U.S. patent application number 09/728217 was filed with the patent office on 2002-06-06 for radio frequency identification tag on a single layer substrate.
Invention is credited to Amand, Roger St., Furey, Lee, Lee, Youbok.
Application Number | 20020067266 09/728217 |
Document ID | / |
Family ID | 24925901 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020067266 |
Kind Code |
A1 |
Lee, Youbok ; et
al. |
June 6, 2002 |
Radio frequency identification tag on a single layer substrate
Abstract
A radio frequency identification (RFID) tag on a single layer
substrate comprises a semiconductor integrated circuit RFID tag
device and antenna circuit. A connection jumper may be used to
bridge over the antenna circuit coil turns. The RFID tag device is
located on the same side as an inductor coil and capacitor which
forms a parallel resonant antenna circuit. The inductor coil has an
inner end and an outer end. The inner or outer end may be connected
directly to the RFID tag device and the outer or inner end be may
connected to the RFID tag device with a jumper over the inductor
coil turns, or the RFID tag device may bridge the inductor coil
turns when being connected to both the inner and outer ends. An
encapsulation (glop top) may be used to seal the RFID tag device
and jumper, and an insulated coating may be used to cover the
entire surface of the substrate to create an inexpensive
"chip-on-tag." The encapsulation may be epoxy, plastic or any
protective material known to one of ordinary skill in the art of
electronic circuit encapsulation. The insulated coating may be of
any type suitable for the application of use of the RFID tag.
Inventors: |
Lee, Youbok; (Chandler,
AZ) ; Furey, Lee; (Phoenix, AZ) ; Amand, Roger
St.; (Tempe, AZ) |
Correspondence
Address: |
Attention of: Paul N. Katz.
Baker Botts L.L.P.
One Shell Plaza
910 Louisiana Street
Houston
TX
77002-4995
US
|
Family ID: |
24925901 |
Appl. No.: |
09/728217 |
Filed: |
December 1, 2000 |
Current U.S.
Class: |
340/572.7 ;
340/572.1 |
Current CPC
Class: |
G06K 19/0726 20130101;
H01L 2224/48091 20130101; H01L 2224/48091 20130101; H01L 2924/01079
20130101; G06K 19/0775 20130101; H01L 2924/19041 20130101; G06K
19/07749 20130101; H01L 2924/00014 20130101 |
Class at
Publication: |
340/572.7 ;
340/572.1 |
International
Class: |
G08B 013/14 |
Claims
What is claimed is:
1. A radio frequency identification (RFID) tag, comprising: a
substrate that is electrically insulated and transparent to radio
frequency signals, said substrate having a surface; an inductor
coil on the surface of said substrate, said inductor coil having an
outer end and an inner end; a RFID tag device on the surface of
said substrate, said RFID tag device connected to the inner end of
said inductor coil; and a jumper conductor disposed over said
inductor coil, wherein said jumper conductor connects the outer end
of said inductor coil to said RFID tag device.
2. The RFID tag of claim 1, further comprising a capacitor on the
surface of said substrate and connected to said inductor coil to
form a resonant circuit antenna.
3. The RFID tag of claim 2, wherein said inductor coil and said
capacitor form a parallel resonant circuit antenna.
4. The RFID tag of claim 2, wherein said inductor coil and said
capacitor form a series resonant circuit antenna.
5. The RFID tag of claim 1, wherein said inductor coil forms a
resonant circuit antenna with an internal capacitor of said RFID
tag device.
6. The RFID tag of claim 5, wherein said inductor coil and the
internal capacitor form a parallel resonant circuit antenna.
7. The RFID tag of claim 1, wherein said inductor coil is a spiral
coil.
8. The RFID tag of claim 7, wherein the spiral coil has a plurality
of coil turns.
9. The RFID tag of claim 1, wherein said jumper conductor is a bond
wire.
10. The RFID tag of claim 9, further comprising a connection pad
connected to said RFID tag device and adapted for connect to the
bond wire.
11. The RFID tag of claim 7, further comprising a plurality of
connection pads located between the plurality of coil turns and
adapted for connection to a plurality of bond wires and a one of
the plurality of connection pads also being connected to said RFID
tag device.
12. The RFID tag of claim 1, wherein said jumper conductor is an
electrical conductor insulated from said inductor coil where
crossing thereover.
13. The RFID tag of claim 10, wherein said RFID tag device is a
flipchip connected to said inductor coil and the connection
pad.
14. The RFID tag of claim 1, further comprising protective
encapsulation over said RFID tag device and jumper.
15. The RFID tag of claim 1, further comprising an insulation
coating over said inductor coil.
16. The RFID tag of claim 1, further comprising test connection
pads on said substrate and connected to said RFID tag device.
17. The RFID tag of claim 1, further comprising programming
connection pads on said substrate and connected to said RFID tag
device.
18. A method of fabricating an inexpensive radio frequency
identification (RFID) tag, said method comprising the steps of:
providing a substrate that is electrically insulated and
transparent to radio frequency signals, wherein said substrate has
a surface; forming an inductor coil on the surface of said
substrate, said inductor coil having an outer end and an inner end;
disposing a RFID tag device on the surface of said substrate;
connecting said RFID tag device to the inner end of said inductor
coil; disposing a jumper conductor over said inductor coil; and
connecting the outer end of said inductor coil to said RFID tag
device with said jumper conductor.
19. The method of claim 18, further comprising the step of
encapsulating said RFID tag device and said jumper conductor with a
protective material.
20. The method of claim 19, wherein the protective material is
epoxy.
21. The method of claim 18, further comprising applying an
insulating coating to said inductor coil on the surface of said
substrate.
22. The method of claim 18, further comprising providing test
connection pads on said substrate and connecting said test
connection pads to said RFID tag device.
23. The method of claim 18, further comprising providing
programming connection pads on said substrate and connecting said
programming connection pads to said RFID tag device.
24. The RFID tag of claim 1, wherein material for said substrate is
selected from the group consisting of PET, mylar, paper, plastic,
silicon, kapton, ceramic, polyimide and polyvinylchloride
(PVC).
25. The RFID tag of claim 1, wherein material for said inductor
coil is selected from the group consisting of copper, aluminum,
gold, plated metal, and electrically conductive organic and
inorganic materials.
26. A radio frequency identification (RFID) tag, comprising: a
substrate that is electrically insulated and transparent to radio
frequency signals, said substrate having a surface; an inductor
coil on the surface of said substrate, said inductor coil having an
outer end and an inner end; a RFID tag device positioned over a
portion of said inductor coil on the surface of said substrate,
wherein said RFID tag device connects to the inner and outer ends
of said inductor coil.
27. The RFID tag of claim 26, further comprising a conductive trace
through said RFID tag device, wherein said conductive trace is
adapted for connecting a capacitor to said inductor coil.
28. The RFID tag of claim 27, further comprising a capacitor
located on the surface of said substrate and connected to said
inductor coil
29. The RFID tag of claim 28, wherein the capacitor is connected in
parallel with said inductor coil.
30. The RFID tag of claim 28, wherein the capacitor is connected in
series with said inductor coil.
31. The RFID tag of claim 26, wherein said inductor coil forms a
resonant circuit antenna with an internal capacitor of said RFID
tag device.
32. The RFID tag of claim 31, wherein said inductor coil and the
internal capacitor form a parallel resonant circuit antenna.
33. The RFID tag of claim 26, wherein said RFID tag device is a
flipchip having solder bump connections which are adapted to
connect to the inner and outer ends of said inductor coil.
34. The RFID tag of claim 26, wherein said RFID tag device connects
to the inner and outer ends of said inductor coil with bond
wires
35. The RFID tag of claim 26, wherein said inductor coil turns have
a substantially constant width.
36. The RFID tag of claim 35, wherein said inductor coil turns have
a low resistance and a high quality factor (Q).
37. The RFID tag of claim 26, further comprising an electrically
insulating layer between said RFID tag device and the portion of
said inductor coil.
38. The RFID tag of claim 37, wherein the electrically insulating
layer is selected from the group consisting of mylar, mica,
plastic, teflon, kapton and polyimide
39. The RFID tag of claim 37, wherein the electrically insulating
layer is attached to the portion of said inductor coil and said
RFID tag device.
40. A method of fabricating an inexpensive radio frequency
identification (RFID) tag, said method comprising the steps of:
providing a substrate that is electrically insulated and
transparent to radio frequency signals, wherein said substrate has
a surface; forming an inductor coil on the surface of said
substrate, said inductor coil having an outer end and an inner end;
disposing a RFID tag device over a portion of said inductor coil on
the surface of said substrate; and connecting said RFID tag device
to the inner and outer ends of said inductor coil.
41. The method of claim 40, further comprising the step of
providing a conductive trace through said RFID tag device, wherein
said conductive trace is adapted for connecting a capacitor to said
inductor coil.
42. The method of claim 41, further comprising the steps of
locating a capacitor on the surface of said substrate and
connecting said capacitor to said inductor coil
43. The method of claim 42, wherein the capacitor is connected in
parallel with said inductor coil.
44. The method of claim 42, wherein the capacitor is connected in
series with said inductor coil.
45. The method of claim 40, further comprising the steps of
providing an internal capacitor of said RFID tag device and
connecting said internal capacitor to said inductor coil to form a
resonant circuit antenna.
46. The method of claim 45, wherein said inductor coil and the
internal capacitor form a parallel resonant circuit antenna.
47. The method of claim 40, wherein said RFID tag device is a
flipchip having solder bump connections which are adapted for
connecting to the inner and outer ends of said inductor coil.
48. The method of claim 40, further comprising the steps of
connecting said RFID tag device to the inner and outer ends of said
inductor coil with bond wires
49. The method of claim 40, wherein said inductor coil turns have a
substantially constant width.
50. The method of claim 49, wherein said inductor coil turns have a
low resistance and a high quality factor (Q).
Description
RELATED PATENT APPLICATION
[0001] This application is related to commonly owned U.S. patent
application Ser. No. ______ entitled "INDUCTIVELY TUNABLE ANTENNA
FOR A RADIO FREQUENCY IDENTIFICATION TAG" by Youbok Lee, Lee Furey
and Roger St. Amand, and is hereby incorporated by reference for
all purposes.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to a radio frequency
identification (RFID) tag, and more particularly, to a RFID tag on
a single layer substrate comprising a semiconductor integrated
circuit RFID tag device and antenna circuit.
DESCRIPTION OF THE RELATED TECHNOLOGY
[0003] A radio frequency identification (RFID) tag is a device that
stores identification information and sends back this
identification information, and may also include other information,
when the device is powered-up by a radio frequency (RF) signal.
RFID tags utilize radio frequencies that have much better
penetration characteristics to material than do optical signals,
and will work under more hostile environmental conditions than bar
code labels. Therefore, the RFID tags may be read through paint,
water, dirt, dust, human bodies, concrete, or through the tagged
item itself. RFID tags are used in conjunction with a radio
frequency tag reader (interrogator) which transmits RF signals and
receives data signals from the RFID tag. These RFID tags may be
used in managing inventory, automatic identification of cars on
toll roads, security systems, electronic access cards, keyless
entry and the like. More applications are becoming commercially
feasible as the cost of the RFID tags decrease.
[0004] The passive RFID tag has no internal power source, rather it
uses the incoming RF signal as a power source. Once the RFID tag is
activated, it sends stored information to the interrogator. The
RFID tag transmits this stored information to the
reader-interrogator by modulating the amplitude of the RF carrier
signal from the reader by detuning a resonant circuit of the RFID
tag that is initially tuned to the RF carrier signal (de-Qing or
loading, for example by resistive loading, of the resonant circuit
in the RFID tag may also be used to modulate the amplitude of the
RF carrier signal of the reader-interrogator). The resonant circuit
of the RFID tag may be, for example, a parallel connected inductor
and capacitor which is used as an antenna and is resonant (tuned)
to the frequency of the RF carrier signal of the interrogator. A
semiconductor integrated circuit is connected to the parallel
resonant antenna circuit and comprises an RF to direct current (DC)
converter, a modulation circuit to send the stored information to
the reader-interrogator, a logic circuit which stores coded
information, a memory array that stores digitized information, and
controller logic that controls the overall functionality of the
RFID tag.
[0005] The inductor of the parallel resonant antenna circuit
generally may be formed into a coil using wire or printed circuit
conductors positioned on one surface of a planar dielectric
(electrically insulated) substrate with connections being made
between this coil and the RFID tag device semiconductor integrated
circuit. These connections generally require the use of both sides
of the planar substrate and increase the cost and complexity in
manufacturing the RFID tag and decreases reliability thereof.
Therefore, what is needed is a more reliable, simpler, lower cost,
and easier to manufacture RFID tag.
SUMMARY OF THE INVENTION
[0006] The invention overcomes the above-identified problems as
well as other shortcomings and deficiencies of existing
technologies by providing an RFID tag comprising a semiconductor
integrated circuit (RFID tag device) connected to an inductor coil
of a parallel resonant circuit antenna and a jumper to one end of
the parallel resonant circuit antenna, all being on one side of a
dielectric substrate. The inductor coil may resonate with a
discrete capacitor connected to the inductor coil, or a capacitor
that is part of and internal to the semiconductor integrated
circuit RFID tag device. A series resonant circuit antenna is also
contemplated and within the scope of the invention.
[0007] In an embodiment of the invention, a RFID tag comprises a
dielectric (electrically non-conductive and transparent to radio
frequency signals) substrate having an antenna formed as an
inductor by using electrically conductive material on only one side
of the substrate. The substrate may be, for example but not limited
to; PET, mylar, paper, plastic, kapton, ceramic, silicon,
polyimide, polyvinylchloride (PVC), etc., and combinations thereof.
A RFID tag device semiconductor integrated circuit die is attached
to the substrate on the same side as the antenna inductor and is
electrically connected thereto. The antenna inductor may be a
spiral coil having two ends, an inner and an outer end. The inner
end is connected to an inside spiral turn of the spiral coil and
the outer end is connected to an outside spiral turn of the spiral
coil. Generally, the semiconductor integrated circuit die is
located on the inside of the spiral coil and is easily connected to
the inner end of the spiral coil, since the inner end and the die
may be in close proximity.
[0008] Connection to the RFID tag device semiconductor integrated
circuit die may be by wire bonding, flipchip (C4), etc., or any
combination thereof. The dielectric substrate may also have other
connection pads that may be used for testing and/or programming the
RFID tag. The semiconductor integrated die may be attached directly
to the surface of the substrate, and the coil (and the other
connection pads) may be formed on the same surface by printing,
etching, hot stamping and the like. This type of coil construction
allows better conductance (inverse of resistance) which results in
a higher Q of the coil. The coil material is electrically
conductive and may be, for example but not limited to; metal such
as copper, aluminum, gold, plated metal, electrically conductive
organic and inorganic materials, etc.
[0009] The outer end of the spiral coil is connected to the RFID
tag device integrated circuit die with a jumper that is also on the
same side of the substrate as the antenna coil and integrated
circuit die. The jumper goes over the spiral coil from the outer
end to a bond pad of the integrated circuit die in the case of wire
bonding where the back of the die is attached to the surface of the
substrate and the connection pads of the integrated circuit die are
facing away from the surface of the substrate.
[0010] The jumper may be a bond wire connected by thermal
compression bonding, ball bonding and the like. The jumper may also
be any type of conductor that is cut, etched, deposited and the
like which can be insulated from the inductor coil when passing
thereover.
[0011] When using wire bonding, all connections to the integrated
circuit die are made by bond wires, i.e., inner and outer ends of
the coil, programming and test pads, etc. After the bond wires are
installed, an encapsulation (glop top) cover may be used to protect
the integrated circuit die and bond wires. This form of
construction is easy to manufacture and low in cost. Intermediate
pads may be used between the coil turns to reduce the length of the
bond wire going from the outer end of the coil to the bond pad of
the integrated circuit die. The inductor coil may be coated with a
insulating coating so as to make the RFID tag completely insulated.
Thus, a low cost "chip-on-tag" is created with no further
processing required.
[0012] The semiconductor integrated circuit die may also be
attached to connection pads on the substrate by using flipchip or
C4 connections wherein "solder ball bumps" on bond pads of the die
attach to the substrate pads and all other connections to these
pads are by printed circuit conductors and a bond wire (jumper
across coil turns). A thin insulating layer such as polyimide may
be used between the coil jumper and the inductor coil turns to
prevent shorting of the coil, however, once the encapsulation (glop
top) is in place and has cured, no movement of the jumper bond wire
can occur.
[0013] In another embodiment of the invention, a flipchip die
straddles the inductor coil turns so that one solder ball bump of
the flipchip die connects to the outer end of the inductor coil and
another solder ball bump of the flipchip die connects to the inner
end of the inductor coil. A conductive trace may also be provided
within the flipchip die that is a conductive circuit within the die
that may serve as a jumper over the turns of the inductor coil. The
conductive trace may be adapted to connect an external capacitor in
parallel with the inductor coil. The external capacitor may be
located inside or outside of the inductor coil turns and may be on
the same side of the substrate as the inductor coil and die.
[0014] In still another embodiment, a die may be attached over a
portion of the inductor coil turns with an insulating layer of
material therebetween. The insulating layer may be a B-staged
kapton or epoxy that may be cured so as to attach the die to the
substrate. Mylar, mica, plastic, teflon, kapton, polyimide and the
like may be used as an insulating layer that is attached to the
substrate and the die. The die has bond pads thereon and wire
bonding (bond wires) may be used to connect the die bond pads to
the inner and outer ends of the inductor coil turns. The bond wires
may be used as jumpers over the inductor coil turns and further may
allow the inductor coil turns to remain at full width while passing
under the die. By allowing the inductor coil turns to remain at
full width, the coil turns have a lower resistance and thus yield a
higher quality factor (higher Q). A conductive trace may also be
provided within the die that is a conductive circuit through the
die that may be adapted to connect an external capacitor in
parallel with the inductor coil. The external capacitor may be
located inside or outside of the inductor coil turns and may be on
the same side of the substrate as the inductor coil and die.
[0015] Features and advantages of the invention will be apparent
from the following description of presently preferred embodiments,
given for the purpose of disclosure and taken in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 illustrates a schematic block diagram of an RFID tag
system that includes both a radio frequency reader (Interrogator)
and a RFID tag;
[0017] FIG. 2 illustrates a schematic plan view of an RFID tag
according to an embodiment of the invention;
[0018] FIG. 3 is a schematic elevational view of a section of the
embodiment illustrated in FIG. 2;
[0019] FIG. 4 is a schematic plan view of an alternate embodiment
of the jumper connection of FIG. 2;
[0020] FIG. 5 is a schematic plan view of an embodiment of the
invention having flipchip or C4 connections;
[0021] FIG. 6 is a schematic plan view of the underside of an
embodiment of an RFID tag;
[0022] FIG. 7 is a schematic plan view of the top of the embodiment
of FIG. 6;
[0023] FIG. 8 is a schematic plan view of a flipchip embodiment of
an RFID tag;
[0024] FIG. 9 is a schematic plan view of a portion of the RFID tag
illustrated in FIG. 8;
[0025] FIG. 10 is a schematic plan view of a bond wire embodiment
of an RFID tag;
[0026] FIG. 11 is a schematic elevational view of a portion of the
RFID tag illustrated in FIG. 10; and
[0027] FIG. 12 is a schematic plan view of a portion of the RFID
tag illustrated in FIG. 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] The present invention is directed to a radio frequency
identification (RFID) tag comprising a RFID tag device
semiconductor integrated circuit, and a parallel resonant antenna
circuit comprising a coil inductor and a capacitor all being on the
same side of a dielectric substrate of the RFID tag. The RFID tag
device may be connected to one end of the parallel resonant antenna
circuit with a jumper located on the same side as the coil
inductor, capacitor and RFID tag device on the substrate. In
addition, the RFID tag device may bridge over the coil inductor and
directly attach to each end of the coil inductor or connect to each
end of the coil inductor with bond wires on the same side of the
substrate thereon.
[0029] Referring now to the drawings, the details of preferred
embodiments of the invention are schematically illustrated. Like
elements in the drawings will be represented by like numbers, and
similar elements will be represented by like numbers with a
different lower case letter suffix.
[0030] FIG. 1 illustrates a schematic block diagram of a RFID
system that includes a radio frequency generator/interrogator/tag
reader 720 and an RFID tag 200. The tag reader 720 has a tuned
circuit 706 comprising an inductor 708 and a capacitor 710
connected in series. RF generator/interrogator/tag reader 720
produces continuous wave (CW) radio frequency (RF) power across the
turned circuit 706. This CW RF power is electro-magnetically
coupled by alternating current action to a parallel resonant
circuit antenna 106 of the RFID tag 200. The CW RF electromagnetic
power is generally represented by the numeral 722. The RFID tag 200
has a power converter circuit that converts some of the CW RF
electromagnetic power 722 into direct current power for use by the
logic circuits of the RFID tag integrated circuit device 202 (not
illustrated).
[0031] When the parallel resonant circuit antenna 106 of the RFID
tag 200 is in proximity to the tuned circuit 706 of the RF
generator/interrogator/tag reader 720, it develops an AC voltage
across the tuned circuit 106. The AC voltage across the parallel
resonant circuit antenna 106 is rectified and when the rectified
voltage becomes sufficient enough to activate the RFID tag
integrated circuit device 202, the RFID tag 200 is activated and
starts sending stored data in its memory register by modulating the
incoming RF carrier signal 722 of the reader 720. The
interrogator/tag reader 720 detects these modulated signals and
converts them into a detected serial data word bitstream of on/off
pulses representative of the information from the RFID tag 200.
[0032] FIG. 2 illustrates a schematic plan view of an RFID tag 200
according to an embodiment of the invention. The parallel resonant
circuit antenna 106 of the RFID tag 200 comprises an inductor coil
108 and a capacitor 110. The RFID device 202 is a semi-conductor
integrated circuit device that includes electronic logic circuits
for radio frequency identification purposes. A jumper 206 connects
an outer end of the coil 108 to the capacitor 110 and RFID device
202. The coil 108, capacitor 110, RFID device 202 and jumper 206
are all on the same surface of an insulated substrate 204. This
allows single sided substrates which are lower in cost and result
in easier to manufacture RFID tags. The discrete capacitor 110 may
be replaced with a capacitor which is integral with the RFID tag
device 202.
[0033] The substrate 204 has a parallel resonant circuit antenna
106 formed by the inductor coil 108 and the capacitor 110. The
substrate may be, for example but not limited to; PET, mylar,
paper, plastic, kapton, polyimide, etc., and combinations thereof.
The RFID tag device 202 is attached to the substrate 204 on the
same side as the antenna inductor coil 108 and capacitor 110 and is
electrically connected thereto. The antenna inductor coil 108 is a
spiral coil having two ends, an inner end 210 and an outer end 212.
Generally, the RFID tag device 202 is located on the inside of the
coil 108 and is easily connected to the inner end 210, since the
inner end 210 and the RFID tag device 202 are in close proximity. A
connection pad 214 may be used to connect one end of the jumper
206. The jumper 206 may also be connected to a bond pad 214a on the
RFID tag device 202 (see FIG. 3). It is contemplated and within the
scope of the invention that the inductor coil 108 and capacitor 110
also may be connected as a series resonant circuit antenna.
[0034] Connection to the RFID tag device 202 may be by wire
bonding, flipchip (C4), etc., or any combination thereof The
dielectric substrate 204 may also have other connection pads that
may be used for testing and/or programming the RFID tag 200 (see
FIG. 6). The RFID tag device 202 may be attached directly to the
surface of the substrate 204, and the coil 108 (and the other
connection pads) may be formed on the same surface of the substrate
204 by printing, etching, hot stamping and the like. This type of
coil construction allows better conductance (inverse of resistance)
which results in a higher Q of the coil 108. The coil 108 is made
of material that is electrically conductive and may be, for example
but not limited to; metal such as copper and aluminum, plated
metal, electrically conductive organic and inorganic materials,
etc.
[0035] Referring to FIG. 3, an elevational view of a section 3-3 of
the embodiment in FIG. 2 is illustrated. The jumper 206 is
connected to the outer end 212 of the spiral coil 108 and may be
connected directly to the bond pad 214a on the RFID tag device 202
or to the connection pad 214. All connections and components are on
the same side of the substrate 204 as the antenna coil 108. The
connection pad 214 is also connected to the capacitor 110 and the
RFID tag device 202. The jumper 206 goes over the spiral coil 108
from the outer end 212 and may connect to a bond pad 214a of the
RFID tag device 202 in the case of wire bonding where the back of
the device 202 is attached to the surface of the substrate 204 and
the bond pads of the RFID tag device 202 are facing away from the
surface of the substrate 204.
[0036] Referring to FIG. 4, a schematic plan view of an alternate
embodiment of the jumper connection is illustrated. Intermediate
connection pad(s) 414 may be used between the coil turns 108 to
reduce the length of the bond wire 206 (now bond wires 206a and
206b) going from the outer end 212 to the connection pad 214. The
connection pad 214 also is adapted to connect to the RFID tag
device 202 and the capacitor 110.
[0037] Referring to FIG. 5, a schematic plan view of an embodiment
of the invention having flipchip or C4 connections is illustrated.
The RFID tag device 202a is a flipchip or C4 device that is
attached to connection pads 520 and 522 which are connected to
connection pad 214 and inner coil end 210, respectively. The
capacitor 110 is connected between the connection pad 214 and the
inner coil end 210 and the jumper 206 connects the outer end 212 to
the connection pad 214.
[0038] Referring to FIG. 6, a plan view of the underside (substrate
is clear for illustrative purposes) of an embodiment of an RFID tag
is illustrated. The coil 108 is on top of the substrate 204. Test
pads 620, 622, 624 and 626 are illustrated connected to the RFID
tag device 202. These test pads may be used during testing and
programming of the RFID tag 200.
[0039] Referring to FIG. 7, a plan view of the top of the
embodiment of FIG. 6 is illustrated. A thin insulating layer (not
illustrated) such as polyimide may be used between the coil jumper
206 and the inductor coil 108 to prevent shorting of the coil 108,
however, once a glop top 730 is in place and has cured, no movement
of the jumper bond wire 206 can occur. In addition the capacitor
110 may be covered with a glop top 732 and the RFID tag device 202
may be protectively covered with a glop top 734. The inductor coil
108 may be coated with a insulating coating so as to make the RFID
tag 200 completely insulated. Thus, a low cost "chip-on-tag" is
created with no farther processing required. This form of
construction is easy to manufacture and low in cost.
[0040] Referring to FIG. 8, a schematic plan view of a flipchip
embodiment of an RFID tag 200 is illustrated. A flipchip die 202b
straddles an inductor coil 108 so that one solder ball bump of the
flipchip die 202b connects to an outer end 212 of the inductor coil
108 and another solder ball bump of the flipchip die 202b connects
to the inner end 210 of the inductor coil 108. This embodiment
requires no external jumper for connection to both the inner end
210 and the outer end 212 of the inductor coil 108. Referring to
FIG. 9, a conductive trace 930 may also be provided within the
flipchip die 202b that is a conductive connection within the die
202b that may serve as a jumper over the turns of the inductor
coil. The conductive trace 930 may be adapted to connect an
external capacitor 110 in parallel with the inductor coil 108. The
external capacitor 110 may be located inside or outside of the
inductor coil 108 and is preferably on the same side of the
substrate 204 as the inductor coil 108 and flipchip die 202b. The
external capacitor 110 may be a surface mount device attached to
solder pads 924 and 920. The flipchip 202b has solder ball bumps
910, 912 and 914 which attach to corresponding solder pads on the
substrate 204.
[0041] Referring to FIGS. 10 and 11, a schematic plan view of the
RFID tag of a bond wire embodiment and a schematic elevational view
of a portion thereof is illustrated. A RFID tag device die 202c may
be attached over a portion of the inductor coil 108 with an
insulating layer 1120 of material therebetween. The insulating
layer 1120 may be a B-staged kapton or epoxy that may be cured so
as to attach the die 202c to the substrate 204. Mylar, mica,
plastic, teflon, polyimide and the like may be used as an
insulating layer that is attached to the substrate 204 and the die
202c. The die 202c has bond pads 1110 and 1112 thereon and wire
bonding (bond wires) may be used to connect the die bond pads 1110
and 1112 to the inner end 210 and outer end 212 of the inductor
coil 108. The bond wires 1010 and 1012 may be used as jumpers over
the turns of the inductor coil 108 and further may allow the turns
(108a, 108b, 108c and 108d) of the inductor coil 108 to remain at
full width while passing under the die 202c. By allowing the turns
of the inductor coil 108 to remain at full width, the coil turns
108a, 108b, 108c and 108d have a lower resistance and thus yield a
higher quality factor (higher Q). Referring to FIG. 12, a
conductive trace 1220 may also be provided within the die 202c that
is a conductive circuit through the die 202c that may be adapted to
connect an external capacitor 110 in parallel with the inductor
coil 108. The external capacitor 110 may be located inside or
outside of the inductor coil 108 and preferably is on the same side
of the substrate 204 as the inductor coil 108 and die 202c.
[0042] The invention, therefore, is well adapted to carry out the
objects and attain the ends and advantages mentioned, as well as
others inherent therein. While the invention has been depicted,
described, and is defined by reference to particular preferred
embodiments of the invention, such references do not imply a
limitation on the invention, and no such limitation is to be
inferred. The invention is capable of considerable modification,
alternation, and equivalents in form and function, as will occur to
those ordinarily skilled in the pertinent arts. The depicted and
described preferred embodiments of the invention are exemplary
only, and are not exhaustive of the scope of the invention.
Consequently, the invention is intended to be limited only by the
spirit and scope of the appended claims, giving full cognizance to
equivalents in all respects.
* * * * *