Note: Descriptions are shown in the official language in which they were submitted.
C~se No. ~-11,088
PROOESS FOR ELECTRCDEPOSIT~ COPPER
BackgroUnd of the Invention
.
me process c~nprising the present invention broadly
relates ~o the electrodeposition of copper deposits Gn conductive
substrates, and more particularly is directed to the
electroplating of rotGgravure cylinders employed for printing
providing an engineering copper plate ~hich is eminent.Ly suitable
for subsequent mechanical engraving.
A variety of copper electrolyte c~npositions ar.d
processes have heretofore been employed for depositing a copper
plate on the surfaces of rotogravure cylinders at a thickness
sufficient to enable subsequent engraviny thereof. Copper
electrolytes of the type employed for depositing a bright
decorative copper plate provide for good leveling and ductility
of the copper deposit but are subject to the disadvantage that
the copper deposit after deposition i.s sel.f-annealing ~hereby the
deposit becomes progressively soSter foll~ng the plating step
rnaking the deposit unsatisfactory for rnechanical engraving such
as by employing a diamond sty]us. Alternat-ively, copper el,ectro-
lytes have been ernpl.oyed whlch do not give rise to self-annealing
but such copper plates are characterized by Illeir dull. matte ap-
pearance with poor leveling necessi,tating mecllanica'l ~inistl.illg
such as by polishing of the copper deposil t,o l~lace :it in condiTionfor subsequent engravi,ng.
,., ~ .
The present inver.tion provides for a process empl~ying
an aqueouS acidic copper electrolyte which under controlled
conditions iS effective to deposit a suhstantiall~ uniformly
hard, non-annealing, bright, leveled and ductile engineerirg
copper deposit which substantially eliminates or minimizes
subsequent mechanical finishing operations of the copFer deposit
and wherein the copper deposit itself is of satisfactory hardness
in spite of standing for prolonged time periods follcwing the
electrodeposition step to enable satisfactory engraving by
various mechanical means. The process is further characterized
as being of simple and econcmical control and operation for
achieving consistent copper plates of the desired mechanical
properties.
Summary of the In~ention
The benefits and advantages of the present invention
are based on the discovery of a process employing an aqueous
acidic copper electrolyte of a controlled ccmposition which under
controlled operating parameters is operative for electro-
depositing a highly leveled, ductile, bright and substantiallyuniformly hard engineering copper plate which is of a
non-annealing character thereby retaining its hardness for
prolonged time periods following the electrodeposition step
enabling the plate to be engraved by mechanical engraving
techniques and the like.
The copper electrolyte camprises an aqueous acidic
solution containing copper in an amount sufficient to
1~5~
electrodeposit copper on a substrate and a controlled csmbination
of bath soluble and compatible organic brightening agents
including:
(1) an organic polyether ccmpound and mixtures
thereof;
(2) an organic sulfide compound and mixtures thereof;
and
(3) at least one compound selected from each of
the grouPs consisting of:
(A) A oompound corresponding to the structural formula
A,
FORMULA A
2 ~ N ~ ~ ~
R2 f I (~ X~3
¢~ -
Wherein R~ and R2 are radical.s sel.ected frolll the grGup
consisting of hydrogen, methyl and ethyl. rad.i.cals, X is an anion
selected from the group consisting of chlori.de, brosnide, i.odide,
fluori.de, sulfate, bisul.fate and nitrate, `~ is
H,-NH2,-N~CH3)2 and ~N=N-Z, and Y, is an ar~l~tic radi.cal
selected from the group consisti.ng of phen~l., napht:hyl, and
phenyl and naphthyl radicals substitllte<l ~7i.th arni.llcJ, 21kyl
substituted amino, hydroxy and a.lko~y substituent groups;
(B) a substituted pht}laL-.~vallirle compound
corresponding to formula B,
FOR~ B
Pc - (X')n
wherein:
Pc is a phthaloc;yanine radical.;
X' is -~2~R2'-S03M~-cH2sc(NR2)2
R is H, alkyl containi.ng 1-6 carb~n at~s, aryl
con-taining 6 carbon atomLC~ aralJ~l containing 6
carbon atol~s in the aryl portiorl and 1 to 6 car~-ion
atcms in the aLkyl porti.on, heterocyclic
containing 2 to 5 carbon atollls and at least ]
nitrogen, oisygen, sulfur or phosphorus atcm, and
aLkyl, aryl, aralkyl and heterc~clic, as defined
above, containing 1 to S amirlo, hydro~y, sulfonic
or phosphonic groups;
n is 1-6;
Y' is halogen or al.kyl. sul.fate conlainjllg I t-o 4 carbon
atoms i.n the alkyl port:i.on; a
M is ~I, Li, Na, K or Mg;
'I
..~v-, ,
~,,
5C~
2~
(C) an alkylated polyethyleneimine reaction pro-
duct having a quaternary nitrogen, as well as mixtures of
(A), (B) and (C).
The organic 'orightening agents in the aqueous
acidic electrolyte are present to provide a concentration
of the polye-ther compound within a range of about 0.001 to
about 5 grams per liter (g/1), the organic sulfide compound
in a concentration of about 0.0005 to about 1 g/l, and a
concentration of the brighteners comprising group (3) in
admixture of about three or more present in an amount of
at least about 25 milligrams (m g/l) with concentrations
up to about 0.5 g/l being usable.
In accordance with the process aspects of the
present invention, the aqueous acidic copper electrolyte
is employed at a temperature of about 15 to about 38C
(about 60-100F) and the deposition of copper on a conductive
substrate is performed at a cathode c~rrent density of at
least about 6.5 amperes per square decimeter (60 ASF) up
to as high as about 32.4 amperes per square decimeter (300
ASF) to produce an engineering copper deposit of at least
about 0.025 millimeter (0.001 inch) thick. A conforming anode
or plurality of anodes are employed to avoid any low current
density areas less than about 6.5 amps per sq. dm. (60 ASF)
and to further assure a substantially uniform thickness of
copper deposit on the substrate.
Additional benefits and advantages of the present
invention will become apparent upon a reading of ~he nescr;D-
tion of the Preferred Embodiments taken in conjunction with
the accompanying examples.
Description of ~he Preferred Embodiments
In accordance with the practice of the process of the
present invention, an aqueous acidic electrolyte is pr~Jided
which may be of the sulfate type typically containing about 180
to about 250 g/l of copper sulfate and about 30 to about 80 g/l
of sulfuric acid. Alternatively, fluoroborate baths can be
prepared typically containing from about 200 to about 600 g/l of
copper fluoroborate and up to about 60 g/l of fluoboric acid. It
is also contemplated that copper nitrate salts or copper
sulfamate salts can be employed in approximately equivalent
proportions for copper sulfate and the electrolyte can be
acidified employing equivalent amounts of phosphoric acid, nitric
acid, sulfamic acid or sulfuric acid. In accordance with the
preferræ practice of the present mvention, sulfate-type copper
baths are employed.
The aqueous electrolyte may further incorporate halide
ions such as chloride and/or bramide ions in an amount up to
about 0.2 g/l. Concentration of halide ions in excess of about
0.2 g/l have been found undesirable in some instances due to a
loss in the ductility of the copper deposit.
me unique non-annealing characteristics of the copper
deposit in further combination with the desirable physical
characteristics thereof are achieved by employing a specific
ccmbination of organic brighteners of the types as hereinbefore
set forth. The preferred organic polyether compounds are bath
soluble and ccmpatible polyethers containing at least 4 ether
~5~
oxygen atoms and having an average molecular weight ranging from
about 180 up to 1,000,000. Particul~rly satisfactory results are
obtained with polypropylene and polyethylene glycols includir.g
mixtures of the foregoing of an average ~olecular weight of about
600 to akout 6,000, alkoxylated aromatic alcohols having a
lecular weight ranging from about 300 to 2500 and alkoxylated
amines having a molecular weight of about 1000 to about 50,300.
Exemplary of such preferred polyether brightening ccmpounds which
can satisfactorily be employed are polyethylene glycols of an
average molecular weight of from about 400 to about 1,000,000;
ethoxylated naphthols containing 5 to 45 mols ethylene oxide
groups; propoxylated naphthols containing 5 to 15 mols of
propylene oxide g,roups; ethoxylated nonyl phenol containing 5 to
30 mols ethylene oxide groups; propylene glycols of an average
~olecular weight of about 350 to a~out 1,000; block polymers of
polyoxyethylene and polyoxypropylene glycols of an average
molecular weight of about 350 to 250,000; ethoxylated phenols
containing 5 to 100 mols of ethylene oxide groups; propoxylated
phenols containing 5 to 15 mols of propylene oxide groups, and
ethylene diamune blcck polymers having a lecular weight of
about 1600 to about 30,000. Additional polyether ccmpounds
suit~ble for use in the practice of the present process are those
disclosed in United States Patent No. 4,272,335.
The polyether brightening com~ounds are employed in a
range of about 0.001 up to about 5 g/l with the lower
concentrations generally being used with the higher molecular
weight polyethers.
The organic sulfide brightening compound (2) 1,Jhich
can be satisfactorily employed in the practice of the present
process includes the various organic sulfide sulfonic co~ounds
as described in United States Patent No. 3,267,010, and particu-
larly Table I thereof; organic sulfur compounds as disclosed in
United States Patent No. 4,181,582 and particularly Table III
thereof; and the organic polysulfide compounds as disclosed in
United States Patent No. 3,328,273 and particularly Table I there-
of. The organic sulfide compounds containing sulfonic or phos-
phonic groups may also contain various substituent groups, such
as methyl, chloro, bromo, methoxy, ethoxy, carboxy or hydroxy,
on the lecules, especially on the aromatic and heterocyclic
sulfide-sulfonic or phosphonic acids. Such compounds may be used
as the free acids, the alkali metal salts, organic amine salts,
or the like.
other suitable organic divalent sulfur compounds
which can be satisfactorily used include HO3P-(CH2)3-S-S-(CH2)3-
PO3H, as well as mercaptans, thio-carbamates, thiolcarbamates,
thioxanthates, and thiocarbonates which contain at least one
sulfonic or phosphonic group.
A particularly preferred group of organic divalent
sulfur compounds as described in U.S. Patent No. 3,328,273 are
the organic polysulfide c~mpounds of the formula XR1-(S)nP.2SO3H
or XR1-(S)nR2PO3H wherein Pl and R2 are the sam~ or differer~
a ~71ene group containing fram about 1 to 6 carkon atcms, X is
hydrogen, SO3H or PO3H and n is a number frGm about 2 to 5.
These organic divalent sulfur compounds are aliphatic
polysulfides wherein at least two di~lent sulfur atcms are
vicinal and wherein the molecule has one or two terminal sulfonic
ox phosphonic acid groups. The alkylene portion of the molecule
may be substituted with groups such as methyl, ethyl, chloro,
brcmo, ethoxy, hydroxq~, and the like. These compounds may be
added as the free acids or as the alk~l; metal or amine salts.
The organic sulfide brightening compound or mixture of
ccmpounds are present in the electrolyte within a range of about
0.0005 to about 1 g/l.
In addition to the brightening agents (1) polyether
compounds and (2) sulfide compounds, the electrolyte further
contains as an essential brightening agent at least three
brightener ~ ~pounds (3) ccmprising compounds (A), IB), and.
~C). Brightening comFound (A) corresponding to Formula A as
hereinabove set forth may typioally ccmprise those as set forth
in United States Patent No. 2,882,209, and specifically Table II
. thereof. Such typical brighteners include Diethyl safranine
azo dimethyl aniline - Janus Green B, Diethyl safranine azo
phenol - Janus Black, Safranine azo naphthol - Janus Blue, Janus
Gray (Color Index 137, Society of Dyers ~ Colourists, by F. M.
Rowe, 1924), Dimethyl safranine azo dimethyl aniline,
~;~s~
:
Phenosafranine, Fuchsia, Amethyst Violet, and the like.
Brightening ccmpounds corresponding to Formula A can be empl~yed
~ithin a range up to akout 0.5 g/l with concentrations of abcut
25 to about 50 mg/l being preferred.
The brightening agent corresponding to Formula B
comprises a substituted phthalocyanine radical which may be
metal-free or which may contain a stable divalent or trivalent
metal bound by coordination of the isoindole nitrogen at~ns of
the molecule, which metal is selected from the group consisting
of cobalt, nickel, chro~ium, iron or copper, as well as mixtures
of the foregoing of which copper is th~ more typical ar.d
preferred metal. Such phthalocyanine compounds suit~ble for use
in the practice of the present process are those having a ~ath
solubility of at least about 0.1 mg/l and are employed in
concentrations up to about 0.5 g/l with concentrations of about
~5 to about 50 mg/l being preferred. Suitable phthalocyanine
ccmpounds correspond to the structural formula:
~0
~i)b
\==~
(X~ N ( ~ ~ (X~b
'' ~\~
(X)b
hherein:
X is as has keen heretofore defined;
Z is Ni, Co, Cr, Fe or Cu;
a is 0-1; and
B is 0-2, prDvided however thAt the total
number is X substituents is 1-6.
Substituted ph~halo~yanine compounds suitable for use
in the practice of the present invention further include those as
described in Uhited States Patent No. 4,272,335. A particularly
preferred phthalocyanine compound comprises Alcian slue.
11
S~2~
The organic brightening compound (C) co~prises a
reaction product of polyethyleneimine and an organic compound
which will alkylate the nitrogen of the polyethyleneimine to
produce a quaternary nitrogen. Compounds of the foregoing type
satisfactory for use in the practice of the present process are
disclosed in United States Patent No. 3,770,598. The alkylating
agent may comprise aliphatic and aromatic compounds which may
be either saturated or unsaturated. Compounds which have proved
to be of particular value are organic compounds which contain
active halogens, such as the aralkyl halides, the alkyl, alkenyl
and alkynyl halides, acid halides, acyl halides, and the like.
Additionally, compounds such as the alkyl sulfates, alkyl sul-
tones, aldehydes, ketones, isocyanates, thioisocyanates,
- epoxides, acylamides, acids, anhydrides, ureas, cyanamides,
guanidines, and the like, may also be used. It is to be appre-
ciated that in some instances organic compounds may be used
in which the reacting group is attached directly to an aromatic
nucleus, rather than on an alkyl chain. Exe~plary of such
materials is 2,4-dinitrochlorobenzene, which will react with
either the primary or secondary nitrogen of the polyethyleneimine
and/or will quaternize with the tertiary nitrogen. Accordingly,
in referring to the "alkylation" of the nitrogen in the
polyethyleneimine, it is intended to include those cases in which
the nitrogen is attached directly to an aryl or aromatic nucleus,
i2~
~ .
as well as those in~which it is attached to an aliphatic group.
Specific compounds which have been found to give particulæly
good results are benzyl chloride, allyl bromide, dimeth~l
sulfate, and propane sultone. These compounds, h~lever, æe
merely exemplary of the organic ccmFounds which will alkylate t~e
nitrogen of the polyethyleneimine. Preferably the aIkylatir.g
agent is an aromatic halide.
~ ?hen the alkylating agent reacts with the primary or
secondary amine; it will be altered to the secondary and tertiary
amine, respectively. This is accGmplished by adding more
alkylating agent as is desired. Where the alkylation takes place
at the primary and/or secondary nitrogen, there will ke a
splitting off of the alkylating groups on the organic ccopound,
e.g., halogen, sulfate, or the like. In the case of the tertiary
nitrogen, hcwever, a quaternization takes place, forming the
quaternary salt.
It is pre~erred that as many nitrogen atoms as possible
in the polyethyleneumine brightener should be quaternized,
although as little as 5 percent of the nitrogen atoms being
quaternary still gives desirable results, with lOpercent being
more preferred and even more preferably 20 percentO
me polyethyleneimine which is used in forming the
brighte~lng agent additive may have a wide rarge of molecular
weights. Typically, the molecular weight of the
polyethyleneimine may be within the range of about 300 to several
1~ 5~
.,
millions. In many instanceS, haw~v~r, molecular ~eights within
the range of about 300 to l,000~000 are preferred. The organic
brightening ccmpound (C) is employed in am~unts up to a~out 0.5
g/l with concentrations of akout 35 to about 100 mg/1 being
preferred.
The organic brightening agents (A), (B) and (C) are
employed in combination of at least three in an amount of at least
about 25 mg/l with concentrations up to about 0.5 g/l beir.g
satisfactory while amounts of about 30 to about 90 mg/l being
preferred.
In accordance with the practice of the process of the
present invention, an electrolyte of the foregoing camposition is
employed in which an electrically conductive substrate is
immersed and is cathodically charged for a period of time to
deposit the desired thickness of copper thereon. During the
electroplating operation, the bath is controlled within a
temperature of about 60 up to about 100F with temperatures of
from about 70 up to about 90F being typical and preferred.
Temperatures above about 100F are undesirable in many instances
due to the tendency to form copper deposits which are of reduced
ductility. The electrodeposition of the copper plate is
performed at a current density of at least about 60 ASF to
current densities as high as about 300 ASF and even higher in
specialized instances. Preferably, the cathode current density
is controlled within a range of about 100 to about 200 ASF. In
~5~
,,
order to achieve a substantially uniform thickness of cc~per
plate on the substrate, it is preferred that an anode arrange~ent
is employed ~hich provides for a substantially uniform current
density on the cathode over substantially the entire surface
thereof. For this purpose, in accordance with conventional
practice in the electroplating of rotogravure cylinders, a
conforming anode, or in the alternative, a plurality of anodes
disposed at spaced intervals are employed so as to achieve a
substantially uniform cathode current density.
The unique copper plate deposited in accordance with
the practice of the present invention which is bright, leveled,
ductile, substantially pure copper is eminently adapted for a
variety of engineering applications such as for electroforming
molds, manufacture of audio and video discs, for rotogravure
cylinders and the like. The copper plate is further
characterized as being of relatively uniform hardness, usually
above 200 Diamond Pyramid Hardness Number at a 100 gram load and
further characterized by a highly uniform, homogeneous, equiaxed
crystalline structure of a grain size less than about 1 micron.
The engineering ccpper deposit produced by the present process is
distinguishable from conventional decorative copper deposits
because of the thickness ~7hich is at least about 0~001 inch to as
high as 0.050 inch and even thicker as weIl as in the unique
nonannealmg characteristics of the engineering copper plate.
me process of ~he present invention furthermore, is inapplicable
for producing so-called decorative copper deposits due to the
~s~
formation of dark striations in all :lc~w currer)t del1si ty areas
havin~ average cathode urrent densi ties belc~/ 6(~ ASF ~Jhich
renders such decorative deposit unacceptable.
In order to Eurther illust:rate the proces, of the
present invention, the fol].owi.ng typi.c~l. exan~les are prov;ded.
It will be appreciated that the e~cunp 1 es are pr.ovi.ded for
illustrative purposes and are not intende(l to 1~ I.imi.tinc3 of the
scope of the present i.nvention as herein descri bed and as set
forth in the subjoinecl claims.
An aqueous acidic copper e Lectrolyte is prepared
containing about 195 g/l of copper sulfate pentahydrate,
75 g/l of sulfuric acid, about 20 to about 100 mg/l
chloride ions and a combination oE organic brightening
agents comprising brighteners ( 1 ) po].ypropylene oxide
(mol wt. 750) present in an amollnt of about 120 mg~
(2) Bis (3-sulfopropyl disulEide disodium salt) present
in an amount of about 21 mg/l, brightener (3)
corresponding to Formula (A ) compri.si.ng Janus Green B
present in amount of about 15 mg/:l, brightener (3)
correspond i ng to Formul a ( B ) compr i. s i ng Me th i c Turql~o i se
present in an amount of about 15 mg/l and brightener ( 3)
(C) comprising polyethyleneimine quaterni zed with benzyl
chloride present in an amount of about 12 mg/l.
The bath is controlled at a ten~era-t ure of about 80F
and a roto~.ravure cylinder is i~ersed in t he bath surrounded by
conforming copper anodes while being Lotatecl at lO0 rpm and electric
current is passed between the anodes and catlll)dical1y chanJed
work piece to provide a cathocle currenl dellsily oE about l5() ASF.
~16
.. ,~ . .
The resultant copper deposit is observed to be fully bright wi~h
good leveling, good ductility and of a substantially uniform
hardrless above 200 Diamond Pyramid Hardness Nu~ber at a 100 gram
load (DPH~. The copper deposit is substantially non-annealing as
evidenced by no significant reduction in hardness after stardirg
for a period of 48 hours following the electrodeposition of the
copper plating.
EX~MPLE 2
An aqueous acidic copper electrolyte is prepared
containing about 195 g/l of copper sulfate pentahydrate, 75 g/l
of sulfuric acid, akout 20 to akout 100 mg/l chloride ions and a
ccmbination of organic brightening agents comprising brighteners
(1) polyethylene oxide ( 1 wt. 3350) present in an amount Or
akout 60 mg/l, (2) Bis (3-sulfopropyl disulfide disodium salt)
present in an amount of about 30 mg/l, and brightener (3)
corresponding to Formula (A) comprising Janus Green ~ present in
an amount of a~out 10 mg/l, Methic Turquoise corresponding to
formula B present in an amount of 10 mg/l and 10 mg/l of
brightener (3)(C) comprising polyethyleneimine quaternized with
benzyl chloride.
The bath is controlled at a temperature of akout 75F
and a rotogravure cylinder is immersed in the bath surrounded by
conforming copper anodes while rotated at 3Q0 rpm and electric
current is passed between the anodes and cathodically charged
work piece to provide an average cathcde current density of about
100 ASF. The resultant copper deposit is observed to be fully
bright, leveled and ductile with a hardness above about 200 DPH
at 100 gram load. The resultant copper deposit is substantially
nonannealing.
EYl~PLE 3
An aqueous acidic copper electrolyte is prepared
containing about 195 g/l of copper sulfate pentahydrate,
75 g/l of sulfuric acid, about 20 to about 100 mg/l
chloride ion5 and a combination of organic brightening
agents comprising brighteners (1) polypropylene oxide (mol
wt. 750) present in an amount of about 120 mg/l, (2) Bis
(3-sulfopropyl disulfide disodium salt) present in an
amount of about 30 mg/l, and brightener (3) corresponding
to Formula (A) comprising Janus Green B present n an
amount of about 8 mg/l, brightener (3) corresponding to
Formula ~B) comprising Methic Turquoise present in an
amount of about 22 mg/l and brightener (3) corresponding
to Formula (C) comprising polyethyleneimine quaternized
with benzylchloride present in an amount of about 3 mg/l.
The bath is controlled at a temperature of about 70F
and a rotogravure cylinder is immersed in the bath surrounded by
conforming copper anodes while rotated at 180 rpm and electric
current is passed between the anodes and cathodically ~harged
work piece to provide an average cathode current density of about
150 ASF. The resultant copper deposit is observed to be fully
bright, leveled and ductile with a hardness above 200 DPH at a
100 gram load. me copper deposit is suhstantially nonannealing.
While it will be appQrent that the preferred
emaxln~nts of the invention disclosed are well calculated to
fulfill the objects above stated, it will be appreciated that the
invention is susceptible to mcdification, variation and change
without departing frcm the proper scope or fair meaning of the
subjoined claims.
