JP2017183655A - Powder-compressed molded magnetic body, magnetic core, and coil type electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder-compressed molded magnetic body which can be easily manufactured with excellent insulation characteristics while maintaining a stable quality, and has less deterioration of magnetic characteristics, a magnetic core made of the magnetic body, and a coil type electronic component having the magnetic core.SOLUTION: A powder-compressed molded magnetic body includes an alloy particle 2 constructed by Fe-Si-Cr-based soft magnetic alloy. In the powder-compressed molded magnetic body, phosphorus of 40 to 100 ppm is included. A Cr oxide film 4 including phosphorus is formed on a front surface of the alloy particle 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compacted magnetic body, a magnetic core, and a coil-type electronic component.

  In general, a magnetic core made of a dust-molded magnetic body having conventional soft magnetic alloy particles has a problem of poor insulation properties. Thus, it has been studied to coat the surface of the alloy particles with, for example, a phosphoric acid-based chemical film (for example, Patent Document 1).

  However, the technique of coating the surface of alloy particles with a phosphoric acid-based chemical conversion film has problems such as an increase in the number of manufacturing steps. Further, there is a problem that the magnetic properties such as μ are deteriorated by coating the surfaces of the alloy particles.

  Therefore, various measures such as mixing alloy particles having different particle diameters are used together. However, the quality of the magnetic material may become unstable, and the manufacturing process becomes complicated.

JP 2008-63651 A

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a dust-molded magnetic body that is easy to manufacture, stabilizes quality, has excellent insulating characteristics, and has little deterioration in magnetic characteristics, and the magnetic body. And a coil-type electronic component having the magnetic core.

In order to achieve the above object, a compacted magnetic body according to the first aspect of the present invention comprises:
A compacted magnetic body comprising alloy particles composed of a Fe-Si-Cr soft magnetic alloy,
Contains 40-100 ppm phosphorus,
A Cr oxide film containing phosphorus is formed on the surface of the alloy particles.

  According to the compacting magnetic body according to the first aspect of the present invention, since the Cr oxide film containing phosphorus is formed on the surface of the alloy particles, compared with the compacting magnetic body not containing phosphorus, Insulation is significantly improved. Further, it has been found by the present inventors that the compacted magnetic body according to the first aspect of the present invention has little deterioration in magnetic properties such as μ.

  Furthermore, the powder compacted magnetic body according to the first aspect of the present invention can be produced simply by including a predetermined amount of phosphorus in the soft magnetic alloy powder as a raw material and appropriately selecting the heat treatment conditions. Therefore, manufacture is easy and quality can be stabilized.

In order to achieve the above object, a compacted magnetic body according to a second aspect of the present invention is:
A compacted magnetic body comprising alloy particles composed of a Fe-Si-Cr soft magnetic alloy,
Contains 40-100 ppm phosphorus,
A powder compacted magnetic body, wherein grain boundaries between the alloy particles contain phosphorus.

  According to the powder compacted magnetic body according to the second aspect of the present invention, since the grain boundaries of the alloy particles contain phosphorus, the insulation is significantly improved compared to the powder compacted magnetic body that does not contain phosphorus. To do. Further, it has been found by the present inventors that the powder molded magnetic body according to the second aspect of the present invention has little deterioration in magnetic properties such as μ.

  Furthermore, the compacting magnetic body according to the second aspect of the present invention can be manufactured by simply including phosphorus in a predetermined amount in the soft magnetic alloy powder as a raw material and appropriately selecting the heat treatment conditions. Therefore, manufacture is easy and quality can be stabilized.

  The magnetic core which concerns on this invention is comprised from the above-mentioned compacting magnetic body.

  A coil-type electronic component according to the present invention has the magnetic core described above.

FIG. 1 is a STEM image of a cross section of a compacted magnetic body according to an embodiment of the present invention. FIG. 2 is a graph showing changes in phosphorus content, insulation characteristics, and μi characteristics of powder-molded magnetic bodies according to examples and comparative examples of the present invention.

Hereinafter, the present invention will be described based on embodiments.
The magnetic core for coil-type electronic components according to the present embodiment is a magnetic core made of a dust-molded magnetic body that is molded by dust-molding. The compacting is a method for obtaining a compact by filling a material containing a soft magnetic alloy powder in a die of a press machine and pressurizing the material with a predetermined pressure.

  Examples of the shape of the magnetic core according to the present embodiment include a toroidal type, FT type, ET type, EI type, UU type, EE type, EER type, UI type, drum type, pot type, cup type, and the like. be able to. A desired coil-type electronic component can be obtained by winding a predetermined number of turns around the magnetic core.

  The magnetic core for a coil-type electronic component according to the present embodiment is composed of the dust-molded magnetic body according to the present embodiment.

  As shown in FIG. 1, the compacted magnetic body according to the present embodiment includes a plurality of soft magnetic alloy particles 2 and grain boundaries 6 existing between the soft magnetic alloy particles. The soft magnetic alloy particles 2 are composed of an Fe—Si—Cr based soft magnetic alloy.

  The Fe—Si—Cr soft magnetic alloy contains 0.1 to 9% by mass of silicon in terms of Si, 0.1 to 15% by mass of chromium in terms of Cr, and the balance is made of iron (Fe). It is preferable. More preferably, silicon is 1.4 to 9% by mass in terms of Si, particularly preferably 4.5 to 8.5% by mass, and chromium is 1.5 to 8% by mass in terms of Cr, particularly preferably 3 to 3. It is preferable that the content is 7% by mass and the balance is composed of iron (Fe).

  Fe-Ni-Si-Cr-based soft magnetic alloy containing 3-15% by mass of nickel in terms of Ni, 0.1-9% by mass of silicon in terms of Si, and 0.1-15% by mass of chromium in terms of Cr And it is preferable that the remainder is comprised with iron (Fe). More preferably, nickel is 3 to 10% by mass in terms of Ni, silicon is 1.4 to 9% by mass in terms of Si, particularly preferably 4.5 to 8.5% by mass, and chromium is 1. It is preferable to contain 5 to 8% by mass, particularly preferably 3 to 7% by mass, with the balance being composed of iron (Fe).

  The average crystal particle diameter of the soft magnetic alloy particles 2 according to this embodiment is preferably 30 to 60 μm. By making the average crystal particle diameter within the above range, it is possible to easily realize a thin magnetic core.

  A Cr oxide film 4 is formed on the surface of the soft magnetic alloy particle 2. The Cr oxide film 4 is a phase containing oxygen and Cr, and may be a complex oxide containing elements other than Cr and oxygen, such as Si. The Cr oxide film 4 may be a Si—Cr composite oxide phase in which there is more Cr than in the alloy particles 2. The Si—Cr composite oxide phase is not particularly limited, and examples thereof include an amorphous phase containing Si and Cr.

  Moreover, in the powder-molded magnetic body according to the present embodiment, the oxide phase may further contain one or both of Bi and V. Examples of the oxide phase containing Bi and V include, for example, an oxide phase in which Bi oxide, V oxide, and the like are dispersed, and Bi and V are a part of components constituting the soft magnetic alloy particles. And a complex oxide phase formed by chemically bonding to the compound.

  The Cr oxide film 4 preferably covers the entire surface of the particle 2, but may be formed intermittently. The thickness of the Cr oxide film 4 is not particularly limited, but is preferably 0.05 to 0.2 μm, and more preferably 0.1 to 0.2 μm. The film thickness of the Cr oxide film 4 may not be uniform, and the composition may not be uniform.

  In the present embodiment, the Cr oxide film 4 contains phosphorus. In the present embodiment, the grain boundary 6 also contains phosphorus. The method for detecting that the Cr oxide film 4 contains phosphorus and that the grain boundary 6 contains phosphorus is not particularly limited. For example, it is determined by analyzing a mapping image of phosphorus (P). Also good.

  The alloy particles 2 and the grain boundaries 6 can be distinguished by observing the magnetic core using a scanning transmission electron microscope (STEM). Specifically, a cross section of the magnetic core is photographed with a STEM to obtain a bright field (BF) image. In this bright field image, a region present between the soft magnetic alloy particles and the soft magnetic alloy particles and having a contrast different from that of the soft magnetic alloy particles is defined as a grain boundary. The determination of whether or not the contrast is different may be made by visual observation, or may be made by software or the like that performs image processing.

  Further, whether or not the Cr oxide film 4 is present on the surface of the alloy particle 2 can be detected by EDS or EPMA. Further, the fact that the film formed on the surface of the alloy particle 2 is the Cr oxide film 4 is detected by mapping Cr and O by EDS or EPMA mapping, and whether Cr and O overlap. be able to.

  For example, by defining an observation point from an arbitrary cross section of the magnetic core and performing EDS analysis or EPMA analysis, it is possible to observe a portion where P exists. Specifically, a mapping image can be obtained using the qualitative analysis function of these analyses. In the mapping image, it is possible to distinguish a portion where there are many elements to be observed by color. Whether or not P exists in the Cr oxide film 4 or the grain boundary 6 can be determined by visual observation or analysis software.

  Furthermore, according to these analyses, it is possible to confirm the concentration distribution of various components inside the alloy particle 2 and on the surface thereof. Further, according to the STEM analysis, it is possible to specify whether the Cr oxide film 4 formed on the surface of the alloy particle 2 is amorphous or crystalline. In the present embodiment, the Cr oxide film 4 may be amorphous or crystalline.

  In the compacted magnetic body according to the present embodiment, elements other than P (Fe, Si, Cr, O, etc.) are also applied to the surfaces and grain boundaries of the soft magnetic alloy particles by the same method as in the case of P. It can be determined whether or not various elements are present.

  In the powder molded magnetic body according to the present embodiment, the content of phosphorus (P) is 40 to 100 ppm, more preferably 60 to 100 ppm, with respect to 100% by mass of the powder molded magnetic body. By satisfying the above-described range, the insulating property is remarkably improved in the magnetic core according to the present embodiment without deteriorating the magnetic characteristics (particularly, the initial magnetic permeability μi). In the compacted magnetic body, the content of phosphorus (P) can be measured by ICP.

  According to the powder compacted magnetic body according to the present embodiment, the Cr oxide film 4 containing phosphorus is formed on the surface of the alloy particle 2 and P is contained in the grain boundary 6, so that the insulating property is exceptional. To improve. Moreover, according to the compacting magnetic body which concerns on this embodiment, there is little deterioration of magnetic characteristics, such as (micro | micron | mu).

  Furthermore, as will be described later, the compacted magnetic body according to the present embodiment can be produced by simply including phosphorus in a predetermined amount in the raw soft magnetic alloy powder and appropriately selecting the heat treatment conditions. Therefore, manufacture is easy and quality can be stabilized.

  The powder compacted magnetic body according to the present embodiment may contain components such as carbon (C) and zinc (Zn) in addition to the constituent components of the soft magnetic alloy particles.

  In addition, it is thought that C originates in the organic compound component used in the manufacturing process of a compacting magnetic body. Further, it is considered that Zn is derived from zinc stearate added to the mold in order to reduce the punching pressure of the apparatus when the compacted magnetic body is obtained by compacting.

  The content of carbon (C) in the green compact magnetic body according to this embodiment is preferably less than 0.25% by mass, and more preferably 0.10 to 0.20% by mass.

  The zinc (Zn) content in the compacted magnetic body according to this embodiment is preferably 0.004 to 0.2 mass%, more preferably 0.01 to 0.2 mass%.

  In addition to the above components, the powder compacted magnetic body according to the present embodiment may contain inevitable impurities.

  As yet another embodiment, Si may be further present at the grain boundaries of the compacted magnetic body. Thereby, intensity | strength can be improved further, maintaining a high magnetic characteristic. In particular, even when molded at a relatively low molding pressure, sufficient strength as a magnetic core can be obtained, so that the burden on the mold is reduced and productivity is improved.

  In the compacted magnetic body according to the present embodiment, Si contains Si at grain boundaries 6 formed between two particles or at grain boundaries (such as triple points) existing between three or more particles. It may exist as a phase.

  As a result of the presence of Si-containing phases at the grain boundaries, the magnetic core according to the present embodiment can obtain sufficient strength as a magnetic core even when molded with a relatively low molding pressure. Can do. Furthermore, such a phase containing Si plays a role of an insulator by being present at a grain boundary.

  The phase containing Si according to the present embodiment is preferably a Si oxide phase or a Si composite oxide phase. The Si oxide phase and the Si composite oxide phase are not particularly limited, and examples thereof include an amorphous phase containing Si, amorphous silicon, silica, and a Si—Cr composite oxide.

  Further, in the compacted magnetic body according to the present embodiment, the phase containing Si may also exist on the surface of the soft magnetic alloy particle 2 (interface with the grain boundary 6). For example, the Cr oxide film 4 may be composed of a Si—Cr composite oxide phase. The phase containing Si according to the present embodiment is preferably made of an amorphous material. Note that a part thereof may be made of a crystalline material.

Next, an example of a method for manufacturing a magnetic core according to the present embodiment will be described.
The magnetic core made of the compacted magnetic body of the present embodiment can be produced by heat-treating a molded body containing soft magnetic alloy powder and a binder (binder resin). Hereinafter, a preferable production method will be described in detail.

The method for producing a compacted magnetic body according to this embodiment is preferably:
Mixing a soft magnetic alloy powder and a binder to obtain a mixture;
After the mixture is dried to obtain a lump-shaped dried body, the dried body is pulverized to form granulated powder,
Forming a mixture or granulated powder into the shape of a compacted magnetic body to be produced to obtain a molded body;
And a step of obtaining a dust core by heating the obtained molded body.

  The shape of the soft magnetic alloy powder is not particularly limited, but is preferably spherical or elliptical from the viewpoint of maintaining inductance up to a high magnetic field range. Among these, an elliptical shape is desirable from the viewpoint of increasing the strength of the dust core. The average particle size of the soft magnetic alloy powder is preferably 10 to 80 μm, more preferably 30 to 60 μm.

  The soft magnetic alloy powder can be obtained by a method similar to a known method for preparing a soft magnetic alloy powder. At this time, it can be prepared using a gas atomizing method, a water atomizing method, a rotating disk method or the like. Among these, the water atomization method is preferable in order to easily produce a soft magnetic alloy powder having desired magnetic characteristics.

  The method of including phosphorus in the soft magnetic alloy powder is not particularly limited. For example, the following several methods are conceivable.

  When the raw material is melted and mixed at the time of producing the soft magnetic alloy powder, phosphorus can be included in the soft magnetic alloy powder by mixing phosphorus alone in addition to phosphorus contained in the raw material of simple iron. In addition, the addition amount of phosphorus (P) is adjusted so that it may become 40-100 ppm after the heat processing of a molded object. It is considered that the content of phosphorus (P) does not change before and after the heat treatment.

  When the soft magnetic alloy powder and the binder are mixed to obtain a mixture, a low melting point oxide may be included. The low melting point oxide may include at least one of Bi and V. Thereby, at least one of Bi and V can be efficiently formed at the grain boundary. Examples of such a low melting point oxide include bismuth oxide and vanadium oxide.

  The addition amount of such a low melting point oxide is preferably 0.1 to 5.0 parts by mass in terms of Bi2O3 or V2O5 with respect to 100 parts by weight of the soft magnetic alloy powder. By satisfy | filling the said range, Bi and V can be formed efficiently in the grain boundary of a soft-magnetic composition, and the intensity | strength of a magnetic core can be improved.

  More preferably, the low melting point oxide contains at least Bi. The addition amount of the low melting point oxide contained in such bismuth (Bi) is preferably 0.1 to 5.0% by mass, more preferably 0.1% by mass in terms of Bi2O3 with respect to 100% by mass of the soft magnetic material alloy. 0.1 to 1.0% by mass. By satisfying the above range, the magnetic properties (particularly, the initial magnetic permeability μi) can be kept high while improving the strength.

  As the binder, known resins can be used, and examples thereof include various organic polymer resins, silicone resins, phenol resins, epoxy resins, and water glass.

  Especially, in this embodiment, Preferably, what contains a silicone resin as a binder is used. By using silicone as the binder, a Si-containing phase is effectively formed at the grain boundary of the soft magnetic composition. A magnetic core composed of such a powder-molded magnetic body exhibits sufficient strength even when molded with a relatively low molding pressure.

  The amount of the binder added varies depending on the required characteristics of the magnetic core, but preferably 1 to 10 parts by weight can be added, more preferably 100 parts by weight of the soft magnetic alloy powder. The amount is 2 to 5 parts by weight with respect to 100 parts by weight of the soft magnetic alloy powder.

  Moreover, you may add an organic solvent to the said mixture or granulated powder as needed in the range which does not inhibit the effect of this invention.

  The organic solvent is not particularly limited as long as it can dissolve the binder, and examples thereof include various solvents such as toluene, isopropyl alcohol, acetone, methyl ethyl ketone, chloroform, and ethyl acetate.

  In addition, various additives, lubricants, plasticizers, thixotropic agents, and the like may be added to the mixture or the granulated powder as necessary, as long as the effects of the present invention are not hindered.

  Examples of the lubricant include aluminum stearate, barium stearate, magnesium stearate, calcium stearate, zinc stearate and strontium stearate. These are used singly or in combination of two or more. Among these, it is preferable to use zinc stearate as a lubricant from the viewpoint that so-called spring back is small.

  When a lubricant is used, the amount added is preferably 0.1 to 0.9 parts by weight, more preferably 100 parts by weight of soft magnetic alloy powder, with respect to 100 parts by weight of soft magnetic alloy powder. Is 0.3 to 0.7 parts by weight. If the amount of the lubricant is too small, it is difficult to remove the mold after molding, and molding cracks tend to occur. On the other hand, when there is too much lubricant, the molding density is lowered and the magnetic permeability is reduced.

  In particular, when zinc stearate is used as the lubricant, the amount of zinc (Zn) contained in the obtained compacted magnetic body is in the range of 0.004 to 0.2 mass%. Is preferably adjusted.

  The method for obtaining the mixture is not particularly limited, and can be obtained by mixing soft magnetic alloy powder, binder and organic solvent by a conventionally known method. In addition, you may add various additives as needed.

  For mixing, for example, a mixer such as a pressure kneader, an attawriter, a vibration mill, a ball mill, or a V mixer, or a granulator such as a fluid granulator or a rolling granulator can be used.

  Moreover, as temperature and time of a mixing process, Preferably it is about 1 to 30 minutes at room temperature.

  Although it does not specifically limit as a method to obtain granulated powder, After drying a mixture by a conventionally well-known method, it obtains by crushing the dried mixture.

  The temperature and time for the drying treatment are preferably about room temperature to 200 ° C. and 5 to 60 minutes.

  If necessary, a lubricant can be added to the granulated powder. After adding the lubricant to the granulated powder, it is desirable to mix for 5 to 60 minutes.

  The method for obtaining the molded body is not particularly limited, but a conventionally known method is used to form a mold having a cavity having a desired shape, and the mixture or granulated powder is filled into the cavity. The mixture is preferably compression-molded at a molding temperature and a predetermined molding pressure.

  The molding conditions in the compression molding are not particularly limited, and may be appropriately determined according to the shape and size of the soft magnetic alloy powder, the shape, size, and density of the dust core. For example, the maximum pressure is usually about 100 to 1000 MPa, preferably about 400 to 800 MPa, and the time for maintaining the maximum pressure is about 0.5 seconds to 1 minute.

  If the molding pressure is too low, it is difficult to achieve high density and high magnetic permeability by molding, and it is difficult to obtain sufficient mechanical strength. On the other hand, if the molding pressure at the time of molding is too high, the pressure application effect tends to saturate, the manufacturing cost tends to increase and productivity and economy tend to be impaired, and the molding die deteriorates. It tends to be easy and the durability tends to decrease.

  The molding temperature is not particularly limited, but is usually preferably about room temperature to 200 ° C. In addition, the density of the compact tends to increase as the molding temperature at the time of molding increases, but if it is too high, the oxidation of the soft magnetic alloy particles is promoted, and the performance of the resulting dust core tends to deteriorate, In addition, the manufacturing cost may increase and productivity and economy may be impaired.

  The method of heat-treating the molded body obtained after molding is not particularly limited, but it is preferable to heat-treat the molded body formed into an arbitrary shape by molding at a predetermined temperature using an annealing furnace.

  Although the processing temperature at the time of heat processing is not specifically limited, About 700-1000 degreeC is preferable, More preferably, it is 800 degreeC-1000 degreeC, Most preferably, it is 800-900 degreeC. If the treatment temperature during the heat treatment is too low, it becomes difficult to form the Cr oxide film 4 containing P, and it becomes difficult to form the grain boundaries 6 containing P, and it is difficult to improve the insulation. . On the other hand, if the heat treatment temperature is too high, the alloy particles 2 are oxidized and the insulating property tends to be lowered.

  The heat treatment step is preferably performed in an oxygen-containing atmosphere. Here, the oxygen-containing atmosphere is not particularly limited, and examples thereof include an air atmosphere (usually containing 20.95% oxygen) or a mixed atmosphere with an inert gas such as argon or nitrogen. It is done. Preferably, it is under atmospheric atmosphere. By performing the heat treatment in an oxygen-containing atmosphere, it becomes easy to form the Cr oxide film 4 containing P and to easily form the grain boundary 6 containing P.

The dust core thus obtained preferably has a molding density of 5.50 g / cm ³ or more. A dust core that has been densified to a molding density of 5.50 g / cm ³ or more tends to be excellent in various performances such as high magnetic permeability, high strength, high core resistance, and low core loss.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, You may modify | change in various aspects within the scope of the present invention.

  For example, in the above-described embodiment, a magnetic core (powder magnetic core) is manufactured by compacting a mixture or granulated powder, but the magnetic core is formed by stacking the mixture into a sheet shape. It may be manufactured. In addition to dry molding, a molded body may be obtained by wet molding, extrusion molding, or the like.

  In the above-described embodiment, the magnetic core according to this embodiment is used as a coil-type electronic component. However, the magnetic core is not particularly limited, and various types such as a motor, a switching power supply, a DC-DC converter, a transformer, and a choke coil are used. It can also be suitably used as a magnetic core for electronic components. Especially, it is more suitable as a portable DC-DC converter.

  Furthermore, in embodiment mentioned above, although the magnetic core is comprised with the compacting | molding magnetic body which concerns on this invention, the element | base_body main body of an electronic component and another molded object other than a magnetic core are used for this invention. You may comprise the powder compacting magnetic body which concerns.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

Example 1
[Preparation of soft magnetic alloy powder]
First, ingots, chunks, or shots (particles) of simple Fe, simple Cr, and simple Si were prepared. Next, they were mixed so as to have a composition of 89.5 mass% Fe, 6.5 mass% Si, and 4.0 mass% Cr, and accommodated in a crucible disposed in a water atomizer. Next, using a work coil provided outside the crucible in an inert atmosphere, the crucible was heated to 1600 ° C. or higher by high frequency induction, and the ingot, chunk or shot in the crucible was melted and mixed to obtain a melt.

  Next, the melt in the crucible is ejected from a nozzle provided in the crucible, and at the same time, a high-pressure (50 MPa) water flow is collided with the melt and rapidly cooled, thereby soft magnets composed of Fe-Si-Cr-based particles. Alloy powder (average particle size: 50 μm) was prepared.

  As a result of analyzing the composition of the obtained soft magnetic alloy powder by fluorescent X-ray analysis, it was confirmed that it was consistent with the charged composition. In addition, the phosphorus content contained in the soft magnetic alloy powder is adjusted by adjusting the amount of phosphorus contained in the raw material of the iron simple substance when the raw material is melted and mixed during the production of the soft magnetic alloy powder. It was.

[Production of dust core]
6 parts by weight of a silicone resin (manufactured by Toray Dow Corning Silicon Co., Ltd .: SR2414LV) was added to 100 parts by weight of the obtained soft magnetic alloy powder, and these were mixed with a pressure kneader at room temperature for 30 minutes. The mixture was then dried in air at 150 ° C. for 20 minutes. To 100 parts by weight of the soft magnetic alloy powder, 0.5 parts by weight of zinc stearate (manufactured by Nitto Kasei: zinc stearate) as a lubricant was added to the dried magnetic powder and mixed for 10 minutes by a V mixer. .

  Then, the obtained mixture was shape | molded to the square sample of 5 mm x 5 mm x 10 mm, and the molded object was produced. The molding pressure was 600 MPa. The pressed compact was heat-treated in the atmosphere at 800 ° C. for 60 minutes to obtain a magnetic core (dust core) made of the compacted magnetic body.

[Various evaluations]
<Observation of grain boundaries>
First, the dust core was cut. This cut surface was observed with a scanning transmission electron microscope (STEM), and the soft magnetic alloy particles 2 and the grain boundaries 6 were discriminated. Further, the presence of Cr, O, P, and Si at the surface of the particle 2 and the grain boundary 6 was confirmed by EDS analysis, respectively.

<Initial permeability (μi)>
A copper wire was wound around the dust core sample for 10 turns, and an initial magnetic permeability μi was measured using an LCR meter (Hewlett Packard 4284A). The measurement conditions were a measurement frequency of 1 MHz, a measurement temperature of 23 ° C., and a measurement level of 0.4 A / m.

<Insulation resistance (IR)>
The insulation resistance IR was calculated | required on the conditions of 50V using High Resistance Meter (Agilent 4339B) for the dust core sample.

<Evaluation>
The content of phosphorus (P) contained in the dust core was changed from 0.003 mass% (30 ppm) to 0.011 mass% (110 ppm), and the results of investigating changes in initial permeability and insulation resistance were as follows. As shown in FIG.

  As shown in FIG. 2, the IR content is significantly improved by reducing the phosphorus (P) content from 0.004 mass% (40 ppm) to 0.010 mass% (100 ppm), and the deterioration of μi. It was confirmed that there was little. When the phosphorus (P) content is less than 0.004 mass% (40 ppm), the insulation resistance is too low, which is not preferable, and when the phosphorus (P) content is more than 0.010 mass% (100 ppm). , Μi is not preferable because the decrease rate of μi is 20% or more.

  Moreover, the powder magnetic core sample whose content of phosphorus (P) is 0.004 mass% (40 ppm) to 0.010 mass% (100 ppm) is cut, and the scanning transmission electron microscope ( As a result of performing EDS analysis on Cr, O, P, and Si, as shown in FIG. 1 which is a STEM image, a Cr oxide film 4 containing phosphorus is formed on the surface of the alloy particle 2. It was confirmed that the grain boundaries 6 also contained phosphorus.

(Comparative Example 1)
A dust core sample was prepared in the same manner as in Example 1 except that the heat treatment temperature was 500 ° C., and the same measurement was performed. No Cr oxide film containing phosphorus was observed on the surface of the alloy particles, and no phosphorus was observed at the grain boundaries. Moreover, even if phosphorus content was 40-100 ppm, as shown in FIG. 2, the increase in insulation resistance was not observed. Since the heat treatment temperature is low, a Cr oxide film containing phosphorus is not observed on the surface of the alloy particles, and phosphorus is not observed at the grain boundaries, and it is considered that an increase in insulation resistance is not observed.

(Example 2)
A dust core sample similar to that of Example 1 was prepared and the same measurement was performed except that non-silicone resin (manufactured by Nagase ChemteX Corp .: DENATEITE XNR 4338) was used as the binder resin. . The same results as in Example 1 were obtained.

2 ... Soft magnetic alloy particles 4 ... Phosphorus-containing 6 ... Cr oxide film

Claims (4)

A compacted magnetic body comprising alloy particles composed of a Fe-Si-Cr soft magnetic alloy,
Contains 40-100 ppm phosphorus,
A compacted magnetic body, wherein a Cr oxide film containing phosphorus is formed on the surface of the alloy particles. A compacted magnetic body comprising alloy particles composed of a Fe-Si-Cr soft magnetic alloy,
Contains 40-100 ppm phosphorus,
A powder compacted magnetic body, wherein grain boundaries between the alloy particles contain phosphorus.   A magnetic core comprising the compacted magnetic material according to claim 1.   A coil-type electronic component comprising the magnetic core according to claim 3.