Coil component

Abstract

Provided is a coil component that reduces occurrence of cracks in the vicinity of an interface with a coil inside an element body. A coil component according to the present disclosure comprises: an element body 10 provided with an Fe-containing magnetic material; a coil embedded in the element body 10; and an external electrode E provided on a mounting surface of the element body 10 and electrically connected to the coil. In the coil, a plurality of coil conductors CM are electrically connected in a lamination direction. The element body 10 includes a contact layer CL in contact with the coil conductor CM, and a non-contact layer NL not in contact with the coil conductor CM. The contact layer CL includes an oxidation reduction material OR for reducing oxidation of Fe.

Description

Coil parts

[0001] The present disclosure relates to a coil component.

[0002] Patent Document 1 discloses a coil component in which a spiral coil portion covered by a magnetic material portion is in direct contact with the magnetic material portion, the coil portion containing Ag, and the magnetic material portion containing Fe—Cr—Si alloy particles.

[0003] JP 2012-164958 A

[0004] The coil component described in Patent Document 1 is subjected to a heat treatment of the element body in a sintering furnace or the like. This heat treatment bonds the alloy particles together via an oxide film on the surface of the Fe—Cr—Si alloy particles that make up the element body. The formation of an oxide film on the surface of the Fe—Cr—Si alloy particles is particularly pronounced near the interface with the Ag-containing coil portion, improving the adhesion strength between the coil portion and the alloy particles. Furthermore, when the element body of the coil component described in Patent Document 1 is subjected to a heat treatment, the magnetic portion containing Fe—Cr—Si alloy particles is less likely to undergo sintering shrinkage, but the coil portion is more likely to undergo sintering shrinkage. Therefore, the coil component described in Patent Document 1 has the potential for cracks to occur near the contact interface between the magnetic portion and the coil portion due to a mismatch in shrinkage behavior.

[0005] The inventors of the present application discovered the cause of the cracks as follows: The Fe-based metal magnetic particles that make up the magnetic body have a greater tendency to ionize than the Ag that makes up the coil. Therefore, in the region near the interface where the coil portion and the metal magnetic particles come into contact, the Ag that makes up the coil is reduced during heat treatment, which facilitates the oxidation of the Fe-based metal magnetic particles that make up the magnetic body near the coil, improving adhesion strength. Therefore, the sintering shrinkage of the coil portion during heat treatment pulls on the magnetic body portion, which is less susceptible to sintering shrinkage, and cracks may occur due to a mismatch between the improved adhesion strength and the shrinkage behavior.

[0006] An object of the present disclosure is to provide a coil component that reduces the occurrence of cracks inside the element body near the interface with the coil.

[0007] The coil component according to the present disclosure comprises: a base body including a magnetic material containing Fe; a coil embedded in the base body; and an external electrode provided on the mounting surface of the base body and electrically connected to the coil; the coil has multiple coil conductors electrically connected in the stacking direction; the base body includes a contact layer in contact with the coil conductors and a non-contact layer that does not contact the coil conductors; and the contact layer includes an oxidation reduction material that reduces oxidation of Fe.

[0008] According to the present disclosure, it is possible to provide a coil component that reduces the occurrence of cracks inside the element body near the interface with the coil.

[0009] Fig. 1 is a perspective view of a coil component according to the present disclosure. Fig. 2 is an exploded perspective view of a first embodiment of the coil component according to the present disclosure. Fig. 3 is a cross-sectional view taken along the arrow III-III in Fig. 2. Fig. 4 is an enlarged cross-sectional view of an area defined by a dashed line in Fig. 3. Fig. 5 is an enlarged cross-sectional view of a coil component according to a second embodiment. Fig. 6 is a cross-sectional view of a coil component according to a third embodiment. Fig. 7 is an enlarged cross-sectional view of an area defined by a dashed line in Fig. 6.

[0010] The coil component of the present disclosure will be described below. Note that the present disclosure is not limited to the following configurations and may be modified as appropriate without departing from the spirit and scope of the present disclosure. In addition, a combination of multiple individual preferred configurations described below also constitutes the present disclosure.

[0011] The coil component of the present disclosure is used in, for example, a DC-DC converter, but can also be used in applications other than DC-DC converters.

[0012] In this specification, terms indicating the relationship between elements (e.g., "parallel," "orthogonal," etc.) and terms indicating the shape of elements do not only mean the strict literal form, but also mean a range that is substantially equivalent, for example, a range that includes a difference of about a few percent. Note that in this specification, the direction in which the magnetic layers and coil conductors that make up the element body are stacked is referred to as the "stacking direction."

[0013] Furthermore, in the description of this specification, references to directions or orientations are made merely for the convenience of explanation and are not intended to limit the scope of the present disclosure unless otherwise explicitly stated. For example, relative terms such as "outside (or outer, external, or outer circumference)" and "inside (or inner, internal, or inner circumference)" and their derivatives should be understood to refer to the direction as described or illustrated. In other words, unless otherwise explicitly stated, the invention is not necessarily limited to a specific direction, orientation, form, or the like. Similarly, terms such as "provided," "disposed," and "connected" and their derivatives may refer to a configuration in which other elements, such as intervening elements, are present, rather than being limited to a direct configuration, unless otherwise explicitly stated.

[0014] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, scale, etc. may differ from those of the actual product.

[0015] <Coil Component of First Embodiment> A coil component of a first embodiment of the present disclosure will be described with reference to Figures 1 to 4. The coil component 1 of the present disclosure includes an element body 10, a coil C, and an external electrode E.

[0016] -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.

[0017] 1, the length direction, width direction, and height direction of the coil component 1 and the element body 10 are indicated as the L direction, the W direction, and the T direction, respectively. The length direction L, the width direction W, and the height direction T are perpendicular to one another. The mounting surface of the coil component 1 is, for example, a surface (LW surface) parallel to the length direction L and the width direction W.

[0018] 1 has a first main surface 11 and a second main surface 12 that face each other in the height direction T, a first side surface 15 and a second side surface 16 that face each other in the width direction W, and a first end surface 13 and a second end surface 14 that face each other in the length direction L. 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. When the second main surface 12 is the mounting surface of the element body 10, through-hole conductors TH to external electrodes E, which will be described later, may be drawn out toward the second main surface 12.

[0019] The element body 10 has a laminated structure in which a plurality of element body layers, each having a magnetic layer ML and a coil conductor CM, are stacked in a stacking direction (e.g., height direction T). In this embodiment, the element body 10 is constructed by stacking element body layers G1 to G7 as shown in FIG. 2 . A coil is constructed by stacking a plurality of coil conductors CM. By constructing a coil by stacking coil conductors CM, it is possible to make the coil more compact than a wire-wound coil in which a conductor wire is wound. Note that the boundaries between the layers in the laminated structure of the element body 10 disappear. Note that the number of layers is not limited to the element body layers G1 to G7, and may be more or less than this number depending on the number of turns of the coil. Furthermore, each of the element body layers G1 to G7 may be constructed by stacking an appropriate number of layers so that each layer has a predetermined thickness depending on the characteristics.

[0020] (Element Layer G1) As shown in FIG. 2, the element layer G1 includes a layer G11 and a layer G12.

[0021] Layer G11 The layer G11 is a layer that constitutes the second main surface 12 of the element body 10. The layer G11 corresponds to a non-contact layer because it does not contact the coil conductor (e.g., the element body layer G2). The layer G11 is composed of a magnetic layer (non-contact layer NL) containing Fe. In other words, the non-contact layer NL may be composed of the same material as the magnetic layer ML described below.

[0022] Layer G12 The layer G12 includes a contact layer CL that contacts the coil conductor CM of the base layer G2. A magnetic layer ML may be provided around the contact layer CL in plan view. The magnetic layer ML will be described in detail later.

[0023] The contact layer CL is provided to correspond to the winding shape of the coil conductor CM of the body layer G2. In a planar perspective, the planar area of ​​the contact layer CL is designed to be larger than the planar area of ​​the coil conductor CM of the body layer G2. In other words, the contact layer CL may have an area that contacts the coil conductor CM and an area that protrudes from the coil conductor CM in a planar perspective.

[0024] (Base Layer G2) The base layer G2 may include a coil conductor CM that forms part of a coil, and a magnetic layer ML that is arranged around the coil conductor CM.

[0025] The coil conductor CM of the body layer G2 constitutes one winding of the coil. More specifically, the coil conductor CM is arranged substantially along the outer periphery of the magnetic layer ML. One end of the coil conductor CM is connected to the via conductor VD of the body layer G3, and the other end of the coil conductor CM is connected to the second through-hole conductor TH2 for electrical connection to the second external electrode E2.

[0026] (Element Layer G3) As shown in FIG. 2, the element layer G3 includes a layer G31, a layer G32, and a layer G33.

[0027] Layer G31 The layer G31 includes a contact layer CL in contact with the coil conductor CM of the base layer G2, a magnetic layer ML arranged around the contact layer CL, via conductors VD, and second through-hole conductors TH2.

[0028] The contact layer CL is provided to correspond to the winding shape of the coil conductor CM of the element layer G2. In a planar perspective view, the plane area of ​​the contact layer CL is designed to be larger than the plane area of ​​the coil conductor CM of the element layer G2.

[0029] The via conductor VD is disposed at a position where it connects to one end of the coil conductor CM of the element layer G2. Although the contact layer CL described above is disposed around the via conductor VD in Fig. 2, the contact layer CL does not necessarily have to be disposed around the via conductor VD.

[0030] The second through-hole conductor TH2 connects the second through-hole conductors TH2 of the element layers G2 and G4 adjacent in the stacking direction, and is electrically connected to the second external electrode E2. In addition, although the contact layer CL is arranged around the second through-hole conductor TH2 in Fig. 2, the contact layer CL does not necessarily have to be arranged around the second through-hole conductor TH2.

[0031] Layer G32 The layer G32 includes a magnetic layer (non-contact layer NL), via conductors VD, and second through-hole conductors TH2. That is, the layer G32 corresponds to a non-contact layer that is not in contact with the coil conductor CM. The via conductors VD and second through-hole conductors TH2 of the layer G32 are arranged to correspond to the via conductors VD and second through-hole conductors TH2 of the layer G31, respectively.

[0032] Layer G33 The layer G33 includes a contact layer CL in contact with the coil conductor CM of the base layer G4, a magnetic layer ML arranged around the contact layer CL, via conductors VD, and second through-hole conductors TH2.

[0033] The contact layer CL is provided to correspond to the winding shape of the coil conductor CM of the element layer G4. In a planar perspective view, the plane area of ​​the contact layer CL is designed to be larger than the plane area of ​​the coil conductor CM of the element layer G4.

[0034] The via conductors VD and the second through-hole conductors TH2 of the layer G33 are arranged corresponding to the via conductors VD and the second through-hole conductors TH2 of the layer G32, respectively. In addition, although the contact layer CL is arranged around the via conductors VD of the layer G33 in Fig. 2, the contact layer CL does not necessarily have to be arranged around the via conductors VD of the layer G33.

[0035] (Base Layer G4) The base layer G4 has a coil conductor CM that forms part of the coil, a magnetic layer ML that is arranged around the coil conductor CM, and a second through-hole conductor TH2.

[0036] The coil conductor CM of the body layer G4 constitutes one winding of the coil. More specifically, the coil conductor CM is arranged substantially along the outer periphery of the magnetic layer ML. One end of the coil conductor CM is connected to the via conductor VD of the body layer G3, and the other end of the coil conductor CM is connected to the via conductor VD of the body layer G5.

[0037] The second through-hole conductor TH2 connects the second through-hole conductors TH2 of the element layers G3 and G5 adjacent in the stacking direction, and is electrically connected to the second external electrode E2.

[0038] (Element Layer G5) As shown in FIG. 2, the element layer G5 includes a layer G51, a layer G52, and a layer G53.

[0039] Layer G51 The layer G51 includes a contact layer CL in contact with the coil conductor CM of the base layer G4, a magnetic layer ML arranged around the contact layer CL, via conductors VD, and second through-hole conductors TH2.

[0040] The contact layer CL is provided to correspond to the winding shape of the coil conductor CM of the element layer G4. In a planar perspective view, the plane area of ​​the contact layer CL is designed to be larger than the plane area of ​​the coil conductor CM of the element layer G4.

[0041] The via conductor VD is disposed at a position where it connects to the other end of the coil conductor CM of the element layer G4. Although the contact layer CL described above is disposed around the via conductor VD in FIG. 2, the contact layer CL does not necessarily have to be disposed around the via conductor VD.

[0042] The second through-hole conductor TH2 connects the second through-hole conductors TH2 of the element layers G4 and G6 adjacent in the stacking direction, and is electrically connected to the second external electrode E2.

[0043] Layer G52 The layer G52 includes a magnetic layer (non-contact layer NL), via conductors VD, and second through-hole conductors TH2. The layer G52 corresponds to a non-contact layer that is not in contact with the coil conductor CM. The via conductors VD and second through-hole conductors TH2 of the layer G52 are arranged to correspond to the via conductors VD and second through-hole conductors TH2 of the layer G51, respectively.

[0044] Layer G53 The layer G53 includes a contact layer CL in contact with the coil conductor CM of the base layer G6, a magnetic layer ML arranged around the contact layer CL, via conductors VD, and second through-hole conductors TH2.

[0045] The contact layer CL is provided to correspond to the winding shape of the coil conductor CM of the element layer G6. In a planar perspective view, the plane area of ​​the contact layer CL is designed to be larger than the plane area of ​​the coil conductor CM of the element layer G6.

[0046] The via conductors VD and the second through-hole conductors TH2 of the layer G53 are arranged corresponding to the via conductors VD and the second through-hole conductors TH2 of the layer G52, respectively. In addition, although the contact layer CL is arranged around the via conductors VD of the layer G53 in Fig. 2, the contact layer CL does not necessarily have to be arranged around the via conductors VD of the layer G53.

[0047] (Element Layer G6) The element layer G6 has a coil conductor CM that forms part of the coil, a magnetic layer ML that is arranged around the coil conductor CM, and a second through-hole conductor TH2.

[0048] The coil conductor CM of the body layer G6 constitutes one winding of the coil. More specifically, the coil conductor CM is arranged substantially along the outer periphery of the magnetic layer ML. One end of the coil conductor CM is connected to the via conductor VD of the body layer G5, and the other end of the coil conductor CM is connected to the first through-hole conductor TH1 of the body layer G7.

[0049] The second through-hole conductor TH2 connects the second through-hole conductors TH2 of the element layers G5 and G7 adjacent in the stacking direction, and is electrically connected to the second external electrode E2.

[0050] (Element Layer G7) As shown in FIG. 2, the element layer G7 includes a layer G71 and a layer G72.

[0051] Layer G71 The layer G71 includes a contact layer CL in contact with the coil conductor CM of the base layer G6, a magnetic layer ML arranged around the contact layer CL, a second through-hole conductor TH2, and a first through-hole conductor TH1.

[0052] The contact layer CL is provided to correspond to the winding shape of the coil conductor CM of the element layer G6. In a planar perspective view, the plane area of ​​the contact layer CL is designed to be larger than the plane area of ​​the coil conductor CM of the element layer G6.

[0053] The second through-hole conductor TH2 is connected to the second through-hole conductor TH2 of the element layer G6 adjacent in the stacking direction, and is electrically connected to the second external electrode E2.

[0054] The first through-hole conductor TH1 is connected to the first through-hole conductor TH1 of the element layer G6 adjacent in the stacking direction, and is electrically connected to the first external electrode E1. Note that, although the contact layer CL is arranged around the first through-hole conductor TH1 in Fig. 2, the contact layer CL does not necessarily have to be arranged around the first through-hole conductor TH1.

[0055] Layer G72 The layer G72 includes a magnetic layer (non-contact layer NL), a first through-hole conductor TH1, and a second through-hole conductor TH2. The layer G72 is a layer that constitutes the first main surface 11 of the element body 10, and is a layer similar to the non-contact layer NL. Specifically, the layer G72 is composed of a magnetic layer. The first through-hole conductor TH1 and the second through-hole conductor TH2 of the layer G72 are arranged to correspond to the first through-hole conductor TH1 and the second through-hole conductor TH2 of the layer G71, respectively.

[0056] As described above, when the element body 10 has a layered structure including element body layers G1 to G7, the degree of freedom in designing the coil component 1 is increased. For example, when manufacturing a coil component 1 including the first external electrode E1 and the second external electrode E2 on the bottom surface (first main surface 11) of the element body 10, it becomes easier to extend the coil to the bottom surface side. Note that the layered structure including the element body layers G1 to G7 may be formed by stacking them by sequential printing (e.g., screen printing) from the second main surface 12 side or the first main surface 11 side of the element body 10. In this case, printing may be repeated on each of the element body layers G1 to G7 until the desired thickness is achieved.

[0057] The magnetic layer ML of each element layer G1 to G7 includes metal magnetic particles MP made of a magnetic material and a resin (see FIG. 4). The metal magnetic particles MP include metal particles and an oxide layer formed on the surface of the metal particles, with adjacent metal magnetic particles MP bonded to each other via the oxide layer. Resin is present in the element body after heat treatment, except in areas where there is no oxide layer on the metal magnetic particles MP and in areas where adjacent metal magnetic particles MP are bonded to each other by the oxide.

[0058] The average particle size of the metal magnetic particles MP may be preferably 0.2 μm or more and 50 μm or less, more preferably 2 μm or more and 30 μm or less, and even more preferably 2 μm or more and 20 μm or less. By making the average particle size of the metal magnetic particles MP relatively small, such as within the above numerical range, the number of metal magnetic particles MP can be increased. As a result, the number of metal magnetic particles MP that are insulated from each other by the oxide layer described below increases, thereby improving insulation properties.

[0059] The average particle size of the metal magnetic particles MP can be measured using the procedure described below. An inductor sample is cut to obtain a cross section. Specifically, the sample cross section is obtained by cutting the sample through the center of the element body and the winding axis of the coil, perpendicular to the mounting surface and end surface of the element body. The sample cross section may be flattened by ion milling or other methods. Three randomly selected locations in the center of the element body 10 are photographed using an SEM (magnification of approximately 1000x to 5000x). The average particle size of the confirmed metal magnetic particles MP is then determined using image analysis software (e.g., WinROOF2021 (manufactured by Mitani Corporation)). Note that the term "average particle size" used herein may refer to the average particle size D50 (particle size equivalent to a cumulative percentage of 50% on a volume basis).

[0060] The metal particles contain Fe (iron) and Si. More specifically, they may be particles or alloy particles containing Fe and Si. Examples of metal particles include Fe-Si alloys, Fe-Si-Cr (chromium) alloys, Fe-Si-Al (aluminum) alloys, Fe-Si-B (boron)-P (phosphorus)-Cu (copper)-C (carbon) alloys, and Fe-Si-B-Nb (niobium)-Cu alloys. The metal particles may also contain impurities unintended during manufacturing, such as Cr, Mn (manganese), Cu, Ni (nickel), P, S (sulfur), or Co (cobalt). By adding Si to the metal particles, oxidation of the Fe element contained in the metal particles can be suppressed, thereby further increasing the magnetic permeability of the coil component 1. The metal magnetic particles may also be contained in a magnetic paste for forming a magnetic layer. Therefore, the metal particles may contain elements (e.g., Cr, Al, Li (lithium), Zn (zinc)) that are more easily oxidized than the Fe added when the magnetic paste is prepared. By adding an element that is more easily oxidized than Fe to the magnetic paste, the element that is more easily oxidized than Fe is oxidized first to form an oxide when the element body is heat-treated, thereby suppressing oxidation of the Fe element contained in the metal particles. Note that the resin component contained in the magnetic paste may disappear during the heat-treatment of the element body, or it may remain.

[0061] The surfaces of the metal particles are covered with an oxide layer, which can improve the insulating properties between the metal particles.

[0062] The oxide layer is a layer produced by oxidation of metal particles. That is, it may contain oxygen. The thickness of the oxide film may be preferably 1 nm to 50 nm, more preferably 1 nm to 30 nm, and even more preferably 1 nm to 20 nm. For example, a cross section of an inductor sample obtained by ion milling can be photographed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the thickness of the oxide film covering the surface of the metal particles can be measured from the obtained SEM image.

[0063] To increase the strength of element body 10, the element body may be impregnated with resin after heat treatment of the element body formed by stacking the above-mentioned element layers, thereby causing the resin to be present in the gaps between the metal magnetic particles MP. As an example, the resin impregnated after heat treatment of the element body may be one or more resins selected from the group consisting of epoxy resin, phenolic resin, polyester resin, polyimide resin, polyolefin resin, silicone resin, acrylic resin, polyvinyl butyral resin, cellulose resin, alkyd resin, etc.

[0064] (Characteristic Configuration of the Element Body) The element body 10 of the present disclosure includes a non-contact layer NL that is not in contact with the coil conductor CM, and a contact layer CL that is in contact with the coil conductor CM (see FIG. 4).

[0065] The non-contact layers NL correspond to the layers G11, G32, G52, and G72 in the element layers G1 to G7 shown in Figure 2. The non-contact layers NL contain the metal magnetic particles MP described above. Therefore, compared to the contact layer CL described below, the non-contact layers NL have a higher magnetic material content (Fe content) and therefore better magnetic properties.

[0066] The contact layers CL are included in layers G12, G31, G33, G51, G53, and G71 in the element layers G1 to G7 shown in FIG. 2 . The contact layers CL contain an oxidation-reducing material OR that reduces Fe oxidation more than the non-contact layers NL (see FIG. 4 ). As used herein, "reducing Fe oxidation" refers to making it difficult for iron oxide to form in the Fe component with the highest composition ratio in the composition of the contact layers CL—in other words, suppressing Fe oxidation. By making it difficult for iron oxide to form in the contact layers CL that contact the coil conductors CM, the adhesion between the contact layers CL and the coil conductors CM can be reduced. This reduces the influence of a mismatch in shrinkage behavior near the contact interface between the contact layers CL and the coil conductors CM during heat treatment of the element, thereby reducing cracks near the contact interface.

[0067] Specific embodiments of the oxidation-reducing material contained in the contact layer CL will be described below.

[0068] First Aspect of the Oxidation Reduction Material: As one aspect of the oxidation reduction material OR, the material may contain particles containing Fe with a lower Fe ratio than the particles containing Fe contained in the non-contact layer NL. Specifically, the contact layer CL may contain metal magnetic particles with a lower Fe ratio than the non-contact layer NL. As an example, the material may contain an Fe-Si alloy, an Fe-Si-Cr (chromium) alloy, or the like, with a lower Fe ratio than the non-contact layer NL. In this way, by increasing the Si and / or Cr ratio in the contact layer CL relative to Fe, the easily oxidizable elements (Si and / or Cr) are oxidized first, thereby preventing Fe oxidation. Furthermore, due to the reduced Fe ratio resulting from the inclusion of Si and / or Cr, the total amount of oxide film (the amount of iron oxide produced) can be reduced. This reduces the likelihood of iron oxide production in the contact layer CL that contacts the coil conductor CM, thereby reducing cracks near the contact interface between the contact layer CL and the coil conductor CM.

[0069] Regarding the Fe ratio of the oxidation-reducing material OR, the Fe content in the contact layer CL may be 3% to 10% lower than the Fe content in the non-contact layer NL. Specifically, the Fe content (wt%) of the entire contact layer CL may be 3% to 10% lower than the Fe content (wt%) of the entire non-contact layer NL. This Fe ratio can favorably reduce the oxidation of Fe and reduce cracks near the contact interface between the contact layer CL and the coil conductor CM.

[0070] Furthermore, regarding the Fe ratio, the Fe content in the contact layer CL may be 50% or more based on the entire contact layer CL. With such an Fe content, a sufficient amount of magnetic material is contained, and good magnetic properties can be achieved.

[0071] The material of the oxide layer can be identified, for example, by ion milling a sample of the inductor to obtain a cross section, photographing it with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and then performing compositional analysis and elemental analysis using EDX or the like.

[0072] Second Aspect of the Oxidation-Reducing Material In another aspect of the oxidation-reducing material, the oxidation-reducing material OR may be formed by coating particles containing Fe with an insulating coating material. By coating the particles containing Fe with the insulating coating material, oxidation of the particles containing Fe can be prevented, and cracks near the contact interface between the contact layer CL and the coil conductor CM can be reduced.

[0073] A suitable insulating coating material may contain at least one element selected from the group consisting of Si, P, Zn, and Zr. Such an insulating coating material will oxidize prior to Fe during heat treatment of the element body, forming an oxide, thereby effectively preventing oxidation of the Fe-containing particles.

[0074] Third Aspect of the Oxidation-Reducing Material In another aspect of the oxidation-reducing material, the oxidation-reducing material OR may be formed by adding an easily oxidizable metal material that is more easily oxidized than Fe to particles containing Fe. In this specification, the term "easily oxidizable metal material that is more easily oxidized than Fe" refers to a material that has a greater tendency to ionize than Fe. Adding an easily oxidizable metal material to the contact layer CL can cause oxidation of the easily oxidizable metal material, making it difficult for Fe to oxidize. This reduces oxidation of Fe and reduces cracks near the contact interface between the contact layer CL and the coil conductor CM.

[0075] A suitable easily oxidizable metal material may be at least one selected from the group consisting of Zn, Zr, Al, and Cr. When such an easily oxidizable metal material is used, elements that are more easily oxidized than Fe are oxidized first to form oxides during heat treatment of the element body, thereby making it possible to suitably prevent oxidation of Fe.

[0076] (Additional Configuration of the Element Body) As an additional configuration of the element body, as shown in Fig. 3, the contact layer CL may extend from the outer edge of the coil conductor CM in a direction perpendicular to the stacking direction. In other words, as shown in layers G12, G31, G33, G51, G53, and G71 in Fig. 2, the planar area of ​​the contact layer CL may be designed to be larger than the planar area of ​​the coil conductor CM in a planar perspective view. With this configuration, the contact layer CL can be brought into appropriate contact with the coil conductor CM, and contact between the non-contact layer NL and the coil conductor CM can be appropriately prevented.

[0077] - Coil - A coil in which multiple coil conductors CM are electrically connected is buried inside the element body. In the example shown in Figures 2 and 3, the coil conductors CM in element body layers G2, G4, and G6 are electrically connected in the stacking direction, and a single coil is provided inside the element body. The thicknesses of the coil conductors CM in element body layers G2, G4, and G6 may all be the same.

[0078] In the illustrated example (FIGS. 2 and 3), one coil is provided within the element body 10, but the present invention is not limited to this. For example, two or more coils may be provided along the stacking direction. Furthermore, a coil array may be configured by arranging multiple coils side by side within the element body 10 in a direction intersecting the stacking direction (direction L in FIG. 1).

[0079] The material of the coil conductor CM may be a material with a lower ionization tendency than Fe. Examples of materials that may be used for the coil conductor CM include metal conductors such as Ag, Cu, Au, and alloys thereof. The coil conductor CM may be formed, for example, by printing a conductive paste on the magnetic layer ML.

[0080] -External Electrodes- The external electrodes E are provided on the mounting surface (first main surface 11) of the element body 10 and are electrically connected to the coils. In the example shown in Fig. 2, the external electrodes E include a second external electrode E2 electrically connected to the other end of the coil conductor CM of the element body layer G2, and a first external electrode E1 electrically connected to the other end of the coil conductor CM of the element body layer G6. Two external electrodes are provided for each coil. Therefore, if the number of coils is two, the number of external electrodes may be four.

[0081] The external electrodes E may be made of various materials such as Cu and Ni, for example. The external electrodes E may be formed of a single layer or may have a laminated structure of two or more layers. The external electrodes E may be formed by any method, but may be plated electrodes formed by plating (e.g., electroless plating), for example.

[0082] -Other Coil Component Configurations- Through-hole conductors TH may be used to connect the coil C and the external electrodes E. That is, first through-hole conductors TH1 and second through-hole conductors TH2 may be provided corresponding to the first external electrode E1 and the second external electrode E2. Furthermore, the first through-hole conductors TH1 and second through-hole conductors TH2 may extend along the stacking direction.

[0083] Via conductors VD may be used for electrical connection between the coil conductors CM in the stacking direction, and the via conductors VD may extend along the stacking direction.

[0084] Examples of materials for the first through-hole conductor TH1, the second through-hole conductor TH2, and the via conductor VD may include metal conductors such as Ag and Cu. Furthermore, the materials for the first through-hole conductor TH1, the second through-hole conductor TH2, and the via conductor VD may be the same as or different from the coil conductor CM. The first and second through-hole conductors and the via conductors may be formed, for example, by forming through-holes in the magnetic layer ML and printing a conductive paste into the through-holes. Alternatively, the first and second through-hole conductors and the via conductors may be formed by printing a conductive paste for forming the through-hole conductors and the via conductors and then printing the magnetic layer ML on the outside of the conductive paste.

[0085] As described above, the coil component 1 of this embodiment includes the contact layer CL that contacts the coil conductor CM and the non-contact layer NL that does not contact the coil conductor CM, thereby reducing the adhesion between the contact layer CL and the coil conductor CM. This makes it difficult for iron oxide to form in the contact layer CL that contacts the coil conductor CM, thereby reducing cracks near the contact interface between the contact layer CL and the coil conductor CM.

[0086] <Coil Component of Second Embodiment> Next, a coil component of a second embodiment will be described with reference to Fig. 5. In describing the coil component of the second embodiment, explanations of points common to the configuration of the coil component of the first embodiment will be omitted as appropriate. In other words, the following description will focus on configurations that differ from the coil component of the first embodiment.

[0087] 5, in the coil component of the second embodiment, the average particle size of the Fe-containing magnetic material contained in the non-contact layer NL (specifically, the average particle size of the metal magnetic particles MP) may be larger than the average particle size of the oxidation reduction material OR. As described above, the average particle size may refer to the average particle size D50 (particle size corresponding to a cumulative percentage of 50% on a volume basis). According to the coil component of the second embodiment, the oxidation reduction material OR with a small average particle size can be densely packed between the non-contact layer NL and the coil conductor CM in the stacking direction, preventing contact between the non-contact layer NL and the coil conductor CM and reducing cracks near the contact interface between the contact layer CL and the coil conductor CM.

[0088] As an example, it is preferable that the average particle size of the metal magnetic particles MP contained in the non-contact layer NL is approximately 20 μm or more and 30 μm or less, and the average particle size of the oxidation reduction material OR contained in the contact layer CL is 2 μm or less. In other words, it is preferable that the average particle size of the metal magnetic particles MP contained in the non-contact layer NL is 10 times or more the average particle size of the oxidation reduction material OR contained in the contact layer CL.

[0089] <Coil Component of Third Embodiment> Next, a coil component of a third embodiment will be described with reference to Fig. 6 and Fig. 7. In describing the coil component of the third embodiment, a description of the points common to the configuration of the coil component of the first embodiment will be omitted as appropriate. In other words, the following description will focus on the configuration that differs from the coil component of the first embodiment.

[0090] 6 and 7 , in the coil component of the third embodiment, a contact layer CL and a non-contact layer NL are arranged in this order on the upper surface of the coil conductor CM in the uppermost layer in the stacking direction, a contact layer CL and a non-contact layer NL are arranged in this order on the lower surface of the coil conductor CM in the lowermost layer in the stacking direction, and only the contact layer CL may be arranged in the position sandwiched between the coil conductors CM. Specifically, the coil component of the third embodiment is intended to be a coil component in which the layers G32 and G52 in FIG. 2 have been removed. In other words, the contact layer CL and the non-contact layer NL on the upper surface of the coil conductor CM in the uppermost layer in the stacking direction correspond to the layers G12 and G11, respectively, and the contact layer CL and the non-contact layer NL on the lower surface of the coil conductor CM in the lowermost layer in the stacking direction correspond to the layers G71 and G72, respectively.

[0091] According to the coil component 1 of the third embodiment, the product thickness can be reduced by the amount corresponding to the removal of the layers G32 and G52 compared to the coil component 1 of the first embodiment. Furthermore, the layers G33 and G53 may also be removed. This allows the product thickness to be further reduced.

[0092] Furthermore, in the coil component of the third embodiment, the oxidation-reducing material OR in the contact layer CL may be the oxidation-reducing material OR having an average particle size of 2 μm or less, as described in the second embodiment. If the oxidation-reducing material OR has such an average particle size, the product thickness can be further reduced.

[0093] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. The technical scope of the present disclosure also includes all modifications within the scope and meaning equivalent to the claims.

[0094] The coil component of the present disclosure is as follows: <1> A coil component comprising: an element body including a magnetic material containing Fe; a coil embedded in the element body; and an external electrode provided on a mounting surface of the element body and electrically connected to the coil, wherein the coil has a plurality of coil conductors electrically connected in the stacking direction; the element body includes a contact layer in contact with the coil conductors and a non-contact layer not in contact with the coil conductors, and the contact layer includes an oxidation reduction material that reduces oxidation of Fe. <2> The coil component of <1>, wherein the oxidation reduction material includes Fe-containing particles having a lower Fe content than the Fe-containing particles contained in the non-contact layer. <3> The coil component of <1> or <2>, wherein the Fe content of the contact layer is 3% to 10% lower than the Fe content of the non-contact layer. <4> The coil component of <3>, wherein the Fe content of the contact layer is 50% or more based on the entire contact layer. <5> The coil component according to any one of <1> to <4>, wherein the oxidation reduction material is composed of particles containing Fe coated with an insulating coating material. <6> The inductor according to <5>, wherein the insulating coating material includes at least one selected from the group consisting of Si, P, Zn, and Zr. <7> The coil component according to any one of <1> to <6>, wherein the oxidation reduction material is composed of particles containing Fe and an easily oxidizable metal material that is more easily oxidized than Fe. <8> The inductor according to <7>, wherein the easily oxidizable metal material includes at least one selected from the group consisting of Zn, Zr, Al, and Cr. <9> The coil component according to any one of <1> to <8>, wherein the contact layer extends from an outer edge of the coil conductor in a direction perpendicular to the stacking direction. <10> A coil component according to any one of <1> to <9>, wherein the contact layer and the non-contact layer are arranged in this order on the upper surface of the coil conductor in the uppermost row in the stacking direction, the contact layer and the non-contact layer are arranged in this order on the lower surface of the coil conductor in the lowermost row in the stacking direction, and only the contact layer is arranged on the element portion sandwiched between the coil conductors.<11> The coil component according to any one of <1> to <10>, wherein the average particle size of the magnetic material containing Fe contained in the non-contact layer is larger than the average particle size of the oxidation reduction material.

[0095] The coil component of the present disclosure can be suitably used as an electronic component that reduces the occurrence of cracks inside the element body near the interface with the coil.

[0096] REFERENCE SIGNS LIST 1 coil component 10 element body 11 first main surface 12 second main surface 13 first end surface 14 second end surface 15 first side surface 16 second side surface C coil CM coil conductor CL contact layer NL non-contact layer MP metal magnetic particles ML magnetic layer OR oxidation reduction material E external electrode E1 first external electrode E2 second external electrode G1 to G7 element body layer TH through-hole conductor TH1 first through-hole conductor TH2 second through-hole conductor VD via conductor

Claims

1. A coil component comprising: an element body comprising a magnetic material containing Fe; a coil embedded in the element body; and an external electrode provided on the mounting surface of the element body and electrically connected to the coil, wherein the coil has multiple coil conductors electrically connected in the stacking direction, the element body includes a contact layer in contact with the coil conductors and a non-contact layer that does not contact the coil conductors, and the contact layer includes an oxidation-reducing material that reduces oxidation of Fe.

2. The coil component according to claim 1, wherein the oxidation-reducing material includes particles containing Fe that have a lower Fe content than the particles containing Fe contained in the non-contact layer.

3. A coil component according to claim 1 or 2, wherein the Fe content in the contact layer is 3% to 10% lower than the Fe content in the non-contact layer.

4. The coil component according to claim 3, wherein the content of Fe contained in the contact layer is 50% or more based on the entire contact layer.

5. A coil component according to any one of claims 1 to 4, wherein the oxidation-reducing material is composed of particles containing Fe coated with an insulating coating material.

6. The coil component according to claim 5, wherein the insulating coating material contains at least one element selected from the group consisting of Si, P, Zn, and Zr.

7. A coil component according to any one of claims 1 to 6, wherein the oxidation-reducing material is composed of particles containing Fe and an easily oxidizable metal material that is more easily oxidized than Fe.

8. The coil component according to claim 7, wherein the easily oxidizable metal material comprises at least one selected from the group consisting of Zn, Zr, Al and Cr.

9. A coil component according to any one of claims 1 to 8, wherein the contact layer extends from an outer edge of the coil conductor in a direction perpendicular to the stacking direction.

10. A coil component according to any one of claims 1 to 9, wherein the contact layer and the non-contact layer are arranged in this order on the upper surface of the coil conductor in the uppermost row in the stacking direction, the contact layer and the non-contact layer are arranged in this order on the lower surface of the coil conductor in the lowermost row in the stacking direction, and only the contact layer is arranged on the element portion sandwiched between the coil conductors.

11. A coil component according to any one of claims 1 to 10, wherein the average particle size of the Fe-containing magnetic material contained in the non-contact layer is larger than the average particle size of the oxidation-reducing material.

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