JPH05343234A - Noise filter - Google Patents

Abstract

PURPOSE:To provide a noise filter that can reduce its manufacturing cost and that can be surface-mounted. CONSTITUTION:The noise filter consists of a core 12 having a groove 16 therein, a winding 18 formed in the groove 16, a rectangular column like package 22 formed around the core 12 and winding 18, and external electrodes 28 formed on the package 22 and electrically connected to the winding 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise filter, and more particularly to a noise filter having a winding formed around a core.

[0002]

2. Description of the Related Art FIG. 9 is an illustrative view showing an example of a conventional noise filter which is the background of the present invention. The noise filter 1 includes a core 2. The core 2 is formed of, for example, a cylindrical shape using a magnetic material. Then, the conductive wire 3 is provided around the core 2.
The noise filter 1 is formed by winding. In the noise filter 1, the diameter of the conductor wire 3 or the diameter of the core 2 is adjusted according to the current flowing through the conductor wire 3.

[0003]

However, in such a conventional noise filter, the step of winding the conductive wire around the core becomes large and the manufacturing cost becomes large.
Further, such a noise filter is difficult to be surface-mounted.

Therefore, a main object of the present invention is to provide a noise filter which can be manufactured at a reduced cost and can be surface-mounted.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a core having a spiral groove, a winding formed in the groove, a prismatic exterior material formed around the core and the winding, and an exterior. It is a noise filter including an external electrode formed on a surface of a material and electrically connected to a winding.

[0006]

The winding in the groove of the core can be formed by filling the groove with a conductive paste and firing. Since the exterior material has a prismatic shape, a flat surface is formed on the outer surface of the exterior material. Since external electrodes are formed on the surface of this exterior material,
The external electrodes come into contact with the surface of the printed circuit board or the like on which the noise filter is placed.

[0007]

According to the present invention, since the winding can be formed without winding the conducting wire, the manufacturing process can be simplified. Therefore, the manufacturing cost of the noise filter can be reduced. Further, since the outer surface of the exterior material has a flat portion, the noise filter can be stably mounted on a printed circuit board or the like. In this state,
Since the pattern electrode of the printed board and the external electrode of the noise filter can be brought into contact with each other, soldering or the like is easy. Therefore, surface mounting is possible by using this noise filter.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments below with reference to the drawings.

[0009]

1A is a perspective view showing an embodiment of the present invention, and FIG. 1B is a schematic view thereof. The noise filter 10 includes a core 12. The core 12 is formed into a columnar shape using, for example, an oxide magnetic material, and an inclined portion 14 that is inclined from the side surface toward the end surface is formed. Further, a spiral groove 16 is formed on the side surface of the core 12, and a winding 18 is formed in the groove 16. Core 1
The end face electrodes 20 are formed on both ends of the end face electrode 2.
The winding 18 is connected to 0.

An exterior material 22 is formed on the outer peripheral sides of the core 12 and the winding wire 18. The exterior material 22 is formed into a quadrangular prism shape, for example, of an oxide magnetic material. Another inclined portion 24 is formed at a position corresponding to the inclined portion 14 of the core 12 at the inner surface end portion of the exterior material 22. Therefore, the inclined portion 14 of the core 12 and the inclined portion 24 of the exterior material 22 form an annular recess 26. Further, an external electrode 28 extending from the inclined portion 24 to the outer peripheral surface through the end of the exterior material 22 is formed at the end of the exterior material 22. Then, the recess 26
At the portion, the end surface electrode 20 of the core 12 and the external electrode 28 of the exterior material 22 are electrically connected by the solder 30 or the like.

Plates 32 made of, for example, epoxy resin are attached to both ends of the noise filter 10. The plate 32 is formed in a disk shape, and the solder 30
Is formed so as to cover. With this plate 32,
For example, when soldering to a printed circuit board or the like, the solder 30 is prevented from flowing out due to heat or the like.

To manufacture such a noise filter 10, first, a cylindrical core 12 as shown in FIG. 2 is prepared. The core 12 is formed, for example, by molding a granulated product of Ni-Zn-Cu ferrite and firing it at 1050 to 1100 ° C. An inclined portion 14 is formed at the end of the core 12. Next, as shown in FIG. 3, a spiral groove 16 is formed on the side surface of the core 12. Groove 16
Is formed by, for example, a lathe. Then, as shown in FIG. 4, a conductive paste is applied to the entire surface of the core 12 in which the groove 16 is formed and baked at 800 to 900 ° C., whereby the full surface electrode 40 is formed. Then, by the centerless polishing or the like up to the position shown by the dotted line A, the entire surface electrode 4
0 and some of the threads of the core 12 are ground. In this way, as shown in FIG. 5, the winding 18 and the end face electrode 20 are formed on the core 12. At this time, since the inclined portion 14 is formed on the core 12, the inclined portion 14 is formed.
The groove 16 always appears somewhere. Therefore, the winding 18 and the end surface electrode 20 are reliably connected.

Next, as shown in FIG. 6, the exterior material 22 is prepared. The exterior material 22 is formed in a rectangular parallelepiped shape by firing a molded ferrite material at 1050-1100 ° C. A columnar hole 42 penetrating in the axial direction is formed in the exterior material 22. An inclined portion 24 is formed at the end of the hole 42 so that the inner diameter of the exterior material 22 expands. External electrodes 28 are formed on both ends of the exterior material 22. As shown in FIG. 7, the external electrode 28 includes the inclined portion 2
4 is formed so as to be drawn out to the outer peripheral surface through the end portion of the exterior material 22. The external electrode 28 may be formed, for example, by applying a conductive paste and baking it, or by a method such as sputtering.

As shown in FIG. 8, the core 1 in which the winding 18 and the end face electrode 20 are formed in the hole 42 of the exterior material 22.
2 is inserted. At this time, the inclined portion 14 of the core 12 and the inclined portion 24 of the exterior material 22 form an annular recess 26. When the core 12 is inserted into the exterior material 22, they may be fixed with an adhesive or the like. This recess 26
In the portion, the end surface electrode 20 of the core 12 and the external electrode 28 of the exterior material 22 are soldered. In addition, solder 3
Plate 32 made of epoxy resin or the like so as to cover 0
Are glued together. In this way, the noise filter 10 shown in FIG. 1 is formed.

As described above, when manufacturing the noise filter 10, the step of winding the conductive wire is not necessary. for that reason,
The manufacturing cost can be reduced as compared with a conventional noise filter in which a conductive wire is wound to form a winding. Further, since the exterior material 22 is formed in a prismatic shape, the noise filter 10 can be stably placed on a printed circuit board or the like. At this time, the external electrodes 28 come into contact with the pattern electrodes or the like of the printed circuit board, so that soldering or the like is easy. As described above, the noise filter 10 can be easily formed into a chip and can be surface-mounted.

In this noise filter 10, the exterior material 22 is used.
Since it is made of a magnetic material, it is close to the closed magnetic circuit structure and has a large shielding effect. Therefore, the leakage magnetic flux from the noise filter 10 is small, and the influence of the magnetic flux on the elements arranged in the vicinity of the noise filter 10 is small. Therefore, the distance between the noise filter 10 and other elements can be reduced, and high-density mounting can be achieved. The exterior material 22 may be formed of a non-magnetic material such as epoxy resin, in which case the noise filter 10 has an open magnetic circuit structure. In this case, the core 12 is less likely to be magnetically saturated and has a large current capacity.

By changing the width and depth of the groove 16 of the core 12, the cross-sectional area of the winding 18 can be changed and the current capacity can be adjusted. Further, the groove 16
By changing the interval of, the stray capacitance between the adjacent windings 18 can be adjusted, and the impedance characteristic can be adjusted.

[Brief description of drawings]

FIG. 1A is a perspective view showing an embodiment of the present invention, and FIG. 1B is a plan view showing the same.

FIG. 2 is a perspective view showing an example of a core used to manufacture the noise filter shown in FIG.

FIG. 3 is a plan view showing a state where grooves are formed in the core shown in FIG.

FIG. 4 is an illustrative view showing a state where a full-face electrode is formed on the core shown in FIG.

5 is a plan view showing a state where the entire surface electrode of the core shown in FIG. 4 is polished.

6 is a perspective view showing an example of an exterior material used to manufacture the noise filter shown in FIG.

FIG. 7 is an illustrative view of the exterior material shown in FIG.

8 is an illustrative view showing a state in which the core shown in FIG. 5 is inserted into the exterior material shown in FIG.

FIG. 9 is an illustrative view showing one example of a conventional noise filter which is a background of the present invention.

[Explanation of symbols]

 10 Noise Filter 12 Core 16 Groove 18 Winding 22 Exterior Material 28 External Electrode

Claims (1)

[Claims] 1. A core having a spiral groove, a winding formed in the groove, a prismatic exterior material formed around the core and the winding, and a surface formed on the exterior material. A noise filter including an external electrode electrically connected to the winding.