Manufacturing method of powder magnetic core

Abstract

To provide a manufacturing method of powder magnetic core capable of achieving both magnetic properties and insulation properties.SOLUTION: The manufacturing method of a powder magnetic core includes: a first step of obtaining granular powder by mixing a metal magnetic powder consisting of multiple metal magnetic particles with a resin and metal soap (step S10); a second step of obtaining a molded body by pressing and molding the obtained granulated powder (step S20); and a third step of annealing the resulting molded body (step S40). In the first step, the mixed metal soap is liquid at 25°C, and contains a Zr element.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a powder magnetic core. [Background technology]

[0002] Conventionally, oxide magnetic materials such as ferrite and metal magnetic materials have been used as magnetic materials for the magnetic cores of inductors and transformers. Magnetic cores using these magnetic materials include, for example, powder magnetic cores formed by compressing metal magnetic powder. Such powder magnetic cores have a high saturation magnetic flux density and are advantageous for miniaturizing components such as inductors and transformers. Furthermore, because powder magnetic cores can be molded using a mold, there is a high degree of freedom in the shape of the magnetic core. Furthermore, even complex shapes can be manufactured with a simple process and with high precision, making their usefulness highly sought after.

[0003] For example, Patent Document 1 discloses a method for producing a powder magnetic core in which a magnetic powder and a coupling agent are mixed and subjected to a first heat treatment, a resin is further added and the mixture is pressure-molded to form a powder magnetic core, and the powder magnetic core is then subjected to a second heat treatment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-117484 Summary of the Invention [Problem to be solved by the invention]

[0005] In dust cores, there is a need to improve the packing density of metal magnetic powder in order to reduce size and improve magnetic properties. Furthermore, when using metal magnetic powder as the magnetic powder in dust cores, it is also necessary to improve the insulation between particles of the metal magnetic powder in order to prevent damage to the dust core. However, in dust cores, improving the packing density of metal magnetic powder to improve magnetic properties reduces the gaps between particles of the metal magnetic powder, which tends to reduce insulation. Therefore, there is a problem in that it is difficult to achieve both magnetic properties and insulation in dust cores using metal magnetic powder.

[0006] Therefore, an object of the present disclosure is to provide a method for producing a powder magnetic core that can achieve both magnetic properties and insulating properties. [Means for solving the problem]

[0007] A method for manufacturing a powder magnetic core according to one embodiment of the present disclosure includes a first step of mixing a metal magnetic powder composed of a plurality of metal magnetic particles, a resin, and a metal soap to obtain a granulated powder, a second step of press-molding the obtained granulated powder to obtain a molded body, and a third step of annealing the obtained molded body, wherein the metal soap mixed in the first step is liquid at 25°C and contains Zr element. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to achieve both magnetic properties and insulating properties of a powder magnetic core. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1A is a schematic perspective view illustrating a configuration of a coil component according to an embodiment. [Figure 1B] FIG. 1B is an exploded perspective view illustrating the configuration of the coil component according to the embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the configuration of the magnetic material according to the embodiment. [Figure 3]FIG. 3 is a flowchart showing a method for manufacturing a powder magnetic core according to an embodiment. [Figure 4] FIG. 4 is a flowchart showing the steps of producing granulated powder according to the embodiment. [Figure 5] FIG. 5 is a diagram showing the relationship between the amount of Zr-based additive and magnetic permeability in powder magnetic core samples. [Figure 6] FIG. 6 is a diagram showing the relationship between the amount of Zr-based additive and the breakdown voltage in the powder magnetic core samples. [Figure 7] FIG. 7 is a diagram showing the relationship between the heat treatment temperature and the magnetic permeability in the powder magnetic core samples. [Figure 8] FIG. 8 is a diagram showing the relationship between the heat treatment temperature and the breakdown voltage for the powder magnetic core samples. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] Note 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 described in independent claims are described as optional components.

[0012] 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.

[0013] 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.

[0014] (Embodiment) A powder magnetic core according to an embodiment and a coil component using the powder magnetic core will be described below.

[0015] [composition] First, the configuration of a coil component using a powder magnetic core according to this embodiment will be described with reference to FIGS. 1A, 1B, and 2. FIG.

[0016] Fig. 1A is a schematic perspective view showing the configuration of a coil component 1 according to the present embodiment. Fig. 1B is an exploded perspective view showing the configuration of coil component 1 according to the present embodiment. Fig. 2 is a cross-sectional view showing the configuration of a powder magnetic core 12 according to the present embodiment. Fig. 2 is an enlarged view of a portion of the cross section of powder magnetic core 12.

[0017] The coil component 1 according to this embodiment is composed of a magnetic core (dust core) formed of a powder magnetic core 12 and a coil portion disposed inside the magnetic core. The coil component 1 is, for example, an inductor. In this embodiment, the coil component 1 will be described as one example of use of the powder magnetic core 12, but the powder magnetic core 12 can be used simply as a magnetic material, and the use example is not limited to the coil component 1 according to this embodiment.

[0018] 1A and 1B, the coil device 1 includes two powder magnetic cores 12, a conductor 13, and two coil supports 14. The two powder magnetic cores 12, which are two split magnetic cores, form a magnetic core, and the conductor 13 and the two coil supports 14 form a coil portion.

[0019] 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 magnetic material into a predetermined shape.

[0020] 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 a coil support 14.

[0021] 1B, each of the two coil supports 14 includes 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.

[0022] 2, the powder magnetic core 12 includes a metal magnetic powder 17 made up of a plurality of metal magnetic particles, and an insulating material 18. In the powder magnetic core 12, the metal magnetic powder 17 is compacted, and a film of insulating material 18 is formed on the surface of each metal magnetic particle of the metal magnetic powder 17. The insulating material 18 covering the surfaces of adjacent metal magnetic particles of the metal magnetic powder 17 is bonded to each other. In other words, the insulating material 18 is disposed between each metal magnetic particle of the metal magnetic powder 17, and the metal magnetic particles of the metal magnetic powder 17 are insulated from each other.

[0023] Metal magnetic powders such as Fe-Si-Al, Fe-Si, Fe-Si-Cr, Fe-Si-Cr-B, or Fe-Si-Cr-BC are used as the metal magnetic powder 17. Metal magnetic powder 17 has a higher saturation magnetic flux density than magnetic powders such as ferrite, and is therefore useful for use under large currents.

[0024] For example, when Fe-Si-Al-based metal magnetic powder is used, the composition elements are Si with a content of 8 wt% to 12 wt%, Al with a content of 4 wt% to 6 wt%, and the remaining composition elements are Fe and unavoidable impurities. Here, examples of unavoidable impurities include Mn, Ni, P, S, and C. By setting the contents of the composition elements that make up the metal magnetic powder 17 within the above composition ranges, high magnetic permeability and low coercive force can be obtained.

[0025] For example, when using an Fe-Si based metal magnetic powder, the composition elements are Si with a content of 1 wt% to 8 wt%, with the remaining composition elements being Fe and unavoidable impurities, which are the same as those described above.

[0026] For example, when using an Fe-Si-Cr based metal magnetic powder, the composition elements are Si with a content of 1 wt% to 8 wt%, Cr with a content of 2 wt% to 8 wt%, and the remaining composition elements are Fe and unavoidable impurities, which are the same as those described above.

[0027] For example, when using an Fe-Si-Cr-B based metal magnetic powder, the composition elements are Si with a content of 1 wt% to 8 wt%, Cr with a content of 2 wt% to 8 wt%, B with a content of 1 wt% to 8 wt%, and the remaining composition elements are Fe and unavoidable impurities, which are the same as those described above.

[0028] For example, when using an Fe-Si-Cr-BC based metal magnetic powder, the composition elements are Si with a content of 1 wt% to 8 wt%, Cr with a content of 2 wt% to 8 wt%, B with a content of 1 wt% to 8 wt%, C with a content of 0.01 wt% to 1 wt%, and the remaining composition elements are Fe and unavoidable impurities, such as Mn, Ni, P, and S.

[0029] The role of Si in the composition elements of the above-mentioned metal magnetic powder 17 is to reduce magnetic anisotropy and magnetostriction constant, increase electrical resistance, and reduce eddy current loss. By making the Si content in the composition elements 1 wt% or more, it is possible to obtain an improvement effect on soft magnetic properties, and by making it 8 wt% or less, it is possible to suppress a decrease in saturation magnetization and thus a decrease in DC bias characteristics.

[0030] Furthermore, the effect of improving weather resistance can be imparted by including Cr in the metal magnetic powder 17. By making the Cr content in the composition elements 2 wt% or more, the weather resistance improvement effect can be obtained, and by making it 8 wt% or less, the deterioration of soft magnetic properties can be suppressed.

[0031] The method for producing the metal magnetic powder 17 according to this embodiment is not particularly limited, and various atomization methods and various pulverization methods can be used.

[0032] The median diameter D50 of these metal magnetic powders 17 is, for example, 5.0 μm or more and 35 μm or less. In order to alleviate electric field concentration between particles, insulating properties can be ensured by making the median diameter D50 of the metal magnetic powder 17 small. Furthermore, by setting the median diameter D50 as described above, a high filling rate and ease of handling can be ensured. Furthermore, by setting the median diameter D50 of the metal magnetic powder 17 to 35 μm or less, core loss, particularly eddy current loss, can be reduced in the high-frequency range. Furthermore, the metal magnetic powder 17 may be a mixture of two or more types of powders with different median diameters D50. The median diameter D50 of the metal magnetic powder 17 is the particle diameter measured by a particle size distribution analyzer using a laser diffraction scattering method, counting from the smallest particle diameter to the total, at which the cumulative value reaches 50% of the total.

[0033] The insulating material 18 is formed so as to cover the surface of the metal magnetic powder 17, and adjacent metal magnetic particles of the metal magnetic powder 17 are insulated by the insulating material 18. The insulating material 18 contains Zr element derived from metal soap. The insulating material 18 contains, for example, a reaction product of metal soap containing Zr element as a component containing Zr element. Furthermore, the insulating material 18 may contain, for example, a residue after degreasing of a resin used in manufacturing the dust core 12 described below.

[0034] [Manufacturing method] Next, a method for manufacturing the above-mentioned powder magnetic core 12 will be described.

[0035] FIG. 3 is a flowchart showing a method for manufacturing a powder magnetic core according to this embodiment.

[0036] 3, in the method for manufacturing powder magnetic core 12 according to this embodiment, first, metal magnetic substance powder 17, resin, and metal soap are mixed together to produce granular granulated powder containing the metal magnetic substance powder 17, resin, and metal soap (step S10). Step S10 is an example of the first step. In step S10, for example, after obtaining a mixture of metal magnetic substance powder 17 and metal soap, the mixture is mixed with resin to obtain granulated powder.

[0037] 4 is a flowchart showing the steps of producing granulated powder according to this embodiment. In step S10, granulated powder is obtained by performing the steps shown in FIG.

[0038] As shown in FIG. 4, in producing the granulated powder, first, the metal magnetic powder 17 and the metal soap are mixed (step S11). This results in a mixture of the metal magnetic powder 17 and the metal soap. In step S11, the mixture does not substantially contain resin. Furthermore, the mixing in step S11 is performed at room temperature, for example, about 25°C, without any particular temperature control such as heating or cooling. Note that if the ambient temperature is low, the mixture may be heated to a temperature of about 40°C or less before mixing in order to maintain the metal soap in a liquid state.

[0039] The metal soap contains Zr element. Specifically, the metal soap is a fatty acid zirconium. The mixed metal soap is liquid at 25°C (room temperature). That is, the melting point of the metal soap is below 25°C. Therefore, in step S11, the metal magnetic powder 17 and the liquid metal soap are mixed. The liquid metal soap has, for example, a branch in the hydrocarbon chain of the fatty acid to lower the melting point. The metal soap is produced, for example, by a direct method or a metathesis method. The direct method is a method in which a fatty acid is directly reacted with a metal oxide or metal hydroxide. The metathesis method is a method in which a basic compound is reacted with a fatty acid in an aqueous solution to form a basic compound of the fatty acid, and then a metal salt containing a metal or metalloid is reacted with the basic compound.

[0040] In this way, by mixing the metal magnetic powder 17 with the liquid metal soap before mixing with the resin, the surfaces of the metal magnetic particles of the metal magnetic powder 17 and the hydrophilic parts of the metal soap can easily interact with each other, allowing the metal soap to function effectively. In addition, because the metal soap is in liquid form, it has high dispersibility, making it easier for the metal soap to act uniformly on the surfaces of the metal magnetic particles of the metal magnetic powder 17.

[0041] In step S11, a solvent may be further added to facilitate mixing of the metal magnetic powder 17 and the metal soap. If a solvent is added, the mixture is evaporated and removed from the mixture after mixing by heating at a temperature of, for example, 65°C or higher and 150°C or lower. Examples of the solvent that can be used include toluene, xylene, ethanol, isopropyl alcohol, acetone, and methyl ethyl ketone.

[0042] Next, the mixture of metal magnetic powder 17 and metal soap obtained in step S11 is subjected to heat treatment (step S12). By such heat treatment, a strong coating derived from the metal soap is formed on the surface of the metal magnetic particles of metal magnetic powder 17. The heating method is not particularly limited, but heating is performed using a heating furnace such as an electric furnace. Note that, if the mixture is heated in step S11 to remove the solvent, the heat treatment may be performed immediately after the solvent is removed.

[0043] The heat treatment in step S12 is carried out, for example, at a temperature of 200°C or higher and 800°C or lower. This allows the heat treatment to be carried out at a temperature higher than the resin hardening temperature and at a temperature at which sintering of the metal magnetic powder 17 is unlikely to occur, thereby effectively forming a coating derived from the metal soap. From the viewpoint of enhancing the functionality of the coating derived from the metal soap, the temperature condition for the heat treatment may be 200°C or higher and 600°C or lower, or 500°C or higher and 600°C or lower. The time for the heat treatment (the time for treatment at the target temperature) is, for example, 20 minutes or higher and 120 minutes or lower.

[0044] In step S12, the mixture is heat-treated in a non-oxidizing atmosphere such as nitrogen gas, for example, which prevents the mixture from being altered due to oxidation.

[0045] In this way, in the production of granulated powder, after obtaining the mixture, the mixture is subjected to heat treatment before mixing the mixture with the resin.

[0046] Next, resin is further added to the mixture that has been heat-treated in step S12, and the mixture and resin are mixed (step S13). As a result, a granulated powder containing the metal magnetic powder 17, resin, and metal soap is obtained. The mixing in step S13 is performed at room temperature, for example, about 25°C, without any temperature control such as heating or cooling.

[0047] The resin to be mixed in step S13 is used in a state in which it has been dissolved in a solvent in advance, for example. Note that the resin to be mixed in step S13 does not have to be dissolved in a solvent. As the solvent, for example, the solvents exemplified as those used in step S11 above can be used.

[0048] The resin is, for example, a thermosetting resin. Examples of thermosetting resins include epoxy resin, phenol resin, silicone resin, and polyimide resin. When the resin is a silicone resin, residues such as silicon oxide remain even after degreasing, which will be described later, and these residues become part of the insulating material 18. The resin may also be a thermoplastic resin. Two or more types of resins may be mixed in step S13.

[0049] In step S13, the mixture heat-treated in step S12 is mixed with resin, and then heated at a temperature of, for example, 65°C to 150°C to evaporate the solvent. The mixture after solvent evaporation is pulverized to obtain a granular granulated powder (composite magnetic material) with good moldability. Furthermore, this granulated powder may be classified to obtain granulated powder with particle sizes within a predetermined range. This can further improve moldability.

[0050] The mixing in steps S11 and S13 is carried out using, for example, a mortar, a mixer, a ball mill, a V-type mixer, a cross rotary, or the like.

[0051] In step S11 and / or step S13, other materials such as a coupling agent may be further added and mixed as needed. The other materials may also include insulating particles.

[0052] In the manufacturing of granulated powder, the metal magnetic substance powder 17, the resin, and the metal soap are mixed to obtain granular granulated powder containing the metal magnetic substance powder 17, the resin, and the metal soap. The resin in the granulated powder functions as a binder that binds the metal magnetic substance powder 17 in the pressure molding of the granulated powder, which will be described later.

[0053] In producing the granulated powder, the mixing ratio of the metal soap to the metal magnetic powder 17 (i.e., the ratio of the amount of metal soap added to the amount of metal magnetic powder 17 added) is, for example, 1.98 wt% or less. This can improve the magnetic properties of the powder core 12. The mixing ratio of the metal soap is, for example, 0.01 wt% or more. From the perspective of further improving the magnetic properties of the powder core 12, the mixing ratio of the metal soap may be 0.01 wt% or more and 1.0 wt% or less, or 0.3 wt% or more and 1.0 wt% or less.

[0054] In producing the granulated powder, the mixing ratio of the resin to the metal magnetic powder 17 (that is, the ratio of the amount of resin added to the amount of metal magnetic powder 17 added) is, for example, 1 wt % or more and 10 wt % or less.

[0055] Alternatively, the granulated powder may be obtained by not performing step S12 but by mixing the mixture of the metal magnetic powder 17 that has not been subjected to heat treatment and the metal soap with the resin in step S13.

[0056] In the above, the mixing of the metal magnetic powder 17, the resin, and the metal soap is performed in separate steps S11 and S13, but this is not limiting. The mixing procedure of the metal magnetic powder 17, the resin, and the metal soap may be different from that described above as long as a granular granulated powder containing the metal magnetic powder 17, the resin, and the metal soap is obtained. For example, the metal magnetic powder 17, the resin, and the metal soap may be mixed at the same time. Furthermore, a combination of materials different from that described above may be mixed in two or more separate steps.

[0057] Referring again to FIG. 3, after step S10, the granulated powder produced in step S10 is press-molded into a predetermined shape to obtain a green body (step S20). Step S20 is an example of the second step. Specifically, in step S20, the granulated powder is placed in a molding die and compressed to produce a green body. At this time, for example, 4 ton / cm 2 More than 12ton / cm 2Uniaxial molding is performed at a constant pressure as follows. After molding, the resin (binder) is cured as needed. Note that the resin may not be cured at this stage, but may be cured before degreasing, which will be described later, or by heating during degreasing.

[0058] The shape of the compact is, for example, the shape of the powder magnetic core 12 shown in Fig. 1B. However, the shape of the compact is not limited to this, and for example, the compact may have a shape in which the core portion 12b of the powder magnetic core 12 is configured as a separate body.

[0059] Next, the compact obtained in step S20 is degreased (step S30). In degreasing, for example, the compact is heated in the atmosphere at a temperature condition of 200°C or higher and 450°C or lower. This removes at least a portion of the resin contained in the compact. Note that degreasing may be performed under a predetermined oxygen partial pressure or in a non-oxidizing atmosphere.

[0060] Next, the compact degreased in step S30 is annealed (step S40), thereby obtaining the powder magnetic core 12. Step S40 is an example of the third step. The annealing in step S40 may be performed consecutively with the degreasing in step S30.

[0061] By performing annealing, the distortion that has occurred in the compact due to the compression during the pressure molding in step S20 is alleviated, and as a result, the magnetic properties can be improved.

[0062] In the annealing in step S40, the compact is heated to, for example, 400° C. or more and 1000° C. or less. From the viewpoint of the strain relaxation effect and maintaining the properties of the insulating material 18, the annealing may be performed at a temperature condition of 400° C. or more and 600° C. or less.

[0063] In step S40, the annealing is performed in a non-oxidizing atmosphere such as nitrogen gas, which prevents the compact from being oxidized and degraded. The annealing may be performed in the air or under a predetermined oxygen partial pressure.

[0064] The heating time in annealing (the time for treatment at the target temperature) is, for example, 10 minutes or more and 120 minutes or less.

[0065] It is also possible to omit the above step S30 and anneal the undegreased compact in step S40.

[0066] When manufacturing the coil component 1, the obtained powder magnetic core 12 is assembled with the above-described conductor 13 and coil support 14 to complete the coil component 1. In assembling the coil component 1, for example, first, a coil is formed by winding the conductor 13 a predetermined number of times. Next, the powder magnetic core 12, the conductor 13, and the coil support 14 are assembled. As shown in FIG. 1B , the conductor 13 is arranged so as to surround the periphery of the core portion 12b of the two powder magnetic cores 12. At this time, the cylindrical portion 14b of each of the two coil supports 14 is arranged between the conductor 13 and each of the core portions 12b of the two powder magnetic cores 12. Furthermore, the annular base portion 14a of each of the two coil supports 14 is arranged between the conductor 13 and each of the bases 12a of the two powder magnetic cores 12. At this time, the end portions of the cylindrical portions 14b of the two coil supports 14 opposite the side on which the annular base portion 14a is formed are arranged to abut against each other.

[0067] 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 1. 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 powder magnetic core 12 becomes a magnetic core in which the core portion 12b penetrates the conductor 13 in the direction of the winding axis of the conductor 13. Furthermore, the assembled coil component 1 may be molded with a resin material.

[0068] As described above, the manufacturing method of dust core 12 according to this embodiment includes a first step (step S10) of mixing metal magnetic powder 17, resin, and metal soap to obtain a granulated powder, a second step (step S20) of pressure-molding the obtained granulated powder to obtain a compact, and a third step (step S40) of annealing the obtained compact. In the first step, the mixed metal soap is liquid at 25°C and contains Zr element.

[0069] As a result, in the manufacturing process of the powder core 12, the liquid metal soap containing Zr element coats the surfaces of the metal magnetic particles of the metal magnetic substance powder 17. As a result, the liquid metal soap containing Zr element forms a strong coating on the surfaces of the metal magnetic substance particles of the metal magnetic substance powder 17, making it difficult for the metal magnetic substance particles to come into contact with each other, improving the insulating properties of the powder core 12. Furthermore, because the metal soap improves the affinity between the metal magnetic substance powder 17 and the resin, the gaps between the metal magnetic substance particles of the metal magnetic substance powder 17 tend to narrow during compaction, improving the magnetic properties of the powder core 12. Therefore, the manufacturing method of the powder core 12 according to this embodiment can achieve both good magnetic properties and good insulating properties for the powder core 12.

[0070] Furthermore, since the Zr element contained in the liquid metal soap is a tetravalent metal element, the number of fatty acids relative to the metal element is greater than in the case of metal soaps containing divalent or trivalent metal elements, and metal soaps containing the Zr element can further increase the affinity between the metal magnetic powder 17 and the resin.

[0071] [Evaluation of powder magnetic cores] Next, evaluation results of the powder magnetic cores according to the embodiments will be described. Specifically, the powder magnetic cores were fabricated as described below, and the fabricated powder magnetic cores were evaluated. Note that the present embodiments are not limited to the evaluations described below.

[0072] <Production of powder magnetic core> First, the preparation of the powder magnetic core samples used for evaluation will be described.

[0073] In preparing the samples used for evaluation, first, a metal magnetic powder, a resin, and a Zr-based additive were prepared.

[0074] The metallic magnetic powder used was Fe-Si based metallic magnetic powder.

[0075] The resin used was a modified silicone resin with methyl and phenyl groups on the side chains, dissolved in a solvent (isopropyl alcohol) in advance (concentration: 50 wt%). The amount of resin added relative to the amount of metal magnetic powder added was 2.5 wt%. Note that the amount of resin added is the amount added by weight excluding the solvent.

[0076] The Zr-based additives used were metal soaps containing Zr element (hereinafter also referred to as "Zr-containing metal soaps") or zirconium-based coupling agents (hereinafter also referred to as "Zr-based coupling agents"). The Zr-containing metal soaps used were fatty acid zirconium salts that were liquid at 25°C and had a branched hydrocarbon chain. The Zr-based coupling agents used were those that were liquid at 25°C. The amounts of Zr-based additives added relative to the amount of metal magnetic powder added were the amounts (wt%) shown in Tables 1 and 2. As shown in Table 1, no Zr-based additives were added to some samples.

[0077] Using these materials, first, a metal magnetic powder, a liquid Zr-based additive, and toluene were mixed. The mixture of the metal magnetic powder and Zr-based additive was then heated at 90°C for 90 minutes to remove the toluene, and then heat-treated for 30 minutes under the temperature conditions shown in Table 2. The heat treatment was performed under nitrogen gas. For the samples shown in Table 1, only the toluene was removed, and no heat treatment was performed. Next, a resin was added to the mixture and mixed, and the mixture was heated to remove the solvent, and then pulverized to produce a granulated powder. In other words, the granulated powder was produced using the method described above with reference to Figure 4.

[0078] The granulated powder was heated at room temperature at 8 ton / cm 2The resin was then cured to produce a ring core with an outer diameter of 14.4 mm, an inner diameter of 10.3 mm, and a thickness of 4.4 mm for evaluation of magnetic permeability. The resulting ring core was then degreased by heating at 280°C in air for 6.5 hours, and then annealed by heating to 500°C in nitrogen gas and holding for 30 minutes to produce a ring-shaped powder magnetic core sample.

[0079] The granulated powder was then heated at room temperature at 8 ton / cm 2 The resin was then cured to produce a plate-shaped compact measuring 12 mm in length, 12 mm in width, and 0.70 mm in thickness for evaluation of breakdown voltage. The resulting plate-shaped compact was then degreased by heating at 280°C in air for 6.5 hours, and then annealed by heating to 500°C in nitrogen gas and holding for 30 minutes to produce a plate-shaped powder magnetic core sample.

[0080] In the preparation of the above samples, the resin was hardened after pressure molding, but it is also possible to obtain a molded body without hardening it, and then harden the resin by heating it before degreasing or during degreasing.

[0081] <Method of calculating magnetic permeability> The magnetic permeability was determined by measuring the inductance L of the ring-shaped powder core using an LCR meter in an applied magnetic field of 0 oersted (Oe), and calculating the initial magnetic permeability (magnetic permeability μi below) using the following formula (1) (measurement frequency: 100 kHz). A high magnetic permeability μi indicates that the magnetic properties of the powder core are good.

[0082] μi=(L×le) / (μ0×Ae×n 2 ) ···(1)

[0083] Here, le is the effective magnetic path length, μ0 is the magnetic permeability of a vacuum, Ae is the cross-sectional area, and n is the number of turns of the measuring coil.

[0084] <Evaluation method for breakdown voltage> To measure the breakdown voltage, which is an indicator of insulation, a plate-shaped powder core sample was sandwiched between conductive rubber on both main surfaces, and an initial DC voltage of 10 V was applied. The applied voltage was then increased continuously at a rate of 5 V / min, and the breakdown voltage of each powder core was determined by dividing the applied voltage just before breakdown occurred by the thickness of the compact (V / mm). A high breakdown voltage indicates high insulation properties of the powder core.

[0085] <Evaluation result 1> First, the results of evaluating the magnetic properties and insulating properties by changing the type and amount of Zr-based additive used to prepare the granulated powder will be described with reference to Table 1, FIGS. 5 and 6.

[0086] Table 1 shows the type and amount of Zr-based additive, magnetic permeability, and breakdown voltage of each powder magnetic core sample used in the evaluation. FIG. 5 shows the relationship between the amount of Zr-based additive added and magnetic permeability for the samples shown in Table 1. FIG. 6 shows the relationship between the amount of Zr-based additive added and breakdown voltage for the samples shown in Table 1. In other words, FIGS. 5 and 6 are graphs of the data in Table 1. In FIG. 5, the vertical axis represents magnetic permeability, and the horizontal axis represents the amount of Zr-based additive added. In FIG. 6, the vertical axis represents breakdown voltage, and the horizontal axis represents the amount of Zr-based additive added. In addition, in Figures 5 and 6, the evaluation results of sample A1, which did not use a Zr-based additive ("No Zr-based additive" in the legend in the figure), the evaluation results of samples B1 and B2, which used a Zr-based coupling agent as a Zr-based additive ("Zr-based coupling agent" in the legend in the figure), and the evaluation results of samples C1 to C4, which used a Zr-containing metal soap ("Zr-containing metal soap" in the legend in the figure), are shown with markers of different shapes.

[0087] [Table 1]

[0088] As shown in Table 1, sample A1 is a sample to which no Zr-based additive was added. Samples B1 and B2 are samples prepared using a Zr-based coupling agent as the Zr-based additive, with the amount of Zr-based coupling agent added being varied. Samples C1 to C4 are samples prepared using a Zr-containing metallic soap as the Zr-based additive, with the amount of Zr-containing metallic soap added being varied. As mentioned above, the samples shown in Table 1 were not subjected to heat treatment in the production of the granulated powder.

[0089] As shown in Table 1 and Figure 5, samples C1 to C4, which use a Zr-containing metallic soap as a Zr-based additive, have higher magnetic permeability than sample A1, which does not contain a Zr-based additive. Furthermore, samples C1 to C4, which use a Zr-containing metallic soap, have higher magnetic permeability than samples B1 and B2, which use a Zr-based coupling agent as a Zr-based additive, when compared at the same amount of Zr-based additive. Because Zr-containing metallic soaps have long hydrocarbon chains, they have a higher affinity with resins than Zr-based coupling agents, making it easier to reduce the gaps between metal magnetic particles during molding. This is thought to be why the magnetic permeability of powder magnetic cores using Zr-containing metallic soaps has improved.

[0090] Furthermore, in the evaluation of samples C1 to C4, the magnetic permeability tended to decrease as the amount of Zr-containing metallic soap added increased. This is thought to be because the effect of the Zr-containing metallic soap is to increase the affinity between the metal magnetic powder and the resin, making it easier to narrow the gaps between the metal magnetic particles during molding. However, as the amount added increases, the amount of components derived from the Zr-containing metallic soap increases, making it easier for the gaps between the metal magnetic particles to widen. If the magnetic permeability evaluation results of samples C1 to C4 are extrapolated by linear approximation in the direction of increasing the amount of Zr-containing metallic soap added, the magnetic permeability becomes equivalent to that of sample A1 at an amount of Zr-containing metallic soap added of 1.98 wt%. In other words, it is thought that if the amount of Zr-containing metallic soap added is 1.98 wt% or less, magnetic permeability equivalent to or greater than that of sample A1, which does not contain Zr-based additives, will be achieved.

[0091] Furthermore, as shown in Table 1 and Figure 6, sample A1, which does not contain a Zr-based additive, and samples B1 and B2, which use a Zr-based coupling agent as a Zr-based additive, have very low or zero breakdown voltages, indicating almost no insulating properties. On the other hand, samples C1 to C4, which use a Zr-containing metal soap as a Zr-based additive, have high breakdown voltages, and the breakdown voltage increases as the amount of Zr-containing metal soap added increases. Zr-containing metal soaps are more likely to be present on the surfaces of metal magnetic particles than Zr-based coupling agents, and this is thought to be why powder magnetic cores using Zr-containing metal soaps have high breakdown voltages.

[0092] As described above, by adding Zr-containing metallic soap in the production of granulated powder, both magnetic properties and insulating properties are improved, and both magnetic properties and insulating properties can be achieved.

[0093] <Evaluation result 2> Next, the results of evaluation of the magnetic properties and insulating properties of samples that were heat-treated in the production of granulated powder will be described with reference to Table 2, FIGS. 7 and 8.

[0094] Table 2 shows the type and amount of Zr-based additive, heat treatment temperature, magnetic permeability, and breakdown voltage for each powder magnetic core sample used in the evaluation. FIG. 7 is a graph showing the relationship between the heat treatment temperature and magnetic permeability for the samples shown in Table 2. FIG. 8 is a graph showing the relationship between the heat treatment temperature and breakdown voltage for the samples shown in Table 2. In other words, FIGS. 7 and 8 are graphs of the data in Table 2. In FIG. 7, the vertical axis represents magnetic permeability, and the horizontal axis represents the heat treatment temperature for the heat treatment of the mixture of the metal magnetic powder and the Zr-based additive. In addition, in FIG. 8, the vertical axis represents the breakdown voltage, and the horizontal axis represents the heat treatment temperature for the heat treatment of the mixture of the metal magnetic powder and the Zr-based additive. In addition, in Figures 7 and 8, the evaluation results of samples B2 to B4, which used a Zr-based coupling agent as the Zr-based additive ("Zr-based coupling agent" in the legend in the figures), and the evaluation results of samples C2, C5, and C6, which used a Zr-containing metallic soap ("Zr-containing metallic soap" in the legend in the figures), are shown with markers of different shapes.

[0095] [Table 2]

[0096] Table 2 also shows the evaluation results of some of the samples of the powder magnetic cores shown in Table 1. The same samples in Table 2 as those in Table 1 are given the same identification symbols.

[0097] As shown in Table 2, samples B3 and B4 were prepared by using 0.50 wt% of a Zr-based coupling agent as a Zr-based additive and varying the heat treatment temperature, while samples C5 and C6 were prepared by using 0.50 wt% of a Zr-containing metallic soap as a Zr-based additive and varying the heat treatment temperature.

[0098] As shown in Table 2 and Figure 7, samples B3 and B4, in which a mixture of metal magnetic powder and a Zr-based coupling agent was heat-treated, have a lower magnetic permeability than sample B2, which was not heat-treated. In contrast, samples C5 and C6, in which a mixture of metal magnetic powder and a Zr-containing metallic soap was heat-treated, have a higher magnetic permeability than sample C2, which was not heat-treated. This is thought to be because the heat treatment fixes the Zr-containing metallic soap to the surface of the metal magnetic particles to form a coating, effectively increasing the affinity between the metal magnetic powder and the resin and making it easier to reduce the gaps between the metal magnetic particles during molding.

[0099] Furthermore, as shown in Table 2 and Figure 8, samples C5 and C6, in which a heat treatment was performed on a mixture of metal magnetic powder and Zr-containing metal soap, had a higher breakdown voltage than sample C2, which was not heat-treated. Furthermore, when a Zr-containing metal soap was used as the Zr-based additive, the breakdown voltage was more likely to increase with heat treatment than when a Zr-based coupling agent was used as the Zr-based additive. This is thought to be because the Zr-containing metal soap, which tends to be present on the surface of the metal magnetic particles, was fixed to the surface of the metal magnetic particles by heat treatment to form a coating, effectively suppressing contact between the metal magnetic powders.

[0100] <Summary> The above evaluation results of the powder magnetic cores showed that by mixing liquid Zr-containing metallic soap with metal magnetic powder at 25°C when producing the granulated powder, the magnetic permeability and breakdown voltage of the powder magnetic core increased, making it possible to achieve both the magnetic properties and insulating properties of the powder magnetic core.

[0101] Furthermore, it was found that by subjecting a mixture of Zr-containing metallic soap and metallic magnetic powder to heat treatment in the production of granulated powder, the magnetic permeability and breakdown voltage of the powder core can be further increased, and the magnetic properties and insulating properties of the powder core can be further improved.

[0102] (Other embodiments, etc.) Although the powder magnetic core according to the embodiment of the present disclosure has been described above, the present disclosure is not limited to this embodiment.

[0103] 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.

[0104] Furthermore, the present disclosure is not limited to the above-described embodiments, and various modifications conceivable by those skilled in the art to the present embodiments and configurations constructed by combining components of different embodiments may also be included within the scope of one or more aspects, as long as they do not deviate from the spirit of the present disclosure.

[0105] Below, an example of the method for manufacturing a powder magnetic core according to the present disclosure, which has been described based on the above embodiment, will be shown. The method for manufacturing a powder magnetic core according to the present disclosure is not limited to the following example.

[0106] For example, a method for manufacturing a powder magnetic core according to a first aspect of the present disclosure includes a first step of mixing a metal magnetic powder composed of a plurality of metal magnetic particles, a resin, and a metal soap to obtain a granulated powder, a second step of press-molding the obtained granulated powder to obtain a molded body, and a third step of annealing the obtained molded body, wherein the metal soap mixed in the first step is liquid at 25°C and contains Zr element.

[0107] Also, for example, a method for manufacturing a powder magnetic core according to a second aspect of the present disclosure is the method for manufacturing a powder magnetic core according to the first aspect, wherein in the first step, the mixing ratio of the metal soap to the metal magnetic powder is 1.98 wt% or less.

[0108] Furthermore, for example, a method for manufacturing a powder magnetic core according to a third aspect of the present disclosure is a method for manufacturing a powder magnetic core according to the first or second aspect, in which, in the first step, a mixture is obtained by mixing the metal magnetic powder and the metal soap, and then the mixture is mixed with the resin to obtain the granulated powder.

[0109] Furthermore, for example, a method for producing a powder magnetic core according to a fourth aspect of the present disclosure is the method for producing a powder magnetic core according to the third aspect, wherein in the first step, after obtaining the mixture, the mixture is heat-treated at a temperature of 200°C or higher and 800°C or lower before mixing the mixture with the resin.

[0110] Furthermore, for example, a method for producing a powder magnetic core according to a fifth aspect of the present disclosure is the method for producing a powder magnetic core according to the fourth aspect, wherein the temperature condition for the heat treatment is 500°C or higher and 600°C or lower.

[0111] Furthermore, for example, a method for producing a powder magnetic core according to a sixth aspect of the present disclosure is the method for producing a powder magnetic core according to the fourth or fifth aspect, wherein in the first step, the heat treatment is carried out in a non-oxidizing atmosphere. [Industrial Applicability]

[0112] The powder magnetic core according to the present disclosure can be used as a material for the magnetic core of high-frequency inductors, transformers, and the like. [Explanation of symbols]

[0113] 1 Coil parts 12 Powder magnetic core 12a base 12b Core 12c wall 13 Conductor 14 Coil support 14a base 14b Cylindrical part 17 Metal magnetic powder 18 Insulation

Claims

1. A first step of mixing a metal magnetic powder composed of a plurality of metal magnetic particles, a resin, and a metal soap to obtain a granulated powder; a second step of press-molding the obtained granulated powder to obtain a green body; a third step of annealing the obtained compact; Including, In the first step, the metal soap to be mixed is liquid at 25°C and contains Zr element. A method for manufacturing a powder magnetic core.

2. In the first step, the mixing ratio of the metal soap to the metal magnetic powder is 1.98 wt % or less. A method for producing the powder magnetic core according to claim 1.

3. In the first step, the metal magnetic substance powder and the metal soap are mixed to obtain a mixture, and then the mixture is mixed with the resin to obtain the granulated powder. The method for producing the powder magnetic core according to claim 1 or 2.

4. In the first step, after obtaining the mixture, the mixture is subjected to a heat treatment under a temperature condition of 200° C. or more and 800° C. or less before mixing the mixture with the resin. The method for producing the powder magnetic core according to claim 3 .

5. The temperature condition of the heat treatment is 500°C or higher and 600°C or lower. The method for producing the powder magnetic core according to claim 4 .

6. In the first step, the heat treatment is performed in a non-oxidizing atmosphere. The method for producing the powder magnetic core according to claim 4 .

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