Patent Publication Number: US-2011073648-A1

Title: Reader/writer and manufacturing method thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a reader/writer for reading and writing information on IC tags and IC cards in a non-contact manner and a manufacturing method thereof. 
     2. Description of the Related Art 
     Nowadays, IC tags (also referred to as RFID tags) and IC cards are attached to objects of products and substances (hereafter referred to as objects) for information management. Information about the objects obtained from the IC tags via a reader/writer is managed using a computer in order to improve the efficiency of business. 
       FIG. 1  is a plan view showing a conventional reader/writer. As shown in  FIG. 1 , a reader/writer  100  comprises a circuit board  101 , a communication control portion  102 , a matching circuit portion  103 , an antenna  104 , and a mold resin  105 . 
     The circuit board  101  includes a conductor pattern such as wiring, vias (neither is shown in the drawings), and the like. The communication control portion  102 , the matching circuit portion  103 , and the antenna  104  are mounted on the same plane of the circuit board  101 . The communication control portion  102  comprises an IC chip, a passive component such as LCR, and the like and the communication control portion  102  is sealed with the mold resin  105 . The communication control portion  102  is configured to transmit/receive information with IC tags via the antenna  104  and electrically connected to the matching circuit portion  103 . 
     The matching circuit portion  103  is electrically connected to the antenna  104  and the communication control portion  102 . The matching circuit portion  103  is configured to perform matching in accordance with the frequency of electromagnetic waves used for communication and the impedance of input/output. 
     The antenna  104  is disposed on the circuit board  101  such that the antenna  104  surrounds the communication control portion  102 . The antenna  104  is configured to supply. IC tags with electric power and transmit/receive information via electromagnetic induction (refer to Patent document 1, for example).
     Patent Document 1: Japanese Laid-Open Patent Application No. 2005-12673   

     However, in the conventional reader/writer  100 , the communication control portion  102 , the matching circuit portion  103 , and the antenna  104  are mounted on the same plane of the circuit board  101 , so that the size of the circuit board  101  is increased. This is problematic in that miniaturizing the reader/writer  100  is difficult. 
       FIG. 2  is a schematic diagram showing the relationship between a magnetic flux generated from an antenna and an eddy current. In  FIG. 2 , the same components as in the reader/writer  100  shown in  FIG. 1  are provided with the same numerical reference. 
     Further, when the circuit board  101  including the antenna  104  is assumed to be embedded in other device, the circuit board  101  may be disposed on a metallic material  106  (such as other circuit board, a battery, a frame, or the like) due to the restriction of position. In this case, a magnetic flux B 1  generated from the antenna  104  collides with the metallic material  106  and an eddy current I 1  is generated on a surface of the metallic material  106 . Because of the eddy current I 1 , a new magnetic flux B 2  is generated and the magnetic flux B 1  is attenuated. This is problematic in that the reliability of communication between IC tags and the reader/writer  100  is reduced. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the aforementioned problems. 
     It is a general object of the present invention to provide an improved and useful reader/writer and a manufacturing method thereof in which the above-mentioned problems are eliminated. 
     A more specific object of the present invention is to provide a miniaturized reader/writer capable of improving the reliability of communication with IC tags and IC cards, and to provide a manufacturing method thereof. 
     According to one aspect, the present invention provides a reader/writer comprising: a circuit board; a communication control portion mounted on the circuit board and configured to perform communication with IC tags; sealing resin for sealing the communication control portion; and an antenna electrically connected to the communication control portion, in which a resin layer is disposed on the sealing resin, the resin layer having a higher adhesiveness to a conductive film used as the antenna than that of the sealing resin, and the antenna is disposed on the resin layer. 
     According to the present invention, the resin layer is disposed on the sealing resin for sealing the communication control portion, the resin layer having a higher adhesiveness to the conductive film used as the antenna than that of the sealing resin. And the antenna is disposed on the resin layer. Thus, it is possible to improve the adhesiveness between the resin layer and the antenna and to reduce the size of the circuit board, thereby miniaturizing the reader/writer. 
     Further, in the aforementioned structure, resin containing soft magnetic metallic powder may be used as the resin layer. By disposing the resin layer including the resin containing soft magnetic metallic powder between the circuit board and the antenna, it is possible to prevent the generation of an eddy current and improve the reliability of communication between IC tags and the reader/writer. 
     According to another aspect, the present invention provides a method for manufacturing a reader/writer including a communication control portion for communicating with IC tags, sealing resin for sealing the communication control portion, and an antenna electrically connected to the communication control portion mounted on a circuit board. The method comprises the steps of: mounting the communication control portion on the circuit board; forming the sealing resin; forming a resin layer on the sealing resin, the resin layer having a higher adhesiveness to a conductive film used as the antenna than that of the sealing resin; and forming the antenna on the resin layer. 
     According to the present invention, the resin layer is formed on the sealing resin having a poor adhesiveness to the conductive film used as the antenna, the resin layer having a higher adhesiveness to the conductive film used as the antenna than that of the sealing resin. Thus, it is possible to form the antenna above the sealing resin. 
     Moreover, the step of forming other resin layer including resin containing soft magnetic metallic powder may be included between the sealing resin forming step and the resin layer forming step. By forming other resin layer including the resin containing soft magnetic metallic powder between the sealing resin forming step and the resin layer forming step, it is possible to prevent the generation of an eddy current and improve the reliability of communication between IC tags and the reader/writer. 
     According to the present invention, a reader/writer can be miniaturized and the present invention provides a reader/writer capable of improving the reliability of communication with IC tags and IC cards and a manufacturing method thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view showing a conventional reader/writer; 
         FIG. 2  is a schematic diagram showing a relationship between a magnetic flux generated from an antenna and an eddy current; 
         FIG. 3  is a cross-sectional view of a reader/writer according to a first embodiment of the present invention; 
         FIG. 4  is a perspective view of the reader/writer shown in  FIG. 3 ; 
         FIG. 5  is a diagram showing a first step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 6  is a diagram showing a second step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 7  is a diagram showing a third step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 8  is a diagram showing a fourth step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 9  is a diagram showing a fifth step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 10  is a diagram showing a sixth step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 11  is a diagram showing a seventh step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 12  is a diagram showing an eighth step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 13  is a diagram showing a ninth step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 14  is a diagram showing a tenth step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 15  is a diagram showing an eleventh step of manufacturing a reader/writer according to the first embodiment; 
         FIG. 16  is a cross-sectional view of a reader/writer according to a second embodiment of the present invention; 
         FIG. 17  is a schematic diagram showing a magnetic flux generated from an antenna of a reader/writer according to the second embodiment; 
         FIG. 18  is a cross-sectional view of a reader/writer according to a third embodiment of the present invention; 
         FIG. 19  is a diagram showing a first step of manufacturing a reader/writer according to the third embodiment; 
         FIG. 20  is a diagram showing a second step of manufacturing a reader/writer according to the third embodiment; 
         FIG. 21  is a diagram showing a third step of manufacturing a reader/writer according to the third embodiment; 
         FIG. 22  is a diagram showing a fourth step of manufacturing a reader/writer according to the third embodiment; 
         FIG. 23  is a cross-sectional view of a reader/writer according to a fourth embodiment of the present invention; 
         FIG. 24  is a diagram showing a first step of manufacturing a reader/writer according to the fourth embodiment; 
         FIG. 25  is a diagram showing a second step of manufacturing a reader/writer according to the fourth embodiment; 
         FIG. 26  is a diagram showing a third step of manufacturing a reader/writer according to the fourth embodiment; and 
         FIG. 27  is a diagram showing a fourth step of manufacturing a reader/writer according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, embodiments of the present invention will be described with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 3  is a cross-sectional view of a reader/writer according to a first embodiment of the present invention.  FIG. 4  is a perspective view of the reader/writer shown in  FIG. 3 . In  FIG. 4 , a solder resist  31  is omitted for ease of understanding the form of an antenna  26 . 
     First, with reference to  FIGS. 3 and 4 , a reader/writer  10  according to the first embodiment of the present invention is described. The reader/writer  10  comprises a circuit board  11 , via connection terminals  12  and  13 , a communication control portion  14 , sealing resin  19 , a resin layer  22 , a via  25 , the antenna  26 , and the solder resist  31 . 
     In the circuit board  11 , a conductor pattern (not shown in the drawings) is formed including a plurality of lines of wiring, vias, and the like. The circuit board  11  includes a substrate configured to form the via connection terminals  12  and  13  and to mount the communication control portion  14  thereon. The circuit board  11  may employ a printed board, a flexible board, or the like, for example. 
     The via connection terminals  12  and  13  are disposed on the circuit board  11  such that they are electrically connected to the communication control portion  14 . Upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are exposed from the sealing resin  19  and the resin layer  22 . The upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are electrically connected to the vias  25 . Heights H 1  and H 2  of the via connection terminals  12  and  13  are set such that the positions of the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are higher than that of the communication control portion  14 . 
     The via connection terminals  12  and  13  can be formed by depositing a Cu plated film on the wiring of the circuit board  11  in a columnar manner or by installing a columnar copper material, for example. 
     The communication control portion  14  is mounted on the circuit board  11 . The communication control portion  14  transmits/receives information with IC tags and functions as the reader/writer  10  together with the antenna  26 . The communication control portion  14  includes a control circuit portion  15 , an RF circuit portion  16 , and a matching circuit portion  17 . The control circuit portion  15 , the RF circuit portion  16 , and the matching circuit portion  17  are installed on the circuit board  11 , and they comprise a semiconductor chip and a passive element such as LCR connected to the wiring (not shown in the drawings) of the circuit board  11 , for example. 
     The control circuit portion  15  controls the RF circuit portion  16  and performs communication with the IC tags in accordance with a communications protocol. The control circuit portion  15  also functions as an interface between a host computer (not shown in the drawings) and the reader/writer  10 . 
     The RF circuit portion  16  includes a transmission portion for encoding information to be transmitted to the IC tags and modulating carrier waves (electromagnetic waves), an electric power amplifying portion for supplying the IC tags with electric power, and a receiving portion for demodulating information received from the IC tags. 
     The matching circuit portion  17  is configured to adjust the frequencies of the carrier waves used for communication and the impedance of input/output. 
     The sealing resin  19  is used to seal the communication control portion  14  and disposed so as to cover the control circuit portion  15 , the RF circuit portion  16 , and the matching circuit portion  17 . In the sealing resin  19 , opening portions  21  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed. 
     The sealing resin  19  is used to protect the communication control portion  14  from an external impact and the like. The sealing resin  19  has a smooth surface and roughening the surface thereof is difficult. Thus, the sealing resin  19  has a poor adhesiveness to a conductive film formed by a plating method or a sputtering method, so that the conductive film is detached. Accordingly, it is difficult to directly form the conductive film and dispose the antenna  26  on the sealing resin  19 . The sealing resin  19  may employ mold resin, for example. The mold resin generally includes much filler component (not less than 70 wt %). Thus, even when a roughening process is conducted so as to have adhesiveness to plating, the filler is dropped off (collapsed) and an adhesive structure cannot be maintained. In this case, when the plating is applied on the mold resin, the peel strength is as low as 20 to 60 g/cm (the plating is readily peeled off). The mold resin may employ epoxy mold resin formed by a transfer molding method. The epoxy mold resin includes general epoxy resin into which a softener (phenolic novolak resin) and a filler (fused silica, crystalline silica, or the like) are mixed, for example. A diameter D 1  of an upper end of the opening portion  21  may be 30 μm to 500 μm, for example. 
     The resin layer  22  has a higher adhesiveness to the conductive film to be used as the antenna  26  than that of the sealing resin  19 . Also, the resin layer  22  is capable of roughening and disposed so as to cover an upper surface of the sealing resin  19 . By stacking the resin having a good adhesiveness to plating on the mold resin, when the plating is applied on an upper surface of the resin, the peel strength is not less than 600 g/cm and the adhesiveness to the plating is improved. The resin layer to be stacked on the mold resin may employ epoxy resin, phenolic resin, liquid crystal polymer resin, polyimide resin, or the like. For example, when thermosetting epoxy resin is used as the resin layer, the epoxy resin is sufficiently adhered to the mold resin by thermosetting. In the resin layer  22 , opening portions  23  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed. The resin layer  22  may employ epoxy resin; for example. A thickness M 1  of the resin layer  22  may be 20 μm to 60 μm, for example. Further, an opening diameter D 2  of an upper end of the opening portion  23  may be 20 μm to 400 μm, for example. 
     In this manner, by disposing the resin layer  22  on the sealing resin  19 , the resin layer  22  having a higher adhesiveness to the conductive film to be used as the antenna  26  than that of the sealing resin  19  and capable of roughening, it is possible to roughen the surface of the resin layer  22  and form the antenna  26  on the resin layer  22 . Moreover, it is possible to improve the adhesiveness between the resin layer  22  and the antenna  26 . 
     The resin layer  22  may employ resin such as epoxy resin in which metallic particles such as Pd used as a catalyst for plating are dispersed, for example. This improves the adhesiveness between the conductive film (plated film) disposed on the resin layer  22  and the resin layer  22 . 
     The via  25  is disposed at the opening portion  23  formed on the resin layer  22 . A lower end of the via  25  is electrically connected to one of the via connection terminals  12  and  13 . An upper end of the via  25  is electrically connected to one of antenna portion connection terminals  28  and  29 . The via  25  is used to electrically connect the via connection terminals  12  and  13  to the antenna  26 . 
     The antenna  26  is configured to supply IC tags with electric power and transmit/receive information via electromagnetic induction. The antenna  26  is formed on the resin layer  22 . 
     In this manner, by disposing the antenna  26  on the resin layer  22  disposed on the sealing resin  19 , it is possible to reduce the size (area) of the circuit board  11  as compared with the conventional circuit board  101  and miniaturize the reader/writer  10 . 
     The antenna  26  includes an antenna portion  27  and the antenna portion connection terminals  28  and  29 . A thickness M 2  of the antenna  26  may be 10 μm to 25 μm, for example. 
     The antenna portion  27  has a spiral shape and one end portion is connected to the antenna portion connection terminal  28  and the other end portion is connected to the antenna portion connection terminal  29 . The antenna portion connection terminal  28  is disposed on the resin layer  22  and electrically connected to the via  25  connected to the via connection terminal  12 . The antenna portion connection terminal  29  is disposed on the resin layer  22  and electrically connected to the via  25  connected to the via connection terminal  13 . The antenna portion connection terminals  28  and  29  electrically connect the antenna portion  27  to the via connection terminals  12  and  13  via the vias  25 . 
     The solder resist  31  is disposed on the resin layer  22  so as to cover the antenna  26 . The solder resist  31  is used to protect the antenna  26  from an external impact and the like. 
       FIGS. 5 to 15  are diagrams showing steps for manufacturing a reader/writer according to the present embodiment. In  FIGS. 5 to 15 , the same components as in the reader/writer  10  shown in  FIG. 3  are provided with the same numerical reference. 
     In the following, a method for manufacturing the reader/writer  10  according to the present embodiment is described with reference to  FIGS. 5 to 15 . 
     First, as shown in  FIG. 5 , the via connection terminals  12  and  13  are formed on the circuit board  11 , and then the communication control portion  14  (the control circuit portion  15 , the RF circuit portion  16 , and the matching circuit portion  17 ) is mounted on one side of the circuit board  11  on which the via connection terminals  12  and  13  are formed (a step of mounting the communication control portion). In this case, the height H 2  of the via connection terminal  13  is formed to so as to have substantially the same height as the height H 1  of the via connection terminal  12 . 
     The via connection terminals  12  and  13  can be formed by depositing a Cu plated film on the wiring of the circuit board  11  in a columnar manner or by installing a columnar copper material, for example. 
     Next, as shown in  FIG. 6 , the sealing resin  19  is formed so as to cover the via connection terminals  12  and  13  and the communication control portion  14  (a step of forming the sealing resin). A thickness M 3  from the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  to an upper surface  19 A of the sealing resin  19  may be 10 μm to 600 μm, for example. 
     Next, as shown in  FIG. 7 , the opening portions  21  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed on the sealing resin  19 . The opening portions  21  are formed by laser processing, drill processing, or the like, for example. Further the diameter D 1  of the upper end of the opening portion  21  may be 30 μm to 500 μm, for example. 
     Next, as shown in  FIG. 8 , the resin layer  22  for filling the opening portion  21  and covering the upper surface  19 A of the sealing resin  19  is formed (a step of forming the resin layer). The thickness M 1  of the resin layer  22  may be 20 μm to 60 μm, for example. 
     The resin layer  22  may employ epoxy resin, for example. When a resin film is used as the resin layer  22 , for example, the resin layer  22  can be pressure-bonded to the sealing resin  19  by heating/applying pressure using a vacuum laminating machine. The resin layer  22  may be formed by coating the sealing resin  19  with liquid resin and then heat-curing the liquid resin. The resin layer  22  may employ resin such as epoxy resin in which metallic particles such as Pd used as a catalyst for plating are dispersed, for example. 
     Next, as shown in  FIG. 9 , the opening portions  23  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed on the resin layer  22 . Thereafter, the surface of the resin layer  22  is roughened through desmear process. The opening portions  23  are formed by laser processing, drill processing, or the like, for example. The opening diameter D 2  of the upper end of the opening portion  23  may be 20 μm to 400 μm, for example. 
     In this manner, the resin layer  22  having a higher adhesiveness to the conductive film than that of the sealing resin  19  is formed on the sealing resin  19  difficult to be roughened because of the smooth surface thereof and having a poor adhesiveness to the conductive film formed by a plating method, a sputtering method or the like. Thus, it is possible to roughen the resin layer  22  and form the antenna  26  on the resin layer  22 . 
     Next, as shown in  FIG. 10 , a seed layer  33  is formed on the resin layer  22  and on the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  exposed at the opening portions  23 . The seed layer  33  may employ a Cu layer formed by an electroless plating method, for example. 
     Next, as shown in  FIG. 11 , a resist layer  34  including opening portions  34 A and  34 B is formed on the seed layer  33 . The opening portions  34 A correspond to areas where the antenna portion  27  is formed and the opening portions  34 B correspond to areas where the antenna portion connection terminals  28  and  29  are formed. 
     Next, as shown in  FIG. 12 , a conductive metallic film  35  is formed on the seed layer  33  exposed at the opening portions  34 A and  34 B. Accordingly, the via  25  including the seed layer  33  and the conductive metallic film  35  is formed at the opening portions  23 . The conductive metallic film  35  may employ a Cu film formed by an electrolytic plating method, for example. The thickness M 2  of the conductive metallic film  35  may be 10 μm to 25 μm, for example. 
     Next, as shown in  FIG. 13 , the resist layer  34  is removed using a resist releasing agent. Then, as shown in  FIG. 14 , the seed layer  33  is removed from a portion where the conductive metallic film  35  is not formed, thereby forming the antenna  26  (the antenna portion  27  and the antenna portion connection terminals  28  and  29 ) including the seed layer  33  and the conductive metallic film  35  (a step of forming the antenna). 
     In this manner, by forming the antenna  26  on the resin layer  22  formed on the sealing resin  19 , it is possible to miniaturize the reader/writer  10 . 
     Thereafter, as shown in  FIG. 15 , by forming the solder resist  31  on the resin layer  22  so as to cover the antenna  26 , the reader/writer  10  is manufactured. 
     As mentioned above, according to the present embodiment, the resin layer  22  having a higher adhesiveness to the conductive film as the antenna  26  than that of the sealing resin  19  is disposed on the sealing resin  19  for sealing the communication control portion  14  and the antenna  26  is disposed on the resin layer  22 . Thus, it is possible to reduce the size (area) of the circuit board  11  as compared with the conventional circuit board  101  and miniaturize the reader/writer  10 . 
     In the present embodiment, the method for manufacturing the reader/writer  10  is described based on a case where the antenna  26  is formed by a plating method as an example. However, the antenna  26  may be formed by a vacuum deposition method, a sputtering method, a CVD method, or the like besides the plating method. Moreover, the via  25  may directly be connected to the wiring of the circuit board  11  without disposing the via connection terminals  12  and  13 . 
     Second Embodiment 
       FIG. 16  is a cross-sectional view of a reader/writer according to a second embodiment of the present invention.  FIG. 17  is a schematic diagram showing a magnetic flux generated from an antenna of the reader/writer according to the present embodiment. In  FIGS. 16 and 17 , the same components as in the reader/writer  10  according to the first embodiment are provided with the same numerical reference. In  FIG. 17 , the solder resist  31  is omitted. 
     In the following, a reader/writer  40  according to the second embodiment of the present invention is described with reference to  FIGS. 16 and 17 . The reader/writer  40  includes the circuit board  11 , the via connection terminals  12  and  13 , the communication control portion  14 , the sealing resin  19 , a soft magnetic resin layer  41 , the via  25 , the antenna  26 , and the solder resist  31 . In other words, the reader/writer  40  has the same structure as in the reader/writer  10  except for the soft magnetic resin layer  41  disposed in place of the resin layer  22  disposed on the reader/writer  10  according to the first embodiment. 
     The soft magnetic resin layer  41  is disposed between the sealing resin  19  and the antenna  26  so as to cover the upper surface of the sealing resin  19 . In the soft magnetic resin layer  41 , opening portions  42  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed. The soft magnetic resin layer  41  includes resin containing soft magnetic metallic powder. The aforementioned resin may employ epoxy resin, for example. The soft magnetic metallic powder may employ a metal with an initial permeability of not less than one. Preferably, the soft magnetic metallic powder includes at least one selected from a group consisting of Al, Cr, Mn, Fe, Co, Ni, B, Si, Sr, Nb, Mo, Mg, Zn, and Pt, for example. Also, the soft magnetic metallic powder may employ metallic powder whose surface is coated with an insulating material such as epoxy resin. Accordingly, it is possible to improve the insulation properties between the via connection terminals  12  and  13  and the antenna  26 . A thickness M 4  of the soft magnetic resin layer  41  may be 20 μm to 60 μm, for example. An opening diameter D 3  of an upper end of the opening portion  42  may be 20 μm to 400 μm, for example. 
     In this manner, by disposing the soft magnetic resin layer  41  including the resin containing the soft magnetic metallic powder between the antenna  26  and the sealing resin  19 , a magnetic flux B 3  generated from the antenna  26  does not pass through the circuit board  11 . This prevents the generation of an eddy current on the surface of the circuit board  11 . Thus, the magnetic flux B 3  generated from the antenna  26  is not attenuated, thereby improving the reliability of communication between IC tags and the reader/writer  40 . 
     The soft magnetic metallic powder is preferably mixed with the resin as much as 10 wt % 70 wt % relative to the resin. When the soft magnetic metallic powder mixed with the resin is less than 10 wt %, the magnetic flux B 3  passes through the circuit board  11  and an eddy current is generated, so that the magnetic flux B 3  is attenuated. When the soft magnetic metallic powder is more than 70 wt %, the insulation properties of the soft magnetic resin layer  41  cannot be provided sufficiently. Preferably, the soft magnetic metallic powder is mixed with the resin as much as 50 wt % to 70 wt % relative to the resin. 
     Preferably, an average particle size of the soft magnetic metallic powder is 1 μm to 8 μm. When the average particle size of the soft magnetic metallic powder is less than 1 μm, the magnetic flux B 3  passes through the circuit board  11  and an eddy current is generated, so that the magnetic flux B 3  is attenuated. When the average particle size of the soft magnetic metallic powder is more than 8 μm, the soft magnetic resin layer  41  becomes fragile. 
     In addition, when a resin film is used as the soft magnetic resin layer  41 , for example, the soft magnetic resin layer  41  can be pressure-bonded to the sealing resin  19  by heating/applying pressure using a vacuum laminating machine. The soft magnetic resin layer  41  may be formed by coating the sealing resin  19  with liquid resin and then heat-curing the liquid resin. 
     As mentioned above, according to the present embodiment, by disposing the soft magnetic resin layer  41  including the resin containing the soft magnetic metallic powder between the circuit board  11  and the antenna  26 , it is possible to prevent the attenuation of the magnetic flux B 3  due to an eddy current, the magnetic flux B 3  being generated from the antenna  26 , and to improve the reliability of communication between IC tags and the reader/writer  40 . 
     The reader/writer  40  according to the present embodiment can be manufactured by the same method as in the reader/writer  10  according to the first embodiment. 
     Third Embodiment 
       FIG. 18  is a cross-sectional view of a reader/writer according to a third embodiment of the present invention. In  FIG. 18 , the same components as in the reader/writer  40  according to the second embodiment are provided with the same numerical reference. 
     In the following, a reader/writer  50  according to the third embodiment of the present invention is described with reference to  FIG. 18 . The reader/writer  50  includes the circuit board  11 , the via connection terminals  12  and  13 , the communication control portion  14 , the sealing resin  19 , the resin layer  22 , the antenna  26 , the solder resist  31 , the soft magnetic resin layer  41 , and a via  53 . In other words, the reader/writer  50  has the structure of the reader/writer  40 , in which the resin layer  22  mentioned in the first embodiment is disposed between the sealing resin  19  and the antenna  26  and the via  53  is disposed in place of the via  25 . In the present embodiment, the soft magnetic resin layer  41  corresponds to other layer. 
     In the resin layer  22 , opening portions  52  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed. A diameter D 4  of an upper end of the opening portion  52  may be 10 μm to 300 μm, for example. 
     The via  53  is disposed at the opening portions  52  formed on the resin layer  22 . The via  53  is used to electrically connect the antenna  26  to the via connection terminals  12  and  13 . 
     In this manner, by disposing the resin layer  22  between the soft magnetic resin layer  41  and the antenna  26 , it is possible to sufficiently insulate between the via connection terminals  12  and  13  and the antenna  26 . 
       FIGS. 19 to 22  are diagrams showing steps for manufacturing a reader/writer according to the present embodiment. In  FIGS. 19 to 22 , the same components as in the reader/writer  50  shown in  FIG. 18  are provided with the same numerical reference. 
     In the following, a method for manufacturing the reader/writer  50  according to the present embodiment is described with reference to  FIGS. 19 to 22 . 
     First, the processing (the step of mounting the communication control portion and the step of forming the sealing resin) shown in  FIGS. 5 to 7  is performed. Next, as shown in  FIG. 19 , the soft magnetic resin layer  41  for filling the opening portion  21  and covering the upper surface  19 A of the sealing resin  19  is formed (a step of forming other resin layer). The thickness M 4  of the soft magnetic resin layer  41  may be 20 μm to 60 μm, for example. 
     Next, as shown in  FIG. 20 , the opening portions  42  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed. The opening portions  42  may be formed by laser processing, drill processing, or the like, for example. The opening diameter D 3  of the upper end of the opening portion  42  may be 20 μm to 400 μm, for example. 
     Next, as shown in  FIG. 21 , the resin layer  22  for filling the opening portion  42  and covering the upper surface  41 A of the soft magnetic resin layer  41  is formed (the step of forming the resin layer). The resin layer  22  is capable of roughening through a desmear process or the like. 
     Next, as shown in  FIG. 22 , the opening portions  52  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed on the resin layer  22 . Thereafter, the surface of the resin layer  22  is roughened through the desmear process. The opening portions  52  may be formed by laser processing, drill processing, or the like, for example. The diameter D 4  of the upper end of the opening portion  52  may be 10 μm to 300 μm, for example. 
     Thereafter, by performing the same processing as in the steps shown in  FIGS. 10 to 15  described in the first embodiment, the reader/writer  50  is manufactured. 
     As mentioned above, according to the present embodiment, the reliability of communication between IC tags and the reader/writer  50  is improved using the soft magnetic resin layer  41 . And it is possible to sufficiently insulate between the via connection terminals  12  and  13  and the antenna  26  using the resin layer  22  disposed between the soft magnetic resin layer  41  and the antenna  26 . 
     Fourth Embodiment 
       FIG. 23  is a cross-sectional view of a reader/writer according to a fourth embodiment of the present invention. In  FIG. 23 , the same components as in the reader/writer  50  according to the third embodiment are provided with the same numerical reference. 
     In the following, a reader/writer  60  according to the fourth embodiment of the present invention is described with reference to  FIG. 23 . In the reader/writer  60 , the sealing resin  19  and the soft magnetic resin layer  41  are sequentially stacked, and then opening portions  61  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are disposed on the sealing resin  19  and the soft magnetic resin layer  41 . Except for these elements, the reader/writer  60  has the same structure as that of the reader/writer  50  according to the third embodiment. A diameter D 5  of an upper end of the opening portion  61  may be 30 μm to 500 μm, for example. 
       FIGS. 24 to 27  are diagrams showing steps for manufacturing a reader/writer according to the present embodiment. In  FIGS. 24 to 27 , the same components as in the reader/writer  60  shown in  FIG. 23  are provided with the same numerical reference. 
     Next, the reader/writer  60  according to the fourth embodiment is described with reference to  FIGS. 24 to 27 . 
     First, the steps (the step of mounting the communication control portion and the step of forming the sealing resin) shown in  FIGS. 5 and 6  are performed. Next, as shown in  FIG. 24 , the soft magnetic resin layer  41  is formed so as to cover the upper surface  19 A of the sealing resin  19  (a step of forming other resin layer). 
     Next, as shown in  FIG. 25 , the opening portions  61  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed on the sealing resin  19  and the soft magnetic resin layer  41 . The opening portions  61  may be formed by laser processing, drill processing, or the like, for example. The diameter D 5  of the upper end of the opening portion  61  may be 30 μm to 500 μm, for example. 
     Next, as shown in  FIG. 26 , the resin layer  22  for filling the opening portion  61  and covering the upper surface  41 A of the soft magnetic resin layer  41  is formed (the step of forming the resin layer). The resin layer  22  is capable of roughening through a desmear process or the like. 
     Next, as shown in  FIG. 27 , opening portions  62  for exposing the upper surfaces  12 A and  13 A of the via connection terminals  12  and  13  are formed on the resin layer  22 . Thereafter, the surface of the resin layer  22  is roughened through the desmear process. The opening portions  62  may be formed by laser processing, drill processing, or the like, for example. The diameter D 4  of the upper end of the opening portion  62  may be 20 μm to 400 μm, for example. 
     Thereafter, by performing the same processing as in the steps shown in  FIGS. 10 to 15  described in the first embodiment, the reader/writer  60  is manufactured. 
     By manufacturing the reader/writer  60  according to the present embodiment using the aforementioned method, the steps of forming the opening portions can be reduced to two steps (the opening portions  61  and  62 ) from three steps (the opening portions  21 ,  23 , and  52 ) in the reader/writer  50  according to the second embodiment, thereby reducing the manufacturing cost of the reader/writer  60 . 
     The reader/writers as described in the first to fourth embodiments can be applied to exchanging information with communication media of some kind such as IC cards besides IC tags. 
     According to the present invention, a reader/writer can be miniaturized and the present invention can be applied to a reader/writer capable of improving the reliability of communication with IC tags and IC cards and a manufacturing method thereof. 
     The present invention is not limited to the specifically disclosed embodiment, and variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 2005-119866 filed Apr. 18, 2005 the entire contents of which are hereby incorporated herein by reference.