CN110880394A

CN110880394A - Soft magnetic composition, magnetic core, and coil-type electronic component

Info

Publication number: CN110880394A
Application number: CN201910747970.0A
Authority: CN
Inventors: 松野谦一郎; 伊藤守; 涩谷好孝; 三浦隆之; 伊东直树
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2018-09-05
Filing date: 2019-08-14
Publication date: 2020-03-13
Anticipated expiration: 2039-08-14
Also published as: JP2020038923A; JP7334835B2; JP2022163226A; CN110880394B; JP7128692B2

Abstract

The invention aims to: provided are a soft magnetic material composition, a magnetic core, and a coil-type electronic component, which can realize low core loss. The soft magnetic material composition of the present invention has a plurality of soft magnetic alloy particles, the soft magnetic alloy particles contain an element M and iron, the element M has a stronger ionization tendency than silicon, and the maximum value of the mass ratio of silicon to the element M in the region between the soft magnetic alloy particles is (Si/M)_MAXThen, (Si/M)_MAXSatisfies 1 ≤ (Si/M)_MAX≤10。

Description

Soft magnetic composition, magnetic core, and coil-type electronic component

Technical Field

The invention relates to a soft magnetic material composition, a magnetic core and a coil type electronic component.

Background

The metal magnetic material has an advantage that a high saturation magnetic flux density can be obtained as compared with ferrite. As such a metallic magnetic body, an Fe-Si-Al alloy, an Fe-Si-Cr alloy, or the like is known.

Patent document 1 proposes a coil-type electronic component using a magnetic material containing chromium, aluminum, and silicon and having an improved magnetic permeability.

Examples of the coil-type electronic component include an inductor, an EMC coil, and a transformer.

In recent years, magnetic materials used for these coil-type electronic components are increasingly required to have further reduced core loss.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-249774

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made in view of such circumstances, and an object thereof is to: provided are a soft magnetic material composition, a magnetic core, and a coil-type electronic component, which can realize low core loss.

Technical solution for solving technical problem

In order to achieve the above object, the soft magnetic material composition of the present invention is characterized in that:

having a plurality of soft magnetic alloy particles,

the soft magnetic alloy particles described above contain the element M and iron,

the above element M has a stronger ionization tendency than silicon,

the maximum value of the mass ratio of silicon to the element M in the region between the soft magnetic alloy particles was defined as (Si/M)_MAXWhen the temperature of the water is higher than the set temperature,

above (Si/M)_MAXSatisfies 1 ≤ (Si/M)_MAX≤10。

In the soft magnetic composition of the present invention, the soft magnetic alloy particles contain the element M, and (Si/M)_MAXSatisfies 1 ≤ (Si/M)_MAX10 below, the magnetic core loss can be reduced.

Preferably in the above (Si/M)_MAXAn amorphous layer is present at the site of (a).

Present through an amorphous layer (Si/M)_MAXThe core loss can be reduced.

Preferably in a composition comprising (Si/M)_MAXThe element M is continuously present within a predetermined range including the site of (A),

the predetermined range is a range of 50% or more of the distance between adjacent soft magnetic alloy particles.

By including (Si/M)_MAXThe element M continuously exists within a predetermined range, and the core loss can be reduced.

Further, the magnetic core of the present invention is composed of the soft magnetic material composition described in any one of the above.

Preferably, a coating layer is formed on at least a part of the surface of the magnetic core.

The coil-type electronic component of the present invention has the above-described magnetic core. The coil-type electronic component is not particularly limited, and examples thereof include electronic components such as inductors, EMC coils, and transformers. The coil-type electronic component is particularly suitable for miniaturization which can be surface-mounted on a circuit board.

Drawings

Fig. 1 shows a magnetic core according to an embodiment of the present invention.

Fig. 2 is an enlarged sectional view of a main portion of the magnetic core shown in fig. 1.

Fig. 3 is an enlarged cross-sectional view of a main portion of a magnetic core showing an observation point when performing EDS analysis.

FIG. 4 is a selected area diffraction pattern of the crystal lattice.

Figure 5 is a selected area diffraction pattern of an amorphous layer.

FIG. 6 is the EDS analysis results of example 4 according to the present invention.

Description of the reference numerals

21. 22 … Soft magnetic alloy particles

30. 31 … regions between soft magnetic alloy particles

Detailed Description

The present invention will be described below based on embodiments shown in the drawings.

The magnetic core of the coil-type electronic component of the present embodiment is a magnetic core (powder magnetic core) molded by powder molding. Powder compacting is a method of filling a die of a press machine with a material containing soft magnetic alloy powder, and performing compression molding under a predetermined pressure to obtain a compact.

As the shape of the core (core) of the present embodiment, FT type, ET type, EI type, UU type, EE type, EER type, UI type, drum type, pot type, cup type, and the like can be exemplified in addition to the ring type shown in fig. 1. By winding one or more wires around the magnetic core, a desired coil-type electronic component can be obtained.

The magnetic core for the coil-type electronic component of the present embodiment is made of a soft magnetic composition.

As shown in fig. 2, the soft magnetic material composition of the present embodiment has a plurality of soft

magnetic alloy particles

21 and 22. In the present embodiment, regions from one adjacent soft magnetic alloy particle 21 to another adjacent soft magnetic alloy particle 22 are

regions

30 and 31 between the soft magnetic alloy particles.

The soft

magnetic alloy particles

21 and 22 of the present embodiment contain an element M and iron (Fe). Although not particularly limited, the soft

magnetic alloy particles

21 and 22 of the present embodiment may contain silicon (Si), carbon (C), or zinc (Zn) in addition.

The ionization tendency of the element M is stronger than that of silicon (Si). In addition, the element M tends to form an oxide film on the surfaces of the soft

magnetic alloy particles

21 and 22. Examples of the element M include chromium (Cr), aluminum (Al), magnesium (Mg), titanium (Ti), zirconium (Zr), manganese (Mn), and zinc (Zn), but chromium (Cr) or aluminum (Al) is preferable from the viewpoint of forming a uniform oxide film on the iron alloy particles. Further, the element M is not limited to one kind, and a plurality of kinds of elements may be used.

For example, when the element M is chromium (Cr), the soft

magnetic alloy particles

21 and 22 of the present embodiment contain 1 to 9 mass% of chromium (Cr) in terms of Cr and 0 to 9 mass% of silicon (Si) in terms of Si, and the balance is iron (Fe).

In addition, in the soft

magnetic alloy particles

21 and 22 of the present embodiment, when the element M is aluminum (Al), for example, the soft magnetic alloy particles contain 1 to 9 mass% of aluminum (Al) in terms of Al and 0 to 14 mass% of silicon (Si) in terms of Si, and the balance is iron (Fe).

The content of chromium (Cr) in the soft

magnetic alloy particles

21 and 22 of the present embodiment is preferably 1 to 9 mass% in terms of Cr. Thereby, the (Si/M) is easily made_MAXWithin the specified range. From the above viewpoint, the content of chromium (Cr) in the soft

magnetic alloy particles

21, 22 is more preferably 3 to 7 mass% in terms of Cr.

The content of aluminum (Al) in the soft

magnetic alloy particles

21 and 22 of the present embodiment is preferably 1 to 9 mass% in terms of Al. Thereby, the (Si/M) is easily made_MAXWithin the specified range. From the above viewpoint, the content of aluminum (Al) in the soft

magnetic alloy particles

21, 22 is more preferably 3 to 7 mass% in terms of Al.

The content of silicon (Si) in the soft

magnetic alloy particles

21 and 22 of the present embodiment is preferably 0 to 9 mass%, and more preferably 2 to 8.5 mass%, in terms of Si.

In the soft

magnetic alloy particles

21 and 22 of the present embodiment, the remaining portion may be composed of only iron (Fe).

The soft magnetic material composition of the present embodiment may contain components such as carbon (C) and zinc (Zn) in addition to the components of the soft

magnetic alloy particles

21 and 22.

The content of carbon (C) in the soft magnetic material composition of the present embodiment is preferably less than 0.05 mass%, and more preferably 0.01 to 0.04 mass%.

The content of zinc (Zn) in the soft magnetic material composition of the present embodiment is preferably 0.004 to 0.2 mass%, and more preferably 0.01 to 0.2 mass%.

The soft magnetic material composition of the present embodiment may contain inevitable impurities in addition to the above components.

The average crystal grain size of the soft

magnetic alloy particles

21 and 22 of the present embodiment is preferably 4 to 60 μm. By setting the average crystal grain size in the above range, the core can be easily made thin.

Hereinafter, the "mass ratio of silicon (Si), element M, or iron (Fe) to the total mass of silicon (Si), element M, and iron (Fe)" in the

regions

30 and 31 between the soft

magnetic alloy particles

21 and 22 is referred to as a "ternary element mass ratio".

In the following description, the "mass ratio of oxygen (O), silicon (Si), element M, or iron (Fe) to the total mass of oxygen (O), silicon (Si), element M, and iron (Fe)" in the

regions

30 and 31 between the soft

magnetic alloy particles

21 and 22 is referred to as a "four-element mass ratio".

In this embodiment, an amorphous layer is present in (Si/M)_MAXThe location of (1). Thus, a soft magnetic material composition capable of realizing a low magnetic core loss can be obtained.

From the above viewpoint, it is preferable that Si-M oxide or Si-M composite oxide exists as an amorphous layer in the

regions

30, 31 between the soft

magnetic alloy particles

21, 22.

Further, the Si — M oxide is an oxide mainly composed of silicon (Si), an element M, and oxygen (O). Further, the Si — M composite oxide is an oxide containing silicon (Si), an element M, and oxygen (O), and also containing elements other than these three components (Si, M, and O).

Examples of the elements other than the three components (Si, elements M, and O) contained in the Si — M composite oxide include vanadium (V), nickel (Ni), and copper (Cu).

The Si — M oxide contains less than 0.1 mass% of elements other than silicon (Si), element M, and oxygen (O) in total, relative to 100 mass% of the total mass of silicon (Si), element M, and oxygen (O).

Examples of the elements other than the three components (Si, elements M, and O) contained in the Si — M oxide include vanadium (V), nickel (Ni), and copper (Cu).

In the present embodiment, it is considered that silicon (Si) not derived from the element contained in the soft

magnetic alloy particles

21, 22 is contained in the

regions

30, 31 between the soft

magnetic alloy particles

21, 22. Silicon (Si) not derived from the element contained in the soft

magnetic alloy particles

21 and 22 is not particularly limited, and is, for example, considered to be derived from silicon (Si) contained in a silicone resin used as a binder.

In the present embodiment, the maximum value of the mass ratio of silicon (Si) to the element M in the

regions

30 and 31 between the soft

magnetic alloy particles

21 and 22 is (Si/M)_MAXThen, (Si/M)_MAXSatisfies 1 ≤ (Si/M)_MAXLess than or equal to 10. Thus, a soft magnetic material composition capable of realizing a low magnetic core loss can be obtained.

The Si-M oxide or Si-M composite oxide as an amorphous layer present in the

regions

30, 31 between the soft

magnetic alloy particles

21, 22 is in a tendency as follows: by its randomness, it helps to reduce the eddy current losses crossing in the

regions

30, 31 between the soft

magnetic alloy particles

21, 22. Thus, by (Si/M)_MAXWithin the specified range and in (Si/M)_MAXThe portion (B) has Si-M oxide or Si-M composite oxide as an amorphous layer, so that the eddy current loss is reduced and the core loss tends to be further reduced.

In the present embodiment, the calculation (Si/M)_MAXThe method (2) is not particularly limited, and specific methods are shown below.

First, the

areas

30, 31 between the soft

magnetic alloy particles

21, 22 and the soft

magnetic alloy particles

21, 22 are discriminated by observing the cross section of the core using a Scanning Transmission Electron Microscope (STEM). Specifically, a cross section of the core is photographed by STEM, and a Bright Field (BF) image is obtained. In the bright field image, regions which exist between the soft

magnetic alloy particles

21, 22 and have a different contrast from the soft

magnetic alloy particles

21, 22 are defined as

regions

30, 31 between the soft

magnetic alloy particles

21, 22. The determination of whether or not there is a difference in contrast may be performed visually, or may be performed by software for performing image processing or the like.

As shown in fig. 3, the composition of the

regions

30 and 31 between the soft

magnetic alloy particles

21 and 22 was analyzed by EDS using an EDS apparatus having a sufficiently high resolution attached to STEM on an arbitrarily selected observation line X. Fig. 6 shows the results of EDS analysis according to the present embodiment. The first vertical axis of fig. 6 represents the ternary prime mass ratio, the second vertical axis represents the Si/M mass ratio, and the horizontal axis represents the distance from the origin. Here, the "starting point" is an arbitrary point within the soft magnetic alloy particle 21.

In fig. 6, the three-element mass ratio of silicon (Si) is shown by a solid line, the three-element mass ratio of chromium (Cr) is shown by a broken line, the three-element mass ratio of iron (Fe) is shown by a chain line, and the Si/M mass ratio is shown by a two-dot chain line.

In FIG. 6, the ternary element mass ratio of iron (Fe) is substantially constant in the range of 0 to 0.35 μm from the starting point, in the vicinity of 95 wt%. This region is a soft magnetic alloy particle 21.

In FIG. 6, in the interval of 0.35 to 0.66 μm in distance from the starting point, the ternary element mass ratio of iron (Fe) decreases, becomes approximately constant in the vicinity of 0 wt%, and then increases. This region is a region 31 between the soft

magnetic alloy particles

21, 22.

In FIG. 6, the ternary content of iron (Fe) is again approximately constant in the range of 95 to 98 wt% in the interval of 0.66 to 1.0 μm from the starting point. This region is another soft magnetic alloy particle 22.

Then, based on the obtained values, (Si/M) in the region 31 between the soft

magnetic alloy particles

21, 22 is determined_MAX。

Although not particularly limited, in the present embodiment, when the four-element mass ratio of oxygen (O) is 8 to 65 mass%, the four-element mass ratio of silicon (Si) is 8 to 65 mass%, and the four-element mass ratio of element M is 8 to 65 mass%, the position is determined to be a Si-M oxide or a Si-M composite oxide.

Further, by comparing the map image of oxygen (O), the map image of silicon (Si), and the map image of element M, if oxygen (O), silicon (Si), and element M are present at the same position, it is also possible to judge that the position is a Si-M oxide or a Si-M composite oxide.

In the present embodiment, the method of determining whether or not an amorphous layer is present in the

regions

30 and 31 between the soft

magnetic alloy particles

21 and 22 is not particularly limited, and for example, the determination may be made by analyzing a selective diffraction pattern (SADP) of a reciprocal lattice space of a scanning Transmission Electron Microscope (TEM). In the selected area diffraction pattern, when the selected area diffraction pattern has a regular crystal structure, as shown in fig. 4, diffraction spots reflecting the crystal structure are observed. On the other hand, in the case of an amorphous layer having no regular crystal structure, concentric circles centering on a central spot were observed as shown in fig. 5. In the case of the amorphous layer, no distinct diffraction spots other than the central spot were observed.

In the present embodiment, as shown in FIG. 6, it is preferable to use a composition comprising (Si/M)_MAXThe element M is continuously present within a predetermined range including the site(s). Thus, a soft magnetic material composition capable of realizing a low magnetic core loss can be obtained.

From the above viewpoint, it is preferable to use a compound containing (Si/M)_MAXSilicon (Si) is continuous within a predetermined range including the portion(s).

Here, the predetermined range is preferably a range of 50% or more of the distance between the adjacent soft

magnetic alloy particles

21 and 22.

The term "the element M is continuous in the predetermined range" means that the ternary element mass ratio of the element M is preferably 8 mass% or more, more preferably 10 mass% or more in the predetermined range.

The term "silicon (Si) continuous in the predetermined range" means that the ternary element mass ratio of silicon (Si) is preferably 5 mass% or more, more preferably 8 mass% or more in the predetermined range.

The length of the predetermined range is preferably 0.01 to 0.4. mu.m, more preferably 0.01 to 0.1. mu.m.

A coating layer may be formed on at least a part of the surface of the magnetic core of the present embodiment. This can further reduce the core loss of the core.

The material of the coating layer is not particularly limited, and examples thereof include a glass composition and SiO₂、B₂O₃、ZrO₂Or a resin. The cover layer may be made of a plurality of materials, or may have a laminated structure of a plurality of layers.

The cover layer may be formed on at least a part of the surface of the magnetic core, for example. The ratio of the coating layer to the surface area of the magnetic core (coverage ratio) is preferably 50 to 100%. The higher the coverage, the greater the role of the protective layer as a means of preventing defects and the like in the magnetic core. From the above viewpoint, the coverage is more preferably 90 to 100%.

Next, an example of the method for manufacturing the magnetic core according to the present embodiment will be described.

The magnetic core of the present embodiment can be produced by firing a molded body containing soft magnetic alloy powder and a binder (binder resin). Next, a preferred method for manufacturing the magnetic core of the present embodiment will be described in detail.

The manufacturing method of the present embodiment preferably includes the steps of:

mixing soft magnetic alloy powder and a binder to obtain a mixture;

drying the mixture to form granulated powder;

forming the mixture or granulated powder into the shape of the magnetic core to be produced to obtain a formed body; and

and heating the obtained molded article to obtain a magnetic core.

Further, a cover layer may be formed on the magnetic core.

The magnetic core obtained by the production method of the present embodiment is composed of the soft magnetic material composition of the present embodiment.

As the soft magnetic alloy powder, a powder containing alloy particles containing 1 to 9 mass% of chromium (Cr) in terms of Cr, 0 to 9 mass% of silicon (Si) in terms of Si, and the balance of iron (Fe) can be used.

The shape of the soft magnetic alloy powder is not particularly limited, and is preferably spherical or ellipsoidal from the viewpoint of maintaining the inductance to the high magnetic field region. Among them, from the viewpoint of further increasing the strength of the magnetic core, an elliptical shape is preferable.

The average particle diameter of the soft magnetic alloy powder is preferably 3 to 80 μm. When the average particle diameter of the soft magnetic alloy powder is within the above range, the magnetic permeability is good, eddy current loss is less likely to occur, and the abnormal loss tends to decrease. In addition, handling becomes easy. From the above viewpoint, the average particle diameter of the soft magnetic alloy powder is more preferably 5 to 20 μm.

The soft magnetic alloy powder can be obtained by the same method as the known method for producing a soft magnetic alloy powder. In this case, the coating composition can be prepared by a gas atomization method, a water atomization method, a rotary disk method, or the like. Among them, the water atomization method is preferable because soft magnetic alloy powder having desired magnetic properties can be easily produced.

As the adhesive, an adhesive containing a silicone resin can be used. By using a silicone resin as a binder, silicon (Si) that is not derived from the element contained in the soft

magnetic alloy particles

21, 22 can be effectively contained in the

regions

30, 31 between the soft

magnetic alloy particles

21, 22. As a result, amorphous layers are easily formed in the

regions

30, 31 between the soft

magnetic alloy particles

21, 22.

Other binders may be contained within a range not to impair the effects of the present invention. Examples of the other binders include various organic polymer resins, phenol resins, epoxy resins, and water glass.

The adhesive can be used with a silicone resin alone or in combination with other adhesives. Further, since the content of carbon (C) in the soft magnetic body composition is preferably limited to less than 0.05 mass%, the binder preferably mainly uses a silicone resin. When the content of carbon (C) in the soft magnetic material composition is within the above range, the strength of the obtained magnetic core can be improved.

The amount of the binder added varies depending on the required magnetic core characteristics, and is preferably 0.2 to 10% by mass based on 100% by mass of the soft magnetic alloy powder. When the addition amount of the binder is in the above range, an amorphous layer is easily formed in the

regions

30, 31 between the soft

magnetic alloy particles

21, 22. From the above viewpoint, the amount of the binder to be added is more preferably 0.5 to 6% by mass based on 100% by mass of the soft magnetic alloy powder.

The amount of silicone resin added is preferably 0.2 to 8% by mass relative to 100% by mass of the soft magnetic alloy powder. When the addition amount of the silicone resin is in the above range, an amorphous layer is easily formed in the

regions

30, 31 between the soft

magnetic alloy particles

21, 22. From the above viewpoint, the amount of silicone resin added is more preferably 0.5 to 5% by mass relative to 100% by mass of the soft magnetic alloy powder.

In addition, an organic solvent may be added to the mixture or granulated powder as necessary within a range not to impair the effects of the present invention.

The organic solvent is not particularly limited as long as it is an organic solvent capable of dissolving 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 granulated powder as necessary within a range not to impair the effects of the present invention.

Examples of the lubricant include aluminum stearate, barium stearate, magnesium stearate, calcium stearate, zinc stearate, and strontium stearate. These lubricants may be used singly or in combination of two or more. Among them, zinc stearate is preferably used as the lubricant from the viewpoint of small so-called spring back.

When a lubricant is used, the amount of the lubricant added is preferably 0.1 to 0.9% by mass based on 100% by mass of the soft magnetic alloy powder.

In particular, when zinc stearate is used as the lubricant, the amount of zinc (Zn) is preferably adjusted so that the content of zinc in the obtained soft magnetic material composition is in the range of 0.004 to 0.2 mass%. This tends to improve the strength of the magnetic core.

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

For the mixing, for example, a mixer such as a pressure kneader, a stirring ball mill (アタライタ), a vibration mill, a ball mill, or a V-type mixer, a granulator such as a flow granulator, or a roll granulator, may be used.

The temperature and time of the mixing treatment are preferably about 1 to 30 minutes at room temperature.

The method for obtaining the granulated powder is not particularly limited, and the granulated powder can be obtained by drying the mixture by a known method.

The temperature and time of the drying treatment are preferably about room temperature to 200 ℃ for 1 to 60 minutes.

A lubricant may be added to the granulated powder as needed. Preferably, the granulation powder is mixed for 1 to 60 minutes after the lubricant is added.

The method for obtaining the molded article is not particularly limited, and it is preferable to use a molding die having a cavity of a desired shape by a known method, fill the mixture or granulated powder in the cavity, and compression-mold the mixture at a predetermined molding temperature and a predetermined molding pressure.

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

In the manufacturing method of the present embodiment, the amorphous layer is easily formed in the

regions

30 and 31 between the soft

magnetic alloy particles

21 and 22 constituting the magnetic core by containing the silicone resin in the binder.

The molding temperature is not particularly limited, but is preferably about room temperature to 200 ℃. This increases the density of the molded body and improves the performance of the resulting magnetic core.

Next, the molded body obtained after molding is fired to obtain a magnetic core (firing step).

The holding temperature in the firing step is not particularly limited, but is preferably about 600 to 900 ℃. Thereby, the (Si/M) is easily made_MAXWithin the specified range. From the above viewpoint, the holding temperature during firing is preferably 700 to 850 ℃.

The temperature increase rate in the firing step is not particularly limited, and it is preferable that the molded article is brought to the holding temperature in a short time after the initiation of heating. Thus, heating in a short time makes it easy to obtain (Si/M)_MAXWithin the specified range.

The heating method in the firing step is not particularly limited, and for example, a thin and small-area container having good heat transfer is prepared, and the molded body is placed on the container in a small number (1 to 10) and sufficiently separated from the container. Specifically, the adjacent molded bodies are placed 10 to 100mm apart. Next, a method of directly placing the molded article together with the container into a furnace having reached the holding temperature is exemplified. In addition, a method of directly placing a heating body having reached the holding temperature into the furnace after the heating body is sandwiched between the upper and lower surfaces of the molded body is also exemplified.

The atmosphere in the firing step is not particularly limited, and may be performed in an oxygen-containing atmosphere. Here, the oxygen-containing atmosphere is not particularly limited, and an atmospheric atmosphere (normally, containing 20.95% of oxygen) or a mixed atmosphere with an inert gas such as argon or nitrogen may be mentioned. Alternatively, the reaction may be performed under an inert gas such as argon or nitrogen.

The holding time in the firing step is not particularly limited, and is, for example, 10 minutes to 5 hours.

Next, as necessary, a coating layer before heat treatment, which is made of a glass composition, a binder resin, or the like, is formed on the surface of the obtained magnetic core.

After the heat treatment, a coating layer is formed on the surface of the magnetic core.

The magnetic core thus obtained can be used as a magnetic core.

Of the present embodiment (Si/M)_MAXThe composition of the soft magnetic alloy powder, the type of the binder or the amount added thereto, other additives, or the rate of temperature rise in the firing step in the method for producing the magnetic coreAnd maintaining the temperature or atmosphere.

While the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and it is needless to say that the present invention can be implemented in various forms without departing from the scope of the present invention.

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

In the above-described embodiment, the silicone resin is used as the binder for forming the layer containing silicon (Si) on the grain boundary of the soft magnetic material composition, but a silicon (Si) -containing component such as silica gel or silica particles may be used as the additive instead of the silicone resin.

In the above-described embodiment, a toroidal core made of a soft magnetic material composition is shown, but in addition to this, the soft magnetic material composition of the present embodiment may be made into a core in which a coil is embedded. Specifically, the coil-embedded magnetic core is a magnetic core that surrounds the periphery of the coil and contains a soft magnetic material composition and a resin.

The use of the magnetic core of the present embodiment is not particularly limited, and the magnetic core can be suitably used for various electronic components such as coil-type electronic components, switching power supplies, DC-DC converters, transformers, and choke coils.

[ examples ]

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(example 1)

[ production of Soft magnetic alloy powder ]

Ingots, chunks, or shot (particles) of elemental iron (Fe), elemental chromium (Cr), and elemental silicon (Si) are prepared. Then, they were mixed to a composition of 4 mass% of chromium (Cr), 5 mass% of silicon (Si), and the remainder of iron (Fe), and were stored in a crucible disposed in the water atomization apparatus. Next, the crucible is heated to 1600 ℃ or higher by high-frequency induction using a work coil provided outside the crucible in an inert atmosphere, and the ingot, lump, or pellet in the crucible is melted and mixed to obtain a melt.

Then, while the molten metal in the crucible was discharged from a nozzle provided in the crucible, the discharged molten metal was rapidly cooled by a high-pressure (50MPa) water stream impinging thereon, whereby soft magnetic alloy powder (average particle diameter: 11 μm) composed of Fe-Si-Cr-based particles was produced.

The composition of the obtained soft magnetic alloy powder was analyzed by fluorescent X-ray analysis, and it was confirmed that the composition was consistent with the feed composition.

[ production of magnetic core ]

To 100% by mass of the obtained soft magnetic alloy powder, 4% by mass of a Silicone resin (SR 2414LV, manufactured by Dow corning toray Silicone co., ltd.) was added, and the mixture was mixed for 30 minutes at room temperature using a pressure kneader. Next, the mixture was dried in air at 150 ℃ for 20 minutes. Zinc stearate (manufactured by Nidoku Kogyo Co., Ltd.) was added as a lubricant to the dried soft magnetic alloy powder, and the mixture was mixed for 10 minutes by a V-type mixer. The amount of zinc stearate added was 0.5 mass% based on 100 mass% of the soft magnetic alloy powder.

Then, the obtained mixture was molded into a ring-shaped sample having an outer diameter of 20mm, an inner diameter of 10mm and a thickness of 5mm to prepare a molded article. The molding pressure was 600 MPa.

The heating body having reached the holding temperature is placed in the furnace by being sandwiched from above and below the molded body. In tables 1 and 2, when the temperature of the molded article is raised by this method, the column of "firing conditions" is described as "short-time temperature rise". The molded body was fired at a holding temperature of 650 ℃ for 60 minutes in the air, to obtain a magnetic core.

(examples 2 to 5 and comparative examples 3 and 4)

Magnetic cores were obtained in the same manner as in example 1, except that the holding temperature of the molded article was changed as shown in table 1.

Comparative examples 1 and 2

A magnetic core was obtained in the same manner as in example 1, except that the molded article was placed in a furnace and heated to the holding temperature for 6 hours in comparative example 1, and the molded article was placed in a furnace and heated to the holding temperature for 2 hours in comparative example 2. In comparative examples 1 and 2, the heating body was not sandwiched between the upper and lower surfaces of the molded body.

(examples 11 to 15 and comparative examples 13 and 14)

A soft magnetic alloy powder (average particle size: 9 μm) composed of Fe — Si — Al-based particles was produced by mixing a simple substance Al instead of the simple substance Cr so as to have a composition of 91 mass% of iron (Fe), 5 mass% of aluminum (Al), and 4 mass% of silicon (Si), and a magnetic core was obtained in the same manner as in example 1, except that the holding temperature of the molded body was changed as shown in table 2.

Comparative examples 11 and 12

A magnetic core was obtained in the same manner as in example 11, except that the molded article was placed in the furnace and heated to the holding temperature for 6 hours in comparative example 11, and the molded article was placed in the furnace and heated to the holding temperature for 2 hours in comparative example 12. In comparative examples 11 and 12, the heating body was not sandwiched between the upper and lower surfaces of the molded body.

[ various evaluations ]

＜(Si/M)_MAXIdentification of (1) >

The cross section of the core was observed with a Scanning Transmission Electron Microscope (STEM), and "soft magnetic alloy particles" and "regions between the soft magnetic alloy particles" were discriminated.

Next, as shown in fig. 3, EDS analysis is performed on the arbitrarily selected observation line X using an EDS apparatus having a sufficiently high resolution attached to STEM. Based on the obtained values, find (Si/M)_MAX. The results are shown in tables 1 and 2. The results of example 4 are particularly shown in figure 6. In addition, the first vertical axis of fig. 6 represents the ternary element mass ratio, the second vertical axis represents the Si/M mass ratio, and the horizontal axis represents the distance from the starting point.

< confirmation of amorphous layer >

The presence of the amorphous layer was judged by analyzing the Selected Area Diffraction Pattern (SADP) of the reciprocal lattice space of a scanning Transmission Electron Microscope (TEM).

< magnetic core loss >

A10-turn copper wire was wound around a toroidal powder core sample, and the core loss was measured by using an LCR apparatus (Hewlett-Packard 4284A). The measurement conditions were a measurement frequency of 1MHz, a measurement temperature of 23 ℃ and a measurement level of 0.4A/m. The results are shown in tables 1 and 2.

[ Table 1]

In Table 1, the element M is Cr.

[ Table 2]

In Table 2, the element M is Al.

Confirmed by STEM observation and EDS analysis, (Si/M)_MAXExamples 1 to 5 and (Si/M) exceeding 0.5 and lower than 10.6_MAX10.6 or more of comparative examples 1 to 3 and (Si/M)_MAXThe core loss was lower in comparative example 4, which was 0.5.

It was confirmed by TEM observation that examples 1 to 4 are (Si/M)_MAXAn amorphous layer is present at the site of (a). In comparative example 4, since the holding temperature was high, part of the soft magnetic alloy particles were melted and alloyed (Si/M)_MAXThe amorphous layer is not formed at the portion of (2).

Confirmed by STEM observation and EDS analysis, (Si/M)_MAXExamples 11 to 15 and (Si/M) exceeding 0.7 and lower than 14.0_MAXAre 14.0 or more, comparative examples 11 to 13 and (Si/M)_MAXThe core loss was lower in comparative example 14, which was 0.7.

It was confirmed by TEM observation that examples 11 to 14 are (Si/M)_MAXAn amorphous layer is present at the site of (a). In comparative example 14, since the holding temperature was high, a part of the soft magnetic alloy particles was melted and alloyed, and no amorphous layer was formed.

From the figure6 it was confirmed that the compound of example 4 contains (Si/M)_MAXSilicon (Si) and chromium (Cr) continuously exist within a predetermined range including the portion(s).

In example 4, it was confirmed whether or not silicon (Si) that is not derived from the element contained in the soft magnetic alloy particles was contained in the region between the soft magnetic alloy particles of the magnetic core by the following method.

In fig. 6 (example 4), chromium (Cr) is mostly present in the region between the soft magnetic alloy particles, and is hardly contained in the soft magnetic alloy particles. On the other hand, iron (Fe) is mostly present in the soft magnetic alloy particles, and hardly contains the region between the soft magnetic alloy particles.

Therefore, during the production of the magnetic core, it is considered that chromium (Cr) of the soft magnetic alloy powder moves to the region between the soft magnetic alloy particles, and iron (Fe) of the soft magnetic alloy powder remains in the soft magnetic alloy particles.

Therefore, if the mass ratio of iron (Fe) and silicon (Si) of the raw material of the soft magnetic alloy powder described above is substantially equal to the mass ratio of iron (Fe) and silicon (Si) of the portion of the soft magnetic alloy particles of fig. 6, it can be said that silicon (Si) of the raw material of the soft magnetic alloy powder is directly changed to silicon (Si) of the soft magnetic alloy particles. As a result, it can be said that the silicon (Si) present in the region between the soft magnetic alloy particles is not silicon (Si) derived from the raw material of the soft magnetic alloy powder, but silicon (Si) derived from the silicone resin.

Then, the mass ratio of iron (Fe) and silicon (Si) in the raw material of the soft magnetic alloy powder was calculated to be approximately equal to the mass ratio of iron (Fe) and silicon (Si) in the portion of the soft magnetic alloy particles in fig. 6. Therefore, it can be said that the silicon (Si) present in the region between the soft magnetic alloy particles is not silicon (Si) derived from the raw material of the soft magnetic alloy powder, but silicon (Si) derived from the silicone resin.

Industrial applicability

The magnetic core composed of the soft magnetic composition of the present invention can realize low magnetic core loss.

Claims

1. A soft magnetic body composition characterized by:

having a plurality of soft magnetic alloy particles,

the soft magnetic alloy particles contain the element M and iron,

the element M has a stronger ionization tendency than silicon,

the maximum value of the mass ratio of silicon to the element M in the region between the soft magnetic alloy particles is set to (Si/M)_MAXWhen the temperature of the water is higher than the set temperature,

the (Si/M)_MAXSatisfies 1 ≤ (Si/M)_MAX≤10。

2. A soft magnetic body composition according to claim 1, characterized in that:

in the (Si/M)_MAXAn amorphous layer is present at the site of (a).

3. A soft magnetic body composition according to claim 1, characterized in that:

in the presence of (Si/M)_MAXThe element M is continuously present within a predetermined range including the site of (A),

4. A soft magnetic body composition according to claim 2, characterized in that:

5. A magnetic core, characterized by:

which consists of the soft magnetic body composition as claimed in claim 1.

6. A magnetic core, characterized by:

which consists of the soft magnetic body composition as claimed in claim 2.

7. A magnetic core, characterized by:

which consists of the soft magnetic body composition as claimed in claim 3.

8. A magnetic core, characterized by:

which consists of the soft magnetic body composition as claimed in claim 4.

9. The magnetic core according to claim 5, wherein:

a coating layer is formed on at least a part of the surface of the magnetic core.

10. A coil-type electronic component characterized in that:

having a magnetic core according to any one of claims 5 to 9.