Inductor and method for manufacturing the same

Abstract

To provide an inductor capable of suppressing cracks that occur in a core.SOLUTION: An inductor 10 includes a core 12 in which a planarly extending coil conductor 11 is embedded. The coil conductor 11 has a horizontally flat elliptical cross-sectional shape perpendicular to the plane extending direction. The core 12 has a magnetic metal body with a filling rate of 80 volume% or more and less than 100 volume%. The magnetic metal body bites into a portion of the total length of 75% or more and 100% or less of the circumference of the elliptical outer circumference in the cross-sectional shape of the coil conductor 11.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inductor and a method for manufacturing the same.

Background Art

[0002] A conventional general inductor is composed of a coil formed by winding a wire made of an electrically conductive material around a core made of a ferromagnetic material or a ferrimagnetic material. In recent years, in order to be suitably used in a power supply circuit of a computer operating in a high-frequency region, an inductor provided with a compacted magnetic core in which a coil conductor is embedded in a magnetic metal powder having a high saturation magnetic flux density in a high-frequency current has been proposed (see, for example, Patent Document 1).

[0003] Note that Patent Document 2 discloses a technique for obtaining a core in which magnetic metal powder is highly filled by pressure molding until the magnetic metal powder bites into the surface of the coil conductor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the techniques disclosed in Patent Documents 1 and 2 above, the coil conductor is a flat wire having a rectangular cross section, and there is a problem that cracks are likely to occur in the core starting from the corners of the coil conductor during pressure molding. In addition, in the technique disclosed in Patent Document 2, although the internal strain of the magnetic metal powder is removed by heating after pressure molding, it is difficult to eliminate the cracks.

[0006] In view of the above points, an object of the present invention is to provide an inductor capable of suppressing cracks generated in a core and a method for manufacturing the same.

Means for Solving the Problems

[0007] The inductor of the present invention is an inductor including a core in which a coil conductor extending on a plane is embedded, wherein the cross-sectional shape of the coil conductor perpendicular to the extending direction is an ellipse having a major axis on the plane, the core has a magnetic metal body with a filling rate of 80% by volume or more and less than 100% by volume, and the magnetic metal body bites into a portion of the circumference of the outer periphery of the ellipse in the cross-sectional shape of the coil conductor having a length of 75% or more and 100% or less of the total.

[0008] According to the inductor of the present invention, since the cross-sectional shape of the coil conductor is an ellipse and there are no corners, it is possible to suppress the generation of cracks that are likely to occur in the core starting from the corners. Also, the filling rate of the magnetic metal body in the core is as high as 80% by volume or more, making it possible to obtain an inductor with a high inductance. Furthermore, since the magnetic metal body bites into a portion of the circumference of the outer periphery of the ellipse in the cross-sectional shape of the coil conductor having a length of 75% or more and 100% or less of the total, the adhesion between the coil conductor and the core is high.

[0009] Note that since the cross-sectional shape of the coil conductor may have a magnetic metal body biting into it from its outer periphery, it is not a strict ellipse, and furthermore, it does not have to be line-symmetric in the horizontal direction and the vertical direction, etc. The ellipse defining the outer circumference is the most approximate ellipse obtained using the least squares method after considering the actual cross-sectional shape of the coil conductor as a set of a large number of points. As the least squares method, for example, a linear least squares method, a multivariate linear least squares method, or a multivariate non-linear least squares method may be used. And the length of the portion where the magnetic metal body bites in refers to the length of the outer periphery of the portion where the magnetic metal body exists on or inside the outer periphery of this approximated ellipse.

[0010] In the inductor of the present invention, it is preferable that the magnetic metal body is made of powdered Fe-based amorphous.

[0011] In this case, when the core is formed by pressure molding, by heating at a temperature exceeding the softening temperature of the Fe-based amorphous during pressure molding, the Fe-based amorphous softens and the deformation of the coil conductor becomes easy, so that it is possible to further suppress the occurrence of cracks in the core.

[0012] Further, in the inductor of the present invention, it is preferable that the surface roughness Rz of the actual outer periphery in the cross-sectional shape of the coil conductor is 5 μm or more and 40 μm or less.

[0013] In this case, if the surface roughness Rz of the actual outer periphery in the cross-sectional shape of the coil conductor exceeds 40 μm, the DC resistance increases, and if it is less than 5 μm, there is a problem that the deformation becomes insufficient. The actual outer periphery in the cross-sectional shape of the coil conductor is the actual outer periphery of the cross-sectional shape of the coil conductor, and is not the approximated elliptical outer periphery as described above. The surface roughness Rz of the actual outer periphery may be calculated as the ten-point average roughness by using a roughness curve indicating the deviation in the vertical direction with respect to the average line with the approximated elliptical outer periphery as the average line.

[0014] Further, in the inductor of the present invention, it is preferable that the total length of the actual outer periphery in the cross-sectional shape of the coil conductor is 1.1 times or more and 2.5 times or less the total length of the elliptical outer periphery.

[0015] In this case, if the total length of the actual outer periphery in the cross-sectional shape of the coil conductor is less than 1.1 times the total length of the elliptical outer periphery, the deformation becomes insufficient, and if it exceeds 2.5 times, there is a problem that the DC resistance increases.

[0016] Further, in the inductor of the present invention, an insulator may be present on the elliptical outer periphery in the cross-sectional shape of the coil conductor with a thickness equal to or less than the average particle diameter of the magnetic metal body. Note that the magnetic sex money The thickness may be equal to or less than the average particle diameter of the metal body. sex moneyThe average particle size of the matrix may be the median diameter D50 at which the cumulative particle size frequency is 50%.

[0017] In this case, the adhesion between the coil conductor and the core by the insulator is maintained to some extent. Note that this insulator is, for example, a remaining insulator film that coated the surface of the coil conductor when the core was formed by hot press molding.

[0018] Also, in the inductor of the present invention, the ellipse in the cross-sectional shape in the vertical direction perpendicular to the extending direction of the coil conductor preferably has a major axis that is 1.3 times or more and 2.0 times or less the minor axis.

[0019] In this case, when the core is formed by pressure molding while applying pressure in the vertical direction with a coil conductor made of round wire embedded, the core can be sufficiently pressurized and cracks generated in the core can be suppressed.

[0020] The filling rate of the magnetic metal body in the core located in the horizontal direction of the coil conductor is preferably 0.8 times or more and 1.0 times or less the filling rate of the magnetic metal body in the core located in the vertical direction of the coil conductor.

[0021] In this case, when the core is formed by pressure molding while applying pressure in the vertical direction with the coil conductor embedded, the core is uniformly pressurized.

[0022] The method for manufacturing the inductor of the present invention includes a step of filling a raw material powder containing a magnetic metal powder and a binder into a mold in a state where a coil conductor extending on a plane is embedded so that the plane is horizontal, and a step of pressurizing the mold filled with the raw material powder in the vertical direction while heating, and deforming the coil conductor so that the cross-sectional shape perpendicular to the extending direction has an ellipse having a major axis on the plane.

[0023] According to the method for manufacturing an inductor of the present invention, since the cross-sectional shape of the coil conductor is deformed from circular to elliptical and there are no corners, it is possible to suppress the generation of cracks that are likely to occur in the core starting from the corners.

[0024] In the method for manufacturing an inductor of the present invention, it is preferable that the magnetic metal powder is made of Fe-based amorphous and the heating temperature in the heating exceeds the softening temperature of the Fe-based amorphous.

[0025] In this case, the Fe-based amorphous softens by heating, making it easier to deform the coil conductor, so it is possible to further suppress the occurrence of cracks in the core.

[0026] Also, in the method for manufacturing an inductor of the present invention, it is preferable that an insulator film is coated on the surface of the coil conductor and the heating temperature in the heating exceeds the heat resistance temperature of the insulator film.

[0027] In this case, since all or most of the insulator film disappears by heating, it is possible to improve the adhesion between the coil conductor and the core.

Brief Description of the Drawings

[0028] [Figure 1] Cross-sectional explanatory view showing a method for manufacturing an inductor according to an embodiment of the present invention. [Diagram 2] Explanatory cross-sectional view showing an inductor according to an embodiment of the present invention. [Diagram 3] Explanatory cross-sectional view schematically showing an enlarged view of the periphery of the coil conductor in FIG. 2. [Figure 4] Cross-sectional photograph views of inductors in Examples 1 to 3. [Diagram 5] Cross-sectional photograph views of inductors in Examples 4 and 5. [Figure 6] Cross-sectional photograph views of inductors in Comparative Examples 1 to 3.

Modes for Carrying Out the Invention

[0029] A method for manufacturing an inductor according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. This manufacturing method is a method for manufacturing an inductor 10 according to an embodiment of the present invention described later, and mainly includes a preparation step of filling a raw material powder 2 in which a coil conductor 1 is embedded into a mold 3, and a hot press forming step of performing hot press (hot press) forming using this mold 3. Note that FIGS. 1 to 3 are diagrams for schematically explaining the embodiment, and the dimensions are deformed.

[0030] In the preparation step, first, a raw material powder 2 for forming a core 12 is prepared. The raw material powder 2 is, for example, a granulated powder produced by mixing a magnetic metal powder, a binder, and the like.

[0031] The magnetic metal powder is, for example, an Fe-based soft magnetic metal powder, and is a metal powder made of an Fe-based soft magnetic material containing at least one selected from Fe, Fe-Si-based, Fe-Ni-based, Fe-Ni-Mo-based, Fe-Si-Al-based, Fe-Si-Cr-based, Fe-based amorphous, Fe-based soft magnetic nanocrystals, and the like. When the magnetic metal powder contains two or more of these materials, the ratio thereof is not limited.

[0032] Fe-based amorphous is amorphous without a crystal structure. Since the softening temperature of Fe-based amorphous is equal to or lower than the heating temperature in the hot press forming step and it softens during hot press forming without inhibiting the deformation of the coil conductor 1, it is particularly preferable as the magnetic metal powder.

[0033] The magnetic metal powder has, for example, a particle size of 1 μm or more and 100 μm or less, and more preferably 1 μm or more and 50 μm or less. The particle size distribution of the magnetic metal powder may have one peak or a plurality of peaks. In particular, when the magnetic metal powder is an Fe-based amorphous powder, it softens by heating during hot press forming, and it is not necessarily necessary to improve the filling rate of the magnetic metal powder by making the number of peaks in the particle size distribution plural.

[0034] The binder is preferably a thermosetting resin, and the type of the resin may be appropriately selected according to the use of the inductor 10 and the like. The resin used as the binder is, for example, an epoxy resin, a phenol resin, a silicone resin, a melamine resin, a polyurethane resin, a polyimide resin, an alkyd resin, an unsaturated polyester resin, etc., but is not limited thereto.

[0035] The addition amount of the binder to the magnetic metal powder is preferably 10% by weight or less, more preferably 0.4% by weight or more and 5% by weight or less. Further, the raw material powder 2 may contain a dispersant, a lubricant, an auxiliary agent, etc. in order to impart arbitrary functionality within a range not impairing the effects of the present invention.

[0036] Then, the raw material powder 2 is filled into a highly heat-resistant mold 3 having a shape following the outer shape of the core 12 up to a predetermined height, and the upper surface is leveled.

[0037] Next, the coil conductor 1 is placed on the raw material powder 2 whose upper surface has been leveled.

[0038] The coil conductor 1 is a conductor constituting the coil of the inductor 10. For example, it is made of a metal conductor, but it is particularly preferably made of copper or a copper alloy so as to be easily deformed in the hot press molding process.

[0039] The coil conductor 1 is composed of a single round wire having a circular cross-section (hereinafter referred to as a vertical cross-section) perpendicular to the extending direction. And the coil conductor 1 is bent and extended on a plane so that this round wire has an arbitrary single-stroke shape such as a zigzag shape, a wave shape, an S shape, a Z shape, an N shape, an arc shape, a spiral shape, etc. That is, the coil conductor 1 is a planar coil whose center line is located on a predetermined plane. The coil conductor extending on the plane is embedded in the raw material powder 2 so that its plane becomes horizontal. Although not shown, connection portions to the outside such as lead frames are provided at both ends of the coil conductor 1.

[0040] The diameter of the vertical cross-section of the coil conductor 1 is, for example, 0.3 mm or more and 3 mm or less, more preferably 0.5 mm or more and 2 mm or less. However, the vertical cross-section of the coil conductor 1 is not necessarily limited to a perfect circular shape, and may be a flattened shape, such as an elliptical shape.

[0041] And, in order to prevent surface oxidation until reaching the hot press forming process described later, the coil conductor 1 is preferably coated on the surface with an insulator film 4. The insulator film 4 is made of an insulating resin having a heat resistance temperature equal to or lower than the heating temperature in the hot press forming process, for example, 500 °C or lower, more preferably 300 °C or lower, such as polyurethane or polyamideimide. The thickness of the insulator film 4 may be determined such that all or most of the insulator film 4 disappears in the hot press forming process. Although it varies depending on the material, for example, it is 30 μm or less, more preferably 15 μm or less.

[0042] Next, the raw material powder 2 is also added onto the coil conductor 1, and the inside of the mold 3 is filled with the raw material powder 2. As a result, the coil conductor 1 is embedded in the raw material powder 2. However, the connection portions at both ends of the coil conductor 1 are exposed from the raw material powder 2.

[0043] Next, for example, a hot press forming process is performed in which pressure is applied while heating at a heating temperature of 200 °C or more and 550 °C or less, more preferably 400 °C or more and 500 °C or less, a heating time of 30 seconds or more and 15 minutes or less, more preferably 30 seconds or more and 5 minutes or less, and a pressure of 4 t / cm 2 or more and 15 t / cm 2 or less, more preferably 6 t / cm 2 or more and 10 t / cm 2 or less. The pressing direction is the vertical direction.

[0044] It is preferable to apply pressure simultaneously in both the upper and lower directions using an upper punch and a lower punch. However, pressure may be applied in either the upward or downward direction, or a time difference may be provided between the upward and downward pressure applications. It should be noted that during pressing, it is preferable to heat with a heater (not shown) provided in the press.

[0045] As a result, the inductor 10 according to the embodiment of the present invention is obtained. As will be described below, in the inductor 10, a core 12 including a powdered magnetic metal body is formed by hot press molding, and the coil conductor 1 is deformed such that the cross-sectional shape in the vertical direction becomes an ellipse to form a coil conductor 11. Further, a powdered magnetic metal body bites into at least a part of the surface of the coil conductor 11, and the coil conductor 11 and the core 12 are in close contact with each other with almost no gap therebetween.

[0046] Hereinafter, the inductor 10 according to the embodiment of the present invention will be described. This inductor 10 is a 1T inductor in which the number of turns of the coil conductor 1 is 1.

[0047] In the inductor 10, a coil conductor 11 having an elliptical cross-section in the vertical direction is embedded in a core 12, and the filling rate of the magnetic metal body is 80% by volume or more and less than 100% by volume, resulting in a high inductance.

[0048] Furthermore, referring to FIGS. 3 to 5, in the inductor 10, a powdered magnetic metal body bites into a portion of the length of the outer circumference of the ellipse in the cross-sectional shape of the coil conductor 11 that is 75% or more and 100% or less of the total circumference, and the adhesion between the coil conductor 11 and the core 12 is high.

[0049] Note that the cross-sectional shape of the coil conductor 11 is not a strict ellipse such that a magnetic metal body bites into the outer circumference thereof, and furthermore, it does not have to be line-symmetric in the horizontal direction, the vertical direction, etc. Also, the ellipse defining the outer circumference is the most approximate ellipse obtained using the least squares method after regarding it as a set of a large number of points of the actual cross-sectional shape of the coil conductor 11. As the least squares method, for example, a linear least squares method, a multivariate linear least squares method, a multivariate non-linear least squares method, etc. may be used. And the length of the portion where the magnetic metal body bites in refers to the length of the outer circumference of the portion where the magnetic metal body exists on or inside the outer circumference of this approximated ellipse.

[0050] The filling ratio of the magnetic metal body in the core 12 is 80% by volume or more, preferably 90% by volume or more, in order to obtain a high inductance. The filling ratio of the magnetic metal body can be calculated based on the density obtained by actually measuring the partially cut-out core 12.

[0051] The powdery magnetic metal body that bites into the surface of the coil conductor 11 may be one in which the aforementioned magnetic metal powder remains in its original shape. The powdery magnetic metal body that bites into the surface of the coil conductor 11 has, for example, a particle size of 1 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less.

[0052] Also, the surface roughness Rz of the actual outer periphery in the cross-sectional shape of the coil conductor 11 is, for example, 5 μm or more and 40 μm or less, more preferably 5 μm or more and 30 μm or less. This is because if the surface roughness Rz of this actual outer periphery exceeds 40 μm, the DC resistance increases, and if it is less than 5 μm, there will be a problem that the deformation is insufficient. And the total length of the actual outer periphery in the cross-sectional shape of the coil conductor 11 is, for example, 1.1 times or more and 2.5 times or less the total length of the outer periphery of the elliptical shape.

[0053] Note that the actual outer periphery in the cross-sectional shape of the coil conductor 11 is the actual outer periphery of the cross-sectional shape of the coil conductor 11, and is not the approximated elliptical outer periphery as described above. And the surface roughness Rz of the actual outer periphery may be calculated as the ten-point average roughness using a roughness curve that shows the deviation in the vertical direction with respect to the average line when the approximated elliptical outer periphery is used as the average line.

[0054] The ratio of the major axis (width) w in the horizontal direction (the direction perpendicular to the pressing direction) to the minor axis (height) h of the approximated elliptical shape in the vertical direction (pressing direction) orthogonal to the extending direction of the coil conductor 11 is such that the major axis w is, for example, 1.3 or more and 2.0 or less with respect to the minor axis h of 1, and more preferably 1.5 or more and 1.8 or less. Thereby, an appropriate pressing force acts, the magnetic metal body is highly filled, and it becomes possible to obtain the inductor 10 with high inductance. Further, while the generation of a gap between the magnetic metal body and the coil conductor 11 is suppressed, the generation of cracks in the core 12 is suppressed.

[0055] Also, the ratio of the filling rates of the magnetic metal bodies present in the vertical and horizontal directions of the coil conductor 11 is such that the horizontal direction is, for example, 0.8 or more and 1.0 or less with respect to the vertical direction of 1, and more preferably 0.9 or more and 1.0 or less. Further, the difference between the upward and downward directions and the difference between one side and the other side in the horizontal direction are, for example, 10% or less, and more preferably 5% or less. Thereby, an appropriate pressing force acts, the magnetic metal body is highly filled uniformly, and it becomes possible to obtain the inductor 10 with high inductance. Also, the generation of a gap between the magnetic metal body and the coil conductor 11 is suppressed.

[0056] Note that an insulator film 4 may remain on the surface of the coil conductor 11. The remaining insulator film 4 may exist on the outer periphery of the cross-section of the coil conductor 11 with a thickness equal to or less than the average particle diameter of the powdered magnetic sex money body. Note that the average particle diameter of the magnetic sex money body may be the median diameter D50 at which the cumulative grain size frequency becomes 50%. Also, the remaining insulator film 4 is preferably 10 μm or less.

[0057] In this way, by performing hot press forming with the coil conductor 1 made of round wire embedded in the raw material powder 2, the vertical cross-section of the coil conductor 11 becomes approximately elliptical. Therefore, unlike the case where the coil conductor is made of rectangular wire as in the prior art, since there are no corners in the coil conductor 11, it becomes possible to suppress the generation of cracks that are likely to occur in the core 12 starting from the corners. Note that the coil conductor 1 before hot press forming does not necessarily have to be round wire, but in order to exhibit the effect of suppressing crack generation due to the deformation of the vertical cross-section from circular to elliptical, it is desirable that the conductor be round wire or a conductor with a cross-section close to circular before hot press forming.

[0058] Furthermore, since the coil conductor 1 has a circular vertical cross-section, it easily deforms into an elliptical shape flattened in the horizontal direction by being pressurized from the vertical direction. Also, due to this deformation, the magnetic metal powder also moves, so the filling rate of the magnetic metal body is improved.

[0059] For example, when the coil conductor 1 is rectangular wire as in the prior art, it is difficult to further deform it so as to extend in the horizontal direction, and even if it is deformed, there is a risk of cracks occurring in the core 12 due to springback.

[0060] Furthermore, when the magnetic metal powder is amorphous metal powder, if the heating temperature in the hot press process is higher than the softening temperature, the amorphous metal powder softens and does not prevent the deformation of the coil conductor 1, and the pressing force acts in the horizontal direction to uniformize the core 12, so it becomes possible to further suppress the generation of cracks.

[0061] Furthermore, by performing hot press forming at a heating temperature exceeding the heat resistance temperature of the insulating film 4 covering the surface of the coil conductor 1, it becomes possible to cause all or most of the insulating film 4 to disappear, and since the magnetic metal particles bite into the coil conductor 11, it becomes possible to improve the adhesion between the coil conductor 11 and the core 12.

[0062] Note that the present invention is not limited to the above-described, and can be appropriately changed. For example, although the coil conductor 11 has been described as extending in a horizontal plane, the plane in which the coil conductor 11 extends may be an inclined plane, a vertical plane, or the like.

Example

[0063] (Examples 1 to 5, Comparative Examples 1 to 3) As the raw material powder 2, an amorphous metal powder was used as the magnetic metal powder, and a granulated product using an epoxy resin as a binder was used. The addition amount of the binder with respect to the magnetic metal powder was 0.4% by weight. The first crystallization temperature of the magnetic metal powder was 400°C, and the second crystallization temperature was 500°C.

[0064] In Examples 1 to 5 and Comparative Examples 1 to 3, the coil conductor 1 was a straight bar having a length of 50 mm.

[0065] In Examples 1 to 5, a round wire made of copper and having a circular cross section was used as the coil conductor 1. The diameter of the cross section was 0.10 mm in Example 1, 0.37 mm in Example 2, 0.50 mm in Example 3, 0.17 mm in Example 4, and 0.26 mm in Example 5. And, on the surface of the coil conductor 1 in Examples 1 to 3, polyurethane having a heat resistance temperature of 130°C and a thickness of 12 μm was coated as the insulator film 4. Also, on the surface of the coil conductor 1 in Examples 4 and 5, polyamide-imide having a heat resistance temperature of 220°C and a thickness of 7 μm and 20 μm, respectively, was coated as the insulator film 4.

[0066] In Comparative Examples 1 to 3, a flat wire made of copper and having a rectangular cross section was used as the coil conductor 1. The height and width of the cross section were 0.1 mm in height and 1.0 mm in width in Comparative Example 1, 0.16 mm in height and 1.27 mm in width in Comparative Example 2, and 0.45 mm in height and 1.8 mm in width in Comparative Example 3. And, on the surface of the coil conductor 1 in Comparative Examples 1 to 3, polyamide-imide having a heat resistance temperature of 220°C and a thickness of 15 μm was coated as the insulator film 4.

[0067] The raw material powder 2 was filled into the mold 3 so that the coil conductor 1 extends horizontally at the center. Thus, the preparation process was completed.

[0068] Next, a hot press forming process was performed. As a result, an inductor 10 in which the coil conductor 11 is embedded in the core 12 was obtained. Then, the inductor 10 was cut so that the vertical plane was exposed, and the cut surface was observed with an electron microscope.

[0069] In Examples 1 to 3, as shown in FIG. 4, the vertical cross section of the coil conductor 11 is substantially elliptical, and the powdered magnetic metal body bites into the surface thereof, and it was found that the gap between the coil conductor 11 and the core 12 is small.

[0070] In Examples 4 and 5, as shown in FIG. 5, it was found that the vertical cross section of the coil conductor 11 is substantially elliptical and the powdered magnetic metal body bites into the surface thereof. However, in the micrograph at a magnification of 300 times, the insulator film 4 remained at the upper right part of the cross section of the coil conductor 11 in Example 4, and at the upper and left parts of the cross section of the coil conductor 11 in Example 5.

[0071] In Comparative Examples 1 to 3, as shown in FIG. 6, the vertical cross section of the coil conductor 11 is substantially oblong with a long left-right dimension, and it was found that there are more continuous gaps between the coil conductor 11 and the core 12 compared to Examples 1 to 5, and the adhesion is inferior. Also, in the micrograph at a magnification of 50 times, cracks occurred on the left side of the cross section of the coil conductor 11 in Comparative Example 2, and on the left and right sides of the cross section of the coil conductor 11 in Comparative Example 2.

Explanation of Reference Numerals

[0072] 1... Coil conductor, 2... Raw material powder, 3... Mold, 4... Insulator film, 10... Inductor, 11... Coil conductor, 12... Core.

Claims

1. An inductor comprising a core in which a coil conductor extending on a plane is embedded, wherein the cross-sectional shape of the coil conductor perpendicular to the extending direction has an elliptical shape having a major axis on the plane, the core has a magnetic metal body with a filling rate of 80% by volume or more and less than 100% by volume, the magnetic metal body bites into a portion of the length of the outer circumference of the ellipse in the cross-sectional shape of the coil conductor, which is 75% or more and 100% or less of the total circumference, an insulator exists on the outer circumference of the ellipse in the cross-sectional shape of the coil conductor with a thickness equal to or less than the average particle diameter of the magnetic metal body, and characterized in that it is an inductor.

2. The inductor according to claim 1, wherein the magnetic metal body is made of powdered Fe-based amorphous.

3. The inductor according to claim 1 or 2, wherein the surface roughness Rz of the actual outer circumference in the cross-sectional shape of the coil conductor is 5 μm or more and 40 μm or less.

4. The inductor according to any one of claims 1 to 3, wherein the total length of the actual outer circumference in the cross-sectional shape of the coil conductor is 1.1 times or more and 2.5 times or less of the total length of the outer circumference of the ellipse.

5. The inductor according to any one of claims 1 to 4, wherein the ellipse in the cross-sectional shape in the vertical direction perpendicular to the extending direction of the coil conductor has a major axis that is 1.3 times or more and 2.0 times or less of the minor axis.

6. The inductor according to any one of claims 1 to 5, wherein the filling rate of the magnetic metal body in the core located in the horizontal direction of the coil conductor is 0.8 times or more and 1.0 times or less of the filling rate of the magnetic metal body in the core located in the vertical direction of the coil conductor.

7. A step of filling a raw material powder containing magnetic metal powder and a binder into a mold in a state where a coil conductor extending on a plane is embedded so that the plane is horizontal, A method for manufacturing an inductor, comprising a step of vertically pressing the mold filled with the raw material powder while heating, and deforming the coil conductor so that the cross-sectional shape perpendicular to the extending direction has an elliptical shape having a major axis on the plane, wherein an insulator film is coated on the surface of the coil conductor, and the heating temperature in the heating exceeds the heat resistance temperature of the insulator film, and characterized in that it is a method for manufacturing an inductor.

8. The magnetic metal powder is made of Fe-based amorphous, The manufacturing method of the inductor according to claim 7, characterized in that the heating temperature in the heating exceeds the softening temperature of the Fe-based amorphous.

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