JP4865614B2 - RFID chip and antenna with improved range - Google Patents

Description

  The present invention relates to the field of rfid (radio frequency identification) chips and antenna technology. More particularly, the present invention relates to an associated rf query and read device and an rfid chip and antenna with improved communication range.

  Both a general rfid chip and an antenna are incorporated into an ID tag such as that shown and described in US Pat. Is normal. In general, an ID tag is an antenna that is attached to or enclosed in a thin substrate such as a polyethylene terephthalate (PET) substrate as disclosed in US Pat. And rfid chip. The antenna is typically a small loop antenna or a dipole antenna and must be ohmically connected to the rfid chip. A typical loop antenna is a multi-turn planar ohmic conductor formed by any one of several well-known methods. One such technique is silver paste printing on a suitable substrate such as the PET substrate described above. Another well-known technique for forming loop antennas is copper deposition on a substrate implemented at the RCD Technology Corporation of Bethlehem, Pennsylvania. The coil size (coil diameter and thickness) and the number of turns are determined by the specific application requirements, including constraints on the physical size of the ID tag. The function of the antenna provides electromagnetic transmission between the RFID chip and an external inquiry / reading device such as a host CPU, user reading station, etc., and also allows inductive transfer of power from the external device to the RFID chip. It is to supply power to the active circuit elements in the rfid chip.

  Currently, a wide variety of commercially available rfid chips are known, each having standard internal functional components commonly found in rfid integrated circuits. Such standard components include an RF analog section, a CPU, a ROM, and an EEPROM (see FIG. 9.1.1: RFID transponder IC block diagram of Non-Patent Document 1). The rfid chip receives power via the antenna when queried by the external device and communicates with the external device using a standard protocol such as the ISO 14443 protocol or the ISO 15693 protocol. Before installing the ID tag on the object, information for identifying the object to be mounted is written in a ROM (read only memory) incorporated in the rfid chip. Once this information is written to ROM, it cannot be overwritten or rewritten by the interrogation device. The rfid chip is queried by an external query and read device and only supplies information to the external device, i.e. it cannot change the information stored in the ROM.

  An ID tag of the type described above having an rfid chip and an antenna is very useful for object tracking and is currently used in a variety of such applications. Although this technology can be used more theoretically, its practical use has been limited so far due to size and cost constraints. Such restrictions have recently been overcome by improved semiconductor batch processing technology, as ultra-small rfid chips and antennas are now produced at a cost much lower than the cost of the individual objects to be mounted. For example, Hitachi, LTD. Released a mu series rfid chip and antenna in 2004 with a chip size of 0.4 mm x 0.4 mm and at least one-third the price of the rfid chip sold at that time. Other semiconductor manufacturers are following their precedent competitive products.

  FIG. 1 is a plan view of a prior art ID tag 10 having an rfid chip 12 and a single individual antenna 14 that are both elements attached to a substrate 15. The rfid chip 12 is an integrated circuit that includes the normal circuit configuration required for a functional rfid device and is a device that is fabricated independently. These integrated circuit devices are typically manufactured using batch processing techniques well known to those skilled in the art. In general, multiple copies of the basic device design are made on a large semiconductor wafer, after which individual chips are separated from each other and combined with other individual parts.

  In the ID tag 10 of FIG. 1, another individual component is an antenna 14, whereby the circuit configuration of the rfid chip 12 can be communicated with an external inquiry device, and energy is electromagnetically transmitted to the rfid chip 12 and included therein. Power can be supplied to the electronic circuit configuration. The effective operating range of the rf antenna is directly related to the coil area, and the antenna 14 is ideally a multi-turn coil that occupies a much larger area than the rfid chip 12 in order to provide the widest possible operating range. The antenna 14 is typically either a separately formed individual coil that is later bonded to the substrate 15 or a metal layer that is directly deposited on the substrate 15 during coil formation.

  The ID tag 10 of FIG. 1 is generally constructed by first manufacturing the rfid chip 12 and the antenna 14 as separate parts, attaching the parts 12 and 14 to the substrate 15 and electrically connecting the antenna 14 to the rfid chip 12. Is done. Therefore, two ohmic connection pads 16 and 17 to which the free ends 18 and 19 of the antenna 14 are joined are manufactured on the rfid chip 12.

  Although the manufacturing process of the ID tag 10 looks simple and easy, in practice it is difficult to carry out this process with high repeatability. This difficulty is mainly due to the small dimensions of the connection pads on the rfid chip and the free ends 18, 19 of the antenna 14 need to be accurately positioned on the pads 16, 17 prior to the process bonding step. And the need for an accurate mechanical ohmic connection between the antenna end and the connection pad. The production cost of an ID tag of the type seen in FIG. 1 is estimated to be one third for the rfid chip 12, one third for the antenna 14, and one third for assembly. As the physical size of the rfid chip is reduced, the difficulty and cost of assembling a correctly functioning ID tag will increase accordingly.

  FIG. 2 shows one of the latest methods used in the art to alleviate the difficulty in assembling an ID tag having a single rfid chip and antenna component. As can be seen in the figure, the rfid chip 22 and the antenna 24 integrally formed on the substrate 25 are manufactured in the ID tag 20. Since the antenna 24 is formed with the rfid chip 22 during the chip fabrication process, an ohmic connection is automatically formed between the rfid chip 22 and the free end of the antenna 24. This “coil-on-chip” method eliminates costly bonding steps and associated difficulties.

  While the “coil-on-chip” solution does indeed alleviate the problems associated with joining individual parts in the ID tag assembly process, it places severe restrictions on the effective operating range of ID tags fabricated according to this technology. “Coil-on-chip” ID tags are fabricated using integrated circuit batch processing techniques, but the size of the antenna is significantly limited to the size of the die produced. For example, the published operating range of commercially available “coil-on-chip” ID tags is limited to a maximum distance of 3.0 mm. While this is suitable for some special applications, such a narrow operating range is inappropriate for most of the applications currently envisioned for ID tags.

  One of the attempts to expand the operating range of the “coil-on-chip” ID tag is “Radio Frequency Identification Responder with Integrated Antenna” issued July 31, 2001, whose disclosure is incorporated by reference. Patent Document 3 of Japanese Patent Application Laid-Open No. H11-228707. According to the teaching of this reference, an antenna is formed on a chip mounted above or below the rfid chip. The antenna has several coil turns that together form a helical coil having an axis parallel to the body surface of the rfid chip. In order to increase the inductance of the antenna coil and the operating range of the ID tag, a high permeability layer is formed on the antenna chip. Although this structure certainly extends the operating range of “coil-on-chip” ID tags, it requires several additional processing steps, which can increase manufacturing costs and affect yield, and is relatively narrow in scope. Only an antenna can be obtained.

  Thus, current “coil-on-chip” RFID tags still have serious disadvantages that limit the effective operating range with the associated interrogation and reading device.

US Pat. No. 6,154,137 US Pat. No. 6,373,708 B1 US Pat. No. 6,268,796 1999 IEEE International Solid State Circuit Conference Public Relations 0-7803-5129-0 / 99

  The present invention includes a method and system for providing a “coil-on-chip” RFID tag that has an extended operating range over known ID tags of comparable dimensions.

  The present invention on the device side includes a substrate and an RFID tag including a combination of an rfid chip and an antenna formed integrally on the substrate. The rfid chip has a body surface that is basically parallel to the surface of the substrate.

  The antenna includes a coil having a multi-layered conductive turn having a central opening surrounding a rotation axis disposed at an acute angle with respect to the main surface of the rfid chip, and a magnetically permeable material positioned in the central opening of the coil. Including the core. In a preferred embodiment, the coil has an essentially helical structure with at least two layers, the acute angle is approximately 90 degrees, and the core is annular.

The present invention in terms of process
(A) preparing a substrate;
(B) simultaneously forming an rfid integrated circuit and an antenna coil on the substrate, wherein the coil has a central opening having a rotation axis that forms an acute angle with the body surface of the rfid integrated circuit. A step formed as a turn multilayer coil;
(C) providing a core of magnetically permeable material so as to be positioned in the central opening of the coil;
Including a method of creating an RFID tag.

  The forming step (b) and the providing step (c) are performed simultaneously. Forming step (b) preferably includes forming a coil with a rotation axis that forms an angle of approximately 90 degrees with the body surface of the rfid integrated circuit. The core is formed as an annular body.

  The present invention provides a much wider operating range than known devices while realizing all the advantages of a “coil-on-chip” ID tag. This expansion of the operating range is estimated to be ten times as large as the known “coil-on-chip” ID tag.

  Referring now to the drawings, FIG. 3 is a top view of the preferred embodiment of the present invention, and FIG. 4 shows the multiple coil turns and multiple coil layers of the preferred embodiment, and the magnetically permeable layer of the antenna. 4 is a cross-sectional view taken along line 4-4 of FIG. As seen in these figures, the RFID tag 30 includes an rfid chip 32 and a multi-turn antenna coil 34 arranged in multiple layers. The coil comprises a thin film core 36 made of a material having a relatively high magnetic permeability and arranged in the center. The rfid chip 32, the coil 34, and the core 36 are all supported on the substrate 37. The rfid chip 32 has a main body surface that is parallel to the main support surface of the substrate 37. The multi-layer multi-turn antenna coil 34 has a central rotation shaft 38 having an acute angle with respect to the main surface of the rfid chip 32, preferably about 90 degrees.

  As best seen in FIG. 4, the thin film core 36 is formed as an annular body extending upward from the upper surface of the substrate 37 to the upper surface of the coil 34 in the range of the layers and turns of the coil 34. The thin film core 36 may be made of any one of many well-known materials having the property of relatively high magnetic permeability. One such material is a nickel iron alloy comprised of 81% nickel and 19% iron. Other suitable materials will occur to those skilled in the art. The purpose of the core 36 is to improve the quality factor of the coil 34 and hence the operating range of the ID tag 30.

  The coils 34 are multi-layered and each is multi-turned, and the spatial orientation of the coil 34 in the direction in which the rotation axis of the coil 34 is arranged is an acute angle with respect to the main body surface of the rfid chip 32, basically 90 in the figure. The operating range of the ID tag 30 is also improved by setting the degree.

  The ID tag 30 is fabricated using well-known techniques for manufacturing “coil-on-chip” ID tags. Thus, several layers of rfid chip 32, multi-layer multiturn coil 34 and core 36 can be made simultaneously using well-known deposition, masking, doping and etching techniques.

  Although the invention has been described with respect to particular preferred embodiments, various modifications, alternative constructions, and equivalents may be employed without departing from the spirit of the invention. For example, although the coil 34 has been illustrated and described as a coil having two layers of multi-turn, a multi-turn coil having three or more layers can be easily realized if desired. Further, as described above, the core 36 may be made of a material other than the specific material described. Therefore, the above should not be construed as limiting the invention, which is defined by the appended claims.

It is a top view of a prior art ID tag having an rfid chip and a separate antenna. FIG. 6 is a plan view of a prior art ID tag having an rfid chip and an integrally formed antenna. FIG. 4 is a plan view of an ID tag having an rfid chip and an integrally formed antenna according to the present invention. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 showing a multilayer multi-turn antenna coil.

Explanation of symbols

  30 tags, 32 RFID chip cores, 34 coils, 36 cores, 37 substrates, 38 rotation axes

Claims (7)

A substrate having an upper surface ;
A combination of an rfid chip and an antenna integrally formed on the upper surface of the substrate;
It includes,
The antenna includes a coil having a plurality of layers of conductive turns having a central opening surrounding a rotation axis disposed at an angle to the substrate;
Each layer includes a plurality of conductive turns;
A core of magnetically permeable material positioned in the central opening of the coil and extending from the top surface of the substrate to the central opening in the top layer of the multi-layer coil ;
The coil has a basically helical structure with at least two layers;
An RFID tag , wherein the core is a thin film core having a hollow inside . The invention of claim 1 wherein said angle is approximately 90 degrees. The invention of claim 1 wherein the core is annular. (A) providing a substrate having an upper surface;
  (B) simultaneously forming an rfid integrated circuit and an antenna coil on the substrate, wherein the coil is formed as a multi-layer multi-turn coil having a central opening having a rotation axis that forms an angle with the substrate. Each of the layers includes a plurality of conductive turns;
  (C) providing a core of magnetically permeable material positioned in the central opening of the coil and extending from the upper surface of the substrate to the central opening in the uppermost layer of the multilayer;
The coil is formed as a basically spiral structure comprising at least two layers, and the core is formed as a thin film core having a hollow inside. The method of claim 4, wherein said forming step (b) and said providing step (c) are performed simultaneously. The method of claim 4, wherein said forming step (b) includes forming said coil having a rotational axis that is at an angle of approximately 90 degrees to said upper surface of said substrate. The method of claim 4, wherein the core is formed as an annulus.

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