阅读说明：本技术 电感器及其制造方法 (Inductor and method for manufacturing the same ) 是由 土屋祐一 新井工 远山元气 植松龙太 于 2020-10-16 设计创作，主要内容包括：本发明提供一种高频特性优异的电感器。是具备单元体和外部端子的电感器,所述单元体含有含磁性粉的磁性部和埋设于磁性部内的线圈。磁性粉的基于体积基准的累积粒度分布中的累积50％粒径D50为5μm以下,累积90％粒径D90相对于累积10％粒径D10的比D90/D10为19以下,维氏硬度为1000(kgf/mm～2)以下。磁性部的磁性粉的体积基准的填充率为60％以上。(The invention provides an inductor with excellent high-frequency characteristics. The inductor is provided with a unit body and an external terminal, wherein the unit body comprises a magnetic part containing magnetic powder and a coil embedded in the magnetic part. The magnetic powder has a cumulative 50% particle diameter D50 of 5 μm or less, a cumulative 90% particle diameter D90/cumulative 10% particle diameter D10 ratio D90/D10 of 19 or less, and a Vickers hardness of 1000 (kgf/mm) 2 ) The following. The magnetic powder of the magnetic portion has a volume-based filling rate of 60% or more.)

1. An inductor is provided with a unit body and an external terminal, wherein the unit body comprises a magnetic part containing magnetic powder and a coil embedded in the magnetic part,

the magnetic powder has a cumulative 50% particle diameter D50 of 5 [ mu ] m or less, a cumulative 90% particle diameter D90/cumulative 10% particle diameter D10 ratio D90/D10 of 19 or less, and a Vickers hardness of 1000kgf/mm²In the following, the following description is given,

the magnetic portion has a volume-based filling rate of the magnetic powder of 60% or more.

2. The inductor according to claim 1, wherein the unit cell has a permeability of 10MHz or more.

3. The inductor according to claim 1 or 2, wherein the magnetic powder comprises a soft magnetic material containing iron and silicon.

4. The inductor according to claim 3, wherein the magnetic powder has a silicon content of 1 to 7 mass% and an iron content of 80 mass% or more.

5. The inductor according to any one of claims 1 to 4, wherein the magnetic powder comprises a crystalline soft magnetic material.

6. The inductor according to any one of claims 1 to 5, wherein the magnetic powder has an insulating layer on a surface thereof.

7. The inductor according to claim 6, wherein the insulating layer of the magnetic powder has a thickness of 200nm or less.

8. The inductor according to any one of claims 1 to 7, wherein the unit cell has 2 opposing main faces and end faces adjacently opposing the main faces, and side faces adjacently opposing the main faces and the end faces, one main face being a mounting face,

the coil is a linear metal plate.

9. The inductor according to claim 8, wherein the filling ratio is measured at a position of 30% of a height of the unit body from a main surface opposed to the mount surface toward the mount surface.

10. A method for manufacturing an inductor includes the steps of:

with coils embedded in magnetic materialA step of preparing a magnetic material containing: a cumulative 50% particle diameter D50 in a cumulative particle size distribution on a volume basis is 5 μm or less and a ratio D90/D10 of a cumulative 90% particle diameter D90 to a cumulative 10% particle diameter D10 is 19 or less and a Vickers hardness is 1000kgf/mm²A resin having a content of 5% by mass or less; and

at 5 tons/cm²And a step of pressing and molding the magnetic material in which the coil is embedded under the above pressure to obtain a unit body having a filling rate of the magnetic powder of 60% or more.

Technical Field

The invention relates to an inductor and a manufacturing method thereof.

Background

An inductor in which a coil conductor made of a metal conductor is enclosed in a magnetic portion obtained by mixing and pressure-molding a metal magnetic powder and a binder, and the metal conductor is bent to form a terminal is used in various electronic devices (see, for example, patent document 1). In a DC-DC converter circuit or the like using such an inductor, the operating frequency tends to be higher and larger.

Patent document 1: international publication No. 2009/075110

Disclosure of Invention

In the conventional inductor, it is not possible to sufficiently cope with a high frequency and a large current, and when the inductor is applied to a DC-DC converter circuit or the like, circuit characteristics may be degraded. An object of one embodiment of the present invention is to provide an inductor having excellent high-frequency characteristics.

The inductor according to claim 1 includes a unit body including a magnetic portion containing magnetic powder and a coil embedded in the magnetic portion, and an external terminal. The magnetic powder has a cumulative 50% particle diameter D50 of 5 μm or less, a cumulative 90% particle diameter D90/cumulative 10% particle diameter D10 ratio D90/D10 of 19 or less, and a Vickers hardness of 1000 (kgf/mm)²) The following. The magnetic powder of the magnetic portion has a volume-based filling rate of 60% or more.

A method for manufacturing an inductor according to a second aspect includes the steps of: a step of embedding a coil in a magnetic material, wherein the magnetic material includes: a cumulative 50% particle diameter D50 in a cumulative particle size distribution on a volume basis of 5 μm or less and a ratio D90/D10 of a cumulative 90% particle diameter D90 to a cumulative 10% particle diameter D10 of 19 or less and a Vickers hardness of 1000 (kgf/mm)²) Magnetic powder and resin with a content of 5% by mass or less; and setting the magnetic material with the embedded coil at 5 ton/cm²And pressing the mixture at a pressure higher than the above pressure to form a unit body having a magnetic powder filling rate of 60% or more.

According to one embodiment of the present invention, an inductor having excellent high-frequency characteristics can be provided.

Drawings

Fig. 1 is a perspective view showing an example of an inductor.

Fig. 2 is a cross-sectional view of line AA of fig. 1.

Fig. 3 is a graph showing a relationship between the frequency and the inductance of the inductor.

Fig. 4 is a graph showing a relationship between the frequency and the Q value of the inductor.

Fig. 5 is a graph showing a relationship between the frequency and the resistance value of the inductor.

Description of the symbols

100 inductor, 10 unit body, 12 external terminal

Detailed Description

The inductor includes a unit body including a magnetic portion containing magnetic powder and a coil embedded in the magnetic portion, and an external terminal. The magnetic powder has a cumulative 50% particle diameter D50 of 5 μm or less, a cumulative 90% particle diameter D90/cumulative 10% particle diameter D10 ratio D90/D10 of 19 or less, and a Vickers hardness of 1000 (kgf/mm)²) The following. The magnetic powder of the magnetic portion has a volume-based filling rate of 60% or more.

An inductor having a magnetic portion containing magnetic powder having a small average particle diameter, a narrow particle size distribution, and a hardness of at most a predetermined value can exhibit an excellent Q value while suppressing a decrease in inductance value in a high-frequency region. In addition, an increase in the resistance value in the high frequency region can be suppressed, and a large current can be sufficiently handled.

The unit cell constituting the inductor may have 2 main surfaces facing each other, end surfaces facing each other adjacent to the main surfaces, and side surfaces facing each other adjacent to the main surfaces and the end surfaces. One of the 2 main surfaces may be a mounting surface and the other may be an upper surface. The unit body may have a substantially rectangular parallelepiped shape, and may be defined by a height T, which is a distance between the mounting surface and the upper surface, and a width W, which is a distance between the side surfaces, which is a distance between the end surfaces, and a length L. The length L of the unit cell is, for example, 0.5mm to 3.4mm, preferably 1mm to 3mm, the width W is, for example, 0.5mm to 2.7mm, preferably 0.5mm to 2.5mm, and the height T is, for example, 0.5mm to 2mm, preferably 0.5mm to 1.5 mm. As the size of the unit cell, L.times.W.times.T may be, for example, 1 mm.times.0.5 mm, 1.6 mm.times.0.8 mm.times.0.65 mm, 2 mm.times.1.2 mm.times.0.8 mm, 2.5 mm.times.2 mm.times.1.0 mm.

The coil may be a linear metal plate. If the coil is a linear metal plate, the occurrence of distributed volume is suppressed, and the coil can sufficiently cope with a large current. The metal plate forming the coil may be a conductive metal material such as copper. The thickness of the metal plate forming the coil is, for example, 0.05 to 0.2mm, preferably 0.1 to 0.15mm, and the width in the direction perpendicular to the longitudinal direction and the thickness direction is, for example, 0.3 to 1.0mm, preferably 0.45 to 0.75 mm.

The cumulative 50% particle diameter D50 corresponding to the 50% cumulative volume from the small particle diameter side in the cumulative particle size distribution on a volume basis may be, for example, 5 μm or less, preferably 4 μm or less, or 3.6 μm or less or 3 μm or less. The cumulative 50% particle diameter D50 may be 1 μm or more or 2 μm or more, for example. When the cumulative 50% particle diameter D50 is within the above range, a desired inductance can be easily achieved. In addition, the insulation resistance tends to be further improved, and the withstand voltage tends to be further improved. The cumulative particle size distribution of the magnetic powder can be measured, for example, using a laser diffraction particle size distribution measuring apparatus, and the cumulative 50% particle size D50, the cumulative 10% particle size D10, and the cumulative 90% particle size D90 are also measured by the same apparatus.

The cumulative 10% particle diameter D10 corresponding to 10% by volume of the magnetic powder may be, for example, 3 μm or less, preferably 2.5 μm or less or 2 μm or less. The cumulative 10% particle diameter D10 may be 0.5 μm or more, or 0.1 μm or more, for example. The cumulative 90% particle diameter D90 corresponding to 90% by volume of the magnetic powder may be, for example, 10 μm or less, preferably 8 μm or less or 7 μm or less. The 90% cumulative particle diameter D90 may be, for example, 2 μm or more. The ratio D90/D10 of the cumulative 90% particle diameter D90 to the cumulative 10% particle diameter D10 of the magnetic powder may be 19 or less, preferably 10 or less or 7 or less, for example. The ratio D90/D10 may be 1 or more or 2 or more, for example. When the ratio D90/D10 is in the above range, a desired inductance can be easily realized.

The ratio D10/D50 of the cumulative 10% particle diameter D10 of the magnetic powder to the cumulative 50% particle diameter D50 may be, for example, 0.1 or more, preferably 0.3 or more, and may be 0.4 or more, or 0.5 or more. The ratio D10/D50 may be, for example, 0.9 or less. When the ratio D10/D50 is in the above range, a desired inductance can be easily realized.

The ratio of the cumulative 90% particle diameter D90 of the magnetic powder to the cumulative 50% particle diameter D50D 90/D50 may be 3 or less, preferably 2.5 or less or 2 or less. The ratio D90/D50 may be 1 or more, for example. When the ratio D90/D50 is in the above range, a desired inductance can be easily realized.

The Vickers hardness of the magnetic powder may be, for example, 1000 (kgf/mm)²) Hereinafter, it may preferably be 600 (kgf/mm)²) The following is 500 (kgf/mm)²) The following. The Vickers hardness may be, for example, 100 (kgf/mm)²) The above. When the vickers hardness is in the above range, a desired inductance can be easily realized. The vickers hardness of the magnetic powder can be measured using a commercially available measuring apparatus, for example, nanoindenter ENT-2100 (manufactured by Elionix corporation) based on the description of the operation manual.

The volume-based filling ratio of the magnetic powder constituting the magnetic portion of the cell body may be, for example, 60% or more, and preferably 65% or more, or 70% or more. The volume-based filling ratio of the magnetic powder may be, for example, 95% or less. The filling factor of the magnetic powder in the magnetic portion can be calculated as a ratio of the area of the magnetic powder to the area of an observation field (for example, a rectangle of 1000 magnifications) by observing the cross section of the magnetic portion with a Scanning Electron Microscope (SEM). The area occupied by the magnetic powder of the observation field can be calculated based on the contrast of the SEM image using image processing software. The position at which the filling rate of the magnetic powder is calculated may be the magnetic portion, and may be measured at a position 30% of the height of the unit body from the upper surface facing the mounting surface toward the mounting surface, for example. The cross section observed by SEM may be substantially parallel to the mounting surface, for example.

The magnetic part constituting the unit body is formed of a composite material containing magnetic powder and a binder such as resin. As the magnetic powder, iron-based metal magnetic powder such as Fe, Fe-Si, Fe-Ni, Fe-Si-Cr, Fe-Si-Al, Fe-Ni-Mo, and Fe-Cr-Al, other composition-system metal magnetic powder, amorphous metal magnetic powder, metal magnetic powder whose surface is covered with an insulator such as glass, surface-modified metal magnetic powder, and nano-scale fine metal magnetic powder can be used.

The magnetic powder may contain a soft magnetic material containing iron (Fe) and silicon (Si), or may contain a soft magnetic material of Fe — Si — Cr system. When the magnetic powder includes a soft magnetic material containing iron, silicon, and chromium (Cr), the content of silicon in the soft magnetic material may be, for example, 1 mass% or more, and preferably 3 mass% or more. The content of silicon in the soft magnetic material may be 7 mass% or less, for example. The content of chromium in the soft magnetic material may be, for example, 1 mass% or more, and preferably 3 mass% or more. The content of chromium in the soft magnetic material may be 7 mass% or less, for example. The iron content of the soft magnetic material is, for example, 80 mass% or more, and preferably 90 to 98 mass%. When the magnetic powder is a soft magnetic material containing iron and silicon, the magnetocrystalline anisotropy constant is decreased, and the uniformity and isotropy in the magnetic region are ensured, so that the effects of decreasing the holding power and increasing the magnetic permeability can be obtained. Further, by further containing chromium (Cr) in the soft magnetic material containing iron and silicon, a passive film is formed, and rust is less likely to develop. Further, by providing the magnetic powder with a predetermined composition, desired characteristics can be more easily realized.

The magnetic powder may contain a crystalline soft magnetic material or an amorphous soft magnetic material. The magnetic powder may contain crystalline metal magnetic powder or amorphous metal magnetic powder. In addition, the magnetic powder may have an insulating layer on its surface. The insulating layer may be formed of a material derived from a component of the magnetic powder, or may be formed to contain a component different from a material constituting the magnetic powder. When the magnetic powder has an insulating layer, examples of the material of the insulating layer include inorganic materials. The thickness of the insulating layer may be, for example, 200nm or less, and may preferably be 100nm or less or 50nm or less. The thickness of the insulating layer may be, for example, 10nm or more. When the thickness of the insulating layer is within a predetermined range, the insulation resistance value and the withstand voltage tend to be further improved.

As an example of the resin constituting the binder of the magnetic portion, a thermosetting resin such as an epoxy resin, a polyimide resin, or a phenol resin, a thermoplastic resin such as a polyethylene resin, a polyamide resin, or a liquid crystal polymer can be used. The content of the resin in the magnetic portion may be, for example, 0.5% by mass or more, and preferably 1% by mass or more or 2% by mass or more. The content of the resin in the magnetic portion may be, for example, 5 mass% or less, and preferably 4 mass% or less or 3 mass% or less.

The permeability (μ') of the cell body at 10MHz may be 10 or more, and preferably may be 20 or more or 25 or more. The effect of high inductance can be obtained when the magnetic permeability of the unit body is more than a predetermined value. Note that the magnetic permeability of the cell body can be calculated using EDA software.

The inductor according to claim 1 is excellent in high-frequency characteristics and can sufficiently cope with a large current, and thus can be preferably applied to a DC-DC converter. The frequency used may be, for example, 3MHz or more, preferably 6MHz or more, or 10MHz or more. The inductor according to claim 1 has a high insulation resistance and an excellent withstand voltage. The insulation resistance of the inductor may be 1k Ω/mm or more, for example. The withstand voltage may be 20V/mm or more, for example. The insulation resistance can be measured using a commercially available measuring device, for example, SM-8213 (manufactured by TOA DKK corporation) based on the description of the specification of the operation. The withstand voltage can be measured using a commercially available measuring device, for example, TOS9201 (manufactured by KIKUSUI corporation), based on the description of the operation specification thereof.

The inductor can be manufactured by the following manufacturing method, for example. The method for manufacturing the inductor may include a 1 st step and a 2 nd step, wherein the 1 st step is to embed a coil in a magnetic material, and the magnetic material includes: a cumulative 50% particle diameter D50 in a cumulative particle size distribution on a volume basis of 5 μm or less and a ratio D90/D10 of a cumulative 90% particle diameter D90 to a cumulative 10% particle diameter D10 of 19 or less and a Vickers hardness of 1000 (kgf/mm)²) Magnetic powder and resin with a content of 5% by mass or less; in the 2 nd step, the magnetic material with the coil embedded therein is set at 5 ton/cm²The molding is carried out under the above pressure to obtain a unit body having a magnetic powder filling rate of 60% or more.

By molding a magnetic material containing magnetic powder having predetermined characteristics under a pressure equal to or higher than a predetermined value, an inductor having excellent high-frequency characteristics can be efficiently manufactured. The pressure in the 2 nd step may preferably be 5 tons/cm²Above or 10 tons/cm²The above.

The term "step" in the present specification is not limited to an independent step, and includes the term if the desired purpose of the step can be achieved even when the step is not clearly distinguished from other steps. The content of each component in the composition refers to the total amount of a plurality of substances present in the composition, unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below exemplify an inductor and a method for manufacturing the same for embodying the technical idea of the present invention, and the present invention is not limited to the inductor and the method for manufacturing the same described below. It should be noted that the components shown in the claims are not limited to the components of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements of the constituent members described in the embodiments are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. The sizes, positional relationships, and the like of the components shown in the drawings may be exaggerated for clarity. In the following description, the same names and symbols denote the same or similar members made of the same material, and detailed description thereof will be omitted as appropriate. Each element constituting the present invention may be a system in which a plurality of elements are constituted by the same component and a plurality of elements are shared by one component, or may be realized by sharing the function of one component by a plurality of components. The contents described in some embodiments may be applied to other embodiments.

Examples

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following examples and the like, the respective measured values were measured as follows.

(particle size distribution and Vickers hardness)

The cumulative 10% particle diameter D10, the cumulative 50% particle diameter D50 and the cumulative 90% particle diameter D90 of the magnetic powder were measured by using a laser diffraction particle size distribution measuring apparatus MicroTrack MT 3000-II (manufactured by MicrotracBEL). The Vickers hardness of the magnetic powder was measured using nanoindenter ENT-2100 (manufactured by Elionix).

(magnetic powder filling ratio)

The filling ratio of the magnetic powder in the unit body was calculated by preparing a cross-sectional sample at a position having a height T of 30% from the upper surface of the inductor toward the mounting surface, obtaining an SEM image using a scanning electron microscope (SEM; 1000 times), and processing the obtained SEM image with image processing software.

(electric/magnetic characteristics)

The inductance, Q value, and resistance value of the inductor were measured using a Network Analyzer E5071C (Agilent). The magnetic permeability of the inductor was measured using a material analyzer E4991 (Agilent).

(example 1)

An inductor 100 according to embodiment 1 is described with reference to fig. 1 and 2. Fig. 1 is a schematic perspective view of an inductor 100 according to example 1. Fig. 2 is a schematic sectional view of a surface perpendicular to the mounting surface through the AA line in fig. 1.

As shown in fig. 1 and 2, an inductor 100 according to embodiment 1 includes: a unit body 10 including a magnetic portion 16 containing magnetic powder and a coil 14 embedded in the magnetic portion 16; and an external terminal 12 formed to extend from a coil 14 embedded in the unit body 10 and disposed on the surface of the unit body. The unit body 10 has 2 main surfaces 22, 24 facing each other, end surfaces 26 facing each other adjacent to the main surfaces, and side surfaces 28 facing each other adjacent to the main surfaces and the end surfaces. One of the main surfaces is a mounting surface 22, and the other is an upper surface 24. Unit body 10 is defined by height T, which is the distance between mounting surface 22 and upper surface 24, length L, which is the distance between end surfaces 26, and width W, which is the distance between side surfaces 28.

The coil 14 is formed of a linear metal plate, and is disposed so as to penetrate the magnetic portion 16 in a direction in which the side surfaces thereof face each other. The external terminals 12 are formed by extending metal plates at both ends of the coil 14. The external terminals 12 are respectively led out from the side surfaces 28 of the unit bodies 10, have 2 bent portions on each side, are arranged along the side surfaces 28 of the unit bodies 10, and extend to the mounting surface 22 of the unit bodies 10. The coil 14 and the external terminal 12 are formed of a conductive metal such as copper. The external terminals 12 are disposed so as to contact the side surfaces 28 and the mounting surface 22 of the unit body 10. A recess is provided in the mounting surface 22 of the unit body 10, and a part of the external terminal 12 is accommodated therein.

The magnetic portion 16 constituting the unit body 10 is formed of a composite material containing magnetic powder and a binder such as resin. As the magnetic powder, a magnetic powder including a crystalline Fe — Si — Cr-based soft magnetic material having a silicon content of 3 mass%, a chromium content of 5 mass%, and the balance iron was used. In addition, the magnetic powder had a cumulative 10% particle diameter D10 of 1.43 μm, a cumulative 50% particle diameter D50 of 2.90 μm, a cumulative 90% particle diameter D90 of 5.45 μm, and a Vickers hardness of 400. + -.50. A coil, which is a linear metal plate, was embedded in a composite material containing 2.5 mass% of an epoxy resin as a resin in addition to magnetic powder, and applied at 10 tons/cm²The unit body was formed by the pressure of (1), and the inductor 100 of example 1 was obtained.

The relationship between the operating frequency and the inductance of the obtained inductor is shown in fig. 3, the relationship between the operating frequency and the Q value is shown in fig. 4, and the relationship between the operating frequency and the resistance value is shown in fig. 5. The 10MHz inductance of the inductor was 9.53nH, and the Q value was 87.25.

(example 2)

An inductor of example 2 was obtained in the same manner as in example 1 except that a soft magnetic material having a cumulative 10% particle diameter D10 of 2.05 μm, a cumulative 50% particle diameter D50 of 3.21 μm, and a cumulative 90% particle diameter D90 of 5.05 μm was used as the magnetic powder.

The relationship between the operating frequency and the inductance of the inductor obtained is shown in fig. 3, the relationship between the operating frequency and the Q value is shown in fig. 4, and the relationship between the operating frequency and the resistance value is shown in fig. 5. The 10MHz inductance of the inductor was 9.85nH, with a Q of 81.80.

(example 3)

An inductor of example 3 was obtained in the same manner as in example 1 except that a soft magnetic material having a cumulative 10% particle diameter D10 of 1.77 μm, a cumulative 50% particle diameter D50 of 3.32 μm, and a cumulative 90% particle diameter D90 of 6.13 μm was used as the magnetic powder.

The relationship between the operating frequency and the inductance of the inductor obtained is shown in fig. 3, the relationship between the operating frequency and the Q value is shown in fig. 4, and the relationship between the operating frequency and the resistance value is shown in fig. 5. The 10MHz inductance of the inductor was 10.55nH, and the Q value was 85.71.

(example 4)

An inductor of example 4 was obtained in the same manner as in example 1 except that a soft magnetic material having a cumulative 10% particle diameter D10 of 1.97 μm, a cumulative 50% particle diameter D50 of 3.53 μm, and a cumulative 90% particle diameter D90 of 6.45 μm was used as the magnetic powder.

The relationship between the operating frequency and the inductance of the obtained inductor is shown in fig. 3, the relationship between the operating frequency and the Q value is shown in fig. 4, and the relationship between the operating frequency and the resistance value is shown in fig. 5. The 10MHz inductance of the inductor was 10.82nH, and the Q value was 87.79.

Comparative example 1

An inductor of comparative example 1 was obtained in the same manner as in example 1, except that a soft magnetic material having a cumulative 10% particle diameter D10 of 3.06 μm, a cumulative 50% particle diameter D50 of 6.28 μm, and a cumulative 90% particle diameter D90 of 11.83 μm was used as the magnetic powder.

The relationship between the operating frequency and the inductance of the inductor obtained is shown in fig. 3, the relationship between the operating frequency and the Q value is shown in fig. 4, and the relationship between the operating frequency and the resistance value is shown in fig. 5. The inductor has an inductance of 12.11nH at 10MHz and a Q value of 73.80.

Comparative example 2

An inductor of comparative example 2 was obtained in the same manner as in example 1, except that a soft magnetic material having a cumulative 10% particle diameter D10 of 3.87 μm, a cumulative 50% particle diameter D50 of 9.71 μm, and a cumulative 90% particle diameter D90 of 23.33 μm was used as the magnetic powder.

The relationship between the operating frequency and the inductance of the inductor obtained is shown in fig. 3, the relationship between the operating frequency and the Q value is shown in fig. 4, and the relationship between the operating frequency and the resistance value is shown in fig. 5. The inductor had an inductance of 13.28nH at 10MHz and a Q value of 39.60.

Comparative example 3

An inductor of comparative example 3 was obtained in the same manner as in example 1, except that an amorphous Fe — Si — Cr-based soft magnetic material containing 6.7 mass% of silicon, 2.5 mass% of chromium, 2.5 mass% of boron, and the balance iron was used, and that a soft magnetic material having a cumulative 10% particle diameter D10 of 2.67m, a cumulative 50% particle diameter D50 of 4.28 μm, a cumulative 90% particle diameter D90 of 5.95 μm, and a vickers hardness of 1000 ± 100 was used as the magnetic powder.

The relationship between the operating frequency and the inductance of the inductor thus obtained is shown in fig. 3, the relationship between the operating frequency and the Q value is shown in fig. 4, and the relationship between the operating frequency and the resistance value is shown in fig. 5. The 10MHz inductance of the inductor was 4.10nH, with a Q of 50.00.

[ TABLE 1 ]

The inductors of examples 1 to 4 all showed excellent quality coefficients Q with 10MHz inductance of about 10nH and 80 or more. The inductors of examples 1, 3 and 4 have the highest quality factor Q frequency higher than that of comparative examples 1 and 2, and can be increased in frequency to about 3 to 10 MHz. Even if the average particle size of the magnetic powder is 5 μm or less, the L value can be maintained at about 10nH, and the resistance value can be reduced. Therefore, the inductor of the embodiment can contribute to improvement of circuit characteristics in a DC-DC converter circuit or the like in which an operating frequency is increased and an input current is also increased.