Abstract:
The present invention provides a radio frequency identification (RFID) tag which exchanges information with an external device in a noncontact manner, in which a paste is used as a material for an antenna, and which is designed to prevent sinking of bumps. A stopper for limiting sinking of bumps of a circuit chip caused by a pressing force when the circuit chip is connected to an antenna is provided on the circuit chip or a base at a position adjacent to the bumps.

Description:
BACKGROUND OF THE INVENTION 
     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 and a method of manufacturing the same. 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 “wireless IC tag”. Also, this “RFID” tag includes a noncontact-type IC card. 
     2. Description of the Related Art 
     In recent years, various types of RFID tags capable of noncontact information exchange by means of radio waves with external devices typified by reader/writers have been proposed. One of the various types of RFID tags proposed has an antenna pattern for radio wave communication and an IC chip mounted on a base sheet made of a plastic or paper. A conceivable usage form of such type of RFID tag is that the RFID tag is attached to an article and information about the article is exchanged with an external device for identification or the like of the article. 
       FIG. 1(A)  is a front view and  FIG. 1(B)  is a sectional side view, respectively, of an example of an RFID tag. 
     The RFID tag  1  shown in  FIGS. 1(A) and 1(B)  is constituted by an antenna  12  provided on a base  13  formed of a sheet-like material such as a polyethylene telephthalate (PET) film, an IC chip  11  connected to the antenna  12  through bumps  16 , and a cover sheet  14  bonded to the base  13  by an adhesive  15  so as to cover the antenna  12  and the IC chip  11 . 
     The IC chip  11  constituting the RFID tag  1  is capable of exchanging information with an external device by performing wireless communication through the antenna  12 . 
     Various use forms including the above-mentioned use form have been conceived with respect to this type of RFID tag. In use of this type of RFID tag, how to reduce the manufacturing cost of the RFID tag has been a serious problem and various attempts have been made to solve this problem. 
     As one of the attempts to reduce the manufacturing cost, there is proposed the idea of forming an antenna by using a paste material which is made conductive by blending a metallic filler (Ag in ordinary cases) with a resin material such as an epoxy resin (Japanese Patent Laid-Open No. 2000-311226 (paragraph [0066])). If such a paste material can be used as a material for forming an antenna in place of a thin metallic material such as Cu, Al or Au that is conventionally used, it can largely contribute to a reduction in the manufacturing cost of the RFID tag. 
     When manufacturing the RFID tag in which, as shown in  FIG. 1 , the IC chip  11  is connected to the antenna  12  formed on the surface of the base  13  that is a sheet-like PET member or the like through the bumps (metal protrusions)  16  formed on electrodes of the IC chip  11 , if the antenna  12  is formed by printing a paste material, a problem described below may arise with the connection between the IC chip  11  and the antenna  12 . 
       FIG. 2(A)  shows a case where a metal is used as an antenna material and  FIG. 2(B)  shows a case where a paste is used as an antenna material for comparison. 
     An antenna  121  ( FIG. 2(A) ) formed of a thin sheet of a metal or an antenna  122  formed of a paste material ( FIG. 2(B) ) is formed on the base  13  formed of a PET. The bumps  16  are formed on electrodes  111  formed on the IC chip  11  in each of the cases shown in  FIGS. 2(A) and 2(B) . 
     Each of the states shown in  FIGS. 2(A) and 2(B)  shows a state in which the IC chip  11  with bumps  16  is placed on the base  13  on which the antenna  121  or  122  is formed such that the bumps  16  face the base  13  and the IC chip  11  is connected to the antenna  121  or  122  through the bumps  16 . 
     In  FIGS. 2(A) and 2(B) , illustration of the adhesive  15  and the cover sheet  14  shown in  FIG. 1(B)  is omitted. At the time of connection, the IC chip  11  is pressed from above as viewed in the figure with a jig (not shown). A pressing force is thereby applied from the bumps  16  to the antenna  121  or  122 . In the case of the antenna  121  made of a metallic material as shown in  FIG. 2(A) , there is no problem with this pressing, since the hardness of the antenna  121  is high. In the case of the antenna  122  made of a paste material as shown in  FIG. 2(B) , there is a problem described below. The paste material deforms by the pressing force received by the antenna  122  from the bumps  16  so as to conform to the shape of the bumps  16 , and compression bending of the paste material is thereby caused at the connection between the antenna  122  and the bumps  16 , resulting in pattern breakage and sinking at the bent portion. In this case, the necessary insulation distance cannot be maintained between the IC chip  11  and the antenna  122 . If this distance is changed, characteristics of the RFID tag including a wireless communication characteristic (hereinafter referred to as tag characteristics) are changed, which results in variations in tag characteristics when a large number of RFID tags are manufactured. 
     The method of mounting various types of IC chips on a circuit board apart from the RFID tag is being widely practiced. In ordinary cases, many bumps are formed on an IC chip and the pressing force per bump is small even when a paste material is used as a wiring material on a circuit board and, therefore, protrusion of the paste material is not a serious problem. 
     In contrast, in the case of the RFID tag, since the number of bumps provided in one IC chip for connection to the antenna is about two or four, the pressing force per bump is extremely large and thus the above-mentioned sinking problem arises. In order to reduce the pressing force, it is necessary to reduce the pressing force, which is applied by an apparatus for placing the IC chip on the base when placing the IC chip, to an extremely small value in comparison with the case of placing an ordinary IC chip on which many bumps are formed. Also, since an adhesive exists between the base and the IC chip, it is extremely difficult to reduce the pressing force to an extremely small value while enabling a reliable connection to be made in a short time. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above circumstances and provides an RFID tag using a paste as a material for an antenna and capable of avoiding the problem that the tag characteristics are changed by sinking of bumps, and a method of manufacturing the RFID tag. 
     According to the present invention, there is provided a first RFID tag having: a base; an antenna for communication provided on the base; a circuit chip connected to the antenna through bumps, the circuit chip performing wireless communication through the antenna, wherein the antenna is formed of a paste in which a metallic filler is blended with a resin material; and a stopper for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna is provided adjacent to the bumps. 
     In the first RFID tag of the present invention, the stopper is provided to limit sinking described above with reference to  FIG. 2(B) , thereby avoiding the problem due to variations in tag characteristics. 
     In the first RFID tag of the present invention, the stopper may be formed of a film formed on the circuit chip or the base and having holes in correspondence with the portions to which the bumps are connected. The stopper may alternatively be formed of a protrusion formed on a portion of the base adjacent to the portions to which the bumps are connected. 
     Further, in the first RFID tag of the present invention, a gap between the base and the circuit chip may be filled with an adhesive in which a filler is blended to fix the circuit chip and the base to each other when the circuit chip with the bumps is connected to the antenna, and the filler may constitute the stopper. 
     According to the present invention, there is provided a second RFID tag having: a base; an antenna for communication provided on the base; a circuit chip connected to the antenna through bumps, the circuit chip performing wireless communication through the antenna, wherein the antenna is formed of a paste in which a metallic filler is blended with a resin material; and a hard layer for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna is provided at least at positions right below the bumps between the base and the antenna. 
     In the second RFID tag of the present invention, the hard layer is provided to limit sinking described above with reference to  FIG. 2(B) , thereby avoiding the problem due to variations in tag characteristics. 
     According to the present invention, there is provided a third RFID tag having: a base; an antenna for communication provided on the base; a circuit chip connected to the antenna through bumps, the circuit chip performing wireless communication through the antenna, wherein the antenna is formed of a paste in which a metallic filler is blended with a resin material; and an electroconductive support for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna is provided between the antenna and the bumps. 
     In the third RFID tag of the present invention, the support is provided to limit sinking of the bumps, as in the case of the RFID tags in the first and second aspects of the present invention. Therefore the tag characteristics of the RFID tag can be stabilized. 
     According to the present invention, there is provided a fourth RFID tag having: a base; an antenna for communication provided on the base; and a circuit chip connected to the antenna through bumps, the circuit chip performing wireless communication through the antenna, wherein the antenna is formed of a paste in which a metallic filler is blended with a resin material, and portions of the antenna right below the bumps are formed of a paste in which the ratio of blending of the metallic filler is changed in comparison with that in the paste for the portion other than the portions right below the bumps to limit sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna. 
     In the fourth RFID tag of the present invention, the ratio of blending of the metallic filler for the portions of the antenna immediately below the bumps is changed to limit sinking, thereby stabilizing the tag characteristics of the RFID tag as well as those of the RFID tags in the first to third aspects. 
     According to the present invention, there is provided a fifth RFID tag having: a base; an antenna for communication provided on the base; and a circuit chip connected to the antenna through bumps, the circuit chip performing wireless communication through the antenna, wherein the antenna is formed of a paste in which a metallic filler for giving the necessary conductivity for the antenna to a resin material is blended with the resin material, and a hard filler for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna is also blended with the resin material. 
     In the fifth RFID tag of the present invention, the antenna constituting the RFID tag is formed of a paste in which the hard filler (e.g., Cu, Pd, Ni or the like) as well as the metallic filler (e.g., Ag) are blended, thereby limiting sinking and stabilizing the tag characteristics. 
     According to the present invention, there is provided a first method of manufacturing an RFID tag, including: an antenna printing step of printing an antenna for communication on a base by using a paste in which a metallic filler is blended with a resin material; a circuit chip mounting step of mounting a circuit chip with bumps capable of performing wireless communication through the antenna, the circuit chip and the antenna being connected to each other through the bumps; and a stopper forming step of forming at a position adjacent to the bumps a stopper for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna. 
     According to the present invention, there is provided a second method of manufacturing an RFID tag, including: an antenna printing step of printing an antenna for communication on a base by using a paste in which a metallic filler is blended with a resin material; a circuit chip mounting step of mounting a circuit chip with bumps capable of performing wireless communication through the antenna, the circuit chip and the antenna being connected to each other through the bumps; and a hard layer forming step of forming, at least at positions right below the bumps, between the base and the antenna a hard layer for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna. 
     According to the present invention, there is provided a third method of manufacturing an RFID tag, including: an antenna printing step of printing an antenna for communication on a base by using a paste in which a metallic filler is blended with a resin material; a circuit chip mounting step of mounting a circuit chip with bumps capable of performing wireless communication through the antenna, the circuit chip and the antenna being connected to each other through the bumps; and a support forming step of forming between the antenna and the bumps an electroconductive support for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna. 
     According to the present invention, there is provided a fourth method of manufacturing an RFID tag, including: an antenna printing step of printing an antenna for communication on a base by using a paste in which a metallic filler is blended with a resin material; and a circuit chip mounting step of mounting a circuit chip with bumps capable of performing wireless communication through the antenna, the circuit chip and the antenna being connected to each other through the bumps, wherein the antenna printing step includes a first printing step of printing a portion of the antenna other than the portions to which the bumps are connected by using the paste in which the metallic filler is blended with the resin material, and a second printing step of printing the portions of the antenna to which the bumps are connected by using a paste in which the ratio of blending of the metallic filler is changed in comparison with that in the paste used in the first printing step so as to form on the portions of the antenna to which the bumps are connected a hard electroconductive film for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna. 
     According to the present invention, there is provided a fifth method of manufacturing an RFID tag, including: an antenna printing step of printing an antenna for communication on a base by using a paste in which a metallic filler is blended with a resin material; and a circuit chip mounting step of mounting a circuit chip with bumps capable of performing wireless communication through the antenna, the circuit chip and the antenna being connected to each other through the bumps, wherein the antenna printing step is a step of printing the antenna for communication on the base by using a paste in which a metallic filler for giving the necessary conductivity for the antenna to the resin material is blended with the resin material, and a hard filler for limiting sinking of the bumps caused by a pressing force when the circuit chip with the bumps is connected to the antenna is also blended with the resin material. 
     According to the present invention, as described above, a paste is used as the material of the antenna and sinking of the bumps of the circuit chip caused by a pressing force applied through the bumps is limited to stabilize the tag characteristics. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1(A) and 1(B)  are a front view and a sectional side view respectively of an example of an RFID tag; 
         FIGS. 2(A) and 2(B)  are diagrams respectively showing the case of using a metal as an antenna material and the case of using a paste as an antenna material for comparison; 
         FIG. 3  is a sectional view of an RFID tag according to a first embodiment of the present invention; 
         FIG. 4  is a sectional view of an RFID tag according to a second embodiment of the present invention; 
         FIG. 5  is a sectional view of an RFID tag according to a third embodiment of the present invention; 
         FIGS. 6(A) to 6(C)  show an RFID tag which is an example of a modification of the third embodiment of the present invention; 
         FIG. 7  is a sectional view of an RFID tag according to a fourth embodiment of the present invention; 
         FIG. 8  is a sectional view of an RFID tag according to a fifth embodiment of the present invention; 
         FIG. 9  is a sectional view of an RFID tag according to a sixth embodiment of the present invention; 
         FIG. 10  is a sectional view of an RFID tag according to a seventh embodiment of the present invention; 
         FIG. 11  is a sectional view of an RFID tag according to an eighth embodiment of the present invention; 
         FIG. 12  is a sectional view of base and antenna portions of an RFID tag according to a ninth embodiment of the present invention; 
         FIGS. 13(A) to 13(C)  show a method of forming bumps on electrodes of an IC chip; 
         FIG. 14  is a diagram showing a method of leveling bumps; 
         FIGS. 15(A) to 15(C)  show the bump after leveling; 
         FIGS. 16(A) to 16(D)  show a method of manufacturing the RFID tag having the stopper formed of polyimide film with holes as shown in  FIG. 3 ; 
         FIGS. 17(A) to 17(C)  show a method of manufacturing the RFID tag having a stopper formed of a PET with holes as shown in  FIG. 4 ; 
         FIGS. 18(A) to 18(C)  show a method of manufacturing the RFID tag having a stopper as shown in  FIG. 5 ; 
         FIGS. 19(A) and 19(B)  show a method of manufacturing the RFID tag including a plastic filler shown in  FIG. 7 ; 
         FIGS. 20(A) to 20(D)  show a method of manufacturing the RFID tag shown in  FIG. 8 ; 
         FIGS. 21(A) to 21(D)  show a method of manufacturing the RFID tag shown in  FIG. 9 ; 
         FIGS. 22(A) to 22(D)  show a method of manufacturing the RFID tag shown in  FIG. 10 ; 
         FIGS. 23(A) to 23(C)  show a method of manufacturing the RFID tag shown in  FIG. 11 ; and 
         FIGS. 24(A) and 24(B)  show a method of manufacturing the RFID tag shown in  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described below with respect to embodiments thereof. 
       FIG. 3  is a sectional view of an RFID tag according to the first embodiment of the present invention. 
     In  FIG. 3  and other figures referred to below, constituents corresponding to those of the RFID tag described above with reference to  FIG. 2  are indicated by the same reference numerals and the description for them will not be repeated. Description will be made only of points different from the above-described RFID tag. In  FIG. 3  and the other figures referred to below, illustration of the adhesive  15  between the base  13  and the IC chip  11  and the base sheet  14  (see  FIG. 2(B) ) that covers upper portions of the RFID tag is omitted in principle, as is that in  FIG. 2 . However, a feature of the present invention described below with reference to  FIG. 20  resides in an adhesive. Therefore, the adhesive is shown in  FIG. 20 . Also, in the embodiments described below, the base  13  is formed of a PET and the antenna  122  is formed by using a paste prepared by blending an Ag filler with a resin material such as an epoxy resin unless otherwise specified. 
     In the RFID tag  1 A shown in  FIG. 3 , a polyimide film  21  having holes at positions corresponding to bumps is formed on the IC chip  11 . The polyimide film  21  is slightly lower than the height of bumps  16  (thinner than bumps  16 ). When the IC chip  11  with bumps  16  and polyimide film  21  is connected to the antenna  122 , the polyimide film  21  functions as a stopper to limit sinking of the bumps  16  (see FIG.  2 (B)), thus stabilizing the tag characteristics of the RFID tag. 
       FIG. 4  is a sectional view of an RFID tag according to a second embodiment of the present invention. 
     In the RFID tag  1 B shown in  FIG. 4 , a PET member  22  having holes is adhered to the base  13 . The thickness of the PET member  22  is slightly smaller than the height of the bumps  16 . When the IC chip  11  with the bumps  16  is connected to the antenna  122 , the PET member  22  functions as a stopper to limit sinking of the bumps  16 , thus stabilizing the tag characteristics of the RFID tag. 
       FIG. 5  is a sectional view of an RFID tag according to a third embodiment of the present invention. 
     In the RFID tag IC shown in  FIG. 5 , a protrusion (stopper portion  23 ) slightly lower in height than the bumps  16  is formed on the base  13  side before the IC chip  11  is connected to the antenna  122 . When the IC chip  11  with the bumps  16  is connected to the antenna  122 , sinking of the bumps  16  is limited by the function of the stopper portion  23 . 
       FIGS. 6(A) to 6(C)  show an RFID tag as an example of a modification of the third embodiment of the present invention (See  FIG. 5 ).  FIG. 6(A)  is a sectional view,  FIG. 6(B)  is a plan view showing the base before the IC chip is mounted, and  FIG. 6(C)  is a plan view showing the base after mounting the IC chip. In  FIG. 6(C) , the position of the IC chip is indicated only by the broken line. 
     Also in the RFID tag  1 C′ shown in  FIGS. 6(A) to 6(C) , a protrusion (stopper portion  23 ) slightly lower in height than the bumps  16  is formed on the base  13  side before the IC chip  11  is connected to the antenna  122 , as is that in the case shown in  FIG. 5 . When the IC chip  11  with the bumps  16  is connected to the antenna  122 , sinking of the bumps  16  is limited by the function of the stopper portion  23 . In the case of the RFID tag  1 C′ shown in  FIGS. 6(A) to 6(C) , the stopper portion  23  is formed on the portion of the base  13  on which the IC chip  11  is mounted except the portions on which connections to the bumps  16  are made. That is, the stopper portion  23  extends so as to fill the almost entire region where no antenna portion exists between two ends of the antenna  122 . If the stopper portion  23  conforms to the region where no antenna pattern portion exists, it is possible to maintain the balance (attitude) of the IC chip  11  at the time of mounting of the IC chip  11  on the base  13  as well as to improve the intimate contact between the IC chip  11  and the base  13 . 
       FIG. 7  is a sectional view of an RFID tag according to a fourth embodiment of the present invention. 
     In the RFID tag  1 D shown in  FIG. 7 , a plastic filler  24  having a diameter slightly smaller than the height of the bumps  16  is blended with an adhesive (not shown). When the IC chip  11  with the bumps  16  is connected to the antenna  122 , the plastic filler  24  functions as a stopper to limit sinking of the bumps  16 . 
       FIG. 8  is a sectional view of an RFID tag according to a fifth embodiment of the present invention. 
     In the RFID tag  1 E shown in  FIG. 8 , a hard resin layer  25  is provided between the base  13  formed of a PET and the antenna  122 . When the IC chip  11  with the bumps  16  is connected to the antenna  122 , sinking of the bumps  16  is limited thanks to the existence of the hard resin layer  25 . 
       FIG. 9  is a sectional view of an RFID tag according to a sixth embodiment of the present invention. 
     In the RFID tag  1 F shown in  FIG. 9 , a PET sheet  26  harder than the base  13  is placed between the base  13  formed of a PET and the antenna  122 . When the IC chip  11  with the bumps  16  is connected to the antenna  122 , sinking of the bumps  16  is limited thanks to the existence of the hard PET sheet  26 , as in the case of the RFID tag  1 E shown in  FIG. 8 . 
       FIG. 10  is a sectional view of an RFID tag according to a seventh embodiment of the present invention. 
     In the RFID tag  1 G shown in  FIG. 10 , supports  27  made of a metal are disposed on the portions of the antenna  122  on the base  13  which correspond to the positions of the bumps  16 . The bumps  16  are directly connected to the supports  27  and connected to the antenna  122  through the supports  27 . In the case of this RFID tag  1 G, sinking of the bumps  16  is prevented thanks to the existence of the supports  27 . 
       FIG. 11  is a sectional view of an RFID tag according to an eighth embodiment of the present invention. 
     In the RFID tag  1 H shown in  FIG. 11 , the Ag filler filling factor of bump mount portions  122   a  of the antenna  122  to be connected to the bumps  16  is increased relative to that of the portion other than the bump mount portions  122   a  so that the bump mount portions  122   a  are higher in hardness than the other portion, thereby limiting sinking of the bumps  16  when the antenna  122  receives the pressing force from the bumps  16 . 
       FIG. 12  is a sectional view of base and antenna portions of an RFID tag according to a ninth embodiment of the present invention. 
     Any fault due to the above-described sinking has not been considered in the conventional techniques. Thus, typically, when adopting a paste as the material of the antenna  122 , blending of a filler with the paste, e.g., blending of an Ag filler or the like with a resin material such as an epoxy resin shown in Part (A) of  FIG. 12 , has been performed mainly for the purpose of giving the necessary conductivity to the paste so that the paste functions as the antenna. 
     In contrast, in the case of the RFID tag  1 I having the base and the antenna shown in Part (B) of  FIG. 12 , a filler such as an Ag filler for giving the necessary conductivity to the paste so that the paste functions as the antenna is blended with a resin material such as an epoxy resin, and a filler  28  for giving the necessary hardness to the antenna formed of the paste, e.g., Cu, Pd or Ni is also blended with the resin material. An antenna  122   b  is formed by using the paste in which such fillers are blended. In this way, sinking of the bumps  16  caused by the pressing force from the bumps  16  is prevented. 
     Methods of manufacturing the various RFID tags  1 A to  1 I described above will now be described. 
       FIGS. 13(A) to 13(C)  illustrate a method of forming the bumps on the electrodes of the IC chip. 
     First, a thin metal wire  30  to be formed as bumps is caused to project from the tip of a jig  20  with a hole, as shown in  FIG. 13(A) , and electric discharge is caused between the thin metal wire  30  and a discharge electrode  40 . A portion of the thin metal wire  30  at the tip is molten by the discharge energy to form a metal ball  31 . 
     Subsequently, the metal ball  31  is pressed against the electrode  111  of the IC chip  11  and ultrasonic waves are applied to the metal ball  31  through the jig  20 , as shown in  FIG. 13(B) . The metal ball  31  is joined to the electrode  111  of the IC chip  11  by the ultrasonic waves. When the jig  20  is removed, the metal ball  31  and the thin metal wire  30  at the foot are torn off to form the bump in original form  32  on the electrode  111  of the IC chip  11 , as shown in  FIG. 13(C) . 
       FIG. 14  is a diagram showing a method of leveling the bump, and  FIGS. 15(A) to 15(C)  are diagrams showing the bump after leveling. 
     After being formed on the electrode  111  of the IC chip  11  as shown in  FIG. 13 , the bump in original form  32  is pressed on a flat surface of a glass plate  50 , as shown in  FIG. 14 . The load for this pressing and the pressing height are selected to change the shape of the bump. That is, the bump  16  having the shape shown in  FIG. 15(A)  is formed in the case of low-load high-position pressing; the bump  16  having the shape shown in  FIG. 15(B)  is formed in the case of medium-load medium-position pressing; and the bump  16  having the shape shown in  FIG. 15(C)  is formed in the case of high-load low-position pressing. 
       FIGS. 16(A) to 16(D)  show a method of manufacturing the RFID tag having the stopper formed of the polyimide film with holes shown in  FIG. 3 . 
     The polyimide film  21  is formed on the surface of the IC chip  11  on which the electrodes  111  are provided (FIG.  16 (A)), and only portions of the polyimide film  21  corresponding to the electrodes  111  are removed by laser machining or etching, thereby forming the polyimide film  21  having holes  212  formed in correspondence with the electrodes  111  on which bumps will be formed ( FIG. 16(B) ). Thereafter, the bumps in original form  32  are formed on the electrodes  111  by the method shown in  FIGS. 13(A) to 13(C) , as shown in  FIG. 16(C) . Leveling is performed on the bumps in original form  32  by the method shown in  FIG. 14  and  FIGS. 15(A) to 15(C)  to form the bumps  16  slightly higher in height than polyimide film  21 . The bumps  16  facing the base  13  and the antenna  122  are connected to each other ( FIG. 16(D) ). At this time, the polyimide film  21  functions as a stopper to limit sinking of the bumps  16 . 
       FIGS. 17(A) to 17(C)  show a method of manufacturing the RFID tag having the stopper formed of a PET with holes as shown in  FIG. 4 . 
     The PET member  22  with holes  221  is prepared (FIG.  17 (A)), and is applied to the base  13  on which the antenna  122  is formed, the holes  221  being aligned with the bump connection portions ( FIG. 17(B) ). The IC chip  11  is thereafter mounted ( FIG. 17(C) ). At this time, the PET member  22  functions as a stopper to prevent sinking of bumps  16 . 
       FIGS. 18(A) to 18(C)  show a method of manufacturing the RFID tag having the stopper shown in  FIG. 5 . 
     A film  231  made of an insulating material is formed on the surface of the base  13  on which the antenna  122  is formed ( FIG. 18(A) ). As the material of this film  231 , polyethylene, epoxy, polyester or the like for example can be used. The film  231  thereby formed has a thickness slightly smaller than the height of bumps  16  formed afterward. Unnecessary portions of the film  231  are removed by chemical etching and only a portion of the film  231  adjacent to the portions of the antenna  122  to be connected to the bumps are left, thereby forming the stopper portion  23  on the base  13  ( FIG. 18(B) ). The IC chip  11  with bumps  16  is mounted on the base  13  and the bumps  16  and the antenna  122  are connected to each other. Since the stopper portion  23  is formed so as to be slightly lower in height than the bumps  16  before connection, the bumps  16  are connected to the antenna  122  with reliability, and sinking of the bumps  16  is prevented by the function of the stopper portion  23 . 
     While the method of manufacturing the RFID tag according to the third embodiment shown in  FIG. 5  has been described with reference to  FIGS. 18(A) to 18(C) , the RFID tag shown in  FIGS. 6(A) to 6(C)  as an example of modification of the third embodiment can also be manufactured by forming the stopper portion  23  whose shape however is the one shown in  FIG. 6(B) . 
       FIGS. 19(A) and 19(B)  show a method of manufacturing the RFID tag including the plastic filler shown in  FIG. 7 . 
     As shown in  FIG. 19(A) , the adhesive  15  in which the plastic filler  24  is blended is applied to a portion of the base  13  on which the antenna  122  is formed. The portion of the base  13  to which the plastic filler  24  is applied is adjacent to the portions to be connected to the bumps and is defined at such a position that the filler does not spread to the portions to be connected to the bumps. This application is performed by supplying the adhesive containing the plastic filler  24  from a nozzle tip onto the base  13 . 
     Thereafter, the IC chip  11  with bumps  16  is mounted on the base  13  and the bumps  16  and the antenna  122  are connected to each other, as shown in  FIG. 19(B) . At this time, however, since the plastic filler  24  has a diameter slightly smaller than the height of the bumps  16 , the bumps  16  are connected to the antenna  122  with reliability, and the plastic filler  24  functions as a stopper to prevent sinking of the bumps  16 . 
       FIGS. 20(A) to 20(D)  show a method of manufacturing the RFID tag shown in  FIG. 8 . 
     In this case, a hard resin sheet  251  is prepared ( FIG. 20(A) ) and a hard resin layer  25  is formed by adhering the hard resin sheet  251  to the base  13  by an adhesive  252  ( FIG. 20(B) ). 
     Thereafter, a printing master  80  in which a hole is formed as a pattern for the antenna  122  is placed on the hard resin sheet  251 , and a paste  83  provided as the material of the antenna  122  is printed by being forced into the hole of the printing master  80  with a squeegee  81  ( FIG. 20(C) ). 
     Thereafter, the printing master  80  for forming the protrusion is removed, followed by drying. The antenna  122  is thereby formed. 
     As the printing master  80 , a thin Al or SUS plate or the like having holes formed at desired positions by etching can be used. 
     No method has been described with respect to making of the antenna  122  in the description of the other embodiments since the technique for printing the paste is well known. However, the same method as that described above can be used to form the antenna  122  in the other embodiments. 
     After the antenna  122  has been printed on the hard resin layer  25 , the IC chip  11  is mounted with the bumps  16  pressed on the antenna  122 , as shown in  FIG. 20(D) . At this time, sinking of the bumps  16  is prevented thanks to the existence of the hard resin layer  25 . 
       FIGS. 21(A) to 21(D)  show a method of manufacturing the RFID tag shown in  FIG. 9 . 
     In this case, a PET sheet  26  harder than the base  13  formed of a PET is prepared ( FIG. 21(A) ). The hard PET sheet  26  is adhered to the base  13  by the adhesive  252  ( FIG. 21(B) ). As the material of the base  13 , a polypropylene-based soft PET is used. As the hard PET sheet  26  adhered to the base  13 , a polyester or nylon sheet can be used. 
     The subsequent manufacturing steps are the same as those shown in  FIGS. 20(C) and 20(D) . The antenna  122  is printed on the PET sheet  26  ( FIG. 21(C) ) and the IC chip  11  is mounted ( FIG. 21(D) ). At the time of this mounting, sinking of the bumps  16  is prevented thanks to the existence of the hard PET sheet  26 . 
       FIGS. 22(A) to 22(D)  show a method of manufacturing the RFID tag shown in  FIG. 10 . 
     In this case, after the antenna  122  has been printed on the base  13  (FIG.  22 (A)), an electroconductive adhesive or a pressure-sensitive adhesive  271  is supplied to the portion of the antenna  122  to be connected to the bumps ( FIG. 22(B) ) and the metallic supports  27  are adhered to the surface of the antenna  122  ( FIG. 22(C) ). Thereafter, the IC chip  11  is mounted so that the bumps  16  are placed on the supports  27  ( FIG. 22(D) ). At the time of this mounting, sinking of the bumps  16  is prevented thanks to the existence of the supports  27 . 
       FIGS. 23(A) to 23(C)  show a method of manufacturing the RFID tag shown in  FIG. 11 . 
     In this case, a printing mask  801  for printing the portion of the antenna other than the bump mount portions to be connected to the bumps is prepared and this portion is printed on the base  13  by using a squeegee  81  and a printing paste  83  in which an Ag filler is blended with a resin material such as an epoxy resin ( FIG. 23(A) ). Thereafter, a printing mask  802  for printing the bump mount portions of the antenna is prepared and the bump mount portions are printed on the base  13  by using the squeegee  81  and a printing paste  831  in which the Ag filler blending ratio is changed so that the hardness is increased in comparison with the paste  83  used for printing of the portion other than the bump mount portions ( FIG. 23(B) ). After the antenna  122  including the bump mount portions  122   a  has been formed in this manner, the IC chip  11  is mounted on the base  13  ( FIG. 23(C) ). At the time of this mounting, sinking of the bumps  16  is prevented because the bump mount portions  122   a  to which the bumps  16  are connected have high hardness. 
       FIGS. 24(A) and 24(B)  show a method of manufacturing the RFID tag shown in  FIG. 12 . 
     In this case, the antenna is printed on the base  13  by using as the material of the antenna a paste  832  in which a filter such as a Cu, Pd or Ni filler for hardening to a level high enough to effectively limit sinking of the bumps is blended with a resin material such as an epoxy resin as well as an Ag filler for giving the necessary conductivity for the antenna to the resin material ( FIG. 24(A) ). Thereafter, on the base  13  on which the hard antenna  122   b  has been formed, the IC chip  11  is mounted so that the bumps  16  formed on the IC chip  11  and the antenna  122   b  are connected to each other ( FIG. 24(B) ). At this time, sinking of the bumps  16  is prevented because the antenna  122   b  has sufficiently high hardness.