U.S. patent application number 13/321631 was filed with the patent office on 2012-03-15 for method and device for the electrolytic treatment of high-resistance layers.
This patent application is currently assigned to RENA GMBH. Invention is credited to Egon Huebel.
Application Number | 20120061245 13/321631 |
Document ID | / |
Family ID | 42733505 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120061245 |
Kind Code |
A1 |
Huebel; Egon |
March 15, 2012 |
METHOD AND DEVICE FOR THE ELECTROLYTIC TREATMENT OF HIGH-RESISTANCE
LAYERS
Abstract
A method and a device for electroplating and electrolytically
etching plate-shaped or strip-shaped material in continuous
installations or bath installations having rotating transport and
contact structures along the conveyor belt. The current is fed to
the material in the center, i.e. in the useful zone, thereby
obtaining a layer thickness distribution which is at least as good
as when the current is supplied from both edges. The invention
further allows material of any formats of width and different
contours to be electrolytically treated in any order.
Inventors: |
Huebel; Egon; (Feucht,
DE) |
Assignee: |
RENA GMBH
Guetenbach
DE
|
Family ID: |
42733505 |
Appl. No.: |
13/321631 |
Filed: |
May 18, 2010 |
PCT Filed: |
May 18, 2010 |
PCT NO: |
PCT/DE2010/000596 |
371 Date: |
November 21, 2011 |
Current U.S.
Class: |
205/138 ;
204/275.1; 205/640 |
Current CPC
Class: |
C25D 7/0692 20130101;
C25D 17/00 20130101; C25D 7/0621 20130101; C25D 17/005
20130101 |
Class at
Publication: |
205/138 ;
205/640; 204/275.1 |
International
Class: |
C25D 17/06 20060101
C25D017/06; C25F 3/02 20060101 C25F003/02; C25F 7/00 20060101
C25F007/00; C25D 7/06 20060101 C25D007/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2009 |
DE |
10 2009 023 763.1 |
Claims
1. A method for the electroplating or electrolytic etching of
plate-shaped or strip-shaped material (1) in continuously operating
plant or strip plant for passing material from one roll to the
next, having transport and contact means (2) along a transport
path, characterised in that the material is supplied with the
electrolytic current by means of contacts (3) on the transport and
contact means (2) by way of at least one contact track (15) which
runs inside the useful area (17) of the material (1).
2. A method according to claim 1, characterised in that electrical
contact is made and the electrolytic current is supplied to the
material transversely to the direction of transport, in the centre
zone thereof.
3. A method according to either of claims 1 and 2, characterised in
that material (1) having different contours and/or different
dimensions is brought into electrical contact in any desired
sequence in the continuously operating plant as a result of the
electrical contact made by means of at least one contact track (15)
inside the useful area (17).
4. A method according to one of claims 1 to 3, characterised in
that with structural electroplating or structural etching the
electrolytic current is supplied by way of at least one resist-free
contact track (15).
5. A method according to one of claims 1 to 4, characterised in
that the electrolytic current is supplied by way of at least one
contact track (15) which is kept free within the layout of end
products (14) on the material or by way of at least one contact
track (15) which extends over the end products (14) in the layout
of the material.
6. A method according to one of claims 1 to 5, characterised in
that an individual rectifier (8) associated with each contact (3)
supplies it with electrolytic current, or a common rectifier (8)
supplies a plurality of contacts (3) with electrolytic current.
7. A device for the electroplating or electrolytic etching of
plate-shaped or strip-shaped material in continuously operating
plant or strip plant, having transport and contact means (2) along
the transport path, using the method according to claim 1,
characterised in that, transversely as seen in the direction of
transport, the position of the at least one contact (3) on each
transport and contact means (2) and the at least one corresponding
contact track (15) on the material (1) are located inside the
useful area (17) of the material (1).
8. A device according to claim 7, characterised in that,
transversely as seen in the direction of transport, the position of
the contact (3) on each transport and contact means (2) and the
corresponding contact track (15) on the material (1) are located
approximately or precisely in the centre of the transport path.
9. A device according to either of claims 7 and 8, characterised in
that the usable zone of the material (1) for the end products (14)
is also located in the zone of the contact track(s) (15).
Description
[0001] The invention relates to the electrolytic treatment, in
particular electroplating and etching, of electrically conductive
layers on preferably planar material. It is particularly suitable
for electroplating substrates such as printed circuit boards and
conductive foils as portions in continuously operating plant or
strips of metal or metallized synthetic films in plant for passing
material from one roll to the next. Here, the intention is to apply
as high a current density as possible to deposit or etch a metal
layer of uniform thickness over the entire extent of the surface of
the material even if the base layer is very thin and hence has high
resistance. Tried-and-tested solutions for this already exist.
[0002] It is the object of the invention to describe making
electrical contact in planar material for electroplating or for
electrolytic etching in continuously operating plant and in plant
for treating material which is passed from one roll to the next. In
particular, the preferably rotating electrical contact-making means
of the material is also to be suitable for material having
differing sizes transversely to the direction of transport and
having thin base layers, for uniform electrolytic treatment. In
this case, by comparison with the prior art a high level of
complexity in the plant is to be avoided.
[0003] The object is achieved by the method according to claim 1
and the device according to claim 7. The subclaims describe
advantageous embodiments of the invention.
[0004] Continuously operating plant and plant that produces
material passed from one roll to the next is suitable preferably
for the manufacture of mass-produced products, because it has
little flexibility in respect of the sequence of processes. These
products were called end products above. These are usually small
and miniature printed circuit boards or conductive foils for, for
example, BGAs (ball grid arrays), RFIDs (radio frequency
identification units), MP3 players, memory sticks or indeed for
relatively large printed circuit boards for, for example, mobile
telephones, PCs and the like. On the one hand the invention makes
use of the increasing miniaturisation of these electronic end
products to optimize the layout of the material, and on the other
it supports the precision conductor technology required for
miniaturisation, as a result of the planar electroplating of the
thin base layers necessary therefor. After they have been finished
in the continuously operating plant, and where appropriate further
plant, the end products are separated from the material for their
respective use.
[0005] The material to be treated is in this case for example a
large-scale printed circuit board or conductive foil. In practice,
these large-scale printed circuit boards or conductive foils are
also called panels. They have a useful and a non-useful zone. The
end products are located in the area to be used. By contrast, the
edge zones, including the contact track or tracks located thereon,
are typically not usable for the end products. In the layout of the
printed circuit boards, a large or very large number of, usually,
the same end products are arranged in the area to be used. There
are always a plurality of ways of arranging the many end products
on the printed circuit board or panel. The present invention makes
use of this fact. It takes as a starting point the fact that the
end products are arranged on the panel such that a contact track is
formed on the material and kept free approximately or precisely in
the centre, transversely as seen in the direction of transport.
Similarly approximately or precisely in the centre of the transport
track of the continuously operating plant or strip plant, that is
to say also transversely as seen in the direction of transport,
there is in each case an electrical contact, preferably rotating,
on each of the many contact rolls or contact wheels arranged along
the transport path, which may equally be the transport rolls,
transport wheels or transport means.
[0006] The invention is described in particular by way of the
example of electroplating, in particular that of printed circuit
boards for metalizing the entire surface and providing
uninterrupted contact and for constructing the conductor pattern,
which is structured using resist, for example. However, the
invention is also suitable without restrictions for electrolytic
etching and other electrolytic processes.
[0007] According to the invention, the material is supplied with
the electrical or electrolytic current required for electroplating,
preferably by means of a contact track in the centre. In this case,
the effect on the distribution of layer thickness transversely as
seen in the direction of transport is at least as advantageous
as--or better than--in the prior art with optimally uniform supply
from the two edges. The two oblique planes which are formed
according to the invention face in the opposite direction, however.
The maximum layer thickness is once again achieved in the contact
zone, that is to say in the centre of the material. The differences
in layer thickness in the oblique planes transversely as seen in
the direction of transport are, according to the invention, only
approximately a quarter of the difference achieved when the
electroplating current is supplied from only one edge, regardless
of the contact resistances effective at the particular moment.
[0008] The making of electrical contact in the region of the centre
of the material, that is to say in the useful zone, has the
following substantial advantages by comparison with the prior art:
[0009] The method is suitable for different dimensions of the
material, transversely as seen in the direction of transport,
without re-tooling the plant. For this reason, material having
different dimensions and different layouts can be introduced into
the plant and electroplated in any desired sequence. [0010] Because
the oblique plane is inclined from the centre towards the two
edges, the bone effect at these edges is not disruptive but in some
cases has a useful effect. The layer which is thinner at the edges
is advantageously made thicker by the "bone formation" laid down by
deposition, as a result of which the difference in the layer
thickness from the edge to the centre becomes even smaller than in
the case of supply from both edges, as in the prior art. [0011] The
transport and contact rolls require only one contact. This means
that the technical complexity is reduced. [0012] The electrolytic
current is spread over the material, starting from the centre track
and in all cases reproducibly, to give parts in size in the
direction of the two far edges. For this reason, the
above-mentioned quartering in size of the oblique plane is always
precisely maintained, even in the event of uncontrollable transfer
resistances at the contacts. [0013] Only one contact track is
required on the material, that is to say there is less loss of
useful zone than when there is supply from both edges, with as good
as or better distribution of layer thickness. [0014] The size of
the useful zone can be adapted precisely to the size of the end
products to be arranged thereon, as a result of which an
unnecessarily large amount of waste base material can be avoided.
[0015] The current density can be selected individually, depending
on the requirements. [0016] Even in the event of sporadically
inadequate rotating contact means demetallisation, it is not
possible for there to be different diameters on the two sides,
which would carry the boards away from the track. [0017] Even if,
for unpredictable reasons, the boards did leave the track, the
fault described, requiring unscheduled maintenance of the plant,
would not occur. In the event of leaving the track, electrical
contact with the printed circuit board is maintained. Thus,
unreliably intensive metallisation or damage to the contacts cannot
occur. In the worst case, the quality of end products of the
printed circuit board concerned which are arranged on one side,
next to the contact track, would be impaired. [0018] Where very
reliable electrical contact is made, damage to the surface of the
material on which the contacts roll can be avoided. In this case,
positioning of the contact track on the material and its position
in relation to the rotating contacts are in no way critical,
because the contacts can go into the zone of the end products.
[0019] The width of the contact track can be selected to be smaller
than that in the prior art because the safety margin is not
necessary, which means that the useful zone of the material is made
bigger. [0020] In particular in the case of small end products, it
is possible to dispense entirely with a contact track as a separate
area on the material. The contact track extends in the zone of the
centre of the material, as desired, over some of the end products,
which where applicable are later subjected to a sorting operation
and rejected. In this very advantageous method, the alignment
station which in the prior art is always required upstream of the
electroplating plant can be dispensed with. In particular with thin
and hence very flexible material, alignment stations of this kind
are technically very complex. In this case, according to the
invention the material runs through the continuously operating
plant, unaligned in the lateral direction. Similar unaligned
transport of the material is already performed in wet-chemical
treatment stations and rinsing stations in known manner, both
upstream and downstream of the electroplating plant. [0021] The
format of the material may differ from the conventional rectangular
shape. For example, it may be triangular, round or oval. [0022] As
an extension to the invention, it is also possible to supply the
electroplating current in the useful zone of the material by means
of a plurality of contact tracks which are offset transversely as
seen in the direction of transport. Even when there are two contact
tracks in the useful zone, the local differences in the cell
voltages may be reduced to a sixteenth of that with a one-sided
supply according to the prior art.
[0023] The invention will be further described below with reference
to the schematic FIGS. 1 to 3, which are not to scale.
[0024] FIG. 1a shows, in cross section, a continuously operating
plant or a strip plant, according to the prior art.
[0025] FIG. 1b shows, on a much larger scale, the profile of the
layer thickness to be achieved with the arrangement according to
FIG. 1a.
[0026] FIG. 2a shows, in cross section, a continuously operating
plant or a strip plant, according to the present invention.
[0027] FIG. 2b shows the profile of the layer thickness to be
achieved according to the invention, transversely as seen in the
direction of transport, again on a much larger scale.
[0028] FIG. 3 shows, in plan view, a material having a large number
of end products arranged thereon.
[0029] In FIG. 1a, the material 1 is transported perpendicularly
out of the plane of the drawing. For this purpose there serve upper
and lower transport and contact means 2 which are driven in
rotation. Arranged on the elongate contact means 2 there are, at
both ends, annular or disc-shaped electrical contacts 3. These
contacts 3 roll on the upper and lower sides of the material 1, on
the base layers 4 thereof. During this, the material 1 is
transported and at the same time makes electrical contact. The
electrical contact is made at the two edge zones 5 of the material.
On the upper side and lower side there are soluble or insoluble
anodes 6. Together with the respective anodes 6, the base layer 4,
that is to say the surface of the material 1, forms a respective
electrolytic cell, located in the electrolyte 7. In each case at
least one electroplating current source 8, taking the form of a
direct current source or a unipolar or bipolar pulsed current
source, serves to supply the electrolytic cells with current. The
electrical current is transmitted by way of rotary contacts 9 or
sliding contacts 9 to the rotating transport and contact means 2
and from there to the contacts 3. The width of the material 1
transversely to the direction of transport must be dimensioned such
that the contacts 3 can each roll on a sufficiently wide contact
track at the edges of the material 1. For this reason, only
material 1 of a very particular width can be handled in an existing
plant according to the prior art.
[0030] FIG. 1b shows the profile of the layer thickness on the
material 1 transversely to the direction of transport, as results
from an arrangement according to FIG. 1a. The profile of the
oblique planes, which are illustrated on a very large scale, is
typical. The minimum layer thickness of the electroplated layer 10
occurs in the zone at the centre of the material 1. The effective
cell voltage between the cathodic surface of the material 1 and the
anode 6 is smallest in this zone, because of the voltage drop in
the base layer 4. Accordingly, the local current density and hence
the thickness of the deposited layer are also smallest here. In
this arrangement, there are consequently the following dependent
relationships:
[0031] The difference in the amount deposited between the edge zone
5 and the centre of the material increases when the base layer to
be electroplated is of higher resistance, when the width of the
material transversely to the direction of transport is larger and
when a higher current density is used for the electroplating.
[0032] The so-called deposition bone formation 11 is added to the
profile of the oblique planes at the already higher edges of the
material 1, and this effect is particularly intensive there because
of the electrical edge effect in the zone of greatest local current
density. This increases the difference in the overall depositions
on the material in a highly disadvantageous way. In particular for
the above-mentioned mass-produced products which are made by
precision conductor technology, the distributions of layer
thickness have to be very uniform, and according to the prior art
this can only be achieved using low current densities.
[0033] FIG. 2a shows, in cross section, a continuously operating
plant or a strip plant according to the invention, for
electroplating board-shaped or strip-shaped material 1. In this
plant, there are along the transport path numerous transport and
contact means 2 which transport the material 1 and make electrical
contact. Rolls are illustrated serving as the transport means 2. It
is also possible for rotating rolls having small wheels, or
non-rotating sliding contacts, to be used. The electrical contacts
3, which take the form of rings, small wheels, discs, brushes or
segmented contact wheels, are in this basic arrangement of the
invention located transversely as seen in the direction of
transport, preferably in the centre of the contact means 2 and the
transport path. This arrangement requires only one corresponding
contact track 15 on the material, preferably also running in the
centre of the material 1 inside the useful area 17, as shown in
FIG. 3. This means that a respective useful part-zone or a useful
part-area 12 of the material is located to either side of the
contact track 15. The electroplating current is supplied to the
material by way of the contact track 15 on the material, this track
being kept free separately or not separately within the layout and
running within the entire useful zone thereof. In the case of a
contact track 15 which is not kept free and separate this extends
over the end products 14 arranged in the layout of the material
1.
[0034] An asymmetrical contact track, in the layout of the material
or printed circuit board or the strip to be electroplated, and
corresponding contacts 3 along the transport path of the
continuously operating plant may also be provided.
[0035] Because electrical contact is still made in the event of the
contacts 3 leaving the track unexpectedly, as a result of the
arrangement according to the invention in the useful zone, the
serious consequences for the plant technology which are described
above do not occur. Because of this, there is no need for a safety
margin and the width of the contact track 15 may be narrow in the
layout of the material 1, for example 10 mm with a width of the
contact wheel 3 of for example 5 mm. The contacts always roll
within the useful zone 12 of the material. They cannot fall off the
material and so lose electrical contact. This means that electrical
contact cannot be broken, which among other things means that
faults cannot result in the case of demetallisation of the contacts
because of a thick metallized layer that was not planned for.
[0036] The distribution of layer thickness which can be achieved
according to the invention transversely to the direction of
transport is shown in FIG. 2b. The troughs of the oblique planes
are in the zones away from contact, that is to say at the two edges
13 of the material 1. These thinner edge zones 13 are adjoined, in
the zone of the lowest current density and hence in the trough of
the oblique plane, by the respective deposition bone formation 11.
Thus, the bone formation occurs in the zone of lowest current
density. Because of this, by comparison with the supply on both
sides according to the prior art, in which the deposition bone
formation is in the zone of highest current density, here it is
significantly smaller. In total, therefore, the overall differences
in layer thickness are smaller than with the supply on both sides
according to the prior art. Added to this are the further
advantages described, of making electrical contact with the
material in its centre zone.
[0037] The method according to the invention is highly suited for
example to the requirements currently made of such electroplating
plant in printed circuit board technology. These requirements
include copper base layers down to a minimum of 1.5 .mu.m thick for
printed circuit boards that are 610 mm wide and to which an
electroplated layer up to 25 .mu.m thick is to be applied. In this
case, only differences in layer thickness of at most 1 .mu.m are
acceptable in the zone of the useful area. These requirements can
be met according to the invention.
[0038] In the case of base layers applied by sputtering or
chemically deposited copper layers having a thickness of, for
example, 0.2 .mu.m, it is helpful to extend the concept of the
invention because of the substantially higher resistance. For this,
it is proposed that at least two contact tracks be provided in the
layout of the material and two contact tracks or contacts 3 be
provided on the contact means 2. These two contact tracks are
located inside the useful zone of the material, approximately at
1/4 and 3/4 of the way across the width thereof, transversely as
seen in the direction of transport and approximately symmetrically
in relation to the transport path. Here, a total of four smaller
oblique planes are formed on the upper side and where appropriate
on the lower side of the material. In this case, 1/4 of the total
current of this contact zone flows from each contact in each of the
two directions, transversely as seen in the direction of transport.
At the same time, the length of the current flow in the base layer
of the printed circuit board is reduced to 1/4 of the total width,
resulting in the electrical resistance of the associated current
path being quartered in size. A quarter of the current flowing
through a quarter of the resistance gives, by Ohm's law, a drop in
electrical voltage to only one sixteenth. The differences in layer
thickness on the material are reduced to approximately this
fraction by comparison with the supply of current from one side,
according to the prior art. Once again, the troughs of the oblique
planes are in each case away from the contacts.
[0039] Base layers deposited by sputtering are particularly thin in
the edge zone of the material, or metallisation is completely
absent. The same is true of so-called etched-back full-surface
printed circuit boards. In these, base layers which are for example
12 .mu.m or 17 .mu.m thick are etched back to around 3 .mu.m. Then
the actual treatment of the printed circuit boards takes place. In
particular because of the puddling effect, the edge zones are
etched more intensively than the centre zone. In both these cases,
the fact of supplying the electrolytic current in the centre of the
material, according to the invention, or in a plurality of tracks
of the centre zone proves very advantageous, because that is where
the nominal layer thickness for the base layer always prevails and
so a reliable supply of current is possible. A plurality of contact
wheels arranged transversely as seen in the direction of transport
are preferably arranged symmetrically in relation to the transport
path. The edge of the material is not required for making contact
when supply is in the centre, by means of one or more contact
tracks 15. However, in these cases the layout of the material and
the position of the contacts on the contact means must be adjusted
to one another. If there are a plurality of tracks arranged
transversely as seen in the direction of transport, there is no
longer complete freedom in the selection of parameters, as is
provided by a single supply in the centre. With some mass-produced
products which are manufactured over a long period, this extension
according to the invention is very advantageous, particularly since
there is no economic alternative of comparable simplicity for the
electroplating of very thin and hence high-resistance base layers
on a large material using high current density, that is to say
economic electroplating with a very good distribution of layer
thickness.
[0040] If there are, for example, two contact tracks 15, it is
possible for there to be two contacts 3 on one contact means 2. For
this, two sliding or rotary contacts 9 are required if there are
associated with each contact track one or more individual
rectifiers, which advantageously ensure that there is a current
flow of exactly the same size on all sides, transversely as seen in
the direction of transport. However, it is also possible to equip
each contact means 2 with only one contact 3 and one rotary contact
9. In this case, these contacts 3 are arranged alternately to right
and left on the contact means 2, as seen in the direction of
transport of the material 1. With this lower-cost solution, the
contacts 3 then have to transmit twice the current, however,
regardless of whether both sides are supplied by one rectifier or
by individual rectifiers.
[0041] In particular in the case of high current densities, the
size of the current to each contact also increases. In this case,
it is important that the electrolytic handling current of a common
rectifier is distributed uniformly over all the respectively
involved contacts to avoid damage to the surface of the material
and/or the contacts. This is particularly important when the
contact track(s) in the useful zone run over the end products. As
the number of contacts associated with a rectifier 8 decreases, so
does the possibility of overloading individual contacts. The best
case is when there is a rectifier 8 associated with each individual
contact. The current-regulated rectifier limits the treatment
current to the pre-set current. This reliably prevents the contact
from being overloaded.
[0042] FIG. 3 shows, in plan view and by way of example, a material
1 whereof the layout is constructed for electroplating a large
number of end products 14 in a continuously operating plant or
strip plant according to the invention. The external dimensions of
the material are for example 610 mm.times.610 mm. The useful zone
17, which is edged with a dashed double line and on which the end
products and the at least one contact track 15 are located, is
smaller by the amount of the narrow edge zones 13. The transport
direction arrow 16 indicates the direction of transport of the
material through the electroplating plant. The material may also
include through holes for electroplating and blind holes that are
provided with an electrically conductive layer.
[0043] The useful zone for the end products 14, for example BGAs,
is smaller, for example 580 mm.times.580 mm. The edges 13 are not
usable for end products 14. In the centre of the material 1, or
approximately in the centre, runs the contact track 15, which is
kept free and separate. This track is typically not usable for end
products 14, or only to a limited extent. In particular in the case
of small end products 14, however, it is also possible to cover the
entire useful area in the layout with end products and not to leave
any contact track on the material as a separate area. Electrical
contact is made, in the zone of the centre of the material 1, with
the end products 14 there. If these relatively few end products
become faulty because of the contact made, they can be discarded in
a sorting operation later, once they have been depanelled. This
procedure makes the construction of the layout of the material 1
simpler. Moreover, the course of the actual contact track on the
material during electroplating is then in no way critical. With
small end products, the yield per panel is about the same in both
cases, that is to say with or without the contact track as a
separate area. In this case, there is no need either for a
technically complex alignment station upstream of the continuously
operating plant, which is otherwise required for precise lateral
alignment of the material.
[0044] The invention is also suitable for electroplating structures
which are formed by a structured resist on the material. In this
case, the contact track, like the other areas to be electroplated,
has to be kept free of resist.
[0045] The format of the material according to the invention is not
restricted to a rectangular shape. It is possible for example for
it to have polygonal or round contours. In particular cases, this
may result in a saving of base material.
LIST OF REFERENCE MATERIALS
[0046] 1 Material, printed circuit board, panel
[0047] 2 Contact means, transport means
[0048] 3 Contact, contact ring, contact wheel, contact roll
[0049] 4 Base layer
[0050] 5 Edge zone
[0051] 6 Anode, electrode
[0052] 7 Electrolyte
[0053] 8 Electrolytic current source, rectifier
[0054] 9 Rotary contact, sliding contact
[0055] 10 Electroplated layer, etched layer
[0056] 11 Deposition bone formation
[0057] 12 Useful part-area, useful part-zone
[0058] 13 Edge, edge area
[0059] 14 End product
[0060] 15 Contact track
[0061] 16 Arrow for direction of transport
[0062] 17 Useful area
* * * * *