Patent Publication Number: US-9852839-B2

Title: Coil component and manufacturing method thereof

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a coil component and a manufacturing method of the coil component, and particularly to a coil component that uses a drum core and a manufacturing method thereof. 
     Description of Related Art 
     In recent years, electronic components that are used in information terminal devices such as smartphones have been strongly required to be smaller in size and lower in height. Therefore, as for coil components such as pulse transformers, surface-mount coil components that use drum cores instead of toroidal cores have been frequently used. For example, Japanese Patent Application Laid-Open No. 2012-119568 discloses a step-up transformer of a surface-mount type that uses a drum core. 
     The coil components that use drum cores have been required to be even smaller in size and lower in height. The size of a winding core portion has been decreasing from year to year. In order to secure a required inductance, a coated conductive wire that is thinner in diameter needs to be used. 
     However, the coated conductive wire that is thin in diameter is low in dielectric strength voltage. Accordingly, coil components that need to insulate primary and secondary windings, such as pulse transformers, may be insufficient in dielectric strength voltage. In particular, if wires are connected to terminal electrodes by thereto-compression bonding or laser bonding, heat that is applied at the time of wire connection is conveyed via core material of the coated conductive wire, and the coating film would be degraded. Therefore, the problem is that the component is likely to be insufficient in dielectric strength voltage. 
     SUMMARY 
     It is therefore an object of the present invention to provide a coil component that is high in dielectric strength voltage even when a coated conductive wire that is thin in diameter is used, and a manufacturing method of the coil component. 
     A coil component of the present invention includes: a drum core that includes first and second flange portions having wire connection portions and a winding core portion located between the first and second flange portions; a coated conductive wire that is wound around the winding core portion, each end of the coated conductive wire being connected to respective one of the wire connection portions; and a resin coating layer that covers at least the coated conductive wire located in a first layer in the winding core portion. 
     According to the present invention, the resin coating layer covers the first-layer constituted of the coated conductive wire that is likely to be insufficient in dielectric strength voltage. Therefore, it is possible to improve the dielectric strength voltage. 
     In the case of the present invention, the coated conductive wire preferably includes a primary winding and secondary winding that are insulated from each other. The reason is that a higher dielectric strength voltage is frequently required for this kind of coil component. 
     The coil component of the present invention preferably further includes a plate core that is bonded to the first and second flange portions. According to this configuration, a closed magnetic circuit is formed by the drum core and the plate core. Thus, it is possible to enhance the magnetic properties. 
     In this case, between the first and second flange portions and the plate-like core, the resin coating layer preferably does not exist. According to this configuration, the gap between the drum core and the plate-like core does not widen due to the existence of the resin coating layer. Thus, it is possible to further enhance the magnetic properties. 
     In the case of the present invention, the wire connection portion is preferably not covered with the resin coating layer. According to this configuration, it is possible to prevent a connection failure associated with the resin coating layer, a drop in solder wettability, and the like. 
     In the case of the present invention, at least part of a cross section of the winding core portion that is perpendicular to an axis direction is preferably arc-shaped. According to this configuration, it is possible to further ensure that the resin coating layer covers reliably the first-layer constituted of the coated conductive wire compared with cases where a winding core portion that is rectangular in cross-section is used. 
     A manufacturing method of a coil component according to the present invention includes: winding, around a winding core portion of a drum core, a coated conductive wire including a core material, a coating film that covers the core material, and a resin film that covers the coating film; connecting both ends of the coated conductive wire to wire connection portions that are provided in first and second flange portions of the drum core; and forming a resin coating layer to cover at least the coated conductive wire that is located in a first layer in the winding core portion by melting the resin film. 
     According to the present invention, the resin coating layer is formed as the resin film covering the coating film melts. Therefore, it is possible to improve the dielectric strength voltage. Moreover, there is no need to coat with resin material or the like after the coated conductive wire is wound. Therefore, the number of steps does not increase. 
     According to the present invention, the connecting is preferably carried out by thermo-compression bonding or laser bonding. The reason is that, if the wire is connected by thermo-compression bonding or laser bonding, the dielectric strength voltage tends to become insufficient due to the heat applied at the time of the wire connection. 
     In this case, the coated conductive wires preferably include a first coated conductive wire that is located in the first layer in the winding core portion and a second coated conductive wire that is located in a second or subsequent layer in the winding core portion, and the connecting includes a step of connecting the first coated conductive wire to the wire connection portion and then the second coated conductive wire to the wire connection portion. The reason is that, if the wire connection work is carried out multiple times on the same wire connection portions as described above, the effects of the heat become more significant. 
     The method of producing the coil component of the present invention preferably further includes bonding a plate core to the first and second flange portions, wherein the resin film melts due to heat applied at the bonding step. According to this method, the step of bonding the plate-like core and the step of melting the resin film can be performed at the same time. 
     According to the present invention, it is possible to provide a coil component that is high in dielectric strength voltage even when a coated conductive wire that is thin in diameter is used, and a manufacturing method of the coil component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above features and advantages of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic perspective view showing the appearance structure of a coil component according to a first embodiment of the present invention; 
         FIG. 2  shows an equivalent circuit of the coil component shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along line A-A′ shown in  FIG. 1 ; 
         FIG. 4  is an enlarged view of an area B shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of coated conductive wires; 
         FIG. 6A  is a schematic plan view indicating a state where two coated conductive wires are wound around a winding core portion in a first layer; 
         FIG. 6B  is a schematic plan view indicating a state where another two coated conductive wires are further wound around the winding core portion in a second layer; 
         FIG. 7  is a schematic plan view showing the configuration of a coil component according to a second embodiment of the present invention; and 
         FIG. 8  is a cross-sectional view showing one example of an xz cross-section of a winding core portion of a drum core. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Preferred embodiments of the present invention will be explained below in detail with reference to the accompanying drawings. 
       FIG. 1  is a schematic perspective view showing the appearance structure of a coil component  10  according to the first embodiment of the present invention. 
     The coil component  10  of the present embodiment is a pulse transformer of a surface-mount type. As shown in  FIG. 1 , the coil component  10  includes a drum core  11 , a plate core  12  that is bonded to the drum core  11 , and coated conductive wires S 1  to S 4  that are wound around a winding core portion  11   a  of the drum core  11 . The coil component of the present invention is not limited to the pulse transformer. The coil component of the present invention may be any other transformer component such as a balun transformer or step-up transformer, or may be a filter component such as a common mode choke coil. 
     The drum core  11  and the plate core  12  are made of a magnetic material that is relatively high in magnetic permeability such as a sintered composite of Ni—Zn ferrite or Mn—Zn ferrite, for example. Incidentally, the magnetic material that is high in magnetic permeability such as Mn—Zn ferrite is usually low in specific resistance and electrically conductive. 
     The drum core  11  includes the rod-shaped winding core portion  11   a , and first and second flange portions  11   b  and  11   c  that are provided at both ends in y-direction of the winding core portion  11   a . The winding core portion  11   a  and flange portions  11   b  and  11   c  are integrally formed. The coil component  10  is a component that is mounted on a surface of a printed circuit board at the time of actual use. The coil component  10  is mounted in such a way that z-direction upper surfaces  11   bs  and  11   cs  of the flange portions  11   b  and  11   c  face the printed circuit board. To the opposite sides, or lower surfaces, of the flange portions  11   b  and  11   c  from the upper surfaces  11   bs  and  11   cs , the plate core  12  is bonded with an adhesive. According to this structure, a closed magnetic circuit is formed by the drum core  11  and the plate core  12 . 
     On the upper surface  11   bs  of the first flange portion  11   b , three wire connection portions E 1  to E 3  that serve as terminal electrodes are provided. On the upper surface  11   cs  of the second flange portion  11   c , three wire connection portions E 4  to E 6  that serve as terminal electrodes are provided. The wire connection portions E 1  to E 6  include L-shaped terminal metal fittings that are attached to the corresponding flange portions  11   b  and  11   c . However, the terminal metal fittings are not necessarily required to be used. The wire connection portions E 1  to E 6  may be formed by conductor film that is burned into the surfaces of the corresponding flange portions  11   b  and  11   c . The wire connection portions E 1  to E 3  are arranged in this order from one end side in x-direction as shown in  FIG. 1 . Similarly, the wire connection portions E 4  to E 6  are arranged in this order from one end side in x-direction. Ends of the coated conductive wires S 1  to S 4  are connected to the wire connection portions E 1  to E 6  by thermo-compression bonding or laser bonding. 
     As shown in  FIG. 1 , the distance between the wire connection portions E 2  and E 3  is designed in such a way as to be greater than the distance between the wire connection portions E 1  and E 2 . Similarly, the distance between the wire connection portions E 4  and E 5  is designed in such a way as to be greater than the distance between the wire connection portions E 5  and E 6 . This configuration is intended to improve the withstand voltage between a primary winding that is formed by the coated conductive wires S 1  and S 2  and a secondary winding that is formed by the coated conductive wires S 3  and S 4 . 
     The coated conductive wires S 1  to S 4  include a core material (metal core) that is made of a good conductor, and an insulating coating film that covers the core material. The coated conductive wires S 1  to S 4  are wound around the winding core portion  11   a  in a double-layered structure. While the details will be described later, the coated conductive wires S 1  and S 4  are wound around the winding core portion  11   a  in a bifilar winding pattern in order to form a first layer, and the coated conductive wires S 2  and S 3  are wound around the winding core portion  11   a  in a bifilar winding pattern in order to form a second layer. The numbers of turns of the coated conductive wires S 1  to S 4  may be equal. 
     The winding direction of the coated conductive wires S 1  to S 4  is different between the first and second layers. When the winding direction from the first flange portion  11   b  to the second flange portion  11   c  is seen from the flange portion  11   b &#39;s side, the winding direction of the coated conductive wires S 1  and S 4  is counterclockwise, and the winding direction of the coated conductive wires S 2  and S 3  is clockwise. In this manner, the winding direction of the coated conductive wires S 1  and S 4  is opposite to the winding direction of the coated conductive wires S 2  and S 3 . 
     One end S 1   a  and the other end S 1   b  of the coated conductive wire S 1  are connected to the wire connection portions E 1  and E 4 , respectively. One end S 4   a  and the other end S 4   b  of the coated conductive wire S 4  are connected to the wire connection portions E 3  and E 6 , respectively. One end S 2   a  and the other end S 2   b  of the coated conductive wire S 2  are connected to the wire connection portions E 4  and E 2 , respectively. One end S 1   a  and the other end S 3   b  of the coated conductive wire S 3  are connected to the wire connection portions E 5  and E 3 , respectively. 
       FIG. 2  shows an equivalent circuit of the coil component  10  according to the present embodiment. 
     As shown in  FIG. 2 , the wire connection portions E 1  and E 2  are used as balanced-input positive terminal IN+ and negative terminal IN−, respectively. The wire connection portions E 5  and E 6  are used as balanced-output positive terminal OUT+ and negative terminal OUT−, respectively. The wire connection portions E 3  and E 4  are used as output-side center tap CT and input-side center tap CT, respectively. The coated conductive wires S 1  and S 2  constitute the primary winding of the pulse transfer. The coated conductive wires S 3  and S 4  constitute the secondary winding of the pulse transfer. 
       FIG. 3  is a cross-sectional view taken along line A-A′ shown in  FIG. 1 .  FIG. 4  is an enlarged view of an area B shown in  FIG. 3 . 
     As shown in  FIGS. 3 and 4 , the coated conductive wires S 1  and S 4  are wound as the first layer on the winding core portion  11   a  of the drum core  11 . The coated conductive wires S 2  and S 3  are wound as the second layer on the first layer. That is, the coated conductive wires S 1  to S 4  that are wound around the winding core portion  11   a  have a double-layered structure. At least the surfaces of the coated conductive wires S 1  and S 4  that are located in the first layer are covered with a resin coating layer  20 . The resin coating layer  20  is made of an insulating resin material that is low in melting point, such as polyester, for example. The resin coating layer  20  may cover the coated conductive wires S 2  and S 3  that are located in the second layer. According to the present embodiment, particularly the upper surfaces U of the coated conductive wires S 2  and S 3  that are located in the second layer are partially covered due to a production method described later. 
     As shown in  FIG. 4 , the coated conductive wires S 1  to S 4  have the structure in which the core material (metal core)  31  is covered with a coating film (insulating film)  32 . The resin coating layer  20  is provided in such a way as to cover the coating film  32  of the coated conductive wires S 1  to S 4 . As for the coated conductive wires S 1  and S 4  that are located in the first layer, almost no area of the coating film  32  is exposed, and almost the entire area is covered with the resin coating layer  20 . 
     In that manner, in the coil component  10  of the present embodiment, at least the coated conductive wires S 1  and S 4  that are located in the first layer are covered with the resin coating layer  20 . Therefore, defective portions F of the coating film  32 , such scratches and cracks, can be filled with the resin coating layer  20 . Accordingly, it is possible to prevent a decline in dielectric strength voltage associated with the defective portions F, and to secure a high dielectric strength voltage. 
     The resin coating layer  20  exists only on the winding core portion  11   a  of the drum core  11 . No resin coating layer  20  exists on the flange portions  11   b  and  11   c . This means that no resin coating layer  20  exists between the flange portions  11   b  and  11   c  and the plate core  12 , and that the wire connection portions E 1  to E 6  are not covered with the resin coating layer  20 . 
     A manufacturing method of the coil component  10  according to the present embodiment will be described. 
     As shown in  FIG. 5 , the coated conductive wires S 1  to S 4  of a three-layer structure that includes the core material  31 , the coating film  32 , and a resin film  33  are prepared. The core material  31  is made of a good conductor such as copper (Cu), and the surface thereof is covered with the coating film  32 . The coating film  32  is made of insulating material such as imide-modified polyurethane, and the surface thereof is covered with the thin resin film  33 . The resin film  33  is made of insulating resin material such as polyester. The material of the resin film  33  is selected in such a way as to have a melting point that is sufficiently lower than that of the coating film  32 . In one example, the melting point of imide-modified polyurethane is about 260 degrees Celsius, while the melting point of polyester is about 70 degrees Celsius. 
     As shown in  FIG. 6A , the coated conductive wires S 1  and S 4  are wound around the winding core portion  11   a  in a bifilar winding pattern, and both ends of each of the coated conductive wires S 1  and S 4  are connected to the corresponding wire connection portions E 1 , E 3 , E 4 , and E 6  in order to form the first layer of the windings. More specifically, one ends S 1   a  and S 4   a  of the coated conductive wires S 1  and S 4  are connected by thermo-compression bonding or laser bonding to the wire connection portions E 1  and E 3 , respectively. Then, the drum core  11  is rotated in one direction in order to wound the coated conductive wires S 1  and S 4  around the winding core portion  11   a . After the rotation of the drum core  11  is stopped, the other ends S 1   b  and S 4   b  of the coated conductive wires S 1  and S 4  are connected by thermo-compression bonding or laser bonding to the wire connection portions E 4  and E 6 , respectively. During this process, the heat generated by the thereto-compression bonding or laser bonding is conveyed via the core material  31 . Accordingly, in portions close to the ends, the coating film  32  of the coated conductive wires S 1  and S 4  might be degraded, and defective portions, such as scratches or cracks, could emerge. Furthermore, due to mechanical stress that occurs at the time of winding, the coating film  32  could become defective. Moreover, when the thermo-compression bonding or laser bonding is carried out, the resin film  33  that exists at the one ends S 1   a  and S 4   a  of the coated conductive wires S 1  and S 4  and at the other ends S 1   b  and S 4   b  would change in quality due to the heat. According to the present invention, the resin that has changed in quality due to the heat at the time of wire connection is not part of the resin coating layer  20 . 
     Then, as shown in  FIG. 6B , the coated conductive wires S 2  and S 3  are wound around the winding core portion  11   a  in a bifilar winding pattern, and both ends of each of the coated conductive wires S 2  and S 3  are connected to the corresponding wire connection portions E 2 , E 3 , E 4 , and E 5  in order to form the second layer of the windings. More specifically, the other ends S 2   b  and S 3   b  of the coated conductive wires S 2  and S 3  are connected by thermo-compression bonding or laser bonding to the wire connection portions E 2  and E 3 , respectively. Then, the drum core  11  is rotated in the opposite direction in order to wound the coated conductive wires S 2  and S 3  around the winding core portion  11   a . After the rotation of the drum core  11  is stopped, one ends S 2   a  and S 1   a  of the coated conductive wires S 2  and S 3  are connected by thermo-compression bonding or laser bonding to the wire connection portions E 4  and E 5 , respectively. During this process, the resin film  33  that exists at the one ends S 2   a  and S 1   a  of the coated conductive wires S 2  and S 3  and at the other ends S 2   b  and S 3   b  would change in quality due to heat at the time of wire connection. Furthermore, the heat generated by the thermo-compression bonding or laser bonding is conveyed via the core material  31 . Therefore, in portions close to the ends, the coating film  32  of the coated conductive wires S 1  to S 4  is degraded. 
     The coated conductive wires S 1  and S 4  suffer thermal damage twice, from the heat generated by the thereto-compression bonding or laser bonding during the formation of the first layer and from the heat generated by the thermo-compression bonding or laser bonding during the formation of the second layer. Therefore, the coating film  32  is likely to degrade. That is, the coated conductive wires S 1  and S 4  that constitute the first layer suffers greater damage than the coated conductive wires S 2  and S 3  that constitutes the second layer. Therefore, defective portions such as scratches or cracks are more likely to emerge in the coating film  32  of the coated conductive wires S 1  and S 4 . 
     After the work to wind the coated conductive wires S 1  to S 4  is completed, the plate core  12  is bonded to the drum core  11 . More specifically, a small amount of adhesive is applied to the flange portions  11   b  and  11   c  of the drum core  11 . Then, the plate core  12  is placed on the flange portions  11   b  and  11   c  of the drum core  11 . Then, thermal treatment is carried out to solidify the adhesive, and the plate core  12  is firmly fixed to the drum core  11  as a result. This thermal treatment is carried out at 150 degrees Celsius for about one hour, for example. 
     The resin film  33  that exists on the surfaces of the coated conductive wires S 1  to S 4  melts during the thermal treatment, and is infiltrated into gaps between the coated conductive wires S 1  to S 4 . If defective portions F such as scratches or cracks exist on the coating film  32 , the defective portions F are filled with the resin coating layer  20  which is the melted resin film  33 . The resin coating layer  20  which is the melted resin film  33  gathers around the coated conductive wires S 1  and S 4  located in the first layer because of capillarity. Therefore, at least almost the entire area of the first layer is covered with the resin coating layer  20 . On the other hand, mainly the upper surface U of the second layer may not be covered with the resin coating layer  20 , and the coating film  32  is sometimes being exposed. Incidentally, the resin film  33  that exists in the wire connection portions E 1  to E 6  has changed in quality due to the heat at the time of wire connection. The resin film  33  therefore does not melt during the thermal treatment. 
     Through the steps described above, the coil component  10  of the present embodiment is completed. 
     As described above, according to the present embodiment, the coated conductive wires S 1  to S 4  whose surface is covered with the resin film  33  are used. Then, thermal treatment is carried out so that the resin film  33  melts. In this manner, the resin coating layer  20  is formed. As a result, at least the surfaces of the coated conductive wires S 1  and S 4  that are located in the first layer are automatically covered with the resin coating layer  20 . As described above, the coated conductive wires S 1  and S 4  that are located in the first layer suffer thermal damage twice, and defective portions F are likely to emerge in the coating film  32 . However, according to the present embodiment, the surfaces of the coated conductive wires S 1  and S 4  that are located in the first layer are automatically covered with the resin coating layer  20 . Therefore, it is possible to ensure that defective portions F that emerge in the first-layer coating film  32  are filled with the resin coating layer  20 . Even if defective portions F emerge in the coating film  32 , it is possible to secure a sufficient dielectric strength voltage. 
     Another possible method is to coat with the resin material after the coated conductive wires S 1  to S 4  are wound around the winding core portion  11   a  in order to improve the dielectric strength voltage. However, if the viscosity of the resin material is high, the coated conductive wires S 1  to S 4  cannot be sufficiently coated. If the viscosity of the resin material is low, the resin material can get into the flange portions  11   b  and  11   c  of the drum core  11  because of capillarity. Particularly in the case of a coil component that is low in height with a small difference in height between the winding core portion  11   a  and the flange portions  11   b  and  11   c , the inflow of the resin material inevitably occurs due to capillarity. 
     If the resin material flows to the lower surfaces of the flange portions  11   b  and  11   c , the flow of the resin material creates a gap between the flange portions  11   b  and  11   c  and the plate core  12 , resulting in a decrease in magnetic properties. If the resin material flows to the upper surfaces  11   bs  and lies of the flange portions  11   b  and  11   c , the wire connection portions E 1  to E 6  that are terminal electrodes may be partially covered with the resin material, leading to a decrease in solder wettability at the time of implementation. 
     According to the present embodiment, the coated conductive wires S 1  to S 4  that are wound are not coated later with the resin material. The winding work is performed with the use of the coated conductive wires S 1  to S 4  on the surfaces of which the resin film  33  is provided in advance. After that, the resin film  33  is melted to form the resin coating layer  20 , thereby eliminating the risk that the resin material could flow into the flange portions  11   b  and  11   c . Furthermore, it is possible to ensure that the resin coating layer  20  covers the first layer constituted of the coated conductive wires S 1  and S 4  in which defective portions F are more likely to occur. 
     As described above, in the coil component  10  of the present embodiment, at least the coated conductive wires S 1  and S 4  that are located in the first layer are covered with the resin coating layer  20 . Even if the coated conductive wires that are thin in diameter are used, it is possible to secure a sufficient dielectric strength voltage. Moreover, the resin coating layer  20  does not reach the flange portions  11   b  and  11   c . Therefore, it is possible to prevent a decrease in magnetic properties and a drop in solder wettability. 
       FIG. 7  is a schematic plan view showing the configuration of a coil component  13  according to the second embodiment of the present invention, showing the configuration of a bottom surface side. 
     As shown in  FIG. 7 , the coil component  13  of the second embodiment is characterized in that the number of wire connection portions provided in each of the flange portions  11   b  and  11   c  is not 3 but 4. In the flange portion  11   b , four wire connection portions E 1 , E 2 , E 3   a , and E 3   b  are provided. In the flange portion  11   c , four wire connection portions E 4   a , E 4   b , E 5 , and E 6  are provided. An electrical connection between the other end S 1   b  of the coated conductive wire S 1  and one end S 2   a  of the coated conductive wire S 2  is achieved by a wiring pattern or land pattern on a printed circuit board at a time when the coil component  13  is mounted. Similarly, an electrical connection between the other end S 3   b  of the coated conductive wire S 3  and one end S 4   a  of the coated conductive wire S 4  is achieved by a wiring pattern or land pattern on a printed circuit board at a time when the coil component  13  is mounted. The rest of the configuration is the same as that of the coil component  10  of the first embodiment. Therefore, the same components will be represented by the same reference symbols, and will not be described again. 
     In that manner, in the coil component  13  of the present embodiment, the two wire connection portions E 3   a  and E 3   b  are short-circuited on the printed circuit board. Furthermore, the two wire connection portions E 4   a  and E 4   b  are short-circuited on the printed circuit board. Accordingly, it is possible to realize the same structure as that of the coil component  10  of the first embodiment. Thus, it is possible to achieve the same operation and advantageous effects as the first embodiment. 
       FIG. 8  is a cross-sectional view showing one example of an xz cross-section of a winding core portion  11   a  of a drum core  11 . 
     In the example shown in  FIG. 8 , an upper surface  14  and lower surface  15  of the winding core portion  11   a  are arc-shaped. If the winding core portion  11   a  that has such an arc-shaped cross-section is used, the melted resin film  33  is infiltrated into the corners of the winding core portion  11   a  more easily than when a winding core portion  11   a  that is rectangular in cross-section is used. As a result, it is possible to ensure that the resin coating layer  20  covers the coated conductive wires S 1  and S 4  that are located at the corners of the winding core portion  11   a . If the winding core portion  11   a  is elliptical or circular in cross-section, there are no corners. Therefore, it is possible to ensure that the resin coating layer  20  covers the coated conductive wires S 1  and S 4 . 
     It is apparent that the present invention is not limited to the above embodiments, but may be modified and changed without departing from the scope and spirit of the invention. 
     For example, according to the above embodiments, the coated conductive wires that are wound around the winding core portion constitute a double-layered structure. However, the coil component of the present invention is not limited to this.