Coil device

Abstract

To provide a highly reliable coil device. [Solution] The device comprises a core 6 containing magnetic particles 8 and a winding section 20 in which flat wires 2a are wound edgewise. In the cross-section of the core 6, a gap 4 is formed between adjacent flat wires 2a along the winding axis of the winding section 20, and is continuous from the outside to the inside of the winding section 20. Some of the magnetic particles 8 constituting the core 6 are contained within the gap 4.

Description

[Technical Field]

[0001] The present disclosure relates to a coil device. [Background Art]

[0002] As a coil device used as an inductor or the like, there is known a coil device in which an air-core coil formed by edgewise-winding a rectangular wire is embedded inside a core (Patent Document 1). High inductance can be expected with a small volume in such a coil device.

[0003] However, in such a coil device, since the core is formed by pressure-molding magnetic powder, the pressure may cause a short-circuit defect between adjacent rectangular wires of the wound portion. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 2004-311756 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a highly reliable coil device. [Means for Solving the Problem]

[0006] A coil device according to one aspect of the present disclosure includes: a core containing magnetic particles; and a wound portion formed by edgewise-winding a rectangular wire, the magnetic particles are insulation-coated metal magnetic particles obtained by coating the periphery of a metal magnetic material with an insulating film, in a cross-section of the core, a gap continuous from the outside to the inside of the wound portion is formed between the rectangular wires adjacent to each other along a winding axis of the wound portion, Some of the magnetic particles that make up the core are contained within the gap.

[0007] By using insulating coated metal magnetic particles to constitute the core, the product's properties can be improved, and the risk of short circuits can be reduced. Furthermore, the presence of a continuous gap between adjacent rectangular wires, running from the outside to the inside of the winding section, and the inclusion of insulating coated metal magnetic particles in this gap, reduces the risk of short circuits between adjacent rectangular wires. Additionally, the core volume can be maintained, further improving the product's properties.

[0008] The magnetic particles may include a first particle and a second particle having a smaller average particle size than the first particle. Furthermore, the second particle may be arranged in the gap in a larger proportion than the first particle. By arranging particles of different particle sizes in this way, the gaps between adjacent rectangular wires can be efficiently filled, reducing the risk of short circuits and improving the product's characteristics.

[0009] The magnetic particles may be arranged in the gap such that the ratio of the number of second particles to the number of first particles is greater on the inside, closer to the winding shaft, than on the outside, further from the winding shaft. This arrangement of magnetic particles reduces the risk of short circuits and improves the characteristics of the product.

[0010] The gap may be narrower on the inner side, closer to the winding shaft, than on the outer side, further from the winding shaft. This configuration makes it easier to secure the core volume. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view of a coil device according to one embodiment. [Figure 2] Figure 2 is a perspective view of the coil device shown in Figure 1, viewed from the mounting side. [Figure 3]Figure 3 is a cross-sectional view of the coil device shown in Figure 1, along the line III-III. [Figure 4] Figure 4 is an enlarged view showing the wire configuration shown in Figure 3. [Figure 5] Figure 5 is a magnified view of the gap between the wires shown in Figure 3. [Figure 6] Figure 6 is an enlarged view showing the configuration of the magnetic particles shown in Figure 5. [Modes for carrying out the invention]

[0012] The embodiments of this disclosure will be described below with reference to the drawings. Note that the illustrations are for illustrative purposes only to help understand this disclosure, and the appearance and dimensional ratios may differ from those of the actual product. Furthermore, this disclosure is not limited to the following embodiments.

[0013] The coil device 1 of this embodiment shown in Figure 1 is a surface-mount type inductor and can be mounted, for example, in the power supply circuit of an electronic device. The dimensions of the coil device 1 are not particularly limited, but its width in the X-axis direction is, for example, 1.0 to 7.0 mm, its width in the Y-axis direction is, for example, 1.0 to 7.0 mm, and its width in the Z-axis direction is, for example, 0.5 to 5.0 mm.

[0014] As shown in Figure 1, the coil device 1 includes a coil 2 made of a flat rectangular wire 2a whose surface is covered with an insulating layer 30 (see Figure 4), and a magnetic core 6. In the coil device 1, at least the winding portion 20 of the coil 2 is embedded inside the core 6.

[0015] The shape of the coil device 1 is not particularly limited, but in the example shown in Figure 1, it has a substantially rectangular parallelepiped shape and has a first outer surface 11, a second outer surface 12, a third outer surface 13, a fourth outer surface 14, a fifth outer surface 15, and a sixth outer surface 16. The first outer surface 11 and the second outer surface 12 face each other in a first direction, the third outer surface 13 and the fourth outer surface 14 face each other in a second direction, and the fifth outer surface 15 and the sixth outer surface 16 face each other in a third direction. The first, second, and third directions are mutually orthogonal.

[0016] In the drawings, the X-axis corresponds to a first direction, the Y-axis corresponds to a second direction, and the Z-axis corresponds to a third direction. The origin of the XYZ coordinate system is set at the center of the core 6. It should be noted that the outer shape of the coil device 1 is not limited to a substantially rectangular parallelepiped shape, and may be other polyhedrons such as an octahedron or a decahedron.

[0017] As shown in FIG. 1, the coil 2 is formed of a rectangular wire 2a, and has a wound portion 20 formed by edgewise-winding the rectangular wire 2a. The wound portion 20 is embedded inside the core 6. The coil 2 further includes a pair of lead portions 261 and 262 drawn out from the wound portion 20. The lead portion 261 constitutes one end of the coil 2, and the lead portion 262 constitutes the other end of the coil 2. As shown in FIG. 2, parts of the lead portions 261 and 262 are exposed from the bottom surface (fifth side surface 15) of the core 6.

[0018] FIG. 3 is a cross-sectional view perpendicular to the Y-axis of the coil device 1. As shown in FIG. 3, the wound portion 20 is formed by edgewise-winding the rectangular wire 2a with 5 turns, and includes turn layers 20a to 20e. The turn layers 20a to 20e are arranged so as to overlap in the Z-axis direction. However, the number of turns of the wound portion 20 is not limited, as long as there are 2 or more turns, that is, two or more turn layers. A gap 4 is formed between each of the turn layers 20a to 20e, and a part of the core 6 enters into the gap 4.

[0019] FIG. 4 is an enlarged view of the rectangular wire 2a in the wound portion 20 (each turn layer) shown in FIG. 3. As shown in FIG. 4, the rectangular wire 2a is composed of a wire whose surface is covered with an insulating layer 30. There is no particular limitation on the material of the conductor 2b constituting the rectangular wire 2a, but copper, silver, alloys containing these, or other metals or alloys can be used. There is no particular limitation on the insulating layer 30, and for example, known insulating coatings such as polyamide-imide resin, polyurethane resin and epoxy acrylic resin are used.

[0020] The width W0 of the rectangular wire 2a shown in FIG. 4 is not particularly limited, and is, for example, 0.1 to 0.7 mm, and the thickness thereof in the Z-axis direction is, for example, 0.05 to 0.5 mm. In a cross-section, the rectangular wire 2a in the wound portion 20 has a larger thickness W1 at the inner end 21 close to the winding axis than the thickness W2 at the outer end 22 far from the winding axis. That is, the rectangular wire 2a has a substantially trapezoidal cross-section that is longer on the inner side and shorter on the outer side. In this specification, the cross-section of the rectangular wire refers to a cross-section perpendicular to the direction in which the rectangular wire extends. In this embodiment, since the rectangular wire 2a in the wound portion 20 extends substantially on the XY plane, the cross-section of the rectangular wire 2a is a cross-section along the Z-axis direction. In FIG. 4, the cross-section of the rectangular wire 2a is a cross-section along the Z-axis and the X-axis. In this embodiment, the cross-sectional characteristics of the rectangular wire 2a in the wound portion 20 are common to the cross-sections at any position of the wound portion 20.

[0021] As shown in FIG. 4, in the wound portion 20, the insulating layer 30 entirely covers the conductor 2b along the circumferential direction of the rectangular wire 2a. The thickness of the insulating layer 30 is not particularly limited, and may be, for example, 1 / 50 to 1 / 10 of the thickness of the rectangular wire 2a in the Z-axis direction.

[0022] As shown in FIG. 4, the thickness T1 of the inner end portion 31 of the insulating layer 30 located at the inner end 21 of the rectangular wire 2a is larger than the thickness T2 of the outer end portion 32 of the insulating layer 30 located at the outer end 22. Since the thickness T1 of the inner end portion 31 of the insulating layer 30 is larger than the thickness T2 of the outer end portion 32 of the insulating layer 30, even if the inner end 21 close to the winding shaft of the wound portion is scratched, the scratch is less likely to reach the conductor 2b, thereby preventing short-circuit defects. On the other hand, scratches that lead to short-circuit defects are less likely to occur at the outer end 22, so short-circuit defects can be sufficiently prevented even if the insulating layer is thinner than that at the inner end 21.

[0023] The inner end portion 31 of the insulating layer 30 is the region that includes the innermost end 21a of the rectangular wire 2a, which is closest to the winding axis. The inner end portion 31 connects the inner corner portions 331 and 332 of the insulating layer 30 that form the inner corner portions 231 and 232 of the rectangular wire 2a, which will be described later. The thickness T1 may be uniform in the inner end portion 31, but there may be parts that are thinner or parts that are thicker. In this embodiment, the thickness T1 of the inner end portion 31 of the insulating layer 30 is greatest at the innermost end 21a, but the thickness of the inner end portion 31 at the innermost end 21a can be considered as the thickness T1 of the inner end portion 31 of the insulating layer 30.

[0024] Furthermore, the outer end portion 32 of the insulating layer 30 is the region that includes the outermost end 22a, which is furthest from the winding axis of the rectangular wire 2a. The outer end portion 32 connects the outer corner portions 341 and 342 of the insulating layer 30 that form the outer corner portions 241 and 242 of the rectangular wire 2a, which will be described later. The thickness T2 may be uniform in the outer end portion 32, but there may be parts that are thinner or thicker. In this embodiment, the thickness T2 of the outer end portion 32 of the insulating layer 30 is greatest at the outermost end 22a, but the thickness of the outer end portion 32 at the outermost end 22a can be considered as the thickness T2 of the outer end portion 32 of the insulating layer 30.

[0025] The thickness T1 of the inner end portion 31 and the thickness T2 of the outer end portion 32 of the insulating layer 30 are not particularly limited. For example, the thickness T1 of the inner end portion 31 of the insulating layer 30 may be 1.2 to 3 times the thickness T2 of the outer end portion 32 of the insulating layer 30.

[0026] As shown in Figure 4, the thickness T3 of the inner corner portions 331, 332 of the insulating layer 30 that form the inner corner portions 231, 232 of the rectangular wire 2a may be greater than the thickness T4 of the outer corner portions 341, 342 of the insulating layer 30 that form the outer corner portions 241, 242 of the rectangular wire. For example, the thickness T3 of the inner corner portion 33 of the insulating layer 30 may be 1.2 to 3 times the thickness T4 of the outer corner portion 34 of the insulating layer 30. In this specification, the corner portion of a rectangular wire refers to the vertex of the quadrilateral having the largest area inscribed in the outer surface of the rectangular wire in the cross-section of the rectangular wire. In this embodiment, of the vertices of the largest quadrilateral inscribed in the outer surface of the rectangular wire 2a, the two points closest to the winding axis are called the inner corner portions 231, 232, and the two points farther from the winding axis are called the outer corner portions 241, 242. Hereafter, the inner corner portions 231, 232 will be collectively referred to as the inner corner portion 23. Furthermore, the inner corner portions 331 and 332 of the insulating layer 30 are collectively referred to as the inner corner portion 33. Also, the outer corner portions 241 and 242 are collectively referred to as the outer corner portion 24. Furthermore, the outer corner portions 341 and 342 are collectively referred to as the outer corner portion 34.

[0027] The intermediate portion 351 of the insulating layer 30 located in the intermediate portion 251 between the inner corner portion 231 and the outer corner portion 241 of the rectangular wire 2a may be thicker from the outer corner portion 341 toward the inner corner portion 331. The intermediate portion 352 of the insulating layer 30 located in the intermediate portion 252 between the inner corner portion 232 and the outer corner portion 242 of the rectangular wire 2a may be thicker from the outer corner portion 342 toward the inner corner portion 332. In the following, the intermediate portions 251 and 252 will be collectively referred to as the intermediate portion 25. Also, the intermediate portions 351 and 352 of the insulating layer 30 will be collectively referred to as the intermediate portion 35.

[0028] As shown in Figure 1, the lead-out portion 261 has a terminal portion 261b for connecting to a mounting board or the like, and a connecting portion 261a for connecting the winding portion 20 and the terminal portion 261b. As shown in Figure 1, the connecting portion 261a of the lead-out portion 261 connects the uppermost turn in the Z-axis direction of the winding portion 20 (the turn layer 20e shown in Figure 3 in this embodiment) to the terminal portion 261b. As shown in Figure 3, a part of the terminal portion 261b is exposed below the bottom portion 64 of the core 6.

[0029] As shown in Figure 1, the lead-out portion 262 has a terminal portion 262b (see Figure 2) for connecting to a mounting board or the like, and a connecting portion 262a that connects the winding portion 20 and the terminal portion 262b. As shown in Figure 1, the connecting portion 262a of the lead-out portion 262 connects the lowest turn in the Z-axis direction of the winding portion 20 (the turn layer 20a shown in Figure 3 in this embodiment) to the terminal portion 262b (see Figure 2). As shown in Figure 3, a part of the terminal portion 262b is exposed below the bottom 64 of the core 6.

[0030] In the portions where the terminals 261b and 262b are exposed from the bottom surface of the core 6, the insulating layer 30 described above is peeled off, and a connection layer 38 that can be electrically connected to a wiring board or the like is formed. The connection layer 38 is the portion that is connected to the wiring board or the like. Therefore, the connection layer 38 has solder wettability and plays a role in assisting the connection between the terminals 261b and 262b and the mounting board. For example, a plating film is formed on the connection layer 38. Examples of plating films include metals such as Sn, Au, Ni, Pt, Ag, and Pd, or alloys thereof. The connection layer 38 may also be formed by methods such as sputtering. The thickness of the connection layer 38 is smaller than the thickness of the terminals 261b and 262b, and may be, for example, 3 to 30 μm.

[0031] As shown in Figures 1 and 2, the core 6 covers the coil 2, except for parts of the terminal portions 261b and 262b. As shown in Figure 5, the core 6 is formed from a material containing magnetic particles 8 and resin 9. Examples of magnetic particles 8 forming the core 6 include ceramic magnetic materials and metallic magnetic materials.

[0032] Examples of ceramic magnetic materials that form core 6 include ferrites such as Ni-Zn ferrite and Mn-Zn ferrite. Examples of metallic magnetic materials that form core 6 include, but are not particularly limited, Fe-Ni alloy, Fe-Si alloy, Fe-Si-Cr alloy, Fe-Co alloy, Fe-Si-Al alloy, and amorphous iron.

[0033] The magnetic particles 8 are insulating from the viewpoint of preventing short-circuit defects and improving product characteristics. For example, as shown in Figure 6, they are insulating coated metal magnetic particles in which a metallic magnetic material 82 is coated with an insulating film 84. The insulating film coating the magnetic particles may be an oxide film, or an insulating coating film such as glass or resin.

[0034] Furthermore, as shown in Figure 5, the magnetic particles 8 may include a first particle 8a and a second particle 8b having a smaller average particle diameter (D50) than the first particle 8a. For example, the magnetic particles 8 may contain a first particle 8a with a particle size of 15 μm or more and less than 30 μm, and a second particle 8b with a particle size of 3 μm or more and less than 15 μm. The magnetic particles 8 may also contain a third particle with a particle size smaller than the second particle. For example, the particle size of the third particle may be less than 3 μm.

[0035] Furthermore, the resin 9 forming the core 6 is not particularly limited, but examples include epoxy resin, phenolic resin, polyester resin, polyurethane resin, polyimide resin, other synthetic resins, or other non-magnetic materials.

[0036] As shown in Figure 3, the core 6 generally has a columnar portion 62 positioned inside the winding portion 20 of the coil, a bottom portion 64 positioned below the winding portion 20, an upper portion 66 covering the top of the winding portion 20, and side portions 68 covering the outside of the winding portion 20. The core 6 may be formed by compacting the above material, but from the viewpoint of facilitating assembly, the core 6 may be a combination of a base portion 6a with the columnar portion 62 and bottom portion 64 pre-formed, and an outer casing 6b that fills the gap between the coil and the base portion and forms the parts other than the columnar portion 62 and bottom portion 64.

[0037] The columnar portion 62 does not need to be tall enough to reach above the winding portion 20, but it may penetrate the winding portion 20 along the winding shaft. In a core 6 having the columnar portion 62 inside, the assembly of the coil device 1 is made easier, and short-circuit defects in the product can also be prevented. In the core 6, the base portion 6a and the outer casing 6b may be molded from the same material, or they may be molded from different materials.

[0038] As shown in Figure 3, a gap 4 is formed between each turn layer 20a to 20e, and the filling portion 70 of the core 6 fits into this gap 4. The filling portion 70 is part of the core 6 and contains magnetic particles 8 (see Figure 5). The filling portion 70 of the side portion 68 of the core 6 fits into the gap 4 between the intermediate layer 251 of the turn layer and the intermediate layer 252 of the turn layer adjacent to it in the Z-axis direction. The filling portion 70 is connected to the side portion 68 that covers the outside of the winding portion 20 of the core 6, and fills the gap 4 from the side portion 68 inward. It is preferable that the filling portion 70 completely fills the gap 4, but there may be some blanks.

[0039] Figure 5 is a magnified view of the gaps 4 formed between each turn layer 20 shown in Figure 3, and the core 6 that has entered into the gaps 4. In Figure 5, the gaps 4 between turn layer 20a and turn layer 20b, and the gaps 4 between turn layer 20b and turn layer 20c are shown, but the same applies to the gaps between other adjacent turn layers. The following explanation will mainly focus on the gap 4 between turn layer 20b and turn layer 20c, but this explanation also applies to the gaps between other turn layers.

[0040] As shown in Figure 5, a gap 4 is formed between the turn layer 20b and the turn layer 20c, extending from the outside to the inside of the winding portion 20. That is, the outer corner portion 241, the middle portion 251, and the inner corner portion 231 of the flat rectangular wire 2a of the turn layer 20b are separated from the outer corner portion 242, the middle portion 252, and the inner corner portion 232 of the flat rectangular wire 2a of the turn layer 20c. A gap 4 is formed between the middle portion 252 of the turn layer 20c.

[0041] The gap 4 is not particularly limited as long as it is large enough for the magnetic particles 8 described above to enter. For example, from the viewpoint of properly filling the magnetic particles 8, it is preferable that the gap 4 be 1 μm or larger, and more preferably twice or more the average particle diameter (D50) of the small second particles 8b. Furthermore, from the viewpoint of miniaturizing the product, it is preferable that the size of the gap 4 be twice or less the average particle diameter (D50) of the large first particles 8a. Note that the gap 4 only needs to be formed between any adjacent turn layers, and there may be gaps 4 that are not continuous from the outside to the inside of the winding portion 20, and there may be places where adjacent turn layers are in contact and no gap 4 is formed.

[0042] As shown in Figure 5, the gap 4 is narrower on the inside, closer to the winding shaft, than on the outside, further from the winding shaft. In the filling section 70 that fills the gap 4, the proportion of second particles 8b is greater than that of first particles 8a. By arranging the filling section 70 such that the proportion of second particles 8b is greater than that of first particles 8a, the filling section 70 can efficiently fill the narrow gap 4 between adjacent rectangular wires.

[0043] Furthermore, in the filling section 70, the ratio of the number of second particles 8b to the number of first particles 8a is greater on the inner side closer to the winding shaft than on the outer side further from the winding shaft. This configuration makes it easier for the filling section 70 to continuously fill the gaps 4 between adjacent flat wires 2a from the side 68. As the gaps 4 between adjacent flat wires 2a are filled by the insulating magnetic particles 8 and resin 9 that constitute the filling section 70, the risk of short circuits can be reduced. In addition, it is easier to secure the volume of magnetic particles 8 that constitute the core 6, thereby improving the characteristics of the product.

[0044] The number of magnetic particles 8 in the filling portion 70 of the gap 4 is not particularly limited, but from the viewpoint of reducing the risk of short circuits, it is preferable that 20 or more magnetic particles 8 are present in one gap 4. The number of magnetic particles 8 in the filling portion 70 of the gap 4 can be measured, for example, by taking a cross-sectional image of the gap 4 with a scanning microscope (SEM) and observing the first particles 8a (for example, particles with a particle size of 15 μm or more and less than 30 μm) and second particles 8b (for example, particles with a particle size of 3 μm or more and 15 μm) in the captured gap 4. Furthermore, a comparison of the ratio of the number of second particles 8b to the number of first particles 8a on the outer side far from the winding axis and on the inner side close to the winding axis in the filling portion 70 of the gap 4 can be measured, for example, by observing the number of first particles 8a and second particles 8b on the outer side of the gap 4 and the number of first particles 8a and second particles 8b on the inner side in a cross-sectional image of the gap 4 taken with a scanning microscope (SEM).

[0045] The coil device 1 of this embodiment can be manufactured, for example, as follows. First, a base portion 6a is prepared, with the columnar portion 62 and bottom portion 64 shown in Figure 1 already formed. Then, an air-core coil is formed by edgewise winding using a flat rectangular wire 2 whose surface is covered with the insulating layer 30 as described above. The columnar portion 62 is placed inside the winding portion 20 of the coil 2, and the coil 2 is attached to the base portion 6a such that the terminal portion 261b of the lead portion 261 and the terminal portion 262b of the lead portion 262 are positioned below the bottom portion 64.

[0046] Next, the assembly, which consists of the coil 2 and the base portion 6a, is placed in the cavity of a predetermined mold. The assembly is positioned so that a portion of the terminal portion 261b of the drawer portion 261 and a portion of the terminal portion 262b of the drawer portion 262 are exposed, and the outer casing 6b is insert injection molded around the assembly. The material used to make up the outer casing 6b is a material that is fluid during molding, and a composite magnetic material with a thermoplastic resin or thermosetting resin as a binder may be used. As mentioned above, the core 6 may also be compacted by powder molding as a whole.

[0047] As described above, in the coil device 1 according to this embodiment, as shown in Figure 5, a gap 4 is formed in the cross-section of the core 6 between adjacent flat wires 2a along the winding axis of the winding portion 20, and the gap 4 is continuous from the outside to the inside of the winding portion 20. A portion of the magnetic particles 8 that make up the core 6 are contained in the gap 4. In this way, there is a gap 4 between adjacent flat wires 2a that is continuous from the outside to the inside of the winding portion 20, and the filling portion 70 of the core 6 is contained in the gap 4. Therefore, the volume of the core 6 can be secured, and the characteristics of the product can be improved. As described above, the magnetic particles 8 that make up the filling portion 70 are insulating, and the risk of short circuits between adjacent flat wires 2a can be reduced.

[0048] The magnetic particles 8 consist of a first particle 8a and a second particle 8b, which has a smaller average particle size than the first particle 8a. Furthermore, the gaps 4 are arranged such that the second particle 8b is more numerous than the first particle 8a. This arrangement of particles 8a and 8b with different particle sizes efficiently fills the gaps between adjacent rectangular wires, reducing the risk of short circuits and improving the product's characteristics.

[0049] Magnetic particles 8 are arranged in the gap 4 such that the ratio of the number of second particles 8b to the number of first particles 8a is greater on the inside, closer to the winding shaft, than on the outside, further from the winding shaft. This configuration increases the density of magnetic particles 8 in the gap 4, improving product characteristics while suppressing the risk of short circuits.

[0050] It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0051] In this disclosure, the external shape of the coil device 1 is exemplified by other polyhedra such as a rectangular parallelepiped, but the external shape of the coil device 1 is not limited to polyhedra and may be a columnar body such as a cylinder or an elliptical cylinder from the viewpoint of effective magnetic flux. [Explanation of Symbols]

[0052] 1... Coil device 11...First outer surface 12…Second outer surface 13...Third outer surface 14...Fourth outer surface 15...5th outer surface 16…6th outer surface 2... Coil 2a…Flat wire 2b... Conductor 20... Volume 2 20a~20e... Turn layer 21...Inner end 21a…Innermost end 22...Outer end 22a…Outermost end 23(231,232)...Interior corner 24 (241, 242)... outer corner 25(251,252)...Middle section 261,262...Drawer section 261a,262a...Connection part 261b,262b…Terminal section 30…Insulating layer 31...Inner end part 32...Outer end part 33(331,332)...Interior corner 34(341,342)...Outer corner part 35(351,352)…middle part 38…Connection Layer 4…Gap 6... Core 6a...Base 6b... Exterior 62...Columnar part 64...Bottom 66... ​​Top 68... Side 70…Filling section 8...Magnetic particles 8a...first particle 8b…Second particle 82...Metal magnetic material 84… Insulating film 9… Resin

Claims

1. A core containing magnetic particles, It has a winding section in which a flat wire is wound edgewise, The magnetic particles are insulating coated metal magnetic particles in which a metallic magnetic material is coated with an insulating film. In the cross-section of the core, a gap is formed between adjacent rectangular wires along the winding axis of the winding portion, extending from the outside to the inside of the winding portion. A coil device in which some of the magnetic particles constituting the core are contained within the gap.

2. The magnetic particles include a first particle and a second particle having a smaller average particle size than the first particle. The coil device according to claim 1, wherein the second particles are arranged in the gap such that their number is in a larger proportion than that of the first particles.

3. The coil device according to claim 2, wherein the magnetic particles are arranged in the gap such that the ratio of the number of second particles to the number of first particles is greater on the inside, closer to the winding shaft, than on the outside, further from the winding shaft.

4. The coil device according to claim 1, wherein the gap is narrower on the inside, closer to the winding shaft, than on the outside, further from the winding shaft.

5. The coil device according to claim 1, wherein the thickness of the inner end of the rectangular wire is greater than that of the outer end of the rectangular wire.

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