JP2009110144A - Coin-shaped rfid tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly durable coin-shaped RFID tag in which the molded joint face of a disk-shaped edged resin case and a cover-shaped part are hardly peeled from each other even when an expansion/contraction stress is repeatedly applied due to a change in environment over time, especially a cyclic change in temperature. <P>SOLUTION: The coin-shaped RFID tag having almost uniform thickness is configured by molding a cover-shaped part 9 by injection molding by forming metallic boards 3 for weight adjustment like right and left asymmetrical shapes so that center lines 100A, 100B, 100C and 100D of a gap between the metallic boards 3 can be prevented from being concentrated on one point of the central part, and arranging those metallic board 3 while aligning the front and rear faces so that the cover-shaped part sides can become convex faces against any distortion to be generated in blanking. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a coin-type RFID tag among RFID tags (Radio Frequency Identification) that perform data transmission / reception via radio waves.

RFID tags can read and write data from the outside wirelessly. In recent years, RFID tags are becoming widespread as a means for identifying and managing people and things. It is attracting attention as a fundamental technology for promotion.
There are various types of RFID tags such as a label type, a card type, a coin type, and a stick type, and they are selected according to applications.

As a conventional coin-type RFID tag, for example, an inlet composed of a coiled antenna and IC chips connected to both ends of the coiled antenna is used as a hole in the center of a C-shaped nonmagnetic metal plate. (See Patent Document 1).
However, the expansion and contraction stress is repeatedly applied to the resin due to the temperature change over time, and there has been a problem that the molded joint surface of the circumferential portion of the coin-type RFID tag is finally peeled off.
JP 2003-331250 A

  An object of the present invention is to provide a coin-type RFID tag having high durability even when the environment changes with time.

  In order to solve the above-mentioned problems, the present invention provides a metal plate without an inlet made of a circuit in which a plurality of metal plates are arranged in a ring shape inside the edge of a disk-shaped resin case with an edge, and an antenna and an IC chip are connected. A coin-type RFID tag that is placed in the center and then molded by a lid-shaped part by injection molding to make the thickness substantially uniform, so that the center line of the gap between the metal plates does not concentrate on one point in the center A coin-type RFID tag was constructed by arranging the metal plate.

When a metal plate is formed by punching, a slight warp usually occurs, but there is no problem if the front and back surfaces of the plurality of metal plates are aligned so that the lid-like portion side is a convex surface.

When molding the lid part by injection molding, it is necessary to fix the inlet and the metal plate so that they are not washed away, but the fixing means uses an adhesive or adhesive, or a double-sided tape using them, or It may be a guide created by molding in advance in a disc-shaped resin case with an edge.

  According to the present invention, the metal plate having a shape in which the center line of the gap between the metal plates is not concentrated on one point in the central portion is disposed in the disc-shaped edged resin case. The presence of two metal plates made it possible to disperse the stress. In addition, since the strain is dispersed by adopting such an arrangement, it is difficult to cause defects such as cracks due to contraction / expansion stress of the resin portion. This makes it possible to manufacture a strong coin-type RFID tag that does not separate cracks and joint surfaces against shrinkage and expansion stress caused by the difference in resin shrinkage rate, which can dramatically improve durability. It became.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a plan view of an intermediate product in a process of assembling a coin-type RFID tag according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. As shown in FIG. 1, the coin-type RFID tag according to the present invention includes an inlet 1 including an IC chip 5 and a coiled antenna 6, a metal plate 3, and a disc-shaped edged resin case 2.

As the IC chip 5, an IC chip that operates in a frequency band such as 125 to 135 KHz, 4.9 MHz, 6.5 MHz, 13.56 MHz, or UHF band can be used.
The coiled antenna 6 is electrically connected to the antenna connection terminals 7a and 7b of the lead frame of the IC chip 5, and data communication is performed by an electromagnetic induction method.

The coiled antenna 6 can be made by a method such as winding (covered copper wire), etching, printing, vapor deposition, plating, etc. However, in order to reduce the size, it is easy to wrap and break the circuit. It is preferable to use a wound antenna that has a relatively large area, a small resistance value, and can be manufactured at low cost.
Although there are copper, aluminum, gold, etc. as a material for the wound antenna, copper wire is most often used and there are many types. In general, enameled wire is used as the coated copper wire. When forming a coil, a wire having a hot melt or solvent-soluble adhesive provided on the outside of the insulating coating is used, and the wires are bonded together with an adhesive so that they cannot be unwound while winding the wires.

  As a method of connecting the coiled antenna 6 to the IC chip 5, a method of connecting with heat using a metal such as solder or an alloy, a method of connecting with a conductive adhesive containing metal powder such as silver or copper, Conventional connection methods such as welding in a broad sense including ultrasonic bonding, caulking, and thermocompression bonding between metals can be used. Among these, a connection method using solder and welding with high connection reliability is preferable.

  The metal plate 3 functions as a weight for setting the coin-type RFID tag to a desired weight. However, in the case of a magnetic metal, a non-magnetic metal is used because it affects communication characteristics. As the metal plate 3, a nonmagnetic brass plate, copper plate, phosphor bronze plate, or the like can be used.

  In the present invention, the thickness of the metal plate 3 is 1.5 mm or less. This is because, when a 1.5 mm thick metal plate 3 is provided in a 2.8 mm thick coin-type RFID tag, the thickness of the resin on the metal plate is about 0.4 mm on one side, and the thickness is larger than this. This is because the gap through which the resin flows becomes narrow when the lid-like portion is injection-molded, and it becomes difficult for the resin to sufficiently wrap around. Although depending on the layer configuration, the thickness of the metal plate 3 is preferably 1.5 mm or less from such a viewpoint.

If the weight of the coin-type RFID tag is about 5 g, the metal plate 3 needs a volume of about 300 mm ³ when made of brass. This can be converted to a brass plate in the range of 200 mm ² × 1.5 mm to 500 mm ² × 0.6 mm. In consideration of communication performance, injection moldability, and the free area of the installation portion of the inlet 1, the metal plate 3 is more preferably a brass plate having a thickness in the range of 0.8 mm to 1.2 mm.

  When a metal plate is punched from a large flat metal plate, the central portion becomes convex to some extent. If an expensive mold is used, it is possible to make it flat, but in the present invention, even if the central part is convex to some extent, if the front and back are arranged so that the lid side is convex, there is no problem In addition, a low-cost coin-type RFID tag can be manufactured.

The disc-shaped edged resin case 2 is made of polyester, polycarbonate (PC), acrylic, acrylonitrile-butadiene-styrene (ABS), polypropylene, polyethylene, fluororesin, polyamide, polymer alloy, engineering plastic, etc. It is formed from a thermoplastic resin that is generally injection moldable. Depending on the application, transparent, translucent and opaque ones can be used. Most resins other than transparent resins contain pigments such as titanium oxide, calcium carbonate, silica, carbon, and organic pigments, and additives such as dyes, ultraviolet absorbers, and lubricants. In addition, the completed coin-type RFID tag may be dyed with a dye.
The disc-shaped edged resin case 2 is produced by using a known injection molding method (primary molding). As can be seen from FIG. 2, the disc-shaped edged resin case 2 includes, in this embodiment, a disc-shaped main body portion 2 b and an annular protruding portion 2 a provided along the outer peripheral edge on the surface side of the main body portion 2 b. It is made up of.

  In the present invention, it is necessary to fix the inlet 1 and the metal plate 3 to the surface surrounded by the annular projecting portion 2a in the resin-molded edge-shaped resin case 2 having a primary shape. This is to prevent the metal plate 3 from being washed away by the resin injected at the time of molding the lid portion, thereby preventing the communication performance from being lowered, the center of gravity from moving, and the inlet 1 from being destroyed. It is essential to fix the inlet and the metal plate in order to facilitate handling in the injection molding operation.

As a method of fixing the inlet 1 and the metal plate 3, as a fixing member, (1) an adhesive or pressure-sensitive adhesive, or a fixing method using a double-sided tape 8 using them, (2) when molding a disc-shaped rimmed resin case A fixing method using the guide 10 (see FIG. 5) formed at the same time is conceivable.
The fixing method (1) can be used to fix the inlet 1 and the metal plate 3 simultaneously. As the adhesive to be fixed, general-purpose adhesives such as epoxy, silicone, cyanoacrylate and vinyl can be used, and it is preferable to select the adhesive depending on the material of the resin case used. A general ultraviolet curable resin is difficult to cure because the ultraviolet rays are shielded by a metal plate, and a thermosetting or reactive curing adhesive is preferable. Further, as the adhesive, general-purpose adhesives such as acrylic, silicone, and vinyl can be used. Moreover, a well-known thing can be used as a double-sided tape using it, The thing using paper, a film, a nonwoven fabric, a foam base material etc. as a core material, and the thing without a core material can be used.
In the fixing method (2), a guide 10 having a shape in which a metal plate and an inlet are accommodated is provided, and the metal plate and the inlet are fitted therein.

In the present invention, since the high-temperature resin is pushed out from the central portion of the disc-shaped edged resin case 2 at the time of molding the lid-shaped portion, heat and pressure are strongly applied to the central portion. Since the inlet 1 is disposed in the center of the disc-shaped edged resin case 2, it is preferable to protect the connecting portion between the IC chip and the coiled antenna with a heat-resistant thermosetting adhesive or the like.
This is intended to prevent damage to the IC chip due to heat and pressure during injection molding and disconnection at the connection with the coiled antenna.

FIG. 2 shows an intermediate product of a coin-type RFID tag (inlet 1 and metal plate 3 fixed to a surface surrounded by an annular protrusion 2a in a disc-shaped edged resin case 2). The high temperature resin injected from the central part of the disc-shaped edged resin case 2 is extruded to form a lid-like part. In this way, the inlet 1 side of the disc-shaped edged resin case 2 is covered with the lid-like portion 9, the inlet 1 and the metal plate 3 are sealed, and a coin-type RFID tag is manufactured (see FIG. 3).

As shown in FIG. 1, the metal plates used in the present invention are four asymmetrical shapes in which the center lines 100A, 100B, 100C, and 100D of the gaps between the metal plates are not concentrated on one point in the center. used. Since it is asymmetrical left and right, it is impossible to arrange four in a predetermined position unless the front and back sides are actually coincident with each other, so that all the metal plates are determined in one direction. In the present embodiment, since a relatively soft brass metal plate punched by a punching die is used, deformation occurs due to the cutting force applied to the end surface of the metal plate during punching, resulting in a generally distorted shape. In addition, due to the applied cutting stress, the corners of the metal plate are rounded and pointed. Further, burrs may occur at sharp corners.

  In the case of a metal plate punched with a mold, the above and the back can be made. In this embodiment, the metal plate is arranged with the pointed surface facing the disc-shaped edged resin case. This is because the fixed member 8 is stuck with sharp corners, so that the thickness of the metal plate is suppressed, that is, the flow of the resin is not disturbed, and at the same time, the local stress applied to the resin by substantially rounding the corners by the fixing member 8. This prevents the occurrence of defects such as cracks in the resin part. The round corners of the metal plate are directly formed with the resin of the lid part by injection molding, but since the corners are rounded in advance, local stress is not applied to the resin, so there are also cracks in the resin part. It is possible to suppress the occurrence of inconvenience. Further, if the distortion generated in the metal plate is within a range that does not hinder the flow path of the resin, no substantial problem occurs.

When the front and back of the metal plate are reversed, the round corners of the metal plate are fixed to the fixing member side, and the sharp corners are in contact with the lid-like portion. In this case, local stress is applied to the lid-like portion from the sharp corner of the metal plate, and cracks may occur from this portion over time.

  In this embodiment, the metal plate is produced by punching with a press, but it is also possible to produce by cutting with a laser or water pressure. In this case, the metal plate has a nearly vertical corner, and a flat plate having no distortion as a whole. However, burrs may remain at the corners. Depending on the degree, if the resin is sealed in a state where burrs are generated, the flow of the resin will deteriorate locally, or local stress will be applied to the resin part of the completed coin-type RFID tag. May occur.

  If the metal plate has burrs, it can be deburred by various deburring devices. By removing burrs in this manner, the metal plate produced by these methods can be used without any problem.

  FIG. 4 shows a schematic plan view of a conventional fan-shaped metal plate described in Patent Document 1 and the like. In this case, the central lines 200A and 200B of the gaps between the metal plates are concentrated at one point in the center. Such a shape causes stress concentration in the soft resin portion without metal on the center lines 200A and 200B, which causes cracks in the resin over time. Furthermore, since the arrangement of the IC chip is limited to the central portion, the IC chip is also stressed, causing a communication failure due to breakage of the IC chip and poor connection. On the other hand, in the present invention, the center lines 100A, 100B, 100C, and 100D of the gaps between the metal plates have a shape that does not concentrate on one point in the central portion, that is, the metal plate always exists in any cross section. The structure is such that stress is dispersed as a whole and local stress is not easily applied. With the configuration of the present invention, cracks in the resin portion, IC chip breakage, and poor connection were simultaneously improved, and a dramatic improvement in durability was achieved.

Specific examples of manufacturing the coin-type RFID tag according to the present invention will be described below, but the present invention is not limited to these examples.
The coin-type RFID tags described in the following embodiments can be used for both cards and tags other than those described in the embodiments.

(Example 1)
A coin-type RFID tag substantially similar to the coin-type RFID tag shown in FIGS.

[Production of inlet sheet]

A coil of 13 turns with an inner diameter of 17 mm was prepared with a heat-sealed copper wire with an outer diameter of 0.14 mm (2LOCK Y1 0.14 / manufactured by Tokyo Special Electric Cable Co., Ltd.), and both terminals of the coil are shown in FIG. Thus, the packaged IC chip (SLE55R04 chip / manufactured by Infineon Co., Ltd.) 5 provided with the terminal portions 7a and 7b was connected by resistance welding. Excess heat-fused copper wire was cut and removed so that the tip portion was placed inside the coil, which was used as an inlet.

[Production of coin-type RFID tags]
An edged resin case having a disc-like outer diameter of φ32 mm, an edge of 1.4 mm, and a central part of 0.7 mm was made by injection molding using a mixed resin of ABS / PC (CK10 / Technopolymer Co., Ltd.). The width of the edge portion 4 of the disc-shaped edged resin case is 1 mm. Inside, a double-sided tape (DF8500S-25P / manufactured by Toyo Ink Manufacturing Co., Ltd.) with a base material of PET film is attached to fix the inlet and metal plate, and the center of the inlet and the metal plate are attached. Fixed in place around the periphery. The metal plates used here were made of brass, and four asymmetrical plates with a shape in which the center line of the gap between the metal plates was not concentrated at one point in the central portion were used. In the present example, the metal plate was placed with the pointed surface facing the disc-shaped edged resin case. Next, from the side where the metal plate or the like was attached, the lid-shaped portion was molded with the same resin as the disk-shaped resin case with a rim, thereby obtaining a coin-type RFID tag having a desired thickness of 2.8 mm.

(Comparative Example 1)
A coin-type RFID tag was produced in the same manner as in Example 1 except that a symmetrical metal plate (see FIG. 4) was provided on the edge portion of the disc-shaped edged resin case of Example 1.

[Outline of durability test]

[Communication measurement method]
The resonance frequency of the contactless coin-type RFID tag of the example / comparative example was measured. The resonance frequency of the coin-type RFID tag was measured by a measuring instrument in which a loop antenna having a diameter of 5 cm was connected to a network analyzer (model R3754B / manufactured by Advantest) and confirmed to be 13.56 MHz. In addition, it was confirmed that communication was possible with a reader / writer (HW210 / Sakusa Co., Ltd.) connected to a personal computer.

[Appearance inspection method]
The surface of the contactless coin-type RFID tag of Example / Comparative Example and the connecting portion of the end face 11 were observed to confirm whether there was any cracking or peeling.

[Durability test method]
In order to accelerate the durability test, a thermal shock test was performed under the following conditions.
-40 ° C x 30 minutes ⇔ Normal temperature x 5 minutes ℃ 85 ° C x 30 minutes / cycle 20 samples each

以上のように、本発明に係るコイン型ＲＦＩＤタグは、従来と比較して飛躍的に耐久性が向上したコイン型ＲＦＩＤタグであることを確かめた。
〔Test results〕
The number of defects in 20 samples is shown.

As described above, it was confirmed that the coin-type RFID tag according to the present invention is a coin-type RFID tag whose durability is dramatically improved as compared with the conventional one.

It is a top view which shows the coin type RFID tag intermediate product used for this invention. It is AA 'sectional drawing of FIG. FIG. 3 is a cross-sectional view of a coin-type RFID tag formed by injection molding. It is a top view which shows the conventional coin type RFID tag intermediate product. It is sectional drawing of the coin type RFID tag intermediate product which used the guide for fixation of a metal plate.

Explanation of symbols

1 Inlet 2 Disc-shaped rim resin case
2 a annular projection portion 2 b main body portion 3 metal plate 4 edge 5 IC chip 6 coiled antennas 7a and 7b terminal 8 adhesive or adhesive, or double-sided tape using them 9 lid portion 10 guide 11 end surface 100A, 100B, 100C, 100D, 200A, 200B
Center line of gap between metal plates

Claims (4)

A plurality of metal plates are arranged in a ring shape inside the edge of the resin case with a disc-shaped edge, and an inlet consisting of a circuit connecting the antenna and the IC chip is arranged in the center without the metal plate, and further by injection molding A coin-type RFID tag having a substantially uniform thickness by molding a lid-like portion, characterized in that a metal plate having a shape in which the center line of the gap between the metal plates does not concentrate on one point in the central portion is arranged Coin-type RFID tag.
The coin-type RFID tag according to claim 1, wherein the metal plate is arranged with its front and back aligned so that the lid-like portion side is a convex surface.
The coin-type RFID tag according to claim 1 or 2, wherein the fixing means for the metal plate and the inlet is an adhesive or an adhesive.
The coin-type RFID tag according to claim 1 or 2, wherein the fixing means for the metal plate and the inlet is a guide in a disc-shaped resin case with an edge.

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