HK1259475B - Rfid tag - Google Patents

Description

RFID tags

This application claims the benefit of Japanese Patent Application No. 2016-082202, the entire disclosure of which is hereby incorporated by reference.

Technical Field

The present invention relates to an RFID tag including an antenna for transmitting and receiving signals to and from a reader/writer in a contactless manner.

Background Art

The RFID tag has an IC chip for recording information and an antenna connected to the IC chip. Furthermore, the RFID tag communicates wirelessly with a reader/writer via the antenna, thereby enabling information stored in the IC chip to be read and information to be written to the IC chip.

In recent years, there has been a growing demand for extremely small RFID tags. As a response to this demand, for example, the RFID tag disclosed in Patent Document 1 is known. The antenna of this RFID tag consists of a multilayer antenna that overlaps and is integrally bonded to the IC chip. This multilayer antenna comprises: a substrate having approximately the same outer dimensions as the IC chip; a first coil formed on the substrate; a second coil laminated on the first coil via an insulating film; and a protective film that protects the second coil.

The RFID tag of Patent Document 1 utilizes a multi-layer antenna, resulting in a greater number of turns. This improves antenna efficiency (e.g., communication range). However, the RFID tag still lacks sufficient communication range, leaving room for improvement.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent No. 4713621

Summary of the Invention

Problems to be solved by the invention

The present invention has been made in view of this situation, and an object of the present invention is to provide an RFID tag capable of improving antenna efficiency with a simple structure.

Means for solving problems

In order to solve the above-mentioned problems, the RFID tag of the present invention

An RFID tag comprises: an antenna for transmitting and receiving signals to and from a reader/writer, and an IC chip having a size of less than 0.9 mm square and connected to the antenna, wherein the resonant frequency of the RFID tag is 865 MHz to 928 MHz.

And the RFID tag has:

an insulating layer having the antenna formed thereon,

A plurality of connection terminals are provided at the corners of the insulating layer, closer to the inner side than the outer peripheral edge.

A ring-shaped antenna forming area is formed on the entire periphery of the insulating layer or substantially the entire periphery.

The antenna has one of the plurality of connection terminals as a starting point and one of the remaining connection terminals as an end point, and is formed into a ring shape by winding a conductor wire around the antenna forming area, with the number of turns being 1.5 to 10. The conductor wire is positioned close to the outer peripheral edge to form a conductor pattern, and the aspect ratio of the conductor wire is in the range of 1.0 to 5.0.

The conductor lines adjacent to each other in a radial direction perpendicular to the winding direction of the antenna have substantially the same line width, the line width being set within a range of 2 μm to 7 μm, and the distance between the conductor lines adjacent to each other in the radial direction being set within a range of 2 μm to 7 μm.

The distance from the outermost end of the IC chip to the connection terminal is set to 30 μm to 90 μm.

The RFID tag of the present invention may also have the antenna having 1.5 to 10 turns.

The RFID tag of the present invention may also be such that the insulating layer is a package of the IC chip.

The antenna is provided on the package of the IC chip.

The RFID tag of the present invention may also be such that the insulating layer is a package of the IC chip.

A booster antenna is provided that operates at approximately the same frequency as the antenna.

In the RFID tag of the present invention, the antenna may be configured to perform wireless communication in a UHF band.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1A is a top view of an IC chip equipped with an antenna.

FIG. 1B is an enlarged view of the upper end portion of FIG. 1A .

FIG. 2A is an enlarged view of the left side of the upper end portion of FIG. 1A .

FIG. 2B is a cross-sectional view taken along line II-II in FIG. 1A .

FIG3A is a longitudinal sectional view showing an IC chip housed in a recess of a booster antenna.

FIG. 3B is an enlarged view of region A in FIG. 3A .

FIG3C is a plan view showing an IC chip housed in a recess of the booster antenna.

FIG. 4 is an explanatory diagram showing the magnetic field calculated by electromagnetic field simulation using contour lines.

FIG. 5A is a graph showing the amplitude of the magnetic field with respect to the frequency of the first RFID tag and the first pattern of the present invention.

FIG5B is a plan view showing the periphery of the input/output terminal of the first pattern.

FIG. 6 is a graph showing the amplitude of the magnetic field with respect to the frequency of the first and second RFID tags and the second pattern of the present invention.

FIG. 7 is a graph showing the amplitude of the magnetic field with respect to the frequency of the first RFID tag and the third pattern of the present invention.

FIG. 8A is a graph showing the amplitude of the magnetic field with respect to the frequency of the third RFID tag and the fourth pattern of the present invention.

FIG8B is a top view of the fourth pattern.

DETAILED DESCRIPTION

The following describes a first embodiment of an RFID tag according to the present invention based on the accompanying drawings. FIG1A shows a passive RFID tag 4 having an antenna 3 mounted on the outer periphery of the upper surface of the package (an insulating layer formed of resin) of an IC chip 1, via an insulating layer 2, in an electrically conductive manner.

The IC chip 1 is substantially square in plan view. Alternatively, the IC chip 1 may be circular, elliptical, or polygonal.

The IC chip 1 can be a chip of 0.5 mm square (0.5 mm vertically x 0.5 mm horizontally) to 0.9 mm square (0.9 mm vertically x 0.9 mm horizontally). In this embodiment, an IC chip 1 of 0.9 mm square (0.9 mm vertically x 0.9 mm horizontally) is used.

The IC chip 1 has connection terminals 5A, 5B, 5C, and 5D at four corners. The four connection terminals 5A, 5B, 5C, and 5D are provided on the inner side relative to the outer peripheral edge.

In addition, among the four connection terminals, the two connection terminals 5A and 5B arranged on the upper side of the paper in FIG1A are connected to the antenna. To be more specific, one end of the antenna 3 is connected to the input/output terminal 5A on one side (the upper left side of the paper in FIG1A), and the other end of the antenna 3 is connected to the input/output terminal 5B on the other side (the upper right side of the paper in FIG1A). Among the four connection terminals, the two connection terminals 5C and 5D arranged on the lower side of the paper in FIG1A are dummy terminals. In addition, in this embodiment, in the following description, the connection terminal 5A connected to one end of the antenna 3 and the connection terminal 5B connected to the other end of the antenna 3 are sometimes referred to as the input/output terminal.

Output terminals 5A, 5B.

The insulating layer 2 is made of polyimide, epoxy resin, or silicone resin, and is formed by spin coating, printing, or lamination. Alternatively, the insulating layer 2 can be formed by attaching a sheet or film made of a photosensitive resin such as photosensitive polyimide.

A circular antenna formation area is defined over substantially the entire perimeter of the IC chip 1 package. This is achieved by winding the inwardly wound conductor wire 3a inwardly of the connection terminal 5B, rather than between the outer perimeter edge of the package and the connection terminal 5B, so that the conductor wire 3a connected to the connection terminal 5B does not overlap with the conductor wire 3a wound inwardly of the connection terminal 5B. Furthermore, the antenna formation area is defined to have a predetermined width in a direction perpendicular to its circumferential direction.

Antenna 3 includes a spiral conductor pattern formed in the antenna formation area (the outer periphery of the package's top surface (mounting surface)). The conductor pattern is wound several times (4.75 times in FIG1A ) to form a roughly rectangular shape. The portion where the conductor pattern begins winding extends straight from connection terminal 5B toward the outer periphery of the package and curves just before the outer periphery.

In this embodiment, each portion of the conductor pattern starting from the start of winding is sometimes referred to as a "turn portion." Furthermore, although the innermost portion of the conductor pattern does not reach the length of a full turn, the portion from the first turn to the fourth turn is also referred to as a turn portion.

The conductor pattern can be made of various conductive materials, such as copper, silver, and aluminum. The conductor pattern can be formed by various methods such as a thick film method in which a conductor paste is applied and sintered, sputtering, vapor deposition, vacuum plating, photolithography, or printing.

Each winding portion of the conductor pattern includes multiple conductor wires 3a arranged to correspond to the outer peripheral ends of the upper surface (mounting surface) of the package. These multiple conductor wires 3a are continuous, starting from input/output terminal 5A on one side and ending at input/output terminal 5B on the other side, and are formed into a spiral shape so as to loop within the antenna formation area.

The aspect ratio of the conductor line 3a is set to be in the range of 1.0 to 5.0. A larger aspect ratio of the antenna 3 preferably increases the cross-sectional area of the conductor line 3a and reduces the resistance component of the wiring of the antenna 3.

If the aspect ratio of the antenna 3 exceeds 5.0, manufacturing becomes difficult. Therefore, the limit value of the aspect ratio of the antenna 3 is 5.0.

On the other hand, if the aspect ratio of antenna 3 is less than 1.0, the number of turns of conductor wire 3a must be increased to maintain a sufficient resistance value, which results in a wider conductor pattern. Consequently, it becomes impossible to ensure the number of turns of conductor wire 3a required for communication within the antenna formation area. Therefore, the minimum aspect ratio is 1.0.

As shown in FIG2B , the aspect ratio refers to the ratio (H/L) of the length of the long side (longitudinal dimension) H to the length of the short side (lateral dimension) L in the longitudinal cross-section of the conductor line 3 a. In this embodiment, in the following description, the normal direction of the installation surface of the antenna 3 may be referred to as the longitudinal direction, and the plane direction of the installation surface of the antenna 3 may be referred to as the lateral direction.

As shown in FIG1B , the opening area of the opening portion 3K of the conductor pattern is the area surrounded by the four conductor wires 3a located radially innermost among the conductor wires 3a…, that is, the conductor wire 3a (hereinafter referred to as the first conductor wire 3A) included in the winding portion of the fifth conductor wire counted from the outside of the conductor pattern (refer to FIG1A ).

Furthermore, the line width of the conductor lines 3a, that is, the horizontal dimension L of the conductor lines 3a, 3a (see FIG2A ), is the same or substantially the same over the entire length of the conductor lines 3a. The line width L of the conductor lines 3a, 3a can be set to any value within the range of 2 μm to 7 μm, and is set to 2 μm in this embodiment.

Furthermore, the distance S between radially adjacent conductor lines (so-called line space) can be set to any value within the range of 2 μm to 7 μm.

The conductor pattern is formed by spirally winding the conductor wire 3 a around the outer periphery of the upper surface of the IC chip 1 .

Furthermore, the conductor wire 3a is wound in a spiral shape, shifting inward with each turn. Thus, the conductor wire 3a is wound in a spiral shape at a distance S from the portion previously provided on the upper surface of the IC chip 1. Furthermore, the distance S is constant at each position in the winding direction of the conductor wire 3a.

Here, for the conductor wire 3a, since one end thereof is connected to the input/output terminal 5B on the upper right in FIG. 1A , the conductor pattern is configured such that the portion where the winding starts extends from the input/output terminal 5B toward the outer peripheral edge of the package without contacting the connected conductor wire 3a, and the portion continuous with the portion where the winding starts passes through the inner side of the input/output terminal 5B.

As previously mentioned, IC chip 1 is 0.9 mm square (0.9 mm long x 0.9 mm wide), and the intervals Z1 and Z2 between the outermost end of IC chip 1 and input/output terminal 5A (the upper left input/output terminal is shown in FIG1B ) are 65 μm and 65 μm. Furthermore, conductor line 3a included in the first to fourth turns of the conductor pattern (one turn from the start of winding) is arranged so as to pass between the outermost end of IC chip 1 and input/output terminal 5A.

The conductor line 3a extending from the first to the fourth turn of the conductor pattern also passes between the outermost end of the IC chip 1 and the two dummy terminals 5C and 5D.

In this way, the conductor wire 3a included in the conductor pattern from the first winding circle part to the fourth winding circle part passes through the outside of the connecting terminals 5D, 5C, and 5A (between the connecting terminals 5D, 5C, and 5A and the outer peripheral edge of the package) and the inside of the connecting terminal 5B in this order and is wound in a spiral manner. As a result, the conductor wire 3a is wound into a spiral in a manner that does not overlap in the inner and outer directions.

The conductor line 3a (i.e., first conductor line 3A) included in the fifth turn of the conductor pattern passes inside dummy terminals 5C and 5D. The number of turns of the antenna is 4.75, but can be set to any number between 1.5 and 10 depending on the resonant frequency (here, 920 MHz).

If the line width L of the conductor wire 3a is less than 2 μm, a conductor pattern cannot be produced, and if it exceeds 7 μm, the required number of turns cannot be ensured. Therefore, the line width L of the conductor wire 3a is set to a value within the range of 2 μm to 7 μm.

The distance S between the conductor wires 3a, 3a (the so-called line space) is the same as the line width L of the conductor wire 3a. If it is less than 2μm, the conductor pattern cannot be manufactured, and if it exceeds 7μm, the required number of turns cannot be ensured. Therefore, the distance S is set to a value in the range of 2μm to 7μm.

Furthermore, the intervals Z1 and Z2 from the outermost end of the IC chip 1 to the input/output terminals 5A are not limited to 65 μm and 65 μm, and can be set to any value within the range of 30 μm to 90 μm. Furthermore, while the example herein illustrates the intervals Z1 and Z2 from the outermost end of the IC chip 1 to the input/output terminals 5A being equal, the intervals Z1 and Z2 may also be different.

The resonant frequency of the RFID tag having the above structure is set to 920 MHz. This resonant frequency f is obtained by the following formula.

f＝1/2π×√(LC)

Here, L is the equivalent inductance, and C is the equivalent capacitance of the IC chip generated between the input/output terminals 5A and 5B. Based on the above equation, the required equivalent inductance L of the coil can be calculated by the following equation.

L＝1/(2πf) ² ×C

That is, if the resonance frequency f is set to 920 MHz in the UHF band (it can be any value from 865 MHz to 928 MHz), once the value of either L or C is determined, the value of the other can be determined.

In addition, since C is an inherent value determined for each IC chip 1, the value of L needs to be appropriately set based on the value of C. The value of L is determined according to the aspect ratio of the conductor line 3a, the line width L, and the distance S between the conductor lines 3a and 3a. These values are set within the aforementioned range.

Furthermore, by setting the aspect ratio, line width L, and distance S between conductor lines 3a and 3a within the aforementioned ranges, a conductor pattern 3 is formed in which conductor lines 3A and 3a are arranged close to the outer periphery on the insulating layer. This not only increases the antenna radius, but also the number of turns. This reduces the resistance to current flowing through the conductor lines, and since the antenna radius can be increased, the antenna gain can be increased, thereby improving antenna efficiency (communication range).

The relationship between the coil inductance L, the coil cross-sectional area S, and the number of turns N is L = AN ² S. A is a constant. According to the above formula, increasing the number of turns N and the coil cross-sectional area S increases the inductance L and reduces (lowers) the resonant frequency.

Next, a method for manufacturing an RFID tag by mounting the antenna 3 on the IC chip 1 will be described.

The upper surface of the IC chip 1 is coated with PI (polyimide) as an insulating layer. Then, a seed layer for electroplating is coated on the insulating layer by sputtering. Next, a pattern for a laminated antenna pattern is formed from above the seed layer through photoresist.

Next, the antenna pattern is laminated using the electroplating process. After removing the mold layer, the exposed, unnecessary seed layer is removed. Finally, a protective film is applied using polyimide (PI) coating to protect the antenna pattern, completing the RFID tag manufacturing process.

Next, the second embodiment will be described. As shown in Figures 3A and 3C, the RFID tag 4 of this embodiment includes the antenna 3 and a booster antenna 6 that operates at approximately the same frequency, which are provided on the upper surface of the IC chip 1. The RFID tag 4 of this embodiment has the advantage of being able to improve the transmission and reception sensitivity and thus extend the information transmission distance due to the presence of the booster antenna 6. In addition, since the antenna 3 mounted on the IC chip 1 has the same structure as Figures 1A, 1B and Figures 2A, 2B, the description thereof will be omitted. In addition, the antenna 3 is not shown in Figures 3B and 3C.

Booster antenna 6 includes a conductor pattern (antenna) 9 formed by spirally winding a conductor wire 9a approximately 1.75 times (or more than two times, up to five times) around the outer periphery of a rectangular platform 7 made of ceramic (or other synthetic resin materials) serving as an insulating layer (mounting plane), with ceramic insulating layer 8 interposed therebetween. A ceramic mounting portion 10 is formed on insulating layer 8. This mounting portion 10 has a rectangular recess 10A for mounting IC chip 1. Recess 10A is formed in a plan view.

Antenna 9 is configured to resonate at the same frequency as IC chip 1. Furthermore, antenna 9 is electromagnetically coupled to antenna 3 of IC chip 1, enabling communication. In other words, IC chip 1 communicates with the reader/writer via booster antenna 6. Therefore, while IC chip 1's antenna 3 is relatively small, communication via booster antenna 6, which is larger than IC chip 1's antenna 3, extends the communication distance. Furthermore, a reader/writer is a device capable of communicating with IC chip 1.

Furthermore, the antenna 3 of the IC chip 1 is formed as an on-chip antenna in which the antenna 3 is integrally formed with the IC chip 1 itself. Therefore, a contact point for connecting the IC chip 1 and the antenna 3 is unnecessary.

Furthermore, because the IC chip 1 and booster antenna 6 are electromagnetically bonded, they offer the advantage of strong environmental resistance. For example, in environments such as low temperatures, high temperatures, and vibration, conventional RFID tags can experience thermal expansion or breakage due to vibrations at the connection between the antenna and IC (including the adhesive) or at the antenna's fine pattern due to differences in thermal expansion between the antenna material, substrate, and adhesive. In contrast, the combination of the IC chip 1 with the aforementioned on-chip antenna and the electromagnetically bonded booster antenna 6 requires only that the IC chip 1 be positioned near the center of the booster antenna 6 (recess 10A in FIG. 3A ). This prevents breakage due to thermal expansion or vibration, resulting in a highly environmentally resistant RFID tag. Furthermore, after positioning the IC chip 1 near the center of the booster antenna 6, the booster antenna 6 can be molded using a resin having a thermal expansion coefficient equivalent to, or approximately equivalent to, that of ceramic.

Various conductive materials can be used as the conductor pattern 9, and copper, silver, aluminum, etc. can be used, for example. In addition, the conductor pattern 9 can be formed by various methods such as a thick film method in which a conductor paste is applied and sintered, sputtering, vapor deposition, vacuum plating, photolithography, or printing.

As shown in FIG3C , the opening area of the opening 9K of the conductor pattern 9 is the area surrounded by four first conductor lines 9A, 9A, 9A, 9A (see FIG3C ) located at the innermost periphery among the conductor lines 9 a located in the radial direction.

The conductor wires 9a adjacent in the radial direction have substantially the same line width, that is, the short side length (horizontal dimension) L. The number of turns of the antenna is 1.75, but any number of turns between 1.5 and 10 is preferable.

The RFID tag 4 of the present invention shown in Figures 1A, 1B and 2A, 2B has a conductor pattern with 4.75 turns. However, the RFID tag 4 of the present invention can also have a conductor pattern with 5.75 turns. Electromagnetic field simulation was performed on three RFID tags of different specifications (all with 5.75 turns) and four other RFID tags as comparative examples, some of which differed from the specifications of the RFID tag of the present invention. The calculated magnetic field amplitudes were plotted and examined below. Figure 4 shows the magnetic field calculated based on the electromagnetic field simulation using contour lines. In Figure 4, the point located 2 mm from the package center of the RFID tag along the Z axis is designated as P _obs . The magnetic field at that point P _obs was calculated at 20 MHz intervals between 715 MHz and 1115 MHz. These calculated values are plotted on a graph with frequency (GHz) on the horizontal axis and magnetic field amplitude (AU) on the vertical axis. The magnetic field amplitude at the operating frequency of 915 MHz is important; larger amplitude values increase the communication range.

In Figure 5A, data from the first RFID tag of the present invention is plotted as black circles, while data from the first RFID tag of the comparative example is plotted as +. The first RFID tag of the present invention has an antenna positioned in the antenna-forming region between the outer peripheral edge of the insulating layer and the plurality of connection terminals. The antenna has an aspect ratio of 1.25, a line width of radially adjacent conductor lines 3a of 4 μm, a distance S between conductor lines 3a (so-called line spacing) of 2.83 μm, and a number of turns of 5.75. The first RFID tag, on the other hand, has an antenna positioned in the antenna-forming region between the outer peripheral edge of the insulating layer and the plurality of connection terminals. The antenna has an aspect ratio of 1.25, a line width of radially adjacent conductor lines 3a of 10 μm (a value outside the range of the present invention), a distance S between conductor lines 3a (so-called line spacing) of 8 μm (a value outside the range of the present invention), and a number of turns of 1.75.

The number of turns of the conductor pattern is 1.75 because, as shown in FIG5B , if a conductive material with a line width of 10 μm is wound once, the distance M between the conductor wire 3 a and the connection terminal 5B becomes 25 μm. However, if a conductive material with a line width of 10 μm and an inter-conductor distance of 8 μm is wound twice, the distance between the conductor wires 3 a and the connection terminal 5B also needs to be maintained. Therefore, the line width of 10 μm + the inter-conductor distance of 8 μm × 2 = 26 μm is required, which exceeds the distance M of 25 μm and cannot be wound twice.

Therefore, the number of turns of the conductor pattern is limited to 1.75 turns. The graph in Figure 5A shows that, while the magnitude of the magnetic field at the operating frequency of 915 MHz for the first RFID tag of the present invention exceeds 100 (A.U.), the magnitude of the magnetic field at the operating frequency of 915 MHz for the first RFID tag of the present invention is less than 10 (A.U.), enabling the communication distance of the first RFID tag of the present invention to be longer than that of the first RFID tag of the first model. In the first RFID tag of the first model, the line width of the conductor line 3a and the distance between the conductor lines 3a are outside the scope of the present invention. As in the present invention, it is important that the line width be within the range of 2 μm to 7 μm and the distance between the conductor lines 3a be within the range of 2 μm to 7 μm.

In Figure 6, the data of the first RFID tag of the present invention is drawn by filled (solid) dots, the data of the second RFID tag of the present invention with different specifications from the first RFID tag of the present invention is drawn by filled (solid) triangles, and the data of an RFID tag with different specifications from the first pattern as a comparison example is drawn by hollow rhombuses.

Here, the first RFID tag of the present invention, similarly to the above, configures an antenna in the antenna forming area between the outer peripheral edge on the insulating layer and the multiple connection terminals, and has an aspect ratio of 1.25, a line width of each radially adjacent conductor line 3a of 4 μm, a distance S between the conductor lines 3a, 3a (the so-called line space) of 2.83 μm, and a number of turns of the conductor pattern of 5.75 turns.

In addition, the second RFID tag of the present invention, like the first RFID tag of the present invention, configures an antenna in the antenna forming area between the outer peripheral edge on the insulating layer and the plurality of connection terminals, and has an aspect ratio of 2.5 (a value different from that of the first RFID tag of the present invention), a line width of each radially adjacent conductor line 3a of 4 μm (the same value as that of the first RFID tag of the present invention), a distance S between the conductor lines 3a, 3a (the so-called line space) of 2.29 μm (a value different from that of the first RFID tag of the present invention), and a number of turns of the conductor pattern of 5.75 turns.

In this regard, the second type of RFID tag, like the first RFID tag of the present invention, configures the antenna in the antenna forming area between the outer peripheral edge of the insulating layer and multiple connection terminals, and has an aspect ratio of 0.5, a line width of each radially adjacent conductor line 3a of 4μm (a value within the scope of the present invention), a distance S between the conductor lines 3a, 3a (the so-called line space) of 3μm (a value within the scope of the present invention), and the number of turns of the conductor pattern is 5.75 turns.

The graph in Figure 6 shows that, while the magnetic field magnitude at the operating frequency of 915 MHz for both the first and second RFID tags of the present invention exceeds 100 (A.U.), the magnetic field magnitude at the operating frequency of 915 MHz for the second RFID tag is approximately 80 (A.U.), enabling the communication distance of the first and second RFID tags of the present invention to be longer than that of the second RFID tag. The second RFID tag only has an aspect ratio within the aspect ratio range of 1.0 to 5.0 as specified in the present invention. As in the present invention, it is important to set the aspect ratio within the range of 1.0 to 5.0.

In Figure 7, data from the first RFID tag of the present invention is plotted as filled (solid) dots, while data from a third RFID tag, serving as a comparative example, is plotted as x's. Here, in the first RFID tag of the present invention, as previously described, the antenna is positioned in the antenna-forming region between the outer peripheral edge of the insulating layer and the plurality of connection terminals. The antenna has an aspect ratio of 1.25, a line width of 4 μm for radially adjacent conductor lines 3a, a distance S between conductor lines 3a (so-called line space) of 2.83 μm, and a conductor pattern with 5.75 turns.

In contrast, the third RFID tag has an antenna positioned in the antenna-forming region between the outer peripheral edge of the insulating layer and the plurality of connection terminals. The aspect ratio is set to 0.5 (a value outside the scope of the present invention), the line width of each radially adjacent conductor line 3a is set to 10 μm (a value outside the scope of the present invention), and the distance S between the conductor lines 3a and 3a (the so-called line space) is set to 8 μm (a value outside the scope of the present invention). Similarly to the first RFID tag, the number of turns of the conductor pattern is set to 1.75. The graph in FIG7 shows that while the magnetic field magnitude at the operating frequency of 915 MHz of the first RFID tag of the present invention exceeds 100 (A.U.), the magnetic field magnitude at the operating frequency of 915 MHz of the third RFID tag of the present invention is less than 10 (A.U.), enabling the communication range of the first RFID tag of the present invention to be longer than that of the third RFID tag.

For the third type of RFID tag, all values of the aspect ratio, the line width of the conductor line 3a and the distance between the conductor lines 3a are outside the scope of the present invention. As in the present invention, it is important to keep the aspect ratio within the range of 1.0 to 5.0, the line width of each conductor line 3a within the range of 2μm to 7μm, and the distance between the conductor lines within the range of 2μm to 7μm.

In Figure 8A, data of the third RFID tag of the present invention, whose specifications are different from those of the first RFID tag of the present invention and the second RFID tag of the present invention, are drawn using a filled (solid) quadrilateral, and data of the fourth style RFID tag are drawn using a hollow and downward-facing triangle as a comparison example.

Here, the third RFID tag of the present invention, as described above, configures the antenna in the antenna forming area between the outer peripheral edge on the insulating layer and multiple connection terminals, and makes the aspect ratio of 1.67 (a value different from the first and second RFID tags of the present invention), the line width of each radially adjacent conductor line 3a is 3μm (a value different from the first and second RFID tags of the present invention), the distance S between the conductor lines 3a, 3a is 3.9μm (a value different from the first and second RFID tags of the present invention), and the number of turns of the conductor pattern is 5.75 turns.

As shown in FIG8B , the fourth type of RFID tag is configured so that the antenna is located between the outer peripheral edge on the insulating layer and the two input/output terminals 5A and 5B and forms approximately half of the antenna area R, and the aspect ratio is 1.67 (within the scope of the present invention), the line width of each radially adjacent conductor line 3a is 3 μm (within the scope of the present invention), the distance S between the conductor lines 3a and 3a (the so-called line space) is 2.5 μm (within the scope of the present invention), and the number of turns of the conductor pattern is 5.75 turns.

The graph in FIG8A shows that, while the magnetic field magnitude at the operating frequency of 915 MHz for the first RFID tag of the present invention exceeds 100 (A.U.), the magnetic field magnitude at the operating frequency of 915 MHz for the fourth RFID tag is approximately 75 (A.U.), enabling the communication distance of the first RFID tag of the present invention to be longer than that of the fourth RFID tag. In the fourth RFID tag, approximately half of antenna 3 is positioned in an area offset inward from antenna formation region R formed on the outer periphery of IC chip 1. This is presumably due to the smaller outer diameter of antenna 3.

In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

In the above embodiment, the conductor wire 3a is wound inside the input/output terminal 5B so that the conductor wire 3a wound inward does not overlap with the conductor wire 3a connected to the input/output terminal 5B, and the antenna forming area is formed over substantially the entire outer periphery of the insulating layer. However, the conductor wire 3a connected to the input/output terminal 5B may be wound so that the conductor wire 3a wound inward overlaps with the conductor wire 3a wound inward, and the antenna forming area is formed over the entire outer periphery of the insulating layer. In this case, the overlapping conductor wires 3a, 3a (the conductor wire 3a connected to the input/output terminal 5B and the conductor wire 3a wound inward therefrom) are separated upward so that one conductor wire 3a is not in contact in the vertical direction, and the insulating layer is formed so that the upwardly moved conductor wire 3a is maintained in its position.

In addition, in the above embodiment, the conductor wires 3a are arranged in parallel in a spiral shape to form an antenna, but it can also be configured so that the conductor wires 3a are arranged in parallel in a ring shape on the insulating layer, and the single layer thus formed is stacked into two or more layers to form an antenna wound several times.

In addition, in the above embodiment, although the antenna is formed on the upper surface of the IC chip package, a substrate for mounting the IC chip may be provided, and the antenna may be formed on the substrate. In addition, the substrate may have a plurality of connection terminals for connecting to the IC chip, thereby implementing the present invention.

Description of Reference Signs

1…IC chip, 2…insulating layer, 3…antenna (conductor pattern), 3a…conductor line, 3A…first conductor line, 3K…opening, 4…RFID tag, 5A, 5B…input/output terminals (connection terminals), 5C, 5D…dummy terminals, 6…booster antenna, 7…stage, 8…insulating layer, 9…conductor pattern (antenna), 9a…conductor line, 9A…first conductor line, 9K…opening, 10…carrying portion, 10A…recess, H…long side length, L…short side length (line width), S…distance, Z1, Z2…interval.

Claims (6)

1. An RFID tag comprising: an antenna for transmitting and receiving signals with a reader, and an IC chip, less than 0.9 mm in diameter, connected to the antenna. The resonant frequency of the RFID tag is 865MHz to 928MHz. And the RFID tag has: An insulating layer is formed on which the antenna is formed. Multiple connection terminals are located at the corners of the insulating layer, in a position closer to the inner edge than the outer perimeter. A ring-shaped antenna forming region is formed over the entire or approximately the entire outer periphery of the insulating layer. The antenna, starting from one of the plurality of connection terminals and ending at one of the remaining connection terminals, is formed in a loop by winding a conductor wire around the antenna forming area, with 1.5 to 10 turns. The conductor wire is positioned close to the outer periphery to form a conductor pattern. The aspect ratio of the conductor wire is in the range of 1.0 to 5.0. The linewidths of adjacent conductor lines in the radial direction orthogonal to the coiling direction of the antenna are approximately the same, and the linewidths are set in the range of 2 μm to 7 μm. The distance between adjacent conductor lines in the radial direction is also set in the range of 2 μm to 7 μm. The distance from the outermost end of the IC chip to the connection terminal is set to 30μm to 90μm. 2. The RFID tag according to claim 1, wherein the insulating layer is the encapsulation of the IC chip. The antenna is mounted on the package of the IC chip. 3. The RFID tag according to claim 1, wherein the insulating layer is the encapsulation of the IC chip. It has a gain antenna that operates at approximately the same frequency as the antenna. 4. The RFID tag according to claim 1, wherein the antenna is configured to conduct wireless communication in the UHF band. 5. The RFID tag according to claim 2, wherein the antenna is configured to conduct wireless communication in the UHF band. 6. The RFID tag according to claim 3, wherein the antenna is configured to conduct wireless communication in the UHF band.