Self-adhesive straps for RFID devices

Abstract

An RFID device includes an antenna defining a gap, with an RFID strap electrically coupled to the antenna across the gap. An adhesive is applied over strap and antenna. A liner is covering the adhesive layer until the RFID device is about to be attached to an object. To prevent the strap from detaching when the liner is removed, means to counteract the strain on the strap are applied. This set-up allows to produce RFID devices using less material while providing a high level of reliability.

Description

SELF-ADHESIVE STRAPS FOR RFID DEVICESField of the Disclosure

[0001] The present subject matter relates to a method to produce radio frequency identification ("RFID") devices and the devices made by the method. More particularly, the present subject matter relates to self-adhesive RFID straps and techniques for mounting such RFID straps to antennas.Background

[0002] RFID tags and labels have a combination of antennas and analog and / or digital electronics, which may include for example communications electronics, data memory, and control logic. RFID tags and labels are widely used to associate an object with an identification code. For example, RFID tags are used in conjunction with security locks in cars, for access control to buildings, and for tracking inventory and parcels. Some examples of RFID tags and labels appear in U.S. Pat. Nos. 6,107,920, 6,206,292, and 6,262,692.

[0003] Methods for manufacturing RFID labels are disclosed in PCT Publication No. WO 2001 / 61646 by Moore North America, Inc. The method disclosed in PCT Publication No. WO 2001 / 61646 uses a number of different sources of RFID inlets, each inlet including an antenna and a chip. A plurality of webs are matched together and RFID labels are die cut from the webs, to produce RFID labels with liners. Alternatively, linerless RFID labels are produced from a composite web with a release material on one face and pressure sensitive adhesive on the other, where the labels are formed by perforations in the web. Various alternatives are possible.

[0004] Still other RFID devices and methods for manufacturing RFID labels are disclosed in U.S. Patent Application Publication No. US2001 / 0053675 by Plettner. The devices include a transponder comprising a chip having contact pads and at least two coupling elements, which are conductively connected with the contact pads. The coupling elements are touch-free relative to each other and formed in a self-supported as well as a free-standing way and are essentially extended parallel to the chip plane. The total mounting height of the transponder corresponds essentially to the mounting height of the chip. The size and geometry of the coupling elements are adapted for acting as a dipole antenna or in conjunction with an evaluation unit as a plate capacitor. Typically, the transponders are produced at the wafer level. The coupling elements can be contacted with the contact pads of the chip directly at the wafer level, i.e., before the chips are extracted from the grouping given by the wafer.

[0005] In many applications, it is desirable to reduce the size of the electronics as small as possible. In order to interconnect very small chips with antennas in RFID inlets, it is known to use a structure variously called "straps", "interposers", and "carriers" to facilitate inlay manufacture. Straps include conductive leads or pads that are electrically coupled to the contact pads of the chips for coupling to the antennas. These pads provide a larger effective electrical contact area than Integrated Circuits ("ICs") precisely aligned for direct placement onto the antenna without a strap. The larger area reduces the accuracy required for placement of ICs during manufacture while still providing effective electrical connection. IC placement and mounting are serious limitations for high-speed manufacture. The prior art discloses a variety of RFID strap or strap structures, typically using a flexible substrate that carries the strap's contact pads or leads.

[0006] One type of prior art RFID inlet manufacture process using straps is disclosed in European Patent Application EP 1039543 A2 to Morgan Adhesives Company ("Morgan"). This patent application discloses a method of mounting an integrated circuit chip (IC) using a strap that is connected across a gap between two thin conductive film sections of a conductive film antenna. The strap comprises a thin substrate having two printed conductive ink pads. This method is said to be suitable for mass production of RFIDs by mounting ICs on straps that are then physically and electrically connected to the antenna sections using a pressure sensitive conductive adhesive. The pressure sensitive conductive adhesive provides a direct electrical connection between the strap contact pads and the antenna sections.

[0007] Another type of prior art RFID inlet manufacture using straps is based on a technique for manufacturing microelectronic elements as small electronic blocks, associated with Alien Technology Corporation ("Alien"). Alien has developed techniques to manufacture small electronic blocks and then deposit the small electronic blocks into recesses on an underlying substrate. To receive the small electronic blocks, a planar substrate is embossed with numerous receptor wells. The receptor wells are typically formed in a pattern on the substrate. For instance, the receptor wells may form a simple matrix pattern that may extend over only a predefined portion of the substrate or may extend across substantially the entire width and length of the substrate, as desired. Alien has a number of patents on its technique, including U.S. Pat. Nos. 5,783,856; 5,824,186; 5,904,545; 5,545,291; 6,274,508; and 6,281,038. Further information can be found in Alien's Patent Cooperation Treaty publications, including WO 00 / 49421; WO 00 / 49658; WO 00 / 55915; WO 00 / 55916; WO 00 / 46854 and WO 01 / 33621.

[0008] As noted above, RFID inlets using straps provide an inherent advantage in high speed manufacture by facilitating effective mechanical and electrical connection of ICs to antennas.

[0009] Usually, such RFID devices are covered with an adhesive which enables the RFID device to be attached to an item or surface. However, when a liner that protects the adhesive from the environment is peeled off, or when the RFID device is relocated, the strain that the adhesive transfers to the strap can detach it from the antenna. The disclosed invention suggests features and methods to overcome this disadvantage.Summary

[0010] There are several aspects of the present subject matter which may be embodied separately or together in the devices and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as may be set forth in the claims appended hereto.

[0011] In one aspect or embodiment of the disclosure, the RFID device is comprising an antenna defining a gap. Such antennas can be produced by an etching process, where a layer of metal is covered with an etching mask and the uncovered portions are etched away. Alternatively, the antenna may be cut from metal sheets mechanically or by laser-cutting. Yet another alternative is to print the antenna by using conductive printing materials. An RFID strap comprises an IC chip which is attached to a leadframe. The side of the leadframe on which the IC is attached forms the IC-bearing side. The RFID strap is electrically coupled with the IC-bearing side across the gap in the antenna. The gap's width is enough to take up the IC without physical contact between the IC chip and the antenna material. The RFID strap can be coupled to the antenna capacitively or conductively. A layer of an adhesive is covering the RFID device, i.e. the antenna and the RFID. This allows the RFID device to be attached to an item. A liner material is covering the outside of the adhesive layer, protecting it against drying out or dust or other materials that would attach to the adhesive. Also, the liner material prevents the RFID device to attach to an item unintendedly. When the liner is removed, the liner's adhesion to the adhesive may apply a certain amount of force or strain to the adhesive and the adhesive to the RFID strap and its connection to the antenna. Eventually the connection between the RFID strap and the antenna may be negatively influenced orthe RFID strap may even be disconnected. It is therefore suggested that the second planar side of the RFID strap comprises means to counteractthe effect of the adhesive, so that the RFID strap is not exposed to strain or force when the liner material is removed.

[0012] In another aspect or embodiment of the disclosure, the means to counteract the adhesive is a non-stick material printed or coated on the second planar side. Non-stick material means that the adhesive is not or only badly attaching to this material.

[0013] Alternatively, in yet another aspect or embodiment of the disclosure, said means to counteract the adhesive is a RFID strap made of material that does not bind to the adhesive layer. Instead of coating such a material on the strap, the leadframe could be mounted on a substrate made of non-stick material.

[0014] In a further aspect or embodiment of the disclosure, said means to counteract the adhesive is a deadening adhesive applied on the second planar side. Also, chemicals that react with compounds of the adhesive and counteract or reduce its ability to attach to a surface can be used.

[0015] In a further aspect or embodiment of the disclosure, it is suggested to cover the strap with an anchor strap that covers a slightly bigger area as the strap and is covered with an adhesive, which attaches to a carrier material or substrate of the antenna. Such substrate is typically from PET or paper. Such carrier materials or substrates are used to stabilize the antenna, since antennas of RFID devices are usually made from a very thin metal foil or printed with conductive inks.

[0016] The disclosure also includes a method of assembling an RFID device includes providing an antenna defining a gap, providing an RFID strap, said strap comprising an IC chip attached to a lead- frame from electrically conductive material on an IC-bearing side and a second planar side opposite to the IC-bearing side. The conductive material can be either a thin metal foil or a printed conductive material such as conductive inks or metal pastes. Said RFID is strap electrically coupled to the antenna across the gap with the IC-bearing side; securing the RFID strap to the antenna with the IC-bearing side, so that the RFID strap is electrically coupled to the antenna across the gap; applying means to counteract the effect of an adhesive on the second planar side of the RFID strap, so that any strain on said adhesive is not transferred to the RFID strap; applying a layer of the adhesive on the RFID device, covering the antenna and the RFID strap; applying a liner material on the adhesive to protect the adhesive and prevent unintended adherence.

[0017] In a further aspect or variant of the method said means to counteract the adhesive is a nonstick material printed or coated on the second planar side.

[0018] In yet a further aspect or variant of the method said means to counteract the adhesive is a RFID strap made of material that does not bind to the adhesive layer.

[0019] In a further aspect or variant of the method said means to counteract the adhesive is a patch out of a non-stick material applied on the second planar side.

[0020] Generally, adhesives will not or badly stick to very smooth surfaces. One example of a nonstick material is polytetrafluoroethylene (PTFE). Other examples are certain waxes, silicone, vinyl or greasy surfaces. The materials listed here are just examples and not meant as an exclusive list.

[0021] In yet another aspect or variant of the method said means to counteract the adhesive is a deadening adhesive applied on the second planar side. Besides countering the tack effect of the adhesive, also chemicals can be applied that counteract the adhesive.

[0022] Disclosed is also a system for assembling an RFID device, comprising an antenna creation station configured to form an antenna defining a gap and a strap attach station configured to electrically couple an RFID strap comprising an IC-bearing side and a second planar side to the antenna across the gap with the IC-bearing side, wherein the strap attach station also applies means to counteract the effect of an adhesive to the second planar side and wherein the system also applies a layer of the adhesive covering the antenna and the RFID strap and a liner covering the adhesive.Brief Description of the Drawings

[0023] Fig. 1, shows the schematic drawing of an embodiment of the inventive RFID device;

[0024] Fig. 2, shows the schematic drawing of the different layers of a further embodiment of the inventive RFID device; and

[0025] Fig. 3, shows the schematic drawing of the different layers of another embodiment of the inventive RFID device.Description of the Illustrated Embodiments

[0026] Fig. 1 shows a schematic plan view on an embodiment of the disclosed RFID device 100. The antenna 101 defines a gap 102 over which an RFID strap 103 is placed, so that it is electrically coupled to the antenna 101. To protect the RFID strap 103 from strain or tack, when the liner (not shown in Fig. 1) is peeled off the adhesive (not shown in Fig. 1), the RFID strap 103 is secured by placing an anchor 104 over the second, planar side of the RFID strap 103. The anchor 104 is significantly bigger in its areal extension than the RFID strap 103 and attaches by means of e.g. an adhesive to the substrate 200 (shown in Figs. 2 and 3) which supports the antenna 101 metal, or to the printing material the antenna 101 is printed on. Through the bigger area, the attachment to the antenna 101and substrate 200 is stronger and the RFID strap 103 may withstand the strain when the liner is peeled off or the RFID device 100 is re-placed.

[0027] Fig. 2 shows a schematic cross-section through a further example of the disclosed RFID device 100. The antenna 101 is mounted on a carrier substance or substrate 200. The antenna 101 is made from an electrically conductive material. The antenna 101 defines a gap 102. An RFID strap 103 is provided with a first side on which the IC 203 is mounted. The gap 102 can be designed wide enough, so that the IC 203 will fit in the gap 102, without making contact. This allows for a low-profile set-up. The RFID strap 103 also comprises a second, planar side. The IC-bearing side of the RFID strap 103 is attached to the antenna 101, so that the electrically conductive material of the RFID strap 103 is electrically connected to the antenna 101.

[0028] A deadener material 201 or substance is placed over the second, planar side of the RFID strap 103. The deadener material 201 can be a substance or material that counteracts, to a desired degree, the adhesive feature of the adhesive 202. However, the deadener material 201 could also be a material that sticks to the adhesive 202, but does not have any tack of its own. A paper covered with silicone on the side oriented towards the RFID strap is an example of a simple solution. A layer of adhesive 202 covers the RFID device 100, i.e. antenna 101, RFID strap 103 and deadener material 201. A liner 204 protects the adhesive 202 before such attachment from dust or unintended attachment.

[0029] Fig. 3 shows a schematic cross section through an example of the disclosed RFID device 100. The antenna 101 is mounted on a carrier substance or substrate 200. The antenna 101 is made from an electrically conductive material. This can be a thin metal foil or printed conductive material, such as conductive inks. Such a substrate 200 may be for example PET or paper, but also other substances that are suitable to support the thin metal layer or are suitable for printing conductive patterns may be used.

[0030] The antenna 101 defines a gap 102. An RFID strap 103 is provided with a first side on which the IC 203 is mounted; and a second, planar side. The RFID strap 103 is attached to the antenna 101, so that the RFID strap 103 is electrically connected. This can be achieved e.g. by electrically conductive adhesives or by capacitive coupling or galvanic coupling.

[0031] The second, planar side of the RFID strap 103 is covered with a non-stick material 300 in this example. One example of a non-stick material 300 is polytetrafluoroethylene (PTFE). Other examplesare certain waxes, silicone, vinyl or greasy surfaces. The materials listed here are just examples and not meant as an exclusive list.

[0032] A layer of an adhesive 202 is applied over the whole RFID device 100, i.e. antenna 101, strap 103 and substrate 200, as far as the latter exceeds the dimensions of the antenna 101. This layer of adhesive 202 is applied, so that the RFID device 100 can be attached to an item (not shown). A liner 204 protects the adhesive 202 before such attachment from dust or unintended attachment. A liner 204 may be a silicone covered paper or any other non-stick material 300. It may also be from the same material as the non-stick material 300 that is applied to the RFID strap 103. The liner 204 is then peeled off before attaching the RFID device 100 to an item.

[0033] It will be understood that the embodiments described above are illustrative of some of the applications of the principles of the present subject matter. Numerous modifications may be made by those skilled in the art without departing from the spirit and scope of the claimed subject matter, including those combinations of features that are individually disclosed or claimed herein. For these reasons, the scope hereof is not limited to the above description but is as set forth in the following claims, and it is understood that claims may be directed to the features hereof, including as combinations of features that are individually disclosed or claimed herein.

Claims

CLAIMS1. An RFID device comprising: an antenna defining a gap; an RFID strap comprising an IC chip attached to a leadframe on an IC-bearing side and a second planar side opposite to the IC-bearing side, said RFID strap electrically coupled to the antenna across the gap with the IC-bearing side; a layer of an adhesive covering the RFID device; a liner material that protects the adhesive layer; wherein the RFID device comprises means to counteract the effect of the adhesive, so that the RFID strap is not exposed to strain when the liner material is removed to expose the adhesive.

2. The RFID device of claim 1, wherein said means to counteract the adhesive is a non-stick material printed or coated on the second planar side.

3. The RFID device of claim 1, wherein said means to counteract the adhesive is a RFID strap made of material that does not bind to the adhesive layer.

4. The RFID device of claim 1, wherein said means to counteract the adhesive is a deadening adhesive applied on the second planar side.

5. The RFID device of claim 1, wherein said means to counteract the adhesive deadening substance applied to the adhesive layer in the area of the RFID strap.

6. The RFID device of claim 1, wherein said means to counteract the adhesive is a patch out of a non-stick material applied on the second planar side.

7. A method of assembling an RFID device comprising: providing an antenna defining a gap; providing an RFID strap, said strap comprising an IC chip attached to a lead-frame from electrically conductive material on an IC-bearing side and a second planar side opposite to the IC- bearing side, said RFID strap electrically coupled to the antenna across the gap with the IC-bearing side;securing the RFID strap to the antenna with the IC-bearing side, so that the RFID strap is electrically coupled to the antenna across the gap; applying means to counteract the effect of an adhesive on the second planar side of the RFID strap, so that any strain on said adhesive is not transferred to the RFID strap; applying a layer of the adhesive on the RFID device, covering the antenna and the RFID strap; applying a liner material on the adhesive to protect the adhesive and prevent unintended adherence.

8. The method of claim 7, wherein said means to counteract the adhesive is a non-stick material printed or coated on the second planar side.

9. The method of claim 7, wherein said means to counteract the adhesive is a RFID strap made of material that does not bind to the adhesive layer10. The method of claim 7, wherein said means to counteract the adhesive is a deadening adhesive applied on the second planar side.

11. The method of claim 7, wherein said means to counteract the adhesive deadening substance applied to the adhesive layer in the area of the RFID strap.

12. The method of claim 7, wherein said means to counteract the adhesive is a patch out of a non-stick material applied on the second planar side.

13. A system for assembling an RFID device, comprising: an antenna creation station configured to form an antenna defining a gap; and a strap attach station configured to electrically couple an RFID strap comprising an IC- bearing side and a second planar side to the antenna across the gap with the IC-bearing side, wherein the strap attach station also applies means to counteract the effect of an adhesive to the second planar side and; wherein the system also applies a layer of the adhesive covering the antenna and the RFID strap and a liner covering the adhesive.

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