Note: Descriptions are shown in the official language in which they were submitted.
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Process for Electroplating Metallic and Metal Matrix Composite Foils,
Coatings and Microcomponents
Field of the Invention
The invention relates to a process for forming coatings of pure metals, metal
al-
loys or metal matrix composites on a work piece which is electrically
conductive
or contains an electrically conductive surface layer or forming free-standing
de-
posits of nanocrystalline metals, metal alloys or metal matrix composites by
em-
ploying pulse electrodeposition. The process employs a drum plating process
for
the continuous production of nanocrystalline foils of pure metals, metal
alloys or
metal matrix composites or a selective plating (brush plating) process, the
proc-
esses involving pulse electrodeposition and a non-stationary anode or cathode.
Novel nanocrystalline metal matrix composites are disclosed as well. The inven-
tion also relates to a pulse plating process for the fabrication or coating of
micro-
components. The invention also relates to micro-components with grain sizes be-
low 1,000nm.
The novel process can be applied to establish wear resistant coatings and
foils of
pure metals or alloys of metals selected from the group of Ag, Au, Cu, Co, Cr,
Ni,
2o Fe, Pb, Pd, Pt, Rh, Ru, Sn, V, W and Zn and alloying elements selected from
C, P,
S and Si and metal matrix composites of pure metals or alloys with particulate
additives such as metal powders, metal alloy powders and metal oxide powders
of
Al, Co, Cu, In, Mg, Ni, Si, Sn, V, and Zn; nitrides of Al, B and Si; C
(graphite or
diamond); carbides of B, Cr, Bi, Si, W; and organic materials such as PTFE and
polymer spheres. The selective plating process is particularly suited for in-
situ or
field applications such as the repair or the refurbishment of dies and moulds,
tur-
bine plates, steam generator tubes, core reactor head penetrations of nuclear
power
plants and the like. The continuous plating process is particularly suited for
pro-
ducing nanocrystalline foils e.g. for magnetic applications. The process can
be
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applied to high strength, equiaxed micro-components for use in electronic, bio-
medical, telecommunication, automotive, space and consumer applications.
Description of Prior Art/Background of the Invention
Nanocrystalline materials, also referred to as ultra-fine grained materials,
nano-
phase materials or nanometer-sized materials exhibiting average grains sizes
smaller or equal to 100nm, are known to be synthesized by a number of methods
including sputtering, laser ablation, inert gas condensation, high energy ball
mill-
ing, sol-gel deposition and electrodeposition. Electrodeposition offers the
capa-
bility to prepare a large number of fully dense metal and metal alloy
compositions
at high production rates and low capital investment requirements in a single
syn-
thesis step.
The prior art primarily describes the use of pulse electrodeposition for
producing
nanocrystalline materials.
Erb in US 5,352,266 (1994) and in US 5,433,797 (1995) describes a process for
producing nanocrystalline materials, particularly nanocrystalline nickel. The
nanocrystalline material is electrodeposited onto the cathode in an aqueous
acidic
electrolytic cell by application of a pulsed DC current. The cell also
optionally
contains stress relievers. Products of the invention include wear resistant
coat-
ings, magnetic materials and catalysts for hydrogen evolution.
Mori in US 5,496,463 (1996) describes a process and apparatus for composite
electroplating a metallic material containing SiC, BN, Si3N4, WC, TiC, Ti02,
A1203, ZnB3, diamond, CrC, MoS2, coloring materials, polytetrafluoroethylene
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(PTFE) and microcapsules. The solid particles are introduced in fine form into
the electrolyte.
Adler in US 4,240,894 (1980) describes a drum plater for electrodeposited Cu
foil
production. Cu is plated onto a rotating metal drum that is partially
submersed and
rotated in a Cu plating solution. The Cu foil is stripped from the drum
surface
emerging from the electrolyte, which is clad with electroformed Cu. The
rotation
speed of the drum and the current density are used to adjust the desired
thickness
of the Cu foil. The Cu foil stripped from the drum surface is subsequently
washed
and dried and wound into a suitable coil.
Icxi in US 2,961,395 (1960) discloses a process for electroplating an article
with-
out the necessity to immerse the surface being treated into a plating tank.
The
hand-manipulated applicator serves as anode and applies chemical solutions to
the
metal surface of the work piece to be plated. The work piece to be plated
serves
as cathode. The hand applicator anode with the wick containing the electrolyte
and the work piece cathode are connected to a DC power source to generate a
metal coating on the work piece by passing a DC current.
Micromechanical systems (MEMS) are machines constructed of small moving
and stationary parts having overall dimensions ranging from 1 to 1,000 m e.g.
for
use in electronic, biomedical, telecommunication, automotive, space and con-
sumer technologies.
Such components are made e.g. by photo-electroforming, which is an additive
process in which powders are deposited in layers to build the desired
structure e.g.
by laser enhanced electroless plating. Lithography, electroforming and molding
(LIGA) and other photolithography related processes are used to overcome
aspect
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ratio (parts height to width) related problems. Other techniques employed
include
silicon micromachining, through mask plating and microcontact printing.
3. Summary:
It is an object of the invention to provide a reliable and flexible pulse
plating
process for forming coatings or free-standing deposits of nanocrystalline
metals,
metal alloys or metal matrix composites.
1o It is a further object of the invention to provide micro components with
signifi-
cantly improved property-dependent reliability and improved and tailor-made
desired properties for overall performance enhanced microsystems.
The present invention provides a process for cathodically electrodepositing a
se-
lected metallic material on a permanent or temporary substrate in
nanocrystalline
form with an average grain size of less than 100 nm at a deposition rate of at
least
0.05 mm/h, comprising:
providing an aqueous electrolyte containing ions of said metallic material,
maintaining said electrolyte at a temperature in the range between 0 to 85 C,
agitating the electrolyte at an agitation rate in the range of 0.0001 to 10
litre per
min and per cm2 anode or cathode area or at an agitation rate in the range of
1 to
750 millilitre per min and per Ampere,
providing an anode and a cathode in contact with said electrolyte, passing
single
or multiple D.C. cathodic-current pulses between said anode and said cathode
at a
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cathodic-current pulse frequency in a range of about 0 and 1000 Hz, at pulsed
intervals during which said current passes for a t~athod;,_on time period is
in the
range of 0.1 to 50 msec and does not pass for a tcat,odi~,ff-time period is in
the
range of 0 to 500 msec, and passing single or multiple D.C. anodic-current
pulses
between said cathode and said anode at intervals during which said current
passes
for a tanodic_on time period is in the range of 0 to 50 msec, a duty cycle
being in a
range of 5 to 100% and a cathodic charge (Qcathod;c) per interval being always
lar-
ger than a anodic charge (Qanodic)=
Preferred embodiments of the invention may be defmed as follows.
In the process the single or multiple cathodic-current pulses between said
anode
and said cathode may have a peak current density in the range of about 0.01 to
20
A/cm2.
In the process the peak current density of the cathodic-current pulses may be
in
the range of 0.1 to 20 A/cm2.
In the process the peak current density of the cathodic-current pulses may be
in
the range of 1 to 10 A/cm2.
In the process said selected metallic material may be (a) a pure metal
selected
from the group consisting of Ag, Au, Cu, Co, Cr, Ni, Fe, Pb, Pd, Rt, Rh, Ru,
Sn,
V, W, Zn, or (b) an alloy containing at least one of the elements of group (a)
and
alloying elements selected from the group consisting of C, P, S and Si.
In the process the duty cycle may be in the range of 10 to 95 %.
In the process the duty cycle may be in the range of 20 to 80 %.
In the process the deposition rate may be at least 0.075 mm/h.
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In the process the deposition rate may be at least 0.1 mm/h.
The process may comprise agitating the electrolyte by means of pumps, stirrers
or
ultrasonic agitation.
The process may comprise a relative motion between anode and cathode.
In the process the speed of the relative motion between anode and cathode may
range from 0 to 600 m/min.
In the process the speed of the relative motion between anode and cathode may
range from 0.003 to 10 m/min.
In the process the relative motion may be achieved by rotation of anode and
cath-
ode relative to each other.
In the process a rotational speed of rotation of anode and cathode relative to
each
other may range from 0.003 to 0.15 rpm.
In the process the rotational speed of rotation of anode and cathode relative
to
each other may range from 0.003 to 0.05 rpm.
In the process the relative motion may be achieved by a mechanized motion gen-
erating a stroke of the anode and the cathode relative to each other.
In the process the anode may be wrapped in an absorbent separator.
In the process said electrolyte may contain a stress relieving agent or a
grain refin-
ing agent selected from the group of saccharin, coumarin, sodium lauryl
sulfate
and thiourea.
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In the process said electrolyte may contain particulate additives in
suspension se-
lected from pure metal powders, metal alloy powders or metal oxide powders of
Al, Co, Cu, In, Ng, Ni, Si, Sn, V and Zn, nitrides of Al, B and Si, carbon C
(graphite or diamond), carbides of B, Bi, Si, W, or organic materials such as
PTFE and polymers spheres, whereby the electrodeposited metallic material con-
tains at least 5 % of said particulate additives.
In the process the electrodeposited metallic material may contain at least 10
% of
said particulate additives.
In the process the electrodeposited metallic material may contain at least 20
% of
said particulate additives.
In the process the electrodeposited metallic material may contain at least 30
% of
said particulate additives.
In the process the electro deposited metallic material may contain at least 40
% of
said particulate additives.
In the process the particulate additives average particle size may be below 10
m.
In the process the particulate additives average particle size may be below
1000
nm.
In the process the particulate additives average particle size may be below
500
nm.
In the process the particulate additives average particle size may be below
100
nm.
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The present invention also provides a micro component having a maximum di-
mension of 1 mm with free standing or coated nanocrystalline metallic material
produced by a pulse electrodeposition process as outlined above, wherein the
nanocrystalline metallic material has an average grain size equal to or
smaller than
1000 nm, the ratio between the maximum dimension and the average grain size
being greater than 10.
The ratio between the maximum dimension of the micro component and the aver-
age grain size may be greater than 100.
The micro component may have an equiaxed microstructure.
The present invention provides a pulse plating process, consisting of a single
ca-
thodic on time or multiple cathodic on times of different current densities
and sin-
gle or multiple off times per cycle. Periodic pulse reversal, a bipolar
waveform
alternating between cathodic pulses and anodic pulses, can optionally be used
as
well. The anodic pulses can be inserted into the waveform before, after or in
be-
tween the on pulse and/or before, after or in the off time. The anodic pulse
cur-
rent density is generally equal to or greater than the cathodic current
density. The
anodic charge (Qanodic) of the "reverse pulse" per cycle is always smaller
than the
cathodic charge (Qcathodic)=
Cathodic pulse on times range from 0.1 to 50 msec (1-50), off times from 0 to
500msec (1-100) and anodic pulse times range from 0 to 50 msec, preferably
from
1 to 10msec. The duty cycle, expressed as the cathodic on times divided by the
sum of the cathodic on times, the off times and the anodic times, ranges from
5 to
100 %, preferably from 10 to 95 %, and more preferably from 20 to 80 %. The
frequency of the cathodic pulses ranges from 1 Hz to 1 kHz and more preferably
from l OHz to 350Hz.
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Nanocrystalline coatings or free-standing deposits of metallic materials were
ob-
tained by varying process parameters such as current density, duty cycle, work
piece temperature, plating solution temperature, solution circulation rates
over a
wide range of conditions. The following listing describes suitable operating
pa-
rameter ranges for practicing the invention:
Average current density (if determinable, anodically or cathodically): 0.01 to
20A/cm2, preferably 0,1 to 20A/cm2, more preferably 1 to l OA/cm2
Duty Cycle 5 to 100%
Frequency: 0 to 1000Hz
Electrolyte solution temperature: - 20 to 85 C
Electrolyte solution circulation/agitation rates: <l 0 liter per min per cm2
anode or
cathode area (0.0001 to 101/min.cm)
Work piece temperature: -20 to 45 C
Anode oscillation rate: 0 to 350 oscillations/min
Anode versus cathode linear speed: 0 to 200 meter/min (brush) 0.003 to
0.16m/min (drum)
The present invention preferably provides a process for plating
nanocrystalline
metals, metal matrix composites and microcomponents at deposition rates of at
least 0,05 mm/h, preferably at least 0.075 mm/h, and more preferably at least
0,1
mm/h.
In the process of the present invention the electrolyte preferably may be
agitated
by means of pumps, stirrers or ultrasonic agitation at rates of 0 to 750
ml/min/A
(ml solution per minute per applied Ampere average current), preferably at
rates
of 0 to 500 ml/min/A.
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.
In the process of the present invention optionally a grain refining agent or a
stress
relieving agent selected from the group of saccharin, coumarin, sodium lauryl
sulfate and thiourea can be added to the electrolyte.
This invention provides a process for plating nanocrystalline metal matrix com-
posites on a permanent or temporary substrate optionally containing at least
5%
by volume particulates, preferably 10% by volume particulates, more preferably
20% by volume particulates, even more preferably 30% by volume particulates
and most preferably 40% by volume particulates for applications such as hard
facings, projectile blunting armor, valve refurbishment, valve and machine
tool
coatings, energy absorbing armor panels, sound damping systems, connectors on
pipe joints e.g. used in oil drilling applications, refurbishment of roller
bearing
axles in the railroad industry, computer chips, repair of electric motors and
gen-
erator parts, repair of scores in print rolls using tank, barrel, rack,
selective (e.g.
brush plating) and continuous (e.g. drum plating) plating processes using
pulse
electrodeposition. The particulates can be selected from the group of metal
pow-
ders, metal alloy powders and metal oxide powders of Al, Co, Cu, In, Mg, Ni,
Si,
Sn, V, and Zn; nitrides of Al, B and Si; C (graphite or diamond); carbides of
B,
Bi, Cr, Si, W; MoS2; and organic materials such as PTFE and polymer spheres.
The particulate average particle size is typically below 10 m, preferably
below
1,000nm (1 m), preferably 500nm, and more preferably below l 00nm.
The process of this invention optionally provides a process for continuous
(drum
or belt) plating nanocrystalline foils optionally containing solid particles
in sus-
pension selected from metal powders, metal alloy powders and metal oxide pow-
ders of Al, Co, Cu, In, Mg, Ni, Si, Sn, V, and Zn; nitrides of Al, B and Si; C
(graphite or diamond); carbides of B, Bi, Si, W; MoS2, and organic materials
such
as PTFE and polymer spheres to impart desired properties including hardness,
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wear resistance, lubrication, magnetic properties and the like. The drum or
belt
provides a temporary substrate from which the plated foil can be easily and
con-
tinuously removed.
According to a preferred embodiment of the present invention it is also
possible to
produce nanocrystalline coatings by electroplating without the need to
submerse
the article to be coated into a plating bath. Brush or tampon plating is a
suitable
alternative to tank plating, particularly when only a portion of the work
piece is to
be plated, without the need to mask areas not to be plated. The brush plating
ap-
paratus typically employs a soluble or dimensionally stable anode wrapped in
an
absorbent separator felt to form the anode brush. The brush is rubbed against
the
surface to be plated in a manual or mechanized mode and electrolyte solution
con-
taining ions of the metal or metal alloys to be plated is injected into the
separator
felt. Optionally, this solution also contains solid particles in suspension
selected
from metal powders, metal alloy powders and metal oxide powders of Al, Co, Cu,
In, Mg, Ni, Si, Sn, V, and Zn; nitrides of Al, B and Si; C (graphite or
diamond);
carbides of Bi, Si, W; MoS2i and organic materials such as PTFE and polymer
spheres to impart desired properties including hardness, wear resistance,
lubrica-
tion and the like.
In the case of drum, belt or brush plating the relative motion between anode
and
cathode ranges from 0 to 600meters per minute, preferably from 0.003 to
l Ometers per minute.
In the process of this invention micro components for micro systems including
micro-mechanical systems (MEMS) and micro-optical-systems with grain sizes
equal to or smaller than 1,000nm can be produced. The maximum dimension of
the microcomponent part is equal to or below 1mm and the ratio between the
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maximum outside dimension of the microcomponent part and the average grain
size is equal to or greater than 10, preferably greater than 100.
The micro components of the present invention preferably may have an equiaxed
microstructure throughout the plated component, which is relatively
independent
of component thickness and structure.
It is another aspect of the present invention to provide micro components
where
the average grain size remains at least an order of magnitude smaller than the
ex-
ternal dimensions of the part, thus maintaining a high level of strength.
The micro components according to this invention have significantly improved
property-dependent reliability and improved and tailor-made desired properties
of
MEMS structures for overall performance enhanced microsystems by preferably
equiaxed electrodeposits, eliminating the fine grain to columnar grain
transition in
the microcomponent, and simultaneously reducing the grain size of the deposits
below 1,000nm.
4. Preferred Embodiments of the Invention:
Other features and advantages of this invention will become more apparent in
the
following detailed description and examples of preferred embodiments of the in-
vention, together with the accompanying schematic drawings, in which:
Figure 1 shows a cross-sectional view of a preferred embodiment of a drum plat-
ing apparatus.
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Figure 2 shows a cross sectional view of a preferred embodiment of a brush
plat-
ing apparatus; and
Figure 3 shows a plan view of a mechanized motion apparatus for generating a
mechanized stroke of the anode brush.
Figure 1 schematically shows of a plating tank or vessel (1) filled with an
electro-
lyte (2) containing the ions of the metallic material to be plated. Partially
sub-
mersed into the electrolyte is the cathode in the form of a rotating drum (3)
elec-
trically connected to a power source (4). The drum is rotated by an electric
motor
(not shown) with a belt drive and the rotation speed is variable. The anode
(5) can
be a plate or conforming anode, as shown, which is electrically connected to
the
power source (4). Three different anode dispositions can be used: Conformal an-
odes, as shown in Figure 1, that follow the contour of the submerged section
of
the drum (3), vertical anodes positioned at the walls of the tank (1) and
horizontal
anode positioned on the bottom of the tank (1). In case of a foil (16) of
metallic
material being electrodeposited on the drum (3), the foil (16) is pulled from
the
drum surface emerging from the electrolyte (2), which is clad with the electro-
formed metallic material.
Figure 2 schematically shows a work piece (6) to be plated, which is connected
to
the negative outlet of the power source (4). The anode (5) consists of a
handle (7)
with a conductive anode brush (8). The anode contains channels (9) for
supplying
the electrolyte solution (2) from a temperature controlled tank (not shown) to
the
anode wick (absorbent separator) (10) . The electrolyte dripping from the
absor-
bent separator (10) is optionally collected in a tray (11) and recirculated to
the
tank. The absorbent separator (10) containing the electrolyte (2) also
electrically
insulates the anode brush (8) from the work piece (6) and adjusts the spacing
be-
tween anode (5) and cathode (6). The anode brush handle (4) can be moved over
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the work piece (6) manually during the plating operation, alternatively, the
motion
can be motorized as shown in figure 3.
Figure 3 schematically shows a wheel (12) driven by an adjustable speed motor
(not shown). A traversing arm (13) can be rotatably attached (rotation axis A)
to
the rotating wheel (12) at various positions x at a slot (14) with a bushing
and a
set screw (not shown) to generate a desired stroke. The stroke length can be
ad-
justed by the position x (radius) at which the rotation axis A of traversing
arm is
mounted at the slot (14). In Figure 3 the traversing arm (13) is shown to be
in an
no-stroke, neutral position with rotation axis A in the center of the wheel
(12).
The traversing arm (13) has a second pivot axis B defined by a bearing (not
shown), that is slidably mounted in a track (15). As the wheel (12) rotates,
the
rotation of the traversing arm (13) around axis A at position x causes the
travers-
ing arm (13) to reciprocate in the track (15) and to pivot around axis B. An
anode
(5) having the same features as shown in Fig. 2 is attached to the traversing
arm
(13) and moves over the work piece (6) in a motion depending on the position
x.
Usually the motion has the shape of figure eight. The anode (5) and the work
piece (6) are connected to positive and negative outlets of a power source
(not
shown), respectively. The cinematic relation is very similar to that of a
steam
engine.
This invention relies on producing nanocrystalline coatings, foils and
microsystem
components by pulse electrodeposition. Optionally solid particles are
suspended
in the electrolyte and are included in the deposit.
Nanocrystalline coatings for wear resistant applications to date have focused
on
increasing wear resistance by increasing hardness and decreasing the friction
coef-
ficient though grain size reduction below 100nm. It has now been found that in-
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corporating a sufficient volume fraction of hard particles can further enhance
the
wear resistance of nanocrystalline materials.
The material properties can also be altered by e.g. the incorporation of
lubricants
(such as MoS2 and PTFE). Generally, the particulates can be selected from the
group of metal powders, metal alloy powders and metal oxide powders of Al, Co,
Cu, In, Mg, Ni, Si, Sn, V, and Zn; nitrides of Al, B and Si; C (graphite or
dia-
mond); carbides of B, Bi, Si, W; MoS2; and organic materials such as PTFE and
polymer spheres.
Example 1
Nanocrystalline NiP-B4C nanocomposites were deposited onto Ti and mild steel
cathodes immersed in a modified Watts bath for nickel using a soluble anode
made of a nickel plate and a Dynatronix (Dynanet PDPR 20-30-100) pulse power
supply. The following conditions were used:
Anode/anode area: soluble anode: Ni plate, 80cm2
Cathode/cathode area: Ti or mild steel sheet/appr. 5cm2
Cathode: fixed
Anode: fixed
Anode versus cathode linear speed: N/A
Average cathodic current density: 0.06A/cm2
toõ/toff: 2msec/ 6msec
Frequency: 125Hz
Duty Cycle: 25%
Deposition time: 1 hour
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Deposition Rate: 0.09mm/hr
Electrolyte temperature: 60 C
Electrolyte circulation rate: vigorous agitation (two direction mechanical
impeller)
Basic Electrolyte Formulation:
300g/l NiSO4.7H20
45g/l NiC12.6H20
45g/1 H3B03
18 g/1 H3PO4
0.5-3m1/1 surfactant to a surface tension of <30dyne/cm
0-2g/1 sodium saccharinate
360 g/1 boron carbide, 5gm mean particle diameter
pH 1.5-2.5
The hardness values of metal matrix composites possessing a nanocrystalline ma-
trix structure are typically twice as high as conventional coarse-grained
metal ma-
trix composites. In addition, the hardness and wear properties of a
nanocrystalline
NiP-B4C composite containing 5.9weight% P and 45volume% B4C are compared
with those of pure coarse-grained Ni, pure nanocrystalline Ni and
electrodeposited
Ni-P of an equivalent chemical composition in the adjacent table. Material
hard-
ening is controlled by Hall-Petch grain size strengthening, while abrasive
wear
resistance is concurrently optimized by the incorporation of B4C particulate.
Table: NiP-B4C nanocomposite properties
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Sample Grain Size Vickers Hardness Taber Wear Index
[VHN] [TWI]
Pure Ni 90 m 124 37.0
Pure Ni 13 nm 618 20.9
Ni-5.9P Amorphous 611 26.2
Ni-5.9P-45B4C 12 nm 609 1.5
Example 2
Nanocrystalline Co based nanocomposites were deposited onto Ti and mild steel
cathodes inunersed in a modified Watts bath for cobalt using a soluble anode
made of a cobalt plate and a Dynatronix (Dynanet PDPR 20-30-100) pulse power
supply. The following conditions were used:
Anode/anode area: soluble anode (Co plate)/ 80cm2
Cathode/cathode area: Ti (or mild steel) sheet/appr. 6.5cm2
Cathode: fixed
Anode: fixed
Anode versus cathode linear speed: N/A
Peak cathodic current density: 0.100A/cm2
Peak anodic current density: 0.300A/cm2
Cathodic ton/ toa/ Anodic ton (t,.,,W;j: 16msec / Omsec / 2msec
Frequency: 55.5Hz
Cathodic duty cycle: 89 %
Anodic duty cycle: 11 %
Deposition time: 1 hour
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Deposition Rate: 0.08mm/hr
Electrolyte temperature: 60 C
Electrolyte circulation rate: 0.151iter per min and per cm2 cathode area
Electrolyte Formulation:
300 g/l CoSO4=7H20
45 g/1 CoC12=6H20
45 g/l H3B03
2 g/1 C7H4NO3SNa Sodium Saccharinate
0.1 g/1 C12H25O4SNa Sodium Lauryl Sulfonate (SLS)
100 g/l SiC, <1 m mean particle diameter
pH 2.5
In the adjacent table, the hardness and wear properties of a nanocrystalline
Co-
SiC composite containing 22volume% SiC are compared with those of pure
coarse-grained Co and pure nanocrystalline Co. Hall-Petch grain size
strengthen-
ing controls material hardening, while abrasive wear resistance is
concurrently
optimized by the incorporation of SiC particulate.
Table: Co nanocomposite properties
Sample Grain Size Vickers Hardness Taber Wear Index
[VHN] [TWI]
Pure Co 5 m 270 32.0
Pure Co 14 nm 538 38.0
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Co-22SiC 15 nm 529 7.1
Continuous plating to produce foils e.g. using drum plating nanocrystalline
foils
optionally containing solid particles in suspension selected from pure metals
or
alloys with particulate additives such as metal powders, metal alloy powders
and
metal oxide powders of Al, Co, Cu, In, Mg, Ni, Si, Sn, V, and Zn; nitrides of
Al,
B and Si; C (graphite or diamond); carbides of B, Bi, Si, W; and organic
materials
such as PTFE and polymer spheres to impart desired properties including hard-
ness, wear resistance, lubrication, magnetic properties and the like has been
ac-
complished. Nanocrystalline metal foils were deposited on a rotating Ti drum
partially immersed in a plating electrolyte. The nanocrystalline foil was
electro-
formed onto the drum cathodically, using a soluble anode made of a titanium
con-
tainer filled with anode metal and using a pulse power supply. For alloy foil
pro-
duction, a stream of the additional cation at a predetermined concentration
was
continuously added to the electrolyte solution to establish a steady state
concen-
tration of alloying cations in solution. For metal and alloy foil production
con-
taining matrix composites, a stream of the composite addition was added to the
plating bath at a predetermined rate to establish a steady state content of
the addi-
tive. Three different anode dispositions can be used: Conformal anodes that
fol-
low the contour of the submerged section of the drum, vertical anodes
positioned
at the walls of the vessel and horizontal anode positioned on the bottom of
the
vessel. Foils were produced at average cathodic current densities ranging from
0.01 to 5A/cm2 and preferably from 0.05 to 0.5A/cm2. The rotation speed was
used to adjust the foil thickness and this speed ranged from 0.003 to 0.15rpm
(or
20 to 1000cm/hour) and preferably from 0.003 to 0.05rpm (or 20 to 330cm/hour)
Example 3: metal matrix composite drum plating
CA 02490464 2007-04-24
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Nanocrystalline Co based nanocomposites were deposited onto a rotating Ti drum
as described in example 3 immersed in a modified Watts bath for cobalt. The
nanocrystalline foil, 15cm wide was electroformed onto the drum cathodically,
using a soluble cobalt anode contained in a Ti wire basket and a Dynatronix
(Dy-
nanet PDPR 20-30-100) pulse power supply. The following conditions were
used:
Anode/anode area: conforming soluble anode (Co Pieces in Ti
basket)/undetermined
Cathode/cathode area: Ti 600cm2
Cathode: rotating
Anode: fixed
Anode versus cathode linear speed: 0.018rpm
Average Current Density: 0.075A/cm2
Peak cathodic current density: 0.150A/cm2
Peak anodic current density: N/A
Cathodic toõ/ t ff/ Anodic t n (t di ): lmsec / lmsec / Omsec
Frequency: 500Hz
Cathodic duty cycle: 50 %
Anodic duty cycle: 0%
Deposition time: 1 hour
Deposition Rate: 0.05 mm/hr
Electrolyte temperature: 65 C
Electrolyte circulation rate: 0.151iter per min and per cm2 cathode area
CA 02490464 2007-04-24
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Electrolyte Formulation:
300 g/l CoSO4x7H2O
45 g/1 CoC12x6H2O
45 g/1 H3BO3
2 g/1 C7H4NO3SNa Sodium Saccharinate
0.1 g/l C12H25O4SNa Sodium Lauryl Sulfonate (SLS)
5 g/1 Phosphorous Acid
35 g/1 SiC, <1 m mean particle diameter
.5 g/1 Dispersant
1o pH 1.5
The Co/P-SiC foil had a grain size of 12 nm, a hardness of 690 VHN, contained
1.5% P and 22volume% SiC.
Example 4
Nanocrystalline nickel-iron alloy foils were deposited on a rotating Ti drum
par-
tially immersed in a modified Watts bath for nickel. The nanocrystalline foil,
15cm wide was electroformed onto the drum cathodically, using a soluble anode
made of a titanium wire basket filled with Ni rounds and a Dynatronix (Dynanet
PDPR 50-250-750) pulse power supply. The following conditions were used:
Anode/anode area: conforming soluble anode (Ni rounds in a metal
cage)/undetermined
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Cathode/cathode area: submersed Ti drum/appr. 600cm2
Cathode: rotating at 0.018rpm (or 120cm/hour) Anode: fixed
Anode versus cathode linear speed: 120cm/hour
Average cathodic current density: 0.07A/cm2
t õ/t ff:2msec/2msec
Frequency: 250Hz
Duty Cycle: 50 %
Production run time: 1 day
Deposition Rate: 0.075mm/hr
Electrolyte temperature: 60 C
Electrolyte circulation rate: 0.151iter per min and per cm2 cathode area
Electrolyte Formulation:
260 g/1 NiSO4=7H20
45 g/1 NiC12=6H20
12 g/1 FeC12=4H20
45 g/l H3BO3
46 g/l Sodium Citrate
2 g/l Sodium Saccharinate
2o 2.2 ml/1 NPA-91
pH 2.5
Iron Feed Formulation:
81 g/l FeSO4=7H20
11 g/l FeC12=4H2O
13 g/1 H3BO3
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' 9 g/1 Sodium Citrate
4 g/L H2SO4
0.5 g/1 Sodium Saccharinate
pH 2.2
rate of addition: 0.3 1/hr
Composition: 23-27 wt.%Fe
Average grain size: 15 nm
Hardness: 75OVickers
Selective or brush plating is a portable method of selectively plating
localized
areas of a work piece without submersing the article into a plating tank.
There are
significant differences between selective plating and tank and barrel plating
appli-
cations. In the case of selective plating it is difficult to accurately
determine the
cathode area and therefore the cathodic current density and/or peak current
density
is variable and usually unknown. The anodic current density and/or peak
current
density can be determined, provided that the same anode area is utilized
during
the plating operation, e.g. in the case of flat anodes. In the case of shaped
anodes
the anode area can not be accurately determined e.g. in the case of a shaped
anode
and a shaped cathode the "effective" anode area also changes during the
plating
operation. Selective plating is performed by moving the anode, which is
covered
with the absorbent separator wick and containing the electrolyte, back and
forth
over the work piece, which is typically performed by an operator until the
desired
overall area is coated to the required thickness.
Selective plating techniques are particularly suited for repairing or
refurbishing
articles because brush plating set-ups are portable, easy to operate and do
not re-
CA 02490464 2007-04-24
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quire the disassembly of the system containing the work piece to be plated.
Brush
plating also allows plating of parts too large for immersion into plating
tanks.
Brush plating is used to provide coatings for improved corrosion resistance,
im-
proved wear, improved appearance (decorative plating) and can be used to
salvage
worn or mismachined parts. Brush plating systems and plating solutions are com-
mercially available e.g. from Sifco Selective Plating, Cleveland. Ohio, which
also
provides mechanized and/or automated tooling for use in high volume production
work. The plating tools used comprise the anode (DSA or soluble), covered with
an absorbent, electrically non-conductive material and an insulated handle. In
the
case of DSA anodes, anodes are typically made of graphite or Pt-clad titanium
and
may contain means for regulating the temperature by means of a heat exchanger
system. For instance, the electrolyte used can be heated or cooled and passed
through the anode to maintain the desired temperature range. The absorbent
sepa-
rator material contains and distributes the electrolyte solution between the
anode
and the work piece (cathode), prevents shorts between anode and cathode and
brushes against the surface of the area being plated. This mechanical rubbing
or
brushing motion imparted to the work piece during the plating process
influences
the quality and the surface finish of the coating and enables fast plating
rates.
Selective plating electrolytes are formulated to produce acceptable coatings
in a
wide temperature range ranging from as low as -20 C to 85 C. As the work piece
is frequently large in comparison to the area being coated selective plating
is often
applied to the work piece at ambient temperatures, ranging from as low as -20
C
to as high as 45 C. Unlike "typical" electroplating operations, in the case of
se-
lective plating the temperature of the anode, cathode and electrolyte can vary
sub-
stantially. Salting out of electrolyte constituents can occur at low
temperatures
and the electrolyte may have to be periodically or continuously reheated to
dis-
solve all precipitated chemicals.
A Sifco brush plating unit (model 3030 - 30A max) was set up. The graphite an-
ode tip was inserted into a cotton pouch separator and either attached to a
mecha-
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nized traversing arm in order to generate the "brushing motion" or moved by an
operator by hand back and forth over the work piece, or as otherwise
indicated.
The anode assembly was soaked in the plating solution and the coating was de-
posited by brushing the plating tool against the cathodically charged work
area
that was composed of different substrates. A peristaltic pump was used to feed
the electrolyte at predetermined rates into the brush plating tool. The
electrolyte
was allowed to drip off the work piece into a tray that also served as a
"plating
solution reservoir" from which it was recirculated into the electrolyte tank.
The
anode had flow-through holes/channels in the bottom surface to ensure good
elec-
trolyte distribution and electrolyte/work piece contact. The anode was fixed
to a
traversing arm and the cyclic motion was adjusted to allow uniform strokes of
the
anode against the substrate surface. The rotation speed was adjusted to
increase
or decrease the relative anode/cathode movement speed as well as the an-
ode/substrate contact time at any one particular location. Brush plating was
nor-
mally carried out at a rate of approximately 35-175 oscillations per minute,
with a
rate of 50-85 oscillations per minute being optimal. Electrical contacts were
made
on the brush handle (anode) and directly on the work piece (cathode). Coatings
were deposited onto a number of substrates, including copper, 1018 low carbon
steel, 4130 high carbon steel, 304 stainless steel, a 2.5in OD steel pipe and
a
weldclad 1625 pipe. The cathode size was 8cm2, except for the 2.5in OD steel
pipe where a strip 3cm wide around the outside diameter was exposed and the
weldclad 1625 pipe on which a defect repair procedure was performed.
A Dynatronix programmable pulse plating power supply (Dynanet PDPR 20-30-
100) was employed.
Standard substrate cleaning and activation procedures provided by Sifco were
used.
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' Example 5:
Nanocrystalline pure nickel was deposited onto an 8cm2 area cathode with a
35cm2 anode using the set-up described. Usually, the work piece has a substan-
tially larger area than the anode. In this example a work piece (cathode) was
se-
lected to be substantially smaller than the anode to ensure that the oversized
an-
ode, although being constantly kept in motion, always covered the entire work
piece to enable the determination of the cathodic current density. As a non-
consumable anode was used, NiCO3 was periodically added to the plating bath to
maintain the desired Ni2+ concentration. The following conditions were used:
Anode/anode area: graphite/35cm2
Cathode/cathode area: mild steel/8cm2
Cathode: stationary
Anode: oscillating mechanically automated at 50 oscillations per minute
Anode versus cathode linear speed: 125cm/min
Average cathodic current density: 0.2A/cm2
t n/t ff: 8msec/2msec
Frequency: 100 Hz
Duty Cycle: 80%,
Deposition time: lhour
Deposition rate: 0.125Ynm/hr
Electrolyte temperature: 60 C
Electrolyte circulation rate: lOmi solution per min per cm2 anode area or
220m1
solution per min per Ampere average current applied
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' Electrolyte Formulation:
300 g/l NiSO4=7H2O
45 g/l NiC12=6H20
45 g/1 H3B03
2 g/l Sodium Saccharinate
3 ml/1 NPA-91
pH: 2.5
Average grain size: 19nm
Hardness:600Vickers
Example 6:
Nanocrystalline Co was deposited using the same set up described under the fol-
lowing conditions:
Anode/anode area: graphite/35cm 2
Cathode/cathode area: mild steel/8cm2
Cathode: stationary
Anode: oscillating mechanically automated at 50 oscillations per minute
Anode versus cathode linear speed: 125cm/min
Average cathodic current density: 0.10A/cm2
taõ/toff: 2msec/6msec
Frequency: 125Hz
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' Duty Cycle: 25%
Deposition time: 1 hour
Deposition rate: 0.05mm/hr
Electrolyte temperature: 65 C
Electrolyte circulation rate: 10 ml solution per min per cm2 anode area or 440
ml
solution per min per Ampere average current applied
Electrolyte Formulation:
1o 300 g/L CoSO4=7H20
45 g/L CoC12=6H20
45 g/L H3BO3
2 g/L C7H4NO3SNa Sodium Saccharinate
0.1 g/L C1ZH25O4SNa Sodium Lauryl Sulfonate (SLS)
pH 2.5
Average grain size: 13 nm
Hardness: 600Vickers
Example 7:
Nanocrystalline Ni/20%Fe was deposited using the set up described before. A
1.5in wide band was plated on the OD of a 2.5in pipe by rotating the pipe
along
its longitudinal axis while maintaining a fixed anode under the following
condi-
tions:
CA 02490464 2007-04-24
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Anode/anode area/effective anode area: graphite/35cm2/undetermined
Cathode/cathode area: 2.5inch OD steel pipe made of 210A1 carbon
steel/undetermined
Cathode: rotating at 12 rpm
Anode: stationary
Cathode versus Anode linear speed: 20cm/min
Average cathodic current density: undetermined;
Total current applied: 3.5A
t R/t ff:2msec/6msec
Frequency: 125Hz
Duty Cycle: 25%
Deposition time: lhour
Deposition rate: 0.05mm/hr
Electrolyte temperature: 55 C
Electrolyte circulation rate: 0.44 liter solution per min per Ampere applied
Electrolyte Formulation:
260 g/1 NiSO4=7H20
45 g/1 NiC12=6H20
7.8 g/l FeC12=4H20
45 g/1 H3B03
g/l Na3C6H5O7=2H20, Sodium Citrate
CA 02490464 2007-04-24
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2 g/l Sodium Saccharinate
1 ml/1 NPA-91
pH 3.0
Average grain size: 15 nm
Hardness: 750Vickers
Example 8:
A defect (groove) in a weldclad pipe section was filled in with
nanocrystalline Ni
using the same set up as in Example 1. The groove was about 4.5cm long, 0.5cm
wide and had an average depth of approximately 0.175mm, although the rough
finish of the defect made it impossible to determine its exact surface area.
The
area surrounding the defect was masked off and nano Ni was plated onto the de-
fective area until its original thickness was reestablished.
Anode/anode area: graphite/35cm2
Cathode/cathode area: 1625/undetermined
Cathode: stationary
Anode: oscillating mechanically automated at 50 oscillations per minute
Anode versus cathode linear speed: 125cm/min
Average cathodic current density: undetermined
ton/toff: 2msec/6msec
Frequency: 125Hz
Duty Cycle: 25%
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Deposition time: 2hour
Deposition rate:0.087mm/hr
Electrolyte temperature: 55 C
Electrolyte circulation rate: 0.44 liter solution per min per Ampere average
current
applied
Electrolyte Formulation:
300 g/l NiSO4=7H20
lo 45 g/1 NiC12=6H20
45 g/1 H3BO3
2 g/1 Sodium Saccharinate
3 ml/1 NPA-91
pH 3.0
Average grain size: 20nm
Hardness: 600Vickers
Microcomponents, having overall dimensions below 1,0001im (1mm), are gaining
increasing importance for use in electronic, biomedical, telecommunication,
automotive, space and consumer applications. Metallic macro-system components
with an overall maximum dimension of lcm to over lm containing conventional
grain sized materials (1-1,O00 m) exhibit a ratio between maximum dimension
and grain size ranges from 10 to 106. This number reflects the number of
grains
across the maximum part dimension. When the maximum component size is re-
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duced to below 1 mm using conventional grain-sized material, the component can
be potentially made of only a few grains or a single grain and the ratio
between
the maximum micro-component dimension and the grain size ranges approaches
1. In other words, a single or only a few grains stretch across the entire
part,
which is undesirable. To increase the part reliability of micro-components the
ratio between maximum part dimension and grain size ranges must be increased
to
over 10 through the utilization of a small grained material, as this material
class
typically exhibits grain size values 10 to 10,000 times smaller than
conventional
materials.
For conventional LIGA and other plated micro-components, electrodeposition
initially starts with a fine grain size at the substrate material. With
increasing de-
posit thickness in the growth direction; however, the transition to columnar
grains
is normally observed. The thickness of the columnar grains typically ranges
from
a few to a few tens of micrometers while their lengths can reach hundreds of
mi-
crometers. The consequence of such structures is the development of
anisotropic
properties with increasing deposit thickness and the reaching of a critical
thick-
ness in which only a few grains cover the entire cross section of the
components
with widths below 5 or 10 m. A further decrease in component thickness
results
in a bamboo structure resulting in a significant loss in strength. Therefore
the
microstructure of electrodeposited micro-components currently in use is
entirely
incommensurate with property requirements across both the width and thickness
of the component on the basis of grain shape and average grain size.
Heretofore, parts made of conventionally grain-sized materials that have been
known to suffer from severe reliability problems with respect to mechanical
prop-
erties such as the Young modulus, yield strength, ultimate tensile strength,
fatigue
strength and creep behavior have been shown to be extremely sensitive to
process-
ing parameters associated with the synthesis of these components. Many of the
problems encountered are caused by incommensurate scaling of key microstruc-
CA 02490464 2007-04-24
~
-33-
tural features (i.e. grain size, grain shape, grain orientation) with the
external size
of the component resulting in unusual property variations normally not
observed
in macroscopic components of the same material.
Example 9:
Metal micro-spring fingers are used to contact IC chips with high pad count
and
density and to carry power and signals to and from the chips. The springs
provide
high pitch compliant electrical contacts for a variety of interconnection
structures,
including chip scale semiconductor packages, high-density interposer
connectors,
and probe contactors. The massively parallel interface structures and
assemblies
enable high speed testing of separated integrated circuit devices affixed to a
com-
pliant carrier, and allow test electronics to be located in close proximity to
the
integrated circuit devices under test.
The micro-spring fingers require high yield strength and ductility. A 25 m
thick
layer of nanocrystalline Ni was plated on 500 m long gold-coated CrMo fingers
using the following conditions:
Anode/anode area: Ni/4.5x10"3cm2
Cathode/cathode area: Gold Plated CrMo/approximately 1 cm2
Cathode: stationary
Anode: stationary
Anode versus cathode linear speed: 0 cm/min
Average cathodic current density: 50mA/cm2
ton/toff: l Omsec/20msec
CA 02490464 2007-04-24
. ~ . .
-34-
Frequency: 33Hz
Duty Cycle: 33%
Deposition time: 120 minutes
Deposition Rate: 0.05mm/hr
Electrolyte temperature: 60 C
Electrolyte circulation rate: None
Electrolyte Formulation:
300 g/1 NiSO4=7H20
lo 45 g/1 NiC12=6H20
45 g/l H3BO3
2 g/l Sodium Saccharinate
3 ml/1 NPA-91
pH 3.0
Average grain size: 15-20nm
Hardness: 600Vickers
The nano-fingers exhibited a significantly higher contact force when compared
to
"conventional grain-sized" fingers.
