Soft magnetic powders, magnetic cores and magnetic components

Abstract

To provide a soft magnetic powder capable of producing a magnetic core having both high withstand voltage and high magnetic permeability.SOLUTION: The surface of a soft magnetic powder containing Fe is covered with a covering portion. The covering portion includes a mixed layer. The mixed layer has two or more selected from a borosilicate-based oxide, a bismuth-based oxide, and a phosphoric acid-based oxide. The average thickness of the covering portion is 2.0 nm or more and 100 nm or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a soft magnetic powder, a magnetic core, and a magnetic component. [Background technology]

[0002] Patent Document 1 describes an invention relating to a soft magnetic powder in which a coating is formed by adhering particles of an insulating material. Examples of insulating materials include various glass materials. It also describes that glass materials with a softening point of about 100 to 500°C, such as borate-based glass materials and borophosphate-based glass materials, are preferred.

[0003] Patent Document 2 describes an invention related to an iron-based soft magnetic powder for dust cores, which is characterized in that a coating made of Fe and Co, a phosphate-based conversion coating, and a silicone resin coating are formed in this order on the surface of the iron-based soft magnetic powder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-232225 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-038256 Summary of the Invention [Problem to be solved by the invention]

[0005] It is known that when a magnetic core is made using soft magnetic powder, it is difficult to achieve both high withstand voltage and high magnetic permeability.

[0006] An object of the present invention is to provide a soft magnetic powder that can be used to produce a magnetic core that has both high withstand voltage and high magnetic permeability. [Means for solving the problem]

[0007] In order to achieve the above object, the soft magnetic powder according to the present invention comprises: A soft magnetic powder containing Fe, the surface of the soft magnetic powder is covered with a coating portion, the coating portion includes a mixed layer, the mixed layer contains two or more oxides selected from borosilicate oxides, bismuth oxides, and phosphoric acid oxides, The average thickness of the coating portion is 2.0 nm or more and 100 nm or less.

[0008] In the cross section of the mixed layer, the area ratio of borosilicate oxide is S S , the area ratio of bismuth-based oxides is S B , the area ratio of phosphate oxide is S P Then, S S +S B +S P = 100, S S , S B and S P may all be between 0 and 90.

[0009] The mixed layer may include a borosilicate oxide and a phosphate oxide.

[0010] The coating portion may have a first single layer, the mixed layer, and a second single layer in this order from the side closest to the surface of the soft magnetic powder, The first monolayer may have only one selected from the borosilicate-based oxide and the bismuth-based oxide, The second monolayer may have only one selected from the bismuth-based oxide and the phosphate-based oxide, The first and second monolayers may be made of different oxides.

[0011] The soft magnetic powder may have an amorphous structure.

[0012] The soft magnetic powder may have a nanocrystalline structure.

[0013] The magnetic core according to the present invention contains the soft magnetic powder described above.

[0014] A magnetic component according to the present invention includes the above-described magnetic core. [Brief explanation of the drawings]

[0015] [Figure 1] A ternary diagram showing the ranges of SS, SB and SP. [Figure 2] A ternary diagram showing the ranges of SS, SB and SP. [Figure 3] FIG. 2 is a schematic cross-sectional view of a covering portion. [Figure 4] FIG. 2 is a schematic cross-sectional view of a covering portion. [Figure 5] FIG. 2 is a schematic cross-sectional view of a covering portion. [Figure 6] FIG. 2 is a schematic cross-sectional view of a covering portion. [Figure 7] This is an example of a chart obtained by X-ray crystal structure analysis. [Figure 8] 8 is an example of a pattern obtained by profile fitting the chart of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0017] The soft magnetic powder in this embodiment is A soft magnetic powder containing Fe, the surface of the soft magnetic powder is covered with a coating portion, the coating portion includes a mixed layer, the mixed layer contains two or more oxides selected from borosilicate oxides, bismuth oxides, and phosphoric acid oxides, The average thickness of the coating portion is 2.0 nm or more and 100 nm or less.

[0018] There is no particular limitation on the average particle size (D50) of the powder particles contained in the soft magnetic powder (hereinafter sometimes simply referred to as soft magnetic powder particles). For example, it may be 5.0 μm or more and 200 μm or less. The smaller the average particle size, the lower the magnetic permeability of a magnetic core containing the soft magnetic powder tends to be. The larger the average particle size, the lower the withstand voltage of a magnetic core containing the soft magnetic powder tends to be.

[0019] When the coating portion covering the soft magnetic powder particles includes the above-mentioned mixed layer, the magnetic core containing the soft magnetic powder particles is more likely to achieve both high voltage resistance and high magnetic permeability compared to when the coating portion does not include the above-mentioned mixed layer.

[0020] A schematic cross-sectional view of the coating portion is shown in Fig. 3. As shown in Fig. 3, the surface of the soft magnetic powder particle 11 is covered with the coating portion 21.

[0021] The coating portion includes at least a mixed layer 21. The mixed layer 21 includes a first oxide 31 and a second oxide 32. The mixed layer 21 may also include an oxide other than the first oxide 31 and the second oxide 32.

[0022] The first oxide 31 and the second oxide 32 are different types of oxides. The first oxide 31 and the second oxide 32 are each selected from borosilicate-based oxides, bismuth-based oxides, and phosphate-based oxides.

[0023] The mixed layer 21 may contain borosilicate oxide and phosphoric acid oxide, which tends to increase the withstand voltage of the magnetic core made using the soft magnetic powder.

[0024] The first oxide 31 may be an oxide having a higher glass transition temperature Tg than the second oxide 32. Generally, the order of Tg is highest in borosilicate-based oxides, followed by bismuth-based oxides and phosphoric acid-based oxides.

[0025] Borosilicate oxides are oxides that mainly contain B2O3 and SiO2. Specifically, borosilicate oxides contain 1% by mass or more of B2O3, 10% by mass or more of SiO2, and a total of 20% by mass or more of B2O3 and SiO2.

[0026] The bismuth-based oxide is an oxide that mainly contains Bi2O3. Specifically, the bismuth-based oxide contains 50 mass % or more of Bi2O3.

[0027] Phosphate-based oxides are oxides that mainly contain P2O5. Specifically, phosphoric acid-based oxides contain 40 mass % or more of P2O5.

[0028] The mixed layer 21 is a layer in which the first oxide 31 and the second oxide 32 are mixed. When a line is drawn parallel to the surface of the soft magnetic powder particle 11, the mixed layer 21 is a portion that passes through both the first oxide 31 and the second oxide 32. Furthermore, the length of the portion that passes through the first oxide 31 and the length of the portion that passes through the second oxide 32 are each 10% or more of the length of the line parallel to the surface of the soft magnetic powder particle 11.

[0029] The mixed layer 21 is a layer having a thickness of at least 2 nm or more. That is, even if a line drawn parallel to the surface of the soft magnetic powder particle 11 passes through both the first oxide 31 and the second oxide 32, if the thickness of such a portion is less than 2 nm, it is not considered to be the mixed layer 21.

[0030] There are no particular limitations on the method for confirming whether the coating portion includes the mixed layer 21. For example, there are methods using a transmission electron microscope (TEM), fast Fourier transform processing (FFT) of a TEM image, and electron energy loss spectroscopy (EELS).

[0031] First, a bright-field image near the surface of the soft magnetic powder particle 11 is observed using a TEM. Next, a mapping image of each element is observed using EELS to confirm that the coating portion has a mixed layer 21. The size of the bright-field image is set to be large enough to confirm the presence or absence of the mixed layer 21. For example, the length in a direction approximately parallel to the surface of the soft magnetic powder particle 11 is set to be 0.1 μm or more, and the length in a direction approximately perpendicular to the surface of the soft magnetic powder particle 11 is set to be 5 to 500 times the thickness of the coating portion.

[0032] 3, the mixed layer 21 tends to have a higher proportion of oxides with higher Tg (first oxides 31) closer to the surface of the soft magnetic powder particles 11. Specifically, the mixed layer 21 has a shape in which the first oxides 31 form irregularities on the surfaces of the soft magnetic powder particles 11, and at the same time, the oxides with lower Tg (second oxides 32) fill the recesses of the first oxides 31.

[0033] The average thickness of the coating is 2.0 nm or more and 100 nm or less. If the average thickness of the coating is too thin, the withstand voltage of the magnetic core made using the soft magnetic powder will decrease. If the average thickness of the coating is too thick, the magnetic permeability of the magnetic core made using the soft magnetic powder will decrease.

[0034] There is no particular limitation on the content ratio of each oxide contained in the mixed layer 21. In the cross section of the mixed layer 21, the area ratio of the borosilicate-based oxide is S S , the area ratio of bismuth-based oxides is S B , the area ratio of phosphate oxide is S P Then, S S +S B +S P = 100, S S , S B and S P may all be 0 or more and 93 or less, or may all be 0 or more and 90 or less.

[0035] S S , S B and S PThe range in which all are between 0 and 93, i.e., the range enclosed by the hexagon (including the line) with points A' to F' as vertices on the triangular diagram, is shown in Figure 1, S S , S B and S P Figure 2 shows the range where all are between 0 and 90, that is, the range enclosed by a hexagon (including the line) with points A to F as vertices on a triangular diagram. S , S B and S P When all of the values ​​are 0 or more and 90 or less, the withstand voltage of the magnetic core produced using the soft magnetic powder is likely to be improved.

[0036] The coating portion is not limited to the coating portion shown in Fig. 3. For example, it may be the coating portion shown in Figs. 4 to 6. The coating portions shown in Figs. 4 to 6 will be described below, but parts not specifically described are the same as the coating portion shown in Fig. 3. Also, unlike Fig. 3, boundaries between oxides of the same material are omitted as appropriate in Figs. 4 to 6.

[0037] 4 differs from the coating shown in Fig. 3 in that the second oxide 32 is uniformly dispersed in the first oxide 31 in the mixed layer 21. Similar to the soft magnetic powder having a coating shown in Fig. 3, the soft magnetic powder particles having a coating shown in Fig. 4 can also provide a magnetic core containing the soft magnetic powder particles with both high withstand voltage and high magnetic permeability.

[0038] 3 and 4, the coating portion shown in Fig. 5 includes a single layer A (23) and a single layer B (24) in addition to a mixed layer A (21). The coating portion has a first single layer, a mixed layer, and a second single layer in this order from the side closest to the surface of the soft magnetic powder particle 11, with the single layer A (23) corresponding to the first single layer and the single layer B (24) corresponding to the second single layer. Note that either the single layer A (23) or the single layer B (24) may not be included in the coating portion.

[0039] The monolayer is a layer containing only one oxide selected from borosilicate oxide, bismuth oxide, and phosphate oxide, and the oxide contained in the first monolayer has a higher Tg than the oxide contained in the second monolayer.

[0040] 5, the monolayer A (23) contains only one oxide selected from borosilicate oxides and bismuth oxides, and the monolayer B (24) contains only one oxide selected from bismuth oxides and phosphate oxides. Furthermore, the monolayer A (23) and the monolayer B (24) contain different oxides.

[0041] The average thickness of the single layer A (23) and the average thickness of the single layer B (24) may each be 0.4 nm or more and 9.6 nm or less. Furthermore, the ratio of the average thickness of the mixed layer A (21) to the average thickness of the coating portion may be 50% or more, or 60% or more. When the ratio of the average thickness of the mixed layer A (21) to the average thickness of the coating portion is sufficiently large, the withstand voltage of the magnetic core containing the soft magnetic powder particles can be further improved.

[0042] 6 includes three single layers and a mixed layer between each of the single layers, which are, in order from the side closest to the surface of the soft magnetic powder particle 11, single layer A (23), mixed layer A (21), single layer B (24), mixed layer B (22), and single layer C (25).

[0043] If the coating portion has a first single layer, a mixed layer, and a second single layer in this order from the side closest to the surface of the soft magnetic powder particle 11, the single layer A (23), the mixed layer A (21), and the single layer B (24) may correspond to the first single layer, the mixed layer, and the second single layer, respectively, in this order. Also, the single layer B (24), the mixed layer B (22), and the single layer C (25) may correspond to the first single layer, the mixed layer, and the second single layer, respectively, in this order.

[0044] The oxide (first oxide 31) contained in the monolayer A (23) has the highest Tg, and the oxide (third oxide 33) contained in the monolayer C (25) has the lowest Tg. The oxide (second oxide 32) contained in the monolayer B (24) has a Tg between the Tg of the first oxide 31 and the Tg of the third oxide 33. That is, the monolayer A (23) contains a borosilicate-based oxide, the monolayer B (24) contains a bismuth-based oxide, and the monolayer C (25) contains a phosphate-based oxide.

[0045] In the coating portion shown in Figure 6, the average thickness of each single layer may be 1.0 nm or more and 3.0 nm or less. Furthermore, the ratio of the total average thickness of the mixed layers to the average thickness of the coating portion may be 50% or more, or 60% or more. When the ratio of the total average thickness of the mixed layers to the average thickness of the coating portion is sufficiently large, the withstand voltage of the magnetic core containing the soft magnetic powder particles can be further improved.

[0046] There are no particular restrictions on the composition of the soft magnetic powder, except that it contains Fe. There are also no particular restrictions on the amount of Fe contained; it is sufficient that it contains at least 10% by mass. Furthermore, if the microstructure of the soft magnetic powder is to be a nanocrystalline structure or an amorphous structure, as described below, it is preferable that the composition be such that such a structure can be easily obtained.

[0047] There are no particular restrictions on the microstructure of the soft magnetic powder, but in order to particularly improve magnetic permeability, a nanocrystalline structure or an amorphous structure is preferred, with a nanocrystalline structure being particularly preferred. The microstructure of the soft magnetic powder can be confirmed by XRD. It can also be confirmed using TEM.

[0048] The amorphous structure is a structure containing only amorphous material or a heteroamorphous structure. The heteroamorphous structure is a structure in which primary microcrystals exist in an amorphous material. The average crystal grain size of the primary microcrystals is not particularly limited, but may be 0.3 nm to 10 nm. The amorphous structure has an amorphization rate of 85% or more as determined by XRD. Whether a structure is only amorphous or heteroamorphous can be determined by TEM. The nanocrystalline structure is a structure containing mainly nanocrystals. In a structure containing crystals (nanocrystals), the amorphization rate as determined by XRD is less than 85%. The average crystal grain size of the nanocrystals in the nanocrystalline structure is 0.5 nm to 100 nm. It may be 0.9 nm to 100 nm, 1.0 nm to 50.0 nm, or 5.0 nm to 40.0 nm.

[0049] In this embodiment, soft magnetic metal powders having an amorphization rate X of 85% or more, as shown in the following formula (1), have a structure containing only amorphous or a structure consisting of hetero-amorphous, and soft magnetic metal powders having an amorphization rate X of less than 85% have a structure consisting of crystals. X = 100 - (Ic / (Ic + Ia) × 100) ... (1) Ic: Crystalline scattering integrated intensity Ia: Amorphous scattering integrated intensity

[0050] The amorphous ratio X is calculated by performing X-ray crystal structure analysis on the soft magnetic metal powder by XRD, identifying the phase, reading the peaks of crystallized Fe or a compound (Ic: crystalline scattering integrated intensity, Ia: amorphous scattering integrated intensity), determining the crystallization ratio from the peak intensity, and then calculating the amorphous ratio X using the above formula (1). The calculation method will be explained in more detail below.

[0051] The soft magnetic metal powder according to this embodiment is subjected to X-ray crystal structure analysis by XRD to obtain a chart as shown in Fig. 7. This is subjected to profile fitting using the Lorentz function of the following formula (2), and a crystalline component pattern α showing the crystalline scattering integrated intensity as shown in Fig. 8 is obtained. c , amorphous component pattern α showing amorphous scattering integrated intensity a , and the combined pattern α c+a The amorphization rate X is calculated from the crystalline scattering integrated intensity and amorphous scattering integrated intensity of the obtained pattern using the above formula (1). The measurement range is set to a diffraction angle 2θ of 30° to 60°, where a halo derived from amorphous matter can be confirmed. Within this range, the error between the integrated intensity actually measured by XRD and the integrated intensity calculated using the Lorentz function is set to within 1%.

[0052]

number

[0053] When the soft magnetic alloy powder of this embodiment contains nanocrystals, each particle contains a large number of nanocrystals. That is, the particle size of the soft magnetic alloy powder, which will be described later, is different from the crystal grain size of the nanocrystals.

[0054] The nanocrystals of this embodiment are preferably Fe-based nanocrystals, which are crystals with nano-order particle sizes and Fe crystal structures of bcc (body-centered cubic lattice structure).

[0055] The method for producing the soft magnetic powder according to the present invention will be described below.

[0056] First, soft magnetic powder is prepared before being coated with the coating portion. There are no particular limitations on the method for preparing the soft magnetic powder, and it is sufficient to prepare soft magnetic powder with the desired composition, average particle size, and microstructure using a well-known method. For example, it can be prepared using methods such as water atomization and gas atomization. The obtained soft magnetic powder may be classified to control the average particle size. Commercially available soft magnetic powder may also be prepared.

[0057] Next, a coating portion is formed on the soft magnetic powder particles. First, a glass powder for forming the coating portion is prepared. Specifically, borosilicate glass, bismuth glass, and / or phosphate glass is prepared.

[0058] Then, a mechanofusion device is prepared as the powder coating device. By using the mechanofusion device, a coating portion having a mixed layer can be formed on the soft magnetic powder particles.

[0059] First, soft magnetic powder and / or glass powder are fed into the rotating rotor of the mechanofusion device. The type and amount of glass powder added varies depending on the area ratio of each oxide in the mixed layer. The timing of powder addition varies depending on the configuration of the coating to be formed. Then, the mechanofusion device is operated, and the softened glass powder is fixed to the soft magnetic powder to form the coating.

[0060] Generally, oxides with high Tg tend to coat the surface of soft magnetic powder more easily than oxides with low Tg. In this case, by controlling the temperature reached during coating and the processing time up to that temperature, the oxides with high Tg do not coat the surface of the soft magnetic powder uniformly. In other words, the oxides with high Tg form irregularities on the surface of the soft magnetic powder. At the same time that the oxides with high Tg form irregularities on the surface of the soft magnetic powder, the oxides with low Tg are formed so as to fill in the recesses of the oxides with high Tg, forming a mixed layer.

[0061] The Tg of borosilicate glass, bismuth glass, and phosphate glass varies depending on the composition of each glass. However, the Tg of borosilicate glass is generally within the range of 450°C to 600°C. The Tg of bismuth glass is generally within the range of 350°C to 500°C. The Tg of phosphate glass is generally within the range of 250°C to 400°C. To form the above-mentioned mixed layer, the difference in Tg between each glass is preferably 50°C or more. The difference in Tg between each glass is more preferably 100°C or more, and even more preferably 200°C or more.

[0062] For example, in order to ensure that the resulting coating portion has only a mixed layer in which the proportion of the first oxide tends to increase closer to the surface of the soft magnetic powder particle as shown in Figure 3, the ultimate temperature during coating and the processing time required to reach the ultimate temperature are appropriately controlled. More specifically, the temperature is increased so that the rate of temperature rise to the ultimate temperature is roughly constant. In other words, the temperature is controlled so that the rate of temperature rise to the ultimate temperature does not accelerate. The temperature is also controlled so that it does not stop midway. Furthermore, the ultimate temperature is controlled so that it does not exceed the target temperature.

[0063] For example, to obtain a coating portion in which the second oxide is uniformly dispersed within the first oxide as shown in Figure 4, the ultimate temperature during coating and the processing time required to reach the ultimate temperature are appropriately controlled. More specifically, compared to the case of producing a coating portion having a mixed layer as shown in Figure 3, the ultimate temperature is lowered and the processing time required to reach the ultimate temperature is extended. The ultimate temperature is set to be higher than the softening point of the first oxide and lower than the softening point of the second oxide. To extend the processing time required to reach the ultimate temperature, the temperature is raised slowly from room temperature. Furthermore, the ultimate temperature is controlled so as not to exceed the target temperature.

[0064] For example, to obtain a coating having a single layer A, a mixed layer A, and a single layer B as shown in FIG. 5, the temperature reached during coating and the processing time required to reach the temperature are appropriately controlled. More specifically, the temperature is increased so that the rate of temperature rise to the target temperature is roughly constant. That is, the temperature is controlled so that the rate of temperature rise to the target temperature does not accelerate. The temperature is also controlled so that the temperature rise does not stop midway. Furthermore, the target temperature is controlled so that it does not exceed the target temperature.

[0065] The method for producing a coated part shown in Fig. 3 and the method for producing a coated part shown in Fig. 5 differ particularly in the temperature reached during coating and the processing time required to reach that temperature. The higher the temperature reached during coating, the thicker the mixed layer becomes, making it easier to obtain the coated part shown in Fig. 3. The longer the processing time required to reach the temperature, the thicker the mixed layer becomes, making it easier to obtain the coated part shown in Fig. 3.

[0066] 5, in order to obtain a coating portion having single layers A and B and a mixed layer A, the second oxide 32 may not be initially charged into the rotor, but only the first oxide 31 and the soft magnetic powder may be charged into the rotor to produce only the single layer A. In this case, after the single layer A is produced, the second oxide and the like may be charged into the rotor to produce the mixed layer A and the single layer B.

[0067] For example, to ensure that the resulting coating portion has single layers A to C and mixed layers A to B as shown in FIG. 6, the ultimate temperature during coating and the processing time required to reach the ultimate temperature are appropriately controlled. More specifically, the temperature is increased so that the rate of temperature increase to the ultimate temperature remains roughly constant. That is, the temperature is controlled so that the rate of temperature increase to the ultimate temperature does not accelerate. The temperature is also controlled so that it does not stop midway. Furthermore, the ultimate temperature is controlled so that it does not exceed the target temperature.

[0068] 6, the glass powder containing the first oxide 31 and the glass powder containing the second oxide 32 may be added to the rotor of the mechanofusion device together with the soft magnetic powder, without first adding the glass powder containing the third oxide 33 to the rotor of the mechanofusion device. After forming the coating shown in FIG. 5, the glass powder containing the third oxide 33 may be added and fixed to the coating shown in FIG. 5, thereby obtaining the coating shown in FIG. 6.

[0069] In order to obtain a coating portion having single layers A to C and mixed layers A to B as shown in Fig. 6, first, only glass powder containing first oxide 31 may be added to the rotor of the mechanofusion device together with soft magnetic powder. Then, second oxide 32 and third oxide 33 may be added to the rotor in stages to obtain the coating portion shown in Fig. 6.

[0070] Next, a magnetic core is produced using the obtained soft magnetic powder. There is no particular limitation on the method for producing the magnetic core. For example, the soft magnetic powder is mixed with an appropriate amount of resin, and then the powder is compacted using a mold to obtain a powder core. There is no particular limitation on the compacting pressure during powder compacting. For example, a powder core can be produced using a pressure of 1×10 2 MPa~10×10 2 The higher the molding pressure, the higher the filling rate of the soft magnetic powder in the magnetic core, which tends to decrease the withstand voltage of the magnetic core and improve the magnetic permeability of the magnetic core. There are no particular restrictions on the type and content of resin.

[0071] Then, a coil component, which is a type of magnetic component, is obtained by winding a wire around the magnetic core. There are no particular limitations on the method of winding the wire or the method of manufacturing the coil component. For example, a method of winding at least one turn of wire around the magnetic core manufactured by the above method can be used.

[0072] Furthermore, by pressure molding the wound coil embedded in the soft magnetic powder and resin according to this embodiment and integrating them, it is also possible to manufacture an inductance component in which the wound coil is embedded in the magnetic core according to this embodiment. The molding pressure during pressure molding is preferably the same as the molding pressure during powder molding described above.

[0073] The magnetic core according to this embodiment can be used for any purpose, such as magnetic components, magnetic cores, coil components, inductance components, transformers, motors, etc.

[0074] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. [Example]

[0075] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0076] Experimental Example 1 As soft magnetic powder, Fe 0.832 Nb0.057 B 0.021 Si 0.075 Cu 0.015 A soft magnetic powder having the following properties was prepared.

[0077] In this experimental example, the soft magnetic powder was produced by gas atomization. The melting temperature was set to 1320°C, and other conditions were appropriately controlled so that the average particle size (D50) of the resulting soft magnetic powder particles would be the value shown in Table 1. At this stage, it was confirmed using XRD that the soft magnetic powder had an amorphous structure.

[0078] The soft magnetic powder was then heat-treated to form nanocrystals in the soft magnetic powder. The heat treatment conditions were 600°C for 1 hour in an Ar atmosphere.

[0079] The average particle size (D50) of the obtained soft magnetic powder particles was measured using a particle size distribution measuring device HELOS, and it was confirmed that the value was as shown in Table 1.

[0080] In this experimental example, it was confirmed by XRD that the obtained soft magnetic powder had a structure consisting of nanocrystals, and that the average crystal grain size of the nanocrystals contained in the obtained soft magnetic powder was 1 to 100 nm.

[0081] Next, a coating made of borosilicate oxide, bismuth oxide, and / or phosphate oxide was formed on each soft magnetic powder.

[0082] First, glass powders were prepared as the raw materials for the coating. BaO-ZnO-B2O3-SiO2-Al2O3 powdered glass (8 mass% BaO, 23 mass% ZnO, 19 mass% B2O3, 16 mass% SiO2, 6 mass% Al2O3, and the remainder being other components) was prepared as the borosilicate glass. Bi2O3-ZnO-B2O3-SiO2 powdered glass (80 mass% Bi2O3, 10 mass% ZnO, 5 mass% B2O3, and 5 mass% SiO2) was prepared as the bismuth glass. PO5-ZnO-R2O-Al2O3 powdered glass (50 mass% P2O5, 12 mass% ZnO, 20 mass% R2O, and 6 mass% Al2O3, and the remainder being other components) was prepared as the phosphate glass. Among the above glasses, the borosilicate glass has the highest Tg, and the phosphate glass has the lowest Tg.

[0083] Next, a mechanofusion device (AMS-Lab manufactured by Hosokawa Micron) was prepared as a powder coating device. Next, an Ar atmosphere was created inside the mechanofusion device. Next, the soft magnetic powder and the glass powder required for producing each sample were charged into the rotor. The amount of glass powder charged was appropriately adjusted so that the area ratio of each oxide was the area ratio shown in Table 1 and the thickness of the coating portion was the thickness shown in Table 1. Then, the mechanofusion device was operated, and the glass powder charged to the soft magnetic powder was fixed to form a coating portion.

[0084] During this process, the gap between the inner wall surface of the rotating rotor and the press head, the rotation speed of the rotating rotor, etc. were controlled to prevent the oxides contained in the high-Tg glass powder from uniformly covering the surface of the soft magnetic powder. In other words, irregularities were formed on the surface of the soft magnetic powder contained in the high-Tg glass powder. At the same time as irregularities were formed on the surface of the soft magnetic powder contained in the high-Tg glass powder, the oxides contained in the low-Tg glass powder were formed so as to fill in the recesses of the oxides contained in the high-Tg glass powder, forming a mixed layer.

[0085] The temperature reached during coating and the processing time up to the reached temperature, etc., were appropriately controlled so that the resulting coating portion would have only the type of mixed layer shown in Figure 3, i.e., a mixed layer in which the proportion of oxides with high Tg tends to increase closer to the surface of the soft magnetic powder particle, and would not have each of the single layers shown in Figure 5.

[0086] The coating formed on the soft magnetic powder of each sample was then observed. First, a bright-field image near the particle surface was observed using TEM, and the presence of a coating on the particle surface was confirmed. Next, a mapping image of each element was observed using EELS, and it was confirmed that the area ratio of each oxide in the coating was the area ratio shown in Table 1. The average thickness of the coating was also measured using TEM, FFT, and EELS.

[0087] Furthermore, to evaluate the properties of the magnetic cores made from the soft magnetic powder of each sample, toroidal cores and rectangular cores were made.

[0088] First, the soft magnetic powder of each sample was mixed with an epoxy resin to prepare a resin solution. The mass ratio of the soft magnetic powder in the resin solution was 97.5 mass %. The epoxy resin used was a phenol novolac epoxy resin.

[0089] For the toroidal core, the resulting resin solution was filled into a mold of a predetermined toroidal shape and heated at 100°C for 5 hours to volatilize the solvent. Then, after pressing at the molding pressure shown in Table 1, the core was ground with a fixed grindstone to a uniform thickness of 0.7 mm. The core was then thermally cured at 170°C for 90 minutes to crosslink the epoxy resin, yielding a toroidal core (outer diameter 15 mm, inner diameter 9 mm, thickness 0.7 mm).

[0090] For the rectangular core, the resulting resin solution was filled into a mold of a predetermined rectangular parallelepiped shape. A rectangular magnetic material (4 mm x 4 mm x 1 mm) was obtained in the same manner as for the toroidal core. Furthermore, terminal electrodes with a width of 1.3 mm were provided on both ends of one of the 4 mm x 4 mm faces of the rectangular magnetic material. The distance between the terminal electrodes was 1.4 mm.

[0091] <Filling rate> The obtained toroidal core was cut at an arbitrary cross section, and the cut surface was observed using an SEM at a magnification of 1000x with an observation area of ​​0.128mm x 0.096mm. The filling ratio was calculated by setting five or more different observation areas and averaging the area ratio occupied by particles in each observation area.

[0092] <Magnetic permeability> The magnetic permeability was calculated from the inductance measured at a frequency of 1 MHz using an LCR meter after winding a coil with 30 turns around the obtained toroidal core. In Experimental Example 1, a relative magnetic permeability of 50 or more was considered to be good.

[0093] <Voltage resistance> The withstand voltage was measured by applying a voltage between the terminal electrodes of the obtained rectangular core and measuring the voltage when a current of 2 mA flowed. In Experimental Example 1, a withstand voltage of 50 V / mm or more was considered good, and 55 V / mm or more was considered even better.

[0094] [Table 1]

[0095] From Table 1, it can be seen that the examples in which the coating portion contained only the mixed layer, the mixed layer contained two or more types of oxides, and the average thickness of the coating portion was 2.0 nm or more and 100 nm or less had good withstand voltage and permeability.

[0096] In contrast, the comparative examples in which the coating contained only one type of oxide exhibited a significant decrease in withstand voltage. Also, the comparative examples in which the coating was too thin exhibited a decrease in withstand voltage, and the comparative examples in which the coating was too thick exhibited a decrease in magnetic permeability.

[0097] Experimental Example 2 In Experimental Example 2, the coating portion was formed so as to have only the type of mixed layer shown in Figure 4, that is, a mixed layer in which oxides with high Tg are dispersed approximately evenly in oxides with low Tg.

[0098] Specifically, unlike Experimental Example 1, the rotor was initially rotated at room temperature without heating. Then, the temperature was gradually increased while the rotor was rotating. Furthermore, the ultimate temperature was set to a temperature higher than the softening point of the glass with a low Tg and lower than the softening point of the glass with a high Tg, and the temperature was controlled so as not to exceed the ultimate temperature.

[0099] As a result, the resulting coating portion had only a mixed layer in which oxides with high Tg were dispersed almost uniformly in oxides with low Tg, as shown in FIG.

[0100] In order to ensure that the resulting coating portion has only the type of mixed layer shown in Figure 4, i.e., a mixed layer in which oxides with high Tg are dispersed almost uniformly in oxides with low Tg, the temperature reached during coating and the processing time up to the reached temperature were appropriately controlled.

[0101] Other than the above, the experiment was carried out in the same manner as in Experimental Example 1. The results are shown in Table 2.

[0102] [Table 2]

[0103] From Table 2, it can be seen that the examples in which the coating portion contained only the mixed layer, the mixed layer contained two or more types of oxides, and the average thickness of the coating portion was 2.0 nm or more and 100 nm or less had good withstand voltage and permeability.

[0104] In contrast, the comparative example in which the thickness of the coating portion was too thin exhibited a decrease in withstand voltage, and the comparative example in which the thickness of the coating portion was too thick exhibited a decrease in magnetic permeability.

[0105] Experimental Example 3 In Experimental Example 3, when forming the coating portion, the type of coating portion shown in Figure 5 was used, that is, the coating portion had, in order from the side closest to the surface of the soft magnetic powder, single layer A, mixed layer A, and single layer B, each containing a predetermined type of oxide, and the closer mixed layer A was to the surface of the soft magnetic powder, the higher the proportion of oxides with high Tg tended to be.

[0106] Specifically, first, one type of glass powder (high-Tg glass powder) for forming single layer A was added to the rotor of the mechanofusion device to form single layer A. Next, one type of glass powder (low-Tg glass powder) for forming single layer B was added to the rotor of the mechanofusion device to form single layer B. To form mixed layer A between single layer A and single layer B, oxides contained in the high-Tg glass powder formed irregularities on the surface, and oxides contained in the low-Tg glass powder were formed to fill the recesses of the irregularities. Specifically, the coating temperature and the treatment time were controlled. Furthermore, in the comparative example, only each single layer was formed, and a mixed layer was not formed. Specifically, the heat treatment conditions for forming single layer A by adding only a high-Tg glass powder were set to a higher temperature and longer time than those in the examples. As a result, the surface of single layer A was smoothed. Furthermore, the heat treatment temperature for forming single layer B by adding a low-Tg glass powder was set to a sufficiently low temperature.

[0107] The coating formed on the soft magnetic powder of each sample was then observed. First, a bright-field image near the particle surface was observed using TEM, confirming the presence of a coating on the particle surface. Next, mapping images of each element were observed using EELS, confirming that the coating consisted of a single layer A, a mixed layer A, and a single layer B. Furthermore, it was confirmed that the area ratio of each oxide in the mixed layer A was the area ratio shown in Table 3. The average thickness of each of the single layer A, mixed layer A, and single layer B was measured using TEM, FFT, and EELS.

[0108] Other than the above, the experiment was carried out in the same manner as in Experimental Example 1. The results are shown in Table 3.

[0109] [Table 3]

[0110] From Table 3, it can be seen that the examples in which the coating portion had a mixed layer and the average total thickness of the coating portion was 2.0 nm or more and 100 nm or less had good withstand voltage and magnetic permeability.

[0111] In contrast, the comparative examples in which the coating portion did not have the mixed layer A but only the single layer A and the single layer B exhibited a significant decrease in withstand voltage.

[0112] Experimental Example 4 In Experimental Example 4, the coating portion was formed as shown in Figure 6, that is, the coating portion had single layer A, mixed layer A, single layer B, mixed layer B, and single layer C in that order from the side closest to the surface of the soft magnetic powder. Specifically, single layer A contained borosilicate oxide, single layer B contained bismuth oxide, and single layer C contained phosphate oxide. Mixed layer A was designed to have a coating portion in which the proportion of borosilicate oxide tends to increase as it approaches the surface of the soft magnetic powder. Mixed layer B was designed to have a coating portion in which the proportion of bismuth oxide tends to increase as it approaches the surface of the soft magnetic powder.

[0113] Specifically, borosilicate glass was first placed in the rotor of the mechanofusion device to form monolayer A, then bismuth-based glass was placed in the rotor of the mechanofusion device to form monolayer B, and finally phosphate-based glass was placed in the rotor of the mechanofusion device to form monolayer C. To form mixed layer A between monolayers A and B, the borosilicate oxide contained in the borosilicate glass was allowed to form irregularities on the surface, and the bismuth oxide was allowed to fill the recesses of the irregularities. Specifically, the coating temperature and the processing time were controlled. Furthermore, to form mixed layer B between monolayers B and C, the bismuth oxide contained in the bismuth-based glass was allowed to form irregularities on the surface, and the phosphate oxide was allowed to fill the recesses of the irregularities. Specifically, the coating temperature and the processing time were controlled. In the comparative example, in order to avoid the formation of mixed layers A and B, the heat treatment conditions for forming single layer A by adding only borosilicate glass powder were set to a higher temperature and longer time than in the examples. As a result, the surface of single layer A was smoothed. Next, the heat treatment conditions for forming single layer B by adding only bismuth glass powder were set to a higher temperature and longer time than in the examples. As a result, the surface of single layer B was smoothed. Finally, the heat treatment temperature for forming single layer C by adding only phosphate glass powder was set to a sufficiently low temperature.

[0114] The coating formed on the soft magnetic powder of each sample was then observed. First, a bright-field image near the particle surface was observed using TEM, confirming the presence of a coating on the particle surface. Next, a mapping image of each element was observed using EELS, confirming that the coating had single layers A to C and mixed layers A and B. Furthermore, it was confirmed that the area ratio of each oxide in each mixed layer was the area ratio shown in Table 4. The average thickness of each single layer and each mixed layer was measured using TEM, FFT, and EELS.

[0115] Other than the above, the experiment was carried out in the same manner as in Experimental Example 1. The results are shown in Table 4.

[0116] [Table 4]

[0117] From Table 4, it can be seen that the examples in which the coating portion had mixed layers A and B and the average total thickness of the coating portion was 2.0 nm or more and 100 nm or less had good withstand voltage and magnetic permeability.

[0118] In contrast to this, the comparative examples in which the coating portion did not have the mixed layer but only the single layers A to C exhibited a significant decrease in withstand voltage.

[0119] Experimental Example 5 As soft magnetic powder, Fe 0.873 Si 0.070 Cr 0.025 B 0.025 C 0.007 A soft magnetic powder having the following properties was prepared.

[0120] In this experimental example, the soft magnetic powder was produced by gas atomization. The melting temperature was set to 1320°C, and other conditions were appropriately controlled so that the average particle size (D50) of the resulting soft magnetic powder would be the value shown in Table 5.

[0121] The average particle size (D50) of the obtained soft magnetic powder was measured using a dry particle size distribution measuring instrument HELOS, and it was confirmed that the value was as shown in Table 5.

[0122] In this experimental example, it was confirmed by XRD that the obtained soft magnetic powder had an amorphous structure.

[0123] Other aspects were the same as in Experimental Example 1. In Experimental Example 5, a relative permeability of 40 or more was considered to be good. This is because the permeability of the soft magnetic powder changes depending on the change in the microstructure of the soft magnetic powder. The results are shown in Table 5.

[0124] [Table 5]

[0125] From Table 5, it can be seen that the examples in which the coating portion included only the mixed layer, the mixed layer included two or more types of oxides, and the average thickness of the coating portion was 2.0 nm or more and 100 nm or less had good withstand voltage and permeability.

[0126] In contrast, the comparative examples in which the coating portion contained only one type of oxide exhibited a significant decrease in withstand voltage.

[0127] Experimental Example 6 As soft magnetic powder, Fe 0.935 Si 0.045 Cr 0.020 A soft magnetic powder having the following properties was prepared.

[0128] In this experimental example, the soft magnetic powder was produced by gas atomization. The melting temperature was (1950) °C, and other conditions were appropriately controlled so that the average particle size (D50) of the resulting soft magnetic powder would be the value shown in Table 6.

[0129] The average particle size (D50) of the obtained soft magnetic powder was measured using a particle size distribution measuring device HELOS, and it was confirmed that the value was as shown in Table 6.

[0130] In this experimental example, it was confirmed by XRD that the obtained soft magnetic powder had a structure consisting of crystals larger than nanocrystals, and that the average crystal grain size of the crystals contained in the obtained soft magnetic powder was 1 to 100 nm.

[0131] Other aspects were the same as in Experimental Example 1. In Experimental Example 6, a relative permeability of 30 or more was considered to be good. This is because the permeability changes depending on the microstructure of the soft magnetic powder. The results are shown in Table 6.

[0132] [Table 6]

[0133] From Table 6, it can be seen that the examples in which the coating portion included only the mixed layer, the mixed layer included two or more types of oxides, and the average thickness of the coating portion was 2.0 nm or more and 100 nm or less had good withstand voltage and permeability.

[0134] In contrast, the comparative examples in which the coating portion contained only one type of oxide exhibited a significant decrease in withstand voltage.

[0135] Experimental Example 7 In Experimental Example 7, the soft magnetic powder composition was changed for each of the following cases: when the soft magnetic powder had a nanocrystalline structure (Example 27), when it had a crystalline structure (Example 126), and when it had an amorphous structure (Example 106). For the soft magnetic powder with a nanocrystalline structure, the heat treatment conditions were appropriately changed so that the average crystal grain size was equivalent to that of Experimental Example 1. For the soft magnetic powder with a crystalline structure, the heat treatment conditions were appropriately changed so that the average crystal grain size was equivalent to that of Experimental Example 6. The results are shown in Table 7. Regarding magnetic permeability, when the soft magnetic powder had a nanocrystalline structure, the magnetic permeability was deemed good when the relative magnetic permeability was 50 or more. When the soft magnetic powder had an amorphous structure, the magnetic permeability was deemed good when the relative magnetic permeability was 40 or more. When the soft magnetic powder had a crystalline structure, the magnetic permeability was deemed good when the relative magnetic permeability was 30 or more.

[0136] [Table 7]

[0137] From Table 7, the examples in which the coating portion included only the mixed layer, the mixed layer included two or more types of oxides, and the average thickness of the coating portion was 2.0 nm or more and 100 nm or less had good withstand voltage and permeability.

[0138] Experimental Example 8 In Experimental Example 8, the soft magnetic powder was Fe 0.839 Nb 0.122 B 0.020 P 0.018 S 0.001The experiment was carried out in the same manner as in Example 2 of Experimental Example 1, except that a soft magnetic powder having the formula (I) was prepared and that the heat treatment conditions were changed to give the average crystal grain size of the nanocrystals the values ​​shown in Table 8. The results are shown in Table 8.

[0139] [Table 8]

[0140] As can be seen from Table 8, even when the average crystal grain size of the nanocrystals contained in the soft magnetic powder changed, each example in which the coating portion contained only a mixed layer, the mixed layer contained two or more types of oxides, and the average thickness of the coating portion was 2.0 nm or more and 100 nm or less, had good withstand voltage and magnetic permeability. [Explanation of symbols]

[0141] 11...Soft magnetic powder particles 21, 22...Mixed layer 23~25... Single layer 31-33 Oxides

Claims

1. A soft magnetic powder containing Fe, the surface of the soft magnetic powder is covered with a coating portion, the coating portion includes a mixed layer, the mixed layer contains two or more oxides selected from borosilicate-based oxides, bismuth-based oxides, and phosphoric acid-based oxides, the average thickness of the coating portion is 2.0 nm or more and 100 nm or less, and the thickness of the mixed layer is 2 nm or more; the coating portion has a first single layer, the mixed layer, and a second single layer in this order from the side closest to the surface of the soft magnetic powder, the first monolayer contains only one selected from the borosilicate-based oxide and the bismuth-based oxide; the second monolayer contains only one selected from the bismuth-based oxide and the phosphate-based oxide, The soft magnetic powder contains different types of oxides in the first monolayer and the second monolayer.

2. In the cross section of the mixed layer, the area ratio of borosilicate oxide is S S , the area ratio of bismuth-based oxide is S B , the area ratio of phosphoric acid-based oxide is S P Then, S S +S B +S P = 100, S S , S B and S P 2. The soft magnetic powder according to claim 1, wherein all of the above are 0 or more and 90 or less.

3. 3. The soft magnetic powder according to claim 1, wherein the mixed layer contains a borosilicate oxide and a phosphate oxide.

4. The soft magnetic powder according to any one of claims 1 to 3, wherein the soft magnetic powder has an amorphous structure.

5. The soft magnetic powder according to any one of claims 1 to 3, wherein the soft magnetic powder has a structure consisting of nanocrystals.

6. A magnetic core comprising the soft magnetic powder according to any one of claims 1 to 5.

7. A magnetic component comprising the magnetic core according to claim 6.

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