Inductor and method for manufacturing inductor

Abstract

Provided are an inductor having higher strength in an element body constituting a magnetic body, and a method for manufacturing the inductor. An inductor 1 according to the present disclosure comprises: an element body 10 that contains powder bodies MP1, MP2 and a resin, the element body 10 having a coil built in; and an external electrode E that is formed in the element body 10 and is electrically connected to the coil. The element body 10 is provided with: a first element body part 10a having the coil built in, the first element body part 10a having a first linear expansion coefficient; and a second element body part 10b that is provided to a first main surface facing the lower surface of the coil in the first element body part 10a and / or a second main surface facing the first main surface, the second element body part 10b having a second linear expansion coefficient lower than the first linear expansion coefficient.

Description

Inductor and method for manufacturing the same

[0001] The present disclosure relates to inductors and methods for manufacturing inductors.

[0002] Patent Document 1 discloses a multilayer electronic component in which magnetic layers and conductor patterns are stacked, and the conductor patterns between the magnetic layers are connected to form a coil within the laminate.

[0003] Japanese Patent Application Laid-Open No. 2016-186963

[0004] In an electronic device in which the laminated electronic component described in Patent Document 1 is mounted on a mounting substrate or the like, if the electronic device receives an unintended impact (for example, an impact due to dropping a portable electronic device), the mounting substrate may momentarily bend and deform, and there is a possibility that the laminated electronic component may be affected by the bending and deformation of the mounting substrate.

[0005] The present disclosure has been made in view of the above-mentioned problems. That is, a main object of the present disclosure is to provide an inductor having a magnetic body with higher strength, and a method for manufacturing the inductor.

[0006] The inductor of the present disclosure comprises: an element body containing a powder and a resin and incorporating a coil; and external electrodes formed on the element body and electrically connected to the coil, wherein the element body comprises: a first element body portion incorporating the coil and having a first linear expansion coefficient; and a second element body portion provided on a first main surface of the first element body portion facing the underside of the coil and / or a second main surface facing the first main surface, the second element body portion having a second linear expansion coefficient smaller than the first linear expansion coefficient.

[0007] The method for manufacturing an inductor according to the present disclosure includes a body formation step of forming an element containing a powder and a resin and incorporating a coil, the element formation step including: a first formation step of forming a precursor of a first element portion that incorporates the coil and has a first linear expansion coefficient; a second formation step of forming a precursor of a second element portion that is provided on a first main surface of the precursor of the first element portion that faces the underside of the coil and / or a second main surface that faces the first main surface, the precursor having a second linear expansion coefficient that is smaller than the first linear expansion coefficient; a first heat treatment step of heat treating the precursor of the first element portion and the precursor of the second element portion; and a second heat treatment step of impregnating the heat-treated precursor of the first element portion and the precursor of the second element portion with resin and heat-treating them to obtain the element containing the powder and the resin and comprising a first element portion having the first linear expansion coefficient and a second element portion having the second linear expansion coefficient.

[0008] According to the present disclosure, it is possible to provide an inductor having a stronger element body constituting a magnetic body, and a method for manufacturing an inductor.

[0009] FIG. 1 is a perspective view of an inductor according to the present disclosure. FIG. 2 is an exploded perspective view of an inductor according to a first embodiment. FIG. 3 is a cross-sectional view of the inductor according to the first embodiment. FIG. 4 is an enlarged cross-sectional view of a main portion of FIG. 3. FIG. 5 is an explanatory diagram illustrating deflection deformation in an inductor according to the present disclosure. FIG. 6 is a cross-sectional view of an inductor according to a modified example of the first embodiment. FIG. 7 is a cross-sectional view of an inductor according to another modified example of the first embodiment. FIG. 8 is a cross-sectional view of an inductor according to another modified example of the first embodiment. FIG. 9 is a cross-sectional view of an inductor according to another modified example of the first embodiment. FIG. 10 is an exploded perspective view of an inductor according to a second embodiment. FIG. 11 is a cross-sectional view of an inductor according to the second embodiment. FIG. 12 is an exploded perspective view of an inductor according to a third embodiment. FIG. 13 is a cross-sectional view of an inductor according to the third embodiment. FIG. 14 is a manufacturing flow of a manufacturing method for an inductor according to the present disclosure. FIG. 15 is a table showing the results of a demonstration test of the inductor according to the present disclosure.

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

[0011] The inductor of the present disclosure is used in, for example, a DC-DC converter, and 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] <Inductor of First Embodiment> The inductor of the first embodiment will be described with reference to Figures 1 to 5. Figure 1 is a perspective view of the inductor of the present disclosure, Figure 2 is an exploded perspective view of the inductor of the first embodiment, Figure 3 is a cross-sectional view of the inductor of the first embodiment, Figure 4 is an enlarged cross-sectional view of a main part of Figure 3, and Figure 5 is an explanatory diagram illustrating flexural deformation in the inductor of the present disclosure. Note that the shapes and arrangements of the inductor and each component are not limited to the examples shown in the figures.

[0016] The inductor 1 of the present disclosure comprises a base body 10 containing a powder and a resin and incorporating a coil, and external electrodes E1 to E4 formed on the base body 10 and electrically connected to the coil (see Figure 1).

[0017] In this embodiment, the element body 10 includes a first coil C1 and a second coil C2 disposed above the first coil C1 in the height direction T (see FIG. 3). The first coil C1 is formed by stacking laminate groups G4 and G5 (see FIG. 2) described below, whereby a first coil conductor CD1 is spirally wound with via conductors V (see FIG. 3). The second coil C2 is formed by stacking laminate groups G2 and G3 (see FIG. 2) described below, whereby a second coil conductor CD2 is spirally wound with via conductors (not shown).

[0018] The coil provided inside the element body 10 is not limited to the above configuration, and may include one coil or two or more coils. For example, a coil array may be formed by arranging multiple coils side by side inside the element body 10 in a direction intersecting the stacking direction (the L direction in FIG. 3 ). The number of external electrodes may be increased depending on the number of coils. As an example, if the first coil C1 and the second coil C2 shown in FIG. 2 are arranged side by side in the L direction in FIG. 2 to provide a total of four coils inside the element body 10, eight external electrodes may be provided corresponding to the four coils. If the coil shown in FIG. 2 is composed of either the coil C1 or the second coil C2, two external electrodes may be provided corresponding to one coil.

[0019] Each component will be described in detail below.

[0020] -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.

[0021] 1, the length direction, width direction, and height direction of the inductor 1 and the element body 10 are shown as L direction, W direction, and T direction, respectively. The length direction L, width direction W, and height direction T are perpendicular to each other. The mounting surface of the inductor 1 is, for example, a surface (LW surface) parallel to the length direction L and width direction W.

[0022] 1 has a first main surface 11 and a second main surface 12 that face each other in a height direction T, a first end surface 13 and a second end surface 14 that are perpendicular to the height direction T and face each other in a length direction L, and a first side surface 15 and a second side surface 16 that face each other in a width direction W that is perpendicular to the length direction L and the height direction T. In the example shown in FIG. 1 , the first main surface 11 of the element body 10 corresponds to the mounting surface (bottom surface) of the element body 10. Note that the second main surface 12 may also be the mounting surface of the element body 10.

[0023] The element body 10 has a layered structure in which an element body layer and multiple element body layers on which coil conductors are formed are stacked in a stacking direction (for example, height direction T). In this embodiment, the element body 10 is formed by stacking multilayer groups G1 to G7 as shown in Figure 2. Note that the boundaries between the layers in the layered structure of the element body 10 disappear. Furthermore, each multilayer group layer may be formed by stacking multiple layers of the same pattern.

[0024] The element body 10 includes a first element body portion 10a that houses a first coil C1 and a second coil C2 and has a first linear expansion coefficient, and a second element body portion 10b that has a second linear expansion coefficient that is smaller than the first linear expansion coefficient (see FIG. 3). The first element body portion 10a corresponds to the stacking groups G1 to G6 shown in FIG. 2, and the second element body portion 10b corresponds to the stacking group G7 shown in FIG. 2. The stacking groups G1 to G7 will be described in detail below.

[0025] (Stacking Group G1) The stacking group G1 constituting the first element body part 10a has a first element body layer ML1 and constitutes the second main surface 12 of the element body 10.

[0026] (Stacking group G2) The stacking group G2 constituting the first element body part 10a has a first element body layer ML1 and a second coil conductor CD2 constituting part of the second coil C2 provided in the first element body layer ML1.

[0027] The second coil conductor CD2 of the multilayer group G2 forms one winding of the second coil C2. More specifically, the second coil conductor CD2 is arranged on the first base body layer ML1 along approximately the outer periphery of the first base body layer ML1. One end of the second coil conductor CD2 is connected to a via conductor (not shown) for connection to the second coil conductor CD2 provided on the first base body layer ML1 of the multilayer group G3, and the other end of the second coil conductor CD2 is connected to a fourth through-hole conductor (not shown) for electrical connection to the fourth external electrode E4.

[0028] (Stacking group G3) The stacking group G3 constituting the first element body part 10a has a first element body layer ML1, a second coil conductor CD2 constituting part of the second coil C2 provided in the first element body layer ML1, and a fourth through-hole conductor T4 provided in the first element body layer ML1.

[0029] The second coil conductor CD2 of the multilayer group G3 forms another winding of the second coil C2. More specifically, the second coil conductor CD2 is arranged on the first base body layer ML1 substantially along the outer periphery of the first base body layer ML1. One end of the second coil conductor CD2 is connected to the second coil conductor CD2 provided on the first base body layer ML1 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.

[0030] 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 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 first base layer ML1 located above the fourth external electrode E4.

[0031] (Stacking group G4) The stacking group G4 constituting the first element body part 10a has a first element body layer ML1, a first coil conductor CD1 constituting part of the first coil C1 provided in the first element body layer ML1, and a third through-hole conductor T3 and a fourth through-hole conductor T4 provided in the first element body layer ML1.

[0032] The first coil conductor CD1 of the multilayer group G4 forms one winding of the first coil C1. More specifically, the first coil conductor CD1 is arranged on the first base body layer ML along approximately the outer periphery of the first base body layer ML. One end of the first coil conductor CD1 is provided with a via conductor (not shown) for connection to the first coil conductor CD1 provided on the first base body layer ML1 of the multilayer group G5, 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.

[0033] The third through-hole conductor T3 of the multilayer group G4 connects the third through-hole conductors T3 of the multilayer groups G3 and G5 adjacent in the stacking direction, and is electrically connected to the third external electrode E3. Therefore, the third through-hole conductor T3 may be disposed at a corner of the first base layer ML1 located on the third external electrode E3.

[0034] The fourth through-hole conductor T4 of the multilayer group G4 connects the fourth through-hole conductors T4 of the multilayer groups G3 and G5 adjacent 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 first base layer ML1 located above the fourth external electrode E4.

[0035] (Stacking group G5) The stacking group G5 constituting the first element body part 10a includes a first element body layer ML1, a first coil conductor CD1 constituting part of the first coil C1 provided in the first element body layer ML1, and a second through-hole conductor T2, a third through-hole conductor T3 and a fourth through-hole conductor T4 provided in the first element body layer ML1.

[0036] The first coil conductor CD1 of the multilayer group G5 constitutes another winding of the first coil C1. More specifically, the first coil conductor CD1 is arranged on the first base body layer ML1 along approximately the outer periphery of the first base body layer ML1. One end of the first coil conductor CD1 is connected to the first coil conductor CD1 provided on the first base body layer ML1 of the multilayer group G4, 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.

[0037] The second through-hole conductors T2 of the multilayer group G5 connect the second through-hole conductors T2 of the multilayer groups G4 and G6 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 first base layer ML1 located on the second external electrode E2.

[0038] The third through-hole conductors T3 of the multilayer group G5 connect the third through-hole conductors T3 of the multilayer groups G4 and G6 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 first base layer ML1 located above the third external electrode E3.

[0039] 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. The fourth through-hole conductor T4 may also be disposed at a corner of the first base layer ML1 located above the fourth external electrode E4.

[0040] (Stacking group G6) The stacking group G6 constituting the first element body part 10a has 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 provided at corners of the first element body layer ML1. The areas of the first through-hole conductors T1 to the fourth through-hole conductors T4 of the stacking groups G1 to G6 in plan view from the stacking direction are substantially the same.

[0041] (Lamination group G7) The laminate group G7 constituting the second element body part 10b is provided with first to fourth external electrodes E1 to E4 at corners of the second element body layer ML2, the first to fourth external electrodes E1 to E4 having larger planar areas in a plan view than the first to fourth through-hole conductors T1 to T4 of the laminate group G6. By making the planar areas of the first to fourth external electrodes E1 to E4 of the laminate group G7 larger than the planar areas of the first to fourth through-hole conductors T1 to T4 of the laminate group G6, strength during mounting can be improved. Note that in this specification, "through-hole conductors" and "external electrodes" are clearly different members, and an external electrode refers to an electrode whose planar size is approximately the same as the size of the mounting surface, and does not refer to a member that includes through-hole conductors.

[0042] The thickness of the first coil conductor CD1 and the second coil conductor CD2 in each lamination group may be the same. The first coil conductor CD1 and the second coil conductor CD2 are made of, for example, a metal conductor such as Ag, Cu, Au, Ni, or an alloy thereof. The first coil conductor CD1 and the second coil conductor CD2 may be formed, for example, by printing a conductive paste on the above-mentioned base layer.

[0043] Examples of materials for the first through-hole conductors T1 to T4 and the via conductors include metal conductors such as Ag and Cu. Furthermore, the materials for the first through-hole conductors T1 to T4 and the via conductors may be the same or different materials as those for the first coil conductor CD1 and the second coil conductor CD2 described above. Using materials with the same composition as the coil conductors simplifies the preparation of conductive materials, facilitating the manufacture of inductors. The through-hole conductors and via conductors may be formed, for example, by forming through-holes in the aforementioned base layer and printing a conductive paste into the through-holes. Alternatively, the through-hole conductors and via conductors may be formed by printing the conductive paste and then printing the base layer on top of the conductive paste.

[0044] As described above, when the element body 10 has a layered structure including the multilayer groups G1 to G7, the design flexibility of the inductor 1 is increased. For example, when manufacturing an inductor 1 including the first external electrode E1, the second external electrode E2, the third external electrode E3, and the fourth external electrode E4 on the bottom surface (first main surface 11) of the element body 10, it becomes easier to extend the first coil C1 and the second coil C2 to the bottom surface side. Note that the layered structure including the above-mentioned multilayer groups G1 to G7 may be formed by sequentially printing (e.g., screen printing) the materials constituting the element body layers, the materials constituting the insulators, the materials constituting the coil conductors CD, and the materials constituting the through-hole conductors and via conductors from the second main surface 12 side or the first main surface 11 side of the element body 10. In this case, printing may be repeated for each of the multilayer groups G1 to G7 until the element body layers, the insulators, the coil conductors, the through-hole conductors, and the via conductors reach the desired thickness.

[0045] First element body portion The first element body portion 10a is formed by stacking first element body layers ML1. The first element body layers ML1 contain first powder bodies MP1 (see FIG. 4) made of a magnetic material. The first powder bodies MP1 contain Fe (iron). More specifically, the first powder bodies MP1 may be Fe particles or Fe alloy particles. Examples of the Fe alloy include an Fe-Si alloy, an Fe-Si-Cr (chromium) alloy, an Fe-Si-Al (aluminum) alloy, an Fe-Si-B (boron)-P (phosphorus)-Cu (copper)-C (carbon) alloy, and an Fe-Si-B-Nb (niobium)-Cu alloy. The first powder bodies MP1 may also contain impurities unintentional during manufacturing, such as Cr, Mn (manganese), Cu, Ni (nickel), P, S (sulfur), or Co (cobalt). Furthermore, the first powder MP1, as will be described in detail in the explanation of the manufacturing method, may be contained in a paste containing a resin. Therefore, the first powder MP1 may contain elements (e.g., Cr, Al, Li (lithium), Zn (zinc), Zr (zirconium)) that are more easily oxidized than the Fe added during paste preparation, or oxide components thereof. By including Si in the first powder, oxidation of the Fe element contained in the powder can be suppressed, thereby further increasing the magnetic permeability of the inductor 1. The resin component contained in the magnetic paste may disappear during the first heat treatment process of the element body, which will be described later.

[0046] The surface of the first powder material MP1 is covered with an insulating coating (not shown). In this specification, "insulating" refers to a volume resistivity of 1 MΩcm or greater. Covering the surface of the first powder material MP1 with an insulating coating can improve the insulation between the first powder material MP1. Methods for forming the insulating coating on the surface of the first powder material MP1 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 surface of the first powder material MP1. The thickness of the insulating coating 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, the cross section of a polished inductor sample can be photographed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the thickness of the insulating coating covering the surface of the powder material can be measured from the obtained SEM image.

[0047] The average particle size of the first powder MP1 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 powder MP1 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 coil axis of the element body, perpendicular to the mounting surface and end surface of the element body. Multiple (e.g., five) regions (e.g., 130 μm x 100 μm) of the obtained cross section are photographed using an SEM. The obtained SEM images are analyzed using image analysis software (e.g., the image analysis software "Win R00F" (manufactured by Mitani Shoji Co., Ltd.)) to determine the circle-equivalent diameter of the powder body. The average value of the obtained circle-equivalent diameters is defined as the average particle size of the powder body. Note that the term "average particle size" as used herein may refer to the average particle size D50 (particle size equivalent to 50% cumulative percentage on a volume basis).

[0048] The first element body 10a described above contains a powder and a resin resulting from the resin impregnation described below. Specifically, although the resin component resulting from the resin paste is reduced (or eliminated) by the first heat treatment step of the element body described below, the resin component is contained in the element body due to the subsequent resin impregnation. As a result, the first element body 10a has a first linear expansion coefficient.

[0049] A first coil C1 and a second coil C2 are provided inside the first element body part 10a. The first coil C1 and the second coil C2 may be magnetically coupled. For example, the coupling coefficient between the first coil C1 and the second coil C2 is 0.1 or more and 0.8 or less. Note that the element body 10 may be provided with two coils including only the first coil C1 and the second coil C2, or may be provided with three or more coils including the first coil C1 and the second coil C2.

[0050] (First Coil) The first coil C1 is provided inside the first element body portion 10a and includes a plurality of first coil conductors CD1 connected to each other by via conductors V (see FIG. 3), a first through-hole conductor T1, and a second through-hole conductor T2.

[0051] 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.

[0052] 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.

[0053] (Second Coil) The second coil C2 may be stacked inside the first element body portion 10a, above the first coil C1 in the stacking direction. 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.

[0054] 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.

[0055] 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.

[0056] Second element body portion The second element body portion 10b is provided on the first main surface 11 facing the underside of the coil (first coil C1) in the first element body portion 10a and / or on the second main surface 12 facing the first main surface 11. In this embodiment, the first main surface 11 and the second main surface 12 may be disposed on an extension of the winding axis of the coil. The inductor 1 of the first embodiment shown in FIG. 3 illustrates a configuration in which the second element body portion 10b is provided on the mounting surface (first main surface 11 in FIG. 1) side of the element body 10, and the external electrode E is disposed within the second element body portion 10b. This configuration increases the strength of the element body 10 and also increases the adhesive strength of the external electrode E to the element body 10.

[0057] The second element body portion 10b may be located on the top surface side of the element body 10 (the second main surface 12 side in FIG. 1) as shown in Fig. 6, or may be located on both main surface sides of the element body 10 (both the first main surface 11 side and the second main surface 12 side in FIG. 1) as shown in Fig. 7. The following will mainly describe in detail the embodiment shown in Fig. 3.

[0058] The second element body part 10b is composed of a second element body layer ML2. The second element body layer ML2 includes a second powder body MP2 (see FIG. 4). The second powder body MP2 of the second element body part 10b may be composed of the same type of composition as the first powder body MP1 of the first element body part 10a. By using the same type of composition, the preparation of the powder can be simplified, and the inductor can be manufactured more easily.

[0059] The second powder MP of the second element body 10 b may be composed of a different composition from the first powder MP1 of the first element body 10 a. As an example, the second powder MP2 may be a magnetic powder such as ferrite or metal magnetic powder, a glass powder such as fused silica powder or high-melting-point glass powder, a non-magnetic powder, or an alumina powder.

[0060] In a characteristic configuration of the present disclosure, the second body portion 10b has a second linear expansion coefficient that is smaller than the first linear expansion coefficient. A method for setting the linear expansion coefficient of the second body portion 10b to the second linear expansion coefficient will be described below.

[0061] One method for achieving the second linear expansion coefficient is to reduce the resin component content of the second element body 10b compared to the resin component content of the first element body 10a. One example is to reduce the amount of resin component that penetrates into the second element body 10b by resin impregnation (described below) compared to the amount of resin component that penetrates into the first element body 10a by resin impregnation. More specifically, by reducing the amount of resin component contained in the magnetic paste in the second element body 10b compared to the amount of resin component contained in the first element body 10a, the resin component loss area can be adjusted by the first heat treatment step (described below). This allows the resin component content of the second element body 10b to be reduced compared to the resin component content of the first element body 10a by subsequent resin impregnation. It is generally known that the linear expansion coefficient of resin is higher than the linear expansion coefficient of a powder containing Fe (approximately 12 ppm / K). Therefore, by making the resin component of the second body portion 10b less than the resin component of the first body portion 10a, the linear expansion coefficient of the second body portion 10b can be made smaller than the linear expansion coefficient of the first body portion 10a.

[0062] Another method for achieving the second linear expansion coefficient is to make the volume of resin per unit volume in the regions between the plurality of second powder bodies MP2 in the second element body 10b smaller than the volume of resin per unit volume in the regions between the plurality of first powder bodies MP1 in the first element body 10a. This method also makes it possible to make the amount of resin between the second powder bodies MP2 in the second element body 10b smaller than the amount of resin between the first powder bodies MP1 in the first element body 10a, and to make the linear expansion coefficient of the second element body 10b smaller than the linear expansion coefficient of the first element body 10a. This causes compressive stress to be applied from the second element body 10b to the first element body 10a in the element body 10, and conversely, a force that offsets the compressive stress is applied from the first element body 10a to the second element body 10b, thereby increasing the strength of the element body 10.

[0063] Another method for achieving the second linear expansion coefficient is to make the linear expansion coefficient of the second powder material MP2 of the second element body 10b smaller than the linear expansion coefficient of the first powder material MP1 of the first element body 10a. When using a metal magnetic powder containing Fe for the first powder material MP1, since the linear expansion coefficient of the powder containing Fe is about 12 ppm / K, a material having a linear expansion coefficient smaller than this value is used for the second powder material MP2. As an example, alumina (Al ２ O ３ Alternatively, the second element body 10b and the first element body 10a may contain a resin having a linear expansion coefficient greater than that of the powder, and the amount of resin contained therein may be controlled to achieve a linear expansion coefficient of the second element body 10b less than that of the first element body 10a. For example, by controlling the amount of resin contained therein, the second powder body MP2 may be made of ferrite having a linear expansion coefficient of 12 ppm / K or greater (i.e., a material having a linear expansion coefficient greater than that of the first powder body MP1 may be used for the second powder body MP2). This allows the second element body 10b to have a higher strength than the first element body 10a.

[0064] Furthermore, as an example of the second powder body MP2, if the first powder body MP1 is a metal magnetic powder, the second powder body MP2 may contain one selected from the group consisting of ferrite powder, non-magnetic powder, glass powder, and alumina powder. In other words, the linear expansion coefficients of the first element body 10a and the second element body 10b may be controlled by the linear expansion coefficients of the resins and powders contained in the first element body 10a and the second element body 10b, and the linear expansion coefficient of the second element body 10b may be made smaller than the linear expansion coefficient of the first element body 10a. This allows the strength of the second element body 10b to be greater than the strength of the first element body 10a.

[0065] Furthermore, as an example of the second powder body MP2, if the first powder body MP1 is ferrite powder, the second powder body MP2 may contain one selected from the group consisting of a metal magnetic powder, a non-magnetic powder, and a glass powder. In other words, the linear expansion coefficients of the first element body 10a and the second element body 10b may be controlled by the linear expansion coefficients of the resins and powders contained in the first element body 10a and the second element body 10b, and the linear expansion coefficient of the second element body 10b may be made smaller than the linear expansion coefficient of the first element body 10a. This allows the strength of the second element body 10b to be greater than the strength of the first element body 10a.

[0066] In this specification, the method for measuring the linear expansion coefficient is as follows. First, a measurement sample is prepared by extracting the first element body portion 10a from the element body 10 of the inductor. Specifically, the measurement sample for the first element body portion is obtained by cutting the center of a cross section of the sample, which is cut through the coil winding axis of the element body 10 so as to be perpendicular to the mounting surface and end surface of the element body 10, along the coil winding axis and into a columnar shape with a depth from the surface toward the side surface of the element body 10. When extracting the first element body portion 10a, it is desirable to extract a portion containing the powder and resin, excluding the coil and through-hole conductor portions, as the measurement sample. The length of the measurement sample at room temperature (20°C) is continuously measured for dimensional change from room temperature to 200°C using a TMA device (manufactured by Hitachi High-Tech Corporation, model number TMA7100), and the linear expansion coefficient is determined from the obtained expansion curve. Note that the linear expansion coefficient can be obtained by determining the dimensional change between predetermined temperatures. For example, a length measuring microscope equipped with a heating device or an environmental SEM (e.g., an environmental scanning electron microscope (ESEM)) may be used; the means is not particularly limited. The linear expansion coefficient of the first element body portion 10a can be calculated by comparing the length of the measurement sample at 20°C with the length of the measurement sample at 200°C. To measure the linear expansion coefficient of the second element body portion 10b, a measurement sample is prepared in the same manner as described above. A measurement sample is prepared from the second element body portion 10b of the element body 10, and the linear expansion coefficient of the second element body portion 10b can be calculated by comparing the length of the measurement sample at 20°C with the length of the measurement sample at 200°C using a TMA device (manufactured by Hitachi High-Tech Corporation, model number TMA7100).

[0067] The second body portion 10b described above contains powder and resin resulting from paste, and has a second linear expansion coefficient that is smaller than the first linear expansion coefficient.

[0068] -External Electrodes- The external electrodes E are provided on the bottom surface of the element body 10. The external electrodes E 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 may be electrically connected to the first coil C1. The third external electrode E3 and the fourth external electrode E4 may be electrically connected to the second coil C2. Providing the external electrodes E on the bottom surface (first main surface 11) of the element body 10 allows the inductor 1 to be properly mounted on a mounting board or the like.

[0069] The external electrode E may be made of, for example, a material such as Ag or Cu. The external electrode E may be formed of a single layer or may have a laminated structure of two or more layers. The external electrode E may be formed by any method, but may be formed using a conductive paste, similar to the formation of the coil conductor CD described above.

[0070] In a preferred embodiment of the external electrode E, the side surface Ea of the external electrode E may be covered by the second element body 10b, and the mounting surface Eb of the external electrode E may be exposed from the second element body 10b (see FIG. 3 ). With this configuration, the surfaces of the external electrode E other than the mounting surface Eb are disposed within the second element body 10b, so that the external electrode E, which has a relatively high strength, can be preferably disposed within the second element body 10b, and the strength of the second element body 10b can be further increased.

[0071] In a preferred embodiment of the external electrode E, the linear expansion coefficient of the external electrode E may be smaller than the linear expansion coefficient of the first element body part 10a. With this configuration, the strength of the second element body part 10b containing the external electrode E can be made greater than the strength of the first element body part 10a.

[0072] As described above, the inductor of the present disclosure includes an element body 10 having a first element body portion 10a and a second element body portion 10b. With this element body 10, even if an unintended impact is applied to the mounting board MB and bending deformation occurs, as shown in FIG. 5 , the second element body portion 10b is provided on the first main surface 11 side (or the second main surface 12 side, or both the first main surface 11 side and the second main surface 12 side) of the element body 10, which is susceptible to stress due to bending deformation, when the element body 10 is soldered to a wiring pattern of a mounting board MB or is embedded in a board (not shown) with its external terminals connected to a layer MB having wiring within the board. Furthermore, because the linear expansion coefficient of the second element body portion 10b is smaller than that of the first element body portion 10a, the strength of the portion susceptible to stress due to bending deformation (the first main surface 11 side and / or the second main surface 12 side of the element body 10) can be effectively improved.

[0073] Furthermore, in the inductor of the present disclosure, compressive stress may be generated in the second element body portion 10b. With this configuration, tensile stress acts on the first element body portion 10a, but compressive stress acts on the second element body portion 10b against the tensile stress of the first element body portion 10a. This increases the strength of the element body as a whole. Note that the above-mentioned compressive stress may be generated in the element body 10 even when the inductor of the present disclosure is not mounted on the mounting board MB shown in FIG. 5.

[0074] The inductor of the present disclosure may have second element body portion 10b provided on the second main surface 12 side of element body 10, as shown in Fig. 6, or may have second element body portion 10b provided on both the first main surface 11 side and the second main surface 12 side of element body 10, as shown in Fig. 7. Even in the configurations shown in Figs. 6 and 7, the strength of the areas that are susceptible to stress due to flexural deformation (the first main surface 11 side and / or the second main surface 12 side of element body 10) can be effectively improved.

[0075] In the inductor of the first embodiment, the mounting surface Eb of the external electrode E may protrude from the second element body 10b as shown in FIG. 8 . Configuring the external electrode in this manner allows the mounting position in the height direction to be adjusted. Furthermore, if the mounting surface Eb of the external electrode E protrudes from the second element body 10b, solder can be placed between the wiring of the mounting board and the side surface of the external electrode when the inductor is mounted on the mounting board, improving the bonding strength of the inductor to the mounting board. Furthermore, contrary to the inductor shown in FIG. 8 , the mounting surface Eb of the external electrode E may be exposed and recessed from the second element body 10b as shown in FIG. 9 .

[0076] <Inductor of Second Embodiment> The inductor of the second embodiment will be described with reference to Figs. 10 and 11. Fig. 10 is an exploded perspective view of the inductor of the second embodiment, and Fig. 11 is a cross-sectional view of the inductor of the second embodiment. In describing the inductor of the second embodiment, explanation of points common to the configuration of the inductor of the first embodiment will be omitted as appropriate. In other words, the following description will focus on configurations that differ from the inductor of the first embodiment.

[0077] -Element body- The multilayer groups G1 to G6 that make up the element body 10 are similar to those in the inductor of the first embodiment described above, and make up the first element body portion 10a in the element body 10. On the other hand, the multilayer groups G7 to G8 in the inductor of the second embodiment make up the second element body portion 10b in the element body 10.

[0078] (Stacking group G7) The stacking group G7 constituting the second element body part 10b has first through-hole conductors T1, second through-hole conductors T2, third through-hole conductors T3, and fourth through-hole conductors T4 provided at corners of the second element body layer ML2. The areas of the first through-hole conductors T1 to fourth through-hole conductors T4 of the stacking groups G1 to G7 are substantially the same in plan view from the stacking direction.

[0079] (Lamination group G8) The laminate group G8 constituting the second element body part 10b is provided with first to fourth external electrodes E1 to E4 at corners of the second element body layer ML2, the first to fourth external electrodes E1 to E4 having larger planar areas in a plan view than the first to fourth through-hole conductors T1 to T4 of the laminate group G7. By making the planar areas of the first to fourth external electrodes E1 to E4 of the laminate group G8 larger than the planar areas of the first to fourth through-hole conductors T1 to T4 of the laminate group G7, it is possible to improve strength during mounting.

[0080] By configuring the multilayer groups G7 and G8 as described above, in the inductor 1 of the second embodiment, the surface Ec (see FIG. 11 ) that faces the mounting surface of the external electrode E is located within the second element body portion 10 b. With this configuration, the external electrode E is completely embedded within the second element body portion 10 b, which further increases the strength of the external electrode E with respect to the element body.

[0081] Furthermore, in the inductor 1 of the second embodiment, the thickness of the external electrode E is smaller than the thickness of the second element body portion 10 b. With this configuration, the external electrode E is completely embedded in the second element body portion 10 b, which further increases the strength of the external electrode E to the element body.

[0082] <Inductor of Third Embodiment> The inductor of the third embodiment will be described with reference to Figs. 12 and 13. Fig. 12 is an exploded perspective view of the inductor of the third embodiment, and Fig. 13 is a cross-sectional view of the inductor of the third embodiment. In describing the inductor of the third embodiment, explanation of points common to the configuration of the inductor of the first embodiment will be omitted as appropriate. In other words, the following description will focus on configurations that differ from the inductor of the first embodiment.

[0083] -Element body- The multilayer groups G1 to G6 that make up the element body 10 are similar to those in the inductor of the first embodiment described above, and make up the first element body portion 10a in the element body 10. Furthermore, the multilayer group G7 in the inductor of the second embodiment makes up the first element body portion 10a in the element body 10. Meanwhile, the multilayer group G8 in the inductor of the second embodiment makes up the second element body portion 10b in the element body 10.

[0084] (Multilayer group G7) The multilayer group G7 constituting the first element body part 10a is provided with first to fourth external electrodes E1 to E4 at corners of the first element body layer ML1, which have larger planar areas in a plan view than the first to fourth through-hole conductors T1 to T4 of the multilayer group G6. In other words, the planar areas of the first to fourth external electrodes E1 to E4 of the multilayer group G7 are larger than the planar areas of the first to fourth through-hole conductors T1 to T4 of the multilayer group G6.

[0085] (Stacking group G8) The stacking group G8 constituting the second element body portion 10b has first external electrodes E1 to fourth external electrodes E4 provided at the corners of the second element body layer ML2, with planar areas approximately the same as those of the first external electrodes E1 to fourth external electrodes E4 of the stacking group G7 in a plan view.

[0086] By configuring the multilayer groups G7 and G8 as described above, in the inductor 1 of the third embodiment, the surface Ec (see FIG. 13) that faces the mounting surface of the external electrode E is disposed within the first body portion 10a.

[0087] Furthermore, in the inductor 1 of the third embodiment, the thickness of the external electrodes E is greater than the thickness of the second body portion 10 b. With this configuration, the thickness of the external electrodes E is increased, which can further improve the strength during mounting.

[0088] <Method for Manufacturing an Inductor According to the Present Disclosure> Next, a method for manufacturing an inductor according to the present disclosure will be described with reference to Fig. 14. The method for manufacturing an inductor according to the present disclosure includes an element body forming process. Hereinafter, the method for manufacturing an inductor according to the present disclosure will be described assuming the inductor according to the first embodiment shown in Figs. 2 and 3 .

[0089] -Element Body Forming Process- The element body forming process includes a first forming process, a second forming process, a first heat treatment process, and a second heat treatment process.

[0090] First Formation Step: In the first formation step, a precursor of the first element body portion having a built-in coil and a first linear expansion coefficient is formed. First, paste for forming the first element body layers ML1 of the multilayer groups G1 to G6 described with reference to FIG. 2 and conductor paste for forming the coil conductor CD are prepared.

[0091] As an example of a method for producing the paste that constitutes the first element layer ML1, a metal powder such as an Fe—Si alloy or an Fe—Si—Cr alloy having a volume-based cumulative 50% particle diameter (D50) of 2 μm or more and 20 μm or less is prepared, and a binder such as cellulose or polyvinyl butyral (PVB) and a solvent such as a mixture of terpineol and butyl diglycol acetate (BCA) are added to this metal powder, and the mixture is kneaded to produce a magnetic paste.

[0092] When an Fe—Si alloy is used as the metal magnetic material, the Si content is preferably 2.0 at% or more and 8.0 at% or less. When an Fe—Si—Cr alloy is used as the metal magnetic powder, the Si content is preferably 2.0 at% or more and 8.0 at% or less. Furthermore, when an Fe—Si—Cr alloy is used as the iron powder, the Cr content is preferably 0.2 at% or more and 6.0 at% or less.

[0093] As the conductive paste, for example, a paste containing Ag as a conductive material is prepared.

[0094] The above-described magnetic paste and conductive paste are used to prepare the laminated groups G1 to G6 shown in FIG. 2 by screen printing or the like, and these are laminated to form a precursor of the first element body.

[0095] The second formation step is a step of forming a precursor of the second element body portion having a second linear expansion coefficient smaller than the first linear expansion coefficient. First, paste for forming the second element body layer ML2 of the multilayer group G7 described in FIG. 2 and conductive paste for forming the external electrodes are prepared.

[0096] The paste forming the second element layer ML2 may be the same material as the paste forming the first element layer ML1, or may be a different paste material from the paste forming the first element layer ML1.

[0097] The paste constituting the second element layer ML2 is made to have a smaller linear expansion coefficient than the first element body part 10 a by employing techniques such as: making the resin component of the second element body part 10 b less than the resin component of the first element body part 10 a; making the volume of resin per unit volume in the regions between the plurality of second powder bodies MP2 in the second element body part 10 b smaller than the volume of resin per unit volume in the regions between the plurality of first powder bodies MP1 in the first element body part 10 a; and / or making the linear expansion coefficient of the second powder bodies MP2 in the second element body part 10 b smaller than the linear expansion coefficient of the first powder bodies MP1 in the first element body part 10 a.

[0098] The conductive paste that forms the external electrodes is prepared, for example, a paste containing Ag as a conductive material.

[0099] The above-mentioned magnetic paste or conductive paste is used to prepare the lamination group G7 shown in FIG. 2 by screen printing or the like, and these are laminated to form a precursor of the second element body.

[0100] As a more specific technique for the second forming step, the second forming step may successively stack a precursor for the first element body and a precursor for the second element body. As an example, the precursor for the second element body may be successively stacked on the precursor for the first element body by screen printing. Note that the precursor for the first element body may be successively stacked on the precursor for the second element body by screen printing. According to this technique, the precursor for the first element body and the precursor for the second element body are successively stacked, which allows efficient screen printing and simplifies the manufacturing process.

[0101] As an alternative to the second formation step, the second formation step may involve forming a precursor for the second element body separately from the precursor for the first element body, and then integrating the separately formed precursors for the first element body and the precursor for the second element body. This approach allows the step of forming the precursor for the first element body and the step of forming the precursor for the second element body to be performed separately and in parallel, thereby shortening the process time.

[0102] First heat treatment process: After forming the precursor of the first element body and the precursor of the second element body, the paste is degreased to remove the binder, and then heat treated. By performing the heat treatment, an oxide film is formed on the surface of the metal magnetic particles, bonding the metal magnetic particles via the oxide film and sintering the conductive material in the conductor paste. The heat treatment temperature may be, for example, about 700°C.

[0103] Second Heat Treatment Step: After the first heat treatment step, the heat-treated precursor of the first element body and the precursor of the second element body are impregnated with resin. The resin impregnated into the laminate is typically an epoxy resin, but one or more resins selected from the group consisting of phenolic resin, polyester resin, polyimide resin, polyolefin resin, silicone resin, acrylic resin, polyvinyl butyral resin, cellulose resin, and alkyd resin may also be used. This allows the resin component resulting from the impregnation to fill the area where the resin component resulting from the magnetic paste has disappeared in the first heat treatment step, making it possible to reduce the resin component of the second element body compared to the resin component of the first element body. After the resin impregnation, another heat treatment is performed. The heat treatment temperature in the second heat treatment step may be, for example, approximately 80 to 300°C. Through the above steps, an element body is obtained that includes a first element body having a first linear expansion coefficient and a second element body having a second linear expansion coefficient, contains a powder material and a resin, and has a built-in coil. Furthermore, as the temperature of the element body drops to approximately room temperature after the second heat treatment step, compressive stress is generated in the first element body from the second element body portion.

[0104] 8, when forming an element body in which the external electrodes E protrude from the second element body part 10b, after forming the multilayer group G7, a paste for forming the external electrodes E may be screen-printed onto the layers that will disappear by heat treatment to form the multilayer group G8. By adding this multilayer group, the layers for printing the external electrodes E disappear, and the external electrodes E can be exposed from the element body 10 as shown in FIG.

[0105] A demonstration test on the inductor of the present disclosure will be described in detail with reference to Fig. 15. Specifically, an inductor having the linear expansion coefficient of the first element body part and the linear expansion coefficient of the second element body part shown in Fig. 15 was manufactured, and the flexural strength of the inductor was evaluated.

[0106] As described above, the linear expansion coefficients of the first and second element parts shown in Fig. 15 were calculated by comparing the lengths of samples measured at 20°C with the lengths of samples measured at 200°C using a TMA device. The flexural strength shown in Fig. 15 was determined based on the results of measuring the flexural strength using a flexural strength measuring device (three-point bending device).

[0107] 15 shows that Sample 3 and Samples 5 to 13, which are samples in which the linear expansion coefficient of the first element body portion was greater than the linear expansion coefficient of the second element body portion, had good flexural strength. On the other hand, Samples 1, 2, 4, 14, and 15, which are samples in which the linear expansion coefficient of the first element body portion was greater than the linear expansion coefficient of the second element body portion, had lower flexural strength than Sample 3 and Samples 5 to 13.

[0108] 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.

[0109] The inductor and a method for manufacturing an inductor according to the present disclosure are as follows: <1> An inductor comprising: an element body containing a powder and a resin and incorporating a coil; and an external electrode formed on the element body and electrically connected to the coil, wherein the element body comprises: a first element body portion incorporating the coil and having a first linear expansion coefficient; and a second element body portion provided on a first main surface of the first element body portion facing an underside of the coil and / or a second main surface facing the first main surface, the second element body portion having a second linear expansion coefficient smaller than the first linear expansion coefficient. <2> The inductor according to <1>, wherein the second element body portion is provided on a mounting surface side of the element body, and the external electrode is disposed within the second element body portion. <3> The inductor according to <1> or <2>, wherein a side surface of the external electrode is covered by the second element body portion, and a mounting surface of the external electrode is exposed from the second element body portion. <4> The inductor according to any one of <1> to <3>, wherein the surface of the external electrode facing the mounting surface is disposed within the second element body. <5> The inductor according to any one of <1> to <4>, wherein the thickness of the external electrode is smaller than the thickness of the second element body. <6> The inductor according to any one of <1> to <4>, wherein the surface of the external electrode facing the mounting surface is disposed within the first element body. <7> The inductor according to any one of <1> to <4>, wherein the thickness of the external electrode is larger than the thickness of the second element body. <8> The inductor according to any one of <1> to <7>, wherein the resin component of the second element body is smaller than the resin component of the first element body. <9> The inductor according to any one of <1> to <8>, wherein the volume per unit volume of the region between the plurality of powder bodies of the second element body is smaller than the volume per unit volume of the region between the plurality of powder bodies of the first element body. <10> The inductor according to any one of <1> to <9>, wherein the powder material of the second element body has a linear expansion coefficient smaller than the linear expansion coefficient of the powder material of the first element body. <11> The inductor according to any one of <1> to <9>, wherein the powder material of the first element body and the powder material of the second element body have the same composition.<12> The inductor according to any one of <1> to <9>, wherein the powder material of the first element body is a metal magnetic powder, and the powder material of the second element body contains one selected from the group consisting of ferrite powder, non-magnetic powder, glass powder, and alumina powder. <13> The inductor according to any one of <1> to <9>, wherein the powder material of the first element body is ferrite powder, and the powder material of the second element body contains one selected from the group consisting of metal magnetic powder, non-magnetic powder, and glass powder. <14> The inductor according to any one of <1> to <13>, wherein a material of a through hole electrically connecting the coil and the external electrode has the same composition as that of the material of the coil. <15> The inductor according to any one of <1> to <14>, wherein a plane area in a plan view of the through hole electrically connecting the coil and the external electrode is smaller than a plane area in a plan view of the external electrode. <16> The inductor according to any one of <1> to <15>, wherein the linear expansion coefficient of the external electrodes is smaller than the linear expansion coefficient of the first element body. <17> The inductor according to any one of <1> to <16>, wherein a compressive stress is generated in the second element body. <18> A method for manufacturing an inductor, comprising: a body forming step of forming an element containing a powder and a resin and having a coil built in, the element forming step comprising: a first forming step of forming a precursor of a first element part having the coil built in and a first linear expansion coefficient; a second forming step of forming a precursor of a second element part having a second linear expansion coefficient smaller than the first linear expansion coefficient, the precursor of the first element part being provided on a first main surface facing an underside of the coil and / or a second main surface facing the first main surface of the precursor of the first element part; a first heat treatment step of heat treating the precursor of the first element part and the precursor of the second element part; and a second heat treatment step of impregnating the heat-treated precursor of the first element part and the precursor of the second element part with resin, and heat-treating them to obtain the element containing the powder and the resin and having the coil built in. <19> The inductor manufacturing method according to <18>, wherein the first forming step and the second forming step successively stack a precursor of the first element body and a precursor of the second element body.<20> An inductor manufacturing method described in <18>, in which the second formation process forms a precursor of the second element body portion separately from a precursor of the first element body portion, and then integrates the separately formed precursor of the first element body portion and the precursor of the second element body portion.

[0110] The inductor of the present disclosure can be suitably used as an electronic component having a stronger element body that constitutes a magnetic body.

[0111] 1 inductor 10 element body 10a first element body part 10b second element body part 11 first main surface 12 second main surface 13 first end surface 14 second end surface 15 first side surface 16 second side surface C coil C1 first coil C2 second coil CD coil conductor CD1 first coil conductor CD2 second coil conductor E external electrode E1 first external electrode E2 second external electrode E3 third external electrode E4 fourth external electrode Ea side surface of external electrode Eb mounting surface Ec surface opposite to mounting surface G1 to G8 stacking group MP1 first powder body MP2 second powder body ML1 first element body layer ML2 second element body 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 base body containing a powder and resin, and with a coil built inside, The body comprises an external electrode formed thereon and electrically connected to the coil, The aforementioned body is A first element part having the aforementioned coil built in and having a first coefficient of linear expansion, The first element portion comprises a first main surface facing the lower surface of the coil and / or a second main surface facing the first main surface, and having a second coefficient of thermal expansion smaller than the first coefficient of thermal expansion, An inductor wherein the powdery material of the first element is a metallic magnetic powder, and the powdery material of the second element contains one selected from the group consisting of ferrite powder, non-magnetic powder, glass powder, and alumina powder.

2. The second body portion is provided on the mounting surface side of the body, The inductor according to claim 1, wherein the external electrode is disposed within the second element portion.

3. The inductor according to claim 1, wherein the side surface of the external electrode is covered by the second element, and the mounting surface of the external electrode is exposed from the second element.

4. The inductor according to claim 1, wherein the surface facing the mounting surface of the external electrode is disposed within the second element portion.

5. The inductor according to claim 1, wherein the thickness of the external electrode is smaller than the thickness of the second element.

6. The inductor according to claim 1, wherein the surface facing the mounting surface of the external electrode is disposed within the first element.

7. The inductor according to claim 1, wherein the thickness of the external electrode is greater than the thickness of the second element.

8. The inductor according to claim 1, wherein the resin component of the second element is less than the resin component of the first element.

9. The inductor according to claim 1, wherein the volume of resin per unit volume in the region between the plurality of powdery particles of the second element is smaller than the volume of resin per unit volume in the region between the plurality of powdery particles of the first element.

10. The inductor according to claim 1, wherein the coefficient of linear expansion of the powder in the second element is smaller than the coefficient of linear expansion of the powder in the first element.

11. The inductor according to claim 1, wherein the material of the through-hole that electrically connects the coil and the external electrode is made of the same composition as the material of the coil.

12. The inductor according to claim 1, wherein the planar area of ​​the through-hole electrically connecting the coil and the external electrode is smaller than the planar area of ​​the external electrode.

13. The inductor according to claim 1, wherein the coefficient of linear expansion of the external electrode is smaller than the coefficient of linear expansion of the first element.

14. The inductor according to claim 1, wherein compressive stress is generated in the second element portion.

15. The process includes a body forming step that forms a body containing a powder and a resin, and which incorporates a coil. The aforementioned body formation step is, A first forming step involves forming a precursor of a first element having a first coefficient of linear expansion, which incorporates the aforementioned coil. A second forming step of forming a precursor of the second element, which is provided on a first main surface facing the lower surface of the coil and / or a second main surface facing the first main surface of the precursor of the first element, and which has a second coefficient of linear expansion smaller than the first coefficient of linear expansion; A first heat treatment step involves heat-treating the precursor of the first element and the precursor of the second element, A second heat treatment step is to impregnate the precursor of the first and second base body portions, which have undergone the aforementioned heat treatment, with a resin, and then heat treat them to obtain a base body comprising a first base body portion having a first coefficient of linear expansion and a second base body portion having a second coefficient of linear expansion, the base body containing the powder and the resin, and incorporating the coil. A method for manufacturing an inductor, which includes the following features.

16. The method for manufacturing an inductor according to claim 15, wherein the first forming step and the second forming step involve successively stacking the precursor of the first element and the precursor of the second element.

17. The method for manufacturing an inductor according to claim 15, wherein the second forming step involves forming a precursor for the second element separately from the precursor for the first element, and then integrating the separately formed precursors for the first element and the second element with each other.