium salt of a sulfated fatty acid amide) and Tergitol 08" (a sodium salt of sulfater Z-ethylhexanol).

- Brighteners have heretofore been used in cy- "an'ide copper baths, and some of these brighteners (thio-cyanates, for example) have been found to be of such a nature as to cause pitting, l

though the bath may not be contaminated with striation, etc. in'thc copper cathode deposits even foreign matters such as oils, greases, etc. In the case of such brighteners, it is necessary to use wetting agents to counteract pitting, striations,

etc. Brighteners according to the present invention do not .of themselves cause copper electrodeposits to be pitted or striated, wetting agents in the present bath being added only to counteract the efifect of impurities and contaminants introduced into the bath through careless and faulty operation practice.

What is claimed is:

1. An aqueous cyanide type of bath for electroplating copper having as its essential constituents Cu to 55 grams per liter, free KCN 5 to 13 g./l KOH 7.5 to gJ/l. and 0.005 to 1 g;/-l.' rhodanine as a'brightener addition.

- 2. The method of electroplating smooth and bright copper consisting in immersing agcathode aritcle in an aqueous cyanide type of bath consisting essentially of Cu 20 to grams per liter, free KCN 5 to 13 g./l., KO-H 7.5 to 30 g./l.. 0.005 to 1 g./l. rhodanine as a brightener addition and passing current to the cathode article at a current density between 5 amperes per square foot "and 35'amperes per square foot, with the bath at a temperature between F. and F.

3 An aqueous cyanide type ofbath for electroplating copper having as its essential constituents Cu-20 to 55 grams per liter, free KGN-5 to 13 grams per liter, Kohl-7.5 to 30 grams per liter, and 0,005 to 1 gram per liter of a brightener addition having the general for.- mula S=C2 5C=Rr in which R is a substituent selected from the class consisting of hydrogen, aliphatic, and aromaticisubstituents, and in which R1 is a substituent selected from the class consisting ofil) hydrogen sufficient to saturate the number five carbon atom to which said R1 is attached, (2) an aliphatic substituent connected to said number five carbon atom through a double bond, and (3) an aromatic substituent connected to said number five carbon atom through a double bond.

4. method of electroplating smooth and bright copper consisting of immersing a cathode article in an aqueous cyanide type of bath consisting essentially of Cu-20 to 55 grams per liter, freeKCN-S to 13 grams per liter, KOH7. 5 to 30 grams per liter, and 0.005 to 1 gram per liter of a brightener addition having the general formula in which R is a substituent-selected from the class consisting of hydrogen, aliphatic, and aromatic substituents, and in W'hiCh'Rl is asub- 5 6 stituent selected from the class consisting of (1) REFERENCES CITED hydrogen sufficient to saturate the number five carbon atom to which said R1 is attached, (2) e f01 1owing reference are f record in an aliphatic substituent connected to said numfile of thls Pertent? ber five carbon atom through a double bond, and UNITED STATES PATENTS (3) an aromatic substituent connected to said Number Name Date number five carbon atom through a double bond, 2347448 Wemlund p 1944 and passing current to the cathode article at a current density between 5 amperes per square foot and amperes per square foot, with the 10 FOREIGN PATENTS bath at a temperature between F. and F. Number Country Date FRANK PASSAL. 49,603 Denmark Nov. 21, 1934

Claims (1)

1. 3. AN AQUEOUS CYANIDE TYPE OF BATH FOR ELECTROPLATING COPPER HAVING AS ITS ESSENTIAL CONSTITUENTS CU-20 TO 55 GRAMS PER LITER, FREE KCN-5 TO 13 GRAMS PER LITER, KOH-7.5 TO 30 GRAMS PER LITER, AND 0.005 TO 1 GRAM PER LITER OF A BRIGHTENER ADDITION HAVING THE GENERAL FORMULA