U.S. patent number 3,770,598 [Application Number 05/219,845] was granted by the patent office on 1973-11-06 for electrodeposition of copper from acid baths.
This patent grant is currently assigned to Oxy Metal Finishing Corporation. Invention is credited to Hans-Gerhard Creutz.
United States Patent |
3,770,598 |
Creutz |
November 6, 1973 |
ELECTRODEPOSITION OF COPPER FROM ACID BATHS
Abstract
A bath for electrodepositing ductile, lustrous copper which
comprises an aqueous acidic copper plating bath containing
dissolved therein a brightening amount of the reaction product of
polyethyleneimine and an alkylating agent which will alkylate the
nitrogen of the polyethyleneimine to produce a quaternary nitrogen,
wherein the reaction temperature for the imine and alkylating agent
ranges from about room temperature to about 120.degree.C and the
reaction product is present in the bath in an amount from about 0.1
to 1,000 milligrams per liter.
Inventors: |
Creutz; Hans-Gerhard (Westland,
MI) |
Assignee: |
Oxy Metal Finishing Corporation
(Warren, MI)
|
Family
ID: |
22821015 |
Appl.
No.: |
05/219,845 |
Filed: |
January 21, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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11024 |
Feb 12, 1970 |
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Current U.S.
Class: |
205/296;
205/293 |
Current CPC
Class: |
C25D
3/38 (20130101) |
Current International
Class: |
C25D
3/38 (20060101); C23b 005/20 (); C23b 005/46 () |
Field of
Search: |
;204/52R,44,106,107,108
;106/1 ;117/13E |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Kaplan; G. L.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of Ser. No. 11,024,
filed Feb. 12, 1970, now abandoned.
Claims
What is claimed is:
1. A bath for electrodepositing ductile, lustrous copper which
comprises an aqueous acidic copper plating bath containing
dissolved therein a brightening amount of the reaction product of
polyethyleneimine and an alkylating agent which will alkylate the
nitrogen on the polyethyleneimine to produce a quaternary nitrogen,
said alkylating agent being selected from the group consisting of
benzyl chloride, allyl bromide, propane sultone, and dimethyl
sulfate, and wherein the reaction temperature for the imine and
alkylating agent ranges from about room temperature to about
120.degree.C and the reaction product is present in the bath in an
amount ranging from about 0.1 to 1,000 milligrams per liter.
2. The bath as claimed in claim 1, wherein there is also present a
bath soluble polyether compound and an organic sulfide compound
selected from aliphatic polysulfides and organic sulfides carrying
at least one sulfonic group.
3. The bath as claimed in claim 2, wherein the polyethyleneimine
reaction product is present in an amount within the range of about
0.1 to 1,000 milligrams per liter, the polyether compound is
present in an amount within the range of about 0.01 to 5 grams per
liter and the organic sulfide compound is present in an amount
within the range of about 0.0005 to 0.1 grams per liter.
4. The bath as claimed in claim 3, wherein the reaction product is
formed by the reaction of polyethyleneimine and benzyl chloride,
the polyether is polypropylene glycol and the organic sulfide is
HO.sub.3 S(CH.sub.2).sub.3 -S-S-(CH.sub.2).sub.3 -SO.sub.3 H.
5. The bath of claim 1, wherein the alkylating agent is benzyl
chloride.
6. The bath of claim 1, wherein the alkylating agent is allyl
bromide.
7. A method for electrodepositing a ductile, lustrous copper which
comprises the step of electrodepositing copper from an aqueous
copper plating bath containing dissolved therein a brightening
amount of the reaction product of polyethyleneimine and an
alkylating agent which will alkylate the nitrogen, said alkylating
agent being selected from the group consisting of benzyl chloride,
allyl bromide, propane sultone, and dimethyl sulfate, and wherein
the reaction temperature for the imine and alkylating agent ranges
from about room temperature to about 120.degree.C and the reaction
product is present in the bath in an amount from about 0.1 to 1,000
milligrams per liter.
8. The method as claimed in claim 7, wherein the plating bath also
contains a bath-soluble polyether compound and an organic sulfide
compound selected from aliphatic polysulfides and organic sulfide
compounds carrying at least one sulfonic group.
9. The method as claimed in claim 8, wherein the polyethyleneimine
reaction product is present in the bath in an amount within the
range of about 0.1 to 1,000 milligrams per liter, the polyether
compound is present in the bath in an amount within the range of
about 0.01 to 5 grams per liter and the organic sulfide compound is
present in the bath in an amount within the range of about 0.0005
to 1.0 grams per liter.
10. The method as claimed in claim 9, wherein the reaction product
is formed by the reaction of polyethyleneimine and benzyl chloride,
the polyether compound is polypropylene glycol, and the organic
sulfide compound is HO.sub.3 S-(CH.sub.2).sub.3
-S-S-(CH.sub.2).sub.3 SO.sub.3 H.
11. The method of claim 7, wherein the alkylating agent is benzyl
chloride.
12. The method of claim 7, wherein the alkylating agent is allyl
bromide.
Description
This invention relates to the electrodeposition of copper from
aqueous acidic plating baths, especially from copper sulfate and
fluoroborate 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 deposits over a wider
range of bath concentration and operating current densities.
Heretofore, numerous additives have been proposed for use in
aqueous acidic plating baths for the electrodeposition of copper.
For example, in U.S. Pat. Nos. 3,267,010 and 3,328,273, it is
proposed to use bath-soluble polyether compounds, including those
which are polymers of 1,3-dioxalane, in combination with various
organic sulfide compounds, including organic sulfides which contain
at least one sulfonic group and aliphatic polysulfide compounds.
Although bright, ductile copper electrodeposits are produced from
these baths containing these organic additives, in some instances
the deposits formed have poor leveling characteristics and in low
current density areas a dull plate may be produced. Accordingly,
these patents further disclose the desirability of utilizing, in
addition to the polyether and organic sulfide compounds a phenazine
dye, such as diethyl or dimethyl Safranine Azo dimethyl aniline.
With the addition of such dye materials full bright, leveled copper
deposits are obtained.
See also French Patent 1,515,363 which describes the use of
alkylated polyethyleneimine in copper plating solutions.
While these bright, ductile leveling copper plating baths are in
large commercial use, nevertheless an important improvement would
be the use of higher bath temperatures without causing excessive
dulling of the plate. Even a 5.degree.F increase in the optimum
bath temperature for bright plate would allow a very significant
increase in the current density used and thus in the speed of
plating. With higher speed plating, shorter plating time can, of
course, be used, thus allowing greater production with a given
volume of plating solution.
It has now been found that the reaction product of
polyethyleneimine with benzyl chloride or similar reactive organic
halogen compounds are brightening additives in the acid copper
plating baths, and can be employed instead of phenazine dyes with
definite improvements. These improvements constitute the main
objects of this invention, and are here listed:
1. An object of the present invention is to provide an improved
process for the electrodeposition of copper from an aqueous acidic
copper plating bath, by making possible the use of higher bath
temperatures without causing excessive dulling of the plate.
2. Another object of this invention is to provide an improved
bright plating acid copper bath that provides smooth anode
dissolution (less loose particles than normal.
3. A further object of the present invention is to provide an
improved aqueous acidic bath for the electrodeposition of bright
leveling, ductile, copper deposits over a wider bath temperature
range without excessive dulling of low current density areas while
still making possible brilliant plate at the highest current
density ranges.
These and other objects will become apparent to those skilled in
the art from the description of the invention which follows.
Pursuant to the above objects, the present invention includes a
bath for electrodepositing ductile, lustrous copper which comprises
an aqueous acidic copper plating bath which contains a brightening
amount of a material which is the reaction product of
polyethyleneimine and an organic compound which will alkylate the
nitrogen in the polyethyleneimine. By the use of such additives,
particularly when used in conjunction with organic sulfide
compounds and bath soluble polyether compounds, full bright,
leveled copper deposits, are obtained, along with better anode
dissolution and improved adhesion of subsequently applied plates,
over a wide range of operating temperatures, current densities and
bath concentrations.
More specifically, in the practice of the present invention, the
aqueous acidic copper plating baths contain the reaction product of
the polyethyleneimine and the organic compound which will alkylate
the nitrogen of the polyethyleneimine to produce a quaternary
nitrogen in an amount which is desirably at least about 0.1
milligram per liter and preferably in an amount from about 0.1 to
1000 milligrams per liter. Various organic compounds which will
alkylate the nitrogen of the polyethyleneimine to produce a
quaternary nitrogen may be reacted with the polyethyleneimine to
form the additive materials for use in the present acid copper
plating baths. In this regard, it is to be noted that the
alkylation may take place at the primary, secondary and/or tertiary
nitrogen of the polyethyleneimine and that the number of nitrogen
atoms of each type will vary, depending upon the amount of
branching present in the polyethyleneimine.
When the alkylating agent reacts with the primary or secondary
amine, it will be altered to the secondary and tertiary amine,
respectively. This is accomplished by adding more alkylating agent
as is desired. Where the alkylation takes place at the primary
and/or secondary nitrogen, there will be a splitting off of the
alkylating groups on the organic compound, e.g., halogen, sulfate,
or the like. In the case of the tertiary nitrogen, however, a
quaternization takes place, forming the quaternary salt.
It is preferred that as many nitrogen atoms as possible in the
polyethyleneimine brightener should be quaternized, although as
little as 5 percent of the nitrogen atoms being quaternary still
gives desirable results, with 10% being more preferred and even
more preferably 20 percent.
To effect this alkylation, both aliphatic and aromatic compounds,
which may be either saturated or unsaturated may be used. 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 alkynl halides, acid halides, acyl halides, and
the like. Additionally, compounds such as the alkyl sulfates, alkyl
sultones, aldehydes, ketones, isocyanates, thioisocyanates,
epoxides, acylamindes, acids, anhydrides, ureas, cyanamides,
guanidines, and the like, may also be used. It is to be appreciated
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. Exemplary 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, as well as those in which
it is attached to an aliphatic group. Specific compounds which have
been found to give particularly good results are benzyl chloride,
allyl bromide, dimethyl sulfate, and propane sultone. These
compounds, however, are merely exemplary of the organic compounds
which will alkylate the nitrogen of the polyethyleneimine.
Preferably the alkylating agent is an aromatic halide.
In reacting the polyethyleneimine with the organic alkylating
compound, to form the additive composition for the acid copper
plating baths of the present invention, an excess of the organic
alkylating compound, over the theoretical amount required to
completely react with the polyethyleneimine, is preferred. While an
excess of the alkylating agent is preferred excellent results are
also obtained with lesser degrees of alkylation. This reaction may
be carried out by admixing the polyethyleneimine and the organic
alkylating compound, either with or without a solvent. Illustrative
of solvents which may be used is dioxane. The reaction temperature
may vary from about room temperature to about 120.degree. C,
although where a solvent such as dioxane is used, reaction
temperatures of from about 80.degree. to 100.degree.C are
preferred. The resulting reaction product is then separated from
any unreacted materials, using any convenient techniques. It is to
be appreciated that although it is preferred to use an excess of
the organic alkylating compound, so that substantially complete
alkylation of the nitrogen in the polyethyleneimine is effected,
this has not been found to be essential. In many instances, greatly
improved plating results have been obtained when using a
polyethyleneimine which is only partially or incompletely
alkylated.
The polyethyleneimine which is used in forming the plating bath
additive may have a wide range of molecular weights. Typically, the
molecular wieght of the polyethyleneimine may be within the range
of about 300 to several millions. In many instances, however,
molecular wieghts within the range of about 300 to 1,000,000 are
preferred.
In addition to the above described brightening agent, the aqueous
acid copper plating baths of the present invention also desirably
contain at least one bath-soluble polyether compound. Various
polyether compounds which are soluble in the plating bath may be
used. For example, particularly in high sulfuric acid and low
copper metal baths, non-ionic polyether wetting agents, such as
polyglycols having carbon chains greater than 6 in length, may be
useful. In general, however, the most preferred polyethers are
those containing at least six ether oxygen atoms and being free
from alkyl 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 average molecular weight of from about 360
to 1000, i.e., polyethers which contain a group (C.sub.3 H.sub.6
O).sub.y where y is an integer of from about 6 to 20. Excellent
results have also been obtained with polyethers containing the
group (C.sub.2 H.sub.4 O).sub.x where x is an integer of at least
6. Exemplary of the various preferred polyether compounds which may
be used are those set forth in Table II appearing in columns 5 and
6 of U.S. Pat. No. 3,328,273. Desirably, the plating baths of the
present invention contain these polyether compounds in amounts
within the range of about 0.01 to 5 grams per liter, with the lower
concentrations generally being used with the higher molecular
weight polyethers.
In addition to the polyethyleneimine reaction product and the
polyether compound, the aqueous acidic copper plating baths of the
present invention also desirably contain an organic sulfide
compound. Typical of the suitable organic sulfides which may be
used are sulfonated organic sulfides, i.e., organic sulfide
compounds carrying at least one sulfonic group. These organic
sulfide sulfonic compounds may also contain various substituting
groups, such as methyl, chloro, bromo, methoxy, ethoxy, carboxy and
hydroxy, on the molecules, especially on the aromatic and
heterocyclic sulfide sulfonic acids. The organic sulfide sulfonic
acid may be used as the free acids, the alkali metal salts, organic
amine salts, or the like. Exemplary of specific sulfonate organic
sulfides which may be used are those set forth in Table I in
columns 5 and 6 and columns 7 and 8 of U.S. Pat. No. 3,267,010,
Other suitable organic sulfide compounds which may be used are
mercaptans, thiocarbamates, thiolcarbamates, thioxanthates, and
thiocarbonates which contain at least one sulfonic group.
Additionally, organic polysulfide compound may also be used. Such
organic polysulfide compounds may have the formula XR.sub.1
-(S)n-R.sub.2 -SO.sub.3 H, wherein R.sub.1 and R.sub.2 are the same
or different alkylene group containing from about 1 to 6 carbon
atoms, X is hydrogen or SO.sub.3 H and n is a number from about 2
to 5. These sulfide compounds are aliphatic polysulfides wherein at
least two divalent sulfur atoms are vicinal and wherein the
molecule has one or two terminal sulfonic acid groups. The alkylene
portion of the molecule may be substituted with groups such as
methyl, ethyl, chloro, bromo, ethoxy, hydroxy and the like. These
compounds may be added as the free acids or as the alkali metal or
amine salts. Exemplary of specific organic polysulfide compounds
which may be used are set forth in Table I of column 2 of U.S. Pat.
No. 3,328,273. Desirably, these organic sulfide compounds are
present in the plating baths of the present invention in amounts
within the range of about 0.0005 to 1.0 grams per liter.
The copper plating baths in which the above additives are used may
be either acidic copper sulfate or acidic copper fluoroborate
baths. As is known in the art, such acidic copper sulfate baths
typically contain from about 180 to 250 grams per liter of copper
sulfate and 30 to 80 grams per literof sulfuric acid; while the
acidic copper fluoroborate baths typically contain from about 200
to 600 grams per liter of copper fluoroborate and about 0 to 60
grams per liter of fluoroboric acid. Additionally, it is found that
with the additives of the present invention, these acid copper
plating baths may be operated under conditions of 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 of fluoroboric acid,
excellent plating results are still obtained.
Desirably, these plating baths are operated at current densities
within the range of about 10 to 100 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 low copper and high
acid baths, current densities within the range of about 10 to 50
amps/ft.sup.2 are used. Additionally, in high agitation baths, such
as those used in plating rotogravure cylinders, current densities
up to as high as about 400 amps/ft.sup.2 may be used. The baths may
be operated with air agitation, cathode-rod agitation, or solution
agitation and cathode rod agitation, depending upon the particular
bath and plating conditions which are used. Typical bath
temperatures are within the range of about 25.degree. to 35.degree.
C, although both lower and higher temperatures, e.g., 50.degree. C
or more, may also be used. In this regard, it is to be noted that
the plating baths of the present invention may also be used in
copper electrorefining processes. In such processes, temperatures
up to about 60.degree.-70.degree.C may be used.
Although it has been found to be desirable that chloride 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 bath, e.g., amounts at least as high as about 25
grams per liter, without detrimental effect. It has further been
found that not only do the acid copper plating baths of the present
invention give excellent results when used under conditions of high
acid and low copper metal content, but, additionally the baths have
been found to be particularly well adapted for through-hole
plating, and thus find appreciable utilization in the manufacture
of printed circuit board.
In order that those skilled in the art may better understand the
present invention and the manner in which it may be practiced, the
following specific examples are given. In these examples, unless
otherwise indicated, parts and percent are by weight and
temperatures are in degrees centigrade.
EXAMPLE 1
An aqueous acidic copper electroplating bath was formulated
containing the following components in the amounts indicated:
ounces per gallon Copper metal (from CuSO.5H.sub.2 O) 2 H.sub.2
SO.sub.4 (100%) 30 parts per million HCl (100%) 30 ##SPC1## 10
(Thioxanthate-S-propane sulfonic acid) Polyethylene glycol
(molecular weight about 400,000) 20 Reaction product of
polyethylene- imine (molecular weight about 600) with benzyl
chloride (in molar ratios). The imine reactant contained about 25%
primary nitrogen; 50% secondary and 25% tertiary nitrogen. 1
Instead of the thioxanthate sulfonic acid, the disulfide alkyl
sulfonic compounds such as HO.sub.3 S-(CH.sub.2).sub.3
-S-S-(CH.sub.2).sub.3 -SO.sub.3 H can be used.
EXAMPLE 2
An aqueous acidic copper electroplating bath was formulated
containing the following components in the amounts indicated:
ounces per gallon Copper metal (from Cu(BF.sub.4).sub.2) 2
HBF.sub.4 (100%) 20 H.sub.3 BO.sub.3 1 ##SPC2## parts per 20 llion
Polyethylene glycol (molecular weight 6000) 10 Reaction product of
polyethylene- imine (molecular weight about 1200) with benzyl
chloride (in molar ratios). The imine reactant contained about 25%
primary nitrogen; 50% secondary and 25% tertiary nitrogen. 1/2 HCl
(100%) 30
EXAMPLE 3
An aqueous acidic copper electroplating solution was formulated
containing the following components in the amounts indicated:
ounces per gallon CuSO.sub.4. 5H.sub.2 O 30 H.sub.2 SO.sub.4 (100%)
8 parts per million HCl (100%) 50 ##SPC3## 10
(Dithiocarbamate-S-propane sulfonic acid) Polypropylene glycol 10
(molecular weight 700 ) Reaction product of polyethylene- imine
(molecular weight about 1800) with allyl bromide (in molar ratios
0.3 The amine reactant contained about 25% primary nitrogen; 50%
secondary and 25% tertiary nitrogen
The aqueous acidic copper plating baths of the preceding Examples 1
through 3 were operated using air agitation at an average current
density of about 40 amps per square foot and a temperature of about
25.degree. C. In each instance, full bright, leveled copper plates
were obtained on the cathode and the anodes were evenly corroded on
the surface.
The procedure of the preceding Examples 1-3 is repeated with the
exception that in the preparation of the polyethyleneimine reaction
product, propane sultone and dimethylsulfate are substituted for
the benzyl chloride and the allyl bromide. In each instance,
operation of the resulting plating bath produces full bright,
leveled copper plate on the cathode and even surface corrosion of
the anode.
EXAMPLE 4
Acid copper electroplating solutions are prepared as in Examples
1-3 with the exception that the solutions contained 40 grams/liter
copper (160 grams/liter CuSO.sub.4. 5H.sub.2 0) and 12 percent by
volume H.sub.2 SO.sub.4. These baths are used for copper
electrorefining at current densities of 20 to 40 amps/ft.sup.2 and
temperatures of 55.degree. to 65.degree.C. In each instance a
smooth, pure copper plate is obtained.
While there have been described various embodiments of the
invention, the compositions and methods described are intended to
be understood as limiting the scope of the invention as it is
realized that changes therewithin are possible and it is further
intended that each element recited in any of the following claims
is to be understood as referring to all equivalent elements for
accomplishing substantially the same results in substantially the
same or equivalent manner, it being intended to cover the invention
broadly in whatever form its principle may be utilized.
* * * * *