JP2024056372A - Inductors - Google Patents

Abstract

[Problem] To improve the characteristics of an inductor. [Solution] The inductor includes an element body containing a metal magnetic powder and a resin, with a coil conductor embedded therein, an element body coat 70 covering the surface of the element body, and a pair of external electrodes 4 formed on the surface of the element body and connected to the coil conductor. When the element body is viewed from one end face, the element body coat 70 has one external electrode located on the bottom side and surrounding it, and has a second thickness region 70b that is maximum in thickness when viewed from the end face of the element body, ... the thickness of the second thickness region 70b is maximum when viewed from the end face of the element body, when viewed from the end face of the element body, when viewed from the end face of the element body, when viewed from the end face of the element body, when viewed from the end face of the element body, the first thickness region 70a is thinner than the second thickness region 70b. The periphery of one external electrode 4 is formed on the first thickness region 70a. [Effect] It is possible to prevent a part of the external electrode formed on the element body coat from protruding, and it is possible to increase the outer shape of the element body, thereby improving the characteristics of the inductor. [Selected Figure] FIG. 14

Description

The present invention relates to an inductor.

Patent Document 1 discloses an inductor in which a coil conductor is embedded in an element made of a composite material of resin material and metal powder, and coated with an insulating film. In this inductor, an external electrode is formed by plating on the part where the insulating film has been removed by laser irradiation, and the external electrode is connected to the end of the coil conductor that is exposed from the element.

International Publication No. 2017/135058

In inductors like the one above, the ends of the external electrodes protrude over the insulating film. As a result, in order to make the inductor's external dimensions meet the standard dimensions, it was necessary to reduce the size of the element by the amount of the protruding thickness of the external electrodes, leaving room for improvement in the characteristics.

One aspect of the present invention is an inductor that includes a metal magnetic powder and a resin, and includes an element body having an embedded coil conductor, an element body coat covering the surface of the element body, and a pair of external electrodes formed on the surface of the element body and connected to the coil conductor. When the element body is viewed from one end face, it has one of the external electrodes located on the bottom side and the element body coat surrounding it, and the element body coat has a second thickness region whose thickness is maximum when viewed from a cross section obtained by cutting the element body in the length direction of the element body along a straight line perpendicular to the boundary between the one of the external electrodes and the element body coat when viewed from the one end face, and a first thickness region whose thickness is smaller than that of the second thickness region, and the periphery of one of the external electrodes is formed on the first thickness region.

Another aspect of the present invention is an inductor that includes a body containing a metal magnetic powder and a resin and having a coil conductor embedded therein, a body coat covering the surface of the body, and a pair of external electrodes formed on the surface of the body and connected to the coil conductor, and when the body is viewed from the bottom side, the body coat surrounds one of the external electrodes located on one end side and the other external electrode located on the other end side, and the body coat has a second thickness region in which the thickness is maximum on a cut surface obtained by cutting the body in the thickness direction of the body along a straight line perpendicular to the boundary between one of the external electrodes and the body coat as viewed from the bottom side, and a first thickness region that is thinner than the second thickness region, and the periphery of one of the external electrodes is formed on the first thickness region.

The present invention can prevent a portion of the external electrode formed on the element coating from protruding, allowing the outer dimensions of the element to be enlarged, improving the characteristics of the inductor.

1 is a perspective view of an inductor according to an embodiment of the present invention, viewed from above; FIG. 2 is a perspective view of the inductor as viewed from the bottom side. FIG. 2 is a transparent perspective view showing the internal configuration of an inductor. 1 is a schematic diagram of a manufacturing process of an inductor. FIG. 2 is a plan view showing the internal configuration of an inductor. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5 . 4 is a cross-sectional view of a conductor constituting a conducting wire. FIG. 1A and 1B are diagrams showing the configuration of a winding portion of an inductor in which the winding portion of a coil conductor is wound in a normal winding manner. 4A and 4B are diagrams showing a configuration of a winding part of an inductor according to the present embodiment. 4A and 4B are diagrams showing the configuration of a coil conductor embedded in an element body. XI-XI line cross-sectional view of FIG. 5. FIG. 12 is a cross-sectional view corresponding to FIG. 11 when a normal conductor is used. 1 is a side view of the inductor 1 as viewed from the end face 14 side. 14 is a schematic cross-sectional view taken along line XIV-XIV in FIG. 13. This is a cross-sectional view taken along line XIV-XIV of Figure 13. This is a cross-sectional view taken along line XVI-XVI in Figure 13.

The following describes an embodiment of the present invention with reference to the drawings.

[Overall inductor configuration]
FIG. 1 is a perspective view of an inductor 1 according to this embodiment as viewed from a top surface 12 side, and FIG. 2 is a perspective view of the inductor 1 as viewed from a bottom surface 10 side.
The inductor 1 of this embodiment is configured as a surface-mount type electronic component, and includes a base body 2 having an approximately rectangular parallelepiped shape, which is one form of an approximately hexahedral shape, and a pair of external electrodes 4 provided on the surface of the base body 2.

Hereinafter, in the base body 2, the first main surface that faces a mounting board (not shown) during mounting is defined as the bottom surface 10, the second main surface opposite the bottom surface 10 is referred to as the top surface 12, a pair of third main surfaces perpendicular to the bottom surface 10 are referred to as end surfaces 14, and a pair of fourth main surfaces perpendicular to the bottom surface 10 and the pair of end surfaces 14 are referred to as side surfaces 16.
1, the distance from the bottom surface 10 to the top surface 12 is defined as the thickness T of the element body 2, the distance between a pair of side surfaces 16 is defined as the width W of the element body 2, and the distance between a pair of end surfaces 14 is defined as the length L of the element body 2. In addition, 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.

Hereinafter, a plane along the DL direction and DT direction (a plane perpendicular to the DW direction) will be referred to as an LT plane, a plane along the DT direction and DW direction (a plane perpendicular to the DL direction) will be referred to as a TW plane, and a plane along the DL direction and DW direction (a plane perpendicular to the DT direction) will be referred to as an LW plane. In addition, the cross sections of inductor 1 along the LT plane, TW plane, and LW plane will be referred to as the LT cross section, TW cross section, and LW cross section, respectively.

FIG. 3 is a perspective view showing the internal configuration of the inductor 1. As shown in FIG.
The element 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 sealed in the core 30 .

The core 30 is a molded body that is compression molded into an approximately hexahedral shape by applying pressure and heat to a mixed powder of magnetic particles and resin while containing the coil conductor 20.

In addition, the magnetic particles of this embodiment are made of a soft magnetic material and contain two types of particles: the first magnetic particles, which are large particles with a relatively large average particle size, and the second magnetic particles, which are small particles with a relatively small average particle size. As a result, during compression molding, the second magnetic particles, which are small particles, enter between the first magnetic particles, which are large particles, together with the resin, thereby increasing the filling rate 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. The average particle size of the first magnetic particles is preferably 20 μm or more and 22 μm or less, and the average particle size of the second magnetic particles is preferably 1.5 μm or more and 1.8 μm or less. In addition, the magnetic particles may contain particles with an average particle size different from that of the first magnetic particles and the second magnetic particles, thereby containing particles of three or more types of particle sizes.

The first magnetic particle and the second magnetic particle are both 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. By covering the metal particle with the oxide film and the insulating film, the insulation resistance and the withstand voltage are increased.
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 is composed of two layers, a SiO layer and an Fe ₂ SiO ₄ layer, and the total thickness of the oxide film is 20 nm to 155 nm. The insulating film of the first magnetic particle is formed of phosphate glass with a thickness of 10 nm to 100 nm.

In addition, in the second magnetic particles of this embodiment, carbonyl iron powder is used as the metal particles. The oxide film of the second magnetic particles is iron oxide formed by surface oxidation of the carbonyl iron powder, which is a metal particle. Furthermore, the insulating film of the second magnetic particles is a sol-gel reaction product containing 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 element molding and hardening process of the element 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.

In addition, in the first magnetic particles, the metal particles 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.
In the first magnetic particles, the insulating film may be made of phosphoric acid, zinc phosphate, manganese phosphate, glass, or resin.

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 with improved both the strength and toughness of the element body 2.

In this embodiment, the magnetic powder contained in the mixed powder is such that the first magnetic particles are 70 wt% to 85 wt% and the second magnetic particles are 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 is 2.0 wt% to 3.5 wt% based on the total weight of the magnetic powder and the resin. The first magnetic particles are preferably 70 wt% to 80 wt%, and the second magnetic particles are preferably 20 wt% to 30 wt%. The resin is preferably 2.7 wt% to 30 wt%.

As shown in FIG. 3, the coil conductor 20 includes a winding section 22 in which a conductor wire is wound in a spiral shape around the winding axis K in two layers, one above the other, so that both ends are located on the outer periphery and connected to each other on the inner periphery, a pair of lead-out sections 23 drawn out from the winding section 22, and a pair of external electrode connection sections 24 that are conductor wire portions connected to the lead-out sections 23, respectively, for connecting to external electrodes described below. The winding section 22 includes two winding regions 22a, 22b that overlap along the winding axis K. The winding regions 22a and 22b are connected to each other at a portion of their inner periphery.

The winding portion 22 is, for example, substantially rectangular in plan view when viewed from the direction of the winding axis K. The coil conductor 20 is embedded in the element body 2 so that the winding axis K is aligned with the thickness direction DT of the element body 2, and so that each side of the winding portion 22, which is substantially rectangular in plan view, is aligned (for example, parallel) with each side of the element body 2, which is substantially rectangular in plan view when viewed from the direction of the winding axis K.

The wire constituting the coil conductor 20 is composed of a conductor and a coating layer formed on the surface of the conductor. The wire is a flat wire with a rectangular cross section, and the conductor is a strip-shaped conductor made of copper with a rectangular cross section. The thickness of the conductor is 60 μm to 100 μm, and the width is 160 μm to 200 μm. The coating layer is composed 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.

The lead-out portion 23 is drawn out from the winding portion 22 and is electrically connected to the external electrode 4 via the external electrode connection portions 24 that are 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 constituted by L-shaped members extending from each of the end faces 14 of the element body 2 to the bottom face 10. Each of the external electrodes 4 is connected to an external electrode connection portion 24 of the coil conductor 20 at the end face 14, and a portion 4A (FIG. 2) extending to the bottom face 10 is electrically connected to a wiring of a circuit board by an appropriate mounting means such as solder.

An element protective layer (not shown) is formed on the surface of the element body 2 excluding the area of the external electrode 4. The element protective layer is, for example, a resin in which a phenoxy resin is added to a novolac resin, and contains nanosilica as a filler. The element protective layer is formed on the surface of the element body 2 with a thickness of 10 μm or more and 30 μm or less. The thickness of the element protective layer is preferably 10 μm or more and 20 μm or less, and more preferably 15 μm or less.

The inductor 1 configured as described above can improve the DC superposition characteristics by using a soft magnetic material for the magnetic particles, and is therefore used as an electronic component in an electric circuit through which a large current flows, a choke coil in a DC-DC converter circuit or a power supply circuit, and is also used in electronic components in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, car electronics, and medical and industrial machinery. However, the uses of the inductor 1 are not limited to this, and it can also be used, for example, in tuning circuits, filter circuits, and rectifying and smoothing circuits.

[Inductor manufacturing process overview]
FIG. 4 is a schematic diagram of a manufacturing process for the inductor 1. As shown in FIG.
As shown in the figure, the manufacturing process of the inductor 1 includes a coil conductor forming step, a preform forming step, an element molding and hardening step, an element grinding step, and an external electrode forming step.

The coil conductor formation process is a process for forming the coil conductor 20 from a conducting wire. In this process, the coil conductor 20 is formed into a shape having the above-mentioned winding portion 22, lead-out portion 23, and external electrode connection portion 24 by winding the conducting wire in a manner called "alpha winding." Alpha winding refers to a state in which the conducting wire, which functions as a conductor, is wound in two stages in a spiral shape so that the lead-out portions 23 at the beginning and end of the winding are located on the outer periphery. There is no particular limit to the number of turns in the coil conductor 20.

The preform forming step is a step of forming a preform called a tablet.
The preform is formed by pressing the above-mentioned mixed powder, which is the material of the base body 2, into a solid form 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.

In the element molding and hardening process, the first tablet, the coil conductor, and the second tablet are set in a molding die, and while applying heat, pressure is applied in the overlapping direction of the first tablet and the second tablet, and they are hardened to integrate the first tablet, the coil conductor, and the second tablet. This forms the element 2 with the coil conductor 20 enclosed in the core 30.

In the element grinding process, abrasive grains are applied to the side of the molded body obtained in the element molding and hardening process to scrape off (i.e. grind) the side until the width W becomes a predetermined width. This process results in an element 2 in which the width W of the molded body is downsized to a predetermined width. This downsizing reduces the distance (also called the side gap) between the coil conductor 20 in the element 2 and the side of the element 2, thereby increasing the coil occupancy rate in the radial direction of the winding part 22 of the coil conductor 20. In addition, since the element 2 is obtained by grinding the molded body obtained by compression molding to a predetermined size, the dimensional variation of the element 2 can be reduced compared to when the element 2 is controlled to a predetermined size by compression molding alone. In the element grinding process, polishing (e.g. barrel polishing) may be performed to chamfer the corners generated by grinding the side of the element 2.

The external electrode formation process is a process for forming the external electrode 4 on the element body 2, and includes an element body protective layer formation process, a surface treatment process, and a plating layer formation process.

The element body protection layer formation process is a process in which the entire surface of element body 2 is coated with insulating resin.

The surface treatment process is a process of modifying the surface of the intended electrode location by irradiating the electrode location on the surface of the core 30 with laser light. Here, the intended electrode location refers to the area of the surface of the core 30 where the external electrode 4 is to be formed, including the area where the external electrode connection part 24 is exposed. Specifically, by irradiating the laser light, the element body protection layer on the surface of the element body 2 and the coating layer of the external electrode connection part 24 of the coil conductor 20 are removed in the area of the intended electrode location, the resin on the surface of the core 30 is removed, and the insulating film on the surface of the magnetic particles exposed from the core 30 is removed. 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 intended electrode location of the surface of the core 30 than in other surface parts of the core 30. Note that after the irradiation of the laser light, a cleaning process (e.g., an etching process) may be performed to clean the surface of the intended electrode location.

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 locations irradiated with the laser light. In addition, the plating layer may be formed by providing a Ni plating layer and a Sn plating layer on top of the copper plating layer.

The details of the inductor 1 in this embodiment are explained further below.

A. Coil Conductor
Fig. 5 is a plan view showing the internal configuration of the inductor 1. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5. Fig. 6 shows a TW cross section of the inductor 1.
First, a description will be given of the coil conductor 20 used in the inductor 1. As described above, the coil conductor 20 includes the winding portion 22 around which a conductive wire is wound, a pair of lead-out portions 23, and a pair of external electrode connection portions 24.

The left end of the winding section 22 is drawn out from the lower stage of the winding section 22, which is wound in two stages, and is connected to the left external electrode connection section 24 through the left lead-out 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-out section 23 and extends linearly in the width direction DW. The right end of the winding section 22 is drawn out from the upper stage of the winding section 22, which is wound in two stages, and is connected to the right external electrode connection section 24 through the right lead-out 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-out section 23 and extends linearly in the width direction DW. In other words, the left and right lead-out sections 23 each extend in an extension direction dc that inclines toward one side in the width direction DW as it advances outward in the length direction DL. The left and right external electrode connection parts 24 each extend in an extension direction dp extending from the other side in the width direction DW to the one side in the width direction DW. In FIG. 5, the portion that slopes toward the one side in the width direction DW as it moves toward the outside in the length direction DL of the pull-out part 23 is linear, but at least a portion may be formed in a curved shape. In FIG. 5, the portion of the external electrode connection part 24 that extends from the other side in the width direction DW to the one side in the width direction DW is linear, but at least a portion may be formed in a curved shape.

As shown in FIG. 6, the conducting wire 42 that constitutes the coil conductor 20 has a conductor 43, which is a wire material, and a coating layer that covers the conductor 43 (the coating layer is not shown in FIG. 6 and FIG. 7). The coil conductor 20 is formed by alpha-winding the conducting wire 42. The coil conductor 20 is embedded in a core 30 that contains magnetic particles and resin.

[A-1. Conductive Wire]
Fig. 7 is a cross-sectional view of the conductor 43 constituting the conducting wire 42. Fig. 7 shows a cross section perpendicular to the direction in which the conductor 43 extends.
The conductor 43 is formed such that the shape of the conductor cross section perpendicular to the extension direction is a rectangle with four right-angled corners. In this specification, "right angle", "rectangle", and "same" do not necessarily mean "right angle", "rectangle", and "same" in the strict sense, but may mean substantially "right angle", "rectangle", and "same". In other words, in this specification, "right angle", "rectangle", and "same" may be used to mean "approximately right angle", "approximately rectangular", and "approximately the same" as long as they are substantially "right angle", "rectangle", and "same", respectively.

The conductor 43 has a conductor inner surface 43a on the winding axis K side, a conductor outer surface 43b on the side away from the winding axis K, and a pair of conductor side surfaces 43c, 43d that respectively connect both ends of the conductor inner surface 43a and both ends of the conductor outer surface 43b. A coating layer is formed on the surface of this conductor 43 to form the conductor wire 42.

The maximum length between the conductor side surfaces 43c and 43d in the thickness direction DT of the conductor 43 is defined as the line width La. The maximum length between the conductor inner surface 43a and the conductor outer surface 43b in the direction perpendicular to the thickness direction DT of the conductor 43 is defined as the line thickness Lb.

In detail, the angle between the conductor inner circumferential surface 43a and the conductor side surface 43c is a right angle. The angle between the conductor inner circumferential surface 43a and the conductor side surface 43d is also a right angle. The angle between the conductor outer circumferential surface 43b and the conductor side surface 43c is also a right angle. The angle between the conductor outer circumferential surface 43b and the conductor side surface 43d is also a right angle. In this embodiment, the criterion for a right angle is a corner in which a right angle corner is rounded with a radius of curvature R of 4.5 μm or less at the intersection of the conductor inner circumferential surface 43a or the conductor outer circumferential surface 43b and the conductor side surface 43c, 43d that respectively form a right angle. A method for confirming that the four corners of this conductor are right angles can be confirmed by observing the four corners in the cross section of the conductor with a digital microscope and measuring the radius of curvature of each corner using the measurement function of the digital microscope.

Here, a virtual circumscribing rectangle S1 is set so as to circumscribe the conductor 43 in the conductor cross section. 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. This conductor cross section is a cut surface cut perpendicularly in a direction perpendicular to the length direction DL of the conductor 42 if it is still 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 cut surface. That is, in this cut surface, the circumscribing rectangle S1 is set by making the line width La between the conductor side surfaces 43c and 43d in the thickness direction DT of the conductor 43 and the line thickness Lb between the conductor inner surface 43a and the conductor outer surface 43b in the direction perpendicular to the thickness direction DT of the conductor 43. In addition, when judging the inductor 1 of the product, the conductor cross section per turn of the winding section 22 is observed on a cut surface (cut surface shown in FIG. 6) cut perpendicularly by a virtual line extending in the width direction DW of the element body 2 passing through the winding axis K of the winding section 22 when viewed from above, and the circumscribing rectangle S1 is set. In this embodiment, the average area ratio of the conductor 43 to the circumscribing rectangle S1 per turn of the winding section 22 is 95% or more. Per turn means the average value per turn, and refers to the average value of the area ratios of the conductor cross sections at two locations in one turn in the element cross section. Therefore, for example, in FIG. 6, the average value of the area ratios of the winding positions P1 and P2 may be taken. Also, for example, in FIG. 6, the average value of the area ratios of the winding positions P3 and P4 may be taken.

As shown by the dashed lines in FIG. 7, the normal conductor 81 is formed by crushing a conductor with a circular cross section, so that the conductor inner surface 81a and the conductor outer surface 81b are flat, while the conductor side surfaces 81c and 81d are curved and have a large curvature. For this reason, the area ratio of the normal conductor 81 to the circumscribed rectangle S1 tends to be small. In contrast, the conductor 43 of this embodiment is formed by casting, and is intentionally formed to have four right-angled rectangular shapes. Therefore, compared to the normal conductor 81, the curvature of the curved shape of the conductor side surfaces 43c and 43d is smaller, and the conductor is formed linearly, resulting in a rectangular shape that is closer to the circumscribed rectangle S1.

As shown in FIG. 6, in this embodiment, in the thickness direction DT, the coil conductor 20 is embedded inside the core 30 so that the top surface thickness T11, which is the length from the top surface 12 of the element body 2 to the top 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 element body 2, are the same thickness.

In this embodiment, since the conductor 43 has a rectangular shape, when compared at the same DC resistance value (i.e., the area of the conductor cross section is the same), the line width La 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) in the thickness direction DT of the coil conductor 20, when the size of the element body 2 is approximately the same, it is easy to increase the top surface thickness T11 and the bottom surface thickness T12, and the sum T11+T12 of the top surface thickness T11 and the bottom surface thickness T12 can be increased.

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 T11+T12 of the top surface thickness T11 and the bottom surface thickness T12. Alternatively, the winding thickness T10 may be equal to or less than the sum T11+T12. Specifically, the ratio of the winding thickness T10 to the height of the element body 2 is 55% or less.

This makes it easy to make the sum T11+T12 of the top surface thickness T11 and bottom surface thickness T12 larger than the winding thickness T10, so that even if the position of the winding 22 shifts vertically during manufacturing, the distance between the winding 22 and the top and bottom surfaces of the element 2 can be maintained, and the variation in the DC superimposed rated current of the inductor 1 can be suppressed. Here, the DC superimposed rated current specifies the lower limit current value that can be used for the initial characteristics when no current is superimposed on the inductor, as magnetic saturation occurs in the magnetic material and the inductance decreases when a current flows through the inductor.

In this embodiment, the coil conductor 20 is embedded inside the core 30 so 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 so that the top thickness T11 is greater than the bottom thickness T12. The coil conductor 20 may also be embedded inside the core 30 so that the bottom thickness T12 is greater than the top thickness T11. When either the top thickness T11 or the bottom thickness T12 is greater, the smaller thickness is formed so that it is not smaller than 1/6 of the sum T11+T12 of the top thickness T11 and the bottom thickness T12.

[A-2. Coil conductor]
[A-2-1. Configuration 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. For this reason, the shape of the winding portion 22 embedded in the core 30 of the element body 2 can have a significant effect on the inductance value that can be realized in the inductor 1.

Figure 8 is a diagram for explaining the configuration of the winding portion 85 of the coil conductor 84 in an inductor 83 in which the winding portion of the coil conductor is wound in a normal winding manner. Figures 8(a) and (b) are diagrams of two winding regions 85a and 85b constituting the winding portion 85 of an inductor 83 having a configuration similar to that of Figure 1 in which the winding portion of the coil conductor is wound in a normal winding manner, respectively, viewed from a direction corresponding to the -DT direction in Figure 1 (looking down on the top surface 12). Also, Figure 8(c) is a diagram of a 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.

A coil conductor 84 including a winding section 85 consisting of winding regions 85a and 85b, a lead-out section drawn out from the winding section 85, and an external electrode connection section 88 that is a conductor section connected to the lead-out section and for connecting to an external electrode, constitutes an element body 87 together with a core 86 containing magnetic particles in which the coil conductor 84 is embedded. In FIG. 8(a), the conductor of the winding region 85a that constitutes the winding section 85 winds around the winding axis, is drawn out from the outermost periphery of the winding region 85a to the right side of the figure via the lead-out section, and is connected to the external electrode connection section 88 on the right side of the figure, and in FIG. 8(b), the conductor of the winding region 85b winds around the winding axis, is drawn out from the outermost periphery of the winding region 85b to the left side of the figure via the lead-out section, and is connected to the external electrode connection section 88 on the left side of the figure. Additionally, the conductor of the winding region 85a shown in FIG. 8(a) and the conductor of the winding region 85b shown in FIG. 8(b) are connected to each other at position P80 on the inner circumference of the winding portion 85.

The total number of turns of the winding section 85 is an odd integer, for example 5, rounded off to the nearest whole number, and the winding regions 85a and 85b that overlap along the winding axis to form the winding section 85 are each composed of the same number of turns, about 2.5 turns each. Therefore, in the cross section along the winding axis Kp direction (the normal direction to the paper surface in Figures 8(a) and (b)) of the part where the conductor winds around as viewed from the top surface of the element body 87, the two winding regions 85a and 85b have two ranges R81 and R82 where the number of cross sections of the conductor included in the two winding regions 85a and 85b is different from each other in the adjacent parts along the winding axis Kp direction.

8(c) is a cross-sectional view of the element body 87 along the center line CL80 in the width direction of the element body 87 in FIGS. 8(a) and 8(b), including the cross-sections of the ranges R81 and R82. As shown in FIG. 8(c), in an inductor 83 in which the winding portion of the coil conductor is wound in a normal winding manner, the inner circumferences of the winding regions 85a and 85b are at the same positions P82 and P83. The inner circumferences of the winding regions 85a and 85b are two turns that are stacked vertically and at the same position, while the outermost circumferences of the 0.5 turns are arranged at the outer circumference positions on the left and right sides of the figure. Therefore, the outer circumference of the winding portion 85 has a step S80 between the winding regions 85a and 85b on the left and right sides of the figure. The depth of the step S80 can be equivalent to the thickness T80 of the conductor measured in a direction perpendicular to the winding axis Kp.

Of the core 86 that constitutes the base body 87, this step S80 is dead space and can limit the upper limit of the inductance that can be achieved as the inductor 83.

For this reason, in the inductor 1 of this embodiment, in the portion corresponding to ranges R81 and R82 shown in FIG. 8, the inner circumference of one winding region having a smaller number of cross sections of the conductor wire is shifted toward the outer circumference relative to the inner circumference of the other winding region having a larger number of cross sections of the conductor wire.

Figure 9 is a diagram for explaining 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 winding portion of the coil conductor described above 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 axis K, a pair of lead-out portions 23 drawn out from the winding portion 22, and a pair of external electrode connection portions 24 which are conductor portions connected to each of the lead-out portions 23 for connecting to external electrodes. The winding portion 22 also includes two winding regions 22a and 22b that overlap along the winding axis K.

The wire that constitutes the coil conductor 20 has a conductor and a coating layer that covers the surface of the conductor. The conductor has a rectangular cross section perpendicular to the direction in which the conductor extends, and the four vertices of the rectangle are right angles.

Figures 9(a) and (b) are views of the two winding regions 22a and 22b that make up the winding portion 22, respectively, as viewed from the -DT direction in Figure 1 (looking down on the top surface 12). Also, Figure 9(c) is a view of the cross section of the inductor 1, corresponding to the LT cross section along the center line CL20 of the width W of the element body 2 (see Figure 1), as viewed from the DW direction.

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

The total number of turns of the winding portion 22 shown in FIG. 9 is an odd integer, for example 5, rounded off to the nearest whole number. However, this total number of turns is only an example to explain the difference from the inductor 83 shown in FIG. 8, in which the winding portion of the coil conductor is wound in a normal manner, and the total number of turns of the winding portion 22 can be set to any odd number depending on the inductance value required for the inductor 1.

The winding regions 22a and 22b constituting the winding section 22 are each configured with the same number of windings, approximately 2.5 times each. Therefore, in a cross section along the direction of the winding axis K (the direction normal to the paper surface in Figures 9(a) and (b)) of the portion in which the conductor winds as viewed from the top surface 12 of the element body 2, the two winding regions 22a and 22b have two ranges R20 and R21 in which the number of cross sections of the conductor included in the two winding regions 22a and 22b adjacent along the direction of the winding axis K is different from each other in the one winding region 22a and the other winding region 22b in the portion adjacent along the direction of the winding axis K.

In the inductor 1, the winding portion 22 is approximately rectangular in plan view when viewed from the direction of the winding axis K, and the ranges R20 and R21 are located on two opposing sides of the approximately rectangular shape.

Figure 9(c) is a diagram showing a cross section of element body 2 taken along center line CL20 in the width direction of element body 2 in Figures 9(a) and (b), and includes cross sections of ranges R20 and R21.

As shown in FIG. 9(c), one winding region 22a includes fewer conductors than the other winding region 22b in one range R20, and includes more conductors than the other winding region 22b in the other range R21. Similarly, one winding region 22b includes fewer conductors than the other winding region 22a in one range R21, and includes more conductors than the other winding region 22a in the other range R20.

In this embodiment, the ranges R20 and R21 are arranged on two opposing sides of the winding section 22 that are parallel to the end face 14 of the element body 2, as shown in Figures 9(a) and (b), so that they are not located near position P20 on the inner circumference of the winding section 22 that connects the winding region 22a and the winding region 22b to each other. In particular, as shown in Figure 9(c), in the ranges R20 and R21, the inner circumference of one winding region that has a smaller number of cross sections of the conductor wire in a cross section along the direction of the winding axis K is shifted toward the outer circumference of the winding section 22 with respect to the inner circumference of the other winding region that has a larger number of cross sections of the conductor wire in a cross section along the direction of the winding axis K.

Specifically, in range R20, the inner circumference of winding region 22b, which has a smaller number of cross sections of the conductor wire in a cross section along the direction of the winding axis K, is shifted by a distance D21 toward the outer circumference of winding section 22 relative to the inner circumference of winding region 22a, which has a larger number of cross sections of the conductor wire in a cross section along the direction of the winding axis K. Also, in range R21, the inner circumference of winding region 22a, which has a smaller number of cross sections of the conductor wire in a cross section along the direction of the winding axis K, is shifted by a distance D20 toward the outer circumference of winding section 22 relative to the inner circumference of winding region 22b, which has a larger number of cross sections of the conductor wire in a cross section along the direction of the winding axis K.

In the example of FIG. 9(c), the distances D20 and D21 are both the same as the thickness T20 of the conductor measured in a direction perpendicular to the winding axis K. This ensures that there is no step between the outer periphery of the winding region 22a and the outer periphery of the winding region 22b in each of the ranges R20 and R21. That is, in each of the ranges R20 and R21, the outer peripheries of the two winding regions 22a and 22b are formed so that the difference between the distance from the winding axis K of one winding region and the distance from the winding axis K of the other winding region is within 1/2 of the thickness of the conductor, and in FIG. 9(c), the distances from the winding axis K are approximately the same.

With the above configuration, the winding portion 22 of the inductor 1 does not have a step S80 on the outer periphery of the winding portion 85 that is formed in the inductor 83 in which the winding portion of the coil conductor is wound in the normal winding manner as shown in FIG. 8(c). In other words, since the step S80 as shown in FIG. 8(c) is not formed in the inductor 1, the upper limit of the inductance that can be realized as the inductor 1 can be improved compared to the inductor 83 in which the winding portion of the coil conductor is wound in the normal winding manner. Also, in the inductor 1 shown in FIG. 9, a large winding axis with a high magnetic flux density can be formed in each of the winding regions 22a and 22b.

The two winding regions 22a, 22b do not necessarily need to have the inner circumference of one winding region shifted from the inner circumference of the other winding region in the entire winding direction (circumferential direction centered on the winding axis K) of each of the ranges R20 and R21. In other words, the inner circumference of one winding region having a smaller number of cross sections of the conductor in a cross section along the winding axis K of the two winding regions 22a, 22b may be shifted toward the outer periphery of the winding section 22 with respect to the inner circumference of the other winding region having a larger number of cross sections of the conductor in a cross section along the winding axis K in at least a part of the winding direction of each of the ranges R20 and R21.

The amount of deviation of the inner circumference of one winding region from the inner circumference of the other winding region in ranges R20 and R21, i.e., distances D20 and D21 in FIG. 9(c), may be at least half the thickness T20 of the conductor measured in a direction perpendicular to the winding axis K. In this case, too, the size of the step between winding regions 22a and 22b at the outer periphery of winding portion 22 can be made smaller than step S80 in inductor 83 in which the winding portion of the coil conductor is wound in the normal winding manner as shown in FIG. 8(c), thereby improving the upper limit of inductance that can be achieved by inductor 1 compared to inductor 83 in which the winding portion of the coil conductor is wound in the normal winding manner.

[A-2-2. Configuration of Lead-Out Part and External Electrode Connection Part]
As described above with respect to the background art, in an inductor including an element body including a core containing magnetic particles formed of a soft magnetic material and a coil conductor embedded in the core, such as inductor 1 shown in Fig. 1, variations in the position and exposed area of the lead-out portion on the end face of the element body may occur due to the overall shape of the coil conductor and the attitude of the coil conductor inside the element body, etc. Such variations in the position and exposed area of the lead-out portion on the end face of the element body may cause variations in the electrical connection state between the lead-out portion and the external electrode, and may cause variations in the DC resistance value at the connection portion between the lead-out portion and the external electrode.

For this reason, in the inductor 1 of this embodiment, in a plan view seen from the normal direction of the top surface 12 of the element body 2, the shape of the coil conductor 20, in particular the angle between the lead-out portion 23 drawn out from the winding portion 22 and the external electrode connection portion 24, is configured to satisfy a predetermined condition. Also, in the inductor 1, in a plan view seen from the normal direction of the top surface 12 of the element body 2, the attitude of the coil conductor 20 inside the element body 2, in particular the angle between the normal direction of the end surface 14 of the element body 2 on which the external electrode 4 is formed and the extension direction of the external electrode connection portion 24, is configured to satisfy a predetermined condition.

10 is a view of the coil conductor 20 embedded in the element body 2 in one embodiment of the inductor 1, viewed from above the upper surface 12 of the element body 2 in the -DT direction. In the inductor 1 shown in FIG. 10, as shown particularly in the illustrated left portion of the inductor 1, the boundary between the lead-out portion 23 and the external electrode connection portion 24 is a bent portion 48 in which the conductor is bent, and the first angle θ1 formed by the extension direction dp of the external electrode connection portion 24 extending from the bent portion 48 as a starting point and the normal direction dn of the end face 14 passing through the bent portion 48 toward the inside of the element body 2 is greater than 90 degrees. When this first angle θ1 is smaller than 90 degrees, the entire external electrode connection portion 24 from the base to the tip of the external electrode connection portion 24 moves away from the end face 14 of the element body 2 toward the inside of the element body, and the exposed area of the external electrode connection portion 24 exposed from the end face 14 is reduced. Furthermore, if the first angle θ1 is 90 degrees, the exposed area of the external electrode connection part 24 exposed from the end face 14 can be increased, but if the bent part 48 is misaligned toward the inside of the element body 2, the external electrode connection part 24 may be buried in the element body 2. On the other hand, if the first angle θ1 is greater than 90 degrees, the tip side of the external electrode connection part 24 extends in a direction protruding from the end face 14 of the element body 2, and the tip of the external electrode connection part 24 extends in a state nearly parallel to the end face 14 of the element body 2 by contacting the inner wall of the molding die in the element body molding and hardening process described above, so that the exposed area of the external electrode connection part 24 exposed from the end face 14 can be increased. The lead-out part 23 and the external electrode connection part 24 on the right side of the inductor 1 in the figure can also be configured in the same manner as above, and the first angle θ1 can be defined.

As a result, in the inductor 1, the variation in the exposed area of the external electrode connection portion 24 exposed from the end face 14 can be reduced, and the variation in the DC resistance at the connection portion between the external electrode connection portion 24 and the external electrode 4 can be reduced. Here, when the first angle θ1 is greater than 90 degrees on both the left and right end faces 14 shown in the figure of the inductor 1, the variation in the exposed area of the external electrode connection portion 24 exposed from each end face 14 can be reduced on each of the left and right end faces 14 shown in the figure, and the variation in the DC resistance at the connection portion between the external electrode connection portion 24 and the external electrode 4 can be reduced.

In the inductor 1 shown in FIG. 10, the second angle θ2 between the extension direction dc of the lead-out portion 23 starting from the bent portion 48 and the extension direction dp of the external electrode connection portion 24 extending from the bent portion 48 is equal to or greater than 150 degrees 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 surface 14.

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 is in the range of 100 degrees or less.

Here, in FIG. 10, the coil conductor 20 is embedded in the element body 2 so that the winding axis K is along the normal direction of the top surface 12 (normal direction to the page). In addition, the outer shape of the winding portion 22 in a plan view from the normal direction of the top surface 12 (i.e., the plan view shown in FIG. 10) is such that the first length Wc, which is the maximum length in a direction perpendicular to the side surface 16 (e.g., the DW direction), is equal to or greater than the second length Lc, which is the maximum length measured in a direction perpendicular to the end surface 14 (e.g., 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.

The relationship between the winding portion 22 and the element 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 element 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.

From the viewpoint of reducing the variation in the above-mentioned exposed area of the external electrode connection portion 24, it is further preferable that the width of the bent portion 48 in a direction perpendicular to the pair of side surfaces 16 (e.g., the DW direction) is within a range R25 that is 1/2 the distance Wb between the pair of side surfaces 16 and is centered on a line L25 that passes through the center of the end face 14 and is parallel to the side surfaces 16.

It is preferable that the length of the external electrode connection portion 24 is 30% or more and 50% or less of the distance Wb between the pair of side surfaces 16 of the end face 14.

For example, the element body 2 has a distance Wb between a pair of side surfaces 16 of 1.2 mm to 1.4 mm, and a distance Ld between a pair of end surfaces 14 of 1.4 mm to 1.6 mm. Here, the actual size of the inductor 1 may include an error of about a few percent with respect to the nominal size of the inductor 1 described above, which is 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. Note that the above size of the inductor 1 is the size of the entire inductor 1 including the external electrode 4, and that the size of the element 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.

[B. External electrode]
Next, the connection configuration between the external electrodes and the external electrode connecting portions 24 of the coil conductor 20, and the configuration of the external electrodes on the surface of the element body will be described.
[B-1. Connection configuration between external electrodes and external electrode connecting portions]
Fig. 11 is a cross-sectional view taken along the line XI-XI in Fig. 5. Fig. 11 shows a cross section perpendicular to the extending direction dp of the external electrode connecting portion 24 at the connection portion between the external electrode connecting portion 24 and the external electrode 4. .
A pair of external electrodes 4 are provided on the surface of the element body 2. The external electrodes 4 are connected to a conductor 43 exposed by removing the covering layer 45 of the external electrode connection portion 24. The external electrodes 4 are plated The plated conductor 50 of this embodiment has a copper plating layer 51 as a plating layer of 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 to each other.

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 conductor outer peripheral surface 43b of the external electrode connection portion 24 and the conductor side surfaces 43c and 43d exposed by removing the coating layer 45 of the conductor wire 42 of the external electrode connection portion 24. The exposed amounts of the conductor side surfaces 43c and 43d are different for each of the conductor side surfaces 43c and 43d, as shown in FIG. 11. That is, in FIG. 11, the positions of the ends of the coating layer 45 on the external electrode 4 side are different in the left-right direction between the conductor side surface 43c and the conductor side surface 43d, and the exposed amount of the conductor side surface 43d is greater than that of the conductor side surface 43c.

FIG. 12 is a cross-sectional view of the case where a normal conductor 81 corresponding to FIG. 11 is used.
In a normal conductor 81, the four corners are not rectangular and the length of the conductor outer peripheral surface 81b in the direction of line width La is shorter than the line width La of the conductor 81, and the conductor side surfaces 81c, 81d on both sides of the conductor outer peripheral surface 81b in the direction of line width La tend to become curved surfaces with a large curvature.
Here, in manufacturing an inductor, with a conductive wire 80 of a normal conductor 81, when the coil conductor 20 is embedded in the element body 2, the thickness of the element body 2 on the curved surface where the conductor outer peripheral surface 81b is connected to the conductor side surfaces 81c, 81d (in other words, the length in the longitudinal direction DL from the outer surface of the element body 2 to the curved surface) becomes larger than the thickness of the element body 2 on the conductor outer peripheral surface 81b (in other words, the length in the longitudinal direction DL from the outer surface of the element body 2 to the conductor outer peripheral surface 81b). For this reason, when the coating layer 45 on the conductor outer peripheral surface 81b side of the conductive wire 80 embedded in the element body 2 is peeled off in the surface treatment step, only the coating layer 45 on the conductor outer peripheral surface 81b side is likely to be peeled off due to the difference in thickness of the element body 2, and the coating layer 45 and magnetic particles on the curved surfaces where the conductor outer peripheral surface 81b is connected to the conductor side surfaces 81c, 81d are likely to remain. For this reason, when plating is grown on the conductor outer peripheral surface 81b, a constriction 81e is likely to be formed at the connection portion between the conducting wire 80 and the plated conductor 50. That is, in a normal conductor 81, the conductor outer peripheral surface 81b and the plated conductor 50 are connected in such a way that this constriction 81e is formed, and therefore the connection area between the conductor 81 and the plated conductor 50 is likely to be narrower than the line width La. This causes problems such as an increase in the DC resistance of the external electrode 4 and a decrease in the connection reliability between the external electrode 4 and the conductor 81 of the coil conductor 20.

In contrast, since the conductor 43 in this embodiment has a substantially rectangular shape, when the coil conductor 20 is embedded in the element body 2, the thickness of the element body 2 on the corners of the conductor outer peripheral surface 43b and the conductor side surfaces 43c and 43d is unlikely to become greater than the thickness of the element body 2 on the conductor outer peripheral surface 43b. Therefore, when the coating layer 45 on the conductor outer peripheral surface 43b side of the conductor wire 42 embedded in the element body 2 is peeled off in the surface treatment process, not only the coating layer 45 on the conductor outer peripheral surface 43b but also the coating layer 45 on the conductor side surfaces 43c and 43d on the conductor outer peripheral surface 43b side can be peeled off.

In addition, the position of the end of the coating layer 45 on the conductor side 43c and the conductor side 43d in FIG. 11 differs in the left-right direction due to the direction of laser irradiation in the surface treatment process. That is, in FIG. 11, the resin layer is removed with the laser light while moving the laser light from bottom to top (in the direction from the conductor side 43d to the conductor side 43c relative to the conductor 42). Therefore, the coating layer 45 is easily removed on the conductor side 43d because the laser light moves closer to the conductor side 43d, whereas the coating layer 45 is difficult to remove on the conductor side 43c because the laser light moves farther away from the conductor side 43c. Therefore, the position of the end of the coating layer 45 on the conductor side 43d is removed to the inside of the element body 2 than the position of the end of the coating layer on the conductor side 43c.

At this time, when plating is grown on the conductor outer peripheral surface 43b, plating is likely to be formed not only on the conductor outer peripheral surface 43b but also on the conductor side surfaces 43c and 43d exposed from the coating layer 45 at positions adjacent to the conductor outer peripheral surface 43b, and a plated conductor 50 is formed that protrudes outward in the thickness direction DT from the conductor side surfaces 43c and 43d. Therefore, the shape formed by the conductor outer peripheral surface side of the conductor 43 and the plated conductor 50 can be made to expand toward the outer surface of the element body 2, preventing the occurrence of a constricted shape in the conductor side surfaces 43c and 43d, and the connection area between the conductor outer peripheral surface 43b and the plated conductor 50 can be made to be 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 by the circumscribing line 50a of the plated conductor 50 formed on the conductor outer peripheral surface 43b and the circumscribing line 50b of the plated conductor 50 formed on the conductor side surfaces 43c and 43d.

It can also be expressed as follows. That is, in the cross section shown in FIG. 11, a virtual inscribed rectangle S2 is set so as to inscribe the surface of the copper plating layer 51 formed on the conductor inner circumferential surface 43a, the conductor side surfaces 43c and 43d, and the conductor outer circumferential surface 43b of the conductor 43. This inscribed rectangle S2 is a virtual rectangle set on the conductor 43 side so as to satisfy the following four conditions. First, the inscribed rectangle S2 is set so that the side S2b on the conductor outer circumferential surface 43b side is set so as to inscribe the copper plating layer 51 of the plated conductor 50. Second, the inscribed rectangle S2 is set so that the side S2a on the conductor inner circumferential surface 43a side (side S2a facing side S2b) is inscribed in the conductor 43 (including the case where it is in contact with the end of side S2a, i.e., the corner). Third, the inscribed rectangle S2 is set so that 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 is maximized while satisfying the first and second conditions.

In this embodiment, within the inscribed rectangle S2 thus set, the corners S2e and S2f on the conductor inner surface 43a side are likely to be occupied by the rectangular conductor 43 with right angles, and the corners S2g and S2h on the copper plating layer 51 side are occupied by the copper plating layer 51 on the conductor outer surface 43b. At this time, the area ratio of the conductor 43 and the copper plating layer 51 to the inscribed rectangle S2, i.e., the area ratio of copper, which is the metal of the conductor 43, was 99% or more.

Therefore, in the conductor 43 of this embodiment, the conductor cross section has a rectangular shape with four right-angled corners, which makes it easy to connect to the coil conductor 20 with the copper plating layer 51 that is equal to or larger than the conductor outer peripheral surface 43b, and the conductor 43 and the plated conductor 50 are widely connected. This makes it possible to reduce the DC resistance of the external electrode 4 and improve the connection reliability between the external electrode 4 and the coil conductor 20.
As shown in FIG. 12, when an inscribed rectangle S2 is set for a normal conductor 81 as described above, a constricted shape 81e enters the inscribed rectangle S2.

[B-2. Configuration of external electrodes on element surface]
Next, the configuration of the external electrodes 4 on the surface of the element body will be described.
[B-2-1. Configuration of planned electrode locations and external electrode connection parts]
13 is a side view of the inductor 1 viewed from the end face 14 side of the element body 2. As described above, the external electrode 4 is formed by plating to cover the intended electrode location R30. The intended electrode location R30 is formed by peeling off the element body coat 70, which is an insulating resin that has been applied to the surface of the element body in the element body protective layer formation step, in the surface treatment step. The intended electrode location R30 is formed in a rectangular shape on each of the end face 14 and the bottom face 10 of the element body 2.

As shown in FIG. 13, the intended electrode location R30 is formed in a region that overlaps the portion of the external electrode connection part 24 exposed from the end face 14 of the element body 2. The external electrode connection part 24 is exposed on the end face 14 of the element body 2, straddling the intended electrode location R30 and the coated location R31, which is the region outside the intended electrode location R30, along the width direction DW of the element body 2. Of the external electrode connection part 24 exposed from the end face 14 of the element body 2, the coated portion 64b located at the coated location R31 is located closer to the tip 64c of the external electrode connection part 24 than the peeled portion 64a located at the intended electrode location R30. In other words, the tip 64c of the external electrode connection part 24 is located at the coated location R31. The area of the peeled portion 64a is set to be larger than the cross-sectional area of the conductor that constitutes the coil conductor 20.

As described above, the surface protection layer forming process is carried out after the element body forming/hardening process and the element body grinding process. That is, after the surface protection layer forming process, the entire surface of the external electrode connection portion 24 exposed from the end face 14 is coated with an insulating resin. In addition, in the surface treatment process, part of this coating is peeled off to form the intended electrode portion R30.

At this time, in the external electrode connection portion 24 exposed from the end face 14 of the element body 2, only the coating applied to the peeled portion 64a is peeled off, and the peeled portion 64a is connected to the external electrode 4 in the plating layer formation process. As described above, the area of the peeled portion 64a is set to be larger than the cross-sectional area of the conducting wire that constitutes the coil conductor 20, so that resistance is unlikely to become large at the connection portion between the peeled portion 64a and the external electrode 4.

On the other hand, even after the surface treatment process, the element coat 70 remains at the coating location R31. Therefore, the covering portion 64b is covered by the element coat 70, and at least the tip 64c of the external electrode connection portion 24 is covered by the element coat 70. By covering the covering portion 64b and the tip 64c with the element coat 70, the external electrode connection portion 24 exposed from the end face 14 is fixed to the end face 14 by the element coat 70 on the tip 64c side. Therefore, the external electrode connection portion 24 is unlikely 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 likely to be stable.

13, the coating point R31 has a first thickness region 70a and a second thickness region 70b. The covering 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 element body 2, in the peeled portion 64a, the coating layer of the conductor wire is removed when the coating is removed, and the exposed conductor is connected to the external electrode 4 in the plating layer formation step, and in the coated portion 64b, the coating layer of the conductor wire remains intact and is covered by the element coat 70 (i.e., both the first thickness region 70a and the second thickness region 70b), with the coating layer of the conductor wire being between the conductor and the element coat 70. Furthermore, the area of the region of the external electrode connection portion 24 that is connected to the external electrode has an area equal to or greater than the cross-sectional area of the conductor wire that constitutes the coil conductor 20.

[B-2-2. Configuration of external electrodes and element coating]
As shown in FIG. 13 , when the inductor 1 is viewed from one end face 14 side, the external electrode 4 is arranged biased toward the bottom face 10 side of the end face 14 , and the external electrode 4 is surrounded by an element coat 70 .
The first thickness region 70a is formed in a boundary region between the intended electrode location R30 and the coating location R31. The second thickness region 70b is located farther from the intended electrode location R30 than the first thickness region 70a when viewed from the intended electrode location R30. The first thickness region 70a is provided at a position that surrounds the intended electrode location R30, which is formed on the end surface 14 and the bottom surface 10 of the element body 2, at the end surface 14 and the bottom surface 10.

Figure 14 is a schematic diagram of the XIV-XIV cross section of Figure 13. The XIV-XIV cross section is a cross section perpendicular to the boundary between the intended electrode location R30 and the coating location R31 when viewed from the side of the end face 14 of the element body 2. In other words, the XIV-XIV cross section is a cross section obtained by cutting the element body 2 in the longitudinal direction DL along a straight line perpendicular to the boundary between the external electrode 4 and the element body coat 70 when viewed from the end face 14. In addition, in the XIV-XIV cross section, the DT direction is the direction away from the intended electrode location R30.

The first thickness region 70a is formed by removing a portion of the base coat 70 by irradiating the laser light during the surface treatment process with the irradiation time and irradiation power adjusted so that the irradiation amount is smaller than the amount of laser light irradiated to the intended electrode location R30. Therefore, the thickness of the first thickness region 70a is smaller than the average thickness T30 of the base coat 70.

The average thickness T30 is the average value of the thickness of the body coat 70 at a position sufficiently distant from the intended electrode location R30 among the body coat 70 that covers the entire body 2. The average thickness T30 is calculated, for example, as the average value of the thickness measurements of the body coat 70 measured at any three points in the center of the upper surface centered on the winding axis K on a cross section cut vertically along an imaginary line extending along the longitudinal direction DL of the body 2 passing through the winding axis K of the coil when viewed from above.

The second thickness region 70b is a portion of the base coat 70 formed in the surface protection 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 equal to the average thickness T30 and is greater than the thickness of the first thickness region 70a.

As shown in FIG. 14, in the XIV-XIV cross section, the first thickness region 70a is provided with a flat portion 75 and a step portion 71. The flat portion 75 is a portion of the first thickness region 70a where the thickness of the element coat 70 is approximately constant on average. The step portion 71 is a portion of the first thickness region 70a where the thickness increases rapidly in the direction away from the intended electrode location R30. The step portion 71 connects the flat portion 75 and the second thickness region 70b, which have different thicknesses, and the formation of the step portion 71 makes it easier to form the flat portion 75 and the second thickness region 70b. The step portion 71 is formed at an inclination of, for example, approximately 17 degrees with respect to the flat portion 75.

14, a periphery 65, which is a part of the external electrode 4, is formed on the first thickness region 70a. The tip 65a of the periphery 65 of the external electrode 4, which is located in the direction farthest from the electrode planned location R30, is on the flat portion 75 of the first thickness region 70a. Therefore, the periphery 65 of the external electrode 4 is not formed on the step portion 71 and the second thickness region 70b. In other words, the tip 65a of the periphery 65 of the external electrode 4 is located closer to the electrode planned location R30 than the step portion 71 and the second thickness region 70b. Also, in the direction away from the electrode planned location R30, the length of the periphery 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 electrode planned location R30 is longer than the length of the portion (periphery 65) of the external electrode 4 formed on the element coat 70. This makes it easier for the entire periphery 65 of the external electrode 4 to be formed on the flat portion 75 of the first thickness region 70a.

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 formed slightly on the coating point R31. However, since the element coat 70 is insulating, the thickness of the copper plating layer 51 of the external electrode 4 on the coating point R31, i.e., 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 constituting the element 2 at the electrode planned point R30.

The Ni plating layer 52 is formed by plating after the copper plating layer 51 and is formed on the copper plating layer 51. The Sn plating layer 53 is formed by plating after the Ni plating layer 52 and is formed on the Ni plating layer 52. The Ni plating layer 52 and the Sn plating layer 53 on the periphery 65 of the external electrode 4 are formed on the copper plating layer 51 and the Ni plating layer 52, which are conductors, respectively. Therefore, the thicknesses of the Ni plating layer 52 and the Sn plating layer 53 on the periphery 65 of the external electrode 4 are approximately equal to the thicknesses of the Ni plating layer 52 and the Sn plating layer 53 located at the electrode planned location R30.

The copper plating layer 51 on the periphery 65 of the external electrode 4 is thinner than the copper plating layer 51 in other parts, so the periphery 65 is formed to a thickness smaller than the average thickness T33 of the external electrode 4.

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 surface 14 and the bottom surface 10 more than the element 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 element body 2 (the portion formed at the intended electrode location R30) is greater than the thickness of the second thickness region 70b. This makes it easier for the external electrode 4 to be connected to a substrate or the like when mounted. The average thickness T33 of the external electrode 4 is calculated as the average value of the thicknesses at any three or more points of the external electrode 4, not including the connection portion with the periphery 65 and the peeled portion 64a, on a cut surface cut perpendicularly along a virtual line extending along the longitudinal direction DL of the element body 2 passing through the winding axis K of the coil when viewed from above.

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 equal to or less than 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 in a direction away from the element body 2 in the external electrode 4. That is, the periphery 65 of the external electrode 4 is less likely to protrude outside the end face 14 and bottom face 10 of the element body 2 than the external electrode 4 formed in the electrode planned location R30. In addition, 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 element body 2 and the core 30 than the surface of the second thickness region 70b. Therefore, the tip 65a is less likely to protrude in a direction away from the element body 2.

Furthermore, as described above, the first thickness region 70a is disposed at a position surrounding the intended electrode location R30, so that the first thickness region 70a surrounds the external electrode 4. Therefore, around the external electrode 4, the periphery 65 is less likely to protrude in a direction away from the element body 2 and the core 30.

Figure 15 is a cross-sectional view taken along 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 accuracy of the laser processing in which the element coat 70 is irradiated with laser light. Below, the specific definitions of each element are explained with reference to Figure 15.

The first thickness region 70a is defined as the element coat 70 from the part of the element coat 70 closest to the intended electrode location R30 on the XIV-XIV cross section to the point where the thickness of the element coat 70 reaches the maximum thickness T32 on the XIV-XIV cross section.

The second thickness region 70b is the portion of the element coat 70 where the thickness of the element coat 70 is the maximum thickness T32 on the XIV-XIV cross section. More precisely, the second thickness region 70b is defined as the element coat 70 on the XIV-XIV cross section that is located away from the intended electrode location R30, starting from the portion of the element coat 70 where the thickness of the element coat 70 is the maximum thickness T32 on the XIV-XIV cross section.

Figure 16 is a cross-sectional view taken along line XVI-XVI in Figure 13. The XVI-XVI cross-section is a cross-section of the element body 2 cut in the longitudinal direction DL along a straight line perpendicular to the boundary between the external electrode 4 and the element body coat 70 when viewed from the end face 14. In the XVI-XVI cross-section, the DT direction is the direction away from the intended electrode location R30. As shown in Figure 16, in the XVI-XVI cross-section, in the boundary region between the intended electrode location R30 and the coating location R31, an inclined portion 73 is formed in the element body coat 70, whose thickness increases on average in the direction away from the intended electrode location R30. In other words, the inclined portion 73 is a portion in the XVI-XVI cross-section where the thickness of the element body coat 70 increases on average toward the second thickness region 70b. The inclined portion 73 is formed in the direction away from the intended electrode location R30, from the boundary between the intended electrode location R30 and the coating location R31 to the position where the thickness of the element coat 70 is the maximum thickness T32 in the XVI-XVI cross section. Therefore, the inclined portion 73 is formed in the entire first thickness region 70a in the XVI-XVI cross section. Furthermore, in the XVI-XVI cross section, the first thickness region 70a does not have a flat portion 75.

In addition, in the XVI-XVI cross section, the first thickness region 70a does not have a step portion 71 where the thickness changes suddenly. That is, the difference in thickness between the first thickness region 70a and the second thickness region 70b is formed by a slope portion 73, not a step portion 71 where the thickness of the element coat 70 changes suddenly. In the XVI-XVI cross section, the first thickness region 70a is the element coat 70 from the portion of the element coat 70 closest to the electrode planned location R30 to the portion where the thickness of the element coat 70 is the maximum thickness T32 in the XVI-XVI cross section. In addition, in the XVI-XVI cross section, the second thickness region 70b is the element coat 70 that is located on the side away from the electrode planned location R30 from the portion where the thickness of the element coat 70 is the maximum thickness T32 in the XVI-XVI cross section. By forming the inclined portion 73, it becomes easier to form the first thickness region 70a and the second thickness region 70b even if the step portion 71 is not formed.

In this way, in the body coat 70, the first thickness region 70a and the second thickness region 70b may have a difference in thickness due to the step portion 71, or the thickness may be different due to the inclined portion 73. As in this embodiment, in the body coat 70 of one inductor 1, each cut surface may have a mixture of parts where the step portion 71 is formed and parts where the inclined portion 73 is formed. Also, the body coat 70 of one inductor 1 may be configured so that only one of the step portion 71 or the inclined portion 73 is formed.

Up to this point, in [B-2-2. Configuration of external electrode and element body coating], the explanation based on one end face 14 shown in Figure 13 also applies to the other end face 14 on the opposite side of the element body 2.

In addition, in [B-2-2. Configuration of external electrodes and element coat], the end face 14 has been described using Figures 13 to 16. Incidentally, when the element body 2 is viewed from the bottom face 10 side, the inductor 1 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 an element coat 70 surrounding these two external electrodes 4 (see Figure 2). Therefore, the above description of the end face 14 using Figures 13 to 16 also applies to the bottom face 10. In other words, the above description using the cut faces of Figures 14 to 16 also applies to a cut face cut in the thickness direction DT of the element body 2 along a straight line perpendicular to the boundary between any one of the external electrodes 4 and the element coat 70 when viewed from the bottom face 10.

[Other embodiments]
In the embodiment shown in [B-2-1. Configuration of the intended electrode locations and external electrode connection portions] above, the element coat 70 has been described as having the first thickness region 70a and the second thickness region 70b, but this is just one example. The element coat 70 does not necessarily have to have either the first thickness region 70a or the second thickness region 70b.

In the embodiment shown in [B-2-2. Configuration of the external electrode and element coat] above, the tip 65a of the periphery 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 periphery 65 may be configured to be located on the step portion 71.

In the embodiment shown in [B-2-2. Configuration of the external electrode and element coat] above, it has been explained that the thickness of the portion of the external electrode 4 formed on the surface of the element body 2 is greater than the thickness of the second thickness region 70b in the XIV-XIV cross section, but this is just one example. In other words, in a cross section obtained by cutting the element body 2 in the longitudinal direction DL along a straight line perpendicular to the boundary between the external electrode 4 and the element 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 element body 2 may be smaller than the thickness of the second thickness region 70b.

All of the above-described embodiments and modifications are merely examples of one aspect of the present invention, and any modifications and applications are possible without departing from the spirit of the present invention.
In addition, unless otherwise specified, the horizontal, orthogonal, vertical, and other directions, various numerical values, shapes, and materials in the above-described embodiments include a range in which the same action and effect as those directions, numerical values, shapes, and materials are achieved (a so-called equivalent range).

[Configuration supported by the above embodiment]
The above-described embodiment supports the following configurations.

(Configuration 1) An inductor comprising: an element body containing metal magnetic powder and resin, and having a coil conductor embedded therein; an element body coat covering a surface of the element body; and a pair of external electrodes formed on the surface of the element body and connected to the coil conductor, wherein when the element body is viewed from one end face, it has one of the external electrodes located on the bottom side and the element body coat surrounding it, and the element body coat has a second thickness region whose thickness is greatest when viewed from a cross section obtained by cutting the element body in the length direction of the element body along a straight line perpendicular to the boundary between one of the external electrodes and the element body coat when viewed from the one end face, and a first thickness region whose thickness is smaller than the second thickness region, and the periphery of one of the external electrodes is formed on the first thickness region.
According to the inductor of configuration 1, the portions of the external electrodes formed on the element body coat can be prevented from protruding from the end faces of the element body, which allows the outer dimensions of the element body to be increased and the characteristics of the inductor to be improved.

(Configuration 2) An inductor as described in configuration 1, wherein, when the element body is viewed from the other end face, it has the other external electrode located on the bottom side and the element body coat surrounding it, and the element body coat has a other second thickness region whose thickness when viewed from the other end face of the element body is maximum when viewed from the other cut face obtained by cutting the element body in the length direction along a straight line perpendicular to the boundary between the other external electrode and the element body coat, and a other first thickness region whose thickness is smaller than the other second thickness region, and the periphery of the external electrode is formed on the other first thickness region.
According to the inductor of configuration 2, the portions of both external electrodes formed on the element coat can be prevented from protruding from the end faces of the element, which allows the outer dimensions of the element to be increased and the characteristics of the inductor to be improved.

(Configuration 3) An inductor comprising: an element body containing metal magnetic powder and resin, and having a coil conductor embedded therein; an element body coat covering a surface of the element body; and a pair of external electrodes formed on the surface of the element body and connected to the coil conductor, wherein when the element body is viewed from the bottom side, it has one of the external electrodes located on one end face side and the other external electrode located on the other end face side, and the element body coat surrounding them, wherein the element body coat has a second thickness region whose thickness is greatest when viewed on a cross section obtained by cutting the element body in the thickness direction of the element body along a straight line perpendicular to the boundary between one of the external electrodes and the element body coat when viewed from the bottom side, and a first thickness region whose thickness is smaller than the second thickness region, and the periphery of one of the external electrodes is formed on the first thickness region.
According to the inductor of configuration 3, the portion of the external electrode formed on the element body coat can be prevented from protruding from the bottom surface of the element body, which allows the outer dimensions of the element body to be increased and the characteristics of the inductor to be improved.

(Structure 4) An inductor described in structure 3, wherein the element coat has a second thickness region whose thickness when viewed from the bottom surface of the element is maximum when viewed from the other cut surface of the element coat obtained by cutting the element coat in the thickness direction of the element body along a straight line perpendicular to the boundary between the other external electrode and the element coat, and a first thickness region whose thickness is smaller than the second thickness region, and the periphery of the other external electrode is formed on the first thickness region.
According to the inductor of configuration 4, the portions of both external electrodes formed on the element coat can be prevented from protruding from the bottom surface of the element, which allows the outer dimensions of the element to be increased and improves the characteristics of the inductor.

(Configuration 5) An inductor described in any one of configurations 1 to 4, wherein the first thickness region has a flat portion and a step portion, and the periphery of one of the external electrodes is on the flat portion.
In the inductor of configuration 5, the periphery of the external electrode is located on the flat portion of the first thickness region that is thinner than the second thickness region, so that the periphery of the external electrode is less likely to protrude from the end face or bottom face, allowing the outer dimensions of the element body to be increased.

(Configuration 6) An inductor described in any one of configurations 1 to 4, wherein the first thickness region has a flat portion and a step portion, and the periphery of one of the external electrodes is on the step portion.
In the inductor of configuration 6, the periphery of the external electrode is located at a step portion of the first thickness region that is thinner than the second thickness region, so that the periphery of the external electrode is less likely to protrude from the end face or bottom face, allowing the outer dimensions of the element body to be increased.

(Configuration 7) An inductor described in any one of configurations 1 to 4, wherein the first thickness region has a sloping portion in which the thickness increases on average toward the second thickness region, and the periphery of one of the external electrodes is on the sloping portion.
In the inductor of configuration 7, the periphery of the external electrode is located on the inclined portion of the first thickness region that is thinner than the second thickness region, so that the periphery of the external electrode is less likely to protrude from the end face or bottom face, allowing the outside dimensions of the element body to be increased.

(Configuration 8) An inductor according to configuration 5, wherein, on the cut surface, the length of the flat portion of the first thickness region is longer than the length of the portion of one of the external electrodes formed on the base coat.
According to the inductor of configuration 8, the external electrode formed on the element coat can be easily fixed on the flat portion of the first thickness region, which is thinner than the second thickness region, and therefore the portion of the external electrode formed on the element coat is less likely to protrude from the end face or bottom face, allowing the outer dimensions of the element to be increased.

(Configuration 9) An inductor according to configuration 1 or 2, wherein, at the cut surface, the thickness of a portion of one of the external electrodes formed on the surface of the element body is smaller than the thickness of the second thickness region.
With this configuration, the external electrodes themselves formed on the surface of the element body are formed thin, and furthermore, the peripheral edges of the external electrodes formed on the element body coat are also formed on the first thickness region which is thinner than the second thickness region, making it even more difficult for the external electrodes to protrude from the end faces of the element body, allowing the overall dimensions of the element body to be increased.

(Configuration 10) An inductor according to any one of configurations 1 to 4, wherein, at the cut surface, the thickness of a portion of one of the external electrodes formed on the surface of the body is greater than the thickness of the second thickness region.
According to this configuration, the external electrode itself formed on the surface of the element body is formed thicker than the second thickness region, while the external electrode formed on the element body coat is formed on the first thickness region which is thinner than the second thickness region. Therefore, the periphery of the external electrode formed on the element body coat is less likely to protrude than the external electrode formed on the surface of the element body. This makes it possible to increase the overall dimensions of the element body, and makes it easier to mount an inductor by using the external electrode formed on the surface of the element body thicker than the second thickness region.

1...inductor, 2...element body, 4...external electrode, 10...bottom surface, 12...top surface, 14...end surface, 16...side surface, 20...coil conductor, 22...winding portion, 22a, 22b...winding region, 23...drawing portion, 24...external electrode connection portion, 30...core, 41a...top surface, 41b...bottom surface, 42...conductor, 43...conductor, 43a...conductor inner surface, 43b...conductor outer surface, 43c...conductor side surface, 43d...conductor side surface, 45...coating layer, 48...folded portion, 50...plated conductor, 51...copper plating layer (plating layer), 52...Ni plating layer, 53...tin plating Coating layer, 64a...peeled portion, 64b...coated portion, 64c...tip, 65...periphery, 65a...tip, 70...element coat, 70a...first thickness region, 70b...second thickness region, 71...step portion, 73...inclined portion, 75...flat portion, DT...thickness direction, K...winding axis, R...radius of curvature, R20, R21...range, R30...destination of electrode, R31...coated portion, S1...circumscribed rectangle, S2...inscribed rectangle, T10...winding thickness, T11...top thickness (length), T12...bottom thickness (length), T11+T12...total value.

Claims (10)

An element body containing a metal magnetic powder and a resin and having a coil conductor embedded therein;
an element coat covering a surface of the element;
a pair of external electrodes formed on a surface of the element body and connected to the coil conductor;
When the element body is viewed from one end face, the element body has one of the external electrodes located on a bottom face side and the element body coat surrounding the external electrode,
the element body coating has a second thickness region, the thickness of which is maximum when viewed from a cross section obtained by cutting the element body in a longitudinal direction along a straight line perpendicular to a boundary between one of the external electrodes and the element body coating as viewed from the one end face, and a first thickness region, the thickness of which is smaller than that of the second thickness region;
a periphery of one of the external electrodes is formed on the first thickness region;
Inductor. When the element body is viewed from the other end face, the element body has the other external electrode located on the bottom face side and the element body coat surrounding it,
the element coating has a second thickness region whose thickness, as viewed from the other end face, is maximum when viewed from the other cut surface obtained by cutting the element in a longitudinal direction of the element body along a straight line perpendicular to a boundary between the other external electrode and the element coating, and a first thickness region whose thickness is smaller than that of the second thickness region,
The periphery of the external electrode is formed on the other first thickness region.
2. The inductor of claim 1. An element body containing a metal magnetic powder and a resin and having a coil conductor embedded therein;
an element coat covering a surface of the element;
a pair of external electrodes formed on a surface of the element body and connected to the coil conductor;
When the element body is viewed from the bottom side, the element body has one of the external electrodes located on one end face side and the other of the external electrodes located on the other end face side, and the element body coat surrounding them,
the element body coating has a second thickness region, the thickness of which is maximum when viewed from the bottom surface at a cross section obtained by cutting the element body in a thickness direction of the element body along a straight line perpendicular to a boundary between one of the external electrodes and the element body coating, and a first thickness region, the thickness of which is smaller than that of the second thickness region;
a periphery of one of the external electrodes is formed on the first thickness region;
Inductor. the element body coating has a second thickness region whose thickness as viewed from the bottom surface of the element body in a thickness direction of the element body along a straight line perpendicular to a boundary between the external electrode and the element body coating is maximum on the other cut surface, and a first thickness region whose thickness is smaller than that of the second thickness region,
a periphery of the other external electrode is formed on the other first thickness region;
The inductor according to claim 3 . the first thickness region has a flat portion and a step portion, and a periphery of one of the external electrodes is on the flat portion;
The inductor according to claim 1 or 3. the first thickness region has a flat portion and a step portion, and a periphery of one of the external electrodes is on the step portion;
The inductor according to claim 1 or 3. the first thickness region has an inclined portion whose thickness increases on average toward the second thickness region, and a periphery of one of the external electrodes is on the inclined portion;
The inductor according to claim 1 or 3. a length of the flat portion of the first thickness region is longer than a length of a portion of one of the external electrodes that is formed on the element coat, on the cut surface;
6. The inductor according to claim 5. a thickness of a portion of one of the external electrodes formed on a surface of the element body is smaller than a thickness of the second thickness region at the cut surface;
2. The inductor of claim 1. a thickness of a portion of one of the external electrodes formed on a surface of the element body is greater than a thickness of the second thickness region at the cut surface;
The inductor according to claim 1 or 3.