WO2006101628A1

WO2006101628A1 - Use of a conductive adhesive for bonding and as a radio frequency antenna

Info

Publication number: WO2006101628A1
Application number: PCT/US2006/005585
Authority: WO
Inventors: Winfred C. Otten
Original assignee: Nordson Corporation
Priority date: 2005-03-22
Filing date: 2006-02-17
Publication date: 2006-09-28

Abstract

A method of making a radio frequency antenna on a substrate (22) by applying a conductive adhesive with an adhesive dispenser on a surface of the substrate in a pattern forming a radio frequency antenna (36) for a radio frequency integrated circuit (32). An apparatus for a radio frequency integrated circuit (32) having a conductive adhesive applied with an adhesive dispenser on a first surface of a substrate (22) in a pattern forming a radio frequency antenna (36) for, and electrically connected to, the radio frequency integrated circuit.

Description

USE OF A CONDUCTIVE ADHESIVE FOR BONDING AND AS A RADIO FREQUENCY ANTENNA

Field of the Invention

The present invention relates generally to radio frequency devices and, more particularly, to the use of a conductive adhesive to provide a radio frequency antenna.

Background of the Invention

Radio frequency identification ("RFID") is an area of automatic identification that has come into wide use in recent years and provides a device for handling data that is complimentary in many ways to other data capture technologies, for example, bar code technology. The object of an RFID system is to carry data in transponders, generally known as tags, and to retrieve data, by machine-readable means, at a suitable time and place to satisfy a particular application need. Thus, a tag or transponder includes a chip with a programmable processor and associated memory, which is capable of storing the data and performing necessary demodulation and, if applicable, modulation functions. Data within a tag may provide all manner of information including but not limited to an identification of an item in manufacture by common name, scientific name, manufacturing batch no., color, an expiration date, a subsequent operation or location, a customer, or any other data that may be useful over the life of the item. An RFID system requires, in addition to tags, a means of reading or interrogating the tags and some means of communicating the data to a host computer or information management system. An RFID system often includes a facility for entering or programming data into the tags, if this is not done at source by the manufacturer.

Communication of data between tags and a reader is by wireless communication and is often based upon propagating electromagnetic waves by antenna structures present in both tags and readers. While the RFID circuit and/or chip is relatively small and can be readily mounted at an inconspicuous location on the item, the RFID tag antenna must be sufficiently large to perform its function of communicating radio frequency waves with the RFID reader. RFID tag antennas often require substantially more surface area than the RFID circuit and/or chip and are made as leads or loops in a wide array of shapes and sizes to accommodate the item with which the RFlD tag and antenna are to be used. Some RFID tag antennas are formed by preformed wires attached to a substrate, while other RFID antennas are formed by conductive traces of copper, or other highly conductive metal, plated onto the substrate. RFID antennas are also formed by screen printing or silk screening onto a substrate a conductive material, for example, a conductive ink or a paste made of metal powder, polymer material and solvent. Thus, the manufacture of RFID antennas is complex and expensive and substantially adds to the cost of implementing RFID technology in an item.

Therefore, there is a need to provide apparatus and methods of reducing the cost of implementing RFID technology and, in particular, the cost of manufacturing an RFID antenna.

Summary of the Invention

The present invention provides a method of making a radio frequency antenna that more cost effectively integrates an RFID transponder into an item. With the apparatus and method of the present invention, the manufacture of a radio frequency antenna is simplified and integrated into a manufacturing process of the item with which the RFID transponder is being used. The apparatus and process of the present invention is especially useful in integrating an RFID transponder into an item in which an adhesive is used in its manufacture. According to the principles of the present invention and in accordance with the described embodiments, in one embodiment, the invention provides a method of making a radio frequency antenna on a substrate. A conductive adhesive is applied with an adhesive dispenser on a surface of the substrate in a pattern forming a radio frequency antenna for a radio frequency integrated circuit. In one aspect of the invention, the conductive adhesive is applied with a hot melt adhesive dispensing gun. In a further aspect of this invention, an upper layer is placed over the conductive adhesive to glue the upper layer and the substrate together.

In a further embodiment, the invention provides a method of making an item with a radio frequency antenna. A conductive adhesive is applied with an adhesive dispenser on the first surface of the item in a pattern forming a radio frequency antenna for a radio frequency integrated circuit. In one aspect of this invention, the item is a container; and the first surface is a flap of the container.

In a still further embodiment, the invention provides an apparatus for a radio frequency integrated circuit having a conductive adhesive applied with an adhesive dispenser on a first surface of a substrate in a pattern forming a radio frequency antenna for, and electrically connected to, the radio frequency integrated circuit. In one aspect of this invention, the conductive adhesive forms a radio frequency receiving antenna and/or a radio frequency transmitting antenna for the radio frequency integrated circuit. In other aspects of this invention, the radio frequency integrated circuit is mounted on the substrate and the radio frequency integrated circuit is an RFID device.

In another embodiment, the invention provides a container providing a first surface. A conductive adhesive is applied with an adhesive dispenser on the first surface of the container in a pattern forming a radio frequency antenna for, and electrically connected to, a radio frequency integrated circuit.

These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein.

Brief Description of the Drawings The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention. Fig. 1 is a schematic disassembled view of one embodiment of an item having a conductive adhesive functioning as a radio frequency antenna in accordance with the principles of the present invention.

Fig. 2 is a schematic drawing of another embodiment of an item having a conductive adhesive functioning as a radio frequency antenna in accordance with the principles of the present invention.

Fig. 3 is a schematic drawing of a further embodiment of an item having a conductive adhesive functioning as a radio frequency antenna in accordance with the principles of the present invention. Fig. 4 is a schematic drawing of an embodiment of a label having a conductive adhesive functioning as a radio frequency antenna in accordance with the principles of the present invention.

Detailed Description of the Invention

For purposes of this description, a lower layer or substrate is any supporting or supportive structure, single layer or multilayer. Further, a substrate may be either rigid, such as ceramic, etc., or flexible, such a polyamide, polyester, polyethylene, or a cellulose pulp product, such as paper board, cardboard, etc. In addition, an upper or cover layer may be made of a single layer or mutlilayer material that is rigid or flexible and made from any of a wide range of materials, including but not limited to polymers, cellulose pulp products, one or more layers of ink, etc.

Referring to Fig. 1 , a multilayered item 20 has a lower or substrate layer 22 with an upper surface 24 and an upper or cover layer 26 with a lower surface 28. During manufacture of the item 20, the substrate 22 is often moved on a conveyor 31. In this embodiment, a radio frequency integrated circuit 32, for example, a radio frequency transponder such as an RFID device, is to be used to identify and/or track the item 20 during production and/or its useful life. The RFID device 32 has on its lower surface an electrically conductive contact 34 that functions as a receiving antenna input. At the location of the RFID device 32, a conductive adhesive 36 is dispensed or applied to the upper surface 24 in a configuration forming a receiving antenna for the RFID device 32. The conductive adhesive is applied using a first dispensing gun 33, for example, a hot melt dispensing gun, that is often mounted on a commercially available industrial robot arm 35. Thereafter, the RFID device 32 is placed onto the upper surface 24 at a location that places its antenna input contact 34 in contact with the conductive adhesive 36.

The upper layer 26 is normally attached to the substrate 22 by the conductive adhesive 36 and a nonconductive adhesive 30 that is applied to a lower layer upper surface 24 by a second dispensing gun 37, for example, a hot melt dispensing gun, that is mounted on a second commercially available industrial robot arm 39. The operations of the dispensing guns 33, 37 and robot arms are controlled by one or more programmable controls 41 in a known manner. The upper layer 26 is then placed over the substrate 22. Therefore, in addition to functioning as an antenna for the RFID device 32, the conductive adhesive 36 bonds the RFID device 32 to the surface 24 and also bonds the surfaces 24 and 28 together, thereby forming the item 20.

For purposes of this description, a conductive adhesive is an adhesive material that provides an impedance to an RF signal when dispensed in a geometric pattern and can be reproduced with sufficient accuracy and repeatability that the adhesive material can be reliably used as an antenna in an RF circuit. A nonconductive adhesive as used herein is an adhesive material that is used without regard for whatever electrical properties the adhesive material may have. Further, in this written description, in Fig. 1 , the conductive adhesive 36 can be used in place of the nonconductive adhesive 30, if its use does not interfere with the function of the conductive adhesive 36 as an antenna. Similarly, in other described embodiments, a user may choose to replace a nonconductive adhesive with a conductive adhesive. Such a choice may often be made to provide a lesser manufacturing cost.

Referring to Fig. 2, in another embodiment, a container 40, for example, a paper board or cardboard box, is filled with desired contents. Upon the first, minor flaps 42, 44 being folded over the contents, a nonconductive adhesive 30 is applied to upper surfaces 48, 50 of the respective minor flaps 42, 44. In addition, a first conductive adhesive 52 is dispensed upon the substrate or flap surface 50 in a pattern forming a receiving antenna for an RFID device. Further, a second conductive adhesive 54 is dispensed on the flap surface 50 in a pattern forming a transmitting antenna for an RFID device. Thereafter, the RFID device 56 is placed onto the flap surface 50 at a location placing a receiving antenna contact 58 into the conductive adhesive 52 and a transmitting contact 60 into the conductive adhesive 54. As will be appreciated, the conductive adhesives 52, 54 may be the same or different depending on the desired electrical characteristics for the respective receiving and transmitting antennas. Further, the adhesives 52, 54 can be applied using adhesive dispensing guns, such as hot melt dispensing guns. Upper layers or major flaps 49, 51 are then folded over the minor flaps 42, 44. conductive adhesives 52, 54 and nonconductive adhesive 30 glue the major flap 49 to the minor flaps 42, 44; and the nonconductive adhesive 30 glues the major flap 51 to the minor flaps 42, 44 thereby closing the container 40. It should be noted that when the minor flaps 42, 44 are folded down, respective opposed inner directed edges 55, 57 do not meet or come together. However, when the major flaps 49, 51 are folded over the minor flaps 42, 44, inner directed edges 59, 61 of the respective major flaps 49, 51 most often meet or come together. RFID device 56 and conductive adhesive antennas 52, 54 permit the contents of the container 40 to be tracked during subsequent handling, shipping and sales of the container 40.

Referring to Fig. 3, in a further embodiment, as part of the assembly of a container 62, a conductive adhesive 64 is dispensed onto an upper surface 66 of a substrate or minor flap 68 prior to the folding of major flap 70 thereover. The conductive adhesive 64 is dispensed in a pattern forming a radio frequency antenna for an RFID device 72 that is integrated into a label 74. In this embodiment, the conductive adhesive 64 is not only applied to the top surface 66; but a portion 80 is applied partially down a side surface 76 to form one or more antenna contacts 78. After the adhesive 64 is applied, the label 74 is applied at a location placing an RFID antenna contact 78 within the portion 80 of the electrically conductive adhesive 64 dispensed onto the surface 76.

Thereafter, the flap 70 is folded over the upper surface 66; and the electrically conductive adhesive 64 further functions to join the flap 70 to the upper surface 66. As will be appreciated, in an alternative embodiment, instead of dispensing the conductive adhesive onto the surface 76, the label 74 can have one or more antenna input leads that extends onto the flap upper surface 66. In this alternative embodiment, the label is applied first; and then, the conductive adhesive is dispensed onto the flap upper surface 66 and over the antenna input leads. Further, as in other embodiments, the adhesives 52, 54 can be applied using adhesive dispensing guns, such as hot melt dispensing guns.

Referring to Fig. 4, in a further embodiment, as part of an assembly of a label 84, a conductive adhesive 92 is dispensed onto an upper surface 87 of the substrate 90 to form a radio frequency receiving antenna 94 and a transmitting antenna 96. An RFID device 86 is then placed on the upper surface 87 so that receiving and transmitting antenna contacts 99 are located in portions of the conductive adhesive 92 corresponding to the respective receiving and transmitting antennas. Next, an upper or cover layer 88 of the label 84 is placed over the substrate 90, and the conductive adhesive 92 bonds the two layers 88, 90 together. The upper layer 88 has label indicia 89 printed on an upper surface 91. The label 84 is applied to an item (not shown) by dispensing a nonconductive adhesive onto a lower side 87 of the label 84 or the item and then, placing the label 84 on the item. In another embodiment, the label 84 can be made with a tacky or nontacky nonconductive adhesive applied on the substrate lower surface 97. If a tacky adhesive is used, a removable or peelable protective layer (not shown) is applied over the tacky adhesive in a known manner. In a further embodiment, a nonconductive adhesive 30 may be used in conjunction with the conductive adhesive 92 to bond the layers 88, 90 together. Again, the adhesives 30, 92 can be applied using adhesive dispensing guns, such as hot melt dispensing guns. In a still further embodiment, if the RFID device is a passive device, the conductive adhesive is applied in a pattern forming only the receiving antenna 94. In yet another embodiment, the label structure 84 may be manufactured repeatably on a continuous web to form a roll of labels. The structure of the label 84 may be used to make the label 74 of Fig. 3. In this embodiment, the substrate 90 will have perforations or holes directly over the antenna input contacts 99 on the RFID chip 86. Therefore, when the label 84 is applied over conductive adhesive 80 of Fig. 3, electrical contact will be made between the antenna input contact 99 and the conductive adhesive 80.

The devices and methods described above utilize a conductive adhesive to manufacture an electrical antenna and more particularly, a radio frequency antenna for an RFID device. In the applications described above, the manufacture of the radio frequency antenna with a conductive adhesive becomes part of the process required to manufacture the item in which the RFID device is used. Therefore, in the manufacture of almost any item in which an adhesive is used to join two surfaces, using a conductive adhesive to form an antenna for an RFID device provides a significant increase in flexibility of product design. Further, it eliminates a separate process that is exclusively dedicated to making the antenna from a conductive trace, printed ink, etc. In many applications, finding the geography or surface area on an item that can be dedicated to an RFID antenna is challenging, and integrating the manufacture of the RFID antenna by conductive traces, silk screening or printing into existing manufacturing processes is even more challenging. The RFID antenna and methods described provide a significant cost savings by eliminating a separate manufacturing process exclusively dedicated to making an RFID antenna. Further, the conductive antenna does not effect the outer visual appearance of the container 40. The conductive adhesive forming the antenna can be applied with a hot melt dispensing gun such as that commercially available from Nordson Corporation of Westlake Ohio. In alternative embodiments, the conductive adhesive may be applied using a hand-held brush, roller or adhesive dispenser; a rotating dispensing head, slot nozzle or wheel; a mechanically driven roller; or by stencil printing, ink jet printing, etc.

While the present invention has been illustrated by a description of an embodiment, and while such embodiment has been described in considerable detail, there is no intention to restrict, or in any way limit, the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, in the described embodiment of Fig. 1 , the antenna input contact 34 is located on a bottom side of the RFID device 32. Therefore, the adhesive 36 is applied first; and then, the RFID device antenna input contact 34 is placed in the adhesive 36. As will be appreciated, in an alternative embodiment, the antenna input contact may be located such that, it is better to mount the RFID device first and thereafter, apply the conductive adhesive over the antenna input contact. In a still further embodiment, the RFID device 32 can be mounted on one of the surfaces 24, 28 and the conductive adhesive 36 applied to the other of the conductive surfaces 24, 28. Therefore, when the surfaces 24, 28 are joined, the conductive adhesive 36 contacts the antenna input contact 34. In the illustrated embodiments, the configurations of the various antennas

36, 52, 54, 64, 94, 96 are arbitrarily shown. The RF frequency being used and the electrical design of the transmitting and/or receiving circuits will determine the number of turns in an antenna, whether the antenna is open loop or closed loop, etc. Further, in the illustrated embodiments, the nonconductive adhesive is shown as being applied in a two-dimensional, squiggle pattern. The choice of pattern for applying the nonconductive adhesive 30 is not a part of this invention but is chosen to be linear and/or curved depending on the application as is known in the art.

In the illustrated embodiment of Fig. 2, the conductive adhesive is shown dispensed on a minor flap 44 to form antennas 52, 54; however, in an alternative embodiment, the conductive adhesive may be dispensed on the major flap 49. In a further alternative embodiment, the adhesive may be dispensed on both the minor flap 44 and the major flap 49 to form separate antennas; and in a still further embodiment, the conductive adhesive may be dispensed on both the minor and major flaps 44, 49 to form a single antenna upon the flaps 44, 49 being folded together.

Therefore, the invention in its broadest aspects is not limited to the specific details shown and described. Consequently, departures may be made from the details described herein without departing from the spirit and scope of the claims which follow.

Claims

What is claimed is:-10-

1. A method of making a radio frequency antenna on a substrate comprising: applying a conductive adhesive with an adhesive dispenser on a surface of the substrate in a pattern forming a radio frequency antenna for a radio frequency integrated circuit.

2. The method of claim 1 further comprising applying the conductive adhesive with a hot melt adhesive dispenser.

3. The method of claim 1 further comprising applying the conductive adhesive with a roller.

4. The method of claim 1 further comprising applying an upper layer over the conductive adhesive to glue the upper layer and the substrate together.

5. The method of claim 1 wherein the radio frequency integrated circuit is an RFID device.

6. A method of making an item with a radio frequency antenna comprising: providing an item having a first surface; and applying a conductive adhesive with an adhesive dispenser on the first surface of the item in a pattern forming a radio frequency antenna for a radio frequency integrated circuit.

7. The method of claim 6 further comprising applying the conductive adhesive with a hot melt adhesive dispenser.

8. The method of claim 6 wherein the item has a second surface and the method further comprises placing the second surface over the conductive adhesive to glue the first surface and the second surface together.

9. The method of claim 8 wherein the item is a container and the second surface is located on a flap.

10. The method of claim 9 wherein the first surface is located on a flap.

11. The method of claim 6 wherein the radio frequency integrated circuit is an RFID device.

12. A method of making an RFID apparatus for use with an item having at least two surfaces to be joined with an adhesive, the method comprising: applying a conductive adhesive on one of the at least two surfaces in a pattern forming an antenna for a radio frequency transponder, the conductive adhesive joining the at least two surfaces together; and prior to bringing the at least two surfaces together, placing a radio frequency integrated circuit in the conductive adhesive to electrically connect the integrated circuit with the antenna.

13. A method of making an item with an RFID apparatus comprising: providing an item having at least two surfaces; applying a conductive adhesive on one of the at least two surfaces in a pattern forming an antenna for a radio frequency transponder; placing a radio frequency integrated circuit in the conductive adhesive to electrically connect the integrated circuit with the antenna; and bringing the at least two surfaces together to join the at least two surfaces with the conductive adhesive.

14. A method of making an item with an RFID apparatus comprising: providing an item having at least two surfaces; placing a radio frequency integrated circuit on one of the at least two surfaces; applying a conductive adhesive on the one of the at least two surfaces in a pattern forming an antenna for a radio frequency transponder; and bringing the at least two surfaces together to bring the conductive adhesive into contact with an antenna input contact of the radio frequency integrated circuit and to glue the at least two surfaces together.

15. An apparatus for a radio frequency integrated circuit comprising: a substrate having a first surface; and a conductive adhesive applied with an adhesive dispenser on the first surface of the substrate in a pattern forming a radio frequency antenna for, and electrically connected to, the radio frequency integrated circuit.

16. The apparatus of claim 15 wherein the conductive adhesive comprises a radio frequency receiving antenna for the radio frequency integrated circuit.

17. The apparatus of claim 15 wherein the conductive adhesive comprises a radio frequency transmitting antenna for the radio frequency integrated circuit.

18. The apparatus of claim 15 wherein the radio frequency integrated circuit is mounted on the substrate.

19. The apparatus of claim 15 wherein the radio frequency integrated circuit comprises an RFID device.

20. The apparatus of claim 15 further comprising a second surface placed over the conductive adhesive to glue the first surface and the second surface together.

21. An apparatus comprising: a substrate having a first surface; a radio frequency integrated circuit; and a conductive adhesive applied with an adhesive dispenser on the first surface of the substrate in a pattern forming a radio frequency antenna for, and electrically connected to, the radio frequency integrated circuit.

22. The apparatus of claim 21 wherein the substrate comprises a portion of a container.

23. The apparatus of claim 22 wherein the container further comprises a second surface beatable over the conductive adhesive to glue the first surface and the second surface together.

24. The apparatus of claim 23 wherein the container further comprises first and second flaps providing the respective first and second surfaces.

25. The apparatus of claim 24 wherein the radio frequency integrated circuit is mounted on the first flap.

26. The apparatus of claim 24 wherein the radio frequency integrated circuit is mounted on a portion of the container other than the first flap.

27. The apparatus of claim 21 wherein the conductive adhesive comprises a radio frequency receiving antenna for the radio frequency integrated circuit.

28. The apparatus of claim 21 wherein the conductive adhesive comprises a radio frequency transmitting antenna for the radio frequency integrated circuit.

29. The apparatus of claim 21 wherein the radio frequency integrated circuit comprises an RFID device.

30. An RFID apparatus for use with an item having at least two surfaces to be joined with an adhesive, the RFID apparatus comprising: a radio frequency integrated circuit adapted to be mounted on one of the at least two surfaces; and an antenna comprising a conductive adhesive located between the at least two surfaces for joining the surfaces together and electrically connected to the radio frequency integrated circuit.

31. The RFID apparatus of claim 30 wherein the radio frequency integrated circuit comprises a passive RFID device and the antenna comprises a radio frequency receiving antenna.

32. The RFID apparatus of claim 30 wherein the radio frequency integrated circuit comprises an active RFID device and the antenna comprises a radio frequency receiving antenna and a radio frequency transmitting antenna.