Multilayered ceramic capacitor

A technology of multilayer ceramics and capacitors, which is applied in the direction of laminated capacitors, capacitors, fixed capacitors, etc., can solve the problems of insulation resistance reduction and high manufacturing cost, and achieve the effect of small insulation resistance reduction

Active Publication Date: 2009-09-23
KYOCERA CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] However, the multilayer ceramic capacitor using the dielectric layer containing composite particles disclosed in the above-mentioned Patent Document 1 has a problem in that, in the evaluation of the high-temperature load life, the insulation resistance gradually decreases with the time left at high temperature.
[0008] This reoxidation treatment requires labor, time, and expense similar to those of the firing process, which causes high manufacturing costs.

Method used

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no. 1 Embodiment approach

[0029] by figure 1 The multilayer ceramic capacitor of the present invention will be described in detail based on the schematic cross-sectional view of FIG.

[0030] Such as figure 1 As shown, in the multilayer ceramic capacitor of the present invention, external electrodes 3 are formed at both ends of the capacitor body 1 . The external electrodes 3 are formed by, for example, sintering Cu or an alloy paste of Cu and Ni.

[0031] The capacitor main body 1 is formed by alternately laminating dielectric layers 5 and internal electrode layers 7 made of dielectric ceramics. exist figure 1 In , the laminated state of the dielectric layer 5 and the internal electrode layer 7 is shown in simplified form, but the multilayer ceramic capacitor of the present invention is a laminated body of as many as several hundred layers of the dielectric layer 5 and the internal electrode layer 7 .

[0032] The dielectric layer 5 made of dielectric ceramics includes crystal grains 9 and grain b...

no. 2 Embodiment approach

[0091] Next, a second embodiment of the present invention will be described, and descriptions that overlap with the first embodiment will be omitted in some cases. In this embodiment, when the average grain size of the crystal grains 9 constituting the multilayer ceramic capacitor is x and the standard deviation is σ, the coefficient of variation of the grain size represented by x / σ is preferably 40%. the following.

[0092] When the coefficient of variation of the grain size of the crystal grains 9 is 40% or less, there is an advantage in that it is possible to suppress a decrease in insulation resistance that occurs with time in a high-temperature load test.

[0093] In this case, the coefficient of variation of the grain size of the crystal grains 9 is more preferably 37% or less. If the coefficient of variation of the particle size of the crystal grains 9 is 37% or less, it is advantageous in that the insulation resistance after the high-temperature load test for 100 hour...

Embodiment I

[0105] First, prepare BT powder, BCT powder (Ba 0.95 Ca 0.05 TiO 3 ), MgO, MnCO 3 , V 2 o 5 and oxide powders of rare earth elements, and these various powders were mixed in the ratio shown in Table 1. As these raw material powders, powders with a purity of 99.9% were used. In addition, the average particle diameters of the BT powder and the BCT powder were all 100 nm in sample No. 1-22 and 24-27 of Table 1. In addition, for sample No. 23, BT powder with an average particle diameter of 100 nm and BCT powder with an average particle diameter of 150 nm were used. The Ba / Ti ratio of the BT powder was 1.001, and the Ba / Ti ratio of the BCT powder was 1.003. The sintering aid uses SiO 2 =55, BaO=20, CaO=15, Li 2 A glass powder composed of O=10 (mol%). The glass powder was added in an amount of 1 part by mass relative to 100 parts by mass of the BT powder and the BCT powder.

[0106] Next, using zirconia beads having a diameter of 5 mm, a mixed solvent of toluene and alcoh...

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Abstract

The invention provides a multilayered ceramic capacitor which in a high-temperature loading test, can be inhibited from decreasing in insulation resistance with time and whichcan have high insulating properties even when produced without via a reoxidationstep. The multilayered ceramic capacitor is formed by alternately superposing dielectric layers made of dielectric porcelain and inner-electrode layers. The dielectric porcelain is constituted of first crystals comprising crystal particlescomprising barium titanate as the main component and having a calcium concentration of 0.2 at.% or lower and second crystals comprising crystal particles having a calcium concentration of 0.4 at.% or higher. The ratios (C2 / C1) between theconcentrations (C1) of magnesium and rare earth elements in a surface layer of the crystal particles constituting the first crystals and the concentrations (C2)of magnesium and the rare earth elements in a central part of the crystal particles (9a) constituting the first crystals are higher than the corresponding concentration ratios (C4 / C3) in the crystal particles (9b) constituting the second crystals. When the areal proportion of the crystal particles of the first crystals and that of the crystal particles of the second crystals are expressed by a and b, respectively, then b / (a+b) is 0.5-0.8.

Description

technical field [0001] The present invention relates to a multilayer ceramic capacitor, in particular to a small and high-capacity multilayer ceramic capacitor in which the dielectric layer contains barium titanate grains with different Ca concentrations. Background technique [0002] In recent years, with the popularization of mobile devices such as mobile phones and the increase in speed and frequency of semiconductor elements that are the main components of personal computers and the like, there is an increasing demand for smaller and higher capacity multilayer ceramic capacitors mounted in such electronic devices. come higher. Therefore, the dielectric layers constituting the multilayer ceramic capacitor need to be thinned and multilayered. [0003] For example, Patent Document 1 describes that as a dielectric powder constituting a dielectric ceramic, a barium titanate powder (BCT powder) in which a part of the A site (site) is replaced by Ca and a barium titanate powde...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01G4/12C04B35/46
CPCC04B2235/3418C04B2235/3239H01G4/30C04B2235/85C04B2235/36C04B2235/3215C04B2235/663C04B2235/79C04B35/4682C04B2235/3208C04B2235/3203C04B2235/3262H01G4/1227C04B2235/3224C04B2235/3225C04B2235/785C04B35/46H01G4/12
Inventor 山崎洋一大铃英之藤冈芳博福田大辅
Owner KYOCERA CORP
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