Multilayer inductor

Abstract

The purpose of the present invention is to provide a multilayer inductor in which a decrease in magnetic permeability is further reduced while ensuring insulation characteristics. A multilayer inductor according to the present disclosure comprises an element body 10 having: a magnetic body M in which metal magnetic body layers ML containing metal magnetic body particles MP are laminated; a coil disposed inside the magnetic body M and around which coil conductors CD are wound; and an insulator I disposed between the coil conductors CD in the lamination direction. The insulator I has: a contact part I1 with the coil conductor CD extending along a direction intersecting the lamination direction; and a protrusion part I2 provided at both ends in a direction orthogonal to the lamination direction of the contact part I1 and extending toward the outside on both sides in a direction orthogonal to the lamination direction in the coil conductor CD. The thickness of the protrusion part I2 is thinner than the thickness of the contact part I1.

Description

Multilayer inductors

[0001] The present disclosure relates to laminated inductors.

[0002] Patent Document 1 (see claim 1 and FIG. 3) discloses a laminated coil component in which the average particle size of soft magnetic metal powder located inside the coil as viewed in the Z direction is made larger than the average particle size of soft magnetic metal powder located between adjacent coil conductors in the Z direction, thereby increasing the magnetic permeability of the element body.

[0003] Furthermore, Patent Document 2 (see claim 3 and FIG. 3) discloses a coil component in which the width dimension of a plurality of insulating portions perpendicular to one axial direction is equal to or greater than the width dimension of a plurality of winding portions perpendicular to one axial direction, thereby ensuring stable electrical insulation between the winding portions.

[0004] JP 2018-6411 A JP 2017-228768 A

[0005] The multilayer coil component described in Patent Document 1 provides insulation between coil conductors by low-permeability portions composed of soft magnetic metal powder. However, the width of the low-permeability portions in the X direction (see FIG. 3 of Patent Document 1) is approximately the same as the width of the coil conductors in the X direction, raising concerns about insulation reliability.

[0006] In contrast, in the coil component described in Patent Document 2 (see FIG. 3), the width dimension Ws of the insulating portion is set larger than the width dimension Wc of the winding portion. However, the flow of magnetic flux is reduced by the insulating portion protruding from the winding portion, and the magnetic permeability of the entire coil component is reduced.

[0007] The present disclosure has been made in view of the above problem, and aims to provide a multilayer inductor that further reduces the decrease in magnetic permeability while maintaining insulation properties.

[0008] The laminated inductor of the present disclosure comprises an element body having a magnetic body formed by laminating metal magnetic layers containing metal magnetic particles, a coil disposed inside the magnetic body and wound with a coil conductor, and an insulator disposed between the coil conductors in the lamination direction, wherein the insulator has a contact portion with the coil conductor extending along a direction intersecting the lamination direction, and protruding portions provided on both ends of the contact portion in a direction perpendicular to the lamination direction and extending outward on both sides of the coil conductor in the direction perpendicular to the lamination direction, and the thickness of the protruding portions is thinner than the thickness of the contact portion.

[0009] According to the present disclosure, it is possible to provide a laminated inductor that ensures insulation characteristics while further reducing the decrease in magnetic permeability. Specifically, an insulator disposed between the coil conductors in the stacking direction has a contact portion with the coil conductor that extends in a direction intersecting the stacking direction, and protruding portions provided at both ends of the contact portion in a direction perpendicular to the stacking direction and extending outward on both sides of the coil conductor in the direction perpendicular to the stacking direction, thereby ensuring insulation characteristics. Furthermore, in the insulator disposed between the coil conductors in the stacking direction, the thickness of the protruding portions that protrude outward from both sides of the coil conductor is thinner than the thickness of the contact portion that contacts the coil conductor, making it less likely that the insulator will reduce the flow of magnetic flux, thereby further reducing the decrease in magnetic permeability.

[0010] FIG. 1 is a perspective view of a laminated inductor according to the present disclosure. FIG. 2 is an exploded perspective view of a laminated inductor according to a first embodiment. FIG. 3 is a cross-sectional view taken along the arrow III-III in FIG. 2. FIG. 4 is an enlarged cross-sectional view of a main portion of FIG. 3. FIG. 5 is a cross-sectional view of a laminated inductor according to another embodiment. FIG. 6 is a cross-sectional view of a laminated inductor according to a second embodiment. FIG. 7 is an enlarged cross-sectional view of a main portion of FIG. 6. FIGS. 8A to 8G are explanatory views illustrating a method for manufacturing a laminated inductor according to the present disclosure.

[0011] The laminated inductor of the present disclosure will be described below. Note that the present disclosure is not limited to the following configurations and may be modified as appropriate within the scope of the present disclosure. In addition, a combination of multiple individual preferred configurations described below also constitutes the present disclosure.

[0012] The laminated inductor of the present disclosure is used in, for example, a DC-DC converter, and is also applicable to uses other than DC-DC converters.

[0013] In this specification, terms indicating the relationship between elements (e.g., "parallel," "orthogonal," etc.) and terms indicating the shape of elements do not only mean the strict literal form, but also mean a range that is substantially equivalent, for example, a range that includes a difference of about a few percent. Note that in this specification, the direction in which the magnetic layers and coil conductors that make up the element body are stacked is referred to as the "stacking direction."

[0014] Furthermore, in the description of this specification, references to directions or orientations are made merely for the convenience of explanation and are not intended to limit the scope of the present disclosure unless otherwise explicitly stated. For example, relative terms such as "outside (or outer, external, or outer circumference)" and "inside (or inner, internal, or inner circumference)" and their derivatives should be understood to refer to the direction as described or illustrated. In other words, unless otherwise explicitly stated, the invention is not necessarily limited to a specific direction, orientation, form, or the like. Similarly, terms such as "provided," "disposed," and "connected" and their derivatives may refer to a configuration in which other elements, such as intervening elements, are present, rather than being limited to a direct configuration, unless otherwise explicitly stated.

[0015] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, scale, etc. may differ from those of the actual product.

[0016] <Inductor of First Embodiment> A laminated inductor of a first embodiment will be described with reference to Figures 1 to 5. Figure 1 is a perspective view of the laminated inductor of the present disclosure, Figure 2 is an exploded perspective view of the laminated inductor of the first embodiment, Figure 3 is a cross-sectional view taken along the arrow III-III in Figure 2, Figure 4 is an enlarged cross-sectional view of a main portion of Figure 3, and Figure 5 is a cross-sectional view of a laminated inductor of another embodiment. Note that the shapes and arrangements of the laminated inductor and its components are not limited to the examples shown in the figures.

[0017] The laminated inductor 1 of the first embodiment comprises a base body 10 having a magnetic body M formed by laminating metal magnetic layers ML (see Figure 2) containing metal magnetic particles MP (see Figure 4), a coil C disposed inside the magnetic body M and wound with a coil conductor CD, and an insulator I disposed between the coil conductors CD in the stacking direction.

[0018] In this embodiment, the element body 10 includes a first coil C1 and a second coil C2 arranged above the first coil C1 in the height direction T. The first coil C1 is wound within the element body 10 by stacking lamination groups G6 to G8 (see FIG. 2) described below and connecting first coil conductors CD1 between layers in a spiral shape via via conductors V (see FIG. 3). The second coil C2 is wound within the element body 10 by stacking lamination groups G2 to G4 (see FIG. 2) described below and connecting second coil conductors CD2 between layers in a spiral shape via via conductors (not shown).

[0019] The coils provided inside the element body 10 are not limited to the above configuration, and may include one coil or two or more coils. For example, the element body 10 may include four coils C1 to C4 as shown in Fig. 5. Specifically, the third coil C3 provided inside the element body 10 shown in Fig. 5 may be arranged in a direction perpendicular to the stacking direction relative to the first coil C1, and the fourth coil C4 may be arranged in a direction perpendicular to the stacking direction relative to the second coil C2.

[0020] Each component will be described in detail below.

[0021] -Element body- The element body 10 has, for example, a rectangular parallelepiped or approximately rectangular parallelepiped shape having six sides. The corners and ridges of the element body 10 may be rounded. A corner is a portion where three sides of the element body 10 intersect, and a ridge is a portion where two sides of the element body 10 intersect.

[0022] 1, the length direction, width direction, and height direction of the laminated inductor 1 and the element body 10 are shown as L direction, W direction, and T direction, respectively. The length direction L, width direction W, and height direction T are perpendicular to each other. The mounting surface of the laminated inductor 1 is, for example, a surface (LW surface) parallel to the length direction L and width direction W.

[0023] 1 has a first main surface 11 and a second main surface 12 that face each other in a height direction T, a first end surface 13 and a second end surface 14 that are perpendicular to the height direction T and face each other in a length direction L, and a first side surface 15 and a second side surface 16 that face each other in a width direction W that is perpendicular to the length direction L and the height direction T. In the example shown in FIG. 1 , the first main surface 11 of the element body 10 corresponds to the mounting surface (bottom surface) of the element body 10. Note that the second main surface 12 may also be the mounting surface of the element body 10.

[0024] The element body 10 includes a magnetic body M, a coil C, and an insulator I. The element body 10 has a laminated structure in which a metal magnetic body layer ML, a plurality of metal magnetic body layers ML each having an insulator I and a coil conductor CD formed thereon, and a plurality of metal magnetic body layers ML each having an insulator I formed thereon are stacked in a stacking direction (e.g., height direction T). In this embodiment, as shown in FIG. 2 , the element body 10 is configured by stacking laminated groups G1 to G10 each including at least one metal magnetic body layer ML and one coil conductor CD (or only one metal magnetic body layer ML). Note that the boundaries between layers in the laminated structure of the element body 10 disappear. Furthermore, each laminated group layer may be configured by stacking a plurality of identical patterns.

[0025] (Stacking Group G1) The stacking group G1 has a metal magnetic layer ML and constitutes the second main surface 12 of the element body 10.

[0026] (Stacking group G2) The stacking group G2 has a metal magnetic layer ML, an insulator (not shown) provided on the metal magnetic layer ML, and a second coil conductor CD2 that forms part of a second coil C2 formed on the insulator.

[0027] The second coil conductor CD2 of the multilayer group G2 constitutes one winding of the second coil C2. More specifically, the second coil conductor CD2 is disposed on an insulator formed in the thickness direction of the metal magnetic layer ML along substantially the outer periphery of the metal magnetic layer ML. One end of the second coil conductor CD2 is connected to a via conductor (not shown) provided on the insulator of the metal magnetic layer ML of the multilayer group G4 for connection to the second coil conductor CD2, and the other end of the second coil conductor CD2 is connected to a fourth through-hole conductor (not shown) for electrical connection to the fourth external electrode E4.

[0028] (Stacking group G3) The stacking group G3 has a metal magnetic layer ML, an insulator I provided in the metal magnetic layer ML, a via conductor V provided in the insulator I, and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0029] The insulator I of the multilayer group G3 is provided to correspond to the winding shape of the second coil conductor CD2 of the multilayer group G4, which will be described later. In a planar perspective, the planar area of ​​the insulator I of the multilayer group G3 is designed to be larger than the planar area of ​​the second coil conductor CD2 of the multilayer group G4. Therefore, the insulator I of the multilayer group G3 has, in a planar perspective, an area that overlaps with the second coil conductor CD2 and an area that protrudes from the second coil conductor CD2. The area of ​​the insulator I that protrudes from the second coil conductor CD2 (protruding portion I2 (see FIG. 3 or FIG. 4)) will be described in detail later.

[0030] The via conductor V of the multilayer group G3 is disposed at a position where it is connected to one end of the second coil conductor CD2 of the multilayer group G2.

[0031] The fourth through-hole conductor T4 of the multilayer group G3 connects the fourth through-hole conductors T4 of the multilayer groups G2 and G4 adjacent to each other in the stacking direction, and is electrically connected to the fourth external electrode E4. Therefore, the fourth through-hole conductor T4 is disposed above the fourth external electrode E4 in a planar perspective view.

[0032] (Stacking group G4) The stacking group G4 has a metal magnetic layer ML, an insulator (not shown) provided on the metal magnetic layer ML, a second coil conductor CD2 that forms part of a second coil C2 formed on the insulator, and a fourth through-hole conductor T4 provided on the metal magnetic layer ML.

[0033] The second coil conductor CD2 of the multilayer group G4 forms another winding of the second coil C2. More specifically, the second coil conductor CD2 is disposed on an insulator formed in the thickness direction of the metal magnetic layer ML along substantially the outer periphery of the metal magnetic layer ML. One end of the second coil conductor CD2 is connected to the second coil conductor CD2 provided on the insulator of the metal magnetic layer ML of the multilayer group G2, and the other end of the second coil conductor CD2 is connected to a third through-hole conductor (not shown) for electrical connection to the third external electrode E3.

[0034] The fourth through-hole conductor T4 of the multilayer group G4 connects the fourth through-hole conductors T4 of the multilayer groups G3 and G5 adjacent to each other in the stacking direction, and is electrically connected to the fourth external electrode E4. Therefore, the fourth through-hole conductor T4 may be disposed at a corner of the metal magnetic layer ML located on the fourth external electrode E4.

[0035] (Multilayer Group G5) The multilayer group G5 includes a metal magnetic layer ML, an insulator I provided in the metal magnetic layer ML, and a third through-hole conductor T3 and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0036] The insulator I of the multilayer group G5 is provided to correspond to the winding shape of the first coil conductor CD1 of the multilayer group G6, which will be described later. In a planar perspective, the planar area of ​​the insulator I of the multilayer group G5 is designed to be larger than the planar area of ​​the first coil conductor CD1 of the multilayer group G6. Therefore, in a planar perspective, the insulator I of the multilayer group G5 has an area that overlaps with the first coil conductor CD1 and an area that extends beyond the first coil conductor CD1. Furthermore, the insulator I of the multilayer group G5 electrically insulates the first coil C1 and the second coil C2.

[0037] The third through-hole conductor T3 of the multilayer group G5 connects the third through-hole conductors T3 of the multilayer groups G4 and G6 adjacent to each other in the stacking direction, and is electrically connected to the third external electrode E3. Therefore, the third through-hole conductor T3 is disposed on the third external electrode E3 in a planar perspective view.

[0038] The fourth through-hole conductor T4 of the multilayer group G5 connects the fourth through-hole conductors T4 of the multilayer groups G4 and G6 adjacent to each other in the stacking direction, and is electrically connected to the fourth external electrode E4. Therefore, the fourth through-hole conductor T4 is disposed above the fourth external electrode E4 in a planar perspective view.

[0039] (Stacking group G6) The stacking group G6 has a metal magnetic layer ML, an insulator (not shown) provided on the metal magnetic layer ML, a first coil conductor CD1 that forms part of a first coil C1 formed on the insulator, and a third through-hole conductor T3 and a fourth through-hole conductor T4 provided on the metal magnetic layer ML.

[0040] The first coil conductor CD1 of the multilayer group G6 constitutes one winding of the first coil C1. More specifically, the first coil conductor CD1 is disposed on an insulator formed along the approximate outer periphery of the metal magnetic layer ML in the thickness direction of the metal magnetic layer ML. One end of the first coil conductor CD1 is provided with a via conductor (not shown) for connection to the first coil conductor CD1 provided on the insulator of the metal magnetic layer ML of the multilayer group G7, and the other end of the first coil conductor CD1 is provided with a second through-hole conductor (not shown) for electrical connection to the second external electrode E2.

[0041] The third through-hole conductors T3 of the multilayer group G6 connect the third through-hole conductors T3 of the multilayer groups G5 and G7 adjacent to each other in the stacking direction, and are electrically connected to the third external electrode E3. Therefore, the third through-hole conductors T3 may be disposed at the corners of the metal magnetic layers ML located on the third external electrode E3.

[0042] The fourth through-hole conductor T4 of the multilayer group G6 connects the fourth through-hole conductors T4 of the multilayer groups G5 and G7 adjacent to each other in the stacking direction, and is electrically connected to the fourth external electrode E4. Therefore, the fourth through-hole conductor T4 may be disposed at a corner of the metal magnetic layer ML located on the fourth external electrode E4.

[0043] (Stacking group G7) The stacking group G7 has a metal magnetic layer ML, an insulator I provided on the metal magnetic layer ML, a via conductor V provided on the insulator I, and a second through-hole conductor T2, a third through-hole conductor T3 and a fourth through-hole conductor T4 provided on the metal magnetic layer ML.

[0044] The insulator I of the multilayer group G7 is provided to correspond to the winding shape of the first coil conductor CD1 of the multilayer group G8, which will be described later. In a planar perspective view, the planar area of ​​the insulator I of the multilayer group G7 is designed to be larger than the planar area of ​​the first coil conductor CD1 of the multilayer group G8. Therefore, the insulator I of the multilayer group G7 has a region that overlaps with the first coil conductor CD1 in a planar perspective view and a region that extends beyond the first coil conductor CD1.

[0045] The via conductor V of the multilayer group G7 is disposed at a position where it is connected to one end of the first coil conductor CD1 of the multilayer group G6.

[0046] The second through-hole conductor T2 of the multilayer group G7 connects the second through-hole conductors T2 of the multilayer groups G6 and G8 adjacent to each other in the stacking direction, and is electrically connected to the second external electrode E2. Therefore, the second through-hole conductor T2 is disposed on the second external electrode E2 in a planar perspective view.

[0047] The third through-hole conductor T3 of the multilayer group G7 connects the third through-hole conductors T3 of the multilayer groups G6 and G8 adjacent to each other in the stacking direction, and is electrically connected to the third external electrode E3. Therefore, the third through-hole conductor T3 is disposed on the third external electrode E3 in a planar perspective view.

[0048] The fourth through-hole conductor T4 of the multilayer group G7 connects the fourth through-hole conductors T4 of the multilayer groups G6 and G8 adjacent to each other in the stacking direction, and is electrically connected to the fourth external electrode E4. Therefore, the fourth through-hole conductor T4 is disposed above the fourth external electrode E4 in a planar perspective view.

[0049] (Stacking group G8) The stacking group G8 includes a metal magnetic layer ML, an insulator (not shown) provided on the metal magnetic layer ML, a first coil conductor CD1 that forms part of a first coil C1 formed on the insulator, and a second through-hole conductor T2, a third through-hole conductor T3, and a fourth through-hole conductor T4 provided on the metal magnetic layer ML.

[0050] The first coil conductor CD1 of the multilayer group G8 constitutes another winding of the first coil C1. More specifically, the second coil conductor CD2 is disposed on an insulator formed along the approximate outer periphery of the metal magnetic layer ML in the thickness direction of the metal magnetic layer ML. One end of the first coil conductor CD1 is connected to the first coil conductor CD1 provided on the insulator of the metal magnetic layer ML of the multilayer group G6, and the other end of the first coil conductor CD1 is provided with a first through-hole conductor (not shown) for electrical connection to the first external electrode E1.

[0051] The second through-hole conductors T2 of the multilayer group G8 connect the second through-hole conductors T2 of the multilayer groups G7 and G9 adjacent to each other in the stacking direction, and are electrically connected to the second external electrode E2. The second through-hole conductors T2 may also be disposed at corners of the metal magnetic layers ML located on the second external electrode E2.

[0052] The third through-hole conductors T3 of the multilayer group G8 connect the third through-hole conductors T3 of the multilayer groups G7 and G9 adjacent to each other in the stacking direction, and are electrically connected to the third external electrode E3. The third through-hole conductors T3 may also be disposed at corners of the metal magnetic layers ML located on the third external electrode E3.

[0053] The fourth through-hole conductor T4 of the multilayer group G8 connects the fourth through-hole conductors T4 of the multilayer groups G7 and G9 adjacent to each other in the stacking direction, and is electrically connected to the fourth external electrode E4. The fourth through-hole conductor T4 may also be disposed at a corner of the metal magnetic layer ML located on the fourth external electrode E4.

[0054] (Multilayer group G9) In the multilayer group G9, a first through-hole conductor T1, a second through-hole conductor T2, a third through-hole conductor T3, and a fourth through-hole conductor T4 are provided at the corners of the metal magnetic layers ML. The areas of the first through-hole conductors T1 to the fourth through-hole conductors T4 of the multilayer groups G1 to G9 in a plan view from the stacking direction are substantially the same.

[0055] (Multilayer group G10) In the multilayer group G10, first to fourth through-hole conductors T1 to T4 having larger planar areas than the first to fourth through-hole conductors of the multilayer group G9 are provided at the corners of the metal magnetic layers ML. The first to fourth through-hole conductors T1 to T4 are used as base electrodes for the external electrodes E1 to E4. By making the planar areas of the first to fourth through-hole conductors of the multilayer group G10 larger than the planar areas of the first to fourth through-hole conductors of the multilayer group G9, strength during mounting can be improved.

[0056] The thickness of the first coil conductor CD1 and the second coil conductor CD2 in each lamination group may be the same. The first coil conductor CD1 and the second coil conductor CD2 may be made of, for example, a metal conductor such as Ag or Cu. The first coil conductor CD1 and the second coil conductor CD2 may be formed, for example, by printing a conductive paste on the metal magnetic layer ML.

[0057] Examples of materials for the first through-hole conductors T1 to T4 and the via conductors include metal conductors such as Ag and Cu. Furthermore, the materials for the first through-hole conductors T1 to T4 and the via conductors may be the same as or different from the materials used for the first coil conductor CD1 and the second coil conductor CD2. The through-hole conductors and via conductors may be formed, for example, by forming through-holes in the metal magnetic layer ML and printing a conductive paste into the through-holes. Alternatively, the metal magnetic layer ML may be formed by printing the conductive paste and then printing the conductive paste on the outside of the conductive paste.

[0058] As described above, when the element body 10 has a multilayer structure including the multilayer groups G1 to G10, the degree of freedom in designing the multilayer inductor 1 is increased. For example, when manufacturing a multilayer inductor 1 including the first external electrode E1, the second external electrode E2, the third external electrode E3, and the fourth external electrode E4 on the bottom surface (first main surface 11) of the element body 10, it becomes easier to extend the first coil C1 and the second coil C2 to the bottom surface side. Note that the multilayer structure including the above-described multilayer groups G1 to G10 may be formed by sequentially printing (e.g., screen printing) the material constituting the metal magnetic layer ML, the material constituting the insulator I, the material constituting the coil conductor CD, and the material constituting the through-hole conductors and via conductors from the second main surface 12 side or the first main surface 11 side of the element body 10. In this case, printing may be repeated for each of the multilayer groups G1 to G10 until the metal magnetic layer ML, the insulator I, the coil conductors, the through-hole conductors, and the via conductors reach the desired thickness.

[0059] The metal magnetic layer ML includes metal magnetic particles MP (see FIG. 4) made of a magnetic material. The metal magnetic particles MP include Fe (iron). More specifically, they may be Fe particles or Fe alloy particles. Examples of the Fe alloy include an Fe-Si alloy, an Fe-Si-Cr (chromium) alloy, an Fe-Si-Al (aluminum) alloy, an Fe-Si-B (boron)-P (phosphorus)-Cu (copper)-C (carbon) alloy, and an Fe-Si-B-Nb (niobium)-Cu alloy. The metal magnetic particles MP may also contain impurities such as Cr, Mn (manganese), Cu, Ni (nickel), P, S (sulfur), or Co (cobalt) that are not intended during manufacturing. The metal magnetic particles MP may also be contained in a magnetic paste, as will be described in detail in the description of the manufacturing method. Therefore, the metal magnetic particles may contain elements (e.g., Cr, Al, Li (lithium), Zn (zinc)) that are more easily oxidized than the Fe added when the magnetic paste is prepared. By including Si in the metal magnetic particles MP, oxidation of the Fe element contained in the metal magnetic particles is suppressed, thereby further increasing the magnetic permeability of the laminated inductor 1.

[0060] The surfaces of the metal magnetic particles MP made of the above-mentioned metal magnetic material may be covered with an insulating coating (not shown). As used herein, "insulating" refers to a volume resistivity of 1 MΩcm or more. Covering the surfaces of the metal magnetic particles MP with an insulating coating can enhance the insulation between the metal magnetic particles MP. Methods for forming the insulating coating on the surfaces of the metal magnetic particles MP include the sol-gel method and the mechanochemical method. The material constituting the insulating coating may be an oxide of P, Si, or the like. The insulating coating may also be an oxide film formed by oxidizing the surfaces of the metal magnetic particles MP. The thickness of the insulating coating may be preferably 1 nm or more and 50 nm or less, more preferably 1 nm or more and 30 nm or less, and even more preferably 1 nm or more and 20 nm or less. For example, a cross section obtained by polishing an inductor sample can be photographed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the thickness of the insulating coating covering the surfaces of the metal magnetic particles can be measured from the obtained SEM image.

[0061] The average particle size of the metal magnetic particles MP in the metal magnetic layer ML is preferably greater than 2 μm and less than 30 μm, more preferably greater than 2 μm and less than 20 μm, and even more preferably greater than 2 μm and less than 10 μm. The average particle size of the metal magnetic particles MP in the metal magnetic layer ML can be measured using the procedure described below. An inductor sample is cut to obtain a cross section. Specifically, the sample cross section is obtained by cutting the sample through the center of the element body perpendicular to the mounting surface and end surface of the element body. Multiple (e.g., five) regions (e.g., 130 μm x 100 μm) of the obtained cross section are photographed using an SEM. The obtained SEM images are analyzed using image analysis software (e.g., the image analysis software "Win R00F" (manufactured by Mitani Corporation)) to determine the circle-equivalent diameter of the metal magnetic particles. The average of the obtained circle-equivalent diameters is defined as the average particle size of the metal magnetic particles. Note that the term "average particle size" as used herein may refer to the average particle size D50 (the particle size corresponding to a cumulative percentage of 50% on a volume basis).

[0062] When forming the element body 10, a heat treatment is performed. In this case, the metal magnetic grains MP contained in the element body 10 have an oxide film on their surfaces. This oxide film originates from the metal magnetic grains MP and is formed by the heat treatment. In the element body 10, adjacent metal magnetic grains MP are bonded to each other via the oxide film.

[0063] 3 and 4, in the element body 10, insulators I are arranged between the coil conductors CD in the stacking direction. Specifically, as described above, the insulators I may be arranged in the stacking groups G2 to G7 (see FIG. 2). The insulators I have contact portions I1 with the coil conductors CD that extend in a direction intersecting the stacking direction, and protruding portions I2 that protrude outward from both sides of the coil conductors CD in the direction intersecting the stacking direction.

[0064] The term "contact portion" as used herein refers to a region where the coil conductor CD and the insulator I are in contact with each other. Specifically, as shown in Figures 3 and 4, this refers to a region located inside the regions of the coil conductor CD where both ends in the direction perpendicular to the stacking direction are thinner, and inside the outermost non-contact position P1 in the direction perpendicular to the stacking direction where the coil conductor CD and the insulator I are no longer in contact with each other. Whether the coil conductor CD and the insulator I are in contact with each other is determined by observing them with an SEM at a magnification of 1000x so that the coil conductor CD and the insulator I are in the field of view.

[0065] Furthermore, the "protruding portion" referred to in this specification is provided at both ends of the above-mentioned contact portion I1 in the direction perpendicular to the stacking direction. Specifically, it refers not only to the tips protruding from both ends of the coil conductor in the direction perpendicular to the stacking direction, but also to the region where the coil conductor CD and the insulator I are no longer in contact with each other, as shown in Fig. 4, and which includes the outermost non-contact position P1 in the direction perpendicular to the stacking direction as its starting point and extends outward from the coil conductor CD.

[0066] A characteristic structure of the inductor of this embodiment is that the thickness of the protruding portion I2 is thinner (or smaller) than the thickness of the contact portion I1 over the entire area. The thicknesses of the protruding portion I2 and the contact portion I1 can be measured by the procedure described below.

[0067] First, the inductor sample is placed vertically and the periphery of the sample is hardened with resin. The LT plane is exposed. The sample is polished to a depth of approximately half in the W direction using a polishing machine, exposing a cross section parallel to the LT plane. After polishing, the polished surface is processed by ion milling (Ion Milling System IM4000, manufactured by Hitachi High-Tech Corporation) to remove any sagging of the internal conductor caused by polishing. The cross section is photographed at 1000x magnification using an SEM (SEM system manufactured by JEOL Ltd., model number JSM-7900F) so that the coil conductor CD and insulator I are within the field of view.

[0068] The thickness of the contact portion I1 is calculated from the average thickness of three locations: the central portion O1 where the insulator I and the coil conductor CD are in contact, and the intermediate positions O2 and O2 between the central portion O1 and the non-contact position P1, as shown in Figure 4.

[0069] As shown in Figure 4, the thickness of the protruding portion I2 is calculated from the average of the thicknesses measured at three locations: an intermediate position P2 between the non-contact position P1 and the tip PE of the protruding portion I2, an intermediate position P3 between the tip PE and the intermediate position P2, and an intermediate position P4 between the non-contact position P1 and the intermediate position P2, in addition to measuring the thickness at similar positions on the protruding portion I2 on the other side of the contact portion I1.

[0070] As described above, the present disclosure uses the average thickness of the contact portion I1 and the average thickness of the protruding portion I2 as criteria for judgment, and by making the thickness of the protruding portion I2 thinner than the thickness of the contact portion I1, it is possible to make it difficult for the protruding portion I2 of the insulator I to reduce the flow of magnetic flux, while ensuring insulation between the coil conductors CD by the insulator I. Furthermore, it is preferable that the criteria for the average thickness of the contact portion I1 and the average thickness of the protruding portion I2 be satisfied by 50%, and more preferably 80%, or more of the insulator I and the coil conductor CD in the cross section of Figure 3.

[0071] More specifically, the thickness of the insulator I is determined such that the thickness of both ends of the insulator I in the direction perpendicular to the stacking direction is thinner than the thickness of the center of the insulator I in the direction perpendicular to the stacking direction. When the thickness of the insulator I satisfies the above-described relationship, it is possible to ensure insulation between the coil conductors CD by the insulator I while making it difficult for the flow of magnetic flux to be reduced by both ends of the insulator I.

[0072] In a preferred embodiment of thinning the protruding portion I2, a recess RC may be provided on the surface of the protruding portion I2, and metal magnetic particles MP may be arranged in the recess RC. Specifically, as shown in FIG. 4 , the metal magnetic particles MP may enter the recess RC on the surface of the protruding portion I2. The reason why the metal magnetic particles MP enter the recess RC on the surface of the protruding portion I2 will be described in detail in the manufacturing method of the laminated inductor 1 described below. According to this embodiment of thinning the protruding portion I2, it is possible to make it less likely that the protruding portion I2 will cause a decrease in magnetic permeability.

[0073] The size of the recesses RC is equal to or larger than the grain size of the metal magnetic particles. By making the size of the recesses RC equal to or larger than the grain size of the metal magnetic particles, the metal magnetic particles MP can be properly inserted therein.

[0074] The insulator I may be a material having higher insulating properties and lower magnetic permeability than the magnetic material formed by laminating the metal magnetic layers ML. Because the insulator I is such a material, it is possible to ensure the insulating properties while making it more difficult for the magnetic permeability to decrease.

[0075] As a more specific characteristic of the insulator I, the insulator I may have non-magnetic properties. In this specification, the term "non-magnetic properties" refers to properties in which the relative permeability is 1. Even with such a material, the thickness of the protruding portion I2 of the insulator I is thinner than the thickness of the contact portion I1, making it possible to make it more difficult for the magnetic permeability to decrease.

[0076] The material of the insulator I in this embodiment may include at least one selected from the group consisting of non-magnetic ferrite, alumina, glass, and zirconia. By using such a material, the insulation between the coil conductors CD can be further improved.

[0077] A first coil C1 and a second coil C2 are provided inside the element body 10. The first coil C1 and the second coil C2 may be magnetically coupled. For example, the coupling coefficient between the first coil C1 and the second coil C2 is 0.1 or more and 0.8 or less. Note that the element body 10 may be provided with two coils including only the first coil C1 and the second coil C2, or may be provided with three or more coils including the first coil C1 and the second coil C2.

[0078] -First Coil- The first coil C1 is provided inside the element body 10. The first coil C1 includes a plurality of first coil conductors CD1 connected to each other by via conductors V (see FIG. 3), a first through-hole conductor T1, and a second through-hole conductor T2.

[0079] As described above, the multiple first coil conductors CD1 are arranged in two stacking groups (stack groups G6 and G8 (see FIG. 2)). As a result, the first coil C1 has a two-layer structure with 1.75 turns. Furthermore, the length in the stacking direction of the via conductors V connecting the multiple first coil conductors CD1 together may be shorter than the length of the first through-hole conductors T1 or the length of the second through-hole conductors T2.

[0080] The first through-hole conductor T1 electrically connects the first external electrode E1 to the end of the first coil conductor CD1 of the first coil C1 that is closest to the bottom surface (first main surface 11) of the element body 10. The first through-hole conductor T1 extends along the stacking direction of the metal magnetic layers (e.g., the height direction T of the element body). The first through-hole conductor T1 may have a stacked structure.

[0081] The second through-hole conductor T2 electrically connects the other end of the first coil C1 and the second external electrode E2. The second through-hole conductor T2 extends along the stacking direction of the metal magnetic layers (e.g., the height direction T of the element body). The second through-hole conductor T2 may have a stacked structure.

[0082] - Second Coil - The second coil C2 may be provided above the first coil C1 in the stacking direction inside the element body 10. The second coil C2 may include a plurality of second coil conductors CD2 connected to each other by via conductors (not shown), a third through-hole conductor T3, and a fourth through-hole conductor T4.

[0083] As described above, the multiple second coil conductors CD2 may be arranged in two stacking groups (stack groups G2 and G4 (see FIG. 2)). This allows the second coil C2 to have a two-layer structure with 1.75 turns. Furthermore, the length in the stacking direction of the via conductors (not shown) connecting the multiple second coil conductors CD2 together may be shorter than the length of the third through-hole conductors T3 or the length of the fourth through-hole conductors T4.

[0084] The third through-hole conductor T3 may electrically connect the end of the second winding portion of the second coil C2 that is closest to the bottom surface (first main surface 11) of the element body 10 to the third external electrode E3. The third through-hole conductor T3 may extend along the stacking direction of the metal magnetic layers (e.g., the height direction T of the element body). The third through-hole conductor T3 may have a stacked structure.

[0085] The fourth through-hole conductor T4 may connect the other end of the second coil C2 and the fourth external electrode E4. The fourth through-hole conductor T4 may extend along the stacking direction of the metal magnetic layers (e.g., the height direction T of the element body). The fourth through-hole conductor T4 may have a stacked structure.

[0086] As described above, in the laminated inductor 1 of this embodiment, in the insulator I arranged between the coil conductors CD in the stacking direction, the thickness of the protruding portion I2 that protrudes outward from both sides of the coil conductor CD is thinner than the thickness of the contact portion I1 that contacts the coil conductor CD, making it less likely that the insulator I will reduce the flow of magnetic flux, and reducing the decrease in magnetic permeability more than in the prior art.

[0087] In a preferred embodiment of the laminated inductor 1, the thickness D1 of both ends of the coil conductor CD constituting the first coil C1 or the second coil C2 in a direction intersecting the lamination direction may be thinner than the thickness D2 of the central portion of the coil conductor CD in a direction intersecting the lamination direction (see Figure 3).

[0088] Here, the thickness D2 of the central portion of the coil conductor CD may be calculated from the average of the thicknesses at three locations: the central portion and any two locations near the central portion. Furthermore, the thickness D1 of the both end portions of the coil conductor CD may be calculated from the average of the thicknesses at three locations: the tip position of the coil conductor CD and any two locations near the tip. Note that "neighborhood" refers to a region within 10% of the length of the coil conductor CD from the central portion in a direction intersecting the stacking direction. The thickness of the coil conductor CD may be measured based on an SEM image.

[0089] When the thickness of the coil conductor CD satisfies the above-mentioned relationship, the coil conductor CD can appropriately form a magnetic flux.

[0090] -External Electrodes- The external electrodes are provided on the bottom surface of the element body 10. The external electrodes include a first external electrode E1, a second external electrode E2, a third external electrode E3, and a fourth external electrode E4. The first external electrode E1 and the second external electrode E2 are electrically connected to the first coil C1. The third external electrode E3 and the fourth external electrode E4 are electrically connected to the second coil C2. Providing external electrodes on the bottom surface (first main surface 11) of the element body 10 allows the laminated inductor 1 to be properly mounted on a mounting board or the like.

[0091] The external electrodes may be made of various materials, such as copper (Cu) or nickel (Ni). The external electrodes may be formed as a single layer or may have a laminated structure of two or more layers. The external electrodes may be formed by any method, but may be plated electrodes formed by plating (e.g., electroless plating).

[0092] <Laminated Inductor of Second Embodiment> A second embodiment of the laminated inductor of the present disclosure will be described with reference to Figures 6 and 7. Figure 6 is a cross-sectional view of the laminated inductor of the second embodiment, and Figure 7 is an enlarged cross-sectional view of a main portion of Figure 6. The laminated inductor of the second embodiment differs from the laminated inductor of the first embodiment, which uses a non-magnetic material for the insulator I, in that metal magnetic particles are used for the insulator I. The other configurations are as described for the laminated inductor 1 above, so the following description will focus on the differences from the laminated inductor of the first embodiment.

[0093] In the laminated inductor 1 of this embodiment, the insulator I contains metal magnetic particles, and the average particle size of the metal magnetic particles contained in the insulator I is smaller than the average particle size of the metal magnetic particles contained in the magnetic material M.

[0094] Specifically, as described above, the average particle size of the metal magnetic particles contained in the magnetic material M is greater than 2 μm and less than 30 μm, more preferably greater than 2 μm and less than 20 μm, and even more preferably greater than 2 μm and less than 10 μm. On the other hand, the average particle size of the metal magnetic particles contained in the insulator I is less than 2 μm. It is known that metal magnetic particles generally have higher insulation resistance when their average particle size is smaller.

[0095] In this way, when forming the magnetic body M and the insulator I, by using metal magnetic particles with a relatively large average particle size and metal magnetic particles with a relatively small average particle size, the metal magnetic particles with a small average particle size can easily penetrate into the metal magnetic particles with a large average particle size. Therefore, by having the insulator I penetrate the magnetic body M that constitutes the base body 10 and reducing the thickness of both ends of the insulator I, when reducing the flow of magnetic flux at both ends of the insulator I, the particle size of the metal magnetic particles in the insulator I can be reduced and the insulation resistance can be increased. As a result, the insulation of the coil conductor can be ensured even when the magnetic body M of the base body 10 is penetrated into the insulator I.

[0096] The boundary between metal magnetic particles having a relatively large average particle size and metal magnetic particles having a relatively small average particle size can be measured by the procedure described below.

[0097] First, the inductor sample is placed vertically and the periphery of the sample is hardened with resin. The LT plane is exposed. The sample is polished to a depth of approximately half in the W direction using a polishing machine, exposing a cross section parallel to the LT plane. After polishing, the polished surface is processed by ion milling (Ion Milling System IM4000, manufactured by Hitachi High-Tech Corporation) to remove any sagging of the internal conductor caused by polishing. The cross section is photographed at 1000x magnification using an SEM (SEM system manufactured by JEOL Ltd., model number JSM-7900F) so that the coil conductor CD and insulator I are within the field of view.

[0098] The SEM image is loaded into the image analysis software "Win R00F" (Mitani Shoji Co., Ltd.), and the circle-equivalent diameter of the metal magnetic particles near the end between the stacked coil conductors in the direction perpendicular to the stacking direction of the coil conductors is determined. This identifies the positional relationship between the areas with large particle diameters of the metal magnetic powder and the areas with small particle diameters of the metal magnetic powder. Then, the boundary BL between the areas with large particle diameters of the metal magnetic powder and the areas with small particle diameters of the metal magnetic powder is drawn as shown in Figure 7.

[0099] Then, the thickness of the protruding portion I2 and the thickness of the contact portion I1 are measured using the method described above. In the laminated inductor 1 of this embodiment, the thickness of the protruding portion I2 is also thinner than the thickness of the contact portion I1, so that the protruding portion I2 of the insulator I is less likely to reduce the flow of magnetic flux, and the insulator I can ensure insulation between the coil conductors CD.

[0100] In the insulator I of this embodiment, the material of the metal magnetic particles contained in the insulator I contains Fe. That is, the insulator I is a magnetic material, unlike the first embodiment. Therefore, it is less likely to cause a reduction in the flow of magnetic flux, and the decrease in magnetic permeability can be further reduced than in the first embodiment. Note that the material of the metal magnetic particles contained in the insulator I may be the same material as the magnetic material M, or may be a material different from the magnetic material.

[0101] <Method for Manufacturing a Laminated Inductor> Next, a method for manufacturing a laminated inductor according to the present disclosure will be described with reference to Figures 8(A) to 8(G). The method for manufacturing a laminated inductor according to the present disclosure may include an element body forming step.

[0102] -Element Body Forming Process- The element body forming process includes a laminate forming process for forming the laminate that constitutes element body 10, and a firing process for firing the laminate.

[0103] Laminate Formation Process First, the metal magnetic layer ML is prepared. The metal magnetic layer ML is prepared by printing and applying a magnetic paste containing metal magnetic particles MP with an average particle size of preferably 1 μm to 30 μm, more preferably 1 μm to 20 μm, and even more preferably 1 μm to 10 μm. Then, a conductive paste that will become the coil conductor CD is printed on the prepared metal magnetic layer ML to form one laminate group (see FIG. 8A). As an example, the laminate group G8 shown in FIG. 2 is formed.

[0104] A magnetic paste containing the above-mentioned metal magnetic particles MP is applied over the formed laminate group (see FIG. 8(B)). The magnetic paste is applied by printing a metal magnetic layer ML so that the widthwise end portions Ce of the upper surface of the coil conductor CD are covered and the central portion Cc of the upper surface of the coil conductor is exposed.

[0105] Next, an insulator I is printed across the metal magnetic layer ML covering the exposed central portion Cc in the width direction of the top surface of the coil conductor CD and the end portions Ce of the top surface of the coil conductor CD (see FIG. 8(C)). At this time, the insulator I is printed so that the thickness of the central portion Ic in the width direction of the top surface of the coil conductor CD is thicker and the thickness of the end portions Ie in the width direction of the top surface of the coil conductor CD is thinner, and the top surface of the insulator I located at the central portion Ic in the width direction of the top surface of the coil conductor CD protrudes more than the top surfaces of the insulator I located at the end portions Ie in the width direction of the top surface of the coil conductor CD. Note that the top surface of the central portion Ic may be flat and not protrude more than the top surfaces of the end portions Ie.

[0106] Next, magnetic paste is applied around the insulator I to form, for example, the portions of the lamination group G7 and the lamination group G6 on the lamination group G8 shown in Fig. 2 other than the coil conductor (see Fig. 8(D)). Furthermore, conductive paste that will become the coil conductor CD is printed on the formed lamination group (see Fig. 8(E)), and magnetic paste that will become the metal magnetic layer ML is printed around the conductive paste (see Fig. 8(F)). These steps are repeated to stack the lamination groups shown in Fig. 2.

[0107] After stacking the multilayer groups, the multilayer groups are compressed in the stacking direction (see FIG. 8(G)). This compression compresses the insulators I, narrowing the gap between the coil conductors CD and forming a laminate in which the insulators I penetrate into the magnetic material M. This allows the thickness of the above-mentioned protruding portions I2 to be thinner than the thickness of the contact portions I1 in the multilayer inductor 1 of the present disclosure, making it less likely that the protruding portions I2 of the insulators I will reduce the flow of magnetic flux, while ensuring insulation between the coil conductors CD with the insulators I.

[0108] Heat Treatment Step The formed laminate is degreased to remove the binders contained in the magnetic paste and conductive paste, and then heat treated. The heat treatment forms an oxide film, bonding the metal magnetic particles through the oxide film. The heat treatment temperature may be, for example, about 700°C. Furthermore, to increase the strength of the laminate, the laminate may be impregnated with a resin and cured. While epoxy resin is used as the resin impregnated into the laminate, one or more resins selected from the group consisting of phenolic resin, polyester resin, polyimide resin, polyolefin resin, silicone resin, acrylic resin, polyvinyl butyral resin, cellulose resin, alkyd resin, etc. may also be used. Through the above steps, an element body of the laminated inductor of the present disclosure is formed.

[0109] After forming the element body 10 through the above-described process, the laminated inductor 1 of the present disclosure can be manufactured by forming external electrodes E1 to E4 on the mounting surface (first main surface 11) of the element body 10 using a well-known electrode formation method.

[0110] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. For example, a method for making the thickness of the protruding portion of the insulator thinner than the thickness of the contact portion may be employed by forming the insulator with a higher resin content in the insulator paste than in the magnetic paste containing metal magnetic particles, thereby reducing the content of nonmagnetic material ( FIG. 4 ) or metal magnetic powder in the insulator paste. By employing such a method, when the laminated group is compressed in the stacking direction, the insulator is compressed in the compression direction, and the magnetic powder of the laminate penetrates into the protruding portions at both ends of the insulator. During degreasing in the heat treatment process, the magnetic powder of the laminate further penetrates into the protruding portions at both ends of the insulator, thereby further reducing the thickness of both ends of the insulator. Furthermore, the insulator I between the first coil C1 and the second coil C2 may be configured to be formed around the entire circumference of the coil and have the same area as the metal magnetic layer. Furthermore, it is not necessary to provide an insulator I between the first coil C1 and the second coil C2, but if an insulator I is provided between the first coil C1 and the second coil C2, the withstand voltage between the coils can be improved and the coupling between the coils can be adjusted.

[0111] Furthermore, the technical scope of the present invention is not interpreted solely by the above-described embodiments, but is defined based on the claims, and includes all modifications within the scope and meaning equivalent to the claims.

[0112] The inductor of the present disclosure includes the following aspects. <1> A laminated inductor comprising an element body including a magnetic body formed by stacking metal magnetic layers containing metal magnetic particles, a coil disposed inside the magnetic body and wound with a coil conductor, and an insulator disposed between the coil conductors in the stacking direction, wherein the insulator has a contact portion with the coil conductor extending in a direction intersecting the stacking direction, and protruding portions provided on both ends of the contact portion in a direction perpendicular to the stacking direction and extending outward on both sides of the coil conductor in the direction perpendicular to the stacking direction, the protruding portions having a thickness thinner than that of the contact portion. <2> The laminated inductor according to <1>, wherein a recess is provided on a surface of the protruding portion, and the metal magnetic particles are disposed in the recess. <3> The laminated inductor according to <1> or <2>, wherein the material of the metal magnetic particles contained in the magnetic body contains Fe and Si. <4> The laminated inductor according to any one of <1> to <3>, wherein the insulator is a material with higher insulating properties and lower magnetic permeability than the magnetic body. <5> The laminated inductor according to any one of <1> to <4>, wherein the insulator is nonmagnetic. <6> The laminated inductor according to <5>, wherein the material of the nonmagnetic metal magnetic particles contained in the insulator includes at least one selected from the group consisting of nonmagnetic ferrite, alumina, glass, and zirconia. <7> The laminated inductor according to any one of <1> to <6>, wherein the insulator contains metal magnetic particles, and the average particle size of the metal magnetic particles contained in the insulator is smaller than the average particle size of the metal magnetic particles contained in the magnetic body. <8> The laminated inductor according to <7>, wherein the metal magnetic particles contained in the insulator are metal magnetic powder containing Fe or metal magnetic powder containing Fe and Si. <9> The laminated inductor according to any one of <1> to <8>, wherein the thickness of both end portions of the insulator in a direction intersecting the stacking direction is thinner than the thickness of the central portion of the insulator in a direction intersecting the stacking direction.<10> The laminated inductor according to any one of <1> to <9>, wherein the thickness of each of the coil conductors at both ends in a direction perpendicular to the lamination direction is thinner than the thickness of each of the coil conductors at a center portion in the direction perpendicular to the lamination direction.

[0113] The present disclosure can be used for a laminated inductor that ensures insulation properties while further reducing the decrease in magnetic permeability.

[0114] 1 laminated inductor 10 element body 11 first main surface 12 second main surface 13 first end surface 14 second end surface 15 first side surface 16 second side surface C coil C1 first coil C2 second coil C3 third coil C4 fourth coil CD coil conductor CD1 first coil conductor CD2 second coil conductor E1 first external electrode E2 second external electrode E3 third external electrode E4 fourth external electrode G1 to G10 laminated group I insulator I1 contact portion I2 protruding portion M magnetic material MP metal magnetic particle ML metal magnetic layer RC recess T1 first through-hole conductor T2 second through-hole conductor T3 third through-hole conductor T4 fourth through-hole conductor V via conductor D1 thickness of both ends of coil conductor D2 thickness of both ends of coil conductor Cc center portion of coil Ce End of coil BL Boundary

Claims

1. A laminated inductor comprising an element having a magnetic body formed by stacking metal magnetic layers containing metal magnetic particles, a coil disposed inside the magnetic body and wound with a coil conductor, and an insulator disposed between the coil conductors in the stacking direction, wherein the insulator has a contact portion with the coil conductor extending along a direction intersecting the stacking direction, and protruding portions provided on both ends in a direction perpendicular to the stacking direction of the contact portion and extending outward on both sides of the coil conductor in the direction perpendicular to the stacking direction, and the thickness of the protruding portions is thinner than the thickness of the contact portions.

2. The laminated inductor according to claim 1, wherein a recess is provided on the surface of said protruding portion, and said metal magnetic particles are disposed in said recess.

3. A laminated inductor according to claim 1 or 2, wherein the material of the metallic magnetic particles contained in the magnetic body contains Fe and Si.

4. The laminated inductor according to any one of claims 1 to 3, wherein the insulator is a material having higher insulating properties and lower magnetic permeability than the magnetic material.

5. The laminated inductor according to any one of claims 1 to 4, wherein the insulator is non-magnetic.

6. The laminated inductor according to claim 5, wherein the material of the non-magnetic metal magnetic particles contained in the insulator includes at least one selected from the group consisting of non-magnetic ferrite, alumina, glass and zirconia.

7. A laminated inductor as claimed in any one of claims 1 to 6, wherein the insulator contains metal magnetic particles, and the average particle size of the metal magnetic particles contained in the insulator is smaller than the average particle size of the metal magnetic particles contained in the magnetic body.

8. The laminated inductor according to claim 7, wherein the metallic magnetic particles contained in the insulator are metallic magnetic powder containing Fe or metallic magnetic powder containing Fe and Si.

9. A laminated inductor as claimed in any one of claims 1 to 8, wherein the thickness of the insulator at both ends in a direction perpendicular to the lamination direction is thinner than the thickness of the insulator at a central portion in the direction perpendicular to the lamination direction.

10. A laminated inductor as claimed in any one of claims 1 to 9, wherein the thickness of both ends of the coil conductor in a direction perpendicular to the lamination direction is thinner than the thickness of the center part of the coil conductor in the direction perpendicular to the lamination direction.

Images