JP2016056076A - Laminated ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated ceramic capacitor having higher high-temperature load reliability than that of conventional laminated ceramic capacitors.SOLUTION: In a laminated ceramic capacitor 50 comprising a ceramic laminate (capacitor body) 10 having a plurality of dielectric ceramic layers 11 formed of a dielectric ceramic and a plurality of internal electrodes 12 laminated to each other through the dielectric ceramic layer 11, the dielectric ceramic layers 11 are formed of a dielectric ceramic containing a perovskite-type compound including Ba and Ti, and Zr, Mn, and V, and having a ratio of the molar amount of Zr to the total molar amount of Mn and V in a range of 10-150%, the ratio of the molar amount of Zr to the total molar amount of Mn and V is 40-100%, and the average thickness of the internal electrode 12 is 0.5 μm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multilayer ceramic capacitor, and more particularly, to a multilayer ceramic capacitor including a ceramic multilayer body (capacitor body) having a plurality of dielectric ceramic layers and a plurality of internal electrodes laminated via the dielectric ceramic layers.

  In recent years, with the reduction in size and weight of electronic devices, multilayer ceramic capacitors that are small in size and capable of acquiring a large capacity are widely used. For example, the multilayer ceramic capacitor is externally connected to the outer surface of a multilayer body having a plurality of dielectric layers and a plurality of internal electrodes disposed at a plurality of interfaces between the dielectric layers so as to be electrically connected to the internal electrodes. Those having a structure in which electrodes are arranged are widely known.

As such a multilayer ceramic capacitor, a general formula ABO ₃ (where A is one or more elements selected from Ba, Ca, Sr and Mg, and B is Ti, Zr and Hf). A perovskite-type crystal represented by [A] / [B] (molar ratio) of 0.990 ≦ [A] / [B] <1.03) A main component including a compound having a structure, a first subcomponent such as MgO, a second subcomponent which is a sintering aid, and an oxide of rare earth R (where R is Y, Dy, Tb, Gd and Ho) A third subcomponent including at least one selected from the group consisting of: a fourth subcomponent including MnO; and a fifth subcomponent that is an oxide of Re (rhenium). The ratio of subcomponents is as follows: first subcomponent: 0.1 to 3 mol, second subcomponent : Dielectric of 0.1 to 12 mol, third subcomponent: 0.01 to 10 mol, fourth subcomponent: 0.05 to 1.0 mol, fifth subcomponent: 0.01 to 1.0 mol A multilayer ceramic capacitor having a dielectric layer using a body ceramic composition and an internal electrode layer has been proposed.

  In the case of this multilayer ceramic capacitor, it is said that the dielectric layer can be thinned and the product can be miniaturized.

  However, in recent years, multilayer ceramic capacitors have come to be used under various severe conditions and environments. Even in the multilayer ceramic capacitor disclosed in Patent Document 1, for example, high temperature load reliability is not always necessary. It cannot be said that sufficient characteristics are secured, and a more reliable multilayer ceramic capacitor has been demanded.

JP 2008-254934 A

  The present invention solves the above-described problems, and an object of the present invention is to provide a multilayer ceramic capacitor having higher high-temperature load reliability than a conventional multilayer ceramic capacitor.

In order to solve the above problems, the multilayer ceramic capacitor of the present invention is
A ceramic laminate comprising a plurality of dielectric ceramic layers and a plurality of internal electrodes laminated via the dielectric ceramic layers, and an external electrode disposed in the ceramic laminate so as to be electrically connected to the internal electrodes A multilayer ceramic capacitor comprising:
The dielectric ceramic layer contains a perovskite type compound containing Ba and Ti, Zr, Mn, and V,
The ratio of the molar amount of Zr determined by the following formula (1) to the total molar amount of Mn and V is in the range of 10 to 150%.
Ratio of molar amount of Zr to total molar amount of Mn and V (%) = {Zr molar amount / (Mn molar amount + V molar amount)} × 100 (1)

  In the multilayer ceramic capacitor of the present invention, it is preferable that the ratio of the molar amount of Zr to the total molar amount of Mn and V obtained by the above formula (1) is 40 to 100%.

  By setting the ratio of the molar amount of Zr to the total molar amount of Mn and V to be the above-mentioned appropriate ratio (40 to 100%), the insulating properties and reliability of the grain boundary and shell part of the dielectric ceramic layer are improved. To do. As a result, it is possible to obtain a multilayer ceramic capacitor with high temperature load reliability.

  The average thickness of the internal electrodes is preferably 0.5 μm or less.

  By setting the thickness of the internal electrode layer to 0.5 μm or less, the high temperature load reliability is further improved.

  For example, when the internal electrode is made of Ni, when the thickness of the internal electrode is increased, the diffusion of Ni into the dielectric ceramic layer increases, and it is obtained by allowing Zr, Mn, and V to exist at appropriate ratios. The above-mentioned effect is hindered, and the high temperature load reliability is lowered.

  On the other hand, by making the thickness of the internal electrode layer 0.5 μm or less, Zr, Mn, and V are present at appropriate ratios, thereby insulating and reliability of the grain boundaries and shell portions of the dielectric ceramic layer. It becomes possible not to impair the effect of improving the resistance, and it becomes possible to provide a highly reliable multilayer ceramic capacitor.

In the multilayer ceramic capacitor of the present invention, the dielectric ceramic layer contains a perovskite type compound containing Ba and Ti, Zr, Mn, and V, and the following formula (1):
Ratio of molar amount of Zr to total molar amount of Mn and V (%) = {Zr molar amount / (Mn molar amount + V molar amount)} × 100 (1)
The ratio of the molar amount of Zr determined in step 1 to the total molar amount of Mn and V is in the range of 10 to 150%, so that the insulation and reliability of the grain boundaries and the shell part are improved. Can do.
As a result, it is possible to provide a multilayer ceramic capacitor with high temperature load reliability.

  In addition, although the mechanism by which high temperature load reliability improves by this invention is not necessarily clear, it estimates as follows.

Mn and V are added to ensure insulation resistance. However, there is a tendency to increase oxygen vacancies, and if too much, reliability is lowered. On the other hand, Zr tends to reduce oxygen vacancies.
Therefore, it is considered that by controlling the Zr / (Mn + V) value, for example, 10% or more, the formation of oxygen vacancies is suppressed to an appropriate range, so that the high temperature load reliability is improved.
Mn and V promote sinterability, but Zr reduces sinterability. Therefore, when the Zr / (Mn + V) value is larger than 150%, it is considered that the sinterability is lowered and the reliability is lowered.

  Therefore, as in the present invention, by setting the Zr / (Mn + V) value to 10% or more and 150% or less, it becomes possible to obtain a multilayer ceramic capacitor having high high temperature load reliability.

It is sectional drawing which shows the structure of the multilayer ceramic capacitor concerning embodiment of this invention. 1 is a perspective view showing a configuration of a multilayer ceramic capacitor according to an embodiment of the present invention. It is a figure explaining the method to measure the thickness of the internal electrode of the multilayer ceramic capacitor of this invention.

  Embodiments of the present invention will be described below to describe the features of the present invention in more detail.

[Embodiment 1]
A) Production of Dielectric Material Powder First, high-purity BaCO ₃ and TiO ₂ powders were prepared and prepared as starting materials for BaTiO _{3 as} the main component.
Next, this blended powder was wet-mixed with a ball mill and uniformly dispersed, and then subjected to a drying treatment to obtain an adjusted powder.
Next, the obtained adjusted powder was calcined at a temperature of 1000 ° C. to 1200 ° C. (in this embodiment, 1200 ° C.) to obtain a main component powder having an average particle size of 0.10 μm.

On the other hand, powders of Al ₂ O ₃ , SiO ₂ , MgCO ₃ , Dy ₂ O ₃ , MnO ₂ , V ₂ O ₅ and ZrO ₂ were prepared as subcomponents.
Next, powders of Al ₂ O ₃ , SiO ₂ , MgCO ₃ , Dy ₂ O ₃ , MnO ₂ , V ₂ O ₅ , ZrO ₂ are mixed with Al, Si, Mg, Dy, Mn, V, and Zr with respect to Ti. The mixed powder was obtained by measuring so that content might become predetermined, and adding to the main ingredient powder obtained as mentioned above.

  The ratio of each additive component is such that Dy = 0.8 mol%, Mg = 1.1 mol%, Al = 0.5 mol%, Si = 1.3 mol% with respect to Ti = 100 mol%. I made it.

  Moreover, Zr, Mn, and V amount were mixed in the ratio shown in Table 1. Table 1 also shows the value of “{Zr molar amount / (Mn molar amount + V molar amount)} × 100”.

  Next, this mixed powder was wet-mixed with a ball mill and uniformly dispersed, and then subjected to a drying treatment to obtain a ceramic raw material. When this ceramic raw material was analyzed by ICP, it was confirmed that it was consistent with the blended composition.

B) Production of Multilayer Ceramic Capacitor A polyvinyl butyral binder, a plasticizer and ethanol as an organic solvent were added to the ceramic raw material, and these were wet mixed by a ball mill to produce a ceramic slurry.

  Next, this ceramic slurry was formed into a sheet by a lip method to obtain a rectangular ceramic green sheet.

  Then, a conductive paste containing Ni was screen-printed on the ceramic green sheet to form a conductive paste film (internal electrode pattern) to be an internal electrode.

  Next, a plurality of ceramic green sheets on which the conductive paste film was formed were stacked so that the side from which the conductive paste film was drawn was alternated, and an unfired stacked body to be a capacitor body was obtained.

Next, this laminate was heated in a N ₂ atmosphere at a temperature of 300 ° C. for 3 hours to burn the binder, and then the temperature rising rate was 100 ° C./min and the oxygen partial pressure was 10 ⁻⁹ to 10 ^−12. In a reducing atmosphere consisting of H ₂ —N ₂ —H ₂ O gas of 10 MPa (10 ⁻⁹ MPa in this embodiment), firing is performed at 1200 ° C. for 10 minutes to obtain a sintered laminate that is a capacitor body. It was.

Next, a Cu paste containing glass frit was applied to both end faces of the capacitor body, and baked at a temperature of 800 ° C. in an N ₂ atmosphere to form an external electrode electrically connected to the internal electrode. Thereby, samples (multilayer ceramic capacitors) of sample numbers 1 to 30 in Table 1 were obtained.
The laminated body after removing the external electrodes of the multilayer ceramic capacitor was dissolved with an acid and subjected to ICP emission spectroscopic analysis. As a result, it was confirmed that the composition was consistent with the composition except for Ni as an internal electrode component.

  As shown in FIGS. 1 and 2, the multilayer ceramic capacitor 50 includes a plurality of laminated dielectric ceramic layers 11 and a plurality of internal electrodes disposed at a plurality of interfaces between the dielectric ceramic layers 11. 12 and a pair of external electrodes 13a disposed on both end faces of the ceramic laminate 10 so as to be electrically connected to the internal electrodes 12 drawn alternately on the opposite end faces. , 13b. The external electrodes 13a and 13b may be configured to include a Ni plating layer and a Sn plating layer.

  The external dimensions of the multilayer ceramic capacitor thus obtained are as follows: length L = 0.6 mm when the dimension in the L direction in FIG. 2 is the length, the dimension in the W direction is the width, and the dimension in the T direction is the thickness. The width W was 0.3 mm and the thickness T was 0.3 mm.

Other conditions were as follows.
1) Thickness of one dielectric ceramic layer: 0.8 μm,
2) Thickness of one layer of internal electrode: 0.7 μm,
3) Number of effective dielectric ceramic layers: 160 layers
4) Counter electrode area per dielectric ceramic layer: 0.15 mm ²

The thickness of the internal electrode layer was measured by the following method.
First, three samples (multilayer ceramic capacitors) of sample numbers 1 to 30 in Table 1 were prepared, and a surface (LT surface) defined by the length direction (L direction) and the thickness direction (T direction) of the sample. Each sample was hardened with a resin in such a manner that is exposed.

  Next, the LT side surface of the sample was polished by a polishing machine. At this time, polishing was performed to a depth of about ½ of the width direction (W direction) of the sample to expose the LT surface (LT polished end surface) as a polished surface. In order to eliminate sagging of the internal electrode due to polishing, the polished surface was processed by ion milling after polishing.

For the polished sample, the thickness of the internal electrode was measured. In measuring the thickness of the internal electrode, first, as shown in FIG. 3, a straight line L1 substantially perpendicular to the internal electrode 12 is drawn at a position of about 1/2 of the L polished end surface of the sample in the L direction (assumed). ).
Next, the region where the internal electrode 12 of the sample was laminated was divided into three equal parts in the T direction, and was divided into three regions: an upper region, an intermediate region, and a lower region.

Except for the outermost internal electrode in each region, 15 layers of internal electrodes on the straight line L1 were randomly selected in each region, and the thickness was measured. However, those incapable of measurement due to the lack of internal electrodes on the straight line L1 and the connection of dielectric ceramic layers sandwiching the internal electrodes were excluded. The thickness of the internal electrode layer was measured using a scanning electron microscope.
Therefore, the average thickness of the internal electrodes in Embodiment 1 is the average value of the thicknesses of the internal electrodes in the number of samples 3 × 3 regions × 15 layers = 135 locations.
However, parts that could not be measured due to a lack of internal electrodes were excluded from the measurement target.

C) Characteristic evaluation Next, the following evaluation was performed for each sample (multilayer ceramic capacitor) of sample numbers 1 to 30 in Table 1.

(1) High-temperature load reliability test 72 samples (multilayer ceramic capacitors as test samples) were prepared for each sample.

In this high temperature load reliability test, a DC voltage of 6.3 V was applied to each multilayer ceramic capacitor at 85 ° C., and insulation resistance at room temperature was confirmed after a certain time (1000 hr, 2000 hr, 3000 hr, 4000 hr). did.
A failure was determined when the insulation resistance value of each multilayer ceramic capacitor was 1 MΩ or less.

Table 2 shows the test results.
In Table 2, the columns of 1000 hr, 2000 hr, 3000 hr, and 4000 hr indicate the relationship between the number of failed samples and the number of samples subjected to the test (number of failed samples / sample subjected to the test). Number).

  In Tables 1 and 2, the sample numbered with * is a sample that does not have the requirements of the present invention.

  From Table 1 and Table 2, in each of the sample numbers 1 to 5, 9, 10, 21, 26, 27, and 28 that do not have the requirements of the present invention, the failure was detected at 1000 hr in the high temperature load reliability test. Occurrence was observed.

  On the other hand, in the case of a sample satisfying the requirements of the present invention, the occurrence of a failure is not recognized at the time of 1000 hr of the high temperature load reliability test and at the time of 2000 hr, and the high temperature load reliability is greatly improved. Was confirmed.

  Further, in the case of a sample satisfying the requirements of the present invention, it was confirmed that the number of failures was small even at the time of 3000 hr and 4000 hr of the high temperature load reliability test as compared with the sample not having the requirements of the present invention.

  From this result, by providing the requirements of the present invention, that is, by setting the value of “{Zr mole amount / (Mn mole amount + V mole amount)} × 100” to a range of 10 to 150%, high temperature load reliability It can be seen that a monolithic ceramic capacitor having a high value can be obtained.

[Embodiment 2]
Embodiment 1 described above, except that the average thickness of the internal electrodes of the ceramic laminate (capacitor body) obtained after firing was changed in the range shown in Table 3, that is, in the range of 0.28 to 0.71 μm. In the same manner as described above, multilayer ceramic capacitors (samples of sample numbers 31 to 37 in Table 3) were produced.

  Table 3 shows the amounts of Zr, Mn, and V in the dielectric ceramic layer. Table 3 further shows the value of “{Zr molar amount / (Mn molar amount + V molar amount)} × 100” and the thickness of the internal electrode.

Then, a high-temperature load reliability test was performed on each manufactured sample under the same method and the same conditions as in the first embodiment.
The results are shown in Table 4.

  The columns of 1000 hr, 2000 hr, 3000 hr, and 4000 hr in Table 4 indicate the relationship between the number of failed samples and the number of samples subjected to the test (number of failed samples / sample subjected to the test). Number).

  According to Table 4, in the case of a sample having an internal electrode thickness of 0.5 μm or less (sample Nos. 34, 35, 36, and 37), no failure was observed even at the time of 4000 hours of the high temperature load reliability test. It was confirmed that a multilayer ceramic capacitor with particularly excellent high temperature load reliability can be obtained.

  Therefore, in the multilayer ceramic capacitor of the present invention, when further excellent high-temperature load reliability is desired, the thickness of the internal electrode is desirably 0.5 μm or less.

  In addition, this invention is not limited to the said embodiment, A various application and deformation | transformation are possible within the scope of the invention.

10 Capacitor body (ceramic laminate)
DESCRIPTION OF SYMBOLS 11 Dielectric ceramic layer 12 Internal electrode 13a, 13b External electrode 50 Multilayer ceramic capacitor L Length of multilayer ceramic capacitor T Height of multilayer ceramic capacitor W Width of multilayer ceramic capacitor

Claims (3)

A ceramic laminate comprising a plurality of dielectric ceramic layers and a plurality of internal electrodes laminated via the dielectric ceramic layers, and an external electrode disposed in the ceramic laminate so as to be electrically connected to the internal electrodes A multilayer ceramic capacitor comprising:
The dielectric ceramic layer contains a perovskite type compound containing Ba and Ti, Zr, Mn, and V,
A monolithic ceramic capacitor characterized in that the ratio of the molar amount of Zr to the total molar amount of Mn and V determined by the following formula (1) is in the range of 10 to 150%.
Ratio of molar amount of Zr to total molar amount of Mn and V (%) = {Zr molar amount / (Mn molar amount + V molar amount)} × 100 (1)   2. The multilayer ceramic capacitor according to claim 1, wherein a ratio of the molar amount of Zr to the total molar amount of Mn and V obtained by the formula (1) is 40 to 100%.   3. The multilayer ceramic capacitor according to claim 1, wherein an average thickness of the internal electrodes is 0.5 μm or less.

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