inductor

Abstract

Provided is an inductor in which the binding strength in the vicinity of a boundary between a metal magnetic body and an internal conductor is increased. An inductor 1 according to the present disclosure comprises an element body 10 in which a metal magnetic layer ML containing metal magnetic particles DP and an internal conductor CL are laminated, wherein: the metal magnetic particles DP contain iron as a main component; a boundary vicinity region BR is provided toward the metal magnetic layer including a boundary between the metal magnetic layer ML and the internal conductor CL; and in the boundary vicinity region BR, the content ratio of a main component of the internal conductor CL to iron is 0.01-1.0.

Description

Inductor

[0001] This disclosure relates to an inductor.

[0002] In Patent Document 1, an inductor array is formed by juxtaposing inductors in which an internal electrode mainly composed of Ag is embedded in a ceramic body (ferrite body), and at least one of S (sulfur) or Cl (chlorine) is contained in the internal electrode. A multilayer electronic component is disclosed in which the ratio of S (sulfur) and Cl (chlorine) to Ag particles in the surface layer (a range of 1 μm in the depth direction from the surface of the internal electrode) is S / Ag ≤ 0.10 and Cl / Ag ≤ 0.05 in terms of atomic ratio.

[0003] Japanese Patent Application Laid-Open No. 2004-55759

[0004] In recent years, instead of the ferrite body described in Patent Document 1, the development of a body composed of a metal magnetic material has been promoted. A body composed of a metal magnetic material is known to be useful for miniaturization of electronic components because, for example, it has excellent DC superposition characteristics.

[0005] Here, there was room for improvement in the binding property between the metal magnetic material and the internal conductor constituting the coil in the body manufactured using metal magnetic particles. Specifically, in the heat treatment process when manufacturing the inductor, since the strength of the body was insufficient against the sintering shrinkage stress of the internal conductor constituting the coil, cracks might occur near the boundary between the metal magnetic material and the internal conductor.

[0006] In view of such problems, the main object of this disclosure is to provide an inductor that improves the binding strength near the boundary between a metal magnetic material and an internal conductor.

[0007] The inductor of this disclosure is an inductor provided with a body in which a metal magnetic layer containing metal magnetic particles and an internal conductor are laminated, the metal magnetic particles are mainly composed of iron, a boundary near region is provided on the metal magnetic layer side including the boundary between the metal magnetic layer and the internal conductor, and in the boundary near region, the content ratio of the main component of the internal conductor and the iron is 0.01 or more and 1.0 or less.

[0008] According to the inductor of this disclosure, the ratio of the main component of the internal conductor to the iron content in the boundary region including the boundary between the metal magnetic layer and the internal conductor is 0.01 or more and 1.0 or less. Therefore, it is possible to improve the bonding strength between the metal magnetic material and the internal conductor while reducing electrical short circuits between the internal conductors. Specifically, since the internal conductor is diffused in the boundary region including the boundary between the metal magnetic layer and the internal conductor, the bonding strength between the metal magnetic material and the internal conductor can be improved.

[0009] Figure 1 is a perspective view of the inductor of this disclosure. Figure 2 is an exploded perspective view of the inductor of this disclosure. Figure 3 is a cross-sectional view of the inductor of this disclosure. Figure 4 is an enlarged cross-sectional view of the dashed line area in Figure 3. Figure 5 is a table showing the results of the demonstration test for the inductor of this disclosure.

[0010] The inductor described herein will be explained in detail below. While the drawings will be referenced as necessary, the illustrations are for illustrative purposes only to aid in understanding this disclosure, and their appearance and dimensional ratios may differ from those of the actual product. The following drawings are schematic, and their dimensions, aspect ratios, etc., may differ from those of the actual product.

[0011] In this specification, terms describing relationships between elements (e.g., "parallel," "orthogonal," etc.) and terms describing the shape of elements mean not only strictly defined aspects but also substantially equivalent ranges, such as ranges with differences of a few percent. In this specification, the direction in which the magnetic layer and coil conductor layer constituting the element are stacked is defined as the "stacking direction." Furthermore, a plan view refers to a plan view of the element seen from above (in the height direction).

[0012] <Inductor of this Disclosure> The inductor 1 of this disclosure comprises a base body 10 and an external electrode 20 provided on the mounting surface of the base body 10.

[0013] The base body 10 is, for example, a hexahedron with six faces. As an example, it may be a rectangular prism or a roughly rectangular prism. The base body 10 may have rounded corners and edges. The corners are the parts where three faces of the base body 10 intersect, and the edges are the parts where two faces of the base body 10 intersect.

[0014] Figure 1 shows the long side direction, short side direction, and height direction of the inductor 1 and the element 10 as the L direction, W direction, and T direction, respectively. The long side direction L, the short side direction W, and the height direction T are mutually orthogonal.

[0015] The base body 10 shown in Figure 1 has a first main surface 11 and a second main surface 12 facing the height direction T, a first end surface 13 and a second end surface 14 facing the long side direction L, and a first side surface 15 and a second side surface 16 facing the short side direction W. In the example shown in Figure 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 base body 10, and the first main surface 11 of the base body 10 corresponds to the mounting surface (bottom surface of the base body) of the inductor 1.

[0016] Figure 2 is a schematic exploded perspective view showing an example of the internal structure of the inductor 1 of this disclosure. As shown in Figure 2, the base body 10 is constructed by laminating an internal conductor CL, a metal magnetic layer ML containing metal magnetic particles, and a through-hole conductor TH. Inside the base body 10, as an example, two coils (a first coil and a second coil) are provided by the internal conductor CL. The number of coils provided inside the base body 10 may be three or more, or it may be just one.

[0017] The base body 10 is made up of stacked stacking groups G1 to G7, with the first external electrodes 21 to the fourth external electrodes 24 formed on the underside of stacking group G7. The boundaries between each layer of the stacked structure of the base body 10 may disappear. Multiple stacking groups G1 to G7 may be stacked to achieve a desired thickness.

[0018] The laminated group G1 has a metallic magnetic layer ML and constitutes the second main surface 12 of the base body 10 (see Figure 1).

[0019] Laminated groups G2 and G3 are provided to constitute a second coil. In other words, the internal conductors CL are laminated to constitute a second coil. The internal conductors CL of laminated group G2 and the internal conductors CL of laminated group G3 may be connected to each other by via conductors (not shown).

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

[0021] Laminated groups G4 and G5 are provided to constitute the first coil. That is, the internal conductors CL are laminated to constitute the first coil. The internal conductors CL of laminated group G4 and the internal conductors CL of laminated group G5 may be connected to each other by via conductors (not shown).

[0022] One end of the first coil is provided with a first through-hole conductor TH1 that is 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 that is electrically connected to the second external electrode 22. A metallic magnetic layer ML is arranged around the internal conductor CL and the first through-hole conductors TH1 to the fourth through-hole conductors TH4.

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

[0024] To further improve the strength of the base body 10, the base body 10 may be impregnated with a resin material after firing. As an example of a resin that enhances the strength of the base body, epoxy resin and / or phenolic resin and / or silicone resin may be used.

[0025] As described above, if the base body 10 has a laminated structure comprising laminated groups G1 to G7, the design freedom of the inductor 1 is increased. For example, when manufacturing an inductor 1 having first external electrodes 21 to fourth external electrodes 24 on the bottom surface (first main surface 11) of the base body 10, it becomes easier to draw out the coil to the bottom surface side using a through-hole conductor. The laminated structure comprising the above-mentioned laminated groups G1 to G7 may be laminated from the second main surface 12 side or the first main surface 11 side of the base body 10. Furthermore, the material constituting the through-hole conductor TH and / or via conductor may be repeatedly printed sequentially by, for example, screen printing until the desired thickness of the via conductor is achieved, or it may be formed by sputtering, inkjet printing, or other known methods.

[0026] As described above, the base body 10 contains an internal conductor CL and a metallic magnetic layer ML. The elements constituting the base body 10 will be described in detail below.

[0027] -Internal Conductor- The internal conductor CL may be wound along the winding axis in the stacking direction (see Figure 2). Adjacent internal conductors CL in the stacking direction may be connected via conductors as described above. In the embodiment shown in Figure 2, the first coil is formed by stacking group G4 and stacking group G5. The second coil is formed by stacking group G2 and stacking group G3. The thickness of the internal conductor CL may be the same for each stacking group, or it may have different thicknesses.

[0028] The internal conductor CL may contain Ag (silver) or Cu (copper) as its main component, as an example of its material. In this specification, "main component" refers to the component that is present in the largest quantity among the components that make up the structure. In other words, "internal conductor CL with Ag as the main component" means that among the elements that make up the internal conductor CL, Ag is present in the largest quantity. Furthermore, if Ag is the main component, other elements may also be present. In addition, the internal conductor CL may be formed by printing a conductive paste onto the metal magnetic layer ML, as described in the "Method for Manufacturing an Inductor" below.

[0029] -Metal Magnetic Layer- The metal magnetic layer ML may contain metal magnetic particles DP composed of a metallic magnetic material (see Figure 4). The metal magnetic particles DP are mainly composed of Fe (iron). Specifically, they may contain Fe and Si, which are the main components. 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, Fe-Si-B-Nb-Cu alloys, etc. Furthermore, the metal magnetic particles DP may contain impurities such as Cr, Mn, Cu, Ni, P, S, or Co that are not intended during manufacturing. The metal magnetic particles DP may also be contained in a magnetic paste. Therefore, the metallic magnetic particles DP may contain elements that are more easily oxidized than Fe added during the preparation of the magnetic paste (for example, Cr, Al, Li, Zn, Zr).

[0030] The surface of the metal magnetic particle DP described above may be covered with an insulating film OL (see Figure 4). When the surface of the metal magnetic particle DP is covered with an insulating film OL, the insulation between the metal magnetic particle DP can be increased, improving the dielectric strength of the inductor and suppressing eddy currents generated in the metal magnetic particle DP. As a method for forming the insulating film OL on the surface of the metal magnetic particle DP, the sol-gel method, the mechanochemical method, etc., can be used. The materials constituting the insulating film OL may be oxides of P, Si, etc., zinc phosphate, manganese phosphate. The insulating film OL may also be an oxide film formed by oxidation of the surface of the metal magnetic particle DP with oxygen in the atmosphere, or an oxide film of an element that is more easily oxidized than Fe. The thickness of the insulating film OL is preferably 1 nm to 50 nm, more preferably 1 nm to 30 nm, and even more preferably 1 nm to 20 nm. For example, a cross-section obtained by polishing an inductor sample can be photographed with a scanning electron microscope (SEM), and the thickness of the insulating film OL covering the surface of the metallic magnetic particle DP can be measured from the resulting SEM image.

[0031] The average particle size of the metallic magnetic particles DP is preferably 0.2 μm to 50 μm, more preferably 1 μm to 20 μm, and even more preferably 1 μm to 10 μm. The average particle size of the metallic magnetic particles DP can be measured by the procedure described below. A sample of the inductor is cut to obtain a sample cross-section. Specifically, a sample cross-section is obtained by cutting through the center of the main body so as to be perpendicular to the mounting surface and end face of the inductor. Multiple areas (e.g., 130 μm × 100 μm) of the obtained cross-section are photographed with an SEM, and the obtained SEM images are analyzed using image analysis software (e.g., image analysis software WinROOF2021 (manufactured by Mitani Corporation)) to determine the equivalent circle diameter of the metallic magnetic particles DP. The average value of the obtained equivalent circle diameters is taken as the average particle size of the metallic magnetic particles DP.

[0032] When forming the base body 10, heat treatment may be applied. In this case, the metallic magnetic particles DP contained in the base body 10 have an oxide film (insulating film OL) on their surface. This oxide film originates from the metallic magnetic particles DP and is formed by heat treatment. In the base body 10, adjacent metallic magnetic particles DP are joined to each other via the oxide film to form a metallic magnetic layer ML. In this specification, "composed of multiple metallic magnetic particles joined together" may include not only configurations in which the particle shape can be confirmed by SEM observation, etc., but also configurations in which multiple metallic magnetic particles DP are mixed together by heat treatment, etc., to form a dense structure (for example, a sintered body).

[0033] A characteristic configuration of this disclosure, as shown in Figures 3 and 4, is that the metal magnetic layer ML has a boundary region BR on the metal magnetic layer ML side, including the boundary B between the metal magnetic layer ML and the internal conductor CL, and the boundary region BR has a content ratio of iron to the main component of the internal conductor CL (content of the main component of the internal conductor / content of Fe) of 0.01 or more and 1.0 or less.

[0034] Here, the term "near-boundary region" in this specification refers to the region from the boundary B between the metal magnetic layer ML and the internal conductor CL to a predetermined distance away. More specifically, when the distance between internal conductors CL in the stacking direction is D, the region refers to the region from boundary B to D / 5 in the stacking direction. The distance D between internal conductors CL may be the average value measured at any 10 locations using cross-sectional SEM images, or it may be derived from the results obtained using image analysis software (WinROOF2021).

[0035] Furthermore, in this specification, the "ratio of the main component of the internal conductor to the iron content" can be measured by EDX (energy-dispersive X-ray fluorescence spectrometer) or WDX (wavelength-dispersive X-ray fluorescence spectrometer). Specifically, measurements by EDX or WDX are performed on any region in the boundary region BR described above (for example, a region of 2.5 μm (corresponding to D / 5 described above) × 10 μm). Note that the content ratio may be measured using atomic ratios.

[0036] In this embodiment, in the boundary region BR, the ratio of the main component of the internal conductor CL to the iron content (content of the main component of the internal conductor CL / content of Fe) is 0.01 or more and 1.0 or less, and the internal conductor CL is diffused into the boundary region BR on the metal magnetic layer ML side. Therefore, the bonding strength between the metal magnetic layer ML and the internal conductor CL can be improved by the diffusion of the internal conductor CL.

[0037] Furthermore, as will be described in detail in the later-described examples, the boundary region BR may preferably have a content ratio of iron to the main component of the internal conductor CL (content of the main component of the internal conductor CL / content of Fe) of 0.03 or more and 0.7 or less. With the above content ratio, the bonding strength between the metal magnetic layer ML and the internal conductor CL can be further improved.

[0038] A more preferable boundary region BR may have a content ratio of iron to the main component of the internal conductor CL (content of the main component of the internal conductor CL / content of Fe) of 0.05 or more and 0.5 or less. With the above content ratio, the bonding strength between the metal magnetic layer ML and the internal conductor CL can be further improved.

[0039] Furthermore, in the region BR near the boundary, the ratio of the chlorine (Cl) content to the iron content (chlorine content / Fe content) may be between 0.0001 and 0.01. The "content ratio" may be derived by measurement using EDX or WDX for any region in the region BR near the boundary (for example, a region of 2.5 μm (corresponding to D / 5 above) × 10 μm), as described above.

[0040] Generally, it is known that when chlorine (Cl) forms a compound with a typical metal used for the internal conductor CL (Ag or Cu), its melting and / or boiling point decreases. For example, the melting and boiling points of Ag are 962°C and 2162°C, respectively, while those of AgCl are 455°C and 1547°C, respectively. In other words, the melting and boiling points of AgCl are lower than those of Ag. Therefore, by controlling the chlorine concentration in the near-boundary region BR, the diffusion of the internal conductor CL by heat treatment in the near-boundary region BR can be appropriately achieved.

[0041] The chlorine in the boundary region BR is contained in the materials used to produce the conductor paste, as will be described in detail later in the "Method for Manufacturing an Inductor". Specifically, chlorine is contained in the binder in the conductor paste. Therefore, the heat treatment during the formation of the base body 10 causes the internal conductor CL to diffuse into the boundary region BR along with the chlorine, thereby improving the bonding strength between the metal magnetic layer ML and the internal conductor CL.

[0042] Here, if the diffusion of chlorine and the internal conductor CL increases, the near-boundary region BR will increase, and there is a risk that adjacent internal conductors CL will short-circuit. For this reason, the near-boundary region BR, which diffuses the internal conductor CL, may be set to be near the boundary between the metal magnetic layer ML and the internal conductor CL (specifically, the region from boundary B to D / 5 in the stacking direction). Because the near-boundary region BR is set in this way, it is prevented that the internal conductors CL diffused in the near-boundary region BR will short-circuit each other.

[0043] Regarding the content ratio of chlorine in the vicinity of the suitable boundary, the content ratio of Cl (chlorine) to the content of iron (content of chlorine / content of Fe) may be 0.0001 or more and 0.005 or less. With such a content ratio, the bonding strength between the metal magnetic layer ML and the internal conductor CL can be improved, and it is possible to preferably prevent the internal conductors CL from being short-circuited due to the internal conductor CL diffused into the vicinity of the boundary region BR.

[0044] Regarding a more suitable content ratio of chlorine in the vicinity of the boundary, the content ratio of Cl (chlorine) to the content of iron (content of chlorine / content of Fe) may be 0.0001 or more and 0.001 or less. With such a content ratio, the bonding strength between the metal magnetic layer ML and the internal conductor CL can be improved, and it is possible to more preferably prevent the internal conductors CL from being short-circuited due to the internal conductor CL diffused into the vicinity of the boundary region BR.

[0045] Regarding the content ratio of chlorine in the internal conductor CL, the content ratio of Cl (chlorine) to the content of the main component of the internal conductor CL (content of Cl / content of the main component of the internal conductor CL) may be 0.0005 or more and 0.05 or less. More preferably, it may be 0.001 or more and 0.02 or less. Even more preferably, it may be 0.005 or more and 0.01 or less. With such a content ratio, the bonding strength between the metal magnetic layer ML and the internal conductor CL can be improved, and it is possible to preferably prevent the internal conductors CL from being short-circuited due to the internal conductor CL diffused into the vicinity of the boundary region BR. Note that the "content ratio" on the side of the internal conductor CL may be derived by measurement using EDX or WDX for an arbitrary region inside the internal conductor CL (for example, a region of 5 μm × 5 μm).

[0046] <Explanation of the manufacturing method of the inductor> Next, the manufacturing method of the inductor of the present disclosure will be described. The manufacturing method of the inductor of the present disclosure includes a lamination step and a heat treatment step. As will be described later, a degreasing step may be optionally provided.

[0047] -Lamination step- First, prepare the magnetic material (magnetic paste) constituting the metal magnetic layer ML of the lamination groups G1 to G8 described in FIG. 2 and the conductor paste constituting the internal conductor CL.

[0048] As an example of a method for producing a magnetic paste, a metal powder mainly composed of Fe, such as an Fe—Si alloy or an Fe—Si—Cr alloy, having a D50 (the cumulative 50% particle diameter based on volume) of 2 μm or more and 20 μm or less is prepared. This metal powder is made to contain, as a binder, cellulose or polyvinyl butyral (PVB) or the like, and as a solvent, a mixture of terpineol and butyl diglycol acetate (BCA) or the like, kneaded with a planetary mixer, and further dispersed with a three-roll mill to produce a magnetic paste.

[0049] As the conductor paste, for example, Ag or Cu powder as a conductive material is prepared. This metal powder is mixed with a binder, a solvent, and a dispersant, and dispersed with a three-roll mill to produce a conductor paste. Here, the binder may be ethyl cellulose, the solvent may be terpineol and butyl diglycol acetate, and the dispersant may be an anionic dispersant such as a polycarboxylic acid type. The ethyl cellulose used as the binder may contain chlorine. Note that, as the binder, a binder that usually does not contain chlorine, such as PVB (polyvinyl acetal resin) or acrylic, may be used, and chlorine may be intentionally contained in the binder by exposing it to dilute hydrochloric acid or the like.

[0050] Using the above-described magnetic paste and conductor paste, the laminated groups G1 to G8 shown in FIG. 2 are prepared and laminated by screen printing or the like. Then, after laminating the laminated groups G1 to G8, a pressure treatment (for example, warm isostatic pressing) is performed with a pressing device to form a laminate.

[0051] - Debinding step (optional additional step) - As a manufacturing step of a suitable method for manufacturing a laminated inductor, a debinding step may be provided. The debinding step is a step of optimizing the binder contained in the magnetic paste and the conductor paste. As an example, debinding is performed at a temperature of about 300° C. or higher and 500° C. or lower. Thereby, the binder contained in the magnetic paste and the conductor paste is optimized.

[0052] - Heat Treatment Process - Heat treatment is performed after the degreasing process. The heat treatment temperature is such that the coil conductor layer sintersects, and the heat treatment conditions are such that the ratio of the main component of the internal conductor CL to Fe (iron) in the boundary region BR on the metal magnetic layer ML side, including the boundary between the metal magnetic layer ML and the internal conductor CL, is 0.01 or more and 1.0 or less. As an example, it may be around 550°C to 850°C. Note that the content ratio in the boundary region BR may be achieved by adjusting the amount of Cl (chlorine) contained in the binder of the conductor paste.

[0053] The heat treatment process of this disclosure may be performed in an air atmosphere or in a low-oxygen concentration atmosphere. By performing the heat treatment, the internal conductor CL is diffused into the vicinity region BR from the boundary B between the metal magnetic layer ML and the internal conductor CL to a predetermined distance away. Therefore, the bonding strength between the metal magnetic layer ML and the internal conductor CL can be improved.

[0054] Furthermore, after the heat treatment process of this disclosure, the ratio of chlorine content to Fe (iron) in the boundary region BR may be 0.0001 or more and 0.01 or less. This prevents the internal conductors CL diffused into the boundary region BR from causing a short circuit between them.

[0055] Subsequently, to increase the strength of the base material, the base material may be impregnated with resin and cured. The resin used to impregnate the base material is epoxy resin, but one or more resins selected from the group consisting of phenolic resin, polyester resin, polyimide resin, polyolefin resin, silicone resin, acrylic resin, polyvinyl butyral resin, cellulose resin, and alkyd resin may also be used. By going through the above steps, the base material for the laminated inductor of this disclosure is formed.

[0056] Subsequently, external electrodes electrically connected to the coil conductor layer are formed on the formed body. The external electrodes are formed by electroplating at positions where the through-hole conductors are exposed on the mounting surface (first main surface 11) of the body 10. The plating material may be Cu plating. Other materials include, but are not limited to, Ni-Sn, Ni-Au, Ni-Cu and / or Cu-Ni-Au. After forming the external electrodes, the element can be cut into individual components to manufacture the multilayer inductor of this embodiment.

[0057] As described above, the inductor manufacturing method described in this embodiment makes it possible to manufacture an inductor with improved bonding strength between the metallic magnetic material and the internal conductor.

[0058] The demonstration tests concerning the inductors of this disclosure will be described in detail. Specifically, the inductors described in the following examples and comparative examples were manufactured.

[0059] -Inductor of Example 1- An inductor was manufactured according to the above-described inductor manufacturing method, through a lamination process, a degreasing process, and a heat treatment process. In the inductor of Example 1, in order to make the ratio of the main component of the internal conductor to the content of Fe (iron) in the region near the boundary 0.01 or more and 1.0 or less, the heat treatment conditions in the heat treatment process were set to 550°C for 30 minutes.

[0060] -Inductor of Example 2- The manufacturing process was the same as that of the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were 550°C for 120 minutes.

[0061] -Inductor of Example 3- The manufacturing process was the same as that of the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were 600°C for 30 minutes.

[0062] -Inductor of Example 4- The manufacturing process was the same as that of the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were 650°C for 30 minutes.

[0063] -Inductor of Example 5- The manufacturing process was the same as that of the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were 800°C for 30 minutes.

[0064] -Inductor of Example 6- The manufacturing process was the same as that of the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were 800°C for 120 minutes.

[0065] -Inductor of Example 7- The manufacturing process was the same as that of the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were 800°C for 300 minutes.

[0066] -Inductor of Example 8- The manufacturing process was the same as that of the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were 850°C for 30 minutes.

[0067] -Inductor of Comparative Example 1- The inductor followed the same manufacturing process as the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were heat treatment at 900°C for 30 minutes.

[0068] -Inductor of Comparative Example 2- The manufacturing process was the same as that of the inductor of Example 1, except that the heat treatment conditions in the heat treatment process were 500°C for 30 minutes.

[0069] The following evaluations were performed on the inductors of Examples 1 to 8 and Comparative Examples 1 to 2 that were manufactured.

[0070] - Crack Evaluation - A sample cross-section was created by cutting the sample through the center of the base material, perpendicular to the mounting surface and end face of the inductor. Multiple locations (e.g., 10 locations) of the obtained cross-section were photographed using an SEM, and the presence or absence of cracks was evaluated based on the SEM images.

[0071] -Short-circuit evaluation- Ten measurement samples were created by cutting and polishing the manufactured inductor so that the internal conductor was exposed. The interlayer resistance of the exposed internal conductor was measured in the measurement samples. The resistance value of the interlayer resistance was then calculated to be 10 ３ A short circuit was determined when the value was less than Ω·cm.

[0072] The evaluation results are shown in Figure 5. As shown in Figure 5, the probability of short circuits increased as the ratio of the main component of the internal conductor to the content of Fe (iron) increased, and as the ratio of the content of Cl (chlorine) to Fe (iron) decreased, it inhibited the bonding strength between the metallic magnetic material and the internal conductor, and the probability of cracks tended to increase. For this reason, although there were no short circuits in Example 1, 10% of the samples were judged to have cracks. Also, the inductors of Examples 2 to 6 had no cracks or short circuits. Furthermore, although there were no cracks in Examples 7 and 8, 10% of the samples in Example 7 and 20% of the samples in Example 8 were judged to have short circuits. On the other hand, 50% of the inductors in Comparative Example 1 were judged to have short circuits, which is higher than in the Examples, and 30% of the inductors in Comparative Example 2 were judged to have cracks, which is higher than in the Examples. Therefore, inductors such as those in Examples 1 to 3, in which the ratio of the main component of the internal conductor (Ag) to the content of Fe (iron) in the region near the boundary is 0.01 or more and 1.0 or less, showed that at least electrical short circuits between the internal conductors were reduced while the bonding strength near the boundary between the metallic magnetic material and the internal conductor was improved.

[0073] The embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Therefore, the technical scope of this disclosure is not construed solely by the embodiments described above, but is defined based on the claims. Furthermore, the technical scope of this disclosure includes all modifications within the meaning and scope of equivalence to the claims.

[0074] The embodiments of the multilayer inductor and method for manufacturing the multilayer inductor of the present disclosure are as follows: <1> An inductor comprising a substrate in which a metal magnetic layer containing metal magnetic particles and an internal conductor are laminated, wherein the metal magnetic particles are mainly composed of iron, and the metal magnetic layer side includes a region near the boundary, including the boundary between the metal magnetic layer and the internal conductor, and the ratio of the content of the main component of the internal conductor to the iron in the region near the boundary is 0.01 or more and 1.0 or less. <2> The inductor according to <1>, wherein the ratio of the content of the main component of the internal conductor to the iron in the region near the boundary is 0.03 or more and 0.7 or less. <3> The inductor according to <1> or <2>, wherein the ratio of the content of the main component of the internal conductor to the iron in the region near the boundary is 0.05 or more and 0.5 or less. <4> The inductor according to any one of <1> to <3>, wherein the ratio of the content of chlorine to the iron in the region near the boundary is 0.0001 or more and 0.01 or less. <5> The inductor according to any one of <1> to <4>, wherein the main component of the internal conductor is silver or copper. <6> The inductor according to any one of <1> to <5>, wherein the boundary vicinity region is the region from the boundary to D / 5 in the stacking direction, when the distance between the internal conductors in the stacking direction is D.

[0075] The inductor of this disclosure can be suitably used as an electronic component with improved bonding strength near the boundary between the metallic magnetic material and the internal conductor.

[0076] 1 Inductor 10 Base 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 electrodes 21-24 First external electrodes to fourth external electrodes B Boundary BR Boundary vicinity region CL Internal conductor D Distance DP Metallic magnetic particles G1-G8 Laminated group ML Metallic magnetic layer OL Insulating coating TH Through-hole conductor TH1-TH4 First through-hole conductor to fourth through-hole conductor

Claims

1. An inductor comprising a substrate in which a metal magnetic layer containing metal magnetic particles and an internal conductor are laminated, wherein the metal magnetic particles are mainly composed of iron, and the metal magnetic layer side includes a boundary region including the boundary between the metal magnetic layer and the internal conductor, and the ratio of the content of the main component of the internal conductor to the content of iron in the boundary region is 0.01 or more and 1.0 or less.

2. The inductor according to claim 1, wherein the ratio of the content of the main component of the internal conductor to the iron content in the boundary vicinity region is 0.03 or more and 0.7 or less.

3. The inductor according to claim 1 or 2, wherein the ratio of the content of the main component of the internal conductor to the iron content in the boundary vicinity region is 0.05 or more and 0.5 or less.

4. The inductor according to any one of claims 1 to 3, wherein the ratio of chlorine content to iron in the region near the boundary is 0.0001 or more and 0.01 or less.

5. The inductor according to any one of claims 1 to 4, wherein the main component of the internal conductor is silver or copper.

6. The inductor according to any one of claims 1 to 5, wherein the boundary vicinity region is the region from the boundary to D / 5 in the stacking direction, when D is the distance between the internal conductors in the stacking direction.

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