JPH04286305A - Inductor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an inductor having no magnetic gap and the like, high induction coefficient and improved reliability. CONSTITUTION:Magnetic bodies 6 and 11 have a first green compact 6, which is formed by pre-pressure molding magnetic powder containing a bonding agent, and a second green compact 11 which is formed by pre-pressure molding magnetic powder containing the above-mentioned bonding agent, and a coil 5 is integrally formed with the above-mentioned magnetic bodies 6 and 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductor used in electronic circuits and a method of manufacturing the same.

0002

2. Description of the Related Art As shown in FIG. 11, a conventional inductor has a winding bobbin 42 made of a magnetic material or a material other than magnetic material. The winding bobbin 42 is provided with a winding coil 45 around which an insulated electric wire is wound. Electrode terminals 4 are attached to both ends of the wire of the wound coil 45.
3 and 44 are connected. A magnetic core is placed in the winding bobbin 42, and then it is filled with magnetic powder-containing resin 41, etc., and the coil 45 is covered with the magnetic powder-containing resin 41 to prevent leakage of magnetic flux to the outside.

0003

[Problems to be Solved by the Invention] However, in the inductor, due to the joining of magnetic materials of the same or different types in the magnetic path of the generated magnetic flux Φ4, a magnetic gap is formed at the interface G4 of this joining portion. This magnetic gap causes the inductor to have a low induction coefficient, resulting in reduced reliability.

[0004] In order to increase the induction coefficient, the filling degree of the magnetic powder can be increased by lowering the resin ratio when mixing the magnetic powder and the resin, and then applying a large amount by pressure molding or other methods. The coil 45 must be covered with magnetic powder. At that time, it is necessary to increase the pressure of pressure molding. However, although the molding pressure was increased, the coil 45
Since the coil 45 is filled in magnetic powder that is easier to compress than the magnetic powder, the pressure borne by the coil 45 during pressurization increases. For this reason, the molding pressure of the magnetic powder itself cannot be effectively increased, and there is a problem that the coil 45 itself is crushed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a highly reliable inductor that is small in size and has large inductance and impedance, and a method for manufacturing the same.

[0006]

[Means for Solving the Problems] According to the present invention, in an inductor including a magnetic body, a coil attached to the magnetic body, and a terminal portion drawn out from the coil to the outside of the magnetic body, the magnetic body has a first green compact obtained by pressing and preforming a binder-containing magnetic powder, and a second compact by pressure-preforming the binder-containing magnetic powder or the binder-containing magnetic powder, The terminal portion and the coil are sandwiched between the magnetic body, and the coil is sealed within the magnetic body and is integrally formed with the magnetic body by pressure molding. An inductor is obtained. Further, according to the present invention, the coil is an air-core coil, and has terminal portions electrically connected to both ends of the air-core coil, and the binder is a thermosetting material that binds the magnetic powder. The inductor is made of resin, and the first green compact and the second green compact have the terminal portion and the coil sandwiched between the magnetic bodies, and are integrated. can get. Further, according to the present invention, the first compacted powder body is formed by pressurizing and preforming the binder-containing magnetic powder using a mold, the coil having a terminal portion is installed in the mold, and the coil setting the binder-containing magnetic powder or a second compact formed by press-preforming the binder-containing magnetic powder in a mold on the opposite side of the first compact, based on the first compact; A molding obtained by butting the second powder compact against the first powder compact, and performing main press molding of the first powder compact and the second powder compact together with the mold. demolding the body from the mold;
A method for manufacturing an inductor is obtained, which comprises subsequently subjecting the molded body to heat curing treatment.

[0007]

[Operation] The inductor constructed and manufactured by the above method has no magnetic gap and has a high induction coefficient because it has no interface due to joining of magnetic materials in the magnetic path of the generated magnetic flux when current is passed through the coil. In addition, since the magnetic powder is compacted in advance and fitted with the coil, the packing density of the magnetic powder is high and the induction coefficient is high, so the number of turns can be reduced to obtain the same inductance or impedance, and the DC resistance is also reduced. Furthermore, a highly reliable inductor can be obtained both from the viewpoint of preventing a decrease in reliability due to the presence of the bonding interface of the magnetic material, which has conventionally occurred, and from the viewpoint of reducing collapse of the internal coil.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The inductor of the present invention and its manufacturing method will be explained below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of an inductor of the present invention. 2 to 5 are schematic diagrams showing the manufacturing process of the inductor of FIG. 1.

The inductor has magnetic bodies 6 and 11, a coil 5 attached to the magnetic bodies 6 and 11, and terminal parts 3 and 4 drawn out from the coil 5 to the outside of the magnetic bodies 6 and 11. . The magnetic bodies 6 and 11 are a first compact 6 which is preformed under pressure of magnetic powder containing a binder, and a second compact which is preformed under pressure of magnetic powder containing a binder or magnetic powder containing a binder. 11. The terminal parts 3 and 4 and the coil 5 are sandwiched between the magnetic bodies 6 and 11. The coil 5 is enclosed within the magnetic bodies 6 and 11, and is integrally formed with the magnetic bodies 6 and 11 by press molding. The terminal parts 3 and 4 are lead terminals from which both ends of the coil 5 are drawn out, or terminal electrodes connected to both ends of the coil 5. The inductor provides desired inductance or impedance to these terminal portions 3 and 4.

Further, the coil 5 uses an air-core coil. Terminal portions 3 and 4 are electrically connected to both ends of this coil 5, respectively. The binder is a thermosetting resin that binds the magnetic powder, and the first compact 1 and the second compact 11 connect the terminal parts 3 and 4 and the coil 5 to the magnetic bodies 6 and 11.
It is sandwiched between. The terminal parts 3 and 4 and the coil 5 are integrated with the magnetic bodies 6 and 11.

Next, a method of manufacturing this inductor will be explained with reference to FIGS. 2 to 5. First, magnetic powder 1 such as ferrite mixed with a binder made of thermosetting resin such as epoxy resin is molded into a cap shape using only vertical pressure using upper and lower pressure molds 8 and 9.
A green compact 6 is made. At this time, the magnetic powder 1 is molded without curing the resin. The first powder compact 6 is formed into a Roman letter E shape in cross section so that the coil 5 just fits therein. Thereafter, while leaving the first powder compact 6 in the mold 7, as shown in FIGS. 3 and 4, the magnetic powder 1 is placed in the lower mold 10.
A second powder compact 11 equivalent to the above is inserted, and a coil 5 with terminal electrodes 3 and 4 electrically connected between the upper and lower molds 7 and 10 is installed. Next, as shown in FIG.
and 10 are piled up and subjected to vertical pressure using the upper and lower pressing molds 12 and 13 to perform integral press molding to produce a molded body. At this time, the terminal parts 3 and 4 are sandwiched between the upper and lower molds 7 and 10, and the coil 5 is connected to the first and second compacts 6 and 1.
Confined within 1. Thereafter, the upper and lower molds 7 and 10 are released, and the powder bonding resin is cured by post-heating. With this manufacturing method, there is no interface between the magnetic bodies 6 and 11 constituted by the first powder compact 6 and the second powder compact 11, and the magnetic powder on the side surface of the coil 5 and the center core of the coil 5 is eliminated. An inductor with high density can be obtained.

6 to 9 show a second embodiment of the inductor manufacturing method of the present invention.

First, as shown in FIG. 6, a magnetic powder 21 such as ferrite mixed with a binder made of a thermosetting resin such as an epoxy resin is placed in a mold 2 for pressurizing the top and bottom without hardening the resin.
8 and 29, the first powder compact 26 is formed into a cap shape using only vertical pressure. First green compact 26
is formed into a Roman letter E shape in cross section so that the coil 25 can fit therein. The first green compact 26 remains in the mold 27. In addition, as shown in FIG. 7, magnetic powder 2 is placed in another mold 30.
A magnetic powder 31 equivalent to 1 is inserted into the first green compact 2 described above.
6, and press molded with the upper and lower pressing molds 35 and 36 without curing the bonding resin in the same manner as described above, and then press the second powder body into the mold 30 and abut against the first compact 31. As shown in FIGS. 8 and 9, the molds 27 and 30 are stacked, and the terminal electrodes 23 and 2 are placed in between.
A coil 25 to which 4 is electrically connected is installed. Next, as shown in FIG. 10, integral pressure molding is performed by applying pressure in the vertical direction using molds 32 and 33 for vertical pressure. Thereafter, the inductor is obtained by releasing the mold from the upper and lower molds 27 and 30, and then heating to harden the powder binding resin. With this manufacturing method, there is no interface between the magnetic bodies 6 and 11 in FIG. An inductor with a high density of magnetic powder can be obtained.

[0014]

[Effect of the invention] The inductor thus obtained is
There is no magnetic gap G4 shown in FIG. 11, the induction coefficient is high, and the reliability concerns caused by the polishing of the conventional magnetic joint portion are eliminated, and an inductor with improved reliability can be obtained.

[0015] Furthermore, since the coil is covered in advance with a high-density magnetic powder compact and then integrally molded, the concentration of pressure on the coil can be alleviated. A highly reliable inductor with reduced coil collapse can be obtained.

[0016] The binder used in this example is not limited to epoxy resin, but also phenol resin, silicone resin, or other resins, as long as they are thermosetting resins, this effect can be obtained. . Further, the magnetic powder is not limited to ferrite powder, and the effects of the present invention can be obtained even with metallic magnetic powder as long as insulation between the powders is ensured.

[Brief explanation of the drawing]

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

2 is a schematic diagram showing one step of the molding process in the first example of the manufacturing process of the inductor shown in FIG. 1; FIG.

FIG. 3 is a schematic diagram showing one step of a molding process following the manufacturing process of the inductor of FIG. 2;

FIG. 4 is a perspective view showing the arrangement of the coil and green compact shown in FIG. 3;

5 is a schematic diagram showing one step of a molding process following the manufacturing process of the inductor of FIG. 2; FIG.

FIG. 6 is a schematic diagram showing a first example of the manufacturing process of the inductor shown in FIG. 1, and showing one step of the molding process.

7 is a schematic diagram showing one step of a molding process following the manufacturing process of the inductor of FIG. 6. FIG.

8 is a schematic diagram showing one step of a molding process following the manufacturing process of the inductor of FIG. 7. FIG.

9 is a perspective view showing the arrangement of the coil and green compact shown in FIG. 8. FIG.

10 is a schematic diagram showing one step of a molding process following the manufacturing process of the inductor of FIG. 8. FIG.

FIG. 11 is a cross-sectional view of a conventional inductor and an enlarged cross-sectional view of a joint portion of this inductor.

[Explanation of symbols]

1 Magnetic powder 3 Terminal section 5 Coil 6 First green compact 7 Molding mold 8 Molding mold 11 Second green compact 21 Magnetic powder 26 First green compact 31 Magnetic powder 34 Second green compact 41 Magnetic powder with binder 42 roll bobbin 44 Terminal section 45 Coil

Claims (3)

[Claims] 1. An inductor comprising a magnetic material, a coil attached to the magnetic material, and a terminal portion drawn out from the coil to the outside of the magnetic material, wherein the magnetic material is prepared by pressurizing a binder-containing magnetic powder. It has a molded first powder compact and a second powder compact obtained by pressurizing and preforming the binder-containing magnetic powder or the binder-containing magnetic powder, and the terminal portion and the coil are formed of the magnetic powder. an inductor, wherein the coil is enclosed within the magnetic body and is integrally formed with the magnetic body by press-forming. 2. The coil is an air-core coil, and has terminal portions electrically connected to both ends of the air-core coil, and the binder is a thermosetting resin that binds the magnetic powder. 2. The first powder compact and the second powder compact have the terminal portion and the coil sandwiched between the magnetic bodies, and are integrated. inductor. 3. Forming a first green compact by pressurizing and preforming a binder-containing magnetic powder using a mold, installing a coil having a terminal portion in the mold, and using the coil as a reference. installing the binder-containing magnetic powder or a second compact obtained by press-preforming the binder-containing magnetic powder in a mold on the opposite side of the first compact; The second green compact is butted against the powder, and the first green compact and the second green compact are integrally pressed and main-molded using the mold. A method for manufacturing an inductor, which comprises releasing the molded body from a mold, and then subjecting the molded body to heat curing treatment.