JP2003306702A - Method of producing chip type inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a chip type inductor by which the occurrence of cracks can be prevented. <P>SOLUTION: Magnetic powder containing a binder consisting of a thermosetting resin is compacted to form a green compact 11 with a coil 12 buried at the inside. After that, the green compact 11 is placed in a pressure vessel 30 filled with micro granules 40. The green compact 11 is heated and hardened in a state where the green compact 11 is pressurized via the micro granules 40. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a chip-type inductor having a coil inside a magnetic body.

[0002]

2. Description of the Related Art FIG. 5 shows an example of this type of chip inductor 10. A coil 12 is embedded inside a powder compact 11 made of a magnetic material, and both terminals of the coil 12 are electrodes.
Connected to 13. As the raw material of the green compact 11, for example, magnetic powder obtained by wrapping metal magnetic powder such as iron or sendust or permalloy with a binder (bonding agent) made of a thermosetting resin is used. The magnetic powder is pressed to obtain a green compact.
After 11 is molded, the binder is heated and reacted to be hardened.

Conventionally, such an inductor has been manufactured as follows. First, the magnetic powder having the coil 12 embedded therein is placed in a mold to pressurize at a pressure of about 2 tons per square cm to form the green compact 11. At this time, the binder made of the thermosetting resin contained in the green compact 11 is in an unreacted state, and the green compact 11 is hardened into a predetermined shape, but is not yet hardened. So, this inductor 10
Is passed through a high-temperature furnace and heated to react the binder with it
11 had been cured.

[0004]

However, due to the internal stress of the green compact 11 and the effect of thermal expansion of each material, when the green compact 11 is hardened, especially in the vicinity of the contact with the electrode 13 or the uneven portion. There is a problem that cracks are likely to occur. Therefore, the present invention is to provide a method for manufacturing a chip-type inductor that can prevent the occurrence of cracks.

[0005]

In the method of manufacturing a chip-type inductor according to the present invention, a magnetic powder containing a binder made of a thermosetting resin is pressure-molded to form a powder compact 11 having a coil 12 embedded therein. After that, the powder compact 11 is housed in a pressure container filled with the fine particles, and the powder compact 11 is cured while the powder compact 11 is pressed through the fine particles.

[0006]

EXAMPLE FIG. 2 is a sectional view of the chip inductor 10 in the process of being manufactured, showing a state immediately after the magnetic powder having the coil 12 embedded therein is pressed by a mold to form the green compact 11. Then, the binder made of a thermosetting resin contained in the green compact 11 is reacted to harden the green compact 11 and the electrode 13 is bent to form a chip-type inductor as shown in FIG. .

The method of manufacturing a chip-type inductor according to the present invention is characterized by the step of hardening the green compact of the inductor. Hereinafter, taking the inductor 10 shown in FIG. 2 as an example, a process of hardening the green compact 11 will be described with reference to the drawings.

FIG. 1 shows an outline of an apparatus for curing a powder compact 11 of an inductor 10. A plurality of inductors 10 mounted on a holder 20 are housed inside a cylindrical pressure vessel 30. There are no gaps in the remaining space inside the pressure vessel 30
40 is filled, and the inductor 10 is in a state of being buried in the fine particles 40 as shown in FIG.

The openings at both ends of the pressure vessel 30 are closed in a sealed state by a slidable side plate 32 within a certain area of the pressure vessel 30. A pressure in the direction of the arrow in FIG. 1 is applied to the two side plates 32, and the fine particles 40 filling the inside of the pressure vessel 30 are pressed from both sides so as to be compressed.

As the fine particles 40, spherical bodies made of glass, stainless steel, ceramics or the like are used. The size of the sphere is determined according to the external dimensions of the green compact 11 and the state of the irregularities, but in the case of a normal inductor, the diameter is 50 to 3
It will be about 00 μm. By selecting a fine particle 40 having a smooth surface and a low friction coefficient, a property similar to a liquid can be obtained, and a pressing force is propagated like a liquid. Therefore, the pressure applied by the side plate 32 acts on the entire outer periphery of the powder compact 11 of the inductor 10 via the fine particles 40.

Then, the green compact 11 is heated together with the pressure container 30 while maintaining the pressed state of the green compact 11 through the fine particles 40. As a result, the temperature of the green compact 11 rises, the binder reacts, and the green compact 11 is hardened under the condition that pressure is applied to the entire outer circumference. After that, the side plate 32 is opened to release the pressure in the pressure vessel 30, and the electrodes of the taken out inductor 10 are bent and formed to complete a chip-type inductor.

FIG. 4 shows a configuration example in which the apparatus of FIG. 1 is further embodied. This is one in which the two side plates 32 that close the openings at both ends of the pressure vessel 30 are urged inward by the elasticity of the spring 50 to apply pressure. In this example, three springs 50 arranged at equal intervals are mounted between the two side plates 32. Instead of using the spring 50, the side plate 32 may be composed of a piston that can enter the pressure vessel 30.

The temperature at which the binder of the green compact 11 is hardened is determined according to the temperature characteristics of the magnetic powder used for the green compact 11. Depending on the binder material, heating for curing may not be necessary. Inductor 10 and fine particles taken out from the pressure vessel 30 after the green compact 11 was cured
In order to facilitate separation from the inductor 40, the inductor 10 as a whole or the powder compact 11 portion may be covered with a thin film sheet made of polyethylene resin or the like and then placed in the pressure container 30 and cured.

[0014]

[Effects of the Invention] When the outer shape of the green compact has large irregularities, cracks are particularly likely to occur. However, according to the present invention, the entire outer surface of the green compact is cured while being pressed uniformly. Therefore, it is possible to obtain a good green compact having no cracks. Further, even when the raw material and the compounding ratio of the magnetic powder are changed, it is possible to easily cope with the occurrence of cracks by adjusting the pressure applied to the green compact. Even when the thermosetting resin gels during the reaction process, pressure is continuously applied from the entire outer circumference, so the density variation of the green compact is reduced and the electrical characteristics of the inductor are also stabilized. is there.

[Brief description of drawings]

FIG. 1 is a partial sectional front view showing a basic structure of an apparatus used in a manufacturing process of the present invention.

FIG. 2 is a front sectional view of an inductor in the process of being manufactured.

FIG. 3 is a conceptual diagram of an inductor in a pressure vessel.

FIG. 4 is a front view showing a specific configuration example of a curing device according to the present invention.

FIG. 5 is a front view showing an example of a chip inductor.

[Explanation of symbols]

10 inductor 11 Green compact 12 coils 30 pressure vessel 40 small particles

Claims (4)

[Claims] 1. A magnetic powder containing a binder made of a thermosetting resin is pressure-molded to form a powder compact having a coil embedded therein, and the powder compact is then filled in a pressure container filled with fine particles. And a method of manufacturing a chip-type inductor, characterized in that the powder compact is cured while the powder compact is housed in a state of being pressed through the fine particles. 2. At the same time as pressurizing the green compact with fine particles,
The method for manufacturing a chip-type inductor according to claim 1, wherein the green compact is heated. 3. The method for producing a chip-type inductor according to claim 1, wherein the fine particles are made of a material selected from glass, stainless steel, and ceramics. 4. The method for producing a chip-type inductor according to claim 1, wherein the surface of the powder compact in the high-pressure container is covered with a thin film sheet, and the powder compact is pressed through the fine particles and the thin film sheet.