JPH09129490A - Laminated capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated capacitor having a high quality factor on a high frequency region and also having no defect in the internal structure. SOLUTION: A capacitor is formed by alternately laminating two electrode groups 24a and 24b, consisting of internal electrodes 23a to 23d having prescribed width D and thickness t2 , and dielectric layers 21A, 21C and 21E by interposing dielectric layers 21B and 21D and leaving the prescribed interval t1 . At this instance, the width D and the thickness t2 of the internal electrodes 23a to 23d and the interval t1 between the two internal electrodes of the electrode groups 24a and 24b are set in such a manner that the ratio (D/t1 ) of the width D and the interval t1 becomes the prescribed value of 0.86 to 5.60 and the ratio t1 /t2 of the interval t1 and the thickness t2 becomes the prescribed value of 1.5 to 29.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer capacitor, and more particularly to a high-frequency multilayer capacitor having a small capacitance.

[0002]

2. Description of the Related Art FIGS. 2 to 4 show a conventional multilayer capacitor. 2 is an exploded perspective view, FIG. 3 is a plan view, and FIG.
3 is a sectional view taken along line AA of FIG.

[0003] In the drawing, reference numeral 10 denotes a multilayer capacitor in which a dielectric body 13 formed by alternately laminating dielectric layers 11 and internal electrodes 12 and internal electrodes are alternately connected in parallel at both ends of the dielectric body 13. And a pair of external electrodes 14.

The internal electrode 12 is composed of an internal electrode piece 12a provided near the central region of the dielectric layer 11 and an internal electrode lead portion 12b provided along the external electrode 14 and connected to the external electrode 14. The internal electrode piece 12a is connected to the external electrode 14 via the internal electrode lead-out portion 12b.

[0005] The dielectric layer 11 is formed of a ceramic sintered body on a rectangular sheet, and the ceramic sintered body is formed of a dielectric ceramic material containing, for example, barium titanate as a main component. The internal electrode 12 is formed of a metal thin film obtained by sintering a metal paste. As the metal paste, for example, an electrode mainly containing a noble metal material such as Pd or Ag-Pd is used. It is formed of the same material as the part electrode 12 without the external electrode 14, and its surface is plated with solder to improve solder wettability.

[0006]

In recent years, communication frequencies used in mobile communication devices and the like have been changed to high frequency bands (G-bands).
(Hz band), and accordingly, multilayer capacitors used in mobile communication devices and the like have to be adapted to the high frequency band.

In order to make a multilayer capacitor compatible with a high frequency band, it is necessary to increase the Q value of a multilayer capacitor having a low capacitance, for example, a capacitance of 10 pF or less in a high frequency range.

As described above, in order to increase the Q value of a low-capacitance multilayer capacitor in a high-frequency range, it is necessary to reduce the electric resistance of internal electrodes.

As a method of reducing the electric resistance of the internal electrode, there are methods of increasing the area of the internal electrode and increasing the thickness of the internal electrode.

However, when the area of the internal electrodes is increased, the capacitance becomes too large. Therefore, it is necessary to increase the distance between the internal electrodes and reduce the number of layers.
For this reason, the electric resistance between the internal electrodes increases or the Q value decreases.

When the internal electrode is made thicker, the electric resistance of the internal electrode is lowered. However, due to the local accumulation of the internal electrode, the portion is locally thickened and the internal strain is increased.
Due to oxidative expansion of the internal electrode made of d or the like, the incidence of structural defects (delamination, cracks, etc.) increases.

In view of the above problems, an object of the present invention is to provide a multilayer capacitor having a high Q value in a high frequency range and free from internal structural defects.

[0013]

In order to achieve the above-mentioned object, the present invention has at least a predetermined width D and a thickness t ₂ which are provided in parallel with each other with a dielectric layer interposed and at a predetermined interval t _1. An element body formed by alternately laminating an electrode group composed of two internal electrodes and a dielectric layer, and a pair of external electrodes in which the electrode groups are alternately connected in parallel at both ends of the element body are provided. So that the ratio (D / t ₁ ) of the width D of the internal electrode to the interval t ₁ between the two internal electrodes in the electrode group becomes a predetermined value of 0.86 or more and 5.60 or less. Also, the ratio (t ₁ / t ₂ ) of the distance t ₁ between the two internal electrodes in the electrode group and the thickness t ₂ of the internal electrodes is set to a predetermined value of 1.5 or more and 29.0 or less. the interval t ₁ between the two inner electrodes in the width D and the thickness t ₂ and the electrode group of the internal electrodes is set Suggest layer capacitor.

According to the multilayer capacitor, an electrode group consisting of at least two internal electrodes having a predetermined width D and a thickness t ₂ which are provided in parallel with each other with a dielectric layer interposed therebetween and having a predetermined interval t ₁ therebetween, and a dielectric A multilayer capacitor is formed by providing a pair of external electrodes that alternately connect the electrode groups in parallel at both ends of an element body that is formed by alternately stacking body layers. Here, the ratio (D / t ₁ ) of the width D of the internal electrode to the interval t ₁ between the two internal electrodes in the electrode group is set to a predetermined value of 0.86 or more and 5.60 or less. The ratio (t ₁ / t ₂ ) of the distance t ₁ between the two internal electrodes in the electrode group and the thickness t ₂ of the internal electrodes is 1.5 or more and 29.0 or more.
The width D and the thickness t ₂ of the internal electrode and the interval t ₁ between the two internal electrodes in the electrode group are set so as to have the following predetermined values.

By setting the ratio (D / t ₁ ) to the interval t ₁ between the two internal electrodes in the electrode group to a predetermined value of 0.86 or more and 5.60 or less, the two electrodes The electrode group composed of the internal electrodes has the same function as an electrode having the same thickness, and it is possible to reduce the loss in the internal electrodes in the high frequency range and also reduce the electrical resistance. Furthermore, the ratio (t ₁ / t ₂ ) of the distance t ₁ between the two internal electrodes in the electrode group and the thickness t ₂ of the internal electrodes is set to 1.5.
By setting the internal electrode to a predetermined value of 29.0 or less, the internal electrode can be formed to be as thin as necessary, so that internal strain due to local accumulation of the internal electrode can be avoided.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an external view of the multilayer capacitor according to the present embodiment, FIG. 5 is an exploded perspective view of main parts, and FIG. 6 is a side sectional view. In FIG. 1, reference numeral 20 is a multilayer capacitor, and an element body 21 formed by laminating dielectric layers and internal electrodes,
It is composed of a pair of external electrodes 22a, 22b provided so as to be connected to the internal electrodes 23 at both ends of the element body 21.

Further, as shown in FIGS. 5 and 6, the element body 21 has therein, for example, first to fifth dielectric layers 21A to 21A.
21E, the internal electrodes 23a and 23b are formed on the upper and lower surfaces of the second dielectric layer 21B, and one electrode group 24a is formed.

These internal electrodes 23a and 23b have the same shape, are connected to one external electrode 22a at one longitudinal end of the dielectric layer 21B, and extend from this one end toward the other end by a predetermined length. There is. The distance t ₁ between the internal electrodes 23a and 23b is set to 18 μm, and the width D of each internal electrode 23a and 23b is 100 μm.
The thickness t ₂ is set to 12 μm.

Similarly, internal electrodes 23c and 23d are formed on the upper and lower surfaces of the fourth dielectric layer 21D, respectively.
One electrode group 24b is configured. These internal electrodes 23c, 23d also have the same shape as described above, and the other external electrode 22 is formed at the other end in the longitudinal direction of the dielectric layer 21D.
It is connected to b and is formed by extending a predetermined length from here to one end side. In addition, these internal electrodes 23c, 23
The distance t ₁ , the width D, and the thickness t ₂ of d are the same as those of the second dielectric layer 21.
18 μm, 100 μ, similar to the internal electrode formed on B
m and 12 μm.

As a result, the one electrode group 24a and the other electrode group 24b overlap each other in a predetermined area in the substantially central portion thereof with the third dielectric layer 21C interposed therebetween, and their respective planes face each other for high frequency. A small capacitance is obtained.

Here, the width D of the internal electrodes 23a-23d
And the ratio (D / t ₁ ) of the distance t ₁ between the two internal electrodes in the electrode group to a predetermined value of 0.86 or more and 5.60 or less, and the two internal electrodes in the electrode group. the spacing t ₁ between, as the ratio of the thickness t ₂ of the internal electrodes (t ₁ / t ₂₎ becomes a predetermined value of 1.5 or more 29.0 or less, and the width D of the internal electrode 23a~23d Thickness t _{2 and} electrode group 24
It is preferable to set the interval t ₁ between the two internal electrodes at a and 24b.

That is, when D / t ₁ <0.86 or when t ₁ / t ₂ > 29.0, the Q value in the high frequency range is lowered. Further, when D / t ₁ > 5.60, the latent internal stress strain increases, cracks and delamination easily occur, and structural defects increase. Further, when t ₁ / t ₂ <1.5, a thick internal electrode and a thin dielectric layer are laminated,
This leads to deterioration of the stacking accuracy, and tends to cause cracks and dielectric breakdown.

According to the present embodiment having the above-mentioned configuration,
The electrode groups 24a and 24b composed of two internal electrodes have the same function as the internal electrodes having the same thickness, and the loss in the internal electrodes in the high frequency region can be reduced and the electric resistance can be reduced, so that the high frequency region can be reduced. It is possible to increase the Q value at.

Further, since the internal electrodes 23a to 23d can be formed to be as thin as necessary, internal strain due to local accumulation of the internal electrodes 23a to 23d can be avoided, so that delamination due to oxidative expansion of the internal electrodes made of Pd or the like can be avoided. The occurrence rate of structural defects such as cracks and cracks can be significantly reduced, and a highly reliable multilayer capacitor can be obtained.

Each set value in this embodiment is an example, and the present invention is not limited to this. For example, the internal electrode 2
Even when the intervals t ₁ , width D, and thickness t ₂ of 3a to 23d are set to 58 μm, 50 μm, and 2 μm in the experiment, respectively, almost the same effect is obtained. Also,
The set value range of each value described above is obtained by an experiment.

Further, in this embodiment, two sets of electrode groups 24 are provided.
Although a capacitor is formed by laminating a and 24b, the same effect can be obtained by forming a capacitor in which a plurality of electrode groups are laminated, and as shown in FIG. Also in the case of a multilayer capacitor in which two electrode groups are provided in parallel, the same effect can be obtained as long as each electrode group is set within the set value range described above.

Further, in the present embodiment, one internal electrode group is composed of two internal electrodes, but one internal electrode group may be composed of three or more internal electrodes.

[0028]

As described above, according to the present invention, 2
An electrode group consisting of a single internal electrode functions similarly to an electrode having the same thickness, and it is possible to reduce loss in the internal electrode in the high frequency range and electrical resistance, thus increasing the Q value in the high frequency range. be able to. Furthermore, since the internal electrodes can be formed to the minimum necessary thickness, internal strain due to local accumulation of the internal electrodes can be avoided, so that structural defects (delamination, cracks, etc.) due to oxidative expansion of the internal electrodes made of Pd or the like occur. The rate can be significantly reduced, and a highly reliable multilayer capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 is an external view showing a multilayer capacitor according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a conventional multilayer capacitor.

FIG. 3 is a cross-sectional plan view showing a conventional multilayer capacitor.

FIG. 4 is a sectional view taken along the line AA of FIG.

FIG. 5 is an exploded perspective view of essential parts of the multilayer capacitor according to the embodiment of the present invention.

FIG. 6 is a side sectional view of the multilayer capacitor according to the embodiment of the present invention.

FIG. 7 is an exploded perspective view of essential parts showing another embodiment of the present invention.

[Explanation of symbols]

20 ... Multilayer capacitor, 21 ... Element body, 21A-21E ...
Dielectric layers, 22a, 22b ... External electrodes, 23, 23a ...
23d ... internal electrodes, 24a, 24b ... electrode group.

Claims (1)

[Claims] 1. An electrode group composed of at least two internal electrodes having a predetermined width D and a thickness t ₂ and arranged in parallel with a dielectric layer interposed at a predetermined interval t ₁ and the dielectric layer are alternated. And a pair of external electrodes in which the electrode groups are alternately connected in parallel at both ends of the element body, and the width D of the internal electrode and 2 in the electrode group. The ratio (D / t ₁ ) to the interval t ₁ between the two internal electrodes is a predetermined value of 0.86 or more and 5.60 or less, and the interval t ₁ between the two internal electrodes in the electrode group is The width D and the thickness t of the internal electrode are set so that the ratio (t ₁ / t ₂ ) of the internal electrode to the thickness t ₂ of the internal electrode becomes a predetermined value of 1.5 or more and 29.0 or less.
_{2 and} the interval t between two internal electrodes in the electrode group
A multilayer capacitor characterized in that ₁ is set.