JP2007266223A - Laminated ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated ceramic capacitor where a dielectric layer of a capacity part and a protection layer are sintered firmly even if titanic acid barium calcium crystal grains are used for the dielectric layer and peeling between the capacity part and the protection layer can be prevented even in a heat-resistant shock test. <P>SOLUTION: The dielectric layer 5a is constituted of the titanic acid barium calcium crystal grains. The protection layer 7 is formed of titanic acid barium crystal grains 9b, and it comprises at least scandium oxide or yttrium oxide, and one type or above selected from gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide and ytterbium oxide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  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.

  As a dielectric material used as the dielectric layer 105, barium titanate (hereinafter referred to as BT) is generally used, but barium calcium titanate (hereinafter referred to as BCT) is more stable than conventional BT. In recent years, the BCT has been attempted to be applied to a multilayer ceramic capacitor having B characteristics or X7R characteristics (see, for example, Patent Document 1) because of the temperature characteristics of the dielectric constant. It has been proposed to use a composite dielectric material (BT-BCT) as a dielectric material for the dielectric layer 105a (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 a dielectric layer and a protective layer even when BCT or BT-BCT is used.

  The multilayer ceramic capacitor of the present invention includes (1) a capacitor body in which a protective layer is provided on the upper and lower surfaces of a capacitor portion in which dielectric layers containing barium calcium titanate crystal particles and internal electrode layers are alternately laminated; In the multilayer ceramic capacitor comprising an external electrode connected to an end face from which the internal electrode layer of the capacitor body is derived, the protective layer includes at least one of scandium oxide and yttrium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, It is characterized by comprising barium titanate crystal particles containing one or more selected from holmium oxide, erbium oxide and ytterbium oxide.

  In the multilayer ceramic capacitor of the present invention, (2) the dielectric layer is composed of composite crystal particles of the barium calcium titanate crystal particles and barium titanate crystal particles, and (3) the protective layer is configured. It is desirable that the average particle size of the barium titanate crystal particles is smaller than any of the average particle size of the barium calcium titanate crystal particles and the composite crystal particles constituting the dielectric layer.

  Here, the barium titanate crystal particles are crystal particles mainly composed of barium titanate having a Ca content of 0.2 atomic% or less, while the barium calcium titanate crystal particles are Ca content. It refers to barium titanate crystal particles having an amount of 0.4 atomic% to 1 atomic%. The barium titanate crystal particles and the barium calcium titanate crystal particles are collectively referred to as barium titanate crystal particles. Further, a combination of barium titanate crystal particles and barium calcium titanate crystal particles in the dielectric layer is called a composite particle.

  The multilayer ceramic capacitor of the present invention uses BT as a protective layer when BCT or BT-BCT is used as the dielectric material of the dielectric layer constituting the capacitor portion of the capacitor body, and gadolinium oxide, By including at least one selected from terbium, dysprosium oxide, holmium oxide, erbium oxide, and ytterbium oxide, the protective layer using BT is more easily contracted at a low temperature, and the contraction difference from the dielectric layer is reduced. In addition, diffusion of the rare earth element oxide into the dielectric layer of the capacitor adjacent to the protective layer improves adhesion with the dielectric layer and suppresses peeling.

  The dielectric layer contains at least one of scandium oxide and yttrium oxide and at least one selected from gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, and ytterbium oxide. Moreover, the grain growth of the barium titanate crystal grains in the dielectric layer can be suppressed, and the dielectric properties can be improved.

  Further, according to the present invention, by making the average particle size of the barium titanate crystal particles constituting the protective layer smaller than the average particle size of the barium calcium titanate crystal particles and the composite particles constituting the dielectric layer, The strength of the protective layer is increased, and further, the peeling between the capacity portion and the protective layer can be more effectively suppressed, and the thermal shock resistance can be further enhanced.

  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.

In the multilayer ceramic capacitor of the present invention, the dielectric layer 5 is composed not only of the barium calcium titanate crystal particles 9a described above but also composed of composite crystal particles 9ab of the barium calcium titanate crystal particles 9b and the barium calcium titanate crystal particles 9a. It is characterized by that. 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 of the barium titanate crystal grains 9b and the barium calcium titanate crystal grain 9a is, the area occupied by A _BT barium titanate crystal grains 9b in the cross section of the dielectric layer _5, the barium calcium titanate crystal grains 9a of when the occupied area was _{a BCT, a BCT / (a} BCT + a BT) ratio is desirably coexist in a tissue proportions having a relationship 0.1-3, in particular, the relative dielectric constant, A _BT / A _BCT = 0.3 to 2 is preferable in terms of further improving the temperature characteristics and the DC bias characteristics.

  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 increases and the dielectric layer 5a of the capacitor 5 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.

  Further, 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 strong. In addition, there is an advantage that the growth of the barium titanate crystal particles 9b does not increase even when the oxide of the above 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 the above. In this case, yttrium oxide is the same as in the case of the protective layer 7 in that the sinterability is improved while suppressing the grain growth of the barium titanate crystal particles 9a constituting the dielectric layer 5a, and the thermal shock resistance is improved. And terbium oxide is preferred. 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, The compositional change of the dielectric ceramic between the two layers is suppressed, the proper firing temperature range of the dielectric layer 5 and the protective layer 7 is widened, and the manufacturing yield can be increased. 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 .

Further, the dielectric layer 5a and the protective layer 7 described above are used in addition to the rare earth element in order to control the dielectric properties of the barium titanate crystal particles 9a, the barium calcium titanate crystal particles 9b, and the composite particles 9ab constituting them. It is desirable to contain Mg and Mn, and the content of Mg and Mn contained in these crystal particles 9a, 9b, 9ab is Mg = 0.5 to 100 mol% of crystal particles mainly composed of BaTiO _3. If it is 2 mol% and Mn = 0.2 to 0.5 mol%, the temperature characteristics of the capacitance can be further stabilized and the insulation can be increased, and the reliability in the high-temperature load test can be enhanced. Since Mg, rare earth elements, and Mn are derived from the sintering aid, these elements are dissolved in the crystal grains 9a, 9b, 9ab, but are partly present in the grain boundary phase. It tends to exist as amorphous.

  That is, in the dielectric layer 5 in the multilayer ceramic capacitor of the present invention, Mg and rare earth elements are components having the core-shell structure of the barium titanate crystal particles 9a and the barium calcium titanate crystal particles 9b, while Mn is a reducing atmosphere. It is possible to compensate for oxygen defects in the BT crystal particles 9b and the BCT crystal particles 9a generated by firing in the process, and to improve the 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, 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 particle thereof is more preferable. Desirably smaller than the average particle size of 9ab. The Ca content constituting the protective layer 7 has an average particle diameter D9b of the barium titanate crystal particles 9b smaller than the average particle diameter of the barium calcium titanate crystal particles 9a or the composite particles 9ab constituting the dielectric layer 5a. Further, the mechanical strength of the protective layer 7 is increased, and the grain growth of the barium calcium titanate crystal particles 9a of the dielectric layer 5a can be suppressed. There is an advantage that it can be applied to the B characteristics.

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 (BT powder), or titanium A mixed powder of barium calcium oxide powder and barium titanate powder (BT powder) containing no 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.

  Here, a method of adding an additive for controlling dielectric properties to a barium titanate powder such as barium titanate powder or barium calcium titanate powder will be described. First, a predetermined amount of Mg, Mn and at least one rare earth element oxide or carbonate are 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 producing a green sheet for a protective layer, except for using barium titanate powder, this also uses a slurry and a method for forming a dielectric green sheet when producing a dielectric green sheet for the dielectric layer 5a. And

  In the production method of the multilayer ceramic capacitor of the present invention, it is desirable that the average particle diameter of the barium calcium titanate powder used as the dielectric layer 5a is 0.05 μm or more and 0.25 μm or less, and the barium titanate used as the protective layer 7. The average particle size of the powder is smaller than the average particle size of the barium calcium titanate powder, and is preferably 0.04 to 0.24 μm.

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

Next, a conductive paste containing a base metal is applied to the surface of the dielectric green sheet for the dielectric layer 5a by a known printing method such as a screen printing method, a gravure printing, an offset printing method, and the internal electrode pattern is formed. Form. 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.

The conductive paste uses a base metal, such as Ni, and has an average particle size of 0.1 to 0.00 as a common material.
It is formed by using 2 μm barium titanate-based powders and dispersing them in a predetermined 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% by mass. For example, the barium titanate powder is 20 to 35% by mass with respect to 45% by mass of Ni powder, and the balance is Yuki vehicle. The reason why the content of the barium titanate-based powder in the conductive paste is 20 to 35% by mass is that the shrinkage of the internal electrode layer 5b can be relaxed and a flat internal electrode layer 5b can be formed within this range. It is.

  Next, a plurality of dielectric green sheets on which internal electrode patterns are formed are laminated and pressure-bonded to produce a laminated molded body. 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 500 to 800 ° C. in a low oxygen atmosphere having an oxygen partial pressure of 0.1 to 1 Pa, and then 2 to 1100 to 1200 ° C. in a non-oxidizing atmosphere. Bake for 3 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, Cu paste is applied and baked on each end face where the internal electrode layer 5b of the obtained capacitor body 1 is exposed, Ni / Sn plating is performed, and the external electrode 3 electrically connected to the internal electrode layer 5b is formed. A multilayer ceramic capacitor can be produced by forming the multilayer ceramic capacitor.

BaTiO ₃ having an average particle diameter (BT _{powder), Ba 0.95 Ca 0.05 TiO 3} (BCT powder) and _Ba 0.9 _Ca 0.1 Table 1 barium titanate powder is _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. In addition, the rare earth element oxide powder contains at least one part of scandium oxide and yttrium oxide in one mole part, and at least one selected from gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, and ytterbium oxide. 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. A dielectric green sheet for use was laminated so that the thickness of the capacitor body after firing was 0.5 mm as follows, and was heated and pressed by a press to form a base laminate.

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, 10 ⁻⁷ Pa
In an oxygen / nitrogen atmosphere at a temperature shown in Table 2 for 2 hours, and 10 ⁻² Pa of oxygen /
A reoxidation treatment was performed at 1000 ° C. in a nitrogen atmosphere to obtain a capacitor body. After firing, Cu paste was baked at 900 ° C. on the end face of the capacitor body, and further Ni / Sn plating was performed to form external terminals 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. At this time, the Ca concentration of each crystal particle is evaluated at an arbitrary location near the center using a transmission electron microscope and energy dispersive analysis (EDS), and barium titanate crystal particles (BT crystal particles) having a low Ca concentration and The average particle size was determined from 10 extracted crystal particles of barium calcium titanate crystal particles (BCT crystal particles) having a high Ca concentration. At that time, barium titanate crystal particles (BT crystal particles) having a low Ca concentration with respect to those having a Ca concentration lower than 0.2 atomic% (rounded to the second decimal place), while the Ca concentration is 0.4 atomic% The barium calcium titanate crystal particles (BCT crystal particles) having a high Ca concentration with respect to those higher than that (rounded to the second decimal place).

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 (3)

Capacitor body in which protective layers are provided on the upper and lower surfaces of a capacitor portion in which dielectric layers and internal electrode layers containing barium calcium titanate crystal particles are alternately laminated, and the internal electrode layer of the capacitor body is derived In the multilayer ceramic capacitor having an external electrode connected to the end face, the protective layer is made of at least one of scandium oxide and yttrium oxide, and gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, and ytterbium oxide. A multilayer ceramic capacitor comprising: barium titanate crystal particles containing at least one selected from the above. The multilayer ceramic capacitor according to claim 1, wherein the dielectric layer is composed of composite crystal particles of the barium calcium titanate crystal particles and the barium titanate crystal particles. The average particle size of the barium titanate crystal particles constituting the protective layer is smaller than any of the average particle size of the barium calcium titanate crystal particles and the composite crystal particles constituting the dielectric layer. Multilayer ceramic capacitor.

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