JP2000252164A - Multilayer ceramic filter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To digitally selectively pass noise of two kinds of frequencies. A multilayer ceramic filter capable of preventing the occurrence of structural defects due to variations in capacitance, Q value, equivalent series resistance value of a capacitor, and an excessively thick conductor layer. SOLUTION: A plurality of internal electrodes 2, 3, 4, 5 are arranged between dielectric layers of a laminated filter body 10 formed by laminating a plurality of rectangular dielectric layers 1, and the laminated filter body 10 is provided. Terminal electrodes 6 and 7 connected to the internal electrodes 2, 3, 4 and 5 are formed on a pair of end surfaces, and the capacitance values are different between the terminal electrodes 6 and 7 and the equivalent series resistance components are substantially the same. Is a multilayer ceramic filter including the two capacitor sections C ₁ and C ₂ .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic filter used for highly integrated surface mounting of small electronic devices or module components.

[0002]

2. Description of the Related Art Generally, a multilayer ceramic capacitor has a predetermined impedance-frequency characteristic according to its configuration. The impedance Z of the capacitor is the resonance frequency f
Below ₀ , Z = 1 / ωC, but above resonance frequency f ₀ , Z = ωL. As described above, above the resonance frequency f ₀ , the relationship with the relative permittivity of the dielectric material no longer exists, and only the noise component is present.

Here, C is the capacitance, ω = 2πf, and L is the inductance. F ₀ = １ ／ π (LC)
^Represented by ^1/2 . That is, the lower the capacitance of the capacitor, the higher the resonance frequency. By utilizing this characteristic, it is also possible to use a filter for passing a signal of a predetermined frequency component or blocking noise. In addition, since it is a laminated ceramic capacitor used for such an application, it is hereinafter referred to as a laminated ceramic filter.

However, such a multilayer ceramic filter operates according to the above-described principle, has only one resonance point, and is difficult to apply to an actual high-frequency circuit. For this reason, Japanese Unexamined Patent Application Publication No.
No. 68, in order to reduce the impedance to a certain value over a wide range from the low frequency range to the high frequency range,
Two multilayer ceramic capacitors having different capacitances have been proposed.

[0005] In Japanese Patent Application Laid-Open No. 8-162368, the width of a pair of internal electrodes constituting one of the capacitor portions is defined as:
There has been proposed a multilayer ceramic capacitor in which a pair of internal electrodes constituting the other capacitor portion have mutually different electrode widths. In addition, a multilayer ceramic capacitor has been proposed in which the internal electrodes constituting each capacitor section have the same electrode width and the number of stacked internal electrodes is different.

[0006]

However, the above-mentioned multilayer ceramic capacitor is a capacitor for obtaining low impedance in a wide frequency range from a low frequency region to a high frequency region. In the multilayer ceramic capacitor disclosed in Japanese Patent Application Laid-Open No. 8-162368, although there is a resonance point where the impedance is lowered at a specific frequency, there is no particular problem in using the capacitor, but the two resonance points are used as a filter. In operation,
The peak valley with sufficient impedance could not be obtained.

In particular, when used as a multilayer ceramic filter, it is desirable to lower the impedance at two resonance points generated at different frequencies, and if the impedances are not substantially the same, the impedance is reduced at the two resonance frequencies. There is a problem that a stable operation cannot be obtained due to a difference in signal selectivity.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a multilayer ceramic filter capable of deriving a stable selection characteristic by making impedances of two resonance points substantially the same and deriving a small size. To provide.

[0009]

According to a first aspect of the present invention, there is provided a multilayer ceramic filter including two capacitor portions each including internal electrodes facing each other with a dielectric layer interposed therebetween, wherein the internal electrodes of the two capacitor portions are provided. This is a multilayer ceramic filter in which capacitance values generated due to mutual opposition are different from each other, the electrode widths of internal electrodes constituting both capacitor portions are substantially the same, and the equivalent series resistance components are substantially the same. That is, a first dielectric layer in which a first internal electrode forming one capacitor section and a first internal electrode forming the other capacitor section are juxtaposed, and a second internal electrode forming one capacitor section And a second dielectric layer in which the other internal electrodes constituting the other capacitor part are juxtaposed,
A first internal electrode and a second internal electrode constituting each capacitor portion are laminated so as to face each other to form a laminate, and the two capacitor portions are connected in parallel to a pair of ends of the laminate. Is a multilayer ceramic filter having two built-in capacitor portions each having a terminal electrode connected thereto, wherein the two capacitor portions have mutually different capacitance values and substantially the same equivalent series resistance components.

According to a second aspect of the present invention, the internal electrode of the one capacitor portion is divided into a plurality of parts, and a plurality of capacitance components generated by facing the divided internal electrodes are connected in series. This is a laminated ceramic filter. That is, the first internal electrode and the second internal electrode constituting the one and the other capacitor portions have substantially the same electrode width, respectively, and the other capacitor portion has the first internal electrode divided into a plurality between the pair of terminal electrodes. The multilayer ceramic filter includes an electrode and a second internal electrode, and includes a capacitance component in which a plurality of capacitance components generated by opposing a plurality of locations of the first internal electrode and the second internal electrode are connected in series.

[0011]

As described above, in the first aspect, the capacitance values of the two capacitor sections are different, and the equivalent series resistance components are substantially the same. Therefore, the impedance-frequency characteristic of the two capacitor units has two resonance points,
In addition, the impedance attenuation at the two resonance points can be made substantially equal. This makes it very easy to selectively transmit two types of frequencies. here,
Since the electrode width of the internal electrode between the pair of terminal electrodes constituting one capacitor portion is the same as the electrode width of the plurality of divided internal electrodes constituting the other capacitor portion, one capacitor portion and the other capacitor electrode have the same electrode width. The equivalent resistance components of the capacitor section can be made substantially the same.

However, the structure is such that the terminal electrodes are formed at both ends of the laminated filter main body formed by laminating the dielectric layers and the internal electrodes, so that it is possible to achieve a very small size.

In order to increase the peak valley at the resonance point and sharpen the impedance curve, it is important to minimize the equivalent series resistance. In the multilayer ceramic filter of the present invention, the equivalent series resistance component can be reduced, the impedance curve becomes sharp, and noise of a required frequency can be passed digitally.

In the second invention, one capacitor portion is a capacitance component generated at a portion opposed to a pair of internal electrodes, and the other capacitor portion is a capacitance component generated at an internal electrode divided between a pair of terminal electrodes. Is composed of a series capacitance component. As a result, since the internal electrodes constituting the two capacitor portions can all be sandwiched between the same dielectric materials, the variation in Q value, equivalent series resistance value,
Since the thicknesses of the internal electrodes can be made the same, the occurrence of structural defects can be prevented.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multilayer ceramic filter according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a multilayer ceramic filter 1 according to the present invention.
FIG. FIG. 2A is a cross-sectional view taken along the line AA in FIG. ₁ , showing _one capacitor portion C1, and FIG.
(B) is a is a cross-sectional view sectional view taken along line B-B in FIG. 1, shows the other capacitor portion C _2, FIG. 3 (a), (b) shows an internal electrode formed on the dielectric layer It is a top view.

The multilayer ceramic filter of the present invention includes a multilayer filter (hereinafter, referred to as a filter main body) 10 and a pair of terminal electrodes 2 and 3 of the filter main body 10. And two capacitor sections C ₁ and C ₂ .

The filter body 10 includes dielectric layers 1a, 1
b, 1c (collectively denoted as 1) and the internal electrodes 2, 3, 4a to 4d (collectively denoted as 4) and 4a to 4c (collectively denoted as 5) disposed on the dielectric layer Are laminated.

The dielectric layer 1 is made of a dielectric ceramic such as barium titanate or strontium titanate, and is formed between the dielectric layers 1a and 1b, between the dielectric layers 1c and 1d, for example, as shown in FIG. On the first dielectric layer 1b shown in (a), a first internal electrode 2 constituting _one capacitor portion C1 is formed.
And the first divided constituting the other capacitor portion C ₂
Internal electrodes 4a, 4b, 4c, and 4d are formed.

The first internal electrode 2 constituting _one capacitor section C1 shown in FIG. 3A extends to one end of the dielectric layer 1b and the other capacitor section C1. The divided internal electrodes 4a, 4b, 4 constituting C ₂
c and 4d are divided and arranged in four from one end to the other end of the dielectric layer 1b, and the divided internal electrode 4a extends to one end of the dielectric layer 1b and is divided. The internal electrode 4d extends to the other end of the dielectric layer 1b.

One capacitor portion C is provided between the dielectric layers 1b and 1c, between the dielectric layers 1d and 1e, for example, on the second dielectric layer 1c shown in FIG. second internal electrodes 5a divided second constituting the internal electrode 3 and the other capacitor portion C ₂ constituting the _1, 5b, 5c are formed.

Then, the second internal electrode 3 constituting the second internal electrode 3 constituting _one capacitor section C ₁ shown in FIG. 3B extends to the other end of the dielectric layer 1c. cage, and the second internal electrodes 5a, 5b, 5c are arranged from one end of the dielectric layer 1c is divided into three to the other end is divided to constitute the other capacitor portion C ₂ ing. The divided internal electrodes 5a, 5b, 5c
Are the above-mentioned divided internal electrodes 4a, 4b, 4c, 4d
For example, the internal electrode 5a is located at the other end of the internal electrode 4a and the one end of the internal electrode 4b, and the internal electrode 5b is located at the other end of the internal electrode 4b. At one end of the internal electrode 4c, the internal electrode 5c is formed so as to face the other end of the internal electrode 4c and the one end of the internal electrode 5c, respectively.

The electrode widths of the internal electrodes 2 and 3 and the divided internal electrodes 4a to 4d and 5a to 5c, that is, the electrode widths connected to the terminal electrodes 6 and 7 have substantially the same width W. are doing. The internal electrodes 2, 3, 4, and 5 are Pt, Pd,
It is made of a simple substance of a noble metal such as Ag, or a material such as an alloy containing the same.

The dielectric layers 1b, 1c,.
And a filter body 10 formed by laminating a dielectric layer 1a on which no electrode is formed.
A terminal electrode 6 and a terminal electrode 7 are respectively formed on a pair of ends of the zero. Although the terminal electrodes 6 and 7 are not shown,
A thick underlayer conductor film made of, for example, an Ag-based material and a plating layer for facilitating solder bonding to a printed wiring board are formed on the surface of the thick underlayer conductor film from the filter body 10 side. For example, a Ni-based Ni-based conductor film
A plating layer and a solder plating layer are applied.

The terminal electrode 6 at one end of the filter body 10 is electrically connected to the internal electrode 2 and the divided internal electrode 4a, and the terminal electrode 7 at the other end is connected to the internal electrode 3
And is electrically connected to the divided internal electrode 4d.

With such a structure, the filter body 10
A predetermined capacitance component is formed in the dielectric layers 1b, 1c,... Of the portion facing the internal electrode 2 connected to the terminal electrode 6 and the internal electrode 3 connected to the terminal electrode 7 formed at the other end. occurs, one of the capacitor section C ₁ is constituted by these combined capacitance.

An internal electrode 4a connected to one terminal electrode 6 and an internal electrode 4d connected to the other terminal electrode 7 are provided.
, A capacitance component generated between the internal electrode 4a and the internal electrode 5a, a capacitance component generated between the internal electrode 5a and the internal electrode 4b, and a capacitance component generated between the internal electrode 4b and the internal electrode 5c. capacitance component, capacitance component generated between the internal electrode 5c and the internal electrode 4d are connected in series with each other, further the other capacitor portion C ₂ is constituted by a synthetic capacitance of the series capacitor component.

According to the above configuration, since the electrode widths of the internal electrodes 2 and 3 and the electrode widths of the internal electrodes 4 and 5 are the same, the capacitance value of _one capacitor C ₁ and one capacitor C ₁ Although the capacitance value of C ₂ is different from each other, the series resistance component (ESR) between the terminal electrodes 6 and 7 can be made substantially the same in both capacitor sections C ₁ and C ₂ .

This is because the internal electrode 2 and the internal electrode 4 are formed on the same dielectric layer, for example, 1b, on the internal electrode 3 and the internal electrode 5
Are formed on the same dielectric layer, for example, 1c, the electrode width is the same, and the distance between the pair of terminal electrodes 6 and 7 is the same for both. _1, conductor resistance of C ₂ is substantially the same.

Accordingly, the capacitance values of the _two capacitor sections C ₁ and C ₂ are different, and the equivalent series resistance components are substantially the same. The impedance-frequency characteristics of the _two capacitor sections C ₁ and C ₂ are, as shown in FIG.
And two resonance points a and b, and the impedance attenuation amounts of these two resonance points can be made substantially equal.
This makes it very easy to selectively transmit two types of frequencies.

For example, when the internal resistance components of the _two capacitor sections C ₁ and C ₂ are different, for example, as shown by an arrow a ′ in FIG. 4, the impedance of one resonance point a becomes large.

Further, since the internal electrodes 2, 3, 4, 5 constituting the two capacitor portions are arranged between the dielectric layers 1 made of the same dielectric material, the capacitor portions C
_1, the capacitance of C _2, Q value, the variation of the equivalent series resistance, it is possible to equalize the thickness of the internal electrodes 2, 3, 4, 5, to prevent the occurrence of structural defects that occur when laminated Can be.

In order to increase the peak valley at the resonance point and sharpen the impedance curve, it is important to minimize the equivalent series resistance in one or the other of the capacitor sections C ₁ and C ₂ . For example, 10
It is desirable to set it to mΩ or less.

FIGS. 5 and 6A and 6B show a multilayer ceramic filter showing another embodiment. 2 and 3
The same reference numerals are given to the same parts.

In the above embodiment, the other capacitor section C
Internal electrodes 4a to 4d, 5a to 5c obtained by dividing the configuration of ₂
Whereas it constituted by the capacitance component generated by the other in the capacitor section C ₂ of the present embodiment, in that with a series of internal electrodes 8 and 9 which are not divided as one capacitor section C ₁ is there. In addition, FIG.
Corresponds to the cross section of line B shows a cross-sectional structure of the other capacitor portion C _2.

When the internal electrodes 8 and 9 are compared with the internal electrodes 3 and 4 constituting _one capacitor section C1, the electrode width of the internal electrodes 8 and 9 is substantially equal to the electrode width of the internal electrodes 2 and 3. They have the same width W. The opposing area of the internal electrode 8 and the internal electrode 9 is smaller than the opposing area of the internal electrodes 2 and 3 constituting _one capacitor section C1.

That is, the length of the internal electrodes 8 and 9 (the length in the direction between the two terminal electrodes) is shorter than those of the internal electrodes 2 and 3.

[0038] More this, the opposing area of the other of the capacitor section C ₂ side of the internal electrodes 8 and 9, one of the capacitor section C ₁
Since the area of the internal electrodes 2 and 3 is smaller than the facing area of the internal electrodes 2 and 3, and the number of the internal electrodes 2 and 8 and the number of the internal electrodes 3 and 9 are the same, The capacitance values of the _two capacitor sections C ₁ and C ₂ are different, and the equivalent series resistance components can be substantially the same. As a result, the impedance-frequency characteristics of the _two capacitor portions C ₁ and C ₂ can make the impedances of the two resonance points substantially equal as shown in FIG. 4, and it is very easy to selectively transmit two types of frequencies. Become.

In the first embodiment, the number of divided internal electrodes 4 and 5 can be arbitrarily changed according to the frequency of the resonance point.

In the above-described embodiment, the area facing the internal electrodes 2 and 3 and the number of divided internal electrodes 4 and 5 and their facing areas, and the area facing the internal electrodes 8 and 9 are as follows. It can be arbitrarily changed according to the frequencies of the two resonance points.

In addition, minimizing the equivalent resistance component is as follows:
This is important for steepening the resonance characteristics. For this reason, for example, a thin film dielectric layer in which the dielectric layer is formed by a thin film technique, a spin coating method, or the like is advantageous. At this time, the internal electrodes 2,
For 3, 4, 5, 8, and 9, it is effective to form a metal electrode thin film by a thin film technique and a metal layer by a spin coating method and to perform an etching treatment in a predetermined shape.
It is also possible to form a thick resin conductor film which can be formed by a thermosetting treatment or a thin film technique.

[0042]

According to the present invention, two capacitor sections having different capacitances and substantially the same equivalent series resistance component are arranged in one filter main body.

This makes it easy to handle with a small size and to provide two resonance points in the impedance-frequency characteristics. Moreover, since the impedance at the resonance point can be made substantially the same, a multilayer ceramic filter that is very easy to handle is obtained.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a multilayer ceramic filter according to the present invention.

FIGS. 2A and 2B show a cross section of the multilayer ceramic filter of the present invention. FIG. 2A is a cross sectional view taken along line AA in FIG. 1, and FIG.
It is sectional drawing of the BB line in FIG.

FIGS. 3A and 3B are plan views showing internal electrodes used in the multilayer ceramic filter of the present invention, wherein FIGS. 3A and 3B show internal electrodes formed on different dielectric layers. FIGS.

FIG. 4 is a characteristic diagram showing frequency-impedance characteristics of the multilayer ceramic filter of the present invention.

FIG. 5 is a sectional view corresponding to line BB of FIG. 1 in another multilayer ceramic filter of the present invention.

6A and 6B are plan views showing internal electrodes used in the multilayer ceramic filter shown in FIG. 5, wherein FIGS. 6A and 6B show internal electrodes formed on different dielectric layers.

[Explanation of symbols]

10 Filter body 1, 1a, 1b, 1c Dielectric layer 2 First internal electrode of one capacitor section 3 Second internal electrode of one capacitor section 4, 8 ... other capacitor portion of the first internal electrode 5,9 ... other second internal electrode 4a~4d capacitor portion, bodies 5a to 5c ... divided internal electrodes 6, 7 ... terminal electrodes C ₁ one of the capacitor section · · · C ₂ · · · other capacitor portion

Claims (2)

[Claims] 1. A multilayer ceramic filter having two built-in capacitor portions each including internal electrodes opposed to each other via a dielectric layer, wherein a capacitance value generated by the internal electrodes of the two capacitor portions facing each other is mutually reduced. A multilayer ceramic filter characterized in that the electrode widths of the internal electrodes constituting both capacitor portions are substantially the same and the equivalent series resistance components are substantially the same. 2. An internal electrode of said one capacitor portion is divided into a plurality of parts, and a plurality of capacitance components generated by facing the divided internal electrodes are connected in series. The multilayer ceramic filter according to claim 1.