WO2014141318A1

WO2014141318A1 - Magnetic component, soft magnetic metal powder used in same, and method for producing same

Info

Publication number: WO2014141318A1
Application number: PCT/JP2013/001638
Authority: WO
Inventors: 和正碇; 後藤　昌大; 吉田　貴行
Original assignee: Ｄｏｗａエレクトロニクス株式会社
Priority date: 2013-03-13
Filing date: 2013-03-13
Publication date: 2014-09-18
Also published as: KR20140121810A; CN103999170A; EP2801424A4; TW201426773A; EP2801424B1; EP2801424A1; KR101496626B1; TWI471876B; CN103999170B

Abstract

This magnetic component of an inductor, antenna, or the like and using a metal magnetic powder has a greater complex component of the magnetic permeability, which is loss in the GHz band. It is possible to suppress the loss coefficient in the GHz band to a low level by means of the magnetic component, which is formed from a soft magnetic metal powder that has iron as the primary component and that is characterized by having an average particle size of no greater than 300 nm, a coercivity (Hc) of 16-119 kA/m (200-1500 Oe), a saturation magnetization of at least 90 Am²/kg, and a volume resistivity measured by means of a four-point probe method of a molded body formed by vertically compressing 1.0 g of the metal powder at 64 MPa (20 kN) of at least 1.0×10¹ Ω·cm.

Description

Magnetic component, soft magnetic metal powder used therefor, and method for producing the same

The present invention relates to a magnetic component used in a high frequency band, a soft magnetic metal powder constituting the magnetic component, and a method for producing the soft magnetic metal powder.

In recent years, signals used in electronic devices such as mobile phones, notebook PCs, and liquid crystal televisions have been increased in frequency. Currently, signals in the GHz band have already been put into practical use, and in the future, use of a frequency band exceeding 10 GHz is expected. As the frequency of such devices increases, performance improvements in the high-frequency region are also required for individual components such as electronic circuits and other passive elements.

Also, these devices are being reduced in size and power consumption for the purpose of being used as mobile devices. Therefore, individual components are required to have characteristics in the high frequency band and low loss. However, among the components that make up equipment, the characteristics of passive elements are often determined based on the physical properties of the material, and it is not easy to improve the characteristics in the high frequency band.

For example, it can be said that the product characteristics of magnetic parts such as inductors and antennas are determined by physical characteristics such as permittivity and permeability. An inductor is a component that uses magnetic flux flowing in the body of the component. In order to obtain an inductor that can be used in a high frequency band, it is necessary to develop a magnetic material that not only possesses magnetic permeability in the high frequency region but also has a small loss in the high frequency region.

In the case of antennas, it is necessary to mount antennas corresponding to a plurality of frequency bands as the communication method or technology advances. Moreover, it is desired that the area occupied by the antenna in the electronic device be as small as possible. It is known that the antenna length for receiving a predetermined frequency may be a length inversely proportional to the 1/2 power of the product of the real part of the magnetic permeability and the real part of the dielectric constant. That is, in order to shorten the antenna length, a magnetic material having high permeability in the frequency range to be used must be developed. Furthermore, since it is most important that the antenna has a small loss, a magnetic material having a small loss in the high frequency region is required.

Currently, magnetic iron oxides typified by ferrite, metal magnetic materials centered on iron and their alloys (hereinafter referred to as “conventional magnetic materials”) are used as magnetic materials used in such inductors and antennas. . However, in the high frequency range of several hundred MHz or more, there is a problem that the loss due to these magnetic materials increases, so that it cannot be suitably used. The cause is that the particle diameter is larger than the magnetic domain size, which causes the domain wall to move when the magnetization is reversed, resulting in a large hysteresis loss, and the large eddy current loss due to the particle diameter being larger than the skin size. This is thought to be due to the occurrence of

In such a background, Patent Document 1 proposes nano-order flat particles as metal magnetic particles used for an antenna.

JP 2010-103427 A

The use of nano-order magnetic particles for magnetic components used in the high frequency band is intended to reduce hysteresis loss associated with the movement of the domain wall by reversing the magnetization in smaller units where the domain wall is formed. Furthermore, the eddy current loss is also reduced by making the magnetic particles smaller than the skin size. In other words, it is considered that nano-order magnetic particles may be able to obtain a low-loss magnetic component in the high frequency band.

However, although the magnetic component using the metal magnetic particles of Patent Document 1 has less loss than the conventional magnetic material, the value of tan δ indicating the loss at 1 GHz is 0.18 according to the description in paragraph 0104, which is much lower. It is desirable to make it a lossy material.

Therefore, an object of the present invention is to provide a magnetic component having a sufficiently low loss, a nano-order soft magnetic metal powder for obtaining the magnetic component, and a manufacturing method thereof.

The above problem can be solved by forming a magnetic part using soft magnetic metal powder having a specific configuration.

More specifically, the soft magnetic metal powder is
Iron as the main component,
An average particle size of 300 nm or less,
The coercive force (Hc) is 16 to 119 kA / m (200 to 1500 Oe),
The saturation magnetization is 90 Am ² / kg or more,
In a state where 1.0 g of the soft magnetic metal powder is vertically pressurized at 64 MPa (20 kN),
The volume resistivity measured by a four-point probe method is 1.0 × 10 ¹ Ω · cm or more.

The soft magnetic metal powder is further
The soft magnetic metal powder forms a core / shell structure, the core contains iron or iron-cobalt alloy, the shell contains at least one of iron, cobalt, aluminum, silicon, rare earth elements (including Y), and magnesium. It is a complex oxide.

The soft magnetic metal powder is
The iron-cobalt ratio in the iron-cobalt alloy is Co / Fe = 0.0 to 0.6 in terms of atomic ratio.

The soft magnetic metal powder contains aluminum, and the atomic ratio of the sum of Fe and Co is the sum of the sum of Al / Fe and Co = 0.01 to 0.30.

The soft magnetic metal powder is
When the soft magnetic metal powder and the epoxy resin are mixed at a mass ratio of 80:20 and pressure-molded,
The real part of the complex permeability is μ ′, the imaginary part is μ ″, and the loss coefficient is tan δ (= μ ″ / μ ′).
Μ ′> 1.5 and μ ″ <0.5, tan δ <0.15 at a frequency of 1 GHz, and μ ′> 1.5 and μ ″ <1.5, tan δ <0.5 at a frequency of 2 GHz. It is characterized by being.

The present invention also provides an inductor and an antenna using the soft magnetic metal powder.

The method for producing the soft magnetic metal powder of the present invention comprises:
While blowing an oxygen-containing gas into a solution containing iron ions, at least one aqueous solution of aluminum, silicon, rare earth elements (including Y), and magnesium is added, and aluminum, silicon, rare earth elements (including Y) are added. A precursor forming step of forming a precursor containing at least one kind of magnesium;
A precursor reduction step of reducing the precursor to form a metal powder;
And a gradual oxidation step in which oxygen is further applied to the metal powder obtained in the precursor reduction step to form an oxide film on the surface of the metal powder.

In the above production method, the solution containing iron ions is an aqueous solution of an iron compound and a cobalt compound.

In the above production method, the precursor obtained in the precursor forming step exhibits a spinel crystal structure by a powder X-ray diffraction method.

In the above production method, the precursor reduction step is characterized in that the precursor is exposed to a reducing gas at a temperature of 250 ° C. to 650 ° C.

In the manufacturing method, the gradual oxidation step is a step of exposing the metal powder to a gas containing oxygen in an inert gas at a temperature of 20 ° C. to 150 ° C.

According to the soft magnetic metal powder of the present invention, it is possible to obtain a low-loss magnetic component in which μ ′, which is the real part of the magnetic permeability at 1 GHz, is 1.5 or more and the loss coefficient is 0.15 or less.

It is a figure which illustrates the structure of the antenna which is a magnetic component of this invention. It is a figure which illustrates the composition of the coil component which is the magnetic component of the present invention. It is a TEM photograph of soft magnetic powder concerning the present invention. It is a TEM photograph of soft magnetic powder concerning the present invention.

Hereinafter, the magnetic component of the present invention, the soft magnetic metal powder used for the magnetic component, and the manufacturing method thereof will be described. However, this embodiment exemplifies one embodiment of the present invention, and the following contents can be changed without departing from the gist of the present invention.

The magnetic component of the present invention is constituted by a molded body obtained by compression molding the soft magnetic metal powder of the present invention. In particular, examples of the magnetic component include an antenna and a coil component.

FIG. 1 is a diagram showing an example of an antenna to which a high-frequency magnetic material is applied. The illustrated antenna 10 includes a radiation plate 4 disposed on a conductor plate 1, and includes a feeding point 2 and a short-circuit plate 3 for feeding power to the radiation plate 4, and the antenna 10 is soft between the conductor plate 1 and the radiation plate 4. It has a structure in which the compact 5 made of magnetic metal powder is sandwiched. By providing such a structure, the wavelength can be shortened and the antenna 10 can be downsized.

FIG. 2 is a diagram showing an example of a coil component configured using a high-frequency magnetic material. The illustrated coil component 12 includes an electrode 6, a flange 7, a winding 8, and a winding core 9. The core 9 that is a compact of the soft magnetic metal powder is an elongated columnar rectangular parallelepiped, and the cross section in the minor axis direction of the rectangular parallelepiped has a rectangular cross section. The flange 7 has a rectangular cross section larger than the rectangular cross section of the core 9, and has a rectangular parallelepiped structure with a small thickness in the major axis direction of the core 9. The collar 7 may also be formed of a soft magnetic metal powder compact.

Next, the soft magnetic metal powder of the present invention will be described in detail.

<Composition of soft magnetic metal powder>
The soft magnetic metal powder of the present invention includes at least Fe (iron), Fe and Co (cobalt), Al (aluminum), Si (silicon), rare earth elements (including Y (yttrium)), and Mg (magnesium). One kind (hereinafter referred to as “Al etc.”) is included.

Regarding the Al content, etc., the content of Al, etc. with respect to the total of Fe and Co is within a range of 20 at% or less. In the state of the precursor before the reduction treatment, Al or the like is dissolved in Fe or Fe and Co, and the precursor is then reduced to form a metal powder. The reduced metal powder contains a large amount of Fe and Co that are easily reduced inside the particle, and a large amount of aluminum oxide that is not reduced exists on the surface of the particle.

Thereafter, an insulating film containing Al or the like is formed by oxidizing the surface of the metal powder. As a result, the electric resistance of the particles constituting the metal powder is increased, and the loss based on eddy current loss or the like is improved when the magnetic component is formed. Further, by increasing the amount of Al to be contained, an oxide film containing a large amount of Al can be formed on the surface layer, and since the electrical resistance of the particles is increased, eddy current loss can be reduced and tan δ is reduced. In addition, not only Al etc. but Fe or Fe and Co may remain on the surface.

When Co is contained, the Co content is 0 to 60 at% in terms of atomic ratio of Co to Fe (hereinafter referred to as “Co / Fe atomic ratio”). More preferably, the Co / Fe atomic ratio is 5 to 55 at%, more preferably 10 to 50 at%. Within such a range, the soft magnetic metal powder has a high saturation magnetization and can easily obtain stable magnetic characteristics.

Al and the like also have a sintering preventing effect, and suppress the coarsening of particles due to sintering during heat treatment. In the present specification, Al and the like are treated as one of “sintering prevention elements”. However, Al or the like is a non-magnetic component, and if it is contained too much, the magnetic properties are diluted, which is not preferable. The content of Al or the like with respect to the total of Fe and Co is preferably 1 at% to 20 at%, more preferably 3 at% to 18 at%, and even more preferably 5 at% to 15 at%.

<Production method>
The method for producing a soft magnetic metal powder of the present invention includes a precursor forming step for forming a precursor and a precursor reducing step for reducing the obtained precursor to form a soft magnetic metal powder. Further, after the precursor reduction step, a gradual oxidation step in which an oxide film is slightly formed on the surface of the soft magnetic metal powder may be added for easy handling. The precursor formation process is a wet process, and the precursor reduction process and the gradual oxidation process are dry processes.

The precursor forming step is a step of obtaining particles (precursor) composed of the element as a raw material by oxidizing the aqueous solution containing the element as the raw material to cause an oxidation reaction.

The precursor reduction step is a step of reducing the precursor to remove oxygen contained in the precursor formation step to obtain a soft magnetic metal powder made of the element as a raw material. The gradual oxidation step is a step of forming a slight oxide film on the surface of the obtained soft magnetic metal powder. Nano-order (soft magnetic) metal powder has high activity and is easily oxidized at room temperature. When an oxide film is formed on the surface, it can be stably present even in air. Each step will be described in detail below.

<Precursor formation step>
In the precursor forming step, a water-soluble iron compound is preferably used as a raw material. As the water-soluble iron compound, iron sulfate, iron nitrate, iron chloride and the like can be preferably used, and iron sulfate is more preferably used. The reaction is carried out by forming an iron oxide by passing a gas containing oxygen through an aqueous solution of an iron compound or adding an aqueous solution of an oxidizing agent such as hydrogen peroxide.

The oxidation reaction is preferably performed in an environment in which divalent iron (Fe ²⁺ ) and trivalent iron (Fe ³⁺ ) coexist. By allowing irons having different valences to coexist, it becomes easier to form nuclei and particles of an appropriate size can be obtained. Here, the abundance ratio of divalent iron and trivalent iron is important for controlling the particle size of the final precursor, and Fe ²⁺ / Fe ³⁺ is preferably in a range of 1 to 300 in terms of molar ratio, preferably Is in the range of 10 to 150, more preferably in the range of 15 to 100.

When Fe ²⁺ / Fe ³⁺ exceeds 300, the particle size distribution is deteriorated, which is not preferable. Further, as the ratio of Fe ²⁺ / Fe ³⁺ increases, the number of nuclei decreases and the number of particles decreases, so that the particle size increases. On the contrary, when the ratio of Fe ²⁺ / Fe ³⁺ decreases, the number of nuclei increases and the number of particles increases, so the particle size decreases. Trivalent iron may be produced by adding a trivalent iron compound or by oxidizing divalent iron.

As a raw material, cobalt may be added to iron. As the cobalt raw material, a water-soluble cobalt compound is preferably used. This is because the reaction is performed wet. As the water-soluble cobalt, cobalt sulfate, cobalt nitrate, cobalt chloride and the like can be preferably used, and cobalt sulfate is more preferably used.

Cobalt is preferably added before nucleation, and more preferably at the same time as the iron raw material. In addition, it can also be added and deposited after completion of the oxidation reaction.

For the oxidation for growing the nuclei, it is preferable to blow air or oxygen into the aqueous solution. This is because the flow rate and flow velocity can be easily adjusted, and even if the manufacturing apparatus is enlarged, the solution can be uniformly oxidized by adding the outlets. In addition, it can also oxidize by the method of adding an oxidizing agent.

In addition to iron or iron and cobalt, elements such as aluminum, silicon, rare earth elements (including Y), and magnesium may be added to the raw materials. These elements are also preferably water-soluble compounds. These elements are preferably added after iron or iron and cobalt are added to the reaction vessel, and can be added in the middle of the oxidation reaction to be dissolved in the precursor, or added after the end of the oxidation reaction. It may be deposited. The addition method may be one-time addition or continuous addition.

<Precursor reduction process>
The precursor obtained through the wet process as described above is continuously processed in the dry process. In the precursor reduction step, the precursor is exposed to a reducing gas such as carbon monoxide, acetylene, or hydrogen at a temperature of 250 ° C. to 650 ° C. to perform a heat reduction treatment. At this time, multistage reduction may be performed. Multi-stage reduction refers to performing a reduction process of holding an object to be processed at a predetermined temperature for a predetermined time a plurality of times while changing the temperature. By appropriately controlling the holding temperature and time, it is possible to control the properties of the finished metal magnetic powder. As an atmosphere for this reduction treatment, it is also preferable to use a reducing gas added with water vapor.

<Slow oxidation process>
What is obtained after the heat reduction is an alloy magnetic particle powder, but if it is handled in the air as it is, there is a risk of rapid oxidation, so an oxide layer is formed by the following gradual oxidation step. The gradual oxidation step is a step of forming an oxide layer on the particle surface by treating the inert gas at a temperature of 20 to 300 ° C. for a predetermined time while gradually increasing the amount of oxidizing gas. Actually, it is preferable that the powder after the reduction is cooled to a temperature at which this gradual oxidation step is performed, and gradual oxidation is preferably performed at that temperature, and the surface of the particles is oxidized by a weak oxidizing gas at this temperature. It is preferable to form a physical layer and perform a stabilization treatment. In this step, a weakly oxidizing gas with a slow oxidation treatment added with water vapor may be used, and the addition of water vapor is preferable because a denser film can be formed. .

The powder characteristics and composition of the soft magnetic metal powder obtained after the slow oxidation step thus obtained were examined by the following method.

<Average particle size>
The average particle diameter is an image obtained by observing the metal magnetic powder in a bright field at a accelerating voltage of 100 kV using a transmission electron microscope (JEM-100CXMark-II type manufactured by JEOL Ltd.) (for example, 58000 times magnification) ) And taking a picture (for example, the vertical and horizontal magnification is 9 times), randomly selecting 300 monodisperse particles from a plurality of photographs, measuring the particle size of each particle, Obtained from the average value.

<BET specific surface area>
The BET specific surface area was calculated | required by BET method using 4 Sorb US made from Your Scionics.

<Evaluation of magnetic properties and weather resistance of soft magnetic metal powder>
As the magnetic properties (bulk properties) of the obtained soft magnetic metal powder, a VSM device (VSM-7P) manufactured by Toei Kogyo Co., Ltd. was used, with an external magnetic field of 10 kOe (795.8 kA / m) and a coercive force Hc. (Oe and kA / m), saturation magnetization σs (Am ² / kg), and squareness ratio SQ were measured. Further, as an index (Δσs) for evaluating the weather resistance of the soft magnetic metal powder, the soft magnetic metal powder is kept in a constant temperature and humidity container at a set temperature of 60 ° C. and a relative humidity of 90% for one week, and the constant temperature and humidity are maintained. The saturation magnetization σs before and after holding was measured and determined according to (σ before storage−σ after storage) / σs before storage × 100 (%).

<Composition analysis of soft magnetic metal powder particles>
The composition of the soft magnetic metal powder particles was determined by mass analysis of the entire particle including the metal magnetic phase and the oxide film. Co, Al, Y, Mg, and Si were quantified using a high frequency induction plasma emission analyzer ICP (IRIS / AP) manufactured by Nippon Jarrell Ash. For the determination of Fe, a Hiranuma automatic titration apparatus (COMTIME-980) manufactured by Hiranuma Sangyo Co., Ltd. was used. Further, oxygen was quantified using NITRROGEN / OXYGEN DETERMETER (TC-436 type) manufactured by LECO Corporation. Since these quantitative results are given as mass%, the Co / Fe atomic ratio and Al / (Fe + Co) atomic ratio were determined by appropriately converting to atomic% (at%).

<Measurement of volume resistivity of soft magnetic metal powder>
The volume resistivity of the soft magnetic metal powder is measured using a powder resistance measurement unit (MCP-PD51) manufactured by Mitsubishi Chemical Analytech Co., Ltd. and a low resistance powder measurement system software (MCP-PDLGPWIN) manufactured by Mitsubishi Chemical Analytech Co., Ltd. Then, 1.0 g of powder was measured by a four-probe method in a state where the powder was vertically pressurized at 64 MPa (20 kN).

<Creation of soft magnetic metal powder compact>
The obtained soft magnetic metal powder is kneaded with a resin to obtain a molded body. As the resin used at this time, any known thermosetting resin can be used. The thermosetting resin can be selected from phenol resin, epoxy resin, unsaturated polyester resin, isocyanate compound, melamine resin, urea resin, silicone resin and the like. As the epoxy resin, either a monoepoxy compound, a polyvalent epoxy compound, or a mixture thereof is used.

Examples of the monoepoxy compound include butyl glycidyl ether, hexyl glycidyl ether, phenyl glycidyl ether, allyl glycidyl ether, para-tert-butylphenyl glycidyl ether, ethylene oxide, propylene oxide, paraxyl glycidyl ether, glycidyl acetate, glycidyl butyrate Glycidyl hexoate, glycidyl benzoate and the like.

Examples of the polyvalent epoxy compound include bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol AD, tetramethyl bisphenol S, tetrabromobisphenol A, and tetrachlorobisphenol A. Bisphenol-type epoxy resin obtained by glycidylation of bisphenols such as tetrafluorobisphenol A; epoxy resin obtained by glycidylation of other dihydric phenols such as biphenol, dihydroxynaphthalene and 9,9-bis (4-hydroxyphenyl) fluorene; 1,1,1-tris (4-hydroxyphenyl) methane, 4,4- (1- (4- (1- (4-hydroxyphenyl) -1-methylethyl) fe E) Ethylidene) Epoxy resins glycidylated with trisphenols such as bisphenol; Epoxy resins glycidylated with tetrakisphenols such as 1,1,2,2, -tetrakis (4-hydroxyphenyl) ethane; Phenol novolac, Cresol Novolak type epoxy resin obtained by glycidylation of novolaks such as novolak, bisphenol A novolak, brominated phenol novolak, brominated bisphenol A novolak, etc .; Glycidylated aliphatic ether type epoxy resin; ether ester type epoxy resin obtained by glycidylation of hydroxycarboxylic acid such as p-oxybenzoic acid and β-oxynaphthoic acid; phthalic acid , Ester-type epoxy resins obtained by glycidylation of polycarboxylic acids such as terephthalic acid; glycidyl compounds of amine compounds such as 4,4-diaminodiphenylmethane and m-aminophenol, and glycidyl such as amine-type epoxy resins such as triglycidyl isocyanurate Type epoxy resins and alicyclic epoxides such as 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate.

Among the above-mentioned epoxy resins, a polyvalent epoxy compound is preferable from the viewpoint of enhancing storage stability. Among polyhydric epoxy compounds, productivity is overwhelmingly high, so glycidyl-type epoxy resins are preferable, and more preferably epoxy obtained by glycidylation of polyhydric phenols because of excellent adhesion and heat resistance of cured products. It is preferable to use a resin. A bisphenol type epoxy resin is more preferable, and an epoxy resin obtained by glycidylating bisphenol A and an epoxy resin obtained by glycidylating bisphenol F are particularly preferable.

Further, the resin is preferably in a liquid form. In order to keep the composition solid, the epoxy equivalent is preferably 300 or more.

The mixing ratio of the soft magnetic metal powder and the epoxy resin is preferably 30/70 to 99/1, more preferably 50/50 to 95/5, and even more preferably 70 in terms of mass ratio when expressed in terms of metal / resin. / 30 to 90/10. This is because if the amount of the resin is too small, a molded body is not obtained, and if the amount is too large, desired magnetic properties cannot be obtained.

The soft magnetic metal powder of the present invention can be formed into an arbitrary shape by compression molding. What is supplied in practical use is the shape illustrated in FIGS. 1 and 2. However, in the following examples, it was molded into a donut shape, and the characteristics as a magnetic part were evaluated.

The soft magnetic metal powder and the epoxy resin were weighed at a weight ratio of 80:20, and dispersed in an epoxy resin using a vacuum agitation / defoaming mixer (V-mini300) manufactured by EME Co., Ltd. to obtain a paste. This paste was dried on a hot plate at 60 ° C. for 2 hours to obtain a soft magnetic metal powder-resin composite. This composite is pulverized to prepare a composite powder. 0.2 g of this composite powder is placed in a donut-shaped container, and a load of 1 t is applied by a hand press machine. A 3 mm toroidal shaped body was obtained.

<High-frequency characteristics evaluation of soft magnetic metal powder-resin composite>
As a high frequency characteristic of the obtained soft magnetic metal powder-resin composite molded body, a network analyzer (E8362C) manufactured by Agilent Technology Co., Ltd. and a coaxial S-parameter method sample holder kit manufactured by Kanto Electronics Co., Ltd. ( Product model: CSH2-APC7, sample size: φ7.0mm-φ3.04mm × 5mm), real part of magnetic permeability (μ ′), imaginary part of magnetic permeability (μ ”), loss at 0.5-3GHz Tan δ representing the coefficient was measured.

[Example 1]
The precursor formation process was performed as follows. In a 5000 mL beaker, 3000 mL of pure water and 100 mL of 12 mol / L sodium hydroxide were added and stirred while maintaining the temperature at 40 ° C. with a temperature controller. 900 mL of a solution obtained by mixing a 2 mol / L ferric sulfate (special grade reagent) solution and a 1 mol / L ferrous sulfate (special grade reagent) aqueous solution at a mixing ratio of Fe ²⁺ / Fe ³⁺ = 20 was added thereto.

Thereafter, the temperature was raised to 90 ° C., and air was further vented at 200 mL / min to continue oxidation for 40 minutes. After aging for 10 minutes after switching the air to nitrogen, add 80 ml of 0.3 mol / L aluminum sulfate (special grade reagent), ventilate air at 200 mL / min and continue the oxidation for 50 minutes to complete the oxidation. It was. In this way, precursor particles in which Al was dissolved in Fe were obtained. The precursor was filtered and washed with water by a conventional method, and then dried at 110 ° C. to obtain a precursor dry solid (also referred to as precursor powder).

Next, a precursor reduction step was performed. The precursor powder in which Al is dissolved in Fe is put into a bucket that can be ventilated, the bucket is placed in a penetration type reduction furnace, and reduction treatment is performed at 500 ° C. for 60 minutes while ventilating hydrogen gas. gave. After the reduction treatment, metallic iron powder (soft magnetic metal powder) was obtained.

Thereafter, in order to shift to the gradual oxidation step, the atmosphere in the furnace was converted from hydrogen to nitrogen, and the temperature in the furnace was lowered to 80 ° C. at a temperature lowering rate of 20 ° C./min in a state where nitrogen was passed. In the gradual oxidation process, at the initial stage of oxide film formation, a gas mixed with an air amount of 1/125 with respect to N ₂ is added into the furnace so that the metal iron powder is not rapidly oxidized, and oxygen / nitrogen is added. The oxygen concentration in the atmosphere was increased by forming an oxide film in the mixed atmosphere and gradually increasing the supply amount of air.

Flow rate of the air that is finally supplied to the mixing amount of 1/25 relative to N _2. At that time, the total amount of gas introduced into the furnace was kept almost constant by adjusting the flow rate of nitrogen. This slow oxidation treatment was carried out in an atmosphere maintained at approximately 80 ° C.

Thus, the final soft magnetic metal powder (having a surface oxide film) was obtained. Various physical properties and bulk characteristics of the obtained soft magnetic metal powder are shown in Table 2, and high frequency characteristics of a molded body using the soft magnetic metal powder are shown in Table 3. The conditions of the composition and the precursor reduction step and the gradual oxidation step are shown in Table 1 including other examples.

[Example 2]
In a 5000 mL beaker, 3000 mL of pure water and 100 mL of 12 mol / L sodium hydroxide were added and stirred while maintaining the temperature at 40 ° C. with a temperature controller. 900 mL of a solution in which a 1 mol / L ferrous sulfate (special grade reagent) aqueous solution and a 1 mol / L cobalt sulfate (special grade reagent) solution were mixed at a mixing ratio of 4: 1 was further added to 900 mL, and (Fe ²⁺ + Co ²⁺ ) An amount of 2 mol / L of ferric sulfate (special grade reagent) solution was added at the same time so that / Fe ³⁺ = 20. Thereafter, the same procedure as in Example 1 was repeated to obtain a soft magnetic metal powder (a part of Fe having a surface oxide film substituted with Co). Various physical properties and bulk characteristics of the obtained soft magnetic metal powder are shown in Table 2, and high frequency characteristics of a molded body using the soft magnetic metal powder are shown in Table 3.

[Example 3]
In Example 2, the same procedure as in Example 2 was repeated except that the mixing ratio of the 1 mol / L ferrous sulfate (special grade reagent) aqueous solution and the 1 mol / L cobalt sulfate (special grade reagent) solution was changed to 8: 5. It was. Various physical properties and bulk characteristics of the obtained soft magnetic metal powder are shown in Table 2, and high frequency characteristics of a molded body using the soft magnetic metal powder are shown in Table 3.

Here, Examples 1 to 3 are considered. Compared with Example 1 containing no Co, Examples 2 and 3 containing Co resulted in higher μ ′. It can be considered that by containing Co and making an FeCo alloy, the magnetic moment is increased and the saturation magnetization is increased, thereby increasing the magnetic permeability. In other words, the inclusion of Co has the effect of increasing μ ′.

Further, normally, when μ ′ increases, the resonance frequency shifts to the lower frequency side, and tan δ tends to deteriorate (become larger). However, in this embodiment, even if μ ′ is increased by increasing the amount of Co. As a result, tan δ did not deteriorate (does not increase). The reason for this seems to be that by containing Co, a denser oxide film could be formed, so that the volume resistivity of the powder increased and eddy current loss could be reduced. That is, it has been found that the inclusion of Co has an effect of improving μ ′ without deteriorating (increasing) tan δ.

[Example 4]
In Example 2, the amount of Fe ³⁺ for forming nuclei was changed to (Fe ²⁺ + Co ²⁺ ) / Fe ³⁺ = 33, and 0.3 mol / L aluminum sulfate (special grade reagent) added during the oxidation reaction. ) Was changed to 45 ml, and the same procedure as in Example 2 was repeated. Various physical properties and bulk characteristics of the obtained soft magnetic metal powder are shown in Table 2, and high frequency characteristics of a molded body using the soft magnetic metal powder are shown in Table 3.

[Examples 5 to 8]
For Examples 5 to 8, the same procedure as in Example 4 was repeated except that the amount of aluminum sulfate in Example 4 was changed to the amount shown in Table 1. Various physical properties and bulk characteristics of the obtained soft magnetic metal powder are shown in Table 2, and high frequency characteristics of a molded body using the soft magnetic metal powder are shown in Table 3.

Here, Examples 4 to 8 are considered. It has been found that increasing the amount of Al contained has the effect of reducing tan δ. In the present invention, when a precursor containing Fe, Co, and Al is reduced, Fe and Co that are easily reduced are present inside the particle, and aluminum oxide that is not easily reduced is present on the particle surface. An oxide film containing Al is formed. For this reason, when the amount of Al to be included is increased, an oxide film containing more aluminum oxide is formed on the particle surface, so that the volume resistivity of the particles is increased, eddy current loss is reduced, and tan δ is It seems to have become smaller.

Further, a TEM photograph of the powder obtained in Example 7 is shown in FIG. This TEM image was taken with an acceleration voltage of 100 kV, and the contrast was adjusted so that the core portion appeared black. As a result, in FIG. 3 shown as a confirmed example, there is a spherical portion that appears dark at the center of the substantially spherical particle, and a portion that appears thin and substantially transparent appears in the periphery. As shown in this photograph, the soft magnetic metal powder obtained by the present invention is formed of a core portion made of metal and a shell portion made of an oxide film.

Examples of the composition analysis of the core / shell particles include ICP emission analysis, ESCA, TEM-EDX, XPS, SIMS, and the like. In particular, according to ESCA, a change in composition from the particle surface in the depth direction can be confirmed, and a core portion formed of metal and a shell portion formed of oxide can be distinguished. In addition, according to TEM-EDX, the particle is focused to irradiate EDX and semi-quantitatively to confirm the rough composition of the particle. The core part formed of metal and the shell formed of oxide The part can be discriminated (for example, refer to paragraph [0078] of JP-A-2006-128535).

[Examples 9 to 10]
For Examples 9 to 10, the same procedure as in Example 8 was repeated except that the reduction temperature in Example 8 was changed to the temperature described in Table 1. Various physical properties and bulk characteristics of the obtained soft magnetic metal powder are shown in Table 2, and high frequency characteristics of a molded body using the soft magnetic metal powder are shown in Table 3.

Here, although Examples 7, 9, and 10 have different precursor reduction temperatures, it was found that the higher the reduction temperature, the higher the value of μ ′. This is probably because the reduction and the alloying of Fe and Co were promoted by raising the reduction temperature.

[Example 11]
In Example 2, the same procedure as in Example 2 was repeated except that the reduction temperature with hydrogen gas in the through-type reduction furnace was changed to 600 ° C. Various physical properties and bulk characteristics of the obtained soft magnetic metal powder are shown in Table 2, and high frequency characteristics of a molded body using the soft magnetic metal powder are shown in Table 3.

[Example 12]
In Example 11, the same procedure as in Example 11 was repeated except that the amount of Fe ³⁺ for forming nuclei was changed to (Fe ²⁺ + Co ²⁺ ) / Fe ³⁺ = 85. Various physical properties and bulk characteristics of the obtained soft magnetic metal powder are shown in Table 2, high frequency characteristics of a molded body using the soft magnetic metal powder are shown in Table 3, and a TEM photograph of the obtained powder is shown in FIG. Also from this photograph, it can be seen that the soft magnetic metal powder obtained in the present invention is formed of a core portion formed of metal and a shell portion formed of an oxide film.

[Comparative Example 1]
As the soft magnetic metal powder of Comparative Example 1, a commercially available Mn—Zn ferrite powder was used. Table 2 shows various physical properties and bulk characteristics of the soft magnetic metal powder, and Table 3 shows high-frequency characteristics of a molded body using the soft magnetic metal powder.

[Comparative Example 2]
As the soft magnetic metal powder of Comparative Example 2, a commercially available Fe—Cr—Si powder was used. Table 2 shows various physical properties and bulk characteristics of the soft magnetic metal powder, and Table 3 shows high-frequency characteristics of a molded body using the soft magnetic metal powder.

The soft magnetic metal powder of the present invention is used not only for inductors and antennas but also for soft magnetic applications such as magnetic heads, lower layers of magnetic recording media, iron cores of electromagnets, transformer cores, antennas, electromagnetic shielding materials, and radio wave absorbers. be able to.

DESCRIPTION OF SYMBOLS 1 Conductor plate 2 Feeding point 3 Short-circuit plate 4 Radiation plate 5 Molded body 6 Electrode 7 鍔 8 Winding 9 Winding core 10 Antenna 11 Coil 12 Coil parts

Claims

It is a soft magnetic metal powder mainly composed of iron,
An average particle size of 300 nm or less,
The coercive force (Hc) is 16 to 119 kA / m (200 to 1500 Oe),
The saturation magnetization is 90 Am 2 / kg or more,
In a state where 1.0 g of the soft magnetic metal powder is vertically pressurized at 64 MPa (20 kN),
A soft magnetic metal powder having a volume resistivity of 1.0 × 10 1 Ω · cm or more measured by a four-point probe method.
The soft magnetic metal powder forms a core / shell structure, the core contains iron or iron-cobalt alloy, the shell contains at least one of iron, cobalt, aluminum, silicon, rare earth elements (including Y), and magnesium. The soft magnetic metal powder according to claim 1, which is a composite oxide.
The soft magnetic metal powder according to claim 2, wherein the iron-cobalt ratio in the iron-cobalt alloy is Co / Fe = 0.0 to 0.6 in terms of atomic ratio.
4. The soft magnetic metal powder according to claim 1, wherein the soft magnetic metal powder contains aluminum, and an atomic ratio of the sum of Fe and Co is a sum of the sum of Al / Fe and Co = 0.01 to 0.30. The soft magnetic metal powder according to the above.
When the soft magnetic metal powder and the epoxy resin are mixed at a mass ratio of 80:20 and pressure-molded,
The real part of the complex permeability is μ ′, the imaginary part is μ ″, and the loss coefficient is tan δ (= μ ″ / μ ′).
Μ ′> 1.5 and μ ″ <0.5, tan δ <0.15 at a frequency of 1 GHz, and μ ′> 1.5 and μ ″ <1.5, tan δ <0.5 at a frequency of 2 GHz. The soft magnetic metal powder according to any one of claims 1 to 4, wherein
An inductor formed using the soft magnetic metal powder according to any one of claims 1 to 5.
An antenna formed using the soft magnetic metal powder according to any one of claims 1 to 5.
While blowing an oxygen-containing gas into a solution containing iron ions, at least one aqueous solution of aluminum, silicon, rare earth elements (including Y), and magnesium is added, and aluminum, silicon, rare earth elements (including Y) are added. A precursor forming step of forming a precursor containing at least one kind of magnesium;
A precursor reduction step of reducing the precursor to form a metal powder;
A method for producing a soft magnetic metal powder, further comprising a gradual oxidation step in which oxygen is further applied to the metal powder obtained in the precursor reduction step to form an oxide film on the surface of the metal powder.
The method for producing a soft magnetic metal powder according to claim 8, wherein the solution containing iron ions is an aqueous solution of an iron compound and a cobalt compound.
The method for producing a soft magnetic metal powder according to claim 8 or 9, wherein the precursor obtained in the precursor forming step exhibits a spinel crystal structure by a powder X-ray diffraction method.
The method for producing a soft magnetic metal powder according to any one of claims 8 to 10, wherein in the precursor reduction step, the precursor is exposed to a reducing gas at a temperature of 250 ° C to 650 ° C.
The soft magnetic metal powder according to any one of claims 8 to 11, wherein the gradual oxidation step is a step of exposing the metal powder to a gas containing oxygen in an inert gas at a temperature of 20 ° C to 150 ° C. Manufacturing method.