Method for manufacturing powder magnetic core

Abstract

Provided is a method for manufacturing a powder magnetic core capable of improving insulating properties. This method for manufacturing a powder magnetic core comprises: a first step (step S10) in which a metal magnetic material powder comprising a plurality of metal magnetic material particles, a resin, and a metal soap are mixed to obtain a granulated powder; a second step (step S20) in which the obtained granulated powder is press-molded to obtain a molded body; and a third step (step S40) in which the obtained molded body is annealed. In the first step, the mixed metal soap is in a liquid state at 25 DEG C and contains Si element.

Description

Technical Field

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

[0002] In the past, oxide magnetic materials and metal magnetic materials, represented by ferrite, were used as magnetic materials for magnetic cores of inductors and transformers. Magnetic cores using these magnetic materials include, for example, powdered magnetic cores formed by compressing metal magnetic powder. Such powdered magnetic cores have a high saturation magnetic flux density and are advantageous for miniaturizing components such as inductors and transformers. Furthermore, powdered magnetic cores can be formed using molds, resulting in a high degree of freedom in the shape of the core. Furthermore, even complex shapes can be manufactured with high precision using simple processes, thus attracting attention for their usefulness.

[0003] For example, Patent Document 1 discloses a method for manufacturing a powder magnetic core, wherein magnetic powder and a coupling agent are mixed and subjected to a first heat treatment, resin is further added and pressure-molded to form a powder magnetic core, and the powder magnetic core is subjected to a second heat treatment.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-117484 Summary of the Invention

[0007] Increasing the filling capacity of metal magnetic powder in dust cores is required to achieve miniaturization and improve magnetic properties. Furthermore, when using metal magnetic powder as the magnetic powder in dust cores, improving the insulation between the metal magnetic powder particles is also required to prevent damage to the dust core. However, increasing the filling capacity of metal magnetic powder in dust cores to improve magnetic properties reduces the gaps between the metal magnetic powder particles, which can lead to a decrease in insulation.

[0008] Therefore, an object of the present disclosure is to provide a method for manufacturing a dust core capable of improving insulation.

[0009] One embodiment of the present invention relates to a method for manufacturing a powdered magnetic core, comprising: 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 granular granulated powder; a second step of pressurizing the obtained granulated powder to obtain a compact; and a third step of annealing the obtained compact, wherein the mixed metal soap in the first step is liquid at 25°C and contains Si element.

[0010] According to the present disclosure, the insulation properties of the powder magnetic core can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] [ Figure 1A ] Figure 1A It is a schematic perspective view showing the structure of a coil component according to an embodiment.

[0012] [ Figure 1B ] Figure 1B It is an exploded perspective view showing the structure of the coil component according to the embodiment.

[0013] [ Figure 2 ] Figure 2 It is a cross-sectional view showing the structure of a magnetic material according to an embodiment.

[0014] [ Figure 3 ] Figure 3 This is a flowchart showing a method for manufacturing a dust core according to an embodiment.

[0015] [ Figure 4 ] Figure 4 This is a flowchart showing the steps of producing granulated powder according to the embodiment.

[0016] [ Figure 5 ] Figure 5 This is a graph showing the relationship between the breakdown voltage and the magnetic permeability of the powder core samples.

[0017] [ Figure 6 ] Figure 6 This is a graph showing the relationship between the breakdown voltage and the magnetic permeability of the powder core samples. DETAILED DESCRIPTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0019] In addition, the embodiments described below each represent a specific example of the present disclosure. The numerical values, shapes, materials, constituent elements, configuration positions of constituent elements, connection methods, steps (processes), and the order of steps (processes) shown in the following embodiments are examples and are not intended to limit the present disclosure. In addition, the constituent elements in the following embodiments that are not described in the independent claims are described as arbitrary constituent elements.

[0020] In addition, each figure is a schematic diagram and may not be strictly illustrated. Therefore, for example, the scales etc. in each figure may not be consistent. In addition, in each figure, the same reference numerals are used for substantially the same structure, and repeated descriptions are omitted or simplified.

[0021] In addition, in this specification, terms such as parallel or orthogonal that indicate the relationship between elements, terms such as rectangle or cuboid that indicate the shape of elements, and numerical ranges do not express only strict meanings, but also indicate that they also include essentially the same range, such as a difference of several percent.

[0022] (Implementation Method)

[0023] Hereinafter, a powder magnetic core according to an embodiment and a coil component using the powder magnetic core will be described.

[0024] [constitute]

[0025] First, refer to Figure 1A 、 Figure 1B and Figure 2 The configuration of a coil component using the powder magnetic core of this embodiment will be described.

[0026] Figure 1A It is a schematic perspective view showing the structure of the coil component 1 according to the present embodiment. Figure 1B It is an exploded perspective view showing the structure of the coil component 1 according to the present embodiment. Figure 2 It is a cross-sectional view showing the structure of the dust core 12 according to the present embodiment.

[0027] The coil component 1 of this embodiment is composed of a magnetic core (compressed powder iron core) formed of a powdered magnetic core 12 and a coil portion arranged inside the magnetic core. The coil component 1 is, for example, an inductor. In this embodiment, the coil component 1 is described as one example of the use of the powdered magnetic core 12. However, the powdered magnetic core 12 can be used only as a magnetic material, and the use example is not limited to the coil component 1 of this embodiment.

[0028] like Figure 1A and Figure 1B As shown, coil component 1 includes two powder cores 12, a conductor 13, and two coil supports 14. The two powder cores 12 as two split cores form a magnetic core, and the conductor 13 and two coil supports 14 form a coil portion.

[0029] The powder core 12 includes a base 12a and a cylindrical core portion 12b formed on one surface of the base 12a. Furthermore, wall portions 12c are formed on two opposing sides of the base 12a, extending from the edge of the base 12a. The core portion 12b and the wall portion 12c are positioned at the same height from one surface of the base 12a. Each of the two powder cores 12 is formed by pressing a magnetic material into a predetermined shape.

[0030] The two powder cores 12 are arranged so that their core portions 12b and wall portions 12c abut against each other (i.e., one core portion 12b abuts against the other core portion 12b, and one wall portion 12c abuts against the other wall portion 12c). At this point, the conductor 13 is arranged so as to surround the core portions 12b. The conductor 13 is assembled to the powder core 12 via a coil support 14.

[0031] like Figure 1B As shown, the two coil supports 14 include an annular base portion 14a and a cylindrical portion 14b. The core portion 12b of the powder core 12 is disposed inside the cylindrical portion 14b, and the conductor 13 is disposed on the outer periphery of the cylindrical portion 14b.

[0032] like Figure 2 As shown, the powder core 12 includes a metal magnetic powder 17 composed of a plurality of metal magnetic particles and an insulating material 18. In the powder core 12, the metal magnetic powder 17 is compacted by pressure, and the insulating material 18 is formed into a film 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 adheres to each other. In other words, the insulating material 18 is disposed between each metal magnetic particle of the metal magnetic powder 17 and adjacent metal magnetic particles, thereby isolating each metal magnetic particle of the metal magnetic powder 17 from adjacent metal magnetic particles.

[0033] Metal magnetic powder 17 uses Fe-Si-Al, Fe-Si, Fe-Si-Cr, or Fe-Si-Cr-B based metal magnetic powders. Metal magnetic powder 17 has a higher saturation magnetic flux density than magnetic powders such as ferrite, and is therefore useful for use with high currents.

[0034] For example, when using Fe-Si-Al based metal magnetic powder, the composition includes Si at 8% to 12% by weight, Al at 4% to 6% by weight, and the remainder being Fe and unavoidable impurities. Examples of unavoidable impurities include Mn, Ni, P, S, and C. By setting the content of the elements constituting the metal magnetic powder 17 within the above composition range, high magnetic permeability and low coercivity can be achieved.

[0035] For example, when Fe-Si based metal magnetic powder is used, the content of Si as a constituent element is 1 wt% to 8 wt% inclusive, and the remainder is Fe and inevitable impurities.

[0036] For example, when using Fe-Si-Cr based metal magnetic powder, the composition includes Si at 1% to 8% by weight, Cr at 2% to 8% by weight, and the remainder being Fe and unavoidable impurities. The unavoidable impurities are the same as those described above.

[0037] For example, when using Fe-Si-Cr-B based metal magnetic powder, the composition includes Si at 1% to 8% by weight, Cr at 2% to 8% by weight, B at 1% to 8% by weight, and the remaining composition is Fe and unavoidable impurities. The unavoidable impurities are the same as those described above.

[0038] Si, a component of the metal magnetic powder 17, reduces magnetic anisotropy and magnetostriction, increases electrical resistance, and reduces eddy current loss. By setting the Si content to 1% by weight or greater, soft magnetic properties are improved. By setting the Si content to 8% by weight or less, a decrease in saturation magnetization can be suppressed, thereby minimizing the degradation of DC superposition characteristics.

[0039] Furthermore, the metal magnetic powder 17 can improve weather resistance by containing Cr. Setting the Cr content in the composition to 2 wt% or more improves weather resistance, while setting it to 8 wt% or less suppresses deterioration of soft magnetic properties.

[0040] The method for producing the metal magnetic powder 17 of this embodiment is not particularly limited, and various atomization methods and various pulverization methods can be used.

[0041] The median particle size D50 of these metal magnetic powders 17 is, for example, not less than 5.0 μm and not more than 35 μm. In order to alleviate the electric field concentration between particles, the median particle size D50 of the metal magnetic powder 17 is made smaller, thereby ensuring insulation. In addition, by setting the median particle size D50 to the above-mentioned value, a high filling rate and handleability can be ensured. In addition, by setting the median particle size D50 of the metal magnetic powder 17 to not more than 35 μm, the core loss in the high-frequency region can be reduced, especially the eddy current loss can be reduced. It should be noted that the median particle size D50 of the metal magnetic powder 17 is the particle size measured by the laser diffraction scattering method, which is the particle size when the cumulative value reaches 50% of the total, starting from the smallest particle size and counting using a particle size distribution meter.

[0042] Insulating material 18 is formed to cover the surface of metal magnetic powder 17, and adjacent metal magnetic particles of metal magnetic powder 17 are insulated from each other by insulating material 18. Insulating material 18 contains elemental Si derived from a metal soap. For example, insulating material 18 contains a product of a metal soap containing elemental Si as a component containing elemental Si. Alternatively, insulating material 18 may contain, for example, residue from degreasing the resin used in manufacturing the dust core 12, described later.

[0043] [Manufacturing method]

[0044] Next, a method for manufacturing the above-mentioned dust core 12 will be described.

[0045] Figure 3 1 is a flowchart showing a method for manufacturing a dust core according to the present embodiment.

[0046] like Figure 3 As shown, in the method for manufacturing the dust core 12 according to this embodiment, first, metal magnetic powder 17, resin, and metal soap are mixed to produce granular powder containing the metal magnetic 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 containing the metal magnetic powder 17 and the metal soap, the mixture is mixed with the resin to produce granular powder.

[0047] Figure 4 This is a flow chart showing the production process of granulated powder according to this embodiment. Figure 4 The granulated powder is obtained by the steps shown.

[0048] like Figure 4 As shown, in the production of granulated powder, metal magnetic powder 17 and metal soap are first mixed (step S11). This produces a mixture of metal magnetic powder 17 and metal soap. In step S11, the mixture contains substantially no resin. Furthermore, mixing in step S11 is performed at room temperature of approximately 25°C without any special temperature control, such as heating or cooling. It should be noted that in low ambient temperatures, mixing can be performed by heating to a temperature of approximately 40°C or less to maintain the metal soap in a liquid state.

[0049] The metal soap contains Si element. Specifically, the metal soap is fatty acid silicon. In addition, the mixed metal soap is liquid at 25°C (normal temperature). That is, the melting point of the metal soap is lower than 25°C. Therefore, in step S11, the metal magnetic powder 17 is mixed with the liquid metal soap. The liquid metal soap has a branched chain in the hydrocarbon chain of the fatty acid in order to lower the melting point. The metal soap is manufactured, for example, by a direct method or a double decomposition method. The direct method is a method of directly reacting a fatty acid with a metal oxide or a metal hydroxide. The double decomposition method is a method of reacting an alkaline compound with a fatty acid in an aqueous solution to produce an alkaline compound of the fatty acid, and then reacting it with a metal salt containing a metal or a semimetal.

[0050] 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 portion of the metal soap can interact easily, allowing the metal soap to effectively function. Furthermore, since the metal soap is in liquid form, it has high dispersibility, allowing the metal soap to easily and evenly act on the surfaces of the metal magnetic particles of the metal magnetic powder 17.

[0051] In step S11, a solvent may be further added to facilitate mixing of the metal magnetic powder 17 and the metal soap. When a solvent is added, after mixing, the mixture is heated at a temperature of 65°C to 150°C to evaporate the solvent and remove it from the mixture. Examples of the solvent include toluene, xylene, ethanol, isopropyl alcohol, acetone, or methyl ethyl ketone.

[0052] Next, the mixture of metal magnetic powder 17 and metal soap obtained in step S11 is heat treated (step S12). This heat treatment forms a strong coating from the metal soap on the surface of the metal magnetic particles of metal magnetic powder 17. The heating method is not particularly limited, and heating can be performed using a heating furnace such as an electric furnace. In addition, if the mixture is heated in step S11 to remove the solvent, the heat treatment can also be performed continuously with the removal of the solvent.

[0053] The heat treatment in step S12 is performed at a temperature of, for example, 200°C to 800°C. This allows the heat treatment to be performed at a temperature higher than the resin curing temperature and at a temperature at which sintering of the metal magnetic powder 17 is less likely to occur, thereby effectively forming a film derived from the metal soap. To enhance the functionality of the film derived from the metal soap, the heat treatment temperature may be 400°C to 600°C. The heat treatment time (the time spent at the target temperature) is, for example, 20 minutes to 120 minutes.

[0054] In step S12, the mixture is heat-treated in a non-oxidizing atmosphere such as nitrogen, thereby suppressing degradation of the mixture due to oxidation.

[0055] Thus, in the production of granulated powder, after obtaining the mixture, the mixture is heat-treated before being mixed with the resin.

[0056] Next, resin is added to the mixture heat-treated in step S12, and the mixture is mixed with the resin (step S13). This produces a granulated powder containing a mixture of metal magnetic powder 17, resin, and metal soap. The mixing in step S13 is performed at room temperature, approximately 25°C, without any particular temperature control, such as heating or cooling.

[0057] The resin mixed in step S13 is used in a state of being dissolved in a solvent in advance, for example. Alternatively, the resin mixed in step S13 may not be dissolved in a solvent. As the solvent, for example, the solvents exemplified as the solvents used in step S11 above can be used.

[0058] The resin is, for example, a thermosetting resin. Examples of thermosetting resins include epoxy resins, phenolic resins, silicone resins, and polyimide resins. Even after degreasing (described below), residues such as silicon oxide remain, and these residues become part of insulating material 18. Alternatively, the resin may be a thermoplastic resin. Furthermore, in step S13, two or more resins may be mixed.

[0059] In step S13, the mixture heat-treated in step S12 is mixed with a resin and then heated, for example, at a temperature of 65°C to 150°C to evaporate the solvent. The mixture after evaporation is pulverized to obtain a granular powder (composite magnetic material) with good formability. Furthermore, the granulated powder can be classified to obtain granulated powder with a particle size uniformly within a predetermined range. This can further improve formability.

[0060] The mixing in step S11 and step S13 is performed using, for example, a mortar, a mixer, a ball mill, a V-type mixer, or a cross-rotating machine.

[0061] In step S11 or step S13, other materials such as a coupling agent may be further added and mixed as needed. In addition, insulating particles may be included in the other materials.

[0062] Through the above steps, metal magnetic powder 17, resin, and metal soap are mixed to produce granular granulated powder containing a mixture of metal magnetic powder 17, resin, and metal soap. The resin in the granulated powder functions as a binder that binds metal magnetic powder 17 during the pressurization of the granulated powder, which will be described later.

[0063] In the production of 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, 2.0 wt% or less. This effectively improves the insulation of the powder core 12. In addition, from the perspective of further improving the insulation of the powder core 12, the mixing ratio of the metal soap can be from 0.01 wt% to 2.0 wt%, or from 0.025 wt% to 2.0 wt%. In addition, from the perspective of improving the magnetic properties in addition to the insulation of the powder core 12, the mixing ratio of the metal soap can be from 0.025 wt% to 0.5 wt%. In addition, wt% means weight%.

[0064] In the preparation of granulated powder, the mixing ratio of the resin to the metal magnetic powder 17 (ie, the ratio of the added amount of the resin to the added amount of the metal magnetic powder 17 ) is, for example, 1 wt % or more and 10 wt % or less.

[0065] Alternatively, the above-mentioned step S12 may not be performed, and in step S13 , a mixture of the metal magnetic powder 17 and the metal soap that has not been subjected to heat treatment may be mixed with a resin to obtain granulated powder.

[0066] In the above description, the mixing of metal magnetic powder 17, resin, and metal soap is performed separately in steps S11 and S13, but this is not limiting. As long as a granulated powder containing a mixture of metal magnetic powder 17, resin, and metal soap is obtained, the order of mixing metal magnetic powder 17, resin, and metal soap may be different from the above. For example, metal magnetic powder 17, resin, and metal soap may be mixed all at once. Furthermore, different combinations of materials may be mixed in two or more separate steps.

[0067] Refer again Figure 3 After step S10, the granulated powder obtained in step S10 is pressed and formed into a predetermined shape to obtain a compact (step S20). Step S20 is an example of the second step. Specifically, in step S20, the granulated powder is placed in a forming mold and compressed to produce a compact. At this time, for example, 4 tons / cm 2 Above and 12 tons / cm 2Uniaxial forming is performed at the following constant pressure. Furthermore, after forming, the resin (binder) may be cured as needed. Alternatively, the resin may be cured before degreasing, described later, or by heating during degreasing. 1 ton = 1000 kg, and 1 kg weight = 9.80665 N.

[0068] The shape of the molded body is, for example, Figure 1B The shape of the powder core 12 is shown. The shape of the compact is not limited to this, and for example, the core portion 12b of the powder core 12 may be a separate body.

[0069] Next, the molded body obtained in step S20 is degreased (step S30). During degreasing, the molded body is heated, for example, in air at a temperature of 200°C to 450°C. This removes at least a portion of the resin contained in the molded body. Degreasing can be performed under a predetermined oxygen partial pressure or in a non-oxidizing atmosphere.

[0070] Next, the compact degreased in step S30 is annealed (step S40). Thus, the powder magnetic core 12 is obtained. Step S40 is an example of the third step. The annealing in step S40 may be performed continuously with the degreasing in step S30.

[0071] Annealing can alleviate the strain generated in the compact due to compression during the press forming in step S20, thereby improving the magnetic properties.

[0072] In the annealing in step S40 , the formed body is heated at, for example, 400° C. to 1000° C. In order to alleviate the strain and maintain the characteristics of the insulating material 18 , the annealing may be performed at 400° C. to 600° C.

[0073] In step S40, annealing is performed in a non-oxidizing atmosphere such as nitrogen. This suppresses degradation of the formed body due to oxidation. Alternatively, annealing may be performed in the atmosphere or under a predetermined oxygen partial pressure.

[0074] The heating time in annealing (the time for treatment at the target temperature) is, for example, 10 minutes to 120 minutes.

[0075] Alternatively, the above-mentioned step S30 may not be performed, and the formed body that has not been degreased may be annealed in step S40.

[0076] When manufacturing the coil component 1, the obtained powder core 12, the conductor 13 and the coil support 14 are assembled 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. Then, the powder core 12, the conductor 13 and the coil support 14 are assembled. Figure 1B As shown, the conductor 13 is arranged so as to surround the core portions 12b of the two powder cores 12. At this time, the cylindrical portion 14b of each of the two coil supports 14 is arranged between the conductor 13 and the core portions 12b of each of the two powder cores 12. In addition, the annular base portion 14a of each of the two coil supports 14 is arranged between the conductor 13 and the base 12a of each of the two powder cores 12. At this time, the ends of the cylindrical portions 14b of the two coil supports 14 on the side opposite to the side where the annular base portion 14a is formed are arranged to abut each other.

[0077] In addition, the two pressed powder cores 12 are arranged in such a manner that their respective core portions 12b and wall portions 12c abut against each other (i.e., the core portion 12b of one side abuts against the core portion 12b of the other side, and the wall portion 12c of one side abuts against the wall portion 12c of the other side). In this way, the conductor 13 is loaded into the pressed powder core 12 via the coil support 14, thereby being assembled into the coil component 1. Thus, the structure in which the conductor 13 is wound around the core portion 12b of the pressed powder core 12 is completed. That is, the pressed powder core 12 becomes a magnetic core in which the core portion 12b passes through the conductor 13 in the winding axis direction of the conductor 13. In addition, the assembled coil component 1 can also be molded using a resin material.

[0078] As described above, the method for manufacturing the dust core 12 of this embodiment includes: a first step (step S10) of mixing metal magnetic powder 17, resin, and metal soap to obtain granular granulated powder; a second step (step S20) of compacting the obtained granulated powder under pressure 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 elemental Si.

[0079] Thus, during the manufacturing process of the dust core 12, the liquid metal soap containing the Si element covers the surfaces of the metal magnetic particles of the metal magnetic powder 17. As a result, the liquid metal soap containing the Si element forms a strong coating on the surfaces of the metal magnetic particles of the metal magnetic powder 17, making it difficult for the metal magnetic particles to come into contact with each other, thereby improving the insulation properties of the dust core. Therefore, the method for manufacturing the dust core 12 according to this embodiment can improve the insulation properties of the dust core 12. In addition, the metal soap improves the affinity between the metal magnetic powder 17 and the resin, thereby easily reducing the gaps between the metal magnetic particles of the metal magnetic powder 17 during press molding, thereby improving the magnetic properties of the dust core 12.

[0080] [Evaluation of Dust Cores]

[0081] Next, the evaluation results of the dust cores according to the embodiment will be described. Specifically, dust cores were produced as described below, and the produced dust cores were evaluated. It should be noted that this embodiment is not limited in any way by the evaluation described below.

[0082] <Production of Dust Cores>

[0083] First, the preparation of samples of the dust core used for evaluation will be described.

[0084] In preparing samples used for evaluation, first, metal magnetic powder, resin, and Si-based additives were prepared.

[0085] As the metal magnetic powder, the metal magnetic powder shown in Tables 1 and 2 below (Fe—Si—Cr-based metal magnetic powder or Fe—Si-based metal magnetic powder) was used.

[0086] The resin used was a modified silicone resin having methyl and phenyl groups in its side chains dissolved in a solvent (isopropyl alcohol) (concentration 50%). The amount of resin added relative to the amount of metal magnetic powder added was as shown in Tables 1 and 2 (wt%). The amount of resin added is based on the weight excluding the solvent.

[0087] The Si-based additive used was a metal soap containing Si element (hereinafter also referred to as "Si-containing metal soap") or a silane coupling agent. The Si-containing metal soap used was a fatty acid silicon that was liquid at 25°C and had a branched hydrocarbon chain. The silane coupling agent used was a coupling agent that was liquid at 25°C. The amount of Si-based additive added relative to the amount of metal magnetic powder added was the amount (wt%) shown in Tables 1 and 2.

[0088] Using these materials, first, metal magnetic powder, liquid Si-based additive and toluene are mixed. Then, the mixture of metal magnetic powder and Si-based additive, from which toluene has been removed by heating at 90°C for 90 minutes, is heat-treated for 30 minutes under the temperature conditions shown in Table 2. The heat treatment is carried out under nitrogen. In addition, for the samples shown in Table 1, only toluene is removed, and no heat treatment is performed. Next, resin is added to the mixture and mixed, and the solvent is removed by heating and then pulverized to produce granular granulated powder. That is, by using the above Figure 4 Granulated powder was prepared by the method described.

[0089] The prepared granulated powder was heated to 8 ton / cm 2 The resin was then pressed and molded with a pressure of 100°C. The resin was then cured to produce a toroidal 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 toroidal core was then heated at 280°C in air for 6.5 hours for degreasing. The core was then annealed under nitrogen at the temperatures shown in Tables 1 and 2 for 30 minutes to produce toroidal powder core samples.

[0090] In addition, the prepared granulated powder was heated at room temperature at a weight of 8 ton / cm 2 The molded plate was press-formed with a pressure of 100°C, and the resin was then cured to produce a plate-shaped compact with a length of 12 mm, a width of 12 mm, and a thickness of 0.70 mm for evaluation of the breakdown voltage. The resulting plate-shaped compact was then heated at 280°C in air for 6.5 hours for degreasing. The compact was then annealed under nitrogen at the temperatures shown in Tables 1 and 2 and held for 30 minutes to produce a plate-shaped powder core sample.

[0091] It should be noted that in the preparation of the above samples, the resin was cured after press molding. However, it is also possible to obtain a molded body without curing, and then cure the resin by heating before or during degreasing.

[0092] <Calculation Method of Magnetic Permeability>

[0093] For the ring-shaped powder core, the inductance L under an applied magnetic field of 0 oersted (Oe) was measured using an LCR meter. The initial magnetic permeability (hereinafter referred to as magnetic permeability μi) was calculated according to the following formula (1), and the magnetic permeability was obtained from this (measurement frequency 100 kHz). A high magnetic permeability μi indicates good magnetic properties of the powder core.

[0094] μi=(L×le) / (μ0×Ae×n 2 ) (1)

[0095] In addition, le represents the effective magnetic path length, μ0 represents the magnetic permeability of vacuum, Ae represents the cross-sectional area, and n represents the number of turns of the measuring coil. In addition, Oersted (Oe) is the unit of magnetic field strength, 1Oe = (1 / 4π)10 3 A / m. π is the circumference of a circle.

[0096] <Evaluation Method of Destruction Voltage>

[0097] To measure the breakdown voltage, an indicator of insulation performance, a sample of a plate-shaped powder core is sandwiched between conductive rubber sheets placed on both main surfaces. An initial DC voltage of 10V is applied, and the applied voltage is continuously increased at a rate of 5V / min. The applied voltage value immediately before insulation breakdown is divided by the thickness of the compact (V / mm) to obtain the breakdown voltage of each powder core. A higher breakdown voltage indicates higher insulation performance. Note that 1 minute = 60 seconds.

[0098] <Evaluation Results 1>

[0099] First, refer to Table 1 and Figure 5 The following describes the results of evaluating magnetic properties and insulation properties by changing the type and amount of Si-based additive used in preparing the granulated powder.

[0100] Table 1 shows the type of metal magnetic powder, the amount of resin added, the type and amount of Si-based additives added, the annealing temperature, the magnetic permeability, and the breakdown voltage of each of the dust core samples used in the evaluation. Figure 5 This is a graph showing the relationship between the breakdown voltage and magnetic permeability in the samples shown in Table 1. Figure 5 This is a graph that plots the data in Table 1. Figure 5 In the figure, the vertical axis represents the magnetic permeability and the horizontal axis represents the breakdown voltage. Figure 5 In the figure, it can be seen that the samples that are plotted on the upper right are more likely to have both magnetic properties and insulation properties. Figure 5 In the figures, the evaluation results of Sample A1, which used only a silane coupling agent as a Si-based additive ("Silane Coupling Agent" in the figure legend), and the evaluation results of Samples B1 to B4, which used only Si-containing metal soap ("Si-containing Metal Soap" in the figure legend), are represented by symbols of different shapes. In addition, each symbol is indicated with the sample identification code and the amount of Si-based additive added.

[0101] Table 1

[0102]

[0103] As shown in Table 1, Sample A1 was prepared using a silane coupling agent at an addition rate of 0.05 wt% as the Si-based additive. Samples B1 to B4 were prepared using Si-containing metal soap as the Si-based additive, with the addition rates of the Si-containing metal soap varying from one another. As mentioned above, the samples shown in Table 1 did not undergo heat treatment during the preparation of the granulated powders.

[0104] As shown in Table 1 and Figure 5 As shown, when heat treatment is not performed during the preparation of the granulated powder, Sample A1, which uses a silane-based coupling agent as the Si-based additive, has a very low breakdown voltage and exhibits almost no insulating properties. On the other hand, Samples B1 to B4, which use Si-containing metal soap as the Si-based additive, have high breakdown voltages, and the breakdown voltage increases with increasing amounts of Si-containing metal soap added. Compared to silane-based coupling agents, Si-containing metal soaps are more likely to form a film on the surface of metallic magnetic particles and are therefore more likely to be present on the surface of metallic magnetic particles. Therefore, it is believed that the breakdown voltage is higher in powder cores using Si-containing metal soaps.

[0105] Furthermore, samples B1 to B3, which contained Si-containing metal soap at an addition level of 0.25 wt% or less, exhibited higher magnetic permeabilities than sample A1, which used a silane coupling agent. Si-containing metal soaps have long hydrocarbon chains and, compared to silane coupling agents, have a higher affinity for resins, making it easier to reduce gaps between metal magnetic particles during molding. Therefore, it is believed that the magnetic permeability of the powder cores using Si-containing metal soaps is improved.

[0106] Furthermore, in the evaluation of samples B1 to B4, the magnetic permeability tended to decrease as the amount of Si-containing metal soap added increased. This is believed to be because the Si-containing metal soap improves the affinity between the metal magnetic powder and the resin, making it easier to narrow the gaps between the metal magnetic particles during molding. On the other hand, as the amount added increases, the Si-containing metal soap-derived components increase, and the gaps between the metal magnetic particles tend to widen.

[0107] <Evaluation Results 2>

[0108] Next, refer to Table 2 and Figure 6 The evaluation results of the magnetic characteristics and insulation properties of samples subjected to heat treatment temperatures during the preparation of granulated powder will be described.

[0109] Table 2 shows the type of metal magnetic powder, the amount of resin added, the type and amount of Si-based additives, heat treatment temperature, annealing temperature, pressure during molding, magnetic permeability, and breakdown voltage of each of the dust core samples used in the evaluation. Figure 6 This is a graph showing the relationship between the breakdown voltage and magnetic permeability in the samples shown in Table 2. That is, Figure 6 This is a graph that plots the data in Table 2. Figure 6In the figure, the vertical axis represents the magnetic permeability and the horizontal axis represents the breakdown voltage. Figure 6 In the figure, it can be seen that the samples that are plotted on the upper right are more likely to have both magnetic properties and insulation properties. Figure 6 In the figures, the evaluation results of samples A1 and A2, which used only a silane coupling agent as a Si-based additive ("Silane coupling agent" in the legend of the figure), and the evaluation results of samples B2 and B5 to B9, which used only a Si-containing metal soap ("Si-containing metal soap" in the legend of the figure), are represented by symbols of different shapes. In addition, each symbol indicates the sample identification code, annealing temperature, and heat treatment temperature.

[0110] Table 2

[0111]

[0112] Table 2 also shows the evaluation results of some of the dust core samples shown in Table 1. The same samples as those in Table 1 are given the same identification symbols in Table 2.

[0113] As shown in Table 2, Sample A2 was prepared using a silane coupling agent at a 0.05 wt% addition rate as a Si-based additive, followed by heat treatment and annealing at 500°C. Samples B5 to B9 were prepared using a Si-containing metal soap at a 0.05 wt% addition rate as a Si-based additive, with the heat treatment and annealing temperatures varied. It should be noted that, as shown in Table 2, the compositions of the metal magnetic powders in Samples A1 and B2, which were not heat-treated during granulation, differed from those in Samples A2 and B5 to B9, which were heat-treated during granulation.

[0114] As shown in Table 2 and Figure 6 As shown in Figure 2, when comparing samples B5 to B9 using Si-containing metal soaps and sample A2 using a silane coupling agent, the magnetic permeability of all samples using the same Si-based additive increased compared to samples A1 and B2 that were not heat-treated. This is believed to be because the Si-based additive adheres to the surface during heat treatment, making it easier to reduce the gaps between the metal magnetic particles during molding.

[0115] In addition, in sample A2 using a silane coupling agent, the breakdown voltage increased significantly by heat treatment. On the other hand, in samples B5 to B9 using Si-containing metal soaps, no significant change in the breakdown voltage was observed even after heat treatment. This is believed to be because Si-containing metal soaps can form a coating on the surface of the metal magnetic particles even without heat treatment. In contrast, in silane coupling agents, heat treatment is required to form a coating on the surface of the metal magnetic particles. In addition, the Fe-Si-based metal magnetic powders used in heat-treated samples A2 and B5 to B9 have a property that their insulation properties are easily reduced compared to the Fe-Si-Cr-based metal magnetic powders used in samples A1 and B2 that were not heat-treated.

[0116] Furthermore, when comparing heat-treated samples, samples B5 to B9, which used Si-containing metal soaps, exhibited higher breakdown voltages and magnetic permeabilities than sample A2, which used a silane coupling agent. This indicates that the use of Si-containing metal soaps improves both insulation and magnetic properties compared to using a silane coupling agent. This is believed to be because, after heat treatment, Si-containing metal soaps with long hydrocarbon chains adhere more firmly to the surfaces of the metal magnetic particles than silane coupling agents and more easily form a coating with a high affinity for the resin. Furthermore, samples B5 to B9, treated at heat treatment and annealing temperatures ranging from 400°C to 600°C, exhibited insulation and magnetic properties comparable to or better than those of sample A2, which used a silane coupling agent.

[0117] Summary

[0118] The above evaluation results of the dust cores show that mixing liquid Si-containing metal soap with metal magnetic powder at 25° C. during the preparation of granulated powder can provide a dust core with a high breakdown voltage and improve the insulation properties of the dust core.

[0119] Furthermore, it was found that, in the preparation of the granulated powder, by heat-treating the mixture of the Si-containing metal soap and the metal magnetic powder, the magnetic permeability is further increased, and a powder magnetic core having both good magnetic properties and insulating properties can be produced.

[0120] (Other embodiments, etc.)

[0121] As mentioned above, the dust core according to the embodiment of the present invention has been described, but the present invention is not limited to this embodiment.

[0122] For example, electrical components using the above-mentioned powder magnetic cores are also included in the present disclosure. Examples of electrical components include high-frequency reactors, inductors, transformers, and other inductive components. In addition, power supply devices equipped with the above-mentioned electrical components are also included in the present disclosure.

[0123] In addition, the present disclosure is not limited to the above-mentioned embodiments. As long as it does not depart from the main purpose of the present disclosure, various modifications that can be thought of by those skilled in the art to the present embodiment and combinations of components in different embodiments may also be included in the scope of one or more embodiments.

[0124] Hereinafter, an example of the method for producing the dust core of the present disclosure described in the above embodiment will be described. The method for producing the dust core of the present disclosure is not limited to the following example.

[0125] For example, the first embodiment of the present invention involves a method for manufacturing a powdered magnetic core, including: 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 granular granulated powder; a second step of pressurizing the obtained granulated powder to obtain a formed body; and a third step of annealing the obtained formed body, wherein the mixed metal soap in the first step is liquid at 25°C and contains Si element.

[0126] Furthermore, for example, the method for producing a dust core according to the second aspect of the present disclosure is the method for producing a dust core according to the first aspect, wherein in the first step, the mixing ratio of the metal soap to the metal magnetic powder is 2.0 wt % or less.

[0127] In addition, for example, the third embodiment of the present disclosure involves a method for manufacturing a powder magnetic core, which is the method for manufacturing a powder magnetic core involved in the first embodiment or the second embodiment. In the first step, after obtaining a mixture of the metal magnetic powder and the metal soap, the granulated powder is obtained by mixing the mixture with the resin.

[0128] In addition, for example, the fourth embodiment of the present disclosure involves a method for manufacturing a compressed magnetic core, which is, in the method for manufacturing a compressed magnetic core involved in the third embodiment, after obtaining the mixture and before mixing the mixture and the resin, the mixture is heat treated under temperature conditions of greater than 200°C and less than 800°C.

[0129] Furthermore, for example, a fifth aspect of the present disclosure provides a method for manufacturing a dust core according to the fourth aspect, wherein the heat treatment is performed at a temperature of 400° C. to 600° C.

[0130] Furthermore, for example, a method for manufacturing a dust core according to a sixth aspect of the present disclosure is the method for manufacturing a dust core according to the fourth or fifth aspect, wherein in the first step, the heat treatment is performed in a non-oxidizing atmosphere.

[0131] Furthermore, for example, a seventh aspect of the present disclosure relates to the method for manufacturing a powder magnetic core according to any one of the first to sixth aspects, wherein in the third step, the annealing is performed at a temperature of 400° C. to 600° C.

[0132] Furthermore, for example, a method for manufacturing a dust core according to an eighth aspect of the present disclosure is the method for manufacturing a dust core according to any one of the first to seventh aspects, wherein in the third step, the annealing is performed in a non-oxidizing atmosphere.

[0133] Industrial Applicability

[0134] The powder magnetic core according to the present disclosure can be applied to materials for magnetic cores of high-frequency inductors and transformers, and the like.

[0135] Reference numerals

[0136] 1 Coil components

[0137] 12 Powder core

[0138] 12a Abutment

[0139] 12b core

[0140] 12c Wall

[0141] 13 Conductors

[0142] 14 Coil support

[0143] 14a base

[0144] 14b cylindrical part

[0145] 17 Metal magnetic powder

[0146] 18 Insulation Materials

Claims

1. A method for manufacturing a powder magnetic core, comprising: In the first step, a metal magnetic powder composed of a plurality of metal magnetic particles, a resin and a metal soap are mixed to obtain a granular granulated powder; The second step is to pressurize and shape the obtained granulated powder to obtain a shaped body; as well as The third step is to anneal the obtained formed body. In the first step, the mixed metal soap is liquid at 25° C. and contains Si element.

2. The method for manufacturing a powder magnetic core according to claim 1, wherein: In the first step, the mixing ratio of the metal soap to the metal magnetic powder is 2.0 wt % or less.

3. The method for manufacturing a powder magnetic core according to claim 1, wherein: In the first step, after obtaining a mixture of the metal magnetic powder and the metal soap, the granulated powder is obtained by mixing the mixture with the resin.

4. The method for manufacturing a powder magnetic core according to claim 3, wherein: In the first step, after the mixture is obtained and before the mixture is mixed with the resin, the mixture is heat-treated under a temperature condition of 200° C. or higher and 800° C. or lower.

5. The method for manufacturing a powder magnetic core according to claim 4, wherein: The temperature condition of the heat treatment is 400° C. or higher and 600° C. or lower.

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

7. The method for producing a powder magnetic core according to any one of claims 1 to 6, wherein: In the third step, the annealing is performed under a temperature condition of 400° C. or higher and 600° C. or lower.

8. The method for manufacturing a powder magnetic core according to claim 7, wherein: In the third step, the annealing is performed in a non-oxidizing atmosphere.

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