Magnetic core, magnetic component, and electronic apparatus

Abstract

To provide a magnetic core that improves DC superposition characteristics.SOLUTION: A magnetic core includes soft magnetic particles. When the value of D10 in a volume-based particle size distribution of the soft magnetic particles is defined as V10, the value of D50 in the volume-based particle size distribution of the soft magnetic particles is defined as V50, and the value of D50 in a number-based particle size distribution of the soft magnetic particles is defined as N50, the soft magnetic particles include large particles having a particle size of (0.5×V50) or more, and small particles having a particle size of (2×N50) or less. When the distance from a certain small particle to a large particle closest to the small particle is defined as L, and the median of L calculated for all the small particles is defined as L50, L50 is within a specific range.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a magnetic core, a magnetic component, and an electronic device. [Background technology]

[0002] Patent Document 1 describes an inductor in which a dust core obtained by compressing metal magnetic powder is integrally molded with a coil portion.

[0003] When metal magnetic powder is used for the dust core, the core loss tends to be large. By using amorphous alloy powder as the metal magnetic powder, the core loss is reduced. However, it becomes difficult to increase the density of the dust core during molding.

[0004] Patent Documents 2 and 3 describe the use of a mixture of crystalline magnetic alloy powder and amorphous magnetic alloy powder.

[0005] Patent Document 4 describes that by using an amorphous soft magnetic powder having a high average practical sphericity, it is possible to provide an inductor or the like having lower loss than before. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-309024 A [Patent Document 2] JP 2004-197218 A [Patent Document 3] JP 2004-363466 A [Patent Document 4] Patent No. 5110660 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to obtain a magnetic core having improved DC bias characteristics and reduced core loss. [Means for solving the problem]

[0008] In order to achieve the above object, a magnetic core according to an exemplary embodiment of the present invention comprises: A magnetic core comprising soft magnetic particles, The value of D10 in the volume-based particle size distribution (unit: μm) of the soft magnetic particles is V10, the value of D50 in the volume-based particle size distribution of the soft magnetic particles is V50, and the value of D50 in the number-based particle size distribution of the soft magnetic particles is N50, The soft magnetic particles include large particles having a particle diameter of (0.5×V50) or more and small particles having a particle diameter of (2×N50) or less, Let L be the distance from a small particle to the nearest large particle, and let L50 be the median value of L calculated for all small particles. The relationship (2 × N50) ≦ L50 ≦ (0.5 × V10 + 3.0) is satisfied.

[0009] In order to achieve the above object, a magnetic core according to an exemplary embodiment of another aspect of the present invention comprises: A magnetic core comprising soft magnetic particles, The value of D10 in the volume-based particle size distribution of the soft magnetic particles is V10, the value of D50 in the volume-based particle size distribution of the soft magnetic particles is V50, and the value of D50 in the number-based particle size distribution of the soft magnetic particles is N50, The soft magnetic particles include large particles having a particle diameter of (0.5×V50) or more and small particles having a particle diameter of (2×N50) or less, Let L be the distance from a small particle to the nearest large particle, and let L50 be the median value of L calculated for all small particles. The relationship (2 × N50) ≦ L50 ≦ (0.5 × V10) is satisfied.

[0010] The following description applies to the magnetic core of the exemplary embodiments according to any of the above aspects.

[0011] At least a part of the soft magnetic particles has a composition represented by the formula (Fe 1-p X1 p ) 100-(a+b+c+d+e+f) B a P b S c C d X2 e X3 f (atomic ratio), X1 is one or more selected from Co and Ni; X2 is one or more selected from Ti, Cr, Mn, Al, Ga, Ag, Zn, S, Ca, Mg, V, Sn, As, Sb, Bi, N, Au, Cu, rare earth elements, and platinum group elements; X3 is one or more selected from Zr, Nb, Mo, Hf, Ta, and W; 0≦p≦0.5, 2.00≦a≦20.00, 0.00≦b≦14.00, 0.00≦c≦15.00, 0.00≦d≦5.00, 0.00≦e≦3.00, 0.00≦f≦9.00, and It is acceptable to satisfy 70.00≦100-(a+b+c+d+e+f)≦96.00.

[0012] V10 may be 3.0 μm or more and 20.0 μm or less.

[0013] V50 may be 8.0 μm or more and 40.0 μm or less.

[0014] At least some of the soft magnetic particles may contain Fe, Co, and / or Ni.

[0015] The magnetic component of the exemplary embodiment of the present invention includes any of the magnetic cores described above.

[0016] An electronic device according to an exemplary embodiment of the present invention includes any one of the magnetic cores described above. [Brief description of the drawings]

[0017] [Figure 1] 1 is an SEM image of a cross section of sample number 5. [Diagram 2] 1 is a graph showing the distribution of various lengths. [Diagram 3] This is an example of a chart obtained by X-ray crystal structure analysis. [Figure 4] 4 is an example of a pattern obtained by profile fitting the chart of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described.

[0019] (First embodiment) The magnetic core according to the present embodiment includes soft magnetic particles, which include at least large particles and small particles, which will be described later.

[0020] There is no particular limit to the method for observing the soft magnetic particles contained in the magnetic core. For example, a method of observing the cross section of the magnetic core using a SEM or TEM can be used. In addition, the magnetic core may be cut and the cross section obtained may be polished.

[0021] There is no particular limit to the size of the observation area in the cross section of the magnetic core. The observation area is set so that the total number of soft magnetic particles contained in the observation area is 10,000 or more. It is preferable to set one observation area or multiple continuous observation areas. However, multiple observation areas may be set at locations separated from each other.

[0022] There are no particular limitations on the magnification and resolution when observing the cross section of the magnetic compact. The magnification may be 500 to 3000 times, and the resolution may be 2560×1920 or more.

[0023] The particle diameter of all magnetic particles included in each observation area is measured. The particle diameter of each soft magnetic particle is the Heywood diameter. The Heywood diameter is the diameter equivalent to a circle with a projected area. The Heywood diameter of the soft magnetic particle in this embodiment is calculated by (4S / π) where S is the area of ​​the soft magnetic particle in the cross section. 1 / 2 It is.

[0024] The volume of each soft magnetic particle is calculated assuming that the shape of each soft magnetic particle is spherical. In other words, the volume of each soft magnetic particle is calculated by (πd 3 ) / 6. The volume of all magnetic particles is calculated using the above method.

[0025] By the above method, the particle size and volume are calculated for all soft magnetic particles contained in each observation area.

[0026] Next, the number-based particle size distribution of the soft magnetic particles is calculated from the particle diameter of each soft magnetic particle calculated by the above method.The volume-based particle size distribution of the soft magnetic particles is calculated from the particle diameter and volume of each soft magnetic particle calculated by the above method.

[0027] It is necessary to set intervals to calculate the particle size distribution. In this embodiment, 100 intervals are set according to the following formula. x i is equal to i and y i is the average particle size in section i (unit: μm). Also, exp(X)=e X where e is the base of the natural logarithms.

[0028] y i =0.02×exp(x i ×0.085)

[0029] For example, the average particle size of the smallest section is calculated by substituting i=1 into the above formula and getting 0.02×e 0.085 = 0.022 μm. Similarly, the average particle size in the second section is 0.02 × e 0.17= 0.024 μm, and the average particle size in the 50th section is 0.02 × e 4.25 = 1.402 μm, and the average particle size in the 100th section is 0.02 × e 8.5 =98.295μm.

[0030] Then, the volume-based particle size distribution and the number-based particle size distribution of the soft magnetic particles are calculated using the intervals set by the above method. An example of the results is shown in Figure 2. Figure 2 (1) is a graph showing the volume-based particle size distribution of the soft magnetic particles. Figure 2 (2) is a graph showing the number-based particle size distribution of the soft magnetic particles. In graphs (1) and (2), the horizontal axis is particle diameter.

[0031] In this embodiment, the value of D10 in the volume-based particle size distribution (unit: μm) of the soft magnetic particles is V10, the value of D50 in the volume-based particle size distribution of the soft magnetic particles is V50, and the value of D50 in the number-based particle size distribution of the soft magnetic particles is N50. Unless otherwise specified, the units of particle size and particle size distribution are μm. In FIG. 2, the positions of V10 and N50 are shown. Note that D10 and D50 in the volume-based particle size distribution of the soft magnetic particles are particle sizes when the cumulative relative frequency on a volume basis is 10% (0.10) and 50% (0.50). D50 in the number-based particle size distribution of the soft magnetic particles is the particle size when the cumulative relative frequency on a number basis is 50% (0.50).

[0032] Soft magnetic particles having a particle diameter of (0.5×V50) or more are defined as large particles, and soft magnetic particles having a particle diameter of (2×N50) or less are defined as small particles. The soft magnetic particles according to this embodiment include large particles and small particles. The soft magnetic particles according to this embodiment may further include particles that are not classified as large particles or small particles, that is, particles having a particle diameter greater than (2×N50) and less than (0.5×V50).

[0033] In the magnetic core of this embodiment, the distribution of the distance between the large particles and the small particles is within a specific range, thereby improving the DC superposition characteristics and reducing core loss compared to when the distribution of the distance between the large particles and the small particles is outside the specific range.

[0034] The distance from a small particle to the nearest large particle is defined as L. Specifically, for a small particle, the distance from the surface of the small particle to the surface of the nearest large particle is measured, and this distance is defined as L.

[0035] Measure L for all small particles within the observation range. Then, calculate the distribution of L. At that time, set 100 intervals in the same manner as above. Note that the above particle diameters are replaced with distances as appropriate.

[0036] Then, the distribution of L is calculated using the intervals set by the above method. An example of the results is shown in Figure 2. (3) in Figure 2 is a graph showing the distribution of L. In graph (3), the horizontal axis is L.

[0037] The median value of L is set to L50. The position of L50 is shown in FIG. 2. The magnetic core structure according to this embodiment satisfies (2×N50)≦L50≦(0.5×V10+3.0). It may also satisfy (2×N50)≦L50≦(0.5×V10+2.5). In the following description, "0.5×V10+3.0" may simply be written as "0.5×V10+3".

[0038] If L50 is too small, the small particles are dispersed in the magnetic core without much aggregation. As a result, the small particles tend to be distributed so as to form a layer of about one layer near the large particles (grain boundaries between two large particles). In other words, a layer of small particles having a thickness equivalent to the diameter of the small particles tends to be formed near the large particles (grain boundaries between two large particles).

[0039] If L50 is too large, there are many small particles agglomerated in the magnetic core, resulting in too many small particles agglomerated near the large particles (at the grain boundaries between two large particles).

[0040] By having L50 within the above range, small particles in the magnetic core tend to aggregate moderately at a position some distance away from the large particles. On the other hand, small particles are less likely to distribute to form a layer of about one layer near the large particles (grain boundaries between two large particles). As a result, an appropriate amount of small particles is contained between the large particles, making it easier to prevent magnetic saturation and improve the DC superposition characteristics. Furthermore, core loss is reduced.

[0041] When the magnetic core structure satisfies (2×N50)≦L50≦(0.5×V10+3), the DC bias characteristics of the magnetic core are improved and core loss is reduced, both when compared to a case where the conditions are essentially the same except that L50 is too small, and when compared to a case where the conditions are essentially the same except that L50 is too large. In particular, core loss is reduced, compared to a case where the conditions are essentially the same except that L50 is too large.

[0042] There are no particular limitations on the values ​​of V10, V50, and N50. For example, V10 may be 2.0 μm or more and 25.0 μm or less, V50 may be 4.0 μm or more and 50.0 μm or less, and N50 may be 0.2 μm or more and 5.0 μm or less. It goes without saying that V10≦V50 is satisfied.

[0043] V10 may be 3.0 μm or more and 20.0 μm or less, and V50 may be 8.0 μm or more and 40.0 μm or less.

[0044] There is no particular limitation on the value of L50, and it may be, for example, 0.8 μm or more and 8.0 μm or less.

[0045] There is no particular limit to the total area ratio of the soft magnetic particles to the entire cross section of the magnetic core. For example, it may be 70% or more and 95% or less. If the total area ratio is too small, the filling rate of the soft magnetic particles in the magnetic core is too low, and the magnetic permeability is likely to decrease.

[0046] The total area ratio of the large particles to the entire cross section may be 70% or more. The total area ratio of the small particles may be 70% or more.

[0047] The large particles constituting the magnetic core may have an average circularity of 0.50 or more. It is preferably 0.85 or more, and more preferably 0.90 or more. The higher the circularity of the large particles, the easier it is to improve the packing of the soft magnetic particles in the magnetic core. The small particles constituting the magnetic core may have an average circularity of 0.50 or more. It is preferably 0.85 or more, and more preferably 0.90 or more. The higher the circularity of the small particles, the easier it is to improve the packing of the soft magnetic particles in the magnetic core. This is true for both large and small particles, as the circularity is higher.

[0048] In addition, the large particles and / or small particles according to this embodiment may have a coating on the surface. The coating may be an insulating coating. There is no particular limitation on the type of the coating, and it may be a coating formed by a coating that is commonly used in this technical field. For example, iron oxides, phosphates, silicates (water glass), soda-lime glass, borosilicate glass, lead glass, aluminosilicate glass, borate glass, sulfate glass, etc. are included. Examples of phosphates include magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate. Examples of silicates include sodium silicate. There is also no particular limitation on the thickness of the coating. For example, it may be 5 nm or more and 100 nm or less on average.

[0049] In addition, the magnetic core according to the present embodiment may contain a resin in addition to the soft magnetic particles. There is no particular limit to the type of resin. Examples include silicone resin and epoxy resin. There is no particular limit to the content of the resin in the magnetic core. For example, it may be 1.0 parts by mass or more and 5.0 parts by mass or less, or 1.5 parts by mass or more and 3.5 parts by mass or less, per 100 parts by mass of the soft magnetic particles. If there is too much resin, the filling rate of the soft magnetic powder tends to decrease, and the magnetic permeability tends to decrease. If the filling rate of the soft magnetic powder is increased to improve the magnetic permeability, the DC superposition characteristics tend to decrease.

[0050] Furthermore, the portion of the cross section of the magnetic core other than the magnetic material (for example, soft magnetic particles) may be occupied by resin, or resin and voids.

[0051] There is no particular restriction on the microstructure of the soft magnetic particles. For example, the soft magnetic particles may have a structure including amorphous matter, or may have a structure made of crystals. The soft magnetic particles (particularly the large particles) may have a nanoheterostructure. The nanoheterostructure refers to a structure containing initial microcrystals with an average crystal grain size of 0.3 nm to 10 nm in an amorphous material. When the filling rate is approximately the same, when the soft magnetic particles (particularly the large particles) have a nanoheterostructure, the relative permeability is improved compared to when the soft magnetic particles (particularly the large particles) have a structure made of only amorphous matter. Furthermore, the soft magnetic particles (particularly the large particles) may have a structure made of crystals with an average crystal grain size of 1 nm to 30 nm, and a maximum crystal grain size of 100 nm or less (nanocrystalline structure). When the filling rate is approximately the same, when the soft magnetic particles (particularly the large particles) have a nanocrystalline structure, the relative permeability of the magnetic core is further improved. Note that in soft magnetic particles containing crystals, particularly nanocrystals, one particle usually contains a large number of crystals. In other words, the particle size of the soft magnetic particles is different from the crystal grain size. There is no particular limit to the method for calculating the crystal grain size. For example, there is a method for calculating the crystal grain size by observing the crystals using a TEM.

[0052] Furthermore, the nanocrystals contained in the soft magnetic particles (particularly large particles) may be Fe-based nanocrystals. Fe-based nanocrystals are crystals whose average crystal grain size is on the nano-order (specifically, 0.1 nm or more and 100 nm or less) and whose Fe crystal structure is bcc (body-centered cubic lattice structure). There is no particular limit to the method of calculating the average crystal grain size of Fe-based nanocrystals. For example, there is a method of calculating the crystal grain size by observing using a TEM. There is also no particular limit to the method of confirming that the crystal structure is bcc. For example, there is a method of confirming by analyzing the electron beam diffraction pattern obtained using a TEM.

[0053] In this embodiment, the Fe-based nanocrystals may have an average crystal grain size of 1 to 30 nm. Such soft magnetic particles having a structure made of Fe-based nanocrystals tend to have a high saturation magnetic flux density and a low coercive force. That is, the soft magnetic properties are easily improved. That is, by including the soft magnetic particles, the magnetic core (particularly the magnetic compact) is easily made to have a low coercive force and a high relative permeability. Furthermore, the saturation magnetic flux density of the magnetic core (particularly the magnetic compact) containing the soft magnetic particles increases, and the DC superposition properties of the magnetic core (particularly the magnetic compact) are improved. As described above, by using soft magnetic particles having a structure made of Fe-based nanocrystals, the properties of the magnetic core (particularly the magnetic compact) are easily improved.

[0054] There is no particular limit to the method for confirming the microstructure of the soft magnetic particles. For example, by observing the cross section with a TEM, it is possible to confirm whether the soft magnetic particles have an amorphous structure or a crystalline structure. Specifically, it is possible to confirm by analyzing the halo pattern derived from the amorphous structure from the electron diffraction pattern obtained by the TEM. In addition, even if the magnetic core contains two or more types of soft magnetic particles with different microstructures, the microstructure of each soft magnetic particle can be confirmed by observing the cross section with a TEM.

[0055] The composition of the soft magnetic particles is not particularly limited, and the composition of the soft magnetic particles described below may be the average composition of all the soft magnetic particles contained in the magnetic core.

[0056] At least some of the soft magnetic particles have a composition represented by the formula (Fe 1-p X1 p ) 100-(a+b+c+d+e+f) B a P b S c C d X2 e X3 f (atomic ratio), X1 is one or more selected from Co and Ni; X2 is one or more selected from Ti, Cr, Mn, Al, Ga, Ag, Zn, S, Ca, Mg, V, Sn, As, Sb, Bi, N, Au, Cu, rare earth elements, and platinum group elements; X3 may be one or more selected from Zr, Nb, Mo, Hf, Ta, and W; 0≦p≦0.5, 2.00≦a≦20.00, 0.00≦b≦14.00, 0.00≦c≦15.00, 0.00≦d≦5.00, 0.00≦e≦3.00, 0.00≦f≦9.00, and It is acceptable to satisfy 70.00≦100-(a+b+c+d+e+f)≦96.00.

[0057] A magnetic core containing soft magnetic particles having a composition within the above range tends to be a magnetic core having excellent DC bias characteristics.

[0058] The composition of at least some of the soft magnetic particles may be the average composition of the larger particles.

[0059] There is no particular limitation on the method for analyzing the composition of the soft magnetic particles. For example, it can be confirmed by ICP analysis. Also, a cross section of a molded body containing soft magnetic particles may be analyzed using SEM-EDS, EPMA, or the like.

[0060] Each component of the soft magnetic particles will now be described in detail.

[0061] X1 is one or more selected from Co and Ni. The soft magnetic particles may contain soft magnetic particles in which 0≦p≦0.5. A magnetic core containing soft magnetic particles in which the Fe content is equal to or greater than the combined content of Co and Ni is likely to have excellent DC bias characteristics.

[0062] The magnetic core may contain soft magnetic particles having a B content (a) that satisfies 2.00≦a≦20.00. A magnetic core containing soft magnetic particles having a B content within the above range tends to have excellent DC bias characteristics.

[0063] The magnetic core may contain soft magnetic particles having a P content (b) that satisfies 0.00≦b≦14.00. A magnetic core containing soft magnetic particles having a P content within the above range tends to have excellent DC bias characteristics.

[0064] The magnetic core may contain soft magnetic particles having a Si content (c) that satisfies 0.00≦c≦15.00. A magnetic core containing soft magnetic particles having a Si content within the above range tends to have excellent DC bias characteristics.

[0065] The magnetic core may contain soft magnetic particles having a C content (d) that satisfies 0.00≦d≦5.00. A magnetic core containing soft magnetic particles having a C content within the above range tends to have excellent DC bias characteristics.

[0066] The magnetic core may contain soft magnetic particles whose X2 content (e) satisfies 0.00≦e≦3.00. A magnetic core containing soft magnetic particles whose X2 content is within the above range tends to have excellent DC bias characteristics.

[0067] The magnetic core may contain soft magnetic particles whose X3 content (f) satisfies 0.00≦f≦9.00. A magnetic core containing soft magnetic particles whose X3 content is within the above range tends to have excellent DC bias characteristics.

[0068] The soft magnetic particles may satisfy the condition 70.00≦100-(a+b+c+d+e+f)≦96.00. The soft magnetic particles have a total content of Fe and X1 of 70.00 at% or more and 96.00 at% or less. A magnetic core containing soft magnetic particles having a total content of Fe and X1 within the above range is likely to have excellent DC bias characteristics.

[0069] The soft magnetic particles may further contain oxygen. The oxygen content may be 0 ppm or more and 10,000 ppm or less by mass relative to 100% by mass of the soft magnetic particles. A magnetic core containing soft magnetic particles with an oxygen content within the above range is likely to have excellent DC bias characteristics.

[0070] The soft magnetic particles may contain elements other than Fe, X1, B, P, Si, C, X2, and X3 as inevitable impurities to the extent that they do not significantly affect the characteristics. The oxygen content is as described above. In addition, the inevitable impurities may contain elements other than oxygen in an amount of 0.1% by mass or less relative to 100% by mass of the soft magnetic particles.

[0071] At least some of the soft magnetic particles may contain Fe, Co, and / or Ni as a main component.

[0072] Containing Fe, Co, and / or Ni as the main components means that the total content of Fe, Co, and / or Ni in the soft magnetic particles is 50 at % or more and 100 at % or less.

[0073] In addition, when the main components include Fe, Co, and / or Ni, there is no particular restriction on the type of elements other than the main components. Examples of the elements include Cr, Al, Si, B, P, C, O, Nb, Zr, Ta, Mn, V, Cu, S, etc.

[0074] When soft magnetic particles (especially large particles) have a structure made of nanocrystals, examples of compositions of the soft magnetic particles that are likely to have a structure made of nanocrystals include Fe-Si-B-Nb-Cu, Fe-BP-Si-Cu, and Fe-BP-Si-Nb-Cr systems.

[0075] In the manufacturing method of the magnetic core described later, when the soft magnetic powder containing the soft magnetic particles having the above composition is heat-treated, Fe-based nanocrystals are easily precipitated in the soft magnetic particles. In other words, the soft magnetic powder having the above composition is easily used as the starting material for the soft magnetic powder having the soft magnetic particles with the Fe-based nanocrystals precipitated therein.

[0076] When Fe-based nanocrystals are precipitated on soft magnetic particles by heat treatment, the soft magnetic particles before heat treatment may have a structure consisting of only amorphous matter, or may have a nanoheterostructure in which primary crystallites exist in the amorphous matter. The primary crystallites may have an average grain size of 0.3 nm to 10 nm.

[0077] When soft magnetic particles (especially large particles) have an amorphous structure, examples of compositions of the soft magnetic particles that are likely to have an amorphous structure include Fe-Co-BP-Si-Cr, Fe-Co-BP-Si, Fe-B-Si-C-Cr, and Fe-B-Si-C systems.

[0078] When soft magnetic particles (especially large particles) have a crystalline structure, examples of the composition of the soft magnetic particles include compositions that are likely to have a crystalline structure, such as Fe-based, Fe-Co-based, Fe-Si-based, Fe-Co-Si-based, Fe-Si-Cr-based, Fe-Co-Si-Cr-based, and Fe-Si-Al-based compositions.

[0079] There is no particular limitation on the composition of the soft magnetic particles (particularly the small particles), and they may contain Fe, Co, and / or Ni as main components.

[0080] When the soft magnetic particles (particularly small particles) have the above composition, a high saturation magnetic flux density is easily obtained, and a magnetic core having high magnetic properties can be easily produced.

[0081] A method for manufacturing the magnetic core according to this embodiment will be described below, but the method for manufacturing the magnetic core is not limited to the method described below.

[0082] First, a soft magnetic powder containing the soft magnetic particles according to the present embodiment is prepared. The soft magnetic powder according to the present embodiment may be obtained by mixing a soft magnetic powder that will ultimately be mostly large particles with a soft magnetic powder that will ultimately be mostly small particles.

[0083] The soft magnetic powder, which ultimately becomes mostly large particles, can be produced by, for example, water atomization or gas atomization. Gas atomization will be explained below, but water atomization is similar to gas atomization except that the high-pressure gas sprayed toward the molten metal is replaced with water.

[0084] In the gas atomization method, the raw material metal is melted and the molten metal is powdered using the gas atomization method to produce soft magnetic powder. The composition of the molten metal is the same as that of the soft magnetic particles to be ultimately obtained. At this time, the molten metal is dripped from a container with an outlet toward a cooling section. The temperature of the molten metal is the spray temperature. There is no particular limit to the spray temperature. For example, it is between 1200°C and 1600°C. The higher the spray temperature, the easier it is for the average circularity to approach 1 and the easier it is for the average particle size to become smaller.

[0085] In addition, a gas injection nozzle equipped with a gas injection port is arranged so as to surround the discharge port. From the gas injection port, high-pressure gas (gas with an injection pressure (gas pressure) of 2.0 MPa or more and 10 MPa or less) is injected toward the molten metal dropped from the discharge port. As a result, the molten metal becomes a large number of droplets. By controlling the pressure of the high-pressure gas at this time, it is possible to change the particle size and shape of the soft magnetic powder finally obtained. Specifically, when the amount of molten metal injected is the same, the higher the pressure of the high-pressure gas, the smaller the particle size of the soft magnetic powder finally obtained. In other words, the particle size and shape of the soft magnetic powder can be changed by the ratio of the pressure of the high-pressure gas to the amount of molten metal injected.

[0086] The gas to be injected from the gas injection port is preferably an inert gas such as nitrogen gas, argon gas, or helium gas, or a reducing gas such as an ammonia decomposition gas, etc. Also, air may be used if the molten metal is not easily oxidized.

[0087] The shape of the cooling section onto which the molten metal is dripped is not particularly limited, but may be, for example, a cylinder formed with a cooling liquid flow inside to collide with the molten metal. In this case, the particle size and average circularity of the large particles in the finally obtained magnetic core can be changed by controlling the amount of molten metal sprayed, the high-pressure gas pressure, and the water pressure of the cooling liquid flow as described above. In other words, the particle size and average circularity of the soft magnetic particles are controlled by the balance between the amount of molten metal sprayed, the high-pressure gas pressure, and the water pressure of the cooling liquid flow. The amount of molten metal sprayed may be 0.5 kg / min or more and 4.0 kg / min or less, and the water pressure may be 5.0 MPa or more and 20.0 MPa or less. Specifically, the larger the amount of sprayed, the larger the particle size tends to be. Also, the lower the water pressure, the easier it is for the average circularity of the large particles to approach 1.

[0088] The molten metal discharged into the cooling liquid flow collides with the cooling liquid flow, and is further divided and finely divided, changes shape, and is cooled and solidified to become solid soft magnetic powder. The soft magnetic powder discharged together with the cooling liquid is separated from the cooling liquid in an external storage tank or the like and taken out. There is no particular limitation on the type of cooling liquid. For example, cooling water is used.

[0089] The obtained soft magnetic powder may be subjected to a heat treatment. There is no particular limitation on the conditions of the heat treatment. For example, the heat treatment may be performed at 400 to 700°C for 0.1 to 10 hours. By performing the heat treatment, when the microstructure of the soft magnetic particles is a structure having only amorphous matter or a nanoheterostructure in which primary crystallites exist in the amorphous matter, the microstructure of the soft magnetic particles is likely to become a structure consisting of nanocrystals.

[0090] There is no particular restriction on the method for producing the soft magnetic powder, the majority of which ultimately becomes small particles, and it may be produced by various powdering methods, such as a liquid phase method, a spray pyrolysis method, a melting method, etc.

[0091] The average particle size of the soft magnetic powder, most of which will ultimately be small particles, can be controlled by appropriately removing coarse particles and / or fine particles using an air classifier.

[0092] A method for confirming the microstructure of the soft magnetic particles contained in each powder will be described below.

[0093] There is no particular limitation on the method for confirming the microstructure of the soft magnetic particles contained in each powder before compaction, which will be described later. TEM may be used in the same manner as the method for confirming the microstructure of the soft magnetic particles contained in the magnetic core.

[0094] When confirming the microstructure of the soft magnetic particles contained in each powder before compaction, which will be described later, it may be confirmed by XRD. When calculating the crystal grain size contained in the soft magnetic particles, the crystal grain size may be calculated by analyzing the half-width by XRD and evaluating the crystallite size.

[0095] When the soft magnetic particles have a structure consisting of only amorphous matter or a nano-hetero structure, the amorphization rate described below is 85% or more. When the soft magnetic particles have a structure consisting of crystals, the amorphization rate described below is less than 85%. In addition, it is possible to confirm that the crystal structure of Fe is bcc by XRD.

[0096] A method for confirming the microstructure of soft magnetic particles by XRD will be described in detail below.

[0097] Soft magnetic particles having an amorphization rate X of 85% or more, as shown in the following formula (1), have an amorphous structure or a nanoheterostructure, while soft magnetic particles having an amorphization rate X of less than 85% have a crystalline structure. X = 100 - (Ic / (Ic + Ia) × 100) ... (1) Ic: Crystalline scattering integrated intensity Ia: Amorphous scattering integrated intensity

[0098] The amorphous ratio X is calculated by performing X-ray crystal structure analysis by XRD on the soft magnetic metal powder, identifying the phase, reading the peaks of crystallized Fe or compounds (Ic: crystalline scattering integrated intensity, Ia: amorphous scattering integrated intensity), determining the crystallization ratio from the peak intensity, and calculating the amorphous ratio X using the above formula (1). The calculation method will be described in more detail below.

[0099] X-ray crystal structure analysis is performed on the soft magnetic particles according to this embodiment by XRD, and a chart as shown in Fig. 3 is obtained. This is then profile-fitted using the Lorentz function of the following formula (2), to obtain a crystalline component pattern α c , amorphous component pattern α showing amorphous scattering integral intensity a , and the combined pattern α c+a From the crystalline scattering integrated intensity and the amorphous scattering integrated intensity of the obtained pattern, the amorphization rate X is calculated by the above formula (1). The measurement range is the diffraction angle 2θ=30° to 60°, where a halo derived from amorphous matter can be confirmed. In this range, the error between the integrated intensity actually measured by XRD and the integrated intensity calculated using the Lorentz function is set to within 1%.

[0100]

number

[0101] Furthermore, a coating may be formed on each of the soft magnetic powders at this stage, and there is no particular limitation on the method for forming the coating.

[0102] Next, a magnetic core is produced from each of the soft magnetic powders. First, each of the soft magnetic powders is weighed. Hereinafter, the soft magnetic powder that will eventually become mostly large particles will be referred to as powder A, and the soft magnetic powder that will eventually become mostly small particles will be referred to as powder B. There is no particular limit to the mixing ratio of each soft magnetic powder. For example, the ratio of powder A may be 30% by mass or more and 90% by mass or less. The ratio of powder B may be 10% by mass or more and 70% by mass or less.

[0103] In addition to powder A and powder B, powder C whose average particle size is between powder A and powder B may be used. Most of powder C tends to end up being neither large nor small particles. There is no particular restriction on the composition or microstructure of powder C. It may be the same as powder A, may be the same as powder B, or may be different from both powder A and powder B. When powder C whose average particle size is between powder A and powder B is used in addition to powder A and powder B, the total proportion of powder B and powder C may be 10% by mass or more and 70% by mass or less.

[0104] Next, the weighed powder B is aggregated. Specifically, the powder B is mixed with a resin, and then the powder B mixed with the resin is filled into a mold and compressed. The amount of resin added may be 0.1 parts by mass or more and 0.3 parts by mass or less, with the powder B being 100 parts by mass. The smaller the amount of resin added, the less likely the powder B is to aggregate. In addition, the higher the pressure value during compression, the more the aggregation of the powder B progresses, and the larger the L50 of the finally obtained magnetic core is likely to be. The pressure value during compression may be, for example, 10 MPa or more and 1600 MPa or less, 10 MPa or more and 1000 MPa or less, or 40 MPa or more and 600 MPa or less.

[0105] Next, powder A, the aggregated powder B, and resin are kneaded to prepare a resin compound. When powder C is used, powder C is also kneaded. The content of the soft magnetic powder in the resin compound is 100 parts by mass, and the content of the resin may be 1.0 parts by mass or more and 5.0 parts by mass or less, or 1.5 parts by mass or more and 3.5 parts by mass or less. The smaller the amount of resin, the more difficult it is to compression mold the soft magnetic powder. In addition, the strength of the magnetic core obtained by compression molding the soft magnetic powder is likely to decrease, making it difficult to handle.

[0106] The kneading process disintegrates to a certain extent the aggregated powder B. The higher the pressure applied during compression, the more difficult it is to disintegrate powder B, and the lower the pressure applied during compression, the more easily powder B is disintegrated.

[0107] The resin compound thus obtained is then filled into a mold and compression molded to obtain a magnetic core. There is no particular restriction on the molding pressure during compression molding. For example, it may be 98 MPa or more and 981 MPa or less. Furthermore, the resin contained in the obtained magnetic core may be thermally cured.

[0108] The composition and microstructure of the soft magnetic particles contained in the soft magnetic powder before compression molding are usually the same as the composition and microstructure of the soft magnetic particles contained in the magnetic core after compression molding.

[0109] Although the magnetic core (magnetic green compact) according to this embodiment has been described above, the magnetic core (magnetic green compact) of the present invention is not limited to the above embodiment.

[0110] There is also no particular limitation on the applications of the magnetic core of the present invention. For example, coil components (magnetic components) such as inductors, choke coils, and transformers can be mentioned. Furthermore, electronic devices using the magnetic core of the present invention, such as DC-DC converters, can be mentioned.

[0111] Second embodiment The second embodiment will be described below, but matters not specifically mentioned are the same as those in the first embodiment.

[0112] In this embodiment, the structure of the magnetic core satisfies (2×N50)≦L50≦(0.5×V10).

[0113] When the magnetic core structure satisfies (2×N50)≦L50≦(0.5×V10), the DC bias characteristics of the magnetic core are improved and the core loss is reduced, both when compared to a case where the conditions are substantially the same except that L50 is too small and when compared to a case where the conditions are substantially the same except that L50 is too large. In particular, the DC bias characteristics are improved compared to a case where the conditions are substantially the same except that L50 is too large.

[0114] In the second embodiment, the pressure applied when powder B mixed with a resin is filled into a die and compressed may be, for example, 10 MPa or more and 1000 MPa or less, or 40 MPa or more and 600 MPa or less. EXAMPLES

[0115] The present invention will be described below with reference to more detailed examples, but the present invention is not limited to these examples.

[0116] (Experimental Example 1) In Experimental Example 1, Powder A, which would eventually become mostly large particles, was produced by gas atomization. Powder A had a composition of the Fe-Co-BP-Si-Cr system. Specifically, the atomic ratio was 57.4Fe-24.6Co-11.0B-3.0P-3.0Si-1.0Cr.

[0117] The conditions of the gas atomization method were as follows: the pressure of the high-pressure gas was 2.0 MPa to 10 MPa, and the amount of molten metal ejected was 0.5 kg / min to 4.0 kg / min. The atomization conditions and classification conditions were appropriately controlled so that the median diameter (D50) of the obtained powder A on a volume basis was 20 μm. In addition, in the classification of powder A, at least sieve classification using a sieve with an opening of 63 μm was performed.

[0118] It was confirmed by ICP analysis that the composition of the master alloy for each sample was roughly the same as that of Powder A. It was confirmed that the volumetric median diameter (D50) of the obtained Powder A was 20 μm. The volumetric median diameter was measured by the laser diffraction method using a dry particle size distribution measuring device.

[0119] Carbonyl iron powder was used as powder B, which would ultimately become mostly small particles. In other words, the composition of the soft magnetic particles contained in powder B was substantially composed of only Fe. In addition, the median diameter (D50) of powder B on a volume basis was set to 0.8 μm by appropriately removing coarse powder and / or fine powder using an air classifier. It was confirmed by ICP analysis that the composition of powder B was the desired composition. It was confirmed by laser diffraction using a dry particle size distribution measuring device that the median diameter (D50) of the obtained powder B on a volume basis was 0.8 μm.

[0120] X-ray diffraction measurements (XRD) were performed on each powder to measure the amorphization rate X. When the amorphization rate X was 85% or more, it was deemed to have an amorphous structure. When the amorphization rate X was less than 85% and the average crystal grain size was 100 nm or less, it was deemed to have a nanocrystalline structure. When the amorphization rate X was less than 85% and the average crystal grain size was greater than 100 nm, it was deemed to have a crystalline structure. In Experimental Example 1, it was confirmed that all of Powder A had an amorphous structure, and all of Powder B had a crystalline structure.

[0121] Next, powder B was agglomerated. First, powder B was mixed with epoxy resin. The amount of epoxy resin added to powder B was 0.3 parts by mass relative to 100 parts by mass of powder B. Next, 1 g of powder B mixed with epoxy resin was filled into a cylindrical mold with a diameter of 8 mmΦ. Next, the powder was agglomerated by compressing it with the pressure value shown in Table 1. When more than 1 g of agglomerated powder B was to be produced, the above process was repeated multiple times. Note that powder B was not agglomerated in sample number 1.

[0122] Next, powder A, the aggregated powder B, and epoxy resin were kneaded together to obtain a resin compound. In sample number 1, powder A, powder B, and epoxy resin were kneaded together to obtain a resin compound. The mixing ratio of powder A to powder B was 80:20 by mass. The content of the epoxy resin was 2.0 to 3.0 parts by mass, with the total of powder A and powder B being 100 parts by mass. The content of the epoxy resin was controlled so that the relative permeability μ of the finally obtained magnetic core was 30.

[0123] The resin compound was then filled into a toroidal mold and pressure molded to obtain a toroidal molded body. The molding pressure was appropriately controlled within the range of 98 MPa to 981 MPa so that the relative permeability μ of the final magnetic core would be 30.

[0124] The epoxy resin contained in the obtained molded body was then thermally cured to obtain a magnetic core. The heat treatment conditions were 180°C for 60 minutes. The size of the magnetic core was 11 mm in outer diameter, 6.5 mm in inner diameter, and 2.5 mm in thickness.

[0125] For each sample magnetic core, a cross section cut parallel to the molding direction (height direction) was observed using an SEM (Hitachi High-Tech SU-5000), and V10, V50, and N50 were calculated using the above method. The results are shown in Table 1. Figure 1 shows an SEM image of the cross section of sample number 5.

[0126] Furthermore, L50 was calculated using the above method and compared with 2×N50, 0.5×V10, and 0.5×V10+3. The results are shown in Table 1.

[0127] The relative magnetic permeability μ of the toroidal core of each sample was measured by the following method. First, polyurethane copper wire (UEW wire) was wound around the toroidal core. Then, the inductance of the toroidal core at a frequency of 1 MHz was measured using an LCR meter (Agilent Technologies 4284A) without applying a direct current, and the relative magnetic permeability μ was calculated from the obtained inductance. The results are shown in Table 1.

[0128] Furthermore, Isat was measured to evaluate the DC bias characteristics of the toroidal core of each sample. The greater the DC current applied to the toroidal core of each sample, the lower the relative permeability. When measuring the relative permeability of the toroidal core while applying a DC current, the value of the DC current when the relative permeability dropped by 10% from μ was taken as Isat. The results are shown in Table 1.

[0129] Furthermore, the improvement rate of Isat of the sample is shown in Table 1, based on the Isat of a sample under the same conditions except that Powder B was not aggregated. When the improvement rate of Isat is 0.1% or more, the DC bias characteristics are good, when it is 1.0% or more, the DC bias characteristics are better, when it is 5.0% or more, the DC bias characteristics are even better, when it is 10.0% or more, the DC bias characteristics are even better, and when it is 15.0% or more, the DC bias characteristics are particularly good. The results are shown in Table 1.

[0130] Furthermore, the core loss of the toroidal core of each sample was evaluated. Specifically, the primary winding was wound 24 times and the secondary winding 12 times for each toroidal core. The core loss was measured at 2.5MHz, 10mT, and 20-25℃ using a BH analyzer (SY-8232 manufactured by Iwasaki Electric Co., Ltd.).

[0131] Furthermore, the core loss improvement rate of the sample was calculated based on the core loss of a sample that was under the same conditions except that Powder B was not aggregated. The results are shown in Table 1. A core loss improvement rate of 5.0% or more was considered to be good, a core loss improvement rate of 10.0% or more was considered to be even better, and a core loss improvement rate of 15.0% or more was considered to be particularly good. The results are shown in Table 1.

[0132] [Table 1]

[0133] As shown in Table 1, in each of the examples (sample numbers 2 to 10, 10a to 10d) in which (2×N50)≦L50≦(0.5×V10+3) was satisfied by agglomerating powder B, the DC bias characteristics were improved and the core loss was reduced compared to the comparative example (sample number 1) in which L50 was too small because powder B was not agglomerated. However, in the comparative example (sample number 10e) in which L50 was too large because powder B was agglomerated too much, the DC bias characteristics were not sufficiently improved and the core loss was not sufficiently improved compared to sample number 1.

[0134] Furthermore, the examples (sample numbers 2 to 9) that satisfied (2×N50)≦L50≦(0.5×V10) had further improved DC bias characteristics compared to the examples (sample numbers 10, and 10a to 10d) that satisfied L50>0.5×V10.

[0135] (Experimental Example 2) For sample numbers 1 and 5, the experiment was carried out under substantially the same conditions, except that the mixing ratio of powder A to powder B was changed. The results are shown in Table 2. Note that Isat and core loss are omitted in Tables 2 to 22.

[0136] [Table 2]

[0137] As can be seen from Table 2, even when the mixing ratio of powder A and powder B was changed, in each of the examples in which powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3), the DC bias characteristics were sufficiently improved and the core loss was sufficiently reduced compared to the comparative examples which were essentially the same except that L50 was too small because powder B was not agglomerated.

[0138] (Experimental Example 3) The same experiments were carried out for Samples 1 and 5, except that the median diameter (D50) on a volume basis of Powder A was changed. The results are shown in Table 3.

[0139] [Table 3]

[0140] From Table 3, even if the volumetric median diameter (D50) of powder A was changed, each example that satisfied (2×N50)≦L50≦(0.5×V10+3) by agglomerating powder B showed sufficient improvement in DC bias characteristics and sufficient improvement in core loss compared to the comparative example that was substantially the same condition except that L50 was too small because powder B was not agglomerated. In particular, each example in which V10 was 3.0 μm or more and 20.0 μm or less and V50 was 8.0 μm or more and 40.0 μm or less had a higher Isat improvement rate than examples in which V10 and V50 were outside the above ranges.

[0141] (Experimental Example 4) The same experiments were carried out for Samples Nos. 1 and 5, except that the median diameter (D50) on a volume basis of Powder B was changed. The results are shown in Table 4.

[0142] [Table 4]

[0143] As can be seen from Table 4, even when the volumetric median diameter (D50) of Powder B was changed, in each Example in which Powder B was agglomerated to satisfy (2 × N50) ≦ L50 ≦ (0.5 × V10 + 3), the DC bias characteristics were sufficiently improved and the core loss was sufficiently reduced compared to the Comparative Example, which was essentially the same condition except that Powder B was not agglomerated and therefore L50 was too small.

[0144] (Experimental Example 5) Experimental Example 5 was carried out under the same conditions as Samples 1 and 5, except that Powder A was coated with an insulating coating. Specifically, a P-Zn-Al-O oxide glass coating was formed on the surface of Powder A. The thickness of the coating was set to 15 nm. The results are shown in Table 5.

[0145] [Table 5]

[0146] As can be seen from Table 5, even though the covering portion was formed by insulating coating, the example (sample number 44) in which powder B was agglomerated to satisfy (2 × N50) ≦ L50 ≦ (0.5 × V10 + 3) showed sufficient improvement in DC bias characteristics and core loss compared to the comparative example (sample number 43) which was essentially the same condition except that L50 was too small because powder B was not agglomerated.

[0147] (Experimental Example 6) The experiments were carried out under the same conditions as for samples 1 and 5, except that the composition and microstructure of powder A were changed. The results are shown in Table 6.

[0148] In sample numbers 45 and 46, the composition of powder A was 66.8Fe-16.7Co-11.0B-4.5P-1.0Si in atomic ratio. In sample numbers 47 and 48, the composition of powder A was 72.7Fe-10.8B-11.6Si-2.7C-2.2Cr in atomic ratio. In sample numbers 49 and 50, the composition of powder A was 81.6Fe-13.4B-3.4Si-1.6C in atomic ratio. It was confirmed by XRD that all powders A in sample numbers 45 to 50 had an amorphous structure.

[0149] In sample numbers 51 and 52, the composition of powder A was 73.5Fe-13.5Si-9.0B-3.0Nb-1.0Cu in terms of atomic ratio. In sample numbers 53 and 54, the composition of powder A was 82.0Fe-11.0B-5.0P-1.0Si-1.0Cu in terms of atomic ratio. In sample numbers 55 and 56, the composition of powder A was 78.0Fe-9.0B-3.0P-3.0Si-6.0Nb-1.0Cr in terms of atomic ratio. In addition, powder A of sample numbers 51 to 56 was produced by gas atomization and then heat-treated to precipitate nanocrystals with a crystal grain size of 30 nm or less. Specifically, the heat treatment was performed at 400 to 650 °C for 10 to 60 minutes. It was confirmed by XRD that all powder A of sample numbers 51 to 56 had a structure consisting of nanocrystals.

[0150] In sample numbers 57 and 58, the composition of powder A was a composition containing substantially only Fe. In sample numbers 59 and 60, the composition of powder A was 50.0Fe-50.0Co in terms of atomic ratio. In sample numbers 61 and 62, the composition of powder A was 88.0Fe-12.0Si in terms of atomic ratio. In sample numbers 63 and 64, the composition of powder A was 83.6Fe-4.4Co-12.0Si in terms of atomic ratio. In sample numbers 65 and 66, the composition of powder A was 89.4Fe-8.6Si-2.0Cr. In sample numbers 67 and 68, the composition of powder A was 80.5Fe-9.0Co-8.5Si-2.0Cr. In sample numbers 69 and 70, the composition of powder A was 73.7Fe-16.4Si-9.9Al. It was confirmed by XRD that all of powder A in sample numbers 57 to 70 had a structure consisting of crystals.

[0151] [Table 6]

[0152] As can be seen from Table 6, even when the composition and microstructure of Powder A were changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvements in DC bias characteristics and core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0153] (Experimental Example 7) Samples Nos. 1 and 5 were carried out under the same conditions except that the composition of Powder A was changed. The total content of Fe and Co in the composition of Powder A was mainly changed. The results are shown in Table 7. For Experimental Examples 7 to 12, descriptions of the comparative examples, which were essentially the same as the respective samples except that L50 was too small because Powder B was not aggregated, are omitted.

[0154] [Table 7]

[0155] As can be seen from Table 7, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0156] In particular, sample numbers 102 to 117, in which the total content of Fe and Co is 70.00 at% or more and 96.00 at% or less, had a higher improvement rate in core loss than sample number 101, which has a low total content of Fe and Co, and a higher improvement rate in Isat than sample number 118, which has a high total content of Fe and Co. The reason why the improvement rate of core loss of sample number 101 is low is thought to be because the magnetic properties were lower than those of the other samples due to the low content of magnetic elements. The reason why the improvement rate of Isat of sample number 118 is low is thought to be because the amorphous nature of powder A was lower than that of the other samples, and therefore the magnetic properties of powder A were lower than those of the other samples.

[0157] (Experimental Example 8) The comparative example and sample number 106 were essentially the same as those in the comparative example except that L50 was too small because powder B was not aggregated, and the Fe, Co and Ni contents of powder A were varied. The results are shown in Table 8.

[0158] [Table 8]

[0159] As can be seen from Table 8, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0160] In particular, sample numbers 106, 121 to 125, 127 to 131, and 133 to 136, in which the Fe content was equal to or greater than the combined content of Co and Ni, had better Isat improvement rates than sample numbers 126, 132, and 137, in which the Fe content was less than the combined content of Co and Ni. The reason for the lower Isat improvement rates in sample numbers 126, 132, and 137 is believed to be due to their deteriorated magnetic properties compared to the other samples.

[0161] (Experimental Example 9) For sample numbers 47 and 48, the C content and Cr content of powder A were mainly changed. The results are shown in Table 9.

[0162] [Table 9]

[0163] As can be seen from Table 9, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0164] In particular, sample numbers 48 and 142 to 150, in which the C content is 0 at% or more and 5.00 at% or less and the X2 (Cr) content is 0 at% or more and 3.00 at% or less, have a better Isat improvement rate than sample number 141, in which the X2 content exceeds 3.00 at%. The core loss improvement rate is better than sample number 151, in which the C content exceeds 5.00 at%. The reason why the Isat improvement rate of sample number 141 is low is thought to be because the magnetic properties, especially the saturation magnetic flux density, tend to decrease as the X2 content increases. The reason why the core loss improvement rate of sample number 151 is low is thought to be because the amorphous nature of powder A decreases due to the large C content, and the magnetic properties of powder A decrease.

[0165] (Experimental Example 10) For sample numbers 49 and 50, the B content and Fe content of powder A were mainly changed. For sample numbers 51 and 52, the B content and Si content of powder A were mainly changed. For sample numbers 53 and 54, the B content and P content of powder A were mainly changed. For sample numbers 55 and 56, the B content, P content and Nb content of powder A were mainly changed. The results are shown in Table 10.

[0166] [Table 10]

[0167] As can be seen from Table 10, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0168] In particular, sample numbers 50, 52, 54, 56, 161 to 168, 172 to 175, 181 to 185, and 192 to 196, in which the B content was 2.00 at% or more and 20.00 at% or less, the P content was 0 at% or more and 14.00 at% or less, the Si content was 0 at% or more and 15.00 at% or less, and the X3 (Nb) content was 0 at% or more and 9.00 at% or less, had a better improvement rate in core loss than sample number 169, in which the B content exceeded 20.00 at%, and sample number 186, in which the B content was less than 2.00 at% and the P content exceeded 14.00 at%. The Isat improvement rate was better than sample number 171, in which the Si content exceeded 15.00 at%, and sample number 191, in which the X3 content exceeded 9.00 at%. The low core loss improvement rate of sample numbers 169 and 186 is believed to be due to the fact that the magnetic properties deteriorate due to the decrease in amorphousness when the B content is too high or too low, and furthermore, the magnetic properties deteriorate due to the decrease in saturation magnetic flux density when the P content is too high. The low Isat improvement rate of sample number 171 is believed to be due to the fact that the high Si content reduces the saturation magnetic flux density and magnetic properties deteriorate. The low Isat improvement rate of sample number 191 is believed to be due to the fact that the high X3 content reduces the Curie point, reduces the saturation magnetic flux density at room temperature, and magnetic properties deteriorate.

[0169] (Experimental Example 11) A comparative example was conducted under substantially the same conditions as each sample except that L50 was too small because powder B was not aggregated, and each sample was also conducted by mainly changing the type and / or content of X2 in powder A. Note that sample number 200 did not contain X2, and in sample numbers 201 to 262, Fe and Co in sample number 200 were partially replaced with X2. The results are shown in Tables 11A to 11C.

[0170] [Table 11A]

[0171] [Table 11B]

[0172] [Table 11C]

[0173] As can be seen from Tables 11A to 11C, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0174] (Experimental Example 12) A comparative example was carried out under substantially the same conditions as sample number 106, except that M was too small because powder B was not aggregated, and sample number 106 was carried out under the same conditions, except that X2 (Cr) in powder A was replaced with X3 (Nb). Furthermore, for the examples and comparative examples, the type and content of X3 were changed, and the B content, P content, and Si content were changed in accordance with the change in the content of X3. The results are shown in Table 12.

[0175] [Table 12]

[0176] As can be seen from Table 12, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0177] In particular, sample numbers 271 to 274, 276 to 279, 281 to 284, 286 to 289, 291 to 294, and 296 to 299, in which the X3 content was 0 at% or more and 9.00 at% or less, had better Isat improvement rates than sample numbers 275, 280, 285, 290, 295, and 300, in which the X3 content was more than 9.00 at%. The reason why the Isat improvement rates of sample numbers 275, 280, 285, 290, 295, and 300 were low is thought to be because the Curie point was lowered by the large amount of X3, and the saturation magnetic flux density at room temperature was lowered, resulting in a deterioration in magnetic properties.

[0178] (Experimental Example 13) The experiments were carried out under the same conditions as for samples 1 and 5, except that the composition of powder B was changed. The results are shown in Table 13.

[0179] In sample numbers 71 and 72, the composition of powder B was a composition containing essentially only Co. In sample numbers 73 and 74, the composition of powder B was 50.0Fe-50.0Co in terms of atomic ratio. In sample numbers 75 and 76, the composition of powder B was 90.0Fe-10.0Si in terms of atomic ratio. In sample numbers 77 and 78, the composition of powder B was 20.0Fe-80.0Ni in terms of atomic ratio. It was confirmed by XRD that all of powder B in sample numbers 71 to 78 had a crystalline structure.

[0180] [Table 13]

[0181] As can be seen from Table 13, even when the composition and microstructure of Powder B were changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0182] (Experimental Example 14) The same conditions as those of Sample Nos. 1, 5, and 11 to 16 in Experimental Examples 1 and 2 were carried out, except that a part of Powder B having a volumetric median diameter (D50) of 0.8 μm was replaced with Powder C prepared under the same conditions as Powder B except that the volumetric median diameter (D50) was 3 μm. Unlike Powder B, Powder C was not aggregated. The results are shown in Table 14.

[0183] [Table 14]

[0184] As can be seen from Table 14, even when powder C was used in addition to powders A and B, the example in which powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative example, which was essentially the same except for the fact that L50 was too small because powder B was not agglomerated.

[0185] (Experimental Example 15) Sample numbers 87 to 98, 97a to 97c, and 98a to 98c were carried out under the same conditions as sample numbers 81 and 82, except that the composition and microstructure of powder C were changed. The results are shown in Table 15.

[0186] The composition and microstructure of Powder C in Sample Nos. 87 and 88 were the same as the composition and microstructure of Powder B in Sample Nos. 71 and 72. The composition and microstructure of Powder C in Sample Nos. 89 and 90 were the same as the composition and microstructure of Powder B in Sample Nos. 73 and 74. The composition and microstructure of Powder C in Sample Nos. 91 and 92 were the same as the composition and microstructure of Powder B in Sample Nos. 75 and 76. The composition and microstructure of Powder C in Sample Nos. 93 and 94 were the same as the composition and microstructure of Powder B in Sample Nos. 77 and 78.

[0187] The composition and microstructure of Powder C in Sample Nos. 95 and 96 were the same as that of Powder A in Sample Nos. 45 and 46. The composition and microstructure of Powder C in Sample Nos. 97 and 98 were the same as that of Powder A in Sample Nos. 47 and 48. The composition and microstructure of Powder C in Sample Nos. 97a and 98a were the same as that of Powder A in Sample Nos. 51 and 52. The composition and microstructure of Powder C in Sample Nos. 97b and 98b were the same as that of Powder A in Sample Nos. 53 and 54. The composition and microstructure of Powder C in Sample Nos. 97c and 98c were the same as that of Powder A in Sample Nos. 55 and 56.

[0188] [Table 15]

[0189] As can be seen from Table 15, even when the composition and microstructure of Powder C were further changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0190] (Experimental Example 16) In Experimental Example 16, Powder A, which would eventually become mostly large particles, was produced by water atomization. Powder A had a composition of Fe-Co-BP-Si-Cr system. Specifically, the atomic ratio was 57.4Fe-24.6Co-11.0B-3.0P-3.0Si-1.0Cr.

[0191] The conditions for the water atomization method were a pressure of high pressure water of 50.0 MPa to 200 MPa, and a jet rate of molten metal of 0.5 kg / min to 4.0 kg / min.

[0192] The classification method of the powder produced by the water atomization method will be described. First, the obtained powder was classified using a sieve with a mesh size of 250 μm to remove coarse particles. Next, air classification was performed so that the median diameter (D50) based on the volume of powder A became the target value. The air classification was performed using an air classifier (Faculty, manufactured by Hosokawa Micron Corporation) as the classification device, and the classification rotor rotation speed was set to 4000 rpm or more and 20000 rpm or less.

[0193] The atomization conditions and the classification conditions in the air flow classification were appropriately controlled to set the volumetric median diameter (D50) of the obtained Powder A to 0.8 μm and the median diameter (D50) of the obtained Powder B to 0.3 μm, and the epoxy resin content was controlled so that the finally obtained magnetic core had a relative permeability μ of 20. The results are shown in Table 16A.

[0194] The atomization conditions and the classification conditions in the air flow classification were appropriately controlled to set the volumetric median diameter (D50) of the obtained Powder A to 3 μm and the median diameter (D50) of the obtained Powder B to 0.5 μm, and the amount of epoxy resin added was controlled so that the relative permeability μ of the finally obtained magnetic core was 25. The results are shown in Table 16B.

[0195] [Table 16A]

[0196] [Table 16B]

[0197] From Tables 16A and 16B, even if the median diameters of powders A and B are changed, the examples in which (2×N50)≦L50≦(0.5×V10+3) is satisfied by agglomerating powder B have sufficiently improved DC superposition characteristics and improved core loss compared to the comparative examples in which L50 was too small because powder B was not agglomerated, which are essentially the same conditions. However, the comparative example (sample number 314) in which L50 was too large because powder B was agglomerated too much did not have a sufficient improvement in core loss compared to sample number 301. The comparative example (sample number 334) in which L50 was too large because powder B was agglomerated too much did not have a sufficient improvement in core loss compared to sample number 321.

[0198] (Experimental Example 17) Experimental Example 16, Sample Nos. 321 and 329 in Table 16B were carried out under the same conditions, except that the composition of Powder A was changed. The total content ratio of Fe and Co in the composition of Powder A was mainly changed. The results are shown in Table 17. For Experimental Examples 17 to 22, descriptions of the comparative examples, which were substantially the same as the respective samples, except that L50 was too small because Powder B was not aggregated, are omitted.

[0199] [Table 17]

[0200] As can be seen from Table 17, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0201] In particular, sample numbers 329 and 342 to 357, in which the total content of Fe and Co is 70.00 at% or more and 96.00 at% or less, showed a better improvement rate in core loss than sample numbers 341 and 358, in which the total content of Fe and Co is outside the above range. The low improvement rate of core loss in sample number 341 is believed to be due to the deterioration of the soft magnetic properties of powder A. The low improvement rate of core loss in sample number 358 is believed to be due to the deterioration of the soft magnetic properties of powder A, as the amorphous nature of powder A is lower than that of the other samples.

[0202] (Experimental Example 18) The comparative example and sample number 346 were essentially the same as sample number 346 except that L50 was too small because powder B was not aggregated, and the Fe, Co and Ni contents of powder A were varied. The results are shown in Table 18.

[0203] [Table 18]

[0204] As can be seen from Table 18, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except for the fact that M was too small because Powder B was not agglomerated.

[0205] In particular, sample numbers 346, 361 to 365, 367 to 371, and 373 to 376, in which the Fe content was equal to or greater than the combined content of Co and Ni, had better core loss improvement rates than sample numbers 366, 372, and 377, in which the Fe content was less than the combined content of Co and Ni. The lower core loss improvement rates for sample numbers 366, 372, and 377 are believed to be due to the fact that the soft magnetic properties were worse than those of the other samples.

[0206] (Experimental Example 19) The median diameter of powder A was changed to 3 μm, the median diameter of powder B was changed to 0.5 μm, and the pressure applied to powder B was changed. The same operations as for sample numbers 47 and 48 were carried out except that the median diameter of powder A was changed to 3 μm, the median diameter of powder B was changed to 0.5 μm, and the pressure applied to powder B was changed. Sample number 388 was a sample carried out in the same manner as sample number 48 except that the above conditions were changed.

[0207] Furthermore, a comparative example was carried out under substantially the same conditions as sample number 388 except that M was too small because powder B was not aggregated, and sample number 388 was also carried out by mainly changing the C content and Cr content of powder A. The results are shown in Table 19.

[0208] [Table 19]

[0209] As can be seen from Table 19, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0210] In particular, sample numbers 382 to 391, in which the C content was 0 at% or more and 5.00 at% or less and the X2 (Cr) content was 0 at% or more and 3.00 at% or less, had better core loss improvement rates than sample number 381, in which the X2 content was more than 3.00 at%, and sample number 392, in which the C content was more than 5.00 at%. The reason why the core loss improvement rate of sample number 381 was low is thought to be because the soft magnetic properties tend to deteriorate as the X2 content increases. The reason why the core loss improvement rate of sample number 392 was low is thought to be because the amorphous nature decreased due to the large C content, and the soft magnetic properties deteriorated.

[0211] (Experimental Example 20) The median diameter of powder A was changed to 3 μm, the median diameter of powder B was changed to 0.5 μm, and the pressure value of powder B was changed, but the same experiment was carried out as with sample numbers 49 and 50. Sample number 404 was a sample carried out in the same manner as sample number 50, except that the median diameter of powder A was changed. Furthermore, a comparative example and sample number 404 were essentially the same as sample number 404, except that L50 was too small because powder B was not aggregated, and the experiment was carried out mainly by changing the content of B and the content of Fe in powder A. The results are shown in Table 20.

[0212] The median diameter of powder A was changed to 3 μm, the median diameter of powder B was changed to 0.5 μm, and the pressure value of powder B was changed, but the same experiment was carried out as with sample numbers 51 and 52. Sample number 414 was a sample carried out in the same manner as sample number 52, except that the median diameter of powder A was changed. Furthermore, a comparative example and sample number 414 were essentially the same as sample number 414, except that L50 was too small because powder B was not aggregated, and the B content and Si content of powder A were mainly changed. The results are shown in Table 20.

[0213] The median diameter of powder A was changed to 3 μm, the median diameter of powder B was changed to 0.5 μm, and the pressure value of powder B was changed. Sample No. 417 was a sample prepared in the same manner as sample No. 54 except that the median diameter of powder A was changed. Furthermore, a comparative example and sample No. 417 were essentially the same as sample No. 417 except that L50 was too small because powder B was not aggregated, and the content of B and the content of P in powder A were mainly changed. The results are shown in Table 20.

[0214] The median diameter of powder A was changed to 3 μm, the median diameter of powder B was changed to 0.5 μm, and the pressure value of powder B was changed, but the same experiment was carried out as in sample numbers 55 and 56. Sample number 427 was a sample carried out in the same manner as sample number 56, except that the median diameter of powder A was changed. Furthermore, a comparative example and sample number 427, which were essentially the same conditions as sample number 427, except that L50 was too small because powder B was not aggregated, were mainly changed in the B content, P content, and Nb content of powder A. The results are shown in Table 20.

[0215] [Table 20]

[0216] As can be seen from Table 20, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0217] In particular, sample numbers 401 to 409, 412 to 422, and 425 to 430, in which the B content was 2.00 at% or more and 20.00 at% or less, the P content was 0 at% or more and 14.00 at% or less, the Si content was 0 at% or more and 15.00 at% or less, and the X3 (Nb) content was 0 at% or more and 9.00 at% or less, had a more favorable core loss improvement rate than sample number 410, in which the B content exceeded 20.00 at%, sample number 423, in which the B content was less than 2.00 at% and the P content exceeded 14.00 at%, sample number 411, in which the Si content exceeded 15.00 at%, and sample number 424, in which the X3 content exceeded 9.00 at%. The reason why the improvement rate of core loss of sample numbers 410 and 423 is low is thought to be because the amorphous nature of powder A is reduced when the content of B in powder A is too high or too low, which reduces the soft magnetic properties of powder A. The reason why the improvement rate of core loss of sample number 411 is low is thought to be because the saturation magnetic flux density of powder A is reduced due to the high Si content of powder A, which reduces the soft magnetic properties of powder A. The reason why the improvement rate of core loss of sample number 424 is low is thought to be because the Curie point of powder A is reduced due to the high X3 content of powder A, which reduces the saturation magnetic flux density at room temperature of powder A, which reduces the soft magnetic properties.

[0218] (Experimental Example 21) Sample numbers 440 to 502 were carried out in the same manner as sample numbers 200 to 262, except that the median diameter of powder A was changed to 3 μm, the median diameter of powder B was changed to 0.5 μm, and the pressure value of powder B was changed. Furthermore, comparative examples were carried out under substantially the same conditions as each sample, except that L50 was too small because powder B was not aggregated. Note that sample number 440 did not contain X2, and in sample numbers 441 to 502, Fe and Co in sample number 440 were partially replaced with X2. The results are shown in Tables 21A to 21C.

[0219] [Table 21A]

[0220] [Table 21B]

[0221] [Table 21C]

[0222] As can be seen from Tables 21A to 21C, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except for the fact that Powder B was not agglomerated and therefore M was too small.

[0223] (Experimental Example 22) A comparative example was carried out under substantially the same conditions as sample number 346, except that L50 was too small because powder B was not aggregated, and sample number 346 was carried out under the same conditions, except that X2 (Cr) in powder A was replaced with X3 (Nb). Furthermore, for the examples and comparative examples, the type and content of X3 were changed, and the B content, P content, and Si content were changed in accordance with the change in the content of X3. The results are shown in Table 22.

[0224] [Table 22]

[0225] As can be seen from Table 22, even when the composition of Powder A was changed, the examples in which Powder B was agglomerated to satisfy (2×N50)≦L50≦(0.5×V10+3) showed sufficient improvement in DC bias characteristics and improved core loss compared to the comparative examples which were essentially the same except that Powder B was not agglomerated and therefore L50 was too small.

[0226] In particular, sample numbers 511 to 514, 516 to 519, 521 to 524, 526 to 529, 531 to 534, and 536 to 539, in which the content of X3 is 0 at% or more and 9.00 at% or less, had better core loss improvement rates than sample numbers 515, 520, 525, 530, 535, and 540, in which the content of X3 is more than 9.00 at%. The reason why the improvement rates of core loss of sample numbers 495, 500, 505, 510, 515, and 520 are low is considered to be because the Curie point of powder A is lowered due to the large content of X3 in powder A, and the saturation magnetic flux density at room temperature of powder A is lowered, resulting in a deterioration of soft magnetic properties.

[0227] The soft magnetic particles contained in the magnetic cores of the samples obtained in the above Experimental Examples 1 to 22 were subjected to electron beam diffraction patterns by TEM to confirm their microstructures. It was confirmed that the microstructures of the soft magnetic particles derived from Powder A, Powder B, and Powder C did not change substantially between before and after compaction.

Claims

1. A magnetic core comprising soft magnetic particles, The value of D10 in the volume-based particle size distribution (unit: μm) of the soft magnetic particles is V10, the value of D50 in the volume-based particle size distribution of the soft magnetic particles is V50, and the value of D50 in the number-based particle size distribution of the soft magnetic particles is N50, The soft magnetic particles include large particles having a particle diameter of (0.5×V50) or more and small particles having a particle diameter of (2×N50) or less, The distance from a small particle to the nearest large particle is defined as L, and the median value of L calculated for all small particles is defined as L50. A magnetic core that satisfies (2 x N50) ≦ L50 ≦ (0.5 x V10 + 3.0).

2. A magnetic core comprising soft magnetic particles, The value of D10 in the volume-based particle size distribution of the soft magnetic particles is V10, the value of D50 in the volume-based particle size distribution of the soft magnetic particles is V50, and the value of D50 in the number-based particle size distribution of the soft magnetic particles is N50, The soft magnetic particles include large particles having a particle diameter of (0.5×V50) or more and small particles having a particle diameter of (2×N50) or less, The distance from a small particle to the nearest large particle is defined as L, and the median value of L calculated for all small particles is defined as L50. A magnetic core that satisfies (2 x N50) ≦ L50 ≦ (0.5 x V10).

3. At least a part of the soft magnetic particles has a composition represented by the formula (Fe 1-p X1 p ) 100-(a+b+c+d+e+f) B a P b S c C d X2 e X3 f (atomic ratio), X1 is one or more selected from Co and Ni; X2 is one or more selected from Ti, Cr, Mn, Al, Ga, Ag, Zn, S, Ca, Mg, V, Sn, As, Sb, Bi, N, Au, Cu, rare earth elements, and platinum group elements; X3 is one or more selected from Zr, Nb, Mo, Hf, Ta, and W; 0≦p≦0.5, 2.00≦a≦20.00, 0.00≦b≦14.00, 0.00≦c≦15.00, 0.00≦d≦5.00, 0.00≦e≦3.00, 0.00≦f≦9.00, and 3. The magnetic core according to claim 1, wherein 70.00≦100−(a+b+c+d+e+f)≦96.00 is satisfied.

4. 3. The magnetic core according to claim 1, wherein V10 is 3.0 μm or more and 20.0 μm or less.

5. 3. The magnetic core according to claim 1, wherein V50 is 8.0 μm or more and 40.0 μm or less.

6. 3. The magnetic core according to claim 1, wherein at least a portion of the soft magnetic particles contain Fe, Co, and / or Ni.

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

8. 3. An electronic device comprising the magnetic core according to claim 1.

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