Soft magnetic powders, dust cores, magnetic elements and electronic devices

Abstract

To provide a soft-magnetic powder allowed to make a green compact having a high insulation resistance value and a high magnetic permeability, a magnetic powder core and magnetic element containing such a soft-magnetic powder, and an electronic appliance comprising the magnetic element.SOLUTION: A soft-magnetic powder contains a particle having a composition represented by FexCuaNbb(Si1-yBy)100-x-a-b [a, b, x are respectively numbers having a unit of atom% and satisfy 0.3≤a≤2.0, 2.0≤b≤4.0, and 73.0≤x≤79.5. Also, y is a number satisfying f(x)≤y≤0.99, f(x)=(4×10-34)x17.56.] so that, when a XPS spectrum is acquired for the particle and fitting processing is done on a O1 s peak, separation is caused into a first element peak of 532 eV or lower and a second element peak of over 532 eV and, provided that the first element peak has an area of S1 and the second element peak has an area of S2, S2 / S1 is given 1.5 or greater.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a soft magnetic powder, a dust core, a magnetic element, and an electronic device. [Background technology]

[0002] In order to achieve miniaturization and higher output in various mobile devices equipped with magnetic elements containing powder magnetic cores, switching power supplies must be able to handle high frequencies and high currents in their conversion frequencies. Accordingly, the soft magnetic powder contained in powder magnetic cores must also be able to handle high frequencies and high currents.

[0003] Patent Document 1 describes Fe x Cu a Nb b (Si 1-y B y ) 100-x-a-b [where a, b, and x are atomic percent and are numbers that satisfy 0.3≦a≦2.0, 2.0≦b≦4.0, and 73.0≦x≦79.5. Also, y is a number that satisfies f(x)≦y<0.99. Note that f(x)=(4×10 -34 )x 17.56 The soft magnetic powder has a composition represented by the formula: and contains 30% by volume or more of a crystalline structure having a particle size of 1.0 nm to 30.0 nm. By including minute crystals in such a soft magnetic powder, it is possible to reduce iron loss at high frequencies. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-189928 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the soft magnetic powder described in Patent Document 1 still has room for improvement in terms of stably realizing excellent soft magnetism while improving the insulation between particles. Specifically, there is a demand for a green compact that can achieve high insulation resistance and high magnetic permeability when produced by compacting soft magnetic powder. [Means for solving the problem]

[0006] The soft magnetic powder according to the application example of the present invention is Fe x Cu a Nb b (Si 1-y B y ) 100-x-a-b [a, b, x are each a number expressed in atomic percent, 0.3≦a≦2.0, 2.0≦b≦4.0, 73.0≦x≦79.5 Meet the following. Also, y is a number that satisfies f(x)≦y≦0.99, and f(x)=(4×10 -34 )x 17.56 ] The particles have a composition represented by The particles contain crystal grains having a particle size of 1.0 nm or more and 30.0 nm or less, When an XPS spectrum is obtained by X-ray photoelectron spectroscopy for the particle and a fitting process is performed to separate the O1s peak of the XPS spectrum into a plurality of different chemical states, The O1s peak is separated into at least one first component peak having a peak top binding energy of 532 eV or less and at least one second component peak having a peak top binding energy of more than 532 eV; When the total area of ​​the first component peaks is S1 and the total area of ​​the second component peaks is S2, S2 / S1 is 1.5 or more 3.1 or below It is characterized in that:

[0007] A powder magnetic core according to an application example of the present invention includes: The soft magnetic powder according to the application example of the present invention is included.

[0008] The magnetic element according to the application example of the present invention includes: The present invention is characterized by including a powder magnetic core according to an application example of the present invention.

[0009] The electronic device according to the application example of the present invention includes: The magnetic element according to the application example of the present invention is included. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing a region in which the range of x and the range of y in the composition formula of the soft magnetic powder according to the embodiment overlap in a two-axis orthogonal coordinate system in which x is the horizontal axis and y is the vertical axis. [Figure 2] FIG. 2 is an enlarged view of the O1s peak in the XPS spectrum obtained from particles of soft magnetic powder. [Figure 3] FIG. 3 is a diagram showing four peaks separated by fitting processing for the O1s peak shown in FIG. 2. [Figure 4] The areas of the four peaks shown in FIG. 3 were measured, and then the ratios to the total area were calculated as chemical state ratios, and these were compared in a bar graph. [Figure 5] FIG. 2 is an enlarged view of the Si2p peak contained in the XPS spectrum obtained from the particles of the soft magnetic powder. [Figure 6] 1 is a table showing the results of qualitative and quantitative analysis obtained for the soft magnetic powder according to the present embodiment (results of qualitative and quantitative analysis of Examples) and the results of qualitative and quantitative analysis of Comparative Examples. [Figure 7] FIG. 1 is a vertical cross-sectional view showing an example of an apparatus for producing soft magnetic powder by a rotary water jet atomization method. [Figure 8] FIG. 1 is a plan view schematically showing a toroidal type coil component. [Figure 9] FIG. 1 is a transparent perspective view schematically showing a closed magnetic circuit type coil component. [Figure 10]FIG. 1 is a perspective view showing the configuration of a mobile personal computer, which is an electronic device including a magnetic element according to an embodiment. [Figure 11] FIG. 1 is a plan view showing the configuration of a smartphone, which is an electronic device including a magnetic element according to an embodiment. [Figure 12] FIG. 1 is a perspective view showing the configuration of a digital still camera, which is an electronic device including a magnetic element according to an embodiment. [Figure 13] FIG. 2 is an enlarged view of the O1s peak in the XPS spectrum obtained from particles of soft magnetic powder. [Figure 14] FIG. 14 is a diagram showing four peaks separated by fitting processing for the O1s peak shown in FIG. 13. [Figure 15] The areas of the four peaks shown in FIG. 14 were measured, and then the ratios to the total area were calculated as chemical state ratios, and these were compared in a bar graph. [Figure 16] FIG. 2 is an enlarged view of the Si2p peak contained in the XPS spectrum obtained from the particles of the soft magnetic powder. [Figure 17] 1 is a table showing the results of qualitative and quantitative analysis obtained for the soft magnetic powder according to the present embodiment (results of qualitative and quantitative analysis of Examples) and the results of qualitative and quantitative analysis of Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] The soft magnetic powder, dust core, magnetic element, and electronic device of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

[0012] 1. Soft magnetic powder The soft magnetic powder according to the embodiment is a metal powder exhibiting soft magnetism. Such soft magnetic powder can be used for any purpose, but for example, the particles are bound together via a binder and used to produce various compacts such as dust cores and electromagnetic wave absorbers.

[0013] The soft magnetic powder according to the embodiment contains Fe x Cu a Nb b (Si1-y B y ) 100-x-a-b The particles include particles having a composition represented by the formula:

[0014] a, b, and x are each a number expressed in atomic percent, where a satisfies 0.3≦a≦2.0, b satisfies 2.0≦b≦4.0, and x satisfies 73.0≦x≦79.5.

[0015] Also, y satisfies f(x)≦y≦0.99. And, f(x)=(4×10 -34 )x 17.56 is.

[0016] Furthermore, the particles contained in the soft magnetic powder according to the embodiment contain crystal grains with a particle size of 1.0 nm or more and 30.0 nm or less.

[0017] An XPS spectrum is obtained by X-ray photoelectron spectroscopy for particles having such a composition and crystal grains, and a fitting process is performed to separate the O1s peak of the XPS spectrum into multiple different chemical states. At this time, the O1s peak is separated into at least one first component peak having a peak top binding energy of 532 eV or less and at least one second component peak having a peak top binding energy of more than 532 eV. When the total area of ​​the first component peaks is S1 and the total area of ​​the second component peaks is S2, the soft magnetic powder according to the embodiment has an S2 / S1 ratio of 1.5 or more.

[0018] According to this configuration, a soft magnetic powder can be obtained that, when compacted, can produce a compact having a high insulation resistance value and high magnetic permeability.

[0019] The soft magnetic powder according to the embodiment will be described in detail below. 1.1. Composition Fe (iron) has a significant effect on the basic magnetic properties and mechanical properties of the soft magnetic powder according to the embodiment.

[0020] The Fe content x is 73.0 atomic % or more and 79.5 atomic % or less, preferably 75.0 atomic % or more and 78.5 atomic % or less, and more preferably 75.5 atomic % or more and 78.0 atomic % or less. If the Fe content x is below the lower limit, the saturation magnetic flux density of the soft magnetic powder may decrease. On the other hand, if the Fe content x is above the upper limit, an amorphous structure cannot be stably formed during the production of the soft magnetic powder, and it may be difficult to form crystal grains with the above-mentioned fine particle size.

[0021] When the soft magnetic powder according to the embodiment is produced from raw materials, copper (Cu) tends to separate from iron. Therefore, the inclusion of Cu causes fluctuations in the composition, resulting in regions within the particles that are prone to crystallization. As a result, the precipitation of the body-centered cubic Fe phase, which is relatively prone to crystallization, is promoted, making it easier to form crystal grains with the aforementioned small particle size.

[0022] The Cu content a is 0.3 atomic % or more and 2.0 atomic % or less, preferably 0.5 atomic % or more and 1.5 atomic % or less, and more preferably 0.7 atomic % or more and 1.3 atomic % or less. If the Cu content a is below the lower limit, the refinement of the crystal grains may be impaired, and it may be impossible to form crystal grains with a particle size within the aforementioned range. On the other hand, if the Cu content a is above the upper limit, the mechanical properties of the soft magnetic powder may be reduced, and the powder may become brittle.

[0023] When powder containing a large amount of amorphous structure is heat-treated, Nb (niobium) contributes to the refinement of crystal grains together with Cu, making it easier to form crystal grains with the fine grain size described above.

[0024] The Nb content b is 2.0 atomic % or more and 4.0 atomic % or less, preferably 2.5 atomic % or more and 3.5 atomic % or less, and more preferably 2.7 atomic % or more and 3.3 atomic % or less. If the Nb content b is below the lower limit, the refinement of the crystal grains may be impaired, and it may be impossible to form crystal grains with a particle size within the aforementioned range. On the other hand, if the Nb content b is above the upper limit, the mechanical properties of the soft magnetic powder may be reduced, and the soft magnetic powder may become brittle. Furthermore, the magnetic permeability of the soft magnetic powder may be reduced.

[0025] Silicon (Si) promotes amorphization when the soft magnetic powder according to the embodiment is produced from raw materials. Therefore, when producing the soft magnetic powder according to the embodiment, a homogeneous amorphous structure is first formed, and then crystallization of the amorphous structure facilitates the formation of crystal grains with a more uniform particle size. The uniform particle size contributes to averaging the magnetocrystalline anisotropy of each crystal grain, thereby reducing the coercive force and increasing the magnetic permeability, thereby improving the soft magnetic properties.

[0026] B (boron) promotes amorphization when the soft magnetic powder according to the embodiment is produced from raw materials. Therefore, when producing the soft magnetic powder according to the embodiment, a homogeneous amorphous structure is first formed, and then crystallization of the amorphous structure facilitates the formation of crystal grains with a more uniform particle size. Furthermore, the uniform particle size contributes to averaging the magnetocrystalline anisotropy of each crystal grain, thereby reducing the coercive force and increasing the magnetic permeability, thereby improving the soft magnetic properties. Furthermore, by using Si and B together, the difference in atomic radii of the two elements can synergistically promote amorphization.

[0027] Here, when the sum of the contents of Si and B is 1 and the ratio of the content of B to this total is y, the ratio of the content of Si to the total is (1-y).

[0028] This y is a number that satisfies f(x)≦y≦0.99. And, f(x), which is a function of x, is f(x)=(4×10 -34 )x 17.56is.

[0029] FIG. 1 is a diagram showing a region in a two-axis orthogonal coordinate system in which x is the horizontal axis and y is the vertical axis, where the range of x and the range of y in the composition formula of the soft magnetic powder according to the embodiment overlap.

[0030] In FIG. 1, an area A where the x range and the y range overlap is inside the solid line drawn on the Cartesian coordinate system.

[0031] Specifically, region A is a closed region surrounded by three straight lines and one curve when the (x, y) coordinates that satisfy the four equations x=73.0, x=79.5, y=f(x), and y=0.99 are plotted on a Cartesian coordinate system.

[0032] Furthermore, y is preferably a number that satisfies f'(x)≦y≦0.97. And, f'(x), which is a function of x, is expressed as f'(x)=(4×10 -29 )x 14.93 is.

[0033] The dashed line in FIG. 1 indicates a region B where the above-mentioned preferable range of x and the above-mentioned preferable range of y overlap.

[0034] Specifically, region B is a closed region surrounded by three straight lines and one curve when the (x, y) coordinates that satisfy the four equations x=75.0, x=78.5, y=f'(x), and y=0.97 are plotted on a Cartesian coordinate system.

[0035] Furthermore, y is more preferably a number that satisfies f"(x)≦y≦0.95. And, f"(x), which is a function of x, is expressed as f"(x)=(4×10 -29 )x 14.93 It is +0.05.

[0036] The dashed dotted line in FIG. 1 indicates a region C where the above-mentioned more preferable range of x and the above-mentioned more preferable range of y overlap.

[0037] Specifically, region C is a closed region enclosed by three straight lines and one curve when the (x, y) coordinates that satisfy the four equations x = 75.5, x = 78.0, y = f"(x), and y = 0.95 are plotted on a Cartesian coordinate system.

[0038] Soft magnetic powders in which x and y fall within at least region A can form a homogeneous amorphous structure with a high probability during production. Therefore, by crystallizing the powder, crystal grains with a particularly uniform particle size can be formed. This results in soft magnetic powders with sufficiently reduced coercivity. Furthermore, by using this soft magnetic powder, the iron loss of the powder core can be kept sufficiently low.

[0039] Furthermore, soft magnetic powders in which x and y are at least within region A can form uniform crystal grains even when the Fe content is sufficiently increased. This allows for the production of soft magnetic powders with sufficiently increased saturation magnetic flux density. As a result, a powder magnetic core can be obtained that has a high saturation magnetic flux density while achieving sufficiently low iron loss.

[0040] If the value of y is smaller than that of region A, the balance between the Si content and the B content is lost, making it difficult to form a homogeneous amorphous structure when producing the soft magnetic powder. As a result, crystal grains with a small particle size cannot be formed, and the coercive force cannot be reduced sufficiently.

[0041] On the other hand, when the value of y is larger than that of region A, the balance between the Si content and the B content is lost, making it difficult to form a homogeneous amorphous structure when producing the soft magnetic powder. As a result, crystal grains with a small particle size cannot be formed, and the coercive force cannot be reduced sufficiently.

[0042] Note that f(x) is preferably 0.30 or more, more preferably 0.45 or more, and even more preferably 0.55 or more, which allows the soft magnetic powder to have a higher saturation magnetic flux density.

[0043] Furthermore, since regions B and C are regions where the value of x is large even within region A, the Fe content is particularly high. This makes it easy to increase the saturation magnetic flux density of the soft magnetic powder. Therefore, by using soft magnetic powder in which x and y fall within at least region B, it is possible to reduce the size and increase the output of powder cores and magnetic elements.

[0044] Furthermore, the sum of the Si content and the B content, (100-xab), is not particularly limited, but is preferably 15.0 atomic % or more and 24.0 atomic % or less, more preferably 16.0 atomic % or more and 23.0 atomic % or less, and even more preferably 16.0 atomic % or more and 22.0 atomic % or less. By having (100-xab) within the above range, crystal grains with a particularly uniform particle size can be formed in the soft magnetic powder.

[0045] Considering the above, y(100-xab) corresponds to the content of B in the soft magnetic powder. y(100-xab) is set appropriately taking into consideration the coercive force and saturation magnetic flux density as described above, and preferably satisfies 5.0≦y(100-xab)≦17.0, more preferably 7.0≦y(100-xab)≦16.0, and even more preferably 8.0≦y(100-xab)≦15.0.

[0046] This results in a soft magnetic powder containing a relatively high concentration of B (boron). Even if the soft magnetic powder contains a high content of Fe, it is possible to form a homogeneous amorphous structure during production. Therefore, subsequent heat treatment can form crystal grains with small and relatively uniform grain sizes, achieving a high magnetic flux density while sufficiently reducing the coercive force.

[0047] If y(100-xab) is below the lower limit, the B content will be small, which may make it difficult to achieve amorphousness depending on the overall composition when producing the soft magnetic powder. On the other hand, if y(100-xab) is above the upper limit, the B content will be large and the Si content will be relatively low, which may reduce the magnetic permeability of the soft magnetic powder and the saturation magnetic flux density.

[0048] In addition, the soft magnetic powder according to the embodiment contains the above-mentioned Fe x Cu a Nb b (Si 1-y B y ) 100-x-a-b In addition to the composition represented by the formula (I), impurities may be contained. Examples of impurities include any elements other than those mentioned above, but it is preferable that the total content of impurities is 0.50 atomic % or less. Within this range, impurities are unlikely to impair the effects of the present invention, so their inclusion is permitted.

[0049] The content of each impurity element is preferably 0.05 atomic % or less, and within this range, the impurities are not likely to impair the effects of the present invention, so their inclusion is permitted.

[0050] The composition of the soft magnetic powder according to the embodiment has been described above, but the composition and impurities are identified by the following analytical method.

[0051] Examples of analytical methods include iron and steel - atomic absorption spectrometry specified in JIS G 1257:2000, iron and steel - inductively coupled plasma (ICP) atomic emission spectrometry specified in JIS G 1258:2007, iron and steel - spark discharge atomic emission spectrometry specified in JIS G 1253:2002, iron and steel - X-ray fluorescence analysis specified in JIS G 1256:1997, and gravimetric / titration / absorptiometry specified in JIS G 1211 to G 1237.

[0052] Specific examples include a solid-state optical emission spectrometer manufactured by SPECTRO, in particular a spark discharge optical emission spectrometer, model: SPECTROLAB, type: LAVMB08A, and an ICP device, model CIROS120 manufactured by Rigaku Corporation.

[0053] In particular, when identifying carbon (C) and sulfur (S), the oxygen flow combustion (high-frequency induction heating furnace combustion)-infrared absorption method specified in JIS G 1211:2011 is also used. Specifically, the LECO CS-200 carbon / sulfur analyzer can be used.

[0054] In particular, when specifying N (nitrogen) and O (oxygen), the nitrogen determination method for iron and steel specified in JIS G 1228:1997 and the oxygen determination method for metallic materials specified in JIS Z 2613:2006 are also used. Specific examples include the LECO oxygen and nitrogen analyzer TC-300 / EF-300.

[0055] 1.2.Crystal Grains The particles of the soft magnetic powder according to the embodiment contain crystal grains with a crystal grain size of 1.0 nm or more and 30.0 nm or less. Because crystal grains with such a grain size are small, the magnetic anisotropy of each crystal grain is easily averaged. This allows for a reduced coercive force, resulting in a particularly magnetically soft powder. Furthermore, when a certain number of crystal grains are contained within such a grain size, the magnetic permeability of the soft magnetic powder increases. As a result, a powder rich in soft magnetic properties, with low coercive force and high magnetic permeability, is obtained. Furthermore, the increased magnetic permeability makes it less likely to saturate even under high currents, thereby increasing the saturation magnetic flux density of the soft magnetic powder.

[0056] In the particles, the content ratio of crystal grains in the above particle size range is not particularly limited, but is preferably 30% by volume or more, more preferably 40% by volume to 99% by volume or less, and even more preferably 55% by volume to 95% by volume or less. If the content ratio of crystal grains in the above particle size range is below the above lower limit, the proportion of crystal grains with small particle sizes decreases, which may result in insufficient averaging of the magnetic crystal anisotropy, resulting in a decrease in the magnetic permeability of the soft magnetic powder or an increase in the coercive force of the soft magnetic powder. On the other hand, the content ratio of crystal grains in the above particle size range may exceed the above upper limit, but as described below, the effect of the coexistence of amorphous structure may be insufficient.

[0057] Furthermore, the soft magnetic powder according to the embodiment may contain crystal grains with particle sizes outside the aforementioned range, i.e., grains with particle sizes less than 1.0 nm or more than 30.0 nm. In this case, the crystal grains with particle sizes outside the range are preferably kept to 10% by volume or less, and more preferably kept to 5% by volume or less. This prevents the aforementioned effects from being reduced by the crystal grains with particle sizes outside the range.

[0058] The particle size of the crystal grains of the soft magnetic powder can be determined, for example, by observing a cross section of the particle of the soft magnetic powder with an electron microscope and reading the size from the observed image. In this method, a perfect circle having the same area as the crystal grain is assumed, and the diameter of the perfect circle, i.e., the equivalent circle diameter, can be taken as the particle size of the crystal grain.

[0059] The volume ratio of the crystal grains is considered to be approximately equal to the area ratio of the crystal grains to the area of ​​the cut surface, so the area ratio may be regarded as the content ratio.

[0060] The average grain size of the crystal grains is preferably 2.0 nm or more and 25.0 nm or less, and more preferably 5.0 nm or more and 20.0 nm or less, which makes the above-mentioned effect, i.e., the effect of low coercive force and high magnetic permeability, more pronounced.

[0061] The average particle size of the crystal grains of the soft magnetic powder can be determined, for example, by determining the particle size of the crystal grains as described above and averaging them, or by determining the width of the peak derived from Fe in the X-ray diffraction pattern of the soft magnetic powder and calculating from that value using the Halder-Wagner method.

[0062] The particles of the soft magnetic powder according to the embodiment may further contain an amorphous structure. The coexistence of crystal grains within the particle size range and an amorphous structure cancel each other out, thereby making it possible to further reduce the magnetostriction of the soft magnetic powder. As a result, a soft magnetic powder with particularly high magnetic permeability is obtained. In addition, a soft magnetic powder with easy-to-control magnetization is obtained. Furthermore, the inclusion of an amorphous structure makes it easier to maintain the crystal grain size finer and more uniform.

[0063] The volumetric ratio of the amorphous structure in the particles is preferably 5.0 times or less, more preferably 0.02 to 2.0 times, and even more preferably 0.10 to less than 1.0 times, of the content of crystal grains in the above particle size range. This optimizes the balance between the crystal grains and the amorphous structure, and the effect of the coexistence of the crystal grains and the amorphous structure becomes more pronounced.

[0064] 1.3.Evaluation of Powders by X-ray Photoelectron Spectroscopy When chemical state analysis is performed on particles of the soft magnetic powder according to the embodiment using X-ray photoelectron spectroscopy, an XPS spectrum corresponding to the chemical state of the elements contained on the particle surface can be obtained. For the soft magnetic powder according to the embodiment, the obtained XPS spectrum contains an O1s peak. Therefore, a fitting process is performed on this O1s peak to separate it into multiple different chemical states. The fitting process can be performed using XPS spectrum analysis software.

[0065] 1.3.1.Features (1) In the soft magnetic powder according to the embodiment, when an XPS spectrum is obtained for the particles contained therein, the obtained XPS spectrum satisfies the following characteristic (1).

[0066] Specifically, the obtained XPS spectrum includes an O1s peak. This O1s peak is separated by fitting into at least one first component peak having a peak top binding energy of 532 eV or less and at least one second component peak having a peak top binding energy of more than 532 eV. Feature (1) is that, when the total area of ​​the first component peaks is S1 and the total area of ​​the second component peaks is S2, in the soft magnetic powder according to the embodiment, S2 / S1 is 1.5 or more.

[0067] Examples of the first component peak include a peak derived from Me-O (oxygen bonded to a metal) and a peak derived from Me-OH (hydroxyl group bonded to a metal). Examples of the second component peak include a peak derived from SiOx (silicon oxide) and a peak derived from COx (carbon oxide). Therefore, the fact that the S2 / S1 ratio is within the above range confirms that the amount of silicon oxide and carbon oxide relative to the amount of Fe oxide and hydroxide is relatively high. That is, when the S2 / S1 ratio is within the above range, it is presumed that the amount of Fe oxide and hydroxide is reduced and the amount of elemental Fe is increased, and that the amount of silicon oxide and carbon oxide is increased, compared to when the S2 / S1 ratio is outside the above range. Therefore, when the S2 / S1 ratio is within the above range, the magnetic properties due to elemental Fe can be improved, and the insulating properties due to silicon oxide and the like can be improved, compared to when the S2 / S1 ratio is outside the above range. Therefore, the soft magnetic powder according to this embodiment can realize a magnetic element having a high insulation resistance value and high magnetic permeability when compacted.

[0068] The following description will be given taking the XPS spectrum shown in Fig. 2 as an example. Fig. 2 is an enlarged view of the O1s peak of the XPS spectrum obtained from particles of soft magnetic powder. In Fig. 2, the O1s peak corresponding to this embodiment (the O1s peak of the example) is shown by a solid line, and the O1s peak not corresponding to this embodiment (the O1s peak of the comparative example) is shown by a dashed line.

[0069] As shown in Fig. 2, the O1s peak is a peak located in the vicinity of a binding energy of 529 to 535 eV. As a result of fitting, the O1s peak shown in Fig. 2 is separated into peaks belonging to four chemical states.

[0070] Fig. 3 shows four peaks separated by fitting for the O1s peak shown in Fig. 2. Here, the peaks belonging to the four chemical states are designated as Peak A, Peak B, Peak C, and Peak D, in order from the lowest binding energy side.

[0071] Peak A and Peak B are peaks with peak top binding energies of 532 eV or less, and are the first element peaks described above. Therefore, Peak A and Peak B are peaks derived mainly from oxygen and hydroxyl groups bonded to metals, and are attributed to substances that cause a decrease in the magnetic permeability of the soft magnetic powder.

[0072] Peaks C and D are peaks with peak top binding energies exceeding 532 eV and are the second component peaks mentioned above. Therefore, Peaks C and D are peaks derived mainly from silicon oxide and carbon oxide, and are attributed to substances that enhance the insulation between particles of the soft magnetic powder.

[0073] Fig. 4 is a bar graph comparing the chemical state ratios calculated by measuring the areas of the four peaks shown in Fig. 3 and then calculating the ratios to the total area. In Fig. 4, the solid line shows the results of fitting to the O1s peak of the example, and the dashed line shows the results of fitting to the O1s peak of the comparative example.

[0074] When the total area of ​​Peak A and Peak B is S1 and the total area of ​​Peak C and Peak D is S2, the solid line shown in FIG. 2 satisfies 1.5≦S2 / S1, while the dashed line shown in FIG. 2 does not.

[0075] When S2 / S1 is within the above range, the soft magnetic powder according to this embodiment can be used to produce a green compact having high magnetic properties due to the Fe element and high insulating properties due to silicon oxide, etc. Therefore, the soft magnetic powder according to this embodiment can produce a green compact having a high insulation resistance value and high magnetic permeability.

[0076] Furthermore, S2 / S1 is preferably 1.6 or more and 3.5 or less, and more preferably 1.7 or more and 2.8 or less. S2 / S1 may exceed the upper limit, but soft magnetic powders that satisfy this limit are difficult to stably produce, and there is a risk of large production variations.

[0077] In the example of Fig. 2, peak A is a peak derived from Me-O (oxygen bonded to a metal), and peak B is a peak derived from Me-OH (hydroxyl group bonded to a metal). In addition, in the example of Fig. 2, peak C and peak D are peaks derived from SiOx (silicon oxide) or COx (carbon oxide).

[0078] The number of first component peaks and the number of second component peaks separated by fitting processing are not particularly limited, but are preferably 1 or more and 5 or less, and more preferably 1 or more and 3 or less.

[0079] 1.3.2.Features (2) In the soft magnetic powder according to the embodiment, when an XPS spectrum is obtained for the particles contained therein, it is preferable that the obtained XPS spectrum satisfies the following characteristic (2).

[0080] Feature (2) is that the O1s peak includes, as second component peaks, Peak C located in the binding energy range of more than 532 eV and less than 533 eV, and Peak D located in the binding energy range of 533 eV or more and less than 535 eV. Feature (2) is also that, when the area of ​​Peak C is SC and the area of ​​Peak D is SD, SD / SC is 0.15 or more and 0.60 or less.

[0081] By satisfying this characteristic (2), the soft magnetic powder according to this embodiment contains a higher concentration of SiOx (silicon oxide). The high concentration of SiOx makes it easier for an oxide film containing a large amount of SiOx to form on the surface of the particles. This oxide film can further improve the interparticle insulation. Furthermore, when an insulating coating is formed on the particle surface, the oxide film serves as a base for the insulating coating. This further improves the adhesion of the insulating coating to the particles. As a result, it is possible to suppress a decrease in insulation during compaction.

[0082] Fig. 5 is an enlarged view of the Si2p peaks contained in the XPS spectrum obtained from the particles of the soft magnetic powder. In Fig. 5, the Si2p peaks corresponding to this embodiment (Si2p peaks of the example) are indicated by a solid line, and the Si2p peaks not corresponding to this embodiment (Si2p peaks of the comparative example) are indicated by a dashed line.

[0083] 5, the Si2p peak is a peak located in the vicinity of a binding energy of 98 to 105 eV. The Si2p peak is separated into peak E, which has a peak top binding energy of 101 eV or less and is attributed to Si, and peak F, which has a peak top binding energy of more than 101 eV and is attributed to SiOx.

[0084] The solid line shown in Figure 5 has a waveform with a lower peak E and a higher peak F than the dashed line shown in Figure 3. As mentioned above, this waveform confirms that the soft magnetic powder according to this embodiment contains a higher concentration of SiOx. Furthermore, since XPS is an analytical method that is particularly sensitive to particle surfaces, the results shown in Figure 5 clearly represent the state of the particle surfaces, i.e., the state of the oxide film mentioned above.

[0085] Furthermore, SD / SC is preferably 0.20 or more and 0.50 or less, more preferably 0.25 or more and 0.40 or less. If SD / SC is below the lower limit, the concentration of SiOx decreases, so the oxide film formed on the particle surface becomes thin, and the above-mentioned effect may not be fully obtained. On the other hand, SD / SC may exceed the upper limit, but soft magnetic powders satisfying this may be difficult to stably produce and may have large production variations.

[0086] 1.3.3.Features (3) In the soft magnetic powder according to the embodiment, it is preferable that the results of the qualitative and quantitative analysis based on the above-mentioned XPS spectrum satisfy the following characteristic (3).

[0087] Feature (3) is that when the concentration of Si in terms of atomic ratio is R(Si) and the concentration of Fe in terms of atomic ratio is R(Fe), R(Si) / R(Fe) is 2.5 or more.

[0088] By satisfying characteristic (3), the soft magnetic powder according to this embodiment has a low Fe concentration and a high Si concentration on the particle surface. Characteristic (3) confirms that the oxide film on the particle surface contains little Fe, i.e., iron oxide, and that the Fe contained inside the oxide film, i.e., metallic Fe, is abundant. At the same time, characteristic (3) also confirms that the oxide film on the particle surface contains a lot of Si, i.e., silicon oxide. Therefore, soft magnetic powders that satisfy characteristic (3) contribute to the realization of magnetic elements that have high insulation resistance and high magnetic permeability when compacted.

[0089] 6 is a table showing the results of qualitative and quantitative analysis of the soft magnetic powder according to the present embodiment (the results of the qualitative and quantitative analysis of the example) and the results of the qualitative and quantitative analysis of the comparative example. The numerical values ​​shown in FIG. 6 represent concentrations in atomic ratios, and the unit is atomic %.

[0090] 6, in the example, R(Si) / R(Fe) is 2.5 or more, whereas in the comparative example, R(Si) / R(Fe) is less than 2.5.

[0091] Furthermore, R(Si) / R(Fe) is preferably 5.0 or more and 20.0 or less, more preferably 7.0 or more and 15.0 or less. If R(Si) / R(Fe) is below the lower limit, the oxide film formed on the particle surface may become thin, and the above-mentioned effects may not be fully obtained. On the other hand, although R(Si) / R(Fe) may exceed the upper limit, soft magnetic powders satisfying this may be difficult to stably produce, and there is a risk of large production variations.

[0092] 1.3.4. Analysis by X-ray photoelectron spectroscopy Analysis by X-ray photoelectron spectroscopy can be performed under the following conditions. X-ray photoelectron spectrometer: Thermo Fisher Scientific ESCALAB250 ·X-ray source: AlKα radiation X-ray incident angle to sample: 45°

[0093] 1.4.Various characteristics The soft magnetic powder according to the embodiment preferably has a Vickers hardness of 1000 or more and 3000 or less, and more preferably 1200 or more and 2500 or less. When soft magnetic powder containing particles with such hardness is compression-molded to form a powder core, deformation at the contact points between particles is minimized. This keeps the contact area small, thereby improving the insulation between particles in the powder core.

[0094] If the Vickers hardness is below the lower limit, depending on the average particle size of the soft magnetic powder, the particles may be easily crushed at their contact points when the soft magnetic powder is compression-molded. This increases the contact area, which may reduce the insulation between particles in the powder core. On the other hand, if the Vickers hardness is above the upper limit, depending on the average particle size of the soft magnetic powder, the powder compactibility may be reduced, reducing the density of the powder core, which may reduce the saturation magnetic flux density of the magnetic element.

[0095] The Vickers hardness of soft magnetic powder particles is measured at the center of the particle's cross section using a micro Vickers hardness tester. The center of the particle's cross section is the location at the midpoint of the long axis on the cross section when the particle is cut. The indenter load during the test is 1.96 N.

[0096] The average particle size D50 of the soft magnetic powder according to the embodiment is not particularly limited, but is preferably 1 μm to 50 μm, more preferably 10 μm to 45 μm, and even more preferably 20 μm to 40 μm. By using soft magnetic powder with such an average particle size, the path through which eddy currents flow can be shortened, and therefore, a magnetic element can be manufactured that can sufficiently suppress eddy current loss generated within the particles of the soft magnetic powder.

[0097] Furthermore, when the average particle size of the soft magnetic powder is particularly 10 μm or more, by mixing it with a soft magnetic powder having a smaller average particle size, a mixed powder that can achieve a high green compaction density can be produced. This mixed powder is also one embodiment of the soft magnetic powder according to the present invention. Such a mixed powder can increase the packing density of a powder magnetic core and increase the saturation magnetic flux density and magnetic permeability of a magnetic element.

[0098] The average particle size D50 of the soft magnetic powder is determined as the particle size at which the cumulative 50% from the smallest diameter side is reached in the volume-based particle size distribution obtained by laser diffraction.

[0099] If the average particle size of the soft magnetic powder is below the lower limit, the soft magnetic powder may become too fine, which may reduce the packing ability of the soft magnetic powder. This reduces the compaction density of the powder core, which may reduce the saturation magnetic flux density and magnetic permeability of the powder core depending on the composition and mechanical properties of the soft magnetic powder. On the other hand, if the average particle size of the soft magnetic powder is above the upper limit, depending on the composition and mechanical properties of the soft magnetic powder, it may not be possible to sufficiently suppress eddy current loss generated within the particles, which may increase the iron loss of the magnetic element.

[0100] For the soft magnetic powder according to the embodiment, in the volume-based particle size distribution obtained by laser diffraction, when D10 is the particle size at 10% cumulative from the smallest diameter side and D90 is the particle size at 90% cumulative from the smallest diameter side, (D90-D10) / D50 is preferably 1.0 or more and 2.5 or less, more preferably 1.2 or more and 2.3 or less. (D90-D10) / D50 is an index indicating the degree of spread of the particle size distribution, and when this index is within the above range, the packing property of the soft magnetic powder is improved. As a result, a magnetic element having particularly high magnetic properties such as magnetic permeability and saturation magnetic flux density can be obtained.

[0101] The coercive force of the soft magnetic powder according to the embodiment is not particularly limited, but is preferably less than 2.0 Oe (less than 160 A / m), and more preferably 0.1 Oe to 1.5 Oe (39.9 A / m to 120 A / m). By using soft magnetic powder with such a low coercive force, it is possible to manufacture a magnetic element that can sufficiently suppress hysteresis loss even at high frequencies.

[0102] The coercive force of the soft magnetic powder can be measured using a vibrating sample magnetometer such as TM-VSM1230-MHHL manufactured by Tamagawa Seisakusho Co., Ltd.

[0103] The soft magnetic powder according to the embodiment preferably has a magnetic permeability of 15 or more at a measurement frequency of 100 MHz when compacted, and more preferably 18 to 50. Such soft magnetic powder contributes to the realization of a magnetic element having excellent magnetic properties such as saturation magnetic flux density.

[0104] The magnetic permeability of a green compact is the effective magnetic permeability calculated from the self-inductance of the closed magnetic core coil when the green compact is formed into a toroidal shape. The magnetic permeability is measured using an impedance analyzer such as the Agilent Technologies 4194A, with a measurement frequency of 100 MHz. The number of turns of the winding is 7, and the wire diameter of the winding is 0.6 mm.

[0105] The saturation magnetic flux density of the soft magnetic powder according to the embodiment is preferably 1.00 [T] or more, and more preferably 1.10 [T] or more.

[0106] The saturation magnetic flux density of the soft magnetic powder is measured, for example, by the following method. First, the true specific gravity ρ of the soft magnetic powder is measured using a fully automatic gas displacement density meter, AccuPyc1330, manufactured by Micromeritics. Next, the maximum magnetization Mm of the soft magnetic powder is measured using a vibrating sample magnetometer, VSM system, TM-VSM1230-MHHL, manufactured by Tamagawa Seisakusho Co., Ltd. Then, the saturation magnetic flux density Bs is calculated using the following formula. Bs=4π / 10000×ρ×Mm

[0107] The soft magnetic powder according to the embodiment is formed into a cylindrical compact having an inner diameter of 8 mm and a mass of 0.7 g. When this compact is compressed in the axial direction under a load of 20 kgf, the resistance of the compact in the axial direction is preferably 0.3 kΩ or more, and more preferably 1.0 kΩ or more. Soft magnetic powders capable of producing compacts with such resistance values ​​ensure sufficient insulation between particles. Therefore, such soft magnetic powders contribute to the realization of magnetic elements capable of suppressing eddy current loss.

[0108] The upper limit of the resistance value is not particularly limited, but in consideration of suppressing variations, it is preferably 30.0 kΩ or less, and more preferably 9.0 kΩ or less.

[0109] In the soft magnetic powder according to the embodiment, not all particles need to have the above-described structure, and the powder may contain particles that do not have the above-described structure, but it is preferable that 95% by mass or more of the particles have the above-described structure.

[0110] Furthermore, the soft magnetic powder according to the embodiment may be mixed with other soft magnetic powders or non-soft magnetic powders, and the mixed powder may be used for producing a powder core or the like.

[0111] 1.5. Effects of the embodiment As described above, the soft magnetic powder according to this embodiment contains Fe x Cu a Nb b (Si 1-y B y ) 100-x-a-b [where a, b, and x are numbers in atomic percent, and satisfy the conditions 0.3≦a≦2.0, 2.0≦b≦4.0, and 73.0≦x≦79.5. Also, y is a number that satisfies the condition f(x)≦y≦0.99, and f(x)=(4×10 -34 )x 17.56 The particles include particles having a composition represented by the formula: The particles contain crystal grains having a grain size of 1.0 nm or more and 30.0 nm or less.

[0112] Furthermore, an XPS spectrum is obtained for this particle by X-ray photoelectron spectroscopy, and a fitting process is performed to separate the O1s peak of the XPS spectrum into multiple different chemical states. As a result, the O1s peak is separated into at least one first component peak having a peak top binding energy of 532 eV or less and at least one second component peak having a peak top binding energy of more than 532 eV. When the total area of ​​the first component peaks is S1 and the total area of ​​the second component peaks is S2, S2 / S1 is 1.5 or more.

[0113] It is presumed that when S2 / S1 is within the above range, Fe oxides and hydroxides are reduced and elemental Fe is increased, and silicon oxide and carbon oxide are increased, compared to when S2 / S1 is outside the above range. Thus, when S2 / S1 is within the above range, the magnetic properties due to elemental Fe can be improved, and the insulating properties due to silicon oxide and the like can be improved, compared to when S2 / S1 is outside the above range. Therefore, when the soft magnetic powder according to this embodiment is compacted, it is possible to realize a magnetic element having a high insulation resistance value and high magnetic permeability.

[0114] Furthermore, in the soft magnetic powder according to this embodiment, when qualitative and quantitative analysis of the particles is performed based on the XPS spectrum, and the concentration of Si in terms of atomic ratio is R(Si) and the concentration of Fe in terms of atomic ratio is R(Fe), it is preferable that R(Si) / R(Fe) is 2.5 or more.

[0115] Such soft magnetic powder has a low Fe concentration and a high Si concentration on the particle surface. By satisfying the above ranges, a soft magnetic powder can be obtained that satisfies the following conditions: a large amount of metallic Fe is present inside the oxide film, and the oxide film contains a large amount of silicon oxide. When such soft magnetic powder is compacted, it can be used to obtain a magnetic element with high insulation resistance and high magnetic permeability.

[0116] Furthermore, in the soft magnetic powder according to this embodiment, the content ratio of crystal grains with a crystal grain size of 1.0 nm to 30.0 nm in the particles is preferably 30% by volume or more, which sufficiently increases the ratio of crystal grains with a small grain size, thereby sufficiently averaging the magnetocrystalline anisotropy, increasing the magnetic permeability of the soft magnetic powder, and sufficiently reducing the coercive force of the soft magnetic powder.

[0117] Furthermore, the soft magnetic powder according to this embodiment preferably has an average particle size of 1 μm or more and 50 μm or less. By using soft magnetic powder with such an average particle size, the path along which eddy currents flow can be shortened, and thus a magnetic element can be manufactured that can sufficiently suppress eddy current loss occurring within the particles of the soft magnetic powder.

[0118] 2. Manufacturing method of soft magnetic powder Next, a method for producing the soft magnetic powder according to the embodiment will be described.

[0119] The soft magnetic powder may be produced by any production method, for example, by various powdering methods such as atomization methods such as water atomization, gas atomization, and rotary water flow atomization, reduction methods, carbonyl methods, and pulverization methods.

[0120] Atomization methods include water atomization, gas atomization, and rotary water atomization, depending on the type of coolant and the device configuration. Of these, soft magnetic powders are preferably produced by atomization, more preferably by water atomization or rotary water atomization, and even more preferably by rotary water atomization. Atomization is a method of producing powder by pulverizing and cooling molten metal by colliding it with a fluid such as a liquid or gas sprayed at high speed. Using such atomization methods, a high cooling rate can be achieved, thereby promoting amorphization. As a result, crystal grains with a more uniform particle size can be formed by heat treatment.

[0121] In this specification, the term "water atomization" refers to a method of producing metal powder by using a liquid such as water or oil as a coolant, spraying it in an inverted cone shape that converges to one point, and then causing molten metal to flow down and collide with the converging point, thereby pulverizing the molten metal.

[0122] Furthermore, the rotary water jet atomization method allows the molten metal to be cooled extremely rapidly, so that the disordered atomic arrangement of the molten metal can be maintained to a high degree during solidification. Therefore, by carrying out a crystallization treatment after that, soft magnetic powder having crystal grains of uniform size can be efficiently produced.

[0123] The method for producing soft magnetic powder by the rotary water jet atomization method will be further described below. In the rotary water atomization method, a cooling liquid is sprayed along the inner surface of a cooling cylinder and rotated along the inner surface of the cooling cylinder, forming a cooling liquid layer on the inner surface. Meanwhile, the raw material for the soft magnetic powder is melted, and the resulting molten metal is allowed to fall naturally while a liquid or gas jet is sprayed onto it. This causes the molten metal to splash and become entrained in the cooling liquid layer. As a result, the splashed, finely pulverized molten metal is rapidly cooled and solidified, yielding soft magnetic powder.

[0124] FIG. 7 is a vertical cross-sectional view showing an example of an apparatus for producing soft magnetic powder by the rotary water jet atomization method.

[0125] The powder manufacturing apparatus 30 shown in FIG. 7 includes a cooling cylinder 1, a crucible 15, a pump 7, and a jet nozzle 24. The cooling cylinder 1 is a cylinder for forming a cooling liquid layer 9 on its inner circumferential surface. The crucible 15 is a supply container for supplying molten metal 25 so that it flows down into a space 23 inside the cooling liquid layer 9. The pump 7 supplies the cooling liquid to the cooling cylinder 1. The jet nozzle 24 sprays a gas jet 26 that breaks the flowing molten metal 25 into droplets in the form of a thin stream. The molten metal 25 is prepared according to the composition of the soft magnetic powder.

[0126] The cooling cylinder 1 has a cylindrical shape and is installed so that the axis of the cylinder is aligned vertically or tilted at an angle of 30° or less relative to the vertical.

[0127] The upper opening of the cooling cylinder 1 is closed by a lid 2. The lid 2 is formed with an opening 3 for supplying the flowing molten metal 25 to the space 23 of the cooling cylinder 1.

[0128] A cooling liquid ejection pipe 4 is provided at the top of the cooling cylinder 1 to eject cooling liquid onto the inner circumferential surface of the cooling cylinder 1. A plurality of ejection ports 5 of the cooling liquid ejection pipe 4 are provided at equal intervals along the circumferential direction of the cooling cylinder 1.

[0129] The coolant jetting pipe 4 is connected to a tank 8 via a pipe connected to a pump 7, and the coolant in the tank 8 is pumped up by the pump 7 and jetted into the cooling cylinder 1 via the coolant jetting pipe 4. As a result, the coolant gradually flows down while rotating along the inner surface of the cooling cylinder 1, forming a coolant layer 9 along the inner surface. Note that a cooler may be interposed in the tank 8 or along the circulation flow path as needed. In addition to water, oils such as silicone oil may be used as the coolant, and various additives may also be added. Furthermore, by removing dissolved oxygen from the coolant in advance, oxidation of the powder produced during cooling can be suppressed.

[0130] In addition, a layer thickness adjusting ring 16 for adjusting the thickness of the coolant layer 9 is detachably provided on the lower part of the inner circumferential surface of the cooling cylinder 1. By providing this layer thickness adjusting ring 16, the flow rate of the coolant is reduced, and the thickness of the coolant layer 9 can be ensured and made uniform.

[0131] Furthermore, a cylindrical draining mesh 17 is connected to the bottom of the cooling cylinder 1, and a funnel-shaped powder collection container 18 is provided below this draining mesh 17. A coolant collection cover 13 is provided around the draining mesh 17 so as to cover it, and a drain port 14 formed at the bottom of this coolant collection cover 13 is connected to the tank 8 via piping.

[0132] Jet nozzle 24 is provided in space 23. Jet nozzle 24 is attached to the tip of gas supply pipe 27 inserted through opening 3 of lid 2, and is positioned so that its nozzle is directed toward molten metal 25 in the form of a thin stream.

[0133] To produce soft magnetic powder in such powder production apparatus 30, first, pump 7 is operated to form a coolant layer 9 on the inner circumferential surface of cooling cylinder 1. Next, molten metal 25 in crucible 15 is caused to flow down into space 23. When gas jet 26 is blown onto the flowing molten metal 25, molten metal 25 is scattered, and the finely powdered molten metal 25 is caught in coolant layer 9. As a result, the finely powdered molten metal 25 cools and solidifies, and soft magnetic powder is obtained.

[0134] In the rotary water jet atomization method, a continuous supply of cooling liquid allows for a stable, extremely high cooling rate, which stabilizes the amorphous state of the soft magnetic powder produced before heat treatment. As a result, by carrying out the subsequent heat treatment, soft magnetic powder having crystal grains of uniform size can be efficiently produced.

[0135] Furthermore, the molten metal 25 atomized to a certain size by the gas jet 26 falls by inertia until it is caught in the cooling liquid layer 9, and at that time the droplets are made spherical. As a result, soft magnetic powder can be produced.

[0136] For example, the amount of molten metal 25 flowing down from crucible 15 varies depending on the size of the apparatus and is not particularly limited, but it is preferable to keep it to 1 kg or less per minute. This ensures that when molten metal 25 scatters, it scatters as droplets of appropriate size, resulting in soft magnetic powder with the average particle size described above. Furthermore, by limiting the amount of molten metal 25 supplied per certain period to a certain extent, a sufficient cooling rate can be obtained. Note that, for example, by reducing the amount of molten metal 25 flowing down within the above range, adjustments can be made to reduce the average particle size.

[0137] On the other hand, the outer diameter of the thin stream of molten metal 25 flowing down from crucible 15, i.e., the inner diameter of the outlet of crucible 15, is not particularly limited, but is preferably 1 mm or less. This makes it easier to uniformly apply gas jet 26 to the thin stream of molten metal 25, making it easier to uniformly scatter droplets of an appropriate size. As a result, soft magnetic powder with the average particle size described above is obtained. Furthermore, since the amount of molten metal 25 supplied per unit time is also reduced, a sufficient cooling rate is also obtained.

[0138] Furthermore, the flow velocity of the gas jet 26 is not particularly limited, but is preferably set to 100 m / s or more and 1000 m / s or less. This allows the molten metal 25 to be scattered as droplets of appropriate size, thereby obtaining soft magnetic powder with the average particle size described above. Furthermore, since the gas jet 26 has sufficient velocity, the scattered droplets are also given sufficient velocity, making the droplets finer and shortening the time it takes for the droplets to become entrained in the cooling liquid layer 9. As a result, the droplets can be sphericalized in a short time and cooled in a short time. Note that, for example, by increasing the flow velocity of the gas jet 26 within the above range, the average particle size can be reduced.

[0139] As other conditions, for example, it is preferable to set the pressure of the coolant supplied to the cooling cylinder 1 at the time of ejection to about 5 MPa or more and 200 MPa or less, and the liquid temperature to about -10°C or more and 40°C or less. This optimizes the flow rate of the coolant layer 9, and allows the pulverized molten metal 25 to be cooled appropriately and evenly.

[0140] Furthermore, the temperature of the molten metal 25 is preferably set to about Tm+20° C. or more and Tm+200° C. or less, where Tm is the melting point of the soft magnetic powder to be produced, and more preferably set to about Tm+50° C. or more and Tm+150° C. or less. This makes it possible to particularly minimize the variation in properties between particles when the molten metal 25 is pulverized by the gas jet 26, and also to more reliably amorphize the soft magnetic powder to be produced before heat treatment. The gas jet 26 can be replaced with a liquid jet if necessary.

[0141] In addition, the cooling rate when cooling the molten metal 25 in the atomization method is 1×10 4 °C / s or more, and 1 × 10 5 °C / s or more is more preferable, and 1 × 10 6 It is more preferable that the cooling rate is 100°C / s or more. Such rapid cooling allows for particularly stable amorphization, ultimately resulting in soft magnetic powder having crystal grains with uniform particle size. Furthermore, it is possible to suppress variations in the composition ratio between particles of the soft magnetic powder.

[0142] The soft magnetic powder produced as described above is subjected to a crystallization treatment, whereby at least a portion of the amorphous structure is crystallized to form crystal grains.

[0143] The crystallization treatment can be carried out by subjecting the soft magnetic powder containing an amorphous structure to a heat treatment. The heat treatment temperature is not particularly limited, but is preferably 520°C to 640°C, more preferably 530°C to 630°C, and even more preferably 540°C to 620°C. Furthermore, the heat treatment time is preferably maintained at the temperature for 1 minute to 180 minutes, more preferably 3 minutes to 120 minutes, and even more preferably 5 minutes to 60 minutes. By setting the heat treatment temperature and time within the above ranges, crystal grains with a more uniform particle size can be produced.

[0144] If the heat treatment temperature or time is below the lower limit, depending on the composition of the soft magnetic powder, crystallization may be insufficient and the particle size may not be uniform. On the other hand, if the heat treatment temperature or time is above the upper limit, crystallization may be excessive and the particle size may not be uniform, depending on the composition of the soft magnetic powder.

[0145] The heating rate and cooling rate in the crystallization treatment affect the grain size and uniformity of the grain size of the crystal grains produced by the heat treatment, the formation of an oxide film on the grain surface, and reactions such as the reduction of metal oxides.

[0146] The heating rate is preferably 10°C / min to 35°C / min, more preferably 10°C / min to 30°C / min, and even more preferably 15°C / min to 25°C / min. By setting the heating rate within the above range, the grain size, distribution and grain size of Cu segregated regions, and Cu concentration can be kept within the above range. If the heating rate is below the lower limit, the time of exposure to high temperature increases, which may result in the grain size of the crystal grains becoming too large. If the heating rate is above the upper limit, the grain size of the crystal grains may become too small, the distribution of Cu segregated regions may become too shallow, the grain size of the Cu segregated regions may become too small, or the Cu concentration may become too low.

[0147] The temperature drop rate is preferably 40°C / min to 80°C / min, more preferably 50°C / min to 70°C / min, and even more preferably 55°C / min to 65°C / min. By setting the temperature drop rate within the above range, the grain size, distribution and grain size of Cu segregated regions, and Cu concentration can be kept within the above range. If the temperature drop rate is below the lower limit, the time of exposure to high temperature increases, which may result in the grain size of the crystal grains becoming too large. If the temperature drop rate is above the upper limit, the grain size of the crystal grains may become too small, the distribution of Cu segregated regions may become too shallow, the grain size of the Cu segregated regions may become too small, or the Cu concentration may become too low.

[0148] The atmosphere for the crystallization treatment is not particularly limited, but is preferably an inert gas atmosphere such as nitrogen or argon, a reducing gas atmosphere such as hydrogen or ammonia decomposition gas, or a reduced pressure atmosphere thereof, which allows crystallization while suppressing oxidation of the metal, and results in a soft magnetic powder with excellent magnetic properties.

[0149] The oxygen concentration in the crystallization atmosphere affects reactions such as the formation of oxide films on particle surfaces and the reduction of metal oxides. These reactions are also influenced by the temperature rise and fall rates during the crystallization treatment. Therefore, to produce the soft magnetic powder according to the embodiment described above, the crystallization treatment is performed at the aforementioned temperature rise and fall rates, and the oxygen concentration in the crystallization atmosphere is preferably 1000 ppm or less by volume, more preferably 5 ppm to 500 ppm, and even more preferably 10 ppm to 200 ppm. This facilitates the reduction of Fe oxides and hydroxides and the oxidation of Si to form SiOx. As a result, the soft magnetic powder according to the embodiment can be efficiently produced. Furthermore, considering the above reactions, the crystallization atmosphere is preferably an inert gas atmosphere, and the pressure of the atmosphere is preferably atmospheric pressure (50 kPa to 150 kPa). In this manner, the soft magnetic powder according to this embodiment can be manufactured.

[0150] The soft magnetic powder thus obtained may be classified as necessary. Examples of classification methods include dry classification such as sieving classification, inertial classification, centrifugal classification, and air classification, and wet classification such as sedimentation classification.

[0151] If necessary, an insulating film may be formed on the surface of each particle of the obtained soft magnetic powder. Examples of materials constituting this insulating film include inorganic materials such as phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and silicates such as sodium silicate, ceramic materials such as silica, alumina, magnesia, zirconia, and titania, and glass materials such as borosilicate glass and silica glass.

[0152] 3. Powder cores and magnetic elements Next, the powder magnetic core and the magnetic element according to the embodiment will be described.

[0153] The magnetic element according to the embodiment can be applied to various magnetic elements having a magnetic core, such as a choke coil, an inductor, a noise filter, a reactor, a transformer, a motor, an actuator, a solenoid valve, a generator, etc. Furthermore, the powder magnetic core according to the embodiment can be applied to the magnetic cores provided in these magnetic elements.

[0154] Two types of coil components will be described below as representative examples of magnetic elements. 3.1.Toroidal type First, a toroidal type coil component will be described as an example of a magnetic element according to the embodiment. FIG. 8 is a plan view schematically showing a toroidal type coil component.

[0155] 8 has a ring-shaped powder magnetic core 11 and a conductive wire 12 wound around this powder magnetic core 11. Such a coil component 10 is generally called a toroidal coil.

[0156] The powder magnetic core 11 is obtained by mixing the soft magnetic powder according to the embodiment with a binder, feeding the resulting mixture into a molding die, and then pressurizing and molding it. That is, the powder magnetic core 11 is a compact containing the soft magnetic powder according to the embodiment. Such a powder magnetic core 11 has high insulation properties and high magnetic permeability. As a result, when the powder magnetic core 11 is installed in an electronic device or the like, it is possible to reduce the power consumption of the electronic device or the like and improve its performance, thereby contributing to improving the reliability of the electronic device or the like. The binder may be added as needed, or may be omitted.

[0157] Furthermore, the coil component 10 as a magnetic element including such a powder magnetic core 11 has low iron loss and high magnetic permeability.

[0158] Examples of binder materials used in producing the powder magnetic core 11 include organic materials such as silicone resins, epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyphenylene sulfide resins, and inorganic materials such as phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and silicates such as sodium silicate. Thermosetting polyimide or epoxy resins are particularly preferred. These resin materials are easily cured by heating and have excellent heat resistance. This improves the ease of production and heat resistance of the powder magnetic core 11.

[0159] The ratio of binder to soft magnetic powder varies slightly depending on the desired saturation magnetic flux density, mechanical properties, allowable eddy current loss, etc. of the powder core 11 to be produced, but is preferably about 0.5% by mass to 5% by mass, and more preferably about 1% by mass to 3% by mass. This allows the soft magnetic powder particles to be sufficiently bound together, and enables the production of powder core 11 with excellent magnetic properties such as saturation magnetic flux density and magnetic permeability. If necessary, various additives may be added to the mixture for any purpose.

[0160] The conductive wire 12 may be made of a highly conductive material, such as a metal material containing Cu, Al, Ag, Au, Ni, etc. If necessary, an insulating film may be provided on the surface of the conductive wire 12.

[0161] The shape of the powder magnetic core 11 is not limited to the ring shape shown in FIG. 8, but may be, for example, a shape in which a part of the ring is missing, or a shape in which the longitudinal direction is linear.

[0162] Furthermore, the powder magnetic core 11 may contain soft magnetic powder other than the soft magnetic powder according to the embodiment described above or non-magnetic powder, as needed.

[0163] 3.2.Closed magnetic circuit type Next, a closed magnetic circuit type coil component, which is an example of a magnetic element according to the embodiment, will be described. FIG. 9 is a see-through perspective view that schematically shows a closed magnetic circuit type coil component.

[0164] The closed magnetic circuit type coil component will be described below, but the following description will focus on the differences from the toroidal type coil component, and a description of similar points will be omitted.

[0165] 9, the coil component 20 according to this embodiment is formed by embedding a conductor wire 22 formed into a coil shape inside a powder magnetic core 21. That is, the coil component 20 is formed by molding the conductor wire 22 with the powder magnetic core 21. This powder magnetic core 21 has a configuration similar to that of the powder magnetic core 11 described above.

[0166] A relatively small coil component 20 having this configuration can be easily obtained, and a small coil component 20 having low iron loss and high magnetic permeability can be obtained.

[0167] Furthermore, because the conductive wire 22 is embedded inside the powder core 21, gaps are unlikely to occur between the conductive wire 22 and the powder core 21. This makes it possible to suppress vibrations caused by magnetostriction of the powder core 21, and also to suppress the generation of noise associated with this vibration.

[0168] When manufacturing the coil device 20 according to the present embodiment as described above, first, the conductive wire 22 is placed in the cavity of a molding die, and the cavity is filled with granulated powder containing the soft magnetic powder according to the embodiment. That is, the granulated powder is filled so as to encompass the conductive wire 22.

[0169] Next, the granulated powder is pressed together with the conductive wire 22 to obtain a compact. Next, similarly to the above embodiment, the compact is subjected to a heat treatment, thereby hardening the binder and obtaining the powder core 21 and the coil component 20.

[0170] The powder magnetic core 21 may contain soft magnetic powder other than the soft magnetic powder according to the embodiment described above or non-magnetic powder, as needed.

[0171] 4.Electronic equipment Next, an electronic device including the magnetic element according to the embodiment will be described with reference to FIGS.

[0172] Fig. 10 is a perspective view showing the configuration of a mobile personal computer, which is an electronic device equipped with a magnetic element according to the embodiment. The personal computer 1100 shown in Fig. 10 includes a main body 1104 equipped with a keyboard 1102, and a display unit 1106 equipped with a display unit 100. The display unit 1106 is rotatably supported on the main body 1104 via a hinge structure. Such a personal computer 1100 includes a magnetic element 1000, such as a choke coil or inductor for a switching power supply, or a motor.

[0173] Fig. 11 is a plan view showing the configuration of a smartphone, which is an electronic device including the magnetic element according to the embodiment. The smartphone 1200 shown in Fig. 11 includes a plurality of operation buttons 1202, an earpiece 1204, and a mouthpiece 1206. A display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. Such a smartphone 1200 includes a magnetic element 1000, such as an inductor, a noise filter, or a motor, built in.

[0174] 12 is a perspective view showing the configuration of a digital still camera, which is an electronic device equipped with a magnetic element according to the embodiment. The digital still camera 1300 photoelectrically converts an optical image of a subject using an imaging element such as a CCD (Charge Coupled Device) to generate an imaging signal.

[0175] 12 includes a display unit 100 provided on the back of a case 1302. The display unit 100 functions as a viewfinder that displays an object as an electronic image. A light receiving unit 1304 including an optical lens, a CCD, etc. is provided on the front side of the case 1302, i.e., on the back side in the figure.

[0176] When the photographer checks the subject image displayed on the display unit 100 and presses the shutter button 1306, the image signal from the CCD at that time is transferred to and stored in memory 1308. This digital still camera 1300 also incorporates magnetic elements 1000 such as inductors and noise filters.

[0177] Examples of electronic devices according to the embodiments include the personal computer of FIG. 10, the smartphone of FIG. 11, and the digital still camera of FIG. 12, as well as mobile phones, tablet terminals, watches, inkjet ejection devices such as inkjet printers, laptop personal computers, televisions, video cameras, video tape recorders, car navigation devices, pagers, electronic organizers, electronic dictionaries, calculators, electronic game devices, word processors, workstations, videophones, security television monitors, electronic binoculars, POS terminals, medical devices such as electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasound diagnostic devices, and electronic endoscopes, fish finders, various measuring devices, instruments for vehicles, aircraft, and ships, mobile object control devices such as automobile control devices, aircraft control devices, railway vehicle control devices, and ship control devices, and flight simulators.

[0178] As described above, such electronic devices include the magnetic element according to the embodiment, thereby enjoying the effects of the magnetic element, such as low iron loss and high magnetic permeability, and enabling the electronic devices to be reduced in power consumption, miniaturized, and have high output.

[0179] The soft magnetic powder, dust core, magnetic element, and electronic device of the present invention have been described above based on preferred embodiments, but the present invention is not limited to these.

[0180] For example, in the above embodiment, a powder compact such as a powder core has been described as an example of an application of the soft magnetic powder of the present invention, but the application is not limited to this and may be, for example, a magnetic fluid, a magnetic head, or other magnetic device. Furthermore, the shapes of the powder core and the magnetic element are not limited to those shown in the drawings and may be any shape. [Example]

[0181] Next, specific examples of the present invention will be described. 5. Manufacturing of powder magnetic cores 5.1. Sample No. 1 First, the raw materials were melted in a high-frequency induction furnace and pulverized by a rotary water jet atomization method to obtain soft magnetic powder. The resulting powder was then classified using an air classifier. The composition of the resulting soft magnetic powder is shown in Table 1. The composition was determined using a SPECTRO solid-state optical emission spectrometer, model SPECTROLAB, type LAVMB08A. The total impurity content was found to be 0.50 atomic % or less.

[0182] Next, the particle size distribution of the obtained soft magnetic powder was measured. This measurement was performed using a laser diffraction particle size distribution measuring device, Microtrac HRA9320-X100, manufactured by Nikkiso Co., Ltd. The average particle size D50 of the soft magnetic powder was determined from the particle size distribution and was found to be 20 μm.

[0183] The obtained soft magnetic powder was then heated in a nitrogen atmosphere under the heating conditions shown in Table 1.

[0184] Next, the obtained soft magnetic powder was mixed with an epoxy resin as a binder to obtain a mixture, where the amount of epoxy resin added was 2 parts by mass per 100 parts by mass of the soft magnetic powder.

[0185] The resulting mixture was then stirred and dried for a short time to obtain a dried mass. The dried mass was then sieved through a 400 μm mesh sieve and pulverized to obtain a granulated powder. The resulting granulated powder was dried at 50° C. for 1 hour.

[0186] Next, the obtained granulated powder was filled into a molding die, and a molded body was obtained under the following molding conditions.

[0187] <Molding conditions> Molding method: Press molding Shape of molding: Ring-shaped - Dimensions of the molded body: outer diameter 14mm, inner diameter 8mm, thickness 3mm ·Molding pressure: 3t / cm 2 (294MPa)

[0188] Next, the compact was heated in an air atmosphere at a temperature of 150°C for 0.5 hours to harden the binder, thereby obtaining a powder magnetic core.

[0189] 5.2. Samples No. 2 to 19 Powder cores were obtained in the same manner as Sample No. 1, except that the manufacturing conditions for the soft magnetic powder and the manufacturing conditions for the powder core were changed as shown in Table 1. The average particle size D50 of each sample was within the range of 10 μm or more and 30 μm or less.

[0190] [Table 1]

[0191] In Table 1, among the soft magnetic powders of each sample number, those that correspond to the present invention are indicated as "Examples," and those that do not correspond to the present invention are indicated as "Comparative Examples."

[0192] Furthermore, when x and y in the alloy composition of the soft magnetic powder of each sample number were located inside region C, they were entered as "C" in the region column, when they were located outside region C but inside region B, they were entered as "B" in the region column, and when they were located outside region B but inside region A, they were entered as "A" in the region column. When they were located outside region A, they were entered as "-" in the region column.

[0193] 6. Evaluation of soft magnetic powders and dust cores 6.1. Evaluation of the particle structure of soft magnetic powder The soft magnetic powder obtained in each of the examples and comparative examples was processed into thin pieces by a focused ion beam device to obtain test pieces.

[0194] Next, the obtained test piece was observed using a scanning transmission electron microscope, and an elemental analysis was carried out to obtain an area analysis image.

[0195] Next, the grain size was measured from the observed image, and the area ratio of grains falling within a specific range of 1.0 nm to 30.0 nm was calculated, and this was regarded as the volume ratio of grains of the specified grain size. The measurement results are shown in Table 2.

[0196] 6.2.Evaluation of XPS Spectra For the soft magnetic powders obtained in each example and each comparative example, XPS spectra were obtained using an X-ray photoelectron spectrometer. From the XPS spectra, the aforementioned S2 / S1 values, SD / SC values, and R(Si) / R(Fe) values ​​were calculated. The calculation results are shown in Table 2.

[0197] 2 to 6 show the results of chemical state analysis and qualitative and quantitative analysis of the soft magnetic powders of Sample No. 3 (Comparative Example) and Sample No. 5 (Example).

[0198] 13 to 17 show the results of chemical state analysis and qualitative and quantitative analysis obtained for the soft magnetic powders of Sample No. 19 (Comparative Example) and Sample No. 15 (Example).

[0199] Fig. 13 is an enlarged view of the O1s peak of the XPS spectrum obtained from the particles of the soft magnetic powder. In Fig. 13, the O1s peak corresponding to this embodiment (the O1s peak of the example) is shown by a solid line, and the O1s peak not corresponding to this embodiment (the O1s peak of the comparative example) is shown by a dashed line.

[0200] FIG. 14 is a diagram showing four peaks separated by fitting processing for the O1s peak shown in FIG.

[0201] Furthermore, Fig. 15 is a bar graph comparing the chemical state ratios calculated by measuring the areas of the four peaks shown in Fig. 14 and then calculating the ratios to the total area. In Fig. 15, the solid line shows the results of fitting to the O1s peak of the example, and the dashed line shows the results of fitting to the O1s peak of the comparative example.

[0202] FIG. 16 is an enlarged view of the Si2p peak contained in the XPS spectrum obtained from the particles of the soft magnetic powder.

[0203] Furthermore, FIG. 17 is a table showing the results of qualitative and quantitative analysis obtained for the soft magnetic powder according to this embodiment (results of qualitative and quantitative analysis of Examples) and the results of qualitative and quantitative analysis of Comparative Examples.

[0204] 6.3.Electrical Resistivity of Powder Compacts The electrical resistance values ​​of the compacts of the soft magnetic powders obtained in each of the Examples and Comparative Examples were measured, and the measured resistance values ​​were evaluated in accordance with the following evaluation criteria.

[0205] A: Resistance value is 5.0kΩ or more B: Resistance is 3.0kΩ or more and less than 5.0kΩ C: Resistance is 0.3 kΩ or more and less than 3.0 kΩ D: Resistance less than 0.3 kΩ The evaluation results are shown in Table 2.

[0206] 6.4. Measurement of coercive force of soft magnetic powder The coercive force of each of the soft magnetic powders obtained in each of the Examples and Comparative Examples was measured, and the measured coercive force was evaluated in accordance with the following evaluation criteria.

[0207] A: Coercive force less than 0.90 Oe B: Coercive force is 0.90 Oe or more and less than 1.33 Oe C: Coercive force is 1.33 Oe or more and less than 1.67 Oe D: Coercive force is 1.67 Oe or more and less than 2.00 Oe E: Coercive force is 2.00 Oe or more and less than 2.33 Oe F: Coercive force is 2.33 Oe or more The evaluation results are shown in Table 2.

[0208] 6.5. Calculation of saturation magnetic flux density of soft magnetic powder The saturation magnetic flux density of each of the soft magnetic powders obtained in the examples and comparative examples was calculated. The calculation results are shown in Table 2.

[0209] 6.6.Measuring the magnetic permeability of powder compacts The magnetic permeability of each of the compacts of the soft magnetic powder obtained in each of the Examples and Comparative Examples was measured. The measurement results are shown in Table 2.

[0210] 6.7.Measuring Iron Loss in Powder Cores The iron loss of each of the powder magnetic cores obtained in the examples and comparative examples was measured under the following measurement conditions.

[0211] Measurement equipment: BH analyzer, Iwasaki Electric Co., Ltd. SY-8258 Measurement frequency: 900kHz Number of winding turns: Primary 36, Secondary 36 Winding wire diameter: 0.5mm Maximum magnetic flux density: 50mT The measurement results are shown in Table 2.

[0212] [Table 2]

[0213] As is clear from Table 2, the soft magnetic powders obtained in each example achieved both high insulation properties and high magnetic permeability. Therefore, it became clear that the present invention can realize soft magnetic powders that can be used to produce green compacts having high insulation resistance and high magnetic permeability. [Explanation of symbols]

[0214] 1...cooling cylinder, 2...lid, 3...opening, 4...coolant jet pipe, 5...discharge port, 7...pump, 8...tank, 9...coolant layer, 10...coil component, 11...powder core, 12...conductor, 13...coolant recovery cover, 14...drain port, 15...crucible, 16...layer thickness adjusting ring, 17...liquid draining mesh, 18...powder recovery container, 20...coil component, 21...powder core, 22...conductor, 23...space, 24...jet nozzle, 25...molten metal, 26...gas jet, 27...gas supply Supply pipe, 30...powder manufacturing apparatus, 100...display unit, 1000...magnetic element, 1100...personal computer, 1102...keyboard, 1104...main body, 1106...display unit, 1200...smartphone, 1202...operation buttons, 1204...earpiece, 1206...mouthpiece, 1300...digital still camera, 1302...case, 1304...light receiving unit, 1306...shutter button, 1308...memory, A...area, B...area, C...area

Claims

1. Fe ｘ Cổ ａ Nｺ ｂ (Yes) １－ｙ B ｙ ) １００－ｘ－ａ－ｂ [a, b, and x are each a number expressed in atomic %; 0.3≦a≦2.0, 2.0≦b≦4.0, 73.0≦x≦79.5 Meet the following. Furthermore, y is a number that satisfies f(x)≦y≦0.99, and f(x)=(4×10 －３４ ) x １７．５６ It is.] The particles have a composition represented by The particles contain crystal grains having a particle size of 1.0 nm or more and 30.0 nm or less, When an XPS spectrum is obtained by X-ray photoelectron spectroscopy for the particles and a fitting process is performed to separate the O1s peak of the XPS spectrum into a plurality of different chemical states, The O1s peak is separated into at least one first component peak having a peak top binding energy of 532 eV or less and at least one second component peak having a peak top binding energy of more than 532 eV; When the total area of ​​the first component peaks is S1 and the total area of ​​the second component peaks is S2, A soft magnetic powder characterized in that S2 / S1 is 1.5 or more and 3.1 or less.

2. Qualitative and quantitative analysis of the particles was performed based on the XPS spectrum. When the concentration of Si in terms of atomic ratio was defined as R(Si) and the concentration of Fe in terms of atomic ratio was defined as R(Fe), 2. The soft magnetic powder according to claim 1, wherein R(Si) / R(Fe) is 2.5 or more.

3. 2. The soft magnetic powder according to claim 1, wherein the content of the crystal grains in the particles is 30% by volume or more.

4. 4. The soft magnetic powder according to claim 1, wherein the average particle size is 1 μm or more and 50 μm or less.

5. A dust core comprising the soft magnetic powder according to claim 1 .

6. A magnetic element comprising the powder magnetic core according to claim 5 .

7. An electronic device comprising the magnetic element according to claim 6.

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