WO2018207521A1 - Dust core, method for producing said dust core, inductor provided with said dust core, and electronic/electrical device on which said inductor is mounted - Google Patents

Abstract

Provided is a dust core which is suitable as a constituent member for a small and low inductor with a built-in coil, and which contains a powder of a crystalline magnetic material and a powder of an amorphous magnetic material. This dust core is configured such that: a first mixing ratio, which is the mass ratio of the content of the powder of the crystalline magnetic material to the sum of the content of the powder of the crystalline magnetic material and the content of the powder of the amorphous magnetic material, is from 30% by mass to 70% by mass (inclusive); the crystalline magnetic material is composed of an Fe-Si-Cr system alloy; and the median diameter D50C thereof is from 2.5 μm to 6 μm (inclusive).

Description

Dust core, method for manufacturing the dust core, inductor including the dust core, and electronic / electric device mounted with the inductor

The present invention relates to a dust core, a method for producing the dust core, an inductor including the dust core, and an electronic / electrical device on which the inductor is mounted. In this specification, the “inductor” means a passive element including a core material including a dust core and a coil.

In electronic devices such as smartphones, tablet terminals, and notebook computers, there are increasing demands for miniaturization, weight reduction, and high performance. In order to meet such demands, the switching power supply circuit in the electronic device needs to be able to cope with a high frequency. Therefore, the inductor incorporated in the switching power supply circuit is also required to be stably driven at a high frequency.

For the purpose of providing a constituent material of a magnetic element that can cope with a high driving frequency, Patent Document 1 includes first particles having an average first particle size and second particles having an average second particle size. The ratio of the average first particle diameter to the average second particle diameter is 1/8 to 1/3, and the mixing ratio of the first particles to the second particles is 10/90 to volume ratio. A metal magnetic material powder is described which is 25/75.

JP2011-192729A

In recent years, switching power supply circuits, particularly DC-DC converters, have been particularly demanded for miniaturization. As a result of satisfying this requirement, a large direct current flows through an inductor incorporated therein, although it is small. It is becoming. For this reason, the magnetic environment in which the magnetic material constituting the inductor is placed is a fluctuation caused by a current fluctuation (ripple current) based on switching at a high frequency in a state where an induced magnetic field due to the direct current is applied as a bias. It becomes an environment where a magnetic field is further applied. Therefore, the magnetic material constituting the inductor has been required to have appropriate magnetic characteristics (for example, high relative permeability) in such a magnetically harsh environment.

Also, since there is a strong demand for thinning electronic devices, there is a strong demand for lowering the height of components on the board in the device. Inductors, especially coil-embedded inductors, when the profile is reduced, the absolute amount of magnetic material located around the coil decreases, so that the insulation characteristics of the inductor and the mechanical characteristics of the core are maintained. It becomes difficult.

In view of the present situation, the present invention provides a dust core suitable as a constituent member of a small and low-profile built-in coil inductor, a dust core that can be used as an inductor material provided with such a dust core, It is an object of the present invention to provide a manufacturing method, an inductor including the dust core, and an electronic / electrical device on which the inductor is mounted.

In one aspect, the present invention provided to solve the above-described problems is a powder core containing a powder of a crystalline magnetic material and a powder of an amorphous magnetic material, wherein the powder of the crystalline magnetic material The first mixing ratio, which is the mass ratio of the content of the crystalline magnetic material powder to the sum of the content and the content of the amorphous magnetic material powder, is 30% by mass or more and 70% by mass or less, The crystalline magnetic material is a dust core made of an Fe—Si—Cr alloy and having a median diameter D ₅₀ C of 2.5 μm to 6 μm.

As described above, the current value of the current flowing through the inductor fluctuates with the direct current superimposed. For this reason, the magnetic material constituting the dust core is required to have a high magnetic permeability even when the external magnetic field is high to some extent. This permeability in a high magnetic field is a parameter different from the initial permeability, and it cannot be said that it has a strong correlation with the saturation magnetic flux density. One example of a parameter for evaluating the magnetic permeability in such a high magnetic field is μ5500, which is a relative magnetic permeability when the external magnetic field is 5500 A / m. It can be said that the higher this μ5500 is, the magnetic material has excellent magnetic properties even in a high magnetic field. Further, when the inductor is small and low in profile, the volume of the core located around the built-in coil is reduced. In this case, problems that are a concern include core dielectric breakdown and core damage (cracking, chipping). Therefore, the dielectric strength voltage (unit: V / mm) and the crushing strength (unit: MPa) of the core are preferably high. Therefore, an inductor having excellent magnetic properties in a strong magnetic field can be obtained even if it is small and has a low profile by using a dust core with μ5500 × insulation breakdown voltage × crush ring strength.

Therefore, as a result of examining the conditions for providing a dust core having a high μ5500 × insulation pressure resistance × crushing ring strength, the magnetic material powder (magnetic powder) contained in the dust core satisfies the following conditions, thereby achieving a small and low profile. Even if it has a shape, it has been found that the problem of dielectric breakdown or breakage of the core hardly occurs, and that an inductor using such a core can have appropriate magnetic characteristics even when used in a high magnetic field. .
(Item 1) Magnetic powder is a mixture of crystalline magnetic material powder and amorphous magnetic material powder. (Item 2) The first mixing ratio is 30% by mass or more and 70% by mass or less.
(Item 3) The crystalline magnetic material is made of an Fe—Si—Cr alloy, and the median diameter D ₅₀ C is 2.5 μm or more and 6 μm or less.

By satisfying these matters, it is possible to obtain a powder core having a specifically high μ5500 × insulation breakdown voltage × crushing ring strength.

In the above powder core, the median diameter D ₅₀ A of the powder of the amorphous magnetic material is preferably 5 μm or more and 8 μm or less. When the matter 2 is satisfied, the median diameter D ₅₀ A is 5 μm or more, so that the μ5500 × the dielectric strength × the crushing strength can be specifically increased. In this respect, the median diameter D ₅₀ A is more preferably 5.5 μm or more. On the other hand, when the median diameter D ₅₀ A is excessively large, μ5500 × insulation breakdown voltage × compressive ring strength tends to decrease, and iron loss, particularly iron loss at high frequencies, tends to increase. Therefore, the median diameter D ₅₀ A is preferably 8 μm or less, and more preferably 7 μm or less.

In the above powder core, the median diameter D ₅₀ A of the amorphous magnetic material powder and the median diameter D ₅₀ C of the crystalline magnetic material powder preferably satisfy the following formula (1). When the particle diameters of the two types of powders satisfy the relationship of the following formula (1), it is possible to more stably realize μ5500 × insulation breakdown voltage × compression ring strength.
1 ≦ D ₅₀ A / D ₅₀ C ≦ 3.5 (1)

In the above dust core, when the first mixing ratio is 40% by mass or more and 60% by mass or less, μ5500 × insulation breakdown voltage × compression ring strength can be particularly increased.

In the above powder core, the amorphous magnetic material is one selected from the group consisting of an Fe—Si—B alloy, an Fe—PC alloy, and a Co—Fe—Si—B alloy, or Two or more kinds of materials may be included, and the amorphous magnetic material may be preferably made of a Fe—PC alloy.

In the above-mentioned dust core, by containing a binding component that binds the powder of the crystalline magnetic material and the powder of the amorphous magnetic material to another material contained in the dust core In some cases, it is easy to increase the dielectric strength of the dust core or increase the crushing strength. In this case, the binding component may include a component based on a resin material.

In another aspect, the present invention provides a method for producing a powder core containing a binder component including a component based on the resin material. The manufacturing method includes a molding step of obtaining a molded product by a molding process including pressure molding of a mixture including a binder component composed of the crystalline magnetic material powder and the amorphous magnetic material powder and the resin material. . The molding process at this time is preferably compression molding in which pressure is applied at about 0.5 GPa to about 2 GPa in a temperature environment of about room temperature from the viewpoint of increasing productivity.

In another aspect, the present invention is an inductor including the powder core, the coil, and a connection terminal connected to each end of the coil, wherein at least a part of the powder core is the connection Provided is an inductor disposed so as to be located in an induced magnetic field generated by the current when a current is passed through the coil through a terminal. Such an inductor is based on the excellent characteristics of the dust core, and the core is less likely to break down or break even if it is small and low in profile, and has excellent direct current superposition characteristics.

In another aspect, the present invention provides an electronic / electrical device in which the inductor is mounted, wherein the inductor is connected to a substrate at the connection terminal. A circuit in which an inductor is incorporated in such an electronic / electric device is not particularly limited, but when used in a switching power supply circuit such as a DC-DC converter, it is easy to take advantage of the above-described inductor having excellent direct current superposition characteristics. In addition, when the electronic / electrical device is a portable device such as a smartphone, it is easy to utilize the advantages of the above-described inductor that is small and easily adaptable to a low profile.

In the dust core according to the invention, the composition and particle size distribution of the crystalline magnetic material powder and the mixing ratio (first mixing ratio) of the crystalline magnetic material powder and the amorphous magnetic material powder are appropriate. Therefore, it is possible to improve the DC superposition characteristics of an inductor having such a dust core even if it is small and low in profile. Moreover, according to this invention, the manufacturing method of said powder core, the inductor provided with the said powder core, and the electronic / electrical device by which the said inductor was mounted are provided.

It is a perspective view which shows notionally the shape of the powder core which concerns on one Embodiment of this invention. It is a figure which shows notionally the spray dryer apparatus used in an example of the method of manufacturing granulated powder, and its operation | movement. It is a perspective view which shows notionally the shape of the toroidal coil which is 1 type of an inductor provided with the dust core which concerns on one Embodiment of this invention. It is a perspective view which shows notionally the shape of the coil embedding type | mold inductor which is a kind of inductor provided with the powder core which concerns on one Embodiment of this invention. It is a graph which shows the relationship between (micro | micron | mu) 5500 x dielectric strength voltage x pressure ring strength (relative value) and the 1st mixing ratio in Example 1 and Example 2. FIG. A graph showing the results of Example 3 is a graph showing the relationship between a median diameter D _{50 A} powder of core loss Pcv and amorphous magnetic material. A graph showing the results of Example 4 is a graph showing the relationship between the core loss Pcv and the median diameter D _{50 C} of the powder of crystalline magnetic material. A graph showing the results of Example 3 is a graph showing the relationship between a median diameter D _{50 A} powder of amorphous magnetic material as Myu5500 × withstand voltage × radial crushing strength (relative value). A graph showing the results of Example 4 is a graph showing the relationship between Myu5500 × withstand voltage × radial crushing strength (relative value) and the median diameter D _{50 C} of the powder of crystalline magnetic material. A graph showing the results of Example 5 is a graph showing the relationship between a median diameter D _{50 A} powder of amorphous magnetic material as Myu5500 × withstand voltage × radial crushing strength (relative value). A graph showing the results of Example 6 is a graph showing the relationship between Myu5500 × withstand voltage × radial crushing strength (relative value) and the median diameter D _{50 C} of the powder of crystalline magnetic material. The results of Example 5 and Example 6 were normalized by the result of Example 5-2 (ie, Example 6-2), and the powder of the crystalline magnetic material having a median diameter D ₅₀ A of the amorphous magnetic material was used. the ratio of the median diameter _{D 50 C (D 50 a /} D 50 C) is a graph showing as a horizontal axis.

Hereinafter, embodiments of the present invention will be described in detail.
1. A dust core 1 according to one embodiment of the present invention shown in FIG. 1 is a ring-shaped toroidal core, and contains a powder of a crystalline magnetic material and a powder of an amorphous magnetic material. . The powder core 1 according to the present embodiment is manufactured by a manufacturing method including a forming process including pressure forming a mixture containing these powders. As a non-limiting example, the dust core 1 according to the present embodiment includes a crystalline magnetic material powder and an amorphous magnetic material powder as other materials (same type of material) contained in the dust core 1. Or it may be a dissimilar material).

(1) Powder of crystalline magnetic material The crystalline magnetic material that gives the powder of crystalline magnetic material contained in the dust core 1 according to one embodiment of the present invention is crystalline (by general X-ray diffraction measurement, It is made of a Fe—Si—Cr alloy that is ferromagnetic and capable of obtaining a diffraction spectrum having a distinct peak to the extent that the material type can be specified. The Fe—Si—Cr alloy is a material having a relatively high saturation magnetic flux density, a good soft magnetic property, and a high specific resistance among crystalline magnetic materials. Therefore, compared with other crystalline magnetic materials such as carbonyl iron powder, the loss is low even under high magnetic field and high frequency conditions, and good magnetic properties are easily exhibited. Therefore, by making the powder of the crystalline magnetic material contained in the dust core 1 from an Fe—Si—Cr alloy, the content of the powder of the crystalline magnetic material in the dust core 1 and the amorphous Even if the mass ratio of the powder content of the crystalline magnetic material to the total content of the powder of the magnetic material (also referred to as “first mixing ratio” in this specification) is increased, the ratio in a high magnetic field environment is increased. Magnetic permeability, specifically, μ5500 is unlikely to decrease. The Si content and the Cr content in the Fe—Si—Cr alloy are not limited. As a non-limiting example, the Si content is about 2 to 7% by mass, the Cr content is about 2 to 7% by mass, and the balance is Fe and inevitable impurities.

The shape of the powder of the crystalline magnetic material contained in the dust core 1 according to one embodiment of the present invention is not limited. The shape of the powder may be spherical or non-spherical. When it is non-spherical, it may have a shape having shape anisotropy such as a scale shape, an oval shape, a droplet shape, or a needle shape.

The shape of the powder may be a shape obtained at the stage of producing the powder, or a shape obtained by secondary processing of the produced powder. Examples of the former shape include a spherical shape, an oval shape, a droplet shape, and a needle shape, and examples of the latter shape include a scale shape.

The particle size of the powder of the crystalline magnetic material contained in the powder core 1 according to the embodiment of the present invention is such that the cumulative particle size distribution from the small particle size side is 50% in the volume-based particle size distribution ( In this specification, it is also referred to as “crystalline powder median diameter.”) D ₅₀ C is 2.5 μm or more and 6 μm or less. When the crystalline powder median diameter D ₅₀ C is within the above range, when the first mixing ratio is 30% by mass or more and 70% by mass or less, μ5500 × insulation breakdown voltage × compression ring strength can be specifically increased. If the influence of the iron loss Pcv at high frequency, particularly 1 MHz or more is further taken into consideration, the crystalline powder median diameter D ₅₀ C may be preferably 2.5 μm or more and 5.5 μm or less.

Surface insulation treatment may be applied to at least a part of the powder of the crystalline magnetic material. When the surface insulation treatment is performed on the powder of the crystalline magnetic material, the insulation resistance of the dust core 1 tends to be improved. The type of surface insulation treatment applied to the crystalline magnetic material powder is not limited. Examples include phosphoric acid treatment, phosphate treatment, and oxidation treatment.

(2) Amorphous Magnetic Material Powder The amorphous magnetic material that provides the amorphous magnetic material powder contained in the dust core 1 according to an embodiment of the present invention is amorphous (generally As long as the X-ray diffraction measurement does not provide a diffraction spectrum with a clear peak that can identify the material type), and the material is a ferromagnetic material, particularly a soft magnetic material, the specific types are limited. Not. Specific examples of the amorphous magnetic material include Fe—Si—B alloys, Fe—PC alloys, and Co—Fe—Si—B alloys. Said amorphous magnetic material may be comprised from one type of material, and may be comprised from multiple types of material. The magnetic material constituting the powder of the amorphous magnetic material is preferably one or two or more materials selected from the group consisting of the above materials, and among these, an Fe—PC alloy is used. It is preferably contained, and more preferably made of an Fe—PC alloy.

Specific examples of the Fe-P-C-based alloy, composition _formula, shown in _{Fe 100 atomic% -a-b-c-x} -y-z-t Ni a Sn b Cr c P x C y B z Si t 0 atom% ≦ a ≦ 10 atom%, 0 atom% ≦ b ≦ 3 atom%, 0 atom% ≦ c ≦ 6 atom%, 6.8 atom% ≦ x ≦ 13 atom%, 2.2 atom% ≦ Examples include Fe-based amorphous alloys in which y ≦ 13 atomic%, 0 atomic% ≦ z ≦ 9 atomic%, and 0 atomic% ≦ t ≦ 7 atomic%. In the above composition formula, Ni, Sn, Cr, B, and Si are optional added elements.

The addition amount a of Ni is preferably 0 atom% or more and 6 atom% or less, and more preferably 0 atom% or more and 4 atom% or less. The addition amount b of Sn is preferably 0 atom% or more and 2 atom% or less, and may be added in the range of 1 atom% or more and 2 atom% or less. The addition amount c of Cr is preferably 0 atom% or more and 2 atom% or less, and more preferably 1 atom% or more and 2 atom% or less. In some cases, the addition amount x of P is preferably 8.8 atomic% or more. The addition amount y of C may be preferably 5.8 atomic% or more and 8.8 atomic% or less. The addition amount z of B is preferably 0 atom% or more and 3 atom% or less, and more preferably 0 atom% or more and 2 atom% or less. The addition amount t of Si is preferably 0 atom% or more and 6 atom% or less, and more preferably 0 atom% or more and 2 atom% or less.

The shape of the powder of the amorphous magnetic material contained in the dust core 1 according to one embodiment of the present invention is not limited. Since the kind of the powder shape is the same as that of the crystalline magnetic material powder, the description thereof is omitted. In some cases, the amorphous magnetic material can be easily formed into a spherical shape or an elliptical spherical shape because of the manufacturing method. In general, since an amorphous magnetic material is harder than a crystalline magnetic material, it may be preferable to make the crystalline magnetic material non-spherical so that it is easily deformed during pressure molding.

The shape of the powder of the amorphous magnetic material contained in the dust core 1 according to the embodiment of the present invention may be the shape obtained in the stage of producing the powder, or the produced powder is secondary The shape obtained by processing may be sufficient. Examples of the former shape include a sphere, an oval sphere, and a needle shape, and examples of the latter shape include a scale shape.

The particle size of the powder of the amorphous magnetic material contained in the dust core 1 according to one embodiment of the present invention is such that the cumulative particle size distribution from the small particle size side is 50% in the volume-based particle size distribution. (In the present specification, it is also referred to as “amorphous powder median diameter”.) D ₅₀ A is preferably 5 μm or more and 8 μm or less. When the first mixing ratio is not less than 30% by mass and not more than 70% by mass, the amorphous powder median diameter D ₅₀ A is 5 μm or more, so that μ5500 × insulation breakdown voltage × compression ring strength can be specifically increased. In this respect, the amorphous powder median diameter D ₅₀ A is more preferably 5.5 μm or more. On the other hand, when the amorphous powder median diameter D ₅₀ A is excessively large, there is a tendency that μ5500 × insulation breakdown voltage × compressive ring strength decreases or iron loss Pcv, particularly iron loss Pcv at high frequency increases. . Therefore, the amorphous powder median diameter D ₅₀ A is preferably 8 μm or less, and more preferably 7 μm or less.

Moreover, the particle size of the powder of the amorphous magnetic material contained in the dust core 1 according to one embodiment of the present invention is the next to the particle size of the powder of the amorphous magnetic material contained in the dust core 1. You may have a relationship. That is, the amorphous powder median diameter D ₅₀ A and the crystalline powder median diameter D ₅₀ C may satisfy the following formula (1).
1 ≦ D ₅₀ A / D ₅₀ C ≦ 3.5 (1)

When D ₅₀ A / D ₅₀ C is in the range of 1 to 3.5, it is easy to specifically increase μ5500 × insulation breakdown voltage × compression ring strength of the dust core 1. From the viewpoint of more stably realizing μ5500 × dielectric withstand voltage × compressive ring strength, D ₅₀ A / D ₅₀ C may be preferably in the range of 1.2 to 2.5, It may be preferable to be in the range of 1.3 to 2.0.

From the viewpoint of more stably realizing μ5500 × insulation withstand pressure × crushing ring strength with respect to the dust core 1, the first mixing ratio is preferably 40% by mass or more and 60% by mass or less, More preferably, it is at least 55% by mass.

(3) Binder Component The powder core 1 includes a binder component that binds the powder of the crystalline magnetic material and the powder of the amorphous magnetic material to the other materials contained in the powder core 1. It may be. The binder component is a powder of crystalline magnetic material and powder of amorphous magnetic material contained in the dust core 1 according to the present embodiment (in this specification, these powders are collectively referred to as “magnetic powder”). The composition is not limited as long as the material contributes to fixing. As a material constituting the binder component, an organic material such as a resin material and a thermal decomposition residue of the resin material (in this specification, these are collectively referred to as “components based on a resin material”), an inorganic material, and the like Is exemplified. Examples of the resin material include acrylic resin, silicone resin, epoxy resin, phenol resin, urea resin, and melamine resin. The binder component made of an inorganic material is exemplified by a glass-based material such as water glass. The binder component may be composed of one type of material or may be composed of a plurality of materials. The binder component may be a mixture of an organic material and an inorganic material.

An insulating material is usually used as a binding component. Thereby, it becomes possible to improve the insulation as the dust core 1.

2. Manufacturing method of powder core Although the manufacturing method of the powder core 1 which concerns on one embodiment of said this invention is not specifically limited, if the manufacturing method demonstrated below is employ | adopted, the powder core 1 will be manufactured more efficiently. Is realized.

The manufacturing method of the powder core 1 according to an embodiment of the present invention may include a molding step described below, and may further include a heat treatment step.

(1) Molding step First, a mixture containing magnetic powder and a component that provides a binding component in the powder core 1 is prepared. The component that gives the binding component (also referred to as “binder component” in this specification) may be the binding component itself or may be a material different from the binding component. Specific examples of the latter include a case where the binder component is a resin material and the binder component is a thermal decomposition residue thereof. Such a thermal decomposition residue is formed by the heat treatment process performed subsequent to a shaping | molding process so that it may mention later.

A molded product can be obtained by a molding process including pressure molding of this mixture. The pressurizing condition is not limited and is appropriately set based on the composition of the binder component. For example, when the binder component is made of a thermosetting resin, it is preferable to heat the resin together with pressure to advance the resin curing reaction in the mold. On the other hand, in the case of compression molding, although the pressing force is high, heating is not a necessary condition and pressurization is performed for a short time. The pressing force in the case of compression molding is appropriately set. If it illustrates without being limited, it is 0.5 GPa or more and 2 GPa or less, and it may be preferable to set it as 1 GPa or more and 2 GPa or less.

Hereinafter, the case where the mixture is granulated powder and compression molding will be described in some detail. Since the granulated powder is excellent in handleability, it is possible to improve the workability of the compression molding process in which the molding time is short and the productivity is excellent.

(1-1) Granulated powder The granulated powder contains magnetic powder and a binder component. The content of the binder component in the granulated powder is not particularly limited. When this content is too low, it becomes difficult for the binder component to hold the magnetic powder. In addition, when the content of the binder component is excessively low, in the powder core 1 obtained through the heat treatment step, the binder component composed of the thermal decomposition residue of the binder component causes a plurality of magnetic powders to be separated from each other. It becomes difficult to insulate. On the other hand, when the content of the binder component is excessively high, the content of the binder component contained in the powder core 1 obtained through the heat treatment step tends to be high. When the content of the binder component in the dust core 1 is increased, the magnetic properties of the dust core 1 are likely to be reduced. Therefore, the content of the binder component in the granulated powder is preferably set to an amount that is 0.5% by mass or more and 5.0% by mass or less with respect to the entire granulated powder. From the viewpoint of more stably reducing the possibility that the magnetic properties of the dust core 1 will decrease, the content of the binder component in the granulated powder is 1.0 mass% or more with respect to the entire granulated powder. The amount is preferably 5% by mass or less, and more preferably 1.2% by mass or more and 3.0% by mass or less.

The granulated powder may contain materials other than the above magnetic powder and binder component. Examples of such materials include lubricants, silane coupling agents, and insulating fillers. In the case of containing a lubricant, the type is not particularly limited. It may be an organic lubricant or an inorganic lubricant. Specific examples of the organic lubricant include metal soaps such as zinc stearate and aluminum stearate. It is considered that such an organic lubricant is vaporized in the heat treatment step and hardly remains in the powder core 1.

The method for producing the granulated powder is not particularly limited. The ingredients that give the granulated powder may be kneaded as they are, and the resulting kneaded product may be pulverized by a known method to obtain granulated powder, or a dispersion medium (water as an example) It is also possible to obtain a granulated powder by preparing a slurry to which is added, and drying and pulverizing the slurry. Screening and classification may be performed after pulverization to control the particle size distribution of the granulated powder.

As an example of a method for obtaining granulated powder from the above slurry, a method using a spray dryer can be mentioned. As shown in FIG. 2, a rotator 201 is provided in the spray dryer apparatus 200, and the slurry S is injected toward the rotator 201 from the upper part of the apparatus. The rotor 201 rotates at a predetermined number of revolutions, and sprays the slurry S as droplets by centrifugal force in a chamber inside the spray dryer apparatus 200. Further, hot air is introduced into the chamber inside the spray dryer apparatus 200, whereby the dispersion medium (water) contained in the droplet-like slurry S is volatilized while maintaining the droplet shape. As a result, the granulated powder P is formed from the slurry S. The granulated powder P is collected from the lower part of the spray dryer apparatus 200. Each parameter such as the number of rotations of the rotor 201, the temperature of hot air introduced into the spray dryer apparatus 200, and the temperature at the bottom of the chamber may be set as appropriate. As specific examples of the setting ranges of these parameters, the rotational speed of the rotor 201 is 4000 to 8000 rpm, the hot air temperature introduced into the spray dryer apparatus 200 is 100 to 170 ° C., and the temperature at the bottom of the chamber is 80 to 90 ° C. . The atmosphere in the chamber and its pressure may be set as appropriate. As an example, the inside of the chamber is an air atmosphere, and the pressure is ₂ mmH ₂ O (about 0.02 kPa) as a differential pressure from the atmospheric pressure. You may further control the particle size distribution of the obtained granulated powder P by sieving.

(1-2) Pressing conditions The pressing conditions in compression molding are not particularly limited. What is necessary is just to set suitably considering the composition of granulated powder, the shape of a molded article, etc. If the pressure applied when the granulated powder is compression-molded is excessively low, the mechanical strength of the molded product decreases. For this reason, it becomes easy to produce the problem that the handleability of a molded article falls and the mechanical strength of the compacting core 1 obtained from the molded article falls. Moreover, the magnetic characteristics of the dust core 1 may deteriorate or the insulating properties may decrease. On the other hand, if the applied pressure during compression molding of the granulated powder is excessively high, it becomes difficult to create a molding die that can withstand the pressure. From the viewpoint of more stably reducing the possibility that the compression and pressurization process will adversely affect the mechanical properties and magnetic properties of the dust core 1 and facilitating mass production industrially, The applied pressure is preferably 0.3 GPa to 2 GPa, more preferably 0.5 GPa to 2 GPa, and particularly preferably 0.8 GPa to 2 GPa.

In compression molding, pressurization may be performed while heating, or pressurization may be performed at room temperature.

(2) Heat treatment step The molded product obtained in the molding step may be the powder core 1 according to the present embodiment, or the molded product may be subjected to a heat treatment step and pressed as described below. A powder core 1 may be obtained.

In the heat treatment process, the molded product obtained by the above molding process is heated to adjust the magnetic properties by correcting the distance between the magnetic powders and to relax the strain applied to the magnetic powder in the molding process. The powder core 1 is obtained by adjusting the magnetic characteristics.

Since the heat treatment step is intended to adjust the magnetic properties of the dust core 1 as described above, the heat treatment conditions such as the heat treatment temperature are set so that the magnetic properties of the dust core 1 are the best. As an example of a method for setting the heat treatment conditions, it is possible to change the heating temperature of the molded product and to make other conditions constant, such as the heating rate and the holding time at the heating temperature.

The evaluation criteria for the magnetic properties of the dust core 1 when setting the heat treatment conditions are not particularly limited. The iron loss Pcv of the powder core 1 can be given as a specific example of the evaluation item. In this case, what is necessary is just to set the heating temperature of a molded product so that the iron loss Pcv of the powder core 1 may become the minimum. The measurement conditions of the iron loss Pcv are set as appropriate. As an example, the conditions are a frequency of 2 MHz and an effective maximum magnetic flux density Bm of 15 mT.

The atmosphere during the heat treatment is not particularly limited. In the case of an oxidizing atmosphere, the possibility of excessive thermal decomposition of the binder component and the possibility of progress of oxidation of the magnetic powder increases, so that an inert atmosphere such as nitrogen or argon, or a reducing property such as hydrogen Heat treatment is preferably performed in an atmosphere. When the binder component is formed of a resin material, the binder component may become a thermal decomposition residue by the heat treatment as described above. It is considered that the binder component is a thermal decomposition residue when the strain is relaxed as described above.

3. Inductor, Electronic / Electric Device An inductor according to an embodiment of the present invention includes the dust core 1 according to the embodiment of the present invention, a coil, and a connection terminal connected to each end of the coil. Here, at least a part of the dust core 1 is disposed so as to be located in an induced magnetic field generated by the current when a current is passed through the coil via the connection terminal. Since the inductor according to an embodiment of the present invention includes the dust core 1 according to the embodiment of the present invention described above, the inductor has excellent direct current superposition characteristics and excellent insulation characteristics and mechanical characteristics.

An example of such an inductor is the toroidal coil 10 shown in FIG. The toroidal coil 10 includes a coil 2 a formed by winding a coated conductive wire 2 around a ring-shaped dust core (toroidal core) 1. The ends 2d and 2e of the coil 2a can be defined in the portion of the conductive wire located between the coil 2a formed of the wound covered conductive wire 2 and the ends 2b and 2c of the covered conductive wire 2. Thus, in the inductor according to the present embodiment, the member constituting the coil and the member constituting the connection terminal may be composed of the same member.

As another example of the inductor according to the embodiment of the present invention, there is a coil-buried inductor 20 shown in FIG. The coil-embedded inductor 20 can be formed in a small chip shape of several mm square, and includes a dust core 21 having a box shape, and a coil portion 22c in the covered conductive wire 22 is provided therein. Buried. End portions 22a and 22b of the coated conductive wire 22 are located on the surface of the powder core 21 and exposed. Part of the surface of the dust core 21 is covered with connection end portions 23a and 23b that are electrically independent from each other. The connection end portion 23 a is electrically connected to the end portion 22 a of the covered conductive wire 22, and the connection end portion 23 b is electrically connected to the end portion 22 b of the covered conductive wire 22. In the coil-embedded inductor 20 shown in FIG. 4, the end portion 22a of the covered conductive wire 22 is covered with the connection end portion 23a, and the end portion 22b of the covered conductive wire 22 is covered with the connection end portion 23b.

The method for embedding the coil portion 22c of the coated conductive wire 22 in the dust core 21 is not limited. A member around which the coated conductive wire 22 is wound may be placed in a mold, and a mixture (granulated powder) containing magnetic powder may be supplied into the mold to perform pressure molding. Alternatively, a plurality of members obtained by preforming a mixture (granulated powder) containing magnetic powder in advance are prepared, these members are combined, and the coated conductive wire 22 is arranged in the gap formed at that time. A solid may be obtained and this assembly may be pressure molded. The material of the covered conductive wire 22 including the coil portion 22c is not limited. For example, a copper alloy can be used. The coil portion 22c may be an edgewise coil. The material of the connection end portions 23a and 23b is not limited. From the viewpoint of excellent productivity, it may be preferable to include a metallized layer formed from a conductive paste such as a silver paste and a plating layer formed on the metallized layer. The material for forming the plating layer is not limited. Examples of the metal element contained in the material include copper, aluminum, zinc, nickel, iron, and tin.

An electronic / electrical device according to an embodiment of the present invention is an electronic / electrical device in which the inductor according to the above-described embodiment of the present invention is mounted, and the inductor is connected to a substrate at its connection terminal. Is. An example of a circuit including such an inductor is a switching power supply circuit such as a DC-DC converter. The switching power supply circuit tends to increase the switching frequency and increase the amount of current flowing through the circuit in order to meet various demands such as downsizing, weight reduction, and high functionality of electronic and electrical devices. For this reason, the current flowing through the inductor, which is a component of the circuit, also tends to increase the fluctuation frequency and increase the average current amount. In this regard, as described above, an inductor including a dust core according to an embodiment of the present invention can appropriately operate in a high magnetic field environment even if the inductor is small and low-profile. Therefore, in the switching power supply circuit provided with such an inductor, a decrease in efficiency is suppressed, and the above various requirements can be met without causing a problem of heat generation. As described above, an electronic / electrical device on which an inductor according to an embodiment of the present invention is mounted can achieve high functionality while corresponding to downsizing and weight reduction.

The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.
Example 1

(1) Preparation of Fe-based amorphous alloy powder Fe _{71 atomic%} Ni _{6 atomic%} Cr _{2 atomic%} P _{11 atomic%} C _{8 atomic%} B _{2 atomic%} The powder of the amorphous magnetic material (amorphous powder) was produced using the method. The obtained powder of the amorphous magnetic material was classified, and the particle size distribution of the classified powder was measured by volume distribution using “Microtrac particle size distribution measuring device MT3300EX” manufactured by Nikkiso Co., Ltd. In the volume-based particle size distribution, the particle size (amorphous powder median diameter) D ₅₀ A at which the cumulative particle size distribution from the small particle size side becomes 50% was 6.5 μm. As the powder of the crystalline magnetic material, Fe—Si—Cr alloy, specifically, the Si content is 3.5 mass%, the Cr content is 4.5 mass%, and the balance is A powder comprising an alloy composed of Fe and inevitable impurities and having a crystalline powder median diameter D ₅₀ C of 4.0 μm was prepared. Therefore, in the powder according to Example 1, D ₅₀ A / D ₅₀ C was 1.6.

(2) Production of Granulated Powder The above-mentioned amorphous magnetic material powder and crystalline magnetic material powder were mixed so as to have the first mixing ratio shown in Table 1 to obtain a magnetic powder. 97.2 parts by mass of magnetic powder, 2 to 3 parts by mass of an insulating binder made of an acrylic resin and a phenol resin, and 0 to 0.5 parts by mass of a lubricant made of zinc stearate are added to water as a solvent. A slurry was obtained by mixing.

The obtained slurry was granulated under the above-described conditions using the spray dryer apparatus 200 shown in FIG. 2 to obtain granulated powder.

(3) Compression molding The obtained granulated powder was filled in a mold and pressure-molded with a surface pressure of 1 GPa to obtain a molded body having a ring shape with an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 3 mm.

(4) Heat treatment The obtained molded body is placed in a furnace in a nitrogen stream atmosphere, and the furnace temperature is 200 to 400 which is the optimum core heat treatment temperature from room temperature (23 ° C.) at a heating rate of 10 ° C./min. The mixture was heated to 0 ° C., held at this temperature for 1 hour, and then heat-treated to cool to room temperature in a furnace to obtain a toroidal core composed of a dust core.

(Example 2)
Using the amorphous magnetic material powder produced in Example 1, the classification conditions were changed to prepare an amorphous magnetic material powder having an amorphous powder median diameter D ₅₀ A of 5.0 μm. In addition, as a powder of crystalline magnetic material, Fe—Si—Cr alloy, specifically, Si content is 6.4% by mass, Cr content is 3.1% by mass, and the balance is A powder comprising an alloy composed of Fe and inevitable impurities and having a crystalline powder median diameter D ₅₀ C of 2.0 μm was prepared. Therefore, in the powder according to Example 2, D ₅₀ A / D ₅₀ C was 2.5. The above amorphous magnetic material powder and crystalline magnetic material powder were mixed at the first mixing ratio shown in Table 2 to obtain a magnetic powder. Thereafter, a plurality of types of toroidal cores were obtained in the same manner as in Example 1.

(Test Example 1) Measurement of core density ρ The dimensions and weights of the toroidal cores produced in Example 1 and Example 2 were measured, and the density (core density) ρ (unit: g / g) of each toroidal core was determined from these numerical values. cc) was calculated. The results are shown in Tables 1 and 2.

(Test Example 2) Measurement of initial permeability μ0 For toroidal coils obtained by winding the coated copper wires 40 times on the primary side and 10 times on the secondary side respectively on the toroidal cores produced in Example 1 and Example 2, The initial permeability μ 0 was measured using an analyzer (“4192A” manufactured by HP) under the condition of 100 kHz. The results are shown in Tables 1 and 2.

(Test Example 3) Measurement of μ5500 Using the toroidal coil produced in Test Example 2, a direct current was superimposed under the condition of 100 kHz, and a relative permeability μ5500 when the induced magnetic field of the superimposed direct current was 5500 A / m was obtained. It was measured. The measurement results are shown in Table 1.

(Test Example 4) Measurement of crushing strength The toroidal core produced in Example 1 and Example 2 was measured by a test method based on JIS Z2507: 2000, and crushing strength was obtained. The measurement results are shown in Tables 1 and 2.

(Test Example 5) Measurement of dielectric strength voltage The dielectric breakdown voltage (unit: V) of the toroidal core produced in Example 1 and Example 2 was measured (measuring instrument: “TOS5051” manufactured by Kikusui Electronics Corporation). The measurement was performed in accordance with JIS C2110-1, and both end surfaces of the toroidal core shown in FIG. A dielectric breakdown electric field (unit: V / mm) was determined from the obtained dielectric breakdown voltage. The results are shown in Tables 1 and 2.

(Test Example 6) Measurement of iron loss Pcv For the toroidal coil obtained by winding the coated copper wire on the toroidal core produced in Example 1 and Example 2 15 times on the primary side and 10 times on the secondary side, respectively, the BH analyzer (“SY-8217” manufactured by Iwasaki Tsushinki Co., Ltd.) was used to measure the iron loss Pcv (unit: kW / m ³ ) at a measurement frequency of 2 MHz under the condition that the effective maximum magnetic flux density Bm was 15 mT. The measurement results are shown in Tables 1 and 2.

(Evaluation Example 1) μ5500 × Insulation Withstand Pressure × Rubber Strength Based on the results measured in Test Example 3 to Test Example 5, μ5500 × Insulation Withstand Voltage × Rubble Strength was calculated. The calculation results are shown in Tables 3 and 4 and FIG. The “relative value” in the above table and figure is the result of normalizing the values of Example 1-2 to Example 1-9 in Example 1 by μ5500 × Insulation withstand voltage × Drum strength in Example 1-1. Example 2 shows the result of normalizing the values of Example 2-2 to Example 2-8 by μ5500 × insulation breakdown voltage × cylinder strength in Example 2-1.

As shown in Table 3 and Table 4 and FIG. 5, in Example 1, in contrast to Example 2, when the first mixing ratio is 30% by mass or more and 70% by mass or less, the relative value is specifically high. The result was obtained. It turns out that the tendency becomes remarkable especially in 40 mass% or more and 60 mass% or less.

(Example 3)
Using the amorphous magnetic material powder produced in Example 1, the classification conditions were changed to prepare an amorphous magnetic material powder having an amorphous powder median diameter D ₅₀ A shown in Table 5. Further, as a powder of the crystalline magnetic material, a powder of an Fe—Si—Cr-based alloy having a crystalline powder median diameter D ₅₀ C shown in Table 5 was prepared. The above-mentioned amorphous magnetic material powder and crystalline magnetic material powder were mixed so that the first mixing ratio was 50% by mass to obtain a magnetic powder. Thereafter, a plurality of types of toroidal cores were obtained in the same manner as in Example 1. The obtained toroidal core was subjected to various measurements and evaluations in the same manner as in Example 1. The results are shown in Table 5.

Example 4
Using the amorphous magnetic material powder produced in Example 1, the classification conditions were changed to prepare an amorphous magnetic material powder having a median diameter D ₅₀ A of 5.0 μm. Further, as a powder of the crystalline magnetic material, a powder of an Fe—Si—Cr alloy having a median diameter D ₅₀ C shown in Table 6 was prepared. The above-mentioned amorphous magnetic material powder and crystalline magnetic material powder were mixed so that the first mixing ratio was 30% by mass to obtain a magnetic powder. Thereafter, a plurality of types of toroidal cores were obtained in the same manner as in Example 1. The obtained toroidal core was subjected to various measurements and evaluations in the same manner as in Example 1. The results are shown in Table 6.

As shown in Tables 5 and 6 and FIG. 6 and FIG. 7 illustrating the measurement results of the iron loss Pcv, when the median diameter increases for both the amorphous magnetic material powder and the crystalline magnetic material powder, It was confirmed that the iron loss Pcv tends to increase. Further, as shown in Tables 5 and 6 and FIGS. 8 and 9 illustrating the measurement results of the relative values, the median diameter D ₅₀ A of the powder of the amorphous magnetic material is 5 μm or more and 8 μm or less. It was confirmed that when the median diameter D ₅₀ C of the powder of the crystalline magnetic material is 2.5 μm or more and 6 μm or less, μ5500 × insulation breakdown voltage × compressive ring strength is specifically increased.

(Example 5)
Using the powder of the amorphous magnetic material produced in Example 1, the classification conditions were changed, and the median diameter D ₅₀ A was 5.0 μm (Example 5-1), 6.5 μm (Example 5-2), And 11.0 μm (Example 5-3) amorphous magnetic material powder. Further, as a powder of the crystalline magnetic material, a powder of an Fe—Si—Cr alloy having a median diameter D ₅₀ C of 4.0 μm was prepared. The above-mentioned amorphous magnetic material powder and crystalline magnetic material powder were mixed so that the first mixing ratio was 50% by mass to obtain a magnetic powder. Thereafter, a plurality of types of toroidal cores were obtained in the same manner as in Example 1. The obtained toroidal core was subjected to various measurements and evaluations in the same manner as in Example 1. The results are shown in Table 7 and FIG.

(Example 6)
Using the amorphous magnetic material powder produced in Example 1, the classification conditions were changed to prepare an amorphous magnetic material powder having a median diameter D ₅₀ A of 6.5 μm. Further, the powder of the crystalline magnetic material is an Fe—Si—Cr alloy, and the median diameter D ₅₀ C is 2.0 μm (Example 5-1), 4.0 μm (Example 5-2), and A powder of 6.0 μm (Example 5-3) was prepared. The above-mentioned amorphous magnetic material powder and crystalline magnetic material powder were mixed so that the first mixing ratio was 50% by mass to obtain a magnetic powder. Thereafter, a plurality of types of toroidal cores were obtained in the same manner as in Example 1. The obtained toroidal core was subjected to various measurements and evaluations in the same manner as in Example 1. The results are shown in Table 8 and FIG.

The results of Example 5 and Example 6 were normalized by the result of Example 5-2 (ie, Example 6-2), and the powder of the crystalline magnetic material having a median diameter D ₅₀ A of the amorphous magnetic material was used. FIG. 12 is a graph showing the ratio (D ₅₀ A / D ₅₀ C) with respect to the median diameter D ₅₀ C of FIG. As shown in FIG. 12, the dependence of μ5500 × dielectric withstand voltage × compression ring strength on D ₅₀ A / D ₅₀ C is such that D ₅₀ A / D ₅₀ C has a vertex in the range of 1.3 to 2.0. The distribution has a mountain-shaped trend line.

The inductor having the dust core of the present invention can be suitably used as an inductor that is a component of a switching power supply circuit such as a DC-DC converter.

1 ... Compact core (toroidal core)
DESCRIPTION OF SYMBOLS 10 ... Toroidal coil 2 ... Coated conductive wire 2a ... Coils 2b, 2c ... End 2d, 2e of coated conductive wire 2 ... End 20 of coil 2a ... Coil buried type inductor 21 ... Powder core 22 ... Coated conductive wire 22a, 22b ... Ends 23a, 23b ... Connection end 22c ... Coil part 200 ... Spray dryer device 201 ... Rotor S ... Slurry P ... Granulated powder

Claims (11)

1. A powder core containing a powder of crystalline magnetic material and a powder of amorphous magnetic material,
   The first mixing ratio, which is the mass ratio of the content of the crystalline magnetic material powder to the sum of the content of the crystalline magnetic material powder and the content of the amorphous magnetic material powder, is 30% by mass. 70 mass% or less,
   The dust core according to claim 1, wherein the crystalline magnetic material is made of an Fe—Si—Cr alloy and has a median diameter D ₅₀ C of 2.5 μm to 6 μm.
2. The powder core according to claim 1, wherein a median diameter D ₅₀ A of the powder of the amorphous magnetic material is 5 µm or more and 8 µm or less.
3. The powder core according to claim 1 or 2, wherein the median diameter D ₅₀ A of the powder of the amorphous magnetic material and the median diameter D ₅₀ C of the powder of the crystalline magnetic material satisfy the following formula (1).
   1 ≦ D ₅₀ A / D ₅₀ C ≦ 3.5 (1)
4. The powder core according to any one of claims 1 to 3, wherein the first mixing ratio is 40 mass% or more and 60 mass% or less.
5. The amorphous magnetic material includes one or more materials selected from the group consisting of an Fe—Si—B alloy, an Fe—PC alloy, and a Co—Fe—Si—B alloy. The powder core according to any one of claims 1 to 4.
6. The dust core according to claim 5, wherein the amorphous magnetic material is made of an Fe-PC-based alloy.
7. 7. The composition according to claim 1, further comprising a binding component that binds the powder of the crystalline magnetic material and the powder of the amorphous magnetic material to another material contained in the powder core. The dust core according to one item.
8. The powder core according to claim 7, wherein the binding component includes a component based on a resin material.
9. 9. A method for producing a dust core according to claim 8, comprising pressure molding of a mixture comprising a binder component comprising the crystalline magnetic material powder and the amorphous magnetic material powder and the resin material. A method for producing a powder core, comprising a molding step of obtaining a molded product by a molding process.
10. It is an inductor provided with the connecting terminal connected to each end part of the dust core, the coil, and the coil according to any one of claims 1 to 8, wherein at least a part of the dust core is the connection An inductor disposed so as to be located in an induced magnetic field generated by the current when a current is passed through the coil via a terminal.
11. 11. An electronic / electrical device in which the inductor according to claim 10 is mounted, wherein the inductor is connected to a substrate at the connection terminal.

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