Patent Publication Number: US-2021166859-A1

Title: Coil component

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-218754, filed on 3 Dec. 2019, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a coil component. 
     BACKGROUND 
     United States Patent Publication No. 2017-148560 (Patent Literature 1) discloses a coil component having two sets of coil structures formed by a pair of planar coils provided on both surfaces of a substrate. In the coil component of the literature, the inner end portions of the pair of planar coils are electrically connected to each other by a through conductor provided on the substrate. 
     SUMMARY 
     The inventors have conducted research on magnetic coupling between two coil structures included in a coil component and have found a new technique which can easily adjust the magnetic coupling. 
     According to the disclosure, a coil component in which magnetic coupling can be easily adjusted is provided. 
     A coil component according to an aspect of the disclosure includes an elementary body having a mounting surface corresponding to a mounting substrate; a first pair of external terminal electrodes and a second pair of external terminal electrodes provided on the mounting surface; an insulating substrate provided in the elementary body, the insulating substrate extending parallel to the mounting surface; a first planar coil provided on a first main surface of the insulating substrate on a side further from the mounting surface; a second planar coil provided on a second main surface of the insulating substrate on a side closer to the mounting surface and wound around the same magnetic core as a magnetic core of the first planar coil; a first pair of connecting conductors extending inside the insulating substrate and the elementary body in a direction orthogonal to the mounting surface and respectively connecting both end portions of the first planar coil to the first pair of external terminal electrodes; and a second pair of connecting conductors extending inside the elementary body in the direction orthogonal to the mounting surface and respectively connecting both end portions of the second planar coil to the second pair of external terminal electrodes. 
     In the coil component, the first planar coil and the second planar coil are magnetically coupled to each other but form coil structures which are separate from each other. Thus, as compared with a case in which the first planar coil and the second planar coil are electrically connected to each other and form one coil structure, the first planar coil and the second planar coil are less likely to affect each other&#39;s characteristics. Therefore, magnetic coupling between the first planar coil and the second planar coil can be easily adjusted by adjusting a thickness of the insulating substrate while an influence on each other&#39;s characteristics between the first planar coil and the second planar coil is curbed. 
     In the coil component according to another aspect of the disclosure, a height of the first planar coil and a height of the second planar coil in the direction orthogonal to the mounting surface may be different from each other. 
     In the coil component according to another aspect of the disclosure, a pair of through holes through pierced by the first pair of connecting conductors may be provided in the insulating substrate. 
     In the coil component according to another aspect of the disclosure, at least one of the first pair of connecting conductors may pass through an inside of the second planar coil. 
     In the coil component according to another aspect of the disclosure, a pattern shape of the first planar coil and a pattern shape of the second planar coil may be symmetrical. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view of a coil component according to an embodiment. 
         FIG. 2  is a view showing a first planar coil of the coil component of  FIG. 1 . 
         FIG. 3  is a view showing a second planar coil of the coil component of  FIG. 1 . 
         FIG. 4  is a cross-sectional view taken along IV-IV of the coil component shown in  FIG. 1 . 
         FIG. 5  is a cross-sectional view taken along V-V of the coil component shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and duplicate description thereof will be omitted. 
     As shown in  FIG. 1 , the coil component  10  is configured of a main body  12  (an elementary body) having a rectangular parallelepiped shape, and two pairs of external terminal electrodes  14 A,  14 B,  14 C, and  14 D provided on a surface of the main body  12 . The main body  12  has a bottom surface  12   a  (a mounting surface) which faces a mounting substrate, a top surface  12   b , a pair of end surfaces  12   c  and  12   d , and a pair of side surfaces  12   e  and  12   f . The two pairs of external terminal electrodes  14 A,  14 B,  14 C, and  14 D are all provided on the bottom surface  12   a  of the main body  12 . As an example, the coil component  10  is designed with dimensions of a long side of 2.5 mm, a short side of 2.0 mm, and a height of 0.8 to 1.0 mm. 
     As shown in  FIG. 2 , the main body  12  includes an insulating substrate  16 , a pair of planar coils  20  and  22  provided on both surfaces of the insulating substrate  16 , and two pairs of connecting conductors  30 A,  30 B,  30 C, and  30 D which connect the planar coils  20  and  22  to the external terminal electrodes  14 A,  14 B,  14 C, and  14 D. 
     The insulating substrate  16  is a plate-shaped member having a rectangular shape provided inside the main body  12 , and is made of a non-magnetic insulating material. The insulating substrate  16  extends parallel to the bottom surface  12   a  of the main body  12 . An elliptical through hole  16   c  is provided in a central portion of the insulating substrate  16 . A substrate in which a glass cloth is impregnated with an epoxy resin and which has a plate thickness of 40 μm to 100 μm can be used as the insulating substrate  16 . In the embodiment, a thickness h of the insulating substrate  16  is 60 μm. In addition to an epoxy resin, a BT resin, polyimide, aramid and the like can also be used. Ceramic or glass can also be used as a material of the insulating substrate  16 . The material of the insulating substrate  16  may be a mass-produced printed circuit board material, and may be a resin material, in particular, one used for a BT printed circuit board, a FR4 printed circuit board, or an FR5 printed circuit board. 
     The first planar coil  20  is a coil pattern having a planar spiral shape and provided on an upper surface  16   a  of the insulating substrate  16  (a first main surface farther from the bottom surface  12   a ). The first planar coil  20  has a predetermined height H 1  based on the insulating substrate  16 . The number of turns of the first planar coil  20  is about one turn, and both end portions  20   a  and  20   b  are located at two of four corners of the insulating substrate  16 . 
     The second planar coil  22  is a coil pattern having a planar spiral shape and provided on a lower surface  16   b  of the insulating substrate  16  (a second main surface closer to the bottom surface  12   a ). The second planar coil  22  has a predetermined height H 2  based on the insulating substrate  16 . In the embodiment, the height H 2  of the second planar coil  22  is designed to be the same as the height H 1  of the first planar coil  20 . A pattern shape of the second planar coil  22  is designed to be symmetrical with a pattern shape of the first planar coil  20 . Specifically, the pattern shape of the first planar coil  20  and the pattern shape of the second planar coil  22  have a line-symmetrical relationship when seen from the upper surface  16   a  side of the insulating substrate  16 . The number of turns of the second planar coil  22  is about one, like the first planar coil  20 . Both end portions  22   a  and  22   b  of the second planar coil  22  are located at two of the four corners of the insulating substrate  16  at which the end portions  20   a  and  20   b  of the first planar coil  20  are not formed. 
     The first planar coil  20  and the second planar coil  22  can be formed by plating. 
     Side surfaces of the first planar coil  20  and the second planar coil  22  (that is, surfaces orthogonal to the insulating substrate  16 ) are covered with a resin wall  24 . The resin wall  24  is made of an insulating resin material. The resin wall  24  can be provided on the insulating substrate  16  before the first planar coil  20  and the second planar coil  22  are formed, and in this case, the first planar coil  20  and the second planar coil  22  are plated and grown between walls defined in the resin walls  24 . That is, formation regions of the first planar coil  20  and the second planar coil  22  are defined by the resin walls  24  provided on the insulating substrate  16 . The resin walls  24  can be provided on the insulating substrate  16  after the first planar coil  20  and the second planar coil  22  are formed, and in this case, the resin walls  24  are provided on the first planar coil  20  and the second planar coil  22  by filling, coating, or the like. 
     An upper surface of the first planar coil  20  and a lower surface of the second planar coil  22  are covered with a protective film  25  having an insulating property. The protective film  25  is made of a resin such as an epoxy resin or a polyimide resin, and is formed using a photolithography method. 
     A magnetic body  26  integrally covers the insulating substrate  16 , the first planar coil  20 , and the second planar coil  22 . More specifically, the magnetic body  26  covers the insulating substrate  16 , the first planar coil  20 , and the second planar coil  22  in a vertical direction (that is, a thickness direction of the insulating substrate  16 ), and covers the outer periphery of the insulating substrate  16 , the first planar coil  20 , and the second planar coil  22 . Further, the magnetic body  26  fills the inside of the through hole  16   c  of the insulating substrate  16  and also fills inner regions of the first planar coil  20  and the second planar coil  22 . In the magnetic body  26 , a portion of the magnetic body  26  which fills the inside of the through hole  16   c  of the insulating substrate  16  and the inner regions of the planar coils  20  and  22  constitutes a magnetic core Z of the planar coils  20  and  22 . 
     The magnetic body  26  is made of a metal magnetic component-containing resin. The metal magnetic component-containing resin is a binder powder in which metal magnetic powder is bound by a binder resin. The metal magnetic powder of the metal magnetic component-containing resin constituting the magnetic body  26  is configured of, for example, an iron-nickel alloy (a Permalloy alloy), carbonyl iron, an amorphous or crystalline FeSiCr-based alloy, Sendust, or the like. The binder resin is, for example, a thermosetting epoxy resin. In the embodiment, a content of the metallic magnetic powder in the binder powder is 80 to 92 vol % in percentage by volume and 95 to 99 wt % in percentage by mass. From the viewpoint of magnetic properties, the content of the metal magnetic powder in the binder powder may be 85 to 92 vol % in percentage by volume and 97 to 99 wt % in percentage by mass. The magnetic component of the metal magnetic component-containing resin constituting the magnetic body  26  may be a powder having one kind of average particle diameter, or may be a mixed powder having a plurality of kinds of average particle diameter. In the embodiment, the magnetic component of the metal magnetic component-containing resin constituting the magnetic body  26  is a mixed powder having three kinds of average particle diameter. When the magnetic component of the metal magnetic component-containing resin constituting the magnetic body  26  is a mixed powder, the kinds of magnetic components having different average particle diameters may be the same as or different from each other. 
     As shown in  FIGS. 2 to 5 , each of the two pairs of connecting conductors  30 A,  30 B,  30 C, and  30 D extends in a direction orthogonal to the insulating substrate  16  (that is, a normal direction of the bottom surface  12   a ). Each of the connecting conductors  30 A,  30 B,  30 C, and  30 D has a substantially cylindrical exterior. 
     Among the two pairs of connecting conductors  30 A,  30 B,  30 C and  30 D, the first pair of connecting conductors  30 A and  30 B reach from both end portions  20   a  and  20   b  of the first planar coil  20  to the bottom surface  12   a  and are exposed from the bottom surface  12   a . Among the two pairs of connecting conductors  30 A,  30 B,  30 C and  30 D, the second pair of connecting conductors  30 C and  30 D reach from both end portions  22   a  and  22   b  of the second planar coil  22  to the bottom surface  12   a  and are exposed from the bottom surface  12   a . Each of the connecting conductors  30 A,  30 B,  30 C and  30 D can be formed by a plating method. 
     Each of the first pair of connecting conductors  30 A and  30 B includes a first conductor  32  piercing the insulating substrate  16  and a second conductor  34  piercing the magnetic body  26 . The first conductor  32  is provided to fill a through hole  17  provided in the insulating substrate  16 , and an upper end thereof is in contact with the end portions  20   a  and  20   b  of the first planar coil  20 . That is, a pair of through holes  17  through which the connecting conductors  30 A and  30 B pass are provided in the insulating substrate  16 . As shown in  FIGS. 2 and 3 , the connecting conductor  30 A passes through the outside of the second planar coil  22  and extends from the outer end portion  20   b  of the first planar coil  20  to the bottom surface  12   a . As shown in  FIGS. 2 and 3 , the connecting conductor  30 B passes through the inside of the second planar coil  22  and extends from the inner end portion  20   a  of the first planar coil  20  to the bottom surface  12   a.    
     The second pair of connecting conductors  30 C and  30 D extend from both end portions  22   a  and  22   b  of the second planar coil  22  to the bottom surface  12   a  through the inside of the magnetic body  26 . The connecting conductor  30 C extends from the outer end portion  22   b  of the second planar coil  22  to the bottom surface  12   a . The connecting conductor  30 D extends from the inner end portion  22   a  of the second planar coil  22  to the bottom surface  12   a.    
     The two pairs of external terminal electrodes  14 A,  14 B,  14 C, and  14 D provided on the bottom surface  12   a  of the main body  12  are formed at the four corners of the bottom surface  12   a  having a rectangular shape. Among the two pairs of external terminal electrodes  14 A,  14 B,  14 C, and  14 D, the first pair of external terminal electrodes  14 A and  14 B are connected to the first pair of connecting conductors  30 A and  30 B. More specifically, the external terminal electrode  14 A is formed at a corner at which the connecting conductor  30 A is exposed, and is connected to the outer end portion  20   b  of the first planar coil  20 . The external terminal electrode  14 B is formed at a corner at which the connecting conductor  30 B is exposed, and is connected to the inner end portion  20   a  of the first planar coil  20 . Among the two pairs of external terminal electrodes  14 A,  14 B,  14 C, and  14 D, the second pair of external terminal electrodes  14 C and  14 D are connected to the second pair of connecting conductors  30 C and  30 D. More specifically, the external terminal electrode  14 C is formed in a corner at which the connecting conductor  30 C is exposed, and is connected to the outer end portion  22   b  of the second planar coil  22 . The external terminal electrode  14 D is formed at a corner at which the connecting conductor  30 D is exposed, and is connected to the inner end portion  22   a  of the second planar coil  22 . 
     In the above-described coil component  10 , the first planar coil  20  and the second planar coil are wound around a common magnetic core Z and are magnetically coupled to each other. However, the first planar coil  20  and the second planar coil are not electrically connected to each other and form coil structures which are separate from each other. Thus, as compared with a case in which the first planar coil  20  and the second planar coil  22  form one coil structure, the first planar coil  20  and the second planar coil  22  are less likely to affect each other&#39;s characteristics. 
     Therefore, each of the first planar coil  20  and the second planar coil  22  can be freely designed to some extent while the influence on the characteristics of the other planar coil is curbed. For example, since a coupling coefficient between the first planar coil  20  and the second planar coil  22  depends on a thickness h of the insulating substrate  16 , magnetic coupling between the first planar coil  20  and the second planar coil  22  can be easily adjusted by adjusting the thickness h. Further, in the first planar coil  20  and the second planar coil  22 , since it is not necessary to align the inner end portions  20   a  and  22   a  with each other, a degree of freedom in designing the pattern shape and the number of turns is increased. Further, the first planar coil  20  and the second planar coil  22  have an increased degree of freedom in design with respect to a height dimension. Therefore, a magnitude relationship and a height difference between the height H 1  of the first planar coil  20  and the height H 2  of the second planar coil  22  can be appropriately adjusted. For example, the height H 1  of the first planar coil  20  and the height H 2  of the second planar coil  22  may be the same as each other as in the above-described embodiment, or may be different from each other. 
     Further, in the coil component  10 , the connecting conductor  30 B connected to the inner end portion  20   a  of the first planar coil  20  passes through the inside of the second planar coil  22 . As described above, when one or both of the first pair of connecting conductors  30 A and  30 B pass through the inside of the second planar coil  22 , a coil length can be increased, and an inductance value can be increased. 
     The disclosure is not limited to the above-described embodiment, and may take various aspects. 
     For example, the first coil and the second coil do not have to be line symmetric. Further, the number of turns of the first coil and the number of turns of the second coil can be increased or decreased as appropriate.