Coil parts

Abstract

To provide a coil component that can suppress deterioration of DC superimposition characteristics.SOLUTION: Since a coil component 1 employs a magnetic sheet 30, magnetic saturation is likely to occur in the magnetic sheet 30, and it is conceivable that the DC superimposition characteristics of the coil component 1 are degraded. However, since the inner edges of coil structures 40A and 40B are recessed with respect to the inner edge of the magnetic sheet 30, the magnetic fluxes generated in coils C1 and C2 are easily circulated, such that a decrease in DC superimposition characteristics by adopting the magnetic sheet 30 is suppressed.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a coil component. [Background technology]

[0002] Conventionally, coil components in which a pair of coils are overlapped with each other in the coil axis direction are known. The following Patent Document 1 discloses a coil component in which a PCB substrate is interposed between a pair of coils, and a high coupling coefficient is obtained by the PCB substrate, which is a non-magnetic material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-137421 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the coil components according to the above-mentioned conventional technology, if a magnetic sheet, which is a magnetic material, is used instead of the PCB substrate, which is a non-magnetic material, it is thought that magnetic saturation is likely to occur in the magnetic sheet, and the DC superposition characteristics of the coil component will deteriorate.

[0005] As a result of extensive research, the inventors have newly discovered a technique that can suppress degradation of the DC bias characteristics even when a magnetic sheet is used.

[0006] An object of the present invention is to provide a coil component capable of suppressing degradation of DC superposition characteristics. [Means for solving the problem]

[0007] A coil component according to one aspect of the present invention comprises a base body made of resin containing metal powder, a pair of coil structures provided within the base body, each of the pair of coils having a pair of ends that overlap each other in the coil axis direction and extend to the surface of the base body, two pairs of external terminals provided on the surface of the base body and respectively connected to the ends of the pair of coils, and a magnetic sheet provided within the base body and interposed between the pair of coil structures in the coil axis direction, wherein the pair of coil structures and the magnetic sheet each have a through hole extending along the coil axis direction, and at least one inner edge of the pair of coil structures recedes relative to the inner edge of the magnetic sheet.

[0008] In the above coil component, the inner edge of the coil structure recedes from the inner edge of the magnetic sheet, making it easier for the magnetic flux generated from the coil to circulate, and partial concentration of the magnetic flux is alleviated, thereby suppressing deterioration of the DC superposition characteristics.

[0009] In a coil component according to another aspect, in at least one of the pair of coil structures, the position of the inner edge on the side farther from the magnetic sheet in the coil axial direction is recessed from the position of the inner edge on the side closer to the magnetic sheet.

[0010] In a coil component according to another aspect, in a cross section including the coil axis, the outer shapes of the pair of coil structures are axisymmetric with respect to a line perpendicular to the coil axis.

[0011] In a coil component according to another aspect, the magnetic sheet is in contact at its inner edge with metal powder contained in the metal powder-containing resin that constitutes the body.

[0012] In a coil component according to another aspect, the thicknesses of the element portions that overlap the pair of coil structures in the coil axial direction are equal to each other. Effect of the Invention

[0013] According to the present invention, a coil component capable of suppressing deterioration of DC bias characteristics is provided. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic perspective view of a coil component according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing the inside of the coil component of FIG. [Diagram 3] FIG. 3 is an exploded perspective view of the coil structure shown in FIG. [Figure 4] FIG. 4 is a plan view showing the magnetic sheet shown in FIG. [Diagram 5] 5 is a cross-sectional view of the element body shown in FIG. 2 taken along line VV. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI of the element body shown in FIG. [Figure 7] FIG. 7 is an enlarged view of a main part of the cross-sectional view shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view showing a magnetic sheet and a pair of coil structures in an intermediate stage of the manufacture of the coil component of FIG. [Figure 9] FIG. 9 is a cross-sectional view showing a magnetic sheet and a pair of coil structures in an intermediate stage of manufacturing the coil component of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be designated by the same reference numerals, and duplicated descriptions will be omitted.

[0016] The coil component 1 according to the embodiment is a so-called coupling coil. The coupling coil includes two coils in one element, and can reduce the number of components and the mounting area. The coupling coil can be used, for example, as a smoothing coil in a switching power supply such as a DC / DC converter in various electronic devices.

[0017] As shown in Figures 1 and 2, the coil component 1 is composed of a base body 10, a coil structure 20 embedded in the base body 10, and two pairs of external terminal electrodes 60A, 60B, 60C, and 60D provided on the surface of the base body 10.

[0018] The element body 10 has a rectangular parallelepiped outer shape and six faces 10a to 10f. As an example, the element body 10 is designed to have dimensions of a long side of 2.0 mm, a short side of 1.25 mm, and a height of 0.45 mm. Of the faces 10a to 10f of the element body 10, the end face 10a and the end face 10b are parallel to each other, the top face 10c and the bottom face 10d are parallel to each other, and the side face 10e and the side face 10f are parallel to each other. The top face 10c of the element body 10 is a face that faces and is parallel to the mounting surface of the mounting board on which the coil component 1 is mounted.

[0019] The element 10 is made of a resin 12 containing a magnetic metal powder, which is a type of magnetic material. The resin 12 containing a magnetic metal powder contains a metal powder and a resin, and more specifically, is a bound powder in which the magnetic metal powder is bound by a binder resin. The magnetic metal powder of the resin 12 containing a magnetic metal powder is made of, for example, an iron-nickel alloy (permalloy alloy), carbonyl iron, an amorphous, non-crystalline or crystalline FeSiCr-based alloy, sendust, or the like. The binder resin is, for example, a thermosetting epoxy-based resin. In this embodiment, the content of the magnetic metal powder in the bound powder is 80 to 92 vol% in volume percent and 95 to 99 wt% in mass percent. From the viewpoint of magnetic properties, the content of the magnetic metal powder in the bound powder may be 85 to 92 vol% in volume percent and 97 to 99 wt% in mass percent. The magnetic powder of the resin 12 containing a magnetic metal powder may be a powder having one type of average particle size, or may be a mixed powder having a plurality of types of average particle sizes.

[0020] The metal magnetic powder-containing resin 12 of the element body 10 integrally covers the coil structure 20 described below. Specifically, the metal magnetic powder-containing resin 12 covers the coil structure 20 from above and below, and also covers the outer periphery of the coil structure 20. In addition, the metal magnetic powder-containing resin 12 fills the inner periphery of the coil structure 20.

[0021] 2 and 3, the coil structure 20 includes a magnetic sheet 30, an upper coil structure 40A provided on the upper side of the magnetic sheet 30, and a lower coil structure 40B provided on the lower side of the magnetic sheet 30. The coil structure 20 is a laminate in which the upper coil structure 40A, the magnetic sheet 30, and the lower coil structure 40B are stacked in this order, with the magnetic sheet 30 interposed between the upper coil structure 40A and the lower coil structure 40B in the stacking direction.

[0022] The magnetic sheet 30 has a flat plate shape (for example, sheet-like or layer-like), extends between the end faces 10a, 10b of the element body 10, and is designed to be perpendicular to the end faces 10a, 10b. The magnetic sheet 30 also extends parallel to the upper face 10c and the lower face 10d of the element body 10. As shown in FIG. 4, the magnetic sheet 30 has an elliptical ring-shaped coil overlapping part 31 extending along the long side direction of the element body 10, and a pair of frame parts 34A, 34B extending along the short side direction of the element body 10 and sandwiching the coil overlapping part 31 from both sides. An elliptical opening (through hole) 32 extending along the long side direction of the element body 10 is provided in the center part of the coil overlapping part 31. The thickness t of the magnetic sheet 30 can be designed to be, for example, 10 to 100 μm (30 μm as an example).

[0023] The magnetic sheet 30 is made of a magnetic material. In this embodiment, the magnetic sheet 30 is made of resin and magnetic powder (magnetic material powder), and has a configuration in which the magnetic powder is dispersed in the resin. The resin of the magnetic sheet 30 is, for example, an epoxy-based resin. The magnetic powder of the magnetic sheet 30 may be made of, for example, ferrite, permalloy, sendust, Fe-based magnetic material, etc. The magnetic powder of the magnetic sheet 30 may have a flat or needle-like shape, or may be spherical. For example, when the magnetic powder of the magnetic sheet 30 is flat, the magnetic powder may extend in a direction intersecting the thickness direction of the magnetic sheet 30 (for example, a direction perpendicular to the thickness direction of the magnetic sheet 30). The magnetic sheet 30 may be an amorphous foil, an amorphous ribbon, or an amorphous layer made of a magnetic material.

[0024] The magnetic sheet 30 according to this embodiment has a configuration in which flat ferrite powder is dispersed substantially uniformly in epoxy resin, and the flat ferrite powder extends in a direction perpendicular to the thickness direction of the magnetic sheet 30. Therefore, the magnetic sheet 30 has a higher magnetic permeability in the direction perpendicular to the thickness direction than in the thickness direction. In addition, since the flat ferrite powder extends substantially parallel to the extending direction of the magnetic sheet 30, the magnetic permeability is increased while preventing the magnetic sheet 30 from becoming thick.

[0025] 3, the upper coil structure 40A is provided on the sheet upper surface 30a in the coil overlapping portion 31 of the magnetic sheet 30. The upper coil structure 40A includes an insulating layer 30A, a first upper planar coil 41, a second upper planar coil 42, a first upper insulator 51, and a second upper insulator 52, and has a through hole 45A.

[0026] The insulating layer 30A has a flat plate shape (for example, a sheet or layer shape) and extends parallel to the magnetic sheet 30. The insulating layer 30A has substantially the same shape as the magnetic sheet 30 when viewed in the thickness direction. That is, like the magnetic sheet 30, the insulating layer 30A has an elliptical ring-shaped coil overlapping portion 31 extending along the long side direction of the element body 10, and a pair of frame portions 34A, 34B extending along the short side direction of the element body 10 and sandwiching the coil overlapping portion 31 from both sides, and an elliptical opening 32 extending along the long side direction of the element body 10 is provided in the center of the coil overlapping portion 31. The thickness t1 of the insulating layer 30A can be designed to be in the range of 10 to 50 μm (15 μm as an example). The insulating layer 30A is made of an insulating material, and can be made of a resin material such as BT resin.

[0027] The first upper planar coil 41 is a substantially elliptical spiral air-core coil wound around the opening 32 of the coil overlapping portion 31 on the upper surface 30a of the insulating layer 30A in the same layer. The first upper planar coil 41 has a coil axis Z along the thickness direction of the element body 10. The number of turns of the first upper planar coil 41 may be one turn or multiple turns. In this embodiment, the number of turns of the first upper planar coil 41 is 2 to 3. The first upper planar coil 41 has an outer end 41a and an inner end 41b. The outer end 41a is provided on the frame portion 34A, and extends to the end face 10a of the element body 10 and is exposed from the end face 10a. The inner end 41b is provided on the edge of the opening 32. The insulating layer 30A is provided with a through conductor 47 extending in the thickness direction of the insulating layer 30A at a position overlapping the inner end 41b of the first upper planar coil 41 so as to penetrate the insulating layer 30A. The first upper planar coil 41 is made of, for example, Cu and can be formed by electrolytic plating. In this embodiment, the first upper planar coil 41 has an auxiliary outer end 41c that overlaps with an outer end 42a of a second upper planar coil 42 described later with the insulating layer 30A sandwiched therebetween. The auxiliary outer end 41c is electrically connected to the outer end 42a via a through conductor (not shown) that penetrates the insulating layer 30A. By providing the auxiliary outer end 41c to form the outer end into a double structure, the contact area between the outer end and the external terminal electrode is enlarged, improving connectivity.

[0028] The second upper planar coil 42 is symmetrical with the first upper planar coil 41. More specifically, the second upper planar coil 42 has a shape obtained by inverting the first upper planar coil 41 around an axis parallel to the short side of the element body 10. The second upper planar coil 42 shares the coil axis Z with the first upper planar coil 41. The outer end 42a of the second upper planar coil 42 is provided on the frame part 34B, extends to the end face 10b of the element body 10, and is exposed from the end face 10b. The inner end 42b of the second upper planar coil 42 overlaps with the through conductor 47 provided in the insulating layer 30A. Therefore, the inner end 42b of the second upper planar coil 42 is electrically connected to the inner end 41b of the first upper planar coil 41 via the through conductor 47. The second upper planar coil 42 is made of, for example, Cu, and can be formed by electrolytic plating. In this embodiment, the second upper planar coil 42 has an auxiliary outer end 42c that overlaps with the outer end 41a of the first upper planar coil 41 with the insulating layer 30A sandwiched therebetween. The auxiliary outer end 42c is electrically connected to the outer end 41a via a through conductor (not shown) that penetrates the insulating layer 30A. By providing the auxiliary outer end 42c and forming the outer end into a double structure, the contact area between the outer end and the external terminal electrode is enlarged, improving connectivity.

[0029] The thickness of the first upper planar coil 41 and the thickness of the second upper planar coil 42 can be designed to be in the range of 20 to 40 μm (30 μm as an example), for example. The thickness of the first upper planar coil 41 and the thickness of the second upper planar coil 42 may be the same or different. In the upper coil structure 40A, the first upper planar coil 41, the second upper planar coil 42, and the through conductor 47 provided in the insulating layer 30A form a first coil C1 having a coil axis Z.

[0030] The first upper insulator 51 and the second upper insulator 52 cover the insulating layer 30A, the first upper planar coil 41, and the second upper planar coil 42 in the thickness direction of the element body 10 so as to sandwich them. The first upper insulator 51 and the second upper insulator 52 are both made of insulating resin. The first upper insulator 51 and the second upper insulator 52 are both made of insulating resin, and may be made of, for example, PP resin or BT resin. The first upper insulator 51 and the second upper insulator 52 may be a composite member (so-called prepreg) containing resin and glass fiber. The first upper insulator 51 and the second upper insulator 52 can be formed, for example, by vacuum pressing an insulating resin sheet from the thickness direction of the element body 10. As a result, the spaces between the lines of the first upper planar coil 41 and the second upper planar coil 42 are filled with the resin material, and the inner and outer surfaces of the first upper planar coil 41 and the second upper planar coil 42 are covered with the resin material. The first upper insulator 51 and the second upper insulator 52 are formed by blasting, as described below.

[0031] The thickness of the first upper insulator 51 and the thickness of the second upper insulator 52 can be designed to be in the range of 40 to 50 μm (for example, 45 μm). The thickness of the first upper insulator 51 and the thickness of the second upper insulator 52 may be the same or different.

[0032] 3, the lower coil structure 40B is provided on the sheet lower surface 30b in the coil overlapping portion 31 of the magnetic sheet 30. The lower coil structure 40B is configured to include an insulating layer 30B, a first lower planar coil 43, a second lower planar coil 44, a first lower insulator 53, and a second lower insulator 54, and has a through hole 45B.

[0033] The insulating layer 30B of the lower coil structure 40B has a flat plate shape (for example, a sheet or layer shape) similar to the insulating layer 30A of the upper coil structure 40A, and extends parallel to the magnetic sheet 30. The insulating layer 30B has substantially the same shape as the magnetic sheet 30 when viewed in the thickness direction. Like the magnetic sheet 30 and the insulating layer 30A, the insulating layer 30B has an elliptical ring-shaped coil overlapping portion 31 extending along the long side direction of the element body 10, and a pair of frame portions 34A and 34B extending along the short side direction of the element body 10 and sandwiching the coil overlapping portion 31 from both sides, and an elliptical opening 32 extending along the long side direction of the element body 10 is provided in the center of the coil overlapping portion 31. The thickness t2 of the insulating layer 30B can be designed to be in the range of 10 to 50 μm (15 μm as an example), for example. The thickness t2 of the insulating layer 30B may be the same as or different from the thickness t1 of the insulating layer 30A. The insulating layer 30B, like the insulating layer 30A, is made of an insulating material, and may be made of a resin material such as BT resin.

[0034] The first lower planar coil 43 is a substantially elliptical spiral air-core coil wound around the opening 32 of the coil overlapping portion 31 on the upper surface 30a of the insulating layer 30B in the same layer. The first lower planar coil 43 shares the coil axis Z with the upper planar coils 41 and 42. The number of turns of the first lower planar coil 43 may be one turn or multiple turns. In this embodiment, the number of turns of the first lower planar coil 43 is 2 to 3. The first lower planar coil 43 has an outer end 43a and an inner end 43b. The outer end 43a is provided on the frame portion 34A, extends to the end surface 10a of the element body 10, and is exposed from the end surface 10a. The inner end 43b is provided on the edge of the opening 32. The insulating layer 30B is provided with a through conductor 48 extending in the thickness direction of the insulating layer 30B at a position overlapping the inner end 43b of the first lower planar coil 43 so as to penetrate the insulating layer 30B. The first lower planar coil 43 is made of, for example, Cu and can be formed by electrolytic plating. In this embodiment, the first lower planar coil 43 has an auxiliary outer end 43c that overlaps with an outer end 44a of a second lower planar coil 44 described later with the insulating layer 30B sandwiched therebetween. The auxiliary outer end 43c is electrically connected to the outer end 44a via a through conductor (not shown) that penetrates the insulating layer 30B. By providing the auxiliary outer end 43c to form the outer end into a double structure, the contact area between the outer end and the external terminal electrode is enlarged, improving connectivity.

[0035] The second lower planar coil 44 is symmetrical with the first lower planar coil 43. More specifically, the second lower planar coil 44 has a shape obtained by inverting the first lower planar coil 43 around an axis parallel to the short side of the element body 10. The second lower planar coil 44 shares a coil axis Z with the upper planar coils 41, 42 and the first lower planar coil 43. The outer end 44a of the second lower planar coil 44 is provided on the frame part 34B, extends to the end face 10b of the element body 10, and is exposed from the end face 10b. The inner end 44b of the second lower planar coil 44 overlaps with the through conductor 48 provided in the insulating layer 30B. Therefore, the inner end 44b of the second lower planar coil 44 is electrically connected to the inner end 43b of the first lower planar coil 43 via the through conductor 48. The second lower planar coil 44 is made of, for example, Cu, and can be formed by electrolytic plating. In this embodiment, the second lower planar coil 44 has an auxiliary outer end 44c that overlaps with the outer end 43a of the first lower planar coil 43 with the insulating layer 30B sandwiched therebetween. The auxiliary outer end 44c is electrically connected to the outer end 43a via a through conductor (not shown) that penetrates the insulating layer 30B. By providing the auxiliary outer end 44c and forming the outer end into a double structure, the contact area between the outer end and the external terminal electrode is enlarged, improving connectivity.

[0036] The thickness of the first lower planar coil 43 and the thickness of the second lower planar coil 44 can be designed to be in the range of 20 to 40 μm (30 μm as an example), for example. The thickness of the first lower planar coil 43 and the thickness of the second lower planar coil 44 may be the same or different. In the lower coil structure 40B, the first lower planar coil 43, the second lower planar coil 44, and the through conductor 48 provided in the insulating layer 30B form a second coil C2 having a coil axis Z.

[0037] The first lower insulator 53 and the second lower insulator 54 cover the insulating layer 30B, the first lower planar coil 43, and the second lower planar coil 44 in the thickness direction of the element body 10 so as to sandwich them. The first lower insulator 53 and the second lower insulator 54 are both made of insulating resin. The first lower insulator 53 and the second lower insulator 54 are both made of insulating resin, and may be made of, for example, PP resin or BT resin. The first lower insulator 53 and the second lower insulator 54 may be a composite member (so-called prepreg) containing resin and glass fiber. The first lower insulator 53 and the second lower insulator 54 can be formed, for example, by vacuum pressing an insulating resin sheet from the thickness direction of the element body 10. As a result, the spaces between the lines of the first lower planar coil 43 and the second lower planar coil 44 are filled with the resin material, and the inner and outer surfaces of the first lower planar coil 43 and the second lower planar coil 44 are covered with the resin material. The first lower insulator 53 and the second lower insulator 54 are formed by blasting, as described below.

[0038] The thickness of the first lower insulator 53 and the thickness of the second lower insulator 54 can be designed to be in the range of 40 to 50 μm (for example, 45 μm). The thickness of the first lower insulator 53 and the thickness of the second lower insulator 54 may be the same or different.

[0039] 6, the thickness T1 of the element body portion overlapping with the upper coil structure 40A on the upper surface 10c side of the element body 10 is designed to be equal to the thickness T2 of the element body portion overlapping with the lower coil structure 40B on the lower surface 10d side of the element body 10. However, the thicknesses T1 and T2 may be different from each other.

[0040] Two pairs of external terminal electrodes 60A, 60B, 60C, and 60D are provided on end faces 10a, 10b of the element body 10, each of which is parallel to each other.

[0041] Of the pair of external terminal electrodes 60A, 60B provided on the end face 10a, the external terminal electrode 60A is connected to the outer end 43a of the first lower planar coil 43 of the lower coil structure 40B, and the external terminal electrode 60B is connected to the outer end 41a of the first upper planar coil 41 of the upper coil structure 40A. When viewed from the end face 10a side, the external terminal electrode 60A is biased toward the side face 10f and covers the end face 10a up to the vicinity of the side face 10f. Moreover, the external terminal electrode 60B is biased toward the side face 10e and covers the end face 10a up to the vicinity of the side face 10e. When viewed from the end face 10a side, the external terminal electrodes 60A and 60B are spaced apart by a predetermined uniform width.

[0042] Of the pair of external terminal electrodes 60C, 60D provided on the end face 10b, the external terminal electrode 60C is connected to the outer end 44a of the second lower planar coil 44 of the lower coil structure 40B, and the external terminal electrode 60D is connected to the outer end 42a of the second upper planar coil 42 of the upper coil structure 40A. The external terminal electrode 60C is biased toward the side face 10f and covers the end face 10b up to the vicinity of the side face 10f. The external terminal electrode 60D is biased toward the side face 10e and covers the end face 10b up to the vicinity of the side face 10e. When viewed from the end face 10b side, the external terminal electrodes 60C and 60D are spaced apart by a predetermined uniform width.

[0043] The external terminal electrode 60A on the end face 10a and the external terminal electrode 60C on the end face 10b are provided at positions corresponding to each other in the long side direction of the element body 10. Similarly, the external terminal electrode 60B on the end face 10a and the external terminal electrode 60D on the end face 10b are provided at positions corresponding to each other in the long side direction of the element body 10.

[0044] Each of the external terminal electrodes 60A, 60B, 60C, and 60D is bent into an L shape and continuously covers the end faces 10a, 10b and the upper face 10c. In this embodiment, the external terminal electrodes 60A, 60B, 60C, and 60D are made of resin electrodes, for example, made of a resin containing Ag powder.

[0045] In the coil component 1, when a voltage is applied between the external terminal electrode 60B and the external terminal electrode 60D, a current flows through the first coil C1 of the upper coil structure 40A, generating a magnetic flux around the first coil C1. Similarly, when a voltage is applied between the external terminal electrode 60A and the external terminal electrode 60C, a current flows through the second coil C2 of the lower coil structure 40B, generating a magnetic flux around the second coil C2. At this time, magnetic coupling may occur between the first coil C1 and the second coil C2, which share the coil axis Z.

[0046] 4, the magnetic sheet 30 in the coil component 1 has a coil overlapping portion 31 that overlaps with the coils C1 and C2 in an elliptical ring shape, and both the portion corresponding to the inner peripheral region of the coils C1 and C2 and the portion corresponding to the outer peripheral region of the coils C1 and C2 are removed. Similarly, the inner and outer peripheral portions of the through holes 45A and 45B in the coil structures 40A and 40B of the coil component 1 are removed. Therefore, both portions are filled with the magnetic material that constitutes the body 10, forming the inner and outer cores of the coils C1 and C2.

[0047] In the coil component 1, as shown in FIG. 7, the inner edges of the coil structures 40A and 40B (i.e., the edges that define the through holes 45A and 45B) recede relative to the inner edge of the magnetic sheet 30 (i.e., the edges that define the through holes 32). In this embodiment, the inner edge of the magnetic sheet 30 and the inner edges of the coil structures 40A and 40B have a cross-sectional shape that is bent in a dogleg shape, and the inner edges of the coil structures 40A and 40B gradually recede as they move away from the magnetic sheet 30 in the coil axis Z direction. For example, when considering two points in the coil axis Z direction, the inner edge at a position P1 on the side farther from the magnetic sheet 30 recedes from the inner edge at a position P2 on the side closer to the magnetic sheet 30. In this embodiment, in the cross section shown in FIG. 7 including the coil axis Z, the outer shapes of the coil structures 40A and 40B are approximately symmetrical with respect to a virtual straight line L perpendicular to the coil axis Z. Furthermore, in this embodiment, the magnetic sheet 30 is in contact with the metal powder contained in the resin 12 containing metal magnetic powder that constitutes the element body 10 at its inner edge.

[0048] Here, a method for forming the cross-sectional shapes of the magnetic sheet 30 and the coil structures 40A and 40B described above will be described.

[0049] FIG. 8 shows the state after the magnetic sheet 30 and the coil structures 40A and 40B are vacuum pressed, and the through holes have not yet been formed. In this state, a blasting process is performed from the top and bottom directions (i.e., the coil axis Z direction) using a resist mask M to mold the magnetic sheet 30 and the coil structures 40A and 40B. As a result, as shown in FIG. 9, the through holes 32 are formed in the magnetic sheet 30, and the through holes 45A and 45B are formed in the coil structures 40A and 40B. In addition, the outer edges of the magnetic sheet 30 and the coil structures 40A and 40B are formed. At this time, the above-mentioned dog-leg cross-sectional shape can be obtained and the degree of bending of the dog legs can be adjusted by appropriately adjusting the conditions of the blasting process (for example, the grain size and the projection pressure).

[0050] The outer circumferential portions of the coil structures 40A and 40B may or may not be removed.

[0051] In the coil component 1, leakage magnetic flux (i.e., magnetic flux penetrating only the first coil C1 and magnetic flux penetrating only the second coil C2) is easily generated by the magnetic sheet 30 interposed between the first coil C1 and the second coil C2. The coupling coefficient can be adjusted by increasing or decreasing the leakage magnetic flux by the magnetic sheet 30. In this embodiment, the inner edge of the magnetic sheet 30 is in contact with the metal powder contained in the metal magnetic powder-containing resin 12 constituting the element body 10 (i.e., there is no gap between the magnetic sheet 30 and the metal powder), so that the magnetic flux generated in the coils C1 and C2 easily passes through the magnetic sheet 30. For example, by increasing the magnetic permeability of the magnetic sheet 30, the leakage magnetic flux can be increased and the coupling coefficient can be reduced. In addition, by increasing the thickness of the magnetic sheet 30, the magnetic permeability of the magnetic sheet 30 can be increased. In this embodiment, the magnetic sheet 30 is designed to have a higher magnetic permeability than the material of the element body 10 (i.e., the resin 12 containing metal magnetic powder), and also higher than the magnetic permeability of the insulators 52, 53 adjacent to the magnetic sheet 30 in the thickness direction. In particular, increasing the magnetic permeability in the surface direction of the magnetic sheet 30 (the direction perpendicular to the coil axis Z) effectively increases leakage magnetic flux. The magnetic permeability of the magnetic sheet 30 can be adjusted, for example, by the thickness of the magnetic sheet 30, the form of the magnetic powder, the type of magnetic powder, the content of the magnetic powder, etc.

[0052] 7, in this embodiment, the magnetic powder p contained in the magnetic sheet 30 has a flat shape, and each magnetic powder extends along the surface direction of the magnetic sheet 30. In such a magnetic sheet 30, the magnetic permeability in the surface direction is relatively higher than the magnetic permeability in the thickness direction.

[0053] In the coil device 1, the use of the magnetic sheet 30 makes it easier for magnetic saturation to occur in the magnetic sheet 30, which is thought to degrade the DC superposition characteristics of the coil device 1. However, as shown in Fig. 7, the inner edges of the coil structures 40A and 40B are recessed from the inner edge of the magnetic sheet 30, making it easier for the magnetic flux generated in the coils C1 and C2 to rotate, thereby suppressing the degradation of the DC superposition characteristics due to the use of the magnetic sheet 30. Either one of the inner edges of the coil structures 40A and 40B may be recessed from the inner edge of the magnetic sheet 30.

[0054] In addition, the outer edges of the coil structures 40A and 40B also recede from the outer edge of the magnetic sheet 30, so that the magnetic flux generated in the coils C1 and C2 can circulate more easily. This further suppresses the deterioration of the DC superposition characteristics caused by the use of the magnetic sheet 30. Either one of the outer edges of the coil structures 40A and 40B may recede from the outer edge of the magnetic sheet 30.

[0055] The present invention is not limited to the above-described embodiment, and may take various forms. For example, the number of turns of the planar coil constituting the coil may be increased or decreased as appropriate. Also, the element body may include three or more coils. The coil included in each coil structure is not limited to a two-layer structure of a planar coil, but may be a single-layer structure or may be composed of three or more layers. Also, the insulating layer and insulator (upper insulator, lower insulator) included in each coil structure may be omitted as appropriate. [Explanation of symbols]

[0056] 1...coil component, 10...element body, 12...resin containing metal magnetic powder, 30...magnetic sheet, 32...through hole, 60A to 60D...external terminal electrodes, 40A...upper coil structure, 40B...lower coil structure, 41 to 44...planar coil, 45A, 45B...through hole, C1...first coil, C2...second coil, p...magnetic powder.

Claims

1. An element body made of resin containing metal powder; a pair of coil structures each including a pair of coils provided within the element body, the pair of coils overlapping each other in a coil axial direction and each having a pair of end portions extending to a surface of the element body; two pairs of external terminals provided on a surface of the element body and connected to ends of the pair of coils, respectively; a magnetic sheet provided within the element body and interposed between the pair of coil structures in the coil axis direction; Equipped with A coil component, wherein the pair of coil structures and the magnetic sheet each have a through hole extending along the coil axis direction, and an inner edge of at least one of the pair of coil structures recedes relative to an inner edge of the magnetic sheet.

2. The coil component according to claim 1 , wherein in at least one of the pair of coil structures, an inner edge on a side farther from the magnetic sheet in the coil axial direction is recessed from an inner edge on a side closer to the magnetic sheet.

3. The coil component according to claim 1 , wherein in a cross section including the coil axis, the outer shapes of the pair of coil structures are symmetrical with respect to a line perpendicular to the coil axis.

4. The coil component according to any one of claims 1 to 3, wherein the magnetic sheet is in contact with metal powder contained in a metal powder-containing resin that constitutes the element body at an inner edge thereof.

5. The coil component according to claim 1 , wherein the thicknesses of the element parts overlapping with the pair of coil structures in the coil axial direction are equal to each other.

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