Magnetic core, magnetic component, and electronic device

Abstract

A magnetic core containing specific particles is provided. The magnetic core has a surface portion having a small distance from an outermost surface of the magnetic core and a central portion having a large distance from the outermost surface of the magnetic core. The specific particles have an oxide phase having a specific thickness, and the specific particles contained in the surface portion and the specific particles contained in the central portion have a specific relationship in thickness of the oxide phase. Alternatively, the magnetic core contains soft magnetic metal particles. The soft magnetic metal particles have an oxide phase on a surface. A relationship between a maximum thickness portion of the oxide phase and an anti-maximum thickness portion is in a specific relationship.

Description

Technical Field

[0001] This disclosure relates to magnetic cores, magnetic components, and electronic devices. Background Technology

[0002] Patent Document 1 describes an invention related to a coil component. By thickening the oxide film of the metallic magnetic particles at the interface between the magnetic body and the external electrode, the sealing between the magnetic body and the external electrode can be improved while maintaining DC resistance.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2023-103954 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] The purpose of this disclosure is to provide a magnetic core that improves voltage withstand capability while appropriately maintaining specific permeability.

[0008] Technical solutions for solving technical problems

[0009] To achieve the above objectives, a first aspect of this disclosure provides a magnetic core, wherein...

[0010] The magnetic core contains specific particles.

[0011] The magnetic core has a surface portion at a distance of less than 100 μm from the outermost surface of the magnetic core and a central portion at a distance of more than 100 μm from the outermost surface of the magnetic core.

[0012] The specific particles are soft magnetic metal particles with an oxide phase on their surface having a thickness of 0.025 μm or more.

[0013] The specific particles are at least contained in the surface portion.

[0014] Let the average thickness of the oxide phase of the specific particles at the surface portion be T1 [μm], and let the average thickness of the oxide phase of the specific particles at the central portion be T2 [μm].

[0015] T1≥0.050, T2≤0.500, and T1>T2.

[0016] Alternatively, at least a portion of the specific particles may contain Fe and / or Co.

[0017] Alternatively, it could be 0.200≤T1≤5.000.

[0018] To achieve the above objectives, a second aspect of this disclosure provides a magnetic core, wherein...

[0019] The magnetic core contains soft magnetic metal particles.

[0020] The soft magnetic metal particles have an oxide phase on their surface.

[0021] When drawing any straight line containing the center of the soft magnetic metal particles on the cross-section of the magnetic core, the straight line having the maximum thickness portion along which the length of the oxide phase along the straight line is the largest is designated as a specific straight line.

[0022] The portion of the oxide phase located on the opposite side of the maximum thickness portion relative to the center along the specific straight line is designated as the anti-maximum thickness portion.

[0023] Let the length of the maximum thickness portion be T3, and the length of the reverse maximum thickness portion be T4.

[0024] 0 < T4 / T3 ≤ 0.98.

[0025] Alternatively, the soft magnetic metal particles may contain Fe and / or Co.

[0026] Alternatively, it could be 0 < T4 / T3 ≤ 0.90.

[0027] The following account is a common account in both the first and second aspects.

[0028] The magnetic component disclosed herein includes the magnetic core described above.

[0029] The electronic device disclosed herein includes the magnetic core described above. Attached Figure Description

[0030] Figure 1 This is a SEM image of a specific particle from the first embodiment.

[0031] Figure 2 This is a schematic diagram showing the position of the outermost surface of the magnetic core.

[0032] Figure 3 This is a schematic diagram showing the position of the outermost surface of the magnetic core.

[0033] Figure 4 This is a SEM image of the vicinity of the magnetic core in the second embodiment.

[0034] Figure 5 This is a schematic diagram of the cross-section of the soft magnetic metal particles according to the second embodiment.

[0035] Explanation of reference numerals in the attached figures

[0036] 1, 2... magnetic core

[0037] 3… Surface part

[0038] 4…Central Department

[0039] 10… Soft magnetic metal particles

[0040] 11, 111… specific particles

[0041] 11a, 111a… oxide phases

[0042] 11b, 111b... particle body

[0043] 13…resin

[0044] 21, 22... outermost surface

[0045] 21a…Specific Surface

[0046] 101…Inscribed circle

[0047] 101c…center

[0048] 103…a specific straight line Detailed Implementation

[0049] (First Implementation)

[0050] Hereinafter, the magnetic core of the first embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0051] The magnetic core of this embodiment has a surface portion 3 that is 100 μm or less from the outermost surface and a central portion 4 that is more than 100 μm from the outermost surface.

[0052] The magnetic core of this embodiment includes at least the surface portion 3. Figure 1 The specific particle 11 shown.

[0053] Specific particle 11 is a soft magnetic metal particle having an oxide phase 11a with a thickness of 0.025 μm or more on its surface. In other words, specific particle 11 is a soft magnetic metal particle comprising a particle body 11b and an oxide phase 11a with a thickness of 0.025 μm or more covering the particle body 11b. Furthermore, soft magnetic metal particles having only an oxide phase with a thickness of less than 0.025 μm are not considered as specific particle 11.

[0054] use Figure 2 and Figure 3 The outermost surface of this embodiment will be described. Figure 2 The magnetic core 1 shown and Figure 3 The magnetic core 2 shown has a structure in which resin 13 is filled between soft magnetic metal particles 10.

[0055] In this embodiment, the outermost surface refers to the surface that is in contact with the material located on the outermost side of the magnetic core and is parallel to the surface of the magnetic core.

[0056] exist Figure 2 and Figure 3 The image shows a portion of the magnetic core near its surface, with the surface depicted on the upper side.

[0057] exist Figure 2 In this configuration, the surface of the magnetic core 1 becomes the surface of the resin 13, and there are no soft magnetic metal particles 10 on the surface of the magnetic core 1. In this case, as... Figure 2 As shown, the surface of the magnetic core 1 becomes the outermost surface 21.

[0058] exist Figure 3 In this process, a portion of the soft magnetic metal particles 10 are exposed from the resin 13 present on the surface of the magnetic core 2. In this case, the surface that is in contact with the surface of the soft magnetic metal particle 10 that is most exposed from the surface of the magnetic core 2 and is parallel to the surface of the magnetic core 2 is the outermost surface 22.

[0059] In the case of the magnetic core of this embodiment, the average thickness of the oxide phase 11a of the specific particles 11 in the surface portion 3 is set as T1 [μm], and the average thickness of the oxide phase 11a of the specific particles 11 in the central portion 4 is set as T2 [μm]. T1 ≥ 0.050, T2 ≤ 0.50, and T1 > T2.

[0060] There is no specific restriction on the upper limit of T1. For example, it can be below 10.0 or below 5.0. More specifically, it can be 0.050≤T1≤10.0 or 0.20≤T1≤5.0. There is no specific restriction on the lower limit of T2. For example, it can be above 0.000. More specifically, it can be 0.000≤T2≤0.50.

[0061] It can be either T1-T2≥0.001 or T1-T2≥0.01.

[0062] The greater the thickness of the oxide phase 11a relative to the particle size of a specific particle 11, the easier it is for the specific permeability of the magnetic core to decrease.

[0063] The average thickness T1 of the oxide phase 11a in the specific particles 11 of the surface portion 3 is obtained by averaging the thickness of the oxide phase 11a in all the specific particles 11 contained in the surface portion 3. The average thickness T2 of the oxide phase 11a in the specific particles 11 of the central portion 4 is obtained by averaging the thickness of the oxide phase 11a in all the specific particles 11 contained in the central portion 4.

[0064] When a specific particle 11 is repeatedly positioned along the boundary line between the surface portion 3 and the central portion 4, the specific particle 11 is regarded as a specific particle contained in the surface portion 3.

[0065] That is, in this embodiment, the magnetic core includes soft magnetic metal particles with an oxide phase that is thicker on the surface portion 3 than on the central portion 4. This results in a magnetic core that improves voltage withstand capability while appropriately maintaining specific permeability.

[0066] If the surface portion 3 does not contain specific particles 11, then T1 is considered to be 0.000. If the central portion 4 does not contain specific particles 11, then T2 is considered to be 0.000.

[0067] There is no particular limitation on the area ratio of a specific particle 11 at the surface portion 3 included in the cross-section of the magnetic core. For example, it can be more than 1% and less than 85%.

[0068] At least a portion of the specific particles 11 may also contain Fe and / or Co.

[0069] There are no particular restrictions on the composition of the particle body 11b. For example, the particle body 11b may also contain one or more elements selected from Fe, Co, and Ni. In addition, the particle body 11b may also contain one or more elements selected from those commonly contained in soft magnetic metal particles, namely P, Si, B, Na, Al, Ca, Bi, Ba, Zn, C, Nb, Hf, Zr, Cu, Ta, Mo, W, Ti, and V.

[0070] There are no particular restrictions on the total content of Fe, Co, and Ni in the bulk particle 11b. For example, it can be 70 at% to 100 at% or more. There are no particular restrictions on the total content of P, Si, B, Na, Al, Ca, Bi, Ba, and Zn in the bulk particle 11b. For example, it can be 0 at% to 30 at% or more. There are no particular restrictions on the total content of C, Nb, Hf, Zr, Cu, Ta, Mo, W, Ti, and V in the bulk particle 11b. For example, it can be 0 at% to 10 at% or more. Furthermore, the proportion of the bulk particle 11b is usually significantly larger than the proportion of the oxide phase 11a; therefore, it can be presumed that the composition of the bulk particle 11b is substantially the same as the composition of the specific particle 11. Even when the proportion of the bulk particle 11b is not significantly larger than the proportion of the oxide phase 11a, the composition of the bulk particle 11b can still be analyzed and determined. For example, the composition of the bulk particle 11b can also be determined based on cross-sectional SEM-EDS or STEM-EDS analysis.

[0071] Furthermore, the particle body 11b may contain elements other than Fe, Co, Ni, P, Si, B, Na, Al, Ca, Bi, Ba, Zn, C, Nb, Hf, Zr, Cu, Ta, Mo, W, Ti, and V, within a range that does not significantly impair the magnetic properties of the specific particle 11. For example, the total content of elements other than Fe, Co, Ni, P, Si, B, Na, Al, Ca, Bi, Ba, Zn, C, Nb, Hf, Zr, Cu, Ta, Mo, W, Ti, and V in the particle body 11b may be less than 5% by mass.

[0072] There are no particular limitations regarding the composition of oxide phase 11a, except that oxide phase 11a contains oxides. For example, oxide phase 11a may also contain oxides of one or more elements selected from those contained in particle body 11b. That is, oxide phase 11a is a phase containing oxides.

[0073] Alternatively, the oxide phase 11a may also be composed of oxides generated by the oxidation of the particle body 11b. For example, the compositions of the oxide phase 11a and the particle body 11b, without considering oxygen and carbon, may be more than 50% identical on an atomic number basis.

[0074] The oxide phase 11a may also contain Co. By containing Co, the voltage withstand properties of the oxide phase 11a are easily improved. Specifically, the content ratio of Co relative to the total content of Fe, Co and P in the oxide phase 11a (hereinafter, sometimes simply referred to as Co / α) can be 0.10 to 1.00 or 0.17 to 0.70 on an atomic number basis.

[0075] The oxide phase 11a may also contain P. The proportion of P relative to the total content of Fe, Co, and P in the oxide phase 11a (hereinafter sometimes simply referred to as P / α) can be 0.01 to 1.00 or 0.10 to 0.50 based on the atomic number. In particular, when the oxide phase 11a contains Co and the P / α is 0.10 to 0.50, the withstand voltage characteristics are easily improved.

[0076] Alternatively, cracks can also form in the oxide phase 11a. For example, they can extend from the surface of the oxide phase 11a to the surface of the particle body 11b, or they can stop inside the oxide phase 11a.

[0077] There are no particular restrictions on the particle size of the specific particle 11. For example, it can be between 0.5 μm and 100 μm.

[0078] There are no particular limitations on the microstructure of the soft magnetic metal particles in this embodiment. The microstructure of the soft magnetic metal particles can be an amorphous structure, a nanocrystalline structure containing nanocrystals, or a crystalline structure.

[0079] Soft magnetic metal particles containing nanocrystals are sometimes obtained by heating soft magnetic alloy particles containing amorphous material at 400°C to 700°C.

[0080] Here, "amorphous structure (amorphous material structure)" refers to a material state in which long-range order, almost entirely absent like crystals, is present, and the amorphization rate X is 85% or higher. Amorphous structures include structures possessing only an amorphous state and structures composed of heterogeneous amorphous states. Structures composed of heterogeneous amorphous states refer to structures where initial crystallites exist within the amorphous state. The average crystallite diameter of the initial crystallites in structures composed of heterogeneous amorphous states is preferably 0.1 nm to 10 nm.

[0081] Furthermore, "nanocrystalline structure" refers to a structure containing nanocrystals with an amorphization rate of less than 85% and an average crystallite diameter of 0.5 nm to 30 nm. The maximum diameter of the crystallites in the nanocrystalline structure is preferably less than 100 nm.

[0082] On the other hand, crystalline metallic magnetic materials have a crystalline structure that differs from amorphous or nanocrystalline structures. A "crystalline structure" refers to a material state with an amorphization rate (X) of less than 85% and an average crystallite diameter of more than 100 nm.

[0083] In addition, the crystallization ratio is set to P. C Let the proportion of amorphous state be P. A The amorphization rate X (in %) is given by X = (P A / (P C +P A ))×100 represents the amorphization rate X. When calculating the amorphization rate X using XRD, the crystalline scattering integral intensity Ic measured using XRD can be considered as P. C Furthermore, the integrated intensity Ia of amorphous scattering measured using XRD is considered as P. A When calculating the amorphization rate X using EBSD or electron microscopy, the area ratio of the crystalline portion within the grain can also be considered as P. C Furthermore, the area ratio of the amorphous portion within the particle is considered as P. A .

[0084] Materials that can be used to make soft magnetic alloy particles with a fine, amorphous structure include, for example, Fe-Si-B alloy, Fe-B-Si-C alloy, Fe-B-Si-C-Cr alloy, Fe-Co-BP-Si-Cr alloy, Fe-Co-BP-Si alloy, and Fe-Co-BP-Si-C alloy.

[0085] Materials that can be used to make soft magnetic alloy particles with a fine structure that becomes a nanocrystalline structure include, for example, Fe-Si-B-Nb-Cu alloy, Fe-B-Nb alloy, Fe-B-Nb-P alloy, Fe-BP-Si-Cu alloy, Fe-BP-Si-Nb-Cr alloy, Fe-Co-BP-Si-Cu alloy, and Fe-Co-BP-Si-Nb alloy.

[0086] Materials that can be used to make soft magnetic alloy particles with a fine structure that becomes a crystal structure include, for example, pure metal Fe, pure metal Co, pure metal Ni, Fe-Co alloy, Fe-Si alloy, Fe-Ni alloy, Fe-Co-Si alloy, Fe-Si-Cr alloy, Fe-Co-Si-Cr alloy, Fe-Co-V alloy, Fe-Si-Al alloy, Fe-Si-Al-Ni alloy, and Fe-Co-Si-Al alloy.

[0087] The manufacturing method of the magnetic core according to this embodiment will be described below.

[0088] There are no particular limitations on the manufacturing method of the soft magnetic metal powder of this embodiment. For example, the soft magnetic metal powder can be manufactured by water atomization, gas atomization, carbonylation, spray pyrolysis, or other manufacturing methods. Alternatively, the soft magnetic metal powder can be manufactured by pulverizing metal strips, for example. Hereinafter, a method for obtaining the soft magnetic metal powder of this embodiment by gas atomization will be described.

[0089] First, the raw materials containing each element that constitutes the metal particles in the soft magnetic metal powder are prepared and weighed in a manner that results in the desired composition of the metal particles. Then, the raw materials containing each element are melted to create a master alloy. There are no particular restrictions on the melting method. For example, the raw materials containing each element can also be melted by high-frequency heating in a chamber with a specified vacuum level.

[0090] Next, the master alloy is heated to melt it, yielding molten metal. The temperature of the molten metal can be adjusted according to the melting point of the alloy with the desired composition and / or the melting points of the raw materials for each of the aforementioned elements. For example, it can be set to 1200–1600°C.

[0091] Next, molten metal is sprayed into the chamber to produce powder. Specifically, the molten metal is discharged from the outlet toward the cooling section within the chamber. At this time, high-pressure gas is sprayed toward the discharged molten metal. The molten metal is broken and dispersed within the chamber by the spray of high-pressure gas, and the dispersed molten metal is rapidly cooled and solidified by colliding with the cooling section (cooling water), becoming a soft magnetic metal powder containing metal particles 10. In the case of using a water atomization method, water is sprayed instead of high-pressure gas.

[0092] There are no particular restrictions on the type of gas used in high-pressure applications. Examples include inert gases such as nitrogen, argon, and helium. Alternatively, reducing gases such as ammonia decomposition gases can also be used.

[0093] There are no particular limitations on the pressure of the injected high-pressure gas. It can be set to 2.0–10.0 MPa. There are also no particular limitations on the injection rate of molten metal. It can be set to 0.5–16.0 kg / min. By controlling the ratio of the high-pressure gas pressure to the injection rate of molten metal, the particle size of the soft magnetic metal powder can be adjusted.

[0094] The particle size of soft magnetic metal powder can also be adjusted by grading.

[0095] Furthermore, a coating film can also be formed on powder obtained by cooling with cooling water.

[0096] There are no particular restrictions on the type of coating. For example, it can also be a coating containing inorganic materials. Examples of inorganic materials include phosphates, BN, SiO2, MgO, Al2O3, phosphate-based glasses, silicate-based glasses, borosilicate-based glasses, and bismuthate-based glasses.

[0097] Examples of phosphate-based glasses include P-Zn-Al-O glasses and P-Zn-Al-RO glasses (where R is selected from one or more alkali metals). Examples of silicate-based glasses include Si-O glasses. Examples of borosilicate-based glasses include Ba-Zn-B-Si-Al-O glasses. Examples of bismuthate-based glasses include Bi-Zn-Al-O glasses and Bi-Zn-B-Si-Al-O glasses.

[0098] There are no particular restrictions on the method of coating formation. It can also be formed by known formation methods selected according to the type of coating. Examples of coating formation methods include heat treatment, phosphate treatment, mechanical alloying, silane coupling treatment, and hydrothermal synthesis.

[0099] The following sections will provide further details on several methods for forming coatings.

[0100] When forming a coating containing SiO2 (hereinafter sometimes referred to as a SiO2 coating) as a film, a solution containing a silane coupling agent that serves as the Si source can also be sprayed into the powder. Alternatively, the powder can be impregnated with a solution containing a silane coupling agent, followed by drying and / or heat treatment.

[0101] There are no particular restrictions on the type of silane coupling agent. Examples include tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and hexyltrimethylsilane. TEOS is particularly preferred.

[0102] There are no particular restrictions on the type of solvent used in the solution containing the silane coupling agent. Examples include water, ethanol, acetone, and isopropanol. The thickness of the coating film can be controlled by adjusting the concentration of the silane coupling agent in the solution, the spray volume per unit time, and the impregnation time. Higher concentrations of the silane coupling agent, higher spray volumes per unit time, and longer impregnation times result in a thicker coating film.

[0103] When forming a phosphate-containing coating (hereinafter sometimes referred to as a phosphate coating) as a film, it can be achieved through phosphate treatment. Specifically, firstly, a treatment solution is prepared by dissolving a phosphate containing an additive element, or phosphoric acid, in a solvent such as water or alcohol. Then, the treatment solution is applied to the powder by impregnating it with the powder or by spraying the powder with the treatment solution. Afterward, a phosphate coating is formed on the surface of the powder by drying it. Examples of additive elements include alkali metals, alkaline earth metals, Zn, and Al.

[0104] When forming coatings for various glass systems, these coatings can be formed using a mechanochemical method with a mechanical fusion apparatus. Specifically, in the mechanochemical coating formation process, powder for coating formation and a powdered coating agent containing the constituent elements of the coating are introduced into a rotating rotor of the mechanical fusion apparatus, causing the rotor to rotate. A pressure head is provided inside the rotating rotor. When the rotor rotates, the mixture of powder for coating formation and coating agent is compressed in the gap between the inner wall of the rotating rotor and the pressure head, generating frictional heat. Through this frictional heat, the coating agent softens and is fixed to the surface of the powder for coating formation by compression, forming an oxide glass coating.

[0105] There are no particular limitations on the manufacturing method of the magnetic core in this embodiment. Hereinafter, the case where the magnetic core is a powder-pressed core will be described. That is, the method of obtaining the magnetic core by pressure molding will be described.

[0106] The soft magnetic metal powder and resin of this embodiment are mixed to obtain a resin mixture. The resin mixture may also be a granulated powder. In this case, soft magnetic metal powder other than the soft magnetic metal powder of this embodiment, and / or non-magnetic powders, may also be added to the resin mixture. Additionally, modifiers, preservatives, dispersants, etc., may be added. Then, the resin mixture is filled into a mold, pressurized, and then the resin is cured to obtain a magnetic core.

[0107] First, the soft magnetic metal powder and resin are mixed. By mixing the resin, a high-strength molded body can be easily obtained through molding. There are no particular restrictions on the type of resin. For example, phenolic resin and epoxy resin can be used. There are also no particular restrictions on the amount of resin added. If the total mass of all magnetic materials is set to 100 parts by mass, the total amount of the resin added can also be set to between 0.5 and 5.0 parts by mass.

[0108] Granulated powder is obtained by granulating a mixture of soft magnetic metal powder and resin. There are no particular limitations on the granulation method. For example, a mixer can also be used for granulation. There are no particular limitations on the particle size of the granulated powder.

[0109] The obtained granulated powder is pressurized to form a molded body. There are no particular limitations on the molding pressure. For example, the surface pressure can also be 98 MPa (0.1 t / cm²). 2 ) above 1960MPa (20t / cm 2 )the following.

[0110] Then, the resin contained in the molded body can be cured to obtain a magnetic core. There are no particular restrictions on the curing method, and heat treatment can also be performed under conditions that allow the resin used to cure.

[0111] The obtained magnetic core undergoes an oxide phase formation treatment. This treatment oxidizes the surface of the main particles within the magnetic core, forming an oxide phase. Soft magnetic metal particles closer to the core surface tend to form a thicker oxide phase, thus T1 is more likely to be larger than T2.

[0112] The method for treating oxide phase formation is described below.

[0113] First, seal the magnetic core and water into a sealed metal container. There are no particular restrictions on the amount of water added (sealed in). For example, it can be between 0.1 and 25.0 parts by weight relative to 100 parts by weight of the magnetic core.

[0114] Then, the sealed container is filled with gas. There are no particular restrictions on the method of filling the gas. For example, the interior of the sealed container can be depressurized once before being filled with gas and then pressurized. There are no particular restrictions on the type of gas. For example, compressed air, nitrogen, or argon can also be used. There are no particular restrictions on the pressure inside the sealed container. For example, it can be between 0.12 MPa and 0.70 MPa, or between 0.15 MPa and 0.50 MPa.

[0115] Then, by heating a sealed container, the surface of the particle body is oxidized to form an oxide phase. There are no particular restrictions on the holding temperature and holding time during heating. The holding temperature can be, for example, between 50°C and 300°C, or between 90°C and 180°C. The holding time can be, for example, between 0.5 minutes and 300 minutes.

[0116] There is a tendency that the higher the temperature, the more likely T1 will increase. There is also a tendency that the higher the pressure inside a closed container, the more likely T2 will increase.

[0117] There is a trend that the higher the temperature, the easier it is for Co / α to increase and P / α to decrease. Conversely, the longer the holding time, the easier it is for Co / α to decrease and P / α to increase.

[0118] There are no particular limitations on the methods for determining the thicknesses T1 and T2 of the oxide phase. For example, firstly, the cross-section of the magnetic core can be observed using a reflected electron image from TEM or SEM, and EDS can be used to confirm the formation of the oxide phase on the particle surface. Then, the thickness of the oxide phase can be calculated visually based on the reflected electron image. Alternatively, the measurement site through the oxide phase can be set using EDS and line analysis can be performed, with calculations based on the results of the line analysis.

[0119] There are no particular limitations on the methods for determining the Co / α and P / α of oxide phases. For example, EDS can be used to set the measurement sites through the oxide phase and perform line analysis, with calculations based on the results of the line analysis.

[0120] There are no particular restrictions on the number of specific particles used for SEM and EDS determination of T1, T2, Co / α, and P / α. To calculate each parameter with high accuracy, it is sufficient to measure each parameter from a sufficient number of specific particles.

[0121] For example, the thickness and composition of the oxide phase in more than 50 specific particles in the surface and central parts of the magnetic core can be measured and the parameters can be calculated.

[0122] For example, when the uniformity of the magnetic core is high, the thickness of the oxide phase in a specific particle contained in the surface portion can be set as T1. Similarly, when the uniformity of the magnetic core is high, the thickness of the oxide phase in a specific particle contained in the central portion can be set as T2. Furthermore, when the uniformity of the magnetic core is high, Co / α and P / α can be calculated based on the composition of the oxide phase in a specific particle contained in the surface portion.

[0123] There are no particular restrictions on the application of the magnetic core. For example, it can be suitably used as a magnetic core for inductors.

[0124] Furthermore, the aforementioned magnetic core or magnetic components using the aforementioned magnetic core can be suitably used in electronic devices.

[0125] In particular, the aforementioned magnetic core is suitable for applications requiring miniaturization and low profile because it easily improves voltage withstand characteristics while maintaining specific permeability. For example, it can be suitable for use in magnetic components such as inductors, transformers, and choke coils, or in electronic devices using these magnetic components.

[0126] (Second Implementation)

[0127] Hereinafter, the magnetic core of the second embodiment of this disclosure will be described using the accompanying drawings. Unless otherwise specified, matters are the same as in the first embodiment. Furthermore, unless otherwise specified, matters corresponding to the specific particles 11 of the first embodiment also correspond to the specific particles 111 of the second embodiment. Matters corresponding to the oxide phase 11a of the first embodiment also correspond to the oxide phase 111a of the second embodiment. Matters corresponding to the particle body 11b of the first embodiment also correspond to the particle body 111b of the second embodiment.

[0128] In the case of the magnetic core of this embodiment, resin may also be filled between the soft magnetic metal particles.

[0129] Moreover, such as Figure 4 As shown, the magnetic core of this embodiment includes soft magnetic metal particles 111 (hereinafter, sometimes referred to as specific particles 111) having an oxide phase 111a on their surface. In other words, the specific particles 111 include a particle body 111b and an oxide phase 111a covering the particle body 111b.

[0130] There is no particular limitation on the thickness of the oxide phase 111a in the specific particle 111. For example, the average thickness of the oxide phase 111a in the specific particle 111 may be 0.025 μm or more. Alternatively, soft magnetic metal particles with an average thickness of oxide phase 111a of less than 0.025 μm may not be considered as specific particles 111.

[0131] exist Figure 5A schematic diagram showing the cross-section of a specific particle 111 is provided below. Figure 5 The method for determining T3, T4, and T4 / T3 in the specific particle 111 shown will be explained.

[0132] like Figure 5 As shown, an inscribed circle 101 is determined that is inscribed within the surface of a specific particle 111 (the surface of the oxide phase 111a), and the center 101c of the inscribed circle 101 is also determined. The center 101c of this inscribed circle 101 is set as the center 101c of the specific particle 111. This inscribed circle 101 is the inscribed circle whose diameter is the largest.

[0133] Next, draw a straight line containing the center 101c of a specific particle 111. This straight line can be rotated 360°. For example... Figure 5 As shown, when drawing any straight line containing the center 101c of a specific particle 111, the straight line with the maximum thickness portion along which the length of the oxide phase 111a along that straight line is the largest is designated as the specific straight line 103. Figure 5 As shown, the length of the thickest part is set to T3.

[0134] The portion of the oxide phase located along a specific straight line 103, relative to the center 101c, on the opposite side from the maximum thickness portion, is designated as the anti-maximum thickness portion. For example... Figure 5 As shown, the length of the anti-maximum thickness portion is set to T4. The anti-maximum thickness portion may not exist in a specific particle 111. If the oxide phase cannot be confirmed by TEM or SEM observation, T4 is considered to be 0.

[0135] Furthermore, T4 / T3 can be calculated based on T3 and T4 as described above. The magnetic core of this embodiment includes specific particles 111 that satisfy 0 < T4 / T3 ≤ 0.98. It may also include specific particles 111 that satisfy 0 < T4 / T3 ≤ 0.90. In addition, regarding the magnetic core of this embodiment, the specific particles 111 included in the surface portion 3 described later may also satisfy 0 < T4 / T3 ≤ 0.98.

[0136] Furthermore, the average value of T4 / T3, obtained by calculating and averaging T4 / T3 among all the specific particles 111 contained in the magnetic core, can be 0 or more and 0.98 or less, or 0 or more and 0.90 or less. Alternatively, the average value of T4 / T3 can be 0.09 or more and 0.98 or less, or 0.09 or more and 0.90 or less.

[0137] The larger the T4 / T3 ratio, the easier it is to reduce the specific permeability and the easier it is to increase the withstand voltage.

[0138] There are no particular restrictions on T3; for example, T3 can be between 0.005 μm and 10.550 μm. There are also no particular restrictions on T4; for example, T4 can be between 0 and 10.339 μm.

[0139] The larger the T3, the easier it is to reduce the specific permeability and the easier it is to increase the withstand voltage. The larger the T4, the easier it is to reduce the specific permeability and the easier it is to increase the withstand voltage.

[0140] There is no particular limitation on the proportion of specific particles 111 on the cross-section of the magnetic core that satisfy 0 < T4 / T3 ≤ 0.98. For example, the ratio of the total area of ​​specific particles 111 on the cross-section that satisfy 0 < T4 / T3 ≤ 0.98 to the area of ​​the surface portion 3 of the magnetic core can also be more than 1% and less than 85%.

[0141] When the outermost surface of the magnetic core closest to the specific particle 111 is set as the specific surface 21a, such as Figure 5 As shown, the portion with the maximum thickness can also be closer to a specific surface 21a than the portion with the opposite maximum thickness.

[0142] The proportion of a specific particle closer to a specific surface 21a than the maximum thickness portion relative to all specific particles 111 contained in the magnetic core can also be more than 50% on a number basis.

[0143] Alternatively, cracks may form in the oxide phase 111a. For example, the cracks may extend from the surface of the oxide phase 111a to the surface of the particle body 111b, or they may stop inside the oxide phase 111a.

[0144] There is no particular limitation on the particle size of the specific particles 111. For example, it can be between 0.1 μm and 100 μm, measured in terms of the equivalent circular diameter on the cross-section of the magnetic core. Furthermore, there is no particular limitation on the average particle size of all the specific particles 111 contained in the magnetic core. For example, it can be between 0.1 μm and 100 μm, measured in terms of the equivalent circular diameter on the cross-section of the magnetic core. Moreover, the average particle size described above is based on the number of particles.

[0145] The equivalent circle diameter of a specific particle 111 is the diameter of a circle having the same cross-sectional area as that specific particle 111.

[0146] Furthermore, the magnetic core of this embodiment differs from the magnetic core of the first embodiment, and may also have a surface portion 3 at a distance of 50 μm or less from the outermost surface and a central portion 4 at a distance of more than 50 μm from the outermost surface.

[0147] Furthermore, the magnetic core of this embodiment may also contain specific particles 111 at least on the surface portion 3.

[0148] In this embodiment, the magnetic core may have an average thickness of the oxide phase in the specific particles 111 contained in the surface portion 3 set to T5 [μm], and an average thickness of the oxide phase in the specific particles 111 contained in the central portion set to T6 [μm], where T5 ≥ 0.050, T6 ≤ 0.50, and T5 > T6.

[0149] There is no specific upper limit for T5. For example, it can be below 10.0 or below 5.0. More specifically, it can be 0.050≤T5≤10.0 or 0.20≤T5≤5.0. There is no specific lower limit for T6. For example, it can be above 0.000. More specifically, it can be 0.000≤T6≤0.50.

[0150] It can be either T5-T6≥0.001 or T5-T6≥0.01.

[0151] The average thickness T5 of the oxide phase 111a in the specific particles 111 contained in the surface portion 3 is obtained by averaging the average thickness of the oxide phase in all the specific particles 111 contained in the surface portion 3. The average thickness T6 of the oxide phase 111a in the specific particles 111 contained in the central portion is obtained by averaging the average thickness of the oxide phase 111a in all the specific particles 111 contained in the central portion.

[0152] When a specific particle 111 is repeatedly positioned along the boundary line between the surface portion 3 and the central portion 4, the specific particle 111 is regarded as a specific particle contained in the surface portion 3.

[0153] That is, the magnetic core of this embodiment may also include soft magnetic metal particles with an oxide phase that is thicker than that of the central portion 4 in the surface portion 3. As a result, it is easy to obtain a magnetic core that can easily improve voltage withstand while maintaining a suitable specific permeability.

[0154] If the surface portion 3 does not contain specific particles 111, then T5 is considered to be 0.000. If the central portion does not contain specific particles 111, then T6 is considered to be 0.000.

[0155] Co / α, calculated based on the atomic number, can be between 0.10 and 1.00, or between 0.18 and 0.70.

[0156] The method for manufacturing the magnetic core in the second embodiment is the same as that in the first embodiment, except for the following points.

[0157] The magnetic core obtained by the same method as in the first embodiment is subjected to an oxide phase formation process. Through this process, the surface of the main particle body contained in the magnetic core is oxidized to form an oxide phase. The closer the soft magnetic metal particles are to the surface of the magnetic core, the easier it is for a thick oxide phase to form; therefore, T5 is more likely to be larger than T6.

[0158] The method for treating oxide phase formation is described below.

[0159] First, seal the magnetic core and water into a sealed metal container. There are no particular restrictions on the amount of water added (sealed in). For example, it can be 0.1 to 40.0 parts by weight or 0.5 to 30.0 parts by weight relative to 100 parts by weight of the magnetic core.

[0160] There are no particular restrictions on the holding temperature and holding time when heating a sealed container. The holding temperature can be, for example, between 50°C and 250°C, or between 90°C and 200°C. The holding time can be, for example, between 0.5 minutes and 300 minutes.

[0161] There is a trend that the higher the temperature, the more likely T3 and T4 will increase. There is also a trend that the more water is added, the more likely T4 / T3 will increase.

[0162] There is a tendency that the higher the temperature, the more likely T5 will increase. There is also a tendency that the higher the pressure inside a closed container, the more likely T6 will increase.

[0163] There are no particular limitations on the methods for determining the thicknesses T3 and T4 of the oxide phase and calculating T4 / T3. For example, firstly, the cross-section of the magnetic core can be observed using a TEM or SEM electron reflectance image, and EDS can be used to confirm the formation of the oxide phase on the particle surface. Then, the thicknesses T3 and T4 of the oxide phase can be calculated visually based on the electron reflectance image, and T4 / T3 can be calculated. Alternatively, the measurement site through the oxide phase can be set using EDS and line analysis can be performed; T3 and T4 can be calculated based on the line analysis results, and T4 / T3 can be calculated.

[0164] When using SEM or EDS to calculate the average T4 / T3 of the entire magnetic core, there is no particular limitation on the number of specific particles from which T4 / T3 is measured. To calculate T4 / T3 with high accuracy, it is sufficient to measure T4 / T3 for a sufficient number of specific particles. For example, when the magnetic core has high uniformity, the T4 / T3 calculated from a single particle can be taken as the average T4 / T3 of the entire magnetic core.

[0165] There are no particular limitations on the methods for determining the thicknesses T5 and T6 of the oxide phase. For example, firstly, the cross-section of the magnetic core can be observed using a reflected electron image from a SEM, and EDS can be used to confirm the formation of the oxide phase on the particle surface. Then, the thickness of the oxide phase can be calculated visually based on the reflected electron image. Alternatively, the measurement area through the oxide phase can be set using EDS and line analysis can be performed, with calculations based on the results of the line analysis.

[0166] There is no particular limitation on the number of specific particles used to determine T5 and T6 using SEM and EDS. To calculate T5 and T6 with high accuracy, it is sufficient to measure T5 and T6 for a sufficient number of specific particles. For example, if the core has high uniformity, the thickness of the oxide phase in a specific particle on the surface can be set as T5. Similarly, if the core has high uniformity, the thickness of the oxide phase in a specific particle in the central portion can be set as T6.

[0167] Example

[0168] The present disclosure will now be described in detail based on the embodiments.

[0169] (Experimental Example 1)

[0170] Pure Fe metal was prepared as a master alloy. The pure Fe metal was heated to melt it, producing a molten metal at 1600°C. Then, a soft magnetic metal powder composed of pure Fe metal was produced by gas atomization. Specifically, while the molten master alloy was being discharged from the dripping molten metal outlet towards the cooling section (cooling water) within the chamber, high-pressure gas was injected towards the discharged dripping molten metal. The pressure of the high-pressure gas was set to 5 MPa, and the ejection rate of the molten metal was set to 6 kg / min. Then, sieving and classification were performed to obtain a final soft magnetic metal powder (pure iron powder in Experimental Example 1) with an average particle size of 25 μm.

[0171] ICP analysis confirmed that the composition of the master alloy and the soft magnetic metal powder were largely consistent. Furthermore, X-ray diffraction was performed on the soft magnetic metal powder, and the amorphization rate X was calculated using the method described above. A structure with an amorphization rate X of 85% or higher was considered to have an amorphous structure. A structure with an amorphization rate X of less than 85% and an average crystallite diameter of less than 100 nm was considered to have a nanocrystalline structure. A structure with an amorphization rate X of less than 85% and an average crystallite diameter greater than 100 nm was considered to have a crystalline structure. In Experimental Example 1, all soft magnetic metal powders were confirmed to have a crystalline structure. The average particle size of the soft magnetic metal powder was confirmed and calculated using SEM.

[0172] Next, a resin mixture is obtained by mixing soft magnetic metal powder (pure iron powder) and epoxy resin. The amount of epoxy resin added to the resin mixture (resin amount) is set to 3 parts by mass relative to 100 parts by mass of soft magnetic metal powder.

[0173] Next, a ring-shaped molded body is obtained by filling the resin mixture into a mold and applying pressure. The molding pressure is controlled at this time so that the specific permeability (μ) of the magnetic core is 30. The obtained molded body is then heated at 180°C for 60 minutes to cure the epoxy resin and obtain a ring-shaped magnetic core. The outer diameter of the magnetic core is 11 mm, the inner diameter is 6.5 mm, and the thickness is 2.5 mm.

[0174] Next, oxide phase formation treatment was performed on the toroidal magnetic cores other than sample number 1. First, the magnetic cores and water were sealed in a metal container. Then, the inside of the sealed container was depressurized once and pressurized with nitrogen. Then, heating was performed. The heating temperature and the pressure inside the sealed container are shown in Table 1. The amount of water added (sealed in) was set to 15 parts by mass relative to 100 parts by mass of the magnetic core. Then, it was maintained at the temperature shown in Table 1 for 60 minutes.

[0175] Alternatively, a rectangular parallelepiped shape is obtained by filling the resin mixture into another mold and applying pressure. The molding pressure and heat treatment conditions are set to be the same as those for the toroidal magnetic core described above. The bottom surface of the magnetic core is a square of 4.0 mm × 4.0 mm, and the height is 1.0 mm.

[0176] Next, an oxide phase formation treatment was performed on the cuboid-shaped magnetic cores other than sample number 1. The conditions for the oxide phase formation treatment were set to be the same as those for the toroidal-shaped magnetic cores described above.

[0177] (Average thickness of oxide phase)

[0178] The cross-section of the obtained annular magnetic core was observed, and T1 and T2 were measured. First, the cross-section of the magnetic core was observed using SEM. At this time, the observation magnification was set to a low magnification, specifically, a magnification lower than that used to measure the thickness of the oxide phase described later. It was confirmed whether the specific particles found through observation were contained in the surface portion or the central portion. In Experimental Examples 1 to 8, when we say "surface portion," we mean the surface portion of the first embodiment; when we say "central portion," we mean the central portion of the first embodiment; and when we say "specific particles," we mean the specific particles of the first embodiment.

[0179] Subsequently, in order to determine the thickness of the oxide phase in the specific particle, the magnification and the position of the observation range were appropriately adjusted to allow for observation of the entire particle. The magnification was appropriately adjusted within the range of 1000x to 50000x.

[0180] Repeat the above-described methods for identifying specific particles and measuring the thickness of the oxide phase. Measure the thickness of the oxide phase in 50 or more specific particles contained in the surface portion of the magnetic core, average the results, and calculate T1. Measure the thickness of the oxide phase in 50 or more specific particles contained in the central portion of the magnetic core, average the results, and calculate T2.

[0181] In sample number 1, where no oxide phase formation treatment was performed, the surface portion of the magnetic core did not contain specific particles. As described above, when the surface portion of the magnetic core does not contain specific particles, T1 is considered to be 0.000.

[0182] Furthermore, if no more than 50 specific particles are identified on the surface portion, T1 is calculated based on the thickness of the oxide phase in all specific particles identified on the surface portion. If no more than 50 specific particles are identified in the central portion, T2 is calculated based on the thickness of the oxide phase in all specific particles identified in the central portion. That is, T1 is calculated based on the thickness of the oxide phase in one or more specific particles on the surface portion, and T2 is calculated based on the thickness of the oxide phase in one or more specific particles in the central portion.

[0183] In sample number 1 (where no oxide phase formation treatment was performed), samples 2-9 (where the pressure inside the sealed container was less than 0.15 MPa), and sample number 10 (where both the temperature and pressure during the oxide phase formation treatment were slightly lower), the central portion of the magnetic core did not contain specific particles. As described above, when the central portion of the magnetic core does not contain specific particles, T2 is considered to be 0.000.

[0184] (Specific permeability)

[0185] The specific permeability of the obtained toroidal magnetic core was measured. First, polyurethane wire (UEW wire) was wound around the toroidal magnetic core. Then, the specific permeability of the core was measured using an LCR meter (Agilent Technologies: 4284A) at a measurement frequency of 1 MHz. In Table 1, the specific permeability is rounded to the second decimal place. Therefore, even if the specific permeability listed in Table 1 is the same, the rate of decrease in specific permeability may sometimes differ.

[0186] For each sample, the rate of reduction in specific permeability was calculated relative to a comparative example (sample number 1 in Experimental Example 1) subjected to the same conditions, except that no oxide phase formation treatment was performed. The results are shown in the respective tables. Specific permeability is considered good if the rate of reduction is 15.0% or less, and particularly good if it is 10.0% or less.

[0187] (Voltage withstand)

[0188] The withstand voltage of the obtained cuboid-shaped magnetic core was measured. First, one of the two 4.0mm × 4.0mm square faces of the cuboid-shaped magnetic core was selected. Next, terminal electrodes with a width of 1.3mm were placed at both ends of the selected face. The distance between the terminal electrodes was 1.4mm.

[0189] Next, a voltage is applied between the terminal electrodes, and the voltage when a current of 2mA flows is measured as the withstand voltage. In Table 1, the withstand voltage is rounded to the first decimal place. Therefore, even if the withstand voltages listed in Table 1 are the same, the rate of increase in withstand voltage may sometimes differ.

[0190] For each sample, the improvement rate of withstand voltage relative to the comparative example (sample number 1 in Experimental Example 1) performed under the same conditions, except that no oxide phase formation treatment was performed, was calculated. The results are shown in the respective tables. When the improvement rate of withstand voltage is 10.0% or more, the withstand voltage is set as good; when it is 20.0% or more, the withstand voltage is set as particularly good.

[0191] Table 1

[0192]

[0193] According to Table 1, the T1 and T2 of samples 3-29 and 31-33, which underwent oxide phase formation treatment under preferred conditions, are within the specified range. As a result, compared with sample 1, which was subjected to the same conditions except that oxide phase formation treatment was not performed, the withstand voltage can be improved while suppressing the decrease in specific permeability.

[0194] In all the embodiments described later in Experimental Examples 2 to 8, the specific particles contained in the magnetic cores were found to be more than 50% consistent in composition based on atomic number, in both the oxide phase and the particle body, without considering oxygen and carbon.

[0195] In all the embodiments described in Experimental Examples 2 to 8, the area ratio of specific particles in the surface portion of the cross-section of the magnetic core was confirmed to be more than 1% and less than 85%.

[0196] The pressure during the oxide phase formation treatment was too low, resulting in a small T1 for sample number 2. As a result, compared to sample number 1, neither the specific permeability nor the withstand voltage changed.

[0197] The temperature and pressure during the oxide phase formation treatment of sample number 30 were too high, resulting in an excessively large T2. As a result, compared with sample number 1, which was subjected to the same conditions except for the absence of oxide phase formation treatment, the specific permeability was significantly reduced.

[0198] The T2 of sample number 34, which underwent a high oxide phase formation treatment, was excessively large. As a result, compared with sample number 1, which was subjected to the same conditions except for the absence of oxide phase formation treatment, the specific permeability was significantly reduced.

[0199] (Experimental Example 2)

[0200] The composition and microstructure of the soft magnetic metal powder were modified for samples numbered 1, 14, and 15.

[0201] The composition of the soft magnetic metal powder is changed by altering the composition of the master alloy. The temperature of the molten metal is appropriately adjusted within the range of 1200℃ to 1600℃ according to the composition of the molten metal.

[0202] The composition and results of the soft magnetic metal powders are shown in Tables 2A to 2C. The composition is expressed on an atomic number basis. In addition, the specific permeability and withstand voltage are omitted in Experimental Examples 2 to 8, and only the rate of decrease in specific permeability and the rate of increase in withstand voltage relative to the sample with the same composition that has not undergone oxide phase formation treatment are recorded.

[0203] XRD confirmed that all powder samples numbered 35–52, 59–64, and 77–91 had a crystalline structure.

[0204] XRD confirmed that all powder samples numbered 53–55, 65–70, 92–97, and 104–109 had an amorphous structure.

[0205] Powders with sample numbers 56–58, 71–76, and 98–103 were prepared by gas atomization and then subjected to heat treatment to precipitate nanocrystals with a particle size of less than 30 nm. Specifically, the heat treatment was carried out at 400–650 °C for 10–60 minutes. XRD confirmed that all powders with sample numbers 56–58, 71–76, and 98–103 had a structure composed of nanocrystals.

[0206] Table 2A

[0207]

[0208] Table 2B

[0209]

[0210] Table 2C

[0211]

[0212] According to Tables 2A to 2C, even when the type of powder and / or the fine structure were changed from Experimental Example 1, the same trend as in Experimental Example 1 was observed.

[0213] (Experimental Example 3)

[0214] The average particle size of the soft magnetic metal powder was varied for samples 1, 14, and 15 of Experimental Example 1. Furthermore, the processing temperature during oxide phase formation was changed to reduce the average particle size of the soft magnetic metal powder, resulting in smaller T1 and T2 values. Other aspects were performed under the same conditions as in Experimental Example 1. The results are shown in Table 3.

[0215] Table 3

[0216]

[0217] According to Table 3, even when the average particle size, T1, and T2 of the powder were changed from those in Experimental Example 1, the same trend as in Experimental Example 1 was observed.

[0218] (Experimental Example 4)

[0219] The soft magnetic metal powders of samples 1, 14, and 15 were subjected to a coating formation process using a mechanical fusion apparatus (manufactured by Hosokawa Micron Co., Ltd.: AMS-Lab) to form a P-Zn-Al-O oxide glass coating on the surface of the soft magnetic metal powders. The coating thickness was approximately 10 nm. For other aspects, samples 125–127 were treated similarly to those in Experimental Example 1. The results are shown in Table 4.

[0220] For samples 125–127, the type of coating on the soft magnetic metal powder was varied. The types of coatings are shown in Table 4. When the coating type was a P-Zn-Al-Na-O oxide glass coating, a P-Zn-Al-Ca-O oxide glass coating, a Bi-Zn-B-Si-O oxide glass coating, or a Ba-Zn-B-Si-Al-O oxide glass coating, the procedure was the same as for samples 125–127. When the coating type was phosphate coating, the soft magnetic metal powders of samples 1, 14, and 15 were appropriately phosphate treated. When the powder coating type was SiO2 coating, the soft magnetic metal powders of samples 1, 14, and 15 were appropriately silane coupled. The results are shown in Table 4.

[0221] Table 4

[0222]

[0223] According to Table 4, even when the type of coating of the soft magnetic metal powder is changed, the same trend as in Experimental Example 1 is observed.

[0224] Furthermore, in the embodiments in Table 4, in the specific particles obtained by using soft magnetic metal powder with a coating and performing an oxide phase formation process, the boundary between the coating and the oxide phase formed by the oxide phase formation process was not identified.

[0225] (Experimental Example 5)

[0226] The soft magnetic metal powder with an average particle size of 25 μm used in Experimental Example 1 was designated as powder A. The soft magnetic metal powder prepared under the same conditions as powder A, except that the average particle size was set to 3.0 μm, was designated as powder B. The soft magnetic metal powder prepared under the same conditions as powder A, except that the average particle size was set to 0.8 μm, was designated as powder C. Then, powders A to C were mixed according to the proportions shown in Table 5 to obtain a mixed powder.

[0227] Except for the use of a mixed powder, the experiment was conducted under the same conditions as for test samples 1 and 14 of Experimental Example 1. The results are shown in Table 5.

[0228] Table 5

[0229]

[0230] According to Table 5, even when multiple powders with different average particle sizes are mixed, the same trend as in Experimental Example 1 is observed.

[0231] (Experimental Example 6)

[0232] For samples 148 and 149, the same conditions as in Experimental Example 5 were applied, except that the composition of any one or more of powders A through C was changed to the composition shown in Table 6A. Furthermore, for powder A of samples 158, 159, 164, and 165, powder B of samples 170, 171, 176, and 177, and powder C of samples 182, 183, 188, and 189, after preparation by gas atomization, heat treatment was performed to precipitate nanocrystals with a crystal size of less than 30 nm. Specifically, the heat treatment was performed at 400–650 °C for 10–60 minutes. Then, XRD was used to confirm that each powder possessed the fine structure shown in Table 6A. The results are shown in Tables 6A and 6B.

[0233] Table 6A

[0234]

[0235] Table 6B

[0236]

[0237] According to Tables 6A and 6B, even with changes in the composition and fine structure of the powder, the same trend as in Experimental Example 5 was observed.

[0238] (Experiment Example 7)

[0239] For samples 1 and 14, a portion of the powder was replaced with powder prepared under the same conditions except for the average particle size of 1.0 μm. Samples 196–199 were prepared under the same conditions as in Experimental Example 3, except for this difference. For samples 119 and 121, a portion of the powder was replaced with powder prepared under the same conditions except for the average particle size of 1.0 μm. Samples 200–203 were prepared under the same conditions as in Experimental Example 3, except for this difference. For samples 116 and 118, a portion of the powder was replaced with powder prepared under the same conditions except for the average particle size of 1.0 μm. Samples 204–207 were prepared under the same conditions as in Experimental Example 3, except for this difference. The results are shown in Table 7.

[0240] Table 7

[0241]

[0242] According to Table 7, even when multiple powders with different average particle sizes are mixed, the same trend as in Experimental Example 3 is observed.

[0243] (Experimental Example 8)

[0244] For sample number 14 in Experimental Example 1, the processing temperature and time during the oxide phase formation treatment were changed without substantially altering T1 and T2, resulting in samples 301 and 302. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 8.

[0245] For sample number 78 in Experimental Example 2, the treatment temperature and time during oxide formation were changed without substantially altering T1 and T2, resulting in samples 303 and 304. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 8.

[0246] For sample number 96 in Experimental Example 2, the treatment temperature and time during oxide formation were changed without substantially altering T1 and T2, resulting in samples 305 to 312. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 8.

[0247] For sample number 105 in Experimental Example 2, the treatment temperature and time during oxide formation were changed without substantially altering T1 and T2, resulting in samples 313 to 320. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 8.

[0248] For sample number 108 in Experimental Example 2, the treatment temperature and time during oxide formation were changed without substantially altering T1 and T2, resulting in samples 321 to 328. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 8.

[0249] Table 8

[0250]

[0251] According to Table 8, even when the Co / α and P / α in the oxide phase are changed without substantially changing T1 and T2, the same trend as in Experimental Examples 1 and 2 is observed.

[0252] (Experiment Example 9)

[0253] Pure Fe metal was prepared as a master alloy. The pure Fe metal was heated to melt, and after reaching a molten state at 1600°C (molten metal), a soft magnetic metal powder composed of pure Fe metal was produced by gas atomization. Specifically, while discharging the molten master alloy from the dripping molten metal outlet towards the cooling section (cooling water) within the chamber, high-pressure gas was injected towards the discharged dripping molten metal. The pressure of the high-pressure gas was set to 5 MPa, and the ejection rate of the molten metal was set to 6 kg / min. Then, sieving and classification were performed to obtain a final soft magnetic metal powder (pure iron powder in Experimental Example 9) with an average particle size of 25 μm.

[0254] ICP analysis confirmed that the composition of the master alloy and the soft magnetic metal powder were largely consistent. Furthermore, X-ray diffraction was performed on the soft magnetic metal powder, and the amorphization rate X was calculated using the methods described above. When the amorphization rate X was 85% or higher, it was considered to have an amorphous structure. When the amorphization rate X was less than 85% and the average crystallite diameter was less than 100 nm, it was considered to have a nanocrystalline structure. When the amorphization rate X was less than 85% and the average crystallite diameter was greater than 100 nm, it was considered to have a crystalline structure. In Experimental Example 9, it was confirmed that all the soft magnetic metal powder had a crystalline structure. The average particle size of the soft magnetic metal powder was confirmed and calculated using SEM.

[0255] Next, a resin mixture is obtained by mixing soft magnetic metal powder (pure iron powder) and epoxy resin. The amount of epoxy resin added to the resin mixture (resin amount) is set to 3 parts by mass relative to 100 parts by mass of soft magnetic metal powder.

[0256] Next, a ring-shaped molded body is obtained by filling the resin mixture into a mold and applying pressure. The molding pressure is controlled at this time so that the specific permeability (μ) of the magnetic core is 30. The obtained molded body is then heated at 180°C for 60 minutes to cure the epoxy resin, resulting in a ring-shaped magnetic core. The outer diameter of the magnetic core is 11 mm, the inner diameter is 6.5 mm, and the thickness is 2.5 mm.

[0257] Next, oxide phase formation treatment was performed on the toroidal magnetic cores other than sample number 401. First, the magnetic core and water were sealed in a metal container. Then, the inside of the sealed container was depressurized once and pressurized with nitrogen. Then, heating was performed. Table 9 shows the amount of water added per 100 parts by mass of the magnetic core (sealing amount) and the temperature inside the sealed container. In sample number 402, the amount of water added was set to 0. That is, water was not sealed in the sealed container. In samples 402 to 444, the pressure of the atmosphere inside the sealed container was set to 0.20 MPa. Then, the temperature was maintained for 60 minutes at the temperature listed in Table 9.

[0258] Alternatively, a rectangular parallelepiped shape is obtained by filling the resin mixture into another mold and applying pressure. The molding pressure and heat treatment conditions are set to be the same as those for the toroidal magnetic core described above. The bottom surface of the magnetic core is a square of 4.0 mm × 4.0 mm, and the height is 1.0 mm.

[0259] Next, an oxide phase formation treatment was performed on the cuboid-shaped magnetic cores other than sample number 401. The conditions for the oxide phase formation treatment were set to be the same as those for the toroidal-shaped magnetic cores described above.

[0260] (Average thickness of oxide phase)

[0261] The cross-section of the obtained annular magnetic core was observed, and T3 and T4 were measured and T4 / T3 was calculated. First, the cross-section of the magnetic core was observed using SEM. At this time, the observation magnification was set to a low magnification, specifically, a magnification lower than that used to measure the thickness of the oxide phase described later. Through observation, specific particles of oxide phase with a maximum thickness of 0.005 μm or more were found on the surface of the magnetic core. Hereinafter, unless otherwise specified, it is assumed that the specific particles have an oxide phase with a maximum thickness of 0.005 μm or more on the surface. In Experimental Examples 9 to 16, when referring to the surface portion, it refers to the surface portion of the second embodiment; when referring to the central portion, it refers to the central portion of the second embodiment; and when referring to specific particles, it refers to the specific particles of the second embodiment.

[0262] Subsequently, in order to determine the T3 and T4 in the specific particles found, the magnification and the position of the observation range were appropriately adjusted to allow for observation of the entire specific particle. The magnification was appropriately adjusted within the range of 1000x to 50000x.

[0263] Next, T3 and T4 were measured for more than 50 specific particles, and T4 / T3 was calculated. Then, based on the above measurement and calculation results, the average value of T3, the average value of T4, and the average value of T4 / T3 were calculated. The obtained values ​​were set as the average value of T3, the average value of T4, and the average value of T4 / T3 for the entire surface portion of the magnetic core. The average value of T3, the average value of T4, and the average value of T4 / T3 are shown in Table 9.

[0264] In addition, if no more than 50 specific particles are identified on the surface, the average value of T3, the average value of T4, and the average value of T4 / T3 are calculated based on the thickness of the oxide phase in all specific particles identified on the surface.

[0265] In sample number 401, which did not undergo oxide phase formation treatment, and sample number 402, which did not have water added during oxide phase formation treatment, the magnetic core did not contain specific particles.

[0266] In samples 401 and 402, T3 = T4 = 0.000 is considered to be present in all soft magnetic metal particles.

[0267] (Specific permeability)

[0268] The specific permeability of the obtained toroidal magnetic core was measured. First, polyurethane wire (UEW wire) was wound around the toroidal magnetic core. Then, the specific permeability of the core was measured using an LCR meter (Agilent Technologies: 4284A) at a measurement frequency of 1 MHz. In Table 9, the specific permeability is rounded to the second decimal place. Therefore, even if the specific permeability listed in Table 9 are the same, the rate of decrease in specific permeability may sometimes differ.

[0269] For each sample, the rate of reduction in specific permeability was calculated relative to a comparative example (sample number 401 in Experimental Example 9) subjected to the same conditions except for the absence of oxide phase formation treatment. The results are shown in the respective tables. Specific permeability is considered good if the rate of reduction is 15.0% or less, and particularly good if it is 10.0% or less.

[0270] (Voltage withstand)

[0271] The withstand voltage of the obtained cuboid-shaped magnetic core was measured. First, one of the two 4.0mm × 4.0mm square faces of the cuboid-shaped magnetic core was selected. Next, terminal electrodes with a width of 1.3mm were placed at both ends of the selected face. The distance between the terminal electrodes was 1.4mm.

[0272] Next, a voltage is applied between the terminal electrodes, and the voltage when a current of 2mA flows is measured as the withstand voltage. In Table 9, the withstand voltage is rounded to the first decimal place. Therefore, even if the withstand voltages listed in Table 9 are the same, the rate of increase in withstand voltage may sometimes differ.

[0273] For each sample, the improvement rate of withstand voltage was calculated relative to the comparative example (sample number 401 in Experimental Example 9) performed under the same conditions, except that no oxide phase formation treatment was performed. The results are shown in the respective tables. When the improvement rate of withstand voltage is 10.0% or more, the withstand voltage is set as good; when it is 20.0% or more, the withstand voltage is set as particularly good.

[0274] Table 9

[0275]

[0276] According to Table 9, the T4 / T3 of samples 403 to 443, which underwent oxide phase formation treatment under preferred conditions, were within the specified range. As a result, compared with sample 401, which was performed under the same conditions except that no oxide phase formation treatment was performed, the withstand voltage was improved while suppressing the decrease in magnetic permeability.

[0277] Sample 402, which did not have water added during the oxide phase formation treatment, similarly failed to form an oxide phase, just like sample 401. As a result, its specific permeability and withstand voltage remained unchanged compared to sample 401.

[0278] The T4 / T3 ratio of sample 444, which underwent oxide phase formation treatment at a high temperature and with a large amount of water added, was excessively high. As a result, the specific permeability was significantly reduced compared to sample 401, which was treated under the same conditions except for the absence of oxide phase formation treatment.

[0279] (Experimental Example 10)

[0280] The composition and microstructure of the soft magnetic metal powder were modified for samples 401, 433, and 437 in Experimental Example 9.

[0281] The composition of the soft magnetic metal powder is changed by altering the composition of the master alloy. The temperature of the molten metal is appropriately adjusted within the range of 1200℃ to 1600℃ according to the composition of the molten metal.

[0282] The composition and results of the soft magnetic metal powders are shown in Tables 10A to 10C. The composition is expressed on an atomic number basis. Furthermore, in the experimental examples from Experimental Example 10 onwards, the specific permeability and withstand voltage are omitted, and only the rate of decrease in specific permeability and the rate of increase in withstand voltage relative to the sample with the same composition that has not undergone oxide phase formation treatment are recorded.

[0283] XRD confirmed that all powder samples numbered 445–462, 469–474, and 487–501 had a crystalline structure.

[0284] XRD confirmed that all powder samples numbered 463–465, 475–480, 502–507, and 514–519 had an amorphous structure.

[0285] Powders with sample numbers 466–468, 481–486, and 508–513 were prepared by gas atomization and then subjected to heat treatment to precipitate nanocrystals with a particle size of less than 30 nm. Specifically, the heat treatment was carried out at 400–650 °C for 10–60 minutes. XRD confirmed that all powders with sample numbers 466–468, 481–486, and 508–513 had a structure composed of nanocrystals.

[0286] Table 10A

[0287]

[0288] Table 10B

[0289]

[0290] Table 10C

[0291]

[0292] According to Tables 10A to 10C, even when the type of powder and / or fine structure were changed from Experimental Example 9, the same trend as in Experimental Example 9 was observed.

[0293] (Experimental Example 11)

[0294] The average particle size of the soft magnetic metal powder was varied for samples 401, 433, and 437 of Experimental Example 9. Furthermore, the processing temperature during oxide phase formation was changed to reduce the average particle size of the soft magnetic metal powder, resulting in smaller T3 and T4 values. Other aspects were performed under the same conditions as in Experimental Example 9. The results are shown in Table 11.

[0295] Table 11

[0296]

[0297] According to Table 11, even when the average particle size of the powder was changed from Experimental Example 9, the same trend as in Experimental Example 9 was observed.

[0298] (Experimental Example 12)

[0299] The soft magnetic metal powders, samples 401, 433, and 437, were subjected to a coating formation process using a mechanical fusion apparatus (manufactured by Hosokawa Micron Co., Ltd.: AMS-Lab) to form a P-Zn-Al-O oxide glass coating on the surface of the soft magnetic metal powders. The coating thickness was approximately 3 nm. For other aspects, samples 535–537 were treated similarly to those in Experimental Example 9. The results are shown in Table 12.

[0300] The type of coating on the soft magnetic metal powder was varied for each of the samples numbered 535 to 537. The types of coatings are shown in Table 12. When the coating type was a P-Zn-Al-Na-O oxide glass coating, a P-Zn-Al-Ca-O oxide glass coating, a Bi-Zn-B-Si-O oxide glass coating, or a Ba-Zn-B-Si-Al-O oxide glass coating, the procedure was the same as for samples 535 to 537. When the coating type was a phosphate coating, the soft magnetic metal powders of samples 401, 433, and 437 were appropriately subjected to phosphate treatment. When the coating type was a SiO2 coating, the soft magnetic metal powders of samples 401, 433, and 437 were appropriately subjected to silane coupling treatment. The results are shown in Table 12.

[0301] Table 12

[0302]

[0303] According to Table 12, even when the type of coating of the soft magnetic metal powder was changed, the same trend as in Experimental Example 9 was observed. Furthermore, in the case where only the coating was formed without oxide phase formation treatment, no specific particles with an average oxide phase thickness of 0.005 μm or more were present in the magnetic core. This is because, as mentioned above, the coating thickness was approximately 3 nm (0.003 μm). Regarding the case where oxide phase formation treatment was not performed, for convenience, in Table 12, T3 = T4 = 0.000.

[0304] Furthermore, in the embodiments in Table 12, in the specific particles obtained by using soft magnetic metal powder with a coating and performing an oxide phase formation process, the boundary between the coating and the oxide phase formed by the oxide phase formation process was not identified.

[0305] (Experimental Example 13)

[0306] The soft magnetic metal powder with an average particle size of 25 μm used in Experimental Example 9 was designated as powder D. The soft magnetic metal powder prepared under the same conditions as powder D, except that the average particle size was set to 3.0 μm, was designated as powder E. The soft magnetic metal powder prepared under the same conditions as powder D, except that the average particle size was set to 0.8 μm, was designated as powder F. Then, powders D to F were mixed according to the proportions shown in Table 13 to obtain a mixed powder.

[0307] Except for the use of a mixed powder, the experiment was conducted under the same conditions as for test samples 401 and 437 of Experimental Example 9. The results are shown in Table 13.

[0308] Table 13

[0309]

[0310] According to Table 13, even when multiple powders with different average particle sizes are mixed, the same trend as in Experimental Example 9 is observed.

[0311] (Experimental Example 14)

[0312] For samples 558 and 559, the same conditions as in Experimental Example 13 were applied, except that the composition of any one or more of powders D through F was changed to the composition shown in Table 14A. Furthermore, for samples 568, 569, 574, 575, powder D, powder E (samples 580, 581, 586, 587), and powder F (samples 592, 593, 598, 599), after preparation by gas atomization, heat treatment was performed to precipitate nanocrystals with a crystal size of 30 nm or less. Specifically, the heat treatment was performed at 400–650 °C for 10–60 minutes. Moreover, XRD confirmed that each powder possessed the fine structure shown in Table 14A. The results are shown in Tables 14A and 14B.

[0313] Table 14A

[0314]

[0315] Table 14B

[0316]

[0317] According to Tables 14A and 14B, even with changes in the composition and fine structure of the powder, the same trend as in Experimental Example 13 was observed.

[0318] (Experimental Example 15)

[0319] For samples 401 and 437, a portion of the powder was replaced with powder prepared under the same conditions except for the average particle size of 1.0 μm. Samples 606–609 were prepared under the same conditions as in Experimental Example 11, except for this difference. For samples 529 and 531, a portion of the powder was replaced with powder prepared under the same conditions except for the average particle size of 1.0 μm. Samples 610–613 were prepared under the same conditions as in Experimental Example 11, except for this difference. For samples 526 and 528, a portion of the powder was replaced with powder prepared under the same conditions except for the average particle size of 1.0 μm. Samples 614–617 were prepared under the same conditions as in Experimental Example 11, except for this difference. The results are shown in Table 15.

[0320] Table 15

[0321]

[0322] According to Table 15, even when multiple powders with different average particle sizes are mixed, the same trend as in Experimental Example 11 is observed.

[0323] (Experimental Example 16)

[0324] For sample number 437 in Experimental Example 9, the treatment temperature and time during oxide formation were changed without substantially altering T3 and T4, resulting in samples 701 and 702. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 16.

[0325] For sample 489 in Experimental Example 10, samples 703 and 704 were performed by changing the treatment temperature and time during oxide formation treatment without substantially altering T3 and T4. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 16.

[0326] For sample number 507 in Experimental Example 10, the treatment temperature and time during oxide formation were changed without substantially altering T3 and T4, resulting in samples 705 to 712. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 16.

[0327] For sample number 516 in Experimental Example 10, the treatment temperature and time during oxide formation were changed without substantially altering T3 and T4, resulting in samples 713 to 720. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 16.

[0328] For sample 519 of Experimental Example 10, the treatment temperature and time during oxide formation were changed without substantially altering T3 and T4, resulting in samples 721 to 728. Furthermore, the Co / α and P / α ratios in the oxide phase of each sample were determined using SEM-EDS. The results are shown in Table 16.

[0329] Table 16

[0330]

[0331] According to Table 16, even when the Co / α and P / α in the oxide phase are changed without substantially altering T3 and T4, the same trend as in Experimental Examples 9 and 10 is observed.

[0332] In Experimental Examples 9-16, when the surface of the magnetic core closest to the soft magnetic metal particles with oxide phase was designated as a specific surface, it was confirmed that in all embodiments, the magnetic core contained soft magnetic metal particles with the largest thickness portion closer to the specific surface than the opposite largest thickness portion. Furthermore, in the magnetic cores of all embodiments in Experimental Examples 9-16, it was confirmed that the total area of ​​specific particles 111 satisfying 0 < T4 / T3 ≤ 0.98 on the cross-section was 1% to 85% of the area of ​​the surface portion of the magnetic core. Additionally, in the magnetic cores of all embodiments in Experimental Examples 9-16, it was confirmed that the average thickness of the oxide phase in the specific particles contained in the central portion was 0.5 μm or less. Furthermore, it was confirmed that the average thickness of the oxide phase in the specific particles contained in the surface portion was greater than the average thickness of the oxide phase in the specific particles contained in the central portion.

Claims

1. A magnetic core, wherein, The magnetic core contains specific particles. The magnetic core has a surface portion at a distance of less than 100 μm from the outermost surface of the magnetic core and a central portion at a distance of more than 100 μm from the outermost surface of the magnetic core. The specific particles are soft magnetic metal particles with an oxide phase on their surface having a thickness of 0.025 μm or more. The specific particles are at least contained in the surface portion. Let T1 be the average thickness of the oxide phase of the specific particles at the surface portion, and T2 be the average thickness of the oxide phase of the specific particles at the central portion. The units of T1 and T2 are μm. T1≥0.050, T2≤0.500, and T1>T2.

2. The magnetic core according to claim 1, wherein, At least a portion of the specific particles contain Fe and / or Co.

3. The magnetic core according to claim 1 or 2, wherein, 0.200≤T1≤5.000。 4. A magnetic core, wherein, The magnetic core contains soft magnetic metal particles. The soft magnetic metal particles have an oxide phase on their surface. When drawing any straight line containing the center of the soft magnetic metal particles on the cross-section of the magnetic core, the straight line having the maximum thickness portion along which the length of the oxide phase along the straight line is the largest is designated as a specific straight line. The portion of the oxide phase located on the opposite side of the maximum thickness portion relative to the center along the specific straight line is designated as the anti-maximum thickness portion. Let the length of the maximum thickness portion be T3, and the length of the reverse maximum thickness portion be T4. 0 < T4 / T3 ≤ 0.

98.

5. The magnetic core according to claim 4, wherein, The soft magnetic metal particles contain Fe and / or Co.

6. The magnetic core according to claim 4 or 5, wherein, 0 < T4 / T3 ≤ 0.

90.

7. A magnetic component, wherein, The magnetic component comprises the magnetic core according to any one of claims 1 to 6.

8. An electronic device, wherein, The electronic device comprises the magnetic core according to any one of claims 1 to 6.

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