Coil component

Abstract

This invention provides a coil component in which the external stress applied when the upper coil structure, the lower coil structure, and the magnetic sheet overlap is dispersed by the undulations of the two main surfaces of the magnetic sheet. By dispersing the stress in this way, defects such as cracks in the coil structure can be effectively suppressed.

Description

Technical Field

[0001] This disclosure relates to a coil component. Background Technology

[0002] Currently, coil components with a pair of coils overlapping each other in the coil axis are known. Japanese Patent Application Publication No. 2018-137421 discloses a coil component with a PCB substrate between a pair of coils. Summary of the Invention

[0003] The technical problem that the invention aims to solve

[0004] Each coil in the aforementioned coil component consists of two coil layers, forming a multi-layer structure comprising four coil layers and a PCB substrate. In coil components with this multi-layer structure, external stresses such as molding pressure due to overlapping can easily lead to defects such as cracks. These defects affect inductance, coupling coefficient, insulation, and other properties. The inventors conducted in-depth research and discovered a new technology that can suppress the generation of defects caused by external stresses in multi-layer coil components.

[0005] According to this disclosure, a coil component capable of suppressing the generation of defects can be provided.

[0006] Means for solving technical problems

[0007] One aspect of this disclosure provides a coil component comprising: a body; a pair of coils disposed within the body, each having a pair of ends that overlap each other in the coil axial direction and extend to a surface of the body; two pairs of external terminals disposed on the surface of the body and respectively connected to the ends of the pair of coils; and a sheet disposed within the body, positioned between the pair of coils in the coil axial direction, and having undulations on its main surface.

[0008] In the aforementioned coil component, the external stress in the coil axial direction when a pair of coils and sheets overlap is dispersed on the undulations of the main surface of the sheet, thus suppressing the occurrence of defects.

[0009] In another coil component, the sheet is made of a magnetic material containing magnetic powder and resin.

[0010] In another coil component, the magnetic powder contained in the magnetic material is flat and extends in a direction that intersects with the coil axis.

[0011] In another coil component, there is also an insulator located between the coil and the sheet.

[0012] In another coil component, at least one of the portions corresponding to the inner circumferential region of the coil and the portions corresponding to the outer circumferential region of the coil are removed from the sheet.

[0013] In another coil component, the main surface of the sheet has irregular undulations.

[0014] In another coil component, the coil includes an insulating layer and a pair of planar coils formed on both sides of the insulating layer, the thickness of which is greater than the thickness of the insulating layer of the coil.

[0015] In another coil component, the undulations of the main surface of the sheet are greater than the undulations of the main surface of the coil's insulation layer. Attached Figure Description

[0016] Figure 1 This is a general perspective view of the coil component in the embodiment.

[0017] Figure 2 It means Figure 1 A diagram of the interior of the coil component.

[0018] Figure 3 yes Figure 2 An exploded perspective view of the coil structure shown.

[0019] Figure 4 It means Figure 3 A top view of the magnetic sheet shown.

[0020] Figure 5 yes Figure 2 The figure shown is a cross-sectional view of the VV line of the solid.

[0021] Figure 6 yes Figure 2 The figure shown is a cross-sectional view along line VI-VI.

[0022] Figure 7 It is Figure 6 The main part of the cross-sectional view shown is enlarged. Detailed Implementation

[0023] Hereinafter, embodiments of the present 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 repeated descriptions are omitted.

[0024] The coil component 1 in this embodiment is a so-called coupled coil. The coupled coil contains two coils in a single component, enabling a reduction in the number of components and a smaller mounting area. The coupled coil can be used as a smoothing coil in switching power supplies, such as DC / DC converters in various electronic devices.

[0025] like Figure 1 ,2 As shown, the coil component 1 is composed of a body 10, a coil structure 20 embedded in the body 10, and two pairs of external terminal electrodes 60A, 60B, 60C, and 60D disposed on the surface of the body 10.

[0026] The body 10 has a rectangular parallelepiped shape and six faces 10a to 10f. As an example, the body 10 is designed with 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 body 10, end faces 10a and 10b are parallel to each other, the upper surface 10c and the lower surface 10d are parallel to each other, and the side surfaces 10e and 10f are parallel to each other. The upper surface 10c of the body 10 is parallel to the mounting surface of the mounting substrate of the coil component 1.

[0027] The base material 10 is composed of a resin 12 containing metallic magnetic powder, which is a type of magnetic material. The resin 12 containing metallic magnetic powder comprises metal powder and resin; more specifically, the metallic magnetic powder is a binder powder bonded by a binder resin. The metallic magnetic powder in the resin 12 can be, for example, an iron-nickel alloy (permalloy), carbonyl iron, amorphous, amorphous, or crystalline FeSiCr alloys, aluminum-silicon-iron powder, etc. The binder resin is, for example, a thermosetting epoxy resin. In this embodiment, the content of metallic magnetic powder in the binder powder is 80–92 vol% by volume and 95–99 wt% by mass. From the viewpoint of magnetic properties, the content of metallic magnetic powder in the binder powder can also be 85–92 vol% by volume and 97–99 wt% by mass. The magnetic powder in the resin 12 containing metallic magnetic powder can be a powder having a single average particle size or a mixture of powders having multiple average particle sizes.

[0028] The resin 12 containing metallic magnetic powder of the base body 10 integrally covers the coil structure 20 described later. Specifically, the resin 12 containing metallic magnetic powder covers the coil structure 20 from top to bottom and covers the outer periphery of the coil structure 20. In addition, the resin 12 containing metallic magnetic powder fills the inner periphery region of the coil structure 20.

[0029] The coil structure 20 has a multi-layered structure. Specifically, as follows: Figure 2 , 3 As shown, the coil structure 20 comprises a magnetic sheet 30, an upper coil structure 40A disposed on the upper side of the magnetic sheet 30, and a lower coil structure 40B disposed on the lower side of the magnetic sheet 30. The coil structure 20 is a laminate formed by sequentially overlapping the upper coil structure 40A, the magnetic sheet 30, and the lower coil structure 40B, with the magnetic sheet 30 positioned between the upper coil structure 40A and the lower coil structure 40B in the lamination direction.

[0030] The magnetic sheet 30 is sheet-like and extends across the end faces 10a and 10b of the body 10, designed to be orthogonal to the end faces 10a and 10b. Furthermore, the magnetic sheet 30 extends parallel to the upper surface 10c and lower surface 10d of the body 10. Figure 4 As shown, the magnetic sheet 30 has an elliptical coil overlap portion 31 extending along the long side of the body 10, and a pair of frame portions 34A and 34B extending along the short side of the body 10 and sandwiching the coil overlap portion 31 from both sides. An elliptical opening (through hole) 32 extending along the long side of the body 10 is provided in the central portion of the coil overlap portion 31. The thickness t of the magnetic sheet 30 can be designed, for example, within 10 to 100 μm (30 μm as an example).

[0031] The magnetic sheet 30 is made of a magnetic material. In this embodiment, the magnetic sheet 30 comprises resin and magnetic powder (magnetic material powder), and has a structure in which the magnetic powder is dispersed in the resin. The resin of the magnetic sheet 30 is, for example, an epoxy resin. The magnetic powder of the magnetic sheet 30 may be, for example, composed of ferrite, permalloy, aluminum-silicon-iron powder, Fe-based magnetic materials, etc. The magnetic powder of the magnetic sheet 30 may be in the form of flat or needle-like shapes, or in the form of spheres. For example, when the magnetic powder of the magnetic sheet 30 is flat, the magnetic powder may also extend in a direction intersecting the thickness direction of the magnetic sheet 30 (for example, a direction orthogonal to the thickness direction of the magnetic sheet 30). The magnetic sheet 30 may also be an amorphous foil, amorphous ribbon, or amorphous layer made of a magnetic material.

[0032] The magnetic sheet 30 of this embodiment has a structure in which ferrite flat powder is dispersed substantially uniformly in epoxy resin, and the ferrite flat powder extends in a direction orthogonal to the thickness direction of the magnetic sheet 30. Therefore, for the magnetic sheet 30, the magnetic permeability in the direction orthogonal to the thickness direction is higher than that in the thickness direction. In addition, the ferrite flat powder extends substantially parallel to the extension direction of the magnetic sheet 30, thus suppressing the thickening of the magnetic sheet 30 and improving the magnetic permeability.

[0033] like Figure 3 As shown, the upper coil structure 40A is disposed on the upper surface 30a of the coil overlap portion 31 of the magnetic sheet 30. The upper coil structure 40A is composed of 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.

[0034] The insulating layer 30A has a flat plate shape (e.g., a sheet or layer) and extends parallel to the magnetic sheet 30. Viewed in the thickness direction, the insulating layer 30A has virtually the same shape as the magnetic sheet 30. That is, like the magnetic sheet 30, the insulating layer 30A has: an elliptical annular coil overlap portion 31 extending along the long side of the body 10, and a pair of frame portions 34A, 34B extending along the short side of the body 10 and sandwiching the coil overlap portion 31 from both sides. An elliptical opening 32 extending along the long side of the body 10 is provided in the central portion of the coil overlap portion 31. The thickness t1 of the insulating layer 30A can be designed within, for example, a range of 10 to 50 μm (15 μm as an example). The insulating layer 30A is made of an insulating material, for example, a resin material such as BT resin.

[0035] The first upper planar coil 41 is a generally elliptical spiral-shaped hollow coil wound around the opening 32 of the coil overlap portion 31 within the same layer on the upper surface 30a of the insulating layer 30A. The first upper planar coil 41 has a coil axis Z along the thickness direction of the body 10. The number of turns of the first upper planar coil 41 can 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 portion 41a and an inner end portion 41b. The outer end portion 41a is provided on the frame portion 34A, extends to the end face 10a of the body 10, and is exposed from the end face 10a. The inner end portion 41b is provided at the edge of the opening 32. On the insulating layer 30A, a through conductor 47 extending along the thickness direction of the insulating layer 30A is provided at a position overlapping the inner end portion 41b of the first upper planar coil 41 in a manner that penetrates the insulating layer 30A. The first upper planar coil 41 is made of Cu, for example, and can be formed by electroplating. In this embodiment, the first upper planar coil 41 has an auxiliary outer end 41c, which overlaps with the outer end 42a of the second upper planar coil 42 (described later) by sandwiching an insulating layer 30A. The auxiliary outer end 41c is electrically connected to the outer end 42a via a through conductor (not shown) penetrating the insulating layer 30A. By providing the auxiliary outer end 41c and making the outer end a double-layer structure, the contact area between the outer end and the external terminal electrode is increased, and the connectivity is improved.

[0036] The second upper planar coil 42 is symmetrical to the first upper planar coil 41. More specifically, the second upper planar coil 42 has a shape that reverses the shape of the first upper planar coil 41 about an axis parallel to the short side of the body 10. The second upper planar coil 42 and the first upper planar coil 41 share a coil axis Z. The outer end portion 42a of the second upper planar coil 42 is provided in the frame portion 34B, extends to the end face 10b of the body 10, and is exposed from the end face 10b. The inner end portion 42b of the second upper planar coil 42 overlaps with the through conductor 47 provided in the insulating layer 30A. Therefore, the inner end portion 42b of the second upper planar coil 42 is electrically connected to the inner end portion 41b of the first upper planar coil 41 via the through conductor 47. The second upper planar coil 42 is made of Cu, for example, and can be formed by electroplating. In this embodiment, the second upper planar coil 42 has an auxiliary outer end portion 42c, which overlaps with the outer end portion 41a of the first upper planar coil 41, sandwiching an insulating layer 30A. The auxiliary outer end portion 42c is electrically connected to the outer end portion 41a via a through conductor (not shown) penetrating the insulating layer 30A. By providing the auxiliary outer end portion 42c, the outer end portion is made into a double-layer structure, increasing the contact area between the outer end portion and the external terminal electrode, thus improving connectivity.

[0037] The thicknesses of the first upper planar coil 41 and the second upper planar coil 42 can be designed within a range of, for example, 20 to 40 μm (30 μm as an example). The thicknesses of the first upper planar coil 41 and the second upper planar coil 42 can 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 disposed in the insulating layer 30A are used to form a first coil C1 having a coil axis Z.

[0038] The first upper insulator 51 and the second upper insulator 52 are covered by an insulating layer 30A, a first upper planar coil 41, and a second upper planar coil 42 sandwiched in the thickness direction of the substrate 10. Both the first upper insulator 51 and the second upper insulator 52 are made of insulating resin. The first upper insulator 51 and the second upper insulator 52 are made of insulating resin, for example, PP resin or BT resin. The first upper insulator 51 and the second upper insulator 52 can also be composite components containing resin and glass fiber (so-called prepreg). 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 substrate 10. Thus, the spaces between the wires of the first upper planar coil 41 and the second upper planar coil 42 are buried in 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 resin material.

[0039] The thickness of the first upper insulator 51 and the thickness of the second upper insulator 52 can be designed within a range of, for example, 40 to 50 μm (45 μm as an example). The thickness of the first upper insulator 51 and the thickness of the second upper insulator 52 can be the same or different.

[0040] like Figure 3 As shown, the lower coil structure 40B is disposed on the lower surface 30b of the coil overlap portion 31 of the magnetic sheet 30. The lower coil structure 40B is composed of 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.

[0041] The insulating layer 30B of the lower coil structure 40B, like the insulating layer 30A of the upper coil structure 40A, has a flat shape (e.g., a sheet or layer) and extends parallel to the magnetic sheet 30. Viewed in the thickness direction, the insulating layer 30B has substantially the same shape as the magnetic sheet 30. Similar to the magnetic sheet 30 and the insulating layer 30A, the insulating layer 30B has an elliptical coil overlap portion 31 extending along the long side of the body 10, and a pair of frame portions 34A and 34B extending along the short side of the body 10 and sandwiching the coil overlap portion 31 from both sides. An elliptical opening 32 extending along the long side of the body 10 is provided in the central portion of the coil overlap portion 31. The thickness t2 of the insulating layer 30B can be designed within, for example, a range of 10 to 50 μm (15 μm as an example). The thickness t2 of the insulating layer 30B can be the same as or different from the thickness t1 of the insulating layer 30A. Similar to insulating layer 30A, insulating layer 30B is made of insulating material, such as resin material such as BT resin.

[0042] The first lower planar coil 43 is a generally elliptical spiral-shaped hollow coil wound around the opening 32 of the coil overlap portion 31 within the same layer on the upper surface 30a of the insulating layer 30B. The first lower planar coil 43 shares a coil axis Z with the upper planar coils 41 and 42. The number of turns of the first lower planar coil 43 can be one or more. 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 portion 43a and an inner end portion 43b. The outer end portion 43a is provided on the frame portion 34A, extends to the end face 10a of the body 10, and is exposed from the end face 10a. The inner end portion 43b is provided at the edge of the opening 32. On the insulating layer 30B, a through conductor 48 extending along the thickness direction of the insulating layer 30B is provided at a position overlapping the inner end portion 43b of the first lower planar coil 43 in a manner that penetrates the insulating layer 30B. The first lower planar coil 43 is made of Cu, for example, and can be formed by electroplating. In this embodiment, the first lower planar coil 43 has an auxiliary outer end 43c, which overlaps with the outer end 44a of the second lower planar coil 44 (described later) by sandwiching an insulating layer 30B. The auxiliary outer end 43c is electrically connected to the outer end 44a via a through conductor (not shown) penetrating the insulating layer 30B. By providing the auxiliary outer end 43c, the outer end is made into a double-layer structure, increasing the contact area between the outer end and the external terminal electrode and improving connectivity.

[0043] The second lower planar coil 44 is symmetrical to the first lower planar coil 43. More specifically, the second lower planar coil 44 has a shape that reverses the first lower planar coil 43 about an axis parallel to the short side of the body 10. The second lower planar coil 44 shares a coil axis Z with the upper planar coils 41 and 42 and the first lower planar coil 43. The outer end portion 44a of the second lower planar coil 44 is provided in the frame portion 34B, extends to the end face 10b of the body 10, and is exposed from the end face 10b. The inner end portion 44b of the second lower planar coil 44 overlaps with a through conductor 48 provided in the insulating layer 30B. Therefore, the inner end portion 44b of the second lower planar coil 44 is electrically connected to the inner end portion 43b of the first lower planar coil 43 via the through conductor 48. The second lower planar coil 44 is made of Cu, for example, and can be formed by electroplating. In this embodiment, the second lower planar coil 44 has an auxiliary outer end portion 44c, which overlaps with the outer end portion 43a of the first lower planar coil 43, sandwiched by an insulating layer 30B. The auxiliary outer end portion 44c is electrically connected to the outer end portion 43a via a through conductor (not shown) penetrating the insulating layer 30B. By providing the auxiliary outer end portion 44c, the outer end portion is made into a double-layer structure, increasing the contact area between the outer end portion and the external terminal electrode, thus improving connectivity.

[0044] The thicknesses of the first lower planar coil 43 and the second lower planar coil 44 can be designed within a range of, for example, 20 to 40 μm (30 μm as an example). The thicknesses of the first lower planar coil 43 and the second lower planar coil 44 can 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 disposed in the insulating layer 30B constitute a second coil C2 having a coil axis Z.

[0045] The first lower insulator 53 and the second lower insulator 54 are covered by an insulating layer 30B, a first lower planar coil 43, and a second lower planar coil 44 sandwiched in the thickness direction of the substrate 10. Both the first lower insulator 53 and the second lower insulator 54 are made of insulating resin. For example, they may be made of PP resin or BT resin. The first lower insulator 53 and the second lower insulator 54 may also be composite components containing resin and glass fiber (so-called prepreg). 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 substrate 10. Thus, the wires of the first lower planar coil 43 and the second lower planar coil 44 are buried between resin materials, and the inner and outer surfaces of the first lower planar coil 43 and the second lower planar coil 44 are covered by resin materials.

[0046] The thickness of the first lower insulator 53 and the thickness of the second lower insulator 54 can be designed within a range of, for example, 40 to 50 μm (45 μm as an example). The thickness of the first lower insulator 53 and the thickness of the second lower insulator 54 can be the same or different.

[0047] The upper coil structure 40A and the lower coil structure 40B are joined together by overlapping each other in a manner that sandwiches the magnetic sheet 30. This results in a coil structure 20 with a multi-layered structure. Vacuum stamping can be used in the joining of the upper coil structure 40A and the lower coil structure 40B.

[0048] In this embodiment, the thickness of the portion of the body 10 that overlaps with the upper coil structure 40A on the upper surface 10c side is equal to the thickness of the portion of the body 10 that overlaps with the lower coil structure 40B on the lower surface 10d side. However, the two thicknesses can also be different.

[0049] Two pairs of external terminal electrodes 60A, 60B, 60C, and 60D are each provided on the parallel end faces 10a and 10b of the body 10.

[0050] Of the pair of external terminal electrodes 60A and 60B disposed on end face 10a, 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 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 end face 10a, external terminal electrode 60A is biased towards side 10f and covers the vicinity of side 10f on end face 10a. External terminal electrode 60B is biased towards side 10e and covers the vicinity of side 10e on end face 10a. When viewed from end face 10a, external terminal electrodes 60A and 60B are separated by a predetermined uniform width.

[0051] Of the pair of external terminal electrodes 60C and 60D disposed on end face 10b, 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 external terminal electrode 60D is connected to the outer end 42a of the second upper planar coil 42 of the upper coil structure 40A. External terminal electrode 60C is biased towards side 10f and covers the vicinity of side 10f on end face 10b. External terminal electrode 60D is biased towards side 10e and covers the vicinity of side 10e on end face 10b. When viewed from end face 10b, external terminal electrode 60C and external terminal electrode 60D are separated by a predetermined uniform width.

[0052] External terminal electrodes 60A on end face 10a and 60C on end face 10b are positioned at corresponding locations along the long side of the body 10. Similarly, external terminal electrodes 60B on end face 10a and 60D on end face 10b are positioned at corresponding locations along the long side of the body 10.

[0053] External terminal electrodes 60A, 60B, 60C, and 60D are all bent into an L-shape, continuously covering end faces 10a and 10b and the upper surface 10c. In this embodiment, external terminal electrodes 60A, 60B, 60C, and 60D are made of resin electrodes, for example, of resin containing Ag powder.

[0054] In coil component 1, when a voltage is applied between external terminal electrodes 60B and 60D, current flows through the first coil C1 of the upper coil structure 40A, generating magnetic flux around the first coil C1. Similarly, when a voltage is applied between external terminal electrodes 60A and 60C, current flows through the second coil C2 of the lower coil structure 40B, generating magnetic flux around the second coil C2. At this time, magnetic coupling can be generated between the first coil C1 and the second coil C2, which share the same coil axis Z.

[0055] The magnetic sheet 30 in coil component 1, such as Figure 4 As shown, the coil overlap portion 31 overlapping with coils C1 and C2 is an elliptical ring, and both the portion corresponding to the inner circumference of coils C1 and C2 and the portion corresponding to the outer circumference of coils C1 and C2 are removed. For the coil structure 20 of coil component 1, the inner and outer portions of the through hole are also removed. The shape of the coil structure 20 can be formed by sandblasting the coil structure 20 from the vertical direction (i.e., the Z-direction of the coil axis). The inner and outer portions of the through hole of the coil structure 20 are filled with the magnetic material constituting the body 10, forming the inner and outer cores of coils C1 and C2. Furthermore, the outer portion of the coil structure 20 can be removed or not removed.

[0056] In coil component 1, leakage flux (i.e., flux passing only through the first coil C1 and flux passing only through the second coil C2) is easily generated through the magnetic sheet 30 located between the first coil C1 and the second coil C2. At this time, insulators 52 and 53 are located between the pair of coils C1 and C2 and the magnetic sheet 30, respectively. By increasing or decreasing the leakage flux using the magnetic sheet 30, the coupling coefficient can be adjusted. In this embodiment, the inner edge of the magnetic sheet 30 is in contact with the metal powder contained in the resin 12 containing metallic magnetic powder constituting the body 10 (i.e., there is no gap between the magnetic sheet 30 and the metal powder), therefore, the magnetic flux generated in coils C1 and C2 easily causes the magnetic sheet 30 to rotate. For example, by increasing the permeability of the magnetic sheet 30, the leakage flux can be increased and the coupling coefficient reduced. Furthermore, by increasing the thickness of the magnetic sheet 30, the permeability of the magnetic sheet 30 can be increased. In this embodiment, the magnetic permeability of the magnetic sheet 30 is higher than that of the substrate material constituting the body 10 (i.e., the resin 12 containing metallic magnetic powder), and it is designed to have a higher permeability than that of the insulators 52 and 53 adjacent to the magnetic sheet 30 in the thickness direction. In particular, by increasing the permeability of the magnetic sheet 30 in the planar direction (the direction orthogonal to the coil axis Z), the leakage flux is effectively increased. The permeability of the magnetic sheet 30 can be adjusted by, for example, the thickness of the magnetic sheet 30, or the morphology, type, and proportion of the magnetic powder.

[0057] like Figure 7 As shown, in this embodiment, the magnetic powder p contained in the magnetic sheet 30 is flat, and each magnetic powder extends along the surface direction of the magnetic sheet 30. In this magnetic sheet 30, the permeability in the surface direction is relatively higher than the permeability in the thickness direction.

[0058] In addition, such as Figure 7As shown, the two main surfaces (upper surface 30a and lower surface 30b) of the magnetic sheet 30 are undulating or fluctuating. That is, the two main surfaces 30a and 30b of the magnetic sheet 30 have a surface shape with gently undulating, continuous undulations at high and low positions relative to the virtual line L, which is orthogonal to the coil axis Z and bisects the magnetic sheet 30. Regarding the undulations of the two main surfaces 30a and 30b, the interval (period) between the high and low positions is much larger than the height difference and also much larger than the surface roughness. In this embodiment, both the height difference and the period are irregular in the undulations of the two main surfaces 30a and 30b of the magnetic sheet 30. As described above, the magnetic sheet 30 is constructed comprising flat magnetic powder p, and it is believed that the dispersion of the magnetic powder p is one of the reasons for the undulations of the two main surfaces 30a and 30b of the magnetic sheet 30.

[0059] 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 are no substantial undulations on their two main surfaces. Therefore, in this embodiment, the undulations of the two main surfaces 30a and 30b of the magnetic sheet 30 are greater than the undulations of the two main surfaces of the insulating layers 30A and 30B.

[0060] The thickness t of the magnetic sheet 30 can be designed to be thicker than the thicknesses t1 and t2 of the insulating layers 30A and 30B. The thickness t of the magnetic sheet 30 with undulating main surfaces 30a and 30b can be obtained, for example, by the sum of the absolute value of the height of the peak point (highest point in the Z direction of the coil axis) of the upper surface 30a of the magnetic sheet 30 based on the virtual line L and the absolute value of the height of the peak point (highest point) of the lower surface 30b based on the virtual line L.

[0061] As described above, the coil structure 20 of the coil component 1 is formed by overlapping the upper coil structure 40A and the lower coil structure 40B together, sandwiching the magnetic sheet 30. When the upper coil structure 40A, the lower coil structure 40B, and the magnetic sheet 30 are overlapped, external stresses such as molding pressure are applied. At this time, the undulations of the two main surfaces 30a and 30b of the magnetic sheet 30 disperse the aforementioned external stresses in the Z-direction of the coil axis. By dispersing the external stresses in this way, defects such as cracks in the coil structure 20 are effectively suppressed.

[0062] Furthermore, in the coil component 1, when an impact or vibration is applied from the outside in the Z-axis direction of the coil, the stress in the Z-axis direction can be dispersed by the undulations of the two main surfaces 30a and 30b of the magnetic sheet 30. By dispersing the stress in this way, defects such as cracks in the body 10 or the coil structure 20 can be effectively suppressed. That is, high strength in the Z-axis direction of the coil is achieved in the coil component 1.

[0063] Alternatively, only one of the two main surfaces 30a and 30b of the magnetic sheet 30 may be undulated. Furthermore, the coil component 1 may also use a non-magnetic sheet made of a non-magnetic material such as epoxy resin instead of the magnetic sheet 30.

[0064] Furthermore, this disclosure is not limited to the embodiments described above, and various methods can be employed. For example, the number of turns of the planar coil constituting the coil can be appropriately increased or decreased. Alternatively, it is also possible to include three or more coils within the body.

Claims

1. A coil component, wherein, have: body; A pair of coils disposed within the body, each having a pair of ends that overlap each other in the coil axial direction and extend to the surface of the body; Two pairs of external terminals are disposed on the surface of the body and are respectively connected to the ends of the pair of coils; as well as A sheet material disposed within the body, positioned axially between the pair of coils, and having undulations on its main surface.

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 that intersects with the axial direction of the coil.

4. The coil component according to any one of claims 1 to 3, wherein, It also includes an insulator located between the coil and the sheet.

5. The coil component according to any one of claims 1 to 4, wherein, In the sheet, at least one of the portion corresponding to the inner peripheral region of the coil and the portion corresponding to the outer peripheral region of the coil has been removed.

6. The coil component according to any one of claims 1 to 5, wherein, The surface of the sheet is irregularly undulating.

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

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

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