1. Field of the Invention
The present invention relates to a radio frequency identification (RFID) tag that exchanges information with an external device in a noncontact manner. In some cases, among those skilled in the technical field corresponding to the present invention, the “RFID tag” referred to in this specification is called “RFID tag inlay” as an internal constituent member (inlay) for an “RFID tag.” In some other cases, this “RFID tag” is called a “wireless IC tag.” Additionally, this “RFID tag” includes a noncontact-type IC card.
2. Description of the Related Art
Recently there have been proposed various types of RFID tags that are capable of performing noncontact information exchange, by means of radio waves, with external devices typified by reader/writers. One of the RFID tags has an antenna pattern for radio wave communication and an IC chip mounted on a base sheet made of a plastic or paper. This type of the RFID tag is intended to be used by attaching the RFID tag to an article to exchange information about the article with an external device for identification or the like of the article.
FIG. 1 is a side view of an example of the conventional RFID tag. The side view shown here is a drawing in which the internal structure is seen through the side-surface side of the RFID tag. In this specification, drawings hereinafter called a side view are all similar drawings.
The RFID tag 1 of FIG. 1 has an antenna 12 on a base 13 formed of a sheet-type material such as a polyethylene terephthalate (PET) film, an IC chip 11 connected to the antenna 12 through bumps (metal projections) 14, and an adhesive 15 for fixing the IC chip 11 to the base 13.
The IC chip constituting the RFID tag 1 can exchange information through radio wave with an external device by means of the antenna 12.
This type of the RFID tag has a potential to be used in wide range of areas including the above-described usage. However, if the RFID tag is used by being attaching to an easy-to-deform article, for example, clothing, bending stress is applied to the IC chip 11 as the IC chip 11 is less flexible than the base 13. As a result, the IC 11 is likely to be broken or peeled off, which poses a problem. In order to reduce bending stress on the IC chip, various techniques have been proposed (see, for example, Japanese Patent Application Publication Nos. 2001-319211, 2003-288576, 2005-4429, and 2005-4430).
For example, two of the conventional techniques to reduce bending stress on the IC chip are shown below.
FIG. 2 shows one example of conventional techniques to reduce bending stress on an IC chip.
A RFID tag 2 of FIG. 2 has a reinforcing member 16. The reinforcing member 16 covers to fill the whole of the IC chip 11 and part of the antenna 12 so as to disperse bending stress in the area where the reinforcing member is placed, thus contributing to reduction in bending stress applied to the IC chip 11.
FIG. 3 shows another example of conventional techniques to further reduce bending stress on an IC chip than the technique shown in FIG. 2.
A RFID tag 3 of FIG. 3 has reinforcing members 16 provided on and beneath the base 13. A reinforcing plate 17, which is harder than the reinforcing member 16, is placed on the surface of each of the reinforcing members 16 in parallel with the base 13. Accordingly, bending stress in the area where the reinforcing members 16 are placed is further reduced, leading to more reduction in bending stress on the IC chip 11.
However, in this type of the RFID tag with the reinforcing member, bending stress tends to concentrate in where the edge of the reinforcing member meets the antenna and, thus, is likely to cause disconnection of the antenna.