Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Method for producing matt copper deposits
Field of the Invention
The present invention relates to a method for deposition of matt copper
deposits
in the field of decorative coatings.
Background of the Invention
io Matt copper coatings in the field of decorative coatings are required as
a sur-
face finish for e.g. sanitary equipment. Another application of matt copper
coat-
ings is to replace matt nickel layers ("satin nickel") as an intermediate
layer in
decorative multilayer coating systems which becomes more demanding due to
the toxicity of nickel.
A homogeneous matt appearance is required for decorative metal layers. The
homogeneity of the matt appearance can easily be achieved on substrates
which have no complex shape because the current density distribution during
electroplating of matt copper layers is within a narrow range. However, in
cases
where the substrate to be coated has a complex shape, the current density dur-
ing electroplating is within a wide range. Typical substrates having a complex
shape which are to be coated with a matt copper coating are for example show-
er heads and automotive interior parts.
Another requirement for matt copper layers is that their matt level should be
adjustable in order to be able to manufacture copper layers having different
matt levels.
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Plating bath compositions comprising at least one polyglycerine compound for
producing matt copper layers during manufacture of printed circuit boards are
disclosed in US 2004/0020783 Al. It is neither possible to obtain a homogene-
ously matt copper deposit on a substrate having a complex shape nor to adjust
the matt level of such a copper deposit when using the electrolyte disclosed
therein.
Objective of the Invention
It is the objective of the present invention to provide a method for
depositing
copper layers which have a homogeneous and adjustable matt appearance,
especially on substrates having a complex shape.
Summary of the Invention
This objective is solved by a method for deposition of a matt copper coating,
comprising, in this order, the steps
a. Providing a substrate,
b. Depositing a first copper layer onto the substrate from a first aqueous
electrolyte comprising a source of copper ions, at least one acid and at
least one polyether compound wherein said first electrolyte does not
contain an organic compound comprising divalent sulfur
and
c. Depositing a second copper layer onto the first copper layer from a se-
cond aqueous electrolyte comprising a source of copper ions, at least
one acid, a first water soluble sulfur-containing additive selected from
the group consisting of alkyl sulfonic acid derivatives and a second wa-
ter soluble sulfur-containing additive selected from the group consist-
ing of aromatic sulfonic acid derivatives.
The copper coatings obtained by the method according to the present invention
have a homogeneous matt appearance on substrates having a complex shape.
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Furthermore, the matt appearance of the copper coating can be adjusted during
deposition of the individual copper layers.
Detailed Description of the Invention
The method for deposition of a matt copper coating comprises deposition of two
individual copper layers onto a substrate from two individual copper
electrolytes
which are herein denoted first electrolyte from which the first copper layer
is
deposited and second electrolyte from which the second copper layer is depos-
ited onto the first copper layer.
The first electrolyte comprises a source of copper ions, at least one acid and
at
.. least one polyether compound. The first electrolyte does not contain an
organic
compound comprising divalent sulfur, e.g., sulfides, disulfides, thioles, and
de-
rivatives thereof.
Copper ions are added to the first electrolyte in the form of a water-soluble
cop-
per salt or an aqueous solution thereof. Preferably, the source of copper ions
is
selected from copper sulfate and copper methane sulfonate. The concentration
of copper ions in the first electrolyte preferably ranges from 15 to 75 g/I,
more
preferably from 40 to 60 g/I.
The at least one acid in the first electrolyte is selected from the group
compris-
ing sulfuric acid, fluoro boric acid and methane sulfonic acid. The
concentration
of the at least one acid in the first electrolyte preferably ranges from 20 to
400 g/I and more preferably from 40 to 300 g/I.
In case sulfuric acid is used as the acid, it is preferably added in form of a
50 to
96 wt.-% solution. More preferably, sulphuric acid is added to the first
electrolyte
as a 50 wt.-% aqueous solution of sulfuric acid.
The at least one polyether compound in the first electrolyte is selected from
the
group consisting of polyalkylene ethers and polyglycerine compounds.
Suitable polyalkylene ethers are selected from the group consisting of polyeth-
ylene glycol, polypropylene glycol, stearylalcoholpolyglycolether, nonylphenol-
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polyglycolether, octanolpolyalkylenglcolether,
octanediol-bis-
(polyalkylenglycolether),
poly(ethylenglycol-ran-propylenglycol),
poly(ethylenglycol)-biock-poly(propylenglycol)-biock-poly(ethylenglycol)
and
poly-(propylenglycol)-block-poly(ethylenglycol)-biock-poly(propylenglycol).
Suitable polyglycerine compounds are selected from the group consisting of
poly(1,2,3-propantriol), poly(2,3-epoxy-1-propanol) and derivatives thereof
which are represented by formulae (1), (2) and (3):
R600
-n
OR7
(1)
wherein
n is an integer from 1 to 80, preferably from 2 to 30;
R6, R7 and R8 are identical or different and are selected from the group
consist-
ing of hydrogen, alkyl, acyl, phenyl and benzyl, wherein alkyl preferably is
linear
or branched Ci to C18 alkyl and acyl preferably is R10¨CO, wherein R16 is
linear
or branched Ci to 018 alkyl, phenyl or benzyl; alkyl phenyl and benzyl in
formula
(1) may be substituted;
_
- OR8
R600-/-
- n
0
_
0
R8,,,,," H
OR9
- -m
(2)
wherein
n is an integer >1, m is an integer >1 with the provisio n + m is 30;
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R6, R7, 1:18 and R9 are identical or different and are selected from the group
con-
sisting of hydrogen, alkyl, acyl, phenyl and benzyl, wherein alkyl preferably
is
linear or branched Ci to C18 alkyl and acyl preferably is R10¨CO, wherein Rth
is
linear or branched Ci to 018 alkyl, phenyl or benzyl; alkyl phenyl and benzyl
in
formula (2) may be substituted;
R90\, 8
OR
_
n
0 OR7
R60/
(3)
wherein
n is an integer from 1 to 80; preferably from 2 to 20;
and wherein R6, R7 are selected from the group consisting of hydrogen, alkyl,
acyl, phenyl and benzyl, wherein alkyl preferably is linear or branched C1 to
C18
alkyl and acyl preferably is R10¨CO, wherein R1 is linear or branched C1 to
C18
alkyl, phenyl or benzyl; alkyl phenyl and benzyl in formula (3) may be
substitut-
ed.
Polyglycerine compounds are produced according to known methods. Indica-
tions on the conditions of production are disclosed in the following
publications
for example: Cosmet. Sci. Technol. Ser., glycerines, page 106 and
US 3,945,894. Further details on the syntheses of polyglycerine compounds
according to formulae (1), (2) and (3) are disclosed in US 2004/0020783 Al.
Most preferably, the at least one polyether compound in the first electrolyte
is
selected from compounds according to formulae (1), (2) and (3).
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The concentration of the at least one polyether compound or all polyether com-
pounds together in case more than one polyether compound is added prefera-
bly ranges from 0.005 g/I to 20 g/I, more preferably from 0.01 g/I to 5 g/I.
During operation, the temperature of the first electrolyte is preferably
adjusted to
a value in the range of from 30 to 60 C, more preferably from 40 to 50 C.
The current density applied to the substrate during copper deposition from the
first aqueous electrolyte preferably ranges from 0.5 to 5 A/dm2, more
preferably
from 1 to 3 A/dm2.
Optionally, the substrate is rinsed with water before depositing the second
cop-
.. per layer from the second electrolyte.
Copper ions are added to the second electrolyte as a water-soluble copper salt
or an aqueous solution thereof. Preferably, the source of copper ions is
selected
from copper sulfate and copper methane sulfonate. The concentration of copper
ions in the second electrolyte preferably ranges from 15 to 75 g/I, more
prefera-
bly from 40 to 60 g/I.
The at least one acid in the second electrolyte is selected from the group com-
prising sulfuric acid, fluoro boric acid and methane sulfonic acid. The
concentra-
tion of the at least one acid in the second electrolyte preferably ranges from
20
to 400 g/I and more preferably from 40 to 300 g/I.
In case sulfuric acid is used as the acid, it is added in form of a 50 to 96
wt.-%
solution. Preferably, sulfuric acid is added as a 50 wt.-% aqueous solution of
sulfuric to the second electrolyte.
The second electrolyte further comprises a first water-soluble sulfur-
containing
additive and a second water-soluble sulfur-containing additive.
The first water-soluble sulfur-containing compound is an alkyl sulfonic acid
de-
rivative. Preferably, the alkyl sulfonic acid derivative comprises divalent
sulfur.
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The second water-soluble sulfur-containing compound is an aromatic sulfonic
acid derivative. Preferably, the aromatic sulfonic acid derivative comprises
diva-
lent sulfur.
The first sulfur-containing additive is more preferably selected from the
group
consisting of compounds according to formulae (4) and (5):
R1S¨(CH2)n¨SO3R2 (4)
R3S03¨(CH2)m¨S¨S¨(CH2)m¨SO3R3 (5)
wherein
R1 is selected from the group consisting of hydrogen, methyl, ethyl, propyl,
bu-
m tyl, lithium, sodium, potassium and ammonium, more preferably R1 is
selected
from the group consisting of hydrogen, methyl, ethyl, propyl, sodium and potas-
sium;
n is an integer from 1 to 6, more preferably n is an integer from 2 to 4;
R2 is selected from the group consisting of hydrogen, methyl, ethyl, propyl,
bu-
tyl, lithium, sodium, potassium and ammonium, more preferably, R2 is selected
from the group consisting of hydrogen, sodium and potassium;
R3 is selected from the group consisting of hydrogen, methyl, ethyl, propyl,
bu-
tyl, lithium, sodium, potassium and ammonium, more preferably R3 is selected
from the group consisting of hydrogen, sodium, potassium and
rn is an integer from 1 to 6, more preferably m is an integer from 2 to 4.
The concentration of the first sulfur-containing additive in the second
electrolyte
preferably ranges from 0.0001 to 0.05 g/I, more preferably from 0.0002 to
0.025 g/I.
The second sulfur-containing additive in the second electrolyte is more
prefera-
bly selected from the group consisting of compounds according to formulae (6)
and (7):
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R4Sy-X-SO3M (6)
wherein R4 is selected from the group consisting of
CH3 *
it .
SO3M , SO3M and hydrogen;
X is selected from the group consisting of
0
CH3 * and .
= ,
y is an integer from 1 to 4 and M is selected from the group consisting of
hydro-
gen, sodium, potassium and ammonium; and
SO3M
110
R5 (7)
wherein R5 is selected from the group consisting of hydrogen, SH and SO3M
and M is selected from the group consisting of hydrogen, sodium, potassium
and ammonium.
Most preferably, the second sulfur-containing additive is selected from com-
pounds according to formula (6).
The concentration of the second sulfur-containing additive in the second elec-
trolyte preferably ranges from 0.005 to 1 WI, more preferably from 0.01 to
0.25 g/I.
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Optionally, the second electrolyte further comprises one or more carrier
additive
selected from the group consisting of polyvinylalcohol,
carboxymethylcellulose,
polyethylene glycol, polypropylene glycol, stearic acid polyglycolester, alkox-
ylated naphtoles, oleic acid polyglycolester, stearylalcoholpolyglycolether,
nonylphenolpolyglycolether, octanolpolyalkylenglycolether, octanediol-bis-
(polyalkylenglycolether), poly(ethylenglycol-ran-propylenglycol),
poly(ethylengly-
col)-b/ock-poly(propylenglycol)-b/ock-poly(ethylenglycol) and
poly(propylenglycol)-b/ock-poly(ethylenglycol)-b/ock-poly(propylenglycol).
The concentration of the optional carrier additive in the second electrolyte
pref-
erably ranges from 0.005 g/I to 5 g/I, more preferably from 0.01 g/I to 3 g/I.
During operation, the temperature of the second electrolyte is preferably
adjust-
ed to a value in the range of from 20 to 50 C, most preferably of from 25 to
30 C.
The current density applied to the substrate during copper deposition from the
second aqueous electrolytes preferably ranges from 0.5 to 5 A/dm2, more pref-
erably from 1 to 3 A/dm2.
The matt level of the copper surface may be tailored by adjusting the
thickness-
es of the first and second copper layer by simple experimentation. A more matt
appearance may be achieved with a thinner second copper layer, whereas a
less matt appearance may be achieved with a thicker second copper layer.
The following examples further illustrate the present invention.
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Examples
Substrates:
Both ABS (acrylnitrile-butadiene-styrol-copolymer) and brass substrates having
a complex shape were used throughout all examples.
The ABS substrates were etched in chromic acid, activated with a palladium
containing colloid and metallised by electroless plating of nickel from an
acidic
hypophosphite-based electrolyte prior to copper deposition.
The brass substrates were degreased prior to deposition of copper.
Test methods:
The matt appearance of copper coatings was tested by visual inspection of the
copper plated substrates throughout all examples.
Example 1 (comparative)
Copper was deposited on ABS and brass substrates having a complex shape
from an aqueous acidic electrolyte comprising 80 g/I CuSO4 = 5H20, 240 g/I sul-
furic acid, and 1 g/I of a mixture of polyglycerin compounds according to
formula
(1) with n = 2 to 7.
A homogenous, strongly matt copper surface was obtained which is too matt for
decorative applications.
Example 2 (comparative)
Copper was deposited on ABS and brass substrates having a complex shape
from an aqueous acidic electrolyte comprising 80 g/I CuSO4 = 5H20, 240 g/I sul-
furic acid, and 0.5 mg/I of a first sulfur-containing additive according to
formula
(5) with m = 3 and R3 = sodium, 80 mg/I of a second sulfur-containing additive
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*
*
according to formula (6) with R4 = SO3m x y = 2
and
M = sodium and 200 mg/I polyethylene gylcol.
The copper surface obtained has a homogenous technical gloss which is not
desired for decorative applications.
Example 3 (comparative)
A first layer of copper was deposited onto ABS and brass substrates having a
complex shape from the electrolyte used in example 2. Thereon, a second cop-
per layer was deposited from the electrolyte used in example 1.
A homogenous, strongly matt copper surface was obtained which is too matt for
decorative applications.
Example 4 (comparative)
A first copper layer was deposited onto ABS and brass substrates having a
complex shape from the electrolyte used in example 1. Next, a second copper
layer was deposited thereon from a second electrolyte comprising 80 g/I CuSO4
= 5H20, 240 g/I sulfuric acid, and 0.5 mg/I of a sulfur-containing additive
accord-
ing to formula (5) with m = 3 and R3 = sodium. The second electrolyte did not
contain a second sulfur-containing additive selected from compounds according
to formulae (6) and (7).
The resulting copper surface has a non-homogeneous matt appearance which
is not acceptable for decorative applications.
Example 5 (comparative)
A first copper layer was deposited onto ABS and brass substrates having a
complex shape from the electrolyte used in example 1. Next, a second copper
layer was deposited thereon from a second electrolyte comprising 80 g/I CuSO4
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= 5H20, 240 g/I sulfuric acid, and 80 mg/I of a sulfur-containing additive
accord-
* *
0 .
ing to formula (6) with R4 = SO3m , x = y = 2
and M =
sodium. The second electrolyte did not contain a first sulfur-containing
additive
selected from compounds according to formulae (4) and (5).
The copper surface obtained has a matt appearance with burnt areas (shady
black appearance) which is not acceptable for decorative applications.
Example 6
The first copper layer was deposited onto the ABS and brass substrates from
the electrolyte used in Example 1. The second copper layer was deposited
thereon from the electrolyte used in Example 2.
The copper surface obtained has a homogeneous matt appearance which is
desired for decorative applications.
Example 7
The first copper layer was deposited from a first electrolyte comprising 80
g/I
CuSO4 = 5H20, 240 g/I sulfuric acid, and 1 g/I polyethylene glycol. The second
copper layer was deposited thereon from the electrolyte used in Example 2.
The copper surface obtained has a homogeneous matt appearance which is
desired for decorative applications.
12
o
Table 1: First and second electrolytes used in Examples 1 to 6.
ls.)
0
I¨,
Example 1* Example 2* Example 3õ Example 4õ
Example 5* Example 6 Example 7 c..)
First Containing none Containing Containing Containing
Containing Containing poly- ,...)
,..1
(.4
electrolyte mix of poly- additives with mix of poly- mix of
poly- mix of poly- ethyleneglycol;
glycines ac- divalent sulfur glycines
ac- glycines ac- glycines ac- No additive with
cording to according to cording to cording
to cording to divalent sulfur
formula (1); formula (5) formula (1);
formula (1); formula (1);
No additive and (6) No additive No
additive No .. additive
with divalent with divalent with
divalent with divalent
sulfur sulfur sulfur
sulfur p
2
Second none Containing Containing Containing Containing
Containing Containing addi-
6 electrolyte additives with mix of poly- additive with
additive with additives with tives with divalent
,
divalent sulfur glycines ac- divalent sulfur
divalent sulfur divalent sulfur sulfur according to 0
,
according to cording to according to according
to according to formula (5) and (6) 0
.,
formula (5) formula (1); formula (5);
formula (6); formula .. (5) .. .
and (6) No additive No additive No
additive and (6)
with divalent acc. to formu- acc. to formu-
sulfur la (6) la (5)
Optical ap- - - - - -
+ +
pearance
,-o
n
. -
1-q
comparative examples; + = good; -: not sufficient
.0
1,..,
=
L.1
¨07
--1
C44
0\
00
00