Note: Descriptions are shown in the official language in which they were submitted.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
A method for activating a surface of a non-conductive or carbon-fibres
containing substrate
for metallization
Field of the Invention
The present invention relates to the activation of surfaces of typically non-
conductive or car-
bon-fibres containing substrates for subsequent metallization.
In particular, the present invention relates to a method for activating a
surface of a non-
conductive or carbon-fibres containing substrate for metallization, a method
for metallizing
an activated surface of a non-conductive or carbon-fibres containing
substrate, a method for
preparing an aqueous, palladium-free activation composition for activating a
surface of a
non-conductive or carbon-fibres containing substrate for metallization, and an
aqueous, pal-
ladium-free activation composition for activating a surface of a non-
conductive or carbon-
fibres containing substrate for metallization.
Backdround of the Invention
A metallization of typically such substrates is commercially of high interest.
In many aspects
of daily life such substrates are covered with structures or layers of metal,
either for decora-
tive or functional applications. For example, typically non-conductive plastic
substrates are
used to manufacture sanitary articles with a shiny chromium layer.
Furthermore, quite a
number of chromium covered plastic substrates are used in the automotive
industry.
Besides such decorative articles, a functional metallization is essential in
for example man-
ufacturing printed circuit boards. In such boards typically a non-conductive
resin-containing
laminate is used as a base material usually harboring a circuitry of copper
lines.
Carbon-fibres containing substrates experience an increasing potential as
catalytically ac-
tive surfaces in e.g. power-to-gas, power-to-fuel, and power-to-chemicals
applications, and
batteries.
All these applications require a usually multi-step preparation of the non-
conductive or car-
bon-fibres containing substrate to make it receptive for subsequent
metallization.
In a first step usually a cleaning of the surface of the non-conductive or
carbon-fibres con-
taming substrate is carried out, e.g. to remove grease or impurities.
In a second step typically a pre-treatment or conditioning of said surface is
conducted in
order to make the surface receptive to the following activation. Such a pre-
treatment for
example includes in some cases an etching in order to create pores and to
enlarging the
surface.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
2
In a third step the important activation is carried out. In such an activation
usually a very thin
seed or activation layer is deposited/anchored on the surface of the non-
conductive or car-
bon-fibres containing substrate, serving as starting point for a subsequent
first metallization
layer. As a result, an activated surface for metallization is obtained. The
seed or activation
layer usually serves as mediator between said surface of the non-conductive or
carbon-
fibres containing substrate and the one or more following metallization
layers. Typically, the
seed/activation layer is formed by depositing metal nanoparticles on said
surface, for exam-
ple from a colloidal activation composition.
In a fourth step typically said first metallization layer is deposited on the
seed/activation layer,
most commonly by electroless plating. In some cases this electroless plating
includes an
immersion-type plating, i.e. a deposition of a more noble metal on the
seed/activation layer
by means of exchange reaction and in absence of a reducing agent. In other
cases it in-
cludes a deposition of a metal or metal alloy through autocatalytic
deposition, which means
a deposition facilitated by means of a reducing agent.
In a fifth step typically a second metallization layer is deposited on the
first metallization
layer, either again by autocatalytic deposition or by electrolytic deposition.
Basically, the skilled person is well familiar with such a sequence of steps.
Typically, in a
common colloidal activation composition noble metal nanoparticles are
utilized, very often
palladium nanoparticles. However, noble metals are generally expensive and
waste water
treatment is of high concern in order to recycle remaining noble metals.
Alternatively, also
less expensive metal ions are more and more utilized in respective activation
compositions.
Another common disadvantage is that such activation compositions naturally
experience a
form of decay or decomposition. Typically, the nanoparticles agglomerate and
form insolu-
ble, precipitating agglomerates, rendering the composition mostly inoperable.
It is therefore
typically desired to stabilize the nanoparticles after they have been formed
through reducing
respective metal ions. For this purpose, usually stabilizer compounds are
used, altering the
charge distribution of the particles, limiting the particle size, and/or
preventing oxidation of
the particles. In many cases polymers and/or anti-oxidation agents and/or
metal ions (such
as tin ions) are used for these purposes.
For example, ON 107460459 A relates to simple nano-copper activation liquid
utilizing sta-
bilizers and reducing agents to prevent agglomeration and oxidation,
respectively, of the
nanoparticles.
US 4,278,712 discloses a method for the activation of a weakly active
colloidal dispersion
useful in the preparation of non-conductors prior to electroless plating. The
method is based
upon controlled oxidation of otherwise weakly active colloids by treatment
with suitable
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
3
gases and/or chemical agents, which render said controlled oxidation. However,
the pres-
ence of at least one colloid stabilizer is mandatory. In this way a reversible
equilibrium is not
maintained.
Such approaches as described in the art typically have the disadvantage that
they are
sooner or later sensitive to agglomeration and precipitation, mostly because
the stabilizer
compounds do not sufficiently stabilize the particles over time. As a result,
product life time
very strongly depends on the date of production, delivery time, and the
quality of stabiliza-
tion.
Furthermore, it appears that such stabilizer compounds often reduce the
ability of the nano-
particles to effectively activate the respective surface. It seems that the
additives on the one
hand - at least to a certain degree - avoid agglomeration but on the other
hand hinder these
particles to quickly and strongly adsorb on the surface.
Objective of the present Invention
It was therefore an objective of the present invention to provide a method for
activating a
.. surface of a non-conductive or carbon-fibres containing substrate for
metallization and a
respective activation composition, which is on the one hand simple and highly
effective, and
on the other hand is in particular insensitive to agglomeration and
precipitation to ensure a
long service life. Furthermore, such a method and respective composition
should be low-
priced.
It was another objective of the present invention to provide a respective
method with reduced
environmental burden, e.g. with less sophisticated waste-water treatment and
reduced ef-
fective concentrations of chemicals.
It was furthermore an objective of the present invention to provide a
respective method with
increased life time, in particular for the utilized activation composition.
Summary of the Invention
The objectives mentioned above are solved by a method for activating a surface
of a non-
conductive or carbon-fibres containing substrate for metallization, the method
comprising
the steps
(a) providing said substrate,
(b) providing an aqueous, palladium-free activation composition comprising
(i) a first species of dissolved transition metal ions and additionally
metal par-
ticles thereof,
(ii) one or more than one complexing agent,
CA 03135816 2021-10-01
WO 2020/201387
PCT/EP2020/059313
4
(iii) permanently or temporarily one or more than one reducing agent,
(iv) optionally one or more than one second species of dissolved metal ions
being different from the first species,
wherein
- at least of
the first species, the dissolved transition metal ions and the metal
particles thereof are present in a reversible equilibrium, with the proviso
that
- the metal particles are formed from the dissolved transition metal ions
through a continuous or semi-continuous reduction through the one or
more than one reducing agent,
- the dissolved transition metal ions are formed from the metal particles
through continuous or semi-continuous oxidation of said particles, and
- the dissolved transition metal ions and the metal particles thereof, re-
spectively, are repeatedly involved in said reduction and said oxidation
such that no precipitating agglomerates of said metal particles are
formed,
(c) contacting the substrate with said activation composition such that a
transition
metal or a transition metal alloy is deposited on the surface of said
substrate and
an activated surface for metallization is obtained.
Own experiments have shown that in the present invention a very simple and
effective acti-
vation is achieved even without the need of sophisticated stabilization/anti-
oxidation of
formed particles. In contrast to common activation compositions, it turned out
that no stabi-
lization/anti-oxidation of formed particles is needed at all. This means that
in the present
invention particles are not formed with the goal to maintain them as long as
possible but
rather to establish an equilibrium between dissolved transition metal ions and
respective
particles thereof, allowing the particles intentionally/purposely to re-form
again and again
the respective ions thereof by oxidation. Typically, in common activation
compositions oxi-
dation is considered harmful and is therefore minimized and/or suppressed. In
contrast
thereto, in the present invention oxidation is advantageously utilized,
necessary, and con-
sidered to be of great benefit. It turned out, contrary to common thinking,
that it is not nec-
essary to maintain the particles for a long time in a respective activation
composition.
This brings along a number of advantages. For example, in a very simple manner
a respec-
tive activation composition is easily set up/activated at the place where it
is needed by simply
adding the required reducing agent. This means that product delivery time is
irrelevant for
the life time of the product/method.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
The present invention relies on the fact, that the particles are formed again
and again in situ,
which renders any stabilization or stabilizer compounds obsolete. For that the
dissolved
transition metal ions and the metal particles thereof are present in a
reversible equilibrium.
As a result, a very effective and strong activation can be achieved because
fresh particles
5 without a shell of stabilizer compounds around them are formed with a
relatively short life
time. Subsequently, they are reacted back into their ionic form by oxidation.
Upon adding
further reducing agent fresh particles are formed again, i.e. in situ.
In the method of the present invention (for activating) a transition metal or
a transition metal
alloy is deposited on the surface of said substrate and an activated surface
for subsequent
metallization is obtained. This means that the concentration of dissolved
metal ions of the
first species decreases over time due to deposition. However, replenishment of
the first spe-
cies is easily achieved by simply adding ions of that species. Therefore,
replenishment is
extremely easy and simple. This furthermore, significantly increases the life
time of a re-
spective activation composition and a thereto related method.
Furthermore, the respective method and activation composition does not
necessarily require
expensive noble metals but can be carried out with low-priced transition
metals.
Detailed Description of the Invention
In the context of the present invention, "continuous", "continuously", and
"continually", re-
spectively, denote a constantly ongoing doing of a respective action without
significant in-
terruptions of the action while e.g. a respective method or aspect of the
invention is carried
out.
In the context of the present invention, "semi-continuous", "semi-
continuously", and, "semi-
continually", respectively, denote a doing of a respective action with one or
more than one
even significant interruption of the action while e.g. a respective method or
aspect of the
invention is carried out. The interruptions are in some cases longer than the
time during the
action is carried out. It includes even only temporary and brief actions.
In the context of the present invention, "species" (e.g. first species or
second species) de-
notes a chemical element. Thus, "a first species of dissolved transition metal
ions" denotes
dissolved metal ions of a transition metal element of groups 3 to 12 of the
periodic table, e.g.
copper.
In the context of the present invention, "a first species of dissolved
transition metal ions and
additionally metal particles thereof" denotes dissolved metal ions of this
first species and
additionally metal particles of this first species, e.g. in the aqueous,
palladium-free activation
composition.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
6
The substrate:
In step (a) of the method of the present invention (for activating), a non-
conductive or carbon-
fibres containing substrate with a surface is provided. Such a substrate
inherently cannot be
successfully metallized and therefore needs an activation.
In the context of the present invention, activating means to modify the
surface of the non-
conductive or carbon-fibres containing substrate in such a way that it
comprises the transi-
tion metal or transition metal alloy after the respective activation step with
sufficient adhesion
for subsequent metallization. Furthermore, the deposited transition metal and
transition
metal alloy, respectively, is sufficiently adherent to the surface such that a
subsequent met-
allization layer (i) can be deposited thereon and (ii) is altogether also
sufficiently adherent to
the surface of the non-conductive or carbon-fibres containing substrate.
Preferred is a method of the present invention (for activating), wherein the
non-conductive
substrate comprises, preferably is, selected from the group consisting of
plastics, resin-con-
taining laminates, glasses, ceramics, semi-conductors, and mixtures thereof.
Preferred plastics comprise, preferably are, thermoplastics, more preferably
comprise, pref-
erably are, polyacrylates, polyamides, polyimides, polyesters, polycarbonates,
poly-
alkylenes, polyphenylenes, polystyrenes, polyvinyls, or mixtures thereof.
Preferred polyacrylates comprise poly(methyl methacrylate) (PMMA).
Preferred polyimides comprise polyetherimide (PEI).
Preferred polyesters comprise polylactic acid (PLA).
Preferred polycarbonates comprise polycarbonate obtained with bisphenol A
(PC).
Preferred polyalkylenes comprise polyethylene (PE), polypropylene (PP),
polytetrafluoroeth-
ylene (PTFE), polyoxymethylene (POM), or mixtures thereof.
Preferred polyphenylenes comprise poly(phenylene oxide) (PPO), poly(phenylene
ether)
(PPE), or mixtures thereof.
Preferred polystyrenes comprise polystyrene (PS), acrylonitrile butadiene
styrene (ABS),
styrene/butadiene rubber (SBR), styrene-acrylonitrile (SAN).
Preferred polyvinyls comprise polyvinyl chloride (PVC), poly(ethylene-vinyl
acetate) (PEVA),
polyvinylidene difluoride (PVDF), or mixtures thereof.
Preferred resin-containing laminates comprise, preferably are, fiber-enforced
resin-contain-
ing laminates, most preferably glass-fiber-enforced laminates.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
7
Very preferably, the resin-containing laminates comprise as resin one or more
than one
polymer of epoxys, vinylesters, polyesters, amides, imides, phenols,
alkylenes, sulfones, or
mixtures thereof, most preferably epoxy, imides, or mixtures thereof.
A very preferred resin-containing laminate comprises, preferably is, FR4.
Preferred glasses comprise, preferably are, silica glass, soda-lime glass,
float glass, fluoride
glass, aluminosilicate glass, phosphate glass, borate glass, borosilicate
glass, chalcogenide
glass, aluminium oxide glass, or mixtures thereof.
Preferred ceramics comprise, preferably are, glass-ceramics, aluminium oxide
ceramics, or
mixtures thereof.
Preferred semi-conductors comprise, preferably are, silicon-based semi-
conductors, more
preferably silicon-based semi-conductors comprising silicon dioxide and/or
silicon.
Very preferred semi-conductors are wafers.
Preferred is a method of the present invention (for activating), wherein the
carbon-fibres
containing substrate comprise, preferably are, carbon-fibre composites and/or
arrange-
ments of carbon-fibre filaments.
Preferred carbon-fibre composites comprise, preferably are, carbon-fibre
reinforced poly-
mers and/or carbon-fibre containing fabrics, more preferably carbon-fibre
reinforced poly-
mers and/or woven carbon-fibre containing fabrics.
Preferred arrangements of carbon-fibre filaments comprise, preferably are,
fabrics made of
carbon-fibres, most preferably woven fabrics made of carbon-fibres.
An in particularly preferred carbon-fibres containing substrate is a carbon-
fibre containing
felt.
Pre-treatment:
In some cases a pre-treatment of the surface of the non-conductive or carbon-
fibres con-
taming substrate is preferred. Thus, preferred is a method of the present
invention (for acti-
vating), comprising a pre-treatment step for the substrate prior to step (c):
(a-1) treating said substrate with a pre-treatment solution
comprising a nitrogen-
containing compound.
Preferred is a method of the present invention (for activating), wherein the
pre-treatment
solution has an alkaline pH, preferably a pH in a range from 9.0 to 14.0, more
preferably in
a range from 10.0 to 13.5, even more preferably in a range from 10.5 to 13.0,
most preferably
in a range from 11.0 to 12.5.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
8
Preferred is a method of the present invention (for activating), wherein in
the pre-treatment
solution the nitrogen-containing compound is a polymer, preferably a water-
soluble polymer.
More preferred is a method of the present invention (for activating), wherein
in the pre-treat-
ment solution the nitrogen-containing compound is a polymer comprising
pyrrolidine moie-
ties.
Preferably, the polymer is cationic.
Preferably, the nitrogen-containing compound consists of carbon atoms,
nitrogen atoms,
and hydrogen atoms.
Preferred is a method of the present invention (for activating), wherein in
the pre-treatment
io solution the nitrogen-containing compound comprises quaternary nitrogen
atoms.
Most preferred is a method of the present invention (for activating), wherein
the nitrogen-
containing compound comprises, preferably is, Polyquaternium 6.
Preferred is a method of the present invention (for activating), wherein the
pre-treatment
solution during step (a-1) has a temperature in a range from 20 C to 90 C,
preferably in a
range from 25 C to 80 C, more preferably in a range from 30 C to 70 C, most
preferably in
a range from 40 C to 60 C.
Preferred is a method of the present invention (for activating), wherein step
(a-1) is carried
out for 1 minute to 10 minutes, preferably for 2 minutes to 8 minutes, more
preferably for 3
minutes to 6 minutes, most preferably for 3.5 minutes to 5 minutes.
The aqueous, palladium-free activation composition:
In step (b) of the method of the present invention (for activating), an
aqueous, palladium-
free activation composition is provided.
The aqueous composition utilized in the method of the present invention (for
activating) is an
aqueous composition, which means that water is the primary component. Thus,
more than 50
wt.-% of the composition is water, based on the total weight of the aqueous
composition,
preferably at least 70 wt.-%, even more preferably at least 90 wt.-%, most
preferably 95 wt.-
% or more. Only in rare cases it is preferred that the composition comprises
one or more than
one solvent (other than water) that is miscible with water. However, most
preferred (for eco-
logical reasons) is a method, wherein water is the only solvent, and, thus,
most preferably the
composition is substantially free of or does not comprise organic solvents at
all.
In the context of the present invention, the term "substantially free of or
does not comprise"
of a subject-matter (e.g. a compound, a chemical, a material, etc.)
independently denotes
that said subject-matter is not present at all ("does not comprise") or is
present only in (to) a
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
9
very little and undisturbing amount (extent) without affecting the intended
purpose of the
invention ("substantially free of"). For example, such a subject-matter might
be added or
utilized unintentionally, e.g. as unavoidable impurity. "substantially free of
or does not com-
prise" preferably denotes 0 (zero) ppm to 5 ppm, based on the total weight of
e.g. the acti-
vation composition, preferably 0 ppm to 3 ppm, more preferably 0 ppm to 1.5
ppm, even
more preferably 0 ppm to 1 ppm, most preferably 0 ppm to 0.5 ppm, even most
preferably 0
ppm to 0.1 ppm. This principle applies likewise to other subject-matters, e.g.
to the total
weight of the transition metal or transition metal alloy obtained in step (c)
of the method of
the present invention (for activating).
.. The activation composition has an acidic pH, a neutral pH, or an alkaline
pH, preferably an
acidic or neutral pH, most preferably an acidic pH.
Preferred is a method of the present invention (for activating), wherein the
pH of the activation
composition is in a range from 2.0 to 13.0, preferably in a range from 3.0 to
12.0, more
preferably in a range from 4.0 to 11.0, most preferably in a range from 4.5 to
10Ø
In some cases a method of the present invention (for activating) is preferred,
wherein the pH
of the activation composition is in a range from 3.0 to 6.5, preferably in a
range from 4.0
to 6Ø Preferably this applies with the proviso that the one or more than
one reducing agent
comprises a borohydride.
The pH in the activation composition is typically a result of the presence of
(i) to (iv). If an
adjustment of the pH is necessary, it is carried out by typical means.
Preferred acids are
mineral acids and organic acids. A preferred mineral acid is sulfuric acid. A
preferred organic
acid is the acid form of the one or more than one complexing agent. A
preferred alkaline
compound is an alkaline hydroxide, preferably NaOH, an alkaline carbonate,
preferably so-
dium carbonate, and ammonia.
In the context of the present invention, the pH is determined at a temperature
of 20 C, i.e. the
defined pH is referenced to 20 C. Thus, only for the sake of pH determination
the activation
composition has a temperature of 20 C. This does not mean that the activation
composition
in itself is limited to the specific temperature of 20 C. For preferred
temperatures of the acti-
vation composition see below.
If the pH is significantly below 2 or above 13 a mostly insufficient
activation is obtained. If the
pH is too acidic typically acid-sensitive reducing agents decompose too
quickly. On the con-
trary, if the pH is too alkaline, alkaline-sensitive reducing agents decompose
too quickly.
The aqueous composition utilized in the method of the present invention (for
activating) is
palladium-free. Therefore, the activation composition is substantially free of
or does not com-
prise palladium ions. This means that neither compounds comprising palladium
are present
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
nor palladium atoms/particles or palladium ions. Advantageously, the present
invention is an
excellent alternative to palladium-containing activation processes with
identical or at least al-
most identical results in terms of activation.
Preferably, also other noble metals or at least expensive/rare metals are not
necessary in the
5 activation composition. Thus, preferred is a method of the present
invention (for activating),
wherein the activation composition is substantially free of or does not
comprise platinum ions,
gold ions, silver ions, rhodium ions, ruthenium ions, and iridium ions,
preferably is substan-
tially free of or does not comprise platinum, gold, silver, rhodium,
ruthenium, and iridium.
The aqueous composition utilized in the method of the present invention (for
activating) com-
10 prises (i) a first species of dissolved transition metal ions and
additionally metal particles
thereof.
Preferred is an activation composition, wherein said metal particles are
nanoparticles. Prefer-
ably, the metal particles comprise one or more than one elemental metal (Me ),
preferably
(essentially) consist of one or more than one elemental metal (Me ).
Even more preferred is an activation composition, wherein the metal particles
of the first spe-
cies have a particle diameter in a range from 0.1 nm to 500 nm, preferably in
a range from
0.5 nm to 200 nm, more preferably in a range from 1.0 nm to 100 nm, most
preferably in a
range from 3 nm to 50 nm, even most preferably in a range from 5 nm to 15 nm.
More preferred is a method of the present invention (for activating), wherein
the metal parti-
cles of the first species in the activation composition are colloidal metal
particles.
Thus, preferred is a method of the present invention (for activating), wherein
the activation
composition is a colloid, preferably a colloidal suspension. However, the
activation composi-
tion is still a clear but colored solution depending on the coloring effect
caused by the dis-
solved ions, primarily of the first species.
In the activation composition said dissolved transition metal ions of the
first species and said
metal particles thereof form together a total amount of the metal of the first
species. Preferred
is a method of the present invention (for activating), wherein in the
activation composition the
metal ions of the first species and the metal particles thereof form a total
concentration in a
range from 0.05 g/L to 30.0 g/L, based on the total volume of the activation
composition and
based on an ionic, non-particular form, preferably in a range from 0.07 g/L to
18.0 g/L, more
preferably in a range from 0.09 g/L to 12.0 g/L, even more preferably in a
range from 0.11 g/L
to 8.0 g/L, most preferably in a range from 0.15 g/L to 6.0 g/L, even most
preferably in a range
from 0.2 g/L to 3.0 g/L. This means that for determining said total
concentration the transition
metal particles of the first species are considered/calculated as dissolved
metal ions.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
11
Although the method of the present invention (for activating) can be basically
carried out with
comparatively high concentrations of the first species, it turned out that
surprisingly very low
concentrations are already sufficient to obtain very efficient and excellent
results (see exam-
ples). This is in particular advantageous in terms of waste-water treatment
and is thus cost-
.. and ecofriendly.
Preferred is a method of the present invention (for activating), wherein the
first species is
copper or cobalt, preferably copper. Copper and cobalt are cost efficient
metals compared to
commonly used palladium but achieve sufficient activation on the surface of
the non-conduc-
tive or carbon-fibres containing substrate. The aforementioned concentrations
most prefera-
bly apply to copper and cobalt, most preferably to copper.
Preferred is a method of the present invention (for activating), wherein the
source of dis-
solved copper ions is selected from the group consisting of copper sulfate,
copper chloride,
copper nitrate, copper fluoroborate, copper acetate, copper citrate, copper
phenyl sulfonate,
copper para-toluene sulfonate, and copper alkyl sulfonates. A preferred copper
alkyl sul-
fonate is copper methane sulfonate. The most preferred copper source is copper
sulfate,
most preferably CuSO4 * 5 H2O.
Optionally, the aqueous, palladium-free activation composition comprises (iv)
one or more
than one second species of dissolved metal ions being different from the first
species. Pref-
erably, the second species is substantially free of or does not comprise
alkali metals.
Preferred is a method of the present invention (for activating), wherein the
one or more than
one second species is selected from the group consisting of transition metals
and magnesium,
preferably nickel, cobalt, iron, and magnesium, preferably nickel and cobalt,
more preferably
nickel. With the dissolved metal ions of the second species respective
transition alloys are
preferably deposited in step (c) of the method of the present invention (for
activating).
Preferred is a method of the present invention (for activating), wherein the
one or more than
one second species is substantially free of or does not comprise tin.
In addition to the first species and the optional second species, the aqueous,
palladium-free
activation composition comprises (ii) one or more than one complexing agent.
Preferably, the
one or more than one complexing agent is suitable to form complexes with the
dissolved
transition metal ions of at least the first species.
Preferred is a method of the present invention (for activating), wherein the
one or more than
one complexing agent comprises or is an organic complexing agent, preferably a
carboxylic
acid and/or salts thereof, more preferably a di- or tricarboxylic acid and/or
salts thereof, even
more preferably a tricarboxylic acid and/or salts thereof, most preferably a
hydroxy tricarbox-
ylic acid and/or salts thereof, even most preferably citric acid, structural
isomers, and/or salts
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
12
thereof. A preferred structural isomer is iso-citric acid and salts thereof.
Most preferably, the
one or more than one complexing agent defined above (including the preferred
variants) is
the only complexing agent in the activation composition.
Preferred is a method of the present invention (for activating), wherein in
the activation com-
position
- the metal ions of the first species and the metal particles thereof
forming together a total
concentration based on the total volume of the activation composition and
based on an
ionic, non-particular form, and
- the one or more than on complexing agent in a total concentration
are present in a molar ratio in a range from 1.0: 0.2 to 1.0: 100.0,
preferably in a range from
1.0: 0.5 to 1.0: 50.0, more preferably in a range from 1.0: 0.85 to 1.0 :
25.0, even more
preferably in a range from 1.0: 0.95 to 1.0: 15.0, yet even more preferably in
a range from
1.0: 1.0 to 1.0: 10.0, most preferably in a range from 1.0: 1.1 to 1.0: 5Ø
This very prefer-
ably applies, if the one or more than one complexing agent comprises a
tricarboxylic acid
and/or salts thereof, more preferably a hydroxy tricarboxylic acid and/or
salts thereof, most
preferably citric acid, structural isomers, and/or salts thereof.
Preferred is a method of the present invention (for activating), wherein the
one or more than
one complexing agent in the activation composition is present in a total
amount in a range
from 0.01 mol/L to 0.5 mol/L, based on the total volume of the activation
composition, pref-
erably in a range from 0.015 mol/L to 0.35 mol/L, more preferably in a range
from 0.02 mol/L
to 0.3 mol/L, most preferably in a range from 0.023 mol/L to 0.275 mol/L.
In addition to the first species, the optional second species, and the one or
more than one
complexing agent, the aqueous, palladium-free activation composition comprises
perma-
nently or temporarily (iii) one or more than one reducing agent. The one or
more than one
reducing agent is essential for forming the metal particles from the dissolved
transition metal
ions of at least the first species. For that the dissolved transition metal
ions are chemically
reduced, continuous or semi-continuous, in order to form said particles. Thus,
said particles
are either formed continually or semi-continually, respectively, depending on
the presence of
the one or more than one reducing agent in the activation composition, which
is permanent
or temporary. However, when the one or more than one reducing agent is
present, typically
said particles will be formed until said reducing agent is used up or
insufficiently present.
Preferred is a method of the present invention (for activating), wherein the
oxidation affects
said particles and is in constant competition with the reduction. Typically
oxidation starts as
soon as the one or more than one reducing agent is used up, which is
explicitly desired in the
context of the present invention.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
13
Said oxidation is furthermore very relevant if in the method of the present
invention (for acti-
vating) after one or more than one first step (c) the method is interrupted
for a comparatively
long time. In order to prevent precipitating agglomerates during such a time,
in the activation
composition said oxidation is carried out until no particles are any longer
present but rather
only dissolved transition metal ions. Preferably, the oxidation is accelerated
by adding an
oxidizing agent, more preferably a peroxide, most preferably hydrogen
peroxide. Upon re-
suming operation, particles are formed by adding continually or semi-
continually the one or
more than reducing agent to re-form particles. Afterwards, the method of the
present invention
(for activating) is resumed.
Thus, preferably the one or more than one reducing agent is suitable for
reducing the dis-
solved transition metal ions of at least the first species.
In some cases preferred is a method of the present invention (for activating),
wherein the one
or more than one reducing agent comprises one or more than one hydrogen atom
such that
hydrogen is released upon reducing said transition metal ions, which at least
partly adsorbs
on said activated surface.
Preferred is a method of the present invention (for activating), wherein the
one or more than
one reducing agent comprises a boron-containing reducing agent, preferably a
borohydride.
A preferred borohydride comprises an inorganic borohydride and/or an organic
borohydride.
A preferred organic borohydride comprises an alkylaminoborane, most preferably
dimethyla-
minoborane. A preferred inorganic borohydride comprises an alkali borohydride,
most prefer-
ably sodium borohydride. In the method of the present invention (for
activating), most pre-
ferred is an alkali borohydride, preferably sodium borohydride. This allows a
slightly acidic pH
and a temperature in step (c) of the method of the present invention (for
activating), in a
moderate range, preferably from 15 C to 30 C. These are excellent room
temperature condi-
tions. Thus, no additional and cost-intensive heating is necessarily required.
Furthermore,
hydrogen is generated.
Preferably, the boron-containing reducing agent, preferably a borohydride,
more preferably
an alkali borohydride and/or an alkylaminoborane, most preferably sodium
borohydride and/or
dimethylaminoborane is the only reducing agent in the activation composition.
As a result of utilizing a borohydride in the activation composition as one of
the one or more
than one reducing agent, typically boric acid and/or salts thereof are formed.
In some cases a method of the present invention (for activating) is preferred,
wherein the one
or more than one reducing agent comprises an aldehyde, preferably
formaldehyde, glyoxylic
acid, salts of glyoxylic acid, or mixtures thereof, most preferably as the
only reducing agent.
In such a case formation of boric acid is avoided.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
14
In some cases a method of the present invention (for activating) is preferred,
wherein the one
or more than one reducing agent comprises hydrazine, most preferably as the
only reducing
agent. Also, in such a case formation of boric acid is avoided.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition comprises the one or more than one reducing agent in a total
concentration in a range
from 0.2 mmol/L to 500.0 mmol/L, based on the total volume of the activation
composition,
preferably in a range from 0.4 mmol/L to 350.0 mmol/L, more preferably in a
range from 0.6
mmol/L to 250.0 mmol/L, even more preferably in a range from 0.8 mmol/L to
150.0 mmol/L,
most preferably in a range from 1.0 mmol/L to 80.0 mmol/L. An in particular
preferred total
concentration is in a range from 0.9 mmol/L to 50.0 mmol/L, very preferably in
a range from
1.0 mmol/L to 30.0 mmol/L, most preferably in a range from 1.1 mmol/L to 10.0
mmol/L. Most
preferably, this applies to the aforementioned preferred, more preferred, etc.
reducing agents;
most preferably to a borohydride.
Generally preferred is a method of the present invention (for activating),
wherein in the acti-
vation composition
- the metal ions of the first species and the metal particles thereof
forming together a total
concentration based on the total volume of the activation composition and
based on an
ionic, non-particular form, and
- the one or more than on reducing agent (if semi-continually added, in the
moment of addi-
tion) in a total concentration
are present in a molar ratio of more than 0.5, preferably of 1 or more, more
preferably of 2 or
more, even more preferably of 3 or more, most preferably of 3.5 or more. Very
preferred is a
molar ratio in the range from 1 to 20. Thus, in the activation composition the
one or more than
one reducing agent is preferably present (either permanently or temporarily)
in such a total
concentration that the dissolved transition metal ions of the first species
are not quantitatively
reduced into the respective particles. Furthermore, a method of the present
invention (for
activating) is preferred, wherein the activation composition does not
predominantly exhibit a
reductive environment to prevent oxidation of the metal particles. On the
contrary, as already
mentioned, oxidation is required and desired. Thus, preferred is a method of
the present in-
vention (for activating), wherein the activation composition is predominantly
kept in oxidizing
condition to allow oxidation of the metal particles.
Particularly preferred is a method of the present invention (for activating),
wherein in the
activation composition
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
- the metal ions of the first species and the metal particles thereof
forming together a total
concentration based on the total volume of the activation composition and
based on an
ionic, non-particular form, and
- the one or more than on reducing agent (if semi-continually added, in the
moment of
5 addition) in a total concentration
are present in a molar ratio in a range from 0.3 to 60.0, preferably in a
range from 0.5 to 30.0,
more preferably in a range from 1.0 to 20.0, even more preferably in a range
from 1.5 to 10.0,
most preferably in a range from 1.8 to 3Ø
In some cases a method of the present invention (for activating) is preferred,
wherein in the
10 aqueous, palladium-free activation composition the one or more than one
reducing agent is
permanently present. Thus, preferred is that the one or more than one reducing
agent is
added to the activation composition continually, preferably by a permanent
flow of a respec-
tive liquid containing said one or more than one reducing agent. In this
approach oxidation
and reduction are taking place simultaneously over the time during step (c) of
the method of
15 .. the present invention (for activating) is carried out. As a result, the
metal particles are present
in a comparatively constant concentration.
Alternatively, a method of the present invention (for activating) is
preferred, wherein in the
aqueous, palladium-free activation composition the one or more than one
reducing agent is
temporarily present. Thus, preferably the one or more than one reducing agent
is added semi-
continuously; e.g. in consecutive portions with time-wise interruptions
between each portion.
This means that when the one or more than one reducing agent is added fresh
particles are
formed. However, during the interruptions the oxidation, creating the
dissolved transition
metal ions, is very dominant. As a result, the metal particles are present in
a basically varying
concentration. However, depending on the length of the time-wise interruptions
and making
.. sure that the interruptions are not too long, such an approach is fully
sufficient to successfully
activate surfaces of even a plurality of non-conductive or carbon-fibres
containing substrates.
Therefore, this approach is in particular preferred.
However, in either case preferred is a method of the present invention (for
activating), wherein
the one or more than one reducing agent is present in such a way that the
equilibrium remains
reversible. Thus, the reversible equilibrium is not only a side reaction or an
undesired side
reaction.
Upon oxidation, in the activation composition the total concentration of the
dissolved transition
metal ions basically increases as a result of the reversible equilibrium,
wherein the total
amount of said metal particles decreases. This reversible equilibrium is
preferably monitored
.. for a better process control. Therefore, preferred is a method of the
present invention (for
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
16
activating), wherein the reversible equilibrium is monitored by UVNIS
inspection. Preferably,
said dissolved transition metal ions are monitored at a wave length within a
range from 700
nm to 800 nm, preferably within a range from 710 nm to 780 nm, more preferably
within a
range from 720 nm to 760 nm, most preferably within a range from 730 nm to 750
nm. Also
preferred is that said metal particles are monitored at a wave length within a
range from 400
nm to 600 nm, preferably within a range from 450 nm to 550 nm. This allows
determining
when to add one of the one or more than one reducing agent in order to form,
preferably re-
form, said metal particles in order to increase their total amount.
Thus, preferred is a method of the present invention (for activating), wherein
the one or more
than one reducing agent is continually or semi-continually added to the
activation composition
such that further metal particles are continually or semi-continually,
respectively, formed from
the dissolved transition metal ions of the first species, preferably added
after one or more than
one step (c) is carried out.
Preferred is a method of the present invention (for activating), wherein the
metal particles of
the first species are continually or semi-continually formed in situ in the
activation composition
by said reduction after and/or during one or more than one step (c) is carried
out. This prefer-
ably defines that in the method of the present invention (for activating) step
(c) is carried out
more than one time, preferably the method, including step (c), is carried out
repeatedly. It is
very preferred that after one, more than one, or each step (c) of the method
of the present
invention (for activating) metal particles are freshly formed by said
reduction. This is possible
because said oxidation is allowed and desired, leading, preferably continually
but at least
semi-continually, to fresh dissolved transition metal ions ready for re-
reduction. This is con-
trary to common approaches, wherein metal particles are formed (and
stabilized) before the
activation is carried out, which afterwards typically last as long as possible
by particle stabili-
zation until the respective activation composition is unstable and inoperable.
As mentioned throughout the text, in the context of the present invention it
is preferably nec-
essary to add at least semi-continually a reducing agent. Typically, the
reducing agent used
for said reduction reacts with the dissolved transition metal ions and leads
to a reducing agent
degradation product, preferably boric acid and/or salts thereof. Usually, such
degradation
products accumulate in the activation composition, which is not preferred in
the context of the
present invention. Therefore, a method of the present invention (for
activating) is preferred,
wherein the method is performed by bleed and feed. In such an approach, a
certain volume
of the activation composition is removed (e.g. by drag out; thereby removing
also degradation
products) and replaced by a replacement volume (e.g. by means of
replenishment) in such a
way that essential components in the activation composition have a
sufficiently constant con-
centration. This means that the replacement volume typically does not comprise
boric acid
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
17
and/or salts thereof, preferably does not comprise the reducing agent
degradation product.
This is also beneficial for stabilizing the pH to a basically constant pH.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition comprises boric acid and/or salts thereof in a total concentration of 5
g/L or less, based
on the total volume of the activation composition, preferably of 3 g/L or
less, more preferably
of 2 g/L or less, most preferably of 1.2 g/L or less. This preferably applies
with the proviso that
(1) the one or more than one reducing agent comprises a borohydride and (2)
step (c) is
carried out more than one time.
Preferred is a method of the present invention (for activating), wherein the
reversible equilib-
rium is not predominantly shifted to the metal particles over the majority of
time during which
step (c) is carried out.
Preferred is a method of the present invention (for activating), wherein
during and/or after step
(c) the majority of said metal particles is subjected to said oxidation.
Majority preferably de-
notes more than 50% of the particles.
Preferably, the one or more than one reducing agent is substantially free of
or does not com-
prise hypophosphite ions, preferably is substantially free of or does not
comprise a phospho-
rous-containing reducing agent. Own experiments have shown that in some cases
the activa-
tion with such reducing agents is too weak or even incomplete.
As already outlined above, the activation composition does not additionally
require stabilizing
compounds. Therefore, preferred is a method of the present invention (for
activating), wherein
the activation composition is substantially free of or does not comprise a
compound prevent-
ing the oxidation of the metal particles and/or is substantially free of or
does not comprise a
stabilizer compound to stabilize the metal particles. Preferably, the
activation composition is
substantially free of or does not comprise a stabilizer compound to stabilize
the metal particles
by preventing agglomeration of the metal particles. In the context of the
present invention, the
one or more than one reducing agent (temporarily or permanently present in the
activation
composition) and compounds involved in the oxidation, preferably ambient air
and/or oxygen
gas (i.e. most preferably molecular oxygen), are not considered to be such a
compound. The
one or more than one reducing agent is rather required in order to form the
metal particles,
which includes re-forming the particles. This means that the activation
composition is sub-
stantially free of or does not comprise in addition to said one or more than
one reducing agent
and compounds involved in the oxidation a stabilizer compound and/or a
compound prevent-
ing the oxidation of the metal particles. Thus, preferred is a method of the
present invention
(for activating), wherein the one or more than one reducing agent is not
present in a total
amount to prevent the oxidation, preferably is not present in a total amount
to prevent the
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
18
oxidation after or during one or more than one step (c) is carried out. As
outlined, the oxidation,
most preferably through ambient air, is needed to re-form the dissolved
transition metal ions
such that no precipitating agglomerates of said metal particles are formed.
A method of the present invention (for activating) is preferred, wherein the
activation compo-
sition is substantially free of or does not comprise a compound encapsulating
fully or partly
the metal particles or which fully or partly adsorbs onto the surface of the
particles. It is be-
lieved that some stabilizer compounds are based on such a function. In the
context of the
present invention this is not desired.
Generally, a method of the present invention (for activating) is preferred,
wherein the activa-
tion composition is substantially free of or does not comprise a compound
preventing the
equilibrium from being reversible and/or is substantially free of or does not
comprise a com-
pound in order to shift the equilibrium entirely towards the metal particles.
Again, the one or
more than one reducing agent is not considered to be such a compound for the
reasons out-
lined above.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise tin ions, preferably is
substantially free of
or does not comprise tin ions, lead ions, germanium ions, gallium ions,
antimony ions, bismuth
ions, and aluminium ions, more preferably is substantially free of or does not
comprise metal
ions of main groups III, IV, and V of the periodic table of elements. In the
context of the present
invention "metal ions of main group III" does not include respective boron-
containing ions. In
particular tin ions are very well known to prevent oxidation of for example
copper particles in
respective palladium-free copper-tin activation compositions, thereby
preventing the equilib-
rium from being reversible. Such tin ions typically form a reductive
environment, which is by
no means desired in the context of the present invention.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise polyvinylpyrrolidone,
preferably is substan-
tially free of or does not comprise a polyvinyl compound, more preferably is
substantially free
of or does not comprise an organic polymer comprising a vinyl moiety, most
preferably is
substantially free of or does not comprise a dissolved organic polymer.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise a protein, agar, gum
Arabic, sugars, and
polyalcohols.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise glycerol.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
19
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise gelatin.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise thiourea, preferably is
substantially free of
or does not comprise sulfur-containing compounds with divalent sulfur, more
preferably is
substantially free of or does not comprise sulfur-containing compounds with
sulfur in an oxi-
dation number of +5 or below.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise a compound comprising an
aromatic ring
and a sulfonic acid group (including salts thereof), preferably is
substantially free of or does
not comprise a sulfonic acid or salts thereof.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise a compound named Orzan-S.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise urea.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise a dispersing agent.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise polyethylenimine,
preferably is substantially
free of or does not comprise polyalkylenimine, most preferably is
substantially free of or does
not comprise an organic polymer comprising an imine moiety.
In particular polymers as mentioned above are commonly used as stabilizer
compounds in
order to stabilize the metal particles. However, polymers are not necessary in
the context of
the present invention. Furthermore, it is believed that the metal particles
are significantly more
effective / more active if no such molecules are forming a shell around the
particles.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise sodium dodecyl sulfate,
preferably is sub-
stantially free of or does not comprise an alkyl sulfate with 8 to 20 carbon
atoms, more pref-
erably is substantially free of or does not comprise an alkyl sulfate, most
preferably is sub-
stantially free of or does not comprise a surfactant.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise a hydroquinone,
pyrogallol, and/or resor-
cinol, preferably is substantially free of or does not comprise a hydroxy
benzene. In many
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
cases such hydroxy benzenes are commonly used as anti-oxidizing agents,
thereby prevent-
ing the equilibrium from being reversible, which are not needed in the
activation composition.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise a quinone.
5 Preferred is a method of the present invention (for activating), wherein
the activation compo-
sition is substantially free of or does not comprise a fatty alcohol.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise an alkylene glycol,
preferably is substan-
tially free of or does not comprise a glycol.
10 Preferred is a method of the present invention (for activating), wherein
the activation compo-
sition is substantially free of or does not comprise manganese ions.
Preferred is a method of the present invention (for activating), wherein the
activation compo-
sition is substantially free of or does not comprise zinc ions.
As a result and in particular despite the fact that the activation composition
does not comprise
15 a stabilizing compound and/or a compound preventing the oxidation of the
metal particles, a
method of the present invention (for activating) is preferred, wherein the
activation composi-
tion is substantially free of or does not comprise precipitating agglomerates
of said metal par-
ticles. This is achieved because the oxidation is not suppressed (i.e. is not
avoided) but rather
the dissolved transition metal ions of at least the first species and the
metal particles thereof,
20 respectively, are repeatedly involved in said reduction and said
oxidation.
Preferred is a method of the present invention (for activating), wherein
"repeatedly involved"
explicitly includes at least more than once, preferably more than twice, even
more preferably
more than three times, most preferably more than four times, even most
preferably over the
entire life time of the activation composition.
Own experiments have shown that it is in particular the oxidation that
prevents agglomeration.
The metal particles are oxidized back into their ionic/dissolved form. This
means that there is
not sufficient time for the particles to form higher aggregates and to even
form agglomerates.
Although each suitable oxidation agent is basically applicable, ambient air
proved to be an
excellent choice. It is sufficiently strong and ubiquitous available.
Preferred is a method of the
present invention (for activating), wherein the forming of precipitating
agglomerates of said
metal particles is prevented through said oxidation, preferably through
oxidation by ambient
air and/or oxygen gas. Preferred is a method of the present invention (for
activating), wherein
the dissolved transition metal ions are formed from the metal particles
through oxidation by
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
21
ambient air and/or oxygen gas. In both cases the preferred oxidizing agent is
molecular oxy-
gen. Most preferred is a method of the present invention (for activating),
wherein the majority
of the dissolved transition metal ions are formed from the majority of the
metal particles
through oxidation by ambient air and/or oxygen gas.
In some cases a method of the present invention (for activating) is preferred,
wherein the
continuous or semi-continuous oxidation is additionally or solely achieved
through an oxidiz-
ing agent, which is not molecular oxygen, more preferably through a peroxide,
most preferably
hydrogen peroxide. In particular in addition to ambient air this preferably
accelerates the oxi-
dation of the particles if this is required, e.g. if an activation composition
must be inactivated
and stored for longer times.
In order to sufficiently facilitate the oxidation in the activation
composition, preferred is a
method of the present invention (for activating), wherein the activation
composition continually
or semi-continually circulates, preferably by shaking, stirring and/or
pumping. This is preferred
to ensure that the oxidation is equally distributed in the entire activation
composition. In other
words, this ensures that the metal particles are equally contacted with an
oxidizing agent,
which facilitates the oxidation.
Very most preferred is method (for activating) a surface of a non-conductive
or carbon-fibres
containing substrate for metallization, the method comprising the steps
(a) providing said substrate,
(b) providing an aqueous, palladium-free activation composition comprising
(i) a first species of dissolved transition metal ions and additionally
colloidal
metal particles thereof, wherein the first species is copper,
(ii) one or more than one complexing agent comprising a hydroxy
tricarboxylic
acid and/or salts thereof, preferably citric acid, structural isomers, and/or
salts thereof,
(iii) permanently or temporarily one or more than one boron-containing reduc-
ing agent, preferably a borohydride,
(iv) optionally one or more than one second species of dissolved metal ions
being different from the first species, wherein the second species prefera-
bly is nickel,
wherein
- the activation composition is a colloidal suspension, and
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
22
- at least of the first species, the dissolved transition metal ions and
the metal
particles thereof are present in a reversible equilibrium, with the proviso
that
- the metal particles are formed from the dissolved transition metal ions
through a continuous or semi-continuous reduction through the one or
more than one reducing agent,
- the dissolved transition metal ions are formed from the metal particles
through continuous or semi-continuous oxidation of said particles
through oxidation by ambient air,
- the dissolved transition metal ions and the metal particles thereof, re-
spectively, are repeatedly involved in said reduction and said oxidation
such that no precipitating agglomerates of said metal particles are
formed, and
(c) contacting the substrate with said activation composition such
that a transition
metal or a transition metal alloy is deposited on the surface of said
substrate and
an activated surface for metallization is obtained, wherein the metal
particles are
continually or semi-continually formed in situ in the activation composition
by said
reduction after and/or during one or more than one step (c) is carried out.
The present invention is also directed to a method for preparing an aqueous,
palladium-free
activation composition for activating a surface of a non-conductive or carbon-
fibres containing
substrate for metallization (preferably an activation composition as utilized
in the method of
the present invention (for activating)), the method comprising the steps
(1) providing an aqueous starting solution comprising
- a first species of dissolved transition metal ions,
- one or more than one complexing agent, and
- optionally one or more than one second species of dissolved metal ions being
different from the first species,
(2) continually or semi-continually adding one or more than one
reducing agent to
the starting solution such that metal particles of at last the first species
of dis-
solved transition metal ions are continually or semi-continually,
respectively,
formed in the solution,
with the proviso that said metal particles are continually or semi-continually
oxidized to
form dissolved transition metal ions of the first species.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
23
The aforementioned regarding the method of the present invention (for
activating), preferably
applies likewise to the method of the present invention for preparing the
aqueous, palladium-
free activation composition, most preferably as aforementioned defined as
being preferred.
The present invention is also directed to the use of continuous or semi-
continuous reduction
of dissolved transition metal ions of a first species in combination with
continuous or semi-
continuous oxidation of metal particles of the first species in a reversible
equilibrium to con-
tinually or semi-continually form in situ metal particles in an aqueous,
palladium-free activation
composition.
The aforementioned regarding the method of the present invention (for
activating), preferably
applies likewise to the use of the present invention, most preferably as
aforementioned de-
fined as being preferred.
The present invention is also directed to an aqueous, palladium-free
activation composition
for activating a surface of a non-conductive or carbon-fibres containing
substrate for metalli-
zation, the composition comprising
(i) a first species of dissolved transition metal ions and additionally
metal particles
thereof,
(ii) one or more than one complexing agent,
(iii) permanently or temporarily one or more than one reducing agent,
(iv) optionally one or more than one second species of dissolved metal ions
being
different from the first species,
wherein
- at least of the first species, the dissolved transition metal ions and the
metal parti-
cles thereof are present in an reversible equilibrium, with the proviso that
- the metal particles are formed from the dissolved transition metal ions
through
a continuous or semi-continuous reduction through the one or more than one
reducing agent,
- the dissolved transition metal ions are formed from the metal particles
through
continuous or semi-continuous oxidation of said particles, and
- the dissolved transition metal ions and the metal particles thereof,
respectively,
are repeatedly involved in said reduction and said oxidation such that no pre-
cipitating agglomerates of said metal particles are formed.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
24
The aforementioned regarding the method of the present invention (for
activating), preferably
applies likewise to the aqueous, palladium-free activation composition of the
present inven-
tion, most preferably as aforementioned defined as being preferred.
Preferably, the activation composition of the present invention is obtained at
and/or has a
temperature in a range from 10 C to 90 C, preferably in a range from 14 C to
75 C, more
preferably in a range from 16 C to 65 C, most preferably in a range from 18 C
to 45 C, even
most preferably in a range from 20 C to 32 C. In particular preferred is a
temperature in a
range from 18 C to 45 C, preferably in a range from 20 C to 32 C, with the
proviso that the
one or more than one reducing agent is a borohydride, preferably sodium
borohydride. This
in particular preferably also applies to the method of the present invention
(for preparing said
activation composition) and the method of the present invention (for
activating).
More preferably, the activation composition of the present invention is not
obtained at and/or
has not a temperature above 110 C, preferably above 100 C, more preferably
above 95 C.
Most preferably the activation composition of the present invention is not
obtained at a tem-
perature above 110 C. This likewise preferably applies to the method of the
present invention
(for preparing said activation composition) and the method of the present
invention (for acti-
vating).
The activation:
In step (c) of the method of the present invention (for activating), the
substrate is contacted
with the aqueous, palladium-free activation composition in order to obtain an
activated sur-
face for metallization by depositing the metal or metal alloy, i.e. depositing
a seed or activa-
tion layer.
Preferred is a method of the present invention (for activating), wherein in
step (c) the con-
tacting is carried out at a temperature in a range from 10 C to 90 C,
preferably in a range
from 14 C to 75 C, more preferably in a range from 16 C to 65 C, most
preferably in a range
from 18 C to 45 C, even most preferably in a range from 20 C to 32 C. In
particular preferred
is a temperature in step (c) in a range from 18 C to 45 C, preferably in a
range from 20 C
to 32 C, and wherein the reduction through the one or more than one reducing
agent is a
borohydride, preferably sodium borohydride.
Preferred is a method of the present invention (for activating), wherein in
step (c) the con-
tacting is carried out for a time in a range from 1 minute to 10 minutes,
preferably for 2
minutes to 8 minutes, more preferably for 3 minutes to 6 minutes, most
preferably for 3.5
minutes to 5 minutes.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
Preferred is a method of the present invention (for activating), wherein after
step (c) a rinsing
step is carried out. In such a case a rinsed, activated surface for
metallization is obtained.
Preferably, the rinsing is carried out with water.
Preferred is a method of the present invention (for activating), wherein the
method is carried
5 out
for 10 days or more, without replacing the majority of the activation
composition in one
step (i.e. more than 50 vol.-c/o of the composition), preferably 50 days or
more, more prefer-
ably 200 days or more, even more preferably 1 year or more, most preferably 2
years or
more, even most preferably 5 years or more.
The metallization:
10 The
present invention furthermore refers to a method for metallizing an activated
surface of
a non-conductive or carbon-fibres containing substrate, the method comprising
the steps
(A)
providing the non-conductive or carbon-fibres containing substrate with the
acti-
vated surface for metallization obtained by the method of the present
invention
(for activating), preferably as defined throughout the text as being
preferred,
15 (B)
metallizing the activated surface by contacting the activated surface with a
first
metallizing solution such that a first metallization layer is deposited on the
acti-
vated surface.
In step (A) of the method of the present invention (for metallizing) the non-
conductive or
carbon-fibres containing substrate with the activated surface is provided as
obtained by the
20
method of the present invention (for activating); for details see text above.
The aforemen-
tioned regarding the method of the present invention (for activating),
preferably applies to
the method of the present invention for metallization, most preferably as
described as being
preferred.
Preferred is a method of the present invention (for metallizing), wherein in
step (B) the first
25
metallization layer is a distinct layer deposited on the transition metal or
transition metal alloy
obtained in step (c) of the method of the present invention (for activating).
Preferred is a method of the present invention (for metallizing), wherein in
step (B) the first
metallization solution is essentially free of or does not comprise a
reversible equilibrium be-
tween metal ions and particles thereof; more preferably is essentially free of
or does not
comprise metal/metal alloy particles, most preferably is essentially free of
or does not com-
prise any particles.
Preferred is a method of the present invention (for metallizing), wherein in
step (B) the first
metallization solution comprises a reducing agent or does not comprise a
reducing agent.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
26
Preferred is a method of the present invention (for metallizing), wherein step
(B) is carried
out at a temperature in a range from 10 C to 95 C, preferably in a range from
15 C to 85 C,
more preferably in a range from 20 C to 65 C, even more preferably in a range
from 25 C
to 55 C, most preferably in a range from 30 C to 45 C.
Preferred is a method of the present invention (for metallizing), wherein step
(B) is carried
out for 30 seconds to 180 minutes, preferably for 45 seconds to 120 minutes,
more prefera-
bly for 1 minutes to 60 minutes, most preferably for 1.5 minutes to 45
minutes.
Preferred is a method of the present invention (for metallizing), wherein in
step (B) the first
metallization solution does not comprise a reducing agent and is an immersion
type metal-
lization solution, preferably comprising one or more than one species of ions
selected from
the group consisting of palladium ions, platinum ions, silver ions, gold ions,
and mercury
ions, more preferably comprising palladium ions, most preferably comprising
palladium ions
in a total concentration in a range from 0.05 mg/L to 20 mg/L.
More preferred is a method of the present invention (for metallizing), wherein
in step (B) the
first metallization solution is an acidic palladium immersion type
metallization solution.
Preferred is a method of the present invention (for metallizing), wherein in
step (B) the first
metallization solution is an immersion type metallization solution comprising
palladium ions
in a total concentration in a range from 0.09 mg/L to 10.0 mg/L, based on the
total volume
of the metallization solution, preferably in a range from 0.1 mg/L to 5.0
mg/L, more preferably
in a range from 0.12 mg/L to 3.0 mg/L, even more preferably in a range from
0.15 mg/L to
2.0 mg/L, most preferably in a range from 0.2 mg/L to 1 mg/L, even most
preferably in a
range from 0.22 mg/L to 0.75 mg/L. This particularly applies if the
metallization solution is
acidic. In combination with the method of the present invention (for
activating), such a met-
allization solution surprisingly requires a significantly low concentration of
palladium ions
compared to conventional prior art metallization solutions but in the context
of the present
invention without compromising the metallization result/quality.
Alternatively preferred is a method of the present invention (for
metallizing), wherein in step
(B) the first metallization solution comprises a reducing agent and is an
autocatalytic type
metallization solution, preferably comprising one or more than one species of
transition
metal ions, more preferably comprising copper ions and/or nickel ions.
However, irrespective of what type the first metallization solution is,
preferably it is a clear
solution without particles.
Preferred is a method of the present invention (for metallizing) comprising
the steps
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
27
(A) providing the non-conductive or carbon-fibres containing substrate with
the acti-
vated surface for metallization obtained by the method of the present
invention
(for activating), preferably as defined throughout the text as being
preferred,
(B) metallizing the activated surface by contacting the activated surface with
a first
metallizing solution being an autocatalytic type metallization solution
comprising
copper ions and a reducing agent such that a first metallization layer
comprising
copper or a copper alloy is deposited on the activated surface.
Alternatively preferred is a method of the present invention (for metallizing)
comprising the
steps
(A) providing the non-conductive or carbon-fibres containing substrate with
the acti-
vated surface for metallization obtained by the method of the present
invention
(for activating), preferably as defined throughout the text as being
preferred,
(B) metallizing the activated surface by contacting the activated surface with
a first
metallizing solution being an immersion type metallization solution comprising
palladium ions (preferably as described before) such that a first
metallization
layer comprising palladium is at least partly deposited on the activated
surface,
and subsequently
(C) metallizing the first metallization layer by contacting the first
metallization layer
with a second metallizing solution such that a second metallization layer is
de-
posited on the first metallization layer.
Preferred is a method of the present invention (for metallizing), wherein in
step (C) the sec-
ond metallizing solution comprises a reducing agent, preferably comprises a
reducing agent
and nickel ions.
Thus, preferred is a method of the present invention (for metallizing),
wherein in step (C) the
second metallization layer comprises nickel; preferably is a nickel or a
nickel alloy layer.
However, in other cases preferred is a method of the present invention (for
metallization),
wherein in step (C) the second metallizing solution comprises a reducing
agent, preferably
comprises a reducing agent and copper ions.
Thus, preferred is a method of the present invention (for metallizing),
wherein in step (C) the
second metallization layer comprises copper; preferably is a copper or a
copper alloy layer.
In other cases preferred is a method of the present invention (for
metallization), wherein in
step (C) the second metallizing solution comprises a reducing agent,
preferably comprises
a reducing agent and cobalt ions.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
28
Thus, preferred is a method of the present invention (for metallizing),
wherein in step (C) the
second metallization layer comprises cobalt; preferably is a cobalt or a
cobalt alloy layer.
Preferred is a method of the present invention (for metallizing), wherein in
step (C) the sec-
ond metallization layer starts deposition within 8 seconds to 30 seconds,
preferably within
10 seconds to 25 seconds, most preferably within 12 seconds to 20 seconds.
This most
preferably applies if the second metallization layer comprises nickel;
preferably is a nickel
or a nickel alloy layer. Thus, own experiments have shown that a first
metallization layer
comprising palladium functions as a booster for a second metallization layer
of nickel or a
nickel alloy.
The present invention is described in more detail by the following non
limiting examples.
Examples
Providing the substrate:
Throughout all experiments substrates of either FR4 (Substrate 1, a resin-
containing lami-
nate, test panels with 5 x 5 cm) or ABS (Substrate 2, a plastic, test panels
with 3 cm diam-
eter) are used.
Pre-treatment:
If not stated otherwise, each substrate is at least treated with a pre-
treatment solution com-
prising a nitrogen-containing compound, in particular Polyquaternium 6, for 4
minutes at a
temperature of approximately 50 C. Afterwards the pre-treated substrates are
rinsed with
water.
Activation compositions and activation:
Contacting the substrates with the activation compositions (compositions
according to the
invention, abbreviated in the following as AC, and comparative activation
compositions, ab-
breviated in the following as cAC) is carried out for a time sufficient to
obtain activated sur-
faces for subsequent metallization (contacting time).
The activation compositions according to the present invention comprise citric
acid as com-
plexing agent. The first species is copper. The total starting volume of each
activation com-
position is approximately 0.5 L.
Specific and individual parameters of the respective activation compositions
as well as re-
sults are summarized in the following tables. Each activation composition
according to the
present invention does not comprise (i.e. is totally free of) palladium, a
compound intention-
ally preventing the oxidation of the copper particles, and stabilizer
compounds to stabilize
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
29
the copper particles and to prevent agglomeration. In fact, the activation
compositions basi-
cally consist of the herewith mentioned ingredients and reaction products
thereof.
First set of examples:
Table 1: specific and individual parameters of the first set of examples;
concentrations
and molar ratios are initial, i.e. prior to a first step (c)
AC#1 AC#2 AC#3
Cu2+ [mol/L] 0.02 0.02 0.02
Cu2+ [g/L] 1.27 1.27 1.27
Ni2+ [mol/L] 0.005
Ni2+ [g/L] 0.29
Citric acid [mol/L] 0.025 0.03 0.05
Citric acid [g/L] 4.8 5.8 9.6
NaBH4* [mL] / [mmol/L] 25 / 2.6 25 / 2.6 25 / 2.6
Molar ratio 7.6 7.6 7.6
Cu2+ : NaBH4
Molar ratio 0.80 0.67 0.40
Cu2+ : citric acid
pH 4.8 4.8 4.8
T [ C] 22 22 22
Contacting time [s] 240 240 240
Substrate 1 FR4 FR4 FR4
Substrate 2 ABS ABS ABS
Activation Yes Yes Yes
Backlight test [D] 8-9 9 7-8
* Na131-14 solution with c = 2 g/L and comprising NaOH
Regarding the first set of examples, in a first step an aqueous starting
solution is provided
comprising the dissolved copper ions, the citric acid and optionally the
dissolved nickel ions.
The solution is clear and has a typical blue/bluish colour.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
Upon adding the initial amount of NaBH4 (see Table 1) with moderate speed
under stirring,
a boron-containing reducing agent is temporarily present and a part of the
dissolved copper
ions is immediately reduced such that copper nanoparticles are formed.
Typically, not all
copper ions are reduced in this initial reduction. During the reduction
hydrogen gas is
5 formed. Reduction is basically completed when gas formation ends. Upon
particle formation
(particle diameter approximately 10 nm), the starting solution turns into a
colloidal activation
composition. The colour is dark brown, no precipitating agglomerates are
observed. The
compositions are continually stirred and in continuous contact with ambient
air. Thus, oxi-
dation of the formed particles is not prevented at all, in particular after
the reduction is fin-
10 ished. The respective activation compositions are further stirred and
are ready to be utilized
for a first activation while the copper particles are still exposed to
oxidation.
Subsequently, step (c) of the method of the present invention (for activating)
is carried out
for the first time. For each substrate a well adhering copper and copper
alloy, respectively,
which could not be washed away by rinsing, is deposited on the surface of the
respective
15 substrate. The activation is in each case excellent and sufficient for
subsequent metalliza-
tion.
Afterwards, AC#1 to AC#3 are stored under stirring for 2 days (initial +2). A
beginning dis-
coloration is observed, namely from dark brown to light brown accompanied by
an increase
of bluish colour. It indicates that the total amount of copper particles
decreases and the total
20 concentration of dissolved copper ions increases because of the
reversible equilibrium.
However, activation is successfully repeated with AC#1 to AC#3 and a second
set of sub-
strates (FR4 and ABS) with very similar backlight results is obtained (for
further information
regarding backlight test see below).
After activating the second set of substrates, i.e. after initial +2, 5 ml of
the NaBH4 solution
25 (c = 2 g/L) is added to each of AC#1 to AC#3 to re-form copper
particles. Prior to adding the
NaBH4, from samples AC#1 and AC#2 a small volume is separated as a control
(cAC#1 and
cAC#2). No Na131-14 is added to cAC#1 and cAC#2 and no stirring is applied
such that a
continuous or semi-continuous oxidation is mostly prevented therein. After
adding said
amount of Na131-14 to AC#1 to AC#3, a third set of substrates (FR4 and ABS) is
successfully
30 activated with very similar backlight results.
After three days (initial +3) a fourth set of substrates (FR4 and ABS) is
successfully activated
with again very similar backlight results. Subsequently, 2.5 ml of the NaBH4
solution (c = 2
g/L) is added to each composition AC#1 to AC#3 and a fifth set of substrates
(FR4 and ABS)
is successfully activated with again very similar backlight results. This
procedure is repeated
after 4 days (initial +4) with a respective sixth and seventh set of
substrates.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
31
After nine days (initial +9) 10 ml of the NaBH4 solution (c = 2 g/L) is added
to each compo-
sition AC#1 to AC#3 and an eighth set of substrates (FR4 and ABS) is again
successfully
activated.
After adding NaBH4 the pH finally slightly increased to up to 6 and was not
manually re-
adjusted.
Regarding the control samples, cAC#1 showed after 5 days (initial +5) a
bluish/greenish
colour and precipitating agglomerates. cAC#2 appeared blue after initial +5
and was a solu-
tion without particles. Basically, such an activation composition can be
stored and resumed
for use after adding another portion of reducing agent. However, in this
condition no activa-
tion can be obtained with it.
As a final result, AC#1 to AC#3 do not additionally need any anti-oxidizing
compounds
and/or specific stabilizer compounds to prevent agglomeration. In contrast,
the activation
compositions are kept active over time by maintaining the reversible
equilibrium, in particular
by even primarily maintaining an oxidizing environment.
A testing with AC#3, comprising 5.2 mmol/L sodium borohydride instead of 2.6
mmol/L, is
carried out with again excellent results.
Backlight test (metal coverage on a substrate surface):
The coverage is evaluated using an industry standard Backlight test, in which
the respective
substrate is sectioned, so as to allow areas of incomplete coverage to be
detected as bright
spots when viewed over a strong light source (compare US 2008/0038450 Al and
WO 2013/050332). The quality of the coverage is determined by the amount of
light that is
observed under a conventional optical microscope. The results are given on a
scale from
D1 to D10, wherein D1 (little, incomplete coverage) means the worst result and
D10 (com-
plete, strong coverage) the best result.
Second set of examples:
In a second set of examples, activation and subsequent metallization is
tested. For that the
used specific and individual parameters are summarized in Table 2. The general
parameters
as outlined above for the first set of examples apply likewise.
Table 2: specific and individual parameters of the second set of
examples; concentra-
tions and molar ratios are initial, i.e. prior to a first step (c)
AC#4 AC#5 AC#6 AC#7
Cu2+ [mol/L] 0.010 0.010 0.005 0.010
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
32
Cu2+ [g/L] 0.65 0.65 0.30 0.65
Ni2+ [mol/L] 0.005 0.010 0.0005
Ni2+ [g/L] 0.30 0.60 0.03
Citric acid [mol/L] 0.025 0.030 0.030 0.025
Citric acid [g/L] 4.8 5.78 5.78 4.8
NaBH4* [mL] / [mmol/L] 50 / 5.28 50 / 5.28 50 / 5.28 50 / 5.28
Molar ratio 1.9 1.9 0.9 1.9
Cu2+ : NaBH4
Molar ratio 0.40 0.33 0.17 0.40
Cu2+ : citric acid
pH 5.2 5.2 5.2 5.2
T [ C] 22 22 22 22
Contacting time [s] 240 240 240 240
Substrate 1 FR4 FR4 FR4 FR4
Activation Yes Yes Yes Yes
1st metallization layer Cu Cu Cu Cu
1st metallization layer Not tested Ni Ni Ni
* Na131-14 solution with c = 2 g/L and comprising NaOH
Regarding the second set of examples, contacting according to step (c) of the
method of the
present invention (for activating) is carried out after the activation
compositions are pre-
pared.
Subsequently, in a first approach, the method of the present invention (for
metallizing) is
carried out with a fist metallization solution in order to obtain a fist
metallization layer. The
first metallization solution is an electroless, autocatalytic copper bath
comprising copper ions
(approx. 2 g/L Cu2+) and an aldehyde as reducing agent with metallization
parameters as
follows: pH 11, 35 C for 20 minutes. After activation, a well adhering first
metallization layer
of copper is obtained covering entirely the activated surface (no skip plating
observed).
In each of AC#4 to AC#7 the reversible equilibrium is maintained by
intentionally not pre-
venting oxidation through ambient air. Furthermore, Na131-14 solution is semi-
continually
added to re-form particles if needed. No precipitating agglomerates are
observed.
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
33
In a second approach, FR4 samples activated with AC#5 to AC#7, respectively,
are sub-
jected to the method of the present invention (for metallization) with a first
metallization so-
lution comprising nickel instead of copper to deposit a nickel phosphorous
layer; metalliza-
tion parameters: 85 C for more than 5 minutes, pH approximately 5Ø After
activation, dep-
osition of a nickel phosphorous layer as a first metallization layer is
directly possible.
Typically, after preparing an activation composition, e.g. AC#4, boric acid is
present in a
total concentration below 0.2 g/L. To study the effect of boric acid, AC#4 is
furthermore
utilized with the additional modification of intentionally adding boric acid
such that the total
concentration is 1 g/L (AC#4-1) and 10 g/L (AC#4-10). In each case the pH
increases to
io approximately 5.5. However, no difference with respect to activation and
metallization is
observed.
Third set of examples:
In a third set of examples, AC#4 is repeated with dimethylaminoborane (DMAB)
instead of
NaBH4. As a result, AC#8 is obtained. Further specific and individual
parameters are sum-
marized in Table 3.
Table 3: specific and individual parameters of the third set of
examples; concentrations
and molar ratios are initial, i.e. prior to a first step (c)
AC#8
Cu2+ [mol/L] 0.010
Cu2+ [g/L] 0.65
Ni2+ [mol/L]
Ni2+ [g/L]
Citric acid [mol/L] 0.025
Citric acid [g/L] 4.8
DMAB* [mL] / [mmol/L] 8 / 27.2
Molar ratio 0.37
Cu2+ : DMAB
Molar ratio 0.40
Cu2+ : citric acid
pH 4.0
T [ C] 60
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
34
Contacting time [min] 30
Substrate 1 FR4
Activation Yes
Cu metallization Yes
* DMAB solution with c = 100 g/L
Activation with AC#8 is carried out with and without pre-treatment equally
successful. How-
ever, higher temperatures are required to obtain an adequate activation
compared to exam-
ples utilizing sodium borohydride.
Also in AC#8 the reversible equilibrium is maintained by intentionally not
preventing oxida-
tion through ambient air. Furthermore, DMAB solution is semi-continually added
to re-form
particles if needed. No precipitating agglomerates are observed.
Fourth set of examples:
In a fourth set of examples, further parameters are varied as summarized in
Table 4.
Table 4: specific and individual parameters of the fourth set of examples;
concentra-
tions and molar ratios are initial, i.e. prior to a first step (c)
AC#9 AC#10 AC#11 AC#12 AC#13
Cu2+ [mol/L] 0.005 0.010 0.020 0.041 0.610
Cu2+ [g/L] 0.325 6.50 1.30 2.60 3.90
Citric acid [mol/L] 0.025 0.250 0.050 0.100 0.150
Citric acid [g/L] 4.8 48.0 9.6 19.2 28.8
NaBH4* [mL] / [mmol/L] 50 / 5.28
NaBH4** [mL] / [mmol/L] 50 / 10.6
NaBH4*** [mL] / [mmol/L] 50 / 21.1
NaBH4# [mL] / [mmol/L] 50 /31.7
NaBH4/4 [mL] / [mmol/L] 50 / 52.8
Molar ratio 0.95 0.19 1.89 1.94 19.23
Cu2+ : NaBH4
Molar ratio 0.20 0.04 0.40 0.41 4.07
Cu2+ : citric acid
CA 03135816 2021-10-01
WO 2020/201387 PCT/EP2020/059313
pH 5.95 4.62 4.9 5.2 4.8
T [ C] 22 22 22 22 22
Contacting time [s] 240 240 240 240 240
Substrate 1 FR4 FR4 FR4 FR4 FR4
Activation Yes Yes Yes Yes Yes
Cu metallization Yes Yes Yes Yes Yes
Backlight test [D] Not tested 10 10 9-10 10
* NaBH4 solution with c = 2 g/L and comprising NaOH,
** NaBH4 solution with c = 4 g/L and comprising NaOH,
*** NaBH4 solution with c = 8 g/L and comprising NaOH,
NaBH4 solution with c = 12 g/L and comprising NaOH,
5 #41NaBH4 solution with c = 20 g/L and comprising NaOH
Also in AC#9 to AC#13 the reversible equilibrium is maintained by
intentionally not prevent-
ing oxidation through ambient air and reducing agent is semi-continually added
to re-form
particles if needed. No precipitating agglomerates are observed. Excellent
activation is ob-
tained for FR4 with excellent backlight test results.
10 Fifth set of examples:
In a fifth set of examples (details not shown), activation is tested on FR4
and ABS with an
activation composition according to the present invention comprising 0.005
mol/L Cu2+, 0.05
mol/L citric acid, and 1.3 mmol/L sodium borohydride. Again, fully activated
FR4 and ABS
were obtained with excellent backlight test results.
15 Sixth set of examples:
In a sixth set of examples (details not shown), activation is tested on carbon-
fibres containing
felt (4.6 mm thickness; approximately 450 g/m2 area weight, BET surface area
0.4 m2/g) with
various activation compositions according to the present invention as outlined
above in the
first and second set of examples. Again, fully nickel-activated felt was
obtained in each case.
20 Furthermore, the activated surfaces showed significant catalytic
activity in electrolysis form-
ing hydrogen and oxygen gas.
