U.S. patent application number 11/017793 was filed with the patent office on 2005-06-23 for method of producing electrodeposited antennas for rf id tags by means of selectively introduced adhesive.
Invention is credited to Halik, Marcus, Klauk, Hagen, Mueller-Hipper, Andreas, Schmid, Gunter, Weber, Werner, Zschieschang, Ute.
Application Number | 20050133375 11/017793 |
Document ID | / |
Family ID | 34679983 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050133375 |
Kind Code |
A1 |
Schmid, Gunter ; et
al. |
June 23, 2005 |
Method of producing electrodeposited antennas for RF ID tags by
means of selectively introduced adhesive
Abstract
A method is described for producing a structured metal layer
used, for example, as an antenna for RF ID tags. The structured
metal layer is electrodeposited on a cathode, on the surface of
which conducting and non-conducting regions are defined. Applied to
the deposited metal layer in a residual volume is an adhesive with
which the structured metal layer can be made to adhere firmly on a
carrier layer.
Inventors: |
Schmid, Gunter; (Hemhofen,
DE) ; Klauk, Hagen; (Erlangen, DE) ; Halik,
Marcus; (Erlangen, DE) ; Zschieschang, Ute;
(Erlangen, DE) ; Weber, Werner; (Munchen, DE)
; Mueller-Hipper, Andreas; (Regensburg, DE) |
Correspondence
Address: |
EDELL, SHAPIRO, FINNAN & LYTLE, LLC
1901 RESEARCH BOULEVARD
SUITE 400
ROCKVILLE
MD
20850
US
|
Family ID: |
34679983 |
Appl. No.: |
11/017793 |
Filed: |
December 22, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11017793 |
Dec 22, 2004 |
|
|
|
PCT/DE03/01376 |
Apr 29, 2003 |
|
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Current U.S.
Class: |
205/135 |
Current CPC
Class: |
C25D 5/022 20130101;
C25D 1/003 20130101; G06K 19/07783 20130101; G06K 19/07779
20130101; C25D 17/12 20130101; C25D 1/04 20130101 |
Class at
Publication: |
205/135 |
International
Class: |
C25D 005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2002 |
DE |
102 29 166.7 |
Claims
What is claimed is:
1. A method of producing a structured metal layer, comprising:
providing a cathode with conducting and nonconducting regions which
form a mask structure on the surface of the cathode; providing an
anode and arranging the cathode and the anode in an electrolyte
which comprises a substrate metal; applying a voltage between the
cathode and the anode; depositing the substrate metal onto the
conducting regions of the cathode; providing a carrier layer and
bringing the carrier layer into contact with the surface of the
cathode; and transferring the substrate metal deposited onto the
cathode to the carrier layer, the structured metal layer being
obtained.
2. The method as claimed in claim 1, wherein the cathode includes a
cylindrical geometry.
3. The method as claimed in claim 1, wherein the conducting regions
of the cathode are constructed from high-grade steel.
4. The method as claimed in claim 1, wherein the nonconducting
regions of the cathode comprise a plastic and/or a ceramic.
5. The method as claimed in claim 1, wherein the conducting regions
of the cathode surface are arranged in the form of an antenna
structure.
6. The method as claimed in claim 1, wherein the anode comprises
the substrate metal.
7. The method as claimed in claim 6, wherein the substrate metal
includes copper.
8. The method as claimed in claim 1, wherein the depositing of the
substrate metal is controlled such that the layer thickness of the
structured metal layer is less than the depth of the mask
structure, thereby forming a residual volume.
9. The method as claimed in claim 8, further comprising applying an
adhesive to the structured metal layer in the residual volume.
10. The method as claimed in claim 9, wherein the adhesive includes
a thermoplastic adhesive or a reaction adhesive.
11. The method as claimed in claim 1, wherein the electrolyte
comprises sulfuric acid and copper sulfate.
12. The method as claimed in claim 1, wherein the structured metal
layer is supplemented by a microchip to form an RF ID tag after
transfer of the substrate metal deposited onto the cathode to the
carrier layer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of PCT Application No.
PCT/DE03/01376, filed on Apr. 29, 2003, and titled "Method for
Producing Galvanically Deposited Antennae for RFID Labels Using an
Adhesive that is Selectively Applied," which claims priority under
35 U.S.C. .sctn.119 from German Patent Application No. DE 102 29
166.7, filed on Jun. 28, 2002, and titled "Method of Producing
Electrodeposited Antennas for RF ID Tags by Means of Selectively
Introduced Adhesive," the entire contents of which are hereby
incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of producing a
structured metal layer. More particularly, structured metal layers
of this type can be used, for example, as antennas for RF ID
tags.
BACKGROUND
[0003] Modem transponder technology permits contactless reading out
and storing of data from and onto a microchip by means of
electromagnetic carrier waves as the transporting medium. For this
purpose, the microchip is connected to an antenna, which receives
and sends the electromagnetic radiation required for writing to or
reading from the microchip. It is then possible to communicate with
the microchip by means of an external transmitting or receiving
unit. In general, the microchip does not have an energy supply of
its own, so that the electromagnetic radiation used for writing to
or reading from the microchip is also used for supplying energy to
the microchip. However, the production of the RF ID tags comprising
the antenna and the microchip was previously relatively expensive.
For this reason, transponder technology has so far only been used
for relatively high-value or durable articles. For example,
transponder technology is used for finding buried pipelines or for
quickly detecting animals in large herds.
[0004] For example, in large herds of cattle, the animals have a
microchip implanted under the skin. If these animals are driven
past a transmitting and receiving station, the correspondingly
prepared cattle can be identified without any problem by the data
stored on the microchip, since the data are read out without making
contact with the animal. Apart from this application, other areas
of use are also conceivable, such as for example the monitoring and
observation of endangered species of animals in the wild for
research purposes or behavioral studies, since the corresponding
investigations can be conducted without significantly disturbing
the animal's habitat.
[0005] Apart from this, there are further application areas, such
as for example electronic protection against theft of expensive
luxury items such as fur coats, perfumes, CD-ROMs, etc. For this,
however, retailers have to be equipped with corresponding devices
for reading the microchips.
[0006] Transponder technology has so far been used in particular
for items which are very durable or are of very high value.
Introduction of transponder technology on a broad base has been
prevented by the comparatively high costs. If the costs for the
production of the RF ID tag can be drastically lowered, this would
open up the path to many applications which are subject to high
cost pressure.
[0007] There is for instance a conceivable application serving for
bureaucratic purposes, such as for example the monitoring of
important documents and file records in government or
administrative buildings, the files being electronically registered
at the individual processing stations. The path followed by the
file can be traced in a simple way and the file easily relocated if
need be. In the simplest case, for this purpose the corresponding
transmitting or receiving station is installed in the door frame,
so that the file is electronically registered when it enters or
leaves the room.
[0008] A further application example is the administration and
loading of items of baggage at airports, ports, railroad stations
or other item-redistributing stations, the item of baggage having
to be directed to a specific location. In this case, a relatively
small unit price for the RF ID tag, which comprises a memory chip
and a transmitting and receiving unit, is considered just about
profitable for these applications.
[0009] There is great interest in a variant of this technology in
many areas in which a considerable number of data are to be
reliably registered in short time periods. Many examples from
everyday life can be found for this, such as for example the
electronic postage stamp or the use of electronic labels marking
products in the retail trade. In this case, the products located in
a shopping cart can be contactlessly registered at an electronic
cash register and a bill produced for these items. Furthermore,
this also opens up the possibility of transmitting the data on to
stockkeeping and of automatically re-ordering the products
purchased.
[0010] However, the consumer articles referred to generally have a
minimal market value, so that the costs for the electronic tags
must be reduced considerably to allow them to be introduced on the
market.
[0011] To be able to lower the production costs of an RF ID tag,
various approaches are available. The costs of the microchip may be
lowered, but on the other hand so too may be the costs which are
incurred for the transmitting and receiving unit, in particular the
antenna structure.
[0012] In cards used, for example, for controlling access to
sensitive areas in research facilities or production works, a
simple wire coil is used as the antenna structure. However, this
form of antenna structure is far too expensive for the applications
described above. In addition, antennas which are produced from
metal foils are also known, for it then to be applied subsequently
to a separate carrier.
[0013] The antenna structure may in this case be produced by
various techniques.
[0014] One possibility is to laminate a metal foil onto the support
over its full surface area and subsequently carry out structuring
subtractively by selective etching. The antenna structure may,
however, also first be punched out from metal foil and subsequently
laminated onto the carrier.
[0015] In the case of these methods, the antenna structure is
created subtractively, i.e. a full-area copper layer is first
created and subsequently has to be structured. This produces a
considerable amount of copper waste, which has to be recovered.
[0016] If the preparation of macroscopic starting materials is to
be avoided because of the complex processing, the antenna structure
may also be printed or sprayed onto the carrier using electrically
conductive pastes. For this purpose, however, the copper must first
be correspondingly prepared. The copper must be comminuted into
adequately small particles, to allow a paste suitable for printing
to be produced. What is more, corresponding accompanying
substances, such as binders or solvents, must be added.
[0017] Finally, conventional semiconductor technology is also
suitable, with a mask first being defined on the carrier by
photolithography, for example using a photoresist. Subsequently,
the intermediate spaces not covered by the mask on the carrier are
currentlessly metallized. The method consequently requires working
steps in which the photoresist is applied and structured.
Furthermore, costs are incurred for the photoresist itself. This
method is therefore also not suitable for the low-cost production
of antenna structures for RF ID tags.
SUMMARY
[0018] In the case of conventional methods of producing copper
layers, it has previously been customary to create the copper
layers by electrodeposition on a high-grade steel drum connected as
a cathode. The adherence of copper on high-grade steel is
relatively low, so that the copper foil created can simply be
detached from the high-grade steel matrix and laminated onto a
corresponding carrier in the further course of the method. To
facilitate the detachment of the copper from the high-grade steel
matrix, additives may be initially applied to the high-grade steel
drum, such as graphite or molybdenum sulfide for example, which
further reduces the adherence of the copper on the high-grade steel
surface.
[0019] Also decisive for processing at lowest possible cost is that
the copper material to be deposited is deposited on the cathode as
efficiently as possible. For the RF ID tags under discussion, about
100 mg of copper are required per tag. This means that, given an
efficient production procedure, approximately 10,000 antennas can
be produced with an amount of material of 1 kg of copper. However,
in the case of the subtractive structuring methods described
further above, the offcut copper waste generated as scrap must be
recycled, since the price of copper is relatively high.
[0020] The object of the invention is therefore to provide a method
of producing a structured metal layer as used, for example, as an
antenna structure in RF ID tags which can be carried out simply and
inexpensively.
[0021] An aspect of the present invention is achieved by a method
of producing a structured metal layer which comprises at least the
following steps: provision of a cathode, conducting and
nonconducting regions which form a mask structure being defined on
the surface of the cathode and of an anode, the cathode and the
anode being arranged in an electrolyte which contains a substrate
metal, application of a voltage between the cathode and the anode,
depositing of the substrate metal onto the conducting regions of
the cathode, provision of a carrier layer and bringing the carrier
layer into contact with the surface of the cathode, transfer of the
substrate metal deposited onto the cathode to the carrier layer,
and the structured metal layer being obtained.
[0022] The predetermined mask structure on the cathode has the
effect that the desired structure of the metal layer is already
obtained when the substrate metal is electrodeposited. The metal
layer consequently does not have to be subsequently structured and
there is consequently also no offcut waste as scrap. The mask
structure defined on the cathode is formed in a thickness which
corresponds at least to the layer thickness of the metal layer to
be created. The conditions for the electrodeposition are chosen
such that only the substrate metal is selectively deposited and the
structured metal layer is produced in the desired layer thickness,
that is to say, for example, no overfilling of the regions
predetermined by the mask structure takes place. The substrate
metal is in ionic form in the electrolyte and is reduced on the
cathode to form the substrate metal.
[0023] After the electrodeposition, the structured metal layer, for
example an antenna structure for an RF ID tag, is transferred
directly to the desired carrier layer. Further transfer, printing
and etching costs do not arise. The price of producing an antenna
structure for RF ID tags is essentially determined in the case of
the method according to the invention by the pure material costs
and therefore permits low-cost production of high numbers of
units.
[0024] In a preferred embodiment of the method according to the
invention, the cathode has a cylindrical geometry. The cathode is
consequently in the form of a roll, drum or rollers. With such a
cathode, the method according to the invention can be carried out
continuously. The cylindrical cathode is immersed with its lower
portion into the electrolyte and continuously rotated. A specific
portion of the circumferential surface consequently enters the
electrolyte and is moved through it. As this happens, the substrate
metal is deposited on the conducting regions of the portion. The
rotatioal speed of the cylinder is set such that the portion of the
circumferential surface remains in the electrolyte sufficiently
long for the structured metal layer to be deposited in the desired
layer thickness. The portion of the circumferential surface is
moved out of the electrolyte again by further rotation of the
cylinder. A carrier material is then continuously fed to the
circumferential surface, so that the structured metal layer
deposited on the portion of the circumferential surface is
transferred to the carrier layer. By further rotation of the
cylindrical cathode, the portion of the circumferential surface is
immersed once again into the electrolyte and the cycle begins once
again.
[0025] The continuous depositing of the copper layer and the
continuous transfer of the deposited structured metal layer to the
carrier layer consequently permits a continuous working mode. This
eliminates the unproductive times inevitably occurring in the case
of a discontinuous method, thereby permitting an increase in
throughput.
[0026] It is advantageous if at least the conducting regions of the
cathode are constructed from high-grade steel. High-grade steel
has, on the one hand, an adequately high conductivity and is, on
the other hand, adequately corrosion-resistant. The high
conductivity of the high-grade steel permits efficient depositing
of the substrate metal. The corrosion resistance of high-grade
steel provides the cathodes with a long service life, even under
extreme galvanic conditions. Therefore, exchange of the cathode is
required relatively rarely. As a result, the service life and
degree of utilization of the device used for electrodepositing the
substrate metal are increased.
[0027] Furthermore, high-grade steel can be produced and processed
at relatively low cost, meaning that the financial expenditure for
producing the corresponding cathode drums also remains within
restricted limits.
[0028] It is also advantageous if the nonconducting regions on the
surface of the cathode consist of a plastic and/or a ceramic. These
materials are, on the one hand, very inexpensive and, in addition,
have a high specific resistance. The high specific resistance
produces sharp contouring of the mask structure with respect to the
conducting regions. Ceramics and plastics can by now be produced at
very low cost and exhibit good potential for deformability, this
giving rise to possible application to a wide variety of cathode
geometries. A further advantage is also the relatively low density
of these materials, which results in a weight saving and easy
transportability of the cathode objects used.
[0029] In a preferred embodiment of the method according to the
invention, the conducting regions of the cathode surface have the
form of an antenna structure. The method according to the invention
permits the extremely low-cost production of antenna structures for
RF ID tags. Consequently, the costs for the production of such RF
ID tags can be significantly lowered, so that they can also be used
for applications which are under high cost pressure.
[0030] The anode preferably contains the substrate metal. Apart
from its property as a charge pole, the anode also acts as a
reservoir for the substrate material. Consequently, in this case
there is no need for the otherwise required continuous feeding of
the substrate metal into the electrolyte. There is no need for
complex preparation of the substrate metal, since the substrate
metal can also be used in the form of an unpurified crude metal.
The selectivity for the deposition in this case takes place by
means of a suitable voltage difference between the anode and the
cathode. In this way, troublesome or even harmful or toxic
intermediate products can be avoided during the production of the
antenna structure. Furthermore, the anode slurries occurring during
electrochemical depositing can be used for obtaining valuable
precious metals and contribute to reducing overall costs.
Considered electrochemically, these metals are of a higher grade
than the substrate metal, and accordingly have a higher oxidation
potential.
[0031] It is advantageous if the substrate metal is copper. Copper
has a very high conductivity and is relatively inexpensive to
obtain. The price of copper is currently relatively low. The high
conductivity of copper is surpassed only by very few metals, these
metals being much more expensive in costs of procurement. The ratio
of conductivity to price in the case of copper is optimal. A high
conductivity of the substrate metal guarantees high efficiency of
the energy input of the electromagnetic radiation into the antenna
structure and consequently high efficiency for the exchange of
information. At the same time, the response times are relatively
short and consequently a high flow of information can be achieved
with low susceptibility to interference.
[0032] In a preferred embodiment of the method according to the
invention, the depositing of the substrate metal is controlled in
such a way that the layer thickness of the structured metal layer
is less than the depth of the mask structure, so that a residual
volume is formed. A residual volume refers to the space which is
defined between a plane which passes through the surface of the
nonconducting regions of the mask structure and a plane which
passes through the exposed surface of the deposited structured
metal layer. The layer thickness of the structured metal layer can
in this case be controlled by means of the applied current density
or else by means of the dwell time of the cathode or the conducting
portions of the mask structure in the electrolyte.
[0033] Consequently, various layer thicknesses can be realized by
the same depositing device with low expenditure. Various auxiliary
materials can be filled into the residual volume formed.
[0034] In a particularly preferred embodiment, an adhesive is
applied to the structured metal layer in the residual volume.
[0035] The adhesive allows the structured metal layer to be easily
removed from the mask structure, since adequate adherence with
respect to the carrier layer is created. Furthermore, the adhesive
produces permanent fixing of the structured metal layer, preferably
an antenna structure, on the carrier layer.
[0036] The adhesive is preferably selected such that it adheres on
the deposited structured metal layer, but not on the nonconducting
regions of the mask structure. After applying the adhesive and
applying the carrier layer, the latter with the structured metal
layer fixed on it can be readily lifted off again. Furthermore, the
adhesives should not contain any toxic accompanying substances, to
avoid endangering the environment.
[0037] It is particularly advantageous if the adhesive is a
thermoplastic adhesive or a reaction adhesive. A thermally or
photochemically curable adhesive may be used, for example, as the
reaction adhesive. Examples of reaction adhesives are polyether
sulfones, cyanurates, epoxy compounds and similar classes of
compounds. A precondition here is that the corresponding adhesives
permit a solid bond between the structured metal layer and the
carrier layer, but at the same time do not impair the structure of
the structured metal layer with respect to the surface and
dimensional stability.
[0038] If copper is used as the substrate metal, it is advantageous
if the electrolyte contains sulfuric acid and copper sulfate as the
copper-containing salt. Because of its high degree of dissociation,
sulfuric acid increases the conductivity of the electrolyte and
improves the depositing quality of the copper layer. Copper sulfate
has a high solubility in aqueous systems, so that a relatively high
copper ion concentration can be achieved in the electrolyte.
[0039] In addition, further optimizing additives may be added to
the electrolyte, such as triisopropranolamine, gelatin, glue,
thiourea, cellulose ether or chloride ions. The effect of these
additives is either an improvement in the fluid-dynamic properties
of the electrolyte solution (e.g. increase in the viscosity) or an
increase in the conductivity, which leads to an improvement in the
depositing quality. The conductivity-improving additives include,
for example, copper fluoroborate electrolyte (e.g.
copper(II)tetrafluoroborate, borofluoric acid, boric acid).
[0040] For the copper deposition, a bath temperature of up to
75.degree. C. and flow rates of up to 7 m/s with a current density
of up to 150 A/dm2 have proven to be suitable.
[0041] After the transfer of the structured metal layer formed as
an antenna structure to the carrier layer, the antenna structure
can be supplemented by a microchip to form an RF ID tag.
[0042] The above and still further aspects, features and advantages
of the present invention will become apparent upon consideration of
the following definitions, descriptions and descriptive figures of
specific embodiments thereof wherein like reference numerals in the
various figures are utilized to designate like components. While
these descriptions go into specific details of the invention, it
should be understood that variations may and do exist and would be
apparent to those skilled in the art based on the descriptions
herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] The invention is explained in more detail with reference to
the accompanying figures, in which:
[0044] FIG. 1 shows a schematic representation of the process
sequence for producing an antenna structure on a carrier layer.
[0045] FIG. 2 shows an enlarged view of a shadow mask for producing
an antenna structure.
[0046] FIG. 3 shows a radio-frequency identification tag according
to the prior art.
[0047] FIG. 4 shows a schematic representation of an installation
for producing the antenna structures for RF ID tags (isolating mask
structure formed as fixed cathode coating).
[0048] FIG. 5 shows a schematic representation of an installation
for producing the antenna structures for RF ID tags (isolating mask
structure formed as flexible film).
DETAILED DESCRIPTION
[0049] FIG. 1 shows schematic work steps implemented when producing
an antenna structure during the method according to the invention.
Firstly, as represented in FIG. 1a, a cathode 1 is provided, on the
upper side of which web-shaped portions 2 are arranged. The
web-shaped portions 2 comprise an electrically nonconducting
material. As a result, on the surface of the cathode 1 electrically
nonconducting regions are defined in the region of the web-shaped
portions 2 and electrically conducting regions are defined in the
portions 3, in which the cathode 1 is exposed. The structure of the
portions 3 corresponds to the structure of the structured metal
layer, for example an antenna structure. The portions 3 form
trenches, which are laterally bounded in each case by the
web-shaped portions 2. The flanks of the web-shaped portions 2,
represented in cross section in FIG. 1a, run perpendicularly in
relation to the surface of the cathode 1 in the exemplary
embodiment represented. However, it is also possible to make the
portions 3 formed as trenches take such a form that the trenches
taper in the direction of the surface of the cathode 1, so that,
after the depositing of a metal, the structured metal layer formed
in the portions 3 can be removed more easily from the trenches. A
substrate material 4, for example copper, is then deposited into
the portions 3 of a mask structure applied on the cathode 1. In
this case, the electrode depositing is carried out in such a way
that the trenches formed in the portions 3 are not completely
filled with the substrate metal 4, so that, as represented in FIG.
1b, a residual volume 5 remains in the upper portion of the
trenches. An adhesive 6 is introduced onto layer 4 of the substrate
metal in the remaining residual volume 5. The adhesive 6 in this
case fills the residual volume 5. In the cross section represented
in FIG. 1c, only the portions of the adhesive 6 formed by the
residual volume 5 are filled. The upper surfaces of the web-shaped
portions 2 remain uncovered by the adhesive. In principle, an
adhesive may also be applied to the upper surface of the web-shaped
portions 2. However, it is important that the adhesive does not
adhere, or only to a slight extent, on the material of the
web-shaped portions 2.
[0050] As represented in FIG. 1d, only a carrier layer 7 is placed
and possibly pressed onto the surface of the structure represented
in FIG. 1c. As this happens, the adhesive 6 comes into contact with
the surface of the carrier layer 7 and firmly adheres to it. If the
carrier layer 7 is lifted off, the portions of the deposited
substrate metal 7 are also lifted off with it, so that, as
represented in FIG. 1e, a carrier layer 7 is obtained, on the
surface of which webs of an electrically conductive substrate metal
4, e.g. copper, are fixed by an adhesive 6. The webs 4 correspond,
for example, to the windings of an antenna structure.
[0051] FIG. 2 shows a plan view of a mask structure which, in the
method according to the invention, is applied to a cathode to
produce the antenna structure. The mask structure comprises
electrically nonconducting regions 8, for example of
plastic/ceramic, which are represented in black in FIG. 2.
Electrically nonconducting regions 8 of the mask structure bound
portions 9 in which the cathode is exposed. These portions 9 form a
structure which corresponds to the windings to be represented of
the antenna. In the portions 9, the substrate metal is deposited by
the galvanic process. The mask structure consequently represents a
negative structure of the antenna to be produced. After the
production of the antenna, a microchip can be adhesively attached
on the square electrode area 10 with the aid of an electrically
conductive adhesive.
[0052] FIG. 3 shows a radio-frequency identification tag. An
antenna structure 12, constructed from a number of windings, has
been applied on a flexible film 11, which serves as a carrier
layer. The ends of the antenna structure 12 are connected in a
conducting manner to a silicon microchip 13. The carrier layer 11
may be provided on its rear side with an adhesive layer, to allow
the tag to be fastened on an article to be identified, for example
a file. The antenna structure 12 is first produced galvanically by
the process described above and subsequently transferred to the
film 11.
[0053] FIG. 4 schematically shows a section through a device for
electrodepositing antenna structures for RF ID tags. Arranged on
the circumferential surface 19 of a high-grade steel drum 14 is a
mask structure of plastic or ceramic (not represented). In the
regions in which the antenna structure is to be formed, the
circumferential surface 19 of the high-grade steel drum 14 is
exposed. The high-grade steel drum 14 is immersed in a bath 16
filled with electrolyte 15 in such a way that only the lower
portion of the high-grade steel drum 14 is immersed into the
electrolyte 15. In the bath 16 there is also a hollow head
electrode 17, which acts as an anode. The hollow head electrode 17
consists of crude copper. The high-grade steel drum 14 is mounted
rotatably with its axis 18, so that, by rotation of the high-grade
steel drum 14, its circumferential surface 19 is continuously
passed through the electrolyte 15. The rotational speed of the
high-grade steel drum 14 is set such that a specific portion on the
circumferential surface 19 of the high-grade steel drum 14 stays in
the electrolyte for about 1-2 minutes or however long is required
for depositing the desired layer thickness. A suitable voltage is
then applied between the high-grade steel drum 14 acting as the
cathode and the hollow head electrode 17 acting as the anode, so
that copper on the hollow head electrode 17 goes into solution and
the copper is deposited onto the electrically conductive exposed
portions of the high-grade steel drum 14. With a current density of
100 A/dm2 and an efficiency of 70%, the depositing rate is, for
example, 9 .mu.m/min. In this case, the dwell time of the cathode
in the electrolyte 15 can be controlled by the rotational speed of
the high-grade steel drum 14. The composition of the electrolyte is
chosen such that high current densities of up to 150 A/dm2 can be
used. Anode slurries which are deposited during the process are fed
to the precious metal processing.
[0054] In order, for example, to deposit a copper layer 10 .mu.m
thick, the depth of the mask structure is chosen to be 10.5 .mu.m.
The areas exposed by the isolating mask structure are galvanically
coated with a copper layer 10 .mu.m thick. In the remaining
residual depth of 0.5 .mu.m, the adhesive is then introduced in a
gravure printing process. A specific portion on the circumferential
surface is consequently introduced into the electrolyte 15 by
rotation of the high-grade steel drum 14 and moved through it. As
this happens, copper is continuously deposited on the electrically
conductive exposed regions until this portion is moved out of the
electrolyte 15 again by further rotation of the high-grade steel
drum 14. In this case, the depositing of the copper is set such
that a residual volume for the adhesive still remains in the
electrically conducting regions. Once the portion of the
circumferential surface 19 of the high-grade steel drum 14 has been
moved out of the electrolyte 15, it is initially taken past a
rinsing device 20 and a drying device 21. Subsequently, adhesive is
applied to the circumferential surface 19 of the high-grade steel
drum 14 by a roll 22 provided with an adhesive. Excess adhesive is
removed by a stripping device 23, so that the adhesive remains
essentially only in the residual volumes on the previously
deposited copper. The portion of the circumferential surface 19
provided with the adhesive is moved further by rotation of the
high-grade steel drum 14 and reaches a printing roll 24. A carrier
layer 25, for example a sheet of paper or sheet of plastic film, is
fed to the circumferential surface 19 and pressed against it by
means of the printing roll 24. The antenna structure provided with
the adhesive layer is transferred from the circumferential surface
19 to the carrier layer 25. The carrier layer 25 with the antenna
structure (not represented) applied on it is continuously
transported away by the printing roll 24.
[0055] FIG. 5 shows a cross section of a device in which further
degrees of freedom are formed for carrying out the method according
to the invention. The mask structure on the high-grade steel drum
14 formed here as a cathode is in this case created by a
circulating structured belt 26. As explained in the case of FIG. 4,
a high-grade steel drum 14 is arranged in such a way that, when it
rotates about its axis 18, the circumferential surface 19 is moved
through an electrolyte 15. As this happens, as explained above, a
structured metal layer is deposited in the exposed electrically
conductive regions on the circumferential surface 19 of the
high-grade steel drum 14. To define these exposed portions, a belt
26 runs around the circumferential area 19 of the high-grade steel
drum 14. Openings which correspond to the antenna structure to be
represented have been made in the belt 26. The belt 26 has a
thickness which is slightly greater than the thickness of the
antenna structure to be represented, in order to obtain a residual
volume for the adhesive to be applied to the antenna structure. The
belt 26 runs continuously between the high-grade steel drum 14 and
the return drum 27. To improve the sealing effect between the drum
and the belt, magnetic particles are incorporated into the belt 26.
Magnets are integrated into the high-grade steel drum 14. The
magnetic interaction causes the belt to bear closely against the
drum. After the electrodepositing of the antenna structure, the
surface of the belt 26 is firstly rinsed by the rinsing device 20
and dried by the drying device 21. When the high-grade steel drum
14 rotates further, the belt 26 together with the deposited antenna
structure is lifted off from the circumferential surface 19. The
belt 26 is fed to a roll 22, with which the adhesive is applied to
the surface of the belt 26. In order that the belt 26 bears well
against the circumferential surface of the roll 22, provided on the
opposite side of the belt 26 are supporting rollers 28, by which
the belt 26 is pressed against the roll 22. Excess adhesive is
subsequently removed by a stripper 23. After running around the
return drum 27, the belt 26 reaches a printing roll 24, by means of
which a carrier layer 25 is continuously fed to the surface of the
belt 26. In order to press the belt with adequate pressure against
the printing roll 24, supporting rollers 29 are provided on the
opposite side of the belt 26. The adhesive causes the represented
antenna structure to adhere on the surface of the carrier layer 25
and to be removed from the belt 26 and transferred to the carrier
layer 25. The carrier layer 25 with the antenna structure (not
represented) arranged on it is continuously carried away by
rotation of the printing roll 24. The belt 26 is fed back again to
the high-grade steel drum 14, so that a further antenna structure
can be produced.
[0056] Further auxiliary devices may be built into the overall
installation, in order to facilitate the lifting of the antenna
structures out of the structured belt.
[0057] Having described preferred embodiments of a new and improved
method of producing electrodeposited antennas for RF ID tags by
means of selectively introduced adhesive, it is believed that other
modifications, variations and changes will be suggested to those
skilled in the art in view of the teachings set forth herein. It is
therefore to be understood that all such variations, modifications
and changes are believed to fall within the scope of the present
invention as defined by the appended claims. Although specific
terms are employed herein, they are used in generic and descriptive
sense only and not for purposes of limitation.
[0058] List of Designations
[0059] 1 cathode
[0060] 2 webs
[0061] 3 conducting portions
[0062] 4 substrate metal
[0063] 5 residual volume
[0064] 6 adhesive
[0065] 7 carrier layer
[0066] 8 nonconducting regions
[0067] 9 portions
[0068] 10 square electrode area
[0069] 11 flexible film
[0070] 12 antenna structure
[0071] 13 silicon microchip
[0072] 14 high-grade steel drum
[0073] 15 electrolyte
[0074] 16 bath
[0075] 17 hollow head electrode
[0076] 18 axis
[0077] 19 circumferential surface
[0078] 20 rinsing device
[0079] 21 drying device
[0080] 22 roll
[0081] 23 stripping device
[0082] 24 printing roll
[0083] 25 carrier layer
[0084] 26 belt
[0085] 27 return drum
[0086] 28 supporting rollers
[0087] 29 supporting rollers
* * * * *