JPH0613240A - Chip type noise filter - Google Patents

Abstract

PURPOSE:To improve the conductivity of an inner conductor when formed in a miniature size by specifying a content of copper of copper compound component in a ferrite. CONSTITUTION:A molded material in which a platinum wire is molded substantially at a center by press molding is formed by using mixture containing aqueous soluble resin and nickel-zinc series ferrite powder containing 0.5mol% or less of cupric oxide, and baked to manufacture a rectangular parallelepiped sintered ferrite molded form 2 in which a platinum wire 3 is fixed in close contact. Electrodes 4 are provided at both ends as a chip type noise filter 1. Thus, the filter has a resistance value near a theoretical resistance value of an internal conductor and can be sintered at a high temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type noise filter used in various electronic circuits.

[0002]

2. Description of the Related Art A noise filter has an effect of blocking external high frequency waves and cutting high frequency waves generated from an electric current flowing through an internal conductor. As its construction, a through hole is conventionally provided in a molded body made of ferrite. The internal conductor was inserted into the through hole and fixed by an adhesive or the like.

At this time, as the material of the ferrite, a material containing iron oxide as a main component and nickel, zinc, manganese, copper or the like added according to its use and characteristics is used. Especially, nickel-zinc is used for blocking high frequency. The system was preferably used.

However, with the recent increase in the density of electronic equipment, there is an increasing demand for miniaturization and performance improvement thereof. Therefore, the internal conductor and the ferrite are integrated and then sintered to a predetermined length. A so-called laminated chip in which electrodes are provided on both ends by cutting and plating, or internal conductors are provided on a ferrite plate by printing, etc., and ferrite plates of the same shape are stacked and sintered, and then electrodes are provided on both ends. Type noise filters are known. These filters can be more easily downsized than conventional ones, and the inner conductors having a small wire diameter can be used, so that a wider range of high frequency can be blocked.

[0005]

However, although the chip type noise filter manufactured by the above method has a preferable effect, it has the following big problems. That is, if the internal conductor and the ferrite are integrated and sintered, the DC resistance value of the obtained conductor of the noise filter increases. This leads to deterioration in conductivity, which is a fatal problem. In particular, this tendency becomes more remarkable as the diameter of the inner conductor becomes smaller, and the inner conductor cannot be used.

As a result of studying this point, the present inventor has found that a large amount of ferrite exists in the internal conductor after sintering. That is, the ferrite diffuses into the internal conductor due to thermal diffusion at high temperature. Therefore, if the sintering temperature is lowered to prevent thermal diffusion, the resistance value decreases and becomes good, but on the contrary, the strength of the ferrite molded body becomes low, and moreover, strong tightening cannot be obtained,
It was difficult to obtain a sufficient blocking effect itself.

[0007]

As a result of trial and error, the present inventor conducted various experiments focusing on the material of ferrite.
That is, when only the iron oxide is coated on the inner conductor and fired, the iron oxide is diffused but the resistance value is not increased. However, the commonly used nickel, zinc,
The use of ferrite containing manganese, copper, etc. causes the above problems. Then, when materials other than iron oxide were examined, the present invention was completed by finding the fact that the resistance value increased only in ferrite to which copper or its compound component was added.

According to the present invention, in a chip type noise filter in which an internal conductor and a ferrite are adhered to each other by sintering, the content of copper or a copper compound component in the ferrite is 5 mol% or less. Is. Here, the copper compound refers to copper oxide, cupric oxide, or the like.

[0009] Usually, iron oxide alone cannot be used to exert its function as a ferrite, and addition of other materials is indispensable. Among them, copper is preferably used in the sense that it reduces the porosity of the ferrite molded body and improves the strength and the like. However, when the internal conductor and the ferrite are adhered to each other by sintering as in the present invention, copper or a copper compound component is easily diffused in the internal conductor, and the reason is not clear, but these materials are It causes an increase in resistance.

As the ferrite used in the present invention, any one can be used as long as it contains iron oxide as a main component and the content of copper or its compound component is 5 mol% or less, and particularly 1 mol% or less. Things are good. 5 mol%
When it becomes above, the resistance value increases and it becomes unusable. As described above, many noise filters mainly block high frequencies, and normally nickel-zinc type ferrite is good, but of course, the present invention is not limited to this, and manganese-zinc type ferrite and other ferrites. And so on.

The external shape of the noise filter of the present invention is
Although a rectangular parallelepiped, a columnar shape and the like are arbitrary, a rectangular parallelepiped is usually preferable. Also, as the inner conductor in ferrite, silver,
Examples of the lead wire include silver-palladium, palladium, platinum and the like, plated wire, and paste baking. When the platinum lead wire is used, the effect of the present invention becomes remarkable. Further, as the shape of the internal conductor, a linear conductor is typically mentioned, but it is arbitrary such as a sawtooth shape, a rectangular shape, a spring shape, and can be variously selected according to the type of noise to be cut off.

The noise filter of the present invention is manufactured by press molding, extrusion molding, injection molding, casting molding, etc.
After integrating the ferrite with the internal conductor, forming it into a rectangular parallelepiped or cylinder and firing it, then by providing electrodes on both ends by plating etc. in the form of connecting with the internal conductor, or by making a ferrite plate, this plate Forming an inner conductor on top,
The plates are stacked and sintered to provide electrodes on both ends. Of course, this stack may be triple or quadruple.

[0013]

EXAMPLE 1 FIG. 1 is a perspective view showing a chip-type noise filter of the present invention, which comprises a nickel-zinc ferrite powder containing 0.1 mol% of a water-soluble resin and cupric oxide. Platinum wire 3 is formed by pressing a platinum wire into a substantially central portion by press molding using the kneaded product.
A rectangular parallelepiped sintered ferrite molded body 2 in which was adhered and fixed was produced, and electrodes 4 were provided at both ends to obtain a chip type noise filter 1. The size of the chip-type noise filter 1 is length × width × length 1.1 × 1.6 × 3 (unit: mm), and the platinum wire has an outer diameter of 50 μm. When the DC resistance value of this noise filter was measured, it was about 152 mΩ on average for 10 filters.

Comparative Example As a ferrite, a nickel-zinc type ferrite (content of cupric oxide: 8 mol%) which is usually used is used.
A chip type noise filter was prepared in the same manner as in Example 1.
When the DC resistance value of this noise filter was measured,
The average of 10 pieces was about 520 mΩ.

[0015]

As described above, the chip-type noise filter of the present invention has a resistance value close to the theoretical resistance value of the inner conductor, and since it can be sintered at high temperature, the sinterability of ferrite is high. The result was good, and as a result, an excellent noise filter blocking effect was obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a chip-type noise filter according to a first embodiment of the present invention.

[Explanation of symbols]

 1 Chip type noise filter 2 Sintered ferrite compact 3 Platinum wire 4 Electrode

Claims (1)

[Claims] 1. A chip-type noise filter in which an inner conductor and a ferrite molded body are adhered to each other by sintering,
A chip-type noise filter, wherein the content of copper or a copper compound component in the ferrite molded body is 5 mol% or less.