1. Field of the Invention
The present invention relates to a RFID tag that exchanges information with an external device in a non-contact manner. Incidentally, the “RFID tag” employed in the present invention may be called a “RFID tag inlay” by those skilled in the art, citing that the “RFID tag” of the present invention corresponds to an inner component for a RFID tag. Alternatively, the “RFID tag” of the present invention may be called a “wireless tag.”
2. Description of the Related Art
Recently, there have been proposed various kinds of RFID tags that wirelessly exchange information in a non-contact manner with an external device typified by a reader/writer (see, for example, Japanese Patent Application Publication Nos. 2000-311226, 2000-200332, and 2001-351082). One type of such RFID tags has a structure in which an antenna pattern for radio communication and a circuit chip are mounted on a base sheet formed of plastic, paper, etc. Applications of the RFID tag include identification of an article by attaching the RFID tag to the article and thereby exchanging information about the article with an external device.
A RFID tag 10A shown in
Here, if bending stress is applied to the RFID tag 10A in the direction indicated by arrows in
Similarly to the RFID tag 10A shown in
In this example, because the circuit chip 13 is covered with and protected by the potting compound 15, it is possible to prevent breakage and separation of the circuit chip 13. If, however, bending stress is applied to the base 11, stress may concentrate in a portion of the antenna 12 indicated by a circle of broken lines in
A RFID tag 10C shown in
Compared with the RFID tag 10B, the RFID tag 10C of
Here, Japanese Patent Application Publication Nos. 2000-82868 and 2006-196878 disclose the technique to prevent breaking and separation of the antenna on the flexible base. In addition, Japanese Patent Application Publication No. 2000-286309 discloses the technique to suppress warpage of the base. However, none of these techniques effectively solves the above problem.
The present invention has been made in view of the above circumstances and provides a RFID tag that prevents disconnection of an antenna as well as relieves bending stress applied to a circuit chip.
A RFID tag according to the present invention includes: a base that has a belt-like shape and extends in a predetermined longitudinal direction; an antenna for communication that is wired on the base; a circuit chip that is electrically connected to the antenna and conducts radio communication via the antenna; and a sealant that covers a top of the circuit chip and seals the circuit chip in cooperation with the base, wherein a portion of the antenna that is exposed without being covered with the sealant has a shape extending in the width direction perpendicular to the longitudinal direction.
In the RFID tag of the present invention, the circuit chip is covered with the sealant. Thus, even if the base is bent, the circuit chip is free from stress, which prevents breakage and separation of the circuit chip. When the RFID tag is bent, bending stress is applied to the longitudinal direction of the base. In the RFID tag according to the present invention, however, a portion of the antenna that is exposed without being covered with the sealant extends in the width direction. Thus, even when the base is bent, stress to the exposed portion of the antenna is relieved, which prevents disconnection of the antenna.
Here, it is preferable that the RFID tag according to the present invention further includes a reinforcement member that covers the top of the circuit chip, wherein the sealant is an adhesive that fixes the reinforcement member as well as seals the circuit chip in cooperation with the base.
Presence of the reinforcement member prevents stress concentration in the circuit chip more effectively. Further, presence of the reinforcement member does not cause stress concentration in the antenna either.
As described in the above, the present invention provides the RFID tag that is capable of preventing disconnection of an antenna as well as relieving bending stress applied to a circuit chip.
An embodiment of the present invention will be described below with reference to the drawings.
First, a comparative example with respect to the embodiment of the present invention will be described.
A RFID tag 10D shown in
In other words, the RFID tag 10D has a structure in which the circuit chip 13 is mounted on the antenna 12 formed on the flexible base 11 and is fixed with the adhesive 14. The fixed chip 13 is further covered with the potting compound 15 and the reinforcement member 16 that is fixed with the potting compound 15.
The antenna 12 extends linearly in the longitudinal direction of the base 11 as shown in
With the structure of the RFID tag 10D, when the base 11 is bent, stress likely concentrates in a portion of the antenna 12 (indicated by a broken-line circle in
A RFID tag 10E of FIGS. 6,7 has the similar structure to that of the RFID tag 10D of FIGS. 4,5 except that the antenna 12 of the RFID tag 10E has a shape different from that of the RFID tag 10D.
The base 11 of the RFID tag 10E extends in a predetermined longitudinal direction (i.e., lateral direction in the drawing) similarly to the comparative example in FIGS. 4,5, and the antenna 12 extends in the longitudinal direction in the same manner as the base 11. However, the portion of the antenna 12 that is exposed without being covered with the potting compound 15 extends in the width direction perpendicular to the longitudinal direction. As the base 11 is bent in the longitudinal direction, stress does not concentrate in the exposed portion of the antenna 12 that extends in the width direction perpendicular to the longitudinal direction. Thus, disconnection of the antenna 12 can be prevented. In addition, since the top of the circuit chip 13 of the RFID tag 10E is covered with the potting compound 15, the potting compound 15 in cooperation with the base 11 seal the circuit chip 13. Thus, it is possible to prevent stress from concentrating in the circuit chip 13 and thus to prevent breakage and separation of the circuit chip 13. Further, since the RFID tag 10E of this embodiment shown in
Incidentally, although the RFID tag 10E in this embodiment is provided with the reinforcement member 16, the potting compound 15 may be provided alone without the reinforcement member 16 (see
Number | Date | Country | Kind |
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2007-044199 | Feb 2007 | JP | national |