JP4782598B2 - Multilayer ceramic capacitor - Google Patents

Multilayer ceramic capacitor Download PDF

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JP4782598B2
JP4782598B2 JP2006088037A JP2006088037A JP4782598B2 JP 4782598 B2 JP4782598 B2 JP 4782598B2 JP 2006088037 A JP2006088037 A JP 2006088037A JP 2006088037 A JP2006088037 A JP 2006088037A JP 4782598 B2 JP4782598 B2 JP 4782598B2
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barium titanate
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crystal particles
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JP2007266223A (en
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裕章 三野
政浩 西垣
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京セラ株式会社
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  The present invention relates to a multilayer ceramic capacitor, and more particularly to a small and high capacity multilayer ceramic capacitor in which both a dielectric layer and a protective layer are composed of fine barium titanate crystal particles.

  FIG. 2 is a cross-sectional view showing a conventional multilayer ceramic capacitor. As can be seen from FIG. 2, in the multilayer ceramic capacitor, the external electrode 103 is formed on the end face of the capacitor body 101, and the capacitor body 101 has a capacitance portion 105 and a capacitance portion in which dielectric layers 105a and internal electrode layers 105b are alternately laminated. It is comprised from the protective layer 107 provided in the upper and lower surfaces of 105.

The dielectric material used as the dielectric layer 105 is generally barium titanate (hereinafter referred to as BT) having a Ca content of 0.2 atomic% or less, but the Ca content is 0.4. Since barium calcium titanate (hereinafter referred to as BCT) having an atomic% or more and 1 atomic% or less shows temperature characteristics of a relative dielectric constant that is more stable than conventional BT, in recent years, this BCT has B characteristics and X7R characteristics. (See, for example, Patent Document 1), and a dielectric material (BT-BCT) in which BT and BCT are combined is used as a dielectric for the dielectric layer 105a. Use as a material has been proposed (see, for example, Patent Document 2).

  In recent years, multilayer ceramic capacitors have been required to have a dielectric layer 105a and internal electrode layers 105b that are thin and multi-layered. In order to reduce the thickness, dielectric powder and internal electrodes that become the dielectric layer 105a are required. The metal powder to be the layer 105b is atomized.

  The capacitor main body 101 constituting such a multilayer ceramic capacitor has a dielectric green sheet serving as the dielectric layer 105a and an internal electrode pattern serving as the internal electrode layer 105b alternately stacked, and has no internal electrode pattern on the upper and lower surfaces thereof. It is obtained by producing a laminated molded body in which dielectric green sheets are stacked and firing.

  However, when the dielectric green sheets and internal electrode patterns are both thinned and multi-layered, the firing contraction of the internal electrode patterns starts at a lower temperature than that of the dielectric green sheets. The laminated dielectric green sheets have larger firing shrinkage than the dielectric green sheets for the protective layer 107. For this reason, stress concentrates on the interface between the capacitor portion 105 and the protective layer 107, and peeling occurs in the thermal shock test after firing at the interface between the internal electrode layer 105b and the protective layer 107, which has less adhesion than the dielectric layer 105a. May occur.

Therefore, in order to cope with such a problem, the present applicant uses BCT that is sintered at a lower temperature than BT for the protective layer 107 when BT is used for the dielectric layer 105a constituting the capacitor 105. Proposed that. In this case, interface peeling between the dielectric layer 105 and the protective layer 107 in the thermal shock test is improved (see Patent Document 3). This is because by using BCT, which is easier to sinter than BT, for the protective layer 107, the difference between the shrinkage of the capacitor 105 and the shrinkage of the protective layer 107 is reduced, and the stress generated at the interface is reduced.
JP 2000-58378 A JP 2003-40671 A JP 2004-296708 A

  However, when BCT or BT-BCT is used as the dielectric layer 105a, if BT is used as the protective layer 107, peeling becomes severe, so BT cannot be used as the protective layer 107, and other suitable materials. In the thermal shock test, there was a problem that peeling occurred at the interface between the dielectric layer 105a and the protective layer 107.

Accordingly, an object of the present invention is to provide a multilayer ceramic capacitor in which peeling does not easily occur at the interface between the dielectric layer and the protective layer even when BCT or BT-BCT is used as a material constituting the dielectric layer. To do.

Multilayer ceramic capacitor of the present invention comprises a capacitor body which protective layer is provided on the upper and lower surfaces of the capacitor portion which dielectrics layer and internal electrode layers are alternately laminated, said internal electrode layers of the capacitor body is derived In the multilayer ceramic capacitor comprising an external electrode connected to the end face, the dielectric layer is a crystal particle mainly composed of barium titanate having a Ca content of 0.4 atomic% to 1 atomic% , Alternatively, crystal grains mainly composed of barium titanate having a Ca content of 0.4 atomic% or more and 1 atomic% or less and crystal grains mainly composed of barium titanate having a Ca content of 0.2 atomic% or less. Doo is contains composite particles coexist, the protective layer, together with contains crystal grains in which the content of Ca as a main component 0.2 atomic% or less of barium titanate, Contact scandium oxide At least one of fine yttrium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, the content of the Ca that contains one or more selected from among erbium oxide and ytterbium oxide, constituting the protective layer is 0 The average particle diameter of crystal grains mainly composed of 2 atomic% or less of barium titanate is such that the Ca content constituting the dielectric layer is 0.4 atomic% or more and 1 atomic% or less of barium titanate. It is characterized by being smaller than the average particle size of the crystal particles as the main component or the composite particles .
Hereinafter, the crystal particles mainly composed of barium titanate having a Ca content of 0.2 atomic% or less are referred to as barium titanate crystal particles, while the Ca content is 0.4 atomic% or more and 1 atom. The crystal particles mainly composed of barium titanate in an amount of not more than% are referred to as barium calcium titanate crystal particles.

According to the present invention, it is possible to increase the mechanical strength of the protective layer, it is possible to suppress the occurrence of adhesion is improved separation of the dielectrics layer of the capacitor portion adjacent to the protective layer.

  1A and 1B show the structure of the multilayer ceramic capacitor of the present invention. FIG. 1A is a cross-sectional view, and FIG. 1B is an enlarged view of portions A and B of FIG. In the multilayer ceramic capacitor of the present invention, an external electrode 3 is formed on the end face of the capacitor body 1. The capacitor body 1 includes a capacitor portion 5 in which dielectric layers 5 a and internal electrode layers 5 b are alternately stacked, and protective layers 7 provided on the upper and lower surfaces of the capacitor portion 5. Here, in the multilayer ceramic capacitor of the present invention, the thickness of the dielectric layer 5a is preferably 0.5 μm or more and 2 μm or less. When the thickness of the dielectric layer 5a is 0.5 μm or more, there is an advantage that high insulation can be maintained. On the other hand, when the thickness of the dielectric layer 5a is 2 μm or less, there is an advantage that the capacity can be increased. The internal electrode layer 5b is preferably formed of a base metal.

  In the multilayer ceramic capacitor of the present invention, the number of stacked layers is preferably 100 layers or more, particularly 200 layers or more. The present invention provides a multilayer ceramic capacitor having such a number of layers that the number of dielectric layers 5a and internal electrode layers 5b in the capacitor portion 5 increases with respect to the protective layer 7 and stress due to firing shrinkage of the capacitor portion 5 increases. Preferred.

  In the multilayer ceramic capacitor of the present invention, the dielectric layer 5a is formed of barium calcium titanate crystal particles 9a (part A). These barium calcium titanate crystal particles 9a contain 0.4 atomic% or more and 1 atomic% or less of Ca, have a small temperature change rate of relative dielectric constant, and satisfy X7R characteristics and B characteristics which are the standards of multilayer ceramic capacitors. There is an advantage that it is easy to adapt.

  On the other hand, when the dielectric layer 5a composing the capacitor portion 5 is composed of barium titanate crystal particles 9b (B portion) with Ca of 0.2 atomic% or less, the temperature change rate of the relative permittivity is large, and thus the X7R characteristics. It is difficult to adapt to the B characteristics, and the difficulty increases as the thickness of the dielectric layer 5 decreases.

Further, the multilayer ceramic capacitor of the present invention, the dielectric layer 5 is not only only barium calcium titanate crystal grain 9a as described above, barium titanate crystal grains 9b and the barium calcium titanate double if particles children of the crystal grains 9a It is configured by 9ab. When the composite particle 9ab is used for the dielectric layer 5, the high dielectric constant characteristic of the barium titanate crystal particles 9a and the temperature change rate of the relative dielectric constant characteristic of the barium calcium titanate crystal particles 9a are small. There is an advantage that they can be held together. In this case, the area ratio between the barium titanate crystal particles 9b and the barium calcium titanate crystal particles 9a is such that the area occupied by the barium titanate crystal particles 9b in the cross section of the dielectric layer 5 is ABT, and that of the barium calcium titanate crystal particles 9a. When the occupied area is ABCT, the ABCT / (ABCT + ABT) ratio desirably coexists in a systematic ratio having a relationship of 0.1 to 3, and in particular, the relative dielectric constant, temperature characteristics, and DC bias characteristics. ABT / ABCT = 0.3-2 is preferable in terms of further improving the ratio.

  In the multilayer ceramic capacitor of the present invention, the average particle diameter of the barium calcium titanate crystal particles 9a is preferably 0.1 μm or more and 0.3 μm or less. When the average particle diameter of the barium calcium titanate crystal particles 9a is 0.1 μm or more, the tetragonal nature of the barium calcium titanate crystal particles 9a is increased, and thus there is an advantage that a high dielectric constant can be obtained. On the other hand, if the average particle diameter of the barium calcium titanate crystal particles 9a is 0.3 μm or less, the number of grain boundaries between the internal electrode layers increases, and therefore the insulation can be improved, so that the dielectric layer 5a can be easily thinned. There is an advantage of becoming.

  The protective layer 7 constituting the multilayer ceramic capacitor of the present invention is characterized by comprising barium titanate crystal particles 9b. When the protective layer 7 is formed of the barium titanate crystal particles 9b, the grain growth is less likely at the time of firing than the barium calcium titanate crystal particles 9a, so that the mechanical strength of the protective layer 7 is increased and the dielectric layer 5a of the capacitor 5 is increased. And there exists an advantage that the wide firing temperature range for sintering the protective layer 7 appropriately can be ensured.

  On the other hand, when a dielectric material having a Ca content larger than that of the Ca-containing barium calcium titanate crystal particles 9a used in the dielectric layer 5a is applied to the protective layer 7, the protective layer 7 is likely to grow during firing. There is a risk that the mechanical strength of the steel becomes low. In addition, the firing temperature range for appropriately sintering the dielectric layer 5a and the protective layer 7 of the capacitor portion 5 is narrowed, and the manufacturing yield may be reduced.

The protective layer 7 constituting the multilayer ceramic capacitor of the present invention includes at least one of scandium oxide and yttrium oxide in addition to the main component barium titanate, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, It contains at least one selected from ytterbium oxide. By containing the oxide of the metal element in combination as an additive, the sinterability of the barium titanate crystal particles 9b forming the protective layer 7 is increased, and the adhesion with the dielectric layer 5a constituting the capacitor portion 5 is improved. Become stronger. Further, there is an advantage that the growth of the barium titanate crystal particles 9b can be suppressed even when the above-described oxide of the metal element such as scandium oxide is included in the barium titanate. For this reason, compared with the case where barium calcium titanate is used for the protective layer 7, thermal shock resistance can be improved.

  In the present invention, it is particularly preferable to select yttrium oxide and terbium oxide as the metal element oxide added to barium titanate to form the protective layer 7. On the other hand, the protective layer 7 is an oxide of at least one of the above scandium oxide and yttrium oxide and at least one metal element selected from gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, and ytterbium oxide. When no substance is contained, the sinterability of the barium titanate crystal particles 9b cannot be increased, the adhesion between the dielectric layer 5a of the capacitor 5 and the protective layer 7 is weakened, and the thermal shock resistance is lowered.

In the multilayer ceramic capacitor of the present invention, the dielectric layer 5a is also at least one selected from scandium oxide and yttrium oxide, and gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, and ytterbium oxide. It is desirable to contain more than seeds. In this case, is enhanced sintering resistance while suppressing the grain growth of the barium titanate crystal grains 9a constituting the dielectric layer 5a, it is possible to improve the thermal shock resistance. Further, as in the case of the protective layer 7, it is desirable to select yttrium oxide and terbium oxide. Even if the oxide of the metal element contained in the dielectric layer 5a and the protective layer 7 contains the oxide of the same kind of metal element in the vicinity of the interface between the dielectric layer 5a and the protective layer 7, , and the composition change of the dielectric ceramic can be suppressed in both layers, the proper sintering temperature range of the dielectric layer 5 and the protective layer 7 becomes wider, Ru can also be enhanced yield of production. The composition ratio is more preferably in the range of yttrium oxide: terbium oxide = 0.5-2 (mol): 0.1-0.5 (mol). The content of the rare earth element is preferably 0.5 to 3 mol% in total with respect to 100 mol% of crystal particles mainly composed of BaTiO 3 .

The dielectric layer 5a and the protective layer 7 described above, barium titanate crystal grains 9a constituting the these, in order to control the dielectric properties of the barium calcium titanate crystal grain 9b, and the composite particles 9ab, the in addition to rare earth elements, it is desirable to contain Mg and Mn, the content of Mg and Mn contained barium titanate crystal grains 9a, barium calcium titanate crystal grain 9b, and the composite particles 9ab is, BaTiO 3 1 00 Mg = 0.5 to 2 mol% and Mn = 0.2 to 0.5 mol% are good with respect to mol%, which can further stabilize the temperature characteristics of the capacitance and increase the insulation. , Reliability in high temperature load test can be improved. Since Mg, rare earth elements and Mn are derived from the sintering aid, these elements are dissolved in the barium titanate crystal particles 9a, the barium calcium titanate crystal particles 9b, and the composite particles 9ab. , Partly present in the grain boundary phase, particularly easily present as amorphous.

In the multilayer ceramic capacitor of the present invention , Mg and rare earth element are components having a core-shell structure of barium titanate crystal particles 9a and barium calcium titanate crystal particles 9b, while Mn is a BT crystal generated by firing in a reducing atmosphere. It is possible to compensate for oxygen defects in the particles 9b and the BCT crystal particles 9a, and to improve insulation and high temperature load life.

In addition, the dielectric layer 5a and the protective layer 7 in the multilayer ceramic capacitor of the present invention are obtained by converting silicon oxide into SiO 2 as a sintering aid, and the crystal particles 9a, 9b and 9ab 100 mol% mainly composed of BaTiO 3. It is preferable to contain 0.5-5 mol% with respect to.

In the multilayer ceramic capacitor of the present invention, more preferably, the barium calcium titanate crystal particles 9a in which the average particle diameter D9b of the barium titanate crystal particles 9b constituting the protective layer 7 constitutes the dielectric layer 5a , or a composite thereof it is not good less than the average particle diameter of the particles 9ab. When the average particle diameter D9b configuration to Ruchi Tan barium crystal grain 9b of the protective layer 7 is smaller than the average particle diameter of the dielectric layer barium calcium titanate crystal grains 9a 5a constituting or a composite particle 9ab, protection Since the mechanical strength of the layer 7 is increased and the grain growth of the barium calcium titanate crystal particles 9a of the dielectric layer 5a can be suppressed, the temperature characteristics of the capacitance in the capacitor portion 5 constituting the layer 7 can be expressed by X7R characteristics and B Ru can be applied to properties.

Next, a method for producing the multilayer ceramic capacitor of the present invention will be described. First, a dielectric green sheet and a protective layer green sheet used for the dielectric layer 5a constituting the capacitor unit 5 are formed. The dielectric green sheets used for the dielectric layer 5a, the general formula (Ba 1-x Ca x TiO 3 x = 0.05~0.2) barium calcium titanate powder composition (B C T powder), or, A mixed powder of this barium calcium titanate powder and barium titanate powder (BT powder) not containing Ca is used. On the other hand, barium titanate powder is used for the protective layer 7. Here, barium calcium titanate powder and barium titanate powder are collectively referred to as barium titanate powder.

Referring to a method of adding an additive to control the dielectric properties of barium titanate-based powders such as titanium barium powder and the barium calcium titanate powder, firstly, a predetermined amount of barium calcium titanate powder Mg, Mn And at least one rare earth oxide or carbonate is mixed, and if necessary, glass powder is added as a sintering aid and mixed to prepare a raw material powder. Next, an organic vehicle such as a binder or a solvent is added to the mixed powder to prepare a slurry, and then this slurry is pulled up, doctor blade method, reverse roll coater method, gravure coater method, screen printing method, gravure printing, etc. A sheet-like dielectric green sheet is produced by the known molding method.

  When the dielectric layer 5a is a composite particle 9ab of barium calcium titanate crystal particles 9a and barium titanate crystal particles 9b, a mixed powder is prepared by mixing barium calcium titanate powder and barium titanate powder at a predetermined ratio. Then, a dielectric green sheet is produced in the same manner as described above.

When fabricating a green sheet for the protective layer, except for using barium titanate powder it is also Ru used slurry and the dielectric green sheet forming method in the case of producing a dielectric green sheets for the dielectric layer 5a .

In this case , it is desirable that the average particle diameter of the barium calcium titanate powder to be the dielectric layer 5a is 0.05 μm or more and 0.25 μm or less, and the average particle diameter of the barium titanate powder to be the protective layer 7 is The average particle size of the barium calcium titanate powder is preferably 0.04 to 0.24 μm.

Further, the thickness of the dielectric green sheet to be the dielectric layer 5a is preferably 0.5 to 3 μm for the reason of small size and large capacity. On the other hand, it is preferable dielectric green sheet having a thickness of the protective layer 7 is 5 to 20 [mu] m.

Next, the dielectric green sheet surface for the dielectric layer 5a, a conductive paste containing a base metal powder, a screen printing method, gravure printing, coating by a known printing method such as offset printing, the internal electrodes Form a pattern. The thickness of the internal electrode pattern is desirably 2 μm or less, particularly 1 μm or less from the viewpoint of miniaturization and high reliability of the capacitor.

Conductive paste is base metal, for example, using Ni, also using a barium titanate powder having an average particle diameter of 0.1~0.2μm as a co-material, formed by dispersing them in a given vehicle . In this case, it is preferable to use a barium titanate-based powder having the same composition and average particle size as the dielectric green sheet to be printed. The content ratio of the barium titanate powder is 20 to 35 wt%, for example, with respect to the Ni powder 45 wt%, the barium titanate powder was added 20 to 35 wt%, it added an organic vehicle to . If the content of the barium titanate-based powder in the conductive paste is 20 to 35% by mass within this range, the shrinkage of the internal electrode layer 5b is alleviated and a flat internal electrode layer 5b is formed . It is Ru can.

Next, the dielectric green sheets formed of the internal electrode pattern by laminating a plurality crimped to produce a laminated article. On the other hand, a cover layer molded body is produced by laminating and pressing a plurality of dielectric green sheets (sheet-shaped molded bodies for cover layers) on which no internal electrode pattern is formed. Next, the laminated body of the dielectric green sheet on which the internal electrode pattern is printed and the cover layer molded body are pressure-bonded to produce a base laminate, cut into a predetermined size, and the capacitor with the internal electrode pattern exposed on the end face A body compact is produced.

Next, this capacitor body molded body was degreased at 250 to 300 ° C. in the atmosphere or at 500 to 800 ° C. in a low oxygen atmosphere having an oxygen partial pressure of 0.1 to 1 Pa , and then at a temperature of 1100 to 1200 ° C. in a non-oxidizing atmosphere. It fired two to three hours. Furthermore, if desired, a reoxidation treatment is performed at 900 to 1100 ° C. for 5 to 15 hours under a low oxygen partial pressure of about 0.1 to 10 −4 Pa to obtain a capacitor body.

Finally, baked by applying a Cu paste on the end faces of the internal electrode layer 5b of the capacitor body 1 obtained is exposed, by facilities Succoth the Ni / Sn plating, the internal electrode layer 5b which are electrically connected to an external A multilayer ceramic capacitor can be produced by forming the electrode 3.

Table 1 shows barium titanate-based powders having average particle sizes of BaTiO 3 (BT powder), Ba 0.95 Ca 0.05 TiO 3 (BCT powder) and Ba 0.9 Ca 0.1 TiO 3 (BCT powder). Were prepared and prepared so as to have the combinations shown in FIG. In this case, the average particle diameters of BaTiO 3, Ba 0.95 Ca 0.05 TiO 3 and Ba 0.9 Ca 0.1 TiO 3 (BCT powder) are also shown in Table 1. In the case of a mixed powder of BaTiO 3 and Ba 0.95 Ca 0.05 TiO 3 , both powders were equimolar. 1 part by mole of MgCO 3 to these barium titanate powder 100 parts by mole, the MnCO 3 was added 0.3 parts by mole. The rare earth element oxide powder is at least one part of scandium oxide and yttrium oxide in an amount of 1 mol part, and at least one selected from gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, and ytterbium oxide is 0.5. A mole part was added. These MgCO 3 , MnCO 3 and rare earth element oxide powders having an average particle diameter of 0.2 μm were used.

Further, 1.2 parts by mass of glass powder was added when the total amount of the barium titanate-based powder and various additive powders was 100 parts by mass. Glass powder containing SiO 2 : BaO: B 2 O 3 in a ratio of 5: 2: 3 was used. The average particle size of the glass powder was 0.3 μm.

  Next, to the mixed powder of barium titanate-based powder, various additives and glass powder, butyral resin and toluene are further added to prepare a slurry, which is applied onto a PET film by a doctor blade method, A dielectric green sheet with a thickness of 2.5 μm for the dielectric layer 5 a and a green sheet for a protective layer with a thickness of 10 μm for the protective layer 7 were formed.

The conductive paste is prepared by mixing Ni powder having an average particle size of 0.3 μm and a common material, and then mixing an ethyl cellulose binder and a solvent for dissolving the same. The barium titanate-based powder used for the dielectric green sheet was used as the common material used for the conductive paste. The amount added was 30 parts by mass with respect to 100 parts by mass of Ni powder.

Next, a conductive paste is printed on the surface of the produced dielectric green sheet to form a plurality of rectangular internal electrode patterns, and then 100 or 200 of these are laminated, and the protective layer 7 is formed on the upper and lower surfaces. The thickness of the capacitor body after firing the dielectric green sheet is 0 . Lamination was performed so as to be 5 mm, and a base laminate was formed by heating and pressing with a press.

Thereafter, the base laminate is cut into a predetermined chip shape, and is 300 ° C. or 0.000 in the atmosphere.
Deviating was performed by heating to 500 ° C. in an oxygen / nitrogen atmosphere of 1 Pa. Furthermore, it was baked at a temperature shown in Table 1 for 2 hours in an oxygen / nitrogen atmosphere of 10 −7 Pa, and further reoxidized at 1000 ° C. in an oxygen / nitrogen atmosphere of 10 −2 Pa. Obtained. Thereafter, baking at 900 ° C. The Cu paste on the end faces of the capacitor body, further subjected to Ni / Sn plating to form the external electrodes connected to the internal electrodes.

The thickness of the internal electrode layer of the multilayer ceramic capacitor thus obtained was 1.1 μm, and the thickness of the dielectric layer was 2 μm. The size of the capacitor body was 1 × 0.5 × 0.5 mm 3 , and the area of the internal electrode layer was 0.7 mm × 0.3 mm.

  Next, with respect to the obtained multilayer ceramic capacitor, capacitance and temperature characteristics of capacitance (X5R: 85 ° C.) were performed under measurement conditions of a frequency of 1.0 kHz and a measurement voltage of 0.5 Vrms.

Further, the average particle diameter of the barium titanate crystal particles constituting the dielectric layer was determined by a scanning electron microscope (SEM). Etching the polished surface, taking an outline of the crystal particles in an electron micrograph of 100 or more crystal grains, taking the outline as a circle, and determining the diameter of each final particle from the formula for determining the area of the circle. The average value of was obtained. The center section evaluates anywhere near, low barium titanate content of Ca in the crystal particles using the content transmission electron microscopy and energy dispersive analyzer (EDS) of Ca in the crystal particles The average particle size was determined from 10 crystal particles extracted from each of crystal particles (BT crystal particles) and barium calcium titanate crystal particles (BCT crystal particles) having a high Ca content . At that time, the one having a Ca content lower than 0.2 atomic% (rounded to the second decimal place) is defined as barium titanate crystal particles (BT crystal particles), while the Ca content is 0.4 atomic%. Higher (rounded to the second decimal place) was defined as barium calcium titanate crystal particles (BCT crystal particles).

In the thermal shock test, the temperature of the solder bath is set to 325 ° C. (ΔT = 300 ° C.), 395 ° C. (ΔT = 370 ° C.) and immersed for 10 seconds, and then at a magnification of 40 to 100 times using a stereomicroscope. Appearance inspection was performed to evaluate the presence of cracks and delamination. The number of samples was 100 for each sample. The results are shown in Tables 1 and 2.

  From Tables 1 and 2, in the sample of the present invention, although peeling failure was observed at a temperature of 370 ° C. in the thermal shock test, there was no peeling failure at a heat test temperature of 300 ° C. Sample No. in which Y was added alone to the protective layer. In No. 13, in the case of firing at 1100 ° C., a failure was observed in the thermal shock test at a temperature of 370 ° C., but the dielectric layer added with rare earth element oxides of Y and Tb was subjected to the thermal shock test. No defects were found even at a temperature of 370 ° C.

  On the other hand, what used BCT powder for the protective layer showed a defect even at a temperature of 300 ° C. in the thermal shock test.

  In addition, when the dielectric layer was formed of composite particles of BT crystal particles and BCT crystal particles, the capacitance was higher than that of a sample formed only from BCT crystal particles.

The structure of the multilayer ceramic capacitor of this invention is shown, (a) shows sectional drawing, (b) is an enlarged view of A part and B part of (a). It is sectional drawing which shows the structure of the conventional multilayer ceramic capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor body 3 External electrode 5 Capacitance part 5a Dielectric layer 5b Internal electrode layer 7 Protective layer 9a Barium calcium titanate crystal particle 9b Barium titanate crystal particle

Claims (1)

  1. Dielectrics layer and a capacitor body protective layer on the upper and lower surfaces of the capacitor portion which are alternately laminated internal electrode layers are provided, the external electrode to which the internal electrode layer of the capacitor body is connected to an end face that is derived In a multilayer ceramic capacitor comprising:
    The dielectric layer is a crystal particle mainly composed of barium titanate having a Ca content of 0.4 atomic% to 1 atomic%, or a Ca content of 0.4 atomic% to 1 atomic%. It includes composite particles in which crystal particles mainly composed of barium titanate and crystal particles mainly composed of barium titanate having a Ca content of 0.2 atomic% or less coexist,
    The protective layer contains crystal particles mainly composed of barium titanate having a Ca content of 0.2 atomic% or less, and at least one of scandium oxide and yttrium oxide, gadolinium oxide, terbium oxide, and oxidation. Containing one or more selected from dysprosium, holmium oxide, erbium oxide and ytterbium oxide ,
    The average particle diameter of the crystal grains mainly composed of barium titanate having a Ca content of 0.2 atomic% or less constituting the protective layer is such that the Ca content constituting the dielectric layer is 0.00. A monolithic ceramic capacitor, characterized in that it is smaller than the average particle diameter of crystal grains mainly composed of 4 atomic% or more and 1 atomic% or less of barium titanate or the composite particles .
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