Note: Descriptions are shown in the official language in which they were submitted.
CA 02176579 2004-08-24
1
Method and Apparatus for electrolytically metallising or
etching Material
Description:
The invention relates to a method of electrolytically
metallising or etching material.
The economic operation of electrolytic metallising and
etching methods essentially depends on the maximum current
density at which an industrially useful treatment result
may still be obtained. The maximum current density is above
all dependent on the speed at which fresh treatment agent
(electrolyte solution) can reach the surface of the
material to be treated. During electrolytic metallisation,
the precipitated metal ions are consumed in the direct
vicinity of the material for treatment. This reduces the
metallising speed, and the process decelerates. The same
also applies to other electrolytic treatment methods, for
example electrolytic etching.
In order to provide assistance here, fresh treatment
solution can be supplied continuously through flow tubes
which in electrolytic metallisation are disposed between
the anode and the material for treatment (cathode), on to
the surface of the material for treatment. This procedure
2 ~17b579
however is subject to certain fluidic limits; the exchange
of liquid in the direct vicinity of the surface of the
material for treatment (diffusion layer) may only be
increased to a restricted degree. Apart from this, such a
procedure is disadvantageous, as the flow tubes disposed
between the anodes and the material for treatment screen the
electrical field between the anodes and cathodes, so that
metal is irregularly deposited on the material. This
disadvantage is particularly serious when the space between
1o the flow tubes and the surface of the material is small. On
the other hand, for fluidic reasons a small space between
the flow tubes and the material surface would be preferable,
in order to achieve controlled flow direction and the
highest possible current density. In this case high current
Z5 densities would occur at some points on the surface of the
material, so that the additives conventionally included in
electrolytic metallising baths would become oxidised.
Plate-shaped material for treatment, particularly printed
20 circuit boards, is preferably processed in horizontal
treatment installations.
The material is grasped in a horizontal position and passed
through the installation in a horizontal direction, thus
25 being electrolytically treated. In such, installations,
2>>~51~
3
rollers are normally used for transporting and guiding the
material. These also are located in the area between anode
and cathode. Particularly in the case of extremely thin
films, guide members are also necessary in order to
transport them efficiently, in order to prevent the films
from slipping off the transport track and becoming wound
around the transport rollers. Such constructional members,
like the transport rollers mentioned, also hinder the
current flow between the anode and the material for
treatment.
Soluble anodes, produced from the metal to be precipitated,
are normally used for electrolytic metallisation. Their
positioning inside the metallising installation and their
normal shape and size give rise to considerable difficulties
in finding simple constructive solutions to the named
problems. when using insoluble anodes, there is on the other
hand the possibility in horizontal installations of making
these in a longitudinally-extended form, and of disposing
them in such a way that the screening actions described do
not occur. For example, in such arrangements, in repeated
sequences of adjacent insoluble anodes, at least one flow
tube may be disposed for supplying fresh treatment agent to
the surface of the material, and to transport rollers. The
positioning of these individual members. is so selected that
CA 02176579 2004-08-24
4
the material is moved slowly past them during the
metallising process. The length of such an installation is
determined by the geometrical dimensions of the three
members, their necessary spacing apart from one another,
and by their overall number. Such treatment installations
are therefore extremely long and relatively expensive.
In the German Disclosure Document 36 03 856 there is
described a method for continuously electroplating flat
workpieces such as printed circuit boards, in which the
workpieces are passed horizontally through an electroplating
installation, and are grasped and transported inside the
electroplating installation by a cathodically-incorporated
rotating pair of rollers, and in which the electrolyte
solution is transferred on to the workpiece from a likewise
rotating pair of rollers, located in the vicinity of the
cathodic roller pair, and incorporated as anode, the surface
of the said anodic pair of rollers being capable of
absorbing liquid and rotating at a narrow interval from the
surface of the workpiece, so that the electrochemical
deposition of metal is effected ir~ the gap between workpiece
surface and the surface of the anodic roller pair. In this
case the electrolyte solution is sprayed from spray heads
over the anodic rollers, so that the surface of the material
for treatment is permanently supplied with enriched
'' . 5 ~ ~ 76519
electrolyte solution. By means of the rapid rotation of the
rollers, the solution however is centrifuged in all
directions, and caught by the plastics screens located above
the spray heads and the anode rollers. Large quantities of
the electrolyte solution are indeed transported into the
working area. However, only a small proportion thereof
reaches the locus of the treatment point having the largest
current density. This point lies between the anode roller
and the surface of the material. Controllei3 direction of
i0 flow at this point is not possible.
In the case of roller-shaped anodes, the greatest current
density occurs in the vicinity of the surface line of the
anode lying closest to the material for treatment.
IS vertically on either side of the surface line, it reduces
sharply. This leads to a situation in which the
electroplating speed, seen in the direction of the transport
path, fluctuates intensely. In order to obtain a sufficient
medial current density over the entire treatment path,
20 therefore, 'the maximum current density beneath the surface
line of the anode must be high. This demands a controlled
and effective exchange of electrolyte at the diffusion layer
at that point; this cannot be realised by the abovenamed
method.
'' ~~ 7579
6
A further disadvantage in this case is that, at the point of
highest current density, gases such as hydrogen, oxygen and
chlorine are.formed. These gases attack the anode material.
Therefore this material must be provided with coatings of
noble metal in order to restrict their corrosion. In
addition, the gases have to be removed by an additional flow
of electrolyte solution over the anodes. This requires
further technical outlay on the installation.
In the publication EP 0 210 072 AZ there is described an
apparatus with a rotating metallising brush for selectively
metallising metal parts, and in which a roller-shaped anode
surrounded by a porous hydrophobic material serves as a
counter-electrode for the metal pats to be coated, the metal
parts being slidingly moved along the surface line of the
anode, electrolyte solution being caused to flow from the
interior of the anode through the hydrophobic material on to
the metal parts.
In the essay ~Elektrolytische Hochleistungsverzinkung von
Stahlband durch mechanische Grenzschichtbeeinflussung°
(Electrolytic High-performance Galvanisation of Steel Strip
by Mechanical Influence on the Boundary Layer) by B. Meuthen
and D. Wolfhard in the specialist periodical
«Metalloberflache«, vol. 35 (1982) pages 70 - 75, there is
X176579
described a method for high-performance galvanisation of
steel strip. The laboratory installation illustrated
comprises a cathodically-incorporated circular sheet metal
disc which is passed in a rotating fashion along a
perforated anode, fibre fleece attached to the anode being
wiped on its surface during rotation of the cathode. Fresh
electrolyte solution is continuously passed on to the
cathodic metal disc by the anode.
The abovementioned documents disclose methods and apparatus
in which the surface of the material for treatment is wiped
in order continuously to supply it with fresh electrolyte
solution, keeping the diffusion layer as thin as possible.
It becomes apparent however that the surface of the material
for treatment may easily be damaged by wiping. Damage is
only avoided by the use of extremely soft materials as a
covering on the wiper electrodes. On the other hand, the
soft covering is subject to intensified wear, particularly
in the case of plate-shaped workpieces having holes which
have sharp'edges, so that microfine worn-off particles pass
into the electrolyte solution. The particles are again
transported via the electrolyte circuit on to the material
to be treated, and cause problems at that point. These can
hinder metal deposition, particularly in small holes in
printed circuit boards, as they aggregate at that point. It
CA 02176579 2004-08-24
8
has become apparent that the resulting quality problems
cannot be resolved even by expensive additional filter
systems.
The problem underlying the present invention is
therefore to find a method and an apparatus for
electrolytically metallising or etching material for
treatment at a high current density, in which the named
disadvantages of prior art do not appear.
According to the invention, an electrolytic treatment
method with high current density, which may be carried
out in a cost-effective manner, consists in that:
- the material for treatment and electrodes are brought
into contact with a treatment agent, and the electrodes
are electrically polarised with respect to the
material;
- the material is moved linearly, and the electrodes
rotarily, and treatment agent is supplied to the partly
hollow electrodes;
~j76579
- the treatment agent is conveyed out of, or sucked into,
openings in the electrodes lying opposite the surfaces of
the material for treatment, and
- the speed and direction of rotation of the electrodes is
so adjusted that the outer sides of the electrodes are moved
synchronously with the surfaces of the material for
treatment.
By virtue of the fact that the electrodes are polarised with
respect to the material for treatment, and therefore serve
to generate the electrical field necessary for the
electrolytic treatment, and on the other hand undertake the
additional task of continuously supplying fresh treatment
agent to the surface of the material, an extremely simple
I5 configuration of the installation is possible.
If electrode materials with a lower degree of electrical
conductivity are used, such for example as special steel,
high losses are normally to be expected due to the high
current densities, so that the metallic parts can heat up
rapidly. Due to the rotation of the electrodes, and~to the
intensive circulation of the treatment agent in the direct
vicinity of the electrodes, the, resultant heat is however
distributed over the entire electrode, and is thus rapidly
passed off into the electrolyte solution.
~~7b519
Damage to the surface of the material, such as occurs in the
known wiping methods, is not possible, as the speed and
direction of rotation of the electrodes is so adjusted that
the outer sides of the electrodes are moved synchronously
with the surfaces of the material for treatment.
By causing the treatment agent to flow at high speed over
the surface of the material, the resultant~gases, such for
example as hydrogen, oxygen and chlorine, are rapidly
dispersed.
In a preferred embodiment of the invention, the electrodes
also undertake the task of transporting and guiding the
material through the treatment installation, being brought
into direct contact with the surfaces of the material for
treatment. In this way it is possible to transport the
material through the installation by means of the rotated
electrodes.
'
By means of the measures mentioned, it is possible to
produce an extremely short and compact apparatus, as a
plurality of electrodes, generating the flow of current, can
be disposed directly adjacent to one another and lying
directly opposite the material for treatment. It is not
~~16519
necessary, as in installations of a previous type, to
dispose the electrodes lying opposite the material at a
large distance from one, another, in order to provide
guidance and transport devices, and if necessary flow
devices, therebetween. This also means that the current
density at the surface of the material fluctuates only to a
small degree, and does not drop to values near zero between
the electrodes.
This arrangement also offers the advantage that no apparatus
for transporting, guiding or providing flow on the material,
which could screen the field lines between anode and
cathode, need be disposed between the electrodes and the
material.
In a preferred embodiment, the treatment agent is conveyed
almost vertically towards the surfaces of the material. Thus
the treatment agent reaches the precise point at which the
current density on the material surface is highest, so that
at this point, with the greatest conversion of matter, an
effective renewal of the consumed treatment agent takes
place. In addition, the thickness of the diffusion layer is
in this way reduced, so that the conveyance of fresh
treatment agent on to the surface of the material is
likewise improved. If material for treatment is used which
~t7b579
12
contains holes, such for example as printed circuit boards,
both the outer sides of the printed circuit boards and the
walls of the holes are permanently supplied with fresh
treatment agent. Due to the vertical provision of flow on
the material, the treatment agent is also passed through the
holes under pressure, so that even in the case of fine holes
an effective liquid penetration is possible.
The treatment agent may in one alternative ~be conveyed on to
the surfaces of the material for treatment by conveying the
treatment agent out of openings in the hollow electrodes.
Another possible way is to introduce the treatment agent
into the openings in the electrodes by suction, so that it
is conveyed at high speed out of the surrounding space to
the points lying opposite the suction openings on the
surface of the material. In this case the material for
treatment and a suction electrode must be located inside the'
treatment agent, as otherwise it would not be possible to
cause an effective flow at the treatment point.
'
A combination of electrodes out of which treatment agent is
conveyed from suitable openings on to the surface of the
material (flow electrodes), and further electrodes into
which the treatment agent is sucked in through suitable
openings (suction electrodes), is a further preferred
13 ~ 1 X6579
embodiment of the invention. For example, penetration of the
holes in the material may be forced, by causing a flow by
means of flow electrodes disposed on one side of the
material, and suction extraction of the treatment agent,
which has passed through the holes in the material, by means
of suction electrodes disposed on the other side of the
material and lying opposite the flow electrodes. By means of
such an arrangement, even the finest holes may be
effectively penetrated by fresh treatment agent.
l0
In a preferred embodiment of the invention, the material for
treatment is grasped in a horizontal position and is
transported in a horizontal direction. Horizontal
installations suitable for this purpose are used in
particular to treat printed circuit boards.
The electrodes may be used both to metallise the material
for treatment and also to etch, preferably to demetallise
such material. A combination of both procedures is also
possible. For example, in metallising installations, the
material may be moved past a plurality of electrodes
disposed in sequence in the direction of transport and
alternately incorporated anodically or cathodically with
respect to the material, so that the material is
respectively metallised and partly demetallised again. So
~1 ~b5~~
that the material is provided with a metallic layer at the
end of the transport path, it is naturally necessary to
adjust the treatment conditions in such a way that the
quantity of precipitated metal is greater than the quantity
of metal removed again in the demetallising procedure.
An apparatus suitable for carrying out the method according
to the invention includes, in addition to the electrodes
polarisable as anodes or cathodes with respect to the
material for treatment, a means of supply of current for the
electrodes and the material, and a rotary drive means for
the electrodes. Also provided are means for supplying
treatment agent to the flow electrodes, and suitable
openings in the flow electrodes, out of which the treatment
agent flows, or means of supplying treatment agent to the
surfaces of the material for treatment, and further means
for extraction by suction of the treatment agent through
openings in the suction electrodes. The apparatus also
comprises means for linear movement of the material and of
the electrodes relative to one another, and a storage
container for the treatment agent. According to the
invention, means are provided for adjusting the speed and
direction of rotation of the electrodes in such a way that
the outer sides of the electrodes may be moved synchronously
15 ~ 1 l b519
with respect to the surfaces of the material for treatment,
i.e. no nwiping~ relative movement occurs.
According to a preferred embodiment of the invention, the
electrodes are in such form that they grasp the material for
treatment in a horizontal position, and transport it in a
horizontal direction in the treatment installation.
Particularly suitable are longitudinally-extended electrodes
disposed transversely to the direction of the path of
movement of the material, and which are preferably roller-
shaped.
In addition to a current supply and a rotary drive means,
the electrode has a rotatably mounted external electrode
tube with openings for feed or return of the treatment
agent. The openings in the electrode tube are provided over
the entire circumference. The electrode tube serves as a
preferably insoluble anode or cathode, and at the same time
as a transport and guide roller for the material for
treatment, 'when the electrode is in direct contact with the
material. The electrode tube is rotated by a rotary drive
means and transports the material through the installation.
In order to insulate the electrode tube from the surfaces of
the material, liquid- and ion-permeable, electrically non-
Ei~~Sl~
conductive spacer means are provided on the outer sides of
the electrodes. Between these and the electrode tube, in a
further preferred embodiment of the invention, there are
attached closely-fitting metallic or textile structures or
grids, which surround said electrode tube on all sides.
These serve to spread the jet of treatment agent emerging
from the openings in the electrode tube, or to suck the
treatment agent from a larger area on the surface of the
material into the interior of the electrodes.
Provided in the electrode tube is a non-rotatable
electrolyte tube in which, in one embodiment of the
invention, openings are located only on the surface line
opposite the surface of the material for treatment. In this
way a directed flow can be passed on to the surface of the
material. The electrolyte tube is connected to a flexible
pipe for feed or return of the treatment agent to or fxom
the treatment agent circuit and the storage container for
the treatment agent. In a further embodiment of the
invention, 'no electrolyte tube is provided in the electrode
tube. In order in this case to obtain a directed flow at the
point on the surface of the material directly opposite the
electrode, a shell-shaped covering is provided above the
electrode tube, which is open to the outside only opposite
~~16519
the surface of the material. There is a gap between the
covering and the electrode tube.
In order to be able simultaneously to process both sides of
a plate-shaped material for treatment, electrodes are
disposed on both sides. If the electrodes formed according
to the invention are involved here, both surfaces may be
treated simultaneously by the method according to the
invention. It is sufficient if only the electrodes on one
side of the material are provided with a rotary drive means,
while the electrodes opposite on the other side of the
material do not have their own drive means, but merely
absorb the pressure of the transport electrodes and are
entrained by frictional contact with the moving material for
treatment. Both on one side and on the other side of the
material, the electrodes may be disposed in a close sequence
adjacent to one another, so that only short treatment paths
are necessary for a predetermined treatment scope (for
example layer thickness of the precipitated metallic layer,
etching depth). The spaces between two successive electrodes
may be reduced to a small insulating intermediate space.
In the case of a horizontal installation for treating
printed circuit boards, roller-shaped electrodes are
disposed on both sides of the material. On one side,
X176519
preferably the lower side, the electrodes and counter-
rollers are caused to rotate via a drive means, while
counter-rollers and electrodes located on the upper side of
the material are caused to rotate by the material for
treatment.
The material passes through the installation between the
lower and upper rollers. The electrodes disposed on one side
may lie directly opposite those on the other side, or may be
offset thereto. For example, each driven electrode may have
lying opposite it a non-driven electrode of the same size,
or two electrodes with a smaller diameter may be offset to
the upper one. A non-driven electrode may also he offset to
a driven electrode of the same size. In the latter two
cases, the holes in the material for treatment are kept open
beneath or above the flow electrodes, in order to improve
the penetration of liquid.
A particularly preferable embodiment results when flow
electrodes'are provided on one side of the material, and
suction electrodes, lying opposite the latter, are disposed
on the other side of the material. This has the advantage
that the treatment agent is passed effectively even through
the finest holes in the material for treatment. In this case
no further transport means is necessary.on the side of the
CA 02176579 2001-12-14
- 19a -
printed circuit boards, said printed circuit boards
being displaced linearly and the electrodes being
rotatingly d:isplac;Eec.~, and treatment agent being supplied
to the partially l ollow electr_o<~es or removed by suction
therefrom, the treat:ment agent being conveyed from
apertures in the e:electrodes, which are situated opposite
the surfaces of true printed circuit boards, by means of
suitable pump pressure in the treat:ment agent circuit
substantially verv::ical_ly and appropriately towards the
surfaces of t..he prrir~Ated circuit boards or being removed
by suction therefx:om substantially vertically and
appropriately, so that the treatment agent is conveyed
under pressure thrc>ugh the holes in the printed circuit
boards, and the rotational speed ,and direction of t:he
electrodes (9) being so set that the outsides of the
electrodes are displaced synch ronously relative to the
surfaces of the printed circuit boards (5).
According to another aspect of the invention, there: is
provided an apparatus for the electrolytic metallization
or etching of pr_int~~d circuit boards, which are provided
with holes, comprising hollow, roller-like electrodes
(9) , which are polarisable a:> anodes or cathodes
relative to the printed circuit boards (5), a power
supply for the elecl~rodes and the printed circuit boards
as well as a rot:ary drive (11) for the electrodes, means
for supplying treatment agent (3) to the hollow
electrodes and apert=ores (18,47) i_n the electrodes, from
CA 02176579 2001-12-14
_ 1 C~ _
material opposite t=tze driven electrodes. All the
configurations described are also possible with suitable
counter-rollers di4>posed on the side of the material
opposite the flow c>r suction electrodes, said counter-
s rollers not being =in t=he form of flow or suction
electrodes.
In further embodiments, some of the rollers may be used
purely for transport. and provision of flow on the
material for treat:.ment, without being connected to the
current supply. These rollers may be of an electrically
non-conductive structure. Particularly for thin
conductor films, urhc;se transport and guidance through
the treat=ment i.nst:al.lation usually presents problems, a
combination of flc.~w and suction electrodes may be
provided together with transport and flow rollers not
connected to the current suppw~y, the flow and suction
electrodes being alternately opposite one another and
being disposed on both sides of 1=he material for
treatment.
According to one aspect of the invention, there is
provided a method for t:he eI_ectrolyt.ic metallization or
etching of printed circuit boards of high current
density, which are provided with holes, wherein the
printed circuit boards and roller-like electrodes are
brought =into contact with a t:reat:ment agent, and the
electrodes are elect.ric:ally polarised relative to the
CA 02176579 2001-12-14
- 19b -
which the treatment agent flows, or means for supplying
treatment agent to the surfaces of the printed cir~~uit
boards, and addit:'_c-_>~~nal means for removing by suction the
treatment agent though apertures in the electrodes, the
electrodes also being so configured or being provided
with such additional. means that the treatment agent can
be conveyed subst~:mt:ially vertically and appropriai=ely
to the surfaces of: the printed circuit boards or be
removed by suction therefrom, so that the treatment.
agent is conveyed under pressure through the holes in
the printed circuit: boards, means (11,12,13) for setting
such a rotational ~~peed and direction for the electrodes
that the outsides c>f the electrodes (9) are displaceable
synchronously relative to the surfaces of the print=ed
circuit boards, and storage cont<~.iners for the treatment
agent.
According to another aspect oi= the invention, there is
provided a method for electr_olytically metallizing or
etching perforated printed circuit= boards having hcles
therein with a selected current density, comprising the
steps of bringing painted circuit= boards and at least
one partly hollow electrode, with surface openings
therein, into contact with a treatment agent; polarizing
the at least one electrode electrica:Lly relative to the
printed circuit bea.fds; moving the printed circuit
boards in a linear path of travel at a preset speed;
moving the at least one electrode in a rotating fashion
CA 02176579 2001-12-14
- 19c -
with its per:ipherv;~ at a tangential speed equal to .said
predetermined speec't; supplying the treatment agent
through the at le<:~st, one partly hoI_low electrode;
wherein the step of supplying treatment agent includes
passing the treatment agent under relative pressure
through the openirugs in the at Least one electrode while
printed circuit boards are moved opposite the openings,
so that t=he direction of flow of: the treatment agent is
only transverse tc;~ the path of t.ravel of the printed
circuit boards rei.ative to holes of the printed circuit
boards; and wherein the step of passing the treatment
agent through the a.t: least one e:Lectrode includes
suctioning the treatment agent. through the at least. one
electrode.
According to a further aspect of t=he invention, there is
provided an apparatus for elec:trolytically metallizing
or etching perforated printed circuit boards provided
with holes, compris:Lng at lea~;t one hollow electrode
adapted to be polar=Lzed as anode or cathode relative to
the printed circuit boards; a power supply for the at
least one electrode and the printed circuit boards;
means for rotationa7_:Ly moving the at least one
electrode; means fot- supplying treatment agent to one of
the hollow at lease= one electrode with further means for
discharging treatment. agent from the at least one
electrode to the openings in the printed circuit boards;
and the surfaces oa t=he printed circuit boards with
CA 02176579 2001-12-14
- 19d -
further means for Eextracting the treatment agent b:y
suction from the printed circuit boards through opf?nings
in the at least ozue electrode; means for moving the
printed circuit bc:>ards and the at least one electrode in
a linear path of t::ravel while the at least. one electrode
is moved rotationally, with said movements of said at
least one electrode and printed circuit boards being
synchronous to eac::h other; anc~ storage container means
for the treatment agent; wherein the at least one
electrode is generally cy.lindric<~:11y configured and
disposed along the path of trave:L of the printed circuit
boards and in transverse relat:ion thereto, and with the
at least one electrode having openings therein and
including a flexible tr_eat.ment agent flow line connected
to the at Least one electrode, and with a cover
enveloping the at lE~ast one el.ectr_ode; said cover having
a treatment agent passage open only towards the path of
travel of the printed circuit boards.
According to another aspect of the :invention, there is
provided an apparat~.zs for electro.lytically metallizing
or etching perforai~Eed printed circuit boards provided
with holes, compri,s:i.ng at least one hollow electrode
adapted to be pola:r_:i.zed as anode or cathode relative to
the printed c_~rcuit_ boards; a power supply for the <~t
least one electrode <~~nd the printed circuit boards;
means for rotational_l.y moving the at. least one
electrode; means fcar supplying treatment agent to one of
CA 02176579 2001-12-14
- 19e -
the hollow at leawt one electrode with further means for
discharging ~~reatment agent from. the at least one
electrode to the ~:>~_senings in the printed circuit boards;
and the surfaces ~:o the printed circuit boards with
further means for extracting the treatment agent by
suction from the ~:>r:inted circuit boards through openings
in the at. least orie electrode; means for moving the
printed circuit boards and thf= at least one electrode in
a linear path of gravel while the at least one electrode
is moved rotationally, with said movements of said at
least one elect.:rode~ and printed c~.ircuit boards being
synchronous to each other; and storage container means
for the treatment went; and wherein the at least one
electrode carries a non-rotatable electrolyte tube
situated in the at least one electrode, with electrolyte
passway means dispo:~ed to face a surface of a printed
circuit board.
According to another aspect of the invention, there is
provided an apparatus for electrolytically metallizing
or etching pe_rforatied printed ci:rc;uit boards provided
with holes, compris.i.ng at least cJ~ne hollow electrode
adapted to be pola.ri.zed as anode cr cathode relative to
the printed c:ircui~= boards; a power supply for the at
least one electrode and the prinl~ed circuit boards;
means for rotation<.~l:l_y moving the at least one
electrode; means foo supplying treatment agent to one of
the hollow at least: c>ne electrode with further means for
CA 02176579 2001-12-14
- 19f -
discharging treatmfent agent from the at least one
electrode to the o~_senings in the printed circuit boards;
and the surfaces c:>'_ the printed circuit: boards with
further means for extracting the treatment agent by
suction from the ~:>rinted circuit boards through openings
in the at least orie electrode; means for moving the
printed circuit bc:~ards and the at least one electrode in
a linear path of t:rave.l_ while the at least one electrode
is moved rotationally, with said movements of said at
least one electrode and printed circuit boards being
synchronous to each other; and st=orage container means
for the treatment agent; and wherein the at least one
electrode comprises a f_Low electrode, with means for
conveying the treatment agent through the holes in the
printed circuit boards on one side of the pad of travel
of printed circuit k>oards; with at: least one suction
electrode disposed ciirec:tly opposite the at least one
flow electrode, into which the treatment- agent passing
through t=he holes o:f- the printed circuit boards is
sucked, on the other side of the path of travel of
printed circuit boards.
According to yet another aspect of the invention, there
is provided a method for electrol.ytically metallizing or
etching perforated printed circuit boards having holes
therein with a selEcted current density, comprising the
steps of bringing ~:rinted circuit boards and at leap>t
one partly hollow electrode, with surface openings
CA 02176579 2001-12-14
_ 1 c~ g.
therein, into contact with a treatment agent; polarizing
the at least one el.ect:rode electrically relative to the
printed circuit bc:>ards; moving the printed circuit
boards in a linear- path of trave_L at a preset speed;
moving the at leat;t one electrode in a rotating fa~;hion
with its periphery at a tangential speed equal to said
predetermined speed; supplying the treatment agent
through the at least one partly hollow electrode; a.nd
wherein the step of supplying treatment agent includes
passing the treatment agent under relative pressure
through the openings in the ate least one electrode while
printed circuit boards are moved opposite the openings,
so that the direct.i~~~n of flow of the treatment agent is
only transverse to the path of travel of the printed
circuit boards relative to holes of the printed circuit
boards; wherein there are a plurality of electrodes
provided, at least cane on each sp_de of the path of
travel of printed circuit bo<~rds, and wherein treatment
agent emerges though holes z.n the printed circuit boards
in a forced manner by means of po:~itive pressure
treatment agent flow from at .east one electrode on one
side of the path cf travel- of printed circuit boards,
and wherein treatment agent is e~;tracted by suction
through openings in at least one suction electrode
situated on the opposite side of t;he path of travel of
printed circuit boao~ds.
CA 02176579 2001-12-14
- 19 h. -
According to a further aspect of the invention, there is
provided a method for electrolyt:ically metallizing or
etching perforated printed circuit boards having holes
therein with a selected current density, comprising the
steps of bringing printed c=ire:ui~ boards and at least
one partly hollow electrode, with surface openings
therein, into contact with a treatment agent; polarizing
the at least one electrode e:Lectr_ically relative to the
printed circuit boards; moving the printed circuit
boards in a linear oath of travel at a preset speed;
moving the at least one electrode in a rotating fashion
with its periphery ,~t a tangential speed equal to said
predetermined speed; supplying the treatment agent
through the at least one part~.y hollow electrode; and
wherein the step of supplying treatment agent includes
passing the treatment agent under relative pressure
through the openirv.g~ in th.e at: least one electrode while
printed circuit boards are moved opposite the openings,
so that the direction of flow of t;he treatment agent is
only transverse to 1=~~e path of travel of the printed
circuit boards relative to holes of the printed circuit
boards; wherein the step of supplying a treatment agent
comprises supplying the printed circuit boards with a
metallizing solution as the treatment agent, wherein
there are provided <~ plurality of: electrodes, wherein
the plurality ofelectrodes are ~~li_sposed one behind the
other along the path of travel of printed circuit
boards, wherein the printed c:ircui_t boards are moved
CA 02176579 2004-08-24
- 19i -
past the plurality of electrodes, wherein the electrodes
are alternately polarized as anode or cathode with
respect to the printed circuit boards, and wherein the
printed circuit boards in their movement along their
path of travel past the electrodes are respectively
metallized and partly demetallized.
Preferably, the step of passing the treatment agent
through the at least one electrode comprises delivering
the treatment agent under positive pressure to the
printed circuit boards via the openings in at least one
electrode.
Preferably, there are a plurality of electrodes
provided, at least one on each side of the path of
travel of printed circuit boards, and wherein treatment
agent emerges though holes in the printed circuit boards
in a forced manner by means of positive pressure
treatment agent flow from at least one electrode on one
side of the path of travel of printed circuit boards,
and wherein treatment agent is extracted by suction
through openings in at least one suction electrode
situated on the opposite side of the path of travel of
printed circuit boards.
Preferably, the apparatus of the present invention is
characterized by a sleeve enveloping the at least one
CA 02176579 2004-08-24
- 19~ -
electrode on all sides and in firm contact therewith;
said sleeve being one of:
(i) a metallic construction;
(ii) a textile fabric construction; and
(iii) a screen construction.
The invention is illustrated by way of examples of
apparatus according to the invention, with reference to
the diagrammatic Figures 1 to 11. Shown are:
Fig. 1: a longitudinal section through a flow
electrode with an axially-disposed electrolyte
tube;
20 ~ 176579
Fig. 2: a cross-section through the flow electrode in Fig.
1;
Fig. 3: a longitudinal section through a flow electrode
with a non-axial electrolyte tube;
Fig. 4: a cross-section through the flow electrode in Fig.
3;
Fig. 5: a longitudinal section through a one-piece flow
electrode;
Fig. 6: a cross-section through the flow~electrode in Fig.
5;
Fig. 7: an arrangement of electrodes and counter-rollers
along the transport track of the material for
treatment;
Fig. 8: an arrangement of electrodes and counter-rollers
offset thereto, along the transport track of the
material for treatment;
Fig. 9: an arrangement of pairs of electrodes and of
counter-rollers along the transport track of the
material for treatment;
Fig. i0: an arrangement of flow electrodes and suction
electrodes offset thereto, along the transport
track of the material for treatment;
Fig. 11: an electrical circuit,arrangement for an
electrolytic etching installation.
21 ~ 116519
In the Figures, a printed circuit board provided with holes
is illustrated as a material for treatment.
Figure 1 shows a flow electrode 9 in direct contact with
the material for treatment 5, and a counter-roller 10,
opposite said electrode 9, and not serving ~to supply
treatment agent to the surface of the material or to provide
current. This arrangement for example may be incorporated in
a horizontal continuous-flow installation. In order to
simplify the illustration, the working area in which the
printed circuit board is located, is shown in abbreviated
form.
The housing of the continuous-flow installation is indicated'
by 1. In the working container 2 there is a liquid treatment
agent 3, for example a metallising or etching solution. When
a flow electrode is used, the level 4 of the liquid
treatment agent can be below the plane of the material for
treatment. If on the other hand suction electrodes are used,
the level of the treatment agent must be at such a height
that it is above in the suction opening or the material, so
that intake of air is avoided. The space 6 serves as an
2l1b519
22
overflow compartment for the liquid treatment agent.
Therefore no complex seals preventing the outflow of liquid
are necessary in this area (openings 7).
The material for treatment is grasped laterally by a
plurality of clamps 8 and provided with electrical contact.
A plurality.of clamps are distributed long the transport
track, vertically to the plane of the drawing. The clamps
move in the direction of the transport path at a speed with
is at the same time the transport speed for the material.
The circumferential speed of the flow electrode and of its
counter-roller are equal, so that they roll along the
material for treatment. Slippage is avoided between the
~.5 surface of the material and the roller surfaces. In this way
damage to the surface cannot occur. Identical speeds for the
individual arrangements are achieved by synchronisation of
the drive system lI, not shown in detail, of the counter-
roller, with the drive system for the clamps, and by
transmission of the rotation of the counter-rollers via the
gearwheels 12 and 13 to the flow electrode. The transmission
ratio of the gearwheels is adapted to the diameters of the
flow electrode and of the counter-roller. Particularly in
the case of counter-rollers with smaller diameters, the
drive system 11 for the rollers may also act on the
~ ~ ~sST~
23
gearwheel 13, and be transmitted from this point to the
gearwheel 12.
The flow electrode comprises the electrolyte tube 14, which
is secured in its mount against rotation, and a rotating
electrode tube 15. The electrolyte tube has, on the surface
line facing_the material for treatment, openings 16. These
may be slots, separated from one another by webs 17. Holes
are also suitable. Electrolyte flows through these openings
out of the electrolyte tube to the treatment point on the
surface of the material. In the case of a suction electrode,
the liquid treatment agent flows from the treatment point
into the electrolyte tube.
The quantity of exchangeable treatment agent and its flow
speed can be altered within wide limits by the size of the
openings 16, and by the pump pressure in the circuit of
treatment agent. The high treatment agent speeds necessary
for the application of high current densities are thus
easily achievable.
A sufficient quantity of fresh treatment agent can be
supplied to the point on the surface of the material at
which the greatest current density is found. An advantage is
that the treatment agent is supplied almost vertically on to
24 2 ~ ~65~'9
the flat surface of the material for treatment, so that the
holes in the material are penetrated by a flow of fresh
treatment agent.
The electrode tube 15 is rotatably mounted on the
electrolyte tube 14. The preferably metallic electrode tube
is provided, at least in the working area, over its entire
circumference with apertures 18. Therefore treatment agent
flows through each of the apertures, which. are located
precisely in front of the openings 16 in the electrolyte
tube, to the material for treatment, or is sucked by the
latter into the electrode. This flow of liquid may be passed
through a metallic or textile structure or grid 19 through
the electrode tube also into the surface areas 20, which are
located not directly in front of the apertures 18. The
covering 19 also generates a uniformly electrically
conductive electrode surface, and equalises the irregular
electrical field line distribution of the electrode surface
provided with apertures with the surface of the material for
treatment, 'as the diameter of the apertures 18 is
considerably larger than the mesh width of the structure 19.
This is particularly important, is the material, as in the
arrangement shown, is disposed at a very small interval from
the electrically conductive electrode surface, and is being
electrolytically treated with high current densities. The
25 2176579
treatment agent is also uniformly distributed in the region
of the treatment point by the rotation of the electrode
tube, together with the weave structure located above it.
In order to avoid a short-circuit between the electrode and
the surface of the material for treatment, an insulating
means 21 is provided on the electrode surface. As this
latter does not only partly cover the electrode surface
partially, it must be liquid- and ion-permeable. For
example, ceramic particles may be applied by plasma coating
to the outermost raised portions of the weave structure 19.
These are extremely thin, adherent and abrasion-resistant,
leading to a long Life duration. This additional covering is
in direct contact with the surface of the material for
treatment. Thus direct contact between the metallic surfaces
of the electrode and the surfaces of the material is
avoided. By means of the direct contact and rotary
propulsion of the electrode, and the linear movement of the
clamps 8, the material. for treatment is transported through
the treatment installation.
As further insulating means 21, plastics rings may be
disposed above the metallic structure, with or without a
wear-resistant ceramic coating. Combinations of these
insulating means are also possible.
26 ~ j 7b519
The metal portions of the electrode are insoluble in the
treatment agent. Special steel and titanium, with or without
a coating of noble metals or their oxides, may be considered
as materials.
For supply of current, the electrode is provided electrical
contact; it is sufficient to connect only the electrode tube
and/or the metallic mesh to the current supply (not shown).
with the exception of the current supply, the electrode tube
and if necessary the metallic mesh over the electrode tube,
all other parts of the electrode may be made from
electrically non-conductive material. For current supply,
the electrically conductive parts are electrically
conductively connected to a slide ring 22. Sliding on the
slide ring is a spring-loaded contact 23, which produces the
connection via an electrical cable 24 for supply of current.
The counter-pole of this current supply is connected by the
cable 25 and sliding contacts (not shown) to the clamps 8,
by means of'which contact is established with the material
for treatment. During electrolytic metallising, the material
is incorporated as cathode, and the electrode as anode.
During electrolytic etching, the material is the anode, and
the electrode the cathode.
X176579
27
Normally, pieces of the material for treatment having
differing thicknesses are processed. Therefore the space
between the electrode surface and the counter-roller must be
variable. The counter-roller is stationarily mounted, and
adapted to the vertical position of the clamps 8. The same
applies to electrodes disposed beneath the material for
treatment. The receiving means 26 and the sliding bearing 27
may execute a small upward lifting movement against the
pressure of springs. For this purpose the electrode is
secured against rotation in slot-shaped guides 28 and 29.
The gearwheels Z2 and 13 have a tooth configuration which
permits this lifting movement without disengaging. The
contact 23 also can execute this lifting movement against
spring force. Finally, the connection 30 for the feed or
return of treatment agent is of such a flexible construction
that the lifting movement of the electrode is not prevented
from compensating for the thickness of the material.
The counter-roller IO is preferably made of a non-conductive
material. I't may however be made from a metal with a non-
conductive covering 31. The covering 31 is preferably
liquid-permeable, in order not to hinder penetration by the
flow through the holes in the material for treatment. A
profiling on the surface of the counter-roller acts in a
similar way.
2176579
28
Figure 2 shows an electrode in cross-section along the
section line A - B of Figure 1. It will be seen how the
bearing 27 is non-rotatably secured in the guide 29 in order
to compensate for the lifting movement. The area of highest
current density between the electrode and the surface of the
material lies on the surface line 32 of the electrode. To
the right and left thereof, the current density decreases
rapidly, due to the increase in the anode/cathode interval.
Figure 3 shows a further embodiment, preferably for
electrodes with large external diameters. In this case the
electrolyte tube 33 is disposed eccentrically between the
axis 34 and the electrode tube 35 in the area facing the
material for treatment 5. The electrolyte tube is supported
at points 37 towards the axis. The electrode tube slides on
the bearing point 39 on the stationary bearing portion 38.
At the bearing point 40, the axis is slidingly guided. The
bearing portion is secured by pins 41 and secured against
rotation. '
The wall 42 contains slots. It permits the bearing shell 43
to execute a lifting movement to compensate for the
thickness of the material. The other constructional members
29 ~ ~ 16579
correspond with those in Figure 1. Therefore there will be
no description of further details.
Figure 4 shows the embodiment in Figure 3 at the section C -
D. The pins 41 are guided in the elongate slots 44, enabling
the electrode to lift in order to compensate for the
thickness of the material for treatment. The material is
passed towards or away from the electrode by a movable tube
45. In the Figure, the tube is guided upwards, by way of
example.
Figure 5 shows a one-piece electrode. This consists only of
an electrode tube 46 with the openings 47 provided over the
entire circumference in the working area. The electrode tube
is rotatably mounted in the bearing points 48 and 49. The
stationary, yet vertically-movable connection 66 for the
material opens into the rotating electrode tube 46. The
treatment agent is introduced into, or extracted from, the
electrode through the liquid-tight rotary coupling 50, 51;
this rotary coupling also serves to seal off the guide
means of the material for treatment from the exterior.
The treatment agent is prevented from flowing out in all
directions from the openings distributed over the
circumference of the electrode tube by a shell-shaped cover
216579
52 attached above the electrode tube. A narrow gap is left
free between the two parts in order to prevent the electrode
from rubbing on the cover as it rotates. The cover is
secured on the bearing part 53, and also executes its
lifting movements in order to compensate for the differing
thicknesses of the material for treatment. At a point
aligned towards the treatment point, the cover 52 is open.
In this way the treatment agent can be conveyed in a
directed manner on to the treatment point 'on the surface of
the material for treatment, or can be extracted therefrom by
suction. This constructive solution may be used with
particular advantage in the case of narrow working areas,
i.e. in the case of short electrodes. The other constructive
members have already been described with reference to Figure
1.
Figure 6 shows the arrangement shown in Figure 5, in cross-
section along the line E - F. The cover 52 prevents exit or
entry of the treatment agent over the main portion of the
circumference of the electrode. The smaller the gap 54, the
more effective the flow of agent aver the surface of the
material.
31 ~ ~ 76579
Figures 7 to 10 show various arrangements of electrodes and
counter-rollers along the transport track of the material
for treatment in horizontal continuous-flow installations.
In general plate-shaped material for treatment,.such for
example as printed circuit boards, are to be treated in an
identical manner on both sides. Therefore the arrangements
on the upper and lower sides of the material are identical
in structure. The arrows in the drawing show the flow
direction of the treatment agent. The extended arrows 55
apply to flow electrodes from which the treatment agent is
conveyed on to the surface of the material and the holes
therein; the ~hollow~ arrows 56 apply to suction electrodes
by means of which the treatment agent is extracted by
suction from the surfaces of the material, so that a flow of
treatment agent arises to the treatment point between the
electrode and the surface of the material for treatment.
In Figure 7, the electrodes 9 and their counter-rollers 10
are disposed to lie precisely opposite one another. The
electrodes maintain a fixed interval relative to the surface
of the material. In this case it is unnecessary for these
and the lower counter-rollers to execute a lifting movement.
The lifting movement to compensate for the thickness of the
material is, however, provided for the upper counter-
32 2116519
rollers. It is appropriate if the counter-rollers are
provided with a liquid-permeable surface 57. In Figure 8,
the counter-rollers are, offset to the electrodes rolling
along the material for treatment in such a way that, in the
area 58 at the contact point between the electrode and the
surface of the material, treatment agent can flow unhindered
out of the electrode or into it. This offsetting also
reinforces the penetration of the holes. Therefore a liquid-
permeable surface of the counter-rollers can be omitted
here.
In the arrangement according to Figure 9, the area 58 is
kept free by the use of two counter-rollers 10 for each
electrode 9. This arrangement has the advantage that thin
treatment agent, such for example as conductor films, may be
efficiently passed through the treatment installation.
In the arrangement shown in Figure 10, no counter-rollers
are provided. In order to provide better penetration of the
holes, a flow electrode and a suction electrode in each case
i
are disposed opposite one another. On one side, flow and
suction electrodes alternate along the transport track. This
arrangement permits an extremely close sequence of
electrodes, so that the treatment installation can be kept
extremely short.
33 ~ ~ 76579
If the method according to the invention of electrolytically
etching, for example, metallic surfaces, the metal removed
from the material for treatment is deposited on the metal
parts, connected to the current supply, of the electrodes.
It must be continuously or intermittently removed from these
points.
Figure 11 shows an electrical circuit arrangement suitable
for this purpose. The numerals 59 and 60 indicate the
current supply for the etching process on the upper and
lower sides of the material for treatment 5. The electrodes
9 are provided with electrical contact by the carbon brushes
61 and slide rings 22.
Further sources of current supply 62 and 63 serve to remove
the metal deposited on the electrodes, and to deposit it on
the auxiliary cathodes 64 and 65, which if necessary can be
exchanged. Provision of electrical contact between the
sources of'current 62 and 63 and the electrodes is effected
by the same contacts as those of the current supply 59 and
60.
The supplementary supply of electrolyte solution with the
metal ions to be separated during electrolytic metallisation
5
25
~llb5l9
with insoluble anodes is undertaken according to known
methods inside or outside the electrolytic cell.
