Multilayer inductor, multilayer inductor array, and manufacturing method for multilayer inductor

Abstract

To provide a multilayer inductor and a multilayer inductor array with improved strength of an element assembly and a manufacturing method for the multilayer inductor.SOLUTION: The multilayer inductor includes an element assembly B configuring a magnetic body M by laminating magnetic material layers ML containing iron powder and having a coil C with coil conductor CM wound inside the magnetic body M and external electrodes (first external electrode E1, second external electrode) electrically connected to the coil conductor CM. At least a portion of pores in the vicinity of the magnetic material layers ML in gaps in the magnetic body M and on the coil conductor CM are impregnated with resin.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a laminated inductor, a laminated inductor array, and a method for manufacturing a laminated inductor. [Background technology]

[0002] In recent years, as equipment becomes more sophisticated, the DC-DC converters in voltage conversion circuits are becoming larger in current and more efficient, and the rated current of the power inductors used in these devices is also increasing.

[0003] Patent Document 1, which shows an example of the above-mentioned inductor, discloses a multilayer electronic component in which a metal magnetic layer mainly composed of metal magnetic particles and a conductor pattern are laminated and a coil is formed within the laminate, and a manufacturing method thereof. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-27354 A Summary of the Invention [Problem to be solved by the invention]

[0005] In multilayer electronic components, metal magnetic layers, which are mainly composed of metal magnetic particles, have voids between the particles, which causes a problem of reduced strength of the laminate (element) due to the existence of these voids in the metal magnetic layers.

[0006] A primary object of the present disclosure is to provide a laminated inductor and a laminated inductor array having improved element strength, as well as a method for manufacturing a laminated inductor. [Means for solving the problem]

[0007] The laminated inductor of the present disclosure comprises: an element body having a magnetic body formed by laminating magnetic body layers containing iron powder and a coil formed by winding a coil conductor inside the magnetic body; an external electrode electrically connected to the coil conductor; A resin is provided in the gap in the magnetic body, The coil conductor has pores at least near the magnetic layer, The resin is provided in at least some of the pores.

[0008] The laminated inductor array of the present disclosure comprises: an element body having a magnetic body formed by laminating magnetic body layers containing iron powder and a coil formed by winding a coil conductor inside the magnetic body; an external electrode electrically connected to the coil conductor; The coils are arranged in a stacked manner in two or more layers in a plan view from a stacking direction, and are arranged in parallel in a direction intersecting the stacking direction to form a coil array; A resin is provided in the gap in the magnetic body, The resin is provided in at least some of the pores in the coil conductor near the magnetic layer.

[0009] The method for producing a laminated inductor according to the present disclosure includes: a body preparation step of stacking magnetic body layers containing iron powder to form a magnetic body and preparing an element having a coil wound with a coil conductor inside the magnetic body; a resin impregnation step of impregnating resin into voids in the magnetic body and at least a part of the pores in the coil conductor at least near the magnetic body layer; an external electrode forming step of forming an external electrode electrically connected to the coil conductor; It is equipped with: Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a laminated inductor and a laminated inductor array with improved element strength, and a method for manufacturing a laminated inductor. Specifically, in the element of the laminated inductor, a resin is provided in at least a part of the gaps in the magnetic body and the pores in the coil conductor at least near the magnetic body layer, so that the element strength can be increased by reducing the gaps and pores. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view illustrating an example of the laminated inductor according to the first embodiment. [Diagram 2] FIG. 2 is an exploded perspective view of the internal structure of the laminated inductor of the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view of the laminated inductor of the first embodiment. [Figure 4A] FIG. 4A is a partially enlarged cross-sectional view of a portion Z1 in FIG. [Figure 4B] 4B is a partially enlarged cross-sectional view of the Z2 portion of FIG. [Diagram 5] FIG. 5 is a cross-sectional SEM photograph of the laminated inductor of the first embodiment. [Figure 6] FIG. 6 is an elemental analysis photograph illustrating the results of the elemental analysis performed based on FIG. [Figure 7] FIG. 7 is a cross-sectional SEM photograph taken at a position different from that in FIG. [Figure 8] FIG. 8 is a cross-sectional view of a laminated inductor according to a modified example of the first embodiment. [Figure 9] FIG. 9 is a perspective view illustrating an example of the laminated inductor according to the second embodiment. [Figure 10] FIG. 10 is a perspective view illustrating a schematic example of a laminated inductor array according to the present disclosure. [Figure 11] FIG. 11 is a flow diagram showing a method for manufacturing a laminated inductor according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The laminated inductor of the present disclosure will be described below. Note that the present disclosure is not limited to the following configurations, and may be modified as appropriate without departing from the gist of the present disclosure. In addition, a combination of multiple individual preferred configurations described below also constitutes the present disclosure.

[0013] The laminated inductor 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.

[0014] In this specification, terms indicating the relationship between elements (e.g., "parallel," "orthogonal," etc.) and terms indicating the shapes 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."

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

[0016] <First embodiment of multilayer inductor> First, a first embodiment of the laminated inductor of the present disclosure will be described with reference to Figures 1 to 8. Note that the shapes and arrangements of the laminated inductor and its components are not limited to the examples shown in the drawings.

[0017] 1 includes a magnetic body formed by laminating magnetic layers containing iron powder, an element body B having a coil C formed by winding a coil conductor inside the magnetic body, and an external electrode E electrically connected to the coil conductor. Each component will be described in detail below.

[0018] -Base body- The element body B has, for example, a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape having six sides. The corners and ridges of the element body B may be rounded. The corners are the parts where three sides of the element body B intersect, and the ridges are the parts where two sides of the element body B intersect.

[0019] 1, the length direction, width direction, and height direction of the laminated inductor 1 and the element body B are shown as L direction, W direction, and T direction, respectively. The length direction L, width direction W, and height direction T are perpendicular to each other. The mounting surface of the laminated inductor 1 is, for example, a surface (LW surface) parallel to the length direction L and width direction W.

[0020] 1 has a first main surface B1 and a second main surface B2 facing in a height direction T, a first end surface B3 and a second end surface B4 perpendicular to the height direction T and facing in a length direction L, and a first side surface B5 and a second side surface B6 facing in a width direction W perpendicular to the length direction L and the height direction T. In the example shown in FIG. 1, the first main surface B1 of the element body B corresponds to the mounting surface (bottom surface) of the element body B. It is to be noted that the second main surface B2 may be the mounting surface of the element body B.

[0021] The element body B includes a magnetic body M formed by stacking magnetic layers ML, and a coil C formed by winding a coil conductor CM (see Figs. 2 and 3). Specifically, the element body B may include a plurality of magnetic layers ML and coil conductors CM in the stacking direction (e.g., height direction T). In this embodiment, as shown in Fig. 2, the element body B is configured by stacking stacking groups G1 to G7, each of which includes at least one magnetic layer ML and coil conductor CM (or only magnetic layer ML). Note that the boundaries between layers in the stacked structure of the element body B may disappear. Also, each stacking group may be configured by stacking the same pattern a plurality of times.

[0022] The lamination group G1 includes a magnetic layer ML and constitutes the second main surface B2 of the element body B.

[0023] The multilayer group G2 includes magnetic layers ML and coil conductors CM. The coil conductors CM of the multilayer group G2 form one winding of the coil C. More specifically, the coil conductor CM is disposed substantially along the outer periphery of the magnetic layers ML.

[0024] The multilayer group G3 includes a magnetic layer ML, a second through hole TH2 that electrically connects the coil conductor CM and the second external electrode E2 of the multilayer group G2, and a via conductor V that connects adjacent coil conductors CM in the stacking direction. The second through hole TH2 is disposed at a corner of the magnetic layer ML. The via conductor V is disposed adjacent to the second through hole TH2.

[0025] The multilayer group G4 includes a magnetic layer ML, a second through hole TH2 that electrically connects the second through hole TH2 of the multilayer group G3 to the second external electrode E2, and a coil conductor CM. The coil conductor CM of the multilayer group G4 forms one winding of the coil C. More specifically, the coil conductor CM is arranged along the outer periphery of the magnetic layer ML while avoiding the second through hole TH2 with an avoidance portion A, and ends of the coil conductor CM are spaced apart to form a winding structure. To describe the avoidance portion A in more detail, the avoidance portion A provided in the multilayer group G4 may be provided on the inside compared to the coil conductor CM arranged along the outer periphery of the multilayer group G2, and avoid the second through hole TH2.

[0026] The multilayer group G5 includes a magnetic layer ML, a second through hole TH2 that electrically connects the second through hole TH2 of the multilayer group G4 to the second external electrode E2, and a via conductor V for connecting adjacent coil conductors CM in the stacking direction. The via conductor V is located adjacent to the second through hole TH2 at a position where it can be electrically connected to an end of the coil conductor CM of the multilayer group G4.

[0027] The multilayer group G6 includes a magnetic layer ML, a second through hole TH2 that electrically connects the second through hole TH2 of the multilayer group G5 to the second external electrode E2, and a coil conductor CM. The coil conductor CM of the multilayer group G6 forms one winding of the coil C. More specifically, the coil conductor CM is arranged along the outer periphery of the magnetic layer ML while avoiding the second through hole TH2 with an avoidance portion A, and ends of the coil conductor CM are spaced apart to form a winding structure. To describe the avoidance portion A in more detail, the avoidance portion A provided in the multilayer group G6 may be provided on the inside compared to the coil conductor CM arranged along the outer periphery of the multilayer group G2, and avoid the second through hole TH2.

[0028] The multilayer group G7 includes a magnetic layer ML, a second through hole TH2 electrically connecting the second through hole TH2 of the multilayer group G6 to the second external electrode E2, and a first through hole TH1 electrically connecting the coil conductor CM of the multilayer group G6 to the first external electrode E1. The first through hole TH1 is disposed at a corner of the magnetic layer ML.

[0029] As described above, when the element body B has a multilayer structure including the multilayer groups G1 to G7, the degree of freedom in designing the multilayer inductor 1 is increased. For example, when manufacturing a multilayer inductor 1 including the first external electrode E1 and the second external electrode E2 on the bottom surface (first main surface B1) of the element body B, it becomes easier to draw out the coil C to the bottom surface side. The multilayer structure including the multilayer groups G1 to G7 may be formed by stacking the material constituting the magnetic layer ML, the material constituting the coil conductor CM, and the material constituting the through-holes and via conductors by sequentially printing (for example, screen printing, etc.) from the second main surface B2 side or the first main surface B1 side of the element body B. In this case, each of the multilayer groups G1 to G7 may be repeatedly printed until the magnetic layer ML, the coil conductor CM, the through-holes and the via conductors reach a desired thickness.

[0030] ·Magnetic material The magnetic body M (see Figs. 2 to 4) formed by stacking the magnetic layers ML includes iron powder MP made of a magnetic material. The "iron powder" in this specification is not limited to being strictly powdery, but also includes powdery substances bonded together by heat treatment (sintering) described later. The iron powder MP may contain Fe and / or Si. More specifically, it may be Fe particles or Fe alloy particles. The Fe alloy may be an Fe-Si alloy, an Fe-Si-Cr alloy, an Fe-Si-Al alloy, an Fe-Si-BP-Cu-C alloy, and / or an Fe-Si-B-Nb-Cu alloy. The iron powder MP may also contain impurities such as Cr, Mn, Cu, Ni, P, S, and / or Co that are not intended in the manufacturing process. The iron powder MP may also be contained in the magnetic paste, as will be described in detail in the explanation of the manufacturing method. Therefore, the iron powder may contain elements (e.g., Cr, Al, Li, Zn) that are more easily oxidized than Fe added when the magnetic paste is prepared.

[0031] The surface of the iron powder MP may be covered with an insulating film (not shown). When the surface of the iron powder MP is covered with an insulating film, the insulation between the iron powder MP can be improved. The insulating film can be formed on the surface of the iron powder MP by a sol-gel method, a mechanochemical method, or the like. The material constituting the insulating film may be an oxide of P and / or Si. The insulating film may also be an oxide film formed by oxidizing the surface of the iron powder MP. The thickness of the insulating film is preferably 1 nm or more and 50 nm or less, more preferably 1 nm or more and 30 nm or less, and even more preferably 1 nm or more and 20 nm or less. For example, a cross section obtained by polishing an inductor sample is photographed with a scanning electron microscope (SEM), and the thickness of the insulating film covering the surface of the iron powder MP can be measured from the obtained SEM photograph.

[0032] The average particle size of the iron powder MP in the magnetic body M is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and even more preferably 1 μm or more and 10 μm or less. The average particle size of the iron powder MP in the magnetic body M can be measured by the procedure described below. A sample of a laminated inductor is cut to obtain a sample cross section. Specifically, the cross section shown in FIG. 3 (that is, a sample cross section passing through the first through hole of the element body and perpendicular to the mounting surface and end surface of the element body) is obtained. For the obtained cross section, a plurality of (for example, five) regions (for example, 130 μm × 100 μm) are photographed by SEM, and the obtained SEM images are analyzed using image analysis software (for example, image analysis software WinROOF2021 (manufactured by Mitani Shoji Co., Ltd.)) to obtain the circle equivalent diameter of the iron powder MP. The average value of the obtained circle equivalent diameters is taken as the average particle size of the metal magnetic particles.

[0033] Here, as a new finding in the present disclosure, the inventors of the present application have found that even when the iron powder MP contained in the magnetic layer ML is bonded by sintering, voids O (see FIGS. 4A and 4B) are generated between the iron powder MP, and the presence of the voids reduces the strength of the element body. The term "voids" as used in this specification refers to the space between adjacent powder bodies. In other words, it refers to the space determined by the positional relationship between adjacent powder bodies. The voids O can be observed from an SEM image of a cross section of the sample obtained by cutting the sample of the multilayer inductor 1 as described above. As a specific method for identifying the voids O, when an observation area of ​​the cross section of the sample is set to 130 μm×100 μm and an SEM image is obtained, and the voids O and the non-voids in the magnetic body M are analyzed by image analysis software, the area ratio of the voids O to the entire observation area may be 10% to 40%.

[0034] In the laminated inductor 1 of this embodiment, in order to reduce a decrease in the strength of the element body due to the presence of the voids O, the element body B is impregnated with a resin material after firing to provide resin R in the voids O. By providing resin R in the voids O in the magnetic body M, the strength of the element body can be further improved.

[0035] The resin provided in the gap O may contain epoxy resin, silicone resin, or phenol resin. If the resin that fills the gap O in the magnetic body M is epoxy resin or phenol resin, the strength of the body B can be further increased.

[0036] ·coil The coil includes a plurality of coil conductors CM in a lamination direction (for example, a height direction T). The coil of this embodiment may have a number of turns of about 2.75, which is made up of lamination groups G2, G4, and G6, as shown in Figs.

[0037] The thickness of the coil conductor CM in each lamination group may be the same. The coil conductor CM may be a metal conductor such as Ag, Cu, and / or Pd, for example. The coil conductor CM may be formed by printing a conductive paste on the magnetic layer ML.

[0038] Here, as a new finding in this disclosure, the inventors of the present application have found that pores P (see Figs. 4A and 4B) can be generated in the coil conductor CM constituting the coil after firing of the element body, depending on the material of the coil conductor and the firing conditions. In this specification, the term "pore" refers to a minute cavity. As described above, the pores P can be observed from an SEM image of a cross section of a laminated inductor sample obtained by cutting the sample. As an example, the pores P may have a size of about 1 µm in terms of a circle equivalent diameter analyzed by image analysis software. As a more specific method of identifying the pores P, when an observation area of ​​the cross section of the sample is set to 150 µm x 70 µm, the average size of the pores P extracted from the largest 10 pores P present in the observation area may be 1 µm or more and 6 µm or less. As another method for identifying pores P, an observation area of ​​the sample cross section is set to 150 μm x 70 μm, an SEM image is obtained, and the pores P and non-pores within the coil conductor CM are analyzed using image analysis software, and the area ratio of pores P to the entire observation area may be 3% or more and 30% or less.

[0039] In the laminated inductor 1 of this embodiment, in order to reduce the decrease in the strength of the element body due to the presence of the pores P, the element body B is impregnated with a resin material after sintering. By this impregnation, the resin R is provided in the gaps O, and the resin R is provided in the pores P. More specifically, the resin R is provided on the upper and lower surfaces of the coil conductor CM, which is at least a part of the pores P in the coil conductor CM near the magnetic layer ML (see FIG. 4). Note that "near the magnetic layer" in this specification means a range of up to 15 μm from the interface between the coil conductor and the magnetic layer. Therefore, the element body strength can be further improved compared to the laminated electronic component described in the prior art. Note that the resin R in the pores P and the resin R in the gaps O may be the same material, from the viewpoint of being provided by impregnating the element body B with a resin material after sintering.

[0040] Through-hole and via conductors The coil C may include a through hole and a via conductor. The through hole may include a first through hole TH1 and a second through hole TH2. The first through hole TH1 and the second through hole TH2 may be provided inside the element body B. The first through hole TH1 and the second through hole TH2 may be exposed from the mounting surface (first main surface B1) of the element body B.

[0041] The first through hole TH1 may connect the first external electrode E1 to an end of the coil conductor CM that is closest to the bottom surface (first main surface B1) of the element body B among the ends of the coil C. The first through hole TH1 may extend along the stacking direction (e.g., the height direction T). The first through hole TH1 may have a stacked structure.

[0042] The second through hole TH2 may connect the other end of the coil C and the second external electrode E2. The second through hole TH2 may extend along the lamination direction (for example, the height direction T). The second through hole TH2 may have a laminated structure.

[0043] The via conductor V may electrically connect the coil conductors CM provided in the stacking groups adjacent to each other in the stacking direction. In other words, the length of the via conductor V in the stacking direction may be shorter than the length of the first through hole TH1 or the length of the second through hole TH2. The via conductor V may have a stacking structure.

[0044] Examples of materials for the through holes and via conductors include metal conductors such as Ag, Cu, and / or Pd. The materials for the through holes and via conductors may be the same as or different from the coil conductor CM. The through holes and via conductors may be formed, for example, by forming through holes in the magnetic layer ML and printing a conductive paste in the through holes.

[0045] -External electrode- 1, the external electrodes may include a first external electrode E1 and a second external electrode E2. The first external electrode E1 and the second external electrode E2 may be provided on a first main surface B1 (bottom surface) of the element body B and electrically connected to the coil C. Providing the external electrodes on the first main surface B1 of the element body B allows the laminated inductor 1 to be appropriately mounted on a mounting board or the like.

[0046] The first external electrode E1 may act as an input electrode and / or an output electrode for the coil C. The first external electrode E1 may be provided only on the first main surface B1 of the element body B, or may be provided across the first main surface B1 of the element body B and at least one of the second end surface B4, the first side surface B5, or the second side surface B6.

[0047] The second external electrode E2 may act as an input electrode and / or an output electrode for the coil C. The second external electrode E2 may be provided only on the first main surface B1 of the element body B, or may be provided across the first main surface B1 of the element body B and at least one of the first end surface B3, the first side surface B5, or the second side surface B6.

[0048] In a preferred embodiment of the external electrodes, the planar area of ​​the external electrodes viewed from the mounting surface side of the element body B may be larger than the planar area of ​​the through-holes. By making the planar area of ​​the external electrodes relatively large, it becomes easy to align the electrodes of the mounting board with the external electrodes of the laminated inductor 1 when mounting the laminated inductor 1 on a mounting board or the like.

[0049] The external electrodes may be made of various materials such as Cu, Ni and / or Sn. The external electrodes may be formed of a single layer or may have a laminated structure of two or more layers. The external electrodes may be formed by any method, and may be, for example, plated electrodes formed by direct plating (e.g., electrolytic plating) on ​​the through holes. When forming the external electrodes by plating, it is necessary to immerse the element B in a plating solution. However, as described above, since the resin R is provided in the gaps O of the element B (magnetic body M), it is possible to reduce the infiltration of the plating solution into the gaps in the magnetic body.

[0050] As described above, according to the laminated inductor 1 of the present disclosure, resin is provided in the gaps O in the magnetic body M and in at least some of the pores P in the coil conductor CM near the magnetic layer ML, thereby reducing the gaps O and pores P and increasing the strength of the element.

[0051] -Resin impregnation mode- Regarding a preferred resin impregnation mode of the voids O, the resin impregnation rate of the voids O1 in the element body B may be higher than the resin impregnation rate of the voids O2 located on the inner side of the element body B relative to the voids O1. The impregnation rate can be measured by the procedure described below. A sample of the multilayer inductor is cut to obtain a sample cross section. Specifically, the cross section shown in FIG. 3 (that is, a sample cross section passing through the first through hole of the element body and perpendicular to the mounting surface and end surface of the element body) is obtained. The obtained cross section is photographed by SEM-EDX, and the obtained image is analyzed using image analysis software to obtain the impregnation rate. The above mode will be described in detail with reference to FIGS. 3 to 4B.

[0052] A specific method for impregnating resin into element body B will be described in detail in the manufacturing method of a laminated inductor described later, but resin R is impregnated from the outer surface of element body B, and the outside of element body B is more easily impregnated with resin R than the inside of element body B. That is, according to the schematic diagram of Fig. 4A, void O1 in part Z1 of element body B is impregnated with a relatively large amount of resin, and according to the schematic diagram of Fig. 4B, void O2 in part Z2, which is located more inwardly of element body B than void O1 in part Z1, is impregnated with less resin than in Fig. 4A.

[0053] According to this embodiment of resin impregnation, the resin impregnation rate of the voids O1 located on the outer surface side of the element B is higher than the resin impregnation rate of the voids O2, so that when the external electrode is used as a plating electrode, it is possible to further reduce the infiltration of the plating solution into the magnetic body M. The tendency of resin impregnation into the voids O also has a similar tendency into the pores P, and the resin impregnation rate of the pores P1 may be higher than the resin impregnation rate of the pores P2 located further inside the element B than the pores P1.

[0054] As a further preferred embodiment of the resin impregnation, the resin R may be provided in the space SP located between the magnetic layer ML and the coil conductor CM in the stacking direction, in addition to the voids O in the magnetic body M and the pores P in the coil conductor CM. The above embodiment will be described in detail with reference to FIG.

[0055] The "space between the magnetic layer and the coil conductor in the stacking direction" in this specification is a different concept from the "gap" between adjacent powder bodies, and refers to a space specified by the positional relationship between the magnetic layer ML and the coil conductor CM. More specifically, it refers to a space located near the interface between the magnetic layer ML and the coil conductor CM and extending along the interface. Note that the vicinity of the interface refers to a range from the interface between the magnetic layer ML and the coil conductor CM to about the particle diameter of the iron powder MP in the stacking direction, and may be surrounded by the magnetic layer ML. More specifically, it refers to a range from the interface between the magnetic layer and the coil conductor CM to ±15 μm in the stacking direction.

[0056] The spacing of the space SP can be measured by cutting a sample of the laminated inductor to obtain a cross section of the sample as described above, and observing the maximum length of the space SP in the lamination direction from an SEM image of the cross section of the sample. As an example, the size of the space SP may be about 2 μm.

[0057] By providing the resin R in the space SP between the magnetic layer ML and the coil conductor CM in the stacking direction in this manner, the peel strength between the magnetic layer ML and the coil conductor CM can be further improved.

[0058] <Modification of the First Embodiment of the Multilayer Inductor> As a modified example of the laminated inductor 1 of the first embodiment, as shown in FIG. 8, an insulating layer I may be disposed between the magnetic layers ML. More specifically, in the laminated groups G1 to G7 shown in FIG. 2, an insulating layer I may be disposed between the magnetic layers ML in the lamination direction. When the insulating layer I is disposed between the coil conductors CM, a through hole and a via conductor may be provided in the insulating layer I. By disposing the insulating layer I between the coil conductor layers, it is possible to further reduce the coil conductors CM inside the magnetic body M from shorting each other. The insulating layer I may not be disposed between all the magnetic layers ML, but may be disposed only between some of the magnetic layers ML.

[0059] <Second embodiment of multilayer inductor> Next, the laminated inductor 1 of the second embodiment will be described with reference to Fig. 9. The laminated inductor 1 of the second embodiment differs from the inductor of the first embodiment described above in terms of the coil configuration. The following description will focus on the differences from the laminated inductor described in the above embodiment.

[0060] The coils of the laminated inductor 1 of this embodiment may be arranged so that two or more are overlapped when viewed from a plane in the lamination direction. In other words, a first coil C1 and a second coil C2 may be provided inside the element body B. 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, two coils including only the first coil C1 and the second coil C2 may be provided inside the element body B, or three or more coils including the first coil C1 and the second coil C2 may be provided.

[0061] -First coil- The first coil C1 includes a plurality of first coil conductors CM1 constituting the first coil C1 in the stacking direction (e.g., height direction T). Adjacent first coil conductors CM1 are connected to each other through via conductors V. The first coil C1 may have a number of turns of 1.75 by including first coil conductors CM1 formed in two different stacking groups in the stacking direction. The number of turns is not limited to 1.75, and may be, for example, 2 or more, by stacking the first coil conductors CM1 in the stacking direction.

[0062] -Second coil- The second coil C2 is disposed above the first coil C1 in the height direction T, and includes a plurality of second coil conductors CM2 constituting the second coil in the stacking direction (for example, in the height direction T). Adjacent second coil conductors CM2 are connected to each other through via conductors V. The second coil C2 may have a number of turns of 1.75 by including second coil conductors CM2 formed in two different stacking groups in the stacking direction. The number of turns is not limited to 1.75 as shown in the figure, and may be, for example, 2 or more by stacking the first coil conductor CM1 in the stacking direction. The number of stacked layers of the second coil conductor CM2 may be the same as or different from the number of stacked layers of the first coil conductor 51.

[0063] -Through holes and external electrodes- The through holes include a first through hole TH1, a second through hole TH2, a third through hole TH3, and a fourth through hole TH4. The first through hole TH1, the second through hole TH2, the third through hole TH3, and the fourth through hole TH4 are provided inside the element body B. The first through hole TH1, the second through hole TH2, the third through hole TH3, and the fourth through hole TH4 are exposed from the mounting surface (first main surface B1) of the element body B.

[0064] The first through hole TH1 connects the end of the first coil C1 of the first coil conductor CM1 that is closest to the bottom surface (first main surface B1) of the element body B to the first external electrode E1. The first through hole TH1 may extend along the lamination direction (e.g., the height direction T). The first through hole TH1 may have a laminated structure.

[0065] The second through hole TH2 connects the other end of the first coil C1 and the second external electrode E2. The second through hole TH2 may extend along the lamination direction (for example, the height direction T). The second through hole TH2 may have a laminated structure.

[0066] The third through hole TH3 connects the end of the second coil C2 of the second coil conductor CM2 that is closest to the bottom surface (first main surface B1) of the element body B to the third external electrode E3. The third through hole TH3 may extend along the stacking direction (e.g., the height direction T). The third through hole TH3 may have a stacked structure.

[0067] The fourth through hole TH4 connects the other end of the second coil C2 and the fourth external electrode E4. The fourth through hole TH4 may extend along the stacking direction (for example, the height direction T). The fourth through hole TH4 may have a stacked structure.

[0068] 9, the external electrodes include a first external electrode E1, a second external electrode E2, a third external electrode E3, and a fourth external electrode E4. The first external electrode E1 and the second external electrode E2 are provided on the first main surface B1 of the element body B, and are electrically connected to the first coil C1. The third external electrode E3 and the fourth external electrode E4 are provided on the first main surface B1 of the element body B, and are electrically connected to the second coil C2. In the laminated inductor 1, the first main surface B1 of the element body B can be used as a mounting surface.

[0069] Even in the laminated inductor 1 of the second embodiment, resin is provided in the gaps O in the magnetic body M and in some of the pores P in the coil conductor CM at least near the magnetic layer ML. Therefore, by reducing the gaps O and pores P, the strength of the element can be increased.

[0070] <Multilayer inductor array> Next, the laminated inductor array of the present disclosure will be described with reference to FIG. 10. The laminated inductor array 100 of the present disclosure has two or more coils arranged overlapping each other in a plan view from the lamination direction, and arranged side by side in a direction intersecting the lamination direction to form a coil array. Specifically, in addition to the first coil C1 and the second coil C2, the array may include a third coil C3 and a fourth coil C4, as well as a fifth coil C5 and a sixth coil C6. The third coil C3 and the fifth coil C5 have substantially the same structure as the first coil C1, and the fourth coil C4 and the sixth coil C6 have substantially the same structure as the second coil C2.

[0071] The third coil C3 may be electrically connected to the fifth external electrode E5 and the sixth external electrode E6. The end of the third coil C3, that of the third coil conductor layer closest to the bottom surface, may be connected to the fifth external electrode E5 by a fifth through hole TH5. The other end of the third coil conductor layer may be connected to the sixth external electrode E6 by a sixth through hole TH6.

[0072] The fourth coil C4 may be electrically connected to a seventh external electrode (not shown) and an eighth external electrode (not shown). Of the ends of the fourth coil C4, an end of the fourth coil conductor layer closest to the bottom surface may be connected to the seventh external electrode by a seventh through hole. Also, the other end of the fourth coil conductor layer may be connected to the eighth external electrode by an eighth through hole.

[0073] The fifth coil C5 may be electrically connected to the ninth external electrode E9 and the tenth external electrode E10. The end of the fifth coil C5, the end of the fifth coil conductor layer closest to the bottom surface, may be connected to the ninth external electrode E9 by a ninth through hole TH9. The other end of the fifth coil conductor layer may be connected to the tenth external electrode E10 by a tenth through hole TH10.

[0074] The sixth coil C6 may be electrically connected to the eleventh external electrode E11 and the twelfth external electrode E12. Of the ends of the sixth coil C6, the end of the sixth coil conductor layer closest to the bottom surface may be connected to the eleventh external electrode E11 by an eleventh through hole TH11. In addition, the other end of the sixth coil conductor layer may be connected to the twelfth external electrode (not shown) by a twelfth through hole TH12.

[0075] Even in the laminated inductor array 10 of the present disclosure, resin is provided in the gaps O in the magnetic body M and in some of the pores P in the coil conductor CM at least near the magnetic layer ML. Therefore, by reducing the gaps O and pores P, the strength of the element can be increased.

[0076] <Manufacturing method for multilayer inductors> Next, a method for manufacturing a laminated inductor according to the present disclosure will be described with reference to the manufacturing flow shown in Fig. 11. The method for manufacturing a laminated inductor according to the present disclosure may include an element body preparation step, a resin impregnation preparation step, a resin impregnation step, and an external electrode formation step. Each step will be described in detail below.

[0077] ·Body preparation process First, a magnetic paste for forming the magnetic layers ML of the multilayer group described in FIG. 2, a conductor paste for forming the coil conductors CM, and a non-magnetic paste for forming the non-magnetic layers between the coil conductors CM are prepared.

[0078] As an example of a method for producing a magnetic paste, an iron powder such as an Fe-Si alloy or an Fe-Si-Cr alloy with a cumulative 50% particle diameter D50 on a volume basis of 2 μm or more and 20 μm or less is prepared. This iron powder is mixed with a binder such as cellulose or polyvinyl butyral (PVB) and a solvent such as a mixture of terpineol and butyl diglycol acetate (BCA), and then kneaded to produce a magnetic paste.

[0079] When an Fe-Si alloy is used as the iron powder, 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 iron powder, 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 iron powder, the Cr content is preferably 0.2 at% or more and 6.0 at% or less.

[0080] An insulating coating may be provided on the surface of the iron powder. The insulating coating is preferably a coating containing a metal oxide, more preferably an oxide of Si. The method for forming the insulating coating is preferably a sol-gel method. As an example of forming an insulating coating by the sol-gel method, a sol-gel coating agent containing Si alkoxide and an organic chain-containing silane coupling agent are mixed to form a mixed liquid. After this mixed liquid is attached to the surface of the metal magnetic powder, it is dehydrated and bonded by applying a heat treatment. Then, the insulating coating can be formed by drying at a predetermined temperature.

[0081] As an example of a method for producing a non-magnetic paste, Fe2O3, ZnO, CuO, and additional components as necessary are weighed out to obtain a predetermined composition. The weighed items are placed in a ball mill together with pure water, dispersant, and PSZ media, and mixed and pulverized to obtain a slurry. The obtained slurry is dried, and then calcined at a temperature of 700°C or higher and 800°C or lower for 2 hours or more and 3 hours or less to obtain a non-magnetic material (calcined powder). A predetermined amount of solvent (ketone-based solvent, etc.), resin (polyvinyl acetal, etc.), and plasticizer (alkyd-based plasticizer, etc.) are added to the non-magnetic material (calcined powder), kneaded with a planetary mixer, and then further dispersed with a three-roll mill to produce a non-magnetic paste.

[0082] The non-magnetic paste preferably contains Fe in an amount of 40 mol% or more and 49.5 mol% or less calculated as Fe2O3, Cu in an amount of 4 mol% or more and 12 mol% or less calculated as CuO, and the remainder being ZnO as the main component. The non-magnetic paste is more preferably one in which Mn, Bi, Co, Si, Sn, etc. are added as additives to the above main components as necessary. The non-magnetic paste may contain inevitable impurities.

[0083] As the conductive paste, for example, a paste containing Ag as a conductive material is prepared.

[0084] The above-mentioned magnetic paste, non-magnetic paste, and conductive paste are used to prepare the laminate groups G1 to G7 shown in FIG. 2 by screen printing or the like. The unsintered element body is then pressurized by a press process such as warm isostatic pressing (WIP) to form a laminate. After the pressurization process, the laminate body is placed in a firing furnace, degreased, and then fired in the air. The firing temperature is, for example, 600° C. or higher and 800° C. or lower. The firing time is, for example, 30 minutes or higher and 90 minutes or lower. An element body is prepared by this firing.

[0085] Resin impregnation preparation process (optional process) The resin impregnation preparation step is a step that is carried out before the resin impregnation step described below. Specifically, the resin impregnation preparation step is a step of reducing gas or moisture in the element body or lowering the viscosity of the resin.

[0086] One example of the resin impregnation preparation step is to degas the fired body to reduce the amount of gas in the body and make it easier to impregnate the body with resin. Degassing and resin impregnation may be repeated. Another method of the resin impregnation preparation step is to heat the fired body to reduce the amount of moisture in the body and make it easier to impregnate the body with resin. Yet another method of the resin impregnation preparation step is to heat the resin to reduce the viscosity of the resin and make it easier to impregnate the body with resin. By going through these steps, the body can be effectively impregnated with resin.

[0087] Resin impregnation process The fired element is impregnated with resin. The resin may contain epoxy resin, silicone resin, or phenol resin. By impregnating the element with resin, the resin is provided in at least some of the gaps in the magnetic body and in the pores in the coil conductor at least near the magnetic layer. This makes it possible to reduce the gaps and pores, thereby increasing the strength of the element. It also makes it possible to reduce the intrusion of plating solution, moisture, etc. into the element.

[0088] ·External electrode formation process The external electrode forming step is a step of forming external electrodes electrically connected to the coil conductors. The external electrodes are formed by electrolytic plating at positions where the through holes are exposed on the mounting surface (first main surface B1) of the element body B. The plating material may be Cu plating. Other examples include, but are not limited to, Ni-Sn, Ni-Au, Ni-Cu and / or Cu-Ni-Au. After the external electrodes are formed, cutting is performed to separate elements, thereby manufacturing the laminated inductor of this embodiment.

[0089] As described above, according to the manufacturing method of the laminated inductor described in this embodiment, resin is provided in at least some of the voids in the magnetic material and in the pores in the coil conductor at least near the magnetic material layer, making it difficult for the magnetic material layer and the coil conductor to peel off, thereby increasing the strength of the base material. EXAMPLES

[0090] Cross-sectional observation of the laminated inductor of the present disclosure was performed by SEM. The structure of the laminated inductor used for the observation is the structure shown in Figures 2 to 4. That is, as described above, the sintered element body is impregnated with resin, so that resin R is provided in the voids O in the magnetic body M, and resin is provided in at least some of the pores in the coil conductor CM near at least the magnetic layer ML.

[0091] The cross-sectional observation results are shown in Fig. 5, and the elemental analysis results performed based on Fig. 5 are shown in Fig. 6. Fig. 6 shows that the C element contained in the resin R penetrates into the gaps O in the magnetic body M, and also into the pores P in the Ag element contained in the coil conductor CM. The laminated inductor had a higher element strength than a laminated inductor that was not impregnated with resin.

[0092] The technical scope of the present disclosure is not interpreted only by the above-described embodiment, but is defined based on the description of the claims. The technical scope of the present disclosure includes all modifications within the meaning and scope of the claims.

[0093] The laminated inductor, laminated inductor array, and method for manufacturing a laminated inductor according to the present disclosure include the following aspects. <1> an element body having a magnetic body formed by laminating magnetic body layers containing iron powder and a coil formed by winding a coil conductor inside the magnetic body; an external electrode electrically connected to the coil conductor; A resin is provided in the gaps in the magnetic body, A laminated inductor, the coil conductor having pores at least near the magnetic layer, the resin being provided in at least a portion of the pores. <2> a space is provided between the magnetic layer and the coil conductor in a lamination direction; The resin is provided in the space. <1> The laminated inductor according to claim 1. <3> The external electrodes are disposed on one surface in the stacking direction via through holes formed in the element body. <1> or <2> The laminated inductor according to claim 1. <4> The external electrodes are plating electrodes formed directly on the through holes. <3> The laminated inductor according to claim 1. <5> The coils are arranged in a stacked manner in a plan view from the stacking direction. <1> ~ <4> 13. The laminated inductor according to claim 12, <6> a resin impregnation rate of the voids located on the outer surface side of the element body is higher than a resin impregnation rate of the voids located on the inner side of the element body than the voids; <1> ~ <5> 13. The laminated inductor according to claim 12, <7> An insulating layer is disposed between the magnetic layers. <1> ~ <6> 13. The laminated inductor according to claim 12, <8> The resin contains an epoxy resin or a phenolic resin. <1> ~ <7> 13. The laminated inductor according to claim 12, <9> an element body having a magnetic body formed by laminating magnetic body layers containing iron powder and a coil formed by winding a coil conductor inside the magnetic body; an external electrode electrically connected to the coil conductor; The coils are arranged in a stacked manner in two or more layers in a plan view from a stacking direction, and are arranged in parallel in a direction intersecting the stacking direction to form a coil array; A resin is provided in the gap in the magnetic body, A laminated inductor array, wherein the resin is provided in at least a portion of the pores in the coil conductor near the magnetic layer. <10> a body preparation step of stacking magnetic body layers containing iron powder to form a magnetic body and preparing an element having a coil wound with a coil conductor inside the magnetic body; a resin impregnation step of impregnating resin into voids in the magnetic body and at least a part of pores in the coil conductor near at least the magnetic body layer; an external electrode forming step of forming an external electrode electrically connected to the coil conductor; A method for manufacturing a laminated inductor comprising the steps of: <11> The resin impregnation step includes a resin impregnation preparation step of reducing gas or moisture in the body or reducing the viscosity of the resin before the resin is impregnated. <10> A method for manufacturing the laminated inductor according to claim 1. [Industrial Applicability]

[0094] The present disclosure can be used for a laminated inductor having improved strength of the element body. [Explanation of symbols]

[0095] 1. Multilayer inductor 10. Multilayer inductor array A Avoidance part B Base C coil CM Coil Conductor E1 1st external electrode E2 2nd external electrode M Magnetic material MP Iron Powder ML magnetic layer O void P pore SP space TH1 First through hole TH2 2nd through hole

Claims

1. an element body having a magnetic body formed by laminating magnetic body layers containing iron powder and a coil formed by winding a coil conductor inside the magnetic body; an external electrode electrically connected to the coil conductor; A resin is provided in the gap in the magnetic body, The coil conductor has pores at least near the magnetic layer, A laminated inductor, wherein the resin is provided in at least a portion of the pores.

2. a space is provided between the magnetic layer and the coil conductor in a lamination direction; The laminated inductor according to claim 1 , wherein the resin is provided in the space.

3. 2. The multilayer inductor according to claim 1, wherein said external electrodes are disposed on one surface in the lamination direction via through holes formed in said element body.

4. 4. The multilayer inductor according to claim 3, wherein the external electrodes are plated electrodes formed directly on the through holes.

5. The laminated inductor according to claim 1 , wherein two or more of the coils are arranged overlapping each other when viewed from above in the lamination direction.

6. 2. The multilayer inductor according to claim 1, wherein a resin impregnation rate of the void in the element body is higher than a resin impregnation rate of a void located closer to the inside of the element body than the void.

7. The laminated inductor according to claim 1 , further comprising an insulating layer disposed between said magnetic layers.

8. The laminated inductor according to claim 1 , wherein the resin contains an epoxy resin or a phenolic resin.

9. an element body having a magnetic body formed by laminating magnetic body layers containing iron powder and a coil formed by winding a coil conductor inside the magnetic body; an external electrode electrically connected to the coil conductor; The coils are arranged in a stacked manner in two or more layers in a plan view from a stacking direction, and are arranged in parallel in a direction intersecting the stacking direction to form a coil array; A resin is provided in the gap in the magnetic body, A laminated inductor array, wherein the resin is provided in at least a portion of the pores in the coil conductor near the magnetic layer.

10. a body preparation step of stacking magnetic body layers containing iron powder to form a magnetic body and preparing an element having a coil wound with a coil conductor inside the magnetic body; a resin impregnation step of impregnating resin into voids in the magnetic body and at least a part of pores in the coil conductor near at least the magnetic body layer; an external electrode forming step of forming an external electrode electrically connected to the coil conductor; A method for manufacturing a laminated inductor comprising the steps of:

11. 11. The method for manufacturing a laminated inductor according to claim 10, further comprising a resin impregnation preparation step of reducing gas or moisture in the element body or reducing a viscosity of the resin before the resin is impregnated in the resin impregnation step.

Images