Patent Publication Number: US-10325711-B2

Title: Coil component

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of priority to Japanese Patent Application 2016-008993 filed Jan. 20, 2016, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a coil component. Specifically, the present disclosure relates to a laminated coil component. 
     BACKGROUND 
     Conventional laminated coil components employ a form in which one planar spiral wiring wound in one direction is in an interconnection with another planar spiral wiring wound in a direction opposite to the one direction through a connection via along a laminated direction. Japanese Laid-Open Patent Publication No. 2013-225718 discloses a laminated coil component. In the laminated coil component, an inner circumferential end of the one planar spiral wiring is in the interconnection with an inner circumferential end of another planar spiral wiring through one connection via. 
     SUMMARY 
     Problem to be Solved by the Disclosure 
     However, when an inner circumferential end of one planar spiral wiring  101  is in interconnection with an inner circumferential end of another planar spiral wiring  102  through one connection via  103  along a laminated direction as shown in  FIG. 9 , a connection-reliability may not be sufficient. 
     It is therefore an object of an aspect of the present disclosure to provide a coil component capable of improving the connection-reliability between one planar spiral wiring and another planar spiral wiring disposed along the laminated direction. 
     Solutions to the Problems 
     To solve the problem, an aspect of the present disclosure provides, a coil component comprising: 
     a first planar spiral wiring; and 
     a second planar spiral wiring located above the first planar spiral wiring in a laminated direction and interconnected through connection vias to the first planar spiral wiring, wherein the second planar spiral wiring is wound in a direction different from a winding direction of the first planar spiral wiring when viewed in the laminated direction, 
     wherein the first planar spiral wiring and the second planar spiral wiring have respective innermost circumferential overlapping portions overlapping with each other at the innermost circumferential region when viewed in the laminated direction, and 
     wherein at least both end parts of the innermost circumferential overlapping portion of the first planar spiral wiring are in an interconnection with at least both end parts of the innermost circumferential overlapping portion of the second planar spiral wiring through the connection vias. 
     In the coil component of the aspect, at least both end parts of the innermost circumferential overlapping portion of the first planar spiral wiring are in the interconnection with at least both end parts of the innermost circumferential overlapping portion of the second planar spiral wiring through the connection vias, the innermost circumferential overlapping portion of the first planar spiral wiring and the innermost circumferential overlapping portion of the second planar spiral wiring overlapping with each other when viewed in the laminated direction. Thus, the innermost circumferential overlapping portion of the first planar spiral wiring is in the interconnection with the innermost circumferential overlapping portion of the second planar spiral wiring through two connection vias, which results in increased connection points as compared to the case of connecting the inner circumferential ends with each other through one connection via. Therefore, the connection-reliability between the first planar spiral wiring and the second planar spiral wiring can be improved without substantially changing the number of turns, the outermost circumferential diameter, the number of layers, etc. of these planar spiral wirings. 
     In an embodiment, one of end parts of the respective innermost circumferential overlapping portions of the first planar spiral wiring and the second planar spiral wiring are positioned at portions wound by a half circumference from other of end parts of the respective innermost circumferential overlapping portions of the first planar spiral wiring and the second planar spiral wiring. 
     Therefore, as compared to a conventional form of an interconnection between an inner circumferential end of one planar spiral wiring and an inner circumferential end of the other planar spiral wiring through one connection via along the laminated direction, the planar spiral wirings each have one fourth of the circumference additionally wound at the innermost circumferential region. As a result, the regions of the innermost circumferential overlapping portions of the planar spiral wirings can be enlarged while ensuring sufficient wiring distances. Therefore, regions for connecting the innermost circumferential overlapping portions with each other through a plurality of connection vias can be ensured. Thus, the connection-reliability can be improved between the first planar spiral wiring and the second planar spiral wiring. 
     In an embodiment, the innermost circumferential overlapping portion of the first planar spiral wiring between both end parts is in an interconnection with the innermost circumferential overlapping portion of the second planar spiral wiring between both end parts through one or more further connection vias. As a result, in addition to both end parts of the innermost circumferential overlapping portion of the first planar spiral wiring and both end parts of the innermost circumferential overlapping portion of the second planar spiral wiring, the innermost circumferential overlapping portion of the first planar spiral wiring between both end parts is in the interconnection with the innermost circumferential overlapping portion of the second planar spiral wiring between both end parts through the connection vias. Therefore, the connection points can be further increased between the first planar spiral wiring and the second planar spiral wiring. Thus, the connection-reliability can be further improved between the first planar spiral wiring and the second planar spiral wiring. 
     In an embodiment, an entire region of the innermost circumferential overlapping portion of the first planar spiral wiring is in an interconnection with an entire region of the innermost circumferential overlapping portion of the second planar spiral wiring through a connection via. 
     In other words, the connection via is filled between the innermost circumferential overlapping portion of the first planar spiral wiring and the innermost circumferential overlapping portion of the second planar spiral wiring. Therefore, a region of connection provided between the first planar spiral wiring and the second planar spiral wiring can be increased. Thus, the connection-reliability can be further improved between the first planar spiral wiring and the second planar spiral wiring. 
     In an embodiment, the coil component further comprises a magnetic core part extending in a winding center part of the first planar spiral wiring and a winding center part of the second planar spiral wiring. When the magnetic core part is made of a material with a high permeability, the inductance of the coil component can be increased. 
     In an embodiment, a width dimension of the innermost circumferential overlapping portion of the first planar spiral wiring is smaller than that of the portion other than the innermost circumferential overlapping portion of the first planar spiral wiring, and wherein a width dimension of the innermost circumferential overlapping portion of the second planar spiral wiring is smaller than a width dimension of the portion other than the innermost circumferential overlapping portion of the second planar spiral wiring. As a result, the regions of the winding center parts can be enlarged in the first planar spiral wiring and the second planar spiral wiring. Therefore, the magnetic core part extending in the winding center parts of the first planar spiral wiring and the second planar spiral wiring can be enlarged. Thus, the inductance of the coil component can be increased. 
     In an embodiment, a width dimension of the innermost circumferential overlapping portion of the first planar spiral wiring is smaller than the width dimension of a portion other than the innermost circumferential overlapping portion of the first planar spiral wiring, and an outer edge of the innermost circumferential overlapping portion of the first planar spiral wiring continues without unevenness to an outer edge of the portion other than the innermost circumferential overlapping portion of the first planar spiral wiring. Additionally, a width dimension of the innermost circumferential overlapping portion of the second planar spiral wiring is smaller than that of the portion other than the innermost circumferential overlapping portion of the second planar spiral wiring, and an outer edge of the innermost circumferential overlapping portion of the second planar spiral wiring continues without unevenness to an outer edge of the portion other than the innermost circumferential overlapping portion of the second planar spiral wiring. 
     As a result, the inner edges of the innermost circumferential overlapping portions of the first planar spiral wiring can be made discontinuous from the inner edges of other than the innermost circumferential overlapping portions of the first planar spiral wiring, and the inner edges of the innermost circumferential overlapping portions of the second planar spiral wiring can be also made discontinuous from the inner edges of other than the innermost circumferential overlapping portions of the second planar spiral wiring. Therefore, regions bulging outward can respectively be formed at the inner edge regions of the innermost circumferential overlapping portions of the first planar spiral wiring and the second planar spiral wiring. Thus, when the coil component further comprises the magnetic core part extending in the winding center part of the first planar spiral wiring and the winding center part of the second planar spiral wiring, the diameter of the magnetic core part can be increased by the bulges of the regions. Consequently, the inductance of the coil component can be increased. 
     Effect of the Disclosure 
     According to the coil component of the aspects, the connection-reliability can be improved between the first planar spiral wiring and the second planar spiral wiring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a coil component according to an embodiment. 
         FIG. 2  is a schematic plan view of a form in which both end parts of an innermost circumferential overlapping portion of a first planar spiral wiring are in an interconnection with both end parts of an innermost circumferential overlapping portion of a second planar spiral wiring through connection vias, the innermost circumferential overlapping portion of the first planar spiral wiring and the innermost circumferential overlapping portion of the second planar spiral wiring overlapping with each other when viewed in a laminated direction in a line segment  1 - 1  shown in  FIG. 1 . 
         FIG. 3A  is a schematic plan view of a form in which connection vias are disposed in both end parts of the innermost circumferential overlapping portion of the first planar spiral wiring. 
         FIG. 3B  is a schematic plan view of a form in which connection vias are disposed in both end parts of the innermost circumferential overlapping portion of the second planar spiral wiring. 
         FIG. 4A  is a schematic plan view of a form in which a plurality of connection vias are disposed in the innermost circumferential overlapping portion of the first planar spiral wiring. 
         FIG. 4B  is a schematic plan view of a form in which a plurality of connection vias are disposed in the innermost circumferential overlapping portion of the second planar spiral wiring. 
         FIG. 5A  is a schematic plan view of a form in which a connection via is disposed in the entire region of the innermost circumferential overlapping portion of the first planar spiral wiring. 
         FIG. 5B  is a schematic plan view of a form in which a connection via is disposed in the entire region of the innermost circumferential overlapping portion of the second planar spiral wiring. 
         FIG. 6A  is a schematic plan view of a form in which a width dimension of the innermost circumferential overlapping portion of the first planar spiral wiring is smaller than that of the portion other than the innermost circumferential overlapping portion of the first planar spiral wiring. 
         FIG. 6B  is a schematic plan view of a form in which a width dimension of the innermost circumferential overlapping portion of the second planar spiral wiring is smaller than that of the portion other than the innermost circumferential overlapping portion of the second planar spiral wiring. 
         FIG. 7A  is a schematic plan view of another form in which connection vias are disposed in both end parts of the innermost circumferential overlapping portion of the first planar spiral wiring. 
         FIG. 7B  is a schematic plan view of another form in which connection vias are disposed in both end parts of the innermost circumferential overlapping portion of the second planar spiral wiring. 
         FIG. 8A  is a schematic cross-sectional view of a state for forming the first planar spiral wiring on an insulating layer. 
         FIG. 8B  is a schematic cross-sectional view of a state for forming the second planar spiral wiring on an insulating layer. 
         FIG. 8C  is schematic cross-sectional view of a state for further forming an insulating layer covering the second planar spiral wiring. 
         FIG. 8D  is a schematic cross-sectional view of a state for forming a through-hole for disposing a magnetic core part. 
         FIG. 8E  is a schematic cross-sectional view of a state for forming terminals on the insulating layer. 
         FIG. 8F  is a schematic cross-sectional view of a state for forming a magnetic core part and a magnetic body layer. 
         FIG. 8G  is a schematic cross-sectional view of a finally obtained coil component. 
         FIG. 9  is a schematic plan view of a conventional coil component. 
     
    
    
     DETAILED DESCRIPTION 
     A coil component related to a plurality of embodiments according to an aspect of the present disclosure will now be described with reference to the drawings. 
     In this description, a “laminated direction” refers to a direction in which layers are layered. A “first planar spiral wiring” and a “second planar spiral wiring” refer to spirally wound wirings. In this description, a “planar spiral wiring is wound in a different direction” refers to a state in which, for example, one planar spiral wiring is wound clockwise from the outside to the inside (or from the inside to the outside) while the other planar spiral wiring is wound counterclockwise. It is noted that not only when wirings completely overlap in the linewidth direction but also when wirings partially overlap in the linewidth direction, this overlapping portion may be regarded as an innermost circumferential overlapping portion. 
     First Embodiment 
     First, a coil component  1  related to a first embodiment according to an aspect of the present disclosure will be described with reference to  FIGS. 1 to 3B . 
       FIG. 1  is a schematic cross-sectional view of a coil component related to an embodiment.  FIG. 2  is a schematic plan view of a form in which both end parts of an innermost circumferential overlapping portion of a first planar spiral wiring are in an interconnection with both end parts of an innermost circumferential overlapping portion of a second planar spiral wiring through connection vias, the innermost circumferential overlapping portion of the first planar spiral wiring and the innermost circumferential overlapping portion of the second planar spiral wiring overlapping with each other when viewed in a laminated direction in a line segment  1 - 1  shown in  FIG. 1 .  FIG. 3A  is a schematic plan view of a form in which connection vias are disposed in both end parts of the innermost circumferential overlapping portion of the first planar spiral wiring.  FIG. 3B  is a schematic plan view of a form in which connection vias are disposed in both end parts of the innermost circumferential overlapping portion of the second planar spiral wiring. 
     The coil component  1  related to the first embodiment can be used in an electronic device such as a smartphone and a car navigation of an automobile, for example. The coil component  1  related to the first embodiment includes a first planar spiral wiring  2  and a second planar spiral wiring  3  disposed in an insulating layer  12  as shown in  FIG. 1 . As shown in  FIGS. 1 and 2 , a magnetic core part  13  is disposed to extend in a winding center part of the first planar spiral wiring  2  and a winding center part of the second planar spiral wiring  3 . As shown in  FIG. 1 , the magnetic core part  13  is disposed such that both end parts thereof are respectively connected to magnetic body layers  14 . The first planar spiral wiring  2  and the second planar spiral wiring  3  are disposed such that the second planar spiral wiring  3  is located above the first planar spiral wiring  2  along the laminated direction and the winding center parts of the first planar spiral wiring  2  and the second planar spiral wiring  3  overlap with each other. As shown in  FIGS. 3A and 3B , the first and second planar spiral wirings  2 ,  3  have lead parts  2   a ,  3   a  led out linearly from outer circumferential ends with spiral shapes. As shown in  FIG. 1 , the coil component  1  includes a pair of external terminals  39  as terminals for an external connection. One of the external terminals  39  is electrically connected through a connection via to a lead part  3   b  electrically connected to the lead part  2   a  of the first planar spiral wiring  2 , and the other external terminal  39  is electrically connected through a connection via to the lead part  3   a  of the second planar spiral wiring  3 . Although disposed in the same layer, the second planar spiral wiring  3  and the lead part  3   b  are not connected in this layer. 
     The second planar spiral wiring  3  (see  FIG. 3B ) is in the interconnection with the first planar spiral wiring  2  (see  FIG. 3A ) through connection vias along the laminated direction. The first planar spiral wiring  2  and the second planar spiral wiring  3  are each wound more than n times (n: natural number) and less than n+1 times. Therefore, each of the inner circumferential ends of the first planar spiral wiring  2  and the second planar spiral wiring  3  is located in a portion at which they are wound more than n times (n: natural number) and less than n+1 times. Specifically, in the coil component  1 , the first planar spiral wiring  2  is wound 1.5 times counterclockwise from the outside to the inside as shown in  FIG. 3A . In the coil component  1 , the second planar spiral wiring  3  is wound 1.5 times clockwise from the outside to the inside as shown in  FIG. 3B . Portions  5 ,  6  corresponding to portions respectively wound by a half circumference from end parts  7 ,  10  at the innermost circumferential regions of the first planar spiral wiring  2  and the second planar spiral wiring  3  are positioned such that the distance between the first planar spiral wiring  2  and the magnetic core part  13  substantially becomes equal to the distance between the second planar spiral wiring  3  and the magnetic core part  13 . Additionally, the first planar spiral wiring  2  and the second planar spiral wiring  3  respectively have width dimensions which are equal over their entire circumferences and they respectively have the width dimensions which are equal to each other. 
     In this case, as shown in  FIG. 2 , the portion  5  of the first planar spiral wiring  2  and the portion  6  of the second planar spiral wiring  3  form innermost circumferential overlapping portions substantially overlapping with each other at the innermost circumferential region when viewed in the laminated direction. Therefore, in the coil component  1 , the first planar spiral wiring  2  and the second planar spiral wiring  3  have the respective innermost circumferential overlapping portions  5 ,  6 . 
     As described above, in the first embodiment, one of the end parts of the respective innermost circumferential overlapping portions  5 ,  6  of the first planar spiral wiring  2  and the second planar spiral wiring  3  are positioned at portions wound by a half circumference from the other of the end parts of the respective innermost circumferential overlapping portions  5 ,  6  of the first planar spiral wiring  2  and the second planar spiral wiring  3 . Therefore, as compared to a conventional form in which the inner circumferential end of one planar spiral wiring  101  is in the interconnection with the inner circumferential end of the other planar spiral wiring  102  through one connection via  103  along the laminated direction as shown in  FIG. 9 , the first and second planar spiral wirings  2 ,  3  of the coil component  1  each have one fourth of the circumference additionally wound at the innermost circumferential region. In this case, the regions of the innermost circumferential overlapping portions  5 ,  6  of the planar spiral wirings  2 ,  3  can be enlarged while ensuring the wiring distances to the planar spiral wirings  2 ,  3  located immediately outside. 
     In the first embodiment, as shown in  FIG. 2 , the first end part  7  of the first planar spiral wiring  2  forming the one of the end parts of the innermost circumferential overlapping portion  5  is in the interconnection with the first end part  8  of the second planar spiral wiring  3  forming the one of the end parts of the innermost circumferential overlapping portion  6  through a first connection via  4 . The second end part  9  of the first planar spiral wiring  2  forming the other of the end parts of the innermost circumferential overlapping portion  5  is in the interconnection with the second end part  10  of the second planar spiral wiring  3  forming the other of the end parts of the innermost circumferential overlapping portion  6  through a second connection via  11 . Therefore, the two end parts  7 ,  9  of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  are in the interconnection with the two end parts  8 ,  10  of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  through the two connection vias  4 ,  11 . This results in increased connection points as compared to a case where the inner circumferential ends are interconnected through the one connection via  103  as shown in  FIG. 9 . Therefore, as compared to the conventional case where the inner circumferential end of a planar spiral wiring  101  is in the interconnection with the inner circumferential end of a planar spiral wiring  102  through the one connection via  103 , the planar spiral wiring  101  and a planar spiral wiring  102  being laminated with each other, the connection-reliability can be improved between the first planar spiral wiring  2  and the second planar spiral wiring  3 . 
     Additionally, since the innermost circumferential overlapping portion  5  of the planar spiral wirings  2  is in the interconnection with the innermost circumferential overlapping portion  6  of the planar spiral wirings  3  through the two connection vias  4 ,  11  in the coil component  1 , the innermost circumferential regions of the first and second spiral wirings  2 ,  3  are extended along the respective winding directions as compared to the conventional case where the inner circumferential end of the planar spiral wiring  101  is in the interconnection with the planar spiral wiring  102  through the one connection via  103  along the laminated direction. As a result, when viewed in the laminated direction, the planar spiral wirings  2 ,  3  are doubled in the innermost circumferential overlapping portions  5 ,  6 . Additionally, the width dimensions of the innermost circumferential overlapping portions  5 ,  6  of the first and second planar spiral wirings  2 ,  3  are equal to those of the portions other than the innermost circumferential overlapping portions  5 ,  6  of the first and second spiral wirings  2 ,  3 . As a result, the cross-sectional areas are substantially increased in the innermost circumferential overlapping portions  5 ,  6  of the first and second planar spiral wirings  2 ,  3 . Therefore, a direct current resistance value (Rdc) can be reduced in the innermost circumferential overlapping portions  5 ,  6  of the first planar spiral wiring  2  and the second planar spiral wiring  3 . Thus, a direct current resistance value can be reduced in a coil composed of the first planar spiral wiring  2  and the second planar spiral wiring  3 . Furthermore, in the first embodiment, as compared to  FIG. 9 , the innermost circumferential overlapping portions  5 ,  6  can be formed without changing the number of turns of the coil. Therefore, the connection-reliability can be improved and the direct current resistance value can be reduced in the coil composed of the first planar spiral wiring  2  and the second planar spiral wiring  3  without changing the number of turns. Moreover, in the first embodiment, as shown in  FIG. 2 , the outermost portions of the planar spiral wirings  2 ,  3  are not changed in terms of the position and the number of layers as compared to the configuration of  FIG. 9  and thereby, the connection-reliability can be improved and the direct current resistance value can be reduced in the coil composed of the first planar spiral wiring  2  and the second planar spiral wiring  3  without substantially changing the outermost circumferential diameter, the number of layers, etc. In other words, these effects can result from substantially the same outer shape. As described above, when viewed in the laminated direction, the second planar spiral wiring  3  is wound in the direction (corresponding to the clockwise direction from the outside to the inside) different from the winding direction of the first planar spiral wiring  2  (corresponding to the counterclockwise direction from the outside to the inside). As a result, when currents flow through the first and second planar spiral wirings  2 ,  3 , the magnetic fluxes generated are oriented to the same direction as that of the currents, so that a larger inductance (L) can be obtained as compared to a single structure of the first planar spiral wiring  2  or the second planar spiral wiring  3 . 
     Materials used in the coil component  1  will be described. First, while the material of the first planar spiral wiring  2  and the second planar spiral wiring  3  serving as constituent elements of the coil component  1  is not particularly limited, it may be made of metal such as Cu (copper), Ag (silver), and Au (gold) in view of possibilities of a low electric resistance and a narrow pitch. While the material of the insulating layer  12  serving as a constituent element of the coil component  1  is not particularly limited, it may be made of an organic insulating material such as an epoxy-based resin, bismaleimide, liquid crystal polymer, and polyimide, or it may be made of a combination of the organic insulating material and an inorganic filler material such as a silica filler and/or an organic filler material. For example, the material of the insulating layer  12  serving as a constituent element of the coil component  1  may be made of a combination of an epoxy-based resin and a silica filler. While the material of the magnetic core part  13  and the magnetic body layer  14  serving as constituent elements of the coil component  1  is not particularly limited, it may be made of an epoxy-based resin comprising a metal magnetic material made of Fe, Si, Cr, etc. It is preferable that the magnetic core part  13  and the magnetic body layer  14  comprise 90 wt. % or more metal magnetic material made of Fe, Si, Cr, etc. in view of improvements of the inductance value and the direct current superposition characteristics. Additionally, it is preferable that the material of the magnetic core part  13  and the magnetic body layer  14  is obtained by mixing two or more metal magnetic materials different in a particle size distribution in view of an improvement of a filling property. 
     An example of a manufacturing method of the coil component  1  will be described with reference to  FIGS. 8A to 8G . 
     First, on both sides of a peelable and removable dummy substrate  31  (substrate with metal foil), insulating sheets are thermally press-bonded/thermally cured by using a vacuum laminator, a press apparatus, etc. to form an insulating layer  32  on both sides of the dummy substrate  31  as shown in  FIG. 8A . A power feeding film is then formed on the insulating layer  32  by electroless plating, sputtering, vapor deposition, etc. Subsequently, after a photosensitive resist is applied to the power feeding film and patterned by photolithography etc., a metal wiring is formed by an electrolytic plating. After the metal wiring is formed, the photosensitive resist is peeled and removed by a chemical solution, and the power feeding film is then removed by an etching to form the first planar spiral wiring  2  on the insulating layer  32  as shown in  FIG. 8A . 
     Subsequently, an insulating sheet is thermally press-bonded/thermally cured by using a vacuum laminator, a press apparatus, etc. on the insulating layer  32  to cover the first planar spiral wiring  2 , thereby further forming an insulating layer  33  as shown in  FIG. 8B . Through-holes are then formed in the insulating layer  33  by a laser processing etc. along the laminated direction, the through-holes respectively reaching the end part  7  at the innermost circumferential region of the first planar spiral wiring  2 , the portion  9  corresponding to the position wound by a half circumference from the end part, and the outside end part of the lead part  2   a  of the first planar spiral wiring  2 . A power feeding film is then formed in the through-holes and on the insulating layer  33  by electroless plating, sputtering, vapor deposition, etc. Subsequently, after a photosensitive resist is applied to the power feeding film and patterned by photolithography etc., a metal wiring is formed by the electrolytic plating. After the metal wiring is formed, the photosensitive resist is peeled and removed by the chemical solution, and the power feeding film is then removed by the etching to form the first connection via  4 , the second connection via  11 , the second planar spiral wiring  3  and the lead part  3   b  connected through the connection vias  4 ,  11  to the first planar spiral wiring  2  in the insulating layer  33  and on the insulating layer as shown in  FIG. 8B . 
     Subsequently, an insulating sheet is disposed on the insulating layer  33  to cover the second planar spiral wiring  3 , and the insulating sheet is thermally press-bonded/thermally cured by using a vacuum laminator, a press apparatus, etc., thereby further forming an insulating layer  35  as shown in  FIG. 8C . 
     Subsequently, as shown in  FIG. 8D , structures including the first planar spiral wiring  2  and the second planar spiral wiring  3  are separated from the dummy substrate  31 . As shown in  FIG. 8D , a through-hole  36  for disposing the magnetic core part  13  is then formed in the structures including the first planar spiral wiring  2  and the second planar spiral wiring  3  by laser processing etc. 
     Subsequently, through-holes are formed in the insulating layer  35  by the laser processing etc. along the laminated direction, the through-holes respectively reaching the lead part  3   b  and the outside end part of the lead part  3   a  of the second planar spiral wiring  3 . A power feeding film is then formed in the through-holes and on the insulating layer  35  by electroless plating, sputtering, vapor deposition, etc. Subsequently, after a photosensitive resist is applied to the power feeding film and patterned by photolithography etc., a terminal precursor is formed by a semi-additive method. After the terminal precursor is formed, the photosensitive resist is peeled and removed by the chemical solution, and the power feeding film is then removed by the etching to form terminals  38  on the insulating layer  35  as shown in FIG.  8 E, the terminals  38  being respectively electrically connected via connection vias  37  to the lead part  3   b  and the lead part  3   a  of the second planar spiral wiring  3 . 
     Subsequently, an epoxy-based resin part comprising a metal magnetic material is disposed in the through-hole  36  and on the insulating layer  35  including the terminals  38 , and the epoxy-based resin part is thermally press-bonded/thermally cured by using a vacuum laminator, press apparatus, etc. to respectively form the magnetic core part  13  and the magnetic body layer  14  as shown in  FIG. 8F . 
     Subsequently, processing such as grinding and polishing is performed to expose the terminal  38  and followed by processing such as dicing and scribing. In this processing, the terminals  38  are formed as the external terminals  39 . As a result, the coil component  1  is finally obtained as shown in  FIG. 8G . 
     Second Embodiment 
     A coil component related to a second embodiment according to an aspect of the present disclosure will be described with reference to  FIGS. 4A and 4B . 
       FIG. 4A  is a schematic plan view of a form in which a plurality of connection vias are disposed in the innermost circumferential overlapping portion of the first planar spiral wiring.  FIG. 4B  is a schematic plan view of a form in which a plurality of connection vias are disposed in the innermost circumferential overlapping portion of the second planar spiral wiring. 
     In second embodiment, as is the case with the first embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  are respectively wound more than n times (n: natural number) and less than n+1 times. Therefore, each of the inner circumferential ends of the first planar spiral wiring  2  and the second planar spiral wiring  3  is located in a portion at which they are wound more than n times (n: natural number) and less than n+1 times. Specifically, in the second embodiment, as is the case with the first embodiment, the first planar spiral wiring  2  is wound 1.5 times counterclockwise from the outside to the inside as shown in  FIG. 4A . The second planar spiral wiring  3  is wound 1.5 times clockwise from the outside to the inside as shown in  FIG. 4B . The second planar spiral wiring  3  shown in  FIG. 4B  is disposed such that it is located above the first planar spiral wiring  2  shown in  FIG. 4A  along the laminated direction and the winding center part of the first planar spiral wiring  2  and that of the second planar spiral wiring  3  overlap with each other. The portions  5 ,  6  corresponding to portions respectively wound by a half circumference from the end parts  7 ,  10  at the innermost circumferential regions of the first planar spiral wiring  2  and the second planar spiral wiring  3  are positioned such that the distance between the first planar spiral wiring  2  and the magnetic core part  13  substantially becomes equal to the distance between the second planar spiral wiring  3  and the magnetic core part  13 . Additionally, the first planar spiral wiring  2  and the second planar spiral wiring  3  respectively have width dimensions which are equal over the entire circumferences and they respectively have the width dimensions which are equal to each other. In this case, the portion  5  of the first planar spiral wiring  2  shown in  FIG. 4A  and the portion  6  of the second planar spiral wiring  3  shown in  FIG. 4B  form innermost circumferential overlapping portions substantially overlapping with each other at the innermost circumferential region when viewed in the laminated direction. Therefore, in the coil component  1  of the second embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  also have the respective innermost circumferential overlapping portions  5 ,  6 . 
     In the second embodiment, as is the case with the first embodiment, the first end part  7  of the first planar spiral wiring  2  forming one of the end parts of the innermost circumferential overlapping portion  5  is in the interconnection with the first end part  8  of the second planar spiral wiring  3  forming one of the end parts of the innermost circumferential overlapping portion  6  through the first connection via  4 . The second end part  9  of the first planar spiral wiring  2  forming the other of the end parts of the innermost circumferential overlapping portion  5  is in the interconnection with the second end part  10  of the second planar spiral wiring  3  forming the other of the end parts of the innermost circumferential overlapping portion  6  through the second connection via  11 . Additionally, in the second embodiment, the innermost circumferential overlapping portion  5  of first planar spiral wiring  2  between the first end part  7  and the second end part  9  is in the interconnection with the innermost circumferential overlapping portion  6  of second planar spiral wiring  3  between the first end part  8  and the second end part  10  through one or more further connection vias. For example, as shown in  FIG. 4A  and  FIG. 4B , the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  between the first end part  7  and the second end part  9  may be further in the interconnection with the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  between the first end part  8  and the second end part  10  through a third connection via  15  and a fourth connection via  16 . In other words, the innermost circumferential overlapping portion  5  of the planar spiral wiring  2  may be in the interconnection with the innermost circumferential overlapping portion  6  of the planar spiral wiring  3  through four connection vias. As a result, the connection points can be further increased as compared to the first embodiment using two connection vias. Therefore, the connection-reliability between the first planar spiral wiring  2  and the second planar spiral wiring  3  can be further improved. The third connection via  15  and the fourth connection via  16  may be further disposed by forming through-holes at positions corresponding to the third connection via  15  and the fourth connection via  16  upon the arrangements for the first connection via  4  and the second connection via  11 . 
     Third Embodiment 
     A coil component related to a third embodiment according to an aspect of the present disclosure will be described with reference to  FIGS. 5A and 5B . 
       FIG. 5A  is a schematic plan view of a form in which a connection via is disposed in the entire region of the innermost circumferential overlapping portion of the first planar spiral wiring.  FIG. 5B  is a schematic plan view of a form in which a connection via is disposed in the entire region of the innermost circumferential overlapping portion of the second planar spiral wiring. 
     In the third embodiment, as is the case with the first embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  are respectively wound more than n times (n: natural number) and less than n+1 times. Therefore, each of the inner circumferential ends of the first planar spiral wiring  2  and the second planar spiral wiring  3  is located in a portion at which they are wound more than n times (n: natural number) and less than n+1 times. Specifically, in the third embodiment, as is the case with the first embodiment, the first planar spiral wiring  2  is wound 1.5 times counterclockwise from the outside to the inside as shown in  FIG. 5A . The second planar spiral wiring  3  is wound 1.5 times clockwise from the outside to the inside as shown in  FIG. 5B . The second planar spiral wiring  3  shown in  FIG. 5B  is disposed such that it is located above the first planar spiral wiring  2  shown in  FIG. 5A  along the laminated direction and the winding center part of the first planar spiral wiring  2  and that of the second planar spiral wiring  3  overlap with each other. The portions  5 ,  6  corresponding to portions respectively wound by a half circumference from the end parts  7 ,  10  at the innermost circumferential regions of the first planar spiral wiring  2  and the second planar spiral wiring  3  are positioned such that the distance between the first planar spiral wiring  2  and the magnetic core part  13  substantially becomes equal to the distance between the second planar spiral wiring  3  and the magnetic core part  13 . Additionally, the first planar spiral wiring  2  and the second planar spiral wiring  3  respectively have width dimensions which are equal over the entire circumferences and they respectively have the width dimensions which are equal to each other. In the above configuration, the portion  5  of the first planar spiral wiring  2  shown in  FIG. 5A  and the portion  6  of the second planar spiral wiring  3  shown in  FIG. 5B  form innermost circumferential overlapping portions substantially overlapping with each other at the innermost circumferential region when viewed in the laminated direction. Therefore, in the coil component of the third embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  also have the respective innermost circumferential overlapping portions  5 ,  6 . 
     On the other hand, in the third embodiment, unlike the first embodiment, the entire region of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  shown in  FIG. 5A  is continuously in the interconnection with the entire region of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  shown in  FIG. 5B  through a connection via  30 . The connection via  30  is made of the same material as that of the first connection via  4  and the second connection via  11  and electrically connects the first planar spiral wiring  2  and the second planar spiral wiring  3 . In other words, the connection via  30  is filled between the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  and the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3 . This means that the entire region of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  is connected to the connection via  30  such that a connected region therebetween is in a shape of not “points” but “surface” while the entire region of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  is connected to the connection via  30  such that a connected region therebetween is in a shape of not “points” but “surface”. Thus, a connected region between the first planar spiral wiring  2  and the second planar spiral wiring  3  can be increased. Therefore, the connection-reliability between the first planar spiral wiring  2  and the second planar spiral wiring  3  can be further improved. The connection via  30  can be provided, by forming a through-hole with a shape extending on the innermost circumferential overlapping portion  5  of the spiral wiring  2 , for example. Specifically, instead of forming the through-holes respectively reaching the end part at the innermost circumferential region of the first planar spiral wiring  2  and the portion corresponding to the position wound by a half circumference from the end part in the manufacturing method of the first embodiment described above, a through-hole is formed in the insulating layer  33  by laser processing etc., the through-hole reaching substantially the entire surface between the two end parts of the first planar spiral wiring  2 . Subsequently, the through-hole is filled with a material of the connection via  30 . Additionally, after the metal wiring is formed, the photosensitive resist is peeled and removed by the chemical solution, and the power feeding film is removed by etching to finally form the second planar spiral wiring  3  on the insulating layer such that the entire region of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  is continuously in the interconnection with the entire region of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  through the connection via  30 . 
     A coil component related to a fourth embodiment according to an aspect of the present disclosure will be described with reference to  FIGS. 6A and 6B . 
     Fourth Embodiment 
       FIG. 6A  is a schematic plan view of a form in which a width dimension of the innermost circumferential overlapping portion of the first planar spiral wiring is smaller than that of the portion other than the innermost circumferential overlapping portion of the first planar spiral wiring.  FIG. 6B  is a schematic plan view of a form in which a width dimension of the innermost circumferential overlapping portion of the second planar spiral wiring is smaller than that of the portion other than the innermost circumferential overlapping portion of the second planar spiral wiring. 
     In the fourth embodiment, as is the case with the first embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  are respectively wound more than n times (n: natural number) and less than n+1 times. Therefore, each of the inner circumferential ends of the first planar spiral wiring  2  and the second planar spiral wiring  3  is located in a portion at which they are wound more than n times (n: natural number) and less than n+1 times. Specifically, in the fourth embodiment, as is the case with the first embodiment, the first planar spiral wiring  2  is wound 1.5 times counterclockwise from the outside to the inside as shown in  FIG. 6A . The second planar spiral wiring  3  is wound 1.5 times clockwise from the outside to the inside as shown in  FIG. 6B . The second planar spiral wiring  3  shown in  FIG. 6B  is disposed such that it is located above the first planar spiral wiring  2  along the laminated direction and the winding center part of the first planar spiral wiring  2  and that of the second planar spiral wiring  3  overlap with each other. The portions  5 ,  6  corresponding to portions respectively wound by a half circumference from the end parts  7 ,  10  at the innermost circumferential regions of the first planar spiral wiring  2  and the second planar spiral wiring  3  are positioned such that the distance between the first planar spiral wiring  2  and the magnetic core part  13  substantially becomes equal to the distance between the second planar spiral wiring  3  and the magnetic core part  13 . Additionally, the first planar spiral wiring  2  and the second planar spiral wiring  3  respectively have width dimensions over the half circumferences, the width dimensions being equal to each other. In this case, the portion  5  of the first planar spiral wiring  2  shown in  FIG. 6A  and the portion  6  of the second planar spiral wiring  3  shown in  FIG. 6B  form innermost circumferential overlapping portions substantially overlapping with each other at the innermost circumferential region when viewed in the laminated direction. Therefore, in the fourth embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  also have the respective innermost circumferential overlapping portions  5 ,  6 . 
     On the other hand, in the fourth embodiment, unlike the first embodiment, as shown in  FIG. 6A , the width dimension of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  is smaller than that of the portion other than the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2 . Specifically, as shown in  FIG. 6A , the width dimension of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  is smaller than that of the portion other than the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2 , and an outer edge  17  of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  continues without unevenness to an outer edge  18  of the portion other than the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2 . In this case, an inner edge  19  of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  and an inner edge  20  of other than the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  can be made discontinuous. Therefore, a region  21  bulging outward can be formed in the insulating layer  12  at the inner edge  20  side of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2 . The terms “outer edge” and “inner edge” as used herein refer to an edge at the outer circumferential side and an edge at the inner circumferential side, respectively, when the planar spiral wirings are viewed in the laminated direction. 
     Similarly, as shown in  FIG. 6B , the width dimension of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  is smaller than that of the portion other than the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3 . Specifically, as shown in  FIG. 6B , the width dimension of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  is smaller than that of the portion other than the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3 , and an outer edge  22  of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  continues without unevenness to an outer edge  23  of the portion other than the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3 . In this case, an inner edge  24  of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  and an inner edge  25  of other than the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  can be made discontinuous. Therefore, a region  26  bulging outward can be formed in the insulating layer  12  at the inner edge  24  side of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3 . As a result, when the second planar spiral wiring  3  is located above the first planar spiral wiring  2  along the laminated direction, the range of the magnetic core part  29  extending in a winding center part  27  of the first planar spiral wiring  2  and a winding center part  28  of the second planar spiral wiring  3  can be enlarged by the bulges of the regions  21 ,  26 . Thus, an inductance (L) of the coil component can be increased. It is preferable that a total of the width dimension of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  and that of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3  is made equal to or greater than the width dimensions of the portions other than the innermost circumferential overlapping portions  5 ,  6  of the planar spiral wirings  2 ,  3 . In this case, as compared to  FIG. 9 , a reduction in the direct current resistance value can be prevented. It is preferable that the width dimension of the innermost circumferential overlapping portion  5  of the first planar spiral wiring  2  is equal to that of the innermost circumferential overlapping portion  6  of the second planar spiral wiring  3 . In this case, the range of the magnetic core part  29  is not limited by the width dimension of either of the innermost circumferential overlapping portions  5 ,  6 . 
     Finally, a coil component related to a fifth embodiment according to an aspect of the present disclosure will be described with reference to  FIGS. 7A and 7B . 
     Fifth Embodiment 
       FIG. 7A  is a schematic plan view of another form in which connection vias are disposed in both end parts of the innermost circumferential overlapping portion of the first planar spiral wiring.  FIG. 7B  is a schematic plan view of another form in which connection vias are disposed in both end parts of the innermost circumferential overlapping portion of the second planar spiral wiring. 
     In the fifth embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  are respectively wound n times. Specifically, in the fifth embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  are respectively wound once. As shown in  FIG. 7A , the first planar spiral wiring  2  is wound once counterclockwise from the outside to the inside. As shown in  FIG. 7B , the second planar spiral wiring  3  is wound once clockwise from the outside to the inside. As is the case with the first to third embodiments, the magnetic core part  13  is disposed to extend in the winding center part of the first planar spiral wiring  2  and the winding center part of the second planar spiral wiring  3 . The first planar spiral wiring  2  and the second planar spiral wiring  3  are disposed such that the second planar spiral wiring  3  is located above the first planar spiral wiring  2  along the laminated direction and the winding center part of the first planar spiral wiring  2  and that of the second planar spiral wiring  3  overlap with each other. The portions  5 ,  6  corresponding to portions respectively wound by a half circumference from the end parts  9 ,  8  at the innermost circumferential regions of the first planar spiral wiring  2  and the second planar spiral wiring  3  are positioned such that the distance between the first planar spiral wiring  2  and the magnetic core part  13  substantially becomes equal to the distance between the second planar spiral wiring  3  and the magnetic core part  13 . Additionally, the first planar spiral wiring  2  and the second planar spiral wiring  3  respectively have width dimensions which are equal over the entire circumferences and they respectively have the width dimensions which are equal to each other. 
     In this configuration, the portion  5  of the first planar spiral wiring  2  shown in  FIG. 7A  and the portion  6  of the second planar spiral wiring  3  shown in  FIG. 7B  form innermost circumferential overlapping portions substantially overlapping with each other at the innermost circumferential region when viewed in the laminated direction. Therefore, in the fifth embodiment, the first planar spiral wiring  2  and the second planar spiral wiring  3  also have the respective innermost circumferential overlapping portions  5 ,  6 . 
     In other words, in the fifth embodiment, one of the end parts of the respective innermost circumferential overlapping portions  5 ,  6  of the first planar spiral wiring  2  and the second planar spiral wiring  3  are positioned at portions wound by a half circumference from the other of the end parts of the respective innermost circumferential overlapping portions  5 ,  6  of the first planar spiral wiring  2  and the second planar spiral wiring  3 . Therefore, as compared to the conventional form in which the inner circumferential end of the one planar spiral wiring  101  is in the interconnection with that of the other planar spiral wiring  102  through the one connection via  103  along the laminated direction, the innermost circumferential regions of the first and second planar spiral wirings  2 ,  3  respectively have one fourth of the circumference additionally wound at the innermost circumferential regions. Therefore, the regions of the innermost circumferential overlapping portions  5 ,  6  of the planar spiral wirings  2 ,  3  can be enlarged while ensuring the wiring distances. In this state, in the fifth embodiment, as shown in  FIGS. 7A and 7B , the first end part  7  of the first planar spiral wiring  2  forming the one of the end parts of the innermost circumferential overlapping portion  5  is in the interconnection with the first end part  8  of the second planar spiral wiring  3  forming the one of the end part of the innermost circumferential overlapping portion  6  through the first connection via  4 . The second end part  9  of the first planar spiral wiring  2  forming the other of the end parts of the innermost circumferential overlapping portion  5  is in the interconnection with the second end part  10  of the second planar spiral wiring  3  forming the other of the end parts of the innermost circumferential overlapping portion  6  through the second connection via  11 . Therefore, the innermost circumferential overlapping portion of the planar spiral wiring  5  is in the interconnection with the innermost circumferential overlapping portion of the planar spiral wiring  6  through the two connection vias. As a result, the connection-reliability between the first planar spiral wiring  2  and the second planar spiral wiring  3  can be improved. Additionally, in the fifth embodiment, as compared to the conventional form in which the inner circumferential end of the planar spiral wiring  101  is in the interconnection with that of the planar spiral wiring  102  through one connection via  103  as shown in  FIG. 9  along the laminated direction, the innermost circumferential regions of the first and second planar spiral wirings  2 ,  3  are extended along the respective winding directions. As a result, when viewed in the laminated direction, the planar spiral wirings  2 ,  3  are doubled in the innermost circumferential overlapping portions  5 ,  6 . Additionally, the width dimensions of the innermost circumferential overlapping portions  5 ,  6  of the first and second planar spiral wirings  2 ,  3  are equal to that of the portions other than the innermost circumferential overlapping portions  5 ,  6  of the first and second spiral wirings  2 ,  3 . As a result, the cross-sectional areas are substantially increased in the innermost circumferential overlapping portions  5 ,  6  of the first and second planar spiral wirings  2 ,  3 . Therefore, the direct current resistance value can be reduced in the innermost circumferential overlapping portions  5 , 6  of the first planar spiral wiring  2  and the second planar spiral wiring  3 . Thus, the direct current resistance value can be reduced in the coil composed of the first planar spiral wiring  2  and the second planar spiral wiring  3 . 
     Although the coil component related to an aspect of the present disclosure and a manufacturing method thereof have been described, the present disclosure is not limited thereto and it will be understood that various modifications are made by those skilled in the art without departing from the scope of the disclosure defined by claims. For example, the embodiments described above may be combined as needed. In this case, the combination may be made by combining portions of the embodiments with each other.