Magnetic core and magnetic component

Abstract

To provide a magnetic core and a magnetic component that are capable of improving a core loss by an approach different from the prior art.SOLUTION: Provided is a magnetic core containing metal magnetic particles. A total area ratio occupied by the metal magnetic particles on a cross-section of the magnetic core is 75% or more. The metal magnetic particles include: first large particles 11a having an amorphous structure and having a Heywood diameter of 3 μm or more on the cross-section of the magnetic core; and second large particles 11b having a nanocrystal structure and having a Heywood diameter of 3 μm or more on the cross-section of the magnetic core. An insulation coating 4a of the first large particles 11a is thicker than an insulation coating 4b of the second large particles 11b.SELECTED DRAWING: Figure 3A

Description

[Technical field]

[0001] The present invention relates to magnetic cores and magnetic components comprising metallic magnetic powder. [Background technology]

[0002] Magnetic cores (dust cores) containing metallic magnetic powder and resin are used in magnetic components such as inductors, transformers, choke coils, etc. Various attempts have been made to improve the properties of such magnetic cores, such as their magnetic permeability.

[0003] For example, in Patent Documents 1 and 2 shown below, an attempt is made to improve the filling rate of the metal magnetic powder in the magnetic core and to improve the magnetic permeability and core loss (magnetic loss) by using a metal magnetic powder that is a mixture of crystalline alloy powder and amorphous alloy powder.

[0004] Furthermore, in Patent Document 3 shown below, an attempt is made to improve the filling rate of the metal magnetic powder and thereby improve the magnetic permeability by using two types of metal magnetic powder with different particle sizes and adjusting the particle size ratio of the two types of metal magnetic powder within a predetermined range. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-197218 A [Patent Document 2] JP 2004-363466 A [Patent Document 3] JP 2011-192729 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic core and a magnetic component that are capable of improving core loss by an approach different from that of the conventional techniques. [Means for solving the problem]

[0007] In order to achieve the above object, a magnetic core according to one aspect of the present invention comprises: A magnetic core comprising metallic magnetic particles, The total area ratio of the metal magnetic particles in the cross section of the magnetic core is 75% or more; The metal magnetic particles are a first large particle having an amorphous structure and a Heywood diameter of 3 μm or more in a cross section of the magnetic core; A second large particle having a nanocrystalline structure and a Heywood diameter of 3 μm or more in a cross section of the magnetic core; The insulating coating of the first large particles is thicker than the insulating coating of the second large particles.

[0008] Soft magnetic metal materials with nanocrystalline structures have been attracting attention as low-loss materials, but they tend to have a lower Bs than other soft magnetic metal materials. In addition, in order to increase the Bs of the magnetic core, it is necessary to pack the magnetic powder densely, which requires high-pressure molding. In addition, from a material perspective, if amorphous materials with high Bs are used compared to nanocrystalline materials, the effect of magnetostriction is high, and high stress is required to pack densely, which is thought to increase hysteresis loss.

[0009] The inventors discovered that by controlling the thickness of the insulating coating of the first large particles with an amorphous structure and the second large particles with a nanocrystalline structure, it is possible to realize a low-loss core that could not be achieved with a magnetic core obtained by a simple blend, and thus completed the present invention. In other words, it is believed that by making the insulating coating of the first large particles with an amorphous structure thicker than that of the second large particles, a buffer effect is obtained, and as a result, a low-loss core can be realized.

[0010] the average thickness of the insulating coating of the first large particle is T1; The average thickness of the insulating coating of the second large particle is T2, T1 / T2 is preferably 1.3 or more and 40 or less, and more preferably 1.3 or more and 20 or less.

[0011] The average thickness T2 of the insulating coating of the second large particles is preferably 5 nm or more and 50 nm or less.

[0012] The metal magnetic particles may include a group of particles having a Heywood diameter of less than 3 μm in a cross section of the magnetic core, and the group of particles having a Heywood diameter of less than 3 μm may include two or more types of small particles having different coating compositions.

[0013] A magnetic component according to an aspect of the present invention has any one of the magnetic cores described above. The magnetic core is included in various magnetic components such as inductors, choke coils, transformers, and reactors, and contributes to improving the efficiency of the magnetic components. Note that the magnetic component is not limited to a magnetic component having a magnetic core, and may be a magnetic component without a magnetic core.

[0014] For example, a magnetic component according to another aspect of the present invention is a magnetic component having a magnetic body including metal magnetic particles, the total area ratio of the metal magnetic particles in the cross section of the magnetic body is 75% or more; The metal magnetic particles are a first large particle having an amorphous structure and a Heywood diameter of 3 μm or more in a cross section of the magnetic material; a second large particle having a nanocrystalline structure and a Heywood diameter of 3 μm or more in a cross section of the magnetic material; The insulating coating of the first large particles is thicker than the insulating coating of the second large particles. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing a cross section of a magnetic core according to an embodiment. [Figure 2A]FIG. 2A is a graph showing an example of the particle size distribution of metal magnetic particles. [Figure 2B] FIG. 2B is a graph showing an example of the particle size distribution of metal magnetic particles. [Figure 2C] FIG. 2C is a graph showing an example of the particle size distribution of metal magnetic particles. [Figure 3A] FIG. 3A is an enlarged schematic diagram of a cross section of the magnetic core shown in FIG. [Figure 3B] FIG. 3B is an enlarged schematic view of a cross section of the magnetic core according to the second embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of a powder processing apparatus used to form an insulating coating on metal magnetic particles. [Diagram 5] FIG. 5 is a cross-sectional view showing an example of a magnetic component. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The following describes the embodiment.

[0017] First embodiment 1 according to this embodiment, the outer dimensions and shape are not particularly limited as long as the magnetic core 2 has a predetermined shape. The magnetic core 2 includes at least metal magnetic particles 10 and resin 20, and the metal magnetic particles 10 are dispersed in the resin 20. That is, the metal magnetic particles 10 are bound together via the resin 20, so that the magnetic core 2 has a predetermined shape.

[0018] The total area ratio A0 of the metal magnetic particles 10 in the cross section of the magnetic core 2 is preferably 75% or more. The upper limit of the total area ratio is not particularly limited, but from the viewpoint of reducing core loss, A0 may be 90% or less, or may be 89% or less. From the viewpoint of increasing magnetic permeability, the higher A0 is, the more preferable. This total area ratio A0 of the metal magnetic particles 10 corresponds to the packing rate of the metal magnetic particles 10 in the magnetic core 2, and may be calculated by analyzing the cross section of the magnetic core 2 using an electron microscope such as a SEM (scanning electron microscope) or a STEM (scanning transmission electron microscope).

[0019] For example, an arbitrary cross section of the magnetic core 2 is divided into multiple consecutive visual fields and observed, and the area of ​​each metal magnetic particle 10 included in each visual field is measured. The total area of ​​the metal magnetic particles 10 is then divided by the total area of ​​the observed visual fields to calculate the total area ratio A0 (%) of the metal magnetic particles 10. In this cross-sectional analysis, the total area of ​​the visual fields must be at least 1,000,000 μm 2 It is preferable to set the above.

[0020] In addition, in the cross-sectional analysis, if the cut surface of the observation sample (the surface obtained by cutting and polishing the magnetic core 2) does not satisfy the total area of ​​the above-mentioned field of view, after analyzing a predetermined cut surface, the cut surface is polished again by 100 μm or more, and the cross-sectional analysis is performed again, so that the total area of ​​the field of view can be increased to 1,000,000 μm. 2 It may be more than that.

[0021] The metal magnetic particles 10 contained in the magnetic core 2 preferably include a first particle group 10a having a Heywood diameter of 3 μm or more, and further include a second particle group 10b having a Heywood diameter of less than 3 μm. Here, the "Heywood diameter" in this embodiment means the circle-equivalent diameter of each metal magnetic particle 10 observed on the cross section of the magnetic core 2. Specifically, when the area of ​​each metal magnetic particle 10 on the cross section of the magnetic core 2 is S, the Heywood diameter of each metal magnetic particle 10 is expressed as (4S / π) 1 / 2 It is expressed as:

[0022] When the metal magnetic particles 10 include the first particle group 10a and the second particle group 10b, the content of the first particle group 10a and the content of the second particle group 10b are not particularly limited in the magnetic core 2, but from the viewpoint of increasing the magnetic permeability, it is preferable that the content of the first particle group 10a is greater than the content of the second particle group 10b. In other words, in the cross section of the magnetic core 2, if the total area ratio occupied by the first particles 10a is AL and the total area ratio occupied by the second particles 10b is AS, it is preferable that the area ratio of the metal magnetic particles 10 satisfies AL>AS.

[0023] By making the content of the first particles 10a higher than that of the second particles 10b, it is possible to improve the magnetic permeability of the magnetic core 2. The sum of AL and AS is the total area ratio A0 of the metal magnetic particle 10 (AL+AS=A0), and AL and AS can be measured in the same manner as A0.

[0024] In addition, the metal magnetic particles 10 preferably include two or more particle groups with different average particle sizes. For example, the metal magnetic particles 10 may include at least large particles 11 corresponding to the first particle group 10a, but preferably include large particles 11 and small particles 12, and may also include medium particles 13. The large particles 11, small particles 12, and medium particles 13 can be distinguished based on the particle size distribution of the metal magnetic particles 10. The particle size distribution of the metal magnetic particles 10 may be determined by measuring the Heywood diameter of at least 1,000 metal magnetic particles 10 in any cross section of the magnetic core 2.

[0025] For example, the graphs shown in Figures 2A to 2C show the particle size distribution of metal magnetic particles 10. In each of the graphs in Figures 2A to 2C, the vertical axis represents the area-based frequency (%), and the horizontal axis is a logarithmic axis showing the particle diameter (μm) calculated as the Heywood diameter. Note that the particle size distributions shown in Figures 2A to 2C are merely examples, and the particle size distribution of metal magnetic particles 10 is not limited to Figures 2A to 2C.

[0026] When metal magnetic particles 10 are composed of two particle groups (large particles and small particles) with different average particle sizes, the particle size distribution of metal magnetic particles 10 has two peaks as shown in Figure 2A. When metal magnetic particles 10 are composed of three particle groups (large particles, medium particles, and small particles) with different average particle sizes, the particle size distribution of metal magnetic particles 10 has three peaks as shown in Figure 2B.

[0027] 2A and 2B, when the particle size distribution of metal magnetic particles 10 is represented by a series of distribution curves, a particle group belonging to the peak located on the largest diameter side (the peak located on the rightmost side of the horizontal axis) and having a D20 of 3 μm or more is referred to as large particles 11, and a particle group belonging to the peak located on the smallest diameter side (the peak located on the leftmost side of the horizontal axis) and having a D80 of less than 3 μm is referred to as small particles 12. Particles other than large particles 11 and small particles 12 are referred to as medium particles 13.

[0028] Here, "particle group belonging to the peak located on the largest diameter side" means a particle group included in the range from the bottom (rightmost end) of the distribution curve to the local minimum point via the peak top when tracing the distribution curve from the large diameter side (right side of the graph). That is, in the case of the particle size distribution shown in FIG. 2A, the particle group included in the range from EP1 to LP via Peak1 corresponds to "particle group belonging to the peak located on the largest diameter side". In the case of the particle size distribution shown in FIG. 2B, the particle group included in the range from EP1 to LP1 via Peak1 corresponds to "particle group belonging to the peak located on the largest diameter side".

[0029] 2A and 2B, the particle group belonging to Peak 1 has a D20 of 3 μm or more, and the particle group belonging to Peak 1 is large particles 11.

[0030] "Particle group belonging to the peak located on the smallest diameter side" means a particle group included in the range from the tail (leftmost end) of the distribution curve to the local minimum point via the peak top when tracing the distribution curve from the small diameter side (left side of the graph). That is, in the case of the particle size distribution shown in FIG. 2A, the particle group included in the range from EP2 to LP via Peak2 corresponds to "particle group belonging to the peak located on the smallest diameter side". In addition, in the case of the particle size distribution shown in FIG. 2B, the particle group included in the range from EP2 to LP2 via Peak2 corresponds to "particle group belonging to the peak located on the smallest diameter side".

[0031] In addition, D80 means the Heywood diameter at which the cumulative frequency based on area is 80%. In the particle size distribution in FIG. 2A and FIG. 2B, the particle group belonging to Peak 2 has D80 of less than 3 μm, and this particle group belonging to Peak 2 is small particles 12.

[0032] In the particle size distribution shown in FIG. 2B, the particle group from LP1 through Peak 3 to LP2 is the particle group belonging to Peak 3. In this particle group belonging to Peak 3, D20 is less than 3 μm and D80 is 3 μm or more. In other words, the particle group belonging to Peak 3 is medium particles 13 that do not fall into either large particles 11 or small particles 12.

[0033] When the metal magnetic particle 10 includes two or more particle groups with different average particle sizes, the small particles 12 and / or the medium particles 13 may have the same particle composition as the large particles 11, or may have a different particle composition from the large particles 11. Note that "different particle compositions" refers to cases where the types of constituent elements contained in the particle body are different, or cases where the types of constituent elements are the same but the content ratios of each constituent element are different. A constituent element refers to an element that is contained in the particle body at 1 at% or more. In other words, the elements contained in the particle body other than impurity elements are referred to as constituent elements.

[0034] When small particles 12 and / or medium particles 13 have a particle composition different from that of large particles 11, metal magnetic particles 10 may be classified using a combination of composition analysis and particle size analysis. Specifically, when observing the cross section of magnetic core 2 with an electron microscope, an EDX device (energy dispersive X-ray analyzer) or an EPMA (electron probe microanalyzer) is used to analyze the composition of each metal magnetic particle 10 contained in the observation field, and metal magnetic particles 10 are classified based on the composition. Then, by measuring the Heywood diameter of metal magnetic particles 10 belonging to each composition, multiple distribution curves are obtained.

[0035] For example, when metal magnetic particles 10 are composed of four particle groups with different particle compositions, four distribution curves are obtained, as shown in Fig. 2C. In the particle size distribution in Fig. 2C, the distribution curve of the particle group having composition A is shown by a solid line, the distribution curve of the particle group having composition B is shown by a dotted line, the distribution curve of the particle group having composition C is shown by a dashed line, and the distribution curve of the particle group having composition D is shown by a dashed line.

[0036] 2C, when the particle size distribution of metal magnetic particles 10 is represented by multiple distribution curves according to the composition, particle groups having D20 of 3 μm or more are large particles 11, particle groups having D80 of less than 3 μm are small particles 12, and particle groups other than large particles 11 and small particles 12 are medium particles 13. That is, in FIG. 2C, particle groups having composition A and particle groups having composition B are large particles 11, particle groups having composition C are small particles 12, and particle groups having composition D are medium particles 13.

[0037] As described above, the D20 of the large particles 11 is 3 μm or more, and the Heywood diameters of the large particles 11 are preferably 3 μm or more. The average value (arithmetic mean diameter) of the Heywood diameters of the large particles 11 is not particularly limited, and is preferably, for example, 5 μm or more and 40 μm or less, and preferably 10 μm or more and 35 μm or less. The D80 of the small particles 12 is less than 3 μm, and the Heywood diameters of the small particles 12 are preferably, for example, less than 3 μm. The average value (arithmetic mean diameter) of the Heywood diameters of the small particles 12 is not particularly limited, and is preferably, for example, 2 μm or less, and more preferably 0.2 μm or more and less than 2 μm.

[0038] As described above, if the total area ratio of the large particles 11 in the cross section of the magnetic core 2 is AL and the total area ratio of the small particles 12 in the cross section of the magnetic core 2 is AS, then from the viewpoint of increasing the magnetic permeability, it is preferable that AL is larger than AS (AL>AS). Note that in this embodiment, even if AL is equal to or smaller than AS, the effect of reducing core loss can be achieved.

[0039] Specifically, the ratio (AL / A0) of the total area of ​​the large particles 11 to the total area of ​​the metal magnetic particles 10 is not particularly limited, but may be 15% or more and 95% or less, and from the viewpoint of increasing the magnetic permeability, it is preferable that it is more than 50% and 90% or less, and more preferable that it is 60% or more and 88% or less.

[0040] The ratio of the total area of ​​the small particles 12 to the total area of ​​the metal magnetic particles 10 (AS / A0) may be 5% or more and 85% or less, and from the viewpoint of increasing the magnetic permeability, 5% or more and less than 50% is preferable, and 10% or more and 40% or less is more preferable. When the magnetic core 2 contains the small particles 12 together with the large particles 11 in the above ratio, the magnetic permeability can be improved. The above AL and AS may be measured by the same method as A0.

[0041] Metal magnetic particles 10 may contain medium particles 13, and when medium particles 13 are contained, the average Heywood diameter (arithmetic mean diameter) of medium particles 13 is not particularly limited and is preferably, for example, 3 μm or more and 5 μm or less. Furthermore, the ratio (AM / A0) of the total area (AM) of medium particles 13 to the total area (A0) of metal magnetic particles 10 is preferably 30% or less, and more preferably 5 to 20%.

[0042] The average circularity of the large particles 11 in the cross section of the magnetic core 2 is preferably 0.90 or more, and more preferably 0.95 or more. The higher the average circularity of the large particles 11, the more the withstand voltage and DC bias characteristics can be improved. The circularity of each large particle 11 is calculated by S L , where L is the perimeter of each large particle 11, and 2(πS L ) 1 / 2 The circularity of a perfect circle is 1, and the closer the circularity is to 1, the higher the sphericity of the particle. The average circularity of the large particles 11 is preferably calculated by measuring the circularity of at least 100 large particles 11.

[0043] The average circularity of the small particles 12 and the average circularity of the medium particles 13 are not particularly limited, but preferably have a high average circularity, similar to that of the large particles 11. Specifically, the average circularity of the small particles 12 and the average circularity of the medium particles 13 are both preferably 0.80 or more.

[0044] In this embodiment, the method shown in Figures 2A to 2C is presented as a method for classifying metal magnetic particles 10 into large particles 11, small particles 12, etc., but when small particles 12 have the same particle composition as large particles 11, it is preferable to adopt the classification method shown in Figure 2A or Figure 2B, and when small particles 12 have a particle composition different from large particles 11, it is preferable to adopt the classification method shown in Figure 2C.

[0045] In the magnetic core 2 of this embodiment, the large particles 11 can be divided into two types of particle groups having different material states within the particles. Specifically, the large particles 11 include first large particles 11a having an amorphous structure and second large particles 11b having a nanocrystalline structure.

[0046] Here, the term "nanocrystalline structure" refers to a crystal structure in which the degree of amorphousness X is less than 85% and the average crystallite size is 0.5 nm to 30 nm, whereas the term "amorphous structure" refers to a crystal structure in which the degree of amorphousness X is 85% or more, including a heteroamorphous structure.

[0047] The heteroamorphous structure means a structure in which primary microcrystals exist in an amorphous state, and the average diameter of the primary microcrystals in the heteroamorphous structure is preferably 0.1 nm or more and 10 nm or less. In this embodiment, the "crystalline structure" means a crystal structure in which the degree of amorphization X is less than 85% and the average crystallite diameter is 100 nm or more.

[0048] The crystal structure within the grain (i.e., the degree of amorphism X and crystallite size) can be identified by structural analysis using various electron microscopes such as SEM, TEM, and STEM, electron diffraction, XRD (X-ray diffraction), or EBSD (electron backscatter diffraction). For example, EBSD orientation mapping images and bright-field images of electron microscopes allow visual identification of crystalline and amorphous parts, and the degree of amorphism X and average crystallite size can be measured by analyzing such images. In addition, if no crystal-attributed spots are identified by electron diffraction, the particles to be measured can be identified as having an amorphous structure.

[0049] The degree of amorphousness X (unit: %) is the proportion of crystals P C , the amorphous fraction P A Then, X=(P A / (P C +P A When calculating the degree of amorphousness X using XRD, the crystalline fraction P C is measured as the crystalline scattering integral intensity Ic, and the amorphous fraction P A can be measured as the amorphous scattering integral intensity Ia. When calculating the degree of amorphousness X using EBSD or an electron microscope, P C is the area ratio of the crystalline part in the grain, P A can be measured as the area ratio of the amorphous portion.

[0050] When classifying large particles 11 using an electron microscope, as described above, structural analysis is performed on the large particles 11 contained within the observation field of view to identify the material state, but this structural analysis may be performed on arbitrarily selected large particles 11 from within the observation field of view. In this case, the large particles 11 whose material state has been identified are regarded as analysis particles, and other large particles 11 having the same composition as the analysis particle can be regarded as having the same material state as the analysis particle.

[0051] For example, when first large particles 11a of Fe-Co-BP-Si-Cr and second large particles 11b of Fe-Si-B-Nb-Cu are present as large particles 11, they can be identified by area analysis using EDX. Then, for example, if an arbitrary analysis target particle is selected from a group of Fe-Co-BP-Si-Cr particles and a structural analysis is performed, and it is identified that the analysis target particle has an amorphous structure, then all of the group of Fe-Co-BP-Si-Cr particles can be regarded as having an amorphous structure.

[0052] Similarly, if a particle to be analyzed is selected from a group of Fe-Si-B-Nb-Cu particles and a structural analysis is performed, and it is determined that the particle to be analyzed has a nanocrystalline structure, then all particles in the group of Fe-Si-B-Nb-Cu particles can be regarded as having a nanocrystalline structure.

[0053] The amorphous first large particles 11a and the nanocrystalline second large particles 11b are both made of a soft magnetic alloy, and the alloy composition is not particularly limited. The first large particles 11a and the second large particles 11b may have the same alloy composition or different alloy compositions, although they have different material states.

[0054] Examples of soft magnetic alloys having a nanocrystalline structure or soft magnetic alloys having an amorphous structure include Fe-Si-B based alloys, Fe-Si-BC based alloys, Fe-Si-BC-Cr based alloys, Fe-Nb-B based alloys, Fe-Nb-BP based alloys, Fe-Nb-B-Si based alloys, Fe-Co-PC based alloys, Fe-Co-B based alloys, Fe-Co-B-Si based alloys, Fe-Si-B-Nb-Cu based alloys, Fe-Si-B-Nb-P based alloys, Fe-Co-BP-Si based alloys, and Fe-Co-BP-Si-Cr based alloys.

[0055] The total area ratio of the amorphous first large particles 11a in the cross section of the magnetic core 2 is defined as AL1, and the ratio of the total area ratio (AL1) of the first large particles 11a to the total area ratio (A0) of the metal magnetic particles 10 is defined as AL1 / A0. Similarly, the total area ratio of the nanocrystalline second large particles 11b in the cross section of the magnetic core 2 is defined as AL2, and the ratio of the total area ratio (AL2) of the second large particles 11b to the total area ratio (A0) of the metal magnetic particles 10 is defined as AL2 / A0. Although AL1 / A0 and AL2 / A0 are not particularly limited, each is preferably 3% or more, preferably 4% to 78%, and more preferably 7% to 44%.

[0056] Furthermore, AL1 / (AL1+AL2) and AL2 / (AL1+AL2) are not particularly limited, but may each be within the range of, for example, 4% to 96%. From the viewpoint of obtaining excellent DC bias characteristics, it is more preferable that AL1 / (AL1+AL2) is 50% to 96%, and from the viewpoint of further reducing core loss, it is more preferable that AL2 / (AL1+AL2) is 50% to 90%.

[0057] From the viewpoint of improving the core loss and the DC bias characteristics in a well-balanced manner and enhancing the effect of improving the core loss, AL1 / (AL1+AL2) is preferably 10% to 94%, and more preferably 18% to 85%. Note that AL1 and AL2 may be measured in the same manner as the total area proportion A0 of the metal magnetic particles 10.

[0058] When the metal magnetic particle 10 includes the small particles 12, there is no particular limitation on the composition of the small particles 12. The small particles 12 may have an amorphous structure or a nanocrystalline structure, but from the viewpoint of saturation magnetic flux, it is preferable that the small particles 12 have a crystalline structure.

[0059] Examples of soft magnetic metals having a crystalline structure include pure iron such as carbonyl iron, Co, Fe-Ni based alloys, Fe-Si based alloys, Fe-Si-Cr based alloys, Fe-Si-Al based alloys, Fe-Si-Al-Ni based alloys, Fe-Ni-Si-Co based alloys, Fe-Co based alloys, Fe-Co-V based alloys, Fe-Co-Si based alloys, Fe-Co-Si-Al based alloys, and Co based alloys.

[0060] The small particles 12 are preferably pure iron particles, Fe-Ni based alloy particles, Fe-Co based alloy particles, Fe-Si based alloy particles, or Co particles.

[0061] Furthermore, when metal magnetic particle 10 includes medium particles 13, there are no particular limitations on the composition of medium particles 13. For example, medium particles 13 may have a crystalline structure, but from the viewpoint of reducing the coercive force, it is preferable for medium particles 13 to have a nanocrystalline structure or an amorphous structure.

[0062] The composition of the metal magnetic particles 10 can be analyzed, for example, using an EDX device or EPMA attached to an electron microscope. When the first large particles 11a and the second large particles 11b have different particle compositions, the first large particles 11a and the second large particles 11b may be distinguished from each other by area analysis using an EDX device or EPMA. The composition of the metal magnetic particles 10 may also be analyzed using a 3DAP (three-dimensional atom probe).

[0063] When using 3DAP, a small region (e.g., a region of Φ20 nm x 100 nm) can be set inside the metal magnetic particle to be measured and the average composition can be measured, making it possible to identify the composition of the particle itself while excluding the effects of the resin components contained in the magnetic core 2 and oxidation of the particle surface.

[0064] As shown in Fig. 3A, each of the first large particles 11a has an insulating coating 4a covering the particle surface, and each of the second large particles 11b has an insulating coating 4b covering the particle surface. The insulating coating 4a and the insulating coating 4b may cover the entire particle surface or only a part of the particle surface. Each of the insulating coatings 4a and 4b preferably covers 80% or more of the particle surface observed in the cross section of the magnetic core 2.

[0065] Furthermore, each of the insulating coatings 4a and 4b may have thickness deviations within a single particle, but it is preferable that the thickness is as uniform as possible. For example, the arithmetic mean height Ra of the contour curve of the coating surface is preferably 0.5 nm or more and 100 nm or less. The above Ra is a type of line roughness parameter, and may be calculated by identifying the outermost surface part of the insulating coatings (4a, 4b) observed on the cross section of the magnetic core 2 as the contour curve. For example, when determining Ra for any metal particle, the cross section may be observed and evaluated using a transmission electron microscope. As an evaluation method, when observing the cross section using a transmission electron microscope, evaluation may be performed using a contour curve of 5 μm or more.

[0066] The material of the insulating coating 4a and the material of the insulating coating 4b are not particularly limited, and the insulating coating 4a and the insulating coating 4b may have the same composition or different compositions. For example, the insulating coating 4a and the insulating coating 4b may include a coating formed by oxidation of the particle surface and / or a coating containing an inorganic material such as BN, SiO2, MgO, Al2O3, phosphate, silicate, borosilicate, bismuthate, various glasses, etc.

[0067] From the viewpoint of suppressing a decrease in the resistivity of the magnetic core 2, it is preferable that both the insulating coating 4a and the insulating coating 4b have an oxide glass coating containing one or more elements selected from P, Si, Bi, and Zn. In the oxide glass coating, when the total amount of elements contained in the coating excluding oxygen is taken as 100 wt%, the total amount of one or more elements selected from P, Si, Bi, and Zn is preferably the largest, more preferably 50 wt% or more, and even more preferably 60 wt% or more.

[0068] Examples of the oxide glass coatings include phosphate (P2O5)-based glass coatings, bismuthate (Bi2O3)-based glass coatings, and borosilicate (B2O3-SiO2)-based glass coatings.

[0069] Examples of phosphate-based glass include P-Zn-Al-O based glass and P-Zn-Al-RO based glass (where "R" is one or more elements selected from alkali metals), and it is preferable that the phosphate-based glass coating contains 50 wt% or more of P2O5.

[0070] Examples of bismuthate-based glass include Bi-Zn-B-Si-O-based glass and Bi-Zn-B-Si-Al-O-based glass, and it is preferable that the bismuthate-based glass coating contains 50 wt% or more of Bi2O3.

[0071] An example of borosilicate glass is Ba-Zn-B-Si-Al-O glass, and the borosilicate glass coating preferably contains 10 wt % or more of B2O3.

[0072] The insulating coating 4a and the insulating coating 4b may each have a single-layer structure or a multi-layer structure. An example of a multi-layer structure is a laminated structure including an oxide layer on the particle surface and an oxide glass layer covering the oxide layer. When the insulating coating 4a and / or 4b has a multi-layer structure, the total thickness of each layer is defined as the thickness of the insulating coating. The composition of the insulating coatings 4a and 4b can be analyzed by, for example, EDX, EPMA, or EELS (electron energy loss spectroscopy).

[0073] In the magnetic core 2 of this embodiment, the insulating coating 4a of the first large particles 11a is thicker than the insulating coating 4b of the second large particles 11b. The first large particles 11a having an amorphous structure have a thicker insulating coating than the second large particles 11b having a nanocrystalline structure, which makes it possible to reduce core loss while maintaining good DC bias characteristics.

[0074] If the average thickness of the insulating coating 4a of the first large particles 11a is T1 and the average thickness of the insulating coating 4b of the second large particles 11b is T2, T1 / T2 exceeds 1.0 and, from the viewpoint of reducing core loss, is preferably 1.3 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. The upper limit of T1 / T2 is not particularly limited, but from the viewpoint of the insulating properties of the powder, it is preferably 40 or less, or preferably 30 or less, or preferably 20 or less.

[0075] From the viewpoint of the magnetic permeability of the magnetic core, T1 is preferably 200 nm or less. From the viewpoint of reducing core loss while ensuring insulation, T2 is preferably 5 nm or more. The upper limit of T2 is determined based on T1, and may be, for example, 150 nm or less, 100 nm or less, or 50 nm or less.

[0076] T1 may be calculated by observing the cross section of the magnetic core 2 with various electron microscopes, and is preferably calculated by measuring the thickness of the insulating coating 4a for at least ten first large particles 11a. T2 may be calculated in the same manner as T1. Note that the magnetic core 2 may include large particles 11 that do not have an insulating coating 4.

[0077] When the metal magnetic particle 10 includes small particles 12, the small particles 12 do not necessarily have an insulating coating, but each small particle 12 preferably has an insulating coating 6 covering the particle surface. The material of the insulating coating 6 is not particularly limited, and for example, the insulating coating 6 can be a coating (oxide coating) formed by oxidation of the surface of the small particles 12, or a coating containing an inorganic material such as BN, SiO2, MgO, Al2O3, phosphate, silicate, borosilicate, bismuthate, or various glasses, and preferably includes a coating of oxide glass. In addition, the insulating coating 6 may have a single layer structure, or may have a structure in which two or more types of coatings are laminated. The average thickness of the insulating coating 6 is not particularly limited, and for example, it is preferably 5 nm or more and 100 nm or less, and more preferably 5 nm or more and 50 nm or less.

[0078] When metal magnetic particles 10 include medium particles 13, medium particles 13, like other particle groups, preferably have an insulating coating covering the particle surface. The composition of the insulating coating of medium particles 13 is not particularly limited, and may have the same composition as insulating coating 4a or 4b of large particles 11, or may have a different composition from insulating coating 4a or 4b of large particles 11. The average thickness of the insulating coating of medium particles 13 is not particularly limited, and is, for example, preferably 5 nm or more and 200 nm or less, and more preferably 10 nm or more and 50 nm or less.

[0079] As with the insulating coating 4, the insulating coating 6 of the small particles 12 and the insulating coating of the medium particles 13 may cover the entire particle surface or only a portion of the particle surface, and preferably covers 80% or more of the particle surface observed in the cross section of the magnetic core 2. The magnetic core 2 may include small particles 12 and medium particles 13 that do not have an insulating coating.

[0080] 3 functions as an insulating binder that fixes the metal magnetic particles 10 in a predetermined dispersed state. The material of the resin 20 is not particularly limited, and it is preferable that the resin 20 contains a thermosetting resin such as an epoxy resin.

[0081] The magnetic core 2 may contain a modifier for suppressing contact between the soft magnetic metal particles. As the modifier, a polymer material such as polyethylene glycol (PEG), polypropylene glycol (PPG), polycaprolactone (PCL) or the like can be used, and it is preferable to use a polymer material having a polycaprolactone structure.

[0082] Examples of polymers having a polycaprolactone structure include urethane raw materials such as polycaprolactone diol and polycaprolactone tetraol, or some polyesters. The content of the modifier is preferably 0.025 wt% or more and 0.500 wt% or less with respect to the total amount of the magnetic core 2. The above-mentioned modifier is considered to be present by being adsorbed so as to coat the surface of the metal magnetic particles 10.

[0083] An example of a method for manufacturing the magnetic core 2 according to this embodiment will now be described.

[0084] First, a raw material powder containing first large particles 11a and a raw material powder containing second large particles 11b are manufactured as raw material powders of metal magnetic particles 10. When small particles 12 and medium particles 13 are added to magnetic core 2, raw material powders containing small particles 12 and raw material powders containing medium particles 13 are prepared.

[0085] The manufacturing method of each raw material powder is not particularly limited, and a suitable manufacturing method may be adopted depending on the desired particle composition. For example, the raw material powder may be manufactured by an atomization method such as a water atomization method or a gas atomization method. Alternatively, the raw material powder may be manufactured by a synthesis method such as a CVD method using at least one of evaporation, reduction, and thermal decomposition of a metal salt. The raw material powder may also be manufactured by an electrolysis method or a carbonyl method, or by pulverizing a ribbon-shaped or thin plate-shaped starting alloy. In particular, the raw material powder including the first large particles 11a and the raw material powder including the second large particles 11b are preferably manufactured by a quenching gas atomization method.

[0086] The particle size of each raw material powder can be adjusted by the powder production conditions and various classification methods. In addition, the raw material powder that becomes the nanocrystalline second large particles 11b is preferably subjected to a heat treatment to control the crystal structure of the second large particles 11b.

[0087] In addition, when the composition of the small particles 12 is to be the same as that of the large particles 11 (first large particles 11a and / or second large particles 11b), a raw material powder having a wide particle size distribution may be produced and then classified to obtain a raw material powder containing large particles 11 and a raw material powder containing small particles 12.

[0088] Next, a coating is formed on each raw material powder. When manufacturing a magnetic core using a metal magnetic powder containing multiple particle groups, it is common to mix the multiple raw material powders and then perform a coating on the mixed powder at once to simplify the manufacturing process. However, if the coating is performed on the mixed powder, there is a high possibility that the insulating coating of each particle group will have the same thickness (i.e., T1 ≒ T2).

[0089] In this embodiment, in order to make the insulating coating 4a of the first large particles 11a thicker than the insulating coating 4b of the second large particles 11b (i.e., to realize T1>T2), it is preferable to perform a coating formation process on the first large particles 11a and the second large particles 11b separately.

[0090] Examples of the coating formation method include heat treatment, phosphate treatment, mechanical alloying, silane coupling treatment, and hydrothermal synthesis. A suitable coating formation method can be selected depending on the type of insulating coating to be formed.

[0091] For example, when insulating coating 4a and / or insulating coating 4b includes an oxide glass coating, the oxide glass coating is preferably formed by a mechanochemical method using a mechanofusion device. Specifically, in the coating formation process by the mechanochemical method, raw material powder including large particles and a powdered coating material including the constituent elements of the insulating coating are introduced into the rotating rotor of the mechanofusion device, and the rotating rotor is rotated.

[0092] A press head is installed inside the rotor, and when the rotor is rotated, the mixture of raw material powder and coating material is compressed in the gap between the inner wall surface of the rotor and the press head, generating frictional heat. This frictional heat softens the coating material, which then adheres to the surface of the large particles through the compression action, forming an oxide glass coating.

[0093] The thickness of insulating film 4a and the thickness of insulating film 4b may be controlled based on the mixture ratio of the coating materials, the rotation speed, the processing time, and the like.

[0094] When forming an insulating coating 6 on the small particles 12, the insulating coating 6 is preferably formed by mixing a raw material powder containing the small particles 12 with a powdered coating material containing the constituent elements of the insulating coating 6 while applying mechanical impact energy, and more preferably by mixing while applying impact, compression, and shear energy.

[0095] In such a coating process, a powder processing device such as a planetary ball mill or Nobilta manufactured by Hosokawa Micron Corp. can be used as a device capable of applying mechanical energy to the powder. For example, in the coating process on the small particles 12, a powder processing device 60 as shown in Fig. 4, which can mix at a high rotation speed, can be used.

[0096] The powder processing device 60 has a cylindrical cross section and includes a chamber 61, in which a rotatable blade 62 is installed. The raw material powder containing the small particles 12 and the coating material are fed into the chamber 61, and the blade 62 is rotated at a rotation speed of 2000 to 6000 rpm, whereby mechanical impact, compression, and shear energy can be applied to the mixture 63 of the raw material powder and the coating material. By using such a powder processing device 60, the insulating coating 6 can be formed on the particle surface even for small particles 12 having a particularly small particle size.

[0097] When medium particles 13 having an insulating coating are used, the medium particles 13 may be mixed with the first large particles 11a or the second large particles 11b and subjected to a coating formation treatment together with the first large particles 11a or the second large particles 11b to form an insulating coating on the surface of the medium particles 13. Alternatively, only the raw material powder of the medium particles 13 may be subjected to the coating formation treatment individually.

[0098] A method for manufacturing the magnetic core 2 using each raw material powder of the metal magnetic particles 10 will be described below. First, each raw material powder with an insulating coating formed thereon and a resin raw material (such as a thermosetting resin) are kneaded to obtain a resin compound. In this kneading step, various kneading machines such as a kneader, a planetary mixer, a rotation-revolution mixer, or a twin-screw extruder may be used, and modifiers, preservatives, dispersants, non-magnetic powders, etc. may be added to the resin compound.

[0099] Next, the resin compound is filled into a mold and compression molded to obtain a molded body. The molding pressure at this time is not particularly limited, and is preferably, for example, 1250 MPa or more and 2000 MPa or less. The total area ratio of the metal magnetic particles 10 in the magnetic core 2 can be controlled by the amount of resin 20 added, but can also be controlled by the molding pressure. When a thermosetting resin is used as the resin 20, the above molded body is held at 100°C to 200°C for 1 hour to 5 hours to cure the thermosetting resin. Through the above steps, a magnetic core 2 as shown in FIG. 1 is obtained.

[0100] The magnetic core 2 according to this embodiment can be applied to various magnetic components such as, but not limited to, an inductor, a choke coil, a transformer, a reactor, etc. For example, a magnetic component 100 shown in FIG.

[0101] In the magnetic component 100 shown in Fig. 5, the element body is composed of a magnetic core 2 as shown in Fig. 1. A coil 5 is embedded inside the magnetic core 2, which is the element body, and ends 5a, 5b of the coil 5 are each drawn out to an end face of the magnetic core 2. A pair of external electrodes 7, 9 are formed on the end face of the magnetic core 2, and the pair of external electrodes 7, 9 are electrically connected to the ends 5a, 5b of the coil 5, respectively. When the coil 5 is embedded inside the magnetic core 2 as in the magnetic component 100, the area ratios of the metal magnetic particles 10 such as A0, AL (AL1 and AL2), and AS are analyzed in a field of view in which the coil 5 is not visible.

[0102] The magnetic component including the magnetic core 2 is not limited to the embodiment shown in Fig. 5, and may be a magnetic component formed by winding a wire a predetermined number of times around the surface of a magnetic core having a predetermined shape (for example, a ring shape or a drum shape). The use of the magnetic component is not limited to the magnetic component 100 shown in Fig. 5, and is not particularly limited, but examples include magnetic components for relatively low frequency applications with a frequency of about 400 kHz or less (for example, choke coils, reactors, etc.), and the effect of reducing core loss is particularly large in low frequency applications. Note that the magnetic component is not limited to a magnetic component having a magnetic core, and may be a magnetic component without a magnetic core.

[0103] (Summary of the first embodiment) The magnetic core 2 of this embodiment contains metal magnetic particles 10 and resin 20, and the total area ratio A0 of the metal magnetic particles 10 shown in the cross section of the magnetic core 2 is 75% or more. The metal magnetic particles 10 contain first large particles 11a having an amorphous structure and second large particles 11b having a nanocrystalline structure, and the insulating coatings 4a of the first large particles 11a are thicker than the insulating coatings 4b of the second large particles 11b.

[0104] The magnetic core 2 has the above-mentioned characteristics, so that it is possible to reduce core loss while maintaining good DC bias characteristics. Specifically, the following facts have become clear through experiments conducted by the present inventors.

[0105] When comparing a magnetic core containing nanocrystalline particles as the main powder (hereinafter referred to as a nanocrystalline magnetic core) with a magnetic core containing amorphous particles as the main powder (hereinafter referred to as an amorphous magnetic core), the core loss of the nanocrystalline magnetic core is lower than that of the amorphous magnetic core, and the DC superposition characteristics of the amorphous magnetic core are superior to those of the nanocrystalline magnetic core. However, by simply mixing the amorphous particles and the nanocrystalline particles, the core loss can only be calculated from the mixture ratio.

[0106] In the magnetic core 2 of this embodiment, the first large particles 11a having an amorphous structure and a relatively thick insulating coating 4a are mixed with the second large particles 11b having a nanocrystalline structure and a relatively thin insulating coating 4b. In the magnetic core 2 of this embodiment, the core loss can be effectively reduced while maintaining good DC bias characteristics.

[0107] Furthermore, in this embodiment, in order to increase the Bs of the magnetic core 2, even if high-pressure molding of the magnetic powder is performed, the insulating coating 4a of the first large particles 11a having an amorphous structure can be made thicker than the insulating coating 4b of the second large particles 11b having a nanocrystalline structure, thereby making it possible to further reduce core loss while maintaining high magnetic permeability (for example, magnetic permeability of 20 or more, 25 or more, 30 or more, or 35 or more).

[0108] Second embodiment In the second embodiment, a magnetic core 2a shown in Fig. 3B will be described. Note that in the second embodiment, the description of the configuration common to the first embodiment will be omitted and the same reference numerals as in the first embodiment will be used.

[0109] 3B, in the magnetic core 2a of the second embodiment, first large particles 11a having an amorphous structure and second large particles 11b having a nanocrystalline structure are mixed, and the insulating coating 4a of the first large particles 11a is thicker than the insulating coating 4b of the second large particles 11b. Therefore, the magnetic core 2a of the second embodiment can provide the same effects as the magnetic core 2 of the first embodiment.

[0110] The magnetic core 2a includes two or more types of small particles 12 with different compositions of the insulating coating 6. In other words, the small particles 12 included in the metal magnetic particle 10 can be divided into two or more types of small particle groups based on the coating composition. Specifically, the small particles 12 include at least a first small particle 12a having a first insulating coating 6a and a second small particle 12b having a second insulating coating 6b with a composition different from that of the first insulating coating 6a, and may further include a third small particle 12c to an n-th small particle 12x having a coating composition different from that of the other small particle groups. n means the number of small particle groups when the small particles 12 are divided based on the coating composition, and there is no particular upper limit for n. From the viewpoint of simplifying the manufacturing process, it is preferable that n is 4 or less.

[0111] Here, "different coating compositions" means that the types of constituent elements contained in the insulating coating 6 are different, and the constituent elements of the insulating coating 6 mean elements that are contained in the insulating coating 6 at 1 at % or more, where the total content of elements other than oxygen and carbon is taken as 100 at %. The composition of the insulating coating 6 may be analyzed by area analysis or point analysis using an EDX device or EPMA.

[0112] The material of each insulating coating 6 (first insulating coating 6a, second insulating coating 6b, and third insulating coating 6c to n-th insulating coating 6x) of the small particle 12 is not particularly limited. For example, each insulating coating 6 can be a coating (oxide coating) formed by oxidation of the surface of the small particle 12, or a coating containing an inorganic material such as BN, SiO2, MgO, Al2O3, phosphate, silicate, borosilicate, bismuthate, or various glasses, and preferably includes a coating of oxide glass. Examples of oxide glass include silicate (SiO2)-based glass, phosphate (P2O5)-based glass, bismuthate (Bi2O3)-based glass, and borosilicate (B2O3-SiO2)-based glass.

[0113] The first insulating coating 6a and the second insulating coating 6b may have different compositions, and the combination of the coating compositions is not particularly limited. For example, the combination of the first insulating coating 6a and the second insulating coating 6b is preferably a combination of a PO-based glass coating and a P-Zn-Al-O-based glass coating, a combination of a Bi-Zn-B-Si-O-based glass coating and a Si-O-based glass coating, or a combination of a Ba-Zn-B-Si-Al-O-based glass coating and a Si-O-based glass coating, and more preferably a combination of a Ba-Zn-B-Si-Al-O-based glass coating and a Si-O-based glass coating.

[0114] Even when the small particles 12 include the third small particles 12c to the nth small particles 12x in addition to the first small particles 12a and the second small particles 12b, the combination of coating compositions is not particularly limited, and the third small particles 12c to the nth small particles 12x may also have a coating of oxide glass having a composition different from that of the other small particle groups.

[0115] The average thickness of the insulating coating 6 is not particularly limited, and is, for example, preferably from 5 nm to 100 nm, and more preferably from 5 nm to 50 nm. The first insulating coating 6a to the nth insulating coating 6x may have approximately the same average thickness, or may have different average thicknesses.

[0116] The insulating coating 6 such as the first insulating coating 6a and the second insulating coating 6b may have a layered structure in which a plurality of coating layers are stacked. For example, the insulating coating 6 may have a layered structure including an oxide layer on the particle surface and an oxide glass layer covering the oxide layer. When one or more of the insulating coatings 6 of the first small particles 12a to the n-th insulating coating 6x have a layered structure, it is sufficient that the composition of the outermost layer (the coating layer located on the outermost side) is different among the first insulating coating 6a to the n-th insulating coating 6x, and the composition of the other coating layers located between the outermost layer and the particle surface may be the same or different among the first insulating coating 6a to the n-th insulating coating 6x.

[0117] The first small particles 12a to the nth small particles 12x may all have the same particle composition, or may each have a different particle composition. The material state of the first small particles 12a to the nth small particles 12x is not particularly limited, and any one or more types of small particle groups among the first small particles 12a to the nth small particles 12x may be amorphous or nanocrystalline, but as described above, it is preferable that the first small particles 12a to the nth small particles 12x are all crystalline.

[0118] The total area ratios of the first small particle 12a to the n-th small particle 12x in the cross section of the magnetic core 2a are denoted by AS1 to AS n In this case, the total area ratio AS of the small particles 12 in the cross section of the magnetic core 2a is expressed as AS1 to AS n The ratio of the total area ratio AS of the small particles 12 to the total area ratio AS of each small particle group is expressed as AS1 / AS to AS n It can be expressed as AS1 / AS~AS n In each case, / AS is preferably 1% or more, more preferably 6% or more, and further preferably 10% or more.

[0119] When manufacturing the magnetic core 2a, each small particle group (first small particle 12a to nth small particle 12x) is individually subjected to a coating formation process, and for the coating formation process for each small particle group, it is preferable to use a powder processing apparatus 60 as shown in FIG. 4, as described in the first embodiment. Furthermore, the composition of each insulating coating 6 (first insulating coating 6a, second insulating coating 6b, and third insulating coating 6c to nth insulating coating 6x) may be controlled by the type and composition of the coating material mixed with the raw material powder. The manufacturing conditions other than those mentioned above may be the same as those in the first embodiment.

[0120] (Summary of the second embodiment) In the magnetic core 2a of the second embodiment, the second particle group 10b having a Heywood diameter of less than 3 μm includes two or more types of small particles 12 (such as first small particles 12a and second small particles 12b) having coating compositions different from each other.

[0121] As described above, it is believed that the metal magnetic particles 10 contain two or more types of small particles 12 with different coating compositions, which improves the electrical repulsive force between the metal magnetic particles when kneaded with the resin, and suppresses magnetic aggregation of the metal magnetic particles 10. As a result, the DC superposition characteristics of the magnetic core 2a can be further improved.

[0122] The present invention is not limited to the above-described embodiments, and the above-described embodiments can be combined, and various modifications can be made within the scope of the present invention.

[0123] For example, the structure of the magnetic component is not limited to the embodiment shown in Fig. 5, and the magnetic component may be manufactured by combining multiple magnetic cores 2. Furthermore, the manufacturing method of the magnetic core is not limited to the manufacturing method shown in the above embodiment, and the magnetic core 2 and magnetic core 2a may be manufactured by a sheet method or injection molding, or may be manufactured by two-stage compression. In the manufacturing method by two-stage compression, for example, a resin compound may be temporarily compressed to produce multiple pre-molded bodies, and then these pre-molded bodies may be combined and compressed to obtain the magnetic core.

[0124] In addition, the magnetic part is not limited to a magnetic part having a magnetic core, but may be a magnetic part without a magnetic core. In other words, a composite of resin and metal powder may be defined as a magnetic core. For example, a magnetic sheet is an example. EXAMPLES

[0125] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the following examples.

[0126] (Experiment 1) In experiment 1, amorphous magnetic core samples (sample numbers 1 to 6) and nanocrystalline magnetic core samples (sample numbers 7 to 12) were manufactured using metal magnetic particles that were a mixture of one type of large particle and one type of small particle. The magnetic cores of sample numbers 1 to 12 shown in experiment 1 correspond to comparative examples.

[0127] As raw powders of metal magnetic particles, large-diameter powders having an amorphous structure, large-diameter powders having a nanocrystalline structure, and small-diameter powders consisting of small particles of pure iron were prepared. The large-diameter powders having an amorphous structure were Fe-Co-BP-Si-Cr alloy powders, which were produced by the quenching gas atomization method. The average particle size of the Fe-Co-BP-Si-Cr alloy powders was 20 μm, and the degree of amorphization was 85% or more.

[0128] The large-diameter nanocrystalline powder was an Fe-Si-B-Nb-Cu alloy powder, which was produced by subjecting powder obtained by quenching gas atomization to heat treatment. The Fe-Si-B-Nb-Cu alloy powder had an average particle size of 20 μm, an amorphous degree of less than 85%, and an average crystallite size in the range of 0.5 nm to 30 nm. The small-diameter pure iron powder had an average particle size of 1 μm.

[0129] In samples 1 to 6 in experiment 1, a coating process was performed using a mechanofusion device on large-diameter powder with an amorphous structure, and an insulating coating of P-Zn-Al-O oxide glass was formed on the surface of the large particles. On the other hand, in samples 7 to 12 in experiment 1, a coating process was performed using a mechanofusion device on large-diameter powder with a nanocrystalline structure, and an insulating coating of P-Zn-Al-O oxide glass was formed on the surface of the large particles. In the above coating process, the amount of coating material added was controlled so that the average thickness of the insulating coating would be the value shown in Table 1.

[0130] The small-diameter powder used in Experiment 1 was subjected to a coating process using a powder processing device (Nobilta, manufactured by Hosokawa Micron Corporation) as shown in Figure 4, and an insulating coating of Ba-Zn-B-Si-Al-O oxide glass was formed on the surface of the small particles. The average thickness of the insulating coating formed on the small particles was within the range of 15±10 nm for all samples.

[0131] Next, the raw powder (large and small diameter powder) of the metal magnetic particles was kneaded with epoxy resin to obtain a resin compound. More specifically, in sample numbers 1 to 6, the large and small particles of an amorphous structure were mixed to obtain a resin compound. Meanwhile, in sample numbers 7 to 12, the large and small particles of a nanocrystalline structure were mixed to obtain a resin compound. The amount of epoxy resin added (amount of resin) in the resin compound was 2.5 parts by mass per 100 parts by mass of the metal magnetic particles in all samples in experiment 1. In addition, the large and small diameter powders were mixed so that the area ratio of "large particles:small particles = approximately 8:2" in all samples in experiment 1.

[0132] Next, the resin compound was filled into a mold and pressurized to obtain a toroidal shaped compact. The molding pressure was controlled so that the magnetic core had a magnetic permeability (relative magnetic permeability) of about 35. The above compact was then heat-treated at 180°C for 60 minutes to harden the epoxy resin in the compact, obtaining a toroidal shaped magnetic core (outer diameter 11 mm, inner diameter 6.5 mm, thickness 2.5 mm).

[0133] For each sample in Experiment 1, the fabricated magnetic core was evaluated as follows.

[0134] Cross-sectional observation of magnetic core The cross section of the magnetic core was observed by SEM, and the total area of ​​the observation field (1,000,000 μm 2 ) was calculated (total area ratio A0 of metal magnetic particles). For each sample in Experiment 1, the total area ratio A0 of metal magnetic particles was within the range of 80±2%.

[0135] In addition, during SEM observation, the Heywood diameter of each metal magnetic particle was measured, and surface analysis was performed by EDX to identify the composition of each metal magnetic particle, and each metal magnetic particle observed in the cross section of the magnetic core was classified into large particles and small particles. In each sample of Experiment 1, the D20 of the large particles was 3 μm or more, the average particle size (arithmetic mean value of the Heywood diameter) of the large particles was in the range of 10 μm to 30 μm, the D80 of the small particles was less than 3 μm, and the average particle size of the small particles was in the range of 0.5 μm to 1.5 μm. In addition, the total area of ​​the large particles and the total area of ​​the small particles included in the observation field were measured, and the ratio of the total area of ​​the large particles to the total area of ​​the metal magnetic particles (AL / A0) and the ratio of the total area of ​​the small particles to the total area of ​​the metal magnetic particles (AS / A0) were calculated.

[0136] In addition, in the above SEM observation, the thickness of the insulating coating of each large particle present within the observation field was measured, and the average thickness was calculated.

[0137] Evaluation of magnetic permeability and DC superposition characteristics To evaluate the magnetic permeability and DC bias characteristics, first, polyurethane copper wire (UEW wire) was wound around a toroidal magnetic core. Then, the inductance of the magnetic core at a frequency of 20 kHz was measured using an LCR meter (Agilent Technologies 4284A) and a DC bias power supply (Agilent Technologies 42841A). More specifically, the inductance was measured when no DC magnetic field was applied (0 kA / m) and when a DC magnetic field of 8 kA / m was applied, and μ0 (magnetic permeability at 0 A / m) and μHdc (magnetic permeability at 8 kA / m) were calculated from these inductances.

[0138] The DC bias characteristics were evaluated based on the rate of change in magnetic permeability when a DC magnetic field was applied. In other words, the rate of change in magnetic permeability (unit: %) is expressed as (μ0-μHdc) / μ0, and it can be determined that the smaller this rate of change in magnetic permeability is, the better the DC bias characteristics are.

[0139] Core loss evaluation Core loss of each magnetic core (unit: kW / m 3 ) was measured using a BH analyzer (SY-8218 manufactured by Iwatsu Measurement Co., Ltd.) The magnetic flux density when measuring the core loss was set to 200 mT, and the frequency was set to 20 kHz.

[0140] Overall evaluation of experiment 1 The evaluation results of Experiment 1 are shown in Table 1A.

[0141] [Table 1A]

[0142] As shown in Table 1A, the magnetic cores of sample numbers 1 to 6 (amorphous magnetic cores) which use large particles with an amorphous structure as the main powder tend to have better DC bias characteristics but higher core loss than the magnetic cores of sample numbers 7 to 12 (nanocrystalline magnetic cores) which use large particles with a nanocrystalline structure as the main powder. Conversely, the nanocrystalline magnetic cores of sample numbers 7 to 12 tend to have lower core loss but inferior DC bias characteristics compared to the amorphous magnetic cores.

[0143] Furthermore, it was found that in both nanocrystalline and amorphous magnetic cores, thickening the insulating coating on the large particles tends to increase core loss. These results show that it is not easy to achieve both low core loss and good DC bias characteristics when the main powder of a magnetic core is made of only one type of large particles.

[0144] (Experiment 2) In experiment 2, a magnetic core was manufactured using metallic magnetic particles that were a mixture of first large particles with an amorphous structure and second large particles with a nanocrystalline structure, as shown in Tables 1B and 1C.

[0145] In experiment 2, the raw powders for the metal magnetic particles were prepared as follows: Fe-Co-BP-Si-Cr alloy powder (first largest particles with amorphous structure), Fe-Si-B-Nb-Cu alloy powder (second largest particles with nanocrystalline structure), and pure iron powder (small particles) with the same specifications as in experiment 1.

[0146] Next, a mechanofusion device was used to form an insulating coating of P-Zn-Al-O oxide glass on the particle surface of the Fe-Co-BP-Si-Cr alloy powder. At this time, the thickness of the insulating coating was adjusted by controlling the amount of coating material added and the processing time, and six types of first large particles with different average thicknesses T1 were obtained. Similarly, a coating formation process was performed on Fe-Si-B-Nb-Cu alloy powder using a mechanofusion device (forming an insulating coating of P-Zn-Al-O oxide glass), and six types of second large particles with different average thicknesses T2 were obtained. In addition, a coating formation process was performed on pure iron powder using a powder processing device as shown in Figure 4, and an insulating coating of Ba-Zn-B-Si-Al-O oxide glass was formed on the surface of the small particles. The average thickness of the insulating coating of the small particles was within the range of 15±10 nm.

[0147] Next, the first large particles with an amorphous structure, the second large particles with a nanocrystalline structure, the small particles, and the epoxy resin were kneaded together to obtain a resin compound. At this time, the large particles and the small particles were mixed so that the area ratio of the first large particles: the second large particles: the small particles was approximately 4:4:2 in all samples in Experiment 2. In addition, the amount of epoxy resin added (amount of resin) in the resin compound was 2.5 parts by mass per 100 parts by mass of the metal magnetic particles in all samples in Experiment 2.

[0148] Next, the resin compound was filled into a mold and pressed to obtain a toroidal shaped compact. The molding pressure was controlled so that the magnetic core had a magnetic permeability (μ0) of 35. The compact was then heat-treated at 180°C for 60 minutes to harden the epoxy resin in the compact, obtaining a toroidal shaped magnetic core (outer diameter 11 mm, inner diameter 6.5 mm, thickness 2.5 mm).

[0149] In experiment 2, the same evaluations as in experiment 1 (cross-sectional observation of the magnetic core, measurement of magnetic permeability, DC bias characteristics, and core loss) were performed. In the cross-sectional observation of the magnetic core, it was confirmed that in all samples, the D20 of the first large particles and the second large particles was 3 μm or more, the average particle size of the first large particles and the second large particles was within the range of 10 μm to 30 μm, the D80 of the small particles was less than 3 μm, and the average particle size of the small particles was within the range of 0.5 μm to 1.5 μm.

[0150] Furthermore, the average thickness T1 of the insulating coating of the first large particles with an amorphous structure, the average thickness T2 of the insulating coating of the second large particles with a nanocrystalline structure, and the ratios of the total area of ​​each particle group to the total area of ​​the metal magnetic particles (AL1 / A0, AL2 / A0, and AS / A0) are shown in Tables 1B and 1C. In each sample of Experiment 2, the total area ratio A0 of the metal magnetic particles was within the range of 80±2%.

[0151] In experiment 2, the expected value of core loss (calculated value of core loss calculated from the blending ratio) was calculated based on the blending ratio of the first large particle and the second large particle, and the improvement rate of core loss for each sample was calculated based on the expected value. For example, the expected value of core loss for sample number 13 was calculated by the following formula.

[0152] Expected value = [(β1 / α1) × C1] + [(β2 / α7) × C7] α1: Proportion of amorphous large particles in sample number 1 (AL / A0) C1: Core loss of sample number 1 α7: Ratio of large nanocrystalline particles in sample number 7 (AL / A0) C7: Core loss of sample number 7 β1: Proportion of amorphous large particles in sample No. 13 (AL1 / A0) β2: Ratio of large nanocrystalline particles in sample No. 13 (AL2 / A0)

[0153] As described above, when calculating the expected values ​​(calculated values), reference was made to Table 1A and the characteristic values ​​of magnetic cores (sample numbers 1 to 12) containing large particles with the same specifications (same particle composition, coating composition, and average coating thickness) as the large particles used in each sample (sample numbers 13 to 48) were used.

[0154] After calculating the expected value of the core loss using the above method, the improvement rate between the expected value and the actually measured core loss was calculated: [(expected value-measured value) / expected value]. The larger this "improvement rate" is, the more the core loss is reduced. In this experiment, an improvement rate of 5% or more, preferably 10% or more, and more preferably 15% or more was judged to be good. The results are shown in Table 1B and Table 1C.

[0155] As with core loss, the DC bias characteristics were calculated using measured values, as well as expected values ​​(calculated values) and improvement rates. The results are shown in Tables 1B and 1C. For DC bias characteristics, cores with an improvement rate of -1% or more were deemed to be equivalent to or better than the cores shown in Table 1A.

[0156] [Table 1B]

[0157] [Table 1C]

[0158] As shown in Tables 1B and 1C, in each sample of Experiment 2, the core loss could be reduced more than that of the amorphous magnetic cores (samples 1 to 6). In addition, in the comparative examples in which T1 / T2 was 1.0 or less, the core loss was equal to or worse than the expected value calculated from the compounding ratio. In contrast, in the examples in which T1 / T2 was greater than 1.0, the core loss was 15% or more lower than the expected value (calculated value). Regarding the DC bias characteristics, there was no significant difference in the improvement rate between the examples (T1 / T2 greater than 1.0) and the comparative examples (T1 / T2 less than 1.0), and the DC bias characteristics were all improved more than those of the nanocrystalline magnetic cores (samples 7 to 12).

[0159] As described above, it was confirmed that the core loss can be reduced while maintaining good DC superposition characteristics by mixing the first large particles of an amorphous structure having a relatively thick insulating coating with the second large particles of a nanocrystalline structure having a relatively thin insulating coating. In particular, in the magnetic core (embodiment) that satisfies T1>T2, it was confirmed that T1 / T2 is preferably 1.3 or more, more preferably 1.5 or more, and even more preferably 2.0 or more from the viewpoint of reducing the core loss. In addition, from the viewpoint of reducing the core loss while ensuring insulation, T2 is preferably 5 nm or more. It was confirmed that the upper limit of T2 is determined based on T1, and may be, for example, 150 nm or less, 100 nm or less, or 50 nm or less.

[0160] (Experiment 3) In experiment 3, the composition of the insulating coating of the first large particles and the second large particles was changed to manufacture magnetic cores (sample numbers 49 to 56) shown in Table 2. The manufacturing conditions other than the composition of the insulating coating were the same as those for sample number 32 in experiment 2, and the same evaluation as in experiment 1 was performed on each sample in experiment 3.

[0161] Table 2 shows the cross-sectional observation results in Experiment 3, as well as the measurement results of the magnetic permeability, the DC bias characteristics ((μ0-μHdc) / μ0), and the core loss.

[0162] [Table 2]

[0163] In each sample in Experiment 3, the DC bias characteristics and core loss were comparable to those of sample number 32 in Experiment 2, and it was possible to reduce the core loss while maintaining good DC bias characteristics. It was confirmed that the composition of the insulating coating formed on each large particle may be changed as shown in Table 2.

[0164] (Experiment 4) In experiment 4, the ratio of the first large grains with an amorphous structure (AL1 / A0) and the ratio of the second large grains with a nanocrystalline structure (AL2 / A0) were changed to produce the magnetic core samples (sample numbers 57 to 74) shown in Table 3.

[0165] In sample numbers 57 to 62, which are comparative examples, T1 was 15 nm, T2 was 100 nm, and the manufacturing conditions other than the proportion of large particles were the same as sample number 22 in experiment 2. In sample numbers 63 to 68, T1 and T2 were 15 nm, and the manufacturing conditions other than the proportion of large particles were the same as sample number 20 in experiment 2. In sample numbers 69 to 74, T1 was 100 nm, T2 was 15 nm, and the manufacturing conditions other than the proportion of large particles were the same as sample number 32 in experiment 2.

[0166] In experiment 4, the same evaluation as in experiment 2 was carried out. The evaluation results are shown in Table 3.

[0167] [Table 3]

[0168] As shown in Table 3, in the examples where T1>T2 was satisfied, even if the mixing ratio of the first large particles and the second large particles was changed, the core loss could be reduced by 5% or more compared to the amorphous magnetic core. In particular, it was confirmed that AL1 / A0 and AL2 / A0 are both preferably 3% or more, more preferably 4% to 78%, and even more preferably 7% to 44%.

[0169] Furthermore, from the results shown in Table 3, it was confirmed that AL1 / (AL1+AL2) and AL2 / (AL1+AL2) may each be within the range of 4% to 96%, and from the viewpoint of obtaining excellent DC bias characteristics, it is more preferable that AL1 / (AL1+AL2) is 50% to 96%, and from the viewpoint of further reducing core loss, it is more preferable that AL2 / (AL1+AL2) is 50% to 90%.

[0170] Furthermore, it was also confirmed that, from the viewpoint of improving the core loss and the DC bias characteristics in a well-balanced manner and enhancing the effect of improving the core loss, AL1 / (AL1+AL2) is preferably 10% to 94%, and more preferably 18% to 85%.

[0171] (Experiment 5) In experiment 5, the ratio of small particles (AS / A0) was changed to produce magnetic core samples (sample numbers 75 to 92) shown in Table 4. In each sample in experiment 5, large particles with an amorphous structure and large particles with a nanocrystalline structure were mixed in a ratio of approximately "1:1." Other than the ratio of small particles, the manufacturing conditions were the same as in experiment 2, except that the molding pressure was changed according to the mixing ratio of the small particles, and the magnetic permeability, DC bias characteristics ((μ0-μHdc) / μ0), and core loss were measured. The evaluation results are shown in Table 4.

[0172] [Table 4]

[0173] As shown in Table 4, even when the proportion of small particles was changed, the examples in which T1 / T2 was greater than 1.0 had core loss that was 20% or more lower than the comparative examples in which T1 / T2 was 1.0 or less.

[0174] It was confirmed that increasing the proportion of small particles in the magnetic core improves the core loss and DC bias characteristics while decreasing the magnetic permeability. From the viewpoint of improving the core loss and DC bias characteristics while maintaining high magnetic permeability, it was confirmed that the proportion of small particles (AS / A0) is preferably 5% or more and 85% or less, 5% or more and less than 50%, 5% or more and 40% or less, and 10% or more and 40% or less, in that order.

[0175] (Experiment 6) In experiment 6, the filling rate of the metal magnetic particles (i.e., A0) was changed to produce the magnetic core samples shown in Table 5. The filling rate of the metal magnetic particles was controlled based on the amount of epoxy resin added. The amount of resin (epoxy resin content relative to the metal magnetic particles) and the total area ratio A0 of the metal magnetic particles in each sample in experiment 6 are shown in Table 5.

[0176] The other experimental conditions were the same as those in Experiment 2, and the magnetic permeability, DC bias characteristics, and core loss of each sample were evaluated. The results are shown in Table 5.

[0177] [Table 5]

[0178] As shown in Table 5, sample numbers 95, 98, 32 and 101 are examples of Experiment 6. It was confirmed that when A0 was 75% or more and T1 / T2 exceeded 1.0, the core loss was reduced by 20% or more compared to the comparative examples in which T1 / T2 was 1.0 or less.

[0179] As shown in Table 5, it was confirmed that increasing the filling rate of the metal magnetic particles increases the magnetic permeability μ0 while deteriorating the core loss characteristics and DC bias characteristics. From the viewpoint of keeping the core loss low, it was found that A0 is preferably 90% or less, and more preferably 80% or less.

[0180] (Experiment 7) In experiment 7, the specifications of the small particles were changed to produce the magnetic core samples shown in Tables 6 and 7. Specifically, in sample number 105, Fe-Ni alloy particles with an average particle size of 1 μm were used as the small particles, in sample number 106, Fe-Si alloy particles with an average particle size of 1 μm were used as the small particles, in sample number 107, Fe-Co alloy particles with an average particle size of 1 μm were used as the small particles, and in sample number 108, Co particles with an average particle size of 1 μm were used as the small particles. An insulating coating of Ba-Zn-B-Si-Al-O oxide glass with an average thickness of 15±10 nm was formed on the small particles of each sample shown in Table 6. The manufacturing conditions other than the composition of the small particles were the same as those of sample number 32 in experiment 2.

[0181] Two types of small particles with different coating compositions were added to sample numbers 109 and 110 in Table 7. Specifically, sample number 109 contained a mixture of Fe particles (first small particles) coated with a Ba-Zn-B-Si-Al-O-based oxide glass and Fe particles (second small particles) coated with a Si-O-based insulating coating.

[0182] In addition, in sample number 110, Fe particles (first small particles) coated with a Si-Ba-Mn-O oxide glass were mixed with Fe particles (second small particles) coated with a Si-O insulating coating. In both sample numbers 109 and 110, the average thickness of the insulating coating of the small particles was within the range of 15±10 nm. The manufacturing conditions other than those mentioned above were the same as those of sample number 32 in experiment 2.

[0183] The evaluation results of Experiment 7 are shown in Tables 6 and 7.

[0184] [Table 6]

[0185] [Table 7]

[0186] As shown in Table 6, in samples 105 to 108 in which the composition of the small particles was changed, it was possible to reduce core loss while maintaining good DC bias characteristics, similar to sample 32 in experiment 2. From this result, it was found that when small particles are added to the magnetic core, the composition of the small particles is not particularly limited and can be set arbitrarily.

[0187] As shown in Table 7, in sample numbers 109 and 110, the DC bias characteristics were improved more than in sample number 32 of experiment 2 while maintaining low core loss. This result shows that by dispersing two types of small particles with different coating compositions in the magnetic core, it is possible to improve the DC bias characteristics while maintaining low core loss.

[0188] (Experiment 8) In experiment 8, three types of magnetic core samples (sample numbers 111 to 113) shown in Table 8 were manufactured by adding medium particles in addition to the first large particles, the second large particles, and the small particles. Specifically, nanocrystalline Fe-Si-B-Nb-Cu alloy particles with an average particle size of 5 μm were added as medium particles to the magnetic core of sample number 111, crystalline Fe-Si alloy particles with an average particle size of 5 μm were added as medium particles to the magnetic core of sample number 112, and amorphous Fe-Si-B alloy particles with an average particle size of 5 μm were added as medium particles to the magnetic core of sample number 113. Note that the medium particles used in experiment 8 all had a D20 of less than 3 μm and a D80 of 3 μm or more. Note that the medium particles do not need to be coated, but it is better to coat them from the viewpoint of insulation. The medium particles used in this experiment were coated with P-Zn-Al-O oxide glass powder with an average thickness of 15±10 nm, similar to that of the large particles.

[0189] The manufacturing conditions other than those mentioned above were the same as those of sample number 32 in experiment 2, and the magnetic permeability, DC bias characteristics, and core loss were measured. The evaluation results are shown in Table 8.

[0190] [Table 8]

[0191] As shown in Table 8, in each example in which medium particles were added, it was possible to reduce core loss while maintaining good DC bias characteristics, similar to sample number 32 in experiment 2. The evaluation results of experiment 8 showed that it was possible to add medium particles to the magnetic core.

[0192] (Experiment 9) In Experiment 9, the composition of the first large particles having an amorphous structure and the composition of the second large particles having a nanocrystalline structure were changed to produce magnetic core samples shown in Tables 9A and 9B. The average particle size of the first large particles used in Experiment 9 was 20 μm, and the degree of amorphization of the first large particles was 85% or more. The average particle size of the second large particles used in Experiment 9 was 20 μm, and the average crystallite size of the second large particles was within the range of 0.5 nm to 30 nm.

[0193] Sample numbers 114 to 136 shown in Table 9A are comparative examples in which only either the first large particles with an amorphous structure or the second large particles with a nanocrystalline structure were used. The manufacturing conditions of sample numbers 114 to 136, other than the particle composition, were the same as those of sample number 4 or 8 in experiment 1. Each example shown in Tables 9B to 9G is an example in which the first large particles and the second large particles are mixed. The manufacturing conditions of each example, other than the particle composition, were the same as those of sample number 32 in experiment 2.

[0194] The evaluation results of Experiment 9 are shown in Tables 9A to 9G.

[0195] [Table 9A]

[0196] [Table 9B]

[0197] [Table 9C]

[0198] [Table 9D]

[0199] [Table 9E]

[0200] [Table 9F]

[0201] [Table 9G]

[0202] In each of the Examples shown in Tables 9B to 9G, the core loss improvement rate was 15% or more while maintaining good DC bias characteristics. From the results of Experiment 9, it was found that the particle composition of the first large particles and the second large particles is not particularly limited and can be selected arbitrarily. [Explanation of symbols]

[0203] 2 … Magnetic core 10 … Metal magnetic particles 10a … First particle group 11 ... Large particles 11a … First large particle 11b … Second large particle 4 … Large particle insulating coating 4a … Insulating coating of the first large particle 4b … Insulating coating of the second largest particle 10b … Second particle group 12 … small particles 12a … 1st small particle 12b…Second small particle 6 … Small particle insulating coating 6a … First insulating coating 6b … Second insulating coating 13 … medium particles 20 ... Resin 60 … Powder processing equipment 61 … Chamber 62 ... Feather 63 … mixture 100 ... Magnetic parts 5. Coil 5a... End 5b... End 7,9 … External electrode

Claims

1. A magnetic core comprising metallic magnetic particles, The total area ratio of the metal magnetic particles in the cross section of the magnetic core is 75% or more, The metal magnetic particles are a first large particle having an amorphous structure and a Heywood diameter of 3 μm or more in a cross section of the magnetic core; a second large particle having a nanocrystalline structure and a Heywood diameter of 3 μm or more in a cross section of the magnetic core; A magnetic core in which the insulating coating on the first large particles is thicker than the insulating coating on the second large particles.

2. The average thickness of the insulating coating of the first large particles is T1, The average thickness of the insulating coating of the second large particle is T2, 2. The magnetic core according to claim 1, wherein T1 / T2 is 1.3 or more and 40 or less.

3. 3. The magnetic core according to claim 1, wherein the average thickness T2 of the insulating coating of the second large particles is 5 nm or more and 50 nm or less.

4. 3. The magnetic core according to claim 1, wherein the metal magnetic particles include a group of particles having a Heywood diameter of less than 3 μm in a cross section of the magnetic core.

5. 5. The magnetic core of claim 4, wherein said group of particles having a Heywood diameter of less than 3 [mu]m includes two or more types of small particles having different coating compositions.

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

7. A magnetic component having a magnetic body including metal magnetic particles, the total area ratio of the metal magnetic particles in the cross section of the magnetic body is 75% or more; The metal magnetic particles are a first large particle having an amorphous structure and a Heywood diameter of 3 μm or more in a cross section of the magnetic material; a second large particle having a nanocrystalline structure and a Heywood diameter of 3 μm or more in a cross section of the magnetic material; A magnetic component, wherein the insulating coating of the first large particles is thicker than the insulating coating of the second large particles.

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