JP6469899B2 - Multilayer capacitor - Google Patents

Description

  The present invention relates to a multilayer capacitor that can be reduced in size and performance, and a method for manufacturing the same.

  In recent years, with the miniaturization and high performance of electronic devices, there is an increasing demand for miniaturization and large capacity of multilayer capacitors used in electronic devices. In order to meet this demand, multilayer capacitors are becoming increasingly multilayered and thinned.

  As multilayer capacitors are multilayered and thinned, variations in capacitance between dielectric layers of the multilayer capacitor are likely to occur. As a result, the capacitance of the multilayer capacitor deviates from the design value, resulting in manufacturing variations of the multilayer capacitor. Therefore, there is a demand for a technique that can suppress variation in capacitance between the dielectric layers of the multilayer capacitor.

  Patent Document 1 discloses a technique that can change the capacitance for each dielectric layer of a multilayer capacitor. In this technique, the thickness of the internal electrode and the dielectric layer is changed for each layer of the multilayer capacitor so that the capacitance in all the dielectric layers of the multilayer capacitor is uniform.

JP 2007-173725 A

  In addition to the above-described miniaturization and large capacity, multilayer capacitors are strongly required to reduce costs.

  A large-area ceramic sheet is used in a general method for manufacturing a multilayer capacitor. In a manufacturing method in which a large-area ceramic sheet is used, it is possible to collectively print the internal electrodes of a plurality of multilayer capacitors and to laminate them in a lump. Thereby, the multilayer capacitor can be manufactured at low cost.

  In that respect, in the technique described in Patent Document 1, it is necessary to prepare ceramic sheets having different thicknesses for each dielectric layer of the multilayer capacitor. Furthermore, since the thickness of the internal electrode in the multilayer capacitor is changed for each dielectric layer, it is necessary to print the internal electrode under different conditions for each ceramic sheet. As described above, in the technique according to Patent Document 1, the manufacturing process becomes complicated, and the manufacturing cost of the multilayer capacitor increases.

  In view of the circumstances as described above, an object of the present invention is to provide a multilayer capacitor capable of suppressing variation in capacitance between dielectric layers and a method for manufacturing the same.

In order to achieve the above object, a multilayer capacitor according to an aspect of the present invention includes an element body, a first external electrode, and a second external electrode.
The element body includes a laminated body in which a first internal electrode, a dielectric layer, and a second internal electrode are laminated, and first and second protective layers connected to the laminated body.
The first external electrode covers the first end surface of the element body and is connected to the first internal electrode.
The second external electrode covers the second end surface of the element body and is connected to the second internal electrode.

  In this configuration, since the diffusion of oxygen can be controlled by the protective layer having a high manganese content and a low magnesium content, variation in capacitance between the dielectric layers between the first and second internal electrodes is suppressed. The Thereby, the capacity | capacitance of a multilayer capacitor can be made into the capacity | capacitance of the target design.

  The portion adjacent to the protective layer of the laminate has a manganese content greater than that of the dielectric layer ceramic in the central portion of the laminate and less than the ceramics of the first and second protective layers, and contains magnesium. You may be comprised with the ceramic whose quantity is less than the ceramic of the dielectric layer in the center part of the said laminated body, and more than the ceramics of the said 1st and 2nd protective layer.

  In this configuration, the portion of the laminate that is adjacent to the protective layer is made of ceramic that is an intermediate composition between the ceramic in the center of the laminate and the ceramic that forms the protective layer. Thereby, delamination between the laminate and the protective layer is less likely to occur.

In the first and second protective layers, the ceramic particles on the surface of the element body may have a larger average particle size than the ceramic particles adjacent to the laminate.
In this configuration, the strength of the surface of the protective layer that is the outer surface of the multilayer capacitor is improved. Thereby, the impact resistance of the multilayer capacitor is improved.

In the method for manufacturing a multilayer capacitor according to one aspect of the present invention, a first ceramic sheet made of a first ceramic and having a first internal electrode is prepared.
A second ceramic sheet made of the first ceramic and having a second internal electrode is prepared.
A third ceramic sheet composed of a second ceramic having a manganese content higher than that of the first ceramic and a magnesium content lower than that of the first ceramic is prepared.
The first, second and third ceramic sheets are arranged so that the first and second ceramic sheets are alternately arranged, and the third ceramic sheet is arranged with the first and second ceramic sheets interposed therebetween. A laminate is produced by laminating.

  A multilayer capacitor capable of suppressing variation in capacitance between dielectric layers and a method for manufacturing the same can be provided.

1 is a perspective view of a multilayer capacitor according to a first embodiment of the present invention. It is a perspective view of the element body of the multilayer capacitor. It is sectional drawing along the AA 'line of FIG. 2 of the said element | base_body. It is sectional drawing along the BB 'line | wire of FIG. 2 of the said element | base_body. It is a flowchart which shows the manufacturing method of the said multilayer capacitor. It is a perspective view which shows lamination | stacking of the ceramic sheet | seat in the manufacture process of the said multilayer capacitor. It is a perspective view which shows the unbaking element | base_body in the manufacturing process of the said multilayer capacitor. It is a perspective view which shows the unbaked multilayer capacitor in the manufacturing process of the said multilayer capacitor. It is sectional drawing of the multilayer capacitor which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the said multilayer capacitor. It is a top view which shows the Z-axis direction upper surface of the laminated body of the said multilayer capacitor. It is a top view which shows the Z-axis direction lower surface of the laminated body of the said multilayer capacitor. It is sectional drawing of the multilayer capacitor which concerns on the 3rd Embodiment of this invention. It is a perspective view which shows lamination | stacking of the ceramic sheet | seat in the manufacture process of the said multilayer capacitor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the drawing, an X axis, a Y axis, and a Z axis that are orthogonal to each other are shown as appropriate. The X axis, Y axis, and Z axis are common in all drawings.

<First Embodiment>
[Configuration of Multilayer Capacitor 10]
FIG. 1 is a perspective view of the multilayer capacitor 10 according to the first embodiment of the present invention. The multilayer capacitor 10 includes an element body 11, a first external electrode 14, and a second external electrode 15. The external electrodes 14 and 15 are provided at both ends of the element body 11 in the X-axis direction.

  FIG. 2 is a perspective view of the element body 11. 3 is a cross-sectional view of the element body 11 taken along the line AA ′ of FIG. 2, and FIG. 4 is a cross-sectional view of the element body 11 taken along the line BB ′ of FIG. The element body 11 includes a stacked body 16, a first protective layer 17, and a second protective layer 18.

  The stacked body 16 has a rectangular parallelepiped shape having sides along the X axis, the Y axis, and the Z axis. The first protective layer 17 is provided on the upper surface (first main surface) in the Z-axis direction of the multilayer body 16, and the second protective layer 18 is provided on the lower surface (second main surface) in the Z-axis direction of the multilayer body 16. Each of the protective layers 17 and 18 has a flat plate shape extending along the XY plane, and covers the entire upper and lower surfaces of the stacked body 16 in the Z-axis direction.

  The stacked body 16 has a first end face T1 and a second end face T2 perpendicular to the X axis. The stacked body 16 includes a plurality of first internal electrodes 12 and a plurality of second internal electrodes 13. Each of the internal electrodes 12 and 13 has a sheet shape extending along the XY plane, and is alternately stacked along the Z axis. The first internal electrode 12 is exposed at the first end face T1, and the second internal electrode 13 is exposed at the second end face T2.

  As shown in FIG. 1, the first end face T <b> 1 of the multilayer body 16 is covered with the first external electrode 14, and the second end face T <b> 2 of the multilayer body 16 is covered with the second external electrode 15. As a result, the first internal electrode 12 exposed at the first end face T1 is connected to the first external electrode 14, and the second internal electrode 13 exposed at the second end face T2 is connected to the second external electrode 15. ing.

  With the configuration as described above, in the multilayer capacitor 10, when a voltage is applied between the first external electrode 14 and the second external electrode 15, a plurality of portions between the first internal electrode 12 and the second internal electrode 13 are provided. A voltage is applied to the dielectric layer.

The laminate 16 is made of a first ceramic. As the first ceramic, a material having a high dielectric constant is employed in order to increase the capacitance of each dielectric layer between the internal electrodes 12 and 13. As the first ceramic, for example, a material having a perovskite structure including barium (Ba) and titanium (Ti) represented by barium titanate (BaTiO ₃ ) can be used.

  The first ceramics constituting the laminate 16 includes manganese (Mn) and magnesium (Mg). In the first ceramic, reduction resistance is improved by the action of manganese, and temperature characteristics having a flat dielectric constant are obtained by the action of magnesium.

  For example, the manganese content of the first ceramic can be 0.1 to 1.0 mol with respect to 100 mol of barium titanate. Moreover, the magnesium content of the first ceramic can be 0.1 to 1.0 mol with respect to 100 mol of barium titanate.

  In the method for manufacturing the multilayer capacitor 10 according to this embodiment, the element body 11 is fired in a reducing atmosphere. In firing in a reducing atmosphere, if the diffusion of oxygen is not controlled, the variation in capacitance between the dielectric layers of the multilayer body 16 increases, and the capacitance of the multilayer capacitor 10 deviates from the target design capacitance. May end up.

  In the multilayer capacitor 10 according to the present embodiment, the protective layers 17 and 18 are provided in order to suppress variation in capacitance between the dielectric layers by preventing oxygen from entering from the upper and lower surfaces in the Z-axis direction of the multilayer body 16. Is provided.

  The protective layers 17 and 18 are made of a second ceramic. The second ceramics constituting the protective layers 17 and 18 differ from the first ceramics constituting the laminate 16 only in the content of manganese and the content of magnesium. In the second ceramic, the manganese content is higher than that of the first ceramic, and the magnesium content is lower than that of the second ceramic.

  For example, the manganese content of the second ceramic can be set to 0.5 to 2.0 mol with respect to 100 mol of barium titanate. The magnesium content of the second ceramic can be 0 to 0.5 mol with respect to 100 mol of barium titanate.

  In the second ceramics having a high manganese content and a low magnesium content, the diffusion of oxygen can be controlled as compared with the first ceramics.

As a comparative example, a multilayer capacitor in which the protective layers 17 and 18 of the multilayer capacitor 10 according to the present embodiment are made of the same first ceramic as the multilayer body 16 was produced. For this multilayer capacitor, the capacitance of each dielectric layer was measured. Then, using the maximum value C _MAX , the minimum value C _MIN , and the average value C _AVE of each dielectric layer, a variation rate D (= 100 × (C _MAX −C _MIN ) / C _AVE ) [%] is calculated. did. As a result, the variation rate D of the multilayer capacitor according to the comparative example was 7 [%].

  For the multilayer capacitor 10 according to the present embodiment, the same measurement as in the above comparative example was performed, and the variation rate D was calculated. As a result, the variation rate D of the multilayer capacitor 10 according to the present embodiment was 3 [%].

  As described above, in the multilayer capacitor 10 according to this embodiment, diffusion of oxygen during firing can be controlled by the protective layers 17 and 18. Therefore, the capacitance of the multilayer capacitor 10 is unlikely to deviate from the target designed capacitance.

[Method of Manufacturing Multilayer Capacitor 10]
FIG. 5 is a flowchart showing a method for manufacturing the multilayer capacitor 10 according to the present embodiment. 6 to 8 are diagrams showing a manufacturing process of the multilayer capacitor 10. Hereinafter, a method for manufacturing the multilayer capacitor 10 will be described along FIG. 5 with reference to FIGS.

(Step S1: Preparation of ceramic sheet)
FIG. 6 is a diagram for explaining steps S1 to S3 in FIG.

  First, a ceramic sheet 110U for forming the laminate 16 and a ceramic sheet 111U for forming the protective layers 17 and 18 are prepared. The ceramic sheets 110U and 111U are configured as unfired dielectric green sheets. The ceramic sheet 110U is made of a first ceramic, and the ceramic sheet 111U is made of a second ceramic.

  The ceramic sheets 110U and 111U can be formed into a sheet shape using, for example, a roll coater. The ceramic sheets 110U and 111U are not cut for each multilayer capacitor 10, and the subsequent steps S2 and S3 can be performed collectively for the plurality of multilayer capacitors 10.

(Step S2: Internal electrode printing)
The ceramic sheet 112U is obtained by forming the unfired first internal electrode 12U to be the first internal electrode 12 on the ceramic sheet 110U. Further, the ceramic sheet 112U is obtained by forming the unfired second internal electrode 13U to be the second internal electrode 13 on the ceramic sheet 110U. For example, a screen printing method can be used to form the internal electrodes 12U and 13U.

(Step S3: lamination)
As shown in FIG. 6, ceramic sheets 111U, 112U, and 113U are laminated. The ceramic sheets 112U and 113U are alternately arranged in the Z-axis direction. The ceramic sheets 111U on which the internal electrodes 12 and 13 are not formed are arranged at the uppermost part and the lowermost part in the Z-axis direction. The number of ceramic sheets 111U at the uppermost part and the lowermost part in the Z-axis direction can be appropriately determined according to the thickness of the protective layers 17 and 18.

  For convenience of explanation, FIG. 6 shows a state in which the ceramic sheets 111U, 112U, and 113U are cut into the respective multilayer capacitors 10. However, from the viewpoints of work efficiency and handling properties, it is preferable that the ceramic sheets 111U, 112U, and 113U be separated into the respective multilayer capacitors 10 after being laminated.

  By pressing the laminated ceramic sheets 111U, 112U, and 113U, a plurality of ceramic sheets 111U, 112U, and 113U are integrated to obtain a laminated sheet in which a plurality of unfired element bodies 11U are arranged. . As a pressing method, for example, an isostatic pressing method can be used. The laminated sheet is cut for each unfired element body 11U to be each element body 11.

  Of the ceramic sheets 112U and 113U, the ceramic sheets 112U and 113U (the ceramic sheet 113U in FIG. 6) located at the lowest position in the Z-axis direction are formed by the ceramic sheet 111U, not the ceramic sheet 110U. However, this configuration is not essential, and the ceramic sheets 112U and 113U may be formed of the ceramic sheet 110U.

  FIG. 7 is a perspective view of the unfired element body 11U obtained in step S3. In the element body 11U, the ceramic sheets 112U and 113U are the laminated bodies 16U, and the ceramic sheet 111U is the protective layers 17U and 18U. The first internal electrode 12U is exposed at the first end face T1U of the multilayer body 16U, and the second internal electrode 13U is exposed at the second end face T2U of the multilayer body 16U.

(Step S4: External electrode formation)
As shown in FIG. 8, an unfired external electrode 14U is provided so as to cover the first end face T1U of the multilayer body 16U, and an unfired external electrode 15U is provided so as to cover the second end face T2U of the multilayer body 16U. Thereby, the unfired multilayer capacitor 10U is obtained. In the multilayer capacitor 10U, the external electrode 14U is connected to the first internal electrode 12U exposed at the first end face T1U, and the external electrode 15U is connected to the second internal electrode 13U exposed at the second end face T2U.

(Step S5: Firing)
The unfired multilayer capacitor 10U shown in FIG. 8 is fired in a reducing atmosphere to obtain the multilayer capacitor 10 shown in FIG. In this step S5, the diffusion of oxygen from the upper and lower surfaces in the Z-axis direction of the multilayer body 16U can be controlled by the protective layers 17U and 18U provided on the upper and lower surfaces in the Z-axis direction of the multilayer body 16U.

  As described above, in the method for manufacturing the multilayer capacitor 10 according to this embodiment, the multilayer capacitor 10 with less variation in capacitance between the dielectric layers can be obtained. For this reason, the capacity of the multilayer capacitor 10 manufactured by the manufacturing method according to the present embodiment is unlikely to deviate from the target designed capacity.

<Second Embodiment>
A multilayer capacitor according to a second embodiment of the present invention will be described. In the present embodiment, the description of the configuration common to the first embodiment will be omitted as appropriate. Moreover, the code | symbol similar to 1st Embodiment is used for the structure corresponding to 1st Embodiment among the structures of this embodiment.

[Configuration of multilayer capacitor]
9 and 10 are cross-sectional views of the multilayer capacitor element body 21 according to the present embodiment. 9 shows a cross section parallel to the ZX plane of the element body 21, and FIG. 10 shows a cross section parallel to the YZ plane of the element body 21.

  In the multilayer capacitor according to the present embodiment, intermediate portions 27 and 28 are provided in order to prevent peeling (delamination) between the multilayer body 26 and the protective layers 17 and 18 during firing of the multilayer capacitor.

  The first intermediate portion 27 is provided on the upper surface in the Z-axis direction of the stacked body 26, and the second intermediate portion 28 is provided on the lower surface in the Z-axis direction of the stacked body 26. Accordingly, the first intermediate portion 27 is adjacent to the first protective layer 17, and the second intermediate portion 28 is adjacent to the second protective layer 18.

  FIG. 11 is a plan view showing the upper surface of the laminate 16 in the Z-axis direction, and FIG. 12 is a plan view showing the lower surface of the laminate 16 in the Z-axis direction. The first intermediate portion 27 is provided in a region on the upper surface in the Z-axis direction of the stacked body 26 where the first internal electrode 12 is not exposed. The second intermediate portion 28 is provided in an area where the second internal electrode 13 is not exposed on the lower surface in the Z-axis direction of the multilayer body 26.

  Further, the intermediate portions 27 and 28 have a thickness in the Z-axis direction corresponding to one layer of the stacked body 26. That is, the first intermediate portion 27 is disposed in a region from the upper surface in the Z-axis direction of the multilayer body 26 to the second internal electrode 13 in the second layer from the top. The second intermediate portion 28 is disposed in a region from the bottom surface in the Z-axis direction of the multilayer body 26 to the first internal electrode 12 in the second layer from the bottom.

  As described above, in the multilayer capacitor according to the present embodiment, the first ceramics constituting the multilayer body 26 and the second ceramics constituting the protective layers 17 and 18 are not in direct contact with each other, and the intermediate portions 27 and 28 are provided. Connected through.

  In the present embodiment, the intermediate portions 27 and 28 are made of third ceramics. The third ceramics constituting the intermediate portions 27 and 28 differ from the first ceramics constituting the laminated body 16 and the second ceramics constituting the protective layers 17 and 18 only in the contents of manganese and magnesium. More specifically, the manganese content of the third ceramic is greater than that of the first ceramic and less than that of the second ceramic. The magnesium content of the third ceramic is less than that of the first ceramic and higher than that of the second ceramic.

  That is, the third ceramics constituting the intermediate portions 27 and 28 have an intermediate composition between the first ceramics constituting the laminated body 16 and the second ceramics constituting the protective layers 17 and 18. Accordingly, the third ceramic has an intermediate property between the first ceramic and the second ceramic. For example, the shrinkage rate of the third ceramic during firing of the multilayer capacitor is intermediate between the shrinkage rate of the first ceramic and the shrinkage rate of the second ceramic.

  Therefore, the shrinkage rate of the first intermediate portion 27 at the time of firing the multilayer capacitor is equal to the shrinkage rate of the multilayer body 26 made of the first ceramics and the shrinkage rate of the first protective layer 17 made of the second ceramics. Is also close. For this reason, the 1st intermediate part 27 cannot peel easily from the laminated body 26 and the protective layer 17 at the time of baking of a multilayer capacitor, and connects the laminated body 26 and the protective layer 17 favorably.

  Further, the shrinkage rate of the second intermediate portion 28 at the time of firing the multilayer capacitor is equal to the shrinkage rate of the multilayer body 26 made of the first ceramics and the shrinkage rate of the second protective layer 18 made of the second ceramics. Is also close. For this reason, the 2nd intermediate part 28 cannot peel easily from the laminated body 26 and the protective layer 18 at the time of baking of a multilayer capacitor, and connects the laminated body 26 and the protective layer 17 favorably.

  Therefore, in the multilayer capacitor according to the present embodiment, delamination between the multilayer body 26 and the protective layers 17 and 18 hardly occurs due to the action of the intermediate portions 27 and 28.

  Since the intermediate portions 27 and 28 are not disposed between the internal electrodes 12 and 13 of the multilayer body 16, they do not affect the capacitance of the multilayer capacitor. That is, in the multilayer capacitor according to this embodiment, delamination between the multilayer body 16 and the protective layers 17 and 18 can be prevented without changing the capacitance.

  Further, the contents of manganese and magnesium in the third ceramics constituting the intermediate portions 27 and 28 may not be uniform. For example, the third ceramics constituting the intermediate portions 27 and 28 may have a higher manganese content as they are closer to the protective layers 17 and 18. Further, the third ceramics constituting the intermediate portions 27 and 28 may have a lower magnesium content as they are closer to the protective layers 17 and 18.

  Further, in the side margin portion 19 (see FIG. 10) where the internal electrodes 12 and 13 are not provided over the entire range in the Z-axis direction at both ends in the Y-axis direction of the multilayer body 16, the intermediate portions 27 and 28 are Z It may be extended to a deeper position in the axial direction.

[Manufacturing method of multilayer capacitor]
The intermediate portions 27 and 28 of the multilayer capacitor in accordance with the present embodiment can be formed by laminating ceramic sheets with adjusted manganese and magnesium compositions.

  That is, in the laminating step according to the first embodiment (see FIG. 6), unfired intermediate portions 27U and 28U are provided in portions corresponding to the intermediate portions 27 and 28, and unfired intermediate portions 27U and 28U are provided. You may produce the laminated body 16U (refer FIG. 7). Thereby, the multilayer capacitor | condenser which has the intermediate parts 27 and 28 which concern on this embodiment after baking is obtained.

<Third Embodiment>
A multilayer capacitor according to a third embodiment of the present invention will be described. In the present embodiment, the description of the configuration common to the first embodiment will be omitted as appropriate. Moreover, the code | symbol similar to 1st Embodiment is used for the structure corresponding to 1st Embodiment among the structures of this embodiment.

[Configuration of multilayer capacitor]
FIG. 13 is a cross-sectional view of the multilayer capacitor element body 31 according to the present embodiment. FIG. 13 shows a cross section of the element body 31 parallel to the ZX plane.

  Unlike the element body 11 according to the first embodiment, the element body 31 according to the present embodiment includes protective layers 37 and 38 having a three-layer structure. The first protective layer 37 is configured by laminating the first layer 37a, the second layer 37b, and the third layer 37c in this order on the upper surface of the multilayer body 16 in the Z-axis direction. The second protective layer 38 is configured by laminating the first layer 38a, the second layer 38b, and the third layer 38c in this order on the lower surface in the Z-axis direction of the multilayer body 16.

  The first layers 37a and 38a, the second layers 37b and 38b, and the third layers 37c and 38c are all made of the same second ceramic as the protective layers 17 and 18 according to the first embodiment. The average grain sizes of the dielectric crystals constituting the second ceramic are different from each other. Specifically, the average grain size of the dielectric crystals of the first layers 37a and 38a is the smallest, and the average grain size of the dielectric crystals of the third layers 37c and 38c is the largest.

  In this embodiment, the average grain size of the dielectric crystals of the first layers 37a and 38a, the second layers 37b and 38b, and the third layers 37c and 38c is 0.1 to 0.5 μm. On the other hand, the average grain size of the dielectric crystals of the first layers 37a and 38a is 0.1 to 0.5 μm, and the average grain size of the dielectric crystals of the third layers 37c and 38c is 0.2 to 1. 0 μm.

  When the average grain size of the dielectric crystals of the first layers 37a and 38a adjacent to the multilayer body 16 is small, the fluidity of the first layers 37a and 38a during firing of the multilayer capacitor is increased. Thereby, in the multilayer capacitor after firing, high adhesion between the multilayer body 16 and the first layers 37a and 38a is obtained. Therefore, in the multilayer capacitor according to this embodiment, delamination between the multilayer body 16 and the protective layers 37 and 38 can be prevented.

  Further, the third layers 37c and 38c having a large average grain size of the dielectric crystal have high strength. In the multilayer capacitor in accordance with this embodiment, the third layers 37c and 38c constituting the outer surface of the multilayer capacitor have high strength, so that high impact resistance can be obtained.

[Manufacturing method of multilayer capacitor]
As shown in FIG. 14, the protective layers 37 and 38 of the multilayer capacitor in accordance with this embodiment are formed from unfired protective layers 37U and 38U. The protective layers 37U and 38U are configured by first layer sheets 37aU and 38aU, second layer sheets 37bU and 38bU, and third layer sheets 37cU and 38cU that are made of powders of second ceramics having different average particle diameters. The average particle size of the powders of the first layer sheets 37aU and 38aU is the smallest, and the average particle size of the powders of the third layer sheets 37cU and 38cU is the largest.

  By firing the unfired element body produced as described above, a multilayer capacitor having the element body 31 according to the present embodiment is obtained.

  In addition, it is not essential that the protective layers 37 and 38 of the multilayer capacitor according to the present embodiment have a three-layer structure as shown in FIG. In the multilayer capacitor, the average grain size of the dielectric crystal is small on the first surface in contact with the multilayer body 16 in the protective layers 37 and 38, and the dielectric crystal on the second surface opposite to the first surface in the protective layers 37 and 38. If the average particle size is large, the above effect can be obtained.

  Therefore, the protective layers 37 and 38 of the multilayer capacitor in accordance with the present embodiment are such that the second surface opposite to the first surface is the dielectric constituting the second ceramic, rather than the first surface adjacent to the multilayer body 16. What is necessary is just to be comprised so that the average particle diameter of a body crystal may become large.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Multilayer capacitor 11 ... Element 12 ... 1st internal electrode 13 ... 2nd internal electrode 14 ... 1st external electrode 15 ... 2nd external electrode 16 ... Laminate 17 ... 1st protective layer 18 ... 2nd protective layer

Claims (3)

A first internal electrode, a dielectric layer containing 0.1 to 1.0 mol of magnesium and 0.1 to 1.0 mol of manganese with respect to 100 mol of barium titanate (BaTiO ₃ ), and a second internal electrode And a layered body that is connected to the layered body and contains 0 mol to 0.5 mol magnesium and 0.5 mol to 2.0 mol manganese with respect to 100 mol of barium titanate (BaTiO ₃ ) . An element body having first and second protective layers;
A first external electrode covering the first end face of the element body and connected to the first internal electrode;
A second external electrode covering the second end face of the element body and connected to the second internal electrode;
The ceramic of the first and second protective layers has a manganese content higher than that of the dielectric layer ceramic, and a magnesium content lower than that of the dielectric layer ceramic. The multilayer capacitor according to claim 1,
The portion adjacent to the protective layer of the laminate has a manganese content greater than that of the dielectric layer ceramic in the central portion of the laminate and less than the ceramics of the first and second protective layers, and contains magnesium. A multilayer capacitor comprising an amount of ceramic less than that of a dielectric layer in the center of the multilayer body and greater than that of the first and second protective layers. The multilayer capacitor according to claim 1 or 2,
In the first and second protective layers, the ceramic particles on the surface of the element body have a larger average particle size than the ceramic particles adjacent to the multilayer body.

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