AU718414B2

AU718414B2 - Identification element and method of manufacturing the same

Info

Publication number: AU718414B2
Application number: AU87023/98A
Authority: AU
Inventors: Richard Altwasser
Original assignee: Meto International GmbH
Current assignee: Meto International GmbH
Priority date: 1996-11-04
Filing date: 1998-09-23
Publication date: 2000-04-13
Anticipated expiration: 2017-10-29
Also published as: AU8702398A

Description

-1-

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

0.

000 0C 0 0*0e 00 0 000* o 0 *0 0 0* Name of Applicant: Actual Inventor: Address of Service: METO INTERNATIONAL GmbH Richard ALTWASSER BALDWIN SHELSTON WATERS MARGARET STREET SYDNEY NSW 2000 Invention Title: "IDENTIFICATION ELEMENT AND METHOD OF MANUFACTURING THE SAME" Details of Original Application No. 70030/98 dated 29th October 1997 The following statement is a full description of this invention, including the best method of performing it known to us:la- Identification Element and Method of Manufacturing the Same This invention relates to an identification element having an integrated circuit and an antenna coil RFID transponder) connected to the integrated circuit, as well as to a method of manufacturing such an identification element. The advantage of RFID transponders compared to the barcodes predominantly used in particular in the goods marking sector is that they permit a direct exchange of information, meaning that no visual contact is needed between the interrogating device and the transponder for the information transfer. Unlike barcodes, furthermore, it is an easy matter with RFID transponders to change their information content directly as and when 15 required.

9* RFID transponders are constructed as either passive or active elements. If the RFID transponder is used as an active element, the housing enclosing the integrated circuit contains an additional energy source usually in 20 the form of a battery. RFID transponders are able to operate in the most diverse frequency ranges, for example, in the low frequency range at 125 kHz, in the medium frequency range at 13.56 MHz or in the microwave range at typically 2.45 GHz. The present invention relates preferably but by no means exclusively to passive transponders operating in the medium frequency range.

A-data carrier with an integrated circuit is known in the art from EP 0 682 321 A2. The data carrier is comprised of a card body and an integrated circuit connected electrically via contact elements to at least one 2 coil composed of one or several layers. The two elements combine to form a resonant circuit which operates at a predetermined resonant frequency. The purpose of the coil is to supply energy and/or to exchange the data of the integrated circuit with external devices. Circuit and contact elements are constructed as a separate module.

The disadvantage of the known RFID transponders compared to barcodes is the immense difference in price between the two elements. This is also the reason why the use of RFID transponders in the sales sector has been restricted so far to fringe areas. In particular there has Sbeen no interest to date in using RFID transponders to present price information or other data when selling mass s 15 products in department stores and warehouses. Up to now an 00 RFID transponder has cost in the region of DM 10, which naturally makes their use as disposable identification markers completely out of the question.

It will be understood, of course, that RFID transponders find application in the most diverse areas, particularly in the fields of production, further "0 r processing and transportation of goods as well as in security applications. Examples include the identification 25 marking of people and animals, the identification marking 000006 S" of baggage and packages, particularly at airports and post offices, and the identification marking of vehicles during 0000 their production or in multistory car parks.

000060 0 It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

According to one aspect of the invention there is provided an identification element having an integrated circuit and an antenna coil (RFID transponder) connected to the integrated circuit, wherein the integrated circuit is a non-encapsulated chip, and that the antenna coil is comprised of at least one layer of a metallic coating.

3 The preferred embodiment of the present invention provides an economically priced identification element and a method of manufacturing such an identification element.

Costs may be saved by the identification element of the invention in two ways: On the one hand it is possible to dispense with the relatively expensive encapsulation of the chip in a housing, and on the other hand an antenna coil is used that is a low-cost item yet works to optimum effect and has very good adjustment capabilities. In this conneci tion it has proven very advantageous for the antenna coil to be manufactured from punched metal foil made of low-cost aluminum or, alternatively, of copper. The advantage of 0*eS copper is that it displays excellent conductivity and can 15 also be combined to very good effect with other materials.

0* 0 0e It will be understood, of course, that is also possible for the coil to be manufactured by printing with an electrically conductive ink (for example, polymer ink with S 20 silver particles), by etching a coil by chemical means or by using a wire winding. Using a machine to punch the coil out of a suitable metal foil is preferred, however, because this method affords the greatest advantages not only with regard to the manufacturing cost but also with a view to 25 applicable environmental protection regulations.

Metal foils for producing the coil typically come in a thickness of less than 100 m, preferably the thickness lies between 20 and 50 Am. An additional advantage of using these very thin and flexible foils as coil material is that the end product, meaning the finished RFID 4 transponder, is similarly flexible and thin and hence eminently suited for use in the manufacture of labels/tags: The label's/tag's surface waviness caused by integrating a thin coil is likewise so negligible as to enable the practically smooth surface of the label/tag to be printed in the customary way.

In accordance with an advantageous further aspect of the identification element of the present invention, the non-encapsulated chip is connected to the antenna coil by "10 means of a contacting method employed in the production of semiconductors, for example, by the use of conductive [.adhesives, by soldering, by means of the flipchip method, etc. Methods of this type are described in detail on .pages 25/14 to 25/21 of the Electronics Engineer's Refer- 15 ence Book, 6th Edition, "Integrated circuit packaging".

The description of the various contacting methods shall be deemed to be incorporated in the disclosure of the S• present invention by express reference.

an advantageous aspect of the identification ele- 20 ment of the present invention, the antenna coil is constructed to form a resonant circuit. A method of manufacturing such resonant circuits at low cost and high precision, that is, with small tolerance fluctuations in respect of their quality, is disclosed in EP 0 665 705.

The corresponding description of the method proposed in this European Offenlegungsschrift shall be deemed to be equally incorporated in the disclosure content of the present invention by express reference, particularly in the disclosure content of the method of the present invention.

Resonant circuits manufactured in accordance with the method described in EP 0 665 705 are characterized by very small manufacturing tolerances. The punched antenna coils have capacitance tolerances of approximately, whereas capacitors manufactured on a semiconductor chip have a manufacturing tolerance of 20%, approximately.

For this reason it is particularly advantageous if the capacitance is determined essentially by the antenna coil rather than the circuit. In this case it possible to S: t0 dispense with a tuning capacitor in the chip itself olbecause there is generally no longer any need for the o capacitance of the antenna coil to be tuned subsequently on account of the relatively small tolerances. Obviously, dispensing with a tuning capacitor helps to mini- 15 mize the cost of manufacturing the RFID transponder of the invention.

The above statement is made clear below by way of example: A capacitor comprised of two at least partly overlapping coils made of metal foil has a tolerance of 20 3% and less. By contrast, a capacitor integrated in a semiconductor circuit has a tolerance of 20% and more.

If the circuit made the major contribution to the total capacitance, the resonant circuit would need to be tuned after connecting the integrated circuit to the coil in order to obtain an acceptable tolerance of If, on the other hand, the antenna coil makes the major contribution approximately) to the capacitance, as is proposed by the invention, then the tolerance of 5% is obtainable without subsequent tuning.

If it ever proves necessary to tune the frequency of the antenna-coil this can still be done of course after the integrated circuit is connected to the antenna coil.

6 This tuning is performed by changing the capacitance or the inductance, for example. A change of capacitance can also result from a change of distance between two layers of the antenna coil caused by the local input of heat.

It is possible furthermore to subsequently change the size of the capacitor surface. In conclusion it can be said that dispensing with a tuning capacitor in the circuit makes an additional contribution to reducing the cost of the RFID transponder of the present invention.

According to an advantageous aspect of the identification element of the present invention, the quality of the resonant circuit (Q-factor) is high, at least higher than 50. Communication with the RFID transponder can thus be extended to a larger area range.

15 Exactly how sensitive the identification element is to static charges from close lying capacitive bodies such as a hand, a bottle with an aqueous liquid or a coating of plastic material, for example, depends essentially on the total capacitance of the antenna coil. The lower the 20 capacitance, the sooner the resonant circuit turns offresonance by static charges of this type. Let us consider again the difference between the conventional capacitors found in integrated circuits and the antenna coil used in accordance with the invention. When the capacitance is derived fully from the integrated circuit, it typically lies in the range from 10 to 100 pF. Resonant circuits of this type are relatively easy to turn off-resonance, causing the interrogating range to be greatly restricted in an extremely disadvantageous manner. As already pointed out, in the case of the present invention the greater part of the total capacitance is supplied by the antenna coil. The latter 7 typically has a capacitance of 500 pF to 5 nF, meaning that it is practically impossible for the resonant circuit to become off-resonance as the result of static charging through physical contact, for example.

According to an advantageous further aspect of the identification element of the present invention, provision is made for an additional capacitor that stores an amount of energy sufficient to activate the transponder as and when required. The energy stored in the capacitor originates from the interrogating signal of the transmit o•device. Preferably the capacitor has a capacitance in the range of 1 nF, which in the case of the antenna coil itself is obtainable by having at least two partly overlapping metal coatings separated by at least one 15 dielectric layer. As in the case of the antenna coil, S"this form of production has a cost-cutting effect on the RFID transponder of the invention. Aside from its low- S- cost production, the particular configuration of the *I additional capacitor is advantageous because its capacitance is higher by a factor of 10 than the capacitance of a corresponding capacitor on a semiconductor chip. The higher energy available as the result naturally increases the data transmission capacity of the identification element by a considerable amount.

Preferably the identification element of the present invention is used simultaneously as a security element for electronic article surveillance. In this case provision is made for a resonant frequency security element having a resonant frequency that differs from the resonant frequency of the identification element, the resonant frequency security element being tuned to the interrogating field of an electronic article monitoring device 8 and emitting a characteristic signal as soon as it is incited to resonate by the article monitoring device. Such a system is known from EP 0 181 327 BI, for example. The interrogating frequencies for the resonant frequency security element normally lie at 8.2 MHz; the interrogating frequency of the identification element could be situated in the range of 13.56 MHz, for example.

According to a particularly favorable embodiment, the identification element of the present invention and where one exists the resonant frequency security element are arranged on a substrate. The substrate involved is either paper or a synthetic material. Both substrate materials meet the requirements imposed on labels/tags: They are thin, g: 15 flexible, easy-to-print and low-cost items. Plastic material has the additional advantage of being resistant to contact with water or chemical substances.

According to another aspect of the invention there is provided a method of manufacturing an identification element :o-*having an integrated circuit and an antenna coil (RFID transponder) connected to the integrated circuit, wherein a S:-non-encapsulated chip is contacted with the antenna coil comprised of at least one layer of a metallic coating.

According to an advantageous aspect of the method of the present invention, it is proposed performing the contacting between the chip and the antenna coil by means of the methods known in the art from the production of semi-conductors.

Unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

9 FIG. 1 is a top view of a first antenna coil used in the RFID transponder of the present invention; FIG. 2 is a top view of two antenna coils overlapping in certain areas; FIG. 3 is a top view of the two antenna coils of FIG. 2, the antenna coils being interconnected electrically in certain areas; and FIG. 4 is a top view of an advantageous configuration of the RFID transponder of the present invention.

o 10 FIG. 1 shows a top view of a first antenna coil 1 used in the RFID transponder 6 of the present invention.

It is comprised of two coil turns, the outer turn being wound in opposite direction to the inner turn. As becomes apparent from FIG. 2, a second antenna coil 2 of 15 a form essentially corresponding to the first antenna coil 1 is arranged above the first antenna coil 1 but turned 180" relative to it. The two antenna coils 1, 2 are separated in their overlap zone by a dielectric layer, not shown in the Figure. Preferably the two "20 antenna coils i, 2 are punched out of aluminum foil. The resonant circuit shown in FIG. 2 is produced, as previously mentioned, preferably by means of the method described in EP 0 655 705.

The first antenna, coil 1 has an additional section 3, which as becomes apparent from FIG. 4 is used for contacting the antenna coil'l with the chip The antenna coils i, 2 illustrated in FIG. 2 are shown again in FIG. 3 but with the antenna coils i, 2 now interconnected electrically in certain areas 4a, 4b. Two resonant circuits, which are incited to resonate 10 preferably in different frequency ranges, are created by the electrical connection in the areas 4a, 4b.

FIG. 4 shows an advantageous configuration of the RFID transponder 6 of the present invention, comprising an identification element 7 and a security element 8 for electronic article surveillance. The inner resonant circuit and the chip 5 connected to it electrically form the identification element 7. The resonant frequency of this circuit lies at around 13.56 MHz, for example. The con- 10 nection between the chip 5 and the inner resonant circuit is made by one of the contacting methods known from semiconductor technology.

The outer resonant circuit forms the electronic security element 8. The security element 8 is incited in 15 the interrogating field of an article monitoring device to emit a characteristic signal. The interrogating frequency of an article monitoring device lies typically in oo •the range of 8.2 MHz, which means that in the chosen example it deviates from the frequency of the RFID 20 transponder 6. As becomes further apparent from FIG. 4, both the first antenna coil 1 and the second antenna coil 2 are connected electrically to the chip.

The shaded fields 9, 10 of the resonant circuit for the identification element 7 and of the resonant circuit for the security element 8 mark in each case that area which contributes the bigger part to the total capacitance of each resonant circuit. If subsequent tuning of the resonant circuits is necessary it is done preferably in these areas 9, 10. As for suitable tuning methods, attention is drawn to the passages previously mentioned.

Claims

2. The identification element as claimed in claim 1, wherein the antenna coil is constructed to form a resonant circuit.
3. The identification element as claimed in claim 1 or 2, wherein the chip is connected to the antenna coil by means of a contacting method employed in the production of S" semiconductors.
4. The identification element as claimed in any one of 15 claims 1, 2 or 3, wherein the antenna coil makes the major contribution to the total capacitance, while only a minor part of the capacitance originates from the integrated circuit, that is, the chip.
5. The identification element as claimed in any one of the 20 preceding claims, wherein the quality of the resonant circuit, that is, the Q-factor, is high, at least higher than
6. The identification element as claimed in any one of the preceding claims, wherein the capacitance of the resonant circuit is relatively high, exceeding 1 nF.
7. The identification element as claimed in any one of the preceding claims, wherein an additional capacitor is provided that stores an amount of energy sufficient to activate the chip as and when required.
8. The identification element as claimed in any one of the preceding claims, wherein a resonant frequency security ,element is provided having a resonant frequency that differs from the resonant frequency of the identification 12 element, said resonant frequency security element being tuned to the interrogating field of an electronic article monitoring device and emitting a characteristic signal as soon as it is incited to resonate by the article monitoring device.
9. The identification element as claimed in any one of the preceding claims, when the identification element and/or the resonant frequency security element are arranged on a substrate.
10. A method of manufacturing an identification element having an integrated circuit and an antenna coil (RFID transponder) connected to the integrated circuit, wherein a S"non-encapsulated chip is contacted with the antenna coil g* comprised of at least one layer of a metallic coating. S 15 11. The method as claimed in claim 10, wherein the oooS contacting between the chip and the antenna coil is "performed by means of the methods known from the production of semiconductors.
12. An identification element substantially as herein 0 20 described with reference to any one of the embodiments and ee its associated drawings.
13. A method of manufacturing an identification element substantially as herein described with reference to any one of the embodiments and its associated drawings. DATED this 14th Day of February, 2000 METO INTERNATIONAL GmbH Attorney: PETER R. HEATHCOTE Fellow Institute of Patent Attorneys of Australia of BALDWIN SHELSTON WATERS