Wireless IC device

An electromagnetic coupling module includes a wireless IC chip and a functional substrate. The electromagnetic coupling module is mounted on a radiation plate, preferably using an adhesive, for example. On the upper surface of a base material of the radiation plate, two long radiation electrodes are provided. On the undersurface of the functional substrate, capacitive coupling electrodes that individually face inner ends of the radiation electrodes are provided. A matching circuit arranged to perform the impedance matching between the wireless IC chip and each of the radiation electrodes includes the capacitive coupling electrodes. As a result, it is possible to reduce the size, facilitate the design, and reduce the cost of a wireless IC device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless IC device used for an RFID (Radio Frequency Identification) system for performing wireless data communication using electromagnetic waves.

2. Description of the Related Art

Recently, as a product management system, an RFID system has been used in which a reader/writer arranged to generate an induction field communicates with a wireless IC device attached to a product in a wireless manner so as to obtain predetermined information stored in the wireless IC device.

FIG. 1is a diagram illustrating an example of a wireless IC tag (RFID tag) disclosed in Japanese Unexamined Patent Application Publication No. 2005-244778 in which an IC tag label is attached to an IC tag antenna.

In a wireless IC tag T0, a pair of main antenna elements81, an auxiliary antenna element82, and a pair of matching portions83are provided on the surface of a dielectric substrate84.

The main antenna elements81are meandering antennas in which meandering conducting lines are provided, and are symmetrically arranged on the dielectric substrate84. Between the main antenna elements81occupying areas at both ends of the dielectric substrate84, the auxiliary antenna element82is disposed.

The matching portions83are meandering conducting lines (inductors). One end of each of the matching portions83is individually connected to an inner end of the main antenna elements81, and the other end of each of the matching portions83is connected to a wireless IC chip86.

However, the wireless IC tag disclosed in Japanese Unexamined Patent Application Publication No. 2005-244778 has the following problems. Since the matching portions are individually arranged adjacent to the main antennas on the same substrate, the size of the wireless tag is increased.

If the tag is attached to a product having a high dielectric constant, the frequency characteristics of the matching circuit portions are changed due to the influence of the dielectric constant of the product. Accordingly, the frequency characteristic of the tag is significantly changed. If a protection film arranged to cover the surface of a product to which the tag is attached or the surface of the tag, the impedances of the matching portions are changed. Accordingly, it is necessary to design the wireless tag in consideration of the use condition of the wireless tag.

Since the auxiliary antenna is used to increase the design flexibility of the main antenna elements, the size of the tag is increased. Since matching design is performed at portions other than the matching portions, the number of design parameters is increased and the design complexity of the tag is increased.

Since the IC chip must be mounted on a small mounting electrode on a large substrate on which the main antennas and the matching portions are disposed, a high-precision mounting apparatus is required. Since the mounting position adjustment requires a long period of time and the manufacturing time for the tag therefore is increased, the cost of the tag is increased.

Since each of the main antennas is connected to the IC chip so that the DC continuity between them is achieved, static electricity may flow from the main antenna into the wireless IC chip and break the wireless IC chip.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of the present invention reduce the size and cost of a wireless IC device and facilitate the design of the wireless IC device.

A wireless IC device according to a preferred embodiment of the present includes a wireless IC chip, a radiation plate including a radiation electrode, and a functional substrate including an external coupling electrode coupled to the radiation electrode and a matching circuit arranged to perform impedance matching between the wireless IC chip and the radiation electrode. The matching circuit included in the functional substrate is determined such that a relationship between a reactance component of an impedance obtained by viewing the wireless IC chip from a connecting portion connecting the wireless IC chip and the functional substrate to each other and a reactance component of an impedance obtained by viewing the radiation electrode from the connecting portion connecting the wireless IC chip and the functional substrate to each other is a conjugate relationship.

The external coupling electrode is preferably electromagnetically coupled to the radiation electrode. The functional substrate preferably includes a multilayer substrate including laminated dielectric layers on which electrode patterns are provided.

The radiation electrode is preferably relatively long. The external coupling electrode preferably includes first and second external coupling electrodes that individually occupy two areas divided from the functional substrate. One of two ends of the radiation electrode is preferably coupled to the first external coupling electrode and the other one of the two ends of the radiation electrode is preferably coupled to the second external coupling electrode.

The radiation electrode is preferably a loop-shaped radiation electrode having two ends that face each other. One of the ends is preferably coupled to the first external coupling electrode. The other one of the ends is preferably coupled to the second external coupling electrode.

An auxiliary matching circuit portion preferably includes a matching electrode arranged to connect a location near one of the two ends of the radiation electrode to a location near the other one of the two ends of the radiation electrode, a portion of the radiation electrode from one of the two ends to the location near one of the two ends, and to connect a portion of the radiation electrode from the other one of the two ends to the position near the other one of the two ends.

The inductance elements are preferably loop-shaped inductance elements. Winding axes of the loop-shaped inductance elements are arranged so that they cross an area in which the radiation electrode is provided.

The external coupling electrode is preferably a capacitive coupling electrode that faces the radiation electrode and is capacitively coupled to the radiation electrode.

The capacitive coupling electrode is preferably disposed on a surface of the functional substrate facing the radiation plate. The radiation electrode is preferably disposed on a surface of the radiation plate facing the functional substrate. The functional substrate is preferably attached to the radiation plate so that the capacitive coupling electrode and the radiation electrode face each other.

The external coupling electrode included in the functional substrate preferably extends to a surface other than the surface of the functional substrate facing the radiation plate.

The external coupling electrode is preferably a loop-shaped external coupling electrode. The loop-shaped external coupling electrode is magnetically coupled to the radiation electrode.

At least one of the inductance elements preferably has a double helix shape in which two different linear electrodes are adjacent to each other. One end of one of the two different linear electrodes is preferably electrically connected to one end of the other one of the two different linear electrodes.

The radiation electrode preferably is a loop-shaped radiation electrode. The loop-shaped radiation electrode is preferably electromagnetically coupled to the inductance elements included in the functional substrate.

The matching circuit is preferably defined by an element included in the functional substrate and an element mounted on the functional substrate.

At least one of the wireless IC chip, the functional substrate, and the radiation plate is preferably covered with a protection film.

According to various preferred embodiments of the present invention, the following advantages are obtained. Since the wireless IC chip is mounted on the small functional substrate, it is possible to use an IC mounting apparatus in the related art and reduce the cost of mounting the wireless IC chip. Even if a wireless IC chip having a different output impedance is used and an RFID frequency characteristic is changed, it is only necessary to change the design of the matching circuit included in the functional substrate. This significantly reduces design costs.

Since the wireless IC chip and the functional substrate are DC-insulated from the radiation electrode, it is possible to prevent the wireless IC chip and the functional substrate from being broken by static electricity and improve the resistance of the wireless IC device to static electricity.

Since the inductance elements and/or the capacitance element are included in the multilayer substrate, it is possible to stabilize an inductance value and a capacitance value and reduce the change in impedance caused by an external factor, such as a protection film or an attachment product. Accordingly, it is not necessary to change the design of the wireless IC device in consideration of the dielectric constant of a product attached to the wireless IC device.

The first and second external coupling electrodes that individually occupy two areas divided from the functional substrate are provided, one of two ends of the long radiation electrode faces the first external coupling electrode, and the other one of the two ends of the long radiation electrode faces the second external coupling electrode. As a result, it is possible to easily supply electric power to the radiation electrode.

The radiation electrode is a loop-shaped radiation electrode in which both ends face each other, one of the ends is coupled to the first external coupling electrode, and the other one of the ends is coupled to the second external coupling electrode. As a result, a wireless IC device can perform communication using a magnetic field, is not significantly affected by the dielectric constant of an attachment product, and can obtain a more stable characteristic.

An auxiliary matching circuit portion is defined by a matching electrode arranged to connect a location near one of the two ends of the radiation electrode to a location near the other one of the two ends of the radiation electrode, a portion of the radiation electrode from one of the two ends to the location near one of the two ends, and a portion of the radiation electrode from the other one of the two ends to the location near the other one of the two ends. As a result, the impedance matching between the functional substrate and the radiation plate is performed twice. Therefore, it is possible to maintain a state in which the impedance matching between the functional substrate and the radiation plate is achieved in a wide frequency band, that is, to obtain a high gain in a wide frequency band.

The inductance elements are preferably loop-shaped inductance elements, and winding axes of the loop-shaped inductance elements are preferably arranged so that they cross an area in which the radiation electrode is disposed. As a result, magnetic fields are generated at the loop-shaped inductance elements in a direction that is parallel or substantially parallel to the winding axes of the loop-shaped inductance elements and is vertical or substantially vertical to the radiation electrode. Furthermore, a magnetic field is generated around the radiation electrode, since the radiation electrode is a planar electrode provided on a base material. Accordingly, the magnetic field loop generated at the functional substrate and the magnetic field loop generated at the radiation electrode are interlinked with each other. This strengthens the degree of coupling between the inductance elements and the radiation electrode.

Preferably, the external coupling electrode is a capacitive coupling electrode that is capacitively coupled to the radiation electrode. As a result, it is possible to strengthen the degree of coupling between the external coupling electrode and the radiation electrode. Furthermore, it is possible to simplify the shapes of the external coupling electrode and the radiation electrode and reduce the cost of the wireless IC device.

Preferably, the capacitive coupling electrode is provided on a surface of the functional substrate facing the radiation plate, the radiation electrode is arranged on a surface of the radiation plate facing the functional substrate, and the functional substrate is attached to the radiation plate so that the capacitive coupling electrode and the radiation electrode face each other. As a result, the gap between the capacitive coupling electrode and the radiation electrode is reduced, and the capacitance generated at the gap is increased. This strengthens the degree of coupling between the capacitive coupling electrode and the radiation electrode.

Preferably, the external coupling electrode included in the functional substrate extends to a surface other than the surface of the functional substrate facing the radiation plate. As a result, if the external coupling electrode is connected to the radiation electrode via a conductive joining material, such as solder, it is possible to strengthen the connection between the external coupling electrode and the radiation electrode and increase the impact residence of the wireless IC device.

Preferably, the external coupling electrode is a loop-shaped external coupling electrode, and a magnetic field of the loop-shaped external coupling electrode is coupled to a magnetic field of the radiation electrode. As a result, it is possible to mount the functional substrate on the radiation plate in any suitable orientation. Furthermore, it is possible to reduce the influence of the dielectric constant of a joining material used to connect the functional substrate and the radiation plate.

Preferably, at least one of the inductance elements has a double helix shape in which two different linear electrodes are arranged adjacent to each other. As a result, the two different linear electrodes can have different resonance frequencies, since they have different lengths. This increases a frequency band used by the wireless IC device.

Preferably, the radiation electrode is a loop-shaped radiation electrode, and an electromagnetic field of the loop-shaped radiation electrode is coupled to electromagnetic fields of the inductance elements included in the functional substrate. As a result, it is possible to strengthen the degree of coupling between the electromagnetic field of the loop-shaped radiation electrode and each of the electromagnetic fields of the inductance elements included in the functional substrate. Furthermore, since a necessary inductance component can be obtained in a relatively small area, it is possible to reduce the size of the wireless IC device. In addition, since the magnetic field of the loop-shaped portion of the radiation electrode is coupled to the magnetic field of the loop-shaped external coupling electrode, it is possible to obtain a predetermined characteristic regardless of the mounting orientation of the functional substrate with respect to the radiation plate.

Preferably, the matching circuit is defined by an element included in the functional substrate and an element mounted on the functional substrate. As a result, it is possible to reduce the size of the functional substrate by mounting a chip inductor having a large inductance value and a chip capacitor having a large capacitance value on the functional substrate so as to reduce the value of the element included in the functional substrate.

Preferably, the wireless IC device further includes a protection film covering at least one of the wireless IC chip, the functional substrate, and the radiation plate. As a result, it is possible to increase the environmental resistance of the wireless IC device and reduce the change in the characteristic of the wireless IC device due to an environmental change.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

First Preferred Embodiment

A wireless IC device according to the first preferred embodiment of the present invention will be described with reference toFIGS. 2A to 5.FIG. 2Ais a cross-sectional view of a main portion of a wireless IC device according to the first preferred embodiment.FIG. 2Bis a plan view of the main portion of the wireless IC device.

As illustrated inFIG. 2A, a wireless IC device300includes a wireless IC chip1, a functional substrate20, and a radiation plate30. The wireless IC chip1is preferably a semiconductor chip including a signal processing circuit functioning as an RFID tag, for example.

The radiation plate30includes radiation electrodes32aand32bprovided on the upper surface of a base material31, such as a PET film, for example.

The functional substrate20includes a multilayer substrate21. On the upper surface of the multilayer substrate21, mounting electrodes22aand22barranged to mount the wireless IC chip1are disposed. In the multilayer substrate21, capacitive coupling electrodes24aand24bthat are capacitively coupled to the radiation electrodes32aand32b, respectively are provided. The capacitive coupling electrodes24aand24bare external coupling electrodes of the functional substrate20. A matching circuit23including the capacitive coupling electrodes24aand24bperforms impedance matching between the wireless IC chip1and each of the radiation electrodes32aand32bprovided on the radiation plate30.

The functional substrate20is mounted on the radiation plate30via an adhesive40so that the capacitive coupling electrodes24aand24bface the internal ends of the radiation electrodes32aand32b, respectively.

On a surface on which the wireless IC chip1is mounted, a soldering bump or an Au bump, for example, is provided so that an underfill is applied in an area between the wireless IC chip1and the functional substrate20on which the mounting electrodes22aand22bare provided.

FIG. 2Bis a plan view of an area on the upper surface of the radiation plate30in which the radiation electrodes32aand32bare provided. In this drawing, the illustration of the wireless IC chip1and the mounting electrodes22aand22bis omitted. As illustrated inFIG. 2B, the capacitive coupling electrodes24aand24bincluded in the functional substrate20are arranged so that they occupy two areas that are divided from the functional substrate20. The radiation electrodes32aand32bare relatively long. The functional substrate20is disposed on the radiation plate30so that the capacitive coupling electrodes24aand24bface the internal ends of the radiation electrodes32aand32b, respectively.

Thus, the wireless IC chip1supplies electric power to the radiation electrodes32aand32bvia the functional substrate20, so that the radiation electrodes32aand32boperate as a dipole antenna.

There are several procedures for assembling the wireless IC chip1, the functional substrate20, and the radiation plate30into the wireless IC device300. Preferably, a method of creating an electromagnetic coupling module by mounting the wireless IC chip1on the functional substrate20and mounting the created electromagnetic coupling module on the radiation plate30is used. A general method used to mount a semiconductor chip on a substrate can preferably be used for the mounting of the wireless IC chip1on the functional substrate20having a relatively small size. The electromagnetic coupling module can be easily mounted on the radiation plate30having a relatively large size via the adhesive40.

FIG. 3is an exploded perspective view of the multilayer substrate21included in the functional substrate20. In this example, the wireless IC chip1is also illustrated. The multilayer substrate21preferably includes dielectric layers21a,21b,21c,21d,21e,21f, and21g. On the dielectric layer21a, the mounting electrodes22aand22band mounting electrodes22cand22d, which are used to mount the wireless IC chip1, are provided. On the dielectric layers21b,21c,21d,21e, and21f, inductor electrodes23a,23b,23c,23d, and23eare provided, respectively. On the dielectric layers21b,21c, and21d, inductor electrodes23f,23g, and23hare provided, respectively. On the dielectric layer21g, capacitive coupling electrodes24aand24bare provided. As illustrated inFIG. 3, these dielectric layers are preferably connected to one another by a via hole.

FIG. 4is an oblique perspective view of the functional substrate20on which the wireless IC chip1is mounted. The multilayer substrate included in the functional substrate20includes an inductor defined by the inductor electrodes23ato23eand an inductor defined by the inductor electrodes23fto23h.

FIG. 5is an equivalent circuit diagram of the wireless IC chip, the functional substrate, and the radiation plate. As illustrated inFIG. 5, the matching circuit23included in the functional substrate is preferably defined by the radiation plate, capacitors C1and C2, and inductors L1and L2. The inductor L1represents the inductor defined by the inductor electrodes23ato23eillustrated inFIGS. 3 and 4. The inductor L2represents the inductor defined by the inductor electrodes23fto23hillustrated inFIGS. 3 and 4. The capacitor C1represents a capacitor defined between the capacitive coupling electrode24aand the radiation electrode32a. The capacitor C2represents a capacitor defined between the capacitive coupling electrode24band the radiation electrode32b.

An impedance obtained by viewing the wireless IC chip from a connecting portion connecting the wireless IC chip and the functional substrate to each other is represented by RIC+jXIC, and an impedance obtained by viewing the radiation electrodes provided on the radiation plate from a connecting portion connecting the functional substrate and the radiation plate to each other is represented by Rant+jXant. For example, assuming that an impedance obtained by viewing the radiation plate (radiation electrodes) from the connecting portion connecting the wireless IC chip and the functional substrate to each other in or near a frequency range such as UHF is R1+jX1, the circuit constant of the matching circuit23included in the functional substrate is determined so that the relationship between XICand X1is a conjugate relationship, that is, X1=−XIC.

The matching circuit23included in the functional substrate performs impedance matching between the wireless IC chip and the radiation plate (radiation electrodes). If RIC=R1is satisfied, that is, the relationship between RIC+jXICand R1+jX1is a complex conjugate relationship, the perfect impedance matching between the wireless IC chip and the radiation plate (radiation electrodes) can be achieved. However, in reality, it is difficult for the real parts to be equal or substantially equal to each other (RIC=R1). Accordingly, it is necessary to achieve the conjugate relationship at least between reactive components. In the above-described impedance matching, the consistency between imaginary parts is more important than the consistency between real parts.

Thus, according to the first preferred embodiment, since the capacitive coupling electrodes24aand24bincluded in the electromagnetic coupling module obtained by mounting the wireless IC chip1on the functional substrate20are disposed apart from the radiation plate30on which the radiation electrodes32aand32bare provided, the electromagnetic coupling module is DC-insulated from the radiation electrodes32aand32b. As a result, an excellent electrostatic discharge (ESD) characteristic can be obtained.

Furthermore, since the matching circuit23is included in the functional substrate20including the multilayer substrate disposed between the wireless IC chip1and the radiation plate30, that is, since it is not necessary to provide an impedance matching circuit on the side of the radiation plate30, an area required for the radiation electrodes32aand32bon the radiation plate30can be significantly reduced. As a result, the size of the wireless IC device can be reduced.

Still furthermore, since the matching circuit23is included in the multilayer substrate21, a change in the characteristic of the matching circuit23is relatively small, that is, the change in the frequency characteristic of the wireless IC device300is relatively small even if the wireless IC device300is attached to a product having a high dielectric constant. Accordingly, it is not necessary to design a wireless IC device in consideration of a product to which the wireless IC device is attached. Since the matching circuit23is included in the multilayer substrate, it is possible to use a complex matching circuit that cannot easily be provided on a single surface as the matching circuit23. Accordingly, it is possible to improve the impedance matching and obtain a high-gain wireless IC device.

Second Preferred Embodiment

FIG. 6is a plan view illustrating an electrode pattern of a main portion on the upper surface of a radiation plate in a wireless IC device according to the second preferred embodiment of the present invention. On the upper surface of the radiation plate, the long radiation electrodes32aand32band a matching electrode34are provided. The matching electrode34connects a portion of the radiation electrode32aapart from the internal end of the radiation electrode32aby a predetermined distance to a portion of the radiation electrode32bapart from the internal end of the radiation electrode32bby the predetermined distance.

As in the case illustrated inFIG. 2B, near the internal ends of the radiation electrodes32aand32, the functional substrate20is arranged so that the capacitive coupling electrodes24aand24bincluded in the functional substrate20face the internal ends of the radiation electrodes32aand32b, respectively. The illustration of the wireless IC chip mounted on the upper surface of the functional substrate is omitted inFIG. 6.

An auxiliary matching circuit portion35is defined by the matching electrode34, and a portion of the radiation electrode32afrom the internal end of the radiation electrode32ato a location connected to the matching electrode34, and a portion of the radiation electrode32bfrom the internal end of the radiation electrode32bto a location connected to the matching electrode34. Thus, if predetermined portions of the radiation electrodes32aand32bare connected to each other using the matching electrode34, the wireless IC chip performs tap feeding so as to supply electric power to a dipole antenna via the functional substrate20. In an area in which the tap feeding is performed, the auxiliary matching circuit portion35performs impedance matching twice, that is, the impedance matching between the functional substrate20and the radiation electrode32aand the impedance matching between the functional substrate20and the radiation electrode32b. Accordingly, it is possible to maintain a state in which impedance matching is achieved in a wide frequency band, that is, obtain a high gain in a wide frequency band. While the auxiliary matching circuit portion35is provided in the area in which the tap feeding is performed, it is impossible to provide a large inductor on the radiation plate due to limitations of space. Furthermore, it is difficult to provide a capacitor and a circuit in which lines cross each other on the radiation plate. However, if a functional substrate is used, it is possible to provide an inductor, a capacitor, and a circuit in which lines cross each other on the radiation plate. As a result, as described previously, it is possible to maintain a state in which impedance matching is achieved in a wide frequency band, that is, obtain a high gain in a wide frequency band.

Third Preferred Embodiment

FIG. 7is a plan view illustrating an electrode pattern of a main portion on an upper surface of a radiation plate in a wireless IC device according to the third preferred embodiment of the preferred embodiment. On the upper surface of the radiation plate, a loop-shaped radiation electrode36is provided. The loop-shaped radiation electrode36is preferably arranged so that both ends thereof face each other and it surrounds a predetermined area. The functional substrate20is mounted on the radiation plate so that one end of the loop-shaped radiation electrode36faces the capacitive coupling electrode24aincluded in the functional substrate20and the other end of the loop-shaped radiation electrode36faces the capacitive coupling electrode24bincluded in the functional substrate20.

As in the first and second preferred embodiments, a module is obtained by mounting the wireless IC chip on the functional substrate20. The configuration of the functional substrate20according to the third preferred embodiment is substantially the same as that of the functional substrates20according to the first and second preferred embodiments.

Thus, if the wireless IC chip supplies electric power to the radiation electrodes32aand32bvia the functional substrate20, the radiation electrodes32aand32boperate as a magnetic field antenna. As a result, the wireless IC device can communicate with a reader/writer antenna for the wireless IC device using a magnetic field.

Fourth Preferred Embodiment

FIGS. 8A to 8D and 9A to 9Dare cross-sectional views illustrating the configurations of some wireless IC devices according to the fourth preferred embodiment of the present invention. The configurations of the radiation plate30and the wireless IC chip1according to the fourth preferred embodiment are substantially the same as those of the radiation plates30and the wireless IC chips1according to the first to third preferred embodiments. In the fourth preferred embodiment, some examples of a matching circuit included in a functional substrate will be described.

In an example illustrated inFIG. 8A, a matching circuit is defined by the inductors L1, L2, an inductor L3, and the capacitive coupling electrodes24aand24bin a functional substrate120. In the example illustrated inFIG. 5, the mounting electrode22bis through-connected to the capacitor C2. In the matching circuit according to the fourth preferred embodiment, the inductor L3is disposed at the through-connection portion. Accordingly, it is possible to reduce the inductance values of the inductors L1to L3and easily provide the inductors L1to L3in a multilayer substrate.

In an example illustrated inFIG. 8B, a matching circuit is defined by the inductors L1and L3, and the capacitive coupling electrodes24aand24bin a functional substrate121. In this example, a shunt inductor is not disposed between the capacitive coupling electrodes24aand24b. Accordingly, it is possible to easily convert a small impedance. That is, if the above-described shunt inductor has a small inductance value, it significantly changes the impedance of an impedance matching circuit. In this example, since such a shunt inductor is not used, such a problem does not arise.

In an example illustrated inFIG. 8C, a matching circuit is defined by the inductor L3and the capacitive coupling electrodes24aand24bin a functional substrate122. In this example, since only the inductor L3is used, it is possible to achieve the easy configuration of the matching circuit.

In an example illustrated inFIG. 8D, a matching circuit is defined by inductors L11, L12, L21, L31, and L32and the capacitive coupling electrodes24aand24bin a functional substrate123. In this example, since the inductors L12and L32are included, the inductance values of the radiation electrodes32aand32bcan be reduced. Accordingly, the size of the radiation electrodes can be reduced.

In an example illustrated inFIG. 9A, a matching circuit is defined by the inductors L21, L31, and L32and the capacitive coupling electrodes24aand24bin a functional substrate124. In this example, since the inductors L11and L12illustrated inFIG. 8Dare removed, it is possible to provide an easy configuration of the matching circuit while enabling the matching circuit to have the characteristic illustrated inFIG. 8D.

In an example illustrated inFIG. 9B, a matching circuit is defined by the inductors L11, L21, and L32and the capacitive coupling electrodes24aand24bin a functional substrate125. In this example, the location of the inductor L31illustrated inFIG. 9Ais changed. Accordingly, it is possible to provide easy wiring in the multilayer substrate while enabling the matching circuit to have the same or substantially the same effect as that illustrated inFIG. 9A.

In an example illustrated inFIG. 9C, a matching circuit is defined by capacitors C11and C31, inductors L22and L23, and the capacitive coupling electrodes24aand24bin a functional substrate126. In this example, since the matching circuit includes the capacitors C11and C31connected in series to each other, it is possible to achieve the impedance matching between each of the radiation electrodes (antenna) having a capacitive impedance and the wireless IC chip1having a capacitive impedance in a wide frequency range.

In an example illustrated inFIG. 9D, a matching circuit is defined by the inductors L22and L23, the capacitor C31, and the capacitive coupling electrodes24aand24bin a functional substrate127. In this example, since the capacitors C11and C31illustrated inFIG. 3Care integrated into the capacitor C31, it is possible to achieve easy pattern formation in the multilayer substrate while enabling the matching circuit to have the same or substantially the same effect as that illustrated inFIG. 9C.

The circuit constant of each of the matching circuits included in the functional substrates120to127is preferably determined so that the relationship between the reactive component of an impedance obtained by viewing the wireless IC chip from the connecting portion connecting the wireless IC chip and the functional substrate to each other and the reactive component of an impedance obtained by viewing the radiation electrodes from the connecting portion connecting the wireless IC chip and the functional substrate to each other is a conjugate relationship. Thus, a matching circuit including at least one inductance element and at least one capacitance element as required.

Fifth Preferred Embodiment

FIG. 10is a cross-sectional view of a main portion of a wireless IC device according to the fifth preferred embodiment of the present invention. As illustrated inFIG. 10, the wireless IC chip1is mounted on the upper surface of the functional substrate20, and the wireless IC chip1is covered with a resin41on the upper surface of the functional substrate20so that a flat upper surface is obtained. Other configurations are substantially the same as those described in the first preferred embodiment.

Thus, when an electromagnetic coupling module obtained by mounting the wireless IC chip1on the functional substrate20is mounted on the radiation plate30, it is possible to easily grasp the electromagnetic coupling module by suction and chuck the electromagnetic coupling module on the radiation plate30. Since the wireless IC chip1is embedded in the resin41, the environmental resistance of the wireless IC chip1is increased.

A protection film may preferably be arranged on not only the wireless IC chip1but also on the functional substrate20or the radiation plate30. Alternatively, a protection film may preferably be arranged so as to cover all of the wireless IC chip1, the functional substrate20, and the radiation plate30. This is also true for other preferred embodiments of the present invention.

Sixth Preferred Embodiment

FIGS. 11 and 12are cross-sectional views of main portions of wireless IC devices according to the sixth preferred embodiment of the present invention. In an example illustrated inFIG. 11, a functional substrate128includes the multilayer substrate21, and capacitive coupling electrodes224aand224bare arranged so that they are exposed at the undersurface of the multilayer substrate21.

The capacitive coupling electrodes224aand224bface the internal ends of the radiation electrodes32aand32b, respectively, via the adhesive40. As a result, a large capacitance can be generated between the capacitive coupling electrode224aand the internal end of the radiation electrode32aand between the capacitive coupling electrode224band the internal end of the radiation electrode32b.

In an example illustrated inFIG. 12, each of external coupling electrodes225aand225bis arranged so as to extend from the undersurface to the side surface of a functional substrate129. The coupling electrodes225aand225bare preferably connected to the radiation electrodes32aand32b, respectively, via a conductive joining material42, such as solder, for example.

As a result, it is possible to achieve the direct electrical connection between the coupling electrode225aincluded in the functional substrate129and the radiation electrode32aprovided on the radiation plate30and the direct electrical connection between the coupling electrode225bincluded in the functional substrate129and the radiation electrode32bprovided on the radiation plate30. Furthermore, it is possible to increase the mechanical strength of the wireless IC device by increasing a solder connecting area.

Seventh Preferred Embodiment

FIG. 13is a cross-sectional view of a main portion of a wireless IC device according to the seventh preferred embodiment of the present invention. Referring toFIG. 13, a multilayer substrate is included in a functional substrate220. The multilayer substrate includes inductance electrodes and capacitive coupling electrodes. On the upper surface of the multilayer substrate, a chip inductor51that is preferably a discrete component is mounted. A matching circuit is defined by the internal electrodes included in the functional substrate220and the external chip component.

In a wireless IC device having the above-described configuration, it is possible to reduce the size of the functional substrate by mounting a chip inductor having a large inductance value or a chip capacitor having a large capacitance value on the functional substrate so as to reduce the inductance or capacitance value of an element included in the functional substrate.

Eighth Preferred Embodiment

A wireless IC device according to the eighth preferred embodiment of the present invention will be described with reference toFIGS. 14 to 16B.FIG. 14is a cross-sectional view of a main portion of a wireless IC device according to the eighth preferred embodiment. In a radiation plate130, the radiation electrodes32a,32b, and32care provided on the upper surface of the base material31. A functional substrate221includes a loop-shaped external coupling electrode226. An electromagnetic coupling module obtained by mounting the wireless IC chip1on the functional substrate221is mounted on the radiation plate130so that the magnetic field of the loop-shaped external coupling electrode226and the magnetic field of the radiation electrode32care coupled to each other.

FIG. 15is a plan view of radiation electrodes provided on the upper surface of the radiation plate130and a loop-shaped external coupling electrode included in the functional substrate221. The radiation electrodes32aand32b, which are relatively long, are connected to each other by the loop-shaped radiation electrode32c. The loop-shaped external coupling electrode226included in the functional substrate is preferably spirally wound with a plurality of turns and a size that is about the same as the loop-shaped radiation electrode32c.

Thus, the winding axis of the loop-shaped external coupling electrode226that is an inductance element that is spirally wound with a plurality of turns crosses an area in which the radiation electrode32cis provided. As a result, a magnetic field is generated at the loop-shaped external coupling electrode226in a direction that is parallel or substantially parallel to the winding axis and is vertical or substantially vertical to the radiation electrode32c, and a magnetic field is generated around (in and out of) the radiation electrode32c. Accordingly, a magnetic field loop generated at the functional substrate221is interlinked with a magnetic field loop generate at the radiation electrode32c, so that the degree of coupling between the loop-shaped external coupling electrode226and the radiation electrode32ccan be further increased.

In the examples illustrated inFIGS. 14 and 15, the loop-shaped radiation electrode32cis provided. However, instead of a loop-shaped radiation electrode, for example, a dipole electrode may preferably be used as the radiation electrode32c. Such a dipole electrode can also be strongly coupled to the loop-shaped external coupling electrode226, since the magnetic flux of the loop-shaped external coupling electrode226passes around the radiation electrode32cand is then coupled to the magnetic field of the radiation electrode32c.

Furthermore, in the examples illustrated inFIGS. 14 and 15, the loop-shaped external coupling electrode226that is spirally wound is provided. However, a loop-shaped external coupling electrode that is wound with a single turn may preferably be used as the loop-shaped external coupling electrode226.

FIGS. 16A and 16Bare impedance circuit diagrams of the above-described wireless IC chip, the above-described functional substrate, and the above-described radiation plate. Referring toFIG. 16A, an inductor La on the side of the radiation plate is an inductor at the radiation electrode32c, and an inductor Lb on the side of the functional substrate is an inductor at the loop-shaped external coupling electrode226. One terminal of the wireless IC chip1is connected in series to an inductor Lc.

If the mutual inductance between the inductors La and Lb between which a magnetic field coupling is achieved is represented by M, the circuit illustrated inFIG. 16Acan be changed to a circuit illustrated inFIG. 16B. The inductors La, Lb, and Lc illustrated inFIG. 16Aare determined so that the relationship between XICand X1illustrated inFIG. 16Bis a conjugate relationship.

Thus, since a matching circuit includes the inductor at the radiation electrode32c, the impedance matching between an antenna defined by the radiation electrodes32aand32band the wireless IC chip can be achieved.

According to the eighth preferred embodiment, since both of the radiation electrode32con the side of the radiation plate and the loop-shaped external coupling electrode226on the side of the functional substrate are loop-shaped electrodes, the mounting direction of the module, which is obtained by mounting the wireless IC chip1on the functional substrate221, with respect to the radiation plate130has substantially no effect on the characteristics. That is, if the module is mounted on the radiation plate130in any orientation, a predetermined characteristic can be obtained.

Ninth Preferred Embodiment

FIG. 17is a cross-sectional view of a main portion of a wireless IC device according to the ninth preferred embodiment of the present invention. In this example, a functional substrate222includes a double helix external coupling electrode227. The magnetic field of the double helix external coupling electrode227and the magnetic field of the loop-shaped radiation electrode32cprovided on the radiation plate130are coupled to each other.

The double helix external coupling electrode227has a double helix configuration in which two different linear electrodes are adjacent to each other and ends of these linear electrodes are electrically connected to each other. The pattern of the radiation electrodes provided on the radiation plate130is substantially the same as that illustrated inFIG. 15.

FIG. 18is an impedance circuit diagram of the wireless IC chip illustrated inFIG. 17. Inductors Lb1and Lb2included in a functional substrate are inductors at the double helix external coupling electrode227. Capacitors Ca and Cb are capacitors included in the multilayer substrate included in the functional substrate222. The inductor La at a radiation substrate is an inductor at the loop-shaped radiation electrode32c. The magnetic field of the inductor La is coupled to the magnetic fields of the inductors Lb1and Lb2at the double helix external coupling electrode.

The constants of circuit elements of the matching circuit included in the functional substrate are determined so that the relationship between a reactance component XICof an impedance obtained by viewing the wireless IC chip from a connecting portion connecting the wireless IC chip and the functional substrate to each other and a reactance component X1of an impedance obtained by viewing the radiation electrodes32aand32bfrom the connecting portion connecting the wireless IC chip and the functional substrate to each other is a conjugate relationship.

Thus, by using an external coupling electrode having a double helix shape, the degree of coupling between the external coupling electrode and a radiation electrode can be increased. Furthermore, since the two lines included in the double helix external coupling electrode have different lengths, the two lines can have different resonance frequencies. Accordingly, it is possible to increase a frequency band used by the wireless IC device.

Tenth Preferred Embodiment

FIG. 19is a plan view illustrating the configuration of a functional substrate used in a wireless IC device according to the tenth preferred embodiment of the present invention. In this example, an electrode pattern is provided on only the upper surface of a functional substrate223. As illustrated inFIG. 19, a double helix external coupling electrode228is provided on the upper surface of the functional substrate223, and the inner ends of the double helix external coupling electrode228define the mounting electrodes22aand22bfor the wireless IC chip1. Other mounting electrodes22cand22dare provided near the mounting electrodes22aand22b. An electromagnetic coupling module is obtained by mounting the wireless IC chip1on the mounting electrodes22ato22d.

The configuration of a radiation electrode on the side of a radiation plate is substantially the same as that illustrated inFIG. 15. The electromagnetic coupling module illustrated inFIG. 19is preferably arranged so as to face the loop-shaped radiation electrode32cas illustrated inFIG. 15. As a result, the double helix external coupling electrode228is electromagnetically coupled to the loop-shaped radiation electrode32c. Thus, an impedance matching circuit can be obtained without using a multilayer substrate.

In the above-described preferred embodiments, various typical examples of a wireless IC device have been described. However, a wireless IC device may be obtained by combining configurations described in any of the above preferred embodiments.