Inductor

Abstract

To improve an upper limit of an inductance which can be achieved in an inductor having an element assembly including a coil conductor.SOLUTION: An inductor 1 includes an element assembly 2 including a coil conductor 20 and a core 30 which embeds the coil conductor and contains magnetic particles and a resin. The coil conductor has a winding part 22 where a conducting wire is wound around a winding shaft, and the winding part has two overlapping winding region 22a and 22b along the winding shaft. The winding part has such a range that the number of cross sections of the conducting wires included in the two winding regions are different between one winding region and the other winding region, when being viewed from the adjacent parts in a winding shaft direction, in the cross sections in the winding shaft direction, and the inner periphery in the one winding region having the smaller number of cross sections of the conducting wires in the winding shaft direction in the cross sections is deviated to the outer peripheral side of the winding part with respect to the inner periphery of the other winding region having the larger number of cross sections of the conducting wires in the cross sections in the winding shaft direction by 1 / 2 or more of the thickness of the conducting wire measured in a direction perpendicular to the winding shaft, in at least a part of the range.SELECTED DRAWING: Figure 9

Description

Technical Field

[0006] , ,

[0001] The present invention relates to an inductor.

Background Art

[0002] Patent Document 1 discloses a wound inductor including a body including a core containing magnetic particles and a coil conductor embedded in the core, and external electrodes provided on opposite end faces of the body. The coil conductor includes a winding portion and lead portions drawn out from both ends of the winding portion, and the lead portions are exposed from the end faces of the body and connected to the external electrodes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an inductor having the above configuration, when the size of the body is reduced, the shape of the winding portion embedded in the core in the body can have a great influence on the value of the inductance that can be realized in the inductor.

[0005] An object of the present invention is to improve the inductance that can be realized in an inductor including a body including a core containing magnetic particles and a coil conductor embedded in the core.

Means for Solving the Problems

[0006] One aspect of the present invention comprises a body including a coil conductor and a core containing magnetic particles and resin in which the coil conductor is embedded, wherein the coil conductor has a winding portion in which a conductor is wound around a winding shaft perpendicular to the upper surface of the body, the winding portion has two overlapping winding regions along the winding shaft, the winding portion has a substantially rectangular shape in plan view as seen from the direction of the winding shaft, and has two distinct ranges, one on each of the two opposing sides of the substantially rectangular area in which the conductor is wound as seen from the upper surface of the body, and each range has a cross section along the winding axis direction In the above, the number of cross-sections of the conductor included in the two adjacent winding regions along the winding axis differs between one winding region and the other winding region, and in at least a portion of each of the above ranges, the inner circumference of the winding region with fewer cross-sections of the conductor in the cross-section along the winding axis is shifted toward the outer circumference of the winding portion by at least half the thickness of the conductor measured in a direction perpendicular to the winding axis, relative to the inner circumference of the other winding region with more cross-sections of the conductor in the cross-section along the winding axis, and one of the winding regions is In one of the two ranges mentioned above, One of the aforementioned winding regions is other The number of cross-sections of the conductor is less than the number of winding regions, Of the two ranges mentioned above In the other range The first winding region is The inductor includes a greater number of cross-sections of the conductor than the other winding regions. [Effects of the Invention]

[0007] According to the present invention, in an inductor comprising a core containing a magnetic material and a coil conductor embedded in the core, the achievable inductance can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of an inductor according to an embodiment of the present invention, viewed from the top side. [Figure 2] This is a perspective view of the inductor from the bottom side. [Figure 3] This is a perspective view showing the internal structure of an inductor. [Figure 4]It is a schematic diagram of the manufacturing process of the inductor. [Figure 5] It is a plan view showing the internal configuration of the inductor. [Figure 6] It is a sectional view taken along line VI-VI of FIG. 5. [Figure 7] It is a cross-sectional view of the conductor constituting the wire. [Figure 8] It is a diagram showing the configuration of the winding part in an inductor in which the winding part of the coil conductor is wound in a normal winding method. [Figure 9] It is a diagram showing the configuration of the winding part of the inductor according to the present embodiment. [Figure 10] It is a diagram showing the configuration of the coil conductor embedded in the base body. [Figure 11] It is a sectional view taken along line XI-XI of FIG. 5. [Figure 12] It is a sectional view when a normal conductor corresponding to FIG. 11 is used. [Figure 13] It is a side view of the inductor 1 viewed from the side of the end face 14. [Figure 14] It is a diagram schematically showing the cross section in the XIV-XIV cross section of FIG. 13. [Figure 15] It is a sectional view taken along line XIV-XIV of FIG. 13. [Figure 16] It is a sectional view taken along line XVI-XVI of FIG. 13.

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] [Overall Configuration of Inductor] FIG. 1 is a perspective view of the inductor 1 according to the present embodiment viewed from the side of the upper surface 12, and FIG. 2 is a perspective view of the inductor 1 viewed from the side of the bottom surface 10. The inductor 1 of the present embodiment is configured as a surface-mounted electronic component, and includes a substantially rectangular parallelepiped-shaped base body 2 which is a mode of a substantially hexahedral shape, and a pair of external electrodes 4 provided on the surface of the base body 2.

[0011] Hereinafter, in the body 2, a first main surface facing a mounting substrate (not shown in the figure) during mounting is defined as the bottom surface 10, a second main surface facing the bottom surface 10 is called the top surface 12, a pair of third main surfaces orthogonal to the bottom surface 10 are called end surfaces 14, and a pair of fourth main surfaces orthogonal to the bottom surface 10 and the pair of end surfaces 14 are called side surfaces 16. As shown in FIG. 1, the distance from the bottom surface 10 to the top surface 12 is defined as the thickness T of the body 2, the distance between the pair of side surfaces 16 is defined as the width W of the body 2, and the distance between the pair of end surfaces 14 is defined as the length L of the body 2. Also, the direction of the thickness T is defined as the thickness direction DT, the direction of the width W is defined as the width direction DW, and the direction of the length distance is defined as the length direction DL. The nominal size of the inductor 1 as a finished product is, for example, a length L dimension of 1.4 mm, a width W dimension of 1.2 mm, and a thickness T dimension of 0.8 mm.

[0012] Hereinafter, a plane along the DL direction and the DT direction (a plane orthogonal to the DW direction) is called the LT plane, a plane along the DT direction and the DW direction (a plane orthogonal to the DL direction) is called the TW plane, and a plane along the DL direction and the DW direction (a plane orthogonal to the DT direction) is called the LW plane. Also, cross-sections of the inductor 1 along the LT plane, the TW plane, and the LW plane are called the LT cross-section, the TW cross-section, and the LW cross-section, respectively.

[0013] FIG. 3 is a perspective view showing the internal structure of the inductor 1. The body 2 includes a coil conductor 20 and a substantially hexahedral core 30 in which the coil conductor 20 is embedded, and is configured as a molded inductor in which the coil conductor 20 is encapsulated in the core 30.

[0014] The core 30 is a molded body obtained by compression molding a mixed powder of magnetic particles and resin into a substantially hexahedral shape by pressurizing and heating in a state where the coil conductor 20 is enclosed.

[0015] Furthermore, the magnetic particles in this embodiment are made of a soft magnetic material and contain two types of particle sizes: first magnetic particles with a relatively large average particle size and second magnetic particles with a relatively small average particle size. As a result, during compression molding, the second magnetic particles, which are small particles, are interwoven with the resin between the first magnetic particles, which are large particles, thereby increasing the filling density of the magnetic particles in the core 30 and also increasing the magnetic permeability. In this embodiment, the average particle size of the metal particles of the first magnetic particles is 20 μm or more and 28 μm or less, and the average particle size of the metal particles of the second magnetic particles is 1 μm or more and 6 μm or less. Preferably, the average particle size of the first magnetic particles is 20 μm or more and 22 μm or less, and preferably the average particle size of the second magnetic particles is 1.5 μm or more and 1.8 μm or less. Furthermore, the magnetic particles may include particles with average particle sizes different from those of the first and second magnetic particles, thereby containing three or more different particle sizes.

[0016] Both the first and second magnetic particles are particles having a metal particle, an oxide film covering the surface of the metal particle, and an insulating film covering the surface of the oxide film. The covering of the metal particle with the oxide film and insulating film increases its insulation resistance and dielectric strength. In the first magnetic particle of this embodiment, Fe-Si-B amorphous alloy powder is used as the metal particle. The oxide film of the first magnetic particle consists of two layers: an SiO layer and Fe2SiO4, and the total thickness of the oxide film is between 20 nm and 155 nm. The insulating film of the first magnetic particle is formed of phosphate glass with a thickness of between 10 nm and 100 nm.

[0017] Furthermore, in the second magnetic particles of this embodiment, carbonyl iron powder is used as the metal particle. The oxide film of the second magnetic particles is iron oxide formed by surface oxidation of the carbonyl iron powder, which is the metal particle. The insulating film of the second magnetic particles is a sol-gel reaction product with silica as a component. This increases the slipperiness of the surface of the second magnetic particles, making it easier for the second magnetic particles to penetrate between the first magnetic particles during the molding and hardening process of the base body 2, which will be described later. As a result, the density of the magnetic material in the core 30 can be further increased, and the relative permeability of the core 30 can be further increased.

[0018] Furthermore, in the first magnetic particle, the metal particle may be Fe-Si-Cr alloy powder, Fe-Ni-Al alloy powder, Fe-Cr-Al alloy powder, Fe-Si-Al alloy powder, Fe-Ni alloy powder, or Fe-Ni-Mo alloy powder. Furthermore, in the first magnetic particle, the insulating film may be phosphoric acid, zinc phosphate, manganese phosphate, glass, or resin.

[0019] The resin material contained in the mixed powder of this embodiment includes bisphenol A type epoxy resin and rubber-modified epoxy resin. This makes it possible to manufacture an inductor 1 in which both the strength and toughness of the base body 2 are improved.

[0020] In this embodiment, the magnetic powder contained in the mixed powder consists of first magnetic particles at a ratio of 70 wt% to 85 wt% and second magnetic particles at a ratio of 15 wt% to 30 wt%, based on the total weight of the magnetic particles contained in the mixed powder. The resin contained in the mixed powder consists of 2.0 wt% to 3.5 wt%, based on the total weight of the magnetic powder and resin. Preferably, the first magnetic particles are at a ratio of 70 wt% to 80 wt%, and the second magnetic particles are at a ratio of 20 wt% to 30 wt%. Preferably, the resin is at a ratio of 2.7 wt% to 30 wt%.

[0021] As shown in Figure 3, the coil conductor 20 comprises a winding section 22 in which the conductor is wound in a spiral shape along the winding shaft K in two stages, upper and lower, such that both ends of the conductor are located on the outer circumference and connected to each other on the inner circumference; a pair of lead-out sections 23 drawn out from the winding section 22; and a pair of external electrode connection sections 24 connected to each of the lead-out sections 23, which are conductor portions for connecting to the external electrodes described later. The winding section 22 includes two winding regions 22a and 22b that overlap along the winding shaft K. The conductors of the winding regions 22a and 22b are connected to each other in a portion of their inner circumference.

[0022] The winding portion 22 has a substantially rectangular shape in plan view, for example, when viewed from the direction of the winding axis K. The coil conductor 20 is embedded in the base body 2 such that the winding axis K is aligned with the thickness direction DT of the base body 2, and that, in plan view from the direction of the winding axis K, each side of the winding portion 22, which has a substantially rectangular shape in plan view, aligns with each side of the base body 2, which has a substantially rectangular shape in plan view (for example, is parallel to it).

[0023] The conductor constituting the coil conductor 20 consists of a conductor and a coating layer formed on the surface of the conductor. The conductor is a flat wire with a rectangular cross-section, and the conductor is a strip-shaped conductor with a rectangular cross-section made of copper. The thickness of the conductor is 60 μm to 100 μm, and the width is 160 μm to 200 μm. The coating layer consists of an insulating layer formed on the surface of the strip-shaped conductor and a fusion layer formed on the surface of the insulating layer for bonding the overlapping strip-shaped conductors in the winding portion 22. The insulating layer is made of, for example, polyimide amide resin and has a thickness of 3 μm. The fusion layer is made of, for example, polyamide resin and has a thickness of 1 μm to 25 μm.

[0024] The lead-out portion 23 is drawn out from the winding portion 22 and is electrically connected to the external electrode 4 via an external electrode connection portion 24 that is drawn out and exposed to each of the pair of end faces 14. The pair of external electrodes 4 are so-called L-shaped electrodes, consisting of L-shaped members extending from each end face 14 of the base body 2 to the bottom face 10. Each external electrode 4 is connected to the external electrode connection portion 24 of the coil conductor 20 at the end face 14, and the portion 4A (Figure 2) extending to the bottom face 10 is electrically connected to the wiring of the circuit board by appropriate mounting means such as soldering.

[0025] Furthermore, a protective layer (not shown) is formed on the surface of the substrate 2, excluding the area of ​​the external electrode 4. The protective layer is, for example, a resin obtained by adding phenoxy resin to a novolac resin, and contains nanosilica as a filler. The protective layer is formed on the surface of the substrate 2 with a thickness of 10 μm to 30 μm. The thickness of the protective layer is preferably 10 μm to 20 μm, and more preferably 15 μm or less.

[0026] Inductor 1 with this configuration can improve DC superposition characteristics by using soft magnetic material for the magnetic particles, and is therefore used as an electronic component in electrical circuits where large currents flow, as a choke coil in DC-DC converter circuits and power supply circuits, and as an electronic component in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, car electronics, and medical and industrial machinery. However, the applications of inductor 1 are not limited to these, and it can also be used in tuning circuits, filter circuits, and rectifier / smoothing circuits, for example.

[0027] [Overview of the Inductor Manufacturing Process] Figure 4 is a schematic diagram of the manufacturing process for inductor 1. As shown in the figure, the manufacturing process for the inductor 1 includes a coil conductor formation process, a pre-molded body formation process, a base body molding and hardening process, a base body grinding process, and an external electrode formation process.

[0028] The coil conductor formation process is a process of forming a coil conductor 20 from a wire. In this process, the coil conductor 20 is formed by winding the wire using a winding method called "alpha winding," resulting in a shape having the aforementioned winding portion 22, lead portion 23, and external electrode connection portion 24. Alpha winding refers to a state in which the wire, which functions as a conductor, is wound in a spiral shape in two stages such that the lead portions 23 at the beginning and end of the winding are located on the outer circumference. The number of turns of the coil conductor 20 is not particularly limited.

[0029] The pre-molded body formation process is the process of forming pre-molded bodies, which are called tablets. The pre-molded body is formed by pressurizing the mixed powder, which is the material for the base body 2, to create a solid that is easy to handle. In this embodiment, two types of tablets are formed: a first tablet of an appropriate shape (e.g., E-shaped) having a groove into which the coil conductor 20 fits, and a second tablet of an appropriate shape (e.g., I-shaped or plate-shaped) that covers the groove of the first tablet.

[0030] The base body molding and hardening process involves setting the first tablet, coil conductor, and second tablet in a molding die, applying heat, and pressing them in the overlapping direction of the first and second tablets to harden them, thereby integrating the first tablet, coil conductor, and second tablet. This forms a base body 2 with the coil conductor 20 enclosed in the core 30.

[0031] In the base body grinding process, abrasive grains are applied to the side surface of the molded body obtained in the base body molding and hardening process to grind away the side surface until the width W reaches a predetermined width. This process yields a base body 2 with the width W of the molded body downsized to a predetermined width. This downsizing reduces the distance (also called the side gap) between the coil conductor 20 inside the base body 2 and the side surface of the base body 2, thereby increasing the coil's occupancy rate in the radial direction of the winding portion 22 of the coil conductor 20. Furthermore, since the base body 2 is obtained by grinding the molded body obtained by compression molding to a predetermined size, dimensional variations in the base body 2 can be reduced compared to the case where the base body 2 is controlled to a predetermined size by compression molding alone. In the base body grinding process, polishing (e.g., barrel polishing) may be performed to chamfer the corners created by grinding the side surface of the base body 2.

[0032] The external electrode formation step is a step of forming an external electrode 4 on the base body 2, and includes a base body protective layer formation step, a surface treatment step, and a plating layer formation step.

[0033] The base body protective layer formation process involves coating the entire surface of base body 2 with an insulating resin.

[0034] The surface treatment process involves modifying the surface of the electrode area on the core 30 by irradiating it with laser light. Here, the electrode area refers to the area on the surface of the core 30 where the external electrode 4 should be formed, and includes the portion where the external electrode connection portion 24 is exposed. Specifically, by irradiating with laser light, the protective layer on the surface of the base body 2 and the coating layer of the external electrode connection portion 24 of the coil conductor 20 are removed in the area of ​​the electrode area, as well as the resin on the surface of the core 30 and the insulating film on the surface of the magnetic particles exposed from the core 30. As a result, the exposed area of ​​the metal of the magnetic particles per unit area of ​​the surface of the core 30 is larger in the electrode area compared to other parts of the core 30 surface. After irradiation with laser light, a cleaning process (e.g., etching) may be performed to clean the surface of the electrode area.

[0035] In the plating layer formation process, copper is barrel-plated onto the surface of the core 30 to form a copper plating layer at the electrode location where the laser beam will be irradiated. In addition, the plating layer may be formed by further providing a Ni plating layer and a Sn plating layer on top of the copper plating layer.

[0036] The details of the inductor 1 in this embodiment will be further described below.

[0037] [A. Coil Conductor] Figure 5 is a plan view showing the internal structure of inductor 1. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5. Figure 6 shows a cross-sectional view of inductor 1 along the line TW. First, let's describe the coil conductor 20 used in the inductor 1. As mentioned above, the coil conductor 20 comprises a winding portion 22 around which a conductor is wound, a pair of lead-out portions 23, and a pair of external electrode connection portions 24.

[0038] The left end of the winding section 22 is drawn out from the lower section of the winding section 22, which is wound in two upper and lower sections, and connects to the left external electrode connection section 24 via the left lead section 23. The left external electrode connection section 24 is bent in the width direction DW at the bent section 48 at the tip of the left lead section 23 and extends linearly in the width direction DW. The right end of the winding section 22 is drawn out from the upper section of the winding section 22, which is wound in two upper and lower sections, and connects to the right external electrode connection section 24 via the right lead section 23. The right external electrode connection section 24 is bent in the width direction DW at the bent section 48 at the tip of the right lead section 23 and extends linearly in the width direction DW. In other words, the left and right lead sections 23 each extend in an extending direction dc that inclins to one side in the width direction DW as they proceed outward in the length direction DL. Furthermore, the left and right external electrode connection portions 24 each extend in an extension direction dp from one side in the width direction DW to one side in the width direction DW. In Figure 5, the portion of the lead-out portion 23 that slopes toward one side in the width direction DW as it extends outward in the length direction DL is straight, but at least a part of it may be formed in a curved shape. Also, in Figure 5, the portion of the external electrode connection portion 24 that extends from one side in the width direction DW to one side in the width direction DW is straight, but at least a part of it may be formed in a curved shape.

[0039] As shown in Figure 6, the conductor 42 constituting the coil conductor 20 has a wire conductor 43 and a covering layer covering the conductor 43 (the covering layer is not shown in Figures 6 and 7). The coil conductor 20 is constructed by alpha winding the conductor 42. The coil conductor 20 is embedded in a core 30 containing magnetic particles and resin.

[0040] [A-1. Conductor] Figure 7 is a cross-sectional view of the conductor 43 that makes up the wire 42. In Figure 7, the cross-section is shown perpendicular to the direction of extension of the conductor 43. The conductor 43 has a rectangular shape in its conductor cross-section perpendicular to the direction of extension, with four right angles. Here, in this specification, "right angle," "rectangle," and "same" do not necessarily mean strictly "right angle," "rectangle," and "same," respectively, but rather it is sufficient if they are substantially "right angle," "rectangle," and "same." In other words, in this specification, "right angle," "rectangle," and "same" may be used to include "approximately right angle," "approximately rectangular," and "approximately the same," as long as they are substantially "right angle," "rectangle," and "same."

[0041] The conductor 43 has an inner circumferential surface 43a on the winding shaft K side, an outer circumferential surface 43b on the side spaced away from the winding shaft K, and a pair of conductor sides 43c and 43d that connect both ends of the inner circumferential surface 43a and both ends of the outer circumferential surface 43b, respectively. A covering layer is formed on the surface of this conductor 43 to constitute the conductor wire 42.

[0042] The maximum length between the conductor sides 43c and 43d in the thickness direction DT of the conductor 43 is defined as the line width La. Furthermore, the maximum length between the inner circumferential surface 43a and the outer circumferential surface 43b of the conductor 43 in a direction perpendicular to the thickness direction DT is defined as the line thickness Lb.

[0043] In detail, the angle between the inner circumferential surface 43a of the conductor and the side surface 43c of the conductor is a right angle. Also, the angle between the inner circumferential surface 43a of the conductor and the side surface 43d of the conductor is a right angle. Furthermore, the angle between the outer circumferential surface 43b of the conductor and the side surface 43c of the conductor is a right angle. Also, the angle between the outer circumferential surface 43b of the conductor and the side surface 43d of the conductor is a right angle. In this embodiment, the criterion for a right angle is that the corners of the right angle are formed at the point where the inner circumferential surface 43a or outer circumferential surface 43b of the conductor intersects with the side surfaces 43c and 43d of the conductor, with a radius of curvature R of 4.5 μm or less. The method for confirming that the four corners of this conductor are right angles is to observe the four corners in the cross-section of the conductor with a digital microscope and measure the radius of curvature of each corner using the measurement function of the digital microscope.

[0044] Here, in the conductor cross-section, a virtual circumscribing rectangle S1 is set so as to be circumscribing the conductor 43. The circumscribing rectangle S1 is set so that the area ratio of the area occupied by the conductor 43 to the area of ​​the circumscribing rectangle S1 is maximized. If this conductor cross-section remains as a conductor 42, it is a cross-section cut perpendicular to the direction perpendicular to the length direction DL of the conductor 42, and the circumscribing rectangle S1 is set by observing the boundary line between the coating layer and the conductor 41 in this cross-section. That is, in this cross-section, the circumscribing rectangle S1 is set so as to include the line width La between the conductor sides 43c and 43d in the thickness direction DT of the conductor 43 and the line thickness Lb between the inner circumferential surface 43a and the outer circumferential surface 43b of the conductor 43 in the direction perpendicular to the thickness direction DT of the conductor 43. Furthermore, when determining the product inductor 1, the circumscribed rectangle S1 is set by observing the conductor cross-section per turn of the winding section 22 at a cross-section (shown in Figure 6) obtained by cutting perpendicularly with an imaginary line extending in the width direction DW of the conductor 2 through the winding axis K of the winding section 22 when viewing the conductor 2 from above. In this embodiment, the average area ratio of the conductor 43 to the circumscribed rectangle S1 per turn of the winding section 22 is 95% or more. "Per turn" means the average value in one turn, and means the average value of the area ratio of the conductor cross-sections at two locations in one turn in the conductor cross-section of the conductor 22. Therefore, for example, in Figure 6, the average value of the area ratio of winding positions P1 and P2 may be taken. Alternatively, for example, in Figure 6, the average value of the area ratio of winding positions P3 and P4 may be taken.

[0045] Here, as shown by the dashed line in Figure 7, in a normal conductor 81, a conductor with a circular cross-section is formed by compressing it, so the inner surface 81a and outer surface 81b of the conductor are formed in a planar shape, while the conductor sides 81c and 81d are curved surfaces with a large curvature. For this reason, in a normal conductor 81, the area ratio to the circumscribed rectangle S1 tends to be small. In contrast, the conductor 43 of this embodiment is formed by casting so that the four corners are intentionally formed into a rectangular shape with right angles. Therefore, compared to a normal conductor 81, the curvature of the curved shape of the conductor sides 43c and 43d is smaller, and it is formed linearly, resulting in a rectangular shape that more closely approximates the circumscribed rectangle S1.

[0046] As shown in Figure 6, in this embodiment, the coil conductor 20 is embedded inside the core 30 such that, in the thickness direction DT, the upper surface thickness T11, which is the length from the upper surface 12 of the base body 2 to the upper surface 41a of the winding portion 22, and the bottom surface thickness T12, which is the length from the bottom surface 41b of the winding portion 22 to the bottom surface 10 of the base body 2, are the same.

[0047] In this embodiment, since the conductor 43 is rectangular in shape, when comparing with the same DC resistance value (i.e., the same area of ​​the conductor cross-section), the line width La of the conductor 43 can be made smaller than that of a normal conductor 81 by the area of ​​the corners of the conductor 43. Therefore, since the DC resistance value can be secured while reducing the height (thickness) DT in the thickness direction of the coil conductor 20, the top thickness T11 and the bottom thickness T12 can be made larger when the size of the base body 2 is about the same, and the sum of the top thickness T11 and the bottom thickness T12, T11+T12, can be made larger.

[0048] In this embodiment, in the thickness direction DT, which is the direction along the winding axis K, the winding thickness T10, which is the length from the top surface 41a to the bottom surface 41b of the winding portion 22, is the same as the sum of the top surface thickness T11 and the bottom surface thickness T12, T11+T12. Alternatively, the winding thickness T10 may be less than or equal to the sum of T11+T12. Specifically, the ratio of the winding thickness T10 to the height of the base body 2 is 55% or less.

[0049] This makes it easier to increase the sum of the top surface thickness T11 and the bottom surface thickness T12 (T11+T12) relative to the winding thickness T10. Therefore, even if the position of the winding 22 is shifted vertically during manufacturing, the distance between the winding 22 and the upper and lower surfaces of the base body 2 can be maintained, and variations in the DC superimposed rated current of the inductor 1 can be suppressed. Here, the DC superimposed rated current is defined as the lower limit of the current value that is considered usable when the inductor has an initial characteristic where current is not superimposed, after magnetic saturation occurs in the magnetic material when current flows through the inductor, causing the inductance to decrease.

[0050] In this embodiment, the coil conductor 20 is embedded inside the core 30 such that the top thickness T11 and the bottom thickness T12 are the same. However, the coil conductor 20 may be embedded inside the core 30 such that the top thickness T11 is greater than the bottom thickness T12. Alternatively, the coil conductor 20 may be embedded inside the core 30 such that the bottom thickness T12 is greater than the top thickness T11. If either the top thickness T11 or the bottom thickness T12 is greater, the smaller thickness is formed so that it does not become less than 1 / 6 of the sum of the top thickness T11 and the bottom thickness T12 (T11 + T12).

[0051] [A-2. Coil Conductor] [A-2-1. Structure of the winding section] As described above, the size of the inductor 1 is very small, with a length L of 1.4 mm, a width W of 1.2 mm, and a thickness T of 0.8 mm. Therefore, the shape of the winding portion 22 embedded in the core 30 in the base body 2 can have a significant impact on the inductance value that can be achieved in the inductor 1.

[0052] Figure 8 is a diagram illustrating the configuration of the winding portion 85 of the coil conductor 84 in an inductor 83 in which the coil conductor winding portion is wound using a conventional winding method. Figures 8(a) and (b) show the two winding regions 85a and 85b that constitute the winding portion 85 of an inductor 83 having the same configuration as in Figure 1, in which the coil conductor winding portion is wound using a conventional winding method, viewed from a direction corresponding to the -DT direction (direction looking down on the top surface 12) in Figure 1. Figure 8(c) shows the cross-section of the inductor 83 corresponding to the LT cross-section along the center of the width W in Figure 1, viewed from a direction corresponding to the DW direction in Figure 1.

[0053] The coil conductor 84, comprising a winding section 85 consisting of winding regions 85a and 85b, an extension section drawn out from the winding section 85, and an external electrode connection section 88 connected to the extension section and serving as a conductor for connecting to an external electrode, constitutes a base body 87 together with a core 86 containing magnetic particles in which the coil conductor 84 is embedded. In Figure 8(a), the conductor of the winding region 85a constituting the winding section 85 circulates around the winding shaft and is drawn out from the outermost circumference of the winding region 85a to the right side of the figure via the extension section, connecting to the external electrode connection section 88 on the right side of the figure. In Figure 8(b), the conductor of the winding region 85b circulates around the winding shaft and is drawn out from the outermost circumference of the winding region 85b to the left side of the figure via the extension section, connecting to the external electrode connection section 88 on the left side of the figure. Furthermore, the conductor in the winding region 85a shown in Figure 8(a) and the conductor in the winding region 85b shown in Figure 8(b) are connected to each other at position P80 on the inner circumference of the winding portion 85.

[0054] The total number of turns in the winding section 85 is an odd integer when rounded to the nearest whole number, for example, 5. The winding regions 85a and 85b that overlap along the winding axis and constitute the winding section 85 are each composed of approximately 2.5 turns. Therefore, in the portion of the winding where the conductor is routed as viewed from the top surface of the base body 87, the number of cross-sections of the conductor included in the two winding regions 85a and 85b, in a cross-section along the direction of the winding axis Kp (the direction normal to the paper in Figures 8(a) and (b)), has two different ranges R81 and R82 in adjacent portions along the direction of the winding axis Kp, one winding region 85a and the other winding region 85b.

[0055] Figure 8(c) is a cross-sectional view of the main body 87 along the center line CL80 in the width direction of the main body 87 in Figures 8(a) and (b), and includes the cross-sections of ranges R81 and R82. As shown in Figure 8(c), in an inductor 83 in which the coil conductor winding portion is wound using a normal winding method, the inner circumferences of the winding region 85a and winding region 85b are at the same positions P82 and P83. Two turns of the inner circumference of each of the winding region 85a and winding region 85b overlap vertically and are at the same position, while the 0.5 turns located at the outermost circumference are positioned at the left and right outer circumference positions shown in the figure. As a result, the outer circumference of the winding portion 85 has a step difference S80 between the winding region 85a and winding region 85b on the left and right sides shown in the figure. The depth of the step difference S80 may be equivalent to the thickness T80 of the conductor measured in the direction perpendicular to the winding axis Kp.

[0056] Of the core 86 that constitutes the base body 87, this stepped portion S80 is dead space and can limit the upper limit of the inductance that can be realized as an inductor 83.

[0057] Therefore, in the inductor 1 of this embodiment, in the portions corresponding to ranges R81 and R82 shown in Figure 8, the inner circumference of one winding region with fewer wire cross-sections is shifted toward the outer circumference relative to the inner circumference of the other winding region with more wire cross-sections.

[0058] Figure 9 is a diagram illustrating the configuration of the winding portion 22 of the coil conductor 20 in one embodiment of the inductor 1, and corresponds to Figure 8, which shows the configuration of an inductor 83 in which the above-described winding portion of the coil conductor is wound in a normal winding manner. As described above with reference to Figure 3, the coil conductor 20 includes a winding portion 22 in which a conductor is wound around a winding shaft K, a pair of lead portions 23 drawn out from the winding portion 22, and a pair of external electrode connection portions 24 which are conductor portions for connecting to external electrodes and are connected to each of the lead portions 23. The winding portion 22 also includes two winding regions 22a and 22b that overlap along the winding shaft K.

[0059] Furthermore, the wire constituting the coil conductor 20 comprises a conductor and a covering layer that covers the surface of the conductor. The conductor has a rectangular cross-section perpendicular to the direction of its extension, and the four vertices of the rectangle are right angles.

[0060] Figures 9(a) and (b) show the two winding regions 22a and 22b constituting the winding section 22, viewed from the -DT direction (the direction looking down at the top surface 12) in Figure 1. Figure 9(c) shows the cross-section of the inductor 1, which corresponds to the LT cross-section along the center line CL20 of the width W (see Figure 1) of the main body 2, viewed from the DW direction.

[0061] In Figure 9(a), the conductor in the winding region 22a is drawn out to the right and connected to the external electrode connection part 24 on the right side via the lead-out part 23. In Figure 9(b), the conductor in the winding region 22b is drawn out to the left and connected to the external electrode connection part 24 on the left side via the lead-out part 23. Furthermore, the conductor in the winding region 22a shown in Figure 9(a) and the conductor in the winding region 22b shown in Figure 9(b) are connected to each other at position P20 on the inner circumference of the winding part 22.

[0062] The total number of turns in the winding section 22 shown in Figure 9 is an odd number when rounded to the nearest integer, for example, 5. However, this total number of turns is just one example to illustrate the difference from the inductor 83 in which the coil conductor winding section shown in Figure 8 is wound using a normal winding method. The total number of turns in the winding section 22 can be set to any odd number depending on the inductance value required for the inductor 1.

[0063] The winding regions 22a and 22b that constitute the winding section 22 are each composed of approximately 2.5 turns. Therefore, in the portion where the conductor is routed as viewed from the upper surface 12 of the base body 2, the number of cross-sections of the conductor included in the two adjacent winding regions 22a and 22b along the direction of the winding axis K (the direction normal to the plane of the paper in Figures 9(a) and (b)) is different for one winding region 22a and the other winding region 22b in the adjacent portion along the direction of the winding axis K.

[0064] In the inductor 1, the winding portion 22 has a roughly rectangular shape when viewed from the direction of the winding axis K, and the ranges R20 and R21 are located on two opposing sides of the roughly rectangular shape.

[0065] Figure 9(c) is a diagram showing a cross-section of the element 2 along the widthwise center line CL20 in Figures 9(a) and (b), and includes cross-sections of ranges R20 and R21.

[0066] As shown in Figure 9(c), one winding region 22a contains fewer wires in one range R20 than the other winding region 22b, and more wires in the other range R21 than the other winding region 22b. Similarly, one winding region 22b contains fewer wires in one range R21 than the other winding region 22a, and more wires in the other range R20 than the other winding region 22a.

[0067] In this embodiment, ranges R20 and R21 are not located near position P20 on the inner circumference of the winding portion 22 that connects winding region 22a and winding region 22b to each other. For example, as shown in Figures 9(a) and (b), they are arranged on two opposing sides of the winding portion 22 parallel to the end face 14 of the base body 2. In particular, as shown in Figure 9(c), in ranges R20 and R21, the inner circumference of one winding region with fewer wire cross-sections in the cross-section along the winding axis K is shifted towards the outer circumference of the winding portion 22 relative to the inner circumference of the other winding region with more wire cross-sections in the cross-section along the winding axis K.

[0068] Specifically, in range R20, the inner circumference of winding region 22b, where the number of wire cross-sections in the cross-section along the direction of the winding axis K is small, is shifted by a distance D21 toward the outer circumference of the winding portion 22 relative to the inner circumference of winding region 22a, where the number of wire cross-sections in the cross-section along the direction of the winding axis K is large. Also, in range R21, the inner circumference of winding region 22a, where the number of wire cross-sections in the cross-section along the direction of the winding axis K is small, is shifted by a distance D20 toward the outer circumference of the winding portion 22 relative to the inner circumference of winding region 22b, where the number of wire cross-sections in the cross-section along the direction of the winding axis K is large.

[0069] In the example shown in Figure 9(c), distances D20 and D21 are both the same as the thickness T20 of the conductor measured in a direction perpendicular to the winding shaft K. This ensures that no step is created between the outer circumference of winding region 22a and the outer circumference of winding region 22b in each of the ranges R20 and R21. That is, in each of the ranges R20 and R21, the outer circumferences of the two winding regions 22a and 22b are formed such that the difference between the distance of one winding region from the winding shaft K and the distance of the other winding region from the winding shaft K is within 1 / 2 of the thickness of the conductor, and in Figure 9(c), the distances from the winding shaft K are approximately the same for both.

[0070] With the above configuration, the winding portion 22 of inductor 1 does not produce the step S80 on the outer circumference of the winding portion 85 that was formed in inductor 83 in which the coil conductor winding portion is wound in a normal winding manner as shown in Figure 8(c). In other words, inductor 1 does not produce the step S80 as shown in Figure 8(c), so the upper limit of the inductance that can be realized as inductor 1 can be increased compared to inductor 83 in which the coil conductor winding portion is wound in a normal winding manner. Furthermore, in inductor 1 shown in Figure 9, a large winding shaft with a high magnetic flux density can be formed in each of the winding regions 22a and 22b.

[0071] Furthermore, the two winding regions 22a and 22b do not necessarily need to have the inner circumference of one winding region offset from the inner circumference of the other winding region in the entire winding direction (circumferential direction centered on the winding axis K) of each range R20 and R21. In other words, the two winding regions 22a and 22b only need to have the inner circumference of one winding region, which has fewer wire cross-sections in the cross-section along the winding axis K, offset towards the outer circumference of the winding portion 22 in at least a portion of the winding direction of each range R20 and R21, relative to the inner circumference of the other winding region, which has more wire cross-sections in the cross-section along the winding axis K.

[0072] Furthermore, the amount of displacement between the inner circumference of one winding region and the inner circumference of the other winding region in ranges R20 and R21, i.e., the distances D20 and D21 in Figure 9(c), should be at least half the thickness T20 of the conductor measured in a direction perpendicular to the winding axis K. In this case as well, the size of the step difference between winding regions 22a and 22b on the outer circumference of the winding portion 22 can be made smaller than the step difference S80 in the inductor 83 in which the coil conductor winding portion is wound using a normal winding method, as shown in Figure 8(c), thereby increasing the upper limit of the inductance that can be realized as inductor 1 compared to the inductor 83 in which the coil conductor winding portion is wound using a normal winding method.

[0073] [A-2-2. Configuration of the drawer section and external electrode connection section] As described above regarding the background technology, in an inductor such as the inductor 1 shown in Figure 1, which comprises a core containing magnetic particles made of a soft magnetic material and a coil conductor embedded in the core, variations may occur in the position and exposed area of ​​the lead portion at the end face of the body due to the overall shape of the coil conductor and the orientation of the coil conductor inside the body. Such variations in the position and exposed area of ​​the lead portion at the end face of the body can cause variations in the electrical connection state between the lead portion and the external electrode, and can cause variations in the DC resistance value at the connection between the lead portion and the external electrode.

[0074] Therefore, in the inductor 1 of this embodiment, the shape of the coil conductor 20, in particular the angle between the lead portion 23 drawn out from the winding portion 22 and the external electrode connection portion 24, is configured to satisfy predetermined conditions in a plan view taken from the direction normal to the upper surface 12 of the base body 2. In addition, in the inductor 1, the orientation of the coil conductor 20 inside the base body 2, in particular the angle between the direction normal to the end face 14 of the base body 2 where the external electrode 4 is formed and the extending direction of the external electrode connection portion 24, is configured to satisfy predetermined conditions in a plan view taken from the direction normal to the upper surface 12 of the base body 2.

[0075] Figure 10 is a view of a coil conductor 20 embedded in a base body 2 in one embodiment of inductor 1, viewed from above the upper surface 12 of the base body 2 along the -DT direction. In the inductor 1 shown in Figure 10, in particular, as shown for the left side portion of the inductor 1, the boundary between the lead portion 23 and the external electrode connection portion 24 is a bent portion 48 where the conductor is bent, and the first angle θ1 formed by the extending direction dp of the external electrode connection portion 24 extending from the bent portion 48 and the normal direction dn of the end face 14 that passes through the bent portion 48 and goes towards the interior of the base body 2 is greater than 90 degrees. When this first angle θ1 becomes less than 90 degrees, the entire external electrode connection portion 24, from its base to its tip, moves away from the end face 14 of the base body 2 towards the interior of the base body, and the exposed area of ​​the external electrode connection portion 24 exposed from the end face 14 becomes smaller. Furthermore, if the first angle θ1 is 90 degrees, the exposed area of ​​the external electrode connection portion 24 exposed from the end face 14 can be increased, but if the bent portion 48 is misaligned in the inward direction of the base body 2, the external electrode connection portion 24 may become embedded in the base body 2. In contrast, if the first angle θ1 is greater than 90 degrees, the tip of the external electrode connection portion 24 extends in a direction that protrudes from the end face 14 of the base body 2, and the tip of the external electrode connection portion 24 extends in a state that is nearly parallel to the end face 14 of the base body 2 by contacting the inner wall of the molding die in the aforementioned base body molding and hardening process, thereby increasing the exposed area of ​​the external electrode connection portion 24 exposed from the end face 14. Note that the lead portion 23 and the external electrode connection portion 24 on the right side of the inductor 1 can also be configured in the same manner as described above, and the first angle θ1 can be defined accordingly.

[0076] As a result, the inductor 1 can reduce variations in the exposed area of ​​the external electrode connection portion 24 exposed from the end face 14, thereby reducing variations in the DC resistance at the connection between the external electrode connection portion 24 and the external electrode 4. Here, if the first angle θ1 is greater than 90 degrees on both the left and right sides of the inductor 1 as shown, then at each of the left and right end faces 14 as shown, variations in the exposed area of ​​the external electrode connection portion 24 exposed from each end face 14 can be reduced, thereby reducing variations in the DC resistance at the connection between the external electrode connection portion 24 and the external electrode 4.

[0077] Furthermore, in the inductor 1 shown in Figure 10, the second angle θ2 formed by the extending direction dc of the lead portion 23 starting from the bent portion 48 and the extending direction dp of the external electrode connection portion 24 extending from the bent portion 48 is 150 degrees or more and less than 180 degrees. This further reduces the variation in the exposed area of ​​the external electrode connection portion 24 exposed from the end face 14.

[0078] From the viewpoint of reducing the variation in the exposed area of ​​the external electrode connection portion 24, it is preferable that the first angle θ1 is greater than 90 degrees as described above, and also within the range of 100 degrees or less.

[0079] In Figure 10, the coil conductor 20 is embedded in the base body 2 such that the winding shaft K is aligned with the direction normal to the top surface 12 (the direction normal to the paper). Furthermore, in a plan view from the direction normal to the top surface 12 (i.e., the plan view shown in Figure 10), the outer shape of the winding portion 22 is such that the first length Wc, which is the maximum length in the direction perpendicular to the side surface 16 (for example, the DW direction), is greater than or equal to the second length Lc, which is the maximum length measured in the direction perpendicular to the end face 14 (for example, the DL direction). The ratio of the first length Wc to the second length Lc may be in the range of 1 to 1.5.

[0080] The relationship between the winding portion 22 and the main body 2 is such that the first length Wc of the winding portion 22 is longer than the second length Lc, and the distance Ld between the pair of end faces 14 of the main body 2 is longer than the distance Wb between the pair of side faces 16. Here, the distance Ld is equal to the length L of the inductor 1 minus the thickness of the external electrode 4, and the distance Wb is approximately equal to the width W of the inductor 1.

[0081] From the viewpoint of reducing the variation in the exposed area of ​​the external electrode connection portion 24, it is preferable that the bent portion 48 is located within a range R25 in which the width in the direction perpendicular to the pair of side surfaces 16 (for example, the DW direction), centered on a line L25 that passes through the center of the end face 14 and is parallel to the side surface 16, is half the distance Wb between the pair of side surfaces 16.

[0082] The length of the external electrode connection portion 24 is preferably 30% to 50% of the distance Wb between the pair of side surfaces 16 of the end face 14.

[0083] For example, the base body 2 has a distance Wb between a pair of side surfaces 16 of 1.2 mm or more and a distance Ld between a pair of end surfaces 14 of 1.4 mm or more and a distance Ld between a pair of end surfaces 14 of 1.6 mm or more. Here, the actual size of the inductor 1 may contain an error of several percent compared to the nominal size of the inductor 1 described above, which is a length L of 1.4 mm, a width W of 1.2 mm, and a thickness T of 0.8 mm. Also, it should be noted that the above size of the inductor 1 is the size of the entire inductor 1 including the external electrodes 4, and the size of the base body 2 is generally smaller than the size of the inductor 1, and the ratio of the distance Wb between the side surfaces 16 to the distance Ld between the end surfaces 14 may also differ from the ratio of the width W to the length L in the overall external shape of the inductor 1.

[0084] [B. External electrode] Next, the connection configuration between the external electrode and the external electrode connection portion 24 of the coil conductor 20, and the configuration of the external electrode on the surface of the substrate will be described. [B-1. Connection configuration between the external electrode and the external electrode connector] Figure 11 is a cross-sectional view taken along line XI-XI in Figure 5. Figure 11 shows a cross-section perpendicular to the extending direction dp of the external electrode connection portion 24 at the connection point between the external electrode connection portion 24 and the external electrode 4. A pair of external electrodes 4 are provided on the surface of the base body 2. The external electrodes 4 are connected to a conductor 43 that is exposed after the coating layer 45 of the external electrode connection portion 24 is removed. The external electrodes 4 have a plated conductor 50 formed by plating. In this embodiment, the plated conductor 50 has a copper plating layer 51 as a plating layer with the same metal component as the conductor 43. The copper plating layer 51 is a plating layer that plates the surface of the conductor 43. The copper plating layer 51 and the conductor 43 are connected.

[0085] A Ni plating layer 52 is formed on the copper plating layer 51. A Sn plating layer 53 is formed on the Ni plating layer 52. The plated conductor 50 of this embodiment has a copper plating layer 51, a Ni plating layer 52, and a Sn plating layer 53. The plated conductor 50 is formed on the outer conductor surface 43b of the external electrode connection part 24 and on the exposed conductor sides 43c and 43d where the coating layer 45 of the conductor wire 42 of the external electrode connection part 24 has been removed. The amount of exposure of these conductor sides 43c and 43d differs for each conductor side 43c and 43d, as shown in Figure 11. That is, in Figure 11, the position of the end of the coating layer 45 on the external electrode 4 side differs in the left-right direction between the conductor side 43c and the conductor side 43d, with the amount of exposure of the conductor side 43d being greater than that of the conductor side 43c.

[0086] Figure 12 is a cross-sectional view showing the case where a normal conductor 81 corresponding to Figure 11 is used. In a typical conductor 81, because it is not a rectangular shape with four right angles, the length of the conductor outer surface 81b in the direction of the line width La becomes shorter than the line width La of the conductor 81. As a result, the conductor sides 81c and 81d on both sides of the conductor outer surface 81b in the direction of the line width La tend to become curved surfaces with a large curvature. Here, when manufacturing an inductor, with a typical conductor 81 wire 80, when embedding the coil conductor 20 in the base body 2, the thickness of the base body 2 on the curved surface where the conductor outer surface 81b and the conductor sides 81c and 81d connect (in other words, the length DL in the longitudinal direction from the outer surface of the base body 2 to the curved surface) is greater than the thickness of the base body 2 on the conductor outer surface 81b (in other words, the length DL in the longitudinal direction from the outer surface of the base body 2 to the conductor outer surface 81b). Therefore, when peeling off the coating layer 45 on the conductor outer surface 81b side of the wire 80 embedded in the base body 2 during the surface treatment process, because the thickness of the base body 2 is different, only the coating layer 45 on the conductor outer surface 81b side is easily peeled off, and the coating layer 45 and magnetic particles on the curved surface where the conductor outer surface 81b and the conductor sides 81c and 81d connect tend to remain. Therefore, when plating is grown on the outer surface 81b of the conductor, a constricted shape 81e is easily formed at the connection point between the conductor 80 and the plated conductor 50. In other words, in a normal conductor 81, the outer surface 81b of the conductor and the plated conductor 50 are connected in such a way that this constricted shape 81e is formed, so the connection area between the conductor 81 and the plated conductor 50 tends to be smaller than the wire width La. Consequently, there were problems such as an increase in the DC resistance of the external electrode 4 and a decrease in the reliability of the connection between the external electrode 4 and the conductor 81 of the coil conductor 20.

[0087] In contrast, since the conductor 43 of this embodiment is substantially rectangular in shape, when the coil conductor 20 is embedded in the base body 2, the thickness of the base body 2 on the corners of the conductor outer surface 43b and the conductor side surfaces 43c and 43d is less likely to be greater than the thickness of the base body 2 on the conductor outer surface 43b. Therefore, when peeling off the coating layer 45 on the conductor outer surface 43b side of the conductor wire 42 embedded in the base body 2 during the surface treatment process, not only the coating layer 45 on the conductor outer surface 43b but also the coating layer 45 on the conductor outer surface 43b side of the conductor side surfaces 43c and 43d can be peeled off.

[0088] Note that the reason the position of the edge of the coating layer 45 differs in the left-right direction between the conductor side surface 43c and the conductor side surface 43d in Figure 11 is due to the direction of laser irradiation in the surface treatment process. In other words, in Figure 11, the resin layer is removed with the laser beam while moving the laser beam from bottom to top (in the direction from the conductor side surface 43d toward the conductor side surface 43c relative to the conductor 42). As a result, the coating layer 45 is easily removed on the conductor side surface 43d because the laser beam moves toward it, whereas on the conductor side surface 43c, the coating layer 45 is difficult to remove because the laser beam moves toward it. Therefore, the position of the edge of the coating layer 45 on the conductor side surface 43d is scraped further inward than the position of the edge of the coating layer on the conductor side surface 43c.

[0089] At this time, when plating is grown on the outer conductor surface 43b, plating is easily formed not only on the outer conductor surface 43b but also on the conductor side surfaces 43c and 43d exposed from the coating layer 45 at positions adjacent to the outer conductor surface 43b, forming a plated conductor 50 that protrudes outward in the thickness direction DT from the conductor side surfaces 43c and 43d. Therefore, the shape formed by the outer conductor surface side of the conductor 43 and the plated conductor 50 can be made to widen toward the outer surface of the base body 2, thus preventing the occurrence of a constricted shape in the conductor side surfaces 43c and 43d, and making the connection area between the outer conductor surface 43b and the plated conductor 50 the same size as the line width La. Specifically, the plated conductor 50 is formed on the conductor side surfaces 43c and 43d such that the angle θ3 on the conductor 43 side is 90 degrees or less, among the angles θ3 and θ4 formed between the outer tangent line 50a of the plated conductor 50 formed on the outer conductor surface 43b and the outer tangent line 50b of the plated conductor 50 formed on the conductor side surfaces 43c and 43d.

[0090] This can also be rephrased as follows: In the cross-section shown in Figure 11, a virtual inscribed rectangle S2 is set so as to be inscribed within the inner circumferential surface 43a of the conductor 43, the side surfaces 43c and 43d of the conductor 43, and the surface of the copper plating layer 51 formed on the outer circumferential surface 43b of the conductor. This inscribed rectangle S2 is a virtual rectangle set on the conductor 43 side so as to satisfy the following four conditions. First, the side S2b on the outer circumferential surface 43b side of the inscribed rectangle S2 is set so as to be inscribed within the copper plating layer 51 of the plated conductor 50. Second, the side S2a on the inner circumferential surface 43a side of the inscribed rectangle S2 (the side S2a opposite to side S2b) is set so as to be inscribed within the conductor 43 (including cases where it is in contact at the end of side S2a, i.e., at a corner). Third, the inscribed rectangle S2 is set so as to satisfy the first and second conditions, and so as to maximize the area ratio of the area occupied by the conductor 43 and the copper plating layer 51 to the area of ​​the inscribed rectangle S2.

[0091] In this embodiment, within the inscribed rectangle S2 set up in this way, the corners S2e and S2f on the inner circumferential surface 43a of the conductor are easily occupied by the right-angled rectangular conductor 43, while the corners S2g and S2h on the copper plating layer 51 side are occupied by the copper plating layer 51 on the outer circumferential surface 43b of the conductor. At this time, the area ratio of the conductor 43 to the copper plating layer 51 relative to the inscribed rectangle S2, that is, the area ratio of copper, which is the metal of the conductor 43, was 99% or more.

[0092] Therefore, in the conductor 43 of this embodiment, since the four corners of the conductor cross-section are right angles, it is easy to connect it to the coil conductor 20 with a copper plating layer 51 that is larger than the size of the outer surface 43b of the conductor, and the conductor 43 and the plated conductor 50 are connected over a wide area. Thus, the DC resistance of the external electrode 4 can be reduced, and the reliability of the connection between the external electrode 4 and the coil conductor 20 can be improved. As shown in Figure 12, when the inscribed rectangle S2 is set as described above for a normal conductor 81, the constricted shape 81e enters the inscribed rectangle S2.

[0093] [B-2. Configuration of external electrodes on the surface of the substrate] Next, the configuration of the external electrode 4 on the surface of the substrate will be explained. [B-2-1. Configuration of planned electrode locations and external electrode connection sections] Figure 13 is a side view of the inductor 1 as seen from the end face 14 side of the base body 2. As described above, the external electrode 4 is plated to cover the planned electrode area R30. The planned electrode area R30 is formed when the base body coat 70, which is an insulating resin coated on the surface of the base body during the base body protective layer formation process, is peeled off during the surface treatment process. The planned electrode area R30 is formed in a rectangular shape on the end face 14 and the bottom face 10 of the base body 2, respectively.

[0094] As shown in Figure 13, the planned electrode location R30 is formed in the region of the external electrode connection portion 24 that overlaps with the portion exposed from the end face 14 of the base body 2. The external electrode connection portion 24 is exposed along the width direction DW of the base body 2, straddling the planned electrode location R30 and the coating area R31, which is the region outside the planned electrode location R30, on the end face 14 of the base body 2. Of the external electrode connection portion 24 exposed from the end face 14 of the base body 2, the coated portion 64b located at the coating area R31 is located closer to the tip 64c of the external electrode connection portion 24 than the peeled portion 64a located at the planned electrode location R30. That is, the tip 64c of the external electrode connection portion 24 is located at the coating area R31. In addition, the area of ​​the peeled portion 64a is set to be larger than the cross-sectional area of ​​the conductor constituting the coil conductor 20.

[0095] As described above, the surface protection layer formation process is performed after the base body formation and hardening process and the base body grinding process. That is, after the surface protection layer formation process, the entire surface of the external electrode connection portion 24 exposed from the end face 14 is coated with an insulating resin. Furthermore, in the surface treatment process, a portion of this coating is peeled off to form the electrode area R30.

[0096] At this time, only the coating applied to the peeled portion 64a is removed from the external electrode connection portion 24 exposed from the end face 14 of the base body 2, and the peeled portion 64a is connected to the external electrode 4 in the plating layer formation process. As described above, since the area of ​​the peeled portion 64a is set to be larger than the cross-sectional area of ​​the conductor constituting the coil conductor 20, the resistance does not tend to increase at the connection portion between the peeled portion 64a and the external electrode 4.

[0097] On the other hand, even after the surface treatment process, the base coat 70 remains on the coated area R31. Therefore, the coated portion 64b is covered with the base coat 70, and the tip 64c of the external electrode connection portion 24 is covered with the base coat 70 at least. Because the coated portion 64b and the tip 64c are covered with the base coat 70, the external electrode connection portion 24 exposed from the end face 14 is fixed to the end face 14 by the base coat 70 at the tip 64c side. Therefore, the external electrode connection portion 24 is less likely to peel off from the end face 14 until the external electrode 4 is formed, and the connection between the external electrode 4 and the external electrode connection portion 24 is more likely to be stable.

[0098] As shown in Figure 13, the coated area R31 has a first thickness region 70a and a second thickness region 70b. The coated portion 64b is covered by both the first thickness region 70a and the second thickness region 70b. Furthermore, in the external electrode connection portion 24 exposed from the end face 14 of the base body 2, the coating layer of the conductor is removed in the peeled portion 64a when the coating is removed, the exposed conductor is connected to the external electrode 4 in the plating layer formation process, and in the coated portion 64b the conductor coating layer remains as is and is covered by the base body coat 70 (i.e., both the first thickness region 70a and the second thickness region 70b), with the conductor coating layer between the conductor and the base body coat 70. Moreover, the area of ​​the region of the external electrode connection portion 24 that is connected to the external electrode has an area greater than or equal to the cross-sectional area of ​​the conductor constituting the coil conductor 20.

[0099] [B-2-2. Configuration of external electrodes and base coat] As shown in Figure 13, when the inductor 1 is viewed from one end face 14, the external electrodes 4 are positioned biased toward the bottom surface 10 of the end face 14, and the external electrodes 4 are surrounded by the base coat 70. The first thickness region 70a is formed in the boundary region between the planned electrode location R30 and the coating location R31. The second thickness region 70b is located further away from the planned electrode location R30 than the first thickness region 70a when viewed from the planned electrode location R30. The first thickness region 70a is provided in a position that surrounds the planned electrode location R30 formed on the end face 14 and the bottom face 10 of the base body 2 at the end face 14 and the bottom face 10.

[0100] Figure 14 schematically shows the XIV-XIV cross section of Figure 13. The XIV-XIV cross section is a cross section that intersects perpendicularly with the boundary between the planned electrode location R30 and the coating location R31 when viewed from the side of the end face 14 of the base body 2. In other words, the XIV-XIV cross section is a cross-section obtained by cutting the base body 2 in the longitudinal direction DL along a straight line perpendicular to the boundary between the external electrode 4 and the base body coating 70, as viewed from the end face 14. In the XIV-XIV cross section, the DT direction is the direction away from the planned electrode location R30.

[0101] The first thickness region 70a is formed during the surface treatment process by adjusting the irradiation time and output so that the amount of laser light irradiated is less than the amount of laser light irradiated onto the planned electrode location R30, thereby removing a portion of the base coat 70. Therefore, the thickness of the first thickness region 70a is smaller than the average thickness T30 of the base coat 70.

[0102] The average thickness T30 is the average thickness of the base coat 70 covering the entire base body 2, at a position sufficiently far from the planned electrode location R30. The average thickness T30 can be determined, for example, by viewing the base body 2 from above and cutting it perpendicularly along an imaginary line extending along the length direction DL of the base body 2 through the winding axis K, and measuring the thickness of the base coat 70 at any three points in the central part of the top surface centered on the winding axis K.

[0103] The second thickness region 70b is the portion of the base coat 70 formed in the surface protective layer formation process that was not exposed to laser light in the surface treatment process. The thickness of the second thickness region 70b is approximately the same as the average thickness T30 and is greater than the thickness of the first thickness region 70a.

[0104] As shown in Figure 14, in the XIV-XIV cross section, the first thickness region 70a is provided with a flat portion 75 and a stepped portion 71. The flat portion 75 is the part of the first thickness region 70a where the thickness of the base coat 70 is approximately constant on average. The stepped portion 71 is the part of the first thickness region 70a where the thickness increases rapidly in the direction away from the planned electrode location R30. The stepped portion 71 connects the flat portion 75 and the second thickness region 70b, and the formation of the stepped portion 71 makes it easier to form the flat portion 75 and the second thickness region 70b. The stepped portion 71 is formed at an angle of approximately 17 degrees relative to the flat portion 75.

[0105] As shown in Figure 14, a peripheral edge 65, which is part of the external electrode 4, is formed on the first thickness region 70a. The tip 65a of the peripheral edge 65 of the external electrode 4, which is located furthest from the planned electrode location R30, is on the flat portion 75 of the first thickness region 70a. Therefore, the peripheral edge 65 of the external electrode 4 is not formed on the stepped portion 71 and the second thickness region 70b. In other words, the tip 65a of the peripheral edge 65 of the external electrode 4 is located closer to the planned electrode location R30 than the stepped portion 71 and the second thickness region 70b. Also, in the direction away from the planned electrode location R30, the length of the peripheral edge 65 of the external electrode 4 is shorter than the length of the flat portion 75 of the first thickness region 70a. In other words, in the XIV-XIV cross section, the length of the flat portion 75 in the direction away from the planned electrode location R30 is longer than the length of the portion of the external electrode 4 formed on the base coat 70 (periphery 65). Therefore, the entire periphery 65 of the external electrode 4 is more easily formed on the flat portion 75 of the first thickness region 70a.

[0106] The external electrode 4 has a copper plating layer (first plating layer) 51, a Ni plating layer (second plating layer) 52, and a Sn plating layer (third plating layer) 53. The copper plating layer 51 is the first part to be plated in the plating layer formation process. The copper plating layer 51 is also slightly formed on the coating area R31. However, because the base coat 70 is insulating, the thickness of the copper plating layer 51 of the external electrode 4 on the coating area R31, that is, the thickness of the copper plating layer 51 on the periphery 65 of the external electrode 4, is smaller than the thickness of the copper plating layer 51 formed in contact with the core 30 that constitutes the base body 2 at the planned electrode area R30.

[0107] The Ni plating layer 52 is formed after the copper plating layer 51 and is a layer formed on top of the copper plating layer 51. The Sn plating layer 53 is formed after the Ni plating layer 52 and is a layer formed on top of the Ni plating layer 52. The Ni plating layer 52 and Sn plating layer 53 at the periphery 65 of the external electrode 4 are formed on the conductive copper plating layer 51 and Ni plating layer 52, respectively. Therefore, the thickness of the Ni plating layer 52 and Sn plating layer 53 at the periphery 65 of the external electrode 4 is approximately the same as the thickness of the Ni plating layer 52 and Sn plating layer 53 located at the planned electrode location R30.

[0108] Because the copper plating layer 51 on the periphery 65 of the external electrode 4 is thinner than the copper plating layer 51 on other parts, the periphery 65 is formed with a thickness smaller than the average thickness T33 of the external electrode 4.

[0109] The average thickness T33 of the external electrode 4 is greater than the average thickness T30, and the external electrode 4 protrudes outward from the end face 14 and bottom face 10 beyond the base coat 70. In other words, in the XIV-XIV cross section, the thickness of the portion of the external electrode 4 formed on the surface of the base 2 (the portion formed at the planned electrode location R30) is greater than the thickness of the second thickness region 70b. This makes it easier for the external electrode 4 to connect to the substrate during mounting. The average thickness T33 of the external electrode 4 can be determined, for example, by taking a cross section of the base 2 viewed from above and cutting it perpendicularly along a virtual line extending along the length direction DL of the base 2 passing through the coil winding axis K, and taking the average thickness of the external electrode 4 at any three or more points, excluding the peripheral edge 65 and the connection portion with the peeled portion 64a.

[0110] As described above, the periphery 65 of the external electrode 4, which is thinner than the average thickness T33, is formed on the first thickness region 70a, which has a thickness less than or equal to the thickness of the second thickness region 70b. Therefore, the periphery 65 of the external electrode 4 on the first thickness region 70a is less likely to protrude away from the base body 2. In other words, the periphery 65 of the external electrode 4 is less likely to protrude outside the end face 14 and bottom face 10 of the base body 2 than the external electrode 4 formed at the planned electrode location R30. Furthermore, the thickness of the tip 65a of the external electrode 4 is smaller than the difference in thickness between the first thickness region 70a and the second thickness region 70b, and the tip 65a of the external electrode 4 is located closer to the base body 2 and core 30 than the surface of the second thickness region 70b. Therefore, the tip 65a is less likely to protrude away from the base body 2.

[0111] Furthermore, as described above, since the first thickness region 70a is positioned to surround the planned electrode location R30, the first thickness region 70a surrounds the external electrode 4. As a result, the peripheral edge 65 around the external electrode 4 is less likely to protrude away from the base body 2 and the core 30.

[0112] Figure 15 is a cross-sectional view of line XIV-XIV in Figure 13. As shown in Figure 15, in reality, the thickness and shape of the first thickness region 70a vary depending on the precision of the laser processing used to irradiate the base coat 70 with laser light. The specific definitions of each element will be explained below with reference to Figure 15.

[0113] The first thickness region 70a is defined as the base coat 70 in the XIV-XIV cross section, from the part of the base coat 70 closest to the planned electrode location R30 to the point where the thickness of the base coat 70 reaches the maximum thickness T32 in the XIV-XIV cross section.

[0114] The second thickness region 70b is the portion in the XIV-XIV cross-section where the thickness of the base coat 70 is the maximum thickness T32 in the XIV-XIV cross-section. More precisely, the second thickness region 70b is defined as the base coat 70 located in the XIV-XIV cross-section, starting from the portion where the thickness of the base coat 70 is the maximum thickness T32 in the XIV-XIV cross-section, and moving away from the planned electrode location R30.

[0115] Figure 16 is a cross-sectional view taken along the line XVI-XVI in Figure 13. The XVI-XVI section is a cross-section obtained by cutting the base material 2 in the longitudinal direction DL along a straight line perpendicular to the boundary between the external electrode 4 and the base material coating 70, as viewed from the end face 14. In the XVI-XVI section, the DT direction is the direction away from the planned electrode location R30. As shown in Figure 16, in the XVI-XVI section, a sloped portion 73 is formed in the boundary region between the planned electrode location R30 and the coating location R31, where the thickness of the base material coating 70 increases on average in the direction away from the planned electrode location R30. In other words, the sloped portion 73 is the part in the XVI-XVI section where the thickness of the base material coating 70 increases on average toward the second thickness region 70b. The inclined portion 73 is formed in the direction away from the planned electrode location R30, extending from the boundary between the planned electrode location R30 and the coating location R31 to the position where the thickness of the base coat 70 reaches its maximum thickness T32 in the XVI-XVI cross section. Therefore, the inclined portion 73 is formed over the entire first thickness region 70a in the XVI-XVI cross section. Furthermore, no flat portion 75 is formed in the first thickness region 70a in the XVI-XVI cross section.

[0116] Furthermore, in the XVI-XVI cross-section, the first thickness region 70a does not have a stepped portion 71 where the thickness changes abruptly. That is, the difference in thickness between the first thickness region 70a and the second thickness region 70b is formed not by a stepped portion 71 where the thickness of the base coat 70 changes abruptly, but by an inclined portion 73. In the XVI-XVI cross-section, the first thickness region 70a is the base coat 70 from the part of the base coat 70 closest to the planned electrode location R30 to the part where the thickness of the base coat 70 is the maximum thickness T32 in the XVI-XVI cross-section. Also, in the XVI-XVI cross-section, the second thickness region 70b is the base coat 70 located away from the planned electrode location R30 from the part where the thickness of the base coat 70 is the maximum thickness T32 in the XVI-XVI cross-section. The formation of the inclined portion 73 makes it easier to form the first thickness region 70a and the second thickness region 70b, even when the stepped portion 71 is not formed.

[0117] Thus, in the base coat 70, a difference in thickness may be created between the first thickness region 70a and the second thickness region 70b by the stepped portion 71, or by the inclined portion 73. As in this embodiment, in the base coat 70 of one inductor 1, there may be a mixture of portions where the stepped portion 71 is formed and portions where the inclined portion 73 is formed at each cross-section. Furthermore, the base coat 70 of one inductor 1 may be configured to have only one of either the stepped portion 71 or the inclined portion 73 formed.

[0118] Up to this point, the explanation in [B-2-2. Configuration of External Electrodes and Base Coating], based on one end face 14 shown in Figure 13, also applies to the other end face 14 on the opposite side of the base body 2.

[0119] Furthermore, in [B-2-2. Configuration of External Electrodes and Base Coating], the end faces 14 have been explained using Figures 13 to 16. Incidentally, when the base body 2 is viewed from the bottom surface 10 side, the inductor 1 also has an external electrode 4 located on one end face 14 side, an external electrode 4 located on the other end face 14 side, and a base coat 70 surrounding these two external electrodes 4 (see Figure 2). For this reason, the explanation of the end faces 14 using Figures 13 to 16 above also applies to the bottom surface 10. That is, the above explanation using the cross-sectional surfaces in Figures 14 to 16 also applies to a cross-section obtained by cutting the base body 2 in the thickness direction DT along a straight line perpendicular to the boundary between any one of the external electrodes 4 and the base coat 70 when viewed from the bottom surface 10.

[0120] [Other embodiments] In the embodiment shown in [B-2-1. Configuration of Electrode Locations and External Electrode Connection Sections] above, the base coat 70 is described as having a first thickness region 70a and a second thickness region 70b, but this is just one example. The base coat 70 does not necessarily have to have the first thickness region 70a and the second thickness region 70b.

[0121] In the embodiment shown in [B-2-2. Configuration of External Electrode and Base Coat] above, the tip 65a of the peripheral edge 65 of the external electrode 4 is described as being located on the flat portion 75 of the first thickness region 70a, but this is just one example. For example, the tip 65a of the peripheral edge 65 may be located on the stepped portion 71.

[0122] In the embodiment shown in [B-2-2. Configuration of External Electrode and Base Coat] above, it was explained that in the XIV-XIV cross section, the thickness of the portion of the external electrode 4 formed on the surface of the base 2 is greater than the thickness of the second thickness region 70b, but this is just one example. That is, in the cross section obtained by cutting the base 2 in the longitudinal direction DL along a straight line perpendicular to the boundary between the external electrode 4 and the base coat 70 as viewed from the end face 14, the thickness of the portion of the external electrode 4 formed on the surface of the base 2 may be smaller than the thickness of the second thickness region 70b.

[0123] All embodiments and modifications described above illustrate one aspect of the present invention and can be arbitrarily modified and applied without departing from the spirit of the invention. Furthermore, unless otherwise specified, the directions such as horizontal, orthogonal, and vertical, as well as various numerical values, shapes, and materials in the embodiments described above, include a range that produces the same effects as those directions, numerical values, shapes, and materials (the so-called equivalence range).

[0124] [Configurations supported by the above embodiment] The embodiments described above support the following configurations.

[0125] (Configuration 1) An inductor comprising a body including a coil conductor and a core containing magnetic particles and resin in which the coil conductor is embedded, wherein the coil conductor has a winding portion in which a conductor is wound around a winding shaft, the winding portion has two overlapping winding regions along the winding shaft, the winding portion has a range in which, in a cross-section along the winding axis, the number of cross-sections of the conductor included in the two winding regions differs from one winding region to the other when viewed in adjacent portions along the winding axis, in at least a part of the range, the inner circumference of the winding region with fewer cross-sections of the conductor along the winding axis in the cross-section is shifted toward the outer circumference of the winding portion by 1 / 2 or more of the thickness of the conductor measured in a direction perpendicular to the winding shaft, relative to the inner circumference of the other winding region with more cross-sections of the conductor in the cross-section along the winding axis. According to the inductor of configuration 1, in an inductor comprising a core containing magnetic particles and a coil conductor embedded in the core, the size of dead space that does not contribute to the inductance that may occur in the core can be reduced, thereby improving the upper limit of the inductance.

[0126] (Configuration 2) The inductor according to Configuration 1, wherein the total number of turns of the conductor in the winding section is an odd integer when rounded to the nearest whole number, and the number of turns of the conductor in each of the two winding regions is the same as that of the other. In the inductor of configuration 2, adjacent portions with different numbers of wires tend to occur between the two winding regions, and in a configuration where dead space that does not contribute to inductance tends to occur within the core, the size of the dead space can be reduced, thereby improving the upper limit of the achievable inductance.

[0127] (Configuration 3) The inductor according to Configuration 1 or 2, wherein in at least a portion of the range, the difference between the distance of one winding region from the winding axis and the distance of the other winding region from the winding axis is within 1 / 2 of the thickness of the conductor, in the outer circumference of the two winding regions in a cross section along the winding axis. With the inductor of configuration 3, since no step is created on the outer circumference between the two winding regions, dead space within the core that does not contribute to the inductance is eliminated, and the upper limit of the achievable inductance can be further improved.

[0128] (Configuration 4) The inductor according to any one of Configurations 1 to 3, wherein the winding portion has a substantially rectangular shape when viewed in plan from the direction of the winding shaft, and has two of the above-mentioned areas, one on each of the two opposing sides of the substantially rectangular shape, and one of the winding areas includes fewer cross-sections of the conductor than the other winding area, and the other area includes more cross-sections of the conductor than the other winding area. With the inductor of configuration 4, the size of the two dead spaces that do not contribute to the inductance, which may occur at the outer circumference of each of the two winding regions of the winding portion that is substantially rectangular in plan view, can be reduced, thereby improving the upper limit of the achievable inductance.

[0129] (Configuration 5) The inductor according to any one of Configurations 1 to 4, wherein the conductor has a conductor and a covering layer covering the surface of the conductor, and the conductor has a rectangular cross-section perpendicular to the direction of extension of the conductor, and the four vertices of the rectangle are right angles. With the inductor of configuration 5, the gap between conductors in the winding section is reduced, so for example, the cross-sectional size of the conductor can be increased by the amount that the gap is reduced, and the DC resistance of the inductor can also be reduced. In addition, with the inductor of configuration 5, since the four vertices of the conductor are at right angles, when winding the conductor to form the winding section, it is easy to control the position of the conductors using the corners of the conductor as a guide. Therefore, when shifting the position of the conductor towards the outer circumference of the winding section, it becomes easier to control the position of the conductor, and the inner circumference of the winding area can be shifted towards the outer circumference of the winding section at a predetermined position. [Explanation of symbols]

[0130] 1...Inductor, 2...Base body, 4...External electrode, 10...Bottom surface, 12...Top surface, 14...End surface, 16...Side surface, 20...Coil conductor, 22...Winding section, 22a, 22b...Winding region, 23...Outlet section, 24...External electrode connection section, 30...Core, 41a...Top surface, 41b...Bottom surface, 42...Wire, 43...Conductor, 43a...Inner surface of conductor, 43b...Outer surface of conductor, 43c...Side surface of conductor, 43d...Side surface of conductor, 45...Coating layer, 48...Bent section, 50...Plated conductor, 51...Copper plating layer (plating layer), 52...Ni plating layer, 53...Tin Plating layer, 64a... peeled portion, 64b... coated portion, 64c... tip, 65... periphery, 65a... tip, 70... base coat, 70a... first thickness region, 70b... second thickness region, 71... stepped portion, 73... inclined portion, 75... flat portion, DT... thickness direction, K... winding axis, R... radius of curvature, R20, R21... range, R30... planned electrode location, R31... coating location, S1... circumscribed rectangle, S2... inscribed rectangle, T10... winding portion thickness, T11... top surface thickness (length), T12... bottom surface thickness (length), T11 + T12... total value.

Claims

1. The device comprises a body including a coil conductor and a core containing magnetic particles and resin in which the coil conductor is embedded, The coil conductor has a winding portion in which a conductor is wound around a winding shaft perpendicular to the upper surface of the base body, The winding portion has two winding regions that overlap along the winding shaft, The aforementioned winding portion is, The plan view from the direction of the winding shaft is substantially rectangular, The portion of the main body around which the conductor is routed, as viewed from the top surface, has two distinct ranges, one on each of the two opposing sides of the substantially rectangular shape, and in each of these ranges, the number of cross-sections of the conductor included in the two adjacent winding regions along the winding axis differs between one winding region and the other winding region. In at least a portion of each of the aforementioned ranges, the inner circumference of one of the winding regions with fewer cross-sections of the conductor in the cross-section along the winding axis is offset toward the outer circumference of the winding portion by at least half the thickness of the conductor measured in a direction perpendicular to the winding axis, relative to the inner circumference of the other winding region with more cross-sections of the conductor in the cross-section along the winding axis, In one of the two ranges, one winding region includes fewer cross-sections of the conductor than the other winding region. In the other of the two ranges, the first winding region includes a greater number of cross-sections of the conductor than the other winding region. Inductor.

2. The total number of turns of the conductor in the winding section is an odd integer when rounded to the nearest whole number. The number of turns of the conductor in each of the two winding regions is the same. The inductor according to claim 1.

3. In at least a portion of the aforementioned range, the outer circumference of the two winding regions in a cross-section along the winding axis is such that the difference between the distance of one winding region from the winding axis and the distance of the other winding region from the winding axis is within 1 / 2 of the thickness of the conductor. The inductor according to claim 1.

4. The conductor comprises a conductor and a covering layer covering the surface of the conductor, wherein the conductor has a rectangular cross-section perpendicular to the direction of extension of the conductor, and the four vertices of the rectangle are right angles. The inductor according to any one of claims 1 to 3.

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