JPH08162367A - Noise filter - Google Patents

Abstract

PURPOSE: To enable a noise filter to be simplified in structure, broadened in attenuation band width, and improved in general-purpose properties by a method wherein a pair of a first inner electrode and a second inner electrode both belt-like are rolled up overlapping with each other through the intermediary of a proper insulator for the formation of a noise filter main body. CONSTITUTION: An element main body 1 is composed of a first inner electrode 8 and a second inner electrode 9 which are both formed of belt-like metal foil and rolled up overlapping with each other through the intermediary of a belt-like insulator 7. Lead wires 2 and 3 are fixed to the rolling start ends X and Y of the first inner electrode 8 respectively. The inner electrodes 8 and 9 are rolled up, and the side of the second inner electrode 9 is made to protrude or the side opposite to the side where the lead wires 2 and 3 are led out, thus forming an outer electrode lead-out part. Then, the peripheral part of the element main body 1 is pressed to make the main body 1 flat. Thereafter, a lead wire is welded to the outer electrode lead-out part of the second electrode 9. THe lead wires 2 and 3 are led out on the same side as the former lead wire, and the element main body 1 is coated with resin such as thermosetting resin or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved technique for a noise filter for electronic equipment, which is formed by using a plastic film, a metal foil or a metallized film.

[0002]

2. Description of the Related Art As is well known, in recent years, the structure and manufacturing method of the above filter have been studied, and the filter has been put to practical use to be used as a noise countermeasure for various electronic devices.

However, in recent years, new products are being produced for electronic devices and devices, and the environment in which the electronic devices are used is becoming more and more diversified. As a result, new sources of noise and vice versa. Noise is becoming more common.

Therefore, there is a demand for a noise filter which can deal with the above problems and which is higher in quality and less expensive, and in recent years, the distributed constant type which is highly versatile is drawing attention.

FIG. 10 shows a conventional distributed constant type noise filter as shown in Japanese Utility Model Application Laid-Open No. 57-122904.

This noise filter A has a strip-shaped conductor foil (L side) c having lead terminals a and b at both ends, and a conductor foil (C which is wider than this and has a lead terminal d at one end).
The side) e is overlapped and wound to expose the wound side part f of the conductor foil e to form an element serving as an electrode on the ground side. With such an element structure, most of the conductor foil e is connected to the lead-out terminal d, so that the ground impedance can be reduced, and it is effective in removing high frequency spike noise included in a switching regulator or the like. Is to have.

[0007]

However, in the conventional element structure as described above, since the C-side conductor foil e and the L-side conductor foil c have substantially the same length, Equivalently, π is composed of many capacitance and inductance components.
Or T-shaped circuit configuration. In such a case, generally, as shown in FIG. 11, one resonance called a notch type on the characteristic curve is obtained. Therefore, in the conventional structure, although the amount of attenuation is sufficient, the attenuation bandwidth is narrow and the usable bandwidth is limited. In addition, it has been troublesome to use them in combination to obtain the required bandwidth.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention has been made in view of the above points, and an object of the present invention is to provide a noise filter which is structurally simple, has a wide attenuation bandwidth, and is versatile.

[0009]

In order to achieve the above object, the present invention provides an element body by at least a pair of band-shaped first internal electrodes and second internal electrodes which are wound in a layered manner with an appropriate insulator interposed therebetween. The first internal electrode and the second internal electrode have an external electrode lead-out portion located on the opposite side of the winding side portion, and the external electrode lead-out portion of the first internal electrode has a winding start end. And the winding end side of the second internal electrode, the winding end of the second internal electrode is provided in a range that does not exceed the external electrode extraction portion on the winding end side of the first internal electrode in the wound state.

[0010]

With the above configuration, the length of the second internal electrode is shorter than the length of the first internal electrode, and moreover, after the winding end on the second internal electrode side and the first internal electrode. There is no capacitance component formed between
There is only the inductance component of the internal electrodes. Also, the second
The inductance component generated by the internal electrodes is also reduced. Therefore, as shown in FIG. 6, a bandpass filter having a steep attenuation curve and a wide two-resonance bandwidth can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. This noise filter B can be provided with lead wires 2, 3 and 4 on the element body 1 as shown in FIG. 1 and with surface mounted external electrodes 5 and 6 as shown in FIG. is there.

<Embodiment 1> First, the case of the lead-out lead type will be described.

The element body 1 includes a first internal electrode 8 of a strip-shaped metal foil and a second internal electrode 9 of the strip-shaped metal foil, which are stacked on each other with a strip-shaped insulator 7 made of a plastic film or the like as shown in FIG. It is constructed by winding and.

The material of the plastic film is PP, P
ET, PPS, etc. are selected or used in combination as required.

The material of each of the first and second internal electrodes 8 and 9 is made of Al, Zn or an alloy containing such a metal, and has a thickness of several μm in consideration of the allowable current and the element size. To do.

Lead wires (external electrode lead-out members) 2 and 3 are attached to the winding start end side X and the winding start end side Y of the first internal electrode 8 with a predetermined distance from the electrode ends.

The width of the second internal electrode 9 is equal to that of the first internal electrode 8.
Is formed wider than that of the first internal electrode 8 and the length thereof is set within the range from the winding start end of the first internal electrode 8 to the lead wire 3 on the winding end side Y. The optimum length ratio of the second internal electrode 9 is about 60% between the winding start end and the lead wire 3. Further, in this case, it is preferable that the lead wire 2 on the winding start end side X overlaps.

By winding the internal electrodes 8 and 9, the lead wires 2 and 3 of the first internal electrode 8 are drawn out from the side of the second internal electrode 9 as shown in FIG. The external electrode lead-out portion (for grounding) 10 is formed by protruding (exposing) in the direction opposite to the winding side surface.

In the case of forming the element, the case has been described in which both winding start ends are aligned to overlap the first and second internal electrodes 8 and 9, but the invention is not limited to this, and the winding is performed in a staggered state. You can rotate it.

The peripheral side portion 11 of the element body 1 thus wound is pressed to be flat. After that, the lead wire 4 as shown in FIG. 5 is welded to the external electrode extraction portion 10 of the second internal electrode 9. Then, if the lead wires 2 and 3 are also drawn out to the same side and the element body 1 is covered with a resin such as thermosetting resin, a band pass filter having two resonances and a wide frequency band width as shown in FIG. 6 is obtained. can get.

<Second Embodiment> Here, a case of a leadless type will be described. Since the internal electrode structure of the element body 1 is the same as that of the above-described first embodiment, only the points related to the external electrodes will be described.

FIG. 7 shows the filter element 1 in a completed state.
2 is shown. In this case, the lead wires 2 and 3 on the first internal electrode 8 side are cut to an appropriate length, and then the lead wires 2 and 3 are bent in the direction of the arrow, that is, toward the winding side surface. Alternatively, it may be bent and then cut. In this way, each external electrode extraction portion is formed, and metal spraying (metallikon) is performed on the external electrode extraction portion to form a metal layer, thereby forming the external electrodes 5 and 6.

Then, the substantially central portion of the outer electrode 6 on the side of the first inner electrode 8 is cut into an appropriate method, for example, a rotary saw tooth to separate the two outer electrodes 7a and 7b.

As a result, as shown in FIG. 2, it is possible to form a three-terminal filter which is basically chip-shaped and can be surface-mounted on a printed wiring board or the like.

<Embodiment 3> As shown in FIG. 8, the element structure here is such that, as shown in FIG. 8, a first internal electrode 15 made of a strip-shaped metal foil on which the element main body 1 is stacked via a strip-shaped insulator 14 made of a plastic film or the like. And a second inner electrode 16 made of a strip-shaped metallized film wider than this.

The material of the insulator 14 is selected from PP, PET, PPS and the like, or used in combination, as in the above embodiments.

The first internal electrode 15 is made of Al, Zn or an alloy containing a metal such as Al and has a thickness of several μm. A predetermined distance is provided between the winding start end side X and the winding end side Y of the first internal electrode 15 so that the lead wire 1
7 and 18 are attached one by one.

The second internal electrode 16 is formed by depositing a metal such as Al or Zn on a plastic film such as PET, but the entire film surface 19 is not metallized, as shown in FIG. In addition, the metallized portion of the lead wire 18 extends from the winding start end of the first internal electrode 15 to the winding end side Y.
About 60% is optimal compared to the period.

When forming the element, the first internal electrode 15 and the second internal electrode 16 are wound from the winding start end side X via the insulator 14 by a winder (not shown).

When wound in this manner, the second internal electrode 16
The winding side part of is exposed so that it protrudes, and the external electrode extraction part 2
Can be 0. Then, metal winding is sprayed on the winding side surface on the external electrode extraction portion 20 side, and the lead wire 21 is further welded thereon. The lead wire 21 is drawn out as an external electrode in the same direction as the lead wires 17 and 18 on the first internal electrode 15 side. Alternatively, the lead wires 17 and 18 may be folded back and pulled out to the lead wire 21 side. After that, if the element body 1 is covered with a thermosetting resin or the like, the damping characteristics are the same as in Example 1,
A bandpass filter having a wide frequency bandwidth can be formed by two resonances.

The present invention is not limited to the above-mentioned embodiments, and metallized films may be applied to both of the internal electrodes, and a mere lead wire is used as the lead-type external electrode, but a plate-shaped external electrode is used. However, various design changes are possible within the scope of the technical idea described in the claims.

[0032]

As described above, according to the present invention, in the noise filter element, the external electrode lead-out portions such as lead wires are attached to both ends of the first internal electrode and the external electrode lead-out portions protruding from the side portions. The second internal electrode is wound, and in the wound state, the winding end of the second internal electrode is provided in a range that does not exceed the external electrode extraction portion on the winding end side of the first internal electrode. As a distributed constant type filter, structurally, after the end of the second internal electrode, there is no capacitance component formed between the first internal electrode and only the inductance component of the first internal electrode. At this time, two resonance points are generated, and the attenuation characteristic having a wide bandwidth is obtained.
Therefore, a versatile bandpass filter is possible.

[0033]

[Brief description of drawings]

FIG. 1 is a front view showing the external appearance of a noise filter formed by Examples 1 and 3 of the present invention.

FIG. 2 is a perspective view showing the appearance of a chip-type noise filter formed according to the second embodiment.

FIG. 3 is a perspective view showing a developed state of the elements used in the first and second embodiments.

FIG. 4 is a perspective view showing a process of forming a filter element according to the first embodiment.

FIG. 5 is a perspective view showing a filter element completed in the first embodiment.

FIG. 6 is a characteristic curve diagram of the first to third embodiments.

FIG. 7 is a perspective view showing a process of forming a chip-type filter device according to the second embodiment.

FIG. 8 is a perspective view showing a developed state of an element used in the third embodiment.

FIG. 9 is a partially cutaway perspective view in which the inside of the filter element completed in Example 3 is partially cut out so that the inside can be seen.

FIG. 10 is a perspective view showing an element structure of a conventional noise filter.

FIG. 11 is a characteristic curve diagram of the noise filter.

[Explanation of symbols]

 1 Element body 2,3,4 Lead wire 5,6 External electrode 7 Insulator 8 1st internal electrode 9 2nd internal electrode 10 External electrode extraction part 11 Circumferential side part 12 Filter element 13 Notch 14 Insulator 15 1st internal Electrode 16 Second internal electrode 17,18,21 Lead wire 19 Film surface 20 External electrode extraction part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01G 4/18 4/32 301 A 7924-5E 305 Z 7924-5E 7924-5E H01G 4/24 301 B

Claims (2)

[Claims] 1. An element body is composed of a strip-shaped first internal electrode and a second internal electrode which are wound in a layered manner with an appropriate insulator interposed therebetween, and wound around the first internal electrode and the second internal electrode. An external electrode lead-out portion is located on the opposite side of the winding side portion, and the external electrode lead-out portion of the first internal electrode is provided on the winding start end side and the winding end side, and the second internal electrode winding is provided. The noise filter, wherein the winding end is provided in a range in which the winding end does not exceed the external electrode extraction portion on the winding end side of the first internal electrode. 2. The noise filter according to claim 1, wherein the external electrode extraction portion on the side of the second internal electrode is formed by exposing the internal electrode so as to protrude from a winding side surface of the element body.