JP2008033716A - Coin-type RFID tag - Google Patents

Abstract

Provided is a coin-type RFID tag that can have a communication distance and a communication range when reading and writing data larger than those of conventional ones and is less expensive.
An IC chip mounting body in which an annular antenna circuit is connected to antenna connecting terminals a and b of an IC chip 5 and a nonmagnetic metal plate 3 are disposed inside the annular antenna circuit. The IC chip mounting body and the non-magnetic metal plate are sealed by the injection outer shell resin portion that covers the IC chip mounting body side of the outer shell resin base material. The non-magnetic metal plate has a convex shape outward from the outer shell resin base material at the center thereof.
[Selection] Figure 1

Description

  The present invention relates to a coin-type RFID tag (Radio Frequency Identification) that transmits and receives data 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 IC chip mounting body composed of a coil and an IC chip connected to both ends of the coil is used as a central hole in a small disk made of a substantially C-shaped nonmagnetic metal. (See Patent Document 1).
However, according to this configuration, it is expensive to produce a C-shaped non-magnetic metal small disk, and if the size of the RFID tag, particularly its diameter, is to be reduced, the coil of the IC chip mounting body Since the diameter has to be reduced, there has been a problem that the communication distance and communication range when reading / writing data from / to the RFID tag cannot be increased.
JP 2003-331250 A

  An object of the present invention is to provide a coin-type RFID tag that can take a communication distance and a communication range at the time of reading and writing data larger than those of conventional ones and is less expensive.

  In order to solve the above problems, the present invention provides an IC chip mounting body in which an annular antenna circuit is connected to an antenna connection terminal of an IC chip and a nonmagnetic metal plate, and the nonmagnetic metal plate is disposed inside the annular antenna circuit. The IC chip mounting body and the non-injection shell resin portion are arranged on a disk-shaped outer shell resin base so that the metal plate is positioned, and the outer shell resin base covers the IC chip mounting body side of the outer shell resin base. A coin-type RFID tag in which a magnetic metal plate is sealed, wherein the non-magnetic metal plate has a convex shape outwardly from the outer shell resin base material at a central portion thereof. It is a thing.

  In the above configuration, the nonmagnetic metal plate is preferably convex so that a difference in height between the central portion and the peripheral portion with respect to the surface of the outer shell resin base material is 0.5 mm or less. It is preferable that the nonmagnetic metal plate is manufactured by press punching.

  According to the present invention, since the nonmagnetic metal plate is disposed inside the annular antenna circuit of the IC chip mounting body, the diameter of the annular antenna circuit of the IC chip mounting body is increased even if the size of the coin-type RFID tag is reduced. As a result, the communication distance when reading and writing data from and to the RFID tag can be increased, and the communication range can be expanded. Further, when assembling the RFID tag, the area yield of the metal plate is increased, and handling is facilitated, so that the cost can be reduced.

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 the 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 line XX ′ of FIG. Referring to FIG. 1, a coin-type RFID tag according to the present invention includes an IC chip mounting body 1 composed of an IC chip 5 and an annular antenna circuit 6, a nonmagnetic metal plate 3, and a disk-shaped outer shell resin base material 2. And have.

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 annular antenna circuit 6 is electrically connected to the antenna connection terminals 7a and 7b of the lead frame of the IC chip 5 so that data communication is performed by an electromagnetic induction method.

The annular antenna circuit 6 can be formed by a method such as winding (covered copper wire), etching, printing, vapor deposition, plating, etc. However, in order to reduce the size, the lap winding is easy and the circuit is disconnected. 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.
The material of the wound antenna 6 includes copper, aluminum, gold, etc., but copper wire is most frequently used and has many types. The copper wire is generally called a magnet wire and is covered with an insulating resin. 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 annular antenna circuit 6 to the IC chip 5, a method of heat connection using a metal such as solder or an alloy, a method of connection using 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.

  The nonmagnetic metal plate 3 functions as a weight for making the coin-type RFID tag have a desired weight. As the nonmagnetic metal 3, a brass plate, a copper plate, a phosphor bronze plate, or the like can be used. In the present invention, a disc-shaped one is used. By using the disc-shaped nonmagnetic metal plate 3, the area yield is increased, the shape of the punching blade type for producing the nonmagnetic metal disc can be simplified, and handling is facilitated. Therefore, the manufacturing cost can be greatly reduced.

  In the present invention, the thickness of the nonmagnetic metal plate 3 is 1.5 mm or less. This is because, in a coin-type RFID tag with a thickness of 2.8 mm, if a non-magnetic metal plate 3 with a thickness of 1.5 mm is provided at the center, the thickness of the resin on both sides becomes approximately 0.4 mm on one side. This is because if it is larger than this, the gap through which the resin flows during injection molding becomes narrow, and it becomes difficult for the resin to sufficiently wrap around. Although it depends on the layer structure, the thickness of the nonmagnetic metal plate 3 is preferably 1.5 mm or less from such a viewpoint.

Further, assuming that the weight of the coin-type RFID tag is about 5 g and 50% of the weight is occupied by the nonmagnetic metal plate 3, the nonmagnetic metal plate 3 is made of brass (specific gravity 8.45). A volume of about 300 mm ³ is required. This can be converted to a brass plate in the range of 16 mmφ × 1.5 mm to 25 mmφ × 0.6 mm. In consideration of communication performance, injection moldability, and the vacant area of the installation part of the IC chip mounting body 1, a brass plate in the range of 18 to 22 mmφ × 0.8 to 1.2 mmt is more preferable. According to the inventors' trial, in the nonmagnetic metal plate in this range, the difference in height between the central portion and the peripheral portion of the metal plate with respect to the surface of the outer shell resin base material is 0.5 mm or less. It is more preferable for improving the injection moldability. That is, when this value exceeds 0.5 mm, the possibility that the moldability cannot be satisfied increases. If this difference is less than 0.02 mm, the metal plate can be placed in any direction, that is, whether the metal plate is placed outward or convex with respect to the outer shell resin base material. Good injection molding suitability. Therefore, in the case of a nonmagnetic metal plate having a shape range as described above, the height difference between the central portion and the peripheral portion with respect to the outer shell resin base material surface is 0.02 mm or more and 0.5 mm or less. This is very preferable for obtaining a coin-type RFID tag satisfying the feature of the present invention that the later-described injection moldability is good.

  Punching a circular metal plate from a large flat non-magnetic metal plate can be changed from the one that becomes almost flat like a coin to one that has a convex center part to the shape of the punching die. is there. A punching die that can be punched flatly is slightly more expensive than a punching die having a convex center part, and is therefore expensive. In the present invention, it is possible to obtain a low-cost coin-type RFID tag by using a punching die with reduced cost and using a circular non-magnetic metal plate with a slightly convex center part.

The outer shell resin substrate 2 is made of polyester, polycarbonate, acrylic, ABS, polyphenylene sulfide (PPS), polypropylene, polyethylene, Teflon (registered trademark), polyamide, polymer alloy, engineering plastic, etc. It is generally formed from a resin that can be injection molded. 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.
Because it is molded into a coin shape, it may drop frequently and receive external stress. Therefore, it uses a resin with low deformation and high impact resistance, such as ABS and ABS-PC. More preferably.
The outer shell resin base material 2 is produced using a known injection molding method (primary molding). As can be seen from FIGS. 1 and 2, in this embodiment, the outer shell resin base material 2 includes a disk-shaped main body portion 2b and an annular protruding portion provided along the outer peripheral edge on the surface side of the main body portion 2b. 2a.

  In the present invention, it is necessary to fix the IC chip mounting body 1 and the nonmagnetic metal plate 3 to the surface surrounded by the annular protrusion 2a in the primary molded outer shell resin base material 2. This is to prevent the non-magnetic metal plate 3 from being washed away by the resin injected during the secondary molding, thereby reducing the communication performance, moving the center of gravity, and destroying the IC chip mounting body 1. This is essential to facilitate handling in the injection molding operation during secondary molding.

As a method for fixing the IC chip mounting body 1 and the nonmagnetic metal plate 3, (1) a fixing method using an adhesive sheet (double-sided tape) and (2) a fixing method using an adhesive and an adhesive can be considered.
The fixing method (1) can be used to fix the IC chip mounting body 1 and the nonmagnetic metal plate 3 simultaneously. In this case, a well-known thing can be used as an adhesive sheet, The thing using paper, a film, a nonwoven fabric, a foam base material etc. for a core material, and the thing without a core material can be used. The adhesive was initially made circular so that it could be spread inside the outer shell resin base material 2 so that the annular antenna circuit and the chip could be fixed simultaneously. However, there may be a problem that the chip breaks during secondary molding. is there. As a result of trials by the present inventors, a chip that can be directly bonded to the outer shell resin base material and is cut into a circular shape with a partial notch as shown in FIG. 1 is used after a secondary injection molding process. It was found that there were almost no defects. At this time, the chip portion is preferably fixed to the outer shell resin substrate 2 with an adhesive. Further, it is presumed that the annular antenna circuit and the chip are preferably fixed separately.
The adhesive for fixing the chip used here is preferably a thermosetting type or a reactive type. As the type of the adhesive, an adhesive such as an epoxy resin, a silicone resin, a cyanoacrylate resin, or the like that does not have a decrease in adhesive force due to the injection resin at the time of secondary molding is preferable. The viscosity of the adhesive is preferably 500 cps to 100,000 cps. This is because if the viscosity is lower than 500 cps, the adhesive may adhere to the surface of the outer shell resin base material 2 and the like, which causes dirt and the like before being cured. Further, when the viscosity is higher than 100,000 cps, there is a problem that the adhesive is difficult to enter between the chip and the outer shell resin substrate 2 and the workability is poor.
In FIG. 2, the outer shell resin base material 2 and the nonmagnetic metal plate 3 are drawn so as to have a gap. Actually, the edge portion of the nonmagnetic metal plate 3 is partially embedded in the adhesive 4, thereby improving the adhesion between the outer shell resin base material 2 and the nonmagnetic metal plate 3, and at the time of secondary molding. A buffering effect for preventing deformation of the outer shell resin base material 2 due to pressure is obtained.
The thickness and type of the pressure-sensitive adhesive need to be appropriately selected depending on the thickness of the nonmagnetic metal plate 3, the ratio of the convex shape, and the secondary molding conditions. The thickness of the pressure-sensitive adhesive is preferably selected in the range of 20 μm to 200 μm. Further, a thickness of 30 μm to 150 μm is preferable. When the thickness is 20 μm or less, the adhesion and pressure buffering effect is weak, and when it is 200 μm or more, the influence of the entire thickness and the problem of cost appear.
In the fixing method (2), general-purpose adhesives such as epoxy, silicone, cyanoacrylate, and vinyl can be used as the adhesive for fixing the metal plate, and it is selected according to the material of the outer resin used. Is preferred. A general ultraviolet curable resin is not preferable because ultraviolet rays are shielded by a metal plate and are difficult to cure. Thermosetting and reactive curing adhesives are preferred.
When the adhesive is not thick, the edge portion of the non-metal plate may be locally applied to the outer shell resin base material 2 during the secondary molding, and the outer shell resin base material 2 may be deformed. In order to prevent deformation, the pressure buffering effect can be obtained by setting the thickness of the adhesive to a certain value or more. The adhesive preferably contains a general-purpose spacer pigment such as 5 to 100 μm of silica.
An adhesive is used to fix the IC chip mounting body 1. Also in this case, general-purpose pressure-sensitive adhesives such as acrylic, silicone, and vinyl can be used.

In the present invention, since the high-temperature resin is extruded from the central portion of the outer shell resin base material 2 during the secondary molding, the adhesive can be securely fixed to the central portion so that the nonmagnetic metal plate 3 does not move due to heat and pressure. The IC chip mounting body 1 is disposed in the peripheral part of the outer shell resin base material 2 and the peripheral part is less affected by heat and pressure than the central part, and therefore it is preferable to use an adhesive. . By fixing the peripheral part with an adhesive, the attaching operation of the IC chip mounting body 1 becomes easy. The fixing method (2) is easy to automate because an adhesive and an adhesive can be applied.
The purpose is to prevent breakage of the IC chip due to strong pressure during injection molding and disconnection at the connection portion with the annular antenna circuit.

  And, for the intermediate product 10 of the coin-type RFID tag (in which the IC chip mounting body 1 and the nonmagnetic metal plate 3 are fixed to the surface surrounded by the annular protrusion 2a in the outer shell resin base material 2), High temperature resin injected from the central part of the outer shell resin base material 2 is extruded and subjected to secondary molding. In this way, the IC chip mounting body 1 side of the outer shell resin base material 2 is covered with the injection outer shell resin portion 8, the IC chip mounting body 1 and the nonmagnetic metal plate 3 are sealed, and a coin-type RFID tag is manufactured ( (See FIG. 3).

Next, the shape of the convex part of the nonmagnetic metal plate 3 was changed variously, and the relationship with injection moldability was examined.
(Example 1)
In Example 1, a coin-type RFID tag having the configuration shown in FIGS. 1 and 2 was produced.
My Fair / MCC2 package (manufactured by Infineon) was used as the IC chip 5. A 120μm enameled wire (manufactured by Tokyo Special Electric Wire Co., Ltd.) coated with a hot-melt adhesive is heated to a 28mmφ core and bonded to each other for 8 turns. The antenna 6 was used. The connection ends 7a and 7b for both antennas of the IC chip 5 are joined to both ends of the annular antenna circuit 6 by soldering. Unnecessary wire was cut to obtain an IC chip mounting body 1.
The outer shell resin base material 2 (ABS resin) was manufactured by injection molding with an outer diameter of 32 mmφ, an inner diameter of 30 mmφ, a thickness of 0.6 mm, and an edge portion thickness of 1.4 mm.
Adhesive 4 (trade name: No. 500 Nitto Denko) was cut into a 29.5 mmφ circle with a notch in part and pasted inside the outer shell resin base material 2, and 20 mmφ (opening) The non-magnetic metal plate 3 (1.0 mm thick brass plate) punched into an area ratio of 51.0%: metal plate area coverage with respect to the inner surface area of the air core coil) and the IC chip mounting body 1 were attached. The shape of the nonmagnetic metal plate 3 was set such that the central portion was 0.25 mm higher than the peripheral portion.
The chip 5 of the IC chip mounting body 1 is aligned with the cut-out portion of the adhesive cut into a circular shape with a part of the cut-out, and the outer shell resin with a moisture-curing adhesive (trade name: Aron Alpha Toagosei Co., Ltd.) The substrate 2 was directly bonded without using an adhesive.
The intermediate product 10 of the coin-type RFID tag thus assembled was injection molded with ABS resin to obtain a coin-type RFID tag.

(Example 2)
The nonmagnetic metal plate 3 was pressed into a flat surface, and the shape of the nonmagnetic metal plate 3 was the same as in Example 1 except that the central portion was 0.05 mm higher than the peripheral portion.
(Comparative Example 1)
As shown in FIG. 4, the same procedure as in Example 1 was performed except that the nonmagnetic metal plate 3 was disposed upside down (recessed outward with respect to the outer shell resin base material 2).

(Comparison)
For the samples prepared in Examples 1 and 2 and Comparative Example 1, the reading distance was measured with a reader / writer manufactured by NEC Frontier: SR1012-ST3. The measurement results are shown in Table 1 below.

比較例１は樹脂が射出成型出来なかったため、その後の比較検討は行わなかった。
この原因は、次のとおりである。図５は、実施例１における２次成型時の射出樹脂の流れ（矢印Ａ）を示した図であり、図６は、比較例１における２次成型時の射出樹脂の流れ（矢印Ｂ）を示した図である。図５から分かるように、射出される樹脂は、スムーズに全体に行き渡ることなく、中心部分に滞ってしまうため、先に射出された樹脂の粘度が高くなり、後から射出される樹脂の妨げになり、最後に樹脂が中心部分で固まり、周辺部分に樹脂欠損が発生して製品とならなくなる。

In Comparative Example 1, since the resin could not be injection molded, no subsequent comparative study was performed.
The cause is as follows. FIG. 5 is a diagram showing the flow of injection resin (arrow A) during secondary molding in Example 1, and FIG. 6 shows the flow of injection resin (arrow B) during secondary molding in Comparative Example 1. FIG. As can be seen from FIG. 5, the injected resin does not spread smoothly and stays in the center portion, so that the viscosity of the resin injected earlier becomes high and hinders the resin injected later. Finally, the resin hardens in the central part, and resin defects occur in the peripheral part, resulting in no product.

It is a top view of the intermediate product in the assembly process of the coin type RFID tag according to one embodiment of the present invention. It is sectional drawing along the X-X 'line | wire of FIG. FIG. 3 is a cross-sectional view similar to FIG. 2 of a coin-type RFID tag according to an embodiment of the present invention. It is sectional drawing similar to FIG. 2 of the comparative example of a coin-type RFID tag. It is the figure which showed the flow of the injection resin at the time of the secondary molding in the case of the intermediate product of FIG. It is the figure which showed the flow of the injection resin at the time of the secondary molding of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 IC chip mounting body 2 Outer shell resin base material 3 Nonmagnetic metal plate 4 Adhesive 5 IC mounting part 6 Ring antenna circuit 7a, 7b Antenna connection end 8 Outer shell resin part 9 Coin type RFID tag 10 Coin type RFID tag Intermediate products

Claims (3)

An IC chip mounting body in which an annular antenna circuit is connected to an antenna connection terminal of the IC chip and a nonmagnetic metal plate are arranged in a disc-like outer shape so that the nonmagnetic metal plate is positioned inside the annular antenna circuit. A coin-type RFID tag that is disposed on a shell resin base material and in which the IC chip mounting body and the nonmagnetic metal plate are sealed by an injection outer shell resin portion that covers the IC chip mounting body side of the outer shell resin base material. The coin-type RFID tag is characterized in that the non-magnetic metal plate has a convex shape outward from the outer shell resin base material at a central portion thereof.   The said nonmagnetic metal plate is convex shape so that the difference of the height with respect to the said outer shell resin base-material surface of the center part and a peripheral part may be 0.5 mm or less. Coin-type RFID tag.   The coin-type RFID tag according to claim 1 or 2, wherein the nonmagnetic metal plate is manufactured by press punching.

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