Abstract:
An IC tag includes a plane coil which is made by a conductor wire coated with an insulator wound several times in a plane, the plane coil having terminal portions and defining a central vacant area encircled by the wound wires. A semiconductor element is arranged in the central vacant area and placed in the plane and having a thickness substantially same as or smaller than a thickness of the plane coil, the semiconductor element having electrodes which are electrically connected to the terminal portions of the plane coil.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an IC tag or a unit electronics module including a semiconductor element and an antenna coil electrically connected to the semiconductor element, hereinafter referred simply to an “IC tag”, and also relates to a method for the production such an IC tag.  
           [0003]    2. Description of the Related art  
           [0004]    The IC tag is constituted by mounting a semiconductor element onto a substrate in which an antenna circuit is formed, and is capable of readily identifying an article, or another item, carrying the IC tag by the identification data stored therein. Since the IC tags are identifiable in a non-contact manner, they are conveniently and efficiently usable. Also, since a larger amount of information can be stored in the IC tag than in other identification means such as bar codes, a large number of articles can be effectively identified in comparison with the latter. In fact, for example, a large amount of freight has conventionally been classified in the transport industry by attaching an IC tag to each piece of the freight.  
           [0005]    [0005]FIG. 13 shows one example of prior art IC tags. In this IC tag, an antenna pattern  12  is formed in an area of a rectangular substrate  10 , and a semiconductor element  14  mounted on the substrate  10  is electrically connected to the antenna pattern  12 . The semiconductor element  14  is shielded with resin  16 . The substrate  10  may be a printed circuit board, a film substrate or the like.  
           [0006]    Since the IC tags are generally disposable and consumed in large numbers, it is desired that they can be easily produced at low cost. In this respect, the above-mentioned prior art IC tag has a drawback in that an etching process is necessary for forming the antenna pattern  12 . This means that the production cost for producing the IC tags cannot be lowered. More specifically, a method wherein a substrate clad with copper on one side thereof is used and the copper is etched to form the antenna pattern  12  is improper as a method for extremely inexpensively producing the IC tag although it is simple as a production process.  
           [0007]    Also, since the IC tags may be used for various applications, it is required to form the IC tag as small and thin as possible. For example, if the IC tag were as small in size as a postage stamp, it would be possible to adhere the IC tag to an article like a postage stamp. Contrarily, since the prior art IC tag is of a structure wherein the semiconductor element  14  is mounted onto the substrate  10 , there is a lower limit to the size of the IC tag.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention has been made to solve the above drawbacks in the prior art IC tags. Accordingly, an object of the present invention is to provide an IC tag which is thinner, smaller and more compact in size and can be produced at a lower cost than the prior art IC tag, and to provide a method for the production thereof.  
           [0009]    According to the present invention, there is provided an IC tag comprising: a plane coil comprising a conductor wire coated with an electrically insulating layer, the wire being wound several times in a plane to form a spiral loop of wire, the plane coil having respective terminal portions and defining a central vacant area encircled by the wound wire; and a semiconductor element having a thickness substantially same as a thickness of the plane coil and arranged in the central vacant area in the plane, the semiconductor element having electrodes which are electrically connected to the respective terminal portions of the plane coil.  
           [0010]    The semiconductor element may be accommodated in a protective frame, which has a thickness substantially same as the thickness of the semiconductor element, and may be flatly arranged in the central vacant area of the plane coil.  
           [0011]    The semiconductor element may be supported on and adhered to one of surfaces of an adhesive film to which the plane coil is also adhered.  
           [0012]    The adhesive film may have first and second adhesive layers on the respective surfaces thereof, and the plane coil and the semiconductor element may be adhered to the first adhesive layer, while the second adhesive layer is covered with a removable film.  
           [0013]    The semiconductor element may be held in position by means of a resin filled in a gap between an outer circumference of the semiconductor element and an inner periphery of the plane coil.  
           [0014]    The semiconductor element may be supported in position only by a tightening force of the plane coil.  
           [0015]    The wire of the plane coil may be wound in such a manner that adjacent loops of wire are in contact with each other.  
           [0016]    The wire of the plane coil may be further coated with a hot-melting or fusing layer so as to cover the electrically insulating layer of the wire, so that the adjacent loops of wire are tightly connected to each other by means of the hot-melted or fused layer.  
           [0017]    Adjacent loops of wire may be tightly connected to each other by means of a resin which is filled in a gap between outer surfaces of the loops of wire.  
           [0018]    The electrodes of the semiconductor element may be electrically connected to the terminal portions of the plane coil by means of a connecting pattern formed with an electrically conductive paste.  
           [0019]    According to another aspect of the present invention, there is provided a method of producing an IC tag comprising the following steps of: winding a conductor wire coated with an insulator several times in a plane so as to form a plane coil to define a spiral loop of wire and a central vacant area encircled by the wound wire in which a semiconductor element can be arranged; adhering a support film to one of surfaces of the plane coil so as to cover at least central vacant area; arranging the semiconductor element in the central vacant area of the plane coil so that the semiconductor element is supported by the support film; and electrically connecting the semiconductor element to the plane coil.  
           [0020]    According to a still another aspect of the present invention there is provided a method of producing an IC tag comprising the following steps of: clamping a semiconductor element in a thickness direction thereof between a pair of flat clamping jigs;  
           [0021]    forming a plane coil by winding a conductor wire coated with an insulator several times within a gap defined between the pair of clamping jigs around an outer circumference of the semiconductor element while it is being clamped by the jigs so that adjacent loops of wire are in contact with each other; and electrically connecting the semiconductor element to the plane coil.  
           [0022]    According to further aspect of the present invention, there is provided a method of producing an IC tag comprising the following steps of: clamping a semiconductor element and a protective frame in a thickness direction thereof between a pair of flat clamping jigs in such a manner that the semiconductor element is encircled by the protective frame; forming a plane coil by winding a conductor wire coated with an insulator several times within a gap defined between the pair of clamping jigs around an outer circumference of the protective frame during the frame is being clamped by the jigs so that adjacent loops of wire are in contact with each other; and electrically connecting the semiconductor element to the plane coil. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    FIGS.  1 ( a ) and  1 ( b ) are a plan view and a sectional view, respectively, of an IC tag according to the present invention;  
         [0024]    FIGS.  2 ( a ) to  2 ( c ) are plan views, respectively, for illustrating processes for producing the IC tag according to the present invention;  
         [0025]    FIGS.  3 ( a ) to  3 ( d ) are sectional views, respectively, for illustrating processes for producing the IC tag according to the present invention;  
         [0026]    [0026]FIG. 4 illustrates a method for producing the IC tag according to the present invention;  
         [0027]    [0027]FIG. 5 is a sectional view showing that wire portions of the IC tag are bonded to each other;  
         [0028]    FIGS.  6 ( a ) and  6 ( b ) are a plan view and a sectional view, respectively, of a core in which a semiconductor element is protected by a protection frame;  
         [0029]    [0029]FIG. 7 illustrates a method for winding a wire on the core in which the semiconductor element is protected by the protection frame;  
         [0030]    [0030]FIG. 8 is a plan view of another embodiment of an IC tag according to the present invention;  
         [0031]    FIGS.  9 ( a ) and  9 ( b ) illustrate another method for producing the IC tag according to the present invention;  
         [0032]    [0032]FIG. 10 is a sectional view of a further embodiment of an IC tag according to the present invention;  
         [0033]    [0033]FIG. 11 is a plan view of the further embodiment of the IC tag according to the present invention;  
         [0034]    [0034]FIG. 12 is a sectional view of an IC tag which can be adhered to an article according to the present invention; and  
         [0035]    FIGS.  13 ( a ) and  13 ( b ) are a plan view and a side view, respectively, of a prior art IC tag. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]    The present invention will be described in more detail below with reference to the preferred embodiments illustrated in the attached drawings.  
         [0037]    FIGS.  1 ( a ) and  1 ( b ) illustrate a plan view and a sectional view of a first embodiment of an IC tag according to the present invention. The IC tag of this embodiment is of a structure in which a plane coil  20  formed by flatly winding a wire  18  around the outer circumference of a thin semiconductor element  14  in the same plane as that of the semiconductor element  14 . As shown in FIG. 1( b ), a diameter of the wire  18  forming the plane coil  20  is selected to be generally equal to or less than a thickness of the semiconductor element  14 , and the semiconductor element  14  is accommodated in a vacant space defined at a center of the plane coil  20 . Thus, the IC tag can be formed as a planar body which is small in total size.  
         [0038]    Reference numeral  22  denotes a carrier film for supporting the semiconductor element  14  while accommodating the same within a central vacant space of the plane coil  20 . The carrier film  22  is adhered to one side of the plane coil  20  to cover substantially all the side. The semiconductor element  14  is adhesively supported by the carrier film  22 . Reference numeral  24  denotes connection patterns for electrically connecting terminals of the semiconductor element  14  with opposite ends of the plane coil  20 , respectively. The connection patterns  24  are formed between the semiconductor elements  14  and the opposite ends of the plane coil  20  by linearly coating an electro-conductive paste. The electro-conductive paste is a resinous material such as epoxy or polyimide containing an electro-conductive filler such as silver. Reference numeral  25  denotes a protective resin filled in a gap formed between an outer circumference of the semiconductor element  14  and an inner circumference of the plane coil  20 .  
         [0039]    The plane coil  20  disposed on the circumference of the semiconductor element  14  acts as an antenna pattern, through which information stored in the semiconductor element  14  is detected and identified in a non-contact manner by an external detector. A function of the plane coil  20  as an antenna pattern is optionally adjustable by suitably selecting the number of windings (loops) of the plane coil  20 , an area of the plane coil  20 , a diameter of the wire  18  used for the plane coil  20  or other factors.  
         [0040]    The IC tag according to this embodiment can be formed in an extremely small size because the plane coil  20  is disposed in the vicinity of the semiconductor element  14 . Also, since the plane coil  20  is formed by closely winding a wire  18  so that any portion of the wire  18  is brought into contact with other portion thereof, the antenna pattern can be arranged at a high density, which further facilitates the compactness of the IC tag. In addition, since the plane coil  20  is arranged in the same plane as the semiconductor element  14  and formed generally equal to or smaller than the semiconductor element  14  in thickness, it is possible to have an extremely thin IC tag. Semiconductor elements  14  as thin as 50 to 100 μm are available nowadays, and those of such a small thickness can be used for providing convenient IC tags usable as a seal to be adhered to articles.  
         [0041]    [0041]FIGS. 2 and 3 show a method for producing the above-mentioned IC tag. That is, according to this method for the production of IC tag, a wire  18  is first wound to form a plane coil  20 . FIGS.  2 ( a ) and  3 ( a ) are plan view and a sectional view, respectively, of the plane coil  20  thus formed. The plane coil  20  is formed in one plane to have a vacant space at a center thereof for accommodating the semiconductor element  14 .  
         [0042]    FIGS.  2 ( b ) and  3 ( b ) are a plan view and a sectional view, respectively, showing a state wherein a carrier film  22  is adhered to one side of the plane coil  20  to cover generally all the side. The carrier film  22  has an adhesive layer on the side to be adhered to the plane coil  20  and must be adhered to the plane coil  20  to cover at least the vacant space formed at the center thereof.  
         [0043]    [0043]FIG. 3( c ) is a sectional view showing a state wherein the semiconductor element  14  is then mounted to the vacant space formed at the center of the plane coil  20 . The semiconductor element  14  is supported by the carrier film  22  while adhered thereto via the adhesive layer. FIGS.  2 ( c ) and  3 ( d ) are a plan view and a sectional view, respectively, of a state wherein terminals of the semiconductor element  14  are electrically connected to opposite ends of the plane coil  20 , respectively, via connection patterns  24 . As described hereinbefore, the connection patterns  24  may be formed by linearly coating an electro-conductive paste. Instead of coating the electro-conductive paste, the terminals of the semiconductor element  14  may be wire-bonded to the ends of the plane coil  20 . Alternatively, a film having a conductor pattern on one side thereof may be adhered to the plane coil  20  with the semiconductor element  14  being electrically connected to the respective ends of the plane coil  20  via the conductor pattern.  
         [0044]    In this respect, when the protective resin  25  is filled between the outer circumference of the semiconductor element  14  and the inner circumference of the plane coil  20 , the semiconductor element  14  is further securely fixed, although this resin  25  is not indispensable. To further protect the semiconductor element  14 , there is also another method in that, after the semiconductor element  14  has been mounted to the carrier film  22  and the connection patterns  24  have been formed, a resin film may be adhered to the side of the semiconductor element  14  on which the connection patterns  24  are formed, to cover the semiconductor element  14  and the plane coil  20 . A suitable method may be selected from these methods, as mentioned above, in view of the production cost, or other factors, of the IC tag.  
         [0045]    [0045]FIGS. 4 and 5 show a method for forming the plane coil  20  from the wire  18 .  
         [0046]    In FIG. 4, a pair of jigs  26   a ,  26   b  are used for forming the plane coil  20 , wherein a core block  28  is fixed at a center of the lower jig  26   b  to support the upper jig  26   a  to be movable relative to the lower jig in the opening and closing direction. The jigs  26   a ,  26   b  and the core block  28  are driven to rotate as a whole about a center line by means of a rotating mechanism. The jigs  26   a ,  26   b  are formed to have opposed flat surfaces between which is defined a gap allowing a single wire  18  alone to pass therethrough when the jigs are in the closed state.  
         [0047]    The core block  28  is provided for the purpose of providing the vacant space for accommodating the semiconductor element  14  at a center of the plane coil  20 . Reference numeral  27  denotes a fixation hole formed at a position on the upper jig  26   a  closer to the center thereof. One end of the wire  18  is inserted into the fixation hole  27  and secured thereto.  
         [0048]    The method for forming the plane coil  20  by the jigs  26   a ,  26   b  according to this embodiment is as follows; one end of the wire  18  is inserted into the fixation hole  27  and secured thereto, and the jigs  26   a ,  26   b  and the core block  28  are driven to rotate about the center line while the jigs  26   a ,  26   b  are in the closed state, whereby the wire  18  is sequentially drawn into the gap and wound around the outer circumference of the preceding loop portion of the wire on the core block  28  to form a plane coil  20 .  
         [0049]    Such a wire is used for the wire  18  in this embodiment as consisting of a copper core  18   a  covered with an electro-insulating layer  18   b  such as polyurethane which is further covered with a hot-melting or fusing layer  18   c  such as polyamide. After the plane coil  20  has been formed, the wire  18  is heated so that the adjacent wire portions are bonded to each other via the fusing layer  18   c . The plane coil  20  shown in FIGS.  2 ( a ) and  3 ( a ) is a coil wherein the wire  18  is wound in a planar form and heated so that the adjacent portions are fusion-bonded together.  
         [0050]    Even in a state wherein the adjacent wire portions of the wire  18  are bonded together via the fusing layer  18   c , the wire  18  is covered with the electro-insulating layer  18   b  to prevent a short-circuit between the adjacent portions of the wire  18  from occurring. Also when the connection patterns  24  are formed by using the electro-conductive paste, the short-circuit between the adjacent portions of the wire  18  is avoidable since the wire is covered with the electro-insulating layer  18   b.    
         [0051]    In this regard, if the short-circuit is assuredly avoidable between the adjacent portions of the wire  18  by the fusing layer  18   c  alone, it is unnecessary to provide the electro-insulating layer  18   b  on the core  18   a.    
         [0052]    By heating the jigs  26   a  and  26   b  before the wire  18  is flatly wound to form the plane coil  20 , it is possible to bond the adjacent portions of the plane coil  20 , via the fusing layer  18   c , with each other.  
         [0053]    Also, the wire  18  solely provided with the electro-insulating layer  18   b  on the outer circumference of the core  18   a  may be used while coating a fixing adhesive on the wire  18  during the formation of the plane coil  20  by rotating the jigs  26   a ,  26   b  and the core block  28  to result in the integral plane coil  20 .  
         [0054]    In the IC tag of the above-mentioned embodiment, the semiconductor element  14  is mounted after the plane coil  20  having the vacant space has been formed. However, the plane coil  20  may be formed while using the semiconductor  14  itself or a protective frame  30  protecting the outer circumference of the semiconductor element  14  as a core for forming the plane coil  20 .  
         [0055]    FIGS.  6 ( a ) and  6 ( b ) show a core wherein the protective frame  30  is attached to the outer circumference of the semiconductor element  14 . The protective frame  30  has substantially the same thickness as the semiconductor element  14  and is provided at a center thereof with a hole for accommodating the semiconductor element  14 . Although the contour of the protective frame  30  is circular in this embodiment, it is not limited thereto but may be, for example, rectangular and similar to the outline of the semiconductor element  14 . Also, the protective frame  30  may be formed of any material provided that it has a sufficient strength to protect the semiconductor element  14 , such as polyethylene terephthalate, polycarbonate or ferrite.  
         [0056]    [0056]FIG. 7 illustrates a method for forming the plane coil  20  while using the semiconductor element  14 , the outer circumference of which is protected by the protective frame  30 , as a core, wherein the core is clamped by the pair of jigs  26   a ,  26   b  and the wire  18  is flatly wound around the core in a similar manner as in FIG. 4.  
         [0057]    By winding the wire  18  around the core in which the outer circumference of the semiconductor element  14  is protected by the protective frame  30 , the core is held by a fastening force of the plane coil  20  so that a product, wherein the semiconductor element  14  is integral with the plane coil  20 , is obtainable. If the wire  18  has the fusing layer  18   c  on the outer side thereof, the integrity of the semiconductor element  14  and the plane coil  20  is further enhanced by heating the assembly thereof because the plane coil  20  is fusion-bonded to the protective frame  30 .  
         [0058]    [0058]FIG. 8 shows an IC tag formed by winding the wire  18  around the outer circumference of the core accommodating the semiconductor element  14  and then electrically connecting the semiconductor element  14  to the opposite ends of the plane coil  20  via the connection patterns  24 .  
         [0059]    According to this method, there is an advantage in that the integrity of the semiconductor element  14  with the plane coil  20  is further enhanced since the winding force of the wire  18  can be increased because the semiconductor element  14  is protected by the protective frame  30 . The IC tag of this embodiment necessitates no carrier film  22  as shown in FIG. 1( b ).  
         [0060]    In this regard, if the semiconductor element  14  itself has a sufficient rigidity to withstand the operation for winding the wire  18 , it is possible to form the IC tag by flatly winding the wire  18  directly around the semiconductor element  14  which is used as a core without protecting the same by the protective frame  30 . When the semiconductor element  14  is used as a core, the wire  18  can be wound around the outer circumference of the semiconductor element  14  in a similar manner as shown in FIG. 7.  
         [0061]    FIGS.  9 ( a ) and  9 ( b ) show another method for winding the wire  18  around the outer circumference of the semiconductor element  14  while using the latter as a core. According to this method, the wire  18  is wound while being supplied with an adhesive resinous material to form the plane coil  20 . As shown in FIG. 9( a ), the winding of the wire  18  around the outer circumference of the semiconductor element  14  is started. Clamp surfaces of the jigs  26   a ,  26   b  are covered with films  42 ,  42  to prevent a resinous material  40  from sticking to the surfaces of the jigs  26   a  and  26   b . The resinous material  40  is supplied from a nozzle  41  to the wire  18  to coat the surface thereof when the wire  18  is drawn into the gap between the rotating jigs  26   a ,  26   b.    
         [0062]    In FIG. 9( b ), the wire  18  has been wound around the outer circumference of the semiconductor element  14  while being clamped via the films  42  by the jigs  26   a ,  26   b  rotating about the center line. The semiconductor element  14  and the wire  18  are bonded together with the resinous material  40  filled between both the films  42  and the outer circumference of the wire  18 .  
         [0063]    [0063]FIGS. 10 and 11 show a sectional view and a plan view, respectively, of the planar structure of the IC tag in which the semiconductor element  14  is electrically connected with the opposite ends of the plane coil  20  via the connection patterns  24 .  
         [0064]    As shown in FIG. 10, the IC tag according to this embodiment includes the plane coil  20  fixed around the semiconductor element  14  with the resinous material  40  wherein opposite sides of the semiconductor element  14  and the plane coil  20  are covered with the films  42 . The films  42 ,  42  are provided for protecting the clamp surfaces of the jigs  26   a  and  26   b  (FIG. 9( a )) and left on the resultant product, as they are, while being adhered to the semiconductor element  14  and the plane coil  20  in this embodiment. One of the films  42  is provided with through-holes for exposing the electrodes of the semiconductor element which are electrically connected to the connection patterns  24  by means of the through-holes. Of course, the films  42 ,  42  may be removed after the plane coil  20  has been formed by the jigs  26   a ,  26   b , to obtain the IC tag not covered with the films  42 ,  42 . Also in the method of this embodiment, the protective frame  30  may be attached to the outer circumference of the semiconductor element  14  and used as a core, around which the wire  18  is wound.  
         [0065]    [0065]FIG. 12 shows a structure of an IC tag which is easily attachable onto an article such as a piece of freight. The IC tag in this embodiment includes a carrier film  22  to be adhered to the plane coil  20 , having an adhesive layer  50   a  provided on the outer side of the carrier film  22  and covered with a releasable film  50 . By providing the adhesive layer  50   a  on the outer side of the carrier film  22  in such a manner, it is possible to readily adhere the IC tag onto the article of the freight only by releasing the releasable film  50  upon the use, whereby the convenience of the IC tag is furthermore enhanced.  
         [0066]    As described above, according to the IC tag and the method for producing the same in the present invention, since the plane coil  20  is formed by flatly winding the wire  18  in combination with the semiconductor element  14 , the material cost is low and the production process becomes simple to obtain the IC tag at an extremely low cost. Since the plane coil  20  is formed around the outer circumference of the semiconductor element  14 , it is possible to easily obtain the IC tag small in size and in thickness.  
         [0067]    The IC tag of the present invention can be provided as an extremely thin IC tag because the plane coil is formed as an antenna pattern around the outer circumference of the semiconductor element by a wire having a diameter substantially equal to or smaller than a thickness of the semiconductor element, as described before. Also, since the plane coil formed by closely winding the wire is disposed close to the outer circumference of the semiconductor element, on IC tag extremely small in size can be obtained. According to the method for producing the IC tag in the present invention, the plane coil is formed by simply winding the wire, resulting in the IC tag effectively produced at a low cost.  
         [0068]    It should be understood by those skilled in the art that the foregoing description relates to some of the preferred embodiments of the disclosed invention, and that various changes and modifications may be made to the invention without departing the sprit and scope thereof.