Abstract:
A disclosed RFID tag includes: a base member; a semiconductor chip mounted over the base member; and an external member covering the base member and the semiconductor chip, a surface of the external member being provided with a groove at a position away from the semiconductor chip. The groove serves as a fold when the external member is folded.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2014-165483, filed on Aug. 15, 2014, and the Japanese Patent Application No. 2014-192310, filed on Sep. 22, 2014, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to an RFID tag. 
       BACKGROUND 
       [0003]    Along with the advance of the information processing technology and the reduction in size of the semiconductor devices in recent years, RFID (Radio Frequency Identifier) tags are used in various situations in the society. 
         [0004]    The RFID tag includes a semiconductor chip and an antenna, and the semiconductor chip is operated by an electromagnetic wave received by the antenna. The semiconductor chip stores ID information on an article which is the object of management, and a user manages the article by reading the ID information with an external device. 
         [0005]    The object of management includes various articles. For example, merchandise in a shop, transport objects, books, linens, and the like can be managed by using the RFID tags. 
         [0006]    Specifications of the RFID tags are optimized depending on the types of the objects of management. For example, when the RFID tags are attached to linens such as clothes and sheets, the RFID tags is provided with flexibility so that the RFID tags can withstand various pressures applied thereto at the time of washing the linens. 
         [0007]      FIG. 1  is a cross-sectional view schematically illustrating a process to extract water from linens at the time of washing. 
         [0008]    In the example illustrated in  FIG. 1 , linens  2  are put into a water extraction tank  1  and then water is extracted from the linens  2  by application of a pressure from above. When the RFID tags are too rigid, the RFID tags may get broken by the pressure in this process. Accordingly, it is preferable to provide sufficient flexibility to the RFID tags attached to the linens  2 . 
         [0009]    Likewise, a pressure is also applied to the RFID tags during a process of ironing the linens, and hence it is also preferable to use the flexible RFID tags. 
         [0010]    The techniques related to the present application are disclosed in Japanese Laid-open Patent Publications Nos. 2012-212198, 2010-122764, 2003-187201, 2012-84050, and 2011-221599. 
       SUMMARY 
       [0011]    According to one aspect discussed herein, there is provided an RFID tag comprising: a base member; a semiconductor chip mounted over the base member; and an external member covering the base member and the semiconductor chip, a surface of the external member being provided with a groove at a position away from the semiconductor chip, the groove serving as a fold when the external member is folded. 
         [0012]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0013]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a cross-sectional view schematically illustrating a process to extract water from linens at the time of washing; 
           [0015]      FIG. 2  is a cross-sectional view of an RFID tag used for an examination; 
           [0016]      FIG. 3  is a plan view of the RFID tag used for then examination; 
           [0017]      FIGS. 4A and 4B  are plan views of RFID tags folded by washing; 
           [0018]      FIGS. 5A and 5B  are plan views of RFID tags which are folded by washing but semiconductor chips therein are kept from cracking; 
           [0019]      FIG. 6  is a cross-sectional view of an RFID tag according to a first embodiment; 
           [0020]      FIG. 7  is a plan view of the RFID tag according to the first embodiment; 
           [0021]      FIG. 8  is a perspective view of the RFID tag according to the first embodiment; 
           [0022]      FIG. 9  is a side view of an RFID tag not provided with grooves, which is bowed by an external force; 
           [0023]      FIG. 10  is a perspective view of the RFID tag according to the first embodiment in the case where an external force is applied thereto; 
           [0024]      FIG. 11  is a perspective view of the RFID tag according to the first embodiment in the case where a greater external force is applied thereto; 
           [0025]      FIG. 12  is a perspective view of an RFID tag according to a first example of the first embodiment; 
           [0026]      FIG. 13  is a perspective view of an RFID tag according to a second example of the first embodiment; 
           [0027]      FIG. 14  is a perspective view of an RFID tag according to a third example of the first embodiment; 
           [0028]      FIG. 15  is a first perspective view for explaining the folds formed in the RFID tag according to the third example of the first embodiment; 
           [0029]      FIG. 16  is a second perspective view for explaining the folds formed in the RFID tag according to the third example of the first embodiment; 
           [0030]      FIG. 17  is a perspective view of an RFID tag according to a fourth example of the first embodiment; 
           [0031]      FIG. 18  is a perspective view of an RFID tag according to a fifth example of the first embodiment; 
           [0032]      FIG. 19  is a plan view of an RFID tag according to a sixth example of the first embodiment; 
           [0033]      FIG. 20  is a cross-sectional view of an RFID tag according to a seventh example of the first embodiment, which is taken along its longitudinal direction; 
           [0034]      FIG. 21  is a cross-sectional view of an RFID tag according to an eighth example of the first embodiment, which is taken along its longitudinal direction; 
           [0035]      FIG. 22  is a cross-sectional view of an RFID tag according to a ninth example of the first embodiment, which is taken along its longitudinal direction; 
           [0036]      FIG. 23  is a cross-sectional view of an RFID tag according to a tenth example of the first embodiment, which is taken along its longitudinal direction; 
           [0037]      FIG. 24  is a cross-sectional view of an RFID tag according to an eleventh example of the first embodiment, which is taken along its longitudinal direction; 
           [0038]      FIGS. 25A to 25E  are cross-sectional views of the RFID tag of the first embodiment that is in the course of manufacturing; 
           [0039]      FIG. 26  is a perspective view of an RFID tag according to a second embodiment; 
           [0040]      FIG. 27  is an enlarged plan view of the RFID tag for explaining folds in the second embodiment; and 
           [0041]      FIG. 28  is a perspective view for explaining another example of a positional relation between a chip mounting region and folds in the second embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0042]    Prior to the descriptions of embodiments, considerations made by the inventor of the present application will be explained. 
         [0043]    As mentioned above, by providing flexibility to the RFID tag for linen, it is possible to prevent the RFID tag from being broken since its shape is deformed in response to the pressures at the time of washing. On the other hand, such deformation in shape may cause a crack of a semiconductor chip in the RFID tag. 
         [0044]    The inventor of the present application examined as to how the RFID tag is folded by the pressures applied thereto at the time of washing. 
         [0045]      FIG. 2  is a cross-sectional view of an RFID tag used in the examination. 
         [0046]    This RFID tag  10  includes an inlet base member made of a resin such as PET (polyethylene terephthalate), and an antenna  12  provided on a surface of the inlet base member  11 . A semiconductor chip  13  is mounted on the antenna  12 , and a protective sheet  14  is attached onto the semiconductor chip  13 . 
         [0047]    The protective sheet  14  has a function to protect the antenna  12  and the semiconductor chip  13 . For example, a PET sheet can be used as the protective sheet  14 . 
         [0048]    Note that another protective sheet  14  is also attached to a back face of the inlet base member  11  on which the semiconductor chip  13  is not mounted. 
         [0049]    Then, reinforcing members  16  are provided on the respective protective sheets  14  on the front and back sides of the inlet base member  11 . 
         [0050]    The reinforcing members  16  are resin plates made of PET and the like, and are provided at positions to cover the semiconductor chip  13  from the front and back sides thereof. 
         [0051]    Moreover, elastic sheets such as rubber sheets are provided as external members  18  onto the reinforcing members  16  of the front and back sides. 
         [0052]    By using the elastic sheets as the external members  18  in this manner, flexibility is provided to the RFID tag  10   
         [0053]      FIG. 3  is a plan view of the RFID tag  10 . 
         [0054]    As illustrated in  FIG. 3 , the RFID tag  10  has an elongated shape in a plan view. Moreover, a chip mounting region R is provided in the vicinity of the center of the RFID tag  10 , and the semiconductor chip  13  is mounted on the region R. 
         [0055]    The RFID tags  10  were attached to linens and washed together with the linens. As a consequence, folds L were provided to the RFID tags  10  as described below. 
         [0056]      FIGS. 4A and 4B  are plan views of the RFID tags  10  provided with folds L by washing. 
         [0057]    In the example of  FIG. 4A , a fold L parallel to a short side of the RFID tag  10  is provided in such a way as to pass through the chip mounting region R. The fold L is thought to be formed as a result of application of a force in such a way as to fold the RFID tag  10  along the fold L. 
         [0058]    Meanwhile, in the example of  FIG. 4B , a fold L oblique to a longitudinal direction d of the RFID tag  10  is provided in such a way as to pass through the chip mounting region R. The fold L is thought to be formed as a result of application of a force in such a way as to twist the RFID tag  10 . 
         [0059]    In the both examples of  FIGS. 4A and 4B , the semiconductor chips  13  (see  FIG. 3 ) located in the chip mounting region R were cracked since the folds L pass through the regions R. The inventor of the present application confirmed that the probability of the semiconductor chips  13  to be cracked in this manner is about 1/1000. 
         [0060]    In the meantime,  FIGS. 5A and 5B  are plan views of the RFID tags  10  which were provided with folds L by washing but the semiconductor chips  13  does not cracked. 
         [0061]    In the example of  FIG. 5A , a fold L parallel to the short side of the RFID tag  10  is provided as in the case of  FIG. 4A   
         [0062]    Then, in the example of  FIG. 5B , a fold L oblique to the longitudinal direction d of the RFID tag  10  is provided as in the case of  FIG. 4B . 
         [0063]    However, unlike the examples of  FIGS. 4A and 4B , the folds L are located away from the chip mounting regions R in the examples of  FIGS. 5A and 5B . Accordingly, the semiconductor chips  13  were not cracked. 
         [0064]    In addition, although the RFID tag  10  is provided with the antenna  12  (see  FIG. 3 ), the antenna was not disconnected by the folds L and the reliability of the RFID tag  10  was less reduced. 
         [0065]    From this result, it was revealed that the dislocation of the folds L away from the chip mounting region R was effective to prevent the semiconductor chip from cracking and thereby to improve reliability of the RFID tag  10 . 
         [0066]    In the followings, the embodiments will be described. 
       First Embodiment 
       [0067]      FIG. 6  is a cross-sectional view of an RFID tag according to a first embodiment. 
         [0068]    This RFID tag  20  is a flexible tag to be attached to linen such as clothes, and includes an inlet base member  21  and a conductive pattern  22  provided on a surface of the inlet base member  21 . 
         [0069]    The inlet base member  21  is a flexible resin sheet. In this example, a PET sheet having a thickness of about 30 μm to 100 μm is used as the inlet base member  21 . 
         [0070]    Meanwhile, the conductive pattern  22  is a silver pattern, for example, and is served as an antenna to communicate with an external device. 
         [0071]    A semiconductor chip  23  is mounted on the conductive pattern  22 . How to connect the conductive pattern  22  and the semiconductor chip  23  is not particularly limited. In this example, the conductive pattern  22  is connected to the semiconductor chip  23  through terminals  23   a  such as solder bumps and gold bumps. 
         [0072]    Moreover, a protective sheet  24  such as a PET sheet is attached onto the conductive pattern  22  and the semiconductor chip  23 . The conductive pattern  22  and the semiconductor chip  23  are protected by the protective sheet  24 . 
         [0073]    Note that another protective sheet  24  is also attached to a back face of the inlet base member  21  on which the semiconductor chip  23  is not mounted. 
         [0074]    The protective sheet  24  preferably has a sufficiently small thickness so as not to damage flexibility of the RFID tag  20 . In this example, the thickness of the protective sheet  24  is about 50 μm to 300 μm. 
         [0075]    Then, reinforcing members  26  made of a resin are provided on the respective protective sheets  24  on the front and back sides of the inlet base member  21 . Thus, the semiconductor chip  23  is covered with the reinforcing member  26 . 
         [0076]    The reinforcing member  26  has a function to reinforce the RFID tag  20  around the semiconductor chip  23 , and thereby to prevent the RFID tag  20  around the semiconductor chip  23  from being bent by an external force. 
         [0077]    As long as the reinforcing member  26  has this function, the material and the thickness of the reinforcing member  26  are not particularly limited. However, in order to effectively reinforce the RFID tag  20 , it is preferable to use the reinforcing members  26  formed from the material with the thickness that achieves higher rigidity than that of the inlet base member  21 . From this point of view, a PET plate having a thickness of 100 μm to 300 μm is used as the reinforcing member  26  in the present embodiment. 
         [0078]    Here, materials other than PET usable as the material of the reinforcing members  26  include PEN (polyethylene naphthalate) and polyimide, for example. 
         [0079]    Although the reinforcing members  26  are respectively provided on the front side and the back side of the semiconductor chip  23  in this example, the reinforcing member  26  may be provided only on one of the front side and the back side instead. 
         [0080]    Then, elastic sheets such as rubber sheets are provided as external members  28  onto the reinforcing members  26  of the front and back sides. By using the elastic sheets as the external members  28  in this manner, flexibility is provided to the RFID tag  20  as described previously. 
         [0081]    Here, the flexibility of the RFID tag  20  will be lost when the external members  28  are too thick. In the present embodiment, the flexibility of the RFID tag is maintained by setting the thickness of the external member  28  in a range from 0.5 mm to 2.0 mm. 
         [0082]    Furthermore, grooves  28   a  to serve as folds when the RFID tag  20  is folded are provided in a surface of the external member  28 . 
         [0083]      FIG. 7  is a plan view of the RFID tag  20 . 
         [0084]    Here,  FIG. 6  described above corresponds to a cross-sectional view taken along the I-I line in  FIG. 7 . It is to be noted, however, that the protective sheet  24  and the external member  28  on the upper side are omitted in  FIG. 7 . 
         [0085]    As illustrated in  FIG. 7 , the RFID tag  20  has an elongated shape, and a chip mounting region R to mount the semiconductor chip  23  is provided in the vicinity of the center of the RFID tag  20 . 
         [0086]    The reinforcing member  26  has a rectangular shape in a plan view, and is provided at a position to cover the semiconductor chip  23 . 
         [0087]      FIG. 8  is a perspective view of the RFID tag  20 . 
         [0088]    In  FIG. 8  and the subsequent drawings, a lateral direction of the elongated RFID tag  20  is indicated with d 1 , while a longitudinal direction orthogonal to the direction d 1  is indicated with d 2 . 
         [0089]    Then, each groove  28   a  extends straight in the lateral direction d 1  of the external member  28  and is situated at a position away from the chip mounting region R. 
         [0090]    Although the size of the external member  28  is not particularly limited, a length of a short side  28   x  of the external member  28  is set to about 6 mm and a length of a long side  28   y  of the external member  28  is set to about 51 mm in this example. 
         [0091]    Next, a function of the grooves  28   a  will be described. 
         [0092]      FIG. 9  is a side view of the RFID tag  20  that is not provided with the grooves  28   a , which is bowed by an external force. 
         [0093]    A bending moment is generated in the RFID tag  20  in the bowed state in such a way as to counteract the external force. When the RFID tag  20  is provided with no grooves  28   a  as illustrated in  FIG. 9 , mechanical strength is almost the same at any portions of the RFID tag  20 . Accordingly, there exists no portion in the RFID tag  20  which is significantly deformed by the bending moment. 
         [0094]    Meanwhile,  FIG. 10  is a perspective view of the RFID tag  20  provided with the grooves  28   a  as in the present embodiment, illustrating the case where the external force is applied to the RFID tag  20 . 
         [0095]    The portions of the RFID tag  20  where the grooves  28   a  is provided have lower mechanical strength as compared to the other portions. Accordingly, when the external force is applied as illustrated in  FIG. 10 , the grooves  28   a  acts as folds L and the RFID tag  20  is folded. 
         [0096]    In order to make the RFID tag  20  easily foldable in this manner, it is preferable to form the groove  28   a  across the entire width of the RFID tag  20  as illustrated in  FIG. 10 . 
         [0097]    Moreover, when the external force applied to the RFID tag  20  is greater, the RFID tag  20  is lapped at the grooves  28   a  as illustrated in  FIG. 11 . 
         [0098]    Each groove  28   a  functions as a fold of the RFID tag  20  as described above. As long as this function is maintained, a width W (see  FIG. 8 ) and a depth of the groove  28   a  are not limited. In the present embodiment, the width W of the groove  28   a  is set about 1 mm to 2 mm, and the depth of the groove  28   a  is set about 0.2 mm to 0.3 mm. 
         [0099]    As described above, the RFID tag  20  is folded preferentially at the grooves  28   a . Therefore, the portions of the RFID tag  20  other than the grooves  28   a  are less likely to be folded by the external force. 
         [0100]    Accordingly, by locating the grooves  28   a  away from the chip mounting region R as in the present embodiment, it is possible to reduce a risk of a crack of the semiconductor chip  23  in the region R even when the RFID tag  20  is folded by the external force. 
         [0101]    Specifically, the RFID tags  20  attached to linen such as clothes are frequently folded by various pressures at the time when the linen is washed as described previously. Therefore, the application of the present embodiment is a highly practical for the RFID tags  20  attached to linen in order to prevent the semiconductor chips  23  from cracking. 
         [0102]    In addition, since the groove  28  is provided in the uppermost external member  28  that is prone to fold, the RFID tag  20  can be made more foldable than the case where the groove is formed in the inner portions of the RFID tag  20 . 
         [0103]    Moreover, since the rubber serving as the material of the external members  28  is sufficiently elastic, the risk is reduced that the external member  28  break off at the groove  28   a  when the RFID tag  20  is folded. 
         [0104]    Furthermore, the thickness of the external member  28  is reduced only at the grooves  28   a . Accordingly, at the portions other than the grooves  28   a , the base member  21  and the conductive pattern  22  are protected by the sufficiently thick external member  28 . 
         [0105]    Note that the configuration of the grooves  28   a  is not limited only to the above. In the followings, various examples of other configurations of the groove  28   a  are described. 
       First Example 
       [0106]      FIG. 12  is a perspective view of an RFID tag  20  according to a first example. 
         [0107]    In this example, the reinforcing member  26  and the chip mounting region R are provided at a central portion of the external member  28 . 
         [0108]    Then, a distance a from one short side  28   x  of the external member  28  to the groove  28   a  is set equal to a distance b from the reinforcing member  26  to the groove  28   a.    
         [0109]    Since the reinforcing member  26  is highly rigid and is hardly bent, the bending moment is thought to become the maximum at a portion of the RFID tag  20  located at equal distances from the reinforcing member  26  and from the short side  28   x  when the external force acts on the RFID tag  20 . In this example, the groove  28   a  is provided at the portion where the distance from the reinforcing member  26  and the distance from the short side  28   x  are equal. Therefore, the groove  28   a  acts as the fold L and the RFID tag  20  can be easily folded, which in turn reduce the risk that the RFID tag  20  is folded at the portions other than the groove  28   a.    
         [0110]    Moreover, in this example, the groove  28   a  is provided at the position away from the reinforcing member  26  so as to prevent the reinforcing member  26  and the groove  28   a  from overlapping each other. Therefore, when the RFID tag  20  is bent at the grooves  28   a , it is possible to prevent the highly rigid reinforcing members  26  from disturbing the bending of the RFID tag  20 . 
       Second Example 
       [0111]      FIG. 13  is a perspective view of an RFID tag  20  according to a second example. 
         [0112]    In this example as well, the reinforcing member  26  and the chip mounting region R are provided at the central portion of the external member  28 . 
         [0113]    However, in this example, the groove  28   a  is provided closer to the reinforcing member  26  than the short side  28   x.    
         [0114]    When the external force acts on the RFID tag  20 , a stress is thought to be concentrated on the edge  26   x  of the reinforcing member  26 . Accordingly, by providing the groove  28   a  closer to the reinforcing member  26 , the RFID tag  20  can be easily folded at the groove  28   a  serving as the folds L by the stress concentrated on the edges  26   x . Thus, the risk is reduced that the RFID tag  20  is folded at the portions other than the groove  28   a.    
         [0115]    Moreover, the groove  28   a  is located at the positions away from the reinforcing member  26  as in the first example. Accordingly, it is possible to prevent the highly rigid reinforcing member  26  from disturbing the bending of the RFID tag  20 . 
       Third Example 
       [0116]      FIG. 14  is a perspective view of an RFID tag  20  according to a third example. 
         [0117]    In this example as well, the reinforcing member  26  and the chip mounting region R are provided at the central portion of the external member  28 . 
         [0118]    However, in this example, straight grooves  28   a  are provided to extend obliquely to the longitudinal direction d 2  of the external member  28 . In addition, two oblique grooves  28   a  are provided in each of two regions S at the both side of the reinforcing member  26 , and these grooves  28   a  are made to cross each other. 
         [0119]    Here, each groove  28   a  extends from one long side  28   y  of the external member  28  to the other long side  28   y . Moreover, the groove  28   a  and the long side  28   y  are made to cross each other in the vicinity of a corner  26   a  of the reinforcing member  26 . 
         [0120]      FIG. 15  and  FIG. 16  are perspective views for explaining the folds L formed in the RFID tag  20  of this example. 
         [0121]    Since the grooves  28   a  are obliquely provided in this example, even when the RFID tag  20  is twisted in directions indicated with arrows A in  FIG. 15 , the RFID tag  20  is folded while acting the grooves  28   a  as the folds L. Hence, the chip mounting region R located away from the grooves  28   a  is not bent as a consequence. 
         [0122]    Moreover, since each of the regions S includes the two grooves  28   a  with different orientations in this example, even when the RFID tag  20  is twisted in directions indicated with arrows B in  FIG. 16 , the RFID tag  20  is folded while acting the grooves  28   a  different from those in  FIG. 15  as the folds L. 
         [0123]    Accordingly, in this example, the semiconductor chip  23  in the chip mounting region R can be prevented from cracking even when the RFID tag  20  is twisted in any of the directions of the arrows A ( FIG. 15 ) and the directions of the arrows B ( FIG. 16 ). 
         [0124]    Note that when the RFID tag  20  is twisted, a stress is thought to be concentrated on the corners  26   a  of the reinforcing members  26 . Accordingly, by causing the grooves  28   a  and the long sides  28   y  to cross one another in the vicinity of the corners  26   a  as in this example, the RFID tag  20  is easily folded at the grooves  28   a  by the stress concentrated on the corners  26   a . As a consequence, it is possible to reduce a risk that the RFID tag  20  is folded at portions other than the grooves  28   a.    
       Fourth Example 
       [0125]      FIG. 17  is a perspective view of an RFID tag  20  according to a fourth example. 
         [0126]    Similar to the third example, the grooves  28   a  are provided obliquely to the longitudinal direction d 2  of the external member  28  in this example. 
         [0127]    However, in this example, the groove  28   a  extends from the short side  28   x  of the external member  28  to the long side  28   y.    
       Fifth Example 
       [0128]      FIG. 18  is a perspective view of an RFID tag  20  according to a fifth example. 
         [0129]    Similar to the third example and the fourth example, the grooves  28   a  are provided obliquely to the longitudinal direction d 2  of each external member  28  in this example. 
         [0130]    However, in this example, the groove  28   a  is extending from one of the short sides  28   x  of the external member  28  to the other short side  28   x , and an intersection of the two grooves  28   a  is located at the central portion of the external member  28 . 
         [0131]    Note that it is preferable to locate the grooves  28   a  away from the reinforcing member  26  (see  FIG. 7 ) in order for the RFID tag  20  to be bent easily along the grooves  28   a  as described above. Nevertheless, when the RFID tag  20  is partitioned into small regions by the grooves  28   a  and it is difficult to provide the reinforcing member  26  in those small regions in such a way as to be located away from the grooves  28   a , then the reinforcing member  26  may be omitted. This is also the case for a sixth example to be described below. 
       Sixth Example 
       [0132]      FIG. 19  is a plan view of an RFID tag  20  according to a sixth example. 
         [0133]    In this example, a straight groove  28   a  extends in the longitudinal direction d 2  of the external member  28 . Moreover, the chip mounting region R is provided in one of the two regions of the RFID tag  20  partitioned by the groove  28   a.    
         [0134]    This example is effective in the case where a fold L is formed in parallel to the longitudinal direction d 2 . 
         [0135]    Here, it is preferable to form the groove  28   a  across the entire length of the RFID tag  20  in order to make the RFID tag  20  easily foldable along the groove  28   a.    
       Seventh Example 
       [0136]    In the example of  FIG. 6 , the grooves  28   a  are provided to the external members  28  on the front side and the back side respectively. However, the present embodiment is not limited to this. 
         [0137]      FIG. 20  is a cross-sectional view of an RFID tag  20  of this example, which is taken along its longitudinal direction. In  FIG. 20 , the same elements as those described in  FIG. 6  will be denoted by the same reference numerals as in  FIG. 6 , and descriptions thereof will be omitted below. This is also the case for  FIGS. 21 to 23  to be described later. 
         [0138]    In this example, as illustrated in  FIG. 20 , the groove  28   a  is provided only to one of the external members  28  on the front and back sides. 
         [0139]    By providing the grooves  28   a  only to one side of the RFID tag  20  in this manner, the RFID tag  20  can be folded along the groove  28   a , while the groove  28   a  acts as the fold. 
       Eighth Example 
       [0140]      FIG. 21  is a cross-sectional view of an RFID tag  20  of this example, which is taken along its longitudinal direction. In this example, each of the external members  28  on the front and back sides is provided with one groove  28   a , and the grooves  28   a  on the front and back sides are disposed to oppose each other. 
         [0141]    By providing the groove  28   a  one by one on the front and back sides of the RFID tag  20 , the RFID tag  20  can be folded along the groove  28   a , while the groove  28   a  acts as the fold. 
       Ninth Example 
       [0142]      FIG. 22  is a cross-sectional view of an RFID tag  20  of this example, which is taken along its longitudinal direction. 
         [0143]    In this example, of the two faces  28   c  and  28   d  of each external member  28 , the grooves  28   a  are provided in the face  28   d  which is directed to the inlet base member  21 . 
         [0144]    Accordingly, the grooves  28   a  do not appear on the face  28   c  which attracts the attention of a user. Therefore, it is possible to prevent the external appearance of the RFID tag  20  from being defiled by the groove  28   a.    
       Tenth Example 
       [0145]      FIG. 23  is a cross-sectional view of an RFID tag  20  of this example, which is taken along its longitudinal direction. 
         [0146]    In this example, the grooves  28   a  are provided to both of the faces  28   c  and  28   d  of the external member in such a way that grooves oppose each other. By providing the grooves  28   a  to oppose each other in this manner, the portion of the external member  28  where the grooves  28   a  are provided is reduced in thickness, and hence the RFID tag  20  can be bent more easily along the grooves  28   a  that acts as the folds. 
       Eleventh Example 
       [0147]      FIG. 24  is a cross-sectional view of an RFID tag  20  of this example, which is taken along its longitudinal direction. 
         [0148]    In this example, of the front and back faces of the inlet base member  21 , the external member  28  is provided only to the front face on which the semiconductor chip  23  is mounted, while the external member  28  is not provided on the back face of the inlet base member  21 . 
         [0149]    Even when the external member  28  is provided only to one of the front and back faces in this manner, it is still possible to fold the RFID tag  20  while using the grooves  28   a  in the external member  28  as the folds. 
         [0150]    (Manufacturing Method) 
         [0151]    Next, a method of manufacturing the RFID tag of the present embodiment will be described. 
         [0152]      FIGS. 25A to 25E  are cross-sectional views of the RFID tag of the present embodiment that is in the course of manufacturing. 
         [0153]    First, as illustrated in  FIG. 25A , a PET sheet of a thickness of 30 μm to 100 μm is prepared as the inlet base member  21 . Then, a silver layer having a thickness of about 5 μm to 20 μm is formed on the inlet base member  21  by vapor deposition. Then, the silver layer thus formed is patterned into the conductive pattern  22 . 
         [0154]    Next, as illustrated in  FIG. 25B , the semiconductor chip  23  is mounted on the conductive pattern  22 . In this example, the conductive pattern  22  is connected to the semiconductor chip  23  through the terminals  23   a  such as solder bumps and gold bumps. 
         [0155]    Subsequently, as illustrated in  FIG. 25C , a PET sheet of a thickness of 50 μm to 300 μm serving as the protective sheet  24  is attached from the semiconductor chip  23  to the inlet base member  21 . Likewise, the other protective sheet  24  is also attached to the back face of the inlet base member  21  on which the semiconductor chip  23  is not mounted. 
         [0156]    The method of attachment includes, for example, a method of attaching the protective sheets  24  to the inlet base member  21  by using an unillustrated adhesive. 
         [0157]    Next, as illustrated in  FIG. 25D , the reinforcing members  26  are attached onto the protective sheets  24  on the front and back sides of the inlet base member  21  by using an unillustrated adhesive. 
         [0158]    As described previously, the reinforcing members  26  play the role in inhibiting the RFID tag from being bent by the external force. In the present embodiment, a PET plate having a thickness of 100 μm to 300 μm is used as the reinforcing member  26 . 
         [0159]    Thereafter, as illustrated in  FIG. 25E , elastic sheets made of rubber or the like are attached as the external members  28  onto the reinforcing members  26  on the front and back sides, thereby enclosing the inlet base member  21  and the semiconductor chip  23  by the external members  28 . Here, the external members  28  on the front and back sides are attached together by molecular adhesion. 
         [0160]    While the external members  28  are molded into the elongated shape in advance before this step, the above-described grooves  28   a  are also simultaneously formed when molding the external members  28 . Accordingly, a dedicated process to form the grooves  28   a  is not required. 
         [0161]    Thus, the basic structure of the RFID tag  20  of the present embodiment is completed. 
         [0162]    According to the above-described method of manufacturing the RFID tag  20 , the grooves  28   a  can be formed simultaneously with the molding of the external members  28 . Therefore, it is possible to manufacture the RFID tag  20  which can prevent the semiconductor chip  23  from cracking, without causing an increase in the number of steps. 
       Second Embodiment 
       [0163]    In the first embodiment, the grooves  28   a  are provided to the external members  28  as illustrated in  FIG. 10  and the like, and the RFID tag  20  is made foldable by making the grooves  28   a  into the folds L. 
         [0164]    As described below, in the present embodiment, the RFID tag  20  is made foldable without forming the grooves. 
         [0165]      FIG. 26  is a perspective view of the RFID tag  20  of the present embodiment. Note that the elements in  FIG. 26  which are the same as those explained in the first embodiment will be denoted by the same reference numerals as those in the first embodiment, and the their descriptions will be omitted below. 
         [0166]    As illustrated in  FIG. 26 , in the present embodiment, recesses  28   w  are provided in side portions of the external member  28 . The recesses  28   w  function as originating points of the folds L when the RFID tag  20  is bent, and the chip mounting region R is provided away from the folds L. 
         [0167]      FIG. 27  is an enlarged plan view of the RFID tag for explaining the fold L. 
         [0168]    When an external force F acts on the external member  28  provided with the recess  28   w  as illustrated in  FIG. 27 , a stress is concentrated more on the recess  28   w  than is on other portions. Therefore, the RFID tag  20  is folded preferentially along the fold L passing through the recess  28   w.    
         [0169]    Reference is made to  FIG. 26  again. 
         [0170]    As illustrated in  FIG. 26 , in this example, the plurality of recesses  28   w  are respectively provided to the two long sides  28   y  of the external member  28  in such a way that the recesses  28   w  are opposing each other. According to this configuration, the fold L extends in the lateral direction d 1  of the external member  28 . As a consequence, the RFID tag  20  is folded back as in the case illustrated in  FIG. 10  and  FIG. 11  when the external force is applied to the RFID tag  20 . 
         [0171]    In addition, since the RFID tag  20  is folded preferentially along the fold L, the risk is reduced that the RFID tag  20  is bent in the chip mounting region R located away from the fold L. Therefore, it is possible to reduce the possibility that the semiconductor chip  23  (see  FIG. 7 ) located in the region R is cracked. 
         [0172]    Moreover, the recesses  28   w  are formed in the uppermost external member  28  in which the folds can easily be formed. Therefore, the RFID tag  20  can be folded more easily than the case of forming the recesses in the inlet base member  21  and the like located in the RFID tag  20 . 
         [0173]    Moreover, since the rubber used as the material of the external member  28  has sufficient elasticity, there is little risk that the external member  28  is cut from the recesses  28   w  when the RFID tag  20  is folded. 
         [0174]    Note that the size and shape of the recess  28   w  is not particularly limited as long as the recess  28   w  can serve as the originating point of the fold L. In this example, a planar shape of the recess  28   w  is formed into a semicircular shape. 
         [0175]    Furthermore, the positional relation between the chip mounting region R and the fold L is not limited only to the example of  FIG. 26 . 
         [0176]      FIG. 28  is a perspective view for explaining another example of the positional relation between the chip mounting region R and folds L. 
         [0177]    This example assumes the case where the two folds L originating from the recesses  28   w  cross each other as the RFID tag  20  is twisted. 
         [0178]    In this case, it is preferable to shift the position of the chip mounting region R in the longitudinal direction d 2  and away from an intersecting point C of the folds L in order to prevent the semiconductor chip  23  located in the chip mounting region R from cracking. 
         [0179]    All examples and conditional language recited herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.