Coil parts

Abstract

To provide a coil component that suppresses the occurrence of defects.SOLUTION: In a coil component 1, the external stress applied when an upper coil structure 40A, a lower coil structure 40B, and a magnetic sheet 30 are superimposed is dispersed by the undulations of the main surfaces 30a and 30b of the magnetic sheet 30. By dispersing the stress in this manner, the occurrence of defects such as cracks in the coil structure 20 is effectively suppressed.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] 2. Description of the Related Art Conventionally, coil components in which a pair of coils are overlapped with each other in the coil axial direction are known. Patent Document 1 listed below discloses a coil component in which a PCB substrate is interposed between the pair of coils. [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] Each coil of the above-mentioned coil component is composed of two coil layers, and the coil component as a whole has a multi-layer structure including four coil layers and a PCB substrate. Coil components having such a multi-layer structure are prone to defects such as cracks due to external stress such as pressure (molding pressure) during stacking. Defects that occur in coil components affect properties such as inductance value, coupling coefficient, and insulation. After extensive research, the inventors have discovered a new technology that can suppress the occurrence of defects caused by external stress in coil components with a multi-layer structure.

[0005] An object of the present invention is to provide a coil component in which the occurrence of defects is suppressed. [Means for solving the problem]

[0006] A coil component according to one aspect of the present invention comprises a base body, a pair of coils provided within the base body, each having a pair of ends that overlap each other in the coil axial direction and extend to a 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 sheet provided within the base body, interposed between the pair of coils in the coil axial direction, and having a wavy main surface.

[0007] In the above coil component, external stress in the coil axial direction when the pair of coils and the sheet are overlapped is dispersed by the undulations of the main surface of the sheet, thereby preventing defects from occurring.

[0008] In a coil component according to another aspect, the sheet is made of a magnetic material containing magnetic powder and resin.

[0009] In a coil component according to another aspect, the magnetic powder contained in the magnetic material has a flat shape and extends in a direction intersecting with the coil axis direction.

[0010] A coil component according to another aspect further includes an insulator interposed between the coil and the sheet.

[0011] In a coil component according to another aspect, at least one of a portion of the sheet corresponding to an inner peripheral region of the coil and a portion of the sheet corresponding to an outer peripheral region of the coil is removed.

[0012] In a coil component according to another aspect, the waviness of the main surface of the sheet is irregular.

[0013] In a coil component according to another aspect, the coil includes an insulating layer and a pair of planar coils formed on both sides of the insulating layer, and the thickness of the sheet is greater than the thickness of the insulating layer of the coil.

[0014] In a coil component according to another aspect, the waviness of the main surface of the sheet is greater than the waviness of the main surface of the insulating layer of the coil. Effect of the Invention

[0015] According to the present invention, a coil component in which the occurrence of defects is suppressed is provided. [Brief description of the drawings]

[0016] [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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The coil structure 20 has a multi-layer structure. Specifically, as shown in Figs. 2 and 3, the coil structure 20 is configured to include 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, and the magnetic sheet 30 is interposed between the upper coil structure 40A and the lower coil structure 40B in the stacking direction.

[0024] The magnetic sheet 30 has a sheet shape, 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).

[0025] 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.

[0026] 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.

[0027] 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 is configured to include 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The upper coil structure 40A and the lower coil structure 40B are bonded together by stacking them with the magnetic sheet 30 sandwiched therebetween, thereby obtaining the coil structure 20 having a multi-layer structure. The upper coil structure 40A and the lower coil structure 40B can be bonded together by vacuum pressing.

[0042] In this embodiment, the thickness 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 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 two thicknesses may be different from each other.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] As shown in FIG. 4, the magnetic sheet 30 in the coil component 1 has a coil overlapping portion 31 that overlaps 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. The coil structure 20 of the coil component 1 also has the inner and outer peripheral portions of the through holes removed. The outer shape of the coil structure 20 can be formed by performing a blasting process on the coil structure 20 from the top and bottom directions (i.e., the coil axis Z direction). The inner and outer peripheral portions of the through holes of the coil structure 20 are filled with the magnetic material that constitutes the element body 10, and constitute the inner and outer cores of the coils C1 and C2. The outer peripheral portion of the coil structure 20 may or may not be removed.

[0050] In the coil component 1, leakage magnetic flux (i.e., magnetic flux passing only through the first coil C1 and magnetic flux passing only through the second coil C2) is easily generated by the magnetic sheet 30 interposed between the pair of coils C1 and C2 and the magnetic sheet 30. In this case, insulators 52 and 53 are interposed between the pair of coils C1 and C2 and the magnetic sheet 30, respectively. 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 circulates around 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.

[0051] 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.

[0052] As shown in FIG. 7, both main surfaces (upper surface 30a and lower surface 30b) of the magnetic sheet 30 are wavy or corrugated. That is, both main surfaces 30a and 30b of the magnetic sheet 30 have an undulating surface shape in which high and low positions are gently continuous with respect to a virtual line L that is perpendicular to the coil axis Z and bisects the magnetic sheet 30. As for the waviness of both main surfaces 30a and 30b, the interval (period) between the high and low positions is considerably larger than the height difference and is also considerably larger than the surface roughness. In this embodiment, the waviness of both main surfaces 30a and 30b of the magnetic sheet 30 is irregular in both height difference and period. As described above, the magnetic sheet 30 is composed of flat magnetic powder p, and it is considered that the waviness of both main surfaces 30a and 30b of the magnetic sheet 30 is caused in part by the dispersion state of the magnetic powder p.

[0053] In contrast, neither the insulating layer 30A of the upper coil structure 40A nor the insulating layer 30B of the lower coil structure 40B contains magnetic powder, and there is substantially no waviness on either of their main surfaces. Therefore, in this embodiment, the waviness of either of the main surfaces 30a, 30b of the magnetic sheet 30 is greater than the waviness of either of the main surfaces of the insulating layers 30A, 30B.

[0054] The thickness t of the magnetic sheet 30 can be designed to be thicker than the thicknesses t1, t2 of the insulating layers 30A, 30B. The thickness t of the magnetic sheet 30 having undulating main surfaces 30a, 30b can be calculated, for example, by adding the absolute value of the height of the peak point (the highest point in the coil axis Z direction) of the upper surface 30a of the magnetic sheet 30 based on the imaginary line L and the absolute value of the height of the peak point (the highest point) of the lower surface 30b based on the imaginary line L.

[0055] As described above, the coil structure 20 of the coil component 1 is formed by stacking the upper coil structure 40A and the lower coil structure 40B with the magnetic sheet 30 sandwiched between them. When stacking the upper coil structure 40A, the lower coil structure 40B, and the magnetic sheet 30, external stress such as molding pressure is applied. At this time, the undulations of both main surfaces 30a, 30b of the magnetic sheet 30 can disperse the external stress in the coil axis Z direction. By dispersing the external stress in this manner, the occurrence of defects such as cracks in the coil structure 20 is effectively suppressed.

[0056] Furthermore, when the coil device 1 is subjected to an external shock or vibration in the coil axis Z direction, the undulations of both main surfaces 30a, 30b of the magnetic sheet 30 can disperse the stress in the coil axis Z direction. By dispersing the stress in this manner, the occurrence of defects such as cracks in the element body 10 or the coil structure 20 is effectively suppressed. In other words, the coil device 1 achieves high strength in the coil axis Z direction.

[0057] Alternatively, only one of the two main surfaces 30a, 30b of the magnetic sheet 30 may be wavy. In addition, the coil component 1 may use, instead of the magnetic sheet 30, a non-magnetic sheet made of a non-magnetic material such as an epoxy resin.

[0058] 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. In addition, the element may include three or more coils. [Explanation of symbols]

[0059] 1...coil component, 10...element body, 12...resin containing metal magnetic powder, 30...magnetic sheet, 30A, 30B...insulating layer, 32...through hole, 60A to 60D...external terminal electrode, 40A...upper coil structure, 40B...lower coil structure, 41 to 44...planar coil, 51 to 54...magnetic body, C1...first coil, C2...second coil, p...magnetic powder.

Claims

1. The body and 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 ends 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 sheet provided within the element body, interposed between the pair of coils in the coil axial direction, the sheet having a wavy main surface; A coil component comprising:

2. The coil component according to claim 1 , wherein the sheet is made of a magnetic material containing magnetic powder and resin.

3. The coil component according to claim 2 , wherein the magnetic powder contained in the magnetic material is flat and extends in a direction intersecting with the coil axis direction.

4. The coil component according to claim 1 , further comprising an insulator interposed between the coil and the sheet.

5. The coil component according to any one of claims 1 to 4, wherein at least one of a portion of the sheet corresponding to an inner circumferential region of the coil and a portion of the sheet corresponding to an outer circumferential region of the coil is removed.

6. The coil component according to any one of claims 1 to 5, wherein the waviness of the main surface of the sheet is irregular.

7. The coil includes an insulating layer and a pair of planar coils formed on both sides of the insulating layer, The coil component according to any one of claims 1 to 6, wherein the sheet has a thickness greater than a thickness of an insulating layer of the coil.

8. The coil component according to any one of claims 1 to 7, wherein the waviness of the main surface of the sheet is greater than the waviness of the main surface of the insulating layer of the coil.

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