Magnetic cores, magnetic components, and electronic devices

Abstract

The present invention provides a magnetic core that improves voltage resistance while maintaining a suitable relative permeability. [Solution] A magnetic core containing soft magnetic metal particles, wherein the soft magnetic metal particles have an oxide phase 11a on their surface. In the soft magnetic metal particles (specific particles 11), when an arbitrary straight line is drawn in the cross-section of the magnetic core that includes the center 101c of the soft magnetic metal particles, the straight line having the maximum thickness portion where the length of the oxide phase is maximum along the straight line is defined as the specific straight line. The portion of the oxide phase located on the opposite side of the maximum thickness portion from the center along the specific straight line 103 is defined as the anti-maximum thickness portion. Let the length of the maximum thickness portion be T1 and the length of the anti-maximum thickness portion be T2, then 0

Description

[Technical Field]

[0001] This invention relates to magnetic cores, magnetic components, and electronic devices. [Background technology]

[0002] Patent Document 1 describes an invention relating to a coil component. By increasing the thickness of the oxide film on the metallic magnetic particles located at the interface between the magnetic material and the external electrode, it is possible to improve the adhesion between the magnetic material and the external electrode while maintaining low DC resistance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-103954 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a magnetic core that improves voltage resistance while suitably maintaining relative permeability. [Means for solving the problem]

[0005] To achieve the above objective, the magnetic core of the present invention is A magnetic core containing soft magnetic metal particles, The soft magnetic metal particles have an oxide phase on their surface, When drawing an arbitrary straight line in the cross-section of the magnetic core that includes the center of the soft magnetic metal particle, the straight line having the maximum thickness portion along the straight line where the length of the oxide phase is maximum is defined as the specified straight line. The portion of the oxide phase located along the specified straight line on the opposite side of the center from the portion with the maximum thickness is defined as the portion with the maximum thickness. Let T1 be the length of the maximum thickness portion and T2 be the length of the opposite maximum thickness portion. 0 <T2 / T1≦0.98である。

[0006] The soft magnetic metal particles may also contain Fe and / or Co.

[0007] 0 <T2 / T1≦0.90であってもよい。

[0008] The magnetic component of the present invention includes the magnetic core described above.

[0009] The electronic device of the present invention includes the magnetic core described above. [Brief explanation of the drawing]

[0010] [Figure 1] This is a SEM image of the area near the surface of the magnetic core. [Figure 2] This is a schematic diagram of a cross-section of soft magnetic metal particles. [Figure 3] This is a schematic diagram showing the location of the outermost surface of the magnetic core. [Figure 4] This is a schematic diagram showing the location of the outermost surface of the magnetic core. [Modes for carrying out the invention]

[0011] Hereinafter, a magnetic core according to an embodiment of the present invention will be described with reference to the drawings.

[0012] In this embodiment, the magnetic core may have resin filled between soft magnetic metal particles.

[0013] Furthermore, as shown in Figure 1, the magnetic core according to this embodiment includes soft magnetic metal particles 11 (hereinafter sometimes referred to as specific particles 11) having an oxide phase 11a on its surface. In other words, the specific particles 11 include a particle body 11b and an oxide phase 11a that coats the particle body 11b.

[0014] There is no particular limitation on the thickness of the oxide phase 11a in the specific particle 11. For example, the average thickness of the oxide phase 11a in the specific particle 11 may be 0.025 μm or more. Further, soft magnetic metal particles with an average thickness of the oxide phase 11a less than 0.025 μm may not be regarded as the specific particle 11.

[0015] FIG. 2 shows a schematic cross-sectional view of the specific particle 11. Hereinafter, a method for determining T1, T2, and T2 / T1 in the specific particle 11 shown in FIG. 2 will be described.

[0016] As shown in FIG. 2, an inscribed circle 101 inscribed in the surface of the specific particle 11 (the surface of the oxide phase 11a) is determined, and at the same time, the center 101c of the inscribed circle 101 is determined. The center 101c of this inscribed circle 101 is taken as the center 101c of the specific particle 11. This inscribed circle 101 is the inscribed circle with the maximum diameter.

[0017] Next, a straight line passing through the center 101c of the specific particle 11 is drawn. The straight line is rotatable 360°. As shown in FIG. 2, when an arbitrary straight line passing through the center 101c of the specific particle 11 is drawn, the straight line having the maximum thickness portion where the length of the oxide phase 11a is maximized along the straight line is defined as the specific straight line 103. As shown in FIG. 2, the length of the maximum thickness portion is defined as T1.

[0018] The portion of the oxide phase located on the opposite side of the maximum thickness portion with respect to the center 101c along the specific straight line 103 is defined as the anti-maximum thickness portion. As shown in FIG. 2, the length of the anti-maximum thickness portion is defined as T2. The anti-maximum thickness portion may not exist in the specific particle 11. When the oxide phase cannot be confirmed by observation with TEM or SEM, T2 = 0 is regarded as the case. <0,

[0019] Then, T2 / T1 can be calculated from the above T1 and T2. The magnetic core according to the present embodiment includes the specific particle 11 that satisfies 0 < T2 / T1 ≤ 0.98. It may include the specific particle 11 that satisfies 0 < T / T1 ≤ 0.90. Further, in the magnetic core according to the present embodiment, the specific particle 11 included in the surface portion 3 described later may satisfy 0 < T2 / T1 ≤ 0.98.

[0020] Further, the average value of T2 / T1 obtained by calculating and averaging T2 / T1 for all specific particles 11 included in the magnetic core may be 0 or more and 0.98 or less, or may be 0 or more and 0.90 or less. Also, the average value of T2 / T1 may be 0.09 or more and 0.98 or less, or may be 0.09 or more and 0.90 or less.

[0021] The larger the T2 / T1, the more likely the relative permeability is to decrease and the breakdown voltage is to increase.

[0022] There is no particular limitation on T1, but for example, T1 may be 0.005 μm or more and 10.550 μm or less. There is also no particular limitation on T2, but for example, T2 may be 0 or more and 10.339 μm or less.

[0023] The larger the T1, the more likely the relative permeability is to decrease and the breakdown voltage is to increase. The larger the T2, the more likely the relative permeability is to decrease and the breakdown voltage is to increase.

[0024] There is no particular limitation on the ratio of specific particles 11 that satisfy 0 < T2 / T1 ≤ 0.98 in the cross-section of the magnetic core. For example, the total area ratio of specific particles 11 that satisfy 0 < T2 / T1 ≤ 0.98 to the area of the surface portion 3 of the magnetic core in the cross-section may be 1% or more and 85% or less. The definition of the surface portion 3 of the magnetic core will be described later.

[0025] When the outermost surface of the magnetic core closest to the specific particle 11 is defined as the specific surface 21, as shown in FIG. 2, the maximum thickness portion may be closer to the specific surface 21 than the anti-maximum thickness portion. The definition of the outermost surface will be described later.

[0026] For all specific particles 11 included in the magnetic core, the ratio of specific particles where the maximum thickness portion is closer to the specific surface 21 than the anti-maximum thickness portion may be 50% or more on a number basis.

[0027] Furthermore, cracks may be formed in the oxide phase 11a. For example, the cracks may be continuous from the surface of the oxide phase 11a to the surface of the particle body 11b, or they may stop inside the oxide phase 11b.

[0028] There are no particular restrictions on the particle size of the specific particles 11. For example, the equivalent circular diameter in the cross-section of the magnetic core may be between 0.1 μm and 100 μm. Furthermore, there are no particular restrictions on the average particle size of all the specific particles 11 contained in the magnetic core. For example, the equivalent circular diameter in the cross-section of the magnetic core may be between 0.1 μm and 100 μm. Note that the above average particle size is based on the number of particles.

[0029] The equivalent diameter of a specific particle 11 is the diameter of a circle having the same cross-sectional area as the specific particle 11.

[0030] Furthermore, the magnetic core according to this embodiment may 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 greater than 50 μm from the outermost surface.

[0031] Furthermore, the magnetic core according to this embodiment may include specific particles 11 in at least the surface portion 3.

[0032] The outermost surface according to this embodiment will be described with reference to Figures 3 and 4. The magnetic core 1 shown in Figure 3 and the magnetic core 2 shown in Figure 4 have a structure in which resin 13 is filled between soft magnetic metal particles 10.

[0033] In this embodiment, the outermost surface is the surface that is in contact with the outermost material of the magnetic core and is parallel to the surface of the magnetic core.

[0034] Figures 3 and 4 show a portion of the vicinity of the surface of the magnetic core, with the surface shown at the top.

[0035] In Figure 3, the surface of the magnetic core 1 is 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 shown in Figure 3, the surface of the magnetic core 1 becomes the outermost surface 31.

[0036] In Figure 4, some of the soft magnetic metal particles 10 protrude from the resin 13 on the surface of the magnetic core 2. In this case, the surface that is in contact with the soft magnetic metal particle 10 that protrudes the largest from the surface of the magnetic core 2 and is parallel to the surface of the magnetic core 2 becomes the outermost surface 32.

[0037] In this embodiment, the magnetic core may have T3 ≥ 0.050, T4 ≤ 0.50, and T3 > T4, where T3 [μm] is the average thickness of the oxide phase in the specific particles 11 contained in the surface portion 3 and T4 [μm] is the average thickness of the oxide phase in the specific particles 11 contained in the central portion.

[0038] There is no particular upper limit to T3. For example, it may be 10.0 or less, or 5.0 or less. More specifically, it may be 0.050 ≤ T3 ≤ 10.0, or 0.20 ≤ T3 ≤ 5.0. There is no particular lower limit to T4. For example, it may be 0.000 or more. More specifically, it may be 0.000 ≤ T4 ≤ 0.50.

[0039] T3-T4≧0.001 is also acceptable, and T3-T4≧0.01 is also acceptable.

[0040] The average thickness T3 of the oxide phase 11a in the specific particles 11 contained in the surface portion 3 is obtained by averaging the average thickness of the oxide phase in all the specific particles 11 contained in the surface portion 3. The average thickness of the oxide phase 11a in the specific particles 11 contained in the central portion is obtained by averaging the average thickness of the oxide phase 11a in all the specific particles 11 contained in the central portion.

[0041] If a specific particle 11 is located on the boundary line between the surface portion 3 and the central portion 4, the specific particle 11 is considered to be a specific particle included in the surface portion 3.

[0042] In other words, the magnetic core according to this embodiment may contain soft magnetic metal particles having a thicker oxide phase in the surface portion 3 compared to the central portion 4. This makes it easier to obtain a magnetic core with improved dielectric strength while maintaining a suitable relative permeability.

[0043] If the surface portion 3 does not contain the specific particle 11, T3 is considered to be 0.000. If the central portion does not contain the specific particle 11, T4 is considered to be 0.000.

[0044] At least some of the specific particles 11 may contain Fe and / or Co.

[0045] There are no particular restrictions on the composition of the particle body 11b. For example, the particle body 11b may contain one or more elements selected from Fe, Co, and Ni. Alternatively, the particle body 11b may contain one or more elements selected from C, Nb, Hf, Zr, Cu, Ta, Mo, W, Ti, P, Si, B, Na, Al, Ca, Bi, Ba, Zn, and V, which are generally found in soft magnetic metal particles.

[0046] There are no particular restrictions on the total content of Fe, Co, and Ni in the particle body 11b. For example, it may be between 70 at% and 100 at%. There are no particular restrictions on the total content of P, Si, B, Na, Al, Ca, Bi, Ba, and Zn in the particle body 11b. For example, it may be between 0 at% and 30 at%. There are no particular restrictions on the total content of C, Nb, Hf, Zr, Cu, Ta, Mo, W, Ti, and V in the particle body 11b. For example, it may be between 0 at% and 10 at%. Also, since the proportion of particle body 11b is usually significantly larger than the proportion of oxide phase 11a, it can be estimated that the composition of particle body 11b and the composition of specific particle 11 are substantially the same. If the proportion of particle body 11b is not significantly larger than the proportion of oxide phase 11a, the composition of particle body 11b may be analyzed and determined. For example, the composition of particle body 11b may be determined from compositional analysis of the particle body 11b by cross-sectional SEM-EDS or STEM-EDS.

[0047] 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, to the extent that it 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 5% by mass or less.

[0048] Regarding the composition of the oxide phase 11a, there are no particular restrictions other than that the oxide phase 11a contains oxides. For example, the oxide phase 11a may contain oxides of one or more elements selected from the elements contained in the particle body 11b. In other words, the oxide phase 11a is an oxide-containing phase.

[0049] Furthermore, the oxide phase 11a may consist of oxides produced by the oxidation of the particle body 11b. For example, the composition of the oxide phase 11a and the particle body 11b may match by 50% or more on an atomic basis, without considering oxygen and carbon.

[0050] The oxide phase 11a may contain Co. Including Co in the oxide phase 11a tends to improve the dielectric strength. Specifically, the ratio of Co to the total content of Fe, Co, and P in the oxide phase 11a (hereinafter sometimes simply referred to as Co / α) may be 0.10 or more and 1.00 or less on an atomic basis, or 0.18 or more and 0.70 or less.

[0051] The oxide phase 11a may contain phosphorus (P). The ratio of P to the total content of Fe, Co, and P in the oxide phase 11a (hereinafter sometimes simply referred to as P / α) may be 0.01 to 1.00 or 0.10 to 0.50 on an atomic basis. In particular, when the oxide phase 11a contains Co and P / α is 0.10 to 0.50, the dielectric strength tends to improve.

[0052] There are no particular limitations on the microstructure of the soft magnetic metal particles according to this embodiment. The microstructure of the soft magnetic metal particles may be amorphous, a nanocrystalline structure containing nanocrystals, or a crystalline structure.

[0053] Soft magnetic metal particles containing nanocrystals can sometimes be obtained by heating soft magnetic alloy particles containing amorphous material at 400°C to 700°C.

[0054] Here, "amorphous structure" refers to a material state in which there is almost no long-range order like in crystals, and the amorphousness rate X is 85% or more. Amorphous structures include structures consisting only of amorphous material and structures consisting of heteroamorphous material. A heteroamorphous structure refers to a structure in which initial microcrystals exist within the amorphous material. In heteroamorphous structures, the average crystallite size of the initial microcrystals is preferably between 0.1 nm and 10 nm.

[0055] Furthermore, "nanocrystalline structure" refers to a material state having nanocrystals in which the amorphousness rate X is less than 85% and the average crystallite diameter is between 0.5 nm and 30 nm. Preferably, the maximum diameter of the crystallites in the nanocrystalline structure is 100 nm or less.

[0056] On the other hand, crystalline metallic magnetic materials have a crystalline structure, which is different from amorphous or nanocrystalline structures. A "crystalline structure" refers to a material state in which the amorphousness rate X is less than 85% and the average crystallite diameter is 100 nm or more.

[0057] Note that the amorphousness rate X (unit: %) is calculated by dividing the proportion of crystals by P. C P A Let X=(P A / (P C +P A It is expressed as )) × 100. When calculating the amorphous fraction X using XRD, the crystalline scattering integral intensity Ic measured using XRD is P cbe regarded as, and the amorphous scattering integrated intensity Ia measured using XRD as P A may be regarded as. When calculating the amorphization rate X using EBSD or an electron microscope, the area ratio of the crystalline portion within the grains is P C be regarded as, and the area ratio of the amorphous portion within the grains may be regarded as P A as well.

[0058] Examples of the material of the soft magnetic alloy particles having an amorphous structure as the fine structure include Fe—Si—B alloys, Fe—B—Si—C alloys, Fe—B—Si—C—Cr alloys, Fe—Co—B—P—Si—Cr alloys, Fe—Co—B—P—Si alloys, and Fe—Co—B—P—Si—C alloys.

[0059] Examples of the material of the soft magnetic alloy particles having a nanocrystalline structure as the fine structure include Fe—Si—B—Nb—Cu alloys, Fe—B—Nb alloys, Fe—B—Nb—P alloys, Fe—B—P—Si—Cu alloys, Fe—B—P—Si—Nb—Cr alloys, Fe—Co—B—P—Si—Cu alloys, and Fe—Co—B—P—Si—Nb alloys.

[0060] Examples of the material of the soft magnetic alloy particles having a crystalline structure as the fine structure include pure metals of Fe, Co, and Ni, Fe—Co alloys, Fe—Si alloys, Fe—Ni alloys, Fe—Co—Si alloys, Fe—Si—Cr alloys, Fe—Co—Si—Cr alloys, Fe—Co—V alloys, Fe—Si—Al alloys, Fe—Si—Al—Ni alloys, and Fe—Co—Si—Al alloys.

[0061] Hereinafter, the method for manufacturing the magnetic core according to the present embodiment will be described.

[0062] There are no particular restrictions on the method for producing the soft magnetic metal powder. The soft magnetic metal powder according to this embodiment can be produced by methods such as water atomization, gas atomization, carbonyl method, and spray pyrolysis. Alternatively, the soft magnetic metal powder can be produced by, for example, crushing a metal ribbon. The following describes a method for obtaining the soft magnetic metal powder according to this embodiment using the gas atomization method.

[0063] First, the raw materials for each element that constitute the metal particles contained in the soft magnetic metal powder are prepared and weighed to achieve the desired composition of metal particles. Then, the raw materials for each element are dissolved to create a master alloy. There are no particular limitations on the dissolution method. For example, the raw materials for each element may be dissolved by high-frequency heating in a chamber with a predetermined vacuum level.

[0064] Next, the master alloy is heated and melted to obtain molten metal. The temperature of the molten metal can be adjusted according to the melting point of the alloy having the desired composition and / or the melting points of the raw materials of each element mentioned above. For example, it may be 1200 to 1600°C.

[0065] Next, molten metal is ejected into a chamber to produce powder. Specifically, molten metal is ejected from a discharge port towards the cooling section inside the chamber. At this time, high-pressure gas is injected towards the ejected molten metal. The injection of high-pressure gas causes the molten metal to break apart and scatter within the chamber, and the scattered molten metal collides with the cooling section (cooling water), causing it to rapidly cool and solidify, resulting in a soft magnetic metal powder containing metal particles. When using the water atomization method, water is injected instead of high-pressure gas.

[0066] There are no particular restrictions on the type of high-pressure gas. Examples include inert gases such as nitrogen, argon, and helium. Reducing gases such as ammonia decomposition gas may also be used.

[0067] There are no particular restrictions on the pressure of the injected high-pressure gas; it may be between 2.0 and 10.0 MPa. There are also no particular restrictions on the amount of molten metal injected; it may be between 0.5 and 16.0 kg / min. By controlling the ratio of the high-pressure gas pressure to the amount of molten metal injected, the particle size of the soft magnetic metal powder can be adjusted.

[0068] The particle size of the soft magnetic metal powder may be adjusted by classification.

[0069] Furthermore, a coating film may be formed on the powder obtained by cooling it with cooling water.

[0070] There are no particular restrictions on the type of coating film. For example, it may be a coating containing inorganic materials. Examples of inorganic materials include phosphates, BN, SiO2, MgO, Al2O3, phosphate-based glass, silicate-based glass, borosilicate-based glass, and bismuth-based glass.

[0071] Phosphate-based glasses include P-Zn-Al-O glass and P-Zn-Al-RO glass (where R is one or more alkali metals). Silicate-based glasses include Si-O glass. Borosilicate-based glasses include Ba-Zn-B-Si-Al-O glass. Bismuth-based glasses include Bi-Zn-Al-O glass and Bi-Zn-B-Si-Al-O glass.

[0072] There are no particular restrictions on the method of forming the coating film. It may be formed by a well-known method selected according to the type of coating film. Examples of methods for forming the coating film include heat treatment, phosphate treatment, mechanical alloying, silane coupling treatment, and hydrothermal synthesis.

[0073] The following describes in more detail several methods for forming coating films.

[0074] When forming a coating film containing SiO2 (hereinafter sometimes referred to as an SiO2 film), a solution containing a silane coupling agent, which serves as a Si source, may be sprayed onto the powder. Alternatively, the powder may be impregnated with a solution containing a silane coupling agent, and then dried and / or heat-treated.

[0075] There are no particular restrictions on the type of silane coupling agent. Examples include tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and hexyltrimethylsilane. Using TEOS is particularly preferred.

[0076] 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 isopropyl alcohol. The thickness of the coating film can be controlled by controlling the concentration of the silane coupling agent in the solution, the spray volume per unit time, and the penetration treatment time. The higher the concentration of the silane coupling agent, the greater the spray volume per unit time, and the longer the penetration treatment time, the thicker the coating film will be.

[0077] When forming a coating film containing phosphate (hereinafter sometimes referred to as a phosphate film), it can be formed by phosphate treatment. Specifically, first, a treatment solution is prepared by dissolving a phosphate containing additive elements, or phosphoric acid, in a solvent such as water or alcohol. Then, the powder is impregnated into the treatment solution or the treatment solution is sprayed onto the powder. After that, the powder is dried to form a phosphate film on the surface of the powder. Examples of additive elements include alkali metal elements, alkaline earth metal elements, Zn, and Al.

[0078] When forming coating films using various glass-based materials, these films can be formed by a mechanochemical method using a mechanofusion apparatus. Specifically, in the mechanochemical coating process, the powder to be coated and a powdered coating agent containing the constituent elements of the coating film are introduced into the rotating rotor of the mechanofusion apparatus, and the rotor is rotated. A press head is installed inside the rotating rotor. When the rotor rotates, the mixture of the powder to be coated and the coating agent is compressed in the gap between the inner wall of the rotor and the press head, generating frictional heat. This frictional heat softens the coating agent, and through compression, it adheres to the surface of the powder to be coated, forming an oxide glass coating film.

[0079] There are no particular limitations on the method for manufacturing the magnetic core according to this embodiment. The following describes the case where the magnetic core is a compacted magnetic core. Specifically, a method for obtaining the magnetic core by pressure molding will be described.

[0080] A resin compound is obtained by kneading the soft magnetic metal powder according to this embodiment with a resin. The resin compound may be granulated powder. At this time, soft magnetic metal powder other than the soft magnetic metal powder according to this embodiment, and / or non-magnetic powders may be added to the resin compound. Modifiers, preservatives, dispersants, etc. may also be added. Then, the resin compound is filled into a mold, pressure molded, and the resin is cured to obtain a magnetic core.

[0081] First, the soft magnetic metal powder and resin are mixed. Mixing with resin makes it easier to obtain a molded body with high strength through molding. There are no particular restrictions on the type of resin. Examples include phenolic resin and epoxy resin. There are no particular restrictions on the amount of resin added, but the total amount may be between 0.5 parts by mass and 5.0 parts by mass, based on a total mass of 100 parts by mass of the various magnetic materials.

[0082] A mixture of soft magnetic metal powder and resin is granulated to obtain granulated powder. There are no particular restrictions on the granulation method. For example, granulation may be carried out using a stirrer. There are no particular restrictions on the particle size of the granulated powder.

[0083] The resulting granulated powder is subjected to pressure molding to obtain a molded body. There are no particular restrictions on the molding pressure. For example, a surface pressure of 98 MPa (0.1 t / cm²) is used. 2 ) or more 1960MPa (20t / cm 2 The following are also acceptable:

[0084] 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 may be performed under conditions that can cure the resin used.

[0085] The obtained magnetic core is subjected to an oxide phase formation treatment. This treatment oxidizes the surface of the particles contained within the magnetic core, forming an oxide phase. Soft magnetic metal particles closer to the surface of the magnetic core tend to form thicker oxide phases, resulting in a higher T3 value compared to T4.

[0086] The following describes the method for oxide phase formation treatment.

[0087] First, the magnetic core and water are sealed in a metal airtight container. There are no particular restrictions on the amount of water added (sealed amount). For example, the amount may be 0.1 parts by mass or more and 40.0 parts by mass per 100 parts by mass of magnetic core, or 0.5 parts by mass or more and 30.0 parts by mass.

[0088] Then, the sealed container is filled with gas. There are no particular restrictions on the method of filling with gas. For example, the inside of the sealed container may be depressurized once before being filled with gas and pressurized. There are no particular restrictions on the type of gas. For example, compressed air, nitrogen gas, or argon gas may be used. There are no particular restrictions on the pressure inside the sealed container. For example, it may be between 0.12 MPa and 0.70 MPa, or between 0.15 MPa and 0.50 MPa.

[0089] Then, by heating the sealed container, the surface of the particles oxidizes and an oxide phase is formed. There are no particular restrictions on the holding temperature and holding time during heating. The holding temperature may be, for example, 50°C to 250°C, or 90°C to 200°C. The holding time may be, for example, 0.5 minutes to 300 minutes.

[0090] Higher holding temperatures tend to result in higher T1 and T2 values. A larger amount of water added also tends to increase the T2 / T1 ratio.

[0091] The higher the holding temperature, the more likely T3 tends to be. The higher the pressure inside the sealed container, the more likely T4 tends to be.

[0092] The higher the holding temperature, the more likely it is that the Co / α ratio will be higher and the P / α ratio will be lower. The longer the holding time, the more likely it is that the Co / α ratio will be lower and the P / α ratio will be higher.

[0093] There are no particular restrictions on the method for measuring the thicknesses T1 and T2 of the oxide phase and calculating T2 / T1. For example, the cross-section of the magnetic core may first be observed using backscattered electron imaging with a TEM or SEM, and the formation of the oxide phase on the particle surface may be confirmed using EDS. Then, the thicknesses T1 and T2 of the oxide phase may be calculated visually from the backscattered electron imaging, and T2 / T1 may be calculated. Alternatively, a measurement point through which the oxide phase passes may be set using EDS, line analysis may be performed, and T1 and T2 may be calculated from the results of the line analysis, and T2 / T1 may be calculated.

[0094] There are no particular restrictions on the method for measuring the Co / α and P / α of the oxide phase. For example, a measurement point is set up by passing through the oxide phase using EDS, and a line analysis is performed, from which the values ​​can be calculated.

[0095] When calculating the average T2 / T1 of the entire magnetic core using SEM and EDS, there are no particular restrictions on the number of specific particles for which T2 / T1 is measured. It is sufficient to measure T2 / T1 for a sufficient number of specific particles to calculate T2 / T1 with high accuracy. For example, if the magnetic core has high uniformity, the T2 / T1 calculated for a single specific particle may be used as the average T2 / T1 of the entire magnetic core.

[0096] There are no particular restrictions on the method for measuring the oxide phase thicknesses T3 and T4. For example, the cross-section of the magnetic core may first be observed using a backscattered electron image from a scanning electron microscope (SEM), and the formation of the oxide phase on the particle surface may be confirmed using an EDS. Subsequently, the thickness of the oxide phase may be calculated visually from the backscattered electron image. Alternatively, a measurement point through which the oxide phase passes may be set using the EDS, line analysis may be performed, and the thickness may be calculated from the results of the line analysis.

[0097] There are no particular restrictions on the number of specific particles used to measure T3 and T4 using SEM and EDS. It is sufficient to measure T3 and T4 for a sufficient number of specific particles to calculate T3 and T4 with high accuracy. For example, if the magnetic core has high uniformity, the thickness of the oxide phase in a single specific particle on the surface may be used as T3. Similarly, if the magnetic core has high uniformity, the thickness of the oxide phase in a single specific particle in the central part may be used as T4.

[0098] There are no particular restrictions on the number of specific particles used to measure Co / α and P / α using SEM and EDS. It is sufficient to measure Co / α and P / α for a sufficient number of specific particles to calculate them with high accuracy. If the magnetic core has high uniformity, Co / α and P / α may also be calculated from the oxide phase composition of a single specific particle contained on the surface.

[0099] There are no particular restrictions on the applications of the magnetic core. For example, it can be suitably used as a magnetic core for inductors.

[0100] Furthermore, the magnetic cores and magnetic components using the above-mentioned magnetic cores can be suitably used in electronic devices.

[0101] In particular, the above-mentioned magnetic core can be used in fields where miniaturization and low profile are required, as it is relatively easy to maintain a favorable relative permeability while keeping the voltage withstand characteristics low. For example, it can be suitably used in magnetic components such as inductors, transformers, and choke coils, as well as in electronic equipment that uses such magnetic components. [Examples]

[0102] The present invention will be specifically described below based on examples.

[0103] (Experimental Example 1) Pure Fe metal was prepared as the base alloy. The pure Fe metal was heated and melted to a molten state at 1600°C (molten metal), and then soft magnetic metal powder consisting of the pure Fe metal was produced by gas atomization. Specifically, when the molten base alloy was discharged from the dropping molten metal outlet toward the cooling section (cooling water) in the chamber, high-pressure gas was injected toward the discharged dropping molten metal. The pressure of the high-pressure gas was set to 5 MPa, and the discharge rate of the molten metal was set to 6 kg / min. Finally, the soft magnetic metal powder obtained (pure iron powder in Experimental Example 1) was screened and classified so that the average particle size was 25 μm.

[0104] ICP analysis confirmed that the composition of the master alloy and the composition of the soft magnetic metal powder were in general agreement. X-ray diffraction measurements were also performed on the soft magnetic metal powder, and the amorphous ratio X was calculated using the method described above. A structure consisting of amorphous material was considered to exist if the amorphous ratio X was 85% or higher. A structure consisting of nanocrystalline material was considered to exist if the amorphous ratio X was less than 85% and the average crystallite diameter was 100 nm or less. A structure consisting of crystalline material was considered to exist if the amorphous ratio X was less than 85% and the average crystallite diameter was greater than 100 nm. In Experimental Example 1, it was confirmed that all soft magnetic metal powders had a crystalline structure. The average particle size of the soft magnetic metal powder was confirmed and calculated using SEM.

[0105] Next, a resin compound was obtained by kneading soft magnetic metal powder (pure iron powder) and epoxy resin. The amount of epoxy resin added to the resin compound (resin amount) was set to 3 parts by mass per 100 parts by mass of soft magnetic metal powder.

[0106] Next, a toroidal molded body was obtained by filling a mold with resin compound and applying pressure. The molding pressure was controlled so that the relative permeability (μ) of the magnetic core was 30. The resulting molded body was heat-treated at 180°C for 60 minutes to cure the epoxy resin and obtain a toroidal magnetic core. The magnetic core had an outer diameter of 11 mm, an inner diameter of 6.5 mm, and a thickness of 2.5 mm.

[0107] Next, oxide phase formation treatment was performed on toroidal magnetic cores other than sample number 1. First, the magnetic cores and water were sealed in a metal airtight container. Then, the inside of the airtight container was depressurized and then pressurized with nitrogen gas. Finally, it was heated. Table 1 shows the amount of water added (sealed amount) per 100 parts by mass of magnetic core, and the temperature inside the airtight container. For sample number 2, the amount of water added was 0; that is, no water was sealed in the airtight container. For samples 2 to 44, the atmospheric pressure inside the airtight container was set to 0.20 MPa. Then, it was held at the temperature shown in Table 1 for 60 minutes.

[0108] Furthermore, a rectangular parallelepiped-shaped molded body was obtained by filling a separate mold with the resin compound and applying pressure. The molding pressure and heat treatment conditions were the same as those for the toroidal-shaped magnetic core described above. The bottom surface of the magnetic core was a 4.0 mm x 4.0 mm square, and its height was 1.0 mm.

[0109] Next, oxide phase formation treatment was performed on the rectangular prism-shaped magnetic cores other than sample number 1. The conditions for oxide phase formation treatment were the same as those for the toroidal-shaped magnetic cores described above.

[0110] (Average thickness of oxide phase) The cross-section of the obtained toroidal magnetic core was observed, and T1 and T2 were measured to calculate T2 / T1. First, the cross-section of the magnetic core was observed using a scanning electron microscope (SEM). At that time, the observation magnification was set to a low magnification, specifically a magnification lower than the magnification used to measure the thickness of the oxide phase, which will be described later. Through observation, specific particles having an oxide phase with a maximum thickness of 0.005 μm or more were discovered on the surface of the magnetic core. Hereafter, unless otherwise specified, specific particles are assumed to have an oxide phase with a maximum thickness of 0.005 μm or more on their surface.

[0111] Subsequently, in order to measure T1 and T2 in the specific particle discovered, the observation magnification and the position of the observation range were adjusted as appropriate so that the entire specific particle could be observed. The observation magnification was adjusted as appropriate within the range of 1,000x to 50,000x.

[0112] Next, T1 and T2 were measured for each of the more than 50 specific particles, and T2 / T1 was calculated. Then, from the above measurement and calculation results, the average values ​​of T1, T2, and T2 / T1 were calculated. The obtained values ​​were taken as the average values ​​of T1, T2, and T2 / T1 for the entire surface of the magnetic core. The average values ​​of T1, T2, and T2 / T1 are shown in Table 1.

[0113] Furthermore, if no more than 50 specific particles were identified on the surface, the average values ​​of T1, T2, and T2 / T1 were calculated from the thickness of the oxide phase in all specific particles identified on the surface.

[0114] In sample number 1, which did not undergo oxide phase formation treatment, and in sample number 2, which did not have water added during oxide phase formation treatment, the magnetic core did not contain the specific particles.

[0115] In samples 1 and 2, T1=T2=0.000 was assumed for all soft magnetic metal particles. In sample 3, no oxide phase was observed in any specific particle along a specific straight line opposite the maximum thickness region relative to the center. That is, both the average value of T2 and the average value of T2 / T1 were 0.000.

[0116] (relative permeability) The relative permeability of the obtained toroidal magnetic core was measured. First, polyurethane wire (UEW wire) was wound around the toroidal magnetic core. Then, the relative permeability of the magnetic core was measured at a measurement frequency of 1 MHz using an LCR meter (Agilent Technologies: 4284A). In Table 1, the relative permeability is rounded to two decimal places. Therefore, even if the relative permeability listed in Table 1 is the same, the rate of decrease in relative permeability may differ.

[0117] For each sample, the percentage decrease in relative permeability was calculated compared to the comparative example (sample number 1 in Experimental Example 1), which was conducted under the same conditions except that oxide phase formation treatment was not performed. The results are shown in the respective tables. A percentage decrease in relative permeability of 15.0% or less was considered to indicate good relative permeability, and a percentage decrease of 10.0% or less was considered to indicate particularly good relative permeability.

[0118] (Withstand voltage) The dielectric strength of the resulting rectangular magnetic core was measured. First, one of the two 4.0 mm × 4.0 mm square faces of the rectangular magnetic core was selected. Next, terminal electrodes with a width of 1.3 mm were attached to both ends of the selected face. The distance between the terminal electrodes was 1.4 mm.

[0119] Next, a voltage was applied between the terminal electrodes, and the voltage when a current of 2 mA flowed was 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 improvement in withstand voltage may differ.

[0120] For each sample, the improvement in dielectric strength compared to the comparative example (sample number 1 in Experimental Example 1), which was carried out under the same conditions except that oxide phase formation treatment was not performed, was calculated. The results are shown in the respective tables. A dielectric strength improvement of 10.0% or more was considered good, and a dielectric strength improvement of 20.0% or more was considered particularly good.

[0121] [Table 1]

[0122] Table 1 shows that samples 3 to 43, which underwent oxide phase formation treatment under suitable conditions, had T2 / T1 within the specified range. As a result, compared to sample 1, which was performed under the same conditions except for the absence of oxide phase formation treatment, it was possible to improve the dielectric strength while suppressing the decrease in relative permeability. came.

[0123] Sample No. 2, which did not have water added during the oxide phase formation treatment, did not form an oxide phase, similar to Sample No. 1. As a result, neither the relative permeability nor the dielectric strength changed compared to Sample No. 1.

[0124] Sample No. 44, which had a high treatment temperature and a large amount of water added during the oxide phase formation treatment, exhibited an excessively large T2 / T1 ratio. As a result, its relative permeability was significantly reduced compared to Sample No. 1, which was treated under the same conditions except for the absence of oxide phase formation treatment.

[0125] (Experimental Example 2) For samples 1, 33, and 37 of Experimental Example 1, the composition and microstructure of the soft magnetic metal powder were varied during the experiment.

[0126] The composition of the soft magnetic metal powder was changed by altering the composition of the master alloy. The temperature of the molten metal was adjusted as appropriate within the range of 1200°C to 1600°C, depending on the composition of the molten metal.

[0127] The composition and results of the soft magnetic metal powders are shown in Tables 2A to 2C. The composition is given on an atomic basis. In experimental examples 2 and later, the relative permeability and dielectric strength are omitted, and only the decrease in relative permeability and the improvement in dielectric strength compared to a sample with the same composition but without oxidation formation treatment are described.

[0128] XRD confirmed that powders from samples 45-62, 69-74, and 87-101 all have a crystalline structure.

[0129] XRD confirmed that powders from samples 63-65, 75-80, 102-107, and 114-119 all have an amorphous structure.

[0130] Powders from samples 66-68, 81-86, and 108-113 were prepared by gas atomization and then heat-treated to precipitate nanocrystals with a grain size of 30 nm or less. Specifically, the heat treatment was performed at 400-650°C for 10-60 minutes. XRD confirmed that powders from samples 66-68, 81-86, and 108-113 all had a structure consisting of nanocrystals.

[0131] [Table 2A]

[0132] [Table 2B]

[0133] [Table 2C]

[0134] Tables 2A to 2C show that even when the type of powder and / or microstructure was changed from that of Experimental Example 1, a similar trend to that of Experimental Example 1 was observed.

[0135] (Experimental Example 3) For samples 1, 33, and 37 of Experimental Example 1, the average particle size of the soft magnetic metal powder was varied. Furthermore, the processing temperature during oxide phase formation treatment was changed so that T1 and T2 decreased as the average particle size of the soft magnetic metal powder decreased. Other aspects were carried out under the same conditions as in Experimental Example 1. The results are shown in Table 3.

[0136] [Table 3]

[0137] Table 3 shows that even when the average particle size of the powder was changed from that of Experimental Example 1, a similar trend to that of Experimental Example 1 was observed.

[0138] (Experimental Example 4) Soft magnetic metal powders of samples 1, 33, and 37 were subjected to a coating film formation process using a mechanofusion apparatus (Hosokawa Micron Corporation: AMS-Lab) to form a P-Zn-Al-O oxide glass coating film on the surface of the soft magnetic metal powders. The thickness of the coating film was approximately 3 nm. Samples 135 to 137 were subjected to the same procedures as in Experimental Example 1. The results are shown in Table 4.

[0139] For each of the samples numbered 135 to 137, the type of coating film on the soft magnetic metal powder was varied. The types of coating films are shown in Table 4. When the type of coating film 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 carried out in the same manner as for samples numbered 135 to 137. When the type of coating film was a phosphate coating, the soft magnetic metal powders of samples numbered 1, 33, and 37 were appropriately treated with phosphate. When the type of coating film was an SiO2 coating, the soft magnetic metal powders of samples numbered 1, 33, and 37 were treated in the same manner as for samples numbered 1, 33, and 37. The genus powders were subjected to appropriate silane coupling treatments. The results are shown in Table 4.

[0140] [Table 4]

[0141] Table 4 shows that even when the type of coating film on the soft magnetic metal powder was changed, a similar trend to that in Experimental Example 1 was observed. Furthermore, when only the coating film was formed and the oxide phase formation treatment was not performed, the magnetic core did not contain specific particles with an oxide phase of average thickness of 0.005 μm or more. This is because, as mentioned above, the thickness of the coating film is approximately 3 nm (0.003 μm). For convenience, in Table 4, T1=T2=0.000 was assumed for the case where the oxide phase formation treatment was not performed.

[0142] Furthermore, in each example in Table 4, when using soft magnetic metal powder with a coating film formed on it and performing an oxide phase formation treatment on specific particles, no boundary was observed between the coating film and the oxide phase formed by the oxide phase formation treatment.

[0143] (Experimental Example 5) Powder A was prepared using the soft magnetic metal powder with an average particle size of 25 μm used in Experimental Example 1. Powder B was prepared using the same conditions as Powder A, except that the average particle size was 3.0 μm. Powder C was prepared using the same conditions as Powder A, except that the average particle size was 0.8 μm. Powders A to C were then mixed in the proportions shown in Table 5 to obtain a mixed powder.

[0144] The experiment was conducted under the same conditions as in Experimental Example 1, samples 1 and 37, except for the use of a mixed powder. The results are shown in Table 5.

[0145] [Table 5]

[0146] Table 5 shows that even when mixing multiple types of powders with different average particle sizes, a similar trend to that observed in Experimental Example 1 was observed.

[0147] (Experimental Example 6) For samples 158 and 159, the experiment was conducted under the same conditions as in Experimental Example 5, except that the composition of one or more powders from powders A to C was changed to the composition shown in Table 6A. Powder A (samples 168, 169, 174, 175), powder B (samples 180, 181, 186, 187), and powder C (samples 192, 193, 198, 199) were prepared by gas atomization and then heat-treated to precipitate nanocrystals with a grain size of 30 nm or less. Specifically, the heat treatment was performed at 400-650°C for 10-60 minutes. XRD was then used to confirm that each powder possessed the microstructure shown in Table 6A. The results are shown in Tables 6A and 6B.

[0148] [Table 6A]

[0149] [Table 6B]

[0150] Tables 6A and 6B show that the same trend as in Experimental Example 5 was observed even when the powder composition and microstructure were changed.

[0151] (Experimental Example 7) For samples 1 and 37, samples 206-209 were performed under the same conditions as in Experimental Example 3, except that a portion of the powder was replaced with powder prepared under the same conditions, except that the average particle size was 1.0 μm. For samples 129 and 131, samples 210-213 were performed under the same conditions as in Experimental Example 3, except that a portion of the powder was replaced with powder prepared under the same conditions, except that the average particle size was 1.0 μm. For samples 126 and 128, samples 214-217 were performed under the same conditions as in Experimental Example 3, except that a portion of the powder was replaced with powder prepared under the same conditions, except that the average particle size was 1.0 μm. The results are shown in Table 7.

[0152] [Table 7]

[0153] Table 7 shows that even when mixing multiple types of powders with different average particle sizes, a similar trend to that observed in Experimental Example 3 was observed.

[0154] (Experimental Example 8) For sample number 37 in Experimental Example 1, samples 301 and 302 were performed by varying the processing temperature and processing time during oxide formation treatment while substantially maintaining T1 and T2. Furthermore, Co / α and P / α in the oxide phase of each sample were measured using SEM-EDS. The results are shown in Table 8.

[0155] For sample number 89 in Experimental Example 2, samples 303 and 304 were performed by varying the processing temperature and processing time during oxide formation treatment while substantially maintaining T1 and T2. Furthermore, Co / α and P / α in the oxide phase of each sample were measured using SEM-EDS. The results are shown in Table 8.

[0156] For sample number 107 in Experimental Example 2, samples 305-312 were performed by varying the processing temperature and processing time during oxide formation treatment while substantially maintaining T1 and T2. Furthermore, Co / α and P / α in the oxide phase of each sample were measured using SEM-EDS. The results are shown in Table 8.

[0157] For sample number 116 in Experimental Example 2, samples 313-320 were performed by varying the processing temperature and processing time during oxide formation treatment while substantially maintaining T1 and T2. Furthermore, Co / α and P / α in the oxide phase of each sample were measured using SEM-EDS. The results are shown in Table 8.

[0158] For sample number 119 in Experimental Example 2, samples 321-328 were performed by varying the processing temperature and processing time during oxide formation treatment while substantially maintaining T1 and T2. Furthermore, Co / α and P / α in the oxide phase of each sample were measured using SEM-EDS. The results are shown in Table 8.

[0159] [Table 8]

[0160] From Table 8, even when changing Co / α and P / α in the oxide phase without substantially changing T1 and T2, the same tendency as in Experimental Examples 1 and 2 was observed.

[0161] When the surface of the magnetic core closest to the soft magnetic metal particles having an oxide phase is defined as the specific surface, it was confirmed that in the magnetic cores of all the examples, the maximum thickness portion contains soft magnetic metal particles closer to the specific surface than the anti-maximum thickness portion. Also, in the magnetic cores of all the examples, it was confirmed that the total area ratio of the specific particles 11 satisfying 0 < T2 / T1 ≤ 0.98 with respect to the area of the surface portion of the magnetic core in the cross section is 1% or more and 85% or less. Further, in the magnetic cores of all the examples, it was confirmed that the average thickness of the oxide phase in the specific particles contained in the central portion is 0.5 μm or less. Also, it was confirmed that the average thickness of the oxide phase in the specific particles contained in the surface portion is larger than the average thickness of the oxide phase in the specific particles contained in the central portion.

Description of Reference Numerals

[0162] 1, 2... Magnetic core 3... Surface portion 4... Central portion 10... Soft magnetic metal particles 11... Specific particles 11a... Oxide phase 11b... Particle body 13... Resin 21... Specific surface 31, 32... Outermost surface 101... Inscribed circle 101c... Center 103... Specific straight line

Claims

1. A magnetic core containing soft magnetic metal particles, The soft magnetic metal particles have an oxide phase on their surface, When drawing an arbitrary straight line in the cross-section of the magnetic core that includes the center of the soft magnetic metal particle, the straight line having the maximum thickness portion along the straight line where the length of the oxide phase is maximum is defined as the specified straight line. The portion of the oxide phase located along the specified straight line on the opposite side of the center from the portion with the maximum thickness is defined as the portion with the maximum thickness. Let T1 be the length of the maximum thickness portion and T2 be the length of the opposite maximum thickness portion. A magnetic core where 0 < T2 / T1 ≤ 0.

98.

2. The magnetic core according to claim 1, wherein the soft magnetic metal particles comprise Fe and / or Co.

3. A magnetic core according to claim 1 or 2, wherein 0 < T2 / T1 ≤ 0.

90.

4. A magnetic component comprising the magnetic core according to claim 1 or 2.

5. An electronic device comprising a magnetic core according to claim 1 or 2.

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