Abstract:
The electronic apparatus includes a base sheet; a conductive pattern formed on the base sheet; a circuit chip mounted on the base sheet and connected to the conductive pattern; and plural protrusions arranged on at least one of a frontside and a backside of the base sheet to overlap at least a portion of the conductive pattern. The plural protrusions protrude in a direction away from the base sheet.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic apparatus and a method of manufacturing the electronic apparatus, and more particularly to an electronic apparatus where a circuit chip is mounted on a base sheet and a method of manufacturing the electronic apparatus. 
     2. Description of Related Art 
     Conventionally, electronic apparatus have been widely known where a circuit chip is mounted on a substrate, such as a printed circuit board (“PCB”). Such an electronic apparatus is embedded into an electronic device and mainly used to control the electronic device or exchange information with an external device as a unit. As an example of the electronic apparatus, various types of RFID (Radio Frequency Identification) tags are known, which contactlessly and wirelessly exchange information with an external device represented by a readers/writer. As an example of such RFID tags, an RFID tag including an IC (Integrated Circuit) chip and an antenna pattern mounted on a base sheet, which is a conductive pattern for wireless communication and serves as an antenna, has been proposed (for example, see Japanese Patent Application Publication Nos. 2000-311226, 2000-200332, and 2001-351082). This type of RFID tag is used, for example, to perform identification of a product by exchanging information associated with the product with an external device, while being attached to the product. 
     One of applications for such an RFID tag is that the RFID tag is attached to a product, such as a garment, which may be subjected to deformation during use. In this application, a bending stress exerted on the RFID tag may cause the antenna pattern to be disconnected, which may lead to a failure of functions as an antenna. 
       FIG. 1  is a cross sectional view illustrating a conventional RFID tag  10 ′ which has been bent due to a bending stress. 
     The conventional RFID tag  10 ′ includes a base sheet  111  made of a PET film, a conductive antenna pattern  112  for communication arranged on the base sheet  111 , and a circuit chip  12  connected to the antenna pattern  112 . The base sheet  111 , the antenna pattern  112 , and the circuit chip  12  are coated with a rubber coat article  100   a . If a bending stress is exerted on the conventional RFID tag  10 ′ in the direction of an arrow shown in  FIG. 1 , the conventional RFID tag  10 ′ is subject to a bending deformation in this direction following the bending stress. At this time, a large bending stress, which would separate the antenna pattern  112  into two parts, is exerted on an area A′ where bending deformation greatly takes place, and therefore, disconnection of the antenna pattern  112  may easily occur in the area A′. This bending stress becomes stronger as the bending angle of the RFID tag  10 ′ increases. Accordingly, the RFID tag  10 ′ that can be excessively bent is liable to be easily disconnected, and thus becomes poor in durability. 
     Although the above descriptions refer to the case where the conductive pattern serving as an antenna is disconnected, such disconnection of the conductive pattern is not limited only to the RFID tag, but common to all electronic apparatus whose conductive pattern is mounted on the base sheet. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above circumstances and provides an electronic apparatus including: 
     a base sheet; 
     a conductive pattern formed on the base sheet; 
     a circuit chip mounted on the base sheet and connected to the conductive pattern; and 
     a plurality of protrusions arranged on at least one of a frontside and a backside of the base sheet to overlap at least a portion of the conductive pattern, the plurality of protrusions protruding in a direction away from the base sheet. 
     The electronic apparatus according to the present invention have plural protrusions arranged over a range of overlapping at least a portion of the range of the conductive pattern. In a case where a bending stress is exerted on the overlapping range, the electronic apparatus exhibit some flexibility corresponding to such a bending stress, but bending angle thereof is suppressed not to exceed a predetermined level by the plural protrusions. Accordingly, the electronic apparatus maintains sufficient flexibility as well as provides high durability since it is difficult for large bending deformation to take place. 
     In the electronic apparatus according to the present invention, it is preferable that the plurality of protrusions may be higher in rigidity than the base sheet. 
     According to the present invention, the occurrence of great bending deformation, which could cause damage to the base sheet, may be inhibited thanks to the plural protrusions. 
     In addition, in the electronic apparatus according to the present invention, the plurality of protrusions may be a plurality of cone-like articles each of which has a bottom surface shaped like a polygon, and which are arranged such that the bottom surfaces are connected to one another. 
     As used herein, the term “cone-like article” is intended to include a truncated pyramid, such as a truncated triangular pyramid and a truncated quadrangular pyramid, whose tip is flattened, as well as a pyramid, such as a triangular pyramid and a quadrangular pyramid, whose bottom surface is shaped like a polygon. This structure of the cone-like article may permit the electronic apparatus to exhibit a great resistance against a bending stress because the inclined surfaces of the cone-like articles push out each other when the electronic apparatus is bent due to the bending stress exerted on the electronic apparatus. 
     Further preferably, the electronic apparatus according to the present invention may have a protection body which is broader than the circuit chip and narrower than the conductive pattern, and protects the circuit chip by being disposed on at least one of an upperside of the circuit chip and an underside of the circuit chip where the base sheet is interposed between the circuit chip and the protection body, 
     wherein the plurality of protrusions are arranged at least on an area of surroundings of the protection body, the area being provided with the conductive pattern. 
     According to the present invention, the circuit chip itself and its peripheral area may be protected from a bending stress. 
     Further preferably, the plurality of protrusions may be arranged on both the frontside and backside of the base sheet. 
     According to the present invention, there are provided electronic apparatus having durability against both a bending stress that makes the base sheet bent toward the outer surface of the base sheet and a bending stress that makes the base sheet bent toward the inner surface of the base sheet. 
     It is also preferable that a coat article may be provided in which the base sheet, the conductive pattern, the circuit chip, and the protrusions are contained. 
     According to the present invention, the conductive pattern or circuit chip may be protected from external impacts or moisture. 
     In addition, in the electronic apparatus according to the present invention, the conductive pattern may constitute an antenna for wireless communication, and 
     the circuit chip performs wireless communication through the antenna. 
     According to the present invention, an RFID tag may be implemented, which exhibits high durability against a bending stress. 
     A method of manufacturing an electronic apparatus according to another aspect of the present invention includes the steps of: 
     mounting a circuit chip on a base sheet on which a conductive pattern is arranged, and connecting the circuit chip to the conductive pattern; and 
     arranging and forming a plurality of protrusions by arranging, in a direction away from the base sheet, the plurality of protrusions on at least one of a frontside and a backside of the base sheet on which the circuit chip is mounted, such that the arranged protrusions overlap at least a portion of the arranged conductive pattern. 
     In the method of manufacturing the electronic apparatus according to the present invention, electronic apparatus may be manufactured, which have high durability against a bending stress by forming plural protrusions are provided over a range of overlapping at least a portion of a range of the conductive pattern. 
     Further preferably, in the method of manufacturing the electronic apparatus according to the present invention, the step of arranging and forming the plurality of protrusions may be a step in which a mold having a shape corresponding to a shape of the protrusions is placed on at least one of the frontside and the backside of the base sheet on which the circuit chip is mounted, a liquid material for the protrusions is poured between the base sheet and the mold, and the liquid material is cured, thereby forming the plurality of protrusions. 
     According to the present invention, the plural protrusions may be simply formed. 
     As described above, according to the present invention, the electronic apparatus have durability against a bending stress. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view illustrating a conventional RFID tag which has been bent due to a bending stress according to the prior art. 
         FIG. 2  is a view illustrating an RFID tag that is an exemplary embodiment according to the present invention. 
         FIG. 3  is a cross sectional view illustrating the RFID tag shown in  FIG. 2  which has been bent due to a bending stress. 
         FIG. 4  is a view illustrating a method of manufacturing the RFID tag shown in  FIG. 2 . 
         FIG. 5  is a view illustrating an RFID tag according to another exemplary embodiment of the present invention. 
         FIG. 6  is a view illustrating a process for forming a small convex portion on a base sheet. 
         FIG. 7  is a view illustrating a process of embedding a chip reinforcement plate after the small convex portion has been attached to the base sheet in the method of manufacturing the RFID tag shown in  FIG. 5 . 
         FIG. 8  is a view illustrating a process of forming the truncated pyramid shape of the small convex portion by attaching plate-shaped plastics, which is a material of the small convex portion, onto the base sheet and then treating a laser process on the plate-shaped plastics. 
         FIG. 9  is a view illustrating a process of forming the truncated pyramid shape of the small convex portion on the plate-shaped plastics by strongly pressurizing press mold heads. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to accompanying drawings. 
       FIG. 2  is a view illustrating an RFID tag  10  that is an exemplary embodiment of the electronic apparatus according to the present invention. 
     Part (a) of  FIG. 2  depicts a plan view of the RFID tag  10  shown in a state in which an inner structure of the RFID tag  10  is seen through, and  FIG. 2B  depicts a cross sectional view of the RFID tag  10  taken in the longitudinal direction. 
     It is assumed that the RFID tag  10  shown in  FIG. 2  is attached to a product worn by a human, such as a garment, which may be subjected to deformation, and the RFID tag  10  includes an inlay  100  which has a rubber coat article  100   a . The inlay  100  includes a base sheet  111 , an antenna pattern  112 , a circuit chip  12 , and a reinforcement body  14 . The base sheet  111  is formed of a PET film. The antenna pattern  112  is a conductive pattern for communication, which is formed on the base sheet  111 , and serves as an antenna. The circuit chip  12  is electrically connected to the antenna pattern  112  and carries out wireless communication through the antenna pattern  112 . The reinforcement body  14  covers both surfaces of the base sheet  111 . 
     As shown in part (b) of  FIG. 2 , bumps  121  included in the circuit chip  12  are connected to the antenna pattern  112 , and current may flow between the circuit chip  12  and the antenna pattern  112  through the bumps  121 . The circuit chip  12  is secured to the base sheet  111  by an adhesive  13  as shown in part (b) of  FIG. 2 . The adhesive  13  is not shown in part (a) of  FIG. 2 . 
     The reinforcement body  14  includes plural convex portions arranged on both surfaces of the base sheet  111 , each of which is in a shape of a truncated quadrangular pyramid. The reinforcement body  14  consists of a large convex portion  14   a  that covers the circuit chip  12  and plural small convex portions  14   b  each of which is smaller in size than the large convex portion  14   a . The small convex portions  14   b  covers the remaining areas except the peripheral area of the circuit chip  12  covered with the large convex portion  14   a . The reinforcement body  14  may be made of an electrically insulating material having higher rigidity than that of the base sheet  111 . For instance, the reinforcement body  14  may be made of a high-hardness plastic material. In the present invention, a high-hardness ceramic material may be employed for the reinforcement body  14  instead of the plastic material. 
     The base sheet  111 , the antenna pattern  112 , the circuit chip  12 , the reinforcement body  14 , and the coat article  100   a  correspond to an example of the base sheet, an example of the conductive pattern, an example of the circuit chip, an example of the plural protrusions, and an example of the coat article according to the present invention. 
     In the RFID tag  10 , for example, when a garment is deformed, to which the RFID tag  10  is attached, such a deformation of the garment may affect the circuit chip  12  itself or periphery of the circuit chip  12 . However, this deformation may be prevented by covering the periphery of the circuit chip  12  with the large convex portion  14   a  made of a high-hardness plastic material, as shown in part (b) of  FIG. 2 . Accordingly, it is possible to prevent damage to the circuit chip  12  itself, the bumps  121  connected to the antenna pattern  112 , or a connection part between the circuit chip  12  and the base sheet  111 . 
     Generally, in the RFID tag having a chip reinforcement body that protects the periphery of the circuit chip against a bending stress externally exerted onto the RFID tag, the circuit chip itself and its peripheral area, which are covered with the chip reinforcement body, may be protected from such a bending stress. Instead, the bending stress is prone to concentrate on surroundings of the peripheral area of the circuit chip. At this time, a portion where the bending stress concentrates and therefore a great bending stress is applied may be subjected to disconnection, and thus the RFID chip  10  fails to exhibit sufficient durability. 
     In the RFID tag  10  shown in  FIG. 2 , the small convex portion  14   b  is provided in plurality on both surfaces of the base sheet  111  on the upper surface of which the antenna pattern  112  has been arranged as shown in  FIG. 2 . The RFID tag  10  may exhibit flexibility against the bending stress thanks to the small convex portion  14   b , and the bending stress may be suppressed correspondingly as the bending angle of the RFID tag  10  exceeds a predetermined level. Hereinafter, a structure of the RFID tag  10  will be described. 
       FIG. 3  is a cross sectional view illustrating an RFID tag  10  shown in  FIG. 2  which has been bent due to a bending stress. 
     As shown in  FIG. 3 , in the area A which experiences the largest bending deformation, the plural small convex portions  14   b  arranged at the right side of the base sheet  111  compress the coat article  100   a  between two neighboring small convex portions  14   b , so that inclined surfaces of the truncated quadrangular pyramids become adjacent to each other. Accordingly, the RFID tag  10  is not bent as shown in  FIG. 3  despite the bending stress exerted on the RFID tag  10  in the direction of an arrow owing to such small convex portions  14   b . As a consequence, the RFID tag  10  shown in  FIG. 3  is not subjected to disconnection, and thus yields a high-durability. 
     Hereinafter, a method of manufacturing the RFID tag  10  shown in  FIG. 2  will be described. 
       FIG. 4  is a view illustrating a method of manufacturing the RFID tag  10  shown in  FIG. 2 . 
     The manufacturing method illustrated in  FIG. 4  is an example of the method of manufacturing the RFID tag according to the present invention. Parts (a) to (g) of  FIG. 4  sequentially depict each process in the method of manufacturing the RFID tag  10 . 
     Firstly, in part (a) of  FIG. 4 , a base sheet  111 , made of a PET film, on which an antenna pattern  112  is formed, is prepared, and a liquid adhesive  13  is applied on a surface of the base sheet  111  on which the antenna pattern  112  is formed. The liquid adhesive  13  is a heat-curable adhesive that is cured by applying heat. 
     Next, in parts (b) and (c) of  FIG. 4 , the circuit chip  12  is mounted on a portion of the base sheet  111  on which the adhesive  13  has been applied, with a circuit surface  120  on which an electronic circuit of the circuit chip  12  is arranged facing the base sheet  111 . The circuit chip  12  may be positioned so that bumps  121  formed on the circuit surface  120  of the circuit chip  12  align with the antenna pattern  112  of the base sheet  111 . 
     Then, in part (d) of  FIG. 4 , the base sheet  111  is placed on a heating stage  220 , with the circuit chip  12  mounted on the base sheet  111 , and the circuit chip  12  arranged on the base sheet  111  is pressurized toward the heating stage  220  and simultaneously heated by a first heating head  210  having a heater therein. Such heating allows the adhesive  13  to be cured under the circuit chip  12 , so that the circuit chip  12  is secured to the base sheet  111 . 
     Subsequently, in part (e) of  FIG. 4 , the base sheet  111  on which the circuit chip  12  has been mounted is inserted between two molds  310  and  320  for forming the reinforcement body  14  shown in  FIG. 2 , and then a liquid plastic material for forming the reinforcement body  14  is injected into the base sheet  111  between the two molds  310  and  320  through injection holes bored in the molds  310  and  320  as marked with arrows in  FIG. 4 . After a predetermined period of time, the plastic material is cooled and cured, and thus the reinforcement body  14  including the large convex portions  14   a  and the small convex portions  14   b  is formed on the base sheet  111  as shown in  FIG. 2 . 
     Next, in parts (f) and (g) of  FIG. 4 , the base sheet  111  on which the reinforcement body  14  has been formed is inserted between two sheets of plate-shaped rubber materials  100   a ′ for forming the coat article  100   a  shown in  FIG. 2 , and then the rubber materials  100   a ′ are pressurized toward the heating stage  220  and simultaneously heated by a second heating head  410  having its own heater therein. Such heating allows the rubber materials  100   a ′ to be melt so that the melt rubber materials  100   a ′ are drawn into between the large convex portion  14   a  and the small convex portion  14   b , and between the small convex portion  14   b  and its neighboring small convex portion  14   b . The heating is paused a predetermined time after melting, so that the rubber materials  100   a ′ are cured. The cured rubber materials  100 ′ are trimmed by a punching or cutting process, which completes the RFID tag  10  as shown in  FIG. 2 . 
     In the method described above, the convex portions shown in  FIG. 2  may be formed by pouring a liquid state plastic material in molds between which the base sheet  111  is inserted and curing the liquid state plastic material, and therefore, an RFID tag may be simply manufactured, which has high durability against a bending stress. 
     Next, an exemplary RFID tag will be described below according to another exemplary embodiment of the present invention. 
       FIG. 5  is a view illustrating an RFID tag according to another exemplary embodiment of the present invention. 
     In  FIG. 5 , the same components as those of the RFID tag  10  shown in  FIG. 2  refer to the same reference characters, and repetitive descriptions will be omitted.  FIG. 5  is a cross sectional view illustrating an RFID tag  20  taken in the longitudinal direction according to another exemplary embodiment of the present invention. 
     It is assumed that the RFID tag  20  shown in  FIG. 5  may be also attached to a product, such as a garment worn by a human, which is subjected to deformation. The RFID tag  20  has the same configuration as that of the RFID tag  10  shown in  FIG. 2  except that chip reinforcement plates  14   c  are respectively placed over and under the base sheet  111  mounted with the circuit chip  12 , instead of covering the circuit chip  12  with the large convex portion  14   a  as shown in  FIG. 5 . 
     Referring to  FIG. 5 , the circuit chip  12  of the RFID tag  20  is protected by the two chip reinforcement plates  14   c . The small convex portions  14   b  are provided in the RFID tag  20  shown in  FIG. 5 , too, and disconnection of the antenna pattern  112  caused by a bending stress is inhibited by the small convex portions  14   b  as described above with reference to  FIG. 3 . Accordingly, the RFID tag  20  shown in  FIG. 5  seldom experiences disconnection compared to the conventional RFID tag  10 ′ shown in  FIG. 1 , and thus yields a high-durability. 
     Hereinafter, a method of manufacturing the RFID tag  20  shown in  FIG. 5  will be described. 
     The RFID tag  20  shown in  FIG. 5  undergoes the same process as in parts (a) to (d) of  FIG. 4  until the circuit chip  12  is secured to the base sheet  111 . Hereinafter, the process after the circuit chip  12  has been secured to the base sheet  111  will be described. 
       FIG. 6  is a view illustrating a process for forming the small convex portions  14   b  on the base sheet  111 . 
     In the method of manufacturing the RFID tag  20  shown in  FIG. 5 , the circuit chip  12  is secured to the base sheet  111 , and then the small convex portion  14   b  which is shaped as a truncated quadrangular pyramid whose bottom surface is attached with a double-sided adhesive tape  140   b  is attached onto the base sheet  111  as shown in  FIG. 6 . The attachment of the small convex portion  14   b  is made on both top surface and bottom surface of the base sheet  111 . 
       FIG. 7  is a view illustrating a process of the method of manufacturing the RFID tag  20  shown in  FIG. 5 , where the chip reinforcement plates  14   c  are embedded after the small convex portions  14   b  have been attached to the base sheet  111 . 
     After the formation of the small convex portion  14   b , the process of embedding the chip reinforcement plates  14   c  is performed. In this step, two sets, each of which includes two sheets of plate-shaped rubber materials  100   a ′ that are materials of the coat article  100   a  in  FIG. 5  and one chip reinforcement plate  14   c  inserted between the two rubber materials  100   a ′, are prepared, and the base sheet  111  on which the small convex portions  14   b  have been attached is placed between the two sets. Then, the two sets and the base sheet  111  are pressurized and simultaneously heated using the second heating head  410  and the heating stage  220 . The heating allows the rubber materials  100   a ′ to be melt so that the melt rubber materials  100   a ′ are drawn into between the two neighboring small convex portions  14   b , and the two chip reinforcement plates  14   c  are placed over and under the base sheet  111  on which the circuit chip  12  has been mounted, with each of the chip reinforcement plates  14   c  drawn into two sheets of rubber materials  100   a ′. After a predetermined period of time, the heating is paused, so that the rubber materials  100   a ′ are cured. Then, the surplus of the rubber materials  100   a ′ extending off the base sheet  111  in the width direction to both sides of the drawing as in part (g) of  FIG. 4  is removed, which completes the RFID tag  20  as shown in  FIG. 5 . 
     In the method of manufacturing the RFID tag  20  shown in  FIG. 5  as described above, the convex portions may be formed as shown in  FIG. 5  only by attaching on the base sheet  111  the small convex portions  14   b  shaped like a truncated quadrangular pyramid whose bottom surface has been attached with the double-sided adhesive tape  140   b , which makes an RFID tag have high durability against a bending stress. 
     Although a method is employed in the description with reference to  FIG. 6  that the small convex portion  14   b  is attached on the base sheet  111  in forming the small convex portion  14   b  on the base sheet  111 , the present invention is not limited thereto. For example, in the method of manufacturing the RFID tag according to the present invention, plate-shaped plastics, which is a material for forming the small convex portion  14   b , may be attached on the base sheet  111 , and then the truncated quadrangular pyramid of the small convex portion  14   b  may be formed. 
       FIG. 8  is a view illustrating a process of forming the truncated quadrangular pyramid of the small convex portion  14   b  by attaching the plate-shaped plastics, which is a material of the small convex portion  14   b , on the base sheet  111  and then treating a laser process on the plate-shaped plastics.  FIG. 9  is a view illustrating a process of forming the truncated quadrangular pyramid of the small convex portion  14   b  on the plate-shaped plastics by strongly pressurizing press mold heads  610  and  620 . 
     In the process illustrated in  FIG. 8 , the plate-shaped plastics  141   b , which are a material for the small convex portion  14   b , are attached to the base sheet  111 , and then is machined in the shape of the truncated quadrangular pyramid shown in  FIG. 5  by a laser beam emitted from a tip of a laser illuminating device  500  toward the plate-shaped plastics  141   b . This laser machining may have an advantage of providing high accuracy. 
     Instead of the laser machining, it is possible to form the shape of the truncated quadrangular pyramid as shown in  FIG. 5  by pressurizing the plate-shaped plastics  141   b  located on the base sheet  111  with the press mold heads  610  and  620  as shown in  FIG. 9 . The method of pressurizing the plate-shaped plastics  141   b  located on the base sheet  111  with the press mold heads  610  and  620  to form the shape of the truncated quadrangular pyramid is somewhat poor in accuracy compared to the laser machining, but this method has a merit of increased productivity because of shorter processing time. 
     The exemplary embodiments of the present invention have been described as above. 
     Although a case where two chip reinforcement plates  14   c  are arranged over and under the circuit chip  12  has been described above, the present invention is not limited thereto. For instance, a single chip reinforcement plate  14   c  may be arranged only either over the circuit chip  12  or under the circuit chip  12 , or another reinforcement member may be arranged to cover a side of the circuit chip  12  as well as over and under the circuit chip  12 . 
     Although a case where the reinforcement body  14  includes the large convex portion  14   a  and the small convex portions  14   b  has been described above, each of which has a shape of a truncated quadrangular pyramid, the present invention is not limited thereto. For example, the large convex portion  14   a  and the small convex portions  14   b  of the reinforcement body  14  may be shaped like truncated pyramids other than the truncated quadrangular pyramid, or as a pyramid. In addition, each of the large convex portion and the small convex portion may be shaped like any one of a cone, a dome, and a pole.