Metal powder, composite magnetic materials, powder cores and coil components

Abstract

A metal powder (1) according to the present invention contains Fe as a main element, while containing Sn. The content ratio of Sn in the metal powder (1) is 6.3 wt% or more.

Description

[Technical Field]

[0001] The present disclosure relates to a metal powder containing Fe as a primary element, a composite magnetic body containing the metal powder, a dust core, and a coil component. [Background technology]

[0002] Conventionally, coil components have been known that include a powder magnetic core and a coil member disposed inside the powder magnetic core. Powder magnetic cores are made of composite magnetic bodies containing metal powders primarily composed of Fe. Powder magnetic cores are required to reduce magnetic loss, which leads to energy loss.

[0003] For example, Patent Document 1 discloses a metal powder having an alloy composition represented by FeSiCrC. Patent Document 2 discloses a metal powder containing Fe as a main element and having smaller average particle diameters and smaller maximum particle diameters than conventional metal powders. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 054857 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-54569 Summary of the Invention [Problem to be solved by the invention]

[0005] The metal powder disclosed in Patent Document 1 contains chromium (Cr), which can inhibit rust, but there is a problem in that the eddy current loss of the powder magnetic core increases in the high frequency range. The metal powder disclosed in Patent Document 2 reduces eddy current loss by reducing the average particle size of the metal powder, but there is a limit to how fine the metal powder can be made, so there is also a limit to the reduction in eddy current loss. With the metal powders disclosed in Patent Documents 1 and 2, it is difficult to achieve both rust inhibition and eddy current loss reduction.

[0006] In view of the above-mentioned problems, the present disclosure aims to provide a metal powder or the like that can reduce eddy current loss and inhibit rust. [Means for solving the problem]

[0007] The metal powder according to one embodiment of the present disclosure comprises: Composed of Fe, Si and Sn A metal powder comprising: The Si content in the metal powder is 8 wt% or less, The Sn content in the metal powder is 6.3 wt% or more The total content of Si and Sn in the metal powder is less than 20 wt%. .

[0008] A composite magnetic body according to one embodiment of the present disclosure includes the above-described metal powder and a resin.

[0009] A powder magnetic core according to one embodiment of the present disclosure includes the composite magnetic body described above.

[0010] A coil component according to one aspect of the present disclosure includes a magnetic body portion made of the composite magnetic body described above, and a coil member at least a portion of which is provided inside the magnetic body portion. [Effects of the Invention]

[0011] The metal powder and the like according to the present disclosure can reduce eddy current loss and inhibit rust. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic perspective view showing the configuration of a coil component according to an embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing the configuration of the coil component according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing the internal structure of the powder magnetic core according to the embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between the mass magnetization value and the content of non-magnetic elements in Fe-based metal powder. [Figure 5] FIG. 5 is a graph showing magnetic losses of the powder magnetic cores in the examples and comparative examples. [Figure 6]FIG. 6 is a diagram showing the evaluation results of magnetic loss and rust of the powder magnetic cores in the examples and comparative examples. [Figure 7] FIG. 7 shows the results of a weather resistance test of a composite containing metal powder. [Figure 8] FIG. 8 shows SEM images of the metal powders of the examples and the comparative examples. [Figure 9] FIG. 9 shows SEM images of cross sections of metal powders of the examples and comparative examples. [Figure 10] FIG. 10 is an enlarged SEM image of a cross section of the metal powder of the example. [Figure 11] FIG. 11 is an enlarged EDX image of a cross section of the metal powder of the example. [Figure 12] FIG. 12 is a diagram showing the results of X-ray diffraction of the metal powders of the examples and the comparative examples. [Figure 13] FIG. 13 is a diagram showing the weight ratio of Sn to Fe. [Figure 14] FIG. 14 is a flowchart showing the manufacturing process of the coil component according to the embodiment. [Figure 15] FIG. 15 is a flowchart showing a granulated powder manufacturing process according to the embodiment. [Figure 16] FIG. 16 is a flowchart showing a core manufacturing process according to the embodiment. [Figure 17] FIG. 17 is a flowchart showing a coil assembly process according to the embodiment. [Figure 18] FIG. 18 is a schematic perspective view showing a configuration of a coil component according to a modified example of the embodiment. [Figure 19] FIG. 19 is a cross-sectional view showing a configuration of a coil component according to a modified example of the embodiment. [Figure 20] FIG. 20 is a flowchart showing a manufacturing process of a coil component according to a modified example of the embodiment. [Figure 21] FIG. 21 is a flowchart showing a core manufacturing and coil assembly process according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0014] It should be noted that the embodiments described below each illustrate a specific example of the present disclosure. The numerical values, shapes, materials, components, component placement positions, connection configurations, steps (processes), and order of steps (processes) shown in the following embodiments are examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims are described as optional components.

[0015] Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, for example, the scales of the figures do not necessarily match. Furthermore, in each figure, substantially the same components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0016] Furthermore, in this specification, terms indicating the relationship between elements, such as parallel or perpendicular, terms indicating the shape of elements, such as rectangle or rectangular parallelepiped, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0017] (Embodiment) Hereinafter, a metal powder according to an embodiment, a composite magnetic body including the metal powder, a powder magnetic core including the composite magnetic body, and a coil component including the powder magnetic core will be described.

[0018] [Coil component configuration] The coil component 10 according to the present embodiment includes a magnetic part (dust core) made of a composite magnetic material containing metal powder, and a coil member at least a portion of which is provided inside the magnetic part. The coil component 10 is, for example, an inductor.

[0019] Fig. 1 is a schematic perspective view showing the configuration of a coil component 10 according to the present embodiment. Fig. 2 is an exploded perspective view showing the configuration of coil component 10 according to the present embodiment.

[0020] 1 and 2, the coil device 10 includes two powder magnetic cores 12, which are two split magnetic cores, a conductor 13, and two coil supports 14. The two powder magnetic cores 12, which are the two split magnetic cores, form a magnetic body portion, and the conductor 13 and the two coil supports 14 form a coil member.

[0021] The powder magnetic core 12 includes a base 12a and a cylindrical core 12b formed on one surface of the base 12a. Walls 12c standing upright from the edge of the base 12a are formed on two opposing sides of the four sides that make up the base 12a. The core 12b and the wall 12c are at the same height from the one surface of the base 12a. Each of the two powder magnetic cores 12 is a powder magnetic core formed by pressure-molding a composite magnetic body into a predetermined shape.

[0022] The two powder magnetic cores 12 are arranged so that their core portions 12b and wall portions 12c abut against each other. At this time, the conductor 13 is arranged so as to surround the periphery of the core portion 12b. The conductor 13 is incorporated into the powder magnetic core 12 via the coil support 14.

[0023] 2, the two coil supports 14 include an annular base portion 14a and a cylindrical portion 14b. The core portion 12b of the powder magnetic core 12 is disposed inside the cylindrical portion 14b, and the conductor 13 is disposed on the outer periphery of the cylindrical portion 14b.

[0024] [Composition of powder magnetic core] Fig. 3 is a cross-sectional view showing the internal configuration of the powder magnetic core 12. Fig. 3 shows a schematic view of the range of the internal cross section of the powder magnetic core 12 that includes the metal powder 1.

[0025] As shown in FIG. 3, the powder magnetic core 12 includes metal powder 1, which is a magnetic powder, and a non-magnetic resin member 6 that binds the metal powder 1 together. The powder magnetic core 12 may further include a coupling agent for improving the dispersibility of the metal powder 1 and modifying the surface of the metal powder 1, and an organometallic soap as a lubricant. Examples of the coupling agent include silane coupling agents, titanium-based coupling agents, titanium alkoxides, and titanium chelates. Examples of the metal soap include zinc stearate, calcium stearate, magnesium stearate, and barium stearate.

[0026] The non-magnetic resin member 6 bonds the metal powder particles 1 together. The non-magnetic resin member 6 maintains the shape of the powder magnetic core 12. The non-magnetic resin member 6 is made of an insulating resin material. The resin material making up the non-magnetic resin member 6 is, for example, a thermosetting resin. The resin material making up the non-magnetic resin member 6 may be a thermoplastic resin, or a combination of a thermosetting resin and a thermoplastic resin. Examples of thermosetting resins include epoxy resin, phenolic resin, silicone resin, and polyimide. Examples of thermoplastic resins include acrylic resin, polyethylene, polypropylene, and polystyrene. The weight of the non-magnetic resin member 6 is, for example, 1% to 10% of the weight of the metal powder 1.

[0027] A large number of metal powder particles 1 are dispersed in the dust core 12. The surface of each metal powder particle 1 is covered with a non-magnetic resin member 6. The non-magnetic resin members 6 covering the surfaces of adjacent metal powder particles 1 are bonded together. In other words, the non-magnetic resin members 6 are disposed between the metal powder particles 1, and the metal powder particles 1 are insulated from each other.

[0028] The median diameter D50 of the metal powder 1 is, for example, 5 μm or more and 40 μm or less. By setting the median diameter D50 as described above, a high filling rate and easy handling can be ensured. Furthermore, by setting the median diameter D50 of the metal powder 1 to 40 μm or less, core loss can be reduced in the high frequency range, and eddy current loss in particular can be reduced. The median diameter D50 of the metal powder 1 is the particle diameter measured by a particle size distribution analyzer using a laser diffraction scattering method, counting from the smallest particle size to the largest particle size, and the cumulative value reaches 50% of the total.

[0029] [Metal powder composition] The metal powder 1 is, for example, a soft magnetic metal particle whose main element is Fe (iron), and contains Sn (tin) in addition to Fe. The metal powder 1 may further contain Si (silicon). Each element contained in the metal powder 1 will be described below.

[0030] Fe is the main element that makes up metal powder 1. Being the main element means that its content (unit: wt% (weight%)) in metal powder 1 is the highest among multiple elements. From the perspective of the saturation magnetic flux density (Bs) of a powder magnetic core that includes metal powder 1, the Fe content in metal powder 1 is desirably 80 wt% or more and 93.7 wt% or less.

[0031] Sn has a more noble oxidation-reduction potential than Fe and has the effect of reducing magnetic loss, particularly eddy current loss in the high frequency range. Therefore, by including a predetermined amount or more of Sn in the metal powder 1, it is possible to suppress rust formation in the powder core 12 containing the metal powder 1 and reduce eddy current loss. In the metal powder 1 of this embodiment, the Sn content in the metal powder 1 is 6.3 wt% or more. An example in which the Sn content is 6.3% will be described later in the evaluation results.

[0032] Si has the effect of reducing the coercive force of the powder magnetic core, and also has the effect of increasing the electrical resistivity and reducing eddy current loss. Therefore, by including a predetermined amount or more of Si in the metal powder 1, it is possible to reduce the coercive force of the powder magnetic core and also reduce eddy current loss. Note that Si does not necessarily have to be included in the metal powder 1, and therefore in this embodiment, the Si content in the metal powder 1 is 0% or more.

[0033] The above-mentioned Sn and Si are non-magnetic elements, and as the content of Sn and Si increases in the metal powder 1, the content of Fe decreases, resulting in a decrease in the saturation magnetic flux density (Bs). To ensure that the metal powder 1 functions as a magnetic powder, predetermined upper limits are set for the content of Sn and Si relative to Fe.

[0034] Figure 4 shows the relationship between the mass magnetization value and the content of non-magnetic elements in Fe-based metal powder. The relationship is such that the smaller the mass magnetization value of the metal powder, the smaller the saturation magnetic flux density of a powder magnetic core containing the metal powder. Therefore, focusing on the mass magnetization of the Fe-based metal powder, we derived the upper limits of the respective Sn and Si contents.

[0035] Figure 4(a) shows the mass magnetization value of the Fe-based metal powder when the Sn content is changed. The Fe-based metal powder material is composed of Fe, Si, and Sn, as in the embodiment. The Si content is fixed at 5 wt%. As shown in Figure 4(a), the mass magnetization value decreases as the Sn content increases, so in order to ensure the function of the Fe-based metal powder as a magnetic powder, it is desirable that the Sn content be 20 wt% or less, for example.

[0036] Figure 4(b) shows the mass magnetization of Fe-based metal powder when the Si content is changed. Fe-based metal powder is composed of Fe and Si, and does not contain Sn. As shown in Figure 4(b), the mass magnetization value decreases as the Si content increases, so to ensure the functionality of the Fe-based metal powder as a magnetic powder, it is desirable that the Si content be 8 wt% or less. It is even more desirable that the Si content be 5.2 wt% or less.

[0037] That is, the metal powder 1 of this embodiment has a metal composition of Fe 100-x-y Si x Sn y The composition ratio satisfies the relationships 0≦x≦8 and 6.3≦y≦20. From the viewpoint of saturation magnetic flux density, it is desirable that the composition ratio satisfies x+y≦20.

[0038] As described above, the metal powder 1 has Fe as the main element, an Sn content of 6.3 wt% to 20 wt%, and an Si content of 0 wt% to 8 wt%. In particular, in this embodiment, the Sn content is 6.3 wt% or more, which can prevent rust from forming in the powder core 12 containing the metal powder 1 and can reduce eddy current loss.

[0039] Furthermore, the metal powder 1 of this embodiment has the following powder structure in order to suppress rusting and reduce eddy current loss.

[0040] As shown in Fig. 3, the metal powder 1 is composed of a large number of crystals 3. Grain boundaries 4 exist between adjacent crystals 3 within the metal powder 1. In other words, each crystal 3 is surrounded by the grain boundaries 4.

[0041] The metal powder 1 also has an internal region 2 that is the interior of the metal powder 1 and a surface region 5 that surrounds the internal region 2. The surface region 5 of the metal powder 1 is located on the outermost surface of a particle that is made up of a plurality of crystals 3 and crystal grain boundaries 4. The metal powder 1 contacts the non-magnetic resin member 6 via this surface region 5.

[0042] Metallic Sn or an Fe-Sn alloy is present in each of the grain boundaries 4 and the surface region 5. Therefore, the weight ratio of Sn to Fe is higher in each of the grain boundaries 4 and the surface region 5 than in the interior of the crystal 3, resulting in a higher Sn concentration. Note that the region with a high Sn concentration may be at least one of the grain boundaries 4 and the surface region 5.

[0043] To form regions with a high Sn concentration, for example, when producing metal powder 1 using an atomization method, the amount of Sn added to the molten metal can be set to exceed the solubility limit. When the molten metal contains an amount of Sn exceeding the solubility limit, supersaturated Sn precipitates when the molten metal is rapidly cooled from the molten state to form powder. The supersaturated Sn precipitates at the grain boundaries 4 and surface regions 5 as metallic Sn or an Fe-Sn alloy. As a result, the Sn concentration at the grain boundaries 4 and surface regions 5 is higher than that inside the crystals 3.

[0044] According to the above configuration, the crystals 3 in the metal powder 1 can be covered with the crystal grain boundaries 4 having a high weight ratio of Sn. Furthermore, according to the above configuration, the internal regions 2 of the metal powder 1 can be covered with the surface regions 5 having a high weight ratio of Sn. This makes it possible to suppress the occurrence of rust in the dust core 12 containing the metal powder 1 and reduce eddy current loss.

[0045] [Evaluation results for magnetic loss and rust] The effects of the metal powder 1 of the embodiment will be described with reference to FIGS.

[0046] Fig. 5 is a graph showing magnetic loss of the powder magnetic cores in the examples and comparative examples. Fig. 6 is a diagram showing evaluation results of magnetic loss and rust of the powder magnetic cores in the examples and comparative examples.

[0047] First, metal powder 1 of Examples 1 and 2, which are examples of the embodiment, and metal powders of Comparative Examples 1 to 5, which are different from the embodiment, will be described.

[0048] Metal powder 1 of Example 1 is a magnetic powder containing Fe as a primary element, 5.2 wt% Si, and 6.3 wt% Sn. The median diameter D50 of metal powder 1 of Example 1 is 29 μm. Metal powder 1 of Example 1 has not been heat-treated; for example, metal powder produced by atomization has not been subsequently heat-treated.

[0049] Metal powder 1 of Example 2 is a magnetic powder containing Fe as a primary element, 5.2 wt% Si, and 6.3 wt% Sn. Metal powder 1 of Example 2 is a metal powder obtained by subjecting the metal powder of Example 1 to heat treatment; for example, metal powder produced by atomization is subjected to heat treatment at 400°C for 2.5 hours in a nitrogen atmosphere. Metal powder 1 of Examples 1 and 2 has a higher Sn content than Si content. Furthermore, the Sn content of each of Examples 1 and 2 is higher than the Sn content of each of Comparative Examples 1 and 2.

[0050] The metal powder of Comparative Example 1 is a magnetic powder containing Fe as a main element, 5.4 wt% Si, and 1.1 wt% Sn. The median diameter D50 of the metal powder of Comparative Example 1 is 34 μm. The metal powder of Comparative Example 1 is not heat-treated.

[0051] The metal powder of Comparative Example 2 is a magnetic powder containing Fe as a main element, 5.4 wt% of Si, and 1.1 wt% of Sn. 1 For example, metal powder produced by atomization is heat-treated in a nitrogen atmosphere at 400°C for 2.5 hours.

[0052] The metal powder of Comparative Example 3 is a magnetic powder containing Fe as a main element and 5.5 wt% of Si. The median diameter D50 of the metal powder of Comparative Example 3 is 37 μm. The metal powder of Comparative Example 3 does not contain Sn.

[0053] The metal powder of Comparative Example 4 is a magnetic powder containing Fe as a main element, 5.3 wt% Si, and 2.9 wt% Cr. The median diameter D50 of the metal powder of Comparative Example 4 is 35 μm. The metal powder of Comparative Example 4 does not contain Sn.

[0054] The metal powder of Comparative Example 5 is an amorphous magnetic powder containing Fe as a main element and also containing Si, Cr, and B. The median diameter D50 of the metal powder of Comparative Example 5 is 26 μm. The metal powder of Comparative Example 5 does not contain Sn.

[0055] Fig. 5(a) shows a graph with magnetic loss on the vertical axis and frequency on the horizontal axis, and Fig. 5(b) shows a graph with (magnetic loss / frequency) on the vertical axis and frequency on the horizontal axis. As shown in Fig. 5(a), the magnetic loss of the powder magnetic core increases as the frequency increases, but the rate of increase in magnetic loss is smaller in Examples 1 and 2 than in Comparative Examples 1 to 5. That is, in Examples 1 and 2, magnetic loss in the high frequency range is reduced more than in Comparative Examples 1 to 5.

[0056] Figure 6 shows the magnetic loss at frequencies of 300 kHz and 500 kHz, divided into hysteresis loss and eddy current loss. Hysteresis loss is the intercept of the linear equation shown in Figure 5(b), and eddy current loss is the slope of the linear equation shown in Figure 5(b).

[0057] Specifically, the hysteresis loss and eddy current loss shown in Fig. 6 are derived based on the following (Equation 1): Note that in this example, it is assumed that the residual loss is negligible.

[0058]

number

[0059] As shown in Fig. 6, Example 1 containing 6.3 wt% Sn has a smaller eddy current loss than Comparative Example 1 containing 1.1 wt% Sn. Also, Example 2 containing 6.3 wt% Sn has a smaller eddy current loss than Comparative Example 2 containing 1.1 wt% Sn. Thus, by containing 6.3 wt% Sn, it is possible to reduce eddy current loss compared to when containing 1.1 wt% Sn.

[0060] Furthermore, Example 2, which was subjected to heat treatment, had even smaller eddy current loss than Example 1, which was not subjected to heat treatment. Thus, eddy current loss can be further reduced by subjecting metal powder 1 to heat treatment. By performing heat treatment, it becomes possible to precipitate a large amount of Sn in surface region 5 of metal powder 1, thereby further reducing eddy current loss.

[0061] Next, the evaluation results regarding rust will be described.

[0062] FIG. 7 shows the results of a weather resistance test of a composite containing metal powder.

[0063] FIG. 7(a) shows a ring-shaped composite formed from the metal powder of Comparative Example 4 and silicone resin. FIG. 7(b) shows a ring-shaped composite formed from the metal powder 1 of Example 1 and silicone resin. Each figure is an image of the composite taken with a stereomicroscope after a weather resistance test. The weather resistance test involved placing the composite under conditions of 85°C and 85 RH, and evaluating whether or not rust had developed after three weeks.

[0064] As shown in Figure 7(a), no rust occurred in the composite formed with the Cr-containing metal powder of Comparative Example 4. Also, as shown in Figure 7(b), no rust occurred in the composite formed with the metal powder 1 of Example 1.

[0065] In addition, a test similar to the weather resistance test described above was also conducted on Example 2 and Comparative Examples 1 to 3, and cases in which no rust occurred were marked as "absent," and cases in which rust occurred were marked as "present," with the results shown in the right column of FIG. 6.

[0066] 6, no rust occurred in Example 2, but rust occurred in Comparative Examples 1 to 3. By including 6.3 wt% Sn as in Examples 1 and 2, it is possible to suppress rust occurrence compared to when 1.1 wt% Sn is included as in Comparative Examples 1 and 2.

[0067] [Powder structure of metal powder] Next, the powder structures of the metal powders of the examples and comparative examples will be described with reference to Figs. 8 to 12. The SEM image shown in Fig. 8 was obtained using a scanning electron microscope (SEM) analyzer after the metal powder was attached to conductive carbon tape. The SEM and EDX images shown in Figs. 9 to 11 were obtained using an SEM or energy dispersive X-ray (EDX) analyzer after the powder core was embedded in resin and mechanically polished, and then a cross section for observation was formed by ion milling.

[0068] FIG. 8 shows SEM images of the metal powders of the examples and the comparative examples.

[0069] In Figure 8, (a) shows the metal powder 1 of Example 1, (b) shows the metal powder 1 of Example 2, and (c) shows the metal powder of Comparative Example 1. In Figure 8, the metal powder contained in the powder core is shown in gray, and the conductive carbon tape portion is shown in black. As shown in these figures, the metal powders 1 of Examples 1 and 2 have more irregularities on the spherical surfaces than the metal powder of Comparative Example 1. Furthermore, the metal powder 1 of Example 2 has more granular protrusions on its surface than the metal powder 1 of Example 1.

[0070] FIG. 9 shows SEM images of cross sections of metal powders of the examples and comparative examples.

[0071] 9(a) shows metal powder 1 of Example 1, (b) shows metal powder 1 of Example 2, and (c) shows metal powder of Comparative Example 1. Note that FIG. 9(a) is an image captured of the same powder magnetic core as FIG. 8(a), and shows an image of metal powder at a different location from FIG. 8(a). The same relationship applies to FIG. 9(b) and FIG. 8(b), and the same relationship applies to FIG. 9(c) and FIG. 8(c).

[0072] 9, the metal powder contained in the powder magnetic core is shown in gray, and the non-magnetic resin member is shown in black. In addition, in the metal powder 1 of Examples 1 and 2, the crystal grain boundaries 4 within the metal powder 1 are shown in white (a color lighter than gray). In addition, in the metal powder 1 of Example 2, the surface region 5 is shown in white (a color lighter than gray).

[0073] Fig. 10 is an enlarged SEM image of a cross section of metal powder 1 of Example 2. Fig. 11 is an enlarged EDX image of a cross section of metal powder 1 of Example 2.

[0074] 10(a) shows an SEM image of a cross section of the metal powder 1 of Example 2, similar to FIG. 9(b). In the figure, a region (b) including the surface region 5 and a region (c) including the grain boundary 4 are shown.

[0075] (b) of Figure 10 shows an enlarged view of region (b) including surface region 5, in which detection region b1 corresponding to surface region 5 and detection region b2 corresponding to the interior of crystal 3 are shown.

[0076] (c) of Figure 10 shows an enlarged view of region (c) including grain boundary 4, and within region (c) there is shown detection region c1 corresponding to grain boundary 4 and detection region c2 corresponding to the interior of crystal 3.

[0077] Figures 11(a), (b), and (c) show EDX images of the imaging regions corresponding to Figure 10(a), (b), and (c), respectively. In Figure 11, Sn elements detected by EDX are shown in gray (a color lighter than black), and elements other than Sn are shown in black. As shown in Figure 11(b), Sn elements are detected in the surface region 5 of the metal powder 1 of Example 2. As shown in Figure 11(c), Sn elements are detected in the grain boundaries 4 of the metal powder 1 of Example 2.

[0078] 10 and 11, in the metal powder 1 of Example 2, more Sn elements are present in the surface region 5 than in the interior of the crystals 3. In addition, in the metal powder 1 of Example 2, more Sn elements are present in the grain boundaries 4 than in the interior of the crystals 3. It is believed that the Sn elements are present in the form of metallic Sn or an Fe—Sn alloy.

[0079] Here, the amount and state of Sn element present in the detection regions b1, b2, c1 and c2 will be described.

[0080] FIG. 12 is a diagram showing the results of X-ray diffraction of metal powder 1 of the example.

[0081] The data shown in Fig. 12 is data obtained by acquiring an X-ray diffraction pattern using a powder X-ray diffraction (XRD (X-ray Diffraction)) device for metal powder 1 of Example 2. Note that Fig. 12 also shows the X-ray diffraction patterns of the metal powders of Example 1 and Comparative Examples 1 and 2.

[0082] FIG. 12 shows X-ray diffraction peaks corresponding to Fe and Fe—Sn alloys. For example, large peaks in FIG. 12 indicate the presence of a large amount of Fe. Small peaks at the triangle marks indicate the presence of metallic Sn, and small peaks at the star, circle, and diamond marks indicate the presence of an Fe—Sn intermetallic compound, which is an example of an Fe—Sn alloy. As shown in the figure, in Example 2, in addition to Fe, an Fe—Sn intermetallic compound was detected. In Example 2, in addition to Fe, metallic Sn and an Fe—Sn intermetallic compound were also detected.

[0083] Fig. 13 is a diagram showing the weight ratio of Sn to Fe in each of the detection regions b1, b2, c1, and c2 of the metal powder 1 of Example 2. The data shown in Fig. 13 is the weight ratio of Sn to Fe derived from the characteristic X-ray intensity ratio of Fe element and Sn element detected by EDX in the detection regions b1, b2, c1, and c2 shown in Fig. 10. Note that Fig. 13 also shows the weight ratio of Si to Fe.

[0084] 13, the weight ratio of Sn in detection region b1 corresponding to surface region 5 is 0.177, and the weight ratio of Sn in detection region b2 corresponding to the interior of crystal 3 is 0.091. Therefore, the weight ratio of Sn is greater in surface region 5 of metal powder 1 than in the interior of crystal 3. Furthermore, the weight ratio of Sn in detection region c1 corresponding to grain boundary 4 is 0.155, and the weight ratio of Sn in detection region c2 corresponding to the interior of crystal 3 is 0.067. Therefore, the weight ratio of Sn is greater in grain boundary 4 of metal powder 1 than in the interior of crystal 3.

[0085] Thus, in Example 2, the weight ratio of Sn to Fe is higher in each of the grain boundaries 4 and the surface region 5 than in the interior of the crystal 3. This powder structure makes it possible to suppress rust from occurring in the dust core 12 containing the metal powder 1 and reduce eddy current loss, as shown in Fig. 6 .

[0086] [Manufacturing method for coil parts] The following describes the manufacturing method of the metal powder, the powder magnetic core, and the coil component according to this embodiment. Fig. 14 is a flowchart showing the manufacturing process of the coil component 10 according to this embodiment.

[0087] As shown in FIG. 14 , the manufacturing process of coil component 10 according to this embodiment includes, for example, a metal powder manufacturing process (step S10), a granulated powder manufacturing process (step S20), a core manufacturing process (step S30), and a coil assembly process (step S40). In the metal powder manufacturing process, magnetic powder composed of metal powder 1 is produced. In the granulated powder manufacturing process, a composite magnetic body that constitutes powder core 12 described above is produced. In the core manufacturing process, powder core 12 is formed by molding the composite magnetic body. In the coil assembly process, powder core 12 described above, conductor 13, and coil support 14 are assembled to complete coil component 10. Each process will be described in detail below. Note that the following description will be given of a case where a thermosetting resin is used as the material for non-magnetic resin member 6.

[0088] In the metal powder manufacturing process, the atomization method is used to produce metal powder 1. When the molten metal is decomposed and rapidly cooled to form a powder, the supersaturated Sn precipitates as metallic Sn or an Fe-Sn alloy at the grain boundaries and surface regions of the powder. This increases the Sn concentration at the grain boundaries and surface regions of the powder.

[0089] Fig. 15 is a flowchart showing the granulated powder manufacturing process according to this embodiment. As shown in Fig. 15, in the granulated powder manufacturing process, first, the magnetic powder produced in the metal powder manufacturing process, the resin material serving as the raw material for the non-magnetic resin member 6, and an organic solvent are kneaded and dispersed (step S21). This produces a mixture containing the organic solvent, the magnetic powder, and the resin material. In step S21, other materials such as an organometallic soap and a coupling agent may be further added, kneaded, and dispersed, as necessary. Examples of the organic solvent that can be used include toluene, xylene, ethanol, and methyl ethyl ketone.

[0090] The kneading and dispersion are carried out by placing weighed materials such as the magnetic powder, resin material, and organic solvent in a container and mixing and dispersing them in a rotating ball mill. The kneading and dispersion are carried out, for example, at room temperature. The kneading and dispersion are not limited to those using a rotating ball mill, and other kneading and dispersion methods may also be used.

[0091] After kneading and dispersing the magnetic powder, resin material, and organic solvent, the mixture is granulated and dried (step S22). Specifically, the mixture produced in step S21 is heat-treated at a predetermined temperature. This heat treatment removes the organic solvent from the mixture, resulting in granulated powder composed of the magnetic powder and resin material. The predetermined temperature is set, for example, depending on the boiling point of the organic solvent, at a temperature at which the organic solvent can be removed.

[0092] Next, the granulated powder granulated in step S22 is further pulverized to form powder, and the granulated powder is classified into predetermined particle sizes (step S23), thereby obtaining a composite magnetic body made of the granulated powder.

[0093] 16 is a flowchart showing the core manufacturing process according to this embodiment. In the core manufacturing process, the composite magnetic body obtained in the granulated powder manufacturing process is molded to produce powder core 12.

[0094] First, the composite magnetic body is pressure-molded into a predetermined shape (step S31). Specifically, the composite magnetic body is placed in a molding die and compressed to produce a magnetic body part. The shape of the magnetic body part is, for example, the shape of the powder magnetic core 12 shown in FIG. 2. At this time, for example, 6 ton / cm 2 More than 12ton / cm 2 Uniaxial molding is performed at the following molding pressure: 8 ton / cm 2 More than 12ton / cm 2 It may be the following:

[0095] Next, the magnetic material part obtained in step S31 is heated and degreased (step S32). Degreasing is performed in an inert atmosphere such as nitrogen gas or in the air at a temperature of 200°C to 450°C. Note that the degreasing step may be omitted depending on the type and properties of the resin material used.

[0096] Thereafter, the degreased compact is annealed (heat treated) (step S33). The annealing is performed at a predetermined oxygen partial pressure, for example, at a temperature in the range of 600° C. to 1000° C. For example, an atmosphere-controlled electric furnace is used for the annealing.

[0097] Furthermore, the annealed compact is impregnated with a resin material (step S34), which may be, for example, an epoxy resin.

[0098] Through the above steps, a powder magnetic core 12 is formed, which includes magnetic powder made of metal powder 1 and a non-magnetic resin member 6, as shown in FIG. 3. Here, two powder magnetic cores 12 are formed to form the magnetic body portion. The two powder magnetic cores 12 and the coil member are assembled as follows to obtain the coil component 10.

[0099] FIG. 17 is a flowchart showing the coil assembly process according to this embodiment.

[0100] First, a coil is formed by winding the conductor 13 a predetermined number of times (step S41). Note that instead of step S41, a coil may be prepared by winding a pre-formed conductor 13 a predetermined number of times.

[0101] Next, the powder magnetic cores 12, the conductors 13, and the coil supports 14 are assembled (see FIG. 2) (step S42). In this step, the conductors 13 are arranged so as to surround the peripheries of the cores 12b of the two powder magnetic cores 12. At this time, the cylindrical portions 14b of the two coil supports 14 are arranged between the conductor 13 and the cores 12b of the two powder magnetic cores 12. Furthermore, the annular base portions 14a of the two coil supports 14 are arranged between the conductor 13 and the bases 12a of the two powder magnetic cores 12. At this time, the ends of the cylindrical portions 14b of the two coil supports 14 opposite the side on which the annular base portions 14a are formed are arranged so as to abut against each other.

[0102] The two powder magnetic cores 12 are arranged so that their core portions 12b and wall portions 12c abut against each other. In this manner, the conductor 13 is incorporated into the powder magnetic core 12 via the coil support 14, thereby assembling the coil component 10. This completes a configuration in which the conductor 13 is wound around the core portion 12b of the powder magnetic core 12. In other words, the two powder magnetic cores 12 form dust cores in which the core portion 12b penetrates the conductor 13 in the direction of the winding axis of the conductor 13.

[0103] Furthermore, the assembled coil component 10 is molded with a resin material (step S43), thereby completing the coil component 10.

[0104] (Variation) Next, a modified example of the embodiment will be described. While the coil component 10 according to the embodiment is a coil component that uses a so-called dust core as the magnetic body portion, the coil component 20 according to this modified example is a metal composite coil component in which the coil is incorporated into the magnetic body portion during the manufacturing process. In the following description of the modified example, differences from the embodiment will be mainly described, and explanations of commonalities will be omitted or simplified.

[0105] [Configuration of coil component of modified example] Fig. 18 is a schematic perspective view showing the configuration of coil device 20 according to this modified example. Fig. 19 is a cross-sectional view showing the configuration of coil device 20 according to this modified example. Fig. 19 shows a cross section taken along line XIX-XIX in Fig. 18.

[0106] 18 and 19, coil device 20 includes a magnetic material portion made of a composite magnetic material containing metal powder 1, and coil member 23 at least a portion of which is provided inside the magnetic material portion. Coil device 20 is, for example, an inductor.

[0107] Powder core 22 has a cylindrical core portion 22a near the center when viewed from above. The internal configuration of powder core 22 is the same as the internal configuration of powder core 12 shown in FIG. 3. That is, like powder core 12 of coil device 10 according to embodiment 1, powder core 22 includes magnetic powder formed from metal powder 1 and non-magnetic resin member 6. A coil member 23 is disposed around powder core 22a of powder core 22.

[0108] The coil member 23 has a winding portion 23a in which a conductor is wound multiple times, and a wiring portion 23b formed on the outside of the powder magnetic core 22. A core portion 22a of the powder magnetic core 22 is disposed as a winding axis for the wound conductor of the winding portion 23a. The conductor is made of copper, for example. The conductor is made of a material that is not destroyed by heat applied when the coil component 20 is formed.

[0109] The coil member 23 is formed integrally with the powder magnetic core 22. A wound portion 23a of the coil member 23 is embedded in the powder magnetic core 22, and a wiring portion 23b is disposed on the outside of the powder magnetic core 22.

[0110] [Modified Example of Manufacturing Method for Coil Component] A method for manufacturing the coil component 20 according to this modification will be described below.

[0111] FIG. 20 is a flowchart showing the manufacturing process of the coil device 20 according to this modification.

[0112] As shown in FIG. 20, the manufacturing process of coil component 20 includes, for example, a metal powder manufacturing process (step S10), a granulated powder manufacturing process (step S20), and a core manufacturing and coil assembly process (step S50). In the metal powder manufacturing process, magnetic powder made up of metal powder 1 is produced. In the granulated powder manufacturing process, a composite magnetic body that constitutes powder core 22 is produced. In the core manufacturing process, powder core 22, which is a magnetic body part, and coil member 23 are formed, and powder core 22 and coil member 23 are assembled to complete coil component 20. Note that the following description will be given of the case where a thermosetting resin is used as the material for non-magnetic resin member 6.

[0113] The metal powder production process and granulated powder production process in the manufacturing process of the coil component 20 are the same as the metal powder production process and granulated powder production process described in the embodiment, and therefore description thereof will be omitted.

[0114] The core manufacturing and coil assembly processes will now be described in detail.

[0115] FIG. 21 is a flowchart showing the core manufacturing and coil assembly steps according to this modification.

[0116] 21, first, the coil member 23 is formed (step S51). As with the conductor 13 described in the embodiment, the coil member 23 is formed by winding a conductor made of a metal such as copper a predetermined number of times to form the wound portion 23a. Note that, instead of step S51, a pre-formed coil member 23 may be prepared.

[0117] Next, the powder magnetic core 22, which is the magnetic material portion, and the coil member 23 are integrally molded (step S52). The material of the powder magnetic core 22 is a composite magnetic material produced in the granulated powder production process. First, the composite magnetic material classified in the granulated powder production process is placed in a molding die. At this time, the coil member 23 and the composite magnetic material are placed in the molding die so that the composite magnetic material covers the entire area of ​​the coil member 23 except for the ends of the wound portion 23a of the conductor.

[0118] Next, for example, 1 ton / cm 2 More than 6ton / cm 2 The magnetic part is produced by uniaxial molding at the following molding pressure: 4.5 ton / cm 2 More than 6ton / cm 2 The molding pressure at this time may be lower than the pressure applied in the uniaxial molding in the core manufacturing process of the coil device 10 shown in the embodiment, for example. This makes it possible to prevent the coil member 23, which is molded together with the composite magnetic body, from being destroyed during molding.

[0119] The shape of the magnetic material portion is, for example, the shape of the powder magnetic core 22 shown in Figures 18 and 19. However, the shape of the magnetic material portion is not limited to this, and other shapes may also be used.

[0120] Furthermore, the magnetic material portion is thermally cured (step S53). The magnetic material portion is thermally cured, for example, at a predetermined oxygen partial pressure and at a temperature in the range of 100°C to 300°C. This causes, for example, the thermosetting resin that constitutes the non-magnetic resin member 6 to harden. For example, an atmosphere-controlled electric furnace is used for thermally curing the magnetic material portion. Note that other methods may also be used for thermally curing the magnetic material portion.

[0121] Furthermore, after the magnetic material portion is thermally hardened, the wiring portion 23b disposed on the outside of the powder magnetic core 22 may be connected to the end of the wound portion 23a of the coil member 23.

[0122] Through the above steps, the coil component 20 in which the powder magnetic core 22 and the coil member 23 are integrated is completed.

[0123] (summary) The metal powder 1 according to this embodiment is a metal powder containing Fe as a main element and also containing Sn. The Sn content in the metal powder 1 is 6.3 wt % or more.

[0124] By setting the Sn content to 6.3 wt % or more in this way, it is possible to provide metal powder 1 that can reduce eddy current loss and inhibit rust.

[0125] Furthermore, at least one of the grain boundaries 4 in the metal powder 1 and the surface regions 5 of the metal powder 1 may have a higher weight ratio of Sn to Fe than the interior of the crystals 3 of the metal powder 1 .

[0126] According to this configuration, the crystals 3 in the metal powder 1 can be covered with the grain boundaries 4 having a high weight ratio of Sn. Furthermore, according to this configuration, the interior of the metal powder 1 can be covered with the surface region 5 having a high weight ratio of Sn. This makes it possible to provide a metal powder 1 that can reduce eddy current loss and inhibit rust.

[0127] Furthermore, the weight ratio of Sn to Fe may be higher in each of the grain boundaries 4 and the surface region 5 than in the interior of the crystal 3 .

[0128] According to this configuration, the crystals 3 in the metal powder 1 can be covered with the grain boundaries 4 having a high weight ratio of Sn, and the interior of the metal powder 1 can be covered with the surface regions 5 having a high weight ratio of Sn. This makes it possible to provide a metal powder 1 that can reduce eddy current loss and inhibit rust.

[0129] Furthermore, at least one of metallic Sn and an Fe—Sn alloy may be present in the grain boundaries 4 and the surface region 5 .

[0130] This configuration allows the crystals 3 in the metal powder 1 to be covered with at least one of metallic Sn and an Fe—Sn alloy. Also, the interior of the metal powder 1 can be covered with at least one of metallic Sn and an Fe—Sn alloy. This makes it possible to provide a metal powder 1 that can reduce eddy current loss and inhibit rust.

[0131] Furthermore, at least one of the grain boundaries 4 in the metal powder 1 and the surface regions 5 of the metal powder 1 may have a higher Sn concentration than the interior of the crystals 3 of the metal powder 1 .

[0132] According to this configuration, the crystals 3 in the metal powder 1 can be covered with the grain boundaries 4 having a high concentration of Sn. Furthermore, according to this configuration, the interior of the metal powder 1 can be covered with the surface region 5 having a high concentration of Sn. This makes it possible to provide a metal powder 1 that can reduce eddy current loss and inhibit rust.

[0133] The Sn content in the metal powder 1 may be 20 wt % or less.

[0134] This makes it possible to provide metal powder 1 that can suppress magnetic saturation.

[0135] Furthermore, the metal powder 1 may further contain Si, and the content of Si in the metal powder 1 may be 8 wt % or less.

[0136] This makes it possible to provide metal powder 1 that can reduce the coercive force of a powder magnetic core and reduce eddy current loss, for example.

[0137] The composite magnetic body of the present embodiment contains the above-described metal powder 1 and a resin.

[0138] This makes it possible to provide a composite magnetic body that can reduce eddy current loss and inhibit rust.

[0139] The powder magnetic core of the present embodiment includes the above-described composite magnetic body.

[0140] This reduces eddy current loss in the powder magnetic core and also inhibits rust.

[0141] The coil component of this embodiment includes a magnetic body portion made of the composite magnetic body described above, and a coil member at least a portion of which is provided inside the magnetic body portion.

[0142] According to this configuration, it is possible to provide a coil component including a magnetic material portion that can reduce eddy current loss and suppress rust.

[0143] (Other embodiments, etc.) The metal powder, composite magnetic body, dust core, coil component, etc. according to the embodiments and modifications of the present disclosure have been described above, but the present disclosure is not limited to these embodiments and modifications.

[0144] For example, the metal powder 1 may contain trace amounts of impurities other than Fe, Si, and Sn as contamination.

[0145] For example, the present disclosure also includes electrical components using the above-described powder magnetic cores. Examples of electrical components include inductance components such as high-frequency reactors, inductors, and transformers. The present disclosure also includes power supply devices equipped with the above-described electrical components.

[0146] Furthermore, the present disclosure is not limited to the above-described embodiment and modifications. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the present embodiment and modifications, and forms constructed by combining components of different embodiment and modifications may also be included within the scope of one or more aspects. [Explanation of symbols]

[0147] 1 metal powder 2 Internal area 3 crystals 4. Grain boundaries 5 Surface area 6 Non-magnetic resin material 10, 20 Coil parts 12 Powder magnetic core 12a base 12b Core 12c wall 13 Conductor 14 Coil support 14a base 14b Cylindrical part 22 Powder magnetic core 22a Core 23 Coil material 23a Winding section 23b Wiring Section

Claims

1. A metal powder consisting of Fe, Si and Sn, The Si content in the metal powder is 8 wt % or less, the Sn content in the metal powder is 6.3 wt % or more and less than 20 wt %, The total content of Si and Sn in the metal powder is 20 wt % or less. metal powder.

2. At least one of the grain boundaries within the metal powder and the surface region of the metal powder has a higher weight ratio of Sn to Fe than the interior of the crystals of the metal powder. The metal powder of claim 1 .

3. The grain boundaries and the surface region each have a higher Sn to Fe weight ratio than the interior of the crystal. The metal powder according to claim 2 .

4. At least one of metallic Sn and an Fe—Sn alloy is present in the grain boundaries and the surface region. The metal powder according to claim 3.

5. At least one of the grain boundaries within the metal powder and the surface region of the metal powder has a higher Sn concentration than the interior of the crystals of the metal powder. The metal powder of claim 1 .

6. A composite magnetic body comprising the metal powder according to any one of claims 1 to 5 and a resin.

7. A powder magnetic core comprising the composite magnetic body according to claim 6.

8. a magnetic body portion formed of the composite magnetic body according to claim 6; a coil member at least a portion of which is provided inside the magnetic material portion; A coil component comprising:

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