Magnetic material and manufacturing method of magnetic material

Abstract

The present disclosure provides a magnetic material which is a sintered body containing a plurality of metal magnetic material particles having a grain boundary phase, the grain boundary phase containing a metal oxide or metal nitride obtained by oxidizing or nitriding a non-magnetic metal, and the metal magnetic material particles having an equivalent circle diameter of 0.29 [mu] m to 2.33 [mu] m.

Description

Technical Field

[0001] The present disclosure relates to magnetic materials and methods of making magnetic materials. Background Art

[0002] Composite magnetic materials are sometimes used as magnetic materials for magnetic components, etc. Examples of such composite magnetic materials include a resin containing dispersed soft magnetic powder composed of powder particles (see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-143827 Summary of the Invention

[0006] When a composite magnetic material contains resin, if current flows through a magnetic component having a matrix and wiring containing the magnetic material, local concentration of magnetic flux occurs between the powder particles of the soft magnetic powder in the magnetic material, thereby increasing eddy current losses and possibly leading to deterioration of high-frequency characteristics.

[0007] An object of the present disclosure is to provide a magnetic material and a method for manufacturing the same that can achieve improved high-frequency characteristics.

[0008] To achieve the above-mentioned object, the present disclosure provides a magnetic material comprising a sintered body including a plurality of metal magnetic particles having a grain boundary phase.

[0009] The grain boundary phase comprises a metal oxide or metal nitride of a non-magnetic metal,

[0010] The metal magnetic particles have an equivalent circle diameter of 0.29 μm to 2.33 μm.

[0011] In order to achieve the above objectives, the present disclosure provides a method for manufacturing a magnetic material, comprising:

[0012] a step of forming a sintered body comprising a plurality of metal magnetic particles,

[0013] At least at the time when sintering is completed, a grain boundary phase of the plurality of metal magnetic grains including a metal oxide or a metal nitride of a non-magnetic metal is formed.

[0014] According to the present disclosure, it is possible to improve high-frequency characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a partially enlarged cross-sectional view schematically showing the structure of the magnetic material disclosed in the present invention.

[0016] Figure 2 yes Figure 1 A partially enlarged cross-sectional view of the segment indicated by the dotted circle.

[0017] Figure 3 This is a perspective view schematically showing an electronic component including the magnetic material of the present disclosure.

[0018] Figure 4 is Figure 3 Schematic cross-sectional view between line segment a-a.

[0019] Figure 5 This is a perspective view schematically showing an electronic component according to another embodiment. DETAILED DESCRIPTION

[0020] Below, with reference to the attached Figure 1 While the following description will refer to the accompanying drawings as needed, the drawings are merely schematic and illustrative for ease of understanding the present disclosure, and the appearance, dimensional ratios, etc. may differ from the actual objects.

[0021] Figure 1 It is a partially enlarged cross-sectional view schematically showing the structure of the magnetic material disclosed in the present invention.

[0022] Since conventional magnetic materials comprising soft magnetic powder dispersed in resin may deteriorate in high-frequency characteristics, the inventors of the present application conducted intensive research on a new magnetic material having a structure different from such conventional magnetic materials and thus came up with the present invention.

[0023] Specifically, if Figure 1 As shown, the magnetic material 11α of the present disclosure is a sintered body including a plurality of metal magnetic particles 11A having a grain boundary phase 11B. Grain boundary phase 11B can be formed at the boundary between adjacent metal magnetic particles 11A by arranging the plurality of metal magnetic particles 11A in close contact with each other.

[0024] In the present disclosure, the grain boundary phase 11B includes a metal oxide or metal nitride formed by oxidation or nitridation of a non-magnetic metal. Note that the grain boundary phase 11B may include an oxide of the metal magnetic particles 11A.

[0025] When grain boundary phase 11B is in the above-described form, the metal oxide or metal nitride can cover the surface of metal magnetic particle 11A while being in contact with metal magnetic particle 11A.

[0026] The metal oxides or metal nitrides are formed by oxidation or nitridation of non-magnetic metals, and therefore have a higher resistivity than metal magnetic particles. For example, the resistivity of metal oxides or metal nitrides can be 1×10 11 Ω·cm~1×10 16 Ω·cm. In addition, the resistivity of the metal magnetic particles may be 0.089 μΩ·m to 1.76 μΩ·m. In addition, the above-mentioned metal oxide or metal nitride itself may have non-magnetic properties.

[0027] Therefore, grain boundary phase 11B can function as a higher resistance portion than metal magnetic particle 11A. To enhance this function, the metal oxide or metal nitride of grain boundary phase 11B preferably covers the entire surface of metal magnetic particle 11A.

[0028] Although described later, when the base of an electronic component includes the magnetic material 11α of the present disclosure, the presence of a high-resistance portion increases the resistance of the path of eddy current flowing through the magnetic material (corresponding to the sintered body) of the base, thereby reducing eddy current losses. Since these eddy current losses increase with higher frequencies, reducing eddy current losses can improve high-frequency characteristics.

[0029] Furthermore, in the present disclosure, the equivalent circle diameter of metal magnetic particles 11A is 0.29 μm to 2.33 μm. When the substrate of an electronic component includes the magnetic material 11α of the present disclosure, the diameter is preferably 0.29 μm or greater to prevent the formation of oxides of the Fe component contained in metal magnetic particles 11A in the magnetic material of the substrate (corresponding to the sintered body). Furthermore, the diameter is preferably 2.33 μm or less to prevent the skin depth from exceeding 200 MHz, which is assumed in next-generation inductors.

[0030] Furthermore, the metal magnetic particles contain Fe, and the metal oxide or metal nitride may be at least one selected from the group consisting of Si, Al, Cr, Ca, Mg, Ti, Mn, V, Zr, Nb, and Ta, which are elements more easily oxidized than Fe. It should be noted that in this disclosure, Si, which is generally referred to as a semimetal, is considered a metallic element.

[0031] Furthermore, the filling rate of the plurality of metal magnetic particles 11A in the magnetic material 11α of the present disclosure is preferably 66.7% or more from the perspective of ensuring magnetic permeability, that is, preferably ensuring inductance (L value), and is preferably 95.1% or less from the perspective of reducing eddy current loss.

[0032] Figure 3 This is a perspective view schematically showing an electronic component including the magnetic material of the present disclosure. Figure 4 yes Figure 3Schematic cross-sectional view between line segment a-a.

[0033] like Figure 3 and Figure 4 As shown, electronic component 100 includes a substrate 10 containing the magnetic material 5 of the present disclosure, wiring 20, and external electrodes 30 and 40. By including the magnetic material 5 of the present disclosure, substrate 10 includes a sintered body 11. Sintered body 11 itself has at least one metallic magnetic sintered layer. As an example, substrate 10 can have a hexahedral structure. In addition to external electrodes 30 and 40, an insulating coating layer 60 can also be formed covering the surface of substrate 10.

[0034] It should be noted that in the aforementioned sintered body 11, when metal magnetic layers of the same composition are continuously stacked, the boundaries between the metal magnetic layers are difficult to discern. Therefore, even if a sintered body comprises multiple metal magnetic layers, as long as the first insulating layer, described below, is not located between them, it is considered a single sintered body. Furthermore, even if multiple metal magnetic layers of different compositions are stacked and the layers are distinguishable, as long as the first insulating layer, described below, is not located between them, it is considered a single sintered body.

[0035] As an example, the wiring 20 can be provided in the substrate 10. The wiring 20 is a conductive material, for example, at least one selected from silver, copper, aluminum, etc. As a form of the wiring 20, in one example, it can be as follows Figure 3 The wiring is not limited to this, and the wiring may also be coiled. External electrodes 30 and 40 are provided on the surface of the substrate 10. These external electrodes are connected to both ends of the wiring 20, and are arranged to face each other with the substrate 10 spaced apart.

[0036] Since the base 10 includes the magnetic material 5 disclosed herein, it contains a relatively high-resistance metal oxide or metal nitride. This increases the resistance of the path of eddy current flowing through the sintered body 11 of the base 10, thereby reducing eddy current losses. Since these eddy current losses increase with higher frequencies, reducing these losses improves high-frequency characteristics.

[0037] like Figure 3 and Figure 4 As shown, in addition to the sintered body 11, the base 10 may further include a first insulating layer 13. In the present disclosure, a high-resistance region is provided in the grain boundary phase of the metal magnetic grains contained in the magnetic material constituting the sintered body 11 of the base 10, thereby ensuring insulation between the magnetic grains. Therefore, even without necessarily using a first insulating layer, insulation and eddy current loss can be suppressed, resulting in excellent high-frequency characteristics in the 200 MHz band for next-generation inductors.

[0038] The first insulating layer 13 can be continuous in a layered manner from one side to the other side of the sintered body 11 in a direction intersecting the stacking direction L. This configuration can provide two or more sintered bodies 11 divided by the first insulating layer 13 .

[0039] In this case, the base 10 has two or more sintered bodies 11 and a first insulating layer 13, and the adjacent sintered bodies 11 and the adjacent sintered bodies 11 can be stacked with the first insulating layer 13 interposed therebetween. By configuring the first insulating layer 13, a magnetic gap function can be provided compared to a case where it is not configured. In addition, the first insulating layer 13 is preferably non-magnetic. As a result, it is possible to achieve an improvement in DC superposition characteristics by reducing the magnetic permeability of the base 10. It should be noted that this is not limited to the above, and the first insulating layer 13 may not be non-magnetic, but may be a low-permeability insulating layer having a lower magnetic permeability than the sintered body 11. In this case, it is also possible to achieve an improvement in inductance compared to the non-magnetic case.

[0040] It should be noted that wiring 20 covered with an insulator can also be used. In this structure, the portion of wiring 20 other than the ends connected to external electrodes 30 and 40 is directly surrounded by the insulator. This allows the insulator to function as a magnetic gap. Furthermore, the insulator is preferably nonmagnetic.

[0041] This improves the DC superposition characteristics by reducing the magnetic permeability of the base 10. However, this is not limiting, and the insulator may not be non-magnetic but may be a low-permeability insulator with a lower magnetic permeability than the sintered body 11. In this case, the insulator can also be improved compared to the non-magnetic case.

[0042] The first insulating layer 13 may be provided with two or more mutually separated layers. Figure 3 and Figure 4 In the illustrated embodiment, the base 10 includes four sintered bodies 11. In this case, the wiring 20 is arranged between the first insulating layers 13, and the base 10 may include three or more sintered bodies 11. Furthermore, providing two or more first insulating layers 13 allows for a laminated structure in which two or more sintered bodies 11 and first insulating layers 13 are alternately laminated. Providing two or more first insulating layers 13 further provides a magnetic gap function, and if the magnetic permeability of each insulating layer 13 is lower than that of the sintered body 11, the DC superposition characteristics can be further improved.

[0043] In addition, if Figure 3 and Figure 4 As shown, when the base 10 has two or more sintered bodies 11, the first external electrode 30 and the second external electrode 40 are arranged on different surfaces of the sintered bodies 11. With the above arrangement of the external electrodes 30 and 40, the base 10 may further include a second insulating layer 50.

[0044] Specifically, the first external electrode 30 and the second external electrode 40 are disposed on the surfaces of adjacent sintered bodies 11, with the first external electrode 30 disposed on the surface of one sintered body 11 and the second external electrode 30 disposed on the surface of the other sintered body 11. In this configuration, the second insulating layer 50 can be disposed between the sintered body 11 on which the first external electrode 30 is disposed and the sintered body 11 on which the second external electrode 40 is disposed. The provision of the second insulating layer 50 prevents short circuits between the first external electrode 30 and the second external electrode 40.

[0045] In one example, the second insulating layer 50 is arranged to extend in a direction intersecting the extending direction of the first insulating layer 13, for example, in a perpendicular direction, and may be a slit-shaped structure. It should be noted that the second insulating layer 50 should not be arranged so as to intrude into and divide the wiring within the base 10.

[0046] It should be noted that in the present disclosure, the wiring does not necessarily have to be arranged inside the base. Figure 5 As shown, the wiring 20A may be arranged in a state of being wound around the outside of the base 10A.

[0047] Hereinafter, the method for manufacturing the electronic component of the present disclosure will be described.

[0048] <Metal Magnetic Particle Preparation Step>

[0049] First, metal magnetic particles (e.g., FeNiCo particles) containing an Fe component are prepared. Then, in one embodiment, by a sol-gel method, a metal alkoxide containing a non-magnetic metal element that is more easily oxidized than Fe and a solvent (water, alcohol, etc.) are mixed to produce a slurry, and the alkoxide is hydrolyzed. Then, by drying the slurry, metal magnetic particles whose surface is covered with a coating containing an element that is more easily oxidized than Fe are obtained. At this time, a metal alkoxide containing a non-magnetic metal element different from the non-magnetic metal material used in the coating of the first layer can be further used to form a second layer of coating on the coating of the first layer. The coating can be one layer, two layers, or more than three layers.

[0050] Metal alkoxides are represented by the chemical formula M(OR) x (M: non-magnetic metal element, OR: alkoxy group). The metal species M constituting the metal alkoxide can be at least one selected from Si, Al, Cr, Ca, Mg, Ti, Mn, V, Zr, Nb, and Ta. Although not particularly limited, the metal alkoxide is preferably an alkoxide of at least one selected from Si, Ti, Al, and Zr. It should be noted that in this specification, Si, which is generally referred to as a semimetal, is considered a metallic element.

[0051] When the metal alkoxide is an alkoxide of at least one selected from the group consisting of Si, Ti, Al, and Zr, a metal oxide having higher strength and higher resistivity can be formed.

[0052] The alkoxy group OR constituting the metal alkoxide is not particularly limited and may be, for example, an alkoxy group having 10 or less carbon atoms, particularly 5 or less carbon atoms, and more particularly 3 or less carbon atoms. The smaller the number of carbon atoms, the easier the hydrolysis reaction is. The alkoxy group is preferably at least one selected from the group consisting of a methoxy group, an ethoxy group, and a propoxy group.

[0053] Specifically, the metal alkoxide is preferably at least one selected from tetraethyl orthosilicate, titanium tetraisopropoxide, zirconium n-butoxide, and aluminum isopropoxide.

[0054] The slurry may contain a water-soluble polymer, which may be at least one selected from the group consisting of polyvinyl pyrrolidone, polyvinyl alcohol, hydroxypropyl cellulose, poly(2-methyl-2-oxazoline), polyethylene imine, polyacrylic acid, and carboxymethyl cellulose.

[0055] It should be noted that the sol-gel method described above is not limited to the above-mentioned method. A coating film containing an element that is more easily oxidized than Fe can be formed on the surface of the metal magnetic particles. In addition, the metal magnetic particles themselves can further contain an element that is more easily oxidized than Fe as a component. Furthermore, a metal nitride component can be imparted to the surface of the metal magnetic particles. In addition, instead of forming a coating film containing an element that is more easily oxidized than Fe, a metal nitride component of a non-magnetic metal can be imparted to the surface of the metal magnetic particles in advance. Even in this case, the sintered metal nitride component remains in the grain boundary phase and has a high resistivity. It should be noted that metal oxides and metal nitrides of non-magnetic metals are necessarily non-magnetic.

[0056] <Metal Magnetic Paste Preparation Process>

[0057] After the above-mentioned metal magnetic particles are prepared, the metal magnetic particles are mixed with a varnish and a solvent (eg, terpineol) using a stirrer and then dispersed using a roll mill to obtain a metal magnetic paste.

[0058] <Insulation paste preparation process>

[0059] Prepare non-magnetic insulator particles. Then, use a blender to mix the insulator particles with a varnish and a solvent (e.g., terpineol). Then, use a roller mill to disperse the particles to obtain an insulator paste. Examples of non-magnetic insulators used in the insulator paste include a mixture of a dielectric material such as aluminum oxide, silicon dioxide, glass, calcium zirconate, strontium zirconate, and / or barium zirconate, and borosilicate glass.

[0060] Wiring paste preparation process

[0061] Conductive particles are mixed with varnish and a solvent (e.g., terpineol) using a stirrer. The mixture is then dispersed using a roll mill to obtain a wiring paste. Conductive particles can be selected from copper particles, silver particles, and the like.

[0062] <Preparation Step of Unfired Laminated Body>

[0063] After preparing the respective pastes, the aforementioned metal magnetic paste is used to form a metal magnetic layer of a predetermined thickness, for example, by screen printing, and then dried. After drying, a slit groove of a predetermined width is formed by laser processing, and the aforementioned insulating paste is filled into the slit groove by screen printing or other methods, followed by drying. It should be noted that the slit groove is not limited to post-processing by laser processing; a pre-patterned pattern can also be formed using a screen printing plate or the like.

[0064] After the slit grooves are filled with an insulating paste and dried, an insulating layer of a predetermined thickness is formed on the metal magnetic layer using the above-mentioned insulating paste by screen printing and dried. The insulating paste used to form the insulating layer may be of a different type than the insulating paste used to fill the slit grooves.

[0065] Using a wiring paste, a desired wiring shape (e.g., straight line, coil, curved, etc.) is formed by screen printing. After the coil wiring is formed, an insulating layer can be further formed on the coil wiring. By repeatedly forming the metal magnetic layer and optionally forming an insulating layer, an unfired laminate is obtained.

[0066] It should be noted that in the resulting electronic component, if the L value is higher than the desired characteristics, the number of insulating layers can be reduced or removed. This allows the balance between the L value and the DC superposition characteristics to be adjusted. Furthermore, while the above description depicts a method of laminating screen-printed layers formed using a screen printing method, this is not limiting and can also be achieved by preparing separate sheets and laminating these sheets.

[0067] <Single-cutting and firing steps of the unfired laminate>

[0068] The unfired laminate is cut into pieces using a cutting machine or the like, and then the pieces are degreased in a sintering furnace using a nitrogen atmosphere, and then sintered at a temperature of 900 to 1000 degrees for a specified time (e.g., 1 hour) in a reducing atmosphere of H2:3% / N2:97%. This allows for a sintered laminate having a high-resistance portion and an insulating layer inside.

[0069] The high resistance portion in the obtained sintered body may contain an oxide or nitride of an element that is more easily oxidized than Fe. It should be noted that even an element that is less easily oxidized than Fe may be oxidized in another step and then contained in the high resistance portion after sintering.

[0070] In addition, in the above, the formation of a non-magnetic insulating layer is a prerequisite, but by extending the holding time of the maximum temperature during the above-mentioned sintering, the metal magnetic component is allowed to diffuse and invade from the metal magnetic layer into the non-magnetic insulating layer, and a low magnetic permeability insulating layer with some magnetism can be obtained.

[0071] <Formation of External Electrodes>

[0072] The outer surface of the sintered body is then optionally coated with an insulating resin or the like, and the coating is removed from the portions where the wiring and external electrodes are connected using a laser or the like. Plating is then performed to form external electrodes, ultimately yielding the electronic component of the present disclosure. The external electrodes can be made of silver, for example.

[0073] Example

[0074] Hereinafter, embodiments of the present disclosure will be described.

[0075] <Determination of the Filling Rate of Metal Magnetic Particles in a Sintered Body>

[0076] Each fired sample was fixed with resin, ground with a grinding device Tegramin-25 (manufactured by Struers), and ion milling was performed using an ion milling device IM-3000 (manufactured by Hitachi High Technologies Co., Ltd.). Then, SEM images and arbitrary element mapping images were obtained using a field emission scanning electron microscope SU8230 (manufactured by Hitachi High Technologies Co., Ltd.). These acquired images were analyzed using image analysis software WinROOF2021 (manufactured by Mitani Shoji Co., Ltd.), and the filling rate of the metal magnetic particles was calculated. The filling rate is the average value of the analysis values ​​at any three locations near 1 / 2 of the thickness direction of the sintered toroidal core. It should be noted that when calculated from the final electronic component, the filling rate is the average value of the analysis values ​​at a total of 6 locations, namely, any three locations from the uppermost surface of the internal wiring to a position 1 times the thickness of the upper wiring and any three locations from the lowermost surface of the internal wiring to a position 1 times the thickness of the lower wiring. In addition, the "filling rate of the metal magnetic particles in the sintered body" in the present disclosure is represented by the ratio of the area of ​​the metal magnetic particles to the area of ​​the sintered body including voids.

[0077] Ollendorff's approximation

[0078] Ollendorff's approximation is an approximation for theoretically deriving the relative magnetic permeability μη when the filling factor of metal magnetic particles is η. Using Ollendorff's approximation, the preferred filling factor of metal magnetic particles at 200 MHz is calculated as follows.

[0079] According to Ollendorff's approximation, if the filling rate of metal magnetic particles is η, the relative magnetic permeability is μ, and the demagnetization factor is N, the relative magnetic permeability μη at the filling rate η is expressed by the following formula 1.

[0080] [Formula 1]

[0081]

[0082] This time, Fe 10 Ni 20 Co's μ is 70, and N is 0.1, equivalent to a sphere. It's expected that the drive frequency of DC-DC converters will increase to around 200 MHz in the future. At 200 MHz, μη is preferably 15 to 50. Based on the above formula, the filling factor η of this μη is 66.7% to 95.1%.

[0083] When actually manufacturing an electronic component using the sintered body of the present disclosure, the electronic component can be manufactured through the following steps.

[0084] Examples 1 to 4 and Comparative Examples 1 to 2 <Metal Magnetic Particle Preparation Step>

[0085] First, Fe ions with D50 particle sizes of 0.19 μm, 0.40 μm, 0.85 μm, 1.85 μm, 3.10 μm, and 4.80 μm were prepared. 10 Ni 20 Co particles. Next, using a sol-gel method, an Al alkoxide and a solvent (water) are mixed to create a slurry, in which the alkoxide is hydrolyzed. The slurry is then dried to obtain metal magnetic particles whose surfaces are covered with a sol-gel coating containing Al. The film thickness is approximately 10 to 20 nm.

[0086] <Metal Magnetic Paste Preparation Process>

[0087] After the above-mentioned metal magnetic particles are prepared, the metal magnetic particles are mixed with a varnish and terpineol as a solvent using a stirrer and then dispersed using a roll mill to obtain a metal magnetic paste.

[0088] <Insulation paste preparation process>

[0089] Non-magnetic insulating particles of alumina and borosilicate glass with a D50 particle size of approximately 0.1 to 0.5 μm were prepared. These insulating particles were then mixed with a varnish and a solvent, terpineol, using a blender. The mixture was then dispersed using a roll mill to obtain an insulating paste.

[0090] Wiring paste preparation process

[0091] Copper particles having a D50 particle size of about 1 to 5 μm, a varnish, and terpineol as a solvent were mixed with a stirrer and then dispersed with a roll mill to obtain a wiring paste.

[0092] <Preparation Step of Unfired Laminated Body>

[0093] After preparing the pastes, the metal magnetic paste is screen-printed to form a metal magnetic layer of a predetermined thickness, which is then dried. After drying, a slit groove of a predetermined width is formed using laser processing, and the insulator paste is then filled into the slit groove using a screen-printing method or other method, followed by drying.

[0094] After the slit grooves are filled with the insulating paste and dried, an insulating layer having a predetermined thickness is formed on the metal magnetic layer by screen printing using the insulating paste and dried.

[0095] Using the wiring paste, wiring of a desired shape is formed thereon by screen printing. By forming the metal magnetic material layer and the insulating layer as described above, an unfired laminate is obtained.

[0096] <Single-cutting and firing steps of the unfired laminate>

[0097] The unfired laminate is cut into individual pieces using a cutter or the like. The individual pieces are then degreased in a sintering furnace in a nitrogen atmosphere and then sintered at 1000 degrees Celsius for 90 minutes in a reducing atmosphere of H2:3% / N2:97%. This yields a sintered body containing a plurality of metal magnetic particles having high-resistance portions formed in the grain boundary phase of the granular metal magnetic particles.

[0098] <Formation of External Electrodes>

[0099] Next, the outer surface of the sintered body is coated with an insulating resin, and the coating at the portion where the wiring connects to the external electrodes is removed using a laser. Plating is then performed to form the external electrodes. This completes the electronic component. The external electrodes can be made of silver, for example.

[0100] Table 1 shows measured data and various evaluation results for sintered materials actually produced by sintering the metal magnetic paste prepared in the "Metal Magnetic Particle Preparation Step" and "Metal Magnetic Paste Preparation Step" described above in the same manner. The target properties were that no heterogeneous phases other than oxides of the metal (here, Al) used for the sol-gel coating formed in the grain boundary phase, and that the particle size (equivalent circle diameter) of the metal magnetic material surrounded by the high-resistance grain boundary phase was less than the skin depth at 200 MHz. Examples that met these criteria were given an overall evaluation of 0 (suitable).

[0101] [Table 1] Measurement results 1

[0102]

[0103] It should be noted that the calculation of the above-mentioned "epidermal depth" is based on [epidermal depth = (1 / (π×σ×f×μ0×μr)) 0.5 It should be noted that the metal magnetic particles Fe 10 Ni 20 The relative magnetic permeability μr of Co is 70, and the electrical conductivity σ is 2.08×10 6 (S / m), μ0 is the magnetic permeability of vacuum, and f is the frequency. As a result of calculation, the skin depth at 200 MHz is 2.95 μm.

[0104] The equivalent circle diameter of the metal magnetic particles in the sintered body was calculated using the following procedure. Specifically, each sintered sample was fixed with resin, ground using a Tegramin-25 grinding machine (manufactured by Struers), and ion milled using an ion milling machine IM-3000 (manufactured by Hitachi High Technologies Co., Ltd.). SEM images and, if necessary, elemental mapping images were obtained using a field emission scanning electron microscope SU8230 (manufactured by Hitachi High Technologies Co., Ltd.). The magnification was adjusted between 3500 and 60000x.

[0105] The images obtained were analyzed and calculated using the image analysis software WinROOF2021 (manufactured by Mitani Shoji Co., Ltd.). During analysis, the filling rate was the average of 60 analysis values ​​at three random locations near the halfway point in the thickness direction of the sintered toroidal core, with 20 particles at each location. It should be noted that when calculating from the final electronic component, the average of 120 analysis values ​​was calculated from three random locations, from the top surface of the internal wiring to a position equal to 1 times the thickness of the upper wiring, and from three random locations, from the bottom surface of the internal wiring to a position equal to 1 times the thickness of the lower wiring.

[0106] Alternatively, the following method can be used to visualize the high-resistance grain boundary phase. Specifically, each fired sample was fixed with resin, ground using a Tegramin-25 grinding machine (manufactured by Struers), then processed using FIB (focused ion beam) processing to a shape suitable for subsequent SPM (scanning probe microscopy) measurement, and finally cleaned using Ar plane milling.

[0107] Using this processed sample, the diffusion resistance was measured in the SSRM (Scanning Diffusion Resistance Microscope) mode of the SPM. In the SSRM mode, a conductive probe is scanned while applying a bias voltage to the sample, converting the current flowing through each point into a resistance value, thereby visualizing the high-resistance grain boundary phase. It should be noted that the maximum resistance value of the measured metal magnetic particle portion is 10 3 The portion with a resistance value of times or more is regarded as a high-resistance grain boundary phase, and its threshold value can be appropriately adjusted while referring to the element mapping image so as to coincide with the position of high-resistance materials such as oxides and nitrides.

[0108] Based on the above results, in Comparative Example 1, the small particle size of the metal magnetic particles used resulted in a high sintering shrinkage rate during firing, which is believed to have hindered the ingress of the reducing atmosphere gas, leading to the formation of iron oxide, the material of the metal magnetic particles, as a heterogeneous phase. Furthermore, in Comparative Example 2, the large particle size of the metal magnetic particles used exceeded the skin depth of 2.95 μm at 200 MHz, as described above, resulting in an overall judgment of "×" (unsuitable).

[0109] In contrast, in Examples 1 to 4, the equivalent circle diameter of the metal magnetic particles is 0.29 μm to 2.33 μm. In this case, no heterogeneous phase other than the oxide of Al is generated in the grain boundary phase, and the particle size (equivalent circle diameter) of the metal magnetic body surrounded by the high-resistance grain boundary phase is smaller than the skin depth (2.95 μm) at 200 MHz. Therefore, the comprehensive judgment is 0 (suitable). The heterogeneous phase disclosed in the present invention refers to the oxide of the metal magnetic particles. If a heterogeneous phase exists, the saturation magnetic flux density of the sintered body decreases. It should be noted that the "heterogeneous phase judgment" of the oxide of the metal magnetic particles (iron oxide, etc.) is implemented according to the following steps. Specifically, as Figure 2 As shown, when the minimum thickness W2 (W21+W22) of the oxide of the metal magnetic particles covering the entire metal magnetic particles 11A and being thicker than 2 / 3 of the width W1 of the grain boundary phase between the metal magnetic particles 11A, it is determined that a different phase exists.

[0110] The present disclosure includes the following aspects, but is not limited to these aspects.

[0111] <1>

[0112] A magnetic material is a sintered body comprising a plurality of metallic magnetic particles having a grain boundary phase.

[0113] The grain boundary phase comprises a metal oxide or metal nitride formed by oxidation or nitridation of a non-magnetic metal.

[0114] The metal magnetic particles have an equivalent circle diameter of 0.29 μm to 2.33 μm.

[0115] <2>

[0116] The magnetic material according to <1>, wherein the grain boundary phase includes an oxide of the metal magnetic particles.

[0117] <3>

[0118] The magnetic material according to <1> or <2>, wherein the plurality of metal magnetic particles include Fe,

[0119] The above-mentioned metal oxide or the above-mentioned metal nitride is an oxide or nitride of at least one metal selected from Si, Al, Cr, Ca, Mg, Ti, Mn, V, Zr, Nb and Ta, which are elements that are more easily oxidized than Fe.

[0120] <4>

[0121] An electronic component includes a base body made of the magnetic material according to any one of <1> to <3>, and wiring.

[0122] <5> The electronic component according to <4>, wherein the electronic component is an inductor.

[0123] <6>

[0124] A method for producing a magnetic material, comprising the steps of forming a sintered body containing a plurality of metal magnetic particles,

[0125] At least at the time of completion of sintering, a grain boundary phase of the plurality of metal magnetic grains including a metal oxide or a metal nitride formed by oxidation or nitridation of the non-magnetic metal is formed.

[0126] <7>

[0127] The production method according to <6>, wherein the metal oxide or the metal nitride is an oxide or nitride of at least one non-magnetic metal selected from the group consisting of Si, Al, Cr, Ca, Mg, Ti, Mn, V, Zr, Nb, and Ta, which are elements more easily oxidized than Fe.

[0128] <8>

[0129] The production method according to <6> or <7>, wherein a film containing the element more easily oxidized than Fe is previously coated on the surface of the metal magnetic particles before sintering, and the metal magnetic particles coated with the film are sintered.

[0130] <9>

[0131] The production method according to <8>, wherein the surface of the metal magnetic particles is previously coated with the film in two or more layers.

[0132] <10>

[0133] The production method according to any one of <6> to <9>, wherein the metal magnetic particles are sintered using metal magnetic particles containing Fe as a metal element and the element more easily oxidized than Fe.

[0134] While one embodiment of the present disclosure has been described above, this is merely a typical example within the scope of application of the present disclosure. Therefore, the present disclosure is not limited thereto, and it will be readily understood by those skilled in the art that various modifications are possible.

[0135] Industrial applicability

[0136] The electronic component of the present disclosure can be used as an inductor.

[0137] Explanation of symbols

[0138] 100 electronic components

[0139] 10 Matrix

[0140] 11 Sintered body

[0141] 11A Metal magnetic particles

[0142] 11B grain boundary phase

[0143] 11α Magnetic Materials

[0144] 13. First insulation layer

[0145] 20 Wiring

[0146] 30, 40 external electrodes

[0147] 50 Second insulation layer

[0148] 60 coating layer

Claims

1. A magnetic material comprising a sintered body comprising a plurality of metallic magnetic particles having a grain boundary phase, The grain boundary phase comprises a metal oxide or metal nitride formed by oxidation or nitridation of a non-magnetic metal, The metal magnetic particles have an equivalent circle diameter of 0.29 μm to 2.33 μm.

2. The magnetic material according to claim 1, wherein The grain boundary phase includes an oxide of the metal magnetic particles.

3. The magnetic material according to claim 1 or 2, wherein The plurality of metal magnetic particles include Fe, The metal oxide or the metal nitride is an oxide or nitride of at least one metal selected from Si, Al, Cr, Ca, Mg, Ti, Mn, V, Zr, Nb, and Ta, which are elements more easily oxidized than Fe.

4. The magnetic material according to any one of claims 1 to 3, wherein The filling rate of the metal magnetic particles in the sintered body is 66.7% to 95.1%. 5 . An electronic component comprising: a base body comprising the magnetic material according to claim 1 ; and wiring. The electronic component according to claim 5 , wherein The electronic component is an inductor.

7. A method for producing a magnetic material, comprising the steps of forming a sintered body comprising a plurality of metal magnetic particles, in, At least at the time when sintering is completed, a grain boundary phase of the plurality of metal magnetic grains including a metal oxide or a metal nitride formed by oxidation or nitridation of the non-magnetic metal is formed.

8. The production method according to claim 7, wherein: The metal oxide or the metal nitride is an oxide or nitride of at least one non-magnetic metal selected from Si, Al, Cr, Ca, Mg, Ti, Mn, V, Zr, Nb and Ta, which are elements more easily oxidized than Fe.

9. The production method according to claim 7 or 8, wherein: A film containing the element more easily oxidized than Fe is previously coated on the surface of the metal magnetic particles before sintering, and the metal magnetic particles coated with the film are sintered.

10. The production method according to claim 9, wherein: The surfaces of the metal magnetic particles are previously coated with the film in two or more layers.

11. The production method according to any one of claims 7 to 10, wherein Metal magnetic particles containing Fe as a metal element and the element more easily oxidized than Fe are used, and the metal magnetic particles are sintered.

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