U.S. patent application number 09/903197 was filed with the patent office on 2001-11-22 for laminate rfid label and method of manufacture.
Invention is credited to Babb, Susan M..
Application Number | 20010043162 09/903197 |
Document ID | / |
Family ID | 22861119 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010043162 |
Kind Code |
A1 |
Babb, Susan M. |
November 22, 2001 |
Laminate RFID label and method of manufacture
Abstract
A laminated label has a first conductive material defining
electrical attachment pads; a dielectric material surrounding the
attachment pads; a second conductive material deposited on the
dielectric material and forming an antenna electrically connected
to the attachment pads. A layer of expandable material forms a
protective cavity surrounding the attachment pads. An IC chip is
received in the protective cavity and connected to the antenna.
Inventors: |
Babb, Susan M.; (Pewaukee,
WI) |
Correspondence
Address: |
QUARLES & BRADY LLP
411 E. WISCONSIN AVENUE
SUITE 2040
MILWAUKEE
WI
53202-4497
US
|
Family ID: |
22861119 |
Appl. No.: |
09/903197 |
Filed: |
July 11, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09903197 |
Jul 11, 2001 |
|
|
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09229407 |
Jan 13, 1999 |
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Current U.S.
Class: |
343/895 ;
343/873 |
Current CPC
Class: |
Y10T 428/24331 20150115;
H01L 2924/07811 20130101; Y10T 428/1486 20150115; Y10T 428/1476
20150115; Y10T 428/14 20150115; Y10T 428/1481 20150115; H01L
2224/16225 20130101; G06K 19/0775 20130101; Y10T 428/23 20150115;
Y10T 428/24273 20150115; Y10T 428/24322 20150115; H01L 2924/3025
20130101; Y10T 428/1405 20150115; B60C 23/0493 20130101; Y10T
428/24752 20150115; G06K 19/07749 20130101; H01L 2224/16 20130101;
H01Q 1/2241 20130101; H01L 2224/16227 20130101; H01L 2924/07811
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
343/895 ;
343/873 |
International
Class: |
H01Q 001/40; H01Q
001/36 |
Claims
I claim:
1. A method of making a laminated article for use as an RFID label
comprising the steps of: printing a first electrically conductive
material to form two attachment pads; printing a dielectric
material in a layer surrounding said attachment pads; printing a
second electrically conductive material onto said dielectric
material, said second electrically conducting material being shaped
to define an antenna; printing a protective material containing
heat expandable spheres in a layer surrounding said attachment
pads; and expanding said expandable spheres to form a protective
cavity containing said attachment pads.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of patent application
Ser. No. 09/229,407 filed on Jan. 13, 1999.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] (Not Applicable)
BACKGROUND OF THE INVENTION
[0003] The field of invention is radio frequency identification
(RFID) labels, more particularly a laminate label having an
expandable layer.
[0004] RFID devices are known in the art, such as disclosed in U.S.
Pat. No. 5,347,263. These devices are used in systems for access
control, animal feeding and health programs, inventory control,
process control, and security applications.
[0005] A typical RFID system has a passive RFID label having
circuitry therein and a separate RFID reader/writer. The RFID
reader/writer energizes the RFID label circuitry by transmitting a
power signal. The power signal may convey data which is stored in
memory incorporated in the RFID label circuitry. In response to the
power signal the RFID label circuitry may transmit a response
signal containing data stored in its memory. The RFID reader/writer
receives the response signal and interprets the data contained
therein. The data is then transmitted to a host computer for
processing.
[0006] In order to minimize the cost of labels, the labels are
fabricated in large quantities. One particular method of making the
RFID label is to print a conductive material, such as silver
conductive ink, in a pattern defining multiple antennae, onto a
substrate. The ink may be printed using silk screening techniques,
such as in a sheet fed or roll operation. Once the antennae are
printed, each antenna is die cut into individual pieces. Each piece
is placed in a carrier where an integrated circuit (IC) chip, such
as a flip chip, is electrically connected to the antenna using
conventional chip attachment methods. The chip is then encapsulated
in an epoxy material and the entire assembly is sandwiched between
protective layers.
[0007] This particular method of making an RFID label has several
drawbacks. The substrate material is expensive and when die cut,
there is significant waste. Once the individual antennae are die
cut into individual pieces, each piece must be loaded into a
carrier for subsequent processing. If a window is not cut into the
substrate, when the chip is encapsulated, there is a bump on the
label which can result in the chip being easily ripped off of the
label rendering the label inoperative. Finally, the bump on the
chip makes putting the label through marking equipment, such as
thermal transfer, ink jet, or laser printers, difficult.
[0008] Another method of manufacturing an RFID label, described in
U.S. Pat. No. 5,528,222, has an antenna formed as an integral part
of an insulating substrate and a circuit chip mounted on the
substrate. This particular label requires a substrate which
increases the label thickness and the overall cost of the label. To
minimize the label thickness, a window may be cut in the substrate
allowing insertion of the chip into the window. Cutting a window in
the substrate, however, further increases the cost of the
label.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention provides a laminated label having a
first conductive material defining electrical attachment pads; a
dielectric material deposited within a label area and surrounding
the attachment pads; a second conductive material defining an
antenna deposited on the dielectric material and being electrically
connected to the attachment pads; and an expandable material
deposited in the label area, wherein expanding the expandable
material forms a cavity surrounding the attachment pads for
receiving an IC chip.
[0010] A general objective of the invention is to provide a label
which is easy and economical to manufacture. The laminated label
may be formed by silk screening the materials forming the label on
a releasable liner. The laminated label is easily formed using
automated equipment and it does not require a substrate.
[0011] Another objective of the present invention is to provide an
RFID label having an IC chip that does not form a bump on the label
surface. This objective is accomplished by forming a cavity in the
label for receiving the IC chip. The cavity provides a receptacle
for mounting an IC chip and avoiding a bump on the label.
[0012] The foregoing and other objects and advantages of the
invention will appear from the following description. In the
description, reference is made to the accompanying drawings which
form a part hereof, and in which there is shown by way of
illustration a preferred embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a perspective view of an RFID label incorporating
the present invention;
[0014] FIG. 2 is an exploded perspective view of the label of FIG.
1;
[0015] FIG. 3 is a partial perspective view of the label of FIG. 1
showing the first four layers;
[0016] FIG. 4 is a cut-away perspective view of the label of FIG.
1; and
[0017] FIG. 5 is a sectional view of the label of FIG. 1 along line
5-5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Referring to FIGS. 1, 2, and 5, a laminated RFID label 10
has five layers 14, 16, 18, 20, and 22, and forms a protective
cavity 26 for RFID circuitry in the form of an IC chip 30. One of
the layers 22 defines the cavity 26 for the IC chip 30, which is
electrically connected to an antenna 24. The label 10 may be
encapsulated or receive additional protective or functional layers
28 suitable for specific applications.
[0019] Referring to FIGS. 2 and 5, the first layer 14 is an
adhesive material which is deposited on a release liner 32. The
release liner is preferably a silicone coated paper. However, any
liner having releasable properties may be used without departing
from the scope of the present invention. By forming the label 10 on
the release liner 32, a substrate is not required, thus reducing
the cost of the label 10.
[0020] The adhesive first layer 14 may be a UV curable pressure
sensitive adhesive, such as Acheson ML25251 available from Acheson
Colloids Company, Port Huron, Mich. This layer 14 provides an
adhesive surface for the finished label 10 and defines the boundary
of the label area of the generally rectangular label 10. Although,
the label 10 described herein is generally rectangular, the label
10 may be any shape without departing from the scope of the present
invention.
[0021] The second layer 16 is an electrically conductive material
which is selectively deposited onto the first layer 14. It is
formed of a metallic conductive ink, such as Acheson
Electrodag.RTM. 479SS available from Acheson Colloids Company, Port
Huron, Mich. The second layer 16 may be deposited using silk
screening, or other methods known in the art for depositing an
electrically conductive material, such as electro deposition, hot
stamping, etching or the like.
[0022] As shown best in FIG. 2, the electrically conductive
material 16 is deposited onto portions of the first layer 14
defining at least two landing pads 34, 35 for IC chip attachment
and a cross over pass 36. The landing pads 34 provide electrical
attachment pads for electrically connecting the fourth layer 20 to
the IC chip 30. As more clearly described below, in cooperation
with the third layer 18, the cross over pass 36 electrically
connects one of the landing pads 34 to a portion of the antenna 24
without shorting out other antenna portions. Although two landing
pads 34, 35 are described herein, more than two landing pads 34, 35
may be formed for connecting to the IC chip 30 without departing
from the scope of the present invention.
[0023] Referring to FIGS. 2 and 3, the third layer 18 is a
dielectric material, such as Acheson Electrodag.RTM. 451SS
available from Acheson Colloids Company, Port Huron, Mich. It is
deposited within the label boundary and it has an annular shape
which surrounds a small central area 37 containing the landing pads
34, 35. The central area 37 is thus not coated with the dielectric
material 18. The area 37 is sized to accommodate the IC chip 30
which is mounted over and electrically connected to the landing
pads 34, 35. A conductive via 38 for electrically connecting the
cross over pass 36 to the fourth layer 20 is also formed by leaving
a small portion of the cross over pass 36 uncoated by the
dielectric material 18.
[0024] Looking particularly at FIG. 3, the fourth layer 20 is a
metallic conductive ink, such as used in the second layer 16. It is
deposited onto the dielectric third layer 18 in a spiral pattern
defining an antenna 24. The spiral antenna 24 has a plurality of
rings including an inner ring 40 and an outer ring 42. The antenna
inner ring 40 is electrically connected to one of the landing pads
34. The antenna outer ring 42 is deposited over the via 38
electrically connecting the antenna outer ring 42 to the other
landing pad 35 through the cross over pass 36 without electrically
contacting the other antenna rings. Although a spiral antenna is
preferred and described herein, any suitable antenna shape may be
used without departing from the scope of the present invention.
[0025] As shown in FIG. 2, the fifth layer 22 is shaped
substantially the same as the dielectric layer 18. It is formed
from an expandable material, such as a thermally expandable spacer
ink comprising a binder of a polymeric resin system and an
expandable additive, such as thermoplastic hollow spheres
encapsulating a gas, or a blowing agent.
[0026] Preferably, the additive is thermally expandable, such as
the thermoplastic hollow spheres, Expancel.RTM. 551DU, available
from Expancel, Inc., Duluth, Ga. Although Expancel.RTM. 551DU is
preferred, other expandable additives, such as Expancel.RTM. 091DU,
Expancel.RTM. 461DU, or blowing agents may be used without
departing from the scope of the present invention. For example,
blowing agents, such as diazoaminobenzene,
azobis(isobutyronitrile), dinitroso pentamethylene tetramine,
N,N'-dinitroso-N,N'-dimethylterephthalamide, azodicarbonamide,
sulfonyl hydrazides, benzene sulfonyl hydrazide, p-toluene sulfonyl
hydrazide, p,p-oxybis (benzene sulfonyl hydrazide), sulfonyl
semicarbazides, decomposition products of p-toluene sulfonyl
semicarbazide, esters of azodicarboxylic acid, and salts of
azodicarboxylic acid are known in art and may be combined with the
binder to form the expandable layer.
[0027] The polymeric resin system includes a resin and a solvent to
provide a flexible vehicle which does not degrade upon expansion of
the expandable additive. The resin is preferably a polyester,
however it could also be a vinyl, ethylene vinyl acetate, acrylic,
polyurethane, or a combination thereof, which is mixed with a
compatible solvent, such as methyl ethyl ketone, toluene,
cyclohexane, glycol ether, or the like.
[0028] Preferably, the expandable fifth layer 22 is formulated,
such that upon curing, it expands to a thickness substantially
equal to the thickness of the epoxy encapsulated IC chip 30. For a
chip height of approximately 0.35 mm, the expandable material
preferably comprises no more than about 85% solvent, no more than
about 30% resin, and no more than about 15% expandable additive. In
the preferred embodiment, the expandable layer 22 comprises
approximately 70% solvent, 23% resin, and 7% expandable additive.
Typical chip heights range from approximately 0.25-0.9 mm and, of
course, a different chip height will require a different
combination of materials to provide the desired expansion of the
expandable material. Although, the expandable material preferably
has a thickness substantially equal to the thickness of the
encapsulated IC chip, any expandable material thickness greater or
less than the IC chip height will provide some protection to the
chip and may be used without departing from the scope of the
invention.
[0029] Following deposition of the expandable layer 22, the
laminate article 10 is cured causing the layer 22 to expand. As
shown in FIGS. 1, 2, 4, and 5, the expanded material surrounds the
landing pads 34, 35 and defines a protective cavity 26 for
receiving the IC chip 30 and an epoxy encapsulant 44.
Advantageously, by providing the preferred cavity 26 for the IC
chip 30 and the encapsulant 44, the IC chip 30 does not form an
exposed bump on the finished label 10.
[0030] Preferably, the IC chip 10 is a flip chip having a memory
and easily electrically connected to the landing pads 34 using
conventional chip attachment methods. For example, once the
protective cavity 26 is formed, a conductive adhesive, such as a
needle dispensed polymeric conductive adhesive or an anisotropic
conductive adhesive, is deposited into the cavity to electrically
connect the chip 30 to each of the landing pads 34, 35. The IC chip
30 is then placed into the cavity 26 and encapsulated in the epoxy
44. The epoxy 44 deposited into the cavity 26 further protects the
IC chip 30 and secures it in place. Although encapsulating the IC
chip 30 with the epoxy 44 is described herein, encapsulating the
chip is not required to practice the invention and in certain
applications may not be desired.
[0031] One or more additional layers 28, such as a polymeric resin
system comprising resins and solvents described above, may be
deposited onto the fifth layer 22. The additional layers 28 may
provide a layer which is compatible with thermal transfer, ink jet,
or laser printing.
[0032] Alternatively, an overlaminate may be deposited on the
expandable layer 22 or subsequent layers 28 to provide an adhesive
surface to the laminate article 10. An overlaminate is a film, such
as a polyester, cellulose acetate, vinyl, polyethylene,
polypropylene, styrene, or the like, mixed with an adhesive, such
as an acrylic or rubber.
[0033] Preferably, each layer 14, 16, 18, 20, and 22 is formed
using a silk screening process. The silk screening process may be a
sheet fed operation or a roll to roll process. The sheet fed
operation will result in sheets of multiple up labels or individual
labels. The roll to roll process can supply rolls of labels in
addition to sheet forms provided in the sheet fed method.
[0034] Deposition of layer material on the central area 37 around
the landing pads 34, 35 is prevented by placing, a releasable
material, such as foam with a releasable adhesive, over the central
area 37 during the silk screening process. Another method includes
mounting the chip 30 prior to applying the expandable layer 22 and
then notching the squeegee used in the silk screen printing process
to avoid striking the chip 30.
[0035] Although silk screening is preferred, other printing or
deposition techniques, such as rotogravure, may also be used
without departing from the scope of the present invention.
Regardless of the particular technique chosen, the same process is
preferably used to sequentially form each layer 14, 16, 18, 20, and
22 of the laminate article 10.
[0036] While there has been shown and described what are at present
considered the preferred embodiment of the invention, it will be
obvious to those skilled in the art that various changes and
modifications can be made therein without departing from the scope
of the invention defined by the appended claims. For example,
alternative embodiments include eliminating the adhesive first
layer, encapsulating the laminate article into a formed tag, or
applying the adhesive layer last.
[0037] The present invention may also be deposited onto a substrate
if the release liner is not suited to the particular application
and the added cost of the substrate is justified. For example, in
another preferred embodiment an expandable layer may be deposited
onto a conventionally formed RFID circuit with a substrate. As
described above, the expandable layer forms a protective cavity for
an IC chip. A laminated adhesive may then be formed on the
substrate or other layers may be deposited onto the expandable
layer as described above.
* * * * *