RFID MODULE

An RFID module is provided that includes a substrate having first and second main surfaces; an RFIC chip and a coil conductor on the first main surface; and a first conductor pattern within the substrate. The coil conductor includes a plurality of coil elements each having a pair of legs and a bridge connecting first ends of the pair of legs. The coil elements are arranged in a row across a predetermined winding axis; and a second conductor pattern is on the first main surface and connects with the coil elements to form a coil shape. A first end of the RFIC chip is connected to a first end of the coil conductor. The first conductor pattern is between the second ends of the RFIC chip and the coil conductor. The first conductor pattern has a fold-back portion where the direction in which the pattern extends is folded back.

TECHNICAL FIELD

The present disclosure relates to an RFID module having a substrate mounted with a coil conductor.

BACKGROUND

Conventionally, products are managed by attaching a radio-frequency identification (RFID) module, which is a wireless communication device, to the products. One type of the RFID module is one in which a radio-frequency integrated circuit (RFIC) chip and a coil conductor functioning as an antenna are arranged on an insulating substrate.

For example, International Publication No. WO 2018/235714 (hereinafter “Patent Document 1”) describes an RFID module that includes a coil conductor in which coil elements are arranged in a row.

However, in the RFID module disclosed in Patent Document 1, it is difficult to lower the resonance frequency, and when the communication frequency is in a low frequency band, the resonance point may shift. Moreover, if a capacitor, a coil, or the like is used to lower the resonance frequency, the overall size of the module will increase.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the exemplary aspects of the present disclosure to provide an RFID module that does not increase in size while lowering the resonance frequency.

In an exemplary aspect, an RFID module is provided that includes a substrate having a first main surface and a second main surface that oppose other; an RFIC chip on the first main surface side of the substrate; a coil conductor on the first main surface side of the substrate; and a first conductor pattern within the substrate. The coil conductor includes a plurality of coil elements that each have a pair of legs and a bridge connecting one ends of the pair of legs. The plurality of coil elements are arranged in a row across a predetermined winding axis. Moreover, a second conductor pattern is arranged on the first main surface and connects with the coil elements to form a coil shape. A first end of the RFIC chip is connected to a first end of the coil conductor. The first conductor pattern is connected between the second end of the RFIC chip and the second end of the coil conductor. Furthermore, the first conductor pattern has a fold-back portion where the direction in which the pattern extends is folded back.

According to the exemplary aspects of the present disclosure, an RFID module is provided that does not increase in size while also lowering the resonance frequency.

DETAILED DESCRIPTION

An RFID module of a first exemplary aspect includes a substrate having a first main surface and a second main surface that oppose each other; an RFIC chip on the first main surface side of the substrate; a coil conductor on the first main surface side of the substrate; and a first conductor pattern within the substrate. The coil conductor includes a plurality of coil elements that each have a pair of legs and a bridge connecting first ends of the pair of legs. The plurality of coil elements are arranged in a row across a predetermined winding axis; and a second conductor pattern is on the first main surface and connects with the coil elements to form a coil shape. A first end of the RFIC chip is connected to a first end of the coil conductor. The first conductor pattern is connected between the second end of the RFIC chip and the second end of the coil conductor. The first conductor pattern has a fold-back portion where the direction in which the pattern extends is folded back.

In the RFID module of the exemplary aspect, the first conductor pattern as a part of the resonance circuit has the fold-back portion where the direction in which the pattern extends is folded back, so that the pattern length is increased and the inductance of the first conductor pattern is also increased. This configuration effectively lowers the resonance frequency of the RFID module1. Since no coil components or capacitors are required to lower the resonance frequency, the size of the RFID module1does not need to be increased to lower the resonance frequency.

According to a second exemplary aspect of the RFID module, the first conductor pattern is a meandering pattern that has a rectilinear pattern extending in the longitudinal direction of the substrate and the fold-back portion where the direction in which the rectilinear pattern extends is folded back. Since the first conductor pattern is a meandering pattern, it is easier to design the length of the first conductor pattern for a desired resonance frequency.

According to a third exemplary aspect of the RFID module, the substrate includes a first base material layer on the first main surface side and a second base material layer on the second main surface side. The first base material layer is laminated on the first main surface side of the second base material layer, and the first conductor pattern is on the second base material layer. The RFID module includes first and second interlayer connection conductors that each extend through the first base material layer and the second base material layer. The second end of the RFIC chip and a first end of the first conductor pattern are connected via the first interlayer connection conductor, while the second end of the first conductor pattern and the second end of the coil conductor are connected via the second interlayer connection conductor. The first and second interlayer connection conductors confront each other in the longitudinal direction of the first base material layer and the second base material layer, and the first conductor pattern is arranged between the first and second interlayer connection conductors. Since the first conductor pattern is arranged between the first and second interlayer connection conductors, even if the RFID module comes into contact with another article during the manufacturing process or handling after manufacturing, for example, the first conductor pattern is protected from being scraped off.

According to a fourth exemplary aspect of the RFID module, first and second lands that are electrodes are arranged on the first main surface side of the first base material layer; and a second electrode is provided that faces the first land and the second land and is connected to the first interlayer connection conductor. The second end of the RFIC chip is connected to the first land, with a first end of the RFIC chip being connected to the second land. The first land is connected to a first end of the first conductor pattern, and a first end of the coil conductor is connected to the second land. The second electrode is positioned closer to the RFIC chip than the first conductor pattern. Since the second electrode faces the first land and the second land, a capacitance component is generated. Moreover, positioning the second electrode closer to the RFIC chip than the first conductor pattern enables the generation of a greater capacitance component.

According to a fifth exemplary aspect of the RFID module, the second electrode is on the first main surface side of the second base material layer, whereas the first conductor pattern is on the second main surface side of the second base material layer. Since the second electrode and the first conductor pattern are arranged apart from each other, the generation of a capacitance component between the first conductor pattern and the first land and the second land can be reduced, which facilitates designing the area of the second electrode generating a capacitance component and the length of the first conductor pattern generating inductance.

According to a sixth exemplary aspect, the RFID module includes a third base material layer on which the second main surface side of the second base material layer is stacked. Since the third base material layer covers the first conductor pattern on the second major surface side of the second base material layer, the first conductor pattern is prevented from rubbing against another object and peeling off.

According to a seventh exemplary aspect of the RFID module, the second conductor pattern includes a plurality of first electrodes each connected to the other ends of the pair of legs of each of the plurality of coil elements; and a wiring conductor that connects a first electrode connected to one of the second ends of the pair of legs of the coil element and a first electrode connected to the other of the second ends of the pair of legs of a coil element adjacent to the coil element. The plurality of first electrodes and the wiring conductor are arranged on the first main surface side of the first base material layer.

Exemplary embodiments described below each show a specific example of the present disclosure, but it is noted that these embodiments are not limited to these particular configurations. Moreover, it is noted that the numerical values, shapes, configurations, steps, sequence of steps, and the like specifically shown in the following embodiments are merely examples and are not intended to limit the present invention. In all the embodiments, the same applies to configurations in their variants, and the configurations described in the variants may be combined with each other as would be appreciated to one skilled in the art.

Exemplary Embodiments

A schematic configuration of an RFID module1according to an exemplary embodiment will now be described. In particular,FIG.1is an overall perspective view of the RFID module1of the exemplary embodiment.FIG.2is a side transparent view of the RFID module1of the exemplary embodiment. In the figures, the XYZ coordinate system is provided to facilitate understanding of the exemplary embodiment and is not intended to limit the invention. For purposes of this disclosure, the X-axis direction indicates the longitudinal direction of the RFID module1, the Y-axis direction indicates the depth (e.g., width) direction, and the Z-axis direction indicates the thickness direction. The X, Y, and Z directions are orthogonal to each other. In the exemplary embodiment, the positive direction of the Z axis is described as an upward direction, and the negative direction of the Z axis is described as a downward direction.

According to an exemplary aspect, the RFID module1of the exemplary embodiment includes a laminated substrate3, a coil assembly5and an RFIC chip7on a first main surface3a, which is the upper surface of the laminated substrate3, and a resin layer9for sealing the coil assembly5and the RFIC chip7. The RFIC chip7has a first terminal7aand a second terminal7bwhich are input/output terminals (see, e.g.,FIG.5). A second main surface3b, which is the lower surface of the laminated substrate3, and the first main surface3aface each other, i.e., that oppose each other.

Referring toFIGS.5and6, for example, the laminated substrate3has a first base material layer11, a second base material layer13, and a third base material layer15, which are laminated toward the coil assembly5with the third base material layer15as a bottom base material, the second base material layer13laminated on the third base material layer15, and the first base material layer11further laminated on the second base material layer13. The first base material layer11to the third base material layer15are each insulative and are made of, for example, a glass epoxy base material or a ceramic base material.

For purposes of this disclosure, a third main surface11aof the first base material layer11may correspond to the first main surface3aof the laminated substrate3. A fourth main surface11bof the first base material layer11on the second main surface3bside is in contact with a fifth main surface13aof the second base material layer13on the first main surface3aside. A sixth main surface13bof the second base material layer13on the second main surface3bside is in contact with a seventh main surface15aof the third base material layer15on the first main surface3aside. An eighth main surface15b, which is the lower surface of the third base material layer15, faces the seventh main surface15aand corresponds to the second main surface3bof the laminated substrate3.

As further shown, a first resist layer16is laminated on the first main surface3aof the laminated substrate3, and a second resist layer17is laminated on the face of the second main surface3bof the laminated substrate3. The first resist layer16is provided to prevent electrodes and wiring arranged on the first base material layer11from short-circuiting, and the second resist layer17covers and protects the lower ends of a first interlayer connection conductor55and a second interlayer connection conductor57, which will be described below. The first resist layer16and the second resist layer are, for example, insulating resin layers according to an exemplary aspect.

As shown inFIG.4, the coil assembly5includes a plurality of coil elements21and a resin block23that integrates the plurality of coil elements21. The RFID module1includes the plurality of coil elements21of the coil assembly5and a second conductor pattern26located on the third main surface11a, which is the upper surface of the first base material layer11, to thereby form a coil conductor25wound around a winding axis WA (seeFIG.1), the coil conductor25functioning as an antenna. The communication frequency band of the RFID module1of the exemplary embodiment can be, for example, a UHF band from 860 MHz to 960 MHz. The number of turns and dimensions of the coil assembly5can be changed depending on communication characteristics as would be appreciated to one skilled in the art.

As shown inFIG.3, the coil element21includes a pair of legs31arranged substantially parallel to each other, a bridge33connecting first ends of both the legs31, and a substrate connection35bent at approximately 90 degrees at a tip of the second end of each of the legs31.

The block23fixes the state of arrangement of the coil elements21. As shown inFIG.4, the block23can be filled with resin in an area surrounded by the legs31and the bridge33of each coil element21. In other words, the block23does not have a recess for accommodating a coil core. The legs31of each coil element21are exposed from a side surface23aof the block23. The block23is formed of, for example, a thermoplastic resin such as a liquid crystal polymer, or a thermosetting resin according to exemplary aspects.

The coil elements21are each fixed to the block23at a position where the legs31and bridges33straddle the winding axis WA. When the coil assembly5is mounted on the first base material layer11, the coil elements21are arranged and fixed in a direction parallel to the winding axis WA of the coil conductor25, with their respective one legs31located on one side with respect to the winding axis WA and their respective other legs31located on the other side with respect to the winding axis WA (seeFIGS.1and4). It is noted that the substrate connections35of each coil element21are not covered with the block23so that each substrate connection35serves as a connection when the coil assembly5is mounted on the first base material layer11.

The resin layer9seals the coil assembly5and the RFIC chip7and is laminated on the third main surface11aof the first base material layer11and the first resist layer16. The resin layer9is formed of, for example, a general sealing resin such as epoxy resin according to an exemplary aspect.

The laminated substrate3will then be described with reference toFIG.7A to7D.FIG.7A to7Dare plan views showing the base materials of the laminated substrate3.FIG.7Ais a plan view showing the third main surface11aof the uppermost first base material layer11.FIG.7Bis a plan view showing the fifth main surface13aof the intermediate second base material layer13.FIG.7Cis a transparent plan view seen through the fifth main surface13aof the intermediate second base material layer13. FIG.7D is a plan view showing the seventh main surface15aof the lowermost third base material layer15.

As shown inFIG.7A, the third main surface11a, which is the upper surface of the first base material layer11, has thereon a first land41and a second land43connected to a first terminal7aand a second terminal7bof the RFIC chip7, respectively, and the second conductor pattern26connecting with each of the plurality of coil elements21to form a coil shape. The second conductor pattern26includes a plurality of first electrodes27, wiring conductors28,29, and30, and an auxiliary electrode45. The wiring conductor28connects a first electrode27on one side (e.g., a positive side in the Y-axis direction) to a first electrode27on the other side (e.g., a negative side in the Y-axis direction), which is shifted by one in the positive direction of the X-axis. The first land41and the second land43are each a metal electrode (i.e., configured as first and second land electrodes) and are in contact with and electrically connected to the first terminal7aand the second terminal7bof the RFIC chip7, respectively. The first electrode27on the other side farthest from the first land41is electrically connected to the auxiliary electrode45via the wiring conductor29. The first electrode27on one side closest to the first land41is electrically connected to the second land43via the wiring conductor30.

As shown inFIG.7B, a second electrode47is located below the first land41and the second land43on the fifth main surface13a, which is the upper surface of the second base material layer13. The second electrode47faces the first land41and the second land43so that the first land41and the second land43and the second electrode47generate a capacitance C1.

As shown inFIGS.5,6, and7C, auxiliary electrodes49and51and a first conductor pattern53are arranged on the sixth main surface13b, which is the lower surface of the second base material layer13. It is noted thatFIG.7Cis a view seen through the fifth main surface13afrom above.

The laminated substrate3includes the first interlayer connection conductor55and the second interlayer connection conductor57each extending through the first base material layer11and the second base material layer13. The first interlayer connection conductor55is a conductive via that connects the first land41to the second electrode47and the auxiliary electrode49. The second interlayer connection conductor57is a conductive via that connects the auxiliary electrode45and the auxiliary electrode51.

According to an exemplary aspect, the first and second interlayer connection conductors55and57are conductors, for example, that can be formed by solidifying (e.g., metallizing) a conductive paste filled in holes located in the insulating first base material layer11and second base material layer13, but may also be plated-through holes. The first and second interlayer connection conductors55and57are arranged to confront each other in the longitudinal direction of the first base material layer11and the second base material layer13.

Fold-back portions53bof the first conductor pattern53are folded back in the direction in which the wiring pattern extends. The first conductor pattern53is, for example, a meandering pattern that has a rectilinear pattern53aextending in the longitudinal direction of the second base material layer13(e.g., a longitudinal direction of the laminated substrate3) and the fold-back portions53bwhere the direction of extension of the rectilinear pattern53ais folded back. The first conductor pattern53has three or more odd-numbered rectilinear patterns53aand fold-back portions53b, and connects the auxiliary electrode49and the auxiliary electrode51.

In this way, since the amplitude direction of the meandering pattern is the longitudinal direction (i.e., the X-axis direction) of the second base material layer13, the number of the fold-back portions53bcan be reduced and the difference in path length between the center and the inside of the meandering pattern can also be reduced, as compared to the case where the amplitude direction of the meandering pattern is the transverse direction (i.e., the Y-axis direction) of the second base material layer13. Since current flowing through the meandering pattern tends to flow inside the meandering pattern, the difference can be reduced between the designed length of the meandering pattern and the actual length through which current flows, thereby reducing the deviation of the L component of the meandering pattern.

According to the exemplary aspect, the first conductor pattern53is located between the first and second interlayer connection conductors55and57. Thus, since the first conductor pattern53is not located outside the first and second interlayer connection conductors55and57in the longitudinal direction, the first conductor pattern53can be protected from being scraped off in the event of contact or the like between the RFID module and other articles during the manufacturing process or handling after manufacturing, for example.

Moreover, a center axis WB of the amplitude of the first conductor pattern53, which is a meandering pattern, intersects with the winding axis WA of the coil conductor25, for example, orthogonally. This configuration reduces mutual interference between an inductance L1of the coil conductor25and an inductance L2of the first conductor pattern53.

As shown inFIG.7D, the third base material layer15is located below the second base material layer13. By providing the laminated substrate3with the third base material layer15on which the second main surface3bside of the second base material layer13is stacked, the first conductor pattern53is covered with the third base material layer15, which prevents the first conductor pattern53from rubbing and peeling off. It is noted that the first interlayer connection conductor55and the second interlayer connection conductor57extend up to the seventh main surface15a, which is the upper surface of the third base material layer15.

As shown inFIGS.5and6, the second electrode47is positioned closer to the RFIC chip7than the first conductor pattern53is. This configuration provides for a larger capacitance C1to be generated relative to the size of the second electrode47.

The first electrode27, the wiring conductors28,29, and30, the first land41, the second land43, the auxiliary electrode45, the second electrode47, the auxiliary electrodes49and51, and the first conductor pattern53are each a conductor that can be made of a copper foil patterned by photolithography.

A circuit configuration of the RFID module1will be described with reference toFIG.8, which is an equivalent circuit diagram of the RFID module1.

In particular, an LC parallel resonance circuit is configured within the RFID module1and is matched to radio waves at a communication frequency, so that when the coil conductor25receives radio waves at the communication frequency, current flows to the RFIC chip7. The coil conductor25has the inductance L1, and the first conductor pattern53has the inductance L2. The capacitance C1is formed by the first land41, the second land43, the first base material layer11, and the second electrode47. The RFIC chip7has therein a resistance R and a capacitance C2.

In this aspect, a combined inductance L of the RFID module1is L=L1+L2from the inductances L1and L2. A combined capacitance C of the RFID module1is C=C1+C2from the capacitances C1and C2. A resonance frequency f of the RFID module1is calculated from the following formula:

Thus, the longer the length of the coil conductor25, the larger the inductance L1becomes, and the larger the combined inductance L also becomes, resulting in a smaller resonance frequency f. The larger the capacitance C1, the larger the combined capacitance C also becomes, and the smaller the resonance frequency f becomes. Conventional RFID modules cannot cope with the need to reduce the resonance frequency with the communication frequency, but the RFID module1of the first exemplary embodiment can reduce the resonance frequency by lengthening the coil conductor25of the meander pattern, or by increasing the area of the second electrode, or by both such modifications.

As described above, the RFID module1of the exemplary embodiment includes the laminated substrate3having the first main surface3aand the second main surface3bfacing each other, the RFID chip7located on the first main surface3aside of the laminated substrate3, the coil conductor25located on the first main surface3aside of the laminated substrate3, and the first conductor pattern53lying within the laminated substrate3. The coil conductor25includes the plurality of coil elements21arranged in a row across the predetermined winding axis, each having the pair of legs31and the bridge33connecting first ends of the legs31, and the second conductor pattern26located on the first main surface3aand connecting with the coil elements21to form a coil shape. A first end of the RFIC chip7is connected to a first end of the coil conductor25, and the first conductor pattern53is connected between the second end of the RFIC chip7and the second end of the coil conductor25, the first conductor pattern53having the fold-back portions53bwhere the direction of extension of the pattern is folded back.

According to the RFID module1having this configuration, the first conductor pattern53, which is a part of the resonance circuit, has the fold-back portions53bwhere the extending direction of the pattern is folded back, so that the pattern length can be increased and the inductance of the first conductor pattern can also be increased. This configuration enables the resonance frequency of the RFID module1to be lowered. Since no coil components or capacitors are required to lower the resonance frequency, there is no need to increase the size of the RFID module1to lower the resonance frequency.

Moreover, the laminated substrate3includes the first base material layer11located on the first main surface3aside and the second base material layer13located on the second main surface3bside. The first base material layer11is laminated on the first main surface3aside of the second base material layer13, and the first conductor pattern53is located on the second base material layer13. The RFID module1includes first and second interlayer connection conductors55and57that each extend through the first base material layer11and the second base material layer13. The first land41at the second end of the RFIC chip7and a first end of the first conductor pattern53are connected via the first interlayer connection conductor55. The second end of the first conductor pattern53and the auxiliary electrode45at the second end of the coil conductor25are connected via the second interlayer connection conductor57. The first and second interlayer connection conductors55and57confront each other in the longitudinal direction of the first base material layer11and the second base material layer13, and the first conductor pattern53is located between the first and second interlayer connection conductors55and57.

The RFID module1includes the first and second lands41and43, which are electrodes arranged on the first main surface3aside of the first base material layer11, and the second electrode47facing the first and second lands41and43and connected to the first interlayer connection conductor55. The first terminal7aat the second end of the RFIC chip7is connected to the first land41, and the second terminal7bat a first end of the RFIC chip7is connected to the second land43. The first land41and a first end of the first conductor pattern53are connected, and the wiring conductor30at a first end of the coil conductor25is connected to the second land43. The second electrode47is positioned closer to the RFIC chip7than the first conductor pattern53is.

The second electrode47is located on the first main surface side of the second base material layer13, while the first conductor pattern53is located on the second main surface side of the second base material layer13. Since the second electrode47and the first conductor pattern53are arranged apart from each other, the generation of a capacitance component can be reduced between the first conductor pattern53and the first land41and the second land43, thus making it easier to design the area of the second electrode47generating a capacitance component and the length of the first conductor pattern53generating inductance.

As further shown, the second conductor pattern26includes the plurality of first electrodes27that are each connected to the second ends of the pair of legs31of each of the plurality of coil elements21, and the wiring conductor28that connects a first electrode27connected to one of the second ends of the pair of legs of the coil element21and a first electrode27connected to the other of the second ends of the pair of legs31of a coil element21adjacent to the coil element21. The plurality of first electrodes27and the wiring conductor28are arranged on the first main surface3aside of the first base material layer11. As a result, the plurality of coil elements21can be arranged on the laminated substrate3to form the coil conductor25.

A first variant of the exemplary embodiment will then be described with reference toFIG.9. In particular,FIG.9is a transparent plan view showing the sixth main surface13bof the intermediate second base material layer13in the first variant of the exemplary embodiment. The meandering first conductor pattern53may be arranged in an S-shape. The rectilinear pattern53aextending from the auxiliary electrode49toward the auxiliary electrode51may be folded back near the center of the second base material layer13to extend toward the auxiliary electrode49, and again folded back near the center of the second base material layer13to extend toward the auxiliary electrode51. In the first variant, the two fold-back portions53bare arranged on the second base material layer13near the center in the longitudinal direction thereof. Such a configuration can also provide the same effect as that of the RFID module1of the exemplary embodiment as described above.

A second variant of the exemplary embodiment will then be described with reference toFIG.10. In particular,FIG.10is a transparent plan view seen through the fifth main surface13aof the intermediate second base material layer13in the second variant of the embodiment. The rectilinear pattern53aextending from the auxiliary electrode51toward the auxiliary electrode49may be folded back near the center of the second base material layer13to extend toward the auxiliary electrode51, and folded back in the vicinity of the auxiliary electrode51to extend toward the auxiliary electrode49. In the second variant, one of the two fold-back portions53bis located on the second base material layer13near the center in the longitudinal direction thereof. Such a configuration can also provide the same effect as that of the RFID module1of the exemplary embodiment as described above.

A third variant of the exemplary embodiment will then be described with reference toFIG.11. In particular,FIG.11is a transparent plan view seen through the fifth main surface13aof the intermediate second base material layer13in the third variant of the embodiment. The first conductor pattern53may be a loop pattern having fold-back portions instead of the meandering pattern. Such a configuration can also provide the same effect as that of the RFID module1of the exemplary embodiment as described above.

In general, it is noted that the exemplary aspects of the present disclosure are not limited to the embodiments described above, and can be modified and implemented as follows.

In the above embodiments, the amplitude direction of the meandering pattern of the first conductor pattern53is the longitudinal direction (i.e., the X-axis direction) of the second base material layer13, but the exemplary embodiment is not limited thereto. For example, the amplitude direction of the meandering pattern of the first conductor pattern53can be the transverse direction (i.e., the Y-axis direction) of the second base material layer13.

In the above embodiments, the first interlayer connection conductor55and the first land41are arranged inside the second land43in the longitudinal direction of the laminated substrate3, but the exemplary embodiment is not limited thereto. As shown inFIGS.12A to12D, the first interlayer connection conductor55and the first land41can be arranged outside the second land43in the longitudinal direction of the laminated substrate3.

Although the exemplary aspects of the present disclosure have been described in the embodiments with a certain degree of detail, the disclosed contents of these embodiments may vary in the details of the configurations, and the change in the combination and order of elements in each embodiment may be implemented without departing from the scope and ideas of the claimed invention.

EXPLANATION OF REFERENCES