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

[0006] , , ,

[0005] , , , ,

[0007] , , ,

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

Background Art

[0002] In recent years, due to the high functionality of devices, the DC-DC converters of voltage conversion circuits have been increasing in current and efficiency, and the rated current of the power inductors used in these devices has also been increasing.

[0003] Patent Document 1, which shows an example of the above inductor, discloses a laminated 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 in the laminate, and a method for manufacturing the same.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a laminated electronic component, in a metal magnetic layer mainly composed of metal magnetic particles, voids occur between the particles. The reduction in the strength of the laminate (element body) due to the presence of these voids in the metal magnetic layer becomes a problem.

[0006] The main object of the present disclosure is to provide a laminated inductor, a laminated inductor array, and a method for manufacturing a laminated inductor with improved strength of the element body.

Means for Solving the Problems

[0007] The laminated inductor of the present disclosure is A base body comprising a magnetic material formed by laminating magnetic material layers containing iron powder, and a coil having a coil conductor wound inside the magnetic material, The coil conductor is electrically connected to an external electrode, A resin is provided in the void within the magnetic material. The coil conductor has at least a pore near the magnetic layer, The resin is provided in at least a portion of the pore.

[0008] The stacked inductor array of this disclosure is A base body comprising a magnetic material formed by laminating magnetic material layers containing iron powder, and a coil having a coil conductor wound inside the magnetic material, The coil conductor is electrically connected to an external electrode, The coils are arranged in a plan view from the stacking direction, with two or more overlapping, and are arranged in parallel in a direction intersecting the stacking direction to form a coil array. A resin is provided in the void within the magnetic material. The resin is provided in at least a portion of the pores in the vicinity of the magnetic layer in the coil conductor.

[0009] The method for manufacturing a multilayer inductor disclosed herein is: A basic body preparation step involves preparing a basic body having a coil in which a coil conductor is wound inside a magnetic material, formed by laminating magnetic material layers containing iron powder, and a basic body having a coil formed by laminating magnetic material layers. A resin impregnation step in which resin is impregnated into the voids in the magnetic body and at least a portion of the pores in the coil conductor near the magnetic body layer, An external electrode formation step is to form an external electrode that is electrically connected to the coil conductor, It is equipped with. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a laminated inductor and a laminated inductor array with improved substrate strength, as well as a method for manufacturing a laminated inductor. Specifically, in the substrate of the laminated inductor, since resin is provided in at least a part of the voids in the magnetic body and the pores in the vicinity of at least the magnetic body layer in the coil conductor, the substrate strength can be increased by reducing the voids and pores.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a perspective view schematically showing an example of the laminated inductor of the first embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the internal structure of the laminated inductor of the first embodiment. [Figure 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 the Z1 portion of FIG. 3. [Figure 4B] FIG. 4B is a partially enlarged cross-sectional view of the Z2 portion of FIG. 3. [Figure 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 explaining the elemental analysis results performed based on FIG. 5. [Figure 7] FIG. 7 is a cross-sectional SEM photograph at a position different from FIG. 5. [Figure 8] FIG. 8 is a cross-sectional view of a modified example of the laminated inductor of the first embodiment. [Figure 9] FIG. 9 is a perspective view schematically showing an example of the laminated inductor of the second embodiment. [Figure 10] FIG. 10 is a perspective view schematically showing an example of the laminated inductor array of the present disclosure. [Figure 11] FIG. 11 is a flowchart showing a method for manufacturing the laminated inductor of the present disclosure.

Modes for Carrying Out the Invention

[0012] Hereinafter, the laminated inductor of the present disclosure will be described. Note that the present disclosure is not limited to the following configurations and may be appropriately modified without departing from the gist of the present disclosure. In addition, combinations of a plurality of the individual preferred configurations described below are also within the scope of the present disclosure.

[0013] The laminated inductor of the present disclosure is used, for example, in a DC-DC converter. The laminated inductor of the present disclosure is also applicable to uses other than DC-DC converters.

[0014] 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 a strictly literal aspect, but also mean a substantially equivalent range, for example, a range including a difference of about several percent. In this specification, the direction in which the magnetic body layer and the coil conductor constituting the base body are laminated is defined as the "lamination direction".

[0015] The drawings shown below are schematic diagrams, and their dimensions, aspect ratios, scales, etc. may differ from those of actual products.

[0016] <First Embodiment of Laminated Inductor> First, a first embodiment of the laminated inductor of the present disclosure will be described with reference to FIGS. 1 to 8. Note that the shapes and arrangements of the laminated inductor and each component are not limited to the illustrated examples.

[0017] The laminated inductor 1 shown in FIG. 1 includes a base body B having a magnetic body formed by laminating magnetic body layers containing iron powder and having a coil C in which a coil conductor is wound inside the magnetic body, and an external electrode E electrically connected to the coil conductor. Hereinafter, each component will be described in detail.

[0018] -Base body- The base body B has, for example, a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape having six faces. The corners and edges of the base body B may be rounded. A corner is a portion where three faces of the base body B intersect, and an edge is a portion where two faces of the base body B intersect.

[0019] Figure 1 shows the length, width, and height directions of the multilayer inductor 1 and the base body B as the L, W, and T directions, respectively. The length direction L, the width direction W, and the height direction T are orthogonal to each other. The mounting surface of the multilayer inductor 1 is, for example, a surface parallel to the length direction L and the width direction W (LW surface).

[0020] The base body B shown in Figure 1 has a first main surface B1 and a second main surface B2 that are opposite to the height direction T, a first end surface B3 and a second end surface B4 that are perpendicular to the height direction T and opposite to the length direction L, and a first side surface B5 and a second side surface B6 that are perpendicular to the length direction L and the height direction T and opposite to the width direction W. In the example shown in Figure 1, the first main surface B1 of base body B corresponds to the mounting surface (bottom surface) of base body B. The second main surface B2 may also be the mounting surface of base body B.

[0021] The base body B includes a magnetic body M formed by stacking magnetic layers ML and a coil C around which a coil conductor CM is wound (see Figures 2 and 3). Specifically, the base body B may include multiple magnetic layers ML and coil conductors CM in the stacking direction (e.g., the height direction T). In this embodiment, as shown in Figure 2, it is constructed by stacking stacking groups G1 to G7, each containing at least one magnetic layer ML and a coil conductor CM (or only magnetic layer ML). The boundaries between each layer of the stacking structure of the base body B may disappear. Furthermore, each stacking group may be constructed by stacking multiple identical patterns.

[0022] The laminated group G1 has a magnetic layer ML and constitutes the second main surface B2 of the base body B.

[0023] The laminated group G2 is provided with a magnetic layer ML and a coil conductor CM. The coil conductor CM of laminated group G2 constitutes one winding of coil C. More specifically, the coil conductor CM is arranged along the approximate outer edge of the magnetic layer ML.

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

[0025] The laminated group G4 includes a magnetic layer ML, a second through-hole TH2 that electrically connects the second through-hole TH2 of the laminated group G3 to the second external electrode E2, and a coil conductor CM. The coil conductor CM of the laminated group G4 constitutes one winding of the coil C. More specifically, the coil conductor CM is arranged along the outer edge of the magnetic layer ML while avoiding the second through-hole TH2 with an avoidance portion A, and the ends of the coil conductor CM are spaced apart to form a winding structure. More specifically regarding the avoidance portion A, the avoidance portion A provided in the laminated group G4 may be provided further inward compared to the coil conductor CM arranged along the outer edge of the laminated group G2, thereby avoiding the second through-hole TH2.

[0026] The laminated group G5 is provided with a magnetic layer ML, a second through-hole TH2 that electrically connects the second through-hole TH2 of the laminated group G4 to the second external electrode E2, and via conductors V for connecting adjacent coil conductors CM in the laminated direction. The via conductors V are positioned adjacent to the second through-hole TH2 so as to be electrically connectable to the end of the coil conductor CM of the laminated group G4.

[0027] The laminated group G6 includes a magnetic layer ML, a second through-hole TH2 that electrically connects the second through-hole TH2 of the laminated group G5 to the second external electrode E2, and a coil conductor CM. The coil conductor CM of the laminated group G6 constitutes one winding of the coil C. More specifically, the coil conductor CM is arranged along the outer edge of the magnetic layer ML while avoiding the second through-hole TH2 with an avoidance portion A, and the ends of the coil conductor CM are spaced apart to form a winding structure. More specifically regarding the avoidance portion A, the avoidance portion A provided in the laminated group G6 may be provided further inward compared to the coil conductor CM arranged along the outer edge of the laminated group G2, thereby avoiding the second through-hole TH2.

[0028] The laminated group G7 includes a magnetic layer ML, a second through-hole TH2 that electrically connects the second through-hole TH2 of the laminated group G6 to the second external electrode E2, and a first through-hole TH1 that electrically connects the coil conductor CM of the laminated group G6 to the first external electrode E1. The first through-hole TH1 is located in the corner of the magnetic layer ML.

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

[0030] ·Magnetic material The magnetic material M (see Figures 2-4), constructed by laminating magnetic material layers ML, contains iron powder MP composed of magnetic material. In this specification, "iron powder" is not strictly limited to being in powder form, but also includes materials where powdery particles are bonded together by a 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. Examples of Fe alloys include Fe-Si alloys, Fe-Si-Cr alloys, Fe-Si-Al alloys, Fe-Si-BP-Cu-C alloys, and / or Fe-Si-B-Nb-Cu alloys. Furthermore, the iron powder MP may contain impurities such as Cr, Mn, Cu, Ni, P, S, and / or Co, which are not intended during manufacturing. Also, the iron powder MP may be contained in the magnetic paste, as will be detailed in the description of the manufacturing method. Therefore, the iron powder may contain elements that oxidize more easily than Fe added during the production of the magnetic paste (e.g., Cr, Al, Li, Zn).

[0031] The surface of the iron powder MP described above may be covered with an insulating film (not shown). Covering the surface of the iron powder MP with an insulating film can improve the insulation between the iron powder MPs. Methods for forming the insulating film on the surface of the iron powder MP include the sol-gel method and the mechanochemical method. The material constituting the insulating film may be an oxide such as P and / or Si. Alternatively, the insulating film may be an oxide film formed by the oxidation of the surface of the iron powder MP. The thickness of the insulating film is preferably 1 nm to 50 nm, more preferably 1 nm to 30 nm, and even more preferably 1 nm to 20 nm. For example, a cross-section obtained by polishing an inductor sample can be 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 image.

[0032] The average particle size of the iron powder MP in the magnetic material M is preferably 1 μm to 30 μm, more preferably 1 μm to 20 μm, and even more preferably 1 μm to 10 μm. The average particle size of the iron powder MP in the magnetic material M 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 Figure 3 (i.e., a sample cross-section perpendicular to the mounting surface and end face of the base body, passing through the first through-hole of the base body) is obtained. Multiple areas (e.g., 5 areas) of the obtained cross-section (e.g., 130 μm × 100 μm) are photographed with an SEM, and the obtained SEM images are analyzed using image analysis software (e.g., image analysis software WinROOF2021 (manufactured by Mitani Corporation)) to determine the equivalent circle diameter of the iron powder MP. The average value of the obtained equivalent circle diameters is taken as the average particle size of the metallic magnetic particles.

[0033] Herein, as a new finding in this disclosure, the inventors have discovered that even when iron powder MP contained in the magnetic material layer ML is bonded by firing, voids O (see Figures 4A, B) are generated between the iron powder MP, and the presence of these voids reduces the strength of the base material. In this specification, "void" refers to the space between adjacent powder particles. In other words, it refers to the space determined by the positional relationship between adjacent powder particles. The voids O can be observed from the SEM image of the sample cross-section obtained by cutting a sample of the laminated inductor 1, as described above. As a specific method for identifying the voids O, the observation area of ​​the sample cross-section is set to 130 μm × 100 μm, an SEM image is acquired, and when the voids O and non-void areas within the magnetic material M are analyzed using image analysis software, the area ratio of the voids O to the entire observation area may be 10% or more and 40% or less.

[0034] In this embodiment, the laminated inductor 1 reduces the decrease in strength of the base material due to the presence of air gaps O. To achieve this, the base material B is impregnated with a resin material after firing, thereby providing resin R within the air gaps O. By providing resin R in the air gaps O within the magnetic material M, the strength of the base material can be further improved.

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

[0036] ·coil The coil includes multiple coil conductors CM in the stacking direction (e.g., the height direction T). In this embodiment, the coil may have approximately 2.75 turns due to the stacking groups G2, G4, and G6, as shown in Figures 2 and 3, for example.

[0037] The thickness of the coil conductor CM in each laminated group may be the same. The coil conductor CM may be a metallic conductor such as Ag, Cu, and / or Pd, as an example of its material. The coil conductor CM may be formed, for example, by printing a conductive paste onto the magnetic layer ML described above.

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

[0039] In this embodiment, the laminated inductor 1 is impregnated with a resin material after firing of the base body B in order to reduce the decrease in base body strength due to the presence of pores P. This impregnation provides resin R in the voids O and also provides resin R in the pores P. More specifically, resin R is provided on the upper and lower surfaces of the coil conductor CM, which are at least a part of the pores P near the magnetic layer ML of the coil conductor CM (see Figure 4). In this specification, "near the magnetic layer" refers to the range from the interface between the coil conductor and the magnetic layer up to 15 μm. Therefore, the base body strength can be further improved compared to the laminated electronic components described in the prior art. The resin R in the pores P and the resin R in the voids O may be made of the same material, from the viewpoint that they are provided by impregnating the base body B with resin material after firing.

[0040] • Through-hole and via conductors Coil C may have through-holes and via conductors. The through-holes 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 located inside the base 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 base body B.

[0041] The first through-hole TH1 may connect the end of the coil conductor CM closest to the bottom surface (first main surface B1) of the base body B with the first external electrode E1. 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 to the second external electrode E2. The second through-hole TH2 may extend along the stacking direction (e.g., the height direction T). The second through-hole TH2 may have a stacked structure.

[0043] The via conductor V may electrically connect coil conductors CM located in adjacent stacking groups 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 also have a stacked structure.

[0044] Examples of materials for through-holes and via conductors include metal conductors such as Ag, Cu, and / or Pd. Furthermore, the materials for through-holes and via conductors may be the same as those used for the coil conductor CM, or different materials may be used. Through-holes and via conductors may be formed, for example, by forming through-holes in the magnetic layer ML described above and printing conductive paste into these through-holes.

[0045] -External electrode- The external electrodes may include a first external electrode E1 and a second external electrode E2, as shown in Figure 1. The first external electrode E1 and the second external electrode E2 may be provided on the first main surface B1 (bottom surface) of the base body B and electrically connected to the coil C. Providing external electrodes on the first main surface B1 of the base body B makes it possible to properly mount the multilayer inductor 1 on a mounting substrate or the like.

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

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

[0048] A suitable configuration for the external electrodes is such that the planar area of ​​the external electrodes, as viewed from the mounting surface side of the base body B, is larger than the planar area of ​​the through-holes. By making the planar area of ​​the external electrodes relatively large, it becomes easier to align the electrodes of the mounting substrate with the external electrodes of the multilayer inductor 1 when mounting the multilayer inductor 1 onto a mounting substrate or the like.

[0049] The external electrode may be made of various materials, such as Cu, Ni, and / or Sn. The external electrode may be formed as a single layer or as a laminated structure of two or more layers. The external electrode may be formed by any method, but one example is a plated electrode formed directly on a through-hole by plating (e.g., electroplating). When forming the external electrode by plating, it is necessary to immerse the base body B in the plating solution. However, as described above, since resin R is provided in the voids O of the base body B (magnetic material M), it is possible to reduce the penetration of the plating solution into voids within the magnetic material.

[0050] As explained above, in the laminated inductor 1 of this disclosure, resin is provided in the air gaps O within the magnetic material M and in at least a portion of the pores P near the magnetic material layer ML in the coil conductor CM. Therefore, by reducing the air gaps O and pores P, the strength of the base material can be increased.

[0051] -Method of resin impregnation- Regarding a suitable resin impregnation method for void O, the resin impregnation rate of void O1 in the base body B may be higher than the resin impregnation rate of void O2 located further inside the base body B than void 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, a cross-section shown in Figure 3 is obtained (i.e., a sample cross-section perpendicular to the mounting surface and end face of the base body, passing through the first through-hole of the base body). The obtained cross-section is photographed with SEM-EDX, and the obtained image is analyzed using image analysis software to determine the impregnation rate. The above method will be described in detail with reference to Figures 3-4B.

[0052] The specific method for impregnating the base body B with resin will be described in detail in the manufacturing method of the multilayer inductor described later, but the resin R impregnates from the outer surface of the base body B, and the outside of the base body B is more easily impregnated with resin R than the inside of the base body B. In other words, as shown schematically in Figure 4A, the void O1 in part Z1 of the base body B is impregnated with a relatively large amount of resin, and as shown schematically in Figure 4B, the void O2 in part Z2, which is located further inside the base body B than the void O1 in part Z1, is impregnated with less resin than in Figure 4A.

[0053] With this method of resin impregnation, the resin impregnation rate of void O1 located on the outer surface side of the base body B is higher than that of void O2, so when the external electrode is used as a plating electrode, the penetration of the plating solution into the magnetic material M can be further reduced. The tendency of resin impregnation to void O is similar to that of pore P, and the resin impregnation rate of pore P1 may be higher than that of pore P2, which is located inside the base body B.

[0054] In addition to the voids O within the magnetic material M and the pores P of the coil conductor CM, resin R may also be provided in the space SP located between the stacking direction of the magnetic material layer ML and the coil conductor CM. The above embodiments will be described in detail with reference to Figure 7.

[0055] In this specification, the "space between the magnetic layer and the coil conductor in the stacking direction" is a concept different from the "voids" between adjacent powders, and refers to a space determined 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. The vicinity of the interface refers to the range from the interface between the magnetic layer ML and the coil conductor CM to approximately 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 the range from the interface between the magnetic layer and the coil conductor to ±15 μm in the stacking direction.

[0056] The spacing of the spatial SPs can be measured by cutting a sample of the multilayer inductor to obtain a cross-section, and then observing the maximum length of the spatial SPs in the stacking direction from the SEM image of the cross-section. For example, the spatial SPs may be approximately 2 μm in size.

[0057] In this way, by providing a resin R in the space SP between the magnetic layer ML and the coil conductor CM in the lamination direction, the peel strength between the magnetic layer ML and the coil conductor CM can be further improved.

[0058] <Modified example of the first embodiment of a multilayer inductor> As a modification of the laminated inductor 1 of the first embodiment, an insulating layer I may be placed between magnetic material layers ML, as shown in Figure 8. More specifically, in the laminated groups G1 to 7 shown in Figure 2, an insulating layer I may be placed between magnetic material layers ML in the laminated direction. When an insulating layer I is placed between coil conductors CM, through-holes and via conductors may be provided in the insulating layer I. Placing an insulating layer I between coil conductor layers can further reduce the likelihood of the coil conductors CM inside the magnetic material M short-circuiting each other. Note that the insulating layer I may not be placed between all magnetic material layers ML, but only between some of the magnetic material layers ML.

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

[0060] The coils of the multilayer inductor 1 in this embodiment may be arranged in overlapping pairs when viewed from the stacking direction. In other words, a first coil C1 and a second coil C2 may be provided inside the base 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 the base body B may contain only two coils, including the first coil C1 and the second coil C2, or it may contain three or more coils, including the first coil C1 and the second coil C2.

[0061] -Coil 1- The first coil C1 includes a plurality of first coil conductors CM1 that constitute the first coil C1 in the stacking direction (e.g., the height direction T). Adjacent first coil conductors CM1 are connected via conductors V. The first coil C1 may have 1.75 turns 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 2 or more by stacking the first coil conductors CM1 in the stacking direction.

[0062] -Coil 2- The second coil C2 is positioned above the first coil C1 in the height direction T and includes multiple second coil conductors CM2 in the stacking direction (e.g., in the height direction T). Adjacent second coil conductors CM2 are connected via via conductors V. The second coil C2 may have 1.75 turns 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 example, and may be 2 or more by stacking the first coil conductor CM1 in the stacking direction. The number of stacks of the second coil conductor CM2 may be the same as or different from the number of stacks of the first coil conductor 51.

[0063] -Through-hole 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 located inside the base 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 base body B.

[0064] The first through-hole TH1 connects the end of the first coil conductor CM1 closest to the bottom surface (first main surface B1) of the base body B, which is one of the ends of the first coil C1, to the first external electrode E1. 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.

[0065] The second through-hole TH2 connects the other end of the first coil C1 to the second external electrode E2. The second through-hole TH2 may extend along the stacking direction (e.g., the height direction T). The second through-hole TH2 may have a stacked structure.

[0066] The third through-hole TH3 connects the end of the second coil conductor CM2 closest to the bottom surface (first main surface B1) of the base body B, which is one of the ends of the second coil C2, 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 to the fourth external electrode E4. The fourth through-hole TH4 may extend along the stacking direction (e.g., the height direction T). The fourth through-hole TH4 may have a stacked structure.

[0068] As shown in Figure 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 base 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 base body B and are electrically connected to the second coil C2. In the multilayer inductor 1, the first main surface B1 of the base body B can be used as the mounting surface.

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

[0070] <Multilayer inductor array> Next, the stacked inductor array of this disclosure will be described with reference to Figure 10. The stacked inductor array 100 of this disclosure has two or more coils arranged to overlap in a plan view from the stacking direction, and the coils are arranged in parallel in a direction intersecting the stacking direction to form a coil array. Specifically, in addition to the first coil C1 and the second coil C2, it 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. Of the ends of the third coil C3, the end of the third coil conductor layer closest to the bottom surface may be connected to the fifth external electrode E5 by the fifth through-hole TH5. The other end of the third coil conductor layer may be connected to the sixth external electrode E6 by the sixth through-hole TH6.

[0072] The fourth coil C4 may be electrically connected to the seventh external electrode (not shown) and the eighth external electrode (not shown). Of the ends of the fourth coil C4, the 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. In addition, 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. Of the ends 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 the ninth through-hole TH9. The other end of the fifth coil conductor layer may be connected to the tenth external electrode E10 by the 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 the eleventh through-hole TH11. The other end of the sixth coil conductor layer may be connected to the twelfth external electrode (not shown) by the twelfth through-hole TH12.

[0075] Even in the laminated inductor array 10 of this disclosure, resin is provided in the air gaps O within the magnetic material M and in at least a portion of the pores P in the coil conductor CM near the magnetic material layer ML. Therefore, the strength of the base material can be increased by reducing the air gaps O and pores P.

[0076] <Manufacturing method for multilayer inductors> Next, the manufacturing method of the multilayer inductor of this disclosure will be described in accordance with the manufacturing flow shown in Figure 11. The manufacturing method of the multilayer inductor of this disclosure may include a base material preparation step, a resin impregnation preparation step, a resin impregnation step, and an external electrode formation step. The steps will be described in detail below.

[0077] ·Body preparation process First, prepare the magnetic paste that constitutes the magnetic layer ML of the laminated group as described in Figure 2, the conductive paste that constitutes the coil conductor CM, and the non-magnetic paste that constitutes the non-magnetic layer between the coil conductors CM.

[0078] As an example of a method for producing magnetic paste, iron powder such as Fe-Si alloy or Fe-Si-Cr alloy with a D50 (cumulative 50% particle size by volume) of 2 μm or more and 20 μm or less is prepared. A magnetic paste is produced by kneading this iron powder with a binder such as cellulose or polyvinyl butyral (PVB) and a solvent such as a mixture of terpineol and butyl diglycol acetate (BCA).

[0079] When using an Fe-Si alloy as the iron powder, the Si content is preferably 2.0 at% or more and 8.0 at% or less. When using an Fe-Si-Cr alloy as the iron powder, the Si content is preferably 2.0 at% or more and 8.0 at% or less. Furthermore, when using an Fe-Si-Cr alloy as the iron powder, the Cr content is preferably 0.2 at% or more and 6.0 at% or less.

[0080] An insulating film may be provided on the surface of the iron powder. The insulating film is preferably a film containing a metal oxide, and more preferably a silicon oxide. The sol-gel method is preferred as a method for forming the insulating film. As an example of forming an insulating film by the sol-gel method, a mixture is prepared by mixing a sol-gel coating agent containing a Si alkoxide with an organic chain-containing silane coupling agent. After this mixture is applied to the surface of the metal magnetic powder, dehydration bonding is induced by heat treatment. Subsequently, the insulating film can be formed by drying at a predetermined temperature.

[0081] As an example of a method for preparing a non-magnetic paste, Fe2O3, ZnO, CuO, and any necessary additives are weighed to obtain a predetermined composition. The weighed materials are placed in a ball mill together with pure water, a dispersant, and PSZ media, and mixed and pulverized to obtain a slurry. After drying the obtained slurry, it is 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 (such as a ketone-based solvent), resin (such as polyvinyl acetal), and plasticizer (such as an alkyd-based plasticizer) are added to the non-magnetic material (calcined powder), mixed in a planetary mixer, and then dispersed in 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), with ZnO as the main component for the remainder. More preferably, the non-magnetic paste contains Mn, Bi, Co, Si, Sn, etc., as additives to the above main components, as needed. The non-magnetic paste may contain unavoidable impurities.

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

[0084] Using the magnetic paste, non-magnetic paste, and conductive paste described above, laminate groups G1 to G7 shown in Figure 2 are prepared by screen printing or the like. Then, the unfired base material is subjected to pressurization, such as warm hydrostatic pressing (WIP), to form a laminate. After pressurization, the laminate is placed in a firing furnace, degreased, and then fired in the atmosphere. 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. The base material is prepared by this firing process.

[0085] • Resin impregnation preparation process (optional additional process) The resin impregnation preparation process is performed before the resin impregnation process, which will be described later. Specifically, the resin impregnation preparation process is a process to reduce the amount of gas or moisture in the substrate, or to lower the viscosity of the resin.

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

[0087] • Resin impregnation process The substrate is impregnated with resin after firing. The resin may contain epoxy resin, silicone resin, or phenolic resin. By impregnating the substrate with resin, resin is provided in the voids within the magnetic body and in at least a portion of the pores near the magnetic layer in the coil conductor. This reduces the voids and pores, thereby increasing the strength of the substrate. It also reduces the penetration of plating solution or moisture into the substrate.

[0088] ·External electrode formation process The external electrode formation process is a process of forming external electrodes that are electrically connected to the coil conductors. External electrodes are formed by electroplating at positions where through-holes are exposed on the mounting surface (first main surface B1) of the base body B. The plating material may be Cu plating. Other materials include, but are not limited to, Ni-Sn, Ni-Au, Ni-Cu and / or Cu-Ni-Au. After external electrode formation, the element can be cut into individual components to manufacture the multilayer inductor of this embodiment.

[0089] As described above, in the manufacturing method of the multilayer inductor described in this embodiment, since resin is provided in the voids within the magnetic body and in at least a portion of the pores near the magnetic body layer in the coil conductor, the magnetic body layer and the coil conductor become less likely to peel off, thereby increasing the strength of the base material. [Examples]

[0090] Cross-sectional observation of the multilayer inductor of this disclosure was performed using a scanning electron microscope (SEM). The structure of the multilayer inductor used for observation is shown in Figures 2 to 4. In other words, as described above, by impregnating the substrate with resin after firing, resin R is provided in the voids O within the magnetic material M, and resin is provided in at least a portion of the pores in the coil conductor CM near the magnetic material layer ML.

[0091] The cross-sectional observation results are shown in Figure 5, and the elemental analysis results based on Figure 5 are shown in Figure 6. According to Figure 6, the C element contained in the resin R penetrated into the voids O within the magnetic material M, and also penetrated into the pores P within the Ag element contained in the coil conductor CM. As a result, the laminated inductor showed higher structural strength than a laminated inductor that was not impregnated with resin.

[0092] Furthermore, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. The technical scope of this disclosure also includes all modifications within the meaning and scope of the claims.

[0093] The multilayer inductors, multilayer inductor arrays, and methods for manufacturing multilayer inductors of the present disclosure include the following embodiments. <1> A base body comprising a magnetic material formed by laminating magnetic material layers containing iron powder, and a coil having a coil conductor wound inside the magnetic material, The coil conductor is electrically connected to an external electrode, A resin is provided in the void within the magnetic material. A laminated inductor having a pore at least near the magnetic layer in the coil conductor, and the resin provided in at least a portion of the pore. <2> There is a space between the magnetic layer and the coil conductor in the stacking direction, The resin is provided in the space. <1> The multilayer inductor described above. <3> The external electrode is arranged on one surface in the stacking direction via a through-hole formed within the substrate. <1> or <2> The multilayer inductor described above. <4> The external electrode is a plated electrode formed directly on the through-hole. <3> The multilayer inductor described above. <5> The aforementioned coils are arranged in such a way that two or more are overlapping when viewed from the stacking direction. <1> ~ <4> A multilayer inductor as described in any one of the following: <6> In the aforementioned void, the resin impregnation rate of the void located on the outer surface side of the substrate is higher than the resin impregnation rate of the void located on the inner side of the substrate. <1> ~ <5> A multilayer inductor as described in any one of the following: <7> An insulating layer is disposed between the magnetic layers. <1> ~ <6> A multilayer inductor as described in any one of the following: <8> The aforementioned resin contains an epoxy resin or a phenolic resin. <1> ~ <7> A multilayer inductor as described in any one of the following: <9> A base body comprising a magnetic material formed by laminating magnetic material layers containing iron powder, and a coil having a coil conductor wound inside the magnetic material, The coil conductor is electrically connected to an external electrode, The coils are arranged in a plan view from the stacking direction, with two or more overlapping, and are arranged in parallel in a direction intersecting the stacking direction to form a coil array. A resin is provided in the void within the magnetic material. A laminated inductor array in which the resin is provided in at least a portion of the pores near the magnetic layer in the coil conductor. <10> A basic body preparation step involves preparing a basic body having a coil in which a coil conductor is wound inside a magnetic material, formed by laminating magnetic material layers containing iron powder, and a basic body having a coil formed by laminating magnetic material layers. A resin impregnation step in which resin is impregnated into the voids in the magnetic body and at least a portion of the pores near the magnetic body layer in the coil conductor, An external electrode formation step is to form an external electrode that is electrically connected to the coil conductor, A method for manufacturing a multilayer inductor equipped with [the specified feature]. <11> The resin impregnation process includes a resin impregnation preparation step, in which the gas or moisture in the substrate is reduced or the viscosity of the resin is lowered before impregnation with the resin. <10> A method for manufacturing a multilayer inductor as described above. [Industrial applicability]

[0094] This disclosure can be used in multilayer inductors with improved strength of the base material. [Explanation of symbols]

[0095] 1. Multilayer Inductor 10-layer inductor array A Avoidance part B Base Body 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 Second Through Hole

Claims

1. A basic body preparation step involves preparing a basic body having a coil in which a coil conductor is wound inside a magnetic material, formed by laminating magnetic material layers containing iron powder, and a basic body having a coil formed by laminating magnetic material layers. A resin impregnation step in which resin is impregnated into the voids in the magnetic body and at least a portion of the pores near the magnetic body layer in the coil conductor, After the resin impregnation step, an external electrode formation step is performed to form an external electrode that is electrically connected to the coil conductor and electrically connected to a through-hole extending in the lamination direction, A step of performing element individualization cutting after the external electrode formation step, A method for manufacturing a multilayer inductor equipped with [the specified feature].

2. A method for manufacturing a laminated inductor according to claim 1, further comprising a resin impregnation preparation step in which the resin impregnation step reduces the amount of gas or moisture in the substrate or lowers the viscosity of the resin before impregnation.

Images