Coil element and method for manufacturing same

Abstract

This coil element is provided with a base body comprising: a magnetic body in which metal magnetic layers containing first metal magnetic particles are stacked; internal electrodes disposed inside the magnetic body and wound around the internal conductors; and oxide layers, each containing second metal magnetic particles and disposed between the internal conductors adjacent to each other in the stacking direction. The second metal magnetic particles have a higher oxygen content than the first metal magnetic particles.

Description

Coil element and manufacturing method thereof

[0001] The present disclosure relates to a coil element and a method for manufacturing the same.

[0002] Patent Document 1 discloses a coil-type electronic component having a coil inside or on the surface of an element body. In this electronic component, the element body is composed of a group of particles of a soft magnetic alloy containing iron, silicon, and elements that are more easily oxidized than iron, and an oxide layer is formed on the surface of each soft magnetic alloy particle by oxidizing the particle. The oxide layer contains a larger amount of elements that are more easily oxidized than iron compared to the alloy particles, and the particles are bonded to each other via the oxide layer.

[0003] JP 2011-249774 A

[0004] However, as a result of intensive study by the present inventor, it has been found that there is room for improvement in the DC bias characteristics of the coil component of Patent Document 1. Furthermore, as a result of intensive study by the present inventor, it has been found that structural defects (cracks) occur between the internal conductor and the element body, and there is room for improvement in the adhesive strength between the internal conductor and the element body.

[0005] The present disclosure has been made in view of these problems. That is, a primary object of the present disclosure is at least one of providing a coil element in which the DC bias characteristics are improved by reducing the magnetic permeability of the metal magnetic layer disposed between the internal conductors of the coil, and providing a coil element in which the bonding strength between the internal conductors and the base body is improved to suppress the occurrence of structural defects (cracks). Another object of the present disclosure is to provide a method for manufacturing a coil element capable of manufacturing the above-mentioned coil element.

[0006] A coil element according to one embodiment of the present disclosure comprises a base body having a magnetic body in which metal magnetic layers containing first metal magnetic particles are stacked, an internal electrode disposed inside the magnetic body and wound around an internal conductor, and a peroxide layer disposed between the internal electrodes adjacent in the stacking direction and containing second metal magnetic particles, wherein the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0007] A method for manufacturing a coil element according to yet another embodiment of the present disclosure includes producing a coil element by firing a laminate obtained by stacking a first metal magnetic paste containing first metal magnetic particles, a second metal magnetic paste containing second metal magnetic particles, and a conductive paste containing conductive powder, wherein the second metal magnetic paste is disposed between adjacent conductive pastes in the stacking direction, and the coil element comprises an element body having a magnetic body in which metal magnetic layers containing first metal magnetic particles are laminated, an internal electrode disposed inside the magnetic body and winding an internal conductor, and a peroxide layer disposed between adjacent internal conductors in the stacking direction and containing second metal magnetic particles, wherein the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0008] According to a coil element of one aspect of the present disclosure, it is possible to improve DC bias characteristics by reducing the magnetic permeability of the metal magnetic layer disposed between the internal conductors of the coil, and to suppress the occurrence of structural defects (cracks). Also, according to a manufacturing method of a coil element of another aspect of the present disclosure, such a coil element can be manufactured.

[0009] FIG. 1 is a perspective view of a coil element according to the present disclosure. FIG. 2 is an exploded perspective view of a coil element according to a second embodiment of the present disclosure. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1 as viewed from the arrow direction. FIG. 4 is an enlarged cross-sectional view of a coil element according to a third embodiment of the present disclosure. FIG. 5 is an enlarged cross-sectional view of a coil element according to a modified example of the third embodiment of the present disclosure. FIG. 6 is an SEM image of a cross section of a coil element according to the third embodiment of the present disclosure. FIG. 7 is an image obtained by mapping the presence of oxygen elements in FIG. 6. FIG. 8 is an exploded perspective view of a coil element according to a fourth embodiment of the present disclosure. FIG. 9 is a cross-sectional view of FIG. 8. FIG. 10 is an enlarged cross-sectional view (enlarged cross-sectional view of FIG. 9) of a coil element according to the fourth embodiment of the present disclosure. FIG. 11 is an enlarged cross-sectional view of a conventional coil element. FIG. 12 is an SEM image of a cross section of a conventional coil element (an SEM image of the vicinity of the interface between the internal conductor and the magnetic material). FIG. 13 is an SEM image of a coil element according to the fourth embodiment of the present disclosure.

[0010] The coil element according to 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.

[0011] 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 of substantial equivalence, for example, a range including 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."

[0012] 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, or form. 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.

[0013] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, scale, etc. may differ from those of the actual product.

[0014] Various numerical ranges mentioned in this specification are intended to include the lower and upper limit values ​​themselves, unless otherwise specified, such as "less than." That is, for example, a numerical range such as 15 to 35% by volume is interpreted as including the lower limit of 15% by volume and the upper limit of 35% by volume.

[0015] <First embodiment: coil element> The first embodiment relates to a coil element. The coil element according to the first embodiment includes an element body having: a magnetic body formed by laminating metal magnetic layers containing first metal magnetic particles, an internal electrode disposed inside the magnetic body and winding an internal conductor, and a peroxide layer disposed between adjacent internal conductors in the lamination direction and containing second metal magnetic particles, wherein the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0016] The coil element according to the first embodiment can at least one of improve the DC bias characteristics by reducing the magnetic permeability of the metal magnetic layer arranged between the internal conductors of the coil, and suppress the occurrence of structural defects (cracks).

[0017] A method for manufacturing a coil element according to the first embodiment comprises producing a coil element by firing a laminate obtained by laminating a first metal magnetic paste containing first metal magnetic particles, a second metal magnetic paste containing second metal magnetic particles, and a conductive paste containing conductive powder, wherein the second metal magnetic paste is disposed between adjacent conductive pastes in the lamination direction, and the coil element comprises a base body having a magnetic body in which metal magnetic layers containing first metal magnetic particles are laminated, an internal electrode disposed inside the magnetic body and winding an internal conductor, and a peroxide layer disposed between adjacent internal conductors in the lamination direction and containing second metal magnetic particles, and the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0018] <Second Embodiment: Coil Element> The second embodiment relates to a coil element. The second embodiment is particularly characterized by the fact that, in the first embodiment, "the metal magnetic particles contain an Fe—Si alloy." The coil element according to the second embodiment includes an element body having a magnetic body in which metal magnetic layers containing first metal magnetic particles are stacked, an internal electrode disposed inside the magnetic body and winding an internal conductor, and a peroxide layer disposed between adjacent internal conductors in the stacking direction and containing second metal magnetic particles, wherein the metal magnetic particles contain an Fe—Si alloy, and the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0019] [Mechanism of Action] The coil element according to the second embodiment can improve DC bias characteristics by reducing the magnetic permeability of the metal magnetic layer disposed between the internal conductors of the internal electrodes (coils). Without being bound by any particular theory, the reason for this is presumed to be as follows. The coil element according to the second embodiment includes an element body having a peroxide layer containing second metal magnetic particles disposed between the internal conductors adjacent in the stacking direction. Here, the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles. In this way, in the coil element, a peroxide layer containing second metal magnetic particles with a relatively large amount of oxygen is disposed between the internal conductors. The peroxide layer reduces the magnetic permeability between the internal conductors adjacent in the stacking direction. Therefore, the coil element according to the second embodiment can improve DC bias characteristics.

[0020] The coil element (or laminated inductor) according to the second embodiment will be described in more detail with reference to Figures 1 to 3. Figure 1 is a perspective view of the coil element according to the second embodiment of the present disclosure, Figure 2 is an exploded perspective view of the coil element according to the second embodiment, and Figure 3 is a cross-sectional view taken along the line III-III in Figure 1. Note that the shape and arrangement of the coil element and its components are not limited to the examples shown in the figures.

[0021] The coil element 1 according to the second embodiment includes an element body 10. The element body 10 has a magnetic body M formed by laminating metal magnetic layers ML containing first metal magnetic particles, internal electrodes (coils) C1, C2 disposed inside the magnetic body M and wound around internal conductors (coil conductors) CD1, CD2, and a peroxide layer P disposed between the internal conductors CD1, CD2 adjacent in the lamination direction and containing second metal magnetic particles.

[0022] In the second embodiment, the element body 10 includes a first coil C1 and a second coil C2 arranged above the first coil C1. The first coil C1 is wound within the element body 10 by stacking lamination groups G6 to G8 (see FIG. 2 ), which will be described later, and connecting first coil conductors CD1 between the layers in a spiral shape via via conductors V. The second coil C2 is wound within the element body 10 by stacking lamination groups G2 to G4 (see FIG. 2 ), which will be described later, and connecting second coil conductors CD2 between the layers in a spiral shape via via conductors (not shown).

[0023] The coil provided inside the element body 10 is not limited to the above-described configuration, and may be a configuration including one coil or two or more coils.

[0024] (Large Oxygen Content) The second metal magnetic particles have a larger oxygen content than the first metal magnetic particles. In other words, the peroxide layer P containing the second metal magnetic particles (strictly speaking, a peroxide layer essentially consisting of the second metal magnetic particles in the second embodiment) has a larger oxygen content than the magnetic body M on which the metal magnetic layer ML containing the first metal magnetic particles (strictly speaking, a metal magnetic layer essentially consisting of the first metal magnetic particles in the second embodiment) is laminated. The oxygen atomic ratio of the peroxide layer P is 15 to 35% by volume. The oxygen atomic ratio of the magnetic body M is 10% by volume or less. The method for determining these oxygen atomic ratios will be described later. In this specification, "B essentially consisting of A" means that B is essentially composed of A, and specifically, the content of A is 95% or more, 97% or more, 99% or more, or 100% based on B.

[0025] In this specification, the amount of oxygen refers to the volume of oxygen atoms present at a specific location.

[0026] (Method for determining oxygen content) The fact that the second metal magnetic particles have a larger oxygen content than the first metal magnetic particles can be determined by the following method. First, a cross section of the coil element 1 is formed, and an SEM image of the cross section is taken. This cross section includes the winding axis of the coil and is parallel to the winding axis and the long axis direction (L direction) of the coil element 1. Here, the magnification of the SEM image is, for example, 1,000 times, and the adjacent internal conductors are set within the field of view of the SEM image.

[0027] Next, a mapping process is performed on the SEM image of the cross section, and the areas where oxygen atoms are present are colored. From the binarized SEM image of the cross section, the area ratios where oxygen atoms are present (oxygen atomic ratio: volume %) in the peroxide layer P containing the second metal magnetic particles and in the element body 10 containing the first metal magnetic particles are calculated. Based on the relative magnitude of the area ratios where oxygen atoms are present in the peroxide layer P and the magnetic material M, it is determined whether the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles. Note that the oxygen atomic ratio in the peroxide layer P is the above-mentioned "area ratio where oxygen atoms are present in the peroxide layer P," and the oxygen atomic ratio in the magnetic material is the above-mentioned "area ratio where oxygen atoms are present in the magnetic material."

[0028] At this time, the distinction between the peroxidized region P and the non-peroxidized region NP is determined by the color tone in EDX mapping of oxygen. Also, if the second magnetic particles and the first metal magnetic particles have different compositions (for example, different constituent atoms), the SEM image can be subjected to EDX mapping processing to distinguish the first metal magnetic particles and the second magnetic particles based on the material of the metal magnetic particles, thereby distinguishing the peroxidized region P and the non-peroxidized region NP. Alternatively, if the average particle size of the first metal magnetic particles and the average particle size of the second metal magnetic particles are different, the peroxidized region P and the non-peroxidized region NP can also be distinguished by distinguishing the first metal magnetic particles and the second magnetic particles based on their average particle size using SEM images and image analysis software.

[0029] Specifically, the coil element 1 is cut along a TL cross section (a cross section taken along the arrow III-III line in FIG. 3 ) passing through the intersection of the diagonals of the second main surface (top surface) 12 of the approximately rectangular coil element 1 shown in FIG. 1 . Using a scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX), signals derived from the material (oxygen atoms) constituting the element body 10 and the peroxide layer P are measured for the cross section thus formed. Based on the measurement results, a mapping process is performed on the cross-sectional image to create an analysis image showing the distribution of the material. As a result, areas where oxygen atoms are present and areas where metal magnetic particles are present are colored in the analysis image. The total area of ​​areas where oxygen atoms are present and areas where metal magnetic particles are present per unit area in the analysis image corresponding to the peroxide layer P (containing second metal magnetic particles) is calculated, as well as the area of ​​areas where oxygen atoms are present per unit area. From the obtained total area and area, the area ratio of oxygen atoms per unit area in the peroxide layer P is calculated. Similarly, the area ratio of oxygen atoms per unit area in the element body 10 is calculated. From the magnitude relationship of the obtained area ratios, it is determined whether the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0030] (Means for increasing the amount of oxygen) Specific means for realizing that the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles include, for example, that the second metal magnetic particles have a smaller average particle size than the first metal magnetic particles, and that the second metal magnetic particles contain at least one atom (additive atom) selected from the group consisting of Bi, Cl, Na, and K. In more detail, in the state of the raw materials in the manufacturing method of the coil element 1, the average particle size of the second metal magnetic particles and the composition of the second metal magnetic particles (content of additive atoms) are adjusted as described above, so that the second metal magnetic particles are more susceptible to oxidation than the surrounding materials, resulting in a larger amount of oxidation.

[0031] When the second metal magnetic particles have a smaller average particle size than the first metal magnetic particles, the surface area per unit volume of the second metal magnetic particles increases. During the manufacturing method of the coil element, the surfaces of the second metal magnetic particles may be oxidized. As a result, the amount of oxygen in the peroxide layer P increases.

[0032] When the second metal magnetic particles contain additive atoms, oxidation is promoted, and therefore, in the method for manufacturing the coil element, the second metal magnetic particles are oxidized, and the amount of oxygen in the peroxide layer P increases.

[0033] Each component will be described in detail below. [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.

[0034] 1, the length direction, width direction, and height direction of the coil element 1 and the base body 10 are shown as the L direction, the W direction, and the T direction, respectively. The length direction (long axis direction) L, the width direction (short axis direction) W, and the height direction (stacking direction of the internal conductors) T are perpendicular to each other. The mounting surface of the coil element 1 is, for example, a plane (LW plane) parallel to the length direction L and the width direction W.

[0035] 1 has a first main surface 11 and a second main surface 12 that face each other in the 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 the length direction L, and a first side surface 15 and a second side surface 16 that face each other in the 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.

[0036] The element body 10 has a magnetic body M, internal electrodes C1 and C2, and a peroxide layer P, and a coil (internal electrode) C and the peroxide layer P are disposed within the element body 10. The element body 10 also has a laminated structure in which multiple metal magnetic layers ML are stacked in a stacking direction (e.g., height direction T). Specifically, the element body 10 includes multiple metal magnetic layers ML, each having a peroxide layer P or a coil conductor CD formed thereon. In the second embodiment, as shown in FIG. 2 , the element body 10 is configured by stacking multilayer groups G1 to G10, each including at least one metal magnetic layer ML and one coil conductor CD or one peroxide layer P (or only one metal magnetic layer ML). Note that the boundaries between layers in the laminated structure of the element body 10 (particularly, the boundaries between metal magnetic layers ML made of the same material) have disappeared. Each multilayer group layer may be configured by stacking multiple identical patterns.

[0037] (Stacking Groups) The element body 10 will be described using stacking groups G1 to G10 shown in FIG.

[0038] -Lamination Group G1- The lamination group G1 includes a metal magnetic layer ML and constitutes the second main surface 12 of the element body .

[0039] -Lamination Group G2- The lamination group G2 has a metal magnetic layer ML and a second coil conductor CD2 that forms part of the second coil C2.

[0040] The second coil conductor CD2 of the multilayer group G2 constitutes one winding of the second coil C2. More specifically, the metal magnetic layers ML have holes penetrating surfaces facing each other in the stacking direction, and the second coil conductor CD2 is disposed in the holes. One end of the second coil conductor CD2 is connected to a via conductor (not shown) for connection to the second coil conductor CD2 of the multilayer group G4, 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.

[0041] -Layer Group G3- The laminate group G3 has a metal magnetic layer ML, an overoxide layer P, a via conductor V provided in the overoxide layer P, and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0042] The metal magnetic layers ML have holes penetrating the surfaces facing each other in the stacking direction, and the holes are filled with peroxide layers P. The peroxide layers P of the multilayer group G3 are provided to correspond to the winding shape of the second coil conductor CD2 of the multilayer group G4, which will be described later.

[0043] 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.

[0044] 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.

[0045] -Lamination Group G4- The lamination group G4 includes a metal magnetic layer ML, a second coil conductor CD2 that forms part of the second coil C2, and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0046] The second coil conductor CD2 of the multilayer group G4 forms another winding of the second coil C2. More specifically, the metal magnetic layers ML have holes penetrating the surfaces facing each other in the stacking direction, and the second coil conductor CD2 is disposed in the holes. One end of the second coil conductor CD2 is connected to the second coil conductor CD2 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.

[0047] 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.

[0048] -Lamination Group G5- The lamination group G5 includes a metal magnetic layer ML, a peroxide layer P, and a third through-hole conductor T3 and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0049] The peroxide layer P of the multilayer group G5 is provided to correspond to the winding shape of the first coil conductor CD1 of the multilayer group G6 (described later). The metal magnetic layers ML have holes penetrating the surfaces facing each other in the stacking direction, and the peroxide layer P is disposed in the holes. The peroxide layer P of the multilayer group G5 also electrically insulates the first coil C1 and the second coil C2.

[0050] 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.

[0051] 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.

[0052] -Lamination group G6- The laminated group G6 has a metal magnetic layer ML, a first coil conductor CD1 that forms part of the first coil C1, and a third through-hole conductor T3 and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0053] The first coil conductor CD1 of the multilayer group G6 constitutes one winding of the first coil C1. More specifically, the metal magnetic layers ML have holes penetrating surfaces facing each other in the stacking direction, and the first coil conductor CD1 is disposed in the holes. 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 in the multilayer group G8, 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.

[0054] 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.

[0055] 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.

[0056] -Lamination group G7- The laminated group G7 has a metal magnetic layer ML, a peroxide layer P, a via conductor V provided in the peroxide layer P, and a second through-hole conductor T2, a third through-hole conductor T3 and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0057] The peroxide layer P 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. The metal magnetic layers ML have holes penetrating the surfaces facing each other in the stacking direction, and the peroxide layer P is disposed in the holes.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] -Lamination group G8- The laminated group G8 has a metal magnetic layer ML, a first coil conductor CD1 that forms part of the first coil C1, and a second through-hole conductor T2, a third through-hole conductor T3, and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0063] The first coil conductor CD1 of the multilayer group G8 constitutes another winding of the first coil C1. More specifically, the metal magnetic layers ML have holes penetrating surfaces facing each other in the stacking direction, and the first coil conductor CD1 is disposed in the holes. The first coil conductor CD1 is disposed by being wound approximately along the outer periphery of the metal magnetic layers ML. One end of the first coil conductor CD1 is connected to the first coil conductor CD1 of the metal magnetic layers 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] - 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.

[0068] - Multilayer group G10 - The multilayer group G10 has first to fourth through-hole conductors T1 to T4 at the corners of the metal magnetic layers ML, which have larger planar areas than the first to fourth through-hole conductors of the multilayer group G9. 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.

[0069] The thickness of the first coil conductor CD1 and the second coil conductor CD2 in each stacking group may be the same. A peroxide layer P is disposed between all of the coil conductors CD in the stacking direction. Specifically, the peroxide layer P may be disposed in stacking groups G2 to G7 (see FIG. 2).

[0070] (Magnetic Body) The magnetic body M contains first metal magnetic particles. The first metal magnetic particles may have an oxide film covering their surfaces. The first metal magnetic particles also contain an Fe—Si alloy as a magnetic material.

[0071] In one embodiment, the first metal magnetic particles have a Si content of less than 3 mass% relative to the total content of Fe and Si, and a P content of 1000 ppm or less relative to the total content of Fe and Si (100 mass%).

[0072] In another embodiment, the first metal magnetic particles have a Si content of 3 to less than 8 mass% relative to the total content of Fe and Si, and a P content of less than 110 ppm or more than 650 ppm to 1000 ppm relative to the total content of Fe and Si (100 mass%).

[0073] Furthermore, the first metal magnetic particles may contain at least one additive metal element selected from the group consisting of Al, B, Nb, Cu, C, Co, P, and S. Examples of Fe—Si alloys containing such additive metal elements include Fe—Si—Cr (chromium)-based alloys, Fe—Si—Al (aluminum)-based alloys, Fe—Si—B (boron)-P (phosphorus)-Cu (copper)-C (carbon)-based alloys, and Fe—Si—B—Nb (niobium)-Cu-based alloys. Furthermore, the first metal magnetic particles may contain impurities such as Cr, Mn (manganese), Cu, Ni (nickel), P, S (sulfur), or Co (cobalt) that are not intended during manufacturing.

[0074] The surfaces of the first metal magnetic particles may be covered with an insulating coating (not shown). As used herein, "insulating" refers to a volume resistivity of 1 MΩcm or greater. Covering the surfaces of the first metal magnetic particles with an insulating coating can enhance the insulation between the first metal magnetic particles. Examples of methods for forming an insulating coating on the surfaces of the first metal magnetic particles 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 first metal magnetic particles. 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 a coil element 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.

[0075] The first metal magnetic particles may have an oxide film on their surfaces. This oxide film originates from the first metal magnetic particles and may be formed by heat treatment (oxidation treatment). In the element body 10, adjacent first metal magnetic particles may be bonded to each other via the oxide film.

[0076] The average particle size of the first metal magnetic particles 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 first metal magnetic particles in the metal magnetic layer can be measured using the procedure described below. The coil element 1 is cut to obtain a cross section. Specifically, the cross section is obtained by cutting the coil element 1 through the center thereof so as to be perpendicular to the mounting surface and end surface of the element body 10. Multiple regions (e.g., 130 μm × 100 μm) of the obtained cross section (e.g., in FIG. 3 , five regions in the magnetic material M between the outer surface of the internal conductor CD and the outer surface of the element body 10) 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 first metal magnetic particles. The average of the obtained circle-equivalent diameters is defined as the average particle size of the first metal magnetic particles. The average particle size in this specification means the average particle size D50 (particle size corresponding to a cumulative percentage of 50% on a volume basis).

[0077] (Internal Electrode) The internal electrode C is disposed inside the magnetic body M. The internal electrode C is configured by connecting a plurality of internal conductors CD wound on a plane inside the magnetic body through via conductors V. The internal electrode C has a first coil C1 and a second coil C2 disposed above the first coil C1 in the height direction T.

[0078] -First Coil- The first coil C1 has 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)). This gives the first coil C1 a spiral structure within the base body 10. 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 spiral structure within the base body 10. 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 conductor T3 or the length of the fourth through-hole conductor 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] (Peroxide Layer) The peroxide layer P is disposed between the internal conductors CD adjacent in the stacking direction. The peroxide layer P is disposed so as to contact the surface of the internal conductor CD perpendicular to the stacking direction. The peroxide layer P is disposed on the surface of the adjacent internal conductors CD facing each other in the stacking direction, and the peroxide layers P can be connected to each other. More specifically, only the peroxide layer P can be disposed between the adjacent internal conductors CD. In FIG. 2, only the peroxide layer P is disposed between all the adjacent internal conductors CD.

[0087] When only the peroxide layer P is disposed between the adjacent internal conductors CD, the magnetic permeability between the internal conductors decreases, and therefore the DC bias characteristics can be further improved.

[0088] The peroxide layer P contains second metal magnetic particles. The average particle size of the second metal magnetic particles is preferably greater than 1 μm and less than 29 μm, more preferably greater than 1 μm and less than 19 μm, and even more preferably greater than 1 μm and less than 9 μm. From the viewpoint of realizing that the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles, the second metal magnetic particles can have an average particle size smaller than that of the first metal magnetic particles.

[0089] The average particle size of the second metal magnetic particles in the peroxide layer P can be measured using the same procedure as for the first metal magnetic particles. Specifically, the coil element 1 is cut to obtain a cross section. The cross section is obtained by cutting the coil element 1 through the center, perpendicular to the mounting surface and end surface of the element body 10. Multiple regions (e.g., 130 μm × 100 μm) of the obtained cross section (e.g., five regions in the peroxide layer P between adjacent internal conductors CD in FIG. 3 ) are photographed using an SEM. The obtained SEM images are analyzed using image analysis software (e.g., image analysis software "Win R00F" (manufactured by Mitani Corporation)) to determine the circle-equivalent diameter of the second metal magnetic particles. The average value of the obtained circle-equivalent diameters is defined as the average particle size of the second metal magnetic particles. Note that the average particle size in this specification refers to the average particle size D50 (particle size equivalent to 50% cumulative percentage on a volume basis).

[0090] The surfaces of the second metal magnetic particles may be covered with an oxide film, that is, the second metal magnetic particles may have an oxide film on their surfaces.

[0091] The second metal magnetic particles may contain at least one additive metal element selected from the group consisting of Al, B, Nb, Cu, C, Co, P, and S. Examples of Fe—Si alloys containing such additive metal elements include Fe—Si—Cr (chromium)-based alloys, Fe—Si—Al (aluminum)-based alloys, Fe—Si—B (boron)-P (phosphorus)-Cu (copper)-C (carbon)-based alloys, and Fe—Si—B—Nb (niobium)-Cu-based alloys. Furthermore, the second metal magnetic particles may contain impurities such as Cr, Mn (manganese), Cu, Ni (nickel), P, S (sulfur), or Co (cobalt) that are not intended during manufacturing.

[0092] In order to ensure that the second metal magnetic particles have a greater amount of oxygen than the first metal magnetic particles, the second metal magnetic particles may contain at least one atom (additive atom) selected from the group consisting of Bi, Cl, Na and K.

[0093] -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 makes it possible to properly mount the coil element 1 on a mounting board or the like.

[0094] The external electrodes may be made of various materials such as Cu or Ni, for example. The external electrodes may be formed of 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), for example.

[0095] [Method for Manufacturing Coil Element] An example of a method for manufacturing the coil element according to the second embodiment will be described. The method for manufacturing the coil element according to the second embodiment includes laminating the first metal magnetic paste, the second metal magnetic paste, and the conductive paste to form a laminate (laminate formation step), and firing the laminate (laminate firing step).

[0096] (Laminate Forming Process) In the laminate forming process, a first metal magnetic paste, a second metal magnetic paste, and a conductive paste are laminated to form a laminate. Specifically, first, the first metal magnetic paste, the second metal magnetic paste, and the conductive paste are each prepared. The first metal magnetic paste is prepared by dispersing first metal magnetic particles in a solvent. The second metal magnetic paste is prepared by dispersing second metal magnetic particles in a solvent. The conductive paste is prepared by dispersing a conductive powder such as copper powder, silver powder, or gold powder in a solvent. These pastes may further contain a dispersant.

[0097] The prepared pastes are then printed in desired patterns to form the lamination groups G1 to G10. The first metal magnetic paste forms a magnetic material precursor. The second metal magnetic paste forms a peroxide layer precursor. The conductive paste forms an internal electrode precursor, a through-hole conductor precursor, and a via conductor precursor. For example, a layer formed with the second metal magnetic paste (peroxide layer precursor) is printed so as to be positioned entirely between adjacent internal conductor precursors. In this manner, the precursors of the lamination groups G1 to G10 are stacked to form a laminate.

[0098] The laminate may be formed by forming precursors for each of the lamination groups G1 to G10 and then laminating these precursors, or by sequentially laminating the precursors for the lamination groups G1 to G10. The precursors for the lamination groups G1 to G10 may be formed by repeatedly printing the metal magnetic layers ML, peroxide layers P, coil conductors, through-hole conductors, and via conductors until they reach the desired thickness.

[0099] (Laminate firing process) In the laminate firing process, the laminate is fired. By firing the laminate, the magnetic material precursor made of the first metal magnetic paste becomes a magnetic material, the peroxide layer precursor made of the second metal magnetic paste becomes a peroxide layer, and the internal electrode precursor, through-hole conductor precursor, and via conductor precursor made of the conductive paste become internal electrodes, through-hole conductors, and via conductors, respectively.

[0100] Furthermore, in the laminate firing process, the internal electrode precursor, the through-hole conductor precursor, and the via conductor precursor shrink and become denser through firing, resulting in lower resistance. Furthermore, in the laminate firing process, the internal electrode precursor, the through-hole conductor precursor, and the via conductor precursor (particularly the internal electrode precursor) shrink through firing, while the peroxide layer precursor expands as it is oxidized through firing. Therefore, in firing the laminate, the shrinkage of the internal electrode precursor, the through-hole conductor precursor, and the via conductor precursor is offset (or partially offset) by the expansion of the peroxide layer precursor, thereby alleviating internal stress generated during firing. Therefore, compared to a coil element that does not form a peroxide layer, the occurrence of cracks (particularly near the surface of the internal conductor perpendicular to the stacking direction) is suppressed.

[0101] The firing temperature is, for example, 500° C. to 900° C., and the firing time is, for example, 1 to 6 hours.

[0102] Third Embodiment The third embodiment relates to a coil element. The third embodiment has a peroxide layer P Ａ The third embodiment differs from the second embodiment in terms of the arrangement and shape of the components. These differences will be mainly described. In the third embodiment, the same reference numerals as those in the second embodiment represent the same configuration as in the second embodiment, and therefore the description thereof will be omitted in principle.

[0103] The coil element according to the third embodiment will be described with reference to Fig. 4. Fig. 4 shows an enlarged cross-sectional view of the coil element according to the third embodiment. As shown in Fig. 4, in the coil element 1A according to the third embodiment, the peroxide layer P Ａ are respectively disposed on two opposing surfaces of the adjacent internal conductors CD. Ａ are not connected to each other and face each other via the magnetic material M.

[0104] Usually, this can occur when the precursor of the internal conductor shrinks during firing of the laminate in the manufacturing method of the coil element, and internal stress is applied locally between the peroxide layer and the magnetic material. Ａ However, when the peroxide layer precursor is placed on two opposing surfaces of adjacent internal conductors, the peroxide layer precursor expands due to oxidation, which offsets the contraction of the internal conductor precursor, thereby suppressing the occurrence of cracks between the peroxide layer IA and the magnetic material M.

[0105] [Method for manufacturing coil element] In the method for manufacturing the coil element 1A according to the third embodiment, instead of arranging the peroxide layer precursor (i.e., the second metal magnetic paste) over the entire space between the internal conductor precursors adjacent in the stacking direction in the laminate of the second embodiment, the peroxide layer precursor is arranged on two corresponding surfaces of the internal conductor precursors adjacent in the stacking direction, and the two arranged peroxide layer precursors are arranged so as not to be connected to each other.

[0106] [Example] A large amount of oxygen will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a cross-sectional view showing an SEM image of a cross section of a coil element IA according to a third embodiment. Fig. 6 is also an enlarged view of a part of Fig. 4 (enlarged view of part B). Fig. 7 is a view showing an image obtained by mapping the presence of oxygen elements in Fig. 6. The peroxide layer P in Fig. 7 Ａ (The peroxide layer P in FIG. 6 Ａ The oxygen atom ratio of the peroxide layer P (corresponding to a region of the peroxide layer P shown in FIG. 7) was 32.5% by volume. Ａ The oxygen atomic ratio of the magnetic material between them ("part X in FIG. 7" corresponding to one region of magnetic material M in FIG. 6) was 8.1%.

[0107] <Modifications of the Embodiments> The present disclosure is not limited to the above-described embodiments, and design modifications are possible without departing from the spirit of the present disclosure. Furthermore, the features of the second and third embodiments may be combined in various ways.

[0108] In the second embodiment, the peroxide layer P is disposed in contact with the internal conductors CD in a cross-sectional view, but is not limited to this. For example, the peroxide layer P may be disposed between adjacent internal conductors CD without contacting the internal conductors CD.

[0109] In the third embodiment, the peroxide layer P Ａ are arranged on the surface of the peroxide layer 11 and are not connected to each other, but this is not limited thereto. For example, as shown in FIG. 5, two opposing peroxide layers may be connected to each other (in part).

[0110] In the second embodiment, the peroxide layer P is disposed between all adjacent internal conductors as shown in Fig. 3, but this is not limiting. For example, the peroxide layer may be disposed between one to five of six adjacent internal conductors.

[0111] In addition, among the six adjacent internal conductors in the second embodiment, the peroxide layer P of the second embodiment is disposed between any three of them, and the peroxide layer P of the second embodiment is disposed between the remaining three. Ａ may be placed.

[0112] <Fourth Embodiment: Coil Element> The fourth embodiment relates to a coil element. In particular, the coil element according to the fourth embodiment is specified as "arranged between internal conductors adjacent in the stacking direction" in the first embodiment being "arranged in contact with at least one of the mutually opposing surfaces of the internal conductors adjacent in the stacking direction." The coil element according to the fourth embodiment includes an element body having a magnetic body in which metal magnetic layers containing first metal magnetic particles are stacked, an internal electrode arranged inside the magnetic body and winding the internal conductors, and a peroxide layer containing second metal magnetic particles arranged in contact with at least one of the mutually opposing surfaces of the internal conductors adjacent in the stacking direction, wherein the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0113] [Mechanism of Action] The coil element according to the fourth embodiment can suppress the occurrence of structural defects (cracks). Without being bound by any particular theory, the reason for this is presumed to be as follows. The coil element according to the fourth embodiment includes an element body having a peroxide layer disposed in contact with at least one of the opposing surfaces of adjacent internal conductors in the stacking direction. Here, the second metal magnetic particles have a higher oxygen content than the first metal magnetic particles. In this manner, in the coil element, the peroxide layer containing the second metal magnetic particles having a relatively higher oxygen content is disposed in contact with at least one of the opposing surfaces of adjacent internal conductors in the stacking direction. Because the peroxide layer has a high oxygen content, the peroxide layer more firmly connects to the contacting internal conductors and magnetic material. Furthermore, the peroxide layer is disposed at the interface between the internal conductor and the element body, where structural defects (cracks) are likely to occur. Therefore, it is believed that the coil element according to the fourth embodiment can suppress the occurrence of structural defects (cracks). Note that, in this specification, "contact" refers to two members coming into contact with each other, and refers to two members being in direct contact with each other without any intervening material between them.

[0114] In contrast, a conventional coil element will be described with reference to Fig. 11 and Fig. 12. In the conventional coil element 1X, as shown in Fig. 11 and Fig. 12, if a peroxide layer is not disposed on at least one of the opposing surfaces between adjacent internal conductors, or if only an oxide layer is disposed thereon as in Patent Document 1, for example, a method for manufacturing the coil element 1X involves shrinkage of the internal electrode precursor, which causes localized internal stress (indicated by a thick arrow in Fig. 11) to be applied between the internal conductor CD and the magnetic material M (indicated by a dashed line in Fig. 11), resulting in the generation of structural defects (cracks) (in Fig. 12, a crack has occurred below the interface between the internal conductor CD and the magnetic material M).

[0115] The coil element (or laminated inductor) according to the fourth embodiment will be described in more detail mainly with reference to Figs. 8 to 10. Fig. 8 is an exploded perspective view of the coil element according to the fourth embodiment, and Fig. 9 is a cross-sectional view of Fig. 8. Fig. 10 is an enlarged cross-sectional view of the coil element according to the fourth embodiment (enlarged cross-sectional view of Fig. 9). Note that the shape and arrangement of the coil element and its components are not limited to the examples shown in the drawings.

[0116] The coil element 1C according to the fourth embodiment includes an element body 10. The element body 10 includes a magnetic body M formed by laminating metal magnetic layers ML containing first metal magnetic particles, internal electrodes (coils) C1 and C2 arranged inside the magnetic body M and wound around internal conductors (coil conductors) CD1 and CD2, and a peroxide layer P containing second metal magnetic particles arranged between the internal conductors C1 and C2 adjacent in the lamination direction. Ｃ It has the following.

[0117] In the fourth embodiment, the element body 10 includes a first coil C1 and a second coil C2 arranged above the first coil C1. The first coil C1 is wound within the element body 10 by stacking lamination groups G6 to G8 (see FIG. 2 ), which will be described later, and connecting first coil conductors CD1 between the layers in a spiral shape via via conductors V. The second coil C2 is wound within the element body 10 by stacking lamination groups G2 to G4 (see FIG. 2 ), which will be described later, and connecting second coil conductors CD2 between the layers in a spiral shape via via conductors (not shown).

[0118] The coil provided inside the element body 10 is not limited to the above-described configuration, and may be a configuration including one coil or two or more coils.

[0119] (Large Oxygen Content) The second metal magnetic particles have a larger oxygen content than the first metal magnetic particles. That is, the peroxide layer containing the second metal magnetic particles (strictly speaking, the peroxide layer substantially composed of the second metal magnetic particles in the fourth embodiment) P Ｃ has a larger amount of oxygen than the magnetic material M on which the metal magnetic layer ML containing the first metal magnetic particles (strictly speaking, the metal magnetic layer ML substantially made of the first metal magnetic particles in the first embodiment) is laminated. Ｃ The oxygen atomic ratio of the magnetic material M is 15 to 35% by volume. The oxygen atomic ratio of the magnetic material M is 10% by volume or less. The method for determining these oxygen atomic ratios will be described later. In this specification, "B substantially consisting of A" means that B is substantially composed of A, and specifically, the content of A is 95% or more, 97% or more, 99% or more, or 100% based on B.

[0120] In this specification, the amount of oxygen refers to the volume of oxygen atoms present at a specific location.

[0121] (Method for Determining Oxygen Amount) The fact that the second metal magnetic particles have a larger oxygen amount than the first metal magnetic particles can be determined by the following method. First, a cross section of the coil element 1C is formed, and an SEM image of the cross section is taken. This cross section includes the winding axis of the internal electrode (coil) and is parallel to the winding axis and the long axis direction (L direction) of the coil element 1C. Here, the magnification of the SEM image is, for example, 1,000 times, and the adjacent internal conductors are set within the field of view of the SEM image.

[0122] Next, a mapping process is performed on the SEM image of the cross section, and the areas where oxygen atoms are present are colored. From the binarized SEM image of the cross section, the peroxide layer P containing the second metal magnetic particles is identified. Ｃ and the area ratio of oxygen atoms present in the element body 10 containing the first metal magnetic particles (oxygen atom ratio: volume %) are calculated. ＣWhether the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles is determined based on the magnitude relationship between the area ratio of the oxygen atoms in the magnetic material M and the area ratio of the oxygen atoms in the magnetic material M. Ｃ The oxygen atom ratio of the magnetic material is the above-mentioned "area ratio where oxygen atoms exist in the magnetic material."

[0123] At this time, the peroxide region P Ｃ The distinction between the peroxide region P and the non-peroxide region NP is made by determining the color tone in EDX mapping of oxygen. In addition, when the second magnetic particles and the first metal magnetic particles have different compositions (for example, different constituent atoms), the SEM image is subjected to EDX mapping processing to distinguish the first metal magnetic particles from the second magnetic particles based on the material of the metal magnetic particles, and the peroxide region P is made. Ｃ Alternatively, when the average particle size of the first metal magnetic particles and the average particle size of the second metal magnetic particles are different, the first metal magnetic particles and the second magnetic particles can be distinguished by the average particle size using SEM images and image analysis software, and the peroxide region P can be distinguished. Ｃ and non-peroxide regions NP.

[0124] Specifically, the coil element 1C is cut along a TL cross section passing through the intersection of the diagonal lines of the second main surface (top surface) of the substantially rectangular coil element 1C. The element body 10 and the peroxide layer P are analyzed by a scanning electron microscope (SEM) and an energy dispersive X-ray analysis (EDX) to identify the element body 10 and the peroxide layer P. Ｃ The signal derived from the material (oxygen atoms) constituting the layer P is measured. Based on the measurement results, a mapping process is performed on the cross-sectional image to create an analysis image showing the distribution of the material. As a result, in the analysis image, areas where oxygen atoms are present and areas where metal magnetic particles are present are colored. Ｃ The total area of ​​the areas where oxygen atoms exist and the areas where metal magnetic particles exist per unit area, and the area of ​​the areas where oxygen atoms exist per unit area, are calculated. From the obtained total area and area, the peroxide layer P ＣThe area ratio of oxygen atoms per unit area in element body 10 is calculated. Similarly, the area ratio of oxygen atoms per unit area in element body 10 is calculated. From the magnitude relationship of the obtained area ratios, it is determined whether the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0125] (Means for increasing the amount of oxygen) Specific means for realizing that the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles include, for example, that the second metal magnetic particles have a smaller average particle size than the first metal magnetic particles, and that the second metal magnetic particles contain at least one atom (additive atom) selected from the group consisting of P, Bi, Cl, Na, and K. In more detail, in the state of the raw materials in the manufacturing method of coil element 1C, the average particle size of the second metal magnetic particles and the composition of the second metal magnetic particles (inclusion of additive atoms) as described above are adjusted, so that the second metal magnetic particles are more susceptible to oxidation than the surrounding materials, resulting in a larger amount of oxidation.

[0126] When the second metal magnetic particles have a smaller average particle size than the first metal magnetic particles, the surface area per unit volume of the second metal magnetic particles increases. In the manufacturing method of the coil element, the surface of the second metal magnetic particles may be oxidized. As a result, the peroxide layer P Ｃ The amount of oxygen increases.

[0127] When the second metal magnetic particles contain additive atoms, oxidation is promoted. Therefore, in the manufacturing method of the coil element, the second metal magnetic particles are oxidized, and the peroxide layer P Ｃ The amount of oxygen increases.

[0128] Each component will be described in detail below. [Element Body] The element body 10 includes a magnetic body M, internal electrodes C1 and C2, and a peroxide layer P. Ｃ The element body 10 includes a coil (internal electrode) C and an overoxide layer P Ｃ The element body 10 has a laminated structure in which a plurality of metal magnetic layers ML are laminated in a lamination direction (for example, a height direction T). More specifically, the element body 10 has a metal magnetic layer ML and a peroxide layer P ＣAlternatively, a plurality of metal magnetic layers ML on which a coil conductor CD is formed are laminated. In the fourth embodiment, as shown in FIG. 8, at least one metal magnetic layer ML and a coil conductor CD or a peroxide layer P Ｃ The base body 10 is configured by stacking laminated groups G1 to G10 each including a metal magnetic layer ML (or only a metal magnetic layer ML). The boundaries between each layer in the laminated structure of the base body 10 (particularly the boundary portions between metal magnetic layers ML made of the same material) have disappeared. Each laminated group layer may be configured by stacking multiple layers of the same pattern.

[0129] (Stacking Groups) The element body 10 will be described using stacking groups G1 to G10 shown in FIG.

[0130] -Lamination Group G1- The lamination group G1 includes a metal magnetic layer ML and constitutes the second main surface 12 of the element body .

[0131] -Lamination Group G2- The lamination group G2 has a metal magnetic layer ML and a second coil conductor CD2 that forms part of the second coil C2.

[0132] The second coil conductor CD2 of the multilayer group G2 constitutes one winding of the second coil C2. More specifically, the metal magnetic layers ML have holes penetrating surfaces facing each other in the stacking direction, and the second coil conductor CD2 is disposed in the holes. One end of the second coil conductor CD2 is connected to a via conductor (not shown) for connection to the second coil conductor CD2 of the multilayer group G4, 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.

[0133] -Lamination group G3- The lamination group G3 includes a metal magnetic layer ML and a peroxide layer P Ｃ and the peroxide layer P Ｃ and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0134] The metal magnetic layer ML has recesses in cross section on two surfaces facing each other in the stacking direction, and the peroxide layer P Ｃ Here, the cross-sectional view is the peroxide layer PＣ In other words, in a cross section including the peroxide layer P, the peroxide layer P is Ｃ , the metal magnetic layer ML and the peroxide layer P Ｃ The peroxide layer P of the lamination group G3 is stacked in this order. Ｃ is provided in accordance with the winding shape of the second coil conductor CD2 of the lamination group G4, which will be described later.

[0135] 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.

[0136] 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.

[0137] -Lamination Group G4- The lamination group G4 includes a metal magnetic layer ML, a second coil conductor CD2 that forms part of the second coil C2, and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0138] The second coil conductor CD2 of the multilayer group G4 forms another winding of the second coil C2. More specifically, the metal magnetic layers ML have holes penetrating surfaces facing each other in the stacking direction, and the second coil conductor CD2 is disposed in the holes. One end of the second coil conductor CD2 is connected to the second coil conductor CD2 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.

[0139] 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.

[0140] -Lamination group G5- The lamination group G5 includes a metal magnetic layer ML and a peroxide layer PＣ and a third through-hole conductor T3 and a fourth through-hole conductor T4 are provided in the metal magnetic layer ML.

[0141] Peroxide layer P of stacking group G5 Ｃ is provided in accordance with the winding shape of the first coil conductor CD1 of the multilayer group G6, which will be described later. Ｃ The metal magnetic layer ML has recesses in cross section on two surfaces facing each other in the stacking direction, and the peroxide layer P Ｃ That is, the peroxide layer P Ｃ In the cross section including the Ｃ , the metal magnetic layer ML and the peroxide layer P Ｃ are stacked in order.

[0142] 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.

[0143] 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.

[0144] -Lamination group G6- The laminated group G6 has a metal magnetic layer ML, a first coil conductor CD1 that forms part of the first coil C1, and a third through-hole conductor T3 and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0145] The first coil conductor CD1 of the multilayer group G6 constitutes one winding of the first coil C1. More specifically, the metal magnetic layers ML have holes penetrating surfaces facing each other in the stacking direction, and the first coil conductor CD1 is disposed in the holes. 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 in the multilayer group G8, 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.

[0146] 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.

[0147] 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.

[0148] -Lamination group G7- The lamination group G7 includes a metal magnetic layer ML and a peroxide layer P Ｃ and the peroxide layer P Ｃ and a second through-hole conductor T2, a third through-hole conductor T3, and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0149] Peroxide layer P of lamination group G7 Ｃ The metal magnetic layer ML has recesses in cross section on two surfaces facing each other in the stacking direction, and the peroxide layer P Ｃ That is, the peroxide layer P Ｃ In the cross section including the Ｃ , the metal magnetic layer ML and the peroxide layer P Ｃ are stacked in order.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] -Lamination group G8- The laminated group G8 has a metal magnetic layer ML, a first coil conductor CD1 that forms part of the first coil C1, and a second through-hole conductor T2, a third through-hole conductor T3, and a fourth through-hole conductor T4 provided in the metal magnetic layer ML.

[0155] The first coil conductor CD1 of the multilayer group G8 constitutes another winding of the first coil C1. More specifically, the metal magnetic layers ML have holes penetrating surfaces facing each other in the stacking direction, and the first coil conductor CD1 is disposed in the holes. The first coil conductor CD1 is disposed by being wound approximately along the outer periphery of the metal magnetic layers ML. One end of the first coil conductor CD1 is connected to the first coil conductor CD1 of the metal magnetic layers 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] - 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.

[0160] - Multilayer group G10 - The multilayer group G10 has first to fourth through-hole conductors T1 to T4 at the corners of the metal magnetic layers ML, which have larger planar areas than the first to fourth through-hole conductors of the multilayer group G9. 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.

[0161] The thickness of the first coil conductor CD1 and the second coil conductor CD2 in each lamination group may be the same.Ｃ Specifically, the peroxide layer P is arranged in the stacking groups G2 to G7 (see FIG. 8). Ｃ can be arranged.

[0162] (Magnetic Material) The magnetic material M contains first metal magnetic particles. The surfaces of the first metal magnetic particles may be covered with an oxide film. The first metal magnetic particles also contain Fe as a magnetic material. More specifically, the first metal magnetic particles may be Fe particles or Fe alloy particles. Examples of Fe alloys include Fe—Si—Cr (chromium)-based alloys, Fe—Si—Al (aluminum)-based alloys, and Fe—Si—B—Nb (niobium)-Cu-based alloys. The first metal magnetic particles may also contain impurities such as Cr, Mn (manganese), Cu, Ni (nickel), S (sulfur), or Co (cobalt) that are not intended during manufacturing.

[0163] The surfaces of the first metal magnetic particles may be covered with an insulating coating (not shown). As used herein, "insulating" refers to a volume resistivity of 1 MΩcm or greater. Covering the surfaces of the first metal magnetic particles with an insulating coating can enhance the insulation between the first metal magnetic particles. Examples of methods for forming an insulating coating on the surfaces of the first metal magnetic particles include the sol-gel method and the mechanochemical method. The insulating coating may be made of an oxide of P, Si, or the like. The insulating coating may also be an oxide film formed by oxidizing the surfaces of the first metal magnetic particles. 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 a sample of the coil element 1C can be photographed using 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.

[0164] The first metal magnetic particles may have an oxide film on their surfaces. This oxide film originates from the first metal magnetic particles and may be formed by heat treatment (oxidation treatment). In the element body 10, adjacent first metal magnetic particles may be bonded to each other via the oxide film.

[0165] The average particle size of the first metal magnetic particles 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 first metal magnetic particles in the metal magnetic layer can be measured using the procedure described below. The coil element 1C is cut to obtain a cross section. Specifically, the cross section is obtained by cutting the coil element 1C through the center thereof so as to be perpendicular to the mounting surface and end surface of the element body 10. Multiple regions (e.g., 130 μm × 100 μm) of the obtained cross section (e.g., in FIG. 9 , five regions in the magnetic material M between the outer surface of the internal conductor CD and the outer surface of the element body 10) 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 first metal magnetic particles. The average of the obtained circle-equivalent diameters is defined as the average particle size of the first metal magnetic particles. The average particle size in this specification means the average particle size D50 (particle size corresponding to a cumulative percentage of 50% on a volume basis).

[0166] (Internal Electrode) The internal electrode C is disposed inside the magnetic body M. The internal electrode C is configured by connecting a plurality of internal conductors CD wound on a plane inside the magnetic body through via conductors V. The internal electrode C has a first coil C1 and a second coil C2 disposed above the first coil C1 in the height direction T.

[0167] -First Coil- The first coil C1 has a plurality of first coil conductors CD1 connected to each other by via conductors V (see FIG. 9), a first through-hole conductor T1, and a second through-hole conductor T2.

[0168] As described above, the multiple first coil conductors CD1 are arranged in two stacking groups (stack groups G6 and G8 (see FIG. 8)). This gives the first coil C1 a spiral structure within the base body 10. 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.

[0169] 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.

[0170] 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.

[0171] - 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.

[0172] As described above, the multiple second coil conductors CD2 may be arranged in two stacking groups (stack groups G2 and G4 (see FIG. 8)). This allows the second coil C2 to have a spiral structure within the base body 10. 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.

[0173] 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.

[0174] 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.

[0175] (Peroxide layer) Peroxide layer P Ｃ are arranged in contact with at least one of the mutually opposing surfaces of the internal conductors CD adjacent in the stacking direction. More specifically, in the fourth embodiment, they are arranged in contact with both mutually opposing surfaces of the internal conductors CD adjacent in the stacking direction. In FIG. 8, the peroxide layer P Ｃ are placed.

[0176] In one embodiment, as shown in FIGS. 10 and 13, the peroxide layer P is disposed in contact with the mutually facing surfaces of the internal conductors CD adjacent in the stacking direction. Ｃ The sum of the thicknesses is 1 / 3 to 1 of the distance between the opposing surfaces. The above thickness and distance are the thickness and distance in the stacking direction, respectively. The above thickness is measured multiple times (number of measurements n=5) in the SEM image obtained by the method for determining the amount of oxygen, and the average value is obtained. This average value is taken as the thickness. The above distance is also measured in the same way. Figure 13 is an SEM image of the coil element 1C according to the fourth embodiment.

[0177] peroxide layer P Ｃ The magnetic particle contains second metal magnetic particles. The average particle size of the second metal magnetic particles is preferably greater than 1 μm and not greater than 29 μm, more preferably greater than 1 μm and not greater than 19 μm, and even more preferably greater than 1 μm and not greater than 9 μm. From the viewpoint of realizing that the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles, the second metal magnetic particles can have an average particle size smaller than that of the first metal magnetic particles.

[0178] peroxide layer P ＣThe average particle size of the second metal magnetic particles in the coil element 1C can be measured using the same procedure as for the first metal magnetic particles. Specifically, the coil element 1C is cut to obtain a cross section. The cross section is obtained by cutting the coil element 1C through the center thereof so as to be perpendicular to the mounting surface and end surface of the element body 10. The obtained cross section is measured at multiple locations (for example, in FIG. 9, the peroxide layer P between adjacent internal conductors CD). Ｃ An area (e.g., 130 μm × 100 μm) of each of the first and second metallic magnetic particles (five locations within the first and second metallic magnetic particles) is photographed using an SEM, and the resulting SEM image is analyzed using image analysis software (e.g., image analysis software "Win R00F" (manufactured by Mitani Shoji Co., Ltd.)) to determine the circle-equivalent diameter of the second metallic magnetic particles. The average value of the obtained circle-equivalent diameters is defined as the average particle size of the second metallic magnetic particles. Note that the average particle size referred to in this specification means the average particle size D50 (particle size equivalent to 50% cumulative percentage on a volume basis).

[0179] The surfaces of the second metal magnetic particles may be covered with an oxide film, that is, the second metal magnetic particles may have an oxide film on their surfaces.

[0180] The second metal magnetic particles may contain at least one additive metal element selected from the group consisting of Al, B, Nb, Cu, C, Co, and S. Examples of Fe—Si alloys containing such additive metal elements include Fe—Si—Cr (chromium)-based alloys, Fe—Si—Al (aluminum)-based alloys, and Fe—Si—B—Nb (niobium)-Cu-based alloys. The second metal magnetic particles may also contain impurities such as Cr, Mn (manganese), Cu, Ni (nickel), S (sulfur), or Co (cobalt) that are not intended during manufacturing.

[0181] In order to ensure that the second metal magnetic particles have a greater amount of oxygen than the first metal magnetic particles, the second metal magnetic particles may contain at least one atom (additive atom) selected from the group consisting of P, Bi, Cl, Na and K.

[0182] -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 makes it possible to properly mount the coil element 1C on a mounting board or the like.

[0183] The external electrodes may be made of various materials such as Cu or Ni, for example. The external electrodes may be formed of 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), for example.

[0184] [Method for manufacturing coil element] A method for manufacturing a coil element according to the fourth embodiment includes producing a coil element by firing a laminate obtained by laminating a first metal magnetic paste containing first metal magnetic particles, a second metal magnetic paste containing second metal magnetic particles, and a conductive paste containing conductive powder, wherein the second metal magnetic paste is disposed between the conductive pastes adjacent in the lamination direction (more specifically, the second metal magnetic paste is disposed in contact with at least one of the mutually opposing surfaces of the conductive pastes adjacent in the lamination direction), and the coil element 1C includes a magnetic body M formed by laminating metal magnetic layers ML containing the first metal magnetic particles, an internal electrode C disposed inside the magnetic body M and wound around an internal conductor CD, and a peroxide layer P containing the second metal magnetic particles, the peroxide layer P being disposed between the mutually adjacent internal conductors CD in the lamination direction (more specifically, the second metal magnetic paste is disposed in contact with at least one of the mutually opposing surfaces of the internal conductors CD adjacent in the lamination direction), Ｃ The element body 10 has the above structure, and the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

[0185] An example of a method for manufacturing the coil element according to the fourth embodiment will be described below. The method for manufacturing the coil element according to the fourth embodiment includes forming a laminate by stacking the first metal magnetic paste, the second metal magnetic paste, and the conductive paste (laminate formation step), and firing the laminate (laminate firing step).

[0186] (Laminate Forming Process) In the laminate forming process, a first metal magnetic paste, a second metal magnetic paste, and a conductive paste are laminated to form a laminate. Specifically, first, the first metal magnetic paste, the second metal magnetic paste, and the conductive paste are each prepared. The first metal magnetic paste is prepared by dispersing first metal magnetic particles in a solvent. The second metal magnetic paste is prepared by dispersing second metal magnetic particles in a solvent. The conductive paste is prepared by dispersing a conductive powder such as copper powder, silver powder, or gold powder in a solvent. These pastes may further contain a dispersant.

[0187] The prepared pastes are then printed in desired patterns to form the lamination groups G1 to G10. The first metal magnetic paste forms a magnetic material precursor. The second metal magnetic paste forms a peroxide layer precursor. The conductive paste forms an internal electrode precursor, a through-hole conductor precursor, and a via conductor precursor. For example, a layer formed with the second metal magnetic paste (peroxide layer precursor) is printed so as to be in contact with at least one of the opposing surfaces of adjacent internal conductor precursors. In this manner, the precursors of the lamination groups G1 to G10 are stacked to form a laminate.

[0188] The laminate may be formed by laminating the precursors of the laminate groups G1 to G10 after forming each of them, or by sequentially laminating the precursors of the laminate groups G1 to G10. The precursors of the laminate groups G1 to G10 each include a metal magnetic layer ML, a peroxide layer P Ｃ Alternatively, the coil conductors, through-hole conductors, and via conductors may be repeatedly printed until they reach a desired thickness.

[0189] In one embodiment, the second metal magnetic particles have an average particle size smaller than that of the first metal magnetic particles. In another embodiment, the second metal magnetic particles contain at least one atom selected from the group consisting of Bi, Cl, Na, and K, and the surfaces of the second metal magnetic particles are covered with an oxide film.

[0190] (Laminate firing process) In the laminate firing process, the laminate is fired. By firing the laminate, the magnetic material precursor made of the first metal magnetic paste becomes a magnetic material, the peroxide layer precursor made of the second metal magnetic paste becomes a peroxide layer, and the internal electrode precursor, through-hole conductor precursor, and via conductor precursor made of the conductive paste become internal electrodes, through-hole conductors, and via conductors, respectively.

[0191] Furthermore, in the laminate firing process, the internal electrode precursor, the through-hole conductor precursor, and the via conductor precursor shrink and become denser through firing, resulting in lower resistance. Furthermore, in the laminate firing process, the internal electrode precursor, the through-hole conductor precursor, and the via conductor precursor (particularly the internal electrode precursor) shrink through firing, while the peroxide layer precursor expands as it is oxidized through firing. Therefore, in firing the laminate, the shrinkage of the internal electrode precursor, the through-hole conductor precursor, and the via conductor precursor is offset (or partially offset) by the expansion of the peroxide layer precursor, thereby alleviating internal stress generated during firing. Therefore, compared to a coil element that does not form a peroxide layer, the occurrence of cracks (particularly near the surface of the internal conductor perpendicular to the stacking direction) is suppressed.

[0192] The firing temperature is, for example, 500° C. to 900° C., and the firing time is, for example, 1 to 6 hours.

[0193] Other Embodiments The present disclosure is not limited to the above-described embodiments, and design changes are possible without departing from the gist of the present disclosure.

[0194] In the fourth embodiment, the peroxide layer P Ｃ However, the present invention is not limited to this. Ｃ may be located on only one of the faces.

[0195] In the fourth embodiment, as shown in FIG. 9, the peroxide layer P is formed on all of the opposing surfaces of the adjacent internal conductors. Ｃ However, the present invention is not limited to this. For example, among the six adjacent internal conductors, the peroxide layer P Ｃ However, there may be one to five internal conductors arranged on one surface.

[0196] The present disclosure includes the following aspects. <1> A coil element including an element body including: a magnetic body formed by laminating metal magnetic layers containing first metal magnetic particles; internal electrodes disposed inside the magnetic body and winding internal conductors; and a peroxide layer disposed between the internal electrodes adjacent in the lamination direction and containing second metal magnetic particles, wherein the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles. <2> The coil element according to <1>, in which the first metal magnetic particles contain an Fe—Si alloy. <3> The coil element according to <1> or <2>, in which the peroxide layer is disposed in contact with at least one of the opposing surfaces of the internal electrodes adjacent in the lamination direction. <4> The coil element according to any one of <1> to <3>, in which the peroxide layer is disposed in contact with both surfaces of the internal conductors in the lamination direction. <5> The coil element according to any one of <1> to <4>, in which the sum of thicknesses of the peroxide layers disposed in contact with the opposing surfaces of the internal conductors adjacent in the lamination direction is ⅓ to 1 of the distance between the opposing surfaces. <6> The coil element according to any one of <1> to <5>, wherein the second metal magnetic particles have an average particle size smaller than that of the first metal magnetic particles. <7> The coil element according to any one of <1> to <6>, wherein the second metal magnetic particles contain at least one atom selected from the group consisting of P, Bi, Cl, Na, and K, and the surfaces of the second metal magnetic particles are covered with an oxide film. <8> The coil element according to any one of <1> to <7>, wherein the peroxide layer is arranged so as to contact a surface perpendicular to the stacking direction of the internal conductors. <9> The coil element according to any one of <1> to <8>, wherein the peroxide layer is arranged on a surface of adjacent internal conductors facing each other in the stacking direction, and the peroxide layers connect to each other. <10> The coil element according to any one of <1> to <4> and <6> to <9>, wherein only the peroxide layer is arranged between adjacent internal conductors.<11> A method for manufacturing a coil element, comprising: firing a laminate obtained by laminating a first metal magnetic paste containing first metal magnetic particles, a second metal magnetic paste containing second metal magnetic particles, and a conductive paste containing conductive powder, wherein the second metal magnetic paste is disposed between adjacent conductive pastes in a lamination direction, the coil element comprising an element having a magnetic body formed by laminating metal magnetic body layers containing the first metal magnetic particles, an internal electrode disposed inside the magnetic body and winding an internal conductor, and a peroxide layer disposed between adjacent internal conductors in the lamination direction and containing second metal magnetic particles, the second metal magnetic particles having a larger amount of oxygen than the first metal magnetic particles. <12> A method for manufacturing a coil element according to <11>, wherein the second metal magnetic paste is disposed in contact with at least one of the opposing surfaces between the conductive pastes adjacent in the lamination direction, and the peroxide layer is disposed in contact with at least one of the opposing surfaces of the internal electrodes adjacent in the lamination direction. <13> The method for manufacturing a coil element according to <11> or <12>, wherein the second metal magnetic particles have an average particle size smaller than that of the first metal magnetic particles. <14> The method for manufacturing a coil element according to any one of <11> to <13>, wherein the second metal magnetic particles contain at least one atom selected from the group consisting of P, Bi, Cl, Na, and K, and the surfaces of the second metal magnetic particles are covered with an oxide film.

[0197] The coil element according to the present disclosure is used in, for example, a DC-DC converter, and can also be used for purposes other than DC-DC converters.

[0198] 1, 1A, 1B, 1C Coil element 10 Body C Internal electrode (coil) C1 First internal electrode (first coil) C2 Second internal electrode (second coil) CD Internal conductor (coil conductor) CD1 First internal conductor (first coil conductor) CD2 Second internal conductor (second coil conductor) E1 First external electrode E2 Second external electrode E3 Third external electrode E4 Fourth external electrode G1 to G10 Stacking group P, P Ａ , P Ｂ , PＣ Peroxide layer M Magnetic material ML Metallic magnetic material layer T1 First through-hole conductor T2 Second through-hole conductor T3 Third through-hole conductor T4 Fourth through-hole conductor V Via conductor

Claims

1. A coil element comprising an element body having a magnetic body in which metal magnetic layers containing first metal magnetic particles are laminated, an internal electrode disposed inside the magnetic body and wound around an internal conductor, and a peroxide layer containing second metal magnetic particles disposed between the internal conductors adjacent in the lamination direction, wherein the second metal magnetic particles have a larger amount of oxygen than the first metal magnetic particles.

2. The coil element of claim 1, wherein the first metal magnetic particles include an Fe-Si alloy.

3. A coil element according to claim 1, wherein the peroxide layer is disposed in contact with at least one of the opposing surfaces of the internal electrodes adjacent in the stacking direction.

4. A coil element according to claim 3, wherein the peroxide layer is disposed in contact with both surfaces of the internal conductor in the lamination direction.

5. A coil element as described in claim 3 or 4, wherein the sum of the thicknesses of the peroxide layers arranged in contact with the opposing surfaces of the internal conductors adjacent in the stacking direction is 1 / 3 to 1 / 2 the distance between the opposing surfaces.

6. A coil element according to any one of claims 1 to 5, wherein the second metal magnetic particles have an average particle size smaller than that of the first metal magnetic particles.

7. A coil element according to any one of claims 1 to 6, wherein the second metal magnetic particles contain at least one atom selected from the group consisting of P, Bi, Cl, Na, and K, and the surfaces of the second metal magnetic particles are covered with an oxide film.

8. A coil element according to any one of claims 1 to 7, wherein the peroxide layer is disposed so as to contact a surface of the internal conductor that is perpendicular to the lamination direction.

9. A coil element according to any one of claims 1 to 8, wherein the peroxide layers are arranged on surfaces of adjacent internal conductors that face each other in the lamination direction, and the peroxide layers are connected to each other.

10. A coil element as claimed in any one of claims 1, 2 and 6, wherein only the peroxide layer is disposed between adjacent said internal conductors.

11. A method for manufacturing a coil element, comprising: producing a coil element by firing a laminate obtained by laminating a first metal magnetic paste containing first metal magnetic particles, a second metal magnetic paste containing second metal magnetic particles, and a conductive paste containing conductive powder, wherein the second metal magnetic paste is disposed between adjacent conductive pastes in the lamination direction; the coil element comprising an element having a magnetic body formed by laminating metal magnetic layers containing first metal magnetic particles, an internal electrode disposed inside the magnetic body and winding an internal conductor, and a peroxide layer disposed between adjacent internal conductors in the lamination direction and containing second metal magnetic particles; the second metal magnetic particles having a larger amount of oxygen than the first metal magnetic particles.

12. A method for manufacturing a coil element as described in claim 11, wherein the second metal magnetic paste is arranged in contact with at least one of the opposing surfaces between the conductive pastes adjacent in the stacking direction, and the peroxide layer is arranged in contact with at least one of the opposing surfaces of the internal electrodes adjacent in the stacking direction.

13. A method for manufacturing a coil element according to claim 11 or 12, wherein the second metal magnetic particles have an average particle size smaller than that of the first metal magnetic particles.

14. A method for manufacturing a coil element according to any one of claims 11 to 13, wherein the second metal magnetic particles contain at least one atom selected from the group consisting of P, Bi, Cl, Na, and K, and the surfaces of the second metal magnetic particles are covered with an oxide film.

Images