JP4771838B2 - Multilayer ceramic capacitor - Google Patents

Description

  The present invention relates to a multilayer ceramic capacitor, and more particularly to a small-sized and high-capacity multilayer ceramic capacitor having a dielectric layer formed of fine barium titanate crystal grains.

In recent years, in order to reduce the size and increase the capacity of multilayer ceramic capacitors, the dielectric layers and internal electrode layers constituting the multilayer ceramic capacitors have been made thinner and multilayered. The number of laminated layers exceeds 200 layers. The thickness of the layer is 3 μm or less, and the average particle size of the crystal particles constituting the dielectric layer is 0.8 μm or less (see Patent Document 1 and Patent Document 2).
JP 2003-17356 A JP 2005-347509 A

  In such a multilayer ceramic capacitor, the thickness of the internal electrode layer formed between the dielectric layers is greatly influenced by the thinning and multilayering of the dielectric layer, and the portion where the internal electrode layer is formed Steps due to the thickness of the internal electrode layer accumulate between the part where the internal electrode layer is not formed and the surrounding dielectric layer without the internal electrode layer is deformed. There is a problem that the thickness is partially thinner than the thickness, resulting in a decrease in insulation and a decrease in high-temperature load life.

  Accordingly, an object of the present invention is to provide a multilayer ceramic capacitor that is excellent in insulation even when the thickness of the dielectric layer is reduced, and that is excellent in reliability of high-temperature load life.

The multilayer ceramic capacitor of the present invention includes (1) a capacitor main body in which dielectric layers and internal electrode layers made of a plurality of crystal particles are alternately stacked, and opposite end surfaces of the capacitor main body from which the internal electrode layers are derived. In a multilayer ceramic capacitor having a pair of external electrodes provided respectively,
Forming an internal electrode pattern,
Forming a first ceramic pattern on the same surface around the internal electrode pattern;
The inner electrode near the end of the pattern and the first ceramic pattern on the second ceramic average particle diameter D ₂ of the ceramic powder is smaller than the average particle diameter D ₁ of the ceramic powder contained in the first ceramic pattern included Forming a pattern,
On the same surface of the inner side of the second ceramic pattern in the internal electrode pattern, the third average particle diameter D ₃ of the ceramic powder is greater than the average particle diameter D ₂ of the ceramic powder contained in the second ceramic pattern included Form a ceramic sheet to form a pattern sheet,
By laminating and baking the pattern sheet,
A straight line drawn in the laminating direction of the internal electrode layer at the end in the planar direction of the internal electrode layer with respect to the dielectric layer between the internal electrode layers in the cross section of the capacitor body parallel to the end surface on which the external electrode is formed said number crystal grains present in the above, in the central portion in the planar direction of the internal electrode layer, with more than the number of crystal grains which is also present on a line drawn in the stacking direction of the internal electrode layers, the internal The average particle diameter of the crystal particles constituting the dielectric layer on the outer periphery of the same surface as the electrode layer is the average of the crystal grains constituting the end portion of the dielectric layer between the internal electrode layers in the planar direction of the internal electrode layer. It is characterized by being larger than the particle size .

  In the multilayer ceramic capacitor, (2) the crystal particles contain zirconia, and the zirconia content of the crystal particles of the dielectric layer at the end of the internal electrode layer is the center of the internal electrode layer. It is desirable that the content of zirconia in the crystal particles of the dielectric layer is larger.

  Here, the thickness of the straight line is smaller than the minimum diameter of the crystal particles. Further, the end in the planar direction of the internal electrode layer is a position near the end in the planar direction of the internal electrode layer exposed in the cross section of the capacitor body. The ends of the internal electrode layers are places where the ends of the upper and lower internal electrode layers can be connected in a straight line in the stacking direction (a direction perpendicular to the plane direction of the internal electrode layers). Further, the central portion of the internal electrode layer in the planar direction is the central position between the terminal ends of the internal electrode layer exposed in the cross section in the planar direction.

  Normally, when the thickness of the dielectric layer is reduced to a multilayer, the effect of the step due to the thickness of the internal electrode layer increases between the portion where the internal electrode layer is formed and the portion where the internal electrode layer is not formed. Although the surrounding dielectric layer without the electrode layer is easily deformed, according to the multilayer ceramic capacitor of the present invention, due to the deformation of the dielectric layer, the thickness of the dielectric layer at the end of the internal electrode layer is the center of the internal electrode layer. The number of crystal particles in the dielectric layer at the end of the internal electrode layer is smaller than the number of crystal particles in the dielectric layer at the center of the internal electrode layer As a result of the increase, the insulation of the dielectric layer can be improved, and the reliability of the multilayer ceramic capacitor at the high temperature load life can be improved.

  FIG. 1 is a perspective view of the multilayer ceramic capacitor of the present invention. FIG. 2 is a plan view showing the internal electrode layer formed on the dielectric layer inside the capacitor body. The positions of the end and center of the AA cross section shown in FIG. 1 in the plane of the internal electrode layer are shown. It is shown.

3A is a cross-sectional view taken along the line AA of FIG. 1, and FIG. 3B is a schematic diagram showing crystal grains constituting the dielectric layer at the center and the end of FIG. In the multilayer ceramic capacitor of the present invention, a pair of external electrodes 3 a and 3 b are formed on opposite end surfaces of the capacitor body 1. The capacitor body 1 is configured by alternately laminating dielectric layers 5 and internal electrode layers 7. The external electrodes 3a and 3b are connected to the end face from which the internal electrode layer 7 of the capacitor body 1 is led out (direction BB in FIG. 1). Here, the number of laminated ceramic capacitors is preferably 300 or more for high capacity.

  The thickness of the dielectric layer 5 is desirably 2 μm or less, and particularly preferably 1 to 1 and 5 μm. If the thickness of the dielectric layer 5 is 1 μm or more, it becomes highly insulating, and if it is 2 μm or less, the capacity can be increased.

  On the other hand, the thickness of the internal electrode layer 7 is preferably 0.5 to 1.5 μm. If the thickness of the internal electrode layer 7 is 0.5 μm or more, discontinuity after firing is suppressed, the effective area can be increased, and the capacitance can be increased. If the thickness of the internal electrode layer 7 is 1.5 μm or less, it is suitable for reducing the thickness of the multilayer capacitor, and the step of the internal electrode layer 7 can be suppressed.

  In the multilayer ceramic capacitor of the present invention, the dielectric layer 5 is composed of a plurality of crystal grains 9 whose main component is barium titanate. In the present invention, the crystal grain 9 has the following characteristics. That is, in the multilayer ceramic capacitor of the present invention, the dielectric layer 5 between the internal electrode layers 7 in the cross section of the capacitor body 1 parallel to the end surface on which the external electrodes 3a and 3b are formed is the plane of the internal electrode layer 7. The number of crystal grains 9 existing on the straight line 13 drawn in the laminating direction of the internal electrode layer 7 at the end portion 7 a in the direction is also in the laminating direction of the internal electrode layer 7 at the central portion 7 b in the planar direction of the internal electrode layer 7. It is important that the number is larger than the number of crystal grains 9 existing on the straight line 13 drawn. When the number of crystal grains in the dielectric layer 5 near the end 7a of the internal electrode layer 7 is n1, and the number of crystal grains 9 in the dielectric layer 5 in the central part 7b of the internal electrode layer 7 is n2, n1 / The range of n2 = 1.8-2 is preferable. When n1 / n2 = 1.8 or more, the insulation resistance and the high temperature load life are increased. On the other hand, when n1 / n2 is 2 or less, the capacitance can be maintained high. That is, the average particle diameter D1 of the crystal particles 9 forming the dielectric layer 5 at the end portion 7a of the internal electrode layer 7 is equal to the average particle diameter of the crystal particles 9 forming the dielectric layer 5 at the central portion 7b of the internal electrode layer 7. It is smaller than D2. Regarding the average particle diameters D1 and D2 of the crystal particles 9 when the thickness of the dielectric layer 5 is 2 μm or less, the average particle diameter D1 of the crystal particles 9 forming the dielectric layer 5 at the end 7a of the internal electrode layer 7 is Desirably, the average particle diameter D2 of the crystal particles 9 forming the dielectric layer 5 of the central portion 7b of the internal electrode layer 7 is 0.3 to 0.5 μm. Is desirable. When the thickness of the dielectric layer 5 is 2 μm or less, the dielectric layer 5 is thinned and deformed in a small-sized and high-capacity multilayer ceramic capacitor by having the above-mentioned crystal grain size difference. High insulation can be achieved.

  Further, according to the present invention, it is desirable that the grain size of the crystal particles 9 forming the dielectric layer 5 is gradually atomized from the central portion 7b of the internal electrode layer 7 to the end portion 7a of the internal electrode layer. Such a change in particle size can be formed by applying a finer powder than the center portion to an area of about 10 to 30% of the entire width from the end portion of the internal electrode pattern, as shown in a process drawing described later. If it is less than 10% of the total width from the end of the internal electrode pattern, the insulating property tends to be lowered. On the other hand, if it exceeds 30%, the capacitance decreases.

In the multilayer ceramic capacitor of the present invention, the dielectric layer 5 preferably contains rare earth element oxides, MgO and MnO, and the contents of rare earth element oxides, MgO and MnO contained in the crystal grains 9 are BaTiO _3. If the rare earth element oxide and MgO are 0.5 to 2 mol parts and MnO = 0.2 to 0.5 mol parts with respect to 100 mol parts of the crystal grains mainly composed of, the temperature characteristics of capacitance As a result, the insulation is increased and the reliability in the high temperature load test is excellent.

The dielectric layer 5 is a crystal in which the content of zirconia in the crystal particles 9 forming the dielectric layer 5 at the end 7 a of the internal electrode layer 7 forms the dielectric layer 5 in the central portion 7 b of the internal electrode layer 7. The content is preferably larger than the content of zirconia (ZrO ₂ ) in the particles 9. By causing the zirconia component to be dissolved in the crystal particles 9 mainly composed of BaTiO ₃ , grain growth at the time of firing the crystal particles 9 can be suppressed. Further, zirconia is contained in the crystal particles 9 so that the zirconia content of the crystal particles 9 at the end 7 a of the internal electrode layer 7 is larger than the zirconia content of the crystal particles 9 in the central portion 7 b of the internal electrode layer 7. This improves the high temperature load reliability. In this case, the content of zirconia is desirably 0.4 to 2 mole parts in the whole raw material powder. Further, the crystal grains 9 of the present invention can also be used in which a solid solution from the start as _{BaTi 1-x Zr x O 3} (x = 0.005~0.2).

  The internal electrode layer 7 is preferably a base metal such as nickel (Ni) or a nickel alloy in that the manufacturing cost can be suppressed even if the internal electrode layer 7 is highly laminated, and in particular, the nickel (Ni Ni) is more desirable.

  FIG. 4 is a schematic diagram showing a method for evaluating the resistance of a grain boundary in a dielectric layer using AC impedance measurement in the present invention. In FIG. 4, reference numeral 20a denotes a thermostatic chamber in which a multilayer ceramic capacitor as a sample is attached to perform temperature control, 20b denotes a HALT measuring device that applies a DC voltage to the sample, and 20c denotes an impedance measuring device having an AC power source. FIG. 5 is a typical example of (a) the resistance evaluation result of the grain boundary in the dielectric layer using the AC impedance measurement of the present invention, and (b) is the core constituting the dielectric layer constituting the multilayer ceramic capacitor. (Center part), shell (outer peripheral part), grain boundary phase 11, and four components of the interface between the internal electrode layer 7 and the dielectric layer 5 are represented by an equivalent circuit.

  In this case, the multilayer ceramic capacitor has a temperature higher than the Curie temperature indicated by the crystal particles 9 mainly composed of barium titanate constituting the dielectric layer 5 and a voltage equal to or higher than 1/3 of the rated voltage of the multilayer ceramic capacitor. Leave in a high temperature load atmosphere. And before and after leaving to stand in the high temperature load atmosphere of said conditions, the resistance reduction rate of the grain boundary in the dielectric material layer 5 in an alternating current impedance measurement is measured on the same conditions. FIG. 5 shows a graph (Cole-Cole plot) of impedance change at the core (center part), shell (outer peripheral part), grain boundary, and interface between the internal electrode and the dielectric layer of the crystal grain 9 in the multilayer ceramic capacitor of the present invention. An example is shown. In this evaluation, the dielectric layer 5 is divided into four components, ie, the core (center portion), the shell (outer peripheral portion), the grain boundary phase 11 and the interface between the internal electrode layer 7 and the dielectric layer 5 as shown in the equivalent circuit of FIG. Distinguish. The horizontal axis of the graph indicates the real part of the impedance signal, and the vertical axis indicates the imaginary part. The graph showing the change in impedance is the difference between before and after the accelerated life test (HALT), and fitting by simulation. In the present invention, attention is particularly paid to the resistance change at the grain boundary, and the rate of change of the real part is preferably 1% / min or less. This evaluation can be obtained, for example, by dividing the Cole-Cole plot of FIG. 5 before and after the accelerated life test (HALT) into the above four components by using dedicated software. Here, the test temperature is preferably 1.5 times the Curie temperature, and the voltage is preferably 2/5 V or more of the rated voltage. When the test conditions are set as described above, there is an advantage that the diffusion rate of ions and the movement of electrons in the dielectric layer 5 before and after the high-temperature load atmosphere treatment are increased, and the resistance reduction rate of the grain boundary phase 11 can be seen remarkably. is there.

  Next, a method for producing the multilayer ceramic capacitor of the present invention will be described in detail. FIG. 6 is a process diagram showing the method for producing the multilayer ceramic capacitor of the present invention (side margin direction (AA)). FIG. 7 is a process diagram showing the method for producing the multilayer ceramic capacitor of the present invention (end margin direction (BB)).

  In the step (a), a rectangular internal electrode pattern 33 is formed on the substrate 31. The conductor paste to be the internal electrode pattern 33 is prepared by mixing Ni or an alloy powder thereof as a main component metal, mixing ceramic powder as a co-material with this, and adding an organic binder, a solvent and a dispersant. As the ceramic powder, BT powder described later is preferable. However, by including ceramic powder in the conductor paste, columnar ceramic is formed so as to penetrate the internal electrode layer 7 and connect the upper and lower dielectric layers 5. Thereby, peeling between the dielectric layer 5 and the internal electrode layer 7 can be prevented.

Next, in step (b), a first ceramic pattern 35 is formed around the internal electrode pattern 33 so as to be flush with the internal electrode pattern 33. Next, in step (c), the second ceramic pattern 37 is formed on the vicinity 33 a of the internal electrode pattern 33 and on the first ceramic pattern 35. Next, in the step (d) (the step (d) in the end margin direction (BB) in FIG. 7 is omitted), the second ceramic pattern 37 and the second ceramic pattern 37 on the internal electrode pattern 33 are arranged inside the second ceramic pattern 37. The third ceramic pattern 39 is formed so as to be on the same surface, and the pattern sheet 40 is formed on the substrate 31. In this case, it is preferable that the average particle diameter D1 of the ceramic powder included in the first ceramic pattern 35 and the average particle diameter D3 of the ceramic powder included in the third ceramic pattern 39 are equal. On the other hand, the average particle diameter D2 of the ceramic powder included in the second ceramic pattern 35 formed at the end 33a of the internal electrode pattern 33 is based on the average particle diameters D1 and D3 of the ceramic powder included in the first and third ceramic patterns. It is important to be small. That is, it is more preferable than the relationship of D1> D2, D3> D2, and D1 = D3. Here, the thickness of the internal electrode pattern 33 is preferably 0.5 μm or more and 2 μm or less, while the thickness of the second ceramic pattern 35 is preferably 1 μm or more and 3 μm or less. Next, the pattern sheet 39 is peeled from the substrate. Next, in step (e), a desired number of pattern sheets 39 are stacked so that the short sides of the rectangular internal electrode pattern 33 are aligned and the long sides are shifted by a half pattern, and the protective layer sheet 41 is formed on the upper and lower surfaces. The green body 43 is formed by laminating ceramic green sheets. Next, the base laminate 43 is cut along the cutting line 45 to form a capacitor body molded body in which the end faces of the internal electrode pattern 33 are alternately exposed at both ends in the stacking direction. Next, the capacitor body 1 is formed by firing the capacitor body molded body. Next, the external electrode 3 mainly composed of a base metal such as Cu is formed on the end surface of the capacitor body 1 where the internal electrode layer 7 is exposed. For the first to third ceramic patterns 35, 37, and 39, the glass powder is added to the BaTiO ₃ powder together with the above-described additives such as rare earth elements, MgO, and MnO as the raw material powder used in the above process. The glass powder is preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the BaTiO ₃ powder because it can be sintered at a low temperature. The average particle size of the ceramic powder included in the second ceramic pattern 37 is 0.1 to 0.2 μm, while the average particle size of the ceramic powder included in the first and third ceramic patterns 35 and 39 is 0.15 to 0. .35 μm is desirable. Moreover, as a ceramic powder contained in the second ceramic pattern 37, it is desirable to add 0.5 to 1 mol% of zirconia (ZrO ₂ ) powder in a raw material powder mainly composed of BaTiO ₃ . _Furthermore, the same effect also by using _{BaTi 1-x Zr x O 3} (x = 0.005~0.2).

  Further, when a necking powder in which two or more ceramic powders are combined is used as the ceramic powder used for the second ceramic pattern 37 formed on the end 33a of the internal electrode pattern 33, the ceramic powder is oriented in the ceramic pattern. It is possible to form a large number of interfaces in the thickness direction of the dielectric layer 5. The aspect ratio of the necking powder is preferably a long dimension / short dimension ratio of 1.5 or more, and a long dimension / short dimension ratio of 3 or less is preferable because the average diameter of the short dimension is 0.3 μm or less.

  The metal powder used for the internal electrode pattern 33 is preferably Ni or Cu, or an alloy powder thereof, and the average particle diameter of these metal powders is 0.1 to 0.2 μm while suppressing oversintering. It is preferable in the part which can reduce. According to the manufacturing method of the multilayer ceramic capacitor of the present invention described above, by adopting a method of forming a ceramic pattern having ceramic powders having different particle sizes between the central portion and the end portion of the internal electrode pattern 33, Thus, the average particle size of the crystal particles 9 forming the dielectric layer 5 at the end 7a of the internal electrode layer 7 is larger than the average particle size of the crystal particles 9 forming the dielectric layer 5 at the central portion 7b of the internal electrode layer 7. Therefore, it is possible to easily form a multilayer ceramic capacitor including the dielectric layer 5 in which the number of crystal grains 9 on the end portion 7a side is larger than the number of crystal grains 9 forming the dielectric layer 5 in the central portion 7b. .

The multilayer ceramic capacitor of the present invention was produced as follows. As the ceramic powder used for the first and third ceramic patterns, one having an average particle size of 0.3 μm, an average aspect ratio of the powder of 1.1, and a molar ratio of Ba and Ti of 1.003 was used. Barium titanate as the main component powder (BaTiO ₃₎ additive amount for powder for BaTiO ₃ 100 molar parts, 0.5 mole part _MgO, Y 2 _{O 3} and MnCO ₃ 0.5 mole part and MnO As a result, 0.3 mol part was added. A glass powder composed of 50 mol% of SiO _2, 10 mol% of Li ₂ O, 20 mol% of BaO, and 20 mol% of CaO as a sintering aid is 1. added to 100 parts by mass of barium titanate powder. 2 parts by mass were added. The average particle size of the glass powder was 0.5 μm. The ceramic powder used for the second ceramic pattern is shown in Table 1. The additive and the amount added were the same as those of the first and third ceramic patterns. Using a zirconia ball having a diameter of 5 mm, a mixed solvent of toluene and alcohol as a solvent was added to the mixed powder of the above powders and wet mixed to prepare slurry for the first, second and third ceramic patterns, respectively. Next, a conductor paste containing Ni powder having an average particle size of 0.2 μm was prepared. Next, a plurality of internal electrode patterns having a thickness of 1 μm were formed in a predetermined arrangement on a polyester film as a base material. The area of the internal electrode pattern was 1.6 mm for the long side and 0.8 mm for the short side. Next, the first ceramic pattern was formed to have substantially the same thickness around the internal electrode pattern. Next, a second ceramic pattern was formed in a region excluding the central portion of the internal electrode pattern. The second ceramic pattern was formed to have a width of 20% of the entire width of the long side and the short side from the end of the internal electrode pattern. Next, a third ceramic pattern was formed on the upper surface of the internal electrode pattern not provided with the second ceramic pattern by using the same ceramic slurry as the first ceramic pattern to form a pattern sheet. The second ceramic pattern and the third ceramic pattern were formed to have substantially the same thickness. Next, the polyester film and the pattern sheet were peeled off, and a desired number of layers were laminated so that the short sides of the rectangular internal electrode pattern were aligned and the long sides were shifted by a half pattern to form a base laminate. The number of laminated internal electrode patterns was 360 layers, and upper and lower ceramic green sheets having a thickness of 5 μm formed from the ceramic slurry of the first ceramic pattern were laminated on the upper and lower surfaces. The pressing conditions were a temperature of 60 ° C., a pressure of 10 ⁷ Pa, and a time of 10 minutes. Next, the base laminate was cut to form a capacitor body molded body in which the end faces of the internal electrode pattern were alternately exposed at both ends in the stacking direction. Next, the capacitor body was fired to form a capacitor body. Firing is performed by removing the binder at 300 ° C./h in the atmosphere, firing at 1170 ° C. (oxygen partial pressure 10 ⁻⁶ Pa) for 2 hours, and then reoxidation treatment at 1000 ° C. in a nitrogen atmosphere for 7.5 hours. Did. Next, a Cu external electrode was baked on the end surface of the capacitor main body where the internal electrode layer was exposed, and then Ni plating and Sn plating were sequentially performed on the surface of the external electrode to produce a multilayer ceramic capacitor. As for the dimensions of the capacitor body, the surface parallel to the internal electrode layer was 1 mm × 0.5 mm, and the thickness was 1 mm. The area of the internal electrode layer was 0.7 mm × 0.3 mm. The average thickness of the dielectric layer was 2 μm.

The obtained multilayer ceramic capacitor was evaluated as follows. The number of crystal grains existing between the dielectric layers was evaluated. In this case, those having a larger number of crystal particles per dielectric layer have a smaller average particle size. The number of crystal grains was calculated using the following method. First, the external electrode surface of the multilayer ceramic capacitor was buried in a resin and polished to the center of the porcelain using abrasive paper. Next, chemical etching was performed using a solution (HCl = 0.09%, HF = 0.04%) at 25 ° C. for 5 seconds to expose the grain boundaries. Using an electron microscope (SEM), the center and the end (about 0.1 μm from the end of the internal electrode layer) of the dielectric layer sandwiched between the internal electrode layers on the polished surface where the grain boundaries are exposed are respectively used. The photo was taken at 50000x so that the dielectric layer was in the center of the photo. After that, the interface between the dielectric layer and the internal electrode layer at both ends of the photograph taken is connected with a straight line, a perpendicular line is drawn from the straight line in the thickness direction of the dielectric layer, and the crystal electrode existing on the line is connected to the internal electrode. The number of crystal grains between the interface with the layer and the interface with the facing internal electrode layer was evaluated. The number of samples of the multilayer ceramic capacitor was ten. The capacitance was measured using an LCR meter at a temperature of 20 ° C. under the conditions of AC 1 V and measurement frequency 1 kHz. The number of samples was 100 each. The insulation resistance was measured using an insulation resistance meter at a voltage of 2 V and an application time of 1 minute at a temperature of 25 ° C. The number of samples was 100 each. For the resistance reduction rate before and after the high temperature load treatment, the above-described method capable of simply and quickly evaluating the high temperature load test was used. As high temperature load conditions in this case, the temperature was 250 ° C., and the voltage applied to the external electrode of the multilayer ceramic capacitor was 3V. The voltage during measurement was 0.1 V, the frequency was 10 mHz to 10 kHz, and the AC impedance before and after the treatment was evaluated for 30 samples. The HALT (high temperature high voltage acceleration reliability) test was performed with a DC voltage of 22 V applied at 125 ° C. and 135 ° C., and the time when the leakage current exceeded 10 mA was defined as the failure time. After the measurement is completed, conversion is performed at DC = 9.45V (L2 / L1 = (V1 / V2) ⁿ (for example, L2 is a failure time at 9.45V, L1 is a failure time at 22V, V1 is 22V, V1 Was 9.45V, n = 5), 0.3% cumulative failure was determined at 1000 hours, and 1000 hours or more was determined to be non-defective, and the results are shown in Tables 1 and 2.

  As is clear from the results of Tables 1 and 2, the sample of the present invention in which the ceramic powder having a smaller average particle size than the average particle size of the ceramic powder used in the first and third ceramic patterns was used in the second ceramic pattern. No. 2 to 12, the number of crystal particles at the end of the internal electrode layer between the dielectric layers is larger than the number of crystal particles at the center, and the average particle size of the crystal particles per thickness of the dielectric layer on the internal electrode layer Is smaller than the central portion, and the capacitance is 0.79 μF to 0.96 μF. Although the insulation resistance was slightly lower than 1, the insulation resistance was 200 MΩ to 260 MΩ, and the resistance reduction rate before and after the high temperature load treatment was 1% / min or less, and high insulation and high temperature load reliability (HALT) were obtained. . In particular, zirconia is contained in the end portion of the internal electrode layer so that the content of zirconia in the end portion of the internal electrode layer is larger than the content of zirconia in the center portion of the internal electrode layer. Sample No. In 3-5 and 8-10, the resistance reduction rate before and after the high temperature load treatment was 0.7% / min or less, indicating high high temperature load reliability. On the other hand, sample No. 1 using ceramic powder having the same average particle diameter for the first to third ceramic patterns. 1, the capacitance was as high as 1.03 μF, but the insulation resistance was 180 MΩ, and the resistance reduction rate before and after the high temperature load treatment was as large as 1.2% / min.

1 is a perspective view of a multilayer ceramic capacitor of the present invention. It is a top view which shows the internal electrode layer formed on the dielectric material layer inside the capacitor | condenser main body of the multilayer ceramic capacitor of this invention, and the edge part and center of the AA cross section shown in FIG. 1 in the surface of an internal electrode layer This indicates the position of the part. (A) is AA sectional drawing of FIG. 1, (b) is a schematic diagram showing the crystal grain which comprises the dielectric material layer in the center part and edge part of Fig.1 (a). It is a schematic diagram which shows the evaluation method of the resistance of the grain boundary in the dielectric material layer using the alternating current impedance measurement in this invention. (A) It is a typical example of the resistance evaluation result of the grain boundary in the dielectric layer using the alternating current impedance measurement of this invention, (b) is the core (center part) which comprises the dielectric material layer which comprises a multilayer ceramic capacitor The four components of the shell (outer peripheral portion), the grain boundary phase, and the interface between the internal electrode layer and the dielectric layer are represented by an equivalent circuit. It is process drawing which shows the manufacturing method of the multilayer ceramic capacitor of this invention (side margin direction (AA)). It is process drawing which shows the manufacturing method of the multilayer ceramic capacitor of this invention (end margin direction (BB)).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor body 3 External electrode 5 Dielectric layer 7 Internal electrode layer 7a End part 7b Center part 9 Crystal grain

Claims (2)

A capacitor body in which dielectric layers and internal electrode layers made of a plurality of crystal particles are alternately laminated, and a pair of external electrodes provided on opposing end surfaces from which the internal electrode layers of the capacitor body are led out, respectively. In the multilayer ceramic capacitor
Forming an internal electrode pattern,
Forming a first ceramic pattern on the same surface around the internal electrode pattern;
The inner electrode near the end of the pattern and the first ceramic pattern on the second ceramic average particle diameter D ₂ of the ceramic powder is smaller than the average particle diameter D ₁ of the ceramic powder contained in the first ceramic pattern included Forming a pattern,
On the same surface of the inner side of the second ceramic pattern in the internal electrode pattern, the third average particle diameter D ₃ of the ceramic powder is greater than the average particle diameter D ₂ of the ceramic powder contained in the second ceramic pattern included Form a ceramic sheet to form a pattern sheet,
By laminating and baking the pattern sheet,
A straight line drawn in the laminating direction of the internal electrode layer at the end in the planar direction of the internal electrode layer with respect to the dielectric layer between the internal electrode layers in the cross section of the capacitor body parallel to the end surface on which the external electrode is formed said number crystal grains present in the above, in the central portion in the planar direction of the internal electrode layer, with more than the number of crystal grains which is also present on a line drawn in the stacking direction of the internal electrode layers, the internal The average particle diameter of the crystal particles constituting the dielectric layer on the outer periphery of the same surface as the electrode layer is the average of the crystal grains constituting the end portion of the dielectric layer between the internal electrode layers in the planar direction of the internal electrode layer. A multilayer ceramic capacitor characterized by being larger than the particle size .   The crystal particles contain zirconia, and the zirconia content of the crystal particles of the dielectric layer at the end of the internal electrode layer is the zirconia of the crystal particles of the dielectric layer at the center of the internal electrode layer. The multilayer ceramic capacitor according to claim 1, wherein the content is larger than the content.

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