JPH0562855A - Laminated porcelain capacitor - Google Patents

Abstract

PURPOSE:To obtain the title capacitor wherein its resistivity and its reliability are ensured and its capacity can be made large by a method wherein the average particle size of crystal particles in a region close to an electrode layer of a dielectric porcelain layer is made smaller than the particle size of crystal particles in the intermediate region of the electrode layer. CONSTITUTION:The title capacitor is provided with the following: a dielectric porcelain layer; a first electrode layer arranged on one side of the porcelain layer; and a second electrode layer arranged on the other side of the porcelain layer. In such a laminated porcelain capacitor, the average particle size of crystal particles in a region close to the electrode layer of the dielectric porcelain layer is made smaller than the particle size of crystal particles in the intermediate region of the electrode layer. For example, when a porcelain material in which Nd2O3 and MnO in very small quantities have been added to a main component composed of BaTiO3 and BaZrO3 is used as a dielectric, the average particle size of crystal particles of porcelain layers 1a;, 1b' in the center between electrode layers 3', 3a', 3b' is set at 5 to 6mum, and the average particle size of crystal particles of porcelain layers 4', 2a', 4a', 2b' on their both sides is set at 0.2 to 0.4mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly reliable laminated ceramic capacitor.

[0002]

2. Description of the Related Art A laminated ceramic capacitor composed of a plurality of dielectric porcelain layers and internal electrode layers arranged between the porcelain layers is used in various fields.

[0003]

By the way, in order to reduce the size or increase the capacity of the laminated ceramic capacitor, it is necessary to reduce the thickness of the dielectric ceramic layer and increase the crystal grain size to some extent. .. However, when the particle size is increased in the porcelain capacitor, the number of particles arranged in the thickness direction between the pair of electrodes is reduced, and in the extreme case, the number is one. As a result, the specific resistance (resistivity) is lowered, the reliability is lowered, and the tan δ is lowered.

Therefore, an object of the present invention is to provide a laminated ceramic capacitor capable of achieving a large capacity while ensuring the specific resistance and reliability.

[0005]

The present invention for achieving the above object provides a dielectric porcelain layer and a first electrode layer disposed on one side of the porcelain layer and the other side of the porcelain layer. In the laminated ceramic capacitor including the arranged second electrode layer, the average particle size of the crystal particles in the region of the dielectric ceramic layer close to the first and second electrode layers is the first and the second. The present invention relates to a laminated ceramic capacitor characterized by being smaller than the grain size of crystal grains in the intermediate region of the electrode layer.

[0006]

The region near the electrode layer in which the average grain size of the crystal grains is small contributes to the improvement of the specific resistance. Particles with a small particle size in the vicinity of the electrode layer are disadvantageous in terms of capacity, but in the vicinity of the electrode layer, a parallel connection circuit of microcapacitors based on a crystal with a small particle size is equivalently formed, so No decrease occurs.

[0007]

First Example First, 78 mol% of BaTiO ₃ (barium titanate) and BaZrO ₃ (barium zirconate) were used.
A first porcelain material prepared by adding a small amount of Nd ₂ O ₃ (neodymium oxide) and MnO (manganese oxide) to the main component composed of 22 mol% was prepared. The first porcelain material was calcined and was a powder having an average particle size of 0.3 to 0.6 μm. In addition, BaTiO ₃ 78 mol% and BaZrO
_A second porcelain material was prepared in which a slight amount of Nd ₂ O ₃ and MnO was added to the main component composed of 32 mol% of ZrO ₂ (zirconium oxide) and 1.5 mol% of ZrO ₂ . This second porcelain material is a powder that has been calcined and has an average particle size of 0.1 to 0.2 μm.

Next, a slurry is prepared using the first porcelain material, and the slurry has a thickness of about 8 μ shown in FIG.
Dielectric porcelain raw sheet (green sheet) 1 of m was made.

Next, a slurry or paste is prepared by using the above-mentioned second porcelain material, and the slurry or paste is applied onto the porcelain green sheet 1 by a printing method to form a fine particle porcelain having a thickness of 1 to 2 μm shown in FIG. Layer 2 was formed.

Next, after drying the one shown in FIG. 1,
The Pd (palladium) paste is applied on the fine particle porcelain layer 2 in a predetermined pattern and dried to form the electrode layer 3 shown in FIG.
It was formed to a thickness of ˜3 μm.

Next, the paste of the second porcelain material was applied onto the electrode layer 3 by a printing method and dried to form the fine particle porcelain layer 4 shown in FIG. 3 in a thickness of 1 to 2 μm.

Next, the same porcelain green sheet as the lowermost porcelain green sheet 1 in FIG. 3 was placed on the fine grain porcelain layer 4 and these were lightly pressure-bonded to improve mutual adhesion.

Next, as shown in FIG. 4, on the large particle porcelain layer 1a made of the first porcelain material, the fine particle porcelain layer 2, the electrode layer 3, and the fine particle porcelain layer 4 which are substantially the same as the fine particle porcelain layer 2 are formed. Two
a, the electrode layer 3a, and the fine particle porcelain layer 4a are sequentially formed, and further, the large particle porcelain layer 1b, the fine particle porcelain layer 2b, the electrode layer 3b,
The fine particle porcelain layer 4b is repeatedly formed, and finally the first and second layers are formed.
The cover sheets 5 and 6 made of porcelain material having a thickness of about 150 μm were stacked and pressure-bonded.

Next, the laminate was fired at 1320 ° C. in the atmosphere to obtain a sintered body. FIG. 5 is an explanatory view of a sintered body, and each raw material porcelain layer 1, 1a, 1b, 2, 2a of FIG.
2b, 4, 4a, 4b, 5, 6 corresponding to the sintered ceramic layers 1 ', 1a', 1b ', 2', 2a ', 2b',
4 ', 4a', 4b ', 5', 6'occur. Also, the internal electrode layers 3 ', corresponding to the electrode layers 3, 3a, 3b,
3a 'and 3b' are generated. In FIG. 5, for convenience of explanation,
Although the sintered body is shown separately for each porcelain layer, they are actually integrated. The average grain size of the crystal grains of the central porcelain layers 1a 'and 1b' between the electrode layers 3 ', 3a' and 3b 'is 5 to 6
μm, and the porcelain layers 4 ′, 2 a ′, 4 a ′ on both sides of this are
The average particle size of the 2b ′ crystal particles is 0.2 to 0.4 μm. The fine particle porcelain layers 2, 4, 2a, 4a, 2b, 4 of FIG.
Since b contains ZrO ₂ in an excessive amount, it is difficult to generate crystals with a large grain size during firing. The internal electrode layers 3 ', 3 after sintering
The thickness of the porcelain layer between a'and 3b 'is about 7 μm.

Next, Ag paste is applied to the side surfaces of the sintered body shown in FIG. 5 and baked to form a pair of external electrodes 7 and 8.

When the electrical characteristics of the laminated ceramic capacitor of FIG. 5 were measured, the apparent relative permittivity ε at 20 ° C. was 18600, and the dielectric loss tan δ at 20 ° C. was 4.2.
%, The specific resistance at 150 ° C. was 7.1 × 10 ¹² Ωcm, and the breakdown voltage V _BD was 680V. For comparison, the porcelain layers 2, 4, 2a, 4a, 2b, 4b of FIG.
A laminated porcelain capacitor the same as that of the example except that the same first porcelain material as a and 1b was used and the electrical characteristics were measured in the same manner. ε was 19300, tan δ was 6.3%, and the specific resistance was 6.3%. Was 5.2 × 10 ¹¹ Ωcm and V _BD was 410V.

As is apparent from the above comparison, although the apparent relative permittivity is slightly lowered by the structure of this embodiment, tan δ, specific resistance and V _BD are improved. This is because there are porcelain layers 4 ', 2a', 4a ', 2b' having a small grain size near the internal electrode layers 3 ', 3a', 3b '.
This is because the insulating property is improved.

[0017]

[Second Embodiment] A porcelain raw sheet 11 having the same composition as the porcelain raw sheet 1 in the embodiment of FIG.
An electrode layer 12 was formed by applying a Pd (palladium) paste containing fine particles of ZrO ₂ (zirconium oxide) of about 0.2 μm, and these were laminated as shown in FIG.

Next, the laminated body shown in FIG.
By firing at 0 ° C., a sintered body 13 shown in FIG. 7 was obtained. The sintered body 13 has an average particle size of 5 to 5 between the pair of electrode layers 12 '.
Large particle porcelain layer 11a of about 6 μm and average particle size of 0.2 to
It has fine porcelain layers 11b and 11c of about 0.4 μm. Next, the external electrodes 14 and 15 were formed to complete the laminated ceramic capacitor.

When the electrical characteristics of this laminated ceramic capacitor were measured, the apparent relative permittivity ε at 20 ° C. was 1800.
The dielectric loss tan δ at 0 and 20 ° C. is 4.1%, the specific resistance at 150 ° C. is 4.1 × 10 ¹² Ωcm, and the breakdown voltage V _BD is 710.
It was V.

In this second embodiment, ZrO ₂ in the electrode layer 12 of FIG. 6 diffuses into the porcelain near the electrode layer 12 during firing. As a result, the growth of crystal grains in the vicinity of the electrode layer 12 is suppressed, and as shown schematically in FIG. 7, the porcelain layer 11 made of particles having a small grain size is disposed in the vicinity of the electrode layer 12 '.
b and 11c occur, and the characteristics are improved as in the first embodiment.

[0021]

MODIFICATION The present invention is not limited to the above-described embodiments, and the following modifications are possible, for example. (1) The composition of the porcelain is not limited to the examples,
Other various porcelain compositions can be used. (2) The porcelain layers 2 and 4b of FIG. 4 can be omitted.

[0022]

As is apparent from the above, according to the present invention, miniaturization and large capacity can be achieved without deterioration of specific resistance, breakdown voltage and dielectric loss.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a porcelain green sheet and a fine particle porcelain layer for explaining a method for manufacturing a laminated porcelain capacitor of a first embodiment.

FIG. 2 is a cross-sectional view showing a state in which an electrode layer is formed on the porcelain layer of FIG.

3 is a cross-sectional view showing a state in which a fine particle porcelain layer is formed on the electrode layer of FIG.

FIG. 4 is a cross-sectional view showing a laminated body.

FIG. 5 is a sectional view schematically showing a laminated ceramic capacitor.

FIG. 6 is a cross-sectional view showing a laminated body of a second embodiment.

FIG. 7 is a sectional view schematically showing a part of a laminated ceramic capacitor of a second embodiment.

[Explanation of symbols]

 1a ', 1b' Large particle porcelain layer 4 ', 2a', 4a ', 2b' Small particle porcelain layer 3 ', 3a', 3b 'Internal electrode layer

Claims (1)

[Claims] 1. A laminated ceramic capacitor comprising a dielectric porcelain layer, a first electrode layer arranged on one side of the porcelain layer, and a second electrode layer arranged on the other side of the porcelain layer. In, the average grain size of the crystal grains in the region of the dielectric porcelain layer close to the first and second electrode layers is smaller than the grain size of the crystal grains in the intermediate region of the first and second electrode layers. Laminated porcelain capacitor characterized by.