Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
-
This invention relates to the electrodeposition of cop-
per from aqueous acidic plating baths, especially from copper
sulfate and fluorohorate baths, and more particularly it relates
to the use of certain organic compounds in the baths to give
bright, highly ductile, low stress, good leveling copper depo-
sits over a wider range of bath concentration and operating
current densities.
In U.S. Patent No~ 3,770,598, assigned to the assignee
of the present invention, there has been proposed the addition
of certain reaction products to acidic coppex plating baths to
. yield generally the above recited benefits. These prior art
additives are formed by the reaction of polyethylenimines wlth
an alkylating agent, such as benzyl chloride. While these reac-
tion products are efficacious in improving the copper deposit,
often they may be found to be relatively insoluble in the
aqueous acidic plating baths.
SUMMARY OF THE INVENTION
It has been found that improved copper deposits can be
obtained from aqueous acidic copper plating baths by the addi-
tion thereto o-f poly (alkanol quaternary ammonium salts). Such
: salts are more soluble in and more compatible with the aqueous
acidic baths as compared with the previously utilized alkylated
polyethylenimines of the prior art.
More specifically, the invention relates to a bath for
electrodepositing copper comprising an aqueous acidic copper
plating bath having dissolved therein about 0.04 to 1000 mg/l
of a reaction product of an alkoxylated polyalkylenamine with
an alkylating agent as defined below~
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The composition and method of this invention broadly
comprises acidic copper plating haths of either the acidic copper
t ~
- ~
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Case U 10,722
sul~ate or acidic copper rluoroborate type. As is kn~wn in the
art9 such acidic copper sulfate baths typically contain from
about 180 to 250 grams per liter o~ copper sul~ate and 30 to
80 grams per liter of sulfuric acid; while the acidic copper
fluoroborate baths typically contain from about 200 to 600
~rams per liker of copper ~luoroboLate and about 0 to 60
grams per liter of ~luoroboric acld. Additionally, it is
found that with the additives of the present invention, these
acid copper plating baths ~ay be operated under conditions of
; lO high acid and low metal content. Thus, even with plating
baths which contain as little as about 7.5 grams per liter
copper and as much as 350 grams per liter sulfuric acid or
350 grams per liter o~ fluoroboric acid, excellent plating
results are still obtained.
Desirably, these plating baths are operated at cur-
:
rent densities within the range of about lO to lO0 amps per
square foot~, although~ in many instances, current densities
as low as about 0.5 amps per square foot may also be used.
Typically, with lo~1 copper and high acid baths, current den~
sities withln the ran~e o~ about lO to 50 amps,~ft2 are used.
Addltionally, in high agitation baths~ such as those used in
plating roto~ravure cylinders, current densities up to as high
as about 400 amps~t2 may be used. The baths may be operated
with air agitation, cathode-rod agitation, or solution agita- ;
;~25 ~ tion and cathode-rod agitation, depending upon the particular
` bath and plating conditions which are used. Typical bath
temperakures are within the range of about 25 to 35C.,
although both lower and higher temperatures, e.g., 50C. or
more, may also be used. In this regard, it is to be noted
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Case U 10,722
,
that the plating baths of the present invention may also be
- used in copper electrorefining processes In such processes,
temperatures up to about 60-70C. may be used.
Although it has been found to be deslrable that chlo-
rine and~or bromide anions in the bath are below about 0.1 gram
per liter, appreciably greater amounts of many inorganic cations,
such as ferrous iron, nickel, cobalt, zinc, cadmium, and the
like~ may be present in the ba~h, as for example, anl.ounts at
.
least as high as about 25 grams per liter, without detrimental
effect. It has further been ~ound that not only do the acid
.. . .
copper plating baths of the present in~ention ~ive e~cellent
results when used under conditions o~ high acid and low copper
metal content, but, additionally the baths have been found to
be particularly well adapted ror throughhole plating, and thus, ~`
:
~ ~ 15 find appreciable utilization in the manufacture of printed
,
circuit board.
~, . The poly (alkanol ~uaternary amnmon:lum salt) of the
present invention may be prepared in a reaction sequence. One
~; step involves the reaction o~ a m~xture of a polyalkylenamine
with an alkylene o~ide to form a polyalkanolamine. Another
step involves the reaction of the polyalkanola~lne with an
.,
alkylatin~ or quaternizatlon agent to yleld a poly (alkanol
; quaternary ammonium~salt3. This reaction sequence may be
represen~ed as follows~
:
. ~:
..
5~
C~s~ U 10,722
/0\ '
-~-Rl - NH - ~z - NII 7~ ~ m CH2 - CEI - R6
.
7 -~ R1 - I - R2 ~ I tn
R3 R4
. 5 ~ p (alkylating agent)
~.
7~ R5
R~ R2 ~ ~ ~n
I
R3 R4
~ ~ .
. P'~
1.0 i wherein~
Rl = alkylene group of 1-6 carbon atoms;
R2 = alkylene group of 1-6 carbon atoms; ..
OH
R3 = -CH2 - C H - R6 ;
. OH
R~ = -CH~ - C~ - R6 or H ;
R~ a alkyl group of 1-4 carbon atoms;
aralkyl;
~ ~ all~eny:1 group of 2-4 carbon atoms; .
: alkynyl group of 2-4 carbon atoms;
. alkylene sulfonate group of 1-4 carbon
. ` atoms (e.æ. -C}I2CH2CH2SO3~); and
0
C~12 CH - CH2 ~ (R7)3 ~
OH : : :
~ I ..
~ ~.g. CH2 CH - CHz ~ (CH3) 3 C19)
.
:
O
_ 4 _
: .
.....
Case U 10,722
R6 = ~ CH3, -C~201~;
R, = alkyl group of 1~4 carbon atoms ;
m - 1 to 2 ;
~ = C19, l~r~), CH3S04~) ;
5' p ~ 1 to 2;
n ~ 7. 0 to 23,500.
The values of m and p selected must be such that the
~inal product contains some alkanol quaternary ammonium ~roups.
If the value of p is less than 2, it is understood l;ha~ the
number of R5 groups (and quaternary ammonium groups) in the
above ~ormula has a corresponding value. When the alkylating
agent is an alkar.esultone, it is understood that X~ o~ the for-
mula is the sul~onate group (SO~) attached to the alkylene
gY'Oup .
Specifi.c polyalkylenimines which can be utllized may
be expressed as the polymerization product o~:
Ro - CH - CH - R9
\N~ . .
R~o
wherein Ra and Rg may be hydrogen, alkyl o~ ~rom one to three
~20 carbon atoms, and Rlo may be hydrogen~ alkyl, aralkylg or
hydroxy alkyl of from one to three carbon atorns. The pre~erred
polyalkylenimine is unsubstituted polyethylenimlne~ ranging in
molecular weight from about 300 to about 1,000,000.
Speciflc alkylene oxides which can be utili~ed are
: `
ethylene oxide, propylene oxide and glycidol which are reacted
.
with polyethylenimines ~o yield products ranging in molecular
welght from about 300 ~o about 1,000,000, in which case in the
structural rormula set ~orth above," n"has a value o~ 7.0 to 23,500. me
~,
-5-
.
Case U 10,722
polyalkylenimine alkylene oxide reaction products or polyal~nolamlnes when -
reacted with an alkylating agent give products which are solu-
ble in the acidic copper plating bath5 the reaction products
~rom ethylene oxide and glycidol being more soluble than those
from propylene oxide.
Various organic compounds can be reacted ~Ji~h the
polyallcanolamines to alkylate the nitrogen thereof and to ~orm
the reaction products added to the baths of the present inven-
~.
~ tion.
; 10 Specific com~ounds which have been ~ound to give par-
ticularly good resulsts are ~enzyl chloride, allyl bromide,
dimethyl sulfate, propanesultone, and (3-chloro-2 hydroxypropyl~
trimethyl ammonium chloride or [Cl-CH2 CHOH-CH2-N(CH3)33~C1 .
The formation of the reaction pr~duct is relatively
~15 slmple. It is only necessary to dissolvé the requisite amount
of polyalkanolamine in hot water, add the desired amount of al-
kylating agentg and heat the reaction mix~ure to a temperature
from about 50C. to about approximately 100C. The ratio of the
polyalkanolamine~to alkylating agent may be variedg so that not
all o~ the amino groups of ~he polyallcanolamine are alkylated.
To il].ustrate ~he lnvention further3 and assumin~ N-(2-hydroxy-
ethyl)polyethylenimine and benzyl chloride as the reaction ingre-
. ~ ~
dlents, the ~ollowing is believed to take place.
, :
. ~ ~: ... . '
~5~
Case U 10~722
~CH2 - CI~2 ~ C5H~ - CH2 Cl -~
CH~ - CHzOII
.~ ..
CH2 - C6H~
-- CII2 - CH2 ~ _ n C
CH2 - CH 2 OH
.'
- In addition to the above described brightening agent,
the aqueous acid copper plating baths of the pres~nt invention
also desirably contain at least one bath soluble polyether com-
pound. Various polyether compounds which are soluble in the
~10 plating bath ma~ be used. For example, particularly in high
sulfuric acid and low copper metal baths, non-ionic polyether
wetting agents, such as polygycols having carbon chains greater
~than 6 in length, may be useful. In general, however, the most
pre~erred polyethers are those containing at least six ether
oxygen atoms and being f'ree ~rom allcyl chains having more than
six carbon atoms in a straight or branched chain. Of the various
polyether compounds which may be used, excellent results have
been obtained with the polypropylene propanols and glycols of
avera~e molecul~r welght o~ from about 360 to 1,000, i.e.,
polyethers which contain a group (C3HcO)y where y is an integer
of ~rom about 6 to 20. Excellent results have also been obtained
with polyethers containine the group (C2~40)X where x is an `-
integer of at least 6 Exemplary of the various prererred poly~
~ ether compounds which~may be used are those set forth in Table II
: .` '
-: ~ . : .
.
s
C~.,e U 10, 722
appe~rin~, ln Column., 5 and 6 of UOS. Patent No. 3,328,273.
Desirably, th~ platin~ baths o~ the pre3ent invention contain
these polyether compound, in amounts within the range o~ about
0.01 to 5 grams per liter, with khe lo~rer concentrations gen-
erally being used with the higher molecular we~ght pol~ethers.
In addition to the polyethylenimine reaction productand the pol~e~her compound~ the aqueous acidic copper plating
baths of the present lnvention also desirably contain an
orga~ic divalent sulfur compound. Typ~cal of the suitable
or~anic di-Jalent sulfur compounds which ma~ be used are sul-
fonated organic sulfides, i.e., organic sulfide comcounds car-
ryin~ at least- one sulfonic groupO These organic sulfide sul-
~onlc compounds may also contain varlous substituting groups,
such as meth~J1, chloro, bro~o~ methoxy, ethox~, carboxy and
hydroxy, on the molecules, especially on the aromatic and
heteroc~clic sulfide sulfonic acids. The organlc sulfide sul-
fonic acids.may be used as the free acids, the alkali metal
salts, organic amine salts, or the like. Exemplary o~ specific
sulfonate organic sulfides which may be used are those set ~orth
in Table I in Columns 5 and 6 and Columns 7 and 8 of U S. Patent
No 3,267,010. Other suitable organic divalent sulfur compounds
which may be used are mercaptans, thiocarbamates, thiolcarba-
mates, khioxanthates, and thiocarbona~es which contain at least
one sulronic group. Additionally, organic polysulfide compounds~
~25 may also be usedO Such organic polysulfide compounds may have
the rormula XRl -(S~nR2$03~l, wherein Rl and R2 are the same or
; di~ferent alkylene ~roup containing from about 1 to 6 carbon
atoms, X ls hydrogen or S03H and n ls a number from about 2 to
- , : .
-- 8 -
:
~ ' . ' . . . . .
,
51~
Case U 10,722
to 5. These organic divalent sulfur compounds are aliphatic
p~lysulfid2s wherein at least two divalent sulfur atoms are
vicinal an~ wherein the molecule has one or two kerminal sul-
fonic acid groups. The alXylene portion of the mole^ule may
be substituted wikh grou~s such,as methyl, ethyl, chloro, hromo,
ethoxy, hydro~y, and the like. These compounds may be added as
the free acids or as the al~ali metal or amine salts. Exem-
plary of specific organic polysulfide co~pounds which may be
used are set forth in Table I o~ Column 2 of U.S. Patent No.
; ~10~ 3,3?8,273. Desirably, these organic sulfide compounds are
,: : . :
present in the plating baths of khe present in~ention in amounts
with~n the range of about 0.0005 to 1.0 grams per liter.
` The following specific examples of reaction products
and their manner of preparati,on and of speclfic platirl~ baths
and their operation are presented as e~emplary of` the present
inventlon, and not by way o~ limitation. Exemplary methods of
:, , - : :
preparation may be found in a serles of German patents in the
name Or Ulrich, namely, 655~742) 656,934) 676,407) 654,840 and
others. ;~
.
~ b~ S
Case U 10~722
(a) A mi~ture of:
109 parts o~ ethoxylated pol~ethylen~
imine (mol. wt. about 1,200 prepared
with a 1:1 mole ratio of ethylene
oxide to polyethylenimine polymer
repeat unit)
was dissolved in 500 parts o~ ater, to this
- I solution was added
64 parts of benzyl chloride at 80-go c .
This reaction m~xture was heated at 90C. for 5 hours and heat-
ing was continued at 73C. for 13 hours. The reaction product
was cooled and diluted to one liter.
(b) The identical mixture and procedure of (a) above
was repeated, but t~th etho;ylated polyethylen-
imine o~ abouk 360o molecul.ar weight.
(c) The identical ~ixture and procedure of ~a) above
was repeated, but with ethoxylated polyethylen-
imine of about 120,000 molecular weight.
(d) ~ mixture of:
146 parts of propoxylated polyethylen-
imine (mol. wt. about 1,000 prepared
with a 1:2 mole ratio of pro~ylene
oxide to polyethylenimine poiymer repeat unit)
was dissolved in 500 p~rts o~ water, to this
solution was added
64 parts of benzyl chloride at 80-90C.
This reaction mixture was heated at 90C. for 5 hours and heat~
ln~ w~s contirlued ~t 70C. ~or 19 hours. The reaction product
was cooled and diluted to one liter.
(e) A mixture of:
109 p~rts oI propoxylated polyethylen-
imlne (mol. wt. about 3,000 prepared
with a l:l mole ratio of propylene
oxide to poIyethylenimine polymer repeat, unit)
was dissolved and reacted with ben~yl chloride as derined
in (d) above to obtain a r~action produ~t.
0- :
:`: : :
.
. .
s
Case U lOg722
' ~EC~RO LATI~ E'~A~PLL~ ~
EX~MPL~ I
A "J'l shaped polished steel pane] was cleaned and ~lated ~tith
a thin cyanide copper coatin~. The coated panel was rinsed and
then plated in an acid plating bath having the composition:
220 g/l CuS04 5H20
, 60 g/l H2SO4
~ lO m~/l HCl
'~ 15 mg/l HSO3 - (CH2)3' -S~S-(CH2)3 -SO3H
lO m~/l Polyethylene glycol M.W. 9,000
The panel was plated for 20 minutes at 40 amps per square foot~
using air a~itation and a temperature o~ about 25C. The resul-
tant plated panel was uneverl and generally dull.
EXAMPLE 'II
A second l-JII shaped ~olished steel panel was cleaned, coated ,-
,~ - and then plated in a bath having the composition of Example I,
, -~ excep~ for the addition thereto of:
, 0.5 mg/l of the reaction product of
` example (c) above.
2G The resultant ~anel was mir~or bright, even and had improved
leveling characteristics.
EX~MP E III
A "J" shaped polished steel panel was cleaned and coated as in
Example I~ and then,was electroplated in an acidic copper ba~h
,25 ,hav:ing the composition:
,
In~redient_ Ounces/Gal.
'~ , Copper metal E~rom Cu (BF4)~ 2
HBF4 (lOO~) 20
~ Parts/Million
',30 ~' CH9 C6H4-S-S-C6H3-CH3-SO3H 20 ~ ,
. Polyet~ylene glycol ~mol. wt. lO
about 6 ~ ooo )
' ' Reactlon product Or Example (d) l , , ,
above
~Cl 30
The plated panel ~as brl~ht and even ~ith good levelin~.
C~s~ U 10~722
EX~MPLE IV
A "J" shaped ~olished steel panel was cleaned and coated as in
Example I, and then was electroplated in a bath havir.g the
composition:
~ Ounces/Gal.
CuS~4- 5~120 . lO
~2S04 ( 100%) 20
Parts/Mil_ion
: Dithio Carbamate-S-
Propane sulfonic acid 15
~ . .
Ethoxylated Lauryl
Alcohol with 15 moles
: Ethylene oxide 50
Reaction ~roduct of
~ example (a) above 0.4
The plated panel had a full bright, well leveled copper plate
~ evenly deposited thereon.
,' ' '
:, . , . .
: .
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:
, , , , . : ,.. ''
., : .
:
~ 12-
-
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