JP2003168610A - Inductance element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a coil becomes large in DC resistance because a magnetic substance is low in magnetic permeability in a conventional inductance element using metal magnetic powder, the inductance element increases in power loss when it is used for a DC/DC converter, and the DC/DC converter decreases in conversion efficiency. <P>SOLUTION: This inductance element is equipped with a coil 10 provided with a winding 11, an air core 12, and leads 13 and 14 led out from the ends of the winding 11, an insulating magnetic body 20 which is formed by molding first metal magnetic powder and a binding agent by pressure, a magnetic body 30 which is larger in magnetic permeability than the magnetic body 20 and formed by molding second metal magnetic powder and a winding agent by pressure, and a plurality of terminal electrodes 40 electrically connected to the leads 13 and 14 of the coil 10. The winding 11 of the coil 10 is buried in the magnetic body 20, and the magnetic body 30 is arranged in the air core 12. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC / DC integrated in a portable electronic device such as a notebook computer and a video camera.
The present invention relates to a surface mount type inductance element suitable as a circuit element such as a DC converter.

[0002]

2. Description of the Related Art An inductor is used in which a coil is embedded inside a dust core obtained by pressure-molding a metal magnetic powder to which a binder is added. This inductor has a structure in which the terminal electrode is in direct contact with the dust core, so that the insulating property of the magnetic metal powder is required. For this reason, the surface of the particles of the magnetic metal powder is subjected to a chemical insulation treatment, further coated with a bonding agent, and then the magnetic metal powder is pressure-molded.

[0003]

If the insulating coating of the particles of the magnetic metal powder is made thick in order to secure high insulation, the effective magnetic permeability will be significantly reduced. In order to secure a certain inductance by using the magnetic material having the reduced magnetic permeability, it is necessary to increase the number of turns of the coil. As a result, the DC resistance of the coil increases and DC / DC
When used in a converter or the like, there is a problem that the loss increases and the conversion efficiency decreases. Therefore, an object of the present invention is to increase the effective magnetic permeability while ensuring the insulation between terminals, reduce the DC resistance even with a high inductance, and improve the conversion efficiency.

[0004]

The inductance element of the present invention comprises at least one coil having a winding portion, an air-core portion, and lead portions led out from both ends of the winding portion, and a first metallic magnet. An insulative first magnetic body formed by pressure-molding powder and a bonding agent, and a second magnetic body formed by pressure-molding a second metal magnetic powder and a bonding agent and having a magnetic permeability larger than that of the first magnetic body. Magnetic body and a plurality of terminal electrodes which are electrically connected to the lead portion of the coil and exposed to the outside, and the winding portion of the coil is embedded inside the first magnetic body and the second magnetic body is formed in the air-core portion. It is characterized by the arrangement of.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention applied to a surface mount type inductor is shown in FIGS. The coil 10 has a cylindrical winding portion 11 in which a wire having a circular cross section is wound in multiple layers,
It has an air-core part 12 surrounded by a winding part 11 and lead parts 13 and 14 led out from both ends of the winding part 11, respectively. Coil 10
Is embedded in the magnetic body 20, and the columnar second magnetic body 30 is attached to the air-core portion 12 of the coil 10.

The pair of terminal electrodes 40, which are partially embedded in the magnetic body 20 and fixed, have the remaining portions exposed to the outside extending along the surface of the magnetic body 20 from the side surfaces to the bottom surface.
The lead portions 13 and 14 of the coil 10 are connected to different terminal electrodes 40 inside the magnetic body 20 by means such as welding.

The magnetic body 20 is made of metal magnetic powder such as iron or sendust or permalloy which is wrapped with a bonding agent made of a thermosetting resin or a thermoplastic resin.
After being pressure-molded at a pressure of about 2 tons, it is heated and cured at a temperature of about 140 ° C. The particles of the metal magnetic powder of the magnetic body 20 are subjected to an insulation treatment, and the magnetic body 20 is insulative. On the other hand, the second magnetic body arranged in the air core portion 12
30 is a mixture of a magnetic metal powder such as iron or sendust that is not insulation-coated and a bonding agent. The resistivity of the magnetic body 20 insulatively treated with the metal magnetic powder is 10 times or more the resistivity of the magnetic body 30 not insulated.

The metal magnetic powder of the second magnetic body 30 has a mean particle size larger than that of the metal magnetic powder of the magnetic body 20. Carbonyl iron powder having a small average particle size is suitable for the magnetic body 20. In order to increase the metal density of the magnetic body 30, it is desirable to use a soft metal magnetic powder that is largely deformed when pressed to the magnetic body 30. Further, as the magnetic body 30, it is also effective to magnetically orient in the axial direction and increase the magnetic permeability in the axial direction. In addition, the magnetic material 30
The magnetic permeability of is set to a value that is at least twice the magnetic permeability of the magnetic body 20. As a result, the magnetic permeability of the entire inductor is significantly improved as compared with the case where only the insulating magnetic body 20 is used for the magnetic body portion.

FIG. 7 shows the magnetic permeability of the second magnetic body with respect to the magnetic permeability of the first magnetic body in the inductor having the inductance value of 10 μH and the outer dimensions of 5 × 5 × 2 mm and having the structure of FIG.
This is an analysis of the degree of reduction of the coil DC resistance when the number of times is set to 3 times, 3 times or 4 times by the finite element method. FIG. 7 shows that the direct current resistance is significantly reduced by embedding the second magnetic substance having a high magnetic permeability, and that the present invention is effective in reducing the direct current resistance and improving the efficiency.

FIG. 3 shows another embodiment of the second magnetic body 30 arranged in the air-core portion 12 of the coil 10, and has a cross section T having an upper collar 31 for improving workability in assembly. It is a shape.

FIG. 4 shows another embodiment of the present invention.
A coil 50 made of a rectangular wire is used instead of the round wire. The coil 50 includes a winding portion 51 in which a rectangular wire is edgewise wound, an air core portion 52 surrounded by the winding portion 51, and lead portions 53 and 54 at both ends of the winding portion 51. Lead part 53, 54
Has a structure in which it is led out from the two side surfaces of the magnetic body 20 to serve as a terminal electrode as it is. The winding method of the rectangular wire is not limited to the edgewise winding, and may be a spiral shape.

As the coil, it is also possible to use a so-called outer-outer winding coil in which both ends are pulled out from the outermost circumference. FIG. 5 shows an example of the outer-outer wound coil, which is wound in opposite directions from the center of the wire.
It has a column structure. This coil 60 has a single rectangular wire continuously wound in two layers in upper and lower layers, and has lead portions at both ends.
63 and 64 are located on the outermost circumference.

When the coil is wound outside-outside, the lead portion at the beginning of winding does not overlap with the winding portion, which is effective for thinning the entire inductance element. 3 outer coil
It may have a multi-stage structure of more than one step, and may be formed by a round wire instead of the rectangular wire. Although the above embodiments have been described by taking the example of the inductor, the inductance element of the present invention may be configured as a transformer by providing a plurality of coils.

[0014]

According to the present invention, the effective magnetic permeability of the entire inductance element can be increased while ensuring the insulation between the terminal electrodes. As a result, the number of turns of the coil can be reduced and a thick and short wire can be used to reduce the DC resistance.
When used in a / DC converter or the like, it is possible to significantly reduce the loss.

[Brief description of drawings]

FIG. 1 is a front sectional view of an inductor showing a first embodiment of the present invention.

FIG. 2 is a perspective view of the inductor.

FIG. 3 is a front sectional view showing a second embodiment of the present invention.

FIG. 4 is a front sectional view showing a third embodiment of the present invention.

FIG. 5 is a plan view showing another embodiment of the coil.

6 is a sectional view taken along line AA of FIG.

FIG. 7 is a diagram showing an analysis result of DC resistance reduction by the finite element method.

[Explanation of symbols]

10 coils 11 winding part 12 Air core 20 First magnetic body 30 Second magnetic body

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Michiya Nakazawa             No. 18 Gomigaya, Tsurugashima City, Saitama Prefecture Toko             Saitama Office Co., Ltd. (72) Inventor Victor Chibahara             No. 18 Gomigaya, Tsurugashima City, Saitama Prefecture Toko             Saitama Office Co., Ltd. F-term (reference) 5E041 AA20 CA10

Claims (8)

[Claims] 1. At least one coil having a winding part, an air-core part, and lead parts led out from both ends of the winding part, a first metal magnetic powder and a bonding agent are pressure-molded. Conductive to the lead part of the coil, and the second magnetic body having a magnetic permeability higher than that of the first magnetic body, which is formed by press-molding the insulating first magnetic body, the second metal magnetic powder and the bonding agent. A plurality of terminal electrodes exposed to the outside, and
An inductance element characterized in that the second magnetic body is arranged in the air-core part while being embedded in the magnetic body. 2. The inductance element according to claim 1, wherein the average particle size of the second metal magnetic powder is larger than the average particle size of the first metal magnetic powder. 3. The inductance element according to claim 1, wherein the resistivity of the first magnetic body is higher than the resistivity of the second magnetic body. 4. The inductance element according to claim 1, wherein the first magnetic metal powder is carbonyl iron powder. 5. The inductance element according to claim 1, wherein the second magnetic body is magnetically oriented in the axial direction. 6. The coil winding is outer-outer winding.
Inductance element. 7. The inductance element according to claim 1, wherein the coil wire is a rectangular wire. 8. The inductance element according to claim 7, wherein a part of the lead portion of the coil also serves as a terminal electrode.