An inductor includes a wire including a conducting line, and an insulating film disposed on an entire circumferential surface of the conducting line, and a magnetic layer embedding the wire. The magnetic layer contains a magnetic particle. The magnetic layer includes a first layer in contact with the circumferential surface of the wire, a second layer in contact with the surface of the first layer, . . . and the n-th layer (n is a positive number of 3 or more) in contact with the surface of the (n−1)th layer. In the two layers adjacent to each other in the magnetic layer, the relative magnetic permeability of the layer closer to the wire is lower than the relative magnetic permeability of the layer farther from the wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. 371 National Stage Entry PCT/JP2020/004250, filed on Feb. 5, 2020, which claims priority from Japanese Patent Application No. 2019-044776, filed on Mar. 12, 2019, the contents of all of which are herein incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to an inductor.

BACKGROUND ART

Conventionally, it has been known that an inductor is loaded on an electronic device and the like to be used as a passive element for a voltage conversion member and the like.

For example, an inductor including a rectangular parallelepiped chip body portion made of a magnetic material, and an inner conductor made of copper embedded in the interior of the chip body portion has been proposed (ref: for example, Patent Document 1 below).

CITATION LIST

Patent Document

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

However, in the inductor of Patent Document 1, there is a problem that the DC superposition characteristics are insufficient.

The present invention provides an inductor having excellent DC superposition characteristics.

Means for Solving the Problem

The present invention (1) includes an inductor including a wire including a conducting line, and an insulating film disposed on an entire circumferential surface of the conducting line, and a magnetic layer embedding the wire, wherein the magnetic layer contains a magnetic particle, the magnetic layer includes a first layer in contact with the circumferential surface of the wire, a second layer in contact with the surface of the first layer, and the n-th layer (n is a positive number of 3 or more) in contact with the surface of the (n−1)th layer, and in the two lasers adjacent to each other in the magnetic layer, the relative magnetic permeability of the layer closer to the wire is lower than the relative magnetic permeability of the layer farther from the wire.

The present invention (2) includes the inductor described in (1), wherein the wire has a generally circular shape in a cross-sectional view.

The present invention (3) includes the inductor described in (2), wherein any of the second layer to the n-th layer has a generally arc shape in a cross-sectional view sharing a center with the wire.

The present invention (4) includes the inductor described in any one of (1) to (3), wherein any of the first layer to the n-th layer has an extending portion extending from the wire in a direction perpendicular to an extending direction of the wire and a thickness direction of the magnetic layer.

The present invention (5) includes the inductor described in any one of (1) to (4), wherein the magnetic particle contained in the first layer has a generally spherical shape, and the magnetic particle contained in the second layer to the n-th layer has a generally flat shape.

The present invention (6) includes the inductor described in any one of (1) to (5), wherein the magnetic particle contained in at least the second layer is orientated in an outer peripheral surface of the wire.

Effect of the Invention

The inductor of the present invention has excellent DC superposition characteristics.

DESCRIPTION OF EMBODIMENTS

One embodiment of an inductor of the present invention is described with reference toFIG.1.

As shown inFIG.1, an inductor1has a shape extending in a plane direction. Specifically, the inductor1has one surface and the other surface facing each other in a thickness direction, both one surface and the other surface have a flat shape along a first direction perpendicular to a direction which is included in the plane direction and in which a wire2(described later) transmits an electric current (corresponding to the depth direction on the plane of the sheet) and the thickness direction.

The inductor1includes the wire2, and a magnetic layer3.

The wire2has a generally circular shape in a cross-sectional view. Specifically, the wire2has a generally circular shape when cut in a cross-section (cross-section in the first direction) perpendicular to a second direction (transmission direction) (depth direction on the plane of the sheet) which is a direction for transmitting the electric current.

The wire2includes a conducting line4, and an insulating film5covering it.

The conducting line4is a conducting line having a shape extending long in the second direction. Further, the conducting line4has a generally circular shape in a cross-sectional view sharing a central axis with the wire2.

Examples of a material for the conducting line4include metal conductors such as copper, silver, gold, aluminum, nickel, and an alloy of these, and preferably, copper is used. The conducting line4may have a single-layer structure, or a multi-layer structure in which plating (for example, nickel) is applied to the surface of a core conductor (for example, copper).

The insulating film5protects the conducting line4from chemicals and water, and also prevents a short circuit of the conducting line4with the magnetic layer3. The insulating film5covers the entire outer peripheral surface (circumferential surface) of the conducting line4

The insulating film5has a generally circular ring shape in a cross-sectional view sharing a central axis (center) with the wire2.

Examples of a material for the insulating film5include insulating resins such as poly vinyl formal, polyester, polyesterimide, polyamide (including nylon), polyimide, polyamideimide, and polyurethane. These may be used alone or in combination of two or more.

The insulating film5may consist of a single layer or a plurality of layers.

A thickness of the insulating film5is generally uniform in a radial direction of the wire2at any position in a circumferential direction, and is, for example, 1 μm or more, preferably 3 μm or more, and for example, 100 μm or less, preferably 50 μm or less.

A ratio of a radius of the conducting line4to the thickness of the insulating film5is, for example, 1 or more, preferably 5 or more, and for example, 500 or less, preferably 100 or less.

A radius R (=the total sum of the radius of the conducting line4and the thickness of the insulating film5) of the wire2is, for example, 25 μm or more, preferably 50 μm or more, and for example, 2000 μm or less, preferably 200 μm or less.

The magnetic layer3improves the DC superposition characteristics of the inductor1, while improving the inductance of the inductor1. The magnetic layer3covers the entire outer peripheral surface (circumferential surface) of the wire2. Thus, the magnetic layer3embeds the wire2. The magnetic layer3forms the outer shape of the inductor1. Specifically, the magnetic layer3has a rectangular shape extending in the plane direction (the first direction and the second direction). More specifically, the magnetic layer3has one surface and the other surface facing each other in the thickness direction, and one surface and the other surface of the magnetic layer3form one surface and the other surface of the inductor1, respectively.

The magnetic layer3includes a first layer10embedding the wire2, a second layer20in contact with the surface of the first layer10, a third layer30in contact with the surface of the second layer20, and a fourth layer40in contact with the surface of the third layer30.

Further, at a position overlapped with the wire2(overlapped position), the first layer10, the second layer20, the third layer30, and the fourth layer40are arranged from the wire2toward both sides in the thickness direction. In a projected surface projected in the thickness direction, at a position deviated from the wire2in the first direction, the first layer10, the second layer20, the third layer30, and the fourth layer40are arranged from an intermediate portion (central portion) in the thickness direction of the magnetic layer3toward both sides in the thickness direction.

The first layer10has a shape extending in the plane direction, and has one surface11and an other surface12facing each other in the thickness direction. Further, the first layer10covers the entire outer peripheral surface (circumferential surface) of the insulating film5. Thus, the first layer10embeds the insulating film5. Therefore, the first layer10further has an inner peripheral surface13in contact with the outer peripheral surface of the insulating film5.

The first layer10includes a generally arc shape in a cross-sectional view sharing the center with the wire2. Specifically, the first layer10integrally has a one-side first arc portion15, an other-side first arc portion16, and an extending portion17in a cross-sectional view.

The one-side first arc portion15is disposed at one side in the thickness direction from the center of the wire2. The one-side first arc portion15faces a one-side area18at one side in the thickness direction from the center of the wire2on the circumferential surface of the wire2in a cross-sectional view. The one surface11of the one-side first are portion15forms an arc surface sharing the center with the wire2. A central angle of the one-side first arc portion15is, for example, below 180 degrees, preferably 135 degrees or less, and for example, 30 degrees or more, preferably 60 degrees or more.

The other-side first are portion16faces an other-side area19at the other side in the thickness direction from the center of the wire2on the circumferential surface of the wire2in a cross-sectional view. The other surface12of the other-side first are portion16forms an arc surface sharing the center with the wire2. A central angle of the other-side first arc portion16is, for example, below 180 degrees, preferably 135 degrees or less, and for example, 30 degrees or more, preferably 60 degrees or more.

The central angle of the total sum of the one-side first arc portion15and the other-side first arc portion16is, for example, below 360 degrees.

The other-side first are portion16is plane-symmetrical with the one-side first are portion15with respect to a phantom plane passing the center of the wire2along the plane direction.

The extending portion17has a shape extending from the wire2outwardly in the first direction. The two extending portions17are provided in the first layer10. Each of the two extending portions17is disposed at each of both outer sides in the first direction of the wire2. Each of the two extending portions17extends outwardly in the first direction from the circumferential surface of the wire2between the one-side first arc portion15and the other-side first arc portion16to reach each of both end surfaces in the first direction of the inductor1. The one surface11and the other surface12in the extending portion17are parallel. The extending portion17has two flat belt shapes extending in the second direction at both outer sides in the first direction of the wire2when viewed from the top.

A thickness of each of the one-side first arc portion15and the other-side first arc portion16is, for example, 1 μm or more, preferably 5 μm or more, and for example, 1000 μm or less, preferably 800 μm or less. A thickness of the extending portion17is, for example, 2 μm or more, preferably 10 μm or more, and for example, 2000 μm or less, preferably 1600 μm or less.

The thickness of the first layer10corresponds to the total thickness of the one-side first are portion15and the other-side first arc portion16, and also corresponds to the thickness of the extending portion17. Specifically, the thickness of the first layer10is, for example, 2 μm or more, preferably 10 μm or more, and for example, 2000 μm or less, preferably 1600 μm or less, more preferably 100 μm or less, further more preferably 500 μm or less.

A ratio of the thickness of the first layer10to the thickness (described later) of the magnetic layer3is, for example, 0.01 or more, preferably 0.05 or more, more preferably 0.1 or more, further more preferably 0.2 or more, particularly preferably 0.3 or more, and for example, 0.5 or less, preferably 0.4 or less.

When the ratio of the thickness of the first layer10to that of the magnetic layer3is the above-described lower limit or more, a sufficient distance between the second laser20and the wire2is ensured, and the magnetic saturation of the second layer20, the third layer30, and the fourth layer40is suppressed, that is, a layer having higher relative magnetic permeability can be disposed after the second layer20, while maintaining excellent DC superposition characteristics.

The second layer20independently has a one-side second layer21and an other-side second layer22.

The one-side second layer21is in contact with the one surface11of the first layer10. The one-side second layer21has a shape following the one surface11of the one-side first arc portion15and the two extending portions17of the first layer10. The one-side second layer21has an other surface24in contact with the one surface11of the first layer10, and one surface23disposed at one side in the thickness direction of the other surface24at spaced intervals thereto. The one-side second layer21has a one-side second arc portion27in a generally arc shape in a cross-sectional view sharing the center with the wire2.

The other-side second layer22is oppositely disposed at the other side in the thickness direction of the one-side second layer21across the first layer10. The other-side second layer22is in contact with the other surface12of the first laver10. The other-side second layer22has a shape following the other surface12of the other-side first arc portion16and the two extending portions17of the first layer10. The other-side second layer22has one surface25in contact with the other surface12of the first layer10, and an other surface26disposed at the other side in the thickness direction of the one surface25at spaced intervals thereto. The other-side second layer22has an other-side second arc portion28in a generally arc shape in a cross-sectional view sharing the center with the wire2.

The other-side second layer22is plane-symmetrical with the one-side second layer21with respect to a phantom plane passing the center of the wire2along the plane direction.

A thickness of the second layer20is the total thickness of the one-side second layer21and the other-side second layer22, and is, for example, 1 μm or more, preferably 5 μm or more, and for example, 1000 μm or less, preferably 800 μm or less.

A ratio of the thickness of the second layer20to the thickness (described later) of the magnetic layer3is, for example, 0.01 or more, preferably 0.05 or more, and for example, 0.5 or less, preferably 0.4 or less.

A ratio of the thickness of the second layer20to the thickness of the first layer10is, for example, 0.1 or more, preferably 0.2 or more, and for example, 100 or less, preferably 10 or less.

The third layer20independently has a one-side third layer31and an other-side third layer32.

The one-side third layer31is in contact with the one-side second layer21. Further, the one-side third layer31has generally the same thickness over the first direction. The one-side third layer31has an other surface34in contact with the one surface23of the one-side second layer21, and one surface33oppositely disposed at one side in the thickness direction of the other surface34at spaced intervals thereto. The one-side third layer31has a shape extending in the plane direction.

The other-side third layer32is oppositely disposed at the other side in the thickness direction of the one-side third layer31across the first layer1oand the second layer20. The other-side third layer32has generally the same thickness over the first direction. The other-side third layer32has one surface35in contact with the other surface26of the other-side second layer22, and an other surface36oppositely disposed at the other side in the thickness direction of the one surface35at spaced intervals thereto. The other-side third layer32has a shape extending in the plane direction.

The other-side third layer32is plane-symmetrical with the one-side third layer31with respect to a phantom plane passing the center of the wire2along the plane direction.

A thickness of the third layer30is the total thickness of the one-side third layer31and the other-side third layer32, and is, for example, 1 μm or more, preferably 5 μm or more, and for example, 1000 μm or less, preferably 800 μm or less.

A ratio of the thickness of the third layer30to the thickness of the magnetic laver3is, for example, 0.01 or more, preferably 0.05 or more, and for example, 0.5 or less, preferably 0.4 or less.

A ratio of the thickness of the third layer30to the thickness of the second layer20is, for example, 0.1 or more, preferably 0.2 or more, and for example, 100 or less, preferably 10 or less.

The fourth layer40independently has a one-side fourth layer41and an other-side fourth layer42.

The one-side fourth layer41is in contact with the one-side third layer31. Further, the one-side fourth layer41has generally the same thickness over the first direction. The one-side fourth layer41has an other surface44in contact with the one surface33of the one-side third layer31, and one surface43oppositely disposed at one side in the thickness direction of the other surface44at spaced intervals thereto. The one surface43of the one-side fourth layer41is exposed toward one side in the thickness direction. The one surface43has a flat surface along the first direction and the second direction.

The other-side fourth layer42is oppositely disposed at the other side in the thickness direction of the one-side fourth layer41across the first layer10, the second layer20, and the third layer30. The other-side fourth layer42has generally the same thickness over the first direction. The other-side fourth layer42is in contact with the other-side third layer32. The other-side fourth layer42has one surface45in contact with the other surface36of the other-side third layer32, and an other surface46oppositely disposed with respect to the one surface45at spaced intervals thereto. The other surface46is exposed toward the other side in the thickness direction. The other surface46has a flat surface along the first direction and the second direction.

A thickness of the fourth layer40is the total thickness of the one-side fourth layer41and the other-side fourth layer42, and is, for example, 1 μm or more, preferably 5 μm or more, and for example, 1000 μm or less, preferably 800 μm or less.

A ratio of the thickness of the fourth layer42to the thickness of the magnetic layer3is, for example, 0.01 or more, preferably 0.05 or more, and for example, 0.5 or less, preferably 0.4 or less.

A ratio of the thickness of the fourth layer40to the thickness of the third layer30is, for example, 0.1 or more, preferably 0.2 or more, and for example, 100 or less, preferably 10 or less.

The thickness of the magnetic layer3is the total thickness of the first layer10, the second layer20, the third layer30, and the fourth layer40, and is, for example, 2 times or more, preferably, 3 times or more, and for example, 20 times or less the radius of the wire2. Specifically, the thickness of the magnetic layer3is, for example, 100 μm or more, preferably 200 μm or more, and for example, 3000 μm or less, preferably 1500 μm or less, more preferably 950 μm or less, further more preferably 900 μm or less, particularly preferably 850 μm or less. The thickness of the magnetic layer3is a distance between one surface and the other surface of the magnetic layer3.

<Relative Magnetic Permeability of Magnetic Layer>

In the first layer10, the second layer20, the third layer30, and the fourth layer40, in the two layers adjacent to each other, the relative magnetic permeability of the layer closer to the wire2is lower than that of the layer farther from the wire2.

In the magnetic layer3, for example, by appropriately changing the kind, the shape, and the volume ratio of the magnetic particles of each layer, the relative magnetic permeability of the layer closer to the wire2can be set lower than that of the layer farther from the wire2. An embodiment of the detailed adjustment (formulation) thereof is described in the first embodiment to the second embodiment.

The relative magnetic permeability is measured at a frequency of 10 MHz.

Specifically, the relative magnetic permeability of the first layer10is lower than that of the second layer20. The relative magnetic permeability of the second layer20is lower than that of the third layer30. The relative magnetic permeability of the third layer30is lower than that of the fourth layer40.

Further, in the first layer10, the second layer20, the third layer30, and the fourth layer40, in the two layers adjacent to each other, a ratio R of the relative magnetic permeability of the layer closer to the wire2to that of the layer farther from the wire2is, for example, 0.9 or less, preferably 0.7 or less, more preferably 0.5 or less, further more preferably 0.4 or less, particularly preferably 0.3 or less, and for example, 0.01 or more.

Specifically, a ratio R1(relative magnetic permeability of the first layer10/relative magnetic permeability of the second layer20) of the relative magnetic permeability of the first layer10to that of the second layer20is 0.9 or less, preferably 0.7 or less, more preferably 0.5 or less, further more preferably 0.4 or less, particularly preferably 0.3 or less, and for example, 0.1 or more.

A ratio R2(relative magnetic permeability of the second layer20/relative magnetic permeability of the third layer30) of the relative magnetic permeability of the second layer20to that of the third laver30is 0.9 or less, preferably 0.88 or less, more preferably 0.85 or less, and for example, 0.1 or more, preferably 0.2 or more, more preferably 0.4 or more, further more preferably 0.5 or more, still more preferably 0.6 or more, particularly preferably 0.7 or more.

A ratio R3(relative magnetic permeability of the third layer30/relative magnetic permeability of the fourth layer40) of the relative magnetic permeability of the third layer30to that of the fourth layer40is 0.9 or less, preferably 0.8 or less, more preferably 0.75 or less, further more preferably 0.7 or less, and for example, 0.1 or more, preferably 0.2 or more, more preferably 0.3 or more.

The above-described ratios R1to R3may be the same or change, and preferably, the ratio R1is smaller than the ratio R2and the ratio R2is smaller than the ratio R3.

A ratio of the ratio R1to the ratio R2is, for example, 0.9 or less, preferably 0.8 or less, and for example, 0.2 or more, preferably 0.3 or more, more preferably 0.35 or more.

A ratio of the ratio R2to the ratio R3is, for example, 0.8 or less, preferably 0.7 or less, and for example, 0.3 or more, preferably 0.5 or more. Further, in the first layer10, the second layer20, the third layer30, and the fourth layer40, in the two layers adjacent to each other, a value D obtained by subtracting the relative magnetic permeability of the layer closer to the wire2from the relative magnetic permeability of the layer farther from the wire2is, for example, 5 or more, preferably 10 or more, more preferably 15 or more, and for example, 100 or less.

Specifically, a value D1(relative magnetic permeability of the second layer20—relative magnetic permeability of the first layer10) obtained by subtracting the relative magnetic permeability of the first layer10from the relative magnetic permeability of the second laver20is, for example, 5 or more, preferably 10 or more, more preferably 25 or more, and for example, 50 or less.

A value D2(relative magnetic permeability of the third layer30—relative magnetic permeability of the second layer20) obtained by subtracting the relative magnetic permeability of the second layer20from the relative magnetic permeability of the third layer30is, for example, 5 or more, preferably 10 or more, and for example, 50 or less, preferably 40 or less, more preferably 30 or less.

A value D3(relative magnetic permeability of the fourth layer40—relative magnetic permeability of the third layer30) obtained by subtracting the relative magnetic permeability of the third layer30from the relative magnetic permeability of the fourth layer40is, for example, 10 or more, preferably 20 or more, and for example, 70 or less.

The above-described values D1to D3may be the same or change.

When the ratio R (including R1to R3) of the relative magnetic permeability and the difference D (subtracted value) (including D1to D3) described above are the above-described lower limit or more, it is possible to improve the DC superposition characteristics of the inductor1.

Each layer is defined by the relative magnetic permeability of each layer described above.

Specifically, in the magnetic layer3, the relative magnetic permeability of a region (region corresponding to the inner peripheral surface13of the first layer10) in contact with the circumferential surface of the wire2is measured to be subsequently continuously measured so as to move away from the wire2, and a region having the same relative magnetic permeability as that first obtained is defined as the first layer10. This is also carried out for the second layer20, the third layer30, and the fourth layer40in thus order. That is, a region having the same relative magnetic permeability is defined as one layer. In the description above, the measurement of the relative magnetic permeability is carried out from the inner peripheral surface13of the first layer10. Alternatively, for example, it can be also carried out from the one surface43of the fourth layer40.

As described later, when each layer is formed of a plurality of magnetic sheets (described later) (ref: phantom line ofFIG.2), in view of the definition described above, the relative magnetic permeability of the plurality of magnetic sheets for forming each layer is the same.

Further, in a producing method to be described later, the relative magnetic permeability of a first sheet51, a second sheet52, a third sheet53, and a fourth sheet54for forming the magnetic layer3can be measured in advance to be defined as the relative magnetic permeability of the first layer10, the second layer20, the third layer30, and the fourth layer40, respectively.

The magnetic layer3contains magnetic particles. Specifically, an example of a material for the magnetic layer3includes a magnetic composition containing the magnetic particles and a binder.

Examples of a magnetic material constituting the magnetic particles include a soft magnetic body and a hard magnetic body. Preferably, from the viewpoint of inductance and DC superposition characteristics, a soft magnetic body is used.

Examples of the soft magnetic body include a single metal body containing one kind of metal element in a state of a pure material and an alloy body which is a eutectic (mixture) of one or more kinds of metal element (first metal element) and one or more kinds of metal element (second metal element) and/or non-metal element (carbon, nitrogen, silicon, phosphorus, and the like). These may be used alone or in combination.

An example of the single metal body includes a metal single body consisting of only one kind of metal element (first metal element). The first metal element is, for example, appropriately selected from metal elements that can be included as the first metal element of the soft magnetic body such as iron (Fe), cobalt (Co), nickel (Ni), and the like.

Further, examples of the single metal body include an embodiment including a core including only one kind of metal element and a surface layer including an inorganic material and/or an organic material which modify/modifies a portion of or the entire surface of the core, and an embodiment in which an organic metal compound and an inorganic metal compound including the first metal element are decomposed (thermally decomposed and the like). More specifically, an example of the latter embodiment includes an iron powder (may be referred to as a carbonyl iron powder) in which an organic iron compound (specifically, carbonyl iron) including iron as the first metal element is thermally decomposed. The position of a layer including the inorganic material and/or the organic material modifying a portion including only one kind of metal element is not limited to the above-described surface. The organic metal compound and the inorganic metal compound that can obtain the single metal body are not particularly limited, and can be appropriately selected from a known or conventional organic metal compound and inorganic metal compound that can obtain the single metal body of the soft magnetic body.

The alloy body is not particularly limited as long as it is a eutectic of one or more kinds of metal element (first metal element) and one or more kinds of metal element (second metal element) and/or non-metal element (carbon, nitrogen, silicon, phosphorus, and the like), and can be used as an alloy body of a soft magnetic body.

The first metal element is an essential element in the alloy body, and examples thereof include iron (Fe), cobalt (Co), and nickel (Ni). When the first metal element is Fe, the alloy body is referred to as an Fe-based alloy, when the first metal element is Co, the alloy bods is referred to as a Co-based alloy, and when the first metal element is Ni, the alloy body is referred to as a Ni-based alloy.

The second metal element is an element (sub-component) which is secondarily contained in the alloy body, and is a metal element to be compatible with (eutectic to) the first metal element. Examples thereof include iron (Fe) (when the first metal element is other than Fe), cobalt (Co) (when the first metal element is other than Co), nickel (Ni) (when the first metal element is other than Ni), chromium (Cr), aluminum (Al), silicon (Si), copper (Cu), silver (Ag), manganese (Mn), calcium (Ca), barium (Ba), titanium (Ti), zirconium (Zr), hafnium (H), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), ruthenium (Ru), rhodium (Rh), zinc (Zn), gallium (Ga), indium (In), germanium (Ge), tin (Sn), lead (Pb), scandium (Sc), yttrium (Y), strontium (Sr), and various rare earth elements. These may be used alone or in combination of two or more.

The non-metal element is an element (sub-component) which is secondarily contained in the alloy body and is a non-metal element which is compatible with (eutectic to) the first metal element. Examples thereof include boron (B), carbon (C), nitrogen (N), silicon (Si), phosphorus (P), and sulfur (S) These may be used alone or in combination of two or more.

Examples of the Co-based alloy which is one example of an alloy body include Co—Ta—Zr and a cobalt (Co)-based amorphous alloy.

An example of the Ni-based alloy which is one example of an alloy body includes a Ni—Cr alloy.

Preferably, the magnetic material is appropriately selected from these soft magnetic bodies so as to satisfy the above-described relative magnetic permeability of each of the first layer10, the second layer20, the third layer30, and the fourth layer40.

A shape of the magnetic particles is not particularly limited, and examples thereof include a shape showing anisotropy such as a generally flat shape (plate shape) and a generally needle shape (including a generally spindle (football) shape), and a shape showing isotropy such as a generally spherical shape, a generally granular shape, and a generally massive shape. The shape of the magnetic particles is appropriately selected from the description above so as to satisfy the above-described relative magnetic permeability of each of the first layer10, the second layer20, the third layer30, and the fourth layer40.

An average value of the maximum length of the magnetic particles is, for example, 0.1 μm or more, preferably 0.5 μm or more, and for example, 200 μm or less, preferably 150 μm or less. The average value of the maximum length of the magnetic particles can be calculated as a neutral particle size of the magnetic particles.

A volume ratio (filling ratio) of the magnetic particles in the magnetic composition is, for example, 10% by volume or more, preferably 20% by volume or more, and for example, 90% by volume or less, preferably 80% by volume or less.

By appropriately changing the kind, the shape, the size, the volume ratio, and the like of the magnetic particles, the relative magnetic permeability of the first layer10, the second layer20, the third layer30, and the fourth layer40satisfies a desired relationship.

Examples of the binder include thermoplastic components such as an acrylic resin and thermosetting components such as an epoxy resin composition. The acrylic resin contains, for example, a carboxyl group-containing acrylic acid ester copolymer. The epoxy resin composition contains, for example, an epoxy resin (cresol novolak-type epoxy resin and the like) as a main agent, a curing agent for an epoxy resin (phenol resin and the like), and a curing accelerator for an epoxy resin (imidazole compound and the like).

As the binder, a thermoplastic component and a thermosetting component may be used alone or in combination, and preferably, a thermoplastic component and a thermosetting component are used in combination.

A more detailed formulation of the magnetic composition described above is described in Japanese Unexamined Patent Publication No. 2014-165363 and the like.

<Producing Method of Inductor>

A method for producing the inductor1is described with reference toFIG.2.

To produce the inductor1, first, the wire2is prepared.

Subsequently, the two first sheets51, the two second sheets52, the two third sheets53, and the two fourth sheets54are prepared.

By changing the kind, the shape, the volume ratio, and the like of the magnetic particles contained in the first sheet51, the second sheet52, the third sheet53, and the fourth sheet54, the relative magnetic permeability satisfying any of the following formulas (1) to (3) can be obtained.
Relative Magnetic permeability of the first sheet 51<relative Magnetic permeability of the second sheet 52  (1)
Relative Magnetic permeability of the second sheet 52<relative Magnetic permeability of the third sheet 53  (2)
Relative Magnetic permeability of the third sheet 53<relative Magnetic permeability of the fourth sheet 54  (3)

Specifically, the first sheet51, the second sheet52, the third sheet53, and the fourth sheet54containing the magnetic particles are prepared in the above-described formulation to adjust the relative magnetic permeability of the first sheet51, the second sheet52, the third sheet53, and the fourth sheet54.

The first sheet51, the second sheet52, the third sheet53, and the fourth sheet54are magnetic sheets for forming the first layer10, the second layer20, the third layer30, and the fourth layer40, respectively. Each sheet described above is formed from the above-described magnetic composition into a plate shape extending in the plane direction.

One of the first sheets51may be a single layer, or may consist of a plurality, of layers (two or more layers) in accordance with the application and purpose (ref: phantom line ofFIG.2). The same is applied to the other first sheet51, and furthermore, each of the second sheets52, each of the third sheets53, and each of the fourth sheets54.

Then, the first sheet51, the second sheet52, the third sheet53, and the fourth sheet54are disposed in this order at each of both sides in the thickness direction of the wire2. Specifically, the two first sheets51are disposed so as to sandwich the wire2therebetween. The second sheet52, the third sheet53, and the fourth sheet54are disposed in this order so as to move away from the wire2with respect to the first sheet51.

Specifically, the fourth sheet54, the third sheet53, the second sheet52, the first sheet51, the wire2, the first sheet51, the second sheet52, the third sheet53, and the fourth sheet54are disposed in order toward one side in the thickness direction.

Subsequently, for example, they are thermally pressed. In the thermal pressing, for example, a flat plate press is used.

Thus, as shown inFIG.1, the first sheet51, the second sheet52, the third sheet53, and the fourth sheet54are deformed to form the first layer10, the second layer20, the third layer30, and the fourth layer40, respectively.

Specifically, for example, the first sheet51is deformed from the plate shape into a shape having the one-side first arc portion15and the other-side first arc portion16and embedding the wire2, and thus, the first layer10is formed.

The second sheet52is deformed from the plate shape into a shape having the one-side second arc portion27and the other-side second arc portion25and following the one surface11and the other surface12of the first layer10, and thus, the second layer10is formed.

Further, the third layer30and the fourth layer40are formed from the third sheet53and the fourth sheet54, respectively.

When the magnetic composition contains a thermosetting component, the magnetic composition is thermally cured by heating at the same time as or after the thermal pressing.

Thus, the inductor1including the wire2and the magnetic layer3, and in which in the first layer10, the second layer20, the third layer30, and the fourth layer40of the magnetic layer3, in the two layers adjacent to each other, the relative magnetic permeability of the layer closer to the wire2is lower than that of the layer farther from the wire2is produced.

Then, the inductor1includes the magnetic layer3which has the first laser10, the second layer20, the third layer30, and the fourth layer40having the above-described relative magnetic permeability.

This is supposedly because the closer it is to the wire2, the lower the relative magnetic permeability is, and the magnetic saturation is less likely to occur.

Further, in the inductor1, since the first layer10includes the extending portion17, the absolute amount of the magnetic particles (filler) contributing to the improvement of the DC superposition characteristics is increased, and therefore, the DC superposition characteristics are improved.

In the modified examples, the same reference numerals are provided for members and steps corresponding to each of those in one embodiment, and their detailed description is omitted. Also, the modified examples can achieve the same function and effect as that of one embodiment unless otherwise specified. Furthermore, one embodiment and the modified examples thereof can be appropriately used in combination.

In the above-described one embodiment, as shown inFIG.1, the magnetic layer3includes the first layer10to the fourth laser40. However, the magnetic layer3is not particularly limited as long as it has the n-th layer (n is a positive number of 3 or more), and, for example, though not shown, the magnetic layer3may also include the first layer10to the third layer30(embodiment in which n is 3) without including the fourth layer40. Further, the magnetic layer3may also include the first layer10to the fifth layer (embodiment in which n is 5).

Further, in the above-described one embodiment, as shown inFIG.1, the wire2has a generally circular shape in a cross-sectional view. However, the shape thereof in a cross-sectional view is not particularly limited, and though not shown, examples of the shape thereof may also include a generally rectangular shape in a cross-sectional view and a generally elliptical shape in a cross-sectional view.

In one embodiment, the extending portion17extends from the circumferential surface of the wire2to reach the end surface in the first direction of the inductor1. Alternatively, for example, though not shown, the extending portion17can also extend to an intermediate portion between the circumferential surface of the wire2and the end surface in the first direction of the inductor1without reaching the end surface in the first direction of the inductor1from the circumferential surface of the wire2.

In one embodiment, the extending portion17is provided in the first layer10. Alternatively, it can be also provided in any layer in the magnetic layer3, and for example, as shown inFIG.7, it can be provided in the second layer20.

As shown inFIG.7, the first layer10has a generally circular ring shape in a cross-sectional view. The first layer10has the inner peripheral surface13, and an outer peripheral surface14located outwardly in the radial direction with respect to the inner peripheral surface13.

The second layer10has the one-side second are portion27, the other-side second arc portion28, and the extending portion17.

As shown inFIG.8, each of the second layer20, the third layer30, and the fourth layer440may consist of one layer.

The second layer20is disposed on the one surface11of the first layer10. The second layer20has the other surface24in contact with the one surface11of the first layer10, and the one surface23facing the other surface24.

The third layer30is disposed on the one surface23of the second layer20. The third layer30has the other surface34in contact with the one surface23of the second layer20, and the one surface33facing the other surface34.

The fourth layer40is disposed on the one surface33of the third layer30. The fourth layer40has the other surface44in contact with the one surface33of the third laver30, and the one surface43facing the other surface44.

Further, the third layer30may have a generally arc shape in a cross-sectional view.

Then, by appropriately changing the kind, the shape, and the volume ratio of the magnetic particles of each layer in the magnetic layer3, in the first layer10, the second layer20, the third layer30, and the fourth laser40, the relative magnetic permeabilities of the layer closer to the wire2is set lower than that of the layer farther from the wire2.

In the following, in the first to second embodiments, a specific embodiment in which by changing the kind, the shape, the volume ratio, and the like of the magnetic particles of each layer in the magnetic layer3, the relative magnetic permeability of the layer closer to the wire2is set lower than that of the layer farther from the wire2is described with reference toFIGS.3to6.

InFIGS.1to2, the magnetic particles are not drawn, and inFIGS.3to6, the magnetic particles are drawn for easy understanding of the shape of the magnetic particles and the orientation of the second magnetic particles. However, inFIGS.3to6, the shape, the orientation, and the like of the magnetic particles are exaggeratedly drawn.

The inductor1of the first embodiment is described with reference toFIGS.3to4.

As shown inFIG.3, in the inductor1of the first embodiment, the first layer10contains first magnetic particles61having a generally spherical shape, and the second laser20, the third layer30, and the fourth layer40contain second magnetic particles62having a generally flat shape.

The first magnetic particles61are not orientated, and are uniformly (isotropically) dispersed in the first layer10. An average particle size of the first magnetic particles61is, for example, 0.1 μm or more, preferably 0.5 μm or more, and for example, 100 μm or less, preferably 50 μm or less. As a magnetic material for the first magnetic particles61, preferably, an iron powder in which an organic iron compound is thermally decomposed is used, more preferably, a carbonyl iron powder (relative magnetic permeability at 10 MHz: for example, 1.1 or more, preferably 3 or more, and for example, 25 or less, preferably 20 or less) is used.

Since the first layer10contains the first magnetic particles61having a generally spherical shape, the relative magnetic permeability thereof can be reliably set lower than that of the second layer20containing the second magnetic particles62having a generally flat shape to be described later. Further, in the case of the first magnetic particles61having a generally spherical shape, the inductor1has excellent inductance. Furthermore, in the case of the first magnetic particles61having a generally spherical shape, it is possible to suppress the magnetic saturation.

The second magnetic particles62are orientated in a direction along each layer in each of the second layer20, the third layer30, and the fourth layer40.

Specifically, the second magnetic particles62are orientated in the circumferential direction of the wire2in the one-side second arc portion27and the other-side second arc portion28of the second layer20. A case where an angle formed by the plane direction of the second magnetic particles62and a tangent in contact with the circumferential surface of the wire2facing the inner side in the radial direction of the second magnetic particles62is 15 degrees or less is defined that the second magnetic particles62are orientated in the circumferential direction.

The second magnetic particles62are orientated along the plane direction in the third layer30and the fourth layer40.

An average value of the maximum length of the second magnetic particles62is, for example, 3.5 μm or more, preferably 10 μm or more, and for example, 200 μm or less, preferably 150 μm or less.

As a material for the second magnetic particles62, preferably, a Fe—Si alloy (relative magnetic permeability at 10 MHz 25 or more) is used.

For example, when the kind of the second magnetic particles62of the second layer20, the third layer30, and the fourth layer40is the same, a volume ratio of the second magnetic particles62of the second layer20, the third layer30, and the fourth layer40is adjusted. In this case, the volume ratio of the second magnetic particles62in the layer closer to the wire2is set lower than that of the second magnetic particles62in the layer farther from the wire2.

In addition, when the volume ratio of the second magnetic particles62of the second layer20, the third layer30, and the fourth layer40is generally the same, the kind of the second magnetic particles62of the second layer20, the third layer30, and the fourth layer40is changed. In this case, the kind of the second magnetic particles62is selected so that the relative magnetic permeability of the second magnetic particles62in the layer closer to the wire2is set lower than that of the second magnetic particles62in the layer farther from the wire2.

It is also possible to change both the volume ratio and the relative magnetic permeability of the second magnetic particles62.

To produce the inductor1, as shown inFIG.4, the first sheet51containing the first magnetic particles61, and the second sheet52, the third sheet53, and the fourth sheet54containing the second magnetic particles62having the same or different relative magnetic permeability at the same or different volume ratio are prepared. The second magnetic particles62are orientated in the plane direction in each of the second sheet52, the third sheet53, and the fourth sheet54.

Then, in the inductor1, the first layer10contains the first magnetic particles61in a generally spherical shape, and the second layer20, the third layer30, and the fourth layer40have the second magnetic particles62in a generally flat shape.

Then, the second magnetic particles62can be orientated in the circumferential direction in the one-side second arc portion27and the other-side second arc portion28of the second layer20, while the first magnetic particles61are isotropically disposed in the first layer10. Therefore, the inductor1has both excellent DC superposition characteristics and high inductance.

Further, since the second magnetic particles62in a generally flat shape contained in the second layer20are orientated in the outer peripheral surface of the wire2, the inductor1has excellent inductance.

The inductor1of the second embodiment is described with reference toFIGS.5to6.

As shown inFIG.5, in the inductor1of the second embodiment, any of the first layer10, the second layer20, the third layer30, and the fourth layer40contain the second magnetic particles62in a generally flat shape. The second magnetic particles62have a generally flat shape. The second magnetic particles62are orientated in a direction along each layer in each of the first layer10, the second layer20, the third layer30, and the +40.

Specifically, the second magnetic particles62are orientated in the circumferential direction of the wire2in the one-side first arc portion15and the other-side first arc portion16of the first layer10, while being orientated in the plane direction in the extending portion17. Further, the second magnetic particles62are orientated in the circumferential direction of the wire2in the one-side second arc portion27and the other-side second arc portion28. Meanwhile, the second magnetic particles62are orientated in the plane direction in the third layer30and the fourth layer40.

For example, when the kind of the second magnetic particles62of the first layer10, the second layer20, the third layer30, and the fourth layer40is the same, the volume ratio of the second magnetic particles62of the first layer10, the second layer20, the third layer30, and the fourth layer4) is adjusted. In this case, the volume ratio of the second magnetic particles62in the layer closer to the wire2is set lower than that of the second magnetic particles62in the layer farther from the wire2. Specifically, a ratio of the volume ratio of the second magnetic particles62in the first layer10to that of the second magnetic particles62in the second layer20is, for example, below 1, preferably (9 or less, more preferably 0.8 or less, and for example, 0.5 or more, further 0.6 or more. The volume ratio of the second magnetic particles62of the third layer30and the fourth layer40is also the same as the description above.

In addition, when the volume ratio of the second magnetic particles62in the first layer10, the second layer20, the third layer30, and the fourth layer40is generally the same, the kind of the second magnetic particles62of the first layer10, the second layer20, the third layer30, and the fourth layer40are changed. In this case, the kind of the second magnetic particles62is selected so that the relative magnetic permeability of the second magnetic particles62in the laser closer to the wire2is lower than that of the second magnetic particles62in the layer farther from the w ire2.

Also, it is possible to employ both a method of changing the volume ratio of the second magnetic particles62, and a method of changing the relative magnetic permeability of the second magnetic particles62.

From the viewpoint of a wider width of adjustment of the relative magnetic permeability of the first layer10to the fourth layer40, preferably, a method of changing the relative magnetic permeability of the second magnetic particles62is employed as compared with a method of changing the volume ratio of the second magnetic particles62.

On the other hand, from the viewpoint of ensuring excellent productivity, preferably, a method of changing the volume ratio of the second magnetic particles62is employed as compared with a method of changing the relative magnetic permeability of the second magnetic particles62.

Further, of the first embodiment and the second embodiment, preferably, the first embodiment is used. In the first embodiment, the relative magnetic permeability of the first layer10can be reliably and easily lowered than that of the second layer20as compared with the second embodiment.

To produce the inductor1of the second embodiment, as shown inFIG.6, the first sheet51, the second sheet52, the third sheet53, and the fourth sheet54containing the second magnetic particles62having the same or different relative magnetic permeability at the same or different volume ratio are prepared. The second magnetic particles62are orientated in the plane direction in each of the first sheet51, the second sheet52, the third sheet53, and the fourth sheet54.

Thereafter, the wire2, and the first sheet51to the fourth sheet54described above are thermally pressed.

Although not shown, all of the first layer10to the fourth layer40may also contain, for example, isotropic magnetic particles, specifically, the first magnetic particles61in a generally spherical shape.

EXAMPLES

Next, the present invention is further described based on Examples and Comparative Example below. The present invention is however not limited by these Examples and Comparative Example. The specific numerical values in mixing ratio (content ratio), property value, and parameter used in the following description can be replaced with upper limit values (numerical values defined as “or less” or “below”) or lower limit values (numerical values defined as “or more” or “above”) of corresponding numerical values in mixing ratio (content ratio), property value, and parameter described in the above-described “DESCRIPTION OF EMBODIMENTS”.

Preparation Example 1

A binder was prepared in accordance with the formulation described in Table 1.

<Production Example of Inductor Based on First Embodiment>

First, the wire2having a radius of 130 μm was prepared. A radius of the conducting line4was 115 μm, and a thickness of the insulating film5was 15 μm.

The first sheet51, the second sheet52, the third sheet53, and the fourth sheet54were fabricated so as to have the kind and the filling ratio of the magnetic particles described in Table 2.

As the first sheet51, four sheets having a thickness of 60 μm were prepared. As the second sheet52, eight sheets having a thickness of 130 μm were prepared. As the third sheet53, eight sheets having a thickness of 60 μm w ere prepared. As the fourth sheet54, four sheets having a thickness of 100 μm were prepared.

Then, the two fourth sheets54, the four third sheets53, the four second sheets52, the two first sheets51, the wire2, the two first sheets51, the four second sheets52, the four third sheets53, and the two fourth sheets54were disposed in order toward one side in the thickness direction.

Subsequently, they were thermally pressed using a flat plate press, thereby forming the magnetic layer3.

Thus, the inductor1including the wire2, and the magnetic layer3embedding the wire2was produced A thickness of the inductor1was 975 μm.

Example 2 to Comparative Example 1

The inductor1was produced in the same manner as in Example 1, except that the formulation of the magnetic sheet was changed in accordance with Tables 3 to 6.

The inductor1of Example 2 corresponded to the second embodiment (specifically, the embodiment of changing the kind of the magnetic particles of each layer in the magnetic layer).

Further, the inductor1of Example 3 corresponded to the second embodiment (specifically, the embodiment of changing the content ratio (filling ratio) of the magnetic particles of each layer in the magnetic layer).

Further, the inductor1of Example 4 is the second embodiment, and the embodiment of changing both the kind and the content ratio (filling ratio) of the magnetic particles of each layer in the magnetic layer.

The following items are evaluated, and the results are described in Tables 2 to 7.

The relative magnetic permeability of each of the first sheets51of Example 1 to Comparative Example 1, each of the second sheets52of Examples 1 to 4, each of the third sheets53of Examples 1 to 4, and each of the fourth sheets54of Examples 1 and 3 was measured with an impedance analyzer (manufactured by Agilent Technologies Japan, Ltd.: “4291B”) using a magnetic material test fixture.

The DC superimposition characteristics were evaluated by measuring a reduction ratio of inductance by flowing an electric current of 10 A to the conducting line4of the inductor1of Example 1 to Comparative Example 1 using an impedance analyzer (manufactured by Kuwaki Electronics, Co., Ltd., “65120B”) installed with a DC bias test fixture and a DC bias power supply.

The reduction ratio of inductance was calculated based on the following formula.
[Inductance in a state where no DC bias current is applied−Inductance in a state where DC
bias current is applied]/[Inductance in a state where DC bias current is applied]×100(%)

TABLE 7Ex. 1Ex. 2Ex. 3Ex. 4Comparative Ex. 1EmbodimentFirstSecond*ASecond*BThird*D—Thickness975675930805497RelativeFirst Sheet7.927.77012.5140.0MagneticSecond Sheet27.766.693.343.4PermeabilityThird Sheet66.6101.6116.754.1Fourth Sheet101.6—140—DCReduction18.035.556.619.478.5SuperpositionRatio*CofCharacteristicsInductance (%)*AChange of kind (relative magnetic permeability) of magnetic particles in first sheet to nth sheet*BChange of filling ratio of magnetic particles in first sheet to nth sheet*C⁢Reduction⁢⁢ratio⁢⁢of⁢⁢⁢inductance=(Inductance⁢⁢in⁢⁢a⁢⁢state⁢⁢where⁢⁢no⁢⁢DC⁢⁢bias⁢⁢current⁢⁢is⁢⁢applied)-(Inductance⁢⁢in⁢⁢a⁢⁢state⁢⁢where⁢⁢DC⁢⁢bias⁢⁢current⁢⁢is⁢⁢applied)(Inductance⁢⁢in⁢⁢a⁢⁢state⁢⁢where⁢⁢DC⁢⁢bias⁢⁢current⁢⁢is⁢⁢applied)*DChange of kind and filling ratio of magnetic particles in first sheet to nth sheet

INDUSTRIAL APPLICABILITY

The inductor of the present invention is loaded on an electronic device and the like.

DESCRIPTION OF REFERENCE NUMERALS