U.S. patent application number 10/381508 was filed with the patent office on 2004-02-12 for method for selectively metalizing dieletric materials.
Invention is credited to Hupe, Jurgen, Kickelhain, Jorg, Kronenberg, Walter, Meier, Dieter J..
Application Number | 20040026254 10/381508 |
Document ID | / |
Family ID | 8169940 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040026254 |
Kind Code |
A1 |
Hupe, Jurgen ; et
al. |
February 12, 2004 |
Method for selectively metalizing dieletric materials
Abstract
Method for selectively metallizing dielectric materials, the
method includes: adhesively covering dielectric materials with an
activating layer comprising a conductive material, which layer is
subsequently structured by way of laser ablation; and using a
subsequent laser treatment to structure the activating layer in
such a way that discrete conductive structures are formed, which
are subsequently metallized.
Inventors: |
Hupe, Jurgen; (Langenfeld,
DE) ; Kronenberg, Walter; (Koln, DE) ;
Kickelhain, Jorg; (Nestadt am Rubenberge, DE) ;
Meier, Dieter J.; (Nenndorf, DE) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
|
Family ID: |
8169940 |
Appl. No.: |
10/381508 |
Filed: |
August 4, 2003 |
PCT Filed: |
September 21, 2001 |
PCT NO: |
PCT/EP01/10935 |
Current U.S.
Class: |
205/92 ; 205/136;
205/157; 205/158; 205/162; 205/291 |
Current CPC
Class: |
H05K 3/185 20130101;
H05K 3/188 20130101; C23C 18/1893 20130101; C23C 18/1608 20130101;
C25D 5/54 20130101; C25D 5/56 20130101; C25D 5/024 20130101; C23C
18/1612 20130101 |
Class at
Publication: |
205/92 ; 205/136;
205/158; 205/157; 205/162; 205/291 |
International
Class: |
C25D 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 26, 2000 |
EP |
00120884.2 |
Claims
1. Method for selectively metallizing dielectric materials,
characterized in that the respective dielectric material is covered
with an activating layer consisting of conductive material and that
structuring of the activating layer through a subsequent laser
treatment occurs in such a way that discrete conductive structures
are formed, which are subsequently metallized.
2. Method pursuant to claim 1, characterized in that it is applied
in the field of electronics for the production of elements and
components.
3. Method pursuant to claim 1 or 2, characterized in that it is
applied in the production of printed circuit boards.
4. Method pursuant to one or more of the claims 1 through 3,
characterized in that plastics and/or ceramics are used as
dielectric materials.
5. Method pursuant to one or more of the above claims 1 through 4,
characterized in that an activating layer consisting of a
conductive polymer is applied.
6. Method pursuant to claim 5, characterized in that polymerized or
copolymerized pyrrole, furan, tiophene and/or their derivatives are
used as a conductive polymer.
7. Method pursuant to claim 5, characterized in that
poly-3,4-ethylene-dioxythiophene is used as a conductive
polymer.
8. Method pursuant to one or more of the above claims 5 through 7,
characterized in that the conductive polymer is additionally
covered with Pd and/or Cu germs.
9. Method pursuant to one or more of the above claims 1 through 4,
characterized in that the activating layer consists of metal
sulfides and/or metal polysulfides.
10. Method pursuant to one or more of the above claims 1 through 4,
characterized in that the activating layer consists of a thin metal
layer.
11. Method pursuant to one or more of the above claims 1 through
10, characterized in that metallization occurs by way of
electrolytical processes.
12. Method pursuant to one or more of the above claims 1 through
11, characterized in that copper electrolytes are preferably used
for metallization.
13. Method pursuant to one or more of the above claims 1 through
12, characterized in that a KrF, XeCl or Nd-YAG laser is used for
structuring the activating layer.
14. Method pursuant to one or more of the above claims 1 through
13, characterized in that the conductive structures are destroyed
following metallization.
Description
[0001] The present invention describes a method for selectively
metallizing dielectric materials such as those used in the field of
electronics. The products manufactured using that method include,
e.g., printed circuit boards, wiring elements, chip carriers,
interposers, lead frames, or even entire components. The prior art
primarily for the production of printed circuit boards will be
described below.
[0002] Printed circuit boards are wiring carriers featuring a
wiring structure (usually printed circuits made of thin copper
layers generated by way of printing) on an insulating
carrier/supporting boards, and serve to accommodate components.
There are various types of such printed circuit boards, including,
e.g., rigid, flexible or rigid-flex, drilled or non-drilled,
through hole plated or non-through hole plated supporting boards.
Depending on the layers and the number of wiring levels, they are
called one-sided, double-sided or multi-layer printed circuit
boards. Three-dimensional circuits wherein the circuit structures
go across more than two levels are also known in the art.
[0003] For many years various methods for the production of printed
circuit boards have been known (e.g., Gunther Hermann, Handbuch der
Leiterplattentechnik, Eugen Leuze Verlag, 1982, D-88348
Saulgau).
[0004] The simplest, original version is based on copper laminated
dielectric materials, to which a positive print in the shape of the
desired conductive pattern is applied by way of silk
screen-printing or through phototechnical means. During the
subsequent etching, this positive print serves as a protective
layer (etching resist). The exposed copper-plated areas, which are
not protected by such an etching resist, are removed using suitable
etching solutions. The etched copper is a waste product. The
etching resist is afterwards stripped using inorganic or organic
solvents.
[0005] In other types of this so-called subtraction method, a
negative print of the conductive pattern is generated on the
dielectric material to be metallized as a galvanic resist by way of
silkscreen printing or through phototechnical means. Then the strip
conductors are galvanized by metallizing the strip conductors up to
the desired layer thickness (mostly copper). The areas that are
free of strip conductors are protected by the galvanic resist.
Afterwards a metal resist in the form of, e.g., a tin or tin/lead
layer is applied to the metallized strip conductors
galvanic-technically using a common technique, which layer protects
the strip conductors during the subsequent subtractive removal
(etching) of the original copper laminate. Afterwards the metal
resist is removed. Other types are known as well. It should be
noted, however, that this method is not suitable for the production
of fine and very fine (<50 .mu.m) strip conductors, because
etching occurs not only downward but also sideward on the flanks of
the future strip conductors, the so-called sub-etching phenomenon,
with the resulting technical disadvantages of breaking of the edges
as well as a potential for future short circuits. The thicker the
copper layer to be etched off, the greater the degree of
sub-etching.
[0006] In order to avoid the problem of partial sub-etching, one
frequently resorts to the semi-additive method, which uses
non-laminated supporting boards onto which a thin galvanic
conductive layer is applied, generally copper precipitated in the
absence of external power. Additional processing is essentially
similar to the methods described above, except that no so-called
positive etching resist is applied. That means that only the
desired areas of the printed circuit board are galvanically
reinforced with copper. Afterwards the copper areas of varying
thickness are etched down by the degree of the initial
copperplating in the absence of external power. This method,
therefore, produces copper as a waste product as well. In addition,
special care is needed with regard to a very consistent layer
thickness distribution of the copper to be applied
electrolytically.
[0007] The full-additive technique does away with copper etching
altogether, because copper is applied only where it is needed,
i.e., to strip conductors, lands for soldering, etc. Therefore,
this method is widely used. Due to a lack of contacting options,
the copper-plating takes place in the absence of external power.
Most of the time a bonding and activating layer is applied onto the
non-laminated dielectric material, which layer contains catalyst
germs for setting off the copper-plating in the absence of external
power. Once any areas not to be copper-plated are covered by means
of silk screen-printing or with a photo mask, the bonding and
activating agent is solubilized so that copper-plating in the
absence of external power can take place directly thereafter.
[0008] The masks, which generate the discrete strip conductors, can
be generated by way of silk screen-printing or through
phototechnical means. What they have in common; is that an
individual mask for every one of the strip conductor patterns to be
generated needs to be produced respectively. When structuring is
performed using a photo process, so-called "photosensitive resists"
are applied as photosensitive materials onto the dielectric
material to be metallized. Afterward only specific areas are
exposed to light, which represent either the positive or the
negative of the desired strip conductors, depending on which
substance is used.
[0009] Aside from structuring the strip conductors using
phototechnical processes, use of an immersion tin layer with
subsequent structuring by laser is another option, particularly for
three-dimensional parts such as the so-called molded interconnect
devices. Here, use of the laser represents an additional
subtraction technology step. The biggest disadvantage is the large
amount of time required for structuring. On the one hand the
thickness of the tin layer must provide sufficient etching
protection, on the other hand the layer must be as thin as possible
to ensure rapid laser ablation.
[0010] Processes for the ablation of very fine metal films are
already being used in the production of printed circuit boards.
Most of the time one is dealing with tin layers applied to copper,
which are structured by laser and where the remaining copper is
removed using an etching process (E. Tradic: "Haaresbreite
Feinstrukturen fur zukunftige Produktgestaltungen" SMT Edition
1-2/2000, 12).
[0011] Furthermore, there are already known methods for
three-dimensional bodies through which very fine structures are
generated through the use of laser technology. For example, methods
for the laser-supported additive metallizing of thermoplastics for
3D MIDs have been described, which are based on doped plastics and
can be laser-activated and are suitable for subsequent metallizing
in the absence of power for the purpose of building strip
conductors (SMT Edition 4/2000, 20).
[0012] Other methods where various metal layers are being ablated
by laser are known as well. For example, D. Meier describes a
method whereby thin gold layers are ablated by UV lasers in the
course of a mask projection process and are subsequently reinforced
in the absence of power ("Laser Structuring of Fine Lines",
5.sup.th Annual Conference on Flexible Materials Denver/USA 1999,
Proceedings). Laser ablation, particularly with palladium-doped
organic layers, is known as well (J. Kickelhain: Promotionsarbeit
an der Universitt Rostock 1999). However, what all these methods
have in common is the disadvantage that--following the laser
structuring--an additive metallization in the absence of power for
reinforcing the conductive pattern occurs.
[0013] Furthermore, conductive polymers have earned their place in
the metallization of dielectric materials some time ago. They are
used particularly for throughplating and manufacturing of
two-layered and multi-layered printed circuit boards in the
so-called direct plating technology. This is a subtractive
technique where galvanic metallization occurs directly following
activation of the dielectric material with the respective
conductive polymer (PCT/EP 89/00204). The
disadvantage--particularly in the case of two-dimensional
metallization--is the relatively low electric conductivity of these
conductive polymers.
[0014] There are also methods known, which suggest a selective
direct galvanic metallization based on conductive polymers. U.S.
Pat. No. 5,935,405, e.g., describes a method where the supporting
boards are coated with a primer and conductive polymers. A
photo-structurable galleon resist is used to generate the
structure. Following the galvanic coating the resist is first
stripped and then the conductive polymer, which was underneath the
resist, is removed. Disadvantages are the use of a
photo-structurable galvanic resist, because for realizing fine and
very fine line structures high clean-room technology requirements
are necessary, and the removal of conductive polymer, which will
become necessary later on.
[0015] The subject of the invention was to find a simple, safe,
inexpensive and environmentally safe method for selectively
metallizing dielectric materials, which allows for precise
structuring in the under .mu.m range and furthermore does away
completely with the use of resists.
[0016] The method according to the invention provides a technical
solution, whereby the dielectric material to be metallized is
coated with an adhesive conductive activating layer, and
subsequently the desired conductive pattern is structured out of
said layer by using a laser as a precision tool. The remaining
structures of the activating layer continue to be conductive and
can, without a problem, be galvanically metallized, preferably
copper-plated, by applying electric power. This allows for
structuring even within a range below 50 .mu.m.
[0017] Through the method according to the invention limitations of
the state of the art are therefore being overcome in an
advantageous manner. The invention proposes operational steps that
render the method technically advantageous, exceedingly economical,
and effective. Hereinafter the method is described in an exemplary
manner for the production of printed circuit boards, without
limiting its scope to this electronics segment.
[0018] In a first approach to solving the problem, the
electrolytical galvanization through the application of power is
being provided by the method of the invention, through the
application of a thin adhesive and conductive activating layer onto
the dielectric material to be metallized. This conductive
activating layer allows for the electrolytical galvanization.
[0019] The activating layer can vary widely, as long as it is
sufficiently conductive. The use of polymerized or copolymerized
pyrrole, furan, tiophene and/or their derivatives is preferable.
Particularly preferable, however, is the use of a conductive
polymer based on a polythiophene derivative (DMS-E). Furthermore,
metal sulfide layers and/or metal polysulfide layers as well as Pd
and/or copper catalysts can be used. There is also the option of
applying thin metal layers onto the substrate. Copper layers can be
applied in various ways, for example.
[0020] Preferably, the thickness of the activating layer applied
should be in the 0.1 .mu.m range. The method of the invention
discloses a possibility for structuring the conductive activating
layer such that discrete conductive structures are generated. The
invention proposes a new method for this. Pursuant to a
particularly advantageous characteristic of the present invention,
the precise structuring of the activating layer occurs by means of
a laser. The structuring, i.e., the generation of the conductive
pattern, can occur following application of the conductive
polymers, following application of the metal sulfide and/or
polysulfide layer, following application of the Pd or copper
catalyst, or following application of a thin metal layer. The
remaining structures of the activating layer continue to be
conductive and can be metallized galvanically--as long as strip
conductor connection is present. In doing so, insulated areas can
be connected via so-called auxiliary conductors to form an
artificial strip conductor bond. During the subsequent
electrolytical galvanization, the remaining conductive structures
of the activating layer are metallized by applying an external
power source. Applying the method according to the invention,
various metal electrolytes can be used for the electrolytical
galvanization of the structured activating layer; preference is
given to copper electrolytes however. Laser ablation thus allows
for a precise and individual design of the strip conductors within
a range of a few .mu.m. In that context, the method according to
the invention also provides the option of removing the so-called
auxiliary conductors that served as a sort of power bridge between
the insulated strip conductor areas during metallization, once the
metallization has been completed. The destruction of the artificial
strip conductor bond can, e.g., occur through laser treatment.
[0021] Hence, the method specified in the invention provides the
option of doing away with metallizing baths without external power,
such as those used in connection with the additive technology.
Thanks to this, the pollution of the environment with chemical
residue and wastewater is kept at low levels. Furthermore, metal
layers precipitated in the absence of external power are clearly
inferior with regard to their ductility to metal layers generated
electrolytically, which are significantly more finely crystallized
and dense. Due to the fact that, because of the activating layer,
the method specified in the invention allows for direct
electrolytic galvanization through the application of an external
power source, it is being ensured in an advantageous manner, that
the high ductility requirements necessary are being fulfilled,
which will ensure that breakage of the bushes or edges can be
avoided, e.g., by reason of the thermal stress of the soldering
process during the subsequent assembly of the printed circuit
board.
[0022] The method specified in the invention also provides for
metallization in the absence of external power, should this be
necessary and desirable. To that end the adhesive activating layer
used must be adjusted for metallization in the absence of external
power in such a way that the activating layer contains the catalyst
germs required for copperplating in the absence of external power,
and handling is adjusted accordingly.
[0023] The special characteristic of the method specified in the
invention, i.e., structuring of the strip conductors with the help
of a laser, provides another great advantage, namely rapid,
individual design of the strip conductors. This results in more
flexible production options, e.g., through quick reaction to any
desired changes in the course of the strip conductors. This is
achieved, e.g., due to the fact that contrary to any known methods,
no silkscreen, photo or other masks are required that generate the
outlines of the strip conductors, as said outlines are generated by
the laser.
[0024] Due to the fact that traditional photo masks can be
dispensed with, the method specified in the invention is also
characterized advantageously in that it can dispense with resist
substances of any kind, which, for example, form the masks or strip
conductor courses in the subtractive technology. This makes it
possible to save chemicals as well as operational steps, are
neither applying them nor stripping them afterwards is
necessary.
[0025] Another advantage is that due to the precise laser
structuring there is no risk of wild growth of the metal layer.
This ensures precise formation of the strip conductors, thus
keeping the reject rate low.
[0026] The density of the conducting tracks, their structural
density on the printed circuit boards, as well as their high
quality and precision, which the method specified in the invention
allows for, are characteristic of the advantages of the method
specified in the invention, because to achieve the desired decrease
in the mass and volume of electronic devices and to optimize their
operating speed, very short conductive tracks are needed.
Therefore, the method specified in the invention is particularly
suitable for the production of products requiring large-scale
integration. This applies to its use in fields such as computers,
IT, connectivity or medical technology. Furthermore, the method
specified in the invention allows for the problem-free production
of 3D circuits where the circuit structures are no longer needed on
two levels only.
[0027] The laser used for the method specified in the invention
can, e.g., be a KrF, XeCl or Nd-YAG laser. The use of other lasers
is possible as long as the precise laser ablation required can be
achieved.
[0028] Furthermore, the method specified in the invention provides
an option for specifically controlling the laser, e.g., in such a
way that the device is connected to some sort of control module.
This control module can be, for example, a computer.
[0029] Due to the exact structuring, the method specified in the
invention offers the advantage that the amount of raw materials
consumed during metallization is smaller than the amount consumed
with traditional methods, because copper is applied additively only
where it is needed. This fact also results in decreased consumption
of chemicals because steps such as etching and stripping can
largely be dispensed with. In the end, these characteristics of the
method specified in the invention lead to advantageous cost saving
and decreased environmental pollution because a smaller amount of
chemical waste accumulates.
[0030] Furthermore, a great operational advantage with respect to
any method based on photochemical processes is due to the fact that
with the method specified in the invention, there is no need to
undertake any light stabilizing measures. As a laser is being used,
it is no longer necessary to provide special storage capacities and
workshops for the photosensitive resists.
[0031] Additional advantages and characteristics result from the
examples below, which serve to further elucidate the method
specified in the invention:
EXAMPLE 1
[0032] Non-laminated supporting board (e.g. BR 4) is coated with a
conductive polymer according to the DMS-E method. Thus the set of
steps described below are performed:
1 1. Conditioner (Blasolit V) 3 min 40.degree. C. 2. Manox
(KMnO.sub.4/H.sub.3BO.sub.3) 2 min 40.degree. C. 3. Monopol TC (cat
fixation) 4 min RT X Laser structuring: Laser type: Nd: YAG (triple
frequency) Pulses/location: 1
EXAMPLE 2
[0033] Non-laminated supporting board (e.g. BFR 4) is coated with a
conductive polymer according to the DMS-E method. The set of steps
described in Example 1 (steps 1-3) are adopted and the following
steps are added:
2 4. Conditioner PE 3 min RT 5. Ultraplast 2000 (Pd-Kat) 4 min
40.degree. C. 6. Generator (Cu-containing 5 min 63.degree. C.
solution) Then follows the step below X) Laser structuring Laser
type: KrF Wave length: 248 nm Energy density on substrate: 100
mJ/cm.sup.2 Laser engergy: 450 mJ Pulses/location: 2
EXAMPLE 3
[0034] Supporting board is copper-plated and covered with a special
varnish for SBU circuits (e.g. LDD 9056 by Enthone), is treated as
follows:
3 1. Swelling agent 10 min 80.degree. C. 2. KMmnO.sub.4 alkaline 13
min 80.degree. C. 3. Remover Mn (sulfuric, H.sub.2O.sub.2) 2 min
RT
[0035] Following this set of steps the printed circuit boards are
treated as described in Example 2.
EXAMPLE 4
[0036] Non-laminated supporting board (e.g. FR 4) is treated as
follows:
4 1. Plato solution 1 4 min RT 2. Plato solution 3 2 min RT 3.
Plato solution 1 4 min RT 4. Plato solution 3 2 min RT X) Laser
structuring Laser type: KrF Wave length: 248 nm Energy density of
substrate: 150 mJ/cm.sup.2 Laser energy: 450 mJ Pulses/location
1
EXAMPLE 5
[0037] Supporting board is copper-plated and covered with a special
varnish for SBU circuits (e.g. LDD 9056 by Enthone), is treated as
follows:
5 1. Swelling agent (organic 10 min 80.degree. C. alkaline swelling
agent) 2. KMmnO.sub.4 alkaline 13 min 80.degree. C. 3. Remover Mn
(sulfuric, 2 min RT H.sub.2O.sub.2) 1. Plato solution 1 4 min RT 2.
Plato solution 3 2 min RT 3. Plato solution 1 4 min RT 4. Plato
solution 3 2 min RT X) Laser structuring Laser type: KrF Wave
length: 248 nm Energy density of substrate: 180 mJ/cm.sup.2 Laser
energy: 490 mJ Pulses/location 2
EXAMPLE 6
[0038] Non-laminated supporting board (e.g. FR 4) is treated as
follows:
6 1. Conditioner (Blasolit V) 3 min 40.degree. C. 2. Manox
(KMnO.sub.4/H.sub.3BO.sub.3) 2 min 40.degree. C. 3. Monopol TC (cat
4 min RT fixation) 4. Plato solution 1 4 min RT 5. Plato solution 3
2 min RT 6. Plato solution 1 4 min RT 7. Plato solution 3 2 min RT
X) Laser structuring Laser type: KrF Wave length: 248 nm Energy
density of substrate: 200 mJ/cm.sup.2 Laser energy: 450 mJ
Pulses/location 1
EXAMPLE 6a
[0039] It is also possible to change around the order in which the
steps are performed as follows:
[0040] Start with steps 4 through 7. Then complete the steps 1
through 3. Afterwards complete the step X), Laser Structuring.
EXAMPLE 7
[0041] Supporting board is copper-plated and covered with a special
varnish for SBU circuits (e.g. LDD 9056 by Enthone), is treated as
follows:
7 1. Swelling agent EL (organic alkaline swelling agent) 10 min
80.degree. C. 2. KMmnO.sub.4 alkaline 13 min 80.degree. C. 3.
Remover Mn (sulfuric, H.sub.2O.sub.2) 2 min RT
[0042] Then follow the steps 1 through X) from Example 6.
EXAMPLE 7a
[0043] Here it is also possible to change around the order in which
the steps are performed as follows: Start with treatment steps 1
through 3. Them complete treatment steps 4 through 7 from Example 6
and then the treatment steps 1 through 3 from Example 6. Afterwards
complete the treatment step X), Laser Treatment.
EXAMPLE 8
[0044] Non-laminated supporting board (e.g. FR 4) is treated as
follows:
8 1. Conditioner (Blasolit V) 3 min 40.degree. C. 2. Manox
(KMnO.sub.4/H.sub.3BO.sub.3) 4 min 80.degree. C. 3. Catalyst (org.
monomer) 2 min RT 4. Fixative (e.g. org. acid) 2 min RT X) Laser
structuring Laser type: XeCl Wave length: 308 nm Energy density of
substrate: 120 mJ/cm.sup.2 Laser energy: 450 mJ Pulses/location
1
[0045] Prior to laser structuring the following steps can be
completed:
9 5. Conditioner PE 3 min RT 6. Ultraplast 2000 (Pd cat.) 4 min
40.degree. C. 7. Generator (Cu-containing solution) 5 min
63.degree. C.
EXAMPLE 9
[0046] Supporting board is copper-plated and covered with a special
varnish for SBU circuits (e.g. LDD 9056 by Enthone), is treated as
follows:
10 1. Swelling agent (organic alkaline swelling agent) 10 min
80.degree. C. 2. KMmnO.sub.4 alkaline 13 min 80.degree. C. 3.
Remover Mn (sulfuric, H.sub.2O.sub.2) 2 min RT
[0047] Then complete the treatment steps 1 through 4 from Example
8, afterward laser structuring is completed. It is also possible to
complete the steps 5 through 7 prior to laser structuring.
[0048] It is also possible to vary the treatment steps as
follows:
[0049] Supporting board is copper-plated and covered with a special
varnish for SBU circuits (e.g. LDD 9056 by Enthone), is treated as
follows:
11 1. Swelling agent (organic alkaline swelling agent) 10 min
80.degree. C. 2. KMmnO.sub.4 alkaline 13 min 80.degree. C. 3.
Remover Mn (sulfuric, H.sub.2O.sub.2) 2 min RT 4. Plato solution 1
4 min RT 5. Plato solution 3 2 min RT 6. Plato solution 1 4 min RT
7. Plato solution 3 2 min RT 8. Conditioner (Blasolit V) 3 min
40.degree. C. 9. Manox (KMnO.sub.4/H.sub.3BO.sub.3) 4 min
80.degree. C. 10. Catalyst (org. monomer) 2 min RT 11. Fixative
(e.g. org. acid) 2 min RT
[0050] Including the following steps in the process prior to laser
structuring is optional:
12 12. Conditioner PE 3 min RT 13. Ultraplast 2000 (Pd cat.) 4 min
40.degree. C. 14. Generator (Cu-containing solution) 5 min
63.degree. C.
[0051] Following laser structuring the treatment continues as
follows:
[0052] The printed circuit boards are galvanized in a commercially
available copper and/or nickel electrolyte until the conductive
pattern located on the printed circuit boards is completely covered
in metal. With the method described it is possible to realize strip
conductors and strip conductor distances that are only a few .mu.m
large.
* * * * *