JP2016170808A - Radio ic tag and rfid system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio IC tag and an RFID system which are stable in a communication state.SOLUTION: A radio IC tag according to the invention comprises: a laminate formed by stacking a plurality of dielectric layers or magnetic material layers, and including a first principal surface which is one end face in a stacking direction and a second principal surface which is the other end face; a radio IC element mounted on or incorporated in the laminate; and a coil-shaped antenna connected to the radio IC element and formed by stacking a plurality of conductor patterns each having a predetermined aperture diameter. The coil-shaped antenna is formed such that in the laminate the aperture diameter of the conductor pattern close to the second principal surface in proximity to an antenna of a reader/writer is smaller than the aperture diameter of the conductor pattern close to the first principal surface which is the mounting surface to the substrate. The radio IC element is mounted close to the first principal surface.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a wireless IC tag, and more particularly to a wireless IC tag and an RFID system used for an RFID (Radio Frequency Identification) system.

  2. Description of the Related Art Conventionally, as an article management system, an RFID system has been developed in which a reader / writer that generates an induction electromagnetic field communicates with a wireless IC tag that stores predetermined information attached to an article in a non-contact manner and transmits information. Yes. As a wireless IC tag used in this type of RFID system, Patent Document 1 describes an RFID tag in which a minute coiled antenna is formed on an IC chip.

  However, the RFID tag has a problem that the communication state is not stable because the coiled antenna is very small.

JP 2002-183676 A

  Accordingly, an object of the present invention is to provide a wireless IC tag and an RFID system with a stable communication state.

In order to achieve the above object, a wireless IC tag according to one aspect of the present invention is
A laminate having a plurality of dielectric layers or magnetic layers laminated and having a first main surface that is one end surface in the stacking direction and a second main surface that is the other end surface; A wireless IC tag comprising a built-in wireless IC element and a coiled antenna connected to the wireless IC element and laminated with a plurality of conductor patterns having a predetermined opening diameter,
The coiled antenna is formed on the second main surface side where the antenna of the reader / writer is closer than the opening diameter of the conductor pattern on the first main surface side which is a mounting surface on the base material in the laminate. It is formed so that the opening diameter of the conductor pattern is small,
The wireless IC element is mounted on the first main surface side,
It is characterized by.

  According to the present invention, the communication state with the reader / writer is stabilized.

Sectional drawing which shows the radio | wireless IC tag which is 1st Example. Explanatory drawing which shows the magnetic field radiation | emission state of the radio | wireless IC tag shown in FIG. FIG. 2 is an exploded perspective view showing a laminated structure of the wireless IC tag shown in FIG. 1. Sectional drawing which shows the radio | wireless IC tag which is 2nd Example. Explanatory drawing which shows the magnetic field radiation | emission state of the radio | wireless IC tag shown in FIG. Sectional drawing which shows the radio | wireless IC tag which is 3rd Example. Explanatory drawing which shows the magnetic field radiation | emission state of the radio | wireless IC tag shown in FIG. Sectional drawing which shows the radio | wireless IC tag which is 4th Example. Explanatory drawing which shows the magnetic field radiation | emission state of the radio | wireless IC tag shown in FIG. Sectional drawing which shows the radio | wireless IC tag which is 5th Example. Explanatory drawing which shows the magnetic field radiation | emission state of the radio | wireless IC tag shown in FIG. Sectional drawing which shows the radio | wireless IC tag which is 6th Example. Explanatory drawing which shows the magnetic field radiation | emission state of the radio | wireless IC tag shown in FIG. An explanatory view showing an example of an RFID system. The RFID system is shown, (A) is a perspective view of a reader / writer side antenna, (B) is a block diagram of a circuit. Explanatory drawing which shows the magnetic field radiation | emission state in the said RFID system.

  Embodiments of a wireless IC tag and an RFID system according to the present invention will be described below with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same member and part in each figure, and the overlapping description is abbreviate | omitted.

(Refer to the first embodiment, FIG. 1, FIG. 2 and FIG. 3)
As shown in FIG. 1, the wireless IC tag 1A according to the first embodiment includes a wireless IC element 10 that processes a transmission / reception signal having a predetermined frequency, a stacked body 20, and a coiled antenna 30 built in the stacked body 20. And.

  The wireless IC element 10 is configured in a chip shape, includes a clock circuit, a logic circuit, a memory circuit, etc., stores necessary information, and has a pair of input / output terminal electrodes (not shown) on the back surface. And mounted on the laminate 20. The laminate 20 is configured by laminating a plurality of layers mainly composed of a dielectric or magnetic substance.

  As will be described below with reference to FIG. 3, the coiled antenna 30 is formed by stacking coil conductor patterns 33 a to 33 c formed on dielectric or magnetic sheets 21 c to 21 e and connecting via via hole conductors 34 a. By doing so, it is wound in a coil shape. One end of each of the coiled antennas 30 is electrically connected to the input / output terminal electrodes of the wireless IC element 10 via the solder bumps 15.

  As shown in FIG. 1, the wireless IC tag 1 </ b> A is attached to a base material 40 such as a printed wiring board via an adhesive layer 41. As shown in FIG. 2, the coiled antenna 30 is formed such that the spread of the magnetic field H radiated from the antenna 30 is different between the upper surface side and the lower surface side of the multilayer body 20. Specifically, in the coiled antenna 30, the opening diameters of the coil conductor patterns 33a, 33b, and 33c (which means the inner diameter of each pattern in this specification) are directed from the lower surface side to the upper surface side of the multilayer body 20. Are formed to be substantially large.

  The wireless IC tag 1A can communicate with a reader / writer (not shown) of the RFID system, and both constitute an information processing system. In this information processing system, by bringing the reader / writer antenna close to the wireless IC tag 1A, magnetic flux based on a signal of a predetermined frequency (for example, UHF band, HF band) radiated from the antenna penetrates the coiled antenna 30. As a result, a current flows through the antenna 30. This current is supplied to the wireless IC element 10 to operate the wireless IC element 10. On the other hand, a response signal from the wireless IC element 10 is radiated as a magnetic field from the coiled antenna 30 and is read by a reader / writer.

  The magnetic field H radiated from the coiled antenna 30 is as shown by a dotted line in FIG. This coiled antenna 30 is built in the laminate 20, and the magnetic field H generated by the coiled antenna 30 spreads outside the wireless IC tag 1A, and the position of the coiled antenna 30 relative to the reader / writer antenna (not shown). The degree of freedom of the relationship is increased, and stable communication can be performed over a wide range.

  In addition, communication between the reader / writer and the wireless IC tag 1A is mainly performed by a magnetic field. However, since the attenuation of the magnetic field with respect to the distance is larger than the electric field, the communication is performed in a relatively close state. Therefore, communication can be performed only with the wireless IC tag to be read by the reader / writer, and there is no possibility of erroneous communication with the wireless IC tag that is not to be read in the vicinity.

  It is desirable that the imaginary part of the impedance of the wireless IC element 10 and the imaginary part of the impedance of the coiled antenna 30 have a conjugate relationship with the frequency of the signal used for communication. That is, it is desirable that the resonance frequency of the coiled antenna 30 is in the vicinity of the use frequency. It is further desirable that the real parts of the impedance match.

  In particular, when the coiled antenna 30 is a laminated type and has a large opening, a small and large inductance value can be obtained, and as a result, the wireless IC tag 1A itself is miniaturized. By making the operating frequency a short wavelength around 950 MHz, the size is further reduced. In the case of using a UHF band frequency for communication, the wireless IC tag 1A can be summarized into, for example, a size of 3.2 mm in length, 1.6 mm in width, and 0.5 mm in height.

  Here, an example of the laminated structure of the laminated body 20 (coiled antenna 30) will be described with reference to FIG. The laminated body 20 is formed by forming electrodes, conductors, and via-hole conductors on a plurality of sheets 21a to 21e whose main component is a dielectric or magnetic material.

  The first layer sheet 21a has electrodes 31a and 31b connected to input / output terminal electrodes (not shown) of the wireless IC element 10 and mounting electrodes 31c and 31d (connected to mounting terminal electrodes (not shown) of the wireless IC element 10). Connecting conductors 32a and 32b are formed on the second layer sheet 21b, and coil conductor patterns 33a, 33b and 33c are formed on the third to fifth layer sheets 21c to 21e. Is formed.

  The coil conductor patterns 33a, 33b, and 33c are connected in a coil shape via the via-hole conductor 34a to form the antenna 30. One end of the conductor pattern 33a is connected to the electrode 31a via a via-hole conductor 34b, a connecting conductor 32a, and a via-hole conductor 34c. One end of the conductor pattern 33c is connected to the electrode 31b through a via-hole conductor 34d, a connecting conductor 32b, and a via-hole conductor 34e.

  By making the coiled antenna 30 a laminated type, the opening can be enlarged and the operation stability can be achieved. That is, since the capacitance between the coil conductor patterns 33a, 33b, and 33c is determined by the material (sheet material) between them, the influence of the dielectric constant of the article to which the wireless IC tag 1A is attached is small (the fluctuation of the stray capacitance). Less change in the inductance value of the coil. Therefore, the change in the resonance frequency is small and the communication distance is stabilized. In particular, by using a material having a high dielectric constant for the stacked body 20, the impedance of the coil in the stacked body 20 is almost determined, and is less susceptible to the influence of the use environment.

  The coil conductor patterns 33a, 33b, and 33c of the coiled antenna 30 may be configured with a larger number. Moreover, the opening diameter of each pattern should just be formed so that it may become large gradually toward the upper surface side from the lower surface side of the laminated body 20. FIG. Substantially, it does not necessarily need to be continuously and gradually enlarged, and the coil conductor pattern located in the middle has the same opening diameter as the pattern located above and below it, or is lower than the pattern located below A large opening diameter may be used. As described above, the opening diameter of each pattern does not have to change stepwise continuously in the vertical direction, as in the following embodiments.

(Refer to the second embodiment, FIGS. 4 and 5)
As shown in FIG. 4, the wireless IC tag 1B according to the second embodiment has a wireless IC element 10 mounted on the back side of the laminate 20 including the coiled antenna 30 and covers the wireless IC element 10. A stop layer 25 is provided. The top surface of the sealing layer 25 is stuck on a base material 40 such as a printed wiring board via an adhesive layer 41.

  Other configurations of the second embodiment are the same as those of the first embodiment. Accordingly, the operational effects of the second embodiment are the same as those of the first embodiment. In particular, the wireless IC element 10 is protected from the external environment by covering the wireless IC element 10 with the sealing layer 25. That is, it can be protected from mechanical shocks from the outside, and a short circuit due to moisture can be prevented. In addition, since the sealing layer 25 is interposed between the laminate 20 and the base material 40, the distance between the coil-shaped antenna 30 and the surface of the base material 40 is larger than that in the first embodiment, and the coil-shaped antenna 30. The magnetic field H radiated from is formed slightly apart from the substrate 40 (see FIG. 5). Therefore, it is possible to reduce the influence of other mounting components and conductor patterns provided on the base material 40 with respect to the magnetic field H.

(Refer to the third embodiment, FIGS. 6 and 7)
As shown in FIG. 6, the wireless IC tag 1 </ b> C according to the third embodiment has coil conductor patterns 33 a, 33 b, and 33 c constituting the coiled antenna 30 whose opening diameters are from the lower surface side to the upper surface side of the laminate 20. It is formed so as to become substantially smaller toward. Similarly to the second embodiment, the wireless IC element 10 is mounted on the lower surface of the laminate 20 and is covered with a sealing layer 25.

  Other configurations of the third embodiment are the same as those of the first embodiment. In the third embodiment, the magnetic field H radiated from the coiled antenna 30 is as shown by a dotted line in FIG. 7, and the opening diameters of the coil conductor patterns 33 a, 33 b, 33 c are directed toward the upper surface of the multilayer body 20. Since it is formed to be small, the magnetic field H is directed to the inside of the wireless IC tag 1C, and a region having a high magnetic flux density is formed in the central portion of the wireless IC tag 1C, thereby improving communication characteristics. The other operational effects of the third embodiment are basically the same as those of the first and second embodiments.

(Refer to the fourth embodiment, FIGS. 8 and 9)
As shown in FIG. 8, the wireless IC tag 1D according to the fourth embodiment has coil conductor patterns 33a, 33b, 33c constituting the coiled antenna 30 whose opening diameters are from the lower surface side to the upper surface side of the multilayer body 20. It is formed so as to become substantially smaller toward. As in the first embodiment, the wireless IC element 10 is mounted on the upper surface of the laminate 20.

  That is, in the fourth embodiment, the opening diameters of the coil conductor patterns 33a, 33b, and 33c of the coiled antenna 30 become smaller toward the upper surface of the multilayer body 20 as in the third embodiment. It is formed as follows. Accordingly, as indicated by a dotted line in FIG. 9, the magnetic field H is radiated so as to face the inside of the wireless IC tag 1D, and a region having a high magnetic flux density is formed in the central portion of the wireless IC tag 1D. To do. The other functions and effects of the fourth embodiment are basically the same as those of the first embodiment.

(Refer to the fifth embodiment, FIGS. 10 and 11)
As shown in FIG. 10, the wireless IC tag 1E according to the fifth embodiment is basically similar to the first and second embodiments, and each of the coil conductor patterns 33a, 33b, 33c are formed so that their opening diameters become substantially larger from the lower surface side to the upper surface side of the laminated body 20, and the coiled antenna 30 is formed such that the central plane A of the antenna 30 in the laminating direction is the laminated body. It is built in the laminate 20 so as to be located on the opposite side of the base surface 40 with respect to the center plane B of 20. Further, similarly to the second embodiment, the wireless IC element 10 is mounted on the back side of the laminate 20 including the coiled antenna 30, and the sealing layer 25 covering the wireless IC element 10 is provided. The top surface of the sealing layer 25 is stuck on a base material 40 such as a printed wiring board via an adhesive layer 41. Therefore, the coiled antenna 30 is located away from the surface of the base material 40 by the distance C.

  The operational effects of the fifth embodiment are the same as those of the first and second embodiments. In particular, in the fifth embodiment, the magnetic field H radiated from the coiled antenna 30 is as shown by a dotted line in FIG. The coiled antenna 30 is built in the laminated body 20, and the base surface such as a printed wiring board is greater in the center plane A in the stacking direction of the coiled antenna 30 than the center plane B in the stacking direction of the stacked body 20. Since it is located on the opposite side to 40, a large amount of the magnetic field H is generated in the direction away from the substrate 40 and approaching the reader / writer antenna. Therefore, it is difficult to be influenced by other mounting parts provided on the base material 40 and metal objects such as conductor patterns, and the communication distance is not shortened.

(Refer to the sixth embodiment, FIGS. 12 and 13)
As shown in FIG. 12, the wireless IC tag 1F according to the sixth embodiment basically has the coil conductor patterns 33a, 33b, 33c of the coiled antenna 30 as shown in FIG. The coil-shaped antenna 30 is formed so that the center plane A in the stacking direction of the antenna 30 is the center of the stack 20. It is built in the laminate 20 so as to be located on the opposite side of the base material 40 from the surface B. Furthermore, the wireless IC element 10 is mounted on the back side of the laminate 20 including the coiled antenna 30, and the sealing layer 25 covering the wireless IC element 10 is provided. The top surface of the sealing layer 25 is stuck on a base material 40 such as a printed wiring board via an adhesive layer 41. Therefore, the coiled antenna 30 is located away from the surface of the base material 40 by the distance C.

  The operational effects of the sixth embodiment are basically the same as those of the first and third embodiments. In particular, in the sixth embodiment, the magnetic field H radiated from the coiled antenna 30 is as shown by a dotted line in FIG. The coiled antenna 30 is built in the laminated body 20, and the base surface such as a printed wiring board is greater in the center plane A in the stacking direction of the coiled antenna 30 than the center plane B in the stacking direction of the stacked body 20. Since it is located on the opposite side to 40, a large amount of the magnetic field H is generated in the direction away from the substrate 40 and approaching the reader / writer antenna. Therefore, it is difficult to be influenced by other mounting parts provided on the base material 40 and metal objects such as conductor patterns, and the communication distance is not shortened.

(Example of RFID system, see FIGS. 14 to 16)
Next, an example of an RFID system using the wireless IC tags 1B and 1C will be described. Of course, other wireless IC tags 1A and 1D to F than the wireless IC tags 1B and 1C can be used.

  As shown in FIG. 14, this RFID system is a system for transmitting information between a reader / writer and the wireless IC tags 1B and 1C in a non-contact manner, and performs transmission and reception of high-frequency signals in the UHF band or SHF band. . As shown in FIG. 15A, the reader / writer includes an antenna head 50 in which a loop antenna 52 is provided on the surface of a support member 51 made of a hard member such as an epoxy resin. The loop antenna 52 is formed of a one-turn loop conductor having both ends of the power feeding portions 52a and 52b. The power feeding portions 52a and 52b are connected to an information processing circuit (not shown) of the reader / writer via a coaxial cable 55. ing. The wireless IC tag 1B has been described with reference to FIGS. 4 and 5 as the second embodiment, and the wireless IC tag 1C has been described with reference to FIGS. 6 and 7 as the third embodiment. is there.

  As shown in FIG. 15B, a matching circuit composed of a capacitance element C and an inductance element L is interposed between the coaxial cable 55 and the loop antenna 52, and the power feeding part 52 a is an inner conductor of the coaxial cable 55. 56, the power feeding portion 52b is connected to the outer conductor 57 of the coaxial cable 55 via a matching circuit. The coaxial cable 55 is configured as a 50Ω line, and matching between the impedance of the coaxial cable 55 and the impedance of the loop antenna 52 is achieved by a matching circuit. As shown in FIG. 14, the antenna head 50 is attached to the grip 60 via a coaxial cable 55, and is configured as a pen-type head that can be used while being gripped by a human hand.

  In this RFID system, a loop antenna 52 is used as an antenna on the reader / writer side, and a coiled antenna 30 configured to generate a large magnetic field on the reader / writer side as described above is used as an antenna on the wireless IC tag side. ing. Therefore, in the state where the antenna head 50 is brought close to the wireless IC tags 1B and 1C, the magnetic field H1 generated from the loop antenna 52 and the magnetic field H2 generated from the coiled antenna 30 are as shown in FIGS. The high-frequency signals are mutually transmitted between the loop antenna 52 and the coiled antenna 30.

  The magnetic field H1 generated from the loop antenna 52 is concentrated on the opening of the loop antenna 52 and spreads over a wide range. On the other hand, the coiled antenna 30 of the wireless IC tags 1B and 1C generates a large magnetic field H2 on the reader / writer side, so that the magnetic field H2 is concentrated on the opening of the loop antenna 52. Therefore, even if the base material 40 includes a metal material, the metal material is close, or the base material 40 is a metal material, the communication performance does not deteriorate. Furthermore, by using a high-frequency signal in the UHF band or a higher frequency band, the base material 40 on which the wireless IC tag 1C is mounted is a metal material, or other mounting parts mounted on the base material 40, It becomes difficult to be affected by metal members such as various wiring patterns. In addition, even when the wireless IC tags 1A, 1D to 1F are used, the coiled antenna 30 generates a large magnetic field on the loop antenna 52 side of the reader / writer, so that the effects described here are obtained.

  In addition, if the conductor width of the loop antenna 52 is increased, the magnetic field H1 generated from the loop antenna 52 spreads over a wide range mainly in a direction parallel to the loop surface, and the relative position of the loop antenna 52 with respect to the wireless IC tags 1B and 1C is increased. Even if it is slightly deviated, the magnetic fields H1 and H2 are reliably linked, so that necessary communication performance can be ensured. When viewed from the wireless IC tags 1B and 1C, since the magnetic field H2 generated by the coiled antenna 30 spreads outward, the degree of freedom in the positional relationship with the loop antenna 52 is increased. In FIGS. 16A and 16B, the magnetic fields H1 and H2 do not show all the generated magnetic fields.

  In this RFID system, the reader / writer antenna and the wireless IC tag are used close to each other, and communication can be performed only for the target wireless IC tag. In this case, the coiled antenna 30 can be configured to have a small external dimension of 10 mm or less in length and width, and further 5 mm or less. Specifically, the used frequency band is a UHF band of 860 to 960 MHz, the size of the wireless IC tags 1B and 1C is 3.2 mm in length and 1.6 mm in width, and the outer dimensions of the coiled antenna 30 are 3.0 mm in length and width. When 4.0 mm, the conductor width of the loop antenna 52 is 0.5 mm, and the output voltage value is 1 W, communication is possible even if the distance between the loop antenna 52 and the wireless IC tags 1B and 1C is about 6 mm. is there. Of course, it is possible to further increase the communication distance by increasing the output power value or increasing the size of the coiled antenna 30.

(Other examples)
Note that the wireless IC tag and the RFID system according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

  For example, in the above-described embodiment, the wireless IC element is mounted on the stacked body on which the antenna is formed. However, the wireless IC element may be built in the stacked body. Further, two coiled antennas may be juxtaposed in the laminated body in plan view. Further, the number of coiled antennas may be three or more. Alternatively, the wireless IC element and the coiled antenna may be magnetically or electrically coupled in addition to DC coupling.

  As described above, the present invention is useful for wireless IC tags and RFID systems, and is particularly excellent in that communication with a reader / writer is stable.

DESCRIPTION OF SYMBOLS 1A-1F ... Wireless IC tag 10 ... Wireless IC element 20 ... Laminated body 25 ... Sealing layer 30 ... Coiled antenna 33a-33c ... Coil conductor pattern 40 ... Base material 50 ... Antenna head H ... Magnetic field

Claims (5)

A laminate having a plurality of dielectric layers or magnetic layers laminated and having a first main surface that is one end surface in the stacking direction and a second main surface that is the other end surface; A wireless IC tag comprising a built-in wireless IC element and a coiled antenna connected to the wireless IC element and laminated with a plurality of conductor patterns having a predetermined opening diameter,
The coiled antenna is formed on the second main surface side where the antenna of the reader / writer is closer than the opening diameter of the conductor pattern on the first main surface side which is a mounting surface on the base material in the laminate. It is formed so that the opening diameter of the conductor pattern is small,
The wireless IC element is mounted on the first main surface side,
A wireless IC tag characterized by the above. The wireless IC element is disposed on a winding axis of the coiled antenna;
The wireless IC tag according to claim 1.   The wireless IC tag according to claim 1, wherein the coiled antenna is capable of near field communication in a UHF band.   The sealing surface which covers the said radio | wireless IC element is provided in the said 1st main surface side, The top | upper surface of this sealing layer is a sticking surface to the said base material, The thru | or 1 characterized by the above-mentioned. The wireless IC tag according to claim 3.   An RFID system using the wireless IC tag according to any one of claims 1 to 4.