Patent Publication Number: US-11037719-B2

Title: Coil component

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims benefit of priority to Japanese Patent Application No. 2017-222336, filed Nov. 18, 2017, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to coil components and in particular to a coil component including a drum core and a planar core. 
     Background Art 
     One example known technique is described in Japanese Patent No. 5796603. FIG. 14 is created on the based on FIG. 2(a) in Japanese Patent No. 5796603 and illustrates one flange portion 2 of a drum core 1 and a planar core 3 in a coil component. 
     The drum core 1 includes a winding core portion around which a wire is wound and first and second flange portions on the respective end portions of the winding core portion.  FIG. 14  illustrates one flange portion 2 of the first and second flange portions. The flange portion 2 has an inner end surface (not illustrated) facing the winding core portion side and positioning the end portion of the winding core portion, an outer end surface 4 facing an outer side opposite to the winding core portion side, a bottom surface 5 linking the inner end surface and the outer end surface 4 and placed so as to face a mounting substrate side when being mounted, and a top surface 6 opposite to the bottom surface 5. 
     The planar core 3 has a lower principal surface 7 and an upper principal surface 8 facing in mutually opposite directions. The lower principal surface 7 of the planar core 3 is fixed to the top surface 6 with an adhesive 9 interposed therebetween. 
     Japanese Patent No. 5796603 discloses a structure that can provide high bonding strength between the drum core 1 and planar core 3 even with a small amount of the adhesive 9. Specifically, the illustrated flange portion 2 has a flat surface 10 positioned at the highest level in a central portion 11 of the top surface 6 and has inclined surfaces 12 and 13 inclined downward from the flat surface 10 toward the end surfaces. Each of the flat surface 10 and the inclined surfaces 12 and 13 is made of a plane. 
     In the coil component in Japanese Patent No. 5796603, the top surface 6 of the flange portion 2 and the lower principal surface 7 of the planar core 3 are in direct contact with each other at the flat surface 10 in the central portion 11 without the adhesive 9 therebetween and are opposed to each other with a gap interposed therebetween that is gradually narrower from the end surface of the top surface 6 toward the central portion of the top surface 6, and the adhesive 9 is arranged in the gap. 
     With the technique described in Japanese Patent No. 5796603, because a capillary phenomenon can be produced on the central portion side in the vicinity of the flat surface 10 of the top surface 6 in the gap, the space between the flange portion 2 and planar core 3 can be filled with a minimum amount of the adhesive 9. Thus, according to Japanese Patent No. 5796603, a relatively high bonding strength between the drum core 1 and planar core 3 is obtainable with a relatively smaller amount of the adhesive 9. 
     SUMMARY 
     In the case of the coil component described in Japanese Patent No. 5796603, however, the top surface 6 of the flange portion 2 and the lower principal surface 7 of the planar core 3 are in direct contact with each other at the flat surface 10 in the central portion 11 of the top surface 6, and the adhesive 9 is absent in that region. This means a reduction in bonding area. There is no denying that a reduced bonding area leads to a reduction in bonding strength between the top surface 6 of the flange portion 2 and the lower principal surface 7 of the planar core 3. In particular, when the coil component is miniaturized, for example, to plane dimensions of less than about 1 mm, such as about 0.4 mm×about 0.2 mm or about 0.2 mm×about 0.1 mm, the reduction in bonding area has a serious effect on the reduction in bonding strength. 
     In the coil component described in Japanese Patent No. 5796603, one approach to increasing the bonding strength between the top surface 6 of the flange portion 2 and the lower principal surface 7 of the planar core 3 is to decrease the area of the flat surface 10 in the central portion 11 of the top surface 6 and, in return, extend the area of the inclined surfaces 12 and 13, which allow the presence of the adhesive 9. Unfortunately, however, this approach will be confronted with problems described below. 
     In the above-described coil component, each of the drum core 1 and planar core 3 may be made of a magnetic material, such as ferrite. Thus, the planar core 3 constitutes a closed magnetic path in coordination with the drum core 1. In this closed path, a gap between the planar core 3 and drum core 1 causes magnetic resistance. If the area of the inclined surfaces 12 and 13 is increased, as previously described, the magnetic resistance increases, and this results in a reduction in inductance of the coil component. 
     Hence it is difficult to achieve both satisfactory bonding strength and inductance. 
     Accordingly, the present disclosure provides a coil component having a structure capable of both achieving an adequate bonding strength in a portion where a drum core and a planar core are bonded together and suppressing a reduction in inductance. 
     According to one embodiment of the present disclosure, a coil component includes a drum core including a winding core portion and a flange portion disposed on an end portion of the winding core portion in an axial direction thereof and made of a magnetic material, a planar core having a lower principal surface and made of a magnetic material, and a wire wound around the winding core portion. 
     The flange portion includes an inner end surface, an outer end surface, a bottom surface, and a top surface. The inner end surface faces an inner side being near the winding core portion and positions the end portion of the winding core portion. The outer end surface faces an outer side being opposite to the inner side. The bottom surface links the inner end surface and the outer end surface and placed so as to face a mounting substrate side when being mounted. The top surface is opposite to the bottom surface. 
     The lower principal surface of the planar core is fixed to the top surface with an adhesive interposed therebetween. The top surface includes a protrusion with a vertex positioned closer to the inner end surface than to the outer end surface. 
     Because the vertex of the protrusion is positioned closer to the inner end surface, the magnetic resistance in a section with a shorter path of the magnetic path formed of the drum core and planar core can be reduced. In addition, because it is not necessary to have direct contact between the top surface of the flange portion and the lower principal surface of the planar core, a large bonding area can be ensured. 
     The top surface in the above-described coil component may preferably be closest to the lower principal surface at the vertex. In this configuration, a stable magnetic path can be achieved in a section with a shorter path of the magnetic path formed of the drum core and planar core. 
     An interval between the top surface and the lower principal surface on a side near to the outer end surface with respect to the vertex in the above-described coil component may preferably widen from a side near to the inner end surface toward the side near to the outer end surface. In this configuration, the adhesive can be smoothly interposed between the top surface of the flange portion and the lower principal surface of the planar core. 
     The adhesive in the above-described coil component may preferably be present over substantially all of a region where the top surface and the lower principal surface face each other, the region containing the protrusion. In this configuration, the adhesive can be interposed between the flange portion and the planar core without having to rely on capillary action, and the bonding area between the flange portion and the planar core can be enlarged sufficiently. Consequently, the bonding strength between the flange portion and the planar core can be improved sufficiently. 
     The top surface in the above-described coil component may preferably further include a second protrusion with a vertex in a position different from the vertex of the protrusion. In this configuration, the state in which the planar core is supported at two points with respect to the top surface can be achieved, and the attitude of the planar core with respect to the drum core can be maintained stable. 
     The drum core in the above-described coil component may preferably include a second flange portion disposed on a second end portion of the winding core portion opposite to the end portion in the axial direction. The second flange portion may preferably have a second top surface facing the same side as the top surface and including a third protrusion with a vertex positioned closer to a surface of the second flange portion on the inner side than to a surface thereof on the outer side, and when viewed from the axial direction, the vertex of the third protrusion may preferably be located between the vertex of the first protrusion and the vertex of the second protrusion. The vertex of the third protrusion may preferably be positioned in a central portion of the second top surface when viewed from the axial direction. 
     In this configuration, the attitude of the planar core is more stabilized, and the magnetic resistance between the flange portion and the planar core is stable. Therefore, variations in inductance of the coil component can be suppressed. 
     A length of the planar core along the axial direction in the above-described coil component may be shorter than that of the drum core. In this configuration, if the planar core is slightly displaced with respect to the drum core, the external shape of the coil component can be recognized on the basis of the external shape of the drum core in a mounting state, and thus the mounting position of the coil component can be accurately determined by image recognition. 
     According to the present disclosure, the magnetic resistance in a section with a shorter path of the magnetic path formed of the drum core and planar core can be reduced. 
     In addition, a wide bonding area can be ensured. Accordingly, an adequate bonding strength between the drum core and the planar core is obtainable, and at the same time, a reduction in inductance can be suppressed. 
     Other features, elements, characteristics and advantages of the present disclosure will become more apparent from the following detailed description with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view that illustrates an outer appearance of a coil component according to a first embodiment of the present disclosure; 
         FIG. 2  is a perspective view that illustrates a drum core and a planar core included in the coil component illustrated in  FIG. 1  in a state where they are assembled; 
         FIG. 3  is a front view that illustrates the drum core and planar core in the assembled state illustrated in  FIG. 2 ; 
         FIG. 4  is a left side view that illustrates the drum core and planar core in the assembled state illustrated in  FIG. 2 ; 
         FIG. 5  is a front view that illustrates a drum core and a planar core included in a coil component according to a second embodiment of the present disclosure in a state in which they are assembled; 
         FIG. 6  is a front view that illustrates a drum core and a planar core included in a coil component according to a third embodiment of the present disclosure in a state in which they are assembled; 
         FIG. 7  is a left side view that illustrates the drum core and planar core in the assembled state illustrated in  FIG. 6 ; 
         FIG. 8  is a front view that illustrates a drum core and a planar core included in a coil component according to a fourth embodiment of the present disclosure in a state in which they are assembled; 
         FIG. 9  is a left side view that illustrates the drum core and planar core in the assembled state illustrated in  FIG. 8 ; 
         FIG. 10  is a perspective view that illustrates an outer appearance of a drum core included in a coil component according to a fifth embodiment of the present disclosure; 
         FIG. 11  is a front view that illustrates the drum core illustrated in  FIG. 10 ; 
         FIG. 12  is a right side view that illustrates the drum core illustrated in  FIG. 10 ; 
         FIG. 13  is a left side view that illustrates the drum core illustrated in  FIG. 10 ; and 
         FIG. 14  is a side view that illustrates one flange portion of a drum core and a planar core in a coil component described in Japanese Patent No. 5796603. 
     
    
    
     DETAILED DESCRIPTION 
     A coil component  21  according to a first embodiment of the present disclosure is described with reference to  FIGS. 1 to 4 . One example of the illustrated coil component  21  constitutes a common-mode choke coil. 
     The coil component  21  includes a drum core  23  including a winding core portion  22  having first and second end portions opposite to each other in its axial direction. The drum core  23  includes first and second flange portions  24  and  25  disposed on the first and second end portions of the winding core portion  22 , respectively. The drum core  23  is made of a magnetic material, more specifically, a magnetic substance, such as nickel-zinc ferrite, an amorphous metal material, a resin containing magnetic powder, or the like. One example of the winding core portion  22  in the drum core  23  may form a substantially rectangular columnar shape with a substantially rectangular cross section. 
     Each of the first and second flange portions  24  and  25  has an inner end surface  26  facing an inner side being near to the winding core portion  22  and positioning the corresponding end surface of the winding core portion  22  and an outer end surface  27  facing an outer side being opposite to the inner side (side near to the inner end surface  26 ). Each of the first and second flange portions  24  and  25  has first and second side surfaces  28  and  29  linking the inner end surface  26  and outer end surface  27  and facing mutually opposite sides. Each of the first and second flange portions  24  and  25  further includes a bottom surface  30  linking the inner end surface  26  and the outer end surface  27 , linking the first and second side surfaces  28  and  29 , and placed so as to face a mounting substrate side when being mounted and a top surface  31  opposite to the bottom surface  30 . 
     In the illustrated embodiment, the inner end surface  26  is substantially parallel to the outer end surface  27 . The inner end surface  26  may be inclined toward the outer end surface  27 . 
     First and second terminal electrodes  32  and  33  (see  FIG. 4 ) are disposed on the first flange portion  24 . Third and fourth terminal electrodes  34  and  35  (see  FIGS. 1 and 2 ) are disposed on the second flange portion  25 . The first and second terminal electrodes  32  and  33  extend from the bottom surface  30  of the first flange portion  24  to a portion of the outer end surface  27 . The third and fourth terminal electrodes  34  and  35  extend from the bottom surface  30  of the second flange portion  25  to a portion of the outer end surface  27 . 
     The terminal electrodes  32  to  35  may be formed by applying conductive paste containing silver as its conductive component and baking it. The terminal electrodes  32  to  35  may be formed by, instead of baking the conductive paste, bonding a terminal metal part made of a conductive metal to the flange portions  24  and  25 . 
     The terminal electrodes  32  to  35  may be covered with plating if needed. One example plating method used here may be the electrolytic plating method. By the application of plating, for example, a nickel plating film may be formed and a tin plating film may be formed thereon or a copper plating film may be formed, a nickel plating film may be formed thereon, and a tin plating film may be formed thereon. 
     As schematically illustrated in  FIG. 1 , for example, two wires  36  and  37  are spirally wound around the winding core portion  22  in the same direction. One example of the wires  36  and  37  may be made of a copper wire covered with an electrical insulating resin, such as polyurethane or polyesterimide. The wires  36  and  37  may have a multilayer winding structure if needed. Although not specifically illustrated, a first end of the first wire  36  is connected to the first terminal electrode  32 , and a second end of the first wire  36  is connected to the third terminal electrode  34 , the second end being opposite to the first end. A first end of the second wire  37  is connected to the second terminal electrode  33 , and a second end of the second wire  37  is connected to the fourth terminal electrode  35 , the second end being opposite to the first end. These terminal electrodes  32  to  35  and the wires  36  and  37  may be connected by, for example, thermocompression bonding. 
     The coil component  21  further includes a planar core  38  placed over the gap between the first and second flange portions  24  and  25 . The planar core  38  constitutes a closed magnetic path in coordination with the drum core  23 . Like the drum core  23 , the planar core  38  is made of a magnetic material, more specifically, a magnetic substance, such as nickel-zinc ferrite, an amorphous metal material, a resin containing magnetic powder, or the like. 
     The planar core  38  has a lower principal surface  39  and an upper principal surface  40  facing in mutually opposite directions. The planar core  38  is fixed to the top surfaces  31  of the flange portions  24  and  25  in the state where the lower principal surface  39  faces the top surfaces  31  of the flange portions  24  and  25  with adhesive  41  (see  FIG. 1 ) interposed therebetween. One example material of the adhesive  41  may be a material made of a thermosetting epoxy resin. By hot-pressing that material for about 10 minutes at about 150° C., the fixation of the planar core  38  and the flange portions  24  and  25  can be achieved. 
     Next, a characteristic configuration in the coil component  21  is described. 
     Focusing on the top surface  31  of each of the first and second flange portions  24  and  25 , as illustrated well in  FIGS. 3 and 4 , the top surface  31  of the first flange portion  24  includes a first protrusion  42 , and the top surface  31  of the second flange portion  25  includes a third protrusion  43 . A vertex  42   a  of the first protrusion  42  is positioned closer to the inner end surface  26  of the first flange portion  24  than to the outer end surface  27 . A vertex  43   a  of the third protrusion  43  is positioned closer to the inner end surface  26  of the second flange portion  25  than to the outer end surface  27 . Thus, the top surfaces  31  of the first and second flange portions  24  and  25  are closer to the lower principal surface  39  of the planar core  38  at the vertices  42   a  and  43   a  than that at their peripheral portions. 
     In the present embodiment, the top surfaces  31  of the first and second flange portions  24  and  25  are closest to the lower principal surface  39  of the planar core  38  at the vertices  42   a  and  43   a . In this configuration, the magnetic path formed of the drum core  23  and planar core  38  can be stable in a section with a shorter path of the magnetic path. 
     As described above, because the vertex  42   a  of the first protrusion  42  and the vertex  43   a  of the third protrusion  43  are closer to the inner end surface  26  of the first flange portion  24  and that of the second flange portion  25 , respectively, the magnetic resistance can be reduced in a section with a shorter path of the magnetic path formed of the drum core  23  and planar core  38 . Thus, the inductance is efficiently obtainable. 
     In bonding the drum core  23  and planar core  38 , it is not necessary to have direct contact of the top surface  31  of each of the flange portions  24  and  25  with the lower principal surface  39  of the planar core  38 . Therefore, a wide area for bonding by the adhesive  41  can be ensured. Accordingly, an adequate bonding strength between the drum core  23  and planar core  38  is obtainable, and at the same time, a reduction in inductance can be suppressed. 
     In particular, in the present embodiment, although not illustrated explicitly, the adhesive  41  is present all over the region where the top surface  31  of each of the first and second flange portions  24  and  25  and the lower principal surface  39  of the planar core  38  face each other, the region containing a location where the protrusions  42  and  43  face the lower principal surface  39  of the planar core  38 . In this configuration, the adhesive  41  can be interposed between the flange portions  24  and  25  and the planar core  38  without having to rely on capillary action, and the bonding area between the flange portions  24  and  25  and the planar core  38  can be enlarged sufficiently. Consequently, the bonding strength between the flange portions  24  and  25  and the planar core  38  can be improved sufficiently. 
     The above-described phrase “all over the region” indicates substantially all over the region and permits the region to contain a portion where the adhesive  41  is absent at an outer edge or other area, such as a portion on a ridge of the top surfaces  31  of the first and second flange portions  24  and  25 . In particular, in some cases, for example, if the ridge is curved by, for example, barrel finishing, the portion may not be defined as the region where the top surface  31  and the lower principal surface  39  face each other in a strict sense. 
     The present embodiment has a characteristic in which, on the side near to the outer end surfaces  27  with respect to the vertices  42   a  and  43   a , the interval between the top surface  31  of each of the first and second flange portions  24  and  25  and the lower principal surface  39  of the planar core  38  widens from the side near to the inner end surface  26  of each of the first and second flange portions  24  and  25  toward the side near to the outer end surface  27 , as well illustrated in  FIG. 3 . In this configuration, the adhesive  41  can be smoothly interposed between the top surface  31  of each of the flange portions  24  and  25  and the lower principal surface  39  of the planar core  38 . In particular, the magnetic path passing through the side close to the outer end surface  27  and each of the flange portions  24  and  25  has a longer path in the magnetic path formed of the drum core  23  and planar core  38 , and if the interval is extended in this region, the effect on the obtainment of inductance is relatively small. Accordingly, in the above-described configuration, the effect on an inductance reduction occurring with improvement in the bonding strength can be relatively small. 
     When a direction that is substantially perpendicular to the direction in which the winding core portion  22  extends and that is substantially perpendicular to the direction in which the bottom surface  30  and top surface  31  of each of the flange portions  24  and  25  face each other is the width direction, the vertex  42   a  of the first protrusion  42  and the vertex  43   a  of the third protrusion  43  are positioned in central portions of the top surfaces  31  of the flange portions  24  and  25  in the width direction, respectively, as well illustrated in  FIG. 4 . The interval between the top surface  31  of each of the flange portions  24  and  25  and the lower principal surface  39  of the planar core  38  widens from the central portion of each of the flange portions  24  and  25  in the width direction toward the first and second side surfaces  28  and  29 . In this configuration, the adhesive  41  can be smoothly interposed between the top surface  31  of each of the flange portions  24  and  25  and the lower principal surface  39  of the planar core  38 . 
     In the present embodiment, the slope to each of the vertex  42   a  of the first protrusion  42  and the vertex  43   a  of the third protrusion  43  has a convex spherical surface, as well illustrated in  FIGS. 3 and 4 . 
       FIG. 5  is an illustration for describing a second embodiment of the present disclosure and corresponds to  FIG. 3 . In  FIG. 5 , the same reference numerals are used in elements corresponding to the elements illustrated in  FIG. 3 , and redundant description is omitted. 
     According to the characteristic configuration in the first embodiment described above, the top surfaces  31  of the first and second flange portions  24  and  25  include the protrusions  42  and  43  with the vertices  42   a  and  43   a  positioned closer to the inner end surface  26  than to the outer end surface  27 . Thus, the length along the axial direction of the winding core portion  22  of the planar core  38  can be shorter than that of the drum core  23 . The coil component adopting this configuration is the second embodiment illustrated in  FIG. 5 . 
     That is, in the second embodiment, for the length along the axial direction, the length L 1  of the planar core  38  is shorter than the length L 2  of the drum core  23 . In this configuration, if the planar core  38  is slightly displaced with respect to the drum core  23 , the external shape of the coil component can be recognized on the basis of the external shape of the drum core  23  in a mounting state, and thus the mounting position of the coil component can be accurately determined by image recognition. As described above, by positioning the vertex  42   a  of the first protrusion  42  and the vertex  43   a  of the third protrusion  43  on the sides closer to the inner end surfaces  26  of the flange portions  24  and  25 , respectively, the magnetic resistance is reduced on the side closer to each of the inner end surfaces  26 . Therefore, even when the dimension L 1  is shorter than the dimension L 2 , the effect on the inductance can be small. 
       FIGS. 6 and 7  are illustrations for describing a third embodiment of the present disclosure.  FIG. 6  corresponds to  FIG. 3 , and  FIG. 7  corresponds to  FIG. 4 . In  FIGS. 6 and 7 , the same reference numerals are used in elements corresponding to the elements illustrated in  FIGS. 3 and 4 , and redundant description is omitted. 
     In the third embodiment, the shapes of first and third protrusions  44  and  45  are different from those of the first and third protrusions  42  and  43  in the first embodiment. The first and third protrusions  44  and  45  have relatively wide planes at vertices  44   a  and  45   a . In the protrusions  44  and  45 , the slope to each of the vertices  44   a  and  45   a  extends linearly in cross section. 
     The operational advantages from the first and third protrusions  44  and  45  in the third embodiment are substantially the same as those from the first and third protrusions  42  and  43  in the first embodiment. 
       FIGS. 8 and 9  are illustrations for describing a fourth embodiment of the present disclosure.  FIG. 8  corresponds to  FIG. 3 , and  FIG. 9  corresponds to  FIG. 4 . In  FIGS. 8 and 9 , the same reference numerals are used in elements corresponding to the elements illustrated in  FIGS. 3 and 4 , and redundant description is omitted. 
     In the fourth embodiment, the shapes of first and third protrusions  46  and  47  are different from the corresponding ones in the first embodiment. Like in the case of the first and third protrusions  44  and  45  in the third embodiment, the first and third protrusions  46  and  47  have relatively wide planes at vertices  46   a  and  47   a . The vertices  46   a  and  47   a  in the first and third protrusions  46  and  47  are defined by surrounding walls rising substantially perpendicularly from the top surfaces  31  of the flange portions  24  and  25 . 
     The operational advantages from the first and third protrusions  46  and  47  in the fourth embodiment are substantially the same as those from the first and third protrusions  42  and  43  in the first embodiment. 
       FIGS. 10 to 13  are illustrations for describing a fifth embodiment of the present disclosure. Unlike  FIGS. 2 to 4 ,  FIGS. 10 to 13  do not illustrate the planar core  38  and illustrate only the drum core  23 . In  FIGS. 10 to 13 , the same reference numerals are used in elements corresponding to the elements illustrated in  FIGS. 2 to 4 , and redundant description is omitted. 
     In the fifth embodiment, as in the case of the first embodiment, first, the first and second flange portions  24  and  25  include the first and third protrusions  42  and  43  in their respective top surfaces  31 . In the fifth embodiment, the first flange portion  24  further includes a second protrusion  48  in the top surface  31  of the first flange portion  24 , in addition to the first protrusion  42 . In  FIG. 10 , the positions of the vertices  42   a ,  48   a , and  43   a  of the first, second, and third protrusions  42 ,  48 , and  43  are indicated by circles. The vertex  48   a  of the second protrusion  48  is arranged in a position different from the vertex  42   a  of the first protrusion  42 . 
     The positions of the vertices  42   a ,  48   a , and  43   a  of the first, second, and third protrusions  42 ,  48 , and  43  are selected as described below. When a direction that is substantially perpendicular to the direction in which the winding core portion  22  extends and that is substantially perpendicular to the direction in which the bottom surface  30  and top surface  31  of each of the flange portions  24  and  25  face each other is the width direction, as illustrated in  FIGS. 10 to 13 , the position of the vertex  43   a  of the third protrusion  43  in the width direction may preferably be located between the position of the vertex  42   a  of the first protrusion  42  in the width direction and the position of the vertex  48   a  of the second protrusion  48  in the width direction. That is, when viewed from the axial direction, the vertex  43   a  of the third protrusion  43  may preferably be present between the vertex  42   a  of the first protrusion  42  and the vertex  48   a  of the second protrusion  48 . More preferably, each of the vertex  42   a  of the first protrusion  42  and the vertex  48   a  of the second protrusion  48  may be in a position that deviates from the central portion of the top surface  31  of the first flange portion  24  along the width direction, whereas the vertex  43   a  of the third protrusion  43  may be in a central portion of the second top surface  31  of the second flange portion  25  in the width direction. That is, when viewed from the axial direction, the vertex  43   a  of the third protrusion  43  is positioned in the central portion of the second top surface  31  of the second flange portion  25 . In this configuration, the attitude of the planar core (not illustrated) is more stabilized, and the magnetic resistance between the first and second flange portions  24  and  25  and the planar core is stable. Accordingly, variations in inductance of the coil component can be suppressed. 
     According to the fifth embodiment, because the top surface  31  of the first flange portion  24  has the second protrusion  48 , the state in which the planar core (not illustrated) is supported at two points with respect to the top surface  31  of the first flange portion  24  can be achieved, and thus the attitude of the planar core with respect to the drum core  23  can be maintained with stability. 
     As is apparent from the above, the top surface  31  of the first flange portion  24  and the second top surface  31  (surface facing the same side of the top surface  31  of the first flange portion  24 ) of the second flange portion  25  may have different shapes. Accordingly, the coil component may have a configuration in which the top surface  31  of the first flange portion  24  includes the first protrusion  42  and the second top surface  31  of the second flange portion  25  has no protrusion. As in the above-described embodiment, the configuration in which the second top surface  31  has the third protrusion  43  with the vertex  43   a  positioned closer to the inner surface (inner end surface  26 ) of the second flange portion  25  than to the outer surface (outer end surface  27 ) can provide better advantages. 
     The present disclosure is described above in relation to the illustrated embodiments. Various modification examples can be made within the scope of the present disclosure. 
     For example, because the ridge of each of the flange portions  24  and  25  near to the inner end surface  26  may often be a curved surface formed by, for example, barrel finishing, the gap between the planar core  38  and each of the flange portions  24  and  25  on the side near to the inner end surface  26  with respect to the vertices  42   a  to  48   a  may be somewhat extended. 
     The coil component  21 , which constitutes a common-mode choke coil in the above-described embodiments, may constitute a single coil or other devices, such as a transformer or a balun. Accordingly, the number of wires may be any number, that is, one or three or more. In response to the number of wires, the number of terminal electrodes on the flange portions may be changed. 
     In configuring the coil component according to the present disclosure, among different embodiments described in this specification, the configurations may be replaced in part or combined. 
     While some embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.