JP6519726B2 - Multilayer ceramic capacitor - Google Patents

Description

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

  2. Description of the Related Art In recent years, as the size and weight of electronic devices have decreased, multilayer ceramic capacitors that are small and capable of obtaining a large capacity are widely used. The multilayer ceramic capacitor is, for example, externally connected to an 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. Those having a structure in which an electrode is disposed are widely known.

And as such a multilayer ceramic capacitor, a general formula ABO ₃ (wherein, A is one or more elements selected from Ba, Ca, Sr and Mg, and B is Ti, Zr and Hf Perovskite-type crystal represented by [A] / [B] (molar ratio) is 0.990 ≦ [A] / [B] <1.03) A main component containing a compound having a structure, a first subcomponent such as MgO, a second subcomponent which is a sintering aid, and an oxide of a rare earth R (where R is Y, Dy, Tb, Gd and Ho And a fourth subcomponent containing MnO, and a fifth subcomponent which is an oxide of Re (rhenium), and each of the main components is 100 mol The ratio of the minor component, the first minor component: 0.1 to 3 moles, the second minor component Dielectric: 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.

  And, in the case of this laminated ceramic capacitor, it is said that thinning of the dielectric layer is possible, and the product can be miniaturized.

  However, in recent years, multilayer ceramic capacitors have come to be used under various severe conditions and environments, and even with the multilayer ceramic capacitors of Patent Document 1, for example, high temperature load reliability etc. are not necessarily required. It can not be said that sufficient characteristics are secured, and a more reliable laminated ceramic capacitor has been required.

JP 2008-254934 A

  The present invention is intended to solve the above-mentioned problems, and it is an object of the present invention to provide a multilayer ceramic capacitor having high temperature load reliability as compared with 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 layer, and an external electrode disposed on the ceramic laminate so as to be conductive to the internal electrodes A laminated ceramic capacitor comprising
The dielectric ceramic layer contains a perovskite type compound containing Ba and Ti, Ca, Mn and V.
For Ti = 100 mol%,
Ca = 0.44 mol% or less,
V = 0.1 to 0.45 mol%,
The central part of the crystal particle of the perovskite type compound does not contain Ca,
It is characterized in that the ratio of the molar amount of Ca to the total molar amount of Mn and V obtained by the following formula (1) is in the range of 10 to 57 %.
Ratio (%) of the molar amount of Ca to the total molar amount of Mn and V = {Ca molar amount / (Mn molar amount + V molar amount)} × 100 (1)

Further, in the laminated ceramic capacitor of the present invention, it is preferable that the ratio of the molar amount of Ca to the total molar amount of Mn and V, which is determined by the formula (1), be 30 to 57 %.

By setting the ratio of the molar amount of Ca to the total molar amount of Mn and V to an appropriate ratio (30 to 57 %), the insulation and reliability of the grain boundary and shell portion of the dielectric ceramic layer are improved. As a result, the reliability of the multilayer ceramic capacitor can be improved.

  The average thickness of the internal electrode 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, in the case where the internal electrode is formed of Ni, when the thickness of the internal electrode is increased, the diffusion of Ni into the dielectric ceramic layer is increased, which is obtained by causing Ca, Mn, and V to be present in an appropriate ratio. The above-described effects are hampered and the high temperature load reliability is reduced.

  On the other hand, by setting the thickness of the internal electrode layer to 0.5 μm or less, the presence of Ca, Mn, and V in an appropriate ratio causes the insulation and reliability of the grain boundary and shell portion of the dielectric ceramic layer. As a result, it is possible to maintain the effect of improving the reliability of the laminated ceramic capacitor and 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, Ca, Mn, and V, and the following formula (1):
Ratio (%) of the molar amount of Ca to the total molar amount of Mn and V = {Ca molar amount / (Mn molar amount + V molar amount)} × 100 (1)
Since the ratio of the molar amount of Ca to the total molar amount of Mn and V, which is determined in the above, is in the range of 10 to 80%, the insulation and reliability of the grain boundary and the shell are improved. Can.
As a result, it is possible to provide a multilayer ceramic capacitor with high temperature load reliability.

  Although the mechanism by which the high temperature load reliability is improved by the present invention is not necessarily clear, it is presumed as follows.

Although Mn and V are added to secure insulation resistance, they tend to increase the number of oxygen vacancies, and when too large, the reliability is lowered. On the other hand, Ca tends to reduce oxygen vacancies. Therefore, by controlling the Ca / (Mn + V) value to, for example, 10% or more, the formation of oxygen vacancies is suppressed to an appropriate range, and it is considered that the high temperature load reliability may be improved.
Mn and V promote sinterability, but Ca lowers sinterability. Therefore, when the Ca / (Mn + V) value is greater than 80%, the sinterability is considered to be reduced and the reliability is lowered.

  Therefore, by setting the Ca / (Mn + V) value to 10% or more and 80% or less as in the present invention, it is possible to obtain a multilayer ceramic capacitor with high reliability in high temperature load.

FIG. 1 is a cross-sectional view showing a configuration of a laminated ceramic capacitor according to an embodiment of the present invention. FIG. 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 laminated ceramic capacitor of this invention.

  Hereinafter, the features of the present invention will be described in more detail by showing embodiments of the present invention.

Embodiment 1
A) Preparation of Dielectric Raw Material Powder First, powders of high purity BaCO ₃ and TiO ₂ were prepared and prepared as starting materials of BaTiO ₃ which is the main component.
Next, this blended powder was wet mixed in a ball mill, dispersed uniformly, and then subjected to drying treatment to obtain a regulated powder.
Next, the obtained adjusted powder was calcined at a temperature of 1000 ° C. to 1200 ° C. (1200 ° C. in this embodiment) to obtain a main component powder having an average particle diameter 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 CaCO ₃ were prepared as additives.
Next, powders of Al ₂ O ₃ , SiO ₂ , MgCO ₃ , Dy ₂ O ₃ , MnO ₂ , V ₂ O ₅ , and CaCO ₃ were added to Al, Si, Mg, Dy, Mn, V, Ca with respect to Ti. The mixed powder was obtained by weighing so that the content would be predetermined and adding to the main component powder obtained as described 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.

  Further, the amounts of Ca, Mn and V were mixed at the ratios shown in Table 1. Table 1 also shows the value of “{Ca molar amount / (Mn molar amount + V molar amount)} × 100”.

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

B) Preparation of Multilayer Ceramic Capacitor Next, a polyvinyl butyral-based binder, a plasticizer and ethanol as an organic solvent were added to the above-mentioned ceramic raw material, and these were wet-mixed by a ball mill to prepare a ceramic slurry.

  Then, the ceramic slurry was sheet-formed by a lip method to obtain a rectangular ceramic green sheet.

  Next, 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 drawn sides of the conductive paste film were alternately different, to obtain an unfired laminate to be a capacitor body.

Next, this laminate is 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 is 100 ° C./min, the oxygen partial pressure is 10 ^-9 to 10 ^-12. In a reducing atmosphere consisting of H ₂ -N ₂ -H ₂ O gas of 10 MPa (in this embodiment, 10 ^-9 MPa), firing is carried out at 1200 ° C. for 10 minutes to obtain a sintered laminate which is a capacitor body. The

  The laminate was subjected to a dissolution treatment and subjected to ICP analysis, and it was confirmed that the composition was consistent with the composition except for the internal electrode component Ni.

Next, a Cu paste containing a glass frit was applied to both end surfaces 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. Thus, the samples (laminated ceramic capacitors) of sample numbers 1 to 21 in Table 1 were obtained.
The laminate after removing the external electrode of this multilayer ceramic capacitor was subjected to dissolution treatment with acid and ICP emission spectral analysis was performed. As a result, it was confirmed that the composition was consistent with the composition except for the internal electrode component Ni.

  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 surfaces of the ceramic laminate 10 so as to be electrically connected to the internal electrodes 12 drawn to the opposite end surface alternately. , And 13b. In addition, it is also possible to set it as the structure provided with Ni plating layer and Sn plating layer to external electrode 13a, 13b.

  The external dimensions of the multilayer ceramic capacitor thus obtained are as follows: 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 length L = 0.6 mm 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 internal electrode 1 layer: 0.6 μm,
3) Number of effective dielectric ceramic layers: 160 layers,
4) Counter electrode area per dielectric ceramic layer: 0.15 mm ²

  The central portion of the barium titanate crystal particles in the dielectric ceramic layer of the multilayer ceramic capacitor was analyzed by TEM-EDX, and Ca was not detected.

The thickness of the internal electrode layer was measured by the following method.
First, three samples (laminated ceramic capacitors) of sample numbers 1 to 21 in Table 1 are prepared, and a surface (LT surface) defined by the length direction (L direction) and thickness direction (T direction) of the sample Each sample was hardened with resin in such a manner that

  Next, the LT side of the sample was polished by a polisher. At this time, the sample was polished to a depth of about 1/2 of the width direction (W direction) of the sample to expose the LT surface (LT polished end face) which is a polished surface. Then, in order to eliminate sagging of the internal electrode due to polishing, the polishing surface was processed by ion milling after the completion of polishing.

The thickness of the internal electrode was measured for the polished sample. In order to measure 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 about half the L direction of the LT polishing end face of the sample (assuming ).
Next, the region in which the internal electrode 12 of the sample is stacked is divided into three equal portions in the T direction, and divided into three regions of an upper region, an intermediate region, and a lower region.

Except for the outermost internal electrode in each region, in each region, 15 layers of the internal electrode on the straight line L1 were randomly selected, and the thickness was measured. However, the internal electrodes were broken on the straight line L1 and those which could not be measured due to the connection of the 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 electrode in the first embodiment is an average value of the thickness of the internal electrode at the number of samples: 3 × 3 areas × 15 layers = 135.
However, the part which can not be measured because the internal electrode was missing etc. was excluded from the measuring object.

C) Characteristic evaluation Next, the following evaluation was performed about each sample (laminated ceramic capacitor) of the sample numbers 1 to 21 of Table 1.

(1) Measurement of Lifetime Characteristics by High-Temperature Load Test For each sample, 72 samples (laminated ceramic capacitors as test samples) were prepared.

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

Table 2 shows the results of the test.
The columns of 1000 hr, 2000 hr, 3000 hr and 4000 hr in Table 2 show the relationship between the number of samples in which failure occurred and the number of samples used in the test (the number of samples in failure / the number of samples generated in the test). Number is shown.

  In Tables 1 and 2, the samples with * attached to the sample numbers are samples that do not have the requirements of the present invention.

  From Tables 1 and 2, in each of the sample numbers 1 to 5, 10, 11, 16, 17, and 19 which do not have the requirements of the present invention, occurrence of failure occurs at 1000 hours in the high temperature load reliability test. Admitted.

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

  In the case of the sample satisfying the requirements of the present invention, it was also confirmed that the number of failures occurred less at the time of 3000 hr and 4000 hr of the high temperature load reliability test as compared with the sample not having the requirement of the present invention.

  From this result, high temperature load reliability can be achieved by providing the requirements of the present invention, that is, by setting the value of “{Ca molar amount / (Mn molar amount + V molar amount)} × 100” to 10 to 80%. It can be seen that a high laminated ceramic capacitor can be obtained.

Second Embodiment
Except that the average thickness of the internal electrodes of the ceramic laminate (capacitor body) obtained after firing is changed in the range shown in Table 3, ie, 0.27 to 0.73 μm, Embodiment 1 described above A laminated ceramic capacitor (samples of sample numbers 22 to 28 in Table 3) was produced in the same manner as in the above.

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

Then, for each of the prepared samples, a high temperature load reliability test was conducted in the same manner and under the same conditions as in Embodiment 1.
The results are shown in Table 4.

  The columns of 1000 hr, 2000 hr, 3000 hr and 4000 hr in Table 4 show the relationship between the number of samples in which failure occurred and the number of samples used in the test (the number of samples in failure / samples subjected to test) Number is shown.

  From Table 4, in the case of the sample of which the thickness of the internal electrode is 0.5 μm or less (sample of sample numbers 25, 26, 27, 28), no occurrence of failure is recognized even at 4000 hours of the high temperature load reliability test. It has been confirmed that a multilayer ceramic capacitor having particularly excellent high temperature load reliability can be obtained.

  Therefore, in the laminated ceramic capacitor of the present invention, in order to obtain further excellent high temperature load reliability, it is desirable to set the thickness of the internal electrode to 0.5 μm or less.

  The present invention is not limited to the above embodiment, and various applications and modifications can be made within the scope of the invention.

10 Capacitor body (Ceramic laminated body)
DESCRIPTION OF SYMBOLS 11 dielectric material ceramic layer 12 internal electrode 13a, 13b external electrode 50 laminated ceramic capacitor L length of laminated ceramic capacitor T height of laminated ceramic capacitor W width of laminated 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 layer, and an external electrode disposed on the ceramic laminate so as to be conductive to the internal electrodes A laminated ceramic capacitor comprising
The dielectric ceramic layer contains a perovskite type compound containing Ba and Ti, Ca, Mn and V.
For Ti = 100 mol%,
Ca = 0.44 mol% or less,
V = 0.1 to 0.45 mol%,
The central part of the crystal particle of the perovskite type compound does not contain Ca,
Obtained by Equation (1) below, the molar amount of Ca, the ratio of the total molar amount of Mn and V, multilayer ceramic capacitors, characterized in that in the range of 10-57%.
Ratio (%) of the molar amount of Ca to the total molar amount of Mn and V = {Ca molar amount / (Mn molar amount + V molar amount)} × 100 (1) The ratio of the molar amount of said Ca calculated | required by said Formula (1) with respect to the sum total molar amount of Mn and V is 30 to 57 %, The laminated ceramic capacitor of Claim 1 characterized by the above-mentioned.   The average thickness of the said internal electrode is 0.5 micrometer or less, The multilayer ceramic capacitor of Claim 1 or 2 characterized by the above-mentioned.

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