Multi-layer ceramic capacitor and method of producing the same

A multi-layer ceramic capacitor includes: a body, a first external electrode, and a second external electrode. The body includes a first end surface and a second end surface that face each other, a side surface that extends between the first end surface and the second end surface, a first recess that extends along a first ridge of the first end surface and the side surface, a second recess that extends along a second ridge of the second end surface and the side surface, a first internal electrode that is drawn to the first end surface and the first recess, and a second internal electrode that faces the first internal electrode and is drawn to the second end surface and the second recess. The first external electrode covers the body from the first end surface. The second external electrode covers the body from the second end surface.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2016-080787, filed Apr. 14, 2016, which is herein incorporated by reference in its entirety.

BACKGROUND

The present invention relates to a multi-layer ceramic capacitor and a method of producing the multi-layer ceramic capacitor.

Along with miniaturization of electronic devices and achievement of high performance thereof, there have recently been increasingly strong demands for miniaturization and increase in capacity with respect to multi-layer ceramic capacitors used in the electronic devices. In order to meet those demands, it is effective to enlarge internal electrodes of the multi-layer ceramic capacitor. In order to enlarge the internal electrodes, it is necessary to thin side margins for ensuring insulation properties of the periphery of the internal electrodes.

Meanwhile, in a general method of producing a multi-layer ceramic capacitor, it is difficult to form side margins having a uniform thickness because of precision in each step (e.g., patterning of internal electrodes, cutting of a multi-layer sheet, etc.). Therefore, in such a method of producing a multi-layer ceramic capacitor, as the side margins are made thinner, it is more difficult to ensure insulation properties of the periphery of the internal electrodes.

Japanese Patent Application Laid-open Nos. 2012-209539 and 2012-191164 (hereinafter, referred to as Patent Documents 1 and 2) each disclose a technique of providing side margins in a subsequent step. In other words, in those techniques, a multi-layer sheet is cut to produce a multi-layer chip including internal electrodes exposed to side surfaces of the multi-layer chip, and side margins are then provided to the side surfaces of the multi-layer chip to produce a body.

With this configuration, the body including the side margins each having a uniform thickness is obtained in the techniques disclosed in Patent Documents 1 and 2. Therefore, in the multi-layer ceramic capacitors according to those techniques, insulation properties of the periphery of the internal electrodes can be ensured also when the side margins are made thin so as to enlarge the internal electrodes.

Further, aside from the techniques disclosed in Patent Documents 1 and 2, a technique to improve connection strength of an external electrode to a body is expected for the multi-layer ceramic capacitor. Such a technique can prevent the external electrode from being peeled off from the body, and the multi-layer ceramic capacitor can thus obtain high reliability.

Japanese Patent Application Laid-open No. 2013-84871 (hereinafter, referred to as Patent Document 3) discloses a technique capable of improving connection strength of an external electrode to a body. In this technique, dummy electrodes, which are not connected to internal electrodes, are exposed in regions of a body where external electrodes are provided. In this technique, the external electrodes have good connectivity with the dummy electrodes made of metal, so that connection strength of the external electrode to the body is improved.

BRIEF SUMMARY

However, in the techniques of providing the side margins in a subsequent step, which are disclosed in Patent Documents 1 and 2, it is difficult to dispose the dummy electrodes to the side margins, the dummy electrodes being disclosed in Patent Document 3. Therefore, also in the configuration in which the side margins are provided in a subsequent step, the technique capable of improving the connection strength of the external electrodes to the body is expected.

In view of the circumstances as described above, it is desirable to provide a multi-layer ceramic capacitor and a method of producing the multi-layer ceramic capacitor, which are capable of obtaining high connection strength of an external electrode to a body.

According to an embodiment of the present invention, there is provided a multi-layer ceramic capacitor including a body, a first external electrode, and a second external electrode.

The body includes a first end surface and a second end surface that face each other, a side surface that extends between the first end surface and the second end surface, a first recess that extends along a first ridge of the first end surface and the side surface, a second recess that extends along a second ridge of the second end surface and the side surface, a first internal electrode that is drawn to the first end surface and the first recess, and a second internal electrode that faces the first internal electrode and is drawn to the second end surface and the second recess.

The first external electrode covers the body from the first end surface.

The second external electrode covers the body from the second end surface.

In this configuration, the first recess and the second recess at which the first internal electrode and the second internal electrode are respectively exposed are provided. With this configuration, the first external electrode and the second external electrode are respectively connected to the first internal electrode and the second internal electrode not only on the first end surface and the second end surface but also at the first recess and the second recess. In other words, this configuration can ensure a large region where the first external electrode and the second external electrode are respectively connected to the first internal electrode and the second internal electrode. This can provide high connection strength of the first external electrode and the second external electrode to the body.

The body may further include a side margin that is disposed along the side surface to form the first recess and the second recess together with the first end surface and the second end surface, respectively.

In this configuration, providing the side margin in a subsequent step enables the first recess and the second recess to be easily formed.

The first external electrode and the second external electrode may extend to the side surface.

In this configuration, the first end surface and the second end surface, and the whole of the first internal electrode and the second internal electrode that are respectively exposed at the first recess and the second recess are respectively covered with the first external electrode and the second external electrode. This can ensure a larger region where the first external electrode and the second external electrode are respectively connected to the first internal electrode and the second internal electrode.

A depth of the first recess from the first end surface may be 30% or less of an interval between the first end surface and the second internal electrode, and a depth of the second recess from the second end surface may be 30% or less of an interval between the second end surface and the first internal electrode.

In this configuration, insulation properties between the first external electrode and the second internal electrode and insulation properties between the second external electrode and the first internal electrode are more reliably obtained. This improves moisture resistance in the multi-layer ceramic capacitor, so that high reliability can be obtained.

According to another embodiment of the present invention, there is provided a method of producing a multi-layer ceramic capacitor, the method including: producing a body including a first end surface and a second end surface that face each other, a side surface that extends between the first end surface and the second end surface, a first recess that extends along a first ridge of the first end surface and the side surface, a second recess that extends along a second ridge of the second end surface and the side surface, a first internal electrode that is drawn to the first end surface and the first recess, and a second internal electrode that faces the first internal electrode and is drawn to the second end surface and the second recess; forming a first external electrode that covers the body from the first end surface; and forming a second external electrode that covers the body from the second end surface.

Ceramic sheets may be pressure-bonded to produce a multi-layer chip including the first internal electrode and the second internal electrode.

A side margin extending along the side surface may be formed on the multi-layer chip to produce the body, the body being unsintered.

In this configuration, providing the side margin in a subsequent step enables the first recess and the second recess to be easily formed.

The side margin formed on the multi-layer chip may be dried to shrink, to form the first recess and the second recess.

The body may be subjected to processing to form the first recess and the second recess, the body being unsintered.

The processing may include barrel polishing.

The body may be produced, the body being unsintered and including the side margin that is made of a material having a larger shrinking percentage at sintering than a material of the multi-layer chip.

The body may be sintered to form the first recess and the second recess, the body being unsintered.

The side margin may be made of a material that is easier to generate a liquid phase at sintering than the material of the multi-layer chip.

The side margin may be made of a material having a smaller proportion of base powder than the material of the multi-layer chip.

The side margin may be made of a material having a smaller average particle diameter of base powder than the material of the multi-layer chip.

In those configurations, the recesses can be easily formed in the body in a configuration in which the side margin is provided in a subsequent step.

According to the present invention, it is possible to provide a multi-layer ceramic capacitor and a method of producing the multi-layer ceramic capacitor, which are capable of obtaining high connection strength of an external electrode to a body.

DETAILED DESCRIPTION

In the figures, an X axis, a Y axis, and a Z axis orthogonal to one another are shown as appropriate. The X axis, the Y axis, and the Z axis are common in all figures.

1. Overall Configuration of Multi-layer Ceramic Capacitor10

FIGS. 1 to 3each show a multi-layer ceramic capacitor10according to one embodiment of the present invention.FIG. 1is a perspective view of the multi-layer ceramic capacitor10.FIG. 2is a cross-sectional view of the multi-layer ceramic capacitor10taken along the A-A′ line inFIG. 1.FIG. 3is a cross-sectional view of the multi-layer ceramic capacitor10taken along the B-B′ line inFIG. 1.

The multi-layer ceramic capacitor10includes a body11, a first external electrode14, and a second external electrode15. The first external electrode14and the second external electrode15are apart from each other and face each other in an X-axis direction while sandwiching the body11therebetween.

The body11has two end surfaces T1and T2(hereinafter, also referred to as first end surface T1and second end surface T2) oriented in the X-axis direction, two side surfaces S1and S2oriented in a Y-axis direction, and two main surfaces M1and M2oriented in a Z-axis direction. Four ridges connecting the side surfaces S1and S2and the main surfaces M1and M2of the body11are chamfered. Further, four ridges connecting the end surfaces T1and T2and the side surfaces S1and S2of the body11are provided with recesses22and23(seeFIGS. 4 to 6; hereinafter, also referred to as first recess22and second recess23). Detailed configurations of the recesses22and23will be described later.

A dimension of the body11can be optionally determined. For example, in the body11, a dimension thereof in the X-axis direction can be set to 1.0 mm and dimensions thereof in the Y- and Z-axis directions can be set to 0.5 mm.

It should be noted that the form of the body11is not limited to the form as described above. For example, the surfaces of the body11may be curved surfaces, and the body11may be rounded as a whole.

The first external electrode14covers the body11from the first end surface T1and extends to the side surfaces S1and S2and the main surfaces M1and M2, which are connected to the first end surface T1. Further, the second external electrode15covers the body11from the second end surface T2and extends to the side surfaces S1and S2and the main surfaces M1and M2, which are connected to the second end surface T2. With this configuration, both of the first external electrode14and the second external electrode15have U-shaped cross sections in parallel with an X-Z plane and an X-Y plane.

The first external electrode14and the second external electrode15are each formed from a good conductor and function as terminals of the multi-layer ceramic capacitor10. Examples of the good conductor forming the first and second external electrodes14and15include metal mainly containing nickel (Ni), copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), or the like, and an alloy of those metals.

The first and second external electrodes14and15may have a single-layer structure or multi-layer structure.

The first and second external electrodes14and15of the multi-layer structure may be formed to have a double-layer structure including a base film and a surface film, or a three-layer structure including a base film, an intermediate film, and a surface film, for example. The base film can be a baked film made of metal mainly containing nickel, copper, palladium, platinum, silver, gold, or the like, or an alloy of those metals, for example.

The intermediate film can be a plating film made of metal mainly containing platinum, palladium, gold, copper, nickel, or the like, or an alloy of those metals, for example.

The surface film can be a plating film made of metal mainly containing copper, tin, palladium, gold, zinc, or the like, or an alloy of those metals, for example.

The multi-layer chip16includes a capacitance forming unit18, covers19, end margins20and21(hereinafter, also referred to as first end margin20and second end margin21), first internal electrodes12, and second internal electrodes13.

The side margins17each have a flat plate-like shape extending along the X-Z plane and cover both side surfaces P1and P2of the multi-layer chip16that are oriented in the Y-axis direction.

The capacitance forming unit18is provided at the center portion of the body11and is formed to be a functional unit having a function of storing charge of the multi-layer ceramic capacitor10.

The first end margin20and the second end margin21are provided to both sides of the capacitance forming unit18in the X-axis direction. In other words, the first end margin20is disposed between the capacitance forming unit18and the second external electrode15, and the second end margin21is disposed between the capacitance forming unit18and the first external electrode14.

The covers19each have a flat plate-like shape extending along the X-Y plane and cover both main surfaces of the capacitance forming unit18and of the first and second end margins20and21, both the main surfaces being oriented in the Z-axis direction.

The side margins17and the covers19have main functions of protecting the capacitance forming unit18and the first and second end margins20and21and ensuring insulation properties of the periphery of the capacitance forming unit18and the first and second end margins20and21.

The first internal electrodes12and the second internal electrodes13each have a sheet-like shape extending along the X-Y plane and are alternately disposed along the Z-axis direction. The first internal electrodes12are disposed over the capacitance forming unit18and the second end margin21and connected to the first external electrode14. The second internal electrodes13are disposed over the capacitance forming unit18and the first end margin20and connected to the second external electrode15.

Therefore, the first internal electrodes12and the second internal electrodes13intersect with each other and face each other in the capacitance forming unit18. Further, the first internal electrodes12are separated from the second external electrode15by the first end margin20and thus insulated from the second external electrode15. Furthermore, the second internal electrodes13are separated from the first external electrode14by the second end margin21and thus insulated from the first external electrode14.

The first internal electrodes12and the second internal electrodes13are each formed from a good conductor and function as internal electrodes of the multi-layer ceramic capacitor10. Examples of the good conductor forming the first and second internal electrodes12and13include nickel (Ni), copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), and a metal material including an alloy of those metals.

The capacitance forming unit18and the first and second end margins20and21are made of dielectric ceramics. In the multi-layer ceramic capacitor10, in order to increase capacitances of respective layers made of dielectric ceramics (hereinafter, also referred to as dielectric ceramic layers) provided between the first and second internal electrodes12and13, dielectric ceramics having a high dielectric constant is used as a material forming the capacitance forming unit18and the first and second end margins20and21. Examples of the dielectric ceramics having a high dielectric constant include a material having a Perovskite structure containing barium (Ba) and titanium (Ti), which is typified by barium titanate (BaTiO3).

Further, examples of the dielectric ceramics forming the capacitance forming unit18and the first and second end margins20and21may also include a strontium titanate (SrTiO3) based material, a calcium titanate (CaTiO3) based material, a magnesium titanate (MgTiO3) based material, a calcium zirconate (CaZrO3) based material, a calcium zirconate titanate (Ca(Zr,Ti)O3) based material, a barium zirconate (BaZrO3) based material, or a titanium oxide (TiO2) based material, in addition to the barium titanate based material.

The side margins17and the covers19are also made of dielectric ceramics. A material of the side margins17and the covers19only needs to be insulating ceramics, but use of a material having a composition system similar to that of the material of the capacitance forming unit18and the first and second end margins20and21leads to improvement in production efficiency and suppression of internal stress in the body11.

With the configuration described above, when a voltage is applied between the first external electrode14and the second external electrode15in the multi-layer ceramic capacitor10, a voltage is applied to the dielectric ceramic layers between the first and second internal electrodes12and13in the capacitance forming unit18. With this configuration, the multi-layer ceramic capacitor10stores charge corresponding to the voltage applied between the first external electrode14and the second external electrode15.

It should be noted that the configuration of the multi-layer ceramic capacitor10is not limited to a specific configuration, and a well-known configuration can be used as appropriate in accordance with the size and performance expected for the multi-layer ceramic capacitor10. For example, the number of first internal electrodes12and second internal electrodes13in the capacitance forming unit18can be determined as appropriate.

2. Detailed Configuration of Recesses22and23

FIGS. 4 to 6are views of the body11seen through the first and second external electrodes14and15of the multi-layer ceramic capacitor10.FIG. 4is a perspective view of the body11.FIG. 5is a plan view of the body11.FIG. 6is a side view of the body11.FIGS. 4 to 6each show general forms of the first and second external electrodes14and15by broken lines.

The body11includes the first recesses22that extend in the Z-axis direction along first ridges of the first end surface T1and the side surfaces S1and S2. Further, the body11includes the second recesses23that extend in the Z-axis direction along second ridges of the second end surface T2and the side surfaces S1and S2. The first and second recesses22and23are each provided over the entire width of the body11in the Z-axis direction and form respective grooves recessed from the end surfaces T1and T2and the side surfaces S1and S2.

The first recess22and the second recess23are provided on both sides of the side margin17in the X-axis direction. In other words, the side margin17has a smaller dimension than that of the multi-layer chip16in the X-axis direction and is disposed at an interval from each of the end surfaces T1and T2of the multi-layer chip16. With this configuration, side surfaces P1and P2of the second end margin21are exposed at the first recesses22, and side surfaces P1and P2of the first end margin20are exposed at the second recesses23.

The first external electrode14covers the first recesses22, and the second external electrode15covers the second recesses23. As a result, the first external electrode14is connected to the first internal electrodes12not only on the first end surface T1but also at the first recesses22. Further, the second external electrode15is connected to the second internal electrodes13not only on the second end surface T2but also at the second recesses23. In such a manner, in the multi-layer ceramic capacitor10, the body11is provided with the first and second recesses22and23, so that a large region where the first and second external electrodes14and15are respectively connected to the first and the second internal electrodes12and13can be ensured.

The first and second internal electrodes12and13made of a metal material can be connected to the first and second external electrodes14and15more firmly than the first and second internal electrodes12and13made of dielectric ceramics. As a result, in the multi-layer ceramic capacitor10, high connection strength of the first and second external electrodes14and15to the body11is obtained. Therefore, in the multi-layer ceramic capacitor10, the first and second external electrodes14and15can be prevented from being peeled off from the body11, and high reliability is thus obtained.

Further, in the multi-layer ceramic capacitor10, contact areas of the first and second external electrodes14and15and the first and second internal electrodes12and13are increased. Thus, contact resistance of the first and second external electrodes14and15and the first and second internal electrodes12and13is reduced. As a result, in the multi-layer ceramic capacitor10, equivalent series resistance (ESR) can be reduced.

FIG. 6shows a depth D22of the first recess22from the first end surface T1, a depth D23of the second recess23from the second end surface T2, a dimension D20of the first end margin20in the X-axis direction, and a dimension D21of the second end margin21in the X-axis direction.

The depth D22of the first recess22is smaller than the dimension D21of the second end margin21. This can prevent the first external electrode14from being short-circuited with the second internal electrodes13within the first recess22.

Similarly, the depth D23of the second recess23is smaller than the dimension D20of the first end margin20. This can prevent the second external electrode15from being short-circuited with the first internal electrodes12within the second recess23.

As the depth D22of the first recess22and the depth D23of the second recess23become large, a large region where the first and second external electrodes14and15are respectively connected to the first and the second internal electrodes12and13can be ensured. More specifically, as the depth D22of the first recess22and the depth D23of the second recess23are increased, connection strength between the body11and the first and second external electrodes14and15increases in a linear manner. For that reason, from the standpoint of improvement in connection strength between the body11and the first and second external electrodes14and15, it is desirable that the depth D22of the first recess22and the depth D23of the second recess23be large.

Meanwhile, as the depth D22of the first recess22becomes large, the first external electrode14within the first recess22comes closer to the second internal electrodes13. Further, as the depth D23of the second recess23becomes large, the second external electrode15within the second recess23comes closer to the first internal electrodes12. As a result, as the depth D22of the first recess22and the depth D23of the second recess23become large, an insulation failure due to moisture in the atmosphere is easier to occur when the multi-layer ceramic capacitor10is operated, for example.

For those reasons, in the body11, the depth D22of the first recess22is desirably kept to 30% or less of the dimension D21of the second end margin21, and the depth D23of the second recess23is desirably kept to 30% or less of the dimension D20of the first end margin20. With this configuration, in the multi-layer ceramic capacitor10, an insulation failure due to moisture resistance can be effectively prevented from occurring, and high reliability is thus obtained.

3. Method of Producing Multi-Layer Ceramic Capacitor10

FIG. 7is a flowchart showing a method of producing the multi-layer ceramic capacitor10.FIGS. 8A to 13are views each showing a production process of the multi-layer ceramic capacitor10. Hereinafter, the method of producing the multi-layer ceramic capacitor10will be described alongFIG. 7with reference toFIGS. 8A to 13as appropriate.

3.1 Step S01: Preparation of Ceramic Sheets

In Step S01, first ceramic sheets101and second ceramic sheets102for forming the capacitance forming unit18and the first and second end margins20and21, and third ceramic sheets103for forming the covers19are prepared.

FIGS. 8A, 8B, and 8Care plan views of the first, second, and third ceramic sheets101,102, and103, respectively.FIG. 8Ashows the first ceramic sheet101,FIG. 8Bshows the second ceramic sheet102, andFIG. 8Cshows the third ceramic sheet103. The first, second, and third ceramic sheets101,102, and103are configured as unsintered dielectric green sheets and each formed into a sheet shape by using a roll coater or a doctor blade, for example.

At the stage of Step S01, the first, second, and third ceramic sheets101,102, and103are not yet cut into the multi-layer ceramic capacitors10.FIGS. 8A, 8B, and 8Ceach show cutting lines Lx and Ly used when the sheets are cut into the multi-layer ceramic capacitors10. The cutting lines Lx are parallel to the X axis, and the cutting lines Ly are parallel to the Y axis.

As shown inFIGS. 8A, 8B, and 8C, unsintered first internal electrodes112corresponding to the first internal electrodes12are formed on the first ceramic sheet101, and unsintered second internal electrodes113corresponding to the second internal electrodes13are formed on the second ceramic sheet102. It should be noted that no internal electrodes are formed on the third ceramic sheet103corresponding to the cover19.

The first and second internal electrodes112and113can be formed using any electrical conductive paste. For formation of the first and second internal electrodes112and113by use of an electrical conductive paste, a screen printing method or a gravure printing method can be used, for example.

Each of the first and second internal electrodes112and113is disposed over two regions and extends like a belt in the Y-axis direction. The two regions are adjacent to each other in the X-axis direction and divided by the cutting line Ly. The first internal electrodes112are shifted from the second internal electrodes113in the X-axis direction by one row including the regions divided by the cutting lines Ly. In other words, the cutting line Ly passing through the center of the first internal electrode112passes through a region between the second internal electrodes113, and the cutting line Ly passing through the center of the second internal electrode113passes through a region between the first internal electrodes112.

In Step S02, the first, second, and third ceramic sheets101,102, and103prepared in Step S01are laminated, to produce a multi-layer sheet104.

FIG. 9is a perspective view of the multi-layer sheet104obtained in Step S02. For the purpose of description,FIG. 9shows the first, second, and third ceramic sheets101,102, and103in an exploded manner. In an actual multi-layer sheet104, however, the first, second, and third ceramic sheets101,102, and103are pressure-bonded by hydrostatic pressing, uniaxial pressing, or the like for integration. With this configuration, a high-density multi-layer sheet104is obtained.

In the multi-layer sheet104, the first ceramic sheets101and the second ceramic sheets102that correspond to the capacitance forming unit18and the first and second end margins20and21are alternately laminated in the Z-axis direction.

Further, in the multi-layer sheet104, the third ceramic sheets103corresponding to the covers19are laminated on the uppermost and lowermost surfaces of the first and second ceramic sheets101and102alternately laminated in the Z-axis direction. It should be noted that in the example shown inFIG. 9three third ceramic sheets103are laminated on each of the uppermost and lowermost surfaces of the laminated first and second ceramic sheets101and102, but the number of third ceramic sheets103can be changed as appropriate.

In Step S03, the multi-layer sheet104obtained in Step S02is cut to produce unsintered multi-layer chips116.

FIG. 10is a plan view of the multi-layer sheet104after Step S03. The multi-layer sheet104is cut along the cutting lines Lx and Ly while being attached to a tape Tp as a holding member.

With this configuration, the multi-layer sheet104is singulated, and multi-layer chips116shown inFIG. 11are obtained. In each of the multi-layer chips116, cut surfaces on which the first and second internal electrodes112and113are exposed, i.e., the side surfaces P1and P2, are formed.

A method of cutting the multi-layer sheet104is not limited to a specific method. For example, for the cutting of the multi-layer sheet104, a technique using various blades can be used. Examples of the blades usable for the cutting of the multi-layer sheet104include a push-cutting blade and a rotary blade (e.g., dicing blade). Further, for the cutting of the multi-layer sheet104, for example, laser cutting or water jet cutting can be used in addition to the technique using various blades.

The cut multi-layer chips116are cleansed as needed, to remove grinding dust or the like adhering to the side surfaces P1and P2or the like.

3.4 Step S04: Formation of Side Margins

In Step S04, unsintered side margins117are formed on the side surfaces P1and P2of the multi-layer chip116obtained in Step S03.

The side margins117can be formed by, for example, stamping ceramic sheets with use of the side surfaces P1and P2of the multi-layer chip116or applying ceramic slurry to the side surfaces P1and P2of the multi-layer chip116. Examples of a method of applying the ceramic slurry to the side surfaces P1and P2of the multi-layer chip116include a dipping method.

A form of the unsintered body111can be determined in accordance with a form of a sintered body11. For example, in order to obtain the body11with the size of 1.0 mm×0.5 mm×0.5 mm, the unsintered body111with the size of 1.2 mm×0.6 mm×0.6 mm can be produced.

3.5 Step S05: Formation of Recesses

In Step S05, recesses122and123are formed in the unsintered body111shown inFIG. 12obtained in Step S04, to produce the unsintered body111shown inFIG. 13. Step S05can be executed by various methods, and an example thereof will be described as follows.

For example, the side margins117of the unsintered body Ill shown inFIG. 12are dried to shrink in the X-axis direction, so that the recesses122and123of the unsintered body111shown inFIG. 13can be formed. In order to cause the side margins117to easily shrink at the drying, the side margins117are desirably formed by application of ceramic slurry in Step S04(formation of side margins).

Alternatively, processing for forming the recesses122and123in the unsintered body111shown inFIG. 12is performed, so that the unsintered body111shown inFIG. 13can be produced. Examples of the processing for forming the recesses122and123in the unsintered body111include barrel polishing, laser irradiation, and sandblasting. Besides, the recesses122and123may be formed by pressing the side margins117to be deformed.

In one example, a method of performing barrel polishing on the unsintered body111shown inFIG. 12to form the recesses122and123will be described. The barrel polishing can be executed by, for example, putting the unsintered bodies111, a polishing medium, and liquid into a barrel container and imparting rotational motions or vibrations to the barrel container.

As described above, the multi-layer chip116achieves high density by hydrostatic pressing, uniaxial pressing, or the like in Step S02performed before the cutting in Step S03. Meanwhile, in Step S04, in order to prevent the layers of the multi-layer chip116from being peeled off, a large pressure is not applied to the side margins117formed on the multi-layer chip116. Thus, the side margins117are not provided with high density.

Therefore, in the unsintered body111shown inFIG. 12, the side margins117have a lower density than that of the multi-layer chip116. As a result, when the unsintered body111shown inFIG. 12is subjected to barrel polishing, the side margins117having a low density are worn more largely than the multi-layer chip116having a high density. With this configuration, in the unsintered body111shown inFIG. 13obtained after the barrel polishing, both ends of the side margins117in the X-axis direction are largely worn, so that the recesses122and123are formed.

It should be noted that in the unsintered body111shown inFIG. 13obtained after the barrel polishing both ends of the side margins117in the Z-axis direction may also be largely worn in addition to both the ends of the side margins117in the X-axis direction. This allows recesses extending in the X-axis direction to be formed at both sides of the side margins117in the Z-axis direction.

In Step S06, the unsintered body111shown inFIG. 13obtained in Step S05is sintered to produce the body11of the multi-layer ceramic capacitor10shown inFIGS. 1 to 6. Sintering can be performed in a reduction atmosphere or a low-oxygen partial pressure atmosphere, for example.

3.7 Step S07: Formation of External Electrodes

In Step S07, the first external electrode14and the second external electrode15are formed on the body11obtained in Step S06, to produce the multi-layer ceramic capacitor10shown inFIGS. 1 to 6.

In Step S07, first, an unsintered electrode material is applied so as to cover the body11from one of the end surfaces T1and T2and then applied so as to cover the body11from the other one of the end surfaces T1and T2. With this configuration, the body11is covered with the unsintered electrode material from each of the end surfaces T1and T2.

A method of applying the unsintered electrode material is not limited to a specific method as long as the unsintered electrode material can be filled into the first and second recesses22and23of the body11. Examples of the method of applying the unsintered electrode material include a dipping method.

Next, the unsintered electrode material applied to the body11is subjected to baking in a reduction atmosphere or a low-oxygen partial pressure atmosphere, for example, to form base films on the body11. On the base films baked onto the body11, intermediate films and surface films are formed by plating such as electrolytic plating. Thus, the first external electrode14and the second external electrode15are completed.

It should be noted that part of the treatment in Step S07described above may be performed before Step S06. For example, before Step S06, the unsintered electrode material may be applied to the unsintered body111from the end surfaces T1and T2, and in Step S06, the unsintered body111may be sintered and, simultaneously, the unsintered electrode material may be baked to form base layers of the first external electrode14and the second external electrode15.

3.8 Modified Example

In the method of producing the multi-layer ceramic capacitor10, Step S05(formation of recesses) is not obligatory. In other words, if the unsintered body111previously including the recesses122and123shown inFIG. 14is obtained in Step S04(formation of side margins), it is unnecessary to form the recesses122and123posteriori.

For example, when the side margins117that are short in the X-axis direction are disposed on the side surfaces P1and P2of the multi-layer chip116, the unsintered body111shown inFIG. 14is obtained. Further, also when conditions for stamping ceramic sheets with use of the side surfaces P1and P2of the multi-layer chip116are adjusted such that the side margins117become short in the X-axis direction, the unsintered body111shown inFIG. 14is obtained.

Further, in the body111before sintering, the side margins117are made of a material having a larger shrinking percentage at sintering than a material of the multi-layer chip116. This eliminates the necessity of forming the recesses122and123in the body111obtained before sintering. In this case, the side margins117shrink more largely than the multi-layer chip116at the sintering, and the first and second recesses22and23are thus formed in the body11obtained after the sintering.

In this regard, for example, the side margins117can be made of a material that is easier to generate a liquid phase at sintering than that of the multi-layer chip116. In this case, the side margins117can contain a larger amount of silicon oxide, boron nitride, or the like, which forms a glass component, than that of the multi-layer chip116.

Further, in the side margins117, it is also effective to make a proportion of base powder, which becomes a solid component after sintering, smaller than that of the multi-layer chip116.

Furthermore, in the side margins117, it is also effective to make an average particle diameter of the base powder smaller than that of the multi-layer chip116.

4. Other Embodiments

While the embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above, and it should be appreciated that the present invention may be variously modified.

For example, in the embodiment described above, the first and second recesses22and23are each formed over the entire width of the body11in the Z-axis direction, but the first and second recesses22and23only need to expose at least one of the first internal electrodes12and the second internal electrodes13. For example, the first and second recesses22and23may be provided in only regions corresponding to the first and second end margins20and21of the body11and may not be provided in regions corresponding to the covers19.

Further, in the multi-layer ceramic capacitor10, it is desirable to provide the first and second recesses22and23to all of the four ridges of the end surfaces T1and T2and side surfaces S1and S2of the body11as described in the above embodiment, but this configuration is not obligatory. In other words, in the multi-layer ceramic capacitor10, if the first and second recesses22and23are provided to at least one of the four ridges of the body11, effects of the embodiment can be obtained.

Furthermore, in the multi-layer ceramic capacitor10, it is desirable that the first and second external electrodes14and15extend to the side surfaces S1and S2of the body11beyond the first and second recesses22and23as described in the above embodiment, but this configuration is not obligatory. In other words, if the first and second external electrodes14and15respectively cover at least part of the first and second recesses22and23and are respectively connected to the first and second internal electrodes12and13within the first and second recesses22and23, effects of the embodiment can be obtained.