Multilayer inductor

Abstract

Provided is a multilayer inductor that reduces loss resulting from an eddy current with respect to an AC current by reducing resistance in the vicinity of an interface between a coil conductor and a metal magnetic body. A multilayer inductor 1 according to the present disclosure comprises an element body 10 having a metal magnetic body M on which a metal magnetic layer ML containing metal magnetic particles is layered, and a coil conductor CM on which a coil conductor layer CL is layered in the layering direction of the metal magnetic layer ML. The coil conductor CM has unevenness B on side surfaces thereof positioned in an intersection direction intersecting the lamination direction. The metal magnetic layer ML is disposed in recessed sections of the side surfaces. The density of a conductor constituting the coil conductor CM is greater at the side surfaces than at the center.

Description

Multilayer inductors

[0001] The present disclosure relates to laminated inductors.

[0002] Patent Document 1 discloses a coil component including a first conductor pattern extending along a transverse direction that intersects with the vertical direction, an insulator layer stacked on an upper end of the first conductor pattern, a second conductor pattern stacked on the upper end of the insulator layer and extending along the transverse direction, and a base portion covering the first conductor pattern, the insulator layer, and the second conductor pattern, wherein, in the transverse direction, the width W1 of the upper end of the first conductor pattern is greater than the width of the insulator layer, and the width of the lower end of the second conductor pattern is equal to or less than the width of the insulator layer.

[0003] Japanese Patent Application Laid-Open No. 2020-107782

[0004] In the invention described in Patent Document 1, a laminate is obtained by laminating a plurality of sheets including an insulating layer, a conductor pattern, and a magnetic layer, and then thermocompression bonding the laminate. Here, in the laminate described in Patent Document 1, as shown in Figure 5, pores PO (voids) exist throughout the entire conductor pattern CM', and the pores PO lead to high resistance of the conductor pattern.

[0005] In particular, inductors used in high-frequency applications are susceptible to the inductance characteristics being affected by the resistance near the interface between the conductor pattern CM' and the magnetic layer M' (outside the conductor pattern), and as the resistance near the interface increases, the loss due to eddy currents in the inductor increases.

[0006] In view of the above, an object of the present disclosure is to provide a laminated inductor that reduces loss due to eddy currents in AC currents by reducing the resistance near the interface between a coil conductor and a metal magnetic body.

[0007] The laminated inductor according to the present disclosure comprises an element body having a metal magnetic body in which a metal magnetic layer containing metal magnetic particles is laminated, and a coil conductor in which a coil conductor layer is laminated in the lamination direction of the metal magnetic layer, wherein the coil conductor has unevenness on its side surface located in a cross direction that intersects with the lamination direction, the metal magnetic layer is arranged in a recess on the side surface, and the density of the conductor constituting the coil conductor is higher on the side surface side than in the central portion.

[0008] The laminated inductor of the present disclosure can reduce loss due to eddy currents in AC currents by reducing resistance near the interface between the coil conductor and the metal magnetic body. Specifically, the coil conductor has unevenness on its side surface located in a direction intersecting the lamination direction, and a metal magnetic layer is disposed in the recessed portion of the side surface, resulting in a structure in which the coil conductor and the metal magnetic body bite into each other. Therefore, when the element body is pressurized in the lamination direction, the side surface of the coil conductor where the metal magnetic body bites into it is appropriately deformed, thereby reducing pores (cavities) on the side surface of the coil conductor. Therefore, near the interface between the coil conductor and the metal magnetic body, high resistance due to pores is suppressed, and low resistance can be achieved.

[0009] FIG. 1 is a perspective view of a laminated inductor according to the present disclosure. FIG. 2 is an exploded perspective view of the laminated inductor according to the present disclosure. FIG. 3 is a schematic cross-sectional view of the laminated inductor according to the present disclosure. FIG. 4 is an SEM photograph of the laminated inductor according to the present disclosure. FIG. 5 is a schematic cross-sectional view of a conventional laminated inductor. FIG. 6 is a table showing the results of a demonstration test on the laminated inductor according to the present disclosure. FIG. 7A is a schematic diagram of the vicinity of the interface between the coil conductor and the metal magnetic body of Example 1 in the demonstration test (a position corresponding to region VII in FIG. 3 ). FIG. 7B is a schematic diagram of the vicinity of the interface between the coil conductor and the metal magnetic body of Example 2 in the demonstration test (a position corresponding to region VII in FIG. 3 ). FIG. 7C is a schematic diagram of the vicinity of the interface between the coil conductor and the metal magnetic body of Example 3 in the demonstration test (a position corresponding to region VII in FIG. 3 ). FIG. 7D is a schematic diagram of the vicinity of the interface between the coil conductor and the metal magnetic body of Example 4 in the demonstration test (a position corresponding to region VII in FIG. 3 ). FIG. 7E is a schematic diagram of the vicinity of the interface between the coil conductor and the metal magnetic body of Example 5 in the demonstration test (a position corresponding to region VII in FIG. 3).

[0010] The laminated inductor of the present disclosure will be described in detail below. While the description will refer to drawings as necessary, the contents shown are merely shown schematically and exemplarily to facilitate understanding of the present disclosure, and the appearance and dimensional ratios may differ from those of the actual product. The drawings shown below are schematic diagrams, and the dimensions, aspect ratios, and other scales may differ from those of the actual product.

[0011] In this specification, terms indicating the relationship between elements (e.g., "parallel," "orthogonal," etc.) and terms indicating the shape of elements not only refer to the strict literal form, but also refer to a range of substantial equivalence, for example, a range including a difference of about a few percent. Note that in this specification, the direction in which the magnetic layers and coil conductors constituting the element body are stacked is referred to as the "stacking direction." Furthermore, a plan view refers to a plan view of the element body as seen from the top (height direction).

[0012] The laminated inductor 1 of the present disclosure comprises an element body 10 and an external electrode 20 provided on the mounting surface of the element body 10 .

[0013] [Element Body] The element body 10 has, for example, a hexahedral shape having six sides. As an example, it may have a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape. The corners and ridges of the element body 10 may be rounded. A corner is a portion where three sides of the element body 10 intersect, and a ridge is a portion where two sides of the element body 10 intersect.

[0014] 1, the long side direction, short side direction, and height direction of the laminated inductor 1 and the element body 10 are respectively indicated as L direction, W direction, and T direction. The long side direction L, the short side direction W, and the height direction T are perpendicular to each other.

[0015] 1 has a first main surface 11 and a second main surface 12 that face each other in the height direction T, a first end surface 13 and a second end surface 14 that face each other in the long side direction L, and a first side surface 15 and a second side surface 16 that face each other in the short side direction W. In the example shown in Fig. 1, a first external electrode 21, a second external electrode 22, a third external electrode 23, and a fourth external electrode 24 are formed on the first main surface 11 of the element body 10, and the first main surface 11 of the element body 10 corresponds to the mounting surface of the laminated inductor 1 (the bottom surface of the element body).

[0016] Fig. 2 is an exploded perspective view schematically showing an example of the internal structure of the laminated inductor 1 of the present disclosure. As shown in Fig. 2, the element body 10 is formed by laminating a coil conductor layer CL, a metal magnetic layer ML containing metal magnetic particles, and a through-hole conductor TH. As an example, two coils (a first coil and a second coil) are provided inside the element body 10. Note that the number of coils provided inside the element body 10 may be three or more, or may be one.

[0017] The element body 10 is formed by stacking multilayer groups G1 to G7, with the first external electrode 21 to the fourth external electrode 24 formed below the multilayer group G7. Note that the boundaries between the layers in the multilayer structure of the element body 10 may disappear. Each of the multilayer groups G1 to G7 may be configured by stacking multiple layers to achieve a desired thickness.

[0018] The lamination group G1 has a metal magnetic layer ML and constitutes the second main surface 12 of the element body 10 (see FIG. 1).

[0019] The multilayer groups G2 and G3 are provided to form the second coil. That is, the coil conductor layers CL are stacked to form the second coil. The multilayer groups G2 and G3 of the present disclosure may each be configured by stacking multiple layers. Furthermore, each of the multilayer groups G2 and G3 has sawtooth-shaped irregularities B (see FIG. 3 ) on the side surfaces of the coil conductors CM formed by stacking the coil conductor layers CL by stacking patterns of coil conductor layers CL with different line widths. Note that, in addition to the method of stacking patterns with different line widths, methods such as stacking each layer while shifting them in a direction perpendicular to the stacking direction may also be used to form the sawtooth-shaped irregularities. The irregularities B provided on the side surfaces of the coil conductors CM will be described in detail later.

[0020] One end of the second coil is provided with a third through-hole conductor TH3 electrically connected to the third external electrode 23, and the other end of the second coil is provided with a fourth through-hole conductor TH4 electrically connected to the fourth external electrode 24. A metal magnetic layer ML is disposed around the coil conductor layer CL, the third through-hole conductor TH3, and the fourth through-hole conductor TH4.

[0021] The multilayer groups G4 and G5 are provided to form the first coil. That is, coil conductor layers CL are stacked to form the first coil. The multilayer groups G4 and G5 of the present disclosure may be formed by stacking multiple layers. Furthermore, like the first coil, each of the multilayer groups G4 and G5 has an irregularity B (see FIG. 3 ) on the side surface of the coil conductor CM formed by stacking the coil conductor layers CL.

[0022] One end of the first coil is provided with a first through-hole conductor TH1 electrically connected to the first external electrode 21, and the other end of the first coil is provided with a second through-hole conductor TH2 electrically connected to the second external electrode 22. A metal magnetic layer ML is disposed around the coil conductor layer CL and the first through-hole conductors TH1 to TH4.

[0023] The multilayer group G6 and the multilayer group G7 are provided with first through-hole conductors TH1 to 4th through-hole conductors TH4 corresponding to the arrangement of the first external electrodes 21 to 4th external electrodes 24. A metal magnetic layer ML is arranged around the first through-hole conductors TH1 to 4th through-hole conductors TH4. As shown in FIG. 2 , by making the planar area of ​​the first through-hole conductors TH1 to 4th through-hole conductors TH4 of the multilayer group G7 larger than the planar area of ​​the first through-hole conductors TH1 to 4th through-hole conductors TH4 of the multilayer group G6, the alignment of the through-hole conductors can be facilitated.

[0024] As described above, when the element body 10 has a multilayer structure including the multilayer groups G1 to G7, the degree of freedom in designing the multilayer inductor 1 is increased. For example, when manufacturing a multilayer inductor 1 including the first external electrode 21 to the fourth external electrode 24 on the bottom surface (first main surface 11) of the element body 10, it becomes easier to draw the coil conductor CM to the bottom surface side using through-hole conductors. Note that the multilayer structure including the above-mentioned multilayer groups G1 to G7 may be laminated from the second main surface 12 side or the first main surface 11 side of the element body 10. Furthermore, the material constituting the through-hole conductor layer TL and / or the via conductor may be repeatedly printed sequentially by, for example, screen printing or the like until the via conductors reach the desired thickness, or they may be formed by sputtering, inkjet printing, or other known methods.

[0025] As described above, the element body 10 includes a metal magnetic body M formed by laminating metal magnetic layers ML, coils (first coil and second coil) formed by laminating coil conductor layers CL, and through-hole conductors TH. Each element constituting the element body 10 will be described in detail below.

[0026] -Metal Magnetic Material- The metal magnetic material M formed by laminating metal magnetic layers ML may contain metal magnetic particles made of a metal magnetic material. The metal magnetic particles may contain Fe and / or Si. More specifically, they may be Fe particles or Fe alloy particles. Examples of Fe alloys include Fe-Si alloys, Fe-Cr alloys, Fe-Si-Cr alloys, Fe-Si-Al alloys, Fe-Si-B-P-Cu-C alloys, and Fe-Si-B-Nb-Cu alloys. The metal magnetic particles may also contain impurities such as Cr, Mn, Cu, Ni, P, S, or Co that are not intended during manufacturing. The metal magnetic particles may also be contained in a magnetic paste. Therefore, the metal magnetic particles may contain elements (e.g., Cr, Al, Li, Zn, Zr) that are more easily oxidized than the Fe added during magnetic paste production.

[0027] The surfaces of the above-mentioned metal magnetic particles may be covered with an insulating coating. Covering the surfaces of the metal magnetic particles with an insulating coating can improve the insulation between the metal magnetic particles, improving the withstand voltage of the inductor and suppressing eddy currents generated in the metal magnetic particles. Methods for forming the insulating coating on the surfaces of the metal magnetic particles include the sol-gel method and the mechanochemical method. The insulating coating may be made of an oxide of P, Si, or the like, zinc phosphate, or manganese phosphate. The insulating coating may also be an oxide film formed by oxidizing the surfaces of the metal magnetic particles with oxygen in the atmosphere, or an oxide film of an element more easily oxidized than Fe. The thickness of the insulating coating is preferably 1 nm or more and 50 nm or less, more preferably 1 nm or more and 30 nm or less, and even more preferably 1 nm or more and 20 nm or less. For example, the cross section obtained by polishing an inductor sample can be photographed with a scanning electron microscope (SEM), and the thickness of the insulating coating covering the surfaces of the metal magnetic particles can be measured from the obtained SEM photograph.

[0028] The average particle size of the metal magnetic particles in the metal magnetic body M is preferably 0.2 μm or more and 50 μm or less, more preferably 1 μm or more and 20 μm or less, and even more preferably 1 μm or more and 10 μm or less. The average particle size of the metal magnetic particles in the metal magnetic body M can be measured by the following procedure. An inductor sample is cut to obtain a cross section of the sample. Specifically, the sample cross section is obtained by cutting through the center of the element body so as to be perpendicular to the mounting surface and end surface of the laminated inductor. Multiple (e.g., five) regions (e.g., 130 μm × 100 μm) of the obtained cross section are photographed using 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 circle-equivalent diameter of the metal magnetic particles. The average of the obtained circle-equivalent diameters is taken as the average particle size of the metal magnetic particles.

[0029] When forming the element body 10, a heat treatment may be performed. In this case, the metal magnetic particles contained in the element body 10 have an oxide film on their surfaces. This oxide film is derived from the metal magnetic particles and is formed by heat treatment. In the element body 10, adjacent metal magnetic particles are joined to each other via the oxide film to form the metal magnetic layer ML. As used herein, "composed of a plurality of joined metal magnetic particles" may include not only a configuration in which the grain shape can be confirmed by SEM observation or the like, but also a configuration in which metal magnetic particles are used but the plurality of metal magnetic particles are mixed together by heat treatment or the like to form a dense structure (for example, a sintered body).

[0030] In order to further improve the strength of the element body 10, the element body 10 may be impregnated with a resin material after firing the element body 10. As an example of a resin that increases the strength of the element body, an epoxy resin and / or a phenol resin and / or a silicone resin may be used.

[0031] Coils (first coil and second coil) formed by stacking coil conductor layers CL may have a winding axis in the stacking direction. As described above, adjacent coil conductor layers CL in the stacking direction may be connected via via conductors. In the embodiment shown in FIG. 2, the first coil is formed by the stacking group G4 and the stacking group G5. The second coil is formed by the stacking group G2 and the stacking group G3.

[0032] The thickness of the coil conductor layer CL may be the same or different in each lamination group. The coil conductor layer CL may contain Ag as an example of its material, and may further contain a metal conductor such as Cu and / or Pd. More specifically, the material of the coil conductor layer CL may be softer than the metal magnetic material constituting the above-mentioned metal magnetic body. The coil conductor layer CL may be formed, for example, by printing a conductive paste on the above-mentioned metal magnetic layer ML.

[0033] The coil conductor CM, formed by stacking coil conductor layers CL, has sawtooth-shaped irregularities B on both side surfaces in a direction intersecting the stacking direction (e.g., a vertical direction perpendicular to the stacking direction) (see FIG. 3 ), with metal magnetic layers ML disposed at positions corresponding to the recesses on the side surfaces. Note that the top and bottom surfaces of the coil conductor CM do not necessarily have irregularities. In this specification, "having irregularities B on the side surfaces of the coil conductor CM" refers to a structure in which, in the irregularities B shown in FIGS. 3 and 4 , an imaginary line L1 is drawn from the most protruding position P1 (see FIG. 4 ) in the stacking direction, and an imaginary line L2 is drawn from the most recessed position P2 (see FIG. 4 ) in the stacking direction perpendicular to the top and bottom surfaces of the coil conductor CM, with the coil conductor CM and the metal magnetic material M embedded in the side region A1 defined by these imaginary lines L1 and L2. In this case, the metal magnetic particles constituting the element body are embedded in the recesses on the side surfaces of the coil conductor CM. The depth of the recesses is set so as not to reach the central region A2 shown in FIGS. 3 and 4 .

[0034] By providing unevenness B in the side region A1 of the coil conductor CM, when the base body 10 is pressed in the stacking direction with the coil conductor CM and the metal magnetic material M embedded in each other at the side, the metal conductor constituting the coil conductor CM is compressed, but due to the difference in hardness between the metal magnetic particles and the side of the coil conductor CM where the metal magnetic material M is embedded, it is compressed more than in the central region A2, thereby reducing pores (cavities).

[0035] Furthermore, with regard to the pores PO (voids) of the coil conductor CM, the pores on the side surfaces of the coil conductor CM are fewer than the pores in the center of the coil conductor CM. In other words, the metal density on the side surfaces of the conductors constituting the coil conductor CM is higher than the metal density in the center of the conductors constituting the coil conductor CM. As used herein, the "metal density on the side surfaces of the conductors constituting the coil conductor CM" and "metal density in the center of the conductors constituting the coil conductor CM" are measured as follows: (1) A cross section is prepared by cutting the element body 10 in the thickness direction along the longitudinal direction of the element body 10 from the mounting surface side at a position passing through the coil winding axis. (2) This cross section is photographed using an SEM and / or EDX with a field of view (approximately 500x magnification) large enough to confirm the entire line width of the coil conductor CM (see FIG. 4 for an example). (3) Identify the most protruding position P1 and the most recessed position P2 of the unevenness B on the side of the coil conductor CM (see FIG. 4 ), draw a virtual line L1 from the most protruding position P1 in the stacking direction, and draw a virtual line L2 from the most recessed position P2 in the stacking direction, and identify the side region A1 defined by the virtual lines L1 and L2. The area other than the side region A1 is designated as the central region A2 (see FIG. 4 ). (4) Calculate the metal area ratio on the side of the coil conductor by binarizing the image corresponding to the side region A1. The calculated metal area ratio corresponds to the "metal density on the side of the conductor constituting the coil conductor CM" as defined herein. Similarly, calculate the metal area ratio on the central side of the coil conductor by binarizing the image corresponding to the central region A2. The calculated metal area ratio corresponds to the "metal density at the center of the conductor constituting the coil conductor CM" as defined herein.

[0036] In the laminated inductor 1 of the present disclosure, the metal density on the side of the conductor constituting the coil conductor CM is higher than the metal density in the center of the conductor constituting the coil conductor CM, so that high resistance caused by pores is suppressed near the interface between the coil conductor CM and the metal magnetic material M, thereby achieving low resistance.

[0037] In a preferred embodiment of the laminated inductor 1, the volume ratio of the metal magnetic material M to the coil conductor CM in a side region A1 defined by an imaginary line L1 drawn in the stacking direction from the position P1 of the most protruding convex portion of the coil conductor CM and an imaginary line L2 drawn in the stacking direction from the position P2 of the most recessed portion of the coil conductor CM may be 20:80 or more and 70:30 or less. Details of this configuration will be explained in the demonstration tests described in the examples. With this configuration, the required characteristics can be met with respect to the density of the coil conductor CM (resistance characteristics of the coil conductor), high-frequency characteristics, and crack suppression.

[0038] As a specific configuration of the side region A1 and central region A2 described above, the distance D1 from the most protruding convex portion of the coil conductor CM to the most recessed concave portion of the coil conductor CM may be 1% to 15% of the line width of the coil conductor CM. In other words, the length of the side region A1 may correspond to the distance D1. In this specification, the "line width of the coil conductor CM" refers to the overall length of the side region A1, central region A2, and side region A1 shown in FIG. 4. More specifically, it refers to the length from the tip position P1 of the most protruding convex portion on one side to the tip position P1 of the most protruding convex portion on the other side. This line width can be measured using a scanning electron microscope. With this configuration, the pores in the side region A1 are reduced compared to the conventional technique shown in FIG. 5, suppressing high resistance due to pores near the interface between the coil conductor CM and the metal magnetic material M and achieving low resistance.

[0039] Furthermore, in a preferred embodiment of the coil conductor CM and the metal magnetic body M, the elastic modulus of the coil conductor CM may be smaller than the elastic modulus of the metal magnetic body M. With this relationship in elastic modulus, the coil conductor CM is made of a material softer than the metal magnetic body M. Therefore, if the coil conductor CM and the metal magnetic body M are configured to bite into each other on the side surfaces of the coil conductor CM, the side surfaces of the coil conductor CM are more suitably deformed by applying pressure to the element body 10, and pores (cavities) can be reduced. Therefore, near the interface between the coil conductor CM and the metal magnetic body M, high resistance due to pores is suppressed, and low resistance can be achieved.

[0040] As a specific material for the coil conductor CM, the coil conductor CM may contain silver. Using this material can lower the elastic modulus compared to common metal magnetic materials (iron, for example). Therefore, if the coil conductor CM and the metal magnetic material M are configured to bite into each other on the side of the coil conductor CM, the side of the coil conductor CM is more effectively deformed by applying pressure to the element body 10, and high resistance due to pores near the interface between the coil conductor CM and the metal magnetic material M is suppressed, thereby achieving low resistance. The "elastic modulus" described in this specification can be measured at the relevant location on the cut surface of the element body using a nanoindentation device (or nanoindenter).

[0041] Furthermore, as a specific material for the metal magnetic body M, the metal magnetic body M may contain iron. By using iron as the material for the metal magnetic body, it is possible to manufacture a laminated inductor that satisfies the required characteristics as inductance characteristics.

[0042] A suitable coil conductor CM may have multiple turns, and each turn may have an asperity B on its side. In this specification, the term "turn" refers to each coil conductor layer CL when the coil conductor CM is formed by connecting the coil conductor layers CL in a spiral shape as shown in FIG. 2 . Furthermore, "each turn has an asperity B on its side" refers to a configuration in which the asperity B is provided on the side of each coil conductor layer CL in each of the multilayer groups G1 to G7 shown in FIG. 2 . As an example, in the configuration shown in FIG. 2 , the asperity B shown in FIG. 3 may be provided on the side of the coil conductor CM formed by the coil conductor layer CL of the second coil in the multilayer group G2 (or multilayer group G3), which corresponds to a turn. Similarly, the asperity B shown in FIG. 3 may be provided on the side of the coil conductor CM formed by the coil conductor layer CL of the first coil in the multilayer group G4 (or multilayer group G5), which corresponds to a turn. On the other hand, the coil conductor shown in FIG. 5 , which is a conventional technology, has a single turn that is trapezoidal in cross section and does not have the asperity B described in the present disclosure.

[0043] 5 , which is a conventional technology, does not have the irregularities B on the coil conductor, each of whose turns is trapezoidal in cross section, and pores PO are present throughout the coil conductor CM, resulting in a relatively high resistance. In contrast, the laminated inductor 1 of the present disclosure has irregularities B on the side surfaces of each turn, causing the coil conductor CM and the metal magnetic material M to bite into each other on the side surfaces of the coil conductor CM. Therefore, applying pressure to the element body 10 more effectively deforms the side surfaces of the coil conductor CM, suppressing the increase in resistance caused by pores near the interface between the coil conductor CM and the metal magnetic material M and achieving low resistance.

[0044] -Through-Hole Conductors- The through-hole conductors TH (first through-hole conductor TH1 to fourth through-hole conductor TH4) electrically connect the external electrode 20 to one end or the other end of the coil C. The through-hole conductor layer TL may be made of, for example, a metal conductor such as Ag, Cu, and / or Pd. The through-hole conductor layer TL may be formed, for example, by printing a conductive paste on the above-mentioned metal magnetic layer ML.

[0045] [External Electrode] The external electrode 20 is provided on the bottom surface of the element body 10. The external electrode 20 may include a first external electrode 21 to a fourth external electrode 24. The first external electrode 21 to the fourth external electrode 24 are electrically connected to the first through-hole conductor TH1 to the fourth through-hole conductor TH4, respectively. Providing the external electrode 20 on the bottom surface (first main surface 11) of the element body 10 enables the multilayer inductor 1 to be properly mounted on a mounting board or the like.

[0046] The first external electrode 21 to the fourth external electrode 24 may each be provided only on the first main surface 11 of the element body 10, or may be provided across the first main surface 11 of the element body 10 and a surface adjacent to the first main surface 11 (one or two of the first end surface 13, the second end surface 14, the first side surface 15, and the second side surface 16).

[0047] The external electrodes 20 may be made of various materials such as Cu and / or Au, for example. The external electrodes 20 may be formed by any method, but may be plated electrodes formed by plating (for example, electroless plating or sputtering), or may have a laminated structure of two or more layers by forming a plated layer of Ni, Sn, or the like on the external electrodes 20 using a plating method after the external electrodes 20 are formed.

[0048] Demonstration tests were carried out on the laminated inductors of Examples 1 to 5 shown below. First, common points regarding the manufacture of the laminated inductors of Examples 1 to 5 will be described.

[0049] (Common Features of the Laminated Inductors of Examples 1 to 5) Metallic magnetic pastes for forming the metallic magnetic layers ML of the lamination groups G1 to G7 described with reference to FIG. 2 and conductive pastes for forming the coil conductors CM are prepared.

[0050] As an example of a method for producing a metal magnetic paste, a metal powder containing Fe with a volume-based cumulative 50% particle diameter (D50) of 2 μm to 20 μm is prepared. This metal powder is mixed with a binder such as cellulose or polyvinyl butyral (PVB) and a solvent such as a mixture of terpineol and butyl diglycol acetate (BCA), and the mixture is kneaded to produce a metal magnetic paste.

[0051] As the conductive paste, for example, a paste containing Ag as a conductive material is prepared.

[0052] Using the above-described metal magnetic paste and conductor paste, the multilayer groups G1 to G7 shown in Figure 2 are prepared and laminated by screen printing or the like. Here, when manufacturing one multilayer group, the metal magnetic paste and conductor paste are applied multiple times. Furthermore, to form irregularities on the side surfaces of the manufactured coil conductors, one multilayer group is manufactured using multiple patterns of coil conductor layers with different line widths.

[0053] After laminating the multilayer groups G1 to G7, they are compressed under pressure in the lamination direction using hot isostatic pressing (WIP). The compressed laminate is then heat-treated to sinter the silver, forming a coil within the element, and forming an oxide film on the surfaces of the metal magnetic particles, bonding adjacent metal magnetic particles together via the oxide film to obtain a metal magnetic body. This forms the element of the multilayer inductor. External electrodes are then formed on the mounting surface of the formed element to manufacture the multilayer inductor.

[0054] (Differences between the laminated inductors of Examples 1 to 5) In the laminated inductors of Examples 1 to 5, the unevenness formed on the side surface of the coil conductor was formed so as to achieve the following volume ratio of metal magnetic material to coil conductor.

[0055] -Laminated inductor of Example 1- As shown in Figure 7A, for the unevenness formed on the side surface of the coil conductor, the volume ratio of the coil conductor to the total area of ​​the uneven portion was set to 10%, and the volume ratio of the metal magnetic material to the total area of ​​the uneven portion was set to 90%.

[0056] -Laminated inductor of Example 2- As shown in Figure 7B, for the unevenness formed on the side surface of the coil conductor, the volume ratio of the coil conductor to the total area of ​​the uneven portion was set to 20%, and the volume ratio of the metal magnetic material to the total area of ​​the uneven portion was set to 80%.

[0057] -Laminated inductor of Example 3- As shown in Figure 7C, for the unevenness formed on the side surface of the coil conductor, the volume ratio of the coil conductor to the total area of ​​the uneven portion was set to 50%, and the volume ratio of the metal magnetic material to the total area of ​​the uneven portion was set to 50%.

[0058] -Laminated inductor of Example 4- As shown in Figure 7D, for the unevenness formed on the side surface of the coil conductor, the volume ratio of the coil conductor to the total area of ​​the uneven portion was set to 70%, and the volume ratio of the metal magnetic material to the total area of ​​the uneven portion was set to 30%.

[0059] -Laminated inductor of Example 5- As shown in Figure 7E, for the unevenness formed on the side surface of the coil conductor, the volume ratio of the coil conductor to the total area of ​​the uneven portion was set to 90%, and the volume ratio of the metal magnetic material to the total area of ​​the uneven portion was set to 10%.

[0060] (Demonstration Test 1: Measurement of Metal Density in Coil Conductor) The metal density on the side surfaces of the coil conductor and the metal density at the center of the coil conductor were measured using the laminated inductor of Example 5. As described above, the metal density was measured by photographing a cross section cut in the thickness direction of the element body using an SEM and / or EDX, and the photographed image was then binarized to evaluate the "metal density on the side surfaces of the coil conductor" and the "metal density at the center of the coil conductor."

[0061] In the case of the laminated inductor of Example 5, the "metal density on the side surfaces of the coil conductor" was 99.960% (pore density was 0.0040%), and the "metal density at the center of the coil conductor" was 98.661% (pore density was 1.339%). According to the demonstration test, by forming irregularities on the side surfaces of the coil conductor, the metal density on the side surfaces of the coil conductor (99.960%) was higher than the metal density at the center of the coil conductor (98.661%). On the other hand, in the conventional laminated inductor shown in Figure 5, the metal density on the side surfaces and the metal density at the center were equivalent to that of the center of the coil conductor of the present invention (approximately 98.661%).

[0062] (Demonstration Test 2: Measurement of Resistance Value of Coil Conductor of Multilayer Inductor) The resistance values ​​of the multilayer inductors of Examples 1 to 5 were measured. The resistance values ​​of the coil conductors were measured using a Hioki E.E. Corporation resistance meter (RM3545 / measurement current 100 mA). The measurement results are shown as resistance characteristics in FIG.

[0063] The laminated inductors of Examples 1 to 5 all had lower resistance values ​​than the coil component of the prior art shown in Figure 5. In particular, the laminated inductors of Examples 3 to 5, in which the volume ratio of the coil conductor was 50% or more of the total area of ​​the concave-convex portion (the volume ratio of the metal magnetic material was 50% or less of the total area of ​​the concave-convex portion), had lower resistance than the laminated inductors of Examples 1 and 2.

[0064] (Demonstration Test 3: High-Frequency Characteristics of Multilayer Inductors) The high-frequency characteristics were measured for the multilayer inductors of Examples 1 to 5. The high-frequency characteristics were measured using an impedance analyzer (Keysight Corporation, E4990A / measurement voltage OSC 500 mV). The measurement results are shown as high-frequency characteristics in FIG. 6.

[0065] The laminated inductors of Examples 1 to 5 all exhibited better high-frequency characteristics than the coil component of the prior art shown in Fig. 5. In particular, the laminated inductors of Examples 3 to 5, in which the volume ratio of the coil conductor was 50% or more of the total area of ​​the concave-convex portion (the volume ratio of the metal magnetic material was 50% or less of the total area of ​​the concave-convex portion), exhibited better high-frequency characteristics than the laminated inductors of Examples 1 and 2.

[0066] (Demonstration Test 4: Evaluation of Cracks in Coil Conductors of Multilayer Inductors) The multilayer inductors of Examples 1 to 5 were evaluated for cracks in the coil conductors. For the crack evaluation, a cross section cut in the thickness direction of the element body was photographed using an SEM and / or EDX, and the photographed images were then binarized to quantitatively evaluate the size of the cracks. The evaluation results are shown as cracks in FIG. 6.

[0067] The laminated inductors of Examples 1 to 5 all had relatively few cracks and obtained good results. In particular, the laminated inductors of Examples 2, 3, and 4 were able to increase the contact area between the coil conductor and the metal magnetic material compared to the laminated inductors of Examples 1 and 5, and therefore obtained good results in the crack evaluation. In other words, when the volume ratio of the metal magnetic material to the coil conductor was 20:80 or more and 70:30 or less, good results were obtained in terms of the resistance value of the coil conductor, high-frequency characteristics, and crack suppression.

[0068] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined by the claims. The technical scope of the present disclosure also includes all modifications within the meaning and scope of the claims. For example, the side surfaces of via conductors and through-hole conductors TH (see FIG. 2) may also be uneven like the side surfaces of the coil conductor CM.

[0069] The laminated inductor of the present disclosure includes the following aspects. <1> A laminated inductor comprising an element body including a metal magnetic body formed by laminating a metal magnetic layer containing metal magnetic particles, and a coil conductor formed by laminating coil conductor layers in the lamination direction of the metal magnetic layer, wherein the coil conductor has unevenness on a side surface located in a direction intersecting the lamination direction, the metal magnetic layer is disposed in a recess on the side surface, and the density of the conductor constituting the coil conductor is higher on the side surface than in a central portion. <2> The laminated inductor according to <1>, wherein in a region defined by an imaginary line drawn in the lamination direction from the position of the most protruding convex portion of the coil conductor from the position of the most recessed concave portion of the coil conductor, the volume ratio of the metal magnetic body to the coil conductor is 20:80 or more and 70:30 or less. <3> The laminated inductor according to <1> or <2>, wherein the coil conductor contains silver. <4> The laminated inductor according to any one of <1> to <3>, wherein the distance from the most protruding convex portion of the coil conductor to the most recessed concave portion of the coil conductor is 1% to 15% of the line width of the coil conductor. <5> The laminated inductor according to any one of <1> to <4>, wherein the elastic modulus of the metal magnetic body is greater than the elastic modulus of the coil conductor. <6> The laminated inductor according to any one of <1> to <5>, wherein the metal magnetic body contains iron. <7> The laminated inductor according to any one of <1> to <6>, wherein the coil conductor has a plurality of turns, and the asperities are provided on the side surfaces of each of the turns.

[0070] The laminated inductor of the present disclosure can be used as an electronic component that reduces loss due to eddy current in AC current by reducing the resistance near the interface between the coil conductor and the metal magnetic body.

[0071] REFERENCE SIGNS LIST 1 laminated inductor 10 element body 11 first main surface 12 second main surface 13 first end surface 14 second end surface 15 first side surface 16 second side surface 20 external electrode 21 to 24 first external electrode to fourth external electrode A1 side region A2 central region B unevenness CM coil conductor CL coil conductor layer M metal magnetic material ML metal magnetic layer TH through-hole conductor TH1 to TH4 first through-hole conductor to fourth through-hole conductor P1 most protruding position P2 most recessed position CM' conductor pattern PO pore M' magnetic material layer

Claims

1. A laminated inductor comprising an element body having a metal magnetic body on which metal magnetic layers containing metal magnetic particles are laminated, and a coil conductor in which coil conductor layers are laminated in the lamination direction of the metal magnetic layers, wherein the coil conductor has unevenness on its side surface located in a cross direction that intersects with the lamination direction, the metal magnetic layer is disposed in a recess on the side surface, and the density of the conductor constituting the coil conductor is higher on the side surface side than in the central portion.

2. A laminated inductor according to claim 1, wherein in an area defined by an imaginary line drawn in the lamination direction from the position of the most protruding convex portion of the coil conductor and an imaginary line drawn in the lamination direction from the position of the most recessed concave portion of the coil conductor, the volume ratio of the metal magnetic body to the coil conductor is 20:80 or more and 70:30 or less.

3. The laminated inductor according to claim 1 or 2, wherein the coil conductor contains silver.

4. A laminated inductor according to any one of claims 1 to 3, wherein the distance from the most protruding convex portion of the coil conductor to the most recessed concave portion of the coil conductor is 1% or more and 15% or less of the line width of the coil conductor.

5. A laminated inductor according to any one of claims 1 to 4, wherein the modulus of elasticity of the metallic magnetic body is greater than the modulus of elasticity of the coil conductor.

6. The laminated inductor according to any one of claims 1 to 5, wherein the metallic magnetic body contains iron.

7. The laminated inductor according to any one of claims 1 to 6, wherein the coil conductor has a plurality of turns, and the unevenness is provided on the side surface of each of the turns.

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