Soft magnetic powder, pressed magnetic core, magnetic components and electronic equipment

Abstract

This invention provides a soft magnetic powder that combines low coercivity and high saturation magnetic flux density, a pressed magnetic core containing the magnetic powder, magnetic components, and an electronic device capable of miniaturization and high output. The soft magnetic powder is characterized by comprising particles having Fe... x Cu a Nb b (Si 1‑ y B y ) 100‑x‑a‑b [Where, a, b, and x are numbers in atomic percentage, satisfying 0.3 ≤ a ≤ 2.0, 2.0 ≤ b ≤ 4.0, and 73.0 ≤ x ≤ 79.5; furthermore, y is a number satisfying f(x) ≤ y ≤ 0.99, and f(x) = (4 × 10⁻⁶) / ( ... ‑34 )x 17.56 The composition is represented by ], wherein the particles contain crystalline grains with a diameter of 1.0 nm or more and 30.0 nm or less, and include a Cu segregation portion, wherein the Cu segregation portion exists at a depth of more than 30 nm from the surface of the particles, and the maximum Cu concentration of the Cu segregation portion is greater than 6.0 atomic percentage.

Description

Technical Field

[0001] This invention relates to a soft magnetic powder, a pressed magnetic core, a magnetic component, and an electronic device. Background Technology

[0002] In various mobile devices incorporating magnetic components with pressed powder cores, miniaturization and high output require handling high-frequency and high-current switching power supplies. Consequently, the soft magnetic powder contained in the pressed powder cores also needs to withstand high frequencies and high currents.

[0003] Patent document 1 discloses a method using Fe x Cu a Nb b (Si 1-y B y ) 100-x-a-b [Where, a, b, and x are atomic percentages, and are numbers satisfying 0.3 ≤ a ≤ 2.0, 2.0 ≤ b ≤ 4.0, and 73.0 ≤ x ≤ 79.5. Additionally, y is a number satisfying f(x) ≤ y < 0.99. Furthermore, f(x) = (4 × 10⁻⁶) / ( ... -34 )x 17.56 The composition is represented by ], and the soft magnetic powder is characterized by a crystalline structure with a particle size of 1.0 nm or more and 30.0 nm or less, containing 30% or more by volume. Based on this soft magnetic powder, by including tiny crystals, low iron loss at high frequencies can be achieved.

[0004] However, the soft magnetic powder described in Patent Document 1 still has room for improvement in terms of its stable and excellent soft magnetic properties even under high current. Specifically, the challenge is to further increase the saturation magnetic flux density in the soft magnetic powder while further reducing the coercivity so that the pressed powder does not saturate even under high current.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-189928 Summary of the Invention

[0006] The soft magnetic powder involved in the application examples of the present invention is characterized in that it comprises particles having Fe... x Cu a Nb b (Si 1-y B y ) 100-x-a-b [Where, a, b, and x are numbers in atomic percentage, satisfying 0.3 ≤ a ≤ 2.0, 2.0 ≤ b ≤ 4.0, and 73.0 ≤ x ≤ 79.5; furthermore, y is a number satisfying f(x) ≤ y ≤ 0.99, and f(x) = (4 × 10⁻⁶) / ( ... -34)x 17.56 The composition is represented by ], wherein the particles contain crystalline grains with a diameter of 1.0 nm or more and 30.0 nm or less, and include a Cu segregation portion, wherein the Cu segregation portion exists at a depth of more than 30 nm from the surface of the particles, and the maximum Cu concentration of the Cu segregation portion is greater than 6.0 atomic percentage.

[0007] The powder-pressed magnetic core described in the application examples of the present invention is characterized in that it contains the soft magnetic powder described in the application examples of the present invention.

[0008] The magnetic element involved in the application example of the present invention is characterized in that it has the powder core involved in the application example of the present invention.

[0009] The electronic device described in the application examples of the present invention is characterized by having the magnetic element described in the application examples of the present invention. Attached Figure Description

[0010] Figure 1 This is a diagram showing the region where the range of x and the range of y of the composition of the soft magnetic powder involved in the embodiment overlap in an orthogonal coordinate system with x as the horizontal axis and y as the vertical axis.

[0011] Figure 2 A longitudinal sectional view showing an example of an apparatus for producing soft magnetic powder by atomization of rotating water streams.

[0012] Figure 3 A top view schematically illustrating a ring-shaped coil component.

[0013] Figure 4 A perspective perspective view schematically illustrating a coil component with a closed magnetic circuit.

[0014] Figure 5 This is a perspective view showing the structure of a portable personal computer, which is an electronic device equipped with the magnetic element involved in the embodiment.

[0015] Figure 6 This is a top view showing the structure of a smartphone, which is an electronic device equipped with the magnetic element involved in the embodiment.

[0016] Figure 7 This is a perspective view showing the structure of a digital camera, which is an electronic device equipped with the magnetic element involved in the embodiment. Detailed Implementation

[0017] Hereinafter, the soft magnetic powder, pressed magnetic core, magnetic element, and electronic device of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0018] 1. Soft magnetic powder

[0019] The soft magnetic powder involved in the embodiments is a metal powder that exhibits soft magnetic properties. The soft magnetic powder involved can be applied to any application, such as being used to bond particles together with each other via a binder material to manufacture various pressed powder materials such as pressed powder magnetic cores and electromagnetic wave absorbing materials.

[0020] The soft magnetic powder involved in the embodiments comprises particles having Fe x Cu a Nb b (Si 1- y B y ) 100-x-a-b The composition is represented by this.

[0021] a, b, and x are numbers expressed as atomic percentages (atomic %). Furthermore, a satisfies 0.3 ≤ a ≤ 2.0, b satisfies 2.0 ≤ b ≤ 4.0, and x satisfies 73.0 ≤ x ≤ 79.5.

[0022] Furthermore, y satisfies f(x) ≤ y ≤ 0.99. Also, f(x) = (4 × 10⁻⁶) / ( ... -34 )x 17.56 .

[0023] Furthermore, the soft magnetic powder involved in the embodiment contains crystalline grains with a particle size of 1.0 nm or more and 30.0 nm or less, and includes Cu segregated portions. The Cu segregated portions exist at a depth of more than 30 nm from the surface of the particles. In addition, the maximum Cu concentration of the Cu segregated portions exceeds 6.0 atomic percentages.

[0024] This soft magnetic powder achieves a balance between low coercivity and high saturation flux density. Therefore, it is possible to obtain powder-pressed magnetic cores with low iron loss and resistance to saturation even under high current. Furthermore, it is possible to develop magnetic elements that can handle high currents, are miniaturized, and offer high efficiency and high output.

[0025] The composition of the soft magnetic powder particles involved in the embodiments will be described below.

[0026] 1.1. Composition

[0027] Fe (iron) has a significant impact on the basic magnetic and mechanical properties of the soft magnetic powder involved in the implementation method.

[0028] The Fe content x is set to be 73.0 atomic percent or more and 79.5 atomic percent or less, preferably 75.0 atomic percent or more and 78.5 atomic percent or less, and more preferably 75.5 atomic percent or more and 78.0 atomic percent or less. Furthermore, when 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, when the Fe content x is above the upper limit, it is difficult to stably form an amorphous structure during the manufacture of the soft magnetic powder, and therefore it may be difficult to form crystalline grains with the small particle size described above.

[0029] When Cu (copper) is used as a raw material to manufacture the soft magnetic powder involved in the embodiments, it tends to separate from Fe. Therefore, the inclusion of Cu leads to compositional instability and partially creates regions within the particles that are prone to crystallization. As a result, the precipitation of the Fe phase, which has a relatively easy-to-crystallize body-centered cubic lattice, is promoted, thereby enabling the easy formation of crystal grains with the small grain size described above.

[0030] The Cu content 'a' is set to be 0.3 atomic percent or more and 2.0 atomic percent or less, preferably 0.5 atomic percent or more and 1.5 atomic percent or less, and more preferably 0.7 atomic percent or more and 1.3 atomic percent or less. Furthermore, when the Cu content 'a' is below the lower limit, it impairs the refinement of the crystal grains, and therefore it may be impossible to form crystal grains with the particle size range described above. On the other hand, when the Cu content 'a' is above the upper limit, the mechanical properties of the soft magnetic powder decrease, and therefore it may become brittle.

[0031] When niobium (Nb) is heat-treated, it, along with Cu, contributes to the refinement of crystal grains. Therefore, it is easy to form crystal grains with the small grain size described above.

[0032] The Nb content b is set to be 2.0 atomic percent or more and 4.0 atomic percent or less, preferably 2.5 atomic percent or more and 3.5 atomic percent or less, and more preferably 2.7 atomic percent or more and 3.3 atomic percent or less. Furthermore, when the Nb content b is below the lower limit, it impairs the refinement of the crystal grains, and therefore it may be impossible to form crystal grains with the particle size range described above. On the other hand, when the Nb content b is above the upper limit, the mechanical properties of the soft magnetic powder decrease, and it may become brittle. In addition, the magnetic permeability of the soft magnetic powder may decrease.

[0033] Silicon (Si) promotes amorphization when manufacturing the soft magnetic powder according to the embodiments from raw materials. Therefore, when manufacturing the soft magnetic powder according to the embodiments, a uniform amorphous structure is first formed, and then crystallization is carried out, making it easier to form crystal grains with more uniform particle size. Moreover, since the uniform particle size helps to average the crystal magnetic anisotropy in each crystal grain, the coercivity can be reduced and the permeability can be increased, thereby improving the soft magnetic properties.

[0034] Boron (B) promotes amorphization when manufacturing the soft magnetic powder according to the embodiments from raw materials. Therefore, when manufacturing the soft magnetic powder according to the embodiments, a uniform amorphous structure is first formed, and then crystallized, making it easier to form crystal grains with more uniform particle size. Furthermore, since uniform particle size helps to average the crystal magnetic anisotropy in each crystal grain, the coercivity can be reduced and the permeability increased, thus enhancing soft magnetic properties. In addition, by using Si and B together, amorphization can be synergistically promoted based on the difference in their atomic radii.

[0035] Here, when the total content of Si and B is set to 1, and the ratio of the content of B to the total is set to y, the ratio of the content of Si to the total becomes (1-y).

[0036] The y is a number that satisfies f(x) ≤ y ≤ 0.99. Furthermore, f(x) as a function of x is f(x) = (4 × 10⁻⁶) / (x² - y² - 0.99) / (x ... -34 )x 17.56 .

[0037] Figure 1 This is a diagram showing the region where the range of x and the range of y of the composition of the soft magnetic powder involved in the embodiment overlap in an orthogonal coordinate system with x as the horizontal axis and y as the vertical axis.

[0038] exist Figure 1 In the coordinate system, the region A where the ranges of x and y overlap is the inside of the solid line drawn in the orthogonal coordinate system.

[0039] Specifically, region A is a closed region enclosed by three straight lines and one curve when the coordinates of (x,y) satisfying the four equations x=73.0, x=79.5, y=f(x), and y=0.99 are respectively plotted in an orthogonal coordinate system.

[0040] Furthermore, y is preferably a number that satisfies f'(x) ≤ y ≤ 0.97. Moreover, f'(x) as a function of x is f'(x) = (4 × 10^97)^97. -29 )x 14.93 .

[0041] Figure 1The dashed line shown illustrates the overlapping region B of the preferred range of x as described above and the preferred range of y as described above.

[0042] Specifically, region B is a closed region enclosed by three straight lines and one curve when the (x,y) coordinates satisfying the four equations x=75.0, x=78.5, y=f'(x) and y=0.97 are respectively labeled in an orthogonal coordinate system.

[0043] Furthermore, y is more preferably a number that satisfies f(x) ≤ y ≤ 0.95. Moreover, f(x) as a function of x is f(x) = (4 × 10⁻⁶) / (x² - y² - y² - y²) / (x ... -29 )x 14.93 +0.05.

[0044] Figure 1 The single-dotted line shown illustrates the overlapping region C of the more preferred range of x as described above and the more preferred range of y as described above.

[0045] Specifically, region C is a closed region enclosed by three straight lines and one curve when the (x,y) coordinates satisfying the four equations x=75.5, x=78.0, y=f(x), and y=0.95 are respectively plotted in an orthogonal coordinate system.

[0046] The soft magnetic powder, in which x and y are at least contained within region A, can form a uniform amorphous structure with a high probability during manufacturing. Therefore, by crystallizing it, it is particularly possible to form crystalline grains of uniform size. This allows for the acquisition of soft magnetic powder with sufficiently reduced coercivity. Furthermore, by using this soft magnetic powder, the iron loss of the pressed magnetic core can be sufficiently suppressed.

[0047] Furthermore, the soft magnetic powder containing at least x and y within region A can form uniform crystalline grains even with a sufficiently high Fe content. This allows for the acquisition of soft magnetic powder with a sufficiently high saturation magnetic flux density. Consequently, it is possible to obtain a pressed powder magnetic core that achieves both sufficiently low iron loss and high saturation magnetic flux density.

[0048] Furthermore, when the value of y is smaller compared to region A, the balance between the content of Si and the content of B is lost, making it difficult to form a uniform amorphous structure when manufacturing soft magnetic powder. Consequently, it is impossible to form crystals with small particle sizes and to sufficiently reduce the coercivity.

[0049] On the other hand, when the value of y is larger than that in region A, the balance between the content of Si and the content of B is lost. Therefore, it is difficult to form a uniform amorphous structure when manufacturing soft magnetic powder. Consequently, it is impossible to form crystals with small particle sizes and to sufficiently reduce the coercivity.

[0050] Furthermore, the lower limit of y is determined as a function of x as described above, but is preferably 0.30 or higher, more preferably 0.45 or higher, and even more preferably 0.55 or higher. This allows for further increases in the saturation magnetic flux density of the soft magnetic powder.

[0051] Furthermore, especially in regions B and C, and also in region A where x values ​​are relatively high, the Fe content is high. Therefore, it is easier to increase the saturation magnetic flux density of the soft magnetic powder. Thus, by using soft magnetic powder in which x and y are at least contained in region B, miniaturization and high output of pressed magnetic cores and magnetic components can be achieved.

[0052] Furthermore, while (100-xab), which is the total content of Si and B, is not particularly limited, it is preferably 15.0 atomic percent or more and 24.0 atomic percent or less, more preferably 16.0 atomic percent or more and 23.0 atomic percent or less, and even more preferably 16.0 atomic percent or more and 22.0 atomic percent or less. By keeping (100-xab) within this range, it is possible to form crystal grains with particularly uniform particle size in the soft magnetic powder.

[0053] Based on the above, y(100-xab) corresponds to the content of B in the soft magnetic powder. Although y(100-xab) is appropriately set considering coercivity and saturation flux density as described above, it is preferably satisfied that 5.0 ≤ y(100-xab) ≤ 17.0, more preferably that 7.0 ≤ y(100-xab) ≤ 16.0, and even more preferably that 8.0 ≤ y(100-xab) ≤ 15.0.

[0054] Therefore, soft magnetic powders containing a relatively high concentration of boron (B) can be obtained. Even with a high Fe content, the soft magnetic powders described above can form a uniform amorphous structure during manufacturing. Therefore, through subsequent heat treatment, fine-sized and relatively uniform crystalline grains can be formed, and high magnetic flux density can be achieved while sufficiently reducing coercivity.

[0055] Furthermore, since the content of B decreases when y(100-xab) is below the lower limit, it may become difficult to achieve amorphization when manufacturing soft magnetic powder, depending on the overall composition. On the other hand, since the content of B increases when y(100-xab) is above the upper limit, the content of Si decreases relatively, which may reduce the permeability and saturation magnetic flux density of the soft magnetic powder.

[0056] Alternatively, the soft magnetic powder involved in the implementation method may be configured such that, in addition to the Fe described above, it is composed of Fe... x Cu a Nb b (Si 1-y B y ) 100-x-a-b In addition to the indicated composition, the invention also includes impurities. All elements other than those listed above can be considered as impurities, but preferably, the total content of impurities is less than 0.50 atomic percent. If this range is within which impurities are unlikely to hinder the effects of the invention, their presence is permissible.

[0057] The content of each element of the impurity is preferably below 0.05 atomic percentage. If it is within this range, the impurities are unlikely to hinder the effect of the present invention, and therefore their presence is permissible.

[0058] Furthermore, although (100-xab), which is the sum of the Si and B contents, is uniquely determined based on the values ​​of x, a, and b, a deviation of less than ±0.50 atomic percentages centered on (100-xab) is allowed due to manufacturing errors and the influence of impurities.

[0059] While the composition of the soft magnetic powder involved in the embodiments has been described above, the above composition and impurities can also be determined by the analytical methods described below.

[0060] Examples of analytical methods include, for instance, the atomic absorption spectrophotometry method for iron and steel specified in JIS G 1257:2000, the ICP emission spectrophotometry method for iron and steel specified in JIS G 1258:2007, the spark discharge emission spectrophotometry method for iron and steel specified in JIS G 1253:2002, the fluorescence X-ray analysis method for iron and steel specified in JIS G 1256:1997, and the gravimetric / titration / absorbance spectrophotometry methods specified in JIS G 1211 to G 1237.

[0061] Specifically, examples include solid-state emission spectrometry analysis devices manufactured by SPECTRO Corporation, especially spark discharge emission spectrometry analysis devices, model: SPECTROLAB, type: LAMVB08A, or the CIROS120 ICP device manufactured by Rigaku Corporation.

[0062] Furthermore, when specifically determining C (carbon) and S (sulfur), the oxygen flow combustion (high-frequency induction furnace combustion)-infrared absorption method specified in JIS G 1211:2011 can be used. Specifically, the LECO CS-200 carbon / sulfur analyzer can be cited as an example.

[0063] Furthermore, when specifically determining N (nitrogen) and O (oxygen), the quantitative methods for nitrogen in iron and steel as specified in JIS G 1228:1997 and the general rules for quantitative methods for oxygen in metallic materials as specified in JIS Z 2613:2006 can be used. Specifically, the LECO oxygen / nitrogen analyzer and the TC-300 / EF-300 can be cited as examples.

[0064] 1.2. Crystal grains

[0065] The soft magnetic powder particles involved in the embodiment contain crystalline grains with a grain size of 1.0 nm or more and 30.0 nm or less. Since the crystalline grains of such a size are small, the magnetic anisotropy of each crystalline grain is easily averaged. Therefore, the coercivity can be reduced, and in particular, a soft magnetic powder can be obtained. Furthermore, when a certain amount of crystalline grains of such a size are included, the permeability of the soft magnetic powder increases. As a result, a soft magnetic powder with low coercivity and high permeability can be obtained. Moreover, by increasing the permeability, it becomes less prone to saturation even under high current, thus increasing the saturation magnetic flux density of the soft magnetic powder.

[0066] In the particles, the content ratio of crystalline grains within the specified particle size range is preferably 30% by volume or more, but more preferably 40% by volume or more and 99% by volume or less, and even more preferably 55% by volume or more and 95% by volume or less. When the content ratio of crystalline grains within the specified particle size range is lower than the lower limit, the proportion of small-sized crystalline grains decreases, thus the averaging of crystalline magnetic anisotropy becomes insufficient, which may lead to a decrease in the permeability of the soft magnetic powder or an increase in the coercivity of the soft magnetic powder. On the other hand, although the content ratio of crystalline grains within the specified particle size range can also be higher than the upper limit, as described below, the effect caused by the coexistence of amorphous structures may become insufficient.

[0067] Furthermore, the soft magnetic powder involved in the embodiments may also contain crystalline particles with particle sizes outside the range described above, i.e., particle sizes less than 1.0 nm or larger than 30.0 nm. In this case, it is preferable to control the crystalline particles with particle sizes outside the range to less than 10% by volume, and more preferably to less than 5% by volume. This can suppress the reduction of the effects described above caused by crystalline particles with particle sizes outside the range.

[0068] The particle size of the soft magnetic powder crystals can be determined, for example, by observing the cross-section of the soft magnetic powder particles using an electron microscope and reading the image. Alternatively, in this method, a perfect circle with the same area as the crystal grain can be envisioned, and the diameter of this circle, i.e., the equivalent diameter of the circle, can be set as the particle size of the crystal grain.

[0069] It can be assumed that the volume ratio of the crystal grains and the area ratio of the crystal grains relative to the cut surface are almost the same, so the area ratio can also be regarded as the content ratio.

[0070] Furthermore, regarding the soft magnetic powder involved in the embodiment, the average particle size of the crystal grains is preferably 2.0 nm or more and 25.0 nm or less, more preferably 5.0 nm or more and 20.0 nm or less. As a result, the aforementioned effects—namely, lower coercivity and higher permeability—become significant.

[0071] In addition, the average particle size of the crystal grains of the soft magnetic powder can be determined, for example, by obtaining the particle size of the crystal grains and averaging it as described above, or by obtaining the peak width originating from Fe in the X-ray diffraction pattern of the soft magnetic powder and calculating it using the Halder-Wagner method based on its value.

[0072] The soft magnetic powder particles involved in the embodiments may also contain amorphous structures. By allowing crystalline grains and amorphous structures within the aforementioned grain size range to coexist, magnetostriction is mutually canceled out, thereby further reducing the magnetostriction of the soft magnetic powder. As a result, a soft magnetic powder with particularly high magnetic permeability can be obtained. Furthermore, a soft magnetic powder that is easy to control in terms of magnetization can also be obtained. Moreover, by containing amorphous structures, it is easier to make the grain size of the crystalline grains finer and more uniform.

[0073] The proportion of amorphous structure in the particles, expressed as a volume ratio, is preferably 5.0 times or less than the proportion of crystalline grains within the particle size range, more preferably 0.02 times or more and 2.0 times or less, and even more preferably 0.10 times or more and less than 1.0 times. This optimizes the balance between crystalline grains and amorphous structure, thereby making the effects resulting from the coexistence of crystalline grains and amorphous structure more significant.

[0074] 1.3.Cu segregation part

[0075] The soft magnetic powder particles involved in the embodiments contain Cu segregated portions, which are locally segregated from the surrounding Cu. These Cu segregated portions exist at a depth exceeding 30 nm from the particle surface. Furthermore, the maximum Cu concentration in the Cu segregated portions is greater than 6.0 atomic percent.

[0076] By incorporating Cu segregation into the particles, grain coarsening during heat treatment can be suppressed. Consequently, uniform grains can be formed through heat treatment. This results in a soft magnetic powder that balances low coercivity and high saturation magnetic flux density.

[0077] Cu segregation exists at a depth exceeding 30 nm from the particle surface. By placing the Cu segregation at such a depth, the aforementioned effects caused by Cu segregation extend to a deeper location, reaching a greater depth from the particle surface. In other words, this deeper location suppresses grain coarsening during heat treatment. Consequently, grain size minimization and homogenization can be achieved in more areas within the particle, thereby balancing lower coercivity and higher saturation magnetic flux density.

[0078] The depth of the Cu segregation from the particle surface can be determined from a surface analysis image obtained by analyzing a cross-section of the particle using EDX (energy-dispersive X-ray spectroscopy) with a STEM (scanning transmission electron microscope). Specifically, for the particle cross-section, an image is taken over a 250 nm square area including the particle surface, and the Cu segregation is determined by elemental analysis. Furthermore, the depth of the Cu segregation from the particle surface is determined as the distance from the Cu segregation with the highest Cu concentration in the surface analysis image to the particle surface. Preferably, the image shows a range at a depth of 200 nm or more from the particle surface.

[0079] The depth of the Cu segregation is set to be greater than 30 nm as described above, but preferably 40 nm or more and 500 nm or less, and more preferably 50 nm or more and 400 nm or less.

[0080] Furthermore, the maximum Cu concentration in the Cu segregation zone is greater than 6.0 atomic percentage. By including the Cu segregation zone with a high Cu concentration as described above, the Cu segregation zone functions as a nucleation site during heat treatment, thereby facilitating the growth of Fe-based grains. Consequently, grains of uniform size can be produced up to a depth from the particle surface. As a result, both the averaging of crystal magnetic anisotropy and the increase in the proportion of grains with uniform size can be achieved, and a better balance can be struck between lower coercivity and higher saturation magnetic flux density.

[0081] The maximum value of Cu concentration in the Cu segregation zone is obtained by measuring the Cu concentration in the range reflected in the image using EDX-based elemental analysis, and using this as the maximum value.

[0082] The maximum Cu concentration in the Cu segregation zone is set to be greater than 6.0 atomic percent, preferably 10.0 atomic percent or more, and more preferably 16.0 atomic percent or more, as described above. This particularly promotes the growth of grains with Cu segregation zones as nucleation sites. As a result, grains with more uniform particle size can be produced up to particularly deep locations. Furthermore, although the upper limit of the maximum Cu concentration is not particularly limited, from the viewpoint of avoiding uneven distribution of Cu segregation zones, it is preferable to be 70.0 atomic percent or less, and more preferably 60.0 atomic percent or less.

[0083] Furthermore, the Cu concentration in the Cu segregation zone is preferably more than twice that of the parent phase, and more preferably more than three times. This ensures that the Cu concentration in the Cu segregation zone is sufficiently higher than the Cu concentration in the parent phase, thereby more reliably suppressing grain coarsening during heat treatment. Additionally, the parent phase refers to the region at a depth of 500 nm from the particle surface.

[0084] Furthermore, when considering a 200 nm square region containing Cu segregated portions in an area analysis image as described above, the average particle size of the Cu segregated portions can be calculated by accumulating the number of portions for each diameter. Specifically, first, the area analysis image is binarized and analyzed, and the region occupied by the Cu segregated portions is extracted. Next, the circular equivalent diameter of the extracted region, i.e., the particle size of the Cu segregated portions, is calculated. Then, the number of portions for each Cu segregated portion is accumulated, and the average particle size is calculated based on the accumulated result.

[0085] The average particle size of the Cu segregated portion calculated in this way is preferably 3 nm or more and 20 nm or less, more preferably 5 nm or more and 15 nm or less, and even more preferably 5 nm or more and 12 nm or less. If the average particle size of the Cu segregated portion is within this range, sufficiently fine and more uniform crystal grains can be formed by heat treatment. As a result, further demagnetization of the soft magnetic powder can be achieved.

[0086] As described above, the soft magnetic powder involved in this embodiment comprises Fe x Cu a Nb b (Si 1- y B y ) 100-x-a-b The particles represent the composition of the material. Here, a, b, and x are numbers representing atomic percentages. Furthermore, a satisfies 0.3 ≤ a ≤ 2.0, b satisfies 2.0 ≤ b ≤ 4.0, and x satisfies 73.0 ≤ x ≤ 79.5. Additionally, y satisfies f(x) ≤ y ≤ 0.99. Moreover, f(x) = (4 × 10⁻⁶) / ( ... -34 )x 17.56 .

[0087] Furthermore, the soft magnetic powder involved in the embodiment contains crystalline grains with a particle size of 1.0 nm or more and 30.0 nm or less, and includes Cu segregated portions. The Cu segregated portions exist at a depth of more than 30 nm from the surface of the particles. Furthermore, the maximum Cu concentration of the Cu segregated portions is greater than 6.0 atomic percentages.

[0088] Based on this structure, soft magnetic powder that balances low coercivity and high saturation flux density can be obtained. Therefore, pressed powder cores with low iron loss and low saturation even under high current can be achieved. Furthermore, magnetic components capable of handling high currents, being miniaturized, and efficiently achieving high output can be realized.

[0089] 1.4.Si segregation department

[0090] The soft magnetic powder particles involved in the embodiment contain Si segregated portions. These Si segregated portions exist between the Cu segregated portions and the particle surface. By including Si segregated portions present at such locations, the insulation properties of the particles are improved. This, in turn, suppresses the generation of eddy currents that travel along the particle-to-particle paths.

[0091] The depth of the Si segregation portion from the particle surface can be determined from a surface analysis image, which is an image obtained by analysis of a particle cross-section using EDX (energy-dispersive X-ray spectroscopy) with a STEM (scanning electron microscope). Specifically, for the particle cross-section, an image is taken over a 250 nm square area including the particle surface, and the Si segregation is determined by elemental analysis, and the distance from the particle surface to the shallowest Si segregation portion is calculated. Preferably, the image shows a range at a depth of 200 nm or more from the particle surface.

[0092] The maximum Si concentration in the Si segregation zone is preferably 10.0 atomic percent or more, more preferably 15.0 atomic percent or more and 60.0 atomic percent or less, and even more preferably 20.0 atomic percent or more and 50.0 atomic percent or less. Furthermore, when the maximum Si concentration exceeds the aforementioned upper limit, the amount of Si distributed into the crystal grains will be relatively reduced, which may impair the high saturation magnetic flux density originating from the crystal grains.

[0093] Furthermore, such Si segregation occurs when the soft magnetic powder has the composition described above, especially when the relationship between x and y is as follows: Figure 1 It is easily formed when it is within the area shown.

[0094] 1.5. Fe concentration distribution

[0095] In the soft magnetic powder particles involved in the embodiments, it is preferable that the Fe concentration at a position 12 nm from the particle surface is higher than the O concentration in the form of an atomic concentration ratio. This, for example, allows for the prevention of the oxide film, primarily composed of oxides such as SiO2, from becoming thicker than desired. That is, by suppressing the thickness of the oxide film to the required minimum and suppressing the concentration of Si segregated as an oxide film, the amount of Si distributed into the crystal grains can be ensured, and the volume ratio of the crystal grains can be ensured. As a result, soft magnetic powder with a higher saturation magnetic flux density can be obtained.

[0096] The Fe and O concentrations can be determined from the results of surface mapping and line analysis (line scanning) obtained by analyzing the particle cross-section using EDX (energy-dispersive X-ray spectroscopy) with STEM (scanning transmission electron microscopy).

[0097] Furthermore, while the difference between Fe and O concentrations is not particularly limited, it is preferably 10 atomic percent or more, and more preferably 30 atomic percent or more. Additionally, while the upper limit of the difference between Fe and O concentrations is not particularly limited, it is preferably 80 atomic percent or less, and more preferably 60 atomic percent or less.

[0098] Furthermore, although it is not necessary for all particles of the soft magnetic powder involved in the embodiments to have the above-described structure, and it may also contain particles that do not have the above-described structure, it is preferable that 95% or more of the particles have the above-described structure.

[0099] Furthermore, the soft magnetic powder involved in the embodiments can also be mixed with other soft magnetic powders and non-soft magnetic powders, and used as a mixed powder in the manufacture of pressed magnetic cores, etc.

[0100] 1.6. Various characteristics

[0101] The Vickers hardness of the soft magnetic powder particles involved in the embodiment is preferably 1000 or higher and 3000 or lower, more preferably 1200 or higher and 2500 or lower. When soft magnetic powder containing particles of this hardness is compressed into a pressed powder core, deformation at the contact points between the particles can be minimized. Therefore, the contact area can be reduced, thereby improving the interparticle insulation in the pressed powder core.

[0102] Furthermore, when the Vickers hardness is below the lower limit, depending on the average particle size of the soft magnetic powder, the particles may become easily crushed at their contact points when the powder is compressed. This increases the contact area, potentially reducing the interparticle insulation in the pressed powder core. On the other hand, when the Vickers hardness is above the upper limit, depending on the average particle size of the soft magnetic powder, the compressibility decreases, and the density of the pressed powder core decreases, potentially reducing the saturation flux density of the pressed powder core.

[0103] The Vickers hardness of the soft magnetic powder particles was 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 defined as the location corresponding to the midpoint of the major axis of the cut surface when the particle is cut. Furthermore, the indenter load during the test was set to 1.96 N.

[0104] While the average particle size D50 of the soft magnetic powder involved in the embodiments is not particularly limited, it is preferably 1.0 μm or more and 50 μm or less, more preferably 10 μm or more and 45 μm or less, and even more preferably 20 μm or more and 40 μm or less. By using soft magnetic powder with such an average particle size, the path through which eddy currents flow can be shortened, thus enabling the manufacture of pressed powder magnetic cores that can sufficiently suppress eddy current losses generated within the particles of the soft magnetic powder.

[0105] Furthermore, when the average particle size of the soft magnetic powder is 10 μm or more, by mixing it with soft magnetic powder of smaller average particle size, a mixed powder capable of achieving a high compaction density can be produced. This mixed powder is also one embodiment of the soft magnetic powder involved in this invention. Based on such a mixed powder, the filling density of the compacted magnetic core can be increased, thereby improving the magnetic flux density and permeability of the compacted magnetic core.

[0106] The average particle size D50 of the soft magnetic powder is determined as the particle size that becomes 50% cumulatively from the small diameter side in the particle size distribution of the mass standard obtained by laser diffraction.

[0107] When the average particle size of the soft magnetic powder is below the lower limit, the powder becomes too fine, potentially reducing its filling capacity. Consequently, the forming density of the pressed magnetic core, an example of a pressed powder core, decreases, and depending on the material composition and mechanical properties of the soft magnetic powder, the magnetic flux density and permeability of the pressed magnetic core may decrease. On the other hand, when the average particle size of the soft magnetic powder is above the upper limit, eddy current losses generated within the particles cannot be sufficiently suppressed, depending on the material composition and mechanical properties of the powder, potentially increasing the iron loss of the pressed magnetic core.

[0108] For the soft magnetic powder involved in the embodiment, in the particle size distribution based on quality obtained by laser diffraction, when the particle size that accounts for 10% of the total from the small diameter side is defined as D10 and the particle size that accounts for 90% of the total from the small diameter side is defined as D90, it is preferable that (D90-D10) / D50 is 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 representing the breadth of the particle size distribution. By keeping this index within the aforementioned range, the filling properties of the soft magnetic powder are improved. Therefore, it is possible to obtain pressed powder with particularly high magnetic properties such as permeability and magnetic flux density.

[0109] While the coercivity of the soft magnetic powder involved in the embodiments is not particularly limited, it is preferably less than 2.0 [Oe] (less than 160 [A / m]), and more preferably 0.1 [Oe] or more and 1.5 [Oe] or less (39.9 [A / m] or more and 120 [A / m] or less). By using soft magnetic powder with low coercivity as described above, it is possible to manufacture a powder-pressed magnetic core that can sufficiently suppress hysteresis loss even at high frequencies.

[0110] The coercivity of soft magnetic powders can be measured, for example, using a vibrating sample magnetometer such as the TM-VSM1230-MHHL manufactured by Tamagawa Corporation.

[0111] The soft magnetic powder used in the embodiment is preferably one with a permeability of 15 or more at a measurement frequency of 100 MHz when it is formed into a pressed powder core, more preferably 18 or more and 50 or less. Such a soft magnetic powder contributes to the realization of pressed powder cores with excellent magnetic properties such as saturation magnetic flux density.

[0112] The permeability of pressed powder refers to the relative permeability, or effective permeability, obtained from the self-inductance of the core coil in a closed magnetic circuit, for example, when the pressed powder is shaped like a ring. In permeability measurement, for example, an impedance analyzer such as the Agilent Technology 4194A is used, with the measurement frequency set to 100MHz. Furthermore, the number of turns in the winding is set to seven, and the wire diameter is set to 0.6mm.

[0113] The saturation magnetic flux density of the soft magnetic powder involved in the embodiment is preferably 1.00 [T] or more, and more preferably 1.10 [T] or more.

[0114] The saturation magnetic flux density of soft magnetic powder can be measured, for example, by the following methods.

[0115] First, the absolute specific gravity ρ of the soft magnetic powder was measured using a fully automated gas-displacement densitometer, Micromeritics AccuPyc1330. Next, the maximum magnetization Mm of the soft magnetic powder was measured using a vibrating sample magnetometer, Tamagawa Corporation VSM system, TM-VSM1230-MHHL. Furthermore, the saturation magnetic flux density Bs was calculated using the following formula.

[0116] Bs=4π / 10000×ρ×Mm

[0117] The soft magnetic powder involved in the embodiment is configured as a cylindrical pressed powder body with an inner diameter of 8 mm and a mass of 0.7 g. When this pressed powder body is compressed axially under a load of 20 kgf, the axial resistivity of the pressed powder body is preferably 0.3 kΩ or more, and more preferably 1.0 kΩ or more. The soft magnetic powder capable of achieving such a resistivity sufficiently ensures interparticle insulation. Therefore, such a soft magnetic powder contributes to the realization of magnetic components capable of suppressing eddy current losses.

[0118] Furthermore, although the upper limit of the resistance value is not specifically limited, it is preferable to be 30.0kΩ or less, and more preferably 9.0kΩ or less, taking into account factors such as the suppression of deviations.

[0119] 2. Method for manufacturing soft magnetic powder

[0120] Next, the method for manufacturing the soft magnetic powder involved in the embodiments will be described.

[0121] Soft magnetic powder can be a material manufactured by any manufacturing method, such as atomization methods like water atomization, gas atomization, rotating water atomization, reduction, carbonylation, pulverization, etc.

[0122] Atomization methods, depending on the type of cooling medium and the structure of the apparatus, include water atomization, gas atomization, and rotating water atomization. Soft magnetic powder is preferably manufactured using an atomization method, more preferably using water atomization or rotating water atomization, and even more preferably using rotating water atomization. The atomization method involves colliding molten metal with a fluid such as a liquid or gas that is ejected at high speed, thereby simultaneously pulverizing and cooling it to produce powder. Because such atomization methods can achieve a high cooling rate, amorphization is promoted. As a result, heat treatment can form crystals with more uniform particle sizes.

[0123] In addition, the "water atomization method" in this specification refers to a method of producing metal powder by using a liquid such as water or oil as a coolant, and by spraying the liquid in an inverted cone shape that is concentrated at a point, causing molten metal to flow down toward the concentration point and collide with it.

[0124] Furthermore, since the molten metal can be cooled at extremely high speeds using the rotating water jet atomization method, solidification can be achieved while maintaining a highly disordered atomic configuration within the molten metal. Therefore, by subsequently performing a crystallization process, soft magnetic powder with uniformly sized crystalline grains can be effectively manufactured.

[0125] The following describes a method for manufacturing soft magnetic powder based on the rotating water jet atomization method.

[0126] In the rotating water jet atomization method, coolant is sprayed along the inner circumferential surface of a cooling cylinder and rotated along this surface, forming a coolant layer on the inner circumferential surface. Simultaneously, the raw material for the soft magnetic powder is melted, and the resulting molten metal is allowed to fall naturally while a jet of liquid or gas is sprayed onto it. This causes the molten metal to disperse, and the dispersed molten metal is then incorporated into the coolant layer. As a result, the molten metal, micronized through dispersion, is rapidly cooled and solidified, thus obtaining the soft magnetic powder.

[0127] Figure 2 A longitudinal cross-sectional view showing an example of an apparatus for producing soft magnetic powder by atomization of rotating water stream.

[0128] Figure 2 The powder manufacturing apparatus 30 shown includes a cooling cylinder 1, a crucible 15, a pump 7, and a nozzle 24. The cooling cylinder 1 is a cylinder used to form a coolant layer 9 on its inner circumferential surface. The crucible 15 is a supply container for supplying molten metal 25 to the inner space 23 of the coolant layer 9. The pump 7 supplies coolant to the cooling cylinder 1. The nozzle 24 ejects a gas jet 26 that breaks the flowing molten metal 25 into droplets. The molten metal 25 is modulated according to the composition of the soft magnetic powder.

[0129] The cooling cylinder 1 is cylindrical and is configured such that the cylinder axis is inclined at an angle of less than 30° relative to the vertical direction.

[0130] The upper opening of the cooling cylinder 1 is sealed by the cover 2. An opening 3 is formed on the cover 2, which is used to supply molten metal 25 flowing down into the space 23 of the cooling cylinder 1.

[0131] A coolant spray pipe 4 is provided at the upper part of the cooling cylinder 1, and the coolant spray pipe 4 sprays coolant onto the inner circumferential surface of the cooling cylinder 1. Multiple spray outlets 5 of the coolant spray pipe 4 are provided at equal intervals along the circumference of the cooling cylinder 1.

[0132] The coolant spray pipe 4 is connected to the container 8 via a piping connected to the pump 7. The coolant drawn up from the container 8 by the pump 7 is sprayed out through the coolant spray pipe 4 and supplied to the cooling cylinder 1. As a result, the coolant slowly flows down while rotating along the inner circumferential surface of the cooling cylinder 1, forming a coolant layer 9 along the inner circumferential surface. Alternatively, a cooler can be installed in the container 8 or along the circulation channel as needed. As the coolant, oils other than water, such as silicone oil, can be used, and various additives can be added. Furthermore, by pre-removing dissolved oxygen from the coolant, oxidation of the manufactured powder during cooling can be suppressed.

[0133] Furthermore, a layer thickness adjustment ring 16 is provided on the lower part of the inner circumferential surface of the cooling cylinder 1, which can be easily installed and removed. The layer thickness adjustment ring 16 adjusts the layer thickness of the coolant layer 9. By providing this layer thickness adjustment ring 16, the flow rate of the coolant is suppressed, and the layer thickness is made uniform while ensuring the layer thickness of the coolant layer 9.

[0134] In addition, a cylindrical draining mesh 17 is continuously provided at the lower part of the cooling cylinder 1, and a funnel-shaped powder recovery container 18 is provided on the lower side of the draining mesh 17. A coolant recovery cover 13 is provided around the draining mesh 17 to cover it, and a drain port 14 formed at the bottom of the coolant recovery cover 13 is connected to the container 8 via a pipe.

[0135] The nozzle 24 is provided in the space 23. The nozzle 24 is installed at the top of the gas supply pipe 27 that is inserted through the opening 3 of the cover 2, and is configured such that its outlet points to a thin stream of molten metal 25.

[0136] To manufacture soft magnetic powder in such a powder manufacturing apparatus 30, firstly, pump 7 is started, thereby forming a coolant layer 9 on the inner circumferential surface of the cooling cylinder 1. Next, molten metal 25 in crucible 15 is allowed to flow down into space 23. When gas jet 26 is sprayed onto the flowing molten metal 25, the molten metal 25 disperses, and the micronized molten metal 25 is entrained into the coolant layer 9. As a result, the micronized molten metal 25 cools and solidifies, thereby obtaining soft magnetic powder.

[0137] In the rotating water jet atomization method, a very high cooling rate can be stably maintained by continuously supplying coolant, thereby stabilizing the amorphous state of the manufactured soft magnetic powder before heat treatment. As a result, by subsequently performing heat treatment, soft magnetic powder with crystalline grains of uniform particle size can be efficiently manufactured.

[0138] Furthermore, since the molten metal 25, which has been miniaturized into a fixed size by the gas jet 26, falls due to inertia until it is entrained into the coolant layer 9, spherical droplets can be achieved at this point. As a result, soft magnetic powder can be manufactured.

[0139] For example, the flow rate of molten metal 25 from crucible 15 varies depending on the size of the apparatus and is not particularly limited, but is preferably controlled to be less than 1 kg per minute. Thus, when the molten metal 25 disperses, it disperses as droplets of an appropriate size, thereby obtaining a soft magnetic powder with an average particle size as described above. Furthermore, by controlling the amount of molten metal 25 supplied within a fixed time period, a sufficiently high cooling rate can be achieved. Additionally, for example, by reducing the flow rate of molten metal 25 within the stated range, adjustments such as reducing the average particle size can be implemented.

[0140] On the other hand, although 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, it is preferably 1 mm or less. This makes it easier to apply the gas jet 26 evenly to the thin stream of molten metal 25, and thus easier to evenly disperse droplets of appropriate size. As a result, soft magnetic powder with an average particle size as described above can be obtained. Furthermore, since the amount of molten metal 25 supplied within a fixed time period can still be controlled, a sufficiently high cooling rate can be achieved.

[0141] Furthermore, while the flow velocity of the gas jet 26 is not particularly limited, it is preferably set to between 100 m / s and 1000 m / s. This allows the molten metal 25 to still disperse as droplets of appropriate size, thus obtaining a soft magnetic powder with the average particle size described above. Moreover, since the gas jet 26 has sufficient velocity, it is possible to apply sufficient velocity to the dispersed droplets, making them finer, while also shortening the time until they are entrained in the coolant layer 9. As a result, the droplets can be spherically shaped and cooled in a short time. Additionally, for example, by increasing the flow velocity of the gas jet 26 within the aforementioned range, it is possible to adjust the average particle size.

[0142] Furthermore, as other conditions, it is preferable to set, for example, the pressure of the coolant supplied to the cooling cylinder 1 when it is sprayed out to a level of 50 MPa or more and 200 MPa or less, and the liquid temperature to a level of -10°C or more and 40°C or less. This allows for optimization of the flow rate of the coolant layer 9 and enables the micronized molten metal 25 to be cooled appropriately and uniformly.

[0143] Furthermore, the temperature of the molten metal 25 is preferably set to a level between Tm+20°C and Tm+200°C relative to the melting point Tm of the soft magnetic powder to be manufactured. More preferably, it is set to a level between Tm+50°C and Tm+150°C relative to the melting point Tm of the soft magnetic powder to be manufactured. Therefore, when the molten metal 25 is micronized by the gas jet 26, the deviation in properties between particles can be controlled to be particularly small, and the amorphization of the manufactured soft magnetic powder before heat treatment can be achieved more reliably.

[0144] Alternatively, a liquid jet can be used instead of a gas jet 26, depending on the requirements.

[0145] Furthermore, the cooling rate for cooling the molten metal 25 in the atomization method is preferably 1×10⁻⁶. 4 ℃ / s or higher, more preferably 1×10 5 ℃ / s or higher, more preferably 1×10 6 Temperatures above ℃ / s. Such rapid cooling enables highly stable amorphization, ultimately yielding soft magnetic powder with uniformly sized crystalline grains. Furthermore, deviations in the compositional ratio between particles of the soft magnetic powder can be suppressed. Moreover, by increasing the cooling rate, the Fe concentration can be made higher than the O concentration, as described above.

[0146] The soft magnetic powder manufactured as described above is subjected to a crystallization process. This crystallizes at least a portion of the amorphous structure, thereby forming crystalline grains.

[0147] Crystallization can be achieved by heat-treating soft magnetic powder containing an amorphous structure. While the heat treatment temperature is not particularly limited, it is preferably 520°C or higher and 640°C or lower, more preferably 530°C or higher and 630°C or lower, and even more preferably 540°C or higher and 620°C or lower. Furthermore, the heat treatment time is preferably set to maintain the temperature at the specified temperature for 1 minute or more and 180 minutes or less, more preferably 3 minutes or more and 120 minutes or less, and even more preferably 5 minutes or more and 60 minutes or less. By setting the heat treatment temperature and time within these ranges, crystal grains with more uniform particle size can be generated.

[0148] Furthermore, when the heat treatment temperature or time is below the lower limit, depending on the composition of the soft magnetic powder, crystallization may become insufficient, and the uniformity of particle size may deteriorate. On the other hand, when the heat treatment temperature or time is above the upper limit, depending on the composition of the soft magnetic powder, crystallization may be excessively promoted, and the uniformity of particle size may deteriorate.

[0149] The heating and cooling rates during crystallization processes affect the particle size, uniformity, distribution and size of Cu segregation, and Cu concentration of the crystals generated by heat treatment.

[0150] The heating rate is preferably 10°C / min or higher and 35°C / min or lower, more preferably 10°C / min or higher and 30°C / min or lower, and even more preferably 15°C / min or higher and 25°C / min or lower. By setting the heating rate within the specified range, the particle size of the crystals, the distribution and particle size of the Cu segregation portions, and the Cu concentration can be controlled within the specified range. Furthermore, when the heating rate is below the lower limit, the exposure time to high temperatures increases, potentially causing the particle size of the crystals to become excessively large. When the heating rate is above the upper limit, the particle size of the crystals may become too small, the distribution of Cu segregation portions may become too shallow, the particle size of the Cu segregation portions may become too small, or the Cu concentration may become too low.

[0151] The cooling rate is preferably 40°C / min or higher and 80°C / min or lower, more preferably 50°C / min or higher and 70°C / min or lower, and even more preferably 55°C / min or higher and 65°C / min or lower. By setting the cooling rate within the above range, the particle size of the crystals, the distribution and particle size of the Cu segregation portions, and the Cu concentration can be controlled within the above range. Furthermore, when the cooling rate is lower than the lower limit, the time exposed to high temperatures increases accordingly, which may cause the particle size of the crystals to become too large. When the cooling rate is higher than the upper limit, the particle size of the crystals may become too small, or the distribution of the Cu segregation portions may become too shallow, or the particle size of the Cu segregation portions may become too small, or the Cu concentration may become too low.

[0152] While the atmosphere for crystallization is not particularly limited, it 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 of these gases. This allows crystallization to be performed while suppressing metal oxidation, thereby obtaining soft magnetic powders with excellent magnetic properties.

[0153] By means of the method described above, it is possible to manufacture the soft magnetic powder involved in this embodiment.

[0154] Furthermore, the soft magnetic powder obtained in the manner described above can be classified as needed. Examples of classification methods include dry classification such as screening, inertial classification, centrifugal classification, and air classification, and wet classification such as sedimentation classification.

[0155] Furthermore, it can be configured, as needed, to form an insulating film on the surface of each particle of the obtained soft magnetic powder. Examples of materials constituting this insulating film include phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and inorganic materials such as silicates such as sodium silicate. Alternatively, organic materials listed as constituting materials for the binder described later can be appropriately selected.

[0156] 3. Powder-pressed magnetic cores and magnetic components

[0157] Next, the pressed powder core and magnetic elements involved in the implementation method will be described.

[0158] The magnetic components described in the embodiments can be applied to various magnetic components with magnetic cores, such as choke coils, inductors, noise filters, reactors, transformers, motors, actuators, solenoid valves, and generators. Furthermore, the pressed powder magnetic cores described in the embodiments can be applied to the magnetic cores of these magnetic components.

[0159] The following is a representative description of two types of coil components as an example of magnetic elements.

[0160] 3.1. Ring

[0161] First, an example of a ring-shaped coil component, which is a magnetic element involved in the implementation, will be described.

[0162] Figure 3 A top view schematically illustrating a ring-shaped coil component.

[0163] Figure 3 The coil component 10 shown has an annular pressed powder core 11 and a wire 12 wound around the pressed powder core 11. Such a coil component 10 is generally referred to as an annular coil.

[0164] The pressed powder magnetic core 11 is a material obtained by mixing the soft magnetic powder involved in the embodiment with a binder material, feeding the resulting mixture to a molding die, and then pressing it into shape. In other words, the pressed powder magnetic core 11 is a pressed powder body containing the soft magnetic powder involved in the embodiment. As described above, the pressed powder magnetic core 11 results in a higher saturation magnetic flux density and lower iron loss. As a result, when the pressed powder magnetic core 11 is mounted on electronic devices, it can reduce the power consumption of the electronic devices or achieve higher performance, thereby contributing to improved reliability of the electronic devices.

[0165] Additionally, adhesive materials can be added only as needed or omitted altogether.

[0166] Furthermore, the coil component 10 equipped with such a pressed powder core 11 becomes a component that can achieve low iron loss and high performance.

[0167] Examples of constituent materials used as the bonding material in the fabrication of the powder-pressed 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 like magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and silicates like sodium silicate. Thermosetting polyimide or epoxy resins are particularly preferred. These resin materials are easy to cure by heating and have excellent heat resistance. Therefore, the ease of manufacture and heat resistance of the powder-pressed magnetic core 11 can be improved.

[0168] Furthermore, although the ratio of the binder material to the soft magnetic powder may vary depending on the intended magnetic flux density and mechanical properties of the pressed powder core 11 being manufactured, the allowable eddy current loss, etc., it is preferably between 0.5% and 5% by mass, and more preferably between 1% and 3% by mass. This allows for the production of a pressed powder core 11 with excellent magnetic properties such as magnetic flux density and permeability, while ensuring that the individual particles of the soft magnetic powder are sufficiently bonded together.

[0169] Alternatively, it can be configured such that various additives are added to the mixture for any purpose as needed.

[0170] Materials with high conductivity can be used as constituent materials for the conductor 12, such as metallic materials including Cu, Al, Ag, Au, and Ni. Furthermore, an insulating film may be provided on the surface of the conductor 12 as needed.

[0171] Furthermore, the shape of the pressed powder core 11 is not limited to Figure 3 The ring shape shown can be either a shape with a missing part of the ring, or a shape where the long side is a straight line.

[0172] In addition, the pressed powder core 11 may, as needed, contain soft magnetic powder or non-magnetic powder other than the soft magnetic powder involved in the embodiments described above.

[0173] 3.2. Closed magnetic circuit type

[0174] Next, a closed magnetic circuit type coil component will be described as an example of a magnetic element involved in the implementation.

[0175] Figure 4 A perspective perspective view schematically illustrating a coil component with a closed magnetic circuit.

[0176] The following description focuses on the differences between closed magnetic circuit type coil components and toroidal coil components. Similar points will be omitted from the description.

[0177] like Figure 4 As shown, the coil component 20 in this embodiment is a component in which a wire 22, formed into a coil shape, is embedded inside a pressed powder core 21. That is, the coil component 20 is formed by molding the wire 22 using a pressed powder core 21. The pressed powder core 21 has the same structure as the pressed powder core 11 described above.

[0178] This type of coil component 20 is easy to produce in relatively small sizes. Moreover, whenever such a small coil component 20 is manufactured, by using a pressed powder core 21 with a large magnetic flux density and permeability and low loss, it is possible to obtain a small coil component 20 that can handle large currents with low loss / low heat generation.

[0179] Furthermore, since the wire 22 is embedded inside the powder core 21, it is difficult to create a gap between the wire 22 and the powder core 21. Therefore, vibrations caused by the magnetostriction of the powder core 21 can be suppressed, and the generation of noise accompanying such vibrations can also be suppressed.

[0180] In manufacturing the coil component 20 according to this embodiment as described above, firstly, a wire 22 is disposed in the cavity of the 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 in such a way that the wire 22 is included.

[0181] Next, the granulated powder is pressurized together with wire 22 to obtain a molded body.

[0182] Next, as in the embodiment described above, the molded body is subjected to heat treatment. This cures the bonding material, thereby obtaining the pressed powder magnetic core 21 and the coil component 20.

[0183] In addition, the pressed powder core 21 may, as needed, contain soft magnetic powder or non-magnetic powder other than the soft magnetic powder involved in the embodiments described above.

[0184] 4. Electronic devices

[0185] Next, for electronic devices equipped with the magnetic elements involved in the implementation method, based on Figures 5 to 7 Please provide an explanation.

[0186] Figure 5 This is a perspective view of a portable personal computer that is an electronic device equipped with the magnetic element involved in the embodiment. Figure 5The personal computer 1100 shown includes a main body 1104 with a keyboard 1102 and a display unit 1106 with a display unit 100. The display unit 1106 is rotatably supported relative to the main body 1104 via a hinge structure. In this personal computer 1100, for example, magnetic components 1000 such as choke coils, inductors, and motors for switching power supplies are built in.

[0187] Figure 6 This is a top view of a smartphone, which is an electronic device equipped with the magnetic element described in the embodiment. Figure 6 The smartphone 1200 shown includes multiple operation buttons 1202, an earpiece 1204, and a microphone 1206. Furthermore, a display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. This smartphone 1200 incorporates, for example, magnetic components 1000 such as inductors, noise filters, and motors.

[0188] Figure 7 This is a perspective view of a digital camera, which is an electronic device equipped with the magnetic element described in the embodiment. Additionally, in Figure 7 The diagram also briefly illustrates the connection to external devices. The digital camera 1300 uses imaging elements such as a CCD (Charge-Coupled Device) to perform photoelectric conversion on the light image of the subject, thereby generating an image signal.

[0189] Figure 7 The digital camera 1300 shown includes a display unit 100 located on the back of the housing 1302. The display unit 100 functions as a viewfinder that displays the subject as an electronic image. Furthermore, a light-receiving unit 1304, including an optical lens and a CCD, is provided on the front side of the housing 1302, i.e., the back side shown in the figure.

[0190] When the photographer confirms the image of the subject displayed on the display unit 100 and presses the shutter button 1306, the CCD's image signal at that moment is transmitted and stored in the memory 1308. In this digital camera 1300, magnetic components 1000, such as inductors and noise filters, may also be built-in.

[0191] As an electronic device involved in the implementation method, besides Figure 5 Personal computers Figure 6 smartphones, Figure 7Besides digital cameras, other examples include mobile phones, tablets, watches, inkjet printers, laptops, televisions, camcorders, video recorders, car navigation systems, pagers, electronic notebooks, electronic dictionaries, desktop computers, video game consoles, word processors, workstations, video phones, 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 detectors, various measuring devices, measuring instruments for vehicles, airplanes, and ships, mobile control devices such as automobile control equipment, aircraft control equipment, railway vehicle control equipment, and ship control equipment, as well as flight simulators.

[0192] As described above, such an electronic device possesses the magnetic element involved in the embodiment. Therefore, it enjoys the advantages of a magnetic element with low coercivity and high saturation flux density, thereby enabling miniaturization and high output of the electronic device.

[0193] While the soft magnetic powder, pressed magnetic core, magnetic element, and electronic device of the present invention have been described above based on preferred embodiments, the present invention is not limited thereto.

[0194] For example, although the embodiments described herein use examples of the soft magnetic powder of the present invention by way of exemplifying pressed powder cores and other pressed powder materials, the examples of uses are not limited thereto. For example, they can also be used as magnetic fluids, magnetic heads and other magnetic devices.

[0195] Furthermore, the shape of the pressed powder core and magnetic element is not limited to the shape shown in the figure, and can be any shape.

[0196] Example

[0197] Next, specific embodiments of the present invention will be described.

[0198] 5. Manufacturing of pressed powder magnetic cores

[0199] 5.1. Sample No. 1

[0200] First, the raw materials were melted in a high-frequency induction furnace and then pulverized using a rotating water jet atomization method to obtain soft magnetic powder. The flow rate of the molten metal from the crucible was set to 0.5 kg / min, the inner diameter of the crucible's outlet was set to 1 mm, and the gas jet velocity was set to 900 m / s. Next, the powder was classified using an air classifier. Table 1 shows the composition of the obtained soft magnetic powder. Furthermore, a solid-state emission spectrometer (SPECTROLAB, model LAVMB08A) manufactured by SPECTRO Corporation was used to determine the composition. The results showed that the total impurity content was less than 0.50 atomic percent.

[0201] Next, the particle size distribution of the obtained soft magnetic powder was measured. This measurement was performed using a Microtrack HRA9320-X100 laser diffraction particle size distribution measuring device manufactured by Nikkiso Corporation. The average particle size D50 of the soft magnetic powder, determined based on the particle size distribution, was 20 μm. Furthermore, the microstructure of the obtained soft magnetic powder before heat treatment was evaluated using X-ray diffraction to determine whether it was amorphous.

[0202] Next, the obtained soft magnetic powder was heated under a nitrogen atmosphere. The heating conditions are shown in Table 1.

[0203] Next, a mixture is obtained by mixing the obtained soft magnetic powder with epoxy resin as a binder. The amount of epoxy resin added is set to 2 parts by mass relative to 100 parts by mass of soft magnetic powder.

[0204] Next, after stirring the obtained mixture, it was dried for a short time to obtain a block-shaped dried body. The dried body was then separated using a 400 μm mesh sieve and pulverized to obtain granulated powder. The obtained granulated powder was dried at 50°C for one hour.

[0205] Next, the obtained granulated powder is filled into a molding die, and a molded body is obtained based on the molding conditions described below.

[0206] Molding conditions

[0207] • Forming method: stamping

[0208] • Shape of the molded body: Ring-shaped

[0209] • Dimensions of the molded part: outer diameter 14mm, inner diameter 8mm, thickness 3mm

[0210] • Molding pressure: 3t / cm 2 (294MPa)

[0211] Next, the molded body is heated at 150°C for 0.5 hours in an atmospheric atmosphere to cure the bonding material. This yields the pressed powder magnetic core.

[0212] 5.2. Samples No. 2~21

[0213] Except for changes to the manufacturing conditions of the soft magnetic powder and the pressed magnetic core as shown in Table 1, the pressed magnetic core was obtained in the same manner as sample No. 1. Furthermore, the average particle size D50 of each sample was controlled within the range of 10 μm or more and 30 μm or less.

[0214] Table 1

[0215] Table 1

[0216]

[0217] In addition, in Table 1, the parts of the soft magnetic powder of each sample No. that correspond to the present invention are indicated as "Examples", and the parts that do not correspond to the present invention are indicated as "Comparative Examples".

[0218] Furthermore, when x and y in the alloy composition of the soft magnetic powder of each sample No. are located inside region C, they are recorded as "C" in the region column; when x and y are located outside region C and inside region B, they are recorded as "B" in the region column; and when x and y are located outside region B and inside region A, they are recorded as "A" in the region column. Additionally, when x and y are located outside region A, the region column is recorded as "-".

[0219] 6. Evaluation of soft magnetic powder and pressed powder cores

[0220] 6.1. Evaluation of the particle structure of soft magnetic powders

[0221] The soft magnetic powders obtained in each embodiment and each comparative example are processed into thin sheets using a focusing ion beam device to obtain test sheets.

[0222] Next, the obtained test piece was observed using a scanning transmission electron microscope, and elemental analysis was performed to obtain surface analysis images.

[0223] Next, the particle size of the crystal grains was measured by observation, and the area ratio of crystal grains within a specific range of 1.0 nm to 30.0 nm was determined. This area ratio was then considered as the volume ratio of crystal grains with a predetermined particle size. The measurement results are shown in Table 2.

[0224] Furthermore, by analyzing the surface image, various indices shown in Table 2 were obtained for the Cu segregation, Si segregation, Fe concentration distribution, and O concentration distribution.

[0225] Specifically, the portion of Cu segregation with the highest Cu concentration is identified, and the depth of this Cu segregation portion from the particle surface and the maximum Cu concentration are measured. Furthermore, the particle size of the Cu segregation portion is measured, and the average particle size is calculated.

[0226] Furthermore, the Fe and O concentrations at a distance of 12 nm from the particle surface were compared. If the Fe concentration was higher, it was recorded as "Fe > O" in Table 2; if the O concentration was higher, it was recorded as "O > Fe" in Table 2. Additionally, the presence or absence of Si segregation was evaluated.

[0227] 6.2. Resistivity of pressed powder from soft magnetic powder

[0228] For the pressed powder bodies of soft magnetic powder obtained in each embodiment and each comparative example, the resistance value was measured by the method shown below.

[0229] First, a lower punch electrode was installed at the lower end of the cavity of a molding die with a cylindrical cavity having an inner diameter of 8 mm. Next, 0.7 g of soft magnetic powder was filled into the cavity. Next, an upper punch electrode was installed at the upper end of the cavity. The molding die, lower punch electrode, and upper punch electrode were then mounted on a load application device. Next, a load of 20 kgf was applied using a digital force gauge, moving in the direction of increasing distance between the lower and upper punch electrodes. Furthermore, the resistance between the lower and upper punch electrodes was measured under the applied load.

[0230] Furthermore, the measured resistance value is evaluated by comparing it with the following evaluation criteria.

[0231] A: Resistance value above 5.0kΩ

[0232] B: Resistance value is 3.0kΩ or higher and less than 5.0kΩ

[0233] C: Resistance value is 0.3kΩ or higher and less than 3.0kΩ

[0234] D: Resistance value is less than 0.3kΩ

[0235] The evaluation results are shown in Table 2.

[0236] 6.3. Measurement of the coercive force of soft magnetic powders

[0237] The coercivity of the soft magnetic powders obtained in the various embodiments and comparative examples was measured using the following measuring device.

[0238] • Measuring apparatus: Vibrating sample magnetometer, VSM system manufactured by Tamagawa Corporation, TM-VSM1230-MHHL

[0239] Furthermore, the evaluation is conducted by comparing the measured coercivity with the following evaluation criteria.

[0240] A: The coercive force is less than 0.90 Oe.

[0241] B: The coercive force is above 0.90 Oe and less than 1.33 Oe.

[0242] C: Coercivity is above 1.33 Oe and less than 1.67 Oe

[0243] D: Coercivity is 1.67 Oe or higher and less than 2.00 Oe.

[0244] E: Coercivity is above 2.00 Oe and less than 2.33 Oe

[0245] F: Coercivity is above 2.33 Oe

[0246] The evaluation results are shown in Table 2.

[0247] 6.4. Calculation of saturation magnetic flux density of soft magnetic powder

[0248] For the soft magnetic powders obtained in each embodiment and each comparative example, their respective saturation magnetic flux density was calculated in the manner described below.

[0249] First, the absolute specific gravity ρ of the soft magnetic powder was measured using a fully automated gas-displacement densitometer, Micromeritics AccuPyc1330.

[0250] Next, the maximum magnetization Mm of the soft magnetic powder was measured using a vibrating sample magnetometer as described above.

[0251] Next, the saturation magnetic flux density Bs is obtained using the following formula.

[0252] Bs=4π / 10000×ρ×Mm

[0253] The calculation results are shown in Table 2.

[0254] 6.5. Measurement of the permeability of pressed powder magnetic cores

[0255] For the pressed powder magnetic cores obtained in each embodiment and each comparative example, their permeability was measured based on the following measurement conditions.

[0256] • Measuring device: Impedance analyzer, Agilent Technology Corporation 4194A

[0257] • Measurement frequency: 100MHz

[0258] • Number of turns: seven

[0259] • Wire diameter for winding: 0.6mm

[0260] The measurement results are shown in Table 2.

[0261] 6.6. Measurement of Iron Loss in Powdered Magnetic Cores

[0262] For the powder-pressed magnetic cores obtained in each embodiment and each comparative example, the iron loss of each core was measured based on the following measurement conditions.

[0263] • Measuring equipment: BH analyzer, SY-8258 manufactured by Iwasaki Communication Equipment Co., Ltd.

[0264] • Measurement frequency: 900kHz

[0265] • Number of turns of winding: 36 turns on the primary side and 36 turns on the secondary side

[0266] • Wire diameter for winding: 0.5mm

[0267] Maximum magnetic flux density: 50mT

[0268] The measurement results are shown in Table 2.

[0269] Table 2

[0270] Table 2

[0271]

[0272] As shown in Table 2, the soft magnetic powders obtained in each embodiment achieve a balance between low coercivity and high saturation flux density. Furthermore, the pressed magnetic cores containing the soft magnetic powders obtained in each embodiment yielded results with high permeability and low iron loss. In contrast, the soft magnetic powders obtained in the comparative examples either resulted in high coercivity or low saturation flux density.

[0273] Symbol Explanation

[0274] 1…Cooling cylinder; 2…Cover; 3…Opening; 4…Coolant spray pipe; 5…Spray outlet; 7…Pump; 8…Container; 9…Coolant layer; 10…Coil assembly; 11…Powder-pressed magnetic core; 12…Wire; 13…Coolant recovery cover; 14…Drain outlet; 15…Crucible; 16…Layer thickness adjustment ring; 17…Cleansing mesh; 18…Powder recovery container; 20…Coil assembly; 21…Powder-pressed magnetic core; 22…Wire; 23…Space section; 24…Spray nozzle; 25…Molten metal; 26…Gas jet; 27…Gas supply pipe; 30…Powder manufacturing apparatus; 100…Display unit; 1000…Magnetic component; 1100…Personal computer; 1102…Keyboard; 1104…Main body; 1106…Display unit; 1200…Smartphone; 1202…Operation button; 1204…Earpiece; 1206…Microphone; 1300…Digital camera; 1302…Casing; 1304…Light receiving unit; 1306…Shutter button; 1308…Memory; A…Area A; B…Area B; C…Area C.

Claims

1. A soft magnetic powder, characterized in that, It contains particles having the following composition: Fe x Cu a Nb b (Si) 1-y B y ) 100-x-a-b Let f'(x) represent the composition, where a, b, and x are their respective atomic percentages, satisfying 0.3 ≤ a ≤ 2.0, 2.0 ≤ b ≤ 4.0, and 75.0 ≤ x ≤ 78.

5. Furthermore, y is a number satisfying f'(x) ≤ y ≤ 0.97, and f'(x) = (4 × 10⁻⁶) / ( ... -29 )x 14.93 , The particles contain crystalline grains with a diameter of 1.0 nm or more and 30.0 nm or less. The proportion of the crystalline grains in the particles is 30% or more by volume. It also includes Cu segregation portions with Cu segregation and Si segregation portions with Si segregation. The depth of the Cu segregation region from the surface of the particle is the distance from the surface of the Cu segregation region with the highest Cu concentration in the surface analysis image obtained by energy-dispersive X-ray spectroscopy using scanning transmission electron microscopy for the particle cross-section. The Cu segregation exists at a depth of 40 nm or more but less than 500 nm from the surface of the particle. The Cu concentration in the Cu segregation zone is more than three times that of the parent phase, where the parent phase refers to the region at a depth of 500 nm from the surface of the particle. The maximum Cu concentration in the Cu segregation section is greater than 6.0 atomic percentage. The Fe concentration at a position 12 nm from the surface of the particle is higher than the O concentration, and the difference between the Fe concentration and the O concentration is greater than 30 atomic percentages. The Si segregation exists between the Cu segregation and the surface of the particle. The depth of the Si segregation portion from the surface of the particle is the distance in the surface analysis image from the surface of the particle to the Si segregation portion at its shallowest position. The depth of the Si segregation portion from the surface of the particle is less than the depth of the Cu segregation portion from the surface of the particle. The maximum Si concentration in the Si segregation zone is 20.0 atomic percent or more and 50.0 atomic percent or less. For the particle cross-section, an image is taken of a 250 nm square area including the surface of the particle, and the segregation of Si is determined by elemental analysis and calculated as the distance from the surface of the particle to the Si segregation portion at the shallowest position.

2. The soft magnetic powder as described in claim 1, wherein, The maximum Cu concentration in the Cu segregation section is 10.0 atomic percent or more.

3. The soft magnetic powder as described in claim 1, wherein, When a cylindrical powder compactor with an inner diameter of 8 mm and a mass of 0.7 g is compressed along the axial direction under a load of 20 kgf, the resistivity of the powder compactor along the axial direction is greater than 0.3 kΩ.

4. A pressed powder magnetic core, characterized in that, It comprises the soft magnetic powder according to any one of claims 1 to 3.

5. A magnetic element, characterized in that, It possesses the powder-pressed magnetic core as described in claim 4.

6. An electronic device, characterized in that, It has the magnetic element as described in claim 5.

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