Laminated inductor and method for manufacturing same

Abstract

The invention provides a laminated inductor and a method for manufacturing the same, wherein the connection strength between an external electrode and a through hole is improved. This laminated inductor is provided with: a body having a coil, in which a coil conductor is wound, and a through-hole, which is electrically connected to the coil conductor and is exposed from the bottom surface of a magnetic body, in the interior of the magnetic body in which magnetic layers containing iron powder are laminated; an external electrode disposed on the through hole and electrically connected to the through hole; and an external resin layer disposed on the bottom surface of the magnetic body of the green body, the external electrode having a protruding portion protruding in a direction perpendicular to a lamination direction of the magnetic layer at an upper end portion away from the through-hole and a lower end portion close to the through-hole, the protruding portion being disposed on the upper end portion away from the through-hole and the lower end portion close to the through-hole in the lamination direction of the magnetic layer. The exterior resin layer is disposed across the protruding portions of the upper end portion and the lower end portion.

Description

Technical Field

[0001] The present disclosure relates to a stacked inductor and a method of manufacturing the same. Background Art

[0002] In recent years, as devices become more sophisticated, the current and efficiency of DC-DC converters in voltage conversion circuits have continued to increase, and the rated current of power inductors used in these devices has also increased.

[0003] Patent Document 1, which shows an example of the above-mentioned inductor, discloses a passive component including: a base portion; an internal conductor embedded in the base portion; a lead conductor electrically connected to the internal conductor and extending toward the bottom surface of the base portion; and an external electrode electrically connected to the lead conductor.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-141079

[0005] Among the existing passive components, for example Figure 8 As shown, the external electrode 100 is formed only on the lower surface of the base portion 110 and is connected to the lead conductor 105 extending toward the lower surface. Therefore, there is a problem in the connection strength between the external electrode and the lead conductor. Summary of the invention

[0006] A main object of the present disclosure is to provide a laminated inductor having improved connection strength between external electrodes and lead conductors, and a method for manufacturing the same.

[0007] The present disclosure relates to a stacked inductor, comprising:

[0008] A green body having a coil formed by winding a coil conductor inside a magnetic body formed by laminating magnetic layers containing iron powder, and a through hole electrically connected to the coil conductor and extending toward the bottom surface of the magnetic body;

[0009] an external electrode disposed on the through hole and electrically connected to the through hole; and

[0010] The outer resin layer is arranged on the bottom surface of the magnetic body of the green body.

[0011] The external electrode has a protrusion protruding in a direction perpendicular to the stacking direction at an upper end away from the through hole and a lower end close to the through hole in the stacking direction of the magnetic layer.

[0012] The exterior resin layer is disposed between the protrusions at the upper end portion and the lower end portion.

[0013] According to the present disclosure, a laminated inductor and a method for manufacturing the same can be provided, wherein the connection strength between the external electrode and the through hole is improved. Specifically, in the laminated inductor, the external electrode has protrusions at the upper end and the lower end, and the outer resin layer is arranged between the protrusions at the upper end and the lower end, thereby improving the connection strength between the external electrode and the lead conductor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a perspective view schematically showing an example of the laminated inductor according to the first embodiment.

[0015] Figure 2 This is an exploded perspective view for explaining the laminated structure of the laminated inductor according to the first embodiment.

[0016] Figure 3 It is a cross-sectional view of the laminated inductor according to the first embodiment and is an enlarged cross-sectional view of the vicinity of an external electrode.

[0017] Figure 4 yes Figure 3 A partial enlarged cross-sectional view of section Z.

[0018] Figure 5 This is a perspective view schematically showing an example of a laminated inductor according to the second embodiment.

[0019] Figure 6 1 is a perspective view schematically showing an example of a laminated inductor array according to the present disclosure.

[0020] Fig. 7A 1 is a flow chart showing a method for manufacturing the laminated inductor of the present disclosure.

[0021] Figure 7B It is a cross-sectional view showing in detail the outer resin layer forming step in the method for manufacturing the laminated inductor of the present disclosure.

[0022] Figure 8 is a cross-sectional view of a conventional laminated inductor and is an enlarged cross-sectional view of the vicinity of an external electrode.

[0023] Explanation of reference numerals: 1A, 1B…stacked inductor; 1C…stacked inductor array; B…blank; C…coil; CM…coil conductor; E…external electrode; E1…first external electrode; E2…second external electrode; M…magnetic body; MP…iron powder; ML…magnetic layer; SR…external resin layer; TH1…first through hole; TH2…second through hole. DETAILED DESCRIPTION

[0024] The following is an explanation of the laminated inductor of the present disclosure. In addition, the present disclosure is not limited to the following structure, and can be appropriately changed within the scope of the present disclosure. In addition, a combination of a plurality of the preferred structures described below is also the present disclosure.

[0025] The laminated inductor of the present disclosure is used, for example, for a choke coil of a DC-DC converter. The laminated inductor of the present disclosure can also be used for purposes other than DC-DC converters.

[0026] In this specification, terms indicating the relationship between elements (e.g., "parallel", "orthogonal", "perpendicular", etc.) and terms indicating the shape of elements do not only mean strict terms like words, but also mean substantially the same range, for example, a range including a difference of about several percent. In addition, in this specification, the direction in which the magnetic layers and coil conductors constituting the blank are stacked is referred to as the "stacking direction" (e.g., Figure 1 direction T).

[0027] The term "top view" as used in this specification refers to the state of observing an object from the upper side or the lower side along the thickness direction based on the stacking direction (top view or bottom view). In addition, "cross-sectional observation" refers to the state of observing an object from a direction substantially perpendicular to the stacking direction T (for example, Figure 1 The cross-sectional state (cross-sectional view) when observing the object in the direction L or W in the figure. The "up and down directions" and "left and right directions" used directly or indirectly in this specification are equivalent to the up and down directions and left and right directions in the figure, respectively. Unless otherwise specified, the same figure marks or symbols represent the same parts, parts or the same meanings. In a preferred embodiment, it can be understood that the vertical direction downward (i.e., the direction of gravity) is equivalent to the "downward direction", and the opposite direction is equivalent to the "upward direction".

[0028] The drawings shown below are schematic diagrams, and their dimensions, aspect ratios, and other aspects may differ from those of actual products.

[0029] <First Embodiment of Laminated Inductor>

[0030] First, refer to Figure 1 to Figure 6 as well as Fig. 7A and Figure 7B , while explaining the first embodiment of the laminated inductor of the present disclosure. Note that the shapes and arrangements of the laminated inductor and its components are not limited to the examples shown in the drawings.

[0031] Figure 1 FIG. 2 is a perspective view showing a laminated inductor 1A according to the present disclosure. Figure 1As shown, the laminated inductor 1A comprises: a base body B, having a coil C formed by winding a coil conductor inside a magnetic body M formed by laminating magnetic layers containing iron powder, and a through hole TH electrically connected to the coil conductor and extending toward the bottom surface of the magnetic body; an outer resin layer disposed on the bottom surface of the magnetic body and having an opening; and an external electrode E disposed in the opening of the outer resin layer and electrically connected to the through hole. The number of windings of the coil C is 2.5. The following describes each component in detail.

[0032] -Body-

[0033] The blank B is, for example, a six-sided rectangular parallelepiped or substantially rectangular parallelepiped. The blank B may also have rounded corners at the vertices and edges. The vertices are the portions where three faces of the blank B intersect, and the edges are the portions where two faces of the blank B intersect.

[0034] exist Figure 1 In FIG. 1 , the length direction, width direction, and height direction of the laminated inductor 1A and the body B are represented as L direction, W direction, and T direction, respectively. The length direction L, the width direction W, and the height direction T are orthogonal to each other. The mounting surface of the laminated inductor 1A is, for example, a surface (LW surface) parallel to the length direction L and the width direction W.

[0035] Figure 1 The blank B shown has: a first main face B1 and a second main face B2 opposite to each other in the height direction T, a first side face B5 and a second side face B6 opposite to each other in the length direction L orthogonal to the height direction T, and a first end face B3 and a second end face B4 opposite to each other in the width direction W orthogonal to the length direction L and the height direction T. Figure 1 In the example shown, the first main surface B1 of the blank B corresponds to the mounting surface (bottom surface) of the blank B. In addition, the second main surface B2 may also be the mounting surface of the blank B.

[0036] The blank B includes: a magnetic body M obtained by stacking magnetic layers ML; a coil C obtained by winding a coil conductor CM; and a through hole TH electrically connected to the coil conductor and extending toward the bottom surface of the blank B. Specifically, the blank B may include a plurality of magnetic layers ML and a coil conductor CM in a stacking direction (for example, a height direction T).

[0037] Figure 2 1A is an exploded perspective view for explaining the stacked structure of the stacked inductor 1A of the present disclosure. Figure 2 As shown in FIG. 1 , the magnetic layer ML, the coil conductor CM, and the through hole TH are formed by stacking stacked groups G1 to G7.

[0038] The boundaries between the layers of the stacked structure of the base body B may disappear. In addition, each stacked group may be formed by stacking a plurality of layers of the same pattern.

[0039] The stacked inductor 1A can also be formed by stacking the stacking groups G1 to G7 and manufacturing the blank B by firing, further stacking the stacking group G8 including the outer resin layer SR having the opening portion EH (for example, EH1, EH2) for the external electrodes E (for example, E1, E2), and forming the external electrodes E (for example, E1, E2) by the method described later.

[0040] The laminate group G1 includes the magnetic layer ML and constitutes the second main surface B2 of the body B.

[0041] The lamination group G2 includes a magnetic layer ML and a coil conductor CM. The coil conductor CM of the lamination group G2 constitutes approximately one turn of the coil C. More specifically, the coil conductor CM is disposed along the approximate outer periphery of the magnetic layer ML.

[0042] The stacking group G3 is provided with a magnetic layer ML, a second through hole TH2 electrically connecting the coil conductor CM of the stacking group G2 to the second external electrode E2, and a via conductor V for connecting the coil conductors CM adjacent to each other in the stacking direction. The second through hole TH2 is arranged near the corner of the magnetic layer ML. The via conductor V is arranged adjacent to the second through hole TH2. In addition, the "through hole" is used in the concept of a connection path for electrically connecting the coils C (CM) to each other, and the "through hole" is used in the concept of a connection path for electrically connecting the coil C (CM) to the external electrode E.

[0043] The stacking group G4 is provided with a magnetic layer ML, a second through hole TH2 electrically connecting the second through hole TH2 of the stacking group G3 to the second external electrode E2, and a coil conductor CM. The coil conductor CM of the stacking group G4 forms approximately one turn 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 at the avoidance portion Z, and the ends of the coil conductor CM are separated from each other to form a winding structure. If the avoidance portion Z is described in more detail, the avoidance portion Z provided in the stacking group G4 is provided on the inner side compared to the coil conductor CM arranged along the outer periphery of the stacking group G2, so that the second through hole TH2 can be avoided.

[0044] The stacking group G5 is provided with a magnetic layer ML, a second through hole TH2 electrically connecting the second through hole TH2 of the stacking group G4 to the second external electrode E2, and a via-hole conductor V for connecting the coil conductors CM adjacent to each other in the stacking direction. The via-hole conductor V is located at a position capable of being electrically connected to the end of the coil conductor CM of the stacking group G4, and is arranged adjacent to the second through hole TH2.

[0045] The stacking group G6 is provided with a magnetic layer ML, a second through hole TH2 electrically connecting the second through hole TH2 of the stacking group G5 to the second external electrode E2, and a coil conductor CM. The coil conductor CM of the stacking group G6 forms about 0.5 turns 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 in the avoidance portion Z, and the ends of the coil conductor CM are separated from each other to form a winding structure. If the avoidance portion Z is described in more detail, the avoidance portion Z provided in the stacking group G6 is provided on the inner side compared to the coil conductor CM arranged along the outer periphery of the stacking group G2, so that the second through hole TH2 can be avoided.

[0046] The stacked group G7 includes a magnetic layer ML, a second through hole TH2 electrically connecting the second through hole TH2 of the stacked group G6 and the second external electrode E2, and a first through hole TH1 electrically connecting the coil conductor CM of the stacked group G6 and the first external electrode E1. The first through hole TH1 is arranged near a corner of the magnetic layer ML.

[0047] A stacking group G8 is also provided on the fired green body B. The stacking group G8 includes: an outer resin layer SR, in which a first opening EH1 of a first external electrode E1 for electrically connecting to a first through hole TH1 of the stacking group G7 and a second opening EH2 of a second external electrode E2 for electrically connecting to a second through hole TH2 of the stacking group G7 are provided; and an external electrode E is arranged in the first opening EH1 and in the second opening EH2. The first opening EH1 and the second opening EH2 are arranged near corners of the outer resin layer SR, respectively.

[0048] If the base body B has a laminated structure including the laminated groups G1 to G7 as described above, the degree of freedom in designing the laminated inductor 1A becomes higher. For example, the laminated inductor 1A is manufactured with the first external electrode E1 and the second external electrode E2 on the bottom surface (first main surface B1) of the base body B, so that the coil C can be easily led out to the bottom surface side. In addition, the laminated structure including the laminated groups G1 to G7 can be formed in multiple layers by printing (for example, screen printing, etc.) the material constituting the magnetic layer ML, the material constituting the coil conductor CM, and the material constituting the through hole and the via conductor in sequence from the second main surface B2 side or the first main surface B1 side of the base body B. In this case, printing can be repeated for each of the laminated groups G1 to G7 until the magnetic layer ML, the coil conductor CM, the through hole and the via conductor reach the desired thickness.

[0049] In addition, after manufacturing the blank B, the stacked group G8 forms an outer resin layer SR having a first opening EH1 and a second opening EH2 on the first main surface B1 side. The outer resin layer SR may also be formed by printing (e.g., screen printing, etc.) a photosensitive resin material and performing exposure and development photolithography. The outer electrodes E1 and E2 are formed in the first opening EH1 and the second opening EH2 by Cu plating or the like.

[0050] (Magnetic body)

[0051] The magnetic body M (see Figure 1 as well as Figure 2 ) includes iron powder MP composed of a magnetic material. The "iron powder" mentioned in this specification is not strictly limited to powder, and also includes a substance obtained by combining powders with each other through the heat treatment (firing) described later. Iron powder MP may contain Fe and / or Si. More specifically, it may be Fe particles or Fe alloy particles. As Fe alloys, it may be 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. In addition, iron powder MP may also contain impurities such as Cr, Mn, Cu, Ni, P, S and / or Co that are not desirable in manufacturing. In addition, although the iron powder MP is described in detail in the description of the manufacturing method, it may also be included in the magnetic paste. Therefore, elements (for example, Cr, Al, Li, Zn) that are more easily oxidized than Fe added when the magnetic paste is made may also be included in the iron powder.

[0052] The surface of the iron powder MP mentioned above may be covered by an insulating coating (not shown). If the surface of the iron powder MP is covered by an insulating coating, the insulation between the iron powders MP can be improved. As a method for forming an insulating coating on the surface of the iron powder MP, a sol-gel method, a mechanochemical method, etc. can be used. The material constituting the insulating coating may be an oxide such as P and / or Si. In addition, the insulating coating may also be an oxide film formed by oxidizing the surface of the iron powder MP. The thickness of the insulating coating is preferably greater than 1 nm and less than 50 nm, more preferably greater than 1 nm and less than 30 nm, and further preferably greater than 1 nm and less than 20 nm. For example, a cross-section obtained by grinding the center portion of the inductor sample can be photographed using a scanning electron microscope (SEM), and the thickness of the insulating coating covering the surface of the iron powder MP can be measured based on the obtained SEM photograph.

[0053] 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 further 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 according to the steps described below. Cut the sample of the stacked inductor to obtain a sample cross section. Specifically, a cross section (for example, a sample cross section that passes through the center of the first through hole of the blank and is orthogonal to the mounting surface B1 of the blank) is obtained. For the obtained cross section, an area (for example, 130 μm×100 μm) of multiple parts (for example, 5 parts) is photographed using SEM, and the obtained SEM image is analyzed using image analysis software (for example, image analysis software WinROOF2021 (manufactured by Mitani Shoji Co., Ltd.) to obtain the equivalent circle diameter of the iron powder MP. The average value of the obtained equivalent circle diameter is set as the average particle size of the metal magnetic particles. When the through hole is in a polygonal shape, the cut is made perpendicular to the side, and when the through hole is in a circular shape or an elliptical shape, the cut is made perpendicular to the major axis direction.

[0054] Here, even when the iron powder MP contained in the magnetic layer ML is combined by firing, gaps are generated between the iron powder MP, and the strength of the green body is reduced due to the presence of the gaps. The "gap" mentioned in this specification refers to the space between adjacent powders. In other words, it refers to the space determined by the positional relationship between adjacent powders. In addition, the sample of the stacked inductor 1A can be cut as described above to obtain a sample cross section, and the gap can be observed from the SEM image of the sample cross section. As a specific method for determining the gap, the observation area of ​​the sample cross section is set to 130μm×100μm and an SEM image is obtained. In the magnetic body M, when the gap and the area other than the gap are analyzed using image analysis software, the area ratio of the gap relative to the overall reference of the observation area can be greater than 10% and less than 40%.

[0055] In order to reduce the decrease in green body strength due to the presence of voids in the magnetic body, the laminated inductor 1A of this embodiment may be configured such that a resin material is impregnated in the green body B after firing to arrange the resin in the voids. By arranging the resin in the voids in the magnetic body M, the green body strength can be further improved.

[0056] The resin provided in the gaps may contain epoxy resin, silicone resin or phenolic resin. If the resin entering the gaps in the magnetic body M is epoxy resin or phenolic resin, the strength of the blank B can be further improved.

[0057] In the present embodiment, the surface roughness of the bottom surface B1 (first main surface B1) of the magnetic body in the blank B is rougher than the surface roughness of the surface B2 (second main surface B2) on the opposite side of the bottom surface B1 of the magnetic body in the blank B. Such surface roughness of the bottom surface B1 of the magnetic body of the blank B is caused by the grinding process described later. Thus, the adhesion strength between the bottom surface B1 of the magnetic body of the blank B and the outer resin layer SR can be improved.

[0058] The surface roughness of the bottom surface B1 of the magnetic body in the body B is not particularly limited, and may be, for example, 0.3 μm to 1.0 μm, particularly 0.5 μm to 1.0 μm.

[0059] The surface roughness of the surface B2 of the magnetic body in the blank B, which is opposite to the bottom surface B1, is not particularly limited, and may be, for example, 0.1 μm or more and 0.6 μm or less.

[0060] The difference between the surface roughness of the bottom surface B1 of the magnetic body in the blank B and the surface B2 of the magnetic body in the blank B on the opposite side to the bottom surface B1 may usually be 0.1 μm or more and 0.9 μm or less.

[0061] In this specification, the surface roughness of the body B (particularly the magnetic body M) is a surface roughness based on the so-called arithmetic mean roughness Ra, and the average value of values ​​measured at arbitrary 20 points in the center portion of the bottom surface of the body B is used.

[0062] (Coil)

[0063] The coil includes a plurality of coil conductors CM in the stacking direction (eg, height direction T). Figure 2 As shown, the number of windings is about 2.5 by stacking the groups G2, G4, and G6.

[0064] The thickness of the coil conductor CM in each stacked group may be the same. An example of the material of the coil conductor CM may be a metal conductor such as Ag, Cu and / or Pd. The coil conductor CM may be formed by printing a conductive paste on the magnetic layer ML.

[0065] (Through hole and via conductor)

[0066] The coil C may include a through hole TH and a via-hole conductor V. The through hole TH 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 base body B.

[0067] The first through hole TH1 can connect the end of the coil conductor CM closest to the bottom surface (first main surface B1) of the body B among the ends of the coil C to the first external electrode E1. The first through hole TH1 can extend along the stacking direction (for example, the height direction T). The first through hole TH1 can also have a stacking structure.

[0068] 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 (eg, the height direction T). The second through hole TH2 may also have a stacking structure.

[0069] In this way, the through hole TH is arranged inside the base body B (particularly the magnetic body M), and the coil C and the external electrode E are electrically connected.

[0070] The via hole conductor V can electrically connect the coil conductors CM provided in the stacking groups adjacent to each other in the stacking direction. The length of the via hole conductor V in the stacking direction can be shorter than the length of the first through hole TH1, the length of the second through hole TH2, or the length of the through hole. In addition, the via hole conductor V can also have a stacking structure.

[0071] An example of the material of the through hole TH and the via hole conductor V may be a metal conductor such as Ag, Cu and / or Pd (preferably Ag). In addition, the material of the through hole and the via hole conductor may be the same type of material as the coil conductor CM, or a different type of material. The through hole and the via hole conductor may also be formed by, for example, forming a through hole in the magnetic layer ML and printing a conductive paste in the through hole. The through hole and the via hole conductor may also be a sintered body.

[0072] The surface roughness of the bottom surface B1 of the magnetic body of the blank B is coarser than the surface roughness of the through-hole end surface th1. Such surface roughness of the through-hole end surface th1 is caused by the second etching step described later. Thus, the connection strength between the external electrode and the lead conductor is further improved.

[0073] The surface roughness of the through-hole end face th1 is not particularly limited, and may be, for example, 0.1 μm or more and 0.2 μm or less.

[0074] The surface roughness of the outer resin layer forming region of the bottom surface B1 of the magnetic body of the base body B may be the same as the surface roughness of the bottom surface B1 of the magnetic body in the base body B described above.

[0075] The difference between the surface roughness of the through-hole end surface th1 and the surface roughness of the bottom surface B1 of the magnetic body of the blank B may be generally 0.3 μm or more and 0.9 μm or less.

[0076] In this specification, the surface roughness of the through-hole end face th1 is a surface roughness based on so-called arithmetic mean roughness Ra, and is an average value of values ​​measured at arbitrary 20 points using a laser microscope (VK-X1000 manufactured by KEYENCE).

[0077] - External Electrode -

[0078] You can Figure 1 As shown, the external electrodes E include a first external electrode E1 and a second external electrode E2. The first external electrode E1 and the second external electrode E2 can be provided on the first main surface B1 (bottom surface) of the body B and electrically connected to the coil C. If the external electrodes are provided on the first main surface B1 of the body B, the laminated inductor 1A can be appropriately mounted on a mounting substrate or the like.

[0079] The first external electrode E1 can function as an input electrode and / or an output electrode for the coil C. Figure 1 as well as Figure 2 In the embodiment, the shape of the structure is square when viewed from above, but it is not particularly limited and may have a rectangular shape or a circular shape, for example.

[0080] The second external electrode E2 can function as an input electrode and / or an output electrode for the coil C. Figure 1 as well as Figure 2 In the embodiment, the shape of the structure is square when viewed from above, but it is not particularly limited and may have a rectangular shape or a circular shape, for example.

[0081] The external electrodes E ( E1 and E2 ) are usually arranged on the through-hole TH (particularly, the end surface thereof), and are electrically connected to the through-hole TH.

[0082] Figure 3 is an enlarged cross-sectional view of the vicinity of the external electrode in the laminated inductor of the first embodiment, and Figure 1 An enlarged cross-sectional view of the vicinity of the external electrodes of the laminated inductor when it is placed in a state where the top and bottom are reversed. Figure 3 As shown, when observed in cross section, the external electrode E has an upper end 11a and a lower end 11b in the stacking direction T, and the upper end 11a and the lower end 11b respectively have protrusions 13a and 13b protruding in a flange shape in a direction perpendicular to the stacking direction T. The upper end 11a is an end away from the through hole TH in the stacking direction T. The lower end 11b is an end close to the through hole TH in the stacking direction T. In detail, the upper end 11a and the lower end 11b of the external electrode E are the upper end and the lower end of the blank B when the bottom surface B1 of the magnetic body of the blank B is arranged on the upper side and the surface B2 of the magnetic body of the blank B on the opposite side to the bottom surface B1 is arranged on the lower side.

[0083] When viewed in cross section, the widths of the upper end 11a and the lower end 11b of the external electrode E (r1 and r2, respectively) are generally larger than the opening width r3 of the exterior resin layer SR (see Figure 3 ). In particular, when the width r2 of the lower end portion 11b of the external electrode E is larger than the opening width r3 of the external resin layer SR, the anchoring effect of the protrusion 13b of the lower end portion 11b can be further more effectively exerted. When observed in cross section, the opening width r3 of the external resin layer SR is the minimum width in the direction perpendicular to the stacking direction T when the external electrode E is seen through.

[0084] The widths ( r1 and r2 , respectively) of the upper end portion 11 a and the lower end portion 11 b of the external electrode E are not particularly limited, and may be independently 150 μm or more and 400 μm or less, for example.

[0085] The value of the opening width r3 of the outer resin layer SR is not particularly limited, and may be, for example, 1 μm or more and 10 μm or less, particularly 5 μm or more and 10 μm or less. When observed in cross section, the opening width r3 of the outer resin layer SR uses the minimum opening width. As described above, the opening width r3 of the outer resin layer SR corresponds to the minimum width of the external electrode E.

[0086] The protrusions (respectively 13a and 13b) of the upper end portion 11a and the lower end portion 11b have a protruding length that can be confirmed when observing the cross section at a magnification of 5000 times, for example. Figure 4 yes Figure 3 A partial enlarged cross-sectional view of the Z section. Figure 4 As shown, for example, the protrusions (respectively 13a and 13b) of the upper end 11a and the lower end 11b (in Figure 4 In the embodiment, p1 and p2) are independently protruded with a protrusion length of 1 μm or more and 10 μm or less, especially 5 μm or more and 10 μm or less, when observed in cross section. From the viewpoint of further improving the connection strength between the external electrode and the lead conductor, it is preferably protruded with a protrusion length of 2 μm or more and 10 μm or less, more preferably 4 μm or more and 10 μm or less. The protrusion does not have to be strictly protruded in the vertical direction of the stacking direction, and may be protruded in a direction intersecting the stacking direction as long as it protrudes in the vertical direction as a whole.

[0087] The protruding length of the protrusions 13a and 13b is the protruding length based on the minimum width of the external electrode E. Specifically, for example, Figure 4 As shown, the protrusion lengths p1 and p2 in the direction perpendicular to the stacking direction T based on the minimum width are respectively. The minimum width of the external electrode E is a dimension corresponding to the opening width r3 of the exterior resin layer SR described later.

[0088] The thickness of the exterior resin layer SR is not particularly limited, and may be, for example, 0.5 μm to 20 μm, particularly 4 μm to 10 μm. The thickness of the exterior resin layer SR is an average value of values ​​measured at any 20 points.

[0089] The exterior resin constituting the exterior resin layer SR is not particularly limited as long as it is a resin that can withstand etching in the second etching step described later, and may be, for example, an epoxy resin, an acrylic resin, or the like.

[0090] When viewed in cross section, the widths of the upper end 11a and the lower end 11b of the external electrode E (r1 and r2, respectively) are generally smaller than the width R of the through hole TH (see Figure 3 ). Thus, it is possible to suppress the increase in DC resistance and further reduce the plane area of ​​the external electrode E observed from the mounting surface B1 side of the blank B. Therefore, the present disclosure is particularly effective for a stacked inductor for a multi-phase DCDC converter. Multi-phase means that a plurality of coils are integrated into one blank as in the second and third embodiments described later. In particular, in the case of a stacked body, the through hole TH is Figure 3 Therefore, when the cross section is observed, the width R of the through hole TH is the average value of the minimum width and the maximum width in the direction perpendicular to the stacking direction T.

[0091] The width R of the through hole TH is not particularly limited, and may be 250 μm or more and 400 μm or less.

[0092] The difference between the width R of the through hole TH and the width r1 of the upper end portion 11 a and the difference between the width R of the through hole TH and the width r2 of the lower end portion 11 b are not particularly limited, and may be, for example, each independently greater than or equal to 0 μm and less than or equal to 50 μm.

[0093] In the present embodiment, the external electrode E is buried in the external resin layer SR between the protrusions of the upper end portion 11a and the lower end portion 11b. "Buried" means buried and arranged. In the present embodiment, in detail, the external electrode E is not buried in the external resin layer as a whole, but only the portion between the protrusion 13a of the upper end portion 11a and the protrusion 13b of the lower end portion 11b is buried in the external resin layer SR, and the upper surface 11a1 of the upper end portion 11a and the lower surface 11b1 of the lower end portion 11b are not in direct contact with the external resin layer SR. The external resin layer SR is arranged (or filled) between the protrusions (13a and 13b, respectively) of the upper end portion 11a and the lower end portion 11b of the external electrode E in the stacking direction T.

[0094] In this way, the external electrode E has the protrusions 13a and 13b at the upper end 11a and the lower end 11b thereof, and the external resin layer SR is buried therebetween, so that the connection strength between the external electrode E and the body B (particularly the through hole TH) is improved. For example, when the external electrode E is viewed from the stacking direction T, only the upper end 11a is visually recognized, and the lower end 11b is not visually recognized. When the external electrode E is viewed from the stacking direction T, the upper end 11a as an "island" exists in the external resin layer SR as a "sea".

[0095] From another viewpoint of the present embodiment, when viewed in cross section, the external electrode E sandwiches the outer resin layer SR between the protrusion 13a of the upper end portion 11a and the protrusion 13b of the lower end portion 11b. In particular, the protrusion 13b of the lower end portion 11b not only exerts an anchoring effect but also sandwiches the outer resin layer SR together with the protrusion 13a of the upper end portion 11a, thereby further sufficiently improving the connection strength between the external electrode E and the base body B (particularly the through hole TH).

[0096] From the viewpoint of further improving the connection strength between the external electrode and the lead conductor, the thickness of the outer resin layer SR between the protrusions is preferably thicker than the thickness of the outer resin layer SR outside the protrusions. Such a thickness gradient of the outer resin layer is caused by the first and second etching steps (particularly the first etching step) described later.

[0097] like Figure 4 As shown in FIG. 1 , the thickness of the outer resin layer SR between the protrusions is a thickness a1 on a reference line P in the stacking direction T passing through the top of the protrusion 13a at the upper end 11a and the protrusion 13b at the lower end 11b, whichever has the larger protrusion length. The thickness a1 is not particularly limited, and may be, for example, 5 μm or more and 12 μm or less.

[0098] The thickness of the external resin layer SR outside between the protrusions is the thickness of the external resin layer SR in the area where the external electrode is not formed on the bottom surface B1 of the body B, and the average value of the thickness at any 20 points in the external resin layer SR on the magnetic body M is used. The thickness of the external resin layer SR outside between the protrusions is not particularly limited, and may be, for example, 4 μm or more and 10 μm or less.

[0099] exist Figure 3In the embodiment, the external electrode E has protrusions 13a and 13b on the left and right sides of the upper end 11a and the lower end 11b, respectively. However, it is not necessary to have protrusions on both sides. It is sufficient as long as at least the lower end has protrusions on one side (preferably both sides) of the left and right sides. From the viewpoint of further improving the connection strength between the external electrode and the lead conductor, it is preferred that the external electrode has protrusions on the left and right sides of the upper end and the lower end. The protrusion at the lower end of the external electrode is caused by performing the external electrode forming step after performing the second etching step described later.

[0100] As an example, various materials such as Cu, Ni and / or Sn can be used for the external electrode, preferably Cu. The external electrode can also be formed by any method, but as an example, it can be a plated electrode formed directly on the through hole by plating (for example, chemical plating). When the external electrode is formed by plating, it is necessary to immerse the blank B in the plating solution, but as described above, the gap of the blank B (magnetic body M) is configured with resin, so that the plating solution can be reduced. Infiltrate the gap in the magnetic body, etc.

[0101] <Modification 1 of the First Embodiment of the Laminated Inductor>

[0102] In the laminated inductor of the first embodiment, the external electrode E has protrusions 13a and 13b at the upper end 11a and the lower end 11b continuously over the entire circumference of the external electrode E when viewed from the stacking direction. However, the external electrode E does not necessarily have to have the protrusions continuously over the entire circumference, and may have the protrusions discontinuously or intermittently over the entire circumference of the external electrode E when viewed from the stacking direction. For example, the external electrode E may have the protrusions when viewed in any cross section.

[0103] <Modification 2 of the First Embodiment of the Laminated Inductor>

[0104] In the laminated inductor of the first embodiment, the external electrodes E are formed in an island shape (for example, a dot shape) when viewed from the lamination direction. However, for example, Figure 3 In other words, the external electrode E may extend in a wall shape in the W direction of the body. The upper end portion 11a and the lower end portion 11b may have the protrusions 13a and 13b continuously in the extending direction, or may have the protrusions 13a and 13b discontinuously or intermittently.

[0105] <Second Embodiment of Laminated Inductor>

[0106] Next, refer to Figure 5, while describing the laminated inductor 1B of the second embodiment. The structure related to the coil of the laminated inductor 1B of the second embodiment is different from that of the laminated inductor 1A of the first embodiment described above. Specifically, the number of coils, the number of windings of the coils, and the positions of the external electrodes are different. In the following description, the description is centered on the points that are different from the laminated inductor described in the above embodiment. In addition, the structures of the external electrodes E1 to E4 in the laminated inductor 1B of the second embodiment correspond to the structures of the external electrodes E1 to E2 in the laminated inductor 1A of the first embodiment. Therefore, in the second embodiment, as in the first embodiment, the plane area of ​​the external electrodes E (E1 to E4) observed from the mounting surface B1 side of the blank B can be further reduced. Therefore, the laminated inductor 1B of the second embodiment can more effectively utilize the bottom surface (mounting surface) B1 of the blank B based on the reduction in the area of ​​the external electrode E. The structure of the external electrode includes not only the structure of the external electrode itself but also the relationship between the external electrode and the through hole and the exterior resin layer, and the relationship between the through hole and the exterior resin layer.

[0107] The coils of the stacked inductor 1B of this embodiment can be arranged so that two or more coils overlap when viewed from the stacking direction. In other words, the first coil C1 and the second coil C2 can be arranged inside the blank B. The first coil C1 and the second coil C2 can be magnetically coupled. For example, the coupling coefficient between the first coil C1 and the second coil C2 is greater than 0.1 and less than 0.8. In addition, two coils including only the first coil C1 and the second coil C2 can be arranged inside the blank B, or three or more coils including the first coil C1 and the second coil C2 can be arranged.

[0108] -First coil-

[0109] The first coil C1 includes a plurality of first coil conductors CM1 constituting the first coil C1 in the stacking direction (e.g., the height direction T). Adjacent first coil conductors CM1 are connected to each other via via conductors V. In addition, the first coil C1 can be set to 1.75 by including first coil conductors CM1 formed in two different stacking groups in the stacking direction. In addition, the number of windings is not limited to 1.75, and can also be set to, for example, 2 or more by stacking the first coil conductors CM1 in the stacking direction.

[0110] - Second coil -

[0111] The second coil C2 is arranged at a position 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 (e.g., the height direction T). Adjacent second coil conductors CM2 are connected to each other via via conductors V. In addition, the second coil C2 can set the number of windings to 1.75 by including second coil conductors CM2 formed in two different stacking groups in the stacking direction. In addition, the number of windings is not limited to 1.75 as shown in the figure, and can also be set to, for example, more than 2 by stacking the second coil conductors CM2 in the stacking direction. In addition, the number of stacking of the second coil conductor CM2 can be the same as or different from the number of stacking of the first coil conductor CM1.

[0112] -Through holes and external electrodes-

[0113] 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 disposed inside the blank B. Moreover, 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 blank B.

[0114] The first through hole TH1 connects the end of the first coil conductor CM1 closest to the bottom surface of the base B among the ends of the first coil C1 to the first external electrode E1. The first through hole TH1 may extend along the stacking direction (eg, the height direction T). The first through hole TH1 may have a stacking structure.

[0115] 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 (eg, the height direction T). The second through hole TH2 may also have a stacking structure.

[0116] The third through hole TH3 connects the end of the second coil conductor CM2 closest to the bottom surface of the body B among the ends of the second coil C2 to the third external electrode E3. The third through hole TH3 may extend along the stacking direction (eg, the height direction T). The third through hole TH3 may also have a stacking structure.

[0117] 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 (eg, the height direction T). The fourth through hole TH4 may also have a stacking structure.

[0118] like Figure 5As shown, 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 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 body B and are electrically connected to the second coil C2. In the laminated inductor 1B, the first main surface B1 of the body B can be set as the mounting surface.

[0119] Even in the laminated inductor 1B of the second embodiment, resin is provided in at least a part of the gaps between the magnetic body M and the coil conductor. Therefore, by reducing the gaps, the body strength can be improved.

[0120] <Modification of Second Embodiment of Laminated Inductor>

[0121] In the laminated inductor ( Figure 5 ), the external electrodes E are all formed into an island shape (e.g., a dot shape) when viewed from the stacking direction, but an electrode connection structure can also be provided in which the island-shaped external electrodes are used as bridges to couple the parts built thereon. In detail, for example, Figure 5 In the case where the external electrodes E2 and E3 have the same polarity, an electrode connection structure having these external electrodes E2 and E3 as bridges and also having a bridge portion for bridging the external electrodes E2 and E3 may be provided. In such an electrode connection structure, the external electrode as the bridge has a relatively sufficient connection strength with the through hole, so the electrode connection structure also has a relatively sufficient connection strength. The bridge portion of the electrode connection structure may also be made of the same material as the external electrode E.

[0122] <Stacked Inductor Array>

[0123] Next, refer to Figure 6 , while explaining the stacked inductor array of the present invention. In the stacked inductor array 1C of the present invention, the coils are arranged so that two or more are overlapped when viewed from the stacking direction, and are arranged in parallel in a direction intersecting the stacking direction (for example, a direction perpendicular to the stacking direction) to form a coil array. Specifically, in addition to the first coil C1 and the second coil C2, a third coil C3, a fourth coil C4, a fifth coil C5, and a sixth coil C6 may also be included. In addition, the third coil C3 and the fifth coil C5 are of substantially the same structure as the first coil C1, and the fourth coil C4 and the sixth coil C6 are of substantially the same structure as the second coil C2.

[0124] 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 conductor layer closest to the bottom surface among the ends of the third coil C3 may be connected to the fifth external electrode E5 through the fifth through hole TH5. In addition, the other end of the third coil conductor layer may be connected to the sixth external electrode E6 through the sixth through hole TH6.

[0125] The fourth coil C4 may be electrically connected to the seventh external electrode (not shown) and the eighth external electrode (not shown). The end of the fourth coil conductor layer closest to the bottom surface among the ends of the fourth coil C4 may be connected to the seventh external electrode through the seventh through hole. In addition, the other end of the fourth coil conductor layer may be connected to the eighth external electrode through the eighth through hole.

[0126] 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 conductor layer closest to the bottom surface among the ends of the fifth coil C5 may be connected to the ninth external electrode E9 through the ninth through hole TH9. In addition, the other end of the fifth coil conductor layer may be connected to the tenth external electrode E10 through the tenth through hole TH10.

[0127] The sixth coil C6 may be electrically connected to the eleventh external electrode E11 and the twelfth external electrode E12. The end of the sixth coil conductor layer closest to the bottom surface among the ends of the sixth coil C6 may be connected to the eleventh external electrode E11 through the 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) through the twelfth through hole TH12.

[0128] In the laminated inductor array 1C of the present disclosure, the structures of the external electrodes E1 to E12 correspond to the structures of the external electrodes E1 to E2 in the laminated inductor 1A of the first embodiment. Therefore, in the laminated inductor array 1C of the present disclosure, the plane area of ​​the external electrodes E (E1 to E12) viewed from the mounting surface B1 side of the body B can be further reduced, as in the first embodiment. Therefore, the laminated inductor array 1C of the present disclosure can more effectively utilize the bottom surface (mounting surface) B1 of the body B based on the reduction in the area of ​​the external electrodes E.

[0129] <Manufacturing method of laminated inductor>

[0130] Next, use Fig. 7A A method for manufacturing the laminated inductor of the present disclosure will be described. Fig. 7A: is a flow chart showing the manufacturing method of the laminated inductor of the present disclosure. The manufacturing method of the laminated inductor of the present disclosure may include a green body precursor preparation step, a resin impregnation preparation step, a resin impregnation step, a grinding step, a first etching step, an outer resin layer forming step, a second etching step, and an external electrode forming step. In the manufacturing method of the laminated inductor of the present disclosure, it is a cross-sectional view showing the more characteristic resin impregnation step, grinding step, first etching step, outer resin layer forming step, second etching step, and external electrode forming step. The following is a detailed description along the steps.

[0131] [Body precursor preparation process]

[0132] In this step, a green body precursor is prepared, which has a coil formed by winding a coil conductor inside a magnetic body formed by laminating magnetic layers containing iron powder, and a through hole electrically connected to the coil conductor and exposed from the bottom surface of the magnetic body.

[0133] In detail, first, prepare the composition Figure 2 The magnetic paste of the magnetic layers ML of the laminated group described above, the conductor paste constituting the coil conductors CM, and the non-magnetic paste constituting the non-magnetic layers between the coil conductors CM.

[0134] As an example of a method for preparing a magnetic paste, an iron powder such as an Fe-Si alloy or an Fe-Si-Cr alloy having a cumulative 50% particle size on a volume basis, i.e., D50, of 2 μm or more and 20 μm or less is prepared. The magnetic paste is prepared by mixing cellulose or polyvinyl butyral (PVB) or the like as a binder and a mixture of terpineol and diethylene glycol butyl acetate (BCA) or the like as a solvent in the iron powder.

[0135] When Fe-Si alloy is used as iron powder, the content of Si is preferably 2.0 at% to 8.0 at% inclusive. When Fe-Si-Cr alloy is used as iron powder, the content of Si is preferably 2.0 at% to 8.0 at% inclusive. In addition, when Fe-Si-Cr alloy is used as iron powder, the content of Cr is preferably 0.2 at% to 6.0 at% inclusive.

[0136] An insulating coating may also be provided on the surface of the iron powder. The insulating coating is preferably a coating comprising a metal oxide, more preferably an oxide of Si. As a method for forming the insulating coating, a sol-gel method is preferred. As an example of forming an insulating coating by a sol-gel method, a mixed solution is formed by mixing a sol-gel coating agent comprising Si alkoxide and a silane coupling agent containing an organic chain. After the mixed solution is attached to the surface of the metal magnetic powder, it is dehydrated and bonded by applying a heat treatment. Then, by drying at a predetermined temperature, an insulating coating can be formed.

[0137] As an example of a method for making a non-magnetic paste, Fe2O3, ZnO, CuO and components added as needed are weighed in a manner to form a prescribed composition. The weighed object is placed in a ball mill together with pure water, a dispersant, and a PSZ medium, mixed and crushed, and a slurry is obtained. After the obtained slurry is dried, it is calcined at a temperature of more than 700°C and less than 800°C for more than 2 hours and less than 3 hours to obtain a non-magnetic material (calcined powder). A prescribed amount of solvent (ketone solvent, etc.), resin (polyvinyl acetal, etc.) and plasticizer (alkyd plasticizer, etc.) are added to the non-magnetic material (calcined powder), and after mixing with a planetary mixer, it is further dispersed using a three-roll mill to prepare a non-magnetic paste.

[0138] Preferably, the non-magnetic paste contains 40 mol% or more and 49.5 mol% or less of Fe as converted to Fe2O3, 4 mol% or more and 12 mol% or less of Cu as converted to CuO, and ZnO as the remainder. More preferably, the non-magnetic paste contains Mn, Bi, Co, Si, Sn, etc. as additives as needed to the above-mentioned main components. The non-magnetic paste may also contain inevitable impurities.

[0139] As the conductor paste, for example, a paste containing Ag as a conductive material is prepared.

[0140] The magnetic paste, non-magnetic paste and conductive paste are used to prepare Figure 2 The stacked groups G1 to G7 shown. Furthermore, the unfired green body precursor is pressurized by a pressing process such as a warm hydrostatic press (WIP) to form a stacked body. After the pressurization process, the stacked body is placed in a firing furnace, degreased, and then fired in the atmosphere. The firing temperature is, for example, 600° C. to 800° C. The firing time is, for example, 30 minutes to 90 minutes. The green body is prepared by this firing.

[0141] [Resin impregnation preparation step] (optional additional step)

[0142] The resin impregnation preparation step is a step that is arbitrarily performed before the resin impregnation step described below. Specifically, the resin impregnation preparation step is a step of reducing gas or water in the green body or lowering the viscosity of the resin.

[0143] As an example of the resin impregnation preparation process, degassing the fired green body to reduce the gas in the green body so that the resin is more easily impregnated is listed. In addition, degassing and resin impregnation can be repeated. As another method for the resin impregnation preparation process, a method of heating the fired green body to reduce the moisture in the green body so that the resin is more easily impregnated can also be adopted. As another method for the resin impregnation preparation process, a method of heating the resin to reduce the viscosity of the resin so that the resin is easily impregnated into the green body can also be adopted. Through this process, the resin can be effectively impregnated into the green body.

[0144] [Resin impregnation step] (optional additional step)

[0145] In this process, the fired green body precursor is impregnated with resin. This process may also be an additional process. When this process is performed, the resin may contain, for example, epoxy resin, silicone resin or phenolic resin. By impregnating the green body with resin, the resin is provided in at least a portion of the voids in the magnetic body and the coil conductor. Thus, the voids can be reduced and the green body strength can be improved. In addition, the penetration of plating liquid or moisture into the green body can be reduced. In this process, in the green body precursor, the impregnation resin residue RE remains on the bottom surface B1 (first main surface B1) side of the magnetic body ( Fig. 7A (1)).

[0146] [Grinding process]

[0147] In this step, in the green body precursor impregnated with the resin, the impregnation resin residue RE on the bottom surface B1 side of the magnetic body is removed by grinding, and at least the end surface of the through hole TH is exposed, thereby obtaining a green body ( Fig. 7A (2)). By grinding, the above-mentioned surface roughness can be applied to the bottom surface B1 of the magnetic body, and the thickness of the green body can be adjusted to a predetermined thickness. This step can also be performed on a green body precursor that is not impregnated with resin.

[0148] [First etching step] (optional additional step)

[0149] This step is an additional step that is performed arbitrarily before the outer resin layer forming step described later. Specifically, in the bottom surface of the magnetic body of the blank obtained in the grinding step, at least the through-hole end face is etched to obtain a new through-hole end face th0 ( Fig. 7A(3)). Through this process, as described above, on the bottom surface B1 side of the magnetic body, a thickness gradient is obtained in which the thickness of the outer resin layer SR between the protrusions is thicker than the thickness of the outer resin layer SR outside the protrusions, thereby further improving the connection strength between the external electrode and the through hole. The etching liquid uses a liquid that can dissolve the through hole and the magnetic body M. As such an etching liquid, for example, potassium nitrate-ammonia water, sodium cyanide, and phosphoric acid aqueous system can also be used. In addition, if the magnetic body M is impregnated with resin in this process, the magnetic body is hardly etched.

[0150] [Exterior resin layer forming step]

[0151] In this step, an outer resin layer SR ( Fig. 7A (4)). The outer resin layer SR is a protective layer for the second etching process described later, and may be, for example, a solder resist layer. The method for forming the outer resin layer SR is not particularly limited as long as the outer resin layer SR can be selectively formed in an area other than the end surface of the through hole, and, for example, a screen printing method may be used. In the screen printing method, a solution of the above-mentioned resin constituting the outer resin layer SR may also be used as ink.

[0152] In this process, the outer resin layer SR is formed to open in the bottom surface of the magnetic body of the blank in the area roughly corresponding to the end surface of the through hole. In detail, the area of ​​the opening of the outer resin layer SR is smaller than the area of ​​the end surface of the through hole TH. The area of ​​the opening of the outer resin layer SR is smaller than the area of ​​the end surface of the through hole TH, thereby obtaining an overlapping portion of the outer resin layer SR and the through hole TH (especially the end surface) when viewed from above. As a result, in the second etching process described later, a gap is formed between the end surface of the through hole and the outer resin layer, and the protrusion 13b at the lower end of the external electrode is formed through the external electrode forming process described later.

[0153] Figure 7B Detailed cross-sectional view showing the process of forming an outer resin layer in the method for manufacturing a laminated inductor disclosed in the present invention. The opening of the outer resin layer is an opening through which the outer electrode is seen when viewed from the stacking direction T. Figure 7B In FIG. 5 , the region between two reference lines m4 is represented. The reference line m4 is a reference line parallel to the stacking direction T that defines the opening of the exterior resin layer SR.

[0154] The end surface of the through hole TH is, for example, Figure 7BIn the figure, the area between the two reference lines m3 is represented. The reference line m3 is the center line between the reference line m1 parallel to the stacking direction T and defining the maximum diameter of the through hole TH and the reference line m2 parallel to the stacking direction T and defining the minimum diameter of the through hole TH when viewed in cross section. The diameter D of the through hole TH is the maximum diameter defined by the reference line m1, and the laminated inductor can be measured based on an image taken by X-ray fluoroscopy from the bottom side or the side substantially perpendicular to the stacking direction T.

[0155] In this process, in detail, when the base body formed with the external resin layer SR is viewed from the stacking direction, the external resin layer SR is formed to overlap the peripheral portion of the end face of the through hole TH. The dimension n of the overlapping portion in the peripheral portion of the end face of the through hole TH can be any dimension that forms a gap corresponding to the protrusion 13b between the end face of the through hole and the external resin layer in the second etching process described later. The dimension n of the overlapping portion in the peripheral portion of the end face of the through hole TH is represented by the distance between the above-mentioned reference lines m3 and m4, for example, 2 μm or more, and in particular, 50 μm or more. The larger the dimension n is within the range of the opening portion forming the external resin layer SR, the more preferably, so the upper limit value of the dimension n is not particularly limited, for example, the dimension n may be 70 μm or less, and in particular, 20 μm or less.

[0156] [Second Etching Step]

[0157] In this step, the through-hole end face is etched on the bottom surface of the magnetic body of the green body on which the outer resin layer is formed, thereby obtaining a new through-hole end face th1 ( Fig. 7A (5)). After this step, the external electrode forming step described later is performed to form the protrusion 13b at the lower end of the external electrode. Specifically, in this step, the through-hole end face is etched so that the surface of the through-hole end face is lowered to obtain the through-hole end face th1. Thus, a gap corresponding to the protrusion 13b is formed between the through-hole end face and the outer resin layer, and the protrusion 13b at the lower end of the external electrode is formed by the external electrode forming step described later.

[0158] In this process, an etching liquid is used that dissolves the through holes while not dissolving the exterior resin layer SR. As such an etching liquid, for example, a solution containing potassium cyanide, phosphoric acid, nitric acid, acetic acid, or thiourea may be used. The etching time is not particularly limited, and for example, may be 30 seconds or more and 900 seconds or less, preferably 500 seconds or more and 700 seconds or less (particularly 600 seconds).

[0159] [External electrode forming process]

[0160] The external electrode forming step is a step of forming an external electrode E electrically connected to the coil conductor. Fig. 7A(6)). An external electrode is formed by chemical plating at the opening of the outer resin layer SR (the position where the through hole is exposed on the mounting surface (first main surface B1) of the blank B). The plated material may be Cu plating. In addition, Ni-Sn, Ni-Au, Ni-Cu and / or Cu-Ni-Au are listed, but not limited to these.

[0161] In the second etching step, a gap corresponding to the protrusion 13 b is formed between the end surface of the through hole and the exterior resin layer. Therefore, in the external electrode forming step, the protrusion 13 b is formed at the lower end thereof only by forming the external electrode.

[0162] In the external electrode forming step, it is important to form the external electrode higher than the surface of the external resin layer SR. Thus, the protrusion 13a is formed at the upper end of the external electrode.

[0163] When a plurality of laminated inductors are connected in a manner through the exterior resin layer forming step, the laminated inductor of the present embodiment can be manufactured by performing element singulation (dicing step) after the external electrodes are formed.

[0164] The above-mentioned blank precursor preparation step, resin impregnation preparation step, resin impregnation step, grinding step, first etching step, external resin layer forming step, second etching step and external electrode forming step are usually performed in sequence according to the order of the description. In addition, the resin impregnation preparation step and the first etching step can also be omitted independently, or can also be implemented. For example, in the case of omitting the first etching step, in detail, for the blank obtained in the grinding step, the external resin layer forming step, the second etching step and the external electrode forming step can be performed in sequence.

[0165] The technical scope of the present disclosure is not to be interpreted only by the above-mentioned embodiments, but is to be divided based on the description of the claims. In addition, the technical scope of the present disclosure includes all changes within the meaning and scope equivalent to the claims.

[0166] The laminated inductor and the method for manufacturing the same according to the present disclosure include the following aspects.

[0167] <1>

[0168] A stacked inductor, comprising:

[0169] A green body having a coil formed by winding a coil conductor inside a magnetic body formed by laminating magnetic layers containing iron powder, and a through hole electrically connected to the coil conductor and extending toward the bottom surface of the magnetic body;

[0170] an external electrode disposed on the through hole and electrically connected to the through hole; and

[0171] The outer resin layer is arranged on the bottom surface of the magnetic body of the green body.

[0172] The external electrode has a protrusion protruding in a direction perpendicular to the stacking direction at an upper end away from the through hole and a lower end close to the through hole in the stacking direction of the magnetic layer.

[0173] The exterior resin layer is disposed between the protrusions at the upper end portion and the lower end portion.

[0174] <2>

[0175] The multilayer inductor according to <1>, wherein:

[0176] When viewed in cross section, widths of the upper end portion and the lower end portion of the external electrode are larger than a width of an opening of the external resin layer.

[0177] <3>

[0178] The multilayer inductor according to <1> or <2>, wherein:

[0179] When viewed in cross section, widths of the upper end portion and the lower end portion of the external electrode are smaller than a diameter of the through hole.

[0180] <4>

[0181] The multilayer inductor according to any one of <1> to <3>, wherein:

[0182] The thickness of the exterior resin layer on the through hole is thicker than the thickness of the exterior resin layer outside the through hole.

[0183] <5>

[0184] The multilayer inductor according to any one of <1> to <4>, wherein:

[0185] The external electrode is a plated electrode formed directly on the through hole.

[0186] <6>

[0187] The multilayer inductor according to any one of <1> to <5>, wherein:

[0188] The above-mentioned external electrodes are copper-plated electrodes.

[0189] The through hole is a silver sintered body.

[0190] <7>

[0191] The multilayer inductor according to any one of <1> to <6>, wherein:

[0192] The surface roughness of the bottom surface of the magnetic body in the blank is coarser than the surface roughness of the surface of the magnetic body in the blank opposite to the bottom surface.

[0193] <8>

[0194] The multilayer inductor according to any one of <1> to <7>, wherein:

[0195] The surface roughness of the bottom surface of the magnetic body of the blank is coarser than the surface roughness of the end surface of the through hole.

[0196] <9>

[0197] The multilayer inductor according to any one of <1> to <8>, wherein:

[0198] The green body further includes a resin disposed in the voids in the magnetic body.

[0199] <10>

[0200] The laminated inductor according to any one of <1> to <9>, wherein:

[0201] The coils are arranged so as to overlap each other in two or more portions when viewed in plan from the stacking direction.

[0202] <11>

[0203] The laminated inductor according to any one of <1> to <10>, wherein:

[0204] The coils are arranged so that two or more are overlapped when viewed in plan from the stacking direction, and are arranged in parallel in a direction intersecting the stacking direction to form a coil array.

[0205] <12>

[0206] A method for manufacturing a stacked inductor, comprising:

[0207] A green body precursor preparation step of preparing a green body precursor, wherein the green body precursor has a coil formed by winding a coil conductor inside a magnetic body formed by laminating magnetic layers containing iron powder, and a through hole electrically connected to the coil conductor and exposed from a bottom surface of the magnetic body;

[0208] A grinding step of removing the impregnation resin residue on the bottom surface side of the magnetic body in the green body precursor by grinding and exposing the end surface of the through hole to obtain a green body;

[0209] an outer coating resin layer forming step of forming an outer coating resin layer on the bottom surface of the magnetic body of the green body so as to overlap with the peripheral edge of the end surface of the through hole when viewed from the stacking direction;

[0210] an etching step of etching the end surface of the through hole on the surface of the body on which the outer resin layer is formed; and

[0211] The external electrode forming step forms an external electrode electrically connected to the coil conductor on an end surface of the through hole.

[0212] <13>

[0213] The method for manufacturing a laminated inductor according to <12>, wherein:

[0214] A resin impregnation step of impregnating the green body precursor with a resin is further provided between the green body precursor preparation step and the grinding step.

[0215] <14>

[0216] The method for manufacturing a laminated inductor according to claim <12> or <13>, wherein:

[0217] An etching step of etching the end surface of the through hole on the bottom surface of the magnetic body of the green body is further provided between the grinding step and the outer resin layer forming step.

[0218] <15>

[0219] The method for producing a laminated inductor according to any one of <12> to <14>, wherein:

[0220] The laminated inductor according to any one of <1> to <11> is manufactured.

[0221] Industrial Applicability

[0222] The present disclosure can be used for a laminated inductor having improved connection strength between an external electrode and a through hole.

Claims

1. A stacked inductor, wherein: have: A green body having a coil formed by winding a coil conductor inside a magnetic body formed by laminating magnetic layers containing iron powder, and a through hole electrically connected to the coil conductor and extending toward the bottom surface of the magnetic body; an external electrode, disposed on the through hole and electrically connected to the through hole; as well as The outer resin layer is arranged on the bottom surface of the magnetic body of the blank. The external electrode has a protrusion protruding in a direction perpendicular to the stacking direction at an upper end away from the through hole and a lower end close to the through hole in the stacking direction of the magnetic layers. The exterior resin layer is disposed between the protrusions at the upper end portion and the lower end portion.

2. The laminated inductor according to claim 1, wherein: When viewed in cross section, widths of the upper end portion and the lower end portion of the external electrode are larger than a width of an opening of the external resin layer.

3. The laminated inductor according to claim 1 or 2, wherein: When viewed in cross section, the widths of the upper end portion and the lower end portion of the external electrode are smaller than the diameter of the through hole.

4. The laminated inductor according to any one of claims 1 to 3, wherein: The thickness of the exterior resin layer on the through hole is thicker than the thickness of the exterior resin layer outside the through hole.

5. The laminated inductor according to any one of claims 1 to 4, wherein: The external electrode is a plated electrode formed directly on the through hole.

6. The laminated inductor according to any one of claims 1 to 5, wherein: The external electrodes are copper-plated electrodes, The through hole is a silver sintered body.

7. The laminated inductor according to any one of claims 1 to 6, wherein: The surface roughness of the bottom surface of the magnetic body in the blank is coarser than the surface roughness of the surface of the magnetic body in the blank on the opposite side to the bottom surface.

8. The laminated inductor according to any one of claims 1 to 7, wherein: The surface roughness of the bottom surface of the magnetic body of the blank is coarser than the surface roughness of the end surface of the through hole.

9. The laminated inductor according to any one of claims 1 to 8, wherein: The green body further includes a resin disposed in a void in the magnetic body.

10. The laminated inductor according to any one of claims 1 to 9, wherein: The coils are arranged so that two or more are overlapped when viewed in plan from the stacking direction.

11. The laminated inductor according to any one of claims 1 to 10, wherein: The coils are arranged so that two or more are overlapped when viewed in plan from the stacking direction, and are arranged in parallel in a direction intersecting the stacking direction to form a coil array.

12. A method for manufacturing a stacked inductor, wherein: have: A green body precursor preparation step of preparing a green body precursor having a coil formed by winding a coil conductor inside a magnetic body formed by laminating magnetic layers containing iron powder, and a through hole electrically connected to the coil conductor and exposed from a bottom surface of the magnetic body; A grinding step of removing the impregnation resin residue on the bottom surface side of the magnetic body in the green body precursor by grinding and exposing the end surface of the through hole to obtain a green body; an outer coating resin layer forming step of forming an outer coating resin layer on the bottom surface of the magnetic body of the green body so as to overlap with the peripheral edge of the end surface of the through hole when viewed from the stacking direction; an etching step of etching the end surface of the through hole on the surface of the body on which the outer resin layer is formed; and The external electrode forming step is to form an external electrode electrically connected to the coil conductor on an end surface of the through hole.

13. The method for manufacturing a laminated inductor according to claim 12, wherein: A resin impregnation step of impregnating the green body precursor with a resin is further provided between the green body precursor preparation step and the grinding step.

14. The method for manufacturing a laminated inductor according to claim 12 or 13, wherein: An etching step of etching the end surface of the through hole on the bottom surface of the magnetic body of the blank is further provided between the grinding step and the outer resin layer forming step.

15. The method for manufacturing a laminated inductor according to any one of claims 12 to 14, wherein: A laminated inductor according to any one of claims 1 to 11 is manufactured.

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