Radio tag and process for producing the same

The present invention relates to a wireless tag and a method for manufacturing the wireless tag. The present invention is suitable, for example, as a metal-compatible wireless tag that can be attached to a metal.

An RFID (Radio Frequency Identification) system is known as one of wireless communication systems. This RFID system generally includes a wireless tag (also called an RFID tag) and a reader / writer (RW) device, and information is read / written from the RW device to the wireless tag by wireless communication.

There are two types of wireless tags: one that operates with the power supply built into the wireless tag itself (called an active tag) and one that operates using the radio waves received from the RW device as drive power (called a passive tag). Has been done.

In the case of an RFID system using a passive tag, the wireless tag uses the wireless signal from the RW device as drive power to operate integrated circuits such as built-in ICs and LSIs, and various types according to the received wireless signal (control signal). Perform processing. Transmission from the wireless tag to the RW device is performed using the reflected wave of the received wireless signal. That is, information such as the tag ID and the results of the various processes is put on the reflected wave and transmitted to the RW device.

Various frequency bands are used in RFID systems, but recently, the UHF band (860MHz to 960MHz) has been attracting attention. The UHF band is capable of long-distance communication compared to the existing 13.56MHz band and 2.45GHz band. It uses frequencies around 868MHz in Europe, 915MHz in the United States, and 953MHz in Japan. The communication distance of a UHF band wireless tag (hereinafter, also simply referred to as a "tag") is approximately 3 to 5 m, although it depends on the performance of integrated circuits such as IC chips and LSIs used in the tag. The output of the RW device is about 1 watt (W).

As a conventional wireless tag, for example, there are those described in Patent Documents 1 to 3 described later. The technique described in Patent Document 1 is aimed at ensuring the reliability of communication by suppressing a decrease in communication distance even when the RFID tag is used in close proximity to the radio wave absorber. There is. Therefore, Patent Document 1 describes a rectangular dielectric member having a predetermined dielectric constant, an antenna pattern for transmission / reception formed on the surface of the dielectric member by loop-like etching or the like, and a chip on the antenna pattern. An RFID tag with an IC chip that is electrically connected via a mounting pad is described.

According to the RFID tag, when used for an object having a certain conductivity such as a bottle containing liquid or a human body, a minute loop antenna is formed around the dielectric member by an antenna pattern and attached. Since a current loop is also formed in the attachment target, a larger current loop is formed, the gain of the loop antenna is improved, and the communication distance can be extended.

The technique described in Patent Document 2 aims to create an RFID tag that has a long communication distance and is easy to print. Therefore, the RFID tag of Patent Document 2 is configured by laminating the first component and the second component, and the first component is a plate-shaped first base made of a dielectric and the first base thereof. It has a metal layer covering the first surface of the front and back surfaces of the above, and the second component is a sheet-shaped second base and the metal layer of the first component provided on the second base and electrically. A metal pattern connected to a communication antenna to form a communication antenna, a circuit chip connected to the metal pattern for wireless communication via the communication antenna, and the second base of the first base among the front and back surfaces of the first base. It has an adhesive layer for adhering to the second surface with respect to the first surface, and the metal layer of the first component and the metal pattern of the second component are electrically connected by a conductive component.

The technique described in Patent Document 3 aims to provide an RFID tag capable of suppressing changes in resonance frequency and Q value to ensure a good communication state even when it is arranged inside a device containing a metal material. It is supposed to be. Therefore, in Patent Document 3, the tag is composed of a substantially disk-shaped substrate having at least a loop-shaped antenna pattern and an IC, and a disk-shaped magnetic sheet having a diameter substantially equal to that of the substrate. It is described that the inductance can be easily adjusted by cutting out a part around the magnetic sheet with a single straight line.

As a result, even if a metal member or the like is arranged inside the device, the influence can be suppressed by the magnetic sheet, and the decrease in the inductance of the antenna due to the metal material and the increase in the inductance due to the magnetic sheet are offset. By setting the width of the notch portion in this way, changes in the resonance frequency and Q value can be compensated, and a good communication state can be ensured.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2006-53833</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2006-301690</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2006-331101</text></patcit>

<p> When the UHF band wireless tag is attached to metal, impedance matching and gain with integrated circuits such as IC chips and LSIs (hereinafter simply referred to as chips) deteriorate, which may make communication difficult. Therefore, various attempts have been made to make the antenna pattern of the wireless tag into a loop shape as in the techniques described in Patent Documents 1 to 3, but the wireless tag having the loop-shaped antenna pattern has the susceptance of the chip. When the component (the imaginary part of admittance, which is the reciprocal of impedance (usually represented by B)) is large, it is difficult to adjust impedance matching (hereinafter, also simply referred to as matching adjustment).</p><p> That is, since the equivalent circuit of the chip mounted on the wireless tag can be represented by the parallel capacitance component Ccp and the parallel resistance component Rcp, the susceptance component B changes mainly depending on the capacitance component Ccp. However, if the capacitance component Ccp becomes too large, it becomes difficult to design and adjust the antenna impedance that matches this.</p><p> For example, as one of the methods for adjusting the antenna impedance, as shown in FIG. 13 (relative permittivity vs. Ccp characteristic), by changing (reducing) the relative permittivity of the dielectric (base) on which the antenna pattern is formed, The corresponding capacitance component Ccp of the antenna pattern can be increased, but there is a limit to lowering the relative permittivity of the dielectric (the minimum value is the relative permittivity of air = 1), so the corresponding capacitance component that exceeds that limit. It is difficult to handle chips that require Ccp (ES2 in Fig. 13).</p><p> Further, although it is possible to adjust the matching by changing the loop total length of the loop-shaped antenna pattern, if the loop total length is shortened, the gain is lowered.</p><p> The present invention has been devised in view of the above problems, and one of its objects is to provide a wireless tag that can be easily matched and adjusted with a chip while suppressing a decrease in gain.</p><p> It should be noted that the present invention is not limited to the above-mentioned purpose, and it is an action and effect derived by each configuration shown in the best mode for carrying out the invention described later, and it is also possible to exert an action and effect which cannot be obtained by the conventional technique. It can be positioned as one of the purposes of.</p>

<p><u style="single">(1) As a first plan, for example, a chip connecting portion to which a chip is connected, a loop-shaped antenna pattern electrically connected to the chip connecting portion and provided on the surface layer surface of the dielectric member, and the above-mentioned Through the inside of the dielectric member, through holes for conducting the antenna patterns on the opposing surfaces of the dielectric member are provided, and only a part of the inner wall of the through holes is subjected to conductor plating and the conductor is provided. A wireless tag can be used in which the plating area is set smaller as the diameter of the through hole is larger.</u>To.<u style="single"> (2) As a second option, for example, a loop-shaped antenna pattern electrically connected to the chip connection portion to which the chip is connected is formed on the surface layer surface of the dielectric member, and the inside of the dielectric member is formed. Through holes are formed to conduct the antenna patterns on the opposing surfaces of the dielectric member, and conductor plating is applied only to a part of the inner wall of the through holes, and the area of the conductor plating is set to the through holes. A method of manufacturing a wireless tag can be used, in which the larger the diameter of the antenna, the smaller the setting.</u><u style="single"> (3) Here, impedance matching with the chip may be adjusted by changing the spacing between the plurality of conductive members.</u></p>

<p><u style="single"> Ri</u>It is possible to realize a wireless tag that can be easily matched and adjusted with the mounted chip while suppressing a decrease in profit.</p>

<figref num="1">It is a schematic perspective view which shows the structure of the wireless tag which concerns on 1st Embodiment of this invention.</figref><figref num="2">It is AA sectional view of the radio tag shown in FIG.</figref><figref num="3">It is a schematic perspective view which shows the simulation model of the wireless tag shown in FIG. 1 and FIG.</figref><figref num="4">It is a Smith chart which shows the antenna impedance of the simulation model shown in FIG.</figref><figref num="5">It is a Smith chart which shows the antenna impedance of the simulation model shown in FIG.</figref><figref num="6">It is a schematic perspective view which shows the simulation model of the radio tag which shortened the loop length of a loop antenna.</figref><figref num="7">It is a Smith chart which shows the antenna impedance of the simulation model shown in FIG.</figref><figref num="8">It is a schematic perspective view which shows the simulation model when the via of the wireless tag shown in FIG. 3 is made into one.</figref><figref num="9">It is a Smith chart which shows the antenna impedance of the simulation model shown in FIG.</figref><figref num="10">It is a schematic perspective view which shows the structure of the wireless tag which concerns on 2nd Embodiment of this invention.</figref><figref num="11">It is a graph which shows the change of the corresponding capacitance component (Ccp) when the position of the side conductor of the radio tag shown in FIG. 10 is changed.</figref><figref num="12">It is a schematic perspective view which shows the structure of the wireless tag which concerns on 3rd Embodiment of this invention.</figref><figref num="13">It is a graph which shows the change of the corresponding capacitance component (Ccp) when the relative permittivity of the substrate (dielectric) of a wireless tag is changed.</figref>

Code description

1 Substrate (dielectric) 2 Conductor pattern (antenna pattern) 2a 1st loop pattern 2b 2nd loop pattern 3 Chip connection (feeding point) 4 Via (through hole) 5 Integrated circuit (chip package) 6 Exterior resin 7 Adhesive layer 8 Conductor pattern (side conductor) 9 Through hole 91 Metal plating (conductor plating)

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, it goes without saying that the present invention is not limited to the embodiments shown below, and can be variously modified and implemented without departing from the gist of the present invention.

[1] First Embodiment FIG. 1 is a schematic perspective view showing the configuration of the wireless tag according to the first embodiment of the present invention, and FIG. 2 is an AA cross-sectional view of the wireless tag shown in FIG.

As shown in FIGS. 1 and 2, the wireless tag of the present embodiment has a substrate (dielectric member) 1 and each surface excluding the long side side surfaces (a pair of opposite side surfaces) of the substrate 1. The conductor pattern 2 formed in communication with each other on the surface layer surface of the above, that is, the loop (square) -shaped antenna pattern (hereinafter, also referred to as a loop antenna) 2 in the cross-sectional view of FIG. 2 and the long side of the loop antenna 2. A chip connection (feeding point) 3 electrically connected to the loop antenna 2 near the center of the surface of the substrate 1 and a plurality of loop antennas 2 formed on the front and back surfaces of the substrate 1 (FIGS. 1 and 2). A via (also called a through hole) 4 as a conductive member that conducts at two places), an integrated circuit (chip package) 5 such as an IC chip or LSI electrically connected to the chip connection portion 3, and a substrate 1 The exterior resin 6 that covers the entire surface and the adhesive layer 7 provided on the surface of the exterior resin 6 to be attached (attached) to a metal or the like are provided. In FIG. 1, the chip package 5 is not shown, and the exterior resin 6 is partially omitted.

The substrate 1 is made of a dielectric having a predetermined dielectric constant, and can be made of a desired resin such as polytetrafluoroethylene (PTFE) or polyphenylene ether (PPE), for example.

The antenna pattern 2 can be formed by etching or resisting a metal conductor such as copper or silver. Further, the antenna pattern 2 can have a symmetrical pattern that becomes wider in the longitudinal direction from the feeding point 3 on the surface of the substrate 1, for example, as shown in FIG. 1 so as to secure a desired gain.

The via 4 can be formed by forming a conductive layer on the inner wall of the hole penetrating the substrate 1 by conductor plating or the like, and in the examples shown in FIGS. 1 and 2, the via 4 is located symmetrically with respect to the feeding point 3. It is provided. As a result, as shown in the cross-sectional view of FIG. 2, a part of the conductor pattern 2, that is, the conductor patterns 2 formed on the opposing surfaces (front surface and back surface) of the substrate 1 are electrically connected by the via 4. The first loop pattern 2a having the conductor pattern 2 (long side and short side) formed on the surface layer surface (front and back surface and side surface) of the substrate 1 (conducting) and the surface layer surface (front and back surface) of the substrate 1 A part of the conductor pattern 2 formed in the above and a second loop pattern 2b having the via 4 as the inner circumference are formed. That is, each loop pattern 2a and 2b mainly causes two current loops.

The via 4 does not necessarily have to be provided at a symmetrical position, but it is easier to secure the required gain if the via 4 is provided at a symmetrical position. Further, as will be described later, the number of vias provided may be one (location). That is, it is sufficient if a second loop pattern 2b that shares a part of the loop pattern 2 (2a) is configured.

In the wireless tag of this example configured as described above, the second loop pattern 2b is configured without changing the loop length of the first loop pattern 2a, thereby preventing the gain decrease and on the Smith chart. In, the antenna impedance can be rotated (changed) counterclockwise. That is, the corresponding capacitance component Ccp of the antenna pattern 2 can be increased. In addition, the corresponding capacitance component Ccp can be adjusted (increased) by changing (decreasing) the distance between the vias 4. Therefore, impedance matching can be easily performed on an integrated circuit 5 (hereinafter, also referred to as a chip 5 or a tag LSI 5) having a large susceptance component.

As an example, as shown in FIG. 3, the external dimensions of the wireless tag are 69 mm in length × 35 mm in width × 5 mm in thickness, the thickness (conductor thickness) of antenna pattern 2 is 11 μm, and its conductivity is 5 × 10.⁶The Smith chart of FIG. 4 shows the change in antenna impedance when the antenna pattern 2 is modeled as S / m and the via 4 is provided for the antenna pattern 2.

In the Smith chart shown in FIG. 4, the position indicated by 0 indicates the antenna impedance at 950 MHz when the via 4 is not provided, and the position indicated by 1 indicates the antenna impedance when the via 4 is provided. Rotates (changes) counterclockwise, and it can be seen that the corresponding capacitance component Ccp of antenna pattern 2 can be increased. Therefore, as shown in FIG. 5, it is possible to match the impedance of the chip 5 having a large capacitance component, which has a complex conjugate relationship with the position indicated by 1 on the Smith chart.

In addition, as shown in Tables 1 and 2 below, the gain and communication distance due to the provision of via 4 are obtained in both cases where the wireless tag is attached to metal and when it exists in free space. It can be seen that the decrease is small.

<tables num="1"><img file="JP5115558B2_D0001.tif" /></tables>

<tables num="2"><img file="JP5115558B2_D0002.tif" /></tables>

The communication distance (r) shown in Table 2 can be calculated by the following equations (1) and (2).<maths num="1"><img file="JP5115558B2_D0003.tif" /></maths>λ: Wavelength Pt: Power of reader / writer (RW) device Gt: Antenna gain q: Matching coefficient Pth: Minimum operating power of chip 5 Gr: Tag antenna gain Rc, Xc: Resistance of chip 5 (reactance Zc = Rc + jXc) Ra, Xa: Antenna pattern resistance (reactance Za = Ra + jXa)

The calculation conditions for the simulation are shown in Table 3 below.<tables num="3"><img file="JP5115558B2_D0004.tif" /></tables>

In Table 3 above, Rcp corresponds to the conductance (G) component of admittance (Yc = 1 / Zc = G + jB = (1 / Rcp) + jωCcp), which is the reciprocal of the impedance Zc of the chip 5, and Ccp is an integrated circuit. It represents the susceptance (B) component equivalent of 5 admittance (Yc).

Further, as shown in FIG. 6, by shortening the length of the wireless tag from, for example, 69 mm to 42 mm and shortening the loop length of the antenna pattern 2, as shown in FIG. 7, the antenna impedance is counterclockwise on the Smith chart. It is possible to change it clockwise, but in this case, as shown in Tables 1 and 2 above, the loop length of the antenna pattern 2 is shortened, so that the gain is lowered and the communication distance is shortened.

As shown in Tables 1 and 2, the gain is highest when the via 4 is not provided and the loop length is not adjusted, but communication cannot be achieved when the capacitance component Ccp of the chip 5 is large. The distance becomes shorter.

Therefore, it can be said that the overall performance is higher when the via 4 is provided as in this example.

(When there is one via 4) The number of the vias 4 may be one, for example, as shown in FIG. The model shown in FIG. 8 is the same as the model shown in FIG. 3 except for the number of vias. In this way, even when the number of vias is set to one, the inventor of the present application can rotate the antenna impedance counterclockwise on the Smith chart as shown in FIG. 9, and the gain is also the via 4 It has been confirmed by simulation that it is not inferior to the case where two antennas are provided as described above.

However, the amount (angle) of the rotation is larger when two vias 4 are provided. That is, by changing the number of vias, the variable amount of the capacitance component Ccp of the antenna impedance can be adjusted. Therefore, it can be said that the larger corresponding capacitance component Ccp can be dealt with by increasing the number of vias.

[2] Second embodiment FIG. 10 is a schematic perspective view showing the configuration of the wireless tag according to the second embodiment of the present invention. In the wireless tag shown in FIG. 10, instead of providing the via 4, the feeding point 3 of the substrate 1 is present. It extends in the width direction of the substrate 1 from a part of the antenna pattern 2 (two symmetrical positions centered on the feeding point 3) on the surface (surface) to face the surface through the side surface on the long side of the substrate 1. A conductor pattern (side conductor) 8 communicating with the antenna pattern 2 on the front surface (back surface) is provided.

That is, in this example, the side conductor 8 conducts the antenna patterns 2 provided on the front and back surfaces of the substrate 1 through the side surface of the substrate 1, and the side conductor 8 is the via 4 as the conduction member. Will play the same role as. Such a configuration is effective when it is difficult to provide the via 4 on the substrate 1. In FIG. 10, S2 indicates the distance between the side conductors 8. However, in this example as well, the side conductor 8 does not necessarily have to be located symmetrically with respect to the feeding point 3, and may be provided only at one location on the same side surface of the substrate 1.

As a result, in the wireless tag, the first loop pattern having the conductor pattern 2 formed on the front and back surfaces of the substrate 1 as the outer circumference (long side and short side) and the conductor pattern 2 formed on the front and back surfaces of the substrate 1 A second loop pattern with a part of the side conductor 8 as the inner circumference is constructed.

Therefore, it is possible to increase the corresponding capacitance component Ccp of the antenna pattern 2 by rotating (changing) the antenna impedance counterclockwise on the Smith chart while suppressing the gain decrease. In addition, the corresponding capacitance component Ccp can be adjusted (increased) by changing (decreasing) the distance S2 between the side conductors 8. Therefore, impedance matching can be easily performed even for the chip 5 having a large susceptance component.

As an example, the dimensions of the substrate 1 are 70 mm in length × 44 mm in width × 3.14 mm in thickness, and the relative permittivity ε of the substrate 1_r6.05, the dielectric loss angle tan δ is 0.003, the width W of the antenna pattern 2 is 25 mm, the width of the conductor portion extending from the antenna pattern 2 to the side conductor 8 is 5 mm, and the distance S2 between the side conductors 8 is changed. Figure 11 shows the change in the corresponding capacitance component Ccp.

As shown in FIG. 11, in both cases where the operating frequency is 915 MHz or 953 MHz, the corresponding capacitance component Ccp can be increased by reducing the interval S2 of the side conductors 8.

[3] Third Embodiment FIG. 12 is a schematic perspective view showing the configuration of the wireless tag according to the third embodiment of the present invention. The wireless tag shown in FIG. 12 has a hole area larger than that of the via 4 instead of the via 4. A large square columnar through hole 9 is provided, and at least one of the side walls (inner wall) of the through hole 9 is metal-plated (conductor plating) that conducts with the antenna pattern 2 formed on the front and back surfaces of the substrate 1. ) 91 is applied.

That is, in this example, the metal plating 91 applied to the side wall of the through hole 9 conducts the antenna patterns 2 formed on the front and back surfaces of the substrate 1 to each other, and the metal plating 91 is a via as the conduction member described above. It will play the same role as 4. In this example as well, the through hole 9 (metal plating 91) does not necessarily have to be provided at a symmetrical position with respect to the feeding point 3, and may be provided at only one place. Further, the shape of the through hole 9 is not limited to a square prism, and may be a triangular prism or a columnar prism.

Further, in FIG. 10, the metal plating 91 is applied to the entire surface of the side wall at the position farthest from the feeding point 3 among the four side walls of the through hole 9, but even if it is applied to the other side walls. Good. Further, the metal plating 91 can be applied only to a part of the side wall.

For example, when the area (diameter) of the through hole 9 is large and the area of the side wall (inner wall) is large, if metal plating 91 is applied to the entire surface thereof, the current distribution in the antenna pattern 2 tends to be disturbed and the gain tends to decrease. Therefore, it may be desirable to apply metal plating 91 only to a part of the side wall surface. For example, a line-shaped metal plating 91 can be applied to the surface of the side wall. That is, it can be said that the larger the diameter of the through hole 9, the smaller the area of the conductor portion is preferably set.

As a result, in the wireless tag, the first loop pattern in which the conductor pattern 2 formed on the surface of the substrate 1 is a long side (two opposing sides) and a short side (the remaining two opposing sides) and the substrate. 1 A second loop pattern is formed in which a part of the conductor pattern 2 formed on the surface is a long side and the metal plating 91 applied to the side wall of the through hole 9 is a short side.

Even in the wireless tag of this example configured as described above, the second loop pattern is configured without changing the loop length of the first loop pattern, thereby preventing a decrease in gain and on the Smith chart. , The antenna impedance can be rotated (changed) counterclockwise. That is, the corresponding capacitance component Ccp of the antenna pattern 2 can be increased.

In addition, the corresponding capacitance component Ccp can be adjusted (increased) by changing (decreasing) the distance between the through holes 9 (between the metal plating 91). Therefore, impedance matching can be easily performed even for the chip 5 having a large susceptance component. The distance between the metal platings 91 can be changed not only by changing the position where the through hole 9 is provided, but also by changing the position where the metal plating 91 is applied without changing the position where the through hole 9 is provided.

[4] Others In the above embodiment, the antenna impedance (mainly the corresponding capacitance component Ccp) is obtained by changing the number and spacing of conductive members such as the via 4 provided on the substrate 1, the side conductor 8 communicating with the antenna pattern 2, and the through hole 9. Although it is basically adjusted, other adjustment methods may be used in combination. For example, additionally, the width of the antenna pattern 2 can be changed, the mounting position of the chip 5 on the substrate 1 can be changed, and the permittivity of the substrate 1 can be changed.

As described in detail above, according to the present invention, it is possible to realize a wireless tag that can be easily matched and adjusted with the mounted chip while suppressing a decrease in gain. , Inventory, distribution management, POS system, security system, etc. It is considered to be extremely useful in technical fields.