RFID chip package and RFID tag

Abstract

An RFID chip package includes an RFID chip including a voltage booster circuit and processing an RF signal in a UHF band and a power supply circuit connected to the RFID chip and including at least one inductance element. A reactance component of an input/output impedance at an antenna-connecting input/output terminal of the power supply circuit is substantially 0Ω.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an RFID chip package, and in particular, relates to an RFID chip package interposed between an RFID chip and an antenna and an RFID tag in an RFID (Radio Frequency Identification) system.

2. Description of the Related Art

In recent years, an RFID system has been put into practical use as an article information management system, which includes a reader/writer that generates an induction field; and an RFID tag that is attached to an article, and non-contact communication using an electromagnetic field is established between the reader/writer and the RFID tag to transmit predetermined information therebetween. Here, the RFID tag is composed of an RFID chip that has stored predetermined information therein and processes a predetermined RF signal; and an antenna that performs transmission/reception of RF signals.

Meanwhile, in the RFID system, since an RF signal is very weak, for example, a voltage booster circuit such as a multi-stage charge pump is provided in the RFID chip as described in Japanese Unexamined Patent Application Publication No. 2005-202943 and Japanese Unexamined Patent Application Publication No. 2009-130896, and the input/output impedance of the RFID chip is very high. Thus, in the antenna, it is necessary to match its input/output impedance to the input/output impedance of the RFID chip, and hence antenna designing is difficult, and in particular, size reduction and band expansion are difficult.

SUMMARY OF THE INVENTION

Therefore, preferred embodiments of the present invention provide an RFID tag and an RFID chip package, the RFID chip package including an RFID chip and being arranged to match the RFID chip having a high impedance characteristic to an antenna having a low impedance characteristic so as to eliminate difficulty in antenna designing.

An RFID chip package according to a preferred embodiment of the present invention includes an RFID chip including a voltage booster circuit and processing an RF signal in a UHF band; and a power supply circuit connected to the RFID chip and including at least one inductance element. A reactance component of an input/output impedance at an antenna-connecting input/output terminal of the power supply circuit is substantially 0Ω.

An RFID tag according to another preferred embodiment of the present invention includes an antenna element including a connection portion; and an RFID chip package connected to the connection portion. The RFID chip package includes an RFID chip including a voltage booster circuit and processing an RF signal in a UHF band and a power supply circuit connected to the RFID chip and including at least one inductance element. A reactance component of an input/output impedance at an antenna-connecting input/output terminal of the power supply circuit is substantially 0Ω.

In the RFID chip package, the RFID chip preferably includes the voltage booster circuit, and the reactance component of the input/output impedance is about −200Ω. The power supply circuit is connected to the RFID chip, and the reactance component of the input/output impedance of the antenna terminal to which the antenna is connected is substantially 0Ω. Thus, matching can easily be provided with a general antenna such as a dipole type or a patch type, flexibility in antenna designing is increased, and hence band expansion is made easy. In addition, the impedance of a measuring system in measuring the RFID chip is preferably about 50Ω, for example, and thus the measurement of the RFID chip is also made easy.

According to various preferred embodiments of the present invention, an RFID chip having a high impedance characteristic can be suitably matched to an antenna having a low impedance characteristic, difficulty in antenna designing can be eliminated, and an RFID chip package is reduced in size.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an RFID chip package according to a preferred embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram showing a power supply circuit that is a first example of a preferred embodiment of the present invention.

FIG. 3 is a plan view showing respective base layers of a disassembled laminate constituting the power supply circuit that is the first example of a preferred embodiment of the present invention.

FIG. 4 is an equivalent circuit diagram showing a power supply circuit that is a second example of a preferred embodiment of the present invention.

FIG. 5 is a plan view showing respective base layers of a disassembled laminate constituting the power supply circuit that is the second example of a preferred embodiment of the present invention.

FIG. 6 is an equivalent circuit diagram showing a power supply circuit that is a third example of a preferred embodiment of the present invention.

FIG. 7 is a Smith chart showing the impedance matching characteristic of the power supply circuit that is the first example of a preferred embodiment of the present invention.

FIGS. 8A and 8B show a preferred embodiment of an RFID tag according to the present invention, where FIG. 8A is an exploded perspective view, and FIG. 8B is a cross-sectional view.

FIG. 9 is an exploded perspective view showing an RFID tag according to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of an RFID chip package and an RFID tag according to the present invention will be described with reference to the accompanying drawings. It is noted that in the drawings, common elements and portions are denoted by the same reference signs, and the overlap description is omitted.

As shown in FIG. 1, in an RFID chip package according to a preferred embodiment of the present invention, an RFID chip 50 is mounted on a power supply circuit substrate 10 includes a laminate that includes a power supply circuit. It is noted that the RFID chip 50 may be incorporated in the power supply circuit substrate 10 or may be accommodated in a recess (not shown) provided in the substrate 10.

The RFID chip 50 preferably processes, for example, RF signals in the UHF band, includes a clock circuit, a logic circuit, a memory circuit, and the like, and has necessary information stored therein. In addition, the RFID chip 50 also preferably includes a voltage booster circuit such as a charge pump, and with regard to its input/output impedance, the real portion preferably is about 20Ω and the imaginary portion preferably is about −200Ω, for example. A pair of input/output terminal electrodes and a pair of mounting terminal electrodes are provided on the back surface of the RFID chip 50. The input/output terminal electrodes are electrically connected via metal bumps or the like to power supply terminal electrodes 20a and 20b provided on the top surface of the power supply circuit substrate 10, and the mounting terminal electrodes are electrically connected via metal bumps or the like to mounting terminal electrodes 20c and 20d provided on the top surface of the power supply circuit substrate 10. It is noted that Au, solder, or the like can be used as the material of the metal bumps.

The power supply circuit preferably includes at least one inductance element, preferably also includes a capacitance element, and is incorporated in a power supply circuit substrate including a laminate. The reactance component of the input/output impedance of an antenna terminal electrode is set to substantially 0Ω. Hereinafter, a first example, a second example, and a third example of the power supply circuit will be described in detail.

As shown in FIG. 2, a power supply circuit 15A that is a first example of a preferred embodiment of the present invention includes two power supply terminal electrodes 20a and 20b connected to the RFID chip 50 and antenna terminal electrodes 21a and 21b connected to an antenna which is not shown, and includes inductance elements L1 and L2 and capacitance elements C1 and C2. The inductance element L1 and the capacitance element C1 are connected in series between the terminal electrodes 20a and 21a. The inductance element L2 is connected to a connection point between the inductance element L1 and the capacitance element C1 and a connection point between the terminal electrode 20b and the capacitance element C2. The capacitance element C2 is connected in series between the terminal electrodes 20b and 21b.

The inductance elements L1 and L2 are electromagnetically coupled to each other, the inductance element L1 and the capacitance element C1 are coupled to each other via an electromagnetic field, the inductance element L2 and the capacitance element C2 are coupled to each other via an electromagnetic field, and thus a resonant circuit is defined by the respective elements. In addition, as described with reference to FIG. 3, each of coil patterns defining the inductance elements L1 and L2, respectively, has a line capacity.

The power supply circuit 15A transmits a high-frequency signal that is transmitted from the RFID chip 50, is inputted from the terminal electrodes 20a and 20b, and has a predetermined frequency, from the terminal electrodes 21a and 21b to the antenna, and supplies a high-frequency signal received by the antenna, to the RFID chip 50 in the opposite direction. The power supply circuit 15A has a predetermined resonant frequency, and the reactance component of the input/output impedance of the terminal electrodes 21a and 21b is set to substantially 0Ω. Thus, the input impedance, from the RFID chip 50, of which the real portion preferably is about 20Ω and the imaginary portion preferably is about −200Ω becomes an output impedance of which the real portion is substantially 50Ω and the imaginary portion is 0Ω, and hence the impedance is matched to that of the antenna. In addition, the impedance of a measuring system in measuring the RFID chip 50 is preferably about 50Ω, for example, and thus the measurement of the RFID chip 50 is also made easy.

Next, the structure of a laminate (the power supply circuit substrate 10) including the power supply circuit 15A will be described with reference to FIG. 3. The laminate includes base layers 31a to 31k, each of the base layers 31a to 31j is a ceramic sheet formed from a dielectric material or a magnetic material, and the base layer 31k is a transfer sheet. In FIG. 3, each electrode and each conductor are provided on each of the base layers 31a to 31k, and lamination is performed in order in which the base layer 31a is stacked on the base layer 31b and further stacked on the base layers 31c, 31d, . . . etc. The base layer (transfer sheet) 31k which is stacked in the lowermost layer is peeled off after the lamination such that the terminal electrodes 20a to 20d are exposed at the bottom surface of the laminate.

Specifically, the terminal electrodes 21a and 21b, which are connected to the antenna, and a via-hole conductor 29c are provided in the base layer 31a, and capacitance electrodes 22a to 22f and via-hole conductors 29d, 29e, and 29f are provided in the base layers 31b, 31c, and 31d, respectively. Loop conductors 23a to 23f and 24a to 24d and via-hole conductors 29a, 29b, and 29g are provided in the base layers 31e to 31j. The terminal electrodes 20a to 20d and a via-hole conductor 29h are formed in the base layer 31k.

By laminating the base layers 31a to 31k, an equivalent circuit shown in FIG. 2 is defined. In other words, the capacitance element C1 is defined by the capacitance electrodes 22a, 22c, and 22e, and the capacitance element C2 is defined by the capacitance electrodes 22b, 22d, and 22f. In addition, the inductance element L1 is defined by a coil pattern in which the loop conductors 23a to 23f are defined by the via-hole conductor 29a, and the inductance element L2 is defined by a coil pattern in which the loop conductors 24a to 24d are defined by the via-hole conductor 29b.

The impedance matching characteristic of the power supply circuit 15A incorporated in the power supply circuit substrate 10 as described above is shown in a Smith chart in FIG. 7. With regard to the input/output impedance of the RFID chip 50, the real portion preferably is about 20Ω and the imaginary portion preferably is about −200Ω, and with regard to the impedance on the antenna side (after conversion), the real portion preferably is about 50Ω and the imaginary portion is 0Ω, for example.

Meanwhile, the inductance elements L1 and L2 are arranged adjacently in the laminate such that the winding axes of the coil patterns constituting the inductance elements L1 and L2, respectively, are parallel or substantially parallel to each other. The coil patterns are wound such that the directions of magnetic fluxes thereof at a moment are the same (see arrows in FIG. 3). However, the coil patterns may be wound such that these directions are opposite to each other. In addition, the openings of the respective coil patterns are covered with the capacitance electrodes 22e and 22f such that magnetic fluxes passing therethrough are guided to the capacitance elements C1 and C2. In other words, the inductance element L1 and the capacitance element C1 are coupled to each other via an electromagnetic field, and the inductance element L2 and the capacitance element C2 are coupled to each other via an electromagnetic field. In addition, by connecting the capacitance elements C1 and C2 to the antenna terminal electrodes 21a and 21b, an RFID chip package having resistance to ESD can be realized.

As shown in FIG. 4, a power supply circuit 15B that is a second example of a preferred embodiment of the present invention includes two power supply terminal electrodes 20a and 20b connected to the RFID chip 50 and antenna terminal electrodes 21a and 21b connected to an antenna which is not shown, and includes inductance elements L5, L6, and L7. The inductance elements L5 and L6 are connected in series between the terminal electrodes. The inductance element L7 is connected to a connection point between the inductance elements L5 and L6 and between the terminal electrodes 20b and 21b. The inductance elements L5, L6, and L7 are electromagnetically coupled to each other. In addition, as described with reference to FIG. 5, coil patterns defining the inductance elements L5, L6, and L7, respectively include line capacities and define a resonant circuit.

The function of the power supply circuit 15B preferably is basically the same as that of the power supply circuit 15A which is the first example, and the power supply circuit 15B transmits a high-frequency signal that is transmitted from the RFID chip 50, is inputted from the terminal electrodes 20a and 20b, and has a predetermined frequency, from the terminal electrodes 21a and 21b to the antenna, and supplies a high-frequency signal received by the antenna to the RFID chip 50 in the opposite direction. The power supply circuit 15B has a predetermined resonant frequency, and the reactance component of the input/output impedance of the terminal electrodes 21a and 21b preferably is set to substantially 0Ω. Thus, the input impedance, from the RFID chip 50, of which the real portion preferably is about 20Ω and the imaginary portion preferably is about −200Ω becomes an output impedance of which the real portion preferably is substantially 50Ω and the imaginary portion preferably is 0Ω, for example, and hence the impedance is matched to that of the antenna.

Next, the structure of a laminate (the power supply circuit substrate 10) including the power supply circuit 15B will be described with reference to FIG. 5. Each of base layers 41a to 41o is a ceramic sheet formed from a dielectric material or a magnetic material, and a base layer 41p is a transfer sheet. In addition, the order in which the base layers 41a to 41p are laminated is also preferably the same as in the first example. The base layer (transfer sheet) 41p which is stacked in the lowermost layer is peeled off after the lamination causing the terminal electrodes 20a to 20d to be exposed at the bottom surface of the laminate.

Specifically, the terminal electrodes 21a and 21b, which are connected to the antenna, and via-hole conductors 43c and 43g are provided in the base layer 41a, and the via-hole conductors 43c and 43g are provided in the base layer 41b. Loop conductors 42a to 42l and via-hole conductors 43a, 43b, 43d, and 43g are provided in the base layers 41c to 41n, respectively, and via-hole conductors 43e and 43f are provided in the base layer 41o. The terminal electrodes 20a to 20d and the via-hole conductors 43e and 43f are provided in the base layer 41p.

By laminating the base layers 41a to 41p, an equivalent circuit shown in FIG. 4 is defined. In other words, the inductance element L5 is defined by a coil pattern in which a portion of the loop conductor 42d and the loop conductors 42e to 42l are defined by the via-hole conductor 43b. The inductance element L6 is defined by a coil pattern in which the loop conductors 42a to 42c and a portion of the loop conductor 42d are defined by the via-hole conductor 43a. Furthermore, a portion of the loop conductor 42d provided in the base layer 41f defines the inductance element L7. In addition, a line 45a shown in FIG. 4 is defined by the via-hole conductors 43d and 43f, and a line 45b is defined by the via-hole conductor 43g and the via-hole conductor 43d in the base layer 41f.

The impedance matching characteristic of the power supply circuit 15B included in the power supply circuit substrate 10 as described above preferably is basically the same as in the Smith chart in FIG. 7.

As shown in FIG. 6, a power supply circuit 15C that is a third example of a preferred embodiment of the present invention is a circuit in which the inductance element L7 is omitted from the power supply circuit 15B, which is the second example, and the connection point between the inductance elements L5 and L6 and the lines 45a and 45b connecting the terminal electrodes 20b and 21b are connected to each other by a line 45c. The inductance elements L5 and L6 are electromagnetically coupled to each other, and the coil patterns thereof include line capacities and define a resonant circuit. The action and function of the power supply circuit 15C preferably are basically the same as those of the power supply circuit 15B, which is the second example.

Meanwhile, each of the inductance elements L5 and L6 has a function to provide impedance matching between the RFID chip and the antenna. In particular, the inductance element L5 is an inductance inserted in series on the RFID chip side. This inductance mainly has a function to shift the impedance along the imaginary axis direction on an impedance chart. On the other hand, the inductance element L6 is an inductance inserted in series on the antenna side and is arranged so as to extend between the two terminals 21a and 21b on the antenna side. This inductance mainly has a function to shift the impedance on the imaginary axis on an admittance chart. By making the inductance elements L5 and L6 have the above functions, the impedance can be efficiently matched.

In particular, by making the inductance value of the inductance element L5 higher than the inductance value of the inductance element L6, even when, with regard to the impedance on the RFID chip side (the input/output impedance), for example, the real portion is about 20Ω and the imaginary portion is about −200Ω, it can be made to get close to 50Ω with a relatively simple configuration, for example.

In addition, the inductance elements L5 and L6 are preferably coupled to each other via an electromagnetic field (mainly, a magnetic field). As a result, a necessary inductance value can be obtained with a small pattern. Furthermore, when the coil patterns of the inductance elements L5 and L6 are wound and arranged such that magnetic fields generated in the respective coil patterns are in-phase with each other (the directions of the magnetic fields generated in the respective coil patterns are the same), the magnetic fields of the respective coils enhance each other, and a high inductance value can be obtained even though the size of each coil is small. Thus, it is made possible to perform communication by the RFID chip and the power supply circuit substrate in a short range of several centimeters or less (even when an antenna is not connected).

An RFID tag 60A according to a preferred embodiment of the present invention will be described with reference to FIG. 8. In the RFID tag 60A, a first radiating element 65 and a second radiating element 66 that define and serve as a dipole type antenna are provided as a thin-film conductor or a thick-film conductor on a base film 61, and the power supply circuit substrate 15 including the RFID chip 50 mounted thereon is connected to the first radiating element 65 and the second radiating element 66. Specifically, the antenna terminal electrodes 21a and 21b (a third terminal 21a and a fourth terminal 21b) provided on the back surface of the power supply circuit substrate 15 are connected to connection portions 65a and 66a of the first and second radiating elements 65 and 66 via conductive bonding materials 67a and 67b. The power supply terminal electrodes 20a and 20b (a first terminal 20a and a second terminal 20b) provided on the front surface of the power supply circuit substrate 15 are connected to the input/output terminal electrodes of the RFID chip 50 via conductive bonding materials 68a and 68b.

An RFID tag 60B according to another preferred embodiment of the present invention will be described with reference to FIG. 9. In the RFID tag 60B, a radiating element 70 that defines and serves as a loop type antenna is provided as a thin-film conductor or a thick-film conductor on a base film 61, and the power supply circuit substrate 15 including the RFID chip 50 mounted thereon is connected to connection portions 70a and 70b of the radiating element 70. The connection relationship between the power supply circuit substrate 15 and the RFID chip 50, and the connection relationship between the power supply circuit substrate 15 and the connection portions 70a and 70b are preferably the same as in the RFID tag 60A according to preferred embodiment described above.

It is noted that the RFID chip package and the RFID tag according to the present invention are not limited to the preferred embodiments described above, and can be modified in a variety of ways within the scope of the present invention.

As described above, preferred embodiments of the present invention are useful for an RFID chip package and an RFID tag, and in particular, are excellent in that an RFID chip having a high impedance characteristic can be suitably coupled to an antenna having a low impedance characteristic.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.

Claims

1. An RFID chip package comprising: an RFID chip including a voltage booster circuit and processing an RF signal in a UHF band; anda power supply circuit connected to the RFID chip and including at least one inductance element; whereina reactance component of an input/output impedance at an antenna-connecting input/output terminal of the power supply circuit is substantially 0Ω;the RFID chip includes a balanced type input/output terminal including a first input/output terminal and a second input/output terminal;the power supply circuit includes a first terminal connected to the first input/output terminal, a second terminal connected to the second input/output terminal, a third terminal connected to a first connection portion of an antenna element, and a fourth terminal connected to a second connection portion of the antenna element; andthe power supply circuit further includes a first inductance element connected between the first terminal and the second terminal and a second inductance element connected between the third terminal and the fourth terminal.

2. The RFID chip package according to claim 1, wherein an inductance value of the first inductance element is higher than an inductance value of the second inductance element.

3. The RFID chip package according to claim 1, wherein the first inductance element and the second inductance element are coupled to each other via an electromagnetic field.

4. The RFID chip package according to claim 1, wherein the power supply circuit is located in a power supply circuit substrate including the inductance element; andthe RFID chip is mounted on or included within the power supply circuit substrate.

5. The RFID chip package according to claim 4, wherein the power supply circuit substrate is a laminate including a plurality of laminated base layers; andthe inductance element includes a coil pattern in which a loop conductor provided on at least one of the base layers is wound.

6. The RFID chip package according to claim 5, wherein the first inductance element and the inductance element are defined by a first coil pattern and a second coil pattern, respectively; andthe first and second coil patterns are arranged adjacently in the laminate such that winding axes thereof are parallel or substantially parallel to each other.

7. The RFID chip package according to claim 6, wherein the first coil pattern and the second coil pattern are wound and arranged such that magnetic fields generated in the first and second coil patterns are in-phase with each other.

8. The RFID chip package according to claim 5, wherein the power supply circuit further includes a capacitance element; andthe capacitance element includes capacitance electrodes provided on the base layers so as to face each other.

9. An RFID tag including: an antenna element including a connection portion; andan RFID chip package connected to the connection portion; whereinthe RFID chip package includes an RFID chip including a voltage booster circuit and processing an RF signal in a UHF band and a power supply circuit connected to the RFID chip and including at least one inductance element;a reactance component of an input/output impedance at an antenna-connecting input/output terminal of the power supply circuit is substantially 0Ω;the RFID chip includes a balanced type input/output terminal including a first input/output terminal and a second input/output terminal;the power supply circuit includes a first terminal connected to the first input/output terminal, a second terminal connected to the second input/output terminal, a third terminal connected to a first connection portion of an antenna element, and a fourth terminal connected to a second connection portion of the antenna element; andthe power supply circuit further includes a first inductance element connected between the first terminal and the second terminal and a second inductance element connected between the third terminal and the fourth terminal.

10. The RFID tag according to claim 9, wherein an inductance value of the first inductance element is higher than an inductance value of the second inductance element.

11. The RFID tag according to claim 9, wherein the first inductance element and the second inductance element are coupled to each other via an electromagnetic field.

12. The RFID tag according to claim 9, wherein the power supply circuit is located in a power supply circuit substrate including the inductance element; andthe RFID chip is mounted on or included within the power supply circuit substrate.

13. The RFID tag according to claim 12, wherein the power supply circuit substrate is a laminate including a plurality of laminated base layers; andthe inductance element includes a coil pattern in which a loop conductor provided on at least one of the base layers is wound.

14. The RFID tag according to claim 13, wherein the first inductance element and the inductance element are defined by a first coil pattern and a second coil pattern, respectively; andthe first and second coil patterns are arranged adjacently in the laminate such that winding axes thereof are parallel or substantially parallel to each other.

15. The RFID tag according to claim 14, wherein the first coil pattern and the second coil pattern are wound and arranged such that magnetic fields generated in the first and second coil patterns are in-phase with each other.

16. The RFID tag according to claim 13, wherein the power supply circuit further includes a capacitance element; andthe capacitance element includes capacitance electrodes provided on the base layers so as to face each other.