CA1038325A - Compositions and process for the electrodeposition of metals - Google Patents
Compositions and process for the electrodeposition of metalsInfo
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- CA1038325A CA1038325A CA203,082A CA203082A CA1038325A CA 1038325 A CA1038325 A CA 1038325A CA 203082 A CA203082 A CA 203082A CA 1038325 A CA1038325 A CA 1038325A
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- aqueous solution
- metal
- copper
- metal ion
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- 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
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- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Organic Chemistry (AREA)
- Electroplating And Plating Baths Therefor (AREA)
Abstract
TITLE: COMPOSITIONS AND PROCESS FOR THE
ELECTRODEPOSITION OF METALS
INVENTOR: XAVIER KOWALSKI
ABSTRACT
An electrically conductive medium for the electrodeposition of metals comprises an aqueous solu-tion of (a) a metal ion, (b) a carboxy alkylene amino di(methylene phosphonic acid) and optionally, (c) 1-hydroxy alkylidene-1,1-diphosphonic acid.
ELECTRODEPOSITION OF METALS
INVENTOR: XAVIER KOWALSKI
ABSTRACT
An electrically conductive medium for the electrodeposition of metals comprises an aqueous solu-tion of (a) a metal ion, (b) a carboxy alkylene amino di(methylene phosphonic acid) and optionally, (c) 1-hydroxy alkylidene-1,1-diphosphonic acid.
Description
. 43--4106A
' ``` ' :
'. ' '' ~.038325 TITL.E: COMPOSITIONS AND PROCESS FOR THE
ELEC~RODEPOSITION OF M~ALS
INVEN~OR XAVIER KOWALSKI
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to the electrodepo-~ition or electroplating of metals. More particularly, the present invention r~lates to the composition of the electro-plating bath fro~ which the metal is deposited.
Descri~tion of the Prior Art , The electrodeposition of metals from aqueous solu-tlons of metal ions is an old art. Th~ typical electroplating system consists of an electroplating bath and two or more electrodes. The cathode of the electrode system is the object to bs plated. The anode may be carbon or a solid piece of the metal to be plated upon the cathode. A solid metal anode is consumed in the; electroplating process and provides a constant ~ource of metal ions to the plating bath.
Metal ions are maintained in solution in the electro-plating bath by forming salts or metal complexes. Some of themost popular plating compositions utilize inor~anic metal cyanides, and cadmium, brass, copper, silver and zinc can all be plated from cyanide baths.
Electroplating baths comprising aqueous alkaline solution of metal cyanides have several dlsadvantages. Such baths often tend to produce relatively dull and uneven coatings -- 2 -- ~
g~
.. . . .
.
of the plated metal. The use of metal cyanide solut~ons can also be hazardous since i$ the p~ of the electroplating medium ; should drop to neutral or be?ow there is a danger of poisonous hydrogen cyanide gas being produced. Also, the use of metal cyanides presents a disposal problem due to their toxicity, and removing cyanides from waste baths prior to disposal is an expensive undertaking.
The prior art has suggested certain techniques for improving ths p~rformance of cyanid~ plating baths or for even eliminating cyanide from the bath. U.S.P. 2,19S,409 claims to improve the performance of metal cyanide baths by the addition of a nuclear alkyl derivat~ve of an aromatic sulfonic acid of the benzene series. The presence of this material is reported to eliminate pitting, uneven thicknesses and the formation of pinholes in the metal plate, and also improve brightness and uniformity of deposits.
More recently it has been suggested to use certain metal complexing agants in cyanide free plating baths. U.S.P.
3,457,293, for example, suggests the use of certain diphos-phonates or monoamino lower alkylene phosphonates in theelectroplating of divalent metal ions. U.S.P. 3,706,634 and 3,706,635 suggest combinations of ethylene diamine tetra-(methylene phosphonic acidl, l-hydroxy ethylidene-l,l-diphos-phonic acid, and amino tri(methylene phosphonic acid) as particularly useful co~.plexing compositions. U.S.P. 3,617,343 is similarly directad toward a nickel plating systam employing .. . .
certain phosphonic acid compounds. The present invention sup-plements and improves upon these methods of the prior art by providing certain organophosphorus compounds not taught in the prlor art which are useful in electroplating applications.
3 ` ' SUMMARY
In accordance with the present invention there is employed as the electroplating bath an a~ueous solution comprising (a) a divalent or poly~alent metal ion; ~b) a carboxy alkylene amino di~methylene phosphonic acid) having the structure O
.. ..
fH2 -- P -- (OM~2 MOOC ~ ~CH2)n ~ N \
CH2 - P - ~OM)2 wherein M is hydrogen, alkali metal, ammonium, alkyl ammonium or amine and n is an integer of from 3 to about 11 and prefer-ably from 3 to 6; and optionally (c) a l-hydrox~ alkylidene-l,l-diphosphonic acid compound having the structure OH
wherein M is as above defined and R is an alkyl radical having from 1 to 11 and preferably from 1 to 5 carbon atoms. Such electroplating bath compositions are particularly useful in plating divalent metal ions at a pH of about 6.0 to 10Ø
... ..
DESCRIPTION OF PREFERRED EMBODIMæ~TS
In the practice of the present invention the metal to be plated in conjunction with the carboxy alkylene amino ~i(methylene phosphonic acid) compound (hereinafter referred to as carboxy amino phosphonate or CAP) is preferably a divalent transition metal such as-copper, iron, nickel, zinc or cadmium. Trivalent metals, however, such as chromium, may also be electroplated in conjunction with CAP and a~e ~ 4 ~
10~3Z:i included within the scope of the present invention.
The electroplating bath composition of the present invention is an aqueous solution comprising the metal to be plated, the carboxy amino phosphonate, pH adjusters and optionally one or more additives including brighteners, buffering agents, leveler's, and the hydrox~ alkylidene di-phosphonic acid compound (HADP) whi'ch'are intended to improve the pexformance or life of the bath or the quality of the metal deposit, or to impart other beneficial effect. It is common in the electroplating art to utilize many and varied additives which are selected according to the particular system belng used and on the basis of the skill o~ the elec-troplater. The use of such additives in the electroplating bath compositions of the present invention in order to adapt these compositions to individual circumstances are included within the scope o~ the present invention.
The bath is prepared according to conventional techniques by simply dissolving the desired ingredients into a quantity of water. The water is preferably low in mineral content and may be deionized. The metal to be plated is often added in the form of a water soluble salt such as a metal sulfate, chloride, phosphate, citrate, carbonate or acetate. Carbonate and acetate salts are o~ten preferred because the anions of these salts may be thermally decomposed and thereby removed from the bath when the metal ion is released.
The carboxy amino phosphonate may be added directly to the bath in either the acid or a salt form as defined above.
The acid form is generally preferred simply because it does ~ 5 -10383Zs not introduce extraneous metal or ammonium ions into the bath, but the introduction of such anions is usually not detrimental to the electroplating sy~stem. ~hile the alkylene radical of the CAP compound may have from 3 to about 11 carbon atoms as defined above, the preferred compounds are those havin~ alky-lene radicals of from a~out 3 to 6 carbon atom~. N-(5-carboxypentyl) amino di(methylene phosphonic acid) is one particularly preferred CAP compound. CAP compounds use~ul in the practice of this invention ma~ be prepared by the method of copending patent application Serial No. 200,1i4, filed May 16, 1974, which is commonl~ ass-ignea ~ith the instant application.
The optimum concentration of metal salt and CAP in the electroplating bath w`ll be largely determined b~ the identity of the metal and metal salt, and by the characteris-tic50f the individual electroplating system. ~s a rule, the concentrations are limited primarily by the solubilities of the compounds. Generally speaking, there is usually em-ployed sufficient metal salt and CAP to provide from about 1 percent to about 5 percent by we~ght of metal in solution and to provide a mole ratio of CAP to metal of from about 1:1 to about 5:1. The optlmum ratio will again depend to some ext-ent on the metal being plated and the condit~ons and composi-tion of the electroplating bath but as a general rule at least a slight molar excess of CAP is desirable and it is generally preferred that the mole ratio of CAP to metal ion be within the range of from about 1.2:1 to 2:1. In most instances, the concentration of complex formed hetween the metal ion and the CAP should not exceed its solubil~ty at the temperature and pH
employed in the electroplating operation.
The electroplating bath is generally operated within a pH range of from about 6 to 12. The optimum pH will depend to a great extent~upon the identity of the metal being plated, the presence of extraneous anions within the system and the com-posltion and physical nature of the cathode being plated. Since pH is easily adjusted by the addition of alkaline materials such as alkali ~etal hydroxides, or acid materials such as minersl acids, it is a relatively simple matter to adjust the pH in either direction until optimum plating characteristics are achieved. As a general rule it is often found that lower pH values, that is within the range of from about 6 to 8, give better results in the practice of this invention than higher pH levels although exceptions to this rule may be found.
The use of the HADP compound (c) as defined above, i8 found to enhance the perormance of the electroplating bath, particularly with respect to the plating copper. HADP con~pounds useful in the practice of the present invention may be prepared according to the method of U.S.P. 3,551,480. A particularly preferred HADP compound is l-hydroxy ethylidens-l,l-diphosphonic acid ~HEDP). A combination of CAP and HADP is particularly ef-fective to produce bright, uniform, and tightly adhering deposits of copper on brass and steel by èlectroplating at a pH of about 8Ø The concentration of HADP used in the composition of this invention is sufficient to provide a mole ratio of HADP to metal of from about 0.5:1 to about 5:1, although from about 1:1 to about 2:1 is preferred.
While the aforegoiny description is directed primarily to the composition of the electroplating bath, the present in-vention further prov$des a process for the electrodeposition of a divalent or trivalent mstal which comprises the steps ofelectrolyzing an aqueous solution of a metal complex consisting of any of the metal ions hereinbefore dcscribed, a CAP compound, and any of the optional additives hereinbefore described. By the process of this invention, metals such as copper, iron, n~ckel, zinc and cadmium may be electrically deposited upon a cathod~ such as steel, aluminum, brass, zinc and the like.
.._...
During the electrodeposition process, the electro-plating bath is maintained at a temperature within the range of the freezing point to boiling point of the bath, generally within a range of from about 30C. to about 90C. For reasons of current efficiencies it has been found preferable to main-tain,the temperature of the electroplating bath within the range from about 50C. to about 80C.
The amount of current employed in the electro_ deposition may vary widely, depending upon the particular metal being plated, the temperature of the bath and whether or not the bath is agitated during the electroplating process. In general, the amount of currsnt employed will be sufficient to provide a current density of from about 1 to 300 amperes per square foot of electrode surface. Ordinarily when the electro-pIating bath is quiescent or unagitated, the current density will be in the range of from about 5 to 150 amperes per square foot, while when the electroplating bath is agitated current densities up to about 300 amperes per square foot may be utilized.
The optimum or preferred currcnt density for any particular elec-troplating situation will depend upon the individual characteris-tics of the operation and is readily determined by employing conventional electroplating techniques.
The time required to electroplate or to electrically 43-4106~
~, . , deposit the metal will vary with the kind of metal, the cur-rent density, and bath composition and concentration, as well as upon the thickness of the plate or deposit desir~d. Gener-aily, the greater the current density, the shorter will be thQ time required to produce a metal deposit or plate of a glven thickness.
In accordance with a preferred embodim~nt of the __ .
present invention, copper is electrically deposited upon a wide variety of base metals or substrates such as zinc, iron, brass, steel, aluminum and the like. This preferred process comprises passing an electric current, at a density in the range of from about S to about 150 amperes per square foot of cathode surface, through an aqueous solution containing di-valent copper ions and CAP or CAP + HADP and having a pH in the range of from about 6.0 to about 10.0 and prefarably 6.0 to 8Ø The concentration of copper in th~ ~lectroplating bath composition is preferably from about 1% to about 5% by weight, based on the weight of the solution. The tem~erature of the solution is preferably maintained within the range of from about 50C. to about 70C. during the electroplating operation. ~
As stated above, the electroplating solutions of the present invention can contain known brighteners, buffers, and - leveling agents and other additives commonly used in elsctro-plating operations. Boric acid and its salts are compatible buffers for many formulas of the invention, and selenites and:
arsenites are useful brighteners for copper plating baths while aldehydes and ketones are useful for zinc plating. Other additives which may be employed in the electroplating solutions of the present invention include those disclosed in the 39th _ g _ .
; 1038325 Annual Edition of Metal Finishing Guidebook Directory, 1973, ' published by Metals and Plastics Publications, Inc., 99 Rinder-kamack Road, Wcstwood, New Jersey.
Certain preferred embodiments of the present inven-tion concerning the electrodeposition of copper ars illustrated by tho following Example which is not limiting of the invention.
All parts and percentages are by weight unless otherwise speci-fied.
EX~T.T~
Eleven tests were conductsd to illustrate the per-formance of CAP alone and a combination of CAP and ~EDP as compar~d to HEDP alone in the electrodeposition of copper from an electroplating solution containin~ these additives.
The plating solutions identified as Test Nos. 1-9 ~n Table I were individually prepared in deionized water by dissolving measured amounts of CA~ and/or HEDP and copper sulfate to provide 2 percent copper and the molar ratio~of CAP/H~DP/Cu indicated in Table I. The pH of each solution was adjusted to the desired value of 6.0, 8.0, or 10.0 by the addition of potassium hydroxide. When necessary to dissolve the copper sulfate, the solution was heated up to 80C. and stirred vigorously for an additional 20 minutes. The solu-tions were cooled, if necessary, to the plating temperature of 70C. and transferred to a "Hull Cell". The particular additive utilized, the additive of copper mole ratio and the percsnt co~-per in solution are all shown in Table I.
The Hull Cell is constructed substantially as the electrQlysis cell described in U. S. Patent 2,149,344. This type of Hull Cell is standard equipment for the evaluation of -- 10 --.
103B~2S
electroplatlng solutions by the sub~ectlve determinatlon Or "brlghtness rating" as based on the wldth of the brlghtness range, unlformlty of brlghtness, and the presence or absence of smudges, stalns and dlscoloratlon. In addltlon, the efrec-tlveness Or the bath ls also evaluated on the basls of adheslonof plated metal to the cathode. The partlcular cathodes utll-lzed in thls test were brass or steel as lndlcated ln Table I
and were each 12.7 x 8.26 centlmeters ln slze. The anode utlllzed ln these tests was made of copper and was 6.o3 x 5.40 centlmeters ln size. The Hull Cell utlllzed ln thls test had a capaclty of 1,000 mllllllters.
Each test was conducted for a perlod of two mlnutes at a constant current of two amperes and wlth lntermlttent agltatlon. The reæults of these tests are set forth in Table I and partlcular attentlon ls dlrected to the column deslg-nated "Brightness Ratlng" whlch provldes the baslc crlterla ~or an evaluatlon of the electroplatlng effects on an overall basls .
,. . . .
~325 .. . . . .
~ 8 . o ~ ~ ~oo ~ 8 . ~ ~ ~ o.~o;~
. ~ Q. O O . .~ a ~ o~ ., oQ, ~ ~Id . ~ ~D ~ ~
o~ U u ~ 0.
. ~ ~ . . ~ .~s ~ .
o ~ ~ ~ o~ ~ 0 ~ 00~
O~ ~ U P
'~1 ~ O
--æ a a a a P:~ a ~ u~ mm 0~ ~o ~ ~o ~o o o o I ~r~ ~ o o o ~J~ O ~0 ~ ~ g~ ~
m ~u U
H ~ 0 0 07 0 0--I ~1 IQ 0'1 ul _I O
o 0 0 u~ 0 0 a~ a~ 0 0 0 o s r ;;~1 '.~.~ ~ ~ 0 !~ ~ m m m m mu~ u~ m m mtn ~ U
__ ,1 o ~ ~ --- ~o ~
gl ~ ~ W ~
~ ~ u u u u u cl o o o o o o u ~ ~ ~ z ~l 0~ a - 12 .-.
~ eferring to Table I, Test Nos. 1-3 were made utilizing CAP alone with a brass cathoae and a CAP/Cu ratio of 2:1. The results shown under the brightness rating show that the overall electroplatingje$fect was good at the low pH of 6.0, but poor at higher pH values.
Tests Nos. 4-6 in Table I illustrato the advantage gained by utilizing HEDP in combination with CAP.' A particu-lar advantage is noted at ~H o~ 8.0 (Test No. S) where a Brightness Rating of "very good" was registered for plating on both brass and steel cathodes. It was also observed that oopper adhesion on steel was very qood under the conditions of this test. Test No. 5 accordingly r~.presents a particularly preferred embodiment of the present invention.
Tests Nos. 7-9 are controls illustrating the re-sults obtained with HEDP alone under similar electroplating conditions. It is obs~rved that HEDP performs best at th~
hlgher pH of 10.0, but the quality of the plate is still in-ferior to that obtained with the combination of CAP and EEDP.
With further reference to the data in Table I, it is observed that the combination of CAP and HEDP giv~s at least fair results over the entire pH ranga, and that at a pH of 8.0, the combination gives significantly better results than can be obtained with either component alone regardless of pH.
Although the invention has been illustrated by refer-ence to the electrodeposition of copper utilizing the method and compositions of this invention, the present invention is not limited thereto but is also useful in electrodepositing other metals upon other cathode materials as herainabove described.
Accordingly, the present invention is not to be li~ited except as defined in the claims appended hereto.
' ``` ' :
'. ' '' ~.038325 TITL.E: COMPOSITIONS AND PROCESS FOR THE
ELEC~RODEPOSITION OF M~ALS
INVEN~OR XAVIER KOWALSKI
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to the electrodepo-~ition or electroplating of metals. More particularly, the present invention r~lates to the composition of the electro-plating bath fro~ which the metal is deposited.
Descri~tion of the Prior Art , The electrodeposition of metals from aqueous solu-tlons of metal ions is an old art. Th~ typical electroplating system consists of an electroplating bath and two or more electrodes. The cathode of the electrode system is the object to bs plated. The anode may be carbon or a solid piece of the metal to be plated upon the cathode. A solid metal anode is consumed in the; electroplating process and provides a constant ~ource of metal ions to the plating bath.
Metal ions are maintained in solution in the electro-plating bath by forming salts or metal complexes. Some of themost popular plating compositions utilize inor~anic metal cyanides, and cadmium, brass, copper, silver and zinc can all be plated from cyanide baths.
Electroplating baths comprising aqueous alkaline solution of metal cyanides have several dlsadvantages. Such baths often tend to produce relatively dull and uneven coatings -- 2 -- ~
g~
.. . . .
.
of the plated metal. The use of metal cyanide solut~ons can also be hazardous since i$ the p~ of the electroplating medium ; should drop to neutral or be?ow there is a danger of poisonous hydrogen cyanide gas being produced. Also, the use of metal cyanides presents a disposal problem due to their toxicity, and removing cyanides from waste baths prior to disposal is an expensive undertaking.
The prior art has suggested certain techniques for improving ths p~rformance of cyanid~ plating baths or for even eliminating cyanide from the bath. U.S.P. 2,19S,409 claims to improve the performance of metal cyanide baths by the addition of a nuclear alkyl derivat~ve of an aromatic sulfonic acid of the benzene series. The presence of this material is reported to eliminate pitting, uneven thicknesses and the formation of pinholes in the metal plate, and also improve brightness and uniformity of deposits.
More recently it has been suggested to use certain metal complexing agants in cyanide free plating baths. U.S.P.
3,457,293, for example, suggests the use of certain diphos-phonates or monoamino lower alkylene phosphonates in theelectroplating of divalent metal ions. U.S.P. 3,706,634 and 3,706,635 suggest combinations of ethylene diamine tetra-(methylene phosphonic acidl, l-hydroxy ethylidene-l,l-diphos-phonic acid, and amino tri(methylene phosphonic acid) as particularly useful co~.plexing compositions. U.S.P. 3,617,343 is similarly directad toward a nickel plating systam employing .. . .
certain phosphonic acid compounds. The present invention sup-plements and improves upon these methods of the prior art by providing certain organophosphorus compounds not taught in the prlor art which are useful in electroplating applications.
3 ` ' SUMMARY
In accordance with the present invention there is employed as the electroplating bath an a~ueous solution comprising (a) a divalent or poly~alent metal ion; ~b) a carboxy alkylene amino di~methylene phosphonic acid) having the structure O
.. ..
fH2 -- P -- (OM~2 MOOC ~ ~CH2)n ~ N \
CH2 - P - ~OM)2 wherein M is hydrogen, alkali metal, ammonium, alkyl ammonium or amine and n is an integer of from 3 to about 11 and prefer-ably from 3 to 6; and optionally (c) a l-hydrox~ alkylidene-l,l-diphosphonic acid compound having the structure OH
wherein M is as above defined and R is an alkyl radical having from 1 to 11 and preferably from 1 to 5 carbon atoms. Such electroplating bath compositions are particularly useful in plating divalent metal ions at a pH of about 6.0 to 10Ø
... ..
DESCRIPTION OF PREFERRED EMBODIMæ~TS
In the practice of the present invention the metal to be plated in conjunction with the carboxy alkylene amino ~i(methylene phosphonic acid) compound (hereinafter referred to as carboxy amino phosphonate or CAP) is preferably a divalent transition metal such as-copper, iron, nickel, zinc or cadmium. Trivalent metals, however, such as chromium, may also be electroplated in conjunction with CAP and a~e ~ 4 ~
10~3Z:i included within the scope of the present invention.
The electroplating bath composition of the present invention is an aqueous solution comprising the metal to be plated, the carboxy amino phosphonate, pH adjusters and optionally one or more additives including brighteners, buffering agents, leveler's, and the hydrox~ alkylidene di-phosphonic acid compound (HADP) whi'ch'are intended to improve the pexformance or life of the bath or the quality of the metal deposit, or to impart other beneficial effect. It is common in the electroplating art to utilize many and varied additives which are selected according to the particular system belng used and on the basis of the skill o~ the elec-troplater. The use of such additives in the electroplating bath compositions of the present invention in order to adapt these compositions to individual circumstances are included within the scope o~ the present invention.
The bath is prepared according to conventional techniques by simply dissolving the desired ingredients into a quantity of water. The water is preferably low in mineral content and may be deionized. The metal to be plated is often added in the form of a water soluble salt such as a metal sulfate, chloride, phosphate, citrate, carbonate or acetate. Carbonate and acetate salts are o~ten preferred because the anions of these salts may be thermally decomposed and thereby removed from the bath when the metal ion is released.
The carboxy amino phosphonate may be added directly to the bath in either the acid or a salt form as defined above.
The acid form is generally preferred simply because it does ~ 5 -10383Zs not introduce extraneous metal or ammonium ions into the bath, but the introduction of such anions is usually not detrimental to the electroplating sy~stem. ~hile the alkylene radical of the CAP compound may have from 3 to about 11 carbon atoms as defined above, the preferred compounds are those havin~ alky-lene radicals of from a~out 3 to 6 carbon atom~. N-(5-carboxypentyl) amino di(methylene phosphonic acid) is one particularly preferred CAP compound. CAP compounds use~ul in the practice of this invention ma~ be prepared by the method of copending patent application Serial No. 200,1i4, filed May 16, 1974, which is commonl~ ass-ignea ~ith the instant application.
The optimum concentration of metal salt and CAP in the electroplating bath w`ll be largely determined b~ the identity of the metal and metal salt, and by the characteris-tic50f the individual electroplating system. ~s a rule, the concentrations are limited primarily by the solubilities of the compounds. Generally speaking, there is usually em-ployed sufficient metal salt and CAP to provide from about 1 percent to about 5 percent by we~ght of metal in solution and to provide a mole ratio of CAP to metal of from about 1:1 to about 5:1. The optlmum ratio will again depend to some ext-ent on the metal being plated and the condit~ons and composi-tion of the electroplating bath but as a general rule at least a slight molar excess of CAP is desirable and it is generally preferred that the mole ratio of CAP to metal ion be within the range of from about 1.2:1 to 2:1. In most instances, the concentration of complex formed hetween the metal ion and the CAP should not exceed its solubil~ty at the temperature and pH
employed in the electroplating operation.
The electroplating bath is generally operated within a pH range of from about 6 to 12. The optimum pH will depend to a great extent~upon the identity of the metal being plated, the presence of extraneous anions within the system and the com-posltion and physical nature of the cathode being plated. Since pH is easily adjusted by the addition of alkaline materials such as alkali ~etal hydroxides, or acid materials such as minersl acids, it is a relatively simple matter to adjust the pH in either direction until optimum plating characteristics are achieved. As a general rule it is often found that lower pH values, that is within the range of from about 6 to 8, give better results in the practice of this invention than higher pH levels although exceptions to this rule may be found.
The use of the HADP compound (c) as defined above, i8 found to enhance the perormance of the electroplating bath, particularly with respect to the plating copper. HADP con~pounds useful in the practice of the present invention may be prepared according to the method of U.S.P. 3,551,480. A particularly preferred HADP compound is l-hydroxy ethylidens-l,l-diphosphonic acid ~HEDP). A combination of CAP and HADP is particularly ef-fective to produce bright, uniform, and tightly adhering deposits of copper on brass and steel by èlectroplating at a pH of about 8Ø The concentration of HADP used in the composition of this invention is sufficient to provide a mole ratio of HADP to metal of from about 0.5:1 to about 5:1, although from about 1:1 to about 2:1 is preferred.
While the aforegoiny description is directed primarily to the composition of the electroplating bath, the present in-vention further prov$des a process for the electrodeposition of a divalent or trivalent mstal which comprises the steps ofelectrolyzing an aqueous solution of a metal complex consisting of any of the metal ions hereinbefore dcscribed, a CAP compound, and any of the optional additives hereinbefore described. By the process of this invention, metals such as copper, iron, n~ckel, zinc and cadmium may be electrically deposited upon a cathod~ such as steel, aluminum, brass, zinc and the like.
.._...
During the electrodeposition process, the electro-plating bath is maintained at a temperature within the range of the freezing point to boiling point of the bath, generally within a range of from about 30C. to about 90C. For reasons of current efficiencies it has been found preferable to main-tain,the temperature of the electroplating bath within the range from about 50C. to about 80C.
The amount of current employed in the electro_ deposition may vary widely, depending upon the particular metal being plated, the temperature of the bath and whether or not the bath is agitated during the electroplating process. In general, the amount of currsnt employed will be sufficient to provide a current density of from about 1 to 300 amperes per square foot of electrode surface. Ordinarily when the electro-pIating bath is quiescent or unagitated, the current density will be in the range of from about 5 to 150 amperes per square foot, while when the electroplating bath is agitated current densities up to about 300 amperes per square foot may be utilized.
The optimum or preferred currcnt density for any particular elec-troplating situation will depend upon the individual characteris-tics of the operation and is readily determined by employing conventional electroplating techniques.
The time required to electroplate or to electrically 43-4106~
~, . , deposit the metal will vary with the kind of metal, the cur-rent density, and bath composition and concentration, as well as upon the thickness of the plate or deposit desir~d. Gener-aily, the greater the current density, the shorter will be thQ time required to produce a metal deposit or plate of a glven thickness.
In accordance with a preferred embodim~nt of the __ .
present invention, copper is electrically deposited upon a wide variety of base metals or substrates such as zinc, iron, brass, steel, aluminum and the like. This preferred process comprises passing an electric current, at a density in the range of from about S to about 150 amperes per square foot of cathode surface, through an aqueous solution containing di-valent copper ions and CAP or CAP + HADP and having a pH in the range of from about 6.0 to about 10.0 and prefarably 6.0 to 8Ø The concentration of copper in th~ ~lectroplating bath composition is preferably from about 1% to about 5% by weight, based on the weight of the solution. The tem~erature of the solution is preferably maintained within the range of from about 50C. to about 70C. during the electroplating operation. ~
As stated above, the electroplating solutions of the present invention can contain known brighteners, buffers, and - leveling agents and other additives commonly used in elsctro-plating operations. Boric acid and its salts are compatible buffers for many formulas of the invention, and selenites and:
arsenites are useful brighteners for copper plating baths while aldehydes and ketones are useful for zinc plating. Other additives which may be employed in the electroplating solutions of the present invention include those disclosed in the 39th _ g _ .
; 1038325 Annual Edition of Metal Finishing Guidebook Directory, 1973, ' published by Metals and Plastics Publications, Inc., 99 Rinder-kamack Road, Wcstwood, New Jersey.
Certain preferred embodiments of the present inven-tion concerning the electrodeposition of copper ars illustrated by tho following Example which is not limiting of the invention.
All parts and percentages are by weight unless otherwise speci-fied.
EX~T.T~
Eleven tests were conductsd to illustrate the per-formance of CAP alone and a combination of CAP and ~EDP as compar~d to HEDP alone in the electrodeposition of copper from an electroplating solution containin~ these additives.
The plating solutions identified as Test Nos. 1-9 ~n Table I were individually prepared in deionized water by dissolving measured amounts of CA~ and/or HEDP and copper sulfate to provide 2 percent copper and the molar ratio~of CAP/H~DP/Cu indicated in Table I. The pH of each solution was adjusted to the desired value of 6.0, 8.0, or 10.0 by the addition of potassium hydroxide. When necessary to dissolve the copper sulfate, the solution was heated up to 80C. and stirred vigorously for an additional 20 minutes. The solu-tions were cooled, if necessary, to the plating temperature of 70C. and transferred to a "Hull Cell". The particular additive utilized, the additive of copper mole ratio and the percsnt co~-per in solution are all shown in Table I.
The Hull Cell is constructed substantially as the electrQlysis cell described in U. S. Patent 2,149,344. This type of Hull Cell is standard equipment for the evaluation of -- 10 --.
103B~2S
electroplatlng solutions by the sub~ectlve determinatlon Or "brlghtness rating" as based on the wldth of the brlghtness range, unlformlty of brlghtness, and the presence or absence of smudges, stalns and dlscoloratlon. In addltlon, the efrec-tlveness Or the bath ls also evaluated on the basls of adheslonof plated metal to the cathode. The partlcular cathodes utll-lzed in thls test were brass or steel as lndlcated ln Table I
and were each 12.7 x 8.26 centlmeters ln slze. The anode utlllzed ln these tests was made of copper and was 6.o3 x 5.40 centlmeters ln size. The Hull Cell utlllzed ln thls test had a capaclty of 1,000 mllllllters.
Each test was conducted for a perlod of two mlnutes at a constant current of two amperes and wlth lntermlttent agltatlon. The reæults of these tests are set forth in Table I and partlcular attentlon ls dlrected to the column deslg-nated "Brightness Ratlng" whlch provldes the baslc crlterla ~or an evaluatlon of the electroplatlng effects on an overall basls .
,. . . .
~325 .. . . . .
~ 8 . o ~ ~ ~oo ~ 8 . ~ ~ ~ o.~o;~
. ~ Q. O O . .~ a ~ o~ ., oQ, ~ ~Id . ~ ~D ~ ~
o~ U u ~ 0.
. ~ ~ . . ~ .~s ~ .
o ~ ~ ~ o~ ~ 0 ~ 00~
O~ ~ U P
'~1 ~ O
--æ a a a a P:~ a ~ u~ mm 0~ ~o ~ ~o ~o o o o I ~r~ ~ o o o ~J~ O ~0 ~ ~ g~ ~
m ~u U
H ~ 0 0 07 0 0--I ~1 IQ 0'1 ul _I O
o 0 0 u~ 0 0 a~ a~ 0 0 0 o s r ;;~1 '.~.~ ~ ~ 0 !~ ~ m m m m mu~ u~ m m mtn ~ U
__ ,1 o ~ ~ --- ~o ~
gl ~ ~ W ~
~ ~ u u u u u cl o o o o o o u ~ ~ ~ z ~l 0~ a - 12 .-.
~ eferring to Table I, Test Nos. 1-3 were made utilizing CAP alone with a brass cathoae and a CAP/Cu ratio of 2:1. The results shown under the brightness rating show that the overall electroplatingje$fect was good at the low pH of 6.0, but poor at higher pH values.
Tests Nos. 4-6 in Table I illustrato the advantage gained by utilizing HEDP in combination with CAP.' A particu-lar advantage is noted at ~H o~ 8.0 (Test No. S) where a Brightness Rating of "very good" was registered for plating on both brass and steel cathodes. It was also observed that oopper adhesion on steel was very qood under the conditions of this test. Test No. 5 accordingly r~.presents a particularly preferred embodiment of the present invention.
Tests Nos. 7-9 are controls illustrating the re-sults obtained with HEDP alone under similar electroplating conditions. It is obs~rved that HEDP performs best at th~
hlgher pH of 10.0, but the quality of the plate is still in-ferior to that obtained with the combination of CAP and EEDP.
With further reference to the data in Table I, it is observed that the combination of CAP and HEDP giv~s at least fair results over the entire pH ranga, and that at a pH of 8.0, the combination gives significantly better results than can be obtained with either component alone regardless of pH.
Although the invention has been illustrated by refer-ence to the electrodeposition of copper utilizing the method and compositions of this invention, the present invention is not limited thereto but is also useful in electrodepositing other metals upon other cathode materials as herainabove described.
Accordingly, the present invention is not to be li~ited except as defined in the claims appended hereto.
Claims (12)
1. A process for the electrodeposition of divalent and polyvalent metal ions characterized by comprising the steps of electrolyzing an aqueous solution comprising (a) a divalent or polyvalent metal ion, and (b) a carboxy amino phosphonic acid compound of the structure wherein M is hydrogen, alkali metal, ammonium, alkyl ammonium, or amine and n is an integer of from 3 to about 11, the concentration of (a) in said aqueous solution being from about 1 percent to S percent; and the molar ratio of (a):(b) being from about 1:1 to 1:5; the pH of said aqueous solution being from about 6.0 to 10.0, and the temperature of said aqueous solution being from about 30° to 90°C.
2. A process of claim 1 characterized in that said aqueous solution comprises, in addition to (a) and (b), a compound (c) having the structure wherein M is as defined in claim 1, and R is a C1-11 alkyl radical, the molar ratio of (a):(c) being from about 2:1 to 1:5.
3. A process of claim 1 wherein (b) is
4. A process of claim 1, 2 or 3, characterized in that said metal ion (a) is selected from the group consisting of copper, iron, nickel, zinc, cadmium, and chromium.
5. A process of claim 1, 2 or 3, characterized in that said metal ion (a) is copper, and the pH of said aqueous solution is about 6Ø
6. A process of claim 2 wherein R is -CH3.
7. An electroplating bath composition characterized by com-prising an aqueous solution of (a) a divalent or polyvalent metal ion, and (b) a carboxy amino phosphonic acid compound of the structure wherein M is hydrogen, alkali metal, ammonium, alkyl ammonium, or amine and n is an integer of from 3 to about 11, the concentration of (a) in said aqueous solution being from about 1 percent to 5 percent; the molar ratio of (a):(b) being from about 1:1 to 1:5; and the pH of said aqueous solution being from about 6.0 to 10Ø
8. A composition of claim 7 characterized in that said aqueous solution comprises, in addition to (a) and (b) a compound (c) having the structure wherein M is as defined in claim 7, and R is a C1-11 alkyl radical, the molar ratio of (a):(c) being from about 2:1 to 1:5.
9. A composition of claim 8 wherein (b) is
10. A composition of claim 8 wherein R is CH3.
11. A composition of claim 7, 8 or 9, wherein said metal ion (a) is copper.
12. A composition of claim 7, 8 or 9, wherein said metal ion (a) is selected from the group consisting of copper, iron, nickel, zinc, cadmium, and chromium.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US373051A US3914162A (en) | 1973-06-25 | 1973-06-25 | Compositions and process for the electrodeposition of metals |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1038325A true CA1038325A (en) | 1978-09-12 |
Family
ID=23470708
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA203,082A Expired CA1038325A (en) | 1973-06-25 | 1974-06-21 | Compositions and process for the electrodeposition of metals |
Country Status (11)
| Country | Link |
|---|---|
| US (1) | US3914162A (en) |
| JP (1) | JPS5036322A (en) |
| AR (1) | AR207452A1 (en) |
| BE (1) | BE816806A (en) |
| BR (1) | BR7405129D0 (en) |
| CA (1) | CA1038325A (en) |
| DE (1) | DE2430250A1 (en) |
| FR (1) | FR2234388B1 (en) |
| GB (1) | GB1438080A (en) |
| IT (1) | IT1015337B (en) |
| SE (1) | SE7408241L (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52106331A (en) * | 1976-03-05 | 1977-09-06 | Kosaku Kk | Plating bath |
| DE2732777C2 (en) * | 1977-07-20 | 1979-09-13 | Benckiser-Knapsack Gmbh, 6802 Ladenburg | N-carboxyalkane-aminoalkane-polyphosphonic acids and their alkali metal salts and processes for their preparation |
| DE2756516A1 (en) | 1977-12-19 | 1979-06-21 | Hoechst Ag | DETERGENTS AND DETERGENTS |
| US4265715A (en) * | 1979-07-13 | 1981-05-05 | Oxy Metal Industries Corporation | Silver electrodeposition process |
| USH325H (en) | 1980-07-30 | 1987-09-01 | Richardson Chemical Company | Electroless deposition of transition metals |
| DE3347593A1 (en) * | 1983-01-03 | 1984-07-05 | Omi International Corp., Warren, Mich. | AQUEOUS ALKALINE CYANIDE-FREE COPPER ELECTROLYTE AND METHOD FOR GALVANICALLY DEPOSITING A GRAIN-REFINED DUCTILE AND ADHESIVE COPPER LAYER ON A CONDUCTIVE SUBSTRATE |
| US4469569A (en) * | 1983-01-03 | 1984-09-04 | Omi International Corporation | Cyanide-free copper plating process |
| US4979987A (en) * | 1988-07-19 | 1990-12-25 | First Miss Gold, Inc. | Precious metals recovery from refractory carbonate ores |
| US5021324A (en) * | 1990-10-05 | 1991-06-04 | Polychrome Corporation | Printing plate protectant |
| US5266212A (en) * | 1992-10-13 | 1993-11-30 | Enthone-Omi, Inc. | Purification of cyanide-free copper plating baths |
| US5607570A (en) * | 1994-10-31 | 1997-03-04 | Rohbani; Elias | Electroplating solution |
| US7604783B2 (en) | 2004-12-22 | 2009-10-20 | Placer Dome Technical Services Limited | Reduction of lime consumption when treating refractor gold ores or concentrates |
| RU2338814C2 (en) * | 2005-11-18 | 2008-11-20 | Федеральное государственное образовательное учреждение высшего профессионального образования "Астраханский государственный технический университет" | Electrolyte for cadmium electroplating |
| US8061888B2 (en) | 2006-03-17 | 2011-11-22 | Barrick Gold Corporation | Autoclave with underflow dividers |
| US8252254B2 (en) | 2006-06-15 | 2012-08-28 | Barrick Gold Corporation | Process for reduced alkali consumption in the recovery of silver |
| JP6942791B2 (en) * | 2017-03-31 | 2021-09-29 | 日本エレクトロプレイテイング・エンジニヤース株式会社 | Electrolytic silver plating solution |
| CN114892225B (en) * | 2021-09-30 | 2023-03-14 | 深圳市联合蓝海黄金材料科技股份有限公司 | Plating solution for electroplating gold on nickel coating and method for electroplating gold on nickel coating, gold-plated part and application |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2673214A (en) * | 1952-06-11 | 1954-03-23 | Bersworth | Polyhydroxyamino acid compounds |
| US2961311A (en) * | 1955-12-13 | 1960-11-22 | Dow Chemical Co | Metal ion control |
| US3293176A (en) * | 1964-04-01 | 1966-12-20 | Le Roy A White | Method of chelating with an ethergroup-containing sequestering agent |
| DE1496916B1 (en) * | 1964-09-22 | 1969-10-23 | Monsanto Co | Cyanide-free, galvanic bath and process for the deposition of galvanic coatings |
| DE1217950B (en) * | 1965-02-25 | 1966-06-02 | Henkel & Cie Gmbh | Process for the production of new perhydrates from aminoalkylphosphonic acids |
| FR96342E (en) * | 1967-12-09 | 1972-06-16 | ||
| GB1392242A (en) * | 1971-07-26 | 1975-04-30 | Technic | Process for producing by electrodeposition bright deposits of gold and its alloys |
| BE791401A (en) * | 1971-11-15 | 1973-05-14 | Monsanto Co | ELECTROCHEMICAL COMPOSITIONS AND PROCESSES |
-
1973
- 1973-06-25 US US373051A patent/US3914162A/en not_active Expired - Lifetime
-
1974
- 1974-01-01 AR AR254353A patent/AR207452A1/en active
- 1974-06-21 CA CA203,082A patent/CA1038325A/en not_active Expired
- 1974-06-24 GB GB2793974A patent/GB1438080A/en not_active Expired
- 1974-06-24 IT IT24337/74A patent/IT1015337B/en active
- 1974-06-24 BR BR5129/74A patent/BR7405129D0/en unknown
- 1974-06-24 FR FR7421880A patent/FR2234388B1/fr not_active Expired
- 1974-06-24 SE SE7408241A patent/SE7408241L/xx unknown
- 1974-06-24 JP JP49071438A patent/JPS5036322A/ja active Pending
- 1974-06-24 DE DE2430250A patent/DE2430250A1/en not_active Withdrawn
- 1974-06-25 BE BE145834A patent/BE816806A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DE2430250A1 (en) | 1975-01-23 |
| FR2234388B1 (en) | 1978-02-17 |
| FR2234388A1 (en) | 1975-01-17 |
| BE816806A (en) | 1974-12-27 |
| SE7408241L (en) | 1974-12-27 |
| GB1438080A (en) | 1976-06-03 |
| BR7405129D0 (en) | 1975-01-21 |
| IT1015337B (en) | 1977-05-10 |
| USB373051I5 (en) | 1975-01-28 |
| AR207452A1 (en) | 1976-10-08 |
| JPS5036322A (en) | 1975-04-05 |
| US3914162A (en) | 1975-10-21 |
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