U.S. patent application number 17/433065 was filed with the patent office on 2022-05-19 for a method for activating a surface of a non-conductive or carbon-fibres containing substrate for metallization.
The applicant listed for this patent is Atotech Deutschland GmbH. Invention is credited to Josef GAIDA, Lena IVANOVA, Lutz STAMP, Thomas THOMAS.
Application Number | 20220154343 17/433065 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-19 |
United States Patent
Application |
20220154343 |
Kind Code |
A1 |
GAIDA; Josef ; et
al. |
May 19, 2022 |
A METHOD FOR ACTIVATING A SURFACE OF A NON-CONDUCTIVE OR
CARBON-FIBRES CONTAINING SUBSTRATE FOR METALLIZATION
Abstract
Method for activating a surface of a non-conductive or
carbon-fibres containing substrate for metallization, the method
including: (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
particles thereof, (ii) at least one complexing agent, (iii)
permanently or temporarily at least one reducing agent, (iv)
optionally one or more second species of dissolved metal ions
different from the first species, (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.
Inventors: |
GAIDA; Josef; (Berlin,
DE) ; STAMP; Lutz; (Berlin, DE) ; IVANOVA;
Lena; (Berlin, DE) ; THOMAS; Thomas; (Berlin,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Atotech Deutschland GmbH |
Berlin |
|
DE |
|
|
Appl. No.: |
17/433065 |
Filed: |
April 1, 2020 |
PCT Filed: |
April 1, 2020 |
PCT NO: |
PCT/EP2020/059313 |
371 Date: |
August 23, 2021 |
International
Class: |
C23C 18/18 20060101
C23C018/18; C23C 18/20 20060101 C23C018/20 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2019 |
EP |
19167282.3 |
Claims
1. 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 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 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,
respectively, 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.
2. The method of claim 1, wherein during and/or after step (c) the
majority of said metal particles is subjected to said
oxidation.
3. The method of claim 1, wherein the first species is copper or
cobalt.
4. The method of claim 1, wherein the metal particles of the first
species in the activation composition are colloidal metal
particles.
5. The method of claim 1, 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.
6. The method of claim 1, wherein the one or more than one reducing
agent comprises a boron-containing reducing agent.
7. The method of claim 1, wherein the activation composition is
substantially free of or does not comprise any of tin ions, lead
ions, germanium ions, gallium ions, antimony ions, bismuth ions,
and aluminium ions.
8. The method of claim 1, wherein the activation composition is
substantially free of or does not comprise a compound preventing
the oxidation of the metal particles and/or is substantially free
of or does not comprise a stabilizer compound to stabilize the
metal particles.
9. The method of claim 1, 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.
10. The method of claim 1, wherein the dissolved transition metal
ions are formed from the metal particles through oxidation by
ambient air and/or oxygen gas.
11. The method of claim 1, further 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.
12. 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 activated surface for
metallization obtained by a method for activating according to
claim 1, (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 activated
surface.
13. 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, 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 dissolved
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.
14. (canceled)
15. An aqueous, palladium-free activation composition for
activating a surface of a non-conductive or carbon-fibres
containing substrate for metallization, 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 particles 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 precipitating agglomerates of said metal
particles are formed.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the activation of surfaces
of typically non-conductive or carbon-fibres containing substrates
for subsequent metallization.
[0002] 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, palladium-free activation composition for activating a
surface of a non-conductive or carbon-fibres containing substrate
for metallization.
BACKGROUND OF THE INVENTION
[0003] 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 decorative
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.
[0004] Besides such decorative articles, a functional metallization
is essential in for example manufacturing 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.
[0005] Carbon-fibres containing substrates experience an increasing
potential as catalytically active surfaces in e.g. power-to-gas,
power-to-fuel, and power-to-chemicals applications, and
batteries.
[0006] All these applications require a usually multi-step
preparation of the non-conductive or carbon-fibres containing
substrate to make it receptive for subsequent metallization.
[0007] In a first step usually a cleaning of the surface of the
non-conductive or carbon-fibres containing substrate is carried
out, e.g. to remove grease or impurities.
[0008] 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.
[0009] 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
carbon-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 example from a colloidal activation composition.
[0010] 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
includes a deposition of a metal or metal alloy through
autocatalytic deposition, which means a deposition facilitated by
means of a reducing agent.
[0011] 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.
[0012] 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.
[0013] Another common disadvantage is that such activation
compositions naturally experience a form of decay or decomposition.
Typically, the nanoparticles agglomerate and form insoluble,
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.
[0014] For example, CN 107460459 A relates to simple nano-copper
activation liquid utilizing stabilizers and reducing agents to
prevent agglomeration and oxidation, respectively, of the
nanoparticles.
[0015] U.S. Pat. No. 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 gases and/or chemical
agents, which render said controlled oxidation. However, the
presence of at least one colloid stabilizer is mandatory. In this
way a reversible equilibrium is not maintained.
[0016] 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 stabilization.
[0017] Furthermore, it appears that such stabilizer compounds often
reduce the ability of the nanoparticles 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
[0018] 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.
[0019] 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 effective
concentrations of chemicals.
[0020] 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
[0021] 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 [0022] (a) providing said substrate, [0023] (b) providing an
aqueous, palladium-free activation composition comprising [0024]
(i) a first species of dissolved transition metal ions and
additionally metal particles thereof, [0025] (ii) one or more than
one complexing agent, [0026] (iii) permanently or temporarily one
or more than one reducing agent, [0027] (iv) optionally one or more
than one second species of dissolved metal ions being different
from the first species, [0028] wherein [0029] 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 [0030] 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, [0031] the dissolved transition metal ions are formed from
the metal particles through continuous or semi-continuous oxidation
of said particles, and [0032] the dissolved transition metal ions
and the metal particles thereof, respectively, are repeatedly
involved in said reduction and said oxidation such that no
precipitating agglomerates of said metal particles are formed,
[0033] (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.
[0034] Own experiments have shown that in the present invention a
very simple and effective activation 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 stabilization/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 oxidation is considered harmful and is therefore
minimized and/or suppressed. In contrast thereto, in the present
invention oxidation is advantageously utilized, necessary, and
considered to be of great benefit. It turned out, contrary to
common thinking, that it is not necessary to maintain the particles
for a long time in a respective activation composition.
[0035] This brings along a number of advantages. For example, in a
very simple manner a respective 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.
[0036] 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 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.
[0037] 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 species 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 respective activation
composition and a thereto related method.
[0038] 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
[0039] In the context of the present invention, "continuous",
"continuously", and "continually", respectively, denote a
constantly ongoing doing of a respective action without significant
interruptions of the action while e.g. a respective method or
aspect of the invention is carried out.
[0040] 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.
[0041] In the context of the present invention, "species" (e.g.
first species or second species) denotes 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.
[0042] 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.
[0043] The Substrate:
[0044] 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.
[0045] 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 transition
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 metallization 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.
[0046] 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-containing laminates, glasses, ceramics, semi-conductors, and
mixtures thereof.
[0047] Preferred plastics comprise, preferably are, thermoplastics,
more preferably comprise, preferably are, polyacrylates,
polyamides, polyimides, polyesters, polycarbonates, polyalkylenes,
polyphenylenes, polystyrenes, polyvinyls, or mixtures thereof.
[0048] Preferred polyacrylates comprise poly(methyl methacrylate)
(PMMA).
[0049] Preferred polyimides comprise polyetherimide (PEI).
[0050] Preferred polyesters comprise polylactic acid (PLA).
[0051] Preferred polycarbonates comprise polycarbonate obtained
with bisphenol A (PC).
[0052] Preferred polyalkylenes comprise polyethylene (PE),
polypropylene (PP), polytetrafluoroethylene (PTFE),
polyoxymethylene (POM), or mixtures thereof.
[0053] Preferred polyphenylenes comprise poly(phenylene oxide)
(PPO), poly(phenylene ether) (PPE), or mixtures thereof.
[0054] Preferred polystyrenes comprise polystyrene (PS),
acrylonitrile butadiene styrene (ABS), styrene/butadiene rubber
(SBR), styrene-acrylonitrile (SAN).
[0055] Preferred polyvinyls comprise polyvinyl chloride (PVC),
poly(ethylene-vinyl acetate) (PEVA), polyvinylidene difluoride
(PVDF), or mixtures thereof.
[0056] Preferred resin-containing laminates comprise, preferably
are, fiber-enforced resin-containing laminates, most preferably
glass-fiber-enforced laminates.
[0057] 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.
[0058] A very preferred resin-containing laminate comprises,
preferably is, FR4.
[0059] 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.
[0060] Preferred ceramics comprise, preferably are, glass-ceramics,
aluminium oxide ceramics, or mixtures thereof.
[0061] Preferred semi-conductors comprise, preferably are,
silicon-based semi-conductors, more preferably silicon-based
semi-conductors comprising silicon dioxide and/or silicon.
[0062] Very preferred semi-conductors are wafers.
[0063] Preferred is a method of the present invention (for
activating), wherein the carbon-fibres containing substrate
comprise, preferably are, carbon-fibre composites and/or
arrangements of carbon-fibre filaments.
[0064] Preferred carbon-fibre composites comprise, preferably are,
carbon-fibre reinforced polymers and/or carbon-fibre containing
fabrics, more preferably carbon-fibre reinforced polymers and/or
woven carbon-fibre containing fabrics.
[0065] Preferred arrangements of carbon-fibre filaments comprise,
preferably are, fabrics made of carbon-fibres, most preferably
woven fabrics made of carbon-fibres.
[0066] An in particularly preferred carbon-fibres containing
substrate is a carbon-fibre containing felt.
[0067] Pre-Treatment:
[0068] In some cases a pre-treatment of the surface of the
non-conductive or carbon-fibres containing substrate is preferred.
Thus, preferred is a method of the present invention (for
activating), comprising a pre-treatment step for the substrate
prior to step (c): [0069] (a-1) treating said substrate with a
pre-treatment solution comprising a nitrogen-containing
compound.
[0070] 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.
[0071] 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.
[0072] More preferred is a method of the present invention (for
activating), wherein in the pre-treatment solution the
nitrogen-containing compound is a polymer comprising pyrrolidine
moieties.
[0073] Preferably, the polymer is cationic.
[0074] Preferably, the nitrogen-containing compound consists of
carbon atoms, nitrogen atoms, and hydrogen atoms.
[0075] Preferred is a method of the present invention (for
activating), wherein in the pre-treatment solution the
nitrogen-containing compound comprises quaternary nitrogen
atoms.
[0076] Most preferred is a method of the present invention (for
activating), wherein the nitrogen-containing compound comprises,
preferably is, Polyquaternium 6.
[0077] 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.degree. C. to 90.degree. C.,
preferably in a range from 25.degree. C. to 80.degree. C., more
preferably in a range from 30.degree. C. to 70.degree. C., most
preferably in a range from 40.degree. C. to 60.degree. C.
[0078] 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.
[0079] The Aqueous, Palladium-Free Activation Composition:
[0080] In step (b) of the method of the present invention (for
activating), an aqueous, palladium-free activation composition is
provided.
[0081] 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 ecological 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.
[0082] 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 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 comprise"
preferably denotes 0 (zero) ppm to 5 ppm, based on the total weight
of e.g. the activation 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).
[0083] 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.
[0084] Preferred is a method of the present invention (for
activating), wherein the pH of the activation composition is in a
range from .gtoreq.2.0 to .ltoreq.13.0, preferably in a range from
.gtoreq.3.0 to .ltoreq.12.0, more preferably in a range from
.gtoreq.4.0 to .ltoreq.11.0, most preferably in a range from
.gtoreq.4.5 to .ltoreq.10.0.
[0085] 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 .gtoreq.3.0 to .ltoreq.6.5,
preferably in a range from .gtoreq.4.0 to .ltoreq.6.0. Preferably
this applies with the proviso that the one or more than one
reducing agent comprises a borohydride.
[0086] 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 sodium carbonate, and ammonia.
[0087] In the context of the present invention, the pH is
determined at a temperature of 20.degree. C., i.e. the defined pH
is referenced to 20.degree. C. Thus, only for the sake of pH
determination the activation composition has a temperature of
20.degree. C. This does not mean that the activation composition in
itself is limited to the specific temperature of 20.degree. C. For
preferred temperatures of the activation composition see below.
[0088] 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 contrary, if the pH is too alkaline, alkaline-sensitive
reducing agents decompose too quickly.
[0089] 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
comprise palladium ions. This means that neither compounds
comprising palladium are present 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 almost identical results in terms of
activation.
[0090] Preferably, also other noble metals or at least
expensive/rare metals are not necessary in the 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 substantially free of or does not comprise platinum,
gold, silver, rhodium, ruthenium, and iridium.
[0091] The aqueous composition utilized in the method of the
present invention (for activating) comprises (i) a first species of
dissolved transition metal ions and additionally metal particles
thereof.
[0092] Preferred is an activation composition, wherein said metal
particles are nanoparticles. Preferably, the metal particles
comprise one or more than one elemental metal)(Me.sup.0),
preferably (essentially) consist of one or more than one elemental
metal)(Me.sup.0).
[0093] Even more preferred is an activation composition, wherein
the metal particles of the first species 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.
[0094] More preferred is a method of the present invention (for
activating), wherein the metal particles of the first species in
the activation composition are colloidal metal particles.
[0095] 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
composition is still a clear but colored solution depending on the
coloring effect caused by the dissolved ions, primarily of the
first species.
[0096] 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.
[0097] 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 examples). This is
in particular advantageous in terms of waste-water treatment and is
thus cost- and ecofriendly.
[0098] 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-conductive or carbon-fibres
containing substrate. The aforementioned concentrations most
preferably apply to copper and cobalt, most preferably to
copper.
[0099] Preferred is a method of the present invention (for
activating), wherein the source of dissolved 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
sulfonate is copper methane sulfonate. The most preferred copper
source is copper sulfate, most preferably CuSO.sub.4*5
H.sub.2O.
[0100] 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.
Preferably, the second species is substantially free of or does not
comprise alkali metals.
[0101] 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).
[0102] 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.
[0103] 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.
[0104] 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
tricarboxylic acid and/or salts thereof, even most preferably
citric acid, structural isomers, and/or salts 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.
[0105] Preferred is a method of the present invention (for
activating), wherein in the activation composition [0106] 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 [0107] 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 1.0:5.0. This very preferably 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.
[0108] 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, preferably 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.
[0109] 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
permanently 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.
[0110] Said oxidation is furthermore very relevant if in the method
of the present invention (for activating) 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 resuming
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.
[0111] Thus, preferably the one or more than one reducing agent is
suitable for reducing the dissolved transition metal ions of at
least the first species.
[0112] 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.
[0113] 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
dimethylaminoborane. A preferred inorganic borohydride comprises an
alkali borohydride, most preferably sodium borohydride. In the
method of the present invention (for activating), most preferred 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.degree. C. to 30.degree. C. These are excellent
room temperature conditions. Thus, no additional and cost-intensive
heating is necessarily required. Furthermore, hydrogen is
generated.
[0114] 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.
[0115] 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.
[0116] 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.
[0117] 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.
[0118] Preferred is a method of the present invention (for
activating), wherein the activation composition 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.
[0119] Generally preferred is a method of the present invention
(for activating), wherein in the activation composition [0120] 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 [0121] the one or more than on reducing agent (if
semi-continually added, in the moment of addition) 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 invention (for activating), wherein the
activation composition is predominantly kept in oxidizing condition
to allow oxidation of the metal particles.
[0122] Particularly preferred is a method of the present invention
(for activating), wherein in the activation composition [0123] 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 [0124] the one or more than on reducing agent (if
semi-continually added, in the moment of 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 3.0.
[0125] In some cases 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
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 respective 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 the present
invention (for activating) is carried out. As a result, the metal
particles are present in a comparatively constant
concentration.
[0126] 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.
[0127] 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.
[0128] 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
activating), wherein the reversible equilibrium is monitored by
UV/VIS 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 reform, said metal
particles in order to increase their total amount.
[0129] 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.
[0130] 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 preferably 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 contrary 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 stabilization until the respective
activation composition is unstable and inoperable.
[0131] As mentioned throughout the text, in the context of the
present invention it is preferably necessary 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 concentration. This means that the
replacement volume typically does not comprise boric acid 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.
[0132] Preferred is a method of the present invention (for
activating), wherein the activation composition 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.
[0133] Preferred is a method of the present invention (for
activating), wherein the reversible equilibrium is not
predominantly shifted to the metal particles over the majority of
time during which step (c) is carried out.
[0134] 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 denotes more than 50% of the particles.
[0135] Preferably, the one or more than one reducing agent is
substantially free of or does not comprise hypophosphite ions,
preferably is substantially free of or does not comprise a
phosphorous-containing reducing agent. Own experiments have shown
that in some cases the activation with such reducing agents is too
weak or even incomplete.
[0136] 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 preventing 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 substantially 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 preventing 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 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.
[0137] A method of the present invention (for activating) is
preferred, wherein the activation composition 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 believed that some stabilizer
compounds are based on such a function. In the context of the
present invention this is not desired.
[0138] Generally, a method of the present invention (for
activating) is preferred, wherein the activation 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 compound 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 outlined above.
[0139] Preferred is a method of the present invention (for
activating), wherein the activation composition 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 equilibrium from being
reversible. Such tin ions typically form a reductive environment,
which is by no means desired in the context of the present
invention.
[0140] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise polyvinylpyrrolidone, preferably is
substantially 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.
[0141] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise a protein, agar, gum Arabic, sugars,
and polyalcohols.
[0142] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise glycerol.
[0143] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise gelatin.
[0144] Preferred is a method of the present invention (for
activating), wherein the activation composition 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
oxidation number of +5 or below.
[0145] Preferred is a method of the present invention (for
activating), wherein the activation composition 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.
[0146] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise a compound named Orzan-S.
[0147] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise urea.
[0148] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise a dispersing agent.
[0149] Preferred is a method of the present invention (for
activating), wherein the activation composition 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.
[0150] 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.
[0151] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise sodium dodecyl sulfate, preferably is
substantially free of or does not comprise an alkyl sulfate with 8
to 20 carbon atoms, more preferably is substantially free of or
does not comprise an alkyl sulfate, most preferably is
substantially free of or does not comprise a surfactant.
[0152] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise a hydroquinone, pyrogallol, and/or
resorcinol, preferably is substantially free of or does not
comprise a hydroxy benzene. In many cases such hydroxy benzenes are
commonly used as anti-oxidizing agents, thereby preventing the
equilibrium from being reversible, which are not needed in the
activation composition.
[0153] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise a quinone.
[0154] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise a fatty alcohol.
[0155] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise an alkylene glycol, preferably is
substantially free of or does not comprise a glycol.
[0156] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise manganese ions.
[0157] Preferred is a method of the present invention (for
activating), wherein the activation composition is substantially
free of or does not comprise zinc ions.
[0158] As a result and in particular despite the fact that the
activation composition does not comprise 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 composition is substantially free of or does
not comprise precipitating agglomerates of said metal particles.
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,
respectively, are repeatedly involved in said reduction and said
oxidation.
[0159] 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.
[0160] 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 ambient air and/or oxygen gas.
In both cases the preferred oxidizing agent is molecular oxygen.
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.
[0161] 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 oxidizing
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 oxidation
of the particles if this is required, e.g. if an activation
composition must be inactivated and stored for longer times.
[0162] 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.
[0163] 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 [0164] (a) providing
said substrate, [0165] (b) providing an aqueous, palladium-free
activation composition comprising [0166] (i) a first species of
dissolved transition metal ions and additionally colloidal metal
particles thereof, wherein the first species is copper, [0167] (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, [0168] (iii) permanently
or temporarily one or more than one boron-containing reducing
agent, preferably a borohydride, [0169] (iv) optionally one or more
than one second species of dissolved metal ions being different
from the first species, wherein the second species preferably is
nickel, [0170] wherein [0171] the activation composition is a
colloidal suspension, and [0172] 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 [0173]
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, [0174] 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, [0175] the dissolved transition metal
ions and the metal particles thereof, respectively, are repeatedly
involved in said reduction and said oxidation such that no
precipitating agglomerates of said metal particles are [0176] (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.
[0177] 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 [0178] (1) providing
an aqueous starting solution comprising [0179] a first species of
dissolved transition metal ions, [0180] one or more than one
complexing agent, and [0181] optionally one or more than one second
species of dissolved metal ions being different from the first
species, [0182] (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 dissolved
transition metal ions are continually or semi-continually,
respectively, formed in the solution, [0183] with the proviso that
said metal particles are continually or semi-continually oxidized
to form dissolved transition metal ions of the first species.
[0184] 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.
[0185] 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 continually or semi-continually form
in situ metal particles in an aqueous, palladium-free activation
composition.
[0186] 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 defined
as being preferred.
[0187] 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
metallization, the composition comprising [0188] (i) a first
species of dissolved transition metal ions and additionally metal
particles thereof, [0189] (ii) one or more than one complexing
agent, [0190] (iii) permanently or temporarily one or more than one
reducing agent, [0191] (iv) optionally one or more than one second
species of dissolved metal ions being different from the first
species, [0192] wherein [0193] at least of the first species, the
dissolved transition metal ions and the metal particles thereof are
present in an reversible equilibrium, with the proviso that [0194]
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, [0195] the dissolved
transition metal ions are formed from the metal particles through
continuous or semi-continuous oxidation of said particles, and
[0196] the dissolved transition metal ions and the metal particles
thereof, respectively, are repeatedly involved in said reduction
and said oxidation such that no precipitating agglomerates of said
metal particles are formed.
[0197] The aforementioned regarding the method of the present
invention (for activating), preferably applies likewise to the
aqueous, palladium-free activation composition of the present
invention, most preferably as aforementioned defined as being
preferred.
[0198] Preferably, the activation composition of the present
invention is obtained at and/or has a temperature in a range from
10.degree. C. to 90.degree. C., preferably in a range from
14.degree. C. to 75.degree. C., more preferably in a range from
16.degree. C. to 65.degree. C., most preferably in a range from
18.degree. C. to 45.degree. C., even most preferably in a range
from 20.degree. C. to 32.degree. C. In particular preferred is a
temperature in a range from 18.degree. C. to 45.degree. C.,
preferably in a range from 20.degree. C. to 32.degree. 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).
[0199] More preferably, the activation composition of the present
invention is not obtained at and/or has not a temperature above
110.degree. C., preferably above 100.degree. C., more preferably
above 95.degree. C. Most preferably the activation composition of
the present invention is not obtained at a temperature above
110.degree. 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 activating).
[0200] The Activation:
[0201] 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 surface for metallization by depositing the metal or
metal alloy, i.e. depositing a seed or activation layer.
[0202] Preferred is a method of the present invention (for
activating), wherein in step (c) the contacting is carried out at a
temperature in a range from 10.degree. C. to 90.degree. C.,
preferably in a range from 14.degree. C. to 75.degree. C., more
preferably in a range from 16.degree. C. to 65.degree. C., most
preferably in a range from 18.degree. C. to 45.degree. C., even
most preferably in a range from 20.degree. C. to 32.degree. C. In
particular preferred is a temperature in step (c) in a range from
18.degree. C. to 45.degree. C., preferably in a range from
20.degree. C. to 32.degree. C., and wherein the reduction through
the one or more than one reducing agent is a borohydride,
preferably sodium borohydride.
[0203] Preferred is a method of the present invention (for
activating), wherein in step (c) the contacting 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.
[0204] 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.
[0205] Preferred is a method of the present invention (for
activating), wherein the method is carried out for 10 days or more,
without replacing the majority of the activation composition in one
step (i.e. more than 50 vol.-% of the composition), preferably 50
days or more, more preferably 200 days or more, even more
preferably 1 year or more, most preferably 2 years or more, even
most preferably 5 years or more.
[0206] The Metallization:
[0207] 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
[0208] (A) providing the non-conductive or carbon-fibres containing
substrate with the activated surface for metallization obtained by
the method of the present invention (for activating), preferably as
defined throughout the text as being preferred, [0209] (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 activated surface.
[0210] 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
method of the present invention (for activating); for details see
text above. The aforementioned 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.
[0211] Preferred is a method of the present invention (for
metallizing), wherein in step (B) the first 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).
[0212] 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 between 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
comprise any particles.
[0213] 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.
[0214] Preferred is a method of the present invention (for
metallizing), wherein step (B) is carried out at a temperature in a
range from 10.degree. C. to 95.degree. C., preferably in a range
from 15.degree. C. to 85.degree. C., more preferably in a range
from 20.degree. C. to 65.degree. C., even more preferably in a
range from 25.degree. C. to 55.degree. C., most preferably in a
range from 30.degree. C. to 45.degree. C.
[0215] 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 preferably
for 1 minutes to 60 minutes, most preferably for 1.5 minutes to 45
minutes.
[0216] 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
metallization 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.
[0217] 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.
[0218] 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 metallization 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.
[0219] 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.
[0220] However, irrespective of what type the first metallization
solution is, preferably it is a clear solution without
particles.
[0221] Preferred is a method of the present invention (for
metallizing) comprising the steps [0222] (A) providing the
non-conductive or carbon-fibres containing substrate with the
activated surface for metallization obtained by the method of the
present invention (for activating), preferably as defined
throughout the text as being preferred, [0223] (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.
[0224] Alternatively preferred is a method of the present invention
(for metallizing) comprising the steps [0225] (A) providing the
non-conductive or carbon-fibres containing substrate with the
activated surface for metallization obtained by the method of the
present invention (for activating), preferably as defined
throughout the text as being preferred, [0226] (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 [0227]
(C) metallizing the first metallization layer by contacting the
first metallization layer with a second metallizing solution such
that a second metallization layer is deposited on the first
metallization layer.
[0228] Preferred is a method of the present invention (for
metallizing), wherein in step (C) the second metallizing solution
comprises a reducing agent, preferably comprises a reducing agent
and nickel ions.
[0229] 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.
[0230] 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.
[0231] 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.
[0232] 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.
[0233] 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.
[0234] Preferred is a method of the present invention (for
metallizing), wherein in step (C) the second 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.
[0235] The present invention is described in more detail by the
following non limiting examples.
EXAMPLES
[0236] Providing the Substrate:
[0237] Throughout all experiments substrates of either FR4
(Substrate 1, a resin-containing laminate, test panels with 5 x 5
cm) or ABS (Substrate 2, a plastic, test panels with 3 cm diameter)
are used.
[0238] Pre-Treatment:
[0239] If not stated otherwise, each substrate is at least treated
with a pre-treatment solution comprising a nitrogen-containing
compound, in particular Polyquaternium 6, for 4 minutes at a
temperature of approximately 50.degree. C. Afterwards the
pre-treated substrates are rinsed with water.
[0240] Activation Compositions and Activation:
[0241] Contacting the substrates with the activation compositions
(compositions according to the invention, abbreviated in the
following as AC, and comparative activation compositions,
abbreviated in the following as cAC) is carried out for a time
sufficient to obtain activated surfaces for subsequent
metallization (contacting time).
[0242] The activation compositions according to the present
invention comprise citric acid as complexing agent. The first
species is copper. The total starting volume of each activation
composition is approximately 0.5 L.
[0243] Specific and individual parameters of the respective
activation compositions as well as results 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 intentionally preventing the oxidation of the
copper particles, and stabilizer compounds to stabilize the copper
particles and to prevent agglomeration. In fact, the activation
compositions basically consist of the herewith mentioned
ingredients and reaction products thereof.
[0244] First Set of Examples:
TABLE-US-00001 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 Cu.sup.2+ [mol/L]
0.02 0.02 0.02 Cu.sup.2+ [g/L] 1.27 1.27 1.27 Ni.sup.2+ [mol/L] --
0.005 -- Ni.sup.2+ [g/L] -- 0.29 -- Citric acid [mol/L] 0.025 0.03
0.05 Citric acid [g/L] 4.8 5.8 9.6 NaBH.sub.4* [mL]/[mmol/L] 25/2.6
25/2.6 25/2.6 Molar ratio 7.6 7.6 7.6 Cu.sup.2+:NaBH.sub.4 Molar
ratio 0.80 0.67 0.40 Cu.sup.2+:citric acid pH 4.8 4.8 4.8 T
[.degree. 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 *NaBH.sub.4 solution with c = 2 g/L
and comprising NaOH
[0245] 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.
[0246] Upon adding the initial amount of NaBH.sub.4 (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 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, oxidation of the formed particles is not
prevented at all, in particular after the reduction is finished.
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.
[0247] 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 substrate. The
activation is in each case excellent and sufficient for subsequent
metallization.
[0248] Afterwards, AC#1 to AC#3 are stored under stirring for 2
days (initial +2). A beginning discoloration 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 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 substrates (FR4 and ABS) with very similar backlight results
is obtained (for further information regarding backlight test see
below).
[0249] After activating the second set of substrates, i.e. after
initial +2, 5 ml of the NaBH.sub.4 solution (c=2 g/L) is added to
each of AC#1 to AC#3 to re-form copper particles. Prior to adding
the NaBH.sub.4, from samples AC#1 and AC#2 a small volume is
separated as a control (cAC#1 and cAC#2). No NaBH.sub.4 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 NaBH.sub.4 to AC#1 to AC#3, a third set of
substrates (FR4 and ABS) is successfully activated with very
similar backlight results.
[0250] 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 NaBH.sub.4 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.
[0251] After nine days (initial +9) 10 ml of the NaBH.sub.4
solution (c=2 g/L) is added to each composition AC#1 to AC#3 and an
eighth set of substrates (FR4 and ABS) is again successfully
activated.
[0252] After adding NaBH.sub.4 the pH finally slightly increased to
up to 6 and was not manually readjusted.
[0253] 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
solution 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 activation
can be obtained with it.
[0254] 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.
[0255] 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.
[0256] Backlight test (metal coverage on a substrate surface):
[0257] 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 A1 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 (complete, strong coverage) the best
result.
[0258] Second set of examples:
[0259] 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-US-00002 TABLE 2 specific and individual parameters of the
second set of examples; concentrations and molar ratios are
initial, i.e. prior to a first step (c) AC#4 AC#5 AC#6 AC#7
Cu.sup.2+ [mol/L] 0.010 0.010 0.005 0.010 Cu.sup.2+ [g/L] 0.65 0.65
0.30 0.65 Ni.sup.2+ [mol/L] -- 0.005 0.010 0.0005 Ni.sup.2+ [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 NaBH.sub.4* [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
Cu.sup.2+:NaBH.sub.4 Molar ratio 0.40 0.33 0.17 0.40
Cu.sup.2+:citric acid pH 5.2 5.2 5.2 5.2 T [.degree. C.] 22 22 22
22 Contacting time [s] 240 240 240 240 Substrate 1 FR4 FR4 FR4 FR4
Activation Yes Yes Yes Yes 1.sup.st metallization layer Cu Cu Cu Cu
1.sup.st metallization layer Not tested Ni Ni Ni *NaBH.sub.4
solution with c = 2 g/L and comprising NaOH
[0260] 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 prepared.
[0261] Subsequently, in a first approach, the method of the present
invention (for metallizing) is carried out with a first
metallization solution in order to obtain a first metallization
layer. The first metallization solution is an electroless,
autocatalytic copper bath comprising copper ions (approx. 2 g/L
Cu.sup.2+) and an aldehyde as reducing agent with metallization
parameters as follows: pH 11, 35.degree. 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).
[0262] In each of AC#4 to AC#7 the reversible equilibrium is
maintained by intentionally not preventing oxidation through
ambient air. Furthermore, NaBH.sub.4 solution is semi-continually
added to re-form particles if needed. No precipitating agglomerates
are observed.
[0263] In a second approach, FR4 samples activated with AC#5 to
AC#7, respectively, are subjected to the method of the present
invention (for metallization) with a first metallization solution
comprising nickel instead of copper to deposit a nickel phosphorous
layer; metallization parameters: 85.degree. C. for more than 5
minutes, pH approximately 5.0. After activation, deposition of a
nickel phosphorous layer as a first metallization layer is directly
possible.
[0264] 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 approximately 5.5.
However, no difference with respect to activation and metallization
is observed.
[0265] Third set of examples:
[0266] In a third set of examples, AC#4 is repeated with
dimethylaminoborane (DMAB) instead of NaBH.sub.4. As a result, AC#8
is obtained. Further specific and individual parameters are
summarized in Table 3.
TABLE-US-00003 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 Cu.sup.2+ [mol/L] 0.010
Cu.sup.2+ [g/L] 0.65 Ni.sup.2+ [mol/L] -- Ni.sup.2+ [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 Cu.sup.2+:DMAB Molar ratio 0.40 Cu.sup.2+:citric
acid pH 4.0 T [.degree. C.] 60 Contacting time [min] 30 Substrate 1
FR4 Activation Yes Cu metallization Yes *DMAB solution with c = 100
g/L
[0267] Activation with AC#8 is carried out with and without
pre-treatment equally successful. However, higher temperatures are
required to obtain an adequate activation compared to examples
utilizing sodium borohydride.
[0268] Also in AC#8 the reversible equilibrium is maintained by
intentionally not preventing oxidation through ambient air.
Furthermore, DMAB solution is semi-continually added to re-form
particles if needed. No precipitating agglomerates are
observed.
[0269] Fourth set of examples:
[0270] In a fourth set of examples, further parameters are varied
as summarized in Table 4.
TABLE-US-00004 TABLE 4 specific and individual parameters of the
fourth set of examples; concentrations and molar ratios are
initial, i.e. prior to a first step (c) AC#9 AC#10 AC#11 AC#12
AC#13 Cu.sup.2+ [mol/L] 0.005 0.010 0.020 0.041 0.610 Cu.sup.2+
[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
NaBH.sub.4* [mL]/[mmol/L] 50/5.28 NaBH.sub.4** [mL]/[mmol/L]
50/10.6 NaBH.sub.4*** [mL]/[mmol/L] 50/21.1 NaBH.sub.4.sup.#
[mL]/[mmol/L] 50/31.7 NaBH.sub.4.sup.## [mL]/[mmol/L] 50/52.8 Molar
ratio 0.95 0.19 1.89 1.94 19.23 Cu.sup.2+:NaBH.sub.4 Molar ratio
0.20 0.04 0.40 0.41 4.07 Cu.sup.2+:citric acid pH 5.95 4.62 4.9 5.2
4.8 T [.degree. 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 *NaBH.sub.4 solution with c = 2 g/L and
comprising NaOH, **NaBH.sub.4 solution with c = 4 g/L and
comprising NaOH, ***NaBH.sub.4 solution with c = 8 g/L and
comprising NaOH, .sup.#NaBH.sub.4 solution with c = 12 g/L and
comprising NaOH, .sup.##NaBH.sub.4 solution with c = 20 g/L and
comprising NaOH
[0271] Also in AC#9 to AC#13 the reversible equilibrium is
maintained by intentionally not preventing 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 obtained for FR4 with excellent backlight
test results.
[0272] Fifth set of examples:
[0273] 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 Cu.sup.2+, 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.
[0274] Sixth set of examples:
[0275] In a sixth set of examples (details not shown), activation
is tested on carbon-fibres containing felt (4.6 mm thickness;
approximately 450 g/m.sup.2 area weight, BET surface area 0.4
m.sup.2/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. Furthermore, the activated surfaces showed significant
catalytic activity in electrolysis forming hydrogen and oxygen
gas.
* * * * *