JP4753859B2 - Multilayer ceramic capacitor - Google Patents

Description

  The present invention relates to a multilayer ceramic capacitor, and more particularly to a small and high capacity multilayer ceramic capacitor in which a dielectric layer is composed of barium titanate crystal particles having different calcium concentrations.

  Conventionally, with the widespread use of mobile devices such as mobile phones and the high speed and high frequency of semiconductor devices, which are the main components of personal computers, multilayer ceramic capacitors mounted on such electronic devices have been required to be small and have high capacity. For this reason, the dielectric layer and the internal electrode layer have been made thinner and highly laminated.

  As a dielectric material applied to such a small and high-capacity multilayer ceramic capacitor, a new dielectric material with improved dielectric constant and insulation properties by improving the dielectric material mainly composed of barium titanate Have been developed (see, for example, Patent Documents 1 and 2).

  The dielectric layer constituting the multilayer ceramic capacitor disclosed in Patent Document 1 has a barium titanate crystal particle (hereinafter referred to as BT crystal particle) having a calcium concentration of 0.2 atomic% or less and a calcium concentration of 0.4 atom. % Or more barium calcium titanate crystal particles (hereinafter referred to as BCT crystal particles).

  Further, the dielectric layer constituting the multilayer ceramic capacitor disclosed in Patent Document 2 has a calcium concentration of barium titanate crystal particles having a concentration of 0.2 atomic% or less, a calcium concentration of 0.4 atomic% or more, and titanium. It is formed from barium calcium zirconate titanate crystal particles in which a part of the titanium site of barium oxide is substituted with zirconium.

The multilayer ceramic capacitors disclosed in the above Patent Documents 1 and 2 are obtained by combining the crystal particles constituting the dielectric layer, so that the dielectric constant of the dielectric layer, its temperature characteristics, and the high temperature load test It is said that it can improve the service life.
JP 2006-156450 A JP 2006-179773 A

  However, the multilayer ceramic capacitor using the dielectric layer composed of the composite particles disclosed in Patent Documents 1 and 2 has a problem that the insulation resistance gradually decreases with the high temperature standing time in the evaluation of the high temperature load life. It was.

  Furthermore, when manufacturing the above-mentioned multilayer ceramic capacitor, the capacitor body before forming the external electrode immediately after the main firing in a reducing atmosphere at a temperature of about 1200 ° C. has a dielectric layer reduced and is practically insulated. It did not have resistance.

  Therefore, the capacitor body after the main firing usually needs to be reoxidized in an atmosphere at a lower temperature and higher oxygen concentration than the conditions for the main firing.

  This re-oxidation treatment requires the same amount of labor, time, and expense as the firing step, which has caused high manufacturing costs.

  Therefore, the present invention relates to a multilayer ceramic capacitor having a dielectric ceramic layer composed of barium titanate crystal particles and barium calcium zirconate titanate crystal particles as a dielectric layer. An object of the present invention is to provide a monolithic ceramic capacitor having a high insulating property even when reduction treatment is performed.

  The multilayer ceramic capacitor of the present invention includes a barium titanate crystal particle having a calcium concentration of 0.2 atomic% or less, and a barium calcium zirconate titanate crystal particle having a calcium concentration of 0.4 atomic% or more and having a solid solution of zirconium. In the multilayer ceramic capacitor in which the dielectric layers constituted by and the internal electrode layers are alternately laminated, the barium titanate crystal particles and the barium calcium zirconate titanate crystal particles contain magnesium, rare earth elements and vanadium. In addition, the ratio of the contents of magnesium and rare earth elements contained in the central portion of the barium titanate crystal particles to the contents of magnesium and rare earth elements on the surface of the barium titanate crystal particles is the zircon titanate. Barium acid The ratio of the contents of magnesium and rare earth elements contained in the central portion of the barium calcium zirconate titanate crystal particles to the contents of magnesium and rare earth elements on the surface of the ruthenium crystal particles is larger. .

  In the multilayer ceramic capacitor, an average particle size of the barium titanate crystal particles is larger than an average particle size of the barium calcium zirconate titanate crystal particles, and the dielectric layer includes the barium titanate crystal particles and the titanium The content of vanadium is 0.1 to 0. 0 in terms of oxide with respect to 100 mol parts of barium and titanium oxides contained in barium calcium zirconate crystal particles as barium titanate. It is desirable to be 4 mole parts.

  According to the present invention, the dielectric layer constituting the multilayer ceramic capacitor is composed of barium titanate crystal particles and barium calcium zirconate titanate crystal particles, and vanadium is contained in these crystal particles, By making the ratio of magnesium and rare earth elements contained in the barium crystal particles and barium calcium zirconate titanate crystal particles a specific ratio, the barium titanate crystal particles have cubic crystal structures with a collapsed core-shell structure. Can be expensive.

  For this reason, since the barium titanate crystal particles having high cubic crystallinity coexist between the barium calcium zirconate titanate crystal particles, grain growth of the barium calcium zirconate titanate crystal particles is suppressed, and barium titanate is suppressed. The dielectric layer composed of crystal particles and barium calcium zirconate titanate crystal particles has high insulation properties even after the main firing, and obtains a multilayer ceramic capacitor with little decrease in insulation resistance with time change in high temperature load test be able to.

  Fig.1 (a) is a schematic sectional drawing which shows the multilayer ceramic capacitor of this invention. (B) is an enlarged schematic view showing the main crystal grains and the grain boundary phase constituting the dielectric layer. In the multilayer ceramic capacitor of the present invention, external electrodes 3 are formed at both ends of the capacitor body 1. The external electrode 3 is formed, for example, by baking Cu or an alloy paste of Cu and Ni.

  The capacitor body 1 is configured by alternately laminating dielectric layers 5 and internal electrode layers 7. The dielectric layer 5 is composed of crystal grains 9 and a grain boundary phase 11. The thickness is preferably 3 μm or less, particularly 2.5 μm or less in order to reduce the size and capacity of the multilayer ceramic capacitor. Furthermore, in order to stabilize the capacitance variation and capacitance temperature characteristics, The thickness of the layer 5 is more preferably 0.4 μm or more.

  The internal electrode layer 7 is preferably a base metal such as nickel (Ni) or copper (Cu) in that the manufacturing cost can be suppressed even if the internal electrode layer 7 is highly laminated. In particular, simultaneous firing with the dielectric layer 5 according to the present invention is possible. Nickel (Ni) is more preferable in that it can be achieved.

  The crystal particles 9 constituting the dielectric layer 5 in the multilayer ceramic capacitor of the present invention are barium titanate-based crystal particles having a perovskite crystal structure having different calcium concentrations.

  That is, the barium titanate-based crystal particles in the dielectric layer 5 constituting the multilayer ceramic capacitor of the present invention have a part of the A site replaced with calcium (hereinafter referred to as Ca), and the titanium site that is the B site is zirconium. Barium calcium zirconate titanate crystal particles (hereinafter referred to as BCTZ crystal particles) 9a having a perovskite crystal structure substituted with (hereinafter referred to as Zr) and titanium having a perovskite crystal structure containing no Ca Barium acid crystal particles (hereinafter referred to as BT crystal particles) 9b.

  That is, the crystal particle 9 in the present invention contains the BCTZ crystal particle 9a and the BT crystal particle 9b, and as described above, excellent dielectric properties can be obtained by the coexistence of these two types of crystal particles. Show.

Of the crystal particles 9 in the present invention, the BT crystal particle 9b is ideally represented by BaTiO ₃ . In the present invention, the BT crystal particles 9b that do not contain Ca and Zr have analytical values of both Ca and Zr concentrations of 0.2 atomic% or less, but in the BCTZ crystal particles 9a. In which Ca and Zr components contained in are slightly diffused in the BT crystal particles 9b.

  On the other hand, the BCTZ crystal particle 9a has a Ca concentration of 0.4 atomic% or more, and in particular, the Ca concentration is 0.5 in that the BCTZ crystal particle 9a maintains the function as a ferroelectric having a high relative dielectric constant. Desirably, it is ˜2.5 atomic%.

Further, the BCTZ crystal particle 9a is a perovskite barium titanate in which a part of the A site is substituted with Ca and a part of the B site is substituted with Zr as described above. represented by _{Ba 1-x Ca x) m} (Ti 1-y Zr y) O 3.

  In the present invention, the amount of Ca substitution in the A site in the BCTZ crystal particle 9a is preferably x = 0.01 to 0.2, and y = 0.15 to 0.25.

  If the substitution amount of Ca at the A site is within this range, the phase transition point near room temperature is shifted to a sufficiently low temperature side, and the coexistence structure with the BT crystal particles 9b is excellent in the temperature range used as a multilayer ceramic capacitor. This is because the temperature characteristic of the capacitance is shown. Further, if the amount of Zr substitution at the B site is within this range, the dielectric loss is reduced and the relative permittivity is increased.

In the present invention, the BCTZ crystal particles 9a and the BT crystal particles 9b constituting the crystal particles 9 of the dielectric layer 5 are obtained by evaluating the cross section or surface of the dielectric layer 5 in the evaluation based on the index when the Ca concentration is defined. When the ratio of the BCTZ crystal particles 9a is A _BCTZ and the ratio of the BT crystal particles 9b is A _{BT in} the area ratio of each crystal particle in the crystal structure, the relationship of A _BT / A _BCTZ = _0.1-3 is established. It is desirable to coexist in a systematic proportion.

  Further, the average particle diameter of the crystal particles 9 (BCTZ crystal particles 9a and BT crystal particles 9b) in the present invention is 0.45 μm in that high capacity and high insulation are achieved by making the dielectric layer 5 thin. The following is preferred. On the other hand, the lower limit of the particle size of the BCZ crystal particle 9a and the BT crystal particle 9b is 0.1 μm or more because the dielectric constant of the dielectric layer 5 is increased and the temperature dependence of the dielectric constant is suppressed. preferable.

  BCTZ crystal particles 9a and BT crystal particles 9b both contain Mg and a rare earth element. Further, manganese (hereinafter referred to as Mn) is used for the purpose of improving the reduction resistance of dielectric layer 5. .).

The contents of Mg, rare earth element and Mn contained in the dielectric layer 5 are such that each oxide of Ba and Ti contained in the crystal particles (BCT crystal particles 9a and barium titanate crystal particles 9b) is barium titanate. relative to the molar amount of 100 molar parts of the case, 0.5 to 1 molar parts Mg is as MgO, 0.5 to 1 mole unit as the rare earth element _RE 2 _{O 3,} Mn is as MnO 0.1 to 0.3 If it is a molar part, there is an advantage that the temperature characteristic of the capacitance is stabilized, the insulation resistance is increased, and further, the decrease of the insulation resistance in the high temperature load test can be suppressed.

  Further, in the present invention, vanadium is contained in the crystal particle 9, and each of Mg and rare earth element contained in the central portion of the BT crystal particle 9 b with respect to the respective contents of Mg and rare earth element on the surface of the BT crystal particle 9 b. It is important that the ratio of the contents is larger than the ratio of the contents of Mg and rare earth elements contained in the central portion of the BCTZ crystal particles 9a to the contents of Mg and rare earth elements on the surface of the BCTZ crystal particles 9a. is there.

  In contrast, the dielectric layer does not contain vanadium, and each of Mg and rare earth elements contained in the central portion of BT crystal particles 9b with respect to the respective contents of Mg and rare earth elements on the surface of BT crystal particles 9b. The ratio of the contents is equal to the ratio of the respective contents of Mg and rare earth elements contained in the central portion of BCTZ crystal particles 9a to the respective contents of Mg and rare earth elements on the surface of BCTZ crystal particles 9a, or the ratio Is small, the barium titanate crystal particles maintain the core-shell structure, so that the tetragonal nature becomes high, and both the BT crystal particles 9b and the BCTZ crystal particles 9a remain in the state of maintaining the core-shell structure. For this reason, the multilayer ceramic capacitor has a low insulation resistance after the main firing. Note that the central part of the BT crystal particles 9b and the BCTZ crystal particles 9a is a region deeper than the surface of these crystal particles by 60 nm or more based on the embodiment.

  FIG. 2A is a graph showing the concentration distribution of Mg and Y in the BT crystal particles in the dielectric layer constituting the multilayer ceramic capacitor of the present invention, and FIG. 2B is the dielectric constituting the multilayer ceramic capacitor of the present invention. It is a graph which shows density | concentration distribution of Mg and Y in the BCTZ crystal grain in a layer. In this example, sample No. 5 was evaluated. The concentrations of Mg and rare earth elements in the crystal particles 9 are analyzed by a transmission electron microscope and an analyzer (EPMA) attached thereto. In this case, each concentration of Mg and rare earth elements in each crystal particle can be determined by performing elemental analysis by EDX at intervals of 5 nm from the surface to the inside of the selected crystal particle 9 to obtain a concentration distribution. In the graph of FIG. 2, 0 nm as the distance from the grain boundary is the surface of the crystal grain, and the plot point at one end of the graph is the center of the crystal grain.

  As is apparent from FIG. 2, the BT crystal particles 9b constituting the dielectric layer 5 in the multilayer ceramic capacitor of the present invention have Mg and Y concentrations from the surface of the crystal particles 9 to the center as compared with the BCTZ crystal particles 9a. Change is gradual. On the other hand, the BCTZ crystal particle 9a has a large concentration change of Mg and Y from the surface of the crystal particle to the center. Therefore, in the BT crystal particle 9b, Mg and Y are dissolved in the BT crystal particle 9b as compared with the BCTZ crystal particle 9b, so that the core-shell structure in the BT crystal particle 9b is broken.

  That is, as described above, the BCTZ crystal particle 9a has a large change in the concentration of Mg and Y from the surface of the crystal particle 9 to the center, and the concentration of Mg and Y in the crystal particle 9 is low. It is kept.

  Here, the rare earth element in the present invention is preferably at least one of La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu, and Sc.

  On the other hand, when the concentration of either Mg or rare earth element contained in the BT crystal particle 9b is lower than the concentration of either Mg or rare earth element contained in the BCTZ crystal particle 9a, the BT crystal particle 9b is changed to the core shell. It becomes difficult to achieve a cubic structure with a broken structure, and high insulation cannot be achieved.

  In addition, in the present invention, it is desirable that the average particle size of the BT crystal particles 9b is larger than the average particle size of the BCTZ crystal particles 9a. The insulating property of the dielectric layer 5 can be further enhanced by the fact that the average particle size of the highly cubic BT crystal particles 9b is larger than the average particle size of the BCTZ crystal particles 9a.

  In the present invention, when the oxide of barium (Ba) and titanium (Ti) contained in the composite particles composed of the BT crystal particles 9b and the BCTZ crystal particles 9a constituting the dielectric layer 5 is represented as barium titanate. It is desirable that the content of vanadium is 0.1 to 0.4 mol part in terms of oxide with respect to 100 mol part of the content. By containing vanadium as an oxide, there is an advantage that the insulating property of the capacitor body after the main firing in which the reduction treatment is performed can be further enhanced.

  Next, the manufacturing method of the multilayer ceramic capacitor in this invention is demonstrated in detail. FIG. 3 is a process diagram showing a method for producing the multilayer ceramic capacitor of the present invention.

  First, the following raw material powder is mixed with an organic resin such as polyvinyl butyral resin and a solvent such as toluene and alcohol using a ball mill to prepare a ceramic slurry, and then the ceramic slurry is doctor blade or die coater method. The ceramic green sheet 21 is formed on the base material 22 using a sheet forming method such as. The thickness of the ceramic green sheet 21 is preferably 1 to 4 μm from the viewpoint of thinning the dielectric layer for increasing the capacity and maintaining high insulation.

Here, barium calcium zirconate titanate powder (hereinafter referred to as BCTZ powder) having a perovskite crystal structure in which part of the A site is substituted with Ca and part of the B site is substituted with Zr and Ca are used. Barium titanate powder (hereinafter referred to as BT powder) that is not contained is used. These dielectric powder is represented by the respective _{(Ba 1-x Ca) m} (Ti 1-y Zr y) O 3 and BaTiO _3.

  Here, the amount of Ca substitution in the A site in the BCTZ powder is preferably x = 0.01 to 0.2, and y = 0.15 to 0.25.

  The BCTZ powder preferably has an atomic ratio A / B of A site (Ba, Ca) and B site (Ti, Zr), which is a constituent component, of 1.003 or more. These BT powder and BCTZ powder are synthesized by mixing a compound containing a Ba component, a Ca component, a Ti component, and a Zr component so as to have a predetermined composition. These dielectric powders are obtained by a synthesis method selected from a solid phase method, a liquid phase method (including a method of generating via oxalate), a hydrothermal synthesis method, and the like. Among these, the dielectric powder obtained by the hydrothermal synthesis method is desirable because the particle size distribution of the obtained dielectric powder is narrow and the crystallinity is high.

  The average particle size of these BT powder and BCTZ powder is preferably 0.15 to 0.4 μm from the viewpoint of facilitating the thinning of the dielectric layer 5 and increasing the relative dielectric constant of the dielectric powder.

  On the other hand, the BT powder desirably has an A / B of 1.002 or less. When the A / B ratio of the BT powder is 1.002 or less, there is an advantage that the solid solution of additives such as Mg and rare earth elements can be enhanced.

  Mg added to the dielectric powder is 0.4 to 1 mol part in terms of oxide with respect to 100 mol part of the dielectric powder which is a mixture of BCTZ powder and BT powder, and the rare earth element is 100 mol of the dielectric powder. It is preferable that 0.5 to 1 mol part in terms of oxide with respect to part, and Mn is 0.1 to 0.3 mol part in terms of oxide with respect to 100 mol part of the dielectric powder.

The sintering aid added to the dielectric powder is preferably a glass powder composed of Li ₂ O, SiO ₂ , BaO and CaO as constituent components.

  Next, a rectangular internal electrode pattern 23 is printed and formed on the main surface of the obtained ceramic green sheet 21. The conductor paste used as the internal electrode pattern 23 is prepared by mixing Ni, Cu 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 metal powder, Ni is preferable because it enables simultaneous firing with the dielectric powder and is low in cost.

  As the ceramic powder, a BT powder having a low Ca concentration is preferable. However, by including the ceramic powder in the conductor paste, the internal electrode layer 7 constituting the multilayer ceramic capacitor of the present invention penetrates through the internal electrode layer and has upper and lower sides. Columnar ceramics are formed so as to connect the dielectric layers 5. Thereby, peeling between the dielectric layer 5 and the internal electrode layer 7 can be prevented.

  The ceramic powder used here can suppress abnormal grain growth of columnar ceramics during firing, and can increase mechanical strength. Further, by suppressing the abnormal grain growth of the columnar ceramics formed in the internal electrode layer 7, the capacitance temperature dependency of the multilayer ceramic capacitor can be reduced. The thickness of the internal electrode pattern 23 is preferably 1 μm or less because the multilayer ceramic capacitor is miniaturized and the steps due to the internal electrode pattern 23 are reduced.

  According to the present invention, the ceramic pattern 25 is formed around the internal electrode pattern 23 with substantially the same thickness as the internal electrode pattern 23 in order to eliminate the step due to the internal electrode pattern 23 on the ceramic green sheet 21. Is preferred. As the ceramic component constituting the ceramic pattern 25, it is preferable to use the dielectric powder in terms of making the firing shrinkage in the simultaneous firing the same.

  Next, a desired number of ceramic green sheets 21 on which the internal electrode patterns 23 are formed are stacked, so that a plurality of ceramic green sheets 21 on which the internal electrode patterns 23 are not formed and the upper and lower layers have the same number. Overlay to form a temporary laminate. The internal electrode pattern 23 in the temporary laminate is shifted by a half pattern in the longitudinal direction. By such a laminating method, the internal electrode patterns 23 can be alternately exposed on the end faces of the cut laminate.

  In the present invention, as described above, in addition to the method of forming the internal electrode pattern 23 in advance on the main surface of the ceramic green sheet 21 and laminating it, the ceramic green sheet 21 is once brought into close contact with the lower layer side equipment. After the internal electrode pattern 23 is printed and dried, the ceramic green sheet 21 on which the internal electrode pattern 23 is not printed is overlaid and temporarily adhered onto the printed and dried internal electrode pattern 23. It can also be formed by a method in which the adhesion of the ceramic green sheet 21 and the printing of the internal electrode pattern 23 are sequentially performed.

  Next, the temporary laminated body is pressed under conditions of higher temperature and higher pressure than the temperature pressure during the temporary lamination to form a laminated body 29 in which the ceramic green sheet 21 and the internal electrode pattern 23 are firmly adhered.

  Next, the laminated body 29 is cut along the cutting line h, that is, approximately at the center of the ceramic pattern 29 formed in the laminated body in a direction perpendicular to the longitudinal direction of the internal electrode pattern 25 ((( c1) and (c2) of FIG. 4 are cut parallel to the longitudinal direction of the internal electrode pattern 23, and the capacitor body molded body is formed so that the end of the internal electrode pattern 23 is exposed. On the other hand, in the widest portion of the internal electrode pattern 23, the internal electrode pattern is formed in an unexposed state on the side margin portion side.

  Next, this capacitor body molded body is fired under a predetermined atmosphere at a temperature condition to form a capacitor body. In some cases, the capacitor body is chamfered at the ridge line portion, and from the opposite end surface of the capacitor body. Barrel polishing may be performed to expose the exposed internal electrode layer. In the production method of the present invention, degreasing is in the temperature range up to 500 ° C., the heating rate is 5 to 20 ° C./h, the firing temperature is in the range of 1100 to 1250 ° C., and the heating rate from degreasing to the maximum temperature is 200 to 500 ° C./h, holding time at the maximum temperature of 0.5 to 4 hours, rate of cooling from the maximum temperature to 1000 ° C. is 200 to 500 ° C./h, atmosphere is hydrogen-nitrogen, heat treatment after firing (re- Oxidation treatment) It is preferable that the maximum temperature is 900 to 1100 ° C. and the atmosphere is nitrogen.

  Next, an external electrode paste is applied to the opposite ends of the capacitor body 1 and baked to form the external electrode 1. A plating film is formed on the surface of the external electrode 3 in order to improve mountability.

First, as raw material powders, BT powder, BCTZ powder ((Ba _0.95 Ca _0.05 ) _m (Ti _0.8 Zr _0.2 ) O ₃ m = 1), MgO, Y ₂ O ₃ , MnCO ₃ and V ₂ O ₅ was prepared, and these various powders were mixed in the proportions shown in Table 1. These raw material powders having a purity of 99.9% were used. Note that the average particle sizes of the BT powder and the BCTZ powder are shown in Sample No. About 1-22, all were 100 nm. Sample No. For No. 23, those having an average particle size of BT powder of 100 nm and an average particle size of BCTZ powder of 150 nm were used. The Ba / Ti ratio of the BT powder was 1.001. As the sintering aid, glass powder having a composition of SiO ₂ = 55, BaO = 20, CaO = 15, and Li ₂ O = 10 (mol%) was used. The addition amount of the glass powder was 1 part by mass with respect to 100 parts by mass of the barium titanate powder and the BCT powder.

  Next, these raw material powders were wet mixed by adding a mixed solvent of toluene and alcohol as a solvent using zirconia balls having a diameter of 5 mm.

  Next, a polyvinyl butyral resin and a mixed solvent of toluene and alcohol are added to the wet-mixed powder, and wet-mixed using a zirconia ball having a diameter of 5 mm to prepare a ceramic slurry, and a ceramic green sheet having a thickness of 3 μm by the doctor blade method. Was made.

  Next, a plurality of rectangular internal electrode patterns mainly composed of Ni were formed on the upper surface of the ceramic green sheet. The conductor paste used for the internal electrode pattern was Ni powder having an average particle size of 0.3 μm, and 30 parts by mass of barium titanate powder used as a co-material for the green sheet was added to 100 parts by mass of Ni powder.

Next, 360 ceramic green sheets on which internal electrode patterns were printed were laminated, and 20 ceramic green sheets on which the internal electrode patterns were not printed were laminated on the upper and lower surfaces, respectively, using a press machine at a temperature of 60 ° C. and pressure The layers were laminated together under the conditions of 10 ⁷ Pa and time 10 minutes, and cut into predetermined dimensions.

  Next, the laminated molded body was subjected to binder removal treatment at 300 ° C./h in the atmosphere at a heating rate of 10 ° C./h, and the temperature rising rate from 500 ° C. was 300 ° C./h. -A capacitor body was produced by firing (main firing) at 1150 to 1200 ° C for 2 hours in nitrogen. In this case, sample no. About 11-13 and 18, it was set to 1150 degreeC and others set to 1200 degreeC.

The sample was then cooled to 1000 ° C. at a rate of 300 ° C./h, reoxidized at 1000 ° C. for 4 hours in a nitrogen atmosphere, and cooled at a rate of 300 ° C./h to produce a capacitor body. did. The size of the capacitor body was 0.95 × 0.48 × 0.48 mm ³ , and the thickness of the dielectric layer was 2 μm.

  Next, the fired capacitor body was barrel-polished, and then an external electrode paste containing Cu powder and glass was applied to both ends of the capacitor body and baked at 850 ° C. to form external electrodes. Thereafter, using an electrolytic barrel machine, Ni plating and Sn plating were sequentially performed on the surface of the external electrode to produce a multilayer ceramic capacitor.

  Next, the following evaluation was performed on these multilayer ceramic capacitors. The capacitance was measured under the measurement conditions of a frequency of 1.0 kHz and a measurement voltage of 1 Vrms. The insulation resistance was evaluated for the capacitor body after firing with the external electrode formed thereon and with the external electrode formed after the re-oxidation treatment.

  The high temperature load test was evaluated by measuring the insulation resistance after leaving at a temperature of 140 ° C., a voltage of 30 V, and 100 hours. All of these were 30 samples.

  The average particle size of the BT crystal particles and BCTZ type crystal particles constituting the dielectric layer was determined by a scanning electron microscope (SEM). The polished surface was etched, 20 crystal particles in the electron micrograph were arbitrarily selected, the maximum diameter of each crystal particle was determined by the intercept method, and the average value thereof was determined.

  Regarding the Ca concentration, an arbitrary place in the vicinity of the central portion was analyzed using a transmission electron microscope and an analyzer (EPMA). At that time, the one having a Ca concentration higher than 0.4 atomic% (rounded to the second decimal place) was defined as a crystal particle having a high Ca concentration. This analysis was performed on 100 to 150 crystal particles. In the sample used in the examples, the state of the raw material powder used was maintained.

The concentrations of Mg and rare earth elements in the crystal particles were analyzed with a transmission electron microscope and an analyzer (EPMA) attached thereto. In this case, the concentration of Mg and rare earth elements in each crystal particle was determined by performing elemental analysis by EDX at intervals of 5 nm from the surface to the inside of the selected crystal particle to determine the concentration distribution. The concentration ratio between the surface and the center of the crystal grain was determined. A crystal grain having an aspect ratio of 1.3 or less was selected as the center part of the crystal grain, and such a crystal grain was set in the vicinity of an intersection from two longitudinal and lateral directions. The results are shown in Table 1.

As is clear from the results in Table 1, the dielectric layer is composed of BT crystal particles and BCTZ crystal particles, and is included in the central portion of the BT crystal particles with respect to the respective contents of Mg and rare earth elements on the surface of the BT crystal particles. The ratio of the respective contents of Mg and rare earth elements is from the ratio of the respective contents of Mg and rare earth elements contained in the central portion of the BCTZ crystal particles to the respective contents of Mg and rare earth elements on the surface of the BCTZ crystal particles In the sample containing a large amount, the insulation resistance was 10 ⁷ Ω or more even after the main firing, and the insulation resistance after 100 hours of the high temperature load test was 8 × 10 ⁵ Ω or more, indicating high insulation.

Sample No. containing 0.1 to 0.4 mol part of vanadium in terms of oxide when the content of BT in the composite particle was 100 mol part. 3 to 7, the insulation resistance after 100 hours of the high temperature load test was 1 × 10 ⁷ Ω or more.

In contrast, samples (samples No. 9 and 10) in which the dielectric layer is not composed of BT crystal particles and BCTZ crystal particles and sample Nos. To which V ₂ O ₅ is not added. In No. 1, the insulation resistance after the main firing was not measurable.

(A) is a schematic sectional drawing which shows the multilayer ceramic capacitor of this invention. (B) is an enlarged schematic view showing the main crystal grains and the grain boundary phase constituting the dielectric layer. (A) is a graph showing the concentration distribution of Mg and Y in the BT crystal particles in the dielectric layer constituting the multilayer ceramic capacitor of the present invention, and (b) is in the dielectric layer constituting the multilayer ceramic capacitor of the present invention. It is a graph which shows concentration distribution of Mg and Y in BCTZ crystal grain. It is process drawing which shows the manufacturing method of the multilayer ceramic capacitor in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor body 3 External electrode 5 Dielectric layer 7 Internal electrode layer 9 Crystal particle 9a BCT crystal particle 9b BT crystal particle 21 Ceramic green sheet 23 Internal electrode pattern 25 Ceramic pattern 29 Laminate

Claims (3)

A dielectric layer composed of barium titanate crystal particles having a calcium concentration of 0.2 atomic% or less and a barium calcium zirconate titanate crystal particle having a calcium concentration of 0.4 atomic% or more and in which zirconium is solid-solved; In the multilayer ceramic capacitor in which internal electrode layers are alternately laminated, the barium titanate crystal particles and the barium calcium zirconate titanate crystal particles contain magnesium, rare earth elements and vanadium, and the barium titanate crystals The ratio of the content of magnesium and rare earth elements contained in the central portion of the barium titanate crystal particles to the content of magnesium and rare earth elements on the surface of the particles is the surface of the barium calcium zirconate titanate crystal particles Magnesium Beam and each of the respective contents of a multilayer ceramic capacitor being greater than the ratio of magnesium and rare earth elements contained in the central portion of the zirconate titanate, barium calcium crystal grains with respect to the content of the rare earth element. The multilayer ceramic capacitor according to claim 1, wherein an average particle diameter of the barium titanate crystal particles is larger than an average particle diameter of the barium calcium zirconate titanate crystal particles. The dielectric layer is composed of the vanadium with respect to a content of 100 mol parts when the barium and titanium oxides contained in the barium titanate crystal particles and the barium calcium zirconate titanate crystal particles are expressed as barium titanate. The multilayer ceramic capacitor according to claim 1, wherein the content of is 0.1 to 0.4 mol part in terms of oxide.

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